Impaired antigen presentation by splenocytes of ethanol-consuming C57BL/6 mice

The mechanisms underlying alcohol-induced decreased splenic size: A network meta-analysis study

BACKGROUND

Organ weight change is widely accepted as a measure of toxicologic pathology. We and other groups have shown that excessive alcohol exposure leads to decreased spleen weight in rodents. This study explores the mechanisms underlying alcohol-induced splenic injury through a network meta-analysis.

METHODS

QIAGEN Ingenuity Pathway Analysis (IPA) and Mammalian Phenotype (MP) Ontology were used to identify alcohol-related molecules associated with the small spleen phenotype. Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) and IPA bioinformatics tools were then used to analyze the biologic processes and enriched signaling pathways engaging these molecules. In addition, the "downstream effects analysis" algorithm was used to quantify alcohol's effects.

RESULTS

IPA identified 623 molecules affected by alcohol and a Venn diagram revealed that 26 of these molecules overlapped with those associated with the MP Ontology of small spleen. The 26 molecules are TGFB1, CASP8, MTOR, ESR1, CXCR4, CAMK4, NFKBIA, DRD2, BCL2, FAS, PEBP1, TRAF2, ATM, IGHM, EDNRB, MDM2, GLRA1, PRF1, TLR7, IFNG, ALOX5, FOXO1, IL15, APOE, IKBKG, and RORA. Some of the 26 molecules were also associated with the MP Ontology of abnormal white pulp and red pulp morphology of the spleen, abnormal splenic cell ratio, decreased splenocyte number, abnormal spleen physiology, increased splenocyte apoptosis, and reduced splenocyte proliferation. STRING and IPA "Core Analysis" showed that these molecules were mainly involved in pathways related to cell apoptosis, proliferation, migration, and immune responses. IPA's "Molecular Activity Predictor" tool showed that concurrent effects of activation and inhibition of these molecules led to decreased spleen size by modulating apoptosis, proliferation, and migration of splenocytes.

CONCLUSIONS

Our network meta-analysis revealed that excessive alcohol exposure can damage the spleen through a variety of molecular mechanisms, thereby affecting immune function and human health. We found that alcohol-mediated splenic atrophy is largely mediated by increased apoptosis signaling, migration of cells, and inhibition of splenocyte proliferation.

Hypochlorous acid-modified human serum albumin suppresses MHC class II - dependent antigen presentation in pro-inflammatory macrophages

Macrophages are innate immune cells that internalize and present exogenous antigens to T cells via MHC class II proteins. They operate at sites of infection in a highly inflammatory environment, generated in part by reactive oxygen species, in particular the strong oxidant hypochlorous acid (HOCl) produced in the neutrophil respiratory burst. HOCl effectively kills a broad range of pathogens but can also contribute to host tissue damage at sites of inflammation. To prevent tissue injury, HOCl is scavenged by human serum albumin (HSA) and other plasma proteins in interstitial fluids, leading to the formation of variously modified advanced oxidation products (AOPPs) with pro-inflammatory properties. Previously, we showed that HOCl-mediated N-chlorination converts HSA and other plasma proteins into efficient activators of the phagocyte respiratory burst, but the role of these AOPPs in antigen presentation by macrophages remained unclear. Here, we show that physiologically relevant amounts of N-chlorinated HSA can strongly impair the capacity of THP-1-derived macrophages to present antigens to antigen-specific T cells via MHC class II proteins at multiple stages. Initially, N-chlorinated HSA inhibits antigen internalization by converting antigens into scavenger receptor (SR) ligands and competing with the modified antigens for binding to SR CD36. Later steps of antigen presentation, such as intracellular antigen processing and MHC class II expression are negatively affected, as well. We propose that impaired processing of pathogens or exogenous antigens by immune cells at an initial stage of infection prevents antigen presentation in an environment potentially hostile to cells of the adaptive immune response, possibly shifting it towards locations removed from the actual insult, like the lymph nodes. On the flip side, excessive retardation or complete inhibition of antigen presentation by N-chlorinated plasma proteins could contribute to chronic infection and inflammation.

Alcohol Consumption in Rheumatoid Arthritis: A Path through the Immune System

Benefits and harms of different components of human diet have been known for hundreds of years. Alcohol is one the highest consumed, abused, and addictive substances worldwide. Consequences of alcohol abuse are increased risks for diseases of the cardiovascular system, liver, and nervous system, as well as reduced immune system function. Paradoxically, alcohol has also been a consistent protective factor against the development of autoimmune diseases such as type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis (RA). Here, we focused on summarizing current findings on the effects of alcohol, as well as of its metabolites, acetaldehyde and acetate, on the immune system and RA. Heavy or moderate alcohol consumption can affect intestinal barrier integrity, as well as the microbiome, possibly contributing to RA. Additionally, systemic increase in acetate negatively affects humoral immune response, diminishing TFH cell as well as professional antigen-presenting cell (APC) function. Hence, alcohol consumption has profound effects on the efficacy of vaccinations, but also elicits protection against autoimmune diseases. The mechanism of alcohol's negative effects on the immune system is multivariate. Future studies addressing alcohol and its metabolite acetate's effect on individual components of the immune system remains crucial for our understanding and development of novel therapeutic pathways.

Nerve Growth Factor in Alcohol Use Disorders

The nerve growth factor (NGF) belongs to the family of neurotrophic factors. Initially discovered as a signaling molecule involved in the survival, protection, differentiation, and proliferation of sympathetic and peripheral sensory neurons, it also participates in the regulation of the immune system and endocrine system. NGF biological activity is due to the binding of two classes of receptors: the tropomyosin-related kinase A (TrkA) and the low-affinity NGF pan-neurotrophin receptor p75. Alcohol Use Disorders (AUD) are one of the most frequent mental disorders in developed countries, characterized by heavy drinking, despite the negative effects of alcohol on brain development and cognitive functions that cause individual’s work, medical, legal, educational, and social life problems. In addition, alcohol consumption during pregnancy disrupts the development of the fetal brain causing a wide range of neurobehavioral outcomes collectively known as fetal alcohol spectrum disorders (FASD). The rationale of this review is to describe crucial findings on the role of NGF in humans and animals, when exposed to prenatal, chronic alcohol consumption, and on binge drinking.

Alcoholic Cirrhosis Increases Risk for Autoimmune Diseases: A Nationwide Registry-Based Cohort Study

BACKGROUND & AIMS

Alcoholic cirrhosis is associated with hyperactivation and dysregulation of the immune system. In addition to its ability to increase risk for infections, it also may increase the risk for autoimmune diseases. We studied the incidence of autoimmune diseases among patients with alcoholic cirrhosis vs controls in Denmark.

METHODS

We collected data from nationwide health care registries to identify and follow up all citizens of Denmark diagnosed with alcoholic cirrhosis from 1977 through 2010. Each patient was matched with 5 random individuals from the population (controls) of the same sex and age. The incidence rates of various autoimmune diseases were compared between patients with cirrhosis and controls and adjusted for the number of hospitalizations in the previous year (a marker for the frequency of clinical examination).

RESULTS

Of the 24,679 patients diagnosed with alcoholic cirrhosis, 532 developed an autoimmune disease, yielding an overall increased adjusted incidence rate ratio (aIRR) of 1.36 (95% confidence interval [CI], 1.24-1.50). The strongest associations were with Addison's disease (aIRR, 2.47; 95% CI, 1.04-5.85), inflammatory bowel disease (aIRR, 1.56; 95% CI, 1.26-1.92), celiac disease (aIRR, 5.12; 95% CI, 2.58-10.16), pernicious anemia (aIRR, 2.35; 95% CI, 1.50-3.68), and psoriasis (aIRR, 4.06; 95% CI, 3.32-4.97). There was no increase in the incidence rate for rheumatoid arthritis (aIRR, 0.89; 95% CI, 0.69-1.15); the incidence rate for polymyalgia rheumatica decreased in patients with alcoholic cirrhosis compared with controls (aIRR, 0.47; 95% CI, 0.33-0.67).

CONCLUSIONS

Based on a nationwide cohort study of patients in Denmark, alcoholic cirrhosis is a risk factor for several autoimmune diseases.

The impact of alcohol on BCG-induced immunity against Mycobacterium tuberculosis

BACKGROUND

Alcoholics are at heightened risk for developing active tuberculosis. This study evaluates chronic alcohol consumption in a murine model of vaccination with Mycobacterium bovis Bacille Calmette-Guèrin (BCG) and subsequent pulmonary infection with virulent Mycobacterium tuberculosis.

METHODS

BALB/c mice were administered the Lieber-DeCarli liquid ethanol diet or pair-fed the liquid control diet for 3 weeks either before or after subcutaneous vaccination with M. bovis BCG. At least 3 weeks after BCG vaccination, groups of mice on the aforesaid diets were challenged with intratracheal infection with M. tuberculosis H37Rv. Lung mycobacterial burden, and lung and lung-associated lymph node CD4(+) lymphocyte production of tuberculosis-specific interferon (IFN)-γ were assayed. Popliteal lymph node lymphocytes from both dietary regimens undergoing BCG vaccination (in the absence of M. tuberculosis infection) were also evaluated for purified protein derivative-induced IFN-γ production by ELISpot assay.

RESULTS

Mice begun on alcohol prior to vaccination with M. bovis BCG demonstrated impaired control of pulmonary challenge with virulent M. tuberculosis, as well as impaired lung CD4(+) and popliteal lymph node T-cell IFN-γ responses. If BCG vaccination was delivered prior to initiation of alcohol feeding, the mice remained protected against a subsequent challenge with M. tuberculosis, and BCG-induced immunity was not impaired in either the lung or the popliteal lymph nodes.

CONCLUSIONS

Alcohol consumption blunts the development of the adaptive immune response to M. bovis BCG vaccination, which impairs the control of a secondary challenge with M. tuberculosis, but only if the alcohol exposure is begun prior to BCG vaccination. These results provide insight into mechanisms by which alcohol consumption impairs antimycobacterial immunity, including in response to vaccination and subsequent pathogenic challenge.

Dendritic cells in chronic in vivo ethanol exposure models

Dendritic cells (DCs) play a key role in the initiation of effective immune responses against infectious agents because they are unique in their ability to provide antigen-specific activation of naïve T cells. To do this, they must acquire antigen and migrate to spleen or lymph node to present the antigen to T cells in association with costimulatory molecules and cytokines. Murine models of chronic EtOH exposure have been developed for dissecting the mechanisms by which EtOH alters immune cell functions. This chapter details methods for assessing DC functions in such models. Methods are presented for 1) the identification and isolation of various DC subsets from spleen, epidermis, and lung, 2) measurement of LC migration out of epidermis and DC migration into peripheral and peribronchial lymph nodes, and 3) measurement of alloantigen presentation in vitro as well as transgenic T-cell activation in vitro and in vivo.

Ethanol consumption modifies dendritic cell antigen presentation in mice

BACKGROUND

Alcohol consumption impairs type 1 cell-mediated adaptive immune responses both in vivo and in vitro. The present study investigated the effect of alcohol consumption on antigen-presenting cell (APC) populations and cytokine production.

METHODS

BALB/c were fed ethanol-containing, pair-fed isocaloric liquid control, or solid diets for 11 days. Macrophage and dendritic cell (DC) populations were isolated by paramagenetic bead separation and used to present ovalbumin (OVA) to highly purified syngeneic CD4+ T cells derived from DO11.10 T cell receptor transgenic mice in coculture. DC isolated from diet-fed mice were also used to present OVA to highly purified CD4+ T cells derived from antigen-naïve DO11.10Rag2-/- mice that are devoid of memory T cells. In vitro cytokine responses, interleukin (IL) -2, IL-6, IL-12, IL-13, IL-17A, and interferon-gamma (IFN-gamma) were measured by enzyme-linked immunosorbent assay. Flow cytometry measured cell surface molecule expression.

RESULTS

Alcohol consumption impairs delayed hypersensitivity responses (type 1) and enhances serum IgE levels (type 2). CD11c+ DC, but not F4/80+ macrophages, support cytokine responses by purified CD4+ T cells. CD11c+ DC derived from ethanol consuming BALB/c mice show diminished ability to support IFN-gamma responses by purified CD4+ T cells derived from DO11.10 or DO11.10Rag2-/- mice. Subset analysis indicates that of the 3 "conventional" DC subsets found in mouse spleens, CD11c+CD8(alpha)+ DCs are both responsible for OVA presentation and susceptible to the effects of ethanol. Ethanol consumption does not overtly alter the percent of splenic DC, but does increase the surface density of CD11c on these cells. Data show that cocultures containing purified CD4+ T DO11.10 cells and APC derived from alcohol-consuming mice show decreased IL-6, IL-12, IL-17A, and IFN-gamma and increased IL-13 cytokine production in response to OVA stimulation.

CONCLUSIONS

Ethanol alters CD11c+CD8(alpha)+ DC function, affecting cytokines responsible for adaptive immune responses. A unifying hypothesis for the underlying mechanism(s) of ethanol's effect upon adaptive immune function is proposed.

A low blood ethanol level is associated with improved cytokine production in aged mice after traumatic injury

BACKGROUND

Many trauma patients have been consuming alcohol at the time of injury. Although high concentrations of alcohol are correlated with poor outcome, few studies have examined the effects of low levels of alcohol. We examined the effects of low alcohol exposure after burn injury using a murine model.

METHODS

Three- and 18-month-old mice were given ethanol or saline 30 minutes before a 15% total body surface area burn injury. Twenty-four hours after injury, cellular immune responses, including delayed-type hypersensitivity response and splenocyte proliferation were examined, along with production of interferon-gamma, interleukin (IL)-2, and IL-4.

RESULTS

Alcohol administration resulted in a significant increase in interferon-gamma in the aged, but not young, burn-injured mice. Likewise, slight increases in IL-2, IL-4, and the delayed-type hypersensitivity response were observed.

CONCLUSION

Low levels of ethanol at the time of injury are associated with partial restoration of immune responses in aged mice.

Nerve growth factor produced by activated human monocytes/macrophages is severely affected by ethanol

Ethanol intake impairs immune function and increases the incidence of infection in the host. Although the precise cellular target of this immunotoxic action is still unknown, findings of several studies have shown that ethanol acts on the immune response predominantly by interfering with the ability of blood monocyte-derived macrophages to produce cytokines and growth factors. Nerve growth factor (NGF) represents a key molecule in monocyte/macrophage-mediated responses. Thus, we tested the hypothesis that exposure to ethanol would affect NGF synthesis as well as expression of NGF receptor trkA in this cell population. Because NGF has been reported to affect the synthesis of proinflammatory cytokines, we also evaluated whether the production of tumor necrosis factor-alpha would be affected by ethanol-mediated changes in NGF synthesis. The study results demonstrated that the acute exposure of lipopolysaccharide-activated human monocyte/macrophage cultures to ethanol led to a sharp decrease in endogenous-produced NGF, which is associated with a reduced expression of high-affinity NGF receptor on cell membrane, and to a concomitant impairment of tumor necrosis factor-alpha production. Taken together, the current findings support the suggestion that a new mechanism exists by which ethanol can compromise the efficiency of the mononuclear phagocyte system in dealing with infection and host inflammatory response.

Impaired intestinal immunity and barrier function: a cause for enhanced bacterial translocation in alcohol intoxication and burn injury

Alcohol intoxication is being recognized increasingly as the major factor in pathogenesis after burn injury. Findings from multiple studies support the suggestion that, in comparison with burn-injured patients who sustained injury in the absence of alcohol intoxication, burn-injured patients who sustained injury under the influence of alcohol exhibit higher rates of infection and are more likely to die. Thus, infection becomes the primary cause of death in burn-injured patients. Because the intestine is considered to be a major source of bacteria, studies in experimental animals have been designed to examine whether alcohol intoxication before burn injury enhances bacterial translocation from the intestine. Results of these studies have shown a several-fold increase in bacterial translocation from the intestine in the group of animals receiving combined insult of alcohol intoxication and burn injury compared with findings for the groups receiving either insult alone. Alcohol intoxication and burn injury independent of each other have also been shown to cause an increase in bacterial translocation. The gastrointestinal tract normally maintains a physical mucosal and immunologic barrier that provides an effective defense in keeping bacteria within the intestinal lumen. However, in injury conditions these defense mechanisms are impaired. Intestinal bacteria consequently gain access to extraintestinal sites. Intestine-derived bacteria are implicated in causing systemic infection and in subsequent multiple organ dysfunction in both immunocompromised patients and patients with injury, such as burn and trauma. In this article, we discuss three potential mechanisms that are likely to contribute to the increase in bacterial translocation in alcohol intoxication and burn injury: (1) increase in bacterial growth in the intestine, (2) physical disruption of mucosal barrier of the intestine, and (3) suppression of the immune defense in the intestine.

Alcohol, injury, and cellular immunity

It is widely accepted that alcohol exposure is a causative factor in the occurrence of burn or other traumatic injury. It is less well known that individuals who have consumed alcohol before sustaining an injury suffer from increased morbidity and mortality compared with the morbidity and mortality of non-alcohol-consuming subjects with similar injuries. Complications due to bacterial infection are the most common burn sequelae in injured patients and are frequently associated with depressed immunity. Independently, alcohol exposure and injury have been shown to influence cellular immunity negatively. These changes in immunity are closely linked to injury- or alcohol-induced alterations in the cytokine milieu in both clinical studies and animal models. Not surprisingly, the combination of insult of alcohol exposure and burn injury results in immune suppression that is greater in magnitude and duration compared with either insult alone. The combined effects of alcohol and injury on immunity have been examined in a limited number of studies. However, results of these studies support the suggestion that altered cytokine production is an integral part of the immune dysregulation and increased mortality that is observed. In particular, the increased presence of macrophage-derived mediators observed after burn or alcohol exposure alone seems to be synergistically increased in a combined injury model. Although more research is needed, it is likely that therapeutic modalities that include manipulation of cytokine networks to boost cellular immunity may improve outcome for patients who sustain injuries subsequent to consuming alcohol.

Autoantibodies in alcoholic liver disease

Despite many decades of research, the reasons why only a relatively small proportion of individuals who consume excessive quantities of alcohol develop clinically significant liver disease remain unknown. The association with features of autoimmune diseases, including hypergammaglobulinaemia, circulating autoantibodies, inheritance of certain immunogenetic (HLA) markers and response to corticosteroid therapy in some patients has led to a persistent impression that altered immune regulation with a relative loss of self-tolerance underlies susceptibility to the development of the more severe forms of alcoholic liver disease (alcoholic hepatitis and/or cirrhosis). However, review of the data from the numerous studies that have been conducted over the past 30 years fails to reveal sufficiently convincing evidence that autoimmunity plays a primary role in alcohol-related liver damage. In particular, most of the wide range of circulating autoantibodies that have been reported in patients are found mainly at low titres, are not confined to those with severe liver injury, and are probably more likely to be a response to the hepatic insult than causally related to liver damage. Additionally, an association with various HLA phenotypes has not been confirmed by meta-analysis. Interpretation is complicated by evidence that alcohol may have direct effects on some components of the immune system but, if there is an immunogenetic basis for alcoholic liver disease, the present evidence suggests that this might be related more to cytokine gene polymorphisms than to a predisposition to autoimmunity per se.

Intracellular mechanisms responsible for exercise-induced suppression of macrophage antigen presentation

In a previous study, we demonstrated that exhaustive exercise suppressed peritoneal macrophage antigen presentation (AP). In this study, we explored the intracellular mechanism(s) responsible for this suppression. Pathogen-free male BALB/c mice (8 +/- 2 wk) were randomly assigned to either home cage control (HCC) or exhaustive exercise stress (Exh, 18-30 m/min for 3 h/day) treatment groups. The mice underwent treatments for a period of 4 days during induced peritoneal thioglycollate inflammation. Elicited macrophages were harvested, purified, and incubated with chicken ovalbumin (C-Ova, 2. 5 and 10 mg/ml) for 18 h. After macrophages were washed, they were cocultured with C-Ova-specific T cells for 48 h at which time the supernates were harvested and analyzed via ELISA for interleukin (IL)-2 as an indication of macrophage AP. There was no significant (P > 0.05) difference in macrophage AP between cells fixed with paraformaldehyde vs. those that remained unfixed, suggesting that Exh did not affect production of soluble factors influencing macrophage AP (i.e., IL-1, IL-4, PGE(2)). The ability of macrophages to generate C-Ova immunogenic peptides was analyzed using FITC-labeled C-Ova, which shows fluorescence only when degraded intracellularly. There was a significant ( approximately 20%, P < 0. 05) suppression in fluorescence in the Exh compared with HCC, indicating a possible defect in the ability of macrophages from Exh to degrade C-Ova into immunogenic peptides. Macrophages were also incubated with C-Ova immunogenic peptide in a manner identical to that for native C-Ova. We found a similar suppression ( approximately 22-38%, P < 0.05) in macrophage AP using a C-Ova peptide when compared with native C-Ova in the Exh group, indicating reduced major histocompatibility complex (MHC) II loading and/or C-Ova-MHC II complex cell surface expression. In conclusion, these data indicate an intracellular defect in the macrophage antigen processing pathway induced by Exh.

Exercise suppresses macrophage antigen presentation

This study determined the effects of exercise on the ability of macrophages (Mphi) to present antigen to T cells. Pathogen-free male Balb/c mice (8 +/- 2 wk of age) were randomly assigned to either home cage control, moderate exercise (Mod; 18 m/min, 5% grade, 0.5 h/day), exhaustive exercise (Exh, 18-30 m/min, 3 h/day), or treadmill control groups. The mice underwent treatments for 4 days during peritoneal thioglycolate inflammation. Peritoneal Mphi were harvested, purified, and incubated with chicken ovalbumin (C-OVA; 0-10 mg/ml) for 18 h. Mphi were then cocultured with C-OVA-specific T cells for 48 h, and the supernatants were analyzed via ELISA for interleukin-2 as an indication of Mphi antigen presentation (AP). Exh exhibited suppressed ( approximately 25-34%) Mphi AP across a wide range of C-OVA doses when measured immediately, 3, and 24 h postexercise. In contrast, Mod had reduced Mphi AP only at 3 h postexercise. Mphi AP was also lower in the treadmill control (4-27%) compared with the home cage control group, but was significantly higher than Exh. The reduction in Mphi AP was not due to exercise-induced differences in Mphi number, percentage, or expression of intercellular adhesion molecule-1, B7-2, or major histocompatability complex II, molecules important in AP. In conclusion, our data lend evidence that may help explain the increased incidence of infection observed after prolonged exhaustive exercise or overtraining.

Alcohol abuse, alcoholism, and damage to the immune system--a review

Chronic alcohol abuse exacts a major social and medical toll in the United States and other Western countries. One of the least appreciated medical complications of alcohol abuse is altered immune regulation leading to immunodeficiency and autoimmunity. The consequences of the immunodeficiency include increased susceptibility to bacterial pneumonia, tuberculosis, and other infectious diseases. In addition, the chronic alcoholic often has circulating autoantibodies, and recent investigations indicate that the most destructive complications of alcoholism, such as liver disease and liver failure, may have a component of autoimmunity. Current research on altered cytokine balance produced by alcohol is leading to new insights on the regulation of the immune system in the chronic alcoholic. There is also recent development of exciting new techniques designed to improve or restore immune function by manipulation of cytokine balance. Although much remains to be learned, both in the abnormalities produced by alcohol and in the techniques to reverse those abnormalities, current progress reflects a rapidly improving understanding of the basic immune disorders of the alcoholic.

Ethanol impairs the induction of delayed hypersensitivity in C57BL/6 mice

Excessive alcohol consumption impairs T-cell-dependent immune function. Whether this impairment results from the direct inhibition of helper T (Th) cells or from inhibition of the cells that process and present antigen to Th cells is unclear. The present study examines the temporal effect of dietary alcohol on the development of delayed hypersensitivity (DTH) in C57BL/6 mice. We find that ethanol consumption just prior to and during the cognitive phase of the immune response impairs the development of a DTH response. Ethanol consumption initiated after the cognitive phase and during the effector phase of the immune response has no significant effect upon the elicitation of a DTH response. The results suggest that significant ethanol-induced impairment of DTH responses occurs during the cognitive phase of the immune response, when antigen presentation and recognition occur.