Abstract 15487: Boosting Autophagy for the Reduction of Diabetes-Induced Endothelial Dysfunction

Abstract

Introduction: Diabetes is one of the main cause of endothelial dysfunction. The molecular mechanisms underlying the effects of hyperglycaemia in endothelial cells still need to be clarified. Autophagy, a stress-responsive and self-renewal mechanism exerts beneficial effects in the cardiovascular system. However, its role in diabetes-induced endothelial dysfunction is unknown. Hypothesis: Endothelial autophagy is impaired in the presence of diabetes and restoration of autophagy may reduce diabetes-induced endothelial damage. Methods: The effects of hyperglycaemia (HG, 30 mM for 6 and 24 hours) on autophagy, mitophagy and endothelial function were evaluated in vitro in human umbilical endothelial cells (HUVEC). Vascular reactivity experiments were performed in mesenteric arteries from wild-type mice (WT) treated with HG and in human saphenous veins from patients with peripheral artery diseases. Autophagy reactivation was carried out through ATG7 overexpression (ATG7ov) or through spermidine (SP) (100 nM), a natural activator of autophagy and inhibitor of p300. Results: HG reduces autophagy (0.6 fold p<0.05) and mitophagy (1.5 fold p<0.001) in endothelial cells. HG also inhibits stress-induced autophagy in cells undergoing hypoxia (0.6 fold p<0.05). ATG7ov rescues apoptosis (0.52 fold p<0.05) and angiogenesis (2.3 fold p<0.05) in HUVEC exposed to HG treatment. We found increased expression of the histone acetyltransferase p300 (2.27 fold p<0.05), a known inhibitor of autophagy. Knockout mice of autophagy (Beclin 1 +/-) show a reduction in endothelial-dependent vasorelaxation compared to WT mice in response to HG (-19.16 % +-4.97 SEM vs -48.39 % +-2.18 SEM p<0.001). Autophagy reactivation through ATG7ov or spermidine rescues endothelial-dependent relaxation in WT mice treated with HG (ATG7ov -62.48 % +-5.16 SEM; SP -63.01 +-3.22 SEM; HG -40.67 % +-3.82 p<0.001). Finally, we demonstrated that SP improves vascular function in human veins (-37.6 % +-12.76 SEM vs -12.52 % +-5.6 SEM p<0.001). Conclusions: The impairment of autophagy in response to diabetes contributes to endothelial dysfunction. Boosting autophagy with natural activators of autophagy may be a suitable intervention to reduce vascular damage in the presence of metabolic stress.