Biological mechanisms and therapeutic relevance of the gasdermin family

Gasdermins: a dual role in pyroptosis and tumor immunity

The gasdermin (GSDM) protein family plays a pivotal role in pyroptosis, a process critical to the body's immune response, particularly in combatting bacterial infections, impeding tumor invasion, and contributing to the pathogenesis of various inflammatory diseases. These proteins are adept at activating inflammasome signaling pathways, recruiting immune effector cells, creating an inflammatory immune microenvironment, and initiating pyroptosis. This article serves as an introduction to the GSDM protein-mediated pyroptosis signaling pathways, providing an overview of GSDMs' involvement in tumor immunity. Additionally, we explore the potential applications of GSDMs in both innovative and established antitumor strategies.

The pathogenesis and potential therapeutic targets in sepsis

Sepsis is defined as "a life-threatening organ dysfunction caused by dysregulated host systemic inflammatory and immune response to infection." At present, sepsis continues to pose a grave healthcare concern worldwide. Despite the use of supportive measures in treating traditional sepsis, such as intravenous fluids, vasoactive substances, and oxygen plus antibiotics to eradicate harmful pathogens, there is an ongoing increase in both the morbidity and mortality associated with sepsis during clinical interventions. Therefore, it is urgent to design specific pharmacologic agents for the treatment of sepsis and convert them into a novel targeted treatment strategy. Herein, we provide an overview of the molecular mechanisms that may be involved in sepsis, such as the inflammatory response, immune dysfunction, complement deactivation, mitochondrial damage, and endoplasmic reticulum stress. Additionally, we highlight important targets involved in sepsis-related regulatory mechanisms, including GSDMD, HMGB1, STING, and SQSTM1, among others. We summarize the latest advancements in potential therapeutic drugs that specifically target these signaling pathways and paramount targets, covering both preclinical studies and clinical trials. In addition, this review provides a detailed description of the crosstalk and function between signaling pathways and vital targets, which provides more opportunities for the clinical development of new treatments for sepsis.

Functional roles of CcGSDMEa-like in common carp (Cyprinus carpio) after Aeromonas hydrophila infection

GSDMs could punch holes in cell membrane and participate in the immune response to bacterial infections. In current study, the molecular and structural characteristics of CcGSDMEa-like were analyzed, and the role of CcGSDMEa-like in the inflammatory response against Aeromonas hydrophila was studied. The results showed that the CcGSDMEa-like shared the conserved structural characteristics with GSDMEs of other teleosts. The CcGSDMEa-like mRNA and protein expression levels were significantly affected by A. hydrophila challenge. When the CcGSDMEa-like was overexpressed, the expression of CcIL-1β were significantly increased in fish and EPC cells, and bacterial contents were significantly decreased in fish tissues. While, when the CcGSDMEa-like was knocked down, the expression and secretion of CcIL-1β were significantly decreased in vivo and in vitro, and the bacterial contents were increased in vivo after A. hydrophila infection 12 h and 24 h. In brief, CcGSDMEa-like could regulate the content of bacteria in fish through mediating the expression and secretion of CcIL-1β. Bactericidal assay and cytotoxicity assay showed that CcGSDMEa-like had no bactericidal activity to Escherichia coli, and did not disrupt cytomembrane integrity of HEK293T cells. This study suggested that CcGSDMEa-like could play roles in the antibacterial and inflammatory processes in fish.

Roles of pyroptosis in atherosclerosis pathogenesis

Pyroptosis is a pro-inflammatory type of regulated cell death (RCD) characterized by gasdermin protein-mediated membrane pore formation, cell swelling, and rapid lysis. Recent studies have suggested that pyroptosis is closely related to atherosclerosis (AS). Previous studies reported that pyroptosis involving endothelial cells (ECs), macrophages, and smooth muscle cells (SMCs) plays an important role in the formation and development of AS. Pyroptosis not only causes local inflammation but also amplifies the inflammatory response and it aggravates plaque instability, leading to plaque rupture and thrombosis, eventually resulting in acute cardiovascular events. In this review, we clarified some novel pathways and mechanics and presented some potential drugs.

Precise Orchestration of Gasdermins' Pore-Forming Function by Posttranslational Modifications in Health and Disease

Gasdermins (GSDMs) serve as pivotal executors of pyroptosis and play crucial roles in host defence, cytokine secretion, innate immunity, and cancer. However, excessive or inappropriate GSDMs activation is invariably accompanied by exaggerated inflammation and results in tissue damage. In contrast, deficient or impaired activation of GSDMs often fails to promptly eliminate pathogens, leading to the increasing severity of infections. The activity of GSDMs requires meticulous regulation. The dynamic modulation of GSDMs involves many aspects, including autoinhibitory structures, proteolytic cleavage, lipid binding and membrane translocation (oligomerization and pre-pore formation), oligomerization (pore formation) and pore removal for membrane repair. As the most comprehensive and efficient regulatory pathway, posttranslational modifications (PTMs) are widely implicated in the regulation of these aspects. In this comprehensive review, we delve into the complex mechanisms through which a variety of proteases cleave GSDMs to enhance or hinder their function. Moreover, we summarize the intricate regulatory mechanisms of PTMs that govern GSDMs-induced pyroptosis.

Activation Mechanism of CcGSDMEb-1/2 and Regulation for Bacterial Clearance in Common Carp (Cyprinus carpio)

Gasdermin E (GSDME), to date, is considered the only direct executor of the pyroptosis process in teleost and plays an important role in innate immunity. In common carp (Cyprinus carpio), there contains two pairs of GSDME (GSDMEa/a-like and GSDMEb-1/2), and the pyroptotic function and regulation mechanism of GSDME still remain unclear. In this study, we identified two GSDMEb genes of common carp (CcGSDMEb-1/2), which contain a conserved N-terminal pore-forming domain, C-terminal autoinhibitory domain, and a flexible and pliable hinge region. We investigated the function and mechanism of CcGSDMEb-1/2 in association with inflammatory and apoptotic caspases in Epithelioma papulosum cyprinid cells and discovered that only CcCaspase-1b could cleave CcGSDMEb-1/2 through recognizing the sites 244FEVD247 and 244FEAD247 in the linker region, respectively. CcGSDMEb-1/2 exerted toxicity to human embryonic kidney 293T cells and bactericidal activity through its N-terminal domain. Interestingly, after i.p. infection by Aeromonas hydrophila, we found that CcGSDMEb-1/2 were upregulated in immune organs (head kidney and spleen) at the early stage of infection, but downregulated in mucosal immune tissues (gill and skin). After CcGSDMEb-1/2 were knocked down and overexpressed in vivo and in vitro, respectively, we found that CcGSDMEb-1/2 could govern the secretion of CcIL-1β and regulate the bacterial clearance after A. hydrophila challenge. Taken together, in this study, it was demonstrated that the cleavage mode of CcGSDMEb-1/2 in common carp was obviously different from that in other species and played an important role in CcIL-1β secretion and bacterial clearance.

Pyroptosis Modulators: New Insights of Gasdermins in Health and Disease

Pyroptosis is an inflammation-dependent type of cell death that has been in the spotlight for the scientific community in the last few years. Crucial players in the process of pyroptosis are the members of the gasdermin family of proteins, which have been parallelly studied. Upon induction of pyroptosis, gasdermins suffer from structural changes leading to the formation of pores in the membrane that subsequently cause the release of pro-inflammatory contents. Recently, it has been discovered that oxidation plays a key role in the activation of certain gasdermins. Here, we review the current knowledge on pyroptosis and human gasdermins, focusing on the description of the different members of the family, their molecular structures, and their influence on health and disease directly or non-directly related to inflammation. Noteworthy, we have focused on the existing understanding of the role of this family of proteins in cancer, which could translate into novel promising strategies aimed at benefiting human health. In conclusion, the modulation of pyroptosis and gasdermins by natural and synthetic compounds through different mechanisms, including modification of the redox state of cells, has been proven effective and sets precedents for future therapeutic strategies.

Gasdermin D-mediated pyroptosis: mechanisms, diseases, and inhibitors

Gasdermin D (GSDMD)-mediated pyroptosis and downstream inflammation are important self-protection mechanisms against stimuli and infections. Hosts can defend against intracellular bacterial infections by inducing cell pyroptosis, which triggers the clearance of pathogens. However, pyroptosis is a double-edged sword. Numerous studies have revealed the relationship between abnormal GSDMD activation and various inflammatory diseases, including sepsis, coronavirus disease 2019 (COVID-19), neurodegenerative diseases, nonalcoholic steatohepatitis (NASH), inflammatory bowel disease (IBD), and malignant tumors. GSDMD, a key pyroptosis-executing protein, is linked to inflammatory signal transduction, activation of various inflammasomes, and the release of downstream inflammatory cytokines. Thus, inhibiting GSDMD activation is considered an effective strategy for treating related inflammatory diseases. The study of the mechanism of GSDMD activation, the formation of GSDMD membrane pores, and the regulatory strategy of GSDMD-mediated pyroptosis is currently a hot topic. Moreover, studies of the structure of caspase-GSDMD complexes and more in-depth molecular mechanisms provide multiple strategies for the development of GSDMD inhibitors. This review will mainly discuss the structures of GSDMD and GSDMD pores, activation pathways, GSDMD-mediated diseases, and the development of GSDMD inhibitors.

Inflammasome and pyroptosis in autoimmune liver diseases

Autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and IgG4-related sclerosing cholangitis (IgG4-SC) are the four main forms of autoimmune liver diseases (AILDs), which are all defined by an aberrant immune system attack on the liver. Most previous studies have shown that apoptosis and necrosis are the two major modes of hepatocyte death in AILDs. Recent studies have reported that inflammasome-mediated pyroptosis is critical for the inflammatory response and severity of liver injury in AILDs. This review summarizes our present understanding of inflammasome activation and function, as well as the connections among inflammasomes, pyroptosis, and AILDs, thus highlighting the shared features across the four disease models and gaps in our knowledge. In addition, we summarize the correlation among NLRP3 inflammasome activation in the liver-gut axis, liver injury, and intestinal barrier disruption in PBC and PSC. We summarize the differences in microbial and metabolic characteristics between PSC and IgG4-SC, and highlight the uniqueness of IgG4-SC. We explore the different roles of NLRP3 in acute and chronic cholestatic liver injury, as well as the complex and controversial crosstalk between various types of cell death in AILDs. We also discuss the most up-to-date developments in inflammasome- and pyroptosis-targeted medicines for autoimmune liver disorders.

CcGSDMEa functions the pore-formation in cytomembrane and the regulation on the secretion of IL-lβ in common carp (Cyprinus carpio haematopterus)

GSDME is the only direct executor of caspase-dependent pyroptosis in both canonical and non-canonical inflammasomes known to date in fish, and plays an important role in anti-bacterial infection and inflammatory response. In order to determine the regulation of GSDMEa on antibacterial infection in innate immune response, the CcGSDMEa gene in common carp (Cyprinus carpio haematopterus) was first identified and characterized, and then its function related to immune defense was investigated. Our results showed that the expressions of CcGSDMEa at the mRNA and protein levels were both significantly increased after Aeromonas hydrophila intraperitoneal infection at the early stage than that in the control group. We found that CcGSDMEa could be cleaved by inflammatory caspase (CcCaspase-1b) and apoptotic caspases (CcCaspase-3a/b and CcCaspase-7a/b). Interestingly, only the CcGSDMEa-NT (1-252 aa) displayed bactericidal activity to Escherichia coli and could punch holes in the membrane of HEK293T cells, whereas CcGSDMEa-FL (1-532 aa) and CcGSDMEa-CT (257-532 aa) showed no above activity and pore-forming ability. Overexpression of CcGSDMEa increased the secretion of CcIL-1β and the release of LDH, and could reduce the A. hydrophila burdens in fish. On the contrary, knockdown of CcGSDMEa reduced the secretion of CcIL-1β and the release of LDH, and could increase the A. hydrophila burdens in fish. Taken together, the elevated expression of CcGSDMEa was a positive immune response to A. hydrophila challenge in fish. CcGSDMEa could perform the pore-formation in cell membrane and the regulation on the secretion of IL-lβ, and further regulate the bacterial clearance in vivo. These results suggested that CcGSDMEa played an important role in immune defense against A. hydrophila and could provide a new insight into understanding the immune mechanism to resist pathogen invasion in teleost.

Molecular Characteristics of Cell Pyroptosis and Its Inhibitors: A Review of Activation, Regulation, and Inhibitors

Pyroptosis is an active and ordered form of programmed cell death. The signaling pathways of pyroptosis are mainly divided into canonical pathways mediated by caspase-1 and noncanonical pathways mediated by caspase-11. Cell pyroptosis is characterized by the activation of inflammatory caspases (mainly caspase-1, 4, 5, 11) and cleavage of various members of the Gasdermin family to form membrane perforation components, leading to cell membrane rupture, inflammatory mediators release, and cell death. Moderate pyroptosis is an innate immune response that fights against infection and plays an important role in the occurrence and development of the normal function of the immune system. However, excessive pyroptosis occurs and leads to immune disorders in many pathological conditions. Based on canonical pathways, research on pyroptosis regulation has demonstrated several pyroptotic inhibitors, including small-molecule drugs, natural products, and formulations of traditional Chinese medicines. In this paper, we review the characteristics and molecular mechanisms of pyroptosis, summarize inhibitors of pyroptosis, and propound that herbal medicines should be a focus on the research and development for pyroptosis blockers.

NLRP3 and Gut Microbiota Homeostasis: Progress in Research

The inflammasome is a platform for inflammatory signaling, and the NLRP3 inflammasome recognizes stimuli in vitro and in vivo, and releases inflammatory cytokines that trigger inflammation and pyroptosis. In the gut, the NLRP3 inflammasome is a key sensor for protecting the body from damage and exogenous pathogens. It plays a fundamental role in maintaining the stability of the gut's immune system. We focus on the role of NLRP3 as a key node in maintaining the homeostasis of gut microbiota which has not been fully highlighted in the past; gut microbiota and innate immunity, as well as the NLRP3 inflammasome, are discussed in this article.

GSDMD-mediated pyroptosis in retinal vascular inflammatory diseases: a review

PURPOSE

Pyroptosis is a newly discovered form of programmed pro-inflammatory cell death. The main signaling pathways include the classical scorch death pathway that depends on NLRP3 inflammatory vesicles and other activation caspase-1 and the non-classical scorch death pathway that depends on caspase-4 /5/11. The substrate of all inflammatory caspases is GSDMD; a large number of studies have confirmed that pyroptosis is associated with certain infectious diseases, atherosclerotic diseases, metabolic diseases, and aseptic inflammatory diseases of important organs. In recent years, pyroptosis has been studied partially in the ocular field. So, this article reviews the recent literature intending to help readers understand the main mechanisms of cellular scorch death and the progress of GSDMD-mediated cellular scorch death in retinal vascular inflammatory diseases.

METHOD

A detailed review of the literature related to pyroptosis and inflammatory diseases of the retinal vasculature is presented. The following 6 electronic databases were searched: CNKI, Wanfang, VIP, PubMed, The Cochrane Library, and Embase Databases, and the search period was from the database to May 2022. The main search keywords include "Pyroptosis," " GSDMD," "Retinal Vascular Inflammatory Disease," "Diabetic retinopathy," "Retinal vasculitis." The discovery of pyroptosis, the main molecular mechanisms, key proteins, and their pathogenesis and therapeutic prospects in retinal vasculitis diseases are extensively studied and summarized.

RESULT

The mechanisms of gasdermin D-mediated pyroptosis are elaborated and analyzed, with particular emphasis on their key role and potential in the pathogenesis and treatment of inflammatory retinal vascular lesions.

CONCLUSION

Gasdermin D-mediated pyroptosis is a well-studied form of programmed pro-inflammatory cell death, which has a bidirectional regulatory effect on a variety of immune and inflammatory diseases. The literature reveals that pyroptosis is closely related to the pathogenesis of retinal vascular inflammatory diseases, and it may be an important therapeutic target for diabetic retinopathy and other retinal vasculitis eye diseases in the future.

Nuclear Receptors Linking Metabolism, Inflammation, and Fibrosis in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) and its progressive form nonalcoholic steatohepatitis (NASH) comprise a spectrum of chronic liver diseases in the global population that can lead to end-stage liver disease and hepatocellular carcinoma (HCC). NAFLD is closely linked to the metabolic syndrome, and comorbidities such as type 2 diabetes, obesity and insulin resistance aggravate liver disease, while NAFLD promotes cardiovascular risk in affected patients. The pathomechanisms of NAFLD are multifaceted, combining hepatic factors including lipotoxicity, mechanisms of cell death and liver inflammation with extrahepatic factors including metabolic disturbance and dysbiosis. Nuclear receptors (NRs) are a family of ligand-controlled transcription factors that regulate glucose, fat and cholesterol homeostasis and modulate innate immune cell functions, including liver macrophages. In parallel with metabolic derangement in NAFLD, altered NR signaling is frequently observed and might be involved in the pathogenesis. Therapeutically, clinical data indicate that single drug targets thus far have been insufficient for reaching patient-relevant endpoints. Therefore, combinatorial treatment strategies with multiple drug targets or drugs with multiple mechanisms of actions could possibly bring advantages, by providing a more holistic therapeutic approach. In this context, peroxisome proliferator-activated receptors (PPARs) and other NRs are of great interest as they are involved in wide-ranging and multi-organ activities associated with NASH progression or regression. In this review, we summarize recent advances in understanding the pathogenesis of NAFLD, focusing on mechanisms of cell death, immunometabolism and the role of NRs. We outline novel therapeutic strategies and discuss remaining challenges.

E3 ubiquitin ligase SYVN1 is a key positive regulator for GSDMD-mediated pyroptosis

Gasdermin D (GSDMD) participates in the activation of inflammasomes and pyroptosis. Meanwhile, ubiquitination strictly regulates inflammatory responses. However, how ubiquitination regulates Gasdermin D activity is not well understood. In this study, we show that pyroptosis triggered by Gasdermin D is regulated through ubiquitination. Specifically, SYVN1, an E3 ubiquitin ligase of gasdermin D, promotes GSDMD-mediated pyroptosis. SYVN1 deficiency inhibits pyroptosis and subsequent LDH release and PI uptake. SYVN1 directly interacts with GSDMD, and mediates K27-linked polyubiquitination of GSDMD on K203 and K204 residues, promoting GSDMD-induced pyroptotic cell death. Thus, our findings revealed the essential role of SYVN1 in GSDMD-mediated pyroptosis. Overall, GSDMD ubiquitination is a potential therapeutic module for inflammatory diseases.

IL-37 blocks gouty inflammation by shaping macrophages into a non-inflammatory phagocytic phenotype

OBJECTIVE

Interleukin (IL)-37 is a natural suppressor of inflammation. Macrophages play an important role in acute gout flare by dominating the inflammation and spontaneous relief. We have reported IL-37 could limit runaway inflammation in gout. Here we focus on whether IL-37 inhibits gouty inflammation by altering macrophage functions and how it does.

METHODS

Macrophage functions were evaluated in terms of phagocytosis, pyroptosis, polarization, and metabolism. Phagocytosis and polarization of macrophages were detected by side scattering and double-labelling iNOS/Arg-1 using flow cytometry, respectively. Transcription of pyroptosis-related molecules was detected by qPCR. Metabolomics was performed by liquid chromatograph mass spectrometer. Human IL-37 knock-in mice and a model with point mutation (S9A) at mouse Gsk3b locus were created by CRISPR/Cas-mediated genome engineering. MSU was injected into paws and peritoneal cavity to model acute gout. Vernier caliper was used to measure the thickness of the paws. The mice paws and human synovium tissues or tophi were collected for pathological staining. Peritoneal fluid of mice was used to enrich macrophages to detect polarization.

RESULTS

IL-37 promoted non-inflammatory phagocytic activity of macrophages, by enhancing phagocytosis of MSU, reducing pyroptosis-related proteins transcription and inflammatory cytokines releasing, protecting mitochondrial function, and mediating metabolic reprogramming in MSU-treated THP-1 cells. These multifaceted roles of IL-37 were partly depended on the mediation of glycogen synthase kinase-3β (GSK-3β).

CONCLUSIONS

Our study revealed that IL-37 could shape macrophages into a "silent" non-inflammatory phagocytic fashion. IL-37 may become a potentially valuable treatment option for patients of chronic gout, especially for those with tophi.

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.

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.

Protective Effect of Oxytocin on Ventilator-Induced Lung Injury Through NLRP3-Mediated Pathways

Mechanical ventilation is an indispensable life-support treatment for acute respiratory failure in critically ill patients, which is generally believed to involve uncontrolled inflammatory responses. Oxytocin (OT) has been reported to be effective in animal models of acute lung injury. However, it is not clear whether Oxytocin has a protective effect on ventilator-induced lung injury (VILI). Therefore, in this study, we aimed to determine whether OT can attenuate VILI and explore the possible mechanism of this protection. To this end, a mouse VILI model was employed. Mice were pretreated with OT 30 min before the intraperitoneal injection of saline or nigericin and ventilation for 4 h, after which they were euthanized. Pathological changes, lung wet/dry (W/D) weight ratio, myeloperoxidase (MPO) activity, the levels of inflammatory cytokines [i.e., interleukin (IL)-1β, IL-6, and IL-18] in lung tissues and bronchoalveolar lavage fluid (BALF), and expression of NLRP3, Toll-like receptor 4 (TLR4), caspase-1, nuclear factor (NF)-κB, and GSDMD in lung tissues were measured. OT treatment could reduce pathological injury, the W/D ratio, and MPO activity in VILI mice. Our data also indicated that OT administration alleviated the expression of TLR4/My-D88 and the activation of NF-κB, NLRP3, and caspase-1 in lung tissues from the VILI mice model. Furthermore, OT also decreased the levels of IL-1β, IL-6, and IL-18 in the bronchoalveolar lavage fluid. Moreover, the OT administration may alleviate the activation of GSDMD partially through its effects on the NLRP3-mediated pathway. Collectively, OT exerted a beneficial effect on VILI by downregulating TLR4-and NLRP3-mediated inflammatory pathways.

The Curious Case of Earthworms and COVID-19

Simple Summary

Earthworms have been used for centuries in traditional medicine, and more than a century ago were praised by Charles Darwin as one of the most important organisms in the history of the world. These worms are well-studied with a wealth of information available, for example on the genome, the gene expression, the immune system, the general biology, and ecology. These worms live in many habitats, and they had to find solutions for severe environmental challenges. The common compost worm, Eisenia fetida, has developed a unique mechanism to deal with intruding (nano)materials, bacteria, and viruses. It deals with the intruders by covering these with a defence toxin (lysenin) targeted to kill the intruder. We outline how this mechanism probably can be used as a therapeutic model for human COVID-19 (Severe Acute Respiratory Syndrome Coronavirus 2, SARS-CoV-2) and other corona viruses.

Abstract

Earthworms have been used for centuries in traditional medicine and are used globally as an ecotoxicological standard test species. Studies of the earthworm Eisenia fetida have shown that exposure to nanomaterials activates a primary corona-response, which is covering the nanomaterial with native proteins, the same response as to biological invaders such as a virus. We outline that the earthworm Eisenia fetida is possibly immune to COVID-19 (Severe Acute Respiratory Syndrome Coronavirus 2, SARS-CoV-2), and we describe the likely mechanisms of highly receptor-specific pore-forming proteins (PFPs). A non-toxic version of this protein is available, and we hypothesize that it is possible to use the earthworm’s PFPs based anti-viral mechanism as a therapeutic model for human SARS-CoV-2 and other corona viruses. The proteins can be used as a drug, for example, delivered with a nanoparticle in a similar way to the current COVID-19 vaccines. Obviously, careful consideration should be given to the potential risk of toxicity elicited by lysenin for in vivo usage. We aim to share this view to activate its exploration by the wider scientific community while promoting a potential therapeutic development.

Higher-order assemblies in immune signaling: supramolecular complexes and phase separation

Signaling pathways in innate and adaptive immunity play vital roles in pathogen recognition and the functions of immune cells. Higher-order assemblies have recently emerged as a central principle that governs immune signaling and, by extension, cellular communication in general. There are mainly two types of higher-order assemblies: 1) ordered, solid-like large supramolecular complexes formed by stable and rigid protein-protein interactions, and 2) liquid-like phase-separated condensates formed by weaker and more dynamic intermolecular interactions. This review covers key examples of both types of higher-order assemblies in major immune pathways. By placing emphasis on the molecular structures of the examples provided, we discuss how their structural organization enables elegant mechanisms of signaling regulation.

Pyroptosis and Redox Balance in Kidney Diseases

Significance: Kidney diseases remain a worldwide public health problem resulting in millions of deaths each year; they are characterized by progressive destruction of renal function by sustained inflammation. Pyroptosis is a lytic type of programmed cell death involved in inflammation, as well as a key fibrotic mechanism that is critical in the development of kidney pathology. Pyroptosis is induced by the cleavage of Gasdermins by various caspases and is executed by the insertion of the N-terminal fragment of cleaved Gasdermins into the plasma membrane, creating oligomeric pores and allowing the release of diverse proinflammatory products into the extracellular space. Inflammasomes are multiprotein complexes leading to the activation of caspase-1, which will cleave Gasdermin D, releasing several proinflammatory cytokines; this results in the initiation and amplification of the inflammatory response. Recent Advances: The efficacy of Gasdermin D cleavage is reduced by a change in the redox balance. Recently, several studies have shown that the attenuation of reactive oxygen species (ROS) production induced by antioxidant pathways results in a reduction of renal pyroptosis. In this review, we discuss the role of pyroptosis in the pathogenesis of chronic kidney disease (CKD) and acute kidney disease; summarize the clinical outcomes and different molecular mechanisms leading to Gasdermin activation; and examine studies about the capacity of antioxidants, particularly Nrf2 activators, to ameliorate Gasdermin activity. Future Directions: We illustrate the potential influence of the deregulation of redox balance on inflammasome activity and pyroptosis as a novel therapeutic approach for the treatment of kidney diseases. Antioxid. Redox Signal. 35, 40-60.

Curcumin Activates ROS Signaling to Promote Pyroptosis in Hepatocellular Carcinoma HepG2 Cells

BACKGROUND/AIM

Curcumin is a polyphenol that exerts a variety of pharmacological activities and plays an anti-cancer role in many cancer cells. It was recently reported that gasdermin E (GSDME) is involved in the progression of pyroptosis.

MATERIALS AND METHODS

HepG2 cells were treated with various concentrations of curcumin and cell viability was examined using MTT assay, apoptosis was analysed using flow cytometry, reactive oxygen species (ROS) levels using dihydroethidium, LDH release using an LDH cytotoxicity assay, and protein expression using western blot.

RESULTS

Curcumin increased the expression of the GSDME N-terminus and proteins involved in pyrolysis, promoted HspG2 cell pyrolysis and increased intracellular ROS levels. Moreover, inhibition of the production of intracellular ROS with n-acetylcysteine (NAC) improved the degree of apoptosis and pyrolysis induced by curcumin.

CONCLUSION

Curcumin induces HspG2 cell death by increasing apoptosis and pyroptosis, and ROS play a key role in this process. This study improves our understanding of the potential anti-cancer properties of curcumin in liver cancer.

The Mechanism of Stimulating and Mobilizing the Immune System Enhancing the Anti-Tumor Immunity

Cancer immunotherapy is a kind of therapy that can control and eliminate tumors by restarting and maintaining the tumor-immune cycle and restoring the body's normal anti-tumor immune response. Although immunotherapy has great potential, it is currently only applicable to patients with certain types of tumors, such as melanoma, lung cancer, and cancer with high mutation load and microsatellite instability, and even in these types of tumors, immunotherapy is not effective for all patients. In order to enhance the effectiveness of tumor immunotherapy, this article reviews the research progress of tumor microenvironment immunotherapy, and studies the mechanism of stimulating and mobilizing immune system to enhance anti-tumor immunity. In this review, we focused on immunotherapy against tumor microenvironment (TME) and discussed the important research progress. TME is the environment for the survival and development of tumor cells, which is composed of cell components and non-cell components; immunotherapy for TME by stimulating or mobilizing the immune system of the body, enhancing the anti-tumor immunity. The checkpoint inhibitors can effectively block the inhibitory immunoregulation, indirectly strengthen the anti-tumor immune response and improve the effect of immunotherapy. We also found the checkpoint inhibitors have brought great changes to the treatment model of advanced tumors, but the clinical treatment results show great individual differences. Based on the close attention to the future development trend of immunotherapy, this study summarized the latest progress of immunotherapy and pointed out a new direction. To study the mechanism of stimulating and mobilizing the immune system to enhance anti-tumor immunity can provide new opportunities for cancer treatment, expand the clinical application scope and effective population of cancer immunotherapy, and improve the survival rate of cancer patients.

Mechanisms of Neoantigen-Targeted Induction of Pyroptosis and Ferroptosis: From Basic Research to Clinical Applications

Neoantigens are tumor-specific antigens (TSAs) that are only expressed in tumor cells. They are ideal targets enabling T cells to recognize tumor cells and stimulate a potent antitumor immune response. Pyroptosis and ferroptosis are newly discovered types of programmed cell death (PCD) that are different from apoptosis, cell necrosis, and autophagy. Studies of ferroptosis and pyroptosis of cancer cells are increasing, and strategies to modify the tumor microenvironment (TME) through ferroptosis to inhibit the occurrence and development of cancer, improve prognosis, and increase the survival rate are popular research topics. In addition, adoptive T cell therapy (ACT), including chimeric antigen receptor T cell (CAR-T) technology and T cell receptor engineered T cell (TCR-T) technology, and checkpoint blocking tumor immunotherapies (such as anti-PD- 1 and anti-PD-L1 agents), tumor vaccines and other therapeutic technologies that rely on tumor neoantigens are rapidly being developed. In this article, the relationship between neoantigens and pyroptosis and ferroptosis as well as the clinical role of neoantigens is reviewed.

Targeting the gasdermin D as a strategy for ischemic stroke therapy

Stroke is a major cause of death and disability worldwide that triggers a variety of neuropathological conditions, leading to the initiation of several pro-inflammatory mediators and neuronal damage. Neuroinflammation has been considered the potential therapeutic target and contributes to the pathology of ischemia and reperfusion. Pyroptosis is an inflammatory form of programmed cell death that plays an important role in immune protection against stroke. Gasdermin D (GSDMD) is the final executor of pyroptosis upon cleavage by caspases-1/4/5/11, followed by canonical and noncanonical inflammasome activation, leading to a series of inflammatory responses. GSDMD N-terminal domain assembles plasma membrane as well as organelle membrane pores to induce cytolysis, thereby triggering cytokine release and inflammatory-related cell death. In our review, we concisely summarized and highlighted the potential role of GSDMD-regulated pyroptosis and the biological characteristic of GSDMD as a therapeutic target in ischemic stroke. A better understanding of the roles of GSDMD may provide a theoretical basis for the design of novel therapeutic interventions for the treatment of ischemic stroke.

Inflammatory Caspases Drive Pyroptosis in Acute Lung Injury

Acute lung injury (ALI), a critical respiratory disorder that causes diffuse alveolar injury leads to high mortality rates with no effective treatment. ALI is characterized by varying degrees of ventilation/perfusion mismatch, severe hypoxemia, and poor pulmonary compliance. The diffuse injury to cells is one of most important pathological characteristics of ALI. Pyroptosis is a form of programmed cell death distinguished from apoptosis induced by inflammatory caspases, which can release inflammatory cytokines to clear cells infected by pathogens and promote monocytes to reassemble at the site of injury. And pyroptosis not only promotes inflammation in certain cell types, but also regulates many downstream pathways to perform different functions. There is increasing evidence that pyroptosis and its related inflammatory caspases play an important role in the development of acute lung injury. The main modes of activation of pyroptosis is not consistent among different types of cells in lung tissue. Meanwhile, inhibition of inflammasome, the key to initiating pyroptosis is currently the main way to treat acute lung injury. The review summarizes the relationship among inflammatory caspases, pyroptosis and acute lung injury and provides general directions and strategies to conduct further research.

Emerging Role of the Inflammasome and Pyroptosis in Hypertension

Inflammasomes are components of the innate immune response that have recently emerged as crucial controllers of tissue homeostasis. In particular, the nucleotide-binding domain, leucine-rich-containing (NLR) family pyrin domain containing 3 (NLRP3) inflammasome is a complex platform involved in the activation of caspase-1 and the maturation of interleukin (IL)-1β and IL-18, which are mainly released via pyroptosis. Pyroptosis is a caspase-1-dependent type of cell death that is mediated by the cleavage of gasdermin D and the subsequent formation of structurally stable pores in the cell membrane. Through these pores formed by gasdermin proteins cytosolic contents are released into the extracellular space and act as damage-associated molecular patterns, which are pro-inflammatory signals. Inflammation is a main contributor to the development of hypertension and it also is known to stimulate fibrosis and end-organ damage. Patients with essential hypertension and animal models of hypertension exhibit elevated levels of circulating IL-1β. Downregulation of the expression of key components of the NLRP3 inflammasome delays the development of hypertension and pharmacological inhibition of this inflammasome leads to reduced blood pressure in animal models and humans. Although the relationship between pyroptosis and hypertension is not well established yet, pyroptosis has been associated with renal and cardiovascular diseases, instances where high blood pressure is a critical risk factor. In this review, we summarize the recent literature addressing the role of pyroptosis and the inflammasome in the development of hypertension and discuss the potential use of approaches targeting this pathway as future anti-hypertensive strategies.

The Caspase-1/IL-18 Axis of the Inflammasome in Tumor Cells: A Modulator of the Th1/Tc1 Response of Tumor-Infiltrating T Lymphocytes in Colorectal Cancer

In colorectal cancer (CRC), a high density of T lymphocytes represents a strong prognostic marker in subtypes of CRC. Optimized immunotherapy strategies to boost this T-cell response are still needed. A good candidate is the inflammasome pathway, an emerging player in cancer immunology that bridges innate and adaptive immunity. Its effector protein caspase-1 matures IL-18 that can promote a T-helper/cytotoxic (Th1/Tc1) response. It is still unknown whether tumor cells from CRC possess a functional caspase-1/IL-18 axis that could modulate the Th1/Tc1 response. We used two independent cohorts of CRC patients to assess IL-18 and caspase-1 expression by tumor cells in relation to the density of TILs and the microsatellite status of CRC. Functional and multiparametric approaches at the protein and mRNA levels were performed on an ex vivo CRC explant culture model. We show that, in the majority of CRCs, tumor cells display an activated and functional caspase-1/IL-18 axis that contributes to drive a Th1/Tc1 response elicited by TILs expressing IL-18Rα. Furthermore, unsupervised clustering identified three clusters of CRCs according to the caspase-1/IL-18/TIL density/interferon gamma (IFNγ) axis and microsatellite status. Together, our results strongly suggest that targeting the caspase-1/IL-18 axis can improve the anti-tumor immune response in subgroups of CRC.