Decreased miR-199 augments visceral pain in patients with IBS through translational upregulation of TRPV1

Intestinal Permeability in Disorders of Gut-Brain Interaction: From Bench to Bedside

Intestinal barrier function lies at a critical interface of a range of peripheral and central processes that influence disorders of gut-brain interactions (DGBI). Although rigorously tested, the role of barrier dysfunction in driving clinical phenotype of DGBI remains to be fully elucidated. In vitro, in vivo, and ex vivo strategies can test various aspects of the broader permeability and barrier mechanisms in the gut. Luminal mediators of host, bacterial, and dietary origin can influence the barrier function and a disrupted barrier can also influence the luminal milieu. Critical to our understanding is how barrier dysfunction is influenced by stress and other comorbidities that associate with DGBI and the crosstalk between barrier and neural, hormonal, and immune responses. Additionally, the microbiome's significant role in the communication between the brain and gut has led to the integrative model of a microbiome gut-brain axis with reciprocal interactions between brain networks and networks composed of multiple cells in the gut, including immune cells, enterochromaffin cells, gut microbiota and the derived luminal mediators. This review highlights the techniques for assessment of barrier function, appraises evidence for barrier dysfunction in DGBI including mechanistic studies in humans, as well as provides an overview of therapeutic strategies that can be used to directly or indirectly restore barrier function in DGBI patients.

Histone modifications and Sp1 promote GPR160 expression in bone cancer pain within rodent models

Bone cancer pain (BCP) affects ~70% of patients in advanced stages, primarily due to bone metastasis, presenting a substantial therapeutic challenge. Here, we profile orphan G protein-coupled receptors in the dorsal root ganglia (DRG) following tumor infiltration, and observe a notable increase in GPR160 expression. Elevated Gpr160 mRNA and protein levels persist from postoperative day 6 for over 18 days in the affected DRG, predominantly in small-diameter C-fiber type neurons specific to the tibia. Targeted interventions, including DRG microinjection of siRNA or AAV delivery, mitigate mechanical allodynia, cold, and heat hyperalgesia induced by the tumor. Tumor infiltration increases DRG neuron excitability in wild-type mice, but not in Gpr160 gene knockout mice. Tumor infiltration results in reduced H3K27me3 and increased H3K27ac modifications, enhanced binding of the transcription activator Sp1 to the Gpr160 gene promoter region, and induction of GPR160 expression. Modulating histone-modifying enzymes effectively alleviated pain behavior. Our study delineates a novel mechanism wherein elevated Sp1 levels facilitate Gpr160 gene transcription in nociceptive DRG neurons during BCP in rodents.

Mast cell modulation: A novel therapeutic strategy for abdominal pain in irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most prevalent gastrointestinal disorders characterized by recurrent abdominal pain and an altered defecation pattern. Chronic abdominal pain represents the hallmark IBS symptom and is reported to have the most bothersome impact on the patient's quality of life. Unfortunately, effective therapeutic strategies reducing abdominal pain are lacking, mainly attributed to a limited understanding of the contributing mechanisms. In the past few years, exciting new insights have pointed out that altered communication between gut immune cells and pain-sensing nerves acts as a hallmark driver of IBS-related abdominal pain. In this review, we aim to summarize our current knowledge on altered neuro-immune crosstalk as the main driver of altered pain signaling, with a specific focus on altered mast cell functioning herein, and highlight the relevance of targeting mast cell-mediated mechanisms as a novel therapeutic strategy for chronic abdominal pain in IBS patients.

Impact of Enteric Nervous Cells on Irritable Bowel Syndrome: Potential Treatment Options

Irritable bowel syndrome (IBS) is a condition that significantly impacts the lifestyle, health, and habits of numerous individuals worldwide. Its diagnosis and classification are based on the Rome criteria, updated periodically to reflect new research findings in this field. IBS can be classified into different types based on symptoms, each with distinct treatment approaches and some differences in their pathophysiology. The exact pathological background of IBS remains unclear, with many aspects still unknown. Recent research developments suggest that disorders in the brain-gut-microbiota axis are key contributors to the symptoms and severity of IBS. The central nervous system (CNS) interacts bidirectionally with intestinal processes within the lumen and the intestinal wall, with the autonomic nervous system, particularly the vagus nerve, playing an important role. However, the enteric nervous system (ENS) is also crucial in the pathophysiological pathway of IBS. The apeline-corticotropin-releasing factor (CRF)-toll-like receptor 4 (TLR4) signaling route via enteric glia and serotonin production in enteroendocrine cells at the enteric barrier are among the most well-understood new findings that affect IBS through the ENS. Additionally, the microbiota regulates neuronal signals, modifying enteric function by altering the number of enteric bacteria and other mechanisms. Given the limited therapeutic options currently available, it is essential to identify new treatment targets, with the brain-gut axis, particularly the enteric nervous system, being a promising focus. This study aims to delineate the molecular mechanisms that induce IBS and to suggest potential targets for future research and treatment of this potentially debilitating disease.

The role of miRNA in IBS pathogenesis, diagnosis and therapy: The latest thought

IBS is a prevalent clinical condition affecting bowel function. There is a restricted comprehension of its pathogenesis, an absence of particular diagnostic tools, and an insufficiency of efficient pharmacological remedies. MiRNAs are a highly conserved class of non-coding small molecule RNAs, with a length of 20-24 nucleotides. Research has shown the presence of a number of differentially expressed miRNAs in the colonic tissue and peripheral blood of IBS patients. Meanwhile, miRNAs have a critical role in gene expression and the pathology of IBS as they act as significant mediators of post-transcriptional gene silencing. The investigation of miRNA molecular regulatory networks proves useful in examining the convoluted pathogenesis of IBS. This paper presents a review of recent literature on miRNAs associated with IBS, explains how miRNAs contribute to the development of IBS, and assesses the potential usefulness of miRNA analysis for diagnosing and treating IBS.

Macrophages and Gut Barrier Function: Guardians of Gastrointestinal Health in Post-Inflammatory and Post-Infection Responses

The gut barrier is essential for protection against pathogens and maintaining homeostasis. Macrophages are key players in the immune system, are indispensable for intestinal health, and contribute to immune defense and repair mechanisms. Understanding the multifaceted roles of macrophages can provide critical insights into maintaining and restoring gastrointestinal (GI) health. This review explores the essential role of macrophages in maintaining the gut barrier function and their contribution to post-inflammatory and post-infectious responses in the gut. Macrophages significantly contribute to gut barrier integrity through epithelial repair, immune modulation, and interactions with gut microbiota. They demonstrate active plasticity by switching phenotypes to resolve inflammation, facilitate tissue repair, and regulate microbial populations following an infection or inflammation. In addition, tissue-resident (M2) and infiltration (M1) macrophages convert to each other in gut problems such as IBS and IBD via major signaling pathways mediated by NF-κB, JAK/STAT, PI3K/AKT, MAPK, Toll-like receptors, and specific microRNAs such as miR-155, miR-29, miR-146a, and miR-199, which may be good targets for new therapeutic approaches. Future research should focus on elucidating the detailed molecular mechanisms and developing personalized therapeutic approaches to fully harness the potential of macrophages to maintain and restore intestinal permeability and gut health.

Therapeutic Implication of miRNAs as an Active Regulatory Player in the Management of Pain: A Review

Chronic pain is frequently associated with neuropathy, inflammation, or the malfunctioning of nerves. Chronic pain is associated with a significant burden of morbidity due to opioid use, associated with addiction and tolerance, and disability. MicroRNAs (miRs) are emerging therapeutic targets to treat chronic pain through the regulation of genes associated with inflammation, neuronal excitability, survival, or de-differentiation. In this review, we discuss the possible involvement of miRs in pain-related molecular pathways. miRs are known to regulate high-conviction pain genes, supporting their potential as therapeutic targets.

Interoceptive Processing in Functional Gastrointestinal Disorders

Functional gastrointestinal disorders (FGIDs) are characterized by chronic gastrointestinal symptoms in the absence of overt pathology and affect a significant percentage of the worldwide population. They are commonly accompanied by co-morbid psychiatric symptomatology and are associated with significant suffering and great healthcare services utilization. There is growing evidence that dysregulation of the gut-brain axis and disturbances in the processing of afferent interoceptive signals lie at the heart of these disorders. In this context, the aim of the current review was to detect and critically review original articles focusing on the role of interoception in the pathophysiology of FGIDs. Our search yielded 38 relevant studies. FGID patients displayed increased visceral sensitivity, enhanced attention to gastrointestinal interoceptive cues, and greater emotional arousal when coping with gut-derived sensations. Neuroimaging studies have shown significant structural and functional changes in regions of the interoceptive network, while molecular and genetic studies have revealed significant associations between interoceptive signaling and deficits in excitatory neurotransmission, altered endocrine and immune physiological pathways, and aberrant expression of transient receptor potential channel genes. Finally, there were emerging data suggesting that interoception-based interventions may reduce physical symptoms and improve quality of life and should be integrated into FGID clinical management practices.

Global research states and trends of micro RNA in irritable bowel syndrome: a bibliometric analysis

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disorder, but its diagnosis and treatment remain obscure. Non-coding RNAs (ncRNAs), as potential biomarkers, have attracted increasing attention in digestive diseases. Here, we present a comprehensive research status, development trends, and valuable insights in this subject area. The literature search was performed using Web of Science Core Collection. VOSviewer 1.6.20, Citespace 6.2.R4, and Microsoft Excel 2021 were used for bibliometric analysis. A total of 124 articles were included in the analysis. Overall, publication patterns fluctuated. Globally, People's Republic of China, the USA, and Germany were the top three contributors of publications. Guangzhou University of Chinese Medicine, University of California, Mayo Clinic, and University of California, Los Angeles contributed the highest number of publications. The pathways and specific mechanisms by which ncRNAs regulate transcription and translation and thus regulate the pathophysiological processes of IBS are the main research hotspots in this field. We found that microRNA (miRNAs) are intricately involved in the regulation of key pathologies such as viscera sensitivity, intestinal permeability, intestinal mucosal barrier, immunoinflammatory response, and brain-gut axis in the IBS, and these topics have garnered significant attention in research community. Notably, microecological disorders are also associated with IBS pathogenesis, and ncRNA may play an important role in the interactions between host and intestinal flora. This is the first bibliometric study to comprehensively summarize the research hotspots and trends related to IBS and ncRNAs (especially miRNAs). Our findings will help understand the role of ncRNAs in IBS and provide guidance to future studies.

Metabolic biomarkers in irritable bowel syndrome diagnosis

Irritable bowel syndrome (IBS) is a chronic gastrointestinal (GI) disorder characterized by altered bowel habits and abdominal discomfort during defecation. It significantly impacts life quality and work productivity for those affected. Global data suggests a slightly higher prevalence in females than in males. Today, unambiguous diagnosis of IBS remains challenging due to the absence of a specific biochemical, histopathological, or radiological test. Current diagnosis relies heavily on thorough symptom evaluation. Efforts by the Rome committees have established standardized diagnostic criteria (Rome I-IV), improving consistency and clinical applicability. Recent studies in this framework, seem to have successfully employed metabolomics techniques to identify distinct metabolite profiles in breath and stool samples of IBS patients, differentiating them from healthy controls and those with other functional GI disorders, such as inflammatory bowel disease (IBD). Building on this success, researchers are investigating the presence of similar metabolites in easily accessible biofluids such as urine, potentially offering a less invasive diagnostic approach. Accordingly, this review focuses on key metabolites specifically detected in IBS patients' biological specimens, with a focus on urinary metabolites, using various methods, particularly mass spectrometry (MS)-based techniques, including gas chromatography-MS (GC-MS), liquid chromatography-tandem MS (LC-MS/MS), and capillary electrophoresis-MS (CE-MS) metabolomics assays. These findings may make provision for a new set of non-invasive biomarkers for IBS diagnosis and management.

Pathology of pain and its implications for therapeutic interventions

Pain is estimated to affect more than 20% of the global population, imposing incalculable health and economic burdens. Effective pain management is crucial for individuals suffering from pain. However, the current methods for pain assessment and treatment fall short of clinical needs. Benefiting from advances in neuroscience and biotechnology, the neuronal circuits and molecular mechanisms critically involved in pain modulation have been elucidated. These research achievements have incited progress in identifying new diagnostic and therapeutic targets. In this review, we first introduce fundamental knowledge about pain, setting the stage for the subsequent contents. The review next delves into the molecular mechanisms underlying pain disorders, including gene mutation, epigenetic modification, posttranslational modification, inflammasome, signaling pathways and microbiota. To better present a comprehensive view of pain research, two prominent issues, sexual dimorphism and pain comorbidities, are discussed in detail based on current findings. The status quo of pain evaluation and manipulation is summarized. A series of improved and innovative pain management strategies, such as gene therapy, monoclonal antibody, brain-computer interface and microbial intervention, are making strides towards clinical application. We highlight existing limitations and future directions for enhancing the quality of preclinical and clinical research. Efforts to decipher the complexities of pain pathology will be instrumental in translating scientific discoveries into clinical practice, thereby improving pain management from bench to bedside.

Lipopolysaccharide pretreatment increases the sensitivity of the TRPV1 channel and promotes an anti-inflammatory phenotype of capsaicin-activated macrophages

BACKGROUND

The transient receptor potential vanilloid 1 (TRPV1) is well-established in neuronal function, yet its role in immune reactions remains enigmatic. The conflicting data on its inflammatory role, suggesting both pro-inflammatory and anti-inflammatory effects upon TRPV1 stimulation in immune cells, adds complexity. To unravel TRPV1 immunomodulatory mechanisms, we investigated how the TRPV1 agonist capsaicin influences lipopolysaccharide (LPS)-induced pro-inflammatory macrophage phenotypes.

RESULTS

Changes in the surface molecules, cytokine production, and signaling cascades linked to the phenotype of M1 or M2 macrophages of the J774 macrophage cell line and bone marrow-derived macrophages, treated with capsaicin before or after the LPS-induced inflammatory reaction were determined. The functional capacity of macrophages was also assessed by infecting the stimulated macrophages with the intracellular parasite Leishmania mexicana.

CONCLUSION

Our findings reveal that TRPV1 activation yields distinct macrophage responses influenced by the inflammatory context. LPS pre-treatment followed by capsaicin activation prompted increased calcium influx, accompanied by a shift toward an anti-inflammatory M2b-like polarization state.

Pharmacogenetics in IBS: update and impact of GWAS studies in drug targets and metabolism

INTRODUCTION

Medications are frequently prescribed for patients with irritable bowel syndrome (IBS) or disorders of gut brain interaction. The level of drug metabolism and modifications in drug targets determine medication efficacy to modify motor or sensory function as well as patient response outcomes.

AREAS COVERED

The literature search included PubMed searches with the terms: pharmacokinetics, pharmacogenomics, epigenetics, clinical trials, irritable bowel syndrome, disorders of gut brain interaction, and genome-wide association studies. The main topics covered in relation to irritable bowel syndrome were precision medicine, pharmacogenomics related to drug metabolism, pharmacogenomics related to mechanistic targets, and epigenetics.

EXPERT OPINION

Pharmacogenomics impacting drug metabolism [CYP 2D6 (cytochrome P450 2D6) or 2C19 (cytochrome P450 2C19)] is the most practical approach to precision medicine in the treatment of IBS. Although there are proof of concept studies that have documented the importance of genetic modification of transmitters or receptors in altering responses to medications in IBS, these principles have rarely been applied in patient response outcomes. Genome-wide association (GWAS) studies have now documented the association of symptoms with genetic variation but not the evaluation of treatment responses. Considerably more research, particularly focused on patient response outcomes and epigenetics, is essential to impact this field in clinical medicine.

Serotonin receptor 2B induces visceral hyperalgesia in rat model and patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND

Serotonin receptor 2B (5-HT2B receptor) plays a critical role in many chronic pain conditions. The possible involvement of the 5-HT2B receptor in the altered gut sensation of irritable bowel syndrome with diarrhea (IBS-D) was investigated in the present study.

AIM

To investigate the possible involvement of 5-HT2B receptor in the altered gut sensation in rat model and patients with IBS-D.

METHODS

Rectosigmoid biopsies were collected from 18 patients with IBS-D and 10 patients with irritable bowel syndrome with constipation who fulfilled the Rome IV criteria and 15 healthy controls. The expression level of the 5-HT2B receptor in colon tissue was measured using an enzyme-linked immunosorbent assay and correlated with abdominal pain scores. The IBS-D rat model was induced by intracolonic instillation of acetic acid and wrap restraint. Alterations in visceral sensitivity and 5-HT2B receptor and transient receptor potential vanilloid type 1 (TRPV1) expression were examined following 5-HT2B receptor antagonist administration. Changes in visceral sensitivity after administration of the TRPV1 antagonist were recorded.

RESULTS

Here, we observed greater expression of the 5-HT2B receptor in the colonic mucosa of patients with IBS-D than in that of controls, which was correlated with abdominal pain scores. Intracolonic instillation of acetic acid and wrap restraint induced obvious chronic visceral hypersensitivity and increased fecal weight and fecal water content. Exogenous 5-HT2B receptor agonist administration increased visceral hypersensitivity, which was alleviated by successive administration of a TRPV1 antagonist. IBS-D rats receiving the 5-HT2B receptor antagonist exhibited inhibited visceral hyperalgesia.Moreover, the percentage of 5-HT2B receptor-immunoreactive (IR) cells surrounded by TRPV1-positive cells (5-HT2B receptor I+) and total 5-HT2B receptor IR cells (5-HT2B receptor IT) in IBS-D rats was significantly reduced by the administration of a 5-HT2B receptor antagonist.

CONCLUSION

Our finding that increased expression of the 5-HT2B receptor contributes to visceral hyperalgesia by inducing TRPV1 expression in IBS-D patients provides important insights into the potential mechanisms underlying IBS-D-associated visceral hyperalgesia.

Advances in the pathological mechanisms and clinical treatments of chronic visceral pain

Chronic visceral pain stems from internal organs and is frequently associated with functional gastrointestinal disorders, like irritable bowel syndrome (IBS). Since the underlying mechanisms of visceral pain remain largely unclear, clinical management is often limited and ineffective. Comprehensive research into the pathogenesis of visceral pain, along with the development of personalized therapeutic strategies, is crucial for advancing treatment options. Studies suggest that imbalances in purinergic receptors and neural circuit function are closely linked to the onset of visceral pain. In this review, we will explore the etiology and pathological mechanisms underlying visceral pain, with a focus on ion channels, epigenetic factors, and neural circuits, using functional gastrointestinal disorders as case studies. Finally, we will summarize and evaluate emerging treatments and potential initiatives aimed at managing visceral pain.

miR-199a-3p mediates bone cancer pain through upregulation of dnmt3a expression in spinal dorsal horn neurons

Due to its complex pathological mechanisms, bone cancer pain (BCP) has become an increasingly challenging clinical issue, there is an urgent need to identify the underlying mechanisms of BCP. In our present study, we found that decreased expression of miR-199a-3p in spinal dorsal horn (SDH) neurons contributed to BCP hypersensitivity. Intrathecal administration of miR-199a-3p agomir alleviated the initiation of tumor inoculation induced pain hypersensitivity and suppressed the expression of DNMT3A. Subsequently, luciferase assays confirmed direct binding between miR-199a-3p and Dnmt3a mRNA. AAV-DNMT3A-shRNA microinjection relieved mechanical hyperalgesia and upregulated the expression of Nrf2 levels in BCP. In naïve rats, Overexpression of DNMT3A yielded the opposite effects. Finally, increase of DNMT3A by lentiviral vector abolished miR-199a-3p-mediated alleviation hypersensitivity effects on BCP progression. Taken these together, our findings highlighted a novel contribution of miR-199a-3p to BCP and provided a fresh outlook on potential mechanism research for BCP.

MicroRNA-based therapeutics for inflammatory disorders of the microbiota-gut-brain axis

An emerging but less explored shared pathophysiology across microbiota-gut-brain axis disorders is aberrant miRNA expression, which may represent novel therapeutic targets. miRNAs are small, endogenous non-coding RNAs that are important transcriptional repressors of gene expression. Most importantly, they regulate the integrity of the intestinal epithelial and blood-brain barriers and serve as an important communication channel between the gut microbiome and the host. A well-defined understanding of the mode of action, therapeutic strategies and delivery mechanisms of miRNAs is pivotal in translating the clinical applications of miRNA-based therapeutics. Accumulating evidence links disorders of the microbiota-gut-brain axis with a compromised gut-blood-brain-barrier, causing gut contents such as immune cells and microbiota to enter the bloodstream leading to low-grade systemic inflammation. This has the potential to affect all organs, including the brain, causing central inflammation and the development of neurodegenerative and neuropsychiatric diseases. In this review, we have examined in detail miRNA biogenesis, strategies for therapeutic application, delivery mechanisms, as well as their pathophysiology and clinical applications in inflammatory gut-brain disorders. The research data in this review was drawn from the following databases: PubMed, Google Scholar, and Clinicaltrials.gov. With increasing evidence of the pathophysiological importance for miRNAs in microbiota-gut-brain axis disorders, therapeutic targeting of cross-regulated miRNAs in these disorders displays potentially transformative and translational potential. Further preclinical research and human clinical trials are required to further advance this area of research.

Irritable bowel syndrome: Epidemiology, overlap disorders, pathophysiology and treatment

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disease with a significant impact on patients' quality of life and a high socioeconomic burden. And the understanding of IBS has changed since the release of the Rome IV diagnosis in 2016. With the upcoming Rome V revision, it is necessary to review the results of IBS research in recent years. In this review of IBS, we can highlight future concerns by reviewing the results of IBS research on epidemiology, overlap disorders, pathophysiology, and treatment over the past decade and summarizing the latest research.

New insights into irritable bowel syndrome pathophysiological mechanisms: contribution of epigenetics

Irritable bowel syndrome (IBS) is a complex multifactorial condition including alterations of the gut-brain axis, intestinal permeability, mucosal neuro-immune interactions, and microbiota imbalance. Recent advances proposed epigenetic factors as possible regulators of several mechanisms involved in IBS pathophysiology. These epigenetic factors include biomolecular mechanisms inducing chromosome-related and heritable changes in gene expression regardless of DNA coding sequence. Accordingly, altered gut microbiota may increase the production of metabolites such as sodium butyrate, a prominent inhibitor of histone deacetylases. Patients with IBS showed an increased amount of butyrate-producing microbial phila as well as an altered profile of methylated genes and micro-RNAs (miRNAs). Importantly, gene acetylation as well as specific miRNA profiles are involved in different IBS mechanisms and may be applied for future diagnostic purposes, especially to detect increased gut permeability and visceromotor dysfunctions. In this review, we summarize current knowledge of the role of epigenetics in IBS pathophysiology.

Understanding neuroimmune interactions in disorders of gut-brain interaction: from functional to immune-mediated disorders

Functional gastrointestinal disorders-recently renamed into disorders of gut-brain interaction-such as irritable bowel syndrome and functional dyspepsia are highly prevalent conditions with bothersome abdominal symptoms in the absence of structural abnormalities. While traditionally considered as motility disorders or even psychosomatic conditions, our understanding of the pathophysiology has evolved significantly over the last two decades. Initial observations of subtle mucosal infiltration with immune cells, especially mast cells and eosinophils, are since recently being backed up by mechanistic evidence demonstrating increased release of nociceptive mediators by immune cells and the intestinal epithelium. These mediators can activate sensitised neurons leading to visceral hypersensitivity with bothersome symptoms. The interaction between immune activation and an impaired barrier function of the gut is most likely a bidirectional one with alterations in the microbiota, psychological stress and food components as upstream players in the pathophysiology. Only few immune-targeting treatments are currently available, but an improved understanding through a multidisciplinary scientific approach will hopefully identify novel, more precise treatment targets with ultimately better outcomes.

Catechol-O-Methyltransferase Loss Drives Cell-Specific Nociceptive Signaling via the Enteric Catechol-O-Methyltransferase/microRNA-155/Tumor Necrosis Factor α Axis

BACKGROUND & AIMS

The etiology of abdominal pain in postinfectious, diarrhea-predominant irritable bowel syndrome (PI-IBS-D) is unknown, and few treatment options exist. Catechol-O-methyltransferase (COMT), an enzyme that inactivates and degrades biologically active catecholamines, plays an important role in numerous physiologic processes, including modulation of pain perception. Our objective was to determine the mechanism(s) of how decreased colonic COMT in PI-IBS-D patients contributes to the chronic abdominal pain phenotype after enteric infections.

METHODS

Colon neurons, epithelial cells, and macrophages were procured with laser capture microdissection from PI-IBS-D patients to evaluate cell-specific colonic COMT, microRNA-155 (miR-155), and tumor necrosis factor (TNF) α expression levels compared to recovered patients (infection cleared: did not develop PI-IBS-D) and control individuals. COMT-/-, colon-specific COMT-/-, and miR-155-/- mice and human colonoids were used to model phenotypic expression of COMT in PI-IBS-D patients and to investigate signaling pathways linking abdominal pain. Citrobacter rodentium and trinitrobenzene sulfonic acid animal models were used to model postinflammatory changes seen in PI-IBS-D patients.

RESULTS

Colonic COMT levels were significantly decreased and correlated with increased visual analog scale abdominal pain ratings in PI-IBS-D patients compared to recovered patients and control individuals. Colonic miR-155 and TNF-α were increased in PI-IBS-D patients with diminished colonic COMT. COMT-/- mice had significantly increased expression of miR-155 and TNF-α in both colon tissues and dorsal root ganglia. Introduction of cV1q antibody (anti-TNF-α) into mice reversed visceral hypersensitivity after C rodentium and trinitrobenzene sulfonic acid.

CONCLUSIONS

Decreased colonic COMT in PI-IBS-D patients drives abdominal pain phenotypes via the COMT/miR-155/TNF-α axis. These important findings will allow new treatment paradigms and more targeted and personalized medicine approaches for gastrointestinal disorders after enteric infections.

Integrated omics analysis reveals the epigenetic mechanism of visceral hypersensitivity in IBS-D

Background and objective: IBS-D is a common functional bowel disease with complex etiology and without biomarker. The pathological and physiological basis of IBS-D focuses on visceral hypersensitivity. However, its epigenetic mechanism remains elusive. Our study aimed to integrate the relationship between differentially expressed miRNAs, mRNAs and proteins in IBS-D patients in order to reveal epigenetic mechanism of visceral hypersensitivity from transcription and protein levels and provide the molecular basis for discovering biomarkers of IBS-D.

Methods: The intestinal biopsies from IBS-D patients and healthy volunteers were obtained for high-throughput sequencing of miRNAs and mRNAs. The differential miRNAs were selected and verified by q-PCR experiment followed by target mRNA prediction. Biological functions were respectively analyzed for target mRNAs, differential mRNAs and the previously identified differential proteins in order to explore the characteristic involved visceral hypersensitivity. At last, interaction analysis of miRNAs, mRNAs and proteins was performed for the epigenetic regulation mechanism from transcription and protein levels.

Results: Thirty-three miRNAs were found to be differentially expressed in IBS-D and five of them were further confirmed, including upregulated hsa-miR-641, hsa-miR-1843, hsa-let-7d-3p and downregulated hsa-miR-219a-5p, hsa-miR-19b-1-5p. In addition, 3,812 differential mRNAs were identified. Thirty intersecting molecules were found from the analysis on the target mRNAs of miRNAs and mRNAs. Fourteen intersecting molecules were obtained from the analysis on the target mRNAs and proteins, and thirty-six intersecting molecules were identified from analysis on the proteins and different mRNAs. According to the integrated analysis of miRNA-mRNA-protein, we noticed two new molecules COPS2 regulated by hsa-miR-19b-1-5p and MARCKS regulated by hsa-miR-641. Meanwhile some critical signaling pathways in IBS-D were found such as MAPK, GABAergic synapse, Glutamatergic synapse, and Adherens junction.

Conclusion: The expressions of hsa-miR-641, hsa-miR-1843, hsa-let-7d-3p, hsa-miR-219a-5p, and hsa-miR-19b-1-5p in the intestinal tissues of IBS-D patients were significantly different. Moreover, they could regulate a variety of molecules and signaling pathways, which were involved in the multifaceted and multilevel mechanism of visceral hypersensitivity of IBS-D.

Spinal CircKcnk9 Regulates Chronic Visceral Hypersensitivity of Irritable Bowel Syndrome

Dysregulation of circular RNAs (circRNAs) has been reported to be functionally associated with chronic pain, but it is unknown whether and how circRNAs participate in visceral hypersensitivity. The expression of circKcnk9 was increased in spinal neurons of irritable bowel syndrome (IBS)-like rats. ShcircKcnk9 attenuated visceral hypersensitivity and inhibited c-Fos expression in IBS-like rats, whereas overexpression of spinal circKcnk9 induced visceral hypersensitivity and increased c-Fos expression in control rats. Furthermore, circKcnk9 was found to act as a miR-124-3p sponge. MiR-124-3p antagomir restored pain responses downregulated by shcircKcnk9 in IBS-like rats. Finally, the signal transducer and activator of transcription 3 (STAT3), validated as a target of miR-124-3p, could play a critical role in visceral hypersensitivity by regulating NSF/GluR2. PERSPECTIVE: Spinal circKcnk9 functions as a miR-124-3p sponge to promote visceral hypersensitivity by regulating the STAT3/NSF/GluR2 pathway. This pathway might provide a novel epigenetic mechanism of visceral hypersensitivity and a potential circRNA therapeutic target for IBS.

A paraventricular hypothalamic nucleus input to ventral of lateral septal nucleus controls chronic visceral pain

ABSTRACT

Irritable bowel syndrome is a functional gastrointestinal disorder characterized by chronic visceral pain with complex etiology and difficult treatment. Accumulated evidence has confirmed that the sensitization of the central nervous system plays an important role in the development of visceral pain, whereas the exact mechanisms of action of the neural pathways remain largely unknown. In this study, a distinct neural circuit was identified from the paraventricular hypothalamic (PVH) to the ventral of lateral septal (LSV) region. This circuit was responsible for regulating visceral pain. In particular, the data indicated that the PVH CaMKIIα-positive neurons inputs to the LSV CaMKIIα-positive neurons were only activated by colorectal distention rather than somatic stimulations. The PVH-LSV CaMKIIα + projection pathway was further confirmed by experiments containing a viral tracer. Optogenetic inhibition of PVH CaMKIIα + inputs to LSV CaMKIIα-positive neurons suppressed visceral pain, whereas selective activation of the PVH-LSV CaMKIIα + projection evoked visceral pain. These findings suggest the critical role of the PVH-LSV CaMKIIα + circuit in regulating visceral pain.

Autonomic dysfunction and gastroparesis in Gulf War veterans

Over 25% of veterans with Gulf War illness developed chronic gastrointestinal (GI) symptoms of unknown etiology after they returned from deployment to the Persian Gulf. To determine the prevalence of delayed gastric emptying and its association with autonomic dysfunction in returning Gulf War (GW) veterans with chronic GI symptoms, we prospectively studied 35 veterans who were deployed to the Persian Gulf and developed chronic nausea, vomiting, postprandial abdominal pain, and bloating during their tour of duty and 15 asymptomatic controls. All veterans underwent 5 standardized cardiovascular tests to assess autonomic function. Each test was scored from 0 (normal) to 5 (severe disease) and the mean was calculated. A composite score >1.5 was considered abnormal, with 5 representing severe autonomic dysfunction. A standardized gastric emptying test with a solid phase was performed in each veteran. A gastric retention of >50% at 100 minutes was considered abnormal. The composite autonomic score was 3.7 in veterans with GI symptoms (vs 1.3 in controls) (p<0.01). The mean solid phase retention at 100 minutes was 72.6% in the symptomatic veterans versus 24.6% in controls (p<0.001). Our results suggest that autonomic dysfunction and delayed gastric emptying are common in returning GW veterans with GI symptoms. Autonomic dysfunction was positively correlated with the severity of delayed gastric emptying and may account for the GI symptoms of nausea, vomiting, postprandial abdominal pain, and bloating. These new findings are important for an increasing number of veterans who are serving in the Persian Gulf and are at a high risk of developing GI disorders while deployed.

Multi-omics for biomarker approaches in the diagnostic evaluation and management of abdominal pain and irritable bowel syndrome: what lies ahead

Reliable biomarkers for common disorders of gut-brain interaction characterized by abdominal pain, including irritable bowel syndrome (IBS), are critically needed to enhance care and develop individualized therapies. The dynamic and heterogeneous nature of the pathophysiological mechanisms that underlie visceral hypersensitivity have challenged successful biomarker development. Consequently, effective therapies for pain in IBS are lacking. However, recent advances in modern omics technologies offer new opportunities to acquire deep biological insights into mechanisms of pain and nociception. Newer methods for large-scale data integration of complementary omics approaches have further expanded our ability to build a holistic understanding of complex biological networks and their co-contributions to abdominal pain. Here, we review the mechanisms of visceral hypersensitivity, focusing on IBS. We discuss candidate biomarkers for pain in IBS identified through single omics studies and summarize emerging multi-omics approaches for developing novel biomarkers that may transform clinical care for patients with IBS and abdominal pain.

Functional Implications and Clinical Potential of MicroRNAs in Irritable Bowel Syndrome: A Concise Review

MicroRNAs (miRNAs) are tiny (20-24 nucleotides long), non-coding, highly conserved RNA molecules that play a crucial role within the post-transcriptional regulation of gene expression via sequence-specific mechanisms. Since the miRNA transcriptome is involved in multiple molecular processes needed for cellular homeostasis, its altered expression can trigger the development and progression of several human pathologies. In this context, over the last few years, several relevant studies have demonstrated that dysregulated miRNAs affect a wide range of molecular mechanisms associated with irritable bowel syndrome (IBS), a common gastrointestinal disorder. For instance, abnormal miRNA expression in IBS patients is related to the alteration of intestinal permeability, visceral hyperalgesia, inflammatory pathways, and pain sensitivity. Besides, specific miRNAs are differentially expressed in the different subtypes of IBS, and therefore, they might be used as biomarkers for precise diagnosis of these pathological conditions. Accordingly, miRNAs have noteworthy potential as theragnostic targets for IBS. Hence, in this current review, we present an overview of the recent discoveries regarding the clinical relevance of miRNAs in IBS, which might be useful in the future for the development of miRNA-based drugs against this disorder.

Enterochromaffin Cells-Gut Microbiota Crosstalk: Underpinning the Symptoms, Pathogenesis, and Pharmacotherapy in Disorders of Gut-Brain Interaction

Disorders of gut-brain interaction (DGBIs) are common conditions in community and clinical practice. As specialized enteroendocrine cells, enterochromaffin (EC) cells produce up to 95% of total body serotonin and coordinate luminal and basolateral communication in the gastrointestinal (GI) tract. EC cells affect a broad range of gut physiological processes, such as motility, absorption, secretion, chemo/mechanosensation, and pathologies, including visceral hypersensitivity, immune dysfunction, and impaired gastrointestinal barrier function. We aim to review EC cell and serotonin-mediated physiology and pathophysiology with particular emphasis on DGBIs. We explored the knowledge gap and attempted to suggest new perspectives of physiological and pathophysiological insights of DGBIs, such as (1) functional heterogeneity of regionally distributed EC cells throughout the entire GI tract; (2) potential pathophysiological mechanisms mediated by EC cell defect in DGBIs; (3) cellular and molecular mechanisms characterizing EC cells and gut microbiota bidirectional communication; (4) differential modulation of EC cells through GI segment-specific gut microbiota; (5) uncover whether crosstalk between EC cells and (i) luminal contents; (ii) enteric nervous system; and (iii) central nervous system are core mechanisms modulating gut-brain homeostasis; and (6) explore the therapeutic modalities for physiological and pathophysiological mechanisms mediated through EC cells. Insights discussed in this review will fuel the conception and realization of pathophysiological mechanisms and therapeutic clues to improve the management and clinical care of DGBIs.

Expression of TRP Channels in Colonic Mucosa of IBS-D Patients and Its Correlation with the Severity of the Disease

Aim

Lots of researches have endeavored to elucidate the pathogenetic mechanism of visceral hypersensitivity in order to guide the therapy of diarrhea predominant-irritable bowel syndrome (IBS-D). Transient receptor potential (TRP) channels and their role in visceral nociception have been vastly investigated. We investigated the expression of TRP channels in IBS-D colonic biopsies and its correlation with the severity of the disease.

Methods

Sigmoid biopsies were obtained from 34 IBS-D patients and 28 healthy controls (HCs). IBS-D was diagnosed according to Rome IV criteria. Their clinical parameters were assessed through questionnaires. Expression of TRPV1, TRPV4, TRPA1, TRPM2, and TRPM8 was evaluated with immunohistology staining.

Results

Expression levels of TRPV1, TRPV4, and TRPA1 in the colonic mucosa of IBS-D patients were significantly higher than those in HCs (p < 0.05), while there was no obvious difference of TRPM2 and TRPM8 expression between IBS-D patients and HCs. In addition, the expression levels of TRPV1 and TRPA1, but TRPV4, in the colonic mucosa correlated positively with the severity of diseases (r = 0.6303 and 0.4506, respectively, p < 0.05).

Conclusions

Expression of TRPV1, TRPA1, and TRPV4 in the colonic mucosa was enhanced in IBS-D patients compared with HCs with the former two correlated with the severity of the disease. TRP channels might be promising biomarkers in the diagnosis and estimate of the severity in IBS-D.

Expression and Biological Functions of miRNAs in Chronic Pain: A Review on Human Studies

Chronic pain is a major public health problem and an economic burden worldwide. However, its underlying pathological mechanisms remain unclear. MicroRNAs (miRNAs) are a class of small noncoding RNAs that post-transcriptionally regulate gene expression and serve key roles in physiological and pathological processes. This review aims to synthesize the human studies examining miRNA expression in the pathogenesis of chronic primary pain and chronic secondary pain. Additionally, to understand the potential pathophysiological impact of miRNAs in these conditions, an in silico analysis was performed to reveal the target genes and pathways involved in primary and secondary pain and their differential regulation in the different types of chronic pain. The findings, methodological issues and challenges of miRNA research in the pathophysiology of chronic pain are discussed. The available evidence suggests the potential role of miRNA in disease pathogenesis and possibly the pain process, eventually enabling this role to be exploited for pain monitoring and management.

MicroRNA-642b-3p functions as an oncomiR in gastric cancer by down-regulating the CUB and sushi multiple domains protein 1/smad axis

Aberrant expression of microRNAs (miRNAs or miRs) has been involved in the progression of gastric cancer (GC). Our analysis of GC-related gene expression profiles identified the significantly up-regulated miR-642b-3p expression, which has been reported as a mediator in various cancers but rarely mentioned in researches on GC. Herein, this study intends to investigate the role of miR-642b-3p in GC development. Bioinformatics analysis was conducted to predict the downstream target gene of miR-642b-3p. Expression patterns of miR-642b-3p and CUB and sushi multiple domains protein 1 (CSMD1) in GC tissues and cell lines was then determined. Immunofluorescence, wound healing and Transwell invasion assays were performed to observe the malignant behaviors of GC cells with altered expression of miR-642b-3p and CSMD1. Nude mice with xenograft tumors were developed for in vivo validation. miR-642b-3p expression was increased in GC tissues and cell lines. miR-642b-3p targeted CSMD1 and reduced the expression of CSMD1, thereby inhibiting the activation of Smad signaling pathway. By this mechanism, the epithelial–mesenchymal transition (EMT), invasive and migratory potentials of GC cells were repressed. Meanwhile, in vivo data verified that miR-642b-3p enhanced the tumor growth of GC cells, which was associated with blockade of CSMD1-dependent activation of the Smad signaling pathway. Overall, miR-642b-3p acts as an oncomiR promoting tumor development in GC through suppressing CSMD1 expression and inactivating the Smad signaling pathway, which may enable the development of new therapeutic strategies for treatment of GC.

Pan-Cancer Analysis Reveals Genomic and Clinical Characteristics of TRPV Channel-Related Genes

Background

Transient Receptor Potential channels (TRPs), a class of ion channels, were first described two decades ago. Many TRP family members are major participants in nociception and integration of heat and pain signals. Recent studies have revealed that subfamilies of this channel, such as members of transient receptor potential vanilloid (TRPV) channels, play important roles in breast, ovarian, prostate, and pancreatic cancers.

Methods

We performed a comprehensive analysis of TRPVs in 9125 tumor samples of 33 cancer types using multi-omics data extracted from The Cancer Genome Atlas (TCGA). We identified differences in mRNA expression in a pan-cancer analysis, and the genomic characteristics of single nucleotide variations, copy number variations, methylation features, and miRNA–mRNA interactions using data from TCGA. Finally, we evaluated the sensitivity and resistance to drugs targeting TRPV channel-related genes using the Cancer Therapeutics Response Portal (CTRP) and the Genomics of Drug Sensitivity in Cancer (GDSC) database. Finally, we validated the drug sensitive data and the importance of TRPV6 in two cancer cell lines using q-PCR assay, CCK8 assay, EdU assay and scratch assay.

Results

Extensive genetic alterations in TRPV channel-related genes and differences in gene expression were associated with the activity of cancer marker-related pathways. TRPV channel-related genes can be used as prognostic biomarkers. Several potential drugs, such as lapatinib, that may target TRPV channel-related genes were identified by mining the genomics of drug sensitivity.

Conclusion

This study revealed the genomic changes and clinical characteristics of TRPV channel-related regulatory factors in 33 types of tumors. This analysis may help uncover the TRPV channel-related genes associated with tumorigenesis. We also proposed novel strategies for tumor treatment.

Electroacupuncture Attenuates Post-Inflammatory IBS-Associated Visceral and Somatic Hypersensitivity and Correlates With the Regulatory Mechanism of Epac1-Piezo2 Axis

Electroacupuncture (EA) is considered to have a therapeutic effect in the relief of irritable bowel syndrome (IBS)-associated visceral hypersensitivity via the reduction of the level of 5-hydroxytryptamine (5-HT) and 5-HT₃ receptors (5-HT₃R). However, whether Epac1/Piezo2, as the upstream of 5-HT, is involved in this process remains unclear. We investigated whether EA at the ST36 and ST37 acupoints alleviated visceral and somatic hypersensitivity in a post-inflammatory IBS (PI-IBS) model mice via the Epac1-Piezo2 axis. In this study, we used 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced PI-IBS as a mouse model. Visceral sensitivity was assessed by the abdominal withdrawal reflex test. Somatic sensitivity was evaluated by the hind paw withdrawal threshold. Quantitative real-time PCR, immunofluorescence staining, ELISA, and Western blotting were performed to examine the expressions of Epac1, Piezo2, 5-HT, and 5-HT₃R from the mouse distal colon/L5-S2 dorsal root ganglia (DRG). Our results showed that EA improved the increased visceral sensation and peripheral mechanical hyperalgesia in PI-IBS model mice, and the effects of EA were superior to the sham EA. EA significantly decreased the protein and mRNA levels of Epac1 and Piezo2, and reduced 5-HT and 5-HT₃R expressions in the distal colon. Knockdown of colonic Piezo2 eliminated the effect of EA on somatic hypersensitivity. Combined knockdown of colonic Epac1 and Piezo2 synergized with EA in relieving visceral hypersensitivity and blocked the effect of EA on somatic hypersensitivity. Additionally, protein levels of Epac1 and Piezo2 were also found to be decreased in the L5-S2 DRGs after EA treatment. Taken together, our study suggested that EA at ST36 and ST37 can alleviate visceral and somatic hypersensitivity in PI-IBS model mice, which is closely related to the regulation of the Epac1-Piezo2 axis.

NFKB1 Signalling Activation Contributes to TRPV1 Over-expression via Repressing MiR-375 and MiR-455: a Study on Neuropathic Low Back Pain

Transient receptor potential cation channel subfamily V member 1 (TRPV1) has been found over-expressed in low back pain (LBP) patients with neuropathic pain (NP), but the underlying mechanism is still unclear. In the present study, the up-regulation of the TRPV1 protein level in sinuvertebral nerve biopsies from patients with NP was verified by immunoblotting, but the TRPV1 mRNA level was not significantly changed. MiRNAs targeting TRPV1 mRNA were predicted by a bioinformatic tool, and the interactions between the miRNAs and TRPV1 were confirmed by dual luciferase assay. The correlation between NFKB1 signalling and TRPV1 expression was analysed and confirmed by using sNF96.2 cells after lipopolysaccharide stimulation. We found that five out of 18 miRNAs repressed TRPV1 expression, and the levels of miR-375 and miR-455 were negatively correlated with the protein level of TRPV1 in patients with NP. MiR-375 and miR-455 were identified to repress TRPV1 expression via targeting the 3'UTR of TRPV1 mRNA. NFKB1 signalling activation down-regulated the expression of miR-375 and miR-455, and thus up-regulated the TRPV1 protein level. In conclusion, we partially unveiled the mechanism of how TRPV1 is over-expressed in chronic LBP patients with NP and provided two potential candidate miRNAs for NP treatment.

Long noncoding RNA KIF9-AS1 promotes cell apoptosis by targeting the microRNA-148a-3p/suppressor of cytokine signaling axis in inflammatory bowel disease

OBJECTIVE

Inflammatory bowel disease (IBD) is a chronic intestinal disease. This study was attempted to investigate the effects of long noncoding RNA KIF9-AS1 (KIF9-AS1) on the development of IBD and its underlying mechanism of action.

METHODS

Quantitative real time PCR (qRT-PCR) was implemented to examine the expression of KIF9-AS1 and microRNA-148a-3p (miR-148a-3p). The IBD mouse model was induced by dextran sulfate sodium (DSS). The body weight, disease activity index (DAI) score, colon length and histological injury were used to evaluate the colon injury. The levels of proinflammatory cytokines were measured by ELISA. In vitro, IBD was simulated by DSS treatment in colonic cells. Then the apoptosis of colonic cells was detected by flow cytometry assay. Furthermore, a dual-luciferase reporter assay was used to demonstrate the interactions among KIF9-AS1, miR-148a-3p and suppressor of cytokine signaling (SOCS3).

RESULTS

KIF9-AS1 expression was upregulated in IBD patients, DSS-induced IBD mice and DSS-induced colonic cells, whereas miR-148a-3p expression was downregulated. KIF9-AS1 silencing attenuated the apoptosis of DSS-induced colonic cells in vitro and alleviated colon injury and inflammation in DSS-induced IBD mice in vivo. Additionally, the mechanical experiment confirmed that KIF9-AS1 and SOCS3 were both targeted by miR-148a-3p with the complementary binding sites at 3'UTR. Moreover, miR-148a-3p inhibition or SOCS3 overexpression reversed the suppressive effect of KIF9-AS1 silencing on the apoptosis of DSS-induced colonic cells.

CONCLUSION

KIF9-AS1 silencing hampered the colon injury and inflammation in DSS-induced IBD mice in vivo, and restrained the apoptosis of DSS-induced colonic cells by regulating the miR-148a-3p/SOCS3 axis in vitro, providing a new therapeutic target for IBD.

Lnc-PFAR facilitates autophagy and exacerbates pancreatic fibrosis by reducing pre-miR-141 maturation in chronic pancreatitis

Chronic pancreatitis (CP) is described as progressive inflammatory fibrosis of pancreas, accompanied with irreversible impaired endocrine and exocrine insufficiency. Pancreatic stellate cells (PSCs) are widely distributed in the stroma of the pancreas and PSCs activation has been shown as one of the leading causes for pancreatic fibrosis. Our previous study has revealed that autophagy is dramatically activated in CP tissues, which facilitates PSCs activation and pancreatic fibrosis. Long non-coding RNAs (LncRNAs) have been recognized as crucial regulators for fibrosis-related diseases. LncRNAs interact with RNA binding protein or construct competitive endogenous RNA (ceRNA) hypothesis which elicited the fibrotic processes. Until now, the effects of lncRNAs on PSCs activation and pancreatic fibrosis have not been clearly explored. In this study, a novel lncRNA named Lnc-PFAR was found highly expressed in mouse and human CP tissues. Our data revealed that Lnc-PFAR facilitates PSCs activation and pancreatic fibrosis via RB1CC1-induced autophagy. Lnc-PFAR reduces miR-141 expression by suppressing pre-miR-141 maturation, which eventually upregulates the RB1CC1 and fibrosis-related indicators expression. Meanwhile, Lnc-PFAR enhanced PSCs activation and pancreatic fibrosis through trigging autophagy. Our study interrogates a novel lncRNA-induced mechanism in promoting the development of pancreatic fibrosis, and Lnc-PFAR is suggested to be a prospective therapeutic target in clinical scenarios.

Role of microRNAs in Disorders of Gut-Brain Interactions: Clinical Insights and Therapeutic Alternatives

Disorders of gut-brain interactions (DGBIs) are heterogeneous in nature and intertwine with diverse pathophysiological mechanisms. Regular functioning of the gut requires complex coordinated interplay between a variety of gastrointestinal (GI) cell types and their functions are regulated by multiple mechanisms at the transcriptional, post-transcriptional, translational, and post-translational levels. MicroRNAs (miRNAs) are small non-coding RNA molecules that post-transcriptionally regulate gene expression by binding to specific mRNA targets to repress their translation and/or promote the target mRNA degradation. Dysregulation of miRNAs might impair gut physiological functions leading to DGBIs and gut motility disorders. Studies have shown miRNAs regulate gut functions such as visceral sensation, gut immune response, GI barrier function, enteric neuronal development, and GI motility. These biological processes are highly relevant to the gut where neuroimmune interactions are key contributors in controlling gut homeostasis and functional defects lead to DGBIs. Although extensive research has explored the pathophysiology of DGBIs, further research is warranted to bolster the molecular mechanisms behind these disorders. The therapeutic targeting of miRNAs represents an attractive approach for the treatment of DGBIs because they offer new insights into disease mechanisms and have great potential to be used in the clinic as diagnostic markers and therapeutic targets. Here, we review recent advances regarding the regulation of miRNAs in GI pacemaking cells, immune cells, and enteric neurons modulating pathophysiological mechanisms of DGBIs. This review aims to assess the impacts of miRNAs on the pathophysiological mechanisms of DGBIs, including GI dysmotility, impaired intestinal barrier function, gut immune dysfunction, and visceral hypersensitivity. We also summarize the therapeutic alternatives for gut microbial dysbiosis in DGBIs, highlighting the clinical insights and areas for further exploration. We further discuss the challenges in miRNA therapeutics and promising emerging approaches.

Irradiation of the Normal Murine Tongue Causes Upregulation and Activation of Transient Receptor Potential (TRP) Ion Channels

Signal transduction at sensory neurons occurs via transmembrane flux of cations, which is largely governed by the transient receptor potential (TRP) family of ion channels. It is unknown whether TRP channel activation contributes to the pain that accompanies radiation-induced oral mucositis. This study sought to characterize changes in TRP channel expression and function that occur in the locally irradiated tissues and afferent neurons of mice. Female CD-1 mice received single high-dose (27 Gy) tongue irradiation, or sham irradiation. Animals were euthanized either before overt glossitis developed (days 1 and 5 postirradiation), when glossitis was severe (day 11), or after mice had recovered (days 21 and 45). Tongue irradiation caused upregulation of the Trpv1 gene in trigeminal ganglia (TG) neurons. Other TRP genes (Trpv2, Trpv4, Trpa1, Trpm8) and Gfrα3 (which acts upstream of several TRP channels) were also upregulated in TGs and/or tongue tissue, in response to radiation. Ex vivo calcium imaging experiments demonstrated that the proportions of TG neurons responding to histamine (an activator of TRPV1, TRPV4 and TRPA1), TNF-α (an activator of TRPV1, TRPV2 and TRPV4), and capsaicin (a TRPV1 agonist), were increased as early as one day after tongue irradiation; these changes persisted for at least 21 days. In a subsequent experiment, we found that genetic deletion of TRPV1 mitigated weight loss (a surrogate marker of pain severity) in mice with severe glossitis. The results intimate that various TRP channels, and TRPV1 in particular, should be explored as analgesic targets for patients experiencing pain after oral irradiation.

Regulation of serum microRNA expression by acupuncture in patients with diarrhea-predominant irritable bowel syndrome

OBJECTIVE

To screen for differentially expressed serum microRNAs (miRNAs) in patients with diarrhea-predominant irritable bowel syndrome (IBS-D) compared with healthy participants and explore the mechanism of acupuncture in the treatment of IBS-D based on miRNAs.

METHODS

IBS-D patients that met the Rome III diagnostic criteria and age- and sex-matched healthy participants were enrolled between April 2017 and December 2017. Serum miRNA levels were initially determined using a TaqMan low-density array (TLDA) in pooled samples. Markedly altered miRNAs in IBS-D patients were subsequently validated using quantitative real-time polymerase chain reaction (qRT-PCR) on individual samples. All IBS-D patients accepted the acupuncture therapy for 6 weeks. The disease severity was assessed using the IBS symptom severity scale (IBS-SSS) questionnaire before and after treatment. After acupuncture, the patients' serum was re-analyzed for altered expression of the miRNAs by qRT-PCR.

RESULTS

TLDA and qRT-PCR analysis revealed six upregulated miRNAs (miR-1305, miR-575, miR-149-5p, miR-190a-5p, miR-135a-5p, and miR-148a-3p; P < 0.05) and two downregulated miRNAs (miR-194-5p, miR-127-5p; P < 0.05) in IBS-D patients compared with healthy controls. Post acupuncture treatment, total IBS-SSS scores, severity of abdominal pain, duration of abdominal pain, severity of abdominal distention, dissatisfaction with bowel habits and disruption in quality of life decreased significantly (P < 0.001). Furthermore, the upregulated miR-148a-3p levels in IBS-D patients also decreased significantly after acupuncture (P < 0.05).

CONCLUSIONS

The over-expression or reduced expression of several miRNAs may contribute to IBS-D pathogenesis. Acupuncture might downregulate miR-148a-3p through multiple pathways to alleviate or relieve IBS-D symptoms.

TRIAL REGISTRATION NUMBER

ChiCTR-IOR-17010860 (Chinese Clinical Trials Registry).

The Colonic Mucosal MicroRNAs, MicroRNA-219a-5p, and MicroRNA-338-3p Are Downregulated in Irritable Bowel Syndrome and Are Associated With Barrier Function and MAPK Signaling

BACKGROUND & AIMS

Alterations in microRNA (miRNA) and in the intestinal barrier are putative risk factors for irritable bowel syndrome (IBS). We aimed to identify differentially expressed colonic mucosal miRNAs, their targets in IBS compared to healthy controls (HCs), and putative downstream pathways.

METHODS

Twenty-nine IBS patients (15 IBS with constipation [IBS-C], 14 IBS with diarrhea [IBS-D]), and 15 age-matched HCs underwent sigmoidoscopy with biopsies. A nCounter array was used to assess biopsy specimen-associated miRNA levels. A false discovery rate (FDR) < 10% was considered significant. Real-time polymerase chain reaction (PCR) was used to validate differentially expressed genes. To assess barrier function, trans-epithelial electrical resistance (TEER) and dextran flux assays were performed on Caco-2 intestinal epithelial cells that were transfected with miRNA-inhibitors or control inhibitors. Protein expression of barrier function associated genes was confirmed using western blots.

RESULTS

Four out of 247 miRNAs tested were differentially expressed in IBS compared to HCs (FDR < 10%). Real-time PCR validation suggested decreased levels of miR-219a-5p and miR-338-3p in IBS (P = .026 and P = .004), and IBS-C (P = .02 and P = .06) vs. HCs as the strongest associations. Inhibition of miR-219a-5p resulted in altered expression of proteasome/barrier function genes. Functionally, miR-219a-5p inhibition enhanced the permeability of intestinal epithelial cells as TEER was reduced (25-50%, P < .05) and dextran flux was increased (P < .01). Additionally, inhibition of miR-338-3p in cells caused alterations in the mitogen-activated protein kinase (MAPK) signaling pathway genes.

CONCLUSION

Two microRNAs that potentially affect permeability and visceral nociception were identified to be altered in IBS patients. MiR-219a-5p and miR-338-3p potentially alter barrier function and visceral hypersensitivity via neuronal and MAPK signaling and could be therapeutic targets in IBS.

The Role of Epigenomic Regulatory Pathways in the Gut-Brain Axis and Visceral Hyperalgesia

The gut-brain axis (GBA) is broadly accepted to describe the bidirectional circuit that links the gastrointestinal tract with the central nervous system (CNS). Interest in the GBA has grown dramatically over past two decades along with advances in our understanding of the importance of the axis in the pathophysiology of numerous common clinical disorders including mood disorders, neurodegenerative disease, diabetes mellitus, non-alcohol fatty liver disease (NAFLD) and enhanced abdominal pain (visceral hyperalgesia). Paralleling the growing interest in the GBA, there have been seminal developments in our understanding of how environmental factors such as psychological stress and other extrinsic factors alter gene expression, primarily via epigenomic regulatory mechanisms. This process has been driven by advances in next-generation multi-omics methods and bioinformatics. Recent reviews address various components of GBA, but the role of epigenomic regulatory pathways in chronic stress-associated visceral hyperalgesia in relevant regions of the GBA including the amygdala, spinal cord, primary afferent (nociceptive) neurons, and the intestinal barrier has not been addressed. Rapidly developing evidence suggests that intestinal epithelial barrier dysfunction and microbial dysbiosis play a potentially significant role in chronic stress-associated visceral hyperalgesia in nociceptive neurons innervating the lower intestine via downregulation in intestinal epithelial cell tight junction protein expression and increase in paracellular permeability. These observations support an important role for the regulatory epigenome in the development of future diagnostics and therapeutic interventions in clinical disorders affecting the GBA.

Inflammation and Overlap of Irritable Bowel Syndrome and Functional Dyspepsia

Irritable bowel syndrome (IBS) and functional dyspepsia (FD) are common functional gastrointestinal disorders (FGIDs) and account for a large proportion of consulting patients. These 2 disorders overlap with each other frequently. The pathogenesis of IBS or FD is complicated and multi-factors related, in which infectious or non-infectious inflammation and local or systemic immune response play significant roles. There are few studies focusing on the mechanism of inflammation in patients with overlap syndrome of irritable bowel syndrome and functional dyspepsia (IBS-FD). This review focuses on current advances about the role of inflammation in the pathogenesis of IBS and FD and the possible mechanism of inflammation in IBS-FD.

Biomarkers in Irritable Bowel Syndrome: Biological Rationale and Diagnostic Value

BACKGROUND

Patients with irritable bowel syndrome (IBS) usually suffer from nonspecific and overlapping signs that hamper the diagnostic process. In line with this, biomarkers specific for IBS could be of great benefit for diagnosing and managing patients. In IBS, the need is for apparent distinguishing features linked to the disease that improve diagnosis, differentiate from other organic diseases, and discriminate between IBS subtypes.

SUMMARY

Some biomarkers are associated with a possible pathophysiologic mechanism of IBS; others are used for differentiating IBS from non-IBS patients. Implementation of IBS biomarkers in everyday clinical practice is critical for early diagnosis and treatment. However, our knowledge about their efficient use is still scarce. Key Messages: This review discusses the biomarkers implemented for IBS diagnosis and management, such as blood (serum), fecal, immunological, related to the microbiome, microRNAs, and some promising novel biomarkers associated with imaging and psychological features of the disease. We focus on the most commonly studied and validated biomarkers and their biological rationale, diagnostic, and clinical value.

The burden of early life stress on the nociceptive system development and pain responses

For a long time, the capacity of the newborn infant to feel pain was denied. Today it is clear that the nociceptive system, even if still immature, is functional enough in the newborn infant to elicit pain responses. Unfortunately, pain is often present in the neonatal period, in particular in the case of premature infants which are subjected to a high number of painful procedures during care. These are accompanied by a variety of environmental stressors, which could impact the maturation of the nociceptive system. Therefore, the question of the long-term consequences of early life stress is a critical question. Early stressful experience, both painful and non-painful, can imprint the nociceptive system and induce long-term alteration in brain function and nociceptive behavior, often leading to an increase sensitivity and higher susceptibility to chronic pain. Different animal models have been developed to understand the mechanisms underlying the long-term effects of different early life stressful procedures, including pain and maternal separation. This review will focus on the clinical and preclinical data about early life stress and its consequence on the nociceptive system.

Cytokines in the colon, central nervous system and serum of irritable bowel syndrome rats

Objective

The aim of this study was to detect the expression of interleukin (IL)-1β and transforming growth factor (TGF)-β1 in the colonic tissue and serum of irritable bowel syndrome (IBS) rats, as well as the distribution and expression of corticotropin-releasing factor (CRF) in the spinal cord and brain of the visceral hypersensitivity rats, thus to ascertain the mechanism of visceral hypersensitivity signal conduction pathway.

Methods

The expression of IL-1β and TGF-β1 in the colonic tissue and serum of IBS rats was screened by the liquid chip technology and verified by RT-PCR technology. Then the quantitative analysis of CRF in the spinal cord and brain was achieved by the immunohistochemical method and computerized image system.

Result

The rat model with visceral hypersensitivity was successfully established. Among the screened indicators of IL-1β and TGF-β1 in colon tissue and serum, only the expression of IL-1β in the model group was up-regulated (P < 0.05). The immunohistochemical method showed that CRF was expressed in the spinal cord, hypothalamus, and the third ventricle. The positive index number of the model groups was higher than that of the control group (P < 0.01).

Conclusion

From the research, it can be inferred that IL-1β may participate in the pathogenesis mechanism of IBS via regulating the colon function. The increasing expression of CRF linked to stress in the spinal cord, hypothalamus and the third ventricle indicated that it might play an important role in the mechanisms of visceral hypersensitivity signal conduction pathway.

Efficacy of Tong-Xie-Yao-Fang granule and its impact on whole transcriptome profiling in diarrhea-predominant irritable bowel syndrome patients: study protocol for a randomized controlled trial

BACKGROUND

Irritable bowel syndrome (IBS) is one kind of common functional bowel disease with obscure pathogenesis, and exploration about whole transcriptome profiling in IBS-D is still negligible. Conventional medications have limited effects, which makes focus shifted to traditional Chinese medicine (TCM). Tong-Xie-Yao-Fang, as a classic herbal formula in TCM, is pretty effective and safe for the treatment of diarrhea-predominant irritable bowel syndrome (IBS-D), but the underlying therapeutic mechanism remains unknown. We aim to verify the efficacy and safety of TXYF granule (the formula particles mixed together) in IBS-D and elucidate the gene-level mechanism of IBS-D and therapeutic targets of TXYF granule based on whole transcriptome analysis.

METHODS/DESIGN

This is a randomized, double-blind, and placebo-controlled clinical trial consisting of 2 weeks of run-in period, 12 weeks of treatment period, and 8 weeks of follow-up period. We will enroll 120 participants with IBS-D, who will be randomly assigned to the TXYF granule group and the placebo group, and recruit additional 10 healthy individuals as controls for mechanistic outcome. The two groups respectively take TXYF granule or placebo orally for treatment. The primary outcome is the response rate of IBS-Symptom Severity Score (IBS-SSS). The secondary outcomes include adequate relief (AR), IBS-Quality of Life Questionnaire (IBS-QOL), and long-term efficacy. Mechanistic outcome is the whole transcriptome profiling of the intestinal mucosae from IBS participants before and after the treatment and healthy individuals.

DISCUSSION

This trial will prove the effectiveness and safety of TXYF granule with high-quality evidence and provide a penetrating and comprehensive perspective on the molecular mechanism of IBS-D by whole transcriptome analysis, which makes us pinpoint specific biomarkers of IBS-D and therapeutic targets of TXYF.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR-IOR-1900021785 . Registered on 9 March 2019.

Comparative expression profiling in the intestine of patients with Giardia-induced postinfectious functional gastrointestinal disorders

BACKGROUND

A Giardia outbreak in Bergen, Norway, caused postinfectious functional gastrointestinal disorders (PI-FGIDs). Despite the devastating effects of this outbreak, it presented a unique chance to investigate the implication on the dysregulation of genetic pathways in PI-FGID.

METHODS

We performed the first comparative expression profiling of miRNAs and their potential target genes in microdissected rectal biopsies from 20 Giardia-induced PI-FGID patients vs 18 healthy controls by nCounter analysis. Subsequently, candidates were validated on protein level by immunostaining.

KEY RESULTS

miRNA profiling on rectal biopsy samples from 5 diarrhea-predominant PI-IBS cases compared to 10 healthy controls revealed differential expression in the epithelial layer. The top five regulated miRNAs were implicated in GI disease, inflammatory response, and immunological disease. Subsequently, these miRNAs and 100 potential mRNA targets were examined in 20 PI-FGID cases and 18 healthy controls in both the mucosal epithelium and the lamina propria. Although deregulation of the selected miRNAs could not be verified in the larger sample set, mRNAs involved in barrier function were downregulated in the epithelium. Pro-inflammatory genes and genes implicated in epigenetic modifications were upregulated in the lamina propria. Immunostaining for selected candidates on 17 PI-FGID cases and 16 healthy controls revealed increased tryptase levels as well as a decreased and aberrant subcellular expression of occludin.

CONCLUSIONS AND INFERENCES

Genes relevant to immune and barrier function as well as stress response and epigenetic modulation are differentially expressed in PI-FGIDs and may contribute to disease manifestation.