Posts Tagged ‘circadian modulation physiology’

Alteration in Reduced Glutathione level in Red Blood Cells: Role of Melatonin

Author: Shilpa Chakrabarti, PhD

List of abbreviation:
DTNB- 5,5- dithiobis,2-nitrobenzoic acid
t-BHP- Tertiary butyl hydroperoxide
GSH-Reduced glutathione
GSSG- Oxidised glutathione

Objective: The study was taken up to see the effect of melatonin on the alteration of reduced glutathione level in red blood cells.

Pineal melatonin is involved in many physiological functions, the most important among them being sleep promotion and circadian regulation. This pineal product exhibits characteristic diurnal rhythm of synthesis and secretion, which attains its peak at night followed by a gradual decrease during the daytime. Melatonin detoxifies highly toxic hydroxyl and peroxyl radicals in vitro, scavenges hydrochlorous acid, as well as peroxynitrite. It has also been reported to increase the synthesis of glutathione and of several antioxidant enzymes [1].

Method: The present study was undertaken to understand the modulation of intracellular reduced glutathione (GSH) by melatonin in human red blood cells according to the oscillatory circadian changes in levels of this hormone.We have also studied the dose-dependent effect of melatonin on GSH in erythrocytes obtained from blood at two different times, subjected to oxidative stress by incubating with tert-butyl hydroperoxide (t-BHP) [2]. We used t-BHP as pro-oxidant [3]. Erythrocyte GSH was measured following the method of Beutler [4]. The method was based on the ability of the –SH group to reduce 5,5- dithiobis,2-nitrobenzoic acid (DTNB) and form a yellow coloured anionic product whose OD is measured at 412 nm.

A suspension of packed red blood cells in phosphate-buffered saline (PBS) containing glucose was treated with melatonin taken at different concentrations. A stock solution (10mM) of melatonin was prepared in absolute ethanol; further dilutions (100 uM–10 nM) were done with PBS. The concentration of ethanol was alwaysThe in vitro effect of melatonin was evaluated by incubating erythrocytes with melatonin at different doses (10 uM –1 nM final concentration) of melatonin for 30 minutes at 37°C. After washing the erythrocytes with the buffer, to remove any amount of the compound, and finally, packed erythrocytes were used for the assay of GSH. In parallel control experiments, blood was incubated with ethanol (final concentration not more than 0.01% (v/v)) but without melatonin.Oxidative stress was induced in vitro by using tert-butyl hydroperoxide both in presence and absence of melatonin. Use of TBHP is in accordance with the published reports [5].

Results and Discussion: The experiment demonstrated that erythrocyte GSH level increased in nocturnal samples which highlights the role of endogenous melatonin in the circadian changes in cellular glutathione level. Exogenous melatonin demonstrated a protective effect against t-BHP-induced peroxidative damage in both diurnal and nocturnal samples, the effect being more pronounced in aliquots containing very low concentration of melatonin (10 nM – 1 nM) [6]. Melatonin was found to inhibit GSH oxidation in a dose-dependent manner.

Melatonin has been found to upregulate cellular glutathione level to check lipid peroxidation in brain cells [7]. We may say that the incubation of the red cells with melatonin for an extended period (more than 30 minutes) may not have the same effects on the level of glutathione in these cells [12]. Melatonin may act as pro-oxidant in the cells exposed to the indoleamine for longer time. Also, the half-life period of pineal melatonin is for 30 to 60 minutes, as reviewed by Karasek and Winczyk [11].The recycling of glutathione in the cells depends on an NADPH-dependent glutathione enzyme system which includes glutathione peroxidise, glutathione reductase, and γ-glutamyl-cysteine synthase forming a meshwork of an antioxidative system. The stimulatory effect of melatonin on the regulation of the antioxidant enzymes has been reported [8].Since melatonin has an amphiphilic nature, its antioxidative efficiency crosses the cellular membrane barriers in a non-receptor-mediated mechanism. Another explanation of melatonin’s antioxidative activity may be based on its role in the upregulation of some antioxidant enzymes directly. Blanco et al had reported that glutathione reductase and glutathione peroxidase, the major constituents of the glutathione-redox system being stimulated by melatonin [9]. The plasma GSH/GSSG redox state is controlled by multiple processes, which includes synthesis of GSH from its constitutive amino acids, cyclic oxidation and reduction involving GSH peroxidase and GSSG reductase, transport of GSH into the plasma, and the degradation of GSH and GSSG by γ-glutamyltranspeptidase. The increase in erythrocyte GSH concentration after melatonin administration can be related Blanco et al’s report on the known stimulation of γ-glutamylcysteine synthase,a rate-limiting enzyme in reduced glutathione synthesis, by melatonin [10].

Conclusion: On the basis of our study, we may conclude that melatonin affects the glutathione level in red blood cells in a circadian manner. The rhythmic pattern of glutathione level confirms the relationship between physiological melatonin and erythrocyte GSH level and pharmacological dosage of the drug. The role of melatonin as an antioxidant and its activity in relation to these biomarkers has been studied in the above experiments.

Key words: Glutathione, circadian rhythm,, melatonin, biomarkers, oxidative stress


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10. R. A. Blanco, T. R. Ziegler, B. A. Carlson et al., “Diurnal variation in glutathione and cysteine redox states in human plasma,” American Journal of Clinical Nutrition, vol. 86, no. 4, pp. 1016–1023, 2007.
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erythrocytes during prolonged incubation?” Advances in Medical Sciences, vol. 58, no. 1, 2013.



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Day and Night Variation in Melatonin Level affects Plasma Membrane Redox System in Red Blood Cells

Author: Shilpa Chakravarty, PhD

Melatonin is a well-established antioxidant and sleep-regulating hormone. Over the past fifty years, its efficiency as a regulator of circadian rhythm and several other physiological functions has been studied extensively in different species. As a free-radical scavenger, melatonin has shown its activity in coordination with its circadian nature. One of the most important biomarkers of oxidative stress studied in red blood cells is the plasma membrane redox system (PMRS).

As a part of the research activity, PMRS activity has been summarised in this article. The experiments with PMRS and ascorbate free-radical reductase (AFR reductase) have been conducted in vitro.

The study was carried out on 61 healthy individuals of both sexes (aged 20-30) having no acute or chronic diseases (such as diabetes mellitus, asthma, or tuberculosis) or any organ dysfunction and had not taken any medication. Blood samples were collected at two different timings at 10:00AM and 10:00PM.  Red blood cell-membrane, was in retrospect a good experimental system to try to extract and isolate membrane proteins for biochemical assays. Two factors that have favoured it for experimental use are availability and simplicity. Results from its study have been replicated in every other mammalian cell type, and in some crucial points, the patterns shown by RBC
proteins have led the way to such interpretations of extensive physiological studies.

PMRS transfers electrons from extracellular substates to intracellular electron acceptors incorporating AFR reductase. An increase in PMRS activity indicates the ability of the cell to combat oxidative damage.The aging of human red cells may well be attributed to free radical induced oxidative damage. Maintenance of redox state of sulphydryl residues and reduction of lipid hydroperoxides at the expense of electron donors, such as ascorbate and NADH, is essential for normal energy metabolism in the cell. The neutralisation of oxidants also involves some membrane proteins that comprise the PMRS. The rise in PMRS activity is required to maintain a balanced NAD+/NADH ratio that is essential for normal energy metabolism. It leads to cell survival and membrane homeostasis under stress conditions and during calorie restriction in eukaryotes. The day and night variation in PMRS activity shows that the antioxidative behaviour of melatonin is also influenced by its circadian mode of action. While melatonin is an effective antioxidant against cellular toxicity, it also increases the PMRS activity in red blood cells at night. During the day, when the pineal secretion is low, the PMRS activity is also suppressed.

However, if subjected to in vitro treatment with melatonin, at such a concentration that lies close to the maximal melatonin level in the plasma (maximal secretion of melatonin occurs during the scotopic phase of the day), PMRS increases in red blood cells. This shows that the circadian nature of the hormone not only pertains to its pineal production but also to exogenous administration of the drug.


  1. Chakravarty S,  Rizvi SI (2012) Modulation of human erythrocyte redox status by melatonin: A protective mechanism against oxidative damage. Neurosci Lett. 518:32-35.
  2. Karasek M,  Winczyk K (2006) Melatonin in humans. Neurosci Lett518:32-35.
  3. Hardeland R, Pandi-Perumal SR (2005) Melatonin, a potent agent in antioxidative defense: Actions as a natural food constituent, gastrointestinal factor, drug and prodrug. Nutr Metab. (Lond) 2:22.
  4. Hardeland R,  Coto-Montes A, Poeggeler B (2003)  Circadian rhythms, oxidative stress and antioxidative defense mechanisms. Chronobiol Int. 20:921-962.
  5. Hyun D.H., Hernandez J.O., Mattson M.P., de Cabo R., (2006)  The plasma membrane redox system in aging, Ageing Res. Rev. 209–220.
  6. Hyun D.H., Emerson S.S., Jo D.G., Mattson M.P., de Cabo R., (2006) Calorie restriction up-regulates the plasma membrane redox system in brain cells and suppresses oxidative stress during aging, Proceedings of the National Academy of Sciences of the United States of  America 103: 19908–19912.
  7. Rizvi S.I., Jha R., Maurya P.K., (2006)  Erythrocyte plasma membrane redox system in human aging, Rejuvenation Research 9: 470–474.

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