Abstract
Background and Aims
Metformin has been recognized to inhibit renal fibrosis through protection of proximal tubular epithelial cells from inflammation and fibrotic response. However, the role of other segments of renal tubular epithelial cells in the development of renal fibrosis remains unclear. This study aimed to investigate the profibrotic effects of TGF-beta1 and the anti-fibrotic effects of metformin in mouse inner medullary collecting duct cells using mIMCD-3 cell line.
Method
Cultured mIMCD-3 cells were treated with TGF-beta 1 and metformin either alone or in combination. The morphological change of cells was inspected under an inverted microscope. The mRNA of genes associated with renal fibrosis was evaluated by real-time quantitative PCR. The protein expression of E-cadherin, Vimentin, alpha-SMA were evaluated by Western blot.
Results
The shape of mIMCD-3 cells changed from cobblestone to spindle-like after exposure to TGF-beta 1 at 10ng/mL for 72 hours, which can be inhibited by co-treatment with metformin. TGF-beta 1 remarkably increased the expression of alpha-SMA and PAI-1, while decreased E-cadherin mRNA in mIMCD-3 cells. Metformin inhibited TGF-beta 1-induced reduction of E-cadherin and upregulation of PAI-1. The protein level of E-cadherin was also decreased and alpha-SMA increased by TGF-beta 1. Metformin inhibited TGF-beta 1-induced protein expression of alpha-SMA and vimentin, and downregulation of E-cadherin. It has been reported that impaired renal PPARα signaling promoted renal fibrosis. In this study, we found that metformin upregulated basal level of PPARα mRNA. PPARα target genes including Acadvl and Cpt1a were downregulated by TGF-beta 1 in mIMCD-3 cells, which could be prevented by metformin.
Conclusion
Metformin inhibits the profibrotic effects of TGF-beta 1 probably through suppression of EMT and maintaining PPARα signaling in mouse inner medullary collecting duct cells.
Combination of Ginsenoside Rg1 and Astragaloside IV reduces oxidative stress and inhibits TGF-β1/Smads signaling cascade on renal fibrosis in rats with diabetic nephropathy