Oxytocin signalling in dendritic cells regulates immune tolerance in the intestine and alleviates DSS-induced colitis

Oxytocin Alleviates Colitis and Colitis-Associated Colorectal Tumorigenesis via Noncanonical Fucosylation

Colon cancer is increasing worldwide and is commonly regarded as hormone independent, yet recent reports have implicated sex hormones in its development. Nevertheless, the role of hormones from the hypothalamus-hypophysis axis in colitis-associated colorectal cancer (CAC) remains uncertain. In this study, we observed a significant reduction in the expression of the oxytocin receptor (OXTR) in colon samples from both patient with colitis and patient with CAC. To investigate further, we generated mice with an intestinal-epithelium-cell-specific knockout of OXTR. These mice exhibited markedly increased susceptibility to dextran-sulfate-sodium-induced colitis and dextran sulfate sodium/azoxymethane-induced CAC compared to wild-type mice. Our findings indicate that OXTR depletion impaired the inner mucus of the colon epithelium. Mechanistically, oxytocin was found to regulate Mucin 2 maturation through β1-3-N-acetylglucosaminyltransferase 7 (B3GNT7)-mediated fucosylation. Interestingly, we observed a positive correlation between B3GNT7 expression and OXTR expression in human colitis and CAC colon samples. Moreover, the simultaneous activations of OXTR and fucosylation by l-fucose significantly alleviated tumor burden. Hence, our study unveils oxytocin's promising potential as an affordable and effective therapeutic intervention for individuals affected by colitis and CAC.

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.

Identification and Validation of the Diagnostic Markers for Inflammatory Bowel Disease by Bioinformatics Analysis and Machine Learning

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract which is mediated by the inappropriate immune responses. This study was aimed to identify novel diagnostic biomarkers for diagnosis of IBD and explore the relationship between the diagnostic biomarkers and infiltrated immune cells. GSE38713, GSE53306, and GSE75214 downloaded from the Gene Expression Omnibus (GEO) database were split into training and testing sets. Differentially expressed genes (DEGs) were screened using the "limma" package. Gene Ontology (GO) and KEGG pathway enrichment analysis of DEGs were performed by clusterProfiler package. The LASSO regression and support vector machine recursive feature elimination (SVM-RFE) algorithms were conducted to identify novel diagnostic biomarkers. The receiver operating characteristic (ROC) curve was applied to evaluate the diagnostic value of the candidate biomarkers. The relationship of the candidate biomarkers and infiltrating immune cells in IBD were evaluated by CIBERSOTR. Quantitative Real-Time PCR (qRT-PCR) was applied to measure the expression level of the biomarkers in IBD. A total of 289 dysregulated genes were identified as DEGs in IBD. These DEGs were significantly enriched in chemokine signaling pathway and cytokine-cytokine receptor interaction. RHOU was identified as a critical diagnostic gene in IBD, which was confirmed using ROC curve and qRT-PCR assays. Immune cell infiltration analysis showed that RHOU was correlated with macrophages M2, dendritic cells resting, mast cells resting, T cells CD4 memory resting, macrophages M0, and mast cells activated. Our results imply that RHOU may be a potential diagnostic biomarker for IBD.

Lactobacillus reuteri inhibits Staphylococcus aureus-induced mastitis by regulating oxytocin releasing and gut microbiota in mice

Mastitis is the most frequent disease of cows and has well-recognized detrimental effects on animal wellbeing and dairy farm profitability. With the advent of the postantibiotic era, alternative antibiotic agents, especially probiotics, have received increasing attention in the treatment of mastitis. Based on research showing that Lactobacillus reuteri (L. reuteri) has anti-inflammatory effects, this study explored the protective effects and mechanisms of L. reuteri against mastitis induced by Staphylococcus aureus (S. aureus) in mice. First, mice with S. aureus-induced mastitis were orally administered L. reuteri, and the inflammatory response in the mammary gland was observed. The results showed that L. reuteri significantly inhibited S. aureus-induced mastitis. Moreover, the concentration of oxytocin (OT) and protein expression of oxytocin receptor (OTR) were measured, and inhibition of OTR or vagotomy reversed the protective effect of L. reuteri or its culture supernatant (LCS) on S. aureus-induced mastitis. In addition, in mouse mammary epithelial cells (MMECs), OT inhibited the inflammation induced by S. aureus by inhibiting the protein expression of OTR. It was suggested that L. reuteri protected against S. aureus-induced mastitis by releasing OT. Furthermore, microbiological analysis showed that the composition of the microbiota was altered, and the relative abundance of Lactobacillus was significantly increased in gut and mammary gland after treatment with L. reuteri or LCS. In conclusion, our study found the L. reuteri inhibited the mastitis-induced by S. aureus via promoting the release of OT, and treatment with L. reuteri increased the abundance of Lactobacillus in both gut and mammary gland.

Colitis-associated carcinogenesis: crosstalk between tumors, immune cells and gut microbiota

Colorectal cancer (CRC) is the third most common cancer worldwide. One of the main causes of colorectal cancer is inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD). Intestinal epithelial cells (IECs), intestinal mesenchymal cells (IMCs), immune cells, and gut microbiota construct the main body of the colon and maintain colon homeostasis. In the development of colitis and colitis-associated carcinogenesis, the damage, disorder or excessive recruitment of different cells such as IECs, IMCs, immune cells and intestinal microbiota play different roles during these processes. This review aims to discuss the various roles of different cells and the crosstalk of these cells in transforming intestinal inflammation to cancer, which provides new therapeutic methods for chemotherapy, targeted therapy, immunotherapy and microbial therapy.

Phosphatidylinositol 3-kinase signaling pathway and inflammatory bowel disease: Current status and future prospects

Inflammatory bowel disease (IBD) is a chronic life-limiting disease of gastrointestinal tract characterized by widespread enteric inflammation. IBD is a multifactorial disease, and different environmental, microbial, and immune-related factors give rise to the development of disease. Among several factors, the preponderance of pro-inflammatory T helper 17 cells over the anti-inflammatory regulatory T cells augments inflammation in the intestinal mucosa. Prevailing evidence accentuates that PI3K signaling pathway plays a central role in the pathophysiology of the condition by regulating the inflammatory process in the gut mucosa. By recognizing the implications of PI3K in the pathogenesis of IBD, agents that could modulate this pathway have recently been at the focus of research, yielding encouraging results mainly in the experimental IBD models. In this review, we have summarized the recent advances, which may hold the keys to identify novel therapeutic strategies for IBD.

The intestinal microenvironment shapes macrophage and dendritic cell identity and function

The gut comprises the largest body interface with the environment and is continuously exposed to nutrients, food antigens, and commensal microbes, as well as to harmful pathogens. Subsets of both macrophages and dendritic cells (DCs) are present throughout the intestinal tract, where they primarily inhabit the gut-associate lymphoid tissue (GALT), such as Peyer's patches and isolated lymphoid follicles. In addition to their role in taking up and presenting antigens, macrophages and DCs possess extensive functional plasticity and these cells play complementary roles in maintaining immune homeostasis in the gut by preventing aberrant immune responses to harmless antigens and microbes and by promoting host defense against pathogens. The ability of macrophages and DCs to induce either inflammation or tolerance is partially lineage imprinted, but can also be dictated by their activation state, which in turn is determined by their specific microenvironment. These cells express several surface and intracellular receptors that detect danger signals, nutrients, and hormones, which can affect their activation state. DCs and macrophages play a fundamental role in regulating T cells and their effector functions. Thus, modulation of intestinal mucosa immunity by targeting antigen presenting cells can provide a promising approach for controlling pathological inflammation. In this review, we provide an overview on the characteristics, functions, and origins of intestinal macrophages and DCs, highlighting the intestinal microenvironmental factors that influence their functions during homeostasis. Unraveling the mechanisms by which macrophages and DCs regulate intestinal immunity will deepen our understanding on how the immune system integrates endogenous and exogenous signals in order to maintain the host's homeostasis.

Evaluation of the oxytocin effect in a rat model with experimental periodontitis

The aim of the present study was to evaluate the inhibitory effects of oxytocin on the development of periodontitis based on its properties against bone loss and resorption. Thirty-two Wistar albino rats were divided into four equal groups: control, periodontitis + saline, periodontitis + 0.5 mg/kg/day oxytocin, and periodontitis + 1 mg/kg/day oxytocin. Periodontitis groups received 4.0 silk ligatures around their cervixes of the right and left mandibular incisors in an "8" shape, kept for 14 days. Animals in oxytocin groups were injected once every day during 14 days with oxytocin. The mandibles were fixed and scanned using microcomputed tomography to quantify bone resorption and volumetric measurements. Blood samples were collected to analyze the concentrations of macrophage colony-stimulating factor (M-CSF), receptor activator of nuclear factor-κΒ ligand (RANKL), osteoprotegerin (OPG), matrix metalloproteinase-8 (MMP-8), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, glutathione peroxidase (GPx), superoxide dismutase (SOD), and malondialdehyde (MDA). Histopathological evaluations were conducted to examine the gingiva and alveolar bone. Oxytocin prevented the development of periodontitis by decreasing ligament deteriorations and leukocytes in the gingival connective tissue and promoting reintegration with the alveolar bone. Bone resorption in all regions was less in the periodontitis + 1 mg/kg/day oxytocin group than in the periodontitis + saline group. Although TNF-α, IL-6, and RANKL values were lower in the periodontitis + 1 mg/kg/day oxytocin group, OPG was higher than that in the periodontitis + saline group. M-CSF, MMP-8, and MDA were lower in the oxytocin groups than in the periodontitis + saline group. Oxytocin may be an effective agent for periodontal diseases because it decreased bone resorption, oxidative stress, and inflammation in an experimental periodontitis.

Alternative Pharmacological Strategies for the Treatment of Alzheimer's Disease: Focus on Neuromodulator Function

Alzheimer's disease (AD) is a neurodegenerative disorder, comprising 70% of dementia diagnoses worldwide and affecting 1 in 9 people over the age of 65. However, the majority of its treatments, which predominantly target the cholinergic system, remain insufficient at reversing pathology and act simply to slow the inevitable progression of the disease. The most recent neurotransmitter-targeting drug for AD was approved in 2003, strongly suggesting that targeting neurotransmitter systems alone is unlikely to be sufficient, and that research into alternate treatment avenues is urgently required. Neuromodulators are substances released by neurons which influence neurotransmitter release and signal transmission across synapses. Neuromodulators including neuropeptides, hormones, neurotrophins, ATP and metal ions display altered function in AD, which underlies aberrant neuronal activity and pathology. However, research into how the manipulation of neuromodulators may be useful in the treatment of AD is relatively understudied. Combining neuromodulator targeting with more novel methods of drug delivery, such as the use of multi-targeted directed ligands, combinatorial drugs and encapsulated nanoparticle delivery systems, may help to overcome limitations of conventional treatments. These include difficulty crossing the blood-brain-barrier and the exertion of effects on a single target only. This review aims to highlight the ways in which neuromodulator functions are altered in AD and investigate how future therapies targeting such substances, which act upstream to classical neurotransmitter systems, may be of potential therapeutic benefit in the sustained search for more effective treatments.

The Continuum of Microbial Ecosystems along the Female Reproductive Tract: Implications for Health and Fertility

The microbial ecosystem of the female urogenital tract is composed of many niche microenvironments across multiple organ systems in the urinary and reproductive tract. It is complex and contains a variety of bacteria, archaea, viruses, yeast, and protozoa-Many of which are still unidentified or whose functionality is unknown. Unlike the gut microbiome, whose composition is relatively stable in the absence of external perturbations, the urogenital microbiome is constantly shifting in response to biological cycles such as hormonal fluctuations during menstruation. Microbial composition differs between women but the dominance of some microbial families, such as Lactobacillaceae and other lactic acid-producing bacteria, are shared. Research suggests that it is difficult to define a universal healthy urogenital microbiome and consequently map a path to recovery from disease due to dysbiosis. Due to its temporal shifts, the female urogenital microbiome offers a unique opportunity to examine the biological mechanisms that work to restore a microbiome to its baseline. Common functional disorders in women's health are often difficult to diagnose and treat, are prone to recurrence, and can lead to subfertility or infertility. Knowledge of the interconnected microorganism communities along the continuum of the female reproductive tract could revolutionize the quality of women's healthcare.

MPST deficiency promotes intestinal epithelial cell apoptosis and aggravates inflammatory bowel disease via AKT

Background & aims

Excessive inflammatory responses and oxidative stress are considered the main characteristics of inflammatory bowel disease (IBD). Endogenous hydrogen sulfide (H₂S) has been reported to show anti-inflammatory activity in IBD. The main aim of this study was to explore the role of 3-mercaptopyruvate sulfurtransferase (MPST), a key enzyme that regulates endogenous H₂S biosynthesis, in IBD.

Methods

Colonic MPST expression was evaluated in mice and patients with IBD. Various approaches were used to explore the concrete mechanism underlying MPST regulation of the progression of colitis through in vivo and in vitro models.

Results

MPST expression was markedly decreased in colonic samples from patients with ulcerative colitis (UC) or Crohn's disease (CD) and from mice treated with DSS. MPST deficiency significantly aggravated the symptoms of murine colitis, exacerbated inflammatory responses and apoptosis, and inhibited epithelium stem cell-derived organoid formation in an H₂S-independent manner. Consistently, when HT29 cells were treated with TNF-α, inhibition of MPST significantly increased the expression of proinflammatory cytokines, the amount of ROS and the prevalence of apoptosis, whereas overexpression of MPST markedly improved these effects. RNA-seq analysis showed that MPST might play a role in regulating apoptosis through AKT signaling. Mechanistically, MPST directly interacted with AKT and reduced the phosphorylation of AKT. Additionally, MPST expression was positively correlated with AKT expression in human IBD samples. In addition, overexpression of AKT rescued IEC apoptosis caused by MPST deficiency, while inhibition of AKT significantly aggravated it.

Conclusions

MPST protects the intestines from inflammation most likely by regulating the AKT/apoptosis axis in IECs. Our results may provide a novel therapeutic strategy for the treatment of colitis.

Oxytocin: An Old Hormone, A Novel Psychotropic Drug And Possible Use In Treating Psychiatric Disorders

BACKGROUND

Oxytocin is a nonapeptide synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Historically, this molecule has been involved as a key factor in the formation of infant attachment, maternal behavior and pair bonding and, more generally, in linking social signals with cognition, behaviors and reward. In the last decades, the whole oxytocin system has gained a growing interest as it was proposed to be implicated in etiopathogenesis of several neurodevelopmental and neuropsychiatric disorders.

METHODS

With the main goal of an in-depth understanding of the oxytocin role in the regulation of different functions and complex behaviors as well as its intriguing implications in different neuropsychiatric disorders, we performed a critical review of the current state of art. We carried out this work through PubMed database up to June 2021 with the search terms: 1) "oxytocin and neuropsychiatric disorders"; 2) "oxytocin and neurodevelopmental disorders"; 3) "oxytocin and anorexia"; 4) "oxytocin and eating disorders"; 5) "oxytocin and obsessive-compulsive disorder"; 6) "oxytocin and schizophrenia"; 7) "oxytocin and depression"; 8) "oxytocin and bipolar disorder"; 9) "oxytocin and psychosis"; 10) "oxytocin and anxiety"; 11) "oxytocin and personality disorder"; 12) "oxytocin and PTSD".

RESULTS

Biological, genetic, and epigenetic studies highlighted quality and quantity modifications in the expression of oxytocin peptide or in oxytocin receptor isoforms. These alterations would seem to be correlated with a higher risk of presenting several neuropsychiatric disorders belonging to different psychopathological spectra. Collaterally, the exogenous oxytocin administration has shown to ameliorate many neuropsychiatric clinical conditions.

CONCLUSION

Finally, we briefly analyzed the potential pharmacological use of oxytocin in patient with severe symptomatic SARS-CoV-2 infection due to its anti-inflammatory, anti-oxidative and immunoregulatory properties.

Intranasal Oxytocin Attenuates Cognitive Impairment, β-Amyloid Burden and Tau Deposition in Female Rats with Alzheimer's Disease: Interplay of ERK1/2/GSK3β/Caspase-3

Oxytocin is a neuropeptide hormone that plays an important role in social bonding and behavior. Recent studies indicate that oxytocin could be involved in the regulation of neurological disorders. However, its role in modulating cognition in Alzheimer’s disease (AD) has never been explored. Hence, the present study aims to investigate the potential of chronic intranasal oxytocin in halting memory impairment & AD pathology in aluminum chloride-induced AD in female rats. Morris water maze was used to assess cognitive dysfunction in two-time points throughout the treatment period. In addition, neuroprotective effects of oxytocin were examined by assessing hippocampal acetylcholinesterase activity, β-amyloid 1–42 protein, and Tau levels. In addition, ERK1/2, GSK3β, and caspase-3 levels were assessed as chief neurobiochemical mediators in AD. Hippocampi histopathological changes were also evaluated. These findings were compared to the standard drug galantamine alone and combined with oxytocin. Results showed that oxytocin restored cognitive functions and improved animals’ behavior in the Morris test. This was accompanied by a significant decline in acetylcholinesterase activity, 1–42 β-amyloid and Tau proteins levels. Hippocampal ERK1/2 and GSK3β were also reduced, exceeding galantamine effects, thus attenuating AD pathological hallmarks formation. Determination of caspase-3 revealed low cytoplasmic positivity, indicating the ceasing of neuronal death. Histopathological examination confirmed these findings, showing restored hippocampal cells structure. Combined galantamine and oxytocin treatment showed even better biochemical and histopathological profiles. It can be thus concluded that oxytocin possesses promising neuroprotective potential in AD mediated via restoring cognition and suppressing β-amyloid, Tau accumulation, and neuronal death.

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

BACKGROUND

The aim of the current study was to investigate the effect of macrophage polarization on the expression of oxytocin (OT) and the oxytocin receptor (OTR) in enteric neurons.

METHODS

In this study, we used a classic colitis model and D-mannose model to observe the correlation between macrophage polarization and OT signalling system. In order to further demonstrate the effect of macrophages, we examined the expression of OT signalling system after depletion of macrophages.

RESULTS

The data showed that, in vitro, following polarization of macrophages to the M1 type by LPS, the macrophage supernatant contained proinflammatory cytokines (IL-1β, IL-6 and TNF-α) that inhibited the expression of OT and OTR in cultured enteric neurons; following macrophage polarization to the M2 type by IL4, the macrophage supernatant contained anti-inflammatory cytokines (TGF-β) that promoted the expression of OT and OTR in cultured enteric neurons. Furthermore, M1 macrophages decreased the expression of the OT signalling system mainly through STAT3/NF-κB pathways in cultured enteric neurons; M2 macrophages increased the expression of the OT signalling system mainly through activation of Smad2/3 and inhibition of the expression of Peg3 in cultured enteric neurons. In a colitis model, we demonstrated that macrophages were polarized to the M1 type during the inflammatory phase, with significant decreased in the expression of OT and OTR. When macrophages were polarized to the M2 type during the recovery phase, OT and OTR expression increased significantly. In addition, we found that D-mannose increased the expression of OT and OTR through polarization of macrophages to the M2 type.

CONCLUSIONS

This is the first study to demonstrate that macrophage polarization differentially regulates the expression of OT and OTR in enteric neurons.

Oxytocin: much more than childbirth and milk letdown

This commentary deals with the new observations that dendritic cell (DC) oxytocin receptors play a role in the inflammatory response generated in murine animal models of colitis. The overview provides a context of the discovery of oxytocin (OT), its chemical synthesis and the cell biology of its neurohypophysial synthesis and secretion. This perspective provides insight and raises questions to be answered related to the impact of OT in the gastrointestinal tract and to further the exploration of OT as a potentially locally synthesised regulator of intestinal inflammatory pathophysiology.