Cataldi Amelia, Di Giulio Camillo
Department of Biomorphology and Human Anatomy Section, Faculty of Pharmacy, Pescara, Italy.
Curr Aging Sci. 2009 Jul;2(2):95-102. doi: 10.2174/1874609810902020095.
Cell growth is regulated by several factors, including oxygen supply, which influence cell metabolism. Aging is characterized by decreased oxygen supply to tissue, a reduction of tissue PO(2) and of the activity of several enzymes and metabolic factors. The oxygen-gradient diffusion at capillary tissue level is essential for the cellular survival, while the homeostasis of the oxygen in the arterial blood is mediated by reflexes sensitive to oxygen decrease and by release of several factors. Aging is correlated with a reduction of cells' oxygen supply concomitant to a parallel decrease in oxygen demand by tissues. Both chronic hypoxia or hyperoxia are considered as stresses. Indeed, in both conditions, free radical species, which damage structural and functional components of the membrane, are generated. ROS (reactive oxygen species) are physiological products of aerobic life and their accumulation affects aging. Because hypoxia per se modulates mitochondria activity, influencing oxygen consumption, hypoxia and aging could share some link. Moreover, the observation that in hypoxia or hyperoxia there is an accumulation of lipofucsine as a general reaction to stress is consistent with the accumulation of such components during aging. Correlation between hypoxia-hyperoxia and life-span remains open until we solve the question of how and why do cells sense oxygen. In other words, to better understand aging we need to know what O(2) species are being sensed by cells. In conclusion, hypoxia and hyperoxia represent an experimental model adequate for studying aging processes.
细胞生长受多种因素调节，包括影响细胞代谢的氧气供应。衰老的特征是组织氧气供应减少、组织氧分压降低以及多种酶和代谢因子的活性降低。毛细血管组织水平的氧梯度扩散对细胞存活至关重要，而动脉血中氧气的稳态由对氧气减少敏感的反射和多种因子的释放介导。衰老与细胞氧气供应减少以及组织氧气需求平行下降相关。慢性缺氧或高氧都被视为应激。事实上，在这两种情况下，都会产生损害膜结构和功能成分的自由基。活性氧（ROS）是有氧生命的生理产物，其积累会影响衰老。由于缺氧本身会调节线粒体活性，影响氧气消耗，因此缺氧和衰老可能存在一些联系。此外，在缺氧或高氧状态下，脂褐素作为对应激的一般反应而积累，这一观察结果与衰老过程中此类成分的积累一致。在我们解决细胞如何以及为何感知氧气的问题之前，缺氧 - 高氧与寿命之间的相关性仍未明确。换句话说，为了更好地理解衰老，我们需要知道细胞感知的是哪种氧物种。总之，缺氧和高氧是适合研究衰老过程的实验模型。
