Caspase-8: The double-edged sword

Targeting pyroptosis as a preventive and therapeutic approach for stroke

Stroke has caused tremendous social stress worldwide, yet despite decades of research and development of new stroke drugs, most have failed and rt-PA (Recombinant tissue plasminogen activator) is still the accepted treatment for ischemic stroke. the complexity of the stroke mechanism has led to unsatisfactory efficacy of most drugs in clinical trials, indicating that there are still many gaps in our understanding of stroke. Pyroptosis is a programmed cell death (PCD) with inflammatory properties and are thought to be closely associated with stroke. Pyroptosis is regulated by the GSDMD of the gasdermin family, which when cleaved by Caspase-1/Caspase-11 into N-GSDMD with pore-forming activity can bind to the plasma membrane to form small 10-20 nm pores, which would allow the release of inflammatory factors IL-18 and IL-1β before cell rupture, greatly exacerbating the inflammatory response. The pyroptosis occurs mainly in the border zone of cerebral infarction, and glial cells, neuronal cells and brain microvascular endothelial cells (BMECs) all undergo pyroptosis after stroke, which largely exacerbates the breakdown of the blood-brain barrier (BBB) and thus aggravates brain injury. Therefore, pyroptosis may be a good direction for the treatment of stroke. In this review, we focus on the latest mechanisms of action of pyroptosis and the process by which pyroptosis regulates stroke development. We also suggest potential therapeutic stroke drugs that target the pyroptosis pathway, providing additional therapeutic strategies for the clinical management of stroke. The role of pyroptosis after stroke. After stroke, microglia first rush to the damaged area and polarize into M1 and M2 types. Under the influence of various stimuli, microglia undergo pyroptosis, release pro-inflammatory factors, and are converted to the M1 type; astrocytes and neuronal cells also undergo pyroptosis under the stimulation of various pro-inflammatory factors, leading to astrocyte death due to increased osmotic pressure in the membrane, resulting in water absorption and swelling until rupture. BMECs, the main structural component of the BBB, also undergo pyroptosis when stimulated by pro-inflammatory factors released from microglia and astrocytes, leading to the destruction of the structural integrity of the BBB, ultimately causing more severe brain damage. In addition, GSDMD in neutrophils mainly mediate the release of NETs rather than pyroptosis, which also aggravates brain injury. IL-10=interleukin-10; TGF-β = transforming growth factor-β; IL-18=interleukin-18; IL-1β = interleukin-1β; TNF-α = tumor necrosis factor-α; iNOS=induced nitrogen monoxide synthase; MMPs=Matrix metalloproteinases; GSDMD = gasdermin D; BMECs=brain microvascular endothelial cells; BBB = blood-brain barrier.

A novel autophagy-related gene signature associated with prognosis and immune microenvironment in ovarian cancer

Ovarian cancer (OV), the most fatal gynecological malignance worldwide, has high recurrence rates and poor prognosis. Recently, emerging evidence supports that autophagy, a highly regulated multi-step self-digestive process, plays an essential role in OV progression. Accordingly, we filtered 52 potential autophagy-related genes (ATGs) among the 6197 differentially expressed genes (DEGs) identified in TCGA-OV samples (n = 372) and normal controls (n = 180). Based on the LASSO-Cox analysis, we distinguished a 2-gene prognostic signature, namely FOXO1 and CASP8, with promising prognostic value (p-value < 0.001). Together with corresponding clinical features, we constructed a nomogram model for 1-year, 2-year, and 3-year survival, which was validated in both in training (TCGA-OV, p-value < 0.001) and validation (ICGC-OV, p-value = 0.030) cohorts. Interestingly, we evaluated the immune infiltration landscape through the CIBERSORT algorithm, which indicated the upregulation of 5 immune cells, including CD8 + T cells, Tregs, and Macrophages M2, and high expression of critical immune checkpoints (CTLA4, HAVCR2, PDCD1LG2, and TIGIT) in high-risk group. Stepwise, high-risk group exhibited better sensitivity towards chemotherapies of Bleomycin, Sorafenib, Veliparib, and Vinblastine, though less sensitive to immunotherapy. Especially, based on the IHC of tissue microarrays among 125 patients in our institution, we demonstrated that aberrant upregulation of FOXO1 in OV was related to metastasis and poor prognosis. Moreover, FOXO1 could significantly promote tumor invasiveness, migration, and proliferation in OV cell lines, which was assessed through the Transwell, wound-healing, and CCK-8 assay, respectively. Briefly, the autophagy-related signature was a reliable tool to evaluate immune responses and predict prognosis in the realm of OV precision medicine.

Pomiferin targets SERCA, mTOR, and P-gp to induce autophagic cell death in apoptosis-resistant cancer cells, and reverses the MDR phenotype in cisplatin-resistant tumors in vivo

Drug resistance in cancer has been classified as innate resistance or acquired resistance, which were characterized by apoptotic defects and ABC transporters overexpression respectively. Therefore, to preclude or reverse these resistance mechanisms could be a promising strategy to improve chemotherapeutic outcomes. In this study, a natural product from Osage Orange, pomiferin, was identified as a novel autophagy activator that circumvents innate resistance by triggering autophagic cell death via SERCA inhibition and activation of the CaMKKβ-AMPK-mTOR signaling cascade. In addition, pomiferin also directly inhibited the P-gp (MDR1/ABCB1) efflux and reversed acquired resistance by potentiating the accumulation and efficacy of the chemotherapeutic agent, cisplatin. In vivo study demonstrated that pomiferin triggered calcium-mediated tumor suppression and exhibited an anti-metastatic effect in the LLC-1 lung cancer-bearing mouse model. Moreover, as an adjuvant, pomiferin potentiated the anti-tumor effect of the chemotherapeutic agent, cisplatin, in RM-1 drug-resistant prostate cancer-bearing mouse model by specially attenuating ABCB1-mediated drug efflux, but not ABCC5, thereby promoting the accumulation of cisplatin in tumors. Collectively, pomiferin may serve as a novel effective agent for circumventing drug resistance in clinical applications.

A rare immunological disease, caspase 8 deficiency: case report and literature review

BACKGROUND

Caspase-8 is a molecule in the FAS pathway that initiates apoptosis. One of the rarest autoimmune lymphoproliferative syndromes is caspase-8 deficiency. Immunodeficiency, splenomegaly, and lymphadenopathy are the common symptoms of this condition.

CASE PRESENTATION

A two-year-old boy entered this study with a fever of unknown origin (FUO) and dysentery. Moreover, he suffered from failure to thrive and was allergic to the cow's milk protein. His fever and dysentery did not respond to antibiotic therapy. The colonoscopy revealed diffuse ulcerations regions in the sigmoid along with skipped areas, mimicking Crohn's disease aphthous lesions. He represented very early-onset inflammatory bowel disease (IBD) and was diagnosed with the caspase-8 deficiency.

CONCLUSION

There can be diarrhea or dysentery as the first or main symptoms of inborn errors of immunity (IEIs). The cause of diarrhea and dysentery in this case was early-onset IBD. One of the symptoms of IEIs such as caspase-8 deficiency is early-onset of IBD. Patients with early-onset had normal T cell count and low or normal immunoglobulin levels with insufficient immune response.

Regulated cell death in cancer: from pathogenesis to treatment

ABSTRACT

Regulated cell death (RCD), including apoptosis, pyroptosis, necroptosis, and ferroptosis, is regulated by a series of evolutionarily conserved pathways, and is required for development and tissue homeostasis. Based on previous genetic and biochemical explorations of cell death subroutines, the characteristics of each are generally considered distinctive. However, recent in-depth studies noted the presence of crosstalk between the different forms of RCD; hence, the concept of PANoptosis appeared. Cancer, a complex genetic disease, is characterized by stepwise deregulation of cell apoptosis and proliferation, with significant morbidity and mortality globally. At present, studies on the different RCD pathways, as well as the intricate relationships between different cell death subroutines, mainly focus on infectious diseases, and their roles in cancer remain unclear. As cancers are characterized by dysregulated cell death and inflammatory responses, most current treatment strategies aim to selectively induce cell death via different RCD pathways in cancer cells. In this review, we describe five types of RCD pathways in detail with respect to tumorigenesis and cancer progression. The potential value of some of these key effector molecules in tumor diagnosis and therapeutic response has also been raised. We then review and highlight recent progress in cancer treatment based on PANoptosis and ferroptosis induced by small-molecule compounds, immune checkpoint inhibitors, and nanoparticles. Together, these findings may provide meaningful evidence to fill in the gaps between cancer pathogenesis and RCD pathways to develop better cancer therapeutic strategies.

Involvement of inflammasomes in tumor microenvironment and tumor therapies

Inflammasomes are macromolecular platforms formed in response to damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns, whose formation would cause maturation of interleukin-1 (IL-1) family members and gasdermin D (GSDMD), leading to IL-1 secretion and pyroptosis respectively. Several kinds of inflammasomes detecting different types of dangers have been found. The activation of inflammasomes is regulated at both transcription and posttranscription levels, which is crucial in protecting the host from infections and sterile insults. Present findings have illustrated that inflammasomes are involved in not only infection but also the pathology of tumors implying an important link between inflammation and tumor development. Generally, inflammasomes participate in tumorigenesis, cell death, metastasis, immune evasion, chemotherapy, target therapy, and radiotherapy. Inflammasome components are upregulated in some tumors, and inflammasomes can be activated in cancer cells and other stromal cells by DAMPs, chemotherapy agents, and radiation. In some cases, inflammasomes inhibit tumor progression by initiating GSDMD-mediated pyroptosis in cancer cells and stimulating IL-1 signal-mediated anti-tumor immunity. However, IL-1 signal recruits immunosuppressive cell subsets in other cases. We discuss the conflicting results and propose some possible explanations. Additionally, we also summarize interventions targeting inflammasome pathways in both preclinical and clinical stages. Interventions targeting inflammasomes are promising for immunotherapy and combination therapy.

Necroptosis Induced by Delta-Tocotrienol Overcomes Docetaxel Chemoresistance in Prostate Cancer Cells

Prostate cancer (PCa) represents the fifth cause of cancer death in men. Currently, chemotherapeutic agents for the treatment of cancers, including PCa, mainly inhibit tumor growth by apoptosis induction. However, defects in apoptotic cellular responses frequently lead to drug resistance, which is the main cause of chemotherapy failure. For this reason, trigger non-apoptotic cell death might represent an alternative approach to prevent drug resistance in cancer. Several agents, including natural compounds, have been shown to induce necroptosis in human cancer cells. In this study we evaluated the involvement of necroptosis in anticancer activity of delta-tocotrienol (δ-TT) in PCa cells (DU145 and PC3). Combination therapy is one tool used to overcome therapeutic resistance and drug toxicity. Evaluating the combined effect of δ-TT and docetaxel (DTX), we found that δ-TT potentiates DTX cytotoxicity in DU145 cells. Moreover, δ-TT induces cell death in DU145 cells that have developed DTX resistance (DU-DXR) activating necroptosis. Taken together, obtained data indicate the ability of δ-TT to induce necroptosis in both DU145, PC3 and DU-DXR cell lines. Furthermore, the ability of δ-TT to induce necroptotic cell death may represent a promising therapeutical approach to overcome DTX chemoresistance in PCa.

The double-edged functions of necroptosis

Necroptosis refers to a regulated form of cell death induced by a variety of stimuli. Although it has been implicated in the pathogenesis of many diseases, there is evidence to support that necroptosis is not purely a detrimental process. We propose that necroptosis is a "double-edged sword" in terms of physiology and pathology. On the one hand, necroptosis can trigger an uncontrolled inflammatory cascade response, resulting in severe tissue injury, disease chronicity, and even tumor progression. On the other hand, necroptosis functions as a host defense mechanism, exerting antipathogenic and antitumor effects through its powerful pro-inflammatory properties. Moreover, necroptosis plays an important role during both development and regeneration. Misestimation of the multifaceted features of necroptosis may influence the development of therapeutic approaches targeting necroptosis. In this review, we summarize current knowledge of the pathways involved in necroptosis as well as five important steps that determine its occurrence. The dual role of necroptosis in a variety of physiological and pathological conditions is also highlighted. Future studies and the development of therapeutic strategies targeting necroptosis should fully consider the complicated properties of this type of regulated cell death.

Development and validation of a pyroptosis-related genes signature for risk stratification in gliomas

Background: Glioma is a highly heterogeneous disease, causing the prognostic prediction a challenge. Pyroptosis, a programmed cell death mediated by gasdermin (GSDM), is characterized by cell swelling and the release of inflammatory factors. Pyroptosis occurs in several types of tumor cells, including gliomas. However, the value of pyroptosis-related genes (PRGs) in the prognosis of glioma remains to be further clarified. Methods: In this study, mRNA expression profiles and clinical data of glioma patients were acquired from TCGA and CGGA databases, and one hundred and eighteen PRGs were obtained from the Molecular Signatures Database and GeneCards. Then, consensus clustering analysis was performed to cluster glioma patients. The least absolute shrinkage and selection operator (LASSO) Cox regression model was used to establish a polygenic signature. Functional verification of the pyroptosis-related gene GSDMD was achieved by gene knockdown and western blotting. Moreover, the immune infiltration status between two different risk groups were analyzed through the "gsva" R package. Results: Our results demonstrated that the majority of PRGs (82.2%) were differentially expressed between lower-grade gliomas (LGG) and glioblastoma (GBM) in the TCGA cohort. In univariate Cox regression analysis, eighty-three PRGs were shown to be associated with overall survival (OS). A five-gene signature was constructed to divide patients into two risk groups. Compared with patients in the low-risk group, patients in the high-risk group had obviously shorter OS (p < 0.001). Also, we found that the high-risk group showed a higher infiltrating score of immune cells and immune-related functions. Risk score was an independent predictor of OS (HR > 1, p < 0.001). Furthermore, knockdown of GSDMD decreased the expression of IL-1β and cleaved caspase-1. Conclusion: Our study constructed a new PRGs signature, which can be used to predict the prognosis of glioma patients. Targeting pyroptosis might serve as a potential therapeutic strategy for glioma.

Repressing IRS1/2 by NT157 inhibits the malignant behaviors of ovarian cancer through inactivating PI3K/AKT/mTOR pathway and inducing autophagy

Insulin receptor substrate 1 and 2 (IRS1/2) have been found involved in many cancers development and their inhibitors exert significant tumor-suppressive effects. Here, we tried to explore the function of NT157, an IGF1R-IRS1/2 inhibitor, in ovarian cancer. We treated ovarian cancer cells with varying doses of NT157. The MTT assay was employed to evaluate cell proliferation and colony formation assay was used for detecting colony-forming ability. TUNEL assay was adopted to test cell apoptosis. Cell invasion was checked by the Transwell assay. The expression of apoptosis-related proteins, autophagy markers, IRS1/2, and PI3K/AKT/mTOR pathway was compared by Western blot, immunofluorescence, or qRT-PCR. As indicated by the data, NT157 abated the viability, proliferation, and induced autophagy of ovarian cancer cells. Overexpressing IRS1/2 attenuated the tumor-suppressive effect of NT157 and heightened the PI3K/AKT/mTOR pathway activation. Inhibition of the PI3K/AKT/mTOR pathway enhanced the tumor-suppressive effect of NT157 and facilitated NT157-mediated autophagy. However, the autophagy inhibitor 3-MA partly reversed NT-157-mediated antitumor effects. In conclusion, this study disclosed that NT157 suppressed the malignant phenotypes of ovarian cancer cells by inducing autophagy and hampering the expression of IRS1/2 and PI3K/AKT/mTOR pathway.

Duck Circovirus genotype 2 ORF3 protein induces apoptosis through the mitochondrial pathway

Duck circovirus genotype 2 (DuCV2) belongs to the genus Circovirus, family Circoviridae. It can generally cause lymphocyte atrophy and necrosis in ducks, which leads to immunosuppression. The function of the DuCV2 open reading frame 3 (ORF3) protein in viral pathogenesis in host cells remains unclear. Therefore, a series of studies based on ORF3 of the isolate DuCV GH01 strain (belonging to DuCV2) were carried out in duck embryo fibroblasts (DEFs) in this study. The results showed that the ORF3 protein could induce nuclear shrinkage and fragmentation in DEFs. Chromosomal DNA breakage was observed by TUNEL assay. The expression levels of caspase-related genes showed that ORF3 primarily promoted caspase 3 and caspase 9 expression. Furthermore, the protein expression levels of cleaved caspase 3 and cleaved caspase 9 in DEFs were enhanced by ORF3. Thus, ORF3 may activate the mitochondrial apoptosis pathway. When the 20 amino acid residues at the C-terminus of ORF3 (ORF3ΔC₂₀) were deleted, the apoptosis rates were decreased. Moreover, compared to ORF3, ORF3ΔC₂₀ downregulated the mRNA levels of cytochrome c (Cyt c), poly ADP-ribose polymerase (PARP) and apoptosis protease activating factor 1 (Apaf-1), which are the key molecules in the mitochondrial apoptotic pathway. Further study showed that ORF3ΔC₂₀ could reduce the mitochondrial membrane potential (MMP). This study suggested that the DuCV2 ORF3 protein may primarily activate apoptosis through the mitochondrial pathway in DEFs, and this function is ORF3 C₂₀ dependent.

Making the head: Caspases in life and death

The term apoptosis, as a way of programmed cell death, was coined a half century ago and since its discovery the process has been extensively investigated. The anatomy and physiology of the head are complex and thus apoptosis has mostly been followed in separate structures, tissues or cell types. This review aims to provide a comprehensive overview of recent knowledge concerning apoptosis-related molecules involved in the development of structures of head with a particular focus on caspases, cysteine proteases having a key position in apoptotic pathways. Since many classical apoptosis-related molecules, including caspases, are emerging in several non-apoptotic processes, these were also considered. The largest organ of the head region is the brain and its development has been extensively investigated, including the roles of apoptosis and related molecules. Neurogenesis research also includes sensory organs such as the eye and ear, efferent nervous system and associated muscles and glands. Caspases have been also associated with normal function of the skin and hair follicles. Regarding mineralised tissues within craniofacial morphogenesis, apoptosis in bones has been of interest along with palate fusion and tooth development. Finally, the role of apoptosis and caspases in angiogenesis, necessary for any tissue/organ development and maintenance/homeostasis, are discussed. Additionally, this review points to abnormalities of development resulting from improper expression/activation of apoptosis-related molecules.

Salmonella effector SopF regulates PANoptosis of intestinal epithelial cells to aggravate systemic infection

SopF, a newly discovered effector secreted by Salmonella pathogenicity island-1 type III secretion system (T3SS1), was reported to target phosphoinositide on host cell membrane and aggravate systemic infection, while its functional relevance and underlying mechanisms have yet to be elucidated. PANoptosis (pyroptosis, apoptosis, and necroptosis) of intestinal epithelial cells (IECs) has been characterized as a pivotal host defense to limit the dissemination of foodborne pathogens, whereas the effect of SopF on IECs PANoptosis induced by Salmonella is rather limited. Here, we show that SopF can attenuate intestinal inflammation and suppress IECs expulsion to promote bacterial dissemination in mice infected with Salmonella enterica serovar Typhimurium (S. Typhimurium). We revealed that SopF could activate phosphoinositide-dependent protein kinase-1 (PDK1) to phosphorylate p90 ribosomal S6 kinase (RSK) which down-regulated Caspase-8 activation. Caspase-8 inactivated by SopF resulted in inhibition of pyroptosis and apoptosis, but promotion of necroptosis. The administration of both AR-12 (PDK1 inhibitor) and BI-D1870 (RSK inhibitor) potentially overcame Caspase-8 blockade and subverted PANoptosis challenged by SopF. Collectively, these findings demonstrate that this virulence strategy elicited by SopF aggregates systemic infection via modulating IEC PANoptosis through PDK1-RSK signaling, which throws light on novel functions of bacterial effectors, as well as a mechanism employed by pathogens to counteract host immune defense.

Atractylenolide III Ameliorated Autophagy Dysfunction via Epidermal Growth Factor Receptor-Mammalian Target of Rapamycin Signals and Alleviated Silicosis Fibrosis in Mice

Atractylenolide III (ATL-III) is a major active constituent of the natural plant Atractylodes rhizome. Our previous study has shown that ATL-III may alleviate alveolar macrophage apoptosis via the inhibition of the mammalian target of rapamycin (mTOR)-mediated autophagy of human silicosis. Therefore, we aimed to further explore the function of ATL-III in autophagy, apoptosis, and pulmonary fibrosis by establishing the ATL-III-intervened silicosis mouse model in this study. Meanwhile, we sought and then verified potential autophagy-related signaling pathways by matching differentially expressed genes (attained by RNA sequencing) and the autophagy database. In this study, RNA-sequencing results implied that the epidermal growth factor receptor, the crucial upstream activator of mTOR, was seen as a potential autophagy-regulatory molecule in the ATL-III-intervened silicosis mouse model. The finding of this study was that ATL-III might improve the disorder of autophagic degradation via the activation of epidermal growth factor receptor-mTOR signals in the pulmonary tissue of the silicosis mouse model. ATL-III also alleviated cell apoptosis and silicotic fibrosis. Overall, we supposed that ATL-III might be a potential protective medicine, which had a regulatory effect on autophagy, for the intervention of silicotic fibrosis. In the future, the therapeutic drugs for silicosis should be further focused on the development and application of such natural autophagy agents.

ASSOCIATION OF CASPASE-8 LEVELS WITH RESPIRATORY PARAMETERS AND PRESENCE OF HYPERTENSION IN COPD PATIENTS

OBJECTIVE

The aim: To investigate the association between hypertension and serum Caspase-8 levels in COPD patients.

PATIENTS AND METHODS

Materials and methods: 95 COPD patients (GOLD 2nd grade, group B) were included in the study: 47 non-hypertensive COPD patients formed the main group, and 48 patients with concomitant COPD and hypertension formed the comparison group. Patients underwent examination according to GOLD 2022 Guidelines. Caspase-8 serum levels were measured by ELISA.

RESULTS

Results: Performed analysis showed that an increase in Caspase-8 serum levels was significantly associated with the presence of concomitant hypertension in both univariate and multivariate analyses. A significant association was also found regarding FEV1 levels but not FVC.

CONCLUSION

Conclusions: Both presence of concomitant hypertension and spirometry parameters, which indicate the severity of COPD, can be considered strong predictors of the intensification of apoptosis in COPD patients.

Caspase-8 activation in neutrophils facilitates autoimmune kidney vasculitis through regulating CD4+ effector memory T cells

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are closely associated with neutrophil recruitment and activation, but the impact of the neutrophil apoptosis process in autoimmune disease has been rarely explained. Here, by integrating and analyzing single-cell transcriptome datasets, we found that the caspase-8-associated pathway in neutrophils was highly activated in the kidney rather than in the blood. To verify the function of caspase-8 in neutrophils on AAVs progression, we constructed neutrophil-specific caspase-8 knockout mice combined with an AAVs model induced by human ANCA from AAVs patients, a rapid and powerful model developed in this study. Our results show that caspase-8 activation of neutrophils up-regulates the expression of several inflammatory and immunoregulatory factors, especially IL23A, regulating the activation and differentiation of tissue-resident CD4⁺ effector memory T cells. This study reveals that the activation of caspase-8 in neutrophils can worsen glomerulonephritis of AAVs by regulating inflammation and immunity.

Targeting TRAIL Death Receptors in Triple-Negative Breast Cancers: Challenges and Strategies for Cancer Therapy

The tumor necrosis factor (TNF) superfamily member TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis in cancer cells via death receptor (DR) activation with little toxicity to normal cells or tissues. The selectivity for activating apoptosis in cancer cells confers an ideal therapeutic characteristic to TRAIL, which has led to the development and clinical testing of many DR agonists. However, TRAIL/DR targeting therapies have been widely ineffective in clinical trials of various malignancies for reasons that remain poorly understood. Triple negative breast cancer (TNBC) has the worst prognosis among breast cancers. Targeting the TRAIL DR pathway has shown notable efficacy in a subset of TNBC in preclinical models but again has not shown appreciable activity in clinical trials. In this review, we will discuss the signaling components and mechanisms governing TRAIL pathway activation and clinical trial findings discussed with a focus on TNBC. Challenges and potential solutions for using DR agonists in the clinic are also discussed, including consideration of the pharmacokinetic and pharmacodynamic properties of DR agonists, patient selection by predictive biomarkers, and potential combination therapies. Moreover, recent findings on the impact of TRAIL treatment on the immune response, as well as novel strategies to address those challenges, are discussed.

Combined bulk RNA-seq and single-cell RNA-seq identifies a necroptosis-related prognostic signature associated with inhibitory immune microenvironment in glioma

Necroptosis is a programmed cell death playing a significant role in cancer. Although necroptosis has been related to tumor immune environment (TIME) remodeling and cancer prognosis, however, the role of necroptosis-related genes (NRGs) in glioma is still elusive. In this study, a total of 159 NRGs were obtained, and parameters such as mutation rate, copy number variation (CNV), and relative expression level were assessed. Then, we constructed an 18-NRGs-based necroptosis-related signature (NRS) in the TCGA dataset, which could predict the patient's prognosis and was validated in two external CGGA datasets. We also explored the correlation between NRS and glioma TIME, chemotherapy sensitivity, and certain immunotherapy-related factors. The two necroptosis-related subtypes were discovered and could also distinguish the patients' prognosis. Through the glioblastoma (GBM) scRNA-seq data analysis, NRGs' expression levels in different GBM patient tissue cell subsets were investigated and the relative necroptosis status of different cell subsets was assessed, with the microglia score culminating among all. Moreover, we found a high infiltration level of immunosuppressive cells in glioma TIME, which was associated with poor prognosis in the high-NRS glioma patient group. Finally, the necroptosis suppressor CASP8 exhibited a high expression in glioma and was associated with poor prognosis. Subsequent experiments were performed in human glioma cell lines and patients' tissue specimens to verify the bioinformatic analytic findings about CASP8. Altogether, this study provides comprehensive evidence revealing a prognostic value of NRGs in glioma, which is associated with TIME regulation.

Prognostic Impact of Caspase-8, CDK9 and Phospho-CDK9 (Thr 186) Expression in Patients with Uterine Cervical Cancer Treated with Definitive Chemoradiation and Brachytherapy

Introduction: After primary platinum-based chemoradiation of locally advanced uterine cervical cancer, a substantial proportion of women present with persistent, recurrent or metastatic disease, indicating an unmet need for biomarker development. Methods: We evaluated the clinical records of 69 cervical cancer patients (Federation of Gynecology and Obstetrics, FIGO Stage > IB3) who were subjected to definitive CRT. Immunohistochemical scoring of caspase-8, cyclin dependent kinase 9 (CDK9) and phosphorylated (phospho-)CDK9 (threonine (Thr) 186) was performed on pretreatment samples and correlated with the histopathological and clinical endpoints, including relapse-free survival (RFS), distant metastasis-free survival (DMFS), cancer-specific survival (CSS) and overall survival (OS). Results: Lower levels of caspase-8 were more prevalent in patients with a higher T-stage (p = 0.002) and a higher FIGO stage (p = 0.003), and were significantly correlated with CDK9 expression (p = 0.018) and inversely with pCDK9 detection (p = 0.014). Increased caspase-8 levels corresponded to improved RFS (p = 0.005), DMFS (p = 0.038) and CSS (p = 0.017) in the univariate analyses. Low CDK9 expression was associated with worse RFS (p = 0.008), CSS (p = 0.015) and OS (p = 0.007), but not DMFS (p = 0.083), and remained a significant prognosticator for RFS (p = 0.003) and CSS (p = 0.009) in the multivariate analyses. Furthermore, low pCDK9 staining was significantly associated with superior RFS (p = 0.004) and DMFS (p = 0.001), and increased CSS (p = 0.022), and remained significant for these endpoints in the multivariate analyses. Conclusion: Increased caspase-8 and CDK9 levels correlate with improved disease-related outcomes in cervical cancer patients treated with CRT, whereas elevated pCDK9 levels predict worse survival in this patient population.

CircRNA.0007127 triggers apoptosis through the miR-513a-5p/CASP8 axis in K-562 cells

BACKGROUND: Circular RNAs (circRNAs) are covalently closed single-stranded RNAs with multiple biological functions. CircRNA.0007127 is derived from the carbon catabolite repression 4-negative on TATA-less (CCR4-NOT) complex subunit 2 (CNOT2), which was found to regulate tumor cell apoptosis through caspase pathway. METHODS: Potential circRNA.0007127 target microRNAs (miRNAs) were analyzed by miRanda, TargetScan, and RNAhybrid software, and the miRNAs with binding sites for apoptosis-related genes were screened. The roles of circRNA.0007127 and its downstream target, microRNA (miR)‍-513a-5p, were validated by quantitative real-time polymerase chain reaction (qPCR), flow cytometry, mitochondrial membrane potential, immunofluorescence, western blot, and caspase-8 (CASP8) protein activity in vitro in H₂O₂-induced K-562 cells. The circRNA.‍0007127‍‒‍miR-513a-5p and CASP8‍‒‍miR-513a-5p interactions were verified by luciferase reporter assays. RESULTS: Silencing circRNA.0007127 decreased cell apoptosis by inhibiting CASP8 pathway activation in K-562 cells. Compared with the control group, the expression of CASP8 was reduced by 50% and the 43-kD fragment of CASP8 protein was significantly reduced (P≤0.05). The luciferase reporting assay showed that circRNA.0007127 combined with miR-513a-5p or CASP8, with extremely significant differences (P≤0.001). The overexpression of miR-513a-5p inhibited the gene expression level of CASP8 in a human myeloid leukemia cell model (75% change) and the level of a 43-kD fragment of CASP8 protein (P≤0.01). The rescue experiment showed that cotransfection with circRNA.0007127 small-interfering RNA (siRNA) and the miR-513a-5p inhibitor increased CASP8 gene expression and the apoptosis rate, suggesting that the miR-513a-5p inhibitor is a circRNA.0007127 siRNA antagonist. CONCLUSIONS: CircRNA.0007127 regulates K-562 cell apoptosis through the miR-513a-5p/CASP8 axis, which can serve as a novel powerful molecular target for K-562 cells.

Analysis of the potential ferroptosis mechanism and multitemporal expression change of central ferroptosis-related genes in cardiac ischemia–reperfusion injury

Acute myocardial infraction is the most severe type of coronary artery disease and remains a substantial burden to the health care system globally. Although myocardial reperfusion is critical for ischemic cardiac tissue survival, the reperfusion itself could cause paradoxical injury. This paradoxical phenomenon is known as ischemia–reperfusion injury (IRI), and the exact molecular mechanism of IRI is still far from being elucidated and is a topic of controversy. Meanwhile, ferroptosis is a nonapoptotic form of cell death that has been reported to be associated with various cardiovascular diseases. Thus, we explored the potential ferroptosis mechanism and target in cardiac IRI via bioinformatics analysis and experiment. GSE4105 data were obtained from the GEO database and consist of a rat IRI model and control. After identifying differentially expressed ferroptosis-related genes (DEFRGs) and hub genes of cardiac IRI, we performed enrichment analysis, coexpression analysis, drug–gene interaction prediction, and mRNA–miRNA regulatory network construction. Moreover, we validated and explored the multitemporal expression of hub genes in a hypoxia/reoxygenation (H/R)-induced H9C2 cell injury model under different conditions via RT-qPCR. A total of 43 DEFRGs and 7 hub genes (tumor protein p53 [Tp53], tumor necrosis factor [Tnf], hypoxia-inducible factor 1 subunit alpha [Hif1a], interleukin 6 [Il6], heme oxygenase 1 [Hmox1], X-box binding protein 1 [Xbp1], and caspase 8 [Casp8]) were screened based on bioinformatics analysis. The functional annotation of these genes revealed apoptosis, and the related signaling pathways could have association with the pathogenesis of ferroptosis in cardiac IRI. In addition, the expression of the seven hub genes in IRI models were found higher than that of control under different H/R conditions and time points. In conclusion, the analysis of 43 DEFRGs and 7 hub genes could reveal the potential biological pathway and mechanism of ferroptosis in cardiac IRI. In addition, the multitemporal expression change of hub genes in H9C2 cells under different H/R conditions could provide clues for further ferroptosis mechanism exploring, and the seven hub genes could be potential biomarkers or therapeutic targets in cardiac IRI.

Hydroxy-γ-sanshool from Zanthoxylum bungeanum (prickly ash) induces apoptosis of human colorectal cancer cell by activating P53 and Caspase 8

Sanshools, long-chain polyunsaturated amides in Zanthoxylum bungeanum (prickly ash), have important bioactivity. The objective was to assess inhibitory effects and molecular mechanisms of sanshools isolated from supercritical fluid (SCF) extract on human colon adenocarcinoma cells (HCT-116) cultured in vitro. Cells were exposed to various concentrations (0, 50, 90, or 130 μM) of sanshools for 24 or 48 h, with assessment of apoptosis and cell cycle arrest as well as regulatory gene and protein expression associated with apoptosis and the cell cycle. Sanshools profoundly inhibited growth of HCT-116 cells, with hydroxy-γ-sanshool (HRS) being the optimal active component (IC₅₀ = 88.01 μM) inhibiting cell proliferation and having no cytotoxic effect to normal cells (IC₅₀ = 481.52 μM) by CCK-8 assay. In HCT-116 cells, HRS inhibited cell growth, induced morphological distortion, and arrested the cell cycle at G1 phase (50.31 ± 4.13% vs. 72.16 ± 8.14% in Control and 130 μM HRS, respectively), and also caused programmed cell death in a dose-dependent manner. The percentage of apoptotic cells were remarkably increased after treated with HRS (6.2, 11.9, 19.8, and 30.7% for 0, 50, 90, and 130 μM, respectively). Moreover, in HCT-116 cells, HRS significantly inhibited mRNA and protein levels of Cyclin D1, CDK4, PCNA, and increased mRNA and protein levels of P21, P53, Fas, and Caspase 8. Furthermore, inhibitors of P53 and Caspase 8 proteins significantly mitigated the HRS-induced cell cycle arrest and apoptosis. In conclusion, our study provides evidence that HRS induced human colorectal cancer cell apoptosis by up-regulating P53 and Caspase 8.

Anoikis resistance in diffuse glioma: The potential therapeutic targets in the future

Glioma is the most common malignant intracranial tumor and exhibits diffuse metastasis and a high recurrence rate. The invasive property of glioma results from cell detachment. Anoikis is a special form of apoptosis that is activated upon cell detachment. Resistance to anoikis has proven to be a protumor factor. Therefore, it is suggested that anoikis resistance commonly occurs in glioma and promotes diffuse invasion. Several factors, such as integrin, E-cadherin, EGFR, IGFR, Trk, TGF-β, the Hippo pathway, NF-κB, eEF-2 kinase, MOB2, hypoxia, acidosis, ROS, Hsp and protective autophagy, have been shown to induce anoikis resistance in glioma. In our present review, we aim to summarize the underlying mechanism of resistance and the therapeutic potential of these molecules.

Role of Caspase Family in Intervertebral Disc Degeneration and Its Therapeutic Prospects

Intervertebral disc degeneration (IVDD) is a common musculoskeletal degenerative disease worldwide, of which the main clinical manifestation is low back pain (LBP); approximately, 80% of people suffer from it in their lifetime. Currently, the pathogenesis of IVDD is unclear, and modern treatments can only alleviate its symptoms but cannot inhibit or reverse its progression. However, in recent years, targeted therapy has led to new therapeutic strategies. Cysteine-containing aspartate proteolytic enzymes (caspases) are a family of proteases present in the cytoplasm. They are evolutionarily conserved and are involved in cell growth, differentiation, and apoptotic death of eukaryotic cells. In recent years, it has been confirmed to be involved in the pathogenesis of various diseases, mainly by regulating cell apoptosis and inflammatory response. With continuous research on the pathogenesis and pathological process of IVDD, an increasing number of studies have shown that caspases are closely related to the IVDD process, especially in the intervertebral disc (IVD) cell apoptosis and inflammatory response. Therefore, herein we study the role of caspases in IVDD with respect to the structure of caspases and the related signaling pathways involved. This would help explore the strategy of regulating the activity of the caspases involved and develop caspase inhibitors to prevent and treat IVDD. The aim of this review was to identify the caspases involved in IVDD which could be potential targets for the treatment of IVDD.

Salvianolic Acid B Attenuates Iopromide-Induced Renal Tubular Epithelial Cell Injury by Inhibiting the TLR4/NF-κB/NLRP3 Signaling Pathway

Postcontrast acute kidney injury (PC-AKI) is directly caused by the use of contrast, indicating a clear causal relationship between the contrast and the injury. Salvianolic acid B (Sal B), a water-soluble compound of Salvia miltiorrhiza, has a potent anti-inflammatory effect. We conducted a study to explore whether the protective effect of Sal B on iopromide-induced injury in human proximal tubular epithelial cells (HK-2 cells) is related to inhibition of the TLR4/NF-κB/NLRP3 signal pathway. The results showed that 100 μmol/L Sal B counteracted the decrease in cell viability, the increase of ROS and the number of apoptotic cells, and the decrease of mitochondrial membrane potential (ΔΨm) induced by iopromide. Molecular docking analysis showed that Sal B binds TLR4 and NLRP3 proteins. Moreover, 100 μmol/L Sal B also decreased the expression of TLR4, NLRP3, ASC, Caspase-1, IL-18, IL-1β, TNF-α, p-NF-κB, cleaved caspase-3, and the ratio of Bax/Bcl-2 induced by iopromide. TAK-242, a TLR4 antagonist, was added to further explore the mechanism of Sal B. However, the cotreatment group with TAK-242 and Sal B had no significant difference in cell viability and apoptosis rate compared to the treatment group with TAK-242 or Sal B alone. These results indicated that Sal B can inhibit the TLR4/NF-κB/NLRP3 signal pathway, resulting in the alleviation of iopromide-induced HK-2 cell injury.

The Identification of Necroptosis-Related Subtypes, the Construction of a Prognostic Model, and the Characterization of the Tumor Microenvironment in Gliomas

Necroptosis is a recently discovered form of cell death that plays a vital role in the progression of cancer, the spread of metastases, and the immunologic response to tumors. Due to the dual role of necrotic apoptotic processes in tumor pathogenesis and the heterogeneity of gliomas, the function of necroptosis in the glioma microenvironment is still poorly understood. We characterized the expression of necroptosis-related genes (NRGs) within glioma samples at both the genetic and transcriptional levels, identifying three distinct subtypes. Additionally, we constructed a risk score, which is capable of accurately predicting patient prognosis, correlates with tumor mutation burden (TMB), tumor stem cell index (CSC), immune checkpoints, and predicts tumor drug sensitivity. To facilitate its application in the clinic, we developed a nomogram and demonstrated that it predicts the prognosis of glioma patients with good accuracy and reliability using multiple datasets. We examined the function of necroptosis in the tumor microenvironment (TME) and the prognosis of gliomas, which may be useful for guiding individualized treatment plans for gliomas targeting necroptosis.

A pyroptosis-related gene signature predicts prognosis and immune microenvironment in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a highly malignant tumor with a very poor prognosis. Pyroptosis is an inflammatory form of cell death and plays an important role in cancer development. The prognostic value of pyroptosis-related genes (PRGs) in HCC has not been studied extensively.

METHODS

Unsupervised consensus clustering analysis was performed to identify two subtypes based on the expression profiles of prognostic PRGs in the The Cancer Genome Atlas (TCGA) database, and the differences between the two subtypes were compared. A prognostic model based on four PRGs was established by further least absolute shrinkage and selection operator (LASSO) Cox regression analysis and multivariate Cox regression analysis.

RESULTS

Two subtypes (clusters 1 and 2) were identified by consensus clustering based on prognostic PRGs in HCC. Survival outcomes, biological function, genomic alterations, immune cell infiltration, and immune checkpoint genes were compared between the subtypes. Cluster 2 had a worse survival outcome than cluster 1. Cluster 2 was enriched for hallmarks of cancer progression, TP53 mutation, tumor-promoting immune cells, and immune checkpoint genes, which may contribute to the poor prognosis. A prognostic risk signature that predicted the overall survival (OS) of patients was constructed and validated. Consequently, a risk score was calculated for each patient. Combined with the clinical characteristics, the risk score was found to be an independent prognostic factor for survival of HCC patients. Further analysis revealed that the risk score was closely associated with the levels of immune cell infiltration and the expression profiles of immune checkpoint genes.

CONCLUSIONS

Collectively, our study established a prognostic risk signature for HCC and revealed a significant correlation between pyroptosis and the HCC immune microenvironment.

Effects of sulfur dioxide, ozone, and ambient air pollution on lung histopathology, oxidative-stress biomarkers, and apoptosis-related gene expressions in rats

PURPOSE OF THE STUDY

Ambient air pollution (AAP) has become an important health problem globally. Besides, several pieces of evidence indicate that air pollutants such as sulfur dioxide (SO₂) and ozone (O₃) are major contributors to a wide range of non-communicable diseases. The present study investigated the effects of AAP, sulfur dioxide, and ozone on oxidative stress, histopathology, and some apoptosis-related genes expressions of lung tissue in a rat model.

MATERIALS AND METHODS

Thirty-two Wistar rats were randomly divided into the control, AAP, sulfur dioxide (10 ppm), and ozone (0.6 ppm) groups. After five consecutive weeks' exposure to the selected pollutants (3 h/day), lung tissues were harvested and immediately fixed with formalin. The samples were routinely processed, sectioned, stained with hematoxylin and eosin (H&E), and finally assessed for presence of pathological changes. Expression changes of BAX, p-53, EGFR, caspase-3, caspase-8 and caspase-9 were assayed using the RT-qPCR method. One hundred milligrams of lung tissues were extracted and the supernatants were used for assaying malondialdehyde (MDA), total antioxidant capacity (TAC), superoxide dismutase (SOD), glutathione peroxidase (GP_X), and catalase activities.

RESULTS

GPx activity was increased in the ozone (P = 0.05) and AAP (P < 0.001) groups and also MDA level in sulfur dioxide group (P = 0.008). Pathological lesions were mild, moderate, and severe in the sulfur dioxide, ozone, and AAP groups, respectively, as compared to control group (P ˂ 0.05). Exposure to AAP and sulfur dioxide enhanced BAX (P = 0.002) and caspase-8 (P < 0.001) mRNA expression, respectively. Caspases-3 and -8 mRNA expressions were elevated in ozone group (P < 0.001).

CONCLUSIONS

The results indicated induction of oxidative stress. Our results suggest the apoptosis stimuli effect of AAP and also the extrinsic apoptotic pathway trigger effect of sulfur dioxide and ozone in the lung tissue in the concentrations used in the present study. The histopathological and the genes expression changes may be a result of the induced oxidative stress in the lung tissues.

Pan-Caspase Inhibitor zVAD Induces Necroptotic and Autophagic Cell Death in TLR3/4-Stimulated Macrophages

In addition to inducing apoptosis, caspase inhibition contributes to necroptosis and/or autophagy depending on the cell type and cellular context. In macrophages, necroptosis can be induced by co-treatment with Toll-like receptor (TLR) ligands (lipopolysaccharide [LPS] for TLR4 and polyinosinic-polycytidylic acid [poly I:C] for TLR3) and a cell-permeable pan-caspase inhibitor zVAD. Here, we elucidated the signaling pathways and molecular mechanisms of cell death. We showed that LPS/zVAD- and poly I:C/zVAD-induced cell death in bone marrow-derived macrophages (BMDMs) was inhibited by receptor-interacting protein kinase 1 (RIP1) inhibitor necrostatin-1 and autophagy inhibitor 3-methyladenine. Electron microscopic images displayed autophagosome/autolysosomes, and immunoblotting data revealed increased LC3II expression. Although zVAD did not affect LPS- or poly I:C-induced activation of IKK, JNK, and p38, it enhanced IRF3 and STAT1 activation as well as type I interferon (IFN) expression. In addition, zVAD inhibited ERK and Akt phosphorylation induced by LPS and poly I:C. Of note, zVAD-induced enhancement of the IRF3/IFN/STAT1 axis was abolished by necrostatin-1, while zVAD-induced inhibition of ERK and Akt was not. Our data further support the involvement of autocrine IFNs action in reactive oxygen species (ROS)-dependent necroptosis, LPS/zVAD-elicited ROS production was inhibited by necrostatin-1, neutralizing antibody of IFN receptor (IFNR) and JAK inhibitor AZD1480. Accordingly, both cell death and ROS production induced by TLR ligands plus zVAD were abrogated in STAT1 knockout macrophages. We conclude that enhanced TRIF-RIP1-dependent autocrine action of IFNβ, rather than inhibition of ERK or Akt, is involved in TLRs/zVAD-induced autophagic and necroptotic cell death via the JAK/STAT1/ROS pathway.

Prognostic Implications of an Autophagy-related Gene Signature in Pancreatic Ductal Adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is difficult to diagnose and resistant to therapy and has a poor prognosis. Autophagy plays a vital role in PDAC development and progression. This study aimed to establish an autophagy-related gene (ARG) signature to predict the prognosis of patients with PDAC.

MATERIALS AND METHODS

The expression profiles of PDAC and healthy pancreatic tissues were obtained from The Cancer Genome of Atlas (TCGA) and GTEx (Genotype-Tissue Expression) databases, respectively. Univariate and multivariate Cox regression analyses were performed on differentially expressed ARGs to identify the optimal prognosis-related genes.

RESULTS

A total of 73 ARGs demonstrated significant differences in expression levels between PDAC and healthy pancreatic tissues. Several pathways that play crucial roles in biological processes were identified via enrichment analyses. Furthermore, an ARG signature was established based on overall survival-related ARGs (CASP4, BAK1, PIK3R4, CASP8, BIRC5, RPTOR, and CAPN1) using least absolute shrinkage and selection operator (LASSO) regression. Cox regression analysis confirmed that the 7-gene signature was an independent prognostic factor for patients with PDAC (P<0.001). In addition, the GSE21501 and GSE28735 datasets were used to validate the predictive value of the prognostic model for PDAC. We also constructed a clinical nomogram with a concordance index of 0.712 to predict the overall survival of patients by integrating clinical characteristics and the ARG signature. Calibration curves substantiated fine concordance between nomogram prediction and actual observation.

CONCLUSION

We constructed a new ARG-related prognostic model, which can be a prognostic biomarker and offers insights into identifying potential therapeutic targets for PDAC.

Shikonin Inhibits Cell Growth of Sunitinib-Resistant Renal Cell Carcinoma by Activating the Necrosome Complex and Inhibiting the AKT/mTOR Signaling Pathway

Therapy resistance remains a major challenge in treating advanced renal cell carcinoma (RCC), making more effective treatment strategies crucial. Shikonin (SHI) from traditional Chinese medicine has exhibited antitumor properties in several tumor entities. We, therefore, currently investigated SHI's impact on progressive growth and metastatic behavior in therapy-sensitive (parental) and therapy-resistant Caki-1, 786-O, KTCTL-26, and A498 RCC cells. Tumor cell growth, proliferation, clonogenic capacity, cell cycle phase distribution, induction of cell death (apoptosis and necroptosis), and the expression and activity of regulating and signaling proteins were evaluated. Moreover, the adhesion and chemotactic activity of the RCC cells after exposure to SHI were investigated. SHI significantly inhibited the growth, proliferation, and clone formation in parental and sunitinib-resistant RCC cells by G2/M phase arrest through down-regulation of cell cycle activating proteins. Furthermore, SHI induced apoptosis and necroptosis by activating necrosome complex proteins. Concomitantly, SHI impaired the AKT/mTOR pathway. Adhesion and motility were cell line specifically affected by SHI. Thus, SHI may hold promise as an additive option in treating patients with advanced and therapy-resistant RCC.

The mechanism of HMGB1 secretion and release

High mobility group box 1 (HMGB1) is a nonhistone nuclear protein that has multiple functions according to its subcellular location. In the nucleus, HMGB1 is a DNA chaperone that maintains the structure and function of chromosomes. In the cytoplasm, HMGB1 can promote autophagy by binding to BECN1 protein. After its active secretion or passive release, extracellular HMGB1 usually acts as a damage-associated molecular pattern (DAMP) molecule, regulating inflammation and immune responses through different receptors or direct uptake. The secretion and release of HMGB1 is fine-tuned by a variety of factors, including its posttranslational modification (e.g., acetylation, ADP-ribosylation, phosphorylation, and methylation) and the molecular machinery of cell death (e.g., apoptosis, pyroptosis, necroptosis, alkaliptosis, and ferroptosis). In this minireview, we introduce the basic structure and function of HMGB1 and focus on the regulatory mechanism of HMGB1 secretion and release. Understanding these topics may help us develop new HMGB1-targeted drugs for various conditions, especially inflammatory diseases and tissue damage.

A nuclear protein that gets released after cell death or is actively secreted by immune cells offers a promising therapeutic target for treating diseases linked to excessive inflammation. Daolin Tang from the University of Texas Southwestern Medical Center in Dallas, USA, and colleagues review how cellular stresses can trigger the accumulation of HMGB1, a type of alarm signal protein that promotes the recruitment and activation of inflammation-promoting immune cells. The researchers discuss various mechanisms that drive both passive and active release of HMGB1 into the space around cells. These processes, which include enzymatic modifications of the HMGB1 protein, cell–cell interactions and molecular pathways of cell death, could be targeted by drugs to lessen tissue damage and inflammatory disease caused by HMGB1-induced immune responses

Focus on the Mechanisms and Functions of Pyroptosis, Inflammasomes, and Inflammatory Caspases in Infectious Diseases

Eukaryotic cells can initiate several distinct self-destruction mechanisms to display essential roles for the homeostasis maintenance, development, and survival of an organism. Pyroptosis, a key response mode in innate immunity, also referred to as caspase-1-dependent proinflammatory programmed necrotic cell death activated by human caspase-1/4/5, or mouse caspase-1/11, plays indispensable roles in response to cytoplasmic insults and immune defense against infectious diseases. These inflammatory caspases are employed by the host to eliminate pathogen infections such as bacteria, viruses, protozoans, and fungi. Gasdermin D requires to be cleaved and activated by these inflammatory caspases to trigger the pyroptosis process. Physiological rupture of cells results in the release of proinflammatory cytokines, the alarmins IL-1β and IL-18, symbolizing the inflammatory potential of pyroptosis. Moreover, long noncoding RNAs play direct or indirect roles in the upstream of the pyroptosis trigger pathway. Here, we review in detail recently acquired insights into the central roles of inflammatory caspases, inflammasomes, and pyroptosis, as well as the crosstalk between pyroptosis and long noncoding RNAs in mediating infection immunity and pathogen clearance.

PROGNOSTIC POTENTIAL OF LYMPHOCYTE-TO-MONOCYTE RATIO AND CASPASE-8 IN PREDICTION OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE DEVELOPMENT

OBJECTIVE

The aim: To investigate the prognostic potential of lymphocyte-to-monocyte ratio and caspase-8 levels in prognosis of COPD development in healthy individuals.

PATIENTS AND METHODS

Materials and methods: 77 individuals were involved into the study: 47 with COPD and 30 healthy volunteers. Patients underwent examination according to GOLD 2022 Guidelines. Caspase-8 serum levels were measured by ELISA. Lymphocyte-to-monocyte ratio was calculated.

RESULTS

Results: In crude and adjusted models lymphocyte-to-monocyte ratio and caspase-8 were associated with COPD development (respectively OR = 0.371 [95.0 % CI 0.217-0.634], p<0.006 and OR = 12.823 [95.0 % CI 2.104-78.134], p = 0.006). Additionally, systolic blood pressure had direct association with COPD (OR = 1.196 [95.0 % CI 1.028-1.391], p = 0.021). Noteworthy, diastolic blood pressure showed significant reverse association in univariate but not in multivariate analysis: OR = 0.850 [95.0 % CI 0.743-0.974] (p = 0.019) and OR = 0.820 [95.0 % CI 0.665-1.012] (p =0.064).

CONCLUSION

Conclusions: Decreased lymphocyte-to-monocyte ratio and increased caspase-8 levels are important predictors of COPD development and can serve as an additional tool for early diagnosis of COPD in healthy individuals.

Pyroptosis and inflammasomes in diabetic wound healing

Diabetic wound is one of the complications of diabetes and is not easy to heal. It often evolves into chronic ulcers, and severe patients will face amputation. Compared with normal wounds, diabetic wounds have an increased proportion of pro-inflammatory cytokines that are detrimental to the normal healing response. The burden of this disease on patients and healthcare providers is overwhelming, and practical solutions for managing and treating diabetic wounds are urgently needed. Pyroptosis, an inflammatory type of programmed cell death, is usually triggered by the inflammasome. The pyroptosis-driven cell death process is primarily mediated by the traditional signaling pathway caused by caspase -1 and the non-classical signaling pathways induced by caspase -4/5/11. Growing evidence that pyroptosis promotes diabetic complications, including diabetic wounds. In addition, inflammation is thought to be detrimental to wound healing. It is worth noting that the activation of the NLRP3 inflammasome plays a crucial role in the recovery of diabetic wounds. This review has described the mechanisms of pyroptosis-related signaling pathways and their impact on diabetic wounds. It has discussed new theories and approaches to promote diabetic wound healing, as well as some potential compounds targeting pyroptosis and inflammasome signaling pathways that could be new approaches to treating diabetic wounds.

The non-apoptotic function of Caspase-8 in negatively regulating the CDK9-mediated Ser2 phosphorylation of RNA polymerase II in cervical cancer

Cervical cancer is the fourth most frequently diagnosed and fatal gynecological cancer. 15-61% of all cases metastasize and develop chemoresistance, reducing the 5-year survival of cervical cancer patients to as low as 17%. Therefore, unraveling the mechanisms contributing to metastasis is critical in developing better-targeted therapies against it. Here, we have identified a novel mechanism where nuclear Caspase-8 directly interacts with and inhibits the activity of CDK9, thereby modulating RNAPII-mediated global transcription, including those of cell-migration- and cell-invasion-associated genes. Crucially, low Caspase-8 expression in cervical cancer patients leads to poor prognosis, higher CDK9 phosphorylation at Thr186, and increased RNAPII activity in cervical cancer cell lines and patient biopsies. Caspase-8 knock-out cells were also more resistant to the small-molecule CDK9 inhibitor BAY1251152 in both 2D- and 3D-culture conditions. Combining BAY1251152 with Cisplatin synergistically overcame chemoresistance of Caspase-8-deficient cervical cancer cells. Therefore, Caspase-8 expression could be a marker in chemoresistant cervical tumors, suggesting CDK9 inhibitor treatment for their sensitization to Cisplatin-based chemotherapy.

miR-210 Regulates Apoptotic Cell Death during Cellular Hypoxia and Reoxygenation in a Diametrically Opposite Manner

Apoptotic cell death of cardiomyocytes is a characteristic hallmark of ischemia-reperfusion (I/R) injury. The master hypoxamiR, microRNA-210 (miR-210), is considered the primary driver of the cellular response to hypoxic stress. However, to date, no consensus has emerged with regards to the polarity of the miR-210-elicited cellular response, as miR-210 has been shown to exacerbate as well as attenuate hypoxia-driven apoptotic cell death. Herein, in AC-16 cardiomyocytes subjected to hypoxia-reoxygenation (H-R) stress, we unravel novel facets of miR-210 biology and resolve the biological response mediated by miR-210 into the hypoxia and reoxygenation temporal components. Using transient overexpression and decoy/inhibition vectors to modulate miR-210 expression, we elucidated a Janus role miR-210 in the cellular response to H-R stress, wherein miR-210 mitigated the hypoxia-induced apoptotic cell death but exacerbated apoptotic cell death during cellular reoxygenation. We further delineated the underlying cellular mechanisms that confer this diametrically opposite effect of miR-210 on apoptotic cell death. Our exhaustive biochemical assays cogently demonstrate that miR-210 attenuates the hypoxia-driven intrinsic apoptosis pathway, while significantly augmenting the reoxygenation-induced caspase-8-mediated extrinsic apoptosis pathway. Our study is the first to unveil this Janus role of miR-210 and to substantiate the cellular mechanisms that underlie this functional duality.

Differences of Key Proteins between Apoptosis and Necroptosis

Many different types of programmed cell death (PCD) have been identified, including apoptosis and necroptosis. Apoptosis is a type of cell death that is controlled by various genes. It is in charge of eliminating aberrant cells such as cancer cells, replenishing normal cells, and molding the body as it develops. Necroptosis is a type of programmed cell death that combines necrosis and apoptosis. In other words, it takes on a necrotic appearance, although cells die in a controlled manner. Various investigations of these two pathways have revealed that caspase-8, receptor-interacting serine/threonine-protein kinase 1 (RIPK1), and RIPK3 are crucial proteins in charge of the switching between these two pathways, resulting in the activation or inhibition of necroptosis. In this review, we have summarized the key proteins between apoptosis and necroptosis.

Inhibition of PLA2G4E/cPLA2 promotes survival of random skin flaps by alleviating Lysosomal membrane permeabilization-Induced necroptosis

Necrosis that appears at the ischemic distal end of random-pattern skin flaps increases the pain and economic burden of patients. Necroptosis is thought to contribute to flap necrosis. Lysosomal membrane permeabilization (LMP) plays an indispensable role in the regulation of necroptosis. Nonetheless, the mechanisms by which lysosomal membranes become leaky and the relationship between necroptosis and lysosomes are still unclear in ischemic flaps. Based on Western blotting, immunofluorescence, enzyme-linked immunosorbent assay, and liquid chromatography-mass spectrometry (LC-MS) analysis results, we found that LMP was presented in the ischemic distal portion of random-pattern skin flaps, which leads to disruption of lysosomal function and macroautophagic/autophagic flux, increased necroptosis, and aggravated necrosis of the ischemic flaps. Moreover, bioinformatics analysis of the LC-MS results enabled us to focus on the role of PLA2G4E/cPLA2 (phospholipase A2, group IVE) in LMP of the ischemic flaps. In vivo inhibition of PLA2G4E with an adeno-associated virus vector attenuated LMP and necroptosis, and promoted flap survival. In addition, microRNA-seq helped us determine that Mir504-5p was differentially expressed in ischemic flaps. A string of in vitro and in vivo tests was employed to verify the inhibitory effect of Mir504-5p on PLA2G4E, LMP and necroptosis. Finally, we concluded that the inhibition of PLA2G4E by Mir504-5p reduced LMP-induced necroptosis, thereby promoting the survival of random-pattern skin flaps.

Review of cancer cell resistance mechanisms to apoptosis and actual targeted therapies

The apoptosis pathway is a programmed cell death mechanism that is crucial for cellular and tissue homeostasis and organ development. There are three major caspase-dependent pathways of apoptosis that ultimately lead to DNA fragmentation. Cancerous cells are known to highly regulate the apoptotic pathway and its role in cancer hallmark acquisition has been discussed over the past decades. Numerous mutations in cancer cell types have been reported to be implicated in chemoresistance and treatment outcome. In this review, we summarize the mutations of the caspase-dependant apoptotic pathways that are the source of cancer development and the targeted therapies currently available or in trial.

ROS/JNK/C-Jun Pathway is Involved in Chaetocin Induced Colorectal Cancer Cells Apoptosis and Macrophage Phagocytosis Enhancement

There is an urgent need for novel agents for colorectal cancer (CRC) due to the increasing number of cases and drug-resistance related to current treatments. In this study, we aim to uncover the potential of chaetocin, a natural product, as a chemotherapeutic for CRC treatment. We showed that, regardless of 5-FU-resistance, chaetocin induced proliferation inhibition by causing G2/M phase arrest and caspase-dependent apoptosis in CRC cells. Mechanically, our results indicated that chaetocin could induce reactive oxygen species (ROS) accumulation and activate c-Jun N-terminal kinase (JNK)/c-Jun pathway in CRC cells. This was confirmed by which the JNK inhibitor SP600125 partially rescued CRC cells from chaetocin induced apoptosis and the ROS scavenger N-acetyl-L-cysteine (NAC) reversed both the chaetocin induced apoptosis and the JNK/c-Jun pathway activation. Additionally, this study indicated that chaetocin could down-regulate the expression of CD47 at both mRNA and protein levels, and enhance macrophages phagocytosis of CRC cells. Chaetocin also inhibited tumor growth in CRC xenograft models. In all, our study reveals that chaetocin induces CRC cell apoptosis, irrelevant to 5-FU sensitivity, by causing ROS accumulation and activating JNK/c-Jun, and enhances macrophages phagocytosis, which suggests chaetocin as a candidate for CRC chemotherapy.

3-Bromofluoranthene-induced cardiotoxicity of zebrafish and apoptosis in the vascular endothelial cells via intrinsic and extrinsic caspase-dependent pathways

Fluoranthene, a high-molecular-weight polycyclic aromatic hydrocarbon (PAH), is widely present in air pollutants, including fine inhalable particulate matter. 3-Bromofluoranthene (3-BrFlu), which is a brominated fluoranthene and halogenated PAH, is generated from waste combustion, metallurgical processes, cement production, e-waste dismantling, and photoreaction. Vascular endothelial cells have key functions in the homeostasis and the development of the cardiovascular system. The zebrafish model has been widely employed to study cardiotoxicity and embryotoxicity. However, no evidence has indicated that 3-BrFlu induces cytotoxicity in vascular endothelial cells, or cardiotoxicity and embryotoxicity in zebrafish. In this study, 3-BrFlu induced concentration-dependent changes in embryo- and cardiotoxicity. Cytotoxicity was also induced by 3-BrFlu in a concentration-dependent manner through apoptosis and necrosis in vascular endothelial cells, SVEC4-10 cells. The activities of caspase-3, -8, and -9 were induced by 3-BrFlu via an intrinsic pathway constituting Bcl-2 downregulation, Bad upregulation, and mitochondrial dysfunction; the extrinsic pathway included the expression of death receptors, including tumour necrosis factor α and Fas receptors. These results indicated that 3-BrFlu caused cardio- and embryotoxicity in zebrafish through vascular endothelial cells cytotoxicity resulting from caspase-dependent apoptosis through intrinsic and extrinsic pathways.

Nfe2l1 deficiency mitigates streptozotocin-induced pancreatic β-cell destruction and development of diabetes in male mice

Streptozotocin (STZ) is a pancreatic β cell-specific toxicant that is widely used to generate models of diabetes in rodents as well as in the treatment of tumors derived from pancreatic β cells. DNA alkylation, oxidative stress and mitochondrial toxicity have been recognized as the mechanisms for STZ-induced pancreatic β cell damage. Here, we found that pancreatic β cell-specific deficiency of nuclear factor erythroid-derived factor 2-related factor 1 (NFE2L1), a master regulator of the cellular adaptive response to a variety of stresses, in mice led to a dramatic resistance to STZ-induced hyperglycemia. Indeed, fifteen days subsequent to last dosage of STZ, the pancreatic β cell specific Nfe2l1 knockout [Nfe2l1(β)-KO] mice showed reduced hyperglycemia, improved glucose tolerance, higher plasma insulin and more intact islets surrounded by exocrine acini compared to the Nfe2l1-Flox control mice with the same treatment. Immunohistochemistry staining revealed a greater amount of insulin-positive cells in the pancreas of Nfe2l1(β)-KO mice than those in Nfe2l1-Flox mice 15 days after the last STZ injection. In line with this observation, both isolated Nfe2l1(β)-KO islets and Nfe2l1-deficient MIN6 (Nfe2l1-KD) cells were resistant to STZ-induced toxicity and apoptosis. Furthermore, pretreatment of the MIN6 cells with glycolysis inhibitor 2-Deoxyglucose sensitized Nfe2l1-KD cells to STZ-induced toxicity. These findings demonstrated that loss of Nfe2l1 attenuates pancreatic β cells damage and dysfunction caused by STZ exposure, partially due to Nfe2l1 deficiency-induced metabolic switch to enhanced glycolysis.

Antileukemic Natural Product Induced Both Apoptotic and Pyroptotic Programmed Cell Death and Differentiation Effect

Acute myeloid leukemia (AML) is one of the most common forms of leukemia. Despite advances in the management of such malignancies and the progress of novel therapies, unmet medical needs still exist in AML because of several factors, including poor response to chemotherapy and high relapse rates. Ardisianone, a plant-derived natural component with an alkyl benzoquinone structure, induced apoptosis in leukemic HL-60 cells. The determination of dozens of apoptosis-related proteins showed that ardisianone upregulated death receptors and downregulated the inhibitor of apoptosis protein (IAPs). Western blotting showed that ardisianone induced a dramatic increase in tumor necrosis factor receptor 2 (TNFR2) protein expression. Ardisianone also induced downstream signaling by activating caspase-8 and -3 and degradation in Bid, a caspase-8 substrate. Furthermore, ardisianone induced degradation in DNA fragmentation factor 45 kDa (DFF45), a subunit of inhibitors of caspase-activated DNase (ICAD). Q-VD-OPh (a broad-spectrum caspase inhibitor) significantly diminished ardisianone-induced apoptosis, confirming the involvement of caspase-dependent apoptosis. Moreover, ardisianone induced pyroptosis. Using transmission electron microscopic examination and Western blot analysis, key markers including gasdermin D, high mobility group box1 (HMGB1), and caspase-1 and -5 were detected. Notably, ardisianone induced the differentiation of the remaining survival cells, which were characterized by an increase in the expression of CD11b and CD68, two markers of macrophages and monocytes. Wright–Giemsa staining also showed the differentiation of cells into monocyte and macrophage morphology. In conclusion, the data suggested that ardisianone induced the apoptosis and pyroptosis of leukemic cells through downregulation of IAPs and activation of caspase pathways that caused gasdermin D cleavage and DNA double-stranded breaks and ultimately led to programmed cell death. Ardisianone also induced the differentiation of leukemic cells into monocyte-like and macrophage-like cells. The data suggested the potential of ardisianone for further antileukemic development.

GLUT3 as an Intersection of Glycerophospholipid Metabolism and the Innate Immune Response to Candida albicans

Immune cells can optimize the management of metabolic resources to balance their energy requirements in order to regulate immune responses. The interconnection between immunometabolism and fungal infections is becoming increasingly apparent. Using proteome and metabolome assays, we found that stimulation of primary human monocytes by Candida albicans was accompanied by upregulation of glucose transporter 3 (GLUT3) and activation of the glycerophospholipid metabolism pathway. Upregulated GLUT3 expression has been preliminarily confirmed in monocytes from patients with C. albicans bloodstream infection. Our findings support the importance of GLUT3 in the complex network of glycerophospholipid metabolism and the innate immune responses against C. albicans. In summary, this study might contribute to decipher the regulatory mechanism between the monocyte metabolic reprogramming and innate immune response and reveal potential targets for the antifungal treatments.

Synthesis and antitumor potential of new arylidene ursolic acid derivatives via caspase-8 activation

Continuing our studies on NO-donating ursolic acid-benzylidene derivatives as potential antitumor agents, we designed and synthesized a series of new arylidene derivatives containing NO-donating ursolic acid and aromatic heterocyclic units. Compounds 5c and 6c showed a significant broad-spectrum antitumor activity. Compound 5c exhibited nearly three- to nine-fold higher cytotoxicity as compared with the parent drug in A549, MCF-7, HepG-2, HT-29, and HeLa cells, and it was also found to be the most potent apoptosis inducer of MCF-7 cells. More importantly, compound 5c arrested the MCF-7 cell cycle in the G1 phase, which was associated with caspase activation and a decrease of the Bcl-2/Bax ratio. Meanwhile, compound 5c caused changes in morphological features, dissipation of the mitochondrial membrane potential, and accumulation of reactive oxygen species. A docking study revealed that the nitroxyethyl moiety of compound 5c may form hydrogen bonds with caspase-8 amino acid residues (SER256 and HIS255). Together, these data suggest that NO-donating ursolic acid-arylidene derivatives are potent apoptosis inducers in tumor cells.

Endoplasmic reticulum stress, chondrocyte apoptosis and oxidative stress in cartilage of broilers affected by spontaneous femoral head necrosis

With the promotion of the intensive breeding model, the incidence of leg diseases has risen in fast-growing commercial broilers with higher body weight, seriously affecting their feed efficiency and causing animal welfare problems. Femoral head necrosis (FHN) is the most common leg disease in broilers. Previous studies reported that hormone-induced FHN is related to endoplasmic reticulum (ER) stress, apoptosis, and oxidative stress, but no detailed study has been conducted in broilers with spontaneous FHN. In the study, the articular cartilage of 5-wk-old Ross 308 broilers with spontaneous FHN was used to investigate the pathogenesis of the disease. According to the degree of femoral head injury, the birds participating in the experiment were divided into 3 groups, namely a control group, femoral head separation group and femoral head separation with growth plate lacerations group. The morphological changes in articular cartilage were observed by hematoxylin and eosin, toluidine blue, alcian blue and safranine O-solid green staining, and the expressions of genes related to cartilage homeostasis, ER stress, autophagy, apoptosis and oxidative stress was detected using Real-Time Quantitative PCR. In the results, the expression of aggrecan and collagen-2 mRNA levels decreased in the articular cartilage of spontaneous FHN broilers, and the same changes were observed in the tissue staining results, indicating the disordered nature of articular cartilage homeostasis. At the same time, FHN in broilers causes ER stress in articular chondrocytes and regulates oxidative stress by activating the nuclear factor erythroid 2-related factor 2/antioxidant response element pathway through protein kinase RNA-like ER kinase. Autophagy can be activated through the protein kinase RNA-like ER kinase-activating transcription factor-4 pathway, and apoptosis can even be activated through CCAAT-enhancer-binding protein homologous protein. Therefore, the secretory activity of articular chondrocytes in spontaneous FHN broilers is negatively affected, which leads to the disorder of cartilage homeostasis and results in FHN due to ER-stress-mediated chondrocyte apoptosis and oxidative stress.

Targeting CDK9 for Anti-Cancer Therapeutics

Cyclin Dependent Kinase 9 (CDK9) is one of the most important transcription regulatory members of the CDK family. In conjunction with its main cyclin partner-Cyclin T1, it forms the Positive Transcription Elongation Factor b (P-TEFb) whose primary function in eukaryotic cells is to mediate the positive transcription elongation of nascent mRNA strands, by phosphorylating the S2 residues of the YSPTSPS tandem repeats at the C-terminus domain (CTD) of RNA Polymerase II (RNAP II). To aid in this process, P-TEFb also simultaneously phosphorylates and inactivates a number of negative transcription regulators like 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) Sensitivity-Inducing Factor (DSIF) and Negative Elongation Factor (NELF). Significantly enhanced activity of CDK9 is observed in multiple cancer types, which is universally associated with significantly shortened Overall Survival (OS) of the patients. In these cancer types, CDK9 regulates a plethora of cellular functions including proliferation, survival, cell cycle regulation, DNA damage repair and metastasis. Due to the extremely critical role of CDK9 in cancer cells, inhibiting its functions has been the subject of intense research, resulting the development of multiple, increasingly specific small-molecule inhibitors, some of which are presently in clinical trials. The search for newer generation CDK9 inhibitors with higher specificity and lower potential toxicities and suitable combination therapies continues. In fact, the Phase I clinical trials of the latest, highly specific CDK9 inhibitor BAY1251152, against different solid tumors have shown good anti-tumor and on-target activities and pharmacokinetics, combined with manageable safety profile while the phase I and II clinical trials of another inhibitor AT-7519 have been undertaken or are undergoing. To enhance the effectiveness and target diversity and reduce potential drug-resistance, the future of CDK9 inhibition would likely involve combining CDK9 inhibitors with inhibitors like those against BRD4, SEC, MYC, MCL-1 and HSP90.