The effect of macrophage polarization on the expression of the oxytocin signalling system in enteric neurons

Oxytocin-Mediate Modulation of Splenic Immunosuppression in Chronic Social Stress Through Neuroendocrine Pathways

Chronic social stress (CSS) is a significant public health challenge that negatively impacts behavior and immune function through brain-spleen interactions. Oxytocin (OT), a neuropeptide critical for social behavior and immune regulation, is upregulated during CSS, though its underlying mechanisms remain unclear. This study investigates the role of OT in splenic immune modulation using a murine model of CSS. Behavioral evaluations, serum oxytocin quantification, and splenic immunophenotypic analysis were performed. Splenic denervation confirmed OT's neuromodulatory role, whereas OTR antagonism revealed its endocrine function. CSS-induced OT elevation was associated with immunosuppression, characterized by increased Foxp3⁺ regulatory T cells and reduced CD4⁺ T and CD19⁺ B cells. OT also modulated macrophage polarization, inhibiting M1-like (pro-inflammatory) and enhancing M2-like (anti-inflammatory) phenotypes. Denervation or pharmacological blockade of OT signaling partly reversed CSS-induced splenic immunosuppression but adversely affected survival in CSS-exposed mice. Additionally, denervation or OTR antagonism reduced the mice's response to social defeat, as shown by decreased social avoidance behavior. These findings suggest that OT-mediated immunosuppression likely represents a compensatory mechanism in response to chronic social stress. Targeting the OT-immune axis could offer innovative therapeutic approaches for stress-associated disorders by restoring immune homeostasis while maintaining behavioral integrity.

Limosilactobacillus reuteri promotes the expression and secretion of enteroendocrine- and enterocyte-derived hormones

Intestinal microbes can beneficially impact host physiology, prompting investigations into the therapeutic usage of such microbes in a range of diseases. For example, human intestinal microbe Limosilactobacillus reuteri strains ATCC PTA 6475 and DSM 17938 are being considered for use for intestinal ailments, including colic, infection, and inflammation, as well as for non-intestinal ailments, including osteoporosis, wound healing, and autism spectrum disorder. While many of their beneficial properties are attributed to suppressing inflammatory responses, we postulated that L. reuteri may also regulate intestinal hormones to affect physiology within and outside of the gut. To determine if L. reuteri secreted factors impact the secretion of enteric hormones, we treated an engineered jejunal organoid line, NGN3-HIO, which can be induced to be enriched in enteroendocrine cells, with L. reuteri 6475 or 17938 conditioned medium and performed transcriptomics. Our data suggest that these L. reuteri strains affect the transcription of many gut hormones, including vasopressin and luteinizing hormone subunit beta, which have not been previously recognized as produced in the gut epithelium. Moreover, we find that these hormones appear to be produced in enterocytes, in contrast to canonical gut hormones produced in enteroendocrine cells. Finally, we show that L. reuteri conditioned media promote the secretion of enteric hormones, including serotonin, GIP, PYY, vasopressin, and luteinizing hormone subunit beta, and identify by metabolomics metabolites potentially mediating these effects on hormones. These results support L. reuteri affecting host physiology through intestinal hormone secretion, thereby expanding our understanding of the mechanistic actions of this microbe.

Oxytocin-loaded hydrogel promotes cartilage regeneration and regulates microenvironment

Osteoarthritis is a common orthopedic condition, and traditional treatment methods often fail to regenerate cartilage effectively. Oxytocin (OXT) is a neuropeptide that plays a crucial role in the skeletal system. Hyaluronic acid (HAMA) hydrogel has emerged as a key carrier for cartilage repair due to its excellent biocompatibility and biodegradability. Combining OXT with HAMA hydrogel and implanting it at the site of cartilage defects can effectively promote cartilage regeneration. Cartilage damage often results in an altered microenvironment, characterized by macrophage polarization and high levels of reactive oxygen species (ROS). Oxidative stress can stimulate macrophages to produce more pro-inflammatory factors. OXT can inhibit the secretion of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1βby interacting with the STAT3/NF-κB signaling pathway, as well as the PI3K/Akt and mitogen-activated protein kinase pathways, thereby inducing the polarization of macrophages from the M1 phenotype to the M2 phenotype and alleviating the inflammatory response. OXT can also enhance the expression of NRF and HO-1, which helps eliminate ROS and suppress the expression of pro-inflammatory factors. Regulating the microenvironment of cartilage damage is beneficial for cartilage protection and repair. OXT activates the CFOS/AP-1 and STAT1/JAK2 pathways, which together act on MMP2 and MMP9 to alleviate cartilage degeneration. The STAT1/JAK2 pathway can further increase the expression of Col2, thereby protecting chondrocytes. Additionally, OXT can directly boost the protein levels of SOX9 and COMP, promoting chondrocyte proliferation and cartilage protection, ultimately achieving the therapeutic goal for arthritis. This study explores the potential of HAMA hydrogel as a delivery system for OXT and analyzes their impact on cartilage regeneration and anti-inflammatory properties. This research provides a novel strategy for the treatment of cartilage injuries.

Oxytocin Analogues for the Oral Treatment of Abdominal Pain

Abdominal pain presents an onerous reality for millions of people affected by gastrointestinal disorders such as irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBD). The oxytocin receptor (OTR) has emerged as a new analgesic drug target with OTR expression upregulated on colon-innervating nociceptors in chronic visceral hypersensitivity states, accessible via luminal delivery. However, the low gastrointestinal stability of OTR's endogenous peptide ligand oxytocin (OT) is a bottleneck for therapeutic development. Here, we report the development of potent and fully gut-stable OT analogues, laying the foundation for a new area of oral gut-specific peptide therapeutics. Ligand optimisation guided by structure-gut-stability-activity relationships yielded highly stable analogues (t1/2>24 h, compared to t1/2<10 min of OT in intestinal fluid) equipotent to OT (~3 nM) and with enhanced OTR selectivity. Intra-colonic administration of the lead ligand significantly reduced colonic mechanical hypersensitivity in a concentration-dependent manner in a mouse model of chronic abdominal pain. Moreover, oral administration of the lead ligand also displayed significant analgesia in this abdominal pain mouse model. The generated ligands and employed strategies could pave the way to a new class of oral gut-specific peptides to study and combat chronic gastrointestinal disorders, an area with substantial unmet medical needs.

Oxytocin alleviates liver fibrosis via hepatic macrophages

Background & Aims

Previous studies demonstrated oxytocin treatment effectiveness in reducing mortality and reversing liver fibrosis in mice. However, the underlying mechanism remains obscure, given the absence of oxytocin receptor expression in hepatic stellate cells, the primary liver fibrosis effector cells.

Methods

A comprehensive map of cell populations in fibrotic liver was generated using single-cell sequencing. The map enabled our study of the target cells of oxytocin action in the liver in more dimensions. Furthermore, we elucidated the mechanism of the oxytocin signaling system in hepatic macrophages using oxytocin receptor-specific knockout mice and liver fibrosis animal models.

Results

The carbon tetrachloride-induced hepatic fibrosis and bile duct ligation hepatic fibrosis mouse models demonstrated that oxytocin reversed hepatic fibrosis in mice. The mapped liver cell populations demonstrated that oxytocin promoted the phenotypic switch from Ly6high to Ly6Clow in myeloid-derived macrophages. The phenotypic control of oxytocin signaling system activation on this phenotypic switch was validated using myeloid-specific oxytocin receptor knockout mice. Subsequent studies demonstrated that the calcium inward flow induced by oxytocin receptor activation activated the key orphan nuclear receptor NR4A1, which controls macrophage phenotypic switching. Specifically, calcium ions activated CREB, a key target regulator of NR4A1 expression.

Conclusions

The findings established hepatic macrophages as a hub responsible for the oxytocin-mediated alleviation of liver fibrosis. This study revealed a novel pathway where oxytocin regulates macrophage phenotype.

Impact and implications

Previous studies revealed for the first time the expression of oxytocin receptors in the liver. The present study shows that oxytocin reverses hepatic fibrosis and that hepatic macrophages are the central hub of oxytocin-mediated alleviation of hepatic fibrosis by promoting a phenotypic switch in hepatic macrophages, transitioning from Ly6high to Ly6Clow expression. The present study reveals a novel pathway by which oxytocin regulates macrophage phenotype. In addition, the potential applications of oxytocin and its analogues, as traditional drugs for clinical application, in the treatment of liver fibrosis deserve to be further explored.

Protective effect of oxytocin on vincristine-induced gastrointestinal dysmotility in mice

Aims: Vincristine (VCR), an antineoplastic drug, induces peripheral neuropathy characterized by nerve damage, limiting its use and reducing the quality of life of patients. VCR causes myenteric neuron damage, inhibits gastrointestinal motility, and results in constipation or paralytic ileus in patients. Oxytocin (OT) is an endogenous neuropeptide produced by the enteric nerve system, which regulates gastrointestinal motility and exerts neuroprotective effects. This study aimed to investigate whether OT can improve VCR-induced gastrointestinal dysmotility and evaluate the underlying mechanism. Methods: Mice were injected either with saline or VCR (0.1 mg/kg/d, i. p.) for 14 days, and OT (0.1 mg/kg/d, i.p.) was applied 1 h before each VCR injection. Gastrointestinal transit and the contractile activity of the isolated colonic segments were assessed. The concentration of OT in plasma was measured using ELISA. Immunofluorescence staining was performed to analyze myenteric neurons and reactive oxygen species (ROS) levels. Furthermore, the indicators of oxidative stress were detected. The protein expressions of Nrf2, ERK1/2, P-ERK1/2, p38, and P-p38 in the colon were tested using Western blot. Results: VCR reduced gastrointestinal transit and the responses of isolated colonic segments to electrical field stimulation and decreased the amount of neurons. Furthermore, VCR reduced neuronal nitric oxide synthase and choline acetyltransferase immunopositive neurons in the colonic myenteric nerve plexus. VCR increased the concentration of OT in plasma. Exogenous OT pretreatment ameliorated the inhibition of gastrointestinal motility and the injury of myenteric neurons caused by VCR. OT pretreatment also prevented the decrease of superoxide dismutase activity, glutathione content, total antioxidative capacity, and Nrf2 expression, the increase of ROS levels, and the phosphorylation of ERK1/2 and p38 MAPK following VCR treatment. Conclusion: Our results suggest that OT pretreatment can protect enteric neurons from VCR-induced injury by inhibiting oxidative stress and MAPK pathways (ERK1/2, p38). This may be the underlying mechanism by which it alleviates gastrointestinal dysmotility.

Structure characterization of polysaccharides from Cistanche deserticola and their neuroprotective effects against oxidative stress in slow transit constipation mice

Oxidative stress-induced enteric neuropathy is an important factor in slow transit constipation (STC). Cistanche deserticola crude polysaccharides (CDCP) are natural antioxidants with various biological activities. We prepared CDCP through water-extract and alcohol-precipitation methods. The structural characteristics of CDCP were analyzed by infrared spectroscopy and methylation analysis. The results showed that CDCP was primarily composed of (1 → 4)-linked glucans with minor amounts of pectic polysaccharides. Different doses of CDCP (100, 200, and 400 mg/kg) were administered to loperamide-induced STC mice to explore the therapeutic effects of CDCP. Compared with the untreated group, CDCP treatment significantly improved constipation symptoms, relevant gut-regulating peptides levels, colonic pathological damage, and colonic myenteric nerons injury. CDCP enhanced the antioxidant capacity by decreasing Malondialdehyde (MDA) content, increasing Superoxide Dismutase (SOD) activity and Reduced Glutathione (GSH) content. CDCP significantly reduced oxidative stress-induced injury by preserving mitochondrial function in the colonic myenteric plexus. Furthermore, the neuroprotective effects of CDCP might be associated with the Nrf2/Keap1 pathway. Thus, our findings first revealed the potential of CDCP to protect the colonic myenteric plexus against oxidative stress-induced damage in STC, establishing CDCP as promising candidates for natural medicine in the clinical management of STC.

D-Mannose promotes recovery from experimental colitis by inducing AMPK phosphorylation to stimulate epithelial repair

Delayed mucosal healing and impaired intestinal epithelial barrier function have been implicated in the pathogenesis of ulcerative colitis (UC). Accordingly, restoration of epithelial barrier function as a means to reshape mucosal homeostasis represents an important strategy for use in the treatment of UC. In this study, we examined the role and mechanisms of D-mannose in the recovery of colitis as assessed in both animal and cell models. We found that D-mannose ameliorated inflammation, promoted mucosal healing in the colon and therefore was able to induce the recovery of UC. Furthermore, D-mannose increased the expression of tight junction (TJ) proteins and reduced the intestinal permeability during the recovery of colitis. Moreover, D-mannose inhibited M1 macrophage polarization and promoted M2 macrophage polarization via inducing AMPK phosphorylation while reducing mTOR phosphorylation in both models. In addition, increased TJ protein expression and decreased paracellular permeability were observed in NCM460 cells when incubated with the supernatants of D-mannose-treated RAW264.7 cells, suggesting that M1/M2 polarization induced by D-mannose modulates the expression of TJ proteins. Further study showed that D-mannose significantly upregulated the expression of TJ proteins in DSS-treated NCM460 cells by inducing AMPK phosphorylation, indicating a direct protective effect on epithelial cells. Finally, the protective effects of D-mannose were significantly abrogated by the presence of compound C, an AMPK inhibitor. Taken together, our data indicate that D-mannose can alleviate inflammation and foster epithelial restitution in UC recovery by inducing the TJ protein expression, which are achieved by inducing AMPK phosphorylation in the epithelium and/or macrophages.

Macrophage metabolism, phenotype, function, and therapy in hepatocellular carcinoma (HCC)

The pivotal role of the tumor microenvironment (TME) in the initiation and advancement of hepatocellular carcinoma (HCC) is widely acknowledged, as it fosters the proliferation and metastasis of HCC cells. Within the intricate TME of HCC, tumor-associated macrophages (TAMs) represent a significant constituent of non-malignant cells. TAMs engage in direct communication with cancer cells in HCC, while also exerting influence on other immune cells to adopt a tumor-supportive phenotype that facilitates tumor progression. Among the multifaceted mechanisms at play, the metabolic reprogramming of both tumor cells and macrophages leads to phenotypic alterations and functional modifications in macrophages. This comprehensive review elucidates the intricate interplay between cellular metabolism and macrophage phenotype/polarization, while also providing an overview of the associated signaling molecules and potential therapeutic strategies for HCC.

Activation of GABA receptor attenuates intestinal inflammation by modulating enteric glial cells function through inhibiting NF-κB pathway

AIMS

Emerging research indicates that γ-aminobutyric acid (GABA) provides substantial benefits during enteritis. Nevertheless, GABA signaling roles on enteric glial cells (EGCs) remain unknown. The study's objective was to evaluate the underlying mechanisms of GABA signaling on EGCs in vitro and in vivo.

MAIN METHODS

We established LPS-induced mouse models and stimulated EGCs with LPS to mimic intestinal inflammation, and combined GABA, GABAA receptor (GABAAR) or GABAB receptor (GABABR) agonists to explore the exact mechanisms of GABA signaling.

KEY FINDINGS

EGCs were immunopositive for GAD65, GAD67, GAT1, GABAARα1, GABAARα3, and GABABR1, indicating GABAergic and GABAceptive properties. GABA receptor activation significantly inhibited the high secretions of proinflammatory factors in EGCs upon LPS stimulation. Interestingly, we found that EGCs express immune-related molecules such as CD16, CD32, CD80, CD86, MHC II, iNOS, Arg1, and CD206, thus establishing their characterization of E1 and E2 phenotype. EGCs exposed to LPS mainly acted as E1 phenotype, whereas GABABR activation strongly promoted EGCs polarization into E2 phenotype. Transcriptome analysis of EGCs indicated that GABA, GABAAR or GABABR agonists treatment participated in various biological processes, however all of these treatments exhibit inhibitory effects on NF-κB pathway. Notably, in LPS-induced mice, activation of GABABR mitigated intestinal damage through modulating inflammatory factors expressions, strengthening sIgA and IgG levels, inhibiting NF-κB pathway and facilitating EGCs to transform into E2 phenotype.

SIGNIFICANCE

These data demonstrate that the anti-inflammatory actions of GABA signaling system offer in enteritis via regulating EGCs-polarized function through impeding NF-κB pathway, thus providing potential targets for intestinal inflammatory diseases.

Procyanidin improves experimental colitis by regulating macrophage polarization

BACKGROUND

Inflammatory bowel disease (IBD) is a chronic disease with an unclear pathogenesis for which successful treatments are still lacking. It has been reported that procyanidin, a natural antioxidant, relieves colitis, but the specific mechanism is elusive.

PURPOSE

Our present study was designed to investigate the effects of procyanidin on colitis and the regulation of the M1 macrophage phenotype and related signaling pathways.

METHODS

In vivo, we used two classic colitis models to observe the effect of procyanidin on macrophage polarization. In vitro, we further validated the therapeutic effect of procyanidin in the RAW264.7 cell line and peritoneal macrophages.

RESULTS

The current findings provide new evidence that procyanidin ameliorated dextran sulfate sodium (DSS)-induced colitis by preventing the polarization of macrophages to the M1 type and downregulating the levels of proinflammatory factors in cells. We also showed that procyanidin prevented lipopolysaccharide (LPS)-induced elevation of inflammatory cytokines and the activation of proinflammatory macrophages, which was achieved by activating the STAT3 and NF-κB pathways.

CONCLUSIONS

This is the first study to demonstrate that procyanidin alleviates experimental colitis by inhibiting the polarization of proinflammatory macrophages. These data reveal new ideas for the pathogenesis and treatment of inflammatory diseases.

Neuroimmune regulation in Hirschsprung's disease associated enterocolitis

Neuroimmune pathways are important part of the regulation of inflammatory response. Nerve cells regulate the functions of various immune cells through neurotransmitters, and then participate in the inflammatory immune response. Hirschsprung's disease (HD) is a congenital abnormal development of intestinal neurons, and Hirschsprung-associated enterocolitis (HAEC) is a common complication, which seriously affects the quality of life and even endangers the lives of children. Neuroimmune regulation mediates the occurrence and development of enteritis, which is an important mechanism. However, there is a lack of review on the role of Neuroimmune regulation in enterocolitis associated with Hirschsprung's disease. Therefore, this paper summarizes the characteristics of the interaction between intestinal nerve cells and immune cells, reviews the neuroimmune regulation mechanism of Hirschsprung's disease associated enterocolitis (HAEC), and looks forward to the potential clinical application value.

Sesquiterpene lactones-rich fraction from Aucklandia lappa Decne. alleviates dextran sulfate sodium induced ulcerative colitis through co-regulating MAPK and Nrf2/Hmox-1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Aucklandia lappa Decne. (ALDE) is the general name for Asteraceae plants Yunmuxiang, which has traditionally been proven to have the efficacy in relieving depression by regulating qi, alleviating cold by warming, attenuating pain in stomach and relieving diarrhea in intestines. Therefore, ALDE is always recommended as an herbal remedy for gastrointestinal dysfunction.

AIM OF THE STUDY

The purpose of this study was to explore the therapeutic potential and mechanism of action of the sesquiterpene lactone-rich fraction (SLRF) of ALDE extracts in vivo and in vitro.

MATERIALS AND METHODS

An aqueous extract (AE) and SLRF of ALDE were prepared and the contents of the main components were quantified by high performance liquid chromatography (HPLC). The therapeutic effects of the extracts were evaluated in C57BL/6 mice with dextran sulfate sodium (DSS)-induced ulcerative colitis (UC). Body weight, disease activity index (DAI), and colon length were recorded, and histopathological changes in the colon were characterized using hematoxylin and eosin (H&E) staining. The in vitro anti-inflammatory activity and possible mechanisms of the two main sesquiterpene lactones in ALDE (costunolide and dehydrocostus lactone) were studied by quantitative proteomic analysis. Finally, based on bioinformatic analysis, we used polymerase chain reaction (PCR), immunofluorescence, and western blot experiments to verify the anti-inflammatory mechanism of the extracts in C57BL/6 mice.

RESULTS

The SLRF of ALDE significantly improved the pathological symptoms and inflammatory pathology of UC, whereas the AE had a weak protective effect. In RAW264.7 cells stimulated with lipopolysaccharide (LPS), costunolide and dehydrocostus lactone significantly reduced the mRNA levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, suggesting that these two sesquiterpene lactones had strong anti-inflammatory activity. Quantitative proteomics results indicated that the anti-inflammatory mechanism of these lactones was associated with the NF-κB/MAPK and Nrf2-Hmox-1 pathways. These results were further validated in SLRF-treated mice.

CONCLUSION

This study confirmed that the SLRF of ALDE exerted protective activity against UC by regulating the Nrf2-Hmox-1, NF-κB, and MAPK pathways.