Drug development for the irritable bowel syndrome: current challenges and future perspectives

Differential roles of serotonin receptor subtypes in regulation of neurotrophin receptor expression and intestinal hypernociception

OBJECTIVES

Aberrant serotonin (5-hydroxytryptamine, 5-HT) metabolism and neurite outgrowth were associated with abdominal pain in irritable bowel syndrome (IBS). We previously demonstrated that 5-HT receptor subtype 7 (5-HT₇) was involved in visceral hypersensitivity of IBS-like mouse models. The aim was to compare the analgesic effects of a novel 5-HT₇ antagonist to reference standards in mouse models and investigate the mechanisms of 5-HT₇-dependent neuroplasticity.

METHODS

Two mouse models, including Giardia post-infection combined with water avoidance stress (GW) and post-resolution of trinitrobenzene sulfonic acid-induced colitis (PT) were used. Mice were orally administered CYY1005 (CYY, a novel 5-HT₇ antagonist), alosetron (ALN, a 5-HT₃ antagonist), and loperamide (LPM, an opioid receptor agonist) prior to measurement of visceromotor responses (VMR). Levels of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin receptors (NTRs) were assessed.

RESULTS

Peroral CYY was more potent than ALN or LPM in reducing VMR values in GW and PT mice. Increased mucosal 5-HT₇-expressing nerve fibers were associated with elevated Gap43 levels in the mouse colon. We observed higher colonic Ntrk2 and Ngfr expression in GW mice, and increased Bdnf expression in PT mice compared with control mice. Human SH-SY5Y cells stimulated with mouse colonic supernatant or exogenous serotonin exhibited longer nerve fibers, which CYY dose-dependently inhibited. Serotonin increased Ntrk1 and Ngfr expression via 5-HT₇ but not 5-HT₃ or 5-HT₄, while Ntrk2 upregulation was dependent on all three 5-HT receptor subtypes.

CONCLUSIONS

Stronger analgesic effects by peroral CYY were observed compared with reference standards in two IBS-like mouse models. The 5-HT₇-dependent NTR upregulation and neurite elongation may be involved in intestinal hypernociception.

Effects and Mechanisms of Acupuncture on Diarrhea-Predominant Irritable Bowel Syndrome: A Systematic Review

Background

Irritable bowel syndrome (IBS) is a common disorder of gut-brain interaction with challenging treatment. According to evidence-based studies, acupuncture is likely to be a promising therapy and subservient adjunct for IBS. Mechanism study of acupuncture based on related clinical trials of high quality, nevertheless, is still vacant.

Aim

This study aims to assess the results and qualities of current clinical evidence and conclude the relevant pathophysiological mechanisms and therapeutic effects of acupuncture on IBS with diarrhea (IBS-D).

Methods

Literature from four databases, namely, PubMed, Cochrane Library, EMBASE, and Web of Science, was systematically searched to obtain eligible randomized controlled trials (RCTs), which contained mechanism research of acupuncture treatment in IBS-D patients. Two independent reviewers completed data extraction and quality evaluation using the RevMan 5.4.1 software.

Results

Ten trials that covered 19 items related to mechanism research were included in this review. Acupuncture was reported to improve IBS-D symptoms and quality of life, with positive effects in regulating brain-gut peptides, cerebral activities, neuroendocrine functions, psychological state, and inflammatory GI and hypersensitive intestinal tracts.

Conclusion

Acupuncture has potential influence on pathophysiology alterations such as regulating brain-gut peptides, altering cerebral connectivity and activity, promoting neuroendocrine functions and mental state, and mitigating inflammation as well as hypersensitivity of bowels in IBS-D patients, but further studies of high quality are still necessary.

Systematic Review Registration

[https://www.crd.york.ac.uk/PROSPERO], identifier [CRD42022320331].

Effectiveness of Non-Pharmacological Interventions for Irritable Bowel Syndrome: A Systematic Review

Introduction

Given the complexity of the therapeutic management of irritable bowel syndrome (IBS), alternative non-pharmacological therapies are frequently offered to patients. The aim of this study was to conduct a systematic review in order to establish the current evidence base for non-pharmacological interventions (body-directed and mind-body therapies) in the management of IBS.

Materials and Methods

The literature was searched in several electronic databases (PubMed (including Medline), Web of Science (Clarivate Analytics), Scopus (Elsevier), ScienceDirect (Elsevier), Cochrane Library (Wiley), and Wiley Online Library (Wiley)) for randomized controlled trials (RCTs) published in the English language from 1990 to 2020. Effectiveness outcomes were examined through the change in overall IBS symptoms or abdominal pain up to 12 months after treatment.

Results

11 studies (parallel-group RCTs) were identified that enrolled 1590 participants in total. Body-directed therapies (acupuncture and osteopathic medicine) showed a beneficial effect compared with standard medical treatment for overall IBS symptoms at 6 months follow-up, while no study found any difference between body-directed and sham therapies for abdominal pain or overall IBS symptoms. It was not possible to conclude whether hypnotherapy was superior to standard medical treatment or supportive therapy for overall IBS symptoms or abdominal pain due to discordant results.

Conclusions

Although body-directed therapies such as acupuncture and osteopathic medicine may be beneficial for overall IBS symptoms, higher-quality RCTs are needed to establish the clinical benefit of non-pharmacological interventions for IBS. An important challenge will be the definition of the optimal control groups to be used in non-pharmacological trials.

Probiotics Modulate Mouse Gut Microbiota and Influence Intestinal Immune and Serotonergic Gene Expression in a Site-Specific Fashion

Probiotic microorganisms may benefit the host by influencing diverse physiological processes, whose nature and underlying mechanisms are still largely unexplored. Animal models are a unique tool to understand the complexity of the interactions between probiotic microorganisms, the intestinal microbiota, and the host. In this regard, in this pilot study, we compared the effects of 5-day administration of three different probiotic bacterial strains (Bifidobacterium bifidum MIMBb23sg, Lactobacillus helveticus MIMLh5, and Lacticaseibacillus paracasei DG) on three distinct murine intestinal sites (ileum, cecum, and colon). All probiotics preferentially colonized the cecum and colon. In addition, probiotics reduced in the ileum and increased in the cecum and colon the relative abundance of numerous bacterial taxonomic units. MIMBb23sg and DG increased the inducible nitric oxide synthase (iNOS) in the ileum, which is involved in epithelial homeostasis. In addition, MIMBb23sg upregulated cytokine IL-10 in the ileum and downregulated the cyclooxygenase COX-2 in the colon, suggesting an anti-inflammatory/regulatory activity. MIMBb23sg significantly affected the expression of the main gene involved in serotonin synthesis (TPH1) and the gene coding for the serotonin reuptake protein (SERT) in the ileum and colon, suggesting a potential propulsive effect toward the distal part of the gut, whereas the impact of MIMLh5 and DG on serotonergic genes suggested an effect toward motility control. The three probiotics decreased the expression of the permeability marker zonulin in gut distal sites. This preliminary in vivo study demonstrated the safety of the tested probiotic strains and their common ability to modulate the intestinal microbiota. The probiotics affected host gene expression in a strain-specific manner. Notably, the observed effects in the gut were site dependent. This study provides a rationale for investigating the effects of probiotics on the serotonergic system, which is a topic still widely unexplored.

Deciphering the synergistic network regulation of active components from SiNiSan against irritable bowel syndrome via a comprehensive strategy: Combined effects of synephrine, paeoniflorin and naringin

BACKGROUND

SiNiSan (SNS) is an ancient Chinese herbal prescription, and the current clinical treatment of irritable bowel syndrome (IBS) is effective. In the previous study of the research team, the multi-functional co-synergism of SNS against IBS was presented. Some potential drug targets and candidate ligands were predicted.

PURPOSE

This study attempts to explore the crucial ingredient combinations from SNS formula and reveal their synergistic mechanism for IBS therapy.

MATERIALS AND METHODS

In present study, a comprehensive strategy was performed to reveal IBS related pathways and biological modules, and explore synergistic effects of the ingredients, including ADME (absorption, distribution, metabolism, excretion) screening, Text mining, Venn analysis, Gene ontology (GO) analysis, Pathway cluster analysis, Molecular docking, Network construction and Experimental verification in visceral hypersensitivity (VHS) rats.

RESULTS

Three compressed IBS signal pathways were derived from ClueGO KEGG analysis of 63 IBS genes, including Neuroactive ligand-receptor interaction, Inflammatory mediator regulation of TRP (transient receptor potential) channels and Serotonergic synapse. A multi-module network, composed of four IBS therapeutic modules (psychological, inflammation, neuroendocrine and cross-talk modules), was revealed by Target-Pathway network. Nine kernel targets were considered closely associated with the IBS pathways, including ADRA2A, HTR2A, F2RL1, F2RL3, TRPV1, PKC, PKA, IL-1Β and NGF. In silico analysis revealed that three crucial ingredients (synephrine, paeoniflorin and naringin) were assumed to coordinate the network of those IBS therapeutic modules by acting on these kernel targets in the important pathways. In vivo experimental results showed that the crucial ingredient combinations synergistically affected the expressions of the kernel biological molecules, and improved the minimum capacity threshold of AWR in VHS rats.

CONCLUSION

The study proposes the important IBS associated pathways and the network regulation mechanisms of the crucial ingredients. It reveals the multi-target synergistic effect of the crucial ingredient combinations for the novel therapy on IBS.

Deciphering the multicomponent synergy mechanisms of SiNiSan prescription on irritable bowel syndrome using a bioinformatics/network topology based strategy

BACKGROUND

SiNiSan (SNS) is a traditional Chinese medicine (TCM) prescription that has been widely used in the clinical treatment of irritable bowel syndrome (IBS). However, the underlying active substances and molecular mechanisms remain obscure.

PURPOSE

A bioinformatics/topology based strategy was proposed for identification of the drug targets, therapeutic agents and molecular mechanisms of SiNiSan against irritable bowel syndrome.

MATERIALS AND METHODS

In this work, a bioinformatics/network topology based strategy was employed by integrating ADME filtering, text mining, bioinformatics, network topology, Venn analysis and molecular docking to uncover systematically the multicomponent synergy mechanisms. In vivo experimental validation was executed in a Visceral Hypersensitivity (VHS) rat model.

RESULTS

76 protein targets and 109 active components of SNS were identified. Bioinformatics analysis revealed that 116 disease pathways associated with IBS therapy could be classified into the 19 statistically enriched functional sub-groups. The multi-functional co-synergism of SNS against IBS were predicted, including inflammatory reaction regulation, oxidative-stress depression regulation and hormone and immune regulation. The multi-component synergetic effects were also revealed on the herbal combination of SNS. The hub-bottleneck genes of the protein networks including PTGS2, CALM2, NOS2, SLC6A3 and MAOB, MAOA, CREB1 could become potential drug targets and Paeoniflorin, Naringin, Glycyrrhizic acid may be candidate agents. Experimental results showed that the potential mechanisms of SiNiSan treatment involved in the suppression of activation of Dopaminergic synapse and Amphetamine addiction signaling pathways, which are congruent with the prediction by the systematic approach.

CONCLUSION

The integrative investigation based on bioinformatics/network topology strategy may elaborate the multicomponent synergy mechanisms of SNS against IBS and provide the way out to develop new combination medicines for IBS.

IBS clinical management in Italy: The AIGO survey

BACKGROUND

Irritable bowel syndrome (IBS) is the most frequent functional gastrointestinal disorder, both in primary and secondary care.

AIMS

(1) To describe diagnostic tools and treatments suggested to IBS patients by Italian gastroenterologists; (2) To evaluate patients' quality of life and psychological involvement and the relationship of these factors with symptom severity.

METHODS

Twenty-six gastroenterologists recorded the demographic and clinical data of 677 IBS patients. Diagnostic and treatment measures taken in the previous year and those suggested by gastroenterologists were analysed.

RESULTS

IBS with constipation was found in 43.4%, with diarrhoea in 21.6%, mixed-IBS in 35.0%. Routine blood tests, ultrasonography, colonoscopy, barium enema and CT were more frequently requested in the previous year than by the gastroenterologists (p < 0.001). Colonoscopy (11%), and ultrasonography (20.4%) were also suggested by the gastroenterologists in a non-negligible number of patients. Abdominal pain and distension, bowel dissatisfaction, anxiety and depression were more severe in females than in males. Quality of life decreased with increasing IBS-symptom severity.

CONCLUSIONS

IBS diagnosis is still largely based on exclusion criteria even if gastroenterologists try to improve diagnostic appropriateness. However, therapy remains symptom-based also in the gastroenterological setting even if gastroenterologists use a wide variety of approaches, including innovative therapies such as linaclotide and psychotherapy.

Exploring the multicomponent synergy mechanism of Banxia Xiexin Decoction on irritable bowel syndrome by a systems pharmacology strategy

ETHNOPHARMACOLOGICAL RELEVANCE

Banxia Xiexin Decoction (BXD) is a representative prescription to regulate spleen and stomach in "Treatise on Febrile Diseases", which has been proven effective for the clinical treatment of irritable bowel syndrome (IBS) in the past decades. However, the active principles and molecular mechanisms involved in BXD against IBS are vague yet.

AIM OF THE STUDY

To unfold multicomponent synergy mechanism of BXD on irritable bowel syndrome, this work explored active principles, drug targets and crucial pathways using a systems pharmacology strategy.

MATERIALS AND METHODS

In this study, a systems pharmacology based strategy was applied by the procedures integrating compound database construction, ADME evaluation, target identification, functional annotation, pathway enrichment analysis, network analysis, and molecular docking verification. The 158 compounds from BXD were selected for the screening. The Compound-Target network (C-T) and the Target-Pathway network (T-P) were constructed. The bioinformatics and network topology were employed to systematically reveal multicomponent-target interactions of BXD. The affinity between important ingredients and the kernel targets was validated using molecular mechanics simulation.

RESULTS

The 35 potential important ingredients and the 16 associated kernel targets were identified. 27 crucial pathways, in which the kernel targets participated, could regulate the biological processes, such as synthesis of inflammatory mediators, smooth muscle relaxation and synaptic plasticity, closely related to pathological mechanism of IBS. The cross-talk interactions were revealed between TNF signaling pathway, Dopaminergic synapse and cGMP-PKG signaling pathway, which would exert the synergistic influences on the occurrence and treatment of the IBS. PTGS2, CALM, NOS2, SCN5A, and PRSS1 might become novel drug targets for IBS.

CONCLUSIONS

The study demonstrated that the synergy molecular mechanisms of BXD mainly involved three therapeutic modules including inhibiting inflammatory reaction, maintaining intestinal function and improving psychological regulation via the multicomponent-target interaction networks. It may also provide the promising drug targets and therapeutic agents for the development of new medicines.

DA-9701 (Motilitone): A Multi-Targeting Botanical Drug for the Treatment of Functional Dyspepsia

Functional dyspepsia (FD) is the most common functional gastrointestinal disorder (FGID). FD is characterized by bothersome symptoms such as postprandial fullness, early satiety, and epigastric pain or burning sensations in the upper abdomen. The complexity and heterogeneity of FD pathophysiology, which involves multiple mechanisms, make both treatment and new drug development for FD difficult. Current medicines for FD targeting a single pathway have failed to show satisfactory efficacy and safety. On the other hand, multicomponent herbal medicines that act on multiple targets may be a promising alternative treatment for FD. DA-9701 (Motilitone), a botanical drug consisting of Corydalis Tuber and Pharbitidis Semen, has been prescribed for FD since it was launched in Korea in 2011. It has multiple mechanisms of action such as prokinetic effects, fundus relaxation, and visceral analgesia, which are mediated by dopamine D₂ and several serotonin receptors involved in gastrointestinal (GI) functions. In clinical studies, DA-9701 has been found to be beneficial for improvement of FD symptoms and GI functions in FD patients, while showing better safety compared to that associated with conventional medicines. In this review, we provide updated information on the pharmacological effects, safety, and clinical results of DA-9701 for the treatment of FGIDs.

Alleviation of Irritable Bowel Syndrome-Like Symptoms and Control of Gut and Brain Responses with Oral Administration of Dolichos lablab L. in a Mouse Model

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder manifesting as unexplained abdominal pain and bowel habit changes. The pathogenesis of post-infectious IBS is associated with gut–brain axis dysfunction, including low-grade colonic inflammation and anxiety-related long-term brain changes. This study analyzed the efficacy of a standardized extract of Dolichos lablab L. extract (DL), a bean species, in an IBS mouse model resembling post-infectious, diarrhea-dominant IBS. Using a zymosan-induced animal IBS model, we found that oral administration of DL significantly attenuated zymosan-induced increases in colonic macroscopic scores and minimized weight loss without affecting food intake. In the DL-treated mice, the mast cell count and tumor necrosis factor-α level in the colon markedly decreased, similar to results in sulfasalazine-treated mice and in mice with lipopolysaccharide-stimulated bone marrow-derived mast cells. The number of visceral pain-related behaviors was much lower in the DL-treated mice. Anxiety-like behaviors significantly improved, comparable to that after treatment with amitriptyline. The c-Fos expression level in the prefrontal cortex was significantly reduced. Our data suggest that DL could be beneficial for treating IBS by acting on the gut and brain.

Systematic review with meta-analysis: conditioned pain modulation in patients with the irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is common and is characterised by recurrent abdominal pain, which is a major contributor to healthcare seeking. The neurobiological basis of this pain is incompletely understood. Conditioned pain modulation is a neuromodulatory mechanism through which the brain inhibits the nociceptive afferent barrage through the descending pathways. Reduced conditioned pain modulation has been implicated in the pathophysiology of IBS, although to date only in studies with relatively small sample sizes.

AIM

To clarify the relationship between conditioned pain modulation and IBS by undertaking a systemic review and meta-analysis METHODS: A systematic review of MEDLINE and Web of Science databases was searched (up to 10 May 2018). We included studies examining conditioned pain modulation in adults with IBS and healthy subjects. Data were pooled for meta-analysis to calculate the odds ratio and effect size of abnormal conditioned pain modulation in IBS, with 95% confidence intervals (CI).

RESULTS

The search strategy identified 645 studies, of which 13 were relevant and 12 met the inclusion criteria. Conditioned pain modulation in IBS patients vs healthy subjects was significantly reduced, odds ratio 4.84 (95% CI: 2.19-10.71, P < 0.0001), Hedges' g effect size of 0.85 (95% CI: 0.42-1.28, P < 0.001). There was significant heterogeneity in effect sizes (Q-test χ² = 52, P < 0.001, I² = 78.8%) in the absence of publication bias.

CONCLUSION

Conditioned pain modulation is significantly diminished in patients with IBS vs healthy controls. These data suggest that abnormal descending pathways may play an important pathophysiological role in IBS, which could represent an investigation and a therapeutic target in IBS.

Ex vivo study of human visceral nociceptors

OBJECTIVE

The development of effective visceral analgesics free of deleterious gut-specific side effects is a priority. We aimed to develop a reproducible methodology to study visceral nociception in human tissue that could aid future target identification and drug evaluation.

DESIGN

Electrophysiological (single unit) responses of visceral afferents to mechanical (von Frey hair (VFH) and stretch) and chemical (bradykinin and ATP) stimuli were examined. Thus, serosal afferents (putative nociceptors) were used to investigate the effect of tegaserod, and transient receptor potential channel, vanilloid 4 (TRPV₄) modulation on mechanical responses.

RESULTS

Two distinct afferent fibre populations, serosal (n=23) and muscular (n=21), were distinguished based on their differences in sensitivity to VFH probing and tissue stretch. Serosal units displayed sensitivity to key algesic mediators, bradykinin (6/14 units tested) and ATP (4/10), consistent with a role as polymodal nociceptors, while muscular afferents are largely insensitive to bradykinin (0/11) and ATP (1/10). Serosal nociceptor mechanosensitivity was attenuated by tegaserod (-20.8±6.9%, n=6, p<0.05), a treatment for IBS, or application of HC067047 (-34.9±10.0%, n=7, p<0.05), a TRPV₄ antagonist, highlighting the utility of the preparation to examine the mechanistic action of existing drugs or novel analgesics. Repeated application of bradykinin or ATP produced consistent afferent responses following desensitisation to the first application, demonstrating their utility as test stimuli to evaluate analgesic activity.

CONCLUSIONS

Functionally distinct subpopulations of human visceral afferents can be demonstrated and could provide a platform technology to further study nociception in human tissue.

Depolarizing Effects of Daikenchuto on Interstitial Cells of Cajal from Mouse Small Intestine

BACKGROUND

Daikenchuto (DKT; TJ-100, TU-100), a traditional herbal medicineis used in modern medicine to treat gastrointestinal (GI) functional disorders. Interstitial cells of Cajal (ICCs) are the pacemaker cells of the GI tract and play important roles in the regulation of GI motility.

OBJECTIVE

The objective of this study was to investigate the effects of DKT on the pacemaker potentials (PPs) of cultured ICCs from murine small intestine.

MATERIALS AND METHODS

Enzymatic digestions were used to dissociate ICCs from mouse small intestine tissues. All experiments on ICCs were performed after 12 h of culture. The whole-cell patch-clamp configuration was used to record ICC PPs (current clamp mode). All experiments were performed at 30-32°C.

RESULTS

In current-clamp modeDKT depolarized and concentration-dependently decreased the amplitudes of PPs. Y25130 (a 5-HT3 receptor antagonist) or SB269970 (a 5-HT7 receptor antagonist) did not block DKT-induced PP depolarization, but RS39604 (a 5-HT4 receptor antagonist) did. Methoctramine (a muscarinic M2 receptor antagonist) failed to block DKT-induced PP depolarization, but pretreating 4-diphenylacetoxy-N-methylpiperidine methiodide (a muscarinic M3 receptor antagonist) facilitated blockade of DKT-induced PP depolarization. Pretreatment with an external Ca2+-free solution or thapsigargin abolished PPsand under these conditions, DKT did not induce PP depolarization. Furthermore Ginseng radix and Zingiberis rhizomes depolarized PPs, whereas Zanthoxyli fructus fruit (the third component of DKT) hyperpolarized PPs.

CONCLUSION

These results suggest that DKT depolarizes ICC PPs in an internal or external Ca2+-dependent manner by stimulating 5-HT4 and M3 receptors. Furthermore, the authors suspect that the component in DKT largely responsible for depolarization is probably also a component of Ginseng radix and Zingiberis rhizomes.

SUMMARY

Daikenchuto (DKT) depolarized and concentration-dependently decreased the amplitudes of pacemaker potentials (PPs)Y25130 (a 5-HT3 receptor antagonist) or SB269970 (a 5-HT7 receptor antagonist) did not block DKT-induced PP depolarization, but RS39604 (a 5-HT4 receptor antagonist) didMethoctramine (a muscarinic M2 receptor antagonist) failed to block DKT-induced PP depolarization, but pretreating 4-DAMP (a muscarinic M3 receptor antagonist) facilitated blockade of DKT-induced PP depolarizationGinseng radix and Zingiberis rhizomes depolarized PPswhereas Zanthoxyli fructus fruit (the third component of DKT) hyperpolarized PPs. Abbreviation used: DKT: Daikenchuto, GI: Gastrointestinal, ICCs: Interstitial cells of Cajal, PPs: Pacemaker Potentials.

The combination of oligo- and polysaccharides and reticulated protein for the control of symptoms in patients with irritable bowel syndrome: Results of a randomised, placebo-controlled, double-blind, parallel group, multicentre clinical trial

BACKGROUND

A medical device containing the film-forming agent reticulated protein and a prebiotic mixture of vegetable oligo- and polysaccharides has been developed, recently receiving European approval as MED class III for the treatment of chronic/functional or recidivant diarrhoea due to different causes including irritable bowel syndrome (IBS). In the present paper, we evaluate a protein preparation containing these components in comparison with placebo in adult patients with diarrhoea-predominant IBS.

METHODS

In a randomised, placebo-controlled, double-blind, parallel group, multicentre clinical trial, patients were randomly assigned to receive the combination of oligo- and polysaccharides and reticulated protein and placebo (four oral tablets/day for 56 days). Demographic, clinical and quality of life characteristics and presence and intensity of abdominal pain and flatulence (seven-point Likert scale) were assessed at three study visits (baseline and at 28 and 56 days). Stool emissions were recorded on the diary card using the seven-point Bristol Stool Scale.

RESULTS

A total of 128 patients were randomised to receive either tablets containing the combination (n = 63) or placebo (n = 65). Treatment with oligo- and polysaccharides and reticulated protein was safe and well tolerated. A significant improvement in symptoms across the study was observed in patients treated with oligo- and polysaccharides and reticulated protein between visit 2 and visit 3 in abdominal pain (p = 0.0167) and flatulence (p = 0.0373). We also detected a statistically significant increase in the quality of life of patients receiving the active treatment from baseline to visit 3 (p < 0.0001).

CONCLUSIONS

Treatment with oligo- and polysaccharides and reticulated protein is safe, improving IBS symptoms and quality of life of patients with diarrhoea-predominant IBS.

Expression of heat shock protein 70 in intestinal tissue of mice with post-infectious irritable bowel syndrome

AIM: To detect the expression of heat shock protein 70 (HSP70) in intestinal tissue of mice with post-infectious irritable bowel syndrome (PI-IBS).

METHODS: A mouse model for PI-IBS was established by infection of mice with trichinella spiralis in vivo. The inflammatory score of the intestine of PI-IBS mice was calculated, and abdominal withdrawal reflex (AWR) and colon transportation test (CTT) were used to evaluate the clinical features of the PI-IBS mice. Intestinal expression of HSP70 was measured by immunohistochemistry. Spearman correlation analysis was carried out to assess the relationship between the expression of HSP70 and the clinical features of PI-IBS.

RESULTS: The PI-IBS mouse model was established successfully. On the 8^th week, there was no visible inflammation in the intestine (ileal inflammation score: P > 0.05), whereas the clinical features significantly changed, including increased AWR score (P < 0.01) and decreased CTT score (P < 0.01). The expression of HSP70 significantly increased in the ileum but not in the colon of PI-IBS mice at the 8^th week (ileum: P < 0.01; colon: P > 0.05). The expression of HSP70 in the ileum, but not in the colon, was remarkably related with the clinical features of PI-IBS mice, including the negative relationship with AWR (P < 0.01), and the positive relationship with CTT (P < 0.01).

CONCLUSION: HSP70 might be associated with low-grade intestinal inflammation induced visceral hypersensitivity and abnormal intestinal motility in mice with PI-IBS.

Distribution of 5-HT3, 5-HT4, and 5-HT7 Receptors Along the Human Colon

Background/Aims

Several disorders of the gastrointestinal tract are associated with abnormal serotonin (5-HT) signaling or metabolism where the 5-HT₃ and 5-HT₄ receptors are clinically relevant. The aim was to examine the distribution of 5-HT₃, 5-HT₄, and 5-HT₇ receptors in the normal human colon and how this is associated with receptor interacting chaperone 3, G protein coupled receptor kinases, and protein LIN-7 homologs to extend previous observations limited to the sigmoid colon or the upper intestine.

Methods

Samples from ascending, transverse, descending, and sigmoid human colon were dissected into 3 separate layers (mucosa, longitudinal, and circular muscles) and ileum samples were dissected into mucosa and muscle layers (n = 20). Complementary DNA was synthesized by reverse transcription from extracted RNA and expression was determined by quantitative or end point polymerase chain reaction.

Results

The 5-HT₃ receptor subunits were found in all tissues throughout the colon and ileum. The A subunit was detected in all samples and the C subunit was expressed at similar levels while the B subunit was expressed at lower levels and less frequently. The 5-HT₃ receptor E subunit was mainly found in the mucosa layers. All splice variants of the 5-HT₄ and 5-HT₇ receptors were expressed throughout the colon although the 5-HT₄ receptor d, g, and i variants were expressed less often.

Conclusions

The major differences in 5-HT receptor distribution within the human colon are in relation to the mucosa and muscular tissue layers where the 5-HT₃ receptor E subunit is predominantly found in the mucosal layer which may be of therapeutic relevance.

A systems-level "misunderstanding": the plasma metabolome in Huntington's disease

Objective

Huntington’s disease (HD) is a rare neurodegenerative disease caused by the expansion of an N-terminal repeat in the huntingtin protein. The protein is expressed in all cells in the body; hence, peripheral tissues, such as blood, may recapitulate processes in the brain. The plasma metabolome may provide a window into active processes that influence brain health and a unique opportunity to noninvasively identify processes that may contribute to neurodegeneration. Alterations in metabolic pathways in brain have been shown to profoundly impact HD. Therefore, identification and quantification of critical metabolomic perturbations could provide novel biomarkers for disease onset and disease progression.

Methods

We analyzed the plasma metabolomic profiles from 52 premanifest (PHD), 102 early symptomatic HD, and 140 healthy controls (NC) using liquid chromatography coupled with a highly sensitive electrochemical detection platform.

Results

Alterations in tryptophan, tyrosine, purine, and antioxidant pathways were identified, including many related to energetic and oxidative stress and derived from the gut microbiome. Multivariate statistical modeling demonstrated mutually distinct metabolomic profiles, suggesting that the processes that determine onset were likely distinct from those that determine progression. Gut microbiome-derived metabolites particularly differentiated the PHD metabolome, while the symptomatic HD metabolome was increasingly influenced by metabolites that may reflect mutant huntingtin toxicity and neurodegeneration.

Interpretation

Understanding the complex changes in the delicate balance of the metabolome and the gut microbiome in HD, and how they relate to disease onset, progression, and phenotypic variability in HD are critical questions for future research.

Palmitoylethanolamide normalizes intestinal motility in a model of post-inflammatory accelerated transit: involvement of CB₁ receptors and TRPV1 channels

BACKGROUND AND PURPOSE

Palmitoylethanolamide (PEA), a naturally occurring acylethanolamide chemically related to the endocannabinoid anandamide, interacts with targets that have been identified in peripheral nerves controlling gastrointestinal motility, such as cannabinoid CB1 and CB2 receptors, TRPV1 channels and PPARα. Here, we investigated the effect of PEA in a mouse model of functional accelerated transit which persists after the resolution of colonic inflammation (post-inflammatory irritable bowel syndrome).

EXPERIMENTAL APPROACH

Intestinal inflammation was induced by intracolonic administration of oil of mustard (OM). Mice were tested for motility and biochemical and molecular biology changes 4 weeks later. PEA, oleoylethanolamide and endocannabinoid levels were measured by liquid chromatography-mass spectrometry and receptor and enzyme mRNA expression by qRT-PCR.

KEY RESULTS

OM induced transient colitis and a functional post-inflammatory increase in upper gastrointestinal transit, associated with increased intestinal anandamide (but not 2-arachidonoylglycerol, PEA or oleoylethanolamide) levels and down-regulation of mRNA for TRPV1 channels. Exogenous PEA inhibited the OM-induced increase in transit and tended to increase anandamide levels. Palmitic acid had a weaker effect on transit. Inhibition of transit by PEA was blocked by rimonabant (CB1 receptor antagonist), further increased by 5'-iodoresiniferatoxin (TRPV1 antagonist) and not significantly modified by the PPARα antagonist GW6471.

CONCLUSIONS AND IMPLICATIONS

Intestinal endocannabinoids and TRPV1 channel were dysregulated in a functional model of accelerated transit exhibiting aspects of post-inflammatory irritable bowel syndrome. PEA counteracted the accelerated transit, the effect being mediated by CB1 receptors (possibly via increased anandamide levels) and modulated by TRPV1 channels.

Irritable bowel syndrome: a disease still searching for pathogenesis, diagnosis and therapy

Irritable bowel syndrome (IBS) is the most frequently diagnosed functional gastrointestinal disorder in primary and secondary care. It is characterised by abdominal discomfort, pain and changes in bowel habits that can have a serious impact on the patient's quality of life. The pathophysiology of IBS is not yet completely clear. Genetic, immune, environmental, inflammatory, neurological and psychological factors, in addition to visceral hypersensitivity, can all play an important role, one that most likely involves the complex interactions between the gut and the brain (gut-brain axis). The diagnosis of IBS can only be made on the basis of the symptoms of the Rome III criteria. Because the probability of organic disease in patients fulfilling the IBS criteria is very low, a careful medical history is critical and should pay particular attention to the possible comorbidities. Nevertheless, the severity of the patient's symptoms or concerns sometimes compels the physician to perform useless and/or expensive diagnostic tests, transforming IBS into a diagnosis of exclusion. The presence of alarming symptoms (fever, weight loss, rectal bleeding, significant changes in blood chemistry), the presence of palpable abdominal masses, any recent onset of symptoms in patient aged over 50 years, the presence of symptoms at night, and a familial history of celiac disease, colorectal cancer and/or inflammatory bowel diseases all warrant investigation. Treatment strategies are based on the nature and severity of the symptoms, the degree of functional impairment of the bowel habits, and the presence of psychosocial disorders. This review examines and discusses the pathophysiological aspects and the diagnostic and therapeutic approaches available for patients with symptoms possibly related to IBS, pointing out controversial issues and the strengths and weaknesses of the current knowledge.

Irritable bowel syndrome: The evolution of multi-dimensional looking and multidisciplinary treatments

Irritable bowel syndrome (IBS) is common in the society. Among the putative pathogeneses, gut dysmotility results in pain and disturbed defecation. The latter is probably caused by the effect of abnormal gut water secretion. The interaction between abnormal gas accumulation, abdominal pain and bloating remains controversial. Visceral hypersensitivity and its modification along with the central transmission are the characteristics of IBS patients. The identification of biologic markers based on genetic polymorphisms is undetermined. Imbalanced gut microbiota may alter epithelial permeability to activate nociceptive sensory pathways which in turn lead to IBS. Certain food constituents may exacerbate bowel symptoms. The impact of adult and childhood abuses on IBS is underestimated. Using the concept of biopsychosocial dysfunction can integrate multidimensional pathogeneses. Antispasmodics plus stool consistency modifiers to treat the major symptoms and defecation are the first-line drug treatment. New drugs targeting receptors governing bowel motility, sensation and secretion can be considered, but clinicians must be aware of their potential serious side effects. Psychiatric drugs and modalities may be the final options for treating intractable subjects. Probiotics of multi-species preparations are safe and worth to be considered for the treatment. Antibiotics are promising but their long-term safety and effectiveness are unknown. Diet therapy including exclusion of certain food constituents is an economic measure. Using relatively safe complementary and alternative medicines (CAMs) may be optional to those patients who failed classical treatment. In conclusion, IBS is a heterogeneous disorder with multidimensional pathogeneses. Personalized medicines with multidisciplinary approaches using different classes of drugs, psychiatric measures, probiotics and antibiotics, dietary therapy, and finally CAMs, can be considered.

Lubiprostone: pharmacokinetic, pharmacodynamic, safety and regulatory aspects in the treatment of constipation-predominant irritable bowel syndrome

INTRODUCTION

Lubiprostone acts locally (apical membrane of human intestinal epithelial cells) as a highly selective type-2 chloride channel activator. It was approved in the USA for chronic idiopathic constipation (January 2006) and in women aged ≥ 18 years suffering from irritable bowel syndrome with constipation (IBS-C) (April 2008). So far, the only other pro-secretory medication approved in IBS-C and currently available in USA and Europe (since August and November 2012, respectively) is linaclotide.

AREAS COVERED

This review outlines the regulatory history, pharmacokinetic, pharmacodynamic and safety data in the treatment of IBS-C with a European perspective. It is based on publicly available data, namely, published literature, drug labels and the FDA's spontaneous reporting system.

EXPERT OPINION

Although interesting pharmacodynamic data suggest that lubiprostone may have additional mechanisms of action, its beneficial effects in IBS-C must be confirmed in the actual clinical scenario taking into account the new version of European Medicines Agency's guideline. This is especially important with regard to duration of studies (recommended to be at least 6 months) to adequately assess long-term sustained efficacy, withdrawal, rebound and safety. Further research is warranted in uncertain areas (i.e., males, pediatric and elderly patients). On the basis of current data, it is still too early to draw definite conclusions on the overall risk-benefit balance for IBS-C.

Curcuma longa L. as a therapeutic agent in intestinal motility disorders. 2: Safety profile in mouse

BACKGROUND

Curcuma extract exerts a myorelaxant effect on the mouse intestine. In view of a possible use of curcuma extract in motor functional disorders of the gastrointestinal tract, a safety profile study has been carried out in the mouse.

METHODS

Thirty mice were used to study the in vitro effect of curcuma on gallbladder, bladder, aorta and trachea smooth muscular layers and hearth inotropic and chronotropic activity. The myorelaxant effect on the intestine was also thoroughly investigated. Moreover, curcuma extract (200 mg/Kg/day) was orally administered to twenty mice over 28 days and serum liver and lipids parameters were evaluated. Serum, bile and liver bile acids qualitative and quantitative composition was were also studied.

RESULTS

In the intestine, curcuma extract appeared as a not competitive inhibitor through cholinergic, histaminergic and serotoninergic receptors and showed spasmolytic effect on K(+) induced contraction at the level of L type calcium channels. No side effect was observed on bladder, aorta, trachea and heart when we used a dose that is effective on the intestine. An increase in gallbladder tone and contraction was observed. Serum liver and lipids parameters were normal, while a slight increase in serum and liver bile acids concentration and a decrease in bile were observed.

CONCLUSIONS

Although these data are consistent with the safety of curcuma extract as far as its effect on the smooth muscular layers of different organs and on the heart, the mild cholestatic effect observed in absence of alteration of liver function tests must be further evaluated and the effective dose with minimal side effects considered.

Influence of Fagopyrum cymosum tablets on immune inflammation and visceral hypersensitivity in a rat model of diarrhea-predominant irritable bowel syndrome

AIM: To determine the influence of Fagopyrum cymosum tablets on immune inflammation and visceral hypersensitivity in a rat model of diarrhea-predominant irritable bowel syndrome (IBS).

METHODS: IBS was induced in neonatal rats by feeding a high lactose diet, chronic bandaged-stress and inserting the tail. Rats were randomly divided into six groups: a normal control group (group A), a model group (group B), high-, medium- and low-dose Fagopyrum cymosum groups (group C, D and E), and a Gushen Chang'an group (group F). Groups C, D and E received oral administration of 6, 3 and 1.5 g/(kg•d) of Fagopyrum cymosum tablets, respectively, once every day for four weeks; group F received oral administration of 2 g/(kg•d) of Gushen Chang'an; Groups A and B received oral administration of equal volume of normal saline. The colon motion, abdominal withdrawal reflex (AWR) of colorectal distention and abdominal electrical activity were observed. Radioimmunoassay was used to detect serum levels of tumor necrosis factor-α (TNF-α), interleukin 17 (IL-17), IL-10, substance P (SP) and calcitonin gene-related peptide (CGRP). Fluorescent quantitative PCR was used to detect the expression of 5-hydroxytryptamine (5-HT), 5-hydroxytryptamine 3 receptor (5-HT3R), neurokinin receptor 1 (NK1R) and intracellular adhesion molecule-1 (ICAM-1) mRNAs in the intestinal tissue.

RESULTS: Fagopyrum cymosum could decrease colon motion and visceral hypersensitivity in IBS rats (P < 0.05 or 0.01). In the Fagopyrum cymosum treatment groups, serum levels of TNF-α (2.81 ng/L ± 0.67 ng/L, 2.76 ng/L ± 0.31 ng/L, 2.91 ng/L ± 0.77 ng/L vs 3.77 ng/L ± 0.44 ng/L), IL-17 (2.01 ng/L ± 0.76 ng/L, 2.14 ng/L ± 0.29 ng/L, 1.98 ng/L ± 0.11 ng/L vs 2.47 ng/L ± 0.33 ng/L) and SP (38.22 pg/mL ± 3.15 pg/mL, 37.55 pg/mL ± 2.63 pg/mL, 42.01 pg/mL ± 3.79 pg/mL vs 43.19 pg/mL ± 4.28 pg/mL) were significantly lower, and those of IL-10 (137.25 ng/L ± 6.2 ng/L, 135.90 ng/L ± 4.4 ng/L, 121.70 ng/L ± 5.11 ng/L vs 82.09 ng/L ± 5.33 ng/L) and CGRP (155.09 ng/L ± 4.38 ng/L, 142.02 ng/L ± 2.44 ng/L, 158.25 ng/L ± 4.02 ng/L vs 107.31 ng/L ± 3.96 ng/L) were significantly higher than those in the model group (all P < 0.05 or 0.01). The mRNA expression of 5-HT (0.74 ± 0.43, 0.97 ± 0.91, 0.66 ± 0.29 vs 1.27 ± 0.45), 5-HT3R (1.01 ± 0.35, 1.14 ± 0.76, 1.47 ± 0.65 vs 1.61 ± 0.03), NK1R (1.07 ± 0.58, 0.98 ± 0.67, 0.88 ± 0.79 vs 1.47 ± 0.94) and ICAM-1 (0.81 ± 0.55, 0.96 ± 0.19, 0.72 ± 0.93 vs 1.33 ± 0.26) in the intestinal tissue was down-regulated after treatment with Fagopyrum cymosum tablets (P < 0.05 or 0.01), especially in the high-dose group.

CONCLUSION: Fagopyrum cymosum tablets can reduce visceral hypersensitivity and inhibit inflammatory immune response in IBS-D rats in a concentration-dependent manner.