NOX1 is essential for TNFα-induced intestinal epithelial ROS secretion and inhibits M cell signatures

Intestinal Mucosal Immune Barrier: A Powerful Firewall Against Severe Acute Pancreatitis-Associated Acute Lung Injury via the Gut-Lung Axis

The pathogenesis of severe acute pancreatitis-associated acute lung injury (SAP-ALI), which is the leading cause of mortality among hospitalized patients in the intensive care unit, remains incompletely elucidated. The intestinal mucosal immune barrier is a crucial component of the intestinal epithelial barrier, and its aberrant activation contributes to the induction of sustained pro-inflammatory immune responses, paradoxical intercellular communication, and bacterial translocation. In this review, we firstly provide a comprehensive overview of the composition of the intestinal mucosal immune barrier and its pivotal roles in the pathogenesis of SAP-ALI. Secondly, the mechanisms of its crosstalk with gut microbiota, which is called gut-lung axis, and its effect on SAP-ALI were summarized. Finally, a number of drugs that could enhance the intestinal mucosal immune barrier and exhibit potential anti-SAP-ALI activities were presented, including probiotics, glutamine, enteral nutrition, and traditional Chinese medicine (TCM). The aim is to offer a theoretical framework based on the perspective of the intestinal mucosal immune barrier to protect against SAP-ALI.

Genistein prevents the production of hypospadias induced by Di-(2-ethylhexyl) phthalate through androgen signaling and antioxidant response in rats

Environmental estrogen exposure has increased dramatically over the past 50 years. In particular, prenatal exposure to estrogen causes many congenital diseases, among which reproductive system development disorders are extremely serious. In this study, the molecular mechanism of hypospadias and the therapeutic effect of genistein (GEN) were investigated through in vivo models prepared by Di-(2-ethylhexyl) phthalate (DEHP) exposure between 12 and 19 days of gestation. With increased DEHP concentrations, the incidence of hypospadias increased gradually. DEHP inhibited the key enzymes involved in steroid synthesis, resulting in decreasing testosterone synthesis. At the same time, DEHP increased reactive oxygen species (ROS) and produced inflammatory factors via NADPH oxidase-1 (NOX1) and NADPH oxidase-4 (NOX4) pathways. It also inhibited Steroid 5 α Reductase 2 (Srd5α2) and decreased dihydrotestosterone (DHT) synthesis. Additionally, DEHP inhibited the androgen receptor (AR), resulting in reduced DHT binding to the AR that ultimately retarded the development of the external reproductive system. GEN, a phytoestrogen, competes with DEHP for binding to estrogen receptor β (ERβ). This competition, along with GEN's antiestrogen and antioxidant properties, could potentially reverse impairments. The findings of this study provide valuable insights into the role of phytoestrogens in alleviating environmental estrogen-induced congenital diseases.

A novel causative role of imbalanced kynurenine pathway in ulcerative colitis: Upregulation of KMO and KYNU promotes intestinal inflammation

The kynurenine pathway (KP) is the principal metabolic route for the essential amino acid tryptophan (TRP). Recent advances have highlighted a pivotal role for several KP metabolites in inflammatory diseases, including ulcerative colitis (UC). However, the alterations of KP enzymes and their functional impact in UC remain poorly defined. Here, we focused on kynurenine 3-monooxygenase (KMO) and kynureninase (KYNU), which serve as critical branching enzymes in the KP. We observed that dextran sodium sulfate (DSS)-induced colitis mice exhibited disturbed TRP metabolism along with KMO and KYNU upregulated. In patients with active UC, both the expression of KMO and KYNU were positively correlated with inflammatory factors TNF-α and IL-1β. Pharmacological blockade of KMO or genetic silencing of KYNU suppressed IL-1β-triggered proinflammatory cytokines expression in intestinal epithelial cells. Furthermore, blockage of KMO by selective inhibitor Ro 61-8048 alleviated the symptoms of DSS-induced colitis in mice, accompanied by an expanded NAD+ pool and redox balance restoration. The protective role of Ro 61-8048 may be partly due to its effect on KP regulation, particularly in enhancing kynurenic acid production. In summary, our study provides new evidence for the proinflammatory property of KMO and KYNU in intestinal inflammation, hinting at a promising therapeutic approach in UC through targeting these enzymes.

2D Nanozymes Modulate Gut Microbiota and T-Cell Differentiation for Inflammatory Bowel Disease Management

Intestinal commensal microbiota dysbiosis and immune dysfunction are significant exacerbating factors in inflammatory bowel disease (IBD). To address these problems, Pluronic F-127-coated tungsten diselenide (WSe2 @F127) nanozymes are developed by simple liquid-phase exfoliation. The abundant valence transitions of elemental selenium (Se2- /Se4+ ) and tungsten (W4+ /W6+ ) enable the obtained WSe2 @F127 nanozymes to eliminate reactive oxygen/nitrogen species. In addition, the released tungsten ions are capable of inhibiting the proliferation of Escherichia coli. In a model of dextran sodium sulfate-induced colitis, WSe2 @F127 nanozymes modulate the gut microbiota by increasing the abundance of bacteria S24-7 and significantly reducing the abundance of Enterobacteriaceae. Moreover, WSe2 @F127 nanozymes inhibit T-cell differentiation and improve intestinal immune barrier function in a model of Crohn's disease. The WSe2 @F127 nanozymes effectively alleviate IBD by reducing oxidative stress damage, modulating intestinal microbial populations, and remodeling the immune barrier.

Ultrasmall Cu2O@His Nanozymes with RONS Scavenging Capability for Anti-inflammatory Therapy

High concentrations of reactive oxygen and nitrogen species (RONS) are key characteristics of inflammatory sites. Scavenging RONS at the site of inflammation is an effective therapeutic strategy. This study introduces ultrasmall Cu2O@His nanoparticles with RONS-scavenging ability for the treatment of inflammatory bowel disease (IBD) in mice. The strong coordination between the nitrogen atom in histidine (His) and copper enhances the dispersion and stability of Cu2O@His. Due to their small size and large surface area, Cu2O@His exhibits outstanding RONS-clearing ability. Importantly, Cu2O@His can target mitochondrial sites and repair damaged mitochondria. With excellent dispersion and scavenging RONS ability, Cu2O@His demonstrates good efficacy in treating mouse IBD. This work provides a new paradigm for developing nanozymes with an ultrasmall size and multiple scavenging RONS abilities.

Inhibition of RIP1 improves immune reconstitution and reduces GVHD mortality while preserving graft-versus-leukemia effects

Graft-versus-host disease (GVHD) remains the major cause of morbidity and nonrelapse mortality (NRM) after hematopoietic cell transplantation (HCT). Inflammatory cytokines mediate damage to key GVHD targets such as intestinal stem cells (ISCs) and also activate receptor interacting protein kinase 1 (RIP1; RIPK1), a critical regulator of apoptosis and necroptosis. We therefore investigated the role of RIP1 in acute GVHD using samples from HCT patients, modeling GVHD damage in vitro with both human and mouse gastrointestinal (GI) organoids, and blocking RIP1 activation in vivo using several well-characterized mouse HCT models. Increased phospho-RIP1 expression in GI biopsies from patients with acute GVHD correlated with tissue damage and predicted NRM. Both the genetic inactivation of RIP1 and the RIP1 inhibitor GNE684 prevented GVHD-induced apoptosis of ISCs in vivo and in vitro. Daily administration of GNE684 for 14 days reduced inflammatory infiltrates in three GVHD target organs (intestine, liver, and spleen) in mice. Unexpectedly, GNE684 administration also reversed the marked loss of regulatory T cells in the intestines and liver during GVHD and reduced splenic T cell exhaustion, thus improving immune reconstitution. Pharmacological and genetic inhibition of RIP1 improved long-term survival without compromising the graft-versus-leukemia (GVL) effect in lymphocytic and myeloid leukemia mouse models. Thus, RIP1inhibition may represent a nonimmunosuppressive treatment for GVHD.

Precisely Inhibiting Excessive Intestinal Epithelial Cell Apoptosis to Efficiently Treat Inflammatory Bowel Disease with Oral Pifithrin-α Embedded Nanomedicine (OPEN)

The increased incidence of inflammatory bowel disease (IBD) has seriously affected the life quality of patients. IBD develops due to excessive intestinal epithelial cell (IEC) apoptosis, disrupting the gut barrier, colonizing harmful bacteria, and initiating persistent inflammation. The current therapeutic approaches that reduce inflammation are limited. Although IBD can be treated significantly by directly preventing IEC apoptosis, achieving this therapeutic approach remains challenging. Accordingly, the authors are the first to develop an oral pifithrin-α (PFTα, a highly specific p53 inhibitor) embedded nanomedicine (OPEN) to effectively treat IBD by inhibiting excessive IEC apoptosis. As a major hub for various stressors, p53 is a central determinant of cell fate, and its inhibition can effectively reduce excessive IEC apoptosis. The tailored OPEN can precisely inhibit the off-target and inactivation resulting from PFTα entry into the bloodstream. Subsequently, it persistently targets IBD lesions with high specificity to inhibit the pathological events caused by excessive IEC apoptosis. Eventually, OPEN exerts a significant curative effect compared with the clinical first-line drugs 5-aminosalicylic acid (5-ASA) and dexamethasone (DEX). Consequently, the OPEN therapeutic strategy provides new insights into comprehensive IBD therapy.

VEO-IBD NOX1 variant highlights a structural region essential for NOX/DUOX catalytic activity

Inflammatory bowel diseases (IBD) are chronic intestinal disorders that result from an inappropriate inflammatory response to the microbiota in genetically susceptible individuals, often triggered by environmental stressors. Part of this response is the persistent inflammation and tissue injury associated with deficiency or excess of reactive oxygen species (ROS). The NADPH oxidase NOX1 is highly expressed in the intestinal epithelium, and inactivating NOX1 missense mutations are considered a risk factor for developing very early onset IBD. Albeit NOX1 has been linked to wound healing and host defence, many questions remain about its role in intestinal homeostasis and acute inflammatory conditions. Here, we used in vivo imaging in combination with inhibitor studies and germ-free conditions to conclusively identify NOX1 as essential superoxide generator for microbiota-dependent peroxynitrite production in homeostasis and during early endotoxemia. NOX1 loss-of-function variants cannot support peroxynitrite production, suggesting that the gut barrier is persistently weakened in these patients. One of the loss-of-function NOX1 variants, NOX1 p. Asn122His, features replacement of an asparagine residue located in a highly conserved HxxxHxxN motif. Modelling the NOX1-p22phox complex revealed near the distal heme an internal pocket restricted by His119 and Asn122 that is part of the oxygen reduction site. Functional studies in several human NADPH oxidases show that substitution of asparagine with amino acids with larger side chains is not tolerated, while smaller side chains can support catalytic activity. Thus, we identified a previously unrecognized structural feature required for the electron transfer mechanism in human NADPH oxidases.

Genetic Defects in Early-Onset Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) represents a spectrum of disease, which is characterized by chronic gastrointestinal inflammation. Monogenic mutations driving IBD pathogenesis are more highly represented in early-onset compared to adult-onset disease. The pathogenic genes which dysregulate host immune responses in monogenic IBD affect both the innate (ie, intestinal barrier, phagocytes) and adaptive immune systems (ie, T cells, B cells). Advanced genomic and targeted functional testing can improve clinical decision making and present increased opportunities for precision medicine approaches in this important patient population.

TGR5 agonist inhibits intestinal epithelial cell apoptosis via cAMP/PKA/c-FLIP/JNK signaling pathway and ameliorates dextran sulfate sodium-induced ulcerative colitis

Excessive apoptosis of intestinal epithelial cell (IEC) is a crucial cause of disrupted epithelium homeostasis, leading to the pathogenesis of ulcerative colitis (UC). The regulation of Takeda G protein-coupled receptor-5 (TGR5) in IEC apoptosis and the underlying molecular mechanisms remained unclear, and the direct evidence from selective TGR5 agonists for the treatment of UC is also lacking. Here, we synthesized a potent and selective TGR5 agonist OM8 with high distribution in intestinal tract and investigated its effect on IEC apoptosis and UC treatment. We showed that OM8 potently activated hTGR5 and mTGR5 with EC₅₀ values of 202 ± 55 nM and 74 ± 17 nM, respectively. After oral administration, a large amount of OM8 was maintained in intestinal tract with very low absorption into the blood. In DSS-induced colitis mice, oral administration of OM8 alleviated colitis symptoms, pathological changes and impaired tight junction proteins expression. In addition to enhancing intestinal stem cell (ISC) proliferation and differentiation, OM8 administration significantly reduced the rate of apoptotic cells in colonic epithelium in colitis mice. The direct inhibition by OM8 on IEC apoptosis was further demonstrated in HT-29 and Caco-2 cells in vitro. In HT-29 cells, we demonstrated that silencing TGR5, inhibition of adenylate cyclase or protein kinase A (PKA) all blocked the suppression of JNK phosphorylation induced by OM8, thus abolished its antagonizing effect against TNF-α induced apoptosis, suggesting that the inhibition by OM8 on IEC apoptosis was mediated via activation of TGR5 and cAMP/PKA signaling pathway. Further studies showed that OM8 upregulated cellular FLICE-inhibitory protein (c-FLIP) expression in a TGR5-dependent manner in HT-29 cells. Knockdown of c-FLIP blocked the inhibition by OM8 on TNF-α induced JNK phosphorylation and apoptosis, suggesting that c-FLIP was indispensable for the suppression of OM8 on IEC apoptosis induced by OM8. In conclusion, our study demonstrated a new mechanism of TGR5 agonist on inhibiting IEC apoptosis via cAMP/PKA/c-FLIP/JNK signaling pathway in vitro, and highlighted the value of TGR5 agonist as a novel therapeutic strategy for the treatment of UC.

Engineered procyanidin-Fe nanoparticle alleviates intestinal inflammation through scavenging ROS and altering gut microbiome in colitis mice

Inflammatory bowel disease (IBD) is an idiopathic chronic inflammatory bowel disease characterized by inflammation, intestinal barrier injury, and imbalance of gut microbiota. Excess accumulation of reactive oxygen species (ROS) is closely correlated with the development and reoccurrence of IBD. Previous researches demonstrate that procyanidin, as a natural antioxidant, exhibits strong ability of eliminating ROS, thus showing good therapeutic effects in the inflammation-related diseases. Non-etheless, its poor stability and solubility always limits the therapeutic outcomes. Here, we typically designed an antioxidant coordination polymer nanoparticle using the engineering of procyanidin (Pc) and free iron (Fe), named Pc-Fe nanozyme, for effectively scavenging ROS and further inhibiting inflammation while altering the gut microbiome for the treatment of colitis. Furthermore, in vitro experiments uncover that Pc-Fe nanoparticles exert strong multi biomimic activities, including peroxidase, and glutathione peroxidase, for the scavenging of ROS and protecting cells from oxidative injury. In addition, the colon accumulation of Pc-Fe nanozyme effectively protects the intestinal mucosa from oxidative damage while significantly downregulates pro-inflammatory factors, repairs the intestinal barriers and alternates gut microbiome after orally administrated in sodium dextran sulfate (DSS) induced colitis mice. The results collectively illustrate that the multienzyme mimicking Pc-Fe nanozyme owns high potential for treating IBD through scavenging ROS, inhibiting inflammation, repairing gut barriers and alternating gut microbiome, which further promising its clinical translation on IBD treatment and other ROS induced intestinal diseases.

Human intestinal epithelial cells can internalize luminal fungi via LC3-associated phagocytosis

Background

Intestinal epithelial cells (IECs) are the first to encounter luminal microorganisms and actively participate in intestinal immunity. We reported that IECs express the β-glucan receptor Dectin-1, and respond to commensal fungi and β-glucans. In phagocytes, Dectin-1 mediates LC3-associated phagocytosis (LAP) utilizing autophagy components to process extracellular cargo. Dectin-1 can mediate phagocytosis of β-glucan-containing particles by non-phagocytic cells. We aimed to determine whether human IECs phagocytose β-glucan-containing fungal particles via LAP.

Methods

Colonic (n=18) and ileal (n=4) organoids from individuals undergoing bowel resection were grown as monolayers. Fluorescent-dye conjugated zymosan (β-glucan particle), heat-killed- and UV inactivated C. albicans were applied to differentiated organoids and to human IEC lines. Confocal microscopy was used for live imaging and immuno-fluorescence. Quantification of phagocytosis was carried out with a fluorescence plate-reader.

Results

zymosan and C. albicans particles were phagocytosed by monolayers of human colonic and ileal organoids and IEC lines. LAP was identified by LC3 and Rubicon recruitment to phagosomes and lysosomal processing of internalized particles was demonstrated by co-localization with lysosomal dyes and LAMP2. Phagocytosis was significantly diminished by blockade of Dectin-1, actin polymerization and NAPDH oxidases.

Conclusions

Our results show that human IECs sense luminal fungal particles and internalize them via LAP. This novel mechanism of luminal sampling suggests that IECs may contribute to the maintenance of mucosal tolerance towards commensal fungi.

New insights into bacterial mechanisms and potential intestinal epithelial cell therapeutic targets of inflammatory bowel disease

The global incidence of inflammatory bowel disease (IBD) has increased rapidly in recent years, but its exact etiology remains unclear. In the past decade, IBD has been reported to be associated with dysbiosis of gut microbiota. Although not yet proven to be a cause or consequence of IBD, the common hypothesis is that at least some alterations in the microbiome are protective or pathogenic. Furthermore, intestinal epithelial cells (IECs) serve as a protective physical barrier for gut microbiota, essential for maintaining intestinal homeostasis and actively contributes to the mucosal immune system. Thus, dysregulation within the intestinal epithelium increases intestinal permeability, promotes the entry of bacteria, toxins, and macromolecules, and disrupts intestinal immune homeostasis, all of which are associated with the clinical course of IBD. This article presents a selective overview of recent studies on bacterial mechanisms that may be protective or promotive of IBD in biological models. Moreover, we summarize and discuss the recent discovery of key modulators and signaling pathways in the IECs that could serve as potential IBD therapeutic targets. Understanding the role of the IECs in the pathogenesis of IBD may help improve the understanding of the inflammatory process and the identification of potential therapeutic targets to help ameliorate this increasingly common disease.