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Mitochondria play a central role in cellular energy metabolism. Oxidative phosphorylation occurs in the electron transport system of the inner mitochondrial membrane. Cytochrome aa3, b and c1 are encoded by mitochondrial DNA whereas cytochrome c is encoded by the nuclear gene, and these mitochondrial-DNA dependent cytochromes are decreased and electron transport at complex II, III and IV is disturbed in liver carcinomas and during carcinogenesis. The more the decreased cytochrome and oxidase activity are seen, the more significant is the increase in reactive oxygen species (ROS) production. ROS produced in mitochondria may be the main cause of nuclear-gene mutation in carcinogenesis. The mitochondrial dysfunction and overproduction of ROS plays a key role in progression of chronic hepatitis C and ethanol-induced liver injury. Ethanol also causes bacterial translocation in the intestine and the resulting lipopolysaccharides (LPS) activates Kupffer cells to produce pro-inflammatory cytokines. We suspect that non-alcoholic steatohepatitis (NASH) also is the result of increased ROS production in Kupffer cells and hepatocytes.

Altered gene expression in liver sinusoidal endothelial cells (SEC) is associated with a variety of aspects of liver pathophysiology. It is, therefore, possible to envision a new therapeutic strategy for treatment of intractable liver diseases and achievement of graft-specific immunotolerance through modulation of SEC functions by genetic engineering. The SEC possesses unique hyaluronan receptors that recognize and internalize hyaluronic acid (HA). This characteristic was used in the development of a system for targeting foreign DNA to SEC. A gene carrier system was prepared by coupling HA oligomers to poly L-lysine (PLL) in a 1:1 weight ratio by reductive amination reaction. The resulting copolymer (PLL-g-HA) was mixed with various amounts of DNA in 154 mM NaCl. Inter-polyelectrolyte complex formation between PLL-g-HA and DNA exhibited minimal self-aggregation, explaining the highly soluble nature of the complex. Complex formation between PLL-g-HA and DNA was further assessed with a gel retardation assay. The titration point representing the minimum proportion of PLL-g-HA required to retard the DNA completely occurred at a 1:1 copolymer (based on PLL) to DNA charge ratio. Following intravenous injection of (32)P-labeled pSV beta-Gal plasmid complexed to PLL-g-HA in Wistar rats, >90% of the injected counts were shown to be taken up by the liver. Further, it was shown that the PLL-g-HA/DNA complex was distributed exclusively in the SEC. At 72 h after injection of 90 mug of pSV beta-Gal in a PLL-g-HA-complexed form, a large number of SEC expressing beta-galactosidase were detected. So, the PLL-g-HA/DNA system permits targeted delivery of exogenous nucleotide agents selectively to the liver SEC, providing a novel strategy for manipulation of SEC functions.

Chronic cholestasis often results in premature death from liver failure with fibrosis; however, the molecular mechanisms contributing to biliary cirrhosis are not demonstrated. In this article, we show that the death signal mediated by TNF-related apoptosis- inducing ligand (TRAIL) receptor 2/death receptor 5 (DR5) may be a key regulator of cholestatic liver injury. Agonistic anti-DR5 monoclonal antibody treatment triggered cholangiocyte apoptosis, and subsequently induced cholangitis and cholestatic liver injury in a mouse strain-specific manner. TRAIL- or DR5-deficient mice were relatively resistant to common bile duct ligation-induced cholestasis, and common bile duct ligation augmented DR5 expression on cholangiocytes, sensitizing mice to DR5-mediated cholangitis. Notably, anti-DR5 monoclonal antibody-induced cholangitis exhibited the typical histological appearance, reminiscent of human primary sclerosing cholangitis. Human cholangiocytes constitutively expressed DR5, and TRAIL expression and apoptosis were significantly elevated in cholangiocytes of human primary sclerosing cholangitis and primary biliary cirrhosis patients. Thus, TRAIL/DR5-mediated apoptosis may substantially contribute to chronic cholestatic disease, particularly primary sclerosing cholangitis. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we evaluated whether hepatic steatosis affects the viral response to interferon (IFN) and ribavirin combination therapy in Japanese patients with chronic hepatitis C (CHC). Eighty CHC patients treated with IFN α-2b and ribavirin for 24 weeks were evaluated retrospectively. Liver biopsy specimens were assessed histopathologically, and grade of steatosis was scored as follows: grade 0: <5%; grade 1: 5–33%; grade 2: 33–66%; grade 3: >66%. Sustained viral response (SVR) was defined as negative for HCV-RNA by high-sensitivity qualitative reverse transcription-polymerase chain reaction (RT-PCR) at 24 weeks post-treatment. Hepatic steatosis graded 2 and higher was seen in 28.8% patients, whose average BMI were significantly higher than those in grade 0 patients. Grade of steatosis was well correlated with elevation in serum aminotransferases and gamma-glutamyltranspeptidase (γ-GTP) levels, but not with histological degree of inflammation and fibrosis. The SVR rates were significantly lower in the group with overt steatosis (grade 2/3) as compared to the group with less steatosis (grade 0/1), the values being 30.4% and 57.9%, respectively. Moreover, grade of steatosis was selected as an independent negative factor for SVR in multivariate analysis. In conclusion, hepatic steatosis is an important predictor of poor response to therapy of IFNα-2b and ribavirin in patients with CHC. [Copyright &y& Elsevier]

Mitochondria play a central role in cellular energy homeostasis, metabolism, and cell death. Mitochondria generate energy via the electron transport chain located in the inner membrane for the synthesis of ATP. In the mitochondrial respiratory pathway, leakage of electrons induces the production of reactive oxygen species involved in the cellular aging and DNA damage. It is suggested that liver carcinogenesis, chronic hepatitis C, alcoholic liver disease and non-alcoholic fatty liver disease are the result of reactive oxygen species production because of mitochondrial dysfunction. The advancement of therapeutic approaches to protect mitochondria heralds a new strategy to halt progressive liver diseases and carcinogenesis. [Copyright &y& Elsevier]

The author reflects on the purpose and development of the Symposium Organizing Committee. According to the author, the symposium aims to provide good opportunities to discuss liver disease and its pathophysiology from the viewpoints of energy metabolism in mitochondria and oxidative stress. He added that 30 excellent speakers were invited from around the world in this symposium.

Accumulating lines of evidence suggest a possibility that glycine is useful as an immuno-modulating amino acid. Glycine most likely prevents the lipopolysaccharide (LPS)-induced elevation of intracellular Ca2+ concentration in Kupffer cells, thereby minimizing LPS receptor signaling and cytokine production. Moreover, it was reported that dietary glycine inhibits the growth of tumors. Vascular endothelial growth factor (VEGF) plays a critical role in cancer progression by promoting new blood vessel formation. Activation of VEGF receptor has been shown to result in activation of phospholipase C-γ and increases in intracellular Ca2+ concentration. The VEGF-induced cell proliferation is dependent on intracellular Ca2+ concentration. The effects of glycine on VEGF-induced increases in intracellular Ca2+ concentration in endothelial cell line (CPA) were studied. The VEGF increased intracellular Ca2+ concentration rapidly, but glycine blunted increases in intracellular Ca2+ concentration due to VEGF. Further, the inhibitory effects of glycine were prevented by low concentrations of strychnine (1 µmol/L) or incubation with chloride-free buffer. Moreover, glycine increased influx of radiolabeled chloride into CPA cells approximately 10-fold. Furthermore, mRNA 92% identical to the β-subunit of the glycine-gated chloride channel from spinal cord was identified in endothelial cells using reverse transcription–polymerase chain reaction. Finally, glycine significantly diminished serum-stimulated proliferation and migration of endothelial cells. These data indicate that the inhibitory effect of glycine on growth and migration of endothelial cells is due to activation of a glycine-gated chloride channel. This hyperpolarizes the cell membrane and blocks influx of Ca2+, thereby minimizing growth factor-mediated signaling. Therefore, glycine can be used not only for treatment of inflammation, but also for chemoprevention and treatment of carcinoma. [ABSTRACT FROM AUTHOR]

The hepatotoxic effects of alcohol have been described in detail, but mechanisms underlying the hepatotoxicity have been only partially characterized. Recently, increasing lines of evidence indicate that Kupffer cells play multiple roles in initiation and progression of alcoholic steatohepatitis. After ethanol exposure, Kupffer cells are activated via a mechanism dependent on gut-derived endotoxin, and release active mediators such as proinflammatory cytokines and eicosanoids. These mediators are responsible for the pathophysiology of alcoholic steatohepatitis. This review discusses the current concept of Kupffer cell-mediated steatohepatitis and how it relates to the hypothesis on the mechanism by which alcoholic steatohepetitis is caused, as well as several key issues that have to be addressed in this field: (i) How do Kupffer cells undergo priming and activation during alcoholic steatohepatitis?; (ii) What kind of mediators are involved?; and (iii) How does the concept translate into a strategy for therapeutics of alcoholic steatohepatitis? [ABSTRACT FROM AUTHOR]

Obesity and insulin resistance are the key factors for progression of hepatic fibrosis in various chronic liver diseases including non-alcoholic steatohepatitis (NASH). Recently it has been shown that leptin plays a pivotal role in development of hepatic fibrosis. Leptin promotes hepatic fibrogenesis through upregulation of transforming growth factor-β in Kupffer cells and sinusoidal endothelial cells. Further, leptin facilitates proliferation and prevents apoptosis of hepatic stellate cells. There is a paradox, however, in that ob/ob mice and Zucker rats, which are the obese and diabetic strains, had minimal profibrogenic responses in the liver, most likely because they lack leptin and its receptors. To establish a more clinically relevant model to study the mechanism of fibrogenesis under steatohepatitis, fatty changes and profibrogenic responses in the liver caused by methionine–choline deficiency (MCD) were investigated in the KK-Ay mouse, which is an obese and diabetic strain. KK-Ay mice developed more severe hepatic steatosis, inflammation and fibrosis induced by an MCD diet as compared to C57Bl/6 controls. Importantly, KK-Ay mice lack physiological upregulation of adiponectin levels, suggesting that adiponectin plays a pivotal role not only in regulation of insulin sensitivity but also in modulation of inflammatory and profibrogenic responses in dietary steatohepatitis. Collectively, these findings support the hypothesis that the balance of adipocytokine expression is a key regulator for the progression of hepatic fibrosis in the setting of steatohepatitis. [ABSTRACT FROM AUTHOR]

Acetaminophen overdose causes liver injury by mechanisms involving glutathione depletion, oxidative stress and mitochondrial dysfunction. The role of apoptosis in acetaminophen-induced cell killing is still controversial. Here, our aim was to evaluate the mitochondrial permeability transition (MPT) as a key factor in acetaminophen-induced necrotic and apoptotic killing of primary cultured mouse hepatocytes. Acetaminophen (10 μmol/L) induced necrotic killing in approximately 50% of hepatocytes after 6 h and cyclosporin A (CsA), MPT inhibitor, temporarily decreased necrotic killing after 6 h, but cytoprotection was lost after 16 h. Confocal microscopy revealed mitochondrial depolarization and inner membrane permeabilization at approximately 4.5 h after acetaminophen. CsA delayed these changes indicative of the MPT to about 11 h after acetaminophen. TUNEL labeling and caspase 3 activation also increased after acetaminophen. Fructose (20 mmol/L, an ATP-generating glycolytic substrate) plus glycine (5 mmol/L, a membrane stabilizing amino acid) prevented nearly all necrotic cell killing but paradoxically increased apoptosis. In conclusion, acetaminophen induces the MPT and ATP-depletion-dependent necrosis or caspase-dependent apoptosis as determined, in part, by ATP availability from glycolysis. [ABSTRACT FROM AUTHOR]