Changes in the Expression and Distribution of Claudins, Increased Epithelial Apoptosis, and a Mannan-Binding Lectin-Associated Immune Response Lead to Barrier Dysfunction in Dextran Sodium Sulfate-Induced Rat Colitis

Cis-Nerolidol Inhibits MAP Kinase and NF-κB Signaling Pathways and Prevents Epithelial Tight Junction Dysfunction in Colon Inflammation: In Vivo and In Vitro Studies

Inflammation of the GI tract leads to compromised epithelial barrier integrity, which increases intestine permeability. A compromised intestinal barrier is a critical event that leads to microbe entry and promotes inflammatory responses. Inflammatory bowel diseases that comprise Crohn’s disease (CD) and ulcerative colitis (UC) show an increase in intestinal permeability. Nerolidol (NED), a naturally occurring sesquiterpene alcohol, has potent anti-inflammatory properties in preclinical models of colon inflammation. In this study, we investigated the effect of NED on MAPKs, NF-κB signaling pathways, and intestine epithelial tight junction physiology using in vivo and in vitro models. The effect of NED on proinflammatory cytokine release and MAPK and NF-κB signaling pathways were evaluated using lipopolysaccharides (LPS)-stimulated RAW 264.7 macrophages. Subsequently, the role of NED on MAPKs, NF-κB signaling, and the intestine tight junction integrity were assessed using DSS-induced colitis and LPS-stimulated Caco-2 cell culture models. Our result indicates that NED pre-treatment significantly inhibited proinflammatory cytokine release, expression of proteins involved in MAP kinase, and NF-κB signaling pathways in LPS-stimulated RAW macrophages and DSS-induced colitis. Furthermore, NED treatment significantly decreased FITC-dextran permeability in DSS-induced colitis. NED treatment enhanced tight junction protein expression (claudin-1, 3, 7, and occludin). Time-dependent increases in transepithelial electrical resistance (TEER) measurements reflect the formation of healthy tight junctions in the Caco-2 monolayer. LPS-stimulated Caco-2 showed a significant decrease in TEER. However, NED pre-treatment significantly prevented the fall in TEER measurements, indicating its protective role. In conclusion, NED significantly decreased MAPK and NF-κB signaling pathways and decreased tight junction permeability by enhancing epithelial tight junction protein expression.

Emotional-Single Prolonged Stress: A promising model to illustrate the gut-brain interaction

Excessive stress can precipitate depression and anxiety diseases, and damage gastrointestinal functionality and microbiota changes, favoring the development of functional gastrointestinal disorders (FGIDs) - defined by dysregulation in the brain-gut interaction. Therefore, the present study investigated if Emotional-Single Prolonged Stress (E-SPS) induces depressive/anxiety-like phenotype and gut dysfunction in adult Swiss male mice. For this, mice of the E-SPS group were subjected to three stressors sequential exposure: immobilization, swimming, and odor of the predator for 7 days (incubation period). Next, animals performed behavior tests and 24 h later, samples of feces, blood, and colon tissue were collected. E-SPS increased the plasma corticosterone levels, immobility time in the tail suspension and forced swim test, decreased the grooming time in the splash test, OAT%, and OAE% in the elevated plus-maze test, as well as increased anxiety index. Mice of E-SPS had increased % of intestinal transit rate, % of fecal moisture content, and fecal pellets number, and decreased Claudin1 content in the colon. E-SPS decreased the relative abundance of Bacteroidetes phylum, Bacteroidia class, Bacteroidales order, Muribaculaceae and Porphyromonadaceae family, Muribaculum, and Duncaniella genus. However, E-SPS increased Firmicutes and Actinobacteria phylum, Coriobacteriales order, and the ratio of Firmicutes/Bacteroidetes, and demonstrated Mucispirillum genus presence. The present study showed that E-SPS induced depressive/anxiety-like phenotype, predominant diarrhea gut dysfunction, and modulated the gut bacterial microbiota profile in male adult Swiss mice. E-SPS might be a promising model for future studies on the brain-gut interaction and the development of FGIDs with psychological comorbidities.

Mucosal healing and inflammatory bowel disease: Therapeutic implications and new targets

Mucosal healing (MH) is vital in maintaining homeostasis within the gut and protecting against injury and infections. Multiple factors and signaling pathways contribute in a dynamic and coordinated manner to maintain intestinal homeostasis and mucosal regeneration/repair. However, when intestinal homeostasis becomes chronically disturbed and an inflammatory immune response is constitutively active due to impairment of the intestinal epithelial barrier autoimmune disease results, particularly inflammatory bowel disease (IBD). Many proteins and signaling pathways become dysregulated or impaired during these pathological conditions, with the mechanisms of regulation just beginning to be understood. Consequently, there remains a relative lack of broadly effective therapeutics that can restore MH due to the complexity of both the disease and healing processes, so tissue damage in the gastrointestinal tract of patients, even those in clinical remission, persists. With increased understanding of the molecular mechanisms of IBD and MH, tissue damage from autoimmune disease may in the future be ameliorated by developing therapeutics that enhance the body’s own healing response. In this review, we introduce the concept of mucosal healing and its relevance in IBD as well as discuss the mechanisms of IBD and potential strategies for altering these processes and inducing MH.

An evaluation of the protective effects of chlorogenic acid on broiler chickens in a dextran sodium sulfate model: a preliminary investigation

This study was conducted to investigate the protective effects of chlorogenic acid (CGA) on broilers subjected to dextran sodium sulfate (DSS)-induced intestinal damage. One hundred and forty-four 1-day-old male Arbor Acres broiler chicks were allocated into one of 3 groups with 6 replicates of eight birds each for a 21-d trial. The treatments included: 1) Control group: normal birds fed a basal diet; 2) DSS group: DSS-treated birds fed a basal diet; and 3) CGA group: DSS-treated birds fed a CGA-supplemented control diet. An oral DSS administration via drinking water was performed from 15 to 21 d of age. Compared with the control group, DSS administration reduced 21-d body weight and weight gain from 15 to 21 d, but increased absolute weight of jejunum and absolute and relative weight of ileum (P < 0.05). DSS administration elevated circulating D-lactate concentration and diamine oxidase activity (P < 0.05), which were partially reversed when supplementing CGA (P < 0.05). The oral administration with DSS decreased villus height and villus height/crypt depth ratio, but increased crypt depth in jejunum and ileum (P < 0.05). Compared with the control group, DSS administration increased serum glutathione level and jejunal catalase activity and malonaldehyde accumulation, but decreased jejunal glutathione level (P < 0.05). In contrast, feeding a CGA-supplemented diet normalized serum glutathione and jejunal malonaldehyde levels, and increased jejunal glutathione concentration in DSS-administrated birds (P < 0.05). Additionally, CGA supplementation reduced ileal malonaldehyde accumulation in DSS-treated birds (P < 0.05). DSS challenge increased levels of serum interferon-γ and interleukin-6, jejunal interleukin-1β, tumor necrosis factor-α, and interleukin-6, and ileal interleukin-1β and interleukin-6 when compared with the control group (P < 0.05). The elevated serum interferon-γ and ileal interleukin-6 levels were normalized to control values when supplementing CGA (P < 0.05). The results suggested that CGA administration could partially prevent DSS-induced increased intestinal permeability, oxidative damage, and inflammation in broilers, although it did not improve their growth performance and intestinal morphology.

Research progress of tight junction protein claudin-3 in hepatobiliary systemic diseases

Claudin-3 is an important member of the claudin family of tight junction proteins and is the most abundant tight junction protein in the hepatobiliary system. It plays an important role in building tight junctions of hepatobiliary cells, and maintaining cellular barrier function and molecular delivery function. Dysregulation of hepatic claudin-3 expression leads to disruption of hepatobiliary system junctions, metabolic function, barrier function, proliferation capacity, and molecular delivery function, and is closely related to the development of various hepatobiliary diseases such as hepatic malignancies, cholesterol stones, and chronic liver diseases. In this paper, we review the progress in the research of claudin-3 in hepatobiliary diseases.

Zonulin and claudin-5 levels in multisystem inflammatory syndrome and SARS-CoV-2 infection in children

AIM

SARS-CoV-2 infection in children is generally asymptomatic or mild; however, it can lead to a life-threatening clinical condition, multisystem inflammatory syndrome in children (MIS-C), days or weeks after the infection. Increased intestinal permeability isa possible triggering factor at the onset of the hyperinflammation associated with MIS-C. Zonulin and claudin-5 are involved in intestinal permeability. In this study, we aimed to investigate serum zonulin and claudin-5 levels in SARS-CoV-2 infection and MIS-C disease.

METHODS

The study group consisted of children diagnosed with MIS-C or SARS-CoV-2 infection who presented to a university hospital paediatric emergency or infectious diseases departments. The control group included well patients seen at the General Pediatrics units for routine follow-up. Serum zonulin and claudin-5 levels were measured at the time of diagnosis.

RESULTS

Fifteen patients were included in the MIS-C group, 19 in the SARS-CoV-2 infection group and 21 in the control group. The mean zonulin level in the MIS-C group was significantly higher than in the control group (P < 0.001). Mean Claudin-5 levels were Psignificantly lower in the SARS-CoV-2 infection group than in the control group (P < 0.001).

CONCLUSION

These results indicate that increased intestinal permeability may be involved in the pathogenesis of SARS-CoV-2 infection and MIS-C disease. Larger clinical trials are needed to clarify the role of serum zonulin and claudin-5 on intestinal permeability in MIS-C and SARS-CoV-2 infection in children.

Neuroinflammation as an etiological trigger for depression comorbid with inflammatory bowel disease

Patients with inflammatory bowel disease (IBD) suffer from depression at higher rates than the general population. An etiological trigger of depressive symptoms is theorised to be inflammation within the central nervous system. It is believed that heightened intestinal inflammation and dysfunction of the enteric nervous system (ENS) contribute to impaired intestinal permeability, which facilitates the translocation of intestinal enterotoxins into the blood circulation. Consequently, these may compromise the immunological and physiological functioning of distant non-intestinal tissues such as the brain. In vivo models of colitis provide evidence of increased blood–brain barrier permeability and enhanced central nervous system (CNS) immune activity triggered by intestinal enterotoxins and blood-borne inflammatory mediators. Understanding the immunological, physiological, and structural changes associated with IBD and neuroinflammation may aid in the development of more tailored and suitable pharmaceutical treatment for IBD-associated depression.

Natural-Derived Polysaccharides From Plants, Mushrooms, and Seaweeds for the Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease impairing the gastrointestinal tract, and its incidence and prevalence have been increasing over time worldwide. IBD greatly reduces peoples' quality of life and results in several life-threatening complications, including polyp, toxic colonic dilatation, intestinal perforation, gastrointestinal bleeding, and cancerization. The current therapies for IBD mainly include drugs for noncritical patients and operation for critical patients. However, continuous use of these drugs causes serious side effects and increased drug resistance, and the demand of effective and affordable drugs with minimal side effects for IBD sufferers is urgent. Natural-derived polysaccharides are becoming a research hotspot for their therapeutic effects on IBD. This study focuses on the research progress of various natural polysaccharides from plants, seaweeds, and mushrooms for the treatment of IBD during recent 20 years. Regulation of oxidative stress, inflammatory status, gut microbiota, and immune system and protection of the intestinal epithelial barrier function are the underlying mechanisms for the natural-derived polysaccharides to treat IBD. The excellent efficacy and safety of polysaccharides make them promising candidates for IBD therapy.

TREM1 Blockade Ameliorates Lipopolysaccharide-Induced Acute Intestinal Dysfunction through Inhibiting Intestinal Apoptosis and Inflammation Response

OBJECTIVE

The lipopolysaccharide- (LPS-) induced acute intestinal dysfunction model has been widely applied in recent years. Here, our aim was to investigate the effect of triggering receptor expressed on myeloid cells-1 (TREM1) inhibitor in LPS-induced acute intestinal dysfunction.

METHODS

Male rats were randomly assigned into normal (saline injection), model (LPS and saline injection), and LP17 (LPS and LP17 (a synthetic TREM1 inhibitor) injection) groups. The levels of intestinal TREM1 expression were evaluated by immunohistochemistry and western blot. Intestinal permeability and apoptosis were separately assessed by the lactulose/mannitol (L/M) ratio and TUNEL assay. The levels of soluble TREM1 (sTREM1), TNF-α, IL-6, and IL-1β were measured in the plasma and intestinal tissues by ELISA. The expression levels of NF-κB, high-mobility group box 1 (HMGB1), and toll-like receptor 4 (TLR-4) were measured with RT-qPCR and western blot. After transfection with si-TREM1 in LPS-induced intestinal epithelium-6 (IEC-6) cells, p-p65 and p-IκBα levels were detected by western blot.

RESULTS

LP17-mediated TREM1 inhibition alleviated the intestine tissue damage in rats with LPS-induced acute intestinal dysfunction. LP17 attenuated the LPS-induced increase in sTREM1, TNF-α, IL-6, and IL-1β levels in the plasma and intestinal tissues. Furthermore, intestine permeability and epithelial cell apoptosis were ameliorated by LP17. LP17 attenuated the LPS-induced increase in the expression of TREM1, HMGB1, TLR-4, and NF-κB in the intestine tissues. In vitro, TREM1 knockdown inactivated the NF-κB signaling in LPS-induced IEC-6 cells.

CONCLUSION

LP17 could ameliorate LPS-induced acute intestinal dysfunction, which was associated with inhibition of intestinal apoptosis and inflammation response.

Administration of neem (Azadirachta indica A. Juss) leaf extract decreases TNF-α and IL-6 expressions in dextran sodium sulfate-induced colitis in rats

Objective:

We aimed to determine the neem leaf extract’s effect on Tumor Necrosis Factor-alpha (TNF-α) and Interleukin-6 (IL-6) expressions in dextran sodium sulfate (DSS)-induced colitis rats.

Materials and Methods:

In the first phase of the study, colitis was induced by DSS administration in the case group and compared to the control group. In the second phase, 84 colitis rats were divided into groups I, II, and III receiving 7.8 mg/day of mesalazine, 100 mg/200 gm body weight, and 200 mg/200 gm body weight neem leaf extract, respectively.

Results:

TNF-α and IL-6 expressions were significantly increased in the case group compared to the control group. TNF-α and IL-6 expressions were decreasing in all groups receiving treatment. Group III showed an earlier decrease compared to group II. TNF-α and IL-6 expressions in group III were comparable with group I since the second week. This condition was observed in the 4th week between group II and group I.

Conclusion:

It can be concluded that neem leaf extract decreased the expression of TNF-α and IL-6 in DSS-induced colitis.

Cyclic derivative of morphiceptin Dmt-cyclo-(D-Lys-Phe-D-Pro-Asp)-NH2(P-317), a mixed agonist of MOP and KOP opioid receptors, exerts anti-inflammatory and anti-tumor activity in colitis and colitis-associated colorectal cancer in mice

Endogenous opioid system is involved in the maintenance of the intestinal homeostasis. Recently, we proved that stimulation of opioid receptors using P-317, a cyclic morphiceptin analog, resulted in the alleviation of acute colitis in mice. The aim of the current study was to assess the effect of P-317 during colitis and colitis-associated colorectal cancer in mice. Colitis was induced by addition of dextran sodium sulfate (DSS) into drinking water. Colitis-associated colorectal cancer was induced by a single intraperitoneal injection of azoxymethane (AOM) and subsequent addition of DSS into drinking water (week 2, 5, 8). During macroscopic damage evaluation the samples were collected and used for biochemical (MPO activity assay), molecular (qPCR and western blot) and histological studies. In experimental colitis, P-317 induced an anti-inflammatory response as indicated by macroscopic and microscopic scores. In the colitis-associated colorectal cancer model, a significant difference in colorectal tumor development was observed between vehicle- and P-317-treated mice. P-317 decreased the total number of colonic tumors and inhibited MPO activity. Hematoxylin and eosin staining confirmed anti-tumor activity of P-317. The expression of TNF-α was decreased in P-317-treated mice as compared to the vehicle-treated group. P-317 decreased proliferation as well as β-catenin expression in tumors. P-317, a mixed MOP and KOP receptor agonist, induced an anti-inflammatory response in experimental colitis and decreased tumor development in colitis-associated colorectal cancer in mice.

Effects of Vitamin D Supplementation on Inflammation, Colonic Cell Kinetics, and Microbiota in Colitis: A Review

Vitamin D is widely known to regulate bone health, but there is increasing evidence that it may also ameliorate colitis through inflammation, cell proliferation and apoptosis, and the microbiota. The purpose of this review is to systematically examine the mechanisms by which vitamin D reduces colitis. PubMed and Web of Science were searched for articles published between 2008 and 2019 using key words such as "vitamin D," "colitis," "inflammatory bowel disease," "inflammation," "apoptosis," "cell proliferation," and "gut bacteria". Retrieved articles were further narrowed and it was determined whether their title and abstracts contained terminology pertaining to vitamin D in relation to colitis in human clinical trials, animal studies, and cell culture/biopsy studies, as well as selecting the best match sorting option in relation to the research question. In total, 30 studies met the established criteria. Studies consistently reported results showing that vitamin D supplementation can downregulate inflammatory pathways of COX-2, TNF-α, NF-κB, and MAPK, modify cell kinetics, and alter gut microbiome, all of which contribute to an improved state of colitis. Although vitamin D and vitamin D analogs have demonstrated positive effects against colitis, more randomized, controlled human clinical trials are needed to determine the value of vitamin D as a therapeutic agent in the treatment of colitis.

Intestinal epithelial barrier and neuromuscular compartment in health and disease

A number of digestive and extra-digestive disorders, including inflammatory bowel diseases, irritable bowel syndrome, intestinal infections, metabolic syndrome and neuropsychiatric disorders, share a set of clinical features at gastrointestinal level, such as infrequent bowel movements, abdominal distension, constipation and secretory dysfunctions. Several lines of evidence indicate that morphological and molecular changes in intestinal epithelial barrier and enteric neuromuscular compartment contribute to alterations of both bowel motor and secretory functions in digestive and extra-digestive diseases. The present review has been conceived to provide a comprehensive and critical overview of the available knowledge on the morphological and molecular changes occurring in intestinal epithelial barrier and enteric neuromuscular compartment in both digestive and extra-digestive diseases. In addition, our intent was to highlight whether these morphological and molecular alterations could represent a common path (or share some common features) driving the pathophysiology of bowel motor dysfunctions and related symptoms associated with digestive and extra-digestive disorders. This assessment might help to identify novel targets of potential usefulness to develop original pharmacological approaches for the therapeutic management of such disturbances.

African green monkeys avoid SIV disease progression by preventing intestinal dysfunction and maintaining mucosal barrier integrity

Unlike HIV infection, SIV infection is generally nonpathogenic in natural hosts, such as African green monkeys (AGMs), despite life-long high viral replication. Lack of disease progression was reportedly based on the ability of SIV-infected AGMs to prevent gut dysfunction, avoiding microbial translocation and the associated systemic immune activation and chronic inflammation. Yet, the maintenance of gut integrity has never been documented, and the mechanism(s) by which gut integrity is preserved are unknown. We sought to investigate the early events of SIV infection in AGMs, specifically examining the impact of SIVsab infection on the gut mucosa. Twenty-nine adult male AGMs were intrarectally infected with SIVsab92018 and serially sacrificed at well-defined stages of SIV infection, preramp-up (1-3 days post-infection (dpi)), ramp-up (4-6 dpi), peak viremia (9-12 dpi), and early chronic SIV infection (46-55 dpi), to assess the levels of immune activation, apoptosis, epithelial damage and microbial translocation in the GI tract and peripheral lymph nodes. Tissue viral loads, plasma cytokines and plasma markers of gut dysfunction were also measured throughout the course of early infection. While a strong, but transient, interferon-based inflammatory response was observed, the levels of plasma markers linked to enteropathy did not increase. Accordingly, no significant increases in apoptosis of either mucosal enterocytes or lymphocytes, and no damage to the mucosal epithelium were documented during early SIVsab infection of AGMs. These findings were supported by RNAseq of the gut tissue, which found no significant alterations in gene expression that would indicate microbial translocation. Thus, for the first time, we confirmed that gut epithelial integrity is preserved, with no evidence of microbial translocation, in AGMs throughout early SIVsab infection. This might protect AGMs from developing intestinal dysfunction and the subsequent chronic inflammation that drives both HIV disease progression and HIV-associated comorbidities.

Short-term tissue permeability actions of dextran sulfate sodium studied in a colon organ culture system

Dextran sulfate sodium (DSS)-induced colitis is the most commonly used animal model for inflammatory bowel diseases. However, the precise molecular action of DSS, in particular its initial effect on the epithelial tissue permeability, is still poorly understood. In the present work, organ culture of mouse – and pig colon explants were performed for 1–2 h in the presence/absence of 2% DSS together with polar- and lipophilic fluorescent probes. Probe permeability was subsequently assessed by fluorescence microscopy. DSS rapidly increased paracellular permeability of 70-kDa dextran without otherwise affecting the overall epithelial integrity. FITC-conjugated DSS likewise permeated the epithelial barrier and strongly accumulated in nuclei of cells scattered in the lamina propria. By immunolabeling, plasma cells, T cells, macrophages, mast cells, and fibroblasts were identified as possible targets for DSS, indicating that accumulation of the polyanion in nuclei was not confined to a particular type of cell in the lamina propria. In contrast, colonocytes were rarely targeted by DSS, but as visualized by transmission electron microscopy, it induced the formation of vacuole-like structures in the intercellular space between adjacent epithelial cells. Nuclei of various cell types in the lamina propria, including both cells of the innate and adaptive immune system, are novel targets for a rapid action of DSS, and from previous in vitro studies, polyanions like DSS are known to disrupt nucleosomes by binding to the histones. We therefore propose that nuclear targeting is one way whereby DSS exerts its inflammatory action as a colitogen in animal models of inflammatory bowel diseases.

Circadian Rhythm Disruption Aggravates DSS-Induced Colitis in Mice with Fecal Calprotectin as a Marker of Colitis Severity

BACKGROUND

Inflammatory bowel disease (IBD) is a chronic immunologically mediated pathology that remains a major health burden. Circadian rhythm disruption leads to a deregulation in the immune system which is a major risk factor for IBD.

AIMS

Since fecal calprotectin (FC) has been a useful tool for monitoring IBD, we aimed to evaluate the effect of circadian rhythm alteration on gut inflammation status and whether FC is associated with the severity of colitis.

METHODS

C57BL/6J mice were exposed to circadian shifts for 3 months, and then colitis was induced by 2% dextran sulfate sodium (DSS). Colitis was evaluated according to clinical symptoms and histological scoring. Plasma and intestinal inflammatory and permeability markers as well as fecal and intestinal calprotectin were assessed.

RESULTS

Circadian shifts aggravated DSS-induced colitis with increased diarrhea, flatulence, and fecal blood associated with decreased colon length. In addition, intestinal cryptic architecture was lost with the presence of increased inflammation, mucosal muscle thickening, and cryptic abscesses. Plasma tumor necrosis factor alpha, interleukin 1 beta, interleukin 6, and C-reactive protein upregulations were paralleled by the deterioration of intestinal permeability. Calprotectin expression and distribution increased in the intestines and feces of shifted animals, and levels highly correlated with the increases in intestinal inflammation and permeability.

CONCLUSIONS

Circadian rhythm disruption aggravates DSS-induced colitis, whereas fecal and intestinal calprotectin associates with the severity of disease. Calprotectin might be a useful marker and tool for assessing patients at risk of IBD due to lifestyles with disruptive sleep patterns.

Plasma claudin-3 is associated with tumor necrosis factor-alpha-induced intestinal endotoxemia in liver disease

OBJECTIVE

To investigate intestinal endotoxemia (IETM), intestinal permeability (IP) and cytokine activity in patients with liver cirrhosis (LC).

MATERIALS AND METHODS

Twenty-nine patients with chronic hepatitis B (CHB), 28 with compensated LC, 33 with decompensated LC, 24 with spontaneous bacterial peritonitis (SBP), 26 with acute-on-chronic liver failure (ACLF), and 24 with decompensated LC complicated by hepatocellular carcinoma (HCC) were recruited. Thirty-one healthy people were included as a control group. Plasma tumor necrosis factor (TNF)-α, interferon (IFN)-γ, D-lactate, endotoxin, and claudin-3 levels were assayed. Data were compared using Pearson correlation testing and analysis of variance, with P < 0.05 considered significant.

RESULTS

TNF-α, claudin-3, and endotoxin levels were significantly increased (P < 0.05) in the plasma of all patients with liver disease compared with that of controls, particularly in patients with decompensated LC, SBP, ACLF, or HCC (P < 0.01). IFN-γ was significantly higher in HCC than in other liver diseases (P < 0.01). Plasma D-lactate was significantly decreased in all liver diseases, except SBP (P < 0.01). TNF-α, endotoxin, and claudin-3 levels were positively correlated (P < 0.01), but correlations of IFN-γ with endotoxin or claudin-3 were not significant. The plasma D-lactate level did not significantly correlate with either TNF-α, endotoxin, or claudin-3 levels.

CONCLUSION

Plasma claudin-3, but not D-lactate, was found to be a marker of IP in patients with liver diseases. Elevated plasma TNF-α in such patients was likely to have injured the intestinal barrier, leading to IETM, especially in end-stage LC.

Active Vaccination With EMMPRIN-Derived Multiple Antigenic Peptide (161-MAP) Reduces Angiogenesis in a Dextran Sodium Sulfate (DSS)-Induced Colitis Model

Ulcerative colitis (UC) is an autoimmune disease that affects the colon and shares many clinical and histological features with the dextran sulfate sodium (DSS)-induced colitis model in mice. Angiogenesis is a critical component in many autoimmune diseases, as well as in the DSS-induced colitis model, and is it partially mediated by EMMPRIN, a multifunctional protein that can induce the expression of both the potent pro-angiogenic vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs). We asked whether targeting EMMPRIN by active vaccination, using a novel, specific epitope in the protein, synthesized as a multiple antigenic peptide (MAP), could trigger beneficial effects in the DSS-induced colitic C57BL/6J mice. Mice were vaccinated with four boost injections (50 μg each) of either 161-MAP coding for the EMMPRIN epitope or the scrambled control peptide (Scr-MAP) emulsified in Freund's adjuvant. We show that male mice that were vaccinated with 161-MAP lost less weight, demonstrated improved disease activity indices (DAI), had reduced colitis histological score, and their colons were longer in comparison to mice vaccinated with the Scr-MAP. The 161-MAP vaccination also reduced serum and colon levels of EMMPRIN, colon concentrations of VEGF, MMP-9, and TGFβ, and vessel density assessed by CD31 staining. A similar effect was observed in female mice vaccinated with 161-MAP, including weight loss, colitis histological score, colon length, colon levels of EMMPRIN and colon concentrations of VEGF. However, for female mice, the changes in DAI values, EMMPRIN serum levels, and MMP-9 and TGFβ colon concentrations did not reach significance. We conclude that our strategy of alleviating autoimmunity in this model through targeting angiogenesis by actively vaccinating against EMMPRIN was successful and efficient in reducing angiogenesis.

An improved rat model for chronic inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) is an important cause of chronic disability in humans.

METHODS

We characterized a model of chronic IBD in young male Wistar rats by administering dextran sodium sulfate (DSS: 0%, 0.25%, 0.5%, or 1% in drinking water) for six weeks, with 0.5% DSS for twelve weeks, following DSS cessation or together with treatment with sulfasalazine for the last 6 weeks. We measured gastrointestinal characteristics including stool consistency, blood in stools, small intestine and colon length, intestinal transit and permeability, and gut microbiota, as well as extra-intestinal parameters including oral glucose tolerance, systolic blood pressure, fat and lean mass, and left ventricular stiffness.

RESULTS

At 6 weeks, 0.25-1% DSS produced gastrointestinal changes as diarrhea and blood in stools. At 12 weeks, 0.5% DSS produced chronic and sustained gastrointestinal changes, with marked infiltration of inflammatory cells throughout the gastrointestinal tract and crypt distortion. Firmicutes increased and Bacteroidetes and Actinobacteria decreased in DSS-treated rats. Changes were reversed by DSS cessation or sulfasalazine treatment. Gastrointestinal permeability and extra-intestinal parameters did not change, so DSS changes were limited to the gastrointestinal tract.

CONCLUSION

Chronic 0.5% DSS produces selective and reversible gastrointestinal changes, providing an improved chronic model in rats that mimics human IBD for testing new interventions.

Expression of Mucins and Claudins in the Colon during Acute and Chronic Experimental Colitis

We studied changes in the expression of mRNA for mucins and claudins in the medial part of the colon in male C57Bl/6 mice on the model of acute and chronic colitis induced by substitution of drinking water with 1% solution of dextran sodium sulphate for 5 days. In acute colitis, the expression of the main structural component of glycocalyx, mucin Muc3, decreased and expression of pore-forming claudin Cldn2 increased, which reflected enhanced permeability of tight junctions. In the chronic colitis group, in comparison with the normal group, we observed an increase in expression of mRNA of main structural mucus component Muc2, enhanced of expression of Muc1 associated with carcinogenesis, and reduced expression of Muc13, which led to a more severe course of colitis; the expression of pore-forming claudin Cldn2 was elevated. These findings indicate that the imbalance in the expression of mucins and claudins plays an important role in the mechanisms of development of acute and chronic colitis.

Dextran sodium sulfate colitis murine model: An indispensable tool for advancing our understanding of inflammatory bowel diseases pathogenesis

Inflammatory bowel diseases (IBD), including Crohn’s disease and ulcerative colitis, are complex diseases that result from the chronic dysregulated immune response in the gastrointestinal tract. The exact etiology is not fully understood, but it is accepted that it occurs when an inappropriate aggressive inflammatory response in a genetically susceptible host due to inciting environmental factors occurs. To investigate the pathogenesis and etiology of human IBD, various animal models of IBD have been developed that provided indispensable insights into the histopathological and morphological changes as well as factors associated with the pathogenesis of IBD and evaluation of therapeutic options in the last few decades. The most widely used experimental model employs dextran sodium sulfate (DSS) to induce epithelial damage. The DSS colitis model in IBD research has advantages over other various chemically induced experimental models due to its rapidity, simplicity, reproducibility and controllability. In this manuscript, we review the newer publicized advances of research in murine colitis models that focus upon the disruption of the barrier function of the intestine, effects of mucin on the development of colitis, alterations found in microbial balance and resultant changes in the metabolome specifically in the DSS colitis murine model and its relation to the pathogenesis of IBD.

Cinnamicaldehyde regulates the expression of tight junction proteins and amino acid transporters in intestinal porcine epithelial cells

BACKGROUND

Cinnamicaldehyde (CA) is a key flavor compound in cinnamon essential oil possessing various bioactivities. Tight junction (TJ) proteins are vital for the maintenance of intestinal epithelial barrier function, transport, absorption and utilization of dietary amino acids and other nutrients. In this study, we tested the hypothesis that CA may regulate the expression of TJ proteins and amino acid transporters in intestinal porcine epithelial cells (IPEC-1) isolated from neonatal pigs.

RESULTS

Compared with the control, cells incubated with 25 μmol/L CA had increased transepithelial electrical resistance (TEER) and decreased paracellular intestinal permeability. The beneficial effect of CA on mucosal barrier function was associated with enhanced protein abundance for claudin-4, zonula occludens (ZO)-1, ZO-2, and ZO-3. Immunofluorescence staining showed that 25 μmol/L CA promoted the localization of claudin-1 and claudin-3 to the plasma membrane without affecting the localization of other TJ proteins, including claudin-4, occludin, ZO-1, ZO-2, and ZO-3, compared with the control cells. Moreover, protein abundances for rBAT, xCT and LAT2 in IPEC-1 cells were enhanced by 25 μmol/L CA, while that for EAAT3 was not affected.

CONCLUSIONS

CA improves  intestinal mucosal barrier function by regulating the distribution of claudin-1 and claudin-3 in enterocytes, as well as enhancing protein abundance for amino acid transporters rBAT, xCT and LAT2 in enterocytes. Supplementation with CA may provide an effective nutritional strategy to improve intestinal integrity and amino acid transport and absorption in piglets.

Microbiota and Probiotics in Health and HIV Infection

Microbiota play a key role in various body functions, as well as in physiological, metabolic, and immunological processes, through different mechanisms such as the regulation of the development and/or functions of different types of immune cells in the intestines. Evidence indicates that alteration in the gut microbiota can influence infectious and non-infectious diseases. Bacteria that reside on the mucosal surface or within the mucus layer interact with the host immune system, thus, a healthy gut microbiota is essential for the development of mucosal immunity. In patients with human immunodeficiency virus (HIV), including those who control their disease with antiretroviral drugs (ART), the gut microbiome is very different than the microbiome of those not infected with HIV. Recent data suggests that, for these patients, dysbiosis may lead to a breakdown in the gut’s immunologic activity, causing systemic bacteria diffusion and inflammation. Since in HIV-infected patients in this state, including those in ART therapy, the treatment of gastrointestinal tract disorders is frustrating, many studies are in progress to investigate the ability of probiotics to modulate epithelial barrier functions, microbiota composition, and microbial translocation. This mini-review analyzed the use of probiotics to prevent and attenuate several gastrointestinal manifestations and to improve gut-associated lymphoid tissue (GALT) immunity in HIV infection.

Glycine Regulates Expression and Distribution of Claudin-7 and ZO-3 Proteins in Intestinal Porcine Epithelial Cells

BACKGROUND

Glycine traditionally is classified as a nutritionally nonessential amino acid in humans and animals. Because of its abundance in the body and its extensive use via multiple pathways, requirements for glycine are particularly high in neonates. Our recent studies show that dietary glycine supplementation is needed for optimal intestinal development in piglets. Importantly, reduced concentrations of glycine in the lumen of the small intestine are associated with gut dysfunction in low-birth-weight piglets. However, the mechanisms responsible for the beneficial effects of glycine on the intestinal mucosal barrier are largely unknown.

OBJECTIVE

This study tested the hypothesis that glycine may regulate the expression and distribution of tight junction (TJ) proteins, thereby contributing to intestinal mucosal barrier function.

METHODS

Enterocytes isolated from the jejunum of a healthy newborn pig were propagated to establish a stable cell line. The cells were cultured with 0.05 mmol glycine/L (control; concentration in the small intestinal lumen of low-birth-weight piglets) or 0.25 or 1.0 mmol glycine/L for the indicated periods of time. Epithelial barrier integrity and expression and localization of TJ proteins were analyzed by using monolayer transepithelial electrical resistance (TEER) and paracellular permeability, Western blot, and immunofluorescence imaging.

RESULTS

Compared with controls, cells cultured with 0.25 or 1.0 mmol glycine/L increased TEER (P < 0.05) by 46-53% and 80-111%, respectively, at 60-72 h. Correspondingly, paracellular permeability was reduced (P < 0.05) by 6-21% and 18-27% for 0.25 or 1.0 mmol glycine/L treatment, respectively, at 36-72 h. Compared with controls, protein abundances for claudin-3, claudin-7, and zonula occludens (ZO) 3 were enhanced (25-33%, P < 0.05) by 0.25 and 1.0 mmol glycine/L at 8 h, whereas those for occludin, claudin-1, claudin-4, and ZO-2 were not affected. Compared with controls, 1.0 mmol glycine/L reduced the protein abundance of ZO-1 by 20% at 8 h (P < 0.05), but 0.25 mmol glycine/L had no effect. A glycine concentration of 0.25 mmol/L sustained the localization of claudin-7 and ZO-3 to the interface between enterocytes. Interestingly, 1 mmol glycine/L promoted the distribution of claudin-4 and claudin-7 to the cytosol and nucleus, and the localization of ZO-3 to the plasma membranes, while decreasing the distribution of ZO-1 at cell-cell contact sites, compared with control cells.

CONCLUSION

Physiologic concentrations of glycine support intestinal mucosal barrier function by regulating the abundance and distribution of claudin-7 and ZO-3 in enterocytes. Supplementation with glycine may provide an effective nutritional strategy to improve intestinal integrity in piglets.

Therapeutic effect of teduglutide on non-alcoholic fatty liver disease in rats

AIM: To assess the therapeutic effect of glucagon-like peptide (GLP-2) analogue teduglutide on non-alcoholic fatty liver disease (NAFLD) in rats.

METHODS: Thirty SD rats were randomized into a normal diet group and a high-fat diet group. After feeding for 12 weeks, six rats were respectively selected from the two groups to determine whether the NAFLD model was successfully established. From the 13^th week, the rest rats in the normal diet group served as controls (n = 6), and the rest rats of the high-fat diet group were randomized into a NAFLD group (n = 6) and a GLP-2 group (n = 6). The rats in the GLP-2 group were injected with teduglutide and the other two groups were injected with normal saline for 7 d. Then blood samples were collected from the ocular veniplex and rats were sacrificed. NAFLD related biochemical indicators were determined and pathological results were observed.

RESULTS: The NAFLD model was successfully established. Compared to the normal group, triglyceride (TG) and total cholesterol (TC) levels in liver homogenate and NAFLD activity score (NAS) were significantly higher in the high-fat diet group (P < 0.05). Moreover, duodenal mucosal epithelial cells were loosely arranged, and intercellular space and Claudin-2 protein expression were increased (P < 0.05). After treatment with GLP-2, TG and TC levels in liver homogenate and liver NAS were significantly lower than those of the NAFLD group (P < 0.05). Accordingly, the arrangement of intestinal epithelial cells was improved, and intercellular space and Claudin-2 protein expression were decreased (P < 0.05).

CONCLUSION: NAFLD can cause the loose of intestinal mucosal cells and the increase of Claudin-2 protein expression. Teduglutide might exert its therapeutic effect on NAFLD by decreasing the expression of Claudin-2 protein.

Molecular and cellular mechanisms of tight junction dysfunction in the irritable bowel syndrome

The pathophysiological mechanisms of the irritable bowel syndrome (IBS), one of the most prevalent gastrointestinal disorders, are complex and have not been fully elucidated. The present study aimed to investigate the molecular and cellular mechanisms of tight junction (TJ) dysfunction in IBS. Intestinal tissues of IBS and non‑IBS patients were examined to observe cellular changes by cell chemical tracer electron microscopy and transmission electron microscopy, and intestinal claudin‑1 protein was detected by immunohistochemistry, western blot analysis and fluorescence quantitative polymerase chain reaction. Compared with the control group, TJ broadening and the tracer extravasation phenomenon were observed in the diarrhea‑predominant IBS group, and a greater number of neuroendocrine cells and mast cells filled with high‑density particles in the endocrine package pulp as well as a certain extent of vacuolization were present. The expression of claudin‑1 in diarrhea‑predominant IBS patients was decreased, while it was increased in constipation‑predominant IBS patients. In conclusion, the results of the present study indicated that changes in cellular structure and claudin‑1 levels were associated with Tjs in IBS.