Hsa_circ_0003928 regulates the progression of diabetic nephropathy through miR-136-5p/PAQR3 axis

Background: Diabetic nephropathy (DN) is one of the complications of diabetes and has a high mortality, but its specific pathogenesis is not clear. In recent years, researches on the mechanism of circRNAs in DN have been proved a lot, whereas the functional mechanism of circ_0003928 in DN remains open and it must be investigated to value its important role in DN prevention.

Methods: HK-2 cells were treated with high glucose (HG), normal glucose (NG) or Mannitol. Cell counting kit-8 (CCK8) and 5-ethynyl-2'-deoxyuridine (EdU) assays were performed to detect cell proliferation. Enzyme-linked immunosorbent assay (ELISA) was applied to analyze malondialdehyde (MDA) and superoxide dismutase 1 (SOD) levels. Flow cytometry and western blot were preformed to measure cell apoptosis. Real-time quantitative PCR (RT-qPCR) was used to test the levels of circ_0003928, miR-136-5p and progestin and adipoQ receptor family member 3 (PAQR3) mRNA. Western blot was executed to detect Bcl2 associated X (Bax), B cell leukemia/lymphoma 2 (Bcl2), smooth muscle (αSMA), apolipoprotein (C-IV) and PAQR3 levels. Luciferase reporter assay and RNA pull-down assay were used to analyze the target relationship between miR-136-5p and circ_0003928 or PAQR3.

Results: Circ_0003928 and PAQR3 expression were up-regulated, whereas miR-136-5p was decreased in DN serum and HG-induced HK-2 cells. Circ_0003928 knockdown promoted cell proliferation, and inhibit cell apoptosis, oxidative stress, and fibrosis in HK-2 cells under HG condition. MiR-136-5p silencing overturned the protective effects of si-circ_0003928 on HG-induced HK-2 cells. MiR-136-5p was targeted by circ_0003928 and directly targeted PAQR3. Overexpression of PAQR3 counteracted the inhibitory functions of circ_0003928 knockdown or miR-136-5p overexpression on HG-induced HK-2 cell injury.

Conclusion: Circ_0003928 acted as a sponge of miR-136-5p to up-regulating PAQR3 expression, and then regulate the proliferation, oxidative stress, fibrosis and apoptosis in HG-induced HK-2 cells.