Vitamin D modulates tissue factor and protease-activated receptor 2 expression in vascular smooth muscle cells.

Clinical and epidemiologic studies reveal an association between vitamin D deficiency and increased risk of cardiovascular disease. Because vascular smooth muscle cell (VSMC)-derived tissue factor (TF) is suggested to be critical for arterial thrombosis, we investigated whether the vitamin D molecules calcitriol and paricalcitol could reduce the expression of TF induced by the proinflammatory cytokine TNF-α in human aortic VSMCs. We found that, compared with controls, incubation with TNF-α increased TF expression and procoagulant activity in a NF-κB-dependent manner, as deduced from the increased nuclear translocation of nuclear factor κ-light-chain-enhancer of activated B cells protein 65 (p65-NF-κB) and direct interaction of NF-κB to the TF promoter. This was accompanied by the up-regulation of TF signaling mediator protease-activated receptor 2 (PAR-2) expression and by the down-regulation of vitamin D receptor expression in a miR-346-dependent way. However, addition of calcitriol or paricalcitol blunted the TNF-α-induced TF expression and activity (2.01 ± 0.24 and 1.32 ± 0.14 vs. 3.02 ± 0.39 pmol/mg protein, P < 0.05), which was associated with down-regulation of NF-κB signaling and PAR-2 expression, as well as with restored levels of vitamin D receptor and enhanced expression of TF pathway inhibitor. Our data suggest that inflammation promotes a prothrombotic state through the up-regulation of TF function in VSMCs and that the beneficial cardiovascular effects of vitamin D may be partially due to decreases in TF expression and its activity in VSMCs.

Angiotensin II prevents calcification in vascular smooth muscle cells by enhancing magnesium influx.

BACKGROUND: Vascular calcification (VC) is highly prevalent in patients with chronic kidney disease (CKD). Low magnesium levels are associated with VC, and recent in vitro studies confirm a protective role of magnesium, which is mediated by its entry into the VSMCs through the Transient Receptor Potential Melastatin 7 (TRPM7) channel. The role of Angiotensin II (Ang II) on VC is still unclear. As Ang II is able to stimulate TRPM7 activity, we hypothesize that it might prevent VC. Thus, the aim of this study was to dissect the direct effect of Ang II on VC. MATERIALS AND METHODS: We worked with a model of high phosphate (HP)-induced calcification in human aortic smooth muscle cells, which resembles the CKD-related VC. RESULTS: Addition of Ang II to cells growing in HP decreased calcification, which was associated with the upregulation of the osteogenic factors BMP2, Runx2/Cbfa1, Osterix and ALP. A reduction of magnesium entry into the HP-calcifying cells was found. The treatment with Ang II avoided this reduction, which was reversed by the cotreatment with the TRPM7-inhibitor 2-APB. The protective effect of Ang II was related to AT1R-induced ERK1/2 MAPKinase activation. HP-induced calcification was also associated with the upregulation of the canonical Wnt/beta-catenin pathway, while its downregulation was related to attenuation of calcification by Ang II. CONCLUSION: As hypothesized, Ang II prevented phosphate-induced calcification in VSMCs, which appears mediated by the increase of magnesium influx and by the activation of the ERK1/2 and the inhibition of the canonical Wnt/beta-catenin signalling pathways.