Celastrol attenuates arterial and valvular calcification via inhibiting BMP2/Smad1/5 signalling

Vascular calcification is an important risk factor for the mortality and morbidity in chronic kidney disease (CKD). Unfortunately, until now there is no certain medication targeting vascular calcification in CKD. In this study, we explored the inhibitory effect of celastrol on high calcium-induced vascular calcification and the underlying molecular mechanisms. Cell proliferation assay showed that celastrol inhibited aortic valve interstitial cell (VIC) and vascular smooth muscle cell (VSMC) proliferation when its concentration was higher than 0.6 μmol/L. 0.8 μmol/L celastrol inhibited the expression of osteogenic genes and calcium deposition induced by high-calcium medium in both AVICs and VSMCs. In mouse vascular calcification model induced by adenine combined with vitamin D, alizarin red and immunostaining showed that celastrol inhibited pro-calcification gene expression and calcium deposition in aortic wall and aortic valve tissues. At the molecular level, celastrol inhibited the increase of BMP2, phosphorylated Smad1/5 (p-Smad1/5) and non-phosphorylated β-catenin (n-p-β-catenin) induced by high-calcium medium both in vitro and in vivo. Also, BMP2 overexpression reversed the anti-calcification effects of celastrol by recovering the decrease of p-Smad1/5 and n-p-β-catenin. Furthermore, celastrol prevented the up-regulation of BMPRII and down-regulation of Smad6 induced by high calcium, and this protectory effect can be abolished by BMP2 overexpression. In conclusion, our data for the first time demonstrate that celastrol attenuates high calcium-induced arterial and valvular calcification by inhibiting BMP2/Smad1/5 signalling, which may provide a novel therapeutic strategy for arterial and valvular calcification in patients with CKD.