Oxidative Stress in Aging

Over the last decades, a new concept involving the biological effects of highly reactive species (RS) in the processes causing disease has filled the scientific field. These species, mainly free radicals (FR), are found under physiological conditions and can be beneficial when produced at low concentrations. However, they are harmful at high levels especially when the endogenous antioxidant defense systems are overwhelmed. This paradigm has been widely documented for many clinical settings, and a causal relationship has been suggested for oxidative stress (OS) in some highly prevalent pathological conditions like aging. Oxidative stress caused by the overproduction of RS plays an important role in the pathogenesis of aging and these RS derive mainly from mitochondria. This chapter provides the clinical and experimental evidence to support the role of FR in the pathophysiology of aging and senescence. The mitochondrial theory of aging is deeply discussed. It considers the role of mitochondria as source of RS resulting from partial reduction of oxygen in mammalian cells. Other theories of aging, including the free radical, reparation system, and transcription factor theories, are also presented. Besides, this chapter covers the clinical manifestations of aging and discusses novel approaches that bridges the gap between these two entities.