Canonical and noncanonical inflammasomes in intestinal epithelial cells

The interplay between cell death and senescence in cancer

Cellular senescence is a state of permanent proliferative arrest that occurs in response to DNA damage-inducing endogenous and exogenous stresses, and is often accompanied by dynamic molecular changes such as a senescence-associated secretory phenotype (SASP). Accumulating evidence indicates that age-associated increases in the upstream and downstream signals of regulated cell death, including apoptosis, necroptosis, pyroptosis, and ferroptosis, are closely related to the induction of cellular senescence and its phenotype. Furthermore, elevated levels of pro-inflammatory SASP factors with aging can be both a cause and consequence of several cell death modes, suggesting the reciprocal effects of cellular senescence and cells undergoing regulated cell death. Here, we review the critical molecular pathways of the regulated cell death forms and describe the crosstalk between aging-related signals and cancer. In addition, we discuss how targeting regulated cell death could be harnessed in therapeutic interventions for cancer. ABBREVIATIONS: Abbreviations that are not standard in this field are defined at their first occurrence in the article and are used consistently throughout the article.

Inflammasomes in chronic liver disease: Hepatic injury, fibrosis progression and systemic inflammation

Chronic liver disease leads to hepatocellular injury that triggers a pro-inflammatory state in several parenchymal and non-parenchymal hepatic cell types, ultimately resulting in liver fibrosis, cirrhosis, portal hypertension and liver failure. Thus, an improved understanding of inflammasomes - as key molecular drivers of liver injury - may result in the development of novel diagnostic or prognostic biomarkers and effective therapeutics. In liver disease, innate immune cells respond to hepatic insults by activating cell-intrinsic inflammasomes via toll-like receptors and NF-κB, and by releasing pro-inflammatory cytokines (such as IL-1β, IL-18, TNF-α and IL-6). Subsequently, cells of the adaptive immune system are recruited to fuel hepatic inflammation and hepatic parenchymal cells may undergo gasdermin D-mediated programmed cell death, termed pyroptosis. With liver disease progression, there is a shift towards a type 2 inflammatory response, which promotes tissue repair but also fibrogenesis. Inflammasome activation may also occur at extrahepatic sites, such as the white adipose tissue in MASH (metabolic dysfunction-associated steatohepatitis). In end-stage liver disease, flares of inflammation (e.g., in severe alcohol-related hepatitis) that spark on a dysfunctional immune system, contribute to inflammasome-mediated liver injury and potentially result in organ dysfunction/failure, as seen in ACLF (acute-on-chronic liver failure). This review provides an overview of current concepts regarding inflammasome activation in liver disease progression, with a focus on related biomarkers and therapeutic approaches that are being developed for patients with liver disease.

NLRP1B allele 2 does not respond to Val-boro-Pro (VbP) in intestinal epithelial cells

The intestinal mucosa must balance tolerance to commensal microbes and luminal antigens with rapid detection of enteric pathogens in order to maintain homeostasis. This balance is facilitated through the regulation of epithelial layer integrity by innate immune receptors. Certain NOD-like receptors (NLRs) expressed in intestinal epithelial cells, including NLRC4 and NLRP9B, form inflammasomes that protect against pathogens by activating caspase-1 to cause extrusion of infected cells. NLRP1B is a murine NLR encoded by five alleles of a highly polymorphic gene homologous to human NLRP1. NLRP1B forms inflammasomes in response to a variety of pathogens that cause intestinal infections, but it has almost exclusively been studied in immune cells and has not been characterized in cells of the intestinal epithelium. Here, we show that Nlrp1b allele 2 is expressed in ileal and colonic organoids derived for C57BL/6J mice, while the related gene Nlrp1a was not expressed. Nlrp1b was upregulated by interleukin-13 in organoids and by the protozoan Tritrichomonas muris in vivo, suggesting that NLRP1B may be involved in defense against enteric parasites. Surprisingly, while Val-boro-Pro (VbP) activated C57BL/6J-derived bone marrow-derived macrophages, which expressed both Nlrp1a and Nlrp1b, it did not activate intestinal organoids of the same genotype. We furthermore did not detect Nlrp1b in organoids derived from Balb/cJ mice, which express a different allele than the one expressed in C57BL/6J mice. Together, our results suggest that NLRP1B may have an allele-dependent function in murine IECs whose regulation is distinct from that of macrophages, and that the response to VbP might be exclusively driven by NLRP1A in C57BL/6J mice.

Embryo-Derived Cathepsin B Promotes Implantation and Decidualization by Activating Pyroptosis

Embryo implantation and decidualization are crucial for a successful pregnancy. How the inflammatory response is regulated during these processes is undefined. Pyroptosis is an inflammatory form of cell death mediated by gasdermin D (GSDMD). Through in vivo, cultured epithelial cells and organoids, it is shown that pyroptosis occurs in epithelial cells at the implantation site. Compared with those on day 4 of pseudopregnancy and delayed implantation, pyroptosis-related protein levels are significantly increased on day 4 of pregnancy and activated implantation, suggesting that blastocysts are involved in regulating pyroptosis. Blastocyst-derived cathepsin B (CTSB) is stimulated by preimplantation estradiol-17β and induces pyroptosis in epithelial cells. Pyroptosis-induced IL-18 secretion from epithelial cells activates a disintegrin and metalloprotease 12 (ADAM12) to process the epiregulin precursor into mature epiregulin. Epiregulin (EREG) enhances in vitro decidualization in mice. Pyroptosis-related proteins are detected in the mid-secretory human endometrium and are elevated in the recurrent implantation failure endometrium. Lipopolysaccharide treatment in pregnant mice causes implantation failure and increases pyroptosis-related protein levels. Therefore, the data suggest that modest pyroptosis is beneficial for embryo implantation and decidualization. Excessive pyroptosis can be harmful and lead to pregnancy failure.

Delayed Mucosal Antiviral Responses Despite Robust Peripheral Inflammation in Fatal COVID-19

BACKGROUND

While inflammatory and immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in peripheral blood are extensively described, responses at the upper respiratory mucosal site of initial infection are relatively poorly defined. We sought to identify mucosal cytokine/chemokine signatures that distinguished coronavirus disease 2019 (COVID-19) severity categories, and relate these to disease progression and peripheral inflammation.

METHODS

We measured 35 cytokines and chemokines in nasal samples from 274 patients hospitalized with COVID-19. Analysis considered the timing of sampling during disease, as either the early (0-5 days after symptom onset) or late (6-20 days after symptom onset) phase.

RESULTS

Patients that survived severe COVID-19 showed interferon (IFN)-dominated mucosal immune responses (IFN-γ, CXCL10, and CXCL13) early in infection. These early mucosal responses were absent in patients who would progress to fatal disease despite equivalent SARS-CoV-2 viral load. Mucosal inflammation in later disease was dominated by interleukin 2 (IL-2), IL-10, IFN-γ, and IL-12p70, which scaled with severity but did not differentiate patients who would survive or succumb to disease. Cytokines and chemokines in the mucosa showed distinctions from responses evident in the peripheral blood, particularly during fatal disease.

CONCLUSIONS

Defective early mucosal antiviral responses anticipate fatal COVID-19 but are not associated with viral load. Early mucosal immune responses may define the trajectory of severe COVID-19.

Inflammasomes in epithelial innate immunity: front line warriors

Our epithelium represents a battle ground against a variety of insults including pathogens and danger signals. It encodes multiple sensors that detect and respond to such insults, playing an essential role in maintaining and defending tissue homeostasis. One key set of defense mechanisms is our inflammasomes which drive innate immune responses including, sensing and responding to pathogen attack, through the secretion of pro-inflammatory cytokines and cell death. Identification of physiologically relevant triggers for inflammasomes has greatly influenced our ability to decipher the mechanisms behind inflammasome activation. Furthermore, identification of patient mutations within inflammasome components implicates their involvement in a range of epithelial diseases. This review will focus on exploring the roles of inflammasomes in epithelial immunity and cover: the diversity and differential expression of inflammasome sensors amongst our epithelial barriers, their ability to sense local infection and damage and the contribution of the inflammasomes to epithelial homeostasis and disease.

LNCGM1082 in Gut Epithelial Cells Promotes Expulsion of Infected Epithelial Cells and Release of IL-18

Inflammasome NLRC4 (NLR family CARD domain containing 4) can protect mucosal barriers such as intestine from invading bacterial pathogens. However, it was incompletely clear how NLRC4 was activated in intestinal epithelial cells. In this study, we demonstrated that LNCGM1082 could mediate the activation of NLRC4 via binding NLRC4 with protein kinase C (PKC)δ. LNCGM1082 knockout (KO) mice had reduced resistance against Salmonella Typhimurium infection, as well as impaired expulsion of infected gut epithelial cells and release of IL-18 upon exposure to S. Typhimurium. Similar to NLRC4 KO and PKCδ knockdown gut organoids, there also was impaired expulsion of gut epithelial cells and release of IL-18 in LNCGM1082 KO gut organoids. Furthermore, there also was reduced activation of caspase-1 and caspase-8 in these LNCGM1082 KO, NLRC4 KO, and PKCδ knockdown gut organoids upon exposure to S. Typhimurium. Our results show that LNCGM1082 in the ICEs plays a critical role in mediating activation of NLRC4 through binding NLRC4 and PKCδ and promoting expulsion of infected epithelial cells and release of IL-18 upon exposure to bacteria such as S. Typhimurium.

Interplay of G-proteins and Serotonin in the Neuroimmunoinflammatory Model of Chronic Stress and Depression: A Narrative Review

INTRODUCTION

This narrative review addresses the clinical challenges in stress-related disorders such as depression, focusing on the interplay between neuron-specific and pro-inflammatory mechanisms at the cellular, cerebral, and systemic levels.

OBJECTIVE

We aim to elucidate the molecular mechanisms linking chronic psychological stress with low-grade neuroinflammation in key brain regions, particularly focusing on the roles of G proteins and serotonin (5-HT) receptors.

METHODS

This comprehensive review of the literature employs systematic, narrative, and scoping review methodologies, combined with systemic approaches to general pathology. It synthesizes current research on shared signaling pathways involved in stress responses and neuroinflammation, including calcium-dependent mechanisms, mitogen-activated protein kinases, and key transcription factors like NF-κB and p53. The review also focuses on the role of G protein-coupled neurotransmitter receptors (GPCRs) in immune and pro-inflammatory responses, with a detailed analysis of how 13 of 14 types of human 5-HT receptors contribute to depression and neuroinflammation.

RESULTS

The review reveals a complex interaction between neurotransmitter signals and immunoinflammatory responses in stress-related pathologies. It highlights the role of GPCRs and canonical inflammatory mediators in influencing both pathological and physiological processes in nervous tissue.

CONCLUSION

The proposed Neuroimmunoinflammatory Stress Model (NIIS Model) suggests that proinflammatory signaling pathways, mediated by metabotropic and ionotropic neurotransmitter receptors, are crucial for maintaining neuronal homeostasis. Chronic mental stress can disrupt this balance, leading to increased pro-inflammatory states in the brain and contributing to neuropsychiatric and psychosomatic disorders, including depression. This model integrates traditional theories on depression pathogenesis, offering a comprehensive understanding of the multifaceted nature of the condition.

He protec but he also attac - Inflammasomes swinging the sword

This issue of the Biomedical Journal puts an emphasis on inflammasome subunits, the NLR protein family, and the role they play in immunity. CIITA is presented as promising tool for augmenting tumor immunogenicity. Several articles look into the involvement of NLRP3 in inflammatory bowel disease and changes of the gut microbiome, in blood glucose management, in sterile inflammation, and NLRP3's contribution to the development of hepatic encephalopathy. Furthermore, a review concerning small cell neuroendocrine carcinoma of the cervix is presented, insights are provided as to the association of knee pain and patellar malalignment, and the connection between hypoxia and sleep apnea in the case of liver injury is elucidated. Additional articles illuminate the challenge of predicting influenza infections; show how ctDNA may serve as predictor for survival outcome in ovarian carcinoma; and lastly soft tissue changes after bimaxillary rotational surgery are assessed.

Microbiota and Glucidic Metabolism: A Link with Multiple Aspects and Perspectives

The global prevalence of overweight and obesity has dramatically increased in the last few decades, with a significant socioeconomic burden. In this narrative review, we include clinical studies aiming to provide the necessary knowledge on the role of the gut microbiota in the development of diabetic pathology and glucose-metabolism-related disorders. In particular, the role of a certain microbial composition of the fermentative type seems to emerge without a specific link to the development in certain subjects of obesity and the chronic inflammation of the adipose tissues, which underlies the pathological development of all the diseases related to glucose metabolism and metabolic syndrome. The gut microbiota plays an important role in glucose tolerance. Conclusion. New knowledge and new information is presented on the development of individualized therapies for patients affected by all the conditions related to reduced glucose tolerance and insulin resistance.

Toxoplasma gondii profilin induces NLRP3 activation and IL-1β production/secretion in THP-1 cells

Toxoplasma gondii is a highly prevalent protozoan that infects a broad spectrum of warm-blooded animals. Profilin is a critical protein that plays a role in the movement and invasion of T. gondii. In the current study, we assessed how profilin stimulates inflammasomes and how it induces transcription and secretion of IL-1β. For this purpose, we assessed the level of TLR 2, 4, 5, and 9 expressions in a THP-1 cell line treated with profilin from T. gondii (TgP). In addition, we analyzed the expression levels of various inflammasomes, as well as IL-1β, and IL-18 in THP-1 cells treated with the NLRP3 inhibitor MCC950. TgP significantly increased the expression of TLR5 but the expression of TLR2, 4, and 9 was not significantly increased. In addition, TgP did not significantly increase the level of inflammasomes after 5 h. Treatment with MCC950 significantly reduced NLRP3 and IL-1β on both transcription and protein levels. Although the transcription level of NLRP3 was reduced 5 h after treatment with TgP, western blot analysis showed an increase in NLRP3. The western blot and ELISA analysis also showed that TgP increased both pro- and mature IL-1β. In summary, our study showed that NLRP3 most probably plays a pivotal role in the expression and production levels of IL-1β during the interaction between TgP and macrophages.

Exploring immune interactions in triple negative breast cancer: IL-1β inhibition and its therapeutic potential

Triple negative breast cancer (TNBC) has poor prognosis when compared to other breast cancer subtypes. Despite pre-clinical data supporting an immune targeted approach for TNBCs, immunotherapy has failed to demonstrate the impressive responses seen in other solid tumor malignancies. Additional strategies to modify the tumor immune microenvironment and potentiate response to immunotherapy are needed. In this review, we summarise phase III data supporting the use of immunotherapy for TNBC. We discuss the role of IL-1β in tumorigenesis and summarize pre-clinical data supporting IL-1β inhibition as a potential therapeutic strategy in TNBC. Finally, we present current trials evaluating IL-1β in breast cancer and other solid tumor malignancies and discuss future studies that may provide a strong scientific rationale for the combination of IL-1β and immunotherapy in the neoadjuvant and metastatic setting for people with TNBC.

Mechanisms of gut microbiota-immune-host interaction on glucose regulation in type 2 diabetes

Intestinal absorption of food is one of the sources of glucose. Insulin resistance and impaired glucose tolerance caused by lifestyle and diet are the precursors of type 2 diabetes. Patients with type 2 diabetes have trouble controlling their blood sugar levels. For long-term health, strict glycemic management is necessary. Although it is thought to be well correlated with metabolic diseases like obesity, insulin resistance, and diabetes, its molecular mechanism is still not completely understood. Disturbed microbiota triggers the gut immune response to reshape the gut homeostasis. This interaction not only maintains the dynamic changes of intestinal flora, but also preserves the integrity of the intestinal barrier. Meanwhile, the microbiota establishes a systemic multiorgan dialog on the gut-brain and gut-liver axes, intestinal absorption of a high-fat diet affects the host's feeding preference and systemic metabolism. Intervention in the gut microbiota can combat the decreased glucose tolerance and insulin sensitivity linked to metabolic diseases both centrally and peripherally. Moreover, the pharmacokinetics of oral hypoglycemic medications are also influenced by gut microbiota. The accumulation of drugs in the gut microbiota not only affects the drug efficacy, but also changes the composition and function of them, thus may help to explain individual therapeutic variances in pharmacological efficacy. Regulating gut microbiota through healthy dietary patterns or supplementing pro/prebiotics can provide guidance for lifestyle interventions in people with poor glycemic control. Traditional Chinese medicine can also be used as complementary medicine to effectively regulate intestinal homeostasis. Intestinal microbiota is becoming a new target against metabolic diseases, so more evidence is needed to elucidate the intricate microbiota-immune-host relationship, and explore the therapeutic potential of targeting intestinal microbiota.

IL-1β and Allergy: Focusing on Its Role in Allergic Rhinitis

Allergic rhinitis (AR) is a chronic upper airway immune-inflammation response mediated by immunoglobulin E (IgE) to allergens and can seriously affect the quality of life and work efficiency. Previous studies have shown that interleukin-1β (IL-1β) acts as a key cytokine to participate in and promote the occurrence and development of allergic diseases. It has been proposed that IL-1β may be a potential biomarker of AR. However, its definitive role and potential mechanism in AR have not been fully elucidated, and the clinical sample collection and detection methods were inconsistent among different studies, which have limited the use of IL-1β as a clinical diagnosis and treatment marker for AR. This article systematically summarizes the research advances in the roles of IL-1β in allergic diseases, focusing on the changes of IL-1β in AR and the possible interventions. In addition, based on the findings by our team, we provided new insights into the use of IL-1β in AR diagnosis and treatment, in an attempt to further promote the clinical application of IL-1β in AR and other allergic diseases.

Molecular characterization and functional study of the NLRP3 inflammasome genes in Tetraodon nigroviridis

Nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome is an important inflammasome in mammals, which is of great significance to eliminate pathogens. However, the research of the NLRP3 inflammasome in teleost is limited. Tetraodon nigroviridis has the characteristics of small genome and easy feeding, which can be used as a model for the study of fish immune function. In present study, three NLRP3 inflammasome component genes (NLRP3, ASC and caspase-1) in T. nigroviridis has been cloned. Real-time fluorescence quantitative PCR showed that TnNLRP3 (T. nigroviridis NLRP3), TnASC (T. nigroviridis ASC) and Tncaspase-1 (T. nigroviridis caspase-1) mRNA in various tissues from health T. nigroviridis were highly expressed in immune-related tissues, such as spleen, gill, head kidney and intestine. After Vibrio parahemolyticus infection, the expression of TnNLRP3, TnASC and Tncaspase-1 mRNA in spleen, gill, head kidney reached a peak at 24 h, and the expression levels of these genes in intestine were the highest at 48 h. After the transfection of TnASC-pAcGFP-N1 monomer GFP plasmid into cos-7 cells, ASC specks, the activation marker of NLRP3 inflammasome, were observed. Bimolecular fluorescence complementarity and fluorescence colocation experiment showed that TnASC and Tncaspase-1 of TnNLRP3 inflammasome were co-located near the cell nucleus, and potentially interacted with each other. NLRP3 inflammasome inducer nigericin and agonist ATP could significantly induce the expression of TnNLRP3, TnASC and Tncaspase-1 mRNA, and activation of NLRP3 inflammasome could promote the generation of mature TnIL-1β (T. nigroviridis IL-1β). These results uncover that T. nigroviridis NLRP3 inflammasome could participate in the antibacterial immune response and the generation of mature TnIL-1β after activation.

SARS-CoV-2 infection of phagocytic immune cells and COVID-19 pathology: Antibody-dependent as well as independent cell entry

Our review summarizes the evidence that COVID-19 can be complicated by SARS-CoV-2 infection of immune cells. This evidence is widespread and accumulating at an increasing rate. Research teams from around the world, studying primary and established cell cultures, animal models, and analyzing autopsy material from COVID-19 deceased patients, are seeing the same thing, namely that some immune cells are infected or capable of being infected with the virus. Human cells most vulnerable to infection include both professional phagocytes, such as monocytes, macrophages, and dendritic cells, as well as nonprofessional phagocytes, such as B-cells. Convincing evidence has accumulated to suggest that the virus can infect monocytes and macrophages, while data on infection of dendritic cells and B-cells are still scarce. Viral infection of immune cells can occur directly through cell receptors, but it can also be mediated or enhanced by antibodies through the Fc gamma receptors of phagocytic cells. Antibody-dependent enhancement (ADE) most likely occurs during the primary encounter with the pathogen through the first COVID-19 infection rather than during the second encounter, which is characteristic of ADE caused by other viruses. Highly fucosylated antibodies of vaccinees seems to be incapable of causing ADE, whereas afucosylated antibodies of persons with acute primary infection or convalescents are capable. SARS-CoV-2 entry into immune cells can lead to an abortive infection followed by host cell pyroptosis, and a massive inflammatory cascade. This scenario has the most experimental evidence. Other scenarios are also possible, for which the evidence base is not yet as extensive, namely productive infection of immune cells or trans-infection of other non-immune permissive cells. The chance of a latent infection cannot be ruled out either.

Eimeria falciformis secretes extracellular vesicles to modulate proinflammatory response during interaction with mouse intestinal epithelial cells

BACKGROUND

Protozoan parasite secretions can be triggered by various modified media and diverse physicochemical stressors. Equally, host-parasite interactions are known to co-opt the exchange and secretion of soluble biochemical components. Analysis of Eimeria falciformis sporozoite secretions in response to interaction with mouse intestinal epithelial cells (MIECs) may reveal parasite secretory motifs, protein composition and inflammatory activities of E. falciformis extracellular vesicles (EVs).

METHODS

Eimeria falciformis sporozoites were allowed to interact with inactivated MIECs. Parasite secretions were separated into EV and vesicle-free (VF) fractions by discontinuous centrifugation and ultracentrifugation. Secreted EVs were purified in an iodixanol density gradient medium and the protein composition of both EV and VF fractions were analyzed by liquid chromatoraphy-tandem mass spectroscopy. The inflammatory activities of E. falciformis sporozoite EV on MIECs were then investigated.

RESULTS

During the interaction of E. falciformis sporozoites with inactivated MIECs, the parasite secreted VF and vesicle-bound molecules. Eimeria falciformis vesicles are typical pathogenic protozoan EVs with a mean diameter of 264 ± 2 nm, and enclosed heat shock protein (Hsp) 70 as classical EV marker. Refractile body-associated aspartyl proteinase (or eimepsin), GAP45 and aminopeptidase were the main components of E. falciformis sporozoite EVs, while VF proteins include Hsp90, actin, Vps54 and kinases, among others. Proteomic data revealed that E. falciformis EV and VF proteins are aggregates of bioactive, antigenic and immunogenic molecules which act in concert for E. falciformis sporozoite motility, pathogenesis and survival. Moreover, in MIECs, E. falciformis EVs induced upregulation of gene expression and secretion of IL-1β, IL-6, IL-17, IL-18, MCP1 as well as pyroptosis-dependent caspase 11 and NLRP6 inflammasomes with the concomitant secretion of lactate dehydrogenase.

CONCLUSIONS

Eimeria falciformis sporozoite interaction with MIECs triggered the secretion of immunogenic and antigenic proteins. In addition, E. falciformis sporozoite EVs constitute parasite-associated molecular pattern that induced inflammatory response and cell death. This study offers additional insight in the secretion and protein composition of E. falciformis secretomes as well as the proinflammatory functions of E. falciformis sporozoite EVs.

The Age-Related Macular Degeneration (AMD)-Preventing Mechanism of Natural Products

Age-related macular degeneration (AMD) is related to central visual loss in elderly people and, based on the increment in the percentage of the aging population, the number of people suffering from AMD could increase. AMD is initiated by retinal pigment epithelium (RPE) cell death, finally leading to neovascularization in the macula lutea. AMD is an uncurable disease, but the symptom can be suppressed. The current therapy of AMD can be classified into four types: device-based treatment, anti-inflammatory drug treatment, anti-vascular endothelial growth factor treatment, and natural product treatment. All these therapies have adverse effects, however early AMD therapy used with products has several advantages, as it can prevent RPE cell apoptosis in safe doses. Cell death (apoptosis) is caused by various factors, such as oxidative stress, inflammation, carbonyl stress, and a deficiency in essential components for cells, and RPE cell death is related to oxidative stress, inflammation, and carbonyl stress. Some natural products have anti-oxidative effects, anti-inflammation effects, and/or anti-carbonylation effects. The AMD preventive mechanism of natural products varies, with some natural products activating one or more anti-apoptotic pathways, such as the Nrf2/HO-1 anti-oxidative pathway, the anti-inflammasome pathway, and the anti-carbonyl pathway. As AMD drug candidates from natural products effectively inhibit RPE cell death, they have the potential to be developed as drugs for preventing early (dry) AMD.

Identification of NLRP3PYD Homo-Oligomerization Inhibitors with Anti-Inflammatory Activity

Inflammasomes are multiprotein complexes that represent critical elements of the inflammatory response. The dysregulation of the best-characterized complex, the NLRP3 inflammasome, has been linked to the pathogenesis of diseases such as multiple sclerosis, type 2 diabetes mellitus, Alzheimer's disease, and cancer. While there exist molecular inhibitors specific for the various components of inflammasome complexes, no currently reported inhibitors specifically target NLRP3^PYD homo-oligomerization. In the present study, we describe the identification of QM380 and QM381 as NLRP3^PYD homo-oligomerization inhibitors after screening small molecules from the MyriaScreen library using a split-luciferase complementation assay. Our results demonstrate that these NLRP3^PYD inhibitors interfere with ASC speck formation, inhibit pro-inflammatory cytokine IL1-β release, and decrease pyroptotic cell death. We employed spectroscopic techniques and computational docking analyses with QM380 and QM381 and the PYD domain to confirm the experimental results and predict possible mechanisms underlying the inhibition of NLRP3^PYD homo-interactions.

NLRP3 Inflammasome Activation is a Prognostic Marker of Recovery in HEV-Infected Patients

Hepatitis E contributes to 3.3 million acute hepatitis cases worldwide with 30% mortality in pregnant women. Pathogenesis of Hepatitis E is complex; thus, the present study was aimed at inflammasomes and associated cytokines in the immunopathogenesis of viral hepatitis E. PBMCs were isolated from 45 HEV IgM/HEV RNA-positive AVH/ALF and 19 healthy individuals and processed for mRNA expressions of NLRs, RLRs, and cytokines. PBMCs were cultured and stimulated with HEV-pORF-2 peptide in vitro for mRNA expression by RT-PCR and cytokines levels in serum/culture supernatant by ELISA. siRNA transfection and post-silencing effect in AVH PBMCs were also assessed by NLRP3 gene expression and IL-1β and IL-18 levels by ELISA. The results demonstrated high viral load in ALF than AVH cases. mRNA expression of NLRP3 in AVH patients was found to be positively correlated with IL-18 (r = 0.74) and IL-1β (r = 0.68); P < 0.0001***. Significant levels of serum IL-1β and IL-18 cytokines were observed in AVH as compared to ALF patients. The levels of IL-1β in the culture supernatant in mock and stimulated conditions were significantly higher in AVH than in ALF patients. Significant downregulation in NLRP3 gene expression was correlated with the reduced levels of IL-1β and IL-18 cytokines in NLRP3-siRNA-transfected PBMCs. This study highlighted the significance of upregulated NLRP3 inflammasome leading to increased production of IL-18 and IL-1β cytokines in sera of AVH patients. Thus, it indicated the role of Th1 response acting through the NLRP3 pathway which might have been helpful in the recovery of AVH patients. These promising results open multiple treatment avenues where specific inhibitors can be designed to modulate the progress of disease and its pathogenicity.

Inflammasome-independent functions of NAIPs and NLRs in the intestinal epithelium

The gut relies on the complex interaction between epithelial, stromal and immune cells to maintain gut health in the face of food particles and pathogens. Innate sensing by the intestinal epithelium is critical for maintaining epithelial barrier function and also orchestrating mucosal immune responses. Numerous innate pattern recognition receptors (PRRs) are involved in such sensing. In recent years, several Nucleotide-binding-domain and Leucine-rich repeat-containing receptors (NLRs) have been found to partake in pathogen or damage sensing while also being implicated in gut pathologies, such as colitis and colorectal cancer (CRC). Here, we discuss the current literature focusing on NLR family apoptosis inhibitory proteins (NAIPs) and other NLRs that have non-inflammasome roles in the gut. The mechanisms behind NLR-mediated protection often converges on similar signalling pathways, such as STAT3, MAPK and NFκB. Further understanding of how these NLRs contribute to the maintenance of gut homeostasis will be important for understanding gut pathologies and developing new therapies.

Human Placental Trophoblasts Infected by Listeria monocytogenes Undergo a Pro-Inflammatory Switch Associated With Poor Pregnancy Outcomes

The placenta controls the growth of the fetus and ensures its immune protection. Key to these functions, the syncytiotrophoblast (SYN) is a syncytium formed by fusion of underlying mononuclear trophoblasts. The SYN covers the placental surface and is bathed in maternal blood to mediate nutritional and waste exchanges between the mother and fetus. The bacterial pathogen Listeria monocytogenes breaches the trophoblast barrier and infects the placental/fetal unit resulting in poor pregnancy outcomes. In this work, we analyzed the L. monocytogenes intracellular lifecycle in primary human trophoblasts. In accordance with previous studies, we found that the SYN is 20-fold more resistant to infection compared to mononuclear trophoblasts, forming a protective barrier to infection at the maternal interface. We show for the first time that this is due to a significant reduction in L. monocytogenes uptake by the SYN rather than inhibition of the bacterial intracellular division or motility. We here report the first transcriptomic analysis of L. monocytogenes-infected trophoblasts (RNA sequencing). Pathway analysis showed that infection upregulated TLR2, NOD-like, and cytosolic DNA sensing pathways, as well as downstream pro-inflammatory circuitry (NF-κB, AP-1, IRF4, IRF7) leading to the production of mediators known to elicit the recruitment and activation of maternal leukocytes (IL8, IL6, TNFα, MIP-1). Signature genes associated with poor pregnancy outcomes were also upregulated upon infection. Measuring the release of 54 inflammatory mediators confirmed the transcriptomic data and revealed sustained production of tolerogenic factors (IL-27, IL-10, IL-1RA, TSLP) despite infection. Both the SYN and mononuclear trophoblasts produced cytokines, but surprisingly, some cytokines were predominantly produced by the SYN (IL-8, IL-6) or by non-fused trophoblasts (TNFα). Collectively, our data support that trophoblasts act as placental gatekeepers that limit and detect L. monocytogenes infection resulting in a pro-inflammatory response, which may contribute to the poor pregnancy outcomes if the pathogen persists.

Inflammasomes in Teleosts: Structures and Mechanisms That Induce Pyroptosis during Bacterial Infection

Pattern recognition receptors (PRRs) play a crucial role in inducing inflammatory responses; they recognize pathogen-associated molecular patterns, damage-associated molecular patterns, and environmental factors. Nucleotide-binding oligomerization domain-leucine-rich repeat-containing receptors (NLRs) are part of the PRR family; they form a large multiple-protein complex called the inflammasome in the cytosol. In mammals, the inflammasome consists of an NLR, used as a sensor molecule, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) as an adaptor protein, and pro-caspase1 (Casp1). Inflammasome activation induces Casp1 activation, promoting the maturation of proinflammatory cytokines, such as interleukin (IL)-1β and IL-18, and the induction of inflammatory cell death called pyroptosis via gasdermin D cleavage in mammals. Inflammasome activation and pyroptosis in mammals play important roles in protecting the host from pathogen infection. Recently, numerous inflammasome-related genes in teleosts have been identified, and their conservation and/or differentiation between their expression in mammals and teleosts have also been elucidated. In this review, we summarize the current knowledge of the molecular structure and machinery of the inflammasomes and the ASC-spec to induce pyroptosis; moreover, we explore the protective role of the inflammasome against pathogenic infection in teleosts.

Bacterial detection by NAIP/NLRC4 elicits prompt contractions of intestinal epithelial cell layers

The gut epithelium serves to maximize the surface for nutrient and fluid uptake, but at the same time must provide a tight barrier to pathogens and remove damaged intestinal epithelial cells (IECs) without jeopardizing barrier integrity. How the epithelium coordinates these tasks remains a question of significant interest. We used imaging and an optical flow analysis pipeline to study the dynamicity of untransformed murine and human intestinal epithelia, cultured atop flexible hydrogel supports. Infection with the pathogen Salmonella Typhimurium (STm) within minutes elicited focal contractions with inward movements of up to ∼1,000 IECs. Genetics approaches and chimeric epithelial monolayers revealed contractions to be triggered by the NAIP/NLRC4 inflammasome, which sensed type-III secretion system and flagellar ligands upon bacterial invasion, converting the local tissue into a contraction epicenter. Execution of the response required swift sublytic Gasdermin D pore formation, ion fluxes, and the propagation of a myosin contraction pulse across the tissue. Importantly, focal contractions preceded, and could be uncoupled from, the death and expulsion of infected IECs. In both two-dimensional monolayers and three-dimensional enteroids, multiple infection-elicited contractions coalesced to produce shrinkage of the epithelium as a whole. Monolayers deficient for Caspase-1(-11) or Gasdermin D failed to elicit focal contractions but were still capable of infected IEC death and expulsion. Strikingly, these monolayers lost their integrity to a markedly higher extent than wild-type counterparts. We propose that prompt NAIP/NLRC4/Caspase-1/Gasdermin D/myosin-dependent contractions allow the epithelium to densify its cell packing in infected regions, thereby preventing tissue disintegration due to the subsequent IEC death and expulsion process.

Inflammasomes and adaptive immune responses

A fundamental concept in immunology is that the innate immune system initiates or instructs downstream adaptive immune responses. Inflammasomes are central players in innate immunity to pathogens, but how inflammasomes shape adaptive immunity is complex and relatively poorly understood. Here we highlight recent work on the interplay between inflammasomes and adaptive immunity. We address how inflammasome-dependent release of cytokines and antigen activates, shapes or even inhibits adaptive immune responses. We consider how distinct tissue or cellular contexts may alter the effects of inflammasome activation on adaptive immunity and how this contributes to beneficial or detrimental outcomes in infectious diseases, cancer and autoimmunity. We aspire to provide a framework for thinking about inflammasomes and their connection to the adaptive immune response.

Isofraxidin Alleviates Myocardial Infarction Through NLRP3 Inflammasome Inhibition

Isofraxidin is a well-known coumarin compound refined from traditional Chinese medicines. It has been previously demonstrated to play an anti-inflammatory role in various inflammatory conditions. However, the effect of isofraxidin on myocardial infarction (MI) remains uncovered. In this study, we aimed to investigate the effect of isofraxidin on MI. MI mice was created and triphenyltetrazolium chloride (TTC) staining as well as echocardiographic evaluation were conducted to analyze the severity of MI. Oxygen-glucose deprivation (OGD) was used for the mimics of ischemic stress in murine cardiomyocytes, and Cell Counting Kit-8 (CCK-8), Annexin V, and lactate dehydrogenase (LDH) release assays were conducted for cell viability. Western blot was used for the detection of NOD-like receptor family, pyrin domain containing 3 (NLRP3), and adapter protein apoptosis-associated speck-like protein (ASC) in heart tissues and cardiomyocytes. Real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) were applied for the detection of proinflammatory cytokines. We found that isofraxidin alleviated the severity of MI and produced a cardio-protective effect against OGD damage. Isofraxidin also decreased the overall and local inflammatory reaction in MI. Those effects were through the inhibition of the NLRP3 inflammasome. Taken together, we initially reported the cardio-protective and alleviative effect of isofraxidin on MI and uncovered its underlying mechanism related to the NLRP3 inflammasome inhibition.

Targeting microglial autophagic degradation in NLRP3 inflammasome-mediated neurodegenerative diseases

Neuroinflammation is considered as a detrimental factor in neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), etc. Nucleotide-binding oligomerization domain-, leucine-rich repeat- and pyrin domain-containing 3 (NLRP3), the most well-studied inflammasome, is abundantly expressed in microglia and has gained considerable attention. Misfolded proteins are characterized as the common hallmarks of neurodegenerative diseases due to not only their induced neuronal toxicity but also their effects in over-activating microglia and the NLRP3 inflammasome. The activated NLRP3 inflammasome aggravates the pathology and accelerates the progression of neurodegenerative diseases. Emerging evidence indicates that microglial autophagy plays an important role in the maintenance of brain homeostasis and the negative regulation of NLRP3 inflammasome-mediated neuroinflammation. The excessive activation of NLRP3 inflammasome impairs microglial autophagy and further aggravates the pathogenesis of neurodegenerative diseases. In this review article, we summarize and discuss the NLRP3 inflammasome and its specific inhibitors in microglia. The crucial role of microglial autophagy and its inducers in the removal of misfolded proteins, the clearance of damaged mitochondria and reactive oxygen species (ROS), and the degradation of the NLRP3 inflammasome or its components in neurodegenerative diseases are summarized. Understanding the underlying mechanisms behind the sex differences in NLRP3 inflammasome-mediated neurodegenerative diseases will help researchers to develop more targeted therapies and increase our diagnostic and prognostic abilities. In addition, the superiority of the combined use of microglial autophagy inducers with the specific inhibitors of the NLRP3 inflammasome in the inhibition of NLRP3 inflammasome-mediated neuroinflammation requires further preclinical and clinical validations in the future.

Epithelium-autonomous NAIP/NLRC4 prevents TNF-driven inflammatory destruction of the gut epithelial barrier in Salmonella-infected mice

The gut epithelium is a critical protective barrier. Its NAIP/NLRC4 inflammasome senses infection by Gram-negative bacteria, including Salmonella Typhimurium (S.Tm) and promotes expulsion of infected enterocytes. During the first ~12-24 h, this reduces mucosal S.Tm loads at the price of moderate enteropathy. It remained unknown how this NAIP/NLRC4-dependent tradeoff would develop during subsequent infection stages. In NAIP/NLRC4-deficient mice, S.Tm elicited severe enteropathy within 72 h, characterized by elevated mucosal TNF (>20 pg/mg) production from bone marrow-derived cells, reduced regeneration, excessive enterocyte loss, and a collapse of the epithelial barrier. TNF-depleting antibodies prevented this destructive pathology. In hosts proficient for epithelial NAIP/NLRC4, a heterogeneous enterocyte death response with both apoptotic and pyroptotic features kept S.Tm loads persistently in check, thereby preventing this dire outcome altogether. Our results demonstrate that immediate and selective removal of infected enterocytes, by locally acting epithelium-autonomous NAIP/NLRC4, is required to avoid a TNF-driven inflammatory hyper-reaction that otherwise destroys the epithelial barrier.

Epithelial inflammasomes in the defense against Salmonella gut infection

The gut epithelium prevents bacterial access to the host's tissues and coordinates a number of mucosal defenses. Here, we review the function of epithelial inflammasomes in the infected host and focus on their role in defense against Salmonella Typhimurium. This pathogen employs flagella to swim towards the epithelium and a type III secretion system (TTSS) to dock and invade intestinal epithelial cells. Flagella and TTSS components are recognized by the canonical NAIP/NLRC4 inflammasome, while LPS activates the non-canonical Caspase-4/11 inflammasome. The relative contributions of these inflammasomes, the activated cell death pathways and the elicited mucosal defenses are subject to environmental control and appear to change along the infection trajectory. It will be an important future task to explain how this may enable defense against the challenges imposed by diverse bacterial enteropathogens.

ASC-deficiency impairs host defense against Aeromonas hydrophila infection in Japanese medaka, Oryzias latipes

Apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) is a component of inflammasome, which plays crucial roles in the inflammatory response. In mammals, ASC regulates caspase-1 activation, thereby inducing pyroptosis and producing activated inflammatory cytokines. In addition, ASC also interacts with receptor-interacting protein kinase 2 (RIPK2) and induces nuclear factor-κB (NF-κB) activation. However, the role of ASC remains poorly understood in fish. In this study, we focused on elucidating the role of ASC in fish that were infected with Aeromonas hydrophila using Japanese medaka (Oryzias latipes) as fish model, and ASC-knockout (KO) medaka was established using CRISPR-Cas9 system. ASC-KO and wild type (WT) medakas were infected with A. hydrophila, and mortality was observed. ASC-KO medaka demonstrated higher mortality than WT. Moreover, the expression of immune-related genes in the kidney and intestine of the ASC-KO and WT medakas challenged with A. hydrophila were analyzed. Following A. hydrophila infection, the kidney of ASC-KO medaka exhibited significantly lower expression of NF-κB regulated genes (e.g., IL-1β, IL-6, IL-8 and TNF-α) and RIPK2 gene than in WT kidney. Moreover, to investigate the immune response against A. hydrophila via ASC in the medaka, bacterial burden, superoxide anion production, and lactate dehydrogenase release in the kidney cells of ASC-KO medaka were measured. After infection, these responses in ASC-KO medaka were significantly decreased compared to those in WT. These results suggest that the medaka ASC plays a critical role against A. hydrophila infection by inducing inflammatory responses and cell death for bacterial clearance.

From virus to inflammation, how influenza promotes lung damage

Despite seasonal vaccines, influenza-related hospitalization and death rates have remained unchanged over the past 5 years. Influenza pathogenesis has 2 crucial clinical components; first, influenza causes acute lung injury that may require hospitalization. Second, acute injury promotes secondary bacterial pneumonia, a leading cause of hospitalization and disease burden in the United States and globally. Therefore, developing an effective therapeutic regimen against influenza requires a comprehensive understanding of the damage-associated immune-mechanisms to identify therapeutic targets for interventions to mitigate inflammation/tissue-damage, improve antiviral immunity, and prevent influenza-associated secondary bacterial diseases. In this review, the pathogenic immune mechanisms implicated in acute lung injury and the possibility of using lung inflammation and barrier crosstalk for developing therapeutics against influenza are highlighted.

Salmonella enterica Infection of Murine and Human Enteroid-Derived Monolayers Elicits Differential Activation of Epithelium-Intrinsic Inflammasomes

Recent studies have determined that inflammasome signaling plays an important role in driving intestinal epithelial cell (IEC) responses to bacterial infections, such as Salmonella enterica serovar Typhimurium. There are two primary inflammasome pathways, canonical (involving caspase-1) and noncanonical (involving caspase-4 and -5 in humans and caspase-11 in mice). Prior studies identified the canonical inflammasome as the major pathway leading to interleukin-18 (IL-18) release and restriction of S Typhimurium replication in the mouse cecum. In contrast, the human C2Bbe1 colorectal carcinoma cell line expresses little caspase-1 but instead utilizes caspase-4 to respond to S Typhimurium infection. Intestinal enteroid culture has enabled long-term propagation of untransformed IECs from multiple species, including mouse and human. Capitalizing on this technology, we used a genetic approach to directly compare the relative importance of different inflammatory caspases in untransformed mouse and human IECs and transformed human IECs upon S Typhimurium infection in vitro We show that caspase-1 is important for restricting intracellular S Typhimurium replication and initiating IL-18 secretion in mouse IECs but is dispensable in human IECs. In contrast, restriction of intracellular S Typhimurium and production of IL-18 are dependent on caspase-4 in both transformed and untransformed human IECs. Notably, cytosolic replication in untransformed cells from both species was less pronounced than in transformed human cells, suggesting that transformation may impact additional pathways that restrict S Typhimurium replication. Taken together, these data highlight the differences between mouse and human IECs and the utility of studying transformed and untransformed cells in parallel.

The role of inflammasomes in multiple sclerosis

Multiple sclerosis (MS) is considered as an inflammatory autoimmune disease of the central nervous system (CNS), with a complex and heterogenic etiology. However, the involvement of inflammation in its pathophysiology is well documented and current therapies for MS are mainly immunosuppressive drugs. Although the available drugs reduce new lesions and relapses, their long-term outcome is not completely satisfactory. Inflammasomes are multimeric protein complexes that play a critical role in the inflammatory process. Several lines of evidence suggest an association between inflammasome activation and MS. In this paper, we have reviewed current studies that demonstrate the involvement of inflammasomes in MS development, in both animal model and MS patients. Furthermore, prior studies about the effect of inflammasome inhibitor drugs on development and progression of MS are discussed.

Primary Sjogren Syndrome: Focus on Innate Immune Cells and Inflammation

Primary Sjogren Syndrome (pSS) is a complex, multifactorial rheumatic disease that mainly targets salivary and lacrimal glands, inducing epithelitis. The cause behind the autoimmunity outbreak in pSS is still elusive; however, it seems related to an aberrant reaction to exogenous triggers such as viruses, combined with individual genetic pre-disposition. For a long time, autoantibodies were considered as the hallmarks of this disease; however, more recently the complex interplay between innate and adaptive immunity as well as the consequent inflammatory process have emerged as the main mechanisms of pSS pathogenesis. The present review will focus on innate cells and on the principal mechanisms of inflammation connected. In the first part, an overview of innate cells involved in pSS pathogenesis is provided, stressing in particular the role of Innate Lymphoid Cells (ILCs). Subsequently we have highlighted the main inflammatory pathways, including intra- and extra-cellular players. A better knowledge of such processes could determine the detection of new therapeutic targets that are a major need for pSS.

Germ-free and microbiota-associated mice yield small intestinal epithelial organoids with equivalent and robust transcriptome/proteome expression phenotypes

Intestinal epithelial organoids established from gut tissue have become a widely used research tool. However, it remains unclear how environmental cues, divergent microbiota composition and other sources of variation before, during and after establishment confound organoid properties, and how these properties relate to the original tissue. While environmental influences cannot be easily addressed in human organoids, mice offer a controlled assay-system. Here, we probed the effect of donor microbiota differences, previously identified as a confounding factor in murine in vivo studies, on organoids. We analysed the proteomes and transcriptomes of primary organoid cultures established from two colonised and one germ-free mouse colony of C57BL/6J genetic background, and compared them to their tissue of origin and commonly used cell lines. While an imprint of microbiota-exposure was observed on the proteome of epithelial samples, the long-term global impact of donor microbiota on organoid expression patterns was negligible. Instead, stochastic culture-to-culture differences accounted for a moderate variability between independently established organoids. Integration of transcriptome and proteome datasets revealed an organoid-typic expression signature comprising 14 transcripts and 10 proteins that distinguished organoids across all donors from murine epithelial cell lines and fibroblasts and closely mimicked expression patterns in the gut epithelium. This included the inflammasome components ASC, Naip1-6, Nlrc4 and Caspase-1, which were highly expressed in all organoids compared to the reference cell line m-ICc12 or mouse embryonic fibroblasts. Taken together, these results reveal that the donor microbiota has little effect on the organoid phenotype and suggest that organoids represent a more suitable culture model than immortalised cell lines, in particular for studies of intestinal epithelial inflammasomes.

Vying for the control of inflammasomes: The cytosolic frontier of enteric bacterial pathogen-host interactions

Enteric pathogen-host interactions occur at multiple interfaces, including the intestinal epithelium and deeper organs of the immune system. Microbial ligands and activities are detected by host sensors that elicit a range of immune responses. Membrane-bound toll-like receptors and cytosolic inflammasome pathways are key signal transducers that trigger the production of pro-inflammatory molecules, such as cytokines and chemokines, and regulate cell death in response to infection. In recent years, the inflammasomes have emerged as a key frontier in the tussle between bacterial pathogens and the host. Inflammasomes are complexes that activate caspase-1 and are regulated by related caspases, such as caspase-11, -4, -5 and -8. Importantly, enteric bacterial pathogens can actively engage or evade inflammasome signalling systems. Extracellular, vacuolar and cytosolic bacteria have developed divergent strategies to subvert inflammasomes. While some pathogens take advantage of inflammasome activation (e.g. Listeria monocytogenes, Helicobacter pylori), others (e.g. E. coli, Salmonella, Shigella, Yersinia sp.) deploy a range of virulence factors, mainly type 3 secretion system effectors, that subvert or inhibit inflammasomes. In this review we focus on inflammasome pathways and their immune functions, and discuss how enteric bacterial pathogens interact with them. These studies have not only shed light on inflammasome-mediated immunity, but also the exciting area of mammalian cytosolic immune surveillance.

Gut-Liver Axis and Inflammasome Activation in Cholangiocyte Pathophysiology

The Nlrp3 inflammasome is a multiprotein complex activated by a number of bacterial products or danger signals and is involved in the regulation of inflammatory processes through caspase-1 activation. The Nlrp3 is expressed in immune cells but also in hepatocytes and cholangiocytes, where it appears to be involved in regulation of biliary damage, epithelial barrier integrity and development of fibrosis. Activation of the pathways of innate immunity is crucial in the pathophysiology of hepatobiliary diseases, given the strong link between the gut and the liver. The liver secretes bile acids, which influence the bacterial composition of the gut microbiota and, in turn, are heavily modified by microbial metabolism. Alterations of this balance, as for the development of dysbiosis, may deeply influence the composition of the bacterial products that reach the liver and are able to activate a number of intracellular pathways. This alteration may be particularly important in the pathogenesis of cholangiopathies and, in particular, of primary sclerosing cholangitis, given its strong association with inflammatory bowel disease. In the present review, we summarize current knowledge on the gut–liver axis in cholangiopathies and discuss the role of Nlrp3 inflammasome activation in cholestatic conditions.

Vasculitis in Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal-recessive multi-organ disease characterized by airways obstruction, recurrent infections, and systemic inflammation. Vasculitis is a severe complication of CF that affects 2-3% of CF patients and is generally associated with poor prognosis. Various pathogenic mechanisms may be involved in the development of CF-related vasculitis. Bacterial colonization leads to persistent activation of neutrophilic granulocytes, inflammation and damage, contributing to the production of antineutrophil cytoplasmic autoantibodies (ANCAs). The presence of ANCA may on the other hand predispose to bacterial colonization and infection, likely entertaining a vicious circle amplifying inflammation and damage. As a result, in CF-associated vasculitis, ongoing inflammation, immune cell activation, the presence of pathogens, and the use of numerous medications may lead to immune complex formation and deposition, subsequently causing leukocytoclastic vasculitis. Published individual case reports and small case series suggest that patients with CF-associated vasculitis require immune modulating treatment, including non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, hydroxychloroquine, and/or disease-modifying anti-rheumatic drugs (DMARDs). As immunosuppression increases the risk of infection and/or malignancy, which are both already increased in people with CF, possible alternative medications may involve the blockade of individual cytokine or inflammatory pathways, or the use of novel CFTR modulators. This review summarizes molecular alterations involved in CF-associated vasculitis, clinical presentation, and complications, as well as currently available and future treatment options.

Intestinal epithelial NAIP/NLRC4 restricts systemic dissemination of the adapted pathogen Salmonella Typhimurium due to site-specific bacterial PAMP expression

Inflammasomes can prevent systemic dissemination of enteropathogenic bacteria. As adapted pathogens including Salmonella Typhimurium (S. Tm) have evolved evasion strategies, it has remained unclear when and where inflammasomes restrict their dissemination. Bacterial population dynamics establish that the NAIP/NLRC4 inflammasome specifically restricts S. Tm migration from the gut to draining lymph nodes. This is solely attributable to NAIP/NLRC4 within intestinal epithelial cells (IECs), while S. Tm evades restriction by phagocyte NAIP/NLRC4. NLRP3 and Caspase-11 also fail to restrict S. Tm mucosa traversal, migration to lymph nodes, and systemic pathogen growth. The ability of IECs (not phagocytes) to mount a NAIP/NLRC4 defense in vivo is explained by particularly high NAIP/NLRC4 expression in IECs and the necessity for epithelium-invading S. Tm to express the NAIP1-6 ligands-flagella and type-III-secretion-system-1. Imaging reveals both ligands to be promptly downregulated following IEC-traversal. These results highlight the importance of intestinal epithelial NAIP/NLRC4 in blocking bacterial dissemination in vivo, and explain why this constitutes a uniquely evasion-proof defense against the adapted enteropathogen S. Tm.

The zebrafish NLRP3 inflammasome has functional roles in ASC-dependent interleukin-1β maturation and gasdermin E-mediated pyroptosis

The NLR family pyrin domain containing 3 (NLRP3) inflammasome is one of the best-characterized inflammasomes in humans and other mammals. However, knowledge about the NLRP3 inflammasome in nonmammalian species remains limited. Here, we report the molecular and functional identification of an NLRP3 homolog (DrNLRP3) in a zebrafish (Danio rerio) model. We found that DrNLRP3's overall structural architecture was shared with mammalian NLRP3s. It initiates a classical inflammasome assembly for zebrafish inflammatory caspase (DrCaspase-A/-B) activation and interleukin 1β (DrIL-1β) maturation in an apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC)-dependent manner, in which DrNLRP3 organizes DrASC into a filament that recruits DrCaspase-A/-B by homotypic pyrin domain (PYD)-PYD interactions. DrCaspase-A/-B activation in the DrNLRP3 inflammasome occurred in two steps, with DrCaspase-A being activated first and DrCaspase-B second. DrNLRP3 also directly activated full-length DrCaspase-B and elicited cell pyroptosis in a gasdermin E (GSDME)-dependent but ASC-independent manner. These two events were tightly coordinated by DrNLRP3 to ensure efficient IL-1β secretion for the initiation of host innate immunity. By knocking down DrNLRP3 in zebrafish embryos and generating a DrASC-knockout (DrASC^-/-) fish clone, we characterized the function of the DrNLRP3 inflammasome in anti-bacterial immunity in vivo The results of our study disclosed the origin of the NLRP3 inflammasome in teleost fish, providing a cross-species understanding of the evolutionary history of inflammasomes. Our findings also indicate that the NLRP3 inflammasome may coordinate inflammatory cytokine processing and secretion through a GSDME-mediated pyroptotic pathway, uncovering a previously unrecognized regulatory function of NLRP3 in both inflammation and cell pyroptosis.