The P2Y1 Receptor in the Colonic Submucosa of Rats and Its Correlation with Opioid-Induced Constipation

Aims: To explore the expression changes of P2Y1 in the distal colonic submucosa of opioid induced constipation (OIC) rats and its correlation with the occurrence of OIC. Methods: OIC model was generated by intraperitoneal injection of loperamide hydrochloride, a selective agonist of the μ-opioid receptor (MOR). Seven days later, the model was assessing by detecting the fecal traits and calculating the fecal water cotent. The distribution of MOR-containing neurons and P2Y1-containing neurons in colonic submucosal plexus of rat were demonstrated by immunofluorescence histochemistry. Western Blot was used to evaluate the expression changes of MOR, P2Y1 and ATP synthase subunit beta (ATPB) in colonic submucosa, while the RT-PCR analysis was performed to determine the relative mRNA expression of MOR, P2Y1 and ATPB. Results: After seven days, the feces of OIC rats had an appearance of like sausage-shaped pieces, and the fecal water content, stool weight of OIC rats were decreased. Immunofluorescence histochemistry showed the co-expression of MOR and ATPB, P2Y1 and calbindin (CB) in the nerve cells of distal colonic submucosal plexus. RT-PCR showed that MOR mRNA levels were significantly increased in the distal colonic submucosa of OIC rats, while the mRNA levels of P2Y1 were decreased. Western blot results showed that MOR protein expression was increased, and the P2Y1 protein expression was significantly decreased in the distal colonic submucosa of OIC rats.Conclusion: P2Y1 is associated with the occurrence of OIC in rats, and the expression of MOR and P2Y1 and OIC are correlated with each other.

Effect of chemically-induced diabetes mellitus on phenotypic variability of the enteric neurons in the descending colon in the pig

Gastrointestinal neuropathy in diabetes is one of numerous diseases resulting in abnormal functioning of the gastrointestinal tract (GIT), and it may affect any section of the GIT, including the descending colon. In the gastrointestinal system, the neurons are arranged in an interconnecting network defined as the enteric nervous system (ENS) which includes the myenteric plexus and the submucosal plexuses: inner and outer. Regular functioning of the ENS is determined by normal synthesis of the neurotransmitters and neuromodulators. This paper demonstrates the effect of hyperglycaemia on the number of enteric neurons which are immunoreactive to: neural isoform of nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP), galanin (GAL), calcitonin gene-related peptide (CGRP) and cocaine amphetamine-regulated transcript (CART) in the porcine descending colon. It was demonstrated that there was a statistically significant increase in the number of neurons within the myenteric plexus immunoreactive to all investigated substances. In the outer submucosal plexus, the CART-positive neurons were the only ones not to change, whereas no changes were recorded for nNOS or CART in the inner submucosal plexus. This study is the first study to discuss quantitative changes in the neurons immunoreactive to nNOS, VIP, GAL, CGRP and CART in the descending colon in diabetic pigs.

Specific immune modulation of experimental colitis drives enteric alpha-synuclein accumulation and triggers age-related Parkinson-like brain pathology

Background : Intraneuronal accumulation of a-synuclein (αSyn) is key in Parkinson’s disease (PD) pathogenesis. The pathogenic process is suggested to begin in the enteric nervous system decades before diagnosis of PD and then propagate into the brain. The triggers for these events are unclear but, in some patients, colitis might play a critical role. Methods : We administered lipopolysaccharide (LPS) or dextran sulfate sodium (DSS) to assess the effect of different types of experimental colitis on αSyn accumulation in the gut of αSyn transgenic and wild type mice and quantified local gene expression by RT-PCR and level of αSyn accumulation by immunofluorescence imaging. Immune modulation during the DSS colitis paradigm in the αSyn transgenic mice included genetic ablation of Cx3cr1 or treatment with recombinant IL-10. To determine long-term effects of experimental colitis, we induced DSS colitis in young αSyn transgenic mice and aged them under normal conditions up to nine or 21 months before analyzing their brains by immunohistochemistry. In vivo experiments were performed in randomized cohorts. Blinded experimenters performed image analysis and statistical analysis depended on data type (i.e., Student’s t-test, ANOVA, mixed-effects model). Results : We demonstrate that mild sustained or one strong insult of experimental DSS colitis triggers αSyn accumulation in the submucosal plexus of wild type and αSyn transgenic mice, while short-term mild DSS experimental colitis or inflammation induced by LPS does not have such an effect. Lack of macrophage-related Cx3cr1-signalling during DSS colitis increases accumulation of αSyn in the colonic submucosal plexus of αSyn transgenic mice while systemic treatment with immune-dampening IL-10 ameliorates this phenomenon. Additionally, DSS colitis-induced αSyn accumulation in young αSyn transgenic mice persists for months and is exacerbated by lack of Cx3cr1-signaling. Remarkably, experimental colitis at three months of age exacerbates the accumulation of aggregated phospho-Serine 129 αSyn in the midbrain (including the substantia nigra), in 21- but not 9-month-old αSyn transgenic mice. This increase in midbrain αSyn accumulation is accompanied by the loss of tyrosine hydroxylase-immunoreactive nigral neurons. Conclusions : Our data suggest that specific types of intestinal inflammation, mediated by monocyte/macrophage signaling, could play a critical role in the initiation and progression of PD.

Detection of Phosphorylated Alpha-Synuclein in the Muscularis Propria of the Gastrointestinal Tract Is a Sensitive Predictor for Parkinson’s Disease

Background. Parkinson’s disease (PD) is a neurodegenerative disorder characterized by motor and nonmotor impairments, including constipation. Lewy bodies and neurites, the pathological hallmarks of PD, are found in the enteric nervous system (ENS) as well as the central nervous system. Constipation is a well-documented premotor symptom in PD, and recent reports have demonstrated Lewy pathology in gastrointestinal (GI) tissues of PD patients prior to the onset of motor symptoms. Objective. In the present study, we assessed Lewy pathology in the GI tracts of seven PD patients who had undergone a gastrectomy, gastric polypectomy, or colonic polypectomy prior to the onset of motor symptoms in order to assess whether the presence of pathological αSyn in the ENS could be a predictor for PD. Methods. GI tissue samples were collected from control patients and patients with premotor PD. Immunohistochemistry was performed using primary antibodies against α-synuclein (αSyn) and phosphorylated αSyn (pαSyn), after which Lewy pathology in each sample was assessed. Results. In all control and premotor PD patients, accumulation of αSyn was observed in the myenteric plexus in both the stomach and colon. In 82% (18/22) of control patients, mild-to-moderate accumulation of αSyn was observed in the submucosal plexus. However, there was no deposition of pαSyn in the ENS of control patients. In patients with premotor PD, abundant accumulation of αSyn was observed in the myenteric plexus, similar to control patients. On the other hand, pαSyn-positive aggregates were also observed in the nerve fibers in the muscularis propria in all examined patients with premotor PD (100%, 3/3), while the deposition of pαSyn in the submucosal plexus was only observed in one patient (14%, 1/7). Conclusion. Our results suggest that the detection of pαSyn, but not αSyn, especially in the muscularis propria of GI tracts, could be a sensitive prodromal biomarker for PD.

Morphological features of the jejunum and ileum of the middle and heavy goose breeds

We studied the morphological features of the jejunum and ileum in middle and heavy goose breeds. The geese under six month of age of Gorkovskaya and Legart breeds were used in our research. Geese of a heavy breed had a large intestinal mass, length of the jejunum and ileum, thickness of the mucous membrane of the ileum, and a smaller thickness of the muscular tunic of the jejunum. Legart geese had greater villi density and crypt depth in the jejunum and greater height and density of the villi, the width of the crypts, and the ratio of the height of the villi to the depth of the crypts in the ileum. In all the guts of heavier geese, the density of crypts was lower. The geese of the heavy breed had larger number and area of the ganglia of the mental plexus and smaller number and area in the submucosa in the jejunum, while they had larger area of the ganglia of the submucosal plexus in the ileum. The number of argyrophilic and argentaffin apudocytes in the jejunum of geese of different breeds did not differ, when the Legart breed geese had lesser quantity of apudocytes in the ileum.

Xenin-25 induces anion secretion by activating noncholinergic secretomotor neurons in the rat ileum

Xenin-25 is a neurotensin-like peptide that is secreted by enteroendocrine cells in the small intestine. Xenin-8 is reported to augment duodenal anion secretion by activating afferent neural pathways. The intrinsic neuronal circuits mediating the xenin-25-induced anion secretion were characterized using the Ussing-chambered, mucosa-submucosa preparation from the rat ileum. Serosal application of xenin-25 increased the short-circuit current in a concentration-dependent manner. The responses were abolished by the combination of Cl−-free and [Formula: see text]-free solutions. The responses were almost completely blocked by TTX (10−6 M) but not by atropine (10−5 M) or hexamethonium (10−4 M). The selective antagonists for neurotensin receptor 1 (NTSR1), neurokinin 1 (NK1), vasoactive intestinal polypeptide (VIP) receptors 1 and 2 (VPAC1 and VPAC2, respectively), and capsaicin, but not 5-hydroxyltryptamine receptors 3 and 4 (5-HT3 and 5-HT4), NTSR2, and A803467, inhibited the responses to xenin-25. The expression of VIP receptors ( Vipr) in rat ileum was examined using RT-PCR. The Vipr1 PCR products were detected in the submucosal plexus and mucosa. Immunohistochemical staining showed the colocalization of NTSR1 and NK1 with substance P (SP)- and calbindin-immunoreactive neurons in the submucosal plexus, respectively. In addition, NK1 was colocalized with noncholinergic VIP secretomotor neurons. Based on the results from the present study, xenin-25-induced Cl−/[Formula: see text] secretion is involved in NTSR1 activation on intrinsic and extrinsic afferent neurons, followed by the release of SP and subsequent activation of NK1 expressed on noncholinergic VIP secretomotor neurons. Finally, the secreted VIP may activate VPAC1 on epithelial cells to induce Cl−/[Formula: see text] secretion in the rat ileum. Activation of noncholinergic VIP secretomotor neurons by intrinsic primary afferent neurons and extrinsic afferent neurons by postprandially released xenin-25 may account for most of the neurogenic secretory response induced by xenin-25. NEW & NOTEWORTHY This study is the first to investigate the intrinsic neuronal circuit responsible for xenin-25-induced anion secretion in the rat small intestine. We have found that nutrient-stimulated xenin-25 release may activate noncholinergic vasoactive intestinal polypeptide (VIP) secretomotor neurons to promote Cl−/[Formula: see text] secretion through the activation of VIP receptor 1 on epithelial cells. Moreover, the xenin-25-induced secretory responses are mainly linked with intrinsic primary afferent neurons, which are involved in the activation of neurotensin receptor 1 and neurokinin 1 receptor.