The role of Toll-like receptors in neurobiology of alcoholism

The study of the azithromycin effect on gene expression of the toll-like receptor system in the brain nucleus accumbens of rats during ethanol withdrawal and search for possible molecular targets by an in silico method

The brain's nucleus accumbens (NAc) is a key link in the internal reinforcement system, which mediates manifestations of various components of addiction, including ethanol. The neuroinflammatory theory of alcoholism development suggests that changes in the molecular mechanisms of the innate immune system may be involved in the development of this pathology. The aim of our study was to investigate the effect of azithromycin (AZM) on expression of toll-like receptor system genes in the NAc during experimental alcoholization of rats. The objectives of the study also included an in silico search for possible molecular targets for AZM that could be associated with the toll-like receptor system. AZM corrected the changes observed in the expression of toll-like receptor system genes under conditions of alcohol withdrawal after long-term ethanol exposure in the NAc of the brain. The in silico analysis revealed the most probable proteins which could be involved in the interaction with AZM. Based on results of these predictions a number of assumptions about possible ways of implementing the observed pharmacological effect of AZM in the experiment have been made.

Association of Peripheral Markers of Oxidative Stress with Clinical Parameters and Inflammatory Factors in Alcoholic Patients

One of the fundamental problems in studying addiction is elucidation of mechanisms of alcohol dependence (AD) development. Disturbances of cellular redox balance and inflammation play an important role in AD pathogenesis. Deciphering associations between biological and clinical indicators can elucidate molecular mechanisms of disease pathogenesis. The aim of the work was to study peripheral markers of oxidative stress in patients with AD during early abstinence period and to identify their relationship with clinical parameters of the disease and inflammatory factors. In total, 84 patients with AD were studied (average age, 44.3 ± 8.2 years). The analyzed clinical parameters included patient's age, age of alcohol withdrawal syndrome (AWS) formation, disease duration, and AWS duration. The markers of oxidative stress determined in the blood plasma were oxidation products of proteins (protein carbonyls, PCs), lipids (thiobarbituric acid-reactive products, TBA-RPs), and DNA (8-hydroxy-2'-deoxyguanosine, 8-OH-dG). The content of inflammatory mediators, such as proinflammatory cytokines (IFNγ, IL-1β, IL-6, IL-8, IL-17A, TNFα) was determined in the blood serum. Blood samples of 80 conditionally healthy men (average age, 40.9 ± 9.6 years) were used as a control. Patients with AD demonstrated an increase in the content of PCs, TBA-RPs, and all analyzed cytokines (but not 8-OH-dG) compared to the control individuals. There was a direct correlation between the TBA-RP content and disease duration and inverse correlation of the PC content with the age of AWS formation and AWS duration. The content of PCs demonstrated an inverse correlation with the IL-6 concentration in the blood plasma. We also observed a positive correlation between 8-OH-dG and IL-6, TBA-RPs and IL-8, and TBA-RPs and TNFα. Therefore, the early abstinence period in patients with AD was characterized by a pronounced oxidative stress and inflammation. The obtained results expand the knowledge on the integrative contribution of oxidative stress and inflammatory factors to the AD pathogenesis and can be used in the development of new therapies.

Study of Neuroinflammation in the Rat Hippocampus during Ethanol Exposure and Pharmacological Correction with Azithromycin: New Data and Future Perspectives

With prolonged ethanol ingestion, disturbances in the emotional spectrum develop, and memory problems are noted. These symptoms could be mediated by the development of neurochemical changes in the hippocampus of the brain. Although there is evidence that hippocampus is vulnerable to chronic alcohol intoxication and that neuroinflammation and neurodegeneration develop in this brain region, the key molecular mechanisms have not been identified. The aim of the study was to investigate changes in the immune system in the periphery as well as in the hippocampus of rat brain during ethanol exposure and during pharmacological correction with azithromycin (AZM). Long-term ethanol exposure was modeled by injecting rats with a 20% ethanol solution (4 g/kg) for 4 weeks. General biochemical and clinical blood analysis was performed in animals. Expression levels of the cytokine genes (Il1β, Ccl2, Il6, Il11, Il13, Tnfα, Tgfβ), Toll-like receptor system genes (Tlr3, Tl4, Tlr7, Nfkb1, Hmgb1), and TLR system-related microRNA molecules (miR-182, miR-155-5p, miR-96-5p, miR-let-7b) were evaluated in the hippocampus. IL-1β protein content was also assessed in the hippocampus. Prolonged exposure to alcohol caused increase in the mRNA and protein levels of IL-1β, and decrease in the mRNA levels of Tnfα, Il11, Tlr3, and Tlr7. The contents of miRlet7b, miR96, and miR155 were downregulated in the hippocampus after long-term alcohol exposure. Elevated levels of THE Il1β mRNA and protein and Hmgb1 mRNA were maintained under conditions of ethanol abstinence. The Tlr3 mRNA levels were decreased after abstinence. Administration of AZM reduced the IL1β, TLR3, and HMGB1 mRNA levels under conditions of ethanol abstinence; and at higher doses of the drug decrease in the IL-1β protein levels in the hippocampus of rat brain was observed. Thus, the study provided new insights into the mechanisms of neuroinflammation in the hippocampus during prolonged exposure to ethanol and upon abstinence. The obtained results allowed us to suggest a number of tasks for further studies in this direction.

GET73 modulates lipopolysaccharide- and ethanol-induced increase in cytokine/chemokine levels in primary cultures of microglia of rat cerebral cortex

BACKGROUND

- Alcohol-induced pro-inflammatory activation might influence cellular and synaptic pathology, thus contributing to the behavioral phenotypes associated with alcohol use disorders. In the present study, the possible anti-inflammatory properties of N-[(4-trifluoromethyl)-benzyl]4-methoxybutyramide (GET73), a promising therapeutic agent for alcohol use disorder treatment, were evaluated in primary cultures of rat cortical microglia.

METHODS

- Primary cultures of cerebral cortex microglial cells were treated with 100 ng/ml lipopolysaccharide (LPS; 8 h, 37 °C) or 75 mM ethanol (EtOH; 4 days, 37 °C) alone or in the presence of GET73 (1-30 µM). At the end of the incubation period, multiparametric quantification of cytokines/chemokines was performed by using the xMAP technology and Luminex platform. Furthermore, cultured microglial cell viability following the treatment with EtOH and GET73, alone or in combination, has been measured by a colorimetric assay (i.e. MTT assay).

RESULTS

- GET73 (10 and 30 µM) partially or fully prevented the LPS-induced increase of IL-6, IL-1β, RANTES/CCL5 protein and MCP-1/CCL2 levels. On the contrary, GET73 failed to attenuate the TNF-α level increase induced by LPS. Furthermore, GET73 treatment (10-30 µM) significantly attenuated or prevented the EtOH-induced increase of TNF-α, IL-6, IL-1β and MCP-1/CCL2 levels. Finally, at all the concentrations tested (1-30 µM), the GET73 treatment did not alter the EtOH-induced reduction of microglial cell viability.

CONCLUSIONS

- The current results provide the first in vitro evidence of GET73 protective properties against EtOH-induced neuroinflammation. These data add more information on the complex and multifactorial profile of action of the compound, further supporting the significance of developing GET73 as a therapeutic tool for the treatment of individuals with alcohol use disorders.

Alcohol, HMGB1, and Innate Immune Signaling in the Brain

PURPOSE

Binge drinking (i.e., consuming enough alcohol to achieve a blood ethanol concentration of 80 mg/dL, approximately 4-5 drinks within 2 hours), particularly in early adolescence, can promote progressive increases in alcohol drinking and alcohol-related problems that develop into compulsive use in the chronic relapsing disease, alcohol use disorder (AUD). Over the past decade, neuroimmune signaling has been discovered to contribute to alcohol-induced changes in drinking, mood, and neurodegeneration. This review presents a mechanistic hypothesis supporting high mobility group box protein 1 (HMGB1) and Toll-like receptor (TLR) signaling as key elements of alcohol-induced neuroimmune signaling across glia and neurons, which shifts gene transcription and synapses, altering neuronal networks that contribute to the development of AUD. This hypothesis may help guide further research on prevention and treatment.

SEARCH METHODS

The authors used the search terms "HMGB1 protein," "alcohol," and "brain" across PubMed, Scopus, and Embase to find articles published between 1991 and 2023.

SEARCH RESULTS

The database search found 54 references in PubMed, 47 in Scopus, and 105 in Embase. A total of about 100 articles were included.

DISCUSSION AND CONCLUSIONS

In the brain, immune signaling molecules play a role in normal development that differs from their functions in inflammation and the immune response, although cellular receptors and signaling are shared. In adults, pro-inflammatory signals have emerged as contributing to brain adaptation in stress, depression, AUD, and neurodegenerative diseases. HMGB1, a cytokine-like signaling protein released from activated cells, including neurons, is hypothesized to activate pro-inflammatory signals through TLRs that contribute to adaptations to binge and chronic heavy drinking. HMGB1 alone and in heteromers with other molecules activates TLRs and other immune receptors that spread signaling across neurons and glia. Both blood and brain levels of HMGB1 increase with ethanol exposure. In rats, an adolescent intermittent ethanol (AIE) binge drinking model persistently increases brain HMGB1 and its receptors; alters microglia, forebrain cholinergic neurons, and neuronal networks; and increases alcohol drinking and anxiety while disrupting cognition. Studies of human postmortem AUD brain have found elevated levels of HMGB1 and TLRs. These signals reduce cholinergic neurons, whereas microglia, the brain's immune cells, are activated by binge drinking. Microglia regulate synapses through complement proteins that can change networks affected by AIE that increase drinking, contributing to risks for AUD. Anti-inflammatory drugs, exercise, cholinesterase inhibitors, and histone deacetylase epigenetic inhibitors prevent and reverse the AIE-induced pathology. Further, HMGB1 antagonists and other anti-inflammatory treatments may provide new therapies for alcohol misuse and AUD. Collectively, these findings suggest that restoring the innate immune signaling balance is central to recovering from alcohol-related pathology.

Effect of rifampicin on TLR4-signaling pathways in the nucleus accumbens of the rat brain during abstinence of long-term alcohol treatment

AIMS

The treatment with the antibiotic rifampicin (Rif) led to a decrease in the frequency of neurodegenerative pathologies. There are suggestions that the mechanism of action of Rif may be mediated by its effect on toll-like receptor (TLR)4-dependent pathways. We evaluated the expression status of TLR4-dependent genes during abstinence from long-term alcohol treatments in the nucleus accumbens (NAc) of the rat brain, and also studied the effects of Rif to correct these changes.

METHODS

The long-term alcohol treatment was performed by intragastric delivery of ethanol solution. At the end of alcohol treatment intraperitoneal injections of Rif (100 mg/kg) or saline were made. Extraction of the brain structures was performed on the 10th day of abstinence from alcohol. We used the SYBR Green qPCR method to quantitatively analyze the relative expression levels of the studied genes.

RESULTS

The long-term alcohol treatment promotes an increase in the level of TLR4 mRNA and mRNA of its endogenous ligand high-mobility group protein B1 during abstinence drop alcohol in NAc of rats. The use of Rif in our study led to a decrease in the increased expression of high-mobility group protein B1, Tlr4, and proinflammatory cytokine genes (Il1β, Il6) in the NAc of the rat brain during abstinence of long-term alcohol treatment. In addition, Rif administration increased the decreased mRNA levels of anti-inflammatory cytokines (Il10, Il11).

CONCLUSION

The data obtained indicate the ability of Rif to correct the mechanisms of the TLR4 system genes in the NAc of the rat brain during alcohol abstinence.

Novel paradigms for the gut-brain axis during alcohol withdrawal, withdrawal-associated depression, and craving in patients with alcohol use disorder

Introduction

Patients with alcohol use disorder (AUD) exhibit symptoms such as alcohol withdrawal, depression, and cravings. The gut-immune response may play a significant role in manifesting these specific symptoms associated with AUD. This study examined the role of gut dysfunction, proinflammatory cytokines, and hormones in characterizing AUD symptoms.

Methods

Forty-eight AUD patients [men (n = 34) and women (n = 14)] aged 23-63 years were grouped using the Clinical Institute Withdrawal Assessment of Alcohol Scale (CIWA) as clinically significant (CS-CIWA [score > 10] [n = 22]) and a clinically not-significant group (NCS-CIWA [score ≤ 10] [n = 26]). Clinical data (CIWA, 90-day timeline followback [TLFB90], and lifetime drinking history [LTDH]) and blood samples (for testing proinflammatory cytokines, hormones, and markers of intestinal permeability) were analyzed. A subset of 16 AUD patients was assessed upon admission for their craving tendencies related to drug-seeking behavior using the Penn-Alcohol Craving Score (PACS).

Results

CS-CIWA group patients exhibited unique and significantly higher levels of adiponectin and interleukin (IL)-6 compared to NCS-CIWA. In the CS group, there were significant and high effects of association for the withdrawal score with gut-immune markers (lipopolysaccharide [LPS], adiponectin, IL-6, and IL-8) and for withdrawal-associated depression with gut-immune markers (scored using MADRS with LPS, soluble cells of differentiation type 14 [sCD14], IL-6, and IL-8). Craving (assessed by PACS, the Penn-Alcohol Craving Scale) was significantly characterized by what could be described as gut dysregulation (LBP [lipopolysaccharide binding protein] and leptin) and candidate proinflammatory (IL-1β and TNF-α) markers. Such a pathway model describes the heavy drinking phenotype, HDD90 (heavy drinking days past 90 days), with even higher effects (R2 = 0.955, p = 0.006) in the AUD patients, who had higher ratings for cravings (PACS > 5).

Discussion

The interaction of gut dysfunction cytokines involved in both inflammation and mediating activity constitutes a novel pathophysiological gut-brain axis for withdrawal symptoms and withdrawal-associated depression and craving symptoms in AUD. AUD patients with reported cravings show a significant characterization of the gut-brain axis response to heavy drinking.

Trial registration

ClinicalTrials.gov, identifier: NCT# 00106106.

The effect of rifampicin on expression of the toll-like receptor system genes in the forebrain cortex of rats prenatally exposed to alcohol

Ethanol causes long-term changes in the toll-like receptor (TLR) system, promoting activation of neuroinflammation pathways. Alcohol use during pregnancy causes neuroinflammatory processes in the fetus; this can lead to the development of symptoms of fetal alcohol spectrum disorder (FASD). Our study has shown that prenatal alcohol exposure (PAE) induced long-term changes in the TLR system genes (Tlr3, Tlr4, Ticam, Hmgb1, cytokine genes) in the forebrain cortex of rat pups. Administration of rifampicin (Rif), which can reduce the level of pro-inflammatory mediators in various pathological conditions of the nervous system, normalized the altered expression level of the studied TLR system genes. This suggests that Rif can prevent the development of persistent neuroinflammatory events in the forebrain cortex of rat pups caused by dysregulation in the TLR system.

A review on the protective effect of active components in Antrodia camphorata against alcoholic liver injury

ETHNOPHARMACOLOGICAL RELEVANCE

Antrodia camphorata is a genus of wood-rot basidiomycete in the family Fomitopsidaceae. It is a valuable medicinal fungus in China that contains more than 78 kinds of active compounds. A. camphorata has good protection effects on the liver, especially on alcoholic liver injury (ALI).

AIM

This paper summarizes the complex occurrence and development of alcoholic liver disease (ALD). In addition, the effect of ALD on the intestine through the gut-liver axis is summarized. The protective mechanism of A. camphorata on ALI is reviewed to reveal its therapeutic potential, offering insights into future research.

MATERIALS AND METHODS

A comprehensive search in the literature was obtained from books and online databases such as Web of Science, Google Scholar, PubMed, Scopus, Science direct, ACS Publications and Baidu Scholar.

RESULTS

The pathogenesis of ALD mainly includes oxidative stress injury, intestinal microflora imbalance, inflammatory mediator injury and nutritional imbalance. A. camphorata contains rich active components (e.g. polysaccharides, triterpenoids, maleic and succinic acid derivatives, amino acids, superoxide dismutase, vitamins, lignin and sterols). These components have good antioxidant, anti-inflammatory and intestinal protection activities. Therefore, A. camphorata has a wide application in the prevention and treatment of ALI.

CONCLUSIONS

ALD develops from a mild disease to alcoholic hepatitis and cirrhosis, which is the main reason of global morbidity and mortality. At present, there is no effective drug for the treatment of ALD. A. camphorata, as a valuable medicinal fungus unique to Taiwan, has a great protective effect on the liver. It is expected to be an effective drug for ALI treatment. Although many studies have performed the protective effects of A. camphorata on ALI, its regulatory effects on the gut-liver axis of ALD patients need to be further explored.

The Interplay Between Gut Microbiota and Central Nervous System

This review highlights the relationships between gastrointestinal microorganisms and the brain. The gut microbiota communicates with the central nervous system through nervous, endocrine, and immune signalling mechanisms. Our brain can modulate the gut microbiota structure and function through the autonomic nervous system, and possibly through neurotransmitters which directly act on bacterial gene expression. In this context, oxidative stress is one the main factors involved in the dysregulation of the gut-brain axis and consequently in neurodegenerative disorders. Several factors influence the susceptibility to oxidative stress by altering the antioxidant status or free oxygen radical generation. Amongst these, of interest is alcohol, a commonly used substance which can negatively influence the central nervous system and gut microbiota, with a key role in the development of neurodegenerative disorder. The role of "psychobiotics" as a novel contrast strategy for preventing and treating disorders caused due to alcohol use and abuse has been investigated.

Interleukin-11 in Pathologies of the Nervous System

The study of the role of cytokines in various pathological conditions of the body is a topical area in modern biomedicine. Understanding the physiological roles played by cytokines will aid in finding applications for them as pharmacological agents in clinical practice. Interleukin 11 (IL-11) was discovered in 1990 in fibrocyte-like bone marrow stromal cells, but there has been increased interest in this cytokine in recent years. IL-11 has been shown to correct inflammatory pathways in the epithelial tissues of the respiratory system, where the main events occur during SARS-CoV-2 infection. Further research in this direction will probably support the use of this cytokine in clinical practice. The cytokine plays a significant role in the central nervous system; local expression by nerve cells has been shown. Studies show the involvement of IL-11 in the mechanisms of development of a number of pathologies of the nervous system, and therefore it seems relevant to generalize and analyze the experimental data obtained in this direction. This review summarizes information that shows the involvement of IL-11 in the mechanisms of development of brain pathologies. In the near future this cytokine will likely find clinical application for the correction of mechanisms that are involved in the formation of pathological conditions of the nervous system.

[Ginsenosides affect the system of Toll-like receptors in the brain of rats under conditions of long-term alcohol withdrawal]

Long-term alcohol consumption causes the development of neuroinflammation in various brain structures. One of the mechanisms involved in this process is the increased activity of TLR-signaling intracellular pathways. Studies confirm the ability of ginseng extract or its individual ginsenosides to reduce the increased activity of TLR-signaling pathways. The aim of our study was to study the effect of the amount of ginsenosides obtained from the extract of the Panax japonicus cell line on the state of the TLR-signaling system in the nucleus accumbens and hippocampus of the rat brain in a model of long-term alcohol consumption during alcohol withdrawal. The results of the study showed that ginsenosides were able to make changes in the TLR signaling system, which has been altered by long-term alcohol consumption. A significant effect of ginsenosides on the level of TLR3 and TLR4 mRNA in the nucleus accumbens was found, while in the hippocampus, ginsenosides significantly affected the level of TLR7 mRNA. The effect of ginsenosides on the level of mRNA of transcription factors and cytokines involved in TLR-signaling was evaluated. Thus, results of our study confirm that ginsenosides are able to influence the state of TLR-signaling pathways, but this effect is multidirectional in relation to different brain structures. In the future, it seems interesting to evaluate the role of individual ginsenosides in relation to genes of TLR-signaling, as well as the effect of ginsenosides on other brain structures.

TLR3 activation with poly I:C exacerbates escalated alcohol consumption in dependent male C57BL/6J mice

Background: Activation of TLR3 receptors, which are sensitive to viral infection, has emerged as a possible mechanism that increases alcohol intake in rodents.Objectives: These studies examined whether a history of ethanol dependence exacerbated the increase in drinking driven by the TLR3 agonist poly I:C.Methods: Male C57BL/6J mice (>10 per group) were given access to ethanol (20% v/v) 2 hours a day following a history of home cage drinking or after having been rendered ethanol-dependent using a chronic intermittent ethanol (CIE) vapor model. After testing multiple doses, a 5 mg/kg repeated poly I:C challenge was used to probe the effects of repeated immune challenge, alone or in conjunction with repeated cycles of CIE, on voluntary drinking. An ethanol (12% v/v) operant self-administration model was used to test the effects of poly I:C on stress-induced reinstatement of ethanol seeking and consumption.Results: Poly I:C in naive animals resulted in transient, modest increases in ethanol intake in the home cage and in self-administration (p < 0.05). However, poly I:C challenge resulted in sensitized stress-induced ethanol consumption and evoked a strong and persistent escalation of drinking in mice with a history of dependence (p < 0.05 for both).Conclusion: Activation of viral immune defense may affect ethanol consumption in dependence and sensitivity to future stressors. As patients who suffer from alcohol use disorder are at a heightened risk for viral infection, this interaction could generate risk factors for exacerbating behaviors associated with Alcohol Use Disorders via an immune mechanism.

[Effect of ethanol on platelet biology]

In recent years, interest in the study of platelets, significantly increased due to recent discoveries providing convincing evidence that their functions by are not limited to their participation in the blood coagulation mechanism. Many works are devoted to the study of the functional state of platelets under conditions of acute and chronic alcohol exposure. The results of such studies can be useful for the development of new markers of the degree of alcohol intoxication of the body for the subsequent choice of the method drug correction of disorders caused by acute or chronic alcohol effects. The review summarizes results in vivo and in vitro of studies performed during more than 60 years on the effect of ethanol on the biogenesis, number, morphology and biochemistry of platelets.

Effects of a Peripherally Restricted Hybrid Inhibitor of CB1 Receptors and iNOS on Alcohol Drinking Behavior and Alcohol-Induced Endotoxemia

Alcohol consumption is associated with gut dysbiosis, increased intestinal permeability, endotoxemia, and a cascade that leads to persistent systemic inflammation, alcoholic liver disease, and other ailments. Craving for alcohol and its consequences depends, among other things, on the endocannabinoid system. We have analyzed the relative role of central vs. peripheral cannabinoid CB1 receptors (CB1R) using a "two-bottle" as well as a "drinking in the dark" paradigm in mice. The globally acting CB1R antagonist rimonabant and the non-brain penetrant CB1R antagonist JD5037 inhibited voluntary alcohol intake upon systemic but not upon intracerebroventricular administration in doses that elicited anxiogenic-like behavior and blocked CB1R-induced hypothermia and catalepsy. The peripherally restricted hybrid CB1R antagonist/iNOS inhibitor S-MRI-1867 was also effective in reducing alcohol consumption after oral gavage, while its R enantiomer (CB1R inactive/iNOS inhibitor) was not. The two MRI-1867 enantiomers were equally effective in inhibiting an alcohol-induced increase in portal blood endotoxin concentration that was caused by increased gut permeability. We conclude that (i) activation of peripheral CB1R plays a dominant role in promoting alcohol intake and (ii) the iNOS inhibitory function of MRI-1867 helps in mitigating the alcohol-induced increase in endotoxemia.

[The TLR3 induction increases content of interferons in rat's brain by TRAIL signaling during long-term alcoholization]

The pathogenetic mechanisms associated with alcohol use include dysregulation of the innate immune system mechanisms in the brain. TLR3 expression is increased in the postmortem material of the prefrontal cortex of humans. An increase in the TLR3 signaling activity leads to the induction of interferons (IFN). IFN are associated with depressive symptoms and, therefore, may play a role in the pathogenesis of alcoholism; however, the exact mechanisms of intracellular signaling mediated by the influence of ethanol are not fully elucidated and their study was the purpose of this work. The experimental results showed that ethanol and the TLR3 agonist Poly (I:C) increased the content of TLR3, IFNβ, and IFNγ mRNA in the prefrontal cortex. In addition, expression of the TRAIL encoding gene also increased, and this increase positively correlaed with the mRNA content of TLR3, IFNβ and IFNγ both under alcoholization conditions and after injections of the TLR3 agonist. The data obtained may indicate that alcoholization is able to activate TLR3-TRAIL-IFN-signaling in the prefrontal cortex of the brain.

The Immune System through the Lens of Alcohol Intake and Gut Microbiota

The human gut is the largest organ with immune function in our body, responsible for regulating the homeostasis of the intestinal barrier. A diverse, complex and dynamic population of microorganisms, called microbiota, which exert a significant impact on the host during homeostasis and disease, supports this role. In fact, intestinal bacteria maintain immune and metabolic homeostasis, protecting our organism against pathogens. The development of numerous inflammatory disorders and infections has been linked to altered gut bacterial composition or dysbiosis. Multiple factors contribute to the establishment of the human gut microbiota. For instance, diet is considered as one of the many drivers in shaping the gut microbiota across the lifetime. By contrast, alcohol is one of the many factors that disrupt the proper functioning of the gut, leading to a disruption of the intestinal barrier integrity that increases the permeability of the mucosa, with the final result of a disrupted mucosal immunity. This damage to the permeability of the intestinal membrane allows bacteria and their components to enter the blood tissue, reaching other organs such as the liver or the brain. Although chronic heavy drinking has harmful effects on the immune system cells at the systemic level, this review focuses on the effect produced on gut, brain and liver, because of their significance in the link between alcohol consumption, gut microbiota and the immune system.