Altered Intestinal Barrier Function Research Articles

Unraveling the role of gut microbiota by fecal microbiota transplantation in rat model of kidney stone disease

Emerging research on the microbiome highlights the significant role of gut health in the development of kidney stones, indicating that an imbalance in gut bacteria or dysbiosis can influence the formation of stones by altering oxalate metabolism and urinary metabolite profiles. In particular, the overabundance of specific bacteria such as Enterococcus and Oxalobacter spp., which are known to affect oxalate absorption, is observed in patients with urolithiasis. This study investigates the effects of gut dysbiosis on urolithiasis through fecal microbiota transplantation (FMT) from patients to rats and its impact on urinary mineral excretion and stone formation. Fecal samples from eight patients with calcium oxalate stones and ten healthy volunteers were collected to assess the gut microbiome. These samples were then transplanted to antibiotic-pretreated Wistar rats for a duration of four weeks. After transplantation, we evaluated changes in the fecal gut microbiome profile, urinary mineral excretion rates, and expression levels of intestinal zonula occluden-1 (ZO-1), SLC26A6 and renal NF-κB. In humans, patients with urolithiasis exhibited increased urinary calcium and oxalate levels, along with decreased citrate excretion and increased urinary supersaturation index. The fecal microbiota showed a notable abundance of Bacteroidota. In rodents, urolithiasis-FMT rats showed urinary disturbances similar to patients, including elevated pH, oxalate level, and supersaturation index, despite negative renal pathology. In addition, a slight elevation in the expression of renal NF-κB, a significant intestinal SLC26A6, and a reduction in ZO-1 expression were observed. The gut microbiome of urolithiasis-FMT rats showed an increased abundance of Bacteroidota, particularly Muribaculaceae, compared to their healthy FMT counterparts. In conclusion, the consistent overabundance of Bacteroidota in both urolithiasis patients and urolithiasis-FMT rats is related to altered intestinal barrier function, hyperoxaluria, and renal inflammation. These findings suggest that gut dysbiosis, characterized by an overgrowth of Bacteroidota, plays a crucial role in the pathogenesis of calcium oxalate urolithiasis, underscoring the potential of targeting the gut microbiota as a therapeutic strategy.

Sex-dependent effects of a high fat diet on metabolic disorders, intestinal barrier function and gut microbiota in mouse

Obesity is often associated with sex-dependent metabolic complications, in which altered intestinal barrier function and gut microbiota contribute. We aimed to characterize in mice the sex-dependent effects of a high fat diet on these parameters. Male and female C57BL/6 mice received a standard (SD) or high fat diet (HFD; 60% kcal from fat) during 14 weeks (W14). Body composition, glucose tolerance, insulin sensitivity, intestinal permeability, colonic expression of 44 genes encoding factors involved in inflammatory response and gut barrier function, cecal microbiota, plasma adipokines and white adipose tissue response have been assessed. Both male and female HFD mice exhibited an increase of body weight and fat mass gain and glucose intolerance compared to SD mice. However, only male HFD mice tended to develop insulin resistance associated to increased Tnfα and Ccl2 mRNA expression in perigonadal adipose tissue. By contrast, only female HFD mice showed significant intestinal hyperpermeability that was associated with more markedly altered colonic inflammatory response. Cecal microbiota richness was markedly reduced in both sexes (Observed species) with sex-dependent modifications at the phyla or family level, e.g. decreased relative abundance of Bacillota and Lachnospiraceae in females, increased of Bacteroidaceae in males. Interestingly, some of these microbiota alterations were correlated with peripheral metabolic and inflammatory markers. In conclusions, male and female mice exhibit different responses to a high fat diet with specific changes of gut microbiota, intestinal barrier function, colonic and white adipose tissue inflammation, metabolic markers and body weight gain. The underlying mechanisms should be deciphered in further investigations.

Gut microbiota promotes macrophage M1 polarization in hepatic sinusoidal obstruction syndrome via regulating intestinal barrier function mediated by butyrate

ABSTRACT Background The intestinal-liver axis is associated with various liver diseases. Here, we verified the role of the gut microbiota and macrophage activation in the progression of pyrrolizidine alkaloids-induced hepatic sinusoidal obstruction syndrome (PA-HSOS), and explored the possible mechanisms and new treatment options. Methods The HSOS murine model was induced by gavage of monocrotaline (MCT). An analysis of 16S ribosomal DNA (16S rDNA) of the feces was conducted to determine the composition of the fecal microbiota. Macrophage clearance, fecal microbiota transplantation (FMT), and butyrate supplementation experiments were used to assess the role of intestinal flora, gut barrier, and macrophage activation and to explore the relationships among these three variables. Results Activated macrophages and low microflora diversity were observed in HSOS patients and murine models. Depletion of macrophages attenuated inflammatory reactions and apoptosis in the mouse liver. Moreover, compared with control-FMT mice, the exacerbation of severe liver injury was detected in HSOS-FMT mice. Specifically, butyrate fecal concentrations were significantly reduced in HSOS mice, and administration of butyrate could partially alleviated liver damage and improved the intestinal barrier in vitro and in vivo. Furthermore, elevated lipopolysaccharides in the portal vein and high proportions of M1 macrophages in the liver were also detected in HSOS-FMT mice and mice without butyrate treatment, which resulted in severe inflammatory responses and further accelerated HSOS progression. Conclusions These results suggested that the gut microbiota exacerbated HSOS progression by regulating macrophage M1 polarization via altered intestinal barrier function mediated by butyrate. Our study has identified new strategies for the clinical treatment of HSOS.

Understanding Predictors of Crohn’s Disease: Determinants of Altered Barrier Function in Pre-Disease Phase of Crohn’s Disease

Abstract The pathogenesis of Crohn’s disease (CD) remains unknown. The current working theory is that genetic susceptibility influences host–microbe interactions, resulting in chronic inflammation. Case–control studies fail to explain the triggers or pathogenesis of the disease, notably due to confounding factors in patients with established disease. Investigating the pre-disease phase of CD improves the capacity to assess these confounding factors and enables us to identify biomarkers associated with increased risk of CD. The Crohn’s Colitis Canada-Genes, Environment, Microbial (CCC-GEM) project is a prospective cohort of healthy first-degree relatives of patients with CD, allowing us to interrogate the pre-disease phase of CD. The CCC-GEM Project has led to the identification of several demographic, serological, and microbiome composition markers associated with an increased risk of disease in pre-clinical participants. Notably, altered intestinal barrier function, as measured by the fractional urinary excretion of lactulose mannitol ratio, is associated with a significantly increased risk of CD. We review the intrinsic and external factors that are associated with altered intestinal barrier integrity, including genetic risk, subclinical inflammation, serum proteomics, intestinal microbiome composition, and environmental components, such as diet and lifestyle. Providing insights into the factors and mechanisms of altered barrier function contributes to our understanding of the pathogenic mechanisms of CD. These advances may aid in developing strategies for preventing disease in high-risk individuals. Further research and personalized strategies are needed to optimize these mitigation strategies for individuals at-risk for CD.

Centrally administered GLP-1 analogue improves intestinal barrier function through the brain orexin and the vagal pathway in rats

Leaky gut, an altered intestinal barrier function, has been described in many diseases such as irritable bowel syndrome (IBS). We have recently demonstrated that orexin in the brain blocked leaky gut in rats, suggesting that the brain plays a role in regulation of intestinal barrier function. In the present study, we tried to clarify whether GLP-1 acts centrally in the brain to regulate intestinal barrier function and its mechanism. Colonic permeability was estimated in vivo by quantifying the absorbed Evans blue in colonic tissue in rats. Intracisternal injection of GLP-1 analogue, liraglutide dose-dependently abolished increased colonic permeability in response to lipopolysaccharide. Either atropine or surgical vagotomy blocked the central GLP-1-induced improvement of colonic hyperpermeability. Intracisternal GLP-1 receptor antagonist, exendin (9–39) prevented the central GLP-1-induced blockade of colonic hyperpermeability. In addition, intracisternal injection of orexin receptor antagonist, SB-334867 blocked the GLP-1-induced improvement of intestinal barrier function. On the other hand, subcutaneous liraglutide also improved leaky gut but larger doses of liraglutide were needed to block it. In addition, neither atropine nor vagotomy blocked subcutaneous liraglutide-induced improvement of leaky gut, suggesting that central or peripheral GLP-1 system works separately to improve leaky gut in a vagal-dependent or independent manner, respectively. These results suggest that GLP-1 acts centrally in the brain to reduce colonic hyperpermeability. Brain orexin signaling and the vagal cholinergic pathway play a vital role in the process. We would therefore suggest that activation of central GLP-1 signaling may be useful for leaky gut-related diseases such as IBS.

Gut-Kidney Axis Investigations in Animal Models of Chronic Kidney Disease.

Chronic kidney disease (CKD) is an incurable disease in which renal function gradually declines, resulting in no noticeable symptoms during the early stages and a life-threatening disorder in the latest stage. The changes that accompany renal failure are likely to influence the gut microbiota, or the ecosystem of micro-organisms resident in the intestine. Altered gut microbiota can display metabolic changes and become harmful to the host. To study the gut–kidney axis in vivo, animal models should ideally reproduce the disorders affecting both the host and the gut microbiota. Murine models of CKD, but not dog, manifest slowed gut transit, similarly to patient. Animal models of CKD also reproduce altered intestinal barrier function, as well as the resulting leaky gut syndrome and bacterial translocation. CKD animal models replicate metabolic but not compositional changes in the gut microbiota. Researchers investigating the gut–kidney axis should pay attention to the selection of the animal model (disease induction method, species) and the setting of the experimental design (control group, sterilization method, individually ventilated cages) that have been shown to influence gut microbiota.

Intestinal Barrier Function in the Pathogenesis of Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. The mechanisms involved in NAFLD onset are complicated and multifactorial. Recent literature has indicated that altered intestinal barrier function is related to the occurrence and progression of liver disease. The intestinal barrier is important for absorbing nutrients and electrolytes and for defending against toxins and antigens in the enteric environment. Major mechanisms by which the intestinal barrier influences the development of NAFLD involve the altered epithelial layer, decreased intracellular junction integrity, and increased intestinal barrier permeability. Increased intestinal permeability leads to luminal dysbiosis and allows the translocation of pathogenic bacteria and metabolites into the liver, inducing inflammation, immune response, and hepatocyte injury in NAFLD. Although research has been directed to NAFLD in recent decades, the pathophysiological changes in NAFLD initiation and progression are still not completely understood, and the therapeutic targets remain limited. A deeper understanding on the correlation between NAFLD pathogenesis and intestinal barrier regulation must be attained. Therefore, in this review, the components of the intestinal barrier and their respective functions and disruptions during the progression of NAFLD are discussed.

What is the leaky gut? Clinical considerations in humans.

To review the components of the intestinal barrier, the practical measurements of intestinal permeability, and the clinical conditions associated with altered intestinal barrier function, and to summarize the effects of dietary substances that fortify or weaken the intestinal barrier. The intestinal barrier includes surface mucus, epithelial layer, and immune defense mechanisms. Transport across the epithelium may result from increased paracellular transport, apoptosis, or transcellular permeability. Assessment of the intestinal barrier requires measurements beyond the transport across the epithelial layer or the measurement of tight junction expression. Barrier function is most meaningfully tested in vivo using orally administered probe molecules; other approaches are performed in vitro using mucosal biopsies from humans, or exposing colonic mucosa from rats or mice or cell layers to extracts of colonic mucosa or stool from patients. Dietary factors can influence intestinal leakiness: fortifying the barrier with vitamins A and D, zinc, short-chain fatty acids, methionine, glutamine, and probiotics; weakening of the barrier has been reported with fat, bile acids, emulsifiers, and gliadin. Intestinal mucosal leakiness in 'stress' disorders such as major burns is reversed with enteral glutamine. Inflammatory or ulcerating intestinal diseases result in leakiness of the gut barrier; however, no such disease has been cured by simply normalizing intestinal barrier function. Similarly, it is still unproven that restoring barrier function (reversing 'leaky gut') can ameliorate clinical manifestations in nonulcerating gastrointestinal disease or systemic or neurological diseases. On the other hand, dietary and enteral interventions can fortify the intestinal barrier in stress-associated states.

Somatization in patients with predominant diarrhoea irritable bowel syndrome: the role of the intestinal barrier function and integrity

BackgroundIrritable bowel syndrome (IBS) is characterised by gastrointestinal (GI) and psychological symptoms (e.g., depression, anxiety, and somatization). Depression and anxiety, but not somatization, have already been associated with altered intestinal barrier function, increased LPS, and dysbiosis. The study aimed to investigate the possible link between somatization and intestinal barrier in IBS with diarrhoea (IBS-D) patients.MethodsForty-seven IBS-D patients were classified as having low somatization (LS = 19) or high somatization (HS = 28) according to the Symptom Checklist-90-Revised (SCL-90-R), (cut-off score = 63). The IBS Severity Scoring System (IBS-SSS) and the Gastrointestinal Symptom Rating Scale (GSRS) questionnaires were administered to evaluate GI symptoms. The intestinal barrier function was studied by the lactulose/mannitol absorption test, faecal and serum zonulin, serum intestinal fatty-acid binding protein, and diamine oxidase. Inflammation was assessed by assaying serum Interleukins (IL-6, IL-8, IL-10), and tumour necrosis factor-α. Dysbiosis was assessed by the urinary concentrations of indole and skatole and serum lipopolysaccharide (LPS). All data were analysed using a non-parametric test.ResultsThe GI symptoms profiles were significantly more severe, both as a single symptom and as clusters of IBS-SSS and GSRS, in HS than LS patients. This finding was associated with impaired small intestinal permeability and increased faecal zonulin levels. Besides, HS patients showed significantly higher IL-8 and lowered IL-10 concentrations than LS patients. Lastly, circulating LPS levels and the urinary concentrations of indole were higher in HS than LS ones, suggesting a more pronounced imbalance of the small intestine in the former patients.ConclusionsIBS is a multifactorial disorder needing complete clinical, psychological, and biochemical evaluations.Trial registration: https://clinicaltrials.gov/ct2/show/NCT03423069.

Colitis Linked to Endoplasmic Reticulum Stress Induces Trypsin Activity Affecting Epithelial Functions.

Intestinal epithelial cells [IECs] from inflammatory bowel disease [IBD] patients exhibit an excessive induction of endoplasmic reticulum stress [ER stress] linked to altered intestinal barrier function and inflammation. Colonic tissues and the luminal content of IBD patients are also characterized by increased serine protease activity. The possible link between ER stress and serine protease activity in colitis-associated epithelial dysfunctions is unknown. We aimed to study the association between ER stress and serine protease activity in enterocytes and its impact on intestinal functions. The impact of ER stress induced by Thapsigargin on serine protease secretion was studied using either human intestinal cell lines or organoids. Moreover, treating human intestinal cells with protease-activated receptor antagonists allowed us to investigate ER stress-resulting molecular mechanisms that induce proteolytic activity and alter intestinal epithelial cell biology. Colonic biopsies from IBD patients exhibited increased epithelial trypsin-like activity associated with elevated ER stress. Induction of ER stress in human intestinal epithelial cells displayed enhanced apical trypsin-like activity. ER stress-induced increased trypsin activity destabilized intestinal barrier function by increasing permeability and by controlling inflammatory mediators such as C-X-C chemokine ligand 8 [CXCL8]. The deleterious impact of ER stress-associated trypsin activity was specifically dependent on the activation of protease-activated receptors 2 and 4. Excessive ER stress in IECs caused an increased release of trypsin activity that, in turn, altered intestinal barrier function, promoting the development of inflammatory process.

Zinc deficiency induces epithelial barrier dysfunction and altered intestinal ion transport in novel murine model of Shigella flexneri diarrhea

Background: Zinc (Zn) deficiency has been linked with etiology for wide range of gastrointestinal diseases. Although low serum Zn has been associated with diarrhea and growth retardation, however the underlying mechanism of Zn deficiency aggravating the diarrheal manifestation remains elusive. Here, we have studied the physiological cascade elicited during Zn deficiency in both colonic cell lines and murine model leading to altered intestinal barrier function and ion transport. Methods and materials: T84 were grown onto transwell inserts in Zn deficient conditions for measurements of transepithelial electrical resistance (TER) and short-circuit current (Isc). Adult BALB/c mice fed with Zn deficient diet for 14 days and were intraperitoneally challenged with virulent S.flexneri 2a for following assessments of electrophysiological properties of the colonized colon in ussing chamber. Colonization evaluation from feces and colon homogenate were further analyzed for bacterial translocation assay. Results: Zn deficient cells infected with Shigella flexneri 2a showed significant increase in transmigration of the pathogens (6.58 ± 0.13 vs 7.98 ± 0.23 log10 CFU/ml) for 6 h post infection along with poor formation of transepithelial resistance (1014 + 165 Ωcm2 vs 3663 + 293 Ωcm2). Ultrastructure of T84 cells grown in Zn deficient medium showed widened TJ complex and due to few membrane fusion proteins showing distorted TJ morphology and shorthened microvilli. Immunoblotting analysis further showed increased expression of Claudin-2 leaky tight junction protein in Zn deficient cells by modulating ERK dependent pathways. Following studies with Ussing chambers further demonstrated increase in Ca2+ dependent electrogenic Cl− secretion in Zn deficient cells. In vivo studies showed Zn deficient condition in mice increased bacterial translocation, colonization, bacterial shedding and pronounced disruption in intestinal permeability. Conclusion: Our results suggest that in T84 cells and murine of Shigellosis, Zn deficiency causes (1) pronounced barrier dysfunction and (2) altered Cl− secretion leading to heightened diarrheal pathogenesis thus linking micronutrient deficiency with bacterial infection and inflammation.

Leptin Downregulates Angulin-1 in Active Crohn's Disease via STAT3.

Crohn’s disease (CD) has an altered intestinal barrier function, yet the underlying mechanisms remain to be disclosed. The tricellular tight junction protein tricellulin is involved in the maintenance of the paracellular macromolecule barrier and features an unchanged expression level in CD but a shifted localization. As angulins are known to regulate the localization of tricellulin, we hypothesized the involvement of angulins in CD. Using human biopsies, we found angulin-1 was downregulated in active CD compared with both controls and CD in remission. In T84 and Caco-2 monolayers, leptin, a cytokine secreted by fat tissue and affected in CD, decreased angulin-1 expression. This effect was completely blocked by STAT3 inhibitors, Stattic and WP1066, but only partially by JAK2 inhibitor AG490. The effect of leptin was also seen at a functional level as we observed in Caco-2 cells an increased permeability for FITC-dextran 4 kDa indicating an impaired barrier against macromolecule uptake. In conclusion, we were able to show that in active CD angulin-1 expression is downregulated, which leads to increased macromolecule permeability and is inducible by leptin via STAT3. This suggests that angulin-1 and leptin secretion are potential targets for intervention in CD to restore the impaired intestinal barrier.

Increased Intestinal Permeability Is Associated With Later Development of Crohn’s Disease

Increased intestinal permeability has been associated with Crohn's disease (CD), but it is not clear whether it is a cause or result of the disease. We performed a prospective study to determine whether increased intestinal permeability is associated with future development of CD. We assessed the intestinal permeability, measured by the urinary fractional excretion of lactulose-to-mannitol ratio (LMR) at recruitment in 1420 asymptomatic first-degree relatives (6-35 years old) of patients with CD (collected from 2008 through 2015). Participants were then followed up for a diagnosis of CD from 2008 to 2017, with a median follow-up time of 7.8 years. We analyzed data from 50 participants who developed CD after a median of 2.7 years during the study period, along with 1370 individuals who remained asymptomatic until October 2017. We used the Cox proportional hazards model to evaluate time-related risk of CD based on the baseline LMR. An abnormal LMR (>0.03) was associated with a diagnosis of CD during the follow-up period (hazard ratio, 3.03; 95% CI, 1.64-5.63; P= 3.97× 10-4). This association remained significant even when the test was performed more than 3 years before the diagnosis of CD (hazard ratio, 1.62; 95% CI, 1.051-2.50; P= .029). Increased intestinal permeability is associated with later development of CD; these findings support a model in which altered intestinal barrier function contributes to pathogenesis. Abnormal gut barrier function might serve as a biomarker for risk of CD onset.

Stereotaxic Exposure of the Central Nucleus of the Amygdala to Corticosterone Increases Colonic Permeability and Reduces Nerve-Mediated Active Ion Transport in Rats.

Background: Irritable bowel syndrome (IBS) is characterized by visceral pain and abnormal bowel habits that are worsened during stress. Evidence also suggests altered intestinal barrier function in IBS. Previously, we demonstrated that stereotaxic application of the stress hormone corticosterone (CORT) onto the central nucleus of the amygdala (CeA) induces colonic hyperalgesia and anxiety-like behavior in a rat model, however the effect on intestinal permeability and mucosal function remain to be evaluated.Methods: Male Fischer 344 rats underwent bilateral stereotaxic implantation of CORT or inert cholesterol (CHOL)-containing micropellets (30 μg) onto the dorsal margin of the CeA. Seven days later, colonic tissue was isolated to assess tissue permeability in modified Ussing chambers via transepithelial electrical resistance (TEER) and macromolecular flux of horseradish peroxidase (HRP). Secretory responses to electrical field stimulation (EFS) of submucosal enteric nerves as well as activation with forskolin were used to assess movements of ions across the isolated colonic tissues. In a separate cohort, colonic histology, and mast cell infiltration was assessed.Key Results: Compared to CHOL-implanted controls, we determined that exposing the CeA to elevated levels of CORT significantly increased macromolecular flux across the colonic epithelial layer without changing TEER. Nerve-mediated but not cAMP-mediated active transport was inhibited in response to elevated amygdala CORT. There were no histological changes or increases in mast cell infiltration within colonic tissue from CORT treated animals.Conclusion and Inferences: These observations support a novel role for the CeA as a modulator of nerve-mediated colonic epithelial function.

Are self-reported gastrointestinal symptoms among older adults associated with increased intestinal permeability and psychological distress?

BackgroundDespite the substantial number of older adults suffering from gastrointestinal (GI) symptoms little is known regarding the character of these complaints and whether they are associated with an altered intestinal barrier function and psychological distress. Our aim was to explore the relationship between self-reported gut health, intestinal permeability and psychological distress among older adults.MethodsThree study populations were included: 1) older adults with GI symptoms (n = 24), 2) a group of older adults representing the general elderly population in Sweden (n = 22) and 3) senior orienteering athletes as a potential model of healthy ageing (n = 27). Questionnaire data on gut-health, psychological distress and level of physical activity were collected. Intestinal permeability was measured by quantifying zonulin in plasma. The level of systemic and local inflammation was monitored by measuring C-reactive protein (CRP), hydrogen peroxide in plasma and calprotectin in stool samples. The relationship between biomarkers and questionnaire data in the different study populations was illustrated using a Principal Component Analysis (PCA).ResultsOlder adults with GI symptoms displayed significantly higher levels of both zonulin and psychological distress than both general older adults and senior orienteering athletes. The PCA analysis revealed a separation between senior orienteering athletes and older adults with GI symptoms and showed an association between GI symptoms, psychological distress and zonulin.ConclusionsOlder adults with GI symptoms express increased plasma levels of zonulin, which might reflect an augmented intestinal permeability. In addition, this group suffer from higher psychological distress compared to general older adults and senior orienteering athletes. This relationship was further confirmed by a PCA plot, which illustrated an association between GI symptoms, psychological distress and intestinal permeability.

Diet-induced obesity causes metabolic impairment independent of alterations in gut barrier integrity.

The causal relationship between diet-induced obesity and metabolic disorders is not clear yet. One hypothesis is whether the obese state or high-fat diet per se affects intestinal barrier function provoking metabolic comorbidities. In three independent experiments with AKR/J, SWR/J, or BL/6J mice, we addressed the impact of genetic background, excess body fat storage, duration of high-fat feeding, and quality/quantity of dietary fat on glucose tolerance and gut barrier integrity in vivo and ex vivo. Impaired glucose tolerance in diet-induced obese BL/6J and AKR/J mice was not accompanied by an altered intestinal barrier function. Enforced dietary challenge by prolonged feeding and increasing fat quantity in BL/6J mice still failed to aggravate metabolic and intestinal deterioration. Despite a low-grade inflammatory status in adipose tissue, barrier function of BL/6J mice fed lard high-fat diet revealed no evidence for a diet-induced loss in barrier integrity. None of our results provided any evidence that gut barrier function is a subject to dietary regulation and obesity per se seems not to cause gut barrier impairment.

Probiotics normalize the gut-brain-microbiota axis in immunodeficient mice.

The gut-brain-microbiota axis is increasingly recognized as an important regulator of intestinal physiology. Exposure to psychological stress causes activation of the hypothalamic-pituitary-adrenal (HPA) axis and causes altered intestinal barrier function, intestinal dysbiosis, and behavioral changes. The primary aim of this study was to determine whether the effects of psychological stress on intestinal physiology and behavior, including anxiety and memory, are mediated by the adaptive immune system. Furthermore, we wanted to determine whether treatment with probiotics would normalize these effects. Here we demonstrate that B and T cell-deficient Rag1(-/-) mice displayed altered baseline behaviors, including memory and anxiety, accompanied by an overactive HPA axis, increased intestinal secretory state, dysbiosis, and decreased hippocampal c-Fos expression. Both local (intestinal physiology and microbiota) and central (behavioral and hippocampal c-Fos) changes were normalized by pretreatment with probiotics, indicating an overall benefit on health conferred by changes in the microbiota, independent of lymphocytes. Taken together, these findings indicate a role for adaptive immune cells in maintaining normal intestinal and brain health in mice and show that probiotics can overcome this immune-mediated deficit in the gut-brain-microbiota axis.

Modulating dietary vitamin A altered the pathogenicity of Citrobacter rodentium in mice

Vitamin A deficiency (VAD) is associated with increased bacterial infection‐related morbidity and mortality. Citrobacter rodentium (Cr) is a mouse pathogen that mimics many aspects of pathogenic E. coli infections in humans and is used to study mucosal immunity to enteric bacteria. Mice fed VA sufficient (VAS)‐ and VAD‐diets were infected with Cr and groups of infected VAD‐mice were switched to VAS‐diet on day 0 (D0) or seven (D7) post‐infection. Fecal excretion of Cr was monitored and bacterial load in the colon and spleen assessed at necropsy (day 12). The VAD‐mice infected with Cr had higher mortality than VAS‐or VAD‐mice switched to a VAS diet. The VAD‐mice had 3–4 log10 higher levels of Cr in the colon than VAS‐mice and bacteria were recovered from spleens of VAD‐ but not VAS‐mice indicating altered intestinal barrier function. Infected VAD‐mice switched to a VAS diet at D0 or D7 had colonic Cr levels between those of VAD‐ and VAS‐mice, and less bacteria was recovered from their spleens indicating partial restoration of barrier function. Growth of Cr was inhibited by D21 in mice on all diets except VAD‐mice which also had decreased mRNA expression of IFN‐γ and IL12p40 in the colon that correlated with increased Cr levels. In conclusion, the severity of Cr infection in mice is modulated by dietary levels of VA and supports VA's role in mucosal immunity to an enteric pathogen. Funded by USDA/ARS Project Plan 1235–51000‐055–00D.

370 Altered intestinal barrier function, increased immune activation and IgA-endotoxin-antibodies in patients with chronic heart failure compared to controls

370 Altered intestinal barrier function, increased immune activation and IgA-endotoxin-antibodies in patients with chronic heart failure compared to controls

A Role for Corticosterone in Impaired Intestinal Immunity and Barrier Function in a Rodent Model of Acute Alcohol Intoxication and Burn Injury

Alcohol (EtOH) intoxication and burn injury independently activate hypothalamic-pituitary-adrenal (HPA) axis, and glucocorticoids, the end product of the HPA axis, play a role in shaping the immune response under those conditions. By utilizing a rat model of acute EtOH intoxication and burn injury, studies in our laboratory have investigated the role of corticosterone (i.e., glucocorticoids in rodents) in altered intestinal immunity and barrier function following a combined insult of EtOH and burn injury. Results from these studies suggest that EtOH intoxication prior to burn injury augments corticosterone release, which in turn suppresses intestinal T cell function by inhibiting mitogen-activated protein kinase (i.e., p38 and ERK) pathway. Furthermore, we found that corticosterone does not directly alter the intestinal barrier function; rather, it up-regulates interleukin-18, which then directly or indirectly contributes to impaired intestinal barrier function. The loss of intestinal immunity/barrier function may result in increased bacterial translocation and thereby contribute to postinjury pathogenesis, leading to sepsis and organ dysfunction in burn patients as well as in patients with a history of EtOH intoxication.