NOS3 and endothelial dysfunction: Suggested mechanisms for endothelial dysfunction include (1) interaction between NO and superoxide anion leading to increased formation of a highly unstable RNS peroxynitrite, (2) decreased expression and/or uncoupling of endothelial nitric oxide synthase (eNOS), and (3) increased levels of endogenous eNOS inhibitors such as ADMA [1].