The AIM2 inflammasome is essential for host defense against cytosolic bacteria and DNA viruses. Nat Immunol. 2010;11:395-402. [PMID: 20351692 PMCID: PMC2887480 DOI: 10.1038/ni.1864]

Discovery of a novel Thiazole amide inhibitor of Inflammasome and Pyroptosis pathways

Upon the activation of inflammasomes, inflammatory caspases cleave and activate gasdermin D (GSDMD), leading to pore formation that causes cell membrane rupture and amplifies downstream inflammatory responses. Dysregulated inflammasome activation and pyroptosis signaling pathways are implicated in numerous inflammatory diseases. In our work, a set of novel thiazole amide compounds with inhibitory activity against NLRP3 inflammasome-induced pyroptosis was identified. Of all the compounds tested, compound 21 demonstrated the most potent anti-pyroptotic effects. It suppressed GSDMD cleavage and decreased IL-1β and lactate dehydrogenase (LDH) release in a concentration-dependent manner. Compound 21 bound to NLRP3 protein and increased the thermal stability of NLRP3 concentration-dependently. The molecular docking and dynamics simulations revealed that compound 21 binds to the NLRP3 protein's active site, suppressing inflammasome activation. Further investigations showed that compound 21 also partially blocked upstream NF-κB signaling and downstream GSDMD N-terminal domain (GSDMD-NT) oligomerization, which explains its broad inhibitory effects on pyroptosis driven by multiple inflammasomes. Overall, this study presents a promising thiazole amide compound with inhibitory activity against inflammasome activation and subsequent pyroptosis, warranting further exploration.

Inhibition of IFNAR-JAK signaling enhances tolerability and transgene expression of systemic non-viral DNA delivery

Lipid nanoparticles (LNPs) have demonstrated significant therapeutic value for non-viral delivery of mRNA and siRNA. While there is considerable interest in utilizing LNPs for delivering DNA (DNA-LNPs) to address a broad range of genetic disorders, acute inflammatory responses pose significant safety concerns and limit transgene expression below therapeutically relevant levels. However, the mechanisms and immune signaling pathways underlying DNA-LNP-triggered inflammatory responses are not well characterized. Through the use of gene-targeted mouse models, we have identified cGAS-STING and interferon-α/β receptor (IFNAR) pathways as major mediators of acute inflammation triggered by systemic delivery of DNA-LNPs. cGAS-STING activation induces expression of numerous JAK-STAT-activating cytokines, and we show that treatment of mice with the JAK inhibitors ruxolitinib or baricitinib significantly improves tolerability to systemically delivered DNA-LNPs. Furthermore, specific inhibition of IFNAR signaling enhances both DNA-LNP tolerability and transgene expression. Utilization of JAK inhibitors or IFNAR blockade represent promising strategies for enhancing the safety and efficacy of non-viral DNA delivery for gene therapy.

Molecular mechanism of PANoptosis and programmed cell death in neurological diseases

PANoptosis represents a highly coordinated inflammatory programmed cell death governed by the assembly and activation of PANoptosome, which strategically integrate core molecular elements from pyroptosis, apoptosis, and necroptosis. The triple-component cell death pathways set themselves apart from alternative regulated cell death mechanisms through their unique capacity to concurrently integrate and process molecular signals derived from multiple death-signaling modalities, thereby coordinating a multifaceted cellular defense system against diverse pathological insults. Pathogen-associated molecular patterns synergistically interact with cytokine storms, and oncogenic stress to active PANoptosis, establishing this programmed cell death pathway as a critical nexus in inflammatory pathogenesis and tumor immunomodulation. This molecular crosstalk highlights PANoptosis as a promising therapeutic target for managing immune-related disorders and malignant transformation. Emerging evidence links PANoptosis to neuroinflammatory disorders through dysregulated crosstalk between programmed death pathways (apoptosis, necroptosis, pyroptosis) and accidental necrosis, driving neuronal loss and neural damage. Single-cell transcriptomics reveals spatially resolved PANoptosis signatures in Alzheimer's hippocampal microenvironments and multiple sclerosis demyelinating plaques, with distinct molecular clusters correlating to quantifiable neuroinflammatory metrics. Emerging PANoptosis-targeted therapies show preclinical promise in alleviating neurovascular dysfunction while preserving physiological microglial surveillance functions. Accumulating evidence linking dysregulated cell death pathways (particularly PANoptosis) to neurological disorders underscores the urgency of deciphering its molecular mechanisms and developing precision modulators as next-generation therapies. This review systematically deciphers PANoptosome assembly mechanisms and associated cell death cascades, evaluates their pathological roles in neurological disorders through multiscale regulatory networks, and proposes PANoptosis-targeted therapeutic frameworks to advance precision neurology.

A short history of the atrial NLRP3 inflammasome and its distinct role in atrial fibrillation

Inflammasomes are multiprotein complexes of the innate immune system that mediate inflammatory responses to infection and to local and systemic stress and tissue injury. The principal function is to facilitate caspase-1 auto-activation and subsequently maturation and release of the effectors interleukin (IL)-1β and IL-18. The atrial-specific NLRP3 inflammasome is a unifying causal feature of atrial fibrillation (AF) development, progression and recurrence after ablation. Many AF-associated risk factors and co-morbidities converge mechanistically on the activation of this central inflammatory signaling platform. This review presents the historical conceptual development of a distinct atrial inflammasome and its potential causal involvement in AF. We follow the early observations linking systemic and local inflammation with AF, to the emergence of an atrial-intrinsic NLRP3 inflammasome operating within not just immune cells but also in resident atrial fibroblasts and cardiomyocytes. We outline the key developments in understanding how the atrial NLRP3 inflammasome and its effector IL-1β contribute causally to cellular and tissue-level arrhythmogenesis in different pathological settings, and outline candidate therapeutic concepts verified in preclinical models of atrial cardiomyopathy and AF.

PANoptosis: a potential target of atherosclerotic cardiovascular disease

PANoptosis is a newly discovered cell death pathway triggered by the innate immunizer, which in turn promotes the assembly of the PANoptosome and activates downstream effectors. As a special cell death mode, it is characterized by apoptosis, pyroptosis, and necroptosis at the same time; therefore, it is not feasible to inhibit PANoptosis by suppressing a single cell death pathway. However, active ingredients targeting the PANoptosome can effectively inhibit PANoptosis.Given the importance of cell death in disease, targeting PANoptosis would be an important therapeutic tool. Previous studies have focused more on infectious diseases and cancer, and the role of PANoptosis in the cardiovascular field has not been comprehensively addressed. While ASCVD is the number one killer of cardiovascular diseases, it is important to explore new targets to determine future research directions. Therefore, this review focuses on the assembly of PANoptosome, the molecular mechanism of PANoptosis, and the related mechanisms of PANoptosis leading to ASCVD such as myocardial infarction, ischemic cardiomyopathy and ischemic stroke, in order to provide a new perspective for the prevention and treatment of ASCVD.

Enteroviruses Activate Cellular Innate Immune Responses Prior to Adaptive Immunity and Tropism Contributes to Severe Viral Pathogenesis

Numerous innate immune mechanisms have been shown to be activated during viral infections, including pattern recognition receptors (PRRs) functioning outside and inside the cell along with other sensors promoting the production of interferon and other cytokines. Innate cells, including NK cells, NKT cells, γδ T cells, dendritic cells, macrophages, and even neutrophils, have been shown to respond to viral infections. Several innate humoral responses to viral infections have also been identified. Adaptive immunity includes common cell-mediated immunity (CMI) and humoral responses. Th1, Th2, and Tfh CD4+ T cell responses have been shown to help activate cytotoxic T lymphocytes (CTLs) and to help promote the class switching of antiviral antibodies. Enteroviruses were shown to induce innate immune responses and the tropism of the virus that was mediated through viral attachment proteins (VAPs) and cellular receptors was directly related to the risk of severe disease in a primary infection. Adaptive immune responses include cellular and humoral immunity, and its delay in primary infections underscores the importance of vaccination in ameliorating or preventing severe viral pathogenesis.

Shengmai-Yin resists myocardial ischemia reperfusion injury by inhibiting K27 ubiquitination of absent in melanoma 2

ETHNOPHARMACOLOGICAL RELEVANCE

Myocardial ischemia-reperfusion (I/R) injury stands as a significant contributor to cardiovascular disease. Shengmai-Yin (SMY), a traditional Chinese medicine, is widely used in myocardial infarct treatment. However, the specific mechanism of SMY in treating myocardial I/R injury is currently limited.

AIM OF STUDY

The study aimed to investigate the therapeutic efficacy of SMY in addressing myocardial I/R injury and elucidate its specific mechanisms.

MATERIALS AND METHODS

The active components of SMY were quantified using Ultra-high performance liquid chromatography-MS/MS (UPLC-MS/MS). Sprague-Dawley (SD) rats were treated with SMY post-I/R model establishment. Cardiac injury was assessed by heart weight to body weight ratio. Left ventricular function and infarct volume were evaluated using ultrasound cardiography and TTC staining. Tissue lesions were examined via hematoxylin-eosin (HE) and Sirius Red staining. Co-Immunoprecipitation (Co-IP) technology explored absent in melanoma 2 (AIM2) and K27 Ubiquitination Modification (K27-Ub) interactions. Immunofluorescence staining detected Apoptosis-associated Speck-like Protein containing a CARD (ASC) and AIM2 co-localization. Adeno-associated Virus (AAV) was used to upregulate AIM2 levels, while Shikonin was used to downregulate AIM2, to explore its roles in SMY's therapeutic effects on I/R injury.

RESULTS

SMY can reduce infarct size and enhance cardiac function. Furthermore, SMY can inhibit tissue fibrosis. Fibrosis markers and proinflammatory factors were reduced after SMY treatment. Serum levels of Lactate Dehydrogenase (LDH) and Creatine Kinase -MB (CK-MB) were also decreased. Mechanistically, SMY inhibits the activation of the AIM2 inflammasome by downregulating the K27 ubiquitination of AIM2. Overexpression of AIM2 reversed the anti-I/R effect of SMY, suggesting that AIM2 plays a crucial role in I/R injury. The AIM2 inhibitor counteracts the therapeutic effect of SMY.

CONCLUSION

SMY inhibits the K27 ubiquitination modification of AIM2 and inhibits the activation of AIM2 inflammasomes after myocardial I/R injury.

Inflammasomes and Cardiovascular Disease: Linking Inflammation to Cardiovascular Pathophysiology

Cardiovascular diseases (CVDs) remain a leading cause of global mortality, driven by risk factors such as dyslipidemia, hypertension and diabetes. Recent research has highlighted the critical role of inflammasomes, particularly the NLRP3 inflammasome, in the pathogenesis of various CVDs, including hypertension, atherosclerosis, myocardial infarction and heart failure. Inflammasomes are intracellular protein complexes that activate inflammatory responses through the production of pro-inflammatory cytokines such as IL-1β and IL-18, contributing to endothelial dysfunction, plaque formation and myocardial injury. This review provides a comprehensive overview of the structure, activation mechanisms and pathways of inflammasomes, with a focus on their involvement in cardiovascular pathology. Key activation pathways include ion fluxes (K+ efflux and Ca2+ signalling), endoplasmic reticulum (ER) stress, mitochondrial dysfunction and lysosomal destabilisation. The review also explores the therapeutic potential of targeting inflammasomes to mitigate inflammation and improve outcomes in CVDs. Emerging strategies include small-molecule inhibitors, biologics and RNA-based therapeutics, with a particular emphasis on NLRP3 inhibition. Additionally, the integration of artificial intelligence (AI) in cardiovascular research offers promising avenues for identifying novel biomarkers, predicting disease risk and developing personalised treatment strategies. Future research directions should focus on understanding the interactions between inflammasomes and other immune components, as well as genetic regulators, to uncover new therapeutic targets. By elucidating the complex role of inflammasomes in CVDs, this review underscores the potential for innovative therapies to address inflammation-driven cardiovascular pathology, ultimately improving patient outcomes.

Mechanistic insights into gasdermin-mediated pyroptosis

Pyroptosis, a novel mode of inflammatory cell death, is executed by membrane pore-forming gasdermin (GSDM) family members in response to extracellular or intracellular injury cues and is characterized by a ballooning cell morphology, plasma membrane rupture and the release of inflammatory mediators such as interleukin-1β (IL-1β), IL-18 and high mobility group protein B1 (HMGB1). It is a key effector mechanism for host immune defence and surveillance against invading pathogens and aberrant cancerous cells, and contributes to the onset and pathogenesis of inflammatory and autoimmune diseases. Manipulating the pore-forming activity of GSDMs and pyroptosis could lead to novel therapeutic strategies. In this Review, we discuss the current knowledge regarding how GSDM-mediated pyroptosis is initiated, executed and regulated, its roles in physiological and pathological processes, and the crosstalk between different modes of programmed cell death. We also highlight the development of drugs that target pyroptotic pathways for disease treatment.

Ubiquitin Ligases in Control: Regulating NLRP3 Inflammasome Activation

Ubiquitin ligases play pivotal roles in the regulation of NLR family pyrin domain containing 3 (NLRP3) inflammasome activation, a critical process in innate immunity and inflammatory responses. This review explores the intricate mechanisms by which various E3 ubiquitin ligases exert both positive and negative influences on NLRP3 inflammasome activity through diverse post-translational modifications. Negative regulation of NLRP3 inflammasome assembly is mediated by several E3 ligases, including F-box and leucine-rich repeat protein 2 (FBXL2), tripartite motif-containing protein 31 (TRIM31), and Casitas B-lineage lymphoma b (Cbl-b), which induce K48-linked ubiquitination of NLRP3, targeting it for proteasomal degradation. Membrane-associated RING-CH 7 (MARCH7) similarly promotes K48-linked ubiquitination leading to autophagic degradation, while RING finger protein (RNF125) induces K63-linked ubiquitination to modulate NLRP3 function. Ariadne homolog 2 (ARIH2) targets the nucleotide-binding domain (NBD) domain of NLRP3, inhibiting its activation, and tripartite motif-containing protein (TRIM65) employs dual K48 and K63-linked ubiquitination to suppress inflammasome assembly. Conversely, Pellino2 exemplifies a positive regulator, promoting NLRP3 inflammasome activation through K63-linked ubiquitination. Additionally, ubiquitin ligases influence other components critical for inflammasome function. TNF receptor-associated factor 3 (TRAF3) mediates K63 polyubiquitination of apoptosis-associated speck-like protein containing a CARD (ASC), facilitating its degradation, while E3 ligases regulate caspase-1 activation and DEAH-box helicase 33 (DHX33)-NLRP3 complex formation through specific ubiquitination events. Beyond direct inflammasome regulation, ubiquitin ligases impact broader innate immune signaling pathways, modulating pattern-recognition receptor responses and dendritic cell maturation. Furthermore, they intricately control NOD1/NOD2 signaling through K63-linked polyubiquitination of receptor-interacting protein 2 (RIP2), crucial for nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinase (MAPK) activation. Furthermore, we explore how various pathogens, including bacteria, viruses, and parasites, have evolved sophisticated strategies to hijack the host ubiquitination machinery, manipulating NLRP3 inflammasome activation to evade immune responses. This comprehensive analysis provides insights into the molecular mechanisms underlying inflammasome regulation and their implications for inflammatory diseases, offering potential avenues for therapeutic interventions targeting the NLRP3 inflammasome. In conclusion, ubiquitin ligases emerge as key regulators of NLRP3 inflammasome activation, exhibiting a complex array of functions that finely tune immune responses. Understanding these regulatory mechanisms not only sheds light on fundamental aspects of inflammation but also offers potential therapeutic avenues for inflammatory disorders and infectious diseases.

LPS binding caspase activation and recruitment domains (CARDs) are bipartite lipid binding modules

Caspase-11 is an innate immune pattern recognition receptor (PRR) that detects cytosolic bacterial lipopolysaccharides (LPS) through its caspase activation and recruitment domain (CARD). Caspase-11 also detects eukaryotic (i.e., self) lipids. This observation raises the question of whether common or distinct mechanisms govern caspase interactions with self- and nonself-lipids. In this study, using biochemical, computational, and cell-based assays, we report that the caspase-11 CARD functions as a bipartite lipid-binding module. Distinct regions within the CARD bind to phosphate groups and long acyl chains of self- and nonself-lipids. Self-lipid binding capability is conserved across numerous caspase-11 homologs and orthologs. The symmetry in self- and nonself-lipid detection mechanisms enabled us to engineer an LPS-binding domain de novo, using an ancestral CARD-like domain present in the fish Amphilophus citrinellus. These findings offer insights into the molecular basis of LPS recognition by caspase-11 and highlight the fundamental and likely inseparable relationship between self and nonself discrimination.

Altered Cellular Pathways in the Blood of Patients With Guillain-Barre Syndrome

BACKGROUND AND AIMS

Guillain-Barré syndrome (GBS) is a rare disorder, with a global incidence ranging from 1 to 2 individuals per 100,000 people/year. Infections and vaccines have been implicated as causes triggering GBS. The aim of the study was to identify host genes involved in the pathogenesis of GBS when Zika (ZIKV) and Chikungunya viruses (CHIKV) were introduced in Brazil.

METHODS

A case-control study of GBS was performed when ZIKV and CHIKV were introduced into a naïve population. GBS was studied during both acute and postacute phases. RNA sequencing was conducted using whole blood.

RESULTS

GBS typically manifested a week after rash and fever; acute inflammatory demyelinating polyradiculoneuropathy was more frequent. None of the GBS cases had a poor outcome. Serological assays for ZIKV and CHIKV revealed high titers of immunoglobulin G for both viruses in 9 out of 11 subjects. Metatranscriptomic analyses unveiled an increased abundance of reads attributed to Pseudomonas tolaasii and Toxoplasma gondii in the acute phase. Analysis of differentially expressed host genes during the acute phase revealed altered expression of genes associated with axogenesis, synapse assembly, and presynapse organization. Moreover, genes upregulated during acute GBS were primarily related to inflammation and the inflammasome pathways, including AIM2, NLR family genes and LRR-protein genes, and IL-10.

INTERPRETATION

These findings suggest that inflammasome activation via AIM2 could play a role in tissue damage during GBS. Further investigation into the general activation of innate inflammatory responses is warranted to elucidate their potential contribution to the pathology of GBS.

NLRP3 and AIM2 inflammasomes exacerbate the pathogenic Th17 cell response to eggs of the helminth Schistosoma mansoni

Infection with the helminth Schistosoma mansoni can cause exacerbated morbidity and mortality via a pathogenic host CD4 T cell-mediated immune response directed against parasite egg antigens, with T helper (Th) 17 cells playing a major role in the development of severe granulomatous hepatic immunopathology. The role of inflammasomes in intensifying disease has been reported; however, neither the types of caspases and inflammasomes involved, nor their impact on the Th17 response are known. Here we show that enhanced egg-induced IL-1β secretion and pyroptotic cell death required both caspase-1 and caspase-8 as well as NLRP3 and AIM2 inflammasome activation. Schistosome genomic DNA activated AIM2, whereas reactive oxygen species, potassium efflux and cathepsin B, were the major activators of NLRP3. NLRP3 and AIM2 deficiency led to a significant reduction in pathogenic Th17 responses, suggesting their crucial and non-redundant role in promoting inflammation. Additionally, we show that NLRP3- and AIM2-induced IL-1β suppressed IL-4 and protective Type I IFN (IFN-I) production, which further enhanced inflammation. IFN-I signaling also curbed inflammasome- mediated IL-1β production suggesting that these two antagonistic pathways shape the severity of disease. Lastly, Gasdermin D (Gsdmd) deficiency resulted in a marked decrease in egg-induced granulomatous inflammation. Our findings establish NLRP3/AIM2-Gsdmd axis as a central inducer of pathogenic Th17 responses which is counteracted by IFN-I pathway in schistosomiasis.

GSDMD-mediated pyroptosis: molecular mechanisms, diseases and therapeutic targets

Pyroptosis is a regulated form of inflammatory cell death in which Gasdermin D (GSDMD) plays a central role as the key effector molecule. GSDMD-mediated pyroptosis is characterized by complex biological features and considerable heterogeneity in its expression, mechanisms, and functional outcomes across various tissues, cell types, and pathological microenvironments. This heterogeneity is particularly pronounced in inflammation-related diseases and tumors. In the context of inflammatory diseases, GSDMD expression is typically upregulated, and its activation in macrophages, neutrophils, T cells, epithelial cells, and mitochondria triggers both pyroptotic and non-pyroptotic pathways, leading to the release of pro-inflammatory cytokines and exacerbation of tissue damage. However, under certain conditions, GSDMD-mediated pyroptosis may also serve a protective immune function. The expression of GSDMD in tumors is regulated in a more complex manner, where it can either promote immune evasion or, in some instances, induce tumor cell death. As our understanding of GSDMD's role continues to progress, there have been advancements in the development of inhibitors targeting GSDMD-mediated pyroptosis; however, these therapeutic interventions remain in the preclinical phase. This review systematically examines the cellular and molecular complexities of GSDMD-mediated pyroptosis, with a particular emphasis on its roles in inflammation-related diseases and cancer. Furthermore, it underscores the substantial therapeutic potential of GSDMD as a target for precision medicine, highlighting its promising clinical applications.

The 129 strain-derived passenger mutations in ACKR1-deficient mice alter the expression of PYHIN and Fc-gamma receptor genes

Most genetically modified mice have been produced using 129 strain-derived embryonic stem cells. Despite ample backcrosses with other strains, these may retain characteristics for 129 passenger mutations, leading to confounding phenotypes unrelated to targeted genes. Here we show that widely used Ackr1-/-129ES mice have approximately 6 Mb of the 129-derived genome retained adjacently to the Ackr1 locus on chromosome 1, including several characteristic polymorphisms. These most notably affect the expression of PYHIN and Fc-gamma receptor genes in myeloid cells, resulting in the overproduction of IL-1β by activated macrophages and the loss of Fc-gamma receptors on myeloid progenitor cells. Therefore, caution is warranted when interpreting Ackr1-/-129ES mouse phenotypes as being solely due to the ACKR1 deficiency. Our findings call for a careful reevaluation of data from previous studies using Ackr1-/-129ES mice and underscore the limitations and pitfalls inherent to mouse models produced using traditional genetic engineering techniques involving 129 embryonic stem cells.

NLRP3 inflammasome mediates astroglial dysregulation of innate and adaptive immune responses in schizophrenia

Mounting evidence indicates the involvement of neuroinflammation in the development of schizophrenia (SCZ), but the potential role of astroglia in this phenomenon remains poorly understood. We assessed the molecular and functional consequences of inflammasome activation using induced pluripotent stem cell (iPSC)-derived astrocytes generated from SCZ patients and healthy controls (CTRL). Screening protein levels in astrocytes at baseline identified lower expression of the NLRP3-ASC complex in SCZ, but increased Caspase-1 activity upon specific NLRP3 stimulation compared to CTRL. Using transcriptional profiling, we found corresponding downregulations of NLRP3 and ASC/PYCARD in both iPSC-derived astrocytes, and in a large (n = 429) brain postmortem case-control sample. Functional analyses following NLRP3 activation revealed an inflammatory phenotype characterized by elevated production of IL-1β/IL-18 and skewed priming of helper T lymphocytes (Th1/Th17) by SCZ astrocytes. This phenotype was rescued by specific inhibition of NLRP3 activation, demonstrating its dependence on the NLRP3 inflammasome. Taken together, SCZ iPSC-astrocytes display unique, NLRP3-dependent inflammatory characteristics that are manifested via various cellular functions, as well as via dysregulated innate and adaptive immune responses.

DNA Nanotags for Multiplexed Single-Particle Electron Microscopy and In Situ Electron Cryotomography

DNA nanostructures present new opportunities as Nanotags for electron microscopy (EM) imaging, leveraging their high programmability, unique shapes, biomolecule conjugation capability, and stability compatible with standard cryogenic sample preparation protocols. This perspective highlights the potential of DNA Nanotags to enable high-throughput multiplexed EM analysis and facilitate in situ particle identification for cryogenic electron tomography (cryo-ET). Meanwhile, applying Nanotags in live-cell environments requires the efficient cellular uptake of intact structures and successful cytosolic migration. Promising strategies such as employing direct cytosolic delivery platforms and expressing RNA-based Nanotags in situ are discussed, while more systematic studies are needed to fully understand the intracellular trafficking and achieve precise localization of DNA Nanotags.

Absent in melanoma 2: a potent suppressor of retinal pigment epithelial-mesenchymal transition and experimental proliferative vitreoretinopathy

Epithelial-to-mesenchymal transition (EMT) is a critical and complex process involved in normal embryonic development, tissue regeneration, and tumor progression. It also contributes to retinal diseases, such as age-related macular degeneration (AMD) and proliferative vitreoretinopathy (PVR). Although absent in melanoma 2 (AIM2) has been linked to inflammatory disorders, autoimmune diseases, and cancers, its role in the EMT of the retinal pigment epithelium (RPE-EMT) and retinal diseases remains unclear. The present study demonstrated that AIM2 functions as a potent suppressor of RPE cell proliferation and EMT to maintain retinal homeostasis. Transcriptome analysis using RNA-sequencing (RNA-Seq) revealed that AIM2 was significantly downregulated in primary human RPE (phRPE) cells undergoing EMT and proliferation. Consequently, Aim2-deficient mice showed morphological changes and increased FN expression in RPE cells under physiological conditions, whereas AIM2 overexpression in phRPE cells inhibited EMT. In a retinal detachment-induced PVR mouse model, AIM2 deficiency promotes RPE-EMT, resulting in severe experimental PVR. Clinical samples further confirmed the downregulation of AIM2 in the PVR membranes from patients. Kyoto Encyclopedia of Genes and Genome analysis revealed that the PI3K-AKT signaling pathway was significantly related to RPE-EMT and that AIM2 inhibited AKT activation in RPE cells by reducing its phosphorylation. Moreover, treatment with eye drops containing an AKT inhibitor alleviated RPE-EMT and the severity of experimental PVR. These findings provide new insights into the complex mechanisms underlying RPE-EMT and PVR pathogenesis, with implications for rational strategies for potential therapeutic applications in PVR by targeting RPE-EMT.

Activation and evasion of inflammasomes during viral and microbial infection

The inflammasome is a cytoplasmic multiprotein complex that induces the maturation of the proinflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18) or pyroptosis by activating caspases, which play critical roles in regulating inflammation, cell death, and various cellular processes. Multiple studies have shown that the inflammasome is a key regulator of the host defence response against pathogen infections. During the process of pathogenic microbe invasion into host cells, the host's innate immune system recognizes these microbes by activating inflammasomes, triggering inflammatory responses to clear the microbes and initiate immune responses. Moreover, microbial pathogens have evolved various mechanisms to inhibit or evade the activation of inflammasomes. Therefore, we review the interactions between viruses and microbes with inflammasomes during the invasion process, highlight the molecular mechanisms of inflammasome activation induced by microbial pathogen infection, and highlight the corresponding strategies that pathogens employ to evade inflammasome activity. Finally, we also discuss potential therapeutic strategies for the treatment of pathogenic microbial infections via the targeting of inflammasomes and their products.

Transcriptome-wide dynamics of m6A methylation in ISKNV and Siniperca chuatsi cells infected with ISKNV

Infectious spleen and kidney necrosis virus (ISKNV) is a highly virulent and rapidly transmissible fish virus that poses threats to the aquaculture of a wide variety of freshwater and marine fish. N6-methyladenosine (m6A), recognized as a common epigenetic modification of RNA, plays an important regulatory role during viral infection. However, the impact of m6A RNA methylation on the pathogenicity of ISKNV remains unexplored. Here, methylated RNA immunoprecipitation sequencing (MeRIP-seq) coupled with RNA sequencing (RNA-seq) was used to systematically detect variations in m6A methylation and gene expression between ISKNV-infected and noninfected MFF-1 cells, followed by functional enrichment and co-expression joint analysis. The findings revealed that the m6A methylation peaks were located mainly in coding sequences (CDSs), with more than 90% of the transcripts containing 1-5 m6A peaks. Through MeRIP-seq, 4361 differentially m6A-methylated mRNAs were identified. Gene enrichment analysis revealed that m6A-related genes were enriched in biological processes and pathways such as gene expression, cellular structure, immune responses, and cell death. Co-expression analysis revealed that the genes differentially expressed at both the mRNA and m6A modification levels were enriched in pathways such as the hippo, ErbB, and JAK-STAT pathways. The m6A modification at the genome-wide transcription level of ISKNV was subsequently shown to be pronounced in several pivotal genes, such as putative vascular endothelial growth factor, ribonucleotide reductase small subunit, and E3 ubiquitin ligase. This study comprehensively describes the m6A expression profile in ISKNV- and ISKNV-infected MFF-1 cells, providing a basis for investigating the role of m6A modification during ISKNV infection.

Lipotoxicity-driven metabolic dysfunction-associated steatotic liver disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses a spectrum of liver lesions, ranging from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH), that may further progress to cirrhosis. MASLD is estimated to affect more than one third of the general population and it represents a risk factor for end-stage liver failure and liver cancer, substantially contributing to liver-related morbidity and mortality. Although the pathogenesis of MASLD is incompletely understood, it is known to consist of a multifactorial process influenced by extrinsic and intrinsic factors such as metabolic, environmental and demographic features, gut microbiota and genetics. Dysregulation of both extracellular and intracellular lipid composition is known to promote the generation of toxic lipid species, thereby triggering lipotoxicity and cellular stress. These events ultimately lead to the activation of distinct cell death pathways, resulting in inflammation, fibrogenesis and, eventually, carcinogenesis. In this manuscript, we provide a comprehensive review of the role of lipotoxicity during MASLD pathogenesis, discussing the most relevant lipid species and related molecular mechanisms, summarizing the cell type-specific effects and highlighting the most promising putative therapeutic strategies for modulating lipotoxicity and lipid metabolism in MASLD.

The intricate interactions between inflammasomes and bacterial pathogens: Roles, mechanisms, and therapeutic potentials

Inflammasomes are intracellular multiprotein complexes that consist of a sensor, an adaptor, and a caspase enzyme to cleave interleukin (IL)-1β and IL-18 into their mature forms. In addition, caspase-1 and -11 activation results in the cleavage of gasdermin D to form pores, thereby inducing pyroptosis. Activation of the inflammasome and pyroptosis promotes host defense against pathogens, whereas dysregulation of the inflammasome can result in various pathologies. Inflammasomes exhibit versatile microbial signal detection, directly or indirectly, through cellular processes, such as ion fluctuations, reactive oxygen species generation, and the disruption of intracellular organelle function; however, bacteria have adaptive strategies to manipulate the inflammasome by altering microbe-associated molecular patterns, intercepting innate pathways with secreted effectors, and attenuating inflammatory and cell death responses. In this review, we summarize recent advances in the diverse roles of the inflammasome during bacterial infections and discuss how bacteria exploit inflammasome pathways to establish infections or persistence. In addition, we highlight the therapeutic potential of harnessing bacterial immune subversion strategies against acute and chronic bacterial infections. A more comprehensive understanding of the significance of inflammasomes in immunity and their intricate roles in the battle between bacterial pathogens and hosts will lead to the development of innovative strategies to address emerging threats posed by the expansion of drug-resistant bacterial infections.

Guards and decoys: RIPoptosome and inflammasome pathway regulators of bacterial effector-triggered immunity

Virulent microbes produce proteins that interact with host cell targets to promote pathogenesis. For example, virulent bacterial pathogens have proteins called effectors that are typically enzymes and are secreted into host cells. To detect and respond to the activities of effectors, diverse phyla of host organisms evolved effector-triggered immunity (ETI). In ETI, effectors are often sensed indirectly by detection of their virulence activities in host cells. ETI mechanisms can be complex and involve several classes of host proteins. Guards monitor the functional or physical integrity of another host protein, the guardee or decoy, and become activated to initiate an immune response when the guardee or decoy is modified or disrupted by an effector. A guardee typically has an intrinsic anti-pathogen function and is the intended target of an effector. A decoy structurally mimics a host protein that has intrinsic anti-pathogen activity and is unintentionally targeted by an effector. A decoy can be an individual protein, or a protein domain integrated into a guard. Here, we review the origins of ETI and focus on 5 mechanisms, in which the key steps of a pathway can include activation of a caspase by a RIPoptosome or inflammasome, formation of pores in the plasma membrane, release of cytokines and ending in cell death by pyroptosis. Survey of the 5 mechanisms, which have been shown to be host protective in mouse models of bacterial infection, reveal how distinct regulators of RIPoptosome or inflammasome pathways can act as guards or integrated decoys to trigger ETI. Common themes are highlighted and the limited mechanistic understanding of ETI bactericidal activity is discussed.

From fat to fire: The lipid-inflammasome connection

Inflammasomes are multiprotein complexes that play a crucial role in regulating immune responses by governing the activation of Caspase-1, the secretion of pro-inflammatory cytokines, and the induction of inflammatory cell death, pyroptosis. The inflammasomes are pivotal in effective host defense against a range of pathogens. Yet, overt activation of inflammasome signaling can be detrimental. The most well-studied NLRP3 inflammasome has the ability to detect a variety of stimuli including pathogen-associated molecular patterns, environmental irritants, and endogenous stimuli released from dying cells. Additionally, NLRP3 acts as a key sensor of cellular homeostasis and can be activated by disturbances in diverse metabolic pathways. Consequently, NLRP3 is considered a key player linking metabolic dysregulation to numerous inflammatory disorders such as gout, diabetes, and atherosclerosis. Recently, compelling studies have highlighted a connection between lipids and the regulation of NLRP3 inflammasome. Lipids are integral to cellular processes that serve not only in maintaining the structural integrity and subcellular compartmentalization, but also in contributing to physiological equilibrium. Certain lipid species are known to define NLRP3 subcellular localization, therefore directly influencing the site of inflammasome assembly and activation. For instance, phosphatidylinositol 4-phosphate plays a crucial role in NLRP3 localization to the trans Golgi network. Moreover, new evidence has demonstrated the roles of lipid biosynthesis and trafficking in activation of the NLRP3 inflammasome. This review summarizes and discusses these emerging and varied roles of lipid metabolism in inflammasome activation. A deeper understanding of lipid-inflammasome interactions may open new avenues for therapeutic interventions to prevent or treat chronic inflammatory and autoimmune conditions.

Stem cell activity-coupled suppression of endogenous retrovirus governs adult tissue regeneration

Mammalian retrotransposons constitute 40% of the genome. During tissue regeneration, adult stem cells coordinately repress retrotransposons and activate lineage genes, but how this coordination is controlled is poorly understood. Here, we observed that dynamic expression of histone methyltransferase SETDB1 (a retrotransposon repressor) closely mirrors stem cell activities in murine skin. SETDB1 ablation leads to the reactivation of endogenous retroviruses (ERVs, a type of retrotransposon) and the assembly of viral-like particles, resulting in hair loss and stem cell exhaustion that is reversible by antiviral drugs. Mechanistically, at least two molecularly and spatially distinct pathways are responsible: antiviral defense mediated by hair follicle stem cells and progenitors and antiviral-independent response due to replication stress in transient amplifying cells. ERV reactivation is promoted by DNA demethylase ten-eleven translocation (TET)-mediated hydroxymethylation and recapitulated by ablating cell fate transcription factors. Together, we demonstrated ERV silencing is coupled with stem cell activity and essential for adult hair regeneration.

Inflammasomes: potential therapeutic targets in hematopoietic stem cell transplantation

The realm of hematopoietic stem cell transplantation (HSCT) has witnessed remarkable advancements in elevating the cure and survival rates for patients with both malignant and non-malignant hematologic diseases. Nevertheless, a considerable number of patients continue to face challenges, including transplant-related complications, infection, graft failure, and mortality. Inflammasomes, the multi-protein complexes of the innate immune system, respond to various danger signals by releasing inflammatory cytokines and even mediating cell death. While moderate activation of inflammasomes is essential for immune defense and homeostasis maintenance, excessive activation precipitates inflammatory damage. The intricate interplay between HSCT and inflammasomes arises from their pivotal roles in immune responses and inflammation. This review examines the molecular architecture and composition of various types of inflammasomes, highlighting their activation and effector mechanisms within the context of the HSCT process and its associated complications. Additionally, we summarize the therapeutic implications of targeting inflammasomes and related factors in HSCT.

Programmed cell death: molecular mechanisms, biological functions, diseases, and therapeutic targets

Programmed cell death represents a precisely regulated and active cellular demise, governed by a complex network of specific genes and proteins. The identification of multiple forms of programmed cell death has significantly advanced the understanding of its intricate mechanisms, as demonstrated in recent studies. A thorough grasp of these processes is essential across various biological disciplines and in the study of diseases. Nonetheless, despite notable progress, the exploration of the relationship between programmed cell death and disease, as well as its clinical application, are still in a nascent stage. Therefore, further exploration of programmed cell death and the development of corresponding therapeutic methods and strategies holds substantial potential. Our review provides a detailed examination of the primary mechanisms behind apoptosis, autophagy, necroptosis, pyroptosis, and ferroptosis. Following this, the discussion delves into biological functions and diseases associated dysregulated programmed cell death. Finally, we highlight existing and potential therapeutic targets and strategies focused on cancers and neurodegenerative diseases. This review aims to summarize the latest insights on programmed cell death from mechanisms to diseases and provides a more reliable approach for clinical transformation.

Zinc homeostasis regulates caspase activity and inflammasome activation

Inflammasome activation drives pyroptotic cell death and the release of inflammatory cytokines, and many diseases involve its overactivation. Zinc is essential for all organisms as a trace element, but its functions in innate immunity remain undefined. Here, we reported that Zn2+ inhibits caspase-1 to hinder inflammasome activation. We first identified the zinc exporter solute carrier family 30 member 1 (SLC30A1) as an inflammasome regulator, using a genome-wide CRISPR-Cas9-mediated screen. SLC30A1 deficiency suppressed multiple inflammasomes by increasing intracellular levels of Zn2+, which bound and inhibited caspase-1 at its active site residues H237, C244 and C285. Mutation of these residues almost completely blocked zinc binding. Similarly, Zn2+ also inhibited caspase-4/5/11-mediated noncanonical inflammasome activation. Importantly, zinc supplementation significantly relieved cecal ligation and puncture (CLP)-induced sepsis, Imiquimod (IMQ)-induced psoriasis and Alzheimer's disease. Thus, zinc might be used to treat inflammasome-related diseases as a broad-spectrum inflammasome inhibitor.

DNA damage-induced AIM2 pyroptosis in high glucose-induced proximal tubular epithelial cell

Pyroptosis is one of the ways to cause proximal tubular epithelial cell death in diabetic nephropathy (DN), but the exact mechanism remains unclear. Absent in melanoma 2 (AIM2), a sensor for double-stranded DNA, creates an inflammasome that triggers the cleavage of gasdermin D (GSDMD), leading to a type of inflammatory cell death called pyroptosis. This study investigated the role of AIM2 in pyroptosis within proximal tubular epithelial cells in DN. We observed significantly elevated AIM2 expression in renal tubules from DN patients and db/db mice, as well as in high glucose (HG)-induced Human Kidney-2 (HK2) cells. Besides, increased AIM2 expression was accompanied by activation of the pyroptosis pathway (cleaved-caspase-1, GSDMD-FL, GSDMD-NT) in the renal cortex of db/db mice and HG-induced HK2 cells in vitro. Knocking down GSDMD can reduce HG-induced HK2 cell death, indicating that HG triggers pyroptosis in HK2 cells. Furthermore, HG-induced pyroptosis was mitigated in HK2 cells with AIM2 knockdown using siRNA. Additionally, reducing ROS levels using NAC was able to attenuate HG-induced HK2 cells DNA damage, AIM2 activation, and pyroptosis. Notably, AIM2 upregulation was observed in renal biopsies from DN patients, with expression levels positively correlating with serum creatinine and inversely with estimated glomerular filtration rate (eGFR). Collectively, DNA damage caused by HG could result in the activation of the AIM2 inflammasome, leading to the pyroptosis of proximal tubular epithelial cells, indicating that targeting AIM2 could be a potential novel approach for treating DN.

Cytomegalovirus Biology Viewed Through a Cell Death Suppression Lens

Cytomegaloviruses, species-specific members of the betaherpesviruses, encode an impressive array of immune evasion strategies committed to the manipulation of the host immune system enabling these viruses to remain for life in a stand-off with host innate and adaptive immune mechanisms. Even though they are species-restricted, cytomegaloviruses are distributed across a wide range of different mammalian species in which they cause systemic infection involving many different cell types. Regulated, or programmed cell death has a recognized potential to eliminate infected cells prior to completion of viral replication and release of progeny. Cell death also naturally terminates replication during the final stages of replication. Over the past two decades, the host defense potential of known programmed cell death pathways (apoptosis, necroptosis, and pyroptosis), as well as a novel mitochondrial serine protease pathway have been defined through studies of cytomegalovirus-encoded cell death suppressors. Such virus-encoded inhibitors prevent virus-induced, cytokine-induced, and stress-induced death of infected cells while also moderating inflammation. By evading cell death and consequent inflammation as well as innate and adaptive immune clearance, cytomegaloviruses represent successful pathogens that become a critical disease threat when the host immune system is compromised. This review will discuss cell death programs acquired for mammalian host defense against cytomegaloviruses and enumerate the range of modulatory strategies this type of virus employs to balance host defense in favor of lifelong persistence.

Leveraging a comprehensive unbiased RNAseq database to characterize human monocyte-derived macrophage gene expression profiles within commonly employed in vitro polarization methods

Macrophages are pivotal innate immune cells which exhibit high phenotypic plasticity and can exist in different polarization states dependent on exposure to external stimuli. Numerous methods have been employed to simulate macrophage polarization states to test their function in vitro. However, limited research has explored whether these polarization methods yield comparable populations beyond key gene, cytokine, and cell surface marker expression. Here, we employ an unbiased comprehensive analysis using data organized through the all RNA-seq and ChIP-seq sample and signature search (ARCHS4) database, which compiles all RNAseq data deposited into the National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA). In silico analyses were carried out demonstrating that commonly employed macrophage polarization methods generate distinct gene expression profiles in macrophage subsets that remained poorly described until now. Our analyses confirm existing knowledge on broad macrophage polarization, while expanding nuanced differences between M2a and M2c subsets, suggesting non-interchangeable stimuli for M2a polarization. Furthermore, we characterize divergent gene expression patterns in M1 macrophages following standard polarization protocols, indicating significant subset distinctions. Consequently, equivalence cannot be assumed among polarization regimens for in vitro macrophage studies, particularly in simulating diverse pathogen responses.

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.

The emerging role of PANoptosis in viral infections disease

PANoptosis is a distinct inflammatory cell death mechanism that involves interactions between pyroptosis, apoptosis, and necroptosis. It can be regulated by diverse PANoptosome complexes built by integrating components from various cell death modalities. There is a rising interest in PANoptosis' process and functions. Viral infection is an important trigger of PANoptosis. Viruses invade host cells through their unique mechanisms and utilize host cell resources for replication and proliferation. In this process, viruses interfere with the normal physiological functions of host cells, including cell death mechanisms. A variety of viruses, such as influenza A virus (IAV), herpes simplex virus 1 (HSV1) and coronaviruses, have been found to induce PANoptosis in host cells. Given the importance of PANoptosis across the disease spectrum, this review briefly describes the relationships between pyroptosis, apoptosis, and necroptosis, highlights the key molecules in PANoptosome formation and activation, and outlines the multifaceted roles of PANoptosis in viral diseases, including potential therapeutic targets. We also talk about key principles and significant concerns for future PANoptosis research. Improved understanding of PANoptosis and its mechanisms is critical for discovering new treatment targets and methods.

Targeting autophagy in urological system cancers: From underlying mechanisms to therapeutic implications

The urological system, including kidneys, ureters, bladder, urethra and prostate is known to be vital for blood filtration, waste elimination and electrolyte balance. Notably, urological system cancers represent a significant portion of global cancer diagnoses and mortalities. The current therapeutic strategies for early-stage cancer primarily involve resection surgery, which significantly affects the quality of life of patients, whereas advanced-stage cancer often relies on less effective chemo- or radiotherapy. Recently, accumulating evidence has revealed that autophagy, a crucial process in which excess organelles or inclusions within cells are removed to maintain cell homeostasis, has numerous links to urological system cancers. In this review, we focus on summarizing the underlying two-sided mechanisms of autophagy in urological system cancers. We also review the current clinical drugs targeting autophagy, which demonstrate significant potential in improving treatment outcomes for urological system cancers. In addition, we provide an overview of the research status of novel small molecule compounds targeting autophagy that are in the preclinical stages of investigation. Furthermore, drug combinations based on autophagy modulation strategies in urological system cancers are systematically summarized and discussed. These findings provide comprehensive new insight for the future discovery of more autophagy-related drug candidates.

Transcriptomic analysis of spleen-derived macrophages in response to lipopolysaccharide shows dependency on the MyD88-independent pathway in Chinese giant salamanders (Andrias davidianus)

BACKGROUND

Gram-negative bacteria are the main bacterial pathogens infecting Chinese giant salamanders (Andrias davidianus; CGS) in captivity and the wild, causing substantial economic losses in the CGS industry. However, the molecular mechanisms underlying pathogenesis following infection remain unclear.

RESULTS

Spleen-derived macrophages from healthy CGS were isolated, cultured, and identified using density gradient centrifugation and immunofluorescence. A macrophage transcriptome database was established 0, 6, and 12 h post lipopolysaccharide stimulation using RNA-sequencing. In the final database 76,743 unigenes and 4,698 differentially expressed genes (DEGs) were functionally annotated. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment results showed that DEGs were concentrated in toll-like receptor-nuclear factor kappa B-related immune pathways. Ten DEGs were validated 12 h after lipopolysaccharide (LPS) stimulation. Although the common LPS recognition receptor toll-like receptor 4 was not activated and the key adaptor protein MyD88 showed no significant response, we observed significant up-regulation of the following adaptors: toll/interleukin-1 receptor domain-containing adaptor inducing interferon-β, tumour necrosis factor receptor-associated factor 6, and transforming growth factor-β activated kinase 1, which are located downstream of the non-classical MyD88 pathway.

CONCLUSIONS

In contrast to that in other species, macrophage activation in CGS could depend on the non-classical MyD88 pathway in response to bacterial infection. Our study provides insights into the molecular mechanisms regulating CGS antibacterial responses, with implications for disease prevention and understanding immune evolution in amphibians.

The Role of the AIM2 Gene in Obesity-Related Glucose and Lipid Metabolic Disorders: A Recent Update

Absent in melanoma 2 (AIM2) is a protein encoded by the AIM2 gene located on human chromosomes, AIM2 can recognize and bind to double stranded DNA (dsDNA), leading to the assembly of the AIM2 inflammasome. The AIM2 inflammasome plays important proinflammation role in many diseases, and can induce pyroptotic cell death. It has also been closely linked to the development and progression of metabolic diseases and can be activated in obesity, diabetes, nonalcoholic fatty liver disease, and atherosclerosis. In this article, we mainly review the role of AIM2 in glucose metabolism, especially in obesity-related disorders of glucose and lipid metabolism, and provide insights to better understand the role of AIM2 in the pathogenesis, and clinical treatment of metabolic disease.

Inflammasomes: emerging therapeutic targets in hidradenitis suppurativa?

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease characterized by recurrent inflammatory lesions, which affect skin and hair follicles in intertriginous areas. HS has a multifactorial aetiology resulting in barrier dysfunction associated with aberrant immune activation. There is increased evidence for the role of inflammasomes in the pathophysiology of inflammatory skin diseases, including HS. Inflammasomes are multiprotein complexes activated following exposure to danger signals, including microbial ligands and components of damaged host cells. Inflammasome activation induces many signalling cascades and subsequent cleavage of proinflammatory cytokines - most notably interleukin (IL)-1β - which have a role in HS pathogenesis. Limited immunotherapies are approved for treating moderate-to-severe HS, with variable response rates influenced by disease heterogeneity. Inflammasomes represent attractive targets to suppress multiple inflammatory pathways in HS, including IL-1β and IL-17. This review aims to summarize the role of inflammasomes in HS and to evaluate evidence for inflammasomes as therapeutic targets for HS treatment.

LPS binding caspase activation and recruitment domains (CARDs) are bipartite lipid binding modules

Caspase-11 is an innate immune pattern recognition receptor (PRR) that detects cytosolic bacterial lipopolysaccharides (LPS) through its caspase activation and recruitment domain (CARD), triggering inflammatory cell death known as pyroptosis. Caspase-11 also detects eukaryotic (i.e. self) lipids. This observation raises the question of whether common or distinct mechanisms govern the interactions with self and nonself lipids. In this study, using biochemical, computational, and cell-based assays, we report that the caspase-11 CARD functions as a bipartite lipid-binding module. Distinct regions within the CARD bind to phosphate groups and long acyl chains of self and nonself lipids. Self-lipid binding capability is conserved across numerous caspase-11 homologs and orthologs. The symmetry in self and nonself lipid detection mechanisms enabled us to engineer an LPS-binding domain de novo, using an ancestral CARD-like domain present in the fish Amphilophus citrinellus. These findings offer critical insights into the molecular basis of LPS recognition by caspase-11 and highlight the fundamental and likely inseparable relationship between self and nonself discrimination.

Nucleic acid sensing in the central nervous system: Implications for neural circuit development, function, and degeneration

Nucleic acids are a critical trigger for the innate immune response to infection, wherein pathogen-derived RNA and DNA are sensed by nucleic acid sensing receptors. This subsequently drives the production of type I interferon and other inflammatory cytokines to combat infection. While the system is designed such that these receptors should specifically recognize pathogen-derived nucleic acids, it is now clear that self-derived RNA and DNA can also stimulate these receptors to cause aberrant inflammation and autoimmune disease. Intriguingly, similar pathways are now emerging in the central nervous system in neurons and glial cells. As in the periphery, these signaling pathways are active in neurons and glia to present the spread of pathogens in the CNS. They further appear to be active even under steady conditions to regulate neuronal development and function, and they can become activated aberrantly during disease to propagate neuroinflammation and neurodegeneration. Here, we review the emerging new roles for nucleic acid sensing mechanisms in the CNS and raise open questions that we are poised to explore in the future.

Pioglitazone ameliorates sepsis-associated encephalopathy through SIRT1 signaling pathway

Sepsis is a severe immune response to an infection. It is associated with multiple organ dysfunction syndrome (MODs) along with systemic and neuronal inflammatory response. This study focused on the acute neurologic dysfunction associated with sepsis by exploring the role of PPARγ/SIRT1 pathway against sepsis. We studied the role of this axis in ameliorating sepsis-associated encephalopathy (SAE) and its linked neurobehavioral disorders by using pioglitazone (PIO). This PPARγ agonist showed neuroprotective actions in neuroinflammatory disorders. Sepsis was induced in mice by LPS (10 mg/kg). Survival rate and MODs were assessed. Furthermore, behavioral deficits, cerebral oxidative, inflammatory, and apoptotic markers, and the cerebral expression level of SIRT1 were determined. In this study, we observed that PIO attenuated sepsis-induced cerebral injury. PIO significantly enhanced survival rate, attenuated MODs, and systemic inflammatory response in septic mice. PIO also promoted cerebral SIRT1 expression and reduced cerebral activation of microglia, oxidative stress, HMGB, iNOS, NLRP3 and caspase-3 along with an obvious improvement in behavioral deficits and cerebral pathological damage induced by LPS. Most of the neuroprotective effects of PIO were abolished by EX-527, a SIRT1 inhibitor. These results highlight that the neuroprotective effect of PIO in SAE is mainly SIRT1-dependent.

Impact of AIM2 on HNSCC Development

Head and neck squamous cell carcinoma (HNSCC) constitutes 90% of head and neck cancers. HNSCC development is linked to chronic inflammation, while established HNSCC tumors are often immune suppressive. However, both occur through mechanisms that are not fully understood. The cytosolic double-stranded DNA sensor Absent in Melanoma 2 (AIM2) is an inflammasome forming protein that also has inflammasome-distinct roles in restricting tumorigenesis by limited PI3K signaling. Here, we used an experimental mouse model of HNSCC, involving treatment of wild type (WT) and Aim2 -/- mice with the carcinogen 4NQO in drinking water. Compared to WT mice, 4NQO-treated Aim2 -/- mice exhibited larger tumor sizes and increased tissue dysplasia. 4NQO-treated wild type and Aim2 -/- mice displayed similar tongue Il6, Tnf, Il1b, Il12, and Il10 expression and no consistent differences in PI3K or inflammasome activation, suggesting AIM2 may not regulate these factors during HNSCC. Instead, Ifng and Irf1 was elevated in 4NQO-treated Aim2 -/- mice, suggesting AIM2 restricts IFNγ. In line with this, RNA-sequencing of total tongue RNA from 4NQO-treated mice revealed Aim2 -/- mice had enhanced expression of genes related to the MHC protein complex, cell killing, and T cell activation compared to wild type mice. In addition, we observed increased macrophage infiltration into the tongue epithelium of 4NQO-treated Aim2 -/- mice. Lastly, using Aim2 -/- / Rag1 -/- -double deficient animals, we found that the adaptive immune compartment was necessary for the enhanced tumorigenesis during AIM2 deficiency. Taken together, these findings suggest AIM2 limits the progression of oral tumor development partially through regulating IFNγ and adaptive immune responses.

Taking AIM at Influenza: The Role of the AIM2 Inflammasome

Influenza A viruses (IAV) are dynamic and highly mutable respiratory pathogens that present persistent public health challenges. Inflammasomes, as components of the innate immune system, play a crucial role in the early detection and response to infections. They react to viral pathogens by triggering inflammation to promote immune defences and initiate repair mechanisms. While a strong response is necessary for early viral control, overactivation of inflammasomes can precipitate harmful hyperinflammatory responses, a defining characteristic observed during severe influenza infections. The Absent in Melanoma 2 (AIM2) inflammasome, traditionally recognised for its role as a DNA sensor, has recently been implicated in the response to RNA viruses, like IAV. Paradoxically, AIM2 deficiency has been linked to both enhanced and reduced vulnerability to IAV infection. This review synthesises the current understanding of AIM2 inflammasome activation during IAV and explores its clinical implications. Understanding the nuances of AIM2's involvement could unveil novel therapeutic avenues for mitigating severe influenza outcomes.

Changes in Phenotypic and Molecular Features of Naïve and Central Memory T Helper Cell Subsets following SARS-CoV-2 Vaccination

Molecular changes in lymphocytes following SARS-CoV-2 vaccination are incompletely understood. We hypothesized that studying the molecular (transcriptomic, epigenetic, and T cell receptor (TCR) repertoire) changes in CD4+ T cells following SARS-CoV-2 vaccination could inform protective mechanisms and refinement of future vaccines. We tested this hypothesis by reporting alterations in CD4+ T cell subsets and molecular features of CD4+ naïve and CD4+ central memory (CM) subsets between the unvaccinated and vaccinated groups. Compared with the unvaccinated, the vaccinated had higher HLA-DR expression in CD4+ T subsets, a greater number of differentially expressed genes (DEGs) that overlapped with key differentially accessible regions (DARs) along the chromatin linked to inflammasome activation, translation, regulation (of apoptosis, inflammation), and significant changes in clonal architecture beyond SARS-CoV-2 specificity. Several of these differences were more pronounced in the CD4+CM subset. Taken together, our observations imply that the COVID-19 vaccine exerts its protective effects via modulation of acute inflammation to SARS-CoV-2 challenge.

Crosstalk between inflammasome sensors and DNA damage response pathways

Eukaryotic cells encounter diverse threats jeopardizing their integrity, prompting the development of defense mechanisms against these stressors. Among these mechanisms, inflammasomes are well-known for their roles in coordinating the inflammatory response against infections. Extensive research has unveiled their multifaceted involvement in cellular processes beyond inflammation. Recent studies emphasize the intricate relationship between the inflammasome and the DNA damage response (DDR). They highlight how the DDR participates in inflammasome activation and the reciprocal impact of inflammasome on DDR and genome integrity preservation. Moreover, novel functions of inflammasome sensors in DDR pathways have emerged, broadening our understanding of their roles. Finally, this review delves into identifying common signals that drive the activation of inflammasome sensors alongside activation cues for the DNA damage response, offering potential insights into shared regulatory pathways between these critical cellular processes.

Innate immune sensing of cell death in disease and therapeutics

Innate immunity, cell death and inflammation underpin many aspects of health and disease. Upon sensing pathogens, pathogen-associated molecular patterns or damage-associated molecular patterns, the innate immune system activates lytic, inflammatory cell death, such as pyroptosis and PANoptosis. These genetically defined, regulated cell death pathways not only contribute to the host defence against infectious disease, but also promote pathological manifestations leading to cancer and inflammatory diseases. Our understanding of the underlying mechanisms has grown rapidly in recent years. However, how dying cells, cell corpses and their liberated cytokines, chemokines and inflammatory signalling molecules are further sensed by innate immune cells, and their contribution to further amplify inflammation, trigger antigen presentation and activate adaptive immunity, is less clear. Here, we discuss how pattern-recognition and PANoptosome sensors in innate immune cells recognize and respond to cell-death signatures. We also highlight molecular targets of the innate immune response for potential therapeutic development.

Pyroptosis in Skeleton Diseases: A Potential Therapeutic Target Based on Inflammatory Cell Death

Skeletal disorders, including fractures, osteoporosis, osteoarthritis, rheumatoid arthritis, and spinal degenerative conditions, along with associated spinal cord injuries, significantly impair daily life and impose a substantial burden. Many of these conditions are notably linked to inflammation, with some classified as inflammatory diseases. Pyroptosis, a newly recognized form of inflammatory cell death, is primarily triggered by inflammasomes and executed by caspases, leading to inflammation and cell death through gasdermin proteins. Emerging research underscores the pivotal role of pyroptosis in skeletal disorders. This review explores the pyroptosis signaling pathways and their involvement in skeletal diseases, the modulation of pyroptosis by other signals in these conditions, and the current evidence supporting the therapeutic potential of targeting pyroptosis in treating skeletal disorders, aiming to offer novel insights for their management.

No Time to Die: How Cytomegaloviruses Suppress Apoptosis, Necroptosis, and Pyroptosis

Viruses are obligate intracellular pathogens as their replication depends on the metabolism of the host cell. The induction of cellular suicide, known as programmed cell death (PCD), has the potential to hinder viral replication and act as a first line of defense against viral pathogens. Apoptosis, necroptosis, and pyroptosis are three important PCD modalities. Different signaling pathways are involved in their execution, and they also differ in their ability to cause inflammation. Cytomegaloviruses (CMV), beta-herpesviruses with large double-stranded DNA genomes, encode a great variety of immune evasion genes, including several cell death suppressors. While CMV inhibitors of apoptosis and necroptosis have been known and studied for years, the first pyroptosis inhibitor has been identified and characterized only recently. Here, we describe how human and murine CMV interfere with apoptosis, necroptosis, and pyroptosis signaling pathways. We also discuss the importance of the different PCD forms and their viral inhibitors for the containment of viral replication and spread in vivo.

Programmed cell death in Helicobacter pylori infection and related gastric cancer

Programmed cell death (PCD) plays a crucial role in maintaining the normal structure and function of the digestive tract in the body. Infection with Helicobacter pylori (H. pylori) is an important factor leading to gastric damage, promoting the Correa cascade and accelerating the transition from gastritis to gastric cancer. Recent research has shown that several PCD signaling pathways are abnormally activated during H. pylori infection, and the dysfunction of PCD is thought to contribute to the development of gastric cancer and interfere with treatment. With the deepening of studies on H. pylori infection in terms of PCD, exploring the interaction mechanisms between H. pylori and the body in different PCD pathways may become an important research direction for the future treatment of H. pylori infection and H. pylori-related gastric cancer. In addition, biologically active compounds that can inhibit or induce PCD may serve as key elements for the treatment of this disease. In this review, we briefly describe the process of PCD, discuss the interaction between different PCD signaling pathways and the mechanisms of H. pylori infection or H. pylori-related gastric cancer, and summarize the active molecules that may play a therapeutic role in each PCD pathway during this process, with the expectation of providing a more comprehensive understanding of the role of PCD in H. pylori infection.

The roles of AIM2 in neurodegenerative diseases: insights and therapeutic implications

AIM2, a cytosolic innate immune receptor, has the capability to recognize double-stranded DNA (dsDNA). This paper delineates the structural features of AIM2 and its mechanisms of activation, emphasizing its capacity to detect cytosolic DNA and initiate inflammasome assembly. Additionally, we explore the diverse functions of AIM2 in different cells. Insights into AIM2-mediated neuroinflammation provide a foundation for investigating novel therapeutic strategies targeting AIM2 signaling pathways. Furthermore, we present a comprehensive review of the roles of AIM2 in neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Finally, we discuss its therapeutic implications. In conclusion, a profound understanding of AIM2 in neurodegenerative diseases may facilitate the development of effective interventions to mitigate neuronal damage and slow disease progression.

Unanticipated Loss of Inflammasomes in Birds

Inflammasomes are multiprotein complexes that form in response to ligands originating from pathogens as well as alterations of normal cell physiology caused by infection or tissue damage. These structures engage a robust inflammatory immune response that eradicates environmental microbes before they cause disease, and slow the growth of bona fide pathogens. Despite their undeniable utility in immunity, inflammasomes are radically reduced in birds. Perhaps most surprising is that, within all birds, NLRP3 is retained, while its signaling adapter ASC is lost, suggesting that NLRP3 signals via a novel unknown adapter. Crocodilian reptiles and turtles, which share a more recent common ancestor with birds, retain many of the lost inflammasome components, indicating that the deletion of inflammasomes occurred after birds diverged from crocodiles. Some bird lineages have even more extensive inflammasome loss, with songbirds continuing to pare down their inflammasomes until only NLRP3 and CARD8 remain. Remarkably, songbirds have lost caspase-1 but retain the downstream targets of caspase-1: IL-1β, IL-18, and the YVAD-linker encoding gasdermin A. This suggests that inflammasomes can signal through alternative proteases to activate cytokine maturation and pyroptosis in songbirds. These observations may reveal new contexts of activation that may be relevant to mammalian inflammasomes and may suggest new avenues of research to uncover the enigmatic nature of the poorly understood NLRP3 inflammasome.