Cyclooxygenase-dependent alterations in substance P-mediated contractility and tachykinin NK1 receptor expression in the colonic circular muscle of patients with slow transit constipation

Effects of Lactiplantibacillus plantarum GUANKE on Diphenoxylate-Induced Slow Transit Constipation and Gut Microbiota in Mice

Slow transit constipation (STC) is a prevalent gastrointestinal condition with slow transit, and some probiotics can effectively relieve constipation, but the exact mechanisms have not been fully understood. In this study, we evaluate the impact of Lactiplantibacillus plantarum GUANKE (GUANKE) on diphenoxylate-induced slow transit constipation and speculate on the underlying mechanisms in a mouse model. Administration of L. plantarum GUANKE alleviated constipation indexes, including defecation time, fecal output and water content, and gastrointestinal transit ratio. In addition, GUANKE restored the protein expression of constipation-related intestinal factors (aquaporins (AQPs) and interstitial Cajal cells (ICCs)) in colon tissues measured using immunofluorescence staining; regulated the neurotransmitters and hormones, such as increased levels of 5-hydroxytryptamine, substance P, and motilin; and decreased levels of vasoactive intestinal peptide and nitric oxide in serum, as measured by an ELISA. 16S rRNA and correlation analysis of feces indicated that GUANKE administration effectively reduced constipation-induced Prevotella enrichment and suggested a potential contribution of Prevotella to diphenoxylate-induced STC in mice. GUANKE had no effect on short-chain fatty acids (SCFAs) in cecum content. This study revealed that GUANKE may alleviate constipation in mice through regulating intestinal neurotransmitter and hormone release and altering specific bacterial taxa, rather than by affecting SCFAs and the diversity of microbiota in the gut. Further research is needed to confirm if the findings observed in this study will be consistent in other animal studies or clinical trials.

Targeting Mechano-Transcription Process as Therapeutic Intervention in Gastrointestinal Disorders

Mechano-transcription is a process whereby mechanical stress alters gene expression. The gastrointestinal (GI) tract is composed of a series of hollow organs, often encountered by transient or persistent mechanical stress. Recent studies have revealed that persistent mechanical stress is present in obstructive, functional, and inflammatory disorders and alters gene transcription in these conditions. Mechano-transcription of inflammatory molecules, pain mediators, pro-fibrotic and growth factors has been shown to play a key role in the development of motility dysfunction, visceral hypersensitivity, inflammation, and fibrosis in the gut. In particular, mechanical stress-induced cyclooxygenase-2 (COX-2) and certain pro-inflammatory mediators in gut smooth muscle cells are responsible for motility dysfunction and inflammatory process. Mechano-transcription of pain mediators such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) may lead to visceral hypersensitivity. Emerging evidence suggests that mechanical stress in the gut also leads to up-regulation of certain proliferative and pro-fibrotic mediators such as connective tissue growth factor (CTGF) and osteopontin (OPN), which may contribute to fibrostenotic Crohn's disease. In this review, we will discuss the pathophysiological significance of mechanical stress-induced expression of pro-inflammatory molecules, pain mediators, pro-fibrotic and growth factors in obstructive, inflammatory, and functional bowel disorders. We will also evaluate potential therapeutic targets of mechano-transcription process for the management of these disorders.

Gender-Related Differences of Tachykinin NK2 Receptor Expression and Activity in Human Colonic Smooth Muscle

The tachykinin NK2 receptor plays a key role in gastrointestinal motor function. Enteric neurons release neurokinin A (NKA), which activates NK2 receptors on gastrointestinal smooth muscle, leading to contraction and increased motility. In patients with diarrhea-predominant irritable bowel syndrome, the NK2 receptor antagonist ibodutant had a greater therapeutic effect in females than males. The present study aimed to determine whether gender influences the expression and activity of NK2 receptors in human colonic smooth muscle. In vitro functional studies were performed to examine the contractile responses of colonic muscle strips to NKA and the selective NK2 receptor agonist [Lys5,MeLeu9,Nle10]NKA(4-10). Contractions were also measured in the presence of ibodutant to determine its antagonistic potency. The signal transduction pathways coupled to NK2 receptor activation were investigated using second messenger inhibitors. Western blot and fluorescent immunohistochemistry were conducted to determine the protein expression and localization of NK2 receptors. NK2 receptor-mediated contractility was greater in females compared with males. When against NKA, ibodutant was more potent in females. NK2 receptor expression increased with age in females, but not in males. Phospholipase C-mediated signaling was less prominent in females compared with males, whereas Ca2+ sensitization via Rho kinase and protein kinase C appeared to be the dominant pathway in both genders. The distribution of NK2 receptors in the human colon did not differ between the genders. Overall, gender differences exist in the expression and activity of NK2 receptors in colonic smooth muscle. These gender distinctions should be considered in the therapeutic development of NK2 receptor agents. SIGNIFICANCE STATEMENT: The tachykinin NK2 receptor has been identified as a therapeutic target for the treatment of bowel and bladder dysfunctions. The present study has revealed gender-related variations in NK2 receptor activity, signaling transduction pathways, antagonist potency, and changes in expression with age. These factors may underlie the gender differences in the treatment of diarrhea-predominant irritable bowel syndrome with NK2 receptor antagonists. Our findings highlight that gender differences should be considered in the therapeutic development of NK2 receptor agents.

Cystic fibrosis transmembrane conductance regulator modulates enteric cholinergic activities and is abnormally expressed in the enteric ganglia of patients with slow transit constipation

BACKGROUND

Cystic fibrosis transmembrane conductance regulator (CFTR) was recently found in the enteric nervous system, where its role is unclear. We aimed to identify which enteric neuronal structures express CFTR, whether CFTR modulates enteric neurotransmission and if altered CFTR expression is associated with slow transit constipation (STC).

METHODS

Immunofluorescence double labeling was performed to localize CFTR with various neuronal and glial cell markers in the human colon. The immunoreactivity (IR) of CFTR and choline acetyltransferase (ChAT) on myenteric plexus of control and STC colon was quantitatively analyzed. In control colonic muscle strips, electrical field stimulation (EFS) evoked contractile responses and the release of acetylcholine (ACh) was measured in the presence of the CFTR channel inhibitor, CFTR(inh)-172.

RESULTS

CFTR-IR was densely localized to myenteric ganglia, where it was co-localized with neuronal markers HuC/D and β-tubulin, and glial marker S-100 but little with glial fibrillary acidic protein. Vesicular ACh transport was almost exclusively co-localized with CFTR, but neurons expressing nitric oxide synthase were CFTR negative. Significant reductions of CFTR-IR (P < 0.01) and ChAT-IR (P < 0.05) were observed on myenteric ganglia of STC compared to control. Pre-treatment of colonic muscle strips with CFTR(inh)-172 (10 µM) significantly inhibited EFS-evoked contractile responses (P < 0.01) and ACh release (P < 0.05).

CONCLUSIONS

Co-localization of CFTR-IR with cholinergic markers, inhibition of EFS-induced colonic muscle contractility and ACh release by CFTR(inh)-172 suggest that CFTR modulates enteric cholinergic neurotransmission. The downregulation of CFTR and ChAT in myenteric ganglia of STC correlated with the impaired contractile responses to EFS.

The Manufacturing Process of Kiwifruit Fruit Powder with High Dietary Fiber and Its Laxative Effect

Kiwifruit is rich in vitamins, minerals, dietary fiber and other functional components, and it has long been used as a functional food to treat intestinal ailments such as constipation. The current research made full use of the kiwifruit, the juice was prepared by microencapsulation, and the dietary fiber in kiwifruit pomace was modified by enzymatic hydrolysis and grinding, then, the two were mixed to obtain an ultra-micro kiwifruit powder (UKP). In addition, the laxative effect of the UKP was verified by a diphenoxylate induced constipated mice model. The results demonstrated that compared with the raw samples, the retention rate of vitamin C, lutein and catechin in UKP were 83.3%, 81.9% and 88.3%, respectively, thus effectively avoiding the loss of functional components during the processing of kiwifruit. Moreover, α-amylase, protease and the ball milling process effectively reduced the size of dietary fiber in kiwifruit pomace, and its water-holding capacity (WHC), oil-holding capacity (OHC) and swelling capacity (SWC) were enhanced by 1.26, 1.65 and 1.10 times, respectively. Furthermore, to analyze the laxative effect of the UKP, a constipation mice model was established by diphenoxylate treatment (5 mg·kg⁻¹, i.g.) for the last week, with or without UKP supplementation (2.4 g·kg⁻¹ B.W. per day) for 4 weeks. The results demonstrated that UKP significantly increased feces condition (fecal output and dejecta moisture content, gut transit (the intestinal propulsion rates) and substance P (SP) levels in portal vein plasma, and it decreased the whole gut transit time and mucinogen granules secreted by goblet cell in constipated mice.

The role of substance P in the maintenance of colonic hypermotility induced by repeated stress in rats

BACKGROUND

The mechanism underlying chronic stress-induced gastrointestinal (GI) dysmotility has not been fully elucidated and GI hormones have been indicated playing a role in mediating stress-induced changes in GI motor function.

AIMS

Our objective was to study the possible role of substance P (SP) in the colonic hypermotility induced by repeated water avoidance stress (WAS) which mimics irritable bowel syndrome.

METHODS

Male Wistar rats were submitted to WAS or sham WAS (SWAS) (1h/day) for up to 10 consecutive days. Enzyme Immunoassay Kit was used to detect the serum level of SP. The expression of neurokinin-1 receptor (NK1R) was investigated by Immunohistochemistry and Western blotting. The spontaneous contraction of muscle strip was studied in an organ bath system. L-type calcium channel currents (ICa,L) of smooth muscle cells (SMCs) were recorded by whole-cell patch-clamp technique.

RESULTS

Fecal pellet expulsion and spontaneous contraction of proximal colon in rats were increased after repeated WAS. The serum level of SP was elevated following WAS. Immunohistochemistry proved the expression of NK1R in mucosa, muscularis and myenteric plexus. Western blotting demonstrated stress-induced up-regulation of NK1R in colon devoid of mucosa and submucosa. Repeated WAS increased the contractile activities of longitudinal muscle and circular muscle strips induced by SP and this effect was reversed by a selective NK1R antagonist. The ICa,L of SMCs in the WAS rats were drastically increased compared to controls after addition of SP.

CONCLUSIONS

Increased serum SP level and up-regulated NK1R in colon may contribute to stress-induced colonic hypermotility. And L-type calcium channels play a potentially important role in the process of WAS-induced dysmotility.

Brain-Derived Neurotrophic Factor Contributes to Colonic Hypermotility in a Chronic Stress Rat Model

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has prokinetic effects on gut motility and is increased in the colonic mucosa of irritable bowel syndrome.

AIMS

We aimed to investigate the possible involvement of BDNF in stress-induced colonic hypermotility.

METHODS

Male Wistar rats were exposed to daily 1-h water avoidance stress (WAS) or sham WAS for 10 consecutive days. The presence of BDNF and substance P (SP) in the colonic mucosa was determined using enzyme immunoassay kits. Immunohistochemistry and western blotting were performed to assess the expression of BDNF and its receptor, TrkB. The contractions of muscle strips were studied in an organ bath system.

RESULTS

Repeated WAS increased the fecal pellet expulsion and spontaneous contractile activities of the colonic muscle strips. Both BDNF and SP in the colonic mucosa were elevated following WAS. Immunohistochemistry revealed the presence of BDNF and TrkB in the mucosa and myenteric plexus. BDNF and TrkB were both up-regulated in colon devoid of mucosa and submucosa from the stressed rats compared with the control. BDNF pretreatment caused an enhancement of the SP-induced contraction of the circular muscle (CM) strips. TrkB antibody significantly inhibited the contraction of the colonic muscle strips and attenuated the excitatory effects of SP on contractions of the CM strips. Repeated WAS increased the contractile activities of the CM strips induced by SP after BDNF pretreatment, and this effect was reversed by TrkB antibody.

CONCLUSIONS

The colonic hypermotility induced by repeated WAS may be associated with the increased expression of endogenous BDNF and TrkB. BDNF may have potential clinical therapeutic use in modulating gut motility.

Clinical study of electro-acupuncture treatment with different intensities for functional constipation patients

Functional constipation (FC) is a common functional bowel disorder disease that affects life quality of a large number of people. This study aimed to explore the impact of different intensities of electro-acupuncture (EA) treatment for FC patients. Totally, 111 patients with FC meeting the Rome III criteria were randomly assigned to different intensities of EA groups (low and high intensity of EA groups) and medicine-controlled (MC) group. In EA groups, patients were treated with EA at quchi (LI11) and shangjuxu (ST37) bilaterally for 4 weeks, 5 times/week in the first 2 weeks, and 3 times/week in the last 2 weeks. In MC group, 5 mg mosapride citrate was administered orally 3 times/day for 4 weeks. Spontaneous bowel movement frequency each day was recorded using a constipation diary. Self-rating anxiety scale (SAS) and self-rating depression scale (SDS) were used to assess the patients' psychological state. Cortisol (CORT), substance P (SP), and vasoactive intestinal polypeptide (VIP) were evaluated at baseline and at the end of 4 weeks after treatment. As compared with the baseline, there was statistically significant increase in stool frequency every week (P<0.01), but there was no statistically significant difference among the three groups. As compared with the baseline, after 4 weeks of EA therapy, the scores of SDS and serum levels of CORT were decreased significantly in low intensity of EA group (P<0.01), and the serum levels of SP and VIP were increased significantly (P<0.05); the scores of SAS and SDS and serum levels of CORT were decreased significantly in high intensity of EA group (P<0.05), and the serum levels of SP and VIP were increased significantly (P<0.05); the serum levels of CORT and VIP were increased significantly in MC group (P<0.05). As compared with MC group, after 4 weeks of treatment, the serum levels of SP were signifcicantly increased in low intensity of EA group (P<0.01). Low and high intensities of EA could increase the stool frequency, improve the FC patient's anxiety and depression, reduce the serum levels of CORT, and increase the serum levels of SP and VIP effectively. It is concluded that both low and high intensities of EA are effective for FC patients, but there is no significant difference between the low and high intensities of EA.

Cellular and molecular basis of chronic constipation: taking the functional/idiopathic label out

In recent years, the improvement of technology and the increase in knowledge have shifted several strongly held paradigms. This is particularly true in gastroenterology, and specifically in the field of the so-called "functional" or "idiopathic" disease, where conditions thought for decades to be based mainly on alterations of visceral perception or aberrant psychosomatic mechanisms have, in fact, be reconducted to an organic basis (or, at the very least, have shown one or more demonstrable abnormalities). This is particularly true, for instance, for irritable bowel syndrome, the prototype entity of "functional" gastrointestinal disorders, where low-grade inflammation of both mucosa and myenteric plexus has been repeatedly demonstrated. Thus, researchers have also investigated other functional/idiopathic gastrointestinal disorders, and found that some organic ground is present, such as abnormal neurotransmission and myenteric plexitis in esophageal achalasia and mucosal immune activation and mild eosinophilia in functional dyspepsia. Here we show evidence, based on our own and other authors' work, that chronic constipation has several abnormalities reconductable to alterations in the enteric nervous system, abnormalities mainly characterized by a constant decrease of enteric glial cells and interstitial cells of Cajal (and, sometimes, of enteric neurons). Thus, we feel that (at least some forms of) chronic constipation should no more be considered as a functional/idiopathic gastrointestinal disorder, but instead as a true enteric neuropathic abnormality.

Possible role of mast cells and neuropeptides in the recovery process of dextran sulfate sodium-induced colitis in rats

OBJECTIVE

To clarify the role of mast cells and neuropeptides substance P (SP), somatostatin (SS), and vasoactive intestinal peptide (VIP) in dextran sulfate sodium (DSS)-induced colitis in rats.

METHODS

Experimental colitis was induced in Sprague-Dawley rats (180-200 g, n=20) by oral ingestion of 4% (w/v) DSS in drinking water for 7 days. Control rats (n=5) drank water and were sacrificed on day 0. Mast cell number, histamine levels in whole blood and tissue, tissue levels of SP, SS and, VIP in the distal colon of the rats were measured on day 8, day 13, and day 18 of experimentation.

RESULTS

Oral administration of 4% DSS solution for 7 days resulted in surface epithelial loss and crypt loss in the distal colon. Mast cell count increased on day 8 (1.75±1.09/mm vs. 0.38±0.24/mm, P<0.05) and day 13 (1.55±1.01/mm vs. 0.38±0.24/mm, P<0.05) after DSS treatment. Whole blood histamine levels were increased on day 8 (266.93±35.62 ng/mL vs. 76.87±32.28 ng/mL, P<0.01) and gradually decreased by day 13 and day 18 after DSS treatment. Histamine levels in the distal colon were decreased on day 8 (1.77±0.65 ng/mg vs. 3.06±0.87 ng/mg, P<0.05) and recovered to control levels by day 13 after DSS treatment. SP level in the distal colon gradually increased and were raised significantly by day 13 (8777.14±3056.14 pg/mL vs. 4739.66±3299.81 pg/mL, P<0.05) after DSS treatment. SS and VIP levels in the distal colon were not changed.

CONCLUSIONS

Mast cell degranulation followed by histamine release may play an important role in the pathogenesis of colitis induced by DSS. SP may be a significant substance in the progression of inflammation and the recovery process of DSS-induced colitis.

Brain-derived neurotrophic factor enhances the contraction of intestinal muscle strips induced by SP and CGRP in mice

BACKGROUND AND AIMS

Brain-derived neurotrophic factor (BDNF) has been found in the intestinal tract of a variety of species. Its effects on visceral hyperalgesia have been examined to some degree, but limited studies have focused on gut motility. The aim of the present study was to investigate the effects of BDNF on gut motility of mice.

METHODS

Longitudinal muscle (LM) strips were prepared from mice ileum and distal colon. The motility of gut was evaluated by the contraction of LM strips, which was recorded by a polyphisograph in vitro. Firstly, the roles of substance P (SP), calcitonin gene-related peptide (CGRP), and acetylcholine (ACh) on the contraction of LM strips were clarified. Then the exogenous BDNF was administered, and the alterations of SP/CGRP/ACh-induced contractions of the muscle strips were explored. Finally, heterozygous BDNF(+/-) mice and antibody of TrkB were introduced to investigate the role of endogenous BDNF on the SP/CGRP/ACh-induced gut motility.

KEY RESULTS

SP (10(-8)-10(-6) mol L(-1)), CGRP (10(-8)-10(-7) mol L(-1)) and ACh (10(-8)-10(-6) mol L(-1)) dose-dependently caused the contraction of LM strips from ileum and distal colon, while the excitatory effect of CGRP was preceded by a transient inhibition. But 10(-6) mol L(-1) CGRP inhibited the contraction of LM strips. Pretreatment with exogenous BDNF (10(-8) mol L(-1)) remarkably enhanced the contraction of LM strips induced by SP (10(-9)-10(-7) mol L(-1)) and CGRP (10(-8)-10(-9) mol L(-1)). However, exogenous BDNF couldn't affect the contraction induced by ACh (10(-9)-10(-7) mol L(-1)). The excitatory effects of SP (10(-8)-10(-6) mol L(-1)) and CGRP (10(-8)-10(-7) mol L(-1)) on the contractions of LM strips from ileum and distal colon were significantly attenuated in BDNF(+/-) mice compared with those in BDNF(+/+) mice, while no difference of the effects of ACh (10(-8)-10(-6) mol L(-1)) on LM strips was observed between BDNF(+/-) mice and BDNF(+/+) mice. The monoclonal antibody of TrkB (TrkB-Ab) dramatically attenuated the excitatory effects of SP and CGRP on the contractions of LM strips, without affecting the excitatory effects of ACh.

CONCLUSIONS AND INFERENCES

These data clarified the excitatory effects of SP, ACh and bilateral effects of CGRP on gut motility of mice and confirmed an essential role of BDNF on accelerating gut motility by enhancing the excitatory effects of SP/CGRP.

Visceral hypersensitivity in symptomatic diverticular disease and the role of neuropeptides and low grade inflammation

BACKGROUND

  Recurrent abdominal pain is reported by a third of patients with diverticulosis, particularly those with previous episodes of acute diverticulitis. The current understanding of the etiology of this pain is poor. Our aim was to assess visceral sensitivity in patients with diverticular disease and its association with markers of previous inflammation and neuropeptides.

METHODS

  Patients with asymptomatic and symptomatic diverticular disease underwent a flexible sigmoidoscopy and biopsy followed 5-10 days later by visceral sensitivity testing with barostat-mediated rectal distension. Inflammation was assessed by staining of serotonin (5HT) and CD3 positive cells. mRNA levels of tumor necrosis factor alpha (TNF α) and interleukin-6 (IL-6) were quantitated using RT-PCR. Neuropeptide expression was assessed from percentage area staining with substance P (SP) and mRNA levels of the neurokinin 1 & 2 receptors (NK1 & NK2), and galanin 1 receptor (GALR1).

KEY RESULTS

  Thirteen asymptomatic and 12 symptomatic patients were recruited. The symptomatic patients had a lower first reported threshold to pain (28.4 mmHg i.q.r 25.0-36.0) than the asymptomatic patients (47 mmHg i.q.r 36.0-52.5, P < 0.001). Symptomatic patients had a higher median overall pain rating for the stimuli than the asymptomatic patients (P < 0.02). Symptomatic patients had greater median relative expression of NK1 and TNF alpha mRNA compared with asymptomatic patients. There was a significant correlation between barostat VAS pain scores and NK 1 expression (Figure 4, r(2) 0.54, P < 0.02).

CONCLUSIONS & INFERENCES

  Patients with symptomatic diverticular disease exhibit visceral hypersensitivity, and this may be mediated by ongoing low grade inflammation and upregulation of tachykinins.

Characterization of motor patterns in isolated human colon: are there differences in patients with slow-transit constipation?

The patterns of motor activity that exist in isolated full-length human colon have not been described. Our aim was to characterize the spontaneous motor patterns in isolated human colon and determine whether these patterns are different in whole colons obtained from patients with slow-transit constipation (STC). The entire colon (excluding the anus), was removed from patients with confirmed STC and mounted longitudinally in an organ bath ∼120 cm in length, containing oxygenated Krebs' solution at 36°C. Changes in circular muscle tension were recorded from multiple sites simultaneously along the length of colon, by use of isometric force transducers. Recordings from isolated colons from non-STC patients revealed cyclical colonic motor complexes (CMCs) in 11 of 17 colons, with a mean interval and half-duration of contractions of 4.0 ± 0.6 min and 51.5 ± 15 s, respectively. In the remaining six colons, spontaneous irregular phasic contractions occurred without CMCs. Interestingly, in STC patients robust CMCs were still recorded, although their CMC pacemaker frequencies were slower. Intraluminal balloon distension of the ascending or descending colon evoked an ascending excitatory reflex contraction, or evoked CMC, in 8 of 30 trials from non-STC (control) colons, but not from colons obtained from STC patients. In many control segments of descending colon, spontaneous CMCs consisted of simultaneous ascending excitatory and descending inhibitory phases. In summary, CMCs can be recorded from isolated human colon, in vitro, but their intrinsic pacemaker frequency is considerably faster in vitro compared with previous human recordings of CMCs in vivo. The observation that CMCs occur in whole colons removed from STC patients suggests that the intrinsic pacemaker mechanisms underlying their generation and propagation are preserved in vitro, despite impaired transit along these same regions in vivo.

The aging colon: the role of enteric neurodegeneration in constipation

Constipation is a common problem in the elderly, and abnormalities in the neural innervation of the colon play a significant role in abnormalities in colonic motility leading to delayed colonic transit. The scope of this review encompasses the latest advances to enhance our understanding of the aging colon with emphasis on enteric neurodegeneration, considered a likely cause for the development of constipation in the aging gut in animal models. Neural innervation of the colon and the effects of aging on intrinsic and extrinsic nerves innervating the colonic smooth muscle is discussed. Evidence supporting the concept that neurologic disorders, such as Parkinson's disease, not only affect the brain but also cause neurodegeneration within the enteric nervous system leading to colonic dysmotility is presented. Further research is needed to investigate the influence of aging on the gastrointestinal tract and to develop novel approaches to therapy directed at protecting the enteric nervous system from neurodegeneration.