Aims: To determine the regulatory role of a novel miRNA, miR-378, in the development of fibrosis through repression of the MAPK1 (ERK2) pathway. Methods: miR-378 and fibrotic gene expression was examined in streptozotocin (STZ)-induced diabetic mice at 18 weeks or in unilateral ureteral obstruction (UUO) mice at 7 days. miR-378 transfection of proximal tubular epithelial cells, NRK52E, and mesangial cells was assessed with/without endogenous miR-378 knockdown using the locked nucleic acid (LNA) inhibitor. NRK52E cells were co-transfected with the SMAD3 CAGA reporter and miR-378 in the presence of TGF-β1 was assessed.Results: qPCR showed a significant reduction in miR-378 (P<0.05) corresponding with upregulated type I and IV collagen, and α-smooth muscle actin (SMA) in kidneys of STZ or UUO mice, compared to controls. TGF-β1 significantly increased mRNA expression of type I collagen (P<0.05), type IV collagen (P<0.05) and α-SMA (P<0.05) in NRK52E cells, which was significantly reduced (P<0.05) following miR-378 transfection and reversed following addition of the LNA inhibitor of endogenous miR-378. Overexpression of miR-378 inhibited mesangial cell expansion and proliferation in response to TGF-β1, with LNA-miR-378 transfection reversing this protective effect, associated with cell morphological alterations. The protective function of MAPK1 on miR-378 was shown in kidney cells treated with the MAPK1 inhibitor, selumetinib, which inhibited mesangial cell hypertrophy in response to TGF-β1. Taken together, these results suggest that miR-378 acts via regulation of the MAPK1 pathway. Conclusions: These studies demonstrate the protective function of MAPK1, regulated by miR-378, in the induction of kidney cell fibrosis and mesangial hypertrophy.
- chronic kidney disease
- renal fibrosis
- extracellular signal-regulated kinases
- ©2017 The Author(s)
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