Roles of nitric oxide synthases in arteriosclerotic vascular disease: Insights from murine genetic models

Nitric Oxide (NO) exerts a variety of biological actions under both physiological and pathological conditions. NO is synthesized by three distinct NO synthase (NOS) isoforms, encoded by three distinct NOS genes, including neuronal (nNOS), inducible (iNOS), and endothelial NOS (eNOS), all of which are expressed in the human vascular system. Although the roles of the NOSs in arteriosclerotic vascular diseases have been described in pharmacological studies with selective and non-selective NOS inhibitors, the selectivity and specificity of the NOS inhibitors continue to be an issue of debate. To solve this issue, genetically altered animals have been established. All types of NOS gene-deficient animals have been developed, including singly, doubly, and triply NOS-deficient mice and various types of NOS Gene-Transgenic (TG) animals have also been generated, including conditional and non-conditional TG mice bearing site-specific overexpression of each NOS gene. The roles of individual NOS isoforms as well as the entire NOSs system in arteriosclerotic vascular diseases have been extensively investigated in those mice, providing pivotal insights into an understanding of the pathophysiological significance of the NOSs in human arteriosclerotic vascular diseases. The present review, which is based on studies with the murine NOS genetic models, summarizes the latest knowledge about the NOSs and arteriosclerotic vascular diseases.