Regional difference in colonic motility response to electrical field stimulation in Guinea pig

Regional Differences in Intestinal Contractile Responses to Radial Stretch in the Human Lower Gastrointestinal Tract

Background/Aims

Radial stretch evokes an increase or decrease in contractions in the lower gastrointestinal tract via mechanosensory enteric neurons that project into the muscle layers. We aim to elucidate the differences in stretch reflexes according to their location in the human colon.

Methods

We used healthy intestinal smooth muscle tissue excised during elective colon cancer surgery. Conventional intracellular recordings from colonic muscle cells and tension recordings of colonic segments were performed. Radial stretch was evoked through balloon catheter inflation. Changes in the membrane potential and frequency, amplitude, and area under the curve of muscle contractions were recorded before and after the radial stretch at proximal and distal segment sites.

Results

In intracellular circular muscle recordings, hyperpolarization was noted at the distal site of sigmoid colonic segments after radial stretch, in contrast to depolarization at all other sites. In tension recordings at proximal ascending or sigmoid colonic segment sites, contractile activation was observed with statistically significant increases in the frequency, amplitude, and area under the curve after radial stretch. Distal sites of ascending and sigmoid colonic segments showed increase and decrease in contraction, respectively.

Conclusion

Radial stretch in the human colon (in vitro) evokes excitatory activity at both proximal and distal sites of the ascending colon and at the proximal site of the sigmoid colon, whereas it elicits inhibitory activity at the distal site of the sigmoid colon.

Colonic TRPV4 overexpression is related to constipation severity

BACKGROUND

Chronic constipation is prevalent and involves both colon sensitivity and various changes in intestinal bacteria, particularly mucosa-associated microflora. Here we examined regulatory mechanisms of TRPV4 expression by co-culturing colon epithelial cell lines with intestinal bacteria and their derivatives. We also investigated TRPV4 expression in colon epithelium from patients with constipation.

METHODS

Colon epithelial cell lines were co-cultured with various enterobacteria (bacterial components and supernatant), folate, LPS, or short chain fatty acids. TRPV4 expression levels and promoter DNA methylation were assessed using pyrosequencing, and microarray network analysis. For human samples, correlation coefficients were calculated and multiple regression analyses were used to examine the association between clinical background, rectal TRPV4 expression level and mucosa-associated microbiota.

RESULTS

Co-culture of CCD841 cells with P. acnes, C. perfringens, or S. aureus transiently decreased TRPV4 expression but did not induce methylation. Co-culture with clinical isolates and standard strains of K. oxytoca, E. faecalis, or E. coli increased TRPV4 expression in CCD841 cells, and TRPV4 and TNF-alpha expression were increased by E. coli culture supernatants but not bacterial components. Although folate, LPS, IL-6, TNF-alpha, or SCFAs alone did not alter TRPV4 expression, TRPV4 expression following exposure to E. coli culture supernatants was inhibited by butyrate or TNF-alphaR1 inhibitor and increased by p38 inhibitor. Microarray network analysis showed activation of TNF-alpha, cytokines, and NOD signaling. TRPV4 expression was higher in constipated patients from the terminal ileum to the colorectum, and multiple regression analyses showed that low stool frequency, frequency of defecation aids, and duration were associated with TRPV4 expression. Meanwhile, incomplete defecation, time required to defecate, and number of defecation failures per 24 h were associated with increased E. faecalis frequency.

CONCLUSIONS

Colon epithelium cells had increased TRPV4 expression upon co-culture with K. oxytoca, E. faecalis, or E. coli supernatants, as well as TNFα-stimulated TNFαR1 expression via a pathway other than p38. Butyrate treatment suppressed this increase. Epithelial TRPV4 expression was increased in constipated patients, suggesting that TRPV4 together with increased frequency of E. faecalis may be involved in the pathogenesis of various constipation symptoms.

Analyzing fecal loading and retention patterns by abdominal X-rays of hospitalized older adults: A retrospective study

Background

Aging may affect ascending colon (AC) differently from descending colon (DC) and increase the risk of fecal loading (FL) in AC.

Methods

Patients aged ≥65 years admitted to a community hospital were analyzed by abdominal x‐ray for fecal loads and stool retention patterns. FL was scored between 0 and 5 (severe) on each segment of colon with a possible total score 20. Mean segment scores ≥3.5 were designated as high scores for both AC and DC. Logistic regression was performed between groups to identify factors associated with FL patterns.

Results

Groups identified were high FL in both AC and DC (N = 21, 17.2%), FL predominantly in AC (N = 38, 31.1%), low FL in both AC and DC (N=60, 49.2%), and FL low in AC and high in DC (N = 3, 2.5%). Among 71 patients with total FL scores ≥13 (indicating significant stool retention), 37 (52.1%) had the FL predominantly in AC. Patients prescribed antibiotic(s) prior to hospitalization had lower odds of FL predominantly in AC (adjusted odds ratio = 0.18, 95% confidence interval = 0.04–0.84) compared to the group of low FL in both AC and DC with the adjustment of confounders.

Conclusion

This study found that 52.1% of those with significant stool retention on x‐ray had the FL predominantly in AC. Antibiotic use was associated with lower odds of having FL predominately in AC. This study provided insights of FL distribution in colon and AC could be an area for significant stool burden in older adults with stool retention.

Neuromechanism of acupuncture regulating gastrointestinal motility

Acupuncture has been used in China for thousands of years and has become more widely accepted by doctors and patients around the world. A large number of clinical studies and animal experiments have confirmed that acupuncture has a benign adjustment effect on gastrointestinal (GI) movement; however, the mechanism of this effect is unclear, especially in terms of neural mechanisms, and there are still many areas that require further exploration. This article reviews the recent data on the neural mechanism of acupuncture on GI movements. We summarize the neural mechanism of acupuncture on GI movement from four aspects: acupuncture signal transmission, the sympathetic and parasympathetic nervous system, the enteric nervous system, and the central nervous system.

Comparison of Changes in the Interstitial Cells of Cajal and Neuronal Nitric Oxide Synthase-positive Neuronal Cells With Aging Between the Ascending and Descending Colon of F344 Rats

Background/Aims

Neuronal degeneration and changes in interstitial cells of Cajal (ICCs) are important mechanisms of age-related constipation. This study aims to compare the distribution of ICCs and neuronal nitric oxide synthase (nNOS) with regard to age-related changes between the ascending colon (AC) and descending colon (DC) in 6-, 31-, and 74-week old and 2-year old male Fischer-344 rats.

Methods

The amount of fecal pellet and the bead expulsion times were measured. Fat proportion in the muscle layer of the colon was analyzed by hematoxylin and eosin staining. Proto-oncogene receptor tyrosine kinase (KIT) and neuronal nitric oxide synthase (nNOS) expression were analyzed with Western blotting and immunohistochemistry. Isovolumetric contractile measurements and electrical field stimulation were used to assess smooth muscle contractility.

Results

Colon transit and bead expulsion slowed with senescence. Fat in the muscle layer accumulated with age in the AC, but not in the DC. The proportion of KIT-immunoreactive ICCs in the submucosal and myenteric plexus was higher in the DC than in the AC, and it declined with age, especially in the AC. In contrast, the proportion of NOS-immunoreactive neurons in the myenteric plexus was higher in the AC than in the DC, and both decreased in older rats. Nitric oxide levels declined with age in the DC. Muscle strip experiments showed that the inhibitory response mediated by nitric oxide in the circular direction of the DC was reduced in 2-year old rats.

Conclusion

The AC and DC differ in their distribution of ICCs and nNOS, and age-related loss of nitrergic neurons more severely affects the DC than the AC.

Autonomic nerve regulation of colonic peristalsis in Guinea pigs

Background/Aims

Colonic peristalsis is mainly regulated via intrinsic neurons in guinea pigs. However, autonomic regulation of colonic motility is poorly understood. We explored a guinea pig model for the study of extrinsic nerve effects on the distal colon.

Methods

Guinea pigs were sacrificed, their distal colons isolated, preserving pelvic nerves (PN) and inferior mesenteric ganglia (IMG), and placed in a tissue bath. Fecal pellet propagation was conducted during PN and IMG stimulation at 10 Hz, 0.5 ms and 5 V. Distal colon was connected to a closed circuit system, and colonic motor responses were measured during PN and IMG stimulation.

Results

PN stimulation increased pellet velocity to 24.6 ± 0.7 mm/sec (n = 20), while IMG stimulation decreased it to 2.0 ± 0.2 mm/sec (n = 12), compared to controls (13.0 ± 0.7 mm/sec, P < 0.01). In closed circuit experiments, PN stimulation increased the intraluminal pressure, which was abolished by atropine (10⁻⁶ M) and hexamethonium (10⁻⁴ M). PN stimulation reduced the incidence of non-coordinated contractions induced by NG-nitro-L-arginine methyl ester (L-NAME; 10⁻⁴ M). IMG stimulation attenuated intraluminal pressure increase, which was partially reversed by alpha-2 adrenoceptor antagonist (yohimbine; 10⁻⁶ M).

Conclusions

PN and IMG input determine speed of pellet progression and peristaltic reflex of the guinea pig distal colon. The stimulatory effects of PN involve nicotinic, muscarinic and nitrergic pathways. The inhibitory effects of IMG stimulation involve alpha-2 adrenoceptors.