Increase In Mucosal Permeability Research Articles

Paneth Cell-Specific TRPV6 Channel Plays a Crucial Role in Alcohol-Associated Dysbiosis of Gut Microbiota and Tissue Injury at the Gut-Liver Axis

Introduction: Endotoxemia plays an essential role in alcohol-associated tissue injury. Two factors contributing to endotoxemia are gut microbiota dysbiosis and epithelial barrier dysfunction. Previous studies indicated that TRPV6 channel-mediated Ca2+ influx plays a crucial role in alcohol-induced epithelial tight junction (TJ) disruption, mucosal barrier dysfunction, and endotoxemia. Trpv6 knockout mice were resistant to alcohol-induced intestinal barrier dysfunction and modulated microbiota dysbiosis, raising the question of how TRPV6 regulates microbiota composition. In this study, we investigated the role of Paneth cell-specific TRPV6 in alcohol-induced microbiota dysbiosis and barrier dysfunction. Methods: Adult Trpv6fl/fl (WT) and Trpv6fl/fl-Defa6Cre (KO; Paneth cell-specific TRPV6 knockout) mice were fed a Lieber-DiCarli liquid diet with EtOH (0% 2d, 1% 2d, 2% 2d, 4% 1wk, 5% 1wk, & 6% 1wk). Control groups were pair-fed an isocaloric EtOH-free diet. Intestinal permeability was measured by vascular-to-luminal flux of FITC-inulin in vivo, and mucosal inflammation was assessed by RT-PCR for cytokines/chemokines. Plasma lipopolysaccharide (LPS) was measured to evaluate endotoxemia. Gut microbiota was analyzed by 16S rRNA sequencing of colonic flushing. Lipidome in colonic flushing was analyzed using nontargeted liquid chromatography-mass spectrometry. Microbiome and lipidome data were processed by bioinformatic analyses. Results and conclusion: Data show that colon length was reduced, and colonic mucosal permeability in vivo was elevated by EtOH in WT mice. The increase in mucosal permeability was associated with increased plasma LPS levels. EtOH feeding elevated the expression of IL-6, IL-1β, and TNFα in the colon. EtOH-induced changes in colon length, mucosal permeability, cytokine expression, and plasma LPS were absent in KO mice. 16S rRNA sequencing data indicated that the microbiota composition in KO mice differed from that of WT mice. The relative abundance of Prevotellaceae, Xanthomonadaceae, and Streptococaceae were higher, and Psuedomonadaceae and Verrucomicrobiaceae abundance were lower in KO mice compared to WT mice. EtOH-induced increase in the abundance of Norcardiaceae and Psuedomonadaceae was low or absent in KO mice. EtOH increased Rhodococcus, Odoribacter, and Pseudomonas abundance at the genus level in WT but not KO mice. On the other hand, Clostridium, Turicibacter, and Helicobacter abundance were increased by EtOH in KO but not WT mice. Lipidomic analysis of colonic flushing showed that phospholipid contents were higher in KO mice than WT mice, irrespective of sex and treatments. A cluster of sphingolipids was dramatically high in KO female mice, which was reduced by EtOH feeding. Short-chain fatty acid esters of hydroxy fatty acids (AAHFA 3:0/24:0;O) were elevated by EtOH in male WT mice but not in female WT and male or female KO mice. In conclusion, these data indicate that Paneth cell-specific deletion of TRPV6 attenuates alcohol-induced changes in gut microbiota, colonic luminal lipids, mucosal barrier function, and endotoxemia in mice. NIH/NIAAA, RO1-AA029270; Veterans Administration IO1-BX003014. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

81 Measuring biomarkers to assess the effect of diet on the mucosal integrity of the equine large intestine

Alterations in the integrity of the intestinal mucosa can lead to severe health issues, which can manifest as an increase in mucosal permeability and/or in malabsorption of nutrients. In horses, the hindgut acidosis and the disbalance of the intestinal microbiota caused by excessive starch intake may jeopardize mucosal integrity. In other species, studies suggest that polyphenols could play a protective role for maintaining mucosal integrity. Thus, the objective of this study was to evaluate the integrity of the mucosa of the large intestineby measuring biomarkers of intestinal permeability and absorption in horses fed either a high-fiber or a high-starch diet, combined with a polyphenol-rich plant (sainfoin) supplementation. Twelve adult geldings (7 ± 2 years old,515 ± 53 kg BW) were enrolled in a 4 periods × 4 diets Latin square design, including 4 21 d experimental periods separated by 21 d wash-out periods. The 4 iso-caloric and iso-nitrogenous rations included either high-fiber (HF; 18.5g DM hay/kg BW) or high-starch meals (HS; 8.0g DM hay+6.3g DM barley/kg BW; 1.9g starch/kg BW/meal), and were supplemented with ether control (CONT; 3.1g DM sunflower meal+hay/kg BW) or sainfoin pellets (SF; 3.1g DM Equifolia [Multifolia]/kg BW). Feces and blood were sampled at theend of each experimental period to measure fecal and plasma acetate concentrations, and plasma lipopolysaccharides (LPS) concentration. Mixed effect models were used to assess the effect of the diet (HF vs HS), supplementation (CONT vs SF), and their interaction on these parameters. When horses were fed the diet HS, higher concentration of fecal acetate (P < 0.001) and lower concentration of plasma acetate (P = 0.007) were observed compared with diet HF. This might indicate a decreased absorption capacity through the intestinal wall with diet HS. However, no significant effect of the diet was observed on plasma LPS concentration which suggests that the permeability of the intestinal mucosa is not modified after 21 d with these diets. Adding sainfoin to the ration did not alter the monitored parameters related to mucosal integrity. The next step would be to monitor mucosal permeability and absorption for longer periods of time (longer that the 21-d monitoring done here). This might allow to have a better insight on the effect of diet on mucosal integrity.

Hypotonicity-Induced Increase in Duodenal Mucosal Permeability Is Regulated by Cholinergic Receptors in Rats

BackgroundThe role of cholinergic receptors in the regulation of duodenal mucosal permeability in vivo is currently not fully described.AimsTo elucidate the impact of nicotinic and muscarinic acetylcholine receptor signaling in response to luminal hypotonicity (50 mM NaCl) in the proximal small intestine of rat.MethodsThe effect on duodenal blood-to-lumen clearance of 51Cr-EDTA (i.e., mucosal permeability) and motility was studied in the absence and presence of nicotinic and muscarinic receptor agonists and antagonists, a sodium channel blocker (tetrodotoxin), and after bilateral cervical vagotomy.ResultsRats with duodenal contractions responded to luminal hypotonicity by substantial increase in intestinal permeability. This response was absent in animals given a non-selective nicotinic receptor antagonist (mecamylamine) or agonist (epibatidine). Pretreatment with tetrodotoxin reduced the increase in mucosal permeability in response to luminal hypotonicity. Further, the non-selective muscarinic receptor antagonist (atropine) and agonist (bethanechol) reduced the hypotonicity-induced increase in mucosal permeability, while vagotomy was without an effect, suggesting that local enteric reflexes dominate. Finally, neither stimulating nor blocking the α7-nicotinic receptor had any significant effects on duodenal permeability in response to luminal hypotonicity, suggesting that this receptor is not involved in regulation of duodenal permeability. The effect of the different drugs on mucosal permeability was similar to the effect observed for duodenal motility.ConclusionsA complex enteric intramural excitatory neural reflex involving both nicotinic and muscarinic receptor subtypes mediates an increase in mucosal permeability induced by luminal hypotonicity.

Dietary polysaccharides from guavira pomace, a co-product from the fruit pulp industry, display therapeutic application in gut disorders

Inflammatory bowel disease (IBD) includes two distinct diseases: Crohn's disease (CD) and ulcerative colitis (UC). IBD is a chronic systemic disease of the gastrointestinal tract, characterized by an inflammatory process. The mechanisms by which diseases develop are still unknown, but it is known that it results from a complex interaction between genetic variability, the host's immune system, and environmental factors. One of the main complaints of patients is abdominal pain, which may be associated with the release of inflammatory mediators, changes in the normal motility of the digestive tract, and increased intestinal permeability. Currently available drugs for abdominal pain are not satisfactory, therefore, it is extremely necessary to seek new therapeutic options for the treatment of abdominal pain. Polysaccharides extracted from fruits have attracted interest, as these molecules protect the intestinal mucosa and promote wound healing, attenuating inflammation, pain, and altered intestinal motility. In this study, we investigated the ability of pectic polysaccharides obtained from guavira pomace, named CPW to reduce visceral hypersensitivity, regulate intestinal motility, and control diarrhea in mice. Acetic acid, capsaicin, or mustard oil were used to assess visceral pain in normal mice. CPW reduced abdominal writhing, cell migration, and capsaicin-induced visceral nociception. Furthermore, it regulated intestinal motility and all measured parameters of castor oil-induced diarrhea. CPW treatment reversed the increase in mucosal permeability, TEER, and tissue weight caused by acetic acid. In addition, molecular docking analysis showed that specific the CPW units binds to the 3N8V, 5COX, 2J67 and 6RBF proteins. Thus, the results suggest that CPW has attractive therapeutic characteristics for the treatment of abdominal pain and ulcerative colitis.

The Impact of α-Adrenoceptors in the Regulation of the Hypotonicity-Induced Increase in Duodenal Mucosal Permeability In Vivo.

The duodenal mucosa is regularly exposed to a low osmolality, and recent experiments suggest that hypotonicity increases mucosal permeability in an osmolality-dependent manner. The aim was to examine whether the sympathetic nervous system, via action on α-adrenoceptors, affects the hypotonicity-induced increase in duodenal mucosal permeability. The duodenum of anaesthetised rats was perfused in vivo with a 50 mM NaCl solution in the presence of adrenergic α-adrenoceptor drugs. Studied were the effects on mucosal permeability (blood-to-lumen clearance of 51Cr-EDTA), arterial blood pressure, luminal alkalinisation, transepithelial fluid flux, and motility. Hypotonicity induced a six-fold increase in mucosal permeability, a response that was reversible and repeatable. The α2-adrenoceptor agonist clonidine abolished the hypotonicity-induced increase in mucosal permeability, reduced arterial blood pressure, inhibited duodenal motility, and decreased luminal alkalinisation. The α2-adrenoceptor antagonists, yohimbine and idazoxan, prevented the inhibitory effect of clonidine on the hypotonicity-induced increase in mucosal permeability. The α1-agonist phenylephrine or the α1-antagonist prazosin elicited their predicted effect on blood pressure but did not affect the hypotonicity-induced increase in mucosal permeability. None of the α1- or α2-adrenoceptor drugs changed the hypotonicity-induced net fluid absorption. In conclusion, stimulation of the adrenergic α2-adrenoceptor prevents the hypotonicity-induced increase in mucosal permeability, suggesting that the sympathetic nervous system has the capability to regulate duodenal mucosal permeability.

Melatonin-Activated Receptor Signaling Pathways Mediate Protective Effects on Surfactant-Induced Increase in Jejunal Mucosal Permeability in Rats.

A well-functional intestinal mucosal barrier can be compromised as a result of various diseases, chemotherapy, radiation, and chemical exposures including surfactants. Currently, there are no approved drugs targeting a dysfunctional intestinal barrier, which emphasizes a significant medical need. One candidate drug reported to regulate intestinal mucosal permeability is melatonin. However, it is still unclear if its effect is primarily receptor mediated or antioxidative, and if it is associated with enteric neural pathways. The aim of this rat intestinal perfusion study was to investigate the mechanisms of melatonin and nicotinic acetylcholine receptors on the increase in intestinal mucosal clearance of 51Cr-labeled ethylenediaminetetraacetate induced by 15 min luminal exposure to the anionic surfactant, sodium dodecyl sulfate. Our results show that melatonin abolished the surfactant-induced increase in intestinal permeability and that this effect was inhibited by luzindole, a melatonin receptor antagonist. In addition, mecamylamine, an antagonist of nicotinic acetylcholine receptors, reduced the surfactant-induced increase in mucosal permeability, using a signaling pathway not influenced by melatonin receptor activation. In conclusion, our results support melatonin as a potentially potent candidate for the oral treatment of a compromised intestinal mucosal barrier, and that its protective effect is primarily receptor-mediated.

Vitamin D Deficiency Exacerbates Colonic Inflammation Due to Activation of the Local Renin-Angiotensin System in the Colon.

The renin-angiotensin system (RAS) is activated in inflammatory bowel disease (IBD), and vitamin D deficiency aggravates the development of colitis, but the relationship between the local colonic RAS and vitamin D is unclear with regard to the pathogenesis of IBD. To investigate whether vitamin D suppresses the local colonic RAS to prevent colonic mucosal inflammation in a mouse model of experimental colitis. C57BL/6 mice fed vitamin D-deficient (VDD) diet for 8weeks were induced to colitis by 2,4,6-trinitrobenzenesulfonic acid (TNBS), with mice fed vitamin D-sufficient (VDS) diet as controls. Colitis severity was assessed by histology, and pro-inflammatory cytokines, RAS components, and signaling pathways were quantified by real-time RT-PCR and Western blotting. C57BL/6 mice fed the VDD diet for 8weeks exhibited significantly lower serum 25(OH)D3 concentrations compared to mice fed the VDS diet. When these VDD mice were induced to colitis by TNBS, they exhibited more severe colonic inflammation and developed more severe colitis compared to the VDS counterparts. VDD diet feeding resulted in higher production of mucosal pro-inflammatory cytokines, higher activation of the myosin light chain kinase-tight junction regulatory pathway, and greater increases in mucosal permeability. VDD diet feeding also enhanced colonic RAS activation. Treatment with angiotensin II receptor blocker losartan markedly alleviated colitis in TNBS-induced VDD mice. Vitamin D deficiency promotes colonic inflammation at least in part due to over activation of the local RAS in the colon.

Medroxyprogesterone acetate and levonorgestrel increase genital mucosal permeability and enhance susceptibility to genital herpes simplex virus type 2 infection.

Depot-medroxyprogesterone acetate (DMPA) is a hormonal contraceptive especially popular in areas with high prevalence of HIV and other sexually transmitted infections (STI). While observational studies identify DMPA as an important STI risk factor, mechanisms underlying this connection are undefined. Levonorgestrel (LNG) is another progestin used for hormonal contraception, but its effect on STI susceptibility is much less explored. Using a mouse model of genital HSV-2 infection, we herein found DMPA and LNG similarly reduced genital expression of the desmosomal cadherin desmoglein-1α (DSG1α), enhanced access of inflammatory cells to genital tissue by increasing mucosal epithelial permeability, and increased susceptibility to viral infection. Additional studies with uninfected mice revealed DMPA-mediated increases in mucosal permeability promoted tissue inflammation by facilitating endogenous vaginal microbiota invasion. Conversely, concomitant treatment of mice with DMPA and intravaginal estrogen restored mucosal barrier function and prevented HSV-2 infection. Evaluating ectocervical biopsy tissue from women before and 1 month after initiating DMPA remarkably revealed inflammation and barrier protection were altered by treatment identically to changes seen in progestin-treated mice. Together, our work reveals DMPA and LNG diminish the genital mucosal barrier; a first-line defense against all STI, but may offer foundation for new contraceptive strategies less compromising of barrier protection.

Claudin-1 overexpression in intestinal epithelial cells enhances susceptibility to adenamatous polyposis coli-mediated colon tumorigenesis.

BackgroundThe tight junction protein Claudin-1, a claudin family member, has been implicated in several gastro-intestinal pathologies including inflammatory bowel disease (IBD) and colorectal cancer (CRC). In this regard, we have demonstrated that claudin-1 expression in colon cancer cells potentiates their tumorigenic ability while in vivo expression of claudin-1 in the intestinal epithelial cells (IECs) promotes Notch-activation, inhibits goblet cell differentiation and renders susceptibility to mucosal inflammation. Notably, a key role of inflammation in colon cancer progression is being appreciated. Therefore, we examined whether inflammation plays an important role in claudin-1-dependent upregulation of colon carcinogenesis.MethodsAPCmin mice were crossed with Villin-claudin-1 transgenic mice to generate APC-Cldn1 mice. H&E stained colon tissues were assessed for tumor number, size and histological grade. Additionally, microarray and qPCR analyses of colonic tumors were performed to assess molecular changes due to claudin-1 expression. APC-Cldn1 and APCmin controls were assessed for colonic permeability via rectal administration of FITC-dextran, and bacterial translocation via qPCR analysis of 16S rDNA.ResultsClaudin-1 overexpression in APCmin mice significantly increased (~4-fold) colonic tumor growth and size, and decreased survival. Furthermore, transcriptome analysis supported upregulated proliferation, and increased Wnt and Notch-signaling in APC-Cldn1 mice. APC-Cldn1 mice also demonstrated inhibition of mucosal defense genes while expression of pro-inflammatory genes was sharply upregulated, especially the IL-23/IL-17 signaling. We predict that increased Notch/Wnt-signaling underlie the early onset of adenoma formation in APC-Cldn1 mice. An increase in mucosal permeability due to the adenomas and the inherent barrier defect in these mice further facilitate bacterial translocation into the mucosa to induce inflammation, which in turn promote the tumorigenesis.ConclusionTaken together, these results confirm the role of claudin-1 as a promoter of colon tumorigenesis and further identify the role of the dysregulated antigen-tumor interaction and inflammation in claudin-1-dependent upregulation of colon tumorigenesis.

Mo1959 Basolateral IKCA Channel Inhibition by Octreotide Prevents the Increase in Mucosal Permeability Induced by Chemical Hypoxia in Human Colon: Implications for Preventing Sepsis After Major Abdominal Surgery

Background: Intestinal ischemia occurs frequently during major abdominal surgery, causing increasedmucosal permeability and bacterial translocation, thus increasing the risk of postoperative sepsis.We previously showed that chemical hypoxia stimulated basolateral, intermediate conductance, Ca2+-sensitive K+ (IKCa) channels and doubled paracellular shunt conductance (GS) (which reflects mucosal permeability) in human colon in vitro, changes which were completely inhibited by the serosal addition of IKCa channel blockers TRAM-34 and clotrimazole (Am J Physiol Gastrointest Liver Physiol 300:G146-G153,2011). Aim: To determine whether inhibition of basolateral IKCa channels by somatostatin (SOM) and its synthetic analog octreotide (OCT) (Am J Physiol Gastrointest Liver Physiol 277:G967-G975,1999) prevents the increase in GS induced by chemical hypoxia in human colon. Methods: With informed consent, sheets of muscle-stripped normal human distal colon (from cancer patients) were mounted in an Ussing chamber, and bathed with high-K+ gluconate solution (mucosal side) and high-Na+ gluconate solution (serosal side) at 37oC. While passing 2-sec rectangular current pulses (I; 50 μA), transepithelial voltage (VT), total tissue conductance (GT; = I/ΔVT) and calculated short-circuit current (Isc; = VT.GT) were monitored until constant values were obtained. Tissues acting as ‘controls' were gassed throughout with 95%O2/5%CO2. Other tissues gassed with 95%O2/5%CO2 were switched to 95%N2/5%CO2 when 100 μM dinitrophenol (DNP) was added mucosally and serosally to induce chemical hypoxia over 5-min. 2 μM SOM was added to hypoxic tissues either 10-min before or immediately after addition of DNP. Nystatin (500 U/ml) was then added mucosally to permeabilize the apical membrane, and VT, GT and Isc monitored at 10-sec intervals to steady-state. Similar experiments in hypoxic tissues established the dose response to OCT. GS was estimated from the y-axis intercept of the linear relationship between GT and Isc (J Membr Biol 45:81108,1979). Results: GS was significantly greater in hypoxic tissues (5.52±1.22 mS/cm2; n= 10) than in controls (3.65±1.34 mS/cm2; n=11, P<0.005). GS was similar in hypoxic tissues irrespective of whether SOM was added before (3.28±1.56 mS/cm2; n=6) or after (3.48±1.21 mS/cm2; n=6) the application of DNP. GS in both SOM groups was significantly lower than in tissues treated with DNP alone (P<0.05), but similar to GS in controls. Dose response data indicated that 0.2 μM OCT and 2 μM OCT/SOM had the same protective effect on GS. Conclusion: Our results suggest that perioperative administration of OCT (a long-acting synthetic analog of SOM) during major abdominal surgery may prevent the increase in intestinal mucosal permeability associated with intestinal ischemia, thereby decreasing the likelihood of bacterial translocation and post-operative sepsis.

Acyl-homoserine lactones suppresses IEC-6 cell proliferation and increase permeability of isolated rat colon.

We investigated to determine whether a variety of acyl-homoserine lactones (AHLs) influences epithelial cell proliferation and mucosal permeability. 3-Oxo-C12-homoserine lactone (HSL) and 3-oxo-C14-HSL significantly suppressed IEC-6 cell proliferation. A significant increase in mucosal permeability was observed in isolated rat colon tissue exposed to C12-HSL, 3-oxo-C12-HSL, and 3-oxo-C14-HSL. These data indicate that AHLs suppress epithelial proliferation and disrupt barrier function in intestinal mucosa.

Is intra-abdominal hypertension a missing factor that drives multiple organ dysfunction syndrome?

In a recent issue of Critical Care, Cheng and colleagues conducted a rabbit model study that demonstrated that intra-abdominal hypertension (IAH) may damage both gut anatomy and function. With only 6 hours of IAH at 25 mmHg, these authors observed an 80% reduction in mucosal blood flow, an exponential increase in mucosal permeability, and erosion and necrosis of the jejunal villi. Such dramatic findings should remind all caring for the critically ill that IAH may severely damage the normal gut barrier functions and thus may be reasonably expected to facilitate bacterial and mediator translocation. The potential contribution of IAH as a confounding factor in the efficacy of selective decontamination of the digestive tract should be considered.

SerpinB2 Is Critical to Th2 Immunity against Enteric Nematode Infection

SerpinB2, a member of the serine protease inhibitor family, is expressed by macrophages and is significantly upregulated by inflammation. Recent studies implicated a role for SerpinB2 in the control of Th1 and Th2 immune responses, but the mechanisms of these effects are unknown. In this study, we used mice deficient in SerpinB2 (SerpinB2(-/-)) to investigate its role in the host response to the enteric nematode, Heligmosomoides bakeri. Nematode infection induced a STAT6-dependent increase in intestinal SerpinB2 expression. The H. bakeri-induced upregulation of IL-4 and IL-13 expression was attenuated in SerpinB2(-/-) mice coincident with an impaired worm clearance. In addition, lack of SerpinB2 in mice resulted in a loss of the H. bakeri-induced smooth muscle hypercontractility and a significant delay in infection-induced increase in mucosal permeability. Th2 immunity is generally linked to a CCL2-mediated increase in the infiltration of macrophages that develop into the alternatively activated phenotype (M2). In H. bakeri-infected SerpinB2(-/-) mice, there was an impaired infiltration and alternative activation of macrophages accompanied by a decrease in the intestinal CCL2 expression. Studies in macrophages isolated from SerpinB2(-/-) mice showed a reduced CCL2 expression, but normal M2 development, in response to stimulation of Th2 cytokines. These data demonstrate that the immune regulation of SerpinB2 expression plays a critical role in the development of Th2-mediated protective immunity against nematode infection by a mechanism involving CCL2 production and macrophage infiltration.

Melatonin inhibits alcohol-induced increases in duodenal mucosal permeability in rats in vivo

Increased intestinal permeability is often associated with epithelial inflammation, leaky gut, or other pathological conditions in the gastrointestinal tract. We recently found that melatonin decreases basal duodenal mucosal permeability, suggesting a mucosal protective mode of action of this agent. The aim of the present study was to elucidate the effects of melatonin on ethanol-, wine-, and HCl-induced changes of duodenal mucosal paracellular permeability and motility. Rats were anesthetized with thiobarbiturate and a ~30-mm segment of the proximal duodenum was perfused in situ. Effects on duodenal mucosal paracellular permeability, assessed by measuring the blood-to-lumen clearance of ⁵¹Cr-EDTA, motility, and morphology, were investigated. Perfusing the duodenal segment with ethanol (10 or 15% alcohol by volume), red wine, or HCl (25-100 mM) induced concentration-dependent increases in paracellular permeability. Luminal ethanol and wine increased, whereas HCl transiently decreased duodenal motility. Administration of melatonin significantly reduced ethanol- and wine-induced increases in permeability by a mechanism abolished by the nicotinic receptor antagonists hexamethonium (iv) or mecamylamine (luminally). Signs of mucosal injury (edema and beginning of desquamation of the epithelium) in response to ethanol exposure were seen only in a few villi, an effect that was histologically not changed by melatonin. Melatonin did not affect HCl-induced increases in mucosal permeability or decreases in motility. Our results show that melatonin reduces ethanol- and wine-induced increases in duodenal paracellular permeability partly via an enteric inhibitory nicotinic-receptor dependent neural pathway. In addition, melatonin inhibits ethanol-induced increases in duodenal motor activity. These results suggest that melatonin may serve important gastrointestinal barrier functions.

Tu1357 Melatonin Reduce Basal and Ethanol-Induced Increases in Mucosal Permeability in Rat Duodenum In Vivo

Tu1357 Melatonin Reduce Basal and Ethanol-Induced Increases in Mucosal Permeability in Rat Duodenum In Vivo

Pathogenesis of NSAID-induced gastric damage: Importance of cyclooxygenase inhibition and gastric hypermotility

This article reviews the pathogenic mechanism of non-steroidal anti-inflammatory drug (NSAID)-induced gastric damage, focusing on the relation between cyclooxygenase (COX) inhibition and various functional events. NSAIDs, such as indomethacin, at a dose that inhibits prostaglandin (PG) production, enhance gastric motility, resulting in an increase in mucosal permeability, neutrophil infiltration and oxyradical production, and eventually producing gastric lesions. These lesions are prevented by pretreatment with PGE₂ and antisecretory drugs, and also via an atropine-sensitive mechanism, not related to antisecretory action. Although neither rofecoxib (a selective COX-2 inhibitor) nor SC-560 (a selective COX-1 inhibitor) alone damages the stomach, the combined administration of these drugs provokes gastric lesions. SC-560, but not rofecoxib, decreases prostaglandin E₂ (PGE₂) production and causes gastric hypermotility and an increase in mucosal permeability. COX-2 mRNA is expressed in the stomach after administration of indomethacin and SC-560 but not rofecoxib. The up-regulation of indomethacin-induced COX-2 expression is prevented by atropine at a dose that inhibits gastric hypermotility. In addition, selective COX-2 inhibitors have deleterious influences on the stomach when COX-2 is overexpressed under various conditions, including adrenalectomy, arthritis, and Helicobacter pylori-infection. In summary, gastric hypermotility plays a primary role in the pathogenesis of NSAID-induced gastric damage, and the response, causally related with PG deficiency due to COX-1 inhibition, occurs prior to other pathogenic events such as increased mucosal permeability; and the ulcerogenic properties of NSAIDs require the inhibition of both COX-1 and COX-2, the inhibition of COX-1 upregulates COX-2 expression in association with gastric hypermotility, and PGs produced by COX-2 counteract the deleterious effect of COX-1 inhibition.

Osmoregulation in rat duodenum is dependent on nicotinic acetylcholine receptors

We have recently shown that the responsiveness of the duodenum to luminal hypertonicity is markedly enhanced in COX-2 inhibited rats. Compared to control rats, COX-2 inhibited ones respond to perfusion with 700 mosmol/kg NaCl with an increase in mucosal permeability, a greater fluid secretion, inhibition of duodenal motility and a better capability to adjust luminal osmolality. The aim of this study was to elucidate whether the hypertonicity-induced changes of duodenal functions are affected by hexamethonium (HM) and mecamylamine (M), two known nicotinic acetylcholine receptor (nAChR) antagonists, in COX-2 inhibited rats. The proximal duodenum of anesthetized rats were perfused in situ for 60 min with 700 mosmol/kg NaCl and the effects on mucosal permeability, fluid secretion, motility, luminal fluid osmolality and arterial blood pressure (MAP) studied in the absence and presence of intravenous HM (10 mg/kg, h) or luminal M [10−4M]. Results HM and M significantly attenuated the hypertonicity-induced increase in permeability, fluid secretion and the capability to decrease luminal osmolality. Both HM and M decreased duodenal motility but only HM decreased MAP. Conclusions The capability of the duodenum to adjust luminal hypertonicity depends on enteric neural activity involving nAChR. Uppsala University.

The impact of cyclooxygenase inhibition on duodenal motility and mucosal alkaline secretion in anaesthetized rats

Non-steroidal anti-inflammatory drugs (NSAIDs) are effective in the treatment of various human diseases. However, these drugs also have serious adverse effects in the gastrointestinal tract. In the duodenum NSAIDs inhibit mucosal alkaline secretion (DMAS), an important protective mechanism against the acid emptied from the stomach in most species, including humans. Surprisingly, NSAIDs have been shown to stimulate DMAS in an anaesthetized rat model. The aim of this review was to summarize the effects of NSAIDs and selective cyclooxygenase-2 (COX-2) inhibition on duodenal function in the rat and provide an explanation for why these drugs stimulate DMAS. Included are new data examining the effect of α-adrenergic drugs on duodenal motility and DMAS. Experiments were performed in anaesthetized rats. The proximal duodenum was perfused luminally with an isotonic NaCl solution. DMAS, motility, fluid flux and epithelial permeability were assessed in the absence and presence of various COX inhibitors. COX inhibition induced duodenal motility, increased DMAS and augmented the sensitivity as well as the maximal response of the duodenal mucosa to lidocaine- or hypotonicity-induced increases in mucosal permeability. Furthermore, the ability of the duodenum to absorb water and to adjust osmolality in response to luminal hypotonicity was improved in COX-inhibited animals. These improvements are mediated predominately via inhibition of COX-2. Inhibition of COX-2 in rats with postoperative duodenal ileus induces muscle contractions, which in turn activate a nicotinic receptor-dependent intramural reflex that stimulates duodenocytes to increase the activity of apical Cl⁻/HCO₃⁻ exchangers, resulting in a rise in DMAS.

Lactobacillus rhamnosus alleviates intestinal barrier dysfunction in part by increasing expression of zonula occludens-1 and myosin light-chain kinase in vivo

The effects of lactobacilli on impaired intestinal barrier function and paracellular permeability were evaluated in human epithelial Caco-2 cells treated with tumor necrosis factor-α and in mice with colitis induced by dextran sodium sulfate (DSS). Filter-grown Caco-2 monolayers were used as the intestinal epithelial model. Among the 4 lactobacilli studied, Lactobacillus rhamnosus OLL2838 most effectively suppressed barrier impairment and increased IL-8 secretion induced by tumor necrosis factor-α in Caco-2 cells; however, the conditioned medium from OLL2838 did not show any effect on barrier functions. The in vivo effects of OLL2838 on intestinal epithelial barrier function and colonic inflammation were assessed in DSS-induced colitis of BALB/c mice. Oral treatment with both live and heat-killed OLL2838 suppressed weight loss and recovered colon length. Additionally, barrier function was restored by the administration of live and heat-killed OLL2838 to the DSS-treated animals, which conferred protection against the increase in mucosal permeability associated with DSS-induced colitis. This may at least partially be because of the increased expression of zonula occludens-1 (4.8-fold) and myosin light-chain kinase (3.1-fold) in intestinal epithelial cells isolated from mice of the heat-killed OLL2838 group. Therefore, L. rhamnosus OLL2838 would be useful in the treatment of gastrointestinal diseases such as inflammatory bowel disease.

Dietary plasma proteins, the intestinal immune system, and the barrier functions of the intestinal mucosa1

ABSTRACTThe intestinal mucosa contributes to homeostasis by preventing the entrance of biological and chemical agents across the epithelium that could alter the stability of the system. This protective function is especially important at the time of weaning, when animals are exposed to infectious agents and to numerous stresses such as the change of environment and diet. Diets supplemented with spray-dried plasma or plasma protein fractions have been shown to improve growth performance of farm animals and have been proposed as an alternative to antibiotics. In this review, we summarize our findings on the mechanism of action of dietary plasma proteins using a rat model of intestinal inflammation, based on the administration of Staphylococcus aureus enterotoxin B (SEB). Staphylococcal enterotoxin B activates the gut-associated lymphoid tissue (GALT), increasing T-lymphocytes in Peyer's patches and the number of activated T lymphocytes in mesenteric lymph nodes (organized GALT). In the lamina propria SEB increased cytotoxic T δγ and natural killer cell populations of the diffuse GALT. Staphyloccocal enterotoxin B significantly increased proinflammatory cytokines in Peyer's patches and mucosa. Plasma protein supplements modulated the mucosal immune response in organized and diffuse GALT, protecting GALT from possible excessive activation by the SEB challenge. These effects are accompanied by a reduction of proinflammatory cytokine production, supporting the view that changes in cytokine production mediate the effects of dietary plasma proteins during intestinal inflammation. The increase in mucosal permeability and intestinal secretion induced by SEB was associated with decreased expression of mucosal tight-junction and adherent-junction proteins. Both plasma and plasma protein fractions prevented the effects of SEB on intestinal permeability, thus reducing the exposure of the host to microbial and food antigens across the interstitial space. These findings indicate that dietary plasma proteins modulate functional and structural properties of the intestinal mucosa.