Hypoxia inducible factors as mediators of reactive oxygen/nitrogen species homeostasis in physiological normoxia.

Although once considered by biologists almost exclusively for their toxicity, reactive oxygen (ROS) and nitrogen (RNS) species produced within normal cells under baseline physiological conditions are now appreciated as redox regulators of a wide range of protein functions. Two families of enzymes, the NADPH oxidases (NOXs) and nitric oxide synthases (NOSs), are major sources of ROS/RNS from molecular oxygen. Aquaporins (AQPs) are membrane channels capable of transporting some ROS/RNS, in particular hydrogen peroxide and perhaps nitric oxide.