The neurochemical changes in the innervation of human colonic mesenteric and submucosal blood vessels in ulcerative colitis and Crohn's disease

Butyrate Protects Myenteric Neurons Loss in Mice Following Experimental Ulcerative Colitis

The enteric nervous system is affected by inflammatory bowel diseases (IBD). Gut microbiota ferments dietary fibers and produces short-chain fatty acids, such as Butyrate, which bind to G protein-coupled receptors, such as GPR41, and contribute to maintaining intestinal health. This work aimed to study the GPR41 in myenteric neurons and analyze the effect of Butyrate in mice submitted to experimental ulcerative colitis. The 2, 4, 6 trinitrobenzene sulfonic acid (TNBS) was injected intrarectally in C57BL/6 mice (Colitis). Sham group received ethanol (vehicle). One group was treated with 100 mg/kg of Sodium Butyrate (Butyrate), and the other groups received saline. Animals were euthanized 7 days after colitis induction. Analyzes demonstrated colocalization of GPR41 with neurons immunoreactive (-ir) to nNOS and ChAT-ir and absence of colocalization of the GPR41 with GFAP-ir glia. Quantitative results demonstrated losses of nNOS-ir, ChAT-ir, and GPR41-ir neurons in the Colitis group and Butyrate treatment attenuated neuronal loss. The number of GFAP-ir glia increased in the Colitis group, whereas Butyrate reduced the number of these cells. In addition, morphological alterations observed in the Colitis group were attenuated in the Butyrate group. The presence of GPR41 in myenteric neurons was identified, and the treatment with Butyrate attenuated the damage caused by experimental ulcerative colitis.

Vasculature in the mouse colon and spatial relationships with the enteric nervous system, glia, and immune cells

The distribution, morphology, and innervation of vasculature in different mouse colonic segments and layers, as well as spatial relationships of the vasculature with the enteric plexuses, glia, and macrophages are far from being complete. The vessels in the adult mouse colon were stained by the cardiovascular perfusion of wheat germ agglutinin (WGA)-Alexa Fluor 448 and by CD31 immunoreactivity. Nerve fibers, enteric glia, and macrophages were immunostained in the WGA-perfused colon. The blood vessels entered from the mesentery to the submucosa and branched into the capillary networks in the mucosa and muscularis externa. The capillary net formed anastomosed rings at the orifices of mucosa crypts, and the capillary rings surrounded the crypts individually in the proximal colon and more than two crypts in the distal colon. Microvessels in the muscularis externa with myenteric plexus were less dense than in the mucosa and formed loops. In the circular smooth muscle layer, microvessels were distributed in the proximal, but not the distal colon. Capillaries did not enter the enteric ganglia. There were no significant differences in microvascular volume per tissue volume between the proximal and distal colon either in the mucosa or muscularis externa containing the myenteric plexus. PGP9.5-, tyrosine hydroxylase-, and calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibers were distributed along the vessels in the submucosa. In the mucosa, PGP9.5-, CGRP-, and vasoactive intestinal peptide (VIP)-immunoreactive nerves terminated close to the capillary rings, while cells and processes labeled by S100B and glial fibrillary acidic protein were distributed mainly in the lamina propria and lower portion of the mucosa. Dense Iba1 immunoreactive macrophages were closely adjacent to the mucosal capillary rings. There were a few macrophages, but no glia in apposition to microvessels in the submucosa and muscularis externa. In conclusion, in the mouse colon, (1) the differences in vasculature between the proximal and distal colon were associated with the morphology, but not the microvascular amount per tissue volume in the mucosa and muscle layers; (2) the colonic mucosa contained significantly more microvessels than the muscularis externa; and (3) there were more CGRP and VIP nerve fibers found close to microvessels in the mucosa and submucosa than in the muscle layers.

Role of short chain fatty acids in gut health and possible therapeutic approaches in inflammatory bowel diseases

Inflammatory bowel diseases (IBDs) are characterized by inflammation in the gastrointestinal tract and include Ulcerative Colitis and Crohn’s Disease. These diseases are costly to health services, substantially reduce patients’ quality of life, and can lead to complications such as cancer and even death. Symptoms include abdominal pain, stool bleeding, diarrhea, and weight loss. The treatment of these diseases is symptomatic, seeking disease remission. The intestine is colonized by several microorganisms, such as fungi, viruses, and bacteria, which constitute the intestinal microbiota (IM). IM bacteria promotes dietary fibers fermentation and produces short-chain fatty acids (SCFAs) that exert several beneficial effects on intestinal health. SCFAs can bind to G protein-coupled receptors, such as GPR41 and GPR43, promoting improvements in the intestinal barrier, anti-inflammatory, and antioxidant effects. Thus, SCFAs could be a therapeutic tool for IBDs. However, the mechanisms involved in these beneficial effects of SCFAs remain poorly understood. Therefore, this paper aims to provide a review addressing the main aspects of IBDs, and a more detailed sight of SCFAs, focusing on the main effects on different aspects of the intestine with an emphasis on IBDs.

Abdominal Aortic Endothelial Dysfunction Occurs in Female Mice With Dextran Sodium Sulfate-Induced Chronic Colitis Independently of Reactive Oxygen Species Formation

Background and Objective

Inflammatory bowel disease (IBD) produces significant local and systemic inflammation with increased reactive oxygen species (ROS) formation. IBD Patients are at an increased risk for developing endothelial dysfunction and cardiovascular diseases. The present study tested the hypothesis that IBD impairs aortic endothelial function via ROS formation and investigate potential sex-related differences.

Methods and Results

Acute and chronic colitis models were induced in male and female C57BL/6 mice with dextran sodium sulfate (DSS) treatment. Aortic wall stiffness, endothelial function, and ROS levels, as well as serum levels of pro-inflammatory cytokines were evaluated. Acetylcholine (Ach)-induced endothelium-dependent relaxation of abdominal aorta without perivascular adipose tissue (PVAT) was significantly reduced in female mice, not males, with chronic colitis without a change in nitroglycerin-induced endothelium-independent relaxation. PVAT effectively preserved Ach-induced relaxation in abdominal aorta of female mice with chronic colitis. Aortic peak velocity, maximal intraluminal diameters, pulse wave velocity, distensibility and radial strain were preserved in mice with both acute and chronic colitis. Although pro-inflammatory cytokines levels were increased in mice with acute and chronic colitis, aortic ROS levels were not increased.

Conclusion

The data demonstrate that abdominal aortic endothelial function was attenuated selectively in female mice with chronic colitis independent of ROS formation. Further, PVAT played an important role in preserving endothelial function in female mice with chronic colitis.

Somatostatin and Its Receptor System in Colorectal Cancer

Somatostatin (SST)/somatotropin release-inhibiting factor (SRIF) is a well-known neuropeptide, widely distributed in the central and peripheral nervous systems, that regulates the endocrine system and affects neurotransmission via interaction with five SST receptors (SST1-5). In the gastrointestinal tract, the main SST-producing cells include intestinal enteroendocrine cells (EECs) restricted to the mucosa, and neurons of the submucosal and myenteric plexuses. The action of the SRIF system is based on the inhibition of endocrine and exocrine secretion, as well as the proliferative responses of target cells. The SST1–5 share common signaling pathways, and are not only widely expressed on normal tissues, but also frequently overexpressed by several tumors, particularly neuroendocrine neoplasms (NENs). Furthermore, the SRIF system represents the only peptide/G protein-coupled receptor (GPCR) system with multiple approved clinical applications for the diagnosis and treatment of several NENs. The role of the SRIF system in the histogenesis of colorectal cancer (CRC) subtypes (e.g., adenocarcinoma and signet ring-cell carcinoma), as well as diagnosis and prognosis of mixed adenoneuroendocrine carcinoma (MANEC) and pure adenocarcinoma, is poorly understood. Moreover, the impact of the SRIF system signaling on CRC cell proliferation and its potential role in the progression of this cancer remains unknown. Therefore, this review summarizes the recent collective knowledge and understanding of the clinical significance of the SRIF system signaling in CRC, aiming to evaluate the potential role of its components in CRC histogenesis, diagnosis, and potential therapy.

Targeting Enteric Neurons and Plexitis for the Management of Inflammatory Bowel Disease

Ulcerative colitis (UC) and Crohn's disease (CD) are pathological conditions with an unknown aetiology that are characterised by severe inflammation of the intestinal tract and collectively referred to as inflammatory bowel disease (IBD). Current treatments are mostly ineffective due to their limited efficacy or toxicity, necessitating surgical resection of the affected bowel. The management of IBD is hindered by a lack of prognostic markers for clinical inflammatory relapse. Intestinal inflammation associates with the infiltration of immune cells (leukocytes) into, or surrounding the neuronal ganglia of the enteric nervous system (ENS) termed plexitis or ganglionitis. Histological observation of plexitis in unaffected intestinal regions is emerging as a vital predictive marker for IBD relapses. Plexitis associates with alterations to the structure, cellular composition, molecular expression and electrophysiological function of enteric neurons. Moreover, plexitis often occurs before the onset of gross clinical inflammation, which may indicate that plexitis can contribute to the progression of intestinal inflammation. In this review, the bilateral relationships between the ENS and inflammation are discussed. These include the effects and mechanisms of inflammation-induced enteric neuronal loss and plasticity. Additionally, the role of enteric neurons in preventing antigenic/pathogenic insult and immunomodulation is explored. While all current treatments target the inflammatory pathology of IBD, interventions that protect the ENS may offer an alternative avenue for therapeutic intervention.

Risk factors for failure of ileal pouch-anal anastomosis in patients with refractory ulcerative colitis

BACKGROUND

Proctocolectomy with ileal pouch-anal anastomosis is the standard surgical procedure for ulcerative colitis refractory to medical treatment. In a few cases, ileal pouch-anal anastomosis cannot be completed due to intraoperative technical problems. The aim of this single-center study was to identify risk factors for a technically failed ileal pouch-anal anastomosis.

METHODS

In total, 391 patients with ulcerative colitis who received ileal pouch-anal anastomosis were identified. Clinical and perioperative data from patients with successful ileal pouch-anal anastomosis (IPAA+) were compared to data from failed ileal pouch-anal anastomosis (IPAA-). Definition of failed ileal pouch-anal anastomosis was intraoperative failure to perform ileal pouch-anal anastomosis. Risk factors for failed ileal pouch-anal anastomosis were assessed by logistic regression. Cut-off values were calculated on the basis of receiver operating characteristic curves and the Youden Index.

RESULTS

The rate of failed ileal pouch-anal anastomosis was 26 of 391 (6.6%). In 22 of 26 cases (84.6%), there was an insufficient length of the small intestinal mesentery. Patients with failed ileal pouch-anal anastomosis were more often male (80.8% vs 54.5%, P = .009), older (47.1 ± 14.1 vs 39.2 ± 12.8 years, P = .007), had a higher body mass index 27.2 ± 4.5 vs 23.7 ± 4.3 kg/m², P < .001), and had extraintestinal manifestations more frequently (65.4% vs 26.3%, P < .001). Further risk factors for failed ileal pouch-anal anastomosis were hypertension and Cushing's syndrome.

CONCLUSION

Technical failure of ileal pouch-anal anastomosis is elevated in patients with higher body mass index, with refractory ulcerative colitis, and/or extended immunosuppressive medication. Three-staged ileal pouch-anal anastomosis and optimizing preoperative conditions may help to elevate the rate of successful ileoanal pouch construction in these patients.

Role of perivascular nerve and sensory neurotransmitter dysfunction in inflammatory bowel disease

Inflammatory bowel disease (IBD) is associated with both impaired intestinal blood flow and increased risk of cardiovascular disease, but the functional role of perivascular nerves that control vasomotor function of mesenteric arteries (MAs) perfusing the intestine during IBD is unknown. Because perivascular sensory nerves and their transmitters calcitonin gene-related peptide (CGRP) and substance P (SP) are important mediators of both vasodilation and inflammatory responses, our objective was to identify IBD-related deficits in perivascular sensory nerve function and vascular neurotransmitter signaling. In MAs from an interleukin-10 knockout (IL-10-/-) mouse model, IBD significantly impairs electrical field stimulation (EFS)-mediated sensory vasodilation and inhibition of sympathetic vasoconstriction, despite decreased sympathetic nerve density and vasoconstriction. The MA content and EFS-mediated release of both CGRP and SP are decreased with IBD, but IBD has unique effects on each transmitter. CGRP nerve density, receptor expression, hyperpolarization, and vasodilation are preserved with IBD. In contrast, SP nerve density and receptor expression are increased, and SP hyperpolarization and vasodilation are impaired with IBD. A key finding is that blockade of SP receptors restores EFS-mediated sensory vasodilation and enhanced CGRP-mediated vasodilation in MAs from IBD but not Control mice. Together, these data suggest that an aberrant role for the perivascular sensory neurotransmitter SP and its downstream signaling in MAs underlies vascular dysfunction with IBD. We propose that with IBD, SP signaling impedes CGRP-mediated sensory vasodilation, contributing to impaired blood flow. Thus, substance P and NK1 receptors may represent an important target for treating vascular dysfunction in IBD.NEW & NOTEWORTHY Our study is the first to show that IBD causes profound impairment of sensory vasodilation and inhibition of sympathetic vasoconstriction in mesenteric arteries. This occurs alongside decreased SP-containing nerve density and increased expression of NK1 receptors for SP. In contrast, CGRP dilation, nerve density, and receptor expression are unchanged. Blocking NK1 receptors restores sensory vasodilation in MAs and increases CGRP-mediated vasodilation, indicating that SP interference with CGRP signaling may underlie impaired sensory vasodilation with IBD.

Biomarkers and Their Possible Functions in the Intestinal Microenvironment of Chagasic Megacolon: An Overview of the (Neuro)inflammatory Process

The association between inflammatory processes and intestinal neuronal destruction during the progression of Chagasic megacolon is well established. However, many other components play essential roles, both in the long-term progression and control of the clinical status of patients infected with Trypanosoma cruzi. Components such as neuronal subpopulations, enteric glial cells, mast cells and their proteases, and homeostasis-related proteins from several organic systems (serotonin and galectins) are differentially involved in the progression of Chagasic megacolon. This review is aimed at revealing the characteristics of the intestinal microenvironment found in Chagasic megacolon by using different types of already used biomarkers. Information regarding these components may provide new therapeutic alternatives and improve the understanding of the association between T. cruzi infection and immune, endocrine, and neurological system changes.

Convergence of peptidergic and non-peptidergic protein markers in the human dorsal root ganglion and spinal dorsal horn

Peripheral sensory neurons are characterized by their size, molecular profiles, and physiological responses to specific stimuli. In mouse, the peptidergic and non-peptidergic subsets of nociceptors are distinct and innervate different lamina of the spinal dorsal horn. The unique molecular signature and neuroanatomical organization of these neurons supports a labeled line theory for certain types of nociceptive stimuli. However, long-standing evidence supports the polymodal nature of nociceptors in many species. We have recently shown that the peptidergic marker, CGRP, and the non-peptidergic marker, P2X3R, show largely overlapping expression at the mRNA level in human dorsal root ganglion (DRG). Herein, our aim was to assess the protein distribution of nociceptor markers, including their central projections, in the human DRG and spinal cord. Using DRGs obtained from organ donors, we observed that CGRP and P2X3R were co-expressed by approximately 33% of human DRG neurons and TrpV1 was expressed in ~60% of human DRG neurons. In the dorsal spinal cord, CGRP, P2X3R, TrpV1, and Nav1.7 proteins stained the entirety of lamina 1-2, with only P2XR3 showing a gradient of expression. This was confirmed by measuring the size of the substantia gelatinosa using Hematoxylin and Eosin staining of adjacent sections. Our findings are consistent with the known polymodal nature of most primate nociceptors and indicate that the central projection patterns of nociceptors are different between mice and humans. Elucidating how human nociceptors connect to subsets of dorsal horn neurons will be important for understanding the physiological consequences of these species differences.

Advanced Modeling of Peripheral Neuro-Effector Communication and -Plasticity

The peripheral nervous system (PNS) plays crucial roles in physiology and disease. Neuro-effector communication and neuroplasticity of the PNS are poorly studied, since suitable models are lacking. The emergence of human pluripotent stem cells (hPSCs) has great promise to resolve this deficit. hPSC-derived PNS neurons, integrated into organ-on-a-chip systems or organoid cultures, allow co-cultures with cells of the local microenvironment to study neuro-effector interactions and to probe mechanisms underlying neuroplasticity.

Altered Caecal Neuroimmune Interactions in the Neuroligin-3R451C Mouse Model of Autism

The intrinsic nervous system of the gut interacts with the gut-associated lymphoid tissue (GALT) via bidirectional neuroimmune interactions. The caecum is an understudied region of the gastrointestinal (GI) tract that houses a large supply of microbes and is involved in generating immune responses. The caecal patch is a lymphoid aggregate located within the caecum that regulates microbial content and immune responses. People with Autism Spectrum Disorder (ASD; autism) experience serious GI dysfunction, including inflammatory disorders, more frequently than the general population. Autism is a highly prevalent neurodevelopmental disorder defined by the presence of repetitive behavior or restricted interests, language impairment, and social deficits. Mutations in genes encoding synaptic adhesion proteins such as the R451C missense mutation in neuroligin-3 (NL3) are associated with autism and impair synaptic transmission. We previously reported that NL3^R451C mice, a well-established model of autism, have altered enteric neurons and GI dysfunction; however, whether the autism-associated R451C mutation alters the caecal enteric nervous system and immune function is unknown. We assessed for gross anatomical changes in the caecum and quantified the proportions of caecal submucosal and myenteric neurons in wild-type and NL3^R451C mice using immunofluorescence. In the caecal patch, we assessed total cellular density as well as the density and morphology of Iba-1 labeled macrophages to identify whether the R451C mutation affects neuro-immune interactions. NL3^R451C mice have significantly reduced caecal weight compared to wild-type mice, irrespective of background strain. Caecal weight is also reduced in mice lacking Neuroligin-3. NL3^R451C caecal ganglia contain more neurons overall and increased numbers of Nitric Oxide (NO) producing neurons (labeled by Nitric Oxide Synthase; NOS) per ganglion in both the submucosal and myenteric plexus. Overall caecal patch cell density was unchanged however NL3^R451C mice have an increased density of Iba-1 labeled enteric macrophages. Macrophages in NL3^R451C were smaller and more spherical in morphology. Here, we identify changes in both the nervous system and immune system caused by an autism-associated mutation in Nlgn3 encoding the postsynaptic cell adhesion protein, Neuroligin-3. These findings provide further insights into the potential modulation of neural and immune pathways.

Transient receptor potential ankyrin 1 promoter methylation and peripheral pain sensitivity in Crohn's disease

Background

Crohn’s disease is a chronic inflammatory disorder of the gastrointestinal tract associated with abdominal pain and diarrhea. Pain caused by Crohn’s disease likely involves neurogenic inflammation which seems to involve the ion channel transient receptor potential ankyrin 1 (TRPA1). Since the promoter methylation of TRPA1 was shown to influence pain sensitivity, we asked if the expression of TRPA1 is dysregulated in patients suffering from Crohn’s disease.

The methylation rates of CpG dinucleotides in the TRPA1 promoter region were determined from DNA derived from whole blood samples of Crohn patients and healthy participants. Quantitative sensory testing was used to examine pain sensitivities.

Results

Pressure pain thresholds were lower in Crohn patients as compared to healthy participants, and they were also lower in females than in males. They correlated inversely with the methylation rate at the CpG − 628 site of the TRPA1 promoter. This effect was more pronounced in female compared to male Crohn patients. Similar results were found for mechanical pain thresholds. Furthermore, age-dependent effects were detected. Whereas the CpG − 628 methylation rate declined with age in healthy participants, the methylation rate in Crohn patients increased. Pressure pain thresholds increased with age in both cohorts.

Conclusions

The TRPA1 promoter methylation appears to be dysregulated in patients suffering from Crohn’s disease, and this effect is most obvious when taking gender and age into account. As TRPA1 is regarded to be involved in pain caused by neurogenic inflammation, its aberrant expression may contribute to typical symptoms of Crohn’s disease.

Neuroimmune Interactions in the Gut and Their Significance for Intestinal Immunity

Inflammatory bowel diseases (IBD) have a complex, multifactorial pathophysiology with an unmet need for effective treatment. This calls for novel strategies to improve disease outcome and quality of life for patients. Increasing evidence suggests that autonomic nerves and neurotransmitters, as well as neuropeptides, modulate the intestinal immune system, and thereby regulate the intestinal inflammatory processes. Although the autonomic nervous system is classically divided in a sympathetic and parasympathetic branch, both play a pivotal role in the crosstalk with the immune system, with the enteric nervous system acting as a potential interface. Pilot clinical trials that employ vagus nerve stimulation to reduce inflammation are met with promising results. In this paper, we review current knowledge on the innervation of the gut, the potential of cholinergic and adrenergic systems to modulate intestinal immunity, and comment on ongoing developments in clinical trials.

Nitrergic Enteric Neurons in Health and Disease-Focus on Animal Models

Nitrergic enteric neurons are key players of the descending inhibitory reflex of intestinal peristalsis, therefore loss or damage of these neurons can contribute to developing gastrointestinal motility disturbances suffered by patients worldwide. There is accumulating evidence that the vulnerability of nitrergic enteric neurons to neuropathy is strictly region-specific and that the two main enteric plexuses display different nitrergic neuronal damage. Alterations both in the proportion of the nitrergic subpopulation and in the total number of enteric neurons suggest that modification of the neurochemical character or neuronal death occurs in the investigated gut segments. This review aims to summarize the gastrointestinal region and/or plexus-dependent pathological changes in the number of nitric oxide synthase (NOS)-containing neurons, the NO release and the cellular and subcellular expression of different NOS isoforms. Additionally, some of the underlying mechanisms associated with the nitrergic pathway in the background of different diseases, e.g., type 1 diabetes, chronic alcoholism, intestinal inflammation or ischaemia, will be discussed.

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.

The Transient Receptor Potential Vanilloid 1 Is Associated with Active Inflammation in Ulcerative Colitis

The transient receptor potential vanilloid 1 (TRPV1) may play a role in the pathogenesis of ulcerative colitis (UC). The aim of the study was to determine the gene and protein expression of TRPV1 in UC patients and noninflamed controls. Gene expression was performed by RT-PCR, and protein expression was performed by immunohistochemistry. The gene expression of TRPV1 was significantly increased in the remission UC group compared to active UC patients (P = 0.002), and an upregulation of the TRPV1 gene was associated with clinical outcomes such as age at diagnosis (<40 years) (P = 0.02) and clinical disease course characterized by relapsing and continuous activity (P = 0.07). TRPV1 immunoreactive cells were conspicuously higher in all intestinal layers from active UC patients compared with noninflamed control tissue. These findings suggest that TRPV1 might be involved in UC pathogenesis.

Potentiation of capsaicin-induced neurogenic inflammation by 5-HT7 receptors in the rat hind paw: Involvement of calcitonin gen-related peptide

A decrease in the activation threshold of primary sensory neurons to transient receptor potential V1 (TRPV1) stimulation by serotonin 5-HT7 receptors has been reported but no confirmation if this might translate into facilitation of neurogenic inflammation has been provided. We analysed the modulation of capsaicin (CAP)-induced neurogenic inflammation in the rat hind paw by the selective 5-HT7 receptor agonist, LP-44, and the involvement of calcitonin gen-related peptide (CGRP) in this effect. Animals received intra-plantar injections (30 μL) of vehicle, CAP (0.05%, 0.1% and 0.2%), LP-44 (7.5 and 15 nmol) and the combination of LP-44 + CAP; then, the time course of the inflammatory responses was measured. The effect of the 5-HT7 receptor antagonist, SB-269970 (3 mg/kg, s.c.), on responses produced by LP-44 alone and combined with CAP was tested. As expected, CAP produced concentration- and time-dependent inflammatory responses in the hind paw. Interestingly, LP-44 by itself also produced inflammation in a concentration- and time-dependent manner, and magnified CAP-induced responses. Systemic pre-treatment with SB-269970 significantly blunted LP-44 (15 nmol)-induced inflammation as well as magnified inflammatory responses produced by the combination of LP-44 (7.5 and 15 nmol) + CAP (0.1%) thus confirming the involvement of 5-HT7 receptors. Finally, the non-peptide CGRP receptor antagonist, BIBN4096 (3 mg/kg, s.c.), strongly inhibited the potentiated inflammatory responses induced by LP-44 (7.5 and 15 nmol) + CAP (0.1%) thus substantiating their neurogenic nature. Thus, sensitization of CAP-sensitive primary sensory neurons by 5-HT7 receptors may result in facilitation of neurogenic inflammation involving CGRP in the rat hind paw.

Expression Profiling of the Transient Receptor Potential Vanilloid (TRPV) Channels 1, 2, 3 and 4 in Mucosal Epithelium of Human Ulcerative Colitis

The Transient Receptor Potential (TRP) family of selective and non-selective ion channels is well represented throughout the mammalian gastrointestinal track. Several members of the Transient Receptor Potential Vanilloid (TRPV) subfamily have been identified in contributing to modulation of mobility, secretion and sensitivity of the human intestine. Previous studies have focused on the detection of TRPV mRNA levels in colon tissue of patients with inflammatory bowel disease (IBD) whereas little information exists regarding TRPV channel expression in the colonic epithelium. The aim of this study was to evaluate the expression levels of TRPV1, TRPV2, TRPV3 and TRPV4 in mucosa epithelial cells of colonic biopsies from patients with ulcerative colitis (UC) in comparison to colonic resections from non-IBD patients (control group). Immunohistochemistry, using specific antibodies and quantitative analyses of TRPV-immunostained epithelial cells, was performed in semi-serial sections of the samples. TRPV1 expression was significantly decreased whereas TRPV4 expression was significantly increased in the colonic epithelium of UC patients compared to patients in the control group (p < 0.05). No significant difference for TRPV2 and TRPV3 expression levels between UC and control specimens was detected (p > 0.05). There was no correlation between TRPV channel expression and the clinical features of the disease (p > 0.05). Further investigation is needed to clarify the role of TRPV channels in human bowel inflammatory response.

Increased enteric glial cells in proximal margin of resection is associated with postoperative recurrence of Crohn's disease

BACKGROUND AND AIM

The enteric nervous system can amplify or modulate intestinal inflammation through secretion of neuropeptides, and enteric glial cells have been implicated in the pathophysiology of Crohn's disease. The goal of the study was to search for an association between the density of neurons, neuropeptides, and enteric glial cells and postoperative recurrence.

METHODS

The ileal proximal uninflamed section from ileocolonic sample was studied using immunohistochemistry with antibodies directed against vasoactive intestinal polypeptide (VIP), substance P (SP), neuron-specific enolase (NSE), and the glial marker protein S100. The density in the submucosa was calculated, and the relationship of the density of VIP, SP, NSE, and S100 and postoperative disease recurrence was assessed.

RESULTS

There were no significant differences between patients with and without postoperative endoscopic recurrence or clinical recurrence for the density of NSE-positive, VIP-positive, or SP-positive neurons in the proximal margin. Interestingly, the density of S100-positive enteric glial cells was significantly increased in patients with endoscopic and clinical recurrence than in subjects without disease recurrence (P ˂ 0.001). The density of S100-positive enteric glial cells was independently associated with postoperative disease recurrence.

CONCLUSIONS

Increased S100-positive enteric glial cells are associated with a high risk of both endoscopic and clinical recurrence after surgery. These findings have implications in individualized postoperative prophylaxis for Crohn's disease.

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

The enteric nervous system (ENS), localized in the wall of the gastrointestinal tract, regulates the functions of the intestine using a wide range of neuronally-active substances. One of them is the calcitonin gene-related peptide (CGRP), whose participation in pathological states in the large intestine remains unclear. Therefore, the aim of this study was to investigate the influence of inflammation and nerve damage using a double immunofluorescence technique to neurochemically characterize CGRP-positive enteric nervous structures in the porcine descending colon. Both pathological factors caused an increase in the percentage of CGRP-positive enteric neurons, and these changes were the most visible in the myenteric plexus after nerve damage. Moreover, both pathological states change the degree of co-localization of CGRP with other neurochemical factors, including substance P, the neuronal isoform of nitric oxide synthase, galanin, cocaine- and amphetamine-regulated transcript peptide and vesicular acetylcholine transporter. The character and severity of these changes depended on the pathological factor and the type of enteric plexus. The obtained results show that CGRP-positive enteric neurons are varied in terms of neurochemical characterization and take part in adaptive processes in the descending colon during inflammation and after nerve damage.

Evidence-based update on rosacea comorbidities and their common physiologic pathways

Rosacea is a common chronic inflammatory disease affecting the facial skin whose etiology and pathophysiology are the subject of much investigation. Risk factors include genetic and environmental elements that may predispose individuals to localized inflammation and abnormal neurovascular responses to stimuli. Recent studies have introduced an array of systemic rosacea comorbidities, such as inflammatory bowel disease and neurologic conditions, that can be challenging to synthesize. We critically review the current data behind reported rosacea comorbidities and identify and highlight underrecognized physiologic mediators shared among rosacea and associated comorbidities. This information may be helpful in addressing patient questions about potential systemic implications of rosacea and can serve as a candidate platform for future research to understand rosacea and improve treatments.

Impairment of Small Intestinal Function in Ulcerative Colitis: Role of Enteric Innervation

Small intestinal dysfunction has been described in patients with ulcerative colitis and in experimental animal models of colitis. This is demonstrated by a decrease in fluid, electrolyte, amino acid, fat and carbohydrate absorption as well as by deranged intestinal motility. Histopathological changes in the small intestines in colitis have not been consistently demonstrated, but there is evidence of structural and biochemical alterations as shown by increased intestinal permeability and a decrease in the expression of multiple brush border membrane enzymes such as disaccharidases and aminopetidases, in both humans and experimental animals. The pathophysiology of this dysfunction has not been elucidated, but it is thought to include alterations in neural circuitry such as increased neuronal excitability, neuronal damage and changes of neuropeptidergic innervation and receptors as well as an increase in local production of pro-inflammatory cytokines and alterations in the production of some neurohumoral mediators. In the following, we provide an update on the advancement of clinical and scientific contributions to elucidate the underlying mechanisms of the alteration of the functions of apparently intact small intestinal segments, induced by ulcerative colitis.

IBS and IBD - separate entities or on a spectrum?

The acute phase of IBD with inflamed gut and often ulcerated mucosa is clearly different from the apparently normal mucosa characteristic of IBS. However, more detailed assessment has detected immune activation, increased gut permeability, increased mucosal serotonin availability, abnormalities of enteric nerve structure and function, and dysbiosis in gut microbiota in IBS - all features seen in IBD. Furthermore, as treatments for inflammation in IBD have become more effective it is now apparent that ∼1 in 3 patients with IBD in remission from inflammation still have persistent abnormalities of sensation, motility and gut microbiota, which might cause IBS-like symptoms. This Perspective explores the overlap between IBS and IBD and their treatments, proposing future directions for research in this stimulating area.

The Role of the Mesentery in Crohn's Disease: The Contributions of Nerves, Vessels, Lymphatics, and Fat to the Pathogenesis and Disease Course

Crohn's disease (CD) is a complex gastrointestinal disorder involving multiple levels of cross talk between the immunological, neural, vascular, and endocrine systems. The current dominant theory in CD is based on the unidirectional axis of dysbiosis-innate immunity-adaptive immunity-mesentery-body system. Emerging clinical evidence strongly suggests that the axis be bidirectional. The morphologic and/or functional abnormalities in the mesenteric structures likely contribute to the disease progression of CD, to a less extent the disease initiation. In addition to adipocytes, mesentery contains nerves, blood vessels, lymphatics, stromal cells, and fibroblasts. By the secretion of adipokines that have endocrine functions, the mesenteric fat tissue exerts its activity in immunomodulation mainly through response to afferent signals, neuropeptides, and functional cytokines. Mesenteric nerves are involved in the pathogenesis and prognosis of CD mainly through neuropeptides. In addition to angiogenesis observed in CD, lymphatic obstruction, remodeling, and impaired contraction maybe a cause and consequence of CD. Lymphangiogenesis and angiogenesis play a concomitant role in the progress of chronic intestinal inflammation. Finally, the interaction between neuropeptides, adipokines, and vascular and lymphatic endothelia leads to adipose tissue remodeling, which makes the mesentery an active participator, not a bystander, in the disease initiation and precipitation CD. The identification of the role of mesentery, including the structure and function of mesenteric nerves, vessels, lymphatics, and fat, in the intestinal inflammation in CD has important implications in understanding its pathogenesis and clinical management.

Rosacea in Patients with Ulcerative Colitis and Crohn's Disease: A Population-based Case-control Study

BACKGROUND

Cutaneous manifestations are common in patients with inflammatory bowel diseases (IBDs) (ulcerative colitis [UC] and Crohn's disease [CD]). Previous case reports described patients with IBD who developed rosacea. IBD and rosacea are inflammatory epithelial diseases, presumably associated with changes in the innate immune system. We explored the association between IBD and incident rosacea.

METHODS

We conducted a population-based matched (1:1) case-control analysis on the association between IBD and rosacea, stratified by IBD disease duration and severity. We used data from the UK-based Clinical Practice Research Datalink. Cases had an incident diagnosis of rosacea recorded between 1995 and 2013.

RESULTS

Among 80,957 rosacea cases and the same number of controls, a history of UC was associated with an increased risk of rosacea (odds ratio [OR] 1.65, 95% confidence interval [CI], 1.43-1.90), with the highest OR in those with short UC duration (OR 2.85, 95% confidence interval, 1.80-4.50 for patients with <2 years of disease history). A history of CD yielded an overall OR of 1.49 (95% CI, 1.25-1.77), which did not correlate with disease duration. Additional analyses on IBD disease severity yielded evidence for a higher risk of rosacea in those with higher UC and CD activity.

CONCLUSIONS

Our findings provide evidence that patients with IBD may be at increased risk of rosacea (higher in UC), particularly during phases of increased IBD-associated gastrointestinal tract inflammation.

Allogeneic guinea pig mesenchymal stem cells ameliorate neurological changes in experimental colitis

Background

The use of mesenchymal stem cells (MSCs) to treat inflammatory bowel disease (IBD) is of great interest because of their immunomodulatory properties. Damage to the enteric nervous system (ENS) is implicated in IBD pathophysiology and disease progression. The most commonly used model to study inflammation-induced changes to the ENS is 2,4,6-trinitrobenzene-sulfonate acid (TNBS)-induced colitis in guinea pigs; however, no studies using guinea pig MSCs in colitis have been performed. This study aims to isolate and characterise guinea pig MSCs and then test their therapeutic potential for the treatment of enteric neuropathy associated with intestinal inflammation.

Methods

MSCs from guinea pig bone marrow and adipose tissue were isolated and characterised in vitro. In in vivo experiments, guinea pigs received either TNBS for the induction of colitis or sham treatment by enema. MSCs were administered at a dose of 1 × 10⁶ cells via enema 3 h after the induction of colitis. Colon tissues were collected 24 and 72 h after TNBS administration to assess the level of inflammation and damage to the ENS. The secretion of transforming growth factor-β1 (TGF-β1) was analysed in MSC conditioned medium by flow cytometry.

Results

Cells isolated from both sources were adherent to plastic, multipotent and expressed some human MSC surface markers. In vitro characterisation revealed distinct differences in growth kinetics, clonogenicity and cell morphology between MSC types. In an in vivo model of TNBS-induced colitis, guinea pig bone marrow MSCs were comparatively more efficacious than adipose tissue MSCs in attenuating weight loss, colonic tissue damage and leukocyte infiltration into the mucosa and myenteric plexus. MSCs from both sources were equally neuroprotective in the amelioration of enteric neuronal loss and changes to the neurochemical coding of neuronal subpopulations. MSCs from both sources secreted TGF-β1 which exerted neuroprotective effects in vitro.

Conclusions

This study is the first evaluating the functional capacity of guinea pig bone marrow and adipose tissue-derived MSCs and providing evidence of their neuroprotective value in an animal model of colitis. In vitro characteristics of MSCs cannot be extrapolated to their therapeutic efficacy. TGF-β1 released by both types of MSCs might have contributed to the attenuation of enteric neuropathy associated with colitis.

Human adult stem cells derived from adipose tissue and bone marrow attenuate enteric neuropathy in the guinea-pig model of acute colitis

Introduction

Mesenchymal stem cells (MSCs) have been identified as a viable treatment for inflammatory bowel disease (IBD). MSCs derived from bone marrow (BM-MSCs) have predominated in experimental models whereas the majority of clinical trials have used MSCs derived from adipose tissue (AT-MSCs), thus there is little consensus on the optimal tissue source. The therapeutic efficacies of these MSCs are yet to be compared in context of the underlying dysfunction of the enteric nervous system innervating the gastrointestinal tract concomitant with IBD. This study aims to characterise the in vitro properties of MSCs and compare their in vivo therapeutic potential for the treatment of enteric neuropathy associated with intestinal inflammation.

Methods

BM-MSCs and AT-MSCs were validated and characterised in vitro. In in vivo experiments, guinea-pigs received either 2,4,6-trinitrobenzene-sulfonate acid (TNBS) for the induction of colitis or sham treatment by enema. MSCs were administered at a dose of 1x10⁶ cells via enema 3 hours after the induction of colitis. Colon tissues were collected 24 and 72 hours after TNBS administration to assess the level of inflammation and damage to the ENS. MSC migration to the myenteric plexus in vivo was elucidated by immunohistochemistry and in vitro using a modified Boyden chamber assay.

Results

Cells exhibited multipotency and a typical surface immunophenotype for validation as bona fide MSCs. In vitro characterisation revealed distinct differences in growth kinetics, clonogenicity and cell morphology between MSC types. In vivo, BM-MSCs were comparatively more effective than AT-MSCs in attenuating leukocyte infiltration and neuronal loss in the myenteric plexus. MSCs from both sources equally ameliorated body weight loss, gross morphological damage to the colon, changes in the neurochemical coding of neuronal subpopulations and the reduction in density of extrinsic and intrinsic nerve fibres innervating the colon. MSCs from both sources migrated to the myenteric plexus in in vivo colitis and in an in vitro assay.

Conclusions

These data from in vitro experiments suggest that AT-MSCs are ideal for cellular expansion. However, BM-MSCs were more therapeutic in the treatment of enteric neuropathy and plexitis. These characteristics should be considered when deciding on the MSC tissue source.