benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone and Fatty-Liver

Ballooned hepatocytes in non-alcoholic steatohepatitis (NASH) generate sonic hedgehog (SHH). This observation is consistent with a cellular phenotype in which the cell death program has been initiated but cannot be executed. Our aim was to determine whether ballooned hepatocytes have potentially disabled the cell death execution machinery, and if so, can their functional biology be modeled in vitro.. Immunohistochemistry was performed on human NASH specimens. In vitro studies were performed using HuH-7 cells with shRNA targeted knockdown of caspase 9 (shC9 cells) or primary hepatocytes from caspase 3(-/-) mice.. Ballooned hepatocytes in NASH display diminished expression of caspase 9. This phenotype was modeled using shC9 cells; these cells were resistant to lipoapoptosis by palmitate (PA) or lysophosphatidylcholine (LPC) despite lipid droplet formation. During lipid loading by either PA or LPC, shC9 cells activate JNK which induces SHH expression via AP-1. An autocrine hedgehog survival signaling pathway was further delineated in both shC9 and caspase 3(-/-) cells during lipotoxic stress.. Ballooned hepatocytes in NASH downregulate caspase 9, a pivotal caspase executing the mitochondrial pathway of apoptosis. Hepatocytes engineered to reduce caspase 9 expression are resistant to lipoapoptosis, in part, due to a hedgehog autocrine survival signaling pathway.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Caspase 1; Caspase 9; Cell Line, Tumor; Down-Regulation; Fatty Liver; Gene Knockdown Techniques; Hedgehog Proteins; Hepatocytes; Humans; JNK Mitogen-Activated Protein Kinases; Lysophosphatidylcholines; Minute Virus of Mice; Non-alcoholic Fatty Liver Disease; Palmitates; Phosphorylation; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Transcription Factor AP-1

Acute fatty degeneration in the liver is caused by various agents, such as aspirin, valproic acid, and ibuprofen, that directly inhibit mitochondrial beta-oxidation of fatty acid and oxidative phosphorylation. Endogenous molecules, such as cytokines and hormones, are also known to mediate microvesicular steatosis in liver failure. In this study, we examined how interleukin-12 (IL-12) and IL-18 cause steatosis in the liver. Administration of these cytokines in combination caused marked hepatosteatosis and weight loss in mice. There were marked increases in levels of interferon-gamma (IFN-gamma), nitrite (NO(2)/NO(3)), and fibrinogen in the circulation in these mice. On the other hand, the ATP concentration and blood flow in the liver were significantly reduced. These changes, except the production of IFN-gamma and NO, were partially inhibited by Z-VAD-fmk, a synthetic tripeptide inhibitor for NO-induced caspases. These results indicate that IL-12 and IL-18 may mediate inflammatory hepatosteatosis through impairment of the microcirculation, which leads to mitochondrial dysfunction in hepatocytes.

Topics: Adenosine Triphosphate; Amino Acid Chloromethyl Ketones; Animals; Body Weight; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Fatty Liver; Female; Fibrinogen; Interferon-gamma; Interleukin-12; Interleukin-18; Laser-Doppler Flowmetry; Liver; Liver Function Tests; Mice; Mice, Inbred C57BL; Mice, Inbred MRL lpr; Mice, Knockout; Mitochondria, Liver; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitrites; Oxidation-Reduction; Regional Blood Flow; Time Factors