Mechanisms of Gasdermin Family Members in Inflammasome Signaling and Cell Death

Construction of a Pyroptosis-Related Genes Signature to Improve the Prognostic Prediction and Therapeutic Drugs Selection in Patients with Pancreatic Cancer

Background

Effective prognostic assessment and appropriate drug selection are important for the clinical management of pancreatic cancer (PaC). Here, we aimed to establish a pyroptosis-associated genes (PRGs) signature to predict the prognostic outcomes of PaC and guide clinical drug therapy.

Methods

We identified the differentially expressed PRGs between pancreatic adenocarcinoma (n = 178) and control pancreas samples (n = 171) obtained from different databases, and performed Lasso and Cox regression analysis to create a prognosis signature. Kaplan–Meier (K-M) survival curves and time-dependent receiver operating characteristics were further constructed to assess the utility of the risk model. The International Cancer Genome Consortium (ICGC) PACA-AU cohort (n = 95) was used as a validation dataset to examine the validity of this prognostic model. The correlations of risk score (RS) with clinical features, immune cell infiltration, tumor mutation burden and half-maximal inhibitory concentrations (IC50) of chemotherapeutic drugs were analyzed, and the expression levels of PRGs in cell lines were detected.

Results

A prognostic signature was constructed, which consisted of 4 PRGs (AIM2, IL18, GSMDC and PLCG1). K-M analysis demonstrated a remarkable difference in overall survival (OS) time between low-risk (LR) and high-risk (HR) groups (P < 0.001). The RS contributed to the progression of PaC, and could be a significant independent factor for prognostic prediction. The validation of the ICGC cohort confirmed the effectiveness of the proposed signature. The patients with a HR score in the TCGA cohort had higher tumor mutation burden and more sensitivity to paclitaxel, gemcitabine, 5-fluorouracil and cisplatin than those with a LR score. The differential expression levels of signature genes were verified in vitro.

Conclusion

The PRGs signature can be applied for predicting the prognosis of PaC, and may provide useful information for selection of therapeutic drugs.

Spatial localization of cathepsins: Implications in immune activation and resolution during infections

Cathepsins were first described, as endolysosomal proteolytic enzymes in reference to the organelles where they degrade the bulk of endogenous and exogenous substrates in a slightly acidic environment. These substrates include pathogens internalized via endocytosis and/or marked for destruction by autophagy. However, the role of cathepsins during infection far exceeds that of direct digestion of the pathogen. Cathepsins have been extensively investigated in the context of tumour associated immune cells and chronic inflammation. Several cathepsin-dependent immune responses develop in the endocytic pathway while others take place in the cytosol, the nucleus, or in the extracellular space. In this review we highlight the spatial localization of cathepsins and their implications in immune activation and resolution pathways during infection.

A comprehensive analysis of gasdermin family gene as therapeutic targets in pan-cancer

Six members of the gasdermin family are involved in various biological functions in malignant tumors. The present study aimed to perform a comprehensive analysis of gasdermin family genes in pan-cancer. Raw data was acquired from the genotype-tissue expression (GTEx) and the Cancer Genome Atlas. High inter-tumor heterogeneity in the expression between paracancerous and tumor tissues was observed across cancers. Survival analysis confirmed that the risk or protective effects of gasdermin family members on prognosis depended on the cancer types. The mutation frequency appeared to be high, and the mutation group had a worse prognosis. Besides, gasdermin family genes were associated with immune infiltrate subtypes, stromal and immune cell infiltration levels, TMB, MSI, immune checkpoint gene expression, and tumor stemness scores. Moreover, gasdermin family gene expressions affected the expressions of MMR genes and methyltransferases and could predict cancer cells sensitivity to chemotherapeutic drugs. Subsequently, the findings were double-checked in LIHC and PAAD. GSEA results indicated the gasdermin family genes mainly involved in tumor metabolism and immune microenvironment remodeling related signaling pathways. In conclusion, our findings confirmed that gasdermin family genes were potential therapeutic cancer targets in pan-cancer.

Pathogen-selective killing by guanylate-binding proteins as a molecular mechanism leading to inflammasome signaling

Inflammasomes are cytosolic signaling complexes capable of sensing microbial ligands to trigger inflammation and cell death responses. Here, we show that guanylate-binding proteins (GBPs) mediate pathogen-selective inflammasome activation. We show that mouse GBP1 and GBP3 are specifically required for inflammasome activation during infection with the cytosolic bacterium Francisella novicida. We show that the selectivity of mouse GBP1 and GBP3 derives from a region within the N-terminal domain containing charged and hydrophobic amino acids, which binds to and facilitates direct killing of F. novicida and Neisseria meningitidis, but not other bacteria or mammalian cells. This pathogen-selective recognition by this region of mouse GBP1 and GBP3 leads to pathogen membrane rupture and release of intracellular content for inflammasome sensing. Our results imply that GBPs discriminate between pathogens, confer activation of innate immunity, and provide a host-inspired roadmap for the design of synthetic antimicrobial peptides that may be of use against emerging and re-emerging pathogens.

Guanylate-binding proteins (GBP) have a function in inflammasome formation and pathogen defence. Here the authors show that these GBP proteins are able to kill certain bacteria and promote selective inflammasome activation and that this is mediated by specific GBP protein regions.

Identification of pyroptosis-related subtypes and establishment of prognostic model and immune characteristics in asthma

Background

Although studies have shown that cell pyroptosis is involved in the progression of asthma, a systematic analysis of the clinical significance of pyroptosis-related genes (PRGs) cooperating with immune cells in asthma patients is still lacking.

Methods

Transcriptome sequencing datasets from patients with different disease courses were used to screen pyroptosis-related differentially expressed genes and perform biological function analysis. Clustering based on K-means unsupervised clustering method is performed to identify pyroptosis-related subtypes in asthma and explore biological functional characteristics of poorly controlled subtypes. Diagnostic markers between subtypes were screened and validated using an asthma mouse model. The infiltration of immune cells in airway epithelium was evaluated based on CIBERSORT, and the correlation between diagnostic markers and immune cells was analyzed. Finally, a risk prediction model was established and experimentally verified using differentially expressed genes between pyroptosis subtypes in combination with asthma control. The cMAP database and molecular docking were utilized to predict potential therapeutic drugs.

Results

Nineteen differentially expressed PRGs and two subtypes were identified between patients with mild-to-moderate and severe asthma conditions. Significant differences were observed in asthma control and FEV1 reversibility between the two subtypes. Poor control subtypes were closely related to glucocorticoid resistance and airway remodeling. BNIP3 was identified as a diagnostic marker and associated with immune cell infiltration such as, M2 macrophages. The risk prediction model containing four genes has accurate classification efficiency and prediction value. Small molecules obtained from the cMAP database that may have therapeutic effects on asthma are mainly DPP4 inhibitors.

Conclusion

Pyroptosis and its mediated immune phenotype are crucial in the occurrence, development, and prognosis of asthma. The predictive models and drugs developed on the basis of PRGs may provide new solutions for the management of asthma.

Genomic analysis quantifies pyroptosis in the immune microenvironment of HBV-related hepatocellular carcinoma

Pyroptosis, a way of pro-inflammatory death, plays a significant part in the tumor microenvironment (TME). A recent study has shown that the hepatitis C virus changes the TME by inducing pyroptosis against hepatocellular carcinoma (HCC). However, compared to TME in hepatitis C virus-infected HCC, the exploration of immune characteristics and response to immunotherapy associated with the pyroptosis phenotype is still insufficient in hepatitis B virus-related HCC (HBV-HCC). Our study constructed pyroptosis-score (PYS) via principal-component analysis (PCA) to unveil the link between pyroptosis and tumor immunity in 369 HBV-HCC patients. Compared with the low-PYS group, subjects with higher PYS were associated with poor prognosis but were more susceptible to anti-PD-L1 treatment. In addition, we found that PYS can serve independently as a prognostic factor for HBV-HCC, making it possible for us to identify specific small molecule drugs with a potential value in inhibiting tumors via targeting pyroptosis. Also, the target genes predicted by the Weighted gene co-expression network analysis (WGCNA) and pharmacophore model were enriched in the HIF-1 signaling pathway and NF-kB transcription factor activity, which were related to the mechanism of inflammation-driven cancer. The PYS is extremely important in predicting prognosis and responses to immunotherapy. New treatment strategies for inflammation-driven cancers may be found by targeting pyroptosis.

Pyroptosis-Related Signature as Potential Biomarkers for Predicting Prognosis and Therapy Response in Colorectal Cancer Patients

Background: Abnormal mucosal inflammation is a critical risk factor for pathogenesis and progression of colorectal cancer (CRC). As a type of proinflammatory death, pyroptosis can recast a suitable microenvironment to promote tumor growth. However, the potential role of pyroptosis in CRC remains unclear.

Methods: A total of 38 pyroptosis-related gene (PRG) expression profiles and clinical information were collected from multiple public datasets. Bioinformatics methods were used to analyze the clinical significance, functional status, immune infiltration, genomic alteration, and drug sensitivity in different subgroups. Whole-genome microarray analysis was performed to analyze the regulation of gut microbiota on the expression of PRGs.

Results: Two distinct molecular subtypes were identified and suggested that multilayer PRG alterations were associated with patient clinicopathological features, prognosis, and tumor microenvironment (TME) infiltrating characteristics. Furthermore, we obtained eight PRG signatures by applying differential expression analysis and univariate Cox and Lasso regression analyses. A risk prognosis model was constructed for predicting overall survival (OS) and recurrence-free survival (RFS) based on the PRG signature. There were significant differences in clinical characteristics, 22 immune cells, and immune functions between the high- and low-risk groups. In addition, the PRG signature was significantly associated with the microsatellite instability (MSI), tumor mutation burden (TMB), cancer stem cell (CSC) index, immunotherapeutic characteristics, and chemotherapeutic drug sensitivity. Moreover, the in vitro experiments had shown that Fusobacterium nucleatum (F.n) could affect the CASP6 expression, which was associated with the chemoresistance to 5-fluorouracil (5-Fu) in CRC.

Conclusion: Our findings provided a foundation for future research targeting pyroptosis and a new insight into the prognosis and immune cell infiltration of CRC, and they suggested that F.n might influence CRC progression through pyroptosis.

Qingchang Wenzhong Decoction Prevents the Occurrence of Intestinal Tumors by Regulating Intestinal Microbiota and Gasdermin E

Background: Intestinal tumors are the third most common malignant tumors worldwide, accounting for approximately 10% of all new cancer cases worldwide. Cancer prevention is a promising way to limit the intestinal tumor incidence rate; however, challenges remain. Qingchang Wenzhong decoction (QCWZD) can clinically treat mild to moderate ulcerative colitis symptoms. Moreover, the mechanism by which it prevents intestinal tumors has not been clarified. In this study, we explored the mechanism by which QCWZD prevents the occurrence of intestinal tumors.

Methods: To study the preventive mechanism of QCWZD on intestinal tumors, we used two model mice with azoxymethane/dextran sodium sulfate (AOM/DSS)- and Apcmin/+-induced intestinal tumor formation. The two models exhibited colitis-associated cancer and familial adenomatous polyposis, respectively. Colon and small intestine tissues were collected and analyzed based on histopathology and immunohistochemistry analyses. Fecal samples were collected, and 16S rRNA sequencing was used to analyze the correlation between intestinal microbiota and the prevention of intestinal tumors.

Results: In the AOM/DSS mice, the QCWZD reduced the number and size of tumors, as well as tumor load. Similarly, in the Apcmin/+ mice, QCWZD can also reduce the number of tumors and the tumor load. The results of 16S rRNA sequencing confirmed that QCWZD altered the composition of intestinal microbiota in mice, a phenomenon that may prevent the occurrence of intestinal tumors by aiding the increase in the abundance of beneficial bacteria, such as Ralstonia and Butyricicoccus, and reducing that of pathogenic bacteria, such as Desulfobacterota and Bacteroides, in the intestine. Further, immunohistochemistry reveald that QCWZD can improve the expression of intestinal barrier-related proteins and inhibit pyroptosis-related proteins.

Conclusions: QCWZD has the potential to prevent the occurrence of intestinal tumors. The anti-tumor activity may be achieved by regulating the intestinal microbiota, improving the function of the intestinal barrier, and inhibiting GSDME mediated pyroptosis.

Bexarotene-induced cell death in ovarian cancer cells through Caspase-4-gasdermin E mediated pyroptosis

Bexarotene selectively activates retinoid X receptor, which is a commonly used anticancer agent for cutaneous T-cell lymphoma. In this study, we aimed to investigate the anticancer effect of bexarotene and its underlying mechanism in ovarian cancer in vitro. The ES2 and NIH:OVACAR3 ovarian cancer cell lines were treated with 0, 5, 10, or 20 µM of bexarotene. After 24 h, cell number measurement and lactate dehydrogenase (LDH) cytotoxicity assay were performed. The effect of bexarotene on CDKN1A expression, cell cycle-related protein, cell cycle, pyroptosis, and apoptosis was evaluated. Bexarotene reduced cell proliferation in all concentrations in both the cells. At concentrations of > 10 µM, extracellular LDH activity increased with cell rupture. Treatment using 10 µM of bexarotene increased CDKN1A mRNA levels, decreased cell cycle-related protein expression, and increased the sub-G1 cell population in both cells. In ES2 cells, caspase-4 and GSDME were activated, whereas caspase-3 was not, indicating that bexarotene-induced cell death might be pyroptosis. A clinical setting concentration of bexarotene induced cell death through caspase-4-mediated pyroptosis in ovarian cancer cell lines. Thus, bexarotene may serve as a novel therapeutic agent for ovarian cancer.

Role of Pyroptosis in Gynecological Oncology and Its Therapeutic Regulation

With the continuous advances in molecular biotechnology, many new cell death methods have been discovered. Pyroptosis is a programmed cell death process that differs from apoptosis and autophagy in cell morphology and function. Compared with apoptosis and autophagy, pyroptosis is primarily mediated by intracellular inflammasome and gasdermin D of the gasdermin protein family and involves the release of numerous inflammatory factors. Pyroptosis has been found to be involved in the occurrence and development of infectious diseases and other diseases involving the nervous system and the cardiovascular system. Recent studies have also reported the occurrence of pyroptosis in tumor cells. Accordingly, exploring its effect on tumors has become one of the research hotspots. Herein, recent research progress on pyroptosis is reviewed, especially its role in the development of gynecological tumors. As the pathogenesis of gynecological tumor is better understood, new targets have been introduced for the prevention and clinical treatment of gynecological tumors.

Association Between GSDMB Gene Polymorphism and Cervical Cancer in the Northeast Chinese Han Population

Objective: The purpose of this study was to investigate the relationship between GSDMB gene polymorphism and genetic susceptibility to cervical cancer in the Han population in Northeast China. Methods: In this case-control study, the genotypes and alleles of rs8067378 in the GSDMB gene were analyzed by multiplex polymerase chain reaction (PCR) and next-generation sequencing methods in 482 cervical cancer (CC) patients, 775 cervical squamous intraepithelial lesion (SIL) patients, and 495 healthy women. The potential relationships between the SNP of the GSDMB gene with SIL and CC were analyzed by multivariate logistic regression analysis combined with 10,000 permutation tests. Results: In the comparison between the SIL group and the control group, the genotype and allele distribution frequencies of rs8067378 SNP of the GSDMB gene were statistically significant (p = 0.0493 and p = 0.0202, respectively). The allele distribution frequencies of rs8067378 were also statistically significant in the comparison between high-grade cervical squamous intraepithelial lesion (HSIL) and low-grade cervical squamous intraepithelial lesion (LSIL) groups with control group ( p = 0.0483 and p = 0.0330, respectively). Logistic regression analysis showed that after adjusting for age, the rs8067378 SNP of the GSDMB gene was significantly associated with the reduced risk of SIL under the dominant model (p = 0.0213, OR = 0.764, CI = 0.607-0.961) and the additive model (p = 0.0199, OR = 0.814, and CI = 0.684-0.968), and its mutant gene G may play a role in the progression of healthy people to LSIL and even HSIL as a protective factor. However, there was no significant association between cervical cancer and its subtypes with the control group (p > 0.05). After 10,000 permutations, there was still no correlation that has provided evidence for the accuracy of our study. Conclusion: The results of this study showed that rs8067378 single nucleotide polymorphism of the GSDMB gene may reduce the risk of SIL and protect the susceptibility to cervical precancerous lesions in the Northeast Chinese Han population, but it has no significant correlation with the progression of cervical cancer.

Research Progress of Pyroptosis in Alzheimer's Disease

Alzheimer's disease (AD) is a disease characterized by insidious and progressive neurodegeneration, with clinical syndromes of memory and visuospatial skills damage. The pathogenic mechanism of AD is complex in which neural inflammation and neuron death play important roles. Pyroptosis, an inflammatory programmed cell death, has been reported to be involved in neuron death. Pyroptosis is executed by the protein family of gasdermins which punch pores on plasma membrane when activated by the upstream signals including the activation of NLRP3 and caspases, and subsequently triggers the inflammatory cascades featured by the release of interleukin (IL) -1β and IL-18. Herein, we summarized the current research on the roles of neuron pyroptosis in AD, aiming to provide a comprehensive view of the molecular mechanisms underlying AD pathogenesis and potential therapeutic targets for AD.

Gasdermin D-mediated microglial pyroptosis exacerbates neurotoxicity of aflatoxins B1 and M1 in mouse primary microglia and neuronal cultures

Aflatoxin B1 (AFB1) disrupts the blood-brain barrier by poisoning the vascular endothelial cells and astrocytes that maintain it. It is important to examine whether aflatoxin B1 or its metabolite, aflatoxin M1 (AFM1), affect microglia, which as the "immune cells" in the brain may amplify their damaging effects. Here we evaluated the toxicity of AFB1 and AFM1 against primary microglia and found that both aflatoxins decreased the viability of primary microglia and increased the leakage of lactate dehydrogenase, gamma-H2AX expression, nuclear lysis, necrosis and apoptosis in a dose-dependent manner. The potential contribution of microglia to the toxic effects of aflatoxins was assessed in transwell co-culture experiments involving microglia, neurons, astrocytes, oligodendrocytes or neural stem/precursor cells. And we found that the toxic effects of both aflatoxins on various types of nervous system cells were greater in the presence of microglia than in their absence. We also found that both aflatoxins induced gasdermin D-mediated microglial pyroptosis and inflammatory cytokine expression by activating the NLRP3 inflammasome. Blockade of gasdermin D activity in AFB1- or AFM1-treated primary microglia using dimethyl fumarate (DMF) reduced the release of IL-1β, IL-18 and nitric oxide, as well as the neurotoxicity of microglia-conditioned medium to neurons, astrocytes, oligodendrocytes and neural stem/precursor cells. These data suggested that the toxicity of AFB1 and AFM1 on various cells of the central nervous system is due, remarkably, the gasdermin D-mediated microglial pyroptosis exacerbates their neurotoxicity.

Role of Pyroptosis in Inflammatory Bowel Disease (IBD): From Gasdermins to DAMPs

Pyroptosis is a pro-inflammatory cell death executed by gasdermin family proteins that involve the formation of pores on cells, recognition of danger signals, and release of pro-inflammatory cytokines IL-1β and IL-18. Pyroptosis modulates mucosal innate immunity and enteropathogenic bacterial infection. Similarly, the gasdermin family has been reported to be involved in the defense of the intestinal epithelium against bacterial infection and in the regulation of intestinal inflammation. Pyroptosis initiates damage signals that activate multiple pathways to cause inflammation, which may be a potential cause of chronic intestinal inflammation. In this review, we discuss the impact of pyroptosis on inflammatory bowel disease (IBD), with a focus on the executive proteins of pyroptosis (GSDMB, GADMD, and GSDME) and IBD-related endogenous damage-associated molecular patterns (DAMPs) produced by pyroptosis.

The Role of Autophagy and Pyroptosis in Liver Disorders

Pyroptosis is a programmed cell death caused by inflammasomes, which can detect cell cytosolic contamination or disturbance. In pyroptosis, caspase-1 or caspase-11/4/5 is activated, cleaving gasdermin D to separate its N-terminal pore-forming domain (PFD). The oligomerization of PFD forms macropores in the membrane, resulting in swelling and membrane rupture. According to the different mechanisms, pyroptosis can be divided into three types: canonical pathway-mediated pyroptosis, non-canonical pathway-mediated pyroptosis, and caspase-3-induced pyroptosis. Pyroptosis has been reported to play an important role in many tissues and organs, including the liver. Autophagy is a highly conserved process of the eukaryotic cell cycle. It plays an important role in cell survival and maintenance by degrading organelles, proteins and macromolecules in the cytoplasm. Therefore, the dysfunction of this process is involved in a variety of pathological processes. In recent years, autophagy and pyroptosis and their interactions have been proven to play an important role in various physiological and pathological processes, and have gradually attracted more and more attention to become a research hotspot. Therefore, this review summarized the role of autophagy and pyroptosis in liver disorders, and analyzed the related mechanism to provide a basis for future research.

Nurr1 Modulation Mediates Neuroprotective Effects of Statins

The ligand-sensing transcription factor Nurr1 emerges as a promising therapeutic target for neurodegenerative pathologies but Nurr1 ligands for functional studies and therapeutic validation are lacking. Here pronounced Nurr1 modulation by statins for which clinically relevant neuroprotective effects are demonstrated, is reported. Several statins directly affect Nurr1 activity in cellular and cell-free settings with low micromolar to sub-micromolar potencies. Simvastatin as example exhibits anti-inflammatory effects in astrocytes, which are abrogated by Nurr1 knockdown. Differential gene expression analysis in native and Nurr1-silenced cells reveals strong proinflammatory effects of Nurr1 knockdown while simvastatin treatment induces several neuroprotective mechanisms via Nurr1 involving changes in inflammatory, metabolic and cell cycle gene expression. Further in vitro evaluation confirms reduced inflammatory response, improved glucose metabolism, and cell cycle inhibition of simvastatin-treated neuronal cells. These findings suggest Nurr1 involvement in the well-documented but mechanistically elusive neuroprotection by statins.

Identification of duck GSDME: Tissue distribution, proteolysis and cellular location

Gasdermin E (GSDME) is a member of the gasdermin family. Cleavage of mammalian GSDME by apoptotic caspases or granzyme proteases liberates the N-terminal effector domain (GSDME-N), which is capable of forming membrane pores and executing inflammation and cell death. Herein, duck GSDME was first cloned with a total length of 1500 bp and encoding 499 amino acids (aa), which is most evolutionally related to the chicken GSDME. The tissue-distribution profiles of GSDME showed that relatively high levels of GSDME mRNA were detected in immune tissues of duckling and adult ducks. Additionally, GSDME mRNA was significantly upregulated in duck primary embryo fibroblasts (DEFs) and duck primary ovary cells after duck Tembusu virus (DTMUV) infection. Intriguingly, when duck caspase-3 was coexpressed, the duck GSDME produced two GSDME-N fragments with molecular weights of 25 kDa and 30 kDa. Furthermore, both GSDME and cleaved GSDME were observed to be located in the cytoplasm by indirect immunofluorescence assay (IFA). Taken together, our research data show that duck GSDME has similar biological characteristics to mammals. These findings highlight the role of duck GSDME in TMUV infection, indicating that cooperation between GSDME and caspase-3 promotes the proteolytic process.

Analysis of Pyroptosis-Related Signature for Predicting Prognosis and Tumor Immune Microenvironment in Pancreatic Cancer

Pancreatic cancer (PC) has a poor prognosis, which is attributable to its high aggressiveness and lack of effective therapies. Although immunotherapy has been used for the treatment of various tumor, its efficacy in pancreatic cancer is not satisfactory. As a caspase-1-dependent programmed cell death, pyroptosis s involved in the pathological process of many tumors. Nevertheless, the vital role of the pyroptosis-related gene (PRG) in PC remains unknown. In this study, univariate COX regression was performed for 33 pyroptosis-related genes. Based on these prognosis-related PRGs, all PC patients in the Cancer Genome Atlas (TCGA) database were divided into four subtypes. Then, pyroptosis score (PP-score) was established to quantify pyroptosis level for individual PC patients using principal component analysis (PCA) algorithms. Assessment of pyroptosis level within individual PC patients may predict tumor classification and patient prognosis. Finally, a signature was constructed in TCGA and verified in ICGC. In addition, immunocheckpoint analysis revealed the possibility that the low-risk group would benefit more from immunocheckpoint therapy. Taken together, pyroptosis-related genes play a significant role in tumor immunotherapy and can be utilized to predict the prognosis of PC patients.

Clostridium septicum α-toxin activates the NLRP3 inflammasome by engaging GPI-anchored proteins

Clostridium species are a group of Gram-positive bacteria that cause diseases in humans, such as food poisoning, botulism, and tetanus. Here, we analyzed 10 different Clostridium species and identified that Clostridium septicum, a pathogen that causes sepsis and gas gangrene, activates the mammalian cytosolic inflammasome complex in mice and humans. Mechanistically, we demonstrate that α-toxin secreted by C. septicum binds to glycosylphosphatidylinositol (GPI)-anchored proteins on the host plasma membrane, oligomerizing and forming a membrane pore that is permissive to efflux of magnesium and potassium ions. Efflux of these cytosolic ions triggers the activation of the innate immune sensor NLRP3, inducing activation of caspase-1 and gasdermin D, secretion of the proinflammatory cytokines interleukin-1β and interleukin-18, pyroptosis, and plasma membrane rupture via ninjurin-1. Furthermore, α-toxin of C. septicum induces rapid inflammasome-mediated lethality in mice and pharmacological inhibition of the NLRP3 inflammasome using MCC950 prevents C. septicum-induced lethality. Overall, our results reveal that cytosolic innate sensing of α-toxin is central to the recognition of C. septicum infection and that therapeutic blockade of the inflammasome pathway may prevent sepsis and death caused by toxin-producing pathogens.

Gasdermin-A3 pore formation propagates along variable pathways

Gasdermins are main effectors of pyroptosis, an inflammatory form of cell death. Released by proteolysis, the N-terminal gasdermin domain assembles large oligomers to punch lytic pores into the cell membrane. While the endpoint of this reaction, the fully formed pore, has been well characterized, the assembly and pore-forming mechanisms remain largely unknown. To resolve these mechanisms, we characterize mouse gasdermin-A3 by high-resolution time-lapse atomic force microscopy. We find that gasdermin-A3 oligomers assemble on the membrane surface where they remain attached and mobile. Once inserted into the membrane gasdermin-A3 grows variable oligomeric stoichiometries and shapes, each able to open transmembrane pores. Molecular dynamics simulations resolve how the membrane-inserted amphiphilic β-hairpins and the structurally adapting hydrophilic head domains stabilize variable oligomeric conformations and open the pore. The results show that without a vertical collapse gasdermin pore formation propagates along a set of multiple parallel but connected reaction pathways to ensure a robust cellular response.

Secoisolariciresinol diglucoside induces pyroptosis by activating caspase-1 to cleave GSDMD in colorectal cancer cells

Secoisolariciresinol diglucoside (SDG) is the main component of lignans with various biological activities, including anticancer activity. However, whether SDG has obvious anticancer effects on colorectal cancer (CRC) is unclear. Pyroptosis, a form of programmed cell death, has received increasing attention in cancer‐related research. In this study, we aimed to test the anticancer properties and relatecd functional mechanisms of SDG. we found that SDG not only inhibited the cell viability of HCT116 cells, but also induced HCT116 cells to swell with apparent large bubbles, which are typical signs of pyroptosis. Furthermore, SDG induced cell pyroptosis by enhancing cleavage of the N‐terminal fragment of gasdermin D (GSDMD) in CRC cells, accompanied by increased caspase‐1 cleavage. Consistent with this, SDG‐induced GSDMD‐N‐terminal fragment cleavage and pyroptosis were reduced by siRNA‐mediated silencing of caspase‐1 or treatment with the specific caspase‐1 inhibitor VX‐765 treatment, suggesting that active caspase‐1 further induces pyroptosis. A mechanistic study showed that SDG induced reactive oxygen species (ROS) accumulation and inhibits phosphatidylinositol 3‐kinase (PI3K) phosphorylation and increases pyroptosis, while increasing GSDMD and caspase‐1 cleavage and enhancing expression of BCL2‐associated X (BAX), which could be rescued by the ROS scavenger (NAC), suggesting that SDG‐induced GSDME‐dependent pyroptosis is related to the ROS/PI3K/AKT/BAX‐mitochondrial apoptotic pathway. In vivo results showed that SDG significantly inhibited tumor growth and induced pyroptosis in the HCT116‐CRC nude mouse model. In conclusion, our findings suggest that the anticancer activity of SDG in CRC is associated with the induction of GSDMD‐dependent pyroptosis by SDG through the generation of ROS/P13K/AKT/BAK‐mitochondrail apoptosis pathway, providing insights into SDG in its potential new application in cancer treatment.

Regulation of Pyroptosis by ncRNA: A Novel Research Direction

Pyroptosis is a novel form of programmed cell death (PCD), which is characterized by DNA fragmentation, chromatin condensation, cell swelling and leakage of cell contents. The process of pyroptosis is performed by certain inflammasome and executor gasdermin family member. Previous researches have manifested that pyroptosis is closely related to human diseases (such as inflammatory diseases) and malignant tumors, while the regulation mechanism of pyroptosis is not yet clear. Non-coding RNA (ncRNA) such as microRNA (miRNA), long non-coding RNA (lncRNA) and circular RNA (circRNA) have been widely identified in the genome of eukaryotes and played a paramount role in the development of cell function and fate after transcription. Accumulating evidences support the importance of ncRNA biology in the hallmarks of pyroptosis. However, the associations between ncRNA and pyroptosis are rarely reviewed. In this review, we are trying to summarize the regulation and function of ncRNA in cell pyroptosis, which provides a new research direction and ideas for the study of pyroptosis in different diseases.

Streptococcus makes the cut: Gasdermin A-induced pyroptosis

The gasdermin family of cell death executor proteins are activated by different proteases under different physiological conditions. A recent study by Deng et al. in Nature revealed that the cysteine protease SpeB from the human pathogen Streptococcus pyogenes directly cleaves and activates Gasdermin A to induce pyroptosis in skin cells.

Pyroptosis-Related Signature Predicts Prognosis and Immunotherapy Efficacy in Muscle-Invasive Bladder Cancer

Pyroptosis has profound impacts on tumor cell proliferation, invasion, and metastasis and is of great clinical significance for different cancers. However, the role of pyroptosis in the progression and prognosis of muscle invasive bladder cancer (MIBC) remains poorly characterized. Here, we collected multicenter MIBC data and performed integrated analysis to dissect the role of pyroptosis in MIBC and provide an optimized treatment for this disease. Based on transcriptomic data, we developed a novel prognostic model named the pyroptosis-related gene score (PRGScore), which summarizes immunological features, genomic alterations, and clinical characteristics associated with the pyroptosis phenotype. Samples with high PRGScore showed enhancement in CD8⁺ T cell effector function, antigen processing machinery and immune checkpoint and better response to immunotherapy by programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) inhibitors, which indicates that PRGScore is a valuable signature in the identification of populations sensitive to immune checkpoint inhibitors. Collectively, our study provides insights into further research targeting pyroptosis and its tumor immune microenvironment (TME) and offers an opportunity to optimize the treatment of MIBC.

Porcine Gasdermin D Is a Substrate of Caspase-1 and an Executioner of Pyroptosis

Gasdermin (GSDM) family proteins were recently identified as the executioner of pyroptosis. The mechanism of pyroptosis mediated by gasdermin D (GSDMD) (a member of GSDM family) in humans and mice is well understood. In pyroptosis, mouse and human GSDMDs are cleaved by activated proinflammatory caspases (caspase-1, 4, 5, or 11) to produce anamino-terminal domain (GSDMD-NT) and a carboxyl-terminal domain (GSDMD-CT). The GSDMD-NT drives cell membrane rupture, which leads to the pyroptotic death of the cells. The expression of porcine GSDMD (pGSDMD) has recently been determined, but the activation and regulation mechanism of pGSDMD and its ability to mediate pyroptosis are largely unknown. In the present study, the activation of porcine caspase-1 (pcaspase-1) and cleavage of pGSDMD occurred in the duodenum and jejunum of a piglet challenged with enterotoxigenic Escherichia coli were first determined. Then the capability of pcaspase-1 to cleave pGSDMD was determined in a cell-free system and in human embryonic kidney cells. The pGSDMD cleavage by pcaspase-1 occurred after the pGSDMD molecule’s ₂₇₆Phenylalanine-Glutamine-Serine-Aspartic acid₂₇₉ motif. The pGSDMD-NT generated from the pGSDMD cleavage by pcaspase-1 showed the ability to drive cell membrane rupture in eukaryotic cells. When expressed in E. coli competent cells, pGSDMD-NT showed bactericidal activity. These results suggest that pGSDMD is a substate of pcaspase-1 and an executioner of pyroptosis. Our work sheds light on pGSDMD’s activation mechanisms and functions.

Gasdermin E: A Prospective Target for Therapy of Diseases

Gasdermin E (GSDME) is a member of the gasdermin protein family, which mediates programmed cell death including apoptosis and pyroptosis. Recently, it was suggested that GSDME is activated by chemotherapeutic drugs to stimulate pyroptosis of cancer cells and trigger anti-tumor immunity, which is identified as a tumor suppressor. However, GSDME-mediated pyroptosis contributes to normal tissue damage, leading to pathological inflammations. Inhibiting GSDME-mediated pyroptosis might be a potential target in ameliorating inflammatory diseases. Therefore, targeting GSDME is a promising option for the treatment of diseases in the future. In this review, we introduce the roles of GSDME-driven programmed cell death in different diseases and the potential targeted therapies of GSDME, so as to provide a foundation for future research.

GSDMs are potential therapeutic targets and prognostic biomarkers in clear cell renal cell carcinoma

GSDM family is a group of critical proteins that mediate pyroptosis and plays an important role in cell death and inflammation. However, their specific function in clear cell renal cell carcinoma (ccRCC, KIRC) have not been clarified comprehensively. In this study, we assessed the roles of the GSDM family in expression, prognostic value, functional enrichment analysis, genetic alterations, immune infiltration and DNA methylation in ccRCC patients by using different bioinformatics databases. We found that the expression levels of GADMA-E were significantly higher in ccRCC tissues compared with normal tissues, while the expression level of PJVK was decreased. Moreover, survival analysis indicated that upregulation of GSDME was related to poor overall survival (OS) and recurrence-free survival (RFS) of ccRCC patients. The main function of differentially expressed GSDM homologs was related to ion transport. We also found that the expression profiles of the GSDM family were highly correlated with infiltrating immune cells (i.e., CD8+ T cells, CD4+ T cells, B cells, macrophages, neutrophils and dendritic cells), and there were significant differences in the expression of GSDM family in different ccRCC immune subtypes. Furthermore, DNA methylation analysis indicated that the DNA methylation levels of GSDMA/B/D/E were decreased, while the DNA methylation level of PJVK was increased. In conclusion, this study provides integrated information about abnormal GSDM family members as potential biomarkers for the diagnosis and prognosis of ccRCC. Especially, GSDME was a potential clinical target and prognostic biomarkers for patients with ccRCC.

Inflammasome and gasdermin signalling in neutrophils

Inflammasomes and gasdermins mount potent host defence pathways against invading microbial pathogens, however, dysregulation in these pathways can drive a variety of inflammatory disorders. Neutrophils, historically regarded as effector phagocytes that drive host defence via microbial killing, are now emerging as critical drivers of immunity in vivo. Here, we summarise the latest advancement in inflammasome, gasdermin and cell death signalling in neutrophils. We discuss the mechanisms by which neutrophils resist caspase-1-dependent pyroptosis, thsse lytic function of gasdermin D and E during NETosis and Yersinia infection, and the contribution of neutrophil inflammasomes to inflammatory disorders.

Identification of a Pyroptosis-Related Prognostic Signature Combined With Experiments in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide with poor prognosis. There is a necessary search for improvement in diagnosis and treatment methods to improve the prognosis. Some useful prognostic markers of HCC are still lacking. Pyroptosis is a type of programmed cell death caused by the inflammasome. It is still unknown whether pyroptosis-related genes (PRGs) are involved in the prognosis in HCC. The gene expression and clinical data of LIHC (liver hepatocellular carcinoma) patients were downloaded from The Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium database (ICGC). In this study, we identified 40 PRGs that were differentially expressed between LIHC and normal liver tissues. Based on the TCGA-LIHC cohort, a 9-gene prediction model was established with the Least absolute shrinkage and selection operator (LASSO)-penalized Cox regression. The risk score was calculated according to the model in the TCGA-LIHC cohort and the ICGC-LIHC cohort. Utilizing the median risk score from the TCGA cohort, LIHC patients from the ICGC-LIHC cohort were divided into two risk subgroups. The Kaplan–Meier (KM) survival curves demonstrated that patients with lower risk scores had significantly favorable overall survival (OS). Combined with the clinical characteristics, the risk score was an independent factor for predicting the OS of LIHC patients in both the TCGA-LIHC cohort and the ICGC-LIHC cohort. Functional enrichment and immune function analysis were carried out. Furthermore, a nomogram based on risk score, age, gender, and tumor stage was used to predict mortality of patients with LIHC. Moreover, KM survival analysis was performed for 9 genes in the risk model, among which CHMP4A, SCAF11, and GSDMC had significantly different results and the ceRNA network was constructed. Based on the core role of SCAF11, we performed loss-of-function experiments to explore the function of SCAF11 in vitro. Suppression of SCAF11 expression inhibited the proliferation, attenuated the migration and invasion, and induced apoptosis of liver cancer cell lines. In conclusion, the pyroptosis-related model and nomogram can be utilized for the clinical prognostic prediction in LIHC. This study has demonstrated for the first time that SCAF11 promotes the progression of liver cancer.

Gasdermin D Cleavage Assay Following Inflammasome Activation

Gasdermin D (GSDMD) is a recently identified pore-forming protein that is crucial for the execution of pyroptosis, a highly inflammatory form of cell death. GSDMD contains an N-terminal and a C-terminal domain that are separated by a proteolysis-sensitive linker. Upon cleavage of this linker by inflammasome-activated caspases, the N-terminal domain of GSDMD oligomerizes and forms pores at the plasma membrane, allowing cell swelling and subsequently membrane rupture to mediate pyroptosis. GSDMD is a key substrate of inflammatory caspases downstream of inflammasome activation and is driving various pathologies. Here, we describe a simple method to study GSDMD cleavage following canonical inflammasome activation in murine primary macrophages and neutrophils and human cell lines using immunoblotting.

Microcrystalline silica particles induce inflammatory response via pyroptosis in primary human respiratory epithelial cells

The mechanism of the sterile inflammatory response in the respiratory tract induced by exposure to sterile particles has not been fully elucidated. The aim of our study is to explore the earlier events in initiating inflammatory response at molecular and cellular level in primary cultured human airway epithelial cells (AEC) exposed to silica particles in order to provide information for earlier diagnosis and prevention of silica particle-induced toxicity as well as possible information on the genesis of silicosis. We isolated primary AEC from three healthy adults and treated them with silica particles at different concentrations for 48 h. We found evidence for silica-induced inflammasome activation by the co-localization of Caspase-1 and NLRP3, as well as increased levels of IL-1β and IL-18. Lactate dehydrogenase and NucGreen analysis proved the occurrence of pyroptosis. High throughput mRNA sequencing showed that the inflammatory response and NF-κB signaling pathways were significantly enriched in gene ontology and Kyoto encyclopedia of genes and genomes analysis, and pyroptosis-related genes were up-regulated. The miR-455-3p and five lncRNAs (LOC105375913, NEAT1, LOC105375181, LOC100506098, and LOC105369370) were verified as key factors related to the mechanism by ceRNA network analysis. LOC105375913 was first discovered to be associated with inflammation in AEC. These data suggest that microcrystalline silica can induce significant inflammation and pyroptosis in human primary AEC through NLRP3 inflammasome pathway and NF-κB signaling pathway at both the gene and protein levels, and the possible mechanism could be miR-455-3p mediated ceRNA hypothesis. Our data provide a method for the studies of the respiratory toxicity of fine particulate matter and the pathogenesis of early silicosis. The miR-455-3p and five lncRNAs related ceRNA network might be the toxicity mechanism of microcrystalline silica particles to AEC.

A new pyroptosis model can predict the immunotherapy response and immune microenvironment characteristics and prognosis of patients with cutaneous melanoma based on TCGA and GEO databases

Background

Recent studies have shown that pyroptosis is related to cancer development. Our previous study also found that gasdermins (GSDMs) was associated with the tumor immune microenvironment. Therefore, we wanted to observe the relationship between pyroptosis and the immune microenvironment and prognosis of skin cutaneous melanoma (SKCM).

Methods

Pyroptosis-related genes were used for pan-cancer prognostic analysis using the GEPIA2 online analysis website. Prognosis-related genes were clustered using R software and related R packages, and the best clustering results were screened for prognosis analysis. The prognosis-related genes were also used to establish a prognosis-related model. Assess the predictive power of a model by comparing area under the curve (AUC). The t-test was used to analyze the differences of immune-related indicators between the two clusters and between high and low risk groups. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was performed on the differential genes.

Results

By clustering the prognosis-related genes, SKCM could be divided into 2 clusters with significant differences in prognosis P<0.05. A prognostic model can be established using prognosis-related genes. The AUC value of 1 year, 2 years and 3 years was 0.696, 0.702 and 0.664, respectively. The risk score was significantly associated with prognosis in both univariate and multivariate Cox analyses P<0.001. The low-risk group or C2 cluster with better prognosis had higher expression of pyroptosis-related genes, and tended to have a lower exclusion score, greater chemokine expression, more immune cells and higher immune score. However, the C2 cluster or low-risk group was also associated with a higher dysfunction score. At the same time, the C2 or low-risk group was more suitable for immunotherapy because of the higher immunophenoscore (IPS) score P<0.001. Correlation analysis also demonstrated that the risk score was positively correlated with the gene expression of most immunoinhibitors, MHC molecules, immunostimulators, and chemokines and their receptors.

Conclusions

Pyroptosis is associated with melanoma immune microenvironment, immunotherapy response, and prognoses. The constructed risk scores could effectively predict the characteristics of the immune microenvironment, the sensitivity to immunotherapy, and the prognosis of melanoma patients.

The pyroptosis-related gene signature predicts prognosis and indicates immune activity in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) remains one of the most common malignant tumors with poor survival. Pyroptosis is a kind of programmed cell death that can regulate the proliferation, invasion, and metastasis of tumor cells. However, the expression levels of pyroptosis-related genes (PRGs) in HCC and their relationship with prognosis are still unclear.

Methods

Our study identified 35 PRGs through bioinformatics analysis that were differentially expressed between tumor samples and nontumor samples. According to these differentially expressed genes, HCC patients could be divided into two groups, cluster 1 and cluster 2. The least absolute shrinkage and selection operator (LASSO) Cox regression method was performed to construct a 10-gene signature that classified HCC patients in the cancer genome atlas (TCGA) database into low-risk and high-risk groups.

Results

The results showed that the survival rate of HCC patients in the low-risk group was significantly higher than that in the high-risk group (p < 0.001). The validation cohort, the Gene Expression Omnibus (GEO) cohort, was divided into two risk groups based on the median risk score calculated by the TCGA cohort. The overall survival (OS) of the low-risk group was significantly better than that of the high-risk group (p = 0.007). Univariate and multivariate Cox regression analyses revealed that the risk score was an independent factor in predicting OS in HCC patients. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses showed that immune-related high-risk groups were rich in genes and had reduced immune status.

Conclusions

PRGs play a significant role in tumor immunity and have the potential capability to predict the prognosis of HCC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00445-0.

The STING pathway: An uncharacterized angle beneath the gut-retina axis

The gut-retina axis is an emerging concept that describes a close interaction between the gut host-microbiota interface and the retina. Stimulator of interferon genes (STING) is a universally expressed adaptor protein localized in the endoplasmic reticulum. When activated by the cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS), STING induces the activation of the transcription factor interferon regulatory factor 3 (IRF3) and nuclear factor-κB (NF-κB). Downstream effects include inflammation, autophagy, and programmed cell death. Dysregulation of the STING pathway has emerged as a crucial pathogenic mechanism underpinning a broad range of inflammatory diseases, autoimmune diseases, and cancer. Recently, a positive feedback loop between dysbiosis and aberrant activation of the intestinal STING pathway has been demonstrated, concurrently related to increased intestinal permeability. Alternations in the STING pathway have also been reported in the retina of patients with ocular diseases and retinal cells treated with pathological stimuli. Collectively, there is a chance that dysbiosis in patients with retinal diseases disrupts intestinal homeostasis and exacerbates barrier dysfunction through the erroneous accumulation of STING in the gut. Subsequent translocation of microbial products into the bloodstream allows access to the eye via the impaired blood-retina barrier, inducing the chronic activation of the STING pathway in the retina to participate in the disease progression. In this review, we explore how the alterations in the STING pathway could contribute to the gut disturbance and retinal pathologies and discuss its potential as a therapeutic target to treat the gut-retina axis-related diseases, which sheds some light on the better understanding of the crosstalk between the gut and retina.

Development and Validation of a Pyroptosis-Related Signature for Predicting Prognosis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) has emerged as a primary health problem and threat to global mortality, especially in China. Since pyroptosis as a new field for HCC prognosis is not well studied, it is important to open a specific prognostic model. In this study, consensus clustering method for 42 pyroptosis-related genes to classify 374 HCC patients in the TCGA database. After cox regression analysis of the differentially expressed genes between the two clusters, LASSO-Cox analysis was then performed to construct a pyroptosis-related prognostic model with 11 genes including MMP1, KPNA2, LPCAT1, NEIL3, CDCA8, SLC2A1, PSRC1, CBX2, HAVCR1, G6PD, MEX3A. The ICGC dataset was served as the validation cohort. Patients in the high-risk group had significantly lower overall survival (OS) rates than those in the low-risk group (p &lt; 0.05). COX regression analysis showed that our model could be used as an independent prognostic factor to predict prognosis of patients and was significantly correlated with clinicopathological characteristics. Nomogram showing the stability of the model predicting the 1, 3, 5 year survival probability of patients. In addition, based on the risk model, ssGSEA analysis revealed significant differences in the level of immune cell infiltration and activation of immune-related functional pathways between high and low-risk groups, and patients with the high-risk score may benefit more from treatment with immune checkpoint inhibitors. Furthermore, patients in the high-risk group were more tend to develop chemoresistance. Overall, we identified a novel pyroptosis-related risk signature for prognosis prediction in HCC patients and revealed the overall immune response intensity of the tumor microenvironment. All these findings make the pyroptosis signature shed light upon a latent therapeutic strategy aimed at the treatment and prevention of cancers.

Sepsis-Exacerbated Brain Dysfunction After Intracerebral Hemorrhage

Sepsis susceptibility is significantly increased in patients with intracerebral hemorrhage (ICH), owing to immunosuppression and intestinal microbiota dysbiosis. To date, ICH with sepsis occurrence is still difficult for clinicians to deal with, and the mortality, as well as long-term cognitive disability, is still increasing. Actually, intracerebral hemorrhage and sepsis are mutually exacerbated via similar pathophysiological mechanisms, mainly consisting of systemic inflammation and circulatory dysfunction. The main consequence of these two processes is neural dysfunction and multiple organ damages, notably, via oxidative stress and neurotoxic mediation under the mediation of central nervous system activation and blood-brain barrier disruption. Besides, the comorbidity-induced multiple organ damages will produce numerous damage-associated molecular patterns and consequently exacerbate the severity of the disease. At present, the prospective views are about operating artificial restriction for the peripheral immune system and achieving cross-tolerance among organs via altering immune cell composition to reduce inflammatory damage.

Targeting Cell Death: Pyroptosis, Ferroptosis, Apoptosis and Necroptosis in Osteoarthritis

New research has shown that the development of osteoarthritis (OA) is regulated by different mechanisms of cell death and types of cytokines. Therefore, elucidating the mechanism of action among various cytokines, cell death processes and OA is important towards better understanding the pathogenesis and progression of the disease. This paper reviews the pathogenesis of OA in relation to different types of cytokine-triggered cell death. We describe the cell morphological features and molecular mechanisms of pyroptosis, apoptosis, necroptosis, and ferroptosis, and summarize the current research findings defining the molecular mechanisms of action between different cell death types and OA.

The role of inflammasomes in vascular cognitive impairment

There is an increasing prevalence of Vascular Cognitive Impairment (VCI) worldwide, and several studies have suggested that Chronic Cerebral Hypoperfusion (CCH) plays a critical role in disease onset and progression. However, there is a limited understanding of the underlying pathophysiology of VCI, especially in relation to CCH. Neuroinflammation is a significant contributor in the progression of VCI as increased systemic levels of the proinflammatory cytokine interleukin-1β (IL-1β) has been extensively reported in VCI patients. Recently it has been established that CCH can activate the inflammasome signaling pathways, involving NLRP3 and AIM2 inflammasomes that critically regulate IL-1β production. Given that neuroinflammation is an early event in VCI, it is important that we understand its molecular and cellular mechanisms to enable development of disease-modifying treatments to reduce the structural brain damage and cognitive deficits that are observed clinically in the elderly. Hence, this review aims to provide a comprehensive insight into the molecular and cellular mechanisms involved in the pathogenesis of CCH-induced inflammasome signaling in VCI.

Yi-Zhi-Fang-Dai Formula Exerts Neuroprotective Effects Against Pyroptosis and Blood-Brain Barrier-Glymphatic Dysfunctions to Prevent Amyloid-Beta Acute Accumulation After Cerebral Ischemia and Reperfusion in Rats

Background: The dysfunctional blood–brain barrier (BBB)–glymphatic system is responsible for triggering intracerebral amyloid-beta peptide (Aβ) accumulation and acts as the key link between ischemic stroke and dementia dominated by Alzheimer’s disease (AD). Recently, pyroptosis in cerebral ischemia and reperfusion (I/R) injury is demonstrated as a considerable mechanism causing BBB–glymphatic dysfunctions and Aβ acute accumulation in the brain. Targeting glial pyroptosis to protect BBB–glymphatic functions after cerebral I/R could offer a new viewpoint to prevent Aβ accumulation and poststroke dementia. Yi-Zhi-Fang-Dai formula (YZFDF) is an herbal prescription used to cure dementia with multiple effects of regulating inflammatory responses and protecting the BBB against toxic Aβ-induced damage. Hence, YZFDF potentially possesses neuroprotective effects against cerebral I/R injury and the early pathology of poststroke dementia, which evokes our current study.

Objectives: The present study was designed to confirm the potential efficacy of YZFDF against cerebral I/R injury and explore the possible mechanism associated with alleviating Aβ acute accumulation.

Methods: The models of cerebral I/R injury in rats were built by the method of middle cerebral artery occlusion/reperfusion (MCAO/R). First, neurological function assessment and cerebral infarct measurement were used for confirming the efficacy of YZFDF on cerebral I/R injury, and the optimal dosage (YZFDF-H) was selected to conduct the experiments, which included Western blotting detections of pyroptosis, Aβ_1-42 oligomers, and NeuN, immunofluorescence observations of glial pyroptosis, aquaporin-4 (AQP-4), and Aβ locations, brain water content measurement, SMI 71 (a specific marker for BBB)/AQP-4 immunohistochemistry, and Nissl staining to further evaluate BBB–glymphatic functions and neuronal damage.

Results: YZFDF obviously alleviated neurological deficits and cerebral infarct after cerebral I/R in rats. Furthermore, YZFDF could inactivate pyroptosis signaling via inhibiting caspase-1/11 activation and gasdermin D cleavage, ameliorate glial pyroptosis and neuroinflammation, protect against BBB collapse and AQP-4 depolarization, prevent Aβ acute accumulation and Aβ_1-42 oligomers formation, and reduce neuronal damage and increase neurons survival after reperfusion.

Conclusion: Our study indicated that YZFDF could exert neuroprotective effects on cerebral I/R injury and prevent Aβ acute accumulation in the brain after cerebral I/R associated with inhibiting neuroinflammation-related pyroptosis and BBB–glymphatic dysfunctions.

Pulsed electromagnetic field alleviates synovitis and inhibits the NLRP3/Caspase-1/GSDMD signaling pathway in osteoarthritis rats

Low-grade inflammation is a key mediator of the pathogenesis of Osteoarthritis (OA). Pulsed electromagnetic field (PEMF) can improve the symptoms of OA and potentially acts as an anti-inflammatory. The aim of this study was to investigate the effect of the PEMF on OA and its relationship with the NLRP3/Caspase-1/GSDMD signaling pathway.18 Three-month-old Sprague-Dawley (SD) rats were randomly divided into three groups (n = 6 per group): 1) OA group, 2) OA+PEMF group (OA with PEMF exposure), 3) Control group (sham operation with placebo PEMF). Rats in the OA and OA+PEMF groups were subjected to bilateral anterior cruciate ligament transection and ovariectomy. PEMF scheme: Pulse waveform, 3.82 mT, 8 Hz, 40 min/day, 5 days a week, for 12 weeks. The expression levels of NLRP3, Caspase-1, GSDMD, IL-1β, and MMP-13 were detected by qRT-PCR and Western blot. The pathological structures of OA were monitored with Safranin O/fast green staining and hematoxylin eosin staining. Our results showed that PEMF alleviated the degree of inflammation and degeneration of cartilage in rats with OA, based on the histopathological changes and decline of the expression of IL-1β and MMP-13. Moreover, the over-expression of NLRP3, Caspase-1, and GSDMD in the cartilage of the OA rats decreased after PEMF treatment. These results suggested that PEMF could be a highly promising noninvasive strategy to slow down the progression of OA and inhibition of the NLRP3/Caspase-1/GSDMD signaling pathway might be involved in the beneficial effect of PEMF.

The evolution of regulated cell death pathways in animals and their evasion by pathogens

The coevolution of host-pathogen interactions underlies many human physiological traits associated with protection from or susceptibility to infections. Among the mechanisms that animals utilize to control infections are the regulated cell death pathways of pyroptosis, apoptosis, and necroptosis. Over the course of evolution these pathways have become intricate and complex, coevolving with microbes that infect animal hosts. Microbes, in turn, have evolved strategies to interfere with the pathways of regulated cell death to avoid eradication by the host. Here, we present an overview of the mechanisms of regulated cell death in Animalia and the strategies devised by pathogens to interfere with these processes. We review the molecular pathways of regulated cell death, their roles in infection, and how they are perturbed by viruses and bacteria, providing insights into the coevolution of host-pathogen interactions and cell death pathways.

Pyroptosis and inflammasomes in diabetic wound healing

Diabetic wound is one of the complications of diabetes and is not easy to heal. It often evolves into chronic ulcers, and severe patients will face amputation. Compared with normal wounds, diabetic wounds have an increased proportion of pro-inflammatory cytokines that are detrimental to the normal healing response. The burden of this disease on patients and healthcare providers is overwhelming, and practical solutions for managing and treating diabetic wounds are urgently needed. Pyroptosis, an inflammatory type of programmed cell death, is usually triggered by the inflammasome. The pyroptosis-driven cell death process is primarily mediated by the traditional signaling pathway caused by caspase -1 and the non-classical signaling pathways induced by caspase -4/5/11. Growing evidence that pyroptosis promotes diabetic complications, including diabetic wounds. In addition, inflammation is thought to be detrimental to wound healing. It is worth noting that the activation of the NLRP3 inflammasome plays a crucial role in the recovery of diabetic wounds. This review has described the mechanisms of pyroptosis-related signaling pathways and their impact on diabetic wounds. It has discussed new theories and approaches to promote diabetic wound healing, as well as some potential compounds targeting pyroptosis and inflammasome signaling pathways that could be new approaches to treating diabetic wounds.

Construction and validation of a novel pyroptosis-related signature to predict prognosis in patients with cutaneous melanoma

Skin cutaneous melanoma (SKCM) is one of the most malignant skin cancers and remains a health concern worldwide. Pyroptosis is a newly recognized form of programmed cell death and plays a vital role in cancer progression. We aim to construct a prognostic model for SKCM patients based on pyroptosis-related genes (PRGs). SKCM patients from The Cancer Genome Atlas (TCGA) were divided into training and validation cohorts. We used GSE65904 downloaded from GEO database as an external validation cohort. We performed Cox regression and the least absolute shrinkage and selection operator (LASSO) regression to identify prognostic genes and built a risk score. Patients were divided into high- and low-risk groups based on the risk score. Differently expressed genes (DEGs), immune cell infiltration and immune-related pathways activation were compared between the two groups. We established a model containing 4 PRGs, i.e., GSDMA, GSDMC, AIM2 and NOD2. The overall survival (OS) time was significantly different between the 2 groups. The risk score was an independent predictor for prognosis in both the uni- and multi-variable Cox regressions. Gene ontology (GO) and Kyoto Encylopedia of Genes and Genomes (KEGG) analyses showed that DEGs were enriched in immune-related pathways. Most types of immune cells were highly expressed in the low risk group. All immune pathways were significantly up-regulated in the low-risk group. In addition, low-risk patients had a better response to immune checkpoint inhibitors. Our novel pyroptosis-related gene signature could predict the prognosis of SKCM patients and their response to immune checkpoint inhibitors.

Upregulated GSDMB in Clear Cell Renal Cell Carcinoma Is Associated with Immune Infiltrates and Poor Prognosis

Gasdermin B (GSDMB) is part of the gasdermin (GSDM) family, and they use varying means of domain interactions in molecules to adjust their pore-forming and lipid-binding actions. The GSDM family has roles in the regulation of cell differentiation and proliferation, particularly in the process of pyroptosis. Nonetheless, the correlation of GSDMB with immune infiltrates and its prognostic values in clear cell renal cell carcinoma (ccRCC) are still undefined. Therefore, we assessed the correlation of GSDMB with immune infiltrates and its prognostic role in ccRCC. The transcriptional expression profiles of GSDMB in ccRCC tissues in addition to normal tissues were retrieved from The Cancer Genome Atlas (TCGA) and additionally verified in a different independent cohort, which was obtained from the Gene Expression Omnibus (GEO) database. The Human Protein Atlas and the Clinical Proteomic Tumor Analysis Consortium (CPTAC) were used to assess the protein expression of GSDMB. To assess the effectiveness of GSDMB in distinguishing ccRCC from normal samples, the receiver operating characteristic (ROC) curve analysis was performed. Relationships between GSDMB expression, clinicopathological variables, and overall survival (OS) were evaluated with multivariate methods as well as Kaplan-Meier survival curves. Protein-protein interaction (PPI) networks were created with STRING. Functional enrichment analyses were conducted by utilizing the “ClusterProfiler” package. The Tumor Immune Estimation Resource (TIMER) and tumor-immune system interaction database (TISIDB) were utilized to determine the association between the mRNA expression of GSDMB and immune infiltrates. GSDMB expression was significantly more upregulated in ccRCC tissues compared to surrounding normal tissues. An increase in the mRNA expression of GSDMB was related to the high pathologic stage and advanced TNM stage. The analysis of the ROC curve indicated that GSDMB had an AUC value of 0.820 to distinguish between ccRCC tissues and adjacent normal controls. Kaplan-Meier survival analysis indicated that ccRCC patients with high GSDMB had a poorer prognosis compared to those with low GSDMB (P < 0.001). Correlation analysis showed that the mRNA expression of GSDMB was associated with immune infiltrates and the purity of the tumor. Upregulation of GSDMB is significantly related to immune infiltrates and poor survival in ccRCC. The results of this study indicate that GSDMB could be regarded as a biomarker for the detection of poor prognosis and potential target of immune treatment in ccRCC.

GSDMD-mediated pyroptosis: a critical mechanism of diabetic nephropathy

Pyroptosis is a recently identified mechanism of programmed cell death related to Caspase-1 that triggers a series of inflammatory reactions by releasing several proinflammatory factors such as IL-1β and IL-18. The process is characterised by the rupture of cell membranes and the release of cell contents through the mediation of gasdermin (GSDM) proteins. GSDMD is an important member of the GSDM family and plays a critical role in the two pathways of pyroptosis. Diabetic nephropathy (DN) is a microvascular complication of diabetes and a major cause of end-stage renal disease. Recently, it was revealed that GSDMD-mediated pyroptosis plays an important role in the occurrence and development of DN. In this review, we focus on two types of kidney cells, tubular epithelial cells and renal podocytes, to illustrate the mechanism of pyroptosis in DN and provide new ideas for the prevention, early diagnosis and molecular therapy of DN.

Predictive Biomarkers for Postmyocardial Infarction Heart Failure Using Machine Learning: A Secondary Analysis of a Cohort Study

Background

There are few biomarkers with an excellent predictive value for postacute myocardial infarction (MI) patients who developed heart failure (HF). This study aimed to screen candidate biomarkers to predict post-MI HF.

Methods

This is a secondary analysis of a single-center cohort study including nine post-MI HF patients and eight post-MI patients who remained HF-free over a 6-month follow-up. Transcriptional profiling was analyzed using the whole blood samples collected at admission, discharge, and 1-month follow-up. We screened differentially expressed genes and identified key modules using weighted gene coexpression network analysis. We confirmed the candidate biomarkers using the developed external datasets on post-MI HF. The receiver operating characteristic curves were created to evaluate the predictive value of these candidate biomarkers.

Results

A total of 6,778, 1,136, and 1,974 genes (dataset 1) were differently expressed at admission, discharge, and 1-month follow-up, respectively. The white and royal blue modules were most significantly correlated with post-MI HF (dataset 2). After overlapping dataset 1, dataset 2, and external datasets (dataset 3), we identified five candidate biomarkers, including FCGR2A, GSDMB, MIR330, MED1, and SQSTM1. When GSDMB and SQSTM1 were combined, the area under the curve achieved 1.00, 0.85, and 0.89 in admission, discharge, and 1-month follow-up, respectively.

Conclusions

This study demonstrates that FCGR2A, GSDMB, MIR330, MED1, and SQSTM1 are the candidate predictive biomarker genes for post-MI HF, and the combination of GSDMB and SQSTM1 has a high predictive value.

Identification and Validation of a Novel Pyroptosis-Related Gene Signature for Prognosis Prediction in Soft Tissue Sarcoma

Soft tissue sarcoma (STS) represents an uncommon and heterogenous group of malignancies, and poses substantial therapeutic challenges. Pyroptosis has been demonstrated to be related with tumor progression and prognosis. Nevertheless, no studies exist that delineated the role of pyroptosis-related genes (PRGs) in STS. In the present study, we comprehensively and systematically analyzed the gene expression profiles of PRGs in STS. The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases were utilized to identify differentially expressed PRGs. In total, 34 PRGs were aberrantly expressed between STS and normal tissues. Several PRGs were validated with RT-qPCR. Consensus clustering analysis based on PRGs was conducted to divide STS patients into two clusters, and significant survival difference was observed between two distinct clusters (p = 0.019). Differentially expressed genes (DEGs) were identified between pyroptosis-related clusters. Based on the least absolute shrinkage and selection operator (LASSO) COX regression analysis, the pyroptosis-related gene signature with five key DEGs was constructed. The high pyroptosis-related risk score group of TCGA cohort was characterized by poorer prognosis (p < 0.001), with immune infiltration and function significantly decreased. For external validation, STS patients from Gene Expression Omnibus (GEO) were grouped according to the same cut-off point. The survival difference between two risk groups of GEO cohort was also significant (p < 0.001). With the combination of clinical characteristics, pyroptosis-related risk score was identified to serve as an independent prognostic factor for STS patients. In conclusion, this study provided a comprehensive overview of PRGs in STS and the potential role in prognosis, which could be an important direction for future studies.

The Roles of Gasdermin D in Coronavirus Infection and Evasion

Pyroptosis is lytic, programmed cell death and plays a critical role against microbial invasion, functioning as an innate immune effector mechanism. The pore-forming protein gasdermin D (GSDMD), a member of gasdermin family proteins, is a primary effector of pyroptosis. The cleavage of inflammasome-associated inflammatory caspases activates GSDMD to liberate the N-terminal effector domain from the C-terminal inhibitory domain and form pores in the cellular plasma membrane. Emerging evidence shows that the pore-forming activity of GSDMD beyond pyroptosis and modifies non-lytic cytosolic protein secretion in living cells and innate immunity. While the essential roles of GSDMD in bacterial infection and cancer have been widely investigated, the importance of GSDMD in virus infection, including coronaviruses, remains elusive. Here, we review the current literature regarding the activation and functions of GSDMD during virus infections. Last, we further discuss the roles of GSDMD and the therapeutic potential of targeting this GSDMD pore-forming activity in coronavirus diseases.