Cutaneous inflammasome driving ASC / gasdermin-D activation and IL-1ß-secreting macrophages in severe atopic dermatitis.

Atopic dermatitis (AD) is an inflammatory skin disease with intense pruritus, and chronic skin colonization by Staphylococcus aureus. To understand the inflammatory status in AD, we investigated the inflammasome complex, that activates ASC (Apoptosis-associated speck-like protein containing a CARD), caspase-1 and GSDMD (gasdermin-D), and production of IL-1ß and IL-18. We aimed to evaluate the expression of the inflammasome pathway in the skin of adults with AD. Thirty patients with moderate to severe AD and 20 healthy controls were enrolled in the study. We performed the analysis of the inflammasome components NLRP1, NLRP3, AIM-2, IL-1ß, IL-18, Caspase-1, ASC, GSDMD, and CD68 expression (macrophage marker) by immunohistochemistry and immunofluorescence. The main findings included increased expression of NLRP3, NLRP1 and AIM-2 at dermal level of severe AD; augmented IL-18 and IL-1ß expression at epidermis of moderate and severe patients, and in the dermis of severe AD; augmented expression of ASC, caspase-1 and GSDMD in both epidermis and dermis of moderate and severe AD. We detected positive correlation between caspase-1, GSDMD and IL-1ß (epidermis) and caspase-1 (dermis) and AD severity; NLRP3, AIM-2 and IL-1ß, and NLRP3 with IL-18 in the epidermis; ASC, GSDMD and IL-1ß, and NLRP3, AIM-2, caspase-1, and IL-18 in the dermis. We also evidenced the presence of CD68+ macrophages secreting GSDMD, ASC and IL-1ß in moderate and severe AD. Cutaneous macrophages, early detected in moderate AD, have its role in the disease inflammatory mechanisms. Our study indicates a canonical activation pathway of inflammasomes, reinforced by the chronic status of inflammation in AD. The analysis of the inflammasome complex evidenced an imbalance in its regulation, with increased expression of the evaluated components, which is remarkably in severe AD, emphasizing its relevance as potential disease biomarkers and targets for immunomodulatory interventions.

Staphylococcus Aureus Membrane Vesicles Kill Tumor Cells Through a Caspase-1-Dependent Pyroptosis Pathway.

Introduction: Nanosized outer membrane vesicles (OMVs) from Gram-negative bacteria have attracted increasing interest because of their antitumor activity. However, the antitumor effects of MVs isolated from Gram-positive bacteria have rarely been investigated. Methods: MVs of Staphylococcus aureus USA300 were prepared and their antitumor efficacy was evaluated using tumor-bearing mouse models. A gene knock-in assay was performed to generate luciferase Antares2-MVs for bioluminescent detection. Cell counting kit-8 and lactic dehydrogenase release assays were used to detect the toxicity of the MVs against tumor cells in vitro. Active caspase-1 and gasdermin D (GSDMD) levels were determined using Western blot, and the tumor inhibition ability of MVs was determined in B16F10 cells treated with a caspase-1 inhibitor. Results: The vesicular particles of S. aureus USA300 MVs were 55.23 ± 8.17 nm in diameter, and 5 µg of MVs remarkably inhibited the growth of B16F10 melanoma in C57BL/6 mice and CT26 colon adenocarcinoma in BALB/c mice. The bioluminescent signals correlated well with the concentrations of the engineered Antares2-MVs (R2 = 0.999), and the sensitivity for bioluminescence imaging was 4 × 10-3 µg. Antares2-MVs can directly target tumor tissues in vivo, and 20 µg/mL Antares2-MVs considerably reduced the growth of B16F10 and CT26 tumor cells, but not non-carcinomatous bEnd.3 cells. MV treatment substantially increased the level of active caspase-1, which processes GSDMD to trigger pyroptosis in tumor cells. Blocking caspase-1 activation with VX-765 significantly protected tumor cells from MV killing in vitro and in vivo. Conclusion: S. aureus MVs can kill tumor cells by activating the pyroptosis pathway, and the induction of pyroptosis in tumor cells is a promising strategy for cancer treatment.

[Chronic intermittent hypoxia activates NLRP1 inflammasome and causes liver injury].

Objective To investigate the liver injury induced by chronic intermittent hypoxia (CIH) activation of NOD-like receptor pyrin domain containing protein 1 (NLRP1) inflammasome. Methods C57BL/6 male mice were randomly divided into control group and CIH group. Mice in CIH group were put into CIH chamber for molding (8 hours a day for 4 weeks). After 4 weeks of molding, liver tissue cells was observed by HE staining, and the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum of mice were detected by kit. The levels of reactive oxygen species (ROS) in liver tissue were detected by dihydroethidine (DHE). The expression and localization of NLRP1, apoptosis speck-like protein containing a caspase activation and recruiting domain (ASC) and caspase-1 were detected by immunohistochemical staining. The protein expressions of NLRP1, ASC, caspase-1, interleukin 1ß (IL-1ß) and tumor necrosis factor α (TNF-α) were detected by Western blot analysis. The serum levels of IL-1ß and TNF-α were detected by ELISA. Results Compared with the control group, the CIH group exhibited significant pathological changes in hepatocytes. Hepatocytes showed signs of rupture and necrosis, accompanied by inflammatory cell aggregation. Furthermore, the levels of ALT, AST, ROS, IL-1ß and TNF-α were elevated, along with increased protein expressions of NLRP1, ASC, caspase-1, IL-1ß and TNF-α. Conclusion CIH causes liver injury by activating NLRP1 inflammasome.

A potential virulence factor: Brucella flagellin FliK does not affect the main biological properties but inhibits the inflammatory response in RAW264.7 cells.

The bacterial flagellum is an elongated filament that protrudes from the cell and is responsible for bacterial motility. It can also be a pathogen-associated molecular pattern (PAMP) that regulates the host immune response and is involved in bacterial pathogenicity. In contrast to motile bacteria, the Brucella flagellum does not serve a motile purpose. Instead, it plays a role in regulating Brucella virulence and the host's immune response, similar to other non-motile bacteria. The flagellin protein, FliK, plays a key role in assembly of the flagellum and also as a potential virulence factor involved in the regulation of bacterial virulence and pathogenicity. In this study, we generated a Brucella suis S2 flik gene deletion strain and its complemented strain and found that deletion of the flik gene has no significant effect on the main biological properties of Brucella, but significantly enhanced the inflammatory response induced by Brucella infection of RAW264.7 macrophages. Further experiments demonstrated that the FliK protein was able to inhibit LPS-induced cellular inflammatory responses by down-regulating the expression of MyD88 and NF-κB, and by decreasing p65 phosphorylation in the NF-κB pathway; it also inhibited the expression of NLRP3 and caspase-1 in the NLRP3 inflammasome pathway. In conclusion, our study suggests that Brucella FliK may act as a virulence factor involved in the regulation of Brucella pathogenicity and modulation of the host immune response.

Lentinus edodes mycelium polysaccharide inhibits AGEs-induced HUVECs pyroptosis by regulating LncRNA MALAT1/miR-199b/mTOR axis and NLRP3/Caspase-1/GSDMD pathway.

A novel Lentinus edodes mycelia polysaccharide (LMP) prepared in our laboratory has been identified to be effective in inhibiting the damage of islet ß cells induced by glucose toxicity. However, whether it can effectively alleviate the pyroptosis of human umbilical vein endothelial cells (HUVECs) induced by advanced glycation end products (AGEs) remains unclear. Bioinformatics and cell biology techniques were used to explore the mechanism of LMP inhibiting AGEs-induced HUVECs damage. The results indicated that AGEs significantly increased the expression of LncRNA MALAT1, decreased cell viability to 79.67 %, increased intracellular ROS level to 248.19 % compared with the control group, which further led to cell membrane rupture. The release of LDH in cellular supernatant was increased to 149.42 %, and the rate of propidium iodide staining positive cells increased to 277.19 %, indicating the cell pyroptosis occurred. However, the above trend was effectively retrieved after the treatment with LMP. LMP effectively decreased the expression of LncRNA MALAT1 and mTOR, promoted the expression of miR-199b, inhibited AGEs-induced HUVECs pyroptosis by regulating the NLRP3/Caspase-1/GSDMD pathway. LncRNA MALAT1 might be a new target for LMP to inhibit AGEs-induced HUVECs pyroptosis. This study manifested the role of LMP in improving diabetes angiopathy and broadens the application of polysaccharide.

Modulation and Determination of the Status of Inflammasomes in Leishmania-Infected Macrophages.

Leishmania, an intra-macrophage kinetoplastid parasite, modulates a vast array of defensive mechanisms of the host macrophages to create a comfortable environment for their survival. When the host encounters intracellular pathogens, a multimeric protein complex called NLRP3 inflammasome gets turned on, leading to caspase-1 activation-mediated maturation of IL-1ß from its pro-form. However, Leishmania often manages to neutralize inflammasome activation by manipulating negative regulatory molecules of the host itself. Exhaustion of NLRP3 and pro-IL-1ß result from decreased NF-κB activity in infection, which was attributed to increased expression of A20, a negative regulator of NF-κB signalling. Moreover, reactive oxygen species, another key requirement for inflammasome activation, are inhibited by mitochondrial uncoupling protein 2 (UCP2) which is upregulated by Leishmania. Inflammasome activation is a complex event and procedures involved in monitoring inflammasome activation need to be accurate and error-free. In this chapter, we summarize the protocol that includes various experimental procedures required for the determination of the status of inflammasomes in Leishmania-infected macrophages.

Penehyclidine hydrochloride alleviates lung ischemia-reperfusion injury by inhibiting pyroptosis.

OBJECTIVE: The aim of this research was to examine how penehyclidine hydrochloride (PHC) impacts the occurrence of pyroptosis in lung tissue cells within a rat model of lung ischemia-reperfusion injury. METHODS: Twenty-four Sprague Dawley (SD) rats, weighing 250 g to 270 g, were randomly distributed into three distinct groups as outlined below: a sham operation group (S group), a control group (C group), and a test group (PHC group). Rats in the PHC group received a preliminary intravenous injection of PHC at a dose of 3 mg/kg. At the conclusion of the experiment, lung tissue and blood samples were collected and properly stored for subsequent analysis. The levels of malondialdehyde, superoxide dismutase, and myeloperoxidase in the lung tissue, as well as IL-18 and IL-1ß in the blood serum, were assessed using an Elisa kit. Pyroptosis-related proteins, including Caspase1 p20, GSDMD-N, and NLRP3, were detected through the western blot method. Additionally, the dry-to-wet ratio (D/W) of the lung tissue and the findings from the blood gas analysis were also documented. RESULTS: In contrast to the control group, the PHC group showed enhancements in oxygenation metrics, reductions in oxidative stress and inflammatory reactions, and a decrease in lung injury. Additionally, the PHC group exhibited lowered levels of pyroptosis-associated proteins, including the N-terminal segment of gasdermin D (GSDMD-N), caspase-1p20, and nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3). CONCLUSION: Pre-administration of PHC has the potential to mitigate lung ischemia-reperfusion injuries by suppressing the pyroptosis of lung tissue cells, diminishing inflammatory reactions, and enhancing lung function. The primary mechanism behind anti-pyroptotic effect of PHC appears to involve the inhibition of oxidative stress.

[Impact of chaperone-mediated autophagy on bilirubin-induced damage of mouse microglial cells]. / åˆ†å­ä¼´ä¾£ä»‹å¯¼çš„è‡ªå™¬å¯¹èƒ†çº¢ç´ è¯±å¯¼çš„å°é¼ å°èƒ¶è´¨ç»†èƒžæŸä¼¤çš„å½±å“.

OBJECTIVES: To investigate the effect of chaperone-mediated autophagy (CMA) on the damage of mouse microglial BV2 cells induce by unconjugated bilirubin (UCB). METHODS: The BV2 cell experiments were divided into two parts. (1) For the CMA activation experiment: control group (treated with an equal volume of dimethyl sulfoxide), QX77 group (treated with 20 µmol/L QX77 for 24 hours), UCB group (treated with 40 µmol/L UCB for 24 hours), and UCB+QX77 group (treated with both 20 µmol/L QX77 and 40 µmol/L UCB for 24 hours). (2) For the cell transfection experiment: LAMP2A silencing control group (treated with an equal volume of dimethyl sulfoxide), LAMP2A silencing control+UCB group (treated with 40 µmol/L UCB for 24 hours), LAMP2A silencing group (treated with an equal volume of dimethyl sulfoxide), and LAMP2A silencing+UCB group (treated with 40 µmol/L UCB for 24 hours). The cell viability was assessed using the modified MTT method. The expression levels of p65, nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), and cysteinyl aspartate specific proteinase-1 (caspase-1) were detected by Western blot. The relative mRNA expression levels of the inflammatory cytokines interleukin (IL)-1ß, IL-6, and tumor necrosis factor-α (TNF-α) were determined by real-time quantitative polymerase chain reaction. Levels of IL-6 and TNF-α in the cell culture supernatant were measured using ELISA. The co-localization of heat shock cognate protein 70 with p65 and NLRP3 was detected by immunofluorescence. RESULTS: Compared to the UCB group, the cell viability in the UCB+QX77 group increased, and the expression levels of inflammation-related proteins p65, NLRP3, and caspase-1, as well as the mRNA relative expression levels of IL-1ß, IL-6, and TNF-α and levels of IL-6 and TNF-α decreased (P<0.05). Compared to the control group, there was co-localization of heat shock cognate protein 70 with p65 and NLRP3 in both the UCB and UCB+QX77 groups. After silencing the LAMP2A gene, compared to the LAMP2A silencing control+UCB group, the LAMP2A silencing+UCB group showed increased expression levels of inflammation-related proteins p65, NLRP3, and caspase-1, as well as increased mRNA relative expression levels of IL-1ß, IL-6, and TNF-α and levels of IL-6 and TNF-α (P<0.05). CONCLUSIONS: CMA is inhibited in UCB-induced BV2 cell damage, and activating CMA may reduce p65 and NLRP3 protein levels, suppress inflammatory responses, and counteract bilirubin neurotoxicity.

Nucleoside-diphosphate kinase of uropathogenic Escherichia coli inhibits caspase-1-dependent pyroptosis facilitating urinary tract infection.

Uropathogenic Escherichia coli (UPEC) is the most common causative agent of urinary tract infection (UTI). UPEC invades bladder epithelial cells (BECs) via fusiform vesicles, escapes into the cytosol, and establishes biofilm-like intracellular bacterial communities (IBCs). Nucleoside-diphosphate kinase (NDK) is secreted by pathogenic bacteria to enhance virulence. However, whether NDK is involved in UPEC pathogenesis remains unclear. Here, we find that the lack of ndk impairs the colonization of UPEC CFT073 in mouse bladders and kidneys owing to the impaired ability of UPEC to form IBCs. Furthermore, we demonstrate that NDK inhibits caspase-1-dependent pyroptosis by consuming extracellular ATP, preventing superficial BEC exfoliation, and promoting IBC formation. UPEC utilizes the reactive oxygen species (ROS) sensor OxyR to indirectly activate the regulator integration host factor, which then directly activates ndk expression in response to intracellular ROS. Here, we reveal a signaling transduction pathway that UPEC employs to inhibit superficial BEC exfoliation, thus facilitating acute UTI.

Chinese medicinal formula Fu Xin decoction against chronic heart failure by inhibiting the NLRP3/caspase-1/GSDMD pyroptotic pathway.

BACKGROUND: Various heart diseases ultimately lead to chronic heart failure (CHF). In CHF, the inflammatory response is associated with pyroptosis, which is mediated by the NOD-like receptor protein 3 (NLRP3) inflammasome. Fu Xin decoction (FXD) is commonly used in clinical practice to treat CHF and improve inflammatory conditions. However, the specific pharmacological mechanisms of action for FXD in these processes have yet to be fully understood. PURPOSE: The objective of this study was to examine the protective mechanism of FXT against CHF, both in H9c2 cells and mice. METHOD: A CHF mouse model was established, and the effect of FXD was observed via gavage. Cardiac function was evaluated using echocardiography, while serum BNP and LDH levels were analyzed to assess the severity of CHF. Hematoxylin and eosin staining (H&E) and Masson staining were performed to evaluate myocardial pathological changes, and TdT-mediated dUTP Nick-End Labeling staining was used to detect DNA damage. Additionally, doxorubicin was utilized to induce myocardial cell injury in H9c2 cells, establishing a relevant model. CCK8 was used to observe cell viability and detect LDH levels in the cell supernatant. Subsequently, the expression of pyroptosis-related proteins was detected using immunohistochemistry, immunofluorescence, and western blotting. Finally, the pharmacological mechanism of FXD against CHF was further validated by treating H9c2 cells with an NLRP3 activator and inducing NLRP3 overexpression. RESULT: According to current research findings, echocardiography demonstrated a significant improvement of cardiac function by FXD, accompanied by reduced levels of BNP and LDH, indicating the amelioration of cardiac injury in CHF mice. FXD exhibited the ability to diminish serum CRP and MCP inflammatory markers in CHF mice. The results of HE and Masson staining analyses revealed a significant reduction in pathological damage of the heart tissue following FXD treatment. The CCK8 assay demonstrated the ability of FXD to enhance H9c2 cell viability, improve cell morphology, decrease LDH levels in the cell supernatant, and alleviate cell damage. Immunohistochemistry, Western blotting, and immunofluorescence staining substantiated the inhibitory effect of FXD on the NLRP3/caspase-1/GSDMD pyroptosis signaling pathway in both CHF and H9c2 cell injury models. Ultimately, the administration of the NLRP3 activator (Nigericin) and the overexpression of NLRP3 counteract the effects of FXD on cardiac protection and pyroptosis inhibition in vitro. CONCLUSION: FXD exhibits a cardioprotective effect, improving CHF and alleviating pyroptosis by inhibiting the NLRP3/caspase-1/GSDMD pathway.

The inflammasome pathway is activated by dengue virus non-structural protein 1 and is protective during dengue virus infection.

Dengue virus (DENV) is a medically important flavivirus causing an estimated 50-100 million dengue cases annually, some of whom progress to severe disease. DENV non-structural protein 1 (NS1) is secreted from infected cells and has been implicated as a major driver of dengue pathogenesis by inducing endothelial barrier dysfunction. However, less is known about how DENV NS1 interacts with immune cells and what role these interactions play. Here we report that DENV NS1 can trigger activation of inflammasomes, a family of cytosolic innate immune sensors that respond to infectious and noxious stimuli, in mouse and human macrophages. DENV NS1 induces the release of IL-1ß in a caspase-1 dependent manner. Additionally, we find that DENV NS1-induced inflammasome activation is independent of the NLRP3, Pyrin, and AIM2 inflammasome pathways, but requires CD14. Intriguingly, DENV NS1-induced inflammasome activation does not induce pyroptosis and rapid cell death; instead, macrophages maintain cellular viability while releasing IL-1ß. Lastly, we show that caspase-1/11-deficient, but not NLRP3-deficient, mice are more susceptible to lethal DENV infection. Together, these results indicate that the inflammasome pathway acts as a sensor of DENV NS1 and plays a protective role during infection.

High expression of CASP1 induces atherosclerosis.

Atherosclerosis is a chronic, progressive vascular disease. The relationship between CASP1 gene expression and atherosclerosis remains unclear. The atherosclerosis dataset GSE132651 and GSE202625 profiles were downloaded from gene expression omnibus. Differentially expressed genes (DEGs) were screened. The construction and analysis of protein-protein interaction network, functional enrichment analysis, gene set enrichment analysis, and Comparative Toxicogenomics Database analysis were performed. Gene expression heatmap was drawn. TargetScan was used to screen miRNAs that regulate central DEG. 47 DEGs were identified. According to gene ontology analysis, they were mainly enriched in the regulation of stimulus response, response to organic matter, extracellular region, extracellular region, and the same protein binding. Kyoto Encyclopedia of Gene and Genome analysis results showed that the target cells were mainly enriched in the PI3K-Akt signaling pathway, Ras signaling pathway, and PPAR signaling pathway. In the enrichment project of Metascape, vascular development, regulation of body fluid levels, and positive regulation of cell motility can be seen in the gene ontology enrichment project. Eleven core genes (CASP1, NLRP3, MRC1, IRS1, PPARG, APOE, IL13, FGF2, CCR2, ICAM1, HIF1A) were obtained. IRS1, PPARG, APOE, FGF2, CCR2, and HIF1A genes are identified as core genes. Gene expression heatmap showed that CASP1 was highly expressed in atherosclerosis samples and low expressed in normal samples. NLRP3, MRC1, IRS1, PPARG, APOE, IL13, FGF2, CCR2, ICAM1, HIF1A were low expressed in atherosclerosis samples. CTD analysis showed that 5 genes (CASP1, NLRP3, CCR2, ICAM1, HIF1A) were found to be associated with pneumonia, inflammation, cardiac enlargement, and tumor invasiveness. CASP1 gene is highly expressed in atherosclerosis. The higher the CASP1 gene, the worse the prognosis.

Reniformin A suppresses non-small cell lung cancer progression by inducing TLR4/NLRP3/caspase-1/GSDMD-dependent pyroptosis.

Pyroptosis is an inflammatory form of programmed cell death that plays an important role in regulating tumor progression. Reniformin A (RA) is a natural compound isolated from the medicinal herb Isodon excisoides that has been applied as folk medicine in the treatment of esophageal cancer. However, whether RA has an individual function in cancer and the molecular mechanisms remain unclear. Here, we show that in non-small-cell lung cancer (NSCLC), RA inhibits tumor growth by functioning as a pyroptosis inducer to promote TLR4/NLRP3/caspase-1/GSDMD axis. Specially, RA treatment increased Toll-like receptor 4 (TLR4) protein expression level by enhancing the TLR4 stability. Based on the molecular docking, we identified that RA directly bound to TLR4 to activate the NLRP3 inflammasome and promote pyroptosis in A549 cells. Moreover, TLR4 is essential for RA-induced pyroptosis, and loss of TLR4 abolished RA-induced pyroptosis and further reduced the inhibitory effect of RA on NSCLC. In vivo experiments confirmed that RA inhibited the growth of lung tumors in mice by affecting pyroptosis in a dose-dependent manner. Furthermore, TLR4 knockdown abolished RA-induced pyroptosis and inhibited the effect of RA chemotherapy in vivo. In conclusion, we propose that RA has a significant anticancer effect in NSCLC by inducing TLR4/NLRP3/caspase-1/GSDMD-mediated pyroptosis, which may provide a potential strategy for the treatment of NSCLC.

Periplogenin inhibits pyroptosis of fibroblastic synoviocytes in rheumatoid arthritis through the NLRP3/Caspase-1/GSDMD signaling pathway.

Although the pathogenesis of rheumatoid arthritis (RA) remains unclear, an increasing number of studies have confirmed that pyroptosis of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) is an important factor affecting the progression of RA. Periplogenin (PPN) is a natural cardiac glycoside; reportedly, it exerts anti-inflammatory and analgesic effects in diseases by inhibiting cell growth and migration. This study aimed to determine the effect of PPN on the growth, migration, and invasion of RA-FLS and the potential mechanism of pyroptosis regulation. We discovered that PPN could inhibit the migration and invasion abilities of RA-FLS and block their growth cycle, down-regulate the secretion and activation of NLRP3, Caspase-1, GSDMD, IL-1ß, and IL-18, and reduce the number of pyroptosis. In summary, PPN inhibited pyroptosis, reduced the release of inflammatory factors, and improved RA-FLS inflammation by regulating the NLRP3/Caspase-1/GSDMD signaling pathway.

Caspase-1 activates gasdermin A in non-mammals.

Gasdermins oligomerize to form pores in the cell membrane, causing regulated lytic cell death called pyroptosis. Mammals encode five gasdermins that can trigger pyroptosis: GSDMA, B, C, D, and E. Caspase and granzyme proteases cleave the linker regions of and activate GSDMB, C, D, and E, but no endogenous activation pathways are yet known for GSDMA. Here, we perform a comprehensive evolutionary analysis of the gasdermin family. A gene duplication of GSDMA in the common ancestor of caecilian amphibians, reptiles, and birds gave rise to GSDMA-D in mammals. Uniquely in our tree, amphibian, reptile, and bird GSDMA group in a separate clade than mammal GSDMA. Remarkably, GSDMA in numerous bird species contain caspase-1 cleavage sites like YVAD or FASD in the linker. We show that GSDMA from birds, amphibians, and reptiles are all cleaved by caspase-1. Thus, GSDMA was originally cleaved by the host-encoded protease caspase-1. In mammals the caspase-1 cleavage site in GSDMA is disrupted; instead, a new protein, GSDMD, is the target of caspase-1. Mammal caspase-1 uses exosite interactions with the GSDMD C-terminal domain to confer the specificity of this interaction, whereas we show that bird caspase-1 uses a stereotypical tetrapeptide sequence to confer specificity for bird GSDMA. Our results reveal an evolutionarily stable association between caspase-1 and the gasdermin family, albeit a shifting one. Caspase-1 repeatedly changes its target gasdermin over evolutionary time at speciation junctures, initially cleaving GSDME in fish, then GSDMA in amphibians/reptiles/birds, and finally GSDMD in mammals.

Acetyl-CoA synthetase 2 induces pyroptosis and inflammation of renal epithelial tubular cells in sepsis-induced acute kidney injury by upregulating the KLF5/NF-κB pathway.

BACKGROUND: Pyroptosis of the renal tubular epithelial cells (RTECs) and interstitial inflammation are central pathological characteristics of acute kidney injury (AKI). Pyroptosis acts as a pro-inflammatory form of programmed cell death and is mainly dependent on activation of the NLRP3 inflammasome. Previous studies revealed that acetyl-CoA synthetase 2 (ACSS2) promotes inflammation during metabolic stress suggesting that ACSS2 might regulate pyroptosis and inflammatory responses of RTECs in AKI. METHODS AND RESULTS: The expression of ACSS2 was found to be significantly increased in the renal epithelial cells of mice with lipopolysaccharide (LPS)-induced AKI. Pharmacological and genetic strategies demonstrated that ACSS2 regulated NLRP3-mediated caspase-1 activation and pyroptosis through the stimulation of the KLF5/NF-κB pathway in RTECs. The deletion of ACSS2 attenuated renal tubular pathological injury and inflammatory cell infiltration in an LPS-induced mouse model, and ACSS2-deficient mice displayed impaired NLRP3 activation-mediated pyroptosis and decreased IL-1ß production in response to the LPS challenge. In HK-2 cells, ACSS2 deficiency suppressed NLRP3-mediated caspase-1 activation and pyroptosis through the downregulation of the KLF5/NF-κB pathway. The KLF5 inhibitor ML264 suppressed NF-κB activity and NLRP3-mediated caspase-1 activation, thus protecting HK-2 cells from LPS-induced pyroptosis. CONCLUSION: Our results suggested that ACSS2 regulates activation of the NLRP3 inflammasome and pyroptosis by inducing the KLF5/NF-κB pathway in RTECs. These results identified ACSS2 as a potential therapeutic target in AKI.

Type I interferon regulates interleukin-1beta and IL-18 production and secretion in human macrophages.

Inflammasomes are immune complexes whose activation leads to the release of pro-inflammatory cytokines IL-18 and IL-1ß. Type I IFNs play a role in fighting infection and stimulate the expression of IFN-stimulated genes (ISGs) involved in inflammation. Despite the importance of these cytokines in inflammation, the regulation of inflammasomes by type I IFNs remains poorly understood. Here, we analysed RNA-sequencing data from patients with monogenic interferonopathies and found an up-regulation of several inflammasome-related genes. To investigate the effect of type I IFN on the inflammasome, we treated human monocyte-derived macrophages with IFN-α and observed an increase in CASP1 and GSDMD mRNA levels over time, whereas IL1B and NLRP3 were not directly correlated to IFN-α exposure time. IFN-α treatment reduced the release of mature IL-1ß and IL-18, but not caspase-1, in response to ATP-mediated NLRP3 inflammasome activation, suggesting regulation occurs at cytokine expression levels and not the inflammasome itself. However, more studies are required to investigate how regulation by IFN-α occurs and impacts NLRP3 and other inflammasomes at both transcriptional and post-translational levels.

Mahuang Fuzi Xixin decoction alleviates allergic rhinitis by inhibiting NLRP3/Caspase-1/GSDMD-N-mediated pyroptosis.

ETHNOPHARMACOLOGICAL RELEVANCE: Allergic rhinitis (AR) is a prevalent nasal inflammatory disorder, and pyroptosis plays a crucial role in aggravating AR. Current medications for AR treatment still have deficiencies, and finding new agents is of great interest. Mahuang Fuzi Xixin decoction (MFXD), an ancient Chinese medicine, is now commonly used to treat AR, which has anti-inflammatory and immunomodulatory effects, but its underlying mechanism is unknown. AIM OF THIS STUDY: This study aims to evaluate the effects of MFXD on AR and explore its potential mechanisms in view of the regulatory effect on pyroptosis. METHODS: MFXD, Mahuang, Fuzi, and Xixin water extracts were analyzed using ultra high performance liquid chromatography-Orbitrap-high-resolution accurate mass spectrometry. In in vivo study, the effects of MFXD on AR treatment were evaluated in an ovalbumin-induced mouse model. Mice were administered saline (control and model groups), MFXD (1.375, 2.75 g/kg), and dexamethasone (2.5 mg/kg) for 13 days. AR symptoms were evaluated by blinded observers. Immunoglobulin E (IgE) and histamine levels were measured using enzyme-linked immunosorbent assays. Expression of pyroptosis-related proteins (NLRP3, ASC, Caspase-1 p10/p20, GSDMD-N and IL-1ß) in AR mouse nasal mucosa were estimated by immunohistochemistry. In in vivtro study, the effects of MFXD on pyroptosis were assessed in human nasal epithelial cells (HNEpCs) stimulated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP), and incubated with MFXD (12.5, 25, and 50 µg/mL). Pyroptosis-related protein expression was measured by western blotting. RESULTS: Thirty-three compounds in MFXD were identified, including ephedrine, pseudoephedrine, higenamine, aconine, aconitine, benzoylmesaconitine, benzoylhypaconine and hypaconitine. In the in vivo study, oral taken of MFXD/dexamethasone significantly ameliorated AR symptoms, reduced swelling of the nasal mucosa, and decreased the levels of IgE and histamine in AR mice serum. MFXD/dexamethasone attenuated histopathological changes and reduced the expression of pyroptosis-related proteins in nasal mucosa, indicating the inhibitory effect on nasal epithelial pyroptosis. In the in vitro study, MFXD (50 µg/mL) significantly alleviated cytotoxicity, protected cells from swelling and rupture, and downregulated the expression of pyroptosis-related proteins in LPS/ATP-induced HNEpCs. CONCLUSION: MFXD suppressed nasal epithelial pyroptosis by inhibiting the NLRP3/Caspase-1/GSDMD-N signaling pathway, which alleviates AR. Our results offer valuable insights into potential AR therapies and provide evidence for the clinical utilization of MFXD to treat AR.

Expression and correlation of the NOD-like receptor family, pyrin domain-containing 3 inflammasome and the silent information regulator 1 in patients with drug-resistant epilepsy.

BACKGROUND: The NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammatory pathway is implicated in the development of epilepsy and can be suppressed by the activation of the silent information regulator 1 (SIRT1). However, the expression and correlation of the NLRP3 pathway and SIRT1 in drug-resistant epilepsy (DRE) remain unknown. METHODS: This study evaluated the histopathology of the cerebral cortex from nine patients with DRE and eight patients with cavernous haemangioma undergoing surgical treatment. It analysed the expression of the NLRP3, interleukin-1ß (IL-1ß), caspase-1 and SIRT1 using immunohistochemistry. Additionally, the contents of NLRP3, caspase-1, IL-1ß and SIRT1 in the serum samples of the included study participants were determined using ELISA method. The correlation between the NLRP3 pathway and the SIRT1 was assessed using Spearman's correlation analysis. RESULTS: The expression of NLRP3, caspase-1 and IL-1ß in the cerebral cortex of patients with DRE was elevated, with the NLRP3 expression being negatively correlated with the SIRT1 expression. Furthermore, IL-1ß in serum was upregulated in patients with DRE. The correlation between the content of serum SIRT1 and NLRP3, caspase-1 and IL-1ß in patients with DRE was not significant. Notably, serum caspase-1 levels were obviously higher in patients with bilateral hippocampal sclerosis than in patients with unilateral hippocampal sclerosis. CONCLUSIONS: The current results indicate that the expression of the NLRP3/caspase-1/IL-1ß pathway is significantly upregulated in patients with DRE and that it is partially correlated with the SIRT1 expression. This study is important for understanding the pathophysiology of DRE and developing new treatment strategies for it.

Astragaloside IV Alleviates Doxorubicin-Induced Cardiotoxicity by Inhibiting Cardiomyocyte Pyroptosis through the SIRT1/NLRP3 Pathway.

Doxorubicin (DOX) is a powerful anthracycline antineoplastic drug used to treat a wide spectrum of tumors. However, its clinical application is limited due to cardiotoxic side effects. Astragaloside IV (AS IV), one of the major compounds present in aqueous extracts of Astragalus membranaceus, possesses potent cardiovascular protective properties, but the underlying molecular mechanisms are unclear. Thus, the aim of this study was to investigate the effect of AS IV on DOX-induced cardiotoxicity (DIC). Our findings revealed that DOX induced pyroptosis through the caspase-1/gasdermin D (GSDMD) and caspase-3/gasdermin E (GSDME) pathways. AS IV treatment significantly improved the cardiac function and alleviated myocardial injury in DOX-exposed mice by regulating intestinal flora and inhibiting pyroptosis; markedly suppressed the levels of cleaved caspase-1, N-GSDMD, cleaved caspase-3, and N-GSDME; and reversed DOX-induced downregulation of silent information regulator 1 (SIRT1) and activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome in mice. The SIRT1 inhibitor EX527 significantly blocked the protective effects of AS IV. Collectively, our results suggest that AS IV protects against DIC by inhibiting pyroptosis through the SIRT1/NLRP3 pathway.