Alcohol-induced expression of the CD14 endotoxin receptor protein in rat Kupffer cells

System Biology Investigation Revealed Lipopolysaccharide and Alcohol-Induced Hepatocellular Carcinoma Resembled Hepatitis B Virus Immunobiology and Pathogenesis

Hepatitis B infection caused by the hepatitis B virus is a life-threatening cause of liver fibrosis, cirrhosis, and hepatocellular carcinoma. Researchers have produced multiple in vivo models for hepatitis B virus (HBV) and, currently, there are no specific laboratory animal models available to study HBV pathogenesis or immune response; nonetheless, their limitations prevent them from being used to study HBV pathogenesis, immune response, or therapeutic methods because HBV can only infect humans and chimpanzees. The current study is the first of its kind to identify a suitable chemically induced liver cirrhosis/HCC model that parallels HBV pathophysiology. Initially, data from the peer-reviewed literature and the GeneCards database were compiled to identify the genes that HBV and seven drugs (acetaminophen, isoniazid, alcohol, D-galactosamine, lipopolysaccharide, thioacetamide, and rifampicin) regulate. Functional enrichment analysis was performed in the STRING server. The network HBV/Chemical, genes, and pathways were constructed by Cytoscape 3.6.1. About 1546 genes were modulated by HBV, of which 25.2% and 17.6% of the genes were common for alcohol and lipopolysaccharide-induced hepatitis. In accordance with the enrichment analysis, HBV activates the signaling pathways for apoptosis, cell cycle, PI3K-Akt, TNF, JAK-STAT, MAPK, chemokines, NF-kappa B, and TGF-beta. In addition, alcohol and lipopolysaccharide significantly activated these pathways more than other chemicals, with higher gene counts and lower FDR scores. In conclusion, alcohol-induced hepatitis could be a suitable model to study chronic HBV infection and lipopolysaccharide-induced hepatitis for an acute inflammatory response to HBV.

Beef, Chicken, and Soy Proteins in Diets Induce Different Gut Microbiota and Metabolites in Rats

Previous studies have paid much attention to the associations between high intake of meat and host health. Our previous study showed that the intake of meat proteins can maintain a more balanced composition of gut bacteria as compared to soy protein diet. However, the associations between dietary protein source, gut bacteria, and host health were still unclear. In this study, we collected colonic contents from the growing rats fed with casein, beef, chicken or soy proteins for 90 days, and analyzed the compositions of gut microbiota and metabolites. Compared to the casein group (control), the chicken protein group showed the highest relative abundance of Lactobacillus and the highest levels of organic acids, including lactate, which can in turn promote the growth of Lactobacillus. The soy protein group had the highest relative abundance of Ruminococcus but the lowest relative abundance of Lactobacillus. Long-term intake of soy protein led to the up-regulation of transcription factor CD14 receptor and lipopolysaccharide-binding protein (LBP) in liver, an indicator for elevated bacterial endotoxins. In addition, the intake of soy protein also increased the levels of glutathione S-transferases in liver, which implicates elevated defense and stress responses. These results confirmed that meat protein intake may maintain a more balanced composition of gut bacteria and reduce the antigen load and inflammatory response from gut bacteria to the host.

Aryl hydrocarbon receptor-dependent stanniocalcin 2 induction by cinnabarinic acid provides cytoprotection against endoplasmic reticulum and oxidative stress

The aryl hydrocarbon receptor (AhR) is a cytosolic ligand-activated transcription factor historically known for its role in xenobiotic metabolism. Although AhR activity has previously been shown to play a cytoprotective role against intrinsic apoptotic stimuli, the underlying mechanism by which AhR confers cytoprotection against apoptosis is largely unknown. Here, we demonstrate that activation of AhR by the tryptophan catabolite cinnabarinic acid (CA) directly upregulates expression of stanniocalcin 2 (Stc2) to elicit cytoprotection against apoptosis induced by endoplasmic reticulum stress and oxidative stress. Chromatin immunoprecipitation studies demonstrated that CA treatment induces direct AhR binding to a region of the Stc2 promoter containing multiple xenobiotic response elements. Using isolated primary hepatocytes from AhR wild-type (AhR floxed) and liver-specific AhR conditional knockout mice, we showed that pretreatment with CA conferred cytoprotection against hydrogen peroxide (H(2)O(2))-, thapsigargin-, and ethanol-induced apoptosis in an AhR-dependent manner. Furthermore, suppressing Stc2 expression using RNA interference confirmed that the cytoprotective properties of CA against H(2)O(2), thapsigargin, and ethanol injury were absolutely dependent on Stc2. Immunochemistry revealed the presence of Stc2 in the endoplasmic reticulum and on the cell surface, consistent with Stc2 secretion and autocrine and/or paracrine signaling. Finally, in vivo data using a mouse model of acute alcohol hepatotoxicity demonstrated that CA provided cytoprotection against ethanol-induced apoptosis, hepatic microvesicular steatosis, and liver injury. Collectively, our data uncovered a novel mechanism for AhR-mediated cytoprotection in the liver that is dependent on CA-induced Stc2 activity.

Association between CD14-159C>T polymorphisms and the risk for alcoholic liver disease: a meta-analysis

AIMS

The association between CD14-159C>T polymorphisms and alcoholic liver disease (ALD) risk has been investigated in many studies, but the results were inconsistent. Therefore, we performed a meta-analysis to investigate the association between the CD14-159C>T polymorphisms and the risk for ALD.

METHODS

A comprehensive literature search was conducted to identify the relevant studies from PubMed, ISI Web of Science, and Embase. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using either the fixed-effects model or random-effects model on the basis of the heterogeneity test.

RESULTS

A total of eight eligible studies were included in the meta-analyses. The combined results showed no significant association between CD14-159C>T polymorphisms and ALD risk when ALD patients were compared with alcoholics without ALD (T vs. C, OR=1.22, 95% CI 0.84-1.77; TT/TC vs. CC, OR=1.43, 95% CI 0.86-2.37) and when ALD patients were compared with nonalcoholics (T vs. C, OR=1.13, 95% CI 0.90-1.43; TT/TC vs. CC, OR=1.05, 95% CI 0.76-1.46). However, a significant association was observed in the heterozygous comparison (TC vs. CC, OR=3.47, 95% CI 1.93-6.22), whereas a marginal association was observed in the dominant model (TT/CT vs. CC, OR=2.43, 95% CI 1.00-5.91) when alcoholic cirrhosis patients were compared with alcoholics without ALD.

CONCLUSION

This meta-analysis suggests that the CD14-159C>T polymorphism may not be significantly associated with the risk for ALD. Although a significant association was observed between the -159C>T polymorphism and the risk for alcoholic cirrhosis, well-designed studies with large sample sizes are warranted to confirm these results.

Mechanisms of alcohol-induced endoplasmic reticulum stress and organ injuries

Alcohol is readily distributed throughout the body in the blood stream and crosses biological membranes, which affect virtually all biological processes inside the cell. Excessive alcohol consumption induces numerous pathological stress responses, part of which is endoplasmic reticulum (ER) stress response. ER stress, a condition under which unfolded/misfolded protein accumulates in the ER, contributes to alcoholic disorders of major organs such as liver, pancreas, heart, and brain. Potential mechanisms that trigger the alcoholic ER stress response are directly or indirectly related to alcohol metabolism, which includes toxic acetaldehyde and homocysteine, oxidative stress, perturbations of calcium or iron homeostasis, alterations of S-adenosylmethionine to S-adenosylhomocysteine ratio, and abnormal epigenetic modifications. Interruption of the ER stress triggers is anticipated to have therapeutic benefits for alcoholic disorders.

Adiponectin and heme oxygenase-1 suppress TLR4/MyD88-independent signaling in rat Kupffer cells and in mice after chronic ethanol exposure

Alcoholic liver disease is mediated via activation of TLR4 signaling; MyD88-dependent and -independent signals are important contributors to injury in mouse models. Adiponectin, an anti-inflammatory adipokine, suppresses TLR4/MyD88-dependent responses via induction of heme oxygenase-1 (HO-1). Here we investigated the interactions between chronic ethanol, adiponectin, and HO-1 in regulation of TLR4/MyD88-independent signaling in macrophages and an in vivo mouse model. After chronic ethanol feeding, LPS-stimulated expression of IFN-β and CXCL10 mRNA was increased in primary cultures of Kupffer cells compared with pair-fed control mice. Treatment of Kupffer cells with globular adiponectin (gAcrp) normalized this response. LPS-stimulated IFN-β/CXCL10 mRNA and CXCL10 protein was also reduced in RAW 264.7 macrophages treated with gAcrp or full-length adiponectin. gAcrp and full-length adiponectin acted via adiponectin receptors 1 and 2, respectively. gAcrp decreased TLR4 expression in both Kupffer cells and RAW 264.7 macrophages. Small interfering RNA knockdown of HO-1 or inhibition of HO-1 activity with zinc protoporphyrin blocked these effects of gAcrp. C57BL/6 mice were exposed to chronic ethanol feeding, with or without treatment with cobalt protoporphyrin, to induce HO-1. After chronic ethanol feeding, mice were sensitized to in vivo challenge with LPS, expressing increased IFN-β/CXCL10 mRNA and CXCL10 protein in liver compared with control mice. Pretreatment with cobalt protoporphyrin 24 h before LPS challenge normalized this effect of ethanol. Adiponectin and induction of HO-1 potently suppressed TLR4-dependent/MyD88-independent cytokine expression in primary Kupffer cells from rats and in mouse liver after chronic ethanol exposure. These data suggest that induction of HO-1 may be a useful therapeutic strategy in alcoholic liver disease.

The impact of CYP2E1 on the development of alcoholic liver disease as studied in a transgenic mouse model

BACKGROUND/AIMS

CYP2E1 metabolizes ethanol, generates reactive oxygen species, and is suggested to be important for development of alcoholic liver disease. The present study aims to evaluate the role of CYP2E1 in combination with ethanol for development of alcoholic liver disease using mice transgenic for the human CYP2E1 gene.

METHODS

Changes in hepatic gene expression were monitored in controls and mice transgenic for human CYP2E1, treated with ethanol or isocaloric dextrose intragastrically for 4 weeks, and related to pathology using Affymetrix microarrays and TaqMan RealTime PCR.

RESULTS

Presence of the CYP2E1 transgene increased liver injury and increased expression of stress related genes. Microarray analyses revealed the expression of structural genes, particularly cytokeratin 8 and 18, to be highly related to pathology.

CONCLUSIONS

This in vivo study confirms several findings regarding CYP2E1 and alcohol previously found only in vitro. These results provide in vivo evidence that CYP2E1 overexpression aggravates hepatic injury, and suggest that expression of cytokeratins 8 and 18 can be considered as biomakers for the progression of alcoholic liver disease.

Review article: alcoholic liver disease--pathophysiological aspects and risk factors

BACKGROUND

Alcoholic liver disease has a known aetiology but a complex and incompletely known pathogenesis. It is an extremely common disease with significant morbidity and mortality, but the reason why only a relatively small proportion of heavy drinkers progress to advanced disease remains elusive.

AIM

To recognize the factors responsible for the development and progression of alcoholic liver disease, in the light of current knowledge on this matter.

METHODS

We performed a structured literature review identifying studies focusing on the complex pathogenetic pathway and risk factors of alcoholic liver disease. Results In addition to the cumulative amount of alcohol intake and alcohol consumption patterns, factors such as gender and ethnicity, genetic background, nutritional factors, energy metabolism abnormalities, oxidative stress, immunological mechanisms and hepatic co-morbid conditions play a key role in the genesis and progression of alcoholic liver injury.

CONCLUSIONS

Understanding the pathogenesis and risk factors of alcoholic liver disease should provide insight into the development of therapeutic strategies.

Chronic systemic endotoxin exposure: an animal model in experimental hepatic encephalopathy

Plasma levels of gut-derived endotoxins (lipopolysaccharides, LPS) are often elevated in cirrhotics and are thought to contribute to hepatic encephalopathy. Circulating LPS activates macrophages to produce tumor necrosis factor alpha (TNF-alpha) and other potentially cytotoxic proinflammatory mediators. A pathogenic role for endotoxins is supported by studies showing that treatment with Lacto-bacillusor antibiotics, both of which reduce LPS-producing intestinal Gram-negative bacteria, alleviates experimental liver damage. To mimic the "leaky gut" syndrome with endotoxin translocation into the circulation in cirrhotics, a new animal model was developed. Rats were chronically exposed to ethanol and for the four last weeks also infused with endotoxin into the jugular vein from subcutaneously implanted osmotic minipumps. Animals receiving endotoxin had elevated hepatic expression of both pro- and anti-inflammatory cytokines, but compared to ethanol treatment alone hepatic steatosis and inflammatory changes were only marginally increased. This demonstrates marked endotoxin tolerance, probably as a consequence of a counteracting anti-inflammatory cytokine response. The role of gut-derived endotoxin in hepatic encephalopathy has recently received considerable attention. To further delineate the role and actions of endotoxin and its extrahepatic effects, studies applying both acute challenge and chronic infusion seem warranted. The chronic endotoxin model, mimicking the "leaky gut," may best be combined with more robust ways to impair liver function, such as carbon tetrachloride treatment, bile duct ligation, or galactosamine administration.

Different effects of a CD14 gene polymorphism on disease outcome in patients with alcoholic liver disease and chronic hepatitis C infection

AIM: Clinical and experimental data suggest that gut-derived endotoxins are an important pathogenic factors for progression of chronic liver disease. Recently, a C-T (-159) polymorphism in the promoter region of the CD14 gene was detected and found to confer increased CD14 expression and to be associated with advanced alcoholic liver damage. Here, we investigated this polymorphism in patients with less advanced alcoholic liver disease (ALD) and chronic hepatitis C virus (HCV) infection.

METHODS: CD14 genotyping was performed by PCR-RFLP analysis in (a) 121 HCV patients, (b) 62 patients with alcohol-associated cirrhosis (Alc-Ci), (c) 118 individuals with heavy alcohol abuse without evidence of advanced liver damage (Alc-w/o Ci), and (d) 247 healthy controls. Furthermore, serum levels of soluble CD14 (sCD14) and transaminases were determined.

RESULTS: The TT genotype was significantly more frequent in Alc-Ci compared to Alc-w/o Ci or controls (40.3% vs 23.7% or 24.0%, respectively). In Alc-w/o Ci, serum levels of transaminases did not differ significantly between patients with different CD14 genotypes. In HCV patients, TT-homozygotes had significantly higher sCD14 levels and sCD14 serum levels were significantly higher in patients with advanced fibrosis or cirrhosis. However, no association was found between CD14 genotypes and histological staging or grading.

CONCLUSION: Considering serum transaminases as surrogate markers for alcoholic liver damage, the CD14 polymorphism seems to exhibit different effects during the course of ALD. Differences in genotype distribution between cirrhotic HCV patients and alcoholics and the known functional impact of this polymorphism on CD14 expression levels further indicate differences in the pathophysiological role of CD14 and CD14-mediated lipopolysaccharides signal transduction with regard to the stage as well as the type of the underlying liver disease.

Exposure to bacterial cell wall products triggers an inflammatory phenotype in hepatic stellate cells

Activated hepatic stellate cells (HSCs) secrete extracellular matrix components during hepatic fibrosis, but recent studies have shown that HSCs can also release a variety of proinflammatory cytokines. Moreover, bacterial endotoxemia is not only associated with systemic complications in the late stages of liver failure but is also a direct cause of liver damage, activating resident inflammatory cells. In this study, we investigated whether HSCs can respond directly to bacterial cell wall products acquiring a new phenotype. RT-PCR and immunocytochemistry assays were used to show that murine HSCs expressed specific mRNA transcripts and proteins for LPS and lipoteichoic acid (LTA) receptor systems and peptidoglycan recognition proteins. Exposing HSCs to bacterial endotoxins led to phosphorylation of mitogen-activated protein kinase ERK1 and the development of a proinflammatory phenotype. After exposure to LPS, LTA, or N-acetyl muramyl peptide, transforming growth factor-beta1, IL-6, and monocyte chemoattractant protein-1 (MCP-1) mRNA specific transcripts and proteins increased significantly in HSCs, as assayed by quantitative real-time RT-PCR and ELISA. These LPS-mediated effects in HSCs were receptor dependent, because LPS-induced ERK1 phosphorylation, IL-6, and MCP-1 mRNA and protein level upregulation were significantly less pronounced in HSCs isolated from C3H/HeJ mice lacking Toll-like receptor 4. In conclusion, our results show that murine HSCs express functional receptors for bacterial endotoxins, and HSCs exposed to bacterial products develop a strong proinflammatory phenotype. We speculate that high levels of bacterial endotoxins in the portal vein may directly induce a proinflammatory phenotype in HSCs that contributes to liver damage.

Protective function of complement against alcohol-induced rat liver damage

The complement system can promote tissue damage or play a homeostatic role in the clearance and disposal of damaged tissue. We assessed the role of the terminal complement pathway in alcohol-induced liver damage in complement C6 (C6-/-) genetically deficient rats. C6-/- and corresponding C6+/+ rats were continuously exposed to ethanol by feeding ethanol-supplemented liquid diet for six weeks. Liver samples were analyzed for histopathology and complement component deposition by immunofluorescence microscopy. Prostaglandin E receptors and cytokine mRNA levels were analyzed by RT-PCR and plasma cytokines by ELISA. Deposition of complement components C1, C3, C8 and C9 was observed in C6+/+ rats, but not in C6-/- animals. The histopathological changes, the liver weight increase and the elevation of the plasma pro-/anti-inflammatory TNF-alpha/IL-10 ratio were, on the other hand, more marked in C6-/- rats. Furthermore, ethanol enhanced the hepatic mRNA expression of the prostaglandin E receptors EP2R and EP4R exclusively in the C6-/- rats. Our results indicate that a deficient terminal complement pathway predisposes to tissue injury and promotes a pro-inflammatory cytokine response. This suggests that an intact complement system has a protective function in the development of alcoholic liver damage.

Molecular aspects of alcohol metabolism: transcription factors involved in early ethanol-induced liver injury

Alcohol metabolism takes place primarily in the liver. Initial exposures to ethanol have a major impact on the hepatic redox state and intermediary metabolism as a consequence of ethanol metabolism via alcohol dehydrogenase. However, upon continued exposure to ethanol, the progression of liver injury involves ethanol metabolism via CYP2E1 and consequent oxidant stress, as well as potential direct effects of ethanol on membrane proteins that are independent of ethanol metabolism. Multiple organ systems contribute to liver injury, including the innate immune system and adipose tissue. In response to ethanol exposure, specific signal transduction pathways, including NFkappaB and the mitogen-activated protein kinase family members ERK1/2, JNK, and p38, are activated. These complex responses to ethanol exposure translate into activation of nuclear transcription factors and altered gene expression within the liver, leading to the development of steatosis and inflammation in the early stages of alcohol-induced liver injury.

Recent insights into the role of the innate immune system in the development of alcoholic liver disease

The innate immune system is responsible for the rapid, initial response of the organism to potentially dangerous stresses, including pathogens, tissue injury, and malignancy. Pattern-recognition receptors of the toll-like receptor (TLR) family expressed by macrophages provide a first line of defense against microbial invasion. Activation of these receptors results in a stimulus-specific expression of genes required to control the infection, including the production of inflammatory cytokines and chemokines, followed by the recruitment of neutrophils to the site of infection. The early stages in the development of alcoholic liver disease (ALD) follow a pattern characteristic of an innate immune response. Kupffer cells, the resident macrophages in the liver, are activated in response to bacterial endotoxins (lipopolysaccharide, LPS), leading to the production of inflammatory and fibrogenic cytokines, reactive oxygen species, as well as the recruitment of neutrophils to the liver. One mechanism by which chronic ethanol can turn the highly regulated innate immune response into a pathway of disease is by disrupting the signal transduction cascades mediating the innate immune response. Recent studies have identified specific modules in the TLR-4 signaling cascade that are disrupted after chronic ethanol exposure, including CD14 and the mitogen-activated protein kinase family members, ERK1/2 and p38. Enhanced activation of these TLR-4 dependent signaling pathways after chronic ethanol likely contributes to the development of alcoholic liver disease.

Steatosis in chronic hepatitis C: association with increased messenger RNA expression of collagen I, tumor necrosis factor-alpha and cytochrome P450 2E1

BACKGROUND

Increased levels of tumor necrosis factor (TNF)-alpha and oxidative stress have been implicated as factors contributing to hepatic injury in fatty liver diseases. As steatosis is associated with an accelerated progression of fibrosis in chronic hepatitis C (HCV), we hypothesized that the messenger (m)RNA expression of genes involved with the production of reactive oxygen species, inflammation and cellular injury would be increased in liver tissue from subjects with steatosis and chronic HCV.

METHODS

Real-time polymerase chain reaction was performed to determine relative mRNA expression levels of collagen I, TNF-alpha, cytochrome P450 2E1 (CYP 2E1), transforming growth factor-beta1 and CD14 in liver biopsies from 38 patients with chronic HCV. The mRNA expression levels were compared between subjects with and without steatosis, fibrosis, and inflammation.

RESULTS

Multivariate analysis demonstrated that collagen I mRNA expression was increased by 199% in steatosis (P = 0.02), 85% in moderate to severe fibrosis (P = 0.02) and 157% in inflammation (P = 0.03). Livers of patients with steatosis also had an increase in TNF-alpha mRNA expression by 50% (P = 0.03) and CYP 2E1 expression by 37% (P = 0.04) compared with non-steatotic livers. Tumor necrosis factor-alpha protein was localized to Kupffer cells, bile ducts and portal inflammatory cells by immunohistochemistry.

CONCLUSION

Increased expression of TNF-alpha may be involved in the pathogenesis of liver injury and progression of fibrosis in individuals who have steatosis in association with chronic HCV.

Differential expression of toll-like receptors 2 and 4 in patients with liver cirrhosis

OBJECTIVE

Toll-like receptors (TLR) 2 and 4 were shown recently to mediate lipopolysaccharide (LPS)/endotoxin effects in vivo. Absence of clinical features, such as fever and leucocytosis, frequent infections, and up-regulation of anti-inflammatory cytokines suggest systemic differential regulation of LPS effects in patients with chronic endotoxinaemia due to liver cirrhosis.

DESIGN

Regulation of TLR2 and TLR4 represents a possible pathway to control LPS-induced immune responses in liver cirrhosis.

METHODS

We compared the expression of TLR2 and TLR4 in peripheral blood mononuclear cells (PBMC) (n = 28) and in liver biopsies (n = 20) of controls and of patients with liver cirrhosis by applying the reverse transcriptase polymerase chain reaction technique. The data were correlated to serum levels of LPS and CD14.

RESULTS

Expression of TLR2 was up-regulated (P < 0.01 to P < 0.05) in the PBMC of patients with high serum endotoxin levels, while TLR4 expression in patients at Child-Pugh stage A was down-regulated, irrespective of the origin (alcoholic or viral) of cirrhosis. A strong and significant correlation between expression of TLR2 and serum LPS (r = 0.638, P < 0.01) and soluble CD14 (r = 0.550, P < 0.05) was observed. Intrahepatic expression of TLR2/4 was not altered significantly in patients with liver cirrhosis.

CONCLUSION

Our data indicate LPS-driven regulation of TLR2/4 in patients with liver cirrhosis, suggesting involvement in mechanisms of systemic LPS hyporesponsiveness.

ERK1/2 and Egr-1 contribute to increased TNF-alpha production in rat Kupffer cells after chronic ethanol feeding

Activation of Kupffer cells by lipopolysaccharide (LPS) is a critical step in the pathogenesis of alcoholic liver disease. Kupffer cells isolated from rats fed ethanol in their diet for 4 wk accumulated 4.3-fold more tumor necrosis factor (TNF)-alpha in response to LPS compared with pair-fed rats. In contrast, LPS-stimulated interleukin (IL)-1 accumulation was 50% lower after ethanol feeding. LPS-stimulated TNF-alpha mRNA accumulation was twofold higher after ethanol feeding, whereas IL-1beta mRNA accumulation was blunted. To understand the mechanisms for this differential response, we investigated the effects of ethanol on LPS-dependent signal transduction. Chronic ethanol feeding increased LPS-stimulated extracellular receptor-activated kinases 1/2 (ERK1/2) activation. Activation of ERK1/2 was required for maximal increases in TNF-alpha and IL-1beta mRNA and was associated with increased binding of early growth response-1 (Egr-1) to the TNF-alpha promoter after ethanol feeding. In contrast, ethanol feeding completely abrogated activation of nuclear factor-kappaB DNA-binding activity by LPS and had no effect on AP-1 binding. Together, these data suggest that enhanced activation of ERK1/2 and Egr-1 contributes to increased TNF-alpha production after chronic ethanol feeding.

Expression of lipopolysaccharide binding protein and its receptor CD14 in experimental alcoholic liver disease

AIM: To evaluate the relationship between the expression of lipopolysaccharides (LPS) binding protein (LBP) and CD14 mRNA and the severity of liver injury in alcohol-fed rats.

METHODS: Twenty Wistar rats were divided into two groups: ethanol-fed group (group E) and control group (group C). Group E was fed with ethanol (5-12 g·kg¯¹·d¯¹) and group C received dextrose instead of ethanol. Rats of the two groups were sacrificed at 4 wk and 8 wk. Levels of endotoxin and alanine transaminase (ALT) in blood were measured, and liver pathology was observed under light and electronic microscopy. Expressions of LBP and CD14 mRNA in liver tissues were determined by RT-PCR analysis.

RESULTS: Plasma endotoxin levels were increased more significantly in group E (129 ± 21) ng·L¯¹ and (187 ± 35) ng·L¯¹ at 4 and 8 wk than in control rats (48 ± 9) ng·L¯¹ and (53 ± 11) ng·L¯¹, respectively (P < 0.05). Mean values of plasma ALT levels were (1867 ± 250) nkat·L¯¹ and (2450 ± 367) nkat·L¯¹ in Group E. The values were increased more dramatically in ethanol-fed rats than in Group C after 4 and 8 wk. In liver section from ethanol-fed rats, there were marked pathological changes (steatosis, cell infiltration and necrosis). In ethanol-fed rats, ethanol administration led to a significant increase in LBP and CD14 mRNA levels compared with the control group (P < 0.05).

CONCLUSION: Ethanol administration led to a significant increase in endotoxin levels in serum and LBP and CD14 mRNA expressions in liver tissues. The increase of LBP and CD14 mRNA expression might wake the liver more sensitive to endotoxin and liver injury.

The antiestrogen toremifene protects against alcoholic liver injury in female rats

BACKGROUND/AIMS

Females are generally considered to be more susceptible to alcohol-induced liver injury than males. To elucidate whether gonadal hormones are involved, female rats were chronically treated with ethanol and with an antiestrogen.

METHODS

Ethanol was administered in a low-carbohydrate liquid diet. Estrogen action was blocked by daily intubation of toremifene, a non-hepatotoxic second generation estrogen receptor antagonist.

RESULTS

The female rats consuming intoxicating amounts of ethanol diet for 6 weeks developed massive microvesicular/macrovesicular steatosis, frequent inflammatory foci and spotty necrosis. Serum alanine aminotransferase increased 7-fold. Toremifene treatment did not affect steatosis, but significantly reduced inflammation and necrosis. Ethanol increased the expression of CD14 and tumor necrosis factor- (TNF) alpha mRNA and also the production of TNF-alpha by isolated Kupffer cells, but toremifene had no significant counteracting effect. However, toremifene significantly alleviated both ethanol induction of the pro-oxidant enzyme CYP2E1 and ethanol reduction of the oxidant-protective enzyme Se-glutathione peroxidase.

CONCLUSIONS

The partial protection by toremifene against ethanol-induced liver lesions suggests a pathogenic contribution of estrogens, possibly associated with an oxygen radical mediated mechanism.

Kupffer cell inactivation alleviates ethanol-induced steatosis and CYP2E1 induction but not inflammatory responses in rat liver

BACKGROUND/AIMS

Gadolinium chloride inactivates Kupffer cells and alleviates alcohol-induced liver lesions. We investigated the mechanism of gadolinium chloride protection after oral ethanol feeding.

METHODS

Rats were maintained ethanol-intoxicated for 6 weeks by feeding ethanol in a low-carbohydrate/high-fat liquid diet. Macrophages were inactivated by intravenous administrations of gadolinium chloride. At termination, liver samples and cell lysates obtained from the periportal and perivenous region were analyzed for histopathology, mRNA expression of endotoxin-associated parameters and cytokines and for enzymes involved in oxidative stress.

RESULTS

Ethanol treatment alone caused marked microvesicular/macrovacuolar steatosis and focal inflammation. Gadolinium significantly alleviated pathology, by reducing steatosis but not inflammation. Gadolinium treatment eliminated ED2 immunopositive Kupffer cells, which were larger and more frequent periportally. Ethanol significantly increased the mRNA expression of the endotoxin (LPS) receptor CD14 and the LPS binding protein LBP, but not that of the pro-inflammatory cytokines TNF-alpha and IL-1beta. The mRNA of CD14 was found to be expressed preferentially in the perivenous region, but gadolinium treatment had no significant effect on the expression or the distribution. However, gadolinium significantly moderated the ethanol induction of CYP2E1 and this effect correlated to the degree of steatosis. Ethanol increased glutathione transferase and reduced glutathione peroxidase activity, but these changes persisted after gadolinium treatment.

CONCLUSIONS

Our results suggest that gadolinium chloride reduces symptoms of ALD mainly by counteracting steatosis, and that CD14-positive Kupffer cell populations are not involved in gadolinium protection. The strong correlation between pathology and CYP2E1 induction might suggest a steatopathogenic role for this enzyme.

Animal models of acute hepatic failure

The understanding and treatment of acute hepatic failure has developed rapidly over the last 40 years reducing morbidity and mortality from this syndrome. Progress has been made by the study of animal models that reflect the clinical, biochemical and histological pattern of the syndrome seen in man. This is of increasing importance with the use of therapeutic intervention, liver transplantation and the use of extra-corporeal liver support devices. This review examines and critically appraises the various approaches to the study of acute hepatic failure in animal models, including both surgical and pharmacological approaches.

Effect of chronic coadministration of endotoxin and ethanol on rat liver pathology and proinflammatory and anti-inflammatory cytokines

To better understand how gut-derived endotoxins influence alcohol-induced liver injury and the expression of inflammatory cytokines a new animal model was developed. After 2 weeks on a modified ethanol-containing liquid diet, some rats also were infused with endotoxin via osmotic minipumps for 4 additional weeks. Ethanol diet alone increased plasma endotoxin threefold to 9.3 pg/mL. Endotoxin infusion increased the levels to 388 and 513 pg/mL in controls and ethanol-fed animals, respectively. Panlobular macrovesicular and microvesicular steatosis and inflammatory foci were observed in livers from both ethanol- and ethanol-endotoxin-treated animals, but there was no significant potentiation by endotoxin. Only minor changes, mainly polymorphonuclear infiltration, were seen in animals treated with endotoxin alone although the messenger RNA (mRNA) expression of both proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta) and anti-inflammatory cytokines IL-4 and IL-10 were markedly increased, as shown by competitive polymerase chain reaction (PCR) analysis using cyclophilin as standard. The effect of endotoxin infusion on cytokine mRNA expression in ethanol-fed animals was not significantly different. Expression of transforming growth factor beta1 (TGF-beta1) mRNA was increased twofold by ethanol, eightfold by endotoxin, but only threefold by ethanol-endotoxin treatment. The mRNA expression of lipopolysaccharide binding protein (LBP) and CD14 endotoxin receptor was not significantly increased by chronic endotoxin treatment, contrasting with the marked elevation observed after acute endotoxin challenge. These results suggest that the tolerance observed despite sustained hepatic expression of proinflammatory cytokines is counteracted by the anti-inflammatory cytokines and by down-regulation of CD14 and LBP. Furthermore, a similar adaptation may occur in alcoholics with continuous endotoxemia.

Expression of CD14 by hepatocytes: upregulation by cytokines during endotoxemia

Studies were undertaken to examine hepatocyte CD14 expression during endotoxemia. Our results show that lipopolysaccharide (LPS) treatment in vivo caused a marked upregulation in CD14 mRNA and protein levels in rat hepatocytes. Detectable increases in mRNA were seen as early as 1.5 h after LPS treatment; these increases peaked at 20-fold by 3 h and returned to baseline levels by 24 h. In situ hybridization localized the CD14 mRNA expression to hepatocytes both in vitro and in vivo. Increases in hepatic CD14 protein levels were detectable by 3 h and peaked at 12 h. Hepatocytes from LPS-treated animals expressed greater amounts of cell-associated CD14 protein, and more of the soluble CD14 was released by hepatocytes from LPS-treated rats in vitro. The increases in hepatocyte CD14 expression during endotoxemia occurred in parallel to increases of CD14 levels in plasma. To provide molecular identification of the hepatocyte CD14, we cloned the rat liver CD14 cDNA. The longest clone consists of a 1,591-bp insert containing a 1,116-bp open reading frame. The deduced amino acid sequence is 372 amino acids long, has 81.8 and 62.8% homology to the amino acid sequences of mouse and human CD14, respectively, and is identical to the rat macrophage CD14. The expressed CD14 protein from this clone was functional, as indicated by NF-kappaB activation in response to LPS and fluorescein isothiocyanate-LPS binding in CHO cells stably transfected with rat CD14. A nuclear run-on assay showed that CD14 transcription rates were significantly increased in hepatocytes from LPS-treated animals, indicating that the upregulation in CD14 mRNA levels observed in rat hepatocytes after LPS treatment is dependent, in part, on increased transcription. In vitro and in vivo experiments indicated that interleukin-1beta and/or tumor necrosis factor alpha participate in the upregulation of CD14 mRNA levels in hepatocytes. Our data indicate that hepatocytes express CD14 and that hepatocyte CD14 mRNA and protein levels increase rapidly during endotoxemia. Our observations also support the idea that soluble CD14 is an acute-phase protein and that hepatocytes could be a source for soluble CD14 production.