Acetaldehyde inhibits NF-kappaB activation through IkappaBalpha preservation in rat Kupffer cells

A novel comparative pattern count analysis reveals a chronic ethanol-induced dynamic shift in immediate early NF-κB genome-wide promoter binding during liver regeneration

Liver regeneration after partial hepatectomy is a clinically important process that is impaired by adaptation to chronic alcohol intake. We focused on the initial time points following partial hepatectomy (PHx) to analyze the genome-wide binding activity of NF-κB, a key immediate early regulator. We investigated the effect of chronic alcohol intake on immediate early NF-κB genome-wide localization, in the adapted state as well as in response to partial hepatectomy, using chromatin immunoprecipitation followed by promoter microarray analysis. We found many ethanol-specific NF-κB binding target promoters in the ethanol-adapted state, corresponding to the regulation of biosynthetic processes, oxidation-reduction and apoptosis. Partial hepatectomy induced a diet-independent shift in NF-κB binding loci relative to the transcription start sites. We employed a novel pattern count analysis to exhaustively enumerate and compare the number of promoters corresponding to the temporal binding patterns in ethanol and pair-fed control groups. The highest pattern count corresponded to promoters with NF-κB binding exclusively in the ethanol group at 1 h post PHx. This set was associated with the regulation of cell death, response to oxidative stress, histone modification, mitochondrial function, and metabolic processes. Integration with the global gene expression profiles to identify putative transcriptional consequences of NF-κB binding patterns revealed that several of ethanol-specific 1 h binding targets showed ethanol-specific differential expression through 6 h post PHx. Motif analysis yielded co-incident binding loci for STAT3, AP-1, CREB, C/EBP-β, PPAR-γ and C/EBP-α, likely participating in co-regulatory modules with NF-κB in shaping the immediate early response to PHx. We conclude that adaptation to chronic ethanol intake disrupts the NF-κB promoter binding landscape with consequences for the immediate early gene regulatory response to the acute challenge of PHx.

Opposing effects of alcohol on the immune system

Several studies have described a dose-dependent effect of alcohol on human health with light to moderate drinkers having a lower risk of all-cause mortality than abstainers, while heavy drinkers are at the highest risk. In the case of the immune system, moderate alcohol consumption is associated with reduced inflammation and improved responses to vaccination, while chronic heavy drinking is associated with a decreased frequency of lymphocytes and increased risk of both bacterial and viral infections. However, the mechanisms by which alcohol exerts a dose-dependent effect on the immune system remain poorly understood due to a lack of systematic studies that examine the effect of multiple doses and different time courses. This review will summarize our current understanding of the impact of moderate versus excessive alcohol consumption on the innate and adaptive branches of the immune system derived from both in vitro as well as in vivo studies carried out in humans and animal model studies.

In Vivo Zonal Variation and Liver Cell-Type Specific NF-κB Localization after Chronic Adaptation to Ethanol and following Partial Hepatectomy

NF-κB is a major inflammatory response mediator in the liver, playing a key role in the pathogenesis of alcoholic liver injury. We investigated zonal as well as liver cell type-specific distribution of NF-κB activation across the liver acinus following adaptation to chronic ethanol intake and 70% partial hepatectomy (PHx). We employed immunofluorescence staining, digital image analysis and statistical distributional analysis to quantify subcellular localization of NF-κB in hepatocytes and hepatic stellate cells (HSCs). We detected significant spatial heterogeneity of NF-κB expression and cellular localization between cytoplasm and nucleus across liver tissue. Our main aims involved investigating the zonal bias in NF-κB localization and determining to what extent chronic ethanol intake affects this zonal bias with in hepatocytes at baseline and post-PHx. Hepatocytes in the periportal area showed higher NF-κB expression than in the pericentral region in the carbohydrate-fed controls, but not in the ethanol group. However, the distribution of NF-κB nuclear localization in hepatocytes was shifted towards higher levels in pericentral region than in periportal area, across all treatment conditions. Chronic ethanol intake shifted the NF-κB distribution towards higher nuclear fraction in hepatocytes as compared to the pair-fed control group. Ethanol also stimulated higher NF-κB expression in a subpopulation of HSCs. In the control group, PHx elicited a shift towards higher NF-κB nuclear fraction in hepatocytes. However, this distribution remained unchanged in the ethanol group post-PHx. HSCs showed a lower NF-κB expression following PHx in both ethanol and control groups. We conclude that adaptation to chronic ethanol intake attenuates the liver zonal variation in NF-κB expression and limits the PHx-induced NF-κB activation in hepatocytes, but does not alter the NF-κB expression changes in HSCs in response to PHx. Our findings provide new insights as to how ethanol treatment may affect cell-type specific processes regulated by NF-κB activation in liver cells.

The effects of acetaldehyde in vitro on proteasome activities and its potential involvement after alcoholization of rats by inhalation of ethanol vapours

BACKGROUND/AIMS

Some models of chronic ethanol administration resulted in decreased proteasome activities. The mechanisms still remain speculative. In the present study, we tested another model of alcoholization with high blood alcohol levels (BALs) and high acetaldehyde fluxes as well as the in vitro effect of acetaldehyde on proteasome. Methods/

RESULTS

Ethanol vapour chronically inhaled by adult Wistar rats up to a specific protocol, can reach high BALs (200 mg/dl) with significant circulating acetaldehyde levels. After 4 weeks of ethanol intoxication, although cytochrome CYP2E1 was increased, liver lipid peroxidation remained unchanged when protein carbonyls augmented selectively for high molecular weight with a decrease of the proteasome activities in ethanol rats. Several aldehydes inhibit proteasome function; we specifically explored the effects of acetaldehyde, the first alcohol metabolite. Adduction of acetaldehyde in vitro to cytosolic proteins inhibits proteasome in a dose-dependent manner. Acetaldehyde adducted to purified proteasome also exhibits a decrease in its activities. Furthermore, an acetaldehyde-adducted protein, i.e. bovine serum albumin (BSA) is less degraded than a native BSA by purified proteasome. These findings suggest that acetaldehyde, if overproduced, can inhibit proteasome activities and reduce the proteolysis of acetaldehyde-adducted proteins.

CONCLUSIONS

Our study, for the first time, provided the evidence that acetaldehyde by itself inhibits proteasome activities. As the chronic inhalation model used in this study is not associated with an overt lipid peroxidation, one can suggest that high BALs and their subsequent high acetaldehyde fluxes contribute to impairment of proteasome function and accumulation of carbonylated proteins. This early phenomenon may have relevance in experimental alcohol liver disease.

Diverse regulation of NF-kappaB and peroxisome proliferator-activated receptors in murine nonalcoholic fatty liver

Fatty liver is highly sensitive to inflammatory activation. Peroxisome proliferator-activated receptors (PPAR) have anti-inflammatory effects and regulate lipid metabolism in the fatty liver. We hypothesized that fatty liver leads to endotoxin sensitivity through an imbalance between pro- and anti-inflammatory signals. Leptin-deficient, ob/ob mice and their lean littermates were challenged with single or double insults and pro- and anti-inflammatory pathways were tested on cytokine production and activation of nuclear regulatory factors NF-kappaB and peroxisome proliferator receptor element (PPRE). Ob/ob mice produced significantly higher serum tumor necrosis factor alpha (TNF-alpha) and interleukin (IL) 6 and showed increased hepatic NF-kappaB activation compared to lean littermates after stimulation with a single dose of lipopolysaccharide (LPS) or alcohol. In ob/ob mice, double insults with alcohol and LPS augmented proinflammatory responses mediated by increased degradation of inhibitory kappaB (IkappaB)-alpha and IkappaB-beta and preferential induction of the p65/p50 NF-kappaB heterodimer. In lean mice, in contrast, acute alcohol attenuated LPS-induced TNF-alpha, IL-6 production, and NF-kappaB activation through reduced IkappaB-alpha degradation and induction of p50/p50 homodimers. PPRE binding was increased in fatty but not in lean livers after alcohol or LPS stimulation. However, cotreatment with alcohol and LPS reduced both PPRE binding and nuclear levels of PPAR-alpha in fatty livers but increased those in lean livers. In conclusion, our results show opposite PPRE and NF-kappaB activation in fatty and lean livers. PPAR activation may represent an anti-inflammatory mechanism that fails in the fatty liver on increased proinflammatory pressure. Thus, an imbalance between PPAR-mediated anti-inflammatory and NF-kappaB-mediated proinflammatory signals may contribute to increased inflammation in the fatty liver.

Identification of a novel NF-kappaB-binding site with regulation of the murine alpha2(I) collagen promoter

Hepatic fibrosis is due to the increased synthesis and deposition of type I collagen. Acetaldehyde activates type I collagen promoters. Nuclear factor kappaB (NF-kappaB) was previously shown to inhibit expression of murine alpha(1)(I) and human alpha(2)(I) collagen promoters. The present study identifies binding of NF-kappaB, present in nuclear extracts of stellate cells, to a region between -553 and -537 of the murine alpha(2)(I) collagen promoter. The NF-kappaB (p65) expression vector inhibited promoter activity. Mutation of the promoter at the NF-kappaB-binding site increased basal promoter activity and abrogated the activating and inhibitory effects of transforming growth factor beta and tumor necrosis factor alpha, respectively, on promoter activity. Acetaldehyde increased IkappaB-alpha kinase activity and phosphorylated IkappaB-alpha, NF-kappaB nuclear protein, and its binding to the promoter. However, the activating effect of acetaldehyde was not affected by the mutation of the promoter. In conclusion, although acetaldehyde increases the binding of NF-kappaB to the murine alpha(2)(I) collagen promoter, this binding does not mediate the activating effect of acetaldehyde on promoter activity. The effects of acetaldehyde in increasing the translocation of NF-kappaB to the nucleus with increased DNA binding activity may be important in mediating the effects of acetaldehyde on other genes.

Dietary Cholate Is Required for Antiatherogenic Effects of Ethanol in Mouse Models

BACKGROUND

Human consumption of moderate amounts of ethanol is associated with reduced cardiovascular events. Studies examining the effect of ethanol on atherosclerosis in mouse models have yielded conflicting results that may be due to differences in dietary fat and cholate content. To determine if dietary cholate influences ethanol's effect on atherosclerosis, we fed apolipoprotein E-/- and low-density lipoprotein receptor (LDLR)-/- mice different liquid diets with or without ethanol.

METHODS

Apolipoprotein E-/- mice were fed a low-fat or high saturated fat, cholate-containing diet with or without ethanol for 3 to 10 weeks, and LDLR-/- mice were fed a low-fat, high saturated fat, or high saturated fat diet with cholate with or without ethanol for 7 weeks. At the end of the feeding study, aortic root lesion size was determined and compared with serum cholesterol, triglycerides, and high-density lipoprotein cholesterol. Because dietary cholate increases hepatic nuclear factor (NF)-kappaB and ethanol inhibits NF-kappaB, we also examined the effect of ethanol on aortic NF-kappaB binding activity.

RESULTS

Adding ethanol to a low-fat diet had no effect on lesion size. Similarly, ethanol had no effect on lesion size in LDLR-/- mice consuming a high saturated fat diet. Adding ethanol to a high-fat, cholate-containing diet for either strain resulted in a 25% to 50% reduction in lesion size. Dietary cholate increased and ethanol reduced NF-kappaB binding activity in the aorta.

CONCLUSIONS

These results suggest that ethanol inhibits atherosclerosis in the presence of dietary cholate, which may occur via an anti-inflammatory mechanism.

Endotoxin enhances liver alcohol dehydrogenase by action through upstream stimulatory factor but not by nuclear factor-kappa B

Liver alcohol dehydrogenase (ADH) is increased by physiological stress and by chronic administration of growth hormone (GH). Endotoxin plays a role in the pathogenesis of alcoholic liver disease. The effect of lipopolysaccharide (LPS), the endotoxin component of Gram-negative bacteria, was determined on liver ADH. LPS given daily to rats for 3 days increased ADH mRNA, ADH protein, and ADH activity. Nuclear factor-kappaB (NF-kappaB) in the liver nuclear extracts bound to an oligonucleotide specifying region -226 to -194 of the ADH promoter, whereas upstream stimulatory factor (USF) was shown previously to bind to a more proximal site. LPS increased NF-kappaB and USF binding to the ADH promoter. The NF-kappaB (p65) and NF-kappaB (p50) expression vectors inhibited the transfected ADH promoter activity, which contrasts with the previously demonstrated stimulation by an USF expression vector. The binding activities of STAT5b and of C/EBPbeta, which mediate the effect of GH on ADH, were not changed or decreased, respectively, by LPS, indicating that GH plays no intermediary role in the effect of LPS. This study shows that LPS increases ADH and that this effect is mediated by increased binding of USF to the ADH promoter and not by NF-kappaB, which has an inhibitory action.

Curcumin prevents alcohol-induced liver disease in rats by inhibiting the expression of NF-kappa B-dependent genes

Induction of NF-kappaB-mediated gene expression has been implicated in the pathogenesis of alcoholic liver disease (ALD). Curcumin, a phenolic antioxidant, inhibits the activation of NF-kappaB. We determined whether treatment with curcumin would prevent experimental ALD and elucidated the underlying mechanism. Four groups of rats (6 rats/group) were treated by intragastric infusion for 4 wk. One group received fish oil plus ethanol (FE); a second group received fish oil plus dextrose (FD). The third and fourth groups received FE or FD supplemented with 75 mg. kg(-1). day(-1) of curcumin. Liver samples were analyzed for histopathology, lipid peroxidation, NF-kappaB binding, TNF-alpha, IL-12, monocyte chemotactic protein-1, macrophage inflammatory protein-2, cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and nitrotyrosine. Rats fed FE developed fatty liver, necrosis, and inflammation, which was accompanied by activation of NF-kappaB and the induction of cytokines, chemokines, COX-2, iNOS, and nitrotyrosine formation. Treatment with curcumin prevented both the pathological and biochemical changes induced by alcohol. Because endotoxin and the Kupffer cell are implicated in the pathogenesis of ALD, we investigated whether curcumin suppressed the stimulatory effects of endotoxin in isolated Kupffer cells. Curcumin blocked endotoxin-mediated activation of NF-kappaB and suppressed the expression of cytokines, chemokines, COX-2, and iNOS in Kupffer cells. Thus curcumin prevents experimental ALD, in part by suppressing induction of NF-kappaB-dependent genes.

The antioxidant (-)-epigallocatechin-3-gallate inhibits activated hepatic stellate cell growth and suppresses acetaldehyde-induced gene expression

Activated hepatic stellate cells (HSC) are the primary source of excessive production of extracellular matrix during liver fibrogenesis. Although the underlying mechanisms remain incompletely understood, it is widely accepted that oxidative stress plays a critical role in liver fibrogenesis. Suppression of HSC growth and activation, as well as induction of apoptosis, have been proposed as therapeutic strategies for treatment and prevention of this disease. In the present report, we elucidated, for the first time, effects of the antioxidant (-)-epigallocatechin-3-gallate (EGCG), a major (and the most active) component of green tea extracts, on cultured HSC growth and activation. Our results revealed that EGCG significantly inhibited cultured HSC growth by inducing cell cycle arrest and apoptosis in a dose- and time-dependent manner. In addition, EGCG markedly suppressed the activation of cultured HSC as demonstrated by blocking transforming growth factor-beta signal transduction and by inhibiting the expression of alpha1(I) collagen, fibronectin and alpha-smooth muscle actin genes induced by acetaldehyde, the most active metabolite of ethanol. Furthermore, EGCG reacted differently in the inhibition of nuclear factor-kappaB activity between cultured HSC with or without acetaldehyde stimulation. Taken together, our results indicated that EGCG was a novel and effective inhibitor for activated HSC growth and activation in vitro. Further studies are necessary to evaluate the effect of this polyphenol in prevention of quiescent HSC activation in vivo, and to further elucidate the underlying mechanisms.

Dilinoleoylphosphatidylcholine decreases acetaldehyde-induced TNF-alpha generation in Kupffer cells of ethanol-fed rats

We previously reported that dilinoleoylphosphatidylcholine (DLPC) decreases lipopolysaccharide-induced TNF-alpha generation by Kupffer cells of ethanol-fed rats by blocking p38, ERK1/2, and NF-kappaB activation. Here we show that DLPC also decreases TNF-alpha induction by acetaldehyde, a toxic metabolite released by ethanol oxidation. Acetaldehyde induces TNF-alpha generation with a maximal effect at 200 microM and activates p38 and ERK1/2; the latter in turn activates NF-kappaB. This effect is augmented in Kupffer cells of ethanol-fed rats, with upregulation of cytochrome P4502E1 by ethanol. DLPC decreases TNF-alpha generation by blocking p38, ERK1/2, and NF-kappaB activation. Likewise, SB203580, which abolishes p38 activation, and PD098059, which abrogates ERK1/2 and NF-kappaB activation, diminish TNF-alpha generation. Since increased TNF-alpha generation plays a pathogenic role in alcoholic liver disease, the DLPC action on Kupffer cells may explain, in part, its beneficial effects on liver cell injury after ethanol consumption.

Acute ethanol binge followed by withdrawal regulates production of reactive oxygen species and cytokine-induced neutrophil chemoattractant and liver injury during reperfusion after hepatic ischemia

This work tests the hypothesis that withdrawal from an acute ethanol binge regulates the production of reactive oxygen species (ROS) and chemokines by Kupffer cells, and as a result compromises or protects the liver from injury. Male Sprague-Dawley rats received an intravenous ethanol bolus (1.75 g/kg), followed by an intravenous infusion of 200-300 mg/kg/h for 12 h. At 12 h, ethanol infusion was stopped and replaced by saline. At 18 h, rats were subjected to 45 min of partial hepatic ischemia, followed by 0-24 h of reperfusion (I/R). At specific time points, Kupffer cells were isolated for superoxide anion assay and CINC (cytokine-induced neutrophil chemoattractant) and MIP-2 (macrophage inflammatory protein-2) production in vitro. Alanine transferase (ALT) activity, endotoxin, CINC, and MIP-2 were measured in serum samples taken at appropriate intervals. Results show that at 3 h post reperfusion, serum ALT was significantly elevated in the ethanol-treated group + I/R, compared with the saline + I/R group. ROS production by Kupffer cells at this time was also significantly increased compared with the saline + I/R group. However, ethanol withdrawal + I/R did not significantly alter CINC and MIP-2 production at 3 h of reperfusion. After 24 h, serum ALT was lower in the ethanol + I/R group than in the saline + I/R group. Superoxide anion and MIP-2 releases by Kupffer cells were not statistically significantly different between these two groups at this time. CINC production by Kupffer cells from the ethanol-treated + I/R group was significantly lower than in the saline + I/R group. Concomitantly, CINC and nuclear factor-kappaB (NF-kappaB) mRNAs and NF-kappaB translocation and binding in Kupffer cells in this treatment group were down-regulated. Moreover, the number of polymorphonuclear neutrophils (PMNs) sequestered in the liver was significantly lower in the ethanol + I/R group than in the saline-treated group. ROS and chemokine productions in sham animals with or without ethanol were lower than in the I/R group. These data suggest that acute ethanol binge followed by withdrawal may compromise the liver to injury during the early phase, whereas in the later phase it may be protective. Furthermore, these results support the notion that Kupffer cells are involved in hepatic injury in the early phase, whereas PMNs participate more actively during the later phase of reperfusion.

Ethanol metabolism and transcription factor activation in pancreatic acinar cells in rats

BACKGROUND & AIMS

Ethanol metabolism by pancreatic acinar cells and the role of its metabolites in ethanol toxicity to the pancreas remain largely unknown. Here, we characterize ethanol metabolism in pancreatic acinar cells and determine the effects of ethanol metabolites on nuclear factor kappa B (NF-kappa B) and activator protein (AP)-1, transcription factors that are activated in pancreatitis and mediate expression of inflammatory molecules critical for this disease.

METHODS

We measured activities of fatty acid ethyl ester (FAEE) synthase and alcohol dehydrogenase (ADH), as well as accumulation of ethanol metabolites. We measured the effects of ethanol and its metabolites on NF-kappa B and AP-1 activation by using a gel shift assay.

RESULTS

Pancreas metabolizes ethanol via both oxidative and nonoxidative pathways. Acinar cells are the main source of ethanol metabolism in the pancreas. Compared with the liver, FAEE synthase activity in the pancreas is greater, whereas that of ADH is much less. FAEEs activated NF-kappa B and AP-1, whereas acetaldehyde inhibited NF-kappa B activation. Ethanol decreased NF-kappa B binding activity in acinar cells, which was potentiated by cyanamide.

CONCLUSION

Oxidative and nonoxidative ethanol metabolites regulate transcription factors differently in pancreatic acinar cells. Ethanol may regulate NF-kappa B and AP-1 positively or negatively, depending on which metabolic pathway's effect predominates. These regulatory mechanisms may play a role in ethanol toxicity to the pancreas.

Increased severity of alcoholic liver injury in female rats: role of oxidative stress, endotoxin, and chemokines

Alcoholic liver injury is more severe and rapidly developing in women than men. To evaluate the reason(s) for these gender-related differences, we determined whether pathogenic mechanisms important in alcoholic liver injury in male rats were further upregulated in female rats. Male and age-matched female rats (7/group) were fed ethanol and a diet containing fish oil for 4 wk by intragastric infusion. Dextrose isocalorically replaced ethanol in control rats. We analyzed liver histopathology, lipid peroxidation, cytochrome P-450 (CYP)2E1 activity, nonheme iron, endotoxin, nuclear factor-kappa B (NF-kappa B) activation, and mRNA levels of cyclooxygenase-1 (COX-1) and COX-2, tumor necrosis factor-alpha (TNF-alpha), monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-2 (MIP-2). Alcohol-induced liver injury was more severe in female vs. male rats. Female rats had higher endotoxin, lipid peroxidation, and nonheme iron levels and increased NF-kappa B activation and upregulation of the chemokines MCP-1 and MIP-2. CYP2E1 activity and TNF-alpha and COX-2 levels were similar in male and female rats. Remarkably, female rats fed fish oil and dextrose also showed necrosis and inflammation. Our findings in ethanol-fed rats suggest that increased endotoxemia and lipid peroxidation in females stimulate NF-kappa B activation and chemokine production, enhancing liver injury. TNF-alpha and COX-2 upregulation are probably important in causing liver injury but do not explain gender-related differences.

The role of acetaldehyde in the actions of alcohol (update 2000)

BACKGROUND

Recent advances in the field of acetaldehyde (AcH) research have raised the need for a comprehensive review on the role of AcH in the actions of alcohol. This update is an attempt to summarize the available AcH research.

METHODS

The descriptive part of this article covers not only recent research but also the development of the field. Special emphasis is placed on mechanistic analyses, new hypotheses, and conclusions.

RESULTS

Elevated AcH during alcohol intoxication causes alcohol sensitivity, which involves vasodilation associated with increased skin temperature, subjective feelings of hotness and facial flushing, increased heart and respiration rate, lowered blood pressure, sensation of dry mouth or throat associated with bronchoconstriction and allergy reactions, nausea and headache, and also reinforcing reactions like euphoria. These effects seem to involve catecholamine, opiate peptide, prostaglandin, histamine, and/or kinin mechanisms. The contribution of AcH to the pathological consequences of chronic alcohol intake is well established for different forms of cancer in the digestive tract and the upper airways. AcH seems to play a role in the etiology of liver cirrhosis. AcH may have a role in other pathological developments, which include brain damage, cardiomyopathy, pancreatitis, and fetal alcohol syndrome. AcH creates both unpleasant aversive reactions that protect against excessive alcohol drinking and euphoric sensations that may reinforce alcohol drinking. The protective effect of AcH may be used in future treatments that involve gene therapy with or without liver transplantation.

CONCLUSIONS

AcH plays a role in most of the actions of alcohol. The individual variability in these AcH-mediated actions will depend on the genetic polymorphism, not only for the alcohol and AcH-metabolizing enzymes but also for the target sites for AcH actions. The subtle balance between aversive and reinforcing, protecting and promoting factors will determine the overall behavioral and pathological developments.

The role of acetaldehyde in the actions of alcohol (update 2000)

BACKGROUND

Recent advances in the field of acetaldehyde (AcH) research have raised the need for a comprehensive review on the role of AcH in the actions of alcohol. This update is an attempt to summarize the available AcH research.

METHODS

The descriptive part of this article covers not only recent research but also the development of the field. Special emphasis is placed on mechanistic analyses, new hypotheses, and conclusions.

RESULTS

Elevated AcH during alcohol intoxication causes alcohol sensitivity, which involves vasodilation associated with increased skin temperature, subjective feelings of hotness and facial flushing, increased heart and respiration rate, lowered blood pressure, sensation of dry mouth or throat associated with bronchoconstriction and allergy reactions, nausea and headache, and also reinforcing reactions like euphoria. These effects seem to involve catecholamine, opiate peptide, prostaglandin, histamine, and/or kinin mechanisms. The contribution of AcH to the pathological consequences of chronic alcohol intake is well established for different forms of cancer in the digestive tract and the upper airways. AcH seems to play a role in the etiology of liver cirrhosis. AcH may have a role in other pathological developments, which include brain damage, cardiomyopathy, pancreatitis, and fetal alcohol syndrome. AcH creates both unpleasant aversive reactions that protect against excessive alcohol drinking and euphoric sensations that may reinforce alcohol drinking. The protective effect of AcH may be used in future treatments that involve gene therapy with or without liver transplantation.

CONCLUSIONS

AcH plays a role in most of the actions of alcohol. The individual variability in these AcH-mediated actions will depend on the genetic polymorphism, not only for the alcohol and AcH-metabolizing enzymes but also for the target sites for AcH actions. The subtle balance between aversive and reinforcing, protecting and promoting factors will determine the overall behavioral and pathological developments.

Ethanol inhibits cytokine-induced iNOS and sPLA2 in immortalized astrocytes: evidence for posttranscriptional site of ethanol action

Chronic and excessive ethanol consumption is known to alter neuron and glial cell functions in the central nervous system (CNS). Astrocytes comprise the major cell type in the brain. These immune active cells are capable of responding to proinflammatory cytokines and endotoxins, which stimulate transcriptional pathways leading to induction of genes, including the inducible nitric oxide synthase (iNOS) and secretory phospholipase A2 (sPLA2). In this study, we investigate the effects of ethanol on cytokine-induced iNOS and sPLA2 in immortalized astrocytes (DITNC). When DITNC cells were exposed to ethanol (0-200 mM) for 4 h prior to subsequent stimulation with cytokines for 16 h, NO production decreased with increasing ethanol concentrations starting from 50 mM. At ethanol concentrations higher than 100 mM, ethanol also inhibited cytokine-induced sPLA2 release into the culture medium. The inhibitory effect of ethanol on NO production corresponds well with the decrease in iNOS protein and NOS enzyme activity, but not with iNOS and sPLA2 mRNA nor binding of NF-kappaB to DNA. The inhibition of cytokine-induced NO production by ethanol was also dependent on the time of ethanol exposure to the cells, but addition of acetaldehyde up to 200 microM did not elicit any changes. Taken together, these results provide evidence for a posttranscriptional mode of ethanol action on the cytokine induction pathway for NO production in astrocytes.

Enhanced DNA binding and activation of transcription factors NF-kappa B and AP-1 by acetaldehyde in HEPG2 cells

Because transcription factors NF-kappaB and activator protein-1 (AP-1) are known to regulate gene expression, we have analyzed the role of acetaldehyde in the activation of NF-kappaB and AP-1 in HepG2 cells. Binding activity and transactivation of NF-kappaB and AP-1 were determined by gel retardation assays and transfection of a luciferase reporter construct controlled by kappaB and AP-1 binding sites, respectively. Acetaldehyde enhanced the DNA binding of NF-kappaB and AP-1 by 1 and 4 h, respectively, increasing the kappaB- and AP-1-dependent luciferase expression. Supershift assays revealed the presence of NF-kappaB heterodimers p65/p50 and p50/p52, whereas nuclear c-Jun levels correlated with the DNA binding of AP-1. The enhanced binding of NF-kappaB to DNA by acetaldehyde in intact cells was accompanied by the proteolytic degradation of IkappaB-alpha. However, the addition of acetaldehyde to cytostolic extracts from untreated Hep G2 cells did not affect the DNA binding of AP-1 but activated the NF-kappaB heterodimer p65/p50 in the absence of IkappaB-alpha degradation. Preincubation of HepG2 cells with protein kinase C inhibitors abolished the enhanced DNA binding of NF-kappaB and AP-1 caused by acetaldehyde. Hence, these findings uncover a previously unrecognized role for acetaldehyde in the activation of NF-kappaB and AP-1, which may be of relevance in the alcohol-induced liver disease.

Activation of nuclear factor kappa B and cytokine imbalance in experimental alcoholic liver disease in the rat

Inflammatory stimuli and lipid peroxidation activate nuclear factor kappa B (NF-kappaB) and upregulate proinflammatory cytokines and chemokines. The present study evaluated the relationship between pathological liver injury, endotoxemia, lipid peroxidation, and NF-kappaB activation and imbalance between pro- and anti-inflammatory cytokines. Rats (5 per group) were fed ethanol and a diet containing saturated fat, palm oil, corn oil, or fish oil by intragastric infusion. Dextrose isocalorically replaced ethanol in control rats. Pathological analysis was performed and measurements of endotoxin were taken, lipid peroxidation, NF-kappaB, and messenger RNA (mRNA) levels of proinflammatory cytokines (tumor necrosis factor-alpha [TNFalpha], interleukin-1 beta [IL-1beta], interferon-gamma, [IFN-gamma], and IL-12), C-C chemokines (regulated upon activation, normal T cell expressed and secreted [RANTES], monocyte chemotactic protein [MCP]-1, macrophage inflammatory protein [MIP]-1alpha), C-X-C chemokines (cytokine induced neutrophil chemoattractant (CINC), MIP-2, IP-10, and epithelial neutrophil activating protein [ENA]-78), and anti-inflammatory cytokines (IL-10, IL-4, and IL-13). Activation of NF-kappaB and increased expression of proinflammatory cytokines C-C and C-X-C chemokines was seen in the rats exhibiting necroinflammatory injury (fish oil-ethanol [FE] and corn oil-ethanol[CE]). These groups also had the highest levels of endotoxin and lipid peroxidation. Levels of IL-10 and IL-4 mRNA were lower in the group exhibiting inflammatory liver injury. Thus, activation of NF-kappaB occurs in the presence of proinflammatory stimuli and results in increased expression of proinflammatory cytokines and chemokines. The Kupffer cell is probably the major cell type showing activation of NF-kappaB although the contribution of endothelial cells and hepatocytes cannot be excluded. Downregulation of anti-inflammatory cytokines may additionally exacerbate liver injury.