NADPH oxidases： an overview from structure to innate mmunity-associated pathologies

Oxygen-derived free radicals, collectively termed reactive oxygen species （ROS）, play important roles in immunity, cell growth, and ceil signaling. In excess, however, ROS are lethal to cells, and the overproduction of these molecules leads to a myriad of devastating diseases. The key producers of ROS in many cells are the NOX family of NADPH oxidases, of which there are seven members, with various tissue distributions and activation mechanisms. NADPH oxidase is a multisubunit enzyme comprising membrane and cytosolic components, which actively communicate during the host responses to a wide variety of stimuli, including viral and bacterial infections. This enzymatic complex has been implicated in many functions ranging from host defense to cellular signaling and the regulation of gene expression. NOX deficiency might lead to immunosuppression, while the intracellular accumulation of ROS results in the inhibition of viral propagation and apoptosis. However, excess ROS production causes cellular stress, leading to various lethal diseases, including autoimmune diseases and cancer. During the later stages of injury, NOX promotes tissue repair through the induction of angiogenesis and cell proliferation. Therefore, a complete understanding of the function of NOX is important to direct the role of this enzyme towards host defense and tissue repair or increase resistance to stress in a timely and disease-specific manner.

NADPH oxidase family proteins:signaling dynamics to disease management

Reactive oxygen species(ROS)are pervasive signaling molecules in biological systems.In humans,a lack of ROS causes chronic and extreme bacterial infections,while uncontrolled release of these factors causes pathologies due to excessive inflammation.Professional phagocytes such as neutrophils(PMNs),eosinophils,monocytes,and macrophages use superoxide-generating NADPH oxidase(NOX)as part of their arsenal of antimicrobial mechanisms to produce high levels of ROS.NOX is a multisubunit enzyme complex composed of five essential subunits,two of which are localized in the membrane,while three are localized in the cytosol.In resting phagocytes,the oxidase complex is unassembled and inactive;however,it becomes activated after cytosolic components translocate to the membrane and are assembled into a functional oxidase.The NOX isoforms play a variety of roles in cellular differentiation,development,proliferation,apoptosis,cytoskeletal control,migration,and contraction.Recent studies have identified NOX as a major contributor to disease pathologies,resulting in a shift in focus on inhibiting the formation of potentially harmful free radicals.Therefore,a better understanding of the molecular mechanisms and the transduction pathways involved in NOX-mediated signaling is essential for the development of new therapeutic agents that minimize the hyperproduction of ROS.The current review provides a thorough overview of the various NOX enzymes and their roles in disease pathophysiology,highlights pharmacological strategies,and discusses the importance of computational modeling for future NOX-related studies.