Effect of interlukin-22 antibody on diabetic nephropathy via inhibition on Snail1 expression

AIM:To investigate the effect of interlukin-22 (IL-22) on diabetic nephropathy (DN) and its possible mechanism. METHODS:C57BL/6 mice were randomized to normal control (NC) group,DN group, DN+recombinant IL-22 (rIL-22) group and DN+IL-22 antibody (anti-IL-22) group. After successful establishment of diabetes model for 8 weeks, the mice in DN+rIL-22 group and DN+anti-IL-22 group were intraperitoneally injected with rIL-22 (200 μg/kg) and anti-IL-22 (200 μg/kg), respectively, and the mice in NC group and DN group were intraperitoneally injected with 0.1% bovine serum albumin, twice a week for 4 weeks. After the intervention, blood glucose, kidney function, 24 h urine microalbumin (m-Alb) and 24 h urine creatinine (UCr) were measured. The pathological changes of renal tissues were observed under light microscope. The mRNA expression of Snail1 was detected by qPCR. The protein levels of fibronetin (FN) and E-cadherin were determined by Western blot. RESULTS:After the intervention, the ratio of 24 h m-Alb/UCr increased significantly in other model groups compared with NC group (P<0.05). The levels of 24 h m-Alb and 24 h UCr increased significantly in DN+rIL-22 group compared with DN group (P<0.05). However, in DN+anti-IL-22 group, the levels of 24 h m-Alb, 24 h UCr and 24 h m-Alb/UCr ratio were significantly lower than those in DN group and DN+rIL-22 group (P<0.05). The tubular epithelial cell vacuolar degeneration, protein cast formation and glomerular mesangial expansion in the renal tissues from diabetic mice were observed under light microscope. The lesions were more severe in DN+rIL-22 group, but attenuated in DN+anti-IL-22 group. The mRNA expression of Snail1 increased significantly in diabetic mice (P<0.05), but decreased significantly after a 4-week intervention by anti-IL-22 (P<0.05). The expression of FN, an extracellular matrix protein, increased significantly in DN+rIL-22 group (P<0.05). The expression of E-cadherin, an epithelial-mesenchymal transition marker, decreased significantly in DN+rIL-22 group as well (P<0.05). CONCLUSION:IL-22 neutralizing antibody may attenuate microalbuminuria and delay the progression of DN via inhibition of Snail1 expression in the renal tubular epithelial cells.