Gasdermin: A new player to the inflammasome game

Apelin-13's Actions in Controlling Hypertension-Related Cardiac Hypertrophy and the Expressions of Inflammatory Cytokines

As a key molecule for improving cardiovascular diseases, Apelin-13 was surveyed in this work to explain its actions in controlling inflammation, pyroptosis, and myocardial hypertrophy. First, mouse models with myocardial hypertrophy were established. Then, assessments were made on the pathological variation in the heart of mouse, on the cardiac functions, as well as on the expressions of cardiac hypertrophy markers (β-MHC, ANP, and BNP), inflammatory factors (TNF-α, COX2, IL-6, ICAM-1, and VCAM-1), myocardial cell pyroptosis markers (NLRP3, ASC, c-caspase-1, and GSDMD-N), and Hippo pathway proteins (p-YAP, YAP, LATS1, and p-LATS1) by HE staining, echocardiography scanning, and western blot tests separately. The expressions of such inflammatory factors as in myocardial tissue were acquired by ELISA. After inducing the phenotype of H9c2 cell hypertrophy by noradrenaline, we used CCK-8 kits to know about the activity of H9c2 cells treated with Apelin-13, and performed ɑ-actinin staining to measure the changes in volumes of such cells. As unraveled through this work, Apelin-13 refrained the activation of the Hippo pathway, which in turn attenuated the hypertrophy, inflammation, and pyroptosis of myocardial tissue and H9c2 cells. Hence, Apelin-13 can be considered as a target for hypertension treatment.

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.

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.

The Role and Therapeutic Potential of Pyroptosis in Colorectal Cancer: A Review

Colorectal cancer (CRC) is one of the leading causes of cancer-related mortality worldwide. The unlimited proliferation of tumor cells is one of the key features resulting in the malignant development and progression of CRC. Consequently, understanding the potential proliferation and growth molecular mechanisms and developing effective therapeutic strategies have become key in CRC treatment. Pyroptosis is an emerging type of regulated cell death (RCD) that has a significant role in cells proliferation and growth. For the last few years, numerous studies have indicated a close correlation between pyroptosis and the occurrence, progression, and treatment of many malignancies, including CRC. The development of effective therapeutic strategies to inhibit tumor growth and proliferation has become a key area in CRC treatment. Thus, this review mainly summarized the different pyroptosis pathways and mechanisms, the anti-tumor (tumor suppressor) and protective roles of pyroptosis in CRC, and the clinical and prognostic value of pyroptosis in CRC, which may contribute to exploring new therapeutic strategies for CRC.

The Barrier Disruption and Pyroptosis of Intestinal Epithelial Cells Caused by Perfringolysin O (PFO) from Clostridium perfringens

Clostridium perfringens (C. perfringens), a Gram-positive bacterium, produces a variety of toxins and extracellular enzymes that can lead to disease in both humans and animals. Common symptoms include abdominal swelling, diarrhea, and intestinal inflammation. Severe cases can result in complications like intestinal hemorrhage, edema, and even death. The primary toxins contributing to morbidity in C. perfringens-infected intestines are CPA, CPB, CPB2, CPE, and PFO. Amongst these, CPB, CPB2, and CPE are implicated in apoptosis development, while CPA is associated with cell death, increased intracellular ROS levels, and the release of the inflammatory factor IL-18. However, the exact mechanism by which PFO toxins exert their effects in the infected gut is still unidentified. This study demonstrates that a C. perfringens PFO toxin infection disrupts the intestinal epithelial barrier function through in vitro and in vivo models. This study emphasizes the notable influence of PFO toxins on intestinal barrier integrity in the context of C. perfringens infections. It reveals that PFO toxins increase ROS production by causing mitochondrial damage, triggering pyroptosis in IPEC-J2 cells, and consequently resulting in compromised intestinal barrier function. These results offer a scientific foundation for developing preventive and therapeutic approaches against C. perfringens infections.

Pyroptosis in Diabetic Peripheral Neuropathy and its Therapeutic Regulation

Pyroptosis is a pro-inflammatory form of cell death resulting from the activation of gasdermins (GSDMs) pore-forming proteins and the release of several pro-inflammatory factors. However, inflammasomes are the intracellular protein complexes that cleave gasdermin D (GSDMD), leading to the formation of robust cell membrane pores and the initiation of pyroptosis. Inflammasome activation and gasdermin-mediated membrane pore formation are the important intrinsic processes in the classical pyroptotic signaling pathway. Overactivation of the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome triggers pyroptosis and amplifies inflammation. Current evidence suggests that the overactivation of inflammasomes and pyroptosis may further induce the progression of cancers, nerve injury, inflammatory disorders and metabolic dysfunctions. Current evidence also indicates that pyroptosis-dependent cell death accelerates the progression of diabetes and its frequent consequences including diabetic peripheral neuropathy (DPN). Pyroptosis-mediated inflammatory reaction further exacerbates DPN-mediated CNS injury. Accumulating evidence shows that several molecular signaling mechanisms trigger pyroptosis in insulin-producing cells, further leading to the development of DPN. Numerous studies have suggested that certain natural compounds or drugs may possess promising pharmacological properties by modulating inflammasomes and pyroptosis, thereby offering potential preventive and practical therapeutic approaches for the treatment and management of DPN. This review elaborates on the underlying molecular mechanisms of pyroptosis and explores possible therapeutic strategies for regulating pyroptosis-regulated cell death in the pharmacological treatment of DPN.

The roles of pyroptosis in genitourinary diseases

Pyroptosis, a form of programmed cell death distinct from apoptosis and necrosis, is thought to be closely associated with the pathogenesis of diseases. Recently, the association between pyroptosis and urinary diseases has attracted considerable attention, and a comprehensive review focusing on this issue is not available. In this study, we reviewed the role of pyroptosis in the development and progression of benign urinary diseases and urinary malignancies. Based on this, pyroptosis has been implicated in the development of urinary diseases. In summary, this review sheds light on future research directions and provides novel ideas for using pyroptosis as a powerful tool to fight urinary diseases.

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.

Berberine inhibits NLRP3 inflammasome activation by regulating mTOR/mtROS axis to alleviate diabetic cardiomyopathy

Diabetes cardiomyopathy (DCM) refers to myocardial dysfunction and disorganization resulting from diabetes. In this study, we investigated the effects of berberine on cardiac function in male db/db mice with metformin as a positive control. After treatment for 8 weeks, significant improvements in cardiac function and a reduction in collagen deposition were observed in db/db mice. Furthermore, inflammation and pyroptosis were seen to decrease in these mice, as evidenced by decreased expressions of p-mTOR, NOD-like receptor thermal protein domain associated protein 3 (NLRP3), IL-1β, IL-18, caspase-1, and gasdermin D (GSDMD). In vitro experiments on H9C2 cells showed that glucose exposure at 33 mmol/L induced pyroptosis, whereas berberine treatment reduced the expression of p-mTOR and NLRP3 inflammasome components. Moreover, berberine treatment was seen to inhibit the generation of mitochondrial reactive oxygen species (mtROS) and effectively improve cell damage in high glucose-induced H9C2 cells. The mTOR inhibitor, Torin-1, showed a therapeutic effect similar to that of berberine, by reducing the expression of NLRP3 inflammasome components and inhibiting mtROS generation. However, the activation of mTOR by MHY1485 partially nullified berberine's protective effects during high glucose stress. Collectively, our study reveals the mechanism that berberine regulates the mTOR/mtROS axis to inhibit pyroptosis induced by NLRP3 inflammasome activation, thereby alleviating DCM.

Pyroptosis Inhibition in Disease Treatment: Opportunities and Challenges

Programmed cell death (PCD) is at the center of immune responses, with different types of PCD occurring based on bodily conditions at a given moment. The main three types of PCD include pyroptosis, necroptosis, and apoptosis. Both pyroptosis and necroptosis induce an inflammatory response while apoptosis avoids eliciting an inflammatory reaction. Recently, pyroptosis has come to the forefront of immunology research due to tremendous potential that has been revealed surrounding the regulators of pyroptosis. In addition to previously known regulators of pyroptosis (ZBP1 and NLRP3 genes), a family of proteins called Gasdermin has been discovered. Specifically, Gasdermin D (GSDMD), when cleaved, participates in the onset of pyroptosis of inflammatory diseases. The N-terminal cleaved portion of the molecule causes cellular membrane openings releasing interleukin-18 and IL-1β, inducing pyroptosis. It is hypothesized that the inhibition of GSDMD using drugs such as Dimethyl Fumarate (DMF) and Disulfiram may halt the progression of certain inflammatory diseases including Multiple Sclerosis (MS), autoimmune encephalitis etc. While there is not yet a concrete treatment for pyroptic cell death in inflammatory disease using GSDMD inhibition, there is ample evidence to suggest that there may be success in future studies and therapeutic applications of GSDMD.

Gasdermin D kills bacteria

The recognition of pathogen- or damage- associated molecular patterns (PAMPs/DAMPs) signals a series of coordinated responses as part of innate immunity or host cell defense during infection. The inflammasome is an assemblage of multiprotein complexes in the cytosol that activate inflammatory caspases and release pro-inflammatory mediators. This review examines the two-edged sword activity of gasdermin D (GSDMD). Since its discovery in 2015, GSDMD has played a crucial role in the programmed necrotic type of cell death called pyroptosis. Pyroptosis is an important response in host self-protection against danger signals and infection. Although excessive pyroptosis has a deleterious effect on the host, it proves to have a game-changing therapeutic application against pathogenic invasion when controlled. Here, we explore the mechanism utilized by GSDMD, the best studied member of the gasdermin protein family, in host immune defense against many bacteria. While the protein contributes to the clearance of some bacteria, we also discussed results from previous studies and research, that its presence might hinder effective immunity against other pathogens, thus aiding pathogenic invasion and spread.

Role of pyroptosis in the pathogenesis and treatment of diseases

Programmed cell death (PCD) is regarded as a pathological form of cell death with an intracellular program mediated, which plays a pivotal role in maintaining homeostasis and embryonic development. Pyroptosis is a new paradigm of PCD, which has received increasing attention due to its close association with immunity and disease. Pyroptosis is a form of inflammatory cell death mediated by gasdermin that promotes the release of proinflammatory cytokines and contents induced by inflammasome activation. Recently, increasing evidence in studies shows that pyroptosis has a crucial role in inflammatory conditions like cardiovascular diseases (CVDs), cancer, neurological diseases (NDs), and metabolic diseases (MDs), suggesting that targeting cell death is a potential intervention for the treatment of these inflammatory diseases. Based on this, the review aims to identify the molecular mechanisms and signaling pathways related to pyroptosis activation and summarizes the current insights into the complicated relationship between pyroptosis and multiple human inflammatory diseases (CVDs, cancer, NDs, and MDs). We also discuss a promising novel strategy and method for treating these inflammatory diseases by targeting pyroptosis and focus on the pyroptosis pathway application in clinics.

The functions of two GSDMEs in pyroptosis of common carp (Cyprinus carpio L.) in canonical and non-canonical inflammasome pathways

Gasdermin family proteins are important effector proteins mediating pyroptosis and play an important role in innate immune response. GSDME can be cleaved by inflammatory Caspases at specific sites, releasing an active form of N-terminal fragment that binds to the plasma membrane to form pores and release cellular contents. Here, two GSDME genes, CcGSDME-like (CcGSDME-L) and CcGSDMEa, were cloned from common carp. The sequence similarity of the two genes were very high and more similar to DrGSDMEa of zebrafish in evolution. The expression levels of CcGSDME-L and CcGSDMEa can respond to the stimulation of Edwardsiella tarda. The results of cytotoxicity assay showed that CcGSDMEs were cleaved by the activation of canonical CcNLRP1 inflammasome, leading to obvious pyroptosis characteristics and increased cytotoxicity. In EPC cells, three CcCaspases responded to intracellular LPS stimulation and induced significantly cytotoxicity. In order to clarify the molecular mechanism of CcGSDME-induced pyroptosis, the N-terminal of CcGSDME-L (CcGSDME-L-NT) was expressed in 293T cells, which showed strong cytotoxicity and obvious pyroptosis characteristics. Fluorescence localization assay showed that the CcGSDME-L-NT was expressed on cell membrane, and CcGSDMEa-NT was located on the cell membrane or some organelle membranes. These findings can enrich the knowledge of CcNLRP1 inflammasome and GSDMEs mediated pyroptosis in common carp, and provide basic data for the prevention and treatment of fish infectious diseases.

Disulfiram accelerates diabetic foot ulcer healing by blocking NET formation via suppressing the NLRP3/Caspase-1/GSDMD pathway

Diabetic foot ulcer (DFU) is among the most frequent complications of diabetes and is associated with significant morbidity and mortality. Excessive neutrophil extracellular traps (NETs) delay wound healing in diabetic patients. Therefore, interventions targeting NET release need to be developed to effectively prevent NET-based wound healing impairment. Gasdermin D (GSDMD), a pore-forming protein acts as a central executioner of inflammatory cell death and can activate inflammasomes in neutrophils to release NETs. A precise understanding of the mechanism underlying NET-mediated delay in diabetic wound healing may be valuable in identifying potential therapeutic targets to improve clinical outcomes. In this study, we reported that neutrophils were more susceptible to NETosis in diabetic wound environments of patients with DFU. By in vitro experiments and using in vivo mouse models of diabetic wound healing (wide-type, Nlrp3^-/-, Casp-1^-/-, and Gsdmd^-/- mice), we demonstrated that NLRP3/caspase-1/GSDMD pathway on activation controls NET release by neutrophils in diabetic wound tissue. Furthermore, inhibition of GSDMD with disulfiram or genic deletion of Gsdmd abrogated NET formation, thereby accelerating diabetic wound healing. Disulfiram could inhibit NETs-mediated diabetic foot ulcer healing impairment by suppressing the NLRP3/Caspase-1/GSDMD pathway. In summary, our findings uncover a novel therapeutic role of disulfiram in inhibiting NET formation, which is of considerable value in accelerating wound healing in patients with DFU.

Elevated Methionine Flux Drives Pyroptosis Evasion in Persister Cancer Cells

Induction of cell death represents a primary goal of most anticancer treatments. Despite the efficacy of such approaches, a small population of "persisters" develop evasion strategies to therapy-induced cell death. While previous studies have identified mechanisms of resistance to apoptosis, the mechanisms by which persisters dampen other forms of cell death, such as pyroptosis, remain to be elucidated. Pyroptosis is a form of inflammatory cell death that involves formation of membrane pores, ion gradient imbalance, water inflow, and membrane rupture. Herein, we investigate mechanisms by which cancer persisters resist pyroptosis, survive, then proliferate in the presence of tyrosine kinase inhibitors (TKI). Lung, prostate, and esophageal cancer persister cells remaining after treatments exhibited several hallmarks indicative of pyroptosis resistance. The inflammatory attributes of persisters included chronic activation of inflammasome, STING, and type I interferons. Comprehensive metabolomic characterization uncovered that TKI-induced pyroptotic persisters display high methionine consumption and excessive taurine production. Elevated methionine flux or exogenous taurine preserved plasma membrane integrity via osmolyte-mediated effects. Increased dependency on methionine flux decreased the level of one carbon metabolism intermediate S-(5'-adenosyl)-L-homocysteine, a determinant of cell methylation capacity. The consequent increase in methylation potential induced DNA hypermethylation of genes regulating metal ion balance and intrinsic immune response. This enabled thwarting TKI resistance by using the hypomethylating agent decitabine. In summary, the evolution of resistance to pyroptosis can occur via a stepwise process of physical acclimation and epigenetic changes without existing or recurrent mutations.

SIGNIFICANCE

Methionine enables cancer cells to persist by evading pyroptotic osmotic lysis, which leads to genome-wide hypermethylation that allows persisters to gain proliferative advantages.

Naturally-occurring serotype 3 Streptococcus pneumoniae strains that lack functional pneumolysin and autolysin have attenuated virulence but induce localized protective immune responses

Streptococcus pneumoniae is an important cause of fatal pneumonia in humans. These bacteria express virulence factors, such as the toxins pneumolysin and autolysin, that drive host inflammatory responses. In this study we confirm loss of pneumolysin and autolysin function in a group of clonal pneumococci that have a chromosomal deletion resulting in a pneumolysin-autolysin fusion gene Δ(lytA'-ply')593. The Δ(lytA'-ply')593 pneumococci strains naturally occur in horses and infection is associated with mild clinical signs. Here we use immortalized and primary macrophage in vitro models, which include pattern recognition receptor knock-out cells, and a murine acute pneumonia model to show that a Δ(lytA'-ply')593 strain induces cytokine production by cultured macrophages, however, unlike the serotype-matched ply+lytA+ strain, it induces less tumour necrosis factor α (TNFα) and no interleukin-1β production. The TNFα induced by the Δ(lytA'-ply')593 strain requires MyD88 but, in contrast to the ply+lytA+ strain, is not reduced in cells lacking TLR2, 4 or 9. In comparison to the ply+lytA+ strain in a mouse model of acute pneumonia, infection with the Δ(lytA'-ply')593 strain resulted in less severe lung pathology, comparable levels of interleukin-1α, but minimal release of other pro-inflammatory cytokines, including interferon-γ, interleukin-6 and TNFα. These results suggest a mechanism by which a naturally occurring Δ(lytA'-ply')593 mutant strain of S. pneumoniae that resides in a non-human host has reduced inflammatory and invasive capacity compared to a human S. pneumoniae strain. These data probably explain the relatively mild clinical disease in response to S. pneumoniae infection seen in horses in comparison to humans.

COVID-19 Mimics Pulmonary Dysfunction in Muscular Dystrophy as a Post-Acute Syndrome in Patients

Although progressive wasting and weakness of respiratory muscles are the prominent hallmarks of Duchenne muscular dystrophy (DMD) and long-COVID (also referred as the post-acute sequelae of COVID-19 syndrome); however, the underlying mechanism(s) leading to respiratory failure in both conditions remain unclear. We put together the latest relevant literature to further understand the plausible mechanism(s) behind diaphragm malfunctioning in COVID-19 and DMD conditions. Previously, we have shown the role of matrix metalloproteinase-9 (MMP9) in skeletal muscle fibrosis via a substantial increase in the levels of tumor necrosis factor-α (TNF-α) employing a DMD mouse model that was crossed-bred with MMP9-knockout (MMP9-KO or MMP9^-/-) strain. Interestingly, recent observations from clinical studies show a robust increase in neopterin (NPT) levels during COVID-19 which is often observed in patients having DMD. What seems to be common in both (DMD and COVID-19) is the involvement of neopterin (NPT). We know that NPT is generated by activated white blood cells (WBCs) especially the M1 macrophages in response to inducible nitric oxide synthase (iNOS), tetrahydrobiopterin (BH4), and tetrahydrofolate (FH4) pathways, i.e., folate one-carbon metabolism (FOCM) in conjunction with epigenetics underpinning as an immune surveillance protection. Studies from our laboratory, and others researching DMD and the genetically engineered humanized (hACE2) mice that were administered with the spike protein (SP) of SARS-CoV-2 revealed an increase in the levels of NPT, TNF-α, HDAC, IL-1β, CD147, and MMP9 in the lung tissue of the animals that were subsequently accompanied by fibrosis of the diaphragm depicting a decreased oscillation phenotype. Therefore, it is of interest to understand how regulatory processes such as epigenetics involvement affect DNMT, HDAC, MTHFS, and iNOS that help generate NPT in the long-COVID patients.

Role of pyroptosis in inflammation and cancer

Pyroptosis is a form of programmed cell death mediated by gasdermin and is a product of continuous cell expansion until the cytomembrane ruptures, resulting in the release of cellular contents that can activate strong inflammatory and immune responses. Pyroptosis, an innate immune response, can be triggered by the activation of inflammasomes by various influencing factors. Activation of these inflammasomes can induce the maturation of caspase-1 or caspase-4/5/11, both of which cleave gasdermin D to release its N-terminal domain, which can bind membrane lipids and perforate the cell membrane. Here, we review the latest advancements in research on the mechanisms of pyroptosis, newly discovered influencing factors, antitumoral properties, and applications in various diseases. Moreover, this review also provides updates on potential targeted therapies for inflammation and cancers, methods for clinical prevention, and finally challenges and future directions in the field.

Constructing novel molecular subtypes and an 11-gene signature based on pyroptosis signaling for lung adenocarcinoma

Pyroptosis plays important roles in various cancers. In this study, we focused on lung adenocarcinoma (LUAD) and aimed to develop new molecular subtypes based on pyroptosis signaling. Pyroptosis-related genes were used as a basis to classify molecular subtypes through unsupervised consensus clustering. Gene set enrichment analysis was performed to characterize tumor microenvironment (TME) and functional pathways. Univariate Cox regression and least absolute shrinkage and selection operator (LASSO) analysis were conducted to identify prognostic genes for establishing a prognostic model. Three molecular subtypes were established with distinct overall survival, TME and enriched pathways. C3 subtype had the longest survival and the highest immune infiltration. 11 prognostic genes were screened to build a prognostic signature for predicting LUAD prognosis. This study emphasized the important role of pyroptosis in LUAD development. Pyroptosis was considered to play critical roles in regulating TME. Moreover, the 11-gene signature could serve as an indicator for predicting LUAD prognosis, and was potential targets for developing targeted drugs.

Modulation of MAPK- and PI3/AKT-Dependent Autophagy Signaling by Stavudine (D4T) in PBMC of Alzheimer’s Disease Patients

Background: Aβ₄₂ deposition plays a pivotal role in AD pathogenesis by inducing the activation of microglial cells and neuroinflammation. This process is antagonized by microglia-mediated clearance of Aβ plaques. Activation of the NLRP3 inflammasome is involved in neuroinflammation and in the impairments of Aβ-plaque clearance. On the other hand, stavudine (D4T) downregulates the NLRP3 inflammasome and stimulates autophagy-mediated Aβ-clearing in a THP-1-derived macrophages. Methods: We explored the effect of D4T on Aβ autophagy in PBMC from AD patients that were primed with LPS and stimulated with Aβ oligomers in the absence/presence of D4T. We analyzed the NLRP3 activity by measuring NLRP3-ASC complex formation by AMNIS FlowSight and pro-inflammatory cytokine (IL-1β, IL-18 and Caspase-1) production by ELISA. The phosphorylation status of p38, ERK, AKT, p70, and the protein expression of CREB, LAMP2A, beclin-1, Caspase-3 and Bcl2 were analyzed by Western blot. Results: Data showed that D4T: (1) downregulates NLRP3 inflammasome activation and the production of down-stream pro-inflammatory cytokines in PBMC; (2) stimulates the phosphorylation of AKT, ERK and p70 as well as LAMP2A, beclin-1 and Bcl2 expression and reduces Caspase-3 expression, suggesting an effect of this compound on autophagy; (3) increases phospho-CREB, which is a downstream target of p-ERK and p-AKT, inducing anti-inflammatory cytokine production and resulting in a possible decrease of Aβ-mediated cytotoxicity; and (4) reduces the phosphorylation of p38, a protein involved in the production of pro-inflammatory cytokines and tau hyperphosphorylation. Conclusions: D4T reduces the activation of the NLRP3 inflammasome, and it might stimulate autophagy as well as the molecular mechanism that modulates Aβ cytotoxicity, and D4T might reduce inflammation in the cells of AD patients. It could be very interesting to check the possible beneficial effects of D4T in the clinical scenario.

Revisiting Regulated Cell Death Responses in Viral Infections

The fate of a viral infection in the host begins with various types of cellular responses, such as abortive, productive, latent, and destructive infections. Apoptosis, necroptosis, and pyroptosis are the three major types of regulated cell death mechanisms that play critical roles in viral infection response. Cell shrinkage, nuclear condensation, bleb formation, and retained membrane integrity are all signs of osmotic imbalance-driven cytoplasmic swelling and early membrane damage in necroptosis and pyroptosis. Caspase-driven apoptotic cell demise is considered in many circumstances as an anti-inflammatory, and some pathogens hijack the cell death signaling routes to initiate a targeted attack against the host. In this review, the selected mechanisms by which viruses interfere with cell death were discussed in-depth and were illustrated by compiling the general principles and cellular signaling mechanisms of virus–host-specific molecule interactions.

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

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

Excess fatty acids induce pancreatic acinar cell pyroptosis through macrophage M1 polarization

Free fatty acid derived from hyperlipidemia contributes to the development of inflammation in the pancreas. Here we explore the molecular mechanisms of fatty acid-induced pancreatitis through cellular experiments and the construction of a mouse model of hyperlipidemic pancreatitis. We found that palmitic acid stimulation leads to M1 polarization of macrophage, which secretes cathepsin S via exosomes to pancreatic acinar cells and leads to activation of the caspase1-mediated classical pyrolysis pathway, resulting in inflammation and pancreatic tissue damage. In vivo experiments have also demonstrated that the high levels of fatty acids induced by hyperlipidaemia exacerbate the development of pancreatitis, and that cathepsin S inhibitors significantly alleviate hyperlipidemic pancreatitis. Therefore, cathepsin S may be a new target for the clinical treatment of hyperlipidemic pancreatitis.

Intranasal curcumin and dexamethasone combination ameliorates inflammasome (NLRP3) activation in lipopolysachharide exposed asthma exacerbations

The inflammasome NOD-like receptor (NLR) family, the pyrin domain containing 3 (NLRP3) is closely associated with exacerbation of asthma as endotoxin (lipopolysaccharide, LPS) is one of its activators present in the environment. Present study is undertaken to investigate anti-inflammatory effects of a well known phytochemical, curcumin, which might regulate LPS exposed asthma exacerbations by modulating NLRP3 activation if given through intranasal route. Balb/c mice were sensitized with intraperitoneal injection of OVA (Ovalbumin; 100 μg of OVA with alum) from day 1 to 8 and exposed to LPS with 1% OVA aerosol from day 9 to 15. LPS (0.1 μg) was given an hour before sensitization and OVA-aerosol challenge. Significant decrease in inflammatory cell recruitment and restoration of structural changes in lungs, alterations in mRNA and protein expressions of TLR-4, NF-κB, NLRP3, Caspase-1, IL-1β, MMP-9, IL-5 and IL-17 in intranasal curcumin alone and corticosteroid combined pretreatment group.

Gasdermin D inhibition prevents multiple organ dysfunction during sepsis by blocking NET formation

Multiple organ dysfunction is the most severe outcome of sepsis progression and is highly correlated with a worse prognosis. Excessive neutrophil extracellular traps (NETs) are critical players in the development of organ failure during sepsis. Therefore, interventions targeting NET release would likely effectively prevent NET-based organ injury associated with this disease. Herein, we demonstrate that the pore-forming protein gasdermin D (GSDMD) is active in neutrophils from septic humans and mice and plays a crucial role in NET release. Inhibition of GSDMD with disulfiram or genic deletion abrogated NET formation, reducing multiple organ dysfunction and sepsis lethality. Mechanistically, we demonstrate that during sepsis, activation of the caspase-11/GSDMD pathway controls NET release by neutrophils during sepsis. In summary, our findings uncover a novel therapeutic use for disulfiram and suggest that GSDMD is a therapeutic target to improve sepsis treatment.

NLRP3/caspase-1/GSDMD-mediated pyroptosis exerts a crucial role in astrocyte pathological injury in mouse model of depression

Emerging evidence suggests that astrocyte loss is one of the most important pathological features in the hippocampus of patients with major depressive disorder (MDD) and depressive mice. Pyroptosis is a recently discovered form of programmed cell death depending on Caspase-gasdermin D (Casp-GSDMD), which is involved in multiple neuropsychiatric diseases. However, the involvement of pyroptosis in the onset of MDD and glial pathological injury remains obscure. Here, we observed that depressive mice showed astrocytic pyroptosis, which was responsible for astrocyte loss, and selective serotonin reuptake inhibitor (SSRI) treatment could attenuate the pyroptosis induced by the chronic mild stress (CMS) model. Genetic KO of GSDMD, Casp-1, and astrocytic NOD-like receptor protein 3 (NLRP3) inflammasome in mice alleviated depression-like behaviors and inhibited the pyroptosis-associated protein expression. In contrast, overexpression of astrocytic GSDMD-N-terminal domain (GSDMD-N) in the hippocampus could abolish the improvement of behavioral alterations in GSDMD-deficient mice. This work illustrates that targeting the NLRP3/Casp-1/GSDMD-mediated pyroptosis may provide potential therapeutic benefits to stress-related astrocyte loss in the pathogenesis of depression.

Walking down Skeletal Muscle Lane: From Inflammasome to Disease

Over the last decade, innate immune system receptors and sensors called inflammasomes have been identified to play key pathological roles in the development and progression of numerous diseases. Among them, the nucleotide-binding oligomerization domain (NOD-), leucine-rich repeat (LRR-) and pyrin domain-containing protein 3 (NLRP3) inflammasome is probably the best characterized. To date, NLRP3 has been extensively studied in the heart, where its effects and actions have been broadly documented in numerous cardiovascular diseases. However, little is still known about NLRP3 implications in muscle disorders affecting non-cardiac muscles. In this review, we summarize and present the current knowledge regarding the function of NLRP3 in diseased skeletal muscle, and discuss the potential therapeutic options targeting the NLRP3 inflammasome in muscle disorders.

Serum NLRP3: A biomarker for identifying high-risk septic patients

BACKGROUND

Over-activation of the NLRP3 inflammasome can lead to sepsis. NLRP3 is an essential protein in the classical pathway of pyroptosis. This study assessed the use of serum NLRP3 level as a potential inflammatory biomarker in septic patients.

METHODS

Patients were categorized into five groups: healthy controls (n = 30), ICU controls (n = 22), infection (n = 19), septic non-shock (n = 33), and septic shock (n = 83). Serum NLRP3 levels were measured by enzyme-linked immunosorbent assay for all patients upon enrollment. Clinical parameters and laboratory test data (APACHE II, SOFA, and lactate) were also assessed. Moreover, the ability of serum NLRP3 levels to predict sepsis was determined by the area under the curve (AUC) analysis.

RESULTS

The NLRP3 levels in the septic shock group was significantly higher (431.89, 386.61-460.21 pg/mL) than that in the healthy control group (23.24, 9.38-49.73 pg/mL), ICU control group (74.82, 62.71-85.93 pg/mL), infection group (114.34, 99.21-122.56 pg/mL), and septic non-shock group (136.99, 128.80-146.98 pg/mL; P＜0.001 for all comparisons). Additionally, the AUC indicated that the ability of serum NLRP3 levels to predict sepsis and septic shock incidences was not lower than that of the SOFA score. Patients with higher NLRP3 serum levels (>147.72 pg/mL) had significantly increased 30-day mortality rate.

CONCLUSIONS

NLRP3 is useful for the early identification of high-risk septic patients, particularly septic shock patients. Moreover, elevated NRLP3 levels could result in poor septic prediction outcomes.

Gasdermin and Gasdermin-Like Pore-Forming Proteins in Invertebrates, Fungi and Bacteria

The gasdermin family of pore-forming proteins (PFPs) has recently emerged as key molecular players controlling immune-related cell death in mammals. Characterized mammalian gasdermins are activated through proteolytic cleavage by caspases or serine proteases, which remove an inhibitory carboxy-terminal domain, allowing the pore-formation process. Processed gasdermins form transmembrane pores permeabilizing the plasma membrane, which often results in lytic and inflammatory cell death. While the gasdermin-dependent cell death (pyroptosis) has been predominantly characterized in mammals, it now has become clear that gasdermins also control cell death in early vertebrates (teleost fish) and invertebrate animals such as corals (Cnidaria). Moreover, gasdermins and gasdermin-like proteins have been identified and characterized in taxa outside of animals, notably Fungi and Bacteria. Fungal and bacterial gasdermins share many features with mammalian gasdermins including their mode of activation through proteolysis. It has been shown that in some cases the proteolytic activation is executed by evolutionarily related proteases acting downstream of proteins resembling immune receptors controlling pyroptosis in mammals. Overall, these findings establish gasdermins and gasdermin-regulated cell death as an extremely ancient mechanism of cellular suicide and build towards an understanding of the evolution of regulated cell death in the context of immunology. Here, we review the broader gasdermin family, focusing on recent discoveries in invertebrates, fungi and bacteria.

Activation of the NLRP3 Inflammasome Increases the IL-1β Level and Decreases GLUT4 Translocation in Skeletal Muscle during Insulin Resistance

Low-grade chronic inflammation plays a pivotal role in the pathogenesis of insulin resistance (IR), and skeletal muscle has a central role in this condition. NLRP3 inflammasome activation pathways promote low-grade chronic inflammation in several tissues. However, a direct link between IR and NLRP3 inflammasome activation in skeletal muscle has not been reported. Here, we evaluated the NLRP3 inflammasome components and their role in GLUT4 translocation impairment in skeletal muscle during IR. Male C57BL/6J mice were fed with a normal control diet (NCD) or high-fat diet (HFD) for 8 weeks. The protein levels of NLRP3, ASC, caspase-1, gasdermin-D (GSDMD), and interleukin (IL)-1β were measured in both homogenized and isolated fibers from the flexor digitorum brevis (FDB) or soleus muscle. GLUT4 translocation was determined through GLUT4myc-eGFP electroporation of the FBD muscle. Our results, obtained using immunofluorescence, showed that adult skeletal muscle expresses the inflammasome components. In the FDB and soleus muscles, homogenates from HFD-fed mice, we found increased protein levels of NLRP3 and ASC, higher activation of caspase-1, and elevated IL-1β in its mature form, compared to NCD-fed mice. Moreover, GSDMD, a protein that mediates IL-1β secretion, was found to be increased in HFD-fed-mice muscles. Interestingly, MCC950, a specific pharmacological NLRP3 inflammasome inhibitor, promoted GLUT4 translocation in fibers isolated from the FDB muscle of NCD- and HFD-fed mice. In conclusion, we found increased NLRP3 inflammasome components in adult skeletal muscle of obese insulin-resistant animals, which might contribute to the low-grade chronic metabolic inflammation of skeletal muscle and IR development.

Design, synthesis, HER2 inhibition and anticancer evaluation of new substituted 1,5-dihydro-4,1-benzoxazepines

A series of 11 new substituted 1,5-dihydro-4,1-benzoxazepine derivatives was synthesised to study the influence of the methyl group in the 1-(benzenesulphonyl) moiety, the replacement of the purine by the benzotriazole bioisosteric analogue, and the introduction of a bulky substituent at position 6 of the purine, on the biological effects. Their inhibition against isolated HER2 was studied and the structure–activity relationships have been confirmed by molecular modelling studies. The most potent compound against isolated HER2 is 9a with an IC₅₀ of 7.31 µM. We have investigated the effects of the target compounds on cell proliferation. The most active compound (7c) against all the tumour cell lines studied (IC₅₀ 0.42–0.86 µM) does not produce any modification in the expression of pro-caspase 3, but increases the caspase 1 expression, and promotes pyroptosis.

Hepatocyte and immune cell crosstalk in non-alcoholic fatty liver disease

Introduction: Nonalcoholic fatty liver disease (NAFLD) is the most widespread chronic liver disease in the world. It can evolve into nonalcoholic steatohepatitis (NASH) where inflammation and hepatocyte ballooning are key participants in the determination of this steatotic state.Areas covered: To provide a systematic overview and current understanding of the role of inflammation in NAFLD and its progression to NASH, the function of the cells involved, and the activation pathways of the innate immunity and cell death; resulting in inflammation and chronic liver disease. A PubMed search was made with relevant articles together with relevant references were included for the writing of this review.Expert opinion: Innate and adaptive immunity are the key players in the NAFLD progression; some of the markers presented during NAFLD are also known to be immunity biomarkers. All cells involved in NAFLD and NASH are known to have immunoregulatory properties and their imbalance will completely change the cytokine profile and form a pro-inflammatory microenvironment. It is necessary to fully answer the question of what initiators and metabolic imbalances are particularly important, considering sterile inflammation as the architect of the disease. Due to the shortage of elucidation of NASH progression, we discuss in this review, how inflammation is a key part of this development and we presume the targets should lead to inflammation and oxidative stress treatment.

Gasdermin family proteins as a permeabilization factor of cell membrane in pyroptosis process

The type of cell death, i.e. apoptosis, autophagy, necrosis or pyroptosis, depends on the inducing factor and the phase of the cell cycle. The main role in immunological response to microorganisms is played by a process called pyroptosis. Pyroptosis induces various types of inflammatory factors in response to molecular patterns associated with pathogens, e.g., bacterial lipopolysaccharide in the canonical or non-canonical pathway depending on the type of caspases involved. In pyroptosis, the gasdermin D protein belonging to the gasdermin protein family (A, B, C, D, E and DFNB59) plays an important role, which is characterized by specific tissue gene expression mainly in epithelial cells, skin and the digestive system and is responsible for regulating the proliferation and differentiation of cells and is responsible for inhibiting or developing cancers in various organs. The GSDM family is responsible for the formation of pores in the cell membrane, enabling the secretion of proinflammatory cytokines (IL-1β and IL-18) involved in initiating inflammatory response pathways by recruiting and activating immune cells at the site of infection. The gasdermin D protein plays an essential role in the non-canonical pyroptosis process, whose N-terminal forming pores in the cell membrane leads to edema, osmotic lysis and, consequently, to the death of the infected cell.

Role of pyroptosis in diabetic retinopathy and its therapeutic implications

Pyroptosis has recently been established as a term of programmed-inflammatory cell death. Pyroptosis is mainly divided into two molecular signaling pathways, including caspase-1-dependent canonical and caspase-4/5/11-dependent non-canonical inflammasome pathways. Extensive investigations have reported inflammasome activation facilitates the maturation and secretion of the inflammatory factors interleukin-1β/18 (IL-1β/18), cleavage of gasdermin D (GSDMD), and leading to the stimulation of pyroptosis-mediated cell death. Furthermore, accumulating studies report NLRP3 inflammasome activation plays a significant role in triggering the pyroptosis-mediated cell death and promotes the pathogenesis of diabetic retinopathy (DR). Our current review elaborates on the molecular mechanisms of pyroptosis-signaling pathways and their potential roles in the pathogenesis and impact of DR development. We also emphasize several investigational molecules regulating key steps in pyroptotic-cell death to create new comprehensions and findings to explore the pathogenesis of DR advancement. Our narrative review concisely suggests these potential pharmacological agents could be promising therapies to treat and manage DR in the future.

Roles of Inflammasomes in Epstein-Barr Virus-Associated Nasopharyngeal Cancer

Epstein-Barr virus (EBV) infection is recognised as one of the causative agents in most nasopharyngeal carcinoma (NPC) cases. Expression of EBV viral antigens can induce host's antiviral immune response by activating the inflammasomes to produce pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and IL-18. These cytokines are known to be detrimental to a wide range of virus-infected cells, in which they can activate an inflammatory cell death program, called pyroptosis. However, aberrant inflammasome activation and production of its downstream cytokines lead to chronic inflammation that may contribute to various diseases, including NPC. In this review, we summarise the roles of inflammasomes during viral infection, how EBV evades inflammasome-mediated immune response, and progress into tumourigenesis. The contrasting roles of inflammasomes in cancer, as well as the current therapeutic approaches used in targeting inflammasomes, are also discussed in this review. While the inflammasomes appear to have dual roles in carcinogenesis, there are still many questions that remain unanswered. In particular, the exact molecular mechanism responsible for the regulation of the inflammasomes during carcinogenesis of EBV-associated NPC has not been explored thoroughly. Furthermore, the current practical application of inflammasome inhibitors is limited to specific tumour types, hence, further studies are warranted to discover the potential of targeting the inflammasomes for the treatment of NPC.

NLRP3 Inflammasome: Potential Role in Obesity Related Low-Grade Inflammation and Insulin Resistance in Skeletal Muscle

Among multiple mechanisms, low-grade inflammation is critical for the development of insulin resistance as a feature of type 2 diabetes. The nucleotide-binding oligomerization domain-like receptor family (NOD-like) pyrin domain containing 3 (NLRP3) inflammasome has been linked to the development of insulin resistance in various tissues; however, its role in the development of insulin resistance in the skeletal muscle has not been explored in depth. Currently, there is limited evidence that supports the pathological role of NLRP3 inflammasome activation in glucose handling in the skeletal muscle of obese individuals. Here, we have centered our focus on insulin signaling in skeletal muscle, which is the main site of postprandial glucose disposal in humans. We discuss the current evidence showing that the NLRP3 inflammasome disturbs glucose homeostasis. We also review how NLRP3-associated interleukin and its gasdermin D-mediated efflux could affect insulin-dependent intracellular pathways. Finally, we address pharmacological NLRP3 inhibitors that may have a therapeutical use in obesity-related metabolic alterations.

Gasdermin D restricts Burkholderia cenocepacia infection in vitro and in vivo

Burkholderia cenocepacia (B. cenocepacia) is an opportunistic bacterium; causing severe life threatening systemic infections in immunocompromised individuals including cystic fibrosis patients. The lack of gasdermin D (GSDMD) protects mice against endotoxin lipopolysaccharide (LPS) shock. On the other hand, GSDMD promotes mice survival in response to certain bacterial infections. However, the role of GSDMD during B. cenocepacia infection is not yet determined. Our in vitro study shows that GSDMD restricts B. cenocepacia replication within macrophages independent of its role in cell death through promoting mitochondrial reactive oxygen species (mROS) production. mROS is known to stimulate autophagy, hence, the inhibition of mROS or the absence of GSDMD during B. cenocepacia infections reduces autophagy which plays a critical role in the restriction of the pathogen. GSDMD promotes inflammation in response to B. cenocepacia through mediating the release of inflammasome dependent cytokine (IL-1β) and an independent one (CXCL1) (KC). Additionally, different B. cenocepacia secretory systems (T3SS, T4SS, and T6SS) contribute to inflammasome activation together with bacterial survival within macrophages. In vivo study confirmed the in vitro findings and showed that GSDMD restricts B. cenocepacia infection and dissemination and stimulates autophagy in response to B. cenocepacia. Nevertheless, GSDMD promotes lung inflammation and necrosis in response to B. cenocepacia without altering mice survival. This study describes the double-edged functions of GSDMD in response to B. cenocepacia infection and shows the importance of GSDMD-mediated mROS in restriction of B. cenocepacia.

Exenatide Attenuates Non-Alcoholic Steatohepatitis by Inhibiting the Pyroptosis Signaling Pathway

BACKGROUND/AIMS

Exenatide is a glucagon-like polypeptide-1 analog, whose main clinical use is to treat type 2 diabetes. However, the mechanism of exenatide in mitigating non-alcoholic steatohepatitis (NASH) remains unclear. This study aimed to investigate the in vitro and in vivo effect of exenatide on NASH.

METHODS

Leptin receptor-deficient C57BL/KsJ- db/db male mice were fed with methionine-choline-deficient (MCD) diet for 4 weeks to induce NASH, while oleic acid/LPS-treated HepG2 cells were used as an in vitro cell model. Exenatide (20 µg/kg/day, subcutaneous) and specific exenatide inhibitors (20 µg/kg/day, intraperitoneal) were used to determine the effects of exenatide on NASH.

RESULTS

Exenatide treatment inhibited the pyroptosis signaling pathway to attenuate NASH.

CONCLUSION

To the best of our knowledge, this report provides the first evidence showing that exenatide attenuated NASH by inhibiting the pyroptosis signaling pathway. Exenatide thus has important pathophysiological functions in NASH and may represent a useful new therapeutic target.

Regulated Necrotic Cell Death in Alternative Tumor Therapeutic Strategies

The treatment of tumors requires the induction of cell death. Radiotherapy, chemotherapy, and immunotherapy are administered to kill cancer cells; however, some cancer cells are resistant to these therapies. Therefore, effective treatments require various strategies for the induction of cell death. Regulated cell death (RCD) is systematically controlled by intracellular signaling proteins. Apoptosis and autophagy are types of RCD that are morphologically different from necrosis, while necroptosis, pyroptosis, and ferroptosis are morphologically similar to necrosis. Unlike necrosis, regulated necrotic cell death (RNCD) is caused by disruption of the plasma membrane under the control of specific proteins and induces tissue inflammation. Various types of RNCD, such as necroptosis, pyroptosis, and ferroptosis, have been used as therapeutic strategies against various tumor types. In this review, the mechanisms of necroptosis, pyroptosis, and ferroptosis are described in detail, and a potential effective treatment strategy to increase the anticancer effects on apoptosis- or autophagy-resistant tumor types through the induction of RNCD is suggested.

Review: Usnic acid-induced hepatotoxicity and cell death

Increasing prevalence of herbal and dietary supplement-induced hepatotoxicity has been reported worldwide. Usnic acid (UA) is a well-known hepatotoxin derived from lichens. Since 2000, more than 20 incident reports have been received by the US Food and Drug Administration after intake of UA containing dietary supplement resulting in severe complications. Scientists and clinicians have been studying the cause, prevention and treatment of UA-induced hepatotoxicity. It is now known that UA decouples oxidative phosphorylation, induces adenosine triphosphate (ATP) depletion, decreases glutathione (GSH), and induces oxidative stress markedly leading to lipid peroxidation and organelle stress. In addition, experimental rat liver tissues have shown massive vacuolization associated with cellular swellings. Additionally, various signaling pathways, such as c-JNK N-terminal kinase (JNK), store-operated calcium entry, nuclear erythroid 2-related factor 2 (Nrf2), and protein kinase B/mammalian target of rapamycin (Akt/mTOR) pathways are stimulated by UA causing beneficial or harmful effects. Nevertheless, there are controversial issues, such as UA-induced inflammatory or anti-inflammatory responses, cytochrome P450 detoxifying UA into non-toxic or transforming UA into reactive metabolites, and unknown mechanism of the formation of vacuolization and membrane pore. This article focused on the previous and latest comprehensive putative mechanistic findings of UA-induced hepatotoxicity and cell death. New insights on controversial issues and future perspectives are also discussed and summarized.

Innate Immune Receptors, Key Actors in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of death in the industrialized world. Most CVDs are associated with increased inflammation that arises mainly from innate immune system activation related to cardiac damage. Sustained activation of the innate immune system frequently results in maladaptive inflammatory responses that promote cardiovascular dysfunction and remodeling. Much research has focused on determining whether some mediators of the innate immune system are potential targets for CVD therapy. The innate immune system has specific receptors-termed pattern recognition receptors (PRRs)-that not only recognize pathogen-associated molecular patterns, but also sense danger-associated molecular signals. Activation of PRRs triggers the inflammatory response in different physiological systems, including the cardiovascular system. The classic PRRs, toll-like receptors (TLRs), and the more recently discovered nucleotide-binding oligomerization domain-like receptors (NLRs), have been recently proposed as key partners in the progression of several CVDs (e.g., atherosclerosis and heart failure). The present review discusses the key findings related to the involvement of TLRs and NLRs in the progression of several vascular and cardiac diseases, with a focus on whether some NLR subtypes (nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain-containing receptor 3 and nucleotide-binding oligomerization domain-containing protein 1) can be candidates for the development of new therapeutic strategies for several CVDs.

Research progresses of molecular mechanism of pyroptosis and its related diseases

Pyroptosis is a newly discovered untypical form of programmed cell death by inflammatory response, which is dependent on the classic pathway of Caspase-1 and the non-canonical pathway of Caspase-11 in mice or orthologue Caspase-4/-5 in Humans. It has been found that the Gasdermin family of protein is a key molecule in the formation of membrane pores of pyroptosis. After being cleaved by inflammatory caspases, it releases a N-terminal fragment with perforating activity to trigger pyroptosis. That pyroptosis is closely related to the occurrence and development of certain diseases. Now, the molecular mechanism of pyroptosis and pyroptosis-related diseases are reviewed.

Pyroptosis: A new frontier in cancer

Pyroptosis is an inflammatory form of cell death triggered by certain inflammasomes, leading to the cleavage of gasdermin D (GSDMD) and activation of inactive cytokines like IL-18 and IL-1β. Pyroptosis has been reported to be closely associated to some diseases like atherosclerosis and diabetic nephropathy. Recently, some studies found that pyroptosis can influence the proliferation, invasion and metastasis of tumor, which regulated by some non-coding RNAs and other molecules. Hence, we provided an overview of morphological and molecular characteristics of pyroptosis. We also focus on mechanism of regulating pyroptosis in tumor cells as well as the potential roles of pyroptosis in cancer to explore potential diagnostic markers in cancers contributing to the prevention and treatment in cancers.

Teleost Gasdermin E Is Cleaved by Caspase 1, 3, and 7 and Induces Pyroptosis

Pyroptosis is a newly defined gasdermin (GSDM)-dependent inflammatory type of programmed cell death. Different from mammals, which have a panel of pyroptotic GSDM members (e.g., GSDMA-E), teleosts possess only GSDME. The pyroptotic activity and regulation mechanism of teleost GSDME remain to be elucidated. In this work, we investigated the activity of the teleost Cynoglossus semilaevis (tongue sole) GSDME (CsGSDME) in association with different caspases (CASPs). We found that CsGSDME exerted pyroptotic and bactericidal activities through its N-terminal domain. Unlike human GSDME, which is exclusively cleaved by CASP3, CsGSDME was cleaved by C. semilaevis CASP (CsCASP) 1 with high efficiency and by CsCASP3 and 7 with comparatively low efficiencies, and all cleavages occurred at the ₂₄₃FEVD₂₄₆ site in the interdomain linker region of CsGSDME. Mutation of Phe²⁴³ to Asp/Ala and Asp²⁴⁶ to Ala in ₂₄₃FEVD₂₄₆ altered the cleavage preference of CsCASP1, 3, and 7. Treatment with loss-of-function CsCASP mutants or inhibition of CsCASP activity resulted in failure of CsGSDME cleavage. CsCASP1-cleaved CsGSDME induced pyroptosis, whereas CsCASP3/7-cleaved CsGSDME and F243 mutants induced switching of cell death from apoptosis to pyroptosis. Analysis of 54 teleost GSDME sequences revealed a conserved tetrapeptide motif that fits well to the inherent cleavage site of CASP1. Taken together, the results of our study demonstrate a hitherto, to our knowledge, unrecognized GSDME cleavage mode in teleosts that is clearly different from that in mammals, thus providing an important insight into the activation mechanism of CASP-mediated, GSDM-executed pyroptosis in teleosts.

Activation of Pyroptotic Cell Death Pathways in Cancer: An Alternative Therapeutic Approach

Cancer can be considered the result of a series of genetic variations that lead to a normal cell being transformed into a malignant one while avoiding cell death-atypical characteristics of tumor development. Although a large number of genomics and epigenetic alterations have been identified in cells undergoing apoptotic, autophagic or necrotic cell death, the treatment of cancer remains thought-provoking. Pyroptosis is differentiated from other types of programmed cell death and is mainly activated by Caspase-1. To initiate pyroptosis, cells receive specific "death" messages, produce cytokines, swell, burst, and ultimately die. The deficiency of Caspase-1 expression may lead to inflammation-mediated tumor progression. Hence, the molecular mechanisms for the Caspase-1 activation in tumor tissues are yet to be exploited extensively. This review aims to summarise the latest discoveries about pyroptosis and its new exciting role in inducing cancer cell death.

Microbes are off the menu: Defective macrophage phagocytosis in COPD

In this issue of the Biomedical Journal, we learn about the pathophysiology of chronic obstructive pulmonary disease and how defective macrophage phagocytosis may lead to the build up of microbes and pollutants in inflamed lungs. We also focus on new findings that may take us a step closer to full automation in diagnostic bacteriology laboratories. Finally, we highlight the anti-tumor properties of microalgae and the application of algorithms to predict human emotion from electrocardiogram.