Regulation of melatonin on Toll-like receptor 4 signaling in diabetic db/db mice kidneys / 中华肾脏病杂志

ABSTRACT

Objective To investigate the regulation of melatonin (MT) on Toll-like receptor 4 (TLR4) signaling in diabetic db/db mice kidneys.Methods The 48 10-week-old male db/db mice were randomly divided into db/db group,db/db+MT 50 μg/kg group,db/db+MT 100 μg/kg group and db/db+MT 200 μg/kg group,each consisting of 12 mice.These mice received i.p.injections of MT These mice received i.p.injections of MT [dissoved in phosphate buffer solution (PBS)/ dimethylsulfoxide (DMSO) solution,given every day].Alternatively,12 db/m mice served as the control group.db/m and db/db group were injected i.p.with the same volume of PBS/DMSO solution.The animals were sacrificed after 12 weeks of dosage administration.Blood glucose (BG),body weight (BW),kidney weight (KW) and 24 h urinary albumin excretion rate (UAER) were determined;Kidney pathological lesions were evaluated by renal pathological staining.Immunohistochemistry of renal TLR4,NF-κB p65,and ED-1 was performed to determine the immunoreactivity.Western blotting was used to detect the expression of renal TLR4,myeloid differentiation factor 88 (MyD88),TIR-domaincontaining adaptor inducing interferon-β (TRIF),interferon regulatory factor 3 (IRF-3) and NF-κB p65,while the mRNA expressions of renal tumor necrosis factor-α (TNF-α) and monocyte chemotactic protein-1 (MCP-1) were evaluated by real-time PCR.Results Compared with control group,the levels of BG,BW,KW and UAER were much higher in db/db mice group (P ＜ 0.01),while KW in db/db+MT (100,200 μg/kg) groups and UAER level in db/db+MT (50,100,200 μg/kg) groups were distinctly decreased compared with those in db/db group (P ＜ 0.01).In week 12 db/db mice,the glomerular mesangial expansion index and tubulointerstitial injury index were increased compared with those in db/m mice (P ＜ 0.01).The above kidney histopathologic lesions were distinctly ameliorated by 50,100,200 μg/kg MT (P ＜ 0.05).Immunohistochemistry intensity of renal TLR4,NF-κB p65 and ED-1 displayed obvious differences between db/m mice and db/db mice (P ＜ 0.01),and that were remarkably decreased in db/db+MT (50,100,200 μg/kg) mice compared with db/db mice (P ＜ 0.05).Western blotting showed that the protein expression of renal TLR4,MyD88,TRIF,IRF-3 and NF-κB p65 were stronger in db/db group compared with those in db/m group (P ＜ 0.05) and weaker in db/db+ MT (50,100,200 μg/kg) groups compared with those in db/db group (P ＜ 0.05).Futhermore,the mRNA expressions of renal MCP-1 and TNF-α were higher in db/db group compared with those in db/m group (P ＜ 0.01) and lower in db/db+MT (50,100,200 μg/kg) groups compared with those in db/db group (P ＜ 0.01).Conclusion Melatonin may partly down-regulate TLR4 signaling pathway to inhibit Inflammatory reaction and alleviate kidney injury in diabetic db/db mice.