Sophie Leclercq

Intestinal permeability, gut-bacterial dysbiosis, and behavioral markers of alcohol-dependence severity

Significance Alcohol-dependent subjects frequently develop emotional symptoms that contribute to the persistence of alcohol drinking. These subjects are also characterized by gastrointestinal disturbances. In this study, we showed that alcohol-dependent subjects with altered intestinal permeability had also altered gut-microbiota composition and activity and remained with high scores of depression, anxiety, and alcohol craving after a short-term detoxification program. These results are consistent with the existence of a gut–brain axis in alcohol dependence, in which the gut microbiota could alter the gut-barrier function and influence behavior in alcohol dependence. Therefore, this study opens a previously unidentified field of research for the treatment and the management of alcohol dependence, targeting the gut microbiota. Alcohol dependence has traditionally been considered a brain disorder. Alteration in the composition of the gut microbiota has recently been shown to be present in psychiatric disorders, which suggests the possibility of gut-to-brain interactions in the development of alcohol dependence. The aim of the present study was to explore whether changes in gut permeability are linked to gut-microbiota composition and activity in alcohol-dependent subjects. We also investigated whether gut dysfunction is associated with the psychological symptoms of alcohol dependence. Finally, we tested the reversibility of the biological and behavioral parameters after a short-term detoxification program. We found that some, but not all, alcohol-dependent subjects developed gut leakiness, which was associated with higher scores of depression, anxiety, and alcohol craving after 3 wk of abstinence, which may be important psychological factors of relapse. Moreover, subjects with increased gut permeability also had altered composition and activity of the gut microbiota. These results suggest the existence of a gut–brain axis in alcohol dependence, which implicates the gut microbiota as an actor in the gut barrier and in behavioral disorders. Thus, the gut microbiota seems to be a previously unidentified target in the management of alcohol dependence.

Role of intestinal permeability and inflammation in the biological and behavioral control of alcohol-dependent subjects

BACKGROUND AND AIMS Mood and cognition alterations play a role in the motivation for alcohol-drinking. Lipopolysaccharides are known to stimulate inflammation that was shown to induce mood and cognitive changes in rodents and humans. Enhanced intestinal permeability and elevated blood LPS characterize alcohol-dependent mice. However, no data have been published in non-cirrhotic humans. Our first goal was to test whether intestinal permeability, blood LPS and cytokines are increased in non-cirrhotic alcohol-dependent subjects before withdrawal and if they recover after withdrawal. Our second goal was to test correlations between these biochemical and the behavioral variables to explore the possibility of a role for a gut-brain interaction in the development of alcohol-dependence. METHODS Forty alcohol-dependent-subjects hospitalized for a 3-week detoxification program were tested at onset (T1) and end (T2) of withdrawal and compared for biological and behavioral markers with 16 healthy subjects. Participants were assessed for gut permeability, systemic inflammation (LPS, TNFα, IL-6, IL-10, hsCRP) and for depression, anxiety, alcohol-craving and selective attention. RESULTS Intestinal permeability and LPS were largely increased in alcohol-dependent subjects at T1 but recovered completely at T2. A low-grade inflammation was observed at T1 that partially decreased during withdrawal. At T1, pro-inflammatory cytokines were positively correlated with craving. At T2 however, the anti-inflammatory cytokine IL-10 was negatively correlated with depression, anxiety and craving. CONCLUSION Leaky gut and inflammation were observed in non-cirrhotic alcohol-dependent subjects and inflammation was correlated to depression and alcohol-craving. This suggests that the gut-brain axis may play a role in the pathogenesis of alcohol-dependence.

Role of inflammatory pathways, blood mononuclear cells, and gut-derived bacterial products in alcohol dependence

BACKGROUND Inflammation might play a role in the development of several psychiatric diseases. However, the origins of processes that mediate inflammation are unknown. We previously reported increased intestinal permeability, elevated blood lipopolysaccharide levels, and low-grade systemic inflammation associated with psychological symptoms of alcohol dependence in alcohol-dependent subjects. In this study, we tested inflammatory responses of peripheral blood mononuclear cells (PBMCs) to gut-derived bacterial products during detoxification and the relationship to alcohol craving. METHODS In 63 actively drinking noncirrhotic alcohol-dependent subjects, testing was performed at the beginning (day 2) and end (day 18) of alcohol detoxification and compared with testing in 14 healthy subjects. Activation of various intracellular signaling pathways by gut-derived bacterial products was analyzed by quantitative polymerase chain reaction, Western blotting, and DNA binding assays (for transcription factors). Toll-like receptor activation was assessed by cell cultures. RESULTS In addition to lipopolysaccharides, we showed that peptidoglycans may also cross the gut barrier to reach the systemic circulation. Both activate their respective Toll-like receptors in peripheral blood mononuclear cells. Chronic alcohol consumption inhibited the nuclear factor kappa B proinflammatory cytokine pathway but activated the mitogen-activated protein kinase/activator protein 1 pathway, together with the inflammasome complex. This activity resulted in increased messenger RNA and plasma levels of interleukin (IL)-8, IL-1β, and IL-18. Activated proinflammatory pathways, in particular, IL-8 and IL-1β, were positively correlated with alcohol consumption and alcohol-craving scores. Short-term alcohol withdrawal was associated with the recovery of lipopolysaccharide-dependent receptors but not peptidoglycan-dependent receptors. CONCLUSIONS Lipopolysaccharides and peptidoglycans from the gut microbiota stimulate specific inflammatory pathways in peripheral blood mononuclear cells that are correlated with alcohol craving.

Low-dose penicillin in early life induces long-term changes in murine gut microbiota, brain cytokines and behavior

There is increasing concern about potential long-term effects of antibiotics on childrens health. Epidemiological studies have revealed that early-life antibiotic exposure can increase the risk of developing immune and metabolic diseases, and rodent studies have shown that administration of high doses of antibiotics has long-term effects on brain neurochemistry and behaviour. Here we investigate whether low-dose penicillin in late pregnancy and early postnatal life induces long-term effects in the offspring of mice. We find that penicillin has lasting effects in both sexes on gut microbiota, increases cytokine expression in frontal cortex, modifies blood–brain barrier integrity and alters behaviour. The antibiotic-treated mice exhibit impaired anxiety-like and social behaviours, and display aggression. Concurrent supplementation with Lactobacillus rhamnosus JB-1 prevents some of these alterations. These results warrant further studies on the potential role of early-life antibiotic use in the development of neuropsychiatric disorders, and the possible attenuation of these by beneficial bacteria.

The loss of metabolic control on alcohol drinking in heavy drinking alcohol-dependent subjects

Background Most physiological studies interested in alcohol-dependence examined ethanol as a pharmacological agent rather than a nutrient. We conducted two studies, which assessed the metabolic and endocrine factors involved in the regulation of alcohol and nutrient intake in alcohol-dependent (AD) subjects. We also examined the potential role of a disruption in energy balance in alcohol-dependence. Methods and Results In Study-1, quantitative dietetic interviews of eating and drinking habits were conducted with 97 AD subjects. The population was split around a median alcohol intake value of 12.5 kcal/kg/day. The results showed that the “low alcohol” drinking AD subjects had high Body Mass Index (BMI) and Fat Mass (FM) and alcohol intake was compensated for by a decrease in non-alcoholic intakes. “High alcohol” drinking AD subjects, on the other hand, had low BMI and FM and the total caloric intakes were largely above norms. In Study-2, 24 AD inpatients were submitted to dietetic interviews, calorimetry and blood samplings for the measurement of biomarkers of the regulation of metabolism and satiety, on day 2, 5 and 16 of abstinence. These patients were compared with 20 controls matched for age and gender. We observed in AD patients an increase in cortisol, leptin and PYY plasma levels and a decrease in ghrelin, which might explain the observed decrease in non-alcoholic intakes. However, alcoholic and non-alcoholic intakes correlated positively with basal metabolism and negatively with leptin and leptin/BMI. Conclusion For individuals consuming below12.5 kcal/kg/day of alcohol, alcohol intake is compensated for by a decrease in non-alcoholic nutrient intakes, probably due to changes in metabolic and satiety factors. For individuals consuming above 12.5 kcal/kg/day of alcohol, alcohol accelerates metabolism and decreases fat mass and leptin levels, and the total caloric intake largely exceeds norms. A dual model for regulation of energy intake in AD subjects is proposed.

The link between inflammation, bugs, the intestine and the brain in alcohol dependence

In recent years, some new processes have been proposed to explain how alcohol may influence behavior, psychological symptoms and alcohol seeking in alcohol-dependent subjects. In addition to its important effect on brain and neurotransmitters equilibrium, alcohol abuse also affects peripheral organs including the gut. By yet incompletely understood mechanisms, chronic alcohol abuse increases intestinal permeability and alters the composition of the gut microbiota, allowing bacterial components from the gut lumen to reach the systemic circulation. These gut-derived bacterial products are recognized by immune cells circulating in the blood or residing in target organs, which consequently synthesize and release pro-inflammatory cytokines. Circulating cytokines are considered important mediators of the gut–brain communication, as they can reach the central nervous system and induce neuroinflammation that is associated with change in mood, cognition and drinking behavior. These observations support the possibility that targeting the gut microbiota, by the use of probiotics or prebiotics, could restore the gut barrier function, reduce systemic inflammation and may have beneficial effect in treating alcohol dependence and in reducing alcohol relapse.

A role for the peripheral immune system in the development of alcohol use disorders

&NA; Preclinical studies have largely supported that alcohol‐consumption induces the development of an important neuro‐inflammation and this neuro‐inflammation contributes to alcohol‐drinking behaviors, notably through TLR4 and LPS related mechanisms. The neuro‐inflammation originates from a direct interaction of ethanol with the neuronal and immune brain cells, but also from the generation of an inflammation at the periphery. Ethanol in particular interacts with the intestine to develop a gut dysbiosis and an increase in gut permeability, that allows the liberation of bacterial fragments to the systemic circulation and induces a pro‐inflammatory response in the systemic circulation and peripheral organs, and in particular the liver. Peripheral cytokines or activated peripheral cells may cross the blood‐brain barrier and activate neuro‐inflammation. In humans, peripheral inflammation and intestinal dysbiosis are related to symptoms of alcohol use disorders (AUD), such as depression, anxiety and alcohol‐craving, However, the dysbiosis, could also participate in a different manner to the symptomatology of the addiction, possibly by interacting with the stress system, by interfering with the sleep processes and altering the abilities for social interactions. The role of the gut suggests that interventions with probiotics or prebiotics might in the future be of interest for the treatment of the addiction. This article is part of the Special Issue entitled “Alcoholism”. HighlightsA review on peripheral sources of inflammation in AUD is proposed.The intestine appears as a major source of peripheral inflammation.Other peripheral sources of inflammation like the gut‐wall or the liver are also suggested.Mechanisms for transduction of peripheral inflammation to the CNS are evoked.Hypotheses regarding the relation between peripheral inflammation and the symptoms of AUD is are described.

Pathogenesis of Streptococcus urinary tract infection depends on bacterial strain and β-hemolysin/cytolysin that mediates cytotoxicity, cytokine synthesis, inflammation and virulence

Streptococcus agalactiae can cause urinary tract infection (UTI) including cystitis and asymptomatic bacteriuria (ABU). The early host-pathogen interactions that occur during S. agalactiae UTI and subsequent mechanisms of disease pathogenesis are poorly defined. Here, we define the early interactions between human bladder urothelial cells, monocyte-derived macrophages, and mouse bladder using uropathogenic S. agalactiae (UPSA) 807 and ABU-causing S. agalactiae (ABSA) 834 strains. UPSA 807 adhered, invaded and killed bladder urothelial cells more efficiently compared to ABSA 834 via mechanisms including low-level caspase-3 activation, and cytolysis, according to lactate dehydrogenase release measures and cell viability. Severe UPSA 807-induced cytotoxicity was mediated entirely by the bacterial β-hemolysin/cytolysin (β-H/C) because an β-H/C-deficient UPSA 807 isogenic mutant, UPSA 807ΔcylE, was not cytotoxic in vitro; the mutant was also significantly attenuated for colonization in the bladder in vivo. Analysis of infection-induced cytokines, including IL-8, IL-1β, IL-6 and TNF-α in vitro and in vivo revealed that cytokine and chemokine responses were dependent on expression of β-H/C that also elicited severe bladder neutrophilia. Thus, virulence of UPSA 807 encompasses adhesion to, invasion of and killing of bladder cells, pro-inflammatory cytokine/chemokine responses that elicit neutrophil infiltration, and β-H/C-mediated subversion of innate immune-mediated bacterial clearance from the bladder.

A dysbiotic subpopulation of alcohol-dependent subjects

The vast majority of studies that assessed the importance of biological factors for the development of psychiatric disorders focused on processes occurring at the brain level. Alcohol-dependence is a very frequent psychiatric disorder where psycho-pharmacological interventions are only of moderate efficacy. Our laboratory has recently described that a subpopulation of alcohol-dependent subjects, that accounted for approximately 40% of individuals tested, presented with an increased intestinal permeability, with a dysbiosis, with alterations in the metabolomic content of faeces - that could play a role in the increased permeability - and finally with a more severe profile of alcohol-dependence than the other non-dysbiotic subpopulation. In this addendum, we discuss the implications of our observations for the pathophysiology of alcohol dependence where we try to discriminate which addiction dimensions are likely related to the gut microbiota alterations and whether these alterations are the cause or the consequence of drinking habits.

Intestinal dysbiosis and permeability: the yin and yang in alcohol dependence and alcoholic liver disease.

Alcohol dependence and alcoholic liver disease represent a major public health problem with substantial morbidity and mortality. By yet incompletely understood mechanisms, chronic alcohol abuse is associated with increased intestinal permeability and alterations of the gut microbiota composition, allowing bacterial components, bacteria, and metabolites to reach the portal and the systemic circulation. These gut-derived bacterial products are recognized by immune cells circulating in the blood or residing in remote organs such as the liver leading to the release of pro-inflammatory cytokines which are considered important mediators of the liver-gut-brain communication. Although circulating cytokines are likely not the sole factors involved, they can induce liver inflammation/damage and reach the central nervous system where they favor neuroinflammation which is associated with change in mood, cognition, and drinking behavior. In this review, the authors focus on the current evidence describing the changes that occur in the intestinal microbiota with chronic alcohol consumption in conjunction with intestinal barrier breakdown and inflammatory changes sustaining the concept of a gut-liver-brain axis in the pathophysiology of alcohol dependence and alcoholic liver disease.