ARA290 inhibits apoptosis of renal tubular epithelial cells in diabetic rats

Objective To investigate whether erythropoietin (EPO) derived peptide ARA290 can inhibit apoptosis of renal tubular epithelial cells in diabetic rats and its possible mechanism. Methods Diabetic rat model was made by intraperitoneal injection of streptozotocin. Diabetic rats were randomly divided into diabetic model group (DM group) (physiological saline, subcutaneous injection, 0.5 ml, once per two days), ARA290 treatment group (DA group) (subcutaneous injection of ARA290 (50 U/kg), once per two days), EPOR blocking peptide+ARA290 treatment group (DAEB group) (subcutaneous injection of EPOR blocking peptide (10 μg/kg)+ARA290 (50 U/kg), once per two days), and CD131 blocking peptide+ARA290 treatment group (DACB group) (subcutaneous injection of CD131 blocking peptide (10 μg/kg)+ARA290 (50 U/kg); and normal control group (NC group) (subcutaneous injection of physiological saline, 0.5ml, once per two days) was set up at the same time. After 12 weeks of drug intervention, urinary albumin excretion rate (UAER), urinary N-acetylglucosidase (NAG) enzyme, β₂-microglobulin (β₂-MG), α₁-microglobulin (α₁-MG) and serum creatinine (Scr) were measured. The pathological changes of kidney were observed by HE staining of kidney tissue sections. The expressions of EPO receptor (EPOR) and CD131 in kidney were detected by immunofluorescence assay, the apoptosis of renal tubular epithelial cells was detected, by TUNEL assay; and the expression of Caspase-3 in kidney was detected by immunohistochemistry and western blotting. Results Immunofluorescence assay showed that EPOR and CD131 were expressed in rat kidneys, and they were co-localized; TUNEL assay showed that ARA290 could inhibit apoptosis of renal tubular epithelial cells in diabetic rats; immunohistochemistry and western blotting assay showed that ARA290 decreased caspase-3 expression in kidneys of diabetic rats; urinary biochemistry and HE staining showed that ARA290 could reduce UAER, NAG enzyme, β₂-MG, α₁-MG in diabetic rat urine, and alleviate renal pathological damage. In addition, after subcutaneous injection of ARA290 together with EPOR blocking peptide or CD131 blocking peptide into diabetic rats, the protective effects of ARA290 in inhibition of renal tubular epithelial cell apoptosis, decrease of early kidney pathological indices and alleviation of renal pathological injury in diabetic rats were weakened. Conclusions Rat kidneys express EPOR and CD131. ARA290 can inhibit the apoptosis of renal tubular epithelial cells in diabetic rats by mediation of EPOR and CD131, so as to play a renal protective role in diabetic rats.