Downregulation in aquaporin 4 and aquaporin 8 expression of the colon associated with the induction of allergic diarrhea in a mouse model of food allergy

Polystyrene Microplastics Causes Diarrhea and Impairs Intestinal Angiogenesis through the ROS/METTL3 Pathway

Due to the immature intestinal digestion, immunity, and barrier functions, weaned infants are more susceptible to pathogens and develop diarrhea. Microplastics (MPs), pervasive contaminants in food, water, and air, have unknown effects on the intestinal development of weaned infants. This study explored the impact of polystyrene MPs on intestinal development using a weaned piglet model. Piglets in the control group received a basal diet, and those in the experimental groups received a basal diet contaminated with 150 mg/kg polystyrene MPs. The results showed that exposure to polystyrene MPs increased the diarrhea incidence and impaired the intestinal barrier function of weaned piglets. Notably, the exposure led to oxidative stress and inflammation in the intestine. Furthermore, polystyrene MPs-treated weaned piglets showed a reduced level of intestinal angiogenesis. Mechanistically, polystyrene MPs suppressed methyltransferase-like 3 (METTL3) expression by increasing reactive oxygen species (ROS) production, consequently destabilizing angiogenic factors' mRNA and hindering intestinal angiogenesis. In summary, polystyrene MPs contamination in the diet increases diarrhea and compromises intestinal angiogenesis through the ROS/METTL3 pathway, demonstrating their toxic effects on the intestine health of weaned infants.

Nutrition strategies to control post-weaning diarrhea of piglets: From the perspective of feeds

Post-weaning diarrhea (PWD) is a globally significant threat to the swine industry. Historically, antibiotics as well as high doses of zinc oxide and copper sulfate have been commonly used to control PWD. However, the development of bacterial resistance and environmental pollution have created an interest in alternative strategies. In recent years, the research surrounding these alternative strategies and the mechanisms of piglet diarrhea has been continually updated. Mechanically, diarrhea in piglets is a result of an imbalance in intestinal fluid and electrolyte absorption and secretion. In general, enterotoxigenic Escherichia coli (ETEC) and diarrheal viruses are known to cause an imbalance in the absorption and secretion of intestinal fluids and electrolytes in piglets, resulting in diarrhea when Cl- secretion-driven fluid secretion surpasses absorptive capacity. From a perspective of feedstuffs, factors that contribute to imbalances in fluid absorption and secretion in the intestines of weaned piglets include high levels of crude protein (CP), stimulation by certain antigenic proteins, high acid-binding capacity (ABC), and contamination with deoxynivalenol (DON) in the diet. In response, efforts to reduce CP levels in diets, select feedstuffs with lower ABC values, and process feedstuffs using physical, chemical, and biological approaches are important strategies for alleviating PWD in piglets. Additionally, the diet supplementation with additives such as vitamins and natural products can also play a role in reducing the diarrhea incidence in weaned piglets. Here, we examine the mechanisms of absorption and secretion of intestinal fluids and electrolytes in piglets, summarize nutritional strategies to control PWD in piglets from the perspective of feeds, and provide new insights towards future research directions.

Milk-derived Lactobacillus with high production of short-chain fatty acids relieves antibiotic-induced diarrhea in mice

Antibiotic-associated diarrhea (AAD) is a common side effect during antibiotic treatment, and this has warranted research into alternative protocols. In this study, we investigated the potential therapeutic effects of three cohorts, Lactobacillus plantarum KLDS 1.0386, Lactobacillus acidophilus KLDS 1.0901 and a mixed strain of both, on intestinal inflammation, the intestinal mucosal barrier, and microbial community in mice with ampicillin-induced diarrhea. The results showed that Lactobacillus inhibited the activation of the TLR4/NF-κB signaling pathway, decreased the expression of pro-inflammatory cytokines, increased the expression of anti-inflammatory cytokines in the murine intestine, and alleviated the intestinal barrier damage and inflammation induced by ampicillin. In addition, Lactobacillus ameliorates intestinal epithelial barrier damage by increasing the expression of tight junction proteins and aquaporins. After Lactobacillus treatment, the diversity of gut microbiota increased significantly, and the composition and function of gut microbiota gradually recovered. In the gut microbiota, Bacteroidetes and Escherichia Shigella related to the synthesis of short-chain fatty acids (SCFAs) were significantly affected by ampicillin, while Lactobacillus regulates the cascade of the microbial-SCFA signaling pathway, which greatly promoted the generation of SCFAs. Collectively, Lactobacillus showed better results in treating AAD, especially in mixed strains.

How do probiotics alleviate constipation? A narrative review of mechanisms

Constipation is a common gastrointestinal condition, which may occur at any age and affects countless people. The search for new treatments for constipation is ongoing as current drug treatments fail to provide fully satisfactory results. In recent years, probiotics have attracted much attention because of their demonstrated therapeutic efficacy and fewer side effects than pharmaceutical products. Many studies attempted to answer the question of how probiotics can alleviate constipation. It has been shown that different probiotic strains can alleviate constipation by different mechanisms. The mechanisms on probiotics in relieving constipation were associated with various aspects, including regulation of the gut microbiota composition, the level of short-chain fatty acids, aquaporin expression levels, neurotransmitters and hormone levels, inflammation, the intestinal environmental metabolic status, neurotrophic factor levels and the body's antioxidant levels. This paper summarizes the perception of the mechanisms on probiotics in relieving constipation and provides some suggestions on new research directions.

Effects of different dietary protein levels on intestinal aquaporins in weaned piglets

This study was conducted to investigate the relationship between changes in intestinal aquaporins (AQPs) in piglets fed diets with different protein levels and nutritional diarrhoea in piglets. Briefly, 96 weaned piglets were randomly divided into four groups fed diets with crude protein (CP) levels of 18%, 20%, 22% and 24%. The small intestines and colons of the weaned piglets were collected, and several experiments were conducted. In the small intestine, AQP4 protein expression was higher in weaned piglets fed the higher-CP diets (22% and 24% CP) than in those fed the 20% CP diet except at 72 h (p < 0.01). At 72 h, the AQP4 protein expression in the small intestine was lower in the 18% group than in the other three groups (p < 0.01). Under 20% CP feeding, AQP2, AQP4 and AQP9 protein expression in the colons of piglets peaked at certain time points. The AQP2 and AQP4 mRNA levels in the colon and the AQP4 and AQP4 mRNA levels in the distal colon were approximately consistent with the protein expression levels. However, the AQP9 mRNA content in the colon was highest in the 18% group, and the AQP2 mRNA content in the distal colon was significantly higher in the 24% group than in the 20% group. AQP2 and AQP4 were expressed mainly around columnar cells in the upper part of the smooth colonic intestinal villi, and AQP9 was expressed mainly on columnar cells and goblet cells in the colonic mucosa. In conclusion, 20% CP is beneficial to the normal expression of AQP4 in the small intestine, AQP2, AQP4 and AQP9 in the colon of weaned piglets, which in turn maintains the balance of intestinal water absorption and secretion in piglets.

The Genetic Background Is Shaping Cecal Enlargement in the Absence of Intestinal Microbiota

Germ-free (GF) rodents have become a valuable tool for studying the role of intestinal microbes on the host physiology. The major characteristic of GF rodents is an enlarged cecum. The accumulation of mucopolysaccharides, digestion enzymes and water in the intestinal lumen drives this phenotype. Microbial colonization normalizes the cecum size in ex-GF animals. However, whether strain genetics influences the cecal enlargement is unknown. Here we investigated the impact of mouse genetic background on the cecal size in five GF strains frequently used in biomedical research. The cecal weight of GF mice on B6 background (B6J and B6N) represented up to 20% of total body weight. GF NMRI and BALBc mice showed an intermediate phenotype of 5-10%, and those on the C3H background of up to 5%. Reduced cecal size in GF C3H mice correlated with decreased water content, increased expression of water transporters, and reduced production of acidic mucins, but was independent of the level of digestive enzymes in the lumen. In contrast, GF B6J mice with greatly enlarged cecum showed increased water content and a distinct metabolic profile characterized by altered amino acid and bile acid metabolism, and increased acidic mucin production. Together, our results show that genetic background influences the cecal enlargement by regulating the water transport, production of acidic mucins, and metabolic profiles.

Bifidobacterium animalis subsp. lactis XLTG11 improves antibiotic-related diarrhea by alleviating inflammation, enhancing intestinal barrier function and regulating intestinal flora

Antibiotic-associated diarrhea (AAD) is a common side effect during antibiotic treatment. In this study, we evaluated the regulatory effect of Bifidobacterium animalis subsp. lactis XLTG11 on mouse diarrhea caused by antibiotic-induced intestinal flora disturbance. Then, two strains of Bifidobacterium animalis subsp. lactis XLTG11 and Bifidobacterium animalis subsp. lactis BB-12 were administered to AAD mice. We found that the recovery effect of using B. lactis XLTG11 was better than that of B. lactis BB-12. B. lactis XLTG11 reduced the pathological characteristics of the intestinal tract, and significantly reduced the levels of lipopolysaccharide (LPS), D-lactic acid (D-LA) and diamine oxidase (DAO) to decrease intestinal permeability. In addition, these two strains significantly increased the expression of aquaporin and tight junction proteins, and inhibited toll-like receptor 4 (TLR4)/activation of the nuclear factor-κB (NF-κB) signaling pathway, significantly increased the levels of anti-inflammatory cytokines and decreased levels of pro-inflammatory cytokines. Moreover, after treatment with B. lactis XLTG11, the contents of acetic acid, propionic acid, butyric acid and total short-chain fatty acids were significantly increased. Compared with the MC group, B. lactis XLTG11 increased the abundance and diversity of the intestinal flora and changed the composition of the intestinal flora. We found that B. lactis XLTG11 can promote the recovery of intestinal flora and mucosal barrier function, thereby effectively improving AAD-related symptoms, providing a scientific basis for future clinical applications.

Treatment of Gastrointestinal Disorders-Plants and Potential Mechanisms of Action of Their Constituents

The worldwide prevalence of gastrointestinal diseases is about 40%, with standard pharmacotherapy being long-lasting and economically challenging. Of the dozens of diseases listed by the Rome IV Foundation criteria, for five of them (heartburn, dyspepsia, nausea and vomiting disorder, constipation, and diarrhoea), treatment with herbals is an official alternative, legislatively supported by the European Medicines Agency (EMA). However, for most plants, the Directive does not require a description of the mechanisms of action, which should be related to the therapeutic effect of the European plant in question. This review article, therefore, summarizes the basic pharmacological knowledge of synthetic drugs used in selected functional gastrointestinal disorders (FGIDs) and correlates them with the constituents of medicinal plants. Therefore, the information presented here is intended as a starting point to support the claim that both empirical folk medicine and current and decades-old treatments with official herbal remedies have a rational basis in modern pharmacology.

Human Norovirus Induces Aquaporin 1 Production by Activating NF-κB Signaling Pathway

Human norovirus (HuNoV) is one of the major pathogens of acute nonbacterial gastroenteritis. Due to the lack of a robust and reproducible in vitro culture system and an appropriate animal model, the mechanism underlying HuNoV-caused diarrhea remains unknown. In the current study, we found that HuNoV transfection induced the expression of aquaporin 1 (AQP1), which was further confirmed in the context of virus infection, whereas the enterovirus EV71 (enterovirus 71) did not have such an effect. We further revealed that VP1, the major capsid protein of HuNoV, was crucial in promoting AQP1 expression. Mechanistically, HuNoV induces AQP1 production through the NF-κB signaling pathway via inducing the expression, phosphorylation and nuclear translocation of p65. By using a model of human intestinal epithelial barrier (IEB), we demonstrated that HuNoV and VP1-mediated enhancement of small molecule permeability is associated with the AQP1 channel. Collectively, we revealed that HuNoV induced the production of AQP1 by activating the NF-κB signaling pathway. The findings in this study provide a basis for further understanding the significance of HuNoV-induced AQP1 expression and the potential mechanism underlying HuNoV-caused diarrhea.

Organ Specific Differences in Alteration of Aquaporin Expression in Rats Treated with Sennoside A, Senna Anthraquinones and Rhubarb Anthraquinones

Senna and rhubarb are often used as routine laxatives, but there are differences in mechanism of action and potential side effects. Here, we studied metabolites of senna anthraquinones (SAQ), rhubarb anthraquinones (RAQ) and their chemical marker, sennoside A (SA), in a rat diarrhea model. In in vitro biotransformation experiments, SAQ, RAQ and SA were incubated with rat fecal flora solution and the metabolites produced were analyzed using HPLC. In in vivo studies, the same compounds were investigated for purgation induction, with measurement of histopathology and Aqps gene expression in six organs. The results indicated that SAQ and RAQ had similar principal constituents but could be degraded into different metabolites. A similar profile of Aqps down-regulation for all compounds was seen in the colon, suggesting a similar mechanism of action for purgation. However, in the kidneys and livers of the diarrhea-rats, down-regulation of Aqps was found in the RAQ-rats whereas up-regulation of Aqps was seen in the SAQ-rats. Furthermore, the RAQ-rats showed lower Aqp2 protein expression in the kidneys, whilst the SA-rats and SAQ-rats had higher Aqp2 protein expression in the kidneys. This may have implications for side effects of SAQ or RAQ in patients with chronic kidney or liver diseases.

Aquaporins and diseases pathogenesis: From trivial to undeniable involvements, a disease-based point of view

Aquaporins (AQPs), as transmembrane proteins, were primarily identified as water channels with the ability of regulating the transmission of water, glycerol, urea, and other small-sized molecules. The classic view of AQPs involvement in therapeutic plan restricted them and their regulators into managing only a narrow spectrum of the diseases such as diabetes insipidus and the syndrome of inappropriate ADH secretion. However, further investigations performed, especially in the third millennium, has found that their cooperation in water transmission control can be manipulated to handle other burden-imposing diseases such as cirrhosis, heart failure, Meniere's disease, cancer, bullous pemphigoid, eczema, and Sjögren's syndrome.

Role of the Intestinal Epithelium and Its Interaction With the Microbiota in Food Allergy

The intestinal epithelial tract forms a dynamic lining of the digestive system consisting of a range of epithelial cell sub-types with diverse functions fulfilling specific niches. The intestinal epithelium is more than just a physical barrier regulating nutrient uptake, rather it plays a critical role in homeostasis through its intrinsic innate immune function, pivotal regulation of antigen sensitization, and a bi-directional interplay with the microbiota that evolves with age. In this review we will discuss these functions of the epithelium in the context of food allergy.

The Laminin-Induced Phosphorylation of PKCδ Regulates AQP4 Distribution and Water Permeability in Rat Astrocytes

In astrocytes, the water-permeable channel aquaporin-4 (AQP4) is concentrated at the endfeet that abut the blood vessels of the brain. The asymmetric distribution of this channel is dependent on the function of dystroglycan (DG), a co-expressed laminin receptor, and its associated protein complex. We have demonstrated that the addition of laminin to astrocytes in culture causes the clustering of AQP4, DG, and lipid rafts. The last, in particular, have been associated with the initiation of cell signaling. As laminin binding to DG in muscle cells can induce the tyrosine phosphorylation of syntrophin and laminin requires tyrosine kinases for acetylcholine receptor clustering in myotubes, we asked if signal transduction might also be involved in AQP4 clustering in astrocytes. We analyzed the timecourse of AQP4, DG, and monosialotetrahexosylganglioside (GM1) clustering in primary cultures of rat astrocytes following the addition of laminin, and determined that the clustering of DG precedes that of AQP4 and GM1. We also showed that laminin induces the formation of phosphotyrosine-rich clusters and that the tyrosine kinase inhibitor, genistein, disrupts the laminin-induced clustering of both β-DG and AQP4. Using the Kinexus antibody microarray chip, we then identified protein-serine kinase C delta (PKCδ) as one of the main proteins exhibiting high levels of tyrosine phosphorylation upon laminin treatment. Selective inhibitors of PKC and siRNA against PKCδ disrupted β-DG and AQP4 clustering, and also caused water transport to increase in astrocytes treated with laminin. Our results demonstrate that the effects of laminin on AQP4 localization and function are relayed, at least in part, through PKC signaling.

Prophylactic use of probiotic chocolate modulates intestinal physiological functions in constipated rats

BACKGROUND

This study investigated the in vivo prophylactic effect of probiotic chocolate on constipation. Rats were administered chocolate containing 2.5 × 10¹⁰  CFU g^-1 of probiotics daily for 4 weeks and treated with loperamide (5 mg kg^-1 ) daily at the fourth week of treatment.

RESULTS

Probiotic chocolate treatment significantly (P < 0.05) increased the intestinal motility, colon length, fecal moisture content and number of excreted fecal pellets in constipated rats. Moreover, quantitative real-time polymerase chain reaction data and histological images also revealed that both probiotic chocolate LYC and BB12 treatments were capable of upregulating the mRNA expression levels of colonic ZO-1, occludin and AQP8, leading to the maintenance of the defensive barrier function in the constipated rats compared with the negative controls. Interestingly, these treatments also modulated gut bacterial populations by increasing the abundance levels of Lactobacillus and Bifidobacterium, as well as reducing the abundance level of Enterobacteriaceae.

CONCLUSION

The present study demonstrated that probiotic chocolate LYC and BB12 could potentially be used as alternative agents for prophylactic constipation. © 2018 Society of Chemical Industry.

Coculture with Clostridium difficile promotes apoptosis of human intestinal microvascular endothelial cells

OBJECTIVE

The clostridial triose-phosphate isomerase ( tpi) gene is a housekeeping gene that specifically distinguishes Clostridium difficile from other bacteria. This retrospective cohort study was performed to analyze and compare the TPI protein-positive rates in outpatients and hospitalized patients with and without diarrhea (control group).

METHODS

Western blotting, methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay, and flow cytometry were used to investigate the pathogenic mechanism of C. difficile in the development and progression of diarrhea in patients with inflammatory bowel disease (IBD).

RESULTS

The TPI protein-positive rates were significantly higher in patients with diarrhea but without IBD than in the healthy control group as well as in patients with diarrhea and IBD than in patients with diarrhea but without IBD. Coculture with C. difficile inhibited aquaporin-1 protein expression in human intestinal microvascular endothelial cells, which significantly reduced the proliferation of these cells and promoted their apoptosis.

CONCLUSIONS

Clostridium difficile infection is associated with diarrhea and may be an important risk factor for diarrhea in patients with IBD. Coculture with C. difficile may inhibit the proliferation of intestinal mucosal cells and promote their apoptosis, reduce intestinal aquaporin-1 expression, and inhibit intestinal water uptake. Clostridium difficile is one cause of C. difficile-associated diarrhea.

Fluid resuscitation via the rectum ameliorates hemodynamic disorders through adjusting aquaporin expression in an experimental severe acute pancreatitis model

Acute pancreatitis is an acute abdominal disease, with 10-20% of the cases deteriorating rapidly, accompanied by persistent organ failure and further development into severe acute pancreatitis (SAP). The aim of the present study was to investigate the mechanism of fluid resuscitation via the rectum in the early stages of SAP and the role of aquaporins (AQPs). An SAP model was constructed by injection of 5% sterile sodium taurocholate into the biliopancreatic duct of Sprague Dawley rats, and the mean arterial pressure (MAP) was continuously monitored via femoral artery catheterization. At 30 min after the construction of the SAP model, the rats in the fluid resuscitation groups were resuscitated with normal saline at a rate of 4 ml/kg/h through the venous or the rectal route. The AQP and Na⁺-K⁺-ATPase levels, and the correlation of the MAP and colon AQPs at the early stages of SAP were analyzed. The results demonstrated that the mRNA level of AQP-3 and AQP-4 in the distal colon decreased significantly in the group subjected to fluid resuscitation via the rectum, while no significant differences were identified in the Na⁺-K⁺-ATPase levels of the colon in that group. Furthermore, a negative correlation was identified between the expression of AQPs and the MAP (P<0.01). Thus, fluid resuscitation via the rectum appears to ameliorate hemodynamic disorders through adjusting the expression of AQP-3 and AQP-4 in the distal colon in an experimental SAP model.

Aquaporins Alteration Profiles Revealed Different Actions of Senna, Sennosides, and Sennoside A in Diarrhea-Rats

Senna and its main components sennosides are well-known effective laxative drugs and are used in the treatment of intestinal constipation in the world. Their potential side effects have attracted more attention in clinics but have little scientific justification. In this study, senna extract (SE), sennosides (SS), and sennoside A (SA) were prepared and used to generate diarrhea rats. The diarrhea rats were investigated with behaviors, clinical signs, organ index, pathological examination, and gene expression on multiple aquaporins (Aqps) including Aqp1, Aqp2, Aqp3, Aqp4, Aqp5, Aqp6, Aqp7, Aqp8, Aqp9, and Aqp11. Using qRT-PCR, the Aqp expression profiles were constructed for six organs including colon, kidney, liver, spleen, lung, and stomach. The Aqp alteration profiles were characterized and was performed with Principle Component Analysis (PCA). The SE treatments on the rats resulted in a significant body weight loss (p < 0.001), significant increases (p < 0.001) on the kidney index (27.72%) and liver index (42.55%), and distinguished changes with up-regulation on Aqps expressions in the kidneys and livers. The SS treatments showed prominent laxative actions and down regulation on Aqps expression in the colons. The study results indicated that the SE had more influence/toxicity on the kidneys and livers. The SS showed more powerful actions on the colons. We suggest that the caution should be particularly exercised in the patients with kidney and liver diseases when chronic using senna-based products.

Mechanisms of Aquaporin-Facilitated Cancer Invasion and Metastasis

Cancer is a leading cause of death worldwide, and its incidence is rising with numbers expected to increase 70% in the next two decades. The fact that current mainline treatments for cancer patients are accompanied by debilitating side effects prompts a growing demand for new therapies that not only inhibit growth and proliferation of cancer cells, but also control invasion and metastasis. One class of targets gaining international attention is the aquaporins, a family of membrane-spanning water channels with diverse physiological functions and extensive tissue-specific distributions in humans. Aquaporins−1,−2,−3,−4,−5,−8, and−9 have been linked to roles in cancer invasion, and metastasis, but their mechanisms of action remain to be fully defined. Aquaporins are implicated in the metastatic cascade in processes of angiogenesis, cellular dissociation, migration, and invasion. Cancer invasion and metastasis are proposed to be potentiated by aquaporins in boosting tumor angiogenesis, enhancing cell volume regulation, regulating cell-cell and cell-matrix adhesions, interacting with actin cytoskeleton, regulating proteases and extracellular-matrix degrading molecules, contributing to the regulation of epithelial-mesenchymal transitions, and interacting with signaling pathways enabling motility and invasion. Pharmacological modulators of aquaporin channels are being identified and tested for therapeutic potential, including compounds derived from loop diuretics, metal-containing organic compounds, plant natural products, and other small molecules. Further studies on aquaporin-dependent functions in cancer metastasis are needed to define the differential contributions of different classes of aquaporin channels to regulation of fluid balance, cell volume, small solute transport, signal transduction, their possible relevance as rate limiting steps, and potential values as therapeutic targets for invasion and metastasis.

Influence of excessive exercise on immunity, metabolism, and gut microbial diversity in an overtraining mice model

The purpose of this study was to evaluate the negative influence of excessive exercise on immunity, substance and energy metabolism as well as gut microbiota in mice. Firstly, an overtraining model of Male Kunming mice was established by high-intensity swimming exercise for 4 weeks. Then, a series of evaluation indicators, including the routine blood analysis, immune organ coefficient, digestive enzymes, and aquaporins expression levels of small intestine and colon tissue, histological examinations of liver, spleen, small intestine, and colon, were determined based on this model. Furthermore, 16S rRNA gene sequencing was also employed to measure the microbial composition in gut. The results found that immune parameters, substance and energy metabolism of all mice was altered and disturbed after high-intensity swimming for 4 weeks, led to an atrophy of thymus and spleen as well as abnormal structural changes in liver when compared to non-swimming mice. Besides, excessive swimming mice had lower microbial diversity compared to non-swimming mice. However, there was no significant difference in gut microbial taxa between the two groups. The data indicated that excessive exercise exhibits negative impacts on immunity, substance and energy metabolism as well as gut microbial diversity.

Er Shen Wan extract reduces diarrhea and regulates AQP 4 and NHE 3 in a rat model of spleen-kidney Yang deficiency-induced diarrhea

INTRODUCTION

Er Shen Wan (ESW), a traditional Chinese medicinal formula comprised of Psoraleae Fructus (Babchi seeds, from Psoralea corylifolia Linn.) and Myristicae Semen (Nutmeg, from Myristica fragrans Houtt.), is widely used to treat spleen-kidney Yang deficiency (SKYD)-induced diarrhea. Previous studies have demonstrated preliminarily that the petroleum ether extract of ESW (ESWP) exhibits significant anti-diarrheal activity. The present study aimed to evaluate the anti-diarrhea activity of ESWP and to explore the underlying mechanisms with respect to fluid metabolism in a rat model of SKYD-induced diarrhea.

MATERIALS AND METHODS

A high-performance liquid chromatography-diode array detector (HPLC-DAD) approach was developed and validated for qualitative and quantitative analyses of the main constituents of ESWP. SKYD model rats were established and treated with an effective dose (3.5?g/kg) of the extract for two weeks. Anti-diarrheal activity and stool properties were observed. After the experiment, the appearance and histology of the intestines were evaluated. Serum levels of neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) were also determined. Furthermore, to characterize the regulation of aquaporin-4 (AQP 4) and Na⁺/H⁺ exchanger isoform 3 (NHE 3) in the colon, quantitative real-time RT-PCR (qRT-PCR), immunohistochemistry (IHC) and Western blotting (WB) were employed to detect mRNA and protein expression levels.

RESULTS

In the rat models, oral ESWP administration significantly reduced the diarrhea score and the number and weight of wet stools. Jejunal and ileac histological damage was impeded, and the histology score decreased. Serum VIP levels were significantly decreased, in contrast to NPY levels. In addition, AQP 4 and NHE 3 expression levels increased significantly.

CONCLUSIONS

These results showed that ESWP's anti-diarrheal effect might at least partially involve the regulation of hormones intimately involved in maintaining fluid and electrolyte levels, as well as by increasing AQP 4 and NHE 3 expression levels and enhancing the absorption of Na⁺ and water.

N-Acetylcysteine improves intestinal function in lipopolysaccharides-challenged piglets through multiple signaling pathways

This study determined whether N-acetylcysteine (NAC) could improve intestinal function through phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR), epithelial growth factor receptor (EGFR), toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB), adenosine 5'-monophosphate-activated protein kinase (AMPK), and type I interferon (IFN) signaling pathways in a piglet model of lipopolysaccharides (LPS) challenge. Thirty-two piglets (24-day-old) were randomly allocated to one of four treatments, with eight replicates per treatment and one piglet per replicate. The experiment consisted of four treatments in a 2 × 2 factorial arrangement with two diets (supplemented with 0 or 500 mg NAC/kg diet) and saline or LPS administration. On day 20 of the trial, piglets in the LPS and LPS + NAC groups were intraperitoneally injected with 0 (saline) or 100 μg LPS/kg BW. Blood samples were obtained at 3 h and intestinal mucosae were collected at 6 h post LPS or saline injection. The growth performance was not affected by dietary NAC. LPS induced intestinal dysfunction, as indicated by: (1) reductions in the small-intestinal glutathione concentrations and plasma D-xylose levels; (2) elevations in plasma diamine oxidase activity, mucosal MMP3 mRNA levels and caspase-3 protein abundance; (3) reduced the activities of the small-intestinal mucosal maltase, sucrase and lactase. The adverse effects of LPS on porcine intestinal function and redox status were mitigated by NAC supplementation through the activation of multiple signaling pathways involving PI3K/Akt/mTOR, EGFR, TLR4/NF-κB, AMPK, and type I IFN. Our findings provide novel mechanisms for beneficial effects of NAC in protecting the intestine from inflammation in animals.

Uridine stimulate laxative effect in the loperamide-induced constipation of SD rats through regulation of the mAChRs signaling pathway and mucin secretion

Background

Uridine (Urd), which has been reported as a major component of RNA, plays an important role in various biological process including neuroprotection, biochemical modulation and glycolysis, although its role in constipation has yet to be established. Therefore, in this study, we investigated the laxative effects of Urd on chronic constipation.

Methods

The constipation phenotypes and their related mechanisms were investigated in the transverse colons of SD rats with loperamide (Lop)-induced constipation after treatment with 100 mg/kg of Urd.

Results

The number, weight and water contents of stools were significantly higher in the Lop + Urd treated group than the Lop + Vehicle treated group, while food intake and water consumption of the same group were maintained at a constant level. The thickness of the mucosa layer, muscle and flat luminal surface, as well as the number of goblet cells, paneth cells and lipid droplets were enhanced in the Lop + Urd treated group. Furthermore, the expression of the muscarinic acetylcholine receptors M2 and M3 (mAChR M2 and M3) at the transcriptional and translational level was recovered in the Lop + Urd treated group, while some markers such as Gα and inositol triphosphate (IP3) in their downstream signaling pathway were completely recovered by Urd treatment. Moreover, the ability for mucin secretion and the expression of membrane water channel (aquaporine 8, AQP8) were increased significantly in the Lop + Urd treated group compared with Lop + Vehicle treated group. Finally, the activity of Urd was confirmed in primary smooth muscle of rat intestine cells (pRISMC) based on Gα expression and IP3 concentration.

Conclusions

The results of the present study provide the first strong evidence that Urd can be considered an important candidate for improving chronic constipation induced by Lop treatment in animal models.

Characterization of AQPs in Mouse, Rat, and Human Colon and Their Selective Regulation by Bile Acids

In normal individuals, the epithelium of the colon absorbs 1.5–2 l of water a day to generate dehydrated feces. However, in the condition of bile acid malabsorption (BAM), an excess of bile acids in the colon results in diarrhea. Several studies have attempted to address the mechanisms contributing to BAM induced by various bile acids. However, none have addressed a potential dysregulation of aquaporin (AQP) water channels, which are responsible for the majority of transcellular water transport in epithelial cells, as a contributing factor to the onset of diarrhea and the pathogenesis of BAM. In this study, we aimed to systematically analyze the expression of AQPs in colonic epithelia from rat, mouse, and human and determine whether their expression is altered in a rat model of BAM. Mass spectrometry-based proteomics, RT-PCR, and western blotting identified various AQPs in isolated colonic epithelial cells from rats (AQP1, 3, 4, 7, 8) and mice (AQP1, 4, 8). Several AQPs were also detected in human colon (AQP1, 3, 4, 7–9). Immunohistochemistry localized AQP1 to the apical plasma membrane of epithelial cells in the bottom of the crypts, whereas AQP3 (rat, human) and AQP4 (mice, human) were localized predominantly in the basolateral plasma membrane. AQP8 was localized intracellularly and at the apical plasma membrane of epithelial cells. Rats fed sodium cholate for 72 h had significantly increased fecal water content, suggesting development of BAM-associated diarrhea. Colonic epithelial cells isolated from this model had significantly altered levels of AQP3, 7, and 8, suggesting that these AQPs may be involved in the pathogenesis of bile acid-induced diarrhea.

Expression, Distribution and Role of Aquaporin Water Channels in Human and Animal Stomach and Intestines

Stomach and intestines are involved in the secretion of gastrointestinal fluids and the absorption of nutrients and fluids, which ensure normal gut functions. Aquaporin water channels (AQPs) represent a major transcellular route for water transport in the gastrointestinal tract. Until now, at least 11 AQPs (AQP1–11) have been found to be present in the stomach, small and large intestines. These AQPs are distributed in different cell types in the stomach and intestines, including gastric epithelial cells, gastric glands cells, absorptive epithelial cells (enterocytes), goblet cells and Paneth cells. AQP1 is abundantly distributed in the endothelial cells of the gastrointestinal tract. AQP3 and AQP4 are mainly distributed in the basolateral membrane of epithelial cells in the stomach and intestines. AQP7, AQP8, AQP10 and AQP11 are distributed in the apical of enterocytes in the small and large intestines. Although AQP-null mice displayed almost no phenotypes in gastrointestinal tracts, the alterations of the expression and localization of these AQPs have been shown to be associated with the pathology of gastrointestinal disorders, which suggests that AQPs play important roles serving as potential therapeutic targets. Therefore, this review provides an overview of the expression, localization and distribution of AQPs in the stomach, small and large intestine of human and animals. Furthermore, this review emphasizes the potential roles of AQPs in the physiology and pathophysiology of stomach and intestines.

Aquaporins in Health and Disease: An Overview Focusing on the Gut of Different Species

Aquaporins (AQPs) play a pivotal role in gut homeostasis since their distribution and function is modulated both in physiological and in pathophysiological conditions. The transport of water and solutes through gut epithelia is essential for osmoregulation and digestive and absorptive functions. This passage is regulated by different AQP isoforms and characterized by their peculiar distribution in the gastrointestinal tract. To date, AQP localization has been identified in the gut and associated organs of several mammalian species by different techniques (immunohistochemical, western blotting, and RT-PCR). The present review describes the modulation of AQP expression, distribution, and function in gut pathophysiology. At the same time, the comparative description of AQP in animal species sheds light on the full range of AQP functions and the screening of their activity as transport modulators, diagnostic biomarkers, and drug targets. Moreover, the phenotype of knockout mice for several AQPs and their compensatory role and the use of specific AQP inhibitors have been also reviewed. The reported data could be useful to design future research in both basic and clinical fields.

Aquaporins in the Colon as a New Therapeutic Target in Diarrhea and Constipation

Aquaporins (AQPs) play important roles in the water transport system in the human body. There are currently 13 types of AQP, AQP0 through AQP12, which are expressed in various organs. Many members of the AQP family are expressed in the intestinal tract. AQP3 is predominantly expressed in the colon, ultimately controlling the water transport. Recently, it was clarified that several laxatives exhibit a laxative effect by changing the AQP3 expression level in the colon. In addition, it was revealed that morphine causes severe constipation by increasing the AQP3 expression level in the colon. These findings have shown that AQP3 is one of the most important functional molecules in water transport in the colon. This review will focus on the physiological and pathological roles of AQP3 in the colon, and discuss clinical applications of colon AQP3.

Immunohistochemical localization of aquaporin 4 (AQP4) in the porcine gastrointestinal tract

The water channel aquaporin-4 (AQP4) is a protein widely expressed on plasma membrane of a variety of epithelial cells. In this study we investigated the expression of AQP4 in the gastrointestinal tract of the pig using immunohistochemical staining. We found no presence of AQP4 in the different regions of the pig stomach. In the porcine small intestine moderate immunoreactivity to AQP4 was detected in enterocytes (along the villi and in the bottom of the crypts), duodenal Brunner’s glands and in enteric ganglia in cells lying in close vicinity to myenteric as well as submucous neurons. In superficial epithelial cells of the colonic mucosa as well as of caecal and colonic glands a very strong immunoreactivity to AQP4 was found. Both in the myenteric and submucous ganglia of the large intestine AQP4-positive cells surrounding enteric neurons were observed. We concluded that AQP4 expression in the porcine gastrointestinal tract showed some species-dependent differences in relation to other species. Based on the presented distribution pattern of AQP4, it is likely that the aquaporin plays a role in mucous (but not acid) secretion and intestinal absorptive processes in the pig.

Down-regulation of aquaporin3 expression by lipopolysaccharide via p38/c-Jun N-terminal kinase signalling pathway in HT-29 human colon epithelial cells

AIM: To investigate the influence of lipopolysaccharide (LPS) through the p38/c-Jun N-terminal kinase (JNK) signalling pathway on aquaporin 3 (AQP3) expression in HT-29 human colon epithelial cells.

METHODS: HT-29 cells were treated with LPS, and then the membrane localisation of AQP3 was examined by immunofluorescence staining. The mRNA and protein expression of AQP3 with LPS exposure was measured by real-time reverse transcription-PCR and Western blot, respectively. Activation of p38 and JNK was evaluated by detection of phosphorylation of p38 and JNK using Western blot assay. AQP3 protein expression was determined by Western blot in cells after treatment with SB203580, a selective p38 MAPK inhibitor, or SP600125, a selective JNK inhibitor.

RESULTS: In HT-29 cells, the transcription and protein expression of AQP3 were decreased by LPS in a dose- and time-dependent manner, the expression of AQP3 was significantly decreased with the increased concentration of LPS, and at a dose of 100 μg/mL LPS, AQP3 mRNA and protein levels were decreased by a maximum (P < 0.05) of 1.51-fold and 1.49-fold, respectively. When cells were treated with 100 μg/mL LPS for 0, 3, 6, 12, and 24 h, the AQP3 mRNA level was significantly decreased at an early time point of 3 h, and reached about 10% of the control level at 24 h post-treatment (P < 0.05). Down-regulation of AQP3 expression was significantly inhibited by the p38 inhibitor (SB203580) and JNK inhibitor (SP600125).

CONCLUSION: p38 and JNK may be promising targets for the preservation of AQP3 expression and may be beneficial to the clinical management of diarrhoea.

Genistein inhibits rotavirus replication and upregulates AQP4 expression in rotavirus-infected Caco-2 cells

Rotavirus (RV) is the primary cause of severe dehydrating gastroenteritis and acute diarrheal disease in infants and young children. Previous studies have revealed that genistein can inhibit the infectivity of enveloped or nonenveloped viruses. Although the biological properties of genistein are well studied, the mechanisms of action underlying their anti-rotavirus properties have not been fully elucidated. Here, we report that genistein significantly inhibits RV-Wa replication in vitro by repressing viral RNA transcripts, and possibly viral protein synthesis. Interestingly, we also found that aquaporin 4 (AQP4) mRNA and protein expression, which was downregulated in RV-infected Caco-2 cells, can be upregulated by genistein in a time- and dose-dependent manner. Further experiments confirmed that genistein triggers CREB phosphorylation through PKA activation and subsequently promotes AQP4 gene transcription. These findings suggest that the pathophysiological mechanism of RV infection involves decreased expression of AQP4 and that genistein may be a useful candidate for developing a new anti-RV strategy by inhibiting rotavirus replication and upregulating AQP4 expression via the cAMP/PKA/CREB signaling pathway. Further studies on the effect of genistein on RV-induced diarrhea are warranted.

[NET WATER TRANSPORT VIA RAT COLON EPITELIUM UNDER THE EXPERIMENTAL DYSBIOSIS]

The aim of the present study was to investigate the effect of cephalosporin antibiotic ceftriaxone (50 mg/kg, i/m) and mac- rolide antibiotic azithromycin (15 mg/kg, per.os.) on net water transport across rat colonic epithelium. Study was done on male Wistar rats (180-250 g). Azithromycin or ceftriaxone was injected daily for 5 days. Net water transport was evaluated on the 6th day by isolated colonic loop perfusion technique in vivo on anaesthetized rats. Treatment with azithromycin increased 2,4-fold the absorption of water, while ceftriaxone caused decrease 1,9-fold water absorption. The antibiotics treatment within five days didn't change the composition of the fecal and colonic parietal microbiota. Azithromycin-induced increase in water absorption was associated with upregulation of AQP 8 water channel expression (P < 0.05) in colonic mucosa. Ceftriaxone treatment didn't change protein level of AQP8 but induced pro-inflammatory changes in colonic mucosa structure and mast cells degranulation. We showed for the first time the opposite effects ofmacrolide and cephalosporin antibiotics on net water transport across rat colonic epithelium.

Rhubarb tannins extract inhibits the expression of aquaporins 2 and 3 in magnesium sulphate-induced diarrhoea model

Tannins, a group of major active components of Chinese rhubarb and widely distributed in nature, have a significant antidiarrhoeal activity. Aquaporins (AQPs) 2 and 3 play important roles in regulating water transfer during diarrhoea. The present study aims to determine the effect of the total tannins extract of rhubarb on aquaporins (AQPs) 2 and 3 in diarrhoea mice and HT-29 cells both induced by magnesium sulphate (MgSO₄). Our results showed that rhubarb tannins extract (RTE) significantly decreased the faecal water content in colon and evaluation index of defecation of diarrhoea mice. Interestingly, RTE could markedly reduce the mRNA and protein expression levels of AQPs 2 and 3 in apical and lateral mucosal epithelial cells in the colons of diarrhoea mice and HT-29 cells both induced by MgSO₄ in a dose-dependent manner. Furthermore, RTE suppressed the production of cyclic monophosphate- (cAMP-) dependent protein kinase A catalytic subunits α (PKA C-α) and phosphorylated cAMP response element-binding protein (p-CREB, Ser133) in MgSO₄-induced HT-29 cells. Our data showed for the first time that RTE inhibit AQPs 2 and 3 expression in vivo and in vitro via downregulating PKA/p-CREB signal pathway, which accounts for the antidiarrhoeal effect of RTE.

Involvement of aquaporins in a mouse model of rotavirus diarrhea

Rotavirus diarrhea is a major worldwide cause of infantile gastroenteritis; however, the mechanism responsible for intestinal fluid loss remains unclear. Water transfer across the intestinal epithelial membrane seems to occur because of aquaporins (AQPs). Accumulating evidence indicates that alterations in AQPs may play an important role in pathogenesis. Here, we focus on changes in AQPs in a mouse model of rotavirus diarrhea. In the present study, 32 of 35 mice developed diarrhea and mild dehydration within 24 hours after infection with rotavirus strain SA11. Intestinal epithelial cells demonstrated cytoplasmic vacuolation, malaligned villi, and atrophy. AQP1 expression was significantly attenuated in the ileum and colon in comparison with controls; likewise, AQP4 and -8 protein expression were significantly decreased in the colon of rotavirus diarrhea-infected mice. In contrast, AQP3 protein expression was significantly increased in the colon of rotavirus-infected mice in comparison with controls. These results indicate that rotavirus diarrhea is associated with the downregulation of AQP1, -4, and -8 expression. Therefore, AQPs play an important role in rotavirus diarrhea.

Aquaporins: important but elusive drug targets

The aquaporins (AQPs) are a family of small, integral membrane proteins that facilitate water transport across the plasma membranes of cells in response to osmotic gradients. Data from knockout mice support the involvement of AQPs in epithelial fluid secretion, cell migration, brain oedema and adipocyte metabolism, which suggests that modulation of AQP function or expression could have therapeutic potential in oedema, cancer, obesity, brain injury, glaucoma and several other conditions. Moreover, loss-of-function mutations in human AQPs cause congenital cataracts (AQP0) and nephrogenic diabetes insipidus (AQP2), and autoantibodies against AQP4 cause the autoimmune demyelinating disease neuromyelitis optica. Although some potential AQP modulators have been identified, challenges associated with the development of better modulators include the druggability of the target and the suitability of the assay methods used to identify modulators.

Expression of AQPs 3, 8 and 9 in the residual colonic mucosa of rats with extensive colon resection

AIM: To examine the expression of Aquaporins (AQPs) 3, 8 and 9 in the residual colonic mucosa of rats with extensive colon resection.

METHODS: Thirty-two healthy adult SD rats were randomly and equally divided into either a control group or an experimental group. Under general anesthesia, resection of about two-thirds of the colon was performed 5.0 cm from the ileocecal junction, followed by an end-to-end anastomosis with a single-layer 6/0 polypropylene suture. The animals were allowed to eat 24 h after the surgery, and the water content of feces was determined. Rats of the experimental group were killed on days 14 and 28 after surgery, and those of the control group were killed on day 28 to take colonic mucosal samples. RT-PCR was used to determine the expression of AQPs 3, 8 and 9.

RESULTS: After surgery, the water content of feces increased. The relative expression levels of AQPs 3, 8 and 9 were significantly lower in the control group (day 28) than in the experimental group (days 14 and 28) (AQP3: 0.352, 0.425 vs 0.614, both P < 0.01; AQP8: 0.425, 0.518 vs 0.733, both P < 0.01; AQP9: 0.422, 0.516 vs 0.632, both P < 0.01).

CONCLUSION: After extensive colon resection, expression of AQPs 3, 8 and 9 in the remaining colon increases, which may accelerate the absorption of water and increase the moisture of feces.

Influence of coffee (Coffea arabica) and galacto-oligosaccharide consumption on intestinal microbiota and the host responses

Although studies have reported numerous effects of coffee on human health, few studies have examined its specific effects on gut microbiota. This study aimed to clarify the influence of coffee and galacto-oligosaccharide (GOS) consumption on gut microbiota and host responses. After mice consumed coffee and GOS, their intestines were sampled, and the bacterial counts were measured with quantitative RT-PCR. Results showed that GOS consumption significantly increased total bacteria counts in the proximal colon. Although Escherichia coli and Clostridium spp. counts significantly decreased in the proximal colon, Bifidobacterium spp. counts increased remarkably in the same area. A bacterial growth inhibition assay was also conducted, and the results showed that E. coli growth was inhibited only by a coffee agar. Host responses were also investigated, revealing that coffee and GOS consumption remarkably increased aquaporin8 expression in the proximal colon. In conclusion, coffee has antibiotic effects, and GOS significantly decreased E. coli and Clostridium spp. counts, but increased Bifidobacterium spp. counts remarkably. Aquaporin8 expression was also increased with a mixture of coffee and GOS consumption. This is the first study to demonstrate that coffee consumption can regulate gut microbiota and increase aquaporin8, both of which are necessary for maintaining intestinal balance.

5-Fluorouracil induces diarrhea with changes in the expression of inflammatory cytokines and aquaporins in mouse intestines

Although the mechanisms of 5-fluorouracil (5-FU)-induced diarrhea remain unclear, accumulating evidence has indicated that changes in the mucosal immune system and aquaporins (AQPs) may play a role in its pathogenesis. Therefore, we investigated the possible changes in the gene expression of inflammatory cytokines and AQPs in the intestines of mice with 5-FU-induced diarrhea. In the present study, the expressions of mRNAs that encode inflammatory cytokines, TNF-α, IL-1β, IL-6, Il-17A and IL-22, were significantly increased throughout the entire colon of mice that exhibited diarrhea following 5-FU administration. In contrast, the gene expression of IFNγ was upregulated only in the distal colon. These increases were significantly reduced by the administration of etanercept. However, 5-FU-induced diarrhea was not recovered by etanercept. On the other hand, the genes for AQPs 4 and 8 were markedly present in the colon, and these expressions in the intestines were significantly decreased by treatment with 5-FU. These decreases were not reversed by etanercept. These findings suggest TNF-α neutralization had no effect on the acutely 5-FU-induced diarrhea and impaired AQPs but reduced dramatically several inflammatory cytokines.

[Progress in research on correlation between dampness disease and aquaporin]

Pathogenic dampness can cause many diseases, and that is why traditional Chinese medicine pays close attention to pathogenic dampness. In recent years many researches discovered that dampness diseases and aquaporin have close correlation. By analyzing the progress in research on correlation between dampness diseases and aquaporin, it is discovered that aquaporin has close correlation with urinary system, digestive system, respiratory system and central nervous system. Normal expression of aquaporin may be the molecular biological basis of dispelling dampness, while abnormal expression may be one of the main causes for dampness diseases. Studying the correlation between dampness diseases and aquaporin has quite important significance in understanding mechanism of dampness diseases and formulating treatment protocols.

Vitamin D deficiency in mice impairs colonic antibacterial activity and predisposes to colitis

Vitamin D insufficiency is a global health issue. Although classically associated with rickets, low vitamin D levels have also been linked to aberrant immune function and associated health problems such as inflammatory bowel disease (IBD). To test the hypothesis that impaired vitamin D status predisposes to IBD, 8-wk-old C57BL/6 mice were raised from weaning on vitamin D-deficient or vitamin D-sufficient diets and then treated with dextran sodium sulphate (DSS) to induce colitis. Vitamin D-deficient mice showed decreased serum levels of precursor 25-hydroxyvitamin D(3) (2.5 +/- 0.1 vs. 24.4 +/- 1.8 ng/ml) and active 1,25-dihydroxyvitamin D(3) (28.8 +/- 3.1 vs. 45.6 +/- 4.2 pg/ml), greater DSS-induced weight loss (9 vs. 5%), increased colitis (4.71 +/- 0.85 vs. 1.57 +/- 0.18), and splenomegaly relative to mice on vitamin D-sufficient chow. DNA array analysis of colon tissue (n = 4 mice) identified 27 genes consistently (P < 0.05) up-regulated or down-regulated more than 2-fold in vitamin D-deficient vs. vitamin D-sufficient mice, in the absence of DSS-induced colitis. This included angiogenin-4, an antimicrobial protein involved in host containment of enteric bacteria. Immunohistochemistry confirmed that colonic angiogenin-4 protein was significantly decreased in vitamin D-deficient mice even in the absence of colitis. Moreover, the same animals showed elevated levels (50-fold) of bacteria in colonic tissue. These data show for the first time that simple vitamin D deficiency predisposes mice to colitis via dysregulated colonic antimicrobial activity and impaired homeostasis of enteric bacteria. This may be a pivotal mechanism linking vitamin D status with IBD in humans.

Hypertonic saline alters hydraulic conductivity and up-regulates mucosal/submucosal aquaporin 4 in resuscitation-induced intestinal edema

OBJECTIVE

To characterize membrane conductivity by applying mathematical modeling techniques and immunohistochemistry and to localize and predict areas of the bowel where aquaporins may be associated with edema resolution/prevention associated with hypertonic saline. Intestinal edema induced by resuscitation and mesenteric venous hypertension impairs intestinal transit/contractility. Hypertonic saline decreases intestinal edema and improves transit. Aquaporins are water transport membrane proteins that may be up-regulated with edema and/or hypertonic saline.

DESIGN

Laboratory study.

SETTING

University research laboratory.

SUBJECTS

Male Sprague Dawley rats, weighing 270 to 330 g.

INTERVENTIONS

Rats were randomized to control (with and without hypertonic saline) and mesenteric venous hypertension with either 80 mL/kg normal saline (RESUS + VH + VEH) or 80 mL/kg normal saline with hypertonic saline (RESUS + VH + HTS). After 6 hrs, intestinal wet/dry ratios, urine output, peritoneal fluid, and intraluminal fluid were measured. Hydraulic conductivity was calculated from our previously known and published pressure-flow data. The cDNA microarray, Western blot, polymerase chain reaction, and immunohistochemistry studies were conducted for candidate aquaporins and distribution in intestinal edema resolution.

MEASUREMENTS AND MAIN RESULTS

Hypertonic saline decreased edema and increased urine, intraluminal, and peritoneal fluid volume. RESUS + VH favors fluid flux into the interstitium. Hypertonic saline causes increased hydraulic conductivity at the seromuscular and mucosal surfaces at the same time limiting flow into the interstitium. This is associated with increased aquaporin 4 expression in the intestinal mucosa and submucosa.

CONCLUSIONS

Hypertonic saline mitigates intestinal edema development and promotes fluid redistribution secondary to increased membrane conductivity at the mucosal and seromuscular surfaces. This is associated with up-regulation of aquaporin 4 gene expression and protein. Aquaporin 4 may be a useful therapeutic target for strategies to enhance edema resolution.

Alteration of cholinergic, purinergic and sensory neurotransmission in the mouse colon of food allergy model

It is well known that intestinal anaphylaxis results in a disturbed intestinal motility. It is hypothesized that the chronic intestinal anaphylaxis-induced changes in the enteric neuronal circuitry cause intestinal motor malfunctions. However, detailed mechanisms largely remain unclear. The aim of this study was to investigate the pathophysiological role of ATP, which acts as a non-cholinergic neurotransmitter and a neuroimmune modulator, in a disturbed intestinal motility of food allergy (FA). The FA mice developed allergic diarrhea accompanied with chronic inflammation and mast cell hyperplasia in the colon. The excised proximal colons (PCs) were suspended in the longitudinal direction in organ baths. In the PCs precontracted by KCl (50 mM), contractile responses to exogenous ATP (1 mM) were significantly (P < 0.01) higher in FA mice (34.2% of KCl-induced precontractions) as compared to control mice (17.2%). Pretreatment with P2 purinoceptor antagonists [suramin and PPADs] significantly (P < 0.01) reduced the ATP-evoked contractions to 7.7% and 1.5% in FA and control PCs, respectively. Furthermore, in the presence of inhibitors of cholinergic nerves and capsaicin-sensitive sensory nerves the electrical field stimulation (EFS; 10Hz)-evoked contractions were significantly (P < 0.05) higher in FA mice (65.8% of EFS-evoked maximum contractions, n = 6) than those in control mice (47.9%, n = 6). In addition, cumulative application of suramin and PPADs further inhibited EFS-induced contractions by 21.7% in FA mice (n = 6, P < 0.01) and 8.7% in control mice (n = 6, P < 0.05). Thus, the present study suggests that the sustained alteration in cholinergic, purinergic and sensory neurotransmission contribute to the disturbed motility during the chronic intestinal anaphylaxis.

The pathophysiological roles of COX-1 and COX-2 in the intestinal smooth muscle contractility under the anaphylactic condition

Various inflammatory mediators released from antigen-activated mast cells are considered to play a key role in the pathogenesis of food allergy. The aim of the present study was to determine the mechanisms underlying the antigen-induced anaphylactic responses in the rat colons. Wistar rats were sensitized by intraperitoneal injection of ovalbumin (OVA). The contractilities of isolated proximal colons of the sensitized rats were studied in the organ bath. OVA challenges of sensitized tissues induced prolonged contractile responses. The antigen-induced contractions were greatly reduced by mast cell stabilizer doxantrazole (10 microM). However, the contractions were resistant to histamine H1 receptor antagonist and prostaglandin D2 receptor antagonist. In contrast, non-selective cyclooxygenase (COX) inhibitor indomethacin (1 microM) significantly reduced the contractions by 61.0%. Furthermore, selective COX-1 inhibitor FR122047 (10 microM) as well as selective COX-2 inhibitor NS-398 (10 microM) significantly inhibited the contractions by 50.1% and 50.3%, respectively. Nevertheless, the transcript levels of COX-2 as well as COX-1 were not upregulated by OVA in the proximal colons of the sensitized rats. The present results indicate that de novo arachidonic acid metabolites synthesis by constitutive COX-1 as well as constitutive COX-2 within mast cells contribute to the altered smooth muscle contractilities in the colons under the anaphylactic condition.