The gasdermins, a protein family executing cell death and inflammation

GSDMB is increased in IBD and regulates epithelial restitution/repair independent of pyroptosis

Gasdermins are a family of structurally related proteins originally described for their role in pyroptosis. Gasdermin B (GSDMB) is currently the least studied, and while its association with genetic susceptibility to chronic mucosal inflammatory disorders is well established, little is known about its functional relevance during active disease states. Herein, we report increased GSDMB in inflammatory bowel disease, with single-cell analysis identifying epithelial specificity to inflamed colonocytes/crypt top colonocytes. Surprisingly, mechanistic experiments and transcriptome profiling reveal lack of inherent GSDMB-dependent pyroptosis in activated epithelial cells and organoids but instead point to increased proliferation and migration during in vitro wound closure, which arrests in GSDMB-deficient cells that display hyper-adhesiveness and enhanced formation of vinculin-based focal adhesions dependent on PDGF-A-mediated FAK phosphorylation. Importantly, carriage of disease-associated GSDMB SNPs confers functional defects, disrupting epithelial restitution/repair, which, altogether, establishes GSDMB as a critical factor for restoration of epithelial barrier function and the resolution of inflammation.

Comprehensive Analysis of Pyroptosis-Related Long Noncoding RNA Immune Infiltration and Prediction of Prognosis in Patients with Colon Cancer

Colon cancer (CC) is one of the most prevalent malignant tumours of the alimentary canal. It is unclear whether pyroptosis-related lncRNA expression is correlated with CC prognosis. We discovered 20 pyroptosis-related lncRNAs that were expressed differently in CC and normal colon tissues in our investigation. Based on differentially expressed genes (DEGs), we grouped all CC patients into two categories (Clusters 1 and 2). Cluster 1 was shown to be connected with a higher overall survival rate, upregulated expression of immune checkpoints, higher immunoscores, higher estimated scores, and immune cell infiltration. Using data from the Cancer Genome Atlas (TCGA), to create a multigene signature, the predictive significance of each lncRNA linked with pyroptosis for survival was assessed. A 9-lncRNA signature was established using the least absolute shrinkage and selection operator (LASSO) Cox regression method, and all CC patients in the TCGA cohort were classified into low-risk or high-risk groups. The low-risk CC patients had a much greater chance of survival than those in the high-risk group. The risk score is an independent prognostic indicator for predicting survival. In addition, risk characteristics are linked to immune characteristics. In summary, pyroptosis-related lncRNAs can be used to predict CC prognosis and participate in tumour immunity.

Novel Insights Into the Interactions Between the Gut Microbiome, Inflammasomes, and Gasdermins During Colorectal Cancer

Colorectal cancer (CRC) is one of the most prevalent and deadly forms of cancer in Western countries. Inflammation is a well-known driver of colonic carcinogenesis; however, its role in CRC extends beyond colitis-associated cancer. Over the last decades, numerous associations between intestinal dysbiosis and CRC have been identified, with more recent studies providing mechanistic evidence of a causative relationship. Nonetheless, much remains to be discovered regarding the precise implications of microbiome alterations in the pathogenesis of CRC. Research confirms the importance of a bidirectional crosstalk between the gut microbiome and the mucosal immune system in which inflammasomes, multiprotein complexes that can sense "danger signals," serve as conduits by detecting microbial signals and activating innate immune responses, including the induction of microbicidal activities that can alter microbiome composition. Current evidence strongly supports an active role for this "inflammasome-microbiome axis" in the initiation and development of CRC. Furthermore, the gasdermin (GSDM) family of proteins, which are downstream effectors of the inflammasome that are primarily known for their role in pyroptosis, have been recently linked to CRC pathogenesis. These findings, however, do not come without controversy, as pyroptosis is reported to exert both anti- and protumorigenic functions. Furthermore, the multi-faceted interactions between GSDMs and the gut microbiome, as well as their importance in CRC, have only been superficially investigated. In this review, we summarize the existing literature supporting the importance of the inflammasome-microbiota axis, as well as the activation and function of GSDMs, to gain a better mechanistic understanding of CRC pathogenesis.

Regulation of the NLRP3 Inflammasome by Posttranslational Modifications

Inflammasomes are important in human health and disease, whereby they control the secretion of IL-1β and IL-18, two potent proinflammatory cytokines that play a key role in inflammatory responses to pathogens and danger signals. Several inflammasomes have been discovered over the past two decades. NLRP3 inflammasome is the best characterized and can be activated by a wide variety of inducers. It is composed of a sensor, NLRP3, an adapter protein, ASC, and an effector enzyme, caspase-1. After activation, caspase-1 mediates the cleavage and secretion of bioactive IL-1β and IL-18 via gasdermin-D pores in the plasma membrane. Aberrant activation of NLRP3 inflammasomes has been implicated in a multitude of human diseases, including inflammatory, autoimmune, and metabolic diseases. Therefore, several mechanisms have evolved to control their activity. In this review, we describe the posttranslational modifications that regulate NLRP3 inflammasome components, including ubiquitination, phosphorylation, and other forms of posttranslational modifications.

Bacterial gasdermins reveal an ancient mechanism of cell death

[Figure: see text].

Signature Construction and Molecular Subtype Identification Based on Pyroptosis-Related Genes for Better Prediction of Prognosis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. However, there is a lack of adequate means of treatment prognostication for HCC. Pyroptosis is a newly discovered way of programmed cell death. However, the prognostic role of pyroptosis in HCC has not been thoroughly investigated. Here, we generated a novel prognostic signature to evaluate the prognostic value of pyroptosis-related genes (PRGs) using the data from The Cancer Genome Atlas (TCGA) database. The accuracy of the signature was validated using survival analysis through the International Cancer Genome Consortium cohort (n = 231) and the First Affiliated Hospital of Wenzhou Medical University cohort (n = 180). Compared with other clinical factors, the risk score of the signature was found to be associated with better patient outcomes. The enrichment analysis identified multiple pathways related with pyroptosis in HCC. Furthermore, drug sensitivity testing identified six potential chemotherapeutic agents to provide possible treatment avenues. Interestingly, patients with low risk were confirmed to be associated with lower tumor mutation burden (TMB). However, patients at high risk were found to have a higher count of immune cells. Consensus clustering was performed to identify two main molecular subtypes (named clusters A and B) based on the signature. It was found that compared with cluster B, better survival outcomes and lower TMB were observed in cluster A. In conclusion, signature construction and molecular subtype identification of PRGs could be used to predict the prognosis of HCC, which may provide a specific reference for the development of novel biomarkers for HCC treatment.

Inverse regulation of GSDMD and GSDME gene expression during LPS-induced pyroptosis in RAW264.7 macrophage cells

GSDMD and GSDME, members of the gasdermin protein family, are involved in the formation of plasma membrane channels contributing to cell rupture during a certain type of necrosis called pyroptosis. GSDMD is activated in response to immunological stimulation such as lipopolysaccharides (LPS) treatment while GSDME is mainly involved in drug-induced tumor cell death. Here we show that the expression of the GSDMD gene increases significantly during LPS-induced pyroptosis in RAW264.7 murine macrophage cells. In contrast, GSDME expression is decreased in the same cells. The increasing effect of LPS on GSDMD expression was observed only when the cells were cultured in high glucose (4.5 g/l) medium, suggesting that glucose availability is important for this effect. The effect of LPS on GSDMD expression is abolished by 2-deoxyglucose (2DG), confirming that glycolysis plays crucial roles in the increasing effect of LPS. Small interference RNA-mediated knock down of GSDMD or overexpression of GSDME causes LPS-induced pyroptosis to take place through GSDME rather than through GSDMD. Taken together, LPS regulates GSDMD and GSDME expression in opposite directions through, at least in part, its effect on glycolysis. This transcriptional regulation may contribute to the execution of pyroptosis in a GSDMD-dependent manner.

Gasdermin D pores are dynamically regulated by local phosphoinositide circuitry

Gasdermin D forms large, ~21 nm diameter pores in the plasma membrane to drive the cell death program pyroptosis. These pores are thought to be permanently open, and the resultant osmotic imbalance is thought to be highly damaging. Yet some cells mitigate and survive pore formation, suggesting an undiscovered layer of regulation over the function of these pores. However, no methods exist to directly reveal these mechanistic details. Here, we combine optogenetic tools, live cell fluorescence biosensing, and electrophysiology to demonstrate that gasdermin pores display phosphoinositide-dependent dynamics. We quantify repeated and fast opening-closing of these pores on the tens of seconds timescale, visualize the dynamic pore geometry, and identify the signaling that controls dynamic pore activity. The identification of this circuit allows pharmacological tuning of pyroptosis and control of inflammatory cytokine release by living cells.

Evolutionary analyses of the gasdermin family suggest conserved roles in infection response despite loss of pore-forming functionality

BACKGROUND

Gasdermins are ancient (>500million-years-ago) proteins, constituting a family of pore-forming proteins that allow the release of intracellular content including proinflammatory cytokines. Despite their importance in the immune response, and although gasdermin and gasdermin-like genes have been identified across a wide range of animal and non-animal species, there is limited information about the evolutionary history of the gasdermin family, and their functional roles after infection. In this study, we assess the lytic functions of different gasdermins across Metazoa species, and use a mouse model of sepsis to evaluate the expression of the different gasdermins during infection.

RESULTS

We show that the majority of gasdermin family members from distantly related animal clades are pore-forming, in line with the function of the ancestral proto-gasdermin and gasdermin-like proteins of Bacteria. We demonstrate the first expansion of this family occurred through a duplication of the ancestral gasdermin gene which formed gasdermin E and pejvakin prior to the divergence of cartilaginous fish and bony fish ~475 mya. We show that pejvakin from cartilaginous fish and mammals lost the pore-forming functionality and thus its role in cell lysis. We describe that the pore-forming gasdermin A formed ~320 mya as a duplication of gasdermin E prior to the divergence of the Sauropsida clade (the ancestral lineage of reptiles, turtles, and birds) and the Synapsid clade (the ancestral lineage of mammals). We then demonstrate that the gasdermin A gene duplicated to form the rest of the gasdermin family including gasdermins B, C, and D: pore-forming proteins that present a high variation of the exons in the linker sequence, which in turn allows for diverse activation pathways. Finally, we describe expression of murine gasdermin family members in different tissues in a mouse sepsis model, indicating function during infection response.

CONCLUSIONS

In this study we explored the evolutionary history of the gasdermin proteins in animals and demonstrated that the pore-formation functionality has been conserved from the ancient proto-gasdermin protein. We also showed that one gasdermin family member, pejvakin, lost its pore-forming functionality, but that all gasdermin family members, including pejvakin, likely retained a role in inflammation and the physiological response to infection.

Gasdermin D inhibition confers antineutrophil-mediated cardioprotection in acute myocardial infarction

Acute myocardial infarction (AMI) induces blood leukocytosis, which correlates inversely with patient survival. The molecular mechanisms leading to leukocytosis in the infarcted heart remain poorly understood. Using an AMI mouse model, we identified gasdermin D (GSDMD) in activated leukocytes early in AMI. We demonstrated that GSDMD is required for enhanced early mobilization of neutrophils to the infarcted heart. Loss of GSDMD resulted in attenuated IL-1β release from neutrophils and subsequent decreased neutrophils and monocytes in the infarcted heart. Knockout of GSDMD in mice significantly reduced infarct size, improved cardiac function, and increased post-AMI survival. Through a series of bone marrow transplantation studies and leukocyte depletion experiments, we further clarified that excessive bone marrow-derived and GSDMD-dependent early neutrophil production and mobilization (24 hours after AMI) contributed to the detrimental immunopathology after AMI. Pharmacological inhibition of GSDMD also conferred cardioprotection after AMI through a reduction in scar size and enhancement of heart function. Our study provides mechanistic insights into molecular regulation of neutrophil generation and mobilization after AMI, and supports GSDMD as a new target for improved ventricular remodeling and reduced heart failure after AMI.

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.

Activation of the Non-canonical Inflammasome in Mouse and Human Cells

The non-canonical inflammasome is a signaling platform that allows for the detection of cytoplasmic lipopolysaccharides (LPS) in immune and non-immune cells. Upon detection of LPS, this inflammasome activates the signaling proteases caspase-4 and -5 (in humans) and caspase-11 (in mice). Inflammatory caspases activation leads to caspase self-processing and the cleavage of the pore-forming protein Gasdermin D (GSDMD). GSDMD N-terminal fragments oligomerize and form pores at the plasma membranes, leading to an inflammatory form of cell death called pyroptosis. Here, we describe a simple method to activate the non-canonical inflammasome in myeloid and epithelial cells and to measure its activity using cell death assay and immunoblotting.

Live Cell Imaging of T Cell Pyroptosis

Pyroptosis is a lytic, pro-inflammatory cell death program that is tightly regulated by inflammasomes in most cases. Inflammasome-dependent pyroptosis is best characterized in myeloid cells, but there is growing evidence that this cell death program also functions in human T cells. Several studies have suggested a role for inflammasome components in T-cell biology but often do not unambiguously clarify whether this means that T cells progress to pyroptosis. Pyroptosis has distinct morphological features, such as early loss of membrane integrity and ballooning, that allow it to be distinguished from apoptosis in a microscopic experiment. However, the most stringent definition of inflammasome-dependent pyroptosis is that it is genetically dependent on a pro-inflammatory caspase (caspase-1 or caspase-4) and the pore-forming protein gasdermin D (GSDMD). Therefore, using live cell imaging of T cells in combination with a genetic loss-of-function setup is the most reliable tool for us to unequivocally demonstrate that a T cell undergoes pyroptosis. Parallel live cell imaging of T cells and macrophages is limited due to the fact that T cells do not adhere while macrophages do. This can be overcome by using so-called micro-inserts that hold the cells in a limited area that can be monitored by microscopic field of view. Here we describe in detail how live cell imaging of human T cells and monocyte-derived macrophages undergoing pyroptosis can be performed.

Measuring Non-canonical Inflammasome Activation in Neutrophils

Neutrophils are innate immune cells that play critical functions during infections through diverse mechanisms. One such mechanism, the generation of extracellular traps (NETs), enables direct bacterial killing during infections. We recently reported that the activation of the non-canonical inflammasomes in neutrophils allows for the generation of NETs and is an important host defence mechanism in vivo in response to intracellular Gram-negative bacterium. This process is dependent on inflammatory caspases and the cell death effector Gasdermin D. Here, we describe a simple approach to study the functions of the non-canonical inflammasome in murine neutrophils using microscopy and cellular fragmentation assays.

Imaging of Inflammasome Speck Formation in Living Cells

The detection of pathogen- or danger-associated molecular patterns during an inflammatory injury triggers the activation of cytosolic sensors known as inflammasomes. Once stimulated, these protein complexes can connect to the adaptor protein ASC, which in turn recruits the effector enzyme caspase-1, forming a polymeric structure known as ASC speck. This protein scaffold is responsible for processing cytokines of the IL-1 family into their active forms and evoking the cleavage of gasdermin D, ultimately leading to cell death by pyroptosis. Due to its micrometric size, the specks are used as a readout for inflammasome activation and for the better comprehension of this important immune pathway. In this chapter, a detailed protocol is presented for the study of the formation of inflammasome specks in living cells using confocal microscopy.

Treatment of Membranous Nephropathy by Disulfiram through Inhibition of Podocyte Pyroptosis

Introduction

Membranous nephropathy (MN) is a common chronic kidney disease in adults and a major challenge of clinical practice for its treatment. Despite major advances, since the discovery of the phospholipase A2 receptor as the major autoantigen of podocytes in MN, the mechanisms leading to glomerular damage remain elusive. Pyroptosis, a newly discovered type of programed necrotic cell death mainly mediated by gasdermin, was found to be responsible for podocyte injury in MN in our recent work.

Objectives

The aim of this study was to explore the therapeutic effect of an FDA-approved drug, disulfiram (DSF), in the treatment of MN by inhibiting pyroptosis.

Methods and Results

DSF significantly alleviated C3a/C5a-induced podocyte injury in vitro and renal lesions in passive Heymann nephritis (PHN) rats, as reflected by the decreased percentage of propidium iodide staining podocytes, decreased lactate dehydrogenase release from cultured podocytes and improvement in 24-h urine protein, serum albumin, serum creatinine, abnormal alterations of podocyte injury markers Desmin and WT-1 and podocyte foot process fusion in PHN rats. The protective effect of DSF on podocyte injury in vitro and in vivo can be ascribed to its inhibition of the activation and membrane translocation of the pyroptosis executor gasdermin D (GSDMD) in podocytes. DSF also inhibited the increase and activation of the pyroptosis signaling pathway NLRP3-ASC-Caspase-1/IL-18/GSDMD in C3a/C5a-treated podocytes and renal tissue of PHN rats.

Conclusion

DSF is a potential drug for MN treatment, and its clinical application needs to be further investigated.

Plasma membrane perforation by GSDME during apoptosis-driven secondary necrosis

Secondary necrosis has long been perceived as an uncontrolled process resulting in total lysis of the apoptotic cell. Recently, it was shown that progression of apoptosis to secondary necrosis is regulated by Gasdermin E (GSDME), which requires activation by caspase-3. Although the contribution of GSDME in this context has been attributed to its pore-forming capacity, little is known about the kinetics and size characteristics of this. Here we report on the membrane permeabilizing features of GSDME by monitoring the influx and efflux of dextrans of different sizes into/from anti-Fas-treated L929sAhFas cells undergoing apoptosis-driven secondary necrosis. We found that GSDME accelerates cell lysis measured by SYTOX Blue staining but does not affect the exposure of phosphatidylserine on the plasma membrane. Furthermore, loss of GSDME expression clearly hampered the influx of fluorescently labeled dextrans while the efflux happened independently of the presence or absence of GSDME expression. Importantly, both in- and efflux of dextrans were dependent on their molecular weight. Altogether, our results demonstrate that GSDME regulates the passage of compounds together with other plasma membrane destabilizing subroutines.

Radiosensitivity of colorectal cancer and radiation-induced gut damages are regulated by gasdermin E

Although radiotherapy is an important clinical option available for colorectal cancer (CRC), its use is restricted due to low radiosensitivity of CRC and high toxicity to surrounding normal tissues. The purpose of this study is to investigate the molecular mechanism by which CRC is not sensitive to radiation and radiation causes toxicity to surrounding normal tissues. Here we found that GSDME was silenced in CRC but markedly expressed in their surrounding normal tissues. GSDME determines radiation-induced pyroptosis in CRC cells and normal epithelial cells through the caspase-3-dependent pathway. GSDME expression sensitizes radioresistant CRC cells to radiation. In the homograft model, after radiation treatment, the tumor volume and weight were significantly decreased in GSDME-expressed homograft tumors compared to GSDME-knockout homograft tumors. On the mechanism, radiation induced GSDME-mediated pyroptosis in CRC cells, which recruited and activated NK cells to enhance antitumor immunity. In addition, GSDME-knockout mice were protected from radiation-induced weight loss and tissue damages in the intestine, stomach, liver and pancreas compared to wild-type control littermates. In summary, we show that GSDME determines CRC radiosensitivity and radiation-related toxicity to surrounding normal tissues through caspase-3-dependent pyroptosis. Our finding reveals a previously unrecognized link between radiation and pyroptosis.

Gasdermin E mediates photoreceptor damage by all-trans-retinal in the mouse retina

The breakdown of all-trans-retinal (atRAL) clearance is closely associated with photoreceptor cell death in dry age-related macular degeneration (AMD) and autosomal recessive Stargardt's disease (STGD1), but its mechanisms remain elusive. Here, we demonstrate that activation of gasdermin E (GSDME) but not gasdermin D promotes atRAL-induced photoreceptor damage by activating pyroptosis and aggravating apoptosis through a mitochondria-mediated caspase-3-dependent signaling pathway. Activation of c-Jun N-terminal kinase was identified as one of the major causes of mitochondrial membrane rupture in atRAL-loaded photoreceptor cells, resulting in the release of cytochrome c from mitochondria to the cytosol, where it stimulated caspase-3 activation required for cleavage of GSDME. Aggregation of the N-terminal fragment of GSDME in the mitochondria revealed that GSDME was likely to penetrate mitochondrial membranes in photoreceptor cells after atRAL exposure. ABC (subfamily A, member 4) and all-trans-retinol dehydrogenase 8 are two key proteins responsible for clearing atRAL in the retina. Abca4^−/−Rdh8^−/− mice exhibit serious defects in atRAL clearance upon light exposure and serve as an acute model for dry AMD and STGD1. We found that N-terminal fragment of GSDME was distinctly localized in the photoreceptor outer nuclear layer of light-exposed Abca4^−/−Rdh8^−/− mice. Of note, degeneration and caspase-3 activation in photoreceptors were significantly alleviated in Abca4^−/−Rdh8^−/−Gsdme^−/− mice after exposure to light. The results of this study indicate that GSDME is a common causative factor of photoreceptor pyroptosis and apoptosis arising from atRAL overload, suggesting that repressing GSDME may represent a potential treatment of photoreceptor atrophy in dry AMD and STGD1.

Targeting regulated cell death in aortic aneurysm and dissection therapy

Regulated cell death (RCD) is a basic biological phenomenon associated with cell and tissue homeostasis. Recent studies have enriched our understanding of RCD, and many novel cell death types, such as ferroptosis and pyroptosis, have been discovered and defined. Aortic aneurysm and dissection (AAD) is a life-threatening condition, but the pathogenesis remains largely unclear. A series of studies have indicated that the death of smooth muscle cells, endothelial cells and inflammatory cells participates in the development of AAD and that corresponding interventions could alleviate disease progression. Many treatments against cell death have been used to impede the process of AAD in vitro and in vivo, which provides strategies to protect against this condition. In this review, we focus on various types of regulated cell death and provide a framework of their roles in AAD, and the information contributes to further exploration of the molecular mechanisms of AAD.

Identification of the Pyroptosis-Related Gene Signature and Risk Score Model for Colon Adenocarcinoma

The prognosis of advanced colon adenocarcinoma (COAD) remains poor. However, existing methods are still difficult to assess patient prognosis. Pyroptosis, a lytic and inflammatory process of programmed cell death caused by the gasdermin protein, is involved in the development and progression of various tumors. Moreover, there are no related studies using pyroptosis-related genes to construct a model to predict the prognosis of COAD patients. Thus, in this study, bioinformatics methods were used to analyze the data of COAD patients downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases to construct a risk model for the patient prognosis. TCGA database was used as the training set, and GSE39582 downloaded from GEO was used as the validation set. A total of 24 pyroptosis-related genes shown significantly different expression between normal and tumor tissues in COAD and seven genes (CASP4, CASP5, CASP9, IL6, NOD1, PJVK, and PRKACA) screened by univariate and LASSO cox regression analysis were used to construct the risk model. The receiver operating characteristic (ROC) and Kaplan–Meier (K–M curves) curves showed that the model based on pyroptosis-related genes can be used to predict the prognosis of COAD and can be validated by the external cohort well. Then, the clinicopathological factors were combined with the risk score to establish a nomogram with a C-index of 0.774. In addition, tissue validation results also showed that CASP4, CASP5, PRKACA, and NOD1 were differentially expressed between tumor and normal tissues from COAD patients. In conclusion, the risk model based on the pyroptosis-related gene can be used to assess the prognosis of COAD patients well, and the related genes may become the potential targets for treatment.

Lipid specificity of the immune effector perforin

Perforin is a pore forming protein used by cytotoxic T lymphocytes to remove cancerous or virus-infected cells during the immune response. During the response, the lymphocyte membrane becomes refractory to perforin function by accumulating densely ordered lipid rafts and externalizing negatively charged lipid species. The dense membrane packing lowers the capacity of perforin to bind, and the negatively charged lipids scavenge any residual protein before pore formation. Using atomic force microscopy on model membrane systems, we here provide insight into the molecular basis of perforin lipid specificity.

The role of caspases as executioners of apoptosis

Caspases are a family of cysteine aspartyl proteases mostly involved in the execution of apoptotic cell death and in regulating inflammation. This article focuses primarily on the evolutionarily conserved function of caspases in apoptosis. We summarise which caspases are involved in apoptosis, how they are activated and regulated, and what substrates they target for cleavage to orchestrate programmed cell death by apoptosis.

Crossed Pathways for Radiation-Induced and Immunotherapy-Related Lung Injury

Radiation-induced lung injury (RILI) is a form of radiation damage to normal lung tissue caused by radiotherapy (RT) for thoracic cancers, which is most commonly comprised of radiation pneumonitis (RP) and radiation pulmonary fibrosis (RPF). Moreover, with the widespread utilization of immunotherapies such as immune checkpoint inhibitors as first- and second-line treatments for various cancers, the incidence of immunotherapy-related lung injury (IRLI), a severe immune-related adverse event (irAE), has rapidly increased. To date, we know relatively little about the underlying mechanisms and signaling pathways of these complications. A better understanding of the signaling pathways may facilitate the prevention of lung injury and exploration of potential therapeutic targets. Therefore, this review provides an overview of the signaling pathways of RILI and IRLI and focuses on their crosstalk in diverse signaling pathways as well as on possible mechanisms of adverse events resulting from combined radiotherapy and immunotherapy. Furthermore, this review proposes potential therapeutic targets and avenues of further research based on signaling pathways. Many new studies on pyroptosis have renewed appreciation for the value and importance of pyroptosis in lung injury. Therefore, the authors posit that pyroptosis may be the common downstream pathway of RILI and IRLI; discussion is also conducted regarding further perspectives on pyroptosis as a crucial signaling pathway in lung injury treatment.

Gasdermin D and Beyond - Gasdermin-mediated Pyroptosis in Bacterial Infections

The discovery of pyroptosis and its subsequent implications in infection and immunity has uncovered a new angle of host-defence against pathogen assault. At its most simple, gasdermin-mediated pyroptosis in bacterial infection would be expected to remove pathogens from the relative safety of the cytosol or pathogen containing vacuole/phagosome whilst inducing a rapid and effective immune response. Differences in gasdermin-mediated pyroptosis between cell types, stimulation conditions, pathogen and even animal species, however, make things more complex. The excessive inflammation associated with the pathogen-induced gasdermin-mediated pyroptosis contributes to a downward spiral in sepsis. With no currently approved effective treatment options for sepsis understanding how gasdermin-mediated pyroptotic pathways are regulated provides an opportunity to identify novel therapeutic candidates against this complex disease. In this review we cover recent advances in the field of gasdermin-mediated pyroptosis with a focus on bacterial infection and sepsis models in the context of humans and other animal species. Importantly we also consider why there is considerable redundancy set into these ancient immune pathways.

A Novel Risk Signature with Seven Pyroptosis-Related Genes for Prognosis Prediction in Glioma

BACKGROUND

Increasing evidence indicates that pyroptosis is closely linked to the occurrence and progression of cancer. However, the expression and prognostic role of most pyroptosis-related genes in glioma have not been fully elucidated.

METHODS

Herein, we explored the expression profiles and prognostic value of 33 pyroptosis-related genes in glioma. LASSO regression analysis was then used to construct a risk signature to predict glioma outcomes in The Cancer Genome Atlas (TCGA) cohort. Furthermore, we constructed a nomogram based on independent prognostic factors and performed external validation. Finally, functional enrichment analysis was performed to explore the potential biological role of the pyroptosis-related signature in glioma.

RESULTS

The expression of most pyroptosis-related genes (31/33) was significantly different between normal brain and glioma tissue. By univariate Cox regression analysis, 24 genes were found to be significantly correlated with glioma overall survival (OS). Subsequently, we constructed a 7-gene risk signature in the TCGA training cohort, which demonstrated good performance in predicting glioma survival through multidatabase validation. Moreover, a nomogram was established based on independent prognostic factors (age, WHO grade, IDH status and signature) and confirmed to be more effective and accurate through internal evaluation and external validation. Finally, functional enrichment analyses suggested that the signature might be related to invasion ability and immune function.

CONCLUSIONS

The risk signature based on seven pyroptosis-related genes can effectively predict the clinical outcomes of glioma patients. Our study provides novel insights for further understanding the association between pyroptosis-related genes and glioma prognosis.

Molecular and structural aspects of gasdermin family pores and insights into gasdermin-elicited programmed cell death

Pyroptosis is a highly inflammatory and lytic type of programmed cell death (PCD) commenced by inflammasomes, which sense perturbations in the cytosolic environment. Recently, several ground-breaking studies have linked a family of pore-forming proteins known as gasdermins (GSDMs) to pyroptosis. The human genome encodes six GSDM proteins which have a characteristic feature of forming pores in the plasma membrane resulting in the disruption of cellular homeostasis and subsequent induction of cell death. GSDMs have an N-terminal cytotoxic domain and an auto-inhibitory C-terminal domain linked together through a flexible hinge region whose proteolytic cleavage by various enzymes releases the N-terminal fragment that can insert itself into the inner leaflet of the plasma membrane by binding to acidic lipids leading to pore formation. Emerging studies have disclosed the involvement of GSDMs in various modalities of PCD highlighting their role in diverse cellular and pathological processes. Recently, the cryo-EM structures of the GSDMA3 and GSDMD pores were resolved which have provided valuable insights into the pore formation process of GSDMs. Here, we discuss the current knowledge regarding the role of GSDMs in PCD, structural and molecular aspects of autoinhibition, and pore formation mechanism followed by a summary of functional consequences of gasdermin-induced membrane permeabilization.

Identifying the hub genes and immune infiltration related to pyroptosis in rheumatoid arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune joint disorders globally, but its pathophysiological mechanisms have not been thoroughly investigated. Pyroptosis significantly correlates with programmed cell death. However, targeting pyroptosis has not been considered as a therapeutic strategy in RA due to a lack of systematic studies on validated biomarkers. The present study aimed to identify hub pyroptosis biomarkers and immune infiltration in RA. The gene expression profiles of synovial tissues were obtained from the Gene Expression Omnibus (GEO) database to identify differentially expressed pyroptosis genes (DEPGs). Meanwhile, the CIBERSORT algorithm was used to explore the association between immune infiltration and RA. Consequently, two hub DEPGs (EGFR and JUN) were identified as critical genes in RA. Through gene ontology and pathway enrichment analysis. EGFR and JUN were found to be primarily involved in the ErbB signaling pathway, PD-1 checkpoint pathway, GnRH signaling pathway, etc. Furthermore, for immune infiltration analysis, the pyroptosis genes EGFR and JUN were closely connected with four and one immune cell types, respectively. Overall, this study presents a novel method to identify hub DEPGs and their correlation with immune infiltration, which may provide novel perspectives into the diagnosis and treatment of patients with RA.

Epithelial-Mesenchymal Transition Induces GSDME Transcriptional Activation for Inflammatory Pyroptosis

GSDME is a newly recognized executor of cellular pyroptosis, and has been recently implicated in tumor growth and immunity. However, knowledge about the molecular regulators underlying GSDME abundance remains limited. Here, we performed integrative bioinformatics analyses and identified that epithelial-mesenchymal transition (EMT) gene signatures exhibited positive correlation with GSDME levels across human cancers. A causal role was supported by the observation that EMT dictated GSDME reversible upregulation in multiple experimental models. Mechanistically, transcriptional activation of GSDME was directly driven by core EMT-activating transcription factors ZEB1/2, which bound to the GSDME promoter region. Of functional importance, elevated GSDME in mesenchymally transdifferentiated derivatives underwent proteolytic cleavage upon antineoplastic drug exposure, leading to pyroptotic cell death and consequent cytokine release. Taken together, our findings pinpointed a key transcriptional machinery controlling GSDME expression and indicated potential therapeutic avenues to exploit GSDME-mediated inflammatory pyroptosis for the treatment of mesenchymal malignancies.

Ubiquitinated gasdermin D mediates arsenic-induced pyroptosis and hepatic insulin resistance in rat liver

As an environmental toxicant, arsenic exposure may cause insulin resistance (IR). Previous studies have shown that pyroptosis plays an important role in the occurrence and development of IR. Although gasdermin D (GSDMD) functions as an executor of pyroptosis, the relationship between GSDMD-mediated pyroptosis and hepatic IR remains unclear. Here, we observed that sodium arsenite (NaAsO₂) activated NOD-like receptors containing pyrin domain 3 (NLRP3) inflammasomes, promoted GSDMD activation, induced pyroptosis and hepatic IR, while GSDMD knockdown attenuated pyroptosis and hepatic IR caused by NaAsO₂. However, GSDMD interference did not affect NLRP3 activation. Ubiquitination modification is widely involved in protein regulation and intracellular signal transduction, and whether it regulates GSDMD and affects its degradation, and exerts effects on arsenic-induced pyroptosis remain unclear. We observed that NaAsO₂ reduced the K48- and K63-linked ubiquitination of GSDMD, thereby inhibiting its degradation through the ubiquitin-proteasome system (UPS) and the autophagy-lysosome pathway (ALP), causing GSDMD to accumulate and lyse into GSDMD-N, which promoted pyroptosis. In summary, we demonstrated that GSDMD participated in arsenic-induced hepatic IR. Moreover, NaAsO₂ reduced GSDMD ubiquitination and decreased its intracellular degradation, aggravating pyroptosis and hepatic IR. We have revealed the molecular mechanism underpinning arsenic-induced IR, and we provide potential solutions for the prevention and treatment of type 2 diabetes (T2D).

Mitochondrial DNA leakage exacerbates odontoblast inflammation through gasdermin D-mediated pyroptosis

Alleviating odontoblast inflammation is crucial to control the progression of pulpitis. Mitochondrial DNA (mtDNA) is a vital driver of inflammation when it leaks from mitochondria of inflamed odontoblasts into the cytosol. Bacteria-induced inflammation leads to a novel type of cell death named pyroptosis. The canonical pyroptosis is a gasdermin (GSDM)-dependent cytolytic programmed cell death characterized by cell swelling and pore formation in the plasma membrane. To date, whether odontoblast cytosolic mtDNA regulates dental pulp inflammation through the canonical pyroptosis pathway remains to be elucidated. In this study, high gasdermin D (GSDMD) expression was detected in human pulpitis. We found that LPS stimulation of mDPC6T cells promoted BAX translocation from the cytosol to the mitochondrial membrane, leading to mtDNA release. Moreover, overexpression of isolated mtDNA induced death in a large number of mDPC6T cells, which had the typical appearance of pyroptotic cells. Secretion of the inflammatory cytokines CXCL10 and IFN-β was also induced by mtDNA. These results suggest that cytosolic mtDNA participates in the regulation of odontoblast inflammation through GSDMD-mediated pyroptosis in vitro. Interestingly, after overexpression of mtDNA, the expression of inflammatory cytokines CXCL10 and IFN-β was increased and not decreased in GSDMD knockdown mDPC6T cells. We further proposed a novel model in which STING-dependent inflammation in odontoblast-like cell is a compensatory mechanism to control GSDMD-mediated pyroptosis, jointly promoting the immune inflammatory response of odontoblasts. Collectively, these findings provide the first demonstration of the role of the mtDNA-GSDMD-STING in controlling odontoblast inflammation and a detailed description of the underlying interconnected relationship.

Strategies to package recombinant Adeno-Associated Virus expressing the N-terminal gasdermin domain for tumor treatment

Pyroptosis induced by the N-terminal gasdermin domain (GSDM^NT) holds great potential for anti-tumor therapy. However, due to the extreme cytoxicity of GSDM^NT, it is challenging to efficiently produce and deliver GSDM^NT into tumor cells. Here, we report the development of two strategies to package recombinant adeno-associated virus (rAAV) expressing GSDM^NT: 1) drive the expression of GSDM^NT by a mammal specific promoter and package the virus in Sf9 insect cells to avoid its expression; 2) co-infect rAAV-Cre to revert and express the double-floxed inverted GSDM^NT. We demonstrate that these rAAVs can induce pyroptosis and prolong survival in preclinical cancer models. The oncolytic-viruses induce pyroptosis and evoke a robust immune-response. In a glioblastoma model, rAAVs temporarily open the blood-brain barrier and recruit tumor infiltrating lymphocytes into the brain. The oncolytic effect is further improved in combination with anti-PD-L1. Together, our strategies efficiently produce and deliver GSDM^NT into tumor cells and successfully induce pyroptosis, which can be exploited for anti-tumor therapy.

Pyroptosis, a gasdermin-mediated inflammatory cell death, could be harnessed therapeutically to improve response to cancer immunotherapy. Here the authors report the development of recombinant adeno-associated viruses to deliver the pore-forming N-terminal domain of gasdermin into cancer cells, promoting pyroptosis and anti-tumor immune responses in preclinical cancer models.

A novel pyroptosis-related gene signature predicts the prognosis of glioma through immune infiltration

BACKGROUND

Glioma is the most common primary intracranial tumour and has a very poor prognosis. Pyroptosis, also known as inflammatory necrosis, is a type of programmed cell death that was discovered in recent years. The expression and role of pyroptosis-related genes in gliomas are still unclear.

METHODS

In this study, we analysed the RNA-seq and clinical information of glioma patients from The Cancer Genome Atlas (TCGA) database and Chinese Glioma Genome Atlas (CGGA) database. To investigate the prognosis and immune microenvironment of pyroptosis-related genes in gliomas, we constructed a risk model based on the TCGA cohort. The patients in the CGGA cohort were used as the validation cohort.

RESULTS

In this study, we identified 34 pyroptosis-related differentially expressed genes (DEGs) in glioma. By clustering these DEGs, all glioma cases can be divided into two clusters. Survival analysis showed that the overall survival time of Cluster 1 was significantly higher than that of Cluster 2. Using the TCGA cohort as the training set, a 10-gene risk model was constructed through univariate Cox regression analysis and LASSO Cox regression analysis. According to the risk score, gliomas were divided into high-risk and low-risk groups. Survival analysis showed that the low-risk group had a longer survival time than the high-risk group. The above results were verified in the CGGA validation cohort. To verify that the risk model was independent of other clinical features, the distribution and the Kaplan-Meier survival curves associated with risk scores were performed. Combined with the characteristics of the clinical cases, the risk score was found to be an independent factor predicting the overall survival of patients with glioma. The analysis of single sample Gene Set Enrichment Analysis (ssGSEA) showed that compared with the low-risk group, the high-risk group had immune cell and immune pathway activities that were significantly upregulated.

CONCLUSION

We established 10 pyroptosis-related gene markers that can be used as independent clinical predictors and provide a potential mechanism for the treatment of glioma.

Hepatocytes Are Resistant to Cell Death From Canonical and Non-Canonical Inflammasome-Activated Pyroptosis

BACKGROUND

Pyroptosis, gasdermin-mediated programmed cell death, is readily induced in macrophages by activation of the canonical inflammasome (caspase-1) or by intracellular lipopolysaccharide (LPS)-mediated non-canonical inflammasome (caspase-11) activation. However, whether pyroptosis is induced similarly in hepatocytes is still largely controversial but highly relevant to liver pathologies such as alcoholic/nonalcoholic liver disease, drug-induced liver injury, ischemia-reperfusion and liver transplant injury, or organ damage secondary to sepsis.

METHODS AND RESULTS

In this study we found that hepatocytes activate and cleave gasdermin-D (GSDMD) at low levels after treatment with LPS. Overexpression of caspase-1 or caspase-11 p10/p20 activated domains was able to induce typical GSDMD-dependent pyroptosis in hepatocytes both in vitro and in vivo. However, morphologic features of pyroptosis in macrophages (eg, pyroptotic bodies, cell flattening, loss of cell structure) did not occur in pyroptotic hepatocytes, with cell structure remaining relatively intact despite the cell membrane being breached. Our results suggest that hepatocytes activate pyroptosis pathways and cleave GSDMD, but this does not result in cell rupture and confer the same pyroptotic morphologic changes as previously reported in macrophages. This is true even with caspase-1 or caspase-11 artificial overexpression way above levels seen endogenously even after priming or in pathologic conditions.

CONCLUSIONS

Our novel findings characterize hepatocyte morphology in pyroptosis and suggest alternative use for canonical/non-canonical inflammasome activation/signaling and subsequent GSDMD cleavage because there is no rapid cell death as in macrophages. Improved understanding and recognition of the role of these pathways in hepatocytes may result in novel therapeutics for a range of liver diseases.

A Novel Pyroptosis-related Prognostic Model for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the second most lethal malignant tumor because of its significant heterogeneity and complicated molecular pathogenesis. Novel prognostic biomarkers are urgently needed because no effective and reliable prognostic biomarkers currently exist for HCC patients. Increasing evidence has revealed that pyroptosis plays a role in the occurrence and progression of malignant tumors. However, the relationship between pyroptosis-related genes (PRGs) and HCC patient prognosis remains unclear. In this study, 57 PRGs were obtained from previous studies and GeneCards. The gene expression profiles and clinical data of HCC patients were acquired from public data portals. Least absolute shrinkage and selection operator (LASSO) Cox regression analysis was performed to establish a risk model using TCGA data. Additionally, the risk model was further validated in an independent ICGC dataset. Our results showed that 39 PRGs were significantly differentially expressed between tumor and normal liver tissues in the TCGA cohort. Functional analysis confirmed that these PRGs were enriched in pyroptosis-related pathways. According to univariate Cox regression analysis, 14 differentially expressed PRGs were correlated with the prognosis of HCC patients in the TCGA cohort. A risk model integrating two PRGs was constructed to classify the patients into different risk groups. Poor overall survival was observed in the high-risk group of both TCGA (p < 0.001) and ICGC (p < 0.001) patients. Receiver operating characteristic curves demonstrated the accuracy of the model. Furthermore, the risk score was confirmed as an independent prognostic indicator via multivariate Cox regression analysis (TCGA cohort: HR = 3.346, p < 0.001; ICGC cohort: HR = 3.699, p < 0.001). Moreover, the single-sample gene set enrichment analysis revealed different immune statuses between high- and low-risk groups. In conclusion, our new pyroptosis-related risk model has potential application in predicting the prognosis of HCC patients.

Treatment of Severe Acute Pancreatitis and Related Lung Injury by Targeting Gasdermin D-Mediated Pyroptosis

The functional relevance and effects of the pyroptosis executioner gasdermin D (GSDMD) on severe acute pancreatitis (SAP)-associated lung injury are unclear. We established caerulein-induced mouse models of SAP-associated lung injury, which showed that GSDMD-mediated pyroptosis was activated in both pancreatic and lung tissues. Compared with Gsdmd wild-type SAP mouse models, Gsdmd knockout (Gsdmd^–/–) ameliorated SAP-induced pancreas and related lung injury. Additionally, we investigated the effects of disulfiram on the treatment of SAP. Disulfiram is a Food and Drug Administration (FDA)-approved anti-alcoholism drug, which is reported as an effective pyroptosis inhibitor by either directly covalently modifying GSDMD or indirectly inhibiting the cleavage of GSDMD via inactivating Nod-like receptor protein 3 inflammasome. We demonstrated that disulfiram inhibited the cleavage of GSDMD, alleviated caerulein-induced SAP and related lung injury, and decreased the expression levels of proinflammatory cytokines (IL-1β and IL-18). Collectively, these findings disclosed the role of GSDMD-mediated pyroptosis in SAP and the potential application of disulfiram in the treatment of SAP.

The Versatile Gasdermin Family: Their Function and Roles in Diseases

The gasdermin (GSDM) family, a novel group of structure-related proteins, consists of GSDMA, GSDMB, GSDMC, GSDMD, GSDME/DNFA5, and PVJK/GSDMF. GSDMs possess a C-terminal repressor domain, cytotoxic N-terminal domain, and flexible linker domain (except for GSDMF). The GSDM-NT domain can be cleaved and released to form large oligomeric pores in the membrane that facilitate pyroptosis. The emerging roles of GSDMs include the regulation of various physiological and pathological processes, such as cell differentiation, coagulation, inflammation, and tumorigenesis. Here, we introduce the basic structure, activation, and expression patterns of GSDMs, summarize their biological and pathological functions, and explore their regulatory mechanisms in health and disease. This review provides a reference for the development of GSDM-targeted drugs to treat various inflammatory and tissue damage-related conditions.

Hyperlipidemia May Synergize with Hypomethylation in Establishing Trained Immunity and Promoting Inflammation in NASH and NAFLD

We performed a panoramic analysis on both human nonalcoholic steatohepatitis (NASH) microarray data and microarray/RNA-seq data from various mouse models of nonalcoholic fatty liver disease NASH/NAFLD with total 4249 genes examined and made the following findings: (i) human NASH and NAFLD mouse models upregulate both cytokines and chemokines; (ii) pathway analysis indicated that human NASH can be classified into metabolic and immune NASH; methionine- and choline-deficient (MCD)+high-fat diet (HFD), glycine N-methyltransferase deficient (GNMT-KO), methionine adenosyltransferase 1A deficient (MAT1A-KO), and HFCD (high-fat-cholesterol diet) can be classified into inflammatory, SAM accumulation, cholesterol/mevalonate, and LXR/RXR-fatty acid β-oxidation NAFLD, respectively; (iii) canonical and noncanonical inflammasomes play differential roles in the pathogenesis of NASH/NAFLD; (iv) trained immunity (TI) enzymes are significantly upregulated in NASH/NAFLD; HFCD upregulates TI enzymes more than cytokines, chemokines, and inflammasome regulators; (v) the MCD+HFD is a model with the upregulation of proinflammatory cytokines and canonical and noncanonical inflammasomes; however, the HFCD is a model with upregulation of TI enzymes and lipid peroxidation enzymes; and (vi) caspase-11 and caspase-1 act as upstream master regulators, which partially upregulate the expressions of cytokines, chemokines, canonical and noncanonical inflammasome pathway regulators, TI enzymes, and lipid peroxidation enzymes. Our findings provide novel insights on the synergies between hyperlipidemia and hypomethylation in establishing TI and promoting inflammation in NASH and NAFLD progression and novel targets for future therapeutic interventions for NASH and NAFLD, metabolic diseases, transplantation, and cancers.

Microenvironment-Responsive Prodrug-Induced Pyroptosis Boosts Cancer Immunotherapy

The absence of tumor antigens leads to a low response rate, which represents a major challenge in immune checkpoint blockade (ICB) therapy. Pyroptosis, which releases tumor antigens and damage-associated molecular patterns (DAMPs) that induce antitumor immunity and boost ICB efficiency, potentially leads to injury when occurring in normal tissues. Therefore, a strategy and highly efficient agent to induce tumor-specific pyroptosis but reduce pyroptosis in normal tissues is urgently required. Here, a smart tumor microenvironmental reactive oxygen species (ROS)/glutathione (GSH) dual-responsive nano-prodrug (denoted as MCPP) with high paclitaxel (PTX) and photosensitizer purpurin 18 (P18) loading is rationally designed. The ROS/GSH dual-responsive system facilitates the nano-prodrug response to high ROS/GSH in the tumor microenvironment and achieves optimal drug release in tumors. ROS generated by P18 after laser irradiation achieves controlled release and induces tumor cell pyroptosis with PTX by chemo-photodynamic therapy. Pyroptotic tumor cells release DAMPs, thus initiating adaptive immunity, boosting ICB efficiency, achieving tumor regression, generating immunological memory, and preventing tumor recurrence. Mechanistically, chemo-photodynamic therapy and control-release PTX synergistically induce gasdermin E (GSDME)-related pyroptosis. It is speculated that inspired chemo-photodynamic therapy using the presented nano-prodrug strategy can be a smart strategy to trigger pyroptosis and augment ICB efficiency.

Novel Knowledge-Based Transcriptomic Profiling of Lipid Lysophosphatidylinositol-Induced Endothelial Cell Activation

To determine whether pro-inflammatory lipid lysophosphatidylinositols (LPIs) upregulate the expressions of membrane proteins for adhesion/signaling and secretory proteins in human aortic endothelial cell (HAEC) activation, we developed an EC biology knowledge-based transcriptomic formula to profile RNA-Seq data panoramically. We made the following primary findings: first, G protein-coupled receptor 55 (GPR55), the LPI receptor, is expressed in the endothelium of both human and mouse aortas, and is significantly upregulated in hyperlipidemia; second, LPIs upregulate 43 clusters of differentiation (CD) in HAECs, promoting EC activation, innate immune trans-differentiation, and immune/inflammatory responses; 72.1% of LPI-upregulated CDs are not induced in influenza virus-, MERS-CoV virus- and herpes virus-infected human endothelial cells, which hinted the specificity of LPIs in HAEC activation; third, LPIs upregulate six types of 640 secretomic genes (SGs), namely, 216 canonical SGs, 60 caspase-1-gasdermin D (GSDMD) SGs, 117 caspase-4/11-GSDMD SGs, 40 exosome SGs, 179 Human Protein Atlas (HPA)-cytokines, and 28 HPA-chemokines, which make HAECs a large secretory organ for inflammation/immune responses and other functions; fourth, LPIs activate transcriptomic remodeling by upregulating 172 transcription factors (TFs), namely, pro-inflammatory factors NR4A3, FOS, KLF3, and HIF1A; fifth, LPIs upregulate 152 nuclear DNA-encoded mitochondrial (mitoCarta) genes, which alter mitochondrial mechanisms and functions, such as mitochondrial organization, respiration, translation, and transport; sixth, LPIs activate reactive oxygen species (ROS) mechanism by upregulating 18 ROS regulators; finally, utilizing the Cytoscape software, we found that three mechanisms, namely, LPI-upregulated TFs, mitoCarta genes, and ROS regulators, are integrated to promote HAEC activation. Our results provide novel insights into aortic EC activation, formulate an EC biology knowledge-based transcriptomic profile strategy, and identify new targets for the development of therapeutics for cardiovascular diseases, inflammatory conditions, immune diseases, organ transplantation, aging, and cancers.

Dying cells fan the flames of inflammation

[Figure: see text].

Apoptosis, Pyroptosis, and Necroptosis-Oh My! The Many Ways a Cell Can Die

Cell death is an essential process in all living organisms and occurs through different mechanisms. The three main types of programmed cell death are apoptosis, pyroptosis, and necroptosis, and each of these pathways employs complex molecular and cellular mechanisms. Although there are mechanisms and outcomes specific to each pathway, they share common components and features. In this review, we discuss recent discoveries in these three best understood modes of cell death, highlighting their singularities, and examining the intriguing notion that common players shape different individual pathways in this highly interconnected and coordinated cell death system. Understanding the similarities and differences of these cell death processes is crucial to enable targeted strategies to manipulate these pathways for therapeutic benefit.

Pyroptosis, and its Role in Central Nervous System Disease

Pyroptosis is an inflammatory form of cell death executed by transmembrane pore-forming proteins known as gasdermins and can be activated in an inflammasome-dependent or -independent manner. Inflammasome-dependent pyroptosis is triggered in response to pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) and has emerged as an important player in the pathogenesis of multiple inflammatory diseases, mainly by releasing inflammatory contents. More recently, numerous studies have revealed the intricate mechanisms of pyroptosis and its role in the development of neuroinflammation in central nervous system (CNS) diseases. In this review, we summarize current understandings of the molecular and regulatory mechanisms of pyroptosis. In addition, we discuss how pyroptosis can drive different forms of neurological diseases and new promising therapeutic strategies targeting pyroptosis that can be leveraged to treat neuroinflammation.

Exercise-Induced Irisin Decreases Inflammation and Improves NAFLD by Competitive Binding with MD2

Non-alcoholic fatty liver disease (NAFLD) is a global clinical problem. The MD2-TLR4 pathway exacerbates NAFLD progression by promoting inflammation. Long-term exercise is considered to improve NAFLD but the underlying mechanism is still unclear. In this study, we examined the protective effect and molecular mechanism of exercise on high-fat diet (HFD)-induced liver injury. In an HFD-induced NAFLD mouse model, exercise training significantly decreased hepatic steatosis and fibrosis. Interestingly, exercise training blocked the binding of MD2-TLR4 and decreased the downstream inflammatory response. Irisin is a myokine that is highly expressed in response to exercise and exerts anti-inflammatory effects. We found that circulating irisin levels and muscle irisin expression were significantly increased in exercised mice, suggesting that irisin could mediate the effect of exercise on NAFLD. In vitro studies showed that irisin improved lipid metabolism, fibrosis, and inflammation in palmitic acid (PA)-stimulated AML12 cells. Moreover, binding assay results showed that irisin disturbed MD2-TLR4 complex formation by directly binding with MD2 but not TLR4, and interfered with the recognition of stimuli such as PA and lipopolysaccharide with MD2. Our study provides novel evidence that exercise-induced irisin inhibits inflammation via competitive binding with MD2 to improve NAFLD. Thus, irisin could be considered a potential therapy for NAFLD.

Predicting the prognosis of glioma by pyroptosis-related signature

Glioma is the most common malignant primary brain tumour. It is of great significance for the prognosis and personalized treatment of glioma patients to accurate identification of glioma based on biomarkers. Pyroptosis, a kind of programmed cell death, is closely related to tumour progression and tumour immune microenvironment. However, the role of pyroptosis in glioma remained unclear. Herein, we used glioma clinical and expression data from TCGA and CGGA to explore the relationship between pyroptosis and glioma. We first summarized the incidence of copy number variations and somatic mutations of 33 pyroptosis‐related genes and explored prognostic correlation of these genes. Based on pyroptosis‐related genes, three molecular subgroups of glioma related to prognosis were identified. We also found that each subgroup has unique immune and biological behaviours characteristics. Finally, based on 7 pyroptosis‐related genes (CASP3, CASP4, CASP6, CASP8, CASP9, PRKACA and ELANE), we constructed a prognosis model by Lasso and Cox regression, which had a strong predictive power for the overall survival in CGGA test cohort (p < 0.05). In summary, we explored the role of pyroptosis‐related genes in gliomas and the association of these genes with tumour immunity. We found the biomarkers valuable to diagnosis and prognosis, hence, provide reference to the development and treatment of tumorigenesis in glioma.

Mechanisms of cytokine release syndrome and neurotoxicity of CAR T-cell therapy and associated prevention and management strategies

Chimeric antigen receptor (CAR) T-cell therapy has yielded impressive outcomes and transformed treatment algorithms for hematological malignancies. To date, five CAR T-cell products have been approved by the US Food and Drug Administration (FDA). Nevertheless, some significant toxicities pose great challenges to the development of CAR T-cell therapy, most notably cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Understanding the mechanisms underlying these toxicities and establishing prevention and treatment strategies are important. In this review, we summarize the mechanisms underlying CRS and ICANS and provide potential treatment and prevention strategies.

Combination of DNA demethylation and chemotherapy to trigger cell pyroptosis for inhalation treatment of lung cancer

Pyroptosis is an inflammation-dependent and self-cascade amplifying type of programmed cell death, serving as an effective means for activating the local immune response and improving the anticancer efficacy. As the effector of pyroptosis, gasdermin-E (GSDME) is silenced in most tumor cells. The gene silencing can be reversed by DNA demethylation, but the systemic side effects and toxicity of chemotherapeutic agents are inevitable. In this work, inhaled poly(lactic-co-glycolic acid) (PLGA) porous microspheres loaded with Decitabine (DAC) and Doxorubicin (DOX) (denoted as CO-MPs) were prepared to induce cell pyroptosis for orthotopic lung cancer therapy with fewer systemic side effects. The CO-MPs showed a hollow and porous spherical morphology and exhibited an excellent aerodynamic property, lung distribution and a sustained release effect. The CO-MPs could reverse GSDME silencing and elevate the expression of cleaved-caspase 3 in tumor cells. The cleaved-caspase 3 protein cleaved the GSDEM protein to obtain GSDME-N protein, causing the rupture of cell plasma membranes, release of cell contents and activation of the immune system. The CO-MPs could lead to the suppression of lung tumors, the decrease of the lung metastatic nodules in tumor-bearing mice and the induction of immunological memory that provides continuous protection from the tumor rechallenge. The inhalable microspheres loaded with DAC and DOX could be an effective strategy for lung cancer treatment via the pyroptosis mechanism.

Gasdermin D Is a Novel Prognostic Biomarker and Relates to TMZ Response in Glioblastoma

The gasdermin (GSDM) family act as executioners during pyroptosis. However, its expression and biological role in glioma remain to be determined. This study carried out gene expression from six public datasets. Westerns blots and immunohistochemistry (IHC) staining were employed to examine GSDM expression in glioma in an in-house cohort. Kaplan-Meier and Cox regression analyses were performed to evaluate the prognostic role of GSDMs in glioma. Association between gene expression and immune infiltration was assessed by IHC and immunofluorescence (IF) staining of tissue sections. TMZ-induced pyroptosis was assessed by observation of morphological changes, WB and ELISA detection. Only GSDMD expression was upregulated in glioma compared with nontumor brain tissues both in the public datasets and in-house cohort. High GSDMD expression was significantly associated with WHO grade IV, IDH 1/2 wild-type and mesenchymal subtypes. Besides, high GSDMD expression was associated with shorter overall survival and could be used as an independent risk factor for poor outcomes in LGG and GBM. GO enrichment analysis and IHC validation revealed that GSDMD expression might participate in regulating macrophage infiltration and polarization. TMZ treatment induced the pyroptosis in GBM cells and GSDMD expression increased with after treating with TMZ in a time-dependent manner. Moreover, knocking down GSDMD obviously decreased IL-1β expression and reduced TMZ-induced pyroptosis in in vitro. GSDMD was a novel prognostic biomarker, as well as TMZ-treatment response marker in glioma.