Abstract 18476: NO Resistance in Angiotensin II-Induced Hypertension is Associated With Soluble Guanylyl Cyclase Desensitization via Cysteine Oxidation
Nitric oxide (NO) stimulates soluble guanylyl cyclase (sGC) to increase cGMP, which causes vasodilation in vascular smooth muscle cells (SMC). We discovered that disease-associated blunted responses to NO are due to sGC desensitization via S-nitrosation, a thiol oxidation of cysteine (Cys). Because hypertension is associated with increased oxidative stress and NO-cGMP pathway impairment, we hypothesized that sGC is desensitized and thiol-oxidized in Angiotensin II (AngII)-induced hypertension. Infusion of AngII (0.7mg/kg/day) for 7 days increased mean arterial blood pressure (MAP; control: 98 ± 3 mmHg vs. AngII: 139 ± 13 mmHg, n=3, p<0.05) in rats and increased reactive oxygen species in the thoracic aorta compared to controls. In vivo, hypertension caused resistance to relaxation induced by NO donors in rat cremasteric arterioles (n=4, P<0.05), suggesting desensitization of sGC. In support of this, we determined that hypertension decreases NO-stimulated sGC activity (control: 985 ± 115 vs. AngII: 318 ± 99 pmol cGMP/mg tissue, n=4, p<0.01) and increases sGC S-nitrosation in aorta and lungs. Treatment with the antioxidant N-acetyl-cysteine (NAC, 10g/L in drinking water) protects from AngII-induced increased MAP and aorta oxidative stress. Our results confirm that oxidative stress is a key factor in the development of AngII-induced hypertension. To strengthen the correlation between AngII hypertension and sGC dysfunction we are investigating whether NAC treatment also prevents sGC S-nitrosation and desensitization. In vitro, we also found that AngII treatment (100nM, 4h) desensitizes sGC to NO, (60 ± 4 %, P<0.05 vs. vehicle) without affecting its expression in A7r5 SMC infected with sGC-expressing adenoviruses. Cys scanning mutagenesis of sGC identified one Cys, which mediates the AngII-induced sGC desensitization. We conclude that a) AngII-induced vascular oxidative stress impairs sGC function by increasing sGC S-nitrosation, affecting sGC activity; b) sGC impairment contributes to vascular dysfunction in hypertension. (This work was supported by NIH GM067640, HL089771).
- © 2010 by American Heart Association, Inc.