DL-3-n-Butylphthalide Attenuates Myocardial Hypertrophy by Targeting Gasdermin D and Inhibiting Gasdermin D Mediated Inflammation

Pressure overload leads to a hypertrophic milieu that produces deleterious cardiac dysfunction. Inflammation is a key pathophysiological mechanism underpinning myocardial hypertrophy. DL-3-n-butylphthalide (NBP), a neuroprotective agent, also has potent cardioprotective effects. In this study, the potential of NBP to antagonize myocardial hypertrophy was evaluated in C57BL/6 mice in vivo and in rat primary cardiomyocytes in vitro. In mice, NBP treatment reduced cardiac hypertrophy and dysfunction in a transverse aortic constriction (TAC)-induced pressure overload model. In angiotensin (Ang) II-challenged cardiomyocytes, NBP prevents cell size increases and inhibits gasdermin D (GSDMD)-mediated inflammation. Furthermore, overexpression of GSDMD-N reduced the protective effects of NBP against Ang II-induced changes. Using molecular docking and MD simulation, we found that the GSDMD-N protein may be a target of NBP. Our study shows that NBP attenuates myocardial hypertrophy by targeting GSDMD and inhibiting GSDMD-mediated inflammation.

Pleural Fluid GSDMD Is a Novel Biomarker for the Early Differential Diagnosis of Pleural Effusion

OBJECTIVE

Gasdermin D (GSDMD), controlling pyroptosis in cells, has multiple physiological functions. The diagnostic role of GSDMD in pleural effusion (PE) remains unknown.

METHODS

Sandwich ELISA kits that we developed were applied to measure the level of GSDMD for 335 patients with a definite cause of PE, including transudative PE, tuberculous pleural effusion (TPE), parapneumonic pleural effusion (PPE), and malignant pleural effusion (MPE). The diagnostic accuracy of Light's criteria vs. the new marker GSDMD was performed. Clinical follow-up of 40 cases of PPE was conducted and divided into efficacy and non-efficacy groups according to the therapeutic outcome. Nucleated cells (NCs) in PE were isolated and further infected with bacteria to verify the cell source of GSDMD.

RESULTS

The diagnostic accuracy of GSDMD for the diagnosis of PE were 96% (sensitivity) and 94% (specificity). The receiver operating characteristic (ROC) curve indicated that GSDMD can be an efficient biomarker for the differential diagnosis of transudative PE and other groups (all AUC > 0.973). Noteworthily, the highest AUC belonged to tuberculosis diagnosis of 0.990, and the cut-off value was 18.40 ng/mL. Moreover, the same cut-off value of PPE and MPE was 9.35 ng/mL. The combination of GSDMD, adenosine deaminase (ADA), and lactate dehydrogenase (LDH) will further improve the diagnostic efficiency especially between TPE and PPE (AUC = 0.968). The AUC of GSDMD change at day 4, which could predict the therapeutic effect at an early stage, was 0.945 (P < 0.0001). Interestingly, bacterial infection experiments further confirm that the pleural fluid GSDMD was expressed and secreted mainly by the NCs.

CONCLUSION

GSDMD and its combination are candidates as a potentially novel biomarker not only to separate PEs early and effectively, but also monitor disease progression.

LPS induces fibroblast-like synoviocytes RSC-364 cells to pyroptosis through NF-κB mediated dual signalling pathway

Rheumatoid arthritis (RA) is a chronic, progressive, and systemic inflammatory joint disease characterized by synovial inflammation and joint damage. Abnormal activation of fibroblast-like synoviocytes is an initial event of synovial inflammation and joint damage, which can significantly aggravate the progression of RA. Clinical studies have shown that synovitis may be associated with pyroptosis. Therefore, this study is mainly aim for exploring the underlying mechanisms of relationship between inflammation and pyroptosis during synovitis. A cell model of synovitis was constructed by stimulating synovial fibroblasts RSC-364 cells with lipopolysaccharide (LPS). In vitro, we found that LPS can induce pyroptosis of synovial fibroblasts through NOD-like receptor pyrin domain-3/caspase-1/gasdermin D and caspase-3/gasdermin E two signaling pathways, and these two signaling pathways can promote each other. In addition, NF-κB signaling pathway, as the upstream of these two pathways, is involved in regulating the pyroptosis of synovial fibroblast. These results suggest that pyroptosis may be triggered during the occurrence of RA. We hope to provide a new perspective for the study of RA and a new therapeutic target for clinical treatment of RA.

LPS Mediates Bovine Endometrial Epithelial Cell Pyroptosis Directly Through Both NLRP3 Classical and Non-Classical Inflammasome Pathways

As a highly inflammatory form of programmed cell death, pyroptosis is triggered by pro-inflammatory signals and associated with inflammation. It is characterized by cell swelling and large bubbles emerging from the plasma membrane, which release cytokines during inflammation. Compared with other types of cell death, pyroptosis has a distinct morphology and mechanism and involves special inflammasome cascade pathways. However, the inflammasome mechanism through which endometrial epithelial cell pyroptosis occurs in LPS-mediated inflammation remains unclear. We confirmed that there was an increased mRNA and protein expression of the IL-6, TNF-α, IL-1β, IL-18 cytokines, the inflammasome molecules NLRP3, CASPASE-1, CASPASE-4, and GSDMD in LPS-induced primary bovine endometrial epithelial cells (BEECs) in an in vitro established inflammatory model using ELISA, real-time PCR (RT-PCR), vector construction and transfection, and Western blotting. Scanning electron microscopy and lactate dehydrogenase (LDH) activity assays revealed induced cell membrane rupture, which is the main characteristic of pyroptosis. In conclusion, the cytolytic substrate GSDMD’s cleavage by caspase-1 or caspase-4 through the NLRP3 classical and non-classical inflammasome pathways, GSDMD N-terminus bind to the plasma membrane to form pores and release IL -18, IL-1β cause cell death during LPS induced BEECs inflammation.

Exosomes derived from hypoxic bone marrow mesenchymal stem cells rescue OGD-induced injury in neural cells by suppressing NLRP3 inflammasome-mediated pyroptosis

Exosomes have been shown to have therapeutic potential for cerebral ischemic diseases. In this study, we investigated the neuroprotective effects of normoxic and hypoxic bone marrow mesenchymal stromal cells-derived exosomes (N-BM-MSCs-Exo and H-BM-MSCs-Exo, respectively) on oxygen-glucose deprivation (OGD) injury in mouse neuroblastoma N2a cells and rat primary cortical neurons. The proportions of dead cells in N2a and primary cortical neurons after OGD injury were significantly increased, and N-BM-MSCs-Exo (40 μg/ml) could reduce the ratios, noteworthily, the protective effects of H-BM-MSCs-Exo (40 μg/ml) were more potent. Western blotting analysis indicated that N-BM-MSCs-Exo decreased the expression of NLRP3, ASC, Caspase-1, GSDMD-N, cleaved IL-1β and IL-18 in N2a cells. However, H-BM-MSCs-Exo (40 μg/ml) was more powerful in inhibiting the expression of these proteins in comparison with N-BM-MSCs-Exo. Similar results were obtained in primary cortical neurons. Immunofluorescence assays showed that after N-BM-MSCs-Exo and H-BM-MSCs-Exo treatment, the co-localization of NLRP3, ASC, Caspase-1 and the GSDMD translocation from the nucleus to the cytoplasm and membrane after OGD injury were reduced in N2a cells and primary cortical neurons, and H-BM-MSCs-Exo had a more obvious effect. In addition, N-BM-MSCs-Exo and H-BM-MSCs-Exo significantly reduced lactate dehydrogenase (LDH) release and the IL-18 levels in cell culture medium in N2a cells and primary cortical neurons. Once again H-BM-MSCs-Exo induced these effects more potently than N-BM-MSCs-Exo. All of these results demonstrated that N-BM-MSCs-Exo and H-BM-MSCs-Exo have significant neuroprotective effects against NLRP3 inflammasome-mediated pyroptosis. H-BM-MSCs-Exo has a more pronounced protective effect than N-BM-MSCs-Exo and may be used to ameliorate the progression of cerebral ischemia and hypoxia injury in patients.

Role of Pyroptosis in Diabetes and Its Therapeutic Implications

Pyroptosis is mainly considered as a new pro-inflammatory mediated-programmed cell death. In addition, pyroptosis is described by gasdermin-induced pore formation on the membrane, cell swelling and rapid lysis, and several pro-inflammatory mediators interleukin-1β (IL-1β) and interleukin-18 (IL-18) release. Extensive studies have shown that pyroptosis is commonly involved by activating the caspase-1-dependent canonical pathway and caspase-4/5/11-dependent non-canonical pathway. However, pyroptosis facilitates local inflammation and inflammatory responses. Current researches have reported that pyroptosis promotes the progression of several diabetic complications. Emerging studies have suggested that some potential molecules targeting the pyroptosis and inflammasome signaling pathways could be a novel therapeutic avenue for managing and treating diabetes and its complications in the near future. Our narrative review concisely describes the possible mechanism of pyroptosis and its progressive understanding of the development of diabetic complications.

GSDMD contributes to host defence against Staphylococcus aureus skin infection by suppressing the Cxcl1-Cxcr2 axis

Gasdermin D (GSDMD), a member of the gasdermin protein family, is a caspase substrate, and its cleavage is required for pyroptosis and IL-1β secretion. To date, the role and regulatory mechanism of GSDMD during cutaneous microbial infection remain unclear. Here, we showed that GSDMD protected against Staphylococcus aureus skin infection by suppressing Cxcl1–Cxcr2 signalling. GSDMD deficiency resulted in larger abscesses, more bacterial colonization, exacerbated skin damage, and increased inflammatory cell infiltration. Although GSDMD deficiency resulted in defective IL-1β production, the critical role of IL-1β was counteracted by the fact that Caspase-1/11 deficiency also resulted in less IL-1β production but did not aggravate disease severity during S. aureus skin infection. Interestingly, GSDMD-deficient mice had increased Cxcl1 secretion accompanied by increased recruitment of neutrophils, whereas Caspase-1/11-deficient mice presented similar levels of Cxcl1 and neutrophils as wild-type mice. Moreover, the absence of GSDMD promoted Cxcl1 secretion in bone marrow-derived macrophages induced by live, dead, or different strains of S. aureus. Corresponding to higher transcription and secretion of Cxcl1, enhanced NF-κB activation was shown in vitro and in vivo in the absence of GSDMD. Importantly, inhibiting the Cxcl1–Cxcr2 axis with a Cxcr2 inhibitor or anti-Cxcl1 blocking antibody rescued host defence defects in the GSDMD-deficient mice. Hence, these results revealed an important role of GSDMD in suppressing the Cxcl1–Cxcr2 axis to facilitate pathogen control and prevent tissue damage during cutaneous S. aureus infection.

An Apoptotic Caspase Network Safeguards Cell Death Induction in Pyroptotic Macrophages

Pyroptosis has emerged as a key mechanism by which inflammasomes promote host defense against microbial pathogens and sterile inflammation. Gasdermin D (GSDMD)-mediated cell lysis is a hallmark of pyroptosis, but our understanding of cell death signaling during pyroptosis is fragmented. Here, we show that independently of GSDMD-mediated plasma membrane permeabilization, inflammasome receptors engage caspase-1 and caspase-8, both of which redundantly promote activation of apoptotic executioner caspase-3 and caspase-7 in pyroptotic macrophages. Impaired GSDMD pore formation downstream of caspase-1 and caspase-8 activation suffices to unmask the apoptotic phenotype of pyroptotic macrophages. Combined inactivation of initiator caspase-1 and caspase-8, or executioner caspase-3 and caspase-7, is required to abolish inflammasome-induced DEVDase activity during pyroptosis and in apoptotic Gsdmd^-/- cells. Collectively, these results unveil a robust apoptotic caspase network that is activated in parallel to GSDMD-mediated plasma membrane permeabilization and safeguards cell death induction in pyroptotic macrophages.

Role of pyroptosis in diabetic retinopathy and its therapeutic implications

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

Disulfiram inhibits inflammation and fibrosis in a rat unilateral ureteral obstruction model by inhibiting gasdermin D cleavage and pyroptosis

BACKGROUND

As an inhibitor of GSDMD, Disulfiram (DSL) can significantly inhibit cell pyroptosis. Cell pyroptosis plays an important role in renal fibrosis.

METHODS

HK-2 cells were induced by Lps and ATP to form a pyroptosis model, and the cells were treated by DSL. CCK-8 detected the cell activity. Immunofluorescence (IF) detected the GSDMD. ELISA detected the expression of inflammatory cytokines. Flow cytometry and Western blot detected cell apoptosis and pyroptosis. Collagen type I kit detected collagen secretion, and western blot detected fibrosis marker protein expression. Then, a rat model of unilateral ureteral obstruction (UUO) was established. HE staining detected the degree of renal tissue injury, and Masson staining detected the degree of fibrosis. What's more, the apoptosis level of tissue cells was detected by TUNEL. And the inflammatory factors in peripheral blood and renal tissue were detected by ELISA. Furthermore, the expression of GSDMD was detected by immunohistochemistry (IHC), and Western blot was used to detect the expression levels of apoptosis and pyroptosis-related proteins in tissues.

RESULTS

It was found that DSL can inhibit the cell membrane perforation of GSDMD-N by inhibiting the cleavage of GSDMD, hence, it inhibited the occurrence of inflammation, cell pyroptosis, and the fibrosis of HK-2 cells. But if the cell has already undergone pyroptosis, DSL does not provide significant prevention. In vivo experiment, it further verified that pretreated DSL had inhibited renal fibrosis injury.

CONCLUSION

Disulfiram can inhibit inflammation and fibrosis in renal fibrosis rats by inhibiting GSDMD.

Long Non-coding RNA MEG3 Promotes Renal Tubular Epithelial Cell Pyroptosis by Regulating the miR-18a-3p/GSDMD Pathway in Lipopolysaccharide-Induced Acute Kidney Injury

Background and Objective: Acute kidney injury (AKI) is a complication of sepsis. Pyroptosis of gasdermin D (GSDMD)-mediated tubular epithelial cells (TECs) play important roles in pathogenesis of sepsis-associated AKI. Long non-coding RNA (lncRNA) maternally expressed gene 3 (MEG3), an imprinted gene involved in tumorigenesis, is implicated in pyroptosis occurring in multiple organs. Herein, we investigated the role and mechanisms of MEG3 in regulation of TEC pyroptosis in lipopolysaccharide (LPS)-induced AKI.

Materials and Methods: Male C57BL/6 mice and primary human TECs were treated with LPS for 24 h to establish the animal and cell models, respectively, of sepsis-induced AKI. Renal function was assessed by evaluation of serum creatinine and urea levels. Renal tubule injury score was assessed by Periodic acid-Schiff staining. Renal pyroptosis was assessed by evaluating expression of caspase-1, GSDMD, and inflammatory factors IL-1β and IL-18. Cellular pyroptosis was assessed by analyzing the release rate of LDH, expression of IL-1β, IL-18, caspase-1, and GSDMD, and using EtBr and EthD2 staining. MEG3 expression in renal tissues and cells was detected using RT-qPCR. The molecular mechanisms of MEG3 in LPS-induced AKI were assessed through bioinformatics analysis, RNA-binding protein immunoprecipitation, dual luciferase reporter gene assays, and a rescue experiment.

Results: Pyroptosis was detected in both LPS-induced animal and cell models, and the expression of MEG3 in these models was significantly up-regulated. MEG3-knockdown TECs treated with LPS showed a decreased number of pyroptotic cells, down-regulated secretion of LDH, IL-1β, and IL-18, and decreased expression of GSDMD, compared with those of controls; however, there was no difference in the expression of caspase-1 between MEG3 knockdown cells and controls. Bioinformatics analysis screened out miR-18a-3P, and further experiments demonstrated that MEG3 controls GSDMD expression by acting as a ceRNA for miR-18a-3P to promote TECs pyroptosis.

Conclusion: Our study demonstrates that lncRNA MEG3 promoted renal tubular epithelial pyroptosis by regulating the miR-18a-3p/GSDMD pathway in LPS-induced AKI.

Gasdermin E permits interleukin-1 beta release in distinct sublytic and pyroptotic phases

Cellular inflammasome activation causes caspase-1 cleavage of the pore-forming protein gasdermin D (GSDMD) with subsequent pyroptotic cell death and cytokine release. Here, we clarify the ambiguous role of the related family member gasdermin E (GSDME) in this process. Inflammasome stimulation in GSDMD-deficient cells led to apoptotic caspase cleavage of GSDME. Endogenous GSDME activation permitted sublytic, continuous interleukin-1β (IL-1β) release and membrane leakage, even in GSDMD-sufficient cells, whereas ectopic expression led to pyroptosis with GSDME oligomerization and complete liberation of IL-1β akin to GSDMD pyroptosis. We find that NLRP3 and NLRP1 inflammasomes ultimately rely concurrently on both gasdermins for IL-1β processing and release separately from their ability to induce cell lysis. Our study thus identifies GSDME as a conduit for IL-1β release independent of its ability to cause cell death.

Pyroptosis executive protein GSDMD as a biomarker for diagnosis and identification of Alzheimer's disease

OBJECTIVE

This study was mainly conducted to explore the expression changes of GSDMD and conventional markers (including T-Tau, Tau181p, and Aβ_1-42 ) in the cerebrospinal fluid among patients with Alzheimer's disease (AD) and vascular dementia (VD), followed by determination of role of GSDMD in diagnosing and identifying AD and VD.

METHODS

In this study, 60 patients with VD, 60 patients with AD, and 50 healthy controls were enrolled. Lumbar puncture was performed to collect cerebrospinal fluid samples. Patients with VD and patients with AD were evaluated using the Mini-Mental State Examination (MMSE) scale, Montreal Cognitive Assessment (MoCA) scale, Clinical Dementia Rating (CDR) scale, Activity of Daily Living (ADL) scale, and Neuropsychiatric Inventory (NPI) questionnaire, aiming to determine the behavioral ability of patients. ELISA kit was purchased to determine the levels of GSDMD, T-Tau, Tau181p, and Aβ_1-42 in cerebrospinal fluid, and the expression of inflammatory factors, IL-1β and IL-6, was also detected.

RESULTS

(1) The levels of GSDMD, T-Tau, and Tau181p in the cerebrospinal fluid were higher in patients with AD than those of patients with VD and healthy controls, while the levels of Aβ_1-42 in the cerebrospinal fluid were lower in patients with AD than that in healthy controls and patients with VD. (2) GSDMD had good diagnostic accuracy in AD. Additionally, GSDMD, T-Tau, Tau181p, and Aβ_1-42 had good discrimination accuracy in distinguishing AD and VD. (3) The expression levels of inflammatory factors (IL-1β and IL-6) in cerebrospinal fluid were higher in patients with AD than those of healthy controls and patients with VD, which were positively correlated with GSDMD expression.

CONCLUSION

The expression of GSDMD was increased in patients with AD, which could be used as a biomarker for AD diagnosis and identification from VD.

Periodontal Inflammation-Triggered by Periodontal Ligament Stem Cell Pyroptosis Exacerbates Periodontitis

Periodontitis is an immune inflammatory disease that leads to progressive destruction of bone and connective tissue, accompanied by the dysfunction and even loss of periodontal ligament stem cells (PDLSCs). Pyroptosis mediated by gasdermin-D (GSDMD) participates in the pathogenesis of inflammatory diseases. However, whether pyroptosis mediates PDLSC loss, and inflammation triggered by pyroptosis is involved in the pathological progression of periodontitis remain unclear. Here, we found that PDLSCs suffered GSDMD-dependent pyroptosis to release interleukin-1β (IL-1β) during human periodontitis. Importantly, the increased IL-1β level in gingival crevicular fluid was significantly correlated with periodontitis severity. The caspase-4/GSDMD-mediated pyroptosis caused by periodontal bacteria and cytoplasmic lipopolysaccharide (LPS) dominantly contributed to PDLSC loss. By releasing IL-1β into the tissue microenvironment, pyroptotic PDLSCs inhibited osteoblastogenesis and promoted osteoclastogenesis, which exacerbated the pathological damage of periodontitis. Pharmacological inhibition of caspase-4 or IL-1β antibody blockade in a rat periodontitis model lead to the significantly reduced loss of alveolar bone and periodontal ligament damage. Furthermore, Gsdmd deficiency alleviated periodontal inflammation and bone loss in mouse experimental periodontitis. These findings indicate that GSDMD-driven PDLSC pyroptosis and loss plays a pivotal role in the pathogenesis of periodontitis by increasing IL-1β release, enhancing inflammation, and promoting osteoclastogenesis.

Tanshinone II A enhances pyroptosis and represses cell proliferation of HeLa cells by regulating miR-145/GSDMD signaling pathway

Cervical cancer is the fourth most common cancer in women globally. Lack of effective pharmacotherapies for cervical cancer mainly attributed to an elusive understanding of the mechanism underlying its pathogenesis. Pyroptosis plays a key role in inflammation and cancer. Our study identified microRNA (miR) 145 (miR-145)/gasdermin D (GSDMD) signaling pathway as critical mediators in the effect of tanshinone II A on HeLa cells. In the present study, we found that treatment of tanshinone II A led to an obvious repression of cell proliferation and an increase in apoptosis on HeLa cells, especially in high concentration. Compared with the controlled group, tanshinone II A enhanced the activity of caspase3 and caspase9. Notably, the results demonstrated that tanshinone II A regulated cell proliferation of HeLa cells by regulating miR-145/GSDMD signaling pathway. Treatment of tanshinone II A significantly up-regulated the expression of GSDMD and miR-145. After transfection of si-miR-145 plasmids, the effects of tanshinone II A on HeLa cells were converted, including cell proliferation, apoptosis and pyroptosis. In addition, the results showed that tanshinone II A treatment altered the expression level of PI3K, p-Akt, NF-kB p65 and Lc3-I. Collectively, our findings demonstrate that tanshinone II A exerts anticancer activity on HeLa cells by regulating miR-145/GSDMD signaling. The present study is the first time to identify miR-145 as a candidate target in cervical cancer and show an association between miR-145 and pyroptosis, which provides a novel therapy for the treatment of cervical cancer.

Piceatannol inhibits pyroptosis and suppresses oxLDL-induced lipid storage in macrophages by regulating miR-200a/Nrf2/GSDMD axis

As a major bioactive compound from grapes, piceatannol (PIC) has been reported to exert anti-atherosclerotic activity in various studies. Nevertheless, the mechanism underlying the effect of piceatannol against atherosclerosis (AS) is elusive. Our study identified miR-200a/Nrf2/GSDMD signaling pathway as critical mediators in the effect of piceatannol on macrophages. In the present study, we confirmed that treatment of piceatannol repressed the oxLDL-induced lipid storage in macrophages. Compared with control group, piceatannol inhibited TG storage and the activity of caspase1. It is noting that in response to oxLDL challenge, piceatannol abated the pyroptosis in RAW264.7 cells, with a decreased expression of caspase1, gasdermin D (GSDMD), IL-18, IL-1β and NLRP3. Moreover, we investigated the role of microRNA (miR)-200a/Nrf2 signaling pathway in the effect of piceatannol. The results declared that after transfection of si-miR-200a or si-Nrf2 plasmids, the effects of piceatannol on macrophages were converted, including lipid storage and pyroptosis. Importantly, si-miR-200a plasmid reduced the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), indicating that miR-200a acted as an enhancer of Nrf2 in macrophages. Collectively, our findings demonstrate that piceatannol exerts anti-atherosclerotic activity on RAW264.7 cells by regulating miR-200a/Nrf2/GSDMD signaling. The present study is the first time to identify miR-200a as a candidate target in AS and declared an association between miR-200a and pyroptosis, which provides a novel therapy for the treatment of AS.

Role of pyroptosis in atherosclerosis and its therapeutic implications

Atherosclerosis is a significant cardiovascular burden and a leading cause of death worldwide, recognized as a chronic sterile inflammatory disease. Pyroptosis is a novel proinflammatory regulated cell death, characterized by cell swelling, plasma membrane bubbling, and robust release of proinflammatory cytokines (such as interleukin IL-1β and IL-18). Mounting studies have addressed the crucial contribution of pyroptosis to atherosclerosis and clarified the candidate therapeutic agents targeting pyroptosis for atherosclerosis. Herein, we review the initial characterization of pyroptosis, the detailed mechanisms of pyroptosis, current evidence about pyroptosis and atherosclerosis, and potential therapeutic strategies that target pyroptosis in the development of atherosclerosis.

Gasdermin D Inhibits Coronavirus Infection by Promoting the Noncanonical Secretion of Beta Interferon

Pyroptosis, a programmed cell death, functions as an innate immune effector mechanism and plays a crucial role against microbial invasion. Gasdermin D (GSDMD), as the main pyroptosis effector, mediates pyroptosis and promotes releasing proinflammatory molecules into the extracellular environment through pore-forming activity, modifying inflammation and immune responses. While the substantial importance of GSDMD in microbial infection and cancer has been widely investigated, the role of GSDMD in virus infection, including coronaviruses, remains unclear. Enteric coronavirus transmissible gastroenteritis virus (TGEV) and porcine deltacoronavirus (PDCoV) are the major agents for lethal watery diarrhea in neonatal pigs and pose the potential for spillover from pigs to humans. In this study, we found that alphacoronavirus TGEV upregulated and activated GSDMD, resulting in pyroptosis after infection. Furthermore, the fragment of swine GSDMD from amino acids 242 to 279 (242-279 fragment) was required to induce pyroptosis. Notably, GSDMD strongly inhibited both TGEV and PDCoV infection. Mechanistically, the antiviral activity of GSDMD was mediated through promoting the nonclassical release of antiviral beta interferon (IFN-β) and then enhancing the interferon-stimulated gene (ISG) responses. These findings showed that GSDMD dampens coronavirus infection by an uncovered GSDMD-mediated IFN secretion, which may present a novel target of coronavirus antiviral therapeutics. IMPORTANCE Coronaviruses, primarily targeting respiratory and gastrointestinal epithelia in vivo, have a serious impact on humans and animals. GSDMD, a main executioner of pyroptosis, is highly expressed in epithelial cells and involves viral infection pathogenesis. While the functions and importance of GSDMD as a critical regulator of inflammasome activities in response to intracellular bacterial infection have been extensively investigated, the roles of GSDMD during coronavirus infection remain unclear. We here show that alphacoronavirus TGEV triggered pyroptosis and upregulated GSDMD expression, while GSDMD broadly suppressed the infection of enteric coronavirus TGEV and PDCoV by its pore-forming activity via promoting unconventional release of IFN-β. Our study highlights the importance of GSDMD as a regulator of innate immunity and may open new avenues for treating coronavirus infection.

Antidepressant Effect of Paeoniflorin Is Through Inhibiting Pyroptosis CASP-11/GSDMD Pathway

Nod-like receptor protein 3 (NLRP3)-associated neuroinflammation mediated by activated microglia is involved in the pathogenesis of depression. The role of the pore-forming protein gasdermin D (GSDMD), a newly identified pyroptosis executioner downstream of NLRP3 inflammasome mediating inflammatory programmed cell death, in depression has not been well defined. Here, we provide evidence that paeoniflorin (PF), a monoterpene glycoside compound derived from Paeonia lactiflora, ameliorated reserpine-induced mouse depression-like behaviors, characterized as increased mobility time in tail suspension test and forced swimming test, as well as the abnormal alteration of synaptic plasticity in the depressive hippocampus. The molecular docking simulation predicted that PF would interact with C-terminus of GSDMD. We further demonstrated that PF administration inhibited the enhanced expression of GSDMD which mainly distributed in microglia, along with the proteins involved in pyroptosis signaling transduction including caspase (CASP)-11, CASP-1, NLRP3, and interleukin (IL)-1β in the hippocampus of mice treated with reserpine. And also, PF prevented lipopolysaccharide (LPS) and adenosine triphosphate (ATP)-induced pyroptosis in murine N9 microglia in vitro, evidenced by inhibiting the expression of CASP-11, NLRP3, CASP-1 cleavage, as well as IL-1β. Furthermore, VX-765, an effective and selective inhibitor for CASP-1 activation, reduced the expression of inflammasome and pyroptosis-associated proteins in over-activated N9 and also facilitated PF-mediated inhibition of pyroptosis synergistically. Collectively, the data indicated that PF exerted antidepressant effects, alleviating neuroinflammation through inhibiting CASP-11-dependent pyroptosis signaling transduction induced by over-activated microglia in the hippocampus of mice treated with reserpine. Thus, GSDMD-mediated pyroptosis in activated microglia is a previously unrecognized inflammatory mechanism of depression and represents a unique therapeutic opportunity for mitigating depression given PF administration.

c-FLIP regulates pyroptosis in retinal neurons following oxygen-glucose deprivation/recovery via a GSDMD-mediated pathway

Cellular FLICE-inhibitory protein (c-FLIP), an anti-apoptotic regulator, shows remarkable similarities to caspase-8, which plays a key role in the cleavage of gasdermin D (GSDMD). It has been reported that the oxygen-glucose deprivation/recovery (OGD/R) model and lipopolysaccharide (LPS)/adenosine triphosphate (ATP) treatment could induce inflammation and pyroptosis. However, the regulatory role of c-FLIP in the pyroptotic death of retinal neurons is unclear. In this study, we hypothesized that c-FLIP might regulate retinal neuronal pyroptosis by GSDMD cleavage. To investigate this hypothesis, we induced retinal neuronal damage in vitro (OGD/R and LPS/ATP) and in vivo (acute high intraocular pressure [aHIOP]). Our results demonstrated that the three injuries triggered the up-regulation of pyroptosis-related proteins, and c-FLIP could cleave GSDMD to generate a functional N-terminal (NT) domain of GSDMD, causing retinal neuronal pyroptosis. In addition, c-FLIP knockdown in vivo ameliorated the already established visual impairment mediated by acute IOP elevation. Taken together, these findings revealed that decreased c-FLIP expression protected against pyroptotic death of retinal neurons possibly by inhibiting GSDMD-NT generation. Therefore, c-FLIP might provide new insights into the pathogenesis of pyroptosis-related diseases and help to elucidate new therapeutic targets and potential treatment strategies.

GSDMD, an executor of pyroptosis, is involved in IL-1β secretion in Aspergillus fumigatus keratitis

The protein GSDMD is an important performer of pyroptosis and a universal substrate for the inflammatory caspase. However, the role and regulatory mechanism of GSDMD in Aspergillus fumigatus keratitis is remains unknown. Here we detected GSDMD protein in the cornea of normal and fungal-infected C57BL/6 mice. Human corneal epithelial cell (HCECs) were preincubated with a hydrochloride solution (IFNR inhibitor), ruxolitinib (JAK/STAT inhibitor), belnacasan (caspase-1 inhibitor) before infection with A. fumigatus conidia. Mice corneas were infected with Aspergillus fumigatus after pretreatment of GSDMD siRNA via subconjunctival injection. After, samples were harvested at specific time points and the expression of GSDMD and IL-1β was assessed by PCR, Western blot and immunofluorescence staining. Compared with the control group, we observed that the expression of GSDMD in fungal-infected mice cornea was significantly increased. After pretreatment with IFNR, JAK/STAT and caspase-1 inhibitors before fungal infection, the expression of GSDMD was significantly inhibited compared to the DMSO control in HCECs. Moreover, the GSDMD siRNA treatment have significantly weaken corneal inflammatory response, decreasing the proinflammatory factor IL-1β secretion and reducing neutrophils and macrophages recruitment in mice infected corneas. In summary, the data here provided evidences that GSDMD, an executor of pyroptosis, is involved in the early immune response of A. fumigatus keratitis. Additionally, the inhibition of GSDMD expression can affect the secretion of IL-1β and the recruitment of neutrophil and macrophages by blocking IFNR, JAK/STAT and caspase-1 signaling pathway. The protein GSDMD may emerge as a potential therapeutic target for A. fumigatus keratitis.

Zika virus protease induces caspase-independent pyroptotic cell death by directly cleaving gasdermin D

The association of Zika virus (ZIKV) infection with a congenital malformation in fetuses, neurological, and other systemic complications in adults have brought significant global health emergency. ZIKV targets nerve cells in the brain and causes cell death, such as pyroptosis, leading to neuroinflammation. Here we described a novel mechanism of pyroptosis caused by ZIKV protease. We found that ZIKV protease directly cleaved the GSDMD into N-terminal fragment (1-249) leading to pyroptosis in a caspase-independent manner, suggesting a direct mechanism of ZIKV-induced cell death and subsequent inflammation. Our findings might shed new light to explore the pathogenesis of ZIKV infections where ZIKV protease might be a suitable target for the development of antiviral agents.

Priming Is Dispensable for NLRP3 Inflammasome Activation in Human Monocytes In Vitro

Interleukin (IL)-18 and IL-1β are potent pro-inflammatory cytokines that contribute to inflammatory conditions such as rheumatoid arthritis and Alzheimer's disease. They are produced as inactive precursors that are activated by large macromolecular complexes called inflammasomes upon sensing damage or pathogenic signals. NLRP3 inflammasome activation is regarded to require a priming step that causes NLRP3 and IL-1β gene upregulation, and also NLRP3 post-translational licencing. A subsequent activation step leads to the assembly of the complex and the cleavage of pro-IL-18 and pro-IL-1β by caspase-1 into their mature forms, allowing their release. Here we show that human monocytes, but not monocyte derived macrophages, are able to form canonical NLRP3 inflammasomes in the absence of priming. NLRP3 activator nigericin caused the processing and release of constitutively expressed IL-18 in an unprimed setting. This was mediated by the canonical NLRP3 inflammasome that was dependent on K+ and Cl- efflux and led to ASC oligomerization, caspase-1 and Gasdermin-D (GSDMD) cleavage. IL-18 release was impaired by the NLRP3 inhibitor MCC950 and by the absence of NLRP3, but also by deficiency of GSDMD, suggesting that pyroptosis is the mechanism of release. This work highlights the readiness of the NLRP3 inflammasome to assemble in the absence of priming in human monocytes and hence contribute to the very early stages of the inflammatory response when IL-1β has not yet been produced. It is important to consider the unprimed setting when researching the mechanisms of NLRP3 activation, as to not overshadow the pathways that occur in the absence of priming stimuli, which might only enhance this response.

Pyroptosis executioner gasdermin D contributes to host defense and promotes Th 1 immune response during Neospora caninum infection

Neospora caninum (N. caninum) is an intracellular parasite and is the causative agent of neosporosis, which leads to reproductive failure in cattle. Pyroptosis is a recently discovered form of programmed cell death executed by gasdermin D (GSDMD). This cell death mechanism is an important host defense against intracellular pathogens. However, pyroptosis induced by N. caninum is poorly understood. The aim of this study was to explore the roles of GSDMD-mediated pyroptosis during N. caninum infection in vivo. N. caninum-infected wild type mice and GSDMD-deficient mice were used to evaluate host resistance and its ability to affect immune response against this parasite. The results showed that GSDMD deficiency significantly reduced survival and impaired the host's abilities to clear parasite loads in tissues, monocytes/macrophages and neutrophils. Additionally, GSDMD was essential for circulating IL-18 and IFN-γ production induced by N. caninum infection, indicating that GSDMD can mediate the Th 1 immune response against N. caninum infection. Additional data revealed that treatment with exogenous recombinant IL-18 in N. caninum-infected Gsdmd^-/- mice rescues the reduction of circulating IFN-γ production to help eliminate the parasite. Taken together, our data indicate that GSDMD-mediated pyroptosis plays a vital role in maintaining host resistance to N. caninum and is essential for clearing the parasite. This form of programmed cell death promotes the Th 1 immune response by controlling IL-18 release and is considered a host defense against N. caninum. This study expands our understanding of interactions between host immune response/defense and N. caninum infection.

The Yersinia Type III Secretion System as a Tool for Studying Cytosolic Innate Immune Surveillance

Microbial pathogens have evolved complex mechanisms to interface with host cells in order to evade host defenses and replicate. However, mammalian innate immune receptors detect the presence of molecules unique to the microbial world or sense the activity of virulence factors, activating antimicrobial and inflammatory pathways. We focus on how studies of the major virulence factor of one group of microbial pathogens, the type III secretion system (T3SS) of human pathogenic Yersinia, have shed light on these important innate immune responses. Yersinia are largely extracellular pathogens, yet they insert T3SS cargo into target host cells that modulate the activity of cytosolic innate immune receptors. This review covers both the host pathways that detect the Yersinia T3SS and the effector proteins used by Yersinia to manipulate innate immune signaling.

Human Autoinflammatory Diseases Mediated by NLRP3-, Pyrin-, NLRP1-, and NLRC4-Inflammasome Dysregulation Updates on Diagnosis, Treatment, and the Respective Roles of IL-1 and IL-18

Recent research has led to novel findings in inflammasome biology and genetics that altered the diagnosis and management of patients with autoinflammatory syndromes caused by NLRP3-, Pyrin-, NLRP1-, and NLRC4-inflammasomes and spurred the development of novel treatments. The use of next-generation sequencing in clinical practice allows for rapid diagnosis and the detection of somatic mutations that cause autoinflammatory diseases. Clinical differences in patients with NLRP3, pyrin, and NLRP1 inflammasomopathies, and the constitutive elevation of unbound free serum IL-18 that predisposes to the development of macrophage activation syndrome (MAS) in patients with gain-of function mutations in NLRC4 led to the screening and the characterization of novel diseases presenting with constitutively elevated serum IL-18 levels, and start to unravel the biology of "high IL-18 states" that translate into the use of biomarkers that improve diagnosis and monitoring of disease activity and investigations of treatments that target IL-18 and IFN-gamma which promise to improve the management and outcome of these conditions. Lastly, advances in structural modeling by cryo-electron microscopy (cryo-EM) of gasdermin, and of NLRP3- and NLRC4-inflammasome assembly, and the characterization of post-translational modifications (PTM) that regulate inflammasome activation, coupled with high-throughput screening (HTS) of libraries of inflammasome-inhibiting compounds, promise a new generation of treatments for patients with inflammasome-mediated diseases.

Plasma Membrane Pores Drive Inflammatory Cell Death

Necroptosis and pyroptosis are two forms of regulated cell death. They are executed by the proteins mixed-lineage kinase domain-like (MLKL) and gasdermin D (GSDMD), respectively. Once activated by numerous pathways, these proteins form membrane pores that allow the influx and efflux of various ions, proteins, and water, ultimately resulting in the death of the cell. These modalities of cell death are considered highly inflammatory because of the release of inflammatory cytokines and damage-associated molecular patterns, and are thereby not only deleterious for the dying cell itself, but also its environment or the entire organism. The relevance for these processes has been observed in various physiological and pathophysiological conditions, ranging from viral and bacterial infections over autoimmune and chronic inflammatory diseases to ischemic organ damage. In recent years, initial in vitro experiments have shed light on a range of connections between necroptosis and pyroptosis. Initial in vivo studies also indicate that, in many disease models, these two forms of cell death cannot be considered individually, as they demonstrate a complex interaction. In this article, we provide an overview of the currently known structure, pathways of activation, and functions of MLKL and GSDMD. With emerging evidence for an interconnection between necroptosis and pyroptosis in not only in vitro, but also in vivo models of disease, we highlight in particular the clinical relevance of the crosslinks between these two forms of inflammatory cell death and their implications for novel therapeutic strategies in a variety of diseases.

Bacterial outer membrane vesicles induce disseminated intravascular coagulation through the caspase-11-gasdermin D pathway

BACKGROUND

Disseminated intravascular coagulation (DIC), a severe complication of sepsis, promotes multiple organ dysfunctions and lethality. Bacterial infection is the most common cause of sepsis. We previously show an important role of bacteria-released outer membrane vesicles (OMVs) in bacterial infection-induced DIC. In the light of recent advance that activation of caspase-11 and its enzymatic substrate gasdermin D (GSDMD) is able to trigger coagulation, we postulate that OMVs might induce DIC through the caspase-11-GSDMD pathway.

METHODS

Caspase-11- or GSDMD-deficient mice and their wild-type (WT) controls were injected with purified Escherichia coli-derived OMVs. Blood samples were then collected. The development of DIC was assessed in terms of the occurrence of coagulopathy, the organ injuries and the lethality. Peritoneal macrophages derived from WT, Caspase-11- or GSDMD-deficient mice were stimulated with OMVs. Then the cell surface tissue factor (TF) activity and thrombin generation were assessed.

RESULTS

Genetic deletion of Caspase-11 or GSDMD or pharmacological inhibition of caspase-11 markedly attenuated OMVs-induced coagulopathy, multiple organ injuries and mortality. Caspase-11- or GSDMD-deficient macrophages exhibited markedly reduced TF activity after OMVs stimulation.

CONCLUSION

OMVs induce DIC through the caspase-11-GSDMD pathway. These findings might open a new avenue to prevent or treat bacterial infection-induced DIC.

Therapeutic modulation of inflammasome pathways

Inflammasomes are macromolecular complexes formed in response to pathogen‐associated molecular patterns (PAMPs) and danger‐associated molecular patterns (DAMPs) that drive maturation of the pro‐inflammatory cytokines interleukin (IL)‐1β and IL‐18, and cleave gasdermin D (GSDMD) for induction of pyroptosis. Inflammasomes are highly important in protecting the host from various microbial pathogens and sterile insults. Inflammasome pathways are strictly regulated at both transcriptional and post‐translational checkpoints. When these checkpoints are not properly imposed, undue inflammasome activation may promote inflammatory, metabolic and oncogenic processes that give rise to autoinflammatory, autoimmune, metabolic and malignant diseases. In addition to clinically approved IL‐1‐targeted biologics, upstream targeting of inflammasome pathways recently gained interest as a novel pharmacological strategy for selectively modulating inflammasome activation in pathological conditions.

Baicalein Attenuates Neuroinflammation by Inhibiting NLRP3/caspase-1/GSDMD Pathway in MPTP Induced Mice Model of Parkinson's Disease

BACKGROUND

Inflammasome-induced neuroinflammation is a major pathogenic mechanism underlying the degeneration of nigral dopaminergic neurons in Parkinson's disease (PD). Baicalein is a flavonoid isolated from the traditional Chinese medicinal herbal Scutellaria baicalensis Georgi with known anti-inflammatory and neuroprotective efficacy in models of neurodegenerative diseases, including PD. However, its effects on inflammasome-induced neuroinflammation during PD remain unclear.

METHODS

We used N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to induce PD-like pathology in mice. Behavioral assessments including the pole test, rotarod test and open filed test were conducted to evaluate the effects of baicalein on MPTP-induced motor dysfunction. The efficacies of baicalein against MPTP-induced dopaminergic neuron loss and glial cell activation in the substantia nigra compact (SNc) were examined by immunohistochemistry, effects on proinflammatory cytokines by qPCR and enzyme-linked immunosorbent assay (ELISA), effects on inflammasome pathway activation by immunoblotting and flow cytometry.

RESULTS

Administration of baicalein reversed MPTP-induced motor dysfunction, loss of dopaminergic neurons, and pro-inflammatory cytokine elevation. Baicalein also inhibited NLRP3 and caspase-1 activation and suppressed gasdermin D (GSDMD)-dependent pyroptosis. Additionally, baicalein inhibited the activation and proliferation of disease-associated proinflammatory microglia.

CONCLUSIONS

These findings suggest that baicalein can reverse MPTP-induced neuroinflammation in mice by suppressing NLRP3/caspase-1/GSDMD pathway. Our study provides potential insight of baicalein in PD therapy.

GSDMB promotes non-canonical pyroptosis by enhancing caspase-4 activity

Gasdermin B (GSDMB) has been reported to be associated with immune diseases in humans, but the detailed molecular mechanisms remain unsolved. The N-terminus of GSDMB by itself, unlike other gasdermin family proteins, does not induce cell death. Here, we show that GSDMB is highly expressed in the leukocytes of septic shock patients, which is associated with increased release of the gasdermin D (GSDMD) N-terminus. GSDMB expression and the accumulation of the N-terminal fragment of GSDMD are induced by the activation of the non-canonical pyroptosis pathway in a human monocyte cell line. The downregulation of GSDMB alleviates the cleavage of GSDMD and cell death. Consistently, the overexpression of GSDMB promotes GSDMD cleavage, accompanied by increased LDH release. We further found that GSDMB promotes caspase-4 activity, which is required for the cleavage of GSDMD in non-canonical pyroptosis, by directly binding to the CARD domain of caspase-4. Our study reveals a GSDMB-mediated novel regulatory mechanism for non-canonical pyroptosis and suggests a potential new strategy for the treatment of inflammatory diseases.

Role of short-wavelength blue light in the formation of cataracts and the expression of caspase-1, caspase-11, Gasdermin D in rat lens epithelial cells: insights into a novel pathogenic mmechanism of cataracts

Background

With the popularity of blue-rich light-emitting diode (LED)-backlit display devices, our eyes are now exposed to more short-wavelength blue light than they were in the past. The goal of this study was to investigate the pathogenesis of cataracts after short-wavelength light exposure.

Methods

Sprague-Dawley (SD) rats were selected and randomly divided into a control group (10 rats each for the 4-, 8-, and 12-week groups) and an experimental group (10 rats each for the 4-, 8-, and 12-week groups). The rats in the experimental group were exposed to a short-wavelength blue LED lamp for 12 h per day. After exposure to the blue LED lamp, the rats were maintained in total darkness for 12 h, after which a 12-h light/dark cycle was resumed. The intensity of the lamp was 3000 lx. At the end of the short-wavelength blue LED lamp exposure (for 4, 8, and 12 weeks), the expression levels of caspase-1, caspase-11 and gasdermin D (GSDMD) were examined in rat lens epithelial cells (LECs) using qRT-PCR and Western blot analyses. An illuminance of 2500 lx was used to study the potential effect of blue LED light on HLE-B3 hLECs in vitro. AC-YVAD-CMK, a caspase-1 inhibitor, was used to confirm the pyroptosis of LECs by flow cytometry.

Results

After 6 weeks, cataracts developed in the experimental rats (4/20 eyes). The clarity of the lens gradually worsened with the duration of exposure. Twelve weeks later, all of the rat eyes had developed cataracts. The expression levels of caspase-1, caspase-11 and GSDMD at 4, 8, and 12 weeks were significantly higher in the samples from rats exposed to a short-wavelength blue LED lamp than in the samples from control rats (p<0.05). The proportions of double-positive hLECs were significantly increased in the 5-h and 10-h short-wavelength blue light exposure subgroups compared with the 5-h and 10-h caspase-1 inhibitor subgroups (p < 0.05).

Conclusion

The data indicate that pyroptosis plays a key role in cataract induction after short-wavelength blue light exposure. This study might provide new insights into a novel pathogenic mechanism of cataracts.

Overexpression of gasdermin D promotes invasion of adenoid cystic carcinoma

OBJECTIVE

To investigate the relationship between gasdermin D (GSDMD) expression and the invasion of adenoid cystic carcinoma (ACC).

METHODS

Immunohistochemistry (IHC) was used to examine GSDMD expression in tumours and adjacent non-cancerous (ANC) tissues from 33 patients with salivary ACC patients and in tumour samples from 29 patients with pleomorphic adenoma (PA). Lentiviral infection was used to stably overexpress GSDMD in ACC-LM and ACC-83 cells (GSDMD-ov cells), which were subjected to transwell and scratch tests to assess their invasive abilities compared to control cells. Cells overexpressing GSDMD were treated with siRNA targeting GSDMD, and their invasive ability was subsequently examined.

RESULTS

GSDMD expression was significantly higher in ACC tissues than in corresponding ANC tissues (P<0.001). After 24 hours, both the ACC-83 and ACC-LM GSDMD-ov cell lines had more cells that moved through the membrane than did the control cells (P<0.05). For the wound healing experiment, the diameter of the wound in the GSDMD-ov cell lines was smaller than that of the control cells (P<0.001) after 24 hours. The ACC cell lines expressing high GSDMD showed stronger metastatic ability than did the control.

CONCLUSION

GSDMD was highly expressed in ACC tissues compared to ANC tissues, and high GSDMD expression promoted the invasion of ACC cells. These findings suggest that GSDMD expression is related to the invasion of ACC. Our data indicate that we may be able to use GSDMD as an indicator of the invasive or metastatic potential of tumour cells in future research.

New mechanism of nerve injury in Alzheimer's disease: β-amyloid-induced neuronal pyroptosis

The present study was designed to investigate the role of β-amyloid (Aβ1-42 ) in inducing neuronal pyroptosis and its mechanism. Mice cortical neurons (MCNs) were used in this study, LPS + Nigericin was used to induce pyroptosis in MCNs (positive control group), and Aβ1-42 was used to interfere with MCNs. In addition, propidium iodide (PI) staining was used to examine cell permeability, lactate dehydrogenase (LDH) release assay was employed to detect cytotoxicity, immunofluorescence (IF) staining was used to investigate the expression level of the key protein GSDMD, Western blot was performed to detect the expression levels of key proteins, and enzyme-linked immunosorbent assay (ELISA) was utilized to determine the expression levels of inflammatory factors in culture medium, including IL-1β, IL-18 and TNF-α. Small interfering RNA (siRNA) was used to silence the mRNA expression of caspase-1 and GSDMD, and Aβ1-42 was used to induce pyroptosis, followed by investigation of the role of caspase-1-mediated GSDMD cleavage in pyroptosis. In addition, necrosulfonamide (NSA), an inhibitor of GSDMD oligomerization, was used for pre-treatment, and Aβ1-42 was subsequently used to observe the pyroptosis in MCNs. Finally, AAV9-siRNA-caspase-1 was injected into the tail vein of APP/PS1 double transgenic mice (Alzheimer's disease mice) for caspase-1 mRNA inhibition, followed by observation of behavioural changes in mice and measurement of the expression of inflammatory factors and pyroptosis-related protein. As results, Aβ1-42 could induce pyroptosis in MCNs, increase cell permeability and enhance LDH release, which were similar to the LPS + Nigericin-induced pyroptosis. Meanwhile, the expression levels of cellular GSDMD and p30-GSDMD were up-regulated, the levels of NLRP3 inflammasome and GSDMD-cleaved protein caspase-1 were up-regulated, and the levels of inflammatory factors in the medium were also up-regulated. siRNA intervention in caspase-1 or GSDMD inhibited Aβ1-42 -induced pyroptosis, and NSA pre-treatment also caused the similar inhibitory effects. The behavioural ability of Alzheimer's disease (AD) mice was relieved after the injection of AAV9-siRNA-caspase-1, and the expression of pyroptosis-related protein in the cortex and hippocampus was down-regulated. In conclusion, Aβ1-42 could induce pyroptosis by GSDMD protein, and NLRP3-caspase-1 signalling was an important signal to mediate GSDMD cleavage, which plays an important role in Aβ1-42 -induced pyroptosis in neurons. Therefore, GSDMD is expected to be a novel therapeutic target for AD.

Detection of proteins associated with the pyroptosis signaling pathway in breast cancer tissues and their significance

OBJECTIVE

To study the expression of pyroptosis signaling pathway related proteins in breast cancer tissues and paracancer tissues, analyze their relationship with breast cancer clinicopathologic features, and explore their relationship to prognosis.

METHODS

Immunohistochemistry ElivisionTM plus was used to detect the expression of caspase-1, IL-1β and Gasdermin-D (GSDMD) in 108 cases of breast cancer and 23 cases of benign lesions adjacent to breast cancer.

RESULTS

Using 108 cases of breast cancer and 23 cases of para-cancerous benign tissues, the pyroptosis signaling pathway effector proteins caspase-1, IL-1β, and GSDMD were positively correlated with each other. The higher the expression level, the lower the histophologic grade of breast cancer, the smaller the tumor size, the lower the clinical stage, the lower the possibility of lymph node metastasis, the lower the risk of death, and the better the prognosis.

CONCLUSIONS

Pyroptosis signaling pathway effectors caspase-1, IL-1β and GSDMD expression may play an important role in the invasion, metastasis, and prognosis of breast cancer.

FADD and Caspase-8 Regulate Gut Homeostasis and Inflammation by Controlling MLKL- and GSDMD-Mediated Death of Intestinal Epithelial Cells

Pathways controlling intestinal epithelial cell (IEC) death regulate gut immune homeostasis and contribute to the pathogenesis of inflammatory bowel diseases. Here, we show that caspase-8 and its adapter FADD act in IECs to regulate intestinal inflammation downstream of Z-DNA binding protein 1 (ZBP1)- and tumor necrosis factor receptor-1 (TNFR1)-mediated receptor interacting protein kinase 1 (RIPK1) and RIPK3 signaling. Mice with IEC-specific FADD or caspase-8 deficiency developed colitis dependent on mixed lineage kinase-like (MLKL)-mediated epithelial cell necroptosis. However, MLKL deficiency fully prevented ileitis caused by epithelial caspase-8 ablation, but only partially ameliorated ileitis in mice lacking FADD in IECs. Our genetic studies revealed that caspase-8 and gasdermin-D (GSDMD) were both required for the development of MLKL-independent ileitis in mice with epithelial FADD deficiency. Therefore, FADD prevents intestinal inflammation downstream of ZBP1 and TNFR1 by inhibiting both MLKL-induced necroptosis and caspase-8-GSDMD-dependent pyroptosis-like death of epithelial cells.

Minocycline alleviates NLRP3 inflammasome-dependent pyroptosis in monosodium glutamate-induced depressive rats

BACKGROUND

Inflammasome activation and followed by the release of proinflammatory cytokines play a pivotal role in the development and progression of depression. However, the involvement of gasdermin D (GSDMD)-mediated pyroptosis in inflammasome-associated depression has not been studied. The present study aimed to determine the involvement of pyroptosis in the development of depression.

METHODS

The rat depressive model was established by the administration of monosodium glutamate (MSG) in postnatal rats. Minocycline (an anti-inflammatory agent) and VX-765 (a specific inhibitor of caspase-1) were given as intervention treatments when rats were two-month-old. Rat depressive behaviors were evaluated by behavioral tests, including open field test, sucrose preference test, and forced swim test. Rat hippocampi were collected for western blotting and immunofluorescence examination.

RESULTS

MSG administration induced depressive-like behavior in rats. MSG upregulated protein presences of caspase-1, GSDMD, interleukin-1β (IL-1β), interleukin-18 (IL-18), NLR pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein (ASC), high mobility group box 1 protein (HMGB1), and the receptor for advanced glycation end products (RAGE) in the hippocampus. Protein presences of HMGB1, NLRP3 and GSDMD were upregulated in Olig2+ oligodendrocytes in the hippocampus. The data suggest that both HMGB1/RAGE/NLRP3 signalings and GSDMD-dependent pyroptosis were activated. Both minocycline and VX-765 treatments improved depressive-like behaviors. Minocycline treatment significantly reduced both HMGB1/RAGE/NLRP3 inflammasome signalings and GSDMD-dependent pyroptosis. VX-765 downregulated GSDMD-dependent pyroptosis, but not HMGB1/RAGE signalings, indicating that GSDMD-dependent pyroptosis is a key player in the progress of depression.

CONCLUSION

In rats hippocampus, NLRP3 inflammasome activates GSDMD mediated-pyroptosis in the hippocampus of MSG-induced depressive rats.

Mechanism and regulation of pyroptosis-mediated in cancer cell death

Pyroptosis, a form of programmed cell death, has garnered increasing attention as it relates to innate immunity and diseases. The discovery of caspase-1/3/4/5/8/11 function in sensing various challenges expands the spectrum of pyroptosis mediators and also reveals that pyroptosis is not cell type specific. Recent studies have identified that pyroptosis has become a new topic in cancer research because it may affect all stages of carcinogenesis. In this mini-review, we provided a primer on pyroptosis, discussed the induction of pyroptosis in cancer and its implications in cancer management. Moreover, its two important executioners, the gasdermin D (GSDMD) and gasdermin E (GSDME), the functions and mechanisms of them involved in the regulation of cancer therapy were focused on. Small molecules-mediated pyroptosis were found to effectively inhibit various tumor cells. In brief, the findings of pyroptosis-dependent cancer progression, new drugs and therapeutic targets may lead to a promising, novel therapeutic approach for cancer patients.

TMEM173 Drives Lethal Coagulation in Sepsis

The discovery of TMEM173/STING-dependent innate immunity has recently provided guidance for the prevention and management of inflammatory disorders. Here, we show that myeloid TMEM173 occupies an essential role in regulating coagulation in bacterial infections through a mechanism independent of type I interferon response. Mechanistically, TMEM173 binding to ITPR1 controls calcium release from the endoplasmic reticulum in macrophages and monocytes. The TMEM173-dependent increase in cytosolic calcium drives Gasdermin D (GSDMD) cleavage and activation, which triggers the release of F3, the key initiator of blood coagulation. Genetic or pharmacological inhibition of the TMEM173-GSDMD-F3 pathway blocks systemic coagulation and improves animal survival in three models of sepsis (cecal ligation and puncture or bacteremia with Escherichia coli or Streptococcus pneumoniae infection). The upregulation of the TMEM173 pathway correlates with the severity of disseminated intravascular coagulation and mortality in patients with sepsis. Thus, TMEM173 is a key regulator of blood clotting during lethal bacterial infections.

Mechanisms and Therapeutic Regulation of Pyroptosis in Inflammatory Diseases and Cancer

Programmed Cell Death (PCD) is considered to be a pathological form of cell death when mediated by an intracellular program and it balances cell death with survival of normal cells. Pyroptosis, a type of PCD, is induced by the inflammatory caspase cleavage of gasdermin D (GSDMD) and apoptotic caspase cleavage of gasdermin E (GSDME). This review aims to summarize the latest molecular mechanisms about pyroptosis mediated by pore-forming GSDMD and GSDME proteins that permeabilize plasma and mitochondrial membrane activating pyroptosis and apoptosis. We also discuss the potentiality of pyroptosis as a therapeutic target in human diseases. Blockade of pyroptosis by compounds can treat inflammatory disease and pyroptosis activation contributes to cancer therapy.

Baicalin attenuates hepatic injury in non-alcoholic steatohepatitis cell model by suppressing inflammasome-dependent GSDMD-mediated cell pyroptosis

Baicalin (BA), a flavone glycoside, is the constituent of Scutellaria baicalensis, a Chinese herbal medicine used to treat non-alcoholic steatohepatitis (NASH). However, the mechanism of BA on NASH is still not clear. Here, the improving effect of BA on hepatocyte through inhibition of pyroprosis was investigated in vitro. With a cell model of NASH exposing HepG2 cells in free fatty acids (FFA), we revealed that BA could improve hepatocyte from FFA-induced morphological damage and death. And then through transcriptomes screening, a significant down-regulation of NLR pyrin domain containing 3 (Nlrp3), gasdermin D (Gsdmd), andinterleukin-1 beta (IL-1β) expression were found after BA treatment. Further analysis confirmed that BA could decrease the levels of NLRP3 and GSDMD, as well as the release of IL-1β and IL-18, resulting in the reduction of pyroptosis. Moreover, the improving effect of BA could be attenuated by Gsdmd knockdown. In conclusion, BA can reduce pyroptosis of hepatocyte by blocking NLRP3-GSDMD signaling in vitro.

The role of Caspase-1/GSDMD-mediated pyroptosis in Taxol-induced cell death and a Taxol-resistant phenotype in nasopharyngeal carcinoma regulated by autophagy

Taxol has been widely used as a first-line chemotherapeutic agent for the treatment of advanced nasopharyngeal carcinoma (NPC). However, acquired drug resistance has caused great difficulties in clinical treatment. Pyroptosis is a newly discovered programmed cell death pathway, and Caspase-1 and gasdermin D (GSDMD) play key roles in driving canonical pyroptosis. Increasing evidence suggests that pyroptosis is associated with the development of cancer; however, the function and mechanism of pyroptosis in NPC remain obscure. In this study, we observed that Taxol treatment caused pyroptotic cell death, along with activation of Caspase-1 and maturation of IL-1β, as well as cleavage of GSDMD, which is the canonical pyroptosis executor. Furthermore, Taxol-induced pyroptotic cell death could be suppressed by Caspase-1 inhibitor (Z-YVAD-FMK) and GSDMD knockout. Moreover, NPC parental cells demonstrated higher levels of pyroptosis than Taxol-resistant cells, and pyroptosis mediated by Caspase-1/GSDMD suppression induced by a Caspase-1 inhibitor and GSDMD knockout could induce a Taxol-resistant phenotype in vitro and in vivo. By transfecting an siRNA targeting Beclin-1 into NPC Taxol-resistant cells, we discovered that autophagy could negatively regulate pyroptosis by inhibiting Caspase-1/GSDMD activation. Taken together, our results indicated that Caspase-1/GSDMD mediated Taxol-induced pyroptosis and a Taxol-resistant phenotype in NPC cell lines, which may be regulated by autophagy. Thus, we provide novel insight into the mechanisms of Taxol-induced cell death and a promising approach to improve the therapeutic outcomes of patients with advanced NPC.

Casticin elicits inflammasome-induced pyroptosis through activating PKR/JNK/NF-κB signal in 5-8F cells

Casticin is one of the effective ingredients of fructus viticis. Most studies have shown that casticin has a strong anti-proliferation activity against various tumor cells. However, its anti-tumor effect and molecular mechanism in nasopharyngeal carcinoma remain unclear. In this study, we demonstrated that the casticin selectively inhibited the proliferation of 5-8F cells in vitro. Further analysis revealed that casticin treatment significantly increased sub-G2 phase and incited pyroptotic process. Moreover, we demonstrated that PKR participated in in regulating the process of GSDMD-dependent pyroptotic tumor cell death. PKR knockdown alleviated the activation of JNK pathway and the expression of its downstream proteins, including cleaved caspase-1, GSDMD-N, interleukin-1β. These findings indicate that PKR/JNK/NF-κB signal is essential for casticin-induced caspase-1 inflammasome formation and inflammatory cytokines release in 5-8F cell.

Hydrogen inhibits endometrial cancer growth via a ROS/NLRP3/caspase-1/GSDMD-mediated pyroptotic pathway

BACKGROUND

Pyroptosis belongs to a novel inflammatory programmed cell death pathway, with the possible prognosis of endometrial cancer related to the terminal protein GSDMD. Hydrogen exerts a biphasic effect on cancer by promoting tumor cell death and protecting normal cells, which might initiate GSDMD pathway-mediated pyroptosis.

METHODS

We performed immunohistochemical staining and western immunoblotting analysis to observe expression of NLRP3, caspase-1, and GSDMD in human and xenograft mice endometrial cancer tissue and cell lines. We investigated treatment with hydrogen could boost ROS accumulation in endometrial cancer cells by intracellular and mitochondrial sources. GSDMD shRNA lentivirus was used to transfect endometrial cancer cells to investigate the function of GSDMD protein in pyroptosis. Propidium iodide (PI) staining, TUNEL assay, measurement of lactate dehydrogenase (LDH) release and IL-1β ELISA were used to analysis pyroptosis between hydrogen-supplemented or normal culture medium. We conducted in vivo human endometrial tumor xenograft mice model to observe anti-tumor effect in hydrogen supplementation.

RESULTS

We observed overexpression of NLRP3, caspase-1, and GSDMD in human endometrial cancer and cell lines by IHC and western immunoblotting. Hydrogen pretreatment upregulated ROS and the expression of pyroptosis-related proteins, and increased the number of PI- and TUNEL-positive cells, as well as the release of LDH and IL-1β, however, GSDMD depletion reduced their release. We further demonstrated that hydrogen supplementation in mice was sufficient for the anti-tumor effect to inhibit xenograft volume and weight of endometrial tumors, as mice subjected to hydrogen-rich water displayed decreased radiance. Tumor tissue sections in the HRW groups presented moderate-to-strong positive expression of NLRP3, caspase-1 and GSDMD. Hydrogen attenuated tumor volume and weight in a xenograft mouse model though the pyroptotic pathway.

CONCLUSIONS

This study extended our original analysis of the ability of hydrogen to stimulate NLRP3 inflammasome/GSDMD activation in pyroptosis and revealed possible mechanism (s) for improvement of anti-tumor effects in the clinical management of endometrial cancer.

Dendrobium Alkaloids Promote Neural Function After Cerebral Ischemia-Reperfusion Injury Through Inhibiting Pyroptosis Induced Neuronal Death in both In Vivo and In Vitro Models

Pyroptosis is a newly identified lytic form of programmed cell death which is characterized by plasma membrane blebbing and rupture. Pyroptosis occurs in cerebral ischemia injury, and contributes to the activation and secretion of the inflammatory cytokines interleukin (IL)-1β, IL-18, and IL-6. Previous reports have found that Dendrobium alkaloids (DNLA) can exert neuroprotective effects against oxygen-glucose deprivation/reperfusion (OGD/R) damage in vitro, but the mechanisms underlying these effects remain elusive. In this study, we investigated whether DNLA exerted therapeutic benefits against cerebral ischemia-reperfusion (CIR) damage via ameliorating pyroptosis and inflammation. OGD/R damage was induced in HT22 cells pretreated with DNLA (0.03, 0.3, or 3 mg/ml, 24 h prior to OGD/R), MCC950 (10 ng/ml, 1 h prior), and VX765 (10 ng/ml, 1 h prior). Neuronal apoptosis, necrosis, pyroptosis, and pathological changes were analyzed 24 h following OGD/R. Further to this, male C57/BL mice pretreated with different concentrations of DNLA (0.5 or 5 mg/kg, ip.) for 24 h and VX765 (50 mg/kg, ip., 1 h before CIR) underwent transient middle cerebral artery occlusion and reperfusion. We found that DNLA pretreatment resulted in a lower neurologic deficit score, a reduced infarct volume, fewer pyroptotic cells, and reduced levels of inflammatory factors 24 h after CIR. Furthermore, DNLA administration also reduced the levels of the pyroptosis-associated proteins Caspase-1 and gasdermin-D, particularly in the hippocampal CA1 region. Similar decreases were observed in the levels of the inflammatory factors IL-1β, IL-6, and IL-18. OGD/R-associated ultrastructural damage was seen to improve following DNLA administration, likely due to the regulation of the tight junction protein Pannexin-1 by DNLA. Overall, these findings demonstrate that DNLA can protect against CIR damage through inhibiting pyroptosis-induced neuronal death, providing new therapeutic insights for CIR injury.

Atorvastatin inhibits pyroptosis through the lncRNA NEXN-AS1/NEXN pathway in human vascular endothelial cells

BACKGROUND AND AIMS

Many clinical trials have demonstrated that statins convey protective effects against atherosclerosis independent of cholesterol-lowering capacities. Other evidence indicates that pyroptosis, a type of programmed cell death, is likely involved in atherosclerosis, but the effects and mechanisms of statins on pyroptosis must be further revealed.

METHODS

Here, we explored the effects and mechanisms of atorvastatin on pyroptosis in human vascular endothelial cells by quantitative real-time polymerase chain reaction and Western blot analyses.

RESULTS

Atorvastatin upregulated long non-coding RNA (lncRNA) NEXN-AS1 and the expression of NEXN at both the mRNA and protein levels in a concentration- and time-dependent manner. Atorvastatin inhibited pyroptosis by decreasing the expression levels of the canonical inflammasome pathway biomarkers NLRP3, caspase-1, GSDMD, IL-1β, and IL-18 at both the mRNA and protein levels. The promotion effects of atorvastatin on NEXN-AS1 and NEXN expression could be significantly abolished by knockdown of lncRNA NEXN-AS1 or NEXN, and its inhibitory effects on pyroptosis were also markedly offset by knock-down of lncRNA NEXN-AS1 or interference of NEXN.

CONCLUSIONS

These results demonstrated that atorvastatin regulated pyroptosis via the lncRNA NEXN-AS1-NEXN pathway, which provides a new insight into the mechanism of how atorvastatin promotes non-lipid-lower effects against the development of atherosclerosis and gives new directions on how to reverse atherosclerosis.

Pyroptosis: A new frontier in cancer

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

Emerging insights into molecular mechanisms underlying pyroptosis and functions of inflammasomes in diseases

Pyroptosis is a form of necrotic and inflammatory programmed cell death, which could be characterized by cell swelling, pore formation on plasma membranes, and release of proinflammatory cytokines (IL-1β and IL-18). The process of pyroptosis presents as dual effects: protecting multicellular organisms from microbial infection and endogenous dangers; leading to pathological inflammation if overactivated. Two pathways have been found to trigger pyroptosis: caspase-1 mediated inflammasome pathway with the involvement of NLRP1-, NLRP3-, NLRC4-, AIM2-, pyrin-inflammasome (canonical inflammasome pathway) and caspase-4/5/11-mediated inflammasome pathway (noncanonical inflammasome pathway). Gasdermin D (GSDMD) has been proved to be a substrate of inflammatory caspases (caspase-1/4/5/11), and the cleaved N-terminal domain of GSDMD oligomerizes to form cytotoxic pores on the plasma membrane. Here, we mainly reviewed the up to date mechanisms of pyroptosis, and began with the inflammasomes as the activator of caspase-1/caspase-11, 4, and 5. We further discussed these inflammasomes functions in diseases, including infectious diseases, sepsis, inflammatory autoimmune diseases, and neuroinflammatory diseases.

Gasdermin D Exerts Anti-inflammatory Effects by Promoting Neutrophil Death

Gasdermin D (GSDMD) is considered a proinflammatory factor that mediates pyroptosis in macrophages to protect hosts from intracellular bacteria. Here, we reveal that GSDMD deficiency paradoxically augmented host responses to extracellular Escherichia coli, mainly by delaying neutrophil death, which established GSDMD as a negative regulator of innate immunity. In contrast to its activation in macrophages, in which activated inflammatory caspases cleave GSDMD to produce an N-terminal fragment (GSDMD-cNT) to trigger pyroptosis, GSDMD cleavage and activation in neutrophils was caspase independent. It was mediated by a neutrophil-specific serine protease, neutrophil elastase (ELANE), released from cytoplasmic granules into the cytosol in aging neutrophils. ELANE-mediated GSDMD cleavage was upstream of the caspase cleavage site and produced a fully active ELANE-derived NT fragment (GSDMD-eNT) that induced lytic cell death as efficiently as GSDMD-cNT. Thus, GSDMD is pleiotropic, exerting both pro- and anti-inflammatory effects that make it a potential target for antibacterial and anti-inflammatory therapies.

Gasdermins: novel mitochondrial pore-forming proteins

Gasdermin proteins have been extensively characterized for their ability to form necrotic pores in the plasma membrane, however, their interactions with other organelles have yet to be described. We recently demonstrated that some gasdermin proteins can also permeabilize the mitochondria to augment apoptotic signaling which may be important in the context of cancer and hearing loss.