Mitochondrial nitric oxide synthase and its role in the mechanisms of cell adaptation to hypoxia

Mitochondrial nitric oxide synthase (mtNOS) actively participates in mechanisms of regulation of cell adaptation to extreme factors. It is closely interacted with other mitochondrial regulatory factors and is involved in adaptation reactions of cells to hypoxia, ischemia and other pathogenic action. Analysis of the role of mtNOS in cell functioning in hypoxia condition and its influence on apoptosis is presented in the article. Complex mechanism of cell adaptation with participation of mitochondrial nitric oxide (NO) is considered. Mitochondrial NO is a modulator of cell respiration, synthesis of ATP, activity of mitochondrial ATP-sensitive potassium channels, mitochondrial megapore and the specific protein factor to hypoxia adaptation. The possibility of pharmacological regulation of mtNOS activity is discussed. This approach seems to be promising for searching of new drugs for the pharmacotherapy of diseases with hypoxia and ischemia in their pathogenesis. There is possible to regulate cell homeostasis, for example, resistance to hypoxia by modulating the activity of mtNOS and synthesis of mitochondrial NO.

Mitochondrial targets for pharmacological regulation of cell adaptation to hypoxia

The review is devoted to the role of a number of mitochondrial factors in the regulation of cell adaptation to hypoxia and ischemia. The mechanisms of cell adaptation involving factors such as the mitochondrial ATP-dependent potassium channel, mitochondrial megapora, mitochondrial nitric oxide synthase, reactive oxygen species are discussed in the paper. The possibility of pharmacological regulation of cell adaptation with help of target action on mitochondrial components is proposed. This approach is a promising direction for drug discovery for correction of diseases with hypoxia and ischemia in their pathogenesis.

High doses of vitamin E improve mitochondrial dysfunction in rat hippocampus and frontal cortex upon aging

Rat aging from 4 to 12 mo was accompanied by hippocampus and frontal cortex mitochondrial dysfunction, with decreases of 23 to 53% in tissue and mitochondrial respiration and in the activities of complexes I and IV and of mitochondrial nitric oxide synthase (mtNOS) ( P < 0.02). In aged rats, the two brain areas showed mitochondria with higher content (35–78%) of oxidation products of phospholipids and proteins and with higher (59–95%) rates of O2− and H2O2 production ( P < 0.02). Dietary supplementation with vitamin E (2.0 or 5.0 g/kg of food) from 9 to 12 mo of rat age, restored in a dose-dependent manner, the decreases in tissue and mitochondrial respiration (to 90–96%) and complexes I and IV and mtNOS activities (to 86–88%) of the values of 4-mo-old rats ( P < 0.02). Vitamin E prevented, by 73–80%, the increases in oxidation products, and by 62–68%, the increases in O2− and H2O2 production ( P < 0.05). High resolution histochemistry of cytochrome oxidase in the hippocampal CA1 region showed higher staining in vitamin E-treated rats than in control animals. Aging decreased (19%) hippocampus mitochondrial mass, an effect that was restored by vitamin E. High doses of vitamin E seem to sustain mitochondrial biogenesis in synaptic areas.