This document discusses the roles of NADPH oxidases (NOX) enzymes in producing reactive oxygen species. It specifically focuses on NOX1, NOX2, NOX4, and NOX5. NOX1 and NOX2 produce superoxide (O2.-) and require regulatory subunits like p22phox. NOX4 produces hydrogen peroxide (H2O2) and does not require regulatory subunits. NOX5 is activated by calcium and also produces superoxide. NOX1, NOX2, and NOX4 are involved in processes like vascular remodeling, endothelial dysfunction, and improved endothelial function. The document also examines the role of NOX4 in