Neuropeptides and inflammatory bowel disease

Efficacy of the neurotensin receptor 1 analog PD149163 in modulation of the kidney inflammation: Inhibition of the nuclear factor kappa β signaling pathway and oxidative stress in endotoxemic mice

This study elucidated that the neurotensin receptor 1 agonist PD149163 ameliorated the kidney inflammation in endotoxemic mice inhibiting the nuclear factor kappa β (NF-kβ) pathway and reducing the oxidative stress in a dose-dependent manner. Swiss albino female mice (8 weeks; 25 ± 5 gms) were maintained in six groups (n = 6): Group 1/control, Group 2, Group 3 and Group 4 were exposed to lipopolysaccharide/LPS (1 mg/kg bw; i.p; 5 days) followed by PD149163 treatment with low dose/NTS50 (50 μg/kg BW i.p. 28 days) and high dose/NTS100 (100 μg/kg BW i.p. 28 days) to Group 3 and Group 4 respectively. Group 5 and Group 6 mice were only treated with the agonist, similar low and high doses respectively for the same duration. The results showed LPS-induced significant increase in the plasma levels of the NF-kβ, pro-inflammatory cytokines (TNF-α, IL-6) and a decrease in the anti-inflammatory cytokine IL-10. A significant increase in the pro-oxidant (LPx) and decrease of the anti-oxidants (SOD, CAT) in the kidney tissue was noted. Plasma NTS level was significantly decreased along with a significant increase of the corticosterone. The inflammation was reflected in the kidney histopathology. PD149163 significantly reduced inflammation by down-regulating NF-kβ, TNF-α, IL-6, CORT levels, oxidative stress and alleviated kidney injury. PD149163 enhanced the plasma level of NT. The role of PD149163 in the modulation of inflammation of kidney tissue by its anti-inflammatory and anti-oxidative effects is suggested. Further studies may better confirm the efficacy of the NTS analog for therapeutic intervention in inflammation-related diseases of the kidney.

Neurotensin receptor agonist PD149163 modulates LPS-induced enterocyte apoptosis by downregulating TNFR pathway and executioner caspase 3 in endotoxemic mice: insights from in vivo and in silico study

This study was designed to evaluate the dose-dependent efficacy of neurotensin receptor-1 (NTSR1) agonist PD149163 in the amelioration of the lipopolysaccharide (LPS)-induced apoptosis in the gastrointestinal tract (GIT) of mice. PD149163 is an analogue of NTS, a GIT tri-decapeptide with anti-inflammatory and anti-oxidative effects. Swiss-albino mice (female/8 weeks/25 ± 2.5 g) were divided into six groups: control; LPS, LPS + PD149163L, and LPS + PD149163H groups were treated with LPS (0.2 μmol/L/kgBW; 5 days), followed by exposure of PD149163 to LPS + PD149163L (10.6 μmol/L/kgBW), and LPS + PD149163H (21.2 μmol/L/kgBW) for 28 days. OnlyPD149163L (10.6 μmol/L/kgBW) and onlyPD149163H (21.2 μmol/L/kgBW) groups were maintained for 28 days. Both the LPS and PD149163 were given intraperitoneally. PD149163 treatment for 4 weeks alleviated the LPS-induced enterocyte apoptosis in a dose-dependent manner. LPS-induced excessive levels of caspase-3, tumour necrosis factor-α, and leptin (biomarkers of LPS-induced apoptosis) in plasma were decreased by PD149163H treatment. Moreover, LPS-induced gut oxidative stress was ameliorated by PD149163H supplementation, as evidenced by the decreased content of malondialdehyde, lipid-hydroperoxide and increased level of superoxide-dismutase, catalase. Furthermore, PD149163H mediated elevation of the plasma anti-apoptotic protein (B-cell leukaemia/lymphoma-2) along with the NTS level contributed to the modulation of LPS-induced enterocyte apoptosis, reflected in histopathology. In vivo results were substantiated with in silico molecular docking analysis that predicted the binding of PD149163-TLR4 complex, suggesting that PD149163 can act as a TLR4 modulator and inhibit the activation of TLR4. The role of PD149163 in ameliorating GIT apoptosis by its anti-apoptotic and antioxidative effects is suggested. Further research may provide significant insights into the therapeutic intervention of PD149163 in apoptosis-related diseases of GIT.

Exosomes Derived from hucMSCs Primed with IFN-γ Suppress the NF-κB Signal Pathway in LPS-Induced ALI by Modulating the miR-199b-5p/AFTPH Axis

Exosomes (exos) are primarily responsible for the process of mesenchymal stem cells (MSCs) treatment for acute lung injury (ALI), but the mechanism remains unclear, particularly in altered microenvironment. Therefore, this study aimed to investigate the potential mechanism of exos derived from human umbilical cord mesenchymal stem cells (hucMSCs) primed with interferon-gamma (IFN-γ) on ALI and to propose a promising and cell-free strategy. This study extracted exos from hucMSCs supernatant primed and unprimed with IFN-γ marked with IFN-γ-exos and CON-exos, which were identified and traced. IFN-γ-exos administration to ALI models suppressed the NF-κB signaling pathway compared to CON-exos, which were quantified through western blot and immunohistochemical staining. Reverse transcription-quantitative polymerase chain reaction validated miR-199b-5p expression in the IFN-γ-exos and CON-exos treatment groups. Data analysis, a dual-luciferase reporter assay, and cell transfection were conducted to investigate the target binding between miR-199b-5p and Aftiphilin (AFTPH), with AFTPH expression analyzed via cell immunofluorescence and western blot. Co-immunoprecipitation was conducted for the interaction between AFTPH and NF-κB p65. The result revealed that miR-199b-5p was down-regulated in the IFN-γ-exos treatment group, which had a target binding site with AFTPH, and an interaction with NF-κB p65. Consequently, IFN-γ-exos inhibited the NF-κB signaling pathway in ALI in vitro and in vivo through the miR-199b-5p/AFTPH axis. Our results demonstrated new directions of novel and targeted treatment for ALI.

LRRK2 expression in normal and pathologic human gut and in rodent enteric neural cell lines

Leucine-rich repeat kinase 2 (LRRK2) gene, which is the gene most commonly associated with Parkinson's disease (PD), is also a susceptibility gene for Crohn's disease, thereby suggesting that LRRK2 may sit at the crossroads of gastrointestinal inflammation, Parkinson's, and Crohn's disease. LRRK2 protein has been studied intensely in both CNS neurons and in immune cells, but there are only few studies on LRRK2 in the enteric nervous system (ENS). LRRK2 is present in ENS ganglia and the existing studies on LRRK2 expression in colonic biopsies from PD subjects have yielded conflicting results. Herein, we propose to extend these findings by studying in more details LRRK2 expression in the ENS. LRRK2 expression was evaluated in full thickness segments of colon of 16 Lewy body, 12 non-Lewy body disorders cases, and 3 non-neurodegenerative controls and in various enteric neural cell lines. We showed that, in addition to enteric neurons, LRRK2 is constitutively expressed in enteric glial cells in both fetal and adult tissues. LRRK2 immunofluorescence intensity in the myenteric ganglia was not different between Lewy body and non-Lewy body disorders. Additionally, we identified the cAMP pathway as a key signaling pathway involved in the regulation of LRRK2 expression and phosphorylation in the enteric glial cells. Our study is the first detailed characterization of LRRK2 in the ENS and the first to show that enteric glial cells express LRRK2. Our findings provide a basis to unravel the functions of LRRK2 in the ENS and to further investigate the pathological changes in enteric synucleinopathies.

Chronic Exposure to Cigarette Smoke Affects the Ileum and Colon of Guinea Pigs Differently. Relaxin (RLX-2, Serelaxin) Prevents Most Local Damage

Cigarette smoking (CS) is the cause of several organ and apparatus diseases. The effects of smoke in the gut are partially known. Accumulating evidence has shown a relationship between smoking and inflammatory bowel disease, prompting us to investigate the mechanisms of action of smoking in animal models. Despite the role played by neuropeptides in gut inflammation, there are no reports on their role in animal models of smoking exposure. The hormone relaxin has shown anti-inflammatory properties in the intestine, and it might represent a putative therapy to prevent gut damage caused by smoking. Presently, we investigate the effects of chronic smoke exposure on inflammation, mucosal secretion, and vasoactive intestinal peptide (VIP) and substance P (SP) expressions in the ileum and colon of guinea pigs. We also verify the ability of relaxin to counter the smoke-induced effects. Smoke impacted plasma carbon monoxide (CO). In the ileum, it induced inflammatory infiltrates, fibrosis, and acidic mucin production; reduced the blood vessel area; decreased c-kit-positive mast cells and VIP-positive neurons; and increased the SP-positive nerve fibers. In the colon, it reduced the blood vessel area and the goblet cell area and decreased c-kit-positive mast cells, VIP-positive neurons, and SP-positive nerve fibers. Relaxin prevented most of the smoking-induced changes in the ileum, while it was less effective in the colon. This study shows the diverse sensitivity to CS between the ileum and the colon and demonstrates that both VIP and SP are affected by smoking. The efficacy of relaxin proposes this hormone as a potential anti-inflammatory therapeutic to counteract gut damage in humans affected by inflammatory bowel diseases.

Immunomodulatory role of short neuropeptide F in the mud crab Scylla paramamosain

Short neuropeptide F (sNPF) is bioactive peptide secreted by neurons of invertebrates. It is one of the important pleiotropic neural molecules that is associated with a variety of physiological processes in invertebrates. However, little is known about the role of sNPF in the immune response. This study aimed to determine the distribution, localization, functional characteristics and signaling mechanisms of the sNPF gene and sNPF receptor (sNPF-R) gene in the mud crab Scylla paramamosain. Results of this study showed that Sp-sNPF and Sp-sNPF-R were widely expressed in neural tissue and other tissues including hemocytes. Further, in situ hybridization analysis revealed that Sp-sNPF and Sp-sNPF-R have specific localization in cerebral ganglion and hemocytes. It was also found that immune stimuli significantly induced Sp-sNPF expression in cerebral ganglion. The hemocyte-derived Sp-sNPF and Sp-sNPF-R were also efficiently activated upon immune stimulation. In vitro sNPF peptide administration enhanced phagocytic ability of hemocytes. However, this activity could be blocked through knockdown of sNPF-R-dsRNA or using adenylate cyclase inhibitors SQ 22536. The results of this study also demonstrated that the contents of signaling molecule adenylyl cyclase (AC), cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) in hemocytes can be up-regulated after incubation with sNPF peptide. In addition, the results of in vivo experiments showed that sNPF increased concentration of nitric oxide (NO) and enhanced phagocytic potential in S. paramamosain. The sNPF also significantly induced the expression of immune-related molecules at the gene level in S. paramamosain. In conclusion, the findings of this study indicate that sNPF mediates hemocyte phagocytosis via sNPF-R receptor-coupled AC-cAMP-PKA pathway and influences the innate immune processes in S. paramamosain.

Impact of plasma 5-hydroxyindoleacetic acid, a serotonin metabolite, on clinical outcome in septic shock, and its effect on vascular permeability

Septic shock is characterized by dysregulated vascular permeability. We hypothesized that the vascular permeability of endothelial cells (ECs) would be regulated by serotonin via serotonin-Rho-associated kinase (ROCK) signaling. We aimed to determine the impact of 5-hydroxyindoleacetic acid (5-HIAA) on septic shock as a novel biomarker. Plasma 5-HIAA levels and disease severity indices were obtained from 47 patients with sepsis. The association between 5-HIAA levels and severity indices was analyzed. Permeability upon serotonin stimulation was determined using human pulmonary microvascular ECs. 5-HIAA were significantly higher in septic shock patients than in patients without shock or healthy controls (p = 0.004). These elevated levels were correlated with severity indexes (SOFA score [p < 0.001], APACHE II [p < 0.001], and PaO₂:FiO₂ [p = 0.02]), and longitudinally associated with worse clinical outcomes (mechanical ventilation duration [p = 0.009] and ICU duration [p = 0.01]). In the experiment, serotonin increased the permeability of ECs, which was inhibited by the ROCK inhibitor (p < 0.001). Serotonin increases vascular permeability of ECs via ROCK signaling. This suggests a novel mechanism by which serotonin disrupts endothelial barriers via ROCK signaling and causes the pathogenesis of septic shock with a vascular leak. Serotonin serves as a novel biomarker of vascular permeability.

NLRP3 at the crossroads between immune/inflammatory responses and enteric neuroplastic remodelling in a mouse model of diet-induced obesity

BACKGROUND AND PURPOSE

Enteric neurogenic/inflammation contributes to bowel dysmotility in obesity. We examined the role of NLRP3 in colonic neuromuscular dysfunctions in mice with high-fat diet (HFD)-induced obesity.

EXPERIMENTAL APPROACH

Wild-type C57BL/6J and NLRP3-KO (Nlrp3^-/- ) mice were fed with HFD or standard diet for 8 weeks. The activation of inflammasome pathways in colonic tissues from obese mice was assessed. The role of NLRP3 in in vivo colonic transit and in vitro tachykininergic contractions and substance P distribution was evaluated. The effect of substance P on NLRP3 signalling was tested in cultured cells.

KEY RESULTS

HFD mice displayed increased body and epididymal fat weight, cholesterol levels, plasma resistin levels and plasma and colonic IL-1β levels, colonic inflammasome adaptor protein apoptosis-associated speck-like protein containing caspase-recruitment domain (ASC) and caspase-1 mRNA expression and ASC immunopositivity in macrophages. Colonic tachykininergic contractions were enhanced in HFD mice. HFD NLRP3^-/- mice developed lower increase in body and epididymal fat weight, cholesterol levels, systemic and bowel inflammation. In HFD Nlrp3^-/- mice, the functional alterations of tachykinergic pathways and faecal output were normalized. In THP-1 cells, substance P promoted IL-1β release. This effect was inhibited upon incubation with caspase-1 inhibitor or NK₁ antagonist and not observed in ASC^-/- cells.

CONCLUSION AND IMPLICATIONS

In obesity, NLRP3 regulates an interplay between the shaping of enteric immune/inflammatory responses and the activation of substance P/NK₁ pathways underlying the onset of colonic dysmotility. Identifying NLRP3 as a therapeutic target for the treatment of bowel symptoms related to obesity.

Dopamine Transporter Genetic Reduction Induces Morpho-Functional Changes in the Enteric Nervous System

Antidopaminergic gastrointestinal prokinetics are indeed commonly used to treat gastrointestinal motility disorders, although the precise role of dopaminergic transmission in the gut is still unclear. Since dopamine transporter (DAT) is involved in several brain disorders by modulating extracellular dopamine in the central nervous system, this study evaluated the impact of DAT genetic reduction on the morpho-functional integrity of mouse small intestine enteric nervous system (ENS). In DAT heterozygous (DAT^+/-) and wild-type (DAT^+/+) mice (14 ± 2 weeks) alterations in small intestinal contractility were evaluated by isometrical assessment of neuromuscular responses to receptor and non-receptor-mediated stimuli. Changes in ENS integrity were studied by real-time PCR and confocal immunofluorescence microscopy in longitudinal muscle-myenteric plexus whole-mount preparations (). DAT genetic reduction resulted in a significant increase in dopamine-mediated effects, primarily via D1 receptor activation, as well as in reduced cholinergic response, sustained by tachykininergic and glutamatergic neurotransmission via NMDA receptors. These functional anomalies were associated to architectural changes in the neurochemical coding and S100β immunoreactivity in small intestine myenteric plexus. Our study provides evidence that genetic-driven DAT defective activity determines anomalies in ENS architecture and neurochemical coding together with ileal dysmotility, highlighting the involvement of dopaminergic system in gut disorders, often associated to neurological conditions.

Galanin receptor 3 attenuates inflammation and influences the gut microbiota in an experimental murine colitis model

The regulatory (neuro)peptide galanin and its three receptors (GAL1-3R) are involved in immunity and inflammation. Galanin alleviated inflammatory bowel disease (IBD) in rats. However, studies on the galanin receptors involved are lacking. We aimed to determine galanin receptor expression in IBD patients and to evaluate if GAL2R and GAL3R contribute to murine colitis. Immunohistochemical analysis revealed that granulocytes in colon specimens of IBD patients (Crohn's disease and ulcerative colitis) expressed GAL2R and GAL3R but not GAL1R. After colitis induction with 2% dextran sulfate sodium (DSS) for 7 days, mice lacking GAL3R (GAL3R-KO) lost more body weight, exhibited more severe colonic inflammation and aggravated histologic damage, with increased infiltration of neutrophils compared to wild-type animals. Loss of GAL3R resulted in higher local and systemic inflammatory cytokine/chemokine levels. Remarkably, colitis-associated changes to the intestinal microbiota, as assessed by quantitative culture-independent techniques, were most pronounced in GAL3R-KO mice, characterized by elevated numbers of enterobacteria and bifidobacteria. In contrast, GAL2R deletion did not influence the course of colitis. In conclusion, granulocyte GAL2R and GAL3R expression is related to IBD activity in humans, and DSS-induced colitis in mice is strongly affected by GAL3R loss. Consequently, GAL3R poses a novel therapeutic target for IBD.

Expression profiles and prognostic significance of AFTPH in different tumors

Aftiphilin (AFTPH) plays an important role in regulating intracellular trafficking, exocytosis, and the pro‐inflammatory response. However, the potential prognostic role of AFTPH in cancers remains unclear. Here, we examined the expression profiles and prognostic significance of AFTPH in breast invasive carcinoma (BRCA), diffuse large B‐cell lymphoma (DLBC), lung squamous cell carcinoma (LUSC), and pancreatic adenocarcinoma (PADD) using the GEPIA and UALCAN databases. AFTPH expression was observed to be higher in cancer tissues than in normal tissues, but expression did not differ significantly between tumor stages for the four cancer types. AFTPH expression in cancer cell lines was investigated using the CCLE database; AFTPH was found to be highly expressed in four cancer cell lines. The relationship between AFTPH expression and patient prognosis was analyzed using GEPIA, LinkedOmics, and Kaplan–Meier plotter databases. Low expression of AFTPH was associated with improved prognosis for BRCA, DLBC, LUSC, and PAAD. Genetic alterations of AFTPH in cancers were explored using the cBioPortal website, revealing that gene copy number gains and amplification are common in BRCA, DLBC, LUSC, and PAAD. Related genes and markers associated with AFTPH were discovered using the LinkedOmics database. Furthermore, transfection of cells with AFTPH siRNA demonstrated that AFTPH exerts positive effects on cell proliferation in BRCA, LUSC, and PAAD cells. In conclusion, AFTPH may be a potential therapeutic target and prognostic biomarker for BRCA, DLBC, LUSC, and/or PAAD.

Glial-derived neurotrophic factor regulates enteric mast cells and ameliorates dextran sulfate sodium-induced experimental colitis

BACKGROUND & AIMS

Although interactions between enteric glial cells (EGCs) and enteric mast cells have been demonstrated to play an important role in the pathogenesis of inflammatory bowel disease (IBD), the exact mechanisms by which EGCs regulate enteric mast cells are still unknown. The aims of this study were to investigate whether glial-derived neurotrophic factor (GDNF), which has been confirmed to be produced mostly by EGCs, might regulate enteric mast cells and ameliorate dextran sulfate sodium (DSS)-induced experimental colitis.

METHODS

Recombinant adenoviral vectors encoding GDNF (Ad-GDNF) were administered intracolonically in experimental colitis induced by DSS. The disease activity index and histological score were measured. The expression of tumour necrosis factor-α (TNF-α), interleukin-6 and myeloperoxidase (MPO) activity were measured by ELISA assay. The expression of trypsin and β-hexosaminidase were evaluated. GDNF specific receptor (GFR-α1/RET) was detected. The calcium reflux was tested by microplate reader. The expression p-JNK was analyzed by western blot assay.

RESULTS

GDNF resulted in a significant inhibition of the activation of enteric mast cells by down-regulating JNK signal pathway, lessening intracellular calcium influx, and then reducing the degranulation as well as the expression of pro-inflammatory cytokines via combing with its receptor (GFR-α1/RET) in mast cells, and these inhibitory effects were abrogated by treatment with neutralizing antibody against GDNF. Moreover, the administration of GDNF led to an amelioration of experimental colitis.

CONCLUSIONS

GDNF are able to regulate enteric mast cells and ameliorate experimental colitis. GDNF might be an important mediator of the cross-talk between EGCs and enteric mast cells, and GDNF might be a useful therapeutic drug for IBD.

The Neuropeptide System and Colorectal Cancer Liver Metastases: Mechanisms and Management

Colorectal cancer (CRC), classified as the third most prevalent cancer worldwide, remains to be a clinical and research challenge. It is estimated that ~50% of CRC patients die from distant metastases, with treatment of this complication still posing significant difficulties. While liver metastasis (LM) cascade is known in the literature, its mechanisms are still unclear and remain studied in different research models. A connection is suggested between nervous system dysfunctions and a range of Neurotransmitters (Nts) (including Neuropeptides, NPs), Neurotrophins (Ntt) and their receptors (Rs) in CRC liver metastasis development. Studies on the role of NP/NP-Rs in the progression and metastasis of CRC, show the complexity of brain–tumor interactions, caused by their different forms of release to the extracellular environment (endocrine, autocrine, paracrine and neurocrine). Many stages of LM are connected to the activity of pro-inflammatory, e.g., Corticotropin-releasing Hormone Receptor 1 (CRHR1), Neuropeptide Y (NPY) and Neurotensin (NT), anti-inflammatory, e.g., Calcitonin Gene-related Peptide (CGRP), CRHR2 and Vasoactive Intestinal Polypeptide (VIP) or dual role neuropeptides, e.g., Substance P (SP). The regulation of the local immunological profile (e.g., CRH/CRHRs), dysfunctions of enteroprotective role of NPs on epithelial cells (e.g., NT/NT-R), as well as structural-functional changes in enteric nervous system innervation of the tumor are also important. More research is needed to understand the exact mechanisms of communication between the neurons and tumor cells. The knowledge on the mechanisms regulating tumor growth and different stages of metastasis, as well as effects of the action of a numerous group of Nts/NPs/Ntt as growth factors, have implications for future therapeutic strategies. To obtain the best treatment outcomes, it is important to use signaling pathways common for many NPs, as well to develop a range of broad-spectrum antagonists. This review aims to summarize the current knowledge on the importance of neuroactive molecules in the promotion of the invasion-metastasis cascade in CRC, as well as the improvements of clinical management of CRC liver metastasis.

Enteroendocrine Cells: Sensing Gut Microbiota and Regulating Inflammatory Bowel Diseases

Host sensing in the gut microbiota has been crucial in the regulation of intestinal homeostasis. Although inflammatory bowel diseases (IBDs), multifactorial chronic inflammatory conditions of the gastrointestinal tract, have been associated with intestinal dysbiosis, the detailed interactions between host and gut microbiota are still not completely understood. Enteroendocrine cells (EECs) represent 1% of the intestinal epithelium. Accumulating evidence indicates that EECs are key sensors of gut microbiota and/or microbial metabolites. They can secrete cytokines and peptide hormones in response to microbiota, either in traditional endocrine regulation or by paracrine impact on proximal tissues and/or cells or via afferent nerve fibers. Enteroendocrine cells also play crucial roles in mucosal immunity, gut barrier function, visceral hyperalgesia, and gastrointestinal (GI) motility, thereby regulating several GI diseases, including IBD. In this review, we will focus on EECs in sensing microbiota, correlating enteroendocrine perturbations with IBD, and the underlying mechanisms.

A Clinical Approach for the Use of VIP Axis in Inflammatory and Autoimmune Diseases

The neuroendocrine and immune systems are coordinated to maintain the homeostasis of the organism, generating bidirectional communication through shared mediators and receptors. Vasoactive intestinal peptide (VIP) is the paradigm of an endogenous neuropeptide produced by neurons and endocrine and immune cells, involved in the control of both innate and adaptive immune responses. Exogenous administration of VIP exerts therapeutic effects in models of autoimmune/inflammatory diseases mediated by G-protein-coupled receptors (VPAC1 and VPAC2). Currently, there are no curative therapies for inflammatory and autoimmune diseases, and patients present complex diagnostic, therapeutic, and prognostic problems in daily clinical practice due to their heterogeneous nature. This review focuses on the biology of VIP and VIP receptor signaling, as well as its protective effects as an immunomodulatory factor. Recent progress in improving the stability, selectivity, and effectiveness of VIP/receptors analogues and new routes of administration are highlighted, as well as important advances in their use as biomarkers, contributing to their potential application in precision medicine. On the 50th anniversary of VIP's discovery, this review presents a spectrum of potential clinical benefits applied to inflammatory and autoimmune diseases.

Chronic Stress, Inflammation, and Colon Cancer: A CRH System-Driven Molecular Crosstalk

Chronic stress is thought to be involved in the occurrence and progression of multiple diseases, via mechanisms that still remain largely unknown. Interestingly, key regulators of the stress response, such as members of the corticotropin-releasing-hormone (CRH) family of neuropeptides and receptors, are now known to be implicated in the regulation of chronic inflammation, one of the predisposing factors for oncogenesis and disease progression. However, an interrelationship between stress, inflammation, and malignancy, at least at the molecular level, still remains unclear. Here, we attempt to summarize the current knowledge that supports the inseparable link between chronic stress, inflammation, and colorectal cancer (CRC), by modulation of a cascade of molecular signaling pathways, which are under the regulation of CRH-family members expressed in the brain and periphery. The understanding of the molecular basis of the link among these processes may provide a step forward towards personalized medicine in terms of CRC diagnosis, prognosis and therapeutic targeting.

Beneficial Effects of Neurotensin in Murine Model of Hapten-Induced Asthma

Neurotensin (NT) demonstrates ambiguous activity on inflammatory processes. The present study was undertaken to test the potential anti-inflammatory activity of NT in a murine model of non-atopic asthma and to establish the contribution of NTR1 receptors. Asthma was induced in BALB/c mice by skin sensitization with dinitrofluorobenzene followed by intratracheal hapten provocation. The mice were treated intraperitoneally with NT, SR 142948 (NTR1 receptor antagonist) + NT or NaCl. Twenty-four hours after the challenge, airway responsiveness to nebulized methacholine was measured. Bronchoalveolar lavage fluid (BALF) and lungs were collected for biochemical and immunohistological analysis. NT alleviated airway hyperreactivity and reduced the number of inflammatory cells in BALF. These beneficial effects were inhibited by pretreatment with the NTR1 antagonist. Additionally, NT reduced levels of IL-13 and TNF-α in BALF and IL-17A, IL12p40, RANTES, mouse mast cell protease and malondialdehyde in lung homogenates. SR 142948 reverted only a post-NT TNF-α decrease. NT exhibited anti-inflammatory activity in the hapten-induced asthma. Reduced leukocyte accumulation and airway hyperresponsiveness indicate that this beneficial NT action is mediated through NTR1 receptors. A lack of effect by the NTR1 blockade on mast cell activation, oxidative stress marker and pro-inflammatory cytokine production suggests that other pathways can be involved, which requires further research.

Relationship between the gut microbiome and brain function

It has become increasingly evident in recent years that the gut microbiome and the brain communicate in a bidirectional manner, with each possibly affecting the other's functions. Substantial research has aimed to understand the mechanisms of this interaction and to outline strategies for preventing or treating nervous system-related disturbances. This review explores the evidence demonstrating how the gut microbiome may affect brain function in adults, thereby having an impact on stress, anxiety, depression, and cognition. In vitro, in vivo, and human studies reporting an association between a change in the gut microbiome and functional changes in the brain are highlighted, as are studies outlining the mechanisms by which the brain affects the microbiome and the gastrointestinal tract. Possible modes of action to explain how the gut microbiome and the brain functionally affect each other are proposed. Supplemental probiotics to combat brain-related dysfunction offer a promising approach, provided future research elucidates their mode of action and possible side effects. Further studies are warranted to establish how pre- and probiotic interventions may help to balance brain function in healthy and diseased individuals.

Neuro-Immune Networks in Gastrointestinal Disorders

Tissue homeostasis is controlled by multilateral cell interactions. Established in autoimmune diseases of the central nervous system, growing evidence shows a fundamental role of bidirectional communication between the nervous and immune systems in various gastrointestinal disorders. Primarily the primary sensory nervous system seems to play an important role in this cross talk because of its ability for transducing inflammatory signals and to convey them to the central nervous system, which in turn responds in an efferent manner (gut-brain axis vs. brain-gut axis). Moreover, sensory neurons that play a central role in pain processing immediately respond to inflammatory stimuli through releasing a myriad of immunomodulatory neuropeptides and neurotransmitters whose receptors are expressed in different immune cell populations. Thus, a better understanding of neuro-immune networks will pave the way to novel therapeutic strategies in inflammatory as well as functional gastrointestinal disorders.

Interplay between colonic inflammation and tachykininergic pathways in the onset of colonic dysmotility in a mouse model of diet-induced obesity

BACKGROUND

The murine model of high fat diet (HFD)-induced obesity is characterized by an increment of intestinal permeability, secondary to an impairment of mucosal epithelial barrier and enteric inflammation, followed by morphofunctional rearrangement of the enteric nervous system. The present study investigated the involvement of abdominal macrophages in the mechanisms underlying the development of enteric dysmotility associated with obesity.

METHODS

Wild type C57BL/6J mice were fed with HFD (60% kcal from fat) or normocaloric diet (NCD, 18% kcal from fat) for 8 weeks. Groups of mice fed with NCD or HFD were treated with clodronate encapsulated into liposomes to deplete abdominal macrophages. Tachykininergic contractions, elicited by electrical stimulation or exogenous substance P (SP), were recorded in vitro from longitudinal muscle colonic preparations. Substance P distribution was examined by confocal immunohistochemistry. The density of macrophages in the colonic wall was examined by immunohistochemical analysis. Malondialdehyde (MDA, colorimetric assay) and IL-1β (ELISA assay) levels were also evaluated.

RESULTS

MDA and IL-1β levels were increased in colonic tissues from HFD-treated animals. In colonic preparations, electrically evoked tachykininergic contractions were enhanced in HFD mice. Immunohistochemistry displayed an increase in substance P immunoreactivity in myenteric ganglia, as well as in the muscular layers of colonic cryosections from obese mice. Macrophage depletion in HFD mice was associated with a significant reduction of colonic inflammation. In addition, the decrease in macrophage density attenuated the morphofunctional alterations of tachykininergic pathways observed in obese mice.

CONCLUSION

Obesity elicited by HFD determines a condition of colonic inflammation, followed by a marked rearrangement of motor excitatory tachykininergic enteric nerves. Macrophage depletion counteracted the morphofunctional changes of colonic neuromuscular compartment, suggesting a critical role for these immune cells in the onset of enteric dysmotility associated with obesity.

Dual Effects of Alpha-Hydroxy Acids on the Skin

AHAs are organic acids with one hydroxyl group attached to the alpha position of the acid. AHAs including glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid are often used extensively in cosmetic formulations. AHAs have been used as superficial peeling agents as well as to ameliorate the appearance of keratoses and acne in dermatology. However, caution should be exercised in relation to certain adverse reactions among patients using products with AHAs, including swelling, burning, and pruritus. Whether AHAs enhance or decrease photo damage of the skin remains unclear, compelling us to ask the question, is AHA a friend or a foe of the skin? The aim of this manuscript is to review the various biological effects and mechanisms of AHAs on human keratinocytes and in an animal model. We conclude that whether AHA is a friend or foe of human skin depends on its concentration. These mechanisms of AHAs are currently well understood, aiding the development of novel approaches for the prevention of UV-induced skin damage.

Modulation of VIPergic phenotype of enteric neurons by colonic biopsy supernatants from patients with inflammatory bowel diseases: Involvement of IL-6 in Crohn's disease

BACKGROUND

Neuroplastic changes in the enteric nervous system (ENS) observed during IBD might participate in physiopathological processes. Vasoactive intestinal polypeptide has been shown to be involved in intestinal inflammation and barrier functions. We aimed to investigate the modulation of VIP expression in colonic biopsies of IBD patient, the ability of soluble factors from biopsies to reproduce in vitro these modulations and identify soluble factors responsible.

METHODS

VIP and cytokines mRNA expressions were assessed in colonic biopsies of healthy subjects (HS) and IBD patients from inflamed (I) and non-inflamed areas (NI). Supernatants (SUP) of biopsies were applied to primary culture of ENS and VIP and cytokines mRNA expressions were assessed. The role of cytokines in SUP induced changes in VIP expression was evaluated.

KEY RESULTS

VIP mRNA expression was lower in biopsies of patients with Crohn's disease (CD) than Ulcerative Colitis (UC) but unchanged as compared to HS. VIP mRNA and protein expression were lower in primary culture of ENS incubated with SUP-CD than with SUP-UC. Furthermore, in CD but not UC, SUP-I reduced VIP expression in the ENS as compared to SUP-NI. Next, IL-6 but not IL-5, IL-10, IL-17, IFN-γ or TNF-α reduced VIP expression in the ENS. Finally, in CD, SUP-I incubated with anti-IL-6 antibody increased VIP expression as compared to SUP-I alone.

CONCLUSIONS & INFERENCES

Mucosal soluble factors from IBD induce VIP neuroplastic changes in the ENS. IL-6 was identified as a putative soluble factor responsible in part for changes in VIP expression in CD.

Changes in the Distribution of Cocaine- and Amphetamine-Regulated Transcript-Containing Neural Structures in the Human Colon Affected by the Neoplastic Process

The present study analysed changes in the distribution pattern of cocaine- and amphetamine-regulated transcript (CART) in the enteric nervous system (ENS) of the human colon challenged by adenocarcinoma invasion, using the double-labelling immunofluorescence technique. In control specimens, CART immunoreactivity was found in neurons of all studied plexuses, representing 30.1 ± 4.1%, 12.9 ± 5.2%, and 4.1 ± 1.3% of all neurons forming the myenteric plexus (MP), outer submucous plexus (OSP), and inner submucous plexus (ISP), respectively. Tumour growth into the colon wall caused an increase in the relative frequency of CART-like immunoreactive (CART-LI) neurons in enteric plexuses located in the vicinity of the infiltrating neoplasm (to 36.1 ± 6.7%, 32.7 ± 7.3% and 12.1 ± 3.8% of all neurons in MP, OSP and ISP, respectively). The density of CART-LI nerves within particular layers of the intestinal wall did not differ between control and adenocarcinoma-affected areas of the human colon. This is the first detailed description of the CART distribution pattern within the ENS during the adenocarcinoma invasion of the human colon wall. The obtained results suggest that CART probably acts as a neuroprotective factor and may be involved in neuronal plasticity evoked by the progression of a neoplastic process.

NOD1 downregulates intestinal serotonin transporter and interacts with other pattern recognition receptors

Serotonin (5-HT) is an essential gastrointestinal modulator whose effects regulate the intestinal physiology. 5-HT effects depend on extracellular 5-HT bioavailability, which is controlled by the serotonin transporter (SERT) expressed in both the apical and basolateral membranes of enterocytes. SERT is a critical target for regulating 5-HT levels and consequently, modulating the intestinal physiology. The deregulation of innate immune receptors has been extensively studied in inflammatory bowel diseases (IBD), where an exacerbated defense response to commensal microbiota is observed. Interestingly, many innate immune receptors seem to affect the serotonergic system, demonstrating a new way in which microbiota could modulate the intestinal physiology. Therefore, our aim was to analyze the effects of NOD1 activation on SERT function, as well as NOD1's interaction with other immune receptors such as TLR2 and TLR4. Our results showed that NOD1 activation inhibits SERT activity and expression in Caco-2/TC7 cells through the extracellular signal-regulated kinase (ERK) signaling pathway. A negative feedback between 5-HT and NOD1 expression was also described. The results showed that TLR2 and TLR4 activation seems to regulate NOD1 expression in Caco-2/TC7 cells. To assess the extend of cross-talk between NOD1 and TLRs, NOD1 expression was measured in the intestinal tract (ileum and colon) of wild type mice and mice with individual knockouts of TLR2, and TLR4 as well as double knockout TLR2/TLR4 mice. Hence, we demonstrate that NOD1 acts on the serotonergic system decreasing SERT activity and molecular expression. Additionally, NOD1 expression seems to be modulated by 5-HT and other immune receptors as TLR2 and TLR4. This study could clarify the relation between both the intestinal serotonergic system and innate immune system, and their implications in intestinal inflammation.

Chromogranin A cell density in the large intestine of Asian and European patients with irritable bowel syndrome

OBJECTIVE

Patients with irritable bowel syndrome (IBS) in Asia show distinctive differences from those in the western world. The gastrointestinal endocrine cells appear to play an important role in the pathophysiology of IBS. The present study aimed at studying the density of chromogranin A (CgA) cells in the large intestine of Thai and Norwegian IBS patients.

METHODS

Thirty Thai IBS patients and 20 control subjects, and 47 Norwegian IBS patients and 20 control subjects were included. A standard colonoscopy was performed in both the patients and controls, and biopsy samples were taken from the colon and the rectum. The biopsy samples were stained with hematoxylin-eosin and immunostained for CgA. The density of CgA cells was determined by computerized image analysis.

RESULTS

In the colon and rectum, the CgA cell densities were far higher in both IBS and healthy Thai subjects than in Norwegians. The colonic CgA cell density was lower in Norwegian IBS patients than in controls, but did not differ between Thai IBS patients and controls. In the rectum, the CgA cell densities in both Thai and Norwegian patients did not differ from those of controls.

CONCLUSIONS

The higher densities of CgA cells in Thai subjects than Norwegians may be explained by a higher exposure to infections at childhood and the development of a broad immune tolerance, by differences in the intestinal microbiota, and/or differing diet habits. The normal CgA cell density in Thai IBS patients in contrast to that of Norwegians may be due to differences in pathophysiology.

Attenuated GABAergic Signaling in Intestinal Epithelium Contributes to Pathogenesis of Ulcerative Colitis

BACKGROUND

Neuromediators produced by enteric nervous system regulate inflammatory processes via interacting with enteric immune system. Role of γ-aminobutyric acid (GABA), which is also a neuromediator, has been implicated in autoimmune diseases like multiple sclerosis, type 1 diabetes, and rheumatoid arthritis, where they modulate the immune responses. However, its role in ulcerative colitis (UC) has not been defined.

AIMS

This study was carried out to investigate the role of GABA and its signaling components in pathogenesis of UC.

METHODS

Peripheral blood, colon mucosal biopsy, and fecal specimens were collected from UC and control groups. Quantification of GABA was done using ELISA. Expression of GABAergic signal system components was analyzed through RT-PCR analysis. Enumeration of GABA-producing bacteria was done by qPCR analysis. Activity of p38 MAPK and expression of proinflammatory cytokines were determined by immunohistochemistry and RT-PCR analysis, respectively.

RESULTS

GABA levels were significantly reduced in patients with UC as compared to control group when measured in serum and colon biopsy. Altered expression of GABAergic signal system was observed in UC patients. Reduced abundance of selected GABA-producing bacteria was detected in stool samples of UC patients as compared to control. p38 MAPK activity and expression of its downstream effector cytokines were found to be increased in UC patients as compared to control.

CONCLUSIONS

Reduced levels of GABA were observed in patients with UC, and this leads to hyperactivation of p38 MAPK and overexpression of downstream effector cytokines suggesting a role of GABA in pathogenesis of UC.

Colonic motor dysfunctions in a mouse model of high-fat diet-induced obesity: an involvement of A2B adenosine receptors

Adenosine A_2B receptors (A_2BR) regulate several enteric functions. However, their implication in the pathophysiology of intestinal dysmotility associated with high-fat diet (HFD)-induced obesity has not been elucidated. We investigated the expression of A_2BR in mouse colon and their role in the mechanisms underlying the development of enteric dysmotility associated with obesity. Wild-type C57BL/6J mice were fed with HFD (60% kcal from fat) or normocaloric diet (NCD; 18% kcal from fat) for 8 weeks. Colonic A_2BR localization was examined by immunofluorescence. The role of A_2BR in the control of colonic motility was examined in functional experiments on longitudinal muscle preparations (LMPs). In NCD mice, A_2BR were predominantly located in myenteric neurons; in HFD animals, their expression increased throughout the neuromuscular layer. Functionally, the A_2BR antagonist MRS1754 enhanced electrically induced NK₁-mediated tachykininergic contractions in LMPs from HFD mice, while it was less effective in tissues from NCD mice. The A_2B receptor agonist BAY 60-6583 decreased colonic tachykininergic contractions in LMPs, with higher efficacy in preparations from obese mice. Both A_2BR ligands did not affect contractions elicited by exogenous substance P. Obesity is related with a condition of colonic inflammation, leading to an increase of A_2BR expression. A_2BR, modulating the activity of excitatory tachykininergic nerves, participate to the enteric dysmotility associated with obesity.

Gastrointestinal neuroendocrine peptides/amines in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic recurrent condition whose etiology is unknown, and it includes ulcerative colitis, Crohn’s disease, and microscopic colitis. These three diseases differ in clinical manifestations, courses, and prognoses. IBD reduces the patients’ quality of life and is an economic burden to both the patients and society. Interactions between the gastrointestinal (GI) neuroendocrine peptides/amines (NEPA) and the immune system are believed to play an important role in the pathophysiology of IBD. Moreover, the interaction between GI NEPA and intestinal microbiota appears to play also a pivotal role in the pathophysiology of IBD. This review summarizes the available data on GI NEPA in IBD, and speculates on their possible role in the pathophysiology and the potential use of this information when developing treatments. GI NEPA serotonin, the neuropeptide Y family, and substance P are proinflammatory, while the chromogranin/secretogranin family, vasoactive intestinal peptide, somatostatin, and ghrelin are anti-inflammatory. Several innate and adaptive immune cells express these NEPA and/or have receptors to them. The GI NEPA are affected in patients with IBD and in animal models of human IBD. The GI NEPA are potentially useful for the diagnosis and follow-up of the activity of IBD, and are candidate targets for treatments of this disease.

Toll-Like Receptor 4 Modulates Small Intestine Neuromuscular Function through Nitrergic and Purinergic Pathways

Objective: Toll-like receptors (TLRs) play a pivotal role in the homeostatic microflora-host crosstalk. TLR4-mediated modulation of both motility and enteric neuronal survival has been reported mainly for colon with limited information on the role of TLR4 in tuning structural and functional integrity of enteric nervous system (ENS) and in controlling small bowel motility. Methods: Male TLR4 knockout (TLR4^-/-, 9 ± 1 weeks old) and sex- and age-matched wild-type (WT) C57BL/6J mice were used for the experiments. Alterations in ENS morphology and neurochemical code were assessed by immunohistochemistry whereas neuromuscular function was evaluated by isometric mechanical activity of ileal preparations following receptor and non-receptor-mediated stimuli and by gastrointestinal transit. Results: The absence of TLR4 induced gliosis and reduced the total number of neurons, mainly nNOS⁺ neurons, in ileal myenteric plexus. Furthermore, a lower cholinergic excitatory response with an increased inhibitory neurotransmission was found together with a delayed gastrointestinal transit. These changes were dependent on increased ileal non-adrenergic non-cholinergic (NANC) relaxations mediated by a complex neuronal-glia signaling constituted by P2X7 and P2Y1 receptors, and NO produced by nNOS and iNOS. Conclusion: We provide novel evidence that TLR4 signaling is involved in the fine-tuning of P2 receptors controlling ileal contractility, ENS cell distribution, and inhibitory NANC neurotransmission via the combined action of NO and adenosine-5'-triphosphate (ATP). For the first time, this study implicates TLR4 at regulating the crosstalk between glia and neurons in small intestine and helps to define its role in gastrointestinal motor abnormalities during dysbiosis.

Substance P enhances lactic acid and tyramine production in Enterococcus faecalis V583 and promotes its cytotoxic effect on intestinal Caco-2/TC7 cells

Background

Enterococcus faecalis, generally considered as a saprophytic bowel commensal, has recently emerged as an important nosocomial pathogen causing severe urinary tract infections, surgical wound infections, bacteremia, and bacterial endocarditis. This bacterium is capable of forming biofilms on various surfaces and its high level of antibiotic resistance contributes to its pathogenicity. The aim of this study was to evaluate the effect on E. faecalis, of Substance P (SP), an antimicrobial peptide that is produced in the gut and skin.

Results

We found that SP did not have antibacterial activity against E. faecalis V583 (MIC >1000 µg/ml). Conversely, SP stimulated aggregation, hydrophobicity, lactic acid and tyramine production in this bacterium. The cytotoxicity and bacterial translocation were also accelerated when E. faecalis V583 were pretreated with SP before infection of intestinal Caco-2/TC7 cells.

Conclusion

SP can modulate the physiology of E. faecalis. Extensive studies are now needed to screen within the human microbiota which bacteria are responsive to host molecules, and to identify their sensors.

Abnormal differentiation of stem cells into enteroendocrine cells in rats with DSS-induced colitis

The present study aimed to determine whether there is an association between abnormalities in enteroendocrine cells in dextran sulfate sodium (DSS)-induced colitis and the clonogenic and/or proliferative activities of stem cells. A total of 48 male Wistar rats were divided into four groups. Animals in the control group were provided with normal drinking water, whereas DSS colitis was induced in the remaining three groups. The rats with DSS-induced colitis were randomized into the following three groups: i) DSS group, which received 0.5 ml 0.5% carboxymethyl cellulose (CMC; vehicle); ii) DSS-G group, which was treated with 3-[(dodecylthiocarbonyl)-methyl]-glutarimide at 20 mg/kg body weight in 0.5% CMC; and iii) DSS-Q group, which was treated with dehydroxymethylepoxyquinomicin at 15 mg/kg body weight in 0.5% CMC. Treatments were administered intraperitoneally twice daily for 5 days in all groups. Subsequently, tissue samples from the colon were stained with hematoxylin-eosin, or immunostained for chromogranin A (CgA), Musashi 1 (Msi1), Math-1, neurogenin 3 (Neurog3) and neurogenic differentiation D1 (NeuroD1). The densities of CgA, Msi1-, Math-1-, Neurog3- and NeuroD1-immunoreactive cells were determined. DTCM-G, and DHMEQ ameliorated the inflammation in DSS-induced colitis. The density of CgA-, Neurog3- and NeuroD1-immunoreactive cells was significantly higher in the DSS group compared with in the control group, and the density of CgA cells was correlated with the densities of Neurog3- and NeuroD1-immunoreactive cells. There were no significant differences in the densities of Msi1- and Math-1-immunoreactive cells among the four experimental groups. The elevated densities of enteroendocrine cells detected in DSS-induced colitis may be due to the increased differentiation of early enteroendocrine progenitors during secretory lineage. It is probable that the DSS-induced inflammatory processes trigger certain signaling pathways, which control differentiation of the stem-cell secretory lineage into mature enteroendocrine cells.

Abnormalities in endocrine and immune cells are correlated in dextran‑sulfate‑sodium‑induced colitis in rats

The interaction between the gut hormones and the immune system has been suggested to serve an important role in the pathophysiology of inflammatory bowel disease. The aims of the present study were to elucidate the possible abnormalities in the colonic endocrine cells in rats with dextran sodium sulfate (DSS)-induced colitis, and to determine whether they are correlated with alterations in the immune cells. A total of 24 male Wistar rats were divided into two groups: Control and DSS-induced colitis. Colonic tissues were harvested via postmortem laparotomy from all of the animals at the end of the experimental period, and fixed and sectioned for histology. The colonic endocrine and immune cells in those tissue samples were immunostained and their densities quantified by computerized image analysis. The densities of chromogranin A, serotonin, peptide YY and oxyntomodulin cells were significantly higher, and those of pancreatic peptide and somatostatin cells were lower in rats with DSS-induced colitis than in the controls. The densities of mucosal leukocytes, T and B lymphocytes, macrophages/monocytes, and mast cells were significantly higher than in the controls, and these changes were closely associated with the aforementioned changes in all endocrine cell types. These observations indicate an interaction between intestinal hormones and the immune system as represented by immune cells.

Changes in enteroendocrine and immune cells following colitis induction by TNBS in rats

Approximately 3.6 million individuals suffer from inflammatory bowel disease (IBD) in the western world, with an annual global incidence rate of 3–20 cases/100,000 individuals. The etiology of IBD is unknown, and the currently available treatment options are not satifactory for long-term treatment. Patients with inflammatory bowel disease present with abnormalities in multiple intestinal endocrine cell types, and a number of studies have suggested that interactions between gut hormones and immune cells may serve a pivotal role in the pathophysiology of IBD. The aim of the present study was to investigate alterations in colonic endocrine cells in a rat model of IBD. A total of 30 male Wistar rats were divided into control and trinitrobenzene sulfonic acid (TNBS)-induced colitis groups. Colonoscopies were performed in the control and TNBS groups at day 3 following the induction of colitis, and colonic tissues were collected from all animals. Colonic endocrine and immune cells in the obtained tissue samples were immunostained and their densities were quantified. The densities of chromogranin A, peptide YY, and pancreatic polypeptide-producing cells were significantly lower in the TNBS group compared with the control group, whereas the densities of serotonin, oxyntomodulin, and somatostatin-producing cells were significantly higher in the TNBS group. The densities of mucosal leukocytes, B/T-lymphocytes, T-lymphocytes, B-lymphocytes, macrophages/monocytes and mast cells were significantly higher in the TNBS group compared with the controls, and these differences were strongly correlated with alterations in all endocrine cell types. In conclusion, the results suggest the presence of interactions between intestinal hormones and immune cells.

Enteroendocrine cells, stem cells and differentiation progenitors in rats with TNBS-induced colitis

Patients with inflammatory bowel disease (IBD), as well as animal models of human IBD have abnormal enteroendocrine cells. The present study aimed to identify the possible mechanisms underlying these abnormalities. For this purpose, 40 male Wistar rats were divided into 4 groups as follows: the control group, the group with trinitrobenzene sulfonic acid (TNBS)-induced colitis with no treatment (TNBS group), the group with TNBS-induced colitis treated with 3-[(dodecylthiocarbonyl)-methyl]-glutarimide (DTCM-G; an activator protein-1 inhibitor) (DTCM-G group), and the group with TNBS-induced colitis treated with dehydroxymethylepoxyquinomicin (DHMEQ; a nuclear factor-κB inhibitor) treatment (DHMEQ group). Three days following the administration of TNBS, the rats were treated as follows: those in the control and TNBS groups received 0.5 ml of the vehicle [0.5% carboxymethyl cellulose (CMC)], those in the DTCM-G group received DTCM-G at 20 mg/kg body weight in 0.5% CMC, and those in the DHMEQ group received DHMEQ at 15 mg/kg body weight in 0.5% CMC. All injections were administered intraperitoneally twice daily for 5 days. The rats were then sacrificed, and tissue samples were taken from the colon. The tissue sections were stained with hemotoxylin-eosin and immunostained for chromogranin A (CgA), serotonin, peptide YY (PYY), oxyntomodulin, pancreatic polypeptide (PP), somatostatin, Musashi1 (Msi1), Math1, Neurogenin3 (Neurog3) and NeuroD1. The staining was quantified using image analysis software. The densities of CgA-, PYY-, PP-, Msi1-, Neurog3- and NeuroD1-positive cells were significantly lower in the TNBS group than those in the control group, while those of serotonin-, oxyntomodulin- and somatostatin-positive cells were significantly higher in the TNBS group than those in the control group. Treatment with either DTCM-G or DHMEQ restored the densities of enteroendocrine cells, stem cells and their progenitors to normal levels. It was thus concluded that the abnormalities in enteroendocrine cells and stem cells and their differentiation progenitors may be caused by certain signaling substances produced under inflammatory processes, resulting in changes in hormone expression in enteroendocrine cells. These substances may also interfere with the colonogenic activity and the differentiation of the stem-cell secretory lineage into mature enteroendocrine cells.

Chromogranin A and other enteroendocrine markers in inflammatory bowel disease

Changes in the distribution and products of enteroendocrine cells may play a role in immune activation and regulation of gut inflammation. This review aims at critically evaluating the main enteroendocrine markers in inflammatory bowel diseases (IBD). A narrative review was performed by searching inflammatory bowel diseases and enteroendocrine biomarkers in PubMed. Relevant modifications of some enteroendocrine markers, such as Chromogranin A, and their correlation with disease activity have been reported in patients with inflammatory bowel diseases. Even if data about neuroendocrine markers are sometimes contrasting, they may be potentially useful for the diagnosis and clinical management of these patients.

Enteric Neuronal Regulation of Intestinal Inflammation

Recent research has highlighted the importance of the two-way interaction between the nervous and immune systems. This interaction is particularly important in the bowel because of the unique properties of this organ. The lumen of the gut is lined by a very large but remarkably thin surface that separates the body from the enteric microbiome. Immune defenses against microbial invasion are thus well developed and neuroimmune interactions are important in regulating and integrating these defenses. Important concepts in the phylogeny of neuroimmunity, enteric neuronal and glial regulation of immunity, changes that occur in the enteric nervous system during inflammation, the fundamental role of serotonin (5-HT) in enteric neuroimmune mechanisms, and future perspectives are reviewed.

Neuroimmunomodulation in the Gut: Focus on Inflammatory Bowel Disease

Intestinal immunity is finely regulated by several concomitant and overlapping mechanisms, in order to efficiently sense external stimuli and mount an adequate response of either tolerance or defense. In this context, a complex interplay between immune and nonimmune cells is responsible for the maintenance of normal homeostasis. However, in certain conditions, the disruption of such an intricate network may result in intestinal inflammation, including inflammatory bowel disease (IBD). IBD is believed to result from a combination of genetic and environmental factors acting in concert with an inappropriate immune response, which in turn interacts with nonimmune cells, including nervous system components. Currently, evidence shows that the interaction between the immune and the nervous system is bidirectional and plays a critical role in the regulation of intestinal inflammation. Recently, the maintenance of intestinal homeostasis has been shown to be under the reciprocal control of the microbiota by immune mechanisms, whereas intestinal microorganisms can modulate mucosal immunity. Therefore, in addition to presenting the mechanisms underlying the interaction between immune and nervous systems in the gut, here we discuss the role of the microbiota also in the regulation of neuroimmune crosstalk involved in intestinal homeostasis and inflammation, with potential implications to IBD pathogenesis.

Cellular Organization of Neuroimmune Interactions in the Gastrointestinal Tract

The gastrointestinal (GI) tract is the largest immune organ; in vertebrates, it is the only organ whose function is controlled by its own intrinsic enteric nervous system (ENS), but it is additionally regulated by extrinsic (sympathetic and parasympathetic) innervation. The GI nervous and immune systems are highly integrated in their common goal, which is to unite digestive functions with protection from ingested environmental threats. This review discusses the physiological relevance of enteric neuroimmune integration by summarizing the current knowledge of evolutionary and developmental pathways, cellular organization, and molecular mechanisms of neuroimmune interactions in health and disease.

Effects of AP‑1 and NF‑κB inhibitors on colonic endocrine cells in rats with TNBS‑induced colitis

Interactions between intestinal neuroendocrine peptides/amines and the immune system appear to have an important role in the pathophysiology of inflammatory bowel disease (IBD). The present study investigated the effects of activator protein (AP)‑1 and nuclear factor (NF)‑κB inhibitors on inflammation‑induced alterations in enteroendocrine cells. A total of 48 male Wistar rats were divided into the following four groups (n=12 rats/group): Control, trinitrobenzene sulfonic acid (TNBS)‑induced colitis only (TNBS group), TNBS‑induced colitis with 3‑[(dodecylthiocarbonyl)-methyl]-glutarimide (DTCM‑G) treatment (DTCM‑G group), and TNBS‑induced colitis with dehydroxymethylepoxyquinomicin (DHMEQ) treatment (DHMEQ group). A total of 3 days following administration of TNBS, the rats were treated as follows: The control and TNBS groups received 0.5 ml vehicle (0.5% carboxymethyl cellulose; CMC), respectively; the DTCM‑G group received DTCM‑G (20 mg/kg body weight) in 0.5% CMC; and the DHMEQ group received DHMEQ (15 mg/kg body weight) in 0.5% CMC. All injections were performed intraperitoneally twice daily for 5 days. The rats were sacrificed, and tissue samples obtained from the colon were examined histopathologically and immunohistochemically. Inflammation was evaluated using a scoring system. In addition, the sections were immunostained for chromogranin A (CgA), serotonin, peptide YY (PYY), oxyntomodulin, pancreatic polypeptide (PP) and somatostatin, and immunostaining was quantified using image‑analysis software. The density of cells expressing CgA, PYY and PP was significantly lower in the TNBS group compared with in the control group, whereas the density of cells expressing serotonin, oxyntomodulin and somatostatin was significantly higher in the TNBS group compared with in the control group. None of the endocrine cell types differed significantly between the control group and either the DTCM‑G or DHMEQ groups. All of the colonic endocrine cell types were affected in rats with TNBS‑induced colitis. The expression density of these endocrine cell types was restored to control levels following treatment with AP‑1 or NF‑κB inhibitors. These results indicated that the immune system and enteroendocrine cells interact in IBD.

Alteration of colonic excitatory tachykininergic motility and enteric inflammation following dopaminergic nigrostriatal neurodegeneration

BACKGROUND

Parkinson's disease (PD) is frequently associated with gastrointestinal (GI) symptoms, including constipation and defecatory dysfunctions. The mechanisms underlying such disorders are still largely unknown, although the occurrence of a bowel inflammatory condition has been hypothesized. This study examined the impact of central dopaminergic degeneration, induced by intranigral injection of 6-hydroxydopamine (6-OHDA), on distal colonic excitatory tachykininergic motility in rats.

METHODS

Animals were euthanized 4 and 8 weeks after 6-OHDA injection. Tachykininergic contractions, elicited by electrical stimulation or exogenous substance P (SP), were recorded in vitro from longitudinal muscle colonic preparations. SP, tachykininergic NK1 receptor, and glial fibrillary acidic protein (GFAP) expression, as well as the density of eosinophils and mast cells in the colonic wall, were examined by immunohistochemical analysis. Malondialdehyde (MDA, colorimetric assay), TNF, and IL-1β (ELISA assay) levels were also examined. The polarization of peritoneal macrophages was evaluated by real-time PCR.

RESULTS

In colonic preparations, electrically and SP-evoked tachykininergic contractions were increased in 6-OHDA rats. Immunohistochemistry displayed an increase in SP and GFAP levels in the myenteric plexus, as well as NK1 receptor expression in the colonic muscle layer of 6-OHDA rats. MDA, TNF, and IL-1β levels were increased also in colonic tissues from 6-OHDA rats. In 6-OHDA rats, the number of eosinophils and mast cells was increased as compared with control animals, and peritoneal macrophages polarized towards a pro-inflammatory phenotype.

CONCLUSIONS

The results indicate that the induction of central nigrostriatal dopaminergic degeneration is followed by bowel inflammation associated with increased oxidative stress, increase in pro-inflammatory cytokine levels, activation of enteric glia and inflammatory cells, and enhancement of colonic excitatory tachykininergic motility.

Treatment with novel AP-1 and NF-κB inhibitors restores the colonic endocrine cells to normal levels in rats with DSS-induced colitis

The aim of this study was to determine the effects of two anti-inflammatory agents on the abnormalities in colonic endocrine cells in dextran sodium sulfate (DSS)-induced colitis. Colitis was induced in male Wistar rats (n=45) using DSS; a further 15 rats without colitis were included in a healthy control group. The animals with DSS-induced colitis were randomly divided into 3 treatment groups as follows: i) DSS group, rats were treated with 0.5 ml of 0.5% carboxymethyl cellulose (CMC); ii) DSS‑G group, rats were treated with 3-[(dodecylthiocarbonyl)‑methyl]‑glutarimide (DTCM‑G), a novel activator protein 1 (AP-1) inhibitor, 20 mg/kg in CMC; and iii) DSS‑Q group, rats were treated with dehydroxymethylepoxyquinomicin, a nuclear factor κB (NF-κB) inhibitor, 15 mg/kg in CMC. The treatments were administered intraperitoneally, twice daily for 5 days, after which the animals were sacrificed and tissue samples from the colon were immunostained for chromogranin A (CgA), serotonin, peptide YY (PYY), enteroglucagon, pancreatic polypeptide (PP), somatostatin, leukocytes, B/T lymphocytes, B lymphocytes, T lymphocytes, macrophages/monocytes and mast cells. The densities of these endocrine and immune cells were quantified by computer‑aided image analysis. The densities of CgA-, serotonin-, PYY- and enteroglucagon-producing cells were significantly higher, and those of PP- and somatostatin-producing cells were significantly lower in the DSS‑G, DSS‑Q and control groups than in the DSS group. The densities of all the immune cells were lower in the DSS‑G, DSS‑Q and control groups than in the DSS group. The densities of all endocrine cell types and immune cells in both the DSS groups treated with anti‑inflammatory agents were restored to control levels. In conclusion, our data demonstrate that there is an interaction between endocrine and immune cells during inflammation. This interaction with subsequent changes in endocrine cells is responsible for the clinical manifestation of colitis symptoms.

The role of the neuropeptide Y (NPY) family in the pathophysiology of inflammatory bowel disease (IBD)

Inflammatory bowel disease (IBD) includes three main disorders: ulcerative colitis, Crohn's disease, and microscopic colitis. The etiology of IBD is unknown and the current treatments are not completely satisfactory. Interactions between the gut neurohormones and the immune system are thought to play a pivot role in inflammation, especially in IBD. These neurohormones are believed to include members of the neuropeptide YY (NPY) family, which comprises NPY, peptide YY (PYY), and pancreatic polypeptide (PP). Understanding the role of these peptides may shed light on the pathophysiology of IBD and potentially yield an effective treatment tool. Intestinal NPY, PYY, and PP are abnormal in both patients with IBD and animal models of human IBD. The abnormality in NPY appears to be primarily caused by an interaction between immune cells and the NPY neurons in the enteric nervous system; the abnormalities in PYY and PP appear to be secondary to the changes caused by the abnormalities in other gut neurohormonal peptides/amines that occur during inflammation. NPY is the member of the NPY family that can be targeted in order to decrease the inflammation present in IBD.

Epigenetic Regulation of Enteric Neurotransmission by Gut Bacteria

The Human Microbiome Project defined microbial community interactions with the human host, and provided important molecular insight into how epigenetic factors can influence intestinal ecosystems. Given physiological context, changes in gut microbial community structure are increasingly found to associate with alterations in enteric neurotransmission and disease. At present, it is not known whether shifts in microbial community dynamics represent cause or consequence of disease pathogenesis. The discovery of bacterial-derived neurotransmitters suggests further studies are needed to establish their role in enteric neuropathy. This mini-review highlights recent advances in bacterial communications to the autonomic nervous system and discusses emerging epigenetic data showing that diet, probiotic and antibiotic use may regulate enteric neurotransmission through modulation of microbial communities. A particular emphasis is placed on bacterial metabolite regulation of enteric nervous system function in the intestine.

Serotonergic Mechanisms Regulating the GI Tract: Experimental Evidence and Therapeutic Relevance

Serotonin (5-hydroxytryptamine; 5-HT) is best known as a neurotransmitter critical for central nervous system (CNS) development and function. 95% of the body's serotonin, however, is produced in the intestine where it has been increasingly recognized for its hormonal, autocrine, paracrine, and endocrine actions. This chapter provides the most current knowledge of the critical autocrine and paracrine roles of 5-HT in intestinal motility and inflammation as well as its function as a hormone in osteocyte homeostasis. Therapeutic applications in each of these areas are also discussed.

Hepatocyte Growth Factor and MET Support Mouse Enteric Nervous System Development, the Peristaltic Response, and Intestinal Epithelial Proliferation in Response to Injury

Factors providing trophic support to diverse enteric neuron subtypes remain poorly understood. We tested the hypothesis that hepatocyte growth factor (HGF) and the HGF receptor MET might support some types of enteric neurons. HGF and MET are expressed in fetal and adult enteric nervous system. In vitro, HGF increased enteric neuron differentiation and neurite length, but only if vanishingly small amounts (1 pg/ml) of glial cell line-derived neurotrophic factor were included in culture media. HGF effects were blocked by phosphatidylinositol-3 kinase inhibitor and by MET-blocking antibody. Both of these inhibitors and MEK inhibition reduced neurite length. In adult mice, MET was restricted to a subset of calcitonin gene-related peptide-immunoreactive (IR) myenteric plexus neurons thought to be intrinsic primary afferent neurons (IPANs). Conditional MET kinase domain inactivation (Met(fl/fl); Wnt1Cre+) caused a dramatic loss of myenteric plexus MET-IR neurites and 1-1'-dioctodecyl-3,3,3',3'-tetramethylindocarbocyamine perchlorate (DiI) labeling suggested reduced MET-IR neurite length. In vitro, Met(fl/fl); Wnt1Cre+ mouse bowel had markedly reduced peristalsis in response to mucosal deformation, but normal response to radial muscle stretch. However, whole-bowel transit, small-bowel transit, and colonic-bead expulsion were normal in Met(fl/fl); Wnt1Cre+ mice. Finally, Met(fl/fl); Wnt1Cre+ mice had more bowel injury and reduced epithelial cell proliferation compared with WT animals after dextran sodium sulfate treatment. These results suggest that HGF/MET signaling is important for development and function of a subset IPANs and that these cells regulate intestinal motility and epithelial cell proliferation in response to bowel injury.

SIGNIFICANCE STATEMENT

The enteric nervous system has many neuronal subtypes that coordinate and control intestinal activity. Trophic factors that support these neuron types and enhance neurite growth after fetal development are not well understood. We show that a subset of adult calcitonin gene-related peptide (CGRP)-expressing myenteric neurons produce MET, the receptor for hepatocyte growth factor, and that loss of MET activity affects peristalsis in response to mucosal stroking, reduces MET-immunoreactive neurites, and increases susceptibility to dextran sodium sulfate-induced bowel injury. These observations may be relevant for understanding and treating intestinal motility disorders and also suggest that enhancing the activity of MET-expressing CGRP neurons might be a useful strategy to reduce bowel inflammation.

Neuropeptide S inhibits gastrointestinal motility and increases mucosal permeability through nitric oxide

Neuropeptide S (NPS) receptor (NPSR1) polymorphisms are associated with enteral dysmotility and inflammatory bowel disease (IBD). This study investigated the role of NPS in conjunction with nitrergic mechanisms in the regulation of intestinal motility and mucosal permeability. In rats, small intestinal myoelectric activity and luminal pressure changes in small intestine and colon, along with duodenal permeability, were studied. In human intestine, NPS and NPSR1 were localized by immunostaining. Pre- and postprandial plasma NPS was measured by ELISA in healthy and active IBD humans. Effects and mechanisms of NPS were studied in human intestinal muscle strips. In rats, NPS 100-4,000 pmol·kg(-1)·min(-1) had effects on the small intestine and colon. Low doses of NPS increased myoelectric spiking (P < 0.05). Higher doses reduced spiking and prolonged the cycle length of the migrating myoelectric complex, reduced intraluminal pressures (P < 0.05-0.01), and increased permeability (P < 0.01) through NO-dependent mechanisms. In human intestine, NPS localized at myenteric nerve cell bodies and fibers. NPSR1 was confined to nerve cell bodies. Circulating NPS in humans was tenfold below the ∼0.3 nmol/l dissociation constant (Kd) of NPSR1, with no difference between healthy and IBD subjects. In human intestinal muscle strips precontracted by bethanechol, NPS 1-1,000 nmol/l induced NO-dependent muscle relaxation (P < 0.05) that was sensitive also to tetrodotoxin (P < 0.01). In conclusion, NPS inhibits motility and increases permeability in neurocrine fashion acting through NO in the myenteric plexus in rats and humans. Aberrant signaling and upregulation of NPSR1 could potentially exacerbate dysmotility and hyperpermeability by local mechanisms in gastrointestinal functional and inflammatory reactions.

Basal Plasma Levels of Copeptin are Elevated in Inactive Inflammatory Bowel Disease after Bowel Resection

Evidence of interactions between the enteric nervous system, neuropeptides, and the immune system is growing. The aim of this study was to examine basal plasma levels of a variety of peptide precursors in patients with inflammatory bowel disease (IBD). In two middle-aged cohorts, Malmö Preventive Medicine (n = 5,415) and Malmö Diet and Cost Study (n = 6,103), individuals with the diagnosis of IBD were identified. Medical records were scrutinized. Three controls were matched for each patient. Copeptin, midregional fragments of adrenomedullin, pro-atrial natriuretic peptide, and proenkephalin A, as well as N-terminal protachykinin A and proneurotensin were analyzed in the plasma. Sixty-two IBD patients were identified. The only difference between patients and controls was higher copeptin levels in the patients compared with controls (P = 0.006), with higher copeptin levels in resected than unresected patients (P = 0.020). There was no difference in any precursor levels between Crohn’s disease and ulcerative colitis, between different distributions of disease lesions, or between different treatments.

Neurotensin--regulated miR-133α is involved in proinflammatory signalling in human colonic epithelial cells and in experimental colitis

OBJECTIVE

Neurotensin (NT) mediates colonic inflammation through its receptor neurotensin receptor 1 (NTR1). NT stimulates miR-133α expression in colonic epithelial cells. We investigated the role of miR-133α in NT-associated colonic inflammation in vitro and in vivo.

DESIGN

miR-133α and aftiphilin (AFTPH) levels were measured by quantitative PCR. Antisense (as)-miR-133α was administrated intracolonicaly prior to induction of 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)-induced colitis and dextran sodium sulfate (DSS)-induced colitis. The effect of AFTPH was examined by gene silencing in vitro.

RESULTS

NT increased miR-133α levels in NCM-460 overexpressing NTR1 (NCM460-NTR1) and HCT-116 cells. NT-induced p38, ERK1/2, c-Jun, and NF-κB activation, as well as IL-6, IL-8 and IL-1β messenger RNA (mRNA) expression in NCM-460-NTR1 cells were reduced in miR-133α-silenced cells, while overexpression of miR-133α reversed these effects. MiR-133α levels were increased in TNBS (2 day) and DSS (5 day) colitis, while NTR1 deficient DSS-exposed mice had reduced miR-133α levels, compared to wild-type colitic mice. Intracolonic as-miR-133α attenuated several parameters of colitis as well expression of proinflammatory mediators in the colonic mucosa. In silico search coupled with qPCR identified AFTPH as a downstream target of miR-133α, while NT decreased AFTPH expression in NCM-460-NTR1 colonocytes. Gene silencing of AFTPH enhanced NT-induced proinflammatory responses and AFTPH levels were downregulated in experimental colitis. Levels of miR-133α were significantly upregulated, while AFTPH levels were downregulated in colonic biopsies of patients with ulcerative colitis compared to controls.

CONCLUSIONS

NT-associated colitis and inflammatory signalling are regulated by miR-133α-AFTPH interactions. Targeting of miR-133α or AFTPH may represent a novel therapeutic approach in inflammatory bowel disease.