Inhibition of notch signaling alleviated diabetic macrovasculopathy in an in vitro model

Background: Interactions between endothelial cells and vascular smooth muscle cells (VSMCs) through the Notch signal pathway causing diabetic microvasculopathy have been reported. Objectives: The purpose of this study was to investigate whether the effect of high glucose on VSMCs through the Notch-2 signaling pathway could induce extracellular matrix (ECM) accumulation, VSMC proliferation and migration and thus directly mediate diabetic macrovasculopathy. Methods: Rat smooth muscle cells (SV40LT-SMC Clone HEP-SA cells) were cultured in different concentrations of D-glucose to evaluate the impact of high glucose on ECM accumulation including fibronectin and collagen I measured by Western blot analysis, and on VSMC proliferation and migration evaluated by MTT assay and wound healing assay. The expression of Notch-2 intra-cellular domain (Notch-2 ICD) protein was also checked in high glucose-stressed VSMCs. N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT), an inhibitor of γ-secretase, was used to modulate the Notch-2 signaling pathway. Results: High glucose (D-glucose 25 mM) induced fibronectin and collagen I expressions in VSMCs, promoted VSMC proliferation/migration, and enhanced the expression of Notch-2 ICD. DAPT inhibited Notch-2 signal to abolish the expressions of fibronectin and collagen I in VSMCs, and also prevented the proliferation/migration of VSMCs under high glucose (D-glucose 25 mM) stress. Conclusions: Our study suggests that high glucose can enhance the Notch-2 signaling pathway thereby directly mediating diabetic macrovasculopathy. Blocking the Notch-2 signaling pathway decreased fibronectin and collagen I expressions secreted by VSMCs, and reduced the proliferation and migration of VSMCs under high glucose stress. Inhibition of Notch-2 signaling represents a promising target for treating diabetic macrovasculopathy.