Augmenter of Liver Regeneration Attenuates Tubular Cell Apoptosis in Acute Kidney Injury in Rats: The Possible Mechanisms

Augmenter of liver regeneration (ALR), the expression of which increased in rat kidneys after renal ischemia/reperfusion (I/R) injury, enhances renal tubular cell regeneration in vivo and in vitro. We aimed to investigate the effects of ALR on apoptosis of renal tubular cells after renal I/R injury in vivo and consider the possible mechanisms. Rats that were subjected to bilateral renal ischemia for 60 min followed by reperfusion were administered with either vehicle or recombinant human ALR (rhALR). Renal dysfunction and histologic injury were assessed by the measurement of serum biochemical markers and histological grading. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL). Caspase-3 activity was measured using a colorimetric protease assay. Expression of Bcl-2, Bax Fas, phosphorylated-Akt (p-Akt), and phosphorylated-p53 (p-p53) was determined by western blotting. Compared with vehicle-treated rats, renal dysfunction and histologic injury were significantly attenuated by administration of rhALR. The number of TUNEL-positive tubular cells and caspase-3 activity were decreased, Bcl-2 and p-Akt expression was up-regulated, and Bax and p-p53 expression was down-regulated by administration of rhALR. However, administration of rhALR had no effect on Fas protein expression. These results indicate that the protective effect of rhALR on renal I/R injury is associated with its anti-apoptotic action in renal tubular cells. RhALR inhibits apoptosis by increasing the ratio of Bcl-2 to Bax and by decreasing the activity of caspase-3. The activation of Akt and inactivation of p53 are involved in the rhALR anti-apoptosis process.