Active vitamin D prevents podocyte injury via regulation of macrophage M1 and M2 phenotype in diabetic nephropathy rats / 中华肾脏病杂志

ABSTRACT

Objective To investigate the effect of active vitamin D (VD) on macrophage M1 and M2 phenotype and its role in protecting podocyte impairment in diabetic nephropathy (DN).Methods Diabetes mellitus rats were established by intraperitoneal injection with streptozocin.Rats were randomly divided into four groupsnormal-1 (NC-1,n=8),normal-2 (NC-2,n=8,normal rats treated with calcitriol 0.1 μg· kg-1 · d-1 by gavages),DN (n=24) and VD (n=24,DN+calcitriol 0.1 μg· kg-1 · d-1 by gavages).Blood glucose and body weight were assessed,and 24-hour urine was collected regularly.Blood and urine samples were taken for biochemical study,and kidney tissues were used for PAS staining to assess histological changes.Immunohistochemical staining was used to detect number of CD68 + macrophage.Western blotting was used to detect protein expressions of nephrin,podocin,CD68,M1 specific marker of inducible nitric oxide synthase (iNOS),TNF-α and M2 specific marker of CD163,arginase 1 (Arg-1),mannose receptor (MR).Results (1) In DN group,levels of BUN,Scr,urinary protein and glomerular mesangial matrix proliferation were significantly higher (P ＜ 0.05),and the expressions of nephrin,podocin were significantly decreased compared with NC groups (P ＜ 0.05).These above changes were significantly improved in VD group (P ＜ 0.05).(2)Number of CD68 + macrophage infiltration in DN group was increased in a time dependent manner compared with NC groups,which was significantly reduced in VD group (P ＜ 0.05).(3)To further definite M1 and M2 macrophage activation phenotype,the protein expressions of iNOS and TNF-α was increased in DN group at 8th,14th,18th weeks compared with NC groups (P ＜ 0.05),which were significantly decreased in VD group (P ＜ 0.05).Although,there were no significant difference of protein expressions of CD163,Arg-1 and MR between VD and DN group at both 8th and 14th week (P ＞ 0.05),the protein expressions of CD163,Arg-1 and MR were higher in VD group at 18th week than that in DN group (P ＜ 0.05),and the ratio of CD163/CD68 was also enhanced in VD group (P ＜0.05).(4)Moreover,the protein expression of iNOS was negatively correlated with expression of either nephrin or podocin (r =-0.707,P ＜ 0.01; r =-0.712,P ＜ 0.01),whereas the protein expression of CD163 was positively correlated with expression of either nephrin or podocin (r =0.627,P＜ 0.01; r=0.613,P ＜ 0.01).Conclusion Vitamin D can regulate macrophage phenotype,via inhibiting M 1 macrophage activation and enhancing M2 macrophage activation to protect podocyte impairment.