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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. [ABSTRACT FROM AUTHOR]

Caspase-1 and related proteases are key players in inflammation and innate immunity. Here, we characterize the evolutionary history of caspase-1 and its close relatives across 19 primates and 21 rodents, focusing on differences that may cause discrepancies between humans and animal studies. While caspase-1 has been retained in all these taxa, other members of the caspase-1 subfamily (caspase-4, caspase-5, caspase-11, and caspase-12 and CARD16, 17, and 18) each have unique evolutionary trajectories. Caspase-4 is found across simian primates, whereas we identified multiple pseudogenization and gene loss events in caspase-5, caspase-11, and the CARDs. Because caspase-4 and caspase-11 are both key players in the noncanonical inflammasome pathway, we expected that these proteins would be likely to evolve rapidly. Instead, we found that these two proteins are largely conserved, whereas caspase-4's close paralog, caspase-5, showed significant indications of positive selection, as did primate caspase-1. Caspase-12 is a nonfunctional pseudogene in humans. We find this extends across most primates, although many rodents and some primates retain an intact, and likely functional, caspase-12. In mouse laboratory lines, we found that 50% of common strains carry nonsynonymous variants that may impact the functions of caspase-11 and caspase-12 and therefore recommend specific strains to be used (and avoided). Finally, unlike rodents, primate caspases have undergone repeated rounds of gene conversion, duplication, and loss leading to a highly dynamic proinflammatory caspase repertoire. Thus, we uncovered many differences in the evolution of primate and rodent proinflammatory caspases and discuss the potential implications of this history for caspase gene functions. [ABSTRACT FROM AUTHOR]

Abstract Background Intracellular sensing of lipopolysaccharide (LPS) is essential for the immune response against gram-negative bacteria and results in activation of caspase-11 and pyroptotic cell death with fatal consequences in sepsis. We found the neuronal guidance receptor plexin C1 (PLXNC1) influences the intracellular response to LPS. Methods We employed a murine model of sepsis via cecal ligation and binding (CLP), using PLXNC1-/- mice and littermate controls, and additionally transfected murine bone-marrow-derived macrophages (BMDMs) from both genotypes with LPS to achieve activation of the noncanonical inflammasome ex vivo. Additionally, we transfected the PLXNC1 ligand SL4c-d in vivo and ex vivo to examine its effect on intracellular LPS response. Results We found the neuronal guidance receptor PLXNC1 dampens the intracellular response to LPS by interacting with adenylate cyclase 4 (ADCY4) and protein kinase A activity, which in turn diminishes caspase-11 expression. The absence of PLXNC1 results in excessive inflammation marked by increased cytokine release, increased secondary organ injury and reduced sepsis survival in a murine sepsis model induced by CLP. Notably, administration of SL4c-d—peptide ligand of PLXNC1—reduces the inflammatory response during CLP-induced sepsis and improves survival. Conclusions These results elucidate a previously unknown mechanism for PLXNC1 suppressing excessive noncanonical inflammasome activity and offer a new potential target for treatment of sepsis with its detrimental effects.

Summary Inflammasomes are multi‐protein complexes that assemble within the cytoplasm of mammalian cells in response to pathogen‐associated molecular patterns (PAMPs) or damage‐associated molecular patterns (DAMPs), driving the secretion of the pro‐inflammatory cytokines IL‐1β and IL‐18, and pyroptosis. The best‐characterized inflammasome complexes are the NLRP3, NAIP‐NLRC4, NLRP1, AIM2, and Pyrin canonical caspase‐1‐containing inflammasomes, and the caspase‐11 non‐canonical inflammasome. Newer inflammasome sensor proteins have been identified, including NLRP6, NLRP7, NLRP9, NLRP10, NLRP11, NLRP12, CARD8, and MxA. These inflammasome sensors can sense PAMPs from bacteria, viruses and protozoa, or DAMPs in the form of mitochondrial damage, ROS, stress and heme. The mechanisms of action, physiological relevance, consequences in human diseases, and avenues for therapeutic intervention for these novel inflammasomes are beginning to be realized. Here, we discuss these emerging inflammasome complexes and their putative activation mechanisms, molecular and signaling pathways, and physiological roles in health and disease. [ABSTRACT FROM AUTHOR]

Objective: To explore the protective effect and the underlying mechanism of silibinin (SIB), one of the active compounds from Silybum marianum (L.) Gaertn in endotoxemia. Methods: Mouse peritoneal macrophage were isolated via intraperitoneally injection of BALB/c mice with thioglycolate medium. Cell viability was assessed using the cell counting kit-8, while cytotoxicity was determined through lactate dehydrogenase cytotoxicity assay. The protein expressions of interleukin (IL)-1 α, IL-1 β, and IL-18 were determined by enzyme-linked immunosorbent assay. Intracellular lipopolysaccharide (LPS) levels were measured by employing both the limulus amoebocyte lysate assay and flow cytometry. Additionally, proximity ligation assay was employed for the LPS and caspase-11 interaction. Mice were divided into 4 groups: the control, LPS, high-dose-SIB (100 mg/kg), and low-dose-SIB (100 mg/kg) groups (n=8). Zebrafish were divided into 4 groups: the control, LPS, high-dose-SIB (200 εmol/L), and low-dose-SIB (100 εmol/L) groups (n=30 for survival experiment and n=10 for gene expression analysis). The expression of caspase-11, gasdermin D (GSDMD), and N-GSDMD was determined by Western blot and the expressions of caspy2, gsdmeb, and IL-1 β were detected using quantitative real-time PCR. Histopathological observation was performed through hematoxylineosin staining, and protein levels in bronchoalveolar lavage fluid were quantified using the bicinchoninicacid protein assay. Results: SIB noticeably decreased caspase-11 and GSDMD-mediated pyroptosis and suppressed the secretion of IL-1 α, IL-1 β, and IL-18 induced by LPS (P<0.05). Moreover, SIB inhibited the translocation of LPS into the cytoplasm and the binding of caspase-11 and intracellular LPS (P<0.05). SIB also attenuated the expression of caspase-11 and N-terminal fragments of GSDMD, inhibited the relative cytokines, prolonged the survival time, and up-regulated the survival rate in the endotoxemia models (P<0.05). Conclusions: SIB can inhibit pyroptosis in the LPS-mediated endotoxemia model, at least in part, by inhibiting the caspase-11-mediated cleavage of GSDMD. Additionally, SIB inhibits the interaction of LPS and caspase-11 and inhibits the LPS-mediated up-regulation of caspase-11 expression, which relieves caspase-11-dependent cell pyroptosis and consequently attenuates LPS-mediated lethality. [ABSTRACT FROM AUTHOR]

Background: Intracellular sensing of lipopolysaccharide (LPS) is essential for the immune response against gram-negative bacteria and results in activation of caspase-11 and pyroptotic cell death with fatal consequences in sepsis. We found the neuronal guidance receptor plexin C1 (PLXNC1) influences the intracellular response to LPS. Methods: We employed a murine model of sepsis via cecal ligation and binding (CLP), using PLXNC1-/- mice and littermate controls, and additionally transfected murine bone-marrow-derived macrophages (BMDMs) from both genotypes with LPS to achieve activation of the noncanonical inflammasome ex vivo. Additionally, we transfected the PLXNC1 ligand SL4c-d in vivo and ex vivo to examine its effect on intracellular LPS response. Results: We found the neuronal guidance receptor PLXNC1 dampens the intracellular response to LPS by interacting with adenylate cyclase 4 (ADCY4) and protein kinase A activity, which in turn diminishes caspase-11 expression. The absence of PLXNC1 results in excessive inflammation marked by increased cytokine release, increased secondary organ injury and reduced sepsis survival in a murine sepsis model induced by CLP. Notably, administration of SL4c-d—peptide ligand of PLXNC1—reduces the inflammatory response during CLP-induced sepsis and improves survival. Conclusions: These results elucidate a previously unknown mechanism for PLXNC1 suppressing excessive noncanonical inflammasome activity and offer a new potential target for treatment of sepsis with its detrimental effects. [ABSTRACT FROM AUTHOR]

Sepsis is a common complication of infections that significantly impacts the survival of critically patients. Currently, effective pharmacological treatment strategies are lacking. Auranofin, known as an inhibitor of Thioredoxin reductase (TrxR), exhibits anti-inflammatory activity, but its role in sepsis is not well understood. Here, we demonstrate the significant inhibitory effect of Auranofin on sepsis in a cecal ligation and puncture (CLP) mouse model. In vitro, Auranofin inhibits pyroptosis triggered by Caspase-11 activation. Further investigations reveal that inhibiting TrxR1 suppresses macrophage pyroptosis induced by E. coli, while TrxR2 does not exhibit this effect. TrxR1, functioning as a reductase, regulates the oxidative-reductive status of Thioredoxin-1 (Trx-1). Mechanistically, the modulation of Trx-1's reductive activity by TrxR1 may be involved in Caspase-11 activation-induced pyroptosis. Additionally, inhibiting TrxR1 maintains Trx-1 in its oxidized state. The oxidized form of Trx-1 interacts with Caveolin-1 (CAV1), regulating outer membrane vesicle (OMV) internalization. In summary, our study suggests that inhibiting TrxR1 suppresses OMV internalization by maintaining the oxidized form of Trx-1, thereby restricting Caspase-11 activation and alleviating sepsis.

Abstract Sepsis is a leading cause of death worldwide. This syndrome is commonly accompanied by overactivation of coagulation, excessive reactive oxygen species (ROS), and inflammatory cytokine storm. Notably, disseminated intravascular coagulation (DIC) accounts for around 40% of sepsis‐associated deaths. However, anticoagulant therapy is still difficult for sepsis treatment because of the lethal bleeding side effects. Although the relationship between ROS and inflammatory cytokine storm has been described clearly, the pathogenic role of ROS in DIC, however, is still unclear, which renders novel therapeutic approaches hard to achieve bedside for inhibiting DIC. Herein, our new finding reveals that ROS greatly facilitates the entry of lipopolysaccharide (LPS) into the macrophage cytoplasm, which subsequently activates the caspase‐11/gasdermin D pathway, and finally induces DIC through phosphatidylserine exposure. Based on this finding, novel gallic acid‐modified Mo‐based polyoxometalate dots (M‐dots) with outstanding antioxidant activity are developed to provide ideal and efficient inhibition of DIC. As expected, M‐dots are capable of markedly inhibiting sepsis‐caused coagulation, organ injury, and death in sepsis. This therapeutic strategy, blocking the upstream pathway of coagulation rather than coagulation itself, can avoid the side effects of extensive bleeding caused by conventional anticoagulation therapy, and will provide a new avenue for the efficient treatment of sepsis.

Abstract Background The pattern recognition receptor Dectin-1 was initially discovered to play a pivotal role in mediating pulmonary antifungal immunity and promoting neutrophil-driven inflammation. Recent studies have revealed that Dectin-1 is overexpressed in asthma, but the specific mechanism remains elusive. Additionally, Dectin-1 has been implicated in promoting pyroptosis, a hallmark of severe asthma airway inflammation. Nevertheless, the involvement of the non-classical pyroptosis signal caspase-11/4 and its upstream regulatory mechanisms in asthma has not been completely explored. Methods House dust mite (HDM)-induced mice was treated with Dectin-1 agonist Curdlan, Dectin-1 inhibitor Laminarin, and caspase-11 inhibitor wedelolactone separately. Subsequently, inflammatory cells in bronchoalveolar lavage fluid (BALF) were analyzed. Western blotting was performed to measure the protein expression of caspase-11 and gasdermin D (GSDMD). Cell pyroptosis and the expression of chemokine were detected in vitro. The correlation between Dectin-1 expression, pyroptosis factors and neutrophils in the induced sputum of asthma patients was analyzed. Results Curdlan appeared to exacerbate neutrophil airway inflammation in asthmatic mice, whereas wedelolactone effectively alleviated airway inflammation aggravated by Curdlan. Moreover, Curdlan enhanced the release of caspase-11 activation fragments and N-terminal fragments of gasdermin D (GSDMD-N) stimulated by HDM both in vivo or in vitro. In mouse alveolar macrophages (MH-S cells), Curdlan/HDM stimulation resulted in vacuolar degeneration and elevated lactate dehydrogenase (LDH) release. In addition, there was an upregulation of neutrophil chemokines CXCL1, CXCL3, CXCL5 and their receptor CXCR2, which was suppressed by wedelolactone. In asthma patients, a positive correlation was observed between the expression of Dectin-1 on macrophages and caspase-4 (the human homology of caspase-11), and the proportion of neutrophils in induced sputum. Conclusion Dectin-1 activation in asthma induced caspase-11/4 mediated macrophage pyroptosis, which subsequently stimulated the secretion of chemokines, leading to the exacerbation of airway neutrophil inflammation. Graphical Abstract

Abstract Alzheimer’s disease (AD) is the sixth leading cause of death in the USA. It is established that neuroinflammation contributes to the synaptic loss, neuronal death, and symptomatic decline of AD patients. Accumulating evidence suggests a critical role for microglia, innate immune phagocytes of the brain. For instance, microglia release pro-inflammatory products such as IL-1β which is highly implicated in AD pathobiology. The mechanisms underlying the transition of microglia to proinflammatory promoters of AD remain largely unknown. To address this gap, we performed reduced representation bisulfite sequencing (RRBS) to profile global DNA methylation changes in human AD brains compared to no disease controls. We identified differential DNA methylation of CASPASE-4 (CASP4), which when expressed promotes the generation of IL-1β and is predominantly expressed in immune cells. DNA upstream of the CASP4 transcription start site was hypomethylated in human AD brains, which was correlated with increased expression of CASP4. Furthermore, microglia from a mouse model of AD (5xFAD) express increased levels of CASP4 compared to wild-type (WT) mice. To study the role of CASP4 in AD, we developed a novel mouse model of AD lacking the mouse ortholog of CASP4 and CASP11, which is encoded by mouse Caspase-4 (5xFAD/Casp4 −/− ). The expression of CASP11 was associated with increased accumulation of pathologic protein aggregate amyloid-β (Aβ) and increased microglial production of IL-1β in 5xFAD mice. Utilizing RNA-sequencing, we determined that CASP11 promotes unique transcriptomic phenotypes in 5xFAD mouse brains, including alterations of neuroinflammatory and chemokine signaling pathways. Notably, in vitro, CASP11 promoted generation of IL-1β from macrophages in response to cytosolic Aβ through cleavage of downstream effector Gasdermin D (GSDMD). Therefore, here we unravel the role for CASP11 and GSDMD in the generation of IL-1β in response to Aβ and the progression of pathologic inflammation in AD. Overall, our results demonstrate that overexpression of CASP4 due to differential DNA methylation in AD microglia contributes to the progression of AD pathobiology. Thus, we identify CASP4 as a potential target for immunotherapies for the treatment and prevention of AD.

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.

Background: Infection is the leading cause of acute lung injury (ALI). Macrophages, which are pivotal innate immune cells, play a critical role in mediating inflammatory processes. Intracellular lipopolysaccharide (LPS) from invasive Gram-negative bacteria can activate the caspase-11 inflammasome, leading to the induction of pyroptosis in macrophages. This process subsequently triggers the release of inflammatory cytokines and damage-associated molecular patterns from pyroptotic macrophages, thereby exacerbating inflammatory progression in ALI. However, the precise regulatory mechanisms governing caspase-11 activation is still unclear. Sentrin-specific proteases (SENPs) have been identified as notable targets for their anti-inflammatory properties. Nevertheless, the specific role of SENPs in macrophage pyroptosis during the pathogenesis of ALI remains unknown. Methods: We used LPS as an endotoxin to induce ALI. We analyzed the expression and location of sentrin-specific protease 1 (SENP1), pulmonary impairment, macrophage infiltration, caspase-11 inflammasome expression and activation, caspase-11 SUMOylation, and inflammatory cytokine secretion. Results: Upregulated expression of SENP1 in lung tissue and macrophages was observed following LPS stimulation. SENP1 mediates de-SUMOylation and activation of caspase-11 inflammasome in macrophages. Moreover, pharmacological inhibition or genetic deficiency of SENP1 in macrophages significantly improved ALI-related histological damage by reducing the secretion of inflammatory cytokines and suppressing caspase-11-dependent pyroptosis. Conclusions: Collectively, our findings highlight the involvement of SENP1 in caspase-11 activation and inflammatory progression in macrophages, thereby establishing a scientific foundation for the exploration of novel therapeutic strategies aimed at treating ALI.

Sepsis-induced cardiomyopathy (SICM) is common complication in septic patients with a high mortality and is characterized by an abnormal inflammation response, which was precisely regulated by endogenous specialized pro-resolving mediators (SPMs). However, the metabolic changes of cardiac SPMs during SICM and the roles of SPMs subset in the development of SICM remain unknown. In this work, the SPMs concentration was assessed using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) of SICM mice and SICM patients. The cardiac function was measured by echocardiography after the treatment of a SPMs subset, termed Resolvin D2 (RvD2). Caspase-11−/−, GSDMD−/− and double deficient (Caspase-11−/−GSDMD−/−) mice were used to clarify the mechanisms of RvD2 in SICM. We found that endogenous cardiac SPMs were disorders and RvD2 was decreased significantly and correlated with left ventricular ejection fraction (LVEF) and β-BNP, cTnT in Lipopolysaccharide/Cecum ligation and puncture (CLP) induced SICM models. Treatment with RvD2 attenuated lethality, cardiac dysfunction and cardiomyocytes death during SICM. Mechanistically, RvD2 alleviated SICM via inhibiting Caspase-11/GSDMD-mediated cardiomyocytes pyroptosis. Finally, the plasma levels of RvD2 were also decreased and significantly correlated with IL-1β, β-BNP, cTnT and LVEF in patients with SICM. Of note, plasma RvD2 level is indicator of SICM patients from healthy controls or sepsis patients. These findings suggest that decreased cardiac RvD2 may involve in the pathogenesis of SICM. In addition, treatment with RvD2 represents a novel therapeutic strategy for SICM by inhibiting cardiomyocytes pyroptosis. [Display omitted] • Endogenous cardiac RvD2 was decreased and correlated with cardiac function in SICM. • Resolvin D2 ameliorates SICM via inhibiting Caspase-11/GSDMD dependent pyroptosis. • Plasma RvD2 level is indicator of SICM from healthy controls or sepsis patients. [ABSTRACT FROM AUTHOR]

Background: The pattern recognition receptor Dectin-1 was initially discovered to play a pivotal role in mediating pulmonary antifungal immunity and promoting neutrophil-driven inflammation. Recent studies have revealed that Dectin-1 is overexpressed in asthma, but the specific mechanism remains elusive. Additionally, Dectin-1 has been implicated in promoting pyroptosis, a hallmark of severe asthma airway inflammation. Nevertheless, the involvement of the non-classical pyroptosis signal caspase-11/4 and its upstream regulatory mechanisms in asthma has not been completely explored. Methods: House dust mite (HDM)-induced mice was treated with Dectin-1 agonist Curdlan, Dectin-1 inhibitor Laminarin, and caspase-11 inhibitor wedelolactone separately. Subsequently, inflammatory cells in bronchoalveolar lavage fluid (BALF) were analyzed. Western blotting was performed to measure the protein expression of caspase-11 and gasdermin D (GSDMD). Cell pyroptosis and the expression of chemokine were detected in vitro. The correlation between Dectin-1 expression, pyroptosis factors and neutrophils in the induced sputum of asthma patients was analyzed. Results: Curdlan appeared to exacerbate neutrophil airway inflammation in asthmatic mice, whereas wedelolactone effectively alleviated airway inflammation aggravated by Curdlan. Moreover, Curdlan enhanced the release of caspase-11 activation fragments and N-terminal fragments of gasdermin D (GSDMD-N) stimulated by HDM both in vivo or in vitro. In mouse alveolar macrophages (MH-S cells), Curdlan/HDM stimulation resulted in vacuolar degeneration and elevated lactate dehydrogenase (LDH) release. In addition, there was an upregulation of neutrophil chemokines CXCL1, CXCL3, CXCL5 and their receptor CXCR2, which was suppressed by wedelolactone. In asthma patients, a positive correlation was observed between the expression of Dectin-1 on macrophages and caspase-4 (the human homology of caspase-11), and the proportion of neutrophils in induced sputum. Conclusion: Dectin-1 activation in asthma induced caspase-11/4 mediated macrophage pyroptosis, which subsequently stimulated the secretion of chemokines, leading to the exacerbation of airway neutrophil inflammation. [ABSTRACT FROM AUTHOR]

Periodontitis (PD) is the primary cause of tooth loss in adults. Porphyromonas gingivalis (P.g), a keystone pathogen, has been identified as a crucial contributor to this process. Pyroptosis activation in PD is acknowledged, with accumulating evidence underscoring the crucial role of Caspase-11 (described as Caspase-4/5 in humans)–mediated noncanonical pyroptosis. However, the mechanism behind its impact on PD remains unclear. In this study, we delved into the interplay between the Caspase-11–mediated noncanonical pyroptosis, subgingival microbiota alteration, and macrophage polarization. Clinical samples from PD patients revealed heightened expression of Caspase-4, gasdermin-D, and their active fragments, pointing to the activation of the noncanonical pyroptosis. Single-cell sequencing analysis linked Caspase-4 with gingival macrophages, emphasizing their involvement in PD. In vitro cell experiments confirmed that P.g -induced pyroptosis was activated in macrophages, with Casp11 deficiency attenuating these effects. In an experimental PD mouse model, Casp11 deficiency led to an alteration in subgingival microbiota composition and reduced alveolar bone resorption. Casp11 -/- mice cohousing with wild-type mice confirmed the alteration of the subgingival microbiota and aggravated the alveolar bone resorption. Notably, Casp11 deficiency led to decreased M1-polarized macrophages, corresponding with reduced alveolar bone resorption, uncovering a connection between subgingival microbiota alteration, macrophage M1 polarization, and alveolar bone resorption. Taken together, we showed that Caspase-11 fulfilled a crucial role in the noncanonical pyroptosis in PD, potentially influencing the subgingival microbiota and linking to M1 polarization, which was associated with alveolar bone resorption. These findings underscored the pivotal role of the Caspase-11–mediated noncanonical pyroptosis in PD pathogenesis and may provide critical insights into potential therapeutic avenues for mitigating PD. [ABSTRACT FROM AUTHOR]

The nervous system possesses the remarkable ability to undergo changes in order to store information; however, it is also susceptible to damage caused by invading pathogens or neurodegenerative processes. As a member of nucleotide-binding oligomerization domain-like receptor (NLR) family, the NLRP6 inflammasome serves as a cytoplasmic innate immune sensor responsible for detecting microbe-associated molecular patterns. Upon activation, NLRP6 can recruit the adapter protein apoptosis-associated speck-like protein (ASC) and the inflammatory factors caspase-1 or caspase-11. Consequently, inflammasomes are formed, facilitating the maturation and secretion of pro-inflammatory cytokines such as inflammatory factors-18 (IL-18) and inflammatory factors-1β (IL-1β). Precise regulation of NLRP6 is crucial for maintaining tissue homeostasis, as dysregulated inflammasome activation can contribute to the development of various diseases. Furthermore, NLRP6 may also play a role in the regulation of extraintestinal diseases. In cells of the brain, such as astrocytes and neurons, NLRP6 inflammasome are also present. Here, the assembly and subsequent activation of caspase-1 mediated by NLRP6 contribute to disease progression. This review aims to discuss the structure and function of NLRP6, explain clearly the mechanisms that induce and activate NLRP6, and explore its role within the central and peripheral nervous system. [ABSTRACT FROM AUTHOR]

Inflammasomes are intracellular multiprotein complexes that activate inflammatory signaling pathways. Inflammasomes comprise two major classes: canonical inflammasomes, which were discovered first and are activated in response to a variety of pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs), and non-canonical inflammasomes, which were discovered recently and are only activated in response to intracellular lipopolysaccharide (LPS). Although a larger number of studies have successfully demonstrated that canonical inflammasomes, particularly the NLRP3 inflammasome, play roles in various rheumatic diseases, including rheumatoid arthritis (RA), infectious arthritis (IR), gouty arthritis (GA), osteoarthritis (OA), systemic lupus erythematosus (SLE), psoriatic arthritis (PA), ankylosing spondylitis (AS), and Sjögren's syndrome (SjS), the regulatory roles of non-canonical inflammasomes, such as mouse caspase-11 and human caspase-4 non-canonical inflammasomes, in these diseases are still largely unknown. Interestingly, an increasing number of studies have reported possible roles for non-canonical inflammasomes in the pathogenesis of various mouse models of rheumatic disease. This review comprehensively summarizes and discusses recent emerging studies demonstrating the regulatory roles of non-canonical inflammasomes, particularly focusing on the caspase-11 non-canonical inflammasome, in the pathogenesis and progression of various types of rheumatic diseases and provides new insights into strategies for developing potential therapeutics to prevent and treat rheumatic diseases as well as associated diseases by targeting non-canonical inflammasomes. [ABSTRACT FROM AUTHOR]

Alzheimer’s disease (AD) is the sixth leading cause of death in the USA. It is established that neuroinflammation contributes to the synaptic loss, neuronal death, and symptomatic decline of AD patients. Accumulating evidence suggests a critical role for microglia, innate immune phagocytes of the brain. For instance, microglia release pro-inflammatory products such as IL-1β which is highly implicated in AD pathobiology. The mechanisms underlying the transition of microglia to proinflammatory promoters of AD remain largely unknown. To address this gap, we performed reduced representation bisulfite sequencing (RRBS) to profile global DNA methylation changes in human AD brains compared to no disease controls. We identified differential DNA methylation of CASPASE-4 (CASP4), which when expressed promotes the generation of IL-1β and is predominantly expressed in immune cells. DNA upstream of the CASP4 transcription start site was hypomethylated in human AD brains, which was correlated with increased expression of CASP4. Furthermore, microglia from a mouse model of AD (5xFAD) express increased levels of CASP4 compared to wild-type (WT) mice. To study the role of CASP4 in AD, we developed a novel mouse model of AD lacking the mouse ortholog of CASP4 and CASP11, which is encoded by mouse Caspase-4 (5xFAD/Casp4−/−). The expression of CASP11 was associated with increased accumulation of pathologic protein aggregate amyloid-β (Aβ) and increased microglial production of IL-1β in 5xFAD mice. Utilizing RNA-sequencing, we determined that CASP11 promotes unique transcriptomic phenotypes in 5xFAD mouse brains, including alterations of neuroinflammatory and chemokine signaling pathways. Notably, in vitro, CASP11 promoted generation of IL-1β from macrophages in response to cytosolic Aβ through cleavage of downstream effector Gasdermin D (GSDMD). Therefore, here we unravel the role for CASP11 and GSDMD in the generation of IL-1β in response to Aβ and the progression of pathologic inflammation in AD. Overall, our results demonstrate that overexpression of CASP4 due to differential DNA methylation in AD microglia contributes to the progression of AD pathobiology. Thus, we identify CASP4 as a potential target for immunotherapies for the treatment and prevention of AD. [ABSTRACT FROM AUTHOR]

ABSTRACT Caspases are a family of cysteine proteases that act as molecular scissors to cleave substrates and regulate biological processes such as programmed cell death and inflammation. Extensive efforts have been made to identify caspase substrates and to determine factors that dictate substrate specificity. Thousands of putative substrates have been identified for caspases that regulate an immunologically silent type of cell death known as apoptosis, but less is known about substrates of the inflammatory caspases that regulate an immunostimulatory type of cell death called pyroptosis. Furthermore, much of our understanding of caspase substrate specificities is derived from work done with peptide substrates, which do not often translate to native protein substrates. Our knowledge of inflammatory caspase biology and substrates has recently expanded and here, we discuss the recent advances in our understanding of caspase substrate specificities, with a focus on inflammatory caspases. We highlight new substrates that have been discovered and discuss the factors that engender specificity. Recent evidence suggests that inflammatory caspases likely utilize two binding interfaces to recognize and process substrates, the active site and a conserved exosite.

Pengcheng Jiao,1,&ast; Zuntai Li,2,&ast; Birong Li,3 Xingyuan Jiao4 1Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, People’s Republic of China; 2Hospital of Stomatology, Jilin University, Changchun, Jilin, People’s Republic of China; 3Changzhou Hospital of Traditional Chinese Medicine, Changzhou, Jiangsu, People’s Republic of China; 4Department of Surgery, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Xingyuan Jiao, Department of Surgery, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, 510000, People’s Republic of China, Tel +86-13178813750, Email jiaoxingyuan@hotmail.comAbstract: Peri-implantitis is an important cause of oral implant failure. In the past, TLR4 and TLR2 in the Toll-like family were generally considered as the key immune recognition receptors regulating peri-implantitis. However, under the guidance of this theory, there are still some unexplainable peri-implantitis symptoms. With the discovery of novel intracellular LPS receptor Caspase-11, a new understanding of inflammatory signaling and immune regulation in the development of peri-implantitis has been gained. However, the regulatory role of Caspase-11 in peri-implantitis and its crosstalk with the TLR4 pathway remain unclear. The therapeutic effect of drugs targeting Caspase-11 on peri-implantitis is still in its early stages. In view of this situation, this paper reviews the possible role of Caspase-11 in peri-implant inflammation, elaborated the entry process of LPS and the activation mechanism of Caspase-11, and analyzes the differences in Caspase-11 between commonly studied animals, mice and humans. The current research hotspots and challenges are also analyzed to provide new insights and ideas for researchers.Keywords: caspase-11, pyroptosis, inflammation, peri-implantitis

Caspase activation results in pyroptosis, an inflammatory cell death that contributes to several inflammatory diseases by releasing inflammatory cytokines and cellular contents. Fusobacterium nucleatum is a periodontal pathogen frequently detected in human cancer and inflammatory bowel diseases. Studies have reported that F. nucleatum infection leads to NLRP3 activation and pyroptosis, but the precise activation process and disease association remain poorly understood. This study demonstrated that F. nucleatum infection exacerbates acute colitis in mice and activates pyroptosis through caspase‐11‐mediated gasdermin D cleavage in macrophages. Furthermore, F. nucleatum infection in colitis mice induces the enhancement of IL‐1⍺ secretion from the colon, affecting weight loss and severe disease activities. Neutralization of IL‐1⍺ protects F. nucleatum infected mice from severe colitis. Therefore, F. nucleatum infection facilitates inflammation in acute colitis with IL‐1⍺ from colon tissue by activating noncanonical inflammasome through gasdermin D cleavage. [ABSTRACT FROM AUTHOR]

Abstract Chronic wounds seriously affect the quality of life of the elderly, obese people, and diabetic patients. The excessive inflammatory response is a key driver of delayed chronic wound healing. Although lavender essential oil (EO [lav]) has been proven to have anti‐inflammatory and accelerate wound curative effects, the specific molecular mechanism involved is still ambiguous. The results showed that the wounds treated with lipopolysaccharide (LPS) not only had delayed healing, but also the expression levels of pro‐inflammatory cytokines, such as tumor necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), interleukin‐1β (IL‐1β), and the inflammatory mediator protein, high‐mobility group box 1 protein (HMGB‐1), in the wound tissues were significantly increased. However, treatment of LPS‐induced chronic wounds with EO (lav) accelerated wound healing and decreased IL‐1β and HMGB‐1 expression levels. It was further found that LPS induced macrophage pyroptosis to produce IL‐1β. After treatment with EO (lav), the expression level of macrophage pyroptosis marker Gasdermin D (GSDMD) and pyroptosis‐related cytotoxic effects were significantly reduced. Immunofluorescence results also directly indicate that EO (lav) can protect macrophages from LPS‐induced pyroptosis. Moreover, EO (lav) can down‐regulate expression levels of IL‐1β, GSDMD, and nucleotide‐binding oligomerization domain‐like receptor protein 3 (NLRP3) in the caspase‐11‐related pyroptotic signaling pathway. This study demonstrates that EO (lav) can reduce proinflammatory factor production and ameliorate inflammatory response by inhibiting macrophage pyroptosis, which accelerates LPS‐induced chronic wound healing.

Inflammatory caspases are cysteine protease zymogens whose activation following infection or cellular damage occurs within supramolecular organizing centers (SMOCs) known as inflammasomes. Inflammasomes recruit caspases to undergo proximity-induced autoprocessing into an enzymatically active form that cleaves downstream targets. Binding of bacterial LPS to its cytosolic sensor, caspase-11 (Casp11), promotes Casp11 aggregation within a high-molecular-weight complex known as the noncanonical inflammasome, where it is activated to cleave gasdermin D and induce pyroptosis. However, the cellular correlates of Casp11 oligomerization and whether Casp11 forms an LPS-induced SMOC within cells remain unknown. Expression of fluorescently labeled Casp11 in macrophages revealed that cytosolic LPS induced Casp11 speck formation. Unexpectedly, catalytic activity and autoprocessing were required for Casp11 to form LPS-induced specks in macrophages. Furthermore, both catalytic activity and autoprocessing were required for Casp11 speck formation in an ectopic expression system, and processing of Casp11 via ectopically expressed TEV protease was sufficient to induce Casp11 speck formation. These data reveal a previously undescribed role for Casp11 catalytic activity and autoprocessing in noncanonical inflammasome assembly, and shed new light on the molecular requirements for noncanonical inflammasome assembly in response to cytosolic LPS.

Background: Ischemia/reperfusion (I/R) injury is a complication of liver transplantation. I/R-induced inflammatory cell death, namely, pyroptosis, that is triggered by overactive inflammasomes results in the production of proinflammatory cytokines. Hepatic I/R injury correlates with the activation of the Caspase-11-mediated pyroptosis pathway. We investigated whether ghrelin, which is a pleiotropic gut hormone, may have anti-hepatic I/R injury effects, but the mechanism by which Ghrelin ameliorates hepatic I/R -induced injury remains a mystery. Methods: Hepatic I/R injury was induced in a mouse model by clamping the left and right lobes of the liver for 90 min followed by reperfusion for 6 h, 12 h, or 24 h. As treatment, a saline with or without ghrelin was infused via the tail vain. Hepatocytes were isolated using a two-step collagenase liver perfusion method. Results: In our study, treatment with ghrelin protected against hepatic I/R injury as shown by decreased alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels (p < 0.001) and reduced the histological injury in liver tissues compared with untreated controls. The LDH level of primary hepatocytes was increased by hypoxia/reoxygenation (H/R), and it was then restored to normal levels by ghrelin-treatment (p < 0.05). Western blotting analysis showed that ghrelin significantly inhibited the expression of pyroptosis-related proteins, including Caspase-11, GSDMD-N, NLRP3 and HMGB1, both in vivo and in vitro (all p < 0.05) compared with the untreated controls. Immunofluorescence showed that the expression of Gasdamin D (GSDMD) in hepatocytes was increased after I/R or H/R, whereas GSDMD expression was reduced by ghrelin treatment (p < 0.05). Conclusions: Our findings suggest that ghrelin ameliorated I/R-induced hepatic injury by inhibiting Caspase-11-mediated pyroptosis. Ghrelin may be a potential therapeutic option to prevent hepatic I/R injury after liver transplantation. [ABSTRACT FROM AUTHOR]

• The expression of caspase-11 significantly increased after cardiac arrest. • Neuronal pyroptosis was observed in the M1 area of the rat cortex. • GABA B receptor activation attenuates neuronal pyroptosis after cardiac arrest. Brain injury is a major cause of death and disability after cardiac arrest (CA). Previous studies have shown that activating GABA B receptors significantly improves neurological function after CA, but the mechanism of this neuronal protection of damaged neurons remains unclear. Thus, the present study aimed to investigate whether GABA B receptor activation protects against neuronal injury and to reveal the underlying protective mechanisms. In this study, rats underwent 10 min of asphyxia to induce CA, and SH-SY5Y cells were subjected to oxygen and glucose deprivation/reoxygenation (OGD/R) to establish in vivo and in vitro models of hypoxic neuronal injury. Differential gene expression between CA rats and sham-operated rats was identified using RNA-seq. TUNEL and Nissl staining were used to evaluate cortical neuron damage, while Western blotting, qRT-PCR, and immunofluorescence assays were conducted to measure pyroptosis-related indicators. Furthermore, cellular models with high expression of caspase-11 were established to reveal the novel molecular mechanisms by which GABA B receptor activation exerts neuroprotective effects. Intriguingly, our results showed that caspase-11 and GSDMD were highly expressed in rats experiencing cardiac arrest. Specifically, GSDMD was expressed in neurons in the M1 area of the cerebral cortex. Moreover, activation of the GABA B receptor exerted a protective effect on neurons both in vivo and in vitro. Baclofen attenuated caspase-11 activation and neuronal pyroptosis after CA, and the anti-neuronal pyroptosis effect of baclofen was abolished by overexpression of caspase-11 in neuronal cells. In conclusion, GABA B receptor activation may play a neuroprotective role by alleviating neuronal pyroptosis through a mechanism involving caspase-11. [ABSTRACT FROM AUTHOR]

Background & Aims: Klebsiella pneumoniae (KLP), a Gram-negative bacterium belonging to the family of Enterobacteriaceae, is a common cause of antimicrobial-resistant opportunistic infections in hospitalized patients. KLP can colonize in the human gastrointestinal tract, especially in patients with inflammatory bowel diseases. However, effects of KLP on the onset and development of inflammatory bowel disease remain unclear. Methods: We analyzed the relationship between Mayo indexes of ulcerative colitis and KLP using quantitative reverse-transcription polymerase chain reaction and endoscopy. Using caspase-1/11-/-, NLRP3-/-, NLRC4-/-, interleukin (IL)18-/-, and IL22-/- mice, we showed that KLP could induce colitis through caspase-11–mediated release of mature IL18. Through in vitro gut organoid culture, we determined the mechanism for KLP to induce colitis. Results: We first found that there was a positive relationship between the Mayo indexes of ulcerative colitis and KLP. Then, we isolated a strain of KLP, named Klebsiella pneumoniae J (KLPJ), from the colon tissues of patients with colitis. This strain of bacteria could induce the production of mature IL18 in colon epithelial cells and gut organoids, and also induce colitis and promote dextran sodium sulfate–mediated colitis. Using caspase-1/11-/-, NLRP3-/-, NLRC4-/-, IL18-/-, and IL22-/- mice, we showed that KLPJ-mediated colitis occurred through activation of caspase-11, and was dependent on IL18 and partly on IL22. Our data also showed that lipopolysaccharide from KLPJ could bind with caspase-11 to induce mature IL18 in mouse and human colon organoids. Conclusions: KLPJ from the colon tissues of patients with ulcerative colitis can colonize the colon, activate caspase-11 inflammasomes, and contribute to intestinal inflammation.

Background: Acute kidney injury (AKI) is a common complication in patients with severe acute pancreatitis (SAP). Caspase-11-mediated pyroptosis is essential for the progression of multiple diseases, but its role in SAP-induced AKI remains unknown. Aims: This research investigated whether caspase-11-mediated pyroptosis is involved in SAP-induced AKI and whether inhibiting caspase-11-mediated pyroptosis improves SAP-induced AKI. Methods: A rat model of SAP with AKI was established by slowly injecting 5% sodium taurocholate into the biliopancreatic duct, then wedelolactone (25 or 50 mg/kg), an inhibitor of caspase-11, was injected through the intra-peritoneum 1 and 6 h after SAP induction. Serum biochemical indexes, including serum amylase, lipase, interleukin (IL)-6, blood urea nitrogen (BUN), tumor necrosis factor (TNF)-α, and creatinine (Cr) in rats, were evaluated using biochemical test kits. Caspase-11 and gasdermin D (GSDMD) expression in the kidney tissues was evaluated by western blotting and immunohistochemical staining. IL-1β and IL-18 levels in kidney tissues were detected by ELISA kits. Furthermore, histopathological alterations of pancreas and kidney were assessed by H&E staining. Results: The serum biochemical indexes and pyroptosis-related proteins in kidney tissues were significantly increased after SAP induction. Furthermore, wedelolactone decreased the expression of pyroptosis-linked proteins in kidney tissues, reduced serum lipase, amylase, IL-6, TNF-α, BUN, and Cr, and ameliorated the renal and pancreatic histological damage in SAP rats. Conclusion: Caspase-11-mediated pyroptosis contributes to SAP-induced AKI, and targeting caspase-11-mediated pyroptosis might be a novel treatment strategy for SAP-induced AKI.

Acute kidney injury (AKI) is a serious condition with high mortality. The most common cause is kidney ischemia/reperfusion (IR) injury, which is thought to be closely related to pyroptosis. Disulfiram is a well-known alcohol abuse drug, and recent studies have shown its ability to mitigate pyroptosis in mouse macrophages. This study investigated whether disulfiram could improve IR-induced AKI and elucidated the possible molecular mechanism. We generated an IR model in mouse kidneys and a hypoxia/reoxygenation (HR) injury model with murine tubular epithelial cells (MTECs). The results showed that IR caused renal dysfunction in mice and triggered pyroptosis in renal tubular epithelial cells, and disulfiram improved renal impairment after IR. The expression of proteins associated with the classical pyroptosis pathway (Nucleotide-binding oligomeric domain (NOD)-like receptor protein 3 (NLRP3), apoptosis-related specific protein (ASC), caspase-1, N-GSDMD) and nonclassical pyroptosis pathway (caspase-11, N-GSDMD) were upregulated after IR. Disulfiram blocked the upregulation of nonclassical but not all classical pyroptosis pathway proteins (NLRP3 and ASC), suggesting that disulfiram might reduce pyroptosis by inhibiting the caspase-11-GSDMD pathway. In vitro, HR increased intracellular ROS levels, the positive rate of PI staining and LDH levels in MTECs, all of which were reversed by disulfiram pretreatment. Furthermore, we performed a computer simulation of the TIR domain of TLR4 using homology modeling and identified a small molecular binding energy between disulfiram and the TIR domain. We concluded that disulfiram might inhibit pyroptosis by antagonizing TLR4 and inhibiting the caspase-11-GSDMD pathway.

Periodontitis is an oral inflammatory disease characterised by the destruction of periodontal soft tissue and alveolar bone resorption, mainly triggered by plaque microbial infection. Pyroptosis is an inflammatory form of programmed cell death mediated by the pore‐forming gasdermin proteins, which resist the invasion of pathogens into the body's immune system. Many studies have found that pyroptosis is closely related to the occurrence and development of periodontitis. At present, most of these studies focused on the canonical pathway mediated by caspase‐1. Moreover, Gram‐negative bacteria's lipopolysaccharide has been shown to activate a new form of the non‐canonical inflammasome by directly binding to human caspase‐4/5 and mouse caspase‐11 in the cytosol. However, most of the functions of non‐canonical inflammasome are still gradually being studied. Therefore, in this review, we have summarised and analysed the existence and regulation mechanism of the non‐canonical inflammasome in periodontitis. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection triggers activation of the NLRP3 inflammasome, which promotes inflammation and aggravates severe COVID-19. Here, we report that SARS-CoV-2 induces upregulation and activation of human caspase-4/CASP4 (mouse caspase-11/CASP11), and this process contributes to NLRP3 activation. In vivo infections performed in transgenic hACE2 humanized mice, deficient or sufficient for Casp11 , indicate that hACE2 Casp11−/− mice were protected from disease development, with the increased pulmonary parenchymal area, reduced clinical score of the disease, and reduced mortality. Assessing human samples from fatal cases of COVID-19, we found that CASP4 was expressed in patient lungs and correlated with the expression of inflammasome components and inflammatory mediators, including CASP1 , IL1B , IL18, and IL6. Collectively, our data establish that CASP4/11 promotes NLRP3 activation and disease pathology, revealing a possible target for therapeutic interventions for COVID-19. [ABSTRACT FROM AUTHOR]

Inflammasomes are critical sentinels of the innate immune system that respond to threats to the host through recognition of distinct molecules, known as pathogen- or damage-associated molecular patterns (PAMPs/DAMPs), or disruptions of cellular homeostasis, referred to as homeostasis-altering molecular processes (HAMPs) or effector-triggered immunity (ETI). Several distinct proteins nucleate inflammasomes, including NLRP1, CARD8, NLRP3, NLRP6, NLRC4/NAIP, AIM2, pyrin, and caspases-4/-5/-11. This diverse array of sensors strengthens the inflammasome response through redundancy and plasticity. Here, we present an overview of these pathways, outlining the mechanisms of inflammasome formation, subcellular regulation, and pyroptosis, and discuss the wide-reaching effects of inflammasomes in human disease. Inflammasomes are critical initiators of inflammation and adaptive immunity with far-reaching effects on human health and disease. This review provides a 360° view of the mechanisms of inflammasome formation, subcellular regulation, and their effects on cell death and disease. [ABSTRACT FROM AUTHOR]

Chronic wounds seriously affect the quality of life of the elderly, obese people, and diabetic patients. The excessive inflammatory response is a key driver of delayed chronic wound healing. Although lavender essential oil (EO [lav]) has been proven to have anti‐inflammatory and accelerate wound curative effects, the specific molecular mechanism involved is still ambiguous. The results showed that the wounds treated with lipopolysaccharide (LPS) not only had delayed healing, but also the expression levels of pro‐inflammatory cytokines, such as tumor necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), interleukin‐1β (IL‐1β), and the inflammatory mediator protein, high‐mobility group box 1 protein (HMGB‐1), in the wound tissues were significantly increased. However, treatment of LPS‐induced chronic wounds with EO (lav) accelerated wound healing and decreased IL‐1β and HMGB‐1 expression levels. It was further found that LPS induced macrophage pyroptosis to produce IL‐1β. After treatment with EO (lav), the expression level of macrophage pyroptosis marker Gasdermin D (GSDMD) and pyroptosis‐related cytotoxic effects were significantly reduced. Immunofluorescence results also directly indicate that EO (lav) can protect macrophages from LPS‐induced pyroptosis. Moreover, EO (lav) can down‐regulate expression levels of IL‐1β, GSDMD, and nucleotide‐binding oligomerization domain‐like receptor protein 3 (NLRP3) in the caspase‐11‐related pyroptotic signaling pathway. This study demonstrates that EO (lav) can reduce proinflammatory factor production and ameliorate inflammatory response by inhibiting macrophage pyroptosis, which accelerates LPS‐induced chronic wound healing. [ABSTRACT FROM AUTHOR]

Background: Korean Red Ginseng (KRG) was reported to play an anti-inflammatory role, however, previous studies largely focused on the effects of KRG on priming step, the inflammation-preparing step, and the anti-inflammatory effect of KRG on triggering, the inflammation-activating step has been poorly understood. This study demonstrated anti-inflammatory role of KRG in caspase-11 non-canonical inflammasome activation in macrophages during triggering of inflammatory responses. Methods: Caspase-11 non-canonical inflammasome-activated J774A.1 macrophages were established by priming with Pam3CSK4 and triggering with lipopolysaccharide (LPS). Cell viability and pyroptosis were examined by MTT and lactate dehydrogenase (LDH) assays. Nitric oxide (NO)-inhibitory effect of KRG was assessed using a NO production assay. Expression and proteolytic cleavage of proteins were examined by Western blotting analysis. In vivo anti-inflammatory action of KRG was evaluated with the LPS-injected sepsis model in mice. Results: KRG reduced LPS-stimulated NO production in J774A.1 cells and suppressed pyroptosis and IL-1β secretion in caspase-11 non-canonical inflammasome-activated J774A.1 cells. Mechanistic studies demonstrated that KRG suppressed the direct interaction between LPS and caspase-11 and inhibited proteolytic processing of both caspase-11 and gasdermin D in caspase-11 non-canonical inflammasome-activated J774A.1 cells. Furthermore, KRG significantly ameliorated LPS-mediated lethal septic shock in mice. Conclusion: The results demonstrate a novel mechanism of KRG-mediated anti-inflammatory action that operates through targeting the caspase-11 non-canonical inflammasome at triggering step of macrophage-mediated inflammatory response.

Pyroptosis, a type of programmed necrosis associated with inflammatory, is a host defense mechanism against microbial infections. Although Chlamydia has been shown to induce pyroptosis, whether pyroptosis directly impacts the growth of Chlamydia has not been demonstrated. In this study, we found that C. trachomatis L2 infection of the mouse macrophage RAW 264.7 cells induced pyroptosis by monitoring the ultrastructural changes under transmission electron microscopy and the release of LDH and IL-1b. More importantly, this C. trachomatis-triggered pyroptosis with activation of caspase-1 and caspase-11 was also accompanied by gasdermin D (GSDMD) activation. Suppression of these two inflammatory caspases inhibited GSDMD activation. Interestingly, the C. trachomatis-triggered pyroptosis significantly inhibited the intracellular growth of C. trachomatis since inactivation of either GSDMD or caspase-1/11 significantly rescued infectious C. trachomatis yields, which suggests pyroptosis response can be utilized as an intrinsic mechanism to restrict C. trachomatis intracellular infection in addition to the well- documented extrinsic mechanisms by recruiting and enhancing inflammatory responses. This study may reveal novel targets for attenuating C. trachomatis infectivity and/ or pathogenicity. [ABSTRACT FROM AUTHOR]

Gram-negative sepsis is a severe clinical syndrome associated with significant morbidity and mortality. Lipopolysaccharide (LPS), expressed on Gram-negative bacteria, is a potent pro-inflammatory toxin that induces inflammation and coagulation via two separate receptor systems. One is Toll-like receptor 4 (TLR4), expressed on cell surfaces and in endosomes, and the other is the cytosolic receptor caspase-11 (caspases-4 and -5 in humans). Extracellular LPS binds to high mobility group box 1 (HMGB1) protein, a cytokine-like molecule. The HMGB1–LPS complex is transported via receptor for advanced glycated end products (RAGE)-endocytosis to the endolysosomal system to reach the cytosolic LPS receptor caspase-11 to induce HMGB1 release, inflammation, and coagulation that may cause multi-organ failure. The insight that LPS needs HMGB1 assistance to generate severe inflammation has led to successful therapeutic results in preclinical Gram-negative sepsis studies targeting HMGB1. However, to date, no clinical studies have been performed based on this strategy. HMGB1 is also actively released by peripheral sensory nerves and this mechanism is fundamental for the initiation and propagation of inflammation during tissue injury. Homeostasis is achieved when other neurons actively restrict the inflammatory response via monitoring by the central nervous system and the vagus nerve through the cholinergic anti-inflammatory pathway. The neuronal control in Gram-negative sepsis needs further studies since a deeper understanding of the interplay between HMGB1 and acetylcholine may have beneficial therapeutic implications. Herein, we review the synergistic overlapping mechanisms of LPS and HMGB1 and discuss future treatment opportunities in Gram-negative sepsis.

This study investigates the role of Caspase-11 in Chronic Kidney Disease (CKD) and examines the therapeutic potential of inhibiting Caspase-11 using exosome-mediated siRNA. We established a CKD rat model and analyzed the expression of Caspase-11 through immunohistochemistry. The study involved overexpressing Caspase-11 using an adeno-associated virus (AAV) and constructing exosomes loaded with siRNA targeting Caspase-11 (exo-si-Caspase-11). Renal tissue damage and fibrosis were assessed using H&E staining, Masson's trichrome, TUNEL assay, and Sirius Red staining. Additionally, urinary protein and blood urea nitrogen (BUN) levels were measured, alongside analyses of serum calcium and phosphorus levels. H&E staining was performed to evaluate the effects of exo-si-Caspase-11 on damage to the heart, liver, spleen, and lungs. The results showed that the CKD model group experienced significant weight loss, increased blood pressure, and elevated Caspase-11 expression. AAV-mediated Caspase-11 overexpression led to substantial renal fibrosis, increased apoptosis, and elevated urinary protein and BUN levels. Additionally, the group with Caspase-11 overexpression exhibited elevated serum calcium and phosphorus levels. Conversely, treatment with exo-si-Caspase-11 reduced these pathological changes in renal tissue without causing damage to other major organs. These findings suggest that exosome-mediated siRNA delivery targeting Caspase-11 is an effective therapeutic strategy for CKD. • Caspase-11 overexpression significantly promotes renal tissue injury and fibrosis in rats with Chronic Kidney Disease (CKD). • Exosome-mediated siRNA targeting Caspase-11 markedly reduces renal fibrosis, apoptosis, and pathological damage in CKD. • Exo-si-Caspase-11 restores CD31 expression and decreases urinary protein and BUN levels in CKD rats. • Exo-si-Caspase-11 treatment reduces serum calcium and phosphorus levels, thereby decreasing neural tissue damage in CKD. • Exosome-mediated siRNA targeting Caspase-11 offers a promising CKD treatment strategy. [ABSTRACT FROM AUTHOR]

Pyroptosis has been found to contribute to myocardial ischemia/reperfusion (I/R) injury, but the exact mechanisms that initiate myocardial pyroptosis are not fully elucidated. Sonic hedgehog (SHH) signaling is activated in heart suffered I/R, and intervention of SHH signaling has been demonstrated to protect heart from I/R injury. Caspase recruitment domain-containing protein 10 (CARD10)-B cell lymphoma 10 (BCL10)-mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) (CBM) complex could transduce signals from the membrane and induce inflammatory pathways in non-hematopoietic cells, which could be a downstream effector of SHH signaling pathway. This study aims to explore the role of SHH signaling in I/R-induced myocardial pyroptosis and its relationship with the CBM complex. C57BL/6J mice were subjected to 45 min-ischemia followed by 24 h-reperfusion to establish a myocardial I/R model, and H9c2 cells underwent hypoxia/reoxygenation (H/R) to mimic myocardial I/R model in vitro. Firstly, SHH signaling was significantly activated in heart suffered I/R in an autocrine- or paracrine-dependent manner via its receptor PTCH1, and inhibition of SHH signaling decreased myocardial injury via reducing caspase-11-dependent pyroptosis, concomitant with attenuating CBM complex formation. Secondly, suppression of SHH signaling decreased protein kinase C α (PKCα) level, but inhibition of PKCα attenuated CBM complex formation without impacting the protein levels of SHH and PTCH1. Finally, disruption of the CBM complex prevented MALT1 from recruiting of TRAF6, which was believed to trigger the caspase-11-dependent pyroptosis. Based on these results, we conclude that inhibition of SHH signaling suppresses pyroptosis via attenuating PKCα-mediated CARD10-BCL10-MALT1 complex formation in mouse heart suffered I/R. [ABSTRACT FROM AUTHOR]

Introduction: Non-alcoholic fatty liver disease (NAFLD) has a global prevalence of 25% of the population and is a leading cause of cirrhosis and hepatocellular carcinoma. NAFLD ranges from simple steatosis (non-alcoholic fatty liver) to non-alcoholic steatohepatitis (NASH). Hepatic macrophages, specifically Kupffer cells (KCs) and monocyte-derived macrophages, act as key players in the progression of NAFLD. Caspases are a family of endoproteases that provide critical connections to cell regulatory networks that sense disease risk factors, control inflammation, and mediate inflammatory cell death (pyroptosis). Caspase-11 can cleave gasdermin D (GSDMD) to induce pyroptosis and specifically defends against bacterial pathogens that invade the cytosol. However, it’s still unknown whether high fat diet (HFD)-facilitated gut microbiota-generated cytoplasmic lipopolysaccharides (LPS) activate caspase-11 and promote NAFLD. Methods: To examine this hypothesis, we performed liver pathological analysis, RNA-seq, FACS, Western blots, Seahorse mitochondrial stress analyses of macrophages and bone marrow transplantation on HFD-induced NAFLD in WT and Casp11–/– mice. Results and Discussion: Our results showed that 1) HFD increases body wight, liver wight, plasma cholesterol levels, liver fat deposition, and NAFLD activity score (NAS score) in wild-type (WT) mice; 2) HFD increases the expression of caspase-11, GSDMD, interleukin-1b, and guanylate-binding proteins in WT mice; 3) Caspase-11 deficiency decreases fat liver deposition and NAS score; 4) Caspase-11 deficiency decreases bone marrow monocyte-derived macrophage (MDM) pyroptosis (inflammatory cell death) and inflammatory monocyte (IM) surface GSDMD expression; 5) Caspase-11 deficiency re-programs liver transcriptomes and reduces HFD-induced NAFLD; 6) Caspase-11 deficiency decreases extracellular acidification rates (glycolysis) and oxidative phosphorylation (OXPHOS) in inflammatory fatty acid palmitic acid-stimulated macrophages, indicating that caspase-11 significantly contributes to maintain dual fuel bioenergetics— glycolysis and OXPHOS for promoting pyroptosis in macrophages. These results provide novel insights on the roles of the caspase-11-GSDMD pathway in promoting hepatic macrophage inflammation and pyroptosis and novel targets for future therapeutic interventions involving the transition of NAFLD to NASH, hyperlipidemia, type II diabetes, metabolic syndrome, metabolically healthy obesity, atherosclerotic cardiovascular diseases, autoimmune diseases, liver transplantation, and hepatic cancers. [ABSTRACT FROM AUTHOR]

We previously reported that Korean red ginseng (KRG) exerts an anti-inflammatory role through inhibiting caspase-11 non-canonical inflammasome in macrophages; however, the components responsible for the anti-inflammatory role remained unclear. This study explored the anti-inflammatory activity of the KRG saponin fraction (KRGSF) in caspase-11 non-canonical inflammasome-activated macrophages. KRGSF inhibited pyroptosis, pro-inflammatory cytokine secretion, and inflammatory mediator production in caspase-11 non-canonical inflammasome-activated J774A.1 cells. A mechanism study revealed that KRGSF-induced anti-inflammatory action was mediated via suppressing the proteolytic activation of caspase-11 and gasdermin D (GSDMD) in caspase-11 non-canonical inflammasome-activated J774A.1 cells. Moreover, KRGSF increased the survival of lethal septic mice. Taken together, these results reveal KRGSF-mediated anti-inflammatory action with a novel mechanism, by inhibiting caspase-11 non-canonical inflammasome in macrophages. [ABSTRACT FROM AUTHOR]

Background: Acute kidney injury (AKI) is a common complication in patients with severe acute pancreatitis (SAP). Caspase-11-mediated pyroptosis is essential for the progression of multiple diseases, but its role in SAP-induced AKI remains unknown. Aims: This research investigated whether caspase-11-mediated pyroptosis is involved in SAP-induced AKI and whether inhibiting caspase-11-mediated pyroptosis improves SAP-induced AKI. Methods: A rat model of SAP with AKI was established by slowly injecting 5% sodium taurocholate into the biliopancreatic duct, then wedelolactone (25 or 50 mg/kg), an inhibitor of caspase-11, was injected through the intra-peritoneum 1 and 6 h after SAP induction. Serum biochemical indexes, including serum amylase, lipase, interleukin (IL)-6, blood urea nitrogen (BUN), tumor necrosis factor (TNF)-α, and creatinine (Cr) in rats, were evaluated using biochemical test kits. Caspase-11 and gasdermin D (GSDMD) expression in the kidney tissues was evaluated by western blotting and immunohistochemical staining. IL-1β and IL-18 levels in kidney tissues were detected by ELISA kits. Furthermore, histopathological alterations of pancreas and kidney were assessed by H&E staining. Results: The serum biochemical indexes and pyroptosis-related proteins in kidney tissues were significantly increased after SAP induction. Furthermore, wedelolactone decreased the expression of pyroptosis-linked proteins in kidney tissues, reduced serum lipase, amylase, IL-6, TNF-α, BUN, and Cr, and ameliorated the renal and pancreatic histological damage in SAP rats. Conclusion: Caspase-11-mediated pyroptosis contributes to SAP-induced AKI, and targeting caspase-11-mediated pyroptosis might be a novel treatment strategy for SAP-induced AKI. [ABSTRACT FROM AUTHOR]

Acute kidney injury (AKI) is a serious condition with high mortality. The most common cause is kidney ischemia/reperfusion (IR) injury, which is thought to be closely related to pyroptosis. Disulfiram is a well-known alcohol abuse drug, and recent studies have shown its ability to mitigate pyroptosis in mouse macrophages. This study investigated whether disulfiram could improve IR-induced AKI and elucidated the possible molecular mechanism. We generated an IR model in mouse kidneys and a hypoxia/reoxygenation (HR) injury model with murine tubular epithelial cells (MTECs). The results showed that IR caused renal dysfunction in mice and triggered pyroptosis in renal tubular epithelial cells, and disulfiram improved renal impairment after IR. The expression of proteins associated with the classical pyroptosis pathway (Nucleotide-binding oligomeric domain (NOD)-like receptor protein 3 (NLRP3), apoptosis-related specific protein (ASC), caspase-1, N-GSDMD) and nonclassical pyroptosis pathway (caspase-11, N-GSDMD) were upregulated after IR. Disulfiram blocked the upregulation of nonclassical but not all classical pyroptosis pathway proteins (NLRP3 and ASC), suggesting that disulfiram might reduce pyroptosis by inhibiting the caspase-11-GSDMD pathway. In vitro, HR increased intracellular ROS levels, the positive rate of PI staining and LDH levels in MTECs, all of which were reversed by disulfiram pretreatment. Furthermore, we performed a computer simulation of the TIR domain of TLR4 using homology modeling and identified a small molecular binding energy between disulfiram and the TIR domain. We concluded that disulfiram might inhibit pyroptosis by antagonizing TLR4 and inhibiting the caspase-11-GSDMD pathway. [ABSTRACT FROM AUTHOR]

Pyroptosis mediated by gasdermins (GSDMs) plays crucial roles in infection and inflammation. Pyroptosis triggers the release of inflammatory molecules, including damage-associated molecular patterns (DAMPs). However, the consequences of pyroptosis-especially beyond interleukin (IL)-1 cytokines and DAMPs-that govern inflammation are poorly defined. Here, we show intercellular propagation of pyroptosis from dying cells to bystander cells in vitro and in vivo. We identified extracellular vesicles (EVs) released by pyroptotic cells as the propagator of lytic death to naive cells, promoting inflammation. DNA-PAINT super-resolution and immunoelectron microscopy revealed GSDMD pore structures on EVs released by pyroptotic cells. Importantly, pyroptotic EVs transplant GSDMD pores on the plasma membrane of bystander cells and kill them. Overall, we demonstrate that cell-to-cell vesicular transplantation of GSDMD pores disseminates pyroptosis, revealing a domino-like effect governing disease-associated bystander cell death., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The inflammatory response consists of two stages: priming and triggering. The triggering stage is marked by the activation of inflammasomes, which are cytosolic protein complexes acting as platforms for inflammation. Inflammasomes are divided into canonical and noncanonical categories. Inflammatory lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome (ARDS), inflammatory lung injury, and pulmonary fibrosis arise from lung inflammation and damage. While the role of canonical inflammasomes in these diseases is well demonstrated, recent findings emphasize the critical roles of noncanonical inflammasomes in regulating inflammation and various inflammatory conditions. Particularly, new studies highlight their involvement in inflammatory lung diseases. This review delves into recent research on the regulatory roles of noncanonical inflammasomes, such as human caspase-4 and murine caspase-11, in lung inflammation and the development of inflammatory lung diseases, as well as the potential for targeting these inflammasomes for new treatments.

Background: Infection is the leading cause of acute lung injury (ALI). Macrophages, which are pivotal innate immune cells, play a critical role in mediating inflammatory processes. Intracellular lipopolysaccharide (LPS) from invasive Gram-negative bacteria can activate the caspase-11 inflammasome, leading to the induction of pyroptosis in macrophages. This process subsequently triggers the release of inflammatory cytokines and damage-associated molecular patterns from pyroptotic macrophages, thereby exacerbating inflammatory progression in ALI. However, the precise regulatory mechanisms governing caspase-11 activation is still unclear. Sentrin-specific proteases (SENPs) have been identified as notable targets for their anti-inflammatory properties. Nevertheless, the specific role of SENPs in macrophage pyroptosis during the pathogenesis of ALI remains unknown., Methods: We used LPS as an endotoxin to induce ALI. We analyzed the expression and location of sentrin-specific protease 1 (SENP1), pulmonary impairment, macrophage infiltration, caspase-11 inflammasome expression and activation, caspase-11 SUMOylation, and inflammatory cytokine secretion., Results: Upregulated expression of SENP1 in lung tissue and macrophages was observed following LPS stimulation. SENP1 mediates de-SUMOylation and activation of caspase-11 inflammasome in macrophages. Moreover, pharmacological inhibition or genetic deficiency of SENP1 in macrophages significantly improved ALI-related histological damage by reducing the secretion of inflammatory cytokines and suppressing caspase-11-dependent pyroptosis., Conclusions: Collectively, our findings highlight the involvement of SENP1 in caspase-11 activation and inflammatory progression in macrophages, thereby establishing a scientific foundation for the exploration of novel therapeutic strategies aimed at treating ALI., (© 2024 The Author(s). Published by IMR Press.)

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.