Cathepsin G Inhibition by Serpinb1 and Serpinb6 Prevents Programmed Necrosis in Neutrophils and Monocytes and Reduces GSDMD-Driven Inflammation

Prenatal ambient air pollution associations with DNA methylation in asthma- and allergy-relevant genes: findings from ECHO

Prenatal exposure to air pollution is an important risk factor for child health outcomes, including asthma. Identification of DNA methylation changes associated with air pollutant exposure can provide new intervention targets to improve children's health. The aim of this study is to test the association between prenatal air pollutant exposure and DNA methylation in developmental and asthma-/allergy-relevant biospecimens (placenta, buccal, cord blood, nasal mucosa, and lavage). A subset of 2294 biospecimens collected from 1906 child participants enrolled in the Environmental Influences on Child Health Outcomes program with prenatal air pollutant and high-quality Illumina Asthma&Allergy DNA methylation array measures (n = 37 197 probes) were included. Prenatal ozone, nitrogen dioxide, and fine particulate matter were derived using residential history during pregnancy and spatiotemporal models. For each pollutant, biospecimen type, and prenatal exposure window, we estimated the effects of air pollution on gene DNA methylation levels. We compared results across pollutants, biospecimen types, and trimesters and tested for critical months of exposure using distributed lag models. DNA methylation levels at 154 out of 4746 tested genes were associated with air pollution; over 95% were exposure window, pollutant, and biospecimen-type specific. The fewest gene associations were detected in trimester 2, relative to other exposure windows. A variety of trends in methylation patterns were observed in response to lagged monthly pollution levels. Child DNA methylation changes at specific respiratory- and immune-relevant genes are associated with prenatal air pollutant exposures. Future studies should examine the relationship between these pollution-sensitive genes and child health.

Biomarker identification associated with M2 tumor-associated macrophage infiltration in glioblastoma

Purpose

M2 phenotype tumor-associated macrophages (TAMs) can promote tumor growth, invasion, chemotherapy resistance and so on, leading to malignant progression. The aim of this study was to identify novel prognostic profiles in glioblastoma (GBM) by integrating single-cell RNA sequencing (scRNA-seq) with bulk RNA-seq.

Methods

We identified M2-associated genes by intersecting TAM marker genes derived from scRNA-seq with macrophage module genes from WGCNA RNA-seq data. Prognostic M2 TAM-related genes were determined using univariate Cox and LASSO regression analyses. In the following steps, prognostic characteristics, risk groups, and external validation were constructed and validated. The immune landscape of patients with GBM was examined by evaluating immune cells, functions, evasion scores, and checkpoint genes.

Results

Analysis of scRNA-seq and bulk-seq data revealed 107 genes linked to M2 TAMs. Using univariate Cox and LASSO regression, 16 genes were identified as prognostic for GBM, leading to the creation and validation of a prognostic signature for GBM survival prediction.

Conclusion

Our findings reveal the immune landscape of GBM and enhance understanding of the molecular mechanisms associated with M2 TAMs.

Cathepsins and age-related macular degeneration: A Mendelian randomization study unveiling causal relationships

Age-related macular degeneration (AMD) is a leading cause of vision impairment and blindness in older adults, profoundly affecting millions of individuals worldwide. Cathepsins are a crucial class of proteolytic enzymes that participates in multiple biological process. However, the role of cathepsins in AMD still remains unclear. This study aims to probe into the causal relationship between cathepsins and AMD using a 2-sample Mendelian randomization (MR). Instrumental variables associated with exposure (cathepsins) and the outcome (AMD) were sourced from published genome-wide association studies. To estimate the causal effects, methodologies such as inverse variance weighted, MR-Egger, and weighted median estimation (WM) were employed. Reverse MR and multivariate MR analyses were also performed. The elevated levels of cathepsin B significantly increased the risk of dry AMD, with an odds ratio (OR) of 1.068 (95% CI = 1.007-1.133) and a P-value of .029). Sensitivity analyses confirmed the robustness of these findings, with no evidence of heterogeneity or pleiotropy. Reverse MR analyses indicated that total AMD might elevate levels of cathepsin E (OR = 1.04, P = .029). Multivariate MR analysis showed significant associations between specific cathepsins and AMD subtypes, including cathepsin G and cathepsin O with significantly increasing risk. The study revealed a potential causal effect of cathepsin B on AMD, especially dry AMD. These findings provide potential therapeutic targets for AMD, and further research is needed to understand the underlying mechanisms.

Pyroptosis: molecular mechanisms and roles in disease

Pyroptosis is a type of programmed necrosis triggered by the detection of pathogens or endogenous danger signals in the cytosol. Pyroptotic cells exhibit a swollen, enlarged morphology and ultimately undergo lysis, releasing their cytosolic contents - such as proteins, metabolites, and nucleic acids - into the extracellular space. These molecules can function as danger-associated molecular patterns (DAMPs), triggering inflammation when detected by neighboring cells. Mechanistically, pyroptosis is initiated by members of the gasdermin protein family, which were identified a decade ago as pore-forming executors of cell death. Mammalian gasdermins consist of a cytotoxic N-terminal domain, a flexible linker, and a C-terminal regulatory domain that binds to and inhibits the N-terminus. Proteolytic cleavage within the linker releases the N-terminal domain, enabling it to target various cellular membranes, including nuclear, mitochondrial, and plasma membranes, where it forms large transmembrane pores. Gasdermin pores in the plasma membrane disrupt the electrochemical gradient, leading to water influx and cell swelling. Their formation also activates the membrane protein ninjurin-1 (NINJ1), which oligomerizes to drive complete plasma membrane rupture and the release of large DAMPs. Since their discovery as pore-forming proteins, gasdermins have been linked to pyroptosis not only in host defense but also in various pathological conditions. This review explores the history of pyroptosis, recent insights into gasdermin activation, the cellular consequences of pore formation, and the physiological roles of pyroptosis.

Potential Impact of Climate Change-Induced Alterations on Pyroptotic Cell Death in Animal Cells: A Review

Climate change-induced alterations in temperature variation, ozone exposure, water salinity and acidification, and hypoxia might influence immunity and thus survival in diverse groups of animals from fish to mammals. Pyroptosis is a type of lytic pro-inflammatory programmed cell death, which participates in the innate immune response, and is involved in multiple diseases characterized by inflammation and cell death, mostly studied in human cells. Diverse extrinsic factors can induce pyroptosis, leading to the extracellular release of pro-inflammatory molecules such as IL-18. Climate change-related factors, either directly or indirectly, can also promote animal cell death via different regulated mechanisms, impacting organismal fitness. However, pyroptosis has been relatively less studied in this context compared to another cell death process, apoptosis. This review covers previous research pointing to the potential impact of climate change, through various abiotic stressors, on pyroptotic cell death in different animal cells in various contexts. It was proposed that temperature, ozone exposure, water salinity, water acidification and hypoxia have the potential to induce pyroptotic cell death in animal cells and promote inflammation, and that these pyroptotic events should be better understood to be able to mitigate the adverse effects of climate change on animal physiology and health. This is of high importance considering the increasing frequency, intensity and duration of climate-based changes in these environmental parameters, and the critical function of pyroptosis in immune responses of animals and in their predisposition to multiple diseases including cancer. Furthermore, the need for further mechanistic studies showing the more direct impact of climate change-induced environmental alterations on pyroptotic cell death in animals at the organismal level was highlighted. A complete picture of the association between climate change and pyroptosis in animals will be also highly valuable in terms of ecological and clinical applications, and it requires an interdisciplinary approach. SIGNIFICANCE: Climate change-induced alterations might influence animal physiology. Pyroptosis is a form of cell death with pro-inflammatory characteristics. Previous research suggests that temperature variation, ozone exposure, water salinity and acidification, and hypoxia might have the potential to contribute to pyroptotic cell death in certain cell types and contexts. Climate change-induced pyroptotic cell death should be better understood to be able to mitigate the adverse effects of climate change on animal health.

Inflammasome Activation and Neutrophil Extracellular Traps in Atherosclerosis

The deposition of cholesterol containing cholesterol crystals and the infiltration of immune cells are features of atherosclerosis. Although the role of cholesterol crystals in the progression of atherosclerosis have long remained unclear, recent studies have clarified the involvement of cholesterol crystals in inflammatory responses. Cholesterol crystals activate the NLRP3 inflammasome, a molecular complex involved in the innate immune system. Activation of NLRP3 inflammasomes in macrophages cause pyroptosis, which is accompanied by the release of inflammatory cytokines such as IL-1β and IL-1α. Furthermore, NLRP3 inflammasome activation drives neutrophil infiltration into atherosclerotic plaques. Cholesterol crystals trigger NETosis against infiltrated neutrophils, a form of cell death characterized by the formation of neutrophil extracellular traps (NETs), which, in turn, prime macrophages to enhance inflammasome-mediated inflammatory responses. Colchicine, an anti-inflammatory drug effective in cardiovascular disease, is expected to inhibit cholesterol crystal-induced NLRP3 inflammasome activation and neutrophil infiltration. In this review, we illustrate the reinforcing cycle of inflammation that is amplified by inflammasome activation and NETosis.

SerpinB1 targeting safeguards against pathological cardiac hypertrophy and remodelling by suppressing cardiomyocyte pyroptosis and inflammation initiation

AIMS

While the pivotal role of inflammation in pathological cardiac hypertrophy and remodelling is widely acknowledged, the mechanisms triggering inflammation initiation remain largely obscure. This study aims to elucidate the role and mechanism of serpin family B member 1 (SerpinB1) in pro-inflammatory cardiomyocyte pyroptosis, heart inflammation, and cardiac remodelling.

METHODS AND RESULTS

C57BL/6J wild-type, inducible cardiac-specific SerpinB1 overexpression or knockout mice underwent transverse aortic constriction (TAC) surgery. Cardiac hypertrophy and remodelling were assessed through echocardiography and histology. Cardiomyocyte pyroptosis and heart inflammation were monitored. Adeno-associated virus 9 -mediated gene manipulations and molecular assays were employed to explore the mechanisms through which SerpinB1 regulates cardiomyocyte pyroptosis and heart inflammation. Finally, recombinant mouse SerpinB1 protein (rSerpinB1) was administrated both in vivo through osmotic minipump delivery and in vitro to investigate the therapeutic potential of SerpinB1 in cardiac remodelling. Myocardial SerpinB1 overexpression was up-regulated shortly upon TAC or phenylephrine challenge, with no further elevation during prolonged hypertrophic stimuli. It is important to note that cardiac-specific overexpression of SerpinB1 markedly attenuated TAC-induced cardiac remodelling, while deletion of SerpinB1 exacerbated it. At the mechanistic level, SerpinB1 gain-of-function inhibited cardiomyocyte pyroptosis and inflammation in hypertrophic hearts; the protective effect was nullified by overexpression of either cleaved N-terminal gasdermin D or cleaved caspase-1. Co-immunoprecipitation and confocal assays confirmed that SerpinB1 directly interacts with caspase-1 in cardiomyocytes. Remarkably, rSerpinB1 replicated the cardioprotective effect against cardiac hypertrophy and remodelling.

CONCLUSION

SerpinB1 safeguards against pathological cardiac hypertrophy and remodelling by impeding cardiomyocyte pyroptosis to suppress inflammation initiation, achieved through interaction with caspase-1 to inhibit its activation. Targeting SerpinB1 could represent a novel therapeutic strategy for treating pathological cardiac hypertrophy and remodelling.

Role of gasdermins in chronic kidney disease

Gasdermins (GSDMs), functioning as membrane perforating proteins, can be activated by canonical inflammasomes, noncanonical inflammasomes, as well as non-inflammasomes, leading to cell pyroptosis and the subsequent release of inflammatory mediators. Increasing evidence has implicated that GSDMs are associated with chronic kidney disease (CKD), including diabetes nephropathy, lupus nephritis, obstructive nephropathy, and crystalline nephropathy. This review centers on the role of GSDMs-mediated pyroptosis in the pathogenesis of CKD, providing novel ideas for enhancing the prognosis and therapeutic strategies of CKD.

Mechanistic insights into gasdermin-mediated pyroptosis

Pyroptosis, a novel mode of inflammatory cell death, is executed by membrane pore-forming gasdermin (GSDM) family members in response to extracellular or intracellular injury cues and is characterized by a ballooning cell morphology, plasma membrane rupture and the release of inflammatory mediators such as interleukin-1β (IL-1β), IL-18 and high mobility group protein B1 (HMGB1). It is a key effector mechanism for host immune defence and surveillance against invading pathogens and aberrant cancerous cells, and contributes to the onset and pathogenesis of inflammatory and autoimmune diseases. Manipulating the pore-forming activity of GSDMs and pyroptosis could lead to novel therapeutic strategies. In this Review, we discuss the current knowledge regarding how GSDM-mediated pyroptosis is initiated, executed and regulated, its roles in physiological and pathological processes, and the crosstalk between different modes of programmed cell death. We also highlight the development of drugs that target pyroptotic pathways for disease treatment.

Bat adaptations in inflammation and cell death regulation contribute to viral tolerance

Bats are reservoirs for multiple viruses, some of which are known to cause global disease outbreaks. Virus spillovers from bats have been implicated in zoonotic transmission. Some bat species can tolerate viral infections, such as infections with coronaviruses and paramyxoviruses, better than humans and with less clinical consequences. Bat species are speculated to have evolved alongside these viral pathogens, and adaptations within the bat immune system are considered to be associated with viral tolerance. Inflammation and cell death in response to zoonotic virus infections prime human immunopathology. Unlike humans, bats have evolved adaptations to mitigate virus infection-induced inflammation. Inflammatory cell death pathways such as necroptosis and pyroptosis are associated with immunopathology during virus infections, but their regulation in bats remains understudied. This review focuses on the regulation of inflammation and cell death pathways in bats. We also provide a perspective on the possible contribution of cell death-regulating proteins, such as caspases and gasdermins, in modulating tissue damage and inflammation in bats. Understanding the role of these adaptations in bat immune responses can provide valuable insights for managing future disease outbreaks, addressing human disease severity, and improving pandemic preparedness.

GSDMD-mediated pyroptosis: molecular mechanisms, diseases and therapeutic targets

Pyroptosis is a regulated form of inflammatory cell death in which Gasdermin D (GSDMD) plays a central role as the key effector molecule. GSDMD-mediated pyroptosis is characterized by complex biological features and considerable heterogeneity in its expression, mechanisms, and functional outcomes across various tissues, cell types, and pathological microenvironments. This heterogeneity is particularly pronounced in inflammation-related diseases and tumors. In the context of inflammatory diseases, GSDMD expression is typically upregulated, and its activation in macrophages, neutrophils, T cells, epithelial cells, and mitochondria triggers both pyroptotic and non-pyroptotic pathways, leading to the release of pro-inflammatory cytokines and exacerbation of tissue damage. However, under certain conditions, GSDMD-mediated pyroptosis may also serve a protective immune function. The expression of GSDMD in tumors is regulated in a more complex manner, where it can either promote immune evasion or, in some instances, induce tumor cell death. As our understanding of GSDMD's role continues to progress, there have been advancements in the development of inhibitors targeting GSDMD-mediated pyroptosis; however, these therapeutic interventions remain in the preclinical phase. This review systematically examines the cellular and molecular complexities of GSDMD-mediated pyroptosis, with a particular emphasis on its roles in inflammation-related diseases and cancer. Furthermore, it underscores the substantial therapeutic potential of GSDMD as a target for precision medicine, highlighting its promising clinical applications.

Macrophage pyroptosis in atherosclerosis: therapeutic potential

Atherosclerosis (AS) is a chronic inflammatory disease characterized by the accumulation of lipid-rich plaques in arterial walls, leading to cardiovascular events such as myocardial infarction and stroke. Macrophage pyroptosis, a form of programmed cell death driven by the NLRP3 inflammasome and caspase-1 activation, plays a critical role in the progression and destabilization of atherosclerotic plaques. This review explores the molecular mechanisms underlying macrophage pyroptosis and their significant contributions to AS pathogenesis. Recent advancements have highlighted the therapeutic potential of targeting key components of the pyroptotic pathway, including the use of nanotechnology to increase drug delivery specificity. These strategies are promising for reducing inflammation, stabilizing plaques, and mitigating the clinical impact of AS. Future studies should focus on translating these findings into clinical applications to develop effective treatments that can halt or reverse AS progression by modulating macrophage pyroptosis.

Vastly different energy landscapes of the membrane insertions of monomeric gasdermin D and A3

Gasdermin D and gasdermin A3 belong to the same family of pore-forming proteins and executors of pyroptosis, a form of programmed cell death. To unveil the process of their pore formation, we examine the energy landscapes upon insertion of the gasdermin D and A3 monomers into a lipid bilayer by extensive atomistic molecular dynamics simulations. We reveal a lower free energy barrier of membrane insertion for gasdermin D than for gasdermin A3 and a preference of gasdermin D for the membrane-inserted and of gasdermin A3 for the membrane-adsorbed state, suggesting that gasdermin D first inserts and then oligomerizes while gasdermin A3 oligomerizes and then inserts. Gasdermin D stabilizes itself in the membrane by forming more salt bridges and pulling phosphatidylethanolamine lipids and more water into the membrane. Gasdermin-lipid interactions support the pore formation. Our findings suggest that both the gasdermin species and the lipid composition modulate gasdermin pore formation.

Litomosoides sigmodontis microfilariae-induced eosinophil ETosis is dependent on the canonical inflammasome pathway

Granulocytes exert several effector mechanisms, including the release of DNA traps during ETosis. While bacteria-induced ETosis has been linked to the non-canonical inflammasome pathway, the role of the inflammasome activation during ETosis in response to extracellular pathogens has not been investigated. The current study demonstrates that microfilariae (MF) of the rodent filarial nematode Litomosoides sigmodontis induce eosinophil ETosis via the canonical inflammasome pathway. The absence of key components of the canonical inflammasome, including gasdermin D, caspase-1, the adaptor molecule ASC, or AIM2 (double-stranded DNA sensor) prevents MF-induced DNA release in murine eosinophils. While AIM2 activation is not affecting other effector mechanisms such as reactive oxygen species generation and nuclear membrane collapse, it appears to be critical in mediating the release of DNA from the cell during the later stages of ETosis. Finally, the findings on inflammasome-dependent ETosis in response to MF are confirmed in human eosinophils.

New insights into constitutive neutrophil death

Neutrophils undergo rapid aging and death known as constitutive or spontaneous death. Constitutive neutrophil death (CND) contributes to neutrophil homeostasis and inflammation resolution. CND has long been considered to be apoptotic until our findings reveal that it was a heterogeneous combination of diverse death. Furthermore, dead neutrophils retain functional roles via multiple manners. This review provides an overview of current research on the mechanism and modulation of CND. More noteworthy, we also summarize the after-death events of neutrophils. The fate of neutrophils can be changed under pathological conditions, so the involvement of CND in diseases and CND-related therapeutic strategies are also addressed.

Prospects of neutrophilic implications against pathobiology of chronic obstructive pulmonary disease: Pharmacological insights and technological advances

Chronic obstructive pulmonary disease (COPD) is a prevalent chronic inflammatory condition that affects the lungs globally. A key feature of this inflammatory response is the migration and aggregation of polymorphonuclear neutrophils (PMNs). The presence of neutrophilic inflammation within the airways is as distinguishing characteristic of COPD. As research advances, PMNs and their products emerge as central players in the airway inflammatory cascade of COPD patients. Their involvement in phagocytosis, degranulation, and the formation of neutrophil extracellular traps (NETs) significantly contributes to the pathogenesis of COPD. Moreover, studies have shown that excessive biological activities of neutrophils in the lungs can result in airway epithelial injury, emphysema, and mucus hypersecretion. Currently, there is growing empirical support for the moderate targeting neutrophils in the clinical management of COPD. This article delves into the pivotal role of neutrophils in COPD, emphasizing the urgency for novel therapeutic approaches that specifically target neutrophils. Additionally, it explores the potential of utilizing single-cell RNA sequencing to further investigate neutrophils and relevant risk genes as potential biomarkers for COPD treatment. By elucidating these mechanisms, this review aims to pave the way for future strategies to modulate neutrophil function, thereby addressing the pressing need for more effective COPD therapies.

Microsporidian Nosema bombycis secretes serine protease inhibitor to suppress host cell apoptosis via Caspase BmICE

Microsporidia are a group of intracellular pathogens that actively manipulate host cell biological processes to facilitate their intracellular niche. Apoptosis is an important defense mechanism by which host cell control intracellular pathogens. Microsporidia modulating host cell apoptosis has been reported previously, however the molecular mechanism is not yet clear. In this report, we describe that the microsporidia Nosema bombycis inhibits apoptosis of Bombyx mori cells through a secreted protein NbSPN14, which is a serine protease inhibitor (Serpin). An immunofluorescent assay demonstrated that upon infection with N. bombycis, NbSPN14 was initially found in the B. mori cell cytoplasm and then became enriched in the host cell nucleus. Overexpression and RNA-interference (RNAi) of NbSPN14 in B. mori' embryo cell confirmed that NbSPN14 inhibited host cells apoptosis. Immunofluorescent and Co-IP assays verified the co-localization and interaction of NbSPN14 with the BmICE, the Caspase 3 homolog in B. mori. Knocking out of BmICE or mutating the BmICE-interacting P1 site of NbSPN14, eliminated the localization of NbSPN14 into the host nucleus and prevented the apoptosis-inhibiting effect of NbSPN14, which also proved that the interaction between BmICE and NbSPN14 occurred in host cytoplasm and the NbSPN14 translocation into host cell nucleus depends on BmICE. These data elucidate that N. bombycis secretory protein NbSPN14 inhibits host cell apoptosis by directly inhibiting the Caspase protease BmICE, which provides an important insight for understanding pathogen-host interactions and a potential therapeutic target for N. bombycis proliferation.

Inflammasome-mediated pyroptosis in defense against pathogenic bacteria

Macrophages, neutrophils, and epithelial cells are pivotal components of the host's immune response against bacterial infections. These cells employ inflammasomes to detect various microbial stimuli during infection, triggering an inflammatory response aimed at eradicating the pathogens. Among these inflammatory responses, pyroptosis, a lytic form of cell death, plays a crucial role in eliminating replicating bacteria and recruiting immune cells to combat the invading pathogen. The immunological function of pyroptosis varies across macrophages, neutrophils, and epithelial cells, aligning with their specific roles within the innate immune system. This review centers on elucidating the role of pyroptosis in resisting gram-negative bacterial infections, with a particular focus on the mechanisms at play in macrophages, neutrophils, and intestinal epithelial cells. Additionally, we underscore the cell type-specific roles of pyroptosis in vivo in these contexts during defense.

The multifaceted roles of cathepsins in immune and inflammatory responses: implications for cancer therapy, autoimmune diseases, and infectious diseases

The cathepsin family comprises lysosomal proteases that play essential roles in various physiological processes, including protein degradation, antigen presentation, apoptosis, and tissue remodeling. Dysregulation of cathepsin activity has been linked to a variety of pathological conditions, such as cancer, autoimmune diseases, and neurodegenerative disorders. Understanding the functions of cathepsins is crucial for gaining insights into their roles in both health and disease, as well as for developing targeted therapeutic approaches. Emerging research underscores the significant involvement of cathepsins in immune cells, particularly T cells, macrophages, dendritic cells, and neutrophils, as well as their contribution to immune-related diseases. In this review, we systematically examine the impact of cathepsins on the immune system and their mechanistic roles in cancer, infectious diseases, autoimmune and neurodegenerative disorders, with the goal of identifying novel therapeutic strategies for these conditions.

SARS-CoV-2 3CLpro (main protease) regulates caspase activation of gasdermin-D/E pores leading to secretion and extracellular activity of 3CLpro

SARS-CoV-2 3C-like protease (3CLpro or Mpro) cleaves the SARS-CoV-2 polyprotein and >300 intracellular host proteins to enhance viral replication. By lytic cell death following gasdermin (GSDM) pore formation in cell membranes, antiviral pyroptosis decreases 3CLpro expression and viral replication. Unexpectedly, 3CLpro and nucleocapsid proteins undergo unconventional secretion from infected cells via caspase-activated GSDMD/E pores in the absence of cell lysis. Bronchoalveolar lavage fluid of wild-type SARS-CoV-2-infected mice contains 3CLpro, which decreases in Gsdmd-/-Gsdme-/- mice. We identify new 3CLpro cut-sites in GSDMD at LQ29↓30SS, which blocks pore formation by 3CLpro cleavage at LH270↓N lying adjacent to the caspase activation site (NFLTD275↓G). Cleavage inactivation of GSDMD prevents excessive pore formation, thus countering antiviral pyroptosis and increasing 3CLpro secretion. Extracellular 3CLpro retains activity in serum, dampens platelet activation and aggregation, and inactivates antiviral interferon-λ1. Thus, in countering gasdermin pore formation and pyroptosis in SARS-CoV-2 infection, 3CLpro is secreted with extracellular pathological sequelae.

Regulation of epidermal barrier function and pathogenesis of psoriasis by serine protease inhibitors

Serine protease inhibitors (Serpins) are a protein superfamily of protease inhibitors that are thought to play a role in the regulation of inflammation, immunity, tumorigenesis, coagulation, blood pressure and cancer metastasis. Serpins is enriched in the skin and play a vital role in modulating the epidermal barrier and maintaining skin homeostasis. Psoriasis is a chronic inflammatory immune-mediated skin disease. At present, most serpins focus on the pathogenesis of psoriasis vulgaris. Only a small number, such as the mutation of SerpinA1/A3/B3, are involved in the pathogenesis of GPP. SerpinA12 and SerpinG1 are significantly elevated in the serum of patients with psoriatic arthritis, but their specific mechanism of action in psoriatic arthritis has not been reported. Some Serpins, including SerpinA12, SerpinB2/B3/B7, play multiple roles in skin barrier function and pathogenesis of psoriasis. The decrease in the expression of SerpinA12, SerpinB7 deficiency and increase in expression of SerpinB3/4 in the skin can promote inflammation and poor differentiation of keratinocyte, with damaged skin barrier. Pso p27, derived from SerpinB3/B4, is an autoantigen that can enhance immune response in psoriasis. SerpinB2 plays a role in maintaining epidermal barrier integrity and inhibiting keratinocyte proliferation. Here we briefly introduce the structure, functional characteristics, expression and distribution of serpins in skin and focus on the regulation of serpins in the epidermal barrier function and the pathogenic role of serpins in psoriasis.

Diagnostic and prognostic value of the gasdermins in gastric cancer

Pyroptosis has attracted attention due to its role in various cancers. Recently, gasdermins (GSDMs) involved in pyroptosis have been reported to be associated with several types of cancers. However, the role of GSDMs expression in the diagnosis and prognosis of gastric cancer (GC) is still not well understood. We analyzed the transcriptional and prognostic information and the role of GSDMs in patients with GC from TIMER, UALCAN, Human Protein Atlas (HPA), GEPIA, and Kaplan-Meier Plotter databases. The cBioPortal platform was used to discover the genetic alterations, significance, and networks of GSDMs. Furthermore, STRING, Cytoscape, and TIMER were used to explore functional enrichment and immunomodulation. GSDMB, GSDMC, GSDMD, and GSDME were more highly expressed in GC than in normal tissues in the TIMER database. Moreover, survival analyses in two databases showed that high expression of GSDME was related to shorter overall survival (OS) in patients with GC. Additionally, functional enrichment revealed that GSDMs may be involved in endopeptidase activity, peptidase regulatory activity, and cysteine peptidase activity. GSDMs correlated with infiltration levels of immune cells in GC, and GSDME correlated with the infiltrating level of CD4+ T, CD8+ T, neutrophils, macrophages, and dendritic cells. This study indicated the potential diagnostic and prognostic value of GSDMs in GC. Our results showed that GSDME could play a significant oncogenic role in GC diagnosis and prognosis. However, our bioinformatics analyses should be validated in further prospective studies.

The role of pyroptosis in cancer: key components and therapeutic potential

Pyroptosis is a lytic and inflammatory form of gasdermin protein-mediated programmed cell death that is typically initiated by inflammasomes. The inflammasome response is an effective mechanism for eradicating germs and cancer cells in the event of cellular injury. The gasdermin family is responsible for initiating pyroptosis, a process in which holes are made in the cell membrane to allow inflammatory chemicals to escape. Mounting evidence indicates that pyroptosis is critical for controlling the development of cancer. In this review, we provide a general overview of pyroptosis, examine the relationship between the primary elements of pyroptosis and tumors, and stress the necessity of pyroptosis-targeted therapy in tumors. Furthermore, we explore its dual nature as a double-edged sword capable of both inhibiting and facilitating the growth of cancer, depending on the specific conditions. Ultimately, pyroptosis is a phenomenon that has both positive and negative effects on tumors. Using this dual impact in a reasonable manner may facilitate investigation into the initiation and progression of tumors and offer insights for the development of novel treatments centered on pyroptosis.

The Role of Cacao Powder in Enhancing Skin Moisture and Reducing Wrinkles: A 12-Week Clinical Trial and In Vitro Study

Skin aging is driven by a combination of internal and external mechanisms, with ultraviolet (UV) radiation being a prominent external factor contributing to photoaging. Photoaging manifests through several signs, including decreased skin hydration, diminished elasticity, coarse wrinkles, and dyspigmentation. Cacao beans, known for their flavonoids and polyphenols, offer potential anti-aging benefits. To explore this, we conducted a study using both in vitro experiments and clinical trials. Our results demonstrated that cacao powder significantly improved skin hydration and moisture retention in both experimental settings. Specifically, in UVB-damaged human dermal fibroblasts (HDFs) and H2O2-treated keratinocytes (KCs), cacao powder displayed notable antioxidant properties. Furthermore, cacao powder enhanced the activity of antioxidant enzymes and promoted the production of hyaluronic acid in KCs, contributing to better skin hydration. It also effectively inhibited the expression of matrix metalloproteinase-1, an enzyme associated with wrinkle formation, and stimulated collagen synthesis in HDFs. Clinical trials conducted on participants with aged skin revealed a significant improvement in skin hydration and a reduction in skin wrinkles after 12 weeks of cacao powder consumption, supporting the in vitro findings. These results suggest that cacao powder holds promise as a natural ingredient for improving skin hydration and reducing wrinkles, underscoring its potential in anti-aging skincare.

Photothermal induction of pyroptosis in malignant glioma spheroids using (16-mercaptohexadecyl)trimethylammonium bromide-modified cationic gold nanorods

Plasmonic photothermal therapy (PPTT) employing plasmonic gold nanorods (GNRs) presents a potent strategy for eradication of tumors including aggressive brain gliomas. Despite its promise, there is a pressing need for a more comprehensive evaluation of PPTT using sophisticated in vitro models that closely resemble tumor tissues, thereby facilitating the elucidation of therapeutic mechanisms. In this study, we exposed 3D glioma spheroids (tumoroids) to (16-mercaptohexadecyl)trimethylammonium bromide-functionalized gold nanorods (MTAB-GNRs) and a near-infrared (NIR) laser. We demonstrate that the photothermal effect can be fine-tuned by adjusting the nanoparticle concentration and laser power. Depending on the selected parameters, the laser can trigger either regulated or non-regulated cell death (necrosis) in both mouse GL261 and human U-87 MG glioma cell lines, accompanied by translocation of phosphatidylserine in the membrane. Our investigation into the mechanism of regulated cell death induced by PPTT revealed an absence of markers associated with classical apoptosis pathways, such as cleaved caspase 3. Instead, we observed the presence of cleaved caspase 1, gasdermin D, and elevated levels of NLRP3 in NIR-irradiated tumoroids, indicating the activation of pyroptosis. This finding correlates with previous observations of lysosomal accumulation of MTAB-GNRs and the known lysosomal pathway of pyroptosis activation. We further confirmed the absence of toxic breakdown products of GNRs using electron microscopy, which showed no melting or fragmentation of gold nanoparticles under the conditions causing regulated cell death. In conclusion, PPTT using coated gold nanorods offers significant potential for glioma cell elimination occurring through the activation of pyroptosis rather than classical apoptosis pathways.

Pyroptosis: Induction and inhibition strategies for immunotherapy of diseases

Cell death is a central process for organismal health. Pyroptosis, namely pyroptotic cell death, is recognized as a critical type that disrupts membrane and triggers pro-inflammatory cytokine secretion via gasdermins, providing a robust form of cytolysis. Meanwhile, along with the thorough research, a great deal of evidence has demonstrated the dual effects of pyroptosis in host defense and inflammatory diseases. More importantly, the recent identification of abundant gasdermin-like proteins in bacteria and fungi suggests an ancient origin of pyroptosis-based regulated cell death in the life evolution. In this review, we bring a general overview of pyroptosis pathways focusing on gasdermin structural biology, regulatory mechanisms, and recent progress in induction and inhibition strategies for disease treatment. We look forward to providing an insightful perspective for readers to comprehend the frame and challenges of the pyroptosis field, and to accelerating its clinical application.

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.

TLR9-dependent dendritic cell maturation promotes IL-6-mediated upregulation of cathepsin X

Cysteine cathepsins are lysosomal proteases subject to dynamic regulation within antigen-presenting cells during the immune response and associated diseases. To investigate the regulation of cathepsin X, a carboxy-mono-exopeptidase, during maturation of dendritic cells (DCs), we exposed immortalized mouse DCs to various Toll-like receptor agonists. Using a cathepsin X-selective activity-based probe, sCy5-Nle-SY, we observed a significant increase in cathepsin X activation upon TLR-9 agonism with CpG, and to a lesser extent with Pam3 (TLR1/2), FSL-1 (TLR2/6) and LPS (TLR4). Despite clear maturation of DCs in response to Poly I:C (TLR3), cathepsin X activity was only slightly increased by this agonist, suggesting differential regulation of cathepsin X downstream of TLR activation. We demonstrated that cathepsin X was upregulated at the transcriptional level in response to CpG. This occurred at late time points and was not dampened by NF-κB inhibition. Factors secreted from CpG-treated cells were able to provoke cathepsin X upregulation when applied to naïve cells. Among these factors was IL-6, which on its own was sufficient to induce transcriptional upregulation and activation of cathepsin X. IL-6 is highly secreted by DCs in response to CpG but much less so in response to poly I:C, and inhibition of the IL-6 receptor subunit glycoprotein 130 prevented CpG-mediated cathepsin X upregulation. Collectively, these results demonstrate that cathepsin X is differentially transcribed during DC maturation in response to diverse stimuli, and that secreted IL-6 is critical for its dynamic regulation.

Transcriptomics-based anti-tuberculous mechanism of traditional Chinese polyherbal preparation NiuBeiXiaoHe intermediates

Background

Integrated traditional Chinese medicine and biomedicine is an effective method to treat tuberculosis (TB). In our previous research, traditional Chinese medicine preparation NiuBeiXiaoHe (NBXH) achieved obvious anti-TB effects in animal experiments and clinical practice. However, the action mechanism of NBXH has not been elucidated.

Method

Peripheral blood mononuclear cells (PBMCs) were collected to extract mRNA and differentially expressed (DE) genes were obtained using gene microarray technology. Finally, GEO databases and RT-qPCR were used to verify the results of expression profile.

Result

After MTB infection, most upregulated DE genes in mice were immune-related genes, including cxcl9, camp, cfb, c4b, serpina3g, and ngp. Downregulated DE genes included lrrc74b, sult1d1, cxxc4, and grip2. After treatment with NBXH, especially high-dose NBXH, the abnormal gene expression was significantly corrected. Some DE genes have been confirmed in multiple GEO datasets or in pulmonary TB patients through RT-qPCR.

Conclusion

MTB infection led to extensive changes in host gene expression and mainly caused the host's anti-TB immune responses. The treatment using high-dose NBXH partially repaired the abnormal gene expression, further enhanced the anti-TB immunity included autophagy and NK cell-mediated cytotoxicity, and had a certain inhibitory effect on overactivated immune responses.

The role of pyroptosis in the occurrence and development of pregnancy-related diseases

Pyroptosis is a form of programmed cell death that is crucial in the development of various diseases, including autoimmune diseases, atherosclerotic diseases, cancer, and pregnancy complications. In recent years, it has gained significant attention in national and international research due to its association with inflammatory immune overactivation and its involvement in pregnancy complications such as miscarriage and preeclampsia (PE). The mechanisms discussed include the canonical pyroptosis pathway of gasdermin activation and pore formation (caspase-1-dependent pyroptosis) and the non-canonical pyroptosis pathway (cysteoaspartic enzymes other than caspase-1). These pathways work on various cellular and factorial levels to influence normal pregnancy. This review aims to summarize and analyze the pyroptosis pathways associated with abnormal pregnancies and pregnancy complications. The objective is to enhance pregnancy outcomes by identifying various targets to prevent the onset of pyroptosis.

Gasdermins as evolutionarily conserved executors of inflammation and cell death

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

Role of gasdermin D in inflammatory diseases: from mechanism to therapeutics

Inflammatory diseases compromise a clinically common and diverse group of conditions, causing detrimental effects on body functions. Gasdermins (GSDM) are pore-forming proteins, playing pivotal roles in modulating inflammation. Belonging to the GSDM family, gasdermin D (GSDMD) actively mediates the pathogenesis of inflammatory diseases by mechanistically regulating different forms of cell death, particularly pyroptosis, and cytokine release, in an inflammasome-dependent manner. Aberrant activation of GSDMD in different types of cells, such as immune cells, cardiovascular cells, pancreatic cells and hepatocytes, critically contributes to the persistent inflammation in different tissues and organs. The contributory role of GSDMD has been implicated in diabetes mellitus, liver diseases, cardiovascular diseases, neurodegenerative diseases, and inflammatory bowel disease (IBD). Clinically, alterations in GSDMD levels are potentially indicative to the occurrence and severity of diseases. GSDMD inhibition might represent an attractive therapeutic direction to counteract the progression of inflammatory diseases, whereas a number of GSDMD inhibitors have been shown to restrain GSDMD-mediated pyroptosis through different mechanisms. This review discusses the current understanding and future perspectives on the role of GSDMD in the development of inflammatory diseases, as well as the clinical insights of GSDMD alterations, and therapeutic potential of GSDMD inhibitors against inflammatory diseases. Further investigation on the comprehensive role of GSDM shall deepen our understanding towards inflammation, opening up more diagnostic and therapeutic opportunities against inflammatory diseases.

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.

Exogenous serpin B1 restricts immune complex-mediated NET formation via inhibition of a chymotrypsin-like protease and enhances microbial phagocytosis

Immune complex (IC)-driven formation of neutrophil extracellular traps (NETs) is a major contributing factor to the pathogenesis of autoimmune diseases including systemic lupus erythematosus (SLE). Exogenous recombinant human serpin B1 (rhsB1) can regulate NET formation; however, its mechanism(s) of action is currently unknown as is its ability to regulate IC-mediated NET formation and other neutrophil effector functions. To investigate this, we engineered or post-translationally modified rhsB1 proteins that possessed specific neutrophil protease inhibitory activities and pretreated isolated neutrophils with them prior to inducing NET formation with ICs derived from patients with SLE, PMA, or the calcium ionophore A23187. Neutrophil activation and phagocytosis assays were also performed with rhsB1 pretreated and IC-activated neutrophils. rhsB1 dose-dependently inhibited NET formation by all three agents in a process dependent on its chymotrypsin-like inhibitory activity, most likely cathepsin G. Only one variant (rhsB1 C344A) increased surface levels of neutrophil adhesion/activation markers on IC-activated neutrophils and boosted intracellular ROS production. Further, rhsB1 enhanced complement-mediated neutrophil phagocytosis of opsonized bacteria but not ICs. In conclusion, we have identified a novel mechanism of action by which exogenously administered rhsB1 inhibits IC, PMA, and A2138-mediated NET formation. Cathepsin G is a well-known contributor to autoimmune disease but to our knowledge, this is the first report implicating it as a potential driver of NET formation. We identified the rhsB1 C334A variant as a candidate protein that can suppress IC-mediated NET formation, boost microbial phagocytosis, and potentially impact additional neutrophil effector functions including ROS-mediated microbial killing in phagolysosomes.

Quantum Dot-Based Three-Dimensional Single-Particle Tracking Characterizes the Evolution of Spatiotemporal Heterogeneity in Necrotic Cells

Cell death is a fundamental biological process with different modes including apoptosis and necrosis. In contrast to programmed apoptosis, necrosis was previously considered disordered and passive, but it is now being realized to be under regulation by certain biological pathways. However, the intracellular dynamics that coordinates with cellular structure changes during necrosis remains unknown, limiting our understanding of the principles of necrosis. Here, we characterized the spatiotemporal intracellular diffusion dynamics in cells undergoing necrosis, using three-dimensional single-particle tracking of quantum dots. We found temporally increased diffusion rates in necrotic cells and spatially enhanced diffusion heterogeneity in the cell periphery, which could be attributed to the reduced molecular crowding resulting from cell swelling and peripheral blebbing, respectively. Moreover, the three-dimensional intracellular diffusion transits from strong anisotropy to nearly isotropy, suggesting a remodeling of the cytoarchitecture that relieves the axial constraint on intracellular diffusion during necrosis. Our results reveal the remarkable alterations of intracellular diffusion dynamics and biophysical properties in necrosis, providing insight into the well-organized nonequilibrium necrotic cell death from a biophysical perspective.

Palmitoylation at a conserved cysteine residue facilitates gasdermin D-mediated pyroptosis and cytokine release

Gasdermin D (GSDMD)-mediated pyroptotic cell death drives inflammatory cytokine release and downstream immune responses upon inflammasome activation, which play important roles in host defense and inflammatory disorders. Upon activation by proteases, the GSDMD N-terminal domain (NTD) undergoes oligomerization and membrane translocation in the presence of lipids to assemble pores. Despite intensive studies, the molecular events underlying the transition of GSDMD from an autoinhibited soluble form to an oligomeric pore form inserted into the membrane remain incompletely understood. Previous work characterized S-palmitoylation for gasdermins from bacteria, fungi, invertebrates, as well as mammalian gasdermin E (GSDME). Here, we report that a conserved residue Cys191 in human GSDMD was S-palmitoylated, which promoted GSDMD-mediated pyroptosis and cytokine release. Mutation of Cys191 or treatment with palmitoyltransferase inhibitors cyano-myracrylamide (CMA) or 2-bromopalmitate (2BP) suppressed GSDMD palmitoylation, its localization to the membrane and dampened pyroptosis or IL-1β secretion. Furthermore, Gsdmd-dependent inflammatory responses were alleviated by inhibition of palmitoylation in vivo. By contrast, coexpression of GSDMD with palmitoyltransferases enhanced pyroptotic cell death, while introduction of exogenous palmitoylation sequences fully restored pyroptotic activities to the C191A mutant, suggesting that palmitoylation-mediated membrane localization may be distinct from other molecular events such as GSDMD conformational change during pore assembly. Collectively, our study suggests that S-palmitoylation may be a shared regulatory mechanism for GSDMD and other gasdermins, which points to potential avenues for therapeutically targeting S-palmitoylation of gasdermins in inflammatory disorders.

Characterised intron retention profiles in muscle tissue of idiopathic inflammatory myopathy subtypes

OBJECTIVES

Idiopathic inflammatory myopathies (IIMs) are a group of heterogeneous autoimmune diseases. Intron retention (IR) serves as an important post-transcriptional and translational regulatory mechanism. This study aims to identify changes in IR profiles in IIM subtypes, investigating their influence on proteins and their correlations with clinical features.

METHODS

RNA sequencing and liquid chromatography-tandem mass spectrometry were performed on muscle tissues obtained from 174 patients with IIM and 19 controls, following QC procedures. GTFtools and iREAD software were used for IR identification. An analysis of differentially expressed IRs (DEIs), exons and proteins was carried out using edgeR or DEP. Functional analysis was performed with clusterProfiler, and SPIRON was used to assess splicing factors.

RESULTS

A total of 6783 IRs located in 3111 unique genes were identified in all IIM subtypes compared with controls. IIM subtype-specific DEIs were associated with the pathogenesis of respective IIM subtypes. Splicing factors YBX1 and HSPA2 exhibited the most changes in dermatomyositis and immune-mediated necrotising myopathy. Increased IR was associated with reduced protein expression. Some of the IIM-specific DEIs were correlated with clinical parameters (skin rash, MMT-8 scores and muscle enzymes) and muscle histopathological features (myofiber necrosis, regeneration and inflammation). IRs in IFIH1 and TRIM21 were strongly correlated with anti-MDA5+ antibody, while IRs in SRP14 were associated with anti-SRP+ antibody.

CONCLUSION

This study revealed distinct IRs and specific splicing factors associated with IIM subtypes, which might be contributing to the pathogenesis of IIM. We also emphasised the potential impact of IR on protein expression in IIM muscles.

Pharmacological inhibition of RUNX1 reduces infarct size after acute myocardial infarction in rats and underlying mechanism revealed by proteomics implicates repressed cathepsin levels

Myocardial infarction (MI) results in prolonged ischemia and the subsequent cell death leads to heart failure which is linked to increased deaths or hospitalizations. New therapeutic targets are urgently needed to prevent cell death and reduce infarct size among patients with MI. Runt-related transcription factor-1 (RUNX1) is a master-regulator transcription factor intensively studied in the hematopoietic field. Recent evidence showed that RUNX1 has a critical role in cardiomyocytes post-MI. The increased RUNX1 expression in the border zone of the infarct heart contributes to decreased cardiac contractile function and can be therapeutically targeted to protect against adverse cardiac remodelling. This study sought to investigate whether pharmacological inhibition of RUNX1 function has an impact on infarct size following MI. In this work we demonstrate that inhibiting RUNX1 with a small molecule inhibitor (Ro5-3335) reduces infarct size in an in vivo rat model of acute MI. Proteomics study using data-independent acquisition method identified increased cathepsin levels in the border zone myocardium following MI, whereas heart samples treated by RUNX1 inhibitor present decreased cathepsin levels. Cathepsins are lysosomal proteases which have been shown to orchestrate multiple cell death pathways. Our data illustrate that inhibition of RUNX1 leads to reduced infarct size which is associated with the suppression of cathepsin expression. This study demonstrates that pharmacologically antagonizing RUNX1 reduces infarct size in a rat model of acute MI and unveils a link between RUNX1 and cathepsin-mediated cell death, suggesting that RUNX1 is a novel therapeutic target that could be exploited clinically to limit infarct size after an acute MI.

Inflammasome-independent pyroptosis

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

Emerging role of immunogenic cell death in cancer immunotherapy

Cancer immunotherapy, such as immune checkpoint blockade (ICB), has emerged as a groundbreaking approach for effective cancer treatment. Despite its considerable potential, clinical studies have indicated that the current response rate to cancer immunotherapy is suboptimal, primarily attributed to low immunogenicity in certain types of malignant tumors. Immunogenic cell death (ICD) represents a form of regulated cell death (RCD) capable of enhancing tumor immunogenicity and activating tumor-specific innate and adaptive immune responses in immunocompetent hosts. Therefore, gaining a deeper understanding of ICD and its evolution is crucial for developing more effective cancer therapeutic strategies. This review focuses exclusively on both historical and recent discoveries related to ICD modes and their mechanistic insights, particularly within the context of cancer immunotherapy. Our recent findings are also highlighted, revealing a mode of ICD induction facilitated by atypical interferon (IFN)-stimulated genes (ISGs), including polo-like kinase 2 (PLK2), during hyperactive type I IFN signaling. The review concludes by discussing the therapeutic potential of ICD, with special attention to its relevance in both preclinical and clinical settings within the field of cancer immunotherapy.

HIF-1α is Required to Differentiate the Neonatal Macrophage Secretome from Adults

The immune response to stress diverges with age, with neonatal macrophages implicated in tissue regeneration versus tissue scarring and maladaptive inflammation in adults. Integral to the macrophage stress response is the recognition of hypoxia and pathogen-associated molecular patterns (PAMPs), which are often coupled. The age-specific, cell-intrinsic nature of this stress response remains vague. To uncover age-defined divergences in macrophage crosstalk potential after exposure to hypoxia and PAMPs, we interrogated the secreted proteomes of neonatal versus adult macrophages via non-biased mass spectrometry. Through this approach, we newly identified age-specific signatures in the secretomes of neonatal versus adult macrophages in response to hypoxia and the prototypical PAMP, lipopolysaccharide (LPS). Neonatal macrophages polarized to an anti-inflammatory, regenerative phenotype protective against apoptosis and oxidative stress, dependent on hypoxia inducible transcription factor-1α ( HIF-1α). In contrast, adult macrophages adopted a pro-inflammatory, glycolytic phenotypic signature consistent with pathogen killing. Taken together, these data uncover fundamental age and HIF-1α dependent macrophage programs that may be targeted to calibrate the innate immune response during stress and inflammation.

New insights into Gasdermin D pore formation

Gasdermin D (GSDMD) is a pore-forming protein that perforates the plasma membrane (PM) during pyroptosis, a pro-inflammatory form of cell death, to induce the unconventional secretion of inflammatory cytokines and, ultimately, cell lysis. GSDMD is activated by protease-mediated cleavage of its active N-terminal domain from the autoinhibitory C-terminal domain. Inflammatory caspase-1, -4/5 are the main activators of GSDMD via either the canonical or non-canonical pathways of inflammasome activation, but under certain stimuli, caspase-8 and other proteases can also activate GSDMD. Activated GSDMD can oligomerize and assemble into various nanostructures of different sizes and shapes that perforate cellular membranes, suggesting plasticity in pore formation. Although the exact mechanism of pore formation has not yet been deciphered, cysteine residues are emerging as crucial modulators of the oligomerization process. GSDMD pores and thus the outcome of pyroptosis can be modulated by various regulatory mechanisms. These include availability of activated GSDMD at the PM, control of the number of GSDMD pores by PM repair mechanisms, modulation of the lipid environment and post-translational modifications. Here, we review the latest findings on the mechanisms that induce GSDMD to form membrane pores and how they can be tightly regulated for cell content release and cell fate modulation.

The palmitoylation of gasdermin D directs its membrane translocation and pore formation during pyroptosis

Plasma membrane perforation elicited by caspase cleavage of the gasdermin D (GSDMD) N-terminal domain (GSDMD-NT) triggers pyroptosis. The mechanisms underlying GSDMD membrane translocation and pore formation are not fully understood. Here, using a proteomic approach, we identified fatty acid synthase (FASN) as a GSDMD-binding partner. S-palmitoylation of GSDMD at Cys191/Cys192 (human/mouse), catalyzed by palmitoyl acyltransferases ZDHHC5 and ZDHHC9 and facilitated by reactive oxygen species (ROS), directly mediated membrane translocation of GSDMD-NT but not full-length GSDMD (GSDMD-FL). Palmitoylation of GSDMD-FL could be induced before inflammasome activation by stimuli such as lipopolysaccharide (LPS), consequently serving as an essential molecular event in macrophage priming. Inhibition of GSDMD palmitoylation suppressed macrophage pyroptosis and IL-1β release, mitigated organ damage, and enhanced the survival of septic mice. Thus, GSDMD-NT palmitoylation is a key regulatory mechanism controlling GSDMD membrane localization and activation, which may offer an additional target for modulating immune activity in infectious and inflammatory diseases.

The integration of single-cell and bulk RNA-seq atlas reveals ERS-mediated acinar cell damage in acute pancreatitis

BACKGROUND

Acute pancreatitis (AP) is a clinically common acute abdominal disease, whose pathogenesis remains unclear. The severe patients usually have multiple complications and lack specific drugs, leading to a high mortality and poor outcome. Acinar cells are recognized as the initial site of AP. However, there are no precise single-cell transcriptomic profiles to decipher the landscape of acinar cells during AP, which are the missing pieces of jigsaw we aimed to complete in this study.

METHODS

A single-cell sequencing dataset was used to identify the cell types in pancreas of AP mice and to depict the transcriptomic maps in acinar cells. The pathways' activities were evaluated by gene sets enrichment analysis (GSEA) and single-cell gene sets variation analysis (GSVA). Pseudotime analysis was performed to describe the development trajectories of acinar cells. We also constructed the protein-protein interaction (PPI) network and identified the hub genes. Another independent single-cell sequencing dataset of pancreas samples from AP mice and a bulk RNA sequencing dataset of peripheral blood samples from AP patients were also analyzed.

RESULTS

In this study, we identified genetic markers of each cell type in the pancreas of AP mice based on single-cell sequencing datasets and analyzed the transcription changes in acinar cells. We found that acinar cells featured acinar-ductal metaplasia (ADM), as well as increased endocytosis and vesicle transport activity during AP. Notably, the endoplasmic reticulum stress (ERS) and ER-associated degradation (ERAD) pathways activated by accumulation of unfolded/misfolded proteins in acinar cells could be pivotal for the development of AP.

CONCLUSION

We deciphered the distinct roadmap of acinar cells in the early stage of AP at single-cell level. ERS and ERAD pathways are crucially important for acinar homeostasis and the pathogenesis of AP.

Neutrophil proteases are protective against SARS-CoV-2 by degrading the spike protein and dampening virus-mediated inflammation

Studies on severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) have highlighted the crucial role of host proteases for viral replication and the immune response. The serine proteases furin and TMPRSS2 and lysosomal cysteine proteases facilitate viral entry by limited proteolytic processing of the spike (S) protein. While neutrophils are recruited to the lungs during COVID-19 pneumonia, little is known about the role of the neutrophil serine proteases (NSPs) cathepsin G (CatG), elastase (NE), and proteinase 3 (PR3) on SARS-CoV-2 entry and replication. Furthermore, the current paradigm is that NSPs may contribute to the pathogenesis of severe COVID-19. Here, we show that these proteases cleaved the S protein at multiple sites and abrogated viral entry and replication in vitro. In mouse models, CatG significantly inhibited viral replication in the lung. Importantly, lung inflammation and pathology were increased in mice deficient in NE and/or CatG. These results reveal that NSPs contribute to innate defenses against SARS-CoV-2 infection via proteolytic inactivation of the S protein and that NE and CatG limit lung inflammation in vivo. We conclude that therapeutic interventions aiming to reduce the activity of NSPs may interfere with viral clearance and inflammation in COVID-19 patients.

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.

AIRE is expressed in breast cancer TANs and TAMs to regulate the extrinsic apoptotic pathway and inflammation

The autoimmune regulator (AIRE) is a transcriptional regulator expressed in the thymus and is necessary for maintaining immunological self-tolerance. Extrathymic AIRE expression is rare, and a role for AIRE in tumor-associated innate immune cells has not yet been established. In this study, we show that AIRE is expressed in human pro-tumor neutrophils. In breast cancer, AIRE was primarily located to tumor-associated neutrophils (TANs), and to a lesser extent to tumor-associated macrophages (TAMs) and tumor cells. Expression of AIRE in TAN/TAMs, but not in cancer cells, was associated with an adverse prognosis. We show that the functional role for AIRE in neutrophils and macrophages is to regulate expression of immune mediators and the extrinsic apoptotic pathway involving the Fas/TNFR death receptors and cathepsin G. Here, we propose that the role for AIRE in TAN/TAMs in breast tumors is to regulate cell death and inflammation, thus promoting tumor progression.

Caspase-1 activates gasdermin A in non-mammals

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

Selective induction of programmed cell death using synthetic biology tools

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