Aim: 

The oxygen-gradient diffusion of the capillary tissue is essential for cell survival. Maintenance of oxygen homeostasis in arterial blood is mediated by reflexes that are sensitive to oxygen decrease, and by release of several factors. Aging is correlated with a reduction of cell oxygen supply as well as a parallel decrease in oxygen demand by tissues. During aging, reactive oxygen species (ROS) are generated, and these oxidants result in a detrimental effect on structural and functional components of membranes. ROS are generated under hypoxic conditions and the accumulation of free radicals during life reduces the ability of tissues to remove them.

Methods: 

Considering that the life span is correlated with the metabolic rate and that mitochondria are the site of oxygen consumption, the response to acute and chronic hypoxia is represented by an increase in Hypoxic Inducible Factor-1a (HIF) that has a crucial role in hypoxia-adaptation processes. Oxygen is necessary for cell survival and for ATP production, but the correlation among oxygen consumption, ATP production and HIF levels is still not understood.

Results: 

Considering that HIF regulates gene expression and recurrent sleep apnoea that is typical of aging (a condition that would mimic chronic intermittent hypoxia), we found a tight correlation between aging and hypoxia. Indeed, in both conditions, hypoxia and hyperoxia, free radical species are generated, which damage structural and functional components of the membrane. ROS are physiological products of aerobic processes and their accumulation affects aging. Because hypoxia per se modulates mitochondria activity, influencing oxygen consumption, hypoxia and aging could share some link. The exact correlation between hypoxia and life-span remains open, at least until we solve the question of how cells sense oxygen.

Conclusion: 

To better understand aging we need to know what O₂ species are being sensed by cells. Additional research will be required to fully elucidate the correlations between aging and hypoxia but both hypoxia and hyperoxia represent experimental models that are adequate for studying aging processes.