Abstract: Objective To investigate the effect of Bax inhibitor-1 (BI-1) on calcification of vascular smooth muscle cells (VSMCs). Methods VSMCs were isolated from the thoracic aorta of SD rats. VSMCs or BI-1-overexpressing VSMCs (transfected with a BI-1-overexpressing plasmid) were cultured in normal medium or calcified medium containing β- glycerophosphate and calcium chloride, and the cell calcification was examined with Alizarin red staining. Enzyme-linked immunosorbent assay was used to determine the intracellular calcium content and alkaline phosphatase activity. The expression levels of Runt-related transcription factor 2 (RUNX2), bone morphogenetic protein 2 (BMP-2) and caspase-3 were detected with Western blotting. Results After 14 days of culture in the calcified medium, the VSMCs showed significantly reduced expression of BI-1 protein (P=0.001). BI-1 overexpression in the VSMCs caused a significant reduction of calcium level and alkaline phosphatase activities (P=0.0006) and lowered the expression levels of RUNX2 and BMP-2 (P=0.0001) in the cells. The VSMCs with induced calcification exhibited a significantly increased apoptosis rate, but BI-1 overexpression obviously inhibited VSMC apoptosis in the calcified medium (P=0.0003). Conclusion BI-1 may attenuate vascular calcification by inhibiting calcium deposition, osteogenic differentiation and apoptosis.

Key words: Bax inhibitor-1; vascular calcification; osteogenic differentiation; calcium deposition; apoptosis