Inhibition of Notch Signaling Alleviated Diabetic Macrovasculopathy in an In Vitro Model

Interactions between endothelial cells and vascular smooth muscle cells (VSMCs) through the Notch signal pathway causing diabetic microvasculopathy have been reported.

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.

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.

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.

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.