Posts Tagged ‘Mitochondrial disease’

Author and Reporter: Ritu Saxena, Ph.D.  

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Mitochondria is an important cell organelle that is associated with several key cellular functions as energy production, anabolism, calcium homeostasis and cell programmed death, and any abnormalities occurring in mitochondria would lead to alteration of normal cellular function.

Role of mitochondria in cancer has long been implicated. Post published on September 1, 2012 (http://pharmaceuticalintelligence.com/2012/09/01/mitochondria-and-cancer-an-overview/) presents a brief overview of the mechanisms by which mitochondrial defects could be associated with cancer. Different studies on various types of Cancers have tried to determine the mtDNA mutations and the mechanisms involved. An important aspect of cancerous progression is the cancer cell migration and it has been observed that mitochondrial dysfunction is involved in cancer cell migration. However, the molecular mechanism still needs to be deciphered.

A group from Taiwan recently published their findings in the Biochimica et Biophysica Acta journal stating that enhanced β5-integrin expression was involved in promoting cell migration in human gastric cancer cell line as a result of mitochondrial dysfunction.

The authors used human gastric cancer cell line, SC-M1 cells for their studies. The methodology followed was to first create mitochondrial dysfunction in the SC-M1 cells by the use of oxidative phosphorylation inhibitors: oligomycin (Complex V inhibitor) and antimycin A (Complex III inhibitor) thereby inhibiting mitochondrial function. The results indicated that impaired oxidative phosphorylation caused an increase in the intracellular Reactive Oxygen Species (ROS) that lead to an increased cell migration in SC-M1 cells.

Different types of integrin molecules have been implicated in cell migration. Hung et al extracted RNA and protein from SC-M1 cells in order to study the different types of integrins, and observed that the levels of β5-integrin were significantly upregulated in SC-M1 cells.  Simultaneously, the surface expression of the dimer- β5-integrin and αv-integrin, was studied in cancer cells with using FACS. The analysis revealed a higher surface expression of the dimer corresponding to the higher levels of the protein and RNA results of  β5-integrin expression in SC-M1 cells with mitochondrial dysfunction. Infact, a subpopulation of SC-M1 cells that showed higher migration capability (SC-M1-3rd) was observed to harbor a higher lever of β5-integrin expression, correlating β5-integrin expression with cell migration ability. The experiments supported the role of β5-integrin in cell migration in gastric cancer cells.

Finally, authors confirmed the in vitro results in the human gastric cancer samples. Immunohistochemical analysis revealed that β5-integrin was stained positive in around 73% of the cancer samples. Additionally, the higher expression levels of β5-integrin could be correlated with the invasive ability and more aggressive behavior of gastric cancer cells.

Authors stated “our study pinpoints another aspect that links the induction of intracellular ROS level in mitochondrial dysfunction gastric cancer cells with the activation of αvβ5-integrin. Taken together, the induction of β5-integrin is important to gastric cancer metastasis, especially in cancer cells that exhibit mitochondrial dysfunction.”

Thus, blockage of αvβ5-integrin function by antibodies might be tested as a potential therapy for preventing or delaying gastric cancer metastasis, especially in gastric cancers harboring mitochondrial dysfunction.


Research article: http://www.ncbi.nlm.nih.gov/pubmed?term=22561002

Related posts: http://pharmaceuticalintelligence.com/2012/09/01/mitochondria-and-cancer-an-overview/



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Reported by: Dr. Venkat S. Karra, Ph.D.

Mitochondria are responsible for more than 90% of a cell’s energy production via ATP (adenosine triphosphate) generation, in addition to playing a significant role in respiration and many signaling events within most eukaryotic cells. These intracellular powerhouses range in size and quantity within each cell depending on the organism and overall cell function.

Mitochondria consist of a semi-permeable outer membrane, a thin inter-membrane space where oxidative phosphorylation occurs, an impermeable inner membrane that is intricately folded to create layered compartments—or christae—and the matrix that contains ATP-producing enzymes and the organelle’s own independent genome. Each section has a highly specialized function, and any impairment within the organelle can lead to disease or disorders within the overall organism.

Mitochondrial dysfunction may be due to:

1. Hereditary:

Inherited mitochondrial disorders can play a role in prevalent diseases such as cardiac disease and diabetes, and can also result in rare diseases such as Pearson syndrome or Leigh’s disease.

2. Drug Toxicity:

Mitochondrial toxicity as a result of pharmaceutical use may damage key organs, such as the liver and heart. For example:

nefazodone—a depression treatment—was withdrawn from the U.S. market after it was shown to significantly inhibit mitochondrial respiration in liver cells, leading to liver failure.

Troglitazone, an anti-diabetic and anti-inflammatory, was withdrawn from all markets after research concluded that it caused acute mitochondrial membrane depolarization, also leading to liver failure.

Drug recalls are costly to a manufacturer’s bottom line and reputation, and more importantly, can be harmful or even fatal to users. As drug discovery continues to evolve, much lead compound research now includes careful review of its interaction and potential toxicity with mitochondria.

Cell-based mitochondrial assays in microplate format may include mitochondrial membrane potential, total energy metabolism, oxygen consumption, and metabolic activity; and offer a truer environment for mitochondrial function in the presence of drug compounds compared to isolated mitochondria-based tests. Combining more than one assay in a multiplex format increases the amount of data per well while decreasing data variability arising from running the assays separately. The aggregated data also provides a more encompassing analysis of the drug’s effect on mitochondria than a single test.

One example, when testing compound effects on mitochondria, would be to measure cell membrane integrity as a function of cytotoxicity and mitochondrial function via ATP production concurrently, thus distinguishing between compounds that exhibit mitochondrial toxicity versus overt cytotoxicity.

General cytotoxicity is characterized by a decrease in ATP production and a loss of membrane integrity whereas mitochondrial toxicity results in decreased ATP production with little to no change in membrane integrity.

The assay’s efficiency is further enhanced via automation.

Robotic instrumentation ensures repeatable operation within the microplate wells when performing tasks such as cell dispensing, serial titration and transfer of compounds, and reagent dispensing. Additionally, by automating tasks within the assay process, researchers are free to attend to other tasks, reducing overall active time spent on the assay. Multi-mode microplate readers are compact instruments that can detect both fluorescent and luminescent signals. In addition, an automated process—including liquid handling and detection—can increase throughput capacity compared to manual methods.

Multiplexed cell-based mitochondrial assays increase sample throughput and decrease variability, costs, and overall time for project completion. Automating the process with robotic instrumentation allows for rapid compound profiling, repeatability, further throughput increase, and decreased per-assay and overall project time.



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