Streptococcal pyrogenic exotoxin B cleaves GSDMA and triggers pyroptosis

The intricate pathogenicity of Group A Streptococcus: A comprehensive update

Group A Streptococcus (GAS) is a versatile pathogen that targets human lymphoid, decidual, skin, and soft tissues. Recent advancements have shed light on its airborne transmission, lymphatic spread, and interactions with neuronal systems. GAS promotes severe inflammation through mechanisms involving inflammasomes, IL-1β, and T-cell hyperactivation. Additionally, it secretes factors that directly induce skin necrosis via Gasdermin activation and sustains survival and replication in human blood through sophisticated immune evasion strategies. These include lysis of erythrocytes, using red cell membranes for camouflage, resisting antimicrobial peptides, evading phagocytosis, escaping from neutrophil extracellular traps (NETs), inactivating chemokines, and cleaving targeted antibodies. GAS also employs molecular mimicry to traverse connective tissues undetected and exploits the host's fibrinolytic system, which contributes to its stealth and potential for causing autoimmune conditions after repeated infections. Secreted toxins disrupt host cell membranes, enhancing intracellular survival and directly activating nociceptor neurons to induce pain. Remarkably, GAS possesses mechanisms for precise genome editing to defend against phages, and its fibrinolytic capabilities have found applications in medicine. Immune responses to GAS are paradoxical: robust responses to its virulence factors correlate with more severe disease, whereas recurrent infections often show diminished immune reactions. This review focuses on the multifaceted virulence of GAS and introduces novel concepts in understanding its pathogenicity.

Cleavage of cell junction proteins as a host invasion strategy in leptospirosis

Infection and invasion are the prerequisites for developing the disease symptoms in a host. While the probable mechanism of host invasion and pathogenesis is known in many pathogens, very little information is available on Leptospira invasion/pathogenesis. For causing systemic infection Leptospira must transmigrate across epithelial barriers, which is the most critical and challenging step. Extracellular and membrane-bound proteases play a crucial role in the invasion process. An extensive search for the proteins experimentally proven to be involved in the invasion process through cell junction cleavage in other pathogens has resulted in identifying 26 proteins. The similarity searches on the Leptospira genome for counterparts of these 26 pathogenesis-related proteins identified at least 12 probable coding sequences. The proteins were either extracellular or membrane-bound with a proteolytic domain to cleave the cell junction proteins. This review will emphasize our current understanding of the pathogenic aspects of host cell junction-pathogenic protein interactions involved in the invasion process. Further, potential candidate proteins with cell junction cleavage properties that may be exploited in the diagnostic/therapeutic aspects of leptospirosis will also be discussed. KEY POINTS: • The review focussed on the cell junction cleavage proteins in bacterial pathogenesis • Cell junction disruptors from Leptospira genome are identified using bioinformatics • The review provides insights into the therapeutic/diagnostic interventions possible.

GSDME promotes MASLD by regulating pyroptosis, Drp1 citrullination-dependent mitochondrial dynamic, and energy balance in intestine and liver

Dysregulated metabolism, cell death, and inflammation contribute to the development of metabolic dysfunction-associated steatohepatitis (MASH). Pyroptosis, a recently identified form of programmed cell death, is closely linked to inflammation. However, the precise role of pyroptosis, particularly gasdermin-E (GSDME), in MASH development remains unknown. In this study, we observed GSDME cleavage and GSDME-associated interleukin-1β (IL-1β)/IL-18 induction in liver tissues of MASH patients and MASH mouse models induced by a choline-deficient high-fat diet (CDHFD) or a high-fat/high-cholesterol diet (HFHC). Compared with wild-type mice, global GSDME knockout mice exhibited reduced liver steatosis, steatohepatitis, fibrosis, endoplasmic reticulum stress, lipotoxicity and mitochondrial dysfunction in CDHFD- or HFHC-induced MASH models. Moreover, GSDME knockout resulted in increased energy expenditure, inhibited intestinal nutrient absorption, and reduced body weight. In the mice with GSDME deficiency, reintroduction of GSDME in myeloid cells-rather than hepatocytes-mimicked the MASH pathologies and metabolic dysfunctions, as well as the changes in the formation of neutrophil extracellular traps and hepatic macrophage/monocyte subclusters. These subclusters included shifts in Tim4+ or CD163+ resident Kupffer cells, Ly6Chi pro-inflammatory monocytes, and Ly6CloCCR2loCX3CR1hi patrolling monocytes. Integrated analyses of RNA sequencing and quantitative proteomics revealed a significant GSDME-dependent reduction in citrullination at the arginine-114 (R114) site of dynamin-related protein 1 (Drp1) during MASH. Mutation of Drp1 at R114 reduced its stability, impaired its ability to redistribute to mitochondria and regulate mitophagy, and ultimately promoted its degradation under MASH stress. GSDME deficiency reversed the de-citrullination of Drp1R114, preserved Drp1 stability, and enhanced mitochondrial function. Our study highlights the role of GSDME in promoting MASH through regulating pyroptosis, Drp1 citrullination-dependent mitochondrial function, and energy balance in the intestine and liver, and suggests that GSDME may be a potential therapeutic target for managing MASH.

NLRP3 targets HMGB1 to exacerbate the pyroptosis of canine corneal epithelial cells infected with Staphylococcus pseudintermedius

PURPOSE

This study focused on the mechanisms of pyroptosis and oxidative damage exacerbation by NOD-like receptor thermal protein domain associated protein 3 (NLRP3) during the infection of canine corneal epithelial cells (CCECs) with Staphylococcus pseudintermedius.

METHODS

The CCECs treated with dimethyl fumarate (DMF), recombinant high mobility group protein 1 (HMGB1), or N-acetylcysteine (NAC). The gasdermin (GSDM) family and HMGB1 mRNA expression levels were detected using quantitative reverse transcription polymerase chain reaction. Lactate dehydrogenase activity, bacterial counts, the pyroptosis rate, reactive oxygen species (ROS) content, and antioxidant enzyme activity were used to reflect pyroptosis and oxidation level.

RESULTS

Regulation of NLRP3 significantly affected the pyroptosis rate and GSDMD-N expression levels during S. pseudintermedius infection. Inhibition of GSDMD-N protein activation by DMF reversed the exacerbation of pyroptosis induced by NLRP3 overexpression and reduced the levels of cleaved interleukin-1β (IL-1β), cleaved cysteinyl aspartate-specific protease-1, and NLRP3. In addition, NLRP3 was found to target the HMGB1 promoter and regulate its protein expression, to increase ROS accumulation and GSDMD-N expression levels, and activate the NLRP3-HMGB1-ROS-GSDMD signaling axis to aggravate pyroptosis during infection.

CONCLUSIONS

NLRP3 aggravates pyroptosis and oxidative damage associated with the activation of NLRP3-GSDMD and NLRP3-HMGB1-ROS-GSDMD signaling pathways during the infection of CCECs with S. pseudintermedius.

Small-molecule GSDMD agonism in tumors stimulates antitumor immunity without toxicity

Gasdermin-mediated inflammatory cell death (pyroptosis) can activate protective immunity in immunologically cold tumors. Here, we performed a high-throughput screen for compounds that could activate gasdermin D (GSDMD), which is expressed widely in tumors. We identified 6,7-dichloro-2-methylsulfonyl-3-N-tert-butylaminoquinoxaline (DMB) as a direct and selective GSDMD agonist that activates GSDMD pore formation and pyroptosis without cleaving GSDMD. In mouse tumor models, pulsed and low-level pyroptosis induced by DMB suppresses tumor growth without harming GSDMD-expressing immune cells. Protection is immune-mediated and abrogated in mice lacking lymphocytes. Vaccination with DMB-treated cancer cells protects mice from secondary tumor challenge, indicating that immunogenic cell death is induced. DMB treatment synergizes with anti-PD-1. DMB treatment does not alter circulating proinflammatory cytokine or leukocyte numbers or cause weight loss. Thus, our studies reveal a strategy that relies on a low level of tumor cell pyroptosis to induce antitumor immunity and raise the possibility of exploiting pyroptosis without causing overt toxicity.

Seneca Valley virus circumvents Gasdermin A-mediated inflammation by targeting the pore-formation domain for cleavage

Members of the gasdermin (GSDM) family are critical for inducing programmable pyroptosis by forming pores on the cell membrane. GSDMB, GSDMC, GSDMD, and GSDME are activated by caspases or granzyme, leading to the release of their autoinhibitory domains. The protease SpeB from group A Streptococcus has been shown to cleave and activate GSDMA-mediated pyroptosis. Meanwhile, African Swine Fever Virus infection regulates pyroptosis by cleaving porcine GSDMA (pGSDMA) via active caspase-3 and caspase-4. However, it is not known whether virus-encoded proteases also target GSDMA. Here, we show that residues 1-252 of pGSDMA (pGSDMA1-252) is the pore-forming fragment that induces lytic cell death and pyroptosis. Interestingly, Seneca Valley Virus (SVV) infection induces the cleavage of both pGSDMA and human GSDMA and suppresses GSDMA-mediated cell death. Mechanistically, SVV protease 3C cleaves pGSDMA between Q187 and G188 to generate a shorter fragment, pGSDMA1-186, which fails to induce lytic cell death and lactate dehydrogenase release. Furthermore, pGSDMA1-186 does not localize to the plasma membrane and does not induce cell death, thereby promoting viral replication by suppressing host immune responses. These studies reveal a sophisticated evolutionary adaptation of SVV to bypass GSDMA-mediated pyroptosis, allowing it to overcome host inflammatory defenses.

IMPORTANCE

Gasdermin A (GSDMA) remains a protein shrouded in mystery, particularly regarding its regulation by virus-encoded proteases. Previous studies have identified human GSDMA (hGSDMA) as a sensor and substrate of the SpeB from group A Streptococcus, which initiates pyroptosis. However, it is not clear if viral proteases also cleave GSDMA. In this study, we show that a fragment of porcine GSDMA (pGSDMA) containing the first 252 residues constitutes the pore-forming domain responsible for inducing lytic cell death and pyroptosis. Interestingly, picornavirus Seneca Valley Virus (SVV) protease 3C cleaves both pGSDMA and hGSDMA, generating a shorter fragment that fails to associate with the plasma membrane and does not induce pyroptosis. This cleavage by SVV 3C suppresses GSDMA-mediated lactate dehydrogenase release, bactericidal activity, and lytic cell death. This study reveals how SVV subverts host inflammatory defense by disrupting GSDMA-induced pyroptosis, thereby advancing our understanding of antiviral immunity and opening avenues for treating GSDMA-associated autoimmune diseases.

FeSA‐Ir/Metallene Nanozymes Induce Sequential Ferroptosis‐Pyroptosis for Multi‐Immunogenic Responses Against Lung Metastasis

For cancer metastasis inhibition, the combining of nanozymes with immune checkpoint blockade (ICB) therapy remains the major challenge in controllable reactive oxygen species (ROS) generation for creating effective immunogenicity. Herein, new nanozymes with light-controlled ROS production in terms of quantity and variety are developed by conjugating supramolecular-wrapped Fe single atom on iridium metallene with lattice-strained nanoislands (FeSA-Ir@PF NSs). The Fenton-like catalysis of FeSA-Ir@PF NSs effectively produced •OH radicals in dark, which induced ferroptosis and apoptosis of cancer cells. While under second near-infrared (NIR-II) light irradiation, FeSA-Ir@PF NSs showed ultrahigh photothermal conversion efficiency (𝜂, 75.29%), cooperative robust •OH generation, photocatalytic O2 and 1O2 generation, and caused significant pyroptosis of cancer cells. The controllable ROS generation, sequential cancer cells ferroptosis and pyroptosis, led 99.1% primary tumor inhibition and multi-immunogenic responses in vivo. Most importantly, the inhibition of cancer lung metastasis is completely achieved by FeSA-Ir@PF NSs with immune checkpoint inhibitors, as demonstrated in different mice lung metastasis models, including circulating tumor cells (CTCs) model. This work provided new inspiration for developing nanozymes for cancer treatments and metastasis inhibition.

Overview of pyroptosis mechanism and in-depth analysis of cardiomyocyte pyroptosis mediated by NF-κB pathway in heart failure

The pyroptosis of cardiomyocytes has become an essential topic in heart failure research. The abnormal accumulation of these biological factors, including angiotensin II, advanced glycation end products, and various growth factors (such as connective tissue growth factor, vascular endothelial growth factor, transforming growth factor beta, among others), activates the nuclear factor-κB (NF-κB) signaling pathway in cardiovascular diseases, ultimately leading to pyroptosis of cardiomyocytes. Therefore, exploring the underlying molecular biological mechanisms is essential for developing novel drugs and therapeutic strategies. However, our current understanding of the precise regulatory mechanism of this complex signaling pathway in cardiomyocyte pyroptosis is still limited. Given this, this study reviews the milestone discoveries in the field of pyroptosis research since 1986, analyzes in detail the similarities, differences, and interactions between pyroptosis and other cell death modes (such as apoptosis, necroptosis, autophagy, and ferroptosis), and explores the deep connection between pyroptosis and heart failure. At the same time, it depicts in detail the complete pathway of the activation, transmission, and eventual cardiomyocyte pyroptosis of the NF-κB signaling pathway in the process of heart failure. In addition, the study also systematically summarizes various therapeutic approaches that can inhibit NF-κB to reduce cardiomyocyte pyroptosis, including drugs, natural compounds, small molecule inhibitors, gene editing, and other cutting-edge technologies, aiming to provide solid scientific support and new research perspectives for the prevention and treatment of heart failure.

Cisplatin induces acute liver injury by triggering caspase-3/GSDME-mediated cell pyroptosis

BACKGROUND

Cisplatin triggers Gasdermin E (GSDME) cleavage, causing membrane bubble formation, content release, and inflammation. Caspase-3 activation initiates GSDME cleavage, and thus inhibiting this pathway mitigates cisplatin-induced pyroptosis in hepatocytes. This study aimed to delve into how cisplatin induces liver injury via pyroptosis.

METHODS

For animal experiments, C57BL/6J mice were divided into three groups: control, liver injury model group, and Ac-DMLD-CMK (caspase-3 inhibitor) intervention group. The liver histology was evaluated by hematoxylin and eosin staining, immunohistochemistry, immunofluorescence and TUNEL staining. The mRNA and protein levels were detected by real-time polymerase chain reaction (PCR) and Western blot analysis. For in vitro experiments, HL-7702 cells were treated with cisplatin or GSDME siRNA. Cell pyroptosis was determined via cellular morphology, cytotoxicity and viability detection, flow cytometric assay, and Western blot detection for the expression of pyroptosis-related proteins.

RESULTS

Cisplatin-induced distinct liver morphological changes, hepatocellular injury, and inflammation in mice, along with elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and increased pro-inflammatory cytokine expression. Heightened macrophage infiltration and hepatocellular death indicated cisplatin-induced hepatotoxicity. Cisplatin upregulated GSDME activation, along with Bax-mediated caspase-3 cleavage both in vivo and in vitro, implicating caspase-3/GSDME-dependent pyroptosis in liver injury. Treatment with Ac-DMLD-CMK ameliorated cisplatin-induced liver injury, reducing hepatocellular lesions, serum ALT and AST levels, cytokine expression, macrophage infiltration, and hepatocyte death. Ac-DMLD-CMK also attenuated GSDME-dependent pyroptosis post-cisplatin induction, as evidenced by decreased GSDME expression, Bax upregulation, and cleaved caspase-3 activation. For HL-7702 cells, GSDME siRNA transfection reduced GSDME expression, attenuated typical signs of cisplatin-induced pyroptosis, partially restored cell viability, and significantly inhibited cytotoxicity and a decrease in the proportion of propidium iodide-positive cells, indicating protection against cisplatin-induced hepatocyte pyroptosis.

CONCLUSION

Our study underscores the role of the caspase-3/GSDME signaling pathway in mediating cisplatin-induced hepatotoxicity, particularly in cases of excessive or cumulative cisplatin exposure. These findings suggest that targeting GSDME could represent a promising therapeutic approach to mitigate cisplatin-induced liver damage.

Pyroptosis in lung cancer: The emerging role of non-coding RNAs

Lung cancer remains an intractable malignancy worldwide, prompting novel therapeutic modalities. Pyroptosis, a lethal form of programmed cell death featured by inflammation, has been involved in cancer progression and treatment response. Simultaneously, non-coding RNA has been shown to have important roles in coordinating pattern formation and oncogenic pathways, including long non-coding RNA (lncRNAs), microRNA (miRNAs), circular RNA (circRNAs), and small interfering RNA (siRNAs). Recent studies have revealed that ncRNAs can promote or inhibit pyroptosis by interacting with key molecular players such as NLRP3, GSDMD, and various transcription factors. This dual role of ncRNAs offers a unique therapeutic potential to manipulate pyroptosis pathways, providing opportunities for innovative cancer treatments. In this review, we integrate current research findings to propose novel strategies for leveraging ncRNA-mediated pyroptosis as a therapeutic intervention in lung cancer. We explore the potential of ncRNAs as biomarkers for predicting patient response to treatment and as targets for overcoming resistance to conventional therapies.

RACK1 and NEK7 mediate GSDMD-dependent macrophage pyroptosis upon Streptococcus suis infection

Streptococcus suis serotype 2 (SS2) is an important zoonotic pathogen that induces an NLRP3-dependent cytokine storm. NLRP3 inflammasome activation triggers not only an inflammatory response but also pyroptosis. However, the exact mechanism underlying S. suis-induced macrophage pyroptosis is not clear. Our results showed that SS2 induced the expression of pyroptosis-associated factors, including lactate dehydrogenase (LDH) release, propidium iodide (PI) uptake and GSDMD-N expression, as well as NLRP3 inflammasome activation and IL-1β secretion. However, GSDMD deficiency and NLRP3 inhibition using MCC950 attenuated the SS2-induced expression of pyroptosis-associated factors, suggesting that SS2 induces NLRP3-GSDMD-dependent pyroptosis. Furthermore, RACK1 knockdown also reduced the expression of pyroptosis-associated factors. In addition, RACK1 knockdown downregulated the expression of NLRP3 and Pro-IL-1β as well as the phosphorylation of P65. Surprisingly, the interaction between RACK1 and P65 was detected by co-immunoprecipitation, indicating that RACK1 induces macrophage pyroptosis by mediating the phosphorylation of P65 to promote the transcription of NLRP3 and pro-IL-1β. Similarly, NEK7 knockdown decreased the expression of pyroptosis-associated factors and ASC oligomerization. Moreover, the results of co-immunoprecipitation revealed the interaction of NEK7-RACK1-NLRP3 during SS2 infection, demonstrating that NEK7 mediates SS2-induced pyroptosis via the regulation of NLRP3 inflammasome assembly and activation. These results demonstrate the important role of RACK1 and NEK7 in SS2-induced pyroptosis. Our study provides new insight into SS2-induced cell death.

Starvation-induced phosphorylation activates gasdermin A to initiate pyroptosis

Pyroptosis, a pro-inflammatory form of programmed cell death, is crucial for host defense against pathogens and danger signals. Proteolytic cleavage of gasdermin proteins B-E (GSDMB-GSDME) is well established as a trigger for pyroptosis, but the intracellular activation mechanism of GSDMA remains elusive. Here, we demonstrate that severe starvation induces pyroptosis through phosphorylation-induced activation of GSDMA. Nutrient stresses stimulate GSDMA activation via phosphorylation mediated by Unc-51-like autophagy-activating kinase 1 (ULK1). Phosphorylation of Ser353 on human GSDMA by ULK1 or the phospho-mimetic Ser353Asp mutant of GSDMA liberates GSDMA from auto-inhibition, facilitating its membrane targeting and initiation of pyroptosis. To further validate the significance of GSDMA phosphorylation, we generated a constitutively active mutant Ser354Asp of mouse Gsdma, which induced skin inflammation and hyperplasia in mice, reminiscent of phenotypes with activated Gsdma. This study uncovers phosphorylation of GSDMA as a mechanism underlying pyroptosis initiation and cellular response to nutrient stress.

Pyroptosis in health and disease: mechanisms, regulation and clinical perspective

Pyroptosis is a type of programmed cell death characterized by cell swelling and osmotic lysis, resulting in cytomembrane rupture and release of immunostimulatory components, which play a role in several pathological processes. Significant cellular responses to various stimuli involve the formation of inflammasomes, maturation of inflammatory caspases, and caspase-mediated cleavage of gasdermin. The function of pyroptosis in disease is complex but not a simple angelic or demonic role. While inflammatory diseases such as sepsis are associated with uncontrollable pyroptosis, the potent immune response induced by pyroptosis can be exploited as a therapeutic target for anti-tumor therapy. Thus, a comprehensive review of the role of pyroptosis in disease is crucial for further research and clinical translation from bench to bedside. In this review, we summarize the recent advancements in understanding the role of pyroptosis in disease, covering the related development history, molecular mechanisms including canonical, non-canonical, caspase 3/8, and granzyme-mediated pathways, and its regulatory function in health and multiple diseases. Moreover, this review also provides updates on promising therapeutic strategies by applying novel small molecule inhibitors and traditional medicines to regulate pyroptosis. The present dilemmas and future directions in the landscape of pyroptosis are also discussed from a clinical perspective, providing clues for scientists to develop novel drugs targeting pyroptosis.

Cell Death: Mechanisms and Potential Targets in Breast Cancer Therapy

Breast cancer (BC) has become the most life-threatening cancer to women worldwide, with multiple subtypes, poor prognosis, and rising mortality. The molecular heterogeneity of BC limits the efficacy and represents challenges for existing therapies, mainly due to the unpredictable clinical response, the reason for which probably lies in the interactions and alterations of diverse cell death pathways. However, most studies and drugs have focused on a single type of cell death, while the therapeutic opportunities related to other cell death pathways are often neglected. Therefore, it is critical to identify the predominant type of cell death, the transition to different cell death patterns during treatment, and the underlying regulatory mechanisms in BC. In this review, we summarize the characteristics of various forms of cell death, including PANoptosis (pyroptosis, apoptosis, necroptosis), autophagy, ferroptosis, and cuproptosis, and discuss their triggers and signaling cascades in BC, which may provide a reference for future pathogenesis research and allow for the development of novel targeted therapeutics in BC.

Pyroptosis, gasdermins and allergic diseases

Pyroptosis is an inflammatory form of programmed cell death that is distinct from necrosis and apoptosis. Pyroptosis is primarily mediated by the gasdermin family of proteins (GSDMA-E and PVJK), which, when activated by proteolytic cleavage, form pores in the plasma membrane, leading to cell death. While much of the past research on pyroptosis has focused on its role in cancer, metabolic disorders, and infectious diseases, recent experimental and observational studies have begun to implicate pyroptosis in allergic diseases. These studies suggest that gasdermin-mediated pyroptosis contributes to the development of allergic conditions and could offer novel targets for therapy. Here, we review our current understanding of pyroptosis with an emphasis on the role of gasdermins as executioners of pyroptosis and potential mediators to allergic disease. We highlight new discoveries that establish a mechanistic link between the biochemical actions of gasdermins and the onset of allergic diseases. Additionally, we discuss how pyroptosis and gasdermins might contribute to the dysfunction of epithelial barrier, a key factor believed to initiate the progression of various allergic diseases.

Gasdermins as evolutionarily conserved executors of inflammation and cell death

The gasdermins are a family of pore-forming proteins that have recently emerged as executors of pyroptosis, a lytic form of cell death that is induced by the innate immune system to eradicate infected or malignant cells. Mammalian gasdermins comprise a cytotoxic N-terminal domain, a flexible linker and a C-terminal repressor domain. Proteolytic cleavage in the linker releases the cytotoxic domain, thereby allowing it to form β-barrel membrane pores. Formation of gasdermin pores in the plasma membrane eventually leads to a loss of the electrochemical gradient, cell death and membrane rupture. Here we review recent work that has expanded our understanding of gasdermin biology and function in mammals by revealing their activation mechanism, their regulation and their roles in autoimmunity, host defence and cancer. We further highlight fungal and bacterial gasdermin pore formation pointing to a conserved mechanism of cell death induction.

Cell life-or-death events in osteoporosis: All roads lead to mitochondrial dynamics

Mitochondria exhibit heterogeneous shapes and networks within and among cell types and tissues, also in normal or osteoporotic bone tissues with complex cell types. This dynamic characteristic is determined by the high plasticity provided by mitochondrial dynamics and is stemmed from responding to the survival and functional requirements of various bone cells in a specific microenvironments. In contrast, mitochondrial dysfunction, induced by dysregulation of mitochondrial dynamics, may act as a trigger of cell death signals, including common apoptosis and other forms of programmed cell death (PCD). These PCD processes consisting of tightly structured cascade gene expression events, can further influence the bone remodeling by facilitating the death of various bone cells. Mitochondrial dynamics, therefore, drive the bone cells to stand at the crossroads of life and death by integrating external signals and altering metabolism, shape, and signal-response properties of mitochondria. This implies that targeting mitochondrial dynamics displays significant potential in treatment of osteoporosis. Considerable effort has been made in osteoporosis to emphasize the parallel roles of mitochondria in regulating energy metabolism, calcium signal transduction, oxidative stress, inflammation, and cell death. However, the emerging field of mitochondrial dynamics-related PCD is not well understood. Herein, to bridge the gap, we outline the latest knowledge on mitochondrial dynamics regulating bone cell life or death during normal bone remodeling and osteoporosis.

Pyroptosis in Skeleton Diseases: A Potential Therapeutic Target Based on Inflammatory Cell Death

Skeletal disorders, including fractures, osteoporosis, osteoarthritis, rheumatoid arthritis, and spinal degenerative conditions, along with associated spinal cord injuries, significantly impair daily life and impose a substantial burden. Many of these conditions are notably linked to inflammation, with some classified as inflammatory diseases. Pyroptosis, a newly recognized form of inflammatory cell death, is primarily triggered by inflammasomes and executed by caspases, leading to inflammation and cell death through gasdermin proteins. Emerging research underscores the pivotal role of pyroptosis in skeletal disorders. This review explores the pyroptosis signaling pathways and their involvement in skeletal diseases, the modulation of pyroptosis by other signals in these conditions, and the current evidence supporting the therapeutic potential of targeting pyroptosis in treating skeletal disorders, aiming to offer novel insights for their management.

Gasdermin-E-mediated pyroptosis drives immune checkpoint inhibitor-associated myocarditis via cGAS-STING activation

Immune checkpoint inhibitor (ICI)-induced myocarditis involves intensive immune/inflammation activation; however, its molecular basis is unclear. Here, we show that gasdermin-E (GSDME), a gasdermin family member, drives ICI-induced myocarditis. Pyroptosis mediated by GSDME, but not the canonical GSDMD, is activated in myocardial tissue of mice and cancer patients with ICI-induced myocarditis. Deficiency of GSDME in male mice alleviates ICI-induced cardiac infiltration of T cells, macrophages, and monocytes, as well as mitochondrial damage and inflammation. Restoration of GSDME expression specifically in cardiomyocytes, rather than myeloid cells, in GSDME-deficient mice reproduces ICI-induced myocarditis. Mechanistically, quantitative proteomics reveal that GSDME-dependent pyroptosis promotes cell death and mitochondrial DNA release, which in turn activates cGAS-STING signaling, triggering a robust interferon response and myocardial immune/inflammation activation. Pharmacological blockade of GSDME attenuates ICI-induced myocarditis and improves long-term survival in mice. Our findings may advance the understanding of ICI-induced myocarditis and suggest that targeting the GSDME-cGAS-STING-interferon axis may help prevent and manage ICI-associated myocarditis.

Insight into the structure, function and the tumor suppression effect of gasdermin E

Gasdermin E (GSDME), which is also known as DFNA5, was first identified as a deafness-related gene that is expressed in cochlear hair cells, and mutation of this gene causes autosomal dominant neurogenic hearing loss. Later studies revealed that GSDME is mostly expressed in the kidney, placenta, muscle and brain cells, but it is expressed at low levels in tumor cells. The GSDME gene encodes the GSDME protein, which is a member of the gasdermin (GSDM) family and has been shown to participate in the induction of apoptosis and pyroptosis. The current literature suggests that Caspase-3 and Granzyme B (Gzm B) can cleave GSDME to generate the active N-terminal fragment (GSDME-NT), which integrates with the cell membrane and forms pores in this membrane to induce pyroptosis. Furthermore, GSDME also forms pores in mitochondrial membranes to release apoptosis factors, such as cytochrome c (Cyt c) and high-temperature requirement protein A2 (HtrA2/Omi), and subsequently activates the intrinsic apoptosis pathway. In recent years, GSDME has been shown to exert tumor-suppressive effects, suggesting that it has potential therapeutic effects on tumors. In this review, we introduce the structure and function of GSDME and the mechanism by which it induces cell death, and we discuss its tumor suppressive effect.

Gut Dysbiosis Drives Inflammatory Bowel Disease Through the CCL4L2-VSIR Axis in Glycogen Storage Disease

Patients with glycogen storage disease type Ib (GSD-Ib) frequently have inflammatory bowel disease (IBD). however, the underlying etiology remains unclear. Herein, this study finds that digestive symptoms are commonly observed in patients with GSD-Ib, presenting as single or multiple scattered deep round ulcers, inflammatory pseudo-polyps, obstructions, and strictures, which differ substantially from those in typical IBD. Distinct microbiota profiling and single-cell clustering of colonic mucosae in patients with GSD are conducted. Heterogeneous oral pathogenic enteric outgrowth induced by GSD is a potent inducer of gut microbiota immaturity and colonic macrophage accumulation. Specifically, a unique population of macrophages with high CCL4L2 expression is identified in response to pathogenic bacteria in the intestine. Hyper-activation of the CCL4L2-VSIR axis leads to increased expression of AGR2 and ZG16 in epithelial cells, which mediates the unique progression of IBD in GSD-Ib. Collectively, the microbiota-driven pathomechanism of IBD is demonstrated in GSD-Ib and revealed the active role of the CCL4L2-VSIR axis in the interaction between the microbiota and colonic mucosal immunity. Thus, targeting gut dysbiosis and/or the CCL4L2-VISR axis may represent a potential therapy for GSD-associated IBD.

Enhanced pyroptosis induction with pore-forming gene delivery for osteosarcoma microenvironment reshaping

Osteosarcoma is the most common malignant bone tumor without efficient management for improving 5-year event-free survival. Immunotherapy is also limited due to its highly immunosuppressive tumor microenvironment (TME). Pore-forming gasdermins (GSDMs)-mediated pyroptosis has gained increasing concern in reshaping TME, however, the expressions and relationships of GSDMs with osteosarcoma remain unclear. Herein, gasdermin E (GSDME) expression is found to be positively correlated with the prognosis and immune infiltration of osteosarcoma patients, and low GSDME expression was observed. A vector termed as LPAD contains abundant hydroxyl groups for hydrating layer formation was then prepared to deliver the GSDME gene to upregulate protein expression in osteosarcoma for efficient TME reshaping via enhanced pyroptosis induction. Atomistic molecular dynamics simulations analysis proved that the hydroxyl groups increased LPAD hydration abilities by enhancing coulombic interaction. The upregulated GSDME expression together with cleaved caspase-3 provided impressive pyroptosis induction. The pyroptosis further initiated proinflammatory cytokines release, increased immune cell infiltration, activated adaptive immune responses and create a favorable immunogenic hot TME. The study not only confirms the role of GSDME in the immune infiltration and prognosis of osteosarcoma, but also provides a promising strategy for the inhibition of osteosarcoma by pore-forming GSDME gene delivery induced enhanced pyroptosis to reshape the TME of osteosarcoma.

The role of pyroptosis in metabolism and metabolic disease

Pyroptosis is a lytic and pro-inflammatory form of regulated cell death characterized by the formation of membrane pores mediated by the gasdermin protein family. Two main activation pathways have been documented: the caspase-1-dependent canonical pathway and the caspase-4/5/11-dependent noncanonical pathway. Pyroptosis leads to cell swelling, lysis, and the subsequent release of inflammatory mediators, including interleukin-1β (IL-1β) and interleukin-18 (IL-18). Chronic inflammation is a well-established foundation and driver for the development of metabolic diseases. Conversely, metabolic pathway dysregulation can also induce cellular pyroptosis. Recent studies have highlighted the significant role of pyroptosis modulation in various metabolic diseases, including type 2 diabetes mellitus, obesity, and metabolic (dysfunction) associated fatty liver disease. These findings suggest that pyroptosis may serve as a promising novel therapeutic target for metabolic diseases. This paper reviews an in-depth study of the current advancements in understanding the role of pyroptosis in the progression of metabolic diseases.

Depletion of Gsdma1/2/3 alleviates PMA-induced epidermal hyperplasia by inhibiting the EGFR-Stat3/Akt pathway

Homeostasis of the skin barrier is essential for maintaining normal skin function. Gasdermin A (GSDMA) is highly expressed in the skin and associated with many skin diseases, such as melanoma and psoriasis. In mice, GSDMA is encoded by three gene homologues, namely Gsdma1, Gsdma2, and Gsdma3. Although Gsdma3 gain-of-function mutations cause hair loss and skin inflammation, Gsdma3-deficient mice do not show any visible phenotypes in skin and hair structures. To explore the physiological function of GSDMA, we generated conventional Gsdma1/2/3 knockout (KO) mice. These mice showed significantly alleviated epidermal hyperplasia and inflammation induced by phorbol 12-myristate 13-acetate (PMA). Furthermore, the alleviation of epidermal hyperplasia depended on the expression of Gsdma1/2/3 specifically in keratinocytes. Mechanistically, Gsdma1/2/3 depletion downregulated epidermal growth factor receptor (EGFR) ligands, leading to the decreased EGFR-Stat3/Akt signalling. These results demonstrate that depletion of Gsdma1/2/3 alleviates PMA-induced epidermal hyperplasia partially by inhibiting the EGFR-Stat3/Akt pathway.

Gasdermin A (GSDMA) Tissue Expression, Serum and Urinary Concentrations with Clinicopathologic Outcome in Psoriasis

INTRODUCTION

Psoriasis is a frequent and incurable skin disease that is an important issue in contemporary dermatology, although its pathogenesis is still uncertain. Gasdermin A (GSDMA) is a member of the gasdermin protein family which are able to cause pore formation in cellular membranes leading to cell death called pyroptosis.

OBJECTIVE

Our aim was to investigate the role of GSDMA in psoriatic patients.

METHOD

The study enrolled 60 patients with active plaque-type psoriasis and 30 sex- and age-matched volunteers without dermatoses. GSDMA concentration was assessed in serum and urine samples of all participants using ELISA. GSDMA tissue expression was assessed by immunohistochemistry.

RESULTS

GSDMA serum concentration was significantly higher in patients compared to controls, whereas urinary GSDMA/creatinine ratio was insignificantly lower. GSDMA tissue expression was more prominent in psoriatic plaque compared to non-lesional patients' skin and healthy skin of subjects without dermatoses. There was a strong negative correlation between GSDMA serum concentration and ALT activity. GSDMA did not correlate with PASI or psoriasis duration.

CONCLUSIONS

Obtained results point to the probable involvement of GSDMA in psoriasis. GSDMA overexpression may probably lead to keratinocytes hyperproliferation and be responsible for triggering inflammation in psoriatic skin. Serum GSDMA could become psoriasis biomarker, whereas urinary GSDMA, not at this point.

ROS induced pyroptosis in inflammatory disease and cancer

Pyroptosis, a form of caspase-1-dependent cell death, also known as inflammation-dependent death, plays a crucial role in diseases such as stroke, heart disease, or tumors. Since its elucidation, pyroptosis has attracted widespread attention from various sectors. Reactive oxygen species (ROS) can regulate numerous cellular signaling pathways. Through further research on ROS and pyroptosis, the level of ROS has been revealed to be pivotal for the occurrence of pyroptosis, establishing a close relationship between the two. This review primarily focuses on the molecular mechanisms of ROS and pyroptosis in tumors and inflammatory diseases, exploring key proteins that may serve as drug targets linking ROS and pyroptosis and emerging fields targeting pyroptosis. Additionally, the potential future development of compounds and proteins that influence ROS-regulated cell pyroptosis is anticipated, aiming to provide insights for the development of anti-tumor and anti-inflammatory drugs.

A genomic association study revealing subphenotypes of childhood steroid-sensitive nephrotic syndrome in a larger genomic sequencing cohort

Dissecting the genetic components that contribute to the two main subphenotypes of steroid-sensitive nephrotic syndrome (SSNS) using genome-wide association studies (GWAS) strategy is important for understanding the disease. We conducted a multicenter cohort study (360 patients and 1835 controls) combined with a GWAS strategy to identify susceptibility variants associated with the following two subphenotypes of SSNS: steroid-sensitive nephrotic syndrome without relapse (SSNSWR, 181 patients) and steroid-dependent/frequent relapse nephrotic syndrome (SDNS/FRNS, 179 patients). The distribution of two single-nucleotide polymorphisms (SNPs) in ANKRD36 and ALPG was significant between SSNSWR and healthy controls, and that of two SNPs in GAD1 and HLA-DQA1 was significant between SDNS/FRNS and healthy controls. Interestingly, rs1047989 in HLA-DQA1 was a candidate locus for SDNS/FRNS but not for SSNSWR. No significant SNPs were observed between SSNSWR and SDNS/FRNS. Meanwhile, chromosome 2:171713702 in GAD1 was associated with a greater steroid dose (>0.75 mg/kg/d) upon relapse to first remission in patients with SDNS/FRNS (odds ratio = 3.14; 95% confidence interval, 0.97-9.87; P = 0.034). rs117014418 in APOL4 was significantly associated with a decrease in eGFR of greater than 20% compared with the baseline in SDNS/FRNS patients (P = 0.0001). Protein-protein intersection network construction suggested that HLA-DQA1 and HLA-DQB1 function together through GSDMA. Thus, SSNSWR belongs to non-HLA region-dependent nephropathy, and the HLA-DQA/DQB region is likely strongly associated with disease relapse, especially in SDNS/FRNS. The study provides a novel approach for the GWAS strategy of SSNS and contributes to our understanding of the pathological mechanisms of SSNSWR and SDNS/FRNS.

MiPRIME: an integrated and intelligent platform for mining primer and probe sequences of microbial species

MOTIVATION

Accurately detecting pathogenic microorganisms requires effective primers and probe designs. Literature-derived primers are a valuable resource as they have been tested and proven effective in previous research. However, manually mining primers from published texts is time-consuming and limited in species scop.

RESULTS

To address these challenges, we have developed MiPRIME, a real-time Microbial Primer Mining platform for primer/probe sequences extraction of pathogenic microorganisms with three highlights: (i) comprehensive integration. Covering >40 million articles and 548 942 organisms, the platform enables high-frequency microbial gene discovery from a global perspective, facilitating user-defined primer design and advancing microbial research. (ii) Using a BioBERT-based text mining model with 98.02% accuracy, greatly reducing information processing time. (iii) Using a primer ranking score, PRscore, for intelligent recommendation of species-specific primers. Overall, MiPRIME is a practical tool for primer mining in the pan-microbial field, saving time and cost of trial-and-error experiments.

AVAILABILITY AND IMPLEMENTATION

The web is available at {{https://www.ai-bt.com}}.

Burning down the house: Pyroptosis in the tumor microenvironment of hepatocellular carcinoma

A high mortality rate makes hepatocellular carcinoma (HCC) a difficult cancer to treat. When surgery is not possible, liver cancer patients are treated with chemotherapy. However, HCC management and treatment are difficult. Sorafenib, which is a first-line treatment for hepatocellular carcinoma, initially slows disease progression. However, sorafenib resistance limits patient survival. Recent studies have linked HCC to programmed cell death, which has increased researcher interest in therapies targeting cell death. Pyroptosis, which is an inflammatory mode of programmed cell death, may be targeted to treat HCC. Pyroptosis pathways, executors, and effects are examined in this paper. This review summarizes how pyroptosis affects the tumor microenvironment (TME) in HCC, including the role of cytokines such as IL-1β and IL-18 in regulating immune responses. The use of chemotherapies and their ability to induce cancer cell pyroptosis as alternative treatments and combining them with other drugs to reduce side effects is also discussed. In conclusion, we highlight the potential of inducing pyroptosis to treat HCC and suggest ways to improve patient outcomes. Studies on cancer cell pyroptosis may lead to new HCC treatments.

Pyroptosis: A spoiler of peaceful coexistence between cells in degenerative bone and joint diseases

BACKGROUND

As people age, degenerative bone and joint diseases (DBJDs) become more prevalent. When middle-aged and elderly people are diagnosed with one or more disorders such as osteoporosis (OP), osteoarthritis (OA), and intervertebral disc degeneration (IVDD), it often signals the onset of prolonged pain and reduced functionality. Chronic inflammation has been identified as the underlying cause of various degenerative diseases, including DBJDs. Recently, excessive activation of pyroptosis, a form of programed cell death (PCD) mediated by inflammasomes, has emerged as a primary driver of harmful chronic inflammation. Consequently, pyroptosis has become a potential target for preventing and treating DBJDs.

AIM OF REVIEW

This review explored the physiological and pathological roles of the pyroptosis pathway in bone and joint development and its relation to DBJDs. Meanwhile, it elaborated the molecular mechanisms of pyroptosis within individual cell types in the bone marrow and joints, as well as the interplay among different cell types in the context of DBJDs. Furthermore, this review presented the latest compelling evidence supporting the idea of regulating the pyroptosis pathway for DBJDs treatment, and discussed the potential, limitations, and challenges of various therapeutic strategies involving pyroptosis regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In summary, an interesting identity for the unregulated pyroptosis pathway in the context of DBJDs was proposed in this review, which was undertaken as a spoiler of peaceful coexistence between cells in a degenerative environment. Over the extended course of DBJDs, pyroptosis pathway perpetuated its activity through crosstalk among pyroptosis cascades in different cell types, thus exacerbating the inflammatory environment throughout the entire bone marrow and joint degeneration environment. Correspondingly, pyroptosis regulation therapy emerged as a promising option for clinical treatment of DBJDs.

Nanomaterials Enhance Pyroptosis-Based Tumor Immunotherapy

Pyroptosis, a pro-inflammatory and lytic programmed cell death pathway, possesses great potential for antitumor immunotherapy. By releasing cellular contents and a large number of pro-inflammatory factors, tumor cell pyroptosis can promote dendritic cell maturation, increase the intratumoral infiltration of cytotoxic T cells and natural killer cells, and reduce the number of immunosuppressive cells within the tumor. However, the efficient induction of pyroptosis and prevention of damage to normal tissues or cells is an urgent concern to be addressed. Recently, a wide variety of nanoplatforms have been designed to precisely trigger pyroptosis and activate the antitumor immune responses. This review provides an update on the progress in nanotechnology for enhancing pyroptosis-based tumor immunotherapy. Nanomaterials have shown great advantages in triggering pyroptosis by delivering pyroptosis initiators to tumors, increasing oxidative stress in tumor cells, and inducing intracellular osmotic pressure changes or ion imbalances. In addition, the challenges and future perspectives in this field are proposed to advance the clinical translation of pyroptosis-inducing nanomedicines.

Pyroptosis mediates osteoporosis via the inflammation immune microenvironment

Osteoporosis represents a systemic imbalance in bone metabolism, augmenting the susceptibility to fractures among patients and emerging as a notable mortality determinant in the elderly population. It has evolved into a worldwide concern impacting the physical well-being of the elderly, imposing a substantial burden on both human society and the economy. Presently, the precise pathogenesis of osteoporosis remains inadequately characterized and necessitates further exploration. The advancement of osteoporosis is typically linked to the initiation of an inflammatory response. Cells in an inflammatory environment can cause inflammatory death including pyroptosis. Pyroptosis is a recently identified form of programmed cell death with inflammatory properties, mediated by the caspase and gasdermin families. It is regarded as the most inflammatory form of cell death in contemporary medical research. Under the influence of diverse cytokines, macrophages, and other immune cells may undergo pyroptosis, releasing inflammatory factors, such as IL-1β and IL-18. Numerous lines of evidence highlight the pivotal role of pyroptosis in the pathogenesis of inflammatory diseases, including cancer, intestinal disorders, hepatic conditions, and cutaneous ailments. Osteoporosis progression is frequently associated with inflammation; hence, pyroptosis may also play a role in the pathogenesis of osteoporosis to a certain extent, making it a potential target for treatment. This paper has provided a comprehensive summary of pertinent research concerning pyroptosis and its impact on osteoporosis. The notion proposing that pyroptosis mediates osteoporosis via the inflammatory immune microenvironment is advanced, and we subsequently investigate potential targets for treating osteoporosis through the modulation of pyroptosis.

African swine fever virus infection regulates pyroptosis by cleaving gasdermin A via active caspase-3 and caspase-4

African swine fever, caused by the African swine fever virus (ASFV), is a viral hemorrhagic disease that affects domestic pigs and wild boars. ASFV infection causes extensive tissue damage, and the associated mechanism is poorly understood. Pyroptosis is characterized by the activation of inflammatory caspases and pore formation in the cellular plasma membrane, resulting in the release of inflammatory cytokines and cell damage. How ASFV infection regulates pyroptosis remains unclear. Here, using siRNA assay and overexpression methods, we report that ASFV infection regulated pyroptosis by cleaving the pyroptosis execution protein gasdermin A (GSDMA). ASFV infection activated caspase-3 and caspase-4, which specifically cleaved GSDMA at D75-P76 and D241-V242 to produce GSDMA into five fragments, including GSDMA-N1-75, GSDMA-N1-241, and GSDMA-N76-241 fragments at the N-terminal end of GSDMA. Only GSDMA-N1-241, which was produced in the late stage of ASFV infection, triggered pyroptosis and inhibited ASFV replication. The fragments, GSDMA-N1-75 and GSDMA-N76-241, lose the ability to induce pyroptosis. Overall ASFV infection differentially regulates pyroptosis by GSDMA in the indicated phase, which may be conducive to its own replication. Our findings reveal a novel molecular mechanism for the regulation of pyroptosis.

Cleavage of gasdermin by apoptotic caspases triggers pyroptosis restricting bacterial colonization in Hydra

Gasdermin (GSDM) proteins, as the direct executors of pyroptosis, are structurally and functionally conserved among vertebrates and play crucial roles in host defense against infection, inflammation, and cancer. However, the origin of functional GSDMs remains elusive in the animal kingdom. Here, we found that functional GSDME homologs first appeared in the cnidarian. Moreover, these animal GSDME homologs share evolutionarily conserved apoptotic caspase cleavage sites. Thus, we verified the functional conservation of apoptotic caspase-GSDME cascade in Hydra, a representative species of cnidarian. Unlike vertebrate GSDME homologs, HyGSDME could be cleaved by four Hydra caspase homologs with caspase-3 activity at two sites. Furthermore, in vivo activation of Hydra caspases resulted in HyGSDME cleavage to induce pyroptosis, exacerbating injury and restricting bacterial burden, which protects Hydra from pathogen invasion. In conclusion, these results suggest that GSDME-dependent pyroptosis may be an ancient and conserved host defense mechanism, which may contribute to better understanding on the origin and evolution of GSDMs.

Inflammasome-independent pyroptosis

Gasdermins are membrane pore-forming proteins that cause pyroptosis, an inflammatory cell death in which cells burst and release cytokines, chemokines, and other host alarm signals, such as ATP and HMGB1, which recruit and activate immune cells at sites of infection and danger. There are five gasdermins in humans - gasdermins A to E. Pyroptosis was first described in myeloid cells and mucosal epithelia, which express gasdermin D and activate it when cytosolic sensors of invasive infection or tissue damage assemble into large macromolecular structures, called inflammasomes. Inflammasomes recruit and activate inflammatory caspases (caspase 1, 4, 5, and 11), which cut gasdermin D to remove an inhibitory C-terminal domain, allowing the N-terminal domain to bind to membrane acidic lipids and oligomerize into pores. Recent studies have identified inflammasome-independent proteolytic pathways that activate gasdermin D and the other gasdermins. Here, we review inflammasome-independent pyroptosis pathways and what is known about their role in normal physiology and disease.

Cell Membrane Perforation: Patterns, Mechanisms and Functions

Cell membrane is crucial for the cellular activities, and any disruption to it may affect the cells. It is demonstrated that cell membrane perforation is associated with some biological processes like programmed cell death (PCD) and infection of pathogens. Specific developments make it a promising technique to perforate the cell membrane controllably and precisely. The pores on the cell membrane provide direct pathways for the entry and exit of substances, and can also cause cell death, which means reasonable utilization of cell membrane perforation is able to assist intracellular delivery, eliminate diseased or cancerous cells, and bring about other benefits. This review classifies the patterns of cell membrane perforation based on the mechanisms into 1) physical patterns, 2) biological patterns, and 3) chemical patterns, introduces the characterization methods and then summarizes the functions according to the characteristics of reversible and irreversible pores, with the aim of providing a comprehensive summary of the knowledge related to cell membrane perforation and enlightening broad applications in biomedical science.

Chicken gasdermins mediate pyroptosis after the cleavage by caspases

Gasdermin (GSDM) proteins are executioners of pyroptosis in many species. Gasdermin proteins can be cleaved at their linker region between the amino domain (NT) and carboxyl domain (CT) by enzymes. The released GSDM-NTs bind cell membrane and form pores, thereby leading to the release of cellular components and lytic cell death. GSDM-mediated pyroptosis is considered to play important role in immune responses. However, little is known about the GSDM proteins and GSDM-mediated pyroptosis in birds. In the current study, genes encoding chicken gasdermin A (chGSDMA) and chGSDME were cloned. The cleavage of chGSDMA and chGSDME by chicken caspase-1 (chCASP1), chCASP3 and chCASP7 and the cleavage sites were determined. The chGSDMA-NT obtained form chCASP1-mediated cleavage and chGSDME-NT obtained from chCASP3/chCASP7-mediated cleavage could bind and damage cell membrane and lead to cell death of HEK293 cells. chGSDMA-NT also strongly localized to and formed puncta in nucleus. Besides, both chGSDMA-NT and chGSDME-NT showed growth inhibition and bactericidal activity to bacteria. In chickens challenged with Pasteurella multocida and Salmonella typhimurium, the expression of chGSDMA and chGSDME was upregulated and the activation of chCASP3 and the cleavage of chGSDME were observed. The work provides essential information for expanding our knowledge on pyroptosis in birds.

Inflammasomes in epithelial innate immunity: front line warriors

Our epithelium represents a battle ground against a variety of insults including pathogens and danger signals. It encodes multiple sensors that detect and respond to such insults, playing an essential role in maintaining and defending tissue homeostasis. One key set of defense mechanisms is our inflammasomes which drive innate immune responses including, sensing and responding to pathogen attack, through the secretion of pro-inflammatory cytokines and cell death. Identification of physiologically relevant triggers for inflammasomes has greatly influenced our ability to decipher the mechanisms behind inflammasome activation. Furthermore, identification of patient mutations within inflammasome components implicates their involvement in a range of epithelial diseases. This review will focus on exploring the roles of inflammasomes in epithelial immunity and cover: the diversity and differential expression of inflammasome sensors amongst our epithelial barriers, their ability to sense local infection and damage and the contribution of the inflammasomes to epithelial homeostasis and disease.

ROS-dependent S-palmitoylation activates cleaved and intact gasdermin D

Gasdermin D (GSDMD) is the common effector for cytokine secretion and pyroptosis downstream of inflammasome activation and was previously shown to form large transmembrane pores after cleavage by inflammatory caspases to generate the GSDMD N-terminal domain (GSDMD-NT)1-10. Here we report that GSDMD Cys191 is S-palmitoylated and that palmitoylation is required for pore formation. S-palmitoylation, which does not affect GSDMD cleavage, is augmented by mitochondria-generated reactive oxygen species (ROS). Cleavage-deficient GSDMD (D275A) is also palmitoylated after inflammasome stimulation or treatment with ROS activators and causes pyroptosis, although less efficiently than palmitoylated GSDMD-NT. Palmitoylated, but not unpalmitoylated, full-length GSDMD induces liposome leakage and forms a pore similar in structure to GSDMD-NT pores shown by cryogenic electron microscopy. ZDHHC5 and ZDHHC9 are the major palmitoyltransferases that mediate GSDMD palmitoylation, and their expression is upregulated by inflammasome activation and ROS. The other human gasdermins are also palmitoylated at their N termini. These data challenge the concept that cleavage is the only trigger for GSDMD activation. They suggest that reversible palmitoylation is a checkpoint for pore formation by both GSDMD-NT and intact GSDMD that functions as a general switch for the activation of this pore-forming family.

The role of pyroptosis in heart failure and related traditional chinese medicine treatments

Pyroptosis is a type of programmed cell death that is mediated by both typical and atypical pathways and ultimately leads to the lysis and rupture of cell membranes and the release of proinflammatory factors, triggering an intense inflammatory response. Heart failure (HF) is a serious and terminal stage of various heart diseases. Myocardial hypertrophy, myocardial fibrosis, ventricular remodeling, oxidative stress, the inflammatory response and cardiomyocyte ionic disorders caused by various cardiac diseases are all risk factors for and aggravate HF. Numerous studies have shown that pyroptosis can induce and exacerbate these reactions, causing progression to HF. Therefore, targeting pyroptosis is a promising strategy to treat HF. This paper summarizes the role of pyroptosis in the development of HF and the underlying mechanism involved. Recent research progress on the ability of traditional Chinese medicine (TCM) extracts and formulas to inhibit pyroptosis and treat HF was summarized, and some traditional Chinese medicine extracts and formulas can alleviate different types of HF, including heart failure with preserved ejection fraction (HFpEF), heart failure with reduced ejection fraction (HFrEF), and heart failure with midrange ejection fraction (HFmrEF), by targeting pyroptosis. These findings may provide new ideas and evidence for the treatment or adjuvant treatment of HF by targeting pyroptosis.

Synthetic protein circuits for programmable control of mammalian cell death

Natural cell death pathways such as apoptosis and pyroptosis play dual roles: they eliminate harmful cells and modulate the immune system by dampening or stimulating inflammation. Synthetic protein circuits capable of triggering specific death programs in target cells could similarly remove harmful cells while appropriately modulating immune responses. However, cells actively influence their death modes in response to natural signals, making it challenging to control death modes. Here, we introduce naturally inspired "synpoptosis" circuits that proteolytically regulate engineered executioner proteins and mammalian cell death. These circuits direct cell death modes, respond to combinations of protease inputs, and selectively eliminate target cells. Furthermore, synpoptosis circuits can be transmitted intercellularly, offering a foundation for engineering synthetic killer cells that induce desired death programs in target cells without self-destruction. Together, these results lay the groundwork for programmable control of mammalian cell death.

Strategies of bacterial detection by inflammasomes

Mammalian innate immunity is regulated by pattern-recognition receptors (PRRs) and guard proteins, which use distinct strategies to detect infections. PRRs detect bacterial molecules directly, whereas guards detect host cell manipulations by microbial virulence factors. Despite sensing infection through different mechanisms, both classes of innate immune sensors can activate the inflammasome, an immune complex that can mediate cell death and inflammation. Inflammasome-mediated immune responses are crucial for host defense against many bacterial pathogens and prevent invasion by non-pathogenic organisms. In this review, we discuss the mechanisms by which inflammasomes are stimulated by PRRs and guards during bacterial infection, and the strategies used by virulent bacteria to evade inflammasome-mediated immunity.

Intraepithelial mast cells drive gasdermin C-mediated type 2 immunity

A specialized population of mast cells residing within epithelial layers, currently known as intraepithelial mast cells (IEMCs), was originally observed over a century ago, yet their physiological functions have remained enigmatic. In this study, we unveil an unexpected and crucial role of IEMCs in driving gasdermin C-mediated type 2 immunity. During helminth infection, αEβ7 integrin-positive IEMCs engaged in extensive intercellular crosstalk with neighboring intestinal epithelial cells (IECs). Through the action of IEMC-derived proteases, gasdermin C proteins intrinsic to the epithelial cells underwent cleavage, leading to the release of a critical type 2 cytokine, interleukin-33 (IL-33). Notably, mast cell deficiency abolished the gasdermin C-mediated immune cascade initiated by epithelium. These findings shed light on the functions of IEMCs, uncover a previously unrecognized phase of type 2 immunity involving mast cell-epithelial cell crosstalk, and advance our understanding of the cellular mechanisms underlying gasdermin C activation.

Autism risk gene Cul3 alters neuronal morphology via caspase-3 activity in mouse hippocampal neurons

Autism Spectrum Disorders (ASDs) are neurodevelopmental disorders (NDDs) in which children display differences in social interaction/communication and repetitive stereotyped behaviors along with variable associated features. Cul3, a gene linked to ASD, encodes CUL3 (CULLIN-3), a protein that serves as a key component of a ubiquitin ligase complex with unclear function in neurons. Cul3 homozygous deletion in mice is embryonic lethal; thus, we examine the role of Cul3 deletion in early synapse development and neuronal morphology in hippocampal primary neuronal cultures. Homozygous deletion of Cul3 significantly decreased dendritic complexity and dendritic length, as well as axon formation. Synaptic spine density significantly increased, mainly in thin and stubby spines along with decreased average spine volume in Cul3 knockouts. Both heterozygous and homozygous knockout of Cul3 caused significant reductions in the density and colocalization of gephyrin/vGAT puncta, providing evidence of decreased inhibitory synapse number, while excitatory synaptic puncta vGulT1/PSD95 density remained unchanged. Based on previous studies implicating elevated caspase-3 after Cul3 deletion, we demonstrated increased caspase-3 in our neuronal cultures and decreased neuronal cell viability. We then examined the efficacy of the caspase-3 inhibitor Z-DEVD-FMK to rescue the decrease in neuronal cell viability, demonstrating reversal of the cell viability phenotype with caspase-3 inhibition. Studies have also implicated caspase-3 in neuronal morphological changes. We found that caspase-3 inhibition largely reversed the dendrite, axon, and spine morphological changes along with the inhibitory synaptic puncta changes. Overall, these data provide additional evidence that Cul3 regulates the formation or maintenance of cell morphology, GABAergic synaptic puncta, and neuronal viability in developing hippocampal neurons in culture.

Correlation of gasdermin B staining patterns with prognosis, progression, and immune response in colorectal cancer

BACKGROUND

Pyroptosis is a type of programmed cell death mediated by the gasdermin family. Gasdermin B (GSDMB), as a member of gasdermin family, can promote the occurrence of cell pyroptosis. However, the correlations of the GSDMB expression in colorectal cancer with clinicopathological predictors, immune microenvironment, and prognosis are unclear.

METHODS

Specimens from 267 colorectal cancer cases were analyzed by immunohistochemistry to determine GSDMB expression, CD3+, CD4+, and CD8+ T lymphocytes, CD20+ B lymphocytes, CD68+ macrophages, and S100A8+ immune cells. GSDMB expression in cancer cells was scored in the membrane, cytoplasm, and nucleus respectively. GSDMB+ immune cell density was calculated. Univariate and multivariate survival analyses were performed. The association of GSDMB expression with other clinicopathological variables and immune cells were also analyzed. Double immunofluorescence was used to identify the nature of GSDMB+ immune cells. Cytotoxicity assays and sensitivity assays were performed to detect the sensitivity of cells to 5-fluorouracil.

RESULTS

Multivariate survival analysis showed that cytoplasmic GSDMB expression was an independent favorable prognostic indicator. Patients with positive cytoplasmic or nuclear GSDMB expression would benefit from 5-fluorouracil based chemotherapy. The assays in vitro showed that high GSDMB expression enhanced the sensitivity of colorectal cancer cells to 5-fluorouracil. Patients with positive membranous or nuclear GSDMB expression had more abundant S100A8+ immune cells in the tumor invasive front. Positive nuclear GSDMB expression indicated more CD68+ macrophages in the tumor microenvironment. Moreover, GSDMB+ immune cell density in the stroma was associated with a higher neutrophil percentage but a lower lymphocyte counts and monocyte percentage in peripheral blood. Furthermore, the results of double immunofluorescence showed that GSDMB co-expressed with CD68 or S100A8 in stroma cells.

CONCLUSION

The GSDMB staining patterns are linked to its role in cancer progression, the immune microenvironment, systemic inflammatory response, chemotherapeutic efficacy, and prognosis. Colorectal cancer cells with high GSDMB expression are more sensitive to 5-fluorouracil. However, GSDMB expression in immune cells has different effects on cancer progression from that in cancer cells.

Crosstalk between cancer-associated fibroblasts and regulated cell death in tumors: insights into apoptosis, autophagy, ferroptosis, and pyroptosis

Cancer-associated fibroblasts (CAFs), the main stromal component of the tumor microenvironment (TME), play multifaceted roles in cancer progression through paracrine signaling, exosome transfer, and cell interactions. Attractively, recent evidence indicates that CAFs can modulate various forms of regulated cell death (RCD) in adjacent tumor cells, thus involving cancer proliferation, therapy resistance, and immune exclusion. Here, we present a brief introduction to CAFs and basic knowledge of RCD, including apoptosis, autophagy, ferroptosis, and pyroptosis. In addition, we further summarize the different types of RCD in tumors that are mediated by CAFs, as well as the effects of these modes of RCD on CAFs. This review will deepen our understanding of the interactions between CAFs and RCD and might offer novel therapeutic avenues for future cancer treatments.

The gasdermin family: emerging therapeutic targets in diseases

The gasdermin (GSDM) family has garnered significant attention for its pivotal role in immunity and disease as a key player in pyroptosis. This recently characterized class of pore-forming effector proteins is pivotal in orchestrating processes such as membrane permeabilization, pyroptosis, and the follow-up inflammatory response, which are crucial self-defense mechanisms against irritants and infections. GSDMs have been implicated in a range of diseases including, but not limited to, sepsis, viral infections, and cancer, either through involvement in pyroptosis or independently of this process. The regulation of GSDM-mediated pyroptosis is gaining recognition as a promising therapeutic strategy for the treatment of various diseases. Current strategies for inhibiting GSDMD primarily involve binding to GSDMD, blocking GSDMD cleavage or inhibiting GSDMD-N-terminal (NT) oligomerization, albeit with some off-target effects. In this review, we delve into the cutting-edge understanding of the interplay between GSDMs and pyroptosis, elucidate the activation mechanisms of GSDMs, explore their associations with a range of diseases, and discuss recent advancements and potential strategies for developing GSDMD inhibitors.

Gasdermin-E-Dependent Non-Canonical Pyroptosis Promotes Drug-Induced Liver Failure by Promoting CPS1 deISGylation and Degradation

Drug-induced liver injury (DILI) is a significant global health issue that poses high mortality and morbidity risks. One commonly observed cause of DILI is acetaminophen (APAP) overdose. GSDME is an effector protein that induces non-canonical pyroptosis. In this study, the activation of GSDME, but not GSDMD, in the liver tissue of mice and patients with APAP-DILI is reported. Knockout of GSDME, rather than GSDMD, in mice protected them from APAP-DILI. Mice with hepatocyte-specific rescue of GSDME reproduced APAP-induced liver injury. Furthermore, alterations in the immune cell pools observed in APAP-induced DILI, such as the replacement of TIM4+ resident Kupffer cells (KCs) by monocyte-derived KCs, Ly6C+ monocyte infiltration, MerTk+ macrophages depletion, and neutrophil increase, reappeared in mice with hepatocyte-specific rescue of GSDME. Mechanistically, APAP exposure led to a substantial loss of interferon-stimulated gene 15 (ISG15), resulting in deISGylation of carbamoyl phosphate synthetase-1 (CPS1), promoted its degradation via K48-linked ubiquitination, causing ammonia clearance dysfunction. GSDME deletion prevented these effects. Delayed administration of dimethyl-fumarate inhibited GSDME cleavage and alleviated ammonia accumulation, mitigating liver injury. This findings demonstrated a previously uncharacterized role of GSDME in APAP-DILI by promoting pyroptosis and CPS1 deISGylation, suggesting that inhibiting GSDME can be a promising therapeutic option for APAP-DILI.

Caspase-1 activates gasdermin A in non-mammals

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

Selective induction of programmed cell death using synthetic biology tools

Regulated cell death (RCD) controls the removal of dispensable, infected or malignant cells, and is thus essential for development, homeostasis and immunity of multicellular organisms. Over the last years different forms of RCD have been described (among them apoptosis, necroptosis, pyroptosis and ferroptosis), and the cellular signaling pathways that control their induction and execution have been characterized at the molecular level. It has also become apparent that different forms of RCD differ in their capacity to elicit inflammation or an immune response, and that RCD pathways show a remarkable plasticity. Biochemical and genetic studies revealed that inhibition of a given pathway often results in the activation of back-up cell death mechanisms, highlighting close interconnectivity based on shared signaling components and the assembly of multivalent signaling platforms that can initiate different forms of RCD. Due to this interconnectivity and the pleiotropic effects of 'classical' cell death inducers, it is challenging to study RCD pathways in isolation. This has led to the development of tools based on synthetic biology that allow the targeted induction of RCD using chemogenetic or optogenetic methods. Here we discuss recent advances in the development of such toolset, highlighting their advantages and limitations, and their application for the study of RCD in cells and animals.