Ethanol-induced Hepatocyte Apoptosis Research Articles

Cilostazol protects hepatocytes against alcohol-induced apoptosis via activation of AMPK pathway.

Alcoholic liver disease (ALD) is a worldwide health problem and hepatocyte apoptosis has been associated with the development/progression of ALD. However, no definite effective pharmacotherapy for ALD is currently available. Cilostazol, a selective type III phosphodiesterase inhibitor has been shown to protect hepatocytes from ethanol-induced apoptosis. In the present study, the underlying mechanisms for the protective effects of cilostazol were examined. Primary rat hepatocytes were treated with ethanol in the presence or absence of cilostazol. Cell viability and intracellular cAMP were measured. Apoptosis was detected by Hoechst staining, TUNEL assay, and caspase-3 activity assay. The roles of cAMP and AMP-activated protein kinase (AMPK) pathways in the action of CTZ were explored using pharmacological inhibitors and siRNAs. Liver from mice received ethanol (5 g/kg body weight) by oral gavage following cilostazol treatment intraperitoneally was obtained for measurement of apoptosis and activation of AMPK pathway. Cilostazol inhibited ethanol-induced hepatocyte apoptosis and potentiated the increases in cAMP level induced by forskolin. However, the anti-apoptotic effect of cilostazol was not reversed by an inhibitor of adenylyl cyclase. Interestingly, cilostazol activated AMPK and increased the level of LC3-II, a marker of autophagy. The inhibition of AMPK abolished the effects of cilostazol on LC3-II expression and apoptosis. Moreover, the inhibition of LKB1 and CaMKK2, upstream kinases of AMPK, dampened cilostazol-inhibited apoptosis as well as AMPK activation. In conclusion, cilostazol protected hepatocytes from apoptosis induced by ethanol mainly via AMPK pathway which is regulated by both LKB1 and CaMKK2. Our results suggest that cilostazol may have potential as a promising therapeutic drug for treatment of ALD.

Over-Expression of ATPase II Alleviates Ethanol-Induced Hepatocyte Injury in HL-7702 Cells

BackgroundExcessive alcohol consumption can cause hepatocellular injury. ATPase II (ATP8A1) can display an ATP-dependent phospholipid translocase activity. However, the function of ATP8A1 in hepatocyte injury is still unclear. In the present study we explored the effect of ATP8A1 on ethanol-induced hepatocyte injury.Material/MethodA human hepatocyte strain, HL-7702, was pretreated by ethanol with gradient concentration for 2, 4, 8, and 12 h, and were then divided into 6 groups after the cells were transfected. We detected cell viability by use of the Cell Counting Kit-8 (CCK-8) assay. Reactive oxygen species (ROS), apoptosis rate, and mitochondrial membrane potential (MMP) were measured using flow cytometry. We used quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot to measure the mRNA and protein expression, respectively.ResultsEthanol inhibited the viability of HL-7702 cells and suppressed the expression of ATP8A1 in dose- and time-dependent manners. Furthermore, over-expression of ATP8A1 reduced the level of ROS and the apoptosis rate and recovered the MMP. Additionally, over-expressed ATP8A1 regulated the protein and mRNA levels of apoptosis-related molecules. Moreover, over-expression of ATP8A1 enhanced the phosphorylation of phosphatidylinositol 3-kinase (PI3K) and protein kinase B (Akt).ConclusionsOver-expression of ATP8A1 alleviated ethanol-induced hepatocyte injury. Moreover, the PI3K/Akt signaling pathway appears to participate in inhibition of ethanol-induced hepatocyte apoptosis and may provide a candidate target for the treatment of alcoholic liver diseases (ALD).

Dihydroartemisinin inhibits ER stress-mediated mitochondrial pathway to attenuate hepatocyte lipoapoptosis via blocking the activation of the PI3K/Akt pathway

Alcoholic liver disease (ALD), characterized by accumulation of fatty acids in liver cells, is usually caused by Chronic alcohol consumption. Our previous study has identified that DA protects against alcoholic liver injury in alcohol-fed rats through alleviating hepatocyte steatosis. It has emerged that saturated fatty acids could provoke endoplasmic reticulum (ER) stress and apoptosis in hepatocytes. This study was aimed to explore the impact of DA on ALD and further elaborate the underlying mechanisms. Results demonstrated that DA attenuates alcoholic liver injury in mice. Our results also indicated that DA attenuated lipid accumulation in hepatocytes exposed to ethanol. DA attenuates ethanol-induced hepatocyte apoptosis. Results demonstrated that DA dose-dependently ameliorated activation of mitochondrial pathway activation, which plays a critical role in apoptosis attributed to lipotoxicity. Further, DA suppressed the activation of JNK and the expression of CHOP, attributed to the inhibition of ER stress. It has emerged that activation of ER stress-JNK/CHOP-mitochondria cascade is considered as the key mechanisms underlying hepatocyte lipoapoptosis. In addition, DA attenuates PI3K/Akt Pathway in hepatocytes, consistent with our previous finding in HSCs. DA effects were reinforced by PI3K specific inhibitor LY294002. In summary, DA significantly protected hepatocytes against lipoapoptosis via a PI3K/Akt Pathway inhibition-dependent mechanism.

Blockade of hedgehog pathway is required for the protective effects of magnesium isoglycyrrhizinate against ethanol-induced hepatocyte steatosis and apoptosis.

Alcoholic liver disease (ALD), characterized by excessive deposition of lipids in hepatocytes, causes heavy health burden personally and socially. Mechanistically, hedgehog signaling was activated during the development of ALD, and exerted compelling role in regulating lipometabolism. The current promising intervention strategy is inhibition of lipid accumulation and apoptosis in hepatocytes. Magnesium isoglycyrrhizinate (MgIG) has been widely used in various liver diseases for its good hepatoprotective activities. However, the role of MgIG in ALD has not been elucidated. Therefore, this study was aimed to explore the role of MgIG and further identify the potential mechanisms. We found for the first time that MgIG reduced lipid accumulation, including triglyceride, and total cholesterol, probably via inducing peroxisome proliferator-activated receptor-alpha and inhibiting sterol regulatory element-binding protein-1c. Further, MgIG alleviated ethanol-induced oxidative stress, evidenced by reduced abundance of reactive oxygen species and increased levels of glutathione, superoxide dismutase, and mitochondrial transmembrane potential. Besides, MgIG protected hepatocytes from ethanol-induced apoptosis. In addition, MgIG dose-dependently suppressed hedgehog signaling. Of note was that disruption of hedgehog signaling could mimic the effects of MgIG, whereas activation of hedgehog signaling abrogated the effects of MgIG. These findings suggested that MgIG prevented ethanol-induced hepatocyte steatosis and apoptosis via a hedgehog signaling inhibition-dependent mechanism. © 2017 IUBMB Life, 69(7):540-552, 2017.

Blockade of store-operated calcium entry alleviates ethanol-induced hepatotoxicity via inhibiting apoptosis

Extracellular Ca2+ influx has been suggested to play a role in ethanol-induced hepatocyte apoptosis and necrosis. Previous studies indicated that store-operated Ca2+ entry (SOCE) was involved in liver injury induced by ethanol in HepG2 cells. However, the mechanisms underlying liver injury caused by SOCE remain unclear. We aimed to investigate the effects and mechanism of SOCE inhibition on liver injury induced by ethanol in BRL cells and Sprague–Dawley rats. Our data demonstrated that ethanol (0–400mM) dose-dependently increased hepatocyte injury and 100mM ethanol significantly upregulated the mRNA and protein expression of SOC for at least 72h in BRL cells. Blockade of SOCE by pharmacological inhibitors and sh-RNA knockdown of STIM1 and Orai1 attenuated intracellular Ca2+ overload, restored the mitochondrial membrane potential (MMP), decreased cytochrome C release and inhibited ethanol-induced apoptosis. STIM1 and Orai1 expression was greater in ethanol-treated than control rats, and the SOCE inhibitor corosolic acid ameliorated the histopathological findings and alanine transaminase and aspartate transaminase activity as well as decreased cytochrome C release and inhibited alcohol-induced cell apoptosis. These findings suggest that SOCE blockade could alleviate alcohol-induced hepatotoxicity via inhibiting apoptosis. SOCE might be a useful therapeutic target in alcoholic liver diseases.

P1097 : Distinguishing drug induced autoimmune hepatitis from idiopatic autoimmune hepatitis

M30/CK18-cleavage staining, indicators of hepatocyte apoptosis. Indicators of oxidative stress, including the accumulation of 4-HNEprotein adducts and JNK phosphorylation, were also increased. In contrast, mice deficient in MLK3 were protected from ethanolinduced increases in plasma ALT/AST, pro-inflammatory cytokines and hepatic protein expression of RIP3. Ethanol-induced JNK phosphorylation and oxidative stress were also attenuated in MLK3deficient mice. However, MLK3-deficiency did not affect ethanolinduced steatosis or hepatocyte apoptosis. Conclusions: Taken together, these results suggest that MLK3 participates in the development of ethanol-induced oxidative stress, activation of JNK and induction of necroptotic programmed hepatocyte death. Pharmacological intervention of this pathway could be targeted as a potential therapeutic strategy to suppress necroptosis-induced inflammation and hepatocyte injury in patients with ALD.

Moderate, chronic ethanol feeding exacerbates carbon-tetrachloride-induced hepatic fibrosis via hepatocyte-specific hypoxia inducible factor 1α

The hypoxia-sensing transcriptional factor HIF1α is implicated in a variety of hepato-pathological conditions; however, the contribution of hepatocyte-derived HIF1α during progression of alcoholic liver injury is still controversial. HIF1α induces a variety of genes including those involved in apoptosis via p53 activation. Increased hepatocyte apoptosis is critical for progression of liver inflammation, stellate cell activation, and fibrosis. Using hepatocyte-specific HIF1α-deficient mice (ΔHepHIF1α−/−), here we investigated the contribution of HIF1α to ethanol-induced hepatocyte apoptosis and its role in amplification of fibrosis after carbon tetrachloride (CCl4) exposure. Moderate ethanol feeding (11% of kcal) induced accumulation of hypoxia-sensitive pimonidazole adducts and HIF1α expression in the liver within 4 days of ethanol feeding. Chronic CCl4 treatment increased M30-positive cells, a marker of hepatocyte apoptosis in pair-fed control mice. Concomitant ethanol feeding (11% of kcal) amplified CCl4-induced hepatocyte apoptosis in livers of wild-type mice, associated with elevated p53K386 acetylation, PUMA expression, and Ly6c+ cell infiltration. Subsequent to increased apoptosis, ethanol-enhanced induction of profibrotic markers, including stellate cell activation, collagen 1 expression, and extracellular matrix deposition following CCl4 exposure. Ethanol-induced exacerbation of hepatocyte apoptosis, p53K386 acetylation, and PUMA expression following CCl4 exposure was attenuated in livers of ΔHepHIF1α−/− mice. This protection was also associated with a reduction in Ly6c+ cell infiltration and decreased fibrosis in livers of ΔHepHIF1α−/− mice. In summary, these results indicate that moderate ethanol exposure leads to hypoxia/HIF1α-mediated signaling in hepatocytes and induction of p53-dependent apoptosis of hepatocytes, resulting in increased hepatic fibrosis during chronic CCl4 exposure.

Salvianolic acid B protects against acute ethanol-induced liver injury through SIRT1-mediated deacetylation of p53 in rats

Salvianolic acid B (SalB) is isolated from the traditional Chinese medical herb salvia miltiorrhiza. It has many biological and pharmaceutical activities. This study aimed to investigate the effect of SalB on acute ethanol-induced hepatic injury in rats and to explore the role of SIRT1 in this process. The results showed that pretreatment with SalB significantly reduced ethanol-induced elevation in aminotransferase activities, decreased hepatotoxic cytokine levels such as Interleukin-6 (IL-6), and increased the antioxidant enzyme activity. Moreover, SalB pretreatment reversed the increase in NF-κB, cleaved caspase-3 and decrease in B-cell lymphoma-extra large (Bcl-xL) caused by ethanol exposure. Importantly, SalB pretreatment significantly increased the expression of SIRT1, a NAD+-dependent deacetylase, whereas the increase in SIRT1 was accompanied by decreased acetyl-p53 expression. In HepG2 cells, SalB pretreatment increased SIRT1 expression in a time and dose-dependent manner and such an increase was abrogated by siRNA knockdown of SIRT1. Additionally, inhibition of SIRT1 significantly increased the acetylation of p53, and blocked SalB-induced acetylation of p53 down-regulation. Collectively, this study indicated that SalB can alleviate acute ethanol-induced hepatocyte apoptosis through SIRT1-mediated deacetylation of p53 pathway.

Ethanol-induced apoptosis in human liver adenocarcinoma cells (SK-Hep1): Fas- and mitochondria-mediated pathways and interaction with MAPK signaling system

For studying molecular mechanisms regulating the fate of ethanol-treated hepatocytes, involvement of Fas in ethanol-induced apoptosis was examined in human liver adenocarcinoma (SK-Hep1) cells in which the function of Fas-associated death domain (FADD) protein was knocked down by transfection. In FADD-knocked down cells, while ethanol-induced increase in generation of reactive oxygen species (ROS) was unaffected, apoptosis was significantly suppressed, demonstrating the involvement of Fas in ethanol-induced hepatocyte apoptosis more directly than in the past reports. On the other hand, effects of mitogen-activated protein kinase (MAPK), which is well known to determine the fate of various cells, on ethanol-induced apoptosis have not been examined in SK-Hep1 cells. Of three major MAPKs, only p38 MAPK and JNK were found activated by 200mM ethanol treatment. When cells were incubated with inhibitors of p38 MAPK and JNK, ethanol-induced apoptosis was decreased while ROS generation was unaffected, and examination of pro-apoptotic Bax and anti-apoptotic Bcl-2 levels showed decrease of the former and increase of the latter. We concluded that oxidative stress inflicted by ROS triggered Fas-mediated and mitochondria-mediated apoptotic pathways in ethanol-treated SK-Hep1 cells, and that p38 MAPK and JNK were promoting mitochondrial pathway, suggesting interaction between apoptosis and MAPK signaling systems.

Inhibition of store-operated Ca 2+ channels prevent ethanol-induced intracellular Ca 2+ increase and cell injury in a human hepatoma cell line

Elevated intracellular Ca 2+ content is implicated in ethanol-induced hepatocyte apoptosis and necrosis. Extracellular Ca 2+ influx has been suggested to play a role in this process. However, the exact Ca 2+-permeable channel involved in the plasma membrane is still unclear. This study investigated the role of store-operated calcium entry (SOCE) in ethanol-induced cytosolic free Ca 2+ concentrations ([Ca 2+] i) increase and hepatotoxicity. Ethanol (25–800 mM) dose-dependently increased [Ca 2+] i content and hepatocyte damage in HepG2 cells. 2-aminoethoxydiphenyl borate (2-APB), the proved efficient antagonist of SOCs, dose-dependently suppressed the ethanol (200 nM)-increased [Ca 2+] i content and protected against ethanol-induced viability loss and transaminase leakage. Exposure to 200 mM ethanol for 24 h significantly upregulated the mRNA and protein expression of calcium release-activated calcium channel protein 1 (CRACM1, Orai1) and stromal interaction molecule 1 (STIM1), the two main molecular constituents of SOCs, which was sustained for at least 72 h. In addition, small interfering RNA knockdown of STIM1 attenuated the ethanol-increased [Ca 2+] i content and hepatotoxicity. Taken together, these data indicate that the Ca 2+ channel of SOCE may be involved in the pathogenesis of ethanol-induced intracellular Ca 2+ elevation and consequent hepatocyte damage.

The sap of Acer okamotoanum decreases serum alcohol levels after acute ethanol ingestion in rats

In the present study, we examined whether Acer okamotoanum (A. okamotoanum) sap decreased the serum alcohol and acetaldehyde levels after acute ethanol treatment in a rat model. Male rats were orally administered 25, 50 or 100% A. okamotoanum sap 30 min prior to oral challenge with 3 ml of ethanol (15 ml/kg of a 20% ethanol solution in water), and the blood concentrations of alcohol and acetaldehyde were analyzed up to 7 h after the treatment. Pre-treatment with the sap significantly decreased the blood ethanol and acetaldehyde concentrations after 5 h when compared with ethanol treatment alone (a negative control). The expression levels of liver alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) mRNA were increased significantly in animals pre-treated with A. okamotoanum sap when compared with negative and positive controls. The data suggest that sap pre-treatment enhanced the alcohol metabolism rate in the rat liver. To investigate the involvement of mitochondrial regulation in the ethanol-induced hepatocyte apoptosis, we carried out an immunohistochemical analysis of Bax and Bcl-2. Pre-treatment with sap significantly decreased Bax expression and increased Bcl-2 expression 7 h after ethanol administration when compared with the negative control. The data suggest that A. okamotoanum sap pre-treatment may reduce the alcohol-induced oxidative stress in the rat liver.

The Protective Effect of Bee Venom against Ethanol‐Induced Hepatic Injury via Regulation of the Mitochondria‐Related Apoptotic Pathway

Alcohol consumption increases apoptosis of hepatocytes. Death of hepatocytes is a characteristic feature of chronic liver disease for various causes. Bee venom (Apis mellifera) has been traditionally used for the treatment of various chronic diseases, such as chronic inflammatory arthritis and chronic liver disease. However, the precise mechanism for bee venom in chronic liver disease is not still cleared. To assess the effects of bee venom in chronic liver disease, we investigated the potential role of the bee venom in the ethanol-induced hepatocyte apoptosis. Bee venom treatment inhibited the apoptotic cell morphology and increased the cell viability in ethanol-induced hepatocyte apoptosis. With ethanol treatment, bee venom-treated hepatocytes increased activity of Bcl-2 and Bcl-xL, reduced activity of Bax, Caspase and PARP. In conclusion, bee venom treatment in ethanol-induced hepatocyte apoptosis occurred through the regulation of Bcl family with subsequent inactivation of the Caspase and PARP. These results suggest that bee venom could be an effective agent to reduce ethanol-induced hepatocyte apoptosis.

Effects of curcumin on ethanol-induced hepatocyte necrosis and apoptosis: implication of lipid peroxidation and cytochrome c

Ethanol-induced hepatocyte necrosis and apoptosis are valid in vitro models to investigate the modulatory effects of hepatoprotective/toxic agents such as curcumin. In this study, suspension and monolayer cultures of isolated rat hepatocytes were used. Levels of trypan blue uptake, reduced glutathione, and lipid peroxidation were quantified. Chromatin condensation, caspase-3 activity, and cytochrome c extramitochondrial translocation were also evaluated. Results revealed that curcumin did not protect against either ethanol-induced necrosis or glutathione depletion. Neither did curcumin reduce caspase-3 activation nor chromatin condensation. In contrast, curcumin induced glutathione depletion, caspase-3 activation, necrosis, and apoptosis. Fortunately, all tested curcumin concentrations (1 microM-10 mM) diminished the ethanol-induced lipid peroxidation. In addition, 1 microM curcumin decreased cytochrome c translocation in hepatocyte monolayers. In conclusion, low concentrations of curcumin may protect hepatocytes by reducing lipid peroxidation and cytochrome c release. Conversely, higher concentrations provoke glutathione depletion, caspase-3 activation, and hepatocytotoxicity.

Zinc inhibits ethanol-induced HepG2 cell apoptosis

Alcohol consumption produces a variety of metabolic alterations in liver cells, associated with ethanol oxidation and with nonoxidative metabolism of ethanol, among others apoptosis of hepatocytes. As zinc is known as a potent antioxidant and an inhibitor of cell apoptosis, the aim of this paper was to investigate whether zinc supplementation could inhibit ethanol-induced HepG2 apoptosis, and whether this inhibition was connected with attenuation of oxidative stress and modulation of FasR/FasL system expression. The results indicated that zinc supplementation significantly inhibited ethanol-induced HepG2 cell apoptosis (measured by cytochrome c release from mitochondria and caspase-3 activation) by attenuation of reactive oxygen species (ROS) production, increase in the cellular level of GSH, inhibition of ethanol-induced sFasR and FasL overexpression and caspase-8 activation. These results indicate that zinc can inhibit ethanol-induced hepatocyte apoptosis by several independent mechanisms, among others by an indirect antioxidative effect and probably by inhibition of caspase-8 and caspase-9 activation.

Role of MAPK Phosphatase-1 in Sustained Activation of JNK during Ethanol-induced Apoptosis in Hepatocyte-like VL-17A Cells

Ethanol metabolism plays a central role in activating the mitogen-activated protein kinase (MAPK) cascade leading to inflammation and apoptosis. Sustained activation of c-Jun N-terminal kinase (JNK), one of the MAPKs, has been shown to induce apoptosis in hepatocytes. MAPK phosphatase-1 (MKP-1) has been shown to dephosphorylate MAPKs in several cells. The aim of the study is to evaluate the role of MKP-1 in sustained JNK activation as a mechanism to explain ethanol-induced hepatocyte apoptosis. VL-17A cells (HepG2 cells overexpressing alcohol dehydrogenase and cytochrome P450-2E1) were exposed to ethanol for different time periods. Western blots were performed for MKP-1, phospho-JNK, phosphotyrosine, and protein kinase Cdelta (PKCdelta). Electrophoretic mobility shift assays for AP-1 were performed. Apoptosis was measured by caspase-3 activity assay, TUNEL, and 4',6-diamidino-2-phenylindole staining. Reactive oxygen species were neutralized by overexpressing both superoxide dismutase-3 and catalase genes using lentiviral vectors in VL-17A cells. Ethanol incubation markedly decreased the MKP-1 protein levels to 15% of control levels and was associated with sustained phosphorylation of p46 JNK and p54 JNK, as well as increased apoptosis. VL-17A cells overexpressing superoxide dismutase-3 and catalase, treatment with a tyrosine kinase inhibitor, or incubation of the cells with PKCdelta small interference RNAs significantly inhibited the ethanol-induced MKP-1 degradation and apoptosis. Ethanol-induced oxidative stress enhanced the tyrosine phosphorylation of PKCdelta, which in turn caused the proteasomal degradation of MKP-1, leading to sustained JNK activation and increased apoptosis in VL-17A cells.

Abrogation of hepatocyte apoptosis and early appearance of liver dysplasia in ethanol-fed p53-deficient mice

Ethanol consumption represents a major risk factor for cancer development, and a significant fraction of hepatocarcinomas arises in alcoholic liver cirrhosis. Increasing evidence indicates that ethanol acts as a tumor promoter on genetically initiated cells, by increasing the intracellular concentration of reactive oxygen species and promoting tissue necrosis/regeneration and cell proliferation. The tumor suppressor p53 restrains the expansion of carcinogen-initiated cells by inducing cell cycle arrest and apoptosis; accordingly, p53-deficient mice develop spontaneous and chemically induced neoplasms at a much higher frequency than normal mice. In normal mice exposed to a subacute (3 weeks) ethanol intoxication, a significant increase in the number of apoptotic hepatocytes was observed in concomitance with the up-regulation of the mitochondrial superoxide scavenger MnSOD, a reliable indicator of oxidative stress. Cell death occurred in the absence of liver inflammation and necrosis. Ethanol-induced hepatocyte apoptosis was completely abrogated in the p53 null background, suggesting that the tumor suppressor is necessary for hepatocyte death by ethanol. Accordingly, p53 −/− MEF were, unlike wild type cells, completely insensitive up to 0.5M ethanol in the culture medium. Strikingly, marked and widespread signs of dysplasia, with nuclear pleomorphisms and initial loss of normal architecture, heralding malignant transformation, were scored in all the mutant mice exposed to ethanol, but not in the control-fed littermates nor in ethanol-fed normal mice. These observations suggest that p53-dependent apoptosis restrains the tumorigenic effect of ethanol on liver cells, in agreement with the frequent loss of p53 function in HCC, and reveal an unexpected carcinogenic potential of alcohol which appears to be independent from the induction of cirrhosis and hepatocyte regeneration.

Bax interacts with the voltage-dependent anion channel and mediates ethanol-induced apoptosis in rat hepatocytes.

Acute ethanol exposure induces oxidative stress and apoptosis in primary rat hepatocytes. Previous data indicate that the mitochondrial permeability transition (MPT) is essential for ethanol-induced apoptosis. However, the mechanism by which ethanol induces the MPT remains unclear. In this study, we investigated the role of Bax, a proapoptotic Bcl-2 family protein, in acute ethanol-induced hepatocyte apoptosis. We found that Bax translocates from the cytosol to mitochondria before mitochondrial cytochrome c release. Bax translocation was oxidative stress dependent. Mitochondrial Bax formed a protein complex with the mitochondrial voltage-dependent anion channel (VDAC). Prevention of Bax-VDAC interactions by a microinjection of anti-VDAC antibody effectively prevented hepatocyte apoptosis by ethanol. In conclusion, these data suggest that Bax translocation from the cytosol to mitochondria leads to the subsequent formation of a Bax-VDAC complex that plays a crucial role in acute ethanol-induced hepatocyte apoptosis.

Dilinoleoylphosphatidylcholine reproduces the antiapoptotic actions of polyenylphosphatidylcholine against ethanol-induced hepatocyte apoptosis.

Polyenylphosphatidylcholine (PPC), a mixture of polyunsaturated phosphatidylcholines extracted from soybeans, attenuates hepatocyte apoptosis induced by ethanol feeding of rats. Our aims were to evaluate whether dilinoleoylphosphatidylcholine (DLPC), the main component of PPC, reproduces the antiapoptotic actions of PPC against alcohol-induced apoptosis and to identify the apoptotic proteins that are affected by PPC and DLPC. Rats were fed Lieber-DeCarli liquid diets containing ethanol (35% of energy) or an isocaloric amount of carbohydrate for 4 weeks. Another group of rats were given the ethanol diet supplemented with PPC (3 g/liter) or DLPC (1.5 and 3 g/liter). Hepatocyte apoptosis was assessed by terminal transferase-mediated dUTP nick end labeling staining and by caspase 3 enzyme activity. Activity of caspases 3 and 9 was assayed by using fluorogenic peptide substrates. Cytochrome c was quantified by enzyme-linked immunosorbent assay. The protein contents of cytochrome c, procaspase 3, caspase 3, Bcl-x(L), and Bax were analyzed by Western blot and quantified by densitometry. Lobular localization of active caspase 3 was examined by immunoperoxidase staining. PPC and DLPC decreased ethanol-induced increases in hepatocyte apoptosis, cytosolic cytochrome c, and caspase 3 content and its activity. Caspase 3 activity correlated with the number of apoptotic hepatocytes. Active caspase 3 was present predominantly in perivenular hepatocytes, and ethanol feeding extended it to lobular hepatocytes; this ethanol effect was reduced by PPC and DLPC. Ethanol significantly decreased Bcl-x(L) in homogenate, mitochondria, and cytosol, and there was a trend for increased Bcl-x(L) in these fractions after PPC and DLPC supplementation. Microsomal Bcl-x(L) did not differ between treatment groups. Bax was detected in homogenate and cytosol, and its level was not affected by ethanol. DLPC, at a dose contained in PPC, reproduces the antiapoptotic actions of PPC through a reduction in cytosolic cytochrome c concentration and caspase 3 activity, possibly in association with up-regulation of Bcl-x(L) expression. Because DLPC is a pure and well defined compound, it may be more suitable than PPC for intervention against alcohol-induced apoptosis.

Effects of Alcohol and Oxidative Stress on Liver Pathology: The Role of the Mitochondrion

This article represents the proceedings of a symposium at the 2001 Research Society on Alcoholism meeting in Montreal, Canada. The chairs were Alan Cahill and Carol C. Cunningham. The presentations were (1) Mitochondrial regulation of ethanol‐induced hepatocyte apoptosis: possible involvement of proapoptotic Bcl‐2 family protein Bax, by Masayuki Adachi and Hiromasa Ishii; (2) Effects of ethanol on mitochondrial reactive oxygen species production and oxidative protein modification, by Shannon M. Bailey; (3) Acute ethanol binges elicit widespread oxidative mitochondrial DNA damage and depletion: protective effects of antioxidants and inhibitors of ethanol metabolism, by Bernard Fromenty; and (4) Effects of chronic ethanol consumption upon hepatic mtDNA oxidative modification and depletion, by Alan Cahill and Adrian Davies.

Effects of Alcohol and Oxidative Stress on Liver Pathology: The Role of the Mitochondrion

This article represents the proceedings of a symposium at the 2001 Research Society on Alcoholism meeting in Montreal, Canada. The chairs were Alan Cahill and Carol C. Cunningham. The presentations were (1) Mitochondrial regulation of ethanol-induced hepatocyte apoptosis: possible involvement of proapoptotic Bcl-2 family protein Bax, by Masayuki Adachi and Hiromasa Ishii; (2) Effects of ethanol on mitochondrial reactive oxygen species production and oxidative protein modification, by Shannon M. Bailey; (3) Acute ethanol binges elicit widespread oxidative mitochondrial DNA damage and depletion: protective effects of antioxidants and inhibitors of ethanol metabolism, by Bernard Fromenty; and (4) Effects of chronic ethanol consumption upon hepatic mtDNA oxidative modification and depletion, by Alan Cahill and Adrian Davies.