Innate immune signalling and cell death pathways are highly interconnected processes involving receptor-interacting protein kinases (RIPKs) as mediators of potent anti-microbial responses. However, these processes are often antagonised by bacterial type III secretion system (T3SS) effectors, and the cellular mechanisms by which the host retaliates are not completely understood. Here, we demonstrate that during Citrobacter rodentium infection, murine macrophages and colonic epithelial cells exhibit RIPK1 kinase-dependent caspase-8 activation to counteract NleE effector-mediated suppression of pro-inflammatory signalling. While C. rodentium injects into the host cells a second effector, NleB, to block caspase-8 signalling, macrophages respond by triggering RIPK3-mediated necroptosis, whereupon a third T3SS effector, EspL, acts to inactivate necroptosis. We further show that NleB and EspL collaborate to suppress caspase-8 and NLRP3 inflammasome activation in macrophages. Our findings suggest that C. rodentium has evolved to express a complex network of effectors as an adaptation to the importance of cell death for anti-bacterial defence in the host-pathogen arms race.

The intestinal barrier serves as a boundary between the mucosal immune system in the lamina propria and the external environment of the intestinal lumen, which contains a diverse array of microorganisms and ingested environmental factors, including pathogens, food antigens, toxins, and other foreign substances. This barrier has a central role in regulating the controlled interaction between luminal factors and the intestinal immune system. Disruptions of intestinal epithelial cells, which serve as a physical barrier, or the antimicrobial peptides and mucins they produce, which act as a chemical barrier, can lead to a leaky gut. In this state, the intestinal wall is unable to efficiently separate the intestinal flora and luminal contents from the intestinal immune system. The subsequent activation of the immune system has an important role in the pathogenesis of inflammatory bowel disease, as well as in metabolic dysfunction-associated steatohepatitis, primary sclerosing cholangitis, and colorectal cancer. Dysregulated intestinal barrier integrity has also been described in patients with chronic inflammatory diseases outside the gastrointestinal tract, including rheumatoid arthritis and neurodegenerative disorders. Mechanistic studies of barrier dysfunction have revealed that the subsequent local activation and systemic circulation of activated immune cells and the cytokines they secrete, as well as extracellular vesicles, promote proinflammatory processes within and outside the gastrointestinal tract. In this Review, we summarise these findings and highlight several new therapeutic concepts currently being developed that attempt to control inflammatory processes via direct or indirect modulation of intestinal barrier function.

Bovine respiratory disease (BRD) is a prevalent and costly condition in the cattle industry, impacting long-term productivity, antibioticusage, and global food safety. Thus, identifying reliable biomarkers for BRD is crucial for early diagnosis, effective treatment, and monitoring therapeutic outcomes.

This study identified differentially expressed genes (DEGs) associated with BRD by analyzing a blood RNA-seq expression dataset associated with BRD, and conducted a Kyoto Encyclopedia of Genes and Genomes (KEGG) approach enrichment and Gene Ontology (GO) annotation analysis on these DEGs. Meanwhile, the key modules related to BRD were screened by weighted gene co-expression network analysis (WGCNA), and the genes in the module were intersected with DEGs. Subequently, least absolute shrinkage and selection operator (LASSO) and random forest (RF) analysis were employed to identify potential biomarkers. Finally, gene set enrichment analysis (GSEA) was performed to explore the potential mechanisms of the identified biomarkers, and their diagnostic significance was assessed using receiver operator characteristic (ROC) curve analysis and real-time fluorescent quantitative PCR (RT-qPCR). In addition, immune cell infiltration in BRD was evaluated using the CIBERSORT algorithm and the correlation between biomarkers and immune cell infiltration was analyzed.

The results showed that a total of 1,097 DEG were screened. GO and KEGG analysis showed that DEGs was mainly enriched in inflammatory response, defense response, Complement and coagulation cascades and Antigen processing and presentation pathways. WGCNA analysis determined that the cyan module had the highest correlation with BRD. A total of 833 overlapping genes were identified through Venn analysis of the differential and WGCNA results. Lasso and RF analyses identified five potential biomarkers for BRD. RT-qPCR testing and data set analysis showed that the expression levels of these five potential biomarkers in nasal mucus and blood of BRD cattle were significantly higher than those of healthy cattle. In addition, ROC curve analysis showed that potential biomarkers had high diagnostic value. GSEA analysis revealed that potential biomarkers are mainly involved in Neutrophil extracellular trap formation, Complement and coagulation cascades, T cell receptor signaling pathway, B cell receptor signaling pathway, Fc gamma R-mediated phagocytosis and IL-17 signaling pathway. The results from the CIBERSORT algorithm demonstrated a significant difference in immune cell composition between the BRD group and the healthy group, indicating that the diagnostic biomarkers were closely associated with immune cells.

This study identified ADGRG3, CDKN1A, CA4, GGT5, and SLC26A8 as potential diagnostic markers for BRD, providing significant insights for the development of new immunotherapy targets and improving disease prevention and treatment strategies.

Iron deficiency is the most common comorbidity of inflammatory bowel disease (IBD), but the effect of iron supplementation on the repair processes of intestinal injury in weaned mice is unknown. This study aimed to evaluate the potential mechanism of dietary iron on intestinal injury and intestinal regeneration in the dextran sodium sulfate (DSS)-induced colitis of the weaned mouse model. The mice were fed either a control diet containing (45.00 mg/kg Fe) or iron supplemental (448.30 mg/kg Fe) diet for 14 days, followed by a 7-day oral administration of 2.5% DSS to all mice. The result showed that at day 0 of the recovery period (0 DRP), the impact of iron on the gut index and intestinal morphology was found to be more significant in weaned mice compared to adult mice. At 3 DRP, the iron diet alleviated inflammation-induced weight loss, shortening of colon length, thickening of the muscle layer, and disruption of gut morphology. At 0, 3, and 7 DRP, we found that an iron diet increased intestinal stem cell (ISC) viability and protected epithelial integrity. Furthermore, FeSO4 significantly enhanced organoid viability and increased mRNA expression of differentiation, ISC, and retinol metabolism-related marker genes in the organoids compared with the control group. Overall, this study demonstrates that the iron diet accelerates intestinal regeneration after intestinal injury in weaned mice by activating the retinol metabolic pathway to regulate the proliferation and differentiation of ISCs.

The application of apoptotic extracellular vesicles (ApoEVs) derived from stem cell in skin wound healing has garnered significant attention. In recent decades, scholars have shown that extracellular vesicles (EVs) established intercellular communication by carrying proteins or microRNAs, the role of lipids in EVs in wound healing has yet to be clarified. Here, we focus on the key role of group X secretory phospholipase A2 (sPLA2-X) in lipid metabolism. Specifically, sPLA2-X significantly increased the production of the anti-inflammatory lipid mediators, resolvin D5 (RvD5), by hydrolyzing phospholipids in ApoEVs. This change not only promoted the uptake of ApoEVs by macrophages, but also effectively inhibited the expression of tumor necrosis factor-alpha (TNF-α) in macrophages, promoting the healing of skin wounds. In summary, this study contributes to our understanding of the mechanisms by which ApoEVs support skin defect repair and offers a potential theoretical approach for using ApoEVs in skin wound treatment. With further research and optimization, it is expected that more efficient and secure ApoEVs-based treatment strategies will be developed, bringing new breakthroughs in clinical treatment of skin injuries and related diseases.

High-damaging Candida albicans strains tend to form hyphae and exacerbate intestinal inflammation in ulcerative colitis patients through IL-1β-dependent mechanisms. Fungal agglutinin-like sequence (Als) proteins worsen DSS-induced colitis in mouse models. FADD and caspase-8 are important regulators of gut homeostasis and inflammation. However, whether they link directly to fungal proteins is not fully understood. Here, we report that Als proteins induce IL-1β release in immune cells. We show that hyphal Als3 is internalized in macrophages and interacts with caspase-8 and the inflammasome adaptor apoptosis-associated speck-like protein containing a CARD (ASC). Caspase-8 is essential for Als3-mediated ASC oligomerization and IL-1β processing. In non-immune cells, Als3 is associated with cell death core components FADD and caspase-8. N-terminal Als3 (N-Als3) expressed in Jurkat cells partially inhibits apoptosis. Mechanistically, N-Als3 promotes oligomerization of FADD and caspase-8 through their death effector domains (DEDs). N-Als3 variants with a mutation in the peptide-binding cavity or amyloid-forming region are impaired in DED oligomerization. Together, these results demonstrate that DEDs are intracellular sensors of Als3. This study identifies additional potential targets to control hypha-induced inflammation.

Lymphatic vessels are crucial for fluid absorption and the transport of peripheral immune cells to lymph nodes. However, in the small intestine, the lymphatic fluid is rich in diet-derived lipids incorporated into chylomicrons and gut-specific immune cells. Thus, intestinal lymphatic vessels have evolved to handle these unique cargoes and are critical for systemic dietary lipid delivery and metabolism. This Review covers mechanisms of lipid absorption from epithelial cells to the lymphatics as well as unique features of the gut microenvironment that affect these functions. Moreover, we discuss details of the intestinal lymphatics in gut immune cell trafficking and insights into the role of inter-organ communication. Lastly, we highlight the particularities of fat absorption that can be harnessed for efficient lipid-soluble drug distribution for novel therapies, including the ability of chylomicron-associated drugs to bypass first-pass liver metabolism for systemic delivery. In all, this Review will help to promote an understanding of intestinal lymphatic-systemic interactions to guide future research directions.

Inflammatory bowel diseases (IBD) are chronic, incurable pathologies with unknown causes, affecting millions of people. Pediatric-onset IBD, starting before the age of 18 years, are increasing, with more aggressive and extensive features than adult-onset IBD. These differences remain largely unexplained. Intestinal mucosal damage, cell death, DNA release from nuclear, mitochondrial, or microbiota sources, and DNA-sensing activating the cGAS-STING pathway may contribute to disease evolution. Increased colonic cGAS and STING are increasingly reported in experimental and human IBD. However, limited knowledge of the mechanisms involved hinders the development of new therapeutic options. Here, we discuss recent advances and unresolved questions regarding DNA release, DNA sensor activation, and the role and therapeutic potential of the cGAS-STING pathway in inflammatory colitis.

Inflammatory bowel disease (IBD), encompassing ulcerative colitis and Crohn's disease, is a group of chronic, immune-mediated disorders of the gastrointestinal tract that present substantial clinical challenges owing to their complex pathophysiology and tendency to relapse. A treat-to-target approach is recommended, involving iterative treatment adjustments to achieve clinical response, reduce inflammatory markers and achieve long-term goals such as mucosal healing. Lifelong medication is often necessary to manage the disease, maintain remission and prevent complications. The therapeutic landscape for IBD has evolved substantially; however, a ceiling on therapeutic efficacy remains and surgery is sometimes required (owing to uncontrolled disease activity or complications). Effective IBD management involves comprehensive care, including medication adherence and a collaborative clinician-patient relationship. This Review discusses current therapeutic options for IBD, detailing mechanisms of action, efficacy, safety profiles and guidelines for use of each drug class. We also explore emerging therapies and the role of surgery. Additionally, the importance of a multidisciplinary team and personalized care in managing IBD is emphasized, advocating for patient empowerment and involvement in treatment decisions. By synthesizing current knowledge and emerging trends, this Review aims to equip healthcare professionals with a thorough understanding of therapeutic options for IBD, enhancing informed, evidence-based decisions in clinical practice.

Programmed cell death (PCD) plays a crucial role in maintaining tissue homeostasis, with its primary forms including apoptosis, pyroptosis, and necroptosis. The caspase family is central to these processes, and its complex functions across different cell death pathways and other non-cell death roles have been closely linked to the pathogenesis of autoimmune diseases. This article provides a comprehensive review of the role of the caspase family in autoimmune diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), type 1 diabetes (T1D), and multiple sclerosis (MS). It particularly emphasizes the intricate functions of caspases within various cell death pathways and their potential as therapeutic targets, thereby offering innovative insights and a thorough discussion in this field. In terms of therapy, strategies targeting caspases hold significant promise. We emphasize the importance of a holistic understanding of caspases in the overall concept of cell death, exploring their unique functions and interrelationships across multiple cell death pathways, including apoptosis, pyroptosis, necroptosis, and PANoptosis. This approach transcends the limitations of previous studies that focused on singular cell death pathways. Additionally, caspases play a key role in non-cell death functions, such as immune cell activation, cytokine processing, inflammation regulation, and tissue repair, thereby opening new avenues for the treatment of autoimmune diseases. Regulating caspase activity holds the potential to restore immune balance in autoimmune diseases. Potential therapeutic approaches include small molecule inhibitors (both reversible and irreversible), biological agents (such as monoclonal antibodies), and gene therapies. However, achieving specific modulation of caspases to avoid interference with normal physiological functions remains a major challenge. Future research must delve deeper into the regulatory mechanisms of caspases and their associated complexes linked to PANoptosis to facilitate precision medicine. In summary, this article offers a comprehensive and in-depth analysis, providing a novel perspective on the complex roles of caspases in autoimmune diseases, with the potential to catalyze breakthroughs in understanding disease mechanisms and developing therapeutic strategies.

Gastric ulcers (GUs) represent a common gastrointestinal disorder characterized by mucosal damage and inflammation, often precipitated by factors such as Helicobacter pylori infection and the consumption of COX inhibitors. This comprehensive review investigates the role of oxidative stress and inflammation in the pathogenesis of GUs and assesses the potential therapeutic effects of Punica granatum (pomegranate, Pg) supplementation. Utilizing a series of experimental models, including indomethacin, aspirin, and alcohol-induced ulcers, we demonstrate that Pg extracts possess significant gastroprotective properties. The antioxidant activity of Pg is ascribed to its capacity to neutralize reactive oxygen species (ROS), enhance the activity of endogenous antioxidants such as superoxide dismutase (SOD) and catalase (CAT), and diminish lipid peroxidation. Furthermore, the anti-inflammatory effects of Pg are mediated through the suppression of pro-inflammatory cytokines such as TNF-α and IL-1β, in conjunction with the promotion of gastric mucosal protective agents. Histological analyses indicate that Pg extract preserves the architecture of gastric tissue and alleviates ulcer severity. These findings highlight the potential of Pg as a natural remedy for GUs, thereby necessitating further investigation into its mechanisms of action and optimal therapeutic formulations.

Restoration of the intestinal epithelial barrier is crucial for achieving mucosal healing, the therapeutic goal for inflammatory bowel disease (IBD). During homeostasis, epithelial renewal is maintained by crypt stem cells and progenitors that cease to divide as they differentiate into mature colonocytes. Inflammation is a major effector of mucosal damage in IBD and has been found to affect epithelial stemness, regeneration and cellular functions. However, the impact of immune cell-modulating IBD drugs on epithelial homeostasis and repair is poorly understood. It is likely that these drugs will have distinct mechanisms of action (MOA) in intestinal epithelium relevant for homeostasis that will vary among patients. We investigated cellular effects of pan-Janus Kinase (JAK) inhibitor tofacitinib and the corticosteroid budesonide on uninflamed and TNF + Poly(I:C) stimulated human colon organoids (colonoids) from healthy donors and IBD-patients. Our findings reveal that although both tofacitinib and budesonide exhibit anti-inflammatory effects, tofacitinib increased colonoid size and proliferation during differentiation, and promoted epithelial stemness. In contrast, budesonide decreased colonoid size and showed no consistent effect on proliferation or stemness. Our study demonstrates the value of employing human colonoids to investigate how IBD drugs affect intestinal epithelial cells and inter-individual variations relevant to mucosal healing and personalized IBD treatment.

Patients with Crohn's disease (CD) exhibit excessive apoptosis of intestinal epithelial cells (IECs), which contributes to damage to the intestinal barrier structure and function, thereby playing a role in the progression of colitis. Preventing IEC apoptosis and protecting the intestinal barrier are critical to alleviating colitis. Natural plant monomers have been reported to possess multiple pharmacological properties, particularly with the potential to treat CD. This study focuses on Cynaroside (Cyn) to explore its effect on IEC apoptosis and evaluate its pharmacological impact on the intestinal barrier and colitis.

The 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced CD-like colitis mice model was employed in this study. We assessed the therapeutic effect of Cyn on CD-like colitis by evaluating the disease activity index (DAI), body weight changes, intestinal tissue pathological damage, and inflammatory factor levels. Immunofluorescence and Western blotting were used to detect the expression and localization of tight junction (TJ) proteins, allowing us to analyze the intestinal barrier structure. The function of the intestinal barrier was examined using FITC-dextran (FD4), TEER values, and bacterial translocation. Network pharmacology enrichment analysis revealed that Cyn could inhibit cell apoptosis. We also explored the effect and underlying mechanism of Cyn in inhibiting IEC apoptosis on intestinal barrier function and colitis using both the TNF-α-induced colonic organoid model and the TNBS-induced mouse model.

Our findings show that Cyn significantly alleviates TNBS-induced colitis symptoms in mice, as evidenced by reduced body weight loss, colon shortening, DAI score, colon histopathology score, and lower levels of inflammatory factors (IL-1β, TNF-α, and IL-6) compared to the model group. Additionally, the Cyn intervention group showed significant improvements in both the intestinal barrier structure (elevated tight junction protein levels and proper localization) and function (reduced serum FD4 levels, increased intestinal TEER, and decreased bacterial translocation rates in mesenteric lymph nodes [MLNs] and livers). Combining network pharmacology prediction analysis with our validation data from animal models and colonic organoids, we demonstrated that Cyn significantly inhibits IEC apoptosis, as indicated by a decrease in the proportion of TUNEL-positive cells and changes in apoptosis-related protein levels. KEGG enrichment analysis and signaling pathway intervention experiments confirmed that Cyn inhibits the activation of PI3K/AKT signaling.

Cyn inhibits IEC apoptosis by blocking the PI3K/AKT signaling pathway, which is the primary mechanism underlying its protective effects on the intestinal barrier and its ability to improve CD-like colitis. This study also supports the potential of the Chinese medicine monomer Cyn as a promising therapeutic agent for the treatment of CD.

Receptor interacting protein kinase 1 (RIPK1) crucially upregulates necroptosis and is a key driver of inflammation. An effective PET radioligand for imaging brain RIPK1 would be useful for further exploring the role of this enzyme in neuroinflammation and for assisting drug discovery. Here, we report our progress on developing a PET radioligand for RIPK1 based on the phenyl-1H-dihydropyrazole skeleton of a lead RIPK1 inhibitor, GSK'963. The most potent inhibitor from a small structure-activity relationship study,(S)-1-(5-(3-fluorophenyl)-4,5-dihydro-1H-pyrazol-1-yl)-2,2-dimethylpropan-1-one ((S)-SJ1058 or (S)-5d), was labeled with no-carrier-added fluorine-18 (t1/2 = 109.8 min) from a homochiral meta-tri-n-butylstannane precursor [(S)-11c] in 10-15% formulated yields. The lipophilicity measured for [18F](S)-SJ1058 was moderate (log D7.4 = 3.00) and conducive to good brain permeability. PET scans with [18F](S)-SJ1058 in healthy monkeys under baseline and preblock conditions with a RIPK1 inhibitor, either Nec-1s or GSK'963, demonstrated high peak radioactivity uptake in the brain (3.1-3.9 SUV) but no evidence of in vivo RIPK1-specific binding. Moreover, [18F](S)-SJ1058 did not detect neuroinflammation in rats on day 1 and day 8 after systemic lipopolysaccharide administration. We conclude that [18F](S)-SJ1058 is unpromising for imaging human brain RIPK1 in neuroinflammation. Higher-affinity radioligands may be needed for this purpose.

Dysregulation at the intestinal epithelial barrier is a driver of inflammatory bowel disease (IBD). However, the molecular mechanisms of barrier failure are not well understood. Here, we demonstrate dysregulated mitochondrial fusion in intestinal epithelial cells (IECs) of patients with IBD and show that impaired fusion is sufficient to drive chronic intestinal inflammation. We found reduced expression of mitochondrial fusion-related genes, such as the dynamin-related guanosine triphosphatase (GTPase) optic atrophy 1 (OPA1), and fragmented mitochondrial networks in crypt IECs of patients with IBD. Mice with Opa1 deficiency in the gut epithelium (Opa1i∆IEC) spontaneously developed chronic intestinal inflammation with mucosal ulcerations and immune cell infiltration. Intestinal inflammation in Opa1i∆IEC mice was driven by microbial translocation and associated with epithelial progenitor cell death and gut barrier dysfunction. Opa1-deficient epithelial cells and human organoids exposed to a pharmacological OPA1 inhibitor showed disruption of the mitochondrial network with mitochondrial fragmentation and changes in mitochondrial size, ultrastructure, and function, resembling changes observed in patient samples. Pharmacological inhibition of the GTPase dynamin-1-like protein in organoids derived from Opa1i∆IEC mice partially reverted this phenotype. Together, our data demonstrate a role for epithelial OPA1 in regulating intestinal immune homeostasis and epithelial barrier function. Our data provide a mechanistic explanation for the observed mitochondrial dysfunction in IBD and identify mitochondrial fusion as a potential therapeutic target in this disease.

Desmosomes are adhesive cell contacts abundant in tissues exposed to mechanical strain, such as the stratified and simple epithelia of the epidermis and mucous membranes, as well as the myocardium. Besides their role in mechanical cell cohesion, desmosomes also modulate pathways important for tissue differentiation, wound healing and immune responses. Dysfunctional desmosomes, resulting from pathogenic variants in genes encoding desmosomal components, autoantibodies targeting desmosomal adhesion molecules or inflammation, cause the life-threatening diseases arrhythmogenic cardiomyopathy and pemphigus and contribute to the pathogenesis of inflammatory bowel diseases. The Alpine Desmosome Disease Meeting 2024 (ADDM 2024), held in Grainau, Germany in October 2024, connected international researchers from basic sciences with clinical experts from dermatology, cardiology, gastroenterology and surgery. The participants discussed recent advances, identified hot topics in desmosome biology and disease and provided new concepts for pathogenesis and treatment approaches.

The intestinal epithelium, beyond its role in absorption and digestion, serves as a critical protective mechanical barrier that delineates the luminal contents and the gut microbiota from the lamina propria within resident mucosal immune cells to maintain intestinal homeostasis. The barrier is manifested as a contiguous monolayer of specialized intestinal epithelial cells (IEC), interconnected through tight junctions (TJs). The integrity of this epithelial barrier is of paramount. Consequently, excessive IEC death advances intestinal permeability and as a consequence thereof the translocation of bacteria into the lamina propria, subsequently triggering an inflammatory response, which underpins the clinical disease trajectory of inflammatory bowel disease (IBD). A burgeoning body of evidence illustrates a landscape where IEC undergoes several the model of programmed cell death (PCD) in the pathophysiology and pathogenesis of IBD. Apoptosis, necroptosis, and pyroptosis represent the principal modalities of PCD with intricate specific pathways and molecules. Ample evidence has revealed substantial mechanistic convergence and intricate crosstalk among these three aforementioned forms of cell death, expanding the conceptualization of PANoptosis orchestrated by the PNAoptosome complex. This review provides a concise overview of the molecular mechanisms of apoptosis, necroptosis, and pyroptosis. Furthermore, based on the crosstalk between three cell deaths in IEC, this review details the current knowledge regarding PANoptosis in IEC and its regulation by natural products. Our objective is to broaden the comprehension of innovative molecular mechanisms underlying the pathogenesis of IBD and to furnish a foundation for developing more natural drugs in the treatment of IBD, benefiting both clinical practitioners and research workers.

Idiopathic inflammatory myopathy (commonly known as myositis) is a group of immune-related diseases characterized by muscle damage, weakness, and fatigue with unknown causes. Although overactivated innate immunity is a widely believed cause of myositis onset, the mechanism that provokes and maintains a high immune response in myositis patients is still unclear. This study aims to test if brain-derived neurotrophic factor (BDNF) deficiency per se is sufficient to cause myositis and determine its underlying mechanism. We found that ablating BDNF production in skeletal muscle is sufficient to trigger myositis development in mice. Muscle-specific Bdnf knockout (MBKO) mice displayed extensive myocyte necrosis, mononuclear cell infiltration, and myophagocytosis. In association with these damages, elevated production of pro-inflammatory cytokines such as interleukin (IL) 23, IL-1β, IL-18, and tumor necrosis factor α (TNFα) was found in the muscle of MBKO mice. Disruption of sarcolemma integrity was also detected in MBKO mice, which is a result of necroptosis executioner Mixed lineage kinase domain-like protein (MLKL) and pyroptosis executioner Gasdermin D (GSDMD) activation. Mechanistically, diminishing BDNF synthesis in myotubes enhances the accumulation of mitochondrial reactive oxygen species (mtROS), which sensitizes the cells towards TNFα-induced receptor-interacting protein kinase (RIPs) activation and promotes the formation of NLR family pyrin domain containing 3 (NLRP3)-containing inflammasome. BDNF deficiency-induced cell death could be alleviated by scavenging mtROS, suppressing the activity of GSDMD, or inhibiting receptor-interacting kinase 3 (RIP3). Similarly, supplementation of BDNF mimetics, suppression of RIP3 activity, increasing the intramyocellular antioxidant, or enhancing mitophagy ameliorated the myopathies of MBKO mice and improved their muscle strength. Together, our study demonstrates that insufficient BDNF production in mouse muscle causes the development of pathological features of myositis via enhancing oxidative stress, necroptosis, and pyroptosis in myofibers.

Group 3 innate lymphoid cells (ILC3s) are abundant in the developing or healthy intestine to critically support tissue homeostasis in response to microbial colonization. However, intestinal ILC3s are reduced during chronic infections, colorectal cancer, or inflammatory bowel disease (IBD), and the mechanisms driving these alterations remain poorly understood. Here we employed RNA sequencing of ILC3s from IBD patients and observed a significant upregulation of RIPK3, the central regulator of necroptosis, during intestinal inflammation. This was modeled in mice where we found that intestinal ILC3s express RIPK3, with conventional (c)ILC3s exhibiting high RIPK3 and low levels of pro-survival genes relative to lymphoid tissue inducer (LTi)-like ILC3s. ILC3-specific RIPK3 is promoted by gut microbiota, further upregulated following enteric infection, and dependent upon IL-23R and STAT3 signaling. However, lineage-specific deletion of RIPK3 revealed a redundant role in ILC3 survival, due to a blockade of RIPK3-mediated necroptosis by caspase 8, which was also activated in response to enteric infection. In contrast, lineage-specific deletion of caspase 8 resulted in loss of cILC3s from the healthy intestine and all ILC3 subsets during enteric infection, which increased pathogen burdens and gut inflammation. This function of caspase 8 required catalytic activity induced by TNF or TL1A and was dispensable if RIPK3 was simultaneously deleted. Caspase 8 activation and cell death were associated with increased Fas on ILC3s, and the Fas-FasL pathway was upregulated by cILC3s during enteric infection, which could restrain the abundance of intestinal ILC3s. Collectively, these data reveal that interpretation of key cytokine signals controls ILC3 survival following microbial challenge, and that an imbalance of these pathways, such as in IBD or across ILC3 subsets, provokes depletion of tissue-protective ILC3s from the inflamed intestine.

Alterations in ileal Paneth cell (PC) density have been described in gut inflammatory diseases such as Crohn's disease (CD) and could be used as a biomarker for disease prognosis. However, quantifying PCs is time-intensive, a barrier for clinical workflow. Deep learning (DL) has transformed the development of robust and accurate tools for complex image evaluation. Our aim was to use DL to quantify PCs for use as a quantitative biomarker.

A retrospective cohort of whole slide images (WSI) of ileal tissue samples from patients with/without inflammatory bowel disease (IBD) was used for the study. A pathologist-annotated training set of WSI were used to train a U-net two-stage DL model to quantify PC number, crypt number, and PC density. For validation, a cohort of 48 WSIs were manually quantified by study pathologists and compared to the DL algorithm, using root mean square error (RMSE) and the coefficient of determination (r2) as metrics. To test the value of PC quantification as a biomarker, resection specimens from patients with CD (n = 142) and without IBD (n = 48) patients were analysed with the DL model. Finally, we compared time to disease recurrence in patients with CD with low versus high DL-quantified PC density using Log-rank test.

Initial one-stage DL model showed moderate accuracy in predicting PC density in cross-validation tests (RMSE = 1.880, r2 = 0.641), but adding a second stage significantly improved accuracy (RMSE = 0.802, r2 = 0.748). In the validation of the two-stage model compared to expert pathologists, the algorithm showed good performance up to RMSE = 1.148, r2 = 0.708. The retrospective cross-sectional cohort had mean ages of 62.1 years in the patients without IBD and 38.6 years for the patients with CD. In the non-IBD cohort, 43.75% of the patients were male, compared to 49.3% of the patients with CD. Analysis by the DL model showed significantly higher PC density in non-IBD controls compared to the patients with CD (4.04 versus 2.99 PC/crypt). Finally, the algorithm quantification of PCs density in patients with CD showed patients with the lowest 25% PC density (Quartile 1) have significantly shorter recurrence-free interval (p = 0.0399).

The current model performance demonstrates the feasibility of developing a DL-based tool to measure PC density as a predictive biomarker for future clinical practice.

This study was funded by the National Institutes of Health (NIH).

Context: Berberine (BBR) can regulate enteric glial cells (EGCs) and the gut vascular barrier (GVB).Objective: To explore whether BBR regulates GVB permeability via the S100B pathway.Materials and methods: GVB hyperpermeability in C57BL/6J mice was induced by burns or S100B enema. BBR (25 or 50 mg/kg/d, 3 d) was gavaged preburn. S100B monoclonal antibody (S100BmAb) was i.v. injected postburn. Mouse intestinal microvascular endothelial cells (MIMECs) were treated with S100B, S100B plus BBR, or Z-IETD-FMK. GVB permeability was assayed by FITC-dextran, S100B by ELISA, caspase-8, β-catenin, occludin and PV-1 by immunoblot.Results: Burns elevated S100B in serum and in colonic mucosa to a peak (147.00 ± 4.95 ng/mL and 160.30 ± 8.50 ng/mg, respectively) at 36 h postburn, but BBR decreased burns-induced S100B in serum (126.20 ± 6.30 or 90.60 ± 3.78 ng/mL) and in mucosa (125.80 ± 12.40 or 91.20 ± 8.54 ng/mg). Burns raised GVB permeability (serum FITC-dextran 111.40 ± 8.56 pg/mL) at 48 h postburn, but BBR reduced GVB permeability (serum FITC-dextran 89.20 ± 6.98 or 68.60 ± 5.50 ng/mL). S100B enema (1 μM) aggravated burns-raised GVB permeability (142.80 ± 8.07 pg/mL) and PV-1, but the effect of S100B was antagonized by BBR. Z-IETD-FMK (5 μM) increased S100B-induced permeability to FITC-dextran (205.80 ± 9.70 to 263.80 ± 11.04 AUs) while reducing β-catenin in MIMECs. BBR (5 μM) reduced S100B-induced permeability (104.20 ± 9.65 AUs) and increased caspase-8, β-catenin and occludin.Discussion and conclusion: BBR decreases burns-induced GVB hyperpermeability via modulating S100B/caspase-8/β-catenin pathway and may involve EGCs.

Inflammatory bowel disease (IBD), caused by environmental factors associated with the host's genetic traits, is represented by Crohn's disease and ulcerative colitis. Despite the increasing number of patients with IBD, the current treatment is limited to symptomatic therapy. A complex IBD model mimicking the human IBD etiology is required to overcome this limitation. Herein, we developed novel complex IBD models using interleukin 2 receptor subunit gamma (Il2rg)-deficient mice, high-fat diet, dextran sodium sulfate, and Citrobacter rodentium. The more IBD factors applied complexly, colon length shortened and inflammation worsened. The levels of pro-inflammatory cytokines increased with increased IBD factors. Anti-inflammatory cytokine decreased in all factors application but increased in Il2rg deficiency and Westernized diet combination. Additionally, the pro-inflammatory transcription factors and leaky intestinal epithelial marker were upregulated by a combination of IBD factors. Species diversity decreased with IBD factors. Phylogenetic diversity decreased as IBD factors were applied but increased with combined Il2rg deficiency and Westernized diet. The more IBD factors applied complexly, the more severe the dysbiosis. Finally, we developed a novel complex IBD model using various IBD factors. This model more closely mimic human IBD based on colonic inflammation and dysbiosis than the previous models. Based on these results, our novel complex IBD model could be a valuable tool for further IBD research.

Mixed lineage kinase domain-like (MLKL) is a pseudokinase, best known for its role as the terminal effector of the necroptotic cell death pathway. MLKL-mediated necroptosis has long been linked to various age-related pathologies including neurodegeneration, atherosclerosis and male reproductive decline, however many of these attributions remain controversial. Here, we investigated the role of MLKL and necroptosis in the adult mouse testis: an organ divided into sperm-producing seminiferous tubules and the surrounding testosterone-producing interstitium. We find that sperm-producing cells within seminiferous tubules lack expression of key necroptotic mediators and thus are resistant to a pro-necroptotic challenge. By comparison, coordinated expression of the necroptotic pathway occurs in the testicular interstitium, rendering cells within this compartment, especially the lysozyme-positive macrophages, vulnerable to necroptotic cell death. We also uncover a non-necroptotic role for MLKL in regulating testosterone levels. Thus, MLKL serves two roles in the mouse testes - one involving the canonical response of macrophages to necroptotic insult, and the other a non-canonical function in male reproductive hormone control.

Inflammatory bowel disease (IBD) is an idiopathic gastrointestinal disease with drastically increasing incidence rates. Due to its multifactorial etiology, a precise investigation of the pathogenesis is extremely difficult. Although reductionist cell culture models and more complex disease models in animals have clarified the understanding of individual disease mechanisms and contributing factors of IBD in the past, it remains challenging to bridge research and clinical practice. Conventional 2D cell culture models cannot replicate complex host-microbiota interactions and stable long-term microbial culture. Further, extrapolating data from animal models to patients remains challenging due to genetic and environmental diversity leading to differences in immune responses. Human intestine organ-on-chip (OoC) models have emerged as an alternative in vitro model approach to investigate IBD. OoC models not only recapitulate the human intestinal microenvironment more accurately than 2D cultures yet may also be advantageous for the identification of important disease-driving factors and pharmacological interventions targets due to the possibility of emulating different complexities. The predispositions and biological hallmarks of IBD focusing on host-microbiota interactions at the intestinal mucosal barrier are elucidated here. Additionally, the potential of OoCs to explore microbiota-related therapies and personalized medicine for IBD treatment is discussed.

Primary sclerosing cholangitis (PSC), often associated with inflammatory bowel disease (IBD), presents a multifactorial etiology involving genetic, immunologic, and environmental factors. Gut dysbiosis and bacterial translocation have been implicated in PSC-IBD, yet the precise mechanisms underlying their pathogenesis remain elusive. Here, we describe the role of gut pathobionts in promoting liver inflammation and fibrosis due to the release of bacterial outer membrane vesicles (OMVs).

Preclinical mouse models in addition to ductal organoids were used to acquire mechanistic data. A proof-of-concept study including serum and liver biopsies of a patient cohort of PSC (n = 22), PSC-IBD (n = 45), and control individuals (n = 27) was performed to detect OMVs in the systemic circulation and liver.

In both preclinical model systems and in patients with PSC-IBD, the translocation of OMVs to the liver correlated with enhanced bacterial sensing and accumulation of the NLRP3 inflammasome. Using ductal organoids, we were able to precisely attribute the pro-inflammatory and pro-fibrogenic properties of OMVs to signaling pathways dependent on Toll-like receptor 4 and NLRP3-gasdermin-D. The immunostimulatory potential of OMVs could be confirmed in macrophages and hepatic stellate cells. Furthermore, when we administered gut pathobiont-derived OMVs to Mdr2-/- mice, we observed a significant enhancement in liver inflammation and fibrosis. In a translational approach, we substantiated the presence of OMVs in the systemic circulation and hepatic regions of severe fibrosis using a PSC-IBD patient cohort.

This study demonstrates the contribution of gut pathobionts in releasing OMVs that traverse the mucosal barrier and, thus, promote liver inflammation and fibrosis in PSC-IBD. OMVs might represent a critical new environmental factor that interacts with other disease factors to cause inflammation and thus define potential new targets for fibrosis therapy.

The intestinal epithelium forms the boundary between the intestinal immune system in the lamina propria and the outside world, the intestinal lumen, which contains a diverse array of microbial and environmental antigens. Composed of specialized cells, this epithelial monolayer has an exceptional turnover rate. Differentiated epithelial cells are released into the intestinal lumen within a few days, at the villus tip, a process that requires strict regulation. Dysfunction of the epithelial barrier increases the intestinal permeability and paves the way for luminal antigens to pass into the intestinal serosa. Stem cells at the bottom of Lieberkühn crypts provide a constant supply of mature epithelial cells. Differentiated intestinal epithelial cells exhibit a diverse array of mechanisms that enable communication with surrounding cells, fortification against microorganisms, and orchestration of nutrient absorption and hormonal balance. Furthermore, tight junctions regulate paracellular permeability properties, and their disruption can lead to an impairment of the intestinal barrier, allowing inflammation to develop or further progress. Intestinal epithelial cells provide a communication platform through which they maintain homeostasis with a spectrum of entities including immune cells, neuronal cells, and connective tissue cells. This homeostasis can be disrupted in disease, such as inflammatory bowel disease. Patients suffering from inflammatory bowel disease show an impaired gut barrier, dysregulated cellular communication, and aberrant proliferation and demise of cells. This review summarizes the individual cellular and molecular mechanisms pivotal for upholding the integrity of the intestinal epithelial barrier and shows how these can be disrupted in diseases, such as inflammatory bowel disease.

The pyroptosis of cardiomyocytes has become an essential topic in heart failure research. The abnormal accumulation of these biological factors, including angiotensin II, advanced glycation end products, and various growth factors (such as connective tissue growth factor, vascular endothelial growth factor, transforming growth factor beta, among others), activates the nuclear factor-κB (NF-κB) signaling pathway in cardiovascular diseases, ultimately leading to pyroptosis of cardiomyocytes. Therefore, exploring the underlying molecular biological mechanisms is essential for developing novel drugs and therapeutic strategies. However, our current understanding of the precise regulatory mechanism of this complex signaling pathway in cardiomyocyte pyroptosis is still limited. Given this, this study reviews the milestone discoveries in the field of pyroptosis research since 1986, analyzes in detail the similarities, differences, and interactions between pyroptosis and other cell death modes (such as apoptosis, necroptosis, autophagy, and ferroptosis), and explores the deep connection between pyroptosis and heart failure. At the same time, it depicts in detail the complete pathway of the activation, transmission, and eventual cardiomyocyte pyroptosis of the NF-κB signaling pathway in the process of heart failure. In addition, the study also systematically summarizes various therapeutic approaches that can inhibit NF-κB to reduce cardiomyocyte pyroptosis, including drugs, natural compounds, small molecule inhibitors, gene editing, and other cutting-edge technologies, aiming to provide solid scientific support and new research perspectives for the prevention and treatment of heart failure.

Increasing evidence shows the potential threat of gill rot in freshwater fish culture. F. columnare is wide-spread in aquatic environments, which can cause fish gill rot and result in high mortality and losses of fish. This study investigated the effects of myo-inositol (MI) on the proliferation, structural integrity, and different death modes of grass carp (Ctenopharyngodon idella) gill epithelial cells, as well as its possible mechanism. 30 mg/L MI up-regulated CCK8 OD value and the protein level of solute carrier family 5A 3 (SLC5A3), and down-regulated the reactive oxygen species (ROS) content in gill cells and lactate dehydrogenase (LDH) release in the culture medium (P < 0.05). MI up-regulated the protein level of Beclin1, the protein level and fluorescence expression of microtubule-associated protein light chain 3B (LC3B) and down-regulated the protein level of sequestosome-1 (SQSTM1, also called p62) (P < 0.05). MI down-regulated the protein levels of Cysteine aspartate protease-1 (caspase-1), Gasdermin E (GSDME) and Cleaved interleukin 1 beta (IL-1β) (P < 0.05). MI up-regulated the protein level of caspase-8 (P < 0.05), but had no effect on apoptosis (P > 0.05). MI down-regulated the mRNA expressions and protein levels of tumor necrosis factor α (tnfα), TNF receptor 1 (tnfr1), receptor interacting protein 1 (ripk1), receptor interacting protein 3 (ripk3) and mixed lineage kinase domain-like protein (mlkl), and reduce the ratio of p-MLKL/MLKL (P < 0.05). The addition of MI or necrosulfonamide (NSA) alone, or the addition of MI after induction of necroptosis, significantly up-regulated the cell activity and the protein level of SLC5A3 in gill cells, and significantly reduced the LDH release in the culture medium and the intracellular ROS content, the number of necroptosis cells, the protein expression of TNFα, TNFR1 and RIPK1, and the ratio of p-RIPK3/RIPK3 and p-MLKL/MLKL (P < 0.05). It indicated MI induce autophagy may relate to Beclin1/LC3/p62 signaling pathway, inhibits pyroptosis may attribute to Caspase-1/GSDMD/IL-1β signaling pathway, and inhibits necroptosis via MLKL signaling pathway. However, MI had no effect on apoptosis.

Paneth cells play multiple roles in maintaining intestinal homeostasis. However, the clinical role of Paneth cell metaplasia (PCM) in ulcerative colitis (UC) remains unclear. We aimed to investigate the relationship between PCM and relapse in patients with UC and compare the usefulness of PCM with other histological indexes, including mucin depletion (MD) and basal plasmacytosis (BP).

Patients with UC in clinical remission (CR) who underwent colonoscopy to confirm a Mayo endoscopic subscore (MES) ≦1 with biopsies from the distal colon were enrolled into this retrospective cohort study. Biopsy samples were evaluated for histological findings of PCM, MD, and BP. Clinical relapse was defined as partial Mayo score ≧3 or medication escalation. Multivariate analysis was performed to determine independent predictors of relapse among the three histological findings, MES, and patient background, and relapse prediction models were generated.

Eighty-three patients were enrolled in this study (MES 0, n = 47; MES 1, n = 36). The number of PCM cases was significantly higher in patients with prolonged CR than that in those with relapse (p = 0.01). Multivariate analysis showed that the absence of PCM and MD were related to relapse in all the patients. In patients with MES 1, the absence of PCM was the only risk factor significantly and independently associated with relapse (hazard ratio, 4.51 [1.15-17.7]; p = 0.03).

The absence of PCM was a histological risk factor for relapse in patients with MES 1, implying a protective role for PCM in remission and a new index for mucosal healing.

Immune mediators affect multiple biological functions of intestinal epithelial cells (IECs) and, like Paneth and Paneth-like cells, play an important role in intestinal epithelial homeostasis. IFN-γ a prototypical proinflammatory cytokine disrupts intestinal epithelial homeostasis. However, the mechanism underlying the process remains unknown. In this study, using in vivo and in vitro models we demonstrate that IFN-γ is spontaneously secreted in the small intestine. Furthermore, we observed that this cytokine stimulates mitochondrial activity, ROS production, and Paneth and Paneth-like cell secretion. Paneth and Paneth-like secretion downstream of IFN-γ, as identified here, is mTORC1 and necroptosis-dependent. Thus, our findings revealed that the pleiotropic function of IFN-γ also includes the regulation of Paneth cell function in the homeostatic gut.

Necroptosis is a caspase-independent programmed cell death process characterized by morphological similarities to necrosis and the potential to cause significant inflammatory reactions. The initiation, execution, and inhibition of necroptosis involve a complex interplay of various signaling proteins. When death receptors bind to ligands, necroptosis is triggered through the receptor-interacting serine/threonine-protein kinase 1 (RIPK1)/RIPK3/Mixed Lineage Kinase Domain-Like (MLKL) axis, leading to inflammatory reactions in the surrounding tissues. This process encompasses numerous physiological regulatory mechanisms and contributes to the development and progression of certain diseases. The mechanisms of necroptosis were not well conserved across terrestrial and aquatic organisms, with differences in some components and functions. Given the significant challenges that aquatic animal diseases pose to aquaculture, research interest in necroptosis has surged recently, particularly in studies focusing on fish. Understanding necroptosis in fish can lead to interventions that offer potential breakthroughs in disease inhibition and fish health improvement.

Undifferentiated intestinal stem cells (ISCs) are crucial for maintaining homeostasis and resolving injury. Lgr5+ cells in the crypt base constantly divide, pushing daughter cells upward along the crypt axis where they differentiate into specialized cell types. Coordinated execution of complex transcriptional programs is necessary to allow for the maintenance of undifferentiated stem cells while permitting differentiation of the wide array of intestinal cells necessary for homeostasis. Previously, members of the myeloid translocation gene (MTG) family have been identified as transcriptional co-repressors that regulate stem cell maintenance and differentiation programs in multiple organ systems, including the intestine. One MTG family member, myeloid translocation gene related 1 (MTGR1), has been recognized as a crucial regulator of secretory cell differentiation and response to injury. However, whether MTGR1 contributes to the function of ISCs has not yet been examined. Here, using Mtgr1-/- mice, we have assessed the effects of MTGR1 loss specifically in ISC biology. Interestingly, loss of MTGR1 increased the total number of cells expressing Lgr5, the canonical marker of cycling ISCs, suggesting higher overall stem cell numbers. However, expanded transcriptomic and functional analyses revealed deficiencies in Mtgr1-null ISCs, including deregulated ISC-associated transcriptional programs. Ex vivo, intestinal organoids established from Mtgr1-null mice were unable to survive and expand due to aberrant differentiation and loss of stem and proliferative cells. Together, these results indicate that the role of MTGR1 in intestinal differentiation is likely stem cell intrinsic and identify a novel role for MTGR1 in maintaining ISC function.