Recognition and maturation of IL-18 by caspase-4 noncanonical inflammasome

Regulatory roles of noncanonical inflammasomes in kidney diseases

Inflammation is a body's immune defense against infection and injury. The inflammatory response has two main phases: the priming and triggering phases. The triggering phase involves the activation of inflammasomes, cytoplasmic platforms for initiating inflammation, and Inflammasomes are classified into two categories: canonical and noncanonical. Kidney disease, or renal disease, refers to damage or illness affecting the kidneys, leading to a progressive decline in their function. Although the roles of canonical inflammasomes in kidney diseases are well-documented, recent research highlights novel roles of noncanonical inflammasomes in managing various inflammatory conditions. In particular, emerging studies emphasize the regulatory functions of noncanonical inflammasomes in a range of kidney diseases. This review explores recent discoveries regarding the regulatory functions of noncanonical inflammasomes, including human caspase-4/5 and murine caspase-11, in the progression of kidney diseases. It also examines the potential of targeting these inflammasomes as a novel therapeutic approach.

4, 9-dihydroxy-α-lapachone as a potent antiproliferation agent for triple-negative breast cancer via ferroptosis

Triple-negative breast cancer (TNBC) is the most aggressive and malignant breast cancer. Ferroptosis is an oxidative, iron-dependent form of regulated cell death. Ferroptosis-targeted therapies is a promising approach to improving treatment outcomes of TNBC. Combining death pathway inhibitors with relevant indices for ferroptosis and LipROS, this study uncovered that a natural product of 4, 9-dihydroxy-α-lapachone (DLN) from Catalpa bungei "jinsi" exhibited in vitro and in vivo inhibitory activity against TNBC via ferroptosis. The molecular mechanism is an activation of the FTH1 led to iron overload, and then inhibition of cysteine-glutamate antiporter (system Xc-) and GPX4, which further sensitized TNBC cells to ferroptosis. This study clarified the pathway of DLN-induced cell death in TNBC treatment and exhibited its potential as therapeutic agent for TNBC.

Gasdermin-D pores induce an inactivating caspase-4 cleavage that limits IL-18 production in the intestinal epithelium

Intestinal epithelial-derived IL-18 is critical for homeostatic intestinal barrier function and is secreted through Gasdermin D (GSDMD) pores. Inflammasome activation is a prerequisite for both IL-18 maturation and GSDMD pore formation. However, GSDMD pores also cause pyroptotic cell death, which could be detrimental to the intestinal epithelial barrier. How epithelial cells balance the need to secrete IL-18 and to maintain barrier integrity remains poorly understood. In human intestinal epithelial cell lines and in primary human epithelial intestinal organoids, but not in immune cells, GSDMD plasma membrane pore formation by LPS electroporation and by gram-negative bacterial infection induced a non-conventional p37 caspase-4 fragment that was associated with reduced levels of mature IL-18. By contrast, limiting GSDMD plasma membrane pores pharmacologically and via point-mutagenesis prevented caspase-4 cleavage and increased IL-18 production, suggesting that p37 caspase-4 cleavage may regulate IL-18 maturation in the intestinal epithelium. In support, co-expression of caspase-4 cleavage mutants and IL-18 in HEK293T cells revealed that non-cleavable caspase-4 produced more mature IL-18 than cleaved caspase-4. Overall, these studies suggest that epithelial inflammasomes encode feedback pathways that control the balance between cytokine secretion and cell death. This may be an important mechanism to ensure homeostatic IL-18 production in the intestinal epithelium.

Intracellular bacterial LPS drives pyroptosis and promotes aggressive phenotype in oral squamous cell carcinoma

Intracellular bacterial components represent an emerging tumor element that has recently been documented in multiple cancer types, yet their biological functions remain poorly understood. Oral squamous cell carcinoma (OSCC) is a particularly aggressive malignancy lacking highly effective targeted treatments. Here, we explored the functional significance of intracellular bacterial lipopolysaccharide (LPS) in OSCC. Normal human oral keratinocytes (HOKs), HPV-transformed oral keratinocytes (IHGK), and three OSCC cell lines were transfected with ultrapure bacterial LPS. Cytotoxicity was assessed via lactate dehydrogenase (LDH) release assays. Production of interleukin (IL)-1β and IL-18 was measured using ELISA. Impact on tumor progression was evaluated using cell proliferation, migration, invasion, and tubulogenesis assays. Intracellular LPS-induced significant LDH release and increased secretion of IL-18 and IL-1β in IHGK and cancer cells, but not in normal HOKs, indicating selective cytotoxicity and pyroptosis. Notably, metastatic cancer cells exhibited enhanced invasive and vessel-like structures upon LPS exposure, while IHGK cells exhibited increased proliferation without changes in migration. Our findings suggest that intracellular LPS may not merely reside passively within the tumor milieu, but could contribute to OSCC progression by triggering noncanonical inflammasome activation and pyroptosis. This process may enhance pro-inflammatory signaling and more aggressive cellular phenotypes, especially in metastatic settings. Targeting intracellular LPS or its downstream inflammasome pathways may thus represent a promising therapeutic strategy for OSCC, warranting further in vivo and clinical investigations.

Molecular characterization and functional analysis of IL-18 in large yellow croaker (Larimichthys crocea)

Interleukin-18 (IL-18), a pro-inflammatory cytokine of the IL-1 family, is crucial for protecting the host against pathogen infection in mammals. In this study, a IL-18 homolog gene was cloned from large yellow croaker (Larimichthys crocea) (LcIL-18), which has an open reading frame (ORF) of 609 bp that encodes a polypeptide of 202 amino acids. The LcIL-18 C-terminus contains a typical IL-1 family signature and a caspase cleavage site. Phylogenetic analysis showed that LcIL-18 was most closely related to IL-18 of Miichthys miiuy. It was found that LcIL-18 was constitutively expressed in all 12 tissues tested of large yellow croakers, with the highest expression in gills. The expression of LcIL-18 in head kidney, spleen, skin, gills, and liver showed a differential pattern following infection with Pseudomonas plecoglossicida and Vibrio alginolyticus. P. plecoglossicida strongly induced LcIL-18 expression in these tissues. Conversely, in the early stage of infection, V. alginolyticus significantly inhibited LcIL-18 expression in head kidney, spleen, skin, and gills, but not in the liver. In vitro, LPS, Poly(I:C), P. plecoglossicida, and V. alginolyticus significantly upregulated the expression of the LcIL-18 in large yellow croaker head kidney (LYCK) cells. Furthermore, recombinant LcIL-18 (rLcIL-18) significantly increased cell viability and upregulated the expression of pro-inflammatory cytokines (LcIL-1β, LcIL-6, and LcTNF-α1) in LYCK cells. Our findings therefore indicated that LcIL-18 was involved in pro-inflammatory response induced by pathogenic bacteria.

Caspases: structural and molecular mechanisms and functions in cell death, innate immunity, and disease

Caspases are critical regulators of cell death, development, innate immunity, host defense, and disease. Upon detection of pathogens, damage-associated molecular patterns, cytokines, or other homeostatic disruptions, innate immune sensors, such as NLRs, activate caspases to initiate distinct regulated cell death pathways, including non-lytic (apoptosis) and innate immune lytic (pyroptosis and PANoptosis) pathways. These cell death pathways are driven by specific caspases and distinguished by their unique molecular mechanisms, supramolecular complexes, and enzymatic properties. Traditionally, caspases are classified as either apoptotic (caspase-2, -3, -6, -7, -8, -9, and -10) or inflammatory (caspase-1, -4, -5, and -11). However, extensive data from the past decades have shown that apoptotic caspases can also drive lytic inflammatory cell death downstream of innate immune sensing and inflammatory responses, such as in the case of caspase-3, -6, -7, and -8. Therefore, more inclusive classification systems based on function, substrate specificity, or the presence of pro-domains have been proposed to better reflect the multifaceted roles of caspases. In this review, we categorize caspases into CARD-, DED-, and short/no pro-domain-containing groups and examine their critical functions in innate immunity and cell death, along with their structural and molecular mechanisms, including active site/exosite properties and substrates. Additionally, we highlight the emerging roles of caspases in cellular homeostasis and therapeutic targeting. Given the clinical relevance of caspases across multiple diseases, improved understanding of these proteins and their structure-function relationships is critical for developing effective treatment strategies.

A Site-Specific Photo-Crosslinking Proteomics Approach Provides Insights into Noncanonical Pyroptotic Caspase-4 Substrates

Inflammatory caspases (1/4/5) are key effectors in the process of pyroptosis by cleaving and activating the pore-forming protein gasdermin D (GSDMD). Unlike other caspases whose substrates have been well characterized, the substrates for caspase-4, which mediate noncanonical pyroptosis, remain poorly understood. Here, we combined noncanonical amino acids, photo-crosslinking, and proteomics to profile caspase-4 substrates, enabling the capture of transient protein interactions with activated caspase-4. A set of new substrates were identified by photo-crosslinking mass spectrometry, revealing the signaling pathway and biological process affected by pyroptosis. Notably, we found that AKT1 is cleaved at D108, which removes its autoinhibition and membrane localization domain, resulting in the release of activated AKT1. Our results also showed the precursor of caspase-5/12 could be cleaved by caspase-4 to form the p20/p10 active conformation, uncovering a previously unrecognized pyroptotic caspase cascade. Overall, this study presents an approach for identifying caspase-4 substrates and offers further understanding of noncanonical pyroptosis.

Molecular mechanisms of pyroptosis in non-alcoholic steatohepatitis and feasible diagnosis and treatment strategies

Pyroptosis is a distinct form of cell death that plays a critical role in intensifying inflammatory responses. It primarily occurs via the classical pathway, non-classical pathway, caspase-3/6/7/8/9-mediated pathways, and granzyme-mediated pathways. Key effector proteins involved in the pyroptosis process include gasdermin family proteins and pannexin-1 protein. Pyroptosis is intricately linked to the onset and progression of non-alcoholic steatohepatitis (NASH). During the development of NASH, factors such as pyroptosis, innate immunity, lipotoxicity, endoplasmic reticulum stress, and gut microbiota imbalance interact and interweave, collectively driving disease progression. This review analyzes the molecular mechanisms of pyroptosis and its role in the pathogenesis of NASH. Furthermore, it explores potential diagnostic and therapeutic strategies targeting pyroptosis, offering new avenues for improving the diagnosis and treatment of NASH.

Cell-Autonomous Immunity: From Cytosolic Sensing to Self-Defense

As an evolutionarily conserved and ubiquitous mechanism of host defense, non-immune cells in vertebrates possess the intrinsic ability to autonomously detect and combat intracellular pathogens. This process, termed cell-autonomous immunity, is distinct from classical innate immunity. In this review, we comprehensively examine the defense mechanisms employed by non-immune cells in response to intracellular pathogen invasion. We provide a detailed analysis of the cytosolic sensors that recognize aberrant nucleic acids, lipopolysaccharide (LPS), and other pathogen-associated molecular patterns (PAMPs). Specifically, we elucidate the molecular mechanisms underlying key signaling pathways, including the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway, the retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs)-mitochondrial antiviral signaling (MAVS) axis, and the guanylate-binding proteins (GBPs)-mediated pathway. Furthermore, we critically evaluate the involvement of these pathways in the pathogenesis of various diseases, including autoimmune disorders, inflammatory conditions, and malignancies, while highlighting their potential as therapeutic targets.

Pyroptosis in sepsis-associated acute kidney injury: mechanisms and therapeutic perspectives

Sepsis-associated acute kidney injury (S-AKI) is a severe complication characterized by high morbidity and mortality, driven by multi-organ dysfunction. Recent evidence suggests that pyroptosis, a form of programmed cell death distinct from apoptosis and necrosis, plays a critical role in the pathophysiology of S-AKI. This review examines the mechanisms of pyroptosis, focusing on inflammasome activation (e.g., NLRP3), caspase-mediated processes, and the role of Gasdermin D in renal tubular damage. We also discuss the contributions of inflammatory mediators, oxidative stress, and potential therapeutic strategies targeting pyroptosis, including inflammasome inhibitors, caspase inhibitors, and anti-inflammatory therapies. Lastly, we highlight the clinical implications and challenges in translating these findings into effective treatments, underscoring the need for personalized medicine approaches in managing S-AKI.

The dual-function of HSP70 in immune response and tumor immunity: from molecular regulation to therapeutic innovations

Heat shock protein 70 (HSP70) is a highly conserved molecular chaperone that plays a core role in assisting protein folding and maintaining cellular homeostasis. In recent years, studies have revealed that HSP70 has dual functions in immune regulation: on the one hand, it enhances immune responses by activating non-specific immunity (such as Toll-like receptor 2/4 (TLR2/4) signaling pathways) and specific immunity (such as cross-presentation of antigens, T helper 1 (Th1)/T helper 17 (Th17) differentiation); on the other hand, it inhibits excessive immune reactions by inducing the differentiation of regulatory T cells (Treg) and promoting the secretion of anti-inflammatory factors [such as interleukin-10 (IL-10)]. In cancer, the duality of HSP70 is also very prominent: it can drive tumor progression through pathways such as inhibiting apoptosis, promoting angiogenesis, and tumor metastasis, and it can also inhibit tumor growth by activating immunogenic cell death (ICD), enhancing antigen presentation, and natural killer (NK) cell activity. This review aims to systematically analyze the immune regulatory functions of HSP70, focusing on its dual regulatory mechanisms and the "double-edged sword" nature of HSP70 in tumor immunotherapy and the innovative nature of targeted strategies, as well as providing a theoretical basis and research directions for precision medicine in the treatment strategies of related diseases.

Alpha-lipoamide prevents acute kidney injury in mouse by inhibiting renal tubular epithelial cell pyroptosis

Acute kidney injury (AKI) is a critical condition marked by a sudden decline in kidney function, frequently resulting in high morbidity and mortality. Renal ischemia-reperfusion injury (IRI) is a leading cause of AKI, characterized by reactive oxygen species (ROS) release, cell death, and inflammation. Alpha-lipoamide (ALM), a neutral derivative of lipoic acid, is recognized for its antioxidant and organ-protective properties. Prior research indicates that ALM mitigates diabetic nephropathy by decreasing ROS. This study examines ALM's protective role in a mouse model of IRI-induced AKI and its mechanisms using mouse renal tubular epithelial cells (mRTECs). Mice were subjected to IRI by renal artery occlusion for 30 min, followed by reperfusion, and treated with ALM (100 or 200 mg/kg) for three days before surgery. In vitro, mRTECs were exposed to hypoxia/reoxygenation injury, with ALM (200 μM) applied to assess oxidative stress. ALM significantly decreased serum creatinine levels, neutrophil gelatinase-associated lipocalin (NGAL), and kidney injury marker-1 (KIM-1), mitigated kidney injury, and reduced both ROS and Malondialdehyde(MDA) content. ALM increased glutathione (GSH) levels and upregulated SIRT1 expression. This resulted in the deacetylation of the NF-κB p65 subunit, facilitating its nuclear export, suppressing NF-κB signaling, and reducing the expression of the inflammatory marker NLRP3. ALM decreased the levels of pyroptosis-related proteins (Caspase-1, GSDMD, and IL-1β), which in turn suppressed IL-6 secretion and macrophage infiltration. These findings suggest that ALM reduces inflammation and pyroptosis-associated proteins by promoting the upregulation of SIRT1, ultimately preventing IRI-mediated renal tubular epithelial cell damage and inflammation.

Programmed cardiomyocyte death in myocardial infarction

Cardiovascular disease (CVD) is a leading cause of human mortality worldwide, with patients often at high risk of heart failure (HF) in myocardial infarction (MI), a common form of CVD that results in cardiomyocyte death and myocardial necrosis due to inadequate myocardial perfusion. As terminally differentiated cells, cardiomyocytes possess a severely limited capacity for regeneration, and an excess of dead cardiomyocytes will further stress surviving cells, potentially exacerbating to more extensive heart disease. The article focuses on the relationship between programmed cell death (PCD) of cardiomyocytes, including different forms of apoptosis, necrosis, and autophagy, and MI, as well as the potential application of these mechanisms in the treatment of MI. By gaining a deeper understanding of the mechanisms of cardiomyocyte death, it aims to provide new insights into the prevention and treatment of MI.

Caspase-12 exhibits non-redundant functions in response to endoplasmic reticulum stress to promote GSDMD-mediated NETosis, leading to thoracic aortic dissection

BACKGROUND

Thoracic aortic dissection (TAD) is a highly lethal condition that is characterized by inflammatory cell infiltration. Recent evidence has indicated that Gasdermin D (GSDMD) plays an important role in vascular inflammation and degeneration. However, its effects on neutrophil extracellular trap formation and release (NETosis) during TAD remain unknown.

METHODS

A TAD mouse model was generated using four-week-old male neutrophil-specific GSDMD-knockout mice (GSDMDF/F; ElaneCre) and dimethyl fumarate (DMF)-treated C57BL/6J mice by administering β-aminopropionitrile monofumarate (BAPN; 1 g/kg/day) in their drinking water for 4 weeks. Immunoprecipitation and immunofluorescence assays were performed to examine the role of the endoplasmic reticulum (ER) and its associated protein, caspase-12, in GSDMD-induced NETosis.

RESULTS

GSDMD was elevated and co-localized primarily in neutrophils in the aortic tissues of patients with TAD and mice with BAPN-induced TAD. This was accompanied by increased NETosis. Neutrophil-specific GSDMD knockout and the NETosis inhibitor, GSK484, mitigated TAD development in mice. However, GSK484 did not provide additional therapeutic effects against TAD in the neutrophil-specific, GSDMD knockout mice. Mechanistically, ER stress promoted GSDMD cleavage by caspase-4/11, thereby inducing NETosis. Furthermore, caspase-12 exhibited non-redundant functions in the cleavage of GSDMD by caspase-4/11. The GSDMD inhibitor, DMF, partially prevented TAD development.

CONCLUSIONS

The ER stress/GSDMD/NETosis signaling pathway provides a potential therapeutic target for the prevention and treatment of TAD.

BBB breakdown caused by plasma membrane pore formation

The blood-brain barrier, recently reintroduced as the blood-brain border (BBB), is a dynamic interface between the central nervous system (CNS) and the bloodstream. Disruption of the BBB exposes the CNS to peripheral pathogens and harmful substances, causing or worsening various CNS diseases. While traditional views attribute BBB failure to tight junction disruption or increased transcytosis, recent studies highlight the critical role of gasdermin D (GSDMD) pore formation in brain endothelial cells (bECs) during BBB disruption by lipopolysaccharide (LPS) or bacterial infections. This mechanism may also be involved in neurological complications like the 'brain fog' seen in long COVID. Pore formation in bECs may represent a prevalent mechanism causing BBB leakage. Investigating membrane-permeabilizing pores or channels and their effects on BBB integrity is a growing area of research. Further exploration of molecular processes that maintain, disrupt, and restore bEC membrane integrity will advance our understanding of brain vasculature and aid in developing new therapies for BBB-related diseases.

Cell death in acute lung injury: caspase-regulated apoptosis, pyroptosis, necroptosis, and PANoptosis

There has been abundant research on the variety of programmed cell death pathways. Apoptosis, pyroptosis, and necroptosis under the action of the caspase family are essential for the innate immune response. Caspases are classified into inflammatory caspase-1/4/5/11, apoptotic caspase-3/6/7, and caspase-2/8/9/10. Although necroptosis is not caspase-dependent to transmit cell death signals, it can cross-link with pyroptosis and apoptosis signals under the regulation of caspase-8. An increasing number of studies have reiterated the involvement of the caspase family in acute lung injuries caused by bacterial and viral infections, blood transfusion, and ventilation, which is influenced by noxious stimuli that activate or inhibit caspase engagement pathways, leading to subsequent lung injury. This article reviews the role of caspases implicated in diverse programmed cell death mechanisms in acute lung injury and the status of research on relevant inhibitors against essential target proteins of the described cell death mechanisms. The findings of this review may help in delineating novel therapeutic targets for acute lung injury.

Roles of Pyroptosis in the Progression of Pulpitis and Apical Periodontitis

Pyroptosis is a type of programmed cell death that induces proinflammatory cytokine release and is closely related to inflammatory diseases. Pulpitis and apical periodontitis are common inflammatory diseases that lead to alveolar bone destruction and tooth loss. Recent studies have revealed that pyroptosis is crucial in the progression of pulpitis and apical periodontitis, which involves various cell types and leads to different results. Odontoblasts are located at the periphery of dental pulp tissue and are susceptible to various irritants, the lysates from odontoblasts act as alerts and induce immune reactions in the inner pulp after pyroptosis. The expression levels of inflammasomes in dental pulp cells (DPCs) change with the progression of pulpitis, which may serve as a diagnostic marker of pulpitis. Periodontal ligament fibroblasts (PDLFs) undergo pyroptosis when stimulated by bacterial infection or cyclic stretch and are associated with both infection-induced and trauma-induced apical periodontitis. Immune cells can undergo pyroptosis directly after infection or are influenced by the pyroptotic secretome of other cells, which changes their composition. In this review, we briefly introduce the location and function of different cell types involved in the progression of pulpitis and apical periodontitis, summarize the roles of pyroptosis in different cells, and discuss the effects of drugs targeting pyroptosis in the treatment of pulpitis and apical periodontitis.

SUMOylation regulates GSDMD stability and pyroptosis

Various post-translational modifications (PTMs), such as palmitoylation, acetylation, and ubiquitination, have been shown to regulate pyroptosis. However, the role of small ubiquitin-like modifier (SUMO) modification, known as SUMOylation, in regulating GSDMD activity and pyroptosis remains unclear. Here, we demonstrate that inhibition of SUMOylation reduces inflammatory pyroptosis by downregulating GSDMD expression. Identification of key SUMOylation sites on GSDMD-K177, is critical for regulates pyroptosis. Furthermore, we identify SENP3 as a critical deSUMOylating enzyme that binds to GSDMD, suppressing GSDMD SUMO modification, which destabilizes GSDMD and inhibits LDH secretion. These findings highlight the role of SUMOylation in GSDMD mediated-pyroptosis, suggesting SUMO inhibitors as potential therapies for inflammatory diseases.

Lytic coelomocyte death is tuned by cleavage but not phosphorylation of MLKL in echinoderms

Lytic cell death including necroptosis and pyroptosis is induced by mixed lineage kinase domain-like protein (MLKL) phosphorylation and inflammatory caspase specific cleavage Gasdermins in higher mammals, respectively. In this study, we identified a novel MLKL homolog containing a tetrapeptide recognition motif (14-LVAD-17) of inflammatory caspase from Apostichopus japonicus,which was absent of Gasdermins member by genome screening. Functional analysis revealed that AjMLKL was involved in the regulation of Vibrio splendidus AJ01 infection induced lytic coelomocyte death in a cleavage-dependent manner, but not through RIPK3-dependent phosphorylation as mammals. Mechanistically, the activated form of cysteine-aspartic specific proteases-1 (AjCASP-1) bound to the tetrapeptide site of AjMLKL and cleaved it at Asp17. Cleaved AjMLKL18-491 displayed higher binding affinities towards phosphatidylinositol phosphate and cardiolipin compared to those of un-cleaved form. In addition, cleaved AjMLKL18-491 exerted stronger ability in disrupting the membrane integrity of liposome. More importantly, AjMLKL18-491 caused a large non-selective ionic coelomocyte pore and could directly kill the invasive AJ01. Moreover, activation of inflammatory AjCASP-1 was further found to be dependent on forming an inflammasome-like complex via CASc domain of AjCASP-1 and the N-terminal Ig domains of internalized AjNLRC4. All our results proved first evidence that lytic cell death was activated through MLKL cleavage, not MLKL phosphorylation in echinoderm, which offered insights into the functional, evolutionary mechanisms of lytic cell death in invertebrates.

[Autoinflammatory diseases associated with IL-18]

Autoinflammatory diseases (AIDs) are conditions characterized by dysfunction of innate immunity, causing systemic inflammation and various clinical symptoms. The field of AIDs has expanded due to improved comprehension of pathophysiological mechanisms and advancements in genomics techniques. A new emerging category of AIDs is characterized by a significant increase in interleukin 18 (IL-18), a pro-inflammatory cytokine synthesized in macrophages and activated by caspase 1 via various inflammasomes. IL-18 plays a role in the regulation of innate and adaptive immunity. IL-18 is involved in various functions, such as the proliferation, survival, and differentiation of immune cells, tissue infiltration of immune cells, polarization of immune responses, and production of other pro-inflammatory cytokines. This review analyzes the literature on IL-18 regarding its functions and its implications in the diagnosis and treatment of AIDs. IL-18-associated AIDs comprise Still's disease and diseases associated with mutations in NLRC4, XIAP, CDC42, and PSTPIP1, as well as IL-18BP deficiencies. With the exception of PSTPIP1-associated diseases, these conditions all carry a risk of macrophagic activation syndrome. Measuring IL-18 levels in serum can aid in the diagnosis, prognosis, and monitoring of these diseases. Therapies targeting IL-18 and its signaling pathways are currently under investigation.

GBP1 promotes acute rejection after liver transplantation by inducing Kupffer cells pyroptosis

Liver transplantation is currently recognized as the most effective treatment for severe liver diseases. Although survival rates after liver transplantation have improved, rejection of the transplanted liver remains a significant cause of morbidity and transplant failure in patients. Our team previously discovered a close association between high GBP1 expression and acute rejection reactions following liver transplantation. Liver biopsies were conducted on patients who experienced acute rejection or successfully achieved immune tolerance post-transplantation. We confirmed that GBP1 was highly expressed in the acute rejection group after transplantation by Immunohistochemistry. This study aims to confirm that GBP1 promotes acute rejection reactions following liver transplantation through inducing pyroptosis in rat transplanted hepatic macrophages (KCs). We knocked down GBP1 in KCs and examined the extent of pyroptosis and the severity of acute rejection in the transplanted liver post-orthotopic liver transplantation in rats and KCs. These data provide new approaches for the study of liver transplant rejection reactions and identify new targets.

Short IL-18 generated by caspase-3 cleavage mobilizes NK cells to suppress tumor growth

Interleukin (IL)-18 functions primarily through its 18-kDa mature form produced from caspase-1 cleavage. However, IL-18 can also be processed by other proteases, leading to the generation of different fragments with less recognized functions. Here, we discover that, in cancer cells, caspase-3 cleavage of IL-18 generates a 15-kDa form of IL-18, referred to as short IL-18. Unlike mature IL-18, short IL-18 is not secreted, and does not bind IL-18Rα; instead, it translocates into the nucleus, facilitating STAT1 phosphorylation at Ser727 via CDK8, and enhancing the expression and secretion of ISG15. This signaling cascade in cancer cells mobilizes natural killer cells with increased cytotoxicity to eliminate various syngeneic tumors and colitis-associated colorectal cancer in mice. Moreover, patients with colorectal cancer who have an abundance of short IL-18 in the nucleus have a better prognosis. This work highlights a distinct anti-tumor pathway driven by short IL-18.

Chemical Tools Based on the Tetrapeptide Sequence of IL-18 Reveals Shared Specificities between Inflammatory and Apoptotic Initiator Caspases

Caspases are a family of cysteine proteases that act as molecular scissors to cleave substrates and regulate biological processes such as programmed cell death and inflammation. Extensive efforts have been made to identify caspase substrates and to determine factors that dictate substrate specificity. We recently discovered that that the human inflammatory caspases (caspases-1, -4, and -5) cleave the cytokines IL-1β and IL-18 in a sequence-dependent manner. Here, we report the development of a new peptide-based probe and inhibitor based on the tetrapeptide sequence of IL-18 (LESD). We found that this inhibitor was most selective and potent at inhibiting caspase-8 activity (IC50 = 50 nM). We also discovered that our LESD-based inhibitor is more potent than the currently used z-IETD-FMK inhibitor that is thought to be the most selective and potent inhibitor of caspase-8. Accordingly, we demonstrate that the LESD based inhibitor prevents caspase-8 activation during Yersinia pseudotuberculosis infection in primary bone-marrow derived macrophages. Furthermore, we characterize the selectivity and potency of currently known substrates and inhibitors for the apoptotic and inflammatory caspases using the same activity units of each caspase. Our findings reveal that VX-765, a known caspase-1 inhibitor, also inhibits caspase-8 (IC50 = 1 μM) and even when specificities are shared, the caspases have different efficiencies and potencies for shared substrates and inhibitors. Altogether, we report the development of new tools that will facilitate the study of caspases and their roles in biology.

A VgrG2b fragment cleaved by caspase-11/4 promotes Pseudomonas aeruginosa infection through suppressing the NLRP3 inflammasome

The T6SS of Pseudomonas aeruginosa plays an essential role in the establishment of chronic infections. Inflammasome-mediated inflammatory cytokines are crucial for host defense against bacterial infections. We found that P. aeruginosa infection activates the non-canonical inflammasome in macrophages, yet it inhibits the downstream activation of the NLRP3 inflammasome. The VgrG2b of P. aeruginosa is recognized and cleaved by caspase-11, generating a free C-terminal fragment. The VgrG2b C-terminus can bind to NLRP3, inhibiting the activation of the NLRP3 inflammasome by rejecting NEK7 binding to NLRP3. Administration of a specific peptide that inhibits caspase-11 cleavage of VgrG2b significantly improves mouse survival during infection. Our discovery elucidates a mechanism by which P. aeruginosa inhibits host immune response, providing a new approach for the future clinical treatment of P. aeruginosa infections.

Regulated cell death in acute myocardial infarction: Molecular mechanisms and therapeutic implications

Acute myocardial infarction (AMI), primarily caused by coronary atherosclerosis, initiates a series of events that culminate in the obstruction of coronary arteries, resulting in severe myocardial ischemia and hypoxia. The subsequent myocardial ischemia/reperfusion (I/R) injury further aggravates cardiac damage, leading to a decline in heart function and the risk of life-threatening complications. The complex interplay of multiple regulated cell death (RCD) pathways plays a pivotal role in the pathogenesis of AMI. Each RCD pathway is orchestrated by a symphony of molecular regulatory mechanisms, highlighting the dynamic changes and critical roles of key effector molecules. Strategic disruption or inhibition of these molecular targets offers a tantalizing prospect for mitigating or even averting the onset of RCD, thereby limiting the extensive loss of cardiomyocytes and the progression of detrimental myocardial fibrosis. This review systematically summarizes the mechanisms underlying various forms of RCD, provides an in-depth exploration of the pathogenesis of AMI through the lens of RCD, and highlights a range of promising therapeutic targets that hold the potential to revolutionize the management of AMI.

IL-9 sensitizes human TH2 cells to proinflammatory IL-18 signals in atopic dermatitis

BACKGROUND

TH2 cells crucially contribute to the pathogenesis of atopic dermatitis (AD) by secreting high levels of IL-13 and IL-22. Yet the upstream regulators that activate TH2 cells in AD skin remain unclear. IL-18 is a putative upstream regulator of TH2 cells because it is implicated in AD pathogenesis and has the capacity to activate T cells.

OBJECTIVE

We sought to decipher the role of IL-18 in TH2 responses in blood and skin of AD patients.

METHODS

Peripheral blood mononuclear cells and skin biopsy samples from AD patients and healthy donors were used. Functional assays were performed ex vivo using stimulation or blocking experiments. Analysis was performed by flow cytometry, bead-based multiplex assays, RT-qPCR, RNA-Seq, Western blot, and spatial sequencing.

RESULTS

IL-18Rα+ TH2 cells were enriched in blood and lesional skin of AD patients. Of all the cytokines for which TH2 cells express the receptor, only IL-9 was able to induce IL-18R via an IL-9R-JAK1/JAK3-STAT1 signaling pathway. Functionally, stimulation of circulating TH2 cells with IL-18 induced secretion of IL-13 and IL-22, an effect that was enhanced by costimulation with IL-9. Mechanistically, IL-18 induced TH2 cytokines via activation of IRAK4, NF-κB, and AP-1 signaling in TH2 cells, and neutralization of IL-18 inhibited these cytokines in cultured explants of AD skin lesions. Finally, IL-18 protein levels correlated positively with disease severity in lesional AD skin.

CONCLUSION

Our data identify a novel IL-9/IL-18 axis that contributes to TH2 responses in AD. Our findings suggest that both IL-9 and IL-18 could represent upstream targets for future treatment of AD.

Targeting regulated cell death: Apoptosis, necroptosis, pyroptosis, ferroptosis, and cuproptosis in anticancer immunity

In the evolving landscape of cancer treatment, the strategic manipulation of regulated cell death (RCD) pathways has emerged as a crucial component of effective anti-tumor immunity. Evidence suggests that tumor cells undergoing RCD can modify the immunogenicity of the tumor microenvironment (TME), potentially enhancing its ability to suppress cancer progression and metastasis. In this review, we first explore the mechanisms of apoptosis, necroptosis, pyroptosis, ferroptosis, and cuproptosis, along with the crosstalk between these cell death modalities. We then discuss how these processes activate antigen-presenting cells, facilitate the cross-priming of CD8+ T cells, and trigger anti-tumor immune responses, highlighting the complex effects of novel forms of tumor cell death on TME and tumor biology. Furthermore, we summarize potential drugs and nanoparticles that can induce or inhibit these emerging RCD pathways and their therapeutic roles in cancer treatment. Finally, we put forward existing challenges and future prospects for targeting RCD in anti-cancer immunity. Overall, this review enhances our understanding of the molecular mechanisms and biological impacts of RCD-based therapies, providing new perspectives and strategies for cancer treatment.

Ferroptosis and pyroptosis are connected through autophagy: a new perspective of overcoming drug resistance

Drug resistance is a common challenge in clinical tumor treatment. A reduction in drug sensitivity of tumor cells is often accompanied by an increase in autophagy levels, leading to autophagy-related resistance. The effectiveness of combining chemotherapy drugs with autophagy inducers/inhibitors has been widely confirmed, but the mechanisms are still unclear. Ferroptosis and pyroptosis can be affected by various types of autophagy. Therefore, ferroptosis and pyroptosis have crosstalk via autophagy, potentially leading to a switch in cell death types under certain conditions. As two forms of inflammatory programmed cell death, ferroptosis and pyroptosis have different effects on inflammation, and the cGAS-STING signaling pathway is also involved. Therefore, it also plays an important role in the progression of some chronic inflammatory diseases. This review discusses the relationship between autophagy, ferroptosis and pyroptosis, and attempts to uncover the reasons behind the evasion of tumor cell death and the nature of drug resistance.

An integrative analysis reveals cancer risk associated with artificial sweeteners

BACKGROUND

Artificial sweeteners (AS) have been widely utilized in the food, beverage, and pharmaceutical industries for decades. While numerous publications have suggested a potential link between AS and diseases, particularly cancer, controversy still surrounds this issue. This study aims to investigate the association between AS consumption and cancer risk.

METHODS

Targets associated with commonly used AS were screened and validated using databases such as CTD, STITCH, Super-PRED, Swiss Target Prediction, SEA, PharmMapper, and GalaxySagittarius. Cancer-related targets were sourced from GeneCards, OMIM, and TTD databases. AS-cancer targets were identified through the intersection of these datasets. A network visualization ('AS-targets-cancer') was constructed using Cytoscape 3.9.0. Protein-protein interaction analysis was conducted using the STRING database to identify significant AS-cancer targets. GO and KEGG enrichment analyses were performed using the DAVID database. Core targets were identified from significant targets and genes involved in the 'Pathways in cancer' (map05200). Molecular docking and dynamics simulations were employed to verify interactions between AS and target proteins. Pan-cancer and univariate Cox regression analyses of core targets across 33 cancer types were conducted using GEPIA 2 and SangerBox, respectively. Gene chip datasets (GSE53757 for KIRC, GSE21354 for LGG, GSE42568 for BRCA, and GSE46602 for PRAD) were retrieved from the GEO database, while transcriptome and overall survival data were obtained from TCGA. Data normalization and identification of differentially expressed genes (DEGs) were performed on these datasets using R (version 4.3.2). Gene Set Enrichment Analysis (GSEA) was employed to identify critical pathways in the gene expression profiles between normal and cancer groups. A cancer risk prognostic model was constructed for key targets to further elucidate their significance in cancer initiation and progression. Finally, the HPA database was utilized to investigate variations in the expression of key AS-cancer target proteins across KIRC, LGG, BRCA, PRAD, and normal tissues.

RESULTS

Seven commonly used AS (Aspartame, Acesulfame, Sucralose, NHDC, Cyclamate, Neotame, and Saccharin) were selected for study. A total of 368 AS-cancer intersection targets were identified, with 48 notable AS-cancer targets, including TP53, EGFR, SRC, PIK3R1, and EP300, retrieved. GO biological process analysis indicated that these targets are involved in the regulation of apoptosis, gene expression, and cell proliferation. Thirty-five core targets were identified from the intersection of the 48 significant AS-cancer targets and genes in the 'Pathways in cancer' (map05200). KEGG enrichment analysis of these core targets revealed associations with several cancer types and the PI3K-Akt signaling pathway. Molecular docking and dynamics simulations confirmed interactions between AS and these core targets. HSP90AA1 was found to be highly expressed across the 33 cancer types, while EGF showed the opposite trend. Univariate Cox regression analysis demonstrated strong associations of core targets with KIRC, LGG, BRCA, and PRAD. DEGs of AS-cancer core targets across these four cancers were analyzed. GSEA revealed upregulated and downregulated pathways enriched in KIRC, LGG, BRCA, and PRAD. Cancer risk prognostic models were constructed to elucidate the significant roles of key targets in cancer initiation and progression. Finally, the HPA database confirmed the crucial function of these targets in KIRC, LGG, BRCA, and PRAD.

CONCLUSION

This study integrated data mining, machine learning, network toxicology, molecular docking, molecular dynamics simulations, and clinical sample analysis to demonstrate that AS increases the risk of kidney cancer, low-grade glioma, breast cancer, and prostate cancer through multiple targets and signaling pathways. This paper provides a valuable reference for the safety assessment and cancer risk evaluation of food additives. It urges food safety regulatory agencies to strengthen oversight and encourages the public to reduce consumption of foods and beverages containing artificial sweeteners and other additives.

Development of anti-murine IL-18 binding protein antibodies to stimulate IL-18 bioactivity

Interleukin (IL)-18 is an immunoregulatory cytokine that acts as a potent inducer of T helper 1 and cytotoxic responses. IL-18 activity is regulated by its decoy receptor IL-18 binding protein (IL-18BP) which forms a high affinity complex with IL-18 to block binding of the cognate receptors. A disbalance between IL-18 and IL-18BP associated with excessive IL-18 signaling can lead to systemic inflammation. Indeed, the severity of CpG-induced macrophage activation syndrome (MAS) is exacerbated in IL-18BP KO mice. On the contrary, targeting IL-18BP can have promising effects to enhance immune responses against pathogens and cancer. We generated monoclonal rabbit anti-mouse IL-18BP antibodies labeled from 441 to 450. All antibodies, except from antibody 443, captured mIL-18BP when used in a sandwich ELISA. Using an IL-18 bioassay, we showed that antibody 441 did not interfere with the regulatory effect of mIL-18BP, whereas all other antibodies displayed different levels of antagonism. Further experiments were performed using antibody 445 endowed with potent neutralizing activity and antibody 441. Despite binding to IL-18BP with the same affinity, antibody 445, but not antibody 441, was able to release IL-18 from preformed IL-18-IL-18BP complexes. Administration of antibody 445 significantly aggravated the severity of CpG-induced MAS as compared to antibody 441. Additional experiments using naïve WT, IL-18BP KO, and IL-18 KO mice confirmed the specificity of the neutralizing effect of antibody 445 towards IL-18BP. Our studies led to the development of a monoclonal anti-IL-18BP antibody with neutralizing activity that results in the promotion of IL-18 activities.

Balanced regulation of ROS production and inflammasome activation in preventing early development of colorectal cancer

Reactive oxygen species (ROS) production and inflammasome activation are the key components of the innate immune response to microbial infection and sterile insults. ROS are at the intersection of inflammation and immunity during cancer development. Balanced regulation of ROS production and inflammasome activation serves as the central hub of innate immunity, determining whether a cell will survive or undergo cell death. However, the mechanisms underlying this balanced regulation remain unclear. Mitochondria and NADPH oxidases are the two major sources of ROS production. Recently, NCF4, a component of the NADPH oxidase complex that primarily contributes to ROS generation in phagocytes, was reported to balance ROS production and inflammasome activation in macrophages. The phosphorylation and puncta distribution of NCF4 shifts from the membrane-bound NADPH complex to the perinuclear region, promoting ASC speck formation and inflammasome activation, which triggers downstream IL-18-IFN-γ signaling to prevent the progression of colorectal cancer (CRC). Here, we review ROS signaling and inflammasome activation studies in colitis-associated CRC and propose that NCF4 acts as a ROS sensor that balances ROS production and inflammasome activation. In addition, NCF4 is a susceptibility gene for Crohn's disease (CD) and CRC. We discuss the evidence demonstrating NCF4's crucial role in facilitating cell-cell contact between immune cells and intestinal cells, and mediating the paracrine effects of inflammatory cytokines and ROS. This coordination of the signaling network helps create a robust immune microenvironment that effectively prevents epithelial cell mutagenesis and tumorigenesis during the early stage of colitis-associated CRC.

Activation of pregnane X receptor protects against cholestatic liver injury by inhibiting hepatocyte pyroptosis

Our previous study shows that activation of pregnane X receptor (PXR) exerts hepatoprotection against lithocholic acid (LCA)-induced cholestatic liver injury. In this study we investigated whether PXR activation could inhibit hepatocyte pyroptosis, as well as the underlying mechanisms. Male mice were treated with mouse PXR agonist pregnenolone 16α-carbonitrile (PCN, 50 mg·kg-1·d-1, i.p.) for 7 days, and received LCA (125 mg/kg, i.p., bid) from D4, then sacrificed 12 h after the last LCA injection. We showed that LCA injection resulted in severe cholestatic liver injury characterized by significant increases in gallbladder size, hepatocellular necrosis, and neutrophil infiltration with a mortality rate of 68%; PCN treatment significantly inhibited hepatocyte pyroptosis during LCA-induced cholestatic liver injury, as evidenced by reduced serum lactic dehydrogenase (LDH) levels, TUNEL-positive cells and hepatocyte membrane damage. Furthermore, PXR activation suppressed both the NOD-like receptor protein 3 (NLRP3) inflammasome-induced canonical pyroptosis and the apoptosis protease activating factor-1 (APAF-1) pyroptosome-induced non-canonical pyroptosis. Inhibition of the nuclear factor kappa B (NF-κB) and forkhead box O1 (FOXO1) signaling pathways was also observed following PXR activation. Notably, dual luciferase reporter assay showed that PXR activation inhibited the transcriptional effects of NF-κB on NLRP3, as well as FOXO1 on APAF-1. Our results demonstrate that PXR activation protects against cholestatic liver injury by inhibiting the canonical pyroptosis through the NF-κB-NLRP3 axis and the non-canonical pyroptosis through the FOXO1-APAF-1 axis, providing new evidence for PXR as a prospective anti-cholestatic target.

Diverse autoinhibitory mechanisms of FIIND-containing proteins: Insight into regulation of NLRP1 and CARD8 inflammasome

Function-to-find domain (FIIND)-containing proteins, including NLRP1 and CARD8, are vital components of the inflammasome signaling pathway, critical for the innate immune response. These proteins exist in various forms due to autoproteolysis within the FIIND domain, resulting in full-length (FL), cleaved N-terminal (NT), and cleaved C-terminal (CT) peptides, which form autoinhibitory complexes in the steady state. However, the detailed mechanism remains elusive. Here, we found that both NLRP1 paralogs and CARD8 form two conserved autoinhibitory complexes involving NT-CT interactions and FL-CT interactions, but with distinct mechanisms. Specifically, the Linker3 region located between LRR and FIIND in murine NLRP1b (mNLRP1b) plays an essential role in forming the NT-CT autoinhibitory complexes, while the ZU5 of rat NLRP1 (rNLRP1) and CARD8 mediates their NT-CT interaction. In addition, we explored the involvement of the cellular protease dipeptidyl peptidases 9 (DPP9) in these complexes, revealing differential interactions and the significance of domain structure. Besides the FL-DPP9-CT complex, DPP9 interacts with NTs of mNLRP1b, rNLRP1, and CARD8 through their ZU5 subdomains, forming NT-DPP9-CT complex; however, DPP9 cannot bind to NTs of hNLRP1. Further functional assay indicated that although DPP9 is involved in the NT-CT complex of rodent NLRP1 and CARD8, it does not influence the inhibitory activity of NT on CT. Our study enhanced the understanding of the regulatory functions of FIIND-containing proteins in inflammasome autoinhibition and activation and underscored the complexity of their interactions within the immune response.

A rich component of Fructus Aurantii, meranzin hydrate, exerts antidepressant effects via suppressing caspase4 to regulate glial cell and neuronal functions in the hippocampus

Fructus Aurantii, a Chinese herbal medicine, has been indicated to have antidepressant effects in our previous study. However, the main component and specific mechanisms of the antidepressant effects of Fructus Aurantii still need to be further revealed. This study aimed to explore the main antidepressant component of Fructus Aurantii and the underlying mechanisms of its antidepressant effects in the hippocampus. The results showed that the component of meranzin hydrate (MH) was enrichment in Fructus Aurantii. MH could alleviate depressive phenotypes in LPS-induced mice after a single administration 1 day later. High genetic and proteinic levels of caspase4 in the hippocampus in LPS-induced mice were reversed by MH after a single administration 1 day later. Moreover, MH was capable of relieving inflammatory factors (TNF-a and IL-1β) and LPS in the serum in LPS-induced mice. Subsequently, activation of hippocampal caspase4 blocked MH's antidepressant effects and its effects on suppression of microglia and improvement of astrocyte in the hippocampus. Furthermore, MH could increase long-term potential (LTP) in the hippocampal dentate gyrus (DG) and activation of hippocampal caspase4 blocked MH's enhancement on neuronal activities and synaptic plasticity in the hippocampal DG. To sum up, the antidepressant effects of a rich component MH in Fructus Aurantii suppressed the activation of caspase4 by maintaining glial cells function to promote neuronal activities and synaptic plasticity in the hippocampus.

Advances in research on the impact and mechanisms of pathogenic microorganism infections on pyroptosis

Pyroptosis, also known as inflammatory necrosis, is a form of programmed cell death characterized by the activation of gasdermin proteins, leading to the formation of pores in the cell membrane, continuous cell swelling, and eventual membrane rupture. This process results in the release of intracellular contents, including pro-inflammatory cytokines like IL-1β and IL-18, which subsequently trigger a robust inflammatory response. This process is a crucial component of the body's innate immune response and plays a significant role in combating infections. There are four main pathways through which pathogenic microorganisms induce pyroptosis: the canonical inflammasome pathway, the non-canonical inflammasome pathway, the apoptosis-associated caspase-mediated pathway, and the granzyme-mediated pathway. This article provides a brief overview of the effects and mechanisms of pathogen infections on pyroptosis.

Ubiquitination in pyroptosis pathway: A potential therapeutic target for sepsis

Sepsis remains a significant clinical challenge, causing numerous deaths annually and representing a major global health burden. Pyroptosis, a unique form of programmed cell death characterized by cell lysis and the release of inflammatory mediators, is a crucial factor in the pathogenesis and progression of sepsis, septic shock, and organ dysfunction. Ubiquitination, a key post-translational modification influencing protein fate, has emerged as a promising target for managing various inflammatory conditions, including sepsis. This review integrates the current knowledge on sepsis, pyroptosis, and the ubiquitin system, focusing on the molecular mechanisms of ubiquitination within pyroptotic pathways activated during sepsis. By exploring how modulating ubiquitination can regulate pyroptosis and its associated inflammatory signaling pathways, this review provides insights into potential therapeutic strategies for sepsis, highlighting the need for further research into these complex molecular networks.

Crosstalk of pyroptosis and cytokine in the tumor microenvironment: from mechanisms to clinical implication

In the realm of cancer research, the tumor microenvironment (TME) plays a crucial role in tumor initiation and progression, shaped by complex interactions between cancer cells and surrounding non-cancerous cells. Cytokines, as essential immunomodulatory agents, are secreted by various cellular constituents within the TME, including immune cells, cancer-associated fibroblasts, and cancer cells themselves. These cytokines facilitate intricate communication networks that significantly influence tumor initiation, progression, metastasis, and immune suppression. Pyroptosis contributes to TME remodeling by promoting the release of pro-inflammatory cytokines and sustaining chronic inflammation, impacting processes such as immune escape and angiogenesis. However, challenges remain due to the complex interplay among cytokines, pyroptosis, and the TME, along with the dual effects of pyroptosis on cancer progression and therapy-related complications like cytokine release syndrome. Unraveling these complexities could facilitate strategies that balance inflammatory responses while minimizing tissue damage during therapy. This review delves into the complex crosstalk between cytokines, pyroptosis, and the TME, elucidating their contribution to tumor progression and metastasis. By synthesizing emerging therapeutic targets and innovative technologies concerning TME, this review aims to provide novel insights that could enhance treatment outcomes for cancer patients.

Inflammation unleashed: The role of pyroptosis in chronic liver diseases

Pyroptosis, a newly identified form of programmed cell death intertwined with inflammatory responses, is facilitated by the Gasdermin family's pore-forming activity, leading to cell lysis and the release of pro-inflammatory cytokines. This process is a double-edged sword in innate immunity, offering protection against pathogens while risking excessive inflammation and tissue damage when dysregulated. Specifically, pyroptosis operates through two distinct signaling pathways, namely the Caspase-1 pathway and the Caspase-4/5/11 pathway. In the context of chronic liver diseases like fibrosis and cirrhosis, inflammation emerges as a central contributing factor to their pathogenesis. The identification of inflammation is characterized by the activation of innate immune cells and the secretion of pro-inflammatory cytokines such as IL-1α, IL-1β, and TNF-α. This review explores the interrelationship between pyroptosis and the inflammasome, a protein complex located in liver cells that recognizes danger signals and initiates Caspase-1 activation, resulting in the secretion of IL-1β and IL-18. The article delves into the influence of the inflammasome and pyroptosis on various liver disorders, with a specific focus on their molecular and pathophysiological mechanisms. Additionally, the potential therapeutic implications of targeting pyroptosis for liver diseases are highlighted for future consideration.

Pyroptosis in asthma: inflammatory phenotypes, immune and non-immune cells, and novel treatment approaches

Pyroptosis is a form of inflammatory programmed cell death, and is activated by pathogen infections or endogenous danger signals. The canonical pyroptosis process is characterized by the inflammasome (typically NLRP3)-mediated activation of caspase-1, which in turn cleaves and activates IL-1β and IL-18, as well as gasdermin D, which is a pore-forming executor protein, leading to cell membrane rupture, and the release of proinflammatory cytokines and damage-associated molecular pattern molecules. Pyroptosis is considered a part of the innate immune response. A certain level of pyroptosis can help eliminate pathogenic microorganisms, but excessive pyroptosis can lead to persistent inflammatory responses, and cause tissue damage. In recent years, pyroptosis has emerged as a crucial contributor to the development of chronic inflammatory respiratory diseases, such as asthma. The present study reviews the involvement of pyroptosis in the development of asthma, in terms of its role in different inflammatory phenotypes of the disease, and its influence on various immune and non-immune cells in the airway. In addition, the potential therapeutic value of targeting pyroptosis for the treatment of specific phenotypes of asthma is discussed.

Treatment of silicosis with quercetin depolarizing macrophages via inhibition of mitochondrial damage-associated pyroptosis

Macrophage polarization facilitates the inflammatory response and intensified fibrosis in the silicosis microenvironment by a mechanism related to macrophage pyroptosis, although the upstream target remains poorly defined. Currently, there are few reports on the development of drugs that alleviate macrophage polarization by dampening pyroptosis. The present study aims to explore the mechanics of silica mediating macrophage polarization and to investigate whether quercetin (Que) can depolarize macrophages with this mechanism. Silica processing led to prominent M1 polarization of macrophages. Additionally, significant macrophage polarization could be detected in the lung tissue of mice with airway-perfused silica. Further investigation turned out that pronounced mitochondria damage, mtDNA cytoplasmic ectomy, and pyroptosis occurred in response to silica. Nevertheless, Que treatment could effectively attenuate silica-induced mitochondria damage and pyroptosis as demonstrated in vitro and in vivo. Further exploration presented Que could bind to TOM70 and restore silica-induced mitochondrial damage. More importantly, the M1 polarization of macrophage was depressed with the co-treatment of Que and silica, wherein the inflammatory response and pulmonary fibrosis were also mitigated without obvious damage to vital organs. In conclusion, these findings proved that silica leads to mitochondrial damage, thereby evoking pyroptosis and promoting macrophage M1 polarization. Que could bind to TOM70 and restore its function, suppressing mitochondrial damage and pyroptosis, and depolarizing macrophages to reduce fibrosis, which provides a promising strategy for silicosis treatment in the future.

Inflammasome protein scaffolds the DNA damage complex during tumor development

Inflammasome sensors activate cellular signaling machineries to drive inflammation and cell death processes. Inflammasomes also control the development of certain diseases independently of canonical functions. Here, we show that the inflammasome protein NLR family CARD domain-containing protein 4 (NLRC4) attenuated the development of tumors in the Apcmin/+ mouse model. This response was independent of inflammasome signaling by NLRP3, NLRP6, NLR family apoptosis inhibitory proteins, absent in melanoma 2, apoptosis-associated speck-like protein containing a caspase recruitment domain, caspase-1 and caspase-11. NLRC4 interacted with the DNA-damage-sensing ataxia telangiectasia and Rad3-related (ATR)-ATR-interacting protein (ATRIP)-Ewing tumor-associated antigen 1 (ETAA1) complex to promote the recruitment of the checkpoint adapter protein claspin, licensing the activation of the kinase checkpoint kinase-1 (CHK1). Genotoxicity-induced activation of the NLRC4-ATR-ATRIP-ETAA1 complex drove the tumor-suppressing DNA damage response and CHK1 activation, and further attenuated the accumulation of DNA damage. These findings demonstrate a noninflammatory function of an inflammasome protein in promoting the DNA damage response and mediating protection against cancer.

Key genes and immune pathways in T-cell mediated rejection post-liver transplantation identified via integrated RNA-seq and machine learning

Liver transplantation is the definitive treatment for end-stage liver disease, yet T-cell mediated rejection (TCMR) remains a major challenge. This study aims to identify key genes associated with TCMR and their potential biological processes and mechanisms. The GSE145780 dataset was subjected to differential expression analysis, weighted gene co-expression network analysis (WGCNA), and machine learning algorithms to pinpoint key genes associated with TCMR. Gene Set Enrichment Analysis (GSEA), immune infiltration analysis, and regulatory networks were constructed to ascertain the biological relevance of these genes. Expression validation was performed using single-cell RNA-seq (scRNA-seq) data and liver biopsy tissues from patients. We identified 5 key genes (ITGB2, FCER1G, IL-18, GBP1, and CD53) that are associated with immunological functions, such as chemotactic activity, antigen processing, and T cell differentiation. GSEA highlighted enrichment in chemokine signaling and antigen presentation pathways. A lncRNA-miRNA-mRNA network was delineated, and drug target prediction yielded 26 potential drugs. Evaluation of expression levels in non-rejection (NR) and TCMR groups exhibited significant disparities in T cells and myeloid cells. Tissue analyses from patients corroborated the upregulation of GBP1, IL-18, CD53, and FCER1G in TCMR cases. Through comprehensive analysis, this research has identified 4 genes intimately connected with TCMR following liver transplantation, shedding light on the underlying immune activation pathways and suggesting putative targets for therapeutic intervention.

Inflammasome activation in patients with Kaposi sarcoma herpesvirus-associated diseases

ABSTRACT

Kaposi sarcoma herpesvirus (KSHV)-associated diseases include Kaposi sarcoma (KS), primary effusion lymphoma (PEL), KSHV-associated multicentric Castleman disease (MCD), and KS inflammatory cytokine syndrome (KICS). PEL, MCD, and KICS are associated with elevated circulating inflammatory cytokines. However, activation of the inflammasome, which generates interleukin-1β (IL-1β) and IL-18 via active caspase-1/4/5, has not been evaluated in patients with KSHV-associated diseases (KADs). Herein we report that patients with HIV and ≥1 KAD present with higher plasma levels of IL-18 and increased caspase-1/4/5 activity in circulating monocytes compared with HIV-negative healthy volunteers (HVs) or people with HIV (PWH) without KAD. Within KAD subtypes, KICS and MCD shared enhanced caspase-1/4/5 activity and IL-18 production compared with HVs and PWH, whereas patients with PEL showed remarkably high levels of inflammasome complex formation (known as apoptosis-associated speck-like protein containing a caspase recruitment domain). Moreover, caspase-1/4/5 activity and IL-18 plasma levels correlated with KSHV viral load, indicating KSHV-driven inflammasome activation in KAD. Accordingly, factors released by cells latently infected with KSHV triggered inflammasome activation and cytokine production in bystander monocytes in vitro. Finally, both supervised and unsupervised analyses with inflammasome measurements and other inflammatory biomarkers demonstrate a unique inflammatory profile in patients with PEL, MCD, and KICS as compared with KS. Our data indicate that detrimental inflammation in patients with KAD is at least partially driven by KSHV-induced inflammasome activation in monocytes, thus offering novel approaches to diagnose and treat these complex disorders. These trials were registered at www.ClinicalTrials.gov as #NCT01419561, NCT00092222, NCT00006518, and NCT02147405.

IL-18 signaling is regulated by caspase 6/8 and IL-18BP in turbot (Scophthalmus maximus)

Interleukin (IL)-18 is synthesized as a precursor that requires intracellular processing to become functionally active. In human, IL-18 is processed by caspase 1 (CASP1). In teleost, the maturation and signal transduction mechanisms of IL-18 are unknown. We identified two IL-18 variants, IL-18a and IL-18b, in turbot. IL-18a, but not IL-18b, was processed by CASP6/8 cleavage. Mature IL-18a bound specifically to IL-18 receptor (IL-18R) α-expressing cells and induced IL-18Rα-IL-18Rβ association. Bacterial infection promoted IL-18a maturation in a manner that required CASP6 activation and correlated with gasdermin E activation. The mature IL-18a induced proinflammatory cytokine expression and enhanced bacterial clearance. IL-18a-mediated immune response was suppressed by IL-18 binding protein (IL-18BP), which functioned as a decoy receptor for IL-18a. IL-18BP also functioned as a pathogen pattern recognition receptor and directly inhibited pathogen infection. Our findings revealed unique mechanism of IL-18 maturation and conserved mechanism of IL-18 signaling and regulation in turbot, and provided new insights into the regulation and function of IL-18 related immune signaling.

DGA ameliorates severe acute pancreatitis through modulating macrophage pyroptosis

Severe acute pancreatitis (SAP) is an inflammatory disease with varying severity, ranging from mild local inflammation to severe systemic disease, with a high incidence rate and mortality. Current drug treatments are not ideal. Therefore, safer and more effective therapeutic drugs are urgently needed. 7α,14β-dihydroxy-ent-kaur-17-dimethylamino-3,15-dione DGA, a diterpenoid compound derivatized from glaucocalyxin A, exhibits anti-inflammatory activity. In this study, we demonstrated the therapeutic potential of DGA against SAP and elucidated the underlying mechanisms. Treatment with DGA markedly (1) inhibited death of RAW264.7 and J774a.1 cells induced by Nigericin and lipopolysaccharide, (2) alleviated edema, acinar cell vacuolation, necrosis, and inflammatory cell infiltration of pancreatic tissue in mice, and (3) inhibited the activity of serum lipase and the secretion of inflammatory factor IL-1β. DGA significantly reduced the protein expression of IL-1β and NLRP3 and inhibited the phosphorylation of NF-κB. However, DGA exhibited no inhibitory effect on the expression of caspase-1, gasdermin D (GSDMD), NF-κB, TNF-α, or apoptosis-associated speck-like protein (ASC) and on the cleavage of caspase-1 or GSDMD. Molecular docking simulation confirmed that DGA can bind to TLR4 and IL-1 receptor. In conclusion, DGA may effectively alleviate the symptoms of SAP in mice and macrophages by inhibiting the binding of TLR4 and IL-1 receptor to their ligands; therefore, DGA is a promising drug candidate for the treatment of patients with SAP.

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.

Cytokines on the way to secretion

The activation of immune cells by pro-inflammatory or immunosuppressive stimuli is followed by the secretion of immunoregulatory cytokines which serve as messengers to activate the immune response in target cells. Although the mechanisms that control the secretion of cytokines by immune cells are not yet fully understood, several key aspects of this process have recently emerged. This review focuses on cytokine release via exocytosis and highlights the routes of cytokine trafficking leading to constitutive and regulated secretion as well as the impact of sorting receptors on this process. We discuss the involvement of cytoskeletal rearrangements in vesicular transport, secretion, and formation of immunological synapses. Finally, we describe the non-classical pathways of cytokine release that are independent of vesicular ER-Golgi transport. Instead, these pathways are based on processing by inflammasome or autophagic mechanisms. Ultimately, understanding the molecular mechanisms behind cytokine release may help to identify potential therapeutic targets in diseases associated with altered immune responses.

Discovery of a Covalent Inhibitor of Pro-Caspase-1 Zymogen Blocking NLRP3 Inflammasome Activation and Pyroptosis

Caspase-1 plays a central role in innate immunity, as its activation by inflammasomes induces the production of proinflammatory cytokines and pyroptosis. However, specific inhibition of the enzymatic activity of this protease is not effective in suppressing inflammation, owing to its enzyme-independent function. Herein, we identified a cyclohexenyl isothiocyanate compound (CIB-1476) that potently inhibited caspase-1 activity and suppressed the assembly and activation of the NLRP3 inflammasome and gasdermin-D-mediated pyroptosis. Mechanistically, CIB-1476 directly targeted pro-caspase-1 as an irreversible covalent inhibitor by binding to Cys285 and Cys397, resulting in more durable anti-inflammatory effects in the suppression of enzyme-dependent IL-1β production and enzyme-independent nuclear factor κB activation. Chemoproteomic profiling demonstrated the engagement of CIB-1476 with caspase-1. CIB-1476 showed potent therapeutic effects by suppressing inflammasome activation in mice, which was abolished in Casp1-/- mice. These results warrant further development of CIB-1476 along with its analogues as a novel strategy for caspase-1 inhibitors.

Cell Death: Mechanisms and Potential Targets in Breast Cancer Therapy

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

Pyroptosis, gasdermins and allergic diseases

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