Abstract 190: Deletion Of Shp-1 Prevents Diabetes-induced Endothelial Cell Senescence And Restores Blood Flow Reperfusion Following Ischemia

Abstract

Introduction: Ischemia due to narrowing of the femoral artery and distal vessels is also a major cause of peripheral arterial disease and morbidity affecting patients with diabetes. Diabetes-induced premature senescence of endothelial cells has been shown as a potential mechanism of poor angiogenic response to ischemia. Our laboratory has previously shown that hyperglycemia reduced vascular endothelial growth factor (VEGF) activity in ischemic muscle of diabetic mice, which was associated with increased SHP-1 expression, a protein tyrosine phosphatase. The objective of this study is to evaluate the impact of SHP-1 deletion on endothelial cell function and senescence both in vitro and in vivo . Methods: Non-diabetic (NDM) and 3 months diabetic (DM) mice with deletion of SHP-1 specifically in endothelial cells (EC) were used. Ligation of the femoral artery was performed, and blood flow reperfusion was measured by laser Doppler for 4 weeks. Primary EC were exposed to normal (5.6 mM; NG) or high glucose concentrations (25 mM; HG) for 48 h, in normoxia (20% oxygen) or hypoxia (1%) for the last 16h in presence of VEGF. Results: Blood flow reperfusion and limb function (voluntary running wheel) were reduced by 50% and 91%, respectively in DM mice as compared to NDM mice. Specific EC deletion of SHP-1 restored blood flow reperfusion by 55%, limb function by 37% and capillary density in DM mice. Moreover, ablation of SHP-1 only in EC prevented diabetes-induced p21 expression and reduction of Nrf-2. In cultured EC , overexpression of dominant negative of SHP-1 prevented HG-induced inhibition of proliferation, migration, and VEGFR2/Akt phosphorylation following VEGF stimulation. In addition, the expression of senescence markers (increased p21 and beta-galactosidase; reduced Nrf-2) in EC exposed to HG levels were reversed by overexpression of SHP-1 dominant negative. Conclusion: Ablation of SHP-1 expression in EC resulted in the prevention of hyperglycemia-induced EC senescence, reduction of VEGF actions, poor collateral vessel formation and blood flow reperfusion.