Oxidative stress, cellular senescence and ageing

Almost a half century ago, the free radical theory of ageing proposed that the reactive oxygen species (ROS) is a key component which contributes to the pathophysiology of ageing in mammalian cells. Over the years, numerous studies have documented the role of oxidative stress caused by ROS in the ageing process of higher organisms. In particular, several age-associated disease models suggest that ROS and oxidative stress modulate the incidence of age-related pathologies, and that it can strongly influence the ageing process and possibly lifespan. The exact mechanism of ROS and oxidative stress-induced age-related pathologies is not yet very clear. Damage to biological macromolecules caused by ROS is thought to result in many age-related chronic diseases. At the cellular level, increased ROS leads to cellular senescence among other cellular fates including apoptosis, necrosis and autophagy. Cellular senescence is a stable growth arrest phase of cells characterized by the secretion of senescence-associated secretory phenotype (SASP) factors. Recent evidence suggests that cellular senescence via its growth arrest phenotype and SASP factors is a strong contributing factor in the development of age-associated diseases. In addition, we suggest that SASP factors play an important role in the maintenance of age-associated pathologies via a positive feedback mechanism. This review aims to provide an overview of ROS mechanics and its possible role in the ageing process via induction of cellular senescence.