Cytoplasmic LPS activates caspase-11: implications in TLR4-independent endotoxic shock

Regulatory roles of noncanonical inflammasomes in kidney diseases

Inflammation is a body's immune defense against infection and injury. The inflammatory response has two main phases: the priming and triggering phases. The triggering phase involves the activation of inflammasomes, cytoplasmic platforms for initiating inflammation, and Inflammasomes are classified into two categories: canonical and noncanonical. Kidney disease, or renal disease, refers to damage or illness affecting the kidneys, leading to a progressive decline in their function. Although the roles of canonical inflammasomes in kidney diseases are well-documented, recent research highlights novel roles of noncanonical inflammasomes in managing various inflammatory conditions. In particular, emerging studies emphasize the regulatory functions of noncanonical inflammasomes in a range of kidney diseases. This review explores recent discoveries regarding the regulatory functions of noncanonical inflammasomes, including human caspase-4/5 and murine caspase-11, in the progression of kidney diseases. It also examines the potential of targeting these inflammasomes as a novel therapeutic approach.

Pyroptosis and chemical classification of pyroptotic agents

Pyroptosis, as a lytic-inflammatory type of programmed cell death, has garnered considerable attention due to its role in cancer chemotherapy and many inflammatory diseases. This review will discuss the biochemical classification of pyroptotic inducers according to their chemical structure, pyroptotic mechanism, and cancer type of these targets. A structure-activity relationship study on pyroptotic inducers is revealed based on the surveyed pyroptotic inducer chemotherapeutics. The shared features in the chemical structures of current pyroptotic inducer agents were displayed, including an essential cyclic head, a vital linker, and a hydrophilic tail that is significant for π-π interactions and hydrogen bonding. The presented structural features will open the way to design new hybridized classes or scaffolds as potent pyroptotic inducers in the future, which may represent a solution to the apoptotic-resistance dilemma along with synergistic chemotherapeutic advantage.

Gemfibrozil mitigates caspase-11-driven myocardial pyroptosis in ischemia/reperfusion injury in mice

The size of the infarct area following acute myocardial infarction (AMI) is a critical prognostic factor. Caspase-11-dependent pyroptosis has been implicated as a key mechanism driving cardiomyocyte death after AMI. However, no therapeutic agents have been developed to inhibit myocardial cell death by targeting caspase-11. This study investigates the effects of gemfibrozil, a potential caspase-11 inhibitor, on ischemia/reperfusion-induced myocardial pyroptosis in mice. To model AMI, the left coronary artery of C57BL/6 N mice was ligated for 1 h, followed by reperfusion. Levels of cleaved caspase-11 and the N-terminal fragment of gasdermin D (GSDMD-N) in ischemic myocardial tissue increased progressively over time after ischemia/reperfusion. Gemfibrozil treatment during reperfusion significantly attenuated these increases in cleaved caspase-11 and GSDMD-N levels. Moreover, gemfibrozil reduced the extent of myocardial infarct size during reperfusion. In cultured cardiomyocytes isolated from adult mice, hypoxia/reoxygenation-induced increases in caspase-11 and GSDMD cleavage were similarly mitigated by gemfibrozil, which concurrently prevented necrotic cell death. These findings demonstrate the involvement of caspase-11-dependent pyroptosis in myocardial cell death following ischemia/reperfusion and suggest that gemfibrozil holds promise as a therapeutic agent for reducing myocardial infarct size after AMI.

Pyroptosis and its role in intestinal ischemia-reperfusion injury: a potential therapeutic target

Intestinal ischemia-reperfusion injury (II/RI) is a critical acute condition characterized by complex pathological mechanisms, including various modes of cell death. Among these, pyroptosis has garnered significant attention in recent years. This review explores the characteristics, molecular mechanisms, and implications of pyroptosis in II/RI, with a focus on therapeutic strategies targeting the pyroptosis pathway. Key processes such as NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation, caspase-1 activation, and gasdermin D (GSDMD)-mediated membrane pore formation are identified as central to pyroptosis. Compounds like MCC950, CY-09, metformin, and curcumin have shown promise in attenuating II/RI in preclinical studies by modulating these pathways. However, challenges remain in understanding non-canonical pyroptosis pathways, unraveling the exact mechanisms of GSDMD-induced pore formation, and translating these findings into clinical applications. Addressing these gaps will be crucial for developing innovative and effective treatments for II/RI.

NLRP11 is required for canonical NLRP3 and non-canonical inflammasome activation during human macrophage infection with mycobacteria

The NLRP11 protein is only expressed in primates and participates in the activation of the canonical NLRP3 and non-canonical NLRP3 inflammasome activation after infection with gram-negative bacteria. Here, we generated a series of defined NLRP11 deletion mutants to further analyze the role of NLRP11 in NLRP3 inflammasome activation. Like the complete NLRP11 deletion mutant (NLRP11-/-), the NLRP11 mutant lacking the NAIP, C2TA, HET-E, and TP1 (NACHT) and leucine-rich repeat (LRR) domains (NLRP11∆N_LRR) showed reduced activation of the canonical NLRP3 inflammasome, whereas a pyrin domain mutant (NLRP11∆PYD) had no effect on NLRP3 activation. The NLRP11-/- and NLRP11∆N_LRR mutants, but not the NLRP11∆PYD mutant, also displayed reduced activation of caspase-4 during infection with the intracytosolic, gram-negative pathogen Shigella flexneri. We found that the human-adapted, acid-fast pathogen Mycobacterium tuberculosis and the opportunistic pathogen Mycobacterium kansasii both activate the non-canonical NLRP11 inflammasome in a caspase-4/caspase-5-dependent pathway. In conclusion, we show that NLRP11 functions in the non-canonical caspase-4/caspase-5 inflammasome activation pathway and the canonical NLRP3 inflammasome pathway and that NLRP11 is required for full recognition of mycobacteria by each of these pathways. Our work extends the spectrum of bacterial pathogen recognition by the non-canonical NLRP11-caspase4/caspase-5 pathway beyond gram-negative bacteria.IMPORTANCEThe activation of inflammasome complexes plays a crucial role in intracellular pathogen detection. NLRP11 and caspase-4 are essential for recognizing lipopolysaccharide (LPS), a molecule found in gram-negative bacteria such as the human pathogens Shigella spp., which activate both canonical NLRP3 and non-canonical inflammasome pathways. Through a series of deletion mutants, we demonstrate that the NACHT and LRR domains of NLRP11, but not its pyrin domain, are critical for detection of S. flexneri. Notably, our research reveals that the acid-fast bacterium M. tuberculosis is also detected by NLRP11 and caspase-4, despite not producing LPS. These findings significantly expand the range of pathogens recognized by NLRP11 and caspase-4 to now include acid-fast bacteria that do not contain LPS and underscore the versatility of these innate immune components in pathogen detection.

Intracellular bacterial LPS drives pyroptosis and promotes aggressive phenotype in oral squamous cell carcinoma

Intracellular bacterial components represent an emerging tumor element that has recently been documented in multiple cancer types, yet their biological functions remain poorly understood. Oral squamous cell carcinoma (OSCC) is a particularly aggressive malignancy lacking highly effective targeted treatments. Here, we explored the functional significance of intracellular bacterial lipopolysaccharide (LPS) in OSCC. Normal human oral keratinocytes (HOKs), HPV-transformed oral keratinocytes (IHGK), and three OSCC cell lines were transfected with ultrapure bacterial LPS. Cytotoxicity was assessed via lactate dehydrogenase (LDH) release assays. Production of interleukin (IL)-1β and IL-18 was measured using ELISA. Impact on tumor progression was evaluated using cell proliferation, migration, invasion, and tubulogenesis assays. Intracellular LPS-induced significant LDH release and increased secretion of IL-18 and IL-1β in IHGK and cancer cells, but not in normal HOKs, indicating selective cytotoxicity and pyroptosis. Notably, metastatic cancer cells exhibited enhanced invasive and vessel-like structures upon LPS exposure, while IHGK cells exhibited increased proliferation without changes in migration. Our findings suggest that intracellular LPS may not merely reside passively within the tumor milieu, but could contribute to OSCC progression by triggering noncanonical inflammasome activation and pyroptosis. This process may enhance pro-inflammatory signaling and more aggressive cellular phenotypes, especially in metastatic settings. Targeting intracellular LPS or its downstream inflammasome pathways may thus represent a promising therapeutic strategy for OSCC, warranting further in vivo and clinical investigations.

Caspases: structural and molecular mechanisms and functions in cell death, innate immunity, and disease

Caspases are critical regulators of cell death, development, innate immunity, host defense, and disease. Upon detection of pathogens, damage-associated molecular patterns, cytokines, or other homeostatic disruptions, innate immune sensors, such as NLRs, activate caspases to initiate distinct regulated cell death pathways, including non-lytic (apoptosis) and innate immune lytic (pyroptosis and PANoptosis) pathways. These cell death pathways are driven by specific caspases and distinguished by their unique molecular mechanisms, supramolecular complexes, and enzymatic properties. Traditionally, caspases are classified as either apoptotic (caspase-2, -3, -6, -7, -8, -9, and -10) or inflammatory (caspase-1, -4, -5, and -11). However, extensive data from the past decades have shown that apoptotic caspases can also drive lytic inflammatory cell death downstream of innate immune sensing and inflammatory responses, such as in the case of caspase-3, -6, -7, and -8. Therefore, more inclusive classification systems based on function, substrate specificity, or the presence of pro-domains have been proposed to better reflect the multifaceted roles of caspases. In this review, we categorize caspases into CARD-, DED-, and short/no pro-domain-containing groups and examine their critical functions in innate immunity and cell death, along with their structural and molecular mechanisms, including active site/exosite properties and substrates. Additionally, we highlight the emerging roles of caspases in cellular homeostasis and therapeutic targeting. Given the clinical relevance of caspases across multiple diseases, improved understanding of these proteins and their structure-function relationships is critical for developing effective treatment strategies.

A neuroimmune pathway drives bacterial infection

Pathogen-induced septic death presents a substantial public health challenge, with its neuroimmune mechanisms largely unexplored. Our study investigates neurotransmitter modulation of ACOD1 expression, a regulator of immunometabolism activated by bacterial lipopolysaccharide (LPS). Screening neurotransmitters identifies dopamine as a potent inhibitor of LPS-induced ACOD1 expression in innate immune cells. Mechanistically, DRD2 forms a complex with TLR4, initiating MAPK3-dependent CREB1 phosphorylation and subsequent ACOD1 transcription. Conversely, dopamine disrupts TLR4-MYD88 interaction via DRD2 without affecting the formation of the LPS-induced TLR4-MD2-CD14 complex. Enhanced ACOD1 expression induces CD274/PD-L1 production independently of itaconate, precipitating inflammation-associated immunosuppression in sepsis. Delayed administration of pramipexole, a dopamine agonist, mitigates lethality in bacterial sepsis mouse models. Conversely, the dopamine antagonist aripiprazole exacerbates sepsis mortality. Dysregulation of the dopamine-ACOD1 axis correlates with sepsis severity in patients, indicating a potential therapeutic target for modulating this neuroimmune pathway.

Pyroptosis: molecular mechanisms and roles in disease

Pyroptosis is a type of programmed necrosis triggered by the detection of pathogens or endogenous danger signals in the cytosol. Pyroptotic cells exhibit a swollen, enlarged morphology and ultimately undergo lysis, releasing their cytosolic contents - such as proteins, metabolites, and nucleic acids - into the extracellular space. These molecules can function as danger-associated molecular patterns (DAMPs), triggering inflammation when detected by neighboring cells. Mechanistically, pyroptosis is initiated by members of the gasdermin protein family, which were identified a decade ago as pore-forming executors of cell death. Mammalian gasdermins consist of a cytotoxic N-terminal domain, a flexible linker, and a C-terminal regulatory domain that binds to and inhibits the N-terminus. Proteolytic cleavage within the linker releases the N-terminal domain, enabling it to target various cellular membranes, including nuclear, mitochondrial, and plasma membranes, where it forms large transmembrane pores. Gasdermin pores in the plasma membrane disrupt the electrochemical gradient, leading to water influx and cell swelling. Their formation also activates the membrane protein ninjurin-1 (NINJ1), which oligomerizes to drive complete plasma membrane rupture and the release of large DAMPs. Since their discovery as pore-forming proteins, gasdermins have been linked to pyroptosis not only in host defense but also in various pathological conditions. This review explores the history of pyroptosis, recent insights into gasdermin activation, the cellular consequences of pore formation, and the physiological roles of pyroptosis.

Multifunctional Co-Delivery Systems with Downregulation of the Novel Target PIM1 in Macrophages to Ameliorate TF-Mediated Coagulopathy in Sepsis

Disordered coagulation is an independent risk factor for mortality in patients with sepsis and currently lacks effective therapeutic strategies. In this study, PIM1, a novel target predominantly expressed in macrophages during sepsis, is investigated by bioinformatics analysis and clinical evaluation in patients with sepsis compared with healthy individuals. The regulatory mechanism by which PIM1 promotes the release of tissue factors (TF) from macrophages by modulating the phosphorylation levels of mTOR through the AKT and MAPK signaling pathways is demonstrated both in vitro and in vivo. Based on these findings, a multifunctional co-delivery system based on mesoporous polydopamine (MPDA) nanoparticles (NPs) coated with cationic polyethyleneimine (PEI) and macrophage-targeting glucomannan (GM) (MPDA@PEI@GM NPs) is proposed for the co-delivery of the PIM1 inhibitors SMI-4a and small interfering RNA (siPIM1) to downregulate PIM1 expression and improve sepsis-induced coagulopathy. MPDA@SMI-4a@PEI/siPIM1@GM demonstrates negligible cytotoxicity, excellent macrophage-targeting efficiency, prolonged blood circulation, and significantly downregulated PIM1 expression. Notably, treatment with MPDA@SMI-4a@PEI/siPIM1@GM improves the survival rates of septic mice by ameliorating disordered coagulation and alleviating lung injury. Bioinformatic analysis and clinical research-guided MPDA@SMI-4a@PEI/siPIM1@GM co-delivery systems improve TF-mediated coagulopathy in sepsis and alleviate sepsis-induced acute lung injury, marking a significant advancement in the development of clinical antisepsis therapies.

The NLRP3 Inflammasome in inflammatory diseases: Cellular dynamics and role in granuloma formation

The innate immune system recognizes pathogen-associated molecular patterns (PAMPs) and damage associated molecular patterns (DAMPs) through pattern recognition receptors (PRRs). Inflammasomes, cytoplasmic protein complexes, are activated in response to PAMPs and DAMPs, leading to the release of inflammatory cytokines such as IL-1β and IL-18. NLRP3 inflammasome is one of the best characterized inflammasomes and recently its activation has been associated with granuloma formation, structures that aggregate immune cells in response to infections, such as those caused by bacteria, fungi and parasites, and autoinflammatory diseases, such as sarcoidosis. Activation of NLRP3 inflammasomes in macrophages induces the release of cytokines that recruit immune cells, such as monocytes and lymphocytes, to the site of infection. Neutrophils, monocytes, T and B lymphocytes are important in the formation and maintenance of granulomas. Although NLRP3 plays a key role in the immune response, cell recruitment and granuloma formation, many aspects of its function in different cell types remain to be elucidated. In this review, we aim to outline the NLRP3 inflammasome not only as a protein complex that aids innate immune cells in combating intracellular pathogens but also as a platform with broader implications in orchestrating immune responses. This underexplored aspect of the NLRP3 inflammasome presents a novel perspective on its involvement in immunity. Thus, we review the current understanding of the role of the NLRP3 inflammasome in immune cell infiltration and its significance in the organization and formation of granulomas in inflammatory diseases.

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.

Glioblastoma-associated macrophages in glioblastoma: from their function and mechanism to therapeutic advances

Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor in adults and has high mortality rates worldwide. GBM progression, treatment, and prognosis are influenced by the tumor microenvironment (TME), which includes immune, stromal, and tumor cells. Among them, glioblastoma-associated macrophages (GAMs) act as key regulators of GBM pathobiology. GAMs exhibit remarkable plasticity, as they can exhibit both protumor and antitumor effects. However, their function is determined by polarization and the TME. In this review, we provide a comprehensive overview of the current understanding of the biology of GAMs in GBM, including their origins, phenotypic diversity, and functional roles. We discuss the intricate crosstalk between GAMs and tumor cells, as well as other immune and stromal components, and highlight the mechanisms underlying GAM-mediated tumor progression, invasion, angiogenesis, and immune system evasion. Furthermore, we explore the therapeutic implications of targeting GAMs in GBM and discuss emerging strategies aimed at reprogramming GAMs toward an antitumorigenic phenotype or selectively depleting protumorigenic subsets. The final aim is to develop innovative therapeutic approaches that disrupt GBMs. By leveraging our increased understanding of GAM biology, we lay the foundation for transformative advances in GBM treatment to improve patient prognosis.

Pathways regulating the levels of tissue factor-positive extracellular vesicles and activation of coagulation in endotoxemic mice

BACKGROUND

Sepsis and endotoxemia are associated with activation of coagulation as part of the host response to infection, but this can lead to disseminated intravascular coagulation. Lipopolysaccharide (LPS) is detected by the cell surface receptor toll-like receptor (TLR)4 and the intracellular receptor caspase 11.

OBJECTIVES

This study aimed to determine the roles of TLR4, caspase 11, and the NOD-, LRR-, and pyrin domain-containing protein (NLRP)3 inflammasome in increases of extracellular vesicle (EV) tissue factor (TF) activity and activation of coagulation in a mouse endotoxemia model.

METHODS

LPS was injected intraperitoneally into control mice and Tlr4-/-, Casp11-/-, Nlrp3-/-, or Casp1-/- mice or wild-type mice treated with the TLR4 inhibitor TAK-242 or the NLRP3 inhibitor MCC950. Blood samples were collected at 3 and 8 hours for analysis of cells, tumor necrosis factor α, interleukin (IL)-6, IL-1β, soluble intercellular adhesion molecule 1, EV TF activity, and thrombin-antithrombin (TAT) complexes.

RESULTS

LPS induced IL-1β at 3 and 8 hours, indicating inflammasome activation at these times. Tlr4 deficiency was associated with a significant decrease in tumor necrosis factor α and IL-6 but not soluble intercellular adhesion molecule 1 in endotoxemic mice. LPS induction of EV TF activity and TAT reduced significantly in Tlr4-/- mice at both 3 and 8 hours postinjection. In contrast, EV TF activity and TAT were only reduced in Casp11-/- mice at 8 hours post-LPS injection.

CONCLUSION

Our results indicate that TLR4 plays a major role whereas caspase 11 and the NLRP3 inflammasome play minor roles in the generation of TF-positive EVs and activation of coagulation in a mouse model of endotoxemia.

GL-V9 inhibits Caspase-11 activation-induced pyroptosis by suppressing ALOX12-mediated lipid peroxidation to alleviate sepsis

BACKGROUND AND PURPOSE

Sepsis, caused by pathogen infection, poses a serious threat to human life. While the link between sepsis and pyroptosis via Caspase-11 non-canonical inflammasome activation is known, effective treatments remain lacking. Previous studies have confirmed that GL-V9 has antifibrotic and antitumor activities, but whether it has a therapeutic effect on sepsis is unclear. The aim of this study was to investigate the anti-inflammatory activity of GL-V9 and its possible mechanism.

EXPERIMENTAL APPROACH

The caecal ligation and puncture (CLP) model was used to assess the antiseptic effects of GL-V9 in vivo. Mouse bone marrow derived macrophages (BMDMs) and murine macrophages line J774A.1 also served as an in vitro Caspase-11 activation induced pyroptosis model. Cellular functions and molecular mechanism were analysed using cell viability assay, PI uptake assay, western blotting, immunofluorescence and co-immunoprecipitation.

KEY RESULTS

GL-V9 reduced tissue damage and mortality in mice with sepsis, and decreased the secretion of inflammatory factors in vivo. In vitro, GL-V9 suppressed Caspase-11-induced pyroptosis and prevented the release of LPS from early endosomes. Mechanistic studies revealed that GL-V9 limits Caspase-11 activation by inhibiting ALOX12-mediated lipid peroxidation. Further studies confirmed that GL-V9 did not further alleviate the symptoms and inflammatory response of septic mice in Alox12 deficient mice.

CONCLUSION AND IMPLICATIONS

GL-V9 exerts a powerful anti-sepsis effect in vivo, which is associated with the inhibition of Caspase-11 activation. Mechanistically, GL-V9 may block LPS release from early endosomes by inhibiting ALOX12-mediated lipid peroxidation. This suggests that GL-V9 is a potential candidate for the treatment of sepsis.

Salmonella-NLRP3 Inflammasome Crosstalk: Host Defense Activation Versus Bacterial Immune Evasion Strategies

The innate immune system plays a crucial role in defending against Salmonella infection. Inflammasomes are macromolecular complexes that assemble in response to the recognition of pathogen- or danger-associated molecular patterns. These complexes serve as signaling platforms for the activation of inflammatory Caspases, which subsequently triggers the maturation and secretion of the pro-inflammatory cytokines IL-1β and IL-18. This process also initiates pyroptosis, a highly inflammatory form of programmed cell death characterized by lytic cell lysis. Salmonella are intracellular pathogens that proliferate within epithelial cells and macrophages, posing a significant public health risk in both developed and developing countries. During Salmonella infection, the canonical NLRP3 and NLRC4 inflammasome, as well as non-canonical inflammasome, are activated. Unlike NLRC4 and non-canonical inflammasomes, which play crucial roles during intestinal infection phases, the role of NLRP3 inflammasome in resisting Salmonella infection demonstrates a higher degree of complexity and uncertainty. Nonetheless, the activation of NLRP3 inflammasome, along with the downstream innate and adaptive responses, form a robust host immune barrier against potential pathogens. Therefore, successful pathogens must evolve multiple mechanisms to circumvent or counteract these immune barriers. Here we review and discuss the mechanisms of NLRP3 inflammasome activation triggered by intracellular Salmonella, as well as the multiple strategies employed by Salmonella to avoid or delay NLRP3 inflammasome activation. A deeper understanding of how NLRP3 inflammasomes recognize Salmonella and how pathogens evade NLRP3 activation has the potential to facilitate the development of novel prevention and control measures for Salmonella infection.

A complex of NLRP3 with caspase-4 is essential for inflammasome activation by Tannerella forsythia infection

Periodontitis, a chronic inflammatory disease of periodontal tissue, is often associated with a group of pathogenic bacteria known as the "red complex", including Tannerella forsythia. Previous papers showed that T. forsythia induces many kinds of inflammatory cytokines including interleukin (IL)-1β regulated by inflammasome activation. However, the physiological function of periodontitis and the mechanism to induce inflammasome activation by T. forsythia infection are poorly understood. In this study, we demonstrate that the Nod-like receptor pyrin domain containing 3 (NLRP3) and caspase-4 are essential for inflammasome activation by T. forsythia infection, playing a crucial role in IL-1β maturation in THP-1 cells. We also showed that the knockout of ASC or Gasdermin D suppresses pyroptotic cell death. Moreover, co-immunoprecipitation assays confirmed the formation of a complex involving caspase-4, NLRP3, and ASC following T. forsythia infection. Additionally, reactive oxygen species production was identified as a key factor in caspase-4-mediated NLRP3 inflammasome activation by T. forsythia infection. These results enhance our understanding of inflammasome activation in response to T. forsythia infection and provide new insights into the pathogenic mechanisms of periodontitis.

Inflammasomes primarily restrict cytosolic Salmonella replication within human macrophages

Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that utilizes its type III secretion systems (T3SSs) to inject virulence factors into host cells and colonize the host. In turn, a subset of cytosolic immune receptors respond to T3SS ligands by forming multimeric signaling complexes called inflammasomes, which activate caspases that induce interleukin-1 (IL-1) family cytokine release and an inflammatory form of cell death called pyroptosis. Human macrophages mount a multifaceted inflammasome response to Salmonella infection that ultimately restricts intracellular bacterial replication. However, how inflammasomes restrict Salmonella replication remains unknown. We find that caspase-1 is essential for mediating inflammasome responses to Salmonella and restricting bacterial replication within human macrophages, with caspase-4 contributing as well. We also demonstrate that the downstream pore-forming protein gasdermin D (GSDMD) and Ninjurin-1 (NINJ1), a mediator of terminal cell lysis, play a role in controlling Salmonella replication in human macrophages. Notably, in the absence of inflammasome responses, we observed hyperreplication of Salmonella within the cytosol of infected cells as well as increased bacterial replication within vacuoles, suggesting that inflammasomes control Salmonella replication primarily within the cytosol and also within vacuoles. These findings reveal that inflammatory caspases and pyroptotic factors mediate inflammasome responses that restrict the subcellular localization of intracellular Salmonella replication within human macrophages.

BBB breakdown caused by plasma membrane pore formation

The blood-brain barrier, recently reintroduced as the blood-brain border (BBB), is a dynamic interface between the central nervous system (CNS) and the bloodstream. Disruption of the BBB exposes the CNS to peripheral pathogens and harmful substances, causing or worsening various CNS diseases. While traditional views attribute BBB failure to tight junction disruption or increased transcytosis, recent studies highlight the critical role of gasdermin D (GSDMD) pore formation in brain endothelial cells (bECs) during BBB disruption by lipopolysaccharide (LPS) or bacterial infections. This mechanism may also be involved in neurological complications like the 'brain fog' seen in long COVID. Pore formation in bECs may represent a prevalent mechanism causing BBB leakage. Investigating membrane-permeabilizing pores or channels and their effects on BBB integrity is a growing area of research. Further exploration of molecular processes that maintain, disrupt, and restore bEC membrane integrity will advance our understanding of brain vasculature and aid in developing new therapies for BBB-related diseases.

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.

Impact of a High-Fat Diet on the Gut Microbiome: A Comprehensive Study of Microbial and Metabolite Shifts During Obesity

Over the last few decades, the prevalence of metabolic diseases such as obesity, diabetes, non-alcoholic fatty liver disease, hypertension, and hyperuricemia has surged, primarily due to high-fat diet (HFD). The pathologies of these metabolic diseases show disease-specific alterations in the composition and function of their gut microbiome. How HFD alters the microbiome and its metabolite to mediate adipose tissue (AT) inflammation and obesity is not well known. Thus, this study aimed to identify the changes in the gut microbiome and metabolomic signatures induced by an HFD to alter obesity. To explore the changes in the gut microbiota and metabolites, 16S rRNA gene amplicon sequencing and metabolomic analyses were performed after HFD and normal diet (ND) feeding. We noticed that, at taxonomic levels, the number of operational taxonomic units (OTUs), along with the Chao and Shannon indexes, significantly shifted in HFD-fed mice compared to those fed a ND. Similarly, at the phylum level, an increase in Firmicutes and a decrease in Bacteroidetes were noticed in HFD-fed mice. At the genus level, an increase in Lactobacillus and Ruminococcus was observed, while Allobaculum, Clostridium, and Akkermansia were markedly reduced in the HFD group. Many bacteria from the Ruminococcus genus impair bile acid metabolism and restrict weight loss. Firmicutes are efficient in breaking down complex carbohydrates into short-chain fatty acids (SCFAs) and other metabolites, whereas Bacteroidetes are involved in a more balanced or efficient energy extraction. Thus, an increase in Firmicutes over Bacteroidetes enhances the absorption of more calories from food, which may contribute to obesity. Taken together, the altered gut microbiota and metabolites trigger AT inflammation, which contributes to metabolic dysregulation and disease progression. Thus, this study highlights the potential of the gut microbiome in the development of therapeutic strategies for obesity and related metabolic disorders.

Sublethal systemic LPS in mice enables gut-luminal pathogens to bloom through oxygen species-mediated microbiota inhibition

Endotoxin-driven systemic immune activation is a common hallmark across various clinical conditions. During acute critical illness, elevated plasma lipopolysaccharide triggers non-specific systemic immune activation. In addition, a compositional shift in the gut microbiota, including an increase in gut-luminal opportunistic pathogens, is observed. Whether a causal link exists between acute endotoxemia and abundance of gut-luminal opportunistic pathogens is incompletely understood. Here, we model acute, pathophysiological lipopolysaccharide concentrations in mice and show that systemic exposure promotes a 100-10'000-fold expansion of Klebsiella pneumoniae, Escherichia coli, Enterococcus faecium and Salmonella Typhimurium in the gut within one day, without overt enteropathy. Mechanistically, this is driven by a Toll-like receptor 4-dependent increase in gut-luminal oxygen species levels, which transiently halts microbiota fermentation and fuels growth of gut-luminal facultative anaerobic pathogens through oxidative respiration. Thus, systemic immune activation transiently perturbs microbiota homeostasis and favours opportunistic pathogens, potentially increasing the risk of infection in critically ill patients.

Beyond the Toll-Like Receptor 4. Structure-Dependent Lipopolysaccharide Recognition Systems: How far are we?

With an enormous potential in immunology and vaccinology, lipopolysaccharides (LPSs) are among the most extensively studied bacteria-derived molecules. LPS centered studies are countless, and their results reverberate in all areas of the life sciences, including chemistry, biology, genetics, biophysics, and medicine. Most of these research activities are focused on the LPS-induced immune response activation by means of Myeloid Differentiation protein-2/Toll Like Receptor 4 (MD-2/TLR4) complex, which currently is the most largely explored LPS sensing pathway. However, the enormous structural variability of LPS allows interactions with numerous other receptors involved in a wide range of equally important immunological scenarios. In this review, we explore these additional LPS recognition systems, which operate within interconnected signaling cascades, highlighting their role in maintaining physiological homeostasis and their involvement in the development of severe human diseases. Understanding these pathways, their interconnections, and the crosstalk between them and TLR4/MD-2 is essential for guiding the development of pharmacologically active molecules that could specifically modulate the inflammatory response, paving the way to new strategies for combating immune-mediated diseases and resistant infections.

Roles of Pyroptosis in the Progression of Pulpitis and Apical Periodontitis

Pyroptosis is a type of programmed cell death that induces proinflammatory cytokine release and is closely related to inflammatory diseases. Pulpitis and apical periodontitis are common inflammatory diseases that lead to alveolar bone destruction and tooth loss. Recent studies have revealed that pyroptosis is crucial in the progression of pulpitis and apical periodontitis, which involves various cell types and leads to different results. Odontoblasts are located at the periphery of dental pulp tissue and are susceptible to various irritants, the lysates from odontoblasts act as alerts and induce immune reactions in the inner pulp after pyroptosis. The expression levels of inflammasomes in dental pulp cells (DPCs) change with the progression of pulpitis, which may serve as a diagnostic marker of pulpitis. Periodontal ligament fibroblasts (PDLFs) undergo pyroptosis when stimulated by bacterial infection or cyclic stretch and are associated with both infection-induced and trauma-induced apical periodontitis. Immune cells can undergo pyroptosis directly after infection or are influenced by the pyroptotic secretome of other cells, which changes their composition. In this review, we briefly introduce the location and function of different cell types involved in the progression of pulpitis and apical periodontitis, summarize the roles of pyroptosis in different cells, and discuss the effects of drugs targeting pyroptosis in the treatment of pulpitis and apical periodontitis.

NLRP11 is required for canonical NLRP3 and non-canonical inflammasome activation during human macrophage infection with mycobacteria

The NLRP11 protein is only expressed in primates and participates in the activation of the canonical NLRP3 and non-canonical NLRP3 inflammasome activation after infection with gram-negative bacteria. Here, we generated a series of defined NLRP11 deletion mutants to further analyze the role of NLRP11 in NLRP3 inflammasome activation. Like the complete NLRP11 deletion mutant (NLRP11 -/- ), the NLRP11 mutant lacking the NACHT and LRR domains (NLRP11 ΔN_LRR ) showed reduced activation of the canonical NLRP3 inflammasome, whereas a pyrin domain mutant (NLRP11 ΔPYD ) had no effect on NLRP3 activation. The NLRP11 -/- and NLRP11 ΔN_LRR mutants but not the NLRP11 ΔPYD mutant also displayed reduced activation of caspase-4 during infection with the intracytosolic, gram-negative pathogen Shigella flexneri. We found that the human adapted, acid-fast pathogen Mycobacterium tuberculosis and the opportunistic pathogen M. kansasii both activate the non-canonical NLRP11 inflammasome in a caspase-4/5-dependent pathway. In conclusion, we show that NLRP11 functions in the non-canonical caspase-4/5 inflammasome activation pathway and the canonical NRLP3 inflammasome pathway, and that NLRP11 is required for full recognition of mycobacteria by each of these pathways. Our work extends the spectrum of bacterial pathogen recognition by the non-canonical NLRP11-caspase4/5 pathway beyond gram-negative bacteria.

Functional interplay between non-canonical inflammasomes and autophagy in inflammatory responses and diseases

The inflammasome is a cytosolic multiprotein platform that plays a key role in the inflammatory response, an essential innate immune response that protects the body from pathogens and cellular danger signals. Autophagy is a fundamental cellular mechanism that maintains homeostasis through the elimination and recycling of dysfunctional molecules and subcellular elements. Many previous studies have demonstrated a functional interplay between canonical inflammasomes that were earlier discovered and autophagy in inflammatory responses and diseases. Given the increasing evidence that non-canonical inflammasomes are unique and key factors in inflammatory responses, the functional interplay between non-canonical inflammasomes and autophagy is noteworthy. Recent studies have demonstrated that non-canonical inflammasomes and autophagy are functionally correlated with inflammatory responses and diseases. This review comprehensively discusses recent studies that have investigated the functional interplay of non-canonical inflammasomes, such as mouse caspase-11 and human caspase-4, with autophagy and autophagy-related proteins in inflammatory responses and diseases and provides insight into the development of novel anti-inflammatory therapeutics by modulating the functional interplay between non-canonical inflammasomes and autophagy.

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.

A VgrG2b fragment cleaved by caspase-11/4 promotes Pseudomonas aeruginosa infection through suppressing the NLRP3 inflammasome

The T6SS of Pseudomonas aeruginosa plays an essential role in the establishment of chronic infections. Inflammasome-mediated inflammatory cytokines are crucial for host defense against bacterial infections. We found that P. aeruginosa infection activates the non-canonical inflammasome in macrophages, yet it inhibits the downstream activation of the NLRP3 inflammasome. The VgrG2b of P. aeruginosa is recognized and cleaved by caspase-11, generating a free C-terminal fragment. The VgrG2b C-terminus can bind to NLRP3, inhibiting the activation of the NLRP3 inflammasome by rejecting NEK7 binding to NLRP3. Administration of a specific peptide that inhibits caspase-11 cleavage of VgrG2b significantly improves mouse survival during infection. Our discovery elucidates a mechanism by which P. aeruginosa inhibits host immune response, providing a new approach for the future clinical treatment of P. aeruginosa infections.

Role and Mechanism of Mitochondrial Ribosomal Proteins in Septic Myocardial Injury

Objective

To investigate the role of mitochondrial ribosomal proteins (MRPs) in the pathogenesis and progression of septic myocardial injury. Additionally, we aim to propose new technical strategies and experimental foundations for the prevention and treatment of septic myocardial injury.

Methods

Animal and cell models of septic myocardial injury were established. Aberrantly expressed MRPs were screened using transcriptome sequencing, and their expression was verified by RT-qPCR and Western blot. Subsequently, overexpressed and knockdown cell models of myocardial injury were constructed. The effects on CO I, PGC-1α, ATP content, ROS fluorescence intensity, mitochondrial membrane potential, and GSDMD were assessed, along with changes in caspase-4 and IL-1β expression levels.

Results

Transcriptome sequencing revealed a reduction in MRPs expression in mice with septic myocardial injury. Both RT-qPCR and Western blot analysis confirmed the decreased expression of MRPs in animal and cell models of septic myocardial injury. Furthermore, overexpression of both MRPS16 and MRPL47 mitigated the decrease in CO I and PGC-1α levels induced by septic myocardial injury. Additionally, overexpression of MRPS16 and MRPL47 alleviated the elevated levels of IL-1β, caspase-4, and GSDMD caused by septic myocardial injury.

Conclusion

The findings suggest that both MRPS16 and MRPL47 can mitigate mitochondrial injury by attenuating mitochondrial biosynthesis dysfunction, energy metabolism disorders, and Ca2+ disturbances caused by septic myocardial injury. This ultimately reduces cellular damage and alleviates septic myocardial injury.

Bioinformatics Analysis of the Anti-Inflammatory Mechanism and Potential Therapeutic Efficacy of Kezimuke granules in Treating Urinary Tract Infections by Inhibiting NLRP3 Inflammasome Activation

Kezimuke granules (KZMK), derived from traditional Kazakh folk medicine, exhibit a variety of pharmacological properties. Long-term clinical studies have demonstrated their efficacy in clearing heat, detoxifying, promoting qi circulation, and alleviating gonorrhea. However, their specific pharmacological effects on urinary tract infections remain unclear. This study employed UHPLC-MS/MS technology to identify the blood components of KZMK and integrated network pharmacology with bioinformatics analysis for molecular docking validation. The anti-inflammatory activity of KZMK was further evaluated using a rat model of LPS-induced cystitis. A total of 17 components in KZMK were identified as capable of entering the bloodstream. Predictive analysis revealed that its primary targets include Caspase-1, NLRP3, STAT1, TLR4, and TNF, with the NLRP3 inflammasome signaling pathway emerging as the key mechanism. In vivo studies showed that KZMK effectively reduced the white blood cell (WBC) count and bladder index in urine sediments of rats with cystitis. Additionally, KZMK alleviated bladder congestion, edema, and histopathological changes in the animals. Treatment with KZMK led to decreased levels of IL-18 and IL-1β cytokines. KZMK significantly inhibited the expression of NLRP3, GSDMD, and Caspase-1 in LPS-induced cystitis, further confirming its anti-inflammatory effects. These findings indicate that KZMK provides protection against LPS-induced cystitis, primarily by inhibiting the activation of the NLRP3 inflammasome. Collectively, the results suggest that KZMK holds promise as a potential therapeutic option for urinary tract infections.

Caspase-11 and NLRP3 exacerbate systemic Klebsiella infection through reducing mitochondrial ROS production

Introduction

Klebsiella pneumoniae is a Gram-negative bacterium and the third most commonly isolated microorganism in blood cultures from septic patients. Despite extensive research, the mechanisms underlying K. pneumoniae-induced sepsis and its pathogenesis remain unclear. Acute respiratory failure is a leading cause of mortality in systemic K. pneumoniae infections, highlighting the need to better understand the host immune response and bacterial clearance mechanisms.

Method

To investigate the impact of K. pneumoniae infection on organ function and immune response, we utilized a systemic infection model through intraperitoneal injection in mice. Bacterial loads in key organs were quantified, and lung injury was assessed. Survival analysis was performed in wild-type (WT) and gene deficient mice. Mitochondrial damage and reactive oxygen species (ROS) production, as well as cytokine levels were measured in macrophages isolated from these mice to evaluate their contribution to bacterial clearance capacity.

Results

Our findings demonstrate that K. pneumoniae systemic infection results in severe lung injury and significant bacterial accumulation in multiple organs, with the highest burden in the lungs. Deficiency of caspase-11 or NLRP3 led to prolonged survival, a reduction in pulmonary bacterial load, increased blood oxygen levels, and decreased IL-6 levels in the lungs compared to WT controls. Furthermore, caspase-11- and NLRP3-deficient macrophages exhibited elevated mitochondrial ROS production in response to K. pneumoniae, which correlated with more effective bacterial clearance.

Discussion

These results suggest that caspase-11 and NLRP3 contribute to K. pneumoniae-induced sepsis by impairing mitochondrial function and reducing ROS production in macrophages, thereby compromising bacterial clearance. The observed reduction in lung injury and increased survival in caspase-11- and NLRP3-deficient mice indicate that targeting these pathways may offer potential therapeutic strategies to improve host defense against systemic K. pneumoniae infection.

Innate immune sensors and regulators at the blood brain barrier: focus on toll-like receptors and inflammasomes as mediators of neuro-immune crosstalk and inflammation

Cerebral endothelial cells (CEC) that form the brain capillaries are the principal constituents of the blood brain barrier (BBB), the main active interface between the blood and the brain which plays a protective role by restricting the infiltration of pathogens, harmful substances and immune cells into the brain while allowing the entry of essential nutrients. Aberrant CEC function often leads to increased permeability of the BBB altering the bidirectional communication between the brain and the bloodstream and facilitating the extravasation of immune cells into the brain. In addition to their role as essential gatekeepers of the BBB, CEC exhibit immune cell properties as they can receive and transmit signals between the blood and the brain partly via release of inflammatory effectors in pathological conditions. Cerebral endothelial cells express innate immune receptors, including toll like receptors (TLRs) and inflammasomes which are the first sensors of exogenous or endogenous dangers and initiators of immune and inflammatory responses which drive neural dysfunction and degeneration. Accumulating evidence indicates that activation of TLRs and inflammasomes in CEC compromises BBB integrity, promotes aberrant neuroimmune interactions and modulates both systemic and neuroinflammation, common pathological features of neurodegenerative and psychiatric diseases and central nervous system (CNS) infections and injuries. The goal of the present review is to provide an overview of the pivotal roles played by TLRs and inflammasomes in CEC function and discuss the molecular and cellular mechanisms by which they contribute to BBB disruption and neuroinflammation especially in the context of traumatic and ischemic brain injuries and brain infections. We will especially focus on the most recent advances and literature reports in the field to highlight the knowledge gaps. We will discuss future research directions that can advance our understanding of the central contribution of innate immune receptors to CEC and BBB dysfunction and the potential of innate immune receptors at the BBB as promising therapeutic targets in a wide variety of pathological conditions of the brain.

Endothelial GSDMD underlies LPS-induced systemic vascular injury and lethality

Endothelial injury destroys endothelial barrier integrity, triggering organ dysfunction and ultimately resulting in sepsis-related death. Considerable attention has been focused on identifying effective targets for inhibiting damage to endothelial cells to treat endotoxemia-induced septic shock. Global gasdermin D (Gsdmd) deletion reportedly prevents death caused by endotoxemia. However, the role of endothelial GSDMD in endothelial injury and lethality in lipopolysaccharide-induced (LPS-induced) endotoxemia and the underlying regulatory mechanisms are unknown. Here, we show that LPS increases endothelial GSDMD level in aortas and lung microvessels. We demonstrated that endothelial Gsdmd deficiency, but not myeloid cell Gsdmd deletion, protects against endothelial injury and death in mice with endotoxemia or sepsis. In vivo experiments suggested that hepatocyte GSDMD mediated the release of high-mobility group box 1, which subsequently binds to the receptor for advanced glycation end products in endothelial cells to cause systemic vascular injury, ultimately resulting in acute lung injury and lethality in shock driven by endotoxemia or sepsis. Additionally, inhibiting endothelial GSDMD activation via a polypeptide inhibitor alleviated endothelial damage and improved survival in a mouse model of endotoxemia or sepsis. These data suggest that endothelial GSDMD is a viable pharmaceutical target for treating endotoxemia and endotoxemia-induced sepsis.

The role of short-chain fatty acid in metabolic syndrome and its complications: focusing on immunity and inflammation

Metabolic syndrome (Mets) is an important contributor to morbidity and mortality in cardiovascular, liver, neurological, and reproductive diseases. Short-chain fatty acid (SCFA), an organismal energy donor, has recently been demonstrated in an increasing number of studies to be an important molecule in ameliorating immuno-inflammation, an important causative factor of Mets, and to improve lipid distribution, blood glucose, and body weight levels in animal models of Mets. This study reviews recent research advances on SCFA in Mets from an immune-inflammatory perspective, including complications dominated by chronic inflammation, as well as the fact that these findings also contribute to the understanding of the specific mechanisms by which gut flora metabolites contribute to metabolic processes in humans. This review proposes an emerging role for SCFA in the inflammatory Mets, followed by the identification of major ambiguities to further understand the anti-inflammatory potential of this substance in Mets. In addition, this study proposes novel strategies to modulate SCFA for the treatment of Mets that may help to mitigate the prognosis of Mets and its complications.

Patterns of bacterial viability governing noncanonical inflammasome activation

Noncanonical inflammasomes are instrumental in defense against Gram-negative bacteria, activated primarily by bacterial lipopolysaccharide. This review examines commonalities and distinctions in noncanonical inflammasome activation either by virulence factor activity indicating cellular invasion or by detection of bacterial mRNA signaling the undesired presence of live bacteria in sterile tissue. These inflammasome triggers, alongside other examples discussed, reflect properties exclusive to live bacteria. The emerging picture underscores noncanonical inflammasome activation hinging on detection of indicators of bacterial viability such as the presence of certain molecules or activity of specific processes. The complex interpretation of combinatorial signals is essential for inflammasome activation according to the specific facet of infection confronting the host. Decoding these signals and their convergence on inflammasome activation will inform interventions and therapies for infectious diseases.

Palmatine, an isoquinoline alkaloid from Phellodendron amurense Rupr., ameliorated gouty inflammation by inhibiting pyroptosis via NLRP3 inflammasome

ETHNOPHARMACOLOGICAL RELEVANCE

Palmatine (Pal), derived from Daemonorops margaritae (Hance) Becc and Phellodendron amurense Rupr. is a natural isoquinoline alkaloid widely used in clearing heat and drying dampness, purging the pathogenic fire and removing symptoms, detoxifying toxins and healing sores.

AIM OF THE STUDY

Gout is a common metabolic inflammatory disease caused by the deposition of MSU crystals (MSU) in joints and non-articulation structures. Given the multiple toxic side effects of clinical anti-gout medications, there is a need to find a safe and effective alternative. We investigated the therapeutic effects of Pal on MSU crystal-induced acute gouty inflammation, targeting the NLRP3 inflammasome mediated pyroptosis.

MATERIALS AND METHODS

In vitro, mouse peritoneal macrophages (MPM) and rat articular chondrocytes were stimulated with LPS plus MSU in the presence or absence of Palmatine. In vivo, arthritis models include the acute gouty arthritis model by injecting MSU crystals in the paws of mice and the air pouch acute gout model by injecting MSU crystals into the mouse subcutaneous tissue of the back. Expression of NLRP3 inflammasome activation and NETosis formation was determined by Western blot, ELISA kit, immunohistochemistry, and immunofluorescence. In addition, the anti-cartilage damage of Palmatine on MSU-induced arthritis mice were also evaluated.

RESULTS

Pal dose-dependently decreased levels of NLRP3 inflammasome activation related proteins NLRP3, ASC, caspase-1, IL-1β, HMGB1 and Cathepsin B. The NETosis protein levels of caspase-11, histone3, PR3 and PAD4 were remarkably reduced by Pal. Pal effectively blocked the activation of NLRP3 inflammasome, attenuated the caspase-11 mediated noncanonical NLRP3 inflammasome activation and intervened the formation of NETs, thereby inhibiting the pyroptosis. In vivo, Pal attenuated MSU-induced inflammation in gouty arthritis and protect the articular cartilage through inhibiting the pyroptosis of proteins NLRP3, ASC, caspase-1, IL-1β, HMGB1 and Cathepsin B, reducing levels of NETosis relevant proteins caspase-11, histone3, PR3 and PAD4 and up-regulating expression of protein MMP-3.

CONCLUSION

Palmatine ameliorated gouty inflammation by inhibiting pyroptosis via NLRP3 inflammasome.

Research hotspots and future trends in sepsis-associated acute kidney injury: a bibliometric and visualization analysis

Objectives

Sepsis-associated acute kidney injury (SA-AKI) commonly occurs in critically ill patients and is closely associated with adverse outcomes. A comprehensive analysis of the current research landscape in SA-AKI can help uncover trends and key issues in this field. This study aims to provide a scientific basis for research directions and critical issues through bibliometric analysis.

Methods

We searched all articles on SA-AKI indexed in the SCI-Expanded of WoSCC up to May 7, 2024, and conducted bibliometric and visual analyses using bibliometric software CiteSpace and VOSviewer.

Results

Over the past 20 years, there has been a steady increase in literature related to renal repair following AKI. China and the United States contribute over 60% of the publications, driving research in this field. The University of Pittsburgh is the most active academic institution, producing the highest number of publications. J. A. Kellum is both the most prolific and the most cited author in this area. "Shock" and "American Journal of Physiology-Renal Physiology" are the most popular journals, publishing the highest number of articles. Recent high-frequency keywords in this field include "septic AKI," "mitochondrial dysfunction," "inflammasome," "ferroptosis," and "macrophage." The terms "mitochondrial dysfunction," "inflammasome," "ferroptosis," and "macrophage" represent current research hotspots and potential targets in this area.

Conclusion

This is the first comprehensive bibliometric study to summarize the trends and advancements in SA-AKI research in recent years. These findings identify current research frontiers and hot topics, providing valuable insights for scholars studying SA-AKI.

Balanced regulation of ROS production and inflammasome activation in preventing early development of colorectal cancer

Reactive oxygen species (ROS) production and inflammasome activation are the key components of the innate immune response to microbial infection and sterile insults. ROS are at the intersection of inflammation and immunity during cancer development. Balanced regulation of ROS production and inflammasome activation serves as the central hub of innate immunity, determining whether a cell will survive or undergo cell death. However, the mechanisms underlying this balanced regulation remain unclear. Mitochondria and NADPH oxidases are the two major sources of ROS production. Recently, NCF4, a component of the NADPH oxidase complex that primarily contributes to ROS generation in phagocytes, was reported to balance ROS production and inflammasome activation in macrophages. The phosphorylation and puncta distribution of NCF4 shifts from the membrane-bound NADPH complex to the perinuclear region, promoting ASC speck formation and inflammasome activation, which triggers downstream IL-18-IFN-γ signaling to prevent the progression of colorectal cancer (CRC). Here, we review ROS signaling and inflammasome activation studies in colitis-associated CRC and propose that NCF4 acts as a ROS sensor that balances ROS production and inflammasome activation. In addition, NCF4 is a susceptibility gene for Crohn's disease (CD) and CRC. We discuss the evidence demonstrating NCF4's crucial role in facilitating cell-cell contact between immune cells and intestinal cells, and mediating the paracrine effects of inflammatory cytokines and ROS. This coordination of the signaling network helps create a robust immune microenvironment that effectively prevents epithelial cell mutagenesis and tumorigenesis during the early stage of colitis-associated CRC.

Inflammasome-mediated pyroptosis in defense against pathogenic bacteria

Macrophages, neutrophils, and epithelial cells are pivotal components of the host's immune response against bacterial infections. These cells employ inflammasomes to detect various microbial stimuli during infection, triggering an inflammatory response aimed at eradicating the pathogens. Among these inflammatory responses, pyroptosis, a lytic form of cell death, plays a crucial role in eliminating replicating bacteria and recruiting immune cells to combat the invading pathogen. The immunological function of pyroptosis varies across macrophages, neutrophils, and epithelial cells, aligning with their specific roles within the innate immune system. This review centers on elucidating the role of pyroptosis in resisting gram-negative bacterial infections, with a particular focus on the mechanisms at play in macrophages, neutrophils, and intestinal epithelial cells. Additionally, we underscore the cell type-specific roles of pyroptosis in vivo in these contexts during defense.

Targeting HMGB1 and Its Interaction with Receptors: Challenges and Future Directions

High mobility group box 1 (HMGB1) is a nonhistone chromatin protein predominantly located in the nucleus. However, under pathological conditions, HMGB1 can translocate from the nucleus to the cytoplasm and subsequently be released into the extracellular space through both active secretion and passive release mechanisms. The distinct cellular locations of HMGB1 facilitate its interaction with various endogenous and exogenous factors, allowing it to perform diverse functions across a range of diseases. This Perspective provides a comprehensive overview of the structure, release mechanisms, and multifaceted roles of HMGB1 in disease contexts. Furthermore, it introduces the development of both small molecule and macromolecule inhibitors targeting HMGB1 and its interaction with receptors. A detailed analysis of the predicted pockets is also presented, aiming to establish a foundation for the future design and development of HMGB1 inhibitors.

Connexin 43 and Pannexin 1 hemichannels as endogenous regulators of innate immunity in sepsis

Sepsis is a life-threatening organ dysfunction resulting from a dysregulated host response to infections that is initiated by the body's innate immune system. Nearly a decade ago, we discovered that bacterial lipopolysaccharide (LPS) and serum amyloid A (SAA) upregulated Connexin 43 (Cx43) and Pannexin 1 (Panx1) hemichannels in macrophages. When overexpressed, these hemichannels contribute to sepsis pathogenesis by promoting ATP efflux, which intensifies the double-stranded RNA-activated protein kinase R (PKR)-dependent inflammasome activation, pyroptosis, and the release of pathogenic damage-associated molecular pattern (DAMP) molecules, such as HMGB1. Mimetic peptides targeting specific regions of Cx43 and Panx1 can distinctly modulate hemichannel activity in vitro, and diversely impact sepsis-induced lethality in vivo. Along with extensive supporting evidence from others, we now propose that hemichannel molecules play critical roles as endogenous regulators of innate immunity in sepsis.

Phosphate-Containing Glycolipids: A Review on Synthesis and Bioactivity

Phosphate-containing glycolipids (PcGL) are scarcer than the better understood glycolipids. They are composed of arrangements of phosphate, carbohydrates and glycerol units and are always found associated with lipids. PcGL are often found associated with cell membranes, suggesting they play roles in cell membrane structure and intercellular interactions. This article aims to provide an up-to-date overview of the existing knowledge and research on PcGL, emphasizing their synthesis and wide range of biological activities. When it comes to the synthesis of PcGL compounds, the strategies for glycosylation mainly rely on the thioglycoside donor, the trichloroacetamidate donor and halide donor strategies, while phosphorylation is stapled and falls on either phosphite chemistry or phosphoryl chloride chemistry. Certain bacteria utilize PcGLs in their pathogenicity, triggering an inflammatory response within the host's defense mechanisms. The best-known examples of these structures are teichoic acids, lipopolysaccharide and the capsular polysaccharide found in bacteria, all of which are frequently implicated in bacterial infections. Given the degree of variability within PcGL structures, they were found to display a wide range of bioactivities. PcGL compounds were found to: (1) have anti-metastatic properties, (2) behave as agonists or antagonists of platelet aggregation, (3) be mostly pro-inflammatory, (4) display antifungal and antibiotic activity and (5) have neurogenic activity.

Quercetin Ameliorates Acute Lethal Sepsis in Mice by Inhibiting Caspase-11 Noncanonical Inflammasome in Macrophages

Quercetin is a natural polyphenolic flavonoid widely found in plants, fruits, and vegetables, and has been reported to play pharmacological roles in numerous pathogenic conditions. The anti-inflammatory effects of quercetin in various inflammatory conditions and diseases have been well-documented. However, its regulatory role in noncanonical inflammasome activation has not yet been demonstrated. This study investigated the anti-inflammatory effects of quercetin in caspase-11 noncanonical inflammasome-activated inflammatory responses in macrophages and a mouse model of acute lethal sepsis. Quercetin protected J774A.1 macrophages from lipopolysaccharide (LPS)-induced cell death and caspase-11 noncanonical inflammasome-induced pyroptosis. It significantly decreased the production and mRNA expression of pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-18, and IL-6, but not tumor necrosis factor (TNF)-α, and inflammatory molecules, such as nitric oxide (NO) and inducible NO synthase in caspase-11 noncanonical inflammasome-activated J774A.1 cells. Mechanistically, quercetin strongly suppressed the autoproteolysis and secretion of caspase-11 and the proteolysis of gasdermin D in caspase-11 noncanonical inflammasome-activated J774A.1 cells. However, quercetin did not inhibit the direct binding of caspase-11 to LPS. In vivo, the study revealed that quercetin increased the survival rate of mice with acute lethal sepsis and decreased serum levels of pro-inflammatory cytokines without causing significant toxicity. In conclusion, this study highlights quercetin-mediated anti-inflammatory action in inflammatory responses and acute lethal sepsis through a novel mechanism that targets the caspase-11 noncanonical inflammasome in macrophages, suggesting quercetin as a promising anti-inflammatory agent in natural medicine.

The role of NLRP3 and NLRP12 inflammasomes in glioblastoma

Glioblastoma (GBM) is the deadliest malignant brain tumor, with a survival of less than 14 months after diagnosis. The highly invasive nature of GBM makes total surgical resection challenging, leading to tumor recurrence and declined survival. The heterocellular composition of the GBM reprograms its microenvironment, favoring tumor growth, proliferation, and migration. The innate immune cells in the GBM tumor microenvironment, including microglia, astrocytes, and macrophages, express pattern recognition receptors such as NLRs (Nucleotide-binding domain and leucine-rich repeat-containing) that sense pathogen- and damage-associated molecular patterns initiating inflammation. Upon activation, NLRP3 promotes inflammation by NLRP3 inflammasome formation. Auto-proteolytic cleavage and activation of Caspase-1 within the inflammasome leads to caspase-1-mediated cleavage, activation, and conversion of pro-IL-1ß and pro-IL-18 to IL-1ß and IL-18, leading to pyroptosis. In contrast, NLRP12 downregulates inflammatory responses in microglia and macrophages by regulating the NF-κB pathway. NLRP3 and NLRP12 have been implicated in the disease pathophysiology of several cancers with cell-context-dependent, pro- or anti-tumorigenic roles. In this review, we discuss the current literature on the mechanistic roles of NLRP3 and NLRP12 in GBM and the gaps in the scientific literature in the context of GBM pathophysiology with potential for targeted therapeutics.

Dual alarmin-receptor-specific targeting peptide systems for treatment of sepsis

The pathophysiology of sepsis is characterized by a systemic inflammatory response to infection; however, the cytokine blockade that targets a specific early inflammatory mediator, such as tumor necrosis factor, has shown disappointing results in clinical trials. During sepsis, excessive endotoxins are internalized into the cytoplasm of immune cells, resulting in dysregulated pyroptotic cell death, which induces the leakage of late mediator alarmins such as HMGB1 and PTX3. As late mediators of lethal sepsis, overwhelming amounts of alarmins bind to high-affinity TLR4/MD2 and low-affinity RAGE receptors, thereby amplifying inflammation during early-stage sepsis. In this study, we developed a novel alarmin/receptor-targeting system using a TLR4/MD2/RAGE-blocking peptide (TMR peptide) derived from the HMGB1/PTX3-receptors interacting motifs. The TMR peptide successfully attenuated HMGB1/PTX3- and LPS-mediated inflammatory cytokine production by impairing its interactions with TLR4 and RAGE. Moreover, we developed TMR peptide-conjugated liposomes (TMR-Lipo) to improve the peptide pharmacokinetics. In combination therapy, moderately antibiotic-loaded TMR-Lipo demonstrated a significant therapeutic effect in a mouse model of cecal ligation- and puncture-induced sepsis. The identification of these peptides will pave the way for the development of novel pharmacological tools for sepsis therapy.

Inhibition of IRE1α/XBP1 axis alleviates LPS-induced acute lung injury by suppressing TXNIP/NLRP3 inflammasome activation and ERK/p65 signaling pathway

BACKGROUND

Acute lung injury or acute respiratory distress syndrome (ALI/ARDS) is a devastating clinical syndrome with high incidence and mortality rates. IRE1α-XBP1 pathway is one of the three major signaling axes of endoplasmic reticulum stress that is involved in inflammation, metabolism, and immunity. The role and potential mechanisms of IRE1α-XBP1 axis in ALI/ARDS has not well understood.

METHODS

The ALI murine model was established by intratracheal administration of lipopolysaccharide (LPS). Hematoxylin and eosin (H&E) staining and analysis of bronchoalveolar lavage fluid (BALF) were used to evaluate degree of lung injury. Inflammatory responses were assessed by ELISA and RT-PCR. Apoptosis was evaluated using TUNEL staining and western blot. Moreover, western blot, immunohistochemistry, and immunofluorescence were applied to test expression of IRE1α, XBP1, NLRP3, TXNIP, IL-1β, ERK1/2 and NF-κB p65.

RESULTS

The expression of IRE1α significantly increased after 24 h of LPS treatment. Inhibition of the IRE1α-XBP1 axis with 4µ8C notably improved LPS-induced lung injury and inflammatory infiltration, reduced the levels of IL-6, IL-1β, and TNF-α, and decreased cell apoptosis as well as the activation of the NLRP3 inflammasome. Besides, in LPS-stimulated Beas-2B cells, both 4µ8C and knockdown of XBP1 diminished the mRNA levels of IL-6 and IL-1B, inhibited cell apoptosis and reduced the protein levels of TXNIP, NLRP3 and secreted IL-1β. Mechanically, the phosphorylation and nuclear translocation of ERK1/2 and p65 were significantly suppressed by 4µ8C and XBP1 knockdown.

CONCLUSIONS

In summary, our findings suggest that IRE1α-XBP1 axis is crucial in the pathogenesis of ALI/ARDS, whose suppression could mitigate the pulmonary inflammatory response and cell apoptosis in ALI through the TXNIP/NLRP3 inflammasome and ERK/p65 signaling pathway. Our study may provide new evidence that IRE1α-XBP1 may be a promising therapeutic target for ALI/ARDS.

Adipose triglyceride lipase suppresses noncanonical inflammasome by hydrolyzing LPS

Intracellular recognition of lipopolysaccharide (LPS) by mouse caspase-11 or human caspase-4 is a vital event for the activation of the noncanonical inflammasome. Whether negative regulators are involved in intracellular LPS sensing is still elusive. Here we show that adipose triglyceride lipase (ATGL) is a negative regulator of the noncanonical inflammasome. Through screening for genes participating in the noncanonical inflammasome, ATGL is identified as a negative player for intracellular LPS signaling. ATGL binds LPS and catalyzes the removal of the acylated side chains that contain ester bonds. LPS with under-acylated side chains no longer activates the inflammatory caspases. Cells with ATGL deficiency exhibit enhanced immune responses when encountering intracellular LPS, including an elevated secretion of interleukin-1β, decreased cell viability and increased cell cytotoxicity. Moreover, ATGL-deficient mice show exacerbated responses to endotoxin challenges. Our results uncover that ATGL degrades cytosolic LPS to suppress noncanonical inflammasome activation.

The TET3 inflammasome senses unique long HSV-1 proteins for virus particle budding from the nucleus

Inflammasomes play important roles in resisting infections caused by various pathogens. HSV-1 is a highly contagious virus among humans. The process by which HSV-1 particles bud from the nucleus is unique to herpes viruses, but the specific mechanism is still unclear. Here, we screened genes involved in HSV-1 replication. We found that TET3 plays an essential role in HSV-1 infection. TET3 recognizes the UL proteins of HSV-1 and, upon activation, can directly bind to caspase-1 to activate an ASC-independent inflammasome in the nucleus. The subsequent cleavage of GSDMD in the nucleus is crucial for the budding of HSV-1 particles from the nucleus. Inhibiting the perforation ability of GSDMD on the nuclear membrane can significantly reduce the maturation and spread of HSV-1. Our results may provide a new approach for the treatment of HSV-1 in the future.

Bile acid derivatives from gut microbiota promote GBPs-mediated activation of caspase-4/11 by LPS through lncRNA57RIK

Lipopolysaccharide (LPS) mediated caspases-4 (humans) and caspase-11 (rodent) (caspase-4/11) signaling can cause maturation of inflammatory cytokine IL-1β and cellular pyroptosis in the macrophages through guanylate-binding proteins (GBPs). However, how caspase-4/11s bind with GBPs together to activate caspase-4/11 by LPS remains elusive. We here found that BA derivatives from gut microbiota can regulate sensitivity of macrophages to LPS and Gram-negative bacteria through lncRNA57RIK. BA derivatives such as deoxycholic acid (DCA) could induce lncRNA57RIK expression through sphingosine-1-phosphate receptor 2 (S1PR2) in the macrophages of mice and humans. Both murine and human lncRNA57RIK knockout (KO) macrophages did not produce immune response(s) to LPS or gram negative bacteria. LncRNA57RIK KO mice had also reduced inflammatory responses to LPS or Salmonella typhimurium (S. T) infection. Mechanistically, lncRNA57RIK could bind intracellular proteases caspase-4/11 with GBP1 together in the macrophages of human and mice to cause LPS-mediated activation of caspase-4/11. Thus, BA derivatives from gut microbiota promote GBPs-mediated activation of caspase-4/11 by LPS through lncRNA57RIK.

Inflammasomes primarily restrict cytosolic Salmonella replication within human macrophages

Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that utilizes its type III secretion systems (T3SSs) to inject virulence factors into host cells and colonize the host. In turn, a subset of cytosolic immune receptors respond to T3SS ligands by forming multimeric signaling complexes called inflammasomes, which activate caspases that induce interleukin-1 (IL-1) family cytokine release and an inflammatory form of cell death called pyroptosis. Human macrophages mount a multifaceted inflammasome response to Salmonella infection that ultimately restricts intracellular bacterial replication. However, how inflammasomes restrict Salmonella replication remains unknown. We find that caspase-1 is essential for mediating inflammasome responses to Salmonella and restricting bacterial replication within human macrophages, with caspase-4 contributing as well. We also demonstrate that the downstream pore-forming protein gasdermin D (GSDMD) and Ninjurin-1 (NINJ1), a mediator of terminal cell lysis, play a role in controlling Salmonella replication in human macrophages. Notably, in the absence of inflammasome responses, we observed hyperreplication of Salmonella within the cytosol of infected cells as well as increased bacterial replication within vacuoles, suggesting that inflammasomes control Salmonella replication primarily within the cytosol and also within vacuoles. These findings reveal that inflammatory caspases and pyroptotic factors mediate inflammasome responses that restrict the subcellular localization of intracellular Salmonella replication within human macrophages.