Reversal of eNOS uncoupling and upregulation of eNOS expression as a new therapeutic approach to cardiovascular diseases

Nitric oxide (NO) produced by the endothelial NO synthase (eNOS) represents a vasoprotective principle. Cardiovascular diseases are associated with decreased NO bioavailability and eNOS uncoupling (i.e., uncoupling of oxygen reduction from NO synthesis in eNOS). An uncoupled eNOS produces superoxide instead of NO. Therefore, compounds that increase eNOS protein levels are only beneficial when guaranteeing eNOS functionality. Recently, we have found compounds that maintain eNOS functionality in disease, and, at the same time, upregulate expression of the enzyme. Midostaurin upregulates eNOS expression through PKC-independent mechanisms and reduces NADPH oxidase expression via PKC inhibition. Oxidative stress-mediated oxidation of tetrahydrobiopterin (BH4), the essential eNOS cofactor, is likely to be a major cause for eNOS uncoupling. By reducing NADPH oxidase-mediated oxidative stress, midostaurin reverses eNOS uncoupling in spontaneously hypertensive rats and in atherosclerosis-prone apolipoprotein E knockout (apoE-KO) mice, which is associated with NO-mediated vasodilation and blood pressure reduction. AVE9488 and AVE3085 are two small-molecular weight eNOS transcription enhancers. Both compounds stimulate eNOS transcription in endothelial cells in vitro and in vascular tissues in vivo. Importantly, treatment of apoE-KO mice with AVE9488 enhances vascular BH4 levels and reverses eNOS uncoupling. In apoE-KO mice, but not in eNOS-knockout mice, treatment with AVE9488 reduces cuff-induced neointima formation. A 12-week treatment with AVE9488 or AVE3085 reduces atherosclerotic plaque formation in apoE-KO mice, but not in apoE/eNOS-double knockout mice. Also resveratrol reverses eNOS uncoupling and enhances eNOS expression. In conclusion, compounds combining eNOS upregulation with eNOS recoupling may have therapeutic potential for cardiovascular diseases