Abstract 13482: Hydrogen Sulfide Stimulates Ischemic Vascular Remodeling Through Xanthine Oxidase Dependent Nitrite Reduction Activity Stimulating cGMP, HIF-1 And VEGF Mediated Angiogenesis
Introduction Hydrogen sulfide (H2S) therapy is recognized as a modulator of vascular function during tissue ischemia. Although the nitric oxide synthase (NOS) dependent mechanisms of H2S mediated protection during chronic tissue ischemia is slightly known but NOS independent nitrite reduction mechanism is still unknown. Hypothesis To determine NOS independent molecular mechanism involved in H2S regulation of NO metabolism and the importance of these effects during chronic tissue ischemia.
Methods: Left femoral artery ligation and excision were done in wild type and eNOSKO mice (n=8, each group). PBS, 0.1, 0.5 and 1mg/kg sodium sulfide (Na2S) was administered twice daily by retro-orbital injection. Hind limb perfusion was measured using a laser Doppler perfusion probe. Angiogenic and cell proliferation index were determined by the ratio of CD31 to DAPI and Ki67/ DAPI positive staining respectively. NO generation by Na2S and nitrite interaction in the presence of xanthine oxidase (XO) in endothelial cells was measured by NO analyzer. Expression of HIF-1 in ischemic tissues was measured using anti-HIF-1 immunohistochemistry. XO activity, cGMP and VEGF expression were measured by ELISA.
Result: Blood flow, angiogenic index, proliferation index, HIF-1 expression and VEGF expression were all significantly increased in mice treated with Na2S compared to PBS control. These effects were blunted by CPTIO therapy both in vivo and in vitro indicating the involvement of NO in H2S mediated ischemic tissue protection. NO generation was increased after Na2S and nitrite interaction in endothelial cell in the presence of XO. XO activity was increased in Na2S treated mice compared to PBS control indicating the involvement of XO in reduction of nitrite, formation of NO and increase level of cGMP, which were predominant in eNOS KO mice. Lastly, VEGF164 aptamer blocked sulfide induced augmentation of blood flow in mice ischemic tissue indicating VEGF164 as a primary H2S mediated ischemic angiogenesis mediator.
Conclusion: Sodium sulfide therapy restores tissue perfusion of critical limb ischemia through nitrite reduction dependent pathway that increases NO production leading to HIF-1 activation and expression of cGMP and VEGF resulting in ischemic revascularization.
- © 2012 by American Heart Association, Inc.