Reactive oxygen species and oxidative stress

Reactive oxygen species (ROS), intermediates of reduction-oxidation (redox) reactions, play an important role in many physiological processes including host defense, hormone biosynthesis, fertilization, aging, cellular signaling, and neuronal excitation. Increased ROS production (termed oxidative stress) has been implicated in various pathologies, including cardiovascular disease, cancer, and neurological disorders. In the nervous system ROS have multiple actions in that they regulate neural activity and themselves act as neurotransmitters (gasotransmitters). ROS are generated throughout the brain and influence activation of the sympathetic nervous system. Increased sympathetic excitation and diminished parasympathetic suppression of heart rate, cardiac contractility, and vascular tone are associated with cardiovascular diseases such as hypertension, heart failure, and ischemic heart disease. Molecular mechanisms responsible for regulating sympathovagal balance remain unclear, but superoxide (O2−) and hydrogen peroxide (H2O2) may be important. The present review discusses the biology of ROS and highlights the pathophysiological importance of ROS and oxidative stress in the autonomic nervous system.