miR-92b-5p attenuates renal injury and inflammatory response in diabetic nephropathy rats by targeting HMGB1

AIM To investigate the effect of microRNA-92b-5p （miR-92b-5p） on renal injury and inflammatory response in diabetic nephropathy （DN） rats and its mechanism. METHODS The rats were divided into control group， DN group， lentiviral negative control （LV-NC） group， LV-miR-92b group， LV-high mobility group protein B1 （LV-HMGB1） group and miR-92b+HMGB1 group， with 15 rats in each group. After fasting for 12 h， the model rats were intraperitoneally injected with streptozotocin at dose of 60 mg/kg， and the control rats were intraperitoneally injected with an equal volume of citrate buffer. Three days later， the rats in each treatment group were intravenously injected with 100 μL LV-NC， LV-miR-92b and LV-HMGB1 （1×10¹¹ U/L） twice a week for 8 consecutive weeks. Urinary protein， blood glucose， blood urea nitrogen and serum creatinine were detected by an automatic biochemical analyzer. The expression of miR-92b-5p and HMGB1 mRNA was detected by RT-qPCR. The targeting relationship between miR-92b-5p and HMGB1 was verified by dual-luciferase reporter assay. HMGB1 expression in kidney tissue was detected by Western blot. The kidney damage was observed by HE staining. The apoptosis was detected by flow cytometry. The levels of interleukin-6 （IL-6）， IL-1β and tumor necrosis factor-α （TNF-α） in renal tissues were detected by ELISA. RESULTS In DN model rats， miR-92b-5p was down-regulated， while HMGB1 was highly expressed. There was a binding site between miR-92b-5p and HMGB1 3'-untranslated region. High expression of miR-92b-5p inhibited the luciferase activity of the wild-type HMGB1 plasmid （P<0.01）， but had no effect on the luciferase activity of the mutant HMGB1 plasmid. Compared with DN group， urinary protein， blood glucose， serum creatinine and blood urea nitrogen in LV-miR-92b group were significantly reduced （P<0.01）. The degree of hyperplasia， swelling and inflammatory cell infiltration of glomerular mesangium and basement membrane tubules， the apoptosis rate of renal tissues， and the content of IL-6， IL-1β and TNF-α in renal tissues were significantly decreased （P<0.01）. Co-transfection of LV-HMGB1 significantly reversed the effect of miR-92b-5p on DN rats. CONCLUSION miR-92b-5p reduces renal injury and inflammatory response in DN rats by targeting HMGB1 and down-regulating its expression.