RIPK1 Mediates TNF-Induced Intestinal Crypt Apoptosis During Chronic NF-κB Activation

Mechanisms of colon toxicity induced by long-term perfluorooctanoic acid exposure in mice

Perfluorooctanoic acid (PFOA), a persistent organic pollutant known for its chemical stability, is widely dispersed in the environment, posing significant health risks to mammals through various exposure routes such as ingestion, inhalation, and dermal contact. In this study, mice were exposed to PFOA (0, 0.2, 2 mg/L) through drinking water for 180 days to investigate its toxic effects on the colon. We identified differentially expressed genes through RNA sequencing and validated the impact of PFOA on the expression of these genes in colon tissue. Our findings revealed that long-term exposure to PFOA caused inflammatory bowel disease (IBD)-like damage to the mouse colon. We found PFOA could induce damage to the intestinal barrier. Inhibition of the Wnt signaling pathway following PFOA exposure results in impaired stem cell function in the colon of mice. Furthermore, PFOA activated the PPAR signaling pathway, disrupting cellular lipid metabolism in colon tissues. Additionally, PFOA induced inflammatory responses in colon tissue, facilitating NLR family, pyrin domain containing 3 (NLRP3) inflammasome activation and cell apoptosis. This study offers a thorough understanding of the mechanisms responsible for the damage to mouse colon tissue resulting from long-term exposure to PFOA.

Cryptosporidium impacts epithelial turnover and is resistant to induced death of the host cell

Infection with the apicomplexan parasite Cryptosporidium is a leading cause of diarrheal disease. Cryptosporidiosis is of particular importance in infants and shows a strong association with malnutrition, both as a risk factor and as a consequence. Cryptosporidium invades and replicates within the small intestine epithelial cells. This is a highly dynamic tissue that is developmentally stratified along the villus axis. New cells emerge from a stem cell niche in the crypt and differentiate into mature epithelial cells while moving toward the villus tip, where they are ultimately shed. Here, we studied the impact of Cryptosporidium infection on this dynamic architecture. Tracing DNA synthesis in pulse-chase experiments in vivo, we quantified the genesis and migration of epithelial cells along the villus. We found proliferation and epithelial migration to be elevated in response to Cryptosporidium infection. Infection also resulted in significant cell loss documented by imaging and molecular assays. Consistent with these observations, single-cell RNA sequencing of infected intestines showed a gain of young and a loss of mature cells. Interestingly, enhanced epithelial cell loss was not a function of enhanced apoptosis of infected cells. To the contrary, Cryptosporidium-infected cells were less likely to be apoptotic than bystanders, and experiments in tissue culture demonstrated that infection provided enhanced resistance to chemically induced apoptosis to the host but not bystander cells. Overall, this study suggests that Cryptosporidium may modulate cell apoptosis and documents pronounced changes in tissue homeostasis due to parasite infection, which may contribute to its long-term impact on the developmental and nutritional state of children.

IMPORTANCE

The intestine must balance its roles in digestion and nutrient absorption with the maintenance of an effective barrier to colonization and breach by numerous potential pathogens. An important component of this balance is its constant turnover, which is modulated by a gain of cells due to proliferation and loss due to death or extrusion. Here, we report that Cryptosporidium infection changes the dynamics of this process increasing both gain and loss of enterocytes speeding up the villus elevator. This leads to a much more immature epithelium and a reduction of the number of those cells typically found toward the villus apex best equipped to take up key nutrients including carbohydrates and lipids. These changes in the cellular architecture and physiology of the small intestine may be linked to the profound association between cryptosporidiosis and malnutrition.

Breaking Down Barriers: Epithelial Contributors to Monogenic IBD Pathogenesis

Monogenic causes of inflammatory bowel diseases (IBD) are increasingly being discovered. To date, much attention has been placed in those resulting from inborn errors of immunity. Therapeutic efforts have been largely focused on offering personalized immune modulation or curative bone marrow transplant for patients with IBD and underlying immune disorders. To date, less emphasis has been placed on monogenic causes of IBD that pertain to impairment of the intestinal epithelial barrier. Here, we provide a comprehensive review of monogenic causes of IBD that result in impaired intestinal epithelial barrier that are categorized into 6 important functions: (1) epithelial cell organization, (2) epithelial cell intrinsic functions, (3) epithelial cell apoptosis and necroptosis, (4) complement activation, (5) epithelial cell signaling, and (6) control of RNA degradation products. We illustrate how impairment of any of these categories can result in IBD. This work reviews the current understanding of the genes involved in maintaining the intestinal barrier, the inheritance patterns that result in dysfunction, features of IBD resulting from these disorders, and pertinent translational work in this field.

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.

RIPK1 and RIPK3 inhibitors: potential weapons against inflammation to treat diabetic complications

Diabetes mellitus is a metabolic disease that is characterized by chronic hyperglycemia due to a variety of etiological factors. Long-term metabolic stress induces harmful inflammation leading to chronic complications, mainly diabetic ophthalmopathy, diabetic cardiovascular complications and diabetic nephropathy. With diabetes complications being one of the leading causes of disability and death, the use of anti-inflammatories in combination therapy for diabetes is increasing. There has been increasing interest in targeting significant regulators of the inflammatory pathway, notably receptor-interacting serine/threonine-kinase-1 (RIPK1) and receptor-interacting serine/threonine-kinase-3 (RIPK3), as drug targets for managing inflammation in treating diabetes complications. In this review, we aim to provide an up-to-date summary of current research on the mechanism of action and drug development of RIPK1 and RIPK3, which are pivotal in chronic inflammation and immunity, in relation to diabetic complications which may be benefit for explicating the potential of selective RIPK1 and RIPK3 inhibitors as anti-inflammatory therapeutic agents for diabetic complications.

Treatment with Ligilactobacillus murinus lowers blood pressure and intestinal permeability in spontaneously hypertensive rats

One feature of hypertension is a microbial imbalance with increased intestinal permeability. In this study, we examined whether an alteration in the microbiota affects blood pressure and intestinal permeability in spontaneously hypertensive rats (SHRs). We performed a 16S metagenome analysis of feces from 10- to 15-week-old SHRs using a synthetic long-read sequencing approach, and found a candidate for the microbiome treatment, Ligilactobacillus murinus (L. murinus), that was robustly decreased. Oral administration of L. murinus to SHRs for 2 weeks significantly inhibited blood pressure elevation and improved endothelium-dependent vasodilation but did not attenuate enhanced vascular contraction in SHR mesenteric arteries. The proximal colon of SHRs exhibited increased intestinal permeability with decreased levels of the tight junction protein claudin 4, morphological changes such as decreased intestinal crypts and elevated TNF-α levels, which was reversed by treatment with L. murinus. Consistent with these intestinal phenotypes, plasma lipopolysaccharides levels were elevated in SHR but decreased following L. murinus administration. We concluded that oral administration of L. murinus to SHRs exerts protective effects on intestinal permeability via restoration of claudin 4 expression and reversal of morphologic disorder, which may improve low-grade endotoxemia and thus reduce development of hypertension via recovery of endothelial vasodilating functions.

Effects of lactic acid bacteria-fermented formula milk supplementation on colonic microbiota and mucosal transcriptome profile of weaned piglets

Supplemental probiotic fermented milk as a gut modulator can improve growth performance for weaned piglets by promoting the development of the small intestine in digestion and immune function. The effect on colon health might also play a considerable part in the favourable role of probiotic fermented milk in the growth performance improvement of weaned piglets; however, it has yet to be reported. This study aimed to investigate the effects of supplementation with lactic acid bacteria-fermented formula milk (LFM) on colonic morphology, microbiota composition, and mucosal transcriptome profile in weaned piglets. A total of 24 male weaned piglets were randomly divided into two groups: a control (CON) treatment or the LFM-supplemented treatment. Each group consisted of six replicates (cages) with two piglets per cage, and each piglet in the LFM group was supplemented with 80 mL LFM three times a day for 21 d, while the CON group was treated with the same amount of drinking water. Results showed that supplementation of LFM reduced the colonic histological damage scores and significantly increased the number of goblet cells per crypt. Furthermore, LFM consumption decreased the levels of pro-inflammation cytokines in the colonic mucosa. LFM downregulated the expression of inflammatory genes (CXCL9 and CXCL10) involving Toll-like receptor signalling pathway, immune response, and response to bacterium, and up-regulated two active genes (S100A8 and S100A9) involving the IL-17 signalling pathway and Toll-like receptor 4 binding. In addition, LFM could increase the potential probiotic genera containing Lachnospira and Anaerorhabdus furcosa group, which were positively related to short-chain fatty acid (SCFA) production. Correspondingly, LFM-fed piglets had higher total bacterial load and total SCFA concentration in the colonic digesta compared with the CON group. These novel findings support the benefits of LFM in enhancing intestinal homoeostasis and ameliorating weaning stress for weaned piglets, which is associated with the modulation of gut microbiota composition and immune-related genes.

Single-Cell transcriptomes of immune cells provide insights into the therapeutic effects of mycophenolate mofetil on autoimmune uveitis

Mycophenolate mofetil (MMF) is an immunosuppressive agent widely applied in various autoimmune diseases, including autoimmune uveitis, a sight-threatening autoimmune disease mainly affecting the eyes. However, the mechanisms of action are not comprehensively understood. To investigate the potential impact of MMF on uveitis, we generated single-cell RNA sequence data from normal, experimental autoimmune uveitis (EAU) and MMF-treated EAU mice. We observed that some EAU-induced transcriptional changes were reversed by MMF treatment. Transcriptional data indicated that MMF may have a general inhibitory effect on the activation of immune cells during EAU. Each immune cell type showed a different response to MMF treatment. Pseudotime analysis showed that MMF treatment partly reversed the increased differentiation tendency from naïve to effector phenotypes of T and B cells in EAU. The reduced proportion of T-helper (Th)1 and T-helper (Th)17 cells after MMF treatment was confirmed using flow cytometry. MMF treatment downregulated the EAU-associated upregulation of several molecules (such as Cebpd, Pim1, Furin, Bhlhe40, and Hif1a) that promote pathogenic cytokine production by T helper (Th)-1 and Th17 cells. Abnormally enhanced immunoglobulin production, antigen processing, and presentation ability of B cells may also be inhibited by MMF treatment. In addition to T and B cells, MMF treatment countered EAU-induced transcriptional changes in other immune cells to different degrees. Overall, our findings provide novel insights into the mechanisms underlying MMF treatment and indicate that the therapeutic effect of MMF is not driven by a single molecule.

The web of death: the expanding complexity of necroptotic signaling

The past decade has seen the emergence of the necroptosis programmed cell death pathway as an important contributor to the pathophysiology of myriad diseases. The receptor interacting protein kinase (RIPK)1 and RIPK3, and the pseudokinase executioner protein, mixed lineage kinase domain-like (MLKL), have grown to prominence as the core pathway components. Depending on cellular context, these proteins also serve as integrators of signals, such as post-translational modifications and protein or metabolite interactions, adding layers of complexity to pathway regulation. Here, we describe the emerging picture of the web of proteins that tune necroptotic signal transduction and how these events have diverged across species, presumably owing to selective pressures of pathogens upon the RIPK3-MLKL protein pair.

ABIN1 Inhibits Inflammation through Necroptosis-Dependent Pathway in Ulcerative Colitis

Background

Ulcerative colitis (UC) is characterized by chronic, recurrent intestinal inflammation and intestinal epithelial injury including a wide range of epithelial cell death, ulcers, crypt abscesses, and the formation of fibrosis. The intestinal barrier dysfunction runs through the whole process of the occurrence and development of UC. A recent study revealed that an ubiquitin binding protein ABIN1 played a role in tissue homeostasis and autoimmunity diseases which involved in the anti-inflammatory response of intestinal epithelia cells. However, the roles of ABIN1 in ulcerative colitis pathogenesis remain unclear.

Methods

The mRNA and protein expression level of ABIN1 and necroptosis-associated genes (RIPK1, RIPK3, and MLKL) were conducted to investigate the relationship between ABIN1 and necroptosis in clinical UC specimens. Subsequently, the dextran sodium sulfate (DSS)-induced mice colitis model was used to verify the ABIN1 function in vivo. Furthermore, we established ABIN1 gain and loss function assay in CACO-2 to confirm the mechanism in UC in vitro.

Results

We found that ABIN1, RIPK1, RIPK3, and MLKL were upregulated in UC sample and DSS-induced colitis. Upon TNF-α stimulation in the intestinal epithelia cell line, overexpression of ABIN1 significantly inhibits necroptosis in the intestinal inflammation model along with the reduction expression of pro-inflammatory cytokines such as IL1B, IL6, IL8, and TNF-α. Blocking RIPK1 by Nec-1s in vivo and in vitro dramatically alleviated the colitis and cell death which shares the same phenotype with ABIN1 overexpression.

Conclusion

Hence, the dysregulation of ABIN1 may relate to the uncontrolled necroptosis and inflammation in UC, and negatively regulate the occurrence and process of ulcerative colitis. ABIN1 activation may be considered a therapeutic strategy for UC.

Deubiquitinases in cell death and inflammation

Apoptosis, pyroptosis, and necroptosis are distinct forms of programmed cell death that eliminate infected, damaged, or obsolete cells. Many proteins that regulate or are a part of the cell death machinery undergo ubiquitination, a post-translational modification made by ubiquitin ligases that modulates protein abundance, localization, and/or activity. For example, some ubiquitin chains target proteins for degradation, while others function as scaffolds for the assembly of signaling complexes. Deubiquitinases (DUBs) are the proteases that counteract ubiquitin ligases by cleaving ubiquitin from their protein substrates. Here, we review the DUBs that have been found to suppress or promote apoptosis, pyroptosis, or necroptosis.

Microarray Profiling and Co-Expression Network Analysis of LncRNAs and mRNAs in Acute Respiratory Distress Syndrome Mouse Model

Background: Long noncoding RNAs (LncRNAs) play critical roles in many respiratory diseases. Acute respiratory distress syndrome (ARDS) is a destructive clinical syndrome of respiratory diseases. However, the potential mechanism of LncRNAs on ARDS remains largely unknown. Methods: To identify the profiles of LncRNAs and mRNAs in the LPS-induced ARDS mouse model, the microarray analyses were hired to detect the expression of LncRNAs and mRNAs in present study. Subsequently, microarray data were verified by quantitative qRT-PCR. Functional annotation on DE mRNAs and LncRNAs were carried out by bioinformatics analysis. Furthermore, the role of selected DE LncRNAs on correlated genes was confirmed by si-RNA and Western blot. Results: The expression of 2110 LncRNAs and 2690 mRNAs were significantly changed, which were further confirmed by qRT-PCR. GO and KEGG analysis indicated that the up-regulated mRNAs were mainly related to a defense response and tumor necrosis factor (TNF) signaling pathway, respectively. LncRNA-mRNA co-expression analyses showed that LncRNAs NR_003508, ENSMUST00000131638, ENSMUST00000119467, and ENSMUST00000124853 may correlate to MLKL, RIPK3, RIPK1, Caspase1, and NLRP3, respectively, or cooperatively, which were highly involved in the cell necroptosis process. Furthermore, siRNA for NR_003508 confirmed the co-expression analyses results. Conclusion: To summarize, this study implied that the DE LncRNAs could be potent regulators and target genes of ARDS and will provide a novel insight into the regulation of the pathogenesis of ARDS.

Extracellular vesicles of Fusobacterium nucleatum compromise intestinal barrier through targeting RIPK1-mediated cell death pathway

Microbial factors that mediate microbes-host interaction in ulcerative colitis (UC), a chronic disease seriously affecting human health, are not fully known. The emerging oncobacterium Fusobacterium nucleatum (Fn) secretes extracellular vesicles carrying several types of harmful molecules in the intestine which can alter microbes-host interaction, especially the epithelial homeostasis in UC. However, the mechanism is not yet clear. Previously, we isolated EVs by the ultracentrifugation of Fn culture media and characterized them as the potent inducer of pro-inflammatory cytokines. Here, we examined the mechanism in detail. We found that in macrophage/Caco-2 co-cultures, FnEVs significantly promoted epithelial barrier loss and oxidative stress damage, which are related to epithelial necroptosis caused by the activation of receptor-interacting protein kinase 1 (RIPK1) and receptor-interacting protein kinase 3 (RIPK3). Furthermore, FnEVs promoted the migration of RIPK1 and RIPK3 into necrosome in Caco2 cells. Notably, these effects were reversed by TNF-α neutralizing antibody or Necrostatin-1 (Nec-1), a RIPK1 inhibitor. This suggested that FADD-RIPK1-caspase-3 signaling is involved in the process. Moreover, the observed effects were verified in the murine colitis model treated with FnEVs or by adoptive transfer of FnEVs-trained macrophages. In conclusion, we propose that RIPK1-mediated epithelial cell death promotes FnEVs-induced gut barrier disruption in UC and the findings can be used as the basis to further investigate this disease.

Enteric Nervous System in Neonatal Necrotizing Enterocolitis

BACKGROUND

The pathophysiology of necrotizing enterocolitis (NEC) is not clear, but increasing information suggests that the risk and severity of NEC may be influenced by abnormalities in the enteric nervous system (ENS).

OBJECTIVE

The purpose of this review was to scope and examine the research related to ENS-associated abnormalities that have either been identified in NEC or have been noted in other inflammatory bowel disorders (IBDs) with histopathological abnormalities similar to NEC. The aim was to summarize the research findings, identify research gaps in existing literature, and disseminate them to key knowledge end-users to collaborate and address the same in future studies.

METHODS

Articles that met the objectives of the study were identified through an extensive literature search in the databases PubMed, EMBASE, and Scopus.

RESULTS

The sources identified through the literature search revealed that: (1) ENS may be involved in NEC development and post-NEC complications, (2) NEC development is associated with changes in the ENS, and (3) NEC-associated changes could be modulated by the ENS.

CONCLUSION

The findings from this review identify the enteric nervous as a target in the development and progression of NEC. Thus, factors that can protect the ENS can potentially prevent and treat NEC and post-NEC complications. This review serves to summarize the existing literature and highlights a need for further research on the involvement of ENS in NEC.

TNF-α synergises with IFN-γ to induce caspase-8-JAK1/2-STAT1-dependent death of intestinal epithelial cells

Rewiring of host cytokine networks is a key feature of inflammatory bowel diseases (IBD) such as Crohn's disease (CD). Th1-type cytokines-IFN-γ and TNF-α-occupy critical nodes within these networks and both are associated with disruption of gut epithelial barrier function. This may be due to their ability to synergistically trigger the death of intestinal epithelial cells (IECs) via largely unknown mechanisms. In this study, through unbiased kinome RNAi and drug repurposing screens we identified JAK1/2 kinases as the principal and nonredundant drivers of the synergistic killing of human IECs by IFN-γ/TNF-α. Sensitivity to IFN-γ/TNF-α-mediated synergistic IEC death was retained in primary patient-derived intestinal organoids. Dependence on JAK1/2 was confirmed using genetic loss-of-function studies and JAK inhibitors (JAKinibs). Despite the presence of biochemical features consistent with canonical TNFR1-mediated apoptosis and necroptosis, IFN-γ/TNF-α-induced IEC death was independent of RIPK1/3, ZBP1, MLKL or caspase activity. Instead, it involved sustained activation of JAK1/2-STAT1 signalling, which required a nonenzymatic scaffold function of caspase-8 (CASP8). Further modelling in gut mucosal biopsies revealed an intercorrelated induction of the lethal CASP8-JAK1/2-STAT1 module during ex vivo stimulation of T cells. Functional studies in CD-derived organoids using inhibitors of apoptosis, necroptosis and JAKinibs confirmed the causative role of JAK1/2-STAT1 in cytokine-induced death of primary IECs. Collectively, we demonstrate that TNF-α synergises with IFN-γ to kill IECs via the CASP8-JAK1/2-STAT1 module independently of canonical TNFR1 and cell death signalling. This non-canonical cell death pathway may underpin immunopathology driven by IFN-γ/TNF-α in diverse autoinflammatory diseases such as IBD, and its inhibition may contribute to the therapeutic efficacy of anti-TNFs and JAKinibs.

Indole-3-carbinol ameliorates necroptosis and inflammation of intestinal epithelial cells in mice with ulcerative colitis by activating aryl hydrocarbon receptor

Ulcerative colitis (UC) is a disease characterized by inflammation and disruption of the intestinal epithelial barrier. Necroptosis plays a critical role in disease progression. Indole-3-carbinol (I3C), a natural dietary agonist of aryl hydrocarbon receptor (AHR), has shown alleviating effects on UC. However, its mechanisms of action have not been comprehensively elucidated. Therefore, we aimed at investigating the protective role of I3C in DSS-induced colitis mice models. I3C significantly ameliorated body weight loss, colon length shortening and colonic pathological damage in colitis mice, reduced disease activity index (DAI) and histological (HI) scores, as well as alleviated colonic necroptosis and inflammation. In vitro, I3C attenuated necroptosis and inflammation of colonoids and NCM460 cells. AHR, activated by I3C, inhibits activation of receptor-interacting protein kinase 1 (RIPK1) and the subsequent assembly of necrosome in a time-dependent manner, as well as suppressing NF-κB activation and decreasing TNF-α, IL-1β, IL-6 and IL-8 expression. Silencing of AHR aggravated necroptosis and inflammation of NCM460 cells, and did not be ameliorated by I3C. Furthermore, AHR activation induces the expression of inhibitor of apoptosis proteins (IAPs) and the ubiquitination of RIPK1. In conclusion, I3C exerts a protective effect in DSS-induced colitis mice models by alleviating the necroptosis and inflammation of IECs through activating AHR.

MiR-223 promotes pyroptosis of enteritis cells through activating NF-κB signalling pathway by targeting SNIP1 in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a common inflammation-related intestinal disease. Studies have shown that excessive pyroptosis of intestinal cells is involved in the development of IBD. However, the regulatory mechanism of pyroptosis in IBD remains unclear. Here, our study purposed to clarify the underlying regulatory mechanism of miR-223 to promote pyroptosis in IBD.MiR-223 and Smad Nuclear Interacting Protein 1 (SNIP1) expression in colon tissues collected from IBD patients and healthy volunteers were evaluated using qRT-PCR. Cell viability and pyroptosis were evaluated by CCK8 and flow cytometry assay, respectively. Pyroptosis-related proteins and nuclear factor κB (NF-κB) signals were determined by WB. Dual-luciferase reporter gene assay was employed to investigate the binding relationship between miR-223 and SNIP1.MiR-223 was significantly upregulated in IBD colon tissues and cell models, while SNIP1 was significantly decreased. Silence of miR-223 markedly enhanced cell viability and inhibited pyroptosis in the IBD cell model. MiR-223 could bind to 3'-UTR of SNIP1 and SNIP1 could activate NF-κB signalling pathway. Further rescued experiment found that knockdown of SNIP1 dramatically abolished the bio-effects mediated by miR-223 silence on the cell viability and pyroptosis of the IBD cell model. Likewise, the inactivation of NF-κB signalling markedly weakened the regulatory roles of SNIP1 downregulation in the IBD cell model. Besides, inhibition of NF-κB signalling attenuated the pyroptosis-promoting effect of overexpressing miR-223.Our data suggested that miR-223 activated the NF-κB pathway via targeting SNIP1, thus promoting the process of cell pyroptosis, and ultimately participating in the pathogenesis of IBD.

Genetic inactivation of RIP1 kinase activity in rats protects against ischemic brain injury

RIP1 kinase-mediated inflammatory and cell death pathways have been implicated in the pathology of acute and chronic disorders of the nervous system. Here, we describe a novel animal model of RIP1 kinase deficiency, generated by knock-in of the kinase-inactivating RIP1(D138N) mutation in rats. Homozygous RIP1 kinase-dead (KD) rats had normal development, reproduction and did not show any gross phenotypes at baseline. However, cells derived from RIP1 KD rats displayed resistance to necroptotic cell death. In addition, RIP1 KD rats were resistant to TNF-induced systemic shock. We studied the utility of RIP1 KD rats for neurological disorders by testing the efficacy of the genetic inactivation in the transient middle cerebral artery occlusion/reperfusion model of brain injury. RIP1 KD rats were protected in this model in a battery of behavioral, imaging, and histopathological endpoints. In addition, RIP1 KD rats had reduced inflammation and accumulation of neuronal injury biomarkers. Unbiased proteomics in the plasma identified additional changes that were ameliorated by RIP1 genetic inactivation. Together these data highlight the utility of the RIP1 KD rats for target validation and biomarker studies for neurological disorders.

Prevention and Alleviation of Dextran Sulfate Sodium Salt-Induced Inflammatory Bowel Disease in Mice With Bacillus subtilis-Fermented Milk via Inhibition of the Inflammatory Responses and Regulation of the Intestinal Flora

The pathogenesis of inflammatory bowel disease (IBD) might be related to the local inflammatory damage and the dysbacteriosis of intestinal flora. Probiotics can regulate the intestinal flora and ameliorate IBD. The probiotic Bacillus subtilis strain B. subtilis JNFE0126 was used as the starter of fermented milk. However, the therapeutic effects of B. subtilis-fermented milk on IBD remain to be explored. In this research, the therapeutic effect of B. subtilis-fermented milk on dextran sulfate sodium salt (DSS)-induced IBD mouse model was evaluated. Besides, the expression of pro-inflammatory/anti-inflammatory cytokines, the proliferation of the intestinal stem cells, and the reconstruction of the mucosa barrier were investigated. Finally, alteration of the gut microbiota was investigated by taxonomic analysis. As shown by the results, the disease activity index (DAI) of IBD was significantly decreased through oral administration of B. subtilis (JNFE0126)-fermented milk, and intestinal mucosa injury was attenuated. Moreover, B. subtilis could reduce the inflammatory response of the intestinal mucosa, induce proliferation of the intestinal stem cell, and promote reconstruction of the mucosal barrier. Furthermore, B. subtilis could rebalance the intestinal flora, increasing the abundance of Bacillus, Alistipes, and Lactobacillus while decreasing the abundance of Escherichia and Bacteroides. In conclusion, oral administration of the B. subtilis-fermented milk could alleviate DSS-induced IBD via inhibition of inflammatory response, promotion of the mucosal barrier reconstruction, and regulation of the intestinal flora.

The Herbal Medicine Scutellaria-Coptis Alleviates Intestinal Mucosal Barrier Damage in Diabetic Rats by Inhibiting Inflammation and Modulating the Gut Microbiota

Recent studies have confirmed that increased intestinal permeability and gut-origin lipopolysaccharide (LPS) translocation are important causes of metabolic inflammation in type 2 diabetes (T2D), but there are no recognized therapies for targeting this pathological state. Scutellaria baicalensis and Coptis chinensis are a classic herbal pair often used to treat diabetes and various intestinal diseases, and repair of intestinal barrier damage may be at the core of their therapeutic mechanism. This study investigated the effects of oral administration of Scutellaria-Coptis (SC) on the intestinal mucosal barrier in diabetic rats and explored the underlying mechanism from the perspective of anti-inflammatory and gut microbiota-modulatory effects. The main results showed that, in addition to regulating glycolipid metabolism disorders and inhibiting serum inflammatory factors, SC could also upregulate the expression levels of the tight junction proteins claudin-1, occludin, and zonula occludens (ZO-1), significantly improve intestinal epithelial damage, and inhibit excessive LPS translocation into the blood circulation. Furthermore, it was found that SC could reduce the levels of the inflammatory factors interleukin-1β (IL-1β), IL-6, and tumour necrosis factor-α (TNF-α) in intestinal tissue and that the anti-inflammatory effects involved the TLR-4/TRIF and TNFR-1/NF-κB signalling pathways. Moreover, SC had a strong inhibitory effect on some potential enteropathogenic bacteria and LPS-producing bacteria, such as Proteobacteria, Enterobacteriaceae, Enterobacter, Escherichia-Shigella, and Enterococcus, and could also promote the proliferation of butyrate-producing bacteria, such as Lachnospiraceae and Prevotellaceae. Taken together, the hypoglycaemic effects of SC were related to the protection of the intestinal mucosal barrier, and the mechanisms might be related to the inhibition of intestinal inflammation and the regulation of the gut microbiota.

The Balance of TNF Mediated Pathways Regulates Inflammatory Cell Death Signaling in Healthy and Diseased Tissues

Tumor necrosis factor alpha (TNF; TNFα) is a critical regulator of immune responses in healthy organisms and in disease. TNF is involved in the development and proper functioning of the immune system by mediating cell survival and cell death inducing signaling. TNF stimulated signaling pathways are tightly regulated by a series of phosphorylation and ubiquitination events, which enable timely association of TNF receptors-associated intracellular signaling complexes. Disruption of these signaling events can disturb the balance and the composition of signaling complexes, potentially resulting in severe inflammatory diseases.

SMAC mimetics and RIPK inhibitors as therapeutics for chronic inflammatory diseases

New therapeutic approaches for chronic inflammatory diseases such as inflammatory bowel disease, rheumatoid arthritis, and psoriasis are needed because current treatments are often suboptimal in terms of both efficacy and the risks of serious adverse events. Inhibitor of apoptosis proteins (IAPs) are E3 ubiquitin ligases that inhibit cell death pathways and are themselves inhibited by second mitochondria-derived activator of caspases (SMAC). SMAC mimetics (SMs), small-molecule antagonists of IAPs, are being evaluated as cancer therapies in clinical trials. IAPs are also crucial regulators of inflammatory pathways because they influence both the activation of inflammatory genes and the induction of cell death through the receptor-interacting serine-threonine protein kinases (RIPKs), nuclear factor κB (NF-κB)-inducing kinase, and mitogen-activated protein kinases (MAPKs). Furthermore, there is an increasing interest in specifically targeting the substrates of IAP-mediated ubiquitylation, especially RIPK1, RIPK2, and RIPK3, as druggable nodes in inflammation control. Several studies have revealed an anti-inflammatory potential of RIPK inhibitors that either block inflammatory signaling or block the form of inflammatory cell death known as necroptosis. Expanding research on innate immune signaling through pattern recognition receptors that stimulate proinflammatory NF-κB and MAPK signaling may further contribute to uncovering the complex molecular roles used by IAPs and downstream RIPKs in inflammatory signaling. This may benefit and guide the development of SMs or selective RIPK inhibitors as anti-inflammatory therapeutics for various chronic inflammatory conditions.

Methamphetamine Induces Intestinal Inflammatory Injury via Nod-Like Receptor 3 Protein (NLRP3) Inflammasome Overexpression In Vitro and In Vivo

BACKGROUND Methamphetamine (METH), a confirmed neurotoxic drug, has also reportedly caused several intestinal inflammatory injury cases. The NLRP3 (Nod-like receptor 3 protein) inflammasome can induce several inflammatory injuries by activating IL-1ß and IL-18 when overexpressed. We designed experiments to determine whether METH can cause intestinal inflammatory injury via NLRP3 inflammasome overexpression. MATERIAL AND METHODS IEC-6 cells were classified as control, METH (0.5 mM), and METH (0.5 mM)+MCC950 (100 μM) groups. C57BL/6 mice were separated into control, NS, METH (5 mg/kg), and METH (5 mg/kg)+MCC950 (10 mg/kg) groups (n=10). We detected apoptosis, transepithelial electrical resistance (TEER), and proinflammatory factors (IL-6, INF-γ, TNF-alpha, and NF-kappaB) in the METH cell model. We also assessed proinflammatory factors (IL-6, INF-γ, TNF-alpha, and NF-kappaB) and observed intestinal tissues stained with hematoxylin and eosin (HE) in the METH animal model to explore intestinal inflammatory injury due to METH. After adding MCC950 (an NLRP3 inflammasome inhibitor), we additionally detected NLRP3 inflammasome components (NLRP3, Caspase-1, and ASC), IL-1ß, and IL-18 to estimate the relationship of the NLRP3 inflammasome with intestinal inflammatory injury due to METH. RESULTS METH can lead apoptosis, increase proinflammatory factors (e.g., IL-6, INF-γ, TNF-alpha, and NF-kappaB), and decrease TEER in the METH cell model. In the METH animal model, METH can cause obvious injury and increase proinflammatory factors (e.g., IL-6, INF-γ, TNF-alpha, and NF-kappaB). All the intestinal inflammatory changes due to METH depended on overexpression of the NLRP3 inflammasome and could be ameliorated by MCC950, except for ASC and NF-kappaB. CONCLUSIONS METH, in addition to being a confirmed neurotoxic drug, can also cause severe intestinal inflammatory injury via NLRP3 inflammasome overexpression. NF-kappaB may be an activator of the NLRP3 inflammasome in METH intestinal inflammatory injury.