Metformin inhibits TGF‐beta 1‐induced MCP‐1 expression through BAMBI‐mediated suppression of MEK/ERK1/2 signalling.

Aims: Metformin is a biguanide derivative widely used for the treatment of type 2 diabetes mellitus. Recent evidence demonstrates that this anti‐hyperglycaemic drug exerts renal protective effects, yet the mechanisms remain poorly understood. monocyte chemoattractant protein 1 (MCP‐1) has been recognized as a key mediator of renal fibrosis in chronic kidney diseases, including diabetic nephropathy. This study aimed to investigate the effects of metformin on transforming growth factor beta 1 (TGF‐β1)‐induced MCP‐1 expression and the underlying mechanisms in rat renal tubular epithelial cells. Methods: Rat renal tubular epithelial cell line NRK‐52E cells were stimulated with TGF‐β1 and/or metformin. The messenger RNA (mRNA) of MCP‐1 and bone morphogenetic protein and activin membrane‐bound inhibitor (BAMBI) was evaluated by real‐time quantitative polymerase chain reaction. MCP‐1 protein was measured by enzyme linked immunosorbent assay (ELISA). Total and phosphorylated extracellular signal‐regulated kinases 1/2 (ERK1/2) was evaluated by western blot. Down‐ and upregulation of BAMBI were achieved by RNA interference targeting BAMBI and lentiviral vector‐mediated overexpression of the BAMBI gene, respectively. Cell viability was analysed using Cell Counting Kit 8 (CCK‐8) reagents. Results: Stimulation with TGF‐β1 resulted in the increased expression of MCP‐1 and decreased expression of BAMBI in NRK‐52E cells. Metformin inhibited the expression of MCP‐1 in NRK‐52E cells. Pretreatment with metformin suppressed upregulation of MCP‐1 and downregulation of BAMBI, as well as phosphorylation of ERK1/2 induced by TGF‐β1. U0126, a specific inhibitor for mitogen‐activated and extracellular signal‐regulated kinase kinases 1/2 (MEK‐1/2), completely blocked TGF‐β1‐induced MCP‐1 expression. Knockdown of the BAMBI gene promoted phosphorylation of ERK1/2 and TGF‐β1‐induced expression of MCP‐1. Overexpression of BAMBI inhibited phosphorylation of ERK1/2 and TGF‐β1‐induced upregulation of MCP‐1. Conclusion: In rat renal tubular epithelial cells, metformin prevents TGF‐β1‐induced MCP‐1 expression, in which BAMBI‐mediated inhibition of MEK/ERK1/2 might be involved. Summary at a Glance: This study demonstrated that metformin can inhibit TGF‐beta 1‐induced MCP‐1 expression through BAMBI‐mediated suppression of MEK/ERK1/2 signaling in a rat renal tubular epithelial cell line, NRK‐52E. [ABSTRACT FROM AUTHOR]