Acute increases in cellular protein O-GlcNAcylation have been shown to have protective effects in the heart and vasculature. We hypothesize that D-glucosamine (D-GlcN) and Thiamet-G, two agents that increase protein O-GlcNAcylation via different mechanisms, inhibit TNFα-induced oxidative stress and vascular dysfunction by suppressing inducible nitric oxide synthase (iNOS) expression. Rat aortic rings were incubated for 3h at 37 °C with D-GlcN or its osmotic control L-Glucose (L-Glc) or with Thiamet-G or its vehicle control (H2O), followed by the addition of TNFα or vehicle (H2O) for 21h. After incubation, rings were mounted in a myograph to assess arterial reactivity. 24h of incubation of aortic rings with TNFα resulted in: 1) a hypocontractility to 60 mM K+ solution and phenylephrine, 2) blunted endothelium-dependent relaxation responses to acetylcholine (ACh) and substance P, and 3) unaltered relaxing response to the calcium ionophore A23187 and the NO donor sodium nitroprusside compared to aortic rings cultured in the absence of TNFα. D-GlcN and Thiamet-G pretreatment suppressed the TNFα-induced hypocontractility and endothelial dysfunction. Total protein O-GlcNAc levels were significantly higher in aortic segments treated with D-GlcN or Thiamet G compared to controls. Expression of iNOS protein was increased in TNFα-treated rings, and this was attenuated by pretreatment with either D-GlcN or Thiamet-G. Dense immunostaining for nitrotyrosylated proteins was detected in the endothelium and media of the aortic wall, suggesting enhanced peroxynitrite production by iNOS. These findings demonstrate that acute increases in protein O-GlcNAcylation prevent TNFα-induced vascular dysfunction, at least in part, via suppression of iNOS expression.
- Vascular Dysfunction
- Aortic Ring
- Copyright © 2011, American Journal of Physiology - Heart and Circulatory Physiology