Abstract 680: Specific Deletion of SHP-1 in Smooth Muscle Cells Restores PDGF Action in Diabetes

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. Our laboratory has previously shown that hyperglycemia reduced platelet-derived growth factor (PDGF) 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 in smooth muscle cells both in vitro and in vivo. Methods: Non-diabetic (NDM) and 3 months diabetic (DM) mice with deletion of SHP-1 specifically in smooth muscle cells (SMC) were used. Ligation of the femoral artery was performed and blood flow reperfusion was measured by laser Doppler for 4 weeks. Primary SMC were exposed to normal (5.6mM; NG) or high glucose concentrations (25mM; HG) for 48h, in normoxia (20% oxygen) or hypoxia (1%) for the last 24h in presence of PDGF, a pro-angiogenic factor. Results: Blood flow was recovered to 47% in DM mice compared to 80% in NDM mice. Specific SMC deletion of SHP-1 enhanced reperfusion in NDM and DM mice up to 78% and 67%, respectively. In culture, PDGF-induced proliferation, migration, and Akt phosphorylation were reduced by 69%, 50% and 40%, respectively in SMC exposed to HG+hypoxia. Inhibition of PDGF actions was associated with increased SHP-1 phosphatase activity (40%) and enhanced interaction of SHP-1 with the PDGF receptor-β (5.6-fold). Overexpression of the dominant negative form of SHP-1 restored PDGF-induced proliferation and migration as well as Akt and ERK phosphorylation in SMC exposed to HG+hypoxia. Conclusion: High glucose level induced SHP-1 activity and caused inhibition of PDGF pro-angiogenic actions in SMC, whereas the deletion of SHP-1 specifically in SMC restored blood flow reperfusion in diabetes.