Melatonin Ameliorates Renal Fibrosis Through the Inhibition of NF-κB and TGF-β1/Smad3 Pathways in db/db Diabetic Mice

Abstract

Objective: To investigate the effects and molecular mechanism of melatonin (MT) on NF-κB and TGF-β/Smad3 signaling pathways in db/db diabetic mice.

Methods: db/db diabetic mice were divided into five groups treated with melatonin at doses of 50, 100, 200 μg/kg, the urinary concentration was detected by ELISA, renal histology was observed in PAS paining. Mouse mesangial cells were divided into mannitol control group, normal control group, normal control + MT group, high glucose group, high glucose + different concentrations (10, 100, 1000) μmol/L MT group. The proliferation of mesangial cells was detected by EdU kit; the expression of NF-κBp65, ColⅣ and Fn were detected by laser confocal system; the concentrations and mRNA levels of ColⅣ and Fn were detected by ELISA and qRT-PCR. the expressions of ColⅣ, Fn, IκB, p-IκB, TGF-β1, Smad3 and p-Smad3 were detected by Western blot in renal tissues and mesangial cells.

Results: MT treatment could markedly improve the kidney histopathologic lesions. Compared with the db/m mice, 24 h urinary albumin excretion rate (UAER) and the expressions of ColIV, Fn, p-IκB/IκB, NF-κBp65, TGF-β1 and p-Smad3/Smad3 were decreased after melatonin treatment (p <0.05). Compared with the control group, the proliferation function of mesangial cells in high glucose group was significantly enhanced, and the expressions of ColIV, Fn, p-IκB/IκB, NF-κBp65, TGF-β1 and p-Smad3/Smad3 in mesangial cells were significantly up-regulated (p <0.05), and these changes were significantly lowered in MT treatment.

Conclusion: Melatonin can inhibit renal inflammation and fibrosis by inhibiting the NF-κB and TGF-β1/Smad3 signaling pathways, and melatonin may be a promising therapeutic target in diabetic nephropathy.

Keywords: Diabetic nephropathy; Fibrosis; Melatonin; NF-κB; Transforming growth factor-β1.