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Background and Aim: The progression of non-alcoholic fatty liver disease (NAFLD) likely involves a ‘multiple hit’ mechanism. We hypothesized that partial hepatectomy, a procedure performed frequently in patients with NAFLD, would accelerate the progression of disease. Methods: C57BL/6JolaHsd mice were fed a choline-deficient L-amino acid-defined diet (CD-AA) or a choline-sufficient L-amino acid-defined control diet (CS-AA). Part of the mice in the CD-AA group received a diet enriched in vitamin E (~20 mg /day). Two weeks after the start of the diet, mice underwent a partial hepatectomy or a sham operation. Results: In the CD-AA group, NAFLD activity scores were significantly higher at 7 days after partial hepatectomy compared to the sham operated mice (3.7 ± 1.3 vs. 1.8 ± 0.7; P<0.05). In addition, TBARS, a measure for oxidative stress, in liver tissue of the CD-AA group were significantly higher at day 1, 3 and 7 after partial hepatectomy compared to the sham operated mice (P<0.05). Vitamin E therapy significantly reduced TBARS level at day 7 after partial hepatectomy compared to the CD-AA diet group (P< 0.05). Vitamin E suppletion reduced NAFLD activity score at day 7 after partial hepatectomy compared to the CD-AA group (2.3 ± 0.8 vs. 3.8 ± 1.0; P<0.05). Conclusion: Partial hepatectomy accelerates the progression of NAFLD. Disease progression induced by partial hepatectomy is substantially attenuated by vitamin E. [ABSTRACT FROM AUTHOR]

Angiotensin II (AT-II) is a pro-fibrotic compound that acts via membrane-bound receptors (AT-1R/AT-2R) and thereby activates hepatic stellate cells (HSCs). AT-II receptor blockers (ARBs) are thus important candidates in the treatment of liver fibrosis. However, multiple case reports suggest that AT-1R blockers may induce hepatocyte injury. Therefore, we investigated the effect of AT-II and its receptor blockers on cytokine-, oxidative stress- and bile salt-induced cell death in hepatocytes. Primary rat hepatocytes were exposed to TNF- α /Actinomycin D, the ROS-generating agent menadione or the bile salts: glycochenodeoxycholic acid (GCDCA) and tauro-lithocholic acid-3 sulfate (TLCS), to induce apoptosis. AT-II (100 nmol/L) was added 10 minutes prior to the cell death-inducing agent. AT-1R antagonists (Sartans) and the AT-2R antagonist PD123319 were used at 1 mmol/L. Apoptosis (caspase-3 activity, acridine orange staining) and necrosis (Sytox green staining) were quantified. Expression of CHOP (marker for ER stress) and AT-II receptor mRNAs were quantified by QPCR. AT-II dose-dependently reduced GCDCA-induced apoptosis of hepatocytes (250%, p<0.05) without inducing necrosis. In addition, AT-II reduced TLCS-induced apoptosis of hepatocytes (250%, p<0.05). However, AT-II did not suppress TNF/ Act-D and menadione-induced apoptosis. Only the AT-1R antagonists abolished the protective effect of AT-II against GCDCA-induced apoptosis. AT-II increased phosphorylation of ERK and a significant reversal of the protective effect of AT-II was observed when signaling kinases, including ERK, were inhibited. Moreover, AT-II prevented the GCDCA-induced expression of CHOP (the marker of the ER-mediated apoptosis). Conclusion: Angiotensin II protects hepatocytes from bile salt-induced apoptosis through a combined activation of PI3-kinase, MAPKs, PKC pathways and inhibition of bile saltinduced ER stress. Our results suggest a mechanism for the observed hepatocyte-toxicity of Sartans (angiotensin receptor blockers, ARBs) in some patients with chronic liver injury. [ABSTRACT FROM AUTHOR]

Excessive hepatocyte apoptosis is a common event in acute and chronic liver diseases leading to loss of functional liver tissue. Approaches to prevent apoptosis have therefore high potential for the treatment of liver disease. G- protein coupled receptors (GαiPCR) play crucial roles in cell fate (proliferation, cell death) and act through heterotrimeric G-proteins. GaiPCRs have been shown to regulate lipoapoptosis in hepatocytes, but their role in inflammation- or bile acid-induced apoptosis is unknown. Here, we analyzed the effect of inhibiting GaiPCR function, using pertussis toxin (PT), on bile acid- and cytokineinduced apoptosis in hepatocytes. Primary rat hepatocytes, HepG2-rNtcp cells (human hepatocellular carcinoma cells) or H4-II-E cells (rat hepatoma cells) were exposed to glycochenodeoxycholic acid (GCDCA) or tumor necrosis factor-α (TNFα)/ actinomycin D (ActD). PT (50-200 nmol/L) was added 30 minutes prior to the apoptotic stimulus. Apoptosis (caspase-3 activity, acridine orange staining) and necrosis (sytox green staining) were assessed. PT significantly reduced GCDCA- and TNFα/ActD-induced apoptosis in rat hepatocytes (-60%, p<0.05) in a dose-dependent manner (with no shift to necrosis), but not in HepG2-rNtcp cells or rat H-4-II-E cells. The protective effect of pertussis toxin was independent of the activation of selected cell survival signal transduction pathways, including ERK, p38 MAPK, PI3K and PKC pathways, as specific protein kinase inhibitors did not reverse the protective effects of pertussis toxin in GCDCA-exposed hepatocytes. Conclusion: Pertussis toxin, an inhibitor of GaiPCRs, protects hepatocytes, but not hepatocellular carcinoma cells, against bile acid- and cytokine-induced apoptosis and has therapeutic potential as primary hepatoprotective drug, as well as adjuvant in anticancer therapy. [ABSTRACT FROM AUTHOR]