ABSTRACT
OBJECTIVE To investigate the mechanism of nicotinamide mononucleotide (NMN) on inflammation and fibrosis between endogenous nicotinamide phosphoribosyltransferase (NAMPT) and bone morphogenetic protein 7 (BMP-7) in diabetic glomerular cells.METHODS ① In vivo,spontaneous diabetic C57/BL6 mice and wild C57/BL6 mice were divided into two groups.When blood glucose was above (34.2±1.9) mmol· L-1,renal histology of diabetic mice became obvious.The protein expressions of Nampt and nuclear transcription factors-kappa B p65 (NF-κB p65),silent mating type information regulation 2 homolog 1 (SIRT1) and BMP7 were analyzed by lengths of immunofluorescence.② In vitro,rats' glomerular cells HBZY-1 were incubated with glucose 200 mmol· L-1 for different lengths of time (0,24,48 and 72 h) and at different concentrations of NMN (0,50,100 and 200 iμmol· L-1).The protein levels of Nampt and BMP7 were detected by Western blotting and the protein expressions of NF-κB p65 and α-SMA were measured by immunofluorescence assay.The protein levels of Nampt,BMP7 and NF-κB p65 were detected by Western blotting after HBZY-1 cells were treated with NMN 100 μmol· L-1 and FK866 10 μmol· L-1 for 24 h.RESULTS ① In vivo,the glomeruli of diabetic C57/BL6 mice showed obvious atrophy.Fluorescence intensity of Nampt was increased (P＜0.05),but that of BMP7 and SIRT1 in renal glomeruli cells was decreased compared with the wild type (P＜0.01).② In vitro,HBZY-1 cells were cultured in glucose 200 mmol· L-1 for 48 and 72 h.The protein expression of NAMPT was increased,but that of BMP7 was decreased (P＜0.05,P＜0.01).Expressions of NF-κB p65 and α-SMA were increased (P＜0.01) by immunofluorescence.The expression of BMP7 was increased after treatment with glucose 200 mmol· L-1,followed by NMN 50,100 and 200 μmol · L-1 for 24 h (P＜0.01).The expressions of NAMPT and NF-κB p65 were decreased (P＜0.01).The expressions of Nampt and NF-κB p65 in glucose 5.6 mmol· L1 +FK866 and glucose 5.6 mmol· L-1+ NMN groups were increased (P＜0.01),but the expression of BMP7 did not change.CONCLUSION Upregulation of endogenous Nampt obviously intervenes in BMP7 expression in the process of glomerular inflammatory fibrosis in severe diabetes.NMN can affect the protein expression of BMP7 via a special Nampt signaling pathway.