NAMPT Is A Novel Inhibitor of Vascular Calcification in Chronic Kidney Disease

BACKGROUND: Vascular calcification is very common in patients with chronic kidney disease and contributes to the increased risk of cardiovascular events. NAMPT (nicotinamide phosphoribosyltransferase), the rate-limiting enzyme in the salvage pathway of nicotinamide adenine dinucleotide, has been shown to exert an antiaging effect on vascular smooth muscle cells. However, whether NAMPT is involved in the regulation of vascular calcification remains unclear. METHODS: ELISA, immunofluorescence, and Western blot were used to detect NAMPT levels in human blood and tissues. Alizarin red staining, calcium content assay, and microcomputed tomography were used to investigate the role of NAMPT in vascular calcification. Gene expression analysis and coimmunoprecipitation were performed to elucidate the underlying mechanism. RESULTS: ELISA, immunofluorescence, and Western blot showed that NAMPT levels were increased in the blood of patients with chronic kidney disease and human calcified arterial tissues. Alizarin red staining and calcium content assay revealed that pharmacological inhibition or knockdown of NAMPT exacerbated vascular smooth muscle cell calcification, whereas overexpression of NAMPT reduced mineral deposition under osteogenic conditions. Similarly, ex vivo studies revealed that NAMPT inhibited calcification of rat and human arterial rings. Moreover, administration of NAMPT inhibitor FK866 promoted aortic calcification of chronic kidney disease rats, and smooth muscle cell–specific NAMPT knockout mice exhibited aggravated aortic calcification. Furthermore, pharmacological inhibition and knockdown of SIRT1 (sirtuin 1) abrogated the inhibitory effect of NAMPT on vascular calcification. In addition, smooth muscle cell–specific SIRT1 deficiency abrogated the protective effect of recombinant NAMPT on mouse aortic calcification. Coimmunoprecipitation and immunofluorescence assay further revealed that NAMPT inhibited the acetylation of NICD (Notch intracellular domain) and reduced the expression of HES1 (hairy and enhancer of split-1) in a SIRT1-dependent pathway. CONCLUSIONS: Our study unveils that NAMPT could serve as a novel endogenous inhibitor of vascular calcification via modulation of SIRT1-mediated deacetylation of NICD.