Changes in APPL1 expression during renal fibrosis in a mouse model of renal ischemia-reperfusion injury

Abstract

Objective To evaluate the changes in the expression of adaptor protein containing pleckstrin homobgy domain, phosphotyrosine-binding domain and a leucine zipper motif 1(APPL1)during renal fibrosis in a mouse model of renal ischemia-reperfusion(I/R)injury. Methods Twenty-four male C57BL/6 mice, aged 8 weeks, weighing 20-25 g, were divided into 2 groups(n=12 each)using a random number table: sham operation group(S group)and renal I/R group.The model of renal I/R injury was established by clipping the bilateral renal pedicles for 30 min followed by reperfusion in group I/R.Six mice were selected at 2 days of reperfusion, and venous blood samples were collected for determination of serum concentrations of blood urea nitrogen and creatinine.The animals were then sacrificed, the renal specimens were obtained for microscopic examination of tubular necrosis with a light microscope, and the damage to the renal tubules was scored using a semi-quantitative method.Six mice were sacrificed at 14 days of reperfusion, and the renal specimens were obtained for assessment of the degree of renal fibrosis(using picric acid-sirius red staining)and for determination of the expression of collagen type 1, fibronectin and α-smooth muscle actin in renal tissues(by Western blot or immunofluorescence method). At 2 and 14 days of reperfusion, the expression of APPL1 in renal tissues was detected by Western blot and the expression of APPL1 mRNA in renal tissues by real-time polymerase chain reaction. Results Compared with group S, the serum concentrations of blood urea nitrogen and creatinine, scores of renal tubular damage and degree of renal fibrosis were significantly increased at 2 days of reperfusion, the expression of collagen type 1, fibronectin and α-smooth muscle actin in renal tissues was up-regulated at 14 days of reperfusion, and the expression of APPL1 protein and mRNA was up-regulated at 2 and 14 days of reperfusion in group I/R(P<0.05). Conclusion Up-regulated expression of APPL1 may be involved in the process of renal fibrosis in a mouse model of renal I/R injury. Key words: Fibrosis; Kidney; Ischemia-reperfusion; Adaptor proteins, signal transducing