ABSTRACT
Objective To investigate the effect of 1,25(OH)2D3 on high glucose induced macrophage activation and its underlying signal transduction mechanism.Methods RAW 264.7 cells were used to perform cell culture,the activity of intracellular iNOS was measured.VDR siRNA and PPARγ antagonist pre-treatment with macrophages were done before using 10-8 mol/L1,25(OH)2D3 to intervene high glucose pre-incubated macrophages.M1 markers including iNOS,TNF-α,IL-12,M2 markers including MR,Arg-1,IL-10 and nuclear receptors VDR and PPARγ were separately examined.Results The iNOS activity was increased in a glucose-dose and time dependent manner.Particularly,25 mmol/L glucose at 24 h gave the maximum response.After being treated with 25 mmol/L glucose for 24 h,not only inflammatory cytokines of TNF-α,IL-12 in the supernatant were increased,but quantitative real-time PCR and Western blotting analysis showed iNOS was also up-regulated (P ＜ 0.05).However,M2 markers,i.e.MR and Arg-l were significantly decreased (P ＜ 0.05).When in the presence of 1,25(OH),D3,the trends were reversed:the markers of M1,including TNF-α,IL-12 and iNOS were obviously reduced (P ＜ 0.05),while M2 markers,IL-10,Arg-1 and MR were increased (P ＜ 0.05).In addition,VDR and PPARγ were also increased (P ＜ 0.05).However,the above effects of 1,25 (OH)2D3 were abolished when further inhibited the expression of VDR and PPARγby VDR siRNA and PPARγ antagonist.Besides,accompanied by VDR,PPARγwas also decreased upon the treatment with VDR siRNA (P ＜ 0.05).Conclusion 1,25(OH)2D3 can promote high glucose induced classically activated macrophages (M1) converting to alternatively activated macrophages (M2) and this is achieved through VDR-PPARγ pathway.