Effects of ethanol ingestion and dietary fat levels on mitochondrial lipids in male and female rats

Distribution of Phosphatidylethanol in Maternal and Fetal Compartments After Chronic Gestational Binge Alcohol Exposure

BACKGROUND

Phosphatidylethanol (PEth) is a promising biomarker for gestational alcohol exposure. Studies show PEth accumulation in maternal and fetal blood following alcohol exposure; however, distribution of specific PEth homologues (16:0/18:1, 16:0/18:2, 16:0/20:4) in maternal and fetal blood is unknown. Additionally, PEth levels in highly vulnerable FASD targets in maternal and fetal compartments remain unexplored. We hypothesized that all 3 major PEth homologues will be detectable in the maternal and fetal blood, the maternal uterine artery (a reproductive tissue that delivers oxygen and nutrients to fetoplacental unit), and fetal brain regions following gestational binge alcohol exposure and that homologue distribution profiles will be tissue-specific.

METHODS

Pregnant rats received once-daily orogastric gavage of alcohol (Alcohol; BAC 216 mg/dl@4.5g/kg/d; BAC 289 mg/dl@6g/kg/d) or iso-caloric maltose dextrin (Pair-fed control) from gestation days (GD) 5 to 20 or 21. Following chronic exposure, maternal and fetal tissues were analyzed for PEth homologue concentrations utilizing LC-MS/MS technology.

RESULTS

All 3 PEth homologues were detected in alcohol-exposed maternal blood, fetal blood, maternal uterine artery, and fetal brain regions (hippocampus, cerebral cortex, and cerebellum). In both maternal and fetal blood, respectively, PEth 16:0/18:2 was more abundant compared to 16:0/18:1 (p < 0.0001,~66%,↑; p = 0.0159, 20.4%↑) and 16:0/20:4 (p = 0.0072,~25%↑; p = 0.0187, 19.4%↑). Maternal PEth 16:0/20:4 was ~ 42% higher than 16:0/18:1 (p = 0.0015). Maternal PEth 16:0/18:2 and 16:0/20:4 were ~ 25%↑ and ~ 20%↑ higher than in fetal blood (p < 0.05). No homologue differences were detected in the maternal uterine artery. In all fetal brain regions, PEth 16:0/18:1 was significantly higher (p < 0.0001) than 16:0/18:2 (~48 to 78%↑) and 16:0/20:4 (~31 to 62%↑) concentrations. PEth 16:0/20:4 was ~ 18% higher than 16:0/18:1 (p < 0.05) in the fetal hippocampus and cortex.

CONCLUSION

All major PEth homologues were detected in maternal and fetal blood following chronic gestational binge alcohol exposure; homologue distribution profiles were tissue-specific. This study also provides insights into PEth accumulation in critical FASD targets, specifically the maternal uterine artery and fetal brain.

A Novel Mouse Model of Acute-on-Chronic Cholestatic Alcoholic Liver Disease: A Systems Biology Comparison With Human Alcoholic Hepatitis

BACKGROUND

Alcohol-related liver disease is the main cause of liver-related mortality worldwide. The development of novel targeted therapies for patients with advanced forms (i.e., alcoholic hepatitis, AH) is hampered by the lack of suitable animal models. Here, we developed a novel mouse model of acute-on-chronic alcohol liver injury with cholestasis and fibrosis and performed an extensive molecular comparative analysis with human AH.

METHODS

For the mouse model of acute-on-chronic liver injury, we used 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC, 0.05% w/w) diet for 8 weeks to establish cholestatic liver fibrosis. After 1-week washout period, male mice were fed intragastrically for 4 weeks with up to 24 g/kg of ethyl alcohol in a high-fat diet. This animal model was phenotyped using histopathology, clinical chemistry, microbiome, and gene expression approaches. Data were compared to the phenotypes of human alcohol-related liver disease, including AH.

RESULTS

Mice with cholestatic liver fibrosis and subsequent alcohol exposure (DDC + EtOH) exhibited exacerbated liver fibrosis with a pericellular pattern, increased neutrophil infiltration, and ductular proliferation, all characteristics of human AH. DDC administration had no effect on urine alcohol concentration or liver steatosis. Importantly, DDC- and alcohol-treated mice showed a transcriptomic signature that resembled that of patients with AH. Finally, we show that mice in the DDC + EtOH group had an increased gut barrier dysfunction, mimicking an important pathophysiological mechanism of human AH.

CONCLUSIONS

We developed a novel mouse model of acute-on-chronic cholestatic alcoholic liver injury that has considerable translational potential and can be used to test novel therapeutic modalities for AH.

Fas Regulates Macrophage Polarization and Fibrogenic Phenotype in a Model of Chronic Ethanol-Induced Hepatocellular Injury

The role of Fas-mediated apoptosis and its effect on proinflammatory cytokine production in early alcoholic liver disease has not been addressed. Wild-type mice (C57Bl/6) or mice with a functional mutation in the Fas ligand (B6.gld) were given either high-fat control diet or ethanol diet by intragastric cannulation for 2 or 4 weeks. Liver injury, hepatic lipid accumulation, and proinflammatory cytokine production associated with chronic ethanol consumption were largely prevented in B6.gld mice compared with wild-type mice. Conversely, B6.gld mice given ethanol exhibited increases in collagen deposition, hepatic collagen gene expression, and profibrogenic cytokines (eg, transforming growth factor-β and IL-13) and alterations in matrix remodeling proteins (eg, matrix metalloproteinases and tissue inhibitor of metalloproteinases) compared with wild-type mice. Hepatic F4/80(+) macrophage populations were increased significantly in B6.gld mice compared with wild-type mice; hepatic CD3(+) cell populations were not significantly different. Importantly, a shift toward the expression of M2/Th2 cytokines (eg, IL-4 and IL-13) after ethanol exposure was observed in B6.gld mice compared with classical M1 cytokine expression in wild-type mice under similar conditions. In isolated macrophages, stimulation of Fas receptor minimally enhances lipopolysaccharide-induced M1 cytokine production and significantly limits M2 cytokine production. These data support the hypothesis that Fas-mediated signaling is important for an early ethanol-induced proinflammatory response but limits the profibrogenic response, regulating collagen production in response to chronic ethanol.

Interstrain differences in liver injury and one-carbon metabolism in alcohol-fed mice

Alcoholic liver injury is a major public health issue worldwide. Even though the major mechanisms of this disease have been established over the past decades, little is known about genetic susceptibility factors that may predispose individuals who abuse alcoholic beverages to liver damage and subsequent pathological conditions. We hypothesized that a panel of genetically diverse mouse strains may be used to examine the role of endoplasmic reticulum (ER) stress and one-carbon metabolism in the mechanism of interindividual variability in alcoholic liver injury. We administered alcohol (up to 27 mg/kg/d) in a high-fat diet using an intragastric intubation model for 28 days to male mice from 14 inbred strains (129S1/SvImJ, AKR/J, BALB/cJ, BALB/cByJ, BTBR T+tf/J, C3H/HeJ, C57BL/10J, DBA/2J, FVB/NJ, KK/HIJ, MOLF/EiJ, NZW/LacJ, PWD/PhJ, and WSB/EiJ). Profound interstrain differences (more than 3-fold) in alcohol-induced steatohepatitis were observed among the strains in spite of consistently high levels of urine alcohol that were monitored throughout the study. We found that ER stress genes were induced only in strains with the most liver injury. Liver glutathione and methyl donor levels were affected in all strains, albeit to a different degree. The most pronounced effects that were closely associated with the degree of liver injury were hyperhomocysteinemia and strain-dependent differences in expression patterns of one-carbon metabolism-related genes.

CONCLUSION

Our data demonstrate that strain differences in alcohol-induced liver injury and steatosis are striking and independent of alcohol exposure and the most severely affected strains exhibit major differences in the expression of ER stress markers and genes of one-carbon metabolism.

Laboratory models available to study alcohol-induced organ damage and immune variations: choosing the appropriate model

The morbidity and mortality resulting from alcohol-related diseases globally impose a substantive cost to society. To minimize the financial burden on society and improve the quality of life for individuals suffering from the ill effects of alcohol abuse, substantial research in the alcohol field is focused on understanding the mechanisms by which alcohol-related diseases develop and progress. Since ethical concerns and inherent difficulties limit the amount of alcohol abuse research that can be performed in humans, most studies are performed in laboratory animals. This article summarizes the various laboratory models of alcohol abuse that are currently available and are used to study the mechanisms by which alcohol abuse induces organ damage and immune defects. The strengths and weaknesses of each of the models are discussed. Integrated into the review are the presentations that were made in the symposium "Methods of Ethanol Application in Alcohol Model-How Long is Long Enough" at the joint 2008 Research Society on Alcoholism (RSA) and International Society for Biomedical Research on Alcoholism (ISBRA) meeting, Washington, DC, emphasizing the importance not only of selecting the most appropriate laboratory alcohol model to address the specific goals of a project but also of ensuring that the findings can be extrapolated to alcohol-induced diseases in humans.

Mechanism for prevention of alcohol-induced liver injury by dietary methyl donors

Alcohol-induced liver injury (ALI) has been associated with, among other molecular changes, abnormal hepatic methionine metabolism, resulting in decreased levels of S-adenosylmethionine (SAM). Dietary methyl donor supplements such as SAM and betaine mitigate ALI in animal models; however, the mechanisms of protection remain elusive. It has been suggested that methyl donors may act via attenuation of alcohol-induced oxidative stress. We hypothesized that the protective action of methyl donors is mediated by an effect on the oxidative metabolism of alcohol in the liver. Male C57BL/6J mice were administered a control high-fat diet or diet enriched in methyl donors with or without alcohol for 4 weeks using the enteral alcohol feeding model. As expected, attenuation of ALI and an increase in reduced glutathione:oxidized glutathione ratio were achieved with methyl donor supplementation. Interestingly, methyl donors led to a 35% increase in blood alcohol elimination rate, and while there was no effect on alcohol metabolism in the stomach, a profound effect on liver alcohol metabolism was observed. The catalase-dependent pathway of alcohol metabolism was induced, yet the increase in CYP2E1 activity by alcohol was blunted, which may be mitigating production of oxidants. Additional factors contributing to the protective effects of methyl donors in ALI were increased activity of low- and high-K(m) aldehyde dehydrogenases leading to lower hepatic acetaldehyde, maintenance of the efficient mitochondrial energy metabolism, and promotion of peroxisomal beta-oxidation. Profound changes in alcohol metabolism represent additional important mechanism of the protective effect of methyl donors in ALI.

Metformin prevents alcohol-induced liver injury in the mouse: Critical role of plasminogen activator inhibitor-1

BACKGROUND & AIMS

The biguanide drug metformin has recently been found to improve steatosis and liver damage in animal models and in humans with nonalcoholic steatohepatitis.

METHODS

The aim of the present study was to determine whether metformin also prevents steatosis and liver damage in mouse models of acute and chronic alcohol exposure.

RESULTS

Acute ethanol exposure caused a >20-fold increase in hepatic lipids, peaking 12 hours after administration. Metformin treatment significantly blunted the ethanol effect by >60%. Although metformin is a known inducer of AMP kinase (AMPK) activity, the hepatoprotective property of metformin did not correlate with activation of AMPK or of AMPK-dependent pathways. Instead, the protective effects of metformin correlated with complete prevention of the upregulation of plasminogen activator inhibitor (PAI)-1 caused by ethanol. Indeed, a similar protective effect against acute alcohol-induced lipid accumulation was observed in PAI-1-/- mice. Hepatic fat accumulation caused by chronic enteral ethanol feeding was also prevented by metformin or by knocking out PAI-1. Under these conditions, necroinflammatory changes caused by ethanol were also significantly attenuated.

CONCLUSIONS

Taken together, these findings suggest a novel mechanism of action for metformin and identify a new role of PAI-1 in hepatic injury caused by ethanol.

Opposing effects of chronic alcohol consumption on hepatic gluconeogenesis for female versus male rats

BACKGROUND

The impact of chronic alcohol consumption on hepatic gluconeogenesis (HGN) between males and females is unknown. To determine the effects of chronic alcohol consumption (8 weeks) on HGN, the isolated liver perfusion technique was used on 24-hr-fasted male and female Wistar rats.

METHODS

After surgical isolation, livers were perfused (single pass) for 30 min with Krebs-Henseleit bicarbonate buffer and fresh bovine erythrocytes with no added substrate (washout period). After the washout period, livers were perfused with lactate (10 mM) and [U-14C]lactate (15,000 dpm/ml) using the recirculation method.

RESULTS

There was no significant difference in HGN between males and females fed the control diet. In contrast, the females chronically fed the ethanol diet (FE) had significantly lower HGN rates (2.73 +/- 0.37 micromol/min x g liver protein(-1)), whereas males fed the ethanol diet (ME) had significantly higher HGN rates (4.99 +/- 0.45 micromol/min x g liver protein(-1)) than controls (3.83 +/- 0.34 micromol/min x g liver protein(-1)). Concomitant decreases were also observed for both 14C-lactate incorporation into 14C-glucose and rates of lactate uptake for FE, while corresponding increases were observed for 14C-lactate incorporation into 14C-glucose for ME. The livers from ME were able to convert a greater percentage of the lactate into glucose, resulting in the elevation in gluconeogenic capacity.

CONCLUSION

Chronic alcohol consumption lowers the hepatic gluconeogenic capacity from lactate in females and elevates HGN in males.

Cytochrome P450 CYP2E1, but not nicotinamide adenine dinucleotide phosphate oxidase, is required for ethanol-induced oxidative DNA damage in rodent liver

The occurrence of malignant tumors of the upper gastrointestinal tract and liver is, based largely on epidemiological evidence, causally related to the consumption of ethanol. It is widely recognized that oxidants play a key role in alcohol-induced liver injury; however, it is unclear how oxidants may be involved in DNA damage. We asked whether nicotinamide adenine dinucleotide phosphate oxidase, cytochrome P450 CYP2E1, or both are responsible for the production of DNA damage. The rodent Tsukamoto-French model of intragastric ethanol infusion was used. Wistar rats, Cyp2e1-, p47(phox)-null, and hCyp2e1 transgenic mice were used. The abundance of oxidative DNA adducts, mutagenic apurinic/apyrimidinic sites, and expression of base excision DNA repair genes was determined. In rats and wild-type mice, ethanol treatment for 4 weeks led to an increase in oxidative DNA damage and induction of expression of the base excision DNA repair genes that are known to remove oxidative DNA lesions. No increase in either of the endpoints was observed in ethanol-treated Cyp2e1-null mice, whereas the magnitude of response in p47(phox)-null mice and transgenic hCyp2e1 was identical to that in wild types. The increase in expression of DNA repair genes was completely abolished by treatment with the P450 inhibitor 1-aminobenzotriazole. In conclusion, the data support the hypothesis that oxidative stress to DNA is induced in liver by ethanol. Furthermore, although it was shown that nicotinamide adenine dinucleotide phosphate oxidase-derived oxidants are critical for the development of ethanol-induced liver injury, CYP2E1 is required for the induction of oxidative stress to DNA, and thus may play a key role in ethanol-associated hepatocarcinogenesis.

Ethanol-Induced Changes in Lipid Composition of Intestinal Microvillus Membrane in Rats Fed Different Dietary Fats

BACKGROUND/METHOD

The effect of feeding ethanol for 5 weeks on the lipid composition of the intestinal microvillus membrane (MVM) was studied in rats fed a commercial rat pellet (RP) diet or purified diets containing 10% coconut oil (CCO), corn oil (CO) or fish oil (FO).

RESULTS

A low cholesterol/phospholipid ratio and increased saturated fatty acid level were observed in MVM from the CCO or FO groups. Chronic administration of ethanol to RP- or CO-fed animals increased phospholipids, total and free cholesterol, and the triglyceride and ganglioside content of MVM. The free cholesterol and phospholipid content was reduced while the triglyceride level remained unaffected by ethanol treatment in the CCO or FO groups. Ethanol ingestion decreased 10:2 and 20:4 (n-6 fatty acids) but increased the saturated fatty acid content of MVM in all the dietary groups except in CCO-fed animals where the 18:2 level was not affected. An elevated 18:1, but decreased 22:6 percentage was observed in the ethanol-fed FO group. The fatty acid composition of MVM from the CCO-fed group was least affected by ethanol treatment.

CONCLUSION

These observations suggest that the type of dietary fat modifies ethanol-mediated alterations in MVM lipid composition.

Development of Alcoholic Fatty Liver and Fibrosis in Rhesus Monkeys Fed a Low n-3 Fatty Acid Diet

BACKGROUND

The amount and type of dietary fat seem to be important factors that modulate the development of alcohol-induced liver steatosis and fibrosis. Various alcohol-feeding studies in animals have been used to model some of the symptoms that occur in liver disease in humans.

METHODS

Rhesus monkeys (Macaca mulatta) were maintained on a diet that had a very low concentration of alpha-linolenic acid and were given free access to an artificially sweetened 7% ethanol solution. Control and ethanol-consuming animals were maintained on a diet in which the linoleate content was adequate (1.4% of energy); however, alpha-linoleate represented only 0.08% of energy. Liver specimens were obtained, and the fatty acid composition of the liver phospholipids, cholesterol esters, and triglycerides of the two groups were compared at 5 years and histopathology of tissue samples were compared at 3 and 5 years.

RESULTS

The mean consumption of ethanol for this group over a 5-year period was 2.4 g.kg.day. As a consequence of the ethanol-dietary treatment, there were significantly lower concentrations of several polyunsaturated fatty acids in the liver phospholipids of the alcohol-treated group, including arachidonic acid and most of the n-3 fatty acids and particularly docosahexaenoic acid, when compared with dietary controls. Liver specimens from animals in the ethanol group at 5 years showed a marked degree of steatosis, both focal and diffuse cellular necrosis, and an increase in the development of fibrosis compared with specimens obtained at 3 years and with those from dietary controls, in which there was no evidence of fibrotic lesions.

CONCLUSION

These findings suggest that the advancement of ethanol-induced liver disease in rhesus monkeys may be modulated by the amount and type of dietary essential fatty acids and that a marginal intake of n-3 fatty acids may be a permissive factor in the development of liver disease in primates.

Contribution of Angiotensin II to Alcohol-Induced Pancreatic Fibrosis in Rats

The mechanisms by which alcohol causes pancreatic fibrosis remain unknown. Recent studies have demonstrated that angiotensin II contributes to the development of fibrosis in liver, kidney, and heart injury. Here, the effects of angiotensin-converting enzyme inhibitor (captopril) and angiotensin II receptor antagonist (losartan) on alcohol-induced pancreatic fibrosis were examined in an intragastric ethanol-feeding model. Male rats were fed a high-fat liquid diet with either ethanol (16-20 g/kg/day) or isocaloric maltose-dextrin (control) for 4 weeks. Subgroups daily received captopril (60 mg/kg/day), losartan (3 mg/kg/day), or no additional agent included in liquid diets. Mean urine alcohol concentrations in all groups fed ethanol were more than 270 mg/dl and not significantly different. Dietary alcohol caused diffuse gland atrophy and interlobular and intralobular fibrosis with mild structural distortion in the pancreas, an effect that was blunted by captopril or losartan treatment. Alcohol also increased the number of alpha-smooth muscle actin-positive cells and transforming growth factor-beta mRNA expression in the pancreas. These increases were blunted significantly by captopril or losartan treatment. These data suggest that angiotensin II contributes to the development of chronic alcohol-induced pancreatic fibrosis through its stimulation of transforming growth factor-beta expression.

Perspectives on alcohol consumption: liver polyunsaturated fatty acids and essential fatty acid metabolism

In this article, subjects diagnosed with alcoholic liver disease are shown to have lower concentrations of several polyunsaturated fatty acids (PUFAs), including 18:2n6, 18:3n6, 20:3n6, 18:3n3, 22:5n3, and 22:6n3, but not 20:4n6 and 22:4n6, nor 22:5n6, in the total lipid extracts of their livers compared with findings for specimens obtained from patients diagnosed with primary biliary cirrhosis and from control subjects. Findings of studies in animals have demonstrated that prolonged alcohol consumption reduces liver polyunsaturate content. However, the effect of ethanol on the elongation/desaturation of essential fatty acids is complex, as in vitro study results indicate that the direction of the effect of alcohol may be related to the dose of alcohol. Findings of studies in hepatocyte cell culture indicate that ethanol increased delta-5 and delta-6 desaturase activities throughout a broad concentration range. In contrast, lower liver desaturase activity has been reported in animals consuming high concentrations of alcohol (36%-40% energy) over a period of several months. Findings from in vivo isotope tracers studies in nonhuman primates and felines indicate that prolonged periods of moderate (mean consumption 2.6 g kg(-1) d(-1) and 1.2 g kg(-1) d(-1), respectively) alcohol consumption had no effect on the uptake of either linoleic (18:2n6) or alpha-linolenic (18:3n3) acids into the plasma and lead to an increased incorporation of these deuterated precursors into 20:4n6 and 22:6n3. Thus, this likely reflects a stimulated, rather than an inhibited, production of long-chain PUFAs. In numerous studies in various species, investigators have documented that alcohol consumption can increase the level of lipid peroxidation in tissues, and sustained periods of ethanol-induced peroxidation can deplete tissues of PUFAs. A hypothesis to rationalize the long-term effects of alcohol consumption on liver PUFA concentration that takes into consideration the effect of ethanol on essential fatty acid metabolism is presented.

TNF alpha-induced Ras activation due to ethanol promotes hepatocyte proliferation independently of liver injury in the mouse

Tumor necrosis factor alpha (TNFalpha) has been shown to be both proapoptotic and mitogenic for hepatocytes and necessary for alcohol-induced liver injury. Ras, a known proto-oncogene, is very important in the regulation of cellular responses to TNFalpha. Therefore, the purpose of this study was to investigate the role of Ras in alcohol-induced pathogenesis. Male C57Bl/6 mice were fed ethanol or high-fat control diet via intragastric cannulation for 4 weeks. Ras activity was increased significantly after 4 weeks of ethanol and correlated with an increase in pathologic features. However, in mice deficient in the receptor-type 1 for TNFalpha (TNFR1(-/-)), ethanol-induced liver injury and the increase in Ras activity were significantly blunted compared with wild-type mice. Furthermore, it was demonstrated that H-, K-, and R-Ras isoforms were increased after ethanol exposure in wild-type mice. In TNFR1(-/-) mice, R-Ras activity remained elevated by ethanol, whereas H-Ras and K-Ras activity was blunted significantly under these conditions. Interestingly, hepatocellular proliferation, which was elevated approximately fivefold after 4 weeks of chronic ethanol in wild-type mice, was also blunted in TNFR1(-/-) mice given ethanol. Inhibition of Ras with adenovirus containing a dominant-negative Ras had no effect on ethanol-induced liver injury, but significantly blunted ethanol-induced hepatocyte proliferation by more than 50%. Overexpression of mitochondrial superoxide dismutase using recombinant adenovirus blunted lipid peroxidation and attenuated hepatic injury resulting from ethanol, but had no effect on Ras activation and hepatocyte proliferation caused by ethanol. In conclusion, these data support the hypotheses that hepatocellular oxidative stress leads to cell death and that TNFalpha-induced Ras activation is important in hepatic proliferation in response to ethanol-induced liver injury.

Inducible nitric oxide synthase is required in alcohol-induced liver injury: studies with knockout mice

BACKGROUND & AIMS

Oxidative stress contributes to early alcohol-induced liver injury, and superoxide (O(2)*-) production from NADPH oxidase plays a key role. However, the production of the free radical nitric oxide (NO*) by inducible nitric oxide synthase (iNOS) could also be involved.

METHODS

To test this hypothesis, iNOS knockout (B6.129P2-Nos2 (tm1 Lau)) and wild-type mice were fed high-fat control or ethanol-containing diets for 4 weeks.

RESULTS

Mean body weight gains were not significantly different between treatment groups, and average urine ethanol concentrations were similar in wild-type and iNOS knockout mice. After 4 weeks, serum alanine aminotransferase (ALT) levels were increased significantly about 4-fold over control values (29 +/- IU/L) by enteral ethanol (113 +/- 20) in wild-type mice; this effect of ethanol was significantly blunted in iNOS knockout mice (50 +/- 9). Similar protective effects against liver damage were observed if wild-type mice were treated with the iNOS inhibitor N -(3-aminomethyl)benzyl-acetamindine (1400W). Enteral ethanol also caused severe fatty accumulation, mild inflammation, and necrosis in the liver in wild-type mice but had no effect in iNOS knockout mice. The accumulation of 4-hydroxynonenal (lipid peroxidation) and 3-nitrotyrosine (reactive nitrogen species formation) protein adducts caused by alcohol was completely blocked in iNOS knockout mice.

CONCLUSIONS

These data strongly support the hypothesis that iNOS is required for the pathogenesis of early alcohol-induced hepatitis by production of nitric oxide-derived pro-oxidants (e.g., peroxynitrite).

Chronic intragastric alcohol exposure causes hypoxia and oxidative stress in the rat pancreas

The effect of chronic enteral ethanol on pancreatic hypoxia was investigated using the hypoxia marker, pimonidazole. Male Wistar rats were fed an ethanol-containing diet for 3 weeks using an enteral model shown to cause pancreatic damage; pimonidazole (120 mg/kg i.v.) was injected 1h before sacrifice. Pimonidazole and 4-hydroxynonenal (an index of lipid peroxidation) adducts were detected immunochemically. Breathing air with low oxygen content (8% O(2)) for 1h increased pimonidazole adduct accumulation approximately 2-fold in pancreata of nai;ve rats, confirming that this technique will detect increases in hypoxia in pancreata. Pancreata of rats fed ethanol began to show signs of damage after 3 weeks. Ethanol feeding also significantly increased pimonidazole adducts in pancreas approximately 2-fold (1 or 3 weeks of ethanol produced similar values). Concomitant with increasing hypoxia in the pancreas, alcohol also caused a significant increase in 4-hydroxynonenal adducts, indicative of increased oxidative stress. These results indicate that chronic ethanol causes hypoxia at the cellular level in the pancreas in vivo; further, the data support the hypothesis that hypoxia is involved in mechanisms of chronic alcoholic pancreatitis.

Cocoa extract protects against early alcohol-induced liver injury in the rat

Oxidants have been shown to be involved in alcohol-induced liver injury. This study was designed to determine whether cocoa flavonoid extract, composed mostly of epicatechin and epicatechin oligomers, protects against early alcohol-induced liver injury in rats. Male Wistar rats were fed high-fat liquid diets with or without ethanol (10-14 g/kg per day) and cocoa extract (400 mg/kg per day) continuously for 4 weeks using an enteral feeding protocol. Mean body weight gains ( approximately 4 g/day) were not significantly different between treatment groups. Cocoa extract did not affect average daily urine ethanol concentrations ( approximately 200mg/dL). After 4 weeks, serum alanine amino transferase levels of the ethanol group were increased nearly fourfold (110+/-16 IU/L) compared to control values (35+/-3 IU/L); this effect of ethanol was blocked by cocoa extract (60+/-6 IU/L). Additionally, enteral ethanol caused severe fat accumulation, mild inflammation, and necrosis in the liver; cocoa extract significantly blunted these changes. Increases in liver TNFalpha protein levels caused by ethanol were completely blocked by cocoa extract. Further, ethanol significantly increased the accumulation of protein adducts of 4-hydroxynonenal, a product of lipid peroxidation serving as an index of oxidative stress; again this was counteracted by the addition of cocoa extract. These results indicate that dietary flavanols such as those found in cocoa can prevent early alcohol-induced liver injury.

Megamitochondria formation - physiology and pathology

Mitochondria undergo structural changes simultaneously with their functional changes in both physiological and pathological conditions. These structural changes of mitochondria are classified into two categories: simple swelling and the formation of megamitochondria (MG). Data have been accumulated to indicate that free radicals play a crucial role in the mechanism of the MG formation induced by various experimental conditions which are apparently various. These include ethanol-, chloramphenicol- and hydrazine-induced MG formation. Involvement of free radicals in the mechanism of MG formation is showed by the fact that MG formation is successfully suppressed by free radical scavengers such as alpha-tocopherol, coenzyme Q(10), and 4-OH-TEMPO. Detailed mechanisms and pathophysiological meanings of MG formation still remain to be investigated. However, a body of evidence strongly suggests that enormous changes in physicochemical and biochemical properties of the mitochondrial membranes during MG formation take place and these changes are favorable for membrane fusion. A recent report showed that continous exposure of cells with MG to free radicals induces apoptosis, finding which suggests that MG formation is an adaptative process to unfavorable environments at the level of intracellular organelles. Mitochondria try to decrease intracellular reactive oxygen species (ROS) levels by decreasing the consume of oxygen via MG formation. If mitochondria succeed to suppress intracellular ROS levels, MG return to normal both structurally and functionally, and they restore the ability to actively synthesize ATP. If cells are additionally exposed to excess amounts of free radicals, MG become swollen, membrane potential of mitochondria (DeltaPsim) decreases, cytochrome c is released from mitochondria, leading to activation of caspases and apoptosis is induced.

Effect of Kupffer cell inactivation on ethanol-induced protein adducts in the liver

Tissue deposition of protein adducts derived from ethanol metabolism and lipid peroxidation, has been suggested to play a role in the initiation of alcoholic liver disease. The mechanisms modulating adduct formation have, however, remained unclear. We used immunohistochemical methods to examine acetaldehyde (AA) and malondialdehyde (MDA) adducts and cytochrome P4502E1 and P4503A2 expression in rats after administration of (i) an ethanol-diet (n = 6), (ii) ethanol-diet plus gadolinium chloride (GdCl(3)), a selective Kupffer cell toxicant (n = 7), or (iii) control diet (n = 6). A 4 week ethanol treatment resulted in liver steatosis, necrosis, and inflammation and deposition of protein adducts with both AA and MDA, which colocalized with areas of fatty change. The intensities (mean +/- SD) of the immunohistochemical reactions for both AA (2.50 +/- 1.23) and MDA (3.00 +/- 1.10) adducts were significantly higher in the ethanol-fed animals than in the controls (0.083 +/- 0.20) (0.16 +/- 0.25) (p <.001). GdCl(3) prevented adduct accumulation, the mean immunohistochemistry scores being 0.86 +/- 1.07 for AA and 1.64 +/- 0.63 for MDA, the former showing a more striking reduction (p <.01). The hepatic cytochrome enzymes were not different in the ethanol-fed groups with or without GdCl(3). The data indicates that Kupffer cells are involved in the generation of protein adducts with both acetaldehyde and ethanol-induced lipid peroxidation products in alcoholic liver disease.

Production of a cytochrome P450 2E1 transgenic mouse and initial evaluation of alcoholic liver damage

Hepatic metabolism of ethanol by cytochrome P450 2E1 (CYP2E1) is believed to contribute to alcoholic liver damage. To further evaluate CYP2E1 in alcoholic liver disease, we created a transgenic mouse containing human CYP2E1 complementary DNA (cDNA) under the control of mouse albumin enhancer-promoter. Two experiments were performed. In the first experiment, transgenic and nontransgenic mice were fed normal chow. In the second experiment, transgenic and nontransgenic mice were pair fed a nutritionally complete liquid diet for 16 weeks. The liquid diet contained 30% of calories as ethanol (or dextrose) and 25% of calories as corn oil. Liver damage was assessed by measuring serum alanine aminotransferase (ALT) levels and examining liver histology. Transgenic animals reproduced and were phenotypically normal. Hepatic levels of CYP2E1 messenger RNA (mRNA), protein, and enzyme activity did not differ between chow-fed transgenic and nontransgenic mice. Livers from transgenic mice fed the alcohol diet contained significantly more CYP2E1 protein and enzyme activity than livers from nontransgenic mice fed the same diet. Transgenic mice receiving the alcohol diet had significantly higher serum ALT levels than nontransgenic mice. Histologic examination of the livers showed higher histologic scores in transgenic mice fed ethanol compared with nontransgenic mice fed ethanol. Ballooning hepatocytes were seen in livers from transgenic mice fed ethanol. Apoptosis, as determined by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay, did not differ between groups. In conclusion, we have produced a transgenic mouse that expresses human CYP2E1 in the liver. When fed a nutritionally complete alcohol diet, transgenic mice develop more liver damage than nontransgenic mice.

Role of lipopolysaccharide-binding protein in early alcohol-induced liver injury in mice

Cellular responses to endotoxins are enhanced markedly by LPS-binding protein (LBP). Furthermore, it has been demonstrated that endotoxins and proinflammatory cytokines such as TNF-alpha participate in early alcohol-induced liver injury. Therefore, in this study, a long-term intragastric ethanol feeding model was used to test the hypothesis that LBP is involved in alcoholic hepatitis by comparing LBP knockout and wild-type mice. Two-month-old female mice were fed a high-fat liquid diet with either ethanol or isocaloric maltose-dextrin as control continuously for 4 wk. There was no difference in mean urine alcohol concentrations between the groups fed ethanol. Dietary alcohol significantly increased liver to body weight ratios and serum alanine aminotransferase levels in wild-type mice (189 +/- 31 U/L) over high-fat controls (24 +/- 7 U/L), effects which were blunted significantly in LBP knockout mice (60 +/- 17 U/L). Although no significant pathological changes were observed in high-fat controls, 4 wk of dietary ethanol caused steatosis, mild inflammation, and focal necrosis in wild-type animals as expected (pathology score, 5.9 +/- 0.5). These pathological changes were reduced significantly in LBP knockout mice fed ethanol (score, 2.6 +/- 0.5). Endotoxin levels in the portal vein were increased significantly after 4 wk in both groups fed ethanol. Moreover, ethanol increased TNF-alpha mRNA expression in wild-type, but not in LBP knockout mice. These data are consistent with the hypothesis that LBP plays an important role in early alcohol-induced liver injury by enhancing LPS-induced signal transduction, most likely in Kupffer cells.

Green tea extract protects against early alcohol-induced liver injury in rats

Oxidants have been shown to be involved in alcohol-induced liver injury. This study was designed to test the hypothesis that the antioxidant polyphenolic extract of green tea, comprised predominantly of epigallocatechin gallate, protects against early alcohol-induced liver injury in rats. Male Wistar rats were fed high-fat liquid diets with or without ethanol (10-14 g kg(-1) day(-1)) and green tea (300 mg kg(-1) day(-1)) continuously for 4 weeks using an intragastric enteral feeding protocol. Mean body weight gains (approximately 4 g/day) were not significantly different between treatment groups, and green tea extract did not the affect average concentration or the cycling of urine ethanol concentrations (0-550 mg dl(-1) day(-1)). After 4 weeks, serum ALT levels were increased significantly about 4-fold over control values (35+/-3 IU/l) by enteral ethanol (114+/-18); inclusion of green tea extract in the diet significantly blunted this increase (65+/-10). Enteral ethanol also caused severe fatty accumulation, mild inflammation, and necrosis in the liver. While not affecting fat accumulation or inflammation, green tea extract significantly blunted increases in necrosis caused by ethanol. Furthermore, ethanol significantly increased the accumulation of protein adducts of 4-hydroxynonenal, a product of lipid peroxidation and an index of oxidative stress; green tea extract blocked this effect almost completely. TNFalpha protein levels were increased in liver by alcohol; this phenomenon was also blunted by green tea extract. These results indicate that simple dietary antioxidants, such as those found in green tea, prevent early alcohol-induced liver injury, most likely by preventing oxidative stress.

Overexpression of manganese superoxide dismutase prevents alcohol-induced liver injury in the rat

Mitochondria are thought to play a major role in hepatic oxidative stress associated with alcohol-induced liver injury. Thus, the hypothesis that delivery of the mitochondrial isoform of superoxide dismutase (Mn-SOD) via recombinant adenovirus would reduce alcohol-induced liver injury was tested. Rats were given recombinant adenovirus containing Mn-SOD (Ad.SOD2) or beta-galactosidase (Ad.lacZ) and then fed alcohol enterally for 4 weeks. Mn-SOD expression and activity of Ad.SOD2 in liver mitochondria of infected animals was increased nearly 3-fold compared with Ad.lacZ-infected controls. Mitochondrial glutathione levels in Ad.lacZ-infected animals were decreased after 4 weeks of chronic ethanol, as expected, but were unchanged in Ad.SOD2-infected animals. Alanine aminotransferase was elevated significantly by ethanol, an effect that was prevented by Ad.SOD2. Moreover, pathology (e.g. the sum of steatosis, inflammation, and necrosis) was elevated dramatically by ethanol in Ad.lacZ-treated rats. This effect was also blunted in animals infected with Ad.SOD2. Neutrophil infiltration was increased about 3-fold in livers from both Ad.lacZ- and Ad.SOD2-infected rats by ethanol treatment. Moreover, ESR-detectable free radical adducts in bile were increased about 8-fold by ethanol. Using (13)C-labeled ethanol, it was determined that nearly 60% of total adducts were due to the alpha-hydroxyethyl radical adduct. This increase in radical formation was blocked completely by Ad.SOD2 infection. Furthermore, apoptosis of hepatocytes was increased about 5-fold by ethanol, an effect also blocked by Ad.SOD2. Interestingly, tumor necrosis factor-alpha mRNA was elevated to the same extent in both Ad.lacZ- and Ad.SOD2-infected animals follows ethanol exposure. These data suggest that hepatocyte mitochondrial oxidative stress is involved in alcohol-induced liver damage and likely follows Kupffer cell activation, cytokine production, and neutrophil infiltration. These results also support the hypothesis that mitochondrial oxidant production is a critical factor in parenchymal cell death caused by alcohol.

Development of an animal model of chronic alcohol-induced pancreatitis in the rat

This study was designed to develop an animal model of alcoholic pancreatitis and to test the hypothesis that the dose of ethanol and the type of dietary fat affect free radical formation and pancreatic pathology. Female Wistar rats were fed liquid diets rich in corn oil (unsaturated fat), with or without a standard or high dose of ethanol, and medium-chain triglycerides (saturated fat) with a high dose of ethanol for 8 wk enterally. The dose of ethanol was increased as tolerance developed, which allowed approximately twice as much alcohol to be delivered in the high-dose group. Serum pancreatic enzymes and histology were normal after 4 wk of diets rich in unsaturated fat, with or without the standard dose of ethanol. In contrast, enzyme levels were elevated significantly by the high ethanol dose. Increases were blunted significantly by dietary saturated fat. Fibrosis and collagen alpha1(I) expression in the pancreas were not detectable after 4 wk of enteral ethanol feeding; however, they were enhanced significantly by the high dose after 8 wk. Furthermore, radical adducts detected by electron spin resonance were minimal with the standard dose; however, the high dose increased carbon-centered radical adducts as well as 4-hydroxynonenal, an index of lipid peroxidation, significantly. Radical adducts were also blunted by approximately 70% by dietary saturated fat. The animal model presented here is the first to demonstrate chronic alcohol-induced pancreatitis in a reproducible manner. The key factors responsible for pathology are the amount of ethanol administered and the type of dietary fat.

ICAM-1 is involved in the mechanism of alcohol-induced liver injury: studies with knockout mice

To test the hypothesis that leukocyte infiltration mediated by intercellular adhesion molecule (ICAM)-1 is involved in early alcohol-induced liver injury, male wild-type or ICAM-1 knockout mice were fed a high-fat liquid diet with either ethanol or isocaloric maltose-dextrin for 4 wk. There were no differences in mean urine alcohol concentrations between the groups fed ethanol. Alcohol administration significantly increased liver size and serum alanine aminotransferase levels in wild-type mice over high-fat controls, effects that were blunted significantly in ICAM-1 knockout mice. Dietary ethanol caused severe steatosis, mild inflammation, and focal necrosis in livers from wild-type mice. Furthermore, livers from wild-type mice fed ethanol showed significant increases in the number of infiltrating leukocytes, which were predominantly lymphocytes. These pathological changes were blunted significantly in ICAM-1 knockout mice. Tumor necrosis factor (TNF)-alpha mRNA expression was increased in wild-type mice fed ethanol but not in ICAM-1 knockout mice. These data demonstrate that ICAM-1 and infiltrating leukocytes play important roles in early alcohol-induced liver injury, most likely by mechanisms involving TNF-alpha.

Diphenyleneiodonium sulfate, an NADPH oxidase inhibitor, prevents early alcohol-induced liver injury in the rat

The oxidant source in alcohol-induced liver disease remains unclear. NADPH oxidase (mainly in liver Kupffer cells and infiltrating neutrophils) could be a potential free radical source. We aimed to determine if NADPH oxidase inhibitor diphenyleneiodonium sulfate (DPI) affects nuclear factor-kappaB (NF-kappaB) activation, liver tumor necrosis factor-alpha (TNF-alpha) mRNA expression, and early alcohol-induced liver injury in rats. Male Wistar rats were fed high-fat liquid diets with or without ethanol (10-16 g. kg(-1). day(-1)) continuously for up to 4 wk, using the Tsukamoto-French intragastric enteral feeding protocol. DPI or saline vehicle was administered by subcutaneous injection for 4 wk. Mean urine ethanol concentrations were similar between the ethanol- and ethanol plus DPI-treated groups. Enteral ethanol feeding caused severe fat accumulation, mild inflammation, and necrosis in the liver (pathology score, 4.3 +/- 0.3). In contrast, DPI significantly blunted these changes (pathology score, 0.8 +/- 0.4). Enteral ethanol administration for 4 wk also significantly increased free radical adduct formation, NF-kappaB activity, and TNF-alpha expression in the liver. DPI almost completely blunted these parameters. These results indicate that DPI prevents early alcohol-induced liver injury, most likely by inhibiting free radical formation via NADPH oxidase, thereby preventing NF-kappaB activation and TNF-alpha mRNA expression in the liver.

Transgenic and gene "knockout" models in alcohol research

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Paula L. Hoffman and Takeshi Yagi. The presentations were (1) cAMP signaling in ethanol sensitivity and tolerance, by Boris Tabakoff; (2) Synaptic signaling pathways of Fyn-tyrosine kinase, by Takeshi Yagi; (3) Ethanol drinking and sensitization in dopaminergic and serotonergic receptor knockouts, by Tamara J. Phillips; (4) ICAM-1 is involved in early alcohol-induced liver injury in the mouse given enteral alcohol, by Hiroshi Kono; and (5) Strategies for targeted and regulated knockouts, by Robert O. Messing and Doo-Sup Choi.

Delivery of the Cu/Zn-superoxide dismutase gene with adenovirus reduces early alcohol-induced liver injury in rats

BACKGROUND AND AIMS

Alcohol-induced liver injury is associated with an increase in oxidants from a variety of possible sources. Therefore, it was hypothesized that increased and stable expression of the antioxidant enzyme Cu/Zn-superoxide dismutase (SOD1) would diminish oxygen free radicals and reduce alcohol-induced liver injury.

METHODS

To test this hypothesis, rats were given recombinant adenovirus containing Cu/Zn-superoxide dismutase (Ad.SOD1) or beta-galactosidase (Ad.lacZ) and fed ethanol enterally for 3 weeks.

RESULTS

SOD was increased significantly 3-5-fold over endogenous levels in both hepatocytes as well as Kupffer cells 3 weeks after infection. Serum transaminase levels and pathology were elevated significantly in Ad.lacZ-treated animals by using an intragastric feeding model. This effect was blunted significantly in Ad.SOD1-infected animals. Importantly, electron spin resonance-detectable free-radical adducts caused by ethanol were also decreased by SOD1 overexpression. Moreover, the increase in nuclear factor kappaB (NFkappaB), tumor necrosis factor alpha (TNF-alpha), and interleukin 1 messenger RNA (mRNA) caused by ethanol was blunted in animals treated with Ad.SOD1.

CONCLUSIONS

These data support the hypothesis that oxidant production is critical in early alcohol-induced liver injury and that gene delivery of antioxidant enzymes may be useful in prevention and treatment.

Reduced early alcohol-induced liver injury in CD14-deficient mice

Activation of Kupffer cells by gut-derived endotoxin is associated with alcohol-induced liver injury. Recently, it was shown that CD14-deficient mice are more resistant to endotoxin-induced shock than wild-type controls. Therefore, this study was designed to investigate the role of CD14 receptors in early alcohol-induced liver injury using CD14 knockout and wild-type BALB/c mice in a model of enteral ethanol delivery. Animals were given a high-fat liquid diet continuously with ethanol or isocaloric maltose-dextrin as control for 4 wk. The liver to body weight ratio in wild-type mice (5.8 +/- 0.3%) was increased significantly by ethanol (7.3 +/- 0.2%) but was not altered by ethanol in CD14-deficient mice. Ethanol elevated serum alanine aminotransferase levels nearly 3-fold in wild-type mice, but not in CD14-deficient mice. Wild-type and knockout mice given the control high-fat diet had normal liver histology, whereas ethanol caused severe liver injury (steatosis, inflammation, and necrosis; pathology score = 3.8 +/- 0.4). In contrast, CD14-deficient mice given ethanol showed minimal hepatic changes (score = 1.6 +/- 0.3, p < 0.05). Additionally, NF-kappa B, TGF-beta, and TNF-alpha were increased significantly in wild-type mice fed ethanol but not in the CD14 knockout. Thus, chronic ethanol feeding caused more severe liver injury in wild-type than CD14 knockouts, supporting the hypothesis that endotoxin acting via CD14 plays a major role in the development of early alcohol-induced liver injury.

Ebselen prevents early alcohol-induced liver injury in rats

Oxidants have been shown to be involved in alcohol-induced liver injury. Moreover, 2-phenyl-1,2-benzisoselenazole-3(2H)-one (ebselen), an organoselenium compound and glutathione peroxidase mimic, decreases oxidative stress and protects against stroke clinically. This study was designed to test the hypothesis that ebselen protects against early alcohol-induced liver injury in rats. Male Wistar rats were fed high-fat liquid diets with or without ethanol (10-16 g/kg/d) continuously for up to 4 weeks using the intragastric enteral feeding protocol developed by Tsukamoto and French. Ebselen (50 mg/kg twice daily, intragastrically) or vehicle (1% tylose) was administered throughout the experiment. Mean urine ethanol concentrations were not significantly different between treatment groups, and ebselen did not affect body weight gains or cyclic patterns of ethanol concentrations in urine. After 4 weeks, serum ALT levels were increased significantly about 4-fold over control values (37 +/- 5 IU/l) by enteral ethanol (112 +/- 7 IU/l); ebselen blunted this increase significantly (61 +/- 8 IU/l). Enteral ethanol also caused severe fatty accumulation, mild inflammation, and necrosis in the liver (pathology score: 4.3 +/- 0.3). In contrast, these pathological changes were blunted significantly by ebselen (pathology score: 2.5 +/- 0.4). While there were no significant effects of either ethanol or ebselen on glutathione peroxidase activity in serum or liver tissue, ebselen blocked the increase in serum nitrate/nitrite caused by ethanol. Furthermore, ethanol increased the activity of NF-kappaB over 5-fold, the number of infiltrating neutrophils 4-fold, and the accumulation of 4-hydroxynonenal over 5-fold. Ebselen blunted all of these effects significantly. These results indicate that ebselen prevents early alcohol-induced liver injury, most likely by preventing oxidative stress, which decreases inflammation.

Chronic ethanol increases adeno-associated viral transgene expression in rat liver via oxidant and NFkappaB-dependent mechanisms

Recombinant adeno-associated virus (rAAV) transduction is limited in vivo, yet can be enhanced by hydroxyurea, ultraviolet-irradiation, or adenovirus coinfection, possibly via mechanisms involving stress in the host cell. Because chronic ethanol induces oxidative stress, it was hypothesized that chronic ethanol would increase rAAV transduction in vivo. To test this hypothesis, rAAV encoding beta-galactosidase was given to Wistar rats that later received either ethanol diet or high-fat control diet via an enteral-feeding protocol for 3 weeks. Expression and activity of beta-galactosidase in the liver were increased nearly 5-fold by ethanol. The increase in transgene expression was inhibited by antioxidant diphenylene iodonium (DPI), which is consistent with the hypothesis that ethanol causes an increase in rAAV transduction via oxidative stress. Ethanol increased DNA synthesis only slightly; however, it increased the nuclear transcription factor kappaB (NFkappaB) 4-fold, a phenomenon also sensitive to DPI. Moreover, a 6-fold increase in rAAV transgene expression was observed in an acute ischemia-reperfusion model of oxidative stress. Transgene expression was transiently increased 24 hours after ischemia-reperfusion 3 days and 3 weeks after rAAV infection. Further, adenoviral expression of superoxide dismutase or IkappaBalpha superrepressor inhibited rAAV transgene expression caused by ischemia-reperfusion. Therefore, it is concluded that ethanol increases rAAV transgene expression via mechanisms dependent on oxidative stress, and NFkappaB likely through enhancement of cytomegaloviral (CMV) promoter elements. Alcoholic liver disease is an attractive target for gene therapy because consumption of ethanol could theoretically increase expression of therapeutic genes (e.g., superoxide dismutase). Moreover, this study has important implications for rAAV gene therapy and potential enhancement and regulation of transgene expression in liver.

NADPH oxidase-derived free radicals are key oxidants in alcohol-induced liver disease

In North America, liver disease due to alcohol consumption is an important cause of death in adults, although its pathogenesis remains obscure. Despite the fact that resident hepatic macrophages are known to contribute to early alcohol-induced liver injury via oxidative stress, the exact source of free radicals has remained a mystery. To test the hypothesis that NADPH oxidase is the major source of oxidants due to ethanol, we used p47(phox) knockout mice, which lack a critical subunit of this major source of reactive oxygen species in activated phagocytes. Mice were treated with ethanol chronically, using a Tsukamoto-French protocol, for 4 weeks. In wild-type mice, ethanol caused severe liver injury via a mechanism involving gut-derived endotoxin, CD14 receptor, production of electron spin resonance-detectable free radicals, activation of the transcription factor NF-kappaB, and release of cytotoxic TNF-alpha from activated Kupffer cells. In NADPH oxidase-deficient mice, neither an increase in free radical production, activation of NF-kappaB, an increase in TNF-alpha mRNA, nor liver pathology was observed. These data strongly support the hypothesis that free radicals from NADPH oxidase in hepatic Kupffer cells play a predominant role in the pathogenesis of early alcohol-induced hepatitis by activating NF-kappaB, which activates production of cytotoxic TNF-alpha.

Gender differences in early alcohol-induced liver injury: role of CD14, NF-kappaB, and TNF-alpha

The purpose of this study was to determine whether early alcohol-induced liver injury (ALI) in females is associated with changes in CD14 on Kupffer cells, activation of hepatic nuclear factor (NF)-kappaB, and expression of tumor necrosis factor (TNF)-alpha mRNA. Male and female rats were given high-fat control or ethanol-containing diets for 4 wk using the intragastric enteral protocol. Physiological parameters were similar in both genders. Ethanol was increased as tolerance developed with higher blood levels than previously observed, resulting in a fourfold increase in aspartate aminotransferase (males 389 +/- 47 IU/l vs. females 727 +/- 66 IU/l). Hepatic pathology developed more rapidly and was nearly twofold greater and endotoxin levels were significantly higher in females after ethanol. Also, expression of CD14 on Kupffer cells was 1.5-fold greater and binding of transcription factor NF-kappaB in hepatic nuclear extracts and TNF-alpha mRNA expression were threefold greater in females. These data are consistent with the hypothesis that elevated endotoxin after ethanol triggers more activation of Kupffer cells via enhanced CD14 expression in females. NF-kappaB is activated in this process, leading to increases in TNF-alpha mRNA expression in the liver and more severe liver injury in females. It is concluded that gender differences in ALI are dependent on endotoxin and a signaling cascade leading to TNF-alpha.

Medium-chain triglycerides inhibit free radical formation and TNF-alpha production in rats given enteral ethanol

This study determined whether free radical formation by the liver, tumor necrosis factor (TNF)-alpha production by isolated Kupffer cells, and plasma endotoxin are affected by dietary saturated fat. Rats were fed enteral ethanol and corn oil (E-CO) or medium-chain triglycerides (E-MCT) and control rats received corn oil (C-CO) or medium-chain triglycerides (C-MCT) for 2 wk. E-CO rats developed moderate fatty infiltration and slight inflammation; however, E-MCT prevented liver injury. Serum aspartate aminotransferase levels, gut permeability, and plasma endotoxin doubled with E-CO but were blunted approximately 50% with E-MCT. In Kupffer cells from E-CO rats, intracellular calcium was elevated by lipopolysaccharide (LPS) in a dose-dependent manner. In cells from E-MCT rats, increases were blunted by approximately 40-50% at all concentrations of LPS. The LPS-induced increase in TNF-alpha production by Kupffer cells was dose dependent and was blunted by 40% by MCT. E-CO increased radical adducts and was reduced approximately 50% by MCT. MCT prevent early alcohol-induced liver injury, in part, by inhibition of free radical formation and TNF-alpha production by inhibition of endotoxin-mediated activation of Kupffer cells.

The glutathione precursor L-2-oxothiazolidine-4-carboxylic acid protects against liver injury due to chronic enteral ethanol exposure in the rat

L-2-oxothiazolidine-4-carboxylic acid (OTC) is a cysteine prodrug that maintains glutathione in tissues. Here, its effect on alcohol-induced liver injury in an enteral alcohol feeding model was investigated. Male Wistar rats were given control high-fat or ethanol containing diets enterally for 4 weeks. Treated rats received 500 mg/kg/d of dietary OTC. Ethanol delivery, weight gain, and the cyclic pattern of ethanol in the urine were not different between the OTC-ethanol and ethanol groups. After 4 weeks, serum aspartate transaminase (AST), necrosis and inflammation were elevated significantly by ethanol compared with appropriate high-fat controls, effects blocked by OTC. Moreover, ethanol elevated hepatic tumor necrosis factor alpha (TNF-alpha) messenger RNA (mRNA) and the nuclear transcription factor nuclear factor kappaB (NFkappaB) 2-3 fold. NFkappaB in isolated Kupffer cells was also increased by ethanol. These effects were all blocked by OTC treatment. Additionally, superoxide production was higher in Kupffer cells isolated from ethanol-treated rats, an effect blunted by OTC. OTC also increased circulating glutathione (GSH) levels about 2-fold; however, GSH levels were not affected by ethanol or OTC in livers from the groups studied. Surprisingly, GSH was elevated by ethanol and OTC treatment in isolated Kupffer cells about 2-fold. Moreover, GSH (Ki-10 micromol/L) and cysteinyl-glycine, but not oxidized glutathione (GSSG) or OTC, blunted the LPS-induced increase in calcium in isolated Kupffer cells, possibly by activating a glycine-gated chloride channel due to their structural similarity with glycine. Collectively, it is concluded that GSH is protective, in part, by increasing circulating GSH, which blunts activation of Kupffer cells via the glycine-gated chloride channel.

CYP2E1 is not involved in early alcohol-induced liver injury

The continuous intragastric enteral feeding protocol in the rat was a major development in alcohol-induced liver injury (ALI) research. Much of what has been learned to date involves inhibitors or nutritional manipulations that may not be specific. Knockout technology avoids these potential problems. Therefore, we used long-term intragastric cannulation in mice to study early ALI. Reactive oxygen species are involved in mechanisms of early ALI; however, their key source remains unclear. Cytochrome P-450 (CYP)2E1 is induced predominantly in hepatocytes by ethanol and could be one source of reactive oxygen species leading to liver injury. We aimed to determine if CYP2E1 was involved in ALI by adapting the enteral alcohol (EA) feeding model to CYP2E1 knockout (-/-) mice. Female CYP2E1 wild-type (+/+) or -/- mice were given a high-fat liquid diet with either ethanol or isocaloric maltose-dextrin as control continuously for 4 wk. All mice gained weight steadily over 4 wk, and there were no significant differences between groups. There were also no differences in ethanol elimination rates between CYP2E1 +/+ and -/- mice after acute ethanol administration to naive mice or mice receiving EA for 4 wk. However, EA stimulated rates 1.4-fold in both groups. EA elevated serum aspartate aminotransferase levels threefold to similar levels over control in both CYP2E1 +/+ and -/- mice. Liver histology was normal in control groups. In contrast, mice given ethanol developed mild steatosis, slight inflammation, and necrosis; however, there were no differences between the CYP2E1 +/+ and -/- groups. Chronic EA induced other CYP families (CYP3A, CYP2A12, CYP1A, and CYP2B) to the same extent in CYP2E1 +/+ and -/- mice. Furthermore, POBN radical adducts were also similar in both groups. Data presented here are consistent with the hypothesis that oxidants from CYP2E1 play only a small role in mechanisms of early ALI in mice. Moreover, this new mouse model illustrates the utility of knockout technology in ALI research.

Estrogen is involved in early alcohol-induced liver injury in a rat enteral feeding model

The aim of this study was to investigate whether reduction in blood estrogen by removal of the ovaries would decrease the sensitivity of female rats to early alcohol-induced liver injury using an enteral ethanol feeding model, and if so, whether estrogen replacement would compensate. Livers from ovariectomized rats with or without estrogen replacement after 4 weeks of continuous ethanol exposure were compared with nonovariectomized rats in the presence or absence of ethanol. Ethanol increased serum alanine transaminase (ALT) levels from 30 +/- 6 to 64 +/- 7 U/L. This effect was blocked by ovariectomy (31 +/- 7) and totally reversed by estrogen replacement (110 +/- 23). Ethanol increased liver weight and fat accumulation, an effect that was minimized by ovariectomy and reversed partially by estrogen replacement. Infiltrating leukocytes were increased 6. 7-fold by ethanol, an effect that was blunted significantly by ovariectomy and reversed by estrogen replacement. Likewise, a similar pattern of changes was observed in the number of necrotic hepatocytes. Blood endotoxin and hepatic levels of CD14 messenger RNA (mRNA) and protein were increased by ethanol. This effect was blocked in ovariectomized rats and elevated by estrogen replacement. Moreover, Kupffer cells isolated from ethanol-treated rats with estrogen replacement produced more tumor necrosis factor alpha (TNF-alpha) than those from control and ovariectomized rats. It is concluded, therefore, that the sensitivity of rat liver to alcohol-induced injury is directly related to estrogen, which increases endotoxin in the blood and CD14 expression in the liver, leading to increased TNF-alpha production.

Essential role of tumor necrosis factor alpha in alcohol-induced liver injury in mice

BACKGROUND & AIMS

Tumor necrosis factor (TNF)-alpha is associated with increased mortality in alcoholics, but its role in early alcohol-induced liver injury is not fully understood. Recently, it was shown that injury induced by the enteral alcohol delivery model of Tsukamoto and French was reduced by antibodies to TNF-alpha. To obtain clear evidence for or against the hypothesis that TNF-alpha is involved, we studied TNF receptor 1 (TNF-R1, p55) or 2 (TNF-R2, p75) knockout mice.

METHODS

Long-term enteral alcohol delivery was modified for male gene-targeted mice lacking TNF-R1 and TNF-R2. Animals were given a high-fat liquid diet continuously with either ethanol or isocaloric maltose-dextrin as a control for 4 weeks.

RESULTS

Ethanol elevated serum levels of alanine aminotransferase nearly 3-fold in wild-type and TNF-R2 knockout mice but not in TNF-R1 knockout mice. Likewise, ethanol caused severe liver injury in wild-type mice (pathology score, 5.5 +/- 0.6) and TNF-R2 knockout mice (pathology score, 5.0 +/- 0.4), but not in TNF-R1 knockout mice (pathology score, 0.8 +/- 0.4; P < 0.001).

CONCLUSIONS

Long-term ethanol feeding caused liver injury in wild-type and TNF-R2 knockout mice but not in TNF-R1 knockout mice, providing solid evidence in support of the hypothesis that TNF-alpha plays an important role in the development of early alcohol-induced liver injury via the TNF-R1 pathway. Moreover, the long-term enteral ethanol feeding technique we described for the first time for knockout mice provides a useful new tool for alcohol research.

Gadolinium chloride blocks alcohol-dependent liver toxicity in rats treated chronically with intragastric alcohol despite the induction of CYP2E1

Hepatic CYP2E1 is induced in several models of alcohol administration, but clinically relevant pathology is only observed in rats in a model involving the continuous intragastric administration of an ethanol-containing, corn oil-based, high-fat diet. The level of CYP2E1 correlates with the degree of liver pathology in the intragastric feeding model, which leads to the hypothesis that radical production by CYP2E1 is responsible for the pathology. Destruction of the Kupffer cells with gadolinium chloride (GdCl3) prevented the development of ethanol-dependent pathology and decreased the production of radicals that appeared in the bile of intragastrically alcohol-fed rats. If the induction of CYP2E1 and subsequent formation of oxidant species by the enzyme is causative in the ethanol-dependent hepatic pathology, then protection by GdCl3 could be due an inhibition of CYP2E1 induction. In the current study, ethanol-administration for 4 wk produced marked steatosis, necrosis, and inflammation not seen in control rats. Immunochemically, CYP2E1 was induced 5- to 6-fold in microsomes from the ethanol-treated animals. Rates of p-nitrophenol and chlorzoxazone hydroxylation were elevated approximately 3-fold, consistent with CYP2E1 induction. When GdCl3 was administered with ethanol, there was a decrease of approximately 80% in Kupffer cell receptor expression, and there was a significant decrease in hepatic pathology, which confirms previous studies. However, in the ethanol and GdCl3-treated animals, there was no significant decrease in the induction of CYP2E1. CYP2E1 was elevated approximately 5-fold, as estimated by immunoblot analysis, and rates of p-nitrophenol and chlorzoxazone hydroxylation were elevated 3- to 4-fold in ethanol + GdCl3-treated rats. Thus, these results clearly dissociate the induction of CYP2E1 by intragastric infusion of ethanol from the generation of early alcohol-induced liver disease. It is concluded that Kupffer cells rather than CYP2E1 play the major role in the initiation of hepatocyte damage caused by alcohol.

High-fat hypercaloric diet induces obesity, glucose intolerance and hyperlipidemia in normal adult male Wistar rat

There is strong evidence that genetic factors contribute to the development of obesity in humans as well as laboratory animals. Another important factor leading to obesity is an increase in energy intake. However, it is difficult to make normal rats obese by controlling daily food intake. There is no report of normal adult male Wistar rats becoming obese and diabetic on a high-fat diet. The aim of the present study was, therefore, to make normal adult Wistar rats obese by infusing high fat and hypercaloric diet through the cannula without disturbing the free movement and to investigate the influence of an increase in the caloric intake on body weight and glucose metabolism. High-fat hypercaloric diet (360 kcal/kg body wt./day; H group) or control diet (180 kcal/kg body wt./day; C group) was continuously infused into the stomach of normal adult male Wistar rats weighing approximately 300 g through gastric cannulas for 27 days. On day 28 after a 24-h fasting, serum concentrations of aspartate aminotransferase, alanine aminotransferase, total cholesterol, triglyceride, phospholipid, and free fatty acids (FFA) were determined, and intragastric glucose loading test (2 g/kg body wt.) was performed. The average weekly body weight gain in the H group was twice as much as that of the C group (40.0 +/- 2.4 vs. 19.4 +/- 1.9 g/week, P < 0.001). Serum levels of triglyceride, phospholipid, total cholesterol, and FFA were significantly elevated in the H group compared to those in the C group. Liver weight in the H group was significantly higher than that in the C group and showed steatosis. Pancreas weight (-13%) as well as protein (-12%), amylase (-53%) and trypsin content (-26%) were all reduced, whereas pancreatic DNA content was significantly increased in the H group compared to those in the C group. Serum glucose and insulin concentrations before and after glucose loading in the H group were significantly higher than those in the C group. Moreover, the insulin response relative to glucose response in the H group was significantly high compared to that in the C group, indicating the presence of insulin resistance. These results indicate that feeding of high-fat hypercaloric diet makes normal Wistar male adult rat obese associated with hyperlipidemia, hyperinsulinemia, and glucose intolerance.

Role of Kupffer cells in failure of fatty livers following liver transplantation and alcoholic liver injury

Kupffer cells have been implicated in mechanisms of pathophysiology following liver transplantation. Recently, postoperative injury in ethanol-induced fatty liver has been evaluated because fatty livers often fail following transplantation. The low-flow, reflow liver perfusion model was used to study the role of Kupffer cells (KC) in reperfusion injury to fatty livers from rats fed a diet containing ethanol for 4-5 weeks. Treatment with GdCl3, which selectively destroys KC, decreased cell death significantly. Thus, destruction of KC minimized hepatic reperfusion injury, most likely by inhibiting free radical formation and improving microcirculation. Since it was demonstrated recently that destruction of KC prevented the hypermetabolic state observed with acute alcohol exposure, their involvement in events leading to alcohol-induced liver disease was investigated. In rats exposed to ethanol continuously via intragastric feeding for up to 4 weeks, GdCl3 treatment prevented elevation of aspartate aminotransferase (AST) and dramatically reduced the average hepatic pathological score. These results indicate that KC participate in the early phases of alcohol-induced liver injury. Endotoxaemia occurs in alcoholics and activates KC; therefore, we evaluated the effect of minimizing bacterial endotoxin by intestinal sterilization with the antibiotics polymyxin B and neomycin. Antibiotics diminished plasma endotoxin levels significantly and prevented ethanol-induced increases in AST values. These results indicate that endotoxin is involved in the mechanism of ethanol-induced liver injury. A six-line radical spectrum was detected with electron paramagnetic resonance spectroscopy in bile from alcohol-treated rats which was blocked by GdCl3. The free radical adducts had hyperfine coupling constants characteristic of lipid-derived free radical products. In conclusion, these studies demonstrate that KC are involved in reperfusion injury to ethanol-induced fatty livers and hepatic injury due to long-term treatment with ethanol.

Changes in the fatty acid profile of plasma and adipose tissue in rats after long-term ethanol feeding

The effect of chronic ethanol feeding on the fatty acid composition of plasma and abdominal adipose tissue in rats was studied. Animals were maintained on a 30% ethanol solution in drinking water for 3 and 5 months. Control rats were given water. Caloric intake was similar in control and ethanol-fed rats at the end of the experimental period. However, a decrease in body weight was observed in rats that had consumed ethanol. Palmitoleic (16:1n7) and oleic (18:1n9) acids increased markedly, and linoleic acid (18:2n6) decreased in the plasma and in the adipose tissue of ethanol-fed rats with respect to control rats. After 3 months of ethanol ingestion, long-chain polyunsaturated fatty acids were reduced both in plasma and adipose tissue. When ethanol was administered for 5 months, only plasma long-chain polyunsaturated fatty acids of the n-3 series were decreased. This suggest that changes induced by ethanol ingestion in essential fatty acid metabolism is less pronounced when ethanol feeding is maintained for a long period of time.

Acute ethanol dependence or long-term ethanol treatment and abstinence do not reduce hippocampal responses to carbachol

In the hippocampus of human alcoholics, prolonged ethanol treatment reduces the number of muscarinic ligand binding sites present at autopsy suggesting a decrease in functional muscarinic receptors. Whether these changes are due to alcohol-induced brain damage or ethanol dependence and represent a reduced level of cholinergic function is unknown. The present studies tested the impact of ethanol dependence or long-term ethanol treatment and subsequent withdrawal on the function of pre- and postsynaptic muscarinic receptors in the CA1 region of the rat hippocampus. Field excitatory postsynaptic potentials (EPSPs) were inhibited in a concentration-dependent manner by 0.1-100 microM carbachol. This presynaptic inhibitory action of carbachol involving muscarinic receptors was not significantly reduced either by ethanol treatment (12 days), causing physical dependence, or by long-term ethanol treatment (97-120 days) and abstinence (3-6 months). Postspike after hyperpolarizations (AHPs) were inhibited in a concentration-dependent manner by carbachol (6-2000 nM). This postsynaptic excitatory action of muscarinic receptors also was not significantly reduced either by 12-day ethanol treatment or by long-term ethanol treatment. Taken together, these results suggest that neither pre- nor postsynaptic muscarinic receptor function measured electrophysiologically is reduced by either ethanol dependence or long-term ethanol consumption and abstinence in the rat as suggested by reduced muscarinic ligand binding in the hippocampus of human alcoholics.

Antibiotics prevent liver injury in rats following long-term exposure to ethanol

BACKGROUND/AIMS

Kupffer's cells participate in alcohol-induced liver injury, and endotoxemia is observed in human alcoholics and in a rat model. This study evaluated the effect of reducing bacterial endotoxin production by intestinal sterilization on alcohol-induced liver injury.

METHODS

Male Wistar rats were exposed to ethanol continuously for up to 3 weeks via intragastric feeding. The gut was sterilized with polymyxin B and neomycin.

RESULTS

Fecal culture of stool samples from ethanol-fed rats treated with antibiotics showed virtually no growth of gram-negative bacteria. Endotoxin levels of 80-90 pg/mL in plasma of ethanol-fed rats were reduced to < 25 pg/mL by antibiotics. Antibiotic treatment also completely prevented elevated aspartate aminotransferase levels and significantly reduced the average hepatic pathological score in rats exposed to ethanol. Oxygen tension on the surface of the liver measured in vivo was decreased significantly from control values of 48 +/- 1 to 39 +/- 1 mumol/L in ethanol-treated rats. This hypoxia was prevented by treatment with antibiotics. Moreover, the increase in rates of ethanol elimination due to long-term ethanol treatment was prevented by antibiotic treatment.

CONCLUSIONS

Intestinal sterilization prevented alcohol-induced liver injury in the rat, supporting the idea that hypermetabolism and consequent hypoxia caused by activation of Kupffer's cells by endotoxin is involved in the mechanism.

Markedly enhanced cytochrome P450 2E1 induction and lipid peroxidation is associated with severe liver injury in fish oil-ethanol-fed rats

We evaluated the role of changes in cytochrome P-450 2E1 (CYP 2E1) and lipid peroxidation in relation to development of severe liver injury in fish oil-ethanol-fed rats. The experimental animals (male Wistar rats) were divided into 5 rats/group and were fed the following diets for 1 month: corn oil and ethanol (CO+E) or corn oil and dextrose (CO+D), and fish oil and ethanol (FO+E) or fish oil and dextrose (FO+D). For each animal, microsomal analysis of CYP 2E1 protein, aniline hydroxylase activity, fatty acid composition, and conjugated dienes was conducted. Also, evaluation of severity of pathology was done for each rat. The mean +/- SD of the pathology score was significantly higher (p < 0.01) in the FO+E (6.0 +/- 1.3) group than in the CO+E group (3.0 +/- 0.5). No pathological changes were evident in the dextrose-fed controls. The CYP 2E1 protein levels (mean +/- SD) were significantly higher (p < 0.01) in the FO+E group (13.1 +/- 2.0) compared with the CO+E (4.7 +/- 1.2) and FO+D (1.8 +/- 0.5) groups. Higher levels of eicosapentaenoic and docosahexaenoic acids and lower levels of arachidonic acid were detected in liver microsomes from rats fed fish oil compared with corn oil. A significant correlation was obtained between CYP 2E1 protein and conjugated diene levels (r = 0.78, p < 0.01). Our results showing markedly increased CYP 2E1 induction and lipid peroxidation in the FO+E group provides one possible explanation for the greater severity of liver injury in this group.

Inactivation of Kupffer cells prevents early alcohol-induced liver injury

It is well recognized that consumption of alcohol leads to liver disease in a dose-dependent manner; however, the exact mechanisms remain unclear. Hypoxia subsequent to a hypermetabolic state may be involved; therefore, when it was observed recently that inactivation of Kupffer cells prevented stimulation of hepatic oxygen uptake by alcohol, the idea that Kupffer cells participate in early events that ultimately lead to alcohol-induced liver disease became a real possibility. The purpose of this study was to test that hypothesis. Male Wistar rats were exposed to ethanol continuously by means of intragastric feeding for up to 4 weeks using the model developed by Tsukamoto and French. In this model, ethanol causes fatty liver, necrosis and inflammation--changes characteristic of alcohol-induced liver disease in human beings. Kupffer cells were inactivated by twice weekly treatment with gadolinium chloride (GdCl3), a selective Kupffer cell toxicant. AST levels were elevated to 192 +/- 13 and 244 +/- 56 IU/L in rats exposed to ethanol for 2 and 4 wk, respectively (control value, 88 +/- 7). This injury was prevented almost completely by GdCl3 treatment. Fatty changes, inflammation and necrosis were also all reduced dramatically by GdCl3 treatment. The average hepatic pathological score of rats treated with ethanol for 4 wk was 4.3 +/- 0.6, which was reduced significantly in ethanol- and GdCl3-treated rats to 1.8 +/- 0.5 (p < 0.05). Rates of ethanol elimination were elevated 2- to 3-fold in rats exposed to ethanol for 2 to 4 wk. This elevation was blocked by GdCl3 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of chronic ethanol feeding on plasma and liver alpha- and gamma-tocopherol levels in normal and vitamin E-deficient rats. Relationship to lipid peroxidation

The effects of chronic ethanol intake on the levels of alpha-tocopherol and gamma-tocopherol in serum and liver of both vitamin E-deficient and normal rats were studied. An intragastric feeding rat model was used. Both normal and vitamin E-deficient animals were fed a liquid diet and ethanol for 1 month. In pair-fed animals, dextrose was isocalorically replaced by ethanol. The blood ethanol level in the ethanol-fed animals was between 150 and 250 mg/dL. Liver peroxidation was determined by measuring thiobarbituric acid reactive substances (TBARS). Plasma alanine aminotransferase (ALT) was increased by 3-fold in vitamin E-deficient ethanol-fed rats compared with normal ethanol-fed rats. Plasma alpha- and gamma-tocopherol were decreased in the normal ethanol-fed rats by 22.3 and 65%, respectively (P < 0.01). Liver alpha- and gamma-tocopherol were also decreased by 51.7 and 76%, respectively (P < 0.01). Vitamin E-deficient animals had significantly lower mean plasma alpha-tocopherol (5670 vs 530 ng/mL, P < 0.01), and ethanol feeding did not decrease the levels any further. However, ethanol feeding decreased liver alpha- and gamma-tocopherol by 58.5 and 56.5% (P < 0.01), respectively, beyond the already low levels observed in this group. There was an inverse correlation between liver TBARS and liver alpha-tocopherol (r = -0.59, P < 0.05) and gamma-tocopherol (r = -0.65, P < 0.02). Also of significance is that ethanol feeding decreased the plasma and liver gamma-tocopherol more than the alpha-tocopherol in both normal and vitamin E-deficient animals. In conclusion, ethanol feeding markedly decreased both alpha- and gamma-tocopherol in livers of normal and vitamin E-deficient rats, but it only decreased plasma levels of tocopherols in normal rats. The higher ALT in vitamin E-deficient animals and the inverse correlation between TBARS and alpha- and gamma-tocopherol suggest that enhanced lipid peroxidation is associated with greater severity of liver injury induced by ethanol in vitamin E-deficient rats.

Selective reduction of delta 6 and delta 5 desaturase activities but not delta 9 desaturase in micropigs chronically fed ethanol

This study investigated the mechanism by which chronic ethanol feeding reduces arachidonate and other highly unsaturated fatty acids in pig liver phospholipids. Five micropigs were fed a diet providing 89 kcal/kg body wt for 12 mo, with ethanol and fat as 40 and 34% of energy, respectively. Five control pigs were pairfed corn starch instead of ethanol. The activities of delta 6 and delta 5 desaturases (expressed as microsomal conversion of precursor to product) in liver from ethanol-fed pigs were reduced to less than half that of controls, whereas the activity of delta 9 desaturase was unaffected in the ethanol group. delta 5 Desaturase activity showed positive correlation with the abundance of its products in liver total phospholipids and microsomes in the ethanol group, but not in the controls. Correlation between delta 6 desaturase activity and its products showed similar pattern to that of delta 5 desaturase, but did not reach statistical significance. No difference was observed between the two groups in coenzyme A concentration in the liver. These results suggest that the selective reduction of delta 6 and delta 5 desaturase activities, not the microsomal electron transport system, are directly responsible for the altered profile of liver phospholipids.