Cyclooxygenase-2/sclerostin mediates TGF-β1-induced calcification in vascular smooth muscle cells and rats undergoing renal failure

In this study, we studied the effect and possible mechanism of TGF-β1 on vascular calcification. We found that the serum levels of TGF-β1 and cycloxygenase-2 (COX-2) were significantly increased in patients with chronic kidney disease. Phosphate up regulated TGF-β1 in vascular smooth muscle cells (VSMCs). TGF-β1 decreased the markers of VSMCs, but increased osteogenic markers and calcification in aortic segments. The phosphate-induced osteogenic markers were reduced by the TGFβR I inhibitor (LY364947), which also attenuated the potential of phosphate to reduce VSMC markers in VSMCs. Both phosphate and TGF-β1 increased the protein level of β-catenin, which was partially mitigated by LY364947. TGF-β1 decreased sclerostin, and exogenous sclerostin decreased the mineralization induced by TGF-β1. LY364947 reduced the phosphate and TGF-β1 induced COX-2. Meanwhile, the effects of TGF-β1 on osteogenic markers, β-catenin, and sclerostin, were partially reversed by the COX-2 inhibitor. Mechanistically, we found that p-Smad2/3 and p-CREB were both enriched at the promoter regions of sclerostin and β-catenin. TGF-β1 and COX-2 were significantly elevated in serum and aorta of rats undergoing renal failure. Therapeutic administration of meloxicam effectively ameliorated the renal lesion. Our results suggested that COX-2 may mediate the effect of TGF-β1 on vascular calcification through down-regulating sclerostin in VMSCs.