Therapeutic Opportunities for Repair GPCRs during Intestinal Mucosal Wound Healing

Oxytocin/Oxytocin Receptor Signalling in the Gastrointestinal System: Mechanisms and Therapeutic Potential

The neuropeptide hormone oxytocin (OT) is involved in various physiological and pathological processes via the oxytocin receptor (OTR). While OT is most widely known as a reproductive system hormone and a nervous system neurotransmitter, the OT/OTR system has gradually gained much attention for its role in the gastrointestinal (GI) system, such as the GI motility, secretion, and bowel inflammatory reactions. Its importance in GI cancers has also been reported in the past few decades. The promising clinical observations have revealed OT's anti-nociceptive effect, protective effect over gut injury, and the potential of using microbiota to naturally increase endogenous OT levels, which shed a light on the management of GI disorders with lower side effects. However, no current comprehensive review is available on the actions of OT/OTR in the GI tract. This review aims to present the lesser-known role of the OT/OTR system in the GI tract, and the most recent findings are discussed regarding the distribution and functional role of OTR signalling in regulating (patho)physiological functions of the GI tract. Special emphasis is placed on its therapeutic potential for clinical management of GI disorders, such as GI pain, inflammatory bowel disease (IBD), and irritable bowel syndrome (IBS). The recent characterisation of the OTR's crystal structure has advanced research for designing and identifying new OTR-specific molecules. Future in-depth basic and clinical research is needed to further elucidate the involvement and detailed mechanism of OT/OTR in GI disorders, and the development of OTR-specific ligands.

Interferon-gamma signaling drives epithelial TNF-alpha receptor-2 expression during colonic tissue repair

Interferon-gamma (IFNγ) is traditionally recognized for its pro-inflammatory role during intestinal inflammation. Here, we demonstrate that IFNγ also functions as a pro-repair molecule by increasing TNFα receptor 2 (TNFR2 protein/TNFRSF1B gene) expression on intestinal epithelial cells (IEC) following injury in vitro and in vivo. In silico analyses identified binding sites for the IFNγ signaling transcription factor STAT1 in the promoter region of TNFRSF1B. Scratch-wounded IEC exposed to IFNγ exhibited a STAT1-dependent increase in TNFR2 expression. In situ hybridization revealed elevated Tnfrsf1b mRNA levels in biopsy-induced colonic mucosal wounds, while intraperitoneal administration of IFNγ neutralizing antibodies following mucosal injury resulted in impaired IEC Tnfrsf1b mRNA and inhibited colonic mucosal repair. These findings challenge conventional notions that "pro-inflammatory" mediators solely exacerbate damage by highlighting latent pro-repair functions. Moreover, these results emphasize the critical importance of timing and amount in the synthesis and release of IFNγ and TNFα during the inflammatory process, as they are pivotal in restoring tissue homeostasis.

Advancements in hydrogel-based drug delivery systems for the treatment of inflammatory bowel disease: a review

Inflammatory bowel disease (IBD) is a chronic disorder that affects millions of individuals worldwide. However, current drug therapies for IBD are plagued by significant side effects, low efficacy, and poor patient compliance. Consequently, there is an urgent need for novel therapeutic approaches to alleviate IBD. Hydrogels, three-dimensional networks of hydrophilic polymers with the ability to swell and retain water, have emerged as promising materials for drug delivery in the treatment of IBD due to their biocompatibility, tunability, and responsiveness to various stimuli. In this review, we summarize recent advancements in hydrogel-based drug delivery systems for the treatment of IBD. We first identify three pathophysiological alterations that need to be addressed in the current treatment of IBD: damage to the intestinal mucosal barrier, dysbiosis of intestinal flora, and activation of inflammatory signaling pathways leading to disequilibrium within the intestines. Subsequently, we discuss in depth the processes required to prepare hydrogel drug delivery systems, from the selection of hydrogel materials, types of drugs to be loaded, methods of drug loading and drug release mechanisms to key points in the preparation of hydrogel drug delivery systems. Additionally, we highlight the progress and impact of the hydrogel-based drug delivery system in IBD treatment through regulation of physical barrier immune responses, promotion of mucosal repair, and improvement of gut microbiota. In conclusion, we analyze the challenges of hydrogel-based drug delivery systems in clinical applications for IBD treatment, and propose potential solutions from our perspective.

Single-Cell RNA Sequencing Reveals Roles of Fibroblasts During Intestinal Injury and Repair in Rats with Severe Acute Pancreatitis

Purpose

To explore the molecular mechanisms of intestinal injury and treatment by analyzing changes in cellular heterogeneity and composition in rat ileal tissue during injury and treatment processes.

Methods

We constructed a rat model of SAP and evaluated treatment with an injected of monoacylglycerol lipase (MAGL) inhibitor (JZL184) solution using three experimental groups: healthy male Sprague-Dawley (SD) rats injected with vehicle (CON), male SD SAP model rats injected with vehicle (SAP), and male SAP rats injected with JZL184. We obtained and prepared a single-cell suspension of ileal tissue of each rat for single-cell transcriptome sequencing.

Results

This project classified changes in cellular heterogeneity and composition in rat ileal tissue during SAP-induced intestinal injury and MAGL treatment. We found that the number of fibroblast clusters was decreased in the SAP group relative to the CON group, and increased after JZL184 treatment. Further analysis of differences in gene expression between cell clusters in each group reveals that fibroblasts had the greatest number of differentially expressed genes. Most notably, expression of genes involved in communication between cells was found to vary during SAP-induced intestinal injury and JZL184 treatment. Among these changes, the degree of difference in expression of genes involved in communication between fibroblasts and other cells was the highest, indicating that fibroblasts in rat ileal tissue affect intestinal injury and repair through cell-to-cell communication. In addition, our results reveal that differentially expressed RNA-binding proteins in fibroblasts may affect their functions in intestinal injury and treatment by affecting the expression of genes regulating communication between cells.

Conclusion

These findings emphasize the importance of understanding the interactions between fibroblasts and other cells in the context of intestinal injury, providing valuable insights for further exploring molecular mechanisms and insight for discovering new treatment targets and strategies.

IBD disease-modifying therapies: insights from emerging therapeutics

Inflammatory bowel disease (IBD) pathogenesis is associated with gut mucosal inflammation, epithelial damage, and dysbiosis leading to a dysregulated gut mucosal barrier. However, the extent and underlying mechanisms remain largely unknown. Current treatment regimens have focused mainly on treating IBD symptoms; however, such treatment strategies do not address mucosal epithelial repair, barrier homeostasis, or intestinal dysbiosis. Although attempts have been made to identify new therapeutic modalities to enhance gut barrier functions, these are at an early developmental stage and have not been wholly successful. We review conventional therapies, the possible relevant role of gut barrier-protecting agents, and biomaterial strategies relating to combination therapies that may pave the way towards developing new therapeutic approaches for IBD.

Formyl peptide receptor 2 as a potential therapeutic target for inflammatory bowel disease

Inflammatory bowel disease (IBD) is a global health burden whose existing treatment is largely dependent on anti-inflammatory agents. Despite showing some therapeutic actions, their clinical efficacy and adverse events are unacceptable. Resolution as an active and orchestrated phase of inflammation involves improper inflammatory response with three key triggers, specialized pro-resolving mediators (SPMs), neutrophils and phagocyte efferocytosis. The formyl peptide receptor 2 (FPR2/ALX) is a human G protein-coupled receptor capable of binding SPMs and participates in the resolution process. This receptor has been implicated in several inflammatory diseases and its association with mouse model of IBD was established in some resolution-related studies. Here, we give an overview of three reported FPR2/ALX agonists highlighting their respective roles in pro-resolving strategies.

Curcumin alleviates LPS-induced intestinal homeostatic imbalance through reshaping gut microbiota structure and regulating group 3 innate lymphoid cells in chickens

Gastrointestinal dysfunction is associated with a disturbance of immune homeostasis, changes in the intestinal microbiome, alteration of the composition of the bile acid pool, and dynamic imbalance of group 3 innate lymphoid cells (ILC3s). Curcumin (CUR), a polyphenolic compound isolated from turmeric, has been known to attenuate intestinal inflammation in potential therapies for gastrointestinal diseases. It was hypothesized that CUR could target the gut microbiome to modulate bile acid (BA) metabolism and the function of ILC3s in ameliorating lipopolysaccharide (LPS)-induced imbalance of intestinal homeostasis in chickens. Seven hundred and twenty 1-day-old crossbred chickens were randomly divided into four treatments, namely CON_saline (basal diet + saline control), CUR_saline (basal diet + 300 mg kg-1 curcumin + saline), CON_LPS (basal diet + LPS), and CUR_LPS (basal diet + 300 mg kg-1 curcumin + LPS), each consisting of 6 replicates of 30 birds. On days 14, 17, and 21, the chickens in the CON_LPS and CUR_LPS treatments were intraperitoneally injected with LPS at 0.5 mg per kg BW. Dietary CUR supplementation significantly decreased LPS-induced suppression of growth performance and injury to the intestinal tight junctions and decreased the vulnerability to LPS-induced acute inflammatory response by inhibiting pro-inflammatory (interleukin-1β and tumor necrosis factor-α) cytokines. CUR reshaped the cecal microbial community and BA metabolism, contributing to regulation of the intestinal mucosal immunity by promoting the anti-inflammatory (interleukin 10, IL-10) cytokines and enhancing the concentrations of primary and secondary BA metabolites (chenodexycholic acid, lithocholic acid). LPS decreased farnesoid X receptor (FXR) and G protein-coupled receptor class C group 5 member A synthesis, which was reversed by CUR administration, along with an increase in interleukin 22 (IL-22) production from ILC3s. Dietary supplementation of CUR increased the prevalence of Butyricicoccus and Enterococcus and enhanced the tricarboxylic acid cycle of intestinal epithelial cells. In addition, curcumin supplementation significantly increased sirtuin 1 and sirtuin 5 transcription and protein expression, which contributes to regulating mitochondrial metabolic and oxidative stress responses to alleviate LPS-induced enteritis. Our findings demonstrated that curcumin played a pivotal role in regulating the structure of the intestinal microbiome for health promotion and the treatment of intestinal dysbiosis. The beneficial effects of CUR may be attributed to the modulation of the BA-FXR pathway and inhibition of inflammation that induces IL-22 secretion by ILC3s in the intestinal lamina propria.

Nanotechnology for research and treatment of the intestine

The establishment of intestinal in vitro models is crucial for elucidating intestinal cell-microbe intrinsic connections and interaction mechanisms to advance normalized intestinal diagnosis and precision therapy. This review discusses the application of nanomaterials in mucosal therapy and mechanism research in combination with the study of nanoscaffold in vitro models of the gut. By reviewing the original properties of nanomaterials synthesized by different physicochemical principles and modifying the original properties, the contribution of nanomaterials to solving the problems of short survival period, low cell differentiation rate, and poor reduction ability in traditional intestinal models is explored. According to nanomaterials’ different diagnostic mediators and therapeutic targets, the current diagnostic principles in inflammatory bowel disease, intestinal cancer, and other diseases are summarized inductively. In addition, the mechanism of action of nanomedicines in repairing mucosa, inhibiting inflammation, and alleviating the disease process is also discussed. Through such systematic elaboration, it offers a basis for nanomaterials to help advance in vitro research on the intestine and provide precision treatments in the clinic.

Epithelial JAM-A is fundamental for intestinal wound repair in vivo

Junctional adhesion molecule-A (JAM-A) is expressed in several cell types, including epithelial and endothelial cells, as well as some leukocytes. In intestinal epithelial cells (IEC), JAM-A localizes to cell junctions and plays a role in regulating barrier function. In vitro studies with model cell lines have shown that JAM-A contributes to IEC migration; however, in vivo studies investigating the role of JAM-A in cell migration-dependent processes such as mucosal wound repair have not been performed. In this study, we developed an inducible intestinal epithelial-specific JAM-A-knockdown mouse model (Jam-aERΔIEC). While acute induction of IEC-specific loss of JAM-A did not result in spontaneous colitis, such mice had significantly impaired mucosal healing after chemically induced colitis and after biopsy colonic wounding. In vitro primary cultures of JAM-A-deficient IEC demonstrated impaired migration in wound healing assays. Mechanistic studies revealed that JAM-A stabilizes formation of protein signaling complexes containing Rap1A/Talin/β1 integrin at focal adhesions of migrating IECs. Loss of JAM-A in primary IEC led to decreased Rap1A activity and protein levels of Talin and β1 integrin, and it led to a reduction in focal adhesion structures. These findings suggest that epithelial JAM-A plays a critical role in controlling mucosal repair in vivo through dynamic regulation of focal adhesions.

Role of Nutrient-sensing Receptor GPRC6A in Regulating Colonic Group 3 Innate Lymphoid Cells and Inflamed Mucosal Healing

BACKGROUND AND AIMS

Group 3 innate lymphoid cells [ILC3s] sense environmental signals and are critical in gut homeostasis and immune defence. G-protein-coupled receptors [GPCRs] mediate cellular responses to diverse environmental signals. However, the GPCRs' regulation mechanisms of ILC3s is largely unknown.

METHODS

We used wild-type [WT] and GPRC6A-/- mice to investigate the role of GPRC6A in the population and the function of ILC3s. We then purified ILC3s from WT and GPRC6A-/- mice. Colitis was induced in WT mice and GPRC6A-/- mice through dextran sodium sulphate [DSS] administration or C. rodentium infection. Furthermore L-arginine, a selective GPRC6A agonist, was administered to mice with colitis.

RESULTS

We found that colonic ILC3s expressed GPRC6A. The deficiency of GPRC6A decreased ILC3-derived interleukin-22 [IL-22] production and the number of proliferating ILC3s, which led to increased susceptibility to colon injury and pathogen infection and impaired inflamed mucosal healing. Further studies showed that L-arginine, a GPRC6A agonist, promoted colonic ILC3 expansion and function via the mammalian target of rapamycin complex 1 [mTORC1] signalling in vitro. In addition, L-arginine attenuated DSS-induced colitis in vivo. This was associated with a significant increase in IL-22 secretion by ILC3s.

CONCLUSIONS

Our findings unveil a role for the nutrient-sensing receptor GPRC6A in colonic ILC3 function and identify a novel ILC3 receptor signalling pathway modulating inflamed mucosal healing.