Tight Junction Barrier Dysfunction Research Articles

Black Rice Extract Reduces Body Weight, Waist Circumference, Body Mass Index and Lipopolysaccharide in Obese Subjects: A Preliminary Study

BACKGROUND: The prevalence of obesity, or an excessive fat accumulation, is keep increasing. In obesity, inflammation can be induced by leaky gut due to the intestinal tight junction barrier dysfunction. Zonula occludens-1 (ZO-1) plays a role in developing intestinal tight junction barrier dysfunction and gut microbiota imbalance, thus promote the translocation of bacterial endotoxin characterized by lipopolysaccharide (LPS) into circulation. Black rice extract (BRE) has been known to have anti-inflammatory property. This study was conducted to investigate the effect of BRE on body weight (BW), waist circumference (WC), body mass index (BMI), ZO-1 and LPS of obese patients.METHODS: Twenty-three male subjects were divided into non-obese group (NOG), obese group (COG) and BRE-obese group (BOG). Subjects in BOG received a daily dose of 5.6 g/day BRE for 4 weeks. BW, WC and BMI, serum ZO-1 and LPS were measured before and after treatment.RESULTS: BRE was prepared successfully and free from microbial contamination. Treatment of BRE for 4 weeks reduce BW (95.40±5.78 vs. 94.59±6.00 kg, p=0.043), WC (109.25±3.55 vs. 107.50±3.46 cm, p=0.000) BMI (32.65±1.86 vs. 32.18±1.80, p=0.000) and LPS (222.27±38.63 vs. 131.63±9.70 ng/mL, p=0.020) of obese subjects. The pre-post ZO-1 levels in all groups were not significantly different (p>0.05).CONCLUSION: Treatment of 5.6 gr BRE daily for four weeks can reduce BW, WC, BMI and serum LPS, but not serum ZO-1 in obese patients. Therefore, BRE may reduce inflammation in obesity.KEYWORDS: black rice, obesity, BW, WC, BMI, LPS, ZO-1

Activation of the 5-hydroxytryptamine 4 receptor ameliorates tight junction barrier dysfunction in the colon of type 1 diabetic mice.

Hyperglycemia drives dysfunction of the intestinal barrier. 5-Hydroxytryptaine 4 receptor (5-HT 4R) agonists have been considered therapeutics for constipation in clnic. However, the roles of 5-HT 4R activation in mucosa should be fully realized. Here, we investigate the effects of 5-HT 4R activation on diabetes-induced disruption of the tight junction (TJ) barrier in the colon. Not surprisingly, the TJ barrier in diabetic mice with or without 5-HT 4R is tremendously destroyed, as indicated by increased serum fluorescein isothiocyanate (FITC)-dextran and decreased transepithelial electrical resistance (TER). Simultaneously, decreased expressions of TJ proteins are shown in both wild-type (WT) and 5-HT 4R knockout (KO) mice with diabetes. Notably, chronic treatment with intraperitoneal injection of a 5-HT 4R agonist in WT mice with diabetes repairs the TJ barrier and promotes TJ protein expressions, including occludin, claudin-1 and ZO-1, in the colon, whereas a 5-HT 4R agonist does not improve TJ barrier function or TJ protein expressions in 5-HT 4R KO mice with diabetes. Furthermore, stimulation of 5-HT 4R inhibits diabetes-induced upregulation of myosin light chain kinase (MLCK), Rho-associated coiled coil protein kinase 1 (ROCK1), and phosphorylated myosin light chain (p-MLC), which are key molecules that regulate TJ integrity, in the colonic mucosa of WT mice. However, such action induced by a 5-HT 4R agonist is not observed in 5-HT 4R KO mice with diabetes. These findings indicate that 5-HT 4R activation may restore TJ integrity by inhibiting the expressions of MLCK, ROCK1 and p-MLC, improving epithelial barrier function in diabetes.

The Effects of Mucopolysaccharide Polysulfate on Steroid-Induced Tight Junction Barrier Dysfunction in Human Epidermal Keratinocytes and a 3D Skin Model

Introduction: The long-term use of topical corticosteroids (TCS) is associated with side effects such as skin atrophy and barrier deterioration. Moisturizers, such as mucopolysaccharide polysulfate (MPS), have been reported to prevent relapses in atopic dermatitis (AD) when used in combination with TCS. However, the mechanisms underlying the positive effects of MPS in combination with TCS in AD are poorly understood. In the present study, we investigated the effects of MPS in combination with clobetasol 17-propionate (CP) on tight junction (TJ) barrier function in human epidermal keratinocytes (HEKa) and 3D skin models. Methods: The expression of claudin-1, which is crucial for TJ barrier function in keratinocytes, and transepithelial electrical resistance (TEER) was measured in CP-treated human keratinocytes incubated with and without MPS. A TJ permeability assay, using Sulfo-NHS-Biotin as a tracer, was also conducted in a 3D skin model. Results: CP reduced claudin-1 expression and TEER in human keratinocytes, whereas MPS inhibited these CP-induced effects. Moreover, MPS inhibited the increase in CP-induced TJ permeability in a 3D skin model. Conclusion: The present study demonstrated that MPS improved TJ barrier impairment induced by CP. The improvement of TJ barrier function may partially be responsible for the delayed relapse of AD induced by the combination of MPS and TCS.

Porcine reproductive and respiratory syndrome virus induces tight junction barrier dysfunction and cell death in porcine glandular endometrial epithelial cells

Reproductive failure caused by porcine reproductive and respiratory syndrome virus (PRRSV) is characterized by embryonic death and weak-born piglets and is associated with placental cell apoptosis and impairment of endometrial integrity. Here, we aimed to determine whether endometrial epithelial barrier function and viability were altered following PRRSV type 1 or type 2 infection. PRRSV inoculation was examined at the apical or basolateral side of porcine glandular endometrial epithelial cell cultures isolated from 4- to 6-month-old PRRSV-free herd gilts (n = 7 pigs). On the apical side, four days postinfection (4 dpi) with type 2 PRRSV, transepithelial electrical resistance decreased by 31% ± 5%, and paracellular permeability to fluorescein isothiocyanate-dextran (4 kDa) increased by 10-fold as compared with the mock and type 1 infection. Real-time polymerase chain reaction results revealed that both PRRSV types upregulated the mRNA expression of the barrier builder tight junction protein (TJ) Cldn5, but downregulated pore-forming TJ Cldn7. Additionally, the expression of other TJ genes, i.e., Cldn3 and Cldn8, was differentially increased by PRRSV type 1 and that of zonula occludens-1 was increased by PRRSV type 2. MTT assays indicated an increase in porcine glandular endometrial epithelial cell culture at 2–6 dpi following type 2 infection. Analysis of apoptosis using Annexin/propidium iodide staining combined with flow cytometry showed that the percentage of viable cells decreased, accompanied by a significantly higher dead cell population following PRRSV type 2 infection at 2–4 dpi. PRRSV type 1 infection also induced dead cells (>4%) at 2 dpi; however, the cell population recovered at 4 dpi. In conclusion, PRRSV type 2 infection caused more severe TJ barrier dysfunction and reduced cell viability compared with PRRSV type 1 infection in the porcine endometrium. Impairment in the membrane integrity of the maternal glandular endometrium may be the underlying mechanism of PRRSV-induced reproductive failure in pregnant sows.

Salvianolic acid B decreases interleukin-1β-induced colitis recurrence in mice.

BackgroundDegree of mucosal recovery is an important indicator for evaluating the therapeutic effects of drugs in treatment of inflammatory bowel disease (IBD). Increasing evidences has proved that tight junction (TJ) barrier dysfunction is one of the pathological mechanisms of IBD. The aim of this study was to observe whether enhancement of TJ can decrease colitis recurrence.MethodsEighty C57BL/6 mice were randomly divided into four groups including normal group, colitis group, sulfasalazine (SASP) treated group, and traditional Chinese drug salvianolic acid B (Sal B) treated group. Colitis was established in mice by free drinking water containing dextran sulfate sodium, after treatments by SASP and Sal B, recombinant human interleukin-1β (IL-1β) was injected intraperitoneally to induce colitis recurrence.ResultsCompared with sham control, cell apoptosis in colitis group was increased from 100.85 ± 3.46% to 162.89 ± 11.45% (P = 0.0038), and TJ dysfunction marker myosin light chain kinase (MLCK) was also significantly increased from 99.70 ± 9.29% to 296.23 ± 30.78% (P = 0.0025). The increased cell apoptosis was reversed by both SASP (125.99 ± 8.45% vs. 162.89 ± 11.45%, P = 0.0059) and Sal B (104.27 ± 6.09% vs. 162.89 ± 11.45%, P = 0.0044). High MLCK expression in colitis group was reversed by Sal B (182.44 ± 89.42% vs. 296.23 ± 30.78%, P = 0.0028) but not influenced by SASP (285.23 ± 41.04% vs. 296.23 ± 30.78%, P > 0.05). The recurrence rate induced by recombinant human IL-1β in Sal B-treated group was significantly lower than that in SASP-treated group.ConclusionsThese results suggested a link between intestinal mucosal barrier dysfunction, especially TJ barrier dysfunction, and colitis recurrence. The TJ barrier dysfunction in remission stage of colitis increased the colitis recurrence. This study might provide potential treatment strategies for IBD recurrence.

Antibiotics induced intestinal tight junction barrier dysfunction is associated with microbiota dysbiosis, activated NLRP3 inflammasome and autophagy.

Tight junction barrier is critical to intestinal homeostasis. Applying antibiotics to treat infections is common in clinical practice, which may affect intestinal microbiota. Intestinal microbiota dysbiosis is involved in the occurrence of some gastrointestinal diseases. Therefore, this study was aimed to investigate the influence of antibiotics on intestinal tight junction barrier and the possible underlying mechanisms. Healthy adult female C57BL/6 mice were treated with a broad-spectrum antibiotic cocktail for 14 days. 16S rDNA Illumina sequencing and headspace gas chromatography-mass spectrometry (HS-GC/MS) were respectively used to analyze microbial community and to detect short-chain fatty acids (SCFAs) contents. In vivo intestinal paracellular permeability to fluorescein isothiocyanate-dextran (FITC-dextran) was measured. Protein expression was determined by immunoblotting. Immunofluoresence was applied to observe the distributions of ZO-1, LC3B and ASC. Antibiotics remarkably altered intestinal microbiota composition in healthy mice, accompanying reduced SCFAs’ concentrations. In addition, the intestinal tight junction barrier was disrupted by antibiotic treatment, as evidenced by increased intestinal paracellular permeability to FITC-dextran, decreased tight junction protein expressions, and disrupted ZO-1 morphology. Furthermore, NLRP3 inflammasome and autophagy were activated by antibiotic treatment. In conclusion, intestinal epithelial tight junction barrier dysfunction induced by antibiotics is associated with intestinal microbiota dysbiosis, activated NLRP3 inflammasome and autophagy in mice.

Role of Endoplasmic Reticulum Stress-Autophagy Axis in Severe Burn-Induced Intestinal Tight Junction Barrier Dysfunction in Mice.

Severe burn injury induces intestinal barrier dysfunction; however, the underlying mechanisms remain elusive. Our previous studies have shown that the intestinal epithelial tight junction (TJ) barrier dysfunction is associated with both endoplasmic reticulum (ER) stress and autophagy in severely burned mice, but the precise role of ER stress and autophagy in the burn-induced intestinal TJ barrier dysfunction needs to be determined. In this study, female C57/BL6 mice were assigned randomly to either sham burn or 30% total body surface area (TBSA) full-thickness burn. The effects of ER stress and autophagy on the intestinal epithelial TJ barrier were validated by inducing or inhibiting both ER stress and autophagy in mice treated with sham burn or burn injury. The intestinal permeability, expression, and localization of TJ proteins, ER stress, and autophagy were assessed by physiological, morphological, and biochemical analyses. The results showed that inducing ER stress with tunicamycin or thapsigargin caused the activation of autophagy, the increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins in the sham-burned mice, and aggravated the burn-induced activation of autophagy, increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins. In contrast, inhibiting ER stress with 4-phenylbutyrate alleviated the burn-induced activation of autophagy, increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins. In addition, inducing autophagy with rapamycin resulted in the increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins in the sham-burned mice, and aggravated the burn-induced increase of intestinal permeability as well as the reduction and reorganization of TJ proteins. However, inhibiting autophagy with 3-methyladenine attenuated the burn-induced increase of intestinal permeability, as well as the reduction and reorganization TJ proteins. It is suggested that the ER stress-autophagy axis contributes to the intestinal epithelial TJ barrier dysfunction after severe burn injury.

Tea polyphenols protect gingival keratinocytes against TNF-α-induced tight junction barrier dysfunction and attenuate the inflammatory response of monocytes/macrophages

Tea, an aromatic beverage prepared with the leaves of the Camellia sinensis plant, is well known to contain bioactive polyphenols. Green tea contains mainly catechins such as epigallocatechin-3-gallate (EGCG), while black tea is characterized by the presence of theaflavins. TNF-α, which is a pro-inflammatory cytokine that activates the endogenous inflammatory cascade, plays a key role in periodontitis. In the present study, we investigated the ability of tea compounds to attenuate TNF-α-mediated activation of the host inflammatory response in monocytes/macrophages as well as the protective effect of green and black tea polyphenols on gingival keratinocyte barrier dysfunction induced by TNF-α. Tea compounds inhibited both the activation of NF-κB and caspase-1 as well as IL-1β secretion by monocytes/macrophages. TNF-α time-dependently damaged keratinocyte tight junction barrier integrity, as determined by changes in transepithelial electrical resistance and FITC-dextran transport. Green tea extract, EGCG, theaflavins, and to a lesser extent, black tea extract protected keratinocytes against the TNF-α-mediated breakdown of barrier integrity. The treatment of keratinocytes with tea polyphenols markedly mitigated the morphological changes of tight junction proteins such as zonula occludens-1 and occludin compared to cells exposed only to TNF-α, as determined by immunofluorescence. Tea polyphenols also time-dependently decreased the paracellular flux of TNF-α-treated keratinocytes. In conclusion, the ability of tea polyphenols to exert an anti-inflammatory effect and to attenuate the gingival epithelial barrier dysfunction induced by TNF-α supports their potential for the prevention and treatment of periodontal disease.

Endoplasmic Reticulum Stress-Autophagy Axis is Required for Hypoxia-Induced Intestinal Epithelial Tight Junction Barrier Dysfunction

Endoplasmic Reticulum Stress-Autophagy Axis is Required for Hypoxia-Induced Intestinal Epithelial Tight Junction Barrier Dysfunction

Inhibition of Epithelial TNF-α Receptors by Purified Fruit Bromelain Ameliorates Intestinal Inflammation and Barrier Dysfunction in Colitis.

Activation of the TNF-α receptor (TNFR) leads to an inflammatory response, and anti-TNF therapy has been administered to reduce inflammation symptoms and heal mucosal ulcers in inflammatory bowel disease (IBD). Bromelain, a complex natural mixture of proteolytic enzymes, has been shown to exert anti-inflammatory effects. This study aimed to investigate the effect of purified fruit bromelain (PFB)-induced inhibition of epithelial TNFR in a rat colitis model. Colitis was established by intracolonic administration of 2, 4, 6-trinitrobenzene sulfonic acid. Expression of TNFR1 and TNFR2 was measured by quantitative RT-PCR and western blotting. The effect of PFB on colitis was evaluated by examining the inflammatory response and intestinal epithelial barrier function. Our results showed that both TNFR1 and TNFR2 expression were significantly increased in a colitis model, and the increase was significantly reversed by PFB. Colitis symptoms, including infiltration of inflammatory cells, cytokine profiles, epithelial cell apoptosis, and epithelial tight junction barrier dysfunction were significantly ameliorated by PFB. Compared with fruit bromelain and stem bromelain complex, the inhibition of TNFR2 induced by PFB was stronger than that exhibited on TNFR1. These results indicate that PFB showed a stronger selective inhibitory effect on TNFR2 than TNFR1. In other words, purification of fruit bromelain increases its selectivity on TNFR2 inhibition. High expression of epithelial TNFRs in colitis was significantly counteracted by PFB, and PFB-induced TNFR inhibition ameliorated colitis symptoms. These results supply novel insights into potential IBD treatment by PFB.

Urothelial Tight Junction Barrier Dysfunction Sensitizes Bladder Afferents.

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic voiding disorder that presents with pain in the urinary bladder and surrounding pelvic region. A growing body of evidence suggests that an increase in the permeability of the urothelium, the epithelial barrier that lines the interior of the bladder, contributes to the symptoms of IC/BPS. To examine the consequence of increased urothelial permeability on pelvic pain and afferent excitability, we overexpressed in the urothelium claudin 2 (Cldn2), a tight junction (TJ)-associated protein whose message is significantly upregulated in biopsies of IC/BPS patients. Consistent with the presence of bladder-derived pain, rats overexpressing Cldn2 showed hypersensitivity to von Frey filaments applied to the pelvic region. Overexpression of Cldn2 increased the expression of c-Fos and promoted the activation of ERK1/2 in spinal cord segments receiving bladder input, which we conceive is the result of noxious stimulation of afferent pathways. To determine whether the mechanical allodynia observed in rats with reduced urothelial barrier function results from altered afferent activity, we examined the firing of acutely isolated bladder sensory neurons. In patch-clamp recordings, about 30% of the bladder sensory neurons from rats transduced with Cldn2, but not controls transduced with GFP, displayed spontaneous activity. Furthermore, bladder sensory neurons with tetrodotoxin-sensitive (TTX-S) action potentials from rats transduced with Cldn2 showed hyperexcitability in response to suprathreshold electrical stimulation. These findings suggest that as a result of a leaky urothelium, the diffusion of urinary solutes through the urothelial barrier sensitizes bladders afferents, promoting voiding at low filling volumes and pain.

Research progress of relationship between diabetes and intestinal epithelial tight junction barrier and intervetion of berberine

Intestinal tight junction is an important part of the small intestinal mucosa barrier. It plays a very significant role in maintaining the intestinal mucosal permeability and integrity, preventing the bacterial endotoxin and toxic macromolecular substances into the body so as to keep a stable internal environment. Numerous studies have shown that intestinal mucosal barrier dysfunction is closely related to the development of diabetes. Therefore, protecting intestinal tight junction and maintaining the mucosal barrier have great significance in the prevention and treatment of diabetes. The effect of berberine in diabetes treatment is obvious. However, the pharmacological study found that the bioavailability of berberine is extremely low. Some scholars put forward that the major site of pharmaceutical action of berberine might be in the gut. Studies have shown that berberine could regulate the intestinal flora and intestinal hormone secretion, protect the intestinal barrier, inhibit the absorption of glucose, eliminate the intestinal inflammation and so on. Recently studies have found that the hypoglycemic effect of berberine is likely to relate with the influence on intestinal tight junction and the protection of mucosal barrier. Here is the review about the association between intestinal tight junction barrier dysfunction and diabetes, and the related hypoglycemic mechanism of berberine.

Inhibition of miR122a by Lactobacillus rhamnosus GG culture supernatant increases intestinal occludin expression and protects mice from alcoholic liver disease

Alcoholic liver disease (ALD) has a high morbidity and mortality. Chronic alcohol consumption causes disruption of intestinal microflora homeostasis, intestinal tight junction barrier dysfunction, increased endotoxemia, and eventually liver steatosis/steatohepatitis. Probiotic Lactobacillus rhamnosus GG (LGG) and the bacteria-free LGG culture supernatant (LGGs) have been shown to promote intestinal epithelial integrity and protect intestinal barrier function in ALD. However, little is known about how LGGs mechanistically works to increase intestinal tight junction proteins. Here we show that chronic ethanol exposure increased intestinal miR122a expression, which decreased occludin expression leading to increased intestinal permeability. Moreover, LGGs supplementation decreased ethanol-elevated miR122a level and attenuated ethanol-induced liver injury in mice. Similar to the effect of ethanol exposure, overexpression of miR122a in Caco-2 monolayers markedly decreased occludin protein levels. In contrast, inhibition of miR122a increased occludin expression. We conclude that LGGs supplementation functions in intestinal integrity by inhibition of miR122a, leading to occludin restoration in mice exposed to chronic ethanol.

Luminal Leptin Impairs Intestinal Tight Junction Function in vitro through JAK2‐dependent Signaling Pathway

Tight junction (TJ) integrity is a critical for maintaining intestinal barrier function and inflammation. Obesity is also known to alter intestinal function partly through an impairment of intestine TJ integrity. Leptin is associated with inflammation and obesity. However, the role of leptin in TJ function is unknown. This study aimed to investigate the effect of leptin on intestinal TJ integrity in vitro using Caco‐2 BBe cells. Leptin addition to apical compartment, but not in basolateral compartment, caused TJ barrier dysfunction as judged by transepithelial electrical resistance and dextran fluxes. TJ dysfunction by luminal leptin was associated with reduced levels of gene expression related to TJ‐associated proteins, zonula occludens‐3, claudin‐5, and occludin. In addition, leptin treatment caused reduction in total protein level of occludin. Moreover, activation of the Janus family of tyrosine kinase/signal transducer and activator of transcription (JAK2/STAT3) axis has been also observed upon leptin treatment. Conversely, a JAK2 specific inhibitor or a PI3K specific inhibitor pretreatment abolished leptin activity on TJ integrity, indicating an involvement of JAK2 and PI3K signaling pathways in leptin‐impaired TJ function. Therefore, our results reveal previously unknown function of luminal leptin, which potentially links between obesity and its associated intestinal TJ dysfunction.

Enterocyte STAT5 promotes mucosal wound healing via suppression of myosin light chain kinase‐mediated loss of barrier function and inflammation

Epithelial myosin light chain kinase (MLCK)-dependent barrier dysfunction contributes to the pathogenesis of inflammatory bowel diseases (IBD). We reported that epithelial GM-CSF–STAT5 signalling is essential for intestinal homeostatic response to gut injury. However, mechanism, redundancy by STAT5 or cell types involved remained foggy. We here generated intestinal epithelial cell (IEC)-specific STAT5 knockout mice, these mice exhibited a delayed mucosal wound healing and dysfunctional intestinal barrier characterized by elevated levels of NF-κB activation and MLCK, and a reduction of zonula occludens expression in IECs. Deletion of MLCK restored intestinal barrier function in STAT5 knockout mice, and facilitated mucosal wound healing. Consistently, knockdown of stat5 in IEC monolayers led to increased NF-κB DNA binding to MLCK promoter, myosin light chain phosphorylation and tight junction (TJ) permeability, which were potentiated by administration of tumour necrosis factor-α (TNF-α), and prevented by concurrent NF-κB knockdown. Collectively, enterocyte STAT5 signalling protects against TJ barrier dysfunction and promotes intestinal mucosal wound healing via an interaction with NF-κB to suppress MLCK. Targeting IEC STAT5 signalling may be a novel therapeutic approach for treating intestinal barrier dysfunction in IBD.

Epithelial Myosin Light Chain Kinase Activation Induces Mucosal Interleukin-13 Expression to Alter Tight Junction Ion Selectivity

Intestinal barrier function is reduced in inflammatory bowel disease (IBD). Tumor necrosis factor (TNF) and interleukin (IL)-13, which are up-regulated in IBD, induce barrier defects that are associated with myosin light chain kinase (MLCK) activation and increased claudin-2 expression, respectively, in cultured intestinal epithelial monolayers. Here we report that these independent signaling pathways have distinct effects on tight junction barrier properties and interact in vivo. MLCK activation alters size selectivity to enhance paracellular flux of uncharged macromolecules without affecting charge selectivity and can be rapidly reversed by MLCK inhibition. In contrast, IL-13-dependent claudin-2 expression increases paracellular cation flux in vitro and in vivo without altering tight junction size selectivity but is unaffected by MLCK inhibition in vitro. In vivo, MLCK activation increases paracellular flux of uncharged macromolecules and also triggers IL-13 expression, claudin-2 synthesis, and increased paracellular cation flux. We conclude that reversible, MLCK-dependent permeability increases cause mucosal immune activation that, in turn, feeds back on the tight junction to establish long-lasting barrier defects. Interactions between these otherwise distinct tight junction regulatory pathways may contribute to IBD pathogenesis.

Disruption of tight junctions during polymicrobial sepsis in vivo

The disruption of intestinal epithelial tight junctions may result in barrier function dysfunction during polymicrobial sepsis. The pathophysiology of sepsis involves breakdown of barrier integrity, which correlates with adverse outcome during sepsis. However, the mechanisms underlying loss of barrier function in sepsis remain unknown. In the present study in mice, tight junction (TJ) structure was analysed by transmission electron microscopy; intestinal permeability was assessed using molecular tracer measurement; and the distribution of TJ proteins was investigated by immunofluorescence microscopy. The membrane microdomains of TJs were isolated using discontinuous sucrose density gradients and the expression of TJ proteins in these was determined by western blot. Immunofluorescence microscopy revealed that claudins 1, 3, 4, 5, and 8 were present predominantly in the microvillous surface of epithelial cells and along the lateral membranes of the cells; in sepsis, however, labelling of these proteins was present diffusely within cells and was no longer focused at the lateral cell boundaries. Moreover, the expression of claudin-2 was markedly up-regulated in sepsis. Using western blot analysis, we found that occludin and claudins were displaced from raft fractions to non-raft fractions in membrane microdomains of TJs in sepsis. In addition, the disruption of TJ structure was accompanied by increased intestinal permeability. Our results demonstrate for the first time that redistribution of TJ proteins in TJ membrane microdomains and redistribution of claudins in epithelial cells of the colon lead to alteration of TJ architecture and TJ barrier dysfunction during the development of polymicrobial sepsis.