Hyperammonia induces specific liver injury through an intrinsic Ca(2+)-independent apoptosis pathway

BACKGROUND: Numerous pathological processes that affect liver function in patients with liver failure have been identified. Among them, hyperammonia is one of the most common phenomena.The purpose of this study was to determine whether hyperammonia could induced specific liver injury. METHODS: Hyperammonemic cells were established using NH(4)Cl. The cells were assessed by MTT, ELISA, and flow cytometric analyses. The expression levels of selected genes and proteins were confirmed by quantitative RT-PCR and western blot analyses. RESULTS: The effects of 20 mM NH(4)Cl pretreatment on the cell proliferation and apoptosis of primary hepatocytes and other cells were performed by MTT assays and flow cytometric analyses. Significant increasing in cytotoxicity and apoptosis were only observed in hepatocytes. The cell damage was reduced after adding BAPTA-AM but unchanged after adding EGTA. The expression levels of caspase-3, cytochrome C, calmodulin, and inducible nitric oxide synthase were increased and that of bcl-2 was reduced. The Na(+)-K(+)-ATPase activities in hyperammonia liver cells was no signiaficant difference compaired with the control group, but was decreased in astrocytes. NH(4)Cl pretreatment of primary hepatocytes promoted the activation of mitochondrial permeability transition pores and the mitochondria swelled irregularly. CONCLUSIONS: Hyperammonia induces specific liver injury through an intrinsic Ca(2+)-independent apoptosis pathway.