Production and Detection of Reactive Oxygen Species (ROS) in Cancers

Reactive oxygen species include a number of molecules that damage DNA and RNA and oxidize proteins and lipids (lipid peroxydation). These reactive molecules contain an oxygen and include H2O2 (hydrogen peroxide), NO (nitric oxide), O-2(-) (oxide anion), peroxynitrite (ONOO-), hydrochlorous acid (HOCl), and hydroxyl radical (OH-). Oxidative species are produced not only under pathological situations (cancers, ischemic/reperfusion, neurologic and cardiovascular pathologies, infectious diseases, inflammatory diseases (1), autoimmune diseases (2), etc...) but also during physiological (non-pathological) situations such as cellular metabolism (3, 4). Indeed, ROS play important roles in many cellular signaling pathways (proliferation, cell activation 5, 6, migration 7 etc..). ROS can be detrimental (it is then referred to as oxidative and nitrosative stress) when produced in high amounts in the intracellular compartments and cells generally respond to ROS by upregulating antioxidants such as superoxide dismutase (SOD) and catalase (CAT), glutathione peroxidase (GPx) and glutathione (GSH) that protects them by converting dangerous free radicals to harmless molecules (i.e. water). Vitamins C and E have also been described as ROS scavengers (antioxidants). Free radicals are beneficial in low amounts (3). Macrophage and neutrophils-mediated immune responses involve the production and release of NO, which inhibits viruses, pathogens and tumor proliferation (8). NO also reacts with other ROS and thus, also has a role as a detoxifier (ROS scavenger). Finally NO acts on vessels to regulate blood flow which is important for the adaptation of muscle to prolonged exercise (9, 10). Several publications have also demonstrated that ROS are involved in insulin sensitivity (11, 12). Numerous methods to evaluate ROS production are available. In this article we propose several simple, fast, and affordable assays; these assays have been validated by many publications and are routinely used to detect ROS or its effects in mammalian cells. While some of these assays detect multiple ROS, others detect only a single ROS.