Poly (ADP-ribose) polymerase- and cytochrome c-mediated apoptosis induces hepatocyte injury in a rat model of hyperammonia-induced hepatic failure

Hepatic failure (HF) is caused by several factors, which induce liver cell damage and dysfunction. However, the specific mechanism of HF remains to be fully elucidated. The present study aimed to investigate the underlying cause of hepatocyte injury and liver dysfunction. Liver cells were isolated from healthy female Sprague-Dawley rats, aged between 6 and 8 weeks, weighing ~230 g. The liver cells were cultured in RPMI-1640 medium containing 10% fetal bovine serum. An MTT assay was used to examine the inhibitory rate of liver growth in each group. Flow cytometric analysis was performed to detect liver cells undergoing apoptosis. The protein expression levels of poly (ADP-ribose) polymerase (PARP) and cytochrome c (Cyt C) were detected by western blotting. The level of calmodulin-dependent kinase (CaMK) was assessed using an ELISA. The results indicated that the growth inhibitory rate of rat liver cells was significantly increased following treatment with increasing concentrations of NH(4)Cl. The results of flow cytometric analysis demonstrated that the apoptotic rate in the BAPTA-acetoxymethyl ester group was significantly lower compared with the NH(4)Cl group (P<0.05). Treatment with NH(4)Cl increased the protein expression levels of PARP and Cyt C in the liver cells. The mRNA expression of CaMK decreased gradually following treatment with increasing concentrations of NH(4)Cl for 6, 12 and 24 h. The results suggested that hepatocyte injury and liver dysfunction may be caused by inducing apoptosis via the PARP and Cyt C pathways. Additionally, downregulation of CaMK may be associated with the apoptosis observed in hepatocyte injury.