Low expression of miR-203 promoted diabetic nephropathy via increasing TLR4.

Objective: To investigate the relationship between microRNA-203 (miR-203) and diabetic nephropathy and its potential mechanism.
Materials and Methods: The expression of microRNA-203 in mice with diabetic nephropathy and M4200 cells cultured with high glucose was detected by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Toll-like receptor 4 (TLR4), the target gene of microRNA-203, was predicted and screened by bioinformatics method. Real-time quantitative PCR and Western blot were used to detect the endogenous TLR4 level in renal cortex of db/db mice with diabetic nephropathy and glomerular mesangial cells cultured in high glucose or low glucose. The expression of microRNA-203 and TLR4 mRNA were evaluated by RT-PCR after treatment of miR-203 mimics and inhibitor. The protein of TLR4 level was detected by Western blot. Additionally, the proliferation ability of cells was evaluated by Cell Counting Kit-8 (CCK8). The target relationship between microRNA-203 and TLR4 3' UTR was confirmed by luciferase reporter assay RESULTS: The expression of miR-203 was significantly decreased in the kidney of mice with diabetic nephropathy and M4200 cells cultured in high glucose. On the contrary, TLR4 expression was significantly increased. Results of in vitro experiments showed that miR-203 could bind to 3'UTR region of TLR4. Overexpression of microRNA-203 significantly decreased the levels of TLR4 mRNA and protein. Meanwhile, low expression of miR-203 leaded to increased TLR4 expression, resulting in an enhanced proliferation of M4200 cells.
Conclusions: The downregulation of microRNA-203 leaded to an increased level of TLR4, thus promoting proliferation of M4200 cells in the pathogenesis of diabetic nephropathy.