The nonneuronal cholinergic system in the colon: A comprehensive review.

Acetylcholine (ACh) is found not only in cholinergic nerve termini but also in the nonneuronal cholinergic system (NNCS). ACh is released from cholinergic nerves by vesicular ACh transporter (VAChT), but ACh release from the NNCS is mediated by organic cation transporter (OCT). Recent studies have suggested that components of the NNCS are located in intestinal epithelial cells (IECs), crypt-villus organoids, immune cells, intestinal stem cells (ISCs), and vascular endothelial cells (VECs). When ACh enters the interstitial space, its self-modulation or effects on adjacent tissues are part of the range of its biological functions. This review focuses on the current understanding of the mechanisms of ACh synthesis and release in the NNCS. Furthermore, studies on ACh functions in colonic disorders suggest that ACh from the NNCS contributes to immune regulation, IEC and VEC repair, ISC differentiation, colonic movement, and colonic tumor development. As indicated by the features of some colonic disorders, ACh and the NNCS have positive and negative effects on these disorders. Furthermore, the NNCS is located in multiple colonic organs, and the specific effects and cross-talk involving ACh from the NNCS in different colonic tissues are explored.

Label-Free Quantitative Phase Imaging Reveals Spatial Heterogeneity of Extracellular Vesicles in Select Colon Disorders.

Three-dimensional (3D) imaging and quantitative analysis of extracellular vesicles (EVs) remain largely unexplored, mainly because of limitations in detection techniques. In this study, EVs from patients diagnosed with colorectal cancer (CRC) and ulcerative colitis were examined. To investigate the spatial heterogeneity and 3D refractive index (RI) distribution of single EVs, a label-free digital holographic tomography technique was used at a submicrometer spatial resolution. The presented image-processing algorithms were used in quantitative analysis with digital staining and 3D visualization, the determination of the EV size distribution and extraction of fractions with different RIs. Reconstructed 3D RI distributions revealed variations in the spatial heterogeneity of EVs related to tissue specificity, such as CRC, normal colonic mucosa, and ulcerative colitis, as well as the isolation procedures used. The RI values of EVs isolated from solid tissues of frozen CRC samples were also dependent on the tumor grade and cancer cell proliferation. The simultaneous examination of cell culture models confirmed the association of the RI of EVs with the tumor grade. 3D-RI data analysis generates new perspectives with the optical, contact-free, label-free examination of the individual EVs. Depending on the specific tissue and isolation method, EVs exhibit significant spatial heterogeneity. The optical parameters of single EVs enabled their classification into two unique subgroups with different RI values.

Interstitial cells of Cajal and human colon motility in health and disease.

Our understanding of human colonic motility, and autonomic reflexes that generate motor patterns, has increased markedly through high-resolution manometry. Details of the motor patterns are emerging related to frequency and propagation characteristics that allow linkage to interstitial cells of Cajal (ICC) networks. In studies on colonic motor dysfunction requiring surgery, ICC are almost always abnormal or significantly reduced. However, there are still gaps in our knowledge about the role of ICC in the control of colonic motility and there is little understanding of a mechanistic link between ICC abnormalities and colonic motor dysfunction. This review will outline the various ICC networks in the human colon and their proven and likely associations with the enteric and extrinsic autonomic nervous systems. Based on our extensive knowledge of the role of ICC in the control of gastrointestinal motility of animal models and the human stomach and small intestine, we propose how ICC networks are underlying the motor patterns of the human colon. The role of ICC will be reviewed in the autonomic neural reflexes that evoke essential motor patterns for transit and defecation. Mechanisms underlying ICC injury, maintenance, and repair will be discussed. Hypotheses are formulated as to how ICC dysfunction can lead to motor abnormalities in slow transit constipation, chronic idiopathic pseudo-obstruction, Hirschsprung's disease, fecal incontinence, diverticular disease, and inflammatory conditions. Recent studies on ICC repair after injury hold promise for future therapies.

Update on SLC6A14 in lung and gastrointestinal physiology and physiopathology: focus on cystic fibrosis.

The solute carrier family 6 member 14 (SLC6A14) protein imports and concentrates all neutral amino acids as well as the two cationic acids lysine and arginine into the cytoplasm of different cell types. Primarily described as involved in several cancer and colonic diseases physiopathological mechanisms, the SLC6A14 gene has been more recently identified as a genetic modifier of cystic fibrosis (CF) disease severity. It was indeed shown to have a pleiotropic effect, modulating meconium ileus occurrence, lung disease severity, and precocity of P. aeruginosa airway infection. The biological mechanisms explaining the impact of SLC6A14 on intestinal and lung phenotypes of CF patients are starting to be elucidated. This review focuses on SLC6A14 in lung and gastrointestinal physiology and physiopathology, especially its involvement in the pathophysiology of CF disease.

HGF and TSG-6 Released by Mesenchymal Stem Cells Attenuate Colon Radiation-Induced Fibrosis.

Fibrosis is a leading cause of death in occidental states. The increasing number of patients with fibrosis requires innovative approaches. Despite the proven beneficial effects of mesenchymal stem cell (MSC) therapy on fibrosis, there is little evidence of their anti-fibrotic effects in colorectal fibrosis. The ability of MSCs to reduce radiation-induced colorectal fibrosis has been studied in vivo in Sprague-Dawley rats. After local radiation exposure, rats were injected with MSCs before an initiation of fibrosis. MSCs mediated a downregulation of fibrogenesis by a control of extra cellular matrix (ECM) turnover. For a better understanding of the mechanisms, we used an in vitro model of irradiated cocultured colorectal fibrosis in the presence of human MSCs. Pro-fibrotic cells in the colon are mainly intestinal fibroblasts and smooth muscle cells. Intestinal fibroblasts and smooth muscle cells were irradiated and cocultured in the presence of unirradiated MSCs. MSCs mediated a decrease in profibrotic gene expression and proteins secretion. Silencing hepatocyte growth factor (HGF) and tumor necrosis factor-stimulated gene 6 (TSG-6) in MSCs confirmed the complementary effects of these two genes. HGF and TSG-6 limited the progression of fibrosis by reducing activation of the smooth muscle cells and myofibroblast. To settle in vivo the contribution of HGF and TSG-6 in MSC-antifibrotic effects, rats were treated with MSCs silenced for HGF or TSG-6. HGF and TSG-6 silencing in transplanted MSCs resulted in a significant increase in ECM deposition in colon. These results emphasize the potential of MSCs to influence the pathophysiology of fibrosis-related diseases, which represent a challenging area for innovative treatments.

Post-Translational Modifications of Transcription Factors Harnessing the Etiology and Pathophysiology in Colonic Diseases.

Defects in mucosal immune balance can lead to colonic diseases such as inflammatory bowel diseases and colorectal cancer. With the advancement of understanding for the immunological and molecular basis of colonic disease, therapies targeting transcription factors have become a potential approach for the treatment of colonic disease. To date, the biomedical significance of unique post-translational modifications on transcription factors has been identified, including phosphorylation, methylation, acetylation, ubiquitination, SUMOylation, and O-GlcNAcylation. This review focuses on our current understanding and the emerging evidence of how post-translational regulations modify transcription factors involved in the etiology and pathophysiology of colonic disease as well as the implications of these findings for new therapeutic approaches in these disorders.

Walnut phenolic extract inhibits nuclear factor kappaB signaling in intestinal epithelial cells, and ameliorates experimental colitis and colitis-associated colon cancer in mice.

PURPOSE: Walnuts (Juglans regia) are known to have anti-cancer and immunomodulatory effects. However, little information is available on the effects of walnut phenolic extract (WPE) on intestinal inflammation and colitis-associated colon cancer. METHODS: COLO205 cells were pretreated with WPE and then stimulated with tumor necrosis factor (TNF)-α. In the acute colitis model, wild type mice (C57BL/6) were administered 4% dextran sulfate sodium (DSS) for 5 days. In the chronic colitis model, interleukin (IL)-10-/- mice were administered with either the vehicle or WPE (20 mg/kg) by oral gavage daily for 2 weeks. In an inflammation-associated tumor model, wild type mice were administered a single intraperitoneal injection of azoxymethane followed by three cycles of 2% DSS for 5 days and 2 weeks of free water consumption. RESULTS: WPE significantly inhibited IL-8 and IL-1α expression in COLO205 cells. WPE attenuated both the TNF-α-induced IκB phosphorylation/degradation and NF-κB DNA binding activity. The administration of oral WPE significantly reduced the severity of colitis in both acute and chronic colitis models, including the IL-10-/- mice. In immunohistochemical staining, WPE attenuated NF-κB signaling in the colons of both colitis models. Finally, WPE also significantly reduced tumor development in a murine model of colitis-associated colon cancer (CAC). CONCLUSIONS: WPE ameliorates acute and chronic colitis and CAC in mice, suggesting that WPE may have potentials for the treatment of inflammatory bowel disease.

E-cadherin Beyond Structure: A Signaling Hub in Colon Homeostasis and Disease.

E-cadherin is the core component of epithelial adherens junctions, essential for tissue development, differentiation, and maintenance. It is also fundamental for tissue barrier formation, a critical function of epithelial tissues. The colon or large intestine is lined by an epithelial monolayer that encompasses an E-cadherin-dependent barrier, critical for the homeostasis of the organ. Compromised barriers of the colonic epithelium lead to inflammation, fibrosis, and are commonly observed in colorectal cancer. In addition to its architectural role, E-cadherin is also considered a tumor suppressor in the colon, primarily a result of its opposing function to Wnt signaling, the predominant driver of colon tumorigenesis. Beyond these well-established traditional roles, several studies have portrayed an evolving role of E-cadherin as a signaling epicenter that regulates cell behavior in response to intra- and extra-cellular cues. Intriguingly, these recent findings also reveal tumor-promoting functions of E-cadherin in colon tumorigenesis and new interacting partners, opening future avenues of investigation. In this Review, we focus on these emerging aspects of E-cadherin signaling, and we discuss their implications in colon biology and disease.

Suppression of methionine-induced colon injury of young rats by cysteine and N-acetyl-L-cysteine.

Changes in the methionine metabolism can cause a state called hyperhomocysteinemia, inducing oxidative stress in the gut. The production of free radicals is important in the colon damage caused by methionine. This study aimed at evaluating the effect of the use of L-cysteine and N-acetyl-L-cysteine on the colon morphometry of young rats treated with methionine. A total number of 32 male rats were distributed in a randomized experimental design in 4 groups: control group treated with saline; methionine group; cysteine + methionine group, and N-acetyl-L-cysteine + methionine group. After 21 days of treatment, rats were sacrificed and the colon samples were taken for histological and biochemical analysis. Methionine load increased depth of crypts, the lamina muscularis mucosae thickness, the mucosal height, and the number of cells in lamina propria (p < 0.01). Combination of methionine with L-cysteine (C group) and with N-acetyl-L-cysteine (N group) reversed methionine effects. Methionine treatment increased the GPx activity and MDA concentration, while L-cysteine and N-acetyl-L-cysteine increased the catalase activity compared to methionine group. It was concluded that the use of L-cysteine and N-acetyl-L-cysteine was beneficial to decrease intestinal mucosal height and oxidative damage when methionine was used in combination with them.

Faecal but not serum calprotectin levels look promising in predicting active disease in Behçet's syndrome patients with gastrointestinal involvement.

OBJECTIVES: The faecal calprotectin (FC) test is widely used as a non-invasive method for identifying intestinal inflammation. A recent study suggested FC may help to diagnose gastrointestinal involvement of Behçet's syndrome (GIBS). We aimed to determine whether FC helps to distinguish active from inactive intestinal involvement in GIBS. METHODS: We tried to contact 70 GIBS patients registered in our tertiary multidisciplinary clinic. We prospectively collected faecal specimens and serum from 39 GIBS patients who gave informed consent assessing calprotectin and CRP levels followed by a colonoscopy. We included 47 Crohn's disease (CD) patients as controls. Active disease was defined as having ulcer/s on colonoscopy. We filled the Disease Activity Index for Intestinal Behçet's Disease (DAIBD) and Crohn's Disease Activity Index (CDAI). The cut-off for positive FC was defined as ≥150 µg/g. RESULTS: Ulcers were detected in 12/39 GIBS patients. Sensitivity and specificity of the FC test for active disease was 91.7 (95%CI:61.5-99.8) and 74.1% (95%CI:53.7-88.9). Median FC and CRP levels and DAIBD scores were higher among patients with ulcers, whereas serum calprotectin and CDAI scores were not. A negative FC test was the only significant predictor of remission (OR:37.04, 95%CI:2.4-561.6; p=0.009) on multivariate analysis. Among CD patients, 16/25 active patients and 3/22 patients in endoscopic remission had a positive FC test (OR:11, 95%CI:11-49). CONCLUSIONS: FC, but not serum calprotectin seems to be a useful non-invasive tool for assessing disease activity in GIBS. Whether the presence of oral ulcers can cause false positive results remains to be studied.

Bifidobacteria alleviate experimentally induced colitis by upregulating indoleamine 2, 3-dioxygenase expression.

The goal of this study was explore the role of indoleamine 2, 3-dioxygenase (IDO) in the therapeutic effect of probiotics on inflammatory bowel disease (IBD). Trinitrobenzene sulfonic acid (TNBS) was used to induce colitis in mice and 1-methyltryptophan (1-MT) to block expression of IDO. Clinical manifestations and macroscopic and microscopic colonic changes were assessed using a disease activity index (DAI), the Wallace-Keenan, and Curtner scoring systems, respectively. Expression of colonic IDO was detected by western blot. Immunohistochemistry analysis to evaluate numbers of CD11c+ cells and expression of IL-17 and Foxp3 showed that DAI, Wallace-Keenan, and Curtner scores were lower in the Bifidobacteria treatment group than the control group and that the therapeutic effect of Bifidobacteria was blocked by 1-MT (P < 0.05). Additionally, Bifidobacteria were found to increase expression of IDO and the numbers of CD11c+ cells, CD11c+ and IDO double positive cells and Foxp3+ Treg cells, while decreasing the number of IL-17+ cells (P < 0.05). The generation of Foxp3+ Treg cells induced by Bifidobacteria was abrogated by 1-MT (P < 0.05). These findings study suggest that Bifidobacteria attenuate TNBS-induced colitis by inducing expression of IDO, which further increases generation of Foxp3+ Treg cells.

Melatonin alleviates brain and peripheral tissue edema in a neonatal rat model of hypoxic-ischemic brain damage: the involvement of edema related proteins.

BACKGROUND: Previous studies have indicated edema may be involved in the pathophysiology following hypoxic-ischemic encephalopathy (HIE), and melatonin may exhibit neuro-protection against brain insults. However, little is known regarding the mechanisms that involve the protective effects of melatonin in the brain and peripheral tissues after HIE. The present study aimed to examine the effects of melatonin on multiple organs, and the expression of edema related proteins in a neonatal rat model of hypoxic-ischemic brain damage (HIBD). METHODS: One hundred ninety-two neonatal rats were randomly divided into three subgroups that underwent a sham surgery or HIBD. After the HIBD or sham-injury, the rats received an intraperitoneal injection of melatonin or an equal volume vehicle, respectively. We investigated the effects of melatonin on brain, kidney, and colon edema via histological examination and the expression of edema related proteins, including AQP-4, ZO-1 and occludin, via qPCR and western blot. RESULTS: Our data indicated (1) Melatonin reduced the histological injury in the brain and peripheral organs induced by HIBD as assessed via H-E staining and transmission electron microscopy. (2) Melatonin alleviated the HIBD-induced cerebral edema characterized by increased brain water content. (3) HIBD induced significant changes of edema related proteins, such as AQP-4, ZO-1 and occludin, and these changes were partially reversed by melatonin treatment. CONCLUSIONS: These findings provide substantial evidence that melatonin treatment has protective effects on the brain and peripheral organs after HIBD, and the edema related proteins, AQP4, ZO-1, and occludin, may indirectly contribute tothe mechanism of the edema protection by melatonin.

Unsuspected Langerhans cell histiocytosis can be easily missed in a colonic biopsy.

Langerhans cell histiocytosis (LCH) involvement of the gastrointestinal tract (GIT) is rare. The infiltrate in a colonic biopsy can be dissimilar to classic cytomorphologic features. It could be patchy, restricted to the subepithelial lamina propria and the lesional cells might have prominent nucleoli with lymphocytes-dominant background. The GIT manifestations could be confused with infectious, allergic, immunodeficiency and inflammatory bowel diseases. The rarity of GIT lesions, unawareness of some atypical endoscopic and histologic features might lead to false negative results. We report a case of LCH in an 11-month-old baby that was clinically unsuspected and histologically overlooked.

Increased circulating regulatory T cells and decreased follicular T helper cells are associated with colorectal carcinogenesis.

Objective: Colorectal cancer (CRC) is the third most prevalent cancer worldwide and is associated with high morbidity and mortality rates. Colorectal carcinogenesis occurs via the conventional adenoma-to-carcinoma and serrated pathways. Conventional T helper (Th) and innate lymphoid cells (ILCs) play vital roles in maintaining intestinal homeostasis. However, the contribution of these two major lymphoid cell populations and their associated cytokines to CRC development is unclear. Therefore, we aimed to analyze peripheral lymphocyte profiles during colorectal carcinogenesis. Methods: We collected 86 blood samples concurrently, and pathologists confirmed the presence of various pathological conditions (i.e., HPs, adenoma, and carcinoma) using hematoxylin and eosin staining. Ten healthy donors were recruited as healthy controls (HCs) from the physical examination center. We performed flow cytometry on peripheral blood mononuclear cells collected from patients with various pathological conditions and the HCs, and cytokines (interleukin-2, interleukin-4, interleukin-5, interleukin-13, interleukin-17A, interleukin-17F, interleukin-22, interferon-γ, and tumor necrosis factor-α) were quantified. We also analyzed the published single-cell RNA sequence data derived from tissue samples from different stages of colorectal carcinogenesis. Results: The cytokine response in peripheral CD4+ T cells was upregulated during the carcinoma process. The frequency of peripheral regulatory T cells (Tregs) increased in the adenoma and carcinoma stages. While the T follicular helper (Tfh) cell proportion was downregulated in the adenoma and carcinoma processes. Thus, Th cell subsets, especially Tregs and Tfh cells, were involved in colonic diseases. Moreover, the immunological profile characteristics in the HPs were clarified. Conclusion: We comprehensively analyzed circulating ILCs and adaptive T-cell lymphocyte subtypes in colorectal carcinoma progression. Our results show the immunological profile characteristics and support the involvement of Th subsets, especially Treg and Tfh cell populations, in colonic diseases. These findings significantly enhance our understanding of the immune mechanisms underlying CRC and its precancerous lesions. Further investigation of the Treg and Tfh cells' function in colorectal disease development will provide potential therapeutic targets for monitoring and preventing CRC development.

Receptors and ligands role in colon physiology and pathology.

Colonic diseases are more prevalent during the past decade. Colorectal cancer, ulcerative colitis, Crohn's disease, diverticulitis, irritable bowel syndrome are the major reported colonic diseases. Innovative strategies are defensible in order to advance the efficacy of colonic disease treatment. During the past decade there has been an extensive advance in the understanding of receptor signaling both from a clinical as well as a preclinical perspective. A sound knowledge on molecular pathways that characterize cell growth, cell cycle, apoptosis, angiogenesis and invasion has provided novel targets in colorectal cancer therapy and inflammatory pathways in the ulcerative colitis. Receptor signaling has been involved in these pathways. To understand the receptor ligand interaction, one must have the basic knowledge regarding those receptors and ligands. This review summarizes the existing knowledge of the expression and function of various receptors and ligands in the colonic tissue. It also covers their role in the physiological processes and pathological conditions of colon.

Research progress of colon-targeted oral hydrogel system based on natural polysaccharides.

The quality of life is significantly impacted by colon-related diseases. There have been a lot of interest in the oral colon-specific drug delivery system (OCDDS) as a potential carrier to decrease systemic side effects and protect drugs from degradation in the upper gastrointestinal tract (GIT). Hydrogels are effective oral colon-targeted drug delivery carriers due to their high biodegradability, substantial drug loading, and great biocompatibility. Natural polysaccharides give the hydrogel system unique structure and function to effectively respond to the complex environment of the GIT and deliver drugs to the colon. In this paper, the physiological factors of colonic drug delivery and the pathological characteristics of common colonic diseases are summarized, and the latest advances in the design, preparation and characterization of natural polysaccharide hydrogels are reviewed, which are expected to provide new references for colon-targeted oral hydrogel systems using natural polysaccharides as raw materials.

Eutopic endometrium and peritoneal, ovarian and colorectal endometriotic tissues express a different profile of nectin-1, -3, -4 and nectin-like molecule 2.

STUDY QUESTION: How is the expression of nectins and nectin-like molecules (Necls) detected by immunostaining altered by endometriosis? SUMMARY ANSWER: Our results suggest that Nectin-1, -3, -4 and Necl-2 may contribute to the pathogenesis of endometriosis. Immunostaining of nectins and Necls varies according to the anatomical location of endometriosis. WHAT IS KNOWN AND WHAT THIS PAPER ADDS: Nectin and Necl molecules are immunoglobulin-like cell adhesion molecules involved in apoptosis, cell proliferation and in metastases. Previous studies have demonstrated the involvement of adhesion molecules in the development of endometriotic lesions but no data exist on immunostaining of nectins and Necls molecules in endometriosis. DESIGN, PARTICIPANTS AND SETTING: This retrospective study was conducted in a tertiary-care hospital (Tenon Hospital, Paris, France). Samples were collected from 55 women undergoing endometrial biopsy or surgery for endometriosis and 20 controls having hysterectomy or endometrial biopsy for other reasons; multiple samples were collected from 15 women. We studied the immunostaining of Nectin-1, -3, -4 and Necl-2 in secretory and proliferative endometrium from women with (n = 20) or without endometriosis (i.e. control group, n = 20), and in peritoneal (n = 20), ovarian (n = 20) and colorectal endometriosis (n = 20). MAIN RESULTS: Semi-quantitative immunostaining demonstrated that (1) Necl-2 staining was stronger in all types of endometriotic lesions than in the eutopic endometrium from patients with endometriosis (P < 0.0125) and in ovarian endometriotic cysts compared with other locations (P < 0.001); (2) Nectin-3 staining was stronger in the eutopic endometrium of patients with endometriosis compared with controls (P = 0.03) and in all endometriotic lesions compared with the eutopic endometrium from patients with endometriosis (P < 0.0125); (3) Nectin-4, staining was stronger in the eutopic endometrium of patients with endometriosis compared with controls (P = 0.04) and (4) Nectin-1 staining was significantly increased in colorectal endometriosis compared with other locations (P = 0.004). BIAS, CONFOUNDING AND OTHER REASONS FOR CAUTION: We did not assess the pattern of expression in endometriosis of all nectins and Necl molecules. Indeed, Necl-5 is implicated in many pathophysiological processes such as cell movement and proliferation with potential relevance to endometriosis. GENERALISABILITY TO OTHER POPULATIONS: At present, few data on implication of nectins and Necl molecules in endometriosis exist. Hence, our results should be confirmed by further quantitative studies at protein or RNA levels. STUDY FUNDING/COMPETING INTEREST(S): No funding source. All the authors declare no conflict of interest.

[Hepatic encephalopathy and colon pathology in liver cirrhosis].

RESEARCH OBJECTIVE: to define a role of structural and functional changes of a colon, expression indicators of epithelial cells of mucous coat of colon that produce serotonin and hromogranin-A at in encephalopathy development at liver cirrhoses. We have examined 146 patients with liver cirrhosis of various classes using the clinical, endoscopic, morphologic and immunohistochemical methods. It is established that with increase of a class of a cirrhosis frequency of revealing of a hepatic encephalopathy, structural changes, degree dysbacteriosis of a colon. Progressing of a hepatic encephalopathy at liver cirrhoses associates with development destructive and atrophic changes of a mucous membrane of a colon and a dysbacteriosis. The increase in the morphometric rates of epithelial cells of mucous coat of colon that produce serotonin and hromogranin-A at liver cirrhoses plays a part in development of a manifesting of a hepatic encephalopathy.

Unraveling the role of Epac1-SOCS3 signaling in the development of neonatal-CRD-induced visceral hypersensitivity in rats.

AIMS: Visceral hypersensitivity in irritable bowel syndrome (IBS) is widespread, but effective therapies for it remain elusive. As a canonical anti-inflammatory protein, suppressor of cytokine signaling 3 (SOCS3) reportedly relays exchange protein 1 directly activated by cAMP (Epac1) signaling and inhibits the intracellular response to inflammatory cytokines. Despite the inhibitory effect of SOCS3 on the pro-inflammatory response and neuroinflammation in PVN, the systematic investigation of Epac1-SOCS3 signaling involved in visceral hypersensitivity remains unknown. This study aimed to explore Epac1-SOCS3 signaling in the activity of hypothalamic paraventricular nucleus (PVN) corticotropin-releasing factor (CRF) neurons and visceral hypersensitivity in adult rats experiencing neonatal colorectal distension (CRD). METHODS: Rats were subjected to neonatal CRD to simulate visceral hypersensitivity to investigate the effect of Epac1-SOCS3 signaling on PVN CRF neurons. The expression and activity of Epac1 and SOCS3 in nociceptive hypersensitivity were determined by western blot, RT-PCR, immunofluorescence, radioimmunoassay, electrophysiology, and pharmacology. RESULTS: In neonatal-CRD-induced visceral hypersensitivity model, Epac1 and SOCS3 expressions were downregulated and IL-6 levels elevated in PVN. However, infusion of Epac agonist 8-pCPT in PVN reduced CRF neuronal firing rates, and overexpression of SOCS3 in PVN by AAV-SOCS3 inhibited the activation of PVN neurons, reduced visceral hypersensitivity, and precluded pain precipitation. Intervention with IL-6 neutralizing antibody also alleviated the visceral hypersensitivity. In naïve rats, Epac antagonist ESI-09 in PVN increased CRF neuronal firing. Consistently, genetic knockdown of Epac1 or SOCS3 in PVN potentiated the firing rate of CRF neurons, functionality of HPA axis, and sensitivity of visceral nociception. Moreover, pharmacological intervention with exogenous IL-6 into PVN simulated the visceral hypersensitivity. CONCLUSIONS: Inactivation of Epac1-SOCS3 pathway contributed to the neuroinflammation accompanied by the sensitization of CRF neurons in PVN, precipitating visceral hypersensitivity and pain in rats experiencing neonatal CRD.