The Influence of Inflammation and Nerve Damage on the Neurochemical Characterization of Calcitonin Gene-Related Peptide-Like Immunoreactive (CGRP-LI) Neurons in the Enteric Nervous System of the Porcine Descending Colon

TNBS colitis induces architectural changes and alpha-synuclein overexpression in mouse distal colon: A morphological study

Alpha-synuclein (α-syn) is widely expressed in presynaptic neuron terminals, and its structural alterations play an important role in the pathogenesis of Parkinson's disease (PD). Aggregated α-syn has been found in brain, in the peripheral nerves of the enteric nervous system (ENS) and in the intestinal neuroendocrine cells during synucleinopathies and inflammatory bowel disorders. In the present study, we evaluated the histomorphological features of murine colon with 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis, a common model of colitis. Thereafter, we investigated the expression of α-syn, Toll-like receptor 4 (TLR4), choline acetyltransferase (ChAT), vasoactive intestinal peptide (VIP), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), and calcitonin-like receptor (CALCR). Finally, we investigated the presence of phosphorylated α-syn (pS129 α-syn) aggregates and their relationship with inflammatory cells. Colon from TNBS mice showed an increase in inflammatory cells infiltrate and significative changes in the architecture of the intestinal mucosa. α-Syn expression was significantly higher in inflamed colon. VIP was increased in both the mucosa and muscularis externa of TNBS mice, while TH, CGRP, and CALCR were significantly reduced in TNBS mice. Amyloid aggregates of pS129 α-syn were detectable in the ENS, as in the macrophages around the glands of the mucosa correlating with the markers of inflammation. This study describes - for the first time - the altered expression of α-syn and the occurrence of amyloid α-syn aggregates in the inflammatory cells under colitis, supporting the critical role of bowel inflammation in synucleinopathies and the involvement of α-syn in IBD.

Antinociceptive Effects of an Anti-CGRP Antibody in Rat Models of Colon-Bladder Cross-Organ Sensitization

Irritable bowel syndrome (IBS) and bladder pain syndrome/interstitial cystitis (BPS/IC) are comorbid visceral pain disorders seen commonly in women with unknown etiology and limited treatment options and can involve visceral organ cross-sensitization. Calcitonin gene-related peptide (CGRP) is a mediator of nociceptive processing and may serve as a target for therapy. In three rodent models, we employed a monoclonal anti-CGRP F(ab')2 to investigate the hypothesis that visceral organ cross-sensitization is mediated by abnormal CGRP signaling. Visceral organ cross-sensitization was induced in adult female rats via transurethral infusion of protamine sulfate (PS) into the urinary bladder or infusion into the colon of trinitrobenzene sulfonic acid (TNBS). Colonic sensitivity was assessed via the visceromotor response to colorectal distension (CRD). Bladder sensitivity was assessed as the frequency of abdominal withdrawal reflexes to von Frey filaments applied to the suprapubic region. PS- or TNBS-induced changes in colonic and bladder permeability were investigated in vitro via quantification of transepithelial electrical resistance (TEER). Peripheral administration of an anti-CGRP F(ab')2 inhibited PS-induced visceral pain behaviors and colon hyperpermeability. Similarly, TNBS-induced pain behaviors and colon and bladder hyperpermeability were attenuated by anti-CGRP F(ab')2 treatment. PS into the bladder or TNBS into the colon significantly increased the visceromotor response to CRD and abdominal withdrawal reflexes to suprapubic stimulation and decreased bladder and colon TEER. These findings suggest an important role of peripheral CGRP in visceral nociception and organ cross-sensitization and support the evaluation of CGRP as a therapeutic target for visceral pain in patients with IBS and/or BPS/IC. SIGNIFICANCE STATEMENT: A monoclonal antibody against calcitonin gene-related peptide (CGRP) was found to reduce concomitant colonic and bladder hypersensitivity and hyperpermeability. The results of this study suggest that CGRP-targeting antibodies, in addition to migraine prevention, may provide a novel treatment strategy for multiorgan abdominopelvic pain following injury or inflammation.

Colonic motility adjustments in acute and chronic DSS-induced colitis

AIMS

Inflammatory bowel disease is recurrent inflammation that affects the gastrointestinal tract causing changes in intestinal motility. The evolution of these changes is not completely understood. The aim of this study was to evaluate anatomical and functional changes in the colon during the development of acute and chronic DSS-induced ulcerative colitis (UC) in C57Bl/6 mice.

MATERIALS AND METHODS

Mice were relocated into 5 groups: control (GC) and groups exposed to DSS 3 % for 2 (DSS2d), 5 (DSS5d) and 7 DSS7d) days (acute UC) or 3 cycles (DSS3C; Chronic UC). Mice were monitored daily. After euthanasia, colonic tissue was assessed with histological, immunofluorescence and colon manometry methods.

KEY FINDINGS

Ulcerative Colitis is a chronic disease characterized by overt inflammation of the colon. Here we investigate whether the morphological changes caused by UC in the colonic wall, in tuft cells and in enteric neurons also promote any alteration in colonic motility patterns. UC Promotes thickening in the colonic wall, fibrosis, reduction in the number of tuft cells and consequently goblet cells also, without promoting neuronal death however there is a change in the chemical code of myenteric neurons. All of these morphological changes were responsible for causing a change in colonic contractions, colonic migration motor complex, total time of gastrointestinal transit and therefore promoting dysmotility. Further studies stimulating a hyperplasia of tuft cells may be the way to try to keep the colonic epithelium healthy, reducing the damage caused by UC.

SIGNIFICANCE

Increasing disease pathology of DSS-induced UC induces structural and neuroanatomical changes and driven damage to cholinergic neurons causes colonic dysmotility, including increase of cholinergic myenteric neurons, followed by variations in the motility pattern of different regions of the colon that taking together characterize colonic dysmotility.

Topographical organization and morphology of substance P (SP)-immunoreactive axons in the whole stomach of mice

Nociceptive afferents innervate the stomach and send signals centrally to the brain and locally to stomach tissues. Nociceptive afferents can be detected with a variety of different markers. In particular, substance P (SP) is a neuropeptide and is one of the most commonly used markers for nociceptive nerves in the somatic and visceral organs. However, the topographical distribution and morphological structure of SP-immunoreactive (SP-IR) axons and terminals in the whole stomach have not yet been fully determined. In this study, we labeled SP-IR axons and terminals in flat mounts of the ventral and dorsal halves of the stomach of mice. Flat-mount stomachs, including the longitudinal and circular muscular layers and the myenteric ganglionic plexus, were processed with SP primary antibody followed by fluorescent secondary antibody and then scanned using confocal microscopy. We found that (1) SP-IR axons and terminals formed an extensive network of fibers in the muscular layers and within the ganglia of the myenteric plexus of the whole stomach. (2) Many axons that ran in parallel with the long axes of the longitudinal and circular muscles were also immunoreactive for the vesicular acetylcholine transporter (VAChT). (3) SP-IR axons formed very dense terminal varicosities encircling individual neurons in the myenteric plexus; many of these were VAChT immunoreactive. (4) The regional density of SP-IR axons and terminals in the muscle and myenteric plexus varied in the following order from high to low: antrum-pylorus, corpus, fundus, and cardia. (5) In only the longitudinal and circular muscles, the regional density of SP-IR axon innervation from high to low were: antrum-pylorus, corpus, cardia, and fundus. (6) The innervation patterns of SP-IR axons and terminals in the ventral and dorsal stomach were comparable. Collectively, our data provide for the first time a map of the distribution and morphology of SP-IR axons and terminals in the whole stomach with single-cell/axon/synapse resolution. This work will establish an anatomical foundation for functional mapping of the SP-IR axon innervation of the stomach and its pathological remodeling in gastrointestinal diseases.

Involvement of the calcitonin gene-related peptide system in the modulation of inflamed uterus contractile function in pigs

This study analyzed severe acute endometritis action on myometrial density and distribution of protein gene product (PGP)9.5- and calcitonin gene-related peptide (CGRP)-like immunoreactive nerve fibers and calcitonin receptor-like receptor (CLR) expression, and on CGRP receptor (CGRPR) participation in uterine contractility in pigs. E. coli suspension (E. coli group) or saline (SAL group) were injected into the uteri, or only laparotomy was performed (CON group). In the E. coli group myometrium, a lack of significant changes in PGP9.5 and CGRP innervation patterns and increased CLR protein level were revealed. In all groups, compared to the pretreatment period, human αCGRP increased amplitude in the myometrium, while reducing it in endometrium/myometrium. In the E. coli group endometrium/myometrium, human αCGRP lowered amplitude vs other groups. Human αCGRP reduced frequency in CON and SAL groups and enhanced it in the E. coli group endometrium/myometrium. The frequency in E. coli group increased vs other groups. CGRPR antagonist, human αCGRP8-37, reversed (CON, SAL groups) and eliminated (E. coli group) the rise in human αCGRP-induced myometrial amplitude. In endometrium/myometrium, human αCGRP8-37 abolished (CON group) and reversed (SAL group) a decrease in frequency, and reduced the rise in frequency (E. coli group) caused by human αCGRP. Collectively, in the myometrium, endometritis did not change PGP9.5 and CGRP innervation patterns and enhanced CLR protein level. CGRPR also mediated in CGRP action on inflamed uterus contractility.

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 generelated 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.

A Monoclonal Anti-Calcitonin Gene-Related Peptide Antibody Decreases Stress-Induced Colonic Hypersensitivity

Irritable bowel syndrome (IBS) is a brain-gut disorder characterized by abdominal pain and altered bowel habits. Although the etiology of IBS remains unclear, stress in adulthood or in early life has been shown to be a significant factor in the development of IBS symptomatology. Evidence suggests that aberrant calcitonin gene-related peptide (CGRP) signaling may be involved in afferent sensitization and visceral organ hypersensitivity. Here, we used a monoclonal anti-CGRP divalent antigen-binding fragment [F(ab')₂] antibody to test the hypothesis that inhibition of peripheral CGRP signaling reverses colonic hypersensitivity induced by either chronic adult stress or early life stress. A cohort of adult male rats was exposed to repeated water avoidance stress. Additionally, a second cohort consisting of female rats was exposed to a female-specific neonatal odor-attachment learning paradigm of unpredictable early life stress. Colonic sensitivity was then assessed in adult animals via behavioral responses to colorectal distension (CRD). To analyze spinal nociceptive signaling in response to CRD, dorsal horn extracellular signal-regulated kinase (ERK) 1/2 phosphorylation was measured via immunohistochemistry. Repeated psychologic stress in adulthood or unpredictable stress in early life induced colonic hypersensitivity and enhanced evoked ERK1/2 phosphorylation in the spinal cord after CRD in rats. These phenotypes were reversed by administration of a monoclonal anti-CGRP F(ab')₂ fragment antibody. Stress-induced changes in visceral sensitivity and spinal nociceptive signaling were reversed by inhibition of peripheral CGRP signaling, which suggests a prominent role for CGRP in central sensitization and the development of stress-induced visceral hypersensitivity. SIGNIFICANCE STATEMENT: Targeting peripheral calcitonin gene-related peptide (CGRP) with a monoclonal anti-CGRP divalent antigen-binding fragment antibody reduced central sensitization and attenuated colonic hypersensitivity induced by either chronic adult stress or early life stress. CGRP-targeting antibodies are approved for migraine prevention, and the results of this study suggest that targeting CGRP may provide a novel treatment strategy for irritable bowel syndrome-related, stress-induced visceral pain.

The Influence of Bisphenol A (BPA) on the Occurrence of Selected Active Substances in Neuregulin 1 (NRG1)-Positive Enteric Neurons in the Porcine Large Intestine

Bisphenol A (BPA) is a substance used in the manufacture of plastics which shows multidirectional adverse effects on living organisms. Since the main path of intoxication with BPA is via the gastrointestinal (GI) tract, the stomach and intestine are especially vulnerable to the impact of this substance. One of the main factors participating in the regulation of intestinal functions is the enteric nervous system (ENS), which is characterized by high neurochemical diversity. Neuregulin 1 (NRG1) is one of the lesser-known active substances in the ENS. During the present study (performed using the double immunofluorescence method), the co-localization of NRG1 with other neuronal substances in the ENS of the caecum and the ascending and descending colon has been investigated under physiological conditions and after the administration of BPA. The obtained results indicate that NRG1-positive neurons also contain substance P, vasoactive intestinal polypeptide, a neuronal isoform of nitric oxide synthase and galanin and the degree of each co-localization depend on the type of enteric plexus and the particular fragment of the intestine. Moreover, it has been shown that BPA generally increases the degree of co-localization of NRG1 with other substances.

Hyperoside Attenuate Inflammation in HT22 Cells via Upregulating SIRT1 to Activities Wnt/β-Catenin and Sonic Hedgehog Pathways

Neuroinflammation plays important roles in the pathogenesis and progression of altered neurodevelopment, sensorineural hearing loss, and certain neurodegenerative diseases. Hyperoside (quercetin-3-O-β-D-galactoside) is an active compound isolated from Hypericum plants. In this study, we investigate the protective effect of hyperoside on neuroinflammation and its possible molecular mechanism. Lipopolysaccharide (LPS) and hyperoside were used to treat HT22 cells. The cell viability was measured by MTT assay. The cell apoptosis rate was measured by flow cytometry assay. The mRNA expression levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) were determined by quantitative reverse transcription polymerase chain reaction. The levels of oxidative stress indices superoxide dismutase (SOD), reactive oxygen species (ROS), catalase (CAT), glutathione (GSH), and malondialdehyde (MDA) were measured by the kits. The expression of neurotrophic factor and the relationship among hyperoside, silent mating type information regulation 2 homolog-1 (SIRT1) and Wnt/β-catenin, and sonic hedgehog was examined by western blotting. In the LPS-induced HT22 cells, hyperoside promotes cell survival; alleviates the level of IL-1β, IL-6, IL-8, TNF-α, ROS, MDA, Bax, and caspase-3; and increases the expression of CAT, SOD, GSH, Bcl-2, BDNF, TrkB, and NGF. In addition, hyperoside upregulated the expression of SIRT1. Further mechanistic investigation showed that hyperoside alleviated LPS-induced inflammation, oxidative stress, and apoptosis by upregulating SIRT1 to activate Wnt/β-catenin and sonic hedgehog pathways. Taken together, our data suggested that hyperoside acts as a protector in neuroinflammation.

Altered gene expression signatures by calcitonin gene-related peptide promoted mast cell activity in the colon of stress-induced visceral hyperalgesia mice

BACKGROUND

Calcitonin gene-related peptide (CGRP) is possibly involved in recruitment of mucosal mast cells (MCs) in the gut that may be associated with the development of irritable bowel syndrome (IBS), but the role of CGRP on the activation of MCs is still unknown.

METHODS

Using RNA sequencing (RNA-seq), we examined differentially expressed genes (DEGs) in mouse MCs following CGRP treatment. The expression of key genes in colonic MCs and their relationship with CGRP-containing fibers were examined by immunofluorescence in chronic water-avoidance stress (WAS)-induced visceral hyperalgesia mice.

KEY RESULTS

A total of 29 DEGs were found significantly changed with 28 upregulated and 1 downregulated following treatment of MCs with CGRP. Bioinformatics analysis showed that key higher DEGs included those associated with response to corticotropin-releasing hormone (CRH), regulation of transcription, MC activation, and proliferation. These processes are enriched for genes associated with stress-induced MC activation in IBS. Western blot verified changes in representative DEGs (Nr4a3, Crem, Gpr35, FosB, Sphlk1) and real-time cell analysis (RTCA) verified the MC proliferation. The vast majority of colonic MCs nearly CGRP-containing fibers in WAS mice overexpressed only Nr4a3 with little to no FosB, Gpr35, Sphlk1, or Crem expression. Nr4a3 knockdown may attenuate the promotion effect of CGRP on MC viability.

CONCLUSIONS & INFERENCES

Our results suggest that CGRP is a critical regulator of key expressed genes in MC activation. Nr4a3 as a novel regulator of MC function may have an effect on stress-induced visceral hyperalgesia, and this may represent the novel target for drug development.

Chemically-Induced Inflammation Changes the Number of Nitrergic Nervous Structures in the Muscular Layer of the Porcine Descending Colon

Simple Summary

The enteric nervous system (ENS) is the part of the nervous system that is located in the wall of the gastrointestinal tract and regulates the majority of the functions of the stomach and intestine. The ENS is characterized by a complex structure and a high degree of independence from the brain. It is known that the ENS changes under the impact of physiological and pathological stimuli. One of the active substances synthetized by enteric neurons is nitric oxide (NO), which is involved in the regulation of intestinal motility, blood flow, secretory activity, and immunological processes in the gastrointestinal tract. In the present study, the influence of chemically-induced inflammatory process on a number of nitrergic neuronal structures located in the muscular layer of the descending colon is investigated. An increase in the number of structures that nitric oxide takes part in is correlated with the inflammatory processes.

Abstract

The enteric nervous system (ENS) is the part of the nervous system that is located in the wall of the gastrointestinal tract and regulates the majority of the functions of the stomach and intestine. Enteric neurons may contain various active substances that act as neuromediators and/or neuromodulators. One of them is a gaseous substance, namely nitric oxide (NO). It is known that NO in the gastrointestinal (GI) tract may possess inhibitory functions; however, many of the aspects connected with the roles of this substance, especially during pathological states, remain not fully understood. An experiment is performed here with 15 pigs divided into 3 groups: C group (without any treatment), C1 group (“sham” operated), and C2 group, in which experimental inflammation was induced. The aim of this study is to investigate the influence of inflammation on nitrergic nervous structures in the muscular layer of the porcine descending colon using an immunofluorescence method. The obtained results show that inflammation causes an increase in the percentage of nitric oxide synthase (nNOS)-positive neurons in the myenteric plexus of the ENS, as well as the number of nitrergic nerve fibers in the muscular layer of the descending colon. The obtained results suggest that NO is involved in the pathological condition of the large bowel and probably takes part in neuroprotective and/or adaptive processes.

Changes in the Population Size of Calbindin D-28k-Immunoreactive Enteric Neurons in the Porcine Caecum under the Influence of Bisphenol A: A Preliminary Study

Calbindin D-28k (CB) is a calcium-binding protein widely distributed in living organisms that may act as a calcium buffer and sensory protein. CB is present in the enteric nervous system (ENS) situated in the gastrointestinal tract, which controls the majority of activities of the stomach and intestine. The influence of various doses of bisphenol A (BPA)—a chemical compound widely used in plastics production—on the number and distribution of CB-positive enteric neuronal cells in the porcine caecum was investigated with an immunofluorescence technique. The obtained results showed that low dosages of BPA resulted in an increase in the number of CB-positive neuronal cells in the myenteric (MP) and inner submucous (ISP) plexuses, whereas it did not alter the number of such neuronal cells in the outer submucous plexus (OSP). High dosages of BPA caused the increase in the amount of CB-positive perikarya in all the above-mentioned kinds of the caecal neuronal plexuses. These observations strongly suggest that CB in the ENS participates in the processes connected with the toxic activity of BPA. Most likely, the changes noted in this experiment result from the adaptive and protective properties of CB.

Changes in the expression of substance P in nerve fibres of the colonic mucosa in dogs suffering from inflammatory bowel disease

Due to its difficult diagnosis and complicated treatment, inflammatory bowel disease (IBD) in dogs is a challenge for the veterinarian. Several aspects connected with pathological changes during IBD still remain unknown. Since one of these aspects is the participation of intestinal innervation in the evolution of the disease, the aim of this study was to demonstrate changes in the number and distribution of intramucosal colonic nerve fibres immunoreactive to substance P (SP) arising as the disease progresses. SP is one of the most important neuronal factors in intestinal innervation which, among other tasks, takes part in the conduction of pain stimuli. Using routine immunofluorescence technique, the density of nerve fibres containing SP was evaluated within mucosal biopsy specimens collected from the descending colon of healthy dogs and animals suffering from IBD of varying severity. The results of the study indicate that during severe IBD the number of nerve fibres containing SP located in the colonic mucosal layer increases in comparison to control animals. The number of SP-positive intramucosal nerves amounted to 10.99 ± 2.11 nerves per observation field in healthy dogs, 14.62 ± 2.86 in dogs with mild IBD, 14.80 ± 0.91 in dogs with moderate IBD and 19.03 ± 6.11 in animals with severe IBD. The observed changes were directly proportional to the intensity of the disease process. These observations may suggest a role of this neuronal substance in pathological processes occurring during IBD. Although the exact mechanism of the observed changes has not been completely explained, the results obtained in this investigation may contribute to improving the diagnosis and treatment of this disease, as well as the staging of canine IBD in veterinary practice.

Influence of Acrylamide Administration on the Neurochemical Characteristics of Enteric Nervous System (ENS) Neurons in the Porcine Duodenum

The digestive tract, especially the small intestine, is one of the main routes of acrylamide absorption and is therefore highly exposed to the toxic effect of acrylamide contained in food. The aim of this experiment was to elucidate the effect of low (tolerable daily intake—TDI) and high (ten times higher than TDI) doses of acrylamide on the neurochemical phenotype of duodenal enteric nervous system (ENS) neurons using the pig as an animal model. The experiment was performed on 15 immature gilts of the Danish Landrace assigned to three experimental groups: control (C) group—pigs administered empty gelatine capsules, low dose (LD) group—pigs administered capsules with acrylamide at the TDI dose (0.5 μg/kg body weight (b.w.)/day), and the high dose (HD) group—pigs administered capsules with acrylamide at a ten times higher dose than the TDI (5 μg/kg b.w./day) with a morning feeding for 4 weeks. Administration of acrylamide, even in a low (TDI) dose, led to an increase in the percentage of enteric neurons immunoreactive to substance P (SP), calcitonin gene-related peptide (CGRP), galanin (GAL), neuronal nitric oxide synthase (nNOS), and vesicular acetylcholine transporter (VACHT) in the porcine duodenum. The severity of the changes clearly depended on the dose of acrylamide and the examined plexus. The obtained results suggest the participation of these neuroactive substances in acrylamide-inducted plasticity and the protection of ENS neurons, which may be an important line of defence from the harmful action of acrylamide.

Neurochemical characterization of the enteric neurons within the porcine jejunum in physiological conditions and under the influence of bisphenol A (BPA)

BACKGROUND

Bisphenol A (BPA) is commonly used in the production of plastics and has multidirectional, negative effects on the living organisms. It may also affect the enteric nervous system (ENS) located in the wall of the gastrointestinal tract. Enteric neurons express many active substances, which regulate majority of intestinal activities not only in physiological conditions but also under the impact of pathological factors.

METHODS

The influence of various doses of BPA on the ENS of jejunum has been investigated using the double immunofluorescence technique. The commercial antibodies against substance P (SP), vasoactive intestinal polypeptide (VIP), galanin (GAL), vesicular acetylcholine transporter (VAChT), and cocaine- and amphetamine-regulated transcript peptide (CART) were used.

KEY RESULTS

Both doses of BPA studied changed the number of the enteric neurons immunoreactive to SP, VIP, GAL, VAChT, and CART, and the intensity of fluctuations depended on the BPA dose and on the type of the enteric plexus. Bisphenol A causes the increase in the number of neurons immunoreactive to the majority of substances studied. The only exception was VAChT-positive neurons, the number of which was lower under the impact of BPA in the comparison with physiological conditions.

CONCLUSIONS & INFERENCES

Even low doses of BPA cause the changes in neurochemical characterization of the enteric neurons in the jejunum. These changes may be the first sign of subclinical BPA intoxication. The mechanisms of observed changes are probably connected with neurotoxic and/or pro-inflammatory activity of BPA, but their exact mechanisms are not fully explained.

Age and Sex-Dependent Differences in the Neurochemical Characterization of Calcitonin Gene-Related Peptide-Like Immunoreactive (CGRP-LI) Nervous Structures in the Porcine Descending Colon

Neurons of the enteric nervous system (ENS) may undergo changes during maturation and aging, but knowledge of physiological stimuli-dependent changes in the ENS is still fragmentary. On the other hand, the frequency of many ENS-related intestinal illnesses depends on age and/or sex. The double immunofluorescence technique was used to study the influence of both of these factors on calcitonin gene-related peptide (CGRP)—positive enteric nervous structures—in the descending colon in young and adult female and castrated male pigs. The influence of age and gender on the number and neurochemical characterization (i.e., co-localization of CGRP with substance P, nitric oxide synthase, galanin, cocaine- and amphetamine-regulated transcript peptide and vesicular acetylcholine transporter) of CGRP-positive nerve structures in the colonic wall has been shown. These observations strongly suggest the participation of CGRP in adaptive processes in the ENS during GI tract maturation. Moreover, although the castration of males may mask some aspects of sex-dependent influences on the ENS, the sex-specific differences in CGRP-positive nervous structures were mainly visible in adult animals. This may suggest that the distribution and exact role of this substance in the ENS depend on the sex hormones.

The Neurochemical Characterization of Parasympathetic Nerve Fibers in the Porcine Uterine Wall Under Physiological Conditions and After Exposure to Bisphenol A (BPA)

Bisphenol A, a substance commonly used in plastic manufacturing, is relatively well known as an endocrine disruptor, which may bind to estrogen receptors and has multidirectional negative effects on both human and animal organisms. Previous studies have reported that BPA may act on the reproductive organs, but knowledge concerning BPA-induced changes within the nerves located in the uterine wall is extremely scant. The aim of this study was to investigate the impact of various doses of BPA on the parasympathetic nerves located in the corpus and horns of the uterus using a single and double immunofluorescence method. The obtained results have shown that BPA may change not only the expression of vesicular acetylcholine transporter (VAChT—a marker of parasympathetic nervous structures) in the uterine intramural nerve fibers, but also the degree of colocalization of this substance with other neuronal factors, including substance P (SP), vasoactive intestinal polypeptide (VIP), galanin (GAL), and calcitonin gene–related peptide (CGRP). Moreover, BPA caused changes in the density of the overall populations of fibers immunoreactive to the particular neuropeptides mentioned above. The characteristics of the changes clearly depended on the part of the uterus, the neuronal factors studied, and the dosage of BPA. The mechanisms of the observed fluctuations are probably connected with the neurotoxic and/or pro-inflammatory activity of BPA. Moreover, the results have shown that even low doses of BPA are not neutral to living organisms. Changes in the neurochemical characterization of nerves supplying the uterine wall may be the first subclinical sign of intoxication with this substance.

Chemically induced inflammation and nerve damage affect the distribution of vasoactive intestinal polypeptide-like immunoreactive (VIP-LI) nervous structures in the descending colon of the domestic pig

BACKGROUND

The enteric nervous system (ENS), situated in the wall of the gastrointestinal tract, regulates the majority of intestinal activities in physiological conditions and during pathological processes. Enteric neurons are diversified in terms of active substance expression. One of the most important neuropeptides within the ENS is vasoactive intestinal polypeptide (VIP). It seems to be one among the important inhibitory peptides in addition to neuropeptide Y (NPY), nitric oxide (NO), and adenosine triphosphate (ATP) of the intestinal motility and secretion, however, many issues connected with distribution and roles of VIP in the large intestine, especially during pathological states, still remain unknown.

METHODS

Changes in the VIP-like immunoreactivity of the enteric nervous structures under experimental pathological states, including chemically induced inflammation and nerve damage was examined using the double immunofluorescence technique with commercial antibodies.

KEY RESULTS

Generally, both pathological factors studied caused an increase in the number of VIP-like immunoreactive (VIP-LI) neurons and nerve fibers, but the intensity of fluctuations depended on both the acting factor and the part of the ENS studied.

CONCLUSIONS AND INFERENCES

The obtained results suggest that VIP participates in pathological processes concerning the digestive tract, and its exact functions probably depend on the type of damaging factor acting on the intestine.

Alterations in enteric calcitonin gene-related peptide in patients with colonic diverticular disease: CGRP in diverticular disease

Diverticular disease (DD) is one of the most prevalent diseases of the large bowel. Lately, imbalance of neuro-muscular transmission has been recognized as a major etiological factor for DD. Neuronal calcitonin gene-related peptide (CGRP) is a potent gastrointestinal smooth muscle relaxant shown to have a widespread effect within the alimentary tract. Nevertheless, CGRPergic innervation of the enteric ganglia has never been considered in the context of motility impairment observed in DD patients. Changes in CGRP and calcitonin receptor-like receptor (CRLR) abundance within enteric ganglia were investigated in sigmoid samples from symptomatic and asymptomatic DD patients using quantitative fluorescence microscopy. CGRP effect on gastrointestinal smooth muscle was investigated using organ bath technique. We found CGRP levels within the enteric ganglia to be declined by up to 52% in symptomatic DD patients. Conversely, CRLR within the enteric ganglia was upregulated by 41% in symptomatic DD. Longitudinal smooth muscle displayed an elevated (+10.5%) relaxant effect to the exogenous application of CGRP in colonic strips from symptomatic DD patients. Samples from asymptomatic DD patients consistently showed intermediate values across different experiments. In conclusion, the present study demonstrates that CGRPergic signaling is subject to alteration in DD. Our results suggest that a hypersensitization mechanism to gradually decreasing levels of CGRP-IR nerve fibers takes place during DD progression. Alterations to CGRPergic signaling in DD disease may have implications for physiological abnormalities associated with colonic DD.

Distribution and Neurochemistry of the Porcine Ileocaecal Valve Projecting Sensory Neurons in the Dorsal Root Ganglia and the Influence of Lipopolysaccharide from Different Serotypes of Salmonella spp. on the Chemical Coding of DRG Neurons in the Cell Cultures

The ileocecal valve (ICV)—a sphincter muscle between small and large intestine—plays important roles in the physiology of the gastrointestinal (GI) tract, but many aspects connected with the innervation of the ICV remain unknown. Thus, the aim of this study was to investigate the localization and neurochemical characterization of neurons located in the dorsal root ganglia and supplying the ICV of the domestic pig. The results have shown that such neurons mainly located in the dorsal root ganglia (DRG) of thoracic and lumbar neuromers show the presence of substance P (SP), calcitonin gene-related peptide (CGRP), and galanin (GAL). The second part of the experiment consisted of a study on the influence of a low dose of lipopolysaccharide (LPS) from Salmonella serotypes Enteritidis Minnesota and Typhimurium on DRG neurons. It has been shown that the LPS of these serotypes in studied doses does not change the number of DRG neurons in the cell cultures, but influences the immunoreactivity to SP and GAL. The observed changes in neurochemical characterization depend on the bacterial serotype. The results show that DRG neurons take part in the innervation of the ICV and may change their neurochemical characterization under the impact of LPS, which is probably connected with direct actions of this substance on the nervous tissue and/or its pro-inflammatory activity.

Neurochemical characterization of intramural nerve fibres in the porcine oesophagus

The gastrointestinal (GI) tract is innervated by nerve processes derived from the intramural enteric neurons and neurons localized outside the digestive tract. This study analysed the neurochemical characterization of nerves in the wall of the porcine oesophagus using single immunofluorescence technique. Immunoreactivity to vesicular acetylcholine transporter (VAChT), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), somatostatin (SOM), galanin (GAL), neuronal isoform of nitric oxide synthase (nNOS), substance P (SP), leucine enkephalin (LENK), calcitonin gene-related peptide (CGRP) or dopamine beta-hydroxylase (DBH) was investigated in intramuscular and intramucosal nerves of the cervical, thoracic and abdominal oesophagus. The results indicate that all of the substances studied were present in the oesophageal nerves. The density of particular populations of fibres depended on the segment of the oesophagus. The most numerous were fibres immunoreactive to VIP in the longitudinal and circular muscle layers of the abdominal oesophagus: The number of these fibres amounted to 16.4 ± 0.8 and 18.1 ± 3.1, respectively. In turn, the least numerous were CGRP-positive fibres, which were present only in the circular muscle layer of the cervical oesophagus and mucosal layer of the abdominal oesophagus in the number of 0.3 ± 0. The obtained results show that nerves in the porcine oesophageal wall are very diverse in their neurochemical coding, and differences between particular parts of the oesophagus suggest that organization of the innervation clearly depends on the fragment of this organ.

Nitric oxide as an active substance in the enteric neurons of the porcine digestive tract in physiological conditions and under intoxication with bisphenol A (BPA)

Bisphenol A (BPA) is an organic substance, which is commonly used in the production of plastic. It is known that BPA has the negative impact on the living organism, affecting among others the reproductive organs, nervous, endocrine and immune systems. Nevertheless the knowledge about the influence of BPA on the enteric nervous system (ENS) is extremely scanty. On the other hand, nitric oxide is considered to be one of the most important neuronal factors in the ENS. The aim of the study was to investigate the influence of low and high doses of BPA on neuronal isoform nitric oxide synthase - like immunoreactive (nNOS-LI) nervous structures in the various parts of the porcine gastrointestinal (GI) tract using double immunofluorescence technique. The obtained results show that BPA affects nNOS-LI enteric neurons and nerve fibers, and the character and severity of observed changes depend on the fragment of the gastrointestinal tract, part of the ENS and dose of the toxin. It should be pointed out that even relatively low doses of BPA (0.05 mg/kg body weight/day) are not neutral for the organism and may change the number of nitrergic nervous structures in the stomach and intestine. Observed changes are probably connected with neurotoxic activity of BPA, but the exact mechanisms of them still remain unclear.

The Impact of T-2 Toxin on Vasoactive Intestinal Polypeptide-Like Immunoreactive (VIP-LI) Nerve Structures in the Wall of the Porcine Stomach and Duodenum

T-2 toxin is a secondary metabolite of some Fusarium species. It is well-known that this substance can harmfully impact living organisms. Among others, thanks to the ability of crossing the blood–brain barrier, T-2 toxin can affect the central nervous system. Mycotoxins mostly get into the organism through the digestive tract; therefore, first of all they have to break the intestinal barrier, wherein the important component is the enteric nervous system (ENS). However, knowledge about the impact of T-2 toxin on the ENS is rather scant. As a result of the influence of various physiological and pathological agents, ENS can undergo adaptive and reparative processes which manifest as changes in the immunoreactivity of perikaryons for neuronal active substances. So, the aim of the present investigation was to study how low doses of T-2 toxin affect vasoactive intestinal polypeptide-like immunoreactive (VIP-LI) nervous structures in the ENS of the porcine stomach and duodenum. Obtained results have shown that T-2 toxin causes an percentage increase of VIP-LI nerve cells and nerve fibers in every enteric plexus in both fragments of gastrointestinal tract studied. This shows that even low doses of T-2 toxin can have an influence on living organisms.

Changes in Immunoreactivity of Sensory Substances within the Enteric Nervous System of the Porcine Stomach during Experimentally Induced Diabetes

One of the most frequently reported disorders associated with diabetes is gastrointestinal (GI) disturbance. Although pathogenesis of these complications is multifactorial, the complicity of the enteric nervous system (ENS) in this respect has significant importance. Therefore, this paper analysed changes in substance P- (SP-), calcitonin gene-related peptide- (CGRP-), and leu5-enkephalin- (L-ENK-) like immunoreactivity (LI) in enteric stomach neurons caused by chemically induced diabetes in a porcine model. Using double immunofluorescent labelling, it was found that acute hyperglycaemia led to significant changes in the chemical coding of stomach enteric neurons. Generally, the response to artificially inducted diabetes depended on the "kind" of enteric plexus as well as the stomach region studied. A clear increase in the percentage of neurons immunoreactive to SP and CGRP was visible in the myenteric plexus (MP) in the antrum, corpus, and pylorus as well as in the submucosal plexus (SmP) in the corpus. For L-ENK, an increase in the number of L-ENK-LI neurons was observed in the MP of the antrum and SmP in the corpus, while in the MP of the corpus and pylorus, a decrease in the percentage of L-ENK-LI neurons was noted.