Feeds:
Posts
Comments

Posts Tagged ‘nitric oxide’

Curated/reported by : Aviral Vatsa PhD, MBBS

Based on : S Moncada et al

It was in 1980 that Furchgott & Zawadzki first described endothelium- dependent relaxation of the blood vessels by acetylcholine. Further studies in 1984 revealed that other factors such as bradykinin, histamine and 5-hydroxytryptamine release endothelium derived relaxing factor (EDRF), which can modulate vessel tone. EDRF was shown to stimulate soluble guanylate cyclase and was inhibited by haemoglobin. In 1986 it was demonstrated that superoxide (O2–) anions mediated EDRF inactivation and that the inhibitors of EDRF generated superoxide (O2–) anions in solution as a mean to inhibit EDRF. It was later established that all compounds that inhibit EDRF have one property in common, redox activity, which accounted for their inhibitory action on EDRF. One exception was haemoglobin, which inactivates EDRF by binding to it. In 1987 Furchgott proposed that EDRF might be nitric oxide (NO) based on a study of the transient relaxations of endothelium-denuded rings of rabbit aorta to ‘acidified’ inorganic nitrite (NO–) solutions and the observations that superoxide dismutase (SOD, which removes O2–) protected EDRF. Till then NO was not known to be produced in mammalian cells. In 1988 Palmer et al could detect NO production both biologically and chemically by chemiluminescence. The following year in 1989 the enzyme responsible for NO production, NO synthase, was discovered and L-arginine:NO pathway was proposed.

Roles of L-arginine:NO pathway

By 1987 it was proposed that NO is generated in tissues other than endothelium. Hibbs et al and Marletta et al proposed that NO was generated by macrophages. Moreover release of EDRF was demonstrated in cerebellar cells following activation with N-methyl-D- aspartate (NMDA ). Both noradrenergic and cholinergic responses are ‘controlled’ by the nitrergic system so that the release of NO (e.g., during electrical field stimulation) counteracts and dominates the response to the noradrenergic or cholinergic stimulus (Cellek & Moncada, 1997). Mechanism of penile erection was unveiled by the studies on nitrergic neurotransmission that led to therapeutic intervention. Selective damage of nitrergic nerves in disease states was proposed as a potent mechanism of pathophysiology. Broadly three areas of research based on three isoforms of NOS came into being;

  • cardiovascular
  • nervous
  • immunology

Identification of NG-monomethyl-L-arginine (L-NMMA) as an inhibitor of the synthesis of NO lay the basis of future research into investigating the role of NO in biological systems. In 1989 it was demonstrated that intravenous infusion of L-NMMA resulted in increase in blood pressure that was reversible by infusing L-arginine. NO was thus implicated in constantly maintaining blood vessel tone. eNOS knockout studies showed a hypertensive phenotypes in the animal models and over expression of eNOS led to lowering of the blood pressure. Furthermore, eNOS activation was attributed to phosphorylation of a specific tyrosine residue in the enzyme.

NO and Mitochondria 

http://pharmaceuticalintelligence.com/2012/09/16/nitric-oxide-has-a-ubiquitous-role-in-the-regulation-of-glycolysis-with-a-concomitant-influence-on-mitochondrial-function/

NO reacts with some of the complexes of the respiratory chain, and inhibits mitochondrial respiration – this is a well accepted notion. Initially it was believed that the target for NO was soluble guanylate cyclase, which in vasculature would lead to elevation of cGMP that eventually results in NO mediated vasodilatation and platelet aggregation inhibition. In 1994, another potential target, cytochrome c oxidase, for inhibitory effects of NO was discovered. This was a reversible effect, in competition with oxygen concentrations. Increases in NO production were also shown to inhibit cellular respiration irreversibly by selectively inhibiting complex I . Hence in 2002 it was proposed that this might be a mechanism through which cell pathology was initiated in certain conditions. Furthermore, NO was proposed to be implicated in the activation of the grp78-dependent stress response , via modulating calcium-related interaction between mitochondria and endoplasmic reticulum . This host defence mechanism might also have role in vasculature. Further evidence was provided in 2003 to link the role of NO in mitochondrogenesis and thus indicating that NO might be involved in the regulation of the balance between glycolysis and oxidative phosphorylation in cells.

NO and Pathophysiology

Lack of NO: By 2000, NO was established as a haemostatic regulator in the vasculature. Its absence was implicated in pathological states such as hypertension and vasospasm. These pathophysiological states share a common beginning of endothelial dysfunction, which has low NO production as one of its characterstic features. This dysfunction has been observed prior to the appearance of cardiovascular disease in predisposed subjects with family history of essential hypertension and atherosclerosis. The most likely mechanism for endothelial dysfunction is that of a reduced bioavailability of NO . The mechanism of this aspect is discussed elsewhere on this site. Protection against reduction of NO bio-availability in the vasculature is a vital therapeutic target and is extensively explored. This can be achieved by the use of antioxidants and/or augmentation of eNOS expression. In 2003 statins were shown to increase the production of endothelial NO in endothelial cell cultures and in animals by the reduction of oxidative stress or by increasing the coupling of the eNOS. It was way back in 1994 that oestrogen was shown to increase both the activity and expression of eNOS. In addition, more recently in 2003, oestrogen was shown to reduce the breakdown of available NO.

Excess of NO: In 2000 it was shown that NO produced from iNOS in vasculature is involved in extensive vasodilatation in septic shock. Later it was demonstrated that inhibition of mitochondrial respiration is an important component of the NO-induced tissue damage. This inhibition of respiration, which is initially NO-dependent and reversible, becomes persistent with time as a result of oxidative stress . Such metabolic hypoxic states where in tissues cannot utilise available oxygen due to NO, could also contribute to other inflammatory and degenerative conditions. An obvious therapeutic target for reducing NO production in such conditions would be L-NMMA. L-NMM was tested in a clinical trial for septic shock in 2004. The results were however disappointing probably due to the blanket reduction in NO production from other NOS enzymes there by having deleterious effects on the treatment group. More specific inhibitors for NOS forms are being investigated for in different disease states.

In conclusion, the L-arginine: NO pathway has had a major impact in many areas of research, specially vascular biology. A lot has been understood about this pathway and its interactions, therapeutic targets are being aggressively investigated, but further investigations are required to delineate further the role of NO in human health and disease.

Further Reading

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1760731/?tool=pubmed

Nitric Oxide and Platelet Aggregation

Inhaled NO in Pulmonary Artery Hypertension and Right Sided Heart Failure

Cardiovascular Disease (CVD) and the Role of agent alternatives in endothelial Nitric Oxide Synthase (eNOS) Activation and Nitric Oxide Production

Nitric Oxide in bone metabolism

Nitric oxide and signalling pathways

Rationale of NO use in hypertension and heart failure

Interaction of Nitric Oxide and Prostacyclin in Vascular Endothelium

Nitric Oxide has a ubiquitous role in the regulation of glycolysis -with a concomitant influence on mitochondrial function

Read Full Post »

Nitric Oxide has a Ubiquitous Role in the Regulation of Glycolysis – with a Concomitant Influence on Mitochondrial Function

 

Reporter, Editor, and Topic Co-Leader: Larry H. Bernstein, MD, FACP, Clinical Pathologist and Biochemist

 

 

Apoptosis signaling pathways

Apoptosis signaling pathways (Photo credit: AJC1)

This discussion is a followup on a series of articles elucidating the importance of NO, eNOS, iNOS, cardiovascular and vascular endothelium effects, and therapeutic targets.

This mechanism of action and signaling actions have been introduced so that we identify endocrine, paracrine, and such effects in the normal, stressed, and dysfunctional state. The size and breadth of this vital adaptive process is now further explored.

The title is short, befitting a subtitle.  The full topic may be considered “Nitric Oxide has a ubiquitous role in the regulation of glycolysis -with a concomitant influence on mitochondrial function that is active in endothelium, platelets, vascular smooth muscle and neural cells and the balance has a role in chronic inflammation, asthma, hypertension, sepsis and cancer”.

Vascular endothelium

Vascular endothelium (Photo credit: Wikipedia)

Related articles

 

 

Nitric Oxide Synthase

Nitric Oxide Synthase (Photo credit: Wikipedia)

 

 

Nitric Oxide has a ubiquitous role in the regulation of glycolysis with a concomitant influence on mitochondrial function that is active in endothelium, platelets, vascular smooth muscle and neural cells and the balance has a role in chronic inflammation, asthma, hypertension, sepsis and cancer.

Uncoupling of aerobic glycolysis
Potential cytotoxic mediators of endothelial cell (EC) apoptosis include increased formation of reactive oxygen and nitrogen species (ROSRNS) during the atherosclerotic process. Nitric oxide (NO) has a biphasic action on oxidative cell killing with low concentrations protecting against cell death, whereas higher concentrations are cytotoxic. High levels of NO can be produced by inducible nitric-oxide synthase in response to cytokine stimulation, primarily from macrophages, and elevated levels of NO is injurious to endothelium.Ccytochrome c release and caspase activation are involved in NO induced apoptosis. ROS also induces mitochondrial DNA damage in ECs, and this damage is accompanied by a decrease in mitochondrial RNA (mtRNA) transcripts, mitochondrial protein synthesis, and cellular ATP levels. Mitochondria have been recognized to play a pivotal role in the signaling cascade of apoptosis leading to atherosclerosis-induced damage in endothelial cells.
The processes involved in the signaling pathways leading to apoptosis are complex but have some degree of convergence between cell types including those in the vasculature. Release of cytochrome c from mitochondria is a proapoptotic signal, which activates several downstream signaling events including formation of the apoptosome and activation of caspases. Ubiquinol cytochrome c reductase (complex III) is a site for ROS formation, and cytochrome c oxidase (complex IV) is a target for the interaction of NO in mitochondria.
The impact of the inhibition of mitochondrial protein synthesis is particularly important in NO-dependent cytotoxicity, and depends also on other factors such as glycolysis. These authors examined whether the inhibition of mitochondrial protein synthesis by chloramphenicol increases the susceptibility of endothelial cells to undergo NO-dependent apoptosis in glucose-free media. Bovine aortic endothelial cells were treated with chloramphenicol, which resulted in a decreased ratio of mitochondrial complex IV to cytochrome c and increased oxidant production in the cell. Inhibition of mitochondrial protein synthesis was associated with a greater susceptibility of the cells to apoptosis induced by NO in glucose-free medium.
Inhibition of mitochondrial protein synthesis results in increased endothelial cell susceptibility to nitric oxide-induced apoptosis. A Ramachandran, DR Moellering, E Ceaser, S Shiva, J Xu, and V Darley-Usmar. PNAS May 14, 2002: 99(10): 6643–6648 http://www.pnas.orgcgidoi10.1073pnas.102019899

Nitric oxide (NO) is a ubiquitous signaling molecule whose physiological roles mediated through the activation of the soluble guanylate cyclase are now clearly recognized. At physiological concentrations, NO also inhibits the mitochondrial enzyme cytochrome c oxidase (complex IV) in competition with oxygen, and recently we have suggested that the interplay between the two gases allows this enzyme to act as an oxygen sensor in cells. In addition, NO plays a variety of patho-physiological roles, some of which also may be the consequence of its action at a mitochondrial level. We have characterized the sequence of events that follow inhibition of complex IV by continuous exposure to NO.
The mitochondrion is a key organelle in the control of cell death. Nitric oxide (NO) inhibits complex IV in the respiratory chain and is reported to possess both proapoptotic and antiapoptotic actions. We investigated the effects of continuous inhibition of respiration by NO on mitochondrial energy status and cell viability. Serum-deprived human T cell leukemia (Jurkat) cells were exposed to NO at a concentration that caused continuous and complete (;85%) inhibition of respiration. Serum deprivation caused progressive loss of mitochondrial membrane potential (Dcm) and apoptotic cell death. In the presence of NO, Dcm was maintained compared to controls, and cells were protected from apoptosis. Similar results were obtained by using staurosporin as the apoptotic stimulus. As exposure of serum-deprived cells to NO progressed (>5 h), however, Dcm fell, correlating with the appearance of early apoptotic features and a decrease in cell viability. Glucose deprivation or iodoacetate treatment of cells in the presence of NO resulted in a collapse of Dcm, demonstrating involvement of glycolytic ATP in its maintenance. Under these conditions cell viability also was decreased. Treatment with oligomycin and or bongkrekic acid indicated that the maintenance of Dcm during exposure to NO is caused by reversal of the ATP synthase and other electrogenic pumps. Thus, blockade of complex IV by NO initiates a protective action in the mitochondrion to maintain Dcm; this results in prevention of apoptosis. It is likely that during cellular stress involving increased generation of NO this compound will trigger a similar sequence of events, depending on its concentration and duration of release. (mitochondrial membrane potential ; apoptosis ; necrosis)

The effect of nitric oxide on cell respiration: A key to understanding its role in cell survival or death. B Beltra, A Mathur, MR Duchen, JD. Erusalimsky, and S Moncada. PNAS Dec 19, 2000; 97(26):4602–14607.

Another study by this group shows that inhibition of respiration by exogenous nitric oxide (NO) in Jurkat cells leads to mitochondrial membrane hyperpolarization dependent on the utilization of glycolytic ATP by the F1Fo-ATPase and other transporters acting in reverse mode. This process also occurs in astrocytes, which are highly glycolytic cells, but not in neurons , which do not invoke glycolysis to maintain ATP concentrations. In addition, this hyperpolarization correlates with protection against apoptotic cell death. Others found an early phase of mitochondrial hyperpolarization after treatment of a variety of cells with different pro-apoptotic stimuli, which precedes the generation of free. At present, no satisfactory explanation has been proposed to explain the mechanism of hyperpolarization, the reasons why free radicals are released from the mitochondrion, or the connection of these phenomena with apoptosis.
The authors surmise that a pro-apoptotic stimulus, anti-Fas Ab, leads to release of endogenous NO from Jurkat cells in sufficient amounts to inhibit cell respiration and cause a hyperpolarization dependent on the reversal of the F1Fo-ATPase. Moreover, the reduction of the mitochondrial electron transport chain, after inhibition of cytochrome oxidase by NO, leads to generation of superoxide anion (O2). They suggest the process is a cellular defense response that may be overcome by pro-apoptotic mechanisms that occur in parallel.

Inhibition of mitochondrial respiration by endogenous nitric oxide: A critical step in Fas signaling. B Beltran, M Quintero, E Garcıa-Zaragoza, E O’Connor, JV. Esplugues, and Salvador Moncada. PNAS June 25, 2002 99(13): 8892–8897. http://www.pnas.orgcgidoi10.1073pnas.092259799

Nitric oxide has been shown to render cells resistant to oxidative stress. Mechanisms proposed for the ability of nitric oxide to protect cells against oxidative stress include reactions of nitric oxide and the induction of adaptive responses that require protein synthesis. Nitric oxide forms iron complexes preventing the formation of strong oxidants. In addition, reactions of nitric oxide with lipid and or organic radicals protect against membrane peroxidation and peroxidative chemistry-induced cell injury. Exposure to low, nonlethal doses of nitric oxide induces adaptive responses that render cells resistant to lethal concentrations of nitric oxide and or peroxides, such as, the induction of hemoxygenase-1 (HO-1) and Mn superoxide dismutase. The up-regulation of HO-1 was accompanied by an increase in ferritin to account for the release of iron from HO-1, indicating a role of both iron heme and nonheme iron for peroxide-mediated cellular injury. Further, nitric oxide, by regulating critical mitochondrial functions such as respiration, membrane potential, and release of cytochrome c, is able to trigger defense mechanisms against cell death induced by pro-apoptotic stimuli.
This study investigates the potential contribution of nitric oxide’s ability to protect cells from oxidative stress, low steady state levels of nitric oxide generated by endothelial nitric oxide synthase (eNOS) and the mechanisms of protection against H2O2. Spontaneously transformed human ECV304 cells, which normally do not express eNOS, were stably transfected with a green fluorescent-tagged eNOS cDNA. The eNOS-transfected cells were found to be resistant to injury and delayed death following a 2-h exposure to H2O2 (50–150 mM). Inhibition of nitric oxide synthesis abolished the protective effect against H2O2 exposure. The ability of nitric oxide to protect cells depended on the presence of respiring mitochondria. ECV3041 eNOS cells with diminished mitochondria respiration are injured to the same extent as non-transfected ECV304 cells, and recovery of mitochondrial respiration restores the ability of nitric oxide to protect against H2O2-induced death. Nitric oxide had a profound effect in cell metabolism, because ECV3041eNOS cells had lower steady state levels of ATP and higher utilization of glucose via the glycolytic pathway than ECV304 cells. However, the protective effect of nitric oxide against H2O2 exposure is not reproduced in ECV304 cells after treatment with azide and oligomycin suggesting that the dynamic regulation of respiration by nitric oxide represent a critical and unrecognized primary line of defense against oxidative stress.

Dynamic regulation of metabolism and respiration by endogenously produced nitric oxide protects against oxidative stress. E Paxinou, M Weisse, Q Chen, JM Souza, et al. PNAS Sept 25, 2001; 98( 20): 11575–11580. http://www.pnas.orgycgiydoiy10.1073ypnas.201293198.

Nitric oxide (NO) mediates a variety of biological effects including relaxation of blood vessels, cytotoxicity of activated macrophages, and formation of cGMP by activation of glutamate receptors of neurons. NO has also been implicated for such pathophysiological conditions as destruction of tumor cells by macrophages, rheumatoid arthritis, and focal brain ischemia. Some of these effects of NO are associated with hypoxic conditions. O2 radicals and ions that result from reactivity of NO are presumed to be involved in NO cytotoxicity. These investigators report that adaptive cellular response controlled by the transcription factor hypoxia-inducible factor 1 (HIF-1) in hypoxia is suppressed by NO. Induction of erythropoietin and glycolytic aldolase A mRNAs in hypoxically cultured Hep3B cells, a human hepatoma cell line, was completely and partially inhibited, respectively, by the addition of sodium nitroprusside (SNP), which spontaneously releases NO. A reporter plasmid carrying four hypoxia-response element sequences connected to the luciferase structural gene was constructed and transfected into Hep3B cells. Inducibly expressed luciferase activity in hypoxia was inhibited by the addition of SNP and two other structurally different NO donors, S-nitroso-Lglutathione and 3-morpholinosydnonimine, giving IC50 values of 7.8, 211, and 490 mM, respectively. Inhibition by SNP was also observed in Neuro 2A and HeLa cells, indicating that the inhibition was not cell-type-specific. The vascular endothelial growth factor promoter activity that is controlled by HIF-1 was also inhibited by SNP (IC50 5 6.6 mM). Induction generated by the addition of cobalt ion (this treatment mimics hypoxia) was also inhibited by SNP (IC50 5 2.5 mM). Increased luciferase activity expressed by cotransfection of effector plasmids for HIF-1a or HIF-1a-like factor in hypoxia was also inhibited by the NO donor. We also showed that the inhibition was performed by blocking an activation step of HIF-1a to a DNA-binding form.
Inhibition of hypoxia-inducible factor 1 activity by nitric oxide donors in hypoxia. K Sogawa, K Numayama-Tsuruta, M Ema, M Abe, et al. Proc. Natl. Acad. Sci. USA (Biochemistry) June 1998; 95:7368–7373. 1998. The National Academy of Sciences 0027-8424.98.957368-6. http:yywww.pnas.org.

The role of nitrogen metabolism in the survival of prolonged periods of waterlogging was investigated in highly flood-tolerant, nodulated Lotus japonicus plants. Alanine production revealed to be a critical hypoxic pathway. Alanine is the only amino acid whose biosynthesis is not inhibited by nitrogen deficiency resulting from RNA interference silencing of nodular leghemoglobin. The metabolic changes that were induced following waterlogging can be best explained by the activation of alanine metabolism in combination with the modular operation of a split tricarboxylic acid pathway. The sum result of this metabolic scenario is the accumulation of alanine and succinate and the production of extra ATP under hypoxia. The importance of alanine metabolism is discussed with respect to its ability to regulate the level of pyruvate, and this and all other changes are discussed in the context of current models concerning the regulation of plant metabolism.
Glycolysis and the Tricarboxylic Acid Cycle Are Linked by Alanine Aminotransferase during Hypoxia Induced by Waterlogging of Lotus japonicus[W][OA]. M Rocha, F Licausi, WL Arau´ jo, A Nunes-Nesi, et al. Plant Physiology Mar 2010; 152: 1501–1513. http://www.plantphysiol.org 2010 Amer Soc Plant Biologists

DNA damage occurs in ischemia, excitotoxicity, inflammation, and other disorders that affect the central nervous system (CNS). Extensive DNA damage triggers cell death and in the mature CNS, this occurs primarily through activation of the poly(ADP-ribose) polymerase-1 (PARP-1) cell death pathway. PARP-1 is an abundant nuclear enzyme that, when activated by DNA damage, consumes nicotinamide adenine dinucleotide (NAD)+ to form poly(ADP-ribose) on acceptor proteins. The PARP-1 activation leads to cell death. We used mouse astrocyte cultures to explore the bioenergetic effects of NAD+ depletion by PARP-1 and the role of NAD+ depletion in this cell death program. PARP-1 activation led to a rapid but incomplete depletion of astrocyte NAD+, a near-complete block in glycolysis, and eventual cell death. Repletion of intracellular NAD restored glycolytic function and prevented cell death. The addition of non-glucose substrates to the medium, pyruvate, glutamate, or glutamine, also prevented astrocyte death after PARP-1 activation.
These findings suggest a sequence of events in which NAD+ depletion is a key event linking DNA damage to metabolic impairment and cell deathm. A similar scenario has been proposed by Zong et al. (2004), based on the finding that cell types that depend on aerobic glycolysis for ATP production exhibit a particularly high sensitivity to DNA damage and PARP-1 activation. In mature brain, glucose is normally the dominant metabolic substrate due to relatively slow transport of other metabolites across the blood– brain barrier. Oncein brain, glucose may be metabolized directly by neurons and glia or may be metabolized to lactate in glia and thelactate subsequently shuttled to neurons for oxidative metabolism (Dringen et al., 1993; Pellerin and Magistretti,1994; Wender et al., 2000; Dienel and Cruz, 2004). In either case, a block in glycolytic flux produced by NAD depletion will block energy metabolism in both neurons and glia in brain. Interestingly, the lactate shuttle hypothesis raises the possibility that activation of PARP-1 selectively in astroglia might also block energy metabolism in neurons.

These studies suggest PARP-1 activation leads to rapid depletion of the cytosolic but not the mitochondrial NAD+ pool. Depletion of the cytosolic NAD+ pool renders the cells unable to utilize glucose as a metabolic substrate. Under conditions where glucose is the only available metabolic substrate, this leads to cell death. This cell death pathway is particularly germane to brain because glucose is normally the only metabolic substrate that is transported rapidly across the blood–brain barrier. © 2004 Wiley-Liss, Inc.
Key words: mitochondria; permeability transition; poly(ADP-ribose) polymerase; ischemia; peroxynitrite
NAD+as a metabolic link between DNA damage and cell death. DNA damage induced by alkylating agents, oxidative stress, or other agents causes PARP-1 activation. PARP-1 activation leads to depletion in cytosolic NAD with, initially, a relative preservation of mitochondrial NAD and mitochondrial function. The depletion in cytosolic NAD+ blocks glycolysis, and in cells in which glucose is the primary energy substrate, this in turn leads to a block in substrate flux to mitochondria. The resulting mitochondrial dysfunction leads to mitochondrial permeability transition (MPT) and subsequent downstream events culminating in cell death.
NAD+ as a Metabolic Link Between DNA Damage and Cell Death. W Ying, CC Alano, P Garnier, and RA Swanson. Journal of Neuroscience Research 2005;79:216–223
Key words: glycolysis, mitochondrial energy production, nitric oxide
Abbreviations: NO, nitric oxide; SNAP, S-nitroso-N-acetylpenicyllamine; SNP, sodium nitroprusside.
The results indicate that: 1) in porcine platelets NO is able to diminish mitochondrial energy production through the inhibition of cytochrome oxidase, 2) the inhibitory effect of NO on platelet secretion (but not aggregation) can be attributed to the reduction of mitochondrial energy production.
Nitric oxide (NO) has been increasingly recognized as an important intra- and intercellular messenger molecule with a physiological role in vascular relaxation, platelet physiology, neurotransmission and immune responses (Moncada et al., 1991; Radomski et al., 1996; Szabó, 1996; Riedel et al., 1999; Titheradge 1999). In vitro NO is a strong inhibitor of platelet adhesion and aggregation (Radomski et al., 1996; Riedel et al., 1999;nSogo et al., 2000). In the blood stream, platelets remain in contact with NO that is permanently released from the endothelial cells and from activated macrophages (Moncada et al., 1991; Riedel et al., 1999; Titheradge 1999). It has been suggested that the activated platelet itself is able to produce NO (Lantoine et al., 1995; Zhou et al., 1995; Radomski et al., 1996). The mechanism responsible for the inhibitory effect of NO on platelet responses is not entirely clear. It is believed that the main intracellular target for NO in platelets is soluble cytosolic guanylate cyclase (Waldman & Walter 1989; Schmidt et al., 1993; Wang et al., 1998). NO activates the enzyme (Schmidt et al., 1993). Thus, elevated intracellular cGMP level inhibits platelet activation. There are suggestions, however, that elevated cGMP may not be the only intracellular factor directly involved in the inhibition of platelet activation (Gordge et al., 1998; Sogo et al., 2000; Beghetti et al., 2003).
Platelets are fairly active metabolically and have a total ATP turnover rate of about 3–8 times that of resting mammalian muscle (Akkerman, 1978; Akkerman et al., 1978; Holmsen, 1981; Niu et al., 1996). Platelets contain mitochondria which enable these cells to produce energy both in the oxidative and anaerobic way (Holmsen, 1981). Under aerobic conditions, ATP is produced by aerobic glycolysis using glucose or glycogen which can account for 30–50% of total ATP production, and by oxidative metabolism using glucose and glycogen (6–11%), amino-acids (7%) or free fatty acids (20–40%) (Holmsen 1981; Guppy et al., 1990; Niu et al., 1996).
The inhibition of mitochondrial respiration by removing oxygen or by respiratory chain blockers (antimycin A, cyanide, rotenone) results in the stimulation of glycolytic flux (Guppy et al., 1990). This phenomenon is known as Pasteur effect and indicates that in platelets glycolysis and mitochondrial respiration are tightly functionally connected (Akkerman, 1978; Holmsen, 1981; Guppy et al., 1995; Niu et al., 1996). It has been reported that the activation of human platelets by high concentration of thrombin is accompanied by an acceleration of lactate production and an increase in oxygen consumption (Akkerman & Holmsen, 1981; Niu et al., 1996).
The results presented here suggest that also porcine blood platelets stimulated by collagen produce more lactate. This indicates that both glycolytic and oxidativeATP production supports platelet responses. This also indicates that blocking of energy production in platelets may decrease their responses. It is well established that platelet responses have different metabolic energy (ATP) requirements increasing in the order: aggregation< dense and alfa granule secretion < acid hydrolase secretion (Holmsen et al., 1982; Verhoeven et al., 1984; Morimoto & Ogihara, 1996).
The present results indicate that exogenously added NO (in the form of NO donors)stimulates glycolysis in intact porcine platelets. Since in platelets glycolysis and mitochondrial respiration are tightly functionally connected, this can be interpreted to mean that the stimulatory effectof NO on glycolysis in intact platelets may be produced by non-functional mitochondria.This can be really the case since NO donors are able to inhibit both mitochondrial respiration and platelet cytochrome oxidase. Interestingly, the concentrations of NO donors inhibiting mitochondrial respiration and cytochrome oxidase were similar to those stimulating glycolysis in intact platelets.
Studies performed on intact J774 cells have shown that mitochondrial complex I is inhibited only after a prolonged (6–18 h) exposure to NO and that this inhibition appears to result from S-nitrosylation of critical thiols in the enzyme complex (Clementi et al., 1998). Further studies are needed to establish whether long term exposure of platelets to NO affects Mitochondrial complexes I and II.
Comparison of the concentrations of SNP and SNAP affecting cytochrome oxidase activityand mitochondrial respiration with those reducing the platelet responses indicates that NO cannot significantly reduce platelet aggregation through the inhibition of oxidative energy production. By contrast, the concentrations of the NO donors inhibiting platelet secretion, mitochondrial respiration and cytochrome oxidase were similar. This and the fact that the platelet release reaction strongly depends on the oxidative energy production may suggest that in porcine platelets NO can affect platelet secretion through the inhibition of mitochondrial energy production at the step of cytochrome oxidase.

Taking into account that platelets may contain NO synthase and are able to produce significant amounts of NO (Berkels et al., 1997)it seems possible that nitric oxide can function in these cells as a physiological regulator of mitochondrial energy production.
Nitric oxide and platelet energy metabolism. M Tomasiak, H Stelmach, T Rusak and J Wysocka. Acta Biochimica Polonica 2004; 51(3):789–803

These authors previously investigated the bioenergetic consequences of activating J774.A1 macrophages (MФ) with interferon (IFN)γ and lipopolysaccharide (LPS) and found that there is a nitric oxide (NO)-dependent mitochondrial impairment and stabilization of hypoxia inducible factor (HIF)-1α, which synergize to activate glycolysis and generate large
quantities of ATP. We now demonstrate, using TMRM fluorescence and time-lapse confocal microscopy, that these cells maintain a high mitochondrial membrane potential (ΔΨm) despite the complete inhibition of respiration. The maintenance of high ΔΨm is due to the utilization of a significant proportion of glycolytically generated ATP as a defence mechanism against cell death. This is achieved by the reverse functioning of FoF1-ATP synthase and adenine nucleotide translocase (ANT). Treatment of activated MФ with inhibitors of either of these enzymes, but not with inhibitors of the respiratory chain complexes I to IV, led to a collapse in ΔΨm and to an immediate increase in intracellular [ATP], due to the prevention of ATP hydrolysis by the FoF1-ATP synthase. This collapse in ΔΨm was followed by translocation of Bax from cytosol to the mitochondria, release of cytochrome c into the cytosol, activation of caspase 3 and 9 and subsequent apoptotic cell death. Our results indicate that during inflammatory activation “glycolytically competent cells” such as MФ utilize significant amounts of the glycolytically-generated ATP to maintain ΔΨm and thereby prevent apoptosis.

Activated macrophages utilize glycolytic ATP to maintain mitochondrial membranepotential and prevent apoptotic cell death. A Garedew, SO Henderson, S Moncada. Cell Death and Differentiation. 2010. DOI : 10.1038/cdd.2010.27
The effects of the sodium nitroprusside (SNP), a nitric oxide (NO) donor clinically used in the treatment of hypertensive emergencies on the energy production of rat reticulocytes were investigated. Rat reticulocyte-rich red blood cell suspensions were aerobically incubated without (control) or in the presence of different concentrations of SNP (0.1, 0.25, 0.5, 1.0 mM). SNP decreased total and coupled, but increased uncoupled oxygen consumption. This was accompanied by the stimulation of glycolysis, as measured by increased glucose consumption and lactate accumulation. Levels of all glycolytic intermediates indicate stimulation of hexokinase-phosphofructo kinase (HK-PFK), glyceraldehyde 3-phosphate dehydrogenase (GAPD) and pyruvate kinase (PK) activities in the presence of SNP. Due to the decrease of coupled oxygen consumption in the presence of SNP, ATP production via oxidative phosphorylation was significantly diminished. Simultaneous increase of glycolytic ATP production was not enough to provide constant ATP production. In addition, SNP significantly decreased ATP level, which was accompanied with increased ADP and AMP levels. However, the level of total adenine nucleotides was significantly lower, which was the consequence of increased catabolism of adenine nucleotides (increased hypoxanthine level). ATP/ADP ratio and adenylate energy charge level were significantly decreased. In conclusion, SNP induced inhibition of oxidative phosphorylation, stimulation of glycolysis, but depletion of total energy production in rat reticulocytes. These alterations were accompanied with instability of energy status.

Effects of Exogenous Donor of Nitric Oxide – Sodium Nitroprusside on Energy Production of Rat Reticulocytes. SD MALETIĆ, L M DRAGIĆEVIĆ-DJOKOVIĆ, BI OGNJANOVIĆ, RV ŽIKIĆ, AŠ ŠTAJN, MB SPASIĆ.
Physiol. Res. 2004;53: 439-447.

Key points to take from this:
1. The role of NO in regulating cellular death is in many organs and central to this function is the stabilization of mitochondria through sufficient levels of NO. High levels of eNO leads to mitochondrial dysfunction that increases the dependence of ATP generated from glycolysis.
2. This is accompanied by inhibition of oxidative phosphorylation and stimulation of glycolysis, which brings the discussion to a different domain – cancer growth and Warburgh Effect.
3. This is accompanied by PPAR activation, cytoplasmic NAD+ depletion, and inhibition of glycolysis (critical in cells dependent on aerobic glycolysis), depletion of total energy production, and apoptosis.
4. Maintenance of high glycolytic generation of ATP is essential for cellular defense, but the oxygen consumption is uncoupled.
5. NO donors inhibiting mitochondrial respiration and cytochrome oxidase are similar to those stimulating glycolysis

More    (pharmaceuticalintelligence.com)

Read Full Post »

Interaction of Nitric Oxide and Prostacyclin in Vascular Endothelium

Author: Larry H. Bernstein, MD

 

This review identifies the complex interactions and underlying regulatory balances/imbalances between the mechanism of vasorelaxation and vasoconstriction of vascular endothelium by way of nitric oxide (NO), prostacyclin, in response to oxidative stress and intimal injury.

A series of related topics have been covered in this Scientific Web Site: http://pharmaceuticalintelligence.com on the Nitric Oxide series:
Nitric oxide: role in Cardiovascular health and disease
The rationale and use of inhaled NO in Pulmonary Artery Hypertension and Right Sided Heart Failure

Imbalance of Autonomic Tone: The Promise of Intravascular Stimulation of Autonomics

Intravascular Stimulation of Autonomics: A Letter from Dr. Michael Scherlag

Will these findings impact the Clopidogrel market?

Positioning a Therapeutic Concept for Endogenous Augmentation of cEPCs — Therapeutic Indications for Macrovascular Disease: Coronary, Cerebrovascular and Peripheral

Cardiovascular Outcomes: Function of circulating Endothelial Progenitor Cells (cEPCs): Exploring Pharmaco-therapy targeted at Endogenous Augmentation of cEPCs

Endothelial Dysfunction, Diminished Availability of cEPCs, Increasing CVD Risk for Macrovascular Disease – Therapeutic Potential of cEPCs

Outcomes in High Cardiovascular Risk Patients: Prasugrel (Effient) vs. Clopidogrel (Plavix); Aliskiren (Tekturna) added to ACE or added to ARB

Vascular Medicine and Biology: CLASSIFICATION OF FAST ACTING THERAPY FOR PATIENTS AT HIGH RISK FOR MACROVASCULAR EVENTS Macrovascular Disease – Therapeutic Potential of cEPCs

Ethical Considerations in Studying Drug Safety — The Institute of Medicine Report

Nitric Oxide Signalling Pathways

Age-Dependent Depression in Circulating Endothelial Progenitor Cells in Coronary Artery Bypass Grafting Patients

Nitric Oxide: The Nobel Prize in Physiology or Medicine 1998 Robert F. Furchgott, Louis J. Ignarro, Ferid Murad

Nitric Oxide and Platelet Aggregation

Obstructive coronary artery disease diagnosed by RNA levels of 23 genes – CardioDx heart disease test wins Medicare coverage

Coronary Artery Disease – Medical Devices Solutions: From First-In-Man Stent Implantation, via Medical Ethical Dilemmas to Drug Eluting Stents

Nitric Oxide: Chemistry and function

Nitric Oxide: a short historic perspective

Human Embryonic-Derived Cardiac Progenitor Cells for Myocardial Repair

Nitric Oxide production in Systemic sclerosis

Cardiovascular Disease (CVD) and the Role of agent alternatives in endothelial Nitric Oxide Synthase (eNOS) Activation and Nitric Oxide Production

Endothelial Differentiation and Morphogenesis of Cardiac Precursors

Bystolic’s generic Nebivolol – positive effect on circulating Endothelial Progenitor Cells endogenous augmentation

Nitric Oxide in bone metabolism

Circulating Endothelial Progenitor Cells Milestones in the research on Circulating Endothelial Progenitor Cells as diagnostic markers of cardiovascular risk have been reported in NEJM

Transcription Factor Lyl-1 Critical in Producing Early T-Cell Progenitors

Macrovascular Disease – Therapeutic Potential of cEPCs: Reduction Methods for CV Risk

Treatment of Refractory Hypertension via Percutaneous Renal Denervation

Triple Antihypertensive Combination Therapy Significantly Lowers Blood Pressure in Hard-to-Treat Patients with Hypertension and Diabetes

Study Finds Low Methylation Regions Prone to Structural Mutation

Atherosclerosis, studied extensively, has common features in the aorta, coronary, carotid and peripheral arteries. There is commonality in morphology of atheromatous plaques, the degree of thrombus formation and types of ensuing ischemic events, therefore, plaque disruption, the degree of thrombus formation and types of ensuing ischemic coronary syndromes of patients have been extensively studied. A concept of unstable atherosclerotic plaques that are amenable to rupture is central to acute myocardial infarction, stroke, aortic aneurysm and sequellae, and peripheral artery disease. These unstable atherosclerotic plaques: plaques with an unstable morphology are essential to the onset of unstable coronary artery disease. Plaque formation results from complex cellular interactions in the intima of arteries, which take place between resident cells of the vessel wall (smooth muscle cells and endothelial cells) and cells of the immune system (leukocytes). Local flow disturbances, extracellular matrix composed of lipids and debris are defining characteristics of the ‘atheroma’.
Inflammation and repair are key events in the natural course of atherosclerosis, and inflammatory cells have profound effects on the integrity of the plaques . Smooth muscle cells produce by far most of the extracellular matrix components of a plaque. Transforming growth factor beta (TGF-β) is one of the most potent stimulators of connective tissue production by smooth muscle cells, and large amounts of this growth factor are detected in restenosis lesions after PTCA.
Atherosclerotic plaque rupture – pathologic basis of plaque stability and instability. AC Newby, P Libby, and AC. van der Wal. Cardiovasc Res 1999; 41 (2): 334-344. doi: 10.1016/S0008-6363(98)00276-4. Vascular endothelium acts as a paracrine/endocrine organ by secreting a wide range of biologically active mediators that play a key role in regulating immune responses, vascular tone and coagulation, and act on adjacent smooth muscle cells, monocytes, macrophages, fibroblasts and organ specific cells.

The key culprits include:

VASODILITATION

  • vasodilators (prostacycline (PGI2),
  • nitric oxide (NO),
  • endothelium-derived relaxing factor (EDRF) ) and
  • cardiac specific natriuretic peptides;

The chemical nature of EDRF was not known until Palmer, Ferrige and Moncada demonstrated that nitric oxide accounted for most if not all of the biological activity of EDRF. Both EDRF and NO act through the stimulation of soluble guanylate cyclase and subsequent formation of cyclic GMP (cGMP). Cyclic GMP activates cGMP-dependent protein kinases and leads to dephosphorylation of myosin light chains and muscle relaxation.

Palmer RM, Ferrige AG, Moncada S. Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor. Nature 1987; 327:524-6.

Waldman SA, Murad F. Cyclic GMP synthesis and function. Pharma Rev 1987; 39:163-96.

Gryglewski RJ, Botting RM, Vane JR. Mediators produced by the endothelial cell. Hypertension 1988; 12:530-48.

VASOCONSTRICTION

  • vasoconstrictors (endothelin-1 (ET), thromboxane A2, prostaglandin H2 and components of renin-angiotensin system);
  • pro- and anti-thrombotic factors (tissue factor, platelet activating factor (PAF), von Willebrand factor (vWf ) );
  • fibrinolytic activators and inhibitors (tissue plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1));
  • arachidonate metabolites (prostanoids)( Prostanoids are cyclic lipid mediators which arise from enzymic cyclooxygenation of linear polyunsaturated fatty acids, e.g. arachidonic acid (20:4 n 6, AA). Biologically active prostanoids deriving from AA include stable prostaglandins (PGs), e.g. PGE(2), PGF(2alpha), PGD(2), PGJ(2) as well as labile prostanoids, i.e. PG endoperoxides (PGG(2), PGH(2)), thromboxane A(2) (TXA(2)) and prostacyclin (PGI(2)). Stable PGs regulate smooth muscle tone and also modulate inflammatory and immune reactions in this context. PG endoperoxides are intermediates in biosynthesis of all prostanoids. Gryglewski RJ. Prostacyclin among prostanoids. Pharmacol Rep. 2008 Jan-Feb;60(1):3-11.
  • leukocyte adhesion molecules (intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, P-selectin);
  • multiple cytokines transforming growth factor, proinflammatory and anti-inflammatory mediators, tumour necrosis factor, chemokines and steroids.
  • HU Rehman. Vascular Endothelium as an Endocrine Organ. Proc R Coll Physicians Edinb 2001; 31:149-154.

Prostanoids are cyclic lipid mediators which arise from enzymic cyclooxygenation of linear polyunsaturated fatty acids (n-6 PUFAs), e.g. arachidonic acid (20:4 n 6, AA). Labile Thromboxane A(2) (TXA(2)) ( half life of 30 s at 37 degrees C), generated by platelets has powerful vasoconstrictor, cytotoxic and thrombogenic properties.

Prostacyclin (PGI(2)) with a half life of 4 min at 37 degrees C  is produced by the vascular wall (predominantly by the endothelium) and is a physiological antagonist of TXA(2), and is a powerful cytoprotective agent that exerts its action through activation of adenylate cyclase. PGI(2) acts in concert with the system consisting of NO synthase (eNOS)/nitric oxide free radical (NO)/guanylate cyclase/cyclic-GMP. Both cyclic nucleotides (c-AMP and c-GMP) act in synergy as two energetic fists which defend the cellular machinery from being destroyed by endogenous or exogenous aggressors.

Recently, a new partner has been recognized in this endogenous defensive squadron, i.e. a system involving heme oxygenase (HO-1) and carbon monoxide (CO). The expanding knowledge on the pharmacological steering of this enzymic triad (PGI(2)-S/eNOS/HO-1) is likely to contribute to the rational therapy of many systemic diseases such as

  • atherosclerosis,
  • diabetes mellitus,
  • arterial hypertension or
  • Alzheimer diseases.

The discovery of prostacyclin broadened our pathophysiological horizon, and by itself opened new therapeutic possibilities.Gryglewski RJ. Prostacyclin among prostanoids. Pharmacol Rep. 2008 Jan-Feb;60(1):3-11.

Circulating and tissue endothelin immunoreactivity correlate with the severity of atherosclerosis. In patients presenting with stable and unstable angina, circulating endothelin concentrations are elevated in the setting of acute myocardial infarction. Plasma endothelin concentrations are also elevated in patients with moderate to severe congestive heart failure and correlate with the severity of the symptoms.

The vasculature of the kidney is about ten times more sensitive than that of other organs to the vasoconstrictor effects of ET-1. Endothelin affects several aspects of renal function, including

  • vasoconstriction,
  • regulation of tubule function,
  • cellular proliferation and
  • matrix production.

Endothelin is also involved in the pathogenesis of glomerulosclerosis.
Komuro I, Kurihara H, Sugiyama T et al. Endothelin stimulates c-fos and c-myc expression and proliferation of vascular smooth muscle cells. FEBS Lett 1988; 238:249-52. Miyauchi T, Yanagisawa M, Tomizawa T et al. Increased plasma concentrations of endothelin-1 and big endothelin-1 in acute myocardial infarction. Lancet 1989; 2(8653):53-4.

Physical or chemical damage to the cell membrane results in the release of prostacyclin. Other stimulators of prostacyclin release are

  • bradykinin,
  • thrombin,
  • serotonin,
  • platelet-derived growth factor (PDGF),
  • interleukin-1 and
  • adenine nucleotides.

Prostacyclin acts in a paracrine manner, on the abluminal side causing relaxation of the underlying smooth muscle and in the lumen, preventing platelets clumping onto the endothelium. Vasodilator and anti-platelet actions of prostacyclin are mediated by an increase in the concentrations of cyclic adenosine monophosphate (AMP) in smooth muscle cells and platelets. Aspirin and similar substances prevent prostacyclin formation, but have little effect on normal blood pressure.

This discussion has outlined how the vascular system establishes a tight regulation over the production of these endothelium derived vasoactive factors. Its loss allows local or generalized modifications of the vascular tone. This dysregulation is involved in the pathogenesis of

  • hypertension,
  • atherosclerosis,
  • diabetes mellitus and
  • other vasospastic disorders.

HU Rehman. Vascular Endothelium as an Endocrine Organ. Proc R Coll Physicians Edinb 2001; 31:149-154.

Epicrisis

This discussiion is at the limit of comprehension in one sitting. There is much investigation into the complex issue involving interacting biological regulatory pthaways that intersect among major disease categories, which makes targeting of therapies better, but also limited in the ability to achieve meaningful success. That is a topic for further discussion.

I can say with confidence that the story here is incomplete. The final effective solution will require that we tie together the legs of a three legged stool.

The first leg is genomic, which has not reaped as much benefit as we would like, but the successes generate epectations of better.

The second stool is in the opposing balance of nucleotides involved with vascular tone, such as GMP and the action of prostacyclins.

The third led is off the ledger, but will be developed in detail. This involves the essential role of sulfur, in H2S and in the methylation process, in the interpretation of homocysteine levels in the circulation, in the action of Acetyl CoA, S-adenosyl methionine, and GSH, which requires a knowledge of palnt and protein sources of sulfur amino acids, and variable soil conditions.

There also needs to be an understanding of commonalites between

  • infection,
  • metabolic syndrome,
  • immune-mediated inflammatory disease,
  • HIV wasting, and
  • cancer cachexia as importantly as their separatory features.

There are a few more resources to finish the discussion of NO and prostacyclin. Atherogenesis leads to decreased bioactivity of NO and this, in turn, can precipitate enhanced cell adhesion, proliferation, vasoconstriction and accelerate the generation of atherosclerotic lesions.

It is possible that some of the detrimental effects of atherosclerosis on the NO pathway result from the generation of secondary oxidants such as peroxynitrite, a product of the reaction of NO with superoxide. The pharmacologic strategies including

  • the stimulation of generation of endogenous NO,
  • NO-replacement therapy and
  • decreasing oxidative stress may be useful for ameliorating the clinical course of atherosclerosis.

MW Radomski, E Salas. Nitric oxide— biological mediator, modulator and factor of injury: its role in the pathogenesis of atherosclerosis.Atherosclerosis 1995; 118: S69–S80. (Supplement) http://dx.doi.org/10.1016/0021-9150(95)90075-6,

  • The interactions between endothelium-derived nitric oxide (NO) and prostacyclin as inhibitors of platelet aggregation were examined.
  • Porcine aortic endothelial cells released NO in quantities sufficient to account for the inhibition of platelet aggregation
  • small amounts of prostacyclin and EDRF which synergistically inhibited platelet aggregation.
  • A reciprocal potentiation of both the anti- and the disaggregating activity was also observed between low concentrations of prostacyclin and authentic NO or EDRF released from endothelial cells.
  • It is likely that interactions between prostacyclin and NO released by the endothelium play a role in the homeostatic regulation of platelet-vessel wall interactions.

MW Radomski, RMJ Palmer & S Moncada. The anti-aggregating properties of vascular endothelium: interactions between prostacyclin and nitric oxide.  Br. J. Pharmac (1987), 92, 639-646.

The activity of guanylate cyclase is altered to a much larger degree than adenylate cyclase, while cyclic nucleotide phosphodiesterase activity remains unchanged. During the early phases of thrombin- and ADP-induced platelet aggregation a marked activation of the guanylate cyclase occurs whereas aggregation induced by arachidonic acid or epinephrine results in a rapid diminution of this activity.
AJ Barbera. Cyclic nucleotides and platelet aggregation effect of aggregating agents on the activity of cyclic nucleotide-metabolizing enzymes. Biochimica et Biophysica Acta (BBA) – General Subjects 1976; 444(2):579–595.
http://dx.doi.org/10.1016/0304-4165(76)90402-5,

  • We examined the effect of endothelin-1 (ET-1) on basal and isoprenaline-enhanced L-type Ca2P current (ICaL) in guinea-pig ventricular myocytes under nystatin-perforated patch configuration.
  • ET-1 at concentrations of 5 nm had little effect on basal ICa,L, but Ica,L was enhanced by isoprenaline (500 nM) and was significantly attenuated by 5 nm ET-1 by more than 50 %. This effect was reversed upon washout. ICaL enhanced by forskolin was also decreased by ET-1.
  • The inhibitory effect of ET-1 against isoprenaline was completely blocked by the ETA receptor antagonist BQ-123 (1 /LM).
  • Although ET-1 has been shown to activate specific protein kinase C (PKC) isoforms, a significant inhibitory effect of ET-1 was maintained in the presence of the PKC inhibitor bisindolylmaleimide (20 nM). The nitric oxide (NO) donor SIN-1 (10 AM) attenuated but failed to prevent the ET- 1 effect.
  • In summary, our results demonstrate that ET-1 has no effects on basal ica,L. However, it exerts a potent inhibitory effect against isoprenaline-enhanced Ica,L. This effect is mediated through ETA receptors coupled to PTX-sensitive G-proteins and occurs in the presence of PKC inhibition and NO generation.

GP Thomas, SM Sims, M Karmazyn. Differential effects of endothelin- 1 on basal and isoprenaline-enhanced Ca2+ current in guinea-pig ventricular myocytes.  Journal of Physiology 1997;503(1):55-65

(L-arginine methyl ester) L-NAME-sensitive component of endothelium-dependent relaxation was investigated in the preconstricted femoral arteries during isometric conditions as a difference between acetylcholine-induced relaxation before and after acute NG-nitro-L-arginine methyl ester pre-treatment (L-NAME, 10-5 mol/l). Acetylcholine induced vasorelaxation of SHR was significantly greater than that in control WKY. There was a significant positive correlation between BP and L-NAME-sensitive component of relaxation of the femoral artery. There si absence of endothelial dysfunction in the femoral artery of adult borderline and spontaneously hypertensive rats and gradual elevation of L-NAME-sensitive component of vasorelaxation with increasing blood pressure.

A Puzserovap, Z Csizmadiova, I Bernatova. Effect of Blood Pressure on L-NAME-sensitive Component of Vasorelaxation in Adult Rats.  Physiol. Res. 2007:56 (Suppl. 2): S77-S84.

This review concerns the role of nitric oxide (NO) in the pathogenesis of different models of experimental hypertension (NO-deficient, genetic, salt-dependent), which are characterized by a wide range of etiology. Although the contribution of NO may vary between different models of hypertension, a unifying characteristic of these models is the presence of oxidative stress that participates in the maintenance of elevated arterial pressure and seems to be a common denominator underlying endothelial dysfunction in various forms of experimental hypertension. Besides the imbalance between the endothelial production of vasorelaxing and vasoconstricting compounds as well as the relative insufficiency of vasodilator systems to compensate augmented vasoconstrictor systems, there were found numerous structural and functional abnormalities in blood vessels and heart of hypertensive animals.

J Torok. Participation of Nitric Oxide in Different Models of Experimental Hypertension. Physiol. Res. 2008; 57: 813-825.

Cardiac NO–sGC-cGMP signaling blunts cardiac stress responses, including pressure overload–induced hypertrophy. The latter itself depresses signaling through this pathway by reducing NO generation and enhancing cGMP hydrolysis. Pressure overload depresses NO/heme-dependent sGC activation in the heart, consistent with enhanced oxidation. The data reveal a novel additional mechanism for reduced NO-coupled sGC activity related to dynamic shifts in membrane microdomain localization, with Cav3-microdomains protecting sGC from heme-oxidation and facilitating NO responsiveness. Translocation of sGC out of this domain favors sGC oxidation and contributes to depressed NO-stimulated sGC activity.

EJ Tsai, Y Liu, N Koitabashi, D Bedja, et al. Pressure-Overload–Induced Subcellular
Relocalization/Oxidation of Soluble Guanylyl Cyclase in the Heart Modulates Enzyme Stimulation. Circ Res. 2012;110:295-303.

From the studies in several laboratories, we suggest the following mechanisms for the possible regulation of guanylate cyclase activity:

  • factors that could alter the apparent cooperative nature of the enzyme,
  • interactions of metal ions with the substrate or enzyme,
  • factors that could overcome inhibition by ATP,
  • mechanisms that could regulate the interconversion of latent and active forms of the enzyme,
  • possible translocation of particulate and soluble forms of the enzyme, and
  • induction or repression of the enzyme.

H Kimura, F Murada. Two forms of guanylate cyclase in mammalian tissues and possible mechanisms for their regulation. Metabolism 1975; 24(3): 439–445.

 

Read Full Post »

Authour/Curator: Aviral Vatsa PhD MBBS

This post is in continuation with posts on basics of NO metabolism and its effect on physiology. Other topics are covered under the following posts.

  1. Nitric Oxide and Platelet Aggregation

  2. Inhaled NO in Pulmonary Artery Hypertension and Right Sided Heart Failure

  3. Cardiovascular Disease (CVD) and the Role of agent alternatives in endothelial Nitric Oxide Synthase (eNOS) Activation and Nitric Oxide Production

  4. Nitric Oxide in bone metabolism

  5. Nitric oxide and signalling pathways

  6. Rationale of NO use in hypertension and heart failure

Nitric oxide plays wide variety of roles in cardiovascular system and acts as a central point for signal transduction pathway in endothelium. NO modulates vascular tone, fibrinolysis, blood pressure and proliferation of vascular smooth muscles. In cardiovascular system disruption of NO pathways or alterations in NO production can result in preponderance to hypertension, hypercholesterolemia, diabetes mellitus, atherosclerosis and thrombosis. The three enzyme isoforms of NO synthase family are responsible for generating NO in different tissues under various circumstances. The endothelial NOS (eNOS) is expressed in endothelial cells, the inducible NOS (iNOS) is expressed in macrophages and neuronal NOS (nNOS) is expressed in certain neurons and skeletal muscle. Although the basic mechanism of action for NO production is the same for all three NOS isoforms, yet deficiencies of each one of them manifest differently or with varying severity in the body e.g. eNOS deficiency might lead to hypertension, more severe form of vascular injury to cerebral ischaemia and more severe form of atherosclerosis induced by hypercholesterolemic diet whereas nNOS deficiency might show less severe form of vascular injury to cerebral ischaemia and absence of iNOS might lead to reduced hypotension in septic shock.

Reduction in NO production is implicated as one of the initial factors in initiating endothelial dysfunction. This reduction could be due to

  • reduction in eNOS production

  • reduction in eNOS enzymatic activity

  • reduced bioavailability of NO

eNOS production is increased by physiological sheer stress on endothelial cells resulting from normal flow of blood along the arterial walls. Alterations in fluid sheer stress patterns e.g due to arterial constriction has been shown to have detrimental effect on eNOS production in endothelial cells. eNOS production is decreased by LDL, angiotensin II and TNF alpha. eNOS is tightly coupled enzyme and its activity can be significantly reduced by reduction in availability of cofactors and substrates, and by competitive inhibitors such as ADMA. Furthermore, uncoupling of eNOS can result in increased production of reactive species of both oxygen (superoxide) and nitrogen (peroxinitrite), which inturn can further reduce eNOS bioavailability. A range of therapeutic targets aim at increasing bioavailability of eNOS and they are summarised here.

Increased production of ROS and peroxinitrite is associated with endothelial dysfunction. Coronary heart disease risk factors may increase NOS mediated ROS formation and peroxinitrite formation. Such risk factors are associated with decreased NO production levels in the vasculature. However, recent data suggests that reduction in bioavailable NO levels in the arteries could be due to increased local oxidative stress rather than reduction in basal NO production.

Oxidation dependent mechanisms have been implicated in endothelial dysfunction. Oxidized low density lipo-proteins (oxLDL) play an important role in early endothelial dysfunction and hence early atherosclerosis (see figure below)

oxLDL can uncouple eNOS and reduced uptake of L-ariginine that can lead to production of superoxide radical oxygen. OxLDL can interfere with NO production and lead to altered NO signalling in the vascular endothelium. In addition, different arteries can be affected differently by these physiological changes e.g. oxLDL affects carotid artery and not the basilar artery thereby implying that intracranial arteries might be protected from endothelium-mediated oxidative injury and hence atherosclerosis. And finally NO can modulate oxidation mediated apoptotic signals in the vessel wall. Hence atherosclerosis can result from the derangement of fine imbalance between NO bioavailability and local oxidative stress.

Therapeutic targets:

There are various pathways being targeted to modulate the bioavailability of eNOS and NO such as

  1. Recoupling of eNOS to cofactors and substrates

  2. Modulation of eNOS activity by genomic and non genomic mechanisms e.g. by statins, ACE inhibitors, angiotensin II receptor blockers, calcium channel blockers , KLF2 modulators

  3. The suppression of inflammatory signalling pathways by PPAR-α activation

  4. Modulation of caeviolin mediated endocytosis and thus dissociation of eNOS from caevolin

The above list is not exhaustive, but this post here summarises recent developments in therapeutic targets in NO /eNOS regulation.

Based on:

Nitric Oxide and Pathogenic Mechanisms Involved in the Development of Vascular Diseases

Claudio Napoli and Louis J. Ignarro

Arch Pharm Res Vol 32, No 8, 1103-1108, 2009 , DOI 10.1007/s12272-009-1801-1 

 

Read Full Post »

Endothelial Dysfunction, Diminished Availability of cEPCs,  Increasing  CVD Risk — Macrovascular Disease – Therapeutic Potential of cEPCs

Author and Investigator Initiated Study: Aviva Lev-Ari, PhD, RN

In normal conditions, the vascular endothelium produces and secretes substances that modulate vascular tone and protect the vessel wall from inflammatory cell infiltration, thrombus formation, and vascular smooth muscle cell proliferation (Rubanyi, 1993). Pathologic conditions such as hyperlipidemia, hyperglycemia, and hypertension impair the ability of the vascular endothelium to produce vasodilatory and anti-adhesion moieties and increase the production of vasoconstrictor, proadhesion, and pro-thrombotic molecules, leading to elevated vascular tone, enhanced cell adhesion, proliferation of media smooth muscle cells, and propensity toward thrombosis (Drexler & Hornig, 1999),(Endemann & Schiffrin, 2004). Endothelial cell loss and turnover are accelerated in the presence of hemodynamic and biochemical alterations and are a prominent feature of vascular injury resulting from percutaneous coronary intervention (Bennett & O’Sullivan, 2001).

The loss of endothelial function and integrity sets in motion the cascade of events that lead to atherosclerosis and restenosis after percutaneous revascularization (Ross, 1999),(Dzau et al., 2002). Processes of mobilization, growth, differentiation, recruitment, homing, replication and migration characterize cEPCs from the initial cell division of stem cells to cell apoptosis. What are the factors influencing cEPC mobilization, growth, differentiation, recruitment, mobilization, homing, replication and migration?

Physiological Factors

Chemokines

SCF-1, G-CSF, GM-CSF

Effect on cEPCs: recruitment, mobilization (Takahashi et al., 1999), (Kong et al., 2004a), (Kocher et al. 2001), (Shi et al., 1998), (Cho et al., 2003),(Orlic et al., 2001),(Bhattacharya et al., 2000), (Shi et al, 2002)

SDF-1

Effect on cEPCs: recruitment, mobilization, homing (Yamaguchi et al., 2003),(Powell et al., 2005),(Askari et al., 2003), (Hiasa et al., 2004),(George et al., 2003),(George et al., 2004),(Massa et al., 2005)

Cytokines / Growth Factors

FGF, VEGF, PIGF

Effect on cEPCs: mobilization, differentiation (Kalka et al., 2000a),(Ashara et al., 1997),(Kalka et al., 2000b)

                                  Angiopoietin, PDGF

Effect on cEPCs: differentiation

Hormones

Erythropoietin

Effect on cEPCs: mobilization, replication (Heeschen et al., 2003), (George, et. al., 2005).

Estrogen

Effect on cEPCs: mobilization (Strehlow et al., 2003), (Imanishi et al., 2005)

Signaling molecules

NO, Akt

Effect on cEPCs: mobilization, differentiation(Aicher et al., 2003).

 

Pharmacological Factors

3-HMC-CoA Inhibitors (statins)

Effect on cEPCs: mobilization, migration, homing (Werner et al., 2003),(Vasa et al., 2001a),(Walter et al., 2002),(Dimmeler et al., 2001),

(Llevadot et al., 2001),(Spyridopoulos et al., 2004)

             PPAR-gamma Agonists

Effect on cEPCs: mobilization, differentiation (Verma & Szmitko, 2006), (Andrew et al., 2004)

Physical Factors

 

            Exercise, hypoxia

Effect on cEPCs: mobilization (Laufs et al., 2003),(Kleinman et al., 2005),(Goon et al., 2006)

Pathological Factors

Coronary artery disease (CAD)

Effect on cEPCs: mobilization, homing (Kalka et al., 2000a),(Vasa et al., 2001b),(Heeschen et al., 2004)

Acute MI

Effect on cEPCs: mobilization, homing (Shintani et al., 2001),(Valgimigli et al., 2004),(Massa et al., 2005)

Peripheral limb ischemia

Effect on cEPCs: mobilization, homing (Takahashi et al., 1999),(Iwaguro et al., 2002),(Asahara et al., 1997),(Kalka et al., 2000b)

Vascular injury and inflammation

Effect on cEPCs: mobilization, homing (Ross, 1999),( Losordo et al., 2003), (Dimmeler & Zeiher, 2004),(Werner et al., 2003),(Verna et al, 2004).

EPC transplantation has been shown to induce new vessel formation in ischemic myocardium and hind limb (Kalka et al., 2000c),(Kawamoto et al, 2001),(Kocher, 2001) and to accelerate re-endothelialization of injured vessels and prosthetic vascular grafts in humans and in various animal models (Kocher, 2001),(Griese et al., 2003) demonstrating their therapeutic potential as a cell-based strategy for rescue and repair of ischemic tissues and injured blood vessels. Furthermore, EPCs are amenable to genetic manipulation, underscoring their usefulness as vectors for local delivery of therapeutic genes (Griese et al., 2003),(Kong et al., 2004b), (Iwaguro, 2002)

   Clinical Frontiers and Therapeutic Applications of cEPCs

  • Angiogenesis
  • Neovascularization of Artherosclerotic Plaque
  • Risk Factors impairing Collateral Development
  • Inhibitory Effects of Hypercholesterolemia
  • Bone Marrow Cells: Supporting cells in vascular growth processes
  • Inverse Relations: cEPCs and Risk of Macrovascular Events
  • New Stenting Technology:

 

  1.    Stents eluting Nitric Oxide (Verma and Marsden, 2005)
  2.    Stents coated with antiboby specific (anti-CD34) to the EPCs antigen cell     (Chadwick, 2006),(Aoki et al., 2005)
  3.    EPC-covered intravascular stents deployed for prevention of stent  thrombosis and restenosis as well as for rapid  formation of normal tissue architecture (Shirota et al., 2003).

 

  1. Table 1:            Alterations in number and function of cEPCs Disease Characterization and Suitability for ElectEagle an Endogenous Augmentation Method for cEPCs number (not for cEPCs function)

Disease Type

(Dzau et al., 2005)

Number

of

 cEPCs

Function

of

cEPCs

References

Disease Suitability for Endogenous Augmentation of cEPCs
Myocardial
     CAD

down

 down

(Kalka et al., 2000a),(Shintani et al., 2001),(Vasa et al., 2000b),(Hill et al., 2003),(Heeschen et al., 2004)

yes

     CHF

down

down

(Valgimigli et al.,2004),(Massa et al., 2005)

yes

     Unstable angina

down

unknown

(George et al., 2004)

yes

     MI

up

down

(Massa et al., 2005)

No

Vascular
     Atherosclerosis

down

down

(Vasa et al., 2001b),(Heeschen, 2004)(Lusis, 2000)

yes

     Acute Vascular injury and inflammation

up

unknown

(Fuujiyama et al.,2003)(Werner et al., 2003),(Walter et al., 2002),(Strehlow et al., 2003),(Shi et al., 1998),(Gill et al., 2001),

(Chu et al., 2003)

No

     PeripheralLimb ischemia

up

unknown

(Takahashi et al.,1999),(Iwaguro et al., 2002),(Asahara et al., 1997),(Asahara et al., 1999),(Kalka et al., 2000b)(Segal at al., 2006)

No

     Transplantarteriopathy

down

unknown

(Simper at al., 2003)

Yes

     In-stentrestenosis

down

unknown

(George et al., 2003)

yes

     Hypertension

unknown

unknown

No

     Hyperlipidemia

down

down

(Rauscher et al., 2003)

yes

Diabetes

down

down

(Loomans et al.,2004),(Tepper et al., 2002)

yes

Renal Failure
     Hemodialysis

down

down

(Choi et al., 2004)

yes

Source: original table created by Lev-Ari, A.

Based on Table 1, above, Lev-Ari, A. concluded that four Cardiovascualr diseases are NOT candidates for cEPCs therapeutic treatment

List of Disease unsuitable for ElectEagle an Endogenous Augmentation Method for  cEPCs includes:

  • Myocardial infarction
  • Acute Vascular injury and inflammation
  • Peripheral Limb ischemia
  • Hypertension

Table 2:           Therapeutic Angiogenesis Effects achieved by Cell-Based Therapy: Donor, Human; Recipient, Autologous;

Diagnosis, Myocardial Infarction

 

Therapeutic

Effect

Measured

Effect

Method of Delivery

Type and

Source of Cells

References

EjectionFruction

Up

(Stamm et al.,2003)

(Assmus et al., 2002),

(Britten et al., 2003),

(Schachinger et al., 2004),

(Wollert et al., 2004)

(Fernandez-Aviles

et al., 2004),

(Kang et al., 2004)

 

Infarct border

(Stamm et al., 2003)

CD133

(Stamm et al., 2003),

 

BM

(Stamm et al., 2003)

(Stamm et al., 2003)

Collateral flow (SPECT)

Up

(Stamm et al., 2003)

Infarct size

Down

(Strauer et al., 2002)

Intracoronary Balloon

Catheter

(Strauer et al., 2002)

BM

(Strauer et al., 2002)

(Strauer et al., 2002)

Wall motion

Up

(Strauer et al., 2002)

Contractility

Up

(Assmus et al., 2002),

(Britten et al., 2003),

(Schachinger et al., 2004),

(Wollert et al., 2004)

Intracoronary Balloon

Catheter

(Assmus et al., 2002),

(Britten et al., 2003),

(Schachinger et al., 2004),

(Wollert et al., 2004)

BM

PB

MNC

(Assmus et al., 2002),

(Britten et al., 2003),

(Schachinger et al., 2004),

(Wollert et al., 2004)

(Assmus et al., 2002),(Britten et al., 2003),(Schachinger et al., 2004),

(Wollert et al., 2004)

Myocardial perfusion

Up

(Assmus et al., 2002),

(Britten et al., 2003),

(Schachinger et al., 2004),

(Wollert et al., 2004)

Remodeling

Down

(Assmus et al., 2002),

(Britten et al., 2003),

(Schachinger et al., 2004),

(Wollert et al., 2004)

LV wall thickness

Up

(Fernandez-Aviles et al., 2004)

Intracoronary w/PCA

(Fernandez-Aviles et al., 2004)

CD34+

CD117+

AC133+

(Fernandez-Aviles et al., 2004)

End-systolic (ESV) volume

Down

(Fernandez-Aviles et al., 2004)

Exercise time

Up

(Kang et al., 2004)

Intracoronary

G-CSF

CD34+

(Kang et al., 2004)

 

Table 3:          

Therapeutic Angiogenesis Effects achieved by Cell-Based Therapy: Donor, Human; Recipient, Autologous;

Diagnosis, Myocardial Ischemia – Unstable Ischemia

 

Therapeutic

Effect

Measured

Effect

Method of Delivery

Type and

Source of Cells

References

Ejection Fruction

Up

(Perin et al., 2003),

(Tse et al., 2003)

Transendocardial with NOGA mapping

MNCs

(Perin et al., 2003),

(Tse et al., 2003)

BM

(Perin et al., 2003),

(Tse et al., 2003)

(Perin et al., 2003),

(Tse et al., 2003)

Anginal episodes

Down

(Perin et al., 2003),

(Tse et al., 2003)

Wall thickening

Up

(Perin et al., 2003),

(Tse et al., 2003)

Wall motion

Up

(Perin et al., 2003),

(Tse et al., 2003)

REFERENCES

Aicher A, Heeschen C, Mildner-Rihm C, Urbich C, Ihling C, Technau- Ihling K, Zeiher AM, Dimmeler S, (2003). Essential role of endothelial nitric oxide synthase for mobilization of stem cell and progenitor cells. Nat Med., 9:1370-1376.

Anderson T. (1999). Assessment of treatment of endothelial dysfunction. J Am Coll of Cardiology, 34: 631- 8.

Andrew C. Li, Binder, CJ, Gutierrez, A, Brown, KK, Plotkin, CR, Pattison, JW, Valledor, AF, Davis, RA, Willson, TM, Witztum, JL, Palinski, W, Glass, CK. (2004). Differential inhibition of macrophage foam-cell formation and atherosclerosis in mice by PPAR-alpha, Beta/delta, and gamma. J. Clin. Invest. 114:1564-1576

http://www.jci.org/articles/view/18730

Aoki, J., Serruys, P.W., van Beusekom, H., Ong, A.T., McFadden, E.P., Sianos, G., et al. (2005). Endothelial progenitor cell capture by stents coated with antibody against CD34: the HEALING-FIM (Healthy Endothelial Accelerated Lining Inhibits Neointimal Growth-First In Man) Registry. J Am Coll Cardiol 45 (10), 1574–1579.

Asahara T, Murohara T, Sullivan A, Silver M, van der Zee R, Li T, Witzenbichler B, Schatterman G, and Isner JM (1997). Isolation of putative progenitor endothelial cells for angiogenesis. Science 275: 964–967.

Asahara T, Masuda H, Takahashi T, Kalka C, Pastore C, Silver M, Kearne M, Magner M, Isner JM. (1999). Bone marrow origin of endothelial progenitor cells responsible for postnatal vasculogenesis in physiological and pathological neovascularization. Circ Res. 85:221–228.

Askari AT, Unzek S, Popovic ZB, Goldman CK, Forudi F, Kiedrowski M, Rovner A, Ellis SG, Thomas JD, DiCorleto PE, Topol EJ, Penn MS.(2003). Effect of stromal cell-derived factor 1 on stem cell homing and tissue regeneration in ischemic cardiomyopathy. Lancet, 362:697–703.

Assmus B, Schachlinger V, Teupe C, Britten M, Lehmann R, Dobert N, Grunwald F, Aicher A, Urbich C, Martin H, Hoelzer D, Dimmeler S, Zeiher AM, (2002). Transplantation of progenitor cells and regeneration enhancement in acute myocardial infarction (TOPCARE-AMI). Circulation, 106:3009 –3017

Bennett MR, O’Sullivan MO (2001). Mechanisms of angioplasty and stent restenosis: implications for design of rational therapy. Pharmacol Ther., 91:149 –166.

Ben-Shoshan, J and George, J. (2006). Endothelial progenitor cells as therapeutic vectors in cardiovascular disorders: from experimental models to human trials  Pharmacology Therapeutics (impact factor: 8.9). 08/2007; 115(1):25-36.

Bhattacharya V, Shi Q, Ishida A, Sauvage LR, Hammond WP, Wu MH.(2000). Administration of granulocyte colony-stimulating factor enhances endothelialization and microvessel formation in small caliber synthetic vascular grafts. J Vasc Surg., 32:116 –123.

Bonetti PO, et al. (2002). Reactive hyperemia peripheral arterial tonometry, a novel non-invasive index of peripheral vascular function, is attenuated in patients with coronary endothelial dysfunction. Circulation, 106:Suppl II:579.

Bonetti PO, et al. (2003). Enhanced external counterpulsation improves endothelial function in patients with symptomatic coronary artery disease. J Am Coll of Cardiology, 41:1761-8.

Britten MB, Abolmaali ND, Assmus B, Lehman R, Honold J, Schmitt J, Vogl TJ, Martin H, Schachinger V, Dimmeler S, Zeiher AM, (2003). Infarct remodeling after intracoronary progenitor cell treatment in patients with acute myocardial infarction (TOPCARE-AMI): mechanistic insights from serial contrast-enhanced magnetic resonance imaging. Circulation, 108:2212–2218.

Bypass Angioplasty Revascularization Investigation in Type 2 Diabetics (BARI 2D) ClinicalTrials.gov Identifier: NCT00006305, 2000-2007

http://www.nejm.org/doi/full/10.1056/NEJMoa0805796

Caplice NM, Bunch TJ, Stalboerger PG, Wang S, Simper D, Miller DV, Russell SJ, Litzow MR, Edwards WD. (2003). Smooth muscle cells in human coronary atherosclerosis can originate from cells administered at marrow transplantation. Proc Natl Acad Sci U S A. 100: 4754–4759.

Chadwick , D.(2006) OrbusNeich’s Genous Bioengineered R-stent . Cath Lab Digest, 14 (1), 20-26

Cho H-J, Kim H-S, Lee M-M, Kim D-H, Yang H-J, Hur J, Hwang K-K, Oh S, Choi Y-J, Chae I-H, Oh, B-H, Choi Y-S, Walsh K, Park Y-B. (2003).  Mobilized endothelial progenitor cells by granulocyte-macrophage colony-stimulating factor accelerate reendothelialization and reduce vascular inflammation after intravascular radiation. Circulation, 108:2918 –2925.

Choi J-H, Kim KL, Huh W, Kim B, Byun J, Suh W, Sung J, Jeon E-S, Oh H-Y, Kim D-K, (2004). Decreased number and impaired angiogenic function of endothelial progenitors in patients with chronic renal failure. Arterioscler Thromb Vasc Biol.,24:1246 –1252.

Cinamon G, Shinder V, Alon R (2001) Shear forces promote lymphocyte migration across vascular endothelium bearing apical chemokines. Nature Immunology, 2:515

Dimmeler S, Aicher A, Vasa M, Mildner-Rihm C, Adler K, Tiemann M, Rutten H, Fichtlscherer S, Martin H, Zeiher AM, (2001). HMG-CoA reductase inhibitors (statins) increase endothelial progenitor cells via the PI3-kinase/Akt pathway. J Clin Invest., 108:391–397.

Dimmeler S and Zeiher AM, (2004). Vascular repair by circulating endothelial progenitor cells: the missing link in atherosclerosis. J Mol Med. 82:671– 677.

Drexler H and Hornig B, (1999). Endothelial dysfunction in human disease. J Mol Cell Cardiol., 31:51– 60.

Dzau VJ, Braun-Dullaeus RC, Sedding DG. (2002). Vascular proliferation and atherosclerosis: new perspectives and therapeutic strategies. Nat Med.,  8:1249 –1256.

Dzau, VJ, Gnecchi, M, Pachori, AS, Morello F, Melo, LG.(2005).Therapeutic Potential of Endothelial Progenitor Cells in Cardiovascular Diseases.Hypertension,246:7-18.

Edelberg JM, Tang L, Hattori K, Lyden D, Rafii. (2002). Young adult bone marrow-derived endothelial precursor cells restore aging-impaired cardiac angiogenic function. Circ Res., 90:e89–e93.

Endemann DH and Schiffrin EL, (2004). Endothelial dysfunction. J Am Soc Nephrol., 15:1983–1992.

Fadini, G, Avogaro A, Agostini C. (2004), Unambiguous Definition of Endothelial Progenitor Cells. Electronic Letter to the Editor of Heart in reference to article by Eizawa, T, Ikeda U, et al. Decreasing in circulating endothelial progenitor cells in patients with stable CAD, Heart, 2004; 90: 685-686,

http://heart.bmjjournals.com/cgi/eletters/90/6/685#310  retrieved on 6/26/2006Link not found 5/1/2013

Fernandez-Aviles F, San Roman JA, Garcıa-Frade J, Fernandez ME, Penarrubia MJ, de la Fuente Luis, Gomez-Bueno M, Cantalapiedra A, Fernandez J, Gutierrez O, Sanchez PL, Hernandez C, Sanz R, Garcıa- Sancho J, Sa´nchez A, (2004). Experimental and clinical regenerative capability of human bone marrow cells after myocardial infarction. Circ Res., 95:742–748.

Folsom, A.R. Chambless, L.E. Ballantyne, C.M. Coresh, J. Heiss, G. Wu, K.K. Boerwinkle, E. Mosley, T.H. Sorlie, P. Diao, G. Sharrett, A.R. (2006). An Assessment of Incremental Coronary Risk Prediction Using C-Reactive Protein and Other Novel Risk Markers – The Atherosclerosis Risk in Communities Study. Arch Intern. Med. 166, 1368-1373.

Fuujiyama S, Amano K, Uehira K, Yoshida N, Nishiwaki Y, Nozawa Y,  Jin D, Takai S, Miyazaki M, Egashira K, Imada T, Iwasaka T, Matsubara H, (2003). Bone marrow monocyte lineage cells adhere on injured endothelium in a monocyte chemoattractant protein-1-dependent manner and accelerate reendothelialization as endothelial progenitor cells. Circ Res., 93:980-989.

George F, Brisson C, Poncelet P, Laurent JC, Massot O, Arnoux D, Ambrosi P, Klein-Soyer C, Cazenave JP, and Sampol J (1992). Rapid isolation of human endothelial cells from whole blood using S-Endo 1 monoclonal antibody coupled to immunomagnetic beads: demonstration of endothelial injury after angioplasty.Thromb Haemost, 67:147–153.

George J, Herz I, Goldstein E, Abashidze S, Deutch V, Finkelstein A, Michowitz Y, Miller H, Keren G.(2003). Number and adhesive properties of circulating endothelial progenitor cells in patients with in-stent restenosis. Arterioscler Thromb Vasc Biol., 23:e57– e60.

George J, Goldstein E, Abashidze S, Deutsch V, Shmilovich H, Finkelstein A, Herz I, Miller H, Keren G., (2004). Circulating endothelial progenitor cells in patients with unstable angina: association with systemic inflammation. Eur Heart J., 25:1003–1008.

George, J., Goldstein, E., Abashidze, S., Wexler, D., Hamed, S., Shmilovich, H., et al. (2005). Erythropoietin promotes endothelial progenitor cell proliferative and adhesive properties in a PI 3-kinase-dependent manner. Cardiovasc Res 68(2), 299-306.

George J, Shmilovich H, Deutsch V, Miller H, Keren G, Roth A. (2006). Comparative Analysis of Methods for Assessment of Circulating Endothelial Progenitor Cells, Tissue Engineering 12 (2) 331-335

Gerhard-Herman M, et al. (2002). Assessment of endothelial function (nitric oxide) at the tip of a finger. Circulation, 106:Suppl II:170.

Gill M, Dias S, Hattori K, Rivera ML, Hicklin D, Witte L, Girardi L, Yurt R, Himel H, Rafii S, (2001). Vascular trauma induces rapid but transient mobilization of VEGFR2/AC133 endothelial precursor cells. Circ Res., 88:167–174.

Goon, P.K.Y. Lip G.Y.H, Boos, CJ, Stonelake, PS, Blann, AD. (2006). Circulating Endothelial Cells, Endothelial Progenitor Cells, and Endothelial Microparticles in Cancer, Neoplasia, 8:79-88.

Griese DP, Ehsan A, Melo LG, Kong D, Zhang L, Mann MJ, Pratt RE, Mulligan RC, Dzau VJ, (2003). Isolation and transplantation of autologous circulating endothelial cells into denuded vessels and prosthetic grafts: implications for cell-based vascular therapy. Circulation, 108: 2710–2715.

Heeschen C, Aicher A, Lehmann R, Fichtlscherer S, Vasa M, Urbich C, Mildner-Rihm C, Martin H, Zeiher AM, Dimmeler, (2003). Erythropoietin is a potent physiological stimulus for endothelial progenitor cell mobilization. Blood, 102:1340 –1346.

Heeschen C, Lehman R, Honold J, Assmus B, Aicher A, Walter DH, Martin H, Zeiher AM, Dimmeler S. (2004). Profoundly reduced neovascularization capacity of bone marrow mononuclear cells derived from patients with chronic ischemic heart disease.Circulation, 109:1615–1622.

Heissig B, Hattori K, Dias S, Friedrich M, Ferris B, Hackett NR, Crystal RG, Besmer P, Lyden D, Moore MA, Werb Z, Rafii S., (2002). Recruitment of stem and progenitor cells from the bone marrow niche requires MMP-9 mediated release of kit-ligand. Cell;109: 625-637.

Hiasa K, Ishibashi M, Ohtani K, Inoue S, Zhao Q, Kitamoto S, Sata M, Ichiki T, Takeshita A, Egashira K. Gene transfer of stromal cell-derived factor 1 enhances ischemic vasculogenesis and angiogenesis via vascular endothelial growth factor/endothelial nitric oxide synthaserelated pathway: next generation chemokine therapy for therapeutic neovascularization. Circulation, 109:2454 –2461.

Hill JM, Zalos G, Halcox JPG, Schenke WH, Waclawin MA, Quyyumi A, Finkel T. (2003). Circulating endothelial progenitor cells, vascular function and cardiovascular risk. N Engl J Med., 348:593– 600.

Hillebrands J-L, Klatter FA, van DijK WD, Rozing J. (2003). Bone marrow does not contribute substantially to endothelial-cell replacement in transplant arteriosclerosis.Nat Med., 8:194 –195.

Hu Y, Davison F, Zhan Z, Xu Q. (2003). Endothelial replacement and angiogenesis in arteriosclerotic lesions of allografts are contributed by circulating progenitor cells.Circulation, 108:3122–3127.

Hur, J., Yoon, C.H., Kim, H.S., Choi, J.H., Kang, H.J., Hwang, K.K., et al. (2004). Characterization of two types of endothelial progenitor cells and their different contributions to neovasculogenesis. Arterioscler Thromb Vasc Biol 24(2), 288–293.

Imanishi, T., Hano, T. & Nishio, I. (2005) Estrogen reduces endothelial progenitor cell senescence through augmentation of telomerase activity. J Hypertens 23(9):1699-1706.

Iwaguro H, Yamaguchi J, Kalka C, Murasawa S, Masuda H, Hayashi S, Silver M, Li T, Isner JM, Asahara T, (2002). Endothelial progenitor cell vascular endothelial growth factor gene transfer for vascular regeneration. Circulation, 105:732–738.

Kalka C, Tehrani H, Laudernberg B, Vale P, Isner JM, Asahara T, Symes JF, (2000a). Mobilization of endothelial progenitor cells following gene therapy with VEGF165 in patients with inoperable coronary disease. Ann Thorac Surg., 70:829–834.

Kalka C, Masuda H, Takahashi T, Gordon R, Tepper O, Gravereaux E, Pieczek A, Iwaguro H, Hayashi S-I, Isner JM, Asahara T (2000b). Vascular endothelial growth factor165 gene transfer augments circulating endothelial progenitor cells in human subjects. Circ Res., 86:1198 –1202.

Kalka C, Masuda H, Takahashi T, Kalka-Moll WM, Silver M, Kearney M, Li T, Isner JM, Asahara T, (2000c). Transplantation of ex vivo expanded endothelial progenitor cells for therapeutic neovascularization. Proc Natl Acad Sci U S A. 97:3422–3427.

Kang H-J, Kim H-S, Zhang S-Y, Park K-W, Cho H-J, Koo B-K, Kim Y-J, Lee DS, Sohn D-W, Han K-S, Oh B-H, Lee M-M, Park Y-B, (2004). Effects of intracoronary infusion of peripheral blood stem cells mobilized with granulocyte-colony stimulating factor on left ventrricular systolic function and restenosis after coronary stenting in myocardial infarction: the MAGIC cell randomized clinical trial. Lancet, 363:751–756.

Kawamoto A, Gwon H-C, Iwaguro H, Yamaguchi J, Uchida S, Masuda H, Silver M, Ma H, Kearney M, Isner JM, Asahara T, (2001). Therapeutic potential of ex vivo expanded endothelial progenitor cells for myocardial ischemia. Circulation, 103:634–637.

Khan SS, Solomon MA, and McCoy JP Jr, (2005). Detection of circulating-  endothelial cells and endothelial progenitor cells by flow cytometry. Cytometry B Clin Cytom64:1–8.

Kiernan, T.(2006). Endothelial progenitor cells in 2006 – Where are we now? http://www.irishheart.ie/iopen24/catalog/pub/Heartwise/2006/Spring/endothelial.pdf retrieved 6/22/2006. Link not found 5/1/2013

Kim, DH, Leu, HB, Ott, HC & Taylor, DO, Bertolini, F, Mancuso, P & Kerbel, RS, Boos, CJ, Goon, PKY, Lip, GYH, (2005). Multiple comments – Correspondence to the Editor on Circulating Endothelial Progenitor Cells. NEJM, 353:24, 2613-2616

Kleinman, ME, Blei, F, Gurtner, GC, (2005). Circulating Endothelial Progenitor Cells and Vascular Anomalies, Lymphatic Research and Biology, 3;4: 234-239.

Kocher AA, Schuster MD, Szabolcs MJ, Burkhoff D, Wang J, Homma S, Edwards NM, Itescu S. (2001). Neovascularization of ischemic myocardium by human bone-marrow-derived angioblasts prevents cardiomyocyte apoptosis, reduces remodeling and improves cardiac function. Nat Med., 7:430–436.

Kong D, Melo LG, Gnecchi M, Zhang L, Mostoslavski G, Liew CC, Pratt RE, Dzau VJ. (2004a). Cytokine-induced mobilization of circulating endothelial progenitor cells enhances repair of injured arteries. Circulation, 110:2039 –2046.

Kong D, Melo LG, Mangi AA, Zhang L, Lopez-Ilasaca M, Perrella MA, Liew CC, Pratt RE, Dzau VJ, (2004b). Enhanced inhibition of neointimal hyperplasia by genetically engineered endothelial progenitor cells. Circulation, 109:1769 –1775.

Kuvin JT, et al. (2003a). Assessment of peripheral vascular endothelial function with finger arterial pulse wave amplitude. Am Heart J, 146:168-74.

Kuvin JT, et al. (2003b). Peripheral arterial tonometry during hyperemia is blunted in patients with coronary artery disease. J Am Coll of Cardiology, 41:Suppl:269A.

Lapidot T, and Petit, I (2002) Current understanding of stem cell mobilization: The roles of chemokines, proteolytic enzymes, adhesion molecules, cytokines, and stromal cells. Experimental Hematology, 30:973–98

Laufs U, Werner N, Link A, Endres M, Wassmann S, Jurgens K, Miche E, Bohm M, and Nickenig G (2004). Physical training increases endothelial progenitor cells, inhibits neointima formation, and enhances angiogenesis. Circulation 109: 220–226.

Llevadot J, Murasawa S, Kureishi Y, Uchida S, Masuda H, Kawamoto A, Walsh K, Isner JM, Asahara T, (2001). HMG-CoA reductase inhibitor mobilizes bone marrow-derived endothelial progenitor cells. J Clin Invest., 108:399–405.

Lloyd-Jones, D. and Tian, L. (2006). Predicting Cardiovascular Risk, So What Do We Do Now?. Arch Intern. Med, 166, 1342-1343.

Loomans CJM, de Koening EJP, Staal FJT, Rookmaaker MB, Verseyden C, de Boer HC, Verhaar MC, Braam B, Rebelink TJ, van Zonneveld A-J. (2004). Endothelial progenitor cell dysfunction. A novel concept in the pathogenesis of vascular complications of type I diabetes. Diabetes, 53:195–199.

Losordo DW, Isner JM, Diaz-Sandoval LJ, (2003). Endothelial Recovery. The next target in restenosis prevention. Circulation, 107:2635–2637.

Lusis, A.J. (2000). Atherosclerosis. Nature 407(6801), 233–241. DIGITAL LINK N/A

Massa M, Rosti V, Ferrario M, Campanelli R, Ramajoli, Rosso R, De Ferrari GM, Ferlini M, Goffredo L, Bertoletti A, Klersy C, Pecci A, Moratti R, Tavazzi, (2005). Increased circulating hematopoietic and endothelial progenitor cells in the early phase of acute myocardial infarction. Blood,105:199 –206.

Orlic D, Kajstura J, Chimenti S, Limana F, Jakoniuk I, Quaini F, Nadal-Ginard B, Bodine DM, Leri A, Anversa P. (2001). Mobilized bone marrow cells repair the infarcted heart, improving function and survival. Proc Natl Acad Sci U S A. 98:10344 –10349.

Peichev M, Naiyer AJ, Pereira D, Zhu Z, Lane WJ, Williams M, Oz MC, Hicklin DJ, Witte L, Moore MA, and Rafii S (2000). Expression of VEGFR-2 and AC133 by circulating human CD34+ cells identifies a population of functional endothelial precursors. Blood 95: 952–958.

Perin EC, Dohmann HFR, Borojevic R, Silva SA, Sousa AL, Mesquita CT, Rossi MI, Carvalho AC, Dutra HS, Dohmann HJ, Silva GV, Belem L, Vivacqua R, Rangel FO, Esporcatte R, Geng YJ, Vaughn WK, Assad JA, Mesquita ET, Willerson JT, (2003). Transendocardial, autologous bone marrow cell transplantation for severe, chronic ischemic heart failure. Circulation, 107:2294 –2302.

Powell TM, Paul JD, Hill JM, Thompson M, Benjamin M, Rodrigo M, McCoy JP, Read EJ, Khuu HM, (2005). Leitman SF, Finkel T, Cannon RO III. Granulocyte colony stimulating factor mobilizes functional endothelial progenitor cells in patients with coronary artery disease. Arterioscler Thromb Vasc Biol., 25:1– 6.

Rafii S, Lyden D (2003). Therapeutic stem and progenitor cell transplantation for organ vascularisation and regeneration. Nat Med 9: 702–712.

Rauscher FM, Goldschmidt-Clermont PJ, Davis BH, Wang T, Gregg D, Ramaswami P, Pippen AM, Annex BH, Dong C, Taylor DA, (2003). Aging, progenitor cell exhaustion, and atherosclerosis. Circulation, 108:457–463.

Ross R. (1999). Atherosclerosis – An inflammatory disease. N Engl J Med., 340:115–126.

Rubanyi GM. (1993). The role of endothelium in cardiovascular homeostasis and diseases. J Cardiovasc Pharmacol., 22(Suppl):S1–S4.

Sata M, Saiura A, Kunisato A, Tojo A, Okada S, Tokuhisa T, Hirai H, Makuuchi M, Hirata Y, Nagai R. (2002). Hematopoietic stem cells differentiate into vascular cells that participate in the pathogenesis of atherosclerosis. Nat Med., 8:403– 409.

Schachinger V, Assmus B, Britten MB, Honold J, Lehman R, Teupe C, Abolmaali ND, Vogt TJ, Hofmann WK, Martin H, Dimmeler S, Zeiher AM, (2004). Transplantation of progenitor cells and regeneration enhancement in acute myocardial infarction: final one-year results of the TOPCARE-AMI trial. J Am Coll Cardiol., 44:1690 –1699.

Schatteman GC, Hanlon HD, Jiao C, Dodds SG, Christy BA. (2000). Blood derived angioblasts accelerate blood flow restoration in diabetic mice. J Clin Invest., 106:571–578.

Scheubel RJ, Zorn H, Rolf-Edgar S, Kuss O, Morawietz, Holtz J, Simm A. (2003). Age-dependent depression in circulating endothelial progenitor cells in patients undergoing coronary artery bypass grafting. J Am Col Cardiol., 42:2073–2080.

Segal, M.S., Shah, R., Afzal, A., Perrault, C.M., Chang, K., Schuler, A., et al. (2006). Nitric oxide cytoskeletal-induced alterations reverse the endothelial progenitor cell migratory defect associated with diabetes. Diabetes 55(1), 102-109

Shi Q, Raffi, Wu MH, Wijelath ES, Yu C, Ishida A, Fujita Y, Kothari S, Mohle R, Sauvage LR, Moore MAS, Storb RF, Hammond WP. (1998). Evidence of circulating bone-marrow derived endothelial cells. Blood, 92:362–367.

Shi Q, Bhattacharya V, Hong-De Wu M, Sauvage LR. (2002). Utilizing granulocyte colony-stimulating factor to enhance vascular graft endothelialization from circulating blood cells. Ann Vasc Surg., 16:314 –320.

Shintani S, Murohara T, Ikeda H, Ueni T, Honma T, Katoh A, Sasaki K, Shimada T, Oike Y, Imaizumi T, (2001). Mobilization of endothelial progenitor cells in patients with acute myocardial infarction. Circulation, 103:2776 –2779.

Shirota, T., Yasui, H., Shimokawa, H. & Matsuda, T. (2003). Fabrication of endothelial progenitor cell (EPC)-seeded intravascular stent devices and in vitro endothelialization on hybrid vascular tissue. Biomaterials 24(13), 2295–2302.

Simper D, Wang S, Deb A, Holmes D, McGregor C, Frantz R, Kushawa SS, Caplice NM, (2003). Endothelial progenitor cells are decreased in blood of cardiac allograft patients with vasculopathy and endothelial cells of non cardiac origin are enriched in transplant atherosclerosis. Circulation, 107:143–149.

Spyridopoulos I, Haendeler J, Urbich C, Brummendorf TH, Oh H, Schneider MD, Zeiher AM, Dimmeler S, (2004). Statins enhance migratory capacity by upregulation of the telomere repeat-binding factor TRF2 in endothelial progenitor cells. Circulation, 110:3136 –3142.

Stamm C, Westphal B, Kleine H-D, Petzsch M, Kittner C, Klinge H, Schumichen C, Nienaber CA, Freund M, Steinhoff G, (2003). Autologous bonemarrow transplantation for myocardial regeneration. Lancet, 361:45–46.

Strauer BE, Brehm M, Zeus T, Kostering M, Hernandez A, Sorg RV, Kogler G, Wernet P, (2002). Repair of infarcted myocardium by autologous intracoronary mononuclear bone marrow cell transplantation in humans. Circulation, 106:1913–1918.

Strehlow K, Werner N, Berweiler J, Link A, Dirnagl U, Priller J, Laufs K, Ghaeni L, Milosevic M, Bohm M, Nickenig G, (2003). Estrogen increases bone-marrow derived endothelial progenitor cell production and diminishes neointima formation.Circulation, 107:3059 –3065.

Takahashi T, Kalka C, Masuda H, Chen D, Silver M, Kearney M, Magner M, Isner JM, Asahara T, (1999). Ischemia- and cytokine-induced mobilization of bone-marrow-derived endothelial progenitor cells for neovascularization. Nat Med., 5:434–438.

Tepper OM, Galiano RD, Capla JM, Kalka C, Gagne PJ, Jacobwotiz GR, Levine JP, Gurtner GC. (2002). Human endothelial progenitor cells from type II diabetes exhibit impaired proliferation, adhesion, and incorporation into vascular structures.Circulation, 106:2781–2786.

Tse HF, Kwong YL, Chan JK, Lo G, Ho CL, and Lau CP (2003). Angiogenesis in ischaemic myocardium by intramyocardial autologous bone genesis marrow mononuclear cell implantation. Lancet 361: 47–49.

Tung, R, Kaul, S, Diamond, GA, Shah, PK (2006). Drug-Eluting Stents for the Management of Restenosis: A Critical Appraisal of the Evidence. Annals of Internal Medicine, 144;12: 913-919.

Valenzuela-Fernandez A, Planchenault T, Baleux F, et al. (2002) Leukocyte elastase negatively regulates stromal cell-derived factor-1 (SDF)/CXCR4 binding and functions by amino-terminal processing of SDF-1 and CXCR4.  J Biol Chem 277:156

Valgimigli M, Rigolin GM, Fucili A, Della Porta M, Soukhomovskaia O, Malagutti P, Bugli AM, Bragottu LZ, Francolini G, Mauro E, Castoldi G, Ferrari R, (2004). CD34 and endothelial progenitor cells in patients with various degrees of congestive heart failure. Circulation, 110:1209–1212.

Vasa M, Fichtlscherer S, Adler K, Aicher A, Martin H, Zeiher AM, Dimmeler S. (2001a). Increase in circulating endothelial progenitor cells by statin therapy in patients with stable coronary artery disease. Circulation, 103:2885–2890.

Vasa M, Fichtlscherer S, Aicher A, Adler K, Urbich C, Martin H, Zeiher AM, Dimmeler S. (2001b). Number and migratory activity of circulating endothelial progenitor cells inversely correlates with risk factors for coronary artery disease. Circ Res., 89:e1– e7.

Vasan, RS, (2006). Biomarkers of Cardiovascular Disease: Molecular Basis and Practical Considerations, Circulation, 113:2335-2362.

Verma S, Kukiszewski MA, Li S-H, Szmitko PE, Zucco L, Wang C-H, Badiwala MV, Mickle DAG, Weisel RD, Fedak PWM, Stewart DJ, Kutrik MJB, (2004). C-reactive protein attenuates endothelial progenitor cell survival, differentiation, and function.Circulation, 109:r91–r100.

Verma, S. and Marsden, P.A. (2005). Nitric Oxide-Eluting Polyurethanes – Vascular Grafts of the Future? New England Journal Medicine, 353 (7), 730-731.

Verma S, Szmitko, PE, (2006). The vascular biology of peroxisome proliferator-activated receptors: Modulation of atherosclerosis. Can J Cardiol, 22 (Suppl B):12B-17B.

Walter DH, Rittig K, Bahlmann FH, Kirchmair R, Silver M, Murayama T, Nishimura H, Losordo DW, Asahara T, Isner JM, (2002). Statin therapy accelerates reendothelialization: a novel effect involving mobilization and incorporation of bone marrow-derived endothelial progenitor cells. Circulation, 105:3017–3024.

Werner N, Junk S, Laufs L, Link A, Walenta K, Bohm M, Nickenig G., (2003).  Intravenous transfusion of endothelial progenitor cells reduces neointima formation after vascular injury. Circ Res., 93:e17– e24.

Werner N, Kosiol S, Schiegl T, Ahlers P, Walenta K, Link A, Böhm M, Nickenig G. (2005a). Circulating Endothelial Progenitor Cells and Cardiovascular Outcomes,NEJM, 353: 999-1007

Werner, N & Nickenig, G. (2005b). Authors Reply to Correspondence to the Editor on Circulating Endothelial Progenitor Cells. NEJM, 353:24, 2613-2616

Widlansky ME, et al. (2003). The clinical implications of endothelial dysfunction. J Am Coll of Cardiology, 42:1149-60.

Wollert KC, Meyer GP, Latz J, Ringes-Lichtenberg S, Lippolt P, Breindenbach C, Fichtner S, Korte T, Hornig B, Messinger D, Arseniev L, Hartenstein B, Ganser A, Drexler H (2004). Intracoronary autologous bonemarrow cell transfer after myocardial infarction: the BOOST randomised controlled clinical trial. Lancet, 364:141–148.

Yamaguchi J, Kusano KF, Masuo O, Kawamoto A, Silver M, Murasawa S, Bosch-Marce M, Masuda H, Losordo DW, Isner JM, Asahara T. (2003).  Stromal cell-derived factor-1 effects on ex vivo expanded endothelial progenitor cell recruitment for ischemic neovascularization. Circulation, 107:1322–1328.

Yoon YS, Park JS, Tkebuchava T, Luedeman C, Losordo DW. (2004). Unexpected severe calcification after transplantation of bone marrow cells in acute myocardial infarction. Circulation, 109:3154 –3157.

 

 

Read Full Post »

Curator/ Author: Aviral Vatsa, PhD, MBBS

In continuation with the previous posts that dealt with short history and chemistry of nitric oxide (NO), here I will try to highlight the pathways involved in NO chemical signalling.

NO is a very small molecule, with a short half life (<5 sec). It diffuses rapidly to its surroundings and is metabolised to nitrites and nitrates. It can travel short distances, a few micrometers, before it is oxidised. Although it was previously believed that NO can only exert its effect for a very short time as other nitrogen oxides were believed to be biologically inert. Recent data suggests that other NO containing compounds such as S- or N-nitrosoproteins and iron-nitrosyl complexes can be reduced back to produce NO. These NO containing compounds can serve as storage and can reach distant tissues via blood circulation, remote from their place of origin. Hence NO can have both paracrine and ‘endocrine’ effects.

Intracellularly the oxidants present in the cytosol determine the amount of bioacitivity that NO performs. NO can travel roughly 100 microns from NOS enzymes where it is produced. NOS enzymes on the other hand are localised to specific sub-cellular areas, which have relevant proteins in the vicinity as targets for signalling.

NO signalling occurs primarily via three mechanisms (according to Martínez-Ruiz et al):

  1. Classical: This occurs via soluble guanylyl cyclase (sGC). Once NO is produced by NOS it diffuses to sGC intracellularly or even in other cells. SGC is highly sensitive for NO, even nanomolar amounts of NO activates sGC, thus making it a potent target for NO in signalling pathways. sGC in turn increases the conversion of GTP to cGMP. cGMP further mediates the regulation of contractile proteins and gene expression pathways via cGMP-activated protein kinases (PKGs). cGMPs cause confirmational changes in PKGs. Signalling by cGMP is terminated by the action of phosphodiestrases (PDEs). PDEs have become major therapeutic targets in the upcoming exciting research projects.
  2. Less classical: Within the mitochondria NO can compete with O2 and inhibit cytochrome c oxidase (CcO) enzyme. This is a reversible inhibition that depends on O2and NO concentrations and can occur at physiological levels of NO. Various studies have demonstrated that endogenously generated NO can inhibit respiration or that NOS inhibitors can increase respiration at cellular, tissue or whole animal level. Although the exact mechanism of CcO inhibition of NO is still debated, NO-CcO interaction is considered important signalling step in a variety of functions such as inhibition of mitochondrial oxidative phosphorylation, apoptosis and reactive oxygen species (ROS) generation. Interestingly, at higher concentration (~1nM) NO can cause irreversible inhibition of cellular oxidation by reversible and/or irreversible damage to the mitochondrial iron–sulfur centers,In addition to the above mentioned pathways, NO (along with AMP, ROS and O2), can also activate AMP- activated protein kinase (AMPK), an enzyme that plays a central role in regulating intracellular energy metabolism. NO can also regulate hypoxia inducible factor (HIF), an O2-dependent transcription factor that plays a key role in cell adaptation to hypoxia .
  3. Non- classical: S-nitrosylation or S-nitrosation is the covalent insertion of NO into thiol groups such as of cysteine residues of proteins. It is precise, reversible, and spatiotemporally restricted post translational modification. This chemical activity is dependent upon the reactivity between nitrosylating agent (a small molecule) and the target (protein residue). It might appear that this generic interaction results in non-specific, wide spread chemical activity with various proteins. However, three factors might determine the regulation of specificity of s-nitrosylation for signalling purposes:
  • Subcellular compartmentalisation: high concentrations of nitrosylating agents are required in the vicinity of target residues, thus making it a specific activity.
  • Site specificity: certain cysteine residues are more reactive in specific protein microenvironments than others, thus favouring their modification. As a result under physiological conditions only a specific number of cysteine residues would be modified, but under higher NO levels even the slow reacting ones would be modified. Increased impetus in research in this area to determine protein specificity to s-nitrosylation provides huge potential in discovering new therapeutic targets.
  • Denitrosylation: different rates of denitrosylation result in s-nitrosylation specificity.

Other modifications in non classical NO mechanisms include S-glutathionylation and tyrosine nitration

Peroxynitrite: It is one of the important reactive nitrogen species that has immense biological relevance. NO reacts with superoxide to form peroxynitrite. Production of peroxynitrite depletes the bioactivty of NO in physiological systems. Peroxynitrite can diffuse through membranes and react with cellular components such as mitochondrial proteins, DNA, lipids, thiols, and amino acid residues. Peroxynitrite can modify proteins such as haemoglobin, myoglobin and cytochrome c. it can alter calcium homeostasis and promote mitochondrial signalling of cell death. However, NO itself in low concentrations have protective action on mitochondrial signalling of cell death.

More details about various aspects of NO signalling can be obtained from the following references.

The post is based on the following Sources:

  1. http://www.sciencedirect.com/science/article/pii/S089158491100236Xhttp://dx.doi.org/10.1016/j.freeradbiomed.2011.04.010
  2. http://content.karger.com/produktedb/produkte.asp?doi=338150Cardiology 2012;122:55-68 (DOI: 10.1159/000338150)
  3. http://content.onlinejacc.org/article.aspx?articleid=1137266 J Am Coll Cardiol. 2006;47(3):580-581. doi:10.1016/j.jacc.2005.11.016
  4. http://goo.gl/y6oY3

 

In addition, other aspects of NO involvement in biological systems in humans are covered in the following posts on this site:

  1. Nitric Oxide and Platelet Aggregation
  2. Inhaled NO in Pulmonary Artery Hypertension and Right Sided Heart Failure
  3. Cardiovascular Disease (CVD) and the Role of agent alternatives in endothelial Nitric Oxide Synthase (eNOS) Activation and Nitric Oxide Production
  4. Nitric Oxide in bone metabolism

Read Full Post »

 

Author: Larry Bernstein, MD

 

Creagh-BrownBC, Griffiths MJD, Evans TW. “Bench-to-bedside review: Inhaled nitric oxide therapy in adults”. Crit Care.  2009;  13(3): 221. Published online 2009 May 29. doi:  10.1186/cc7734. PMCID: PMC2717403.

This article is modified from a review series on Gaseous mediators, edited by Peter Radermacher.  Other articles in the series can be found online athttp://ccforum.com/series/gaseous_mediators

 

Part I.   Basic and downstream effects of inhaled NO

Inhaled nitric oxide (NO), a mediator of vascular tone produces pulmonary vasodilatation with low pulmonary vascular resistance. The route of administration delivers NO selectively improving oxygenation. Developments in our understanding of the cellular and molecular actions of NO may help to explain the results of randomised controlled trials of inhaled NO.

Introduction

Nitric oxide (NO), a determinant of local blood flow is formed by the action of NO synthase (NOS) on L-arginine in the presence of molecular oxygen. Inhaled NO results in preferential pulmonary vasodilatation it lowers pulmonary vascular resistance (PVR), correcting hypoxic pulmonary vasoconstriction (HPV). However, in the therapeutic use of gaseous NO to patients with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), and related conditions, evidence of a benefit is disappointing.

Administration of inhaled nitric oxide to adults

The licensed indication of inhaled NO is restricted to persistent pulmonary hypertension in neonates. Pharma-ceutical NO is costly, and raises concerns over potential adverse effects of NO. Therefore, an advisory board under the auspices of the European Society of Intensive Care Medicine and the European Association of Cardiothoracic Anaesthesiologists published recommendations in 2005 [1]. The sponsor had no authorship or editorial control over the content of the meetings or any subsequent publication.

The NO is administered as a NO/nitrogen mixture to the tubing of ventilated patients, and the NO and NO2 concen-trations are monitored, with methemoglobin levels measured regularly. Even though rapid withdrawal induces rebound pulmonary hypertension, it is avoided by gradual withdrawal [2]. There is variation in vasodilatory response to administered NO between patients [2] and in the same patient, and there is a leftward shift in the dose-response curve with use. Toxicity and loss of the therapeutic effect is a risk of excessive NO administration [3]. A survey of 54 intensive care units in the UK as well as results of a European survey revealed that the most common usage was in treating ARDS, followed by pulmonary hypertension [4], [5]. The only use of therapeutic inhaled NO usage in US adult patients reported from a single medical site (2000 to 2003) reveals that the most common application was in the treatment of RVF in patients after cardiac surgery and then, in surgical and medical patients for refractory hypoxemia[6].

Inhaled nitric oxide in acute lung injury and acute respiratory distress syndrome

ALI and ARDS are characterised by hypoxemia despite high inspired oxygen (PaO2/FiO2  [arterial partial pressure of oxygen/fraction of inspired oxygen] ratios of less than 300 mm Hg [40 kPa] and less than 200 mm Hg [27 kPa], respectively) in the context of evidence of pulmonary edema, and the absence of left atrial hypertension suggestive of a cardiogenic mechanism [7]. Pathologically, there is alveolar inflammation and injury leading to increased pulmonary capillary permeability and a serous alveolar fluid with inflammatory infiltrate. This is manifest clinically as hypoxemia, inadequate alveolar perfusion, venous-arterial shunting, atelectasis, and reduced compliance.

Since 1993, when the first investigation on the effects of NO on adult patients with ARDS was published [8], there have been several randomised controlled trials (RCTs) examining the effect in ALI/ARDS  ​(Table 1). The first systematic review and meta-analysis [9] found no beneficial effect on mortality or ventilator-free days. A more recent meta-analysis that considered 12 RCTs with a total of 1,237 patients [10] concluded: [1] no mortality benefit, [2] improved oxygenation at 24 hours (13% improvement in PaO2/FiO2 ratio) at the cost of increased risk of renal dysfunction (relative risk 1.50, 95% confidence interval 1.11 to 2.02). Based on a trend to increased mortality in patients receiving NO, the authors suggested that it not be used in ALI/ARDS.  Why the NO fails to improve patient outcomes requires clarifying the effects of inhaled NO that occur outside the pulmonary vasculature.

From:

Published online 2009 May 29. doi: 10.1186/cc7734

Table 1

Studies of inhaled nitric oxide in adult patients with acute lung injury/acute respiratory distress syndrome

The biological action of inhaled nitric oxide

NO was first identified as an endothelium-derived growth factor (EDGF) and an important determinant of local blood flow [11]. NO reacts very rapidly with free radicals, certain amino acids, and transition metal ions. The action of NOS on the semi-essential amino acid L-arginine in the presence of molecular oxygen and its identity with EDGF was the basis for the Nobel discovery of Furthgott and others [12]. Three isoforms of NO are: neuronal NOS, inducible NOS (iNOS or NOS2), and endothelial NOS (eNOS or NOS3). Calcium-independent iNOS generates higher concentrations of NO [13] than the other isoforms and its role has been implicated in the pathogenesis septic shock.

Exogenous NO is administered by controlled inhalation or through intravenous administration of NO donors. It was thought to have no remote or non-pulmonary effects. The effect NO has on circulating targets is shown. (Figure 1).

From:

Published online 2009 May 29. doi: 10.1186/cc7734

Figure 1

New paradigm of inhaled nitric oxide (NO) action. Figure 1 illustrates the interactions between inhaled NO and the contents of the pulmonary capillaries. Although NO was considered to be inactivated by hemoglobin (Hb), proteins including Hb and albumin contain reduced sulphur (thiol) groups that react reversibly with NO causing it to lose its vasodilating properties. A stable derivate, in the presence of oxyhemoglobin, is formed by a reaction resulting in nitrosylation of a cysteine residue of the β subunit of Hb.  The binding of NO to the heme iron predominates in the deoxygenated state [14]. If circulating erythrocytes store and release NO peripherally in areas of low oxygen tension, this augments peripheral blood flow and oxygen delivery via decreased systemic vascular resistance [15]. Thus, NO can act as an autocrine or paracrine mediator but when stabilised may exert endocrine influences [16]. In addition to de novo synthesis, supposedly inert anions nitrate (NO3–) and nitrite (NO2–) can be recycled to form NO, and nitrite might mediate extra-pulmonary effects of inhaled NO [17]. In the hypoxic state, NOS cannot produce NO and deoxy-hemoglobin catalyses NO release from nitrite, potentially providing a hypoxia-specific vasodilatory effect. Given that effects of inhaled NO are mediated in part by S-nitrolysation of circulating proteins, therapies aiming at directly increasing S-nitrosothiols have been developed.

Introduce another effect. When inhaled with high concentrations of oxygen, gaseous NO slowly forms the toxic product NO2, but other potential reactions include nitration (addition of NO2+), nitrosation (addition of NO+), or nitrosylation (addition of NO), and reaction with reactive oxygen species such as superoxide to form reactive nitrogen species (RNS) such as peroxynitrite (ONOO–). These reactions of NO, potentially cytotoxic NO2 , and covalent nitration of tyrosine in proteins by RNS lead to measures of oxidative stress.

In a small observational study, inhaled ethyl nitrite safely reduced PVR without systemic side effects in persistent pulmonary hypertension of the newborn [18]. In animal models, pulmonary vasodilatation was maximal in hypoxia and had prolonged duration of action after cessation of administration [19].

References

  1. Germann P, Braschi A, Della Rocca G, Dinh-Xuan AT, et al. Inhaled nitric oxide therapy in adults: European expert recommendations.  Intensive Care Med. 2005;31:1029–1041. [PubMed]
  2. Griffiths MJ, Evans TW. Inhaled nitric oxide therapy in adults. N Engl J Med. 2005;353:2683–2695. [PubMed]
  3. Gerlach H, Keh D, Semmerow A, Busch T, et al. Dose-response characteristics during long-term inhalation of nitric oxide in patients with severe acute respiratory distress syndrome: a prospective, randomized, controlled study. Am J Respir Crit Care Med. 2003;167:1008–1015. [PubMed]
  4. Cuthbertson BH, Stott S, Webster NR. Use of inhaled nitric oxide in British intensive therapy units. Br J Anaesth. 1997;78:696–700.[PubMed]
  5. Beloucif S. A European survey of the use of inhaled nitric oxide in the ICU. Working Group on Inhaled NO in the ICU of the European Society of Intensive Care Medicine. Intensive Care Med. 1998;24:864–877.[PubMed]
  6. George I, Xydas S, Topkara VK, Ferdinando C, et al. Clinical indication for use and outcomes after inhaled nitric oxide therapy. Ann Thorac Surg. 2006;82:2161–2169. [PubMed]
  7. Bernard GR, Artigas A, Brigham KL, Carlet J,et al. The American-European Consensus Conference on ARDS. Definitions, mechanisms, relevant outcomes, and clinical trial coordination. Am J Respir Crit Care Med. 1994;149:818–824. [PubMed]
  8. Rossaint R, Falke KJ, López F, Slama K, Pison U, Zapol WM. Inhaled nitric oxide for the adult respiratory distress syndrome. N Engl J Med.1993;328:399–405. [PubMed]
  9. Sokol J, Jacobs SE, Bohn D. Inhaled nitric oxide for acute hypoxic respiratory failure in children and adults: a meta-analysis. Anesth Analg. 2003;97:989–998. [PubMed]
  10. Adhikari NK, Burns KE, Friedrich JO, Granton JT, Cook DJ, Meade MO. Effect of nitric oxide on oxygenation and mortality in acute lung injury: systematic review and meta-analysis.  BMJ. 2007;334:779.[PMC free article] [PubMed]
  11. Palmer RM, Ferrige AG, Moncada S. Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor.  Nature. 1987;327:524–526. [PubMed]
  12. Nitric Oxide: The Nobel Prize in Physiology or Medicine 1998 Robert F. Furchgott, Louis J. Ignarro, Ferid Murad. Leaders in Pharmacutical Intelligence.  A blog specializing in Pharmaceutical Intelligence and Analytics
  13. McCarthy HO, Coulter JA, Robson T, Hirst DG. Gene therapy via inducible nitric oxide synthase: a tool for the treatment of a diverse range of pathological conditions. J Pharm Pharmacol. 2008;60:999–1017. [PubMed]
  14. Coggins MP, Bloch KD. Nitric oxide in the pulmonary vasculature.   Arterioscler Thromb Vasc Biol. 2007;27:1877–1885. [PubMed]
  15. McMahon TJ, Doctor A. Extrapulmonary effects of inhaled nitric oxide: role of reversible S-nitrosylation of erythrocytic hemoglobin. Proc Am Thorac Soc. 2006;3:153–160. [PMC free article] [PubMed]
  16. Cokic VP, Schechter AN. Effects of nitric oxide on red blood cell development and phenotype. Curr Top Dev Biol. 2008;82:169–215. [PubMed]
  17. Lundberg JO, Weitzberg E, Gladwin MT. The nitrate-nitrite-nitric oxide pathway in physiology and therapeutics. Nat Rev Drug Discov 2008; 7:156–167. [PubMed]
  18. Moya MP, Gow AJ, Califf RM, Goldberg RN, Stamler JS. Inhaled ethyl nitrite gas for persistent pulmonary hypertension of the newborn. Lancet  2002; 360:141–143. [PubMed]

Creagh-BrownBC, Griffiths MJD, Evans TW. “Bench-to-bedside review: Inhaled nitric oxide therapy in adults”. Crit Care.  2009;  13(3): 221. Published online 2009 May 29. doi:  10.1186/cc7734. PMCID: PMC2717403.

This article is modified from a review series on Gaseous mediators, edited by Peter Radermacher.

Other articles in the series can be found online athttp://ccforum.com/series/gaseous_mediators

Part II. Application of inhaled NO and circulatory effects

Cardiovascular effects

NO activates soluble guanylyl cyclase by binding to its heme group to form cyclic guanosine 3’5′-monophosphate (cGMP)   activating a protein kinase. Consequently, myosin sensitivity to calcium-induced contraction is reduced lowering the intracellular calcium concentration as a result of activating calcium-sensitive potassium channels and inhibiting release of calcium. The smooth muscle cell (SMC) relaxation with decrease in pulmonary vascular resistance (PVR) and decreased RV after load could improve cardiac output. However, left ventricular impairment associated with decrease in PVR allows increased RV output to a greater extent than the left ventricle can accommodate and the increase in left atrial pressure reinforces pulmonary edema.

Inhaled NO augments the normal physiological mechanism of hypoxic pulmonary ventilation (HPV) and improves systemic oxygenation ​(Figure 2). The effects of inhaled NO on systemic oxygenation are limited. Experiments show that intravenously administered vasodilators counteract HPV [3]. However, the non-pulmonary effects of inhaled NO include increased renal and hepatic blood flow and oxygenation [14].

From:

Published online 2009 May 29. doi: 10.1186/cc7734

Figure 2

Hypoxic pulmonary vasoconstriction (HPV).       (a) Normal ventilation-perfusion (VQ) matching. (b) HPV results in VQ matching despite variations in ventilation and gas exchange between lung units. (c) Inhaled nitric oxide (NO) augmenting VQ matching by vasodilating.

Non-cardiovascular effects relevant to lung injury

Neutrophils are important cellular mediators of ALI. Limiting neutrophil production of oxidative species and proteolysis reduces lung injury. In neonates, prolonged administration of NO diminished neutrophil-mediated oxidative stress [19]. Neutrophil deformability and CD18 expression were reduced in animal models [20] accomp-anied by decreases in adhesion and migration [21]. These changes limit damage to the alveolar-capillary membrane and the accumulation of protein-rich fluid within the alveoli. Platelet activation and aggregation, intra-alveolar thrombi, contribute to ALI. Inhaled NO attenuates the procoagulant activity in animal models of ALI [22] and a similar effect is seen in patients with ALI [23], but also in healthy volunteers [23,24]. In patients with ALI, decreased surfactant activity in the alveoli and noncompliance, as we recall is hyaline membrane disease accompanied by impaired pulmonary function [25].  The deleterious effects of the NO damages the alveolar wall with loss of surfactant by reactions with RNS [26]. Finally, prolonged exposure to NO in experimental models impairs cellular respiration [27].

The failure of inhaled NO to improve outcome in ALI/ARDS is therefore potentially due to several factors. First, patients with ALI/ARDS die of multi-organ failure, as the actions of NO are not expected to improve the outcome of multi-organ failure, which is a cytokine driven process leading to circulatory collapse. Indeed, the expected beneficial effect of inhaled NO is abrogated by detrimental downstream systemic effects discussed. Second, ALI/ARDS is a heterogeneous condition with diverse causes. Finally, using inhaled NO without frequent dose titration risks unwanted systemic effects without the expected benefits.

Other clinical uses of inhaled nitric oxide

Pulmonary hypertension and acute right ventricular failure

RVF may develop when there is abnormally elevated PVR and/or impaired RV perfusion.  ​Table 2 lists common causes of acute RVF. The RV responds poorly to inotropic agents but is exquisitely sensitive to after load reduction.

From:

Published online 2009 May 29. doi: 10.1186/cc7734

Table 2

Reducing PVR will have beneficial effects on cardiac output and therefore oxygen delivery. In the context of high RV afterload with low systemic pressures or when there is a limitation of flow within the right coronary artery [28], RV failure triggers a backward failure of venous return, as diagrammatically represented in  ​Figure 3.

From:

Published online 2009 May 29. doi: 10.1186/cc7734

Figure 3

Pathophysiology of right ventricular failure. CO, cardiac output; LV, left ventricle; PAP, pulmonary artery pressure; PVR, pulmonary vascular resistance; RV, right ventricle.

Inhaled NO is used when RV failure complicates cardiac surgery, as cardiopulmonary bypass per se causes diminished endogenous NO production [29]. There is marked variation in response to inhaled NO between patients [30] and in the same patient over time. After prolonged use, there is a leftward shift in the dose-response curve.  The risk of excessive NO administration is associated with toxicity and loss of the therapeutic effect without regular titration against a therapeutic goal [31].  Further, cardiac transplantation may be complicated by pulmonary hypertension and RVF that are improved with NO [32]. Early ischemia-reperfusion injury after lung transplantation manifests clinically as pulmonary edema and is a cause of significant morbidity and mortality [33,34]. Although NO has been administered in this circumstance [35], it hasn’t prevented ischemia-reperfusion injury in clinical lung transplantation [36]. Inhaled NO has been used successfully in patients with cardiogenic shock and RVF associated with acute myocardial infarction [37,38,46], and in patients with acute RVF following acute pulmonary venous thrombo-emboli [39, 47].  An explanation is needed in view of the downstream effects of systemic vasoconstriction and MOF previously identified. No systematic evaluation of inhaled NO and its effect on clinical outcome has been conducted in these conditions.

Acute chest crises of sickle cell disease

Acute chest crises are the second most common cause of hospital admission in patients with sickle cell disease (SCD) and are responsible for 25% of all related deaths [40]. Acute chest crises are manifest by fever, respiratory symptoms or chest pain, and new pulmonary infiltrate on chest  x-ray. The major contributory factors are related to vaso-occlusion. Hemolysis of sickled erythrocytes releasing Hb into the circulation generates reactive oxygen species and reacts with NO [41]. In SCD, the free Hb depletes NO. In addition arginase 1 is released, depleting the arginine needed for NO production, [42]. While secondary PVH is common in adults with SCD the physiological rationale for the use of inhaled NO needs to be considered, except for the complication just referred to. Thus far, iNO has failed to demonstrate either persistent improvements in physiology or beneficial effects on any accepted measure of outcome in clinical trials (other than its licensed indication in neonates). Therefore, inhaled NO is usually reserved for refractory hypoxemia.

Potential problems in designing and conducting RCTs in the efficacy of inhaled NO are numerous. Blinded trials will be difficult to conduct as the effects of inhaled NO are immediately apparent. Recruitment is limited as there is little time for consent/assent or randomization. Finally, industry funding might cast doubt on the independence of the trial results.

Inhaled NO is an unproved tool in the intensivist’s armamentarium of rescue therapies for refractory hypoxemia even though it has an established role in managing complications of cardiac surgery and in heart/lung transplantation. The current place for inhaled NO in the management of ALI/ARDS, acute sickle chest crisis, acute RV failure, and acute pulmonary embolism is a rescue therapy.

Abbreviations

ALI: acute lung injury; ARDS: acute respiratory distress syndrome; Hb: haemoglobin; HPV: hypoxic pulmonary vasoconstriction; iNO: inhaled nitric oxide; iNOS: inducible nitric oxide synthase; NO: nitric oxide; NO2: nitrogen dioxide; NOS: nitric oxide synthase; PaO2/FiO2: arterial partial pressure of oxygen/fraction of inspired oxygen; PVR: pulmonary vascular resistance; RCT: randomised controlled trial; RNS: reactive nitrogen species; RV: right ventricle; RVF: right ventricular failure; SCD: sickle cell disease; SMC: smooth muscle cell.

  1. Hunter CJ. Inhaled nebulized nitrite is a hypoxia-sensitive NO-dependent selective pulmonary vasodilator. Nat Med 2004; 10:1122–1127. [PubMed]
  2. Gessler P, Nebe T, Birle A, Mueller W, Kachel W. A new side effect of inhaled nitric oxide in neonates and infants with pulmonary hypertension: functional impairment of the neutrophil respiratory burst. Intensive Care Med 1996; 22:252–258. [PubMed]
  3. Sato Y, Walley KR, Klut ME, English D, D’yachkova Y, et al. Nitric oxide reduces the sequestration of polymorphonuclear leukocytes in lung by changing deformability and CD18 expression. Am J Respir Crit Care Med 1999; 159:1469–1476. [PubMed]
  4. Bloomfield GL, Holloway S, Ridings PC, Fisher BJ, et al. Pretreatment with inhaled nitric oxide inhibits neutrophil migration and oxidative activity resulting in attenuated sepsis-induced acute lung injury. Crit Care Med 1997; 25:584–593. [PubMed]
  5. Kermarrec N, Zunic P, Beloucif S, Benessiano J, et al. Impact of inhaled nitric oxide on platelet aggregation and fibrinolysis in rats with endotoxic lung injury. Role of cyclic guanosine 5′-monophosphate. Am J Respir Crit Care Med. 1998;158:833–839.[PubMed]
  6. Gries A, Bode C, Peter K, Herr A, Böhrer H, et al. Inhaled nitric oxide inhibits human platelet aggregation, P-selectin expression, and fibrinogen binding in vitro and in vivo. Circulation. 1998;97:1481–1487. [PubMed]
  7. Gries A, Herr A, Motsch J, Holzmann A, Weimann J, et al. Randomized, placebo-controlled, blinded and cross-matched study on the antiplatelet effect of inhaled nitric oxide in healthy volunteers. Thromb Hemost 2000; 83:309–315. [PubMed]
  8. Cheng IW, Ware LB, Greene KE, Nuckton TJ, et al. Prognostic value of surfactant proteins A and D in patients with acute lung injury. Crit Care Med 2003; 31:20–27. [PubMed]
  9. Robbins CG, Davis JM, Merritt TA, Amirkhanian JD et al. Combined effects of nitric oxide and hyperoxia on surfactant function and pulmonary inflammation. Am J Physiol 1995; 269(4 Pt 1):L545–550. [PubMed]
  10. Clementi E, Brown GC, Feelisch M, Moncada S. Persistent inhibition of cell respiration by nitric oxide: crucial role of S-nitro-sylation of mitochondrial complex I and protective action of glutathione. Proc Natl Acad Sci USA 1998; 95:7631–7636. [PMC free article] [PubMed]
  11. Vlahakes GJ. Right ventricular failure following cardiac surgery. Coron Artery Dis 2005; 16:27–30. [PubMed]
  12. Morita K, Ihnken K, Buckberg GD, Sherman MP, Ignarro LJ. Pulmonary vasoconstriction due to impaired nitric oxide production after cardiopulmonary bypass. Ann Thorac Surg 1996; 61:1775–1780.[PubMed]
  13. Wessel DL, Adatia I, Giglia TM, Thompson JE, Kulik TJ. Use of inhaled nitric oxide and acetylcholine in the evaluation of pulmonary hypertension and endothelial function after cardiopulmonary bypass. Circulation 1993; 88 (5 Pt 1):2128–2138. [PubMed]
  14. Solina A, Papp D, Ginsberg S, Krause T, et al. A comparison of inhaled nitric oxide and milrinone for the treatment of pulmonary hypertension in adult cardiac surgery patients. J Cardiothorac Vasc Anesth 2000; 14:12–17. [PubMed]
  15. Ardehali A, Hughes K, Sadeghi A, Esmailian F, et al. Inhaled nitric oxide for pulmonary hypertension after heart transplantation. Transplantation 2001; 72:638–641. [PubMed]
  16. King RC, Binns OA, Rodriguez F, Kanithanon RC, et al. Reperfusion injury significantly impacts clinical outcome after pulmonary transplantation. Ann Thorac Surg 2000; 69:1681–1685. [PubMed]
  17. de Perrot M, Liu M, Waddell TK, Keshavjee S. Ischemia-reperfusion-induced lung injury. Am J Respir Crit Care Med 2003; 167:490–511. [PubMed]
  18. Kemming GI, Merkel MJ, Schallerer A, Habler OP, et al. Inhaled nitric oxide (NO) for the treatment of early allograft failure after lung transplantation. Munich Lung Transplant Group.  Intensive Care Med 1998; 24:1173–1180. [PubMed]
  19. Meade MO, Granton JT, Matte-Martyn A, McRae K, aet al. Toronto Lung Transplant Program A randomized trial of inhaled nitric oxide to prevent ischemia-reperfusion injury after lung transplantation. Am J Respir Crit Care Med 2003; 167:1483–1489.[PubMed]
  20. Fujita Y, Nishida O, Sobue K, Ito H, et al.  Nitric oxide inhalation is useful in the management of right ventricular failure caused by myocardial infarction.  Crit Care Med 2002; 30:1379–1381. [PubMed]
  21. Inglessis I, Shin JT, Lepore JJ, Palacios IF, et al. Hemodynamic effects of inhaled nitric oxide in right ventricular myocardial infarction and cardiogenic shock. J Am Coll Cardiol 2004; 44:793–798. [PubMed]
  22. Szold O, Khoury W, Biderman P, Klausner JM,  et al. Inhaled nitric oxide improves pulmonary functions following massive pulmonary embolism: a report of four patients and review of the literature.  Lung 2006; 184:1–5. [PubMed]
  23. SiddiquiAK, Ahmed S. Pulmonary manifestations of sickle cell disease. Postgrad Med J 2003; 79:384–390. [PMC free article] [PubMed]
  24. Reiter CD, GladwinMT. An emerging role for nitric oxide in sickle cell disease vascular homeostasis and therapy. Curr Opin Hematol 2003; 10:99–107. [PubMed]
  25. GladwinMT, Vichinsky E. Pulmonary complications of sickle cell disease. N Engl J Med 2008; 359:2254–2265. [PubMed]
  26. GladwinMT, Schechter AN. Nitric oxide therapy in sickle cell disease. Semin Hematol  2001; 38:333–342. [PubMed]
  27. Atz AM, Wessel DL. Inhaled nitric oxide in sickle cell disease with acute chest syndrome. Anesthesiology 1997; 87:988–990. [PubMed]
  28. Sullivan KJ, Goodwin SR, Evangelist J, Moore RD, Mehta P. Nitric oxide successfully used to treat acute chest syndrome of sickle cell disease in a young adolescent.  Crit Care Med 1999; 27:2563–2568. [PubMed]
  29. Al Hajeri A, Serjeant GR, Fedorowicz Z. Inhaled nitric oxide for acute chest syndrome in people with sickle cell disease. Cochrane Database Syst Rev 2008;(1):CD006957. [PubMed]
  30. Bigatello LM, Stelfox HT, Hess D. Inhaled nitric oxide therapy in adults – opinions and evidence. Intensive Care Med. 2005;31:1014–1016. [PubMed]
  31. Dellinger RP, Zimmerman JL, Taylor RW, Straube RC, et al. Effects of inhaled nitric oxide in patients with acute respiratory distress syndrome: results of a randomized phase II trial. Inhaled Nitric Oxide in ARDS Study Group. Crit Care Med 1998; 26:15–23. [PubMed]
  32. Michael JR, Barton RG, Saffle JR, Mone M, et al.  Inhaled nitric oxide versus conventional therapy: effect on oxygenation in ARDS. Am J Respir Crit Care Med 1998; 157 (5 Pt 1): 1372–1380. [PubMed]
  33. Troncy E, Collet JP, Shapiro S, Guimond JG, et al. Inhaled nitric oxide in acute respiratory distress syndrome: a pilot randomized controlled study. Am J Respir Crit Care Med 1998; 157 (5 Pt 1):1483–1488. [PubMed]
  34. Lundin S, Mang H, Smithies M, Stenqvist O, Frostell C. Inhalation of nitric oxide in acute lung injury: results of a European multicentre study. The European Study Group of Inhaled Nitric Oxide. Intensive Care Med 1999; 25:911–919. [PubMed]
  35. Park KJ, Lee YJ, Oh YJ, Lee KS, Sheen SS, Hwang SC. Combined effects of inhaled nitric oxide and a recruitment maneuver in patients with acute respiratory distress syndrome. Yonsei Med J 2003; 44:219–226.[PubMed]
  36. Taylor RW, Zimmerman JL, Dellinger RP, Straube RC, et al.  Inhaled Nitric Oxide in ARDS Study Group. Low-dose inhaled nitric oxide in patients with acute lung injury: a randomized controlled trial.  JAMA  2004; 291:1603–1609.[PubMed]

Related articles

 

Read Full Post »

Reporter: Aviva Lev-Ari, PhD, RN

On August 16, 2012 I received an e-mail on New@NEJM.org from this e-mail, I selected to post HERE, the

Cardiology Panel — NEJM Dialogue in Medicine, June 22, 2012

http://pharmaceuticalintelligence.com/2012/08/16/cardiology-panel-nejm-dialogue-in-medicine-june-22-2012/

While listening to the 1:35 minutes of the Video of the Cardiology Panel, the Nobel Prize for Nitric Oxide was mentioned. In light of the thrust, this Scientific Web Site has related to Nitric Oxide in Health and in Disease, I decided to cite here the entire Letter from the Nobel Prize Web Site.

October 12, 1998

The Nobel Assembly at Karolinska Institutet has today decided to award
the Nobel Prize in Physiology or Medicine for 1998 jointly to

Robert F. Furchgott, Louis J. Ignarro and Ferid Murad

for their discoveries concerning “nitric oxide as a signalling molecule in the cardiovascular system”.

Summary

Nitric oxide (NO) is a gas that transmits signals in the organism. Signal transmission by a gas that is produced by one cell, penetrates through membranes and regulates the function of another cell represents an entirely new principle for signalling in biological systems. The discoverers of NO as a signal molecule are awarded this year’s Nobel Prize.

Robert F Furchgott, pharmacologist in New York, studied the effect of drugs on blood vessels but often achieved contradictory results. The same drug sometimes caused a contraction and at other occasions a dilatation. Furchgott wondered if the variation could depend on whether the surface cells (the endothelium) inside the blood vessels were intact or damaged. In 1980, he demonstrated in an ingenious experiment that acetylcholine dilated blood vessels only if the endothelium was intact. He concluded that blood vessels are dilated because the endothelial cells produce an unknown signal molecule that makes vascular smooth muscle cells relax. He called this signal molecule EDRF, the endothelium-derived relaxing factor, and his findings led to a quest to identify the factor.

Ferid Murad, MD and pharmacologist now in Houston, analyzed how nitroglycerin and related vasodilating compounds act and discovered in 1977 that they release nitric oxide, which relaxes smooth muscle cells. He was fascinated by the concept that a gas could regulate important cellular functions and speculated that endogenous factors such as hormones might also act through NO. However, there was no experimental evidence to support this idea at the time.

Louis J Ignarro, pharmacologist in Los Angeles, participated in the quest for EDRF’s chemical nature. He performed a brilliant series of analyses and concluded in 1986, together with and independently of Robert Furchgott, that EDRF was identical to NO. The problem was solved and Furchgott’s endothelial factor identified.

When Furchgott and Ignarro presented their conclusions at a conference in July, 1986, it elicited an avalanche of research activities in many different laboratories around the world. This was the first discovery that a gas can act as a signal molecule in the organism.

Background

Nitric oxide protects the heart, stimulates the brain, kills bacteria, etc.
It was a sensation that this simple, common air pollutant, which is formed when nitrogen burns, for instance in automobile exhaust fumes, could exert important functions in the organism. It was particularly surprising since NO is totally different from any other known signal molecule and so unstable that it is converted to nitrate and nitrite within 10 seconds. NO was known to be produced in bacteria but this simple molecule was not expected to be important in higher animals such as mammals.

Further research results rapidly confirmed that NO is a signal molecule of key importance for the cardiovascular system and it was also found to exert a series of other functions. We know today that NO acts as a signal molecule in the nervous system, as a weapon against infections, as a regulator of blood pressure and as a gatekeeper of blood flow to different organs. NO is present in most living creatures and made by many different types of cells.
– When NO is produced by the innermost cell layer of the arteries, the endothelium, it rapidly spreads through the cell membranes to the underlying muscle cells. Their contraction is turned off by NO, resulting in a dilatation of the arteries. In this way, NO controls the blood pressure and its distribution. It also prevents the formation of thrombi.
– When NO is formed in nerve cells, it spreads rapidly in all directions, activating all cells in the vicinity. This can modulate many functions, from behaviour to gastrointestinal motility.
– When NO is produced in white blood cells (such as macrophages), huge quantities are achieved and become toxic to invading bacteria and parasites.

Importance in medicine today and tomorrow
Heart: In atherosclerosis, the endothelium has a reduced capacity to produce NO. However, NO can be furnished by treatment with nitroglycerin. Large efforts in drug discovery are currently aimed at generating more powerful and selective cardiac drugs based on the new knowledge of NO as a signal molecule.

Shock: Bacterial infections can lead to sepsis and circulatory shock. In this situation, NO plays a harmful role. White blood cells react to bacterial products by releasing enormous amounts of NO that dilate the blood vessels. The blood pressure drops and the patient may become unconscious. In this situation, inhibitors of NO synthesis may be useful in intensive care treatment.

Lungs: Intensive care patients can be treated by inhalation of NO gas. This has provided good results and even saved lives. For instance, NO gas has been used to reduce dangerously high blood pressure in the lungs of infants. But the dosage is critical since the gas can be toxic at high concentrations.

Cancer: White blood cells use NO not only to kill infectious agents such as bacteria, fungi and parasites, but also to defend the host against tumours. Scientists are currently testing whether NO can be used to stop the growth of tumours since this gas can induce programmed cell death, apoptosis.

Impotence: NO can initiate erection of the penis by dilating the blood vessels to the erectile bodies. This knowledge has already led to the development of new drugs against impotence.

Diagnostic analyses: Inflammatory diseases can be revealed by analysing the production of NO from e.g. lungs and intestines. This is used for diagnosing asthma, colitis, and other diseases.

NO is important for the olfactory sense and our capacity to recognise different scents. It may even be important for our memory.

Nitroglycerin
Alfred Nobel invented dynamite, a product in which the explosion-prone nitroglycerin is curbed by being absorbed in kieselguhr, a porous soil rich in shells of diatoms. When Nobel was taken ill with heart disease, his doctor prescribed nitroglycerin. Nobel refused to take it, knowing that it caused headache and ruling out that it could eliminate chest pain. In a letter, Nobel wrote: It is ironical that I am now ordered by my physician to eat nitroglycerin. It has been known since last century that the explosive, nitroglycerin, has beneficial effects against chest pain. However, it would take 100 years until it was clarified that nitroglycerin acts by releasing NO gas.

TO CITE THIS PAGE:
MLA style: “Physiology or Medicine for 1998 – Press Release”. Nobelprize.org. 16 Aug 2012 http://www.nobelprize.org/nobel_prizes/medicine/laureates/1998/press.html

Read Full Post »

Curator/Author: Aviral Vatsa PhD, MBBS

Nitric oxide is one of the smallest molecules involved in physiological functions in the body. It is a diatom and thus seeks formation of chemical bonds with its targets rather than structure-function configuration of say protein receptors. Nitric oxide can exert its effects principally by two ways:

  • Direct
  • Indirect

Direct actions, as the name suggests, result from direct chemical interaction of NO with its targets e.g. with metal complexes, radical species. These actions occur at relatively low NO concentrations (<200 nM)

Indirect actions result from the effects of reactive nitrogen species (RNS) such as NO2 and N2O3. These reactive species are formed by the interaction of NO with superoxide or molecular oxygen. RNS are generally formed at relatively high NO concentrations (>400 nM)

Credits: Nitric Oxide: Biology and Pathobiology By Louis J. Ignarro

Credits: Nitric Oxide: Biology and Pathobiology By Louis J. Ignarro

Although it can be tempting for scientists to believe that RNS will always have deleterious effects and NO will have anabolic effects, this is not entirely true as certain RNS mediated actions mediate important signalling steps e.g. thiol oxidation and nitrosation of proteins mediate cell proliferation and survival, and apoptosis respectively. As depicted in the figure above, NO concentration determines the action it exerts on different proteins. This is highlighted in the following examples from different studies:

  • Cells subjected to NO concentration between 10-30 nM were associated with cGMP dependent phosphorylation of ERK
  • Cells subjected to NO concentration between 30-60 nM were associated with Akt phosphorylation
  • Concentration nearing 100 nM resulted in stabilisation of hypoxia inducible factor-1
  • At nearly 400 nM NO, p53 can be modulated
  • >1μM NO, it nhibits mitochondrial respiration

Besides the concentration, duration of NO exposure also determines how proteins respond to NO. Hence proteins can be ‘immediate’ responders or ‘delayed’ responders. The response can be either ‘transient’ (short lived) or ‘sustained’ (prolonged). Different proteins fall into these different categories. These are not rigid categories rather a functional ‘classification’.

Endogenously generated NO concentration ranges from 2 nM as in endothelial cell to >1 μM in a fully activated macrophage. This wide range, along with the unique chemical reactivity of NO offers immense versatility to the physiological effects that it can exert in different cellular milieu in the body.

In addition to the concentration-dependent effects, other factors that determine the local cellular/tissue milieu add to the complexities involved with signal transduction undertaken by NO. These factors are

  • rate of NO production
  • diffusion distance
  • rates of consumption
  • reactivity of RNS with molecular targets.

These kinetic determinants play vital role in physiological functions and disease states.

Although it is not possible to detail the modes of modulation of biological functions by NO in a short post, but I hope the post gives a taste of the intricacies involved with NO functions and that there are various parameters that determine the exact role of NO in a biological milieu.

Sources

http://www.pnas.org/content/101/24/8894.short

http://onlinelibrary.wiley.com/doi/10.1002/ijc.22336/full

http://cancerres.aacrjournals.org/content/67/1/289.short

http://www.sciencedirect.com/science/article/pii/S0005272806000417

http://goo.gl/eVXFh

Read Full Post »

Author/Curator: Aviral Vatsa PhD, MBBS

Nitric oxide (NO) is of extreme biological interest due to its wide range of physiological functions in almost all the human systems. For long it has been of vital interest to chemists, environmental scientists, metallurgists and other domains. It is only recently that the world of biology has discovered the ubiquitous presence of this small molecule in human body and the scientific exploration of its effects has grown ever since. It was only in 1980s that three different groups demonstrated that NO is indeed produced by mammalian cells and that NO has specific biological roles in the human body. These studies highlighted the role of NO in cardiovascular, nervous and immune systems. In cardiovascular system NO was shown to cause relaxation of vascular smooth muscle cells causing vasodilatation, in nervous system NO acts as a signalling molecule and in immune system it is used against pathogens by the phagocytosis cells. These pioneering studies opened the path of investigation of role of NO in biology. In 1998, three scientists, Robert F Furchgott, Louis J Ignarro, and Ferid Murad, were awarded Nobel Prize for their discoveries concerning ‘nitric oxide as a signalling molecule’.

Since then hundreds and thousands of publications have appeared in the scientific literature. These studies have attributed a wide range of biological functions to NO. A few important examples are:

  • toxic free radical causing injury to proteins, lipids and DNA
  • mediator of synaptic plasticity
  • intercellular neuronal signalling molecule
  • pro and anti inflammatory molecule
  • role in cell degeneration and ischaemia-reperfusion injury
  • role in atherosclerosis and inherited motor disorders
  • role in bone remodelling

The above list is by no means exhaustive, but it gives an idea about the ubiquitous involvement of NO in human systems.

Since NO has been implicated in various disease states, it has also been a prime target to achieve therapeutic benefits. Efforts are ongoing to investigate the therapeutic potential of NO in cardiovascular diseases, sepsis and shock, respiratory ailments, neuronal disease and bone conditions…just to name a few.

Although a lot of progress has happened in our understanding of this small molecule since its discovery, but still there are many challenges that the researchers face today while investigating NO. These are primarily because NO is metabolised very quickly (<5 sec) and it can difuse freely across cellular membranes owing to its chemical structure. This is the precise reason why it can act as a potent signaling molecule across systems in the first place. New techniques are appearing to delineate the role of NO at sub-cellular level and have promising potential to aid NO research in the future.

In the future posts on this topic I will strive to cover different aspects of NO physiology and its role in various disease conditions, techniques for NO detection, signaling mechanism etc.

Sources:

1. The nature of endothelium-derived vascular relaxant factor

Nature 308, 645 – 647 (12 April 1984); doi:10.1038/308645a0

T. M. Griffith, D. H. Edwards, M. J. Lewis, A. C. Newby & A. H. Henderson

2. Nitric oxide: physiology, pathophysiology, and pharmacology.

Pharmacological Rev June 1991 43:109-142

S Moncada, R M Palmer, and E A Higgs

3. Introduction to EDRF research.

J Cardiovasc Pharmacol.1993;22 Suppl 7:S1-2.

Furchgott RF

4. http://www.nobelprize.org/nobel_prizes/medicine/laureates/1998/illpres/

Read Full Post »

« Newer Posts - Older Posts »