Augmented S-nitrosylation contributes to impaired relaxation in angiotensin II hypertensive mouse aorta: role of thioredoxin reductase.

BACKGROUND

Vascular dysfunction, including reduced endothelium-dependent dilation, is a major characteristic of hypertension. We previously investigated that thioredoxin reductase (TrxR) inhibition impairs vasodilation via soluble guanylyl cyclase S-nitrosylation, but S-nitrosylation and TrxR function are not known in hypertension. We hypothesized that S-nitrosylation is associated with reduced vasodilation in hypertensive mice.

METHOD: Aortic rings from normotensive (sham) and angiotensin II (AngII)-induced hypertensive C57BL/6 mice were treated with a TrxR inhibitor, 1-chloro-2,4-dinitrobenzene (DNCB) for 30  min, and relaxation to acetylcholine (ACh) was measured in the rings following contraction with phenylephrine.

RESULTS

DCNB reduced relaxation to ACh compared with vehicle in sham aorta but not in AngII (sham-vehicle E(max) = 77 ± 2, sham-DNCB E(max) = 59 ± 4, P < 0.05). DNCB shifted the concentration-response relaxation to sodium nitroprusside (SNP) to the right in both sham and AngII aortic rings (sham-vehicle pD(2) = 8.8±0.1, sham-DNCB pD(2) = 8.4±0.1, *P < 0.05; AngII-vehicle pD(2) = 8.5±0.1, AngII-DNCB pD(2) = 8.3 ± 0.1, P < 0.05). As downstream signaling of nitric oxide, cyclic GMP level was reduced by DNCB during activation with SNP. The effect of DNCB to increase S-nitrosylation was confirmed by the biotin-switch method and western blot analysis, and total protein S-nitrosylation was increased in AngII aorta (1.5-fold) compared with sham. TrxR activity was inhibited in AngII aorta compared with sham.

CONCLUSION

We conclude that increased S-nitrosylation contributes to impaired relaxation in aorta from AngII-induced hypertensive mice. AngII treatment resulted in inactivation of TrxR and increased S-nitrosylation, indicating that TrxR and S-nitrosylation may provide a critical mechanism in hypertension associated with abnormal vascular reactivity.