Low-dose alcohol exacerbates hyperdynamic circulation and shunting in non-alcoholic cirrhotic rats

BACKGROUND

Portal hypertension affects hepatic, splanchnic and portosystemic collateral systems. Although alcohol is a well-known risk factor for liver cirrhosis, it also affects vascular contractility. However, the relevant effects on portal hypertension have not been evaluated in non-alcoholic cirrhosis. The present study aimed to investigate the impacts of low-dose alcohol on portal hypertension-related derangements in non-alcoholic cirrhotic rats.

METHODS

Sprague-Dawley rats received bile duct ligation to induce cirrhosis or sham operation as controls. The chronic or acute effects of low-dose alcohol (2.4 g/kg/day, oral gavage, approximately 1.3 drinks/day in humans) were evaluated.

RESULTS

The chronic administration of low-dose alcohol did not precipitate liver fibrosis in the sham or cirrhotic rats; however, it significantly increased splanchnic blood inflow (P=0.034) and portosystemic collaterals (P=0.001). Mesenteric angiogenesis and pro-angiogenic proteins were up-regulated in the alcohol-treated cirrhotic rats, and poorer collateral vasoresponsiveness to vasoconstrictors (P<0.001) was noted. Consistently, acute alcohol administration reduced splenorenal shunt resistance. Collateral vasoresponsiveness to vasoconstrictors also significantly decreased (P=0.003).

CONCLUSIONS

In non-alcoholic cirrhosis rats, a single dose of alcohol adversely affected portosystemic collateral vessels due to vasodilatation. Long-term alcohol use precipitated splanchnic hyperdynamic circulation, in which mesenteric angiogenesis played a role. Further studies are warranted to evaluate the benefits of avoiding low-dose alcohol consumption in patients with non-alcoholic cirrhosis.

Soybean polyenylphosphatidylcholine (PPC) is beneficial in liver and extrahepatic tissue injury: An update in experimental research

Polyenylphosphatidylcholine (PPC) is a purified polyunsaturated phosphatidylcholine extract of soybeans. This article updates PPC's beneficial effects on various forms of liver cell injury and other tissues in experimental research. PPC downregulates hepatocyte CYP2E1 expression and associated hepatotoxicity, as well as attenuates oxidative stress, apoptosis, lipoprotein oxidation and steatosis in alcoholic and nonalcoholic liver injury. PPC inhibits pro-inflammatory cytokine production, while stimulating anti-inflammatory cytokine secretion in ethanol or lipopolysaccharide-stimulated Kupffer cells/macrophages. It promotes M2-type macrophage polarization and metabolic reprogramming of glucose and lipid metabolism. PPC mitigates steatosis in NAFLD through inhibiting polarization of pro-inflammatory M1-type Kupffer cells, alleviating metabolic inflammation, remodeling hepatic lipid metabolism, correcting imbalances between lipogenesis and lipolysis and enhancing lipoprotein secretion from hepatocytes. PPC is antifibrotic by preventing progression of alcoholic hepatic fibrosis in baboons and also prevents CCl4-induced fibrosis in rats. PPC supplementation replenishes the phosphatidylcholine content of damaged cell membranes, resulting in increased membrane fluidity and functioning. Phosphatidylcholine repletion prevents increased membrane curvature of the endoplasmic reticulum and Golgi and decreases sterol regulatory element binding protein-1-mediated lipogenesis, reducing steatosis. PPC remodels gut microbiota and affects hepatic lipid metabolism via the gut-hepatic-axis and also alleviates brain inflammatory responses and cognitive impairment via the gut-brain-axis. Additionally, PPC protects extrahepatic tissues from injury caused by various toxic compounds by reducing oxidative stress, inflammation, and membrane damage. It also stimulates liver regeneration, enhances sensitivity of cancer cells to radiotherapy/chemotherapy, and inhibits experimental hepatocarcinogenesis. PPC's beneficial effects justify it as a supportive treatment of liver disease.

Acetic Acid: An Underestimated Metabolite in Ethanol-Induced Changes in Regulating Cardiovascular Function

Acetic acid is a bioactive short-chain fatty acid produced in large quantities from ethanol metabolism. In this review, we describe how acetic acid/acetate generates oxidative stress, alters the function of pre-sympathetic neurons, and can potentially influence cardiovascular function in both humans and rodents after ethanol consumption. Our recent findings from in vivo and in vitro studies support the notion that administration of acetic acid/acetate generates oxidative stress and increases sympathetic outflow, leading to alterations in arterial blood pressure. Real-time investigation of how ethanol and acetic acid/acetate modulate neural control of cardiovascular function can be conducted by microinjecting compounds into autonomic control centers of the brain and measuring changes in peripheral sympathetic nerve activity and blood pressure in response to these compounds.

The effect of varied exercise intensity on antioxidant function, aortic endothelial function, and serum lipids in rats with non-alcoholic fatty liver disease

This study aimed to compare the effects of diet and exercise of different intensities on antioxidant function, aortic endothelial cell function and serum lipids in NAFLD (nonalcoholic fatty liver disease) rats. Fifty Sprague-Dawley (SD) rats (180-220g) were randomly divided into two experimental groups and fed either a standard rodent chow diet (CON; n=10) or a high-fat diet (HFD; n=40). After 16 weeks, the animals that received the HFD were randomly separated into a high-fat control group (HFC; n=10) or three ex-ercise training groups: HFD and low-intensity exercise (LE; n=10), HFD and moderate-intensity exercise (ME; n=10), and HFD and incremental intensity exercise (IE; n=10). These experimental rats keep sedentary or trained for the next six weeks. A detection kit was used to detect nitric oxide synthase (NOs), nitric oxide (NO), malondialdehyde (MDA) and other markers of aor-tic oxidative stress. The expression levels of endothelial nitric oxide synthase (e-NOS) and endothelin-1 (ET-1) were detected by immunohistochemistry. TC, TG, and other lipid metabolism parameters were detected by an auto-matic analyzer. Exercise with different intensities could improve lipid me-tabolism, enhance antioxidant function, reduce MDA (P<0.01), increase NO (P<0.01), and improve the expression of e-NOS and ET-1 (P<0.01) protein levels in NAFLD rats. Decreased blood lipids were exhibited in all exercise groups. Notably, the moderate-intensity exercise demonstrated more effecton increasing glutathione (GSH) contents (P<0.01) and decreased the ex-pression of ET-1protein levels (P<0.01). The results showed that exercise at different intensities improved lipid metabolism and enhanced anti-oxidation function. Moderate exercise could improve the function of aortic endothelial cells.

Neuroprotective and long term potentiation improving effects of vitamin E in juvenile hypothyroid rats

Abstract. Protective effects of vitamin E (Vit E) on long term potentiation (LTP) impairment, neuronal apoptosis and increase of nitric oxide (NO) metabolites in the hippocampus of juvenile rats were examined. The rats were grouped (n=13) as: (1) control; (2) hypothyroid (Hypo) and (3) Hypo-Vit E. Propylthiouracil (PTU) was given in drinking water (0.05%) during 6 weeks. Vit E (20 mg/ kg) was daily injected (IP). To evaluate synaptic plasticity, LTP from the CA1 area of the hippocampus followed by high frequency stimulation to the ipsilateral Schafer collateral pathway was carried out. The cortical and hippocampal tissues were then removed to measure NO metabolites. The brains of 5 animals in each group were removed for apoptosis study. The hypothyroidism status decreased the slope, 10–90% slope and amplitude of field excitatory post synaptic potential (fEPSP) compared to the control group (P<0.01–P<0.001). Injection of Vit E increased the slope, 10–90% slope and amplitude of the fEPSP in the Hypo-Vit E group in comparison to the Hypo group (P<0.05–P<0.01). TUNEL positive neurons and NO metabolites were higher in the hippocampus of the Hypo rats, as compared to those in the hippocampus of the control ones (P<0.001). Treatment of the Hypo rats by Vit E decreased apoptotic neurons (P<0.01–P<0.001) and NO metabolites (P<0.001) in the hippocampus compared to the Hypo rats. The results of the present study showed that Vit E prevented the LTP impairment and neuronal apoptosis in the hippocampus of juvenile hypothyroid rats.

Rho/rho-kinase signalling in chronically alcohol-fed mice

BACKGROUND/AIM

The effects of chronic ethanol consumption on male sexual function are debateable, and its effects on the Rho/Rho-kinase pathway are unknown. Therefore, we investigated smooth muscle reactivity and Rho/Rho-kinase signalling in the corpus cavernosum of ethanol-fed mice.

MATERIALS AND METHODS

Ethanol was added to drinking water at 5% concentration in the first 2 days with 5% increment every subsequent 2 days, up to a final concentration of 20% for 45 days. Corpora cavernosa were isolated and a cumulative dose-response curve to phenylephrine was obtained. Acetylcholine (10-6 M), electrical field stimulation (EFS, 40 V, 8-16 Hz) and Y-27632 (10^-6-10^-5 M)-induced relaxations were compared in the control and ethanol groups.

RESULTS

Blood ethanol levels in the control and ethanol-treated mice were 1.5 ± 0.3 mg/dL and 37.4 ± 4.1 mg/dL (P < 0.001), respectively. Phenylephrine-induced contractile responses were potentiated in the ethanol group, with pD₂ values of 4.92 ± 0.18 and 5.71 ± 0.21 (P < 0.01) in the corpus cavernosum obtained from control and alcohol-fed mice, respectively. The relaxant responses to acetylcholine and EFS, but not Y-27632, were significantly augmented in the corpus cavernosum obtained from ethanol-treated mice. However, expression and activation of Rho-kinase remained unchanged in the alcohol group.

CONCLUSION

Ethanol drinking may increase sensitivity to both vasoconstrictors and vasodilators in the mouse corpus cavernosum without any alteration in Rho/Rho-kinase signalling.

Nitric oxide in liver diseases

Nitric oxide (NO) and its derivatives play important roles in the physiology and pathophysiology of the liver. Despite its diverse and complicated roles, certain patterns of the effect of NO on the pathogenesis and progression of liver diseases are observed. In general, NO derived from endothelial NO synthase (eNOS) in liver sinusoidal endothelial cells (LSECs) is protective against disease development, while inducible NOS (iNOS)-derived NO contributes to pathological processes. This review addresses the roles of NO in the development of various liver diseases with a focus on recently published articles. We present here two recent advances in understanding NO-mediated signaling - nitrated fatty acids (NO2-FAs) and S-guanylation - and conclude with suggestions for future directions in NO-related studies on the liver.

Ethyl nitrite is produced in the human stomach from dietary nitrate and ethanol, releasing nitric oxide at physiological pH: potential impact on gastric motility

BACKGROUND

Nitric oxide ((∙)NO), a ubiquitous molecule involved in a plethora of signaling pathways, is produced from dietary nitrate in the gut through the so-called nitrate-nitrite-NO pathway. In the stomach, nitrite derived from dietary nitrate triggers a network of chemical reactions targeting endogenous and exogenous biomolecules, thereby producing new compounds with physiological activity.

OBJECTIVE

The aim of this study was to ascertain whether compounds with physiological relevance are produced in the stomach upon consumption of nitrate- and ethanol-rich foods.

DESIGN

Human volunteers consumed a serving of lettuce (source of nitrate) and alcoholic beverages (source of ethanol). After 15 min, samples of the gastric headspace were collected and ethyl nitrite was identified by GC-MS. Wistar rats were used to study the impact of ethyl nitrite on gastric smooth muscle relaxation at physiological pH.

RESULT

Nitrogen oxides, produced from nitrite in the stomach, induce nitrosation of ethanol from alcoholic beverages in the human stomach yielding ethyl nitrite. Ethyl nitrite, a potent vasodilator, is produced in vivo upon the consumption of lettuce with either red wine or whisky. Moreover, at physiological pH, ethyl nitrite induces gastric smooth muscle relaxation through a cGMP-dependent pathway. Overall, these results suggest that ethyl nitrite is produced in the gastric lumen and releases (∙)NO at physiological pH, which ultimately may have an impact on gastric motility. Systemic effects may also be expected if ethyl nitrite diffuses through the gastric mucosa reaching blood vessels, therefore operating as a (∙)NO carrier throughout the body.

CONCLUSION

These data pinpoint posttranslational modifications as an underappreciated mechanism for the production of novel molecules with physiological impact locally in the gut and highlight the notion that diet may fuel compounds with the potential to modulate gastrointestinal welfare.

Interleukin-32γ attenuates ethanol-induced liver injury by the inhibition of cytochrome P450 2E1 expression and inflammatory responses

Alcohol abuse and alcoholism lead to alcoholic liver disease (ALD), which is a major type of chronic liver disease worldwide. Interleukin-32 (IL-32) is a novel cytokine involved in inflammation and cancer development. However, the role of IL-32 in chronic liver disease has not been reported. In the present paper, we tested the effect of IL-32γ on ethanol-induced liver injury in IL-32γ-overexpressing transgenic mice (IL-32γ mice) after chronic ethanol feeding. Male C57BL/6 and IL-32γ mice (10–12 weeks old) were fed on a Lieber–DeCarli diet containing 6.6% ethanol for 6 weeks. IL-32γ-transfected HepG2 and Huh7 cells, as well as primary hepatocytes from IL-32γ mice, were treated with or without ethanol. The hepatic steatosis and damage induced by ethanol administration were attenuated in IL-32γ mice. Ethanol-induced cytochrome P450 2E1 expression and hydrogen peroxide levels were decreased in the livers of IL-32γ mice, primary hepatocytes from IL-32γ mice and IL-32γ-overexpressing human hepatic cells. The ethanol-induced expression levels of cyclo-oxygenase-2 (COX-2) and IL-6 were reduced in the livers of IL-32γ mice. Because nuclear transcription factor κB (NF-κB) is a key redox transcription factor of inflammatory responses, we examined NF-κB activity. Ethanol-induced NF-κB activities were significantly lower in the livers of IL-32γ mice than in wild-type (WT) mice. Furthermore, reduced infiltration of natural killer cells, cytotoxic T-cells and macrophages in the liver after ethanol administration was observed in IL-32γ mice. These data suggest that IL-32γ prevents ethanol-induced hepatic injury via the inhibition of oxidative damage and inflammatory responses.

Fucoidan from Fucus vesiculosus protects against alcohol-induced liver damage by modulating inflammatory mediators in mice and HepG2 cells

Fucoidan is an l-fucose-enriched sulfated polysaccharide isolated from brown algae and marine invertebrates. In this study, we investigated the protective effect of fucoidan from Fucus vesiculosus on alcohol-induced murine liver damage. Liver injury was induced by oral administration of 25% alcohol with or without fucoidan (30 mg/kg or 60 mg/kg) for seven days. Alcohol administration increased serum aspartate aminotransferase and alanine aminotransferase levels, but these increases were suppressed by the treatment of fucoidan. Transforming growth factor beta 1 (TGF-β1), a liver fibrosis-inducing factor, was highly expressed in the alcohol-fed group and human hepatoma HepG2 cell; however, the increase in TGF-β1 expression was reduced following fucoidan administration. Treatment with fucoidan was also found to significantly reduce the production of inflammation-promoting cyclooygenase-2 and nitric oxide, while markedly increasing the expression of the hepatoprotective enzyme, hemeoxygenase-1, on murine liver and HepG2 cells. Taken together, the antifibrotic and anti-inflammatory effects of fucoidan on alcohol-induced liver damage may provide valuable insights into developing new therapeutics or interventions.

Vitamin E attenuates neurotoxicity induced by deltamethrin in rats

Background

The safety of Deltamethrin (DM) has been raised as a point of concern. The current investigation was envisaged to explore the responsiveness of oxidative stress parameters, DNA fragmentation and expression levels of TP53, cycloxygenase 2 (COX2) and cytochrome p4502E1 (CYP2E1) as toxicological endpoint in rats treated with DM. as well as attention was provided to the neuroprotective effect of vitamin E (VE).

Methods

Four different groups of rats were used in this study, group I served as control, group II received DM (0.6 mg/kg BW), group III received both DM plus VE and finally group IV received VE only (200 mg/kg BW). The treatment regimen was extending for one month for all groups and the brain tissues were collected for further analysis.

Results

The obtained results showed a highly statistically significant increase in lipid peroxidation (LPO) content, nitric oxide concentration, and DNA fragmentation percentage and expression level of CYP2E1, TP53 and COX2 genes, in addition statistical significant reduction in total antioxidant capacity in DM treated group as compared to control were detected. Oral administration of VE attenuated the neurotoxic effects of DM through improvement of oxidative status, DNA fragmentation percentage and suppressing the expression level of CYP2E1, TP53 and COX2 genes.

Conclusion

From this study we concluded that VE supplementation has beneficial impacts on DM neurotoxicity in rats through its antioxidant and antiapoptotic properties.

Alcohol abuse and the injured host: dysregulation of counterregulatory mechanisms review

Traumatic injury ranks as the number one cause of death for the younger than 44 years age group and fifth leading cause of death overall (www.nationaltraumainstitute.org/home/trauma_statistics.html). Although improved resuscitation of trauma patients has dramatically reduced immediate mortality from hemorrhagic shock, long-term morbidity and mortality continue to be unacceptably high during the postresuscitation period particularly as a result of impaired host immune responses to subsequent challenges such as surgery or infection. Acute alcohol intoxication (AAI) is a significant risk factor for traumatic injury, with intoxicating blood alcohol levels present in more than 40% of injured patients. Severity of trauma, hemorrhagic shock, and injury is higher in intoxicated individuals than that of sober victims, resulting in higher mortality rates in this patient population. Necessary invasive procedures (surgery, anesthesia) and subsequent challenges (infection) that intoxicated trauma victims are frequently subjected to are additional stresses to an already compromised inflammatory and neuroendocrine milieu and further contribute to their morbidity and mortality. Thus, dissecting the dynamic imbalance produced by AAI during trauma is of critical relevance for a significant proportion of injured victims. This review outlines how AAI at the time of hemorrhagic shock not only prevents adequate responses to fluid resuscitation but also impairs the ability of the host to overcome a secondary infection. Moreover, it discusses the neuroendocrine mechanisms underlying alcohol-induced hemodynamic dysregulation and its relevance to host defense restoration of homeostasis after injury.

Role of Mitochondria in Alcoholic Liver Disease

Alcohol-induced liver disease (ALD) is a major health concern of alcohol abuse and a leading cause of liver-related morbidity and mortality. The pathogenesis of ALD is multifactorial and still ill characterized. One of the hallmarks of ALD common for both patients and experimental models is the alteration in the architecture and function of mitochondria. Due to their primordial role in energy production, metabolism and cell fate decisions, these changes in mitochondria caused by alcohol are considered an important contributory factor in ALD. A better understanding of the mechanisms underlying alcohol-mediated mitochondrial alterations may shed light on ALD pathogenesis and provide novel avenues for treatment. The purpose of the current review is to briefly update the latest developments in ALD research regarding morphological and functional mitochondrial regulation including mitochondrial dynamics and biogenesis, mitochondrial protein acetylation and evidence for an endoplasmic reticulum stress-mitochondrial cholesterol link of potential relevance for ALD.

Neuronal nitric oxide synthase mediates the effect of ethanol on IgA

AIMS

We showed previously that the acute effect of ethanol on intestinal immunoglobulin A (IgA) expression might be mediated by endogenous nitric oxide (NO). To extend these findings, this study was designed to investigate a possible role of neuronal NO synthase (nNOS) in the observed phenomenon, using 7-nitroindazole (7-NI), a selective inhibitor of its activity.

METHODS

Adult male Wistar rats were treated with: (a) ethanol (4 g/kg, intraperitoneally, i.p.), (b) 7-NI (25 mg/kg, i.p.) followed by ethanol (4 g/kg, i.p.) 30 min later and (c) 7-NI (25 mg/kg, i.p.) followed by saline 30 min later. Untreated rats were used as controls. The concentrations of serum and intestinal IgA were measured by enzyme-linked immunosorbent assay, while the expression of nNOS was determined using western blot and immunohistochemistry.

RESULTS

Acute ethanol treatment significantly increased the concentration of IgA in the ileal extracts, whereas it decreased its serum level. Inhibition of nNOS activity by 7-NI abolished this action of alcohol on IgA. Additionally, western blot analysis revealed that the acute alcohol administration induced an increase in the expression of intestinal nNOS. Furthermore, nNOS-immunoreactive cells, observed within the lamina propria of small intestine, were numerous in ethanol-treated rats.

CONCLUSION

Taken together, these results extended our previous findings suggesting that nNOS mediates the acute effect of ethanol on IgA and supported an immunomodulatory role of this enzyme isoform.

Cytochrome c oxidase dysfunction in oxidative stress

Cytochrome c oxidase (CcO) is the terminal oxidase of the mitochondrial electron transport chain. This bigenomic enzyme in mammals contains 13 subunits of which the 3 catalytic subunits are encoded by the mitochondrial genes. The remaining 10 subunits with suspected roles in the regulation, and/or assembly, are coded by the nuclear genome. The enzyme contains two heme groups (heme a and a3) and two Cu(2+) centers (Cu(2+) A and Cu(2+) B) as catalytic centers and handles more than 90% of molecular O(2) respired by the mammalian cells and tissues. CcO is a highly regulated enzyme which is believed to be the pacesetter for mitochondrial oxidative metabolism and ATP synthesis. The structure and function of the enzyme are affected in a wide variety of diseases including cancer, neurodegenerative diseases, myocardial ischemia/reperfusion, bone and skeletal diseases, and diabetes. Despite handling a high O(2) load the role of CcO in the production of reactive oxygen species still remains a subject of debate. However, a volume of evidence suggests that CcO dysfunction is invariably associated with increased mitochondrial reactive oxygen species production and cellular toxicity. In this paper we review the literature on mechanisms of multimodal regulation of CcO activity by a wide spectrum of physiological and pathological factors. We also review an array of literature on the direct or indirect roles of CcO in reactive oxygen species production.

Vascular effects of maternal alcohol consumption

Maternal alcohol consumption during pregnancy is a significant field of scientific exploration primarily because of its negative effects on the developing fetus, which is specifically defined as fetal alcohol spectrum disorders. Though the effects on the mother are less explored compared with those on the fetus, alcohol produces multiple effects on the maternal vascular system. Alcohol has major effects on systemic hemodynamic variables, endocrine axes, and paracrine factors regulating vascular resistance, as well as vascular reactivity. Alcohol is also reported to have significant effects on the reproductive vasculature including alterations in blood flow, vessel remodeling, and angiogenesis. Data presented in this review will illustrate the importance of the maternal vasculature in the pathogenesis of fetal alcohol spectrum disorders and that more studies are warranted in this field.

Nitric oxide and hypoxia exacerbate alcohol-induced mitochondrial dysfunction in hepatocytes

Chronic alcohol consumption results in hepatotoxicity, steatosis, hypoxia, increased expression of inducible nitric oxide synthase (iNOS) and decreased activities of mitochondrial respiratory enzymes. The impact of these changes on cellular respiration and their interaction in a cellular setting is not well understood. In the present study we tested the hypothesis that nitric oxide (NO)-dependent modulation of cellular respiration and the sensitivity to hypoxic stress is increased following chronic alcohol consumption. This is important since NO has been shown to regulate mitochondrial function through its interaction with cytochrome c oxidase, although at higher concentrations, and in combination with reactive oxygen species, can result in mitochondrial dysfunction. We found that hepatocytes isolated from alcohol-fed rats had decreased mitochondrial bioenergetic reserve capacity and were more sensitive to NO-dependent inhibition of respiration under room air and hypoxic conditions. We reasoned that this would result in greater hypoxic stress in vivo, and to test this, wild-type and iNOS(-/-) mice were administered alcohol-containing diets. Chronic alcohol consumption resulted in liver hypoxia in the wild-type mice and increased levels of hypoxia-inducible factor 1 α in the peri-venular region of the liver lobule. These effects were attenuated in the alcohol-fed iNOS(-/-) mice suggesting that increased mitochondrial sensitivity to NO and reactive nitrogen species in hepatocytes and iNOS plays a critical role in determining the response to hypoxic stress in vivo. These data support the concept that the combined effects of NO and ethanol contribute to an increased susceptibility to hypoxia and the deleterious effects of alcohol consumption on liver.

Chronic ethanol consumption induces histopathological changes and increases nitric oxide generation in the rat liver

In the present work we evaluated the effect of ethanol consumption in histopathological liver changes and several biochemical biomarkers employed in the detection of hepatic dysfunction. Male Wistar rats were treated with ethanol 20% (vol/vol) for 6 weeks. Histopathological investigation of livers from ethanol-treated animals revealed steatosis. Indices of hepatic function (transaminases) and mitochondrial respiration were not altered in ethanol-treated rats. Chronic ethanol consumption did not alter malondialdehyde (MDA) levels in the liver. Ethanol consumption induced a significant increase on hepatic nitrite and nitrate levels. Treatment with ethanol increased both mRNA expression and immunostaining of iNOS, but not eNOS. Finally, ethanol consumption did not alter hepatic levels of metalloproteinase (MMP)-2 and MMP-9. We conclude that alterations on biochemical biomarkers (nitrite and nitrate levels) and histopathology occurred in ethanol-treated rats, supporting the practice of including both types of evaluation in toxicity studies to detect potential ethanol-related hepatic effects. In our model of ethanol consumption, histopathological liver changes were accompanied by elevation in nitrite and nitrate levels indicating increased nitric oxide (NO) generation. Since iNOS-derived NO contributes to hepatic injury, the increased levels of NO described in our study might contribute to a progressive hepatic damage. Therefore, increases in NO generation may be an early indicator of ethanol-induced liver damage.

Mitochondria-targeted ubiquinone (MitoQ) decreases ethanol-dependent micro and macro hepatosteatosis

Chronic alcohol-induced liver disease results in inflammation, steatosis, and increased oxidative and nitrosative damage to the mitochondrion. We hypothesized that targeting an antioxidant to the mitochondria would prevent oxidative damage and attenuate the steatosis associated with alcoholic liver disease. To test this we investigated the effects of mitochondria-targeted ubiquinone (MitoQ) (5 and 25 mg/kg/day for 4 weeks) in male Sprague-Dawley rats consuming ethanol using the Lieber-DeCarli diet with pair-fed controls. Hepatic steatosis, 3-nitrotyrosine (3-NT), 4-hydroxynonenal (4-HNE), hypoxia inducible factor α (HIF1α), and the activity of the mitochondrial respiratory chain complexes were assessed. As reported previously, ethanol consumption resulted in hepatocyte ballooning, increased lipid accumulation in the form of micro and macrovesicular steatosis, and induction of cytochrome P450 2E1 (CYP2E1). MitoQ had a minor effect on the ethanol-dependent decrease in mitochondrial respiratory chain proteins and their activities; however, it did decrease hepatic steatosis in ethanol-consuming animals and prevented the ethanol-induced formation of 3-NT and 4-HNE. Interestingly, MitoQ completely blocked the increase in HIF1α in all ethanol-fed groups, which has previously been demonstrated in cell culture models and shown to be essential in ethanol-dependent hepatosteatosis.

CONCLUSION

These results demonstrate the antioxidant capacity of MitoQ in alleviating alcohol-associated mitochondrial reactive oxygen species (ROS) and several downstream effects of ROS/RNS (reactive nitrogen species) production such as inhibiting protein nitration and protein aldehyde formation and specifically ROS-dependent HIF1α stabilization.

Betaine prevents ethanol-induced oxidative stress and reduces total homocysteine in the rat cerebellum

Oxidative stress is a hypothesis for the association of reactive oxygen species with cerebrovascular and neurodegenerative diseases. Thus, we examined whether oral betaine can act as a preventive agent in ethanol-induced oxidative stress on the cerebellum of rats. Thirty-two adult male Sprague-Dawley rats were divided into four equal groups (control, ethanol, betaine, and betaine plus ethanol) with different dietary regimens and were followed up for 1 month. Total homocysteine (tHcy) of plasma and cerebellum homogenate was determined by an Axis(®) homocysteine EIA kit, and antioxidant enzyme (glutathione peroxidase (GPx), SOD, and CAT) activities of cerebellum homogenate were measured chemically by a spectrophotometer. Lipid peroxidation of cerebellum was shown by the measurement of thiobarbituric reactive substances (TBARS) via a spectrophotometer. Ethanol-induced hyperhomocysteinemia was manifested by an increase in the concentrations of tHcy in the plasma and cerebellum homogenates of the ethanol group, while ethanol-induced oxidative stress was indicated via an increase in lipid peroxidation marker (TBARS) in cerebellum homogenates of ethanol-treated rats. In contrast, betaine prevented hyperhomocysteinemia and oxidative stress in the betaine plus ethanol group as well as the betaine group. The results of the present investigation indicated that the protective effect of betaine is probably related to its ability to strengthen the cerebellum membrane cells by enhancement of antioxidant enzyme activity principally GPx, while the methyl donor effect of betaine to reduce hyperhomocysteinemia has been explained previously and confirmed in the present study.

Ethanol metabolism by HeLa cells transduced with human alcohol dehydrogenase isoenzymes: control of the pathway by acetaldehyde concentration

BACKGROUND

Human class I alcohol dehydrogenase 2 isoenzymes (encoded by the ADH1B locus) have large differences in kinetic properties; however, individuals inheriting the alleles for the different isoenzymes exhibit only small differences in alcohol elimination rates. This suggests that other cellular factors must regulate the activity of the isoenzymes.

METHODS

The activity of the isoenzymes expressed from ADH1B*1, ADH1B*2, and ADH1B*3 cDNAs was examined in stably transduced HeLa cell lines, including lines which expressed human low K(m) aldehyde dehydrogenase (ALDH2). The ability of the cells to metabolize ethanol was compared with that of HeLa cells expressing rat class I alcohol dehydrogenase (ADH) (HeLa-rat ADH cells), rat hepatoma (H4IIEC3) cells, and rat hepatocytes.

RESULTS

The isoenzymes had similar protein half-lives in the HeLa cells. Rat hepatocytes, H4IIEC3 cells, and HeLa-rat ADH cells oxidized ethanol much faster than the cells expressing the ADH1B isoenzymes. This was not explained by high cellular NADH levels or endogenous inhibitors; but rather because the activity of the β1 and β2 ADHs was constrained by the accumulation of acetaldehyde, as shown by the increased rate of ethanol oxidation by cell lines expressing β2 ADH plus ALDH2.

CONCLUSION

The activity of the human β2 ADH isoenzyme is sensitive to inhibition by acetaldehyde, which likely limits its activity in vivo. This study emphasizes the importance of maintaining a low steady-state acetaldehyde concentration in hepatocytes during ethanol metabolism.

Activity of essential phospholipids (EPL) from soybean in liver diseases

Essential phospholipids (EPL) contain a highly purified extract of polyenylphosphatidylcholine (PPC) molecules from soybean. The main active ingredient is 1,2-dilinoleoylphosphatidylcholine (DLPC), which differentiates it from other phospholipids, lecithins, or extracts from other sources. Although EPLis widely used in liver diseases of various origins, its mode of action and pharmacological and clinical evidence of its efficacy have not yet been concisely reviewed. This paper critically summarizes experimental and clinical results. With regard to in-vitro and animal tests, EPL influenced membrane-dependent cellular functions and showed anti-oxidant, anti-inflammatory, anti-fibrotic, apoptosis-modulating, regenerative, membrane-repairing and -protective, cell-signaling and receptor-influencing, as well as lipid-regulating effects in intoxication models with chemicals or drugs. Clinical studies, primarily from European and Asian countries, have shown improvement in subjective symptoms; clinical, biochemical and imaging findings; and histology in liver indications such as fatty liver of different origin, drug hepatotoxicity, and adjuvant in chronic viral hepatitis and hepatic coma. The available studies characterize EPL as evidence-based medicine, although further long-term controlled clinical trials are required to precisely determine its benefit for alleviating symptoms, improving well-being, inducing histological changes and slowing the progression of liver disease. EPL-related relevant side effects were not observed.

Caffeic acid effects on oxidative stress in rat hippocampus after pilocarpine-induced seizures

The objective of the study was to evaluate the caffeic acid (CA) effects against the oxidative stress (OS) observed during seizures. Wistar rats were intraperitoneally treated with either 0.9% saline (control), CA (4 mg/kg), pilocarpine (400 mg/kg, pilocarpine group), or the association of CA (4 mg/kg) plus pilocarpine (400 mg/kg). The thiobarbituric-acid-reacting substances and the hippocampal nitrite content were significantly increased (89 and 94%, respectively) in pilocarpine group when compared with control. There were marked decreases in lipid peroxidation level (43%) and nitrite content (45%) in CA group when compared with pilocarpine group. There were no marked alterations in superoxide dismutase (SOD) and catalase (CAT) activities in pilocarpine group; however, the SOD and CAT activities were significantly increased (35 and 51%, respectively) after CA pretreatment. Our findings strongly support the hypothesis that OS was indeed generated in hippocampus. CA pretreatment can reduces the OS produced by seizures.

Chronic alcohol consumption enhances myeloid-derived suppressor cells in B16BL6 melanoma-bearing mice

We previously found that chronic alcohol consumption decreases the survival of mice bearing subcutaneous B16BL6 melanoma. The underlying mechanism is still not completely understood. Antitumor T cell immune responses are important to inhibiting tumor progression and extending survival. Therefore, we examined the effects of chronic alcohol consumption on the functionality and regulation of these cells in C57BL/6 mice that chronically consumed 20% (w/v) alcohol and subsequently were inoculated subcutaneously with B16BL6 melanoma cells. Chronic alcohol consumption inhibited melanoma-induced memory T cell expansion and accelerated the decay of interferon (IFN)-gamma producing T cells in the tumor-bearing mice. Foxp3(+)CD4(+)CD25(+) regulatory T cells were not affected; however, the percentage of myeloid-derived suppressor cells (MDSC) was significantly increased in the peripheral blood and spleen. T cell proliferation as determined by carboxyfluorescein succinimidyl ester labeling experiments in vitro was inhibited by alcohol consumption relative to control water-drinking melanoma-bearing mice. Collectively, these data show that chronic alcohol consumption inhibits proliferation of memory T cells, accelerates the decay of IFN-gamma producing CD8(+) T cells, and increases MDSC, all of which could be associated with melanoma progression and reduced survival.

Nitric oxide-mediated intestinal injury is required for alcohol-induced gut leakiness and liver damage

BACKGROUND

Alcoholic liver disease (ALD) requires endotoxemia and is commonly associated with intestinal barrier leakiness. Using monolayers of intestinal epithelial cells as an in vitro barrier model, we showed that ethanol-induced intestinal barrier disruption is mediated by inducible nitric oxide synthase (iNOS) upregulation, nitric oxide (NO) overproduction, and oxidation/nitration of cytoskeletal proteins. We hypothesized that iNOS inhibitors [NG-nitro-l-arginine methyl ester (l-NAME), l-N(6)-(1-iminoethyl)-lysine (l-NIL)] in vivo will inhibit the above cascade and liver injury in an animal model of alcoholic steatohepatitis (ASH).

METHODS

Male Sprague-Dawley rats were gavaged daily with alcohol (6 g/kg/d) or dextrose for 10 weeks +/- l-NAME, l-NIL, or vehicle. Systemic and intestinal NO levels were measured by nitrites and nitrates in urine and tissue samples, oxidative damage to the intestinal mucosa by protein carbonyl and nitrotyrosine, intestinal permeability by urinary sugar tests, and liver injury by histological inflammation scores, liver fat, and myeloperoxidase activity.

RESULTS

Alcohol caused tissue oxidation, gut leakiness, endotoxemia, and ASH. l-NIL and l-NAME, but not the d-enantiomers, attenuated all steps in the alcohol-induced cascade including NO overproduction, oxidative tissue damage, gut leakiness, endotoxemia, hepatic inflammation, and liver injury.

CONCLUSIONS

The mechanism we reported for alcohol-induced intestinal barrier disruption in vitro - NO overproduction, oxidative tissue damage, leaky gut, endotoxemia, and liver injury - appears to be relevant in vivo in an animal model of alcohol-induced liver injury. That iNOS inhibitors attenuated all steps of this cascade suggests that prevention of this cascade in alcoholics will protect the liver against the injurious effects of chronic alcohol and that iNOS may be a useful target for prevention of ALD.

Molecular mechanisms of alcoholic fatty liver

Alcoholic fatty liver is a potentially pathologic condition which can progress to steatohepatitis, fibrosis, and cirrhosis if alcohol consumption is continued. Alcohol exposure may induce fatty liver by increasing NADH/NAD(+) ratio, increasing sterol regulatory element-binding protein-1 (SREBP-1) activity, decreasing peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activity, and increasing complement C3 hepatic levels. Alcohol may increase SREBP-1 activity by decreasing the activities of AMP-activated protein kinase and sirtuin-1. Tumor necrosis factor-alpha (TNF-alpha) produced in response to alcohol exposure may cause fatty liver by up-regulating SREBP-1 activity, whereas betaine and pioglitazone may attenuate fatty liver by down-regulating SREBP-1 activity. PPAR-alpha agonists have potentials to attenuate alcoholic fatty liver. Adiponectin and interleukin-6 may attenuate alcoholic fatty liver by up-regulating PPAR-alpha and insulin signaling pathways while down-regulating SREBP-1 activity and suppressing TNF-alpha production. Recent studies show that paracrine activation of hepatic cannabinoid receptor 1 by hepatic stellate cell-derived endocannabinoids also contributes to the development of alcoholic fatty liver. Furthermore, oxidative modifications and inactivation of the enzymes involved in the mitochondrial and/or peroxisomal beta-oxidation of fatty acids could contribute to fat accumulation in the liver.

Prevention of alcoholic fatty liver and mitochondrial dysfunction in the rat by long-chain polyunsaturated fatty acids

BACKGROUND/AIMS

We reported that reduced dietary intake of polyunsaturated fatty acids (PUFA) such as arachidonic (AA,20:4n6,omega-6) and docosahexaenoic (DHA,22:6n3,omega-3) acids led to alcohol-induced fatty liver and fibrosis. This study was aimed at studying the mechanisms by which a DHA/AA-supplemented diet prevents alcohol-induced fatty liver.

METHODS

Male Long-Evans rats were fed an ethanol or control liquid-diet with or without DHA/AA for 9 weeks. Plasma transaminase levels, liver histology, oxidative/nitrosative stress markers, and activities of oxidatively-modified mitochondrial proteins were evaluated.

RESULTS

Chronic alcohol administration increased the degree of fatty liver but fatty liver decreased significantly in rats fed the alcohol-DHA/AA-supplemented diet. Alcohol exposure increased oxidative/nitrosative stress with elevated levels of ethanol-inducible CYP2E1, nitric oxide synthase, nitrite and mitochondrial hydrogen peroxide. However, these increments were normalized in rats fed the alcohol-DHA/AA-supplemented diet. The number of oxidatively-modified mitochondrial proteins was markedly increased following alcohol exposure but significantly reduced in rats fed the alcohol-DHA/AA-supplemented diet. The suppressed activities of mitochondrial aldehyde dehydrogenase, ATP synthase, and 3-ketoacyl-CoA thiolase in ethanol-exposed rats were also recovered in animals fed the ethanol-DHA/AA-supplemented diet.

CONCLUSIONS

Addition of DHA/AA prevents alcohol-induced fatty liver and mitochondrial dysfunction in an animal model by protecting various mitochondrial enzymes most likely through reducing oxidative/nitrosative stress.

Ethanol induces peroxynitrite-mediated toxicity through inactivation of NADP+-dependent isocitrate dehydrogenase and superoxide dismutase

It has been reported that chronic alcohol administration increases peroxynitrite hepatotoxicity by enhancing concomitant production of nitric oxide and superoxide. Several studies have shown the importance of superoxide dismutase (SOD) in protecting cells against ethanol-induced oxidative stress. Recently, we demonstrated that the control of cytosolic and mitochondrial redox balance and the cellular defense against oxidative damage is one of the primary functions of NADP+-dependent isocitrate dehydrogenase (ICDH) through to supply NADPH for antioxidant systems. In this report, we demonstrate that ethanol induces the peroxynitrite-mediated cytotoxicity in HepG2 cells through inactivation of antioxidant enzymes such as ICDH and SOD. Upon exposure to 100mM ethanol for 3days to HepG2 cells, a significant decrease in the viability and activities of ICDH and SOD was observed. The ethanol-induced inactivation of antioxidant enzymes resulted in the cellular oxidative damage and modulation of redox status as well as mitochondrial dysfunction in HepG2 cells. The cytoxicity of ethanol and inactivation of antioxidant enzymes were effectively protected by manganeses(III) tetrakis(N-methyl-2-pyridyl) porphyrin, a manganese SOD mimetic, and N'-monomethyl-l-arginine, a nitric oxide synthase inhibitor. These results indicate that ethanol toxicity is mediated by peroxynitrite and the peroxynitrite-mediated damage to ICDH and SOD may be resulted in the perturbation of the cellular antioxidant defense systems and subsequently lead to a pro-oxidant condition.

Difficulty of mode of action determination for trichloroethylene: An example of complex interactions of metabolites and other chemical exposures

The mode(s) of action (MOA) of a pollutant for adverse health effects may be dependent on the mixture of metabolites resulting from exposure to a single agent and may also be affected by coexposure to pollutants that have similar targets or affected pathways. Trichloroethylene (TCE) can be an useful example for illustration of the complexity coexposure can present to elucidation of the MOA of an agent. TCE exposure has been associated with increased risk of liver and kidney cancer in both laboratory animal and epidemiologic studies. There are a number of TCE metabolites that could play a role in the induction of these effects. Coexposures of other chemicals with TCE typically occurs as a result of environmental cocontamination that include its own metabolites, such as trichloroacetic acid, dichloroacetic acid, and other pollutants with similar metabolites such as perchloroethylene. Behaviors such as alcohol consumption can also potentially modify TCE toxicity through similar MOAs. The U.S. Environmental Protection Agency (EPA)'s 2001 draft TCE risk assessment, Trichloroethylene (TCE) Health Risk Assessment: Synthesis and Characterization, concluded that it was difficult to determine which of the metabolites of TCE may be responsible for these effects, what key events in their hypothesized MOAs are involved, and the relevance of some of the hypothesized MOAs to humans. Since the publication of U.S. EPA's draft TCE assessment, several studies have been conducted to understand the effects of coexposures to TCE. They cover both pharmacodynamic and pharmacokinetic considerations. This article highlights some of the recently published scientific literature on toxicological interactions between TCE, its metabolites, and other coexposures, including solvents, haloacetates, and ethanol. These studies give insight into both the potential MOAs of TCE exposure itself and putative modulators of TCE toxicity, and illustrate the difficulties encountered in determining the MOAs and modulators of toxicity for pollutants with such complex metabolism and coexposures.

Herbal mixtures consisting of puerarin and either polyenylphosphatidylcholine or curcumin provide comprehensive protection against alcohol-related disorders in P rats receiving free choice water and 15% ethanol in pure water

Chronic alcohol drinking has been associated with the development of a number of abnormalities, including neuron-behavioral disorders, liver, pancreas, and heart-related diseases and inflammation and immune disorders. Because diverse mechanisms are involved in the development of these disorders, the commonly used receptor- or enzyme-specific drugs do not provide comprehensive protection against the adverse effects of alcoholism. This study describes possible therapeutic potency of puerarin (PU) from kudzu root, polyenylphosphatidylcholine from soy (SPCh), and curcumin (CU) from turmeric against alcohol's addiction-related and inflammatory-related abnormalities in alcohol-preferring P rats receiving free choice water and 15% ethanol in water. P-rats were fed once daily either the vehicle (for control) or different doses of PU, SPCh, CU, PU + SPCh, or PU + CU. The rats were divided in two groups: one received water alone, and the other free choice water and ethanol. Four rats from each group were fitted with electroencephalogram (EEG) electrodes for EEG recording. After 70 days of alcohol drinking, alcohol was withdrawn for 2 weeks, and the withdrawal symptoms were assessed. This study showed that alcohol drinking for 70 days (1) caused liver inflammation characterized by elevated tumor necrosis factor-alpha, interleukin-1beta, and matrix metalloproteinase-9 expression and (2) dysregulated lipopolysaccharide (LPS)-induced pleurisy. Alcohol withdrawal after 70 days of drinking generated severe withdrawal symptoms including seizure-type EEG activity. PU suppressed the addiction-mediated abnormalities but did not affect the inflammation-related abnormalities, while SPCh or CU suppressed only the inflammation-related abnormalities in alcohol-drinking rats subjected to LPS-induced pleurisy. A combination of PU with SPCh or CU suppressed both the addiction-related and inflammation-related abnormalities of alcohol drinking. Therefore, a mixture consisting of PU and either SPCh or CU may provide alternative therapy for alcohol-related disorders.

Possible mechanism of acute effect of ethanol on intestinal IgA expression in rat

The purpose of this study was to investigate the possible mechanism of acute effect of ethanol on IgA expression in rat intestine. To this end, adult female Wistar rats showing diestrus day 1 were treated with (a) ethanol (2 or 4 g/kg, i.p.); (b) N omega-nitro-L-arginine-methyl ester (L-NAME), which inhibits the activity of all isoforms of nitric oxide synthase, (30 mg/kg, s.c.) followed by ethanol 3 h later; and (c) L-NAME (30 mg/kg, s.c.) followed by saline 3 h later. Saline-injected and untreated rats were used as controls. The animals were sacrificed 0.5 h after ethanol administration. Intestinal expression of IgA was evaluated by both immunohistochemistry and Western immunoblotting. Morphometric analysis showed that acute ethanol treatment increased the number of IgA-immunoreactive cells in a dose-dependent manner. Pretreatment with L-NAME abolished this action of alcohol. Injection of L-NAME followed by saline had no influence on the number of IgA+cells. The results, obtained by Western immunoblotting, paralleled our immunohistochemical findings. Taken together, these data suggest that acute effect of ethanol on intestinal IgA might be mediated by endogenous nitric oxide.

Inactivation of oxidized and S-nitrosylated mitochondrial proteins in alcoholic fatty liver of rats

Increased oxidative/nitrosative stress is a major contributing factor to alcohol-mediated mitochondrial dysfunction. However, which mitochondrial proteins are oxidatively modified under alcohol-induced oxidative/nitrosative stress is poorly understood. The aim of this study was to systematically investigate oxidized and/or S-nitrosylated mitochondrial proteins and to use a biotin-N-maleimide probe to evaluate their inactivation in alcoholic fatty livers of rats. Binge or chronic alcohol exposure significantly elevated nitric oxide, inducible nitric oxide synthase, and ethanol-inducible CYP2E1. The biotin-N-maleimide-labeled oxidized and/or S-nitrosylated mitochondrial proteins from pair-fed controls or alcohol-fed rat livers were subsequently purified with streptavidin-agarose. The overall patterns of oxidized and/or S-nitrosylated proteins resolved by 2-dimensional polyacrylamide gel electrophoresis were very similar in the chronic and binge alcohol treatment groups. Seventy-nine proteins that displayed differential spot intensities from those of control rats were identified by mass spectrometry. These include mitochondrial aldehyde dehydrogenase 2 (ALDH2), ATP synthase, acyl-CoA dehydrogenase, 3-ketoacyl-CoA thiolase, and many proteins involved in chaperone activity, mitochondrial electron transfer, and ion transport. The activity of 3-ketoacyl-CoA thiolase involved in mitochondrial beta-oxidation of fatty acids was significantly inhibited in alcohol-exposed rat livers, consistent with hepatic fat accumulation, as determined by biochemical and histological analyses. Measurement of activity and immunoblot results showed that ALDH2 and ATP synthase were also inhibited through oxidative modification of their cysteine or tyrosine residues in alcoholic fatty livers of rats. In conclusion, our results help to explain the underlying mechanism for mitochondrial dysfunction and increased susceptibility to alcohol-mediated liver damage.

Dietary restriction protects against chronic-ethanol-induced changes in exploratory behavior in Wistar rats

Chronic ethanol intake causes various types of neural damage and behavioral impairments, probably acting through oxidative stress and excitotoxicity, while dietary restriction is considered by some authors to protect the central nervous system from these kinds of damage. In the present study, a factorial experimental design was used to investigate the effects of chronic ethanol and dietary restriction treatments, associated or not, on Wistar rats' exploratory behavior, spatial memory aspects and cortical and hippocampal acetylcholinesterase (AChE) activity. Dietary restriction lasted for the whole experiment, while ethanol treatment lasted for only 3 weeks. Despite the short ethanol treatment duration, for two behavior categories assessed, moving and rearing, an interaction was observed between the effects of chronic ethanol and dietary restriction. There were no significant differences in AChE activities among the groups. Cerebellar neural nitric oxide synthase (nNOs) activity was measured as a first step to assess oxidative stress. Dietary restriction significantly reduced NO formation. The present results indicate that dietary restriction might exert a protective effect against chronic-ethanol-induced changes in exploratory behavior. It is hypothesized that the mechanisms underlying this protection can involve prevention of oxidative stress.

Mice heterozygous for the Mdr2 gene demonstrate decreased PEMT activity and diminished steatohepatitis on the MCD diet

BACKGROUND/AIMS

The administration of a methionine and choline deficient (MCD) diet to mice serves as an animal model of NASH. The multidrug resistant 2 (Mdr2) P-glycoprotein encodes for the canalicular phospholipid transporter, and Mdr2 (+/-) mice secrete 40% less phosphatidylcholine than wild-type mice. We have hypothesized that phosphatidylethanolamine-N-methyl transferase (PEMT) up-regulation is a consequence of MCD diet administration, and is important for the pathogenesis of steatohepatitis in this model. However, the effect of decreased phosphatidylcholine secretion and modulation of PEMT on the development of diet-induced steatohepatitis in Mdr2 (+/-) mice has not been explored. Thus, the purpose of the study is to examine the effects of the MCD diet on Mdr2 (+/-) mice.

METHODS

Mdr2 (+/-) and Mdr2 (+/+) mice were treated with an MCD or control diet for up to 30 days, and the severity of steatohepatitis, PEMT activity and hepatic S-adenosylmethionine (SAM), and S-adenosylhomocysteine (SAH) levels were measured.

RESULTS

Serum ALT levels, hepatic inflammation, and PEMT activity were significantly lower, and hepatic SAM:SAH ratios were significantly higher in Mdr2 (+/-) mice at 7 and 30 days on the MCD diet.

CONCLUSIONS

Mdr2 (+/-) mice have diminished susceptibility to MCD diet-induced NASH, which is associated with a relative decrease in PEMT activity and increased SAM:SAH ratios.

Recombinant Hep G2 cells that express alcohol dehydrogenase and cytochrome P450 2E1 as a model of ethanol-elicited cytotoxicity

HepG2 cells were transfected with recombinant plasmids, one carrying the murine alcohol dehydrogenase (ADH) gene and the other containing the gene encoding human cytochrome P450 2E1 (CYP2E1). One of recombinant clones called VL-17A exhibited ADH and CYP2E1 specific activities comparable to those in isolated rat hepatocytes. VL-17A cells oxidized ethanol and generated acetaldehyde, the levels of which depended upon the initial ethanol concentration. Compared with unexposed VL-17A cells, ethanol exposure increased the cellular redox (lactate:pyruvate ratio) and caused cell toxicity, indicated by increased leakage of lactate dehydrogenase into the medium,. Exposure of VL-17A cells to 100mM ethanol significantly elevated caspase 3 activity, an indicator of apoptosis, but this ethanol concentration did not affect caspase 3 activity in parental HepG2 cells. Because ethanol consumption causes a decline in hepatic protein catabolism, we examined the influence of ethanol exposure on proteasome activity in HepG2, VL-17A, E-47 (CYP2E1(+)) and VA-13 (ADH(+)) cells. Exposure to 100mM ethanol caused a 25% decline in the chymotrypsin-like activity of the proteasome in VL-17A cells, but the enzyme was unaffected in the other cell types. This inhibitory effect on the proteasome was blocked when ethanol metabolism was blocked by 4-methyl pyrazole. We conclude that recombinant VL-17A cells, which express both ADH and CYP2E1 exhibit hepatocyte-like characteristics in response to ethanol. Furthermore, the metabolism of ethanol by these cells via ADH and CYP2E1 is sufficient to bring about an inhibition of proteasome activity that may lead to apoptotic cell death.

Neonatal alcohol exposure increases malondialdehyde (MDA) and glutathione (GSH) levels in the developing cerebellum

It has been suggested that developmental alcohol-induced brain damage is mediated through increases in oxidative stress. In this study, the concentrations of malondialdehyde (MDA) and reduced glutathione (GSH) were measured to indicate alcohol-mediated oxidative stress. In addition, the ability of two known antioxidants, melatonin (MEL) and lazaroid U-83836E (U), to attenuate alcohol-induced oxidative stress was investigated. Sprague-Dawley rat pups were randomly assigned to six artificially-reared groups, ALC (alcohol), MEL, MEL/ALC, U, U/ALC, and GC (gastrostomy control), and one normal suckle control (to control for artificial-rearing effects on the dependent variables). The daily dosages for ALC, MEL, and U were 6 g/kg, 20 mg/kg, and 20 mg/kg, respectively. Alcohol was administered in 2 consecutive feedings, and antioxidant (MEL or U) was administered for a total of 4 consecutive feedings (2 feedings prior to and 2 feedings concurrently with alcohol). The animals received treatment from postnatal days (PD) 4 through 9. Cerebellar, hippocampal, and cortical samples were collected on PD 9 and analyzed for MDA and GSH content. The results indicated that MDA concentrations in the cerebellum were significantly elevated in animals receiving alcohol; however, MDA levels in the hippocampus and cortex were not affected by alcohol treatment. Additionally, GSH levels in the cerebellum were significantly elevated in groups receiving alcohol, regardless of antioxidant treatment. Neither antioxidant was able to protect against alcohol-induced alterations of MDA or GSH. These findings suggest that alcohol might increase GSH levels indirectly as a compensatory mechanism designed to protect the brain from oxidative-stress-mediated insult.

Decreased proteasome activity is associated with increased severity of liver pathology and oxidative stress in experimental alcoholic liver disease

BACKGROUND

Because of its role in degrading the bulk of intracellular proteins and eliminating damaged proteins, the proteasome is important in maintaining cell viability. Previously, we showed a 35-40% decrease in proteasome peptidase activity when ethanol was administered to rats by intragastric infusion. We hypothesized that this reduction was caused by ethanol-elicited oxidative stress, the degree of which varies depending on the method of ethanol administration. This study examined the relationship of proteasome activity and content with ethanol-induced oxidative stress and the degree of liver injury.

METHODS

Rats were given ethanol or isocaloric dextrose-containing liquid diets by intragastric infusion for 1 month. The diets contained medium-chain triglycerides (MCT), palm oil (PO), corn oil (CO), or fish oil (FO) as the principal source of fat.

RESULTS

Rats given ethanol and MCT exhibited no significant liver pathology, whereas cumulative pathology scores in ethanol-fed rats given PO, CO, or FO were 2.5, 5.4 and 7.0, respectively, indicating that ethanol and FO caused the greatest liver damage. The severity of liver pathology in the last three groups of animals correlated with levels of lipid peroxides and serum 8-isoprostanes. Alpha smooth muscle actin, an indicator of stellate cell activation, was increased relative to controls in the livers of all ethanol-fed rats except FO-fed animals, in which both control and ethanol-fed rats had similar levels of this protein. In livers of CO and FO ethanol-fed rats, proteasome chymotrypsin-like activity was decreased by 55-60%, but there was no quantitative alteration in 20S proteasome subunit content. In contrast, ethanol affected neither proteasome activity nor its content in MCT- and PO-treated animals.

CONCLUSIONS

Our findings indicate that the severity of liver injury and ethanol-induced oxidative stress is associated with a reduction in proteasome catalysis.

Nitroxia: the pathological consequence of dysfunction in the nitric oxide-cytochrome c oxidase signaling pathway

It is now recognized that mitochondria play an integral role in orchestrating the response of the cell to a wide variety of metabolic and environmental stressors. Of particular interest are the interactions of reactive oxygen and nitrogen species with the organelle and their potential regulatory function. The best understood example is the O(2) sensitive binding of NO (nitric oxide) to the heme group in cytochrome c oxidase. We have proposed that this reversible process serves the function of both regulating the formation of hydrogen peroxide from the respiratory chain for the purposes of signal transduction and controlling O(2) gradients in complex organs such as the liver or heart. It now appears that maladaptation in this pathway leads to a mitochondrial dysfunction which has some of the characteristics of hypoxia, such as a deficit in ATP, but occurs in the presence of normal or enhanced levels of O(2). These are the optimal conditions for the formation of reactive nitrogen species (RNS), such as peroxynitrite which lead to the irreversible modification of proteins. We term this unique pathological condition Nitroxia and describe how it may contribute to the pathology of chronic inflammatory diseases using ethanol-dependent hepatotoxicity as an example.

The role of iNOS in alcohol-dependent hepatotoxicity and mitochondrial dysfunction in mice

Nitric oxide (NO) is now known to control both mitochondrial respiration and organelle biogenesis. Under conditions of ethanol-dependent hepatic dysfunction, steatosis is increased, and this is associated with increased expression of inducible nitric oxide synthase (iNOS). We have previously shown that after chronic exposure to ethanol, the sensitivity of mitochondrial respiration to inhibition by NO is enhanced, and we have proposed that this contributes to ethanol-dependent hypoxia. This study examines the role of iNOS in controlling the NO-dependent modification of mitochondrial function. Mitochondria were isolated from the livers of both wild-type (WT) and iNOS knockout (iNOS-/-) mice that were fed an isocaloric ethanol-containing diet for a period of 5 weeks. All animals that consumed ethanol showed some evidence of fatty liver; however, this was to a lesser extent in the iNOS-/- mice compared to controls. At this early stage in ethanol-dependent hepatic dysfunction, infiltration of inflammatory cells and the formation of nitrated proteins was also decreased in response to ethanol feeding in the iNOS-/- animals. Mitochondria isolated from wild-type ethanol-fed mice showed a significant decrease in respiratory control ratio and an increased sensitivity to NO-dependent inhibition of respiration relative to their pair-fed controls. In contrast, liver mitochondria isolated from iNOS-/- mice fed ethanol showed no change in the sensitivity to NO-dependent inhibition of respiration. In conclusion, the hepatic response to chronic alcohol-dependent cytotoxicity involves a change in mitochondrial function dependent on the induction of iNOS.

Peroxynitrite alters the catalytic activity of rodent liver proteasome in vitro and in vivo

The proteasome is an important multicatalytic enzyme complex that degrades misfolded and oxidized proteins, signal transduction factors, and antigenic peptides for presentation. We investigated the in vitro effects of peroxynitrite (PN) on the peptidase activity of both crude 20S and 26S and purified 20S proteasome preparations from rat liver as well as proteasome activity in Hep G2 cells and in mouse liver. Crude and purified proteasome preparations were exposed to PN or to the PN donor, 3-morpholinosydnonimine hydrochloride (SIN-1), and then assayed for chymotrypsin-like activity. For in vivo experiments, mice were treated with molsidomine, which is metabolized to SIN-1 in liver. PN and SIN-1 dose-dependently modulated the chymotrypsin-like activity of the 20S proteasome: lower concentrations enhanced proteasome activity, and higher concentrations caused its decline. The NO donor S-nitroso-N-acetylpenicillamine (SNAP), at all concentrations, suppressed 20S proteasome activity. We observed similar results when liver soluble fractions (S-100) were treated with PN, SIN-1, or SNAP, except that enzyme activity in S-100 fractions was less sensitive than the purified enzymes to these agents. Treatment of Hep G2 cells with 0.01 or 0.1 mmol/L SIN-1 stimulated in situ proteasome activity in these cells, while 1 mmol/L SIN-1 suppressed it. SNAP treatment did not affect proteasome activity in Hep G2 cells. Mice treated with molsidomine had enhanced liver proteasome activity 6 hours after treatment, but after 24 hours enzyme activity declined below control levels. In conclusion, PN dose-dependently modulated proteasome activity, regulating protein degradation by the proteasome in liver cells.

Metabolic, antioxidant, nutraceutical, probiotic, and herbal therapies relating to the management of hepatobiliary disorders

Many nutraceuticals, conditionally essential nutrients, and botanical extracts have been proposed as useful in the management of liver disease. The most studied of these are addressed in terms of proposed mechanisms of action, benefits, hazards, and safe dosing recommendations allowed by current information. While this is an area of soft science, it is important to keep an open and tolerant mind, considering that many major treatment discoveries were in fact serendipitous accidents.

Modification of the mitochondrial proteome in response to the stress of ethanol-dependent hepatotoxicity

Mitochondria are particularly susceptible to increased formation of reactive oxygen and nitrogen species in the cell that can occur in response to pathological and xenobiotic stimuli. Proteomics can give insights into both mechanism of pathology and adaptation to stress. Herein we report the use of proteomics to evaluate alterations in the levels of mitochondrial proteins following chronic ethanol exposure in an animal model. Forty-three proteins showed differential expression, 13 increased and 30 decreased, as a consequence of chronic ethanol. Of these proteins, 25 were not previously known to be affected by chronic ethanol emphasizing the power of proteomic approaches in revealing global responses to stress. Both nuclear and mitochondrially encoded gene products of the oxidative phosphorylation complexes in mitochondria from ethanol-fed rats were decreased suggesting an assembly defect in this integrated metabolic pathway. Moreover mtDNA damage was increased by ethanol demonstrating that the effects of ethanol consumption extend beyond the proteome to encompass mtDNA. Taken together, we have demonstrated that chronic ethanol consumption extends to a modification of the mitochondrial proteome far broader than realized previously. These data also suggest that the response of mitochondria to stress may not involve non-discriminate changes in the proteome but is restricted to those metabolic pathways that have a direct role in a specific pathology.