Role of serotonin in gastrointestinal motility and irritable bowel syndrome

Telotristat ethyl: a novel agent for the therapy of carcinoid syndrome diarrhea

Carcinoid syndrome (CS), characterized by diarrhea and flushing, is present in 20% of patients with neuroendocrine tumors at diagnosis and becomes more frequent with progression. The diarrhea of CS is caused mainly by tumoral secretion of serotonin. It may not be fully controlled by somatostatin analogs, the currently indicated drugs for symptomatic relief. Telotristat ethyl is a novel inhibitor of tryptophan hydroxylase, the rate-limiting enzyme in serotonin biosynthesis. Administration of the drug decreases diarrhea in patients with CS. Telotristat ethyl was approved in February 2017 (USA) and September 2017 (European Commission) for the treatment of CS diarrhea in adults inadequately controlled by somatostatin analog alone. This drug is expected to greatly improve the health and quality of life of patients with CS diarrhea.

Fibromyalgia Syndrome: A Metabolic Approach Grounded in Biochemistry for the Remission of Symptoms

Fibromyalgia syndrome (FMS) is a chronic, complex, and heterogeneous disorder of still poorly understood etiopathophysiology associated with important musculoskeletal widespread pain, fatigue, non-restorative sleep, and mood disturbances. It is estimated to afflict 2–3% of the worldwide population, with clean prevalence among women. The objective of this paper is to propose a novel treatment for symptomatic remission of FMS, grounded in biochemistry and consisting in the withdrawal from the diet of molecules that can indirectly trigger the symptoms. The hypothesis develops from the evidence that low serotonin levels are involved in FMS. Serotonin is synthesized starting from the essential amino acid tryptophan. The presence of non-absorbed molecules in the gut, primarily fructose, reduces tryptophan absorption. Low tryptophan absorption leads to low serotonin synthesis that triggers FMS symptoms. Moreover not-absorbed sugars could also produce a microbiota deterioration activating a positive feedback loop: the increasing microbiota deterioration reduces the functionality of absorption both of fructose and tryptophan in the gut, entering a vicious circle. The therapeutic idea is to sustain serotonin synthesis allowing the proper tryptophan absorption. The core of the cure treatment is the exclusion from the diet of some carbohydrates and the marked reduction of some others. The main target is the limitation of total dietary fructose as marked as possible. It could be an effective strategy to get the remission of symptoms acting on the impaired biochemical pathways. The straying from the treatment is expected to cause the reappear of the symptoms.

Novel serotonin transporter regulators: Natural aristolane- and nardosinane- types of sesquiterpenoids from Nardostachys chinensis Batal

Serotonin transporter (SERT) is a classic target of drug discovery for neuropsychiatric and digestive disorders, and against those disorders, plants of Nardostachys genus have been valued for centuries in the systems of Traditional Chinese Medicine, Ayurvedic and Unani. Herein, chemical investigation on the roots and rhizomes of Nardostachys chinensis Batal. led to the isolation of forty sesquiterpenoids including six new aristolane-type sesquiterpenoids and six new nardosinane-type sesquiterprenoids. Their structures were elucidated by extensive spectroscopic methods, combined with analyses of circular dichroism and single-crystal X-ray diffraction data. To explore natural product scaffolds with SERT regulating activity, a high-content assay for measurement of SERT function in vitro was conducted to evaluate the SERT regulating properties of these isolates. In conclusion, eleven compounds could be potential natural product scaffolds for developing drug candidates targeting SERT. Among which, kanshone C of aristolane-type sesquiterpenoid inhibited SERT most strongly, while desoxo-nachinol A of nardosinane-type sesquiterpenoid instead enhanced SERT potently.

Potential usefulness of methyl gallate in the treatment of experimental colitis

Methyl gallate is a gallotannin widely distributed in nature. Previous studies have demonstrated its antioxidant, anti-inflammatory, antimicrobial and anti-tumor activities. In the present study, the activity of methyl gallate on experimental models of inflammatory bowel disease has been investigated. Experimental colitis was induced in Sprague-Dawley rats through the intracolonic instillation of an acetic acid solution (2 mL, 4% v/v). Methyl gallate (100 and 300 mg/kg, p.o.) and the reference drug mesalazine (100 mg/kg, p.o.) were tested. Methyl gallate induced a significant reduction in the colon weight/length ratio and macroscopic lesion score. Besides, the malondialdehyde content and the GSSG/GSH ratio were remarkably decreased. Furthermore, the administration of methyl gallate reduced the expression of COX₂, IL-6, TNFα and the severity of microscopic tissue damage induced by acetic acid, while the mean goblet cell density was significantly higher in both the group treated with methyl gallate and the one treated with mesalazine, in comparison with untreated animals. The Na⁺K⁺ATPase pump activity was recovered in treated groups (control: 827.2 ± 59.6, colitis: 311.6 ± 54.8, methyl gallate 100 mg/kg: 642.2 ± 175.0, methyl gallate 300 mg/kg: 809.7 ± 100.6, mesalazine: 525.3 ± 81.7). Methyl gallate was also found to induce a significant reduction in the castor oil-induced intestinal motility in Swiss mice, decreasing the peristalsis by 74.5 and 58.82% at 100 and 300 mg/kg p.o., respectively. This compound also antagonized the jejunum contractions induced by Ach and CaCl₂. This study demonstrates that methyl gallate exerts beneficial effects in a preclinical model of intestinal disorders.

Functional Bowel Disorders Are Associated with a Central Immune Activation

Background

Subjects with depression and unexplained neurological symptoms have a high prevalence of gastrointestinal comorbidity probably related to the brain-gut communication. This study explored associations between functional gastrointestinal disorders (FGID) and inflammatory markers in subjects with these disorders.

Methods

The FGID, including irritable bowel syndrome (IBS), were classified according to the Rome III criteria, and degree of symptoms was assessed with IBS symptom severity score (IBS-SSS). A range of interleukins (IL), chemokines and growth factors, tryptophan, and kynurenine were analysed in serum and the cerebrospinal fluid (CSF), and short-chain fatty acids (SCFA) were analysed in the faeces. The results are reported as partial correlation (pc) and p values.

Results

Sixty-six subjects were included. IBS was associated with high levels of tryptophan (p = 0.048) and kynurenine (p = 0.019) and low level of IL-10 (p = 0.047) in the CSF. IBS-SSS was associated with high tumor necrosis factor and low IL-10 in the CSF; pc = 0.341 and p = 0.009 and pc = −0.299 and p = 0.023, respectively. Propionic minus butyric acid in faeces was negatively associated with IL-10 in the CSF (pc = −0.416, p = 0.005).

Conclusions

FGID were associated with a proinflammatory immune activation in the central nervous system and a disturbed tryptophan metabolism that could have been mediated by the faecal microbiota.

Understanding the Gut Microbiota in Inflammatory and Functional Gastrointestinal Diseases

OBJECTIVE

During the last decade, experimental and observational studies have shown that patients with inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) may have an altered intestinal microbial composition compared with healthy individuals. However, no uniform microbial signature has as yet been detected for either IBD or IBS. This review summarizes the current knowledge of microbial dysbiosis and its potential relationship to the pathophysiology in IBD and IBS.

METHODS

A selective review was conducted to summarize the current knowledge of gut microbiota in the pathophysiology of IBD and IBS.

RESULTS

Experimental and observational studies provide good evidence for intestinal microbial dysbiosis in subgroups of IBD and IBS. Still, no uniform disease pattern has been detected. This is most likely due to the heterogeneous nature of IBD and IBS, in combination with the effects of intrinsic and extrinsic factors. Such intrinsic factors include genetics, the gastrointestinal environment, and the host immune system, whereas extrinsic factors include early life diet, breastfeeding, and method of infant delivery.

CONCLUSIONS

Recent and ongoing work to define microbial dysbiosis in IBD and IBS shows promise, but future well-designed studies with well-characterized study individuals are needed. It is likely that the microbial dysbiosis in IBD and IBS is dependent on the natural disease course of IBD and symptom pattern in IBS. Therefore, assessment of the entire microbiota along the gastrointestinal tract, in relationship to confounding factors, symptom fluctuations, and other pathophysiological factors, is needed for further understanding of the etiology of these common diseases.

Effects of Low-Dose Non-Caloric Sweetener Consumption on Gut Microbiota in Mice

Abstract: Non-caloric artificial sweeteners (NASs) provide sweet tastes to food without adding calories or glucose. NASs can be used as alternative sweeteners for controlling blood glucose levels and weight gain. Although the consumption of NASs has increased over the past decade in Japan and other countries, whether these sweeteners affect the composition of the gut microbiome is unclear. In the present study, we examined the effects of sucralose or acesulfame-K ingestion (at most the maximum acceptable daily intake (ADI) levels, 15 mg/kg body weight) on the gut microbiome in mice. Consumption of sucralose, but not acesulfame-K, for 8 weeks reduced the relative amount of Clostridiumcluster XIVa in feces. Meanwhile, sucralose and acesulfame-K did not increase food intake, body weight gain or liver weight, or fat in the epididymis or cecum. Only sucralose intake increased the concentration of hepatic cholesterol and cholic acid. Moreover, the relative concentration of butyrate and the ratio of secondary/primary bile acids in luminal metabolites increased with sucralose consumption in a dose-dependent manner. These results suggest that daily intake of maximum ADI levels of sucralose, but not acesulfame-K, affected the relative amount of the Clostridium cluster XIVa in fecal microbiome and cholesterol bile acid metabolism in mice.

Multipathway Integrated Adjustment Mechanism of Glycyrrhiza Triterpenes Curing Gastric Ulcer in Rats

Background:

Gastric ulcer is a common chronic disease in human digestive system, which is difficult to cure, easy to relapse, and endangers human health seriously. Compared with western medicine, traditional Chinese medicine has a unique advantage in improving the general situation, stablizing medical condition, and with little side effects. Glycyrrhiza known as “king of all the medicine”, has a range of pharmacological activities and is commonly used in a variety of proprietary Chinese medicines and formulations.

Objective:

On the basis of explicit antiulcer effect of Glycyrrhiza triterpenes, the molecular mechanisms of its therapeutic effect on acetic acid induced gastric ulcer in rats were explored.

Materials and Methods:

Acetic acid induced gastric ulcer model in rats was established to evaluate the curing effect of G. triterpenes and all of the rats were randomised into six groups: Control group, model group, omeprazole group (0.8 mg/mL), triterpenes high dose group (378.0 mg/mL), triterpenes middle dose group (126.0 mg/mL), and triterpenes low dose group (42.0 mg/mL). All rats in groups were orally administered the active group solution 1.5 mL once daily (model and control groups with saline) for 7 days. HPLC-TOF-MS analysis method was performed to obtain the plasma metabolites spectrums of control group, model group, triterpenes high, middle and low dose groups.

Results:

A total of 11 differential endogenous metabolites related to the therapeutic effect of G. triterpenes were identified, including tryptophan, phingosine-1-phosphate, pantothenic acid, and so on, among which tryptophan and phingosine-1-phosphate are related with the calcium signaling pathway and arachidonic acid (AA) metabolism. At the same time, in order to verify the above results, quantitative real time polymerase chain reaction were performed to evaluate the expression of H⁺-K⁺-ATPase alpha mRNA and phospholipase a 2 mRNA in relational signaling pathways. Combined with statistical analysis of plasma metabolic spectrum and gene expression in tissue, it is suggested that G. triterpenes has antiulcer effect on gastric ulcer in rats.

Conclusion:

G. triterpenes has a certain regulating effect on the metabolism of tryptophan, AA, sphingosine, and other endogenous metabolites, and we speculated that the antiulcer potential of G. triterpenes can be primarily attributed to its inhibiting gastric acid secretion, reducing the release of inflammatory mediators, and protecting gastric mucosa effects to prevent the further development of gastric ulcer.

SUMMARY

G. triterpenes can obviously relieve the symptoms of gastric ulcer, especially the low dose group.

G. triterpenes can effectively regulate the amount of small molecule metablism in gastric ulcer rats in vivo, including tryptophan, phingosine-1-phosphate, etc.

G. triterpenes resisting gastric ulcer is probably by regulating arachidonic acid metabolism, sphingosine metabolism, etc.

Down-regulation of H+-K+-ATPase alpha subunit mRNA and up-regulation of PLA₂ mRNA in gastric tissue of dose group validated the possible mechanisms of G. triterpenes for the treatment of gastric ulcer

Abbreviations used: HP: Helicobacter pylori, ECL: enterochromaffinlike, TCM: Traditional Chinese medicine; HPLC: High Performance Liquid Chromatography, HPLC/MS: High Performance Liquid chromatography Mass Spectrometry, HPLC-TOF-MS: High Performance Liquid Chromatography and Tof Mass Spectrometry, SD: Sprague Dawley, PCDL: Personal Compound Database and Library, MPP: Mass Profiler Professiona; PCA: principal component analysis, RT-PCR: real time polymerase chain reaction, PGE 2: Prostaglandin E2, COX1: cyclooxygenase 1 S1P: Sphingosine-1-phosphate, AA: Arachidonic acid, 5-HT: 5- hydroxytryptamine.

Anti-ulcer effect and potential mechanism of licoflavone by regulating inflammation mediators and amino acid metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Glycyrrhiza is the dry root and rhizome of the leguminous plant, Glycyrrhiza uralensis Fisch., Glycyrrhiza inflata Bat. or Glycyrrhiza glabra L., which was firstly cited in Shennong's Herbal Classic in Han dynasty and was officially listed in the Chinese Pharmacopoeia, has been widely used in China during the past millennia. Licoflavone is the major component of Glycyrrhiza with anti-ulcer activity. The present study is based on clarifying the anti-ulcer effect of licoflavone, aiming at elucidating the possible molecule mechanisms of its action for treating gastric ulcer rats induced by acetic acid.

MATERIALS AND METHODS

Rats were divided into 7 groups, and drugs were administered from on the day after the onset of gastric ulcer (day 3) until day 11 of the experiment once daily continuously. The plasma were analyzed by high-performance liquid chromatography combined with time-of-flight mass spectrometry (HPLC/ESI-TOF-MS), significant different metabolites were investigated to explain its therapeutic mechanism. Furthermore, quantitative real time polymerase chain reaction (RT-PCR) analysis was performed to detect the expression of RNA in stomach tissue for verifying the above results.

RESULTS

Licoflavone can effectively cure the gastric ulcer, particularly the middle dose group. According to the statistical analysis of the plasma different metabolites from each groups and the expression of genes in tissues, sixteen significant different metabolites, including histamine, tryptophan, arachidonic acid, phingosine-1-phosphate etc., contributing to the treatment of gastric ulcer were discovered and identified. In RT-PCR analysis, the results of the expression of RNA were corresponded with what we discovered.

CONCLUSIONS

Our study indicated licoflavone plays the role of treating gastric ulcer by regulating inflammation mediators and amino acid metabolism. We demonstrated that metabolomics technology combined with gene technology is a useful tool to search different metabolites and to dissect the potential mechanisms of traditional Chinese medicine (TCM) in treating gastric ulcer.

Cyproheptadine: A Potentially Effective Treatment for Functional Gastrointestinal Disorders in Children

Functional gastrointestinal disorders (FGIDs) negatively affect children's quality of life and health care costs. It has been proposed that alteration of gut serotonin leads to gastrointestinal dysmotility, visceral hypersensitivity, altered gastrointestinal secretions, and brain-gut dysfunction. Cyproheptadine, a serotonin antagonist, has been shown to be a potentially effective and safe treatment option in children who meet the clinical criteria for FGIDs. Well-designed multicenter trials with long-term follow-up are needed to further investigate its efficacy. [Pediatr Ann. 2017;46(3):e120-e125.].

Effects of five candidate laxatives derived from Liriope platyphylla on the 5-HT receptor signaling pathway in three cell types present in the transverse colon

The laxative effects of aqueous extract of Liriope platyphylla (AEtLP) on loperamide (Lop)‑induced constipation have been reported; however, the key compounds and the mechanism underlying these effects remain unclear. Therefore, the laxative effects of five candidates derived from L. platyphylla: Diosgenin (DG), 5-hydroxymethylfurfural (5-HMF), adenosine (AD), hydroxypropyl cellulose (HPC) and uridine (UD) were investigated by examining the alteration of G protein α (Gα) expression, protein kinase C (PKC) phosphorylation and inositol triphosphate (IP3) concentration levels in the 5-hydroxytryptamine (5‑HT; serotonin) receptor signaling pathway. Primary rat intestine smooth muscle cells (pRISMCs), intestinal epithelial cells (IEC)‑18 and B35 cells were cotreated with Lop and the five compounds in order to screen the candidates. AEtLP, prucalopride (PCP) and bisacodyl (BS) served as positive controls. In pRISMCs, Gα expression levels were recovered in the majority of candidate‑treated groups, whereas PKC phosphorylation recovery was observed only in the DG, 5‑HMF and AD treatment groups. In IEC‑18 cells, the AD treatment group mimicked the effects of PCP on PKC phosphorylation levels, whereas the DG, 5‑HMF, HPC and UD treatment groups mimicked the effects of AEtLP and BS. In B35 cells, a greater upregulation of PKC phosphorylation levels were observed in the UD treatment group compared with the PCP and BS treatment groups, whereas DG, 5‑HMF and AD treatment reduced the PKC phosphorylation levels to a greater extent than AEtLP treatment. However, effects similar to AEtLP, PCP and BS on Gα expression levels were not detected in any treatment groups in IEC‑18 and B35 cells. Furthermore, the level of IP3 was enhanced only in pRISMCs, in which all five candidates were effective, while the greatest concentration was observed in the UD treatment group. In conclusion, the results of the present study suggest that UD may be considered the compound with the greatest laxative activity, which may regulate the 5‑HT receptor signaling pathway.

A Perspective on the Safety of Supplemental Tryptophan Based on Its Metabolic Fates

Over the past 50 y, tryptophan has been ingested in amounts well in excess of its dietary requirement. This use is based on extensive findings that ingesting tryptophan increases brain tryptophan concentrations, which stimulates the synthesis and release of the neurotransmitter serotonin, from which it is derived. Such increases in serotonin function may improve mood and sleep. However, tryptophan ingestion has other effects, such as increasing serotonin production in the gut, increasing serotonin concentrations in blood, stimulating the production of the hormone melatonin (a tryptophan metabolite), stimulating tryptophan metabolism via the kynurenine pathway, and possibly stimulating the production of tryptophan metabolites in the gut microbiome. Several of the kynurenine metabolites have actions on excitatory glutamate receptors in the gut and brain and on cells of the immune system. In addition, metabolites of tryptophan produced by colonic bacteria are reported to cause adverse effects in some species. This review examines each of these tryptophan pathways to determine if any of the metabolites increase after tryptophan ingestion, and if so, whether effects are seen on target body functions. In this regard, recent research suggests that it may be useful to examine kynurenine pathway metabolites and some microbial tryptophan metabolites to determine whether supplemental tryptophan consumption increases their concentrations in the body and amplifies their actions.

Regulation of the serotonin transporter in the pathogenesis of irritable bowel syndrome

Serotonin (5-HT) and the serotonin transporter (SERT) have earned a tremendous amount of attention regarding the pathogenesis of irritable bowel syndrome (IBS). Considering that enteric 5-HT is responsible for the secretion, motility and perception of the bowel, the involvement of altered enteric 5-HT metabolism in the pathogenesis of IBS has been elucidated. Higher 5-HT availability is commonly associated with depressed SERT mRNA in patients with IBS compared with healthy controls. The expression difference of SERT between IBS patients and healthy controls might suggest that SERT plays an essential role in IBS pathogenesis, and SERT was expected to be a novel therapeutic target for IBS. Progress in this area has begun to illuminate the complex regulatory mechanisms of SERT in the etiology of IBS. In this article, current insights regarding the regulation of SERT in IBS are provided, including aspects of SERT gene polymorphisms, microRNAs, immunity and inflammation, gut microbiota, growth factors, among others. Potential SERT-directed therapies for IBS are also described. The potential regulators of SERT are of clinical importance and are important for better understanding IBS pathophysiology and therapeutic strategies.

The Impact of Prenatal Exposure to Dexamethasone on Gastrointestinal Function in Rats

Antenatal treatment with synthetic glucocorticoids is commonly used in pregnant women at risk of preterm delivery to accelerate tissue maturation. Exposure to glucocorticoids during development has been hypothesized to underlie different functional gastrointestinal (GI) and motility disorders. Herein, we investigated the impact of in utero exposure to synthetic glucocorticoids (iuGC) on GI function of adult rats. Wistar male rats, born from pregnant dams treated with dexamethasone (DEX), were studied at different ages. Length, histologic analysis, proliferation and apoptosis assays, GI transit, permeability and serotonin (5-HT) content of GI tract were measured. iuGC treatment decreased small intestine size and decreased gut transit. However, iuGC had no impact on intestinal permeability. iuGC differentially impacts the structure and function of the GI tract, which leads to long-lasting alterations in the small intestine that may predispose subjects prone to disorders of the GI tract.

Omnivores Going Astray: A Review and New Synthesis of Abnormal Behavior in Pigs and Laying Hens

Pigs and poultry are by far the most omnivorous of the domesticated farm animals and it is in their nature to be highly explorative. In the barren production environments, this motivation to explore can be expressed as abnormal oral manipulation directed toward pen mates. Tail biting (TB) in pigs and feather pecking (FP) in laying hens are examples of unwanted behaviors that are detrimental to the welfare of the animals. The aim of this review is to draw these two seemingly similar abnormalities together in a common framework, in order to seek underlying mechanisms and principles. Both TB and FP are affected by the physical and social environment, but not all individuals in a group express these behaviors and individual genetic and neurobiological characteristics play an important role. By synthesizing what is known about environmental and individual influences, we suggest a novel possible mechanism, common for pigs and poultry, involving the brain-gut-microbiota axis.

Associations of specific phobia and its subtypes with physical diseases: an adult community study

BACKGROUND

Specific phobia is the most prevalent anxiety disorder in the community and is associated with substantial impairment. Comorbidity with physical diseases is assumed and has important implications for etiology, treatment, or prevention of the comorbid conditions. However, due to methodological issues data are limited and subtypes of specific phobia have not been investigated yet. We examined the association of specific phobia and its subtypes with physical diseases in a representative community sample with physician-diagnosed physical diseases and diagnostic criteria of specific phobia.

METHODS

Data of the German Mental Health Survey from 4181 subjects aged 18-65 years were used. Specific phobia was diagnosed using M-CIDI/DIA-X interview; physical diseases were assessed through a self-report questionnaire and a medical interview. Logistic regression analyses adjusted for sex were calculated.

RESULTS

Specific phobia was associated with cardiac diseases, gastrointestinal diseases, respiratory diseases, arthritic conditions, migraine, and thyroid diseases (odds ratios between 1.49 and 2.53). Among the subtypes, different patterns of associations with physical diseases were established. The findings were partially replicated in the Swiss PsyCoLaus Study.

CONCLUSIONS

Our analyses show that subjects with specific phobia have an increased probability for specific physical diseases. From these analyses etiological mechanisms of specific phobia and physical disease can be deduced. As subtypes differed in their patterns of associations with physical diseases, different etiological mechanisms may play a role. The findings are highly relevant for public health in terms of prevention and therapy of the comorbid conditions.

Serotonin syndrome presenting as surgical emergency: A report of two cases

Serotonin syndrome (SS) is an iatrogenic, drug-induced clinical syndrome caused by serotoninergic hyperstimulation. The diagnosis of SS is easily overlooked as most physicians (up to 85%) are unaware of this syndrome as a clinical entity. Diagnosis is also difficult due to its protean manifestations which can mimic a variety of medical conditions. Herein, we describe two cases of SS, who initially presented to the Surgical Department as surgical emergencies. The first case developed urinary retention after the administration of sertraline. The second case developed features mimicking acute intestinal obstruction. Both cases responded to the removal of offending agents and administration of cyproheptadine. There is a need to increase the awareness of SS among physicians because of the widespread use of serotonergic agents all around the world.

Artificial Sweeteners: A Systematic Review and Primer for Gastroenterologists

Artificial sweeteners (AS) are ubiquitous in food and beverage products, yet little is known about their effects on the gastrointestinal (GI) tract, and whether they play a role in the development of GI symptoms, especially in patients with irritable bowel syndrome. Utilizing the PubMed and Embase databases, we conducted a search for articles on individual AS and each of these terms: fermentation, absorption, and GI tract. Standard protocols for a systematic review were followed. At the end of our search, we found a total of 617 eligible papers, 26 of which were included. Overall, there is limited medical literature available on this topic. The 2 main areas on which there is data to suggest that AS affect the GI tract include motility and the gut microbiome, though human data is lacking, and most of the currently available data is derived from in vivo studies. The effect on motility is mainly indirect via increased incretin secretion, though the clinical relevance of this finding is unknown as the downstream effect on motility was not studied. The specific effects of AS on the microbiome have been conflicting and the available studies have been heterogeneous in terms of the population studied and both the AS and doses evaluated. Further research is needed to assess whether AS could be a potential cause of GI symptoms. This is especially pertinent in patients with irritable bowel syndrome, a population in whom dietary interventions are routinely utilized as a management strategy.

Olanzapine May Inhibit Colonic Motility Associated with the 5-HT Receptor and Myosin Light Chain Kinase

OBJECTIVE

To study whether the effects of olanzapine on gastrointestinal motility is related to the serotonin antagonism and myosin light chain kinase.

METHODS

Male Sprague-Dawley rats were randomly divided into four groups. Olanzapine gavage was performed for each treatment group during the course of 30 continuous days, while the same volume of saline was given to the rats in the control group. Defecation of the rats was observed on days 7 and 30 after olanzapine gavage. The effects of olanzapine on contraction of colonic smooth muscles were observed in ex vivo experiments. A Western blot was used to evaluate expression levels of the serotonin transporter (SERT) and MLCK in colon segments of the rats.

RESULTS

ResultsaaCompared to the control group, 5-160 µ M of olanzapine could inhibit dose-dependently the contraction of colonic smooth muscle ex vivo experiments. The maximum smooth muscle contraction effects of 5-HT and acetylcholine significantly decreased after treatment with 40-160 µ M of olanzapine. Constipation was found in the olanzapine-treated rats on day 7 and have sustained day 30 after gavage. Expression of MLCK in olanzapine-treated rats was significantly decreased, whereas the expression of SERT significantly increased on the day 7, then significantly decreased on the day 30 after olanzapine gavage.

CONCLUSION

SERT and MLCK may involve in the inhibition of colonic contraction induced by olanzapine.

Electroacupuncture at ST25 Inhibits Cisapride-Induced Gastric Motility in an Intensity-Dependent Manner

Background. Previous studies have demonstrated the efficacy of frequency-specific EAS. However, evaluation of intensity-response effects is challenging and has yet to be addressed. Aims. Using cisapride to promote gastric emptying, we measured the intensity-response relationship of EA at ST25 on gastric motility. Methods. We determined the effects of EA at ST25 using intensities (0.5, 1, 3, 5, 7, and 9 mA) on gastric motility in rats injected with cisapride (0.2, 0.02, and 0.002 mg/kg). Results. Utilizing three concentrations of cisapride yielded significantly differing levels of gastric motility. Furthermore, log IC₅₀ values for EAS were different within each group. Given the same EA intensity, cisapride antagonism decreased progressively in each group as a function of drug concentration. The relative amount of cisapride antagonized by EAS did not change in a linear fashion. Finally, EAS at different intensities within the three groups induced a similar pattern of cisapride antagonism. Conclusions. The ability of EAS to elicit a decrease in cisapride-induced gastric motility pressure was demonstrated in this study. The study encompasses construct validity to mirror individualized treatment being based on patients' subjective feelings, not on a set fixed EA intensity. Clinically utilizing EAS at the smallest intensity can achieve the desired therapeutic effect.

Serotonergic regulation of distention-induced ATP release from the urothelium

Serotonin [5-hydroxytryptamine (5-HT)] is involved in both motor and sensory functions in hollow organs, especially in the gastrointestinal tract. However, the involvement of 5-HT in visceral sensation of the urinary bladder remains unknown. Because distention-induced ATP release from the urothelium plays an essential role in visceral sensation of the urinary bladder, we investigated the regulation of urothelial ATP release by the 5-HT signaling system. RT-PCR and immunohistochemical analyses of the urothelium revealed specific expression of 5-HT_1D and 5-HT₄ receptors. The addition of 5-HT did not affect urothelial ATP release without bladder distention, but it significantly reduced distention-induced ATP release by physiological pressure during urine storage (5 cmH₂O). The inhibitory effect of 5-HT on distention-elicited ATP release was blocked by preincubation with the 5-HT_1B/1D antagonist GR-127935 but not by the 5-HT₄ antagonist SB-204070. mRNA encoding tryptophan hydroxylase 1 was detected in the urinary bladder by nested RT-PCR amplification, and l-tryptophan or the selective serotonin reuptake inhibitor citalopram also inhibited ATP release, indicating that 5-HT is endogenously synthesized and released in the urinary bladder. The addition of GR-127935 significantly enhanced the distention-elicited ATP release 40 min after distention, whereas SB-204070 reduced the amount of ATP release 20 min after distention. These data suggest that 5-HT₄ facilitates the distention-induced ATP release at an earlier stage, whereas 5-HT_1D inhibits ATP release at a later stage. The net inhibitory effect of 5-HT indicates that the action of 5-HT on the urothelium is mediated predominantly by 5-HT_1D.

Efficacy of Gum Chewing on Bowel Movement After Open Colectomy for Left-Sided Colorectal Cancer: A Randomized Clinical Trial

BACKGROUND

Prolonged intestinal paralysis can be a problem after gastrointestinal surgery. Several systematic reviews and meta-analyses have suggested the efficacy of gum chewing for the prevention of postoperative ileus.

OBJECTIVE

The purpose of this study was to examine the efficacy of gum chewing for the recovery of bowel function after surgery for left-sided colorectal cancer and to determine the physiological mechanism underlying the effect of gum chewing on bowel function.

DESIGN

This was a single-center, placebo-controlled, parallel-group, prospective randomized trial.

SETTINGS

The study was conducted at a general hospital in Japan.

PATIENTS

Forty-eight patients with left-sided colorectal cancer were included.

INTERVENTIONS

The patients were randomly assigned to a gum group (N = 25) and a control group (N = 23). Four patients in the gum group and 1 in the control group were subsequently excluded because of difficulties in continuing the trial, resulting in the analysis of 21 and 22 patients in the respective groups. Patients in the gum group chewed commercial gum 3 times a day for ≥5 minutes each time from postoperative day 1 to the first day of food intake.

MAIN OUTCOME MEASURES

The time to first flatus and first bowel movement after the operation were recorded, and the colonic transit time was measured. Gut hormones (gastrin, des-acyl ghrelin, motilin, and serotonin) were measured preoperatively, perioperatively, and on postoperative days 1, 3, 5, 7, and 10.

RESULTS

Gum chewing did not significantly shorten the time to the first flatus (53 ± 2 vs. 49 ± 26 hours; p = 0.481; gum vs. control group), time to first bowel movement (94 ± 44 vs. 109 ± 34 hours; p = 0.234), or the colonic transit time (88 ± 28 vs. 88 ± 21 hours; p = 0.968). However, gum chewing significantly increased the serum levels of des-acyl ghrelin and gastrin.

LIMITATIONS

The main limitation was a greater rate of complications than anticipated, which limited the significance of the findings.

CONCLUSIONS

Gum chewing changed the serum levels of des-acyl ghrelin and gastrin, but we were unable to demonstrate an effect on the recovery of bowel function.

Genetic epidemiology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder characterized by presence of abdominal pain or discomfort associated with altered bowel habits. It has three main subtypes - constipation predominant IBS (C-IBS), diarrhea predominant IBS (D-IBS) and IBS with mixed features of both diarrhea as well as constipation (M-IBS). Its pathophysiology and underlying mechanisms remain elusive. It is traditionally believed that IBS is a result of multiple factors including hypersensitivity of the bowel, altered bowel motility, inflammation and stress. Initial studies have shown familial aggregation of IBS suggesting shared genetic or environmental factors. Twin studies of IBS from different parts of world have shown higher concordance rates among monozygotic twins than dizygotic twins, and thus suggesting a genetic component to this disorder. Multiple studies have tried to link single-nucleotide polymorphisms (SNPs) to IBS but there is little evidence that these SNPs are functional. Various molecules have been studied and investigated by the researchers. Serotonin, a known neurotransmitter and a local hormone in the enteric nervous system, has been most extensively explored. At this time, the underlying gene pathways, genes and functional variants linked with IBS remain unknown and the promise of genetically-determined risk prediction and personalize medicine remain unfulfilled. However, molecular biological technologies continue to evolve rapidly and genetic investigations offer much promise in the intervention, treatment and prevention of IBS.

Regulatory Effects of 5-Hydroxytryptamine Receptors on Voiding Function

A growing body of evidence suggests that 5-hydroxytryptamine (5-HT; serotonin) has both physiological and pathological functions in the lower urinary tract. A wide variety of 5-HT receptor subtypes are variably expressed in different organs, both peripheral and central. On urinary bladder smooth muscle, 5-HT1A, 5-HT2, 5-HT3, and 5-HT7 subtypes could function as postjunctional receptors. Postjunctional 5-HT2 receptors induce detrusor contraction of the bladder body. 5-HT1A is suggested to have a similar effect to 5-HT2, while 5-HT3 might suppress detrusor contraction evoked by direct muscle stimulation. Postjunctional 5-HT7 is reported to induce relaxation of the bladder neck, which might be required for efficient voiding. 5-HT1A, 5-HT2A, 5-HT2C, 5-HT3, 5-HT4, and 5-HT7 subtypes also could act as prejunctional receptors in autonomic excitatory nerve terminals. 5-HT2A, 5-HT2C, 5-HT3, 5-HT4, and 5-HT7 subtypes facilitate the neurogenic contraction of the detrusor by enhancing cholinergic or purinergic transmission, whereas 5-HT1A receptors might inhibit the release of acetylcholine in the detrusor. Furthermore, 5-HT1D could be involved in the suppression of ATP release from the urothelium, aiding visceral sensation of the urinary bladder. In the central pathways controlling the micturition reflex, 5-HT1A, 5-HT2A, and 5-HT7 are involved in regulation of bladder and urethral sphincter activities. Their functions, especially that of 5-HT1A, vary in a species- and site (spinal or supraspinal)- dependent manner. In addition to urinary bladder, 5-HT could be involved in prostate contraction and cell proliferation. Evidence indicates that 5-HT receptor subtypes may be novel therapeutic targets for lower urinary tract symptoms.

FUNDING

Grants-in-Aid for Scientific Research (C) (KAKENHI 23590707, 24590722, and 26460694) from the Japan Society for the Promotion of Science.

The kynurenine pathway of tryptophan degradation is activated during osteoblastogenesis

The mechanisms involved in the anabolic effect of interferon gamma (IFNγ) on bone have not been carefully examined. Using microarray expression analysis, we found that IFNγ upregulates a set of genes associated with a tryptophan degradation pathway, known as the kynurenine pathway, in osteogenic differentiating human mesenchymal stem cells (hMSC). We, therefore, hypothesized that activation of the kynurenine pathway plays a role in osteoblastogenesis even in the absence of IFNγ. Initially, we observed a strong increase in tryptophan degradation during osteoblastogenesis with and without IFNγ in the media. We next blocked indoleamine 2,3-dioxygenase-1 (IDO1), the most important enzyme in the kynurenine pathway, using a siRNA and pharmacological approach and observed a strong inhibition of osteoblastogenesis with a concomitant decrease in osteogenic factors. We next examined the bone phenotype of Ido1 knockout (Ido1(-/-)) mice. Compared to their wild-type littermates, Ido1(-/-) mice exhibited osteopenia associated with low osteoblast and high osteoclast numbers. Finally, we tested whether the end products of the kynurenine pathway have an osteogenic effect on hMSC. We identified that picolinic acid had a strong and dose-dependent osteogenic effect in vitro. In summary, we demonstrate that the activation of the kynurenine pathway plays an important role during the commitment of hMSC into the osteoblast lineage in vitro, and that this process can be accelerated by exogenous addition of IFNγ. In addition, we found that mice lacking IDO1 activity are osteopenic. These data therefore support a new role for the kynurenine pathway and picolinic acid as essential regulators of osteoblastogenesis and as potential new targets of bone-forming cells in vivo.

Role of serotonin signaling system in gastrointestinal tract: Implications for regulatory effect of acupuncture and moxibustion on irritable bowel syndrome

The 5-hydroxytryptamine (serotonin, or 5-HT) signaling system plays a key role in the gastrointestinal tract. There have been many studies on the 5-HT signaling system involved in the gastrointestinal tract. This article reviews the recent advances in the knowledge of 5-HT signaling pathways in the gastrointestinal tract, including 5-HT receptor types and subtypes, their distribution in the gastrointestinal tract, physiological and pathological roles of the 5-HT signal system in the gastrointestinal tract, and the change of the 5-HT signal pathway in the gastrointestinal tract. On the basis of the understanding of the above knowledge, we discuss how acupuncture and moxibustion regulate gastrointestinal diseases, especially IBS, through the 5-HT signal system.

Immunomodulatory effects mediated by serotonin

Serotonin (5-HT) induces concentration-dependent metabolic effects in diverse cell types, including neurons, entherochromaffin cells, adipocytes, pancreatic beta-cells, fibroblasts, smooth muscle cells, epithelial cells, and leukocytes. Three classes of genes regulating 5-HT function are constitutively expressed or induced in these cells: (a) membrane proteins that regulate the response to 5-HT, such as SERT, 5HTR-GPCR, and the 5HT₃-ion channels; (b) downstream signaling transduction proteins; and (c) enzymes controlling 5-HT metabolism, such as IDO and MAO, which can generate biologically active catabolites, including melatonin, kynurenines, and kynurenamines. This review covers the clinical and experimental mechanisms involved in 5-HT-induced immunomodulation. These mechanisms are cell-specific and depend on the expression of serotonergic components in immune cells. Consequently, 5-HT can modulate several immunological events, such as chemotaxis, leukocyte activation, proliferation, cytokine secretion, anergy, and apoptosis. The effects of 5-HT on immune cells may be relevant in the clinical outcome of pathologies with an inflammatory component. Major depression, fibromyalgia, Alzheimer disease, psoriasis, arthritis, allergies, and asthma are all associated with changes in the serotonergic system associated with leukocytes. Thus, pharmacological regulation of the serotonergic system may modulate immune function and provide therapeutic alternatives for these diseases.

Synthesis, physicochemical characterization and membrane interactions of a homologous series of N-acylserotonins: Bioactive, endogenous conjugates of serotonin with fatty acids

N-Acylserotonins (NASTs), present in the mammalian gastro-intestinal tract and central nervous tissues, exhibit significant biological and pharmacological activities. In the present study, a homologous series of NASTs have been synthesized and characterized. Differential scanning calorimetric studies show that in the dry and hydrated states the transition temperatures, enthalpies, and entropies of NASTs exhibit odd-even alternation. Both odd and even chain length NASTs independently display linear dependence of the transition enthalpies and entropies on the chain length under dry as well as hydrated conditions, suggesting that the molecular packing and intermolecular interactions in each series (odd or even) are likely to be similar for NASTs with different acyl chain lengths in the dry state as well as in the hydrated state. Powder X-ray diffraction studies indicated that the incremental increase in the d-spacing per CH₂group is 1.023 Å, suggesting that the lipid acyl chains are most likely packed in an interdigitated fashion. Results of computational studies are consistent with this and suggest that the acyl chains of the NASTs are tilted with respect to the bilayer normal. Incorporation of N-myristoylserotonin (NMST) into dimyristoylphosphatidylcholine (DMPC) membranes did not significantly affect the phase transition properties at low mole fractions (1-5 mol%), although distinct decrease in the chain-melting transition temperature and increase in the pretransition temperature were observed at higher contents (7.5-30 mol%), suggesting that NMST increases the stability of the tilted gel phase (L(β)') but destabilizes the ripple phase (P(β)'). These observations provide a thermodynamic basis for understanding the functional role of NASTs in their parent tissues.

Genetics of psychotropic medication induced side effects in two independent samples of bipolar patients

The treatment of bipolar disorder (BD) usually requires combination therapies, with the critical issue of the emergence of adverse drug reactions (ADRs) and the possibility of low treatment adherence. Genetic polymorphisms are hypothesized to modulate the pharmacodynamics of psychotropic drugs, representing potential biological markers of ADRs. This study investigated genes involved in the regulation of neuroplasticity (BDNF, ST8SIA2), second messenger cascades (GSK3B, MAPK1, and CREB1), circadian rhythms (RORA), transcription (SP4, ZNF804A), and monoaminergic system (HTR2A and COMT) in the risk of neurological, psychic, autonomic, and other ADRs. Two independent samples of BD patients naturalistically treated were included (COPE-BD n = 147; STEP-BD n = 659). In the COPE-BD 34 SNPs were genotyped, while in the STEP-BD polymorphisms in the selected genes were extracted from the genome-wide dataset. Each ADRs group was categorized as absent-mild or moderate-severe and logistic regression with appropriate covariates was applied to identify possible risk genotypes/alleles. 58.5 and 93.5 % of patients were treated with mood stabilizers, 44.2 and 50.7 % were treated with antipsychotics, and 69.4 and 46.1 % were treated with antidepressants in the COPE-BD and STEP-BD, respectively. Our findings suggested that ST8SIA2 may be associated with psychic ADRs, as shown in the COPE-BD (rs4777989 p = 0.0017) and STEP-BD (rs56027313, rs13379489 and rs10852173). A cluster of RORA SNPs around rs2083074 showed an effect on psychic ADRs in the STEP-BD. Trends supporting the association between HTR2A and autonomic ADRs were found in both samples. Confirmations are needed particularly for ST8SIA2 and RORA since the few available data regarding their role in relation to psychotropic ADRs.

Effects of San-Huang-Xie-Xin-tang, a traditional Chinese prescription for clearing away heat and toxin, on the pacemaker activities of interstitial cells of Cajal from the murine small intestine

ETHNOPHARMACOLOGICAL RELEVANCE

San-Huang-Xie-Xin-Tang (SHXXT) is a traditional Chinese medicinal formula composed of Coptidis rhizoma (Coptis chinesis Franch), Scutellariae radix (Scutellaria baicalensis Georgi), and Rhei rhizoma (Rheum officinale Baill) and is widely used in Eastern Asia, especially to ameliorate the symptoms of gastrointestinal (GI) disorders related to gastritis, gastric bleeding, peptic ulcers, and abnormal GI motility

AIM OF THE STUDY

Interstitial cells of Cajal (ICCs) are pacemaker cells in the GI tract that generate rhythmic oscillations in membrane potentials known as slow waves. Because GI disorders, especially abnormal GI motility, are major lifelong problems, the authors investigated the effects of SHXXT on mouse small intestine ICCs, and sought to identify the receptors and the action mechanisms involved.

MATERIALS AND METHODS

Enzymatic digestions were used to dissociate ICCs from small intestines, and the whole-cell patch-clamp configuration was used to record potentials generated by cultured ICCs.

RESULTS

SHXXT produced membrane depolarization in current-clamp mode, and Y25130 (a 5-HT3 receptor antagonist) and RS39604 (a 5-HT4 receptor antagonist) blocked SHXXT-induced membrane depolarizations, whereas SB269970 (a 5-HT7 receptor antagonist) did not. However, during external Ca2+ free conditions or in the presence of thapsigargin, SHXXT did not exhibit membrane depolarization. Furthermore, the application of flufenamic acid (a nonselective cation channel (NSCC) blocker) or DIDS (a chloride channel blocker) abolished pacemaker potential generation and blocked SHXXT-induced membrane depolarizations. In addition, SHXXT-induced membrane depolarizations, which are dependent on G-protein, in ICCs were blocked by PD 98059 (a p42/44 mitogen-activated protein kinase (MAPK) inhibitor), SB203580 (a p38 MAPK inhibitor), and by a c-jun NH2-terminal kinase (JNK) II inhibitor. Regarding the components of SHXXT, Coptidis rhizome and Rhei rhizoma modulated ICC pacemaking activity, whereas Scutellariae radix did not.

CONCLUSION

SHXXT modulates pacemaker potentials via 5-HT3 and 5-HT4 receptor-mediated pathways, external Ca2+ influx, and Ca2+ release from internal stores. Furthermore, NSCCs and Cl- channels play important roles in the regulation of pacemaking activity in a MAPK dependent manner in ICCs. The regulation of pacemaking activity by SHXXT may be due to the activity of Coptidis rhizome and Rhei rhizome. The study shows SHXXT can modulate the pacemaking activity of ICCs in the GI tract, and thus, suggests SHXXT has potential pharmacological relevance for the treatment of GI motility disorders.

Post-infectious irritable bowel syndrome: Mechanistic insights into chronic disturbances following enteric infection

Irritable bowel syndrome (IBS) is a commonly encountered chronic functional gastrointestinal (GI) disorder. Approximately 10% of IBS patients can trace the onset of their symptoms to a previous a bout of infectious dysentery. The appearance of new IBS symptoms following an infectious event is defined as post-infectious-IBS. Indeed, with the World Health Organization estimating between 2 and 4 billion cases annually, infectious diarrheal disease represents an incredible international healthcare burden. Additionally, compounding evidence suggests many commonly encountered enteropathogens as unique triggers behind IBS symptom generation and underlying pathophysiological features. A growing body of work provides evidence supporting a role for pathogen-mediated modifications in the resident intestinal microbiota, epithelial barrier integrity, effector cell functions, and innate and adaptive immune features, all proposed physiological manifestations that can underlie GI abnormalities in IBS. Enteric pathogens must employ a vast array of machinery to evade host protective immune mechanisms, and illicit successful infections. Consequently, the impact of infectious events on host physiology can be multidimensional in terms of anatomical location, functional scope, and duration. This review offers a unique discussion of the mechanisms employed by many commonly encountered enteric pathogens that cause acute disease, but may also lead to the establishment of chronic GI dysfunction compatible with IBS.

Intestinal inflammation in a murine model of autism spectrum disorders

Autism spectrum disorder (ASD) is a cluster of neurodevelopmental disorders characterized by impairments in communication, social interest and stereotypical behaviour. Dysfunction of the intestinal tract is reported in patients with ASD and implicated in the development and severity of ASD symptoms. However, more research is required to investigate the association of intestinal problems with ASD and the potential underlying mechanisms. The purpose of this study was to investigate comorbid symptoms of intestinal inflammation in a murine model of ASD induced by prenatal exposure to valproic acid (VPA). Pregnant BALB/c females were treated subcutaneously with 600 mg/kg VPA or phosphate buffered saline on gestational day 11. Offspring were housed with their mother until weaning on postnatal day 21 (P21). All pups were exposed to a social behaviour test on P28. Inflammatory correlates and activity of the serotonergic system were measured in brain and intestinal tissue. Here we demonstrate, in addition to reduced social behaviour and increased expression of neuroinflammatory markers in the brain, that VPA in utero- exposed male offspring showed epithelial cell loss and neutrophil infiltration in the intestinal tract. Furthermore, reduced levels of serotonin were not only observed the prefrontal cortex and amygdala of VPA in utero- exposed males, but also in the small intestine. Overall, we demonstrate that gender-specific inflammatory conditions are present in the small intestines of VPA in utero- exposed mice and are accompanied by a disturbed serotonergic system in the brain as well as in the intestinal tract.

Effect of DA-9701 on colorectal distension-induced visceral hypersensitivity in a rat model

BACKGROUND/AIMS

DA-9701 is a newly developed drug made from the vegetal extracts of Pharbitidis semen and Co-rydalis tuber. The aim of this study was to evaluate the effect of DA-9701 on colorectal distension (CRD)-induced visceral hypersensitivity in a rat model.

METHODS

Male Sprague-Dawley rats were subjected to neonatal colon irritation (CI) using CRD at 1 week after birth (CI group). At 6 weeks after birth, CRD was applied to these rats with a pressure of 20 to 90 mm Hg, and changes in the mean arterial pressure (MAP) were measured at baseline (i.e., without any drug administration) and after the administration of different doses of DA-9701.

RESULTS

In the absence of DA-9701, the MAP changes after CRD were significantly higher in the CI group than in the control group at all applied pressures. In the control group, MAP changes after CRD were not significantly affected by the administration of DA-9701. In the CI group, however, the administration of DA-9701 resulted in a significant decrease in MAP changes after CRD. The administration of DA-9701 at a dose of 1.0 mg/kg produced a more significant decrease in MAP changes than the 0.3 mg/kg dose.

CONCLUSIONS

The administration of DA-9701 resulted in a significant increase in pain threshold in rats with CRD-induced visceral hypersensitivity.

Effects of 5-HT2B, 5-HT3 and 5-HT4 receptor antagonists on gastrointestinal motor activity in dogs

AIM: To study the effects of 5-hydroxytryptamine (5-HT) receptor antagonists on normal colonic motor activity in conscious dogs.

METHODS: Colonic motor activity was recorded using a strain gauge force transducer in 5 dogs before and after 5-HT2B, 5-HT3 and 5-HT4 receptor antagonist administration. The force transducers were implanted on the serosal surfaces of the gastric antrum, terminal ileum, ileocecal sphincter and colon. Test materials or vehicle alone was administered as an intravenous bolus injection during a quiescent period of the whole colon in the interdigestive state. The effects of these receptor antagonists on normal gastrointestinal motor activity were analyzed.

RESULTS: 5-HT2B, 5-HT3 and 5-HT4 receptor antagonists had no contractile effect on the fasting canine terminal ileum. The 5-HT3 and 5-HT4 receptor antagonists inhibited phase III of the interdigestive motor complex of the antrum and significantly inhibited colonic motor activity. In the proximal colon, the inhibitory effect was dose dependent. Dose dependency, however, was not observed in the distal colon. The 5-HT2B receptor antagonist had no contractile effect on normal colonic motor activity.

CONCLUSION: The 5-HT3 and 5-HT4 receptor antagonists inhibited normal colonic motor activity. The 5-HT2B receptor antagonist had no contractile effect on normal colonic motor activity.

Expression of 5-hydroxytryptamine 3 receptor in the gastrointestinal tract of rats with slow transit constipation

AIM: To investigate the expression of 5-hydroxytryptamine 3 (5-HT3) receptor in the gastrointestinal of rats with slow transit constipation (STC), and to explore its role in the pathogenesis of STC.

METHODS: Twenty-four healthy Wistar rats were divided into either an experimental group or a control group. The experimental group was daily administered with diphenoxylate (8 mg/kg) for 90 days to induce STC, while the control group was fed equal volume of normal saline. The number and weight of fecal granules and the body weight of rats were recorded every 5 days. An activated charcoal suspension pushing test was performed one week after the administration of diphenoxylate to assess whether STC was successfully induced. RT-PCR was used to detect the expression of 5-HT3 receptor in the stomach, small intestine and colon of rats.

RESULTS: By comparing the number of fecal granule, the mean weight of each fecal granule and the discharge time of the first granule of black feces between the experimental group and control group, we could judge that STC was successfully induced. 5-HT3 receptor could be specifically amplified by RT-PCR. The expression of 5-HT3 receptor in the stomach, small intestine and colon was significantly lower in rats with STC than in control rats (all P < 0.05).

CONCLUSION: The expression of 5-HT3 receptor is decreased in the stomach, small intestine and colon of rats with STC, which may contribute to the pathogenesis of STC.

Ghrelin receptor is activated by naringin and naringenin, constituents of a prokinetic agent Poncirus fructus

ETHNOPHARMACOLOGICAL RELEVANCE

Poncirus fructus (PF), also known as a dried immature fruit of Poncirus trifoliata (L.) Raf. (Rutaceae), has long been traditionally used for the various gastrointestinal disorders in Eastern Asia.

AIM OF STUDY

The aqueous extract of PF (PF-W) has the strong prokinetic effect, yet the underlying mechanism is still elusive. The present study investigated whether PF-W has any effect on motilin receptor or ghrelin receptor, since these receptors enhance intestinal motility when activated.

MATERIALS AND METHODS

The effect of PF-W and its components on motilin or ghrelin receptor was determined by calcium imaging and whole-cell patch clamp methods.

RESULTS

PF-W activates the ghrelin receptor, but not the motilin receptor, resulting in a transient increase of intracellular calcium levels. Furthermore, among various constituents of PF, only naringin and naringenin evoked the intracellular calcium augmentation via the ghrelin receptor. Moreover, cortistatin-8 - a ghrelin receptor inhibitor - specifically blocked naringin- and naringenin-induced calcium increases. In addition, naringin and naringenin induced inward currents in ghrelin receptor-expressing cells under whole-cell patch clamp configuration.

CONCLUSION

PF-W activates the ghrelin receptor, and naringin and naringenin are key constituents responsible for the activation of ghrelin receptor. Therefore, the present study suggests that the ghrelin receptor is a molecular entity responsible for the strong prokinetic activity of PF-W.

Molecular dynamics simulation of tryptophan hydroxylase-1: binding modes and free energy analysis to phenylalanine derivative inhibitors

Serotonin is a neurotransmitter that modulates many central and peripheral functions. Tryptophan hydroxylase-1 (TPH1) is a key enzyme of serotonin synthesis. In the current study, the interaction mechanism of phenylalanine derivative TPH1 inhibitors was investigated using molecular dynamics (MD) simulations, free energy calculations, free energy decomposition analysis and computational alanine scanning. The predicted binding free energies of these complexes are consistent with the experimental data. The analysis of the individual energy terms indicates that although the van der Waals and electrostatics interaction contributions are important in distinguishing the binding affinities of these inhibitors, the electrostatic contribution plays a more crucial role in that. Moreover, it is observed that different configurations of the naphthalene substituent could form different binding patterns with protein, yet lead to similar inhibitory potency. The combination of different molecular modeling techniques is an efficient way to interpret the interaction mechanism of inhibitors and our work could provide valuable information for the TPH1 inhibitor design in the future.

Synthesis and pharmacological properties of a new hydrophilic and orally bioavailable 5-HT4 antagonist

5-HT4 receptor antagonists have been suggested to have clinical potential in treatment of atrial fibrillation, diarrhea-prone irritable bowel syndrome and urinary incontinence. Recently, the use of 5-HT4 antagonists has been suggested to have a therapeutic benefit in heart failure. Affinity for the hERG potassium ion channel and increased risk for prolonged QT intervals and arrhythmias has been observed for several 5-HT4 ligands. Serotonin may also have beneficial effects in the central nervous system (CNS) through stimulation of the 5-HT4 receptor, and reduced distribution of 5-HT4 antagonists to the CNS may therefore be an advantage. Replacing the amide and N-butyl side chain of the 5-HT4 receptor antagonist SB207266 with an ester and a benzyl dimethyl acetic acid group led to compound 9; a hydrophilic 5-HT4 antagonist with excellent receptor binding and low affinity for the hERG potassium ion channel. To increase oral bioavailability of carboxylic acid 9, two different prodrug approaches were applied. The tert-butyl prodrug 11 did not improve bioavailability, and LC-MS analysis revealed unmetabolized prodrug in the systemic circulation. The medoxomil ester prodrug 10 showed complete conversion and sufficient bioavailability of 9 to advance into further preclinical testing for treatment of heart failure.

Relieving visceral hyperalgesia effect of Kangtai capsule and its potential mechanisms via modulating the 5-HT and NO level in vivo

Kangtai capsule (KT) is one type of traditional Chinese medicine preparation derived from the proved recipe, which was frequently applied as an effective clinical treatment of IBS. However, there still lack the reasonable and all-round analytical approach and the scientific studies on its underlying mechanisms. Therefore, our study aimed to develop the novel method for evaluating its quality as well as to interpret the potential mechanisms. In our study, high performance liquid chromatography (HPLC) fingerprint was applied to provide a chemical profile of KT. The neonatal maternal separation (NMS) on Sprague-Dawley pups was employed to evaluate the therapeutic effect of KT by virtue of various parameters including visceral hyperalgesia, serum nitric oxide (NO) level, and tissue 5-hydroxytryptamine (5-HT) level. Consequently, a chromatographic condition, which was carried at 30°C with a flow rate of 0.5 ml/min on AQUA 3μ C18 column with mobile phase of acetonitrile and water-phosphoric acid (100:0.1, v/v), was established to give a common fingerprint chromatography under 254 nm with a similarity index of 0.963 within ten batches of KT samples. On the NMS model, KT markedly elevated the pain threshold of NMS rats. Furthermore, KT at three doses significantly decreased 5-HT content from distal colon of visceral hyperalgesia rats induced by NMS, while the significant decrease of 5-HT content in serum was only observed in the group with KT at high dose. However, compared with that in NMS rats without KT, there was no apparent difference of 5-HT level from brain issue in the rats with various doses. Besides, KT could substantially elevate the concentration of NO in the serum. The results showed our study developed the simple, rapid, accurate, reproducible qualitative and quantitative analysis by HPLC fingerprint for the quality control for KT. Data from the pharmacological investigation suggested that the curative effect of KT to the visceral hypersensitivity may be concerned with the level of 5-HT and NO in vivo, promising its potential in irritable bowel syndrome treatment.

Gastritis and mental disorders

Although previous studies have suggested an association between various gastrointestinal disorders and mood and anxiety disorders, no previous study has examined the relationship between a diagnosis of gastritis and mood and anxiety disorders in the community. This work aimed to investigate the association between physician-diagnosed gastritis and DSM-IV mood and anxiety disorders among adults in the general population, and to examine sex differences in these relationships. Data were drawn from a population-based, representative sample of 4181 adults aged 18-79 in the German National Health Interview and Examination Survey. Anxiety disorders (27.0% vs. 15.3%) and affective disorders (20.1% vs. 11.5%) were significantly more common among adults with compared to without a diagnosis of gastritis. Lifetime and current physician diagnosed gastritis were associated with an increased prevalence of panic attacks, social phobia, any mood disorder and major depression, compared to those without gastritis. There were no significant sex differences in these associations. A diagnosis of gastritis appears to be associated with significantly increased odds of mood and anxiety disorders among adults in the general population. Contrary to findings from animal studies, we found the relationship between gastritis and mood/anxiety consistent among both sexes.

Serotonin: from top to bottom

Serotonin is a monoamine neurotransmitter, which is phylogenetically conserved in a wide range of species from nematodes to humans. In mammals, age-related changes in serotonin systems are known risk factors of age-related diseases, such as diabetes, faecal incontinence and cardiovascular diseases. A decline in serotonin function with aging would be consistent with observations of age-related changes in behaviours, such as sleep, sexual behaviour and mood all of which are linked to serotonergic function. Despite this little is known about serotonin in relation to aging. This review aims to give a comprehensive analysis of the distribution, function and interactions of serotonin in the brain; gastrointestinal tract; skeletal; vascular and immune systems. It also aims to demonstrate how the function of serotonin is linked to aging and disease pathology in these systems. The regulation of serotonin via microRNAs is also discussed, as are possible applications of serotonergic drugs in aging research and age-related diseases. Furthermore, this review demonstrates that serotonin is potentially involved in whole organism aging through its links with multiple organs, the immune system and microRNA regulation. Methods to investigate these links are discussed.