Zinc Inhibits Phosphate-Induced Vascular Calcification through TNFAIP3-Mediated Suppression of NF-κB

Abstract

<b>Background</b> The high cardiovascular morbidity and mortality of patients with CKD may result in large part from medial vascular calcification, a process promoted by hyperphosphatemia and involving osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs). Reduced serum zinc levels have frequently been observed in patients with CKD, but the functional relevance of this remains unclear.<b>Methods</b> We performed experiments in primary human aortic VSMCs; klotho-hypomorphic (<i>kl/kl</i>), subtotal nephrectomy, and cholecalciferol-overload mouse calcification models; and serum samples from patients with CKD.<b>Results</b> In cultured VSMCs, treatment with zinc sulfate (ZnSO₄) blunted phosphate-induced calcification, osteo-/chondrogenic signaling, and NF-<i>κ</i>B activation. ZnSO₄ increased the abundance of zinc-finger protein TNF-<i>α</i>-induced protein 3 (TNFAIP3, also known as A20), a suppressor of the NF-<i>κ</i>B pathway, by zinc-sensing receptor ZnR/GPR39-dependent upregulation of <i>TNFAIP3</i> gene expression. Silencing of TNFAIP3 in VSMCs blunted the anticalcific effects of ZnSO₄ under high phosphate conditions. <i>kl/kl</i> mice showed reduced plasma zinc levels, and ZnSO₄ supplementation strongly blunted vascular calcification and aortic osteoinduction and upregulated aortic Tnfaip3 expression. ZnSO₄ ameliorated vascular calcification in mice with chronic renal failure and mice with cholecalciferol overload. In patients with CKD, serum zinc concentrations inversely correlated with serum calcification propensity. Finally, ZnSO₄ ameliorated the osteoinductive effects of uremic serum in VSMCs.<b>Conclusions</b> Zinc supplementation ameliorates phosphate-induced osteo-/chondrogenic transdifferentiation of VSMCs and vascular calcification through an active cellular mechanism resulting from GPR39-dependent induction of TNFAIP3 and subsequent suppression of the NF-<i>κ</i>B pathway. Zinc supplementation may be a simple treatment to reduce the burden of vascular calcification in CKD.