Beneficial effects of neuronal nitric oxide synthase in atherosclerosis.

Endothelial nitric oxide synthase (eNOS) is the only NOS isoform expressed in normal coronary arteries. However, all 3 NOS isoforms—eNOS, inducible NOS (iNOS), and neuronal NOS (nNOS)—are found in human atherosclerotic plaques.1 Precise studies of knockout mice have uncovered the role of eNOS and iNOS in atherogenesis (Figure). The eNOS isoform protects against atherosclerosis, because mice lacking eNOS have increased atherosclerotic plaques.2,3 In contrast, iNOS is proatherogenic: iNOS knockout mice have decreased atherosclerotic plaque area.4 However, the role of nNOS in atherogenesis has remained a mystery until now.