Ethanol-induced apoptosis in polarized hepatic cells possibly through regulation of the Fas pathway

Alcohol-induced Golgiphagy is triggered by the downregulation of Golgi GTPase RAB3D

The development of alcohol-associated liver disease (ALD) is associated with disorganized Golgi apparatus and accelerated phagophore formation. While Golgi membranes may contribute to phagophores, association between Golgi alterations and macroautophagy/autophagy remains unclear. GOLGA4/p230 (golgin A4), a dimeric Golgi matrix protein, participates in phagophore formation, but the underlying mechanism is elusive. Our prior research identified ethanol (EtOH)-induced Golgi scattering, disrupting intra-Golgi trafficking and depleting RAB3D GTPase from the trans-Golgi. Employing various techniques, we analyzed diverse cellular and animal models representing chronic and chronic/binge alcohol consumption. In trans-Golgi of non-treated hepatocytes, we found a triple complex formed between RAB3D, GOLGA4, and MYH10/NMIIB (myosin, heavy polypeptide 10, non-muscle). However, EtOH-induced RAB3D downregulation led to MYH10 segregation from the Golgi, accompanied by Golgi fragmentation and tethering of the MYH10 isoform, MYH9/NMIIA, to dispersed Golgi membranes. EtOH-activated autophagic flux is evident through increased WIPI2 recruitment to the Golgi, phagophore formation, enhanced LC3B lipidation, and reduced SQSTM1/p62. Although GOLGA4 dimerization and intra-Golgi localization are unaffected, loss of RAB3D leads to an extension of the cytoplasmic N terminal domain of GOLGA4, forming GOLGA4-positive phagophores. Autophagy inhibition by hydroxychloroquine (HCQ) prevents alcohol-mediated Golgi disorganization, restores distribution of ASGR (asialoglycoprotein receptor), and mitigates COL (collagen) deposition and steatosis. In contrast to short-term exposure to HCQ, extended co-treatment with both EtOH and HCQ results in the depletion of LC3B protein via proteasomal degradation. Thus, (a) RAB3D deficiency and GOLGA4 conformational changes are pivotal in MYH9-driven, EtOH-mediated Golgiphagy, and (b) HCQ treatment holds promise as a therapeutic approach for alcohol-induced liver injury.Abbreviation: ACTB: actin, beta; ALD: alcohol-associated liver disease; ASGR: asialoglycoprotein receptor; AV: autophagic vacuoles; EM: electron microscopy; ER: endoplasmic reticulum; EtOH: ethanol; HCQ: hydroxychloroquine; IP: immunoprecipitation; KD: knockdown; KO: knockout; MYH10/NMIIB: myosin, heavy polypeptide 10, non-muscle; MYH9/NMIIA: myosin, heavy polypeptide 9, non-muscle; PLA: proximity ligation assay; ORO: Oil Red O staining; PM: plasma membrane; TGN: trans-Golgi network; SIM: structured illumination super-resolution microscopy.

Alcohol-Induced Liver Injury: Down-regulation and Redistribution of Rab3D Results in Atypical Protein Trafficking

Previous work from our laboratories has identified multiple defects in endocytosis, protein trafficking, and secretion, along with altered Golgi function after alcohol administration. Manifestation of alcohol-associated liver disease (ALD) is associated with an aberrant function of several hepatic proteins, including asialoglycoprotein receptor (ASGP-R), their atypical distribution at the plasma membrane (PM), and secretion of their abnormally glycosylated forms into the bloodstream, but trafficking mechanism is unknown. Here we report that a small GTPase, Rab3D, known to be involved in exocytosis, secretion, and vesicle trafficking, shows ethanol (EtOH)-impaired function, which plays an important role in Golgi disorganization. We used multiple approaches and cellular/animal models of ALD, along with Rab3D knockout (KO) mice and human tissue from patients with ALD. We found that Rab3D resides primarily in trans- and cis-faces of Golgi; however, EtOH treatment results in Rab3D redistribution from trans-Golgi to cis-medial-Golgi. Cells lacking Rab3D demonstrate enlargement of Golgi, especially its distal compartments. We identified that Rab3D is required for coat protein I (COPI) vesiculation in Golgi, and conversely, COPI is critical for intra-Golgi distribution of Rab3D. Rab3D/COPI association was altered not only in the liver of patients with ALD but also in the donors consuming alcohol without steatosis. In Rab3D KO mice, hepatocytes experience endoplasmic reticulum (ER) stress, and EtOH administration activates apoptosis. Notably, in these cells, ASGP-R, despite incomplete glycosylation, can still reach cell surface through ER-PM junctions. This mimics the effects seen with EtOH-induced liver injury. Conclusion: We revealed that down-regulation of Rab3D contributes significantly to EtOH-induced Golgi disorganization, and abnormally glycosylated ASGP-R is excreted through ER-PM connections, bypassing canonical (ER→Golgi→PM) anterograde transportation. This suggests that ER-PM sites may be a therapeutic target for ALD.

Diterpene pekinenal from euphorbia pekinensis radix induced IEC-6 cells apoptosis mediated by mitochondria and death receptors

Pekinenal, a diterpenoid from the roots of Euphorbia pekinensis Rupr., can cause serious intestinal toxicity. However, its toxic mechanism hasn't been comprehensively understood. This present study aims to clarify its toxic effects and investigate the potential mechanism. In vitro effects of pekinenal on cell proliferation, cell cycle and apoptosis were examined by performing experiments on rat intestinal crypt epithelial cells (IEC-6). Proteins and enzymes involved in cell apoptotic pathways were detected by Western blot and enzyme-linked immunosorbent assay (ELISA), and related mRNAs were detected by RT-PCR. The results showed that the cell cycle was arrested in G0/G1 phase, and apoptotic morphology changes in pekinenal-treated cells. Furthermore, pekinenal up-regulated the expression level of apoptotic protein including Bax, AIF, Apaf-1 and the expression level of mRNA such as Fas, FasL, TNFR1 and NF-κB, while down-regulated the expression level of Bcl-2, ultimately triggering the apoptosis of caspase dependence. In conclusion, the above data confirmed that pekinenal inhibited the proliferation of IEC-6 cells and induced cells apoptosis by modulating mitochondrial and death receptor pathways.

Arctium lappa L. root extract induces cell death via mitochondrial-mediated caspase-dependent apoptosis in Jurkat human leukemic T cells

Arctium lappa L. is a perennial herb traditionally consumed to improve well-being. It has been widely reported for its antioxidant properties; however, very little is known for its exact mechanisms underlying the anticancer activity. This study aimed to investigate the mechanisms of anticancer action for different A. lappa root extracts. Arctium lappa root was extracted with ethanol, hexane and ethyl acetate, then examined for in vitro anticancer activity against cancerous HeLa, MCF-7, Jurkat cell lines and non-cancerous 3T3 cell lines. Induction of apoptosis was determined by cellular morphological changes, mitochondrial membrane potential (ΔΨ_m), caspase-3/7 activity and DNA fragmentation. The active compounds present in the most potent root extracts were identified by LC-ESI-MS. Among all the extracts, ethyl acetate root extract has the highest potency with IC₅₀ of 102.2 ± 42.4 μg/ml, followed by ethanolic root extract in Jurkat T cells, at 24 h. None of the extracts were cytotoxic against 3T3 cells, suggesting that the extracts were selective against cancerous cells only. Both ethyl acetate and ethanolic root extracts exhibited significant morphological changes in Jurkat T cells, including the detachment from adjacent cells, appearance of apoptotic bodies and cells shrinkage. The extracts treated cells also displayed an increase in caspase-3/7 activity and alteration in mitochondrial membrane potential. Only ethyl acetate root extract at IC₅₀ induced DNA fragmentation in Jurkat T cells. LC-ESI-MS analysis of the extract revealed the presence of 8 compounds, of which only 6 compounds with various biological activities reported. These findings suggest that the ethyl acetate extract of A. lappa had strong anticancer potential and induced intrinsic apoptosis via loss of ΔΨ_m and activation of caspase-3/7 This study can provide new insight to the discovery of new promising lead compound in chemopreventive and chemotherapeutic strategies.

Membrane Remodeling as a Key Player of the Hepatotoxicity Induced by Co-Exposure to Benzo[a]pyrene and Ethanol of Obese Zebrafish Larvae

The rise in prevalence of non-alcoholic fatty liver disease (NAFLD) constitutes an important public health concern worldwide. Including obesity, numerous risk factors of NAFLD such as benzo[a]pyrene (B[a]P) and ethanol have been identified as modifying the physicochemical properties of the plasma membrane in vitro thus causing membrane remodeling—changes in membrane fluidity and lipid-raft characteristics. In this study, the possible involvement of membrane remodeling in the in vivo progression of steatosis to a steatohepatitis-like state upon co-exposure to B[a]P and ethanol was tested in obese zebrafish larvae. Larvae bearing steatosis as the result of a high-fat diet were exposed to ethanol and/or B[a]P for seven days at low concentrations coherent with human exposure in order to elicit hepatotoxicity. In this condition, the toxicant co-exposure raised global membrane order with higher lipid-raft clustering in the plasma membrane of liver cells, as evaluated by staining with the fluoroprobe di-4-ANEPPDHQ. Involvement of this membrane’s remodeling was finally explored by using the lipid-raft disruptor pravastatin that counteracted the effects of toxicant co-exposure both on membrane remodeling and toxicity. Overall, it can be concluded that B[a]P/ethanol co-exposure can induce in vivo hepatotoxicity via membrane remodeling which could be considered as a good target mechanism for developing combination therapy to deal with steatohepatitis.

Zebrafish larva as a reliable model for in vivo assessment of membrane remodeling involvement in the hepatotoxicity of chemical agents

The easy-to-use in vivo model, zebrafish larva, is being increasingly used to screen chemical-induced hepatotoxicity, with a good predictivity for various mechanisms of liver injury. However, nothing is known about its applicability in exploring the mechanism called membrane remodeling, depicted as changes in membrane fluidity or lipid raft properties. The aim of this study was, therefore, to substantiate the zebrafish larva as a suitable in vivo model in this context. Ethanol was chosen as a prototype toxicant because it is largely described, both in hepatocyte cultures and in rodents, as capable of inducing a membrane remodeling leading to hepatocyte death and liver injury. The zebrafish larva model was demonstrated to be fully relevant as membrane remodeling was maintained even after a 1-week exposure without any adaptation as usually reported in rodents and hepatocyte cultures. It was also proven to exhibit a high sensitivity as it discriminated various levels of cytotoxicity depending on the extent of changes in membrane remodeling. In this context, its sensitivity appeared higher than that of WIF-B9 hepatic cells, which is suited for analyzing this kind of hepatotoxicity. Finally, the protection afforded by a membrane stabilizer, ursodeoxycholic acid (UDCA), or by a lipid raft disrupter, pravastatin, definitely validated zebrafish larva as a reliable model to quickly assess membrane remodeling involvement in chemical-induced hepatotoxicity. In conclusion, this model, compatible with a high throughput screening, might be adapted to seek hepatotoxicants via membrane remodeling, and also drugs targeting membrane features to propose new preventive or therapeutic strategies in chemical-induced liver diseases. Copyright © 2016 John Wiley & Sons, Ltd.

Inhibition of Poly(ADP-Ribose) Polymerase-1 Protects Chronic Alcoholic Liver Injury

Activation of Kupffer cells (KCs) by gut-derived endotoxin plays a pivotal role in the pathogenesis of alcoholic liver diseases (ALD). Limiting the activation of resident KCs attenuates chronic ethanol-induced liver steatosis and injury. Poly (ADP-ribose) polymerase (PARP)-1 is suggested to play a role in a number of chronic inflammatory diseases. In this study, we found a significant increase of hepatic PARP activity in mice with short-term and long-term ethanol-induced ALD. Male mice on a long-term ethanol diet exhibited severe hepatic steatosis and apoptosis and enhanced KC activation and neutrophil infiltration. However, pharmacologic inhibition of PARP activity or genetic depletion of PARP1 significantly attenuated these detrimental effects in vivo. We found that inhibition of PARP1 effectively reduced hepatic expression of genes involved in lipogenesis and elevated hepatic expression of genes involved in lipolysis. Moreover, limited KC activation and neutrophil infiltration were observed in PARP1 knockout mice or PARP inhibitor-treated mice. Furthermore, in vitro experiments found that LPS-induced macrophage activation was limited by PARP inhibitor, and exposure of ethanol-treated hepatocytes to this conditioned medium further decreased the number of apoptotic and steatotic cells. Taken together, these findings suggest that PARP1 inhibition protects against long-term ethanol-induced liver injury, as indicated by limited hepatocytes steatosis, apoptosis, inflammation levels, and neutrophil infiltration, mainly by limiting KC activation during the initiation of ALD.

Tobacco Smoke-Induced Hepatic Injury with Steatosis, Inflammation, and Impairments in Insulin and Insulin-Like Growth Factor Signaling

Background

Alcoholic liver disease (ALD) is associated with impairments in hepatic insulin and insulin-like growth factor (IGF) signaling through cell growth, survival, and metabolic pathways. Since not all heavy drinkers develop ALD, co-factors may be important. Epidemiologic data indicate that most heavy drinkers smoke tobacco and experimental data revealed that low-level nitrosamine exposures, including those from tobacco, can cause steatohepatitis with hepatic insulin/IGF resistance and exacerbate ALD. We hypothesize that cigarette smoke (CS) exposures also cause liver injury with impaired hepatic insulin/IGF signaling, and thereby contribute to ALD.

Methods

Adult male A/J mice were exposed to air for 8 weeks (A8), CS for 4 (CS4) or 8 (CS8) weeks, or CS for 8 weeks with 2 weeks recovery (CS8+R).

Results

CS exposures caused progressive liver injury with disruption of the normal hepatic chord architecture, lobular inflammation, apoptosis or necrosis, micro-steatosis, sinusoidal dilatation, and nuclear pleomorphism. Histopathological liver injury scores increased significantly from A8 to CS4 and then further to CS8 (P<0.0001). The mean histological grade was also higher in CS8+R relative to A8 (P<0.0001) but lower than in CS4, reflecting partial resolution of injury by CS withdrawal. CS exposures impaired insulin and IGF-1 signaling through IRS-1, Akt, GSK-3β, and PRAS40. Livers from CS8+R mice had normalized or elevated levels of insulin receptor, pYpY-Insulin-R, 312S-IRS-1, 473S-Akt, S9-GSK-3β, and pT246-PRAS40 relative to A8, CS4, or CS8, reflecting partial recovery.

Conclusion

CS-mediated liver injury and steatohepatitis with impairments in insulin/IGF signalling are reminiscent of the findings in ALD. Therefore, CS exposures (either first or second-hand) may serve as a co-factor in ALD. The persistence of several abnormalities following CS exposure cessation suggests that some aspects of CS-mediated hepatic metabolic dysfunction are not readily reversible.

Potential contributions of the tobacco nicotine-derived nitrosamine ketone (NNK) in the pathogenesis of steatohepatitis in a chronic plus binge rat model of alcoholic liver disease

AIMS

Alcoholic liver disease (ALD) is linked to binge drinking and cigarette smoking. Heavy chronic ± binge alcohol, or low-level exposures to dietary nitrosamines cause steatohepatitis with insulin resistance and oxidative stress in animal models. This study examines hepatotoxic effects of sub-mutagenic exposures to tobacco-specific nitrosamine (NNK) in relation to ALD.

METHODS

Long Evans rats were fed liquid diets containing 0 or 26% (caloric) ethanol (EtOH) for 8 weeks. In Weeks 3 through 8, rats were treated with NNK (2 mg/kg) or saline by i.p. injection, 3×/week, and in Weeks 7 and 8, EtOH-fed rats were binge-administered 2 g/kg EtOH 3×/week; controls were given saline.

RESULTS

EtOH ± NNK caused steatohepatitis with necrosis, disruption of the hepatic cord architecture, ballooning degeneration, early fibrosis, mitochondrial cytopathy and ER disruption. Severity of lesions was highest in the EtOH+NNK group. EtOH and NNK inhibited insulin/IGF signaling through Akt and activated pro-inflammatory cytokines, while EtOH promoted lipid peroxidation, and NNK increased apoptosis. O(6)-methyl-Guanine adducts were only detected in NNK-exposed livers.

CONCLUSION

Both alcohol and NNK exposures contribute to ALD pathogenesis, including insulin/IGF resistance and inflammation. The differential effects of EtOH and NNK on adduct formation are critical to ALD progression among alcoholics who smoke.

Therapeutic reversal of chronic alcohol-related steatohepatitis with the ceramide inhibitor myriocin

Alcohol-related liver disease (ALD) is associated with steatohepatitis and insulin resistance. Insulin resistance impairs growth and disrupts lipid metabolism in hepatocytes. Dysregulated lipid metabolism promotes ceramide accumulation and oxidative stress, leading to lipotoxic states that activate endoplasmic reticulum (ER) stress pathways and worsen inflammation and insulin resistance. In a rat model of chronic alcohol feeding, we characterized the effects of a ceramide inhibitor, myriocin, on the histopathological and ultrastructural features of steatohepatitis, and the biochemical and molecular indices of hepatic steatosis, insulin resistance and ER stress. Myriocin reduced the severity of alcohol-related steatohepatitis including the abundance and sizes of lipid droplets and mitochondria, inflammation and architectural disruption of the ER. In addition, myriocin-mediated reductions in hepatic lipid and ceramide levels were associated with constitutive enhancement of insulin signalling through the insulin receptor and IRS-2, reduced hepatic oxidative stress and modulation of ER stress signalling mechanisms. In conclusion, ceramide accumulation in liver mediates tissue injury, insulin resistance and lipotoxicity in ALD. Reducing hepatic ceramide levels can help restore the structural and functional integrity of the liver in chronic ALD due to amelioration of insulin resistance and ER stress. However, additional measures are needed to protect the liver from alcohol-induced necroinflammatory responses vis-à-vis continued alcohol abuse.

Protective effects of dioscin against alcohol-induced liver injury

Our previous studies have shown that dioscin has protective effect against liver injury. However, the action of the compound against ethanol-induced liver injury is still unknown. In the present paper, ethanol-induced acute and chronic liver damage rat models were used, and the results showed that dioscin significantly alleviated liver steatosis, reduced the levels of alanine aminotransferase, aspartate aminotransferase, total triglyceride (TG), total cholesterol and malondialdehyde, and increased the levels of high-density lipoprotein, superoxide dismutase, glutathione and glutathione peroxidase. Transmission electron microscopy and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assays showed that dioscin prevented mitochondrial ultrastructural alterations and apoptosis caused by ethanol. In addition, dioscin significantly inhibited ethanol-induced cytochrome P450 2E1 activation, down-regulated the levels of mitogen-activated protein kinases phosphorylation, inhibited the expressions of nuclear factor kappa B, glucose regulated protein 78, activating transcription factor 6 and alpha subunit of translation initiation factor 2 to attenuate oxidative damage, decreased the expressions of tumor necrosis factor alpha and interleukin-6, and down-regulated the expressions of apoptosis-related proteins including p53, caspase-3, caspase-9, poly (ADP-ribose)-polymerase and cytokeratin-18. Further investigation indicated that dioscin markedly increased the expressions of peroxisome proliferators-activated receptor α and its target genes including medium-chain acyl-CoA dehydrogenase, carnitine palmitoyl-CoA transferase I and acyl-CoA oxidase to advance fatty acid β-oxidation, up-regulated the expressions of acyl-CoA synthetase long-chain family member 1, acyl-CoA synthetase long-chain family member 5, alpha-aminoadipic semialdehyde dehydrogenase and acyl-CoA dehydrogenase to promote fatty acid metabolism, and down-regulated the expressions of glycerol-3-phosphate acyltransferase, diacylglycerol acyltransferase 1 and diacylglycerol acyltransferase 2 to accelerate TG synthesis. However, dioscin had no effects on the expressions of sterol regulatory element-binding protein-1c, fatty acid synthase, acetyl-CoA carboxylase 1 and stearoyl-CoA desaturase 1 associated with fatty acid synthesis. In conclusion, dioscin shows excellent protective effect against ethanol-induced liver injury through ameliorating ethanol-induced oxidative stress, mitochondrial function, inflammatory cytokine production, apoptosis and liver steatosis, which should be developed as a new drug for the treatment of ethanol-induced liver injury in the future.

Immunology in alcoholic liver disease

Hepatic fibrosis is a known consequence of long-term use of alcohol and is regarded as a turning point in alcohol-induced liver disease because it can lead to cirrhosis. The mechanisms of injury are not well understood, but recent studies have helped advance the understanding of the earliest events in the process that eventually leads to hepatic injury and, in some cases, fibrosis. It is hoped that increasing understanding of the role played by the immune system in the process will lead to the development of new therapies for these patients.

Insulin resistance, ceramide accumulation and endoplasmic reticulum stress in experimental chronic alcohol-induced steatohepatitis

AIMS

Chronic alcohol abuse causes steatohepatitis with insulin resistance, which impairs hepatocellular growth, survival and metabolism. However, growing evidence supports the concept that progressive alcohol-related liver injury may be mediated by concurrent mal-signaling through other networks that promote insulin resistance, e.g. pro-inflammatory, pro-ceramide and endoplasmic reticulum (ER) stress cascades.

METHODS

Using the Long Evans rat model of chronic ethanol feeding, we characterized the histopathologic and ultrastructural features of steatohepatitis in relation to biochemical and molecular indices of tissue injury, inflammation, insulin resistance, dysregulated lipid metabolism and ER stress.

RESULTS

Chronic steatohepatitis with early chicken-wire fibrosis was associated with enlargement of mitochondria and disruption of ER structure by electron microscopy, elevated indices of lipid storage, lipid peroxidation and DNA damage, increased activation of pro-inflammatory cytokines, impaired signaling through the insulin receptor (InR), InR substrate-1, Akt, ribosomal protein S6 kinase and proline-rich Akt substrate 40 kDa, glycogen synthase kinase 3β activation and constitutive up-regulation of ceramide and ER stress-related genes. Liquid chromatography coupled with tandem mass spectrometry demonstrated altered ceramide profiles with higher levels of C14 and C18, and reduced C16 species in ethanol-exposed livers.

CONCLUSION

The histopathologic and ultrastructural abnormalities in chronic alcohol-related steatohepatitis are associated with persistent hepatic insulin resistance and pro-inflammatory cytokine activation, dysregulated lipid metabolism with altered ceramide profiles and both ER and oxidative stress. Corresponding increases in lipid peroxidation, DNA damage and protein carbonylation may have contributed to the chronicity and progression of disease. The findings herein suggest that multi-pronged therapeutic strategies may be needed for effective treatment of chronic alcoholic liver disease in humans.

Epigenetic regulation of miR-34a expression in alcoholic liver injury

Epigenetic changes are associated with the regulation of transcription of key cell regulatory genes [micro RNAs (miRNAs)] during different types of liver injury. This study evaluated the role of methylation-associated miRNA, miR-34a, in alcoholic liver diseases. We identified that ethanol feeding for 4 weeks significantly up-regulated 0.8% of known miRNA compared with controls, including miR-34a. Treatment of normal human hepatocytes (N-Heps) and cholangiocytes [human intrahepatic biliary epithelial cells (HiBECs)] with ethanol and lipopolysaccharide induced a significant increase of miR-34a expression. Overexpression of miR-34a decreased ethanol-induced apoptosis in both N-Heps and HiBECs. In support of the concept that the 5'-promoter region of miR-34a was noted to be embedded within a CpG island, the expression level of miR-34a was significantly increased after demethylation treatment in N-Heps and HiBECs. By methylation-specific PCR, we confirmed that miR-34a activation is associated with ethanol-linked hypomethylation of the miR-34a promoter. A combination of bioinformatics, dual-luciferase reporter assay, mass spectrometry, and Western blot analysis revealed that caspase-2 and sirtuin 1 are the direct targets of miR-34a. Furthermore, modulation of miR-34a also altered expression of matrix metalloproteases 1 and 2, the mediators involved in hepatic remodeling during alcoholic liver fibrosis. These findings provide the basis for an exciting field in which the epigenomic microRNAs of hepatic cells may be manipulated with potential therapeutic benefits in human alcoholic liver diseases.

The protective effects of carnosine in alcohol-induced hepatic injury in rats

Consumption of alcohol leads to oxidative stress in liver by inducing lipid peroxidation. The aim of this study was to investigate the effects of carnosine (CAR) in alcohol-induced liver injury by biochemical and histomorphological evaluations. The rats were divided into four groups, namely, control group, alcohol (AL) group, CAR group and AL + CAR group. Three doses of ethanol (5 g/kg, 25% (v/v) in distilled water) were given by nasogastric catheter for twice-a-day. CAR (100 mg/kg) was given 1 h before the administration of ethanol using the same method. Levels of alanine aminotransferase, aspartate aminotransferase, myeloperoxidase and malondialdehyde were significantly increased in the AL group compared with control, CAR and AL + CAR groups. Glutathione level was significantly decreased in the AL group, while it was increased in the AL + CAR group. Immunoreactivity of caspase-3 and bax increased in the hepatocytes of AL group when compared with control and AL + CAR groups. Expression of bcl-2 was decreased in AL group than AL + CAR group. Under electron microscopy, dense mitochondria, accumulation of lipid, sinusoidal dilatation, vacuolization and decrease in the number of microvilli were observed in AL group, while these findings were markedly less in the AL + CAR group. In conclusion, pretreatment of CAR is effective for recovering biochemical alterations and morphologic damage in the liver of rats treated with ethanol.

The role of death effector domain-containing proteins in acute oxidative cell injury in hepatocytes

Apoptosis is a mechanism that regulates hepatic tissue homeostasis and contributes to both acute and chronic injury in liver disease. The apoptotic signaling cascade involves activation of the death-inducing signaling complex (DISC) and subsequent recruitment of proteins containing death effector domains (DED), which regulate downstream effector molecules. Prominent among these are the Fas-associated death domain (FADD) and the cellular caspase 8-like inhibitory protein (cFLIP), and alterations in these proteins can lead to severe disruption of physiological processes, including acute liver failure or hepatocellular carcinoma. Their role in cell signaling events independent of the DISC remains undetermined. Oxidative stress can cause cell injury from direct effects on molecules or by activating intracellular signaling pathways including the mitogen-activated protein kinases (MAPKs). In this context, prolonged activation of the cJun N-terminal kinase (JNK)/AP-1/cJun signaling pathway promotes hepatocellular apoptosis, whereas activation of the extracellular signal-regulated kinase (Erk) exerts protection. We investigated the roles of FADD and cFLIP in acute oxidant stress induced by the superoxide generator menadione in hepatocytes. Menadione resulted in dose-dependent predominantly necrotic cell death. Hepatocytes expressing a truncated, dominant-negative FADD protein were partially protected, whereas cFLIP-deficient hepatocytes displayed increased cell death from menadione. In parallel, Erk phosphorylation was enhanced in hepatocytes expressing dnFADD and decreased in cFLIP-deficient hepatocytes. Hepatocyte injury was accompanied by increased release of proapoptotic factors and increased JNK/cJun activation. Thus, FADD and cFLIP contribute to the regulation of cell death from acute oxidant stress in hepatocytes involving MAPK signaling. This implies that DED-containing proteins are involved in the regulation of cellular survival beyond their role in cell death receptor-ligand-mediated apoptosis.

Lysine acetylation induced by chronic ethanol consumption impairs dynamin-mediated clathrin-coated vesicle release

The liver is the major site of ethanol metabolism and thus sustains the most injury from chronic alcohol consumption. Ethanol metabolism by the hepatocyte leads to the generation of reactive metabolites and oxygen radicals that can readily adduct DNA, lipids, and proteins. More recently, it has become apparent that ethanol consumption also leads to increased post-translational modifications of the natural repertoire, including lysine hyperacetylation. Previously, we determined that alcohol consumption selectively impairs clathrin-mediated internalization in polarized hepatocytes. However, neither the step at which the block occurs nor the mechanism responsible for the defect have been identified. To identify the specific step at which clathrin-mediated internalization is impaired, we examined the distributions, levels, and assembly of selected components of the clathrin machinery in control and ethanol-treated cells. To determine whether the impairment is caused by ethanol-induced lysine acetylation, we also examined the same coat components in cells treated with trichostatin A (TSA), a deacetylase inhibitor that leads to protein hyperacetylation in the absence of ethanol.

CONCLUSION

We determined that both ethanol and TSA impair internalization at a late stage before vesicle fission. We further determined that this defect is likely the result of decreased dynamin recruitment to the necks of clathrin-coated invaginations resulting in impaired vesicle budding. These results also raise the exciting possibility that agents that promote lysine deacetylation may be effective therapeutics for the treatment of alcoholic liver disease.

Lipid droplet accumulation and impaired fat efflux in polarized hepatic cells: consequences of ethanol metabolism

Steatosis, an early manifestation in alcoholic liver disease, is associated with the accumulation of hepatocellular lipid droplets (LDs). However, the role ethanol metabolism has in LD formation and turnover remains undefined. Here, we assessed LD dynamics following ethanol and oleic acid treatment to ethanol-metabolizing WIF-B cells (a hybrid of human fibroblasts (WI 38) and Fao rat hepatoma cells). An OA dose-dependent increase in triglyceride and stained lipids was identified which doubled (P < 0.05) in the presence of ethanol. This effect was blunted with the inclusion of an alcohol metabolism inhibitor. The ethanol/ OA combination also induced adipophilin, LD coat protein involved in the attenuation of lipolysis. Additionally, ethanol treatment resulted in a significant reduction in lipid efflux. These data demonstrate that the metabolism of ethanol in hepatic cells is related to LD accumulation, impaired fat efflux, and enhancements in LD-associated proteins. These alterations in LD dynamics may contribute to ethanol-mediated defects in hepatocellular LD regulation and the formation of steatosis.

Effect of lycopene on caspase-3 enzyme activation in liver of methanol-intoxicated rats: comparison with fomepizole

Lycopene is one of the major carotenoids and is found almost exclusively in tomatoes and tomato products. This study was performed to evaluate the effect of lycopene on methanol-induced liver injury and to compare the results with those after fomepizole, which is used in treatment of methanol intoxication. Experiments were carried out with 30 female Wistar rats weighting 180-200 g. Rats were injected with a intraperitoneally dose of 3 g/kg methanol as a 50% solution in isotonic saline once for intoxication. Rats were pretreated with fomepizole (50 mg/kg) and/or lycopene (10 mg/kg) before methanol. After 24 hours all the drug-treated and intoxicated rats were sacrificed under anesthesia. Malondialdehyde (MDA) levels were determined in order to assess lipid peroxidation, and caspase-3 activity was determined by immunostaining of liver tissues to evaluate apoptosis. Methanol administration significantly increased the MDA level and caspase-3 activity in liver. Pretreatment with lycopene and/or fomepizole decreased the MDA levels significantly. Similarly, lycopene and fomepizole decreased methanol-induced caspase-3 activity. The findings of the present study demonstrate that methanol intoxication causes hepatic toxicity in rats and that this is likely a result of reactive oxygen species and apoptosis induction. Lycopene has protective effects against methanol-induced hepatic injury similar to fomepizole. It was demonstrated for the first time that both lycopene and fomepizole prevent methanol-induced hepatic injury by reducing the increase of lipid oxidation and caspase-3 activation.

Rat strain differences in susceptibility to alcohol-induced chronic liver injury and hepatic insulin resistance

The finding of more severe steatohepatitis in alcohol fed Long Evans (LE) compared with Sprague Dawley (SD) and Fisher 344 (FS) rats prompted us to determine whether host factors related to alcohol metabolism, inflammation, and insulin/IGF signaling predict proneness to alcohol-mediated liver injury. Adult FS, SD, and LE rats were fed liquid diets containing 0% or 37% (calories) ethanol for 8 weeks. Among controls, LE rats had significantly higher ALT and reduced GAPDH relative to SD and FS rats. Among ethanol-fed rats, despite similar blood alcohol levels, LE rats had more pronounced steatohepatitis and fibrosis, higher levels of ALT, DNA damage, pro-inflammatory cytokines, ADH, ALDH, catalase, GFAP, desmin, and collagen expression, and reduced insulin receptor binding relative to FS rats. Ethanol-exposed SD rats had intermediate degrees of steatohepatitis, increased ALT, ADH and profibrogenesis gene expression, and suppressed insulin receptor binding and GAPDH expression, while pro-inflammatory cytokines were similarly increased as in LE rats. Ethanol feeding in FS rats only reduced IL-6, ALDH1-3, CYP2E1, and GAPDH expression in liver. In conclusion, susceptibility to chronic steatohepatitis may be driven by factors related to efficiency of ethanol metabolism and degree to which ethanol exposure causes hepatic insulin resistance and cytokine activation.

Complement and alcoholic liver disease: role of C1q in the pathogenesis of ethanol-induced liver injury in mice

BACKGROUND & AIMS

Complement is involved in the development of alcoholic liver disease in mice; however, the mechanisms for complement activation during ethanol exposure have not been identified. C1q, the recognition subunit of the first complement component, binds to apoptotic cells, thereby activating the classical complement pathway. Because ethanol exposure increases hepatocellular apoptosis, we hypothesized that ethanol-induced apoptosis would lead to activation of complement via the classical pathway.

METHODS

Wild-type and C1qa-/- mice were allowed free access to ethanol-containing diets or pair-fed control diets for 4 or 25 days.

RESULTS

Ethanol feeding for 4 days increased apoptosis of Kupffer cells in both wild-type and C1qa-/- mice. Ethanol-induced deposition of C1q and C3b/iC3b/C3c was colocalized with apoptotic Kupffer cells in wild-type, but not C1qa-/-, mice. Furthermore, ethanol-induced increases in tumor necrosis factor-alpha and interleukin-6 expression at this early time point were suppressed in C1q-deficient mice. Chronic ethanol feeding (25 days) increased steatosis, hepatocyte apoptosis, and activity of serum alanine and aspartate aminotransferases in wild-type mice. These markers of hepatocyte injury were attenuated in C1qa-/- mice. In contrast, chronic ethanol (25 days)-induced increases in cytochrome P450 2E1 expression and oxidative stress did not differ between wild-type and C1qa-/- mice.

CONCLUSIONS

For the first time, these data indicate that ethanol activates the classical complement pathway via C1q binding to apoptotic cells in the liver and that C1q contributes to the pathogenesis of ethanol-induced liver injury.

Chronic alcohol consumption is associated with an increased cytotoxic profile of circulating lymphocytes that may be related with the development of liver injury

BACKGROUND

Apoptosis has recently emerged as a key component of acute and chronic liver diseases and it could be related to alcoholic liver disease. In the present study, we attempted to analyze the cytotoxic profile of circulating lymphocytes in chronic alcoholic patients grouped according to ethanol intake status and presence of liver disease.

METHODS

We investigate the phenotypic and functional behavior of different compartments of peripheral blood (PB) cytotoxic T and natural killer (NK) cells in chronic alcoholic patients without liver disease and active ethanol intake (AWLD group; n = 22), and in subjects with alcohol liver cirrhosis (ALC group; n = 22).

RESULTS

AWLD patients showed an expansion of both CD4+/CD8+ cytotoxic T cells and NK/T cells, in association with an enhanced cytolytic activity against K562 cells and a higher ability to induce in vitro expression of the pro-apoptotic protein APO2.7 in HepG2 cells. Conversely, ethanol intake in ALC patients was associated with decreased NK cell numbers, a reduced cytotoxic activity against K562 cells without significant changes in the expression of APO2.7, and a pro-fibrotic profile of cytokine secretion.

CONCLUSIONS

Overall, our results suggest that alcoholic patients display different phenotypical and functional changes in circulating PB cytotoxic lymphocytes according to the presence of alcoholic liver disease, which could be related to the development and progress of liver injury.

Moderate alcohol consumption aggravates high-fat diet induced steatohepatitis in rats

BACKGROUND

Nonalcoholic steatohepatitis (NASH) develops in the absence of chronic and excessive alcohol consumption. However, it remains unknown whether moderate alcohol consumption aggravates liver inflammation in pre-existing NASH condition.

METHODS

Sprague-Dawley rats were first fed ad libitum with Lieber-DeCarli high-fat diet (71% energy from fat) for 6 weeks to induce NASH, as demonstrated previously. Afterwards, these rats were continuously fed with high-fat diet (HFD, 55% total energy from fat) or high fat plus alcohol diet (HFA, 55% energy from fat and 16% energy from alcohol) for an additional 4 weeks. Pathological lesions including fat accumulation and inflammatory foci in liver were examined and graded. Lipid peroxidation and apoptotic hepatocytes in the liver were assessed. The mRNA expressions of tumor necrosis factor-alpha (TNFalpha) and TNF receptor 1 (TNF-R1), Fas death receptor (Fas) and Fas ligant (FasL), IL-1beta and IL-12 were determined by real-time PCR. Protein levels of total and cleaved caspase-3, CYP2E1, Bax, and Bcl-2 were measured by western blotting.

RESULTS

The number of hepatic inflammatory foci and apoptotic hepatocytes were significantly increased in rats fed with HFA as compared with those in HFD-fed rats. The aggravated inflammatory response and cellular apoptosis mediated by HFA were associated with elevated mRNA expression of Fas/FasL and cleaved caspase-3 protein. Although no significant differences were observed between HFD and HFA groups, the levels of lipid peroxidation, Bax and Bcl-2 protein concentration, and mRNA levels of other inflammatory cytokines were significantly higher in these 2 groups than those in the control group.

CONCLUSIONS

These data suggest that even moderate alcohol consumption can cause more hepatic inflammation and cellular apoptosis in a pre-existing NASH condition.

Deficiency in calcineurin activity in liver transplantation candidates with alcoholic cirrhosis or hepatocellular carcinoma

BACKGROUND

Tacrolimus and cyclosporin inhibits the activity of calcineurin, a serine/threonine phosphatase that is involved in many physiological and pathological pathways. However, the baseline calcineurin phosphatase activity (CPA) measured before the transplant is unknown. In this study, we determine baseline CPA in liver transplant (LT) candidates and explore some factors that might modify it.

PATIENTS AND METHODS

Thirty-two consecutive LT candidates (25 men, seven women, average age 53.4 years) were included. Seven millilitres of whole blood was collected from each patient. CPA was determined in lymphocytes quantifying a dephosphorylated peptide phosphorylated previously (D-L-D-V-P-I-P-G-R-F-D-R-R-V-S-V-A-A-E) by high-performance liquid chromatography. The relationship between CPA and the quantitative variables was tested according to Pearson's correlation. A two-way analysis of variance was performed to test the independent role of categorical parameters in CPA.

RESULTS

The median CPA was significantly lower in LT candidates than in healthy volunteers [179.2 (146.9-226.3) vs 247.8 (220.9-292.5) pmol/min/10(6) peripheral blood mononuclear cell (PBMC), respectively, P=0.0002]. CPA was also significantly lower in alcoholic cirrhosis (152.2 vs 211.1 pmol/min/10(6) PBMC, P=0.04) and in the presence of hepatocellular carcinoma (HCC) (152.0 vs 213.5 pmol/min/10(6) PBMC, P=0.0074) compared with other liver diseases. A two-way analysis of variance showed that these parameters were independently associated with lower CPA (P=0.05 for alcohol and P=0.0056 for HCC respectively).

CONCLUSION

This pilot study showed a lower CPA in patients with AC and HCC. This phenomenon may contribute towards lowering the risk of acute rejection in these patients after LT and, on the other hand, may increase the risk of de novo cancers.

The liver-brain axis of alcohol-mediated neurodegeneration: role of toxic lipids

Alcohol abuse causes progressive toxicity and degeneration in liver and brain due to insulin resistance, which exacerbates oxidative stress and pro-inflammatory cytokine activation. Alcohol-induced steatohepatitis promotes synthesis and accumulation of ceramides and other toxic lipids that cause insulin resistance. Ceramides can readily cross the blood-brain barrier, and ceramide exposure causes neurodegeneration with insulin resistance and oxidative stress, similar to the effects of alcohol. Therefore, in addition to its direct neurotoxic effects, alcohol misuse establishes a liver-brain axis of neurodegeneration mediated by toxic lipid trafficking across the blood-brain barrier, leading to progressive white matter degeneration and cognitive impairment.

Relationship between oxidative stress and hepatic glutathione levels in ethanol-mediated apoptosis of polarized hepatic cells

AIM: To investigate the role of reactive oxygen species (ROS) in ethanol-mediated cell death of polarized hepatic (WIF-B) cells.

METHODS: In this work, WIF-B cultures were treated with pyrazole (inducer of cytochrome P4502E1, CYP2E1) and/or L-buthionine sulfoximine (BSO), a known inhibitor of hepatic glutathione (GSH), followed by evaluation of ROS production, antioxidant levels, and measures of cell injury (apoptosis and necrosis).

RESULTS: The results revealed that ethanol treatment alone caused a significant two-fold increase in the activation of caspase-3 as well as a similar doubling in ROS. When the activity of the CYP2E1 was increased by pyrazole pretreatment, an additional two-fold elevation in ROS was detected. However, the CYP2E1-related ROS elevation was not accompanied with a correlative increase in apoptotic cell injury, but rather was found to be associated with an increase in necrotic cell death. Interestingly, when the thiol status of the cells was manipulated using BSO, the ethanol-induced activation of caspase-3 was abrogated. Additionally, ethanol-treated cells displayed enhanced susceptibility to Fas-mediated apoptosis that was blocked by GSH depletion as a result of diminished caspase-8 activity.

CONCLUSION: Apoptotic cell death induced as a consequence of ethanol metabolism is not completely dependent upon ROS status but is dependent on sustained GSH levels.

Exogenous thioredoxin prevents ethanol-induced oxidative damage and apoptosis in mouse liver

Ethanol-induced liver injury is characterized by increased formation of reactive oxygen species (ROS) and inflammatory cytokines, resulting in the development of hepatic steatosis, injury, and cell death by necrosis and apoptosis. Thioredoxin (Trx), a potent antioxidant and antiinflammatory molecule with antiapoptotic properties, protects animals from a number of inflammatory diseases. However, the effects of ethanol on Trx or its role in ethanol-induced liver injury are not known. Female C57BL/6 mice were allowed ad libitum access to a Lieber-deCarli ethanol diet with 5.4% of calories as ethanol for 2 days to acclimate them to the diet, followed by 2 days with 32.4% of calories as ethanol or pair-fed control diet. Hepatic Trx-1 was decreased by ethanol feeding; daily supplementation with recombinant human Trx (rhTrx) prevented this ethanol-induced decrease. Therefore, we tested the hypothesis that administration of rhTrx during ethanol exposure would attenuate ethanol-induced oxidative stress, inflammatory cytokine production, and apoptosis. Mice were treated with a daily intraperitoneal injection of either 5 g/kg of rhTrx or phosphate-buffered saline (PBS).

CONCLUSION

Ethanol feeding increased accumulation of hepatic 4-hydroxynonenal protein adducts, expression of hepatic tumor necrosis factor alpha, and resulted in hepatic steatosis and increased plasma aspartate aminotransferase and alanine aminotransferase. In ethanol-fed mice, treatment with rhTrx reduced 4-hydroxynonenal adduct accumulation, inflammatory cytokine expression, decreased hepatic triglyceride, and improved liver enzyme profiles. Ethanol feeding also increased transferase-mediated dUTP-biotin nick-end labeling-positive cells, caspase-3 activity, and cytokeratin-18 staining in the liver. rhTrx treatment prevented these increases. In summary, rhTrx attenuated ethanol-induced increases in markers of oxidative stress, inflammatory cytokine expression, and apoptosis.

Impact of asialoglycoprotein receptor deficiency on the development of liver injury

The asialoglycoprotein (ASGP) receptor is a well-characterized hepatic receptor that is recycled via the common cellular process of receptor-mediated endocytosis (RME). The RME process plays an integral part in the proper trafficking and routing of receptors and ligands in the healthy cell. Thus, the mis-sorting or altered transport of proteins during RME is thought to play a role in several diseases associated with hepatocyte and liver dysfunction. Previously, we examined in detail alterations that occur in hepatocellular RME and associated receptor functions as a result of one particular liver injury, alcoholic liver disease (ALD). The studies revealed profound ethanol-mediated impairments to the ASGP receptor and the RME process, indicating the importance of this receptor and the maintenance of proper endocytic events in normal tissue. To further clarify these observations, studies were performed utilizing knockout mice (lacking a functional ASGP receptor) to which were administered several liver toxicants. In addition to alcohol, we examined the effects following administration of anti-Fas (CD95) antibody, carbon tetrachloride (CCl(4)) and lipopolysaccharide (LPS)/galactosamine. The results of these studies demonstrated that the knockout mice sustained enhanced liver injury in response to all of the treatments, as shown by increased indices of liver damage, such as enhancement of serum enzyme levels, histopathological scores, as well as hepatocellular death. Overall, the work completed to date suggests a possible link between hepatic receptors and liver injury. In particular, adequate function and content of the ASGP receptor may provide protection against various toxin-mediated liver diseases.

Synergistic premalignant effects of chronic ethanol exposure and insulin receptor substrate-1 overexpression in liver

AIM

Insulin receptor substrate, type 1 (IRS-1) transmits growth and survival signals, and is overexpressed in more than 90% of hepatocellular carcinomas (HCCs). However, experimental overexpression of IRS-1 in the liver was found not to be sufficient to cause HCC. Since chronic alcohol abuse is a risk factor for HCC, we evaluated potential interactions between IRS-1 overexpression and chronic ethanol exposure by assessing premalignant alterations in gene expression.

METHODS

Wild-type (wt) or IRS-1 transgenic (Tg) mice, constitutively overexpressing the human (h) transgene in the liver, were pair-fed isocaloric liquid diets containing 0% or 24% ethanol for 8 weeks. The livers were used for histopathologic study and gene expression analysis, focusing on insulin, insulin-like growth factor (IGF) and wingless (WNT)-Frizzled (FZD) pathways, given their known roles in HCC.

RESULTS

In wt mice, chronic ethanol exposure caused hepatocellular microsteatosis with focal chronic inflammation, reduced expression of proliferating cell nuclear antigen (PCNA) and increased expression of IGF-I and IGF-I receptor. In hIRS-1 Tg mice, chronic ethanol exposure caused hepatic micro- and macrosteatosis, focal chronic inflammation, apoptosis and disordered lobular architecture. These effects of ethanol in hIRS-1 Tg mice were associated with significantly increased expression of IGF-II, insulin, IRS-4, aspartyl-asparaginyl beta hydroxylase (AAH), WNT-1 and FZD 7, as occurs in HCC.

CONCLUSION

In otherwise normal liver, chronic ethanol exposure mainly causes liver injury and inflammation with impaired DNA synthesis. In contrast, in the context of hIRS-1 overexpression, chronic ethanol exposure may serve as a cofactor in the pathogenesis of HCC by promoting expression of growth factors, receptors and signaling molecules known to be associated with hepatocellular transformation.

Insulin resistance in experimental alcohol-induced liver disease

BACKGROUND AND AIM

Chronic ethanol consumption impairs liver regeneration due, in part, to inhibition of insulin signaling. This study characterizes the mechanisms and consequences of ethanol-impaired insulin signaling in relation to oxidative injury and altered gene expression.

METHODS

Long-Evans rats were fed for 8 weeks with isocaloric liquid diets containing 0% (control) or 37% ethanol (caloric content). Livers were used to examine histopathology, indices of oxidative stress, gene expression required for insulin and insulin-like growth factor (IGF) signaling, insulin-responsive gene expression, i.e. glyceraldehydes-3-phosphate dehydrogenase (GAPDH) and aspartyl-asparaginyl-beta-hydroxylase (AAH), and competitive equilibrium binding to the insulin, IGF-I, and IGF-II receptors.

RESULTS

Chronic ethanol exposure caused liver injury with increased hepatocellular steatosis, inflammation, apoptosis, and increased immunoreactivity for activated caspase-3, 8-hydroxy-2'-deoxyguanosine, and 4-hydroxy-2,3-nonenol. These effects were associated with increased expression of IGF-I receptor, IGF-II, and IGF-II receptor, and expression of IGF-I, AAH, and GAPDH, which mediate energy metabolism and cell motility/remodeling, and reduced binding to the insulin receptor.

CONCLUSIONS

Chronic ethanol-induced liver injury causes insulin resistance with inhibition of insulin-responsive genes needed for metabolism, remodeling, and regeneration. In contrast, the IGF-I and IGF-II signaling mechanisms remain relatively preserved, suggesting that insulin-regulated hepatic functions may be selectively vulnerable to the toxic effects of ethanol.

Zinc supplementation inhibits hepatic apoptosis in mice subjected to a long-term ethanol exposure

Hepatocyte apoptosis has been documented in both clinical and experimental alcoholic liver disease. This study was undertaken to examine the effect of dietary zinc supplementation on hepatic apoptosis in mice subjected to a long-term ethanol exposure. Male adult 129S6 mice fed an ethanol-containing liquid diet for 6 months developed hepatitis, as indicated by neutrophil infiltration and elevation of hepatic keratinocyte chemoattractant (KC) and monocyte chemoattractant protein-1 (MCP-1) levels. Apoptotic cell death was detected in ethanol-exposed mice by a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and was confirmed by the increased activities of caspase-3 and -8. Zinc supplementation attenuated alcoholic hepatitis and reduced the number of TUNEL-positive cells in association with inhibition of caspase activities. Ethanol exposure caused oxidative stress, as indicated by reactive oxygen species accumulation, mitochondrial glutathione depletion, and decreased metallothionein levels in the liver, which were suppressed by zinc supplementation. The mRNA levels of tumor necrosis factor (TNF)-alpha, TNF-R1, FasL, Fas, Fas-associated factor-1, and caspase-3 in the liver were upregulated by ethanol exposure, which were attenuated by zinc supplementation. Zinc supplementation also prevented ethanol-elevated serum and hepatic TNF-alpha levels and TNF-R1 and Fas proteins in the liver. In conclusion, zinc supplementation prevented hepatocyte apoptosis in mice subjected to long-term ethanol exposure, and the action of zinc is likely through suppression of oxidative stress and death receptor-mediated pathways.

Melatonin inhibits free radical-mediated mitochondrial-dependent hepatocyte apoptosis and liver damage induced during malarial infection

We showed earlier that malarial infection significantly induces liver apoptosis mediated by oxidative stress mechanisms. Thus, a nontoxic antioxidant-antiapoptotic molecule may be beneficial for hepatoprotection. Melatonin remarkably prevents hepatocyte apoptosis in mice induced during malaria as indicated by caspase 3 and TUNEL assays as well as transmission electron microscopy (TEM) of the liver tissue. The mitochondrial apoptotic pathway, which plays a critical role in liver cell death during malarial infection, was almost completely suppressed by melatonin as it corrects both the overexpression of Bax and down-regulation of bcl-2 as revealed by semiquantitative RT-PCR. Fluorometric studies using JC-1 documented that melatonin also restores mitochondrial transmembrane potential (DeltaPsim) in malaria-infected mice liver. The antiapoptotic effect of melatonin is associated with its antioxidant role because melatonin protects liver from oxidative stress induced during malaria by scavenging the hydroxyl radicals, preventing the depletion of reduced glutathione, inhibiting lipid peroxidation and protein carbonyl formation. The effective antioxidant dose of melatonin to protect liver from oxidative stress during malaria is 20 times lower than that of known antioxidants, vitamin C and vitamin E. Apoptosis of hepatocytes during malarial infection is well correlated with dysfunction of the liver while melatonin offers hepatoprotective effects as indicated by different liver function tests. Thus, melatonin may well be effective in combating oxidative stress-induced apoptosis and liver damage during malaria infection.

Effect of ethanol on pro-apoptotic mechanisms in polarized hepatic cells

Chronic ethanol consumption is associated with serious and potentially fatal alcohol-related liver injuries such as hepatomegaly, alcoholic hepatitis and cirrhosis. Moreover, it has been documented that the clinical progression of alcohol-induced liver damage may be associated with an increase in hepatocellular death that involves apoptotic mechanisms. Although much information has been learned about the clinical manifestations associated with alcohol-related diseases, the search continues for a better understanding of the molecular and/or cellular mechanisms by which ethanol exerts its deleterious effects such as the induction of pro-apoptotic mechanisms and related cell damaging events. As part of the effort to enhance our understanding of those particular cellular pathways and mechanisms associated with ethanol toxicity, researchers over the years have utilized a variety of model systems. Recently, work has come forth demonstrating the utility of a hybrid cell line (WIF-B) as a cell culture model system for the study of alcohol-associated alterations in hepatocellular mechanisms. Success with such emerging model systems could aid in the development of potential therapeutic treatments for the prevention of alcohol-induced apoptotic cell death that may ultimately serve as a significant target in delaying the onset and/or progression of clinical symptoms of alcohol-mediated liver disease. This review article summarizes the current understanding of ethanol-mediated modifications in cell survival and thus the promotion of pro-apoptotic events with emphasis on analyses made in various experimental model systems, particularly the more recently characterized WIF-B cell system.

Alcohol and the liver

PURPOSE OF REVIEW

This review aims to acquaint the reader with advances in 2006 in the epidemiology, genetics, detection, pathogenesis and treatment of alcoholic liver disease.

RECENT FINDINGS

Important discoveries have been made in pathogenesis and mechanism of disease, with great emphasis on the many pathways leading to oxidative stress, and the novel mechanism of endoplasmic reticulum stress that is proving to be important in the pathogenesis of many liver diseases. The reliability of ethyl glucuronide and other biomarkers for the detection of alcohol abuse is being better established. There have been no treatment advances for alcoholic liver disease but, on balance, steroids are still favored for carefully selected patients with alcoholic hepatitis. Many compounds tested in rodents may now be available for consideration for clinical trials. Criteria for patient selection and refusal for liver transplantation are being established but the 6 months abstinence rule still holds.

SUMMARY

Insights are being made into the pathogenesis of alcoholic liver disease but safe and effective therapies for both alcoholic hepatitis and alcoholic cirrhosis have yet to be discovered.