Role of Toll-like receptors in health and diseases of gastrointestinal tract

The human gastrointestinal (GI) tract is colonized by non-pathogenic commensal microflora and frequently exposed to many pathogenic organisms. For the maintenance of GI homeostasis, the host must discriminate between pathogenic and non-pathogenic organisms and initiate effective and appropriate immune and inflammatory responses. Mammalian toll-like receptors (TLRs) are members of the pattern-recognition receptor (PRR) family that plays a central role in the initiation of innate cellular immune responses and the subsequent adaptive immune responses to microbial pathogens. Recent studies have shown that gastrointestinal epithelial cells express almost all TLR subtypes characterized to date and that the expression and activation of TLRs in the GI tract are tightly and coordinately regulated. This review summarizes the current understanding of the crucial dual roles of TLRs in the development of host innate and adaptive immune responses to GI infections and the maintenance of the immune tolerance to commensal bacteria through down-regulation of surface expression of TLRs in intestinal epithelial cells.     

MAPKs represent novel therapeutic targets for gastrointestinal motility disorders

The number of patients suffering from symptoms associated with gastrointestinal(GI) motility disorders is on the rise. GI motility disorders are accompanied by alteration of gastrointestinal smooth muscle functions. Currently available drugs,which can directly affect gastrointestinal smooth muscle and restore altered smooth muscle contractility to normal,are not satisfactory for treating patients with GI motility disorders. We have recently shown that ERK1/2 and p38MAPK signaling pathways play an important role in the contractile response not only of normal intestinal smooth muscle but also of inflamed intestinal smooth muscle. Here we discuss the possibility that ERK1/2 and p38MAPK signaling pathways represent ideal targets for generation of novel therapeutics for patients with GI motility disorders.     

Microbiota alterations in acute and chronic gastrointestinal inflammation of cats and dogs

The intestinal microbiota is the collection of the living microorganisms(bacteria, fungi, protozoa, and viruses) inhabiting the gastrointestinal tract. Novel bacterial identification approaches have revealed that the gastrointestinal microbiota of dogs and cats is, similarly to humans, a highly complex ecosystem. Studies in dogs and cats have demonstrated that acute and chronic gastrointestinal diseases, including inflammatory bowel disease(IBD), are associated with alterations in the small intestinal and fecal microbial communities. Of interest is that these alterations are generally similar to the dysbiosis observed in humans with IBD or animal models of intestinal inflammation, suggesting that microbial responses to inflammatory conditions of the gut are conserved across mammalian host types. Studies have also revealed possible underlying susceptibilities in the innate immune system of dogs and cats with IBD, which further demonstrate the intricate relationship between gut microbiota and host health. Commonly identified microbiome changes in IBD are decreases in bacterial groups within the phyla Firmicutes and Bacteroidetes, and increases within Proteobacteia. Furthermore, a reduction in the diversity of Clostridium clusters XIVa and IV(i.e., Lachnospiraceae and Clostridium coccoides subgroups) are associated with IBD, suggesting that these bacterial groups may play an important role in maintenance of gastrointestinal health. Future studies are warranted to evaluate the functional changes associated with intestinal dysbiosis in dogs and cats.     

Development and distribution of mast cells and neuropeptides in human fetus duodenum

AIM:To study the developmental regularities and heterogeneity of mast cells(MC)in human fetus duodenum and the distribution and developmental regularities of substance P(SP),calcitonin gene-related peptide(CGRP)- immunoreactive(IR)peptidergic nerves in fetus duodenum, as well as the relationship between MC,SP and CGRP-IR peptidergic nerves. METHODS:Duodena from 21 cases of human fetus and one term infant were stained by hematoxylin-eosin(HE), toluidine blue(TB)and immunohistochemical avidin-biotinylated peroxidase complex(ABC)method. RESULTS:Lobe-shape intestinal villi in duodenum were already developed at the twelfth week.At the 21st wk, muscular mucosa appeared gradually,and four layers were observed in the wall of duodenum.TB staining showed that the granules in the immature MC were pale violet, while the mature MC were strong violet in color by TB staining.Connective tissue MC(CTMC)appeared occasionally in submucosa and muscular layer of duodenum at the 16th wk.While the mucosa MC(MMC)appeared at the 18th wk.At the 22nd wk,both CTMC and MMC were activated,and distributed in the surrounding blood vessels and ganglions.The verge of some MC were unclear,and showed degranular phenomena.At the 14th wk,SP and CGRP-IR nerve fibers and cells appeared in the myenteric and submucous plexuses in small intestine,and the responses were turn strongly.Neurons were light to deep brown,and nerve fibers were present as varicose and liner profiles.On the corresponding site of serial sections,SP and CGRP immunohistochemical reactions were coexisted in one nerve fiber or cell.Some of MC showed SP and CGRP-IR positive staining. CONCLUSION:There are two heterogeneous kinds of MC in duodenum,MMC and CTMC.MC might play an important role in regulating blood circulation and sensation.     

Update on clinical and research application of fecal biomarkers for gastrointestinal diseases

Gastrointestinal(GI) diseases comprise a large spectrum of clinical conditions ranging from indigestion to inflammatory bowel diseases(IBDs) and carcinomas. Endoscopy is the usual method employed to diagnose these condition. Another noninvasive way to assess and diagnose GI conditions are fecal biomarkers. Fecal biomarkers provide information regarding a specific disease process and are perhaps more acceptable to clinicians and patients alike because of their non-invasivity compared to endoscopy. Aim of this review was to evaluate the current status of the fecal biomarkers in clinical and research for in GI diseases. Multiple types of fecal biomarkers are discussed in this review including; markers to assess IBD, which are released as a results of an inflammatory insults to intestinal epithelia such as antimicrobial peptides(lactoferrin) or inflammation related proteins(calprotectin). While markers related to function of digestion are primarily related to partially digested food or mucosal proteins such as abnormal amount of fecal fat α1-antitrypsin, elastase and secretary IgA. The upcoming fecal biomarker like M2 pyruvate kinase and neutrophil gelatinase associated lipocalin are discussed as well. Apart from above mention, the fecal biomarkers under exploration for possible clinical use in future are also discussed. These include cathelicidins, osteoprotegerin, β-glucuronidase, Eosinophil proteins, etc.     

Common immunologic mechanisms in inflammatory bowel disease and spondylarthropathies

Spondyloarthropathies （SPA） are commonly observed extra-intestinal manifestations of both Crohn＇s disease （CD） and ulcerative colitis （UC）, the two major forms of inflammatory bowel diseases （[BD）. However, the immunological link between these two clinical entities is still poorly understood. Several lines of evidence indicate that SpA may originate from the relocation to the joints of the immune process primarily induced in the gut. The transfer of the intestinal inflammatory process into the joints implicates that immune cells activated in the gut-draining lymph nodes can localize, at a certain point of the intestinal disease, either into the gut or into the joints. This is indicated by the overlapping expression of adhesion molecules observed on the surface of intestinal and synovial endothelial cells during inflammation. Moreover bacterial antigens and HLA-B27 expression may be implicated in the reactivation of T cells at the articular level. Finally, accumulating evidence indicates that a T helper 17 cell-mediated immune response may contribute to IBD and IBD-related SpA with a crucial role played by tumor necrosis factor-α in CD and to a lesser extent in UC.     

Irritable bowel syndrome: Diagnosis and pathogenesis

Irritable bowel syndrome (IBS) is a common gastro-intestinal (GI) disorder that considerably reduces the quality of life. It further represents an economic burden on society due to the high consumption of healthcare resources and the non-productivity of IBS patients. The diagnosis of IBS is based on symptom assessment and the Rome Ⅲ criteria. A combination of the Rome Ⅲ criteria, a physical examination, blood tests, gastros-copy and colonoscopy with biopsies is believed to be necessary for diagnosis. Duodenal chromogranin A cell density is a promising biomarker for the diagnosis of IBS. The pathogenesis of IBS seems to be multifactorial, with the following factors playing a central role in the pathogenesis of IBS:heritability and genetics, dietary/intestinal microbiota, low-grade inflammation, and disturbances in the neuroendocrine system (NES) of the gut. One hypothesis proposes that the cause of IBS is an altered NES, which would cause abnormal GI motility, secretions and sensation. All of these abnormalities are characteristic of IBS. Alterations in the NES could be the result of one or more of the following:genetic factors, dietary intake, intestinal flora, or lowgrade inflammation. Post-infectious IBS (PI-IBS) and inflammatory bowel disease-associated IBS (IBD-IBS) represent a considerable subset of IBS cases. Patients with PI-and IBD-IBS exhibit low-grade mucosal inflammation, as well as abnormalities in the NES of the gut.     

Intestinal sugar transport

Carbohydrates are an important component of the diet. The carbohydrates that we ingest range from simple monosaccharides (glucose, fructose and galactose) to disaccharides (lactose, sucrose) to complex polysaccharides. Most carbohydrates are digested by salivary and pancreatic amylases, and are further broken down into monosaccharides by enzymes in the brush border membrane (BBM) of enterocytes. For example, lactase-phloridzin hydrolase and sucrase-isomaltase are two disaccharidases involved in the hydrolysis of nutritionally important disaccharides. Once monosaccharides are presented to the BBM, mature enterocytes expressing nutrient transporters transport the sugars into the enterocytes. This paper reviews the early studies that contributed to the development of a working model of intestinal sugar transport, and details the recent advances made in understanding the process by which sugars are absorbed in the intestine.     

Gastrointestinal Symptoms in Women With Endometriosis and Microscopic Colitis in Comparison to Irritable Bowel Syndrome: A Cross-Sectional Study

Background: Gastrointestinal (GI) symptoms similar to irritable bowel syndrome (IBS) are often present in women with endometriosis and microscopic colitis (MC). The objective of this study was to estimate GI symptoms in IBS, endometriosis, and MC, to compare the clinical expression of the diseases.Methods: Women with IBS, endometriosis, and MC were identified by diagnosis codes at a tertiary center. The patients had to complete the visual analog scale for IBS to estimate specific GI symptoms. Women fulfilling Rome III criteria for IBS were diagnosed as IBS (n = 109) and divided into subgroups depending on predominating symptoms. Women diagnosed with endometriosis (n = 158) and MC (n = 88) were evaluated whether they also fulfilled the Rome III criteria for IBS.Results: Women with IBS experienced aggravated abdominal pain, diarrhea, bloating and flatulence, nausea and vomiting, the urgency to defecate, the sensation of incomplete evacuation and intestinal symptom’s influence on daily life, and impaired psychological well-being, compared to women with endometriosis. When patients with endometriosis also fulfilled the criteria for IBS, all symptoms in the 2 cohorts, except intestinal symptom’s influence on daily life, were equal. Women with IBS or diarrhea-predominated IBS experienced aggravated abdominal pain, bloating and flatulence, intestinal symptom’s influence on daily life, and impaired psychological well-being compared to MC, but at equal levels as MC with IBS-like symptoms.Conclusions: Women with IBS generally experience aggravated GI symptoms and impaired psychological well-being compared to endometriosis and MC. Patients with endometriosis or MC, in combination with IBS, express similar symptoms as patients with sole IBS.     

肥大细胞在重症急性胰腺炎肠黏膜屏障功能损伤中的作用

肥大细胞(MC)是神经-免疫-内分泌系统中的关键细胞,参与调节机体多种病理生理过程。重症急性胰腺炎(SAP)发生时,大量MC被激活,释放多种细胞因子以及炎性介质,与SAP并发肠黏膜屏障功能损伤密切相关。本文就MC在SAP肠黏膜屏障功能损伤中的作用作一综述。     

肠道平滑肌动力与炎症性肠病研究进展

肠道平滑肌动力改变与炎症性肠病(IBD)的发病关系得到医学界的重视,并逐渐成为IBD发病机制研究的热点.肠道运动的异常和神经递质的失衡在IBD的发生和进展过程中起了重要作用;白细胞介素能在一定程度上反映肠道运动功能变化.因此,恢复神经递质的失衡并重建肠道动力平衡的策略在IBD治疗过程中有良好的应用前景.     

Mast cells and neuropeptidergic terminals: Experimental studies of the mechanism of visceral hypersensitivity in irritable bowel syndrome

OBJECTIVE: The failure of dysmotility to explain the symptoms of pain in irritable bowel syndrome (IBS) led to studies on visceral hypersensitivity. Mucosal mast cells (MC) may be one factor influencing the response of visceral afferents to mechanical and chemical stimuli because they are found in close proximity to gastrointestinal mucosal sensory nerve terminals containing neuropeptides and a bi‐directional pathway linking the central nervous system, gut and MC has been demonstrated. METHODS: The present study investigated the extent of MC and the neuropeptides, substance P (SP) and vasoactive intestinal peptide (VIP), in the intestinal mucosa of patients with IBS, as well as the location of the MC. The MC and neuropeptidergic terminals were stained histochemically and immunohistochemically, respectively, neuropeptide concentrations were measured by radioimmunoassay (RIA), and the results were investigated qualitatively and quantitatively by color image analyzer. The structural relation between the MC and neuropeptide terminals was studied by ultramicroscopy using in situ embedding technique. RESULTS: In IBS, the number of MC in the terminal ileum, the ileocecal junction, and the ascending colon was significantly increased (P < 0.01), and the MC had great variations in their extent and size. Significantly increased concentrations of VIP and SP were found in the colon of IBS patients compared with controls. A correlation between mucosal MC and the SP(VIP)‐ergic terminals was found, and the MC were close to these terminals in the lamina propria, which demonstrated SP (VIP)‐ergic terminals. CONCLUSIONS: Mast cells and the neuropeptides of intestinal mucosa may play a central role in gut hypersensitivity, resulting in both the motor response and visceral perceptions that occur with IBS.     

青藤碱对炎症性肠病中肠道免疫炎症影响的研究进展

炎症性肠病(IBD)患者肠道免疫炎症反应异常,影响和调控肠道免疫炎性反应是其治疗方法之一.现已证明青藤碱(SN)可以通过抑制淋巴细胞增殖,影响免疫细胞功能,减少炎症介质生成,平衡细胞因子的分泌等多个环节来抑制机体免疫炎症反应.本文从IBD免疫发病机制入手,总结了目前SN对机体免疫功能影响方面的研究进展,为寻求SN调控肠道免疫炎症来治疗IBD提供参考.     

Toll-like receptors in inflammatory bowel disease-stepping into uncharted territory

Ulcerative colitis and Crohn＇s disease are chronic relapsing-remitting inflammatory processes of the intestinal tract. The etiology of these diseases is currently unknown. However, inflammation is hypothesized to result from inappropriate activation of mucosal immunity by luminal antigens in genetically susceptible individuals. Toll-like receptors （TLRs） are a family of transmembrane proteins that act as microbial pattern recognition receptors. They are crucial initiators of innate immune responses. The role of TLRs in the pathogenesis of inflammatory bowel disease （IBD） has not been fully elucidated. In this review, we aim to analyze the available data connecting individual TLRs to intestinal inflammation and IBD.     

The interaction between obesity and visceral hypersensitivity

Obesity has been a worldwide problem associated with numerous chronic diseases such as cardiovascular disease, type 2 diabetes, and metabolic disorders. It may also play a role in visceral hypersensitivity, contributing to irritable bowel syndrome. (i) Adipose tissue secretes various inflammatory mediators, causing intestinal hyperpermeability and nerve endings activation. (ii) Obesity and gastrointestinal microbiota could affect each other, and microbial metabolites can increase sensitivity of the colon. (iii) Vitamin D deficiency contributes to both fat accumulation and disruption of the intestinal mucosal barrier. (iv) Brain-gut axis may be another bridge from obesity to visceral hypersensitivity.     

The mycobiome: Role in health and disease,and as a potential probiotic target in gastrointestinal disease

The human gastrointestinal (GI) tract is home to trillions of microorganisms, some beneficial and others potentially harmful. Recent advances in science have allowed us to identify the multitude of organisms inhabiting the GI tract and parse out those that play a role in inflammatory bowel disease (IBD). Unfortunately, most research has focused on studying only the bacteria while ,overlooking a key player, fungus. In order to address this issue, we have focused our efforts on studying the fungal community in the GI tract known as the mycobiome. We found that patients with Crohn’s disease (CD) tend to have much higher levels of the fungus Candida tropicalis compared to their healthy family members, as well as two bacteria, Escherichia coli and Serratia marcescens. Furthermore, we showed that these three organisms worked together to form robust biofilms capable of exacerbating intestinal inflammation. Herein, we discuss the role of the mycobiome in health and disease, and highlight the importance of maintaining balance of the GI microbiota. Additionally, taking into consideration recent next generation sequencing data, we provide insight into potentially new therapeutic approaches in the treatment of IBD through the use of antifungals and/or probiotics aimed at establishing and maintaining a healthy balance of the GI total microbial community including fungi and bacteria.