Angiotensin II-Mediated Endothelial Dysfunction: Role of Poly(ADP-ribose) Polymerase Activation

Angiotensin ll (AII) contributes to the pathogenesis of many cardiovascular disorders. Oxidant-mediated activation of poly(adenosine diphosphate-ribose) polymerase (PARP) plays a role in the development of endothelial dysfunction and the pathogenesis of various cardiovascular diseases. We have investigated whether activation of the nuclear enzyme PARP contributes to the development of AII-induced endothelial dysfunction. AII in cultured endothelial cells induced DNA single-strand breakage and dose-dependently activated PARP, which was inhibited by the AII subtype 1 receptor antagonist, losartan; the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, apocynin; and the nitric oxide synthase inhibitor, N-nitro-l-arginine methyl ester. Infusion of sub-pressor doses of AII to rats for 7 to 14 d induced the development of endothelial dysfunction ex vivo. The PARP inhibitors PJ34 or INO-1001 prevented the development of the endothelial dysfunction and restored normal endothelial function. Similarly, PARP-deficient mice infused with AII for 7 d were found resistant to the AII-induced development of endothelial dysfunction, as opposed to the wild-type controls. In spontaneously hypertensive rats there was marked PARP activation in the aorta, heart, and kidney. The endothelial dysfunction, the cardiovascular alterations and the activation of PARP were prevented by the angiotensin-converting enzyme inhibitor enalapril. We conclude that AII, via AII receptor subtype 1 activation and reactive oxygen and nitrogen species generation, triggers DNA breakage, which activates PARP in the vascular endothelium, leading to the development of endothelial dysfunction in hypertension.