7-Ketocholesterol, a major oxysterol, promotes Pi-induced vascular calcification in cultured smooth muscle cells

Abstract

Aim: Oxysterols are found in high concentrations in advanced atherosclerotic plaques and are considered as an important factor in the development of vascular calcification. The purpose of this study was to investigate the effect of 7-ketocholesterol (7kc), a major oxysterol in plaques, on in vitro arterial calcification. Methods: Bovine vascular smooth muscle cells (VSMCs) were cultured with inorganic phosphate (Pi), in the presence or absence of 7kc. Calcium deposition was determined by Calcium C-rest Wako and von Kossa staining. Phenotypic change was evaluated by mRNA expression using semi-quantitative reverse transcription-polymerase chain reaction. Cell apoptosis was determined by in situ DNA fragmentation assay. Results: 7kc significantly enhanced the calcium deposition, phenotypic change of VSMCs, and apoptosis in the presence of Pi. Treatment with risedronate, a bisphosphonate, or Y-27632, an Rho kinase inhibitor, completely or partially prevented the effects induced by 7kc in the presence of Pi, respectively. Conclusion: These results suggest that 7kc, a major oxysterol, significantly accelerates vascular calcification in the presence of Pi via the mevalonate pathway and Rho-ROCK signaling pathway. Our present data provide beneficial information on the development of a therapeutic approach for arterial calcification, especially in patients with a mineral imbalance, including hypocalcaemia, hyperphosphatemia, and hypercholesterolemia.