Evans blue permeation of intestinal mucosa in the rat

Role of Stress on Driving the Intestinal Paracellular Permeability

The gut epithelium is a polarized monolayer that exhibits apical and basolateral membrane surfaces. Monolayer cell components are joined side by side via protein complexes known as tight junction proteins (TJPs), expressed at the most apical extreme of the basolateral membrane. The gut epithelium is a physical barrier that determinates intestinal permeability, referred to as the measurement of the transit of molecules from the intestinal lumen to the bloodstream or, conversely, from the blood to the gut lumen. TJPs play a role in the control of intestinal permeability that can be disrupted by stress through signal pathways triggered by the ligation of receptors with stress hormones like glucocorticoids. Preclinical studies conducted under in vitro and/or in vivo conditions have addressed underlying mechanisms that account for the impact of stress on gut permeability. These mechanisms may provide insights for novel therapeutic interventions in diseases in which stress is a risk factor, like irritable bowel syndrome. The focus of this study was to review, in an integrative context, the neuroendocrine effects of stress, with special emphasis on TJPs along with intestinal permeability.

Bifidobacterium breve Bif11 supplementation improves depression-related neurobehavioural and neuroinflammatory changes in the mouse

Gut dysbiosis has been closely linked to the onset and progression of several brain-related disorders such as depression. The administration of microbiota-based formulations such as probiotics helps restore healthy gut flora and plays a role in preventing and treating depression-like behavior. Therefore, we evaluated the efficacy of probiotic supplementation using our recently isolated putative probiotic Bifidobacterium breve Bif11 in ameliorating lipopolysaccharide (LPS)-induced depression-like behavior in male Swiss albino mice. Mice were fed orally with B. breve Bif11 (1 × 10¹⁰ CFU and 2 × 10¹⁰ CFU) for 21 days before being challenged with a single intraperitoneal LPS injection (0.83 mg/kg). Behavioral, biochemical, histological and molecular analysis were done with an emphasis on inflammatory pathways linked to depression-like behavior. Daily supplementation with B. breve Bif11 for 21 days prevented the onset of depression-like behavior induced by LPS injection, besides reducing the levels of inflammatory cytokines such as matrix metalloproteinase-2, c-reactive protein, interleukin-6, tumor necrosis factor-alpha and nuclear factor kappa-light-chain-enhancer of activated B cells. It also prevented the decrease of the brain-derived neurotrophic factor levels and neuronal cell viability in the prefrontal cortex of LPS-treated mice. Furthermore, we observed that gut permeability was reduced, there was an improved short-chain fatty acid profile and reduced gut dysbiosis in the LPS mice fed with B. breve Bif11. Similarly, we observed a decrease in behavioural deficits and restoration of gut permeability in chronic mild stress. Together, these results would help in deciphering the role of probiotics in the management of neurological disorders where depression, anxiety and inflammation are prominent clinical features.

Ghrelin prevents lethality in a rat endotoxemic model through central effects on the vagal pathway and adenosine A2B signaling : Brain ghrelin and anti-septic action

Accumulating evidence suggest that ghrelin plays a role as an antiseptic peptide. The present study aimed to clarify whether the brain may be implicated ghrelin's antiseptic action. We examined the effect of brain ghrelin on survival in a novel endotoxemic model achieved by treating rats with lipopolysaccharide (LPS) and colchicine. The observation of survival stopped three days after chemicals' injection or at death. Intracisternal ghrelin dose-dependently reduced lethality in the endotoxemic model; meanwhile, neither intraperitoneal injection of ghrelin nor intracisternal des-acyl-ghrelin injection affected the mortality rate. The brain ghrelin-induced lethality reduction was significantly blocked by surgical vagotomy. Moreover, intracisternal injection of a ghrelin receptor antagonist blocked the improved survival achieved by intracisternal ghrelin injection or intravenous 2-deoxy-d-glucose administration. Intracisternal injection of an adenosine A2B receptor agonist reduced the lethality and the ghrelin-induced improvement of survival was blocked by adenosine A2B receptor antagonist. I addition, intracisternal ghrelin significantly blocked the colonic hyperpermeability produced by LPS and colchicine. These results suggest that ghrelin acts centrally to reduce endotoxemic lethality. Accordingly, activation of the vagal pathway and adenosine A2B receptors in the brain may be implicated in the ghrelin-induced increased survival. Since the efferent vagus nerve mediates anti-inflammatory mechanisms, we speculate that the vagal cholinergic anti-inflammatory pathway is implicated in the decreased septic lethality caused by brain ghrelin.

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.

Activation of basal forebrain cholinergic neurons improves colonic hyperpermeability through the vagus nerve and adenosine A2B receptors in rats

Intestinal barrier dysfunction, a leaky gut, contributes to the pathophysiology of various diseases such as dementia and irritable bowel syndrome (IBS). We recently clarified that orexin, ghrelin, or adenosine A2B signaling in the brain improved leaky gut through the vagus nerve. The present study was performed to clarify whether basal forebrain cholinergic neurons (BFCNs) are implicated in the central regulation of intestinal barrier function. We activated BFCNs using benzyl quinolone carboxylic acid (BQCA), a positive muscarinic M1 allosteric modulator, and evaluated colonic permeability by quantifying the absorbed Evans blue in rat colonic tissue. Intracisternal (not intraperitoneal) injection of BQCA blocked the increased colonic permeability in response to lipopolysaccharide. Vagotomy blocked BQCA-induced improvement of colonic hyperpermeability. Intracisternally administered pirenzepine, a muscarinic M1 selective antagonist, prevented intestinal barrier function improvement by intravenously administered 2-deoxy-d-glucose, central vagal stimulant. Adenosine A2B receptor antagonist but not dopamine or opioid receptor antagonist prevented BQCA-induced blockade of colonic hyperpermeability. Additionally, intracisternal injection of pirenzepine blocked orexin- or butyrate-induced intestinal barrier function improvement. These results suggest that BFCNs improve leaky gut through adenosine A2B signaling and the vagal pathway. Furthermore, BFCNs mediate orexin- or butyrate-induced intestinal barrier function improvement. Since BFCNs play a role in cognitive function and a leaky gut is associated with dementia, the present finding may lead us to speculate that BFCNs are involved in the development of dementia by regulating intestinal barrier function.

Characterizing the Contributions of Various Clostridium perfringens Enterotoxin Properties to In Vivo and In Vitro Permeability Effects

Clostridium perfringens enterotoxin (CPE) is thought to cause lethal enterotoxemia when absorbed from the intestinal lumen into the circulation. CPE action sequentially involves receptor-binding, oligomerization into a prepore, and pore formation. To explore the mechanistic basis by which CPE alters permeability, this study tested the permeability effects of several recombinant CPE (rCPE) species: rCPE and rCPE_C186A (which form pores), rC-CPE and rCPE_D48A (which bind to receptors but cannot oligomerize), rCPE_C186A/F91C (which binds and oligomerizes without pore formation), and rCPE_Y306A/L315A (which has poor receptor-binding ability). On Caco-2 cells, i) only rCPE and rCPE_C186A were cytotoxic; ii) rCPE and rCPE_C186A affected transepithelial resistance (TEER) and 4 kDa fluorescent dextran (FD4) transit more quickly than binding-capable, but noncytotoxic, rCPE variants; whereas iii) rCPE_Y306A/L315A did not affect TEER or FD4 transit. Using mouse intestinal loops, rCPE (but not noncytotoxic rC-CPE, rCPE_D48A or rCPE_Y306A/L315A) was lethal and caused intestinal histologic damage within 4 h. After 2 h of treatment, rCPE was more strongly absorbed into the serum than those noncytotoxic rCPE species but by 4 h rC-CPE and rCPE_D48A became absorbed similarly as rCPE, while rCPE_Y306A/L315A absorption remained low. This increased rC-CPE and rCPE_D48A absorption from 2 to 4 h did not involve a general intestinal permeability increase because Evans Blue absorption from the intestines did not increase between 2 and 4 h of treatment with rC-CPE or rCPE_D48A. Collectively, these results indicate that CPE receptor binding is sufficient to slowly affect permeability, but CPE-induced cytotoxicity is necessary for rapid permeability changes and lethality. IMPORTANCE Clostridium perfringens enterotoxin (CPE) causes lethal enterotoxemia when absorbed from the intestines into the bloodstream. Testing recombinant CPE (rCPE) or rCPE variants impaired for various specific steps in CPE action showed that full CPE-induced cytotoxicity causes rapid Caco-2 monolayer permeability alterations, as well as enterotoxemic lethality and rapid CPE absorption in mouse small intestinal loops. However, receptor binding-capable, but noncytotoxic, rCPE variants did cause slow-developing in vitro and in vivo permeability effects. Absorption of binding-capable, noncytotoxic rCPE variants from the intestines did not correlate with general intestinal permeability alterations, suggesting that CPE binding can induce its own uptake. These findings highlight the importance of binding and, especially, cytotoxicity for CPE absorption during enterotoxemia and may assist development of permeability-altering rCPE variants for translational purposes.

Oxytocin acts centrally in the brain to improve leaky gut through the vagus nerve and a cannabinoid signaling in rats

Brain oxytocin plays a role in gastrointestinal functions. Among them, oxytocin acts centrally to modulate gastrointestinal motility and visceral sensation. Intestinal barrier function, one of important gut functions, is also regulated by the central nervous system. Little is, however, known about a role of central oxytocin in the regulation of intestinal barrier function. The present study was performed to clarify whether brain oxytocin is also involved in regulation of 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 oxytocin dose-dependently abolished increased colonic permeability in response to lipopolysaccharide while intraperitoneal injection of oxytocin at the same dose failed to block it. Either atropine or surgical vagotomy blocked the central oxytocin-induced improvement of colonic hyperpermeability. Cannabinoid 1 receptor antagonist but not adenosine or opioid receptor antagonist prevented the central oxytocin-induced blockade of colonic hyperpermeability. In addition, intracisternal injection of oxytocin receptor antagonist blocked the ghrelin- or orexin-induced improvement of intestinal barrier function. These results suggest that oxytocin acts centrally in the brain to reduce colonic hyperpermeability. The vagal cholinergic pathway or cannabinoid 1 receptor signaling plays a vital role in the process. The oxytocin-induced improvement of colonic hyperpermeability mediates the central ghrelin- or orexin-induced improvement of intestinal barrier function. We would therefore suggest that activation of central oxytocin signaling may be useful for leaky gut-related diseases such as irritable bowel syndrome and autism.

Barrier effect and wound healing activity of the medical device REF-FTP78 in the treatment of gastroesophageal reflux disease

REF-FTP78 is a class IIb medical device present on the market with different trade names and developed for the treatment of gastroesophageal reflux disease (GERD). This medical device is based on polysaccharides from Aloe Barbadensis and fucoidans from brown seaweeds, such as Undaria pinnatifida and Fucus vesiculosus, and aims to exert a protective effect on the esophageal mucosa against the noxious components of refluxate. The present study reports on the efficacy of REF-FTP78 devoting a particular attention to the barrier effect and wound healing properties, combined with antioxidant and anti-inflammatory activities. Film-forming properties and barrier effect were investigated on in vitro reconstructed human esophageal epithelium, through TEER measurement and evaluation of caffeine and Lucifer yellow permeability, and in an ex vivo swine model of esophageal mucosa damage. Antioxidant and anti-inflammatory properties were evaluated in terms of scavenging activity towards DPPH, ABTS and NO radicals and a wound healing assay was carried out to study the influence of the product on cell migration. The obtained results highlighted a significant barrier effect, with a reduction in caffeine penetration equal to 65.3%, the ability to both repair and prevent the damage caused by an acid insult, confirmed by a good transepithelial resistance for the tissue treated with the tested item, and the capacity to promote wound healing. Furthermore, the tested product showed good antioxidant and anti-inflammatory properties in the performed radical scavenging assays. These findings support the use of REF-FTP78 in the treatment of GERD.

GPR120 prevents colorectal adenocarcinoma progression by sustaining the mucosal barrier integrity

GPR120 (encoded by FFAR4 gene) is a receptor for long chain fatty acids, activated by ω-3 Polyunsaturated Fatty Acids (PUFAs), and expressed in many cell types. Its role in the context of colorectal cancer (CRC) is still puzzling with many controversial evidences. Here, we explored the involvement of epithelial GPR120 in the CRC development. Both in vitro and in vivo experiments were conducted to mimic the conditional deletion of the receptor from gut epithelium. Intestinal permeability and integrity of mucus layer were assessed by using Evans blue dye and immunofluorescence for MUC-2 protein, respectively. Microbiota composition, presence of lipid mediators and short chain fatty acids were analyzed in the stools of conditional GPR120 and wild type (WT) mice. Incidence and grade of tumors were evaluated in all groups of mice before and after colitis-associated cancer. Finally, GPR120 expression was analyzed in 9 human normal tissues, 9 adenomas, and 17 primary adenocarcinomas. Our work for the first time highlights the role of the receptor in the progression of colorectal cancer. We observed that the loss of epithelial GPR120 in the gut results into increased intestinal permeability, microbiota translocation and dysbiosis, which turns into hyperproliferation of epithelial cells, likely through the activation of β -catenin signaling. Therefore, the loss of GPR120 represents an early event of CRC, but avoid its progression as invasive cancer. these results demonstrate that the epithelial GPR120 receptor is essential to maintain the mucosal barrier integrity and to prevent CRC developing. Therefore, our data pave the way to GPR120 as an useful marker for the phenotypic characterization of CRC lesions and as new potential target for CRC prevention.

Activating Transcription Factor 3 Protects against Restraint Stress-Induced Gastrointestinal Injury in Mice

Psychological stress increases the risk of gastrointestinal (GI) tract diseases, which involve bidirectional communication of the GI and nerves systems. Acute stress leads to GI ulcers; however, the mechanism of the native cellular protection pathway, which safeguards tissue integrality and maintains GI homeostasis, remains to be investigated. In a mouse model of this study, restraint stress induced GI leakage, abnormal tight junction protein expression, and cell death of gut epithelial cells. The expression of activating transcription factor 3 (ATF3), a stress-responsive transcription factor, is upregulated in the GI tissues of stressed animals. ATF3-deficient mice displayed an exacerbated phenotype of GI injuries. These results suggested that, in response to stress, ATF3 is part of the native cellular protective pathway in the GI system, which could be a molecular target for managing psychological stress-induced GI tract diseases.

Effects of emodin on intestinal mucosal barrier by the upregulation of miR-218a-5p expression in rats with acute necrotizing pancreatitis

Emodin is an effective component in rhubarb to cure intestinal dysfunction, but the specific mechanism remains unknown. This study aimed to evaluate the protective effects of emodin on intestinal dysfunction caused by acute severe pancreatitis and reveal the functional mechanism of emodin in the treatment of this condition. An acute severe pancreatitis model was prepared using taurocholate. In the treatment group, 50 mg/kg emodin was injected intravenously 2 h before the induction of acute severe pancreatitis at an interval of 8 h. After 24 h, the gene expression and protein levels of miR-218a-5p, RhoA, ROCK1, Akt, Notch1, Bax, Bcl-2, Fas, FasL, caspase-3, and caspase-9 were determined through reverse transcription polymerase chain reaction and Western blot analysis. The protein levels of occludin, zonula occludens-1 (ZO-1), and E-cadherin in the intestinal tract were also determined through Western blot analysis. The effects of miR-218a-5p on the apoptosis of rat intestinal epithelial cell-18 were observed through flow cytometry. The effects of emodin on intestinal cell apoptosis induced by acute severe pancreatitis were observed via TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling). Pathological changes in the pancreas and intestine of rats in each group were observed through hematoxylin and eosin staining. After 24 h of acute severe pancreatitis induced by taurocholate, emodin reduced the expression of miR-218a-5p in the intestinal tract; increased the expression of Notch1 and Bcl-2; decreased the expression levels of RhoA, ROCK1, Akt, Bax, Fas, FasL, caspase-3, and caspase-9; inhibited the intestinal cell apoptosis caused by acute severe pancreatitis; increased the protein expression levels of occludin, zonula occludens-1 (ZO-1), and E-cadherin in the intestinal tract; and alleviated intestinal dysfunction caused by acute severe pancreatitis. Emodin could regulate Notch1 and RhoA/ROCK pathways by regulating the miR-218a-5p expression in the intestine. It could also inhibit intestinal cell apoptosis induced by acute severe pancreatitis and improve the intestinal dysfunction caused by severe acute pancreatitis.

Activation of central adenosine A2B receptors mediate brain ghrelin-induced improvement of intestinal barrier function through the vagus nerve in rats

Leaky gut that is a condition reflecting intestinal barrier dysfunction has been attracting attention for its relations with many diseases such as irritable bowel syndrome or Alzheimer dementia. We have recently demonstrated that ghrelin acts in the brain to improve leaky gut via the vagus nerve. In the present study, we tried to clarify the precise central mechanisms by which ghrelin improves intestinal barrier function through the vagus nerve. Colonic permeability was estimated in vivo by quantifying the absorbed Evans blue in colonic tissue in rats. Adenosine receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), blocked the intracisternal ghrelin-induced improvement of intestinal hyperpermeability while dopamine, cannabinoid or opioid receptor antagonist failed to prevent it. Since DPCPX can block adenosine A1 and adenosine A2B receptors, we examined which subtype is involved in the mechanism. Intracisternal injection of adenosine A2B agonist but not adenosine A1 agonist improved colonic hyperpermeability, while peripheral injection of adenosine A2B agonist failed to improve it. Intracisternal adenosine A2B agonist-induced improvement of colonic hyperpermeability was blocked by vagotomy. Adenosine A2B specific antagonist, alloxazine blocked the ghrelin- or central vagal stimulation by 2-deoxy-d-glucose-induced improvement of intestinal hyperpermeability. These results suggest that activation of adenosine A2B receptors in the central nervous system is capable of improving intestinal barrier function through the vagal pathway, and the adenosine A2B receptors may mediate the ghrelin-induced improvement of leaky gut in a vagal dependent fashion. These findings may help us understand the pathophysiology in not only gastrointestinal diseases but also non-gastrointestinal diseases associated with the altered intestinal permeability.

PARK7 Diminishes Oxidative Stress-Induced Mucosal Damage in Celiac Disease

Coeliac disease (CD) is a chronic, immune-mediated small intestinal enteropathy, accompanied with gluten-triggered oxidative damage of duodenal mucosa. Previously, our research group reported an increased mucosal level of the antioxidant protein Parkinson's disease 7 (PARK7) in children with CD. In the present study, we investigated the role of increased PARK7 level on the epithelial cell and mucosal integrity of the small intestine. The presence of PARK7 was investigated using immunofluorescent staining on duodenal mucosa of children with CD and on FHs74Int duodenal epithelial cells. To investigate the role of oxidative stress, FHs74Int cells were treated with H₂O₂ in the absence or presence of Comp23, a PARK7-binding compound. Intracellular accumulation of reactive oxygen species (ROS) was determined by DCFDA-based assay. Cell viability was measured by MTT, LDH, and Annexin V apoptosis assays. Disruption of cytoskeleton and cell adhesion was investigated by immunofluorescence staining and by real-time RT PCR. Effect of PARK7 on mucosal permeability was investigated ex vivo using intestinal sacs derived from control and Comp-23-pretreated mice. Comp23 treatment reduced the H₂O₂-induced intracellular accumulation of ROS, thus preserving the integrity of the cytoskeleton and also the viability of the FHs74Int cells. Accordingly, Comp23 treatment increased the expression of antioxidants (NRF2, TRX1, GCLC, HMOX1, NQO1), cell-cycle regulators (TP53, CDKN1A, PCNA, BCL2, BAX), and cell adhesion molecules (ZO1, CDH1, VCL, ITGB5) of H₂O₂-treated cells. Pretreatment with Comp23 considerably decreased the small intestinal permeability. In this study, we demonstrate that PARK7-binding Comp23 reduces the oxidative damage of duodenal epithelial cells, via increased expression of NRF2- and P53-regulated genes. Our results suggest that PARK7 plays a significant role in the maintenance of mucosal integrity in CD.

Antidepression and Prokinetic Effects of Paeoniflorin on Rats in the Forced Swimming Test via Polypharmacology

Paeoniflorin, an organic compound extracted from the roots of the white peony (Paeonia lactiflora) plant, has previously been shown to exert antidepression and prokinetic effects. The traditional Chinese prescription Si-Ni-San, of which paeoniflorin is a constituent, is often used in treating depression and functional gastrointestinal disorders. The effectiveness of Si-Ni-San has been shown to be less effective in a paeoniflorin-deleted form. The present study further investigates whether paeoniflorin alone is as effective as herbal prescriptions in which the compound is a constituent, specifically any antidepressive and prokinetic effect on rats subjected to a forced swimming test (FST). The FST was used to establish the depression model. Sprague-Dawley rats were administrated with 10 mg/kg paeoniflorin by gastrogavage three times before the behavioral test and gastrointestinal motility tests, respectively. In antidepression studies, fluoxetine was used as the positive control. In order to determine the effect of paeoniflorin on the gastrointestinal movement, mosapride was used as the positive control. Plasma and hippocampus monoamine, hypothalamic-pituitary-adrenal axis, plasma brain-derived neurotrophic factor (BDNF), superoxide dismutase (SOD), methane dicarboxylic aldehyde (MDA), ghrelin, motilin, and hippocampus nitric oxide (NO) were assessed using an enzyme-linked immunosorbent assay (ELISA). Gastrointestinal (GI) motility was measured in vivo and in vitro. Rats subjected to FST showed decreased gastric emptying and intestinal transit in vivo, decreased plasma and hippocampus 5-hydroxytryptamine, norepinephrine, dopamine, ghrelin, motilin, and reduced plasma BDNF and SOD as well as increased plasma and hippocampus corticotropin-releasing hormone, adrenocorticotropic hormone, corticosterone, plasma MDA, and hippocampus NO. Paeoniflorin reversed these symptoms in a similar manner to fluoxetine and mosapride, respectively. In vitro, paeoniflorin can stimulate the jejunal contract of healthy rats dose-dependently. The results suggest that paeoniflorin can simultaneously exert antidepression and prokinetic effects via polypharmacology.

Antisecretory factor AF-16 improves vascular access to a rat mammary tumour

Tumor tissue often has an insufficient nutritional supply, in part due to compression of the vascular network from an increased interstitial fluid pressure. We have shown that the antisecretory factor peptide AF-16 can reduce this pressure in experimental rat breast tumors. In this work we studied if AF-16 administration opened up to an increased vascular volume in these tumors. Sprague-Dawley rats were given dimethylbenxanthracene and developed mammary tumors which were studied. Evans Blue was used as an intravascular volume indicator. Under anesthesia the rats were given AF-16 or solvent intranasally, and Evans Blue was injected i.v. 45 min later. Tumors and various organs were dissected and Evans Blue was extracted and colorimetrically quantified. Tumors had a significantly higher vascular volume after AF-16 administration as compared to other organs. Liver and renal vascular volumes were also increased but to a lesser degree than in the tumors. The results indicate that AF16 could be a candidate for increasing vascular access for chemotherapy in cancer therapy.

Ghrelin acts in the brain to block colonic hyperpermeability in response to lipopolysaccharide through the vagus nerve

Brain ghrelin plays a role in gastrointestinal functions. Among them, ghrelin acts centrally to stimulate gastrointestinal motility and induce visceral antinociception. Intestinal barrier function, one of important gastrointestinal functions, is also controlled by the central nervous system. Little is, however, known about a role of central ghrelin in regulation of intestinal permeability. The present study was performed to clarify whether brain ghrelin is also involved in regulation of 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 ghrelin dose-dependently abolished increased colonic permeability in response to LPS while intraperitoneal injection of ghrelin at the same dose or intracisternal injection of des-acyl-ghrelin failed to block it. Carbachol potently attenuated LPS-induced intestinal hyperpermeability, and atropine or bilateral subdiaphragmatic vagotomy prevented the improvement of intestinal hyperpermeability by central ghrelin. Intracisternal (D-Lys3)-GHRP-6, a selective ghrelin receptor antagonist, significantly blocked improvement of intestinal barrier function by intravenously administered 2-deoxy-d-glucose, central vagal stimulant. Intracisternal injection of orexin 1 receptor antagonist, SB-334867 blocked intracisternal ghrelin-induced improvement of colonic hyperpermeability. These results suggest that exogenously administered or endogenously released ghrelin acts centrally to improve a disturbed intestinal barrier function through orexinergic signaling and the vagal cholinergic pathway. Central ghrelin may be involved in the pathophysiology and be a novel therapeutic option in not only gastrointestinal diseases such as irritable bowel syndrome but also non-gastrointestinal diseases associated with the altered intestinal permeability.

Scorpio D, Scozzoli M, Bettini G, Forni M, Bacci ML. Preliminary Assessment of the Mucosal Toxicity of Tea Tree (Melaleuca alternifolia) and Rosemary (Rosmarinus officinalis) Essential Oils on Novel Porcine Uterus Models

Antimicrobial resistance, an ever-growing global crisis, is strongly linked to the swine production industry. In previous studies, Melaleucaalternifolia and Rosmarinusofficinalis essential oils have been evaluated for toxicity on porcine spermatozoa and for antimicrobial capabilities in artificial insemination doses, with the future perspective of their use as antibiotic alternatives. The aim of the present research was to develop and validate in vitro and ex vivo models of porcine uterine mucosa for the evaluation of mucosal toxicity of essential oils. The in vitro model assessed the toxicity of a wider range of concentrations of both essential oils (from 0.2 to 500 mg/mL) on sections of uterine tissue, while the ex vivo model was achieved by filling the uterine horns. The damage induced by the oils was assessed by Evans Blue (EB) permeability assay and histologically. The expression of ZO-1, a protein involved in the composition of tight junctions, was assessed through immunohistochemical and immunofluorescence analysis. The results showed that low concentrations (0.2–0.4 mg/mL) of both essential oils, already identified as non-spermicidal but still antimicrobial, did not alter the structure and permeability of the swine uterine mucosa. Overall, these findings strengthen the hypothesis of a safe use of essential oils in inseminating doses of boar to replace antibiotics.

A study of the damage of the intestinal mucosa barrier structure and function of Ctenopharyngodon idella with Aeromonas hydrophila

The aim of this study is to explore the effect of Aeromonas hydrophila on the intestinal mucosal barrier structure and intestinal permeability in grass carp (Ctenopharyngodon idella). Histopathological examinations showed that A. hydrophila induced severe intestinal lesions, including inflammatory cell infiltration and intestinal villus fusion and swelling. Messenger RNA (mRNA) expression of the inflammatory cytokines TNF-α, IL-1β, IL-8, IL-10 and MyD88 was significantly increased after infection with A. hydrophila. The permeability of intestinal mucosa was determined using Evans blue (EB) and D-lactic acid. The results indicated that the levels of EB and serum D-lactic acid were significantly increased after infection with A. hydrophila (p < 0.05). Our results also indicated that the intestinal mucosal barrier injury induced by A. hydrophila infection was closely associated with the expression of the tight junction (TJ) protein zonula occludens-1 (ZO-1), occludin, claudin b and claudin c as well as the activity of Na⁺, K⁺-ATPase and Ca²⁺, Mg²⁺-ATPase. Lower mRNA levels of occludin and lower Na⁺, K⁺-ATPase and Ca²⁺, Mg²⁺-ATPase activity in the intestines were observed after challenge. ZO-1 and claudin c were significantly increased 24 h after infection with A. hydrophila. The most interesting finding was that claudin b also significantly increased 24 h after challenge and then decreased to lower levels at 72, 120 and 168 h post-infection compared to the PBS-treated control group. The results demonstrated that grass carp infection with A. hydrophila induced intestinal inflammation and impaired the structure and function of the intestinal mucosal barrier.

Entamoeba histolytica EhCP112 Dislocates and Degrades Claudin-1 and Claudin-2 at Tight Junctions of the Intestinal Epithelium

During intestinal invasion, Entamoeba histolytica opens tight junctions (TJs) reflected by transepithelial electrical resistance (TEER) dropping. To explore the molecular mechanisms underlying this, we studied in vitro and in vivo the damage produced by the recombinant E. histolytica cysteine protease (rEhCP112) on TJ functions and proteins. rEhCP112 reduced TEER in Caco-2 cells in a dose- and time-dependent manner; and EhCP112-overexpressing trophozoites provoked major epithelial injury compared to control trophozoites. rEhCP112 penetrated through the intercellular space, and consequently the ion flux increased and the TJs fence function was disturbed. However, macromolecular flux was not altered. Functional in vitro assays revealed specific association of rEhCP112 with claudin-1 and claudin-2, that are both involved in regulating ion flux and fence function. Of note, rEhCP112 did not interact with occludin that is responsible for regulating macromolecular flux. Moreover, rEhCP112 degraded and delocalized claudin-1, thus affecting interepithelial adhesion. Concomitantly, expression of the leaky claudin-2 at TJ, first increased and then it was degraded. In vivo, rEhCP112 increased intestinal epithelial permeability in the mouse colon, likely due to apical erosion and claudin-1 and claudin-2 degradation. In conclusion, we provide evidence that EhCP112 causes epithelial dysfunction by specifically altering claudins at TJ. Thus, EhCP112 could be a potential target for therapeutic approaches against amoebiasis.

Adherens junctions and desmosomes are damaged by Entamoeba histolytica: Participation of EhCPADH complex and EhCP112 protease

Entamoeba histolytica trophozoites adhere to epithelium at the cell-cell contact and perturb tight junctions disturbing the transepithelial electrical resistance. Behind tight junctions are the adherens junctions (AJs) that reinforce them and the desmosomes (DSMs) that maintain the epithelium integrity. The damage produced to AJs and DMSs by this parasite is unknown. Here, we studied the effect of the trophozoites, the EhCPADH complex, and the EhCP112 recombinant enzyme (rEhCP112) on AJ and DSM proteins. We found that trophozoites degraded β-cat, E-cad, Dsp l/ll, and Dsg-2 with the participation of EhCPADH and EhCP112. After contact of epithelial cells with trophozoites, immunofluorescence and transmission electron microscopy assays revealed EhCPADH and rEhCP112 at the intercellular space where they colocalised with β-cat, E-cad, Dsp l/ll, and Dsg-2. Moreover, our results suggested that rEhCP112 could be internalised by caveolae and clathrin-coated vesicles. Immunoprecipitation assays showed the interaction of EhCPADH with β-cat and Dsp l/ll. Besides, in vivo assays demonstrated that rEhCP112 concentrates at the cellular borders of the mouse intestine degrading E-cad and Dsp I/II. Our research gives the first clues on the trophozoite attack to AJs and DSMs and point out the role of the EhCPADH and EhCP112 in the multifactorial event of trophozoites virulence.

Effect of mesenchymal stem cells on small intestinal injury in a rat model of acute necrotizing pancreatitis

BACKGROUND

Acute necrotizing pancreatitis (ANP) is often complicated by multiple organ failure. The small intestine is frequently damaged during ANP. Capillary leakage in multiple organs during ANP is one of the most important causes of multiple organ dysfunction. Damage to the capillary endothelial barrier and impaired water transportation could lead to capillary leakage in ANP.

METHODS

Sprague-Dawley (SD) rats were randomized into a control group, the ANP group, the culture media-treated group, or the bone marrow-derived mesenchymal stem cell (BMSC)-treated group (30 rats in each group). Ten rats in each group were sacrificed at 6, 12, and 24 h after induction of experimental models. Serum, ascites, pancreatic, and small intestinal samples were collected. The levels of serum and ascites albumin and amylases were measured, pancreatic histology was assessed, and the connection changes between vessel endothelial cells were evaluated using scanning electron microscopy (SEM). Capillary leakage in small intestinal tissue was observed visually by tracking fluorescein isothiocyanate (FITC)-albumin, and was measured by the Evans blue extravasation method. The location and expression of aquaporin 1 (AQP1) in the small intestine was analyzed using immunohistochemistry, real-time polymerase chain reaction (PCR), and Western blot.

RESULTS

The outcomes showed that the level of serum and ascites amylase is elevated. Conversely, the level of serum albumin is decreased while ascites albumin is elevated. There is damage to pancreatic tissue, and the small intestinal capillary endothelial barrier was aggravated. Furthermore, the expression of AQP1 was reduced significantly after induced ANP. Following treatment with MSCs, the elevation of amylase and the decrease of serum albumin were inhibited, the damage to pancreatic tissue and the level of small intestinal capillary leakage was alleviated, and the downregulation of AQP1 was reversed.

CONCLUSIONS

In conclusion, MSC therapy could alleviate small intestinal injury in rats with ANP, the mechanism of which might be related to reduction of damage to the small intestinal capillary endothelial barrier, and increased expression of AQP1 in the small intestine.

Role of Sulforaphane in Protection of Gastrointestinal Tract Against H. pylori and NSAID-Induced Oxidative Stress

BACKGROUND

Sulforaphane (SFN), a phytochemical found in abundance in broccoli sprouts, potently induces a variety of antioxidant enzymes, and thereby protects cells from injury induced by various kinds of oxidative stresses. It has been suggested that both H. pylori infection and intake of non-steroidal anti-inflammatory drugs (NSAIDs) induce chronic oxidative stress in gastrointestinal (GI) mucosa, thereby causing mucosal injury in the GI tract. Therefore, it would be a reasonable assumption that SFN protects GI mucosa against oxidative injury induced by H. pylori or NSAIDs.

METHODS

We examined the effects of SFN on H. pylori viability in vitro, levels of gastritis in H.pylori-infected mice in vivo, and in H.pylori-infected human subjects. We also examined the effects of SFN on NSAID-induced small intestinal injury in mice.

RESULTS

Our data from the H. pylori infection study clearly demonstrated that SFN inhibited H. pylori viability both in vitro and in vivo, and mitigated H. pylori-induced gastritis in mice and humans. Similarly, our study on NSAID-induced small intestinal injury showed that SFN not only mitigated aspirin-induced injury of small intestinal epithelial cells in vitro, but also ameliorated indomethacin-induced small intestinal injury in mice in vivo.

CONCLUSIONS

These data strongly suggest that SFN contributes to the protection of GI mucosa against oxidative injury induced by H. pylori or NSAIDs.

EhNPC1 and EhNPC2 Proteins Participate in Trafficking of Exogenous Cholesterol in Entamoeba histolytica Trophozoites: Relevance for Phagocytosis

Entamoeba histolytica, the highly phagocytic protozoan causative of human amoebiasis lacks the machinery to synthesize cholesterol. Here, we investigated the presence of NPC1 and NPC2 proteins in this parasite, which are involved in cholesterol trafficking in mammals. Bioinformatics analysis revealed one Ehnpc1 and two Ehnpc2 genes. EhNPC1 appeared as a transmembrane protein and both EhNPC2 as peripheral membrane proteins. Molecular docking predicted that EhNPC1 and EhNPC2 bind cholesterol and interact with each other. Genes and proteins were identified in trophozoites. Serum pulse-chase and confocal microscopy assays unveiled that after trophozoites sensed the cholesterol source, EhNPC1 and EhNPC2 were organized around the plasma membrane in a punctuated pattern. Vesicles emerged and increased in number and size and some appeared full of cholesterol with EhNPC1 or EhNPC2 facing the extracellular space. Both proteins, but mostly EhNPC2, were found out of the cell associated with cholesterol. EhNPC1 and cholesterol formed networks from the plasma membrane to the nucleus. EhNPC2 appeared in erythrocytes that were being ingested by trophozoites, co-localizing with cholesterol of erythrocytes, whereas EhNPC1 surrounded the phagocytic cup. EhNPC1 and EhNPC2 co-localized with EhSERCA in the endoplasmic reticulum and with lysobisphosphatidic acid and EhADH (an Alix protein) in phagolysosomes. Immunoprecipitation assays confirmed the EhNPC1 and EhNPC2 association with cholesterol, EhRab7A and EhADH. Serum starved and blockage of cholesterol trafficking caused a low rate of phagocytosis and incapability of trophozoites to produce damage in the mouse colon. Ehnpc1 and Ehnpc2 knockdown provoked in trophozoites a lower intracellular cholesterol concentration and a diminished rate of phagocytosis; and Ehnpc1 silencing also produced a decrease of trophozoites movement. Trafficking of EhNPC1 and EhNPC2 during cholesterol uptake and phagocytosis as well as their association with molecules involved in endocytosis strongly suggest that these proteins play a key role in cholesterol uptake.

NPC1 and NPC2 proteins are involved in cholesterol trafficking in mammals. Using different approaches, we have detected the orthologues EhNPC1 and EhNPC2 proteins in Entamoeba histolytica. Trophozoites are particularly rich in membranes and vacuoles, but they do not possess the machinery to synthetize cholesterol. Thus, they are completely dependent on molecules able to “fish” cholesterol from the medium. The relevance of our findings lies in the fact that cholesterol is fundamental for endocytosis and motility; and, phagocytosis is an important nutritional and virulence factor for E. histolytica. In silico and experimental strategies, using U18666A to arrest cholesterol trafficking, as well as, knockdown mutants, showed that EhNPC1 and EhNPC2 participate in cholesterol uptake and trafficking in this parasite. They are secreted by trophozoites and directly involved in erythrophagocytosis and motility. Our findings revealed E. histolytica as one of the first protozoa in which these proteins are being characterized. Moreover, E. histolytica provides an excellent and less complicated model to elucidate the intricate event of cholesterol trafficking in eukaryotic cells. The relevance of cholesterol transport for the parasite virulence and the involvement of EhNPC1 and EhNPC2 in this process, make these proteins promising targets for therapy strategies development against the parasite.

Ghrelin Attenuates Intestinal Barrier Dysfunction Following Intracerebral Hemorrhage in Mice

Intestinal barrier dysfunction remains a critical problem in patients with intracerebral hemorrhage (ICH) and is associated with poor prognosis. Ghrelin, a brain-gut peptide, has been shown to exert protection in animal models of gastrointestinal injury. However, the effect of ghrelin on intestinal barrier dysfunction post-ICH and its possible underlying mechanisms are still unknown. This study was designed to investigate whether ghrelin administration attenuates intestinal barrier dysfunction in experimental ICH using an intrastriatal autologous blood infusion mouse model. Our data showed that treatment with ghrelin markedly attenuated intestinal mucosal injury at both histomorphometric and ultrastructural levels post-ICH. Ghrelin reduced ICH-induced intestinal permeability according to fluorescein isothiocyanate conjugated-dextran (FITC-D) and Evans blue extravasation assays. Concomitantly, the intestinal tight junction-related protein markers, Zonula occludens-1 (ZO-1) and claudin-5 were upregulated by ghrelin post-ICH. Additionally, ghrelin reduced intestinal intercellular adhesion molecule-1 (ICAM-1) expression at the mRNA and protein levels following ICH. Furthermore, ghrelin suppressed the translocation of intestinal endotoxin post-ICH. These changes were accompanied by improved survival rates and an attenuation of body weight loss post-ICH. In conclusion, our results suggest that ghrelin reduced intestinal barrier dysfunction, thereby reducing mortality and weight loss, indicating that ghrelin is a potential therapeutic agent in ICH-induced intestinal barrier dysfunction therapy.

Beneficial Effects of Anti-Interleukin-6 Antibodies on Impaired Gastrointestinal Motility, Inflammation and Increased Colonic Permeability in a Murine Model of Sepsis Are Most Pronounced When Administered in a Preventive Setup

BACKGROUND AND OBJECTIVES

During sepsis, gastrointestinal ileus, mucosal barrier dysfunction and bacterial translocation are accepted to be important triggers that can maintain or exacerbate the septic state. In the caecal ligation and puncture animal model of sepsis, we demonstrated that systemic and colonic interleukin-6 levels are significantly increased coinciding with an impaired colonic barrier function. We therefore aimed to study the effect of therapeutic or curative administration of anti-IL6 antibodies on overall GI motility, colonic permeability and translocation of intestinal bacteria in blood and mesenteric lymph nodes in the mouse caecal ligation and puncture model.

METHODS

OF-1 mice were randomized to either the preventive or curative protocol, in which they received 1 mg/kg of antibodies to interleukin-6, or its IgG isotype control solution. They subsequently underwent either the caecal ligation and puncture procedure, or sham-surgery. GI motility was assessed 48 h following the procedure, as well as colonic permeability, serum and colon cytokines, colonic tight junction proteins at the mRNA level; cultures of blood and mesenteric lymph nodes were performed.

RESULTS

Preventive administration of anti-interleukin-6 antibodies successfully counteracted the gastrointestinal motility disturbances and impaired colonic barrier function that could be observed in vehicle-treated septic animals. Serum and colonic levels of proinflammatory cytokines were significantly lower when animals were preventively treated with anti-interleukin-6 antibodies. A repetitive injection 24 h later resulted in the most pronounced effects. Curative treatment significantly lowered systemic and colonic inflammation markers while the effects on transit and permeability were unfortunately no longer significant.

CONCLUSIONS

Caecal ligation and puncture resulted in septic ileus with an increased colonic permeability. Antibodies to interleukin-6 were able to ameliorate gastro-intestinal motility, suppress inflammation and normalize the permeability of the colonic wall, with the preventive administration combined with a repeat injection being far more efficacious than the sole preventive or curative one.

Carcinoembryonic antigen related cellular adhesion molecule 1 alleviates dextran sulfate sodium-induced ulcerative colitis in mice

AIMS

To investigate the effects of exogenous carcinoembryonic antigen related cellular adhesion molecule 1 (CEACAM1) on ulcerative colitis (UC) in a dextran sulfate sodium (DSS)-induced mouse model.

MAIN METHODS

UC mice model was induced by administration of DSS in drinking water for 7days. Treatment of CEACAM1 was performed by a transrectal injection of CEACAM1 gene packed adenovirus in the mice. The severity of UC was evaluated using disease activity index and colon length. Histological changes were observed after hematoxylin and eosin staining. ELISA was used to measure secretion of pro-inflammatory cytokines in the colon tissue. The expression of mRNA and protein were detected using real-time PCR and western blotting. The effect of CEACAM1 on epithelial cell restitution was evaluated using wound-healing test in Caco-2 cells.

KEY FINDINGS

CEACAM1 overexpression attenuated the symptoms of UC as evidenced by decreased DAI score, increased colon length and histopathologic score. In addition, exogenous CEACAM1 reduced the levels of inflammatory cytokines and downregulated COX-2 and iNOS expression levels. Moreover, CEACAM1 overexpression decreased colonic permeability by upregulating expression of tight junction proteins. In the in vitro study, exogenous CEACAM1 promoted proliferation and migration of Caco-2 cell.

SIGNIFICANCE

Exogenous CEACAM1 effectively rescues the symptoms of UC in DSS mice through preventing inflammatory responses, improving epithelial barrier and promoting epithelial cells restitution.

Long-term cannabinoid type 2 receptor agonist therapy decreases bacterial translocation in rats with cirrhosis and ascites

BACKGROUND & AIMS

Intestinal hyperpermeability, impaired peritoneal macrophages (PMs) phagocytosis, and bacterial translocation (BT), resulting in increased systemic and local infection/inflammation such as spontaneous bacterial peritonitis (SBP) together with increased tumor necrosis factor-α (TNFα) levels, are all implicated in the pathogenesis of cirrhosis-related complications. Manipulation of the cannabinoid receptors (CB1R and CB2R), which are expressed on the gut mucosa and PMs, has been reported to modulate intestinal inflammation and systemic inflammatory cytokine release. Our study aims to explore the effects of chronic CB1R/CB2R agonist/antagonist treatments on relevant abnormalities in cirrhotic ascitic rats.

METHODS

Vehicle, archidonyl-2-chloroethylamide (ACEA, CB1R agonist), JWH133 (CB2R agonist), and AM630 (CB2R antagonist) were given to thioacetamide (TAA) and common bile duct ligation (BDL) cirrhotic rats with ascites for two weeks and various measurement were performed.

RESULTS

Compared to sham rats, CB2Rs were downregulated in cirrhotic rat intestines and PMs. The two-week JWH133 treatment significantly decreased systemic/intestinal oxidative stress, TNFα and inflammatory mediators, infection, intestinal mucosal damage and hyperpermeability; the JWH133 treatment also decreased bacterial overgrowth/adhesion, BT and SBP, upregulated intestinal tight junctions and downregulated the PM TNFα receptor/NFκBp65 protein expression in cirrhotic rats. Acute and chronic JWH133 treatment corrected the TNFα-induced suppression of phagocytosis of cirrhotic rat PMs, which then could be reversed by concomitant AM630 treatment.

CONCLUSIONS

Our study suggests that CB2R agonists have the potential to treat BT and various relevant abnormalities through inhibition of systemic/intestinal oxidative stress, inflammatory cytokines and TNFα release in cirrhosis. Overall, the chronic CB2R agonist treatment affects multiple approach mechanisms, and its direct effect on the hyperdynamic circulation is only minor.

A single intraduodenal administration of human adenovirus 40 vaccine effectively prevents anaphylactic shock

Vaccine administration into the intestine is known to induce mucosal tolerance most efficiently. Therefore, developing a delivery system that targets the intestinal mucosa is expected to improve the efficiency of immunosuppression. Human enteric adenovirus serotype 40 (Ad40)-based vectors have the advantage of targeting intestinal mucosa, making them prime candidates as mucosal vaccine carriers for immunosuppression. Here, after both oral and intraduodenal administrations, the vector distribution of replication-defective recombinant Ad40 vectors (rAd40) was significantly higher than that of a conventional Ad vector based on human adenovirus 5 (Ad5) in ilea containing Peyer's patches. Single intraduodenal administration of rAd40 induced antigen-specific mucosal immunoreaction mediated by intestinal mucosal and systemic immunity. In ovalbumin-induced allergy mouse models, this approach inhibited antigen-specific delayed-type hypersensitivity reactions, diarrhea occurrence, and systemic anaphylaxis. Thus, a single intraduodenal administration of rAd40 provides a potent method of inducing allergen-specific mucosal tolerance and a new allergen-specific immunotherapy for overcoming problems with current therapies against life-threatening allergic reactions, including anaphylaxis.

InlA promotes dissemination of Listeria monocytogenes to the mesenteric lymph nodes during food borne infection of mice

Intestinal Listeria monocytogenes infection is not efficient in mice and this has been attributed to a low affinity interaction between the bacterial surface protein InlA and E-cadherin on murine intestinal epithelial cells. Previous studies using either transgenic mice expressing human E-cadherin or mouse-adapted L. monocytogenes expressing a modified InlA protein (InlA(m)) with high affinity for murine E-cadherin showed increased efficiency of intragastric infection. However, the large inocula used in these studies disseminated to the spleen and liver rapidly, resulting in a lethal systemic infection that made it difficult to define the natural course of intestinal infection. We describe here a novel mouse model of oral listeriosis that closely mimics all phases of human disease: (1) ingestion of contaminated food, (2) a distinct period of time during which L. monocytogenes colonize only the intestines, (3) varying degrees of systemic spread in susceptible vs. resistant mice, and (4) late stage spread to the brain. Using this natural feeding model, we showed that the type of food, the time of day when feeding occurred, and mouse gender each affected susceptibility to L. monocytogenes infection. Co-infection studies using L. monocytogenes strains that expressed either a high affinity ligand for E-cadherin (InlA(m)), a low affinity ligand (wild type InlA from Lm EGDe), or no InlA (ΔinlA) showed that InlA was not required to establish intestinal infection in mice. However, expression of InlA(m) significantly increased bacterial persistence in the underlying lamina propria and greatly enhanced dissemination to the mesenteric lymph nodes. Thus, these studies revealed a previously uncharacterized role for InlA in facilitating systemic spread via the lymphatic system after invasion of the gut mucosa.

Fructus Aurantii induced antidepressant effect via its monoaminergic mechanism and prokinetic action in rat

Depression could hardly get a satisfactory effect from the currently available antidepressants. To get a more effective treatment, antidepressant effect and monoaminergic mechanism of Fructus Aurantii (FRA) in the rat forced swimming test (FST) and open field test (OFT), and its prokinetics were examined. FST and OFT were respectively used to evaluate the antidepressant effect and locomotor activity of FRA. We observed the effects of monoamine receptor antagonists on FRA-induced antidepressant effect in rat. The effects of FRA on intestinal transit, gastric emptying and in vitro jejunum contractile activity were assessed. FRA decreased significantly the immobility time (32.6±8.5, 30.3±5.2 vs 56.4±9.4, all p<0.01) in FST, dose-dependent increased the locomotor activity (102±17.5, 120±18.5 vs 89±9.8, p<0.05 or 0.01), significantly accelerated gastric emptying (GE: 48.1±6.3, 39.5±5.7 vs 19.5±3.8, p<0.01) and intestinal transit (IT: 67.3±9.1, 64.2±6.3 vs 49.1±8.2, p<0.01) of the semi-liquid meal, compared with vehicle. And FRA (1 μM, 10 μM) significantly increased the mean amplitude (0.24±0.021 and 0.281±0.015) of contraction in jejunum of rat compared with vehicle (0.149±0.011) in vitro. FRA (10 μM) could induce a largest amplitude (0.281±0.015) of contraction in jejunum. The anti-immobility effect of FRA in FST was prevented by pre-treatment of rat with p-chlorophenylalanine methyl ester, WAY100635, ketanserin, haloperidol, SCH233390, sulpiride, yohimbine, but not prazosin. FRA could simultaneously induce prokinetics and antidepressant effect, deserves further to investigate.

Barrier effect of Esoxx(®) on esophageal mucosal damage: experimental study on ex-vivo swine model

The aim of the present study was to assess the potential barrier effect of Esoxx^®, a new nonprescription medication under development for the relief of gastroesophageal reflux symptoms. Esoxx is based on a mixture of hyaluronic acid and chondroitin sulfate in a bioadhesive suspension of Lutrol^® F 127 polymer (poloxamer 407) which facilitates the product adhesion on the esophageal mucosa. The mucosal damage was induced by 15 to 90 minutes of perfusion with an acidic solution (HCl, pH 1.47) with or without pepsin (2000 U/mL, acidified to pH 2; Sigma-Aldrich). Mucosal esophageal specimens were histologically evaluated and Evans blue dye solution was used to assess the permeability of the swine mucosa after the chemical injury. The results show that: (1) esophageal mucosal damage is related to the perfusion time and to the presence of pepsin, (2) mucosal damage is associated with an increased permeability, documented by an evident Evans blue staining, (3) perfusion with Esoxx is able to reduce the permeability of the injured mucosa, even after saline washing of the swine esophagus. These preliminary results support further clinical studies of Esoxx in the topical treatment of gastroesophageal reflux symptoms.

Agmatine induces gastric protection against ischemic injury by reducing vascular permeability in rats

AIM: To investigate the effect of administration of agmatine (AGM) on gastric protection against ischemia reperfusion (I/R) injury.

METHODS: Three groups of rats (6/group); sham, gastric I/R injury, and gastric I/R + AGM (100 mg/kg, i.p. given 15 min prior to gastric ischemia) were recruited. Gastric injury was conducted by ligating celiac artery for 30 min and reperfusion for another 30 min. Gastric tissues were histologically studied and immunostained with angiopoietin 1 (Ang-1) and Ang-2. Vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein-1 (MCP-1) were measured in gastric tissue homogenate. To assess whether AKt/phosphatidyl inositol-3-kinase (PI3K) mediated the effect of AGM, an additional group was pretreated with Wortmannin (WM) (inhibitor of Akt/PI3K, 15 μg/kg, i.p.), prior to ischemic injury and AGM treatment, and examined histologically and immunostained. Another set of experiments was run to study vascular permeability of the stomach using Evan’s blue dye.

RESULTS: AGM markedly reduced Evan’s blue dye extravasation (3.58 ± 0.975 μg/stomach vs 1.175 ± 0.374 μg/stomach, P < 0.05), VEGF (36.87 ± 2.71 pg/100 mg protein vs 48.4 ± 6.53 pg/100 mg protein, P < 0.05) and MCP-1 tissue level (29.5 ± 7 pg/100 mg protein vs 41.17 ± 10.4 pg/100 mg protein, P < 0.01). It preserved gastric histology and reduced congestion. Ang-1 and Ang-2 immunostaining were reduced in stomach sections of AGM-treated animals. The administration of WM abolished the protective effects of AGM and extensive hemorrhage and ulcerations were seen.

CONCLUSION: AGM protects the stomach against I/R injury by reducing vascular permeability and inflammation. This protection is possibly mediated by Akt/PI3K.

Rebamipide suppresses diclofenac-induced intestinal permeability via mitochondrial protection in mice

AIM: To investigate the protective effect and mechanism of rebamipide on small intestinal permeability induced by diclofenac in mice.

METHODS: Diclofenac (2.5 mg/kg) was administered once daily for 3 d orally. A control group received the vehicle by gavage. Rebamipide (100 mg/kg, 200 mg/kg, 400 mg/kg) was administered intragastrically once a day for 3 d 4 h after diclofenac administration. Intestinal permeability was evaluated by Evans blue and the FITC-dextran method. The ultrastructure of the mucosal barrier was evaluated by transmission electron microscopy (TEM). Mitochondrial function including mitochondrial swelling, mitochondrial membrane potential, mitochondrial nicotinamide adenine dinucleotide-reduced (NADH) levels, succinate dehydrogenase (SDH) and ATPase activities were measured. Small intestinal mucosa was collected for assessment of malondialdehyde (MDA) content and myeloperoxidase (MPO) activity.

RESULTS: Compared with the control group, intestinal permeability was significantly increased in the diclofenac group, which was accompanied by broken tight junctions, and significant increases in MDA content and MPO activity. Rebamipide significantly reduced intestinal permeability, improved inter-cellular tight junctions, and was associated with decreases in intestinal MDA content and MPO activity. At the mitochondrial level, rebamipide increased SDH and ATPase activities, NADH level and decreased mitochondrial swelling.

CONCLUSION: Increased intestinal permeability induced by diclofenac can be attenuated by rebamipide, which partially contributed to the protection of mitochondrial function.

Opposite effects of substance P and calcitonin gene-related peptide in oxazolone colitis

BACKGROUND

Extrinsic sensory neurons play a crucial role in aberrant immune responses in colitis. The activation of peptidergic sensory nerve fibres is accompanied by a release of the neuropeptides calcitonin gene-related peptide (CGRP) and substance P (SP). SP levels increase whilst CGRP levels decrease in colon specimens from patients with inflammatory bowel disease; thus suggesting the pro- and anti-inflammatory roles, respectively, of these neuropeptides.

METHODS

Oxazolone (4-ethoxymethylene-2-phenyl-2-oxazolin-5-one) colitis was induced in wild-type (WT), SP and CGRP knockout ((-/-)) mice. CGRP(-/-) mice were treated with the neurokinin 1-receptor antagonist CP-96345 (CP). The permeability of the mouse colon was evaluated by Evans Blue uptake. Cytokines produced by colonic lamina propria mononuclear cells were measured by ELISA.

RESULTS

Colons of WT, CGRP(-/-) and SP(-/-) mice showed similar tissue architecture and permeability. SP(-/-) mice were protected against oxazolone colitis, whereas CGRP(-/-) showed increased susceptibility to colitis compared to WT mice. SP(-/-) and CP-treated CGRP(-/-) mice showed no significant body weight loss during the period of sickness in contrast to untreated CGRP(-/-) and WT mice. Decreased production of IL-4, IL-5, and IL-13 by colonic lamina propria mononuclear cells of the protected SP(-/-) mice confirms the crucial role of these cytokines in oxazolone colitis.

CONCLUSION

We demonstrate that the neuropeptides CGRP and SP exert opposing effects in oxazolone colitis and provide further evidence for a prominent neuroimmune association in the gut.

Ferulic acid-induced anti-depression and prokinetics similar to Chaihu-Shugan-San via polypharmacology

Selective serotonin reuptake inhibitors (SSRIs), one of popular antidepressants as "one-compound-one-target" paradigm, cannot but discontinue because of inhibiting gut movement. Traditional Chinese medicine (TCM) Chaihu-Sugan-San (CSS) can simultaneously exert anti-depression and prokinetics. From this thread, we aimed to find a new antidepressant with polypharmacological mechanisms. In vivo antidepressive and prokinetic comparisons between CSS and its absorbed compound ferulic acid (FA) were made. And FA's action mechanisms involved in monoaminergic systems, HPA axis and gastrointestinal peptide ghrelin was then studied in forced swimming test (FST) of rat. Lastly, the jejunal contraction activity evoked by FA was measured in vitro. Compared with vehicle, FA reduced immobility time, increased locomotor activity, accelerated gastric emptying and intestinal transit similar to CSS whose absorbable component FA was identified in hippocampus and jejunum. FA's prokinetics in vivo was further supported by its jejunal contraction in vitro. FA-induced anti-immobility was prevented by pretreated with PCPA, WAY-100635, ketanserin, sulpiride, SCH233390, haloperidol and yohimbine, respectively. CRH, ACTH and 5-HT were significantly decreased, but ghrelin was apparently increased compared with vehicle. In summary, FA induced anti-depression and prokinetics similar to CSS via inhibiting serotonin, norepinephrine and dopamine reuptakes, regulating HPA axis, increasing ghrelin and stimulating jejunal contraction simultaneously.

A protective effect of melatonin on intestinal permeability is induced by diclofenac via regulation of mitochondrial function in mice

AIM

This study investigated the effect of intragastrically administered melatonin on intestinal mucosal permeability induced by diclofenac in mice.

METHODS

Intestinal mucosal permeability was induced in mice by intragastric administration of diclofenac (2.5 mg/kg). Melatonin was given intragastrically (10 mg/kg) once per day for 3 d after diclofenac administration. The small intestine was examined macroscopically and microscopically for pathologic injury to the intestinal mucosa. Intestinal mucosal permeability was evaluated by Evans blue and FITC-dextran methods. Mitochondrial functional parameters, including mitochondrial membrane potential, mitochondrial ATPase and succinate dehydrogenase (SDH) activity, were assessed. The malondialdehyde (MDA) and myeloperoxidase (MPO) levels were determined from small intestinal mucosal homogenates.

RESULTS

As compared with control mice, the permeability, pathologic score, MDA and MPO levels and ulceration of the intestinal mucosa were increased significantly by diclofenac treatment, and a broadened junctional complex and enlarged intercellular space were observed by transmission electron microscopy (TEM). Melatonin treatment significantly reduced the intestinal mucosal permeability, pathologic score, MDA, and MPO levels and ulceration of the intestinal mucosa. By TEM, the small intestine villus morphology and intercellular spaces were nearly normal in melatonin-treated mice. At the level of the mitochondria, melatonin treatment significantly restored the activities of ATPase and SDH.

CONCLUSION

The intestinal damage and increased intestinal permeability induced by diclofenac in mice was limited by melatonin; moreover, melatonin preserved several aspects of mitochondrial function.

Meranzin hydrate induces similar effect to Fructus Aurantii on intestinal motility through activation of H1 histamine receptors

This experiment studied the potential effect of meranzin hydrate (MH) and decoction of herb Fructus Aurantii (FA) on rat gut motility. It also investigated the prokinetic mechanism of MH. Experiments were performed on male Sprague–Dawley rats (200–220 g). The study included: (1) qualitation of MH and four other known compounds in FA and jejunum after oral administration of FA decoction to rats; (2) in vitro experiment of MH on rat jejunum contractions; (3) in vivo experiment of FA and MH in rats. Dose-dependently, MH (1–100 μM) increased amplitude in longitudinal and circular jejunum muscles. Pretreatment of jejunum longitudinal strips with benzhydramine (1 μM) remarkably inhibited the contractions induced by histamine (1 μM) and MH (10 or 30 μM). Pretreatment of jejunum longitudinal strips with atropine (1 μM) reduced the contractions induced by acetylcholine (1 μM) but did not influence the contractions induced by MH (10 or 30 μM). Interestingly, the antagonism of benzhydramine to MH was also verified in vivo. MH can be absorbed into the jejunum following oral administration of FA decoction. In healthy rats, MH (7, 14, and 28 mg/kg) and FA (3.3, 10, and 20 g/kg) both promoted intestinal transit and gastric emptying in a dose-dependent manner when gavaged acutely. In cisplatin model rats, MH (14 and 28 mg/kg) significantly reversed cisplatin-induced delay in gastric emptying. Meranzin hydrate can induce similar effect to Fructus Aurantii on intestinal motility and it was, at least in part, mediated by stimulation of H1 histamine receptors.

Assessment of ischemic vascular damage

This protocol describes a model convenient for acute experiments in anesthetized rats, performed by selective occlusion of the superior mesenteric artery. Such a model provides a means for assessing the role played by various pathophysiological mechanisms in the development of intestinal ischemic injury. It is especially suitable for studying different treatments, mainly pharmacological ones, to help cope with this problem in clinical practice. In the form of support protocols, this unit includes functional vascular and chemiluminescence studies, determination of vascular permeability and myeloperoxidase activity, transit time, and mortality.

Glial-derived neurotrophic factor regulates intestinal epithelial barrier function and inflammation and is therapeutic for murine colitis

Although enteric glial cells (EGCs) have been demonstrated to play a key role in maintaining intestinal epithelial barrier integrity, it is not known how EGCs regulate this integrity. We therefore hypothesized that glial-derived neurotrophic factor (GDNF) produced by EGCs might be involved in this regulation. Here we investigated the role of GDNF in regulating epithelial barrier function in vivo. Recombinant adenoviral vectors encoding GDNF (Ad-GDNF) were administered intracolonically in experimental colitis induced by dextran sulphate sodium (DSS). The disease activity index (DAI) and histological score were measured. Epithelial permeability was assayed using Evans blue dye. The anti-apoptotic potency of GDNF in vivo was evaluated. The expression of tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and myeloperoxidase (MPO) activity were measured by ELISA assay and/or RT-PCR. The expression of ZO-1, Akt, caspase-3, and NF-kappaB p65 was analysed by western blot assay. Our results showed that GDNF resulted in a significant reduction in enhanced permeability, inhibited MPO activity, IL-1beta and TNF-alpha expression, and increased ZO-1 and Akt expression. Moreover, GDNF strongly prevented apoptosis in vivo and significantly ameliorated experimental colitis. Our findings indicate that GDNF participates directly in restoring epithelial barrier function in vivo via reduction of increased epithelial permeability and inhibition of mucosal inflammatory response, and is efficacious in DSS-induced colitis. These findings support the notion that EGCs are able to regulate intestinal epithelial barrier integrity indirectly via their release of GDNF in vivo. GDNF is namely an important mediator of the cross-talk between EGCs and mucosal epithelial cells. GDNF may be a useful therapeutic approach to the treatment of inflammatory bowel disease.

The antiinflammatory potential of phenolic compounds from Emblica officinalis L. in rat

Antiinflammatory effects of phenolic compounds from Emblica officinalis were evaluated in carrageenan and cotton pellet induced acute and chronic inflammatory animal model. Fractions of E. officinalis containing free (FPEO) and bounded (BPEO) phenolic compounds were assessed by HPLC technique. The free and bound phenolic compounds were studied for their acute and chronic antiinflammatory activity at dose level of 20 and 40 mg/kg. The carrageenan induced acute inflammation was assessed by measuring rat paw volume at different time of intervals. Further, cotton pellet induced chronic inflammation was assessed by granulomatous tissue mass estimation along with the estimation of tissue biomarker changes (i.e. lipid peroxidation, reduced glutathione, myeloperoxidase and plasma extravasation). The results indicated that in both acute and chronic inflammation, FPEO and BPEO show reduction in the inflammation, but significant effects was observed only at high doses of both fractions which was comparable to diclofenac treated group. In conclusion, phenolic compounds of E. officinalis may serve as potential herbal candidate for amelioration of acute and chronic inflammation due to their modulatory action of free radicals.

Oral administration of mesalazine protects against mucosal injury and permeation in dextran sulfate sodium-induced colitis in rats

OBJECTIVE. Mesalazine, from which 5-aminosalicylic acid is released, is a therapeutic drug for inflammatory bowel disease. There has been no study concerning the effect of orally administered mesalazine on dextran sodium sulfate (DSS)-induced colitis in the rat model of ulcerative colitis. MATERIAL AND METHODS. Colitis was evaluated by means of the length of the colon, white blood cell count (WBC), tissue myeloperoxidase (MPO) activity, and histological inflammation scores. Colonic mucosal permeation was evaluated using Evans blue. The localization of a tight junction protein, occludin, was evaluated immunohistochemically and examined using confocal laser scanning microscopy. RESULTS. Mesalazine significantly improved changes in the length of the colon, tissue MPO activity, WBC, and the histological inflammation score as compared with DSS-induced colitis. Furthermore, the drug completely inhibited the increased permeation in DSS-induced colitis in rats. The immunofluorescence signals of occludin were disrupted and irregularly distributed in DSS-induced colitis, while the signals appeared as a typical reticular pattern but with reduced intensity by the administration of mesalazine, without any reduction in the protein content. In addition, the oral administration of mesalazine significantly improved mucosal permeation, thereby protecting the intestinal mucosa against injury in DSS-induced colitis in rats. CONCLUSIONS. These findings suggest that the recovery of mucosal impairment due to treatment with mesalazine may be associated with the protection of the tight junction protein occludin in DSS-induced colitis.

Clostridium perfringens epsilon toxin increases the small intestinal permeability in mice and rats

Epsilon toxin is a potent neurotoxin produced by Clostridium perfringens types B and D, an anaerobic bacterium that causes enterotoxaemia in ruminants. In the affected animal, it causes oedema of the lungs and brain by damaging the endothelial cells, inducing physiological and morphological changes. Although it is believed to compromise the intestinal barrier, thus entering the gut vasculature, little is known about the mechanism underlying this process. This study characterizes the effects of epsilon toxin on fluid transport and bioelectrical parameters in the small intestine of mice and rats. The enteropooling and the intestinal loop tests, together with the single-pass perfusion assay and in vitro and ex vivo analysis in Ussing's chamber, were all used in combination with histological and ultrastructural analysis of mice and rat small intestine, challenged with or without C. perfringens epsilon toxin. Luminal epsilon toxin induced a time and concentration dependent intestinal fluid accumulation and fall of the transepithelial resistance. Although no evident histological changes were observed, opening of the mucosa tight junction in combination with apoptotic changes in the lamina propria were seen with transmission electron microscopy. These results indicate that C. perfringens epsilon toxin alters the intestinal permeability, predominantly by opening the mucosa tight junction, increasing its permeability to macromolecules, and inducing further degenerative changes in the lamina propria of the bowel.

Vascular stasis, intestinal hemorrhage, and heightened vascular permeability complicate acute portal hypertension in cd39-null mice

Vasoactive factors that regulate splanchnic hemodynamics include nitric oxide, catecholamines, and possibly extracellular nucleosides/nucleotides (adenosine, ATP). CD39/ectonucleoside triphosphate diphosphohydrolase-1 (NTPDase1) is the major vascular ectonucleotidase that hydrolyzes extracellular nucleotides. CD39 activity may be modulated by vascular injury, inflammation, and altered oxygen tension. Altered Cd39 expression by the murine hepatosplanchnic vasculature may impact hemodynamics and portal hypertension (PHT) in vivo. We noted that basal portal pressures (PPs) were comparable in wild-type and Cd39-null mice (n = 9). ATP infusions resulted in increments in PP in wild-type mice, but, in contrast, this significantly decreased in Cd39-null mice (n = 9) post-ATP in a nitric oxide-dependent manner. We then studied Cd39/NTPDase1 deletion in the regulation of portal hemodynamics, vascular integrity, and intestinal permeability in a murine model of PHT. Partial portal vein ligation (PPVL) was performed in Cd39-null (n = 44) and wild-type (n = 23) mice. Sequential measurements obtained after PPVL were indicative of comparable levels of PHT (ranges 14-29 mmHg) in both groups. There was one death in the wild-type group and eight in the Cd39-null group from intestinal bleeding (P = 0.024). Circulatory stasis in the absence of overt portal vein thrombosis, portal congestion, intestinal hemorrhage, and increased permeability were evident in all surviving Cd39-null mice. Deletion of Cd39 results in deleterious outcomes post-PPVL that are associated with significant microcirculatory derangements and major intestinal congestion with hemorrhage mimicking acute mesenteric occlusion. Absent Cd39/NTPDase1 and decreased generation of adenosine in the splanchnic circulation cause heightened vascular permeability and gastrointestinal hemorrhage in PPVL.