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Recent studies have highlighted the role of the innate immune system in initiating the inflammatory cascade which leads to detrimental changes in renal ischemia reperfusion (I/R) injury. The augmenter of liver regeneration (ALR) is an anti-apoptosis factor which is highly expressed in renal tubulars of renal cortex and medulla after inducing renal I/R injury in rats. It has been shown that exogenous ALR can enhance renal tubular regeneration. However, whether ALR's protective effect against renal I/R injury results from its immune regulatory function remains unknown. Using rat renal tubular epithelial cell (NRK-52E), we investigate the effect of recombinant rat ALR (rrALR) on immune inflammatory response in hypoxia re-oxygenation (H/R) injury in vitro, and further discuss the possible mechanisms. Cultured NRK-52E cells subjected to hypoxia for 6 h followed by re-oxygenation for 12, 24 and 72 h are administered with different doses of rrALR. Expression of Toll-like receptor 4 (TLR4) and transcription nuclear factor-κB (NF-κB) is assessed by reverse-transcriptase polymerase chain reaction (RT-PCR) and western blot. Expression of interleukin (IL)-6 and IL-1β are determined by enzyme-linked immunosorbent assay (ELISA). In rrALR intervened H/R cells, TLR4 and NF-κB are down regulated at both mRNA and protein levels compare with those in control cells. Also, rrALR appears to downregulate IL-6 and IL-1β expression in concentration-dependent manners. In conclusion, rrALR protects NRK-52E cells from H/R injury possibly by relieving the inflammatory response through regulation of TLR4-NF-κB signaling pathway.

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.