Immune responses against oxidative stress-derived antigens are associated with increased circulating tumor necrosis factor-alpha in heavy drinkers

Patterns of IgA Autoantibody Generation, Inflammatory Responses and Extracellular Matrix Metabolism in Patients with Alcohol Use Disorder

Recent data have emphasized the role of inflammation and intestinal immunoglobulin A (IgA) responses in the pathogenesis of alcoholic liver disease (ALD). In order to further explore such associations, we compared IgA titers against antigens targeted to ethanol metabolites and tissue transglutaminase with pro- and anti-inflammatory mediators of inflammation, markers of liver status, transferrin protein desialylation and extracellular matrix metabolism in alcohol-dependent patients with or without liver disease and in healthy controls. Serum IgAs against protein adducts with acetaldehyde (HbAch-IgA), the first metabolite of ethanol, and tissue transglutaminase (tTG-IgA), desialylated transferrin (CDT), pro- and anti-inflammatory cytokines, markers of liver status (GT, ALP) and extracellular matrix metabolism (PIIINP, PINP, hyaluronic acid, ICTP and CTx) were measured in alcohol-dependent patients with (n = 83) or without (n = 105) liver disease and 88 healthy controls representing either moderate drinkers or abstainers. In ALD patients, both tTG-IgA and HbAch-IgA titers were significantly higher than those in the alcoholics without liver disease (p < 0.0005 for tTG-IgA, p = 0.006 for Hb-Ach-IgA) or in healthy controls (p < 0.0005 for both comparisons). The HbAch-IgA levels in the alcoholics without liver disease also exceeded those found in healthy controls (p = 0.0008). In ROC analyses, anti-tTG-antibodies showed an excellent discriminative value in differentiating between ALD patients and healthy controls (AUC = 0.95, p < 0.0005). Significant correlations emerged between tTG-IgAs and HbAch-IgAs (rs = 0.462, p < 0.0005), CDT (rs = 0.413, p < 0.0001), GT (rs = 0.487, p < 0.0001), alkaline phosphatase (rs = 0.466, p < 0.0001), serum markers of fibrogenesis: PIIINP (rs = 0.634, p < 0.0001), hyaluronic acid (rs = 0.575, p < 0.0001), ICTP (rs = 0.482, p < 0.0001), pro-inflammatory cytokines IL-6 (rs = 0.581, p < 0.0001), IL-8 (rs = 0.535, p < 0.0001) and TNF-α (rs = 0.591, p < 0.0001), whereas significant inverse correlations were observed with serum TGF-β (rs = -0.366, p < 0.0001) and CTx, a marker of collagen degradation (rs = -0.495, p < 0.0001). The data indicate that the induction of IgA immune responses toward ethanol metabolites and tissue transglutaminaseis a characteristic feature of patients with AUD and coincides with the activation of inflammation, extracellular matrix remodeling and the generation of aberrantly glycosylated proteins. These processes appear to work in concert in the sequence of events leading from heavy drinking to ALD.

Predictive risk markers in alcoholism

The medical disorders of alcoholism rank among the leading public health problems worldwide and the need for predictive and prognostic risk markers for assessing alcohol use disorders (AUD) has been widely acknowledged. Early-phase detection of problem drinking and associated tissue toxicity are important prerequisites for timely initiations of appropriate treatments and improving patient's committing to the objective of reducing drinking. Recent advances in clinical chemistry have provided novel approaches for a specific detection of heavy drinking through assays of unique ethanol metabolites, phosphatidylethanol (PEth) or ethyl glucuronide (EtG). Carbohydrate-deficient transferrin (CDT) measurements can be used to indicate severe alcohol problems. Hazardous drinking frequently manifests as heavy episodic drinking or in combinations with other unfavorable lifestyle factors, such as smoking, physical inactivity, poor diet or adiposity, which aggravate the metabolic consequences of alcohol intake in a supra-additive manner. Such interactions are also reflected in multiple disease outcomes and distinct abnormalities in biomarkers of liver function, inflammation and oxidative stress. Use of predictive biomarkers either alone or as part of specifically designed biological algorithms helps to predict both hepatic and extrahepatic morbidity in individuals with such risk factors. Novel approaches for assessing progression of fibrosis, a major determinant of prognosis in AUD, have also been made available. Predictive algorithms based on the combined use of biomarkers and clinical observations may prove to have a major impact on clinical decisions to detect AUD in early pre-symptomatic stages, stratify patients according to their substantially different disease risks and predict individual responses to treatment.

Blood Cell Responses Following Heavy Alcohol Consumption Coincide with Changes in Acute Phase Reactants of Inflammation, Indices of Hemolysis and Immune Responses to Ethanol Metabolites

Aberrations in blood cells are common among heavy alcohol drinkers. In order to shed further light on such responses, we compared blood cell status with markers of hemolysis, mediators of inflammation and immune responses to ethanol metabolites in alcohol-dependent patients at the time of admission for detoxification and after abstinence. Blood cell counts, indices of hemolysis (LDH, haptoglobin, bilirubin), calprotectin (a marker of neutrophil activation), suPAR, CD163, pro- and anti-inflammatory cytokines and autoantibodies against protein adducts with acetaldehyde, the first metabolite of ethanol, were measured from alcohol-dependent patients (73 men, 26 women, mean age 43.8 ± 10.4 years) at baseline and after 8 ± 1 days of abstinence. The assessments also included information on the quantities of alcohol drinking and assays for biomarkers of alcohol consumption (CDT), liver function (AST, ALT, ALP, GGT) and acute phase reactants of inflammation. At baseline, the patients showed elevated values of CDT and biomarkers of liver status, which decreased significantly during abstinence. A significant decrease also occurred in LDH, bilirubin, CD163 and IgA and IgM antibodies against acetaldehyde adducts, whereas a significant increase was noted in blood leukocytes, platelets, MCV and suPAR levels. The changes in blood leukocytes correlated with those in serum calprotectin (p < 0.001), haptoglobin (p < 0.001), IL-6 (p < 0.02) and suPAR (p < 0.02). The changes in MCV correlated with those in LDH (p < 0.02), MCH (p < 0.01), bilirubin (p < 0.001) and anti-adduct IgG (p < 0.01). The data indicates that ethanol-induced changes in blood leukocytes are related with acute phase reactants of inflammation and release of neutrophil calprotectin. The studies also highlight the role of hemolysis and immune responses to ethanol metabolites underlying erythrocyte abnormalities in alcohol abusers.

Comparison of serum calprotectin, a marker of neutrophil activation, and other mediators of inflammation in response to alcohol consumption

AIMS

Previous studies have indicated that heavy alcohol intake stimulates inflammation and impairs the body's ability to regulate inflammation. The aim of this study was to compare changes in neutrophil calprotectin and a wide spectrum of other inflammatory mediators in response to heavy alcohol drinking.

METHODS

Serum calprotectin (a marker of neutrophil activation), suPAR, CD163, and pro- (IL-6, IL-8, TNF-α) and anti-inflammatory (IL-10, TGF-β) cytokines were measured from 61 alcohol-dependent subjects (46 men, 15 women, mean age 43.6 ± 11.0 years) at the time of admission for detoxification and after 8 ± 2 days of abstinence. These biomarkers were also measured from age- and sex-matched healthy controls representing abstainers or light drinkers. The clinical assessments included detailed clinical interviews on the amounts and patterns of alcohol consumption and assays for biomarkers of alcohol consumption (GGT, CDT, MCV, GGT-CDT) and liver function (AST, ALT).

RESULTS

The subjects with alcohol use disorder showed significantly higher concentrations of serum calprotectin (p < 0.0005), suPAR (p < 0.01), CD163 (p < 0.01), IL-6 (p < 0.0005), IL-8 (p < 0.0005), TNF-α (p < 0.001), and IL-10 (p < 0.0005) than healthy controls. These inflammatory mediators, except for CD163, remained elevated after the 8 ± 2-day period of supervised abstinence, which resulted in significant decreases in the biomarkers of alcohol consumption and indices of liver status. The AUC (0.855) for serum calprotectin in differentiating between the heavy drinkers and healthy controls was equal or equivalent with those of the conventional biomarkers of alcohol consumption (GGT:0.835 or CDT:0.803).

CONCLUSIONS

The data indicate that neutrophil calprotectin is released in response to heavy alcohol intake in a sensitive manner and may be associated with perpetuation of inflammation in patients with alcohol use disorder. Serum calprotectin may also prove to be a useful biomarker for inflammatory activity in alcohol-consuming patients.

Serum Calprotectin, a Marker of Neutrophil Activation, and Other Mediators of Inflammation in Response to Various Types of Extreme Physical Exertion in Healthy Volunteers

Purpose

While extreme physical exertion is known to induce changes in the status of inflammation comparisons of the responses for various mediators of inflammation after acute bouts of high-intensity exercise have been limited.

Subjects and Methods

We examined the responses in serum levels of novel inflammatory proteins, calprotectin, suPAR, CD163, and pro- and anti-inflammatory cytokines in 12 physically active volunteers (10 men, 2 women, mean age 37±14 years) before and after completing various types of extreme physical exertion (marathon run, half-marathon run or 24-h cross-country skiing). For comparisons, the levels of the biomarkers were also measured at rest in 30 healthy controls (25 men, 5 women, mean age 42 ± 12 years) with low or sedentary activity.

Results

Extreme physical exertion induced significant increases in serum calprotectin (p < 0.0005), suPAR (p < 0.01), CD163 (p < 0.05), IL-6 (p < 0.0005), IL-8 (p < 0.01) and IL-10 (p < 0.0005) (pre- vs 3h-post-exercise). These responses were found to normalize within 48 hours. While the increases in blood leukocytes were of similar magnitude following the different types of exercise, markedly more pronounced responses occurred in serum TNF-α (p < 0.01), IL-8 (p < 0.01) and CD163 (p < 0.05) in those with more intense activity. In 3-h post-exercise samples significant correlations were observed between serum calprotectin and IL-6 (r_s = 0.720, p < 0.01), IL-10 (r_s = 0.615, p < 0.05), TNF-α (r_s = 0.594, p < 0.05), suPAR (r_s = 0.587, p < 0.05) and blood leukocytes (r_s = 0.762, p < 0.01).

Conclusion

The present results suggest distinct exercise-intensity dependent changes in mediators of inflammation (including calprotectin, suPAR and CD163) following extreme physical exertion. Our findings indicate that there is a major reversible impact of high-intensity physical exertion on the status of inflammation.

Lipid peroxidation derived reactive aldehydes in alcoholic liver disease

Lipid peroxidation is a known consequence of oxidative stress and is thought to play a key role in numerous disease pathologies, including alcoholic liver disease (ALD). The overaccumulation of lipid peroxidation products during chronic alcohol consumption results in pathogenic lesions on protein, DNA, and lipids throughout the cell. Molecular adducts due to secondary end products of lipid peroxidation impact a host of biochemical processes, including inflammation, antioxidant defense, and metabolism. The aggregate burden of lipid peroxidation which occurs due to chronic alcohol metabolism, including downstream signaling events, contributes to the development and progression of ALD. In this current opinion we highlight recent studies and approaches relating cellular mechanisms of lipid peroxidation to the pathogenesis of alcoholic liver disease.

The role of immune mechanisms in alcoholic and nonalcoholic steatohepatitis: a 2015 update

So far, innate immune mechanisms have been recognized as the main responsible for the evolution of both alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH). However, increasing evidence points toward the possible role of adaptive immune responses, as an additional factor in promoting hepatic inflammation in steatohepatitis. In this article, we discuss recent data involving circulating antibodies and lymphocyte-mediated responses in sustaining the progression of ASH and NASH to fibrosis, as well as the possible mechanisms implicated in favoring the onset of adaptive immunity in the setting of steatohepatitis.

Acute Changes in Inflammatory Biomarker Levels in Recreational Runners Participating in a Marathon or Half-Marathon

Background

Strenuous physical activity activates the participant’s immune responses; however, few studies exist, observing exercise-induced simultaneous changes in mediators of inflammation.

Methods

We examined individual responses in soluble urokinase-type plasminogen activator receptor (suPAR), a marker of immune activation, soluble endocytic receptor for haptoglobin-hemoglobin complexes (CD163), a marker of monocyte-macrophage activation, C-reactive protein (CRP), and pro- and anti-inflammatory cytokines from blood samples drawn at baseline, at 3- and 48-h post-races from recreational runners who successfully completed the marathon (199 ± 8 min, n = 4) or half-marathon (132 ± 4 min, n = 4) run. For comparisons, biomarkers reflecting muscle, heart, kidney, and liver functions were measured.

Results

Significant 3-h post-race increases occurred in levels of suPAR (p < 0.01), CD163 (p < 0.05), white blood cells (p < 0.001), pro-inflammatory cytokines, interleukin-6 (IL-6) (p < 0.001), IL-8 (p < 0.05), and anti-inflammatory cytokine IL-10 (p < 0.05), whereas tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β) remained relatively stable. Full-marathon running lead to more pronounced increases in suPAR, CD163, IL-8, and IL-10 than half-marathon running. In addition, 3-h post-race increases of all these parameters correlated significantly with changes in serum TNF-α and cortisol. The 48-h levels of serum suPAR and both pro- and anti-inflammatory cytokines had decreased to baseline levels, whereas CRP, a marker of acute phase response, increased in those with the most prominent IL-6 and IL-10 elevations in their preceding samples. The highest suPAR, CRP, IL-6, TNF-α, IL-10, and cortisol levels were noted in the individual with the most severe post-race fatigue.

Conclusions

Prolonged running increases mediators of inflammation in an exercise-dose-dependent manner which should be considered in the assessment of health status of physically active individuals after recent acute bouts of strenuous exercise.

Biomarker-Based Approaches for Assessing Alcohol Use Disorders

Although alcohol use disorders rank among the leading public health problems worldwide, hazardous drinking practices and associated morbidity continue to remain underdiagnosed. It is postulated here that a more systematic use of biomarkers improves the detection of the specific role of alcohol abuse behind poor health. Interventions should be initiated by obtaining information on the actual amounts of recent alcohol consumption through questionnaires and measurements of ethanol and its specific metabolites, such as ethyl glucuronide. Carbohydrate-deficient transferrin is a valuable tool for assessing chronic heavy drinking. Activities of common liver enzymes can be used for screening ethanol-induced liver dysfunction and to provide information on the risk of co-morbidities including insulin resistance, metabolic syndrome and vascular diseases. Conventional biomarkers supplemented with indices of immune activation and fibrogenesis can help to assess the severity and prognosis of ethanol-induced tissue damage. Many ethanol-sensitive biomarkers respond to the status of oxidative stress, and their levels are modulated by factors of life style, including weight gain, physical exercise or coffee consumption in an age- and gender-dependent manner. Therefore, further attention should be paid to defining safe limits of ethanol intake in various demographic categories and establishing common reference intervals for biomarkers of alcohol use disorders.

Inflammatory status in human hepatic cirrhosis

This review focuses on new findings about the inflammatory status involved in the development of human liver cirrhosis induced by the two main causes, hepatitis C virus (HCV) infection and chronic alcohol abuse, avoiding results obtained from animal models. When liver is faced to a persistent and/or intense local damage the maintained inflammatory response gives rise to a progressive replacement of normal hepatic tissue by non-functional fibrotic scar. The imbalance between tissue regeneration and fibrosis will determine the outcome toward health recovery or hepatic cirrhosis. In all cases progression toward liver cirrhosis is caused by a dysregulation of mechanisms that govern the balance between activation/homeostasis of the immune system. Detecting differences between the inflammatory status in HCV-induced vs alcohol-induced cirrhosis could be useful to identify specific targets for preventive and therapeutic intervention in each case. Thus, although survival of patients with alcoholic cirrhosis seems to be similar to that of patients with HCV-related cirrhosis (HCV-C), there are important differences in the altered cellular and molecular mechanisms implicated in the progression toward human liver cirrhosis. The predominant features of HCV-C are more related with those that allow viral evasion of the immune defenses, especially although not exclusively, inhibition of interferons secretion, natural killer cells activation and T cell-mediated cytotoxicity. On the contrary, the inflammatory status of alcohol-induced cirrhosis is determined by the combined effect of direct hepatotoxicity of ethanol metabolites and increases of the intestinal permeability, allowing bacteria and bacterial products translocation, into the portal circulation, mesenteric lymph nodes and peritoneal cavity. This phenomenon generates a stronger pro-inflammatory response compared with HCV-related cirrhosis. Hence, therapeutic intervention in HCV-related cirrhosis must be mainly focused to counteract HCV-immune system evasion, while in the case of alcohol-induced cirrhosis it must try to break the inflammatory loop established at the gut-mesenteric lymph nodes-peritoneal-systemic axis.

C57BL/6 and A/J Mice Have Different Inflammatory Response and Liver Lipid Profile in Experimental Alcoholic Liver Disease

Alcoholic liver disease (ALD) is an important worldwide public health issue characterized by liver steatosis, inflammation, necrosis, and apoptosis of hepatocytes with eventual development of fibrosis and cirrhosis. Comparison of murine models with different inflammatory responses for ALD is important for an evaluation of the importance of genetic background in the interpretation of ethanol-induced phenotypes. Here, we investigated the role of inflammation and genetic background for the establishment of ALD using two different mouse strains: C57BL/6 (B6) and A/J. B6 and A/J mice were treated with a high fat diet containing ethanol (HFDE) and compared to the controls for 10 weeks. Hepatomegaly and steatohepatitis were similar in B6 and A/J mice, but only A/J mice were resistant to weight gain. On the other hand, HFDE-fed B6 accumulated more triglycerides (TG) and cholesterol and presented more intense cellular infiltrate in the liver when compared to HFDM-fed mice. Liver inflammatory environment was distinct in these two mouse strains. While HFDE-fed B6 produced more liver IL-12, A/J mice increased the TNF-α production. We concluded that mouse genetic background could dictate the intensity of the HFDE-induced liver injury.

Altered oxidative stress/antioxidant status in blood of alcoholic subjects is associated with alcoholic liver disease

BACKGROUND

Oxidative stress is implicated in pathogenesis of alcoholic liver disease (ALD). This study investigated the possible correlation among the erythrocyte indices of oxidative stress, the leukocyte panels of antioxidant proteins (metallothioneins), the serum biochemical parameters and the liver steatosis grade.

METHODS

A total of 118 cases including 60 alcoholic subjects and 58 controls were enrolled. All the alcoholic subjects were screened for body mass index (BMI), liver steatosis, and blood chemistry and serology. The level of oxidative stress and oxidative stress-related parameters were measured in the blood and correlated with clinical findings.

RESULTS

Alcoholic subjects showed higher BMI, moderate/severe hepatic steatosis, increase in the levels of triglycerides, cholesterol, glucose, γ-glutamyl-transpeptidase (GGT), alanine aminotransferase (ALT), bilirubin, alpha 1 and beta 2 globulins, iron and a decrease in the levels of aspartate aminotransferase (AST) and beta 1 globulin with respect to the reference values. Moreover, alcoholic subjects showed: (i) an increase in Thiobarbituric Acid Reactive Substance (TBARS) content representing a good estimation of global oxidative stress; (ii) a stimulation of the activities of the antioxidant enzymes catalase and SOD; (iii) a modulation of expression of metallothioneins, with a down-regulation of MT-1A and an up-regulation of MT-1E isoforms.

CONCLUSIONS

Our data suggest that alcoholism is strongly associated with altered pattern of blood metallothioneins; this parameter combined with the score calculated by an ad hoc implemented algorithm (HePaTest) could offer a non-invasive alternative approach for evaluating alcohol-related damages and could be used in follow-up of alcoholic patients.

Associations of alcohol use with radiographic disease progression in African Americans with recent-onset rheumatoid arthritis

OBJECTIVE

To investigate the associations of alcohol consumption and radiographic disease progression in African Americans with recently diagnosed rheumatoid arthritis (RA).

METHODS

Patients with RA included in the study were participants in the Consortium for the Longitudinal Evaluation of African Americans with Early Rheumatoid Arthritis (CLEAR) registry. Patients were categorized based on self-reported alcohol consumption; those consuming < 15 beverages per month versus those with ≥ 15 per month. Association of radiographic disease progression over a 1-year to 3-year period of observation with alcohol consumption was evaluated using multivariate generalized estimating equations.

RESULTS

Of 166 patients included in the study, 39% reported that they had never consumed alcohol. Of the 61% who had consumed alcohol, 73% reported that they consumed on average < 15 alcoholic beverages per month and 27% reported consuming ≥ 15 per month. In multivariate analysis, consumption of ≥ 15 alcoholic beverages per month was associated with an increased risk of radiographic disease progression (p = 0.017). There was no evidence of a relationship in those consuming < 15 beverages per month (p = 0.802).

CONCLUSION

There appears to be a dose-dependent relationship between alcohol use and radiographic disease progression in RA. Individuals who consume 15 or more alcoholic beverages per month may have faster rates of radiographic joint damage than those with lower levels of consumption.

Role of adaptive immunity in alcoholic liver disease

Stimulation of innate immunity is increasingly recognized to play an important role in the pathogenesis of alcoholic liver disease (ALD), while the contribution of adaptive immunity has received less attention. Clinical and experimental data show the involvement of Th-1 and Th-17 T-lymphocytes in alcoholic hepatitis. Nonetheless, the mechanisms by which alcohol triggers adaptive immunity are still incompletely characterized. Patients with advanced ALD have circulating IgG and T-lymphocytes recognizing epitopes derived from protein modification by hydroxyethyl free radicals and end products of lipid-peroxidation. High titers of IgG against lipid peroxidation-derived antigens are associated with an increased hepatic production of proinflammatory cytokines/chemokines. Moreover, the same antigens favor the breaking of self-tolerance towards liver constituents. In particular, autoantibodies against cytochrome P4502E1 (CYP2E1) are evident in a subset of ALD patients. Altogether these results suggest that allo- and autoimmune reactions triggered by oxidative stress might contribute to hepatic inflammation during the progression of ALD.

Upregulation of Kupffer cell α2A-Adrenoceptors and downregulation of MKP-1 mediate hepatic injury in chronic alcohol exposure

Alcohol-induced liver disease is associated with unacceptable morbidity and mortality. When activated, Kupffer cells (KCs), the resident macrophages in the liver, release proinflammatory cytokine TNF-α, a key mediator of hepatic damage. Although chronic alcohol causes increase in norepinephrine (NE) release leading to hepatic dysfunction, the mechanism of NE-induced hepatic injury in chronic alcohol exposure has not been elucidated. This study was conducted to determine whether chronic alcohol exposure increases NE and upregulates KC α(2A)-adrenoceptors (α(2A)-AR) to cause TNF-α release. We also examined the role of mitogen activated protein kinase (MAPK) phosphatase-1 (MKP-1) in this process. Male adult rats were fed the Lieber-DeCarli liquid diet containing alcohol as 36% of total calories. The animals were sacrificed after 6 weeks and blood and liver samples were harvested for further analysis. KCs from healthy male rats were cultured with alcohol for 7 days, and cells then harvested for RNA and protein analyses. Chronic alcohol exposure resulted in hepatic damage. Alcohol caused a 276% increase in circulating NE and 86% increase in TNF-α in the liver. There was a 75% and 62% decrease in MKP-1 mRNA and protein levels, respectively in the liver. In-vitro experiments revealed 121% and 98% increase in TNF-α and α(2A)-AR mRNA levels with alcohol exposure, respectively, and a 32% decrease in MKP-1 mRNA compared to controls. In summary, chronic alcohol exposure elevates NE and upregulates KC α(2A)-AR to release TNF-α. Alcohol induced downregulation of MKP-1 leads to further release of TNF-α and hepatic injury.

Maintenance of immune hyporesponsiveness to melanosomal proteins by DHICA-mediated antioxidation: Possible implications for autoimmune vitiligo

Melanocyte destruction in the skin of vitiligo patients has been considered to be a consequence of an autoimmune response against melanosomal proteins. However, little is known about the molecular mechanisms by which the immune system recognizes these sequestered intracellular self-proteins, which are confined in specialized organelles termed melanosomes, and is provoked into an autoimmune response to melanocytes. Here, we utilize a sucrose density-gradient ultracentrifugation protocol to enrich melanosomal components from dopachrome tautomerase (Dct)-mutant or wild-type melanocytes exposed to a pulse of hydrogen peroxide at a noncytotoxic concentration to evaluate their immunogenicity in mice challenged with the corresponding melanosomal proteins. The results demonstrate that enhanced humoral and cellular immune responses to a challenge with late-stage melanosomal proteins, especially with those derived from Dct-mutant melanocytes, are found in the immunized mice. To elucidate whether a reduced 5,6-dihydroxyindole-2-carboxylic acid (DHICA) content in melanin might cause a loss in antioxidative protection to the proteins, we incubated these melanosomal proteins in vitro with synthetic 5,6-dihydroindole (DHI)-melanin or DHI/DHICA (1:1)-melanin and then used them to immunize mice. T cell proliferation and IgG antibody responsiveness to the challenges were significantly induced by melanosomal proteins treated with DHI-melanin, but not by those treated with DHI/DHICA (1:1)-melanin. Moreover, we observed that melanosomal proteins derived from Dct-mutant melanocytes are subject to oxidative modifications that alter their antigenic configurations to attain an enhanced immunogenicity compared with those derived from wild-type melanocytes. From these results, we conclude that DHICA-mediated antioxidation plays a critical role in the maintenance of immune hyporesponsiveness to melanosomal proteins.

Effects of long-term ethanol administration in a rat total enteral nutrition model of alcoholic liver disease

Male Sprague-Dawley rats were chronically fed a high-unsaturated-fat diet for 130 days by using total enteral nutrition (TEN), or the same diet in which ethanol (EtOH) isocalorically replaced carbohydrate calories. Additional groups were supplemented with the antioxidant N-acetylcysteine (NAC) at 1.7 g·kg(-1)·day(-1). Relative to an ad libitum chow-fed group, the high-fat-fed controls had three- to fourfold greater expression of fatty acid transporter CD36 mRNA and developed mild steatosis but little other hepatic pathology. NAC treatment resulted in increased somatic growth relative to controls (4.0 ± 0.1 vs. 3.1 ± 0.1 g/day) and increased hepatic steatosis score (3.5 ± 0.6 vs. 2.7 ± 1.2), associated with suppression of the triglyceride hydrolyzing protein adiponutrin, but produced no elevation in serum alanine aminotransferase (ALT). Chronic EtOH treatment increased expression of fatty acid transport protein FATP-2 mRNA twofold, resulting in marked hepatic steatosis, oxidative stress, and a twofold elevation in serum ALT. However, no changes in tumor necrosis factor-α or transforming growth factor-β expression were observed. Fibrosis, as measured by Masson's trichrome and picrosirius red staining, and a twofold increase in expression of type I and type III collagen mRNA, was only observed after EtOH treatment. Long-term EtOH treatment increased hepatocyte proliferation but did not modify the hepatic mRNAs for hedgehog pathway ligands or target genes or genes regulating epithelial-to-mesenchymal transition. Although the effects of NAC on EtOH-induced fibrosis could not be fully evaluated, NAC had additive effects on hepatocyte proliferation and prevented EtOH-induced oxidative stress and necrosis, despite a failure to reverse hepatic steatosis.

Progression of alcoholic and non-alcoholic steatohepatitis: common metabolic aspects of innate immune system and oxidative stress

Growing evidence indicates that the innate immune system and oxidative stress caused by gut-derived endotoxins play a key role in alcoholic liver disease (ALD). Intracellular mechanisms associated with endotoxin-induced signaling play a crucial role in the initiation and progression of ALD. It is now widely accepted that activation of the innate immune system and increased release of pro-inflammatory cytokines and other mediators play an important role in the development of ALD. Accumulating evidence suggests that alcohol-mediated upregulation of CYP2E1 expression may initiate lipid peroxidation via reactive oxygen species. Non-alcoholic steatohepatitis (NASH) is a liver disease characterized by histopathological features similar to those observed in ALD, but in the absence of significant alcohol consumption. Initial efforts to clarify the mechanisms that promote the progression from steatosis to steatohepatitis somewhat artificially divided disease mechanisms into "first and second hits." This model considered the development of steatosis to be the "first hit," increasing the sensitivity of the liver to the putative "second hit," leading to hepatocyte injury, inflammation, and oxidative stress. We have emphasized the important role of gut-derived bacterial toxins, the innate immune system, and oxidative stress in the common pathogenic mechanism in ALD and NASH progression.

Biomarkers of alcohol consumption and related liver disease

Abstract Alcohol abuse is a major cause of abnormal liver function throughout the world. While measurements of liver enzyme activities (GGT, ALT, AST) are important screening tools for detecting liver disease, due to lack of ethanol-specificity and inconsistencies regarding the definitions of significant alcohol consumption, several other blood tests are usually needed to exclude competing and co-existing causes of abnormal liver function. Information on the specific role of ethanol consumption behind hepatotoxicity may be obtained through measurements of blood ethanol and its specific metabolites (ethyl glucuronide, phosphatidylethanol, protein-acetaldehyde condensates and associated autoimmune responses). Recent studies have indicated that being overweight is another increasingly common cause of abnormal liver enzyme levels and adiposity may also increase the impact of ethanol consumption on liver pathology. Interestingly, increased liver enzyme activities in circulation may reflect not only hepatic function but can also serve as indicators of general health and the status of oxidative stress in vivo. ALT and GGT activities predict insulin resistance, metabolic syndrome, mortality from coronary heart diseases and even mortality from all causes. If the upper reference limits for liver enzyme activities were defined based on the data obtained from normal weight abstainers, the clinical value of liver enzyme measurements as screening tools and in patient follow-up could be significantly improved.

Complement and alcoholic liver disease: role of C1q in the pathogenesis of ethanol-induced liver injury in mice

BACKGROUND & AIMS

Complement is involved in the development of alcoholic liver disease in mice; however, the mechanisms for complement activation during ethanol exposure have not been identified. C1q, the recognition subunit of the first complement component, binds to apoptotic cells, thereby activating the classical complement pathway. Because ethanol exposure increases hepatocellular apoptosis, we hypothesized that ethanol-induced apoptosis would lead to activation of complement via the classical pathway.

METHODS

Wild-type and C1qa-/- mice were allowed free access to ethanol-containing diets or pair-fed control diets for 4 or 25 days.

RESULTS

Ethanol feeding for 4 days increased apoptosis of Kupffer cells in both wild-type and C1qa-/- mice. Ethanol-induced deposition of C1q and C3b/iC3b/C3c was colocalized with apoptotic Kupffer cells in wild-type, but not C1qa-/-, mice. Furthermore, ethanol-induced increases in tumor necrosis factor-alpha and interleukin-6 expression at this early time point were suppressed in C1q-deficient mice. Chronic ethanol feeding (25 days) increased steatosis, hepatocyte apoptosis, and activity of serum alanine and aspartate aminotransferases in wild-type mice. These markers of hepatocyte injury were attenuated in C1qa-/- mice. In contrast, chronic ethanol (25 days)-induced increases in cytochrome P450 2E1 expression and oxidative stress did not differ between wild-type and C1qa-/- mice.

CONCLUSIONS

For the first time, these data indicate that ethanol activates the classical complement pathway via C1q binding to apoptotic cells in the liver and that C1q contributes to the pathogenesis of ethanol-induced liver injury.

Anti-lipid peroxidation effects of taurine ganbo in rats with alcoholic liver disease

AIM: To observe the protective and therapeutic effects and anti-lipid peroxidation effects of taurine ganbo in rats with alcoholic liver disease.

METHODS: A rat model of alcoholic liver disease was established by intragastric infusion of alcohol. Seventy-five male Wistar rats were randomly divided into five groups: normal control group, model group, low-dose taurine ganbo group, middle-dose taurine ganbo group, and high-dose taurine ganbo group. The model group was given dehydrated alcohol (500 mL/L) once a day for 8 weeks. The three taurine ganbo groups were treated as the model group and additionally given taurine ganbo once a day for 8 weeks. The normal control group was given equal volumes of distilled water for the same duration. After treatment, all the rats were killed. Serum alanine aminotransferase (ALT), aspartate amino transferase (AST), triglyceride (TG), total cholesterol (T-CHO), glucose (GLU), and circulating IgG against malondialdehyde-modified human serum albumin (MDA-HSA) were measured. Hepatic pathological changes were observed.

RESULTS: The levels of serum ALT, AST, TG, T-CHO, and GLU were significantly higher in the model group than in the normal control group, the middle- and high-dose taurine ganbo groups (all P < 0.0). The levels of serum ALT, AST and GLU in the low-dose taurine ganbo group were lower than those in the model group (63.67 U/L ± 6.89 U/L vs 81.53 U/L ± 22.85 U/L, 131.2 U/L ± 11.63 U/L vs 156.47 U/L ± 32.23 U/L, and 6.38 mmol/L ± 0.66 mmol/L vs 6.86 mmol/L ± 0.67 mmol/L, respectively; all P < 0.01 or 0.05). The level of circulating IgG against MDA-HSA in the model group was higher than those in the normal control group and the middle- and high-dose taurine ganbo groups (all P < 0.01). Compared to the normal control group, the model group had a much heavier lipid accumulation (P < 0.01). The hepatic pathological changes were milder in the middle- and high-dose groups than in the model group (both P < 0.05).

CONCLUSION: Taurine ganbo can attenuate alcohol-mediated increase in serum ALT, AST, TG and T-CHO levels and exert anti-lipid peroxidation effects in rats with alcoholic liver disease.

Immune mechanisms in alcoholic liver disease

Growing evidence indicates that inflammatory reactions play an important role in the pathogenesis of alcoholic liver disease (ALD). The implication of immunity in fueling chronic inflammation in ALD has emerged from clinical and experimental evidence showing the recruitment and the activation of lymphocytes in the inflammatory infiltrates of ALD and has received further support by the recent demonstration of a role of Th17 lymphocytes in alcoholic hepatitis. Nonetheless, the mechanisms by which alcohol triggers adaptive immune responses are still incompletely characterized. Patients with advanced ALD show a high prevalence of circulating IgG and T-lymphocytes towards epitopes derived from protein modification by hydroxyethyl free radicals (HER) and end-products of lipid peroxidation. In both chronic alcohol-fed rats and heavy drinkers the elevation of IgG against lipid peroxidation-derived antigens is associated with an increased production of pro-inflammatory cytokines/chemokines and with the severity of histological signs of liver inflammation. Moreover, CYP2E1-alkylation by HER favors the development of anti-CYP2E1 auto-antibodies in a sub-set of ALD patients. Altogether, these results suggest that allo- and auto-immune reactions triggered by oxidative stress might contribute to fuel chronic hepatic inflammation during the progression of ALD.

Role of oxidative stress in alcohol-induced liver injury

Reactive oxygen species (ROS) are highly reactive molecules that are naturally generated in small amounts during the body's metabolic reactions and can react with and damage complex cellular molecules such as lipids, proteins, or DNA. Acute and chronic ethanol treatments increase the production of ROS, lower cellular antioxidant levels, and enhance oxidative stress in many tissues, especially the liver. Ethanol-induced oxidative stress plays a major role in the mechanisms by which ethanol produces liver injury. Many pathways play a key role in how ethanol induces oxidative stress. This review summarizes some of the leading pathways and discusses the evidence for their contribution to alcohol-induced liver injury. Special emphasis is placed on CYP2E1, which is induced by alcohol and is reactive in metabolizing and activating many hepatotoxins, including ethanol, to reactive products, and in generating ROS.

Understanding and treating patients with alcoholic cirrhosis: an update

Alcoholic cirrhosis represents the terminal stage of alcoholic liver disease (ALD) and one of the main causes of death among alcohol abusers. The aim of this review was to provide an update on alcoholic cirrhosis, with an emphasis on recent findings. Increased alcohol consumption in developing countries is expected to increase cirrhosis mortality. There is a need, therefore, to develop new approaches to the prevention of ALD, including more attention to co-factors that may increase risk of ALD (i.e., obesity and diabetes, chronic HCV infection, and smoking). Furthermore, a better understanding of the pathological mechanisms on the basis of alcohol cirrhosis represents a cornerstone in order to develop new pharmacological treatments. Inflammatory and immune responses along with oxidative stress and alterations in adipokine secretion might contribute in different ways to the evolution of alcohol-induced fibrosis/cirrhosis. As of this date, patients with severe alcoholic hepatitis with a Maddrey Discriminant Factor (MDF) 32 should be offered pentoxifylline and/or corticosteroids unless contraindications exist. For ambulatory patients, S-adenosylmethionine (SAMe) may be considered in a motivated patient with nutritional support. Current studies do not support use of anti-tumor necrosis factor (TNF)-alpha antibody. Finally, achieving total alcohol abstinence should represent the main aim in the management of patients affected by any stage of cirrhosis. In the last decades, several drugs able to increase abstinence and prevent alcohol relapse have been evaluated and some of them have obtained approval for alcohol dependence. Patients with alcoholic cirrhosis; however, are usually excluded from such treatments. A recent study demonstrated the efficacy and safety of baclofen in inducing and maintaining alcohol abstinence in cirrhotic alcohol-dependent patients with cirrhosis. All together the information available suggests the need of a multimodal approach in the clinical management of these patients.

Alcohol metabolites and lipopolysaccharide: roles in the development and/or progression of alcoholic liver disease

The onset of alcoholic liver disease (ALD) is initiated by different cell types in the liver and a number of different factors including: products derived from ethanol-induced inflammation, ethanol metabolites, and the indirect reactions from those metabolites. Ethanol oxidation results in the production of metabolites that have been shown to bind and form protein adducts, and to increase inflammatory, fibrotic and cirrhotic responses. Lipopolysaccharide (LPS) has many deleterious effects and plays a significant role in a number of disease processes by increasing inflammatory cytokine release. In ALD, LPS is thought to be derived from a breakdown in the intestinal wall enabling LPS from resident gut bacterial cell walls to leak into the blood stream. The ability of adducts and LPS to independently stimulate the various cells of the liver provides for a two-hit mechanism by which various biological responses are induced and result in liver injury. Therefore, the purpose of this article is to evaluate the effects of a two-hit combination of ethanol metabolites and LPS on the cells of the liver to increase inflammation and fibrosis, and play a role in the development and/or progression of ALD.

TNF-induced mitochondrial damage: a link between mitochondrial complex I activity and left ventricular dysfunction

Mitochondrial damage is implicated in the progression of cardiac disease. Considerable evidence suggests that proinflammatory cytokines induce oxidative stress and contribute to cardiac dysfunction. This study was conducted to determine whether a TNF-induced increase in superoxide (O(2)(*)(-)) contributes to mitochondrial damage in the left ventricle (LV) by impairing respiratory complex I activity. We employed an electron paramagnetic resonance (EPR) method to measure O(2)(*)(-) and oxygen consumption in mitochondrial respiratory complexes, using an oxygen label. Adult male Sprague-Dawley rats were divided into four groups: control, TNF treatment (ip), TNF+ apocynin (APO; 200 micromol/kg bw, orally), and TNF+ Tempol (Temp; 300 micromol/kg bw, orally). TNF was injected daily for 5 days. Rats were sacrificed, LV tissue was collected, and mitochondria were isolated for EPR studies. Total LV ROS production was significantly higher in TNF animals than in controls; APO or Temp treatment ameliorated TNF-induced LV ROS production. Total mitochondrial ROS production was significantly higher in the TNF and TNF+ APO groups than in the control and TNF+ Temp groups. These findings suggest that TNF alters the cellular redox state, reduces the expression of four complex I subunits by increasing mitochondrial O(2)(*)(-) production and depleting ATP synthesis, and decreases oxygen consumption, thereby resulting in mitochondrial damage and leading to LV dysfunction.

New concepts in the pathogenesis of alcoholic liver disease

Alcoholic liver disease still represents an important cause for death and disability in most well-developed countries and is becoming a leading cause of disease in developing countries. It is now increasingly clear that, besides the formation of acetaldehyde, alcohol effects on the liver include oxidative stress, disturbances in methionine metabolism, endoplasmic reticulum stress, inflammatory/immune responses and adipokine imbalances. This article will discuss the most recent findings on the mechanisms by which alcohol abuse causes hepatic steatosis and steatohepatitis, and now it contributes to the progression of fibrosis. Although still incomplete, these data shed new light on the multifactorial pathogenesis of alcoholic liver disease and open new possibilities in the understanding of how gender and genetic factors can influence disease progression.