Pro-oxidants

Reactive species (RS) are important factors involved in the vast majority of cell disorders. The generated oxidative damages are underlying factors implicated in many diseases including cancer, diabetes, aging. It is without question that pro-oxidants (pro-oxidant enzymes and non-enzymatic pro-oxidants) mediate oxidative stress and are at the epicenter of these pathophysiological events. Pro-oxidant enzymes (e.g., NADPH oxidase (NOX), myeloperoxidase (MPO), nitric oxide synthase (NOS), xanthine oxidase (XO), and cyclooxygenase (COX)) are of central interest in a variety of biological phenomena. A disturbance in the activity of these enzymes is in most cases in favor of the initiation of oxidative stress. Besides, several pro-oxidant components with no enzymatic activities were identified (e.g., hemoproteins, homocysteine, and transition metal ions) and can have harmful effects on cells. This chapter is an overview of the basic functions of pro-oxidant agents in biological systems. It provides a valuable summary of their physiological roles and discusses the biological consequences of their accumulation during oxidative stress.