Serotonin: a mediator of the brain-gut connection

No synergistic effect of fecal microbiota transplantation and shugan decoction in water avoidance stress-induced IBS-D rat model

Background

It has been reported that 5-hydroxytryptamine (5-HT, serotonin) metabolism is involved in the pathogenesis of irritable bowel syndrome (IBS) and that either Shugan decoction (SGD) or fecal microbiota transplantation (FMT) can alleviate the symptoms of IBS in patients and animal models. But the synergistic effect of FMT and SGD on 5-HT metabolism and IBS symptoms has not been investigated.

Aim

The main purpose of this study is to observe the synergistic effect of FMT with SGD on symptoms and 5-HT metabolism in IBS-D rats induced by water avoidance stress (WAS). Moreover, the possible material basis of the FMT was investigated.

Methods

In experiment I, rats were randomly divided into seven groups. Control group: routine feeding; WAS→ Control group: routine feeding with fecal microbiota liquid (FML) 1 (derived from rats in WAS group) gavage since the fourth day; WAS group: 10 days WAS with routine feeding; SGD group: 10 days WAS with SGD gavage since the fourth day on the base of routine feeding; Control→ WAS group: 10 days WAS with FML2 (derived from rats in Control group) gavage since the fourth day with routine feeding; SGD→ WAS group: 10 days WAS with FML3 (derived from rats in SGD group) gavage since the fourth day with routine feeding; SGD + (Control→ WAS) group: 10 days WAS with SGD and FML2 (derived from rats in Control group) gavage since the fourth day with routine feeding. In experiment II, rats were randomly divided into three groups. Control group: routine feeding; Control→ WAS group: 10 days WAS with FML2 gavage since the fourth day with routine feeding; FControl→ WAS group: 10 days WAS with FML2 filtrate gavage since the fourth day. The number of fecal pellets output (FPT) and the pain pressure threshold (PPT) were recorded. The histological changes in colon mucosa were observed by hematoxylin-eosin (HE) stain. The number of enterochromaffin cells (ECs), the content of 5-HT, and the expression of serotonin reuptake transporter (SERT) protein in the colon were measured by immunofluorescence or western blotting.

Results

Compared with that in the control group, the PPT and the expression of SERT in the WAS group and that in the WAS→ Control group were decreased with the increased number of ECs and the level of 5-HT in colon. But the FPT was not increased in the WAS→ Control group although that was increased in the WAS group. Compared with that in the WAS group, the FPT, the PPT, the number of ECs, the level of 5-HT, and the expression of SERT protein in colon in the SGD group, control→ WAS group, SGD→ WAS group, and SGD+(Control→ WAS) group were all recovered. The recovery of these indicators in the Control→ WAS group and that in the FControl→ WAS group was not significantly different.

Conclusion

No synergistic effect of SGD with FMT on IBS symptoms induced by WAS was found. The metabolites of intestinal microbiota may be the main active substances of the FML derived from normal rats to alleviate WAS-induced IBS symptoms.

Buspirone in the management of refractory irritable bowel syndrome: A case report

RATIONALE

Irritable bowel syndrome (IBS) is a chronic and debilitating functional disorder of the gastrointestinal tract manifested by abdominal pain and bowel habit dysregulation. The pathophysiology is complex and management targets symptom resolution. Therapeutic interventions range from dietary modification, psychological interventions, exercise, to the use of antispasmodics, antibiotics, and antidepressants. Anecdotal reports have suggested that buspirone may be beneficial in the treatment of functional dyspepsia and IBS and its physiological effect of reducing gastric tone provides a rational for its benefit.

PATIENT CONCERNS

A 28-year-old man with unremarkable past medical and psychiatric history presented with worsening abdominal pain, bloating, and bowel movement dysregulation of over 6-year duration.

DIAGNOSES

Physical examination revealed mild distension and discomfort on deep palpation. Thorough blood investigations, stool analysis and culture, and imaging were unremarkable except for the detection of mucus with stool. The patient was diagnosed with irritable bowel syndrome with mixed habits.

INTERVENTIONS

Dietary adjustment and a range of medications (mebeverine, simethicone, loperamide, rifaximin, sertraline and amitriptyline) yielded unsatisfactory response of were not tolerated. Buspirone was eventually introduced.

OUTCOMES

Buspirone was associated with a significant and sustained improvement in IBS symptoms and quality of life.

LESSONS

This case suggests that buspirone was effective in treating refractory IBS. Further research is needed to assess the role of buspirone in IBS management.

Migraine and Its Equivalents: What Do They Share? A Narrative Review on Common Pathophysiological Patterns

Migraine is the first in order of frequency of the neurological disorders, affecting both adult and paediatric populations. It is also the first cause of primary headaches in children. Migraine equivalents are periodic disorders that can be associated with migraine or considered as prognostic features of a future migraine manifestation. Despite the mechanisms underlying migraine and its equivalents are not entirely clear, several elements support the hypothesis of common pathophysiological patterns shared by these conditions. The aim of this review is thus to analyze the literature in order to highlight which currently known mechanisms may be common between migraine and its equivalents.

Importance of the enteric nervous system in the control of the migrating motility complex

The migrating motility complex (MMC), a cyclical phenomenon, represents rudimentary motility pattern in the gastrointestinal tract. The MMC is observed mostly in the stomach and gut of man and numerous animal species. It contains three or four phases, while its phase III is the most characteristic. The mechanisms controlling the pattern are unclear in part, although the neural control of the MMC seems crucial. The main goal of this article was to discuss the importance of intrinsic innervation of the gastrointestinal tract in MMC initiation, migration, and cessation to emphasize that various MMC-controlling mechanisms act through the enteric nervous system. Two main neural regions, central and peripheral, are able to initiate the MMC. However, central regulation of the MMC may require cooperation with the enteric nervous system. When central mechanisms are not active, the MMC can be initiated peripherally in any region of the small bowel. The enteric nervous system affects the MMC in response to the luminal stimuli which can contribute to the initiation and cessation of the cycle, and it may evoke irregular phasic contractions within the pattern. The hormonal regulators released from the endocrine cells may exert a modulatory effect upon the MMC mostly through the enteric nervous system. Their central action could also be considered. It can be concluded that the enteric nervous system is involved in the great majority of the MMC-controlling mechanisms.

Neuroimmunomodulation in the Gut: Focus on Inflammatory Bowel Disease

Intestinal immunity is finely regulated by several concomitant and overlapping mechanisms, in order to efficiently sense external stimuli and mount an adequate response of either tolerance or defense. In this context, a complex interplay between immune and nonimmune cells is responsible for the maintenance of normal homeostasis. However, in certain conditions, the disruption of such an intricate network may result in intestinal inflammation, including inflammatory bowel disease (IBD). IBD is believed to result from a combination of genetic and environmental factors acting in concert with an inappropriate immune response, which in turn interacts with nonimmune cells, including nervous system components. Currently, evidence shows that the interaction between the immune and the nervous system is bidirectional and plays a critical role in the regulation of intestinal inflammation. Recently, the maintenance of intestinal homeostasis has been shown to be under the reciprocal control of the microbiota by immune mechanisms, whereas intestinal microorganisms can modulate mucosal immunity. Therefore, in addition to presenting the mechanisms underlying the interaction between immune and nervous systems in the gut, here we discuss the role of the microbiota also in the regulation of neuroimmune crosstalk involved in intestinal homeostasis and inflammation, with potential implications to IBD pathogenesis.

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.

Gene polymorphisms associated with functional dyspepsia

Functional dyspepsia (FD) is a constellation of functional upper abdominal complaints with poorly elucidated pathophysiology. However, there is increasing evidence that susceptibility to FD is influenced by hereditary factors. Genetic association studies in FD have examined genotypes related to gastrointestinal motility or sensation, as well as those related to inflammation or immune response. G-protein b3 subunit gene polymorphisms were first reported as being associated with FD. Thereafter, several gene polymorphisms including serotonin transporter promoter, interlukin-17F, migration inhibitory factor, cholecystocynine-1 intron 1, cyclooxygenase-1, catechol-o-methyltransferase, transient receptor potential vanilloid 1 receptor, regulated upon activation normal T cell expressed and secreted, p22PHOX, Toll like receptor 2, SCN10A, CD14 and adrenoreceptors have been investigated in relation to FD; however, the results are contradictory. Several limitations underscore the value of current studies. Among others, inconsistencies in the definitions of FD and controls, subject composition differences regarding FD subtypes, inadequate samples, geographical and ethnical differences, as well as unadjusted environmental factors. Further well-designed studies are necessary to determine how targeted genes polymorphisms, influence the clinical manifestations and potentially the therapeutic response in FD.

Serotonin and its implication in the side-effects of interferon-based treatment of patients with chronic viral hepatitis: Pharmacological interventions

Depression is a frequent side-effect of interferon-based treatment of patients with chronic viral hepatitis, that may lead to reduction or discontinuation of treatment. Clinical trials data showed the importance of therapy of psychiatric disorders for a successful antiviral treatment. Emerging evidence suggests that interferon may cause depression affecting serotonin synthesis via increased activity of indoleamine 2,3-dioxygenase. Serotonin reuptake inhibitors significantly improve mood disorders, but the use of these drugs requires caution because some studies reported the emergence of mania in patients treated for depression during antiviral therapy. Therefore, this review will examine and discuss the putative role of serotonin and its metabolism in the development of depression during antiviral therapy, focusing on pharmacological interventions to reduce side-effects.

The enteric serotonergic system is altered in patients with diverticular disease

OBJECTIVE

Disturbances of the enteric serotonergic system have been implicated in several intestinal motility disorders. Patients with diverticular disease (DD) have been reported to exhibit abnormal intestinal motility and innervation patterns. Gene expression profiles of the serotonergic system and distribution of the serotonin type 4 receptor (5HT-4R) were thus studied in patients with DD.

DESIGN

Colonic specimens from patients with DD and controls were subjected to quantitative PCR for serotonin receptors 2B, 3A, 4, serotonin transporter and synthesising enzyme tryptophan hydroxylase. Localisation of 5HT-4R was determined by dual-label immunocytochemistry using smooth muscle actin (α-SMA) and pan-neuronal markers (PGP 9.5) and quantitative analysis was carried out. Site-specific gene expression analysis of 5HT-4R was assessed within myenteric ganglia and muscle layers. Correlation of 5HT-4R with muscarinic receptors 2 and 3 (M2R, M3R) messenger RNA expression was determined.

RESULTS

5HT-4R mRNA expression was downregulated in the tunica muscularis and upregulated in the mucosa of patients with DD, whereas the other components of the serotonergic system remained unchanged. 5HT-4R was detected in ganglia and muscle layers, but was decreased in the circular muscle layer and myenteric ganglia of patients with DD. 5HT-4R mRNA expression correlated with M2R/M3R mRNA expression in controls, but not in patients with DD.

CONCLUSIONS

The serotonergic system is compromised in DD. Altered expression of 5HT-4R at mRNA and protein levels may contribute to intestinal motor disturbances reported in patients with DD. The findings support the hypothesis that DD is associated and possibly promoted by an enteric neuromuscular pathology.

Neuroendocrine markers and psychological features in patients with irritable bowel syndrome

BACKGROUND AND AIMS

The key role of the brain-gut axis in the pathophysiology of irritable bowel syndrome (IBS) has been recognized. The aim of this study was to assess the possible association between IBS, neuroendocrine markers, and psychological features.

METHODS

One hundred and twenty-five consecutive IBS patients and 105 healthy subjects were enrolled. Plasma serotonin, plasma and urinary cortisol, and plasma neuropeptide Y levels were evaluated. All patients were given a questionnaire to assess IBS symptom severity. In 66 patients, a psychodiagnostic assessment was carried out.

RESULTS

A high incidence of specific psychological features, including state anxiety (69.69 %), trait anxiety (54.54 %), obsessions and compulsions (28.78 %), was observed in IBS patients. A positive correlation between neuropeptide Y and state anxiety (r = 0.287, p = 0.024) and simulation/social ingenuity (r = 0.269, p = 0.039) was found in these patients. In diarrhea-predominant IBS, plasma cortisol was linearly related to plasma serotonin (r = 0.5663, p < 0.001).

CONCLUSIONS

In IBS patients, a significant correlation was found between specific psychological features and neuroendocrine markers, especially plasma cortisol and neuropeptide Y; in diarrhea-predominant IBS, a correlation between plasma cortisol and serotonin was found, although it needs to be confirmed in more extensive cohorts.

S100A expression and interleukin-10 polymorphisms are associated with ulcerative colitis and diarrhea predominant irritable bowel syndrome

BACKGROUND

Both ulcerative colitis (UC) and diarrhea-predominant irritable bowel syndrome (IBS-D) are associated with alterations in enteric serotonin (5-HT) signaling.

AIMS

The purpose of this study was to compare the rectal and sigmoid colonic mucosal expression of S100A proteins and functional polymorphisms of the 5-HT transporter (5HTT) and interleukin-10 genes in patients with IBS-D or UC with healthy controls.

METHODS

mRNA expression of S100 proteins was measured in sigmoid and rectal biopsies and in rectal epithelium isolated by laser-captured microdissection. Leucocyte DNA was analyzed by PCR-based reaction fragment length polymorphisms and direct sequencing. Clinical symptoms were assessed by the self-rating depression scale and by the gastrointestinal symptom rating scale.

RESULTS

Fifty patients with IBS-D, 56 with UC and 50 healthy controls were studied. Colonic mucosal expression of S100A8 and S100A9 in UC was significantly higher than in IBS or controls and correlated with the UC disease activity index (r = 0.65, p < 0.001). S100A10 expression in the rectal epithelium of the IBS patients was significantly higher (0.643 vs. 0.402, p = 0.01) than in controls and correlated with the SDS scores (r = 0.41, p = 0.002). The frequency of IL10-819 CC genotype was significantly higher in IBS-D (10.7 vs. 0 %, p = 0.047) and UC (16 vs. 0 %, p = 0.007) than that in controls.

CONCLUSION

Overexpression of S100A10 in the rectum may play a role in IBS as it is involved in modulating 5-HT1B receptors. The IL10-819 CC is a candidate genotype for both IBS and UC in Japanese.

Decreased levels of kynurenic acid in the intestinal mucosa of IBS patients: relation to serotonin and psychological state

OBJECTIVE

Irritable bowel syndrome (IBS) has been associated with psychiatric comorbidity and alterations in serotonergic metabolism. Tryptophan is the precursor of serotonin (5-HT), but it is mainly catabolized through the kynurenine pathway. This pathway may also be involved in the pathogenesis of IBS by virtue of deviating tryptophan from the 5-HT pathway resulting in 5-HT deficiency. We therefore aimed to ascertain the mucosal and systemic concentrations of 5-HT and kynurenic acid (KYNA), a principal kynurenine metabolite.

METHODS

Duodenal mucosal biopsy specimens and platelet poor plasma samples were obtained from 15 healthy volunteers and 15 IBS patients. Psychological state was assessed using the Hospital Anxiety and Depression Scale and the Symptom Checklist-90.

RESULTS

IBS patients showed significantly lower mucosal and higher systemic concentrations of both 5-HT and KYNA compared to healthy controls. Also, significant correlation between mucosal but not plasma concentrations of KYNA and 5-HT and psychological state in IBS was observed.

CONCLUSION

The observation that mucosal KYNA and 5-HT are both decreased in IBS does not support the hypothesis that increased activation along the kynurenic pathway results in relative 5-HT deficiency. However, an increased release of these substances from the intestine to the systemic compartment may lead to a decrease in intestinal KYNA and 5-HT levels, resulting in disturbance of intestinal homeostasis. Thus, changes in psychological states observed in IBS patients may be secondary to alterations in gastrointestinal function, and in particular kynurenine and/or 5-HT metabolism.

Targeted inhibition of serotonin type 7 (5-HT7) receptor function modulates immune responses and reduces the severity of intestinal inflammation

Mucosal inflammation in conditions ranging from infective acute enteritis or colitis to inflammatory bowel disease is accompanied by alteration in serotonin (5-hydroxytryptamine [5-HT]) content in the gut. Recently, we have identified an important role of 5-HT in the pathogenesis of experimental colitis. 5-HT type 7 (5-HT7) receptor is one of the most recently identified members of the 5-HT receptor family, and dendritic cells express this receptor. In this study, we investigated the effect of blocking 5-HT7 receptor signaling in experimental colitis with a view to develop an improved therapeutic strategy in intestinal inflammatory disorders. Colitis was induced with dextran sulfate sodium (DSS) or dinitrobenzene sulfonic acid (DNBS) in mice treated with selective 5-HT7 receptor antagonist SB-269970, as well as in mice lacking 5-HT7 receptor (5-HT7(-/-)) and irradiated wild-type mice reconstituted with bone marrow cells harvested from 5-HT7(-/-) mice. Inhibition of 5-HT7 receptor signaling with SB-269970 ameliorated both acute and chronic colitis induced by DSS. Treatment with SB-269970 resulted in lower clinical disease, histological damage, and proinflammatory cytokine levels compared with vehicle-treated mice post-DSS. Colitis severity was significantly lower in 5-HT7(-/-) mice and in mice reconstituted with bone marrow cells from 5-HT7(-/-) mice compared with control mice after DSS colitis. 5-HT7(-/-) mice also had significantly reduced DNBS-induced colitis. These observations provide us with novel information on the critical role of the 5-HT7 receptor in immune response and inflammation in the gut, and highlight the potential benefit of targeting this receptor to alleviate the severity of intestinal inflammatory disorders such as inflammatory bowel disease.

5-HT2A receptor antagonists inhibit hepatic stellate cell activation and facilitate apoptosis

BACKGROUND

5-hydroxytryptamine (5-HT) receptors are upregulated in activated hepatic stellate cells (HSCs), and are therefore thought to play an important role in their activation.

AIM

The aim of this study was to determine whether 5-HT2A receptor antagonists affect the activation or apoptosis of HSCs in vitro and/or in vivo.

METHODS

For the in vitro experiments, the viability, apoptosis and wound healing ability of LX-2 cells were examined after treatment with various 5-HT2A receptor antagonists. Levels of HSC activation markers (procollagen type I, α-SMA, TGF-β and Smad 2/3) were measured. For in vivo experiments, rats were divided into three groups: (i) a control group, (ii) a disease group, in which cirrhosis was induced by thioacetamide (iii) a treatment group, in which cirrhosis was induced and a 5-HT2A receptor antagonist (sarpogrelate, 30 mg/kg) was administered.

RESULTS

5-HT2A , but not 5-HT2B receptor mRNA increased with time upon HSC activation. 5-HT2A receptor antagonists (ketanserin and sarpogrelate) inhibited viability and wound healing in LX-2 cells and induced apoptosis. Expression of α-SMA and procollagen type I was also inhibited. In the in vivo study, lobular inflammation was reduced in the sarpogrelate-treated group, but there was only slight and statistically insignificant attenuation of periportal fibrosis. Expression of α-SMA, TGF-β and Smad 2/3 was also reduced in the treatment group.

CONCLUSIONS

5-HT2A receptor antagonists can reduce inflammation and the activation of HSCs in this cirrhotic model.

Peptide YY3-36 and 5-hydroxytryptamine mediate emesis induction by trichothecene deoxynivalenol (vomitoxin)

Deoxynivalenol (DON, vomitoxin), a trichothecene mycotoxin produced by Fusarium sp. that frequently occurs in cereal grains, has been associated with human and animal food poisoning. Although a common hallmark of DON-induced toxicity is the rapid onset of emesis, the mechanisms for this adverse effect are not fully understood. Recently, our laboratory has demonstrated that the mink (Neovison vison) is a suitable small animal model for investigating trichothecene-induced emesis. The goal of this study was to use this model to determine the roles of two gut satiety hormones, peptide YY3-36 (PYY3-36) and cholecystokinin (CCK), and the neurotransmitter 5-hydroxytryptamine (5-HT) in DON-induced emesis. Following ip exposure to DON at 0.1 and 0.25mg/kg bw, emesis induction ensued within 15-30min and then persisted up to 120min. Plasma DON measurement revealed that this emesis period correlated with the rapid distribution and clearance of the toxin. Significant elevations in both plasma PYY3-36 (30-60min) and 5-HT (60min) but not CCK were observed during emesis. Pretreatment with the neuropeptide Y2 receptor antagonist JNJ-31020028 attenuated DON- and PYY-induced emesis, whereas the CCK1 receptor antagonist devezapide did not alter DON's emetic effects. The 5-HT3 receptor antagonist granisetron completely suppressed induction of vomiting by DON and the 5-HT inducer cisplatin. Granisetron pretreatment also partially blocked PYY3-36-induced emesis, suggesting a potential upstream role for this gut satiety hormone in 5-HT release. Taken together, the results suggest that both PYY3-36 and 5-HT play contributory roles in DON-induced emesis.

Influence of the serotonin transporter 5HTTLPR polymorphism on symptom severity in irritable bowel syndrome

5HTTLPR polymorphism of serotonin transporter yields short (S) and long (L) alleles. SS and LS genotypes are associated with reduced expression of serotonin transporter. This cross-sectional study investigated the association of 5HTTLPR with symptom severity of irritable bowel syndrome (IBS). Patients with IBS (Rome III) and healthy controls were included. Genomic DNA was extracted from saliva, and 5HTTLPR alleles were assessed by polymerase chain reaction. IBS symptom severity was evaluated by means of IBS-SSS questionnaire. Two hundreds and four IBS patients (159 females; mean age: 39.6±12.3 years; 106 with constipation: C-IBS; 98 with diarrhea: D-IBS) and 200 healthy controls (154 females; mean age: 40.4±15.8 years) were enrolled. The overall IBS-SSS value was higher in LS/SS than LL patients (319.0±71.5 versus 283.8±62.3; P = 0.0006). LS/SS patients had also higher values of abdominal pain (59.7±21.0 versus 51.0±18.8; P = 0.020) and bowel dissatisfaction (80.1±23.9 versus 70.5±22.8; P = 0.035). The overall IBS-SSS values in C-IBS and D-IBS patients were 317.2±68.3 and 296.1±71.4, respectively (P = 0.192), with significantly higher values for abdominal distension (65.0±24.4 versus 51.4±24.8; P = 0.0006), but not for bowel dissatisfaction (80.5±21.7 versus 72.9±25.7; P = 0.138). Frequencies of 5HTTLPR genotypes did not differ significantly when comparing IBS patients (overall or upon stratification in C-IBS and D-IBS) with healthy controls. In conclusion, the LS and SS genotypes are significantly correlated with IBS symptom severity, although their possible direct causal role remains to be proven. In addition, the present findings do not support an association of 5HTTLPR with IBS or its clinical presentation in terms of bowel habit predominance.

Altered neuro-endocrine-immune pathways in the irritable bowel syndrome: the top-down and the bottom-up model

The interaction between the brain and the gut as a pathological mechanism of functional gastrointestinal disorders has been recently recognized in the pathophysiology of the irritable bowel syndrome. Communication between central nervous system and enteric nervous system is two-directional: the brain can influence the function of the enteric nervous system and the gut can influence the brain via vagal and sympathetic afferents. In patients with irritable bowel syndrome, symptoms may be caused by alterations either primarily in the central nervous system (top-down model), or in the gut (bottom-up model), or in a combination of both. The brain-gut axis may be stimulated by various stressors either directed to the central nervous system (exteroreceptive stress) or to the gut (interoceptive stress). Particularly, clinical evidence suggest that in complex and multifactorial diseases such as irritable bowel syndrome, psychological disorders represent significant factors in the pathogenesis and course of the syndrome. Neuroimaging techniques have shown functional differences between central process in healthy subjects and patients with irritable bowel syndrome. Moreover, a high prevalence of psychological/psychiatric disorders have been reported in IBS patients compared to controls. Several data also suggest an alteration of neuro-endocrine and autonomic output to the periphery in these patients. This review will examine and discuss the complex interplay of neuro-endocrine-immune pathways, closely associated with neuropsychiatric disorders.

Genetic polymorphism of pri-microRNA 325, targeting SLC6A4 3'-UTR, is closely associated with the risk of functional dyspepsia in Japan

BACKGROUND

The role of genetics in the susceptibility to functional dyspepsia (FD) remains unclear. We attempted to clarify the association between FD and polymorphisms in SLC6A4. In addition, rs5981521 (C>T) in the pri-microRNA 325 (pri-miR-325) coding region was also investigated.

METHODS

The study was performed in 395 subjects (172 with no upper abdominal symptoms and 223 with FD, including medication-resistant FD). We employed a polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) method to detect gene polymorphisms.

RESULTS

Neither SLC6A4 -185 A>C nor *463 G>T was associated with susceptibility to FD. The number of rs5981521 T alleles was significantly correlated with an increased risk for FD (odds ratio [OR] 1.45, 95 % confidence interval [CI] 1.05-1.98; p = 0.022) and the TT homozygote was more closely associated with the risk for FD (OR 3.01, 95 % CI 1.41-6.42; p = 0.0043). The TT homozygote also had significantly increased risks for both the epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS) subtypes of FD (OR 3.04, 95 % CI 1.25-7.42; p = 0.014 and OR 3.05, 95 % CI 1.14-8.13; p = 0.026, respectively). In addition, Helicobacter pylori-negative TT homozygotes had a greater risk for FD (OR 8.37, 95 % CI 1.78-39.5; p = 0.0072). In subjects with the SLC6A4 5'-untranslated region (UTR) wild homozygote, the number of rs5981521 T alleles was significantly correlated to an increased risk for FD (OR 1.45, 95 % CI 1.03-2.04, p = 0.033). Of note, in subjects who were SLC6A4 3'-UTR mutant carriers, the number of rs5981521 T alleles was also significantly correlated with an increased risk for FD (OR 2.07, 95 % CI 1.08-3.98; p = 0.029).

CONCLUSIONS

Our results suggest that the genetic polymorphism pri-miR-325 is associated with FD and interacts with SLC6A4 polymorphisms in increasing susceptibility to FD in Japanese.

Contributions of the microbial hydrogen economy to colonic homeostasis

Colonic gases are among the most tangible features of digestion, yet physicians are typically unable to offer long-term relief from clinical complaints of excessive gas. Studies characterizing colonic gases have linked changes in volume or composition with bowel disorders and shown hydrogen gas (H(2)), methane, hydrogen sulphide, and carbon dioxide to be by-products of the interplay between H(2)-producing fermentative bacteria and H(2) consumers (reductive acetogens, methanogenic archaea and sulphate-reducing bacteria [SRB]). Clinically, H(2) and methane measured in breath can indicate lactose and glucose intolerance, small intestinal bacterial overgrowth and IBS. Methane levels are increased in patients with constipation or IBS. Hydrogen sulphide is a by-product of H(2) metabolism by SRB, which are ubiquitous in the colonic mucosa. Although higher hydrogen sulphide and SRB levels have been detected in patients with IBD, and to a lesser extent in colorectal cancer, this colonic gas might have beneficial effects. Moreover, H(2) has been shown to have antioxidant properties and, in the healthy colon, physiological H(2) concentrations might protect the mucosa from oxidative insults, whereas an impaired H(2) economy might facilitate inflammation or carcinogenesis. Therefore, standardized breath gas measurements combined with ever-improving molecular methodologies could provide novel strategies to prevent, diagnose or manage numerous colonic disorders.

Tianeptine vs amitriptyline for the treatment of irritable bowel syndrome with diarrhea: a multicenter, open-label, non-inferiority, randomized controlled study

BACKGROUND

Tricyclic antidepressants have good efficacy in irritable bowel syndrome with diarrhea (IBS-D), but their clinical use is limited by considerations of tolerability. Tianeptine, another antidepressant, acts as a selective serotonin reuptake enhancer. We compared tianeptine with amitriptyline for the treatment of patients with IBS-D.

METHODS

We undertook a multicenter, randomized, open-label, non-inferiority clinical study that compared tianeptine with amitriptyline, each in combination with probiotics, for the treatment of IBS-D. Subjects were randomized to receive tianeptine (37.5 mg)/probiotics (Bacillus subtilis + Streptococcus faecium) or amitriptyline (10 mg)/probiotics (Bacillus subtilis + Streptococcus faecium) for 4 weeks. A total of 228 patients were analyzed by the intention-to-treat approach. The primary efficacy endpoint was the proportion of patients who had global relief of IBS symptoms at week 4. The secondary efficacy endpoints were intensity of abdominal pain/discomfort, stool frequency/consistency, quality of life, and overall satisfaction with treatment.

KEY RESULTS

At week 4, non-inferiority of the tianeptine group to the amitriptyline group (treatment difference -15.1%; 95% CI -26.6% to -3.8%) was shown, with 81.1% (99 of 122 patients) of the patients in the tianeptine group and 66.0% (70 of 106 patients) in the amitriptyline group reporting global relief of IBS symptoms. The secondary endpoints also demonstrated non-inferiority of the tianeptine group to the amitriptyline group. Adverse events such as dry mouth and constipation were significantly lower in the tianeptine group than the amitriptyline group (P<0.05).

CONCLUSIONS & INFERENCES

Tianeptine is not inferior to amitriptyline for treating IBS-D in terms of both efficacy and tolerability.

Evolving molecular targets in the treatment of nonmalignant gastrointestinal diseases

Novel treatments for gastrointestinal (GI) diseases are based on molecular targets. Novel pharmacologic and biological agents with greater selectivity and specificity are being developed for a variety of epithelial diseases, including eosinophilic esophagitis (EoE), gastroesophageal reflux disease (GERD), celiac disease, short bowel syndrome (SBS), and inflammatory bowel diseases (IBDs; Crohn's disease and ulcerative colitis). Motility and secretory agents are being developed for gastroparesis, irritable bowel syndrome (IBS), functional constipation, and diarrhea. Here we focus on data from clinical trials involving validated pharmacodynamic or patient response outcomes.

Does acupuncture therapy alter activation of neural pathway for pain perception in irritable bowel syndrome?: a comparative study of true and sham acupuncture using functional magnetic resonance imaging

Background/Aims

Patients with irritable bowel syndrome (IBS) are characterized by abnormal central processing with altered brain activation in response to visceral nociceptive signals. The effect of electroacupuncture (EA) on IBS patients is unclear. The study is set to study the effect of EA on brain activation during noxious rectal distension in IBS patients using a randomized sham-controlled model.

Methods

Thirty IBS-diarrhea patients were randomized to true electroacupuncture or sham acupuncture. Functional MRI was performed to evaluate cerebral activation at the following time points: (1) baseline when there was rectal distension only, (2) rectal distension during application of EA, (3) rectal distension after cessation of EA and (4) EA alone with no rectal distension. Group comparison was made under each condition using SPM5 program.

Results

Rectal distension induced significant activation of the anterior cingulated cortex, prefrontal cortex, thalamus, temporal regions and cerebellum at baseline. During and immediately after EA, increased cerebral activation from baseline was observed in the anterior cingulated cortex, bilateral prefrontal cortex, thalamus, temporal regions and right insula in both groups. However, true electroacupuncture led to significantly higher activation at right insula, as well as pulvinar and medial nucleus of the thalamus when compared to sham acupuncture.

Conclusions

We postulate that acupuncture might have the potential effect of pain modulation in IBS by 2 actions: (1) modulation of serotonin pathway at insula and (2) modulation of mood and affection in higher cortical center via ascending pathway at the pulvinar and medial nucleus of the thalamus.

Irritable bowel syndrome: methods, mechanisms, and pathophysiology. Genetic epidemiology and pharmacogenetics in irritable bowel syndrome

The objectives of this review are twofold. Our first objective is to evaluate the evidence supporting a role for genetics in irritable bowel syndrome (IBS). Specific examples of the associations of genetic variation and symptoms, syndromes, and intermediate phenotypes, including neurotransmitter (serotonergic, α(2)-adrenergic, and cannabinoid) mechanisms, inflammatory pathways (IL-10, TNFα, GNβ3, and susceptibility loci involved in Crohn's disease), and bile acid metabolism, are explored. The second objective is to review pharmacogenetics in IBS, with the focus on cytochrome P-450 metabolism of drugs used in IBS, modulation of motor and sensory responses to serotonergic agents based on the 5-hydroxytryptamine (5-HT) transporter-linked polymorphic region (5-HTTLPR) and 5-HT(3) genetic variants, responses to a nonselective cannabinoid agonist (dronabinol) based on cannabinoid receptor (CNR1) and fatty acid amide hydrolase (FAAH) variation, and responses to a bile acid (sodium chenodeoxycholate) and bile acid binding (colesevelam) based on klothoβ (KLB) and fibroblast growth factor receptor 4 (FGFR4) variation. Overall, there is limited evidence of a genetic association with IBS; the most frequently studied association is with 5-HTTLPR, and the most replicated association is with TNF superfamily member 15. Most of the pharmacogenetic associations are reported with intermediate phenotypes in relatively small trials, and confirmation in large clinical trials using validated clinical end points is still required. No published genome-wide association studies in functional gastrointestinal or motility disorders have been published.

Serotonin-immunoreactive neurons and mast cells in the mouse esophagus suggest involvement of serotonin in both motility control and neuroimmune interactions

BACKGROUND

Serotonin is a major transmitter in the gastrointestinal tract, but little is known about the serotonergic system in the esophagus.

METHODS

The aim of this study was to use multilabel immunofluorescence to characterize serotonin-positive nerve cell bodies and fibers and their relationship with other neuronal and non-neuronal elements in the mouse esophagus. Antibodies against serotonin, vesicular acetylcholine transporter (VAChT), choline acetyltransferase (ChAT), protein gene product 9.5 (PGP 9.5), and α-bungarotoxin (α-BT), were used.

KEY RESULTS

Serotonin-containing perikarya represented ∼10% of all PGP 9.5-positive myenteric neurons. Serotonin-positive varicose nerve fibers were found in the lamina muscularis mucosae and present on ∼13% of α-BT-labeled motor endplates in addition to VAChT-immunoreactive motor terminals. As ChAT-positive neurons of the compact formation of the nucleus ambiguus were negative for serotonin, serotonin-positive varicosities on motor endplates are presumed to be of enteric origin. On the other hand, cholinergic ambiguus neurons were densely supplied with serotonin-positive varicosities. The tela submucosa and tunica adventitia contained large numbers of serotonin-positive mast cells, a few of which were in close association with serotonin-positive nerve fibers.

CONCLUSIONS & INFERENCES

The mouse esophagus is endowed with a rich serotonin-positive intrinsic innervation, including enteric co-innervation of striated muscles. Serotonin may modulate vagal motor innervation of esophageal-striated muscles not only at the central level via projections of the raphe nuclei to the nucleus ambiguus but also at the peripheral level via enteric co-innervation. In addition, mast cells represent a non-neuronal source of serotonin, being involved in neuroimmune processes.

Characteristics of 5-hydroxytryptamine receptors involved in contraction of feline ileal longitudinal smooth muscle

A number of studies have demonstrated that 5-hydroxytryptamine (5-HT) can induce muscle contraction or relaxation response and enhance secretion in the gastrointestinal tract via a multiplicity of 5-HT receptor subtypes. In the present study, we investigated the pharmacological characterization of the 5-HT-induced contractile response in longitudinal smooth muscle isolated from the feline ileum. Addition of 5-HT into muscle chambers enhanced the basal tone and spontaneous activity in a concentration-dependent manner. The neurotoxin tetrodotoxin did not alter the 5-HT-induced contraction of the longitudinal muscles. Neither atropine nor guanethidine affected the contraction. The 5-HT agonists, 5-methylserotonin hydrochloride and mosapride, also evoked concentration-dependent contractions. The 5-HT-induced contraction was enhanced by the 5HT(2) receptor antagonist ketanserin and the 5-HT(3) receptor antagonist ondansetron but was inhibited by the 5-HT(1) receptor antagonist methysergide and 5-HT(4) receptor antagonist GR113808. These results indicate that 5-HT(1) and 5-HT(4) receptors may mediate the contraction of the 5-HT-induced response and 5-HT(2) and 5-HT(3) receptors may mediate 5-HT-induced relaxation in feline ileal longitudinal smooth muscles.

Infection of human enteroendocrine cells with Chlamydia trachomatis: a possible model for pathogenesis in irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a widespread gastrointestinal disorder of unknown etiology. Recently, our group detected chlamydial antigens in enteroendocrine cells (EEC) of jejunum biopsies from patients with IBS. Impairment of EEC secretion upon Chlamydia infection might lead to disturbances of gut functions. We have therefore studied the interaction between Chlamydia and EEC in vitro.

METHODS

Two different human enteroendocrine cell lines were studied: LCC-18 from a neuroendocrine colonic tumour and CNDT2 from a small intestinal carcinoid. Cell lines were infected with C. trachomatis serovar LGV II strain 434. We used Penicillin G for inducing persistent infection. The ultrastructure of infected cells was studied using transmission electron microscopy and immunofluorescence and we used RT-PCR analysis for studying changes in gene expression at different stages of infection.

KEY RESULTS

We found that both cell lines could be infected with C. trachomatis yielding productive infections and persistence could be induced using penicillin G. Immunofluorescence showed different cellular distributions of serotonin and chromogranin A in non-infected (cytoplasmatic distribution) compared with infected cells (serotonin and chromogranin mostly in chlamydial inclusions). In line with the microscopical findings, we found a significant down-regulation of the gene coding for the vesicular monoamine transporter (VMAT1) in infected compared with non-infected EEC (P<0.05).

CONCLUSIONS & INFERENCES

Altered protein distributions together with down-regulation of VMAT1 suggest that chlamydial infection may influence vesicular transport. It is therefore possible that such an infection in vivo could lead to disturbances in the regulation of gut functions.

Gut hormones: emerging role in immune activation and inflammation

Gut inflammation is characterized by mucosal recruitment of activated cells from both the innate and adaptive immune systems. In addition to immune cells, inflammation in the gut is associated with an alteration in enteric endocrine cells and various biologically active compounds produced by these cells. Although the change in enteric endocrine cells or their products is considered to be important in regulating gut physiology (motility and secretion), it is not clear whether the change plays any role in immune activation and in the regulation of gut inflammation. Due to the strategic location of enteric endocrine cells in gut mucosa, these gut hormones may play an important role in immune activation and promotion of inflammation in the gut. This review addresses the research on the interface between immune and endocrine systems in gastrointestinal (GI) pathophysiology, specifically in the context of two major products of enteric endocrine systems, namely serotonin (5-hydroxytryptamine: 5-HT) and chromogranins (Cgs), in relation to immune activation and generation of inflammation. The studies reviewed in this paper demonstrate that 5-HT activates the immune cells to produce proinflammatory mediators and by manipulating the 5-HT system it is possible to modulate gut inflammation. In the case of Cgs the scenario is more complex, as this hormone has been shown to play both proinflammatory and anti-inflammatory functions. It is also possible that interaction between 5-HT and Cgs may play a role in the modulation of immune and inflammatory responses. In addition to enhancing our understanding of immunoendocrine interaction in the gut, the data generated from the these studies may have implications in understanding the role of gut hormone in the pathogenesis of both GI and non-GI inflammatory diseases which may lead ultimately to improved therapeutic strategies in inflammatory disorders.

Serotonin Catabolism and the Formation and Fate of 5-Hydroxyindole Thiazolidine Carboxylic Acid

Serotonin (5-HT) functions as a neurotransmitter and neuromodulator in both the central and enteric nervous systems of mammals. The dynamic degradation of 5-HT metabolites in 5-HT-containing nervous system tissues is monitored by capillary electrophoresis with wavelength-resolved laser-induced native fluorescence detection in an effort to investigate known and novel 5-HT catabolic pathways. Tissue samples from wild type mice, genetically altered mice, Long Evans rats, and cultured differentiated rat pheochromocytoma PC-12 cells, are analyzed before and after incubation with excess 5-HT. From these experiments, several new compounds are detected. One metabolite, identified as 5-hydroxyindole thiazoladine carboxylic acid (5-HITCA), has been selected for further study. In 5-HT-incubated central and enteric nervous system tissue samples and differentiated PC-12 cells, 5-HITCA forms at levels equivalent to 5-hydroxyindole acetic acid, via a condensation reaction between L-cysteine and 5-hydroxyindole acetaldehyde. In the enteric nervous system, 5-HITCA is detected without the addition of 5-HT. The levels of L-cysteine and homocysteine in rat brain mitochondria are measured between 80 and 140 microm and 1.9 and 3.4 microm, respectively, demonstrating that 5-HITCA can be formed using available, free L-cysteine in these tissues. The lack of significant accumulation of 5-HITCA in the central and enteric nervous systems, along with data showing the degradation of 5-HITCA into 5-hydroxyindole acetaldehyde, suggests that an equilibrium coupled to the enzyme, aldehyde dehydrogenase type 2, prevents the accumulation of 5-HITCA. Even so, the formation of 5-HITCA represents a catabolic pathway of 5-HT that can affect the levels of 5-HT-derived compounds in the body.

Effects of Tegaserod on Ileal Peristalsis of Guinea Pig In Vitro

The mechanisms of prokinetic action of tegaserod in the gastrointestinal tract has not been studied in detail. The aim of this study was to investigate the effect of tegaserod on peristaltic reflexes and propagating peristaltic waves in guinea pig ileum. A partitioned organ bath divided into three chambers was used to investigate the effect of tegaserod on peristaltic reflexes. A sensory stimulus was applied to the intermediate chamber, and changes in the circular muscle tension were monitored in a peripheral chamber. Another peristaltic bath was used to investigate the effect of tegaserod on peristaltic waves induced by intraluminal perfusion. Guinea pig ileum exhibited contractions in the circular muscle both orally and anally in response to mucosal stroking. Tegaserod (10(-8) - 10(-6) M) did not influence the maximal amplitude and the area under the curve of contraction both orally and anally to a mucosal stimulus. Intraluminal perfusion of fluid containing tegaserod (10(-8) - 10(-6) M) significantly increased the number of peristaltic waves in a concentration-dependent manner (P<0.05). Also, tegaserod (10(-8) - 10(-6) M) significantly increased the area under the curve of peristaltic waves (P<0.05). It is concluded that tegaserod has prokinetic action on guinea pig ileum by increasing the number of the circular muscle contractions during peristalsis.