The mechanism of akt-mediated APPL1 in chronic renal fibrosis induced by acute renal ischemia-reperfusion injury

Abstract

Objective: To observe the protective mechanism of protein kinase B (Akt)-mediated phosphoserine binding domain and leucine zipper motif 1APPL1) on renal fibrosis in mice with renal ischemia reperfusion injury. Methods: A total of 24 male C57BL/6 mice were selected to randomly divide into 2 groups: Normal mice-sham operation group (WT-C group) and normal mice-renal ischemia reperfusion group (WT-I/R group). Forty-eight mice with APPL1 gene knockout mice were divided into 4 groups randomly:APPL1 gene knockout/sham surgery group (AK-C group), APPL1 gene knockout/renal ischemia reperfusion group (AK-I/R group), APPL1 gene knockout+Akt inhibitor treatment group (AK-L group), and APPL1 gene knockout+saline treatment group (AK-S group). Except the two control groups of WT-C ad AK-C, the renal ischemia reperfusion injury (IRI) model was prepared in the other groups. After the successful preparation of the model of bilateral renal ischemia reperfusion injury in mice, the AK-L group was intraperitoneally injected with LY294002 mg/kg, once every 24 hours till day 7, and the same dose of normal saline was injected in the AK-S group. At 24h after reperfusion, 6 mice were randomly selected from each group and detected for the concentration of serum BUN and Scr to score renal tubular injury and determine APPL1 expression and Akt phosphorylation levels in the renal tissues. At 14 days after reperfusion, 6 mice in each group were randomly sacrificed to obtain kidney tissues. The degree of renal fibrosis was evaluated; expression of collagen 1, fibronectin, α- smooth muscle actin and APLL1 and Akt phosphorylation levels in renal tissue were determined. Results: At 24h after reperfusion, comparisons of serum BUN and Scr concentrations and renal tubular injury scores showed no statistically significant difference between the WT-C group and AK-C group (P>0.05). Compared with the WT-C and AK-C groups, the levels of them in the WT-I/R group, the AK-I/R group, and the AK-S group increased (P<0.05), and the levels in the AK-L group were the highest (P<0.05). At 14 days after reperfusion, the expression of collagen 1, fibronectin and alpha smooth muscle actin in renal tissues and the degree of renal fibrosis showed no significant difference between WT-C group and AK-C group (P>0.05).  Compared with the WT-C and AK-C groups, the levels of expression of fibrosis-related indices were increased in the WT-I/R group, the AK-I/R group, and the AK-S group (P<0.05), with the highest level in the AK-L group (P<0.05).  At 24h and 14 d after reperfusion, APPL1 expression and Akt phosphorylation level in renal tissues in the WT-I/R group were up-regulated compared with those in the WT-C group (P<0.05). At 24h after reperfusion, compared with the AK-C group, Akt phosphorylation level increased in the AK-I/R group and the AK-S group (P<0.05). Compared with the AK-I/R group, Akt phosphorylation level decreased in the AK-L group (P<0.05). Conclusions APPL1 mediated by Akt has protective effect on chronic renal fibrosis in mice with renal ischemia reperfusion injury.