Necroptosis directly induces the release of full-length biologically active IL-33 in vitro and in an inflammatory disease model

PANoptosis opens new treatment options for allergic bronchopulmonary aspergillosis

Background

Allergic bronchopulmonary aspergillosis (ABPA) is a rare airway disorder primarily affecting patients with asthma and cystic fibrosis. Persistent airway inflammation brought on by Aspergillus fumigatus exacerbates the underlying condition and can cause significant respiratory damage. Treatments center on reducing inflammation with the use of corticosteroids and antifungals. PANoptosis is a new concept in the field of cell death and inflammation that posits the existence of cross talk and a master control system for the 3 programmed cell death (PCD) pathways, namely, apoptosis, pyroptosis, and necroptosis. This concept has revolutionized the understanding of PCD and opened new avenues for its exploration. Studies show that Aspergillus is one of the pathogens that is capable of activating PANoptosis via the Z-DNA binding protein 1 (ZBP1) pathway and plays an active role in the inflammation caused by this organism.

Objective

This article explores the nature of inflammation in ABPA and ways in which PCD could lead to novel treatment options.

Method

PubMed was used to review the literature surrounding Aspergillus infection-related inflammation and PANoptosis.

Results

There is evidence that apoptosis and pyroptosis protect against Aspergillus-induced inflammation, whereas necroptosis promotes inflammation.

Conclusion

Experimental medications, in particular, necroptosis inhibitors such as necrosulfonamide and necrostatin-1, should be studied for use in the treatment of ABPA.

Screening, identification and targeted intervention of necroptotic biomarkers of asthma

BACKGROUND

As a pivotal pathway of programmed cell death, necroptosis significantly contributes to the pathogenesis of respiratory disorders. However, its role in asthma is not yet fully elucidated. Therefore, this study aimed to identify markers associated with necroptosis, evaluate their functions in asthma, and explore potential therapeutic agents targeting necroptosis for the management of asthma.

METHODS

Firstly, machine learning algorithms, including Least Absolute Shrinkage and Selection Operator (LASSO), Random Forest, and Support Vector Machine-Recursive Feature Elimination (SVM-RFE), were utilized to identify necroptosis-related differentially expressed genes (NRDEGs) in asthma patients compared to healthy controls. Concurrently, the expression of NRDEGs was validated using external datasets, Western blot, and quantitative real-time polymerase chain reaction (qPCR). Secondly, the clinical relevance of NRDEGs was assessed through Receiver Operating Characteristic (ROC) curve analysis and correlation with clinical indicators. Thirdly, the relationship between NRDEGs and pulmonary immune cell infiltration, as well as the signaling interactions between different cells types, were analyzed through immune infiltration and single-cell analysis. Fourthly, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA), were conducted to elucidate the functional roles of NRDEGs. Finally, compounds targeting NRDEGs were screened, and their binding affinities were evaluated using molecular docking studies.

RESULTS

In asthma, necroptosis is activated, leading to the identification of four NRDEGs: NLRP3, PYCARD, ALOX15, and VDAC3. Among these, NLRP3, PYCARD, and ALOX15 are upregulated, whereas VDAC3 is downregulated in asthma. Comprehensive clinical evaluations indicated that NRDEGs hold diagnostic value for asthma. Specifically, NLRP3 was inversely correlated with forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC), while VDAC3 showed an inverse correlation with sputum neutrophils. Conversely, ALOX15 expression was positively correlated with fractional exhaled nitric oxide (FeNO) levels, as well as sputum eosinophils, blood eosinophils, and blood IgE levels. Subsequent immune infiltration analysis revealed associations between NRDEGs and activated dendritic cells, mast cells, and eosinophils. Single-cell RNA sequencing (scRNA-seq) further confirmed the communication signals between myeloid dendritic cells, fibroblasts, neutrophils, and helper T cells, predominantly related to fibrosis and immune-inflammatory responses. Pathway enrichment analysis demonstrated that NRDEGs are involved in ribosomal function, oxidative phosphorylation, and fatty acid metabolism. Finally, resveratrol and triptonide were identified as potential therapeutic agents targeting the proteins encoded by NRDEGs for asthma treatment.

CONCLUSIONS

The necroptosis pathway is activated in asthma, with NRDEGs-namely PYCARD, NLRP3, ALOX15, and VDAC3-correlated with declines in lung function and airway inflammation. These genes serve as reliable predictors of asthma risk and are involved in the regulation of the immune-inflammatory microenvironment. Resveratrol and triptolide have been identified as promising therapeutic candidates due to their potential to target the proteins encoded by these genes.

Targeting necroptosis: a promising avenue for respiratory disease treatment

Respiratory diseases are a growing concern in public health because of their potential to endanger the global community. Cell death contributes critically to the pathophysiology of respiratory diseases. Recent evidence indicates that necroptosis, a unique form of programmed cell death (PCD), plays a vital role in the molecular mechanisms underlying respiratory diseases, distinguishing it from apoptosis and conventional necrosis. Necroptosis is a type of inflammatory cell death governed by receptor-interacting serine/threonine protein kinase 1 (RIPK1), RIPK3, and mixed-lineage kinase domain-like protein (MLKL), resulting in the release of intracellular contents and inflammatory factors capable of initiating an inflammatory response in adjacent tissues. These necroinflammatory conditions can result in significant organ dysfunction and long-lasting tissue damage within the lungs. Despite evidence linking necroptosis to various respiratory diseases, there are currently no specific alternative treatments that target this mechanism. This review provides a comprehensive overview of the most recent advancements in understanding the significance and mechanisms of necroptosis. Specifically, this review emphasizes the intricate association between necroptosis and respiratory diseases, highlighting the potential use of necroptosis as an innovative therapeutic approach for treating these conditions.

Necroptosis plays a role in TL1A-induced airway inflammation and barrier damage in asthma

BACKGROUND

Airway epithelial cell (AEC) necroptosis contributes to airway allergic inflammation and asthma exacerbation. Targeting the tumor necrosis factor-like ligand 1 A (TL1A)/death receptor 3 (DR3) axis has a therapeutic effect on asthmatic airway inflammation. The role of TL1A in mediating necroptosis of AECs challenged with ovalbumin (OVA) and its contribution to airway inflammation remains unclear.

METHODS

We evaluated the expression of the receptor-interacting serine/threonine-protein kinase 3(RIPK3) and the mixed lineage kinase domain-like protein (MLKL) in human serum and lung, and histologically verified the level of MLKL phosphorylation in lung tissue from asthmatics and OVA-induced mice. Next, using MLKL knockout mice and the RIPK3 inhibitor GSK872, we investigated the effects of TL1A on airway inflammation and airway barrier function through the activation of necroptosis in experimental asthma.

RESULTS

High expression of necroptosis marker proteins was observed in the serum of asthmatics, and necroptosis was activated in the airway epithelium of both asthmatics and OVA-induced mice. Blocking necroptosis through MLKL knockout or RIPK3 inhibition effectively attenuated parabronchial inflammation, mucus hypersecretion, and airway collagen fiber accumulation, while also suppressing type 2 inflammatory factors secretion. In addition, TL1A/ DR3 was shown to act as a death trigger for necroptosis in the absence of caspases by silencing or overexpressing TL1A in HBE cells. Furthermore, the recombinant TL1A protein was found to induce necroptosis in vivo, and knockout of MLKL partially reversed the pathological changes induced by TL1A. The necroptosis induced by TL1A disrupted the airway barrier function by decreasing the expression of tight junction proteins zonula occludens-1 (ZO-1) and occludin, possibly through the activation of the NF-κB signaling pathway.

CONCLUSIONS

TL1A-induced airway epithelial necroptosis plays a significant role in promoting airway inflammation and barrier dysfunction in asthma. Inhibition of the TL1A-induced necroptosis pathway could be a promising therapeutic strategy.

Circulating Markers of Necroptosis in Acute Pancreatitis

OBJECTIVES

Necroptosis, a programmed inflammatory cell death, is involved in the pathogenesis of acute pancreatitis (AP). We compared levels of interleukin (IL)-33 (released upon necroptosis), sST2 (soluble IL-33 receptor), MLKL, RIPK1 and RIPK3 (necroptosis executioner proteins), and proinflammatory cytokines IL-6, TNF and IL-1β at various severity categories and stages of AP.

METHODS

Plasma from 20 patients with early mild AP (MAP) (symptom onset < 72 h), 7 with severe AP (SAP) without and 4 with persistent organ failure (OF) at sampling, 8 patients with late SAP and 20 healthy controls (HC) were studied by ELISAs.

RESULTS

Early sST2 and IL-6 levels predicted the development of SAP and were higher in both MAP and early and late SAP than in HC. RIPK3 levels were higher than in HC in the patients who had or would later have SAP. MLKL levels were associated with the presence of OFs, particularly in the late phase, but were also higher in MAP than in HC.

CONCLUSIONS

sST2, RIPK3 and IL-6 levels may have prognostic value in AP. Elevated MLKL levels are associated with OF in AP. Better understanding of necroptosis in AP pathophysiology is needed to evaluate whether inhibiting and targeting necroptosis is a potential therapeutic option in AP.

Electroacupuncture Inhibits Neuroinflammation Induced by Astrocytic Necroptosis Through RIP1/MLKL/TLR4 Pathway in a Mouse Model of Spinal Cord Injury

Astrocytic necroptosis plays an essential role in the progression and regression of neurological disorders, which contributes to the neuroinflammation and disrupts neuronal regeneration and remyelination of severed axons. Electroacupuncture (EA), an effective therapeutic efficacy against spinal cord injury (SCI), has been proved to reduce neuronal cell apoptosis, inhibit inflammation, and prompt neural stem cell proliferation and differentiations. However, there have been few reports on whether EA regulate astrocytic necroptosis in SCI model. To investigate the effects of EA on astrocytic necroptosis and the mechanisms involved in the inhibition of astrocytic necroptosis after SCI in mice by EA, 8-week-old female C57BL/6 mice were subjected to SCI surgery and randomly divided into EA and SCI groups. Mice receiving sham surgery were included as sham group. "Jiaji" was selected as points for EA treatment, 10 min/day for 14 days. The in vitro data revealed that EA treatment significantly improved the nervous function and pathological changes after SCI. EA also reduced the number of GFAP/P-MLKL, GFAP/MLKL, GFAP/HMGB1, and Iba1/HMGB1 co-positive cells and inhibited the expressions of IL-6, IL-1β, and IL-33. The results indicate a significant reduction in inflammatory reaction and astrocytic necroptosis in mice with SCI by EA. Additionally, the expressions of RIP1, MLKL, and TLR4, which are associated with necroptosis, were found to be downregulated by EA. In this study, we confirmed that EA can inhibit neuroinflammation by reducing astrocytic necroptosis through downregulation of RIP1/MLKL/TLR4 pathway in mice with SCI.

Construction and validation of a necroptosis-related prognostic signature in acute myeloid leukemia

Acute myeloid leukemia (AML), an uncommonly low 5-year survival and high mortality rate, is a potentially catastrophic diagnosed subtype of leukemia. The development of new prognostic markers is urgently needed to guide its treatment. Necroptosis is a newly defined biological process for regulating cell death, and previous studies have confirmed that the abnormality of the physical function can lead to multiple malignancies. Here, we performed necroptosis-related genes (NRGs) to build a predictive model in the Cancer Genome Atlas (TCGA)-AML patients, thus exploring the correlation between the NRG prognosis signature (NRG score) of this model and immune infiltration, pathway activity, clinical features, and immunotherapy. Besides, we computed the statistical measure Spearman rank correlation between the NRG score and the Log IC50 values of therapeutic agents. Subsequently, we divided the TCGA-AML cohort into 2 groups, one with high scores and the other with low scores depending on the model score. AML patients with high NRG scores exhibited a lower estimated overall survival (OS) rate than those with low NRG scores, which was confirmed in the validation set. The prognostic value of the constructed NRG signature to the AML, independent of other variables, was demonstrated by uni- and multivariate stepwise regression analysis. When comparing the infiltrating states of specialized cells associated with immune system from the 2 groups, B cells naive, Plasma cells, and monocytes represented significant differences among various subgroups of samples. Moreover, the 30 hallmark-related pathways related to necroptosis characteristics were remarkably different between the high/low NRG score groups. And patients showed remarkable NRG score distribution in clinical features of bone marrow lymphocyte, category, and FAB classifications. Besides, we found that the BIRB0796, VX680, Vorinostat, and Axitinib positively related with NRG score, whereas CI. 1040, PD. 0325901, Z.L LNle. CHO, and AZD6244 negatively correlated with the NRG score. These drugs may provide a reference for subsequent treatment.

Determining the toxicological effects of indoor air pollution on both a healthy and an inflammatory-comprised model of the alveolar epithelial barrier in vitro

Exposure to indoor air pollutants (IAP) has increased recently, with people spending more time indoors (i.e. homes, offices, schools and transportation). Increased exposures of IAP on a healthy population are poorly understood, and those with allergic respiratory conditions even less so. The objective of this study, therefore, was to implement a well-characterised in vitro model of the human alveolar epithelial barrier (A549 + PMA differentiated THP-1 incubated with and without IL-13, IL-5 and IL-4) to determine the effects of a standardised indoor particulate (NIST 2583) on both a healthy lung model and one modelling a type-II (stimulated with IL-13, IL-5 and IL-4) inflammatory response (such as asthma).Using concentrations from the literature, and an environmentally appropriate exposure we investigated 232, 464 and 608ng/cm2 of NIST 2583 respectively. Membrane integrity (blue dextran), viability (trypan blue), genotoxicity (micronucleus (Mn) assay) and (pro-)/(anti-)inflammatory effects (IL-6, IL-8, IL-33, IL-10) were then assessed 24 h post exposure to both models. Models were exposed using a physiologically relevant aerosolisation method (VitroCell Cloud 12 exposure system).No changes in Mn frequency or membrane integrity in either model were noted when exposed to any of the tested concentrations of NIST 2583. A significant decrease (p < 0.05) in cell viability at the highest concentration was observed in the healthy model. Whilst cell viability in the "inflamed" model was decreased at the lower concentrations (significantly (p < 0.05) after 464ng/cm2). A significant reduction (p < 0.05) in IL-10 and a significant increase in IL-33 was seen after 24 h exposure to NIST 2583 (464, 608ng/cm2) in the "inflamed" model.Collectively, the results indicate the potential for IAP to cause the onset of a type II response as well as exacerbating pre-existing allergic conditions. Furthermore, the data imposes the importance of considering unhealthy individuals when investigating the potential health effects of IAP. It also highlights that even in a healthy population these particles have the potential to induce this type II response and initiate an immune response following exposure to IAP.

Cell type-specific molecular mechanisms and implications of necroptosis in inflammatory respiratory diseases

Necroptosis is generally considered as an inflammatory cell death form. The core regulators of necroptotic signaling are receptor-interacting serine-threonine protein kinases 1 (RIPK1) and RIPK3, and the executioner, mixed lineage kinase domain-like pseudokinase (MLKL). Evidence demonstrates that necroptosis contributes profoundly to inflammatory respiratory diseases that are common public health problem. Necroptosis occurs in nearly all pulmonary cell types in the settings of inflammatory respiratory diseases. The influence of necroptosis on cells varies depending upon the type of cells, tissues, organs, etc., which is an important factor to consider. Thus, in this review, we briefly summarize the current state of knowledge regarding the biology of necroptosis, and focus on the key molecular mechanisms that define the necroptosis status of specific cell types in inflammatory respiratory diseases. We also discuss the clinical potential of small molecular inhibitors of necroptosis in treating inflammatory respiratory diseases, and describe the pathological processes that engage cross talk between necroptosis and other cell death pathways in the context of respiratory inflammation. The rapid advancement of single-cell technologies will help understand the key mechanisms underlying cell type-specific necroptosis that are critical to effectively treat pathogenic lung infections and inflammatory respiratory diseases.

Tollip deficiency exaggerates airway type 2 inflammation in mice exposed to allergen and influenza A virus: role of the ATP/IL-33 signaling axis

Toll-interacting protein (Tollip) is a negative regulator of the pro-inflammatory response to viruses, including influenza A virus (IAV). Genetic variation of Tollip has been associated with reduced airway epithelial Tollip expression and poor lung function in patients with asthma. Whether Tollip deficiency exaggerates type 2 inflammation (e.g., eosinophils) and viral infection in asthma remains unclear. We sought to address this critical, but unanswered question by using a Tollip deficient mouse asthma model with IAV infection. Further, we determined the underlying mechanisms by focusing on the role of the ATP/IL-33 signaling axis. Wild-type and Tollip KO mice were intranasally exposed to house dust mite (HDM) and IAV with or without inhibitors for IL-33 (i.e., soluble ST2, an IL-33 decoy receptor) and ATP signaling (i.e., an antagonist of the ATP receptor P2Y13). Tollip deficiency amplified airway type 2 inflammation (eosinophils, IL-5, IL-13 and mucins), and the release of ATP and IL-33. Blocking ATP receptor P2Y13 decreased IL-33 release during IAV infection in HDM-challenged Tollip KO mice. Furthermore, soluble ST2 attenuated airway eosinophilic inflammation in Tollip KO mice treated with HDM and IAV. HDM challenges decreased lung viral load in wild-type mice, but Tollip deficiency reduced the protective effects of HDM challenges on viral load. Our data suggests that during IAV infection, Tollip deficiency amplified type 2 inflammation and delayed viral clearance, in part by promoting ATP signaling and subsequent IL-33 release. Our findings may provide several therapeutic targets, including ATP and IL-33 signaling inhibition for attenuating excessive airway type 2 inflammation in human subjects with Tollip deficiency and IAV infection.

A novel necroptosis signature for predicting survival in lung adenocarcinoma

BACKGROUND

To explore the necroptosis-related genes (NRGs) signature and its predictive values in lung adenocarcinoma (LUAD).

METHODS

The training cohort consisted of tumor samples from The Cancer Genome Atlas, and the validation set comprised data from the Gene Expression Omnibus. Univariate and multivariate Cox regression analyses were applied to identify the prognostic NRG signature as an independent molecular indicator. Correlation analysis was used for the association assessment between the NRG signature and immune checkpoint molecules.

RESULTS

NRGs involved in necroptosis and immune NOD-like receptor signaling. The NRG signature based on eight NRGs can divide tumors into high-risk and low-risk groups, which was significantly associated with worse survival. Multivariate Cox regression analysis showed that this NRG signature remained an independent prognostic indicator. Stratification analyses demonstrated that this NRG signature was still effective for predicting survival in each stratum of age, gender, and tumor stage. The ROC curve showed a good predictive ability using the NRG signature in the validation cohort (AUC = 0.81). The NRG signature was related to immune checkpoint molecules PD - 1, PD-L1, and PD-L2.

CONCLUSIONS

The NRG signature could be a novel predictor of the prognosis and may become a potential therapeutic target in LUAD.

Dynamics of necroptosis in kidney ischemia-reperfusion injury

Necroptosis, a pathway of regulated necrosis, involves recruitment and activation of RIPK1, RIPK3 and MLKL, leading to cell membrane rupture, cell death and release of intracellular contents causing further injury and inflammation. Necroptosis is believed to play an important role in the pathogenesis of kidney ischemia-reperfusion injury (IRI). However, the dynamics of necroptosis in kidney IRI is poorly understood, in part due to difficulties in detecting phosphorylated MLKL (pMLKL), the executioner of the necroptosis pathway. Here, we investigated the temporal and spatial activation of necroptosis in a mouse model of unilateral warm kidney IRI, using a robust method to stain pMLKL. We identified the period 3-12 hrs after reperfusion as a critical phase for the activation of necroptosis in proximal tubular cells. After 12 hrs, the predominant pattern of pMLKL staining shifted from cytoplasmic to membrane, indicating progression to the terminal phase of necroptotic cell death. Mlkl-ko mice exhibited reduced kidney inflammation at 12 hrs and lower serum creatinine and tubular injury at 24 hrs compared to wild-type littermates. Interestingly, we observed increased apoptosis in the injured kidneys of Mlkl-ko mice, suggesting a relationship between necroptosis and apoptosis in kidney IRI. Together, our findings confirm the role of necroptosis and necroinflammation in kidney IRI, and identify the first 3 hrs following reperfusion as a potential window for targeted treatments.

Non-apoptotic programmed cell deaths in diabetic pulmonary dysfunction: the new side of advanced glycation end products

Diabetes mellitus (DM) is a chronic metabolic disorder that affects multiple organs and systems, including the pulmonary system. Pulmonary dysfunction in DM patients has been observed and studied for years, but the underlying mechanisms have not been fully understood. In addition to traditional mechanisms such as the production and accumulation of advanced glycation end products (AGEs), angiopathy, tissue glycation, oxidative stress, and systemic inflammation, recent studies have focused on programmed cell deaths (PCDs), especially the non-apoptotic ones, in diabetic pulmonary dysfunction. Non-apoptotic PCDs (NAPCDs) including autophagic cell death, necroptosis, pyroptosis, ferroptosis, and copper-induced cell death have been found to have certain correlations with diabetes and relevant complications. The AGE-AGE receptor (RAGE) axis not only plays an important role in the traditional pathogenesis of diabetes lung disease but also plays an important role in non-apoptotic cell death. In this review, we summarize novel studies about the roles of non-apoptotic PCDs in diabetic pulmonary dysfunction and focus on their interactions with the AGE-RAGE axis.

Unpacking the complexity of nuclear IL-33 (nIL-33): a crucial regulator of transcription and signal transduction

Interleukin-33 (IL-33) (NF-HEV), a chromatin-associated nuclear cytokine, is a member of the IL-1 family. IL-33 possesses a nuclear localization signal and a homeodomain (a structure resembling a helix-turn-helix) that can bind to nuclear chromatin. Research has revealed that IL-33 can function as a nuclear factor to regulate various biological processes. This review discusses the cellular localization, functional effects, and immune regulation of full length IL-33 (FLIL-33), cytokine IL-33 (sIL-33) and nuclear IL-33 (nIL-33). In addition, the post-translational modifications of nIL-33 and the hypothesis of using nIL-33 as a treatment method were also summarized. A multidisciplinary approach is required which integrates methods and techniques from genomics, proteomics, cell biology and immunology to provide comprehensive insights into the function and therapeutic potential of nIL-33.

The therapeutic potential of targeting regulated non-apoptotic cell death

Cell death is critical for the development and homeostasis of almost all multicellular organisms. Moreover, its dysregulation leads to diverse disease states. Historically, apoptosis was thought to be the major regulated cell death pathway, whereas necrosis was considered to be an unregulated form of cell death. However, research in recent decades has uncovered several forms of regulated necrosis that are implicated in degenerative diseases, inflammatory conditions and cancer. The growing insight into these regulated, non-apoptotic cell death pathways has opened new avenues for therapeutic targeting. Here, we describe the regulatory pathways of necroptosis, pyroptosis, parthanatos, ferroptosis, cuproptosis, lysozincrosis and disulfidptosis. We discuss small-molecule inhibitors of the pathways and prospects for future drug discovery. Together, the complex mechanisms governing these pathways offer strategies to develop therapeutics that control non-apoptotic cell death.

Necroptosis in the sarcoma immune microenvironment: From biology to therapy

Apoptosis resistance remains a major obstacle to treatment failure in sarcoma. Necroptosis is a caspase-independent programmed cell death, investigated as a novel strategy to eradicate anti-apoptotic tumor cells. The process is mediated by the receptor-interacting proteins kinase family and mixed lineage kinase domain-like proteins, which is morphologically similar to necrosis. Recent studies suggest that necroptosis in the tumor microenvironment has pro- or anti-tumor effects on immune response and cancer development. Necroptosis-related molecules display a remarkable value in prognosis prediction and therapeutic response evaluation of sarcoma. Furthermore, the induction of tumor necroptosis has been explored as a feasible therapeutic strategy against sarcoma and to synergize with immunotherapy. This review discusses the dual roles of necroptosis in the immune microenvironment and tumor progression, and explores the potential of necroptosis as a new target for sarcoma treatment.

A Deep View of the Biological Property of Interleukin-33 and Its Dysfunction in the Gut

Intestinal diseases have always posed a serious threat to human health, with inflammatory bowel disease (IBD) being one of them. IBD is an autoimmune disease characterized by chronic inflammation, including ulcerative colitis (UC) and Crohn's disease (CD). The "alarm" cytokine IL-33, which is intimately associated with Th2 immunity, is a highly potent inflammatory factor that is considered to have dual functions-operating as both a pro-inflammatory cytokine and a transcriptional regulator. IL-33 has been shown to play a crucial role in both the onset and development of IBD. Therefore, this review focuses on the pathogenesis of IBD, the major receptor cell types, and the activities of IL-33 in innate and adaptive immunity, as well as its underlying mechanisms and conflicting conclusions in IBD. We have also summarized different medicines targeted to IL-33-associated diseases. Furthermore, we have emphasized the role of IL-33 in gastrointestinal cancer and parasitic infections, giving novel prospective therapeutic utility in the future application of IL-33.

Airway Epithelial-Derived Immune Mediators in COVID-19

The airway epithelium, which lines the conducting airways, is central to the defense of the lungs against inhaled particulate matter and pathogens such as SARS-CoV-2, the virus that causes COVID-19. Recognition of pathogens results in the activation of an innate and intermediate immune response which involves the release of cytokines and chemokines by the airway epithelium. This response can inhibit further viral invasion and influence adaptive immunity. However, severe COVID-19 is characterized by a hyper-inflammatory response which can give rise to clinical presentations including lung injury and lead to acute respiratory distress syndrome, viral pneumonia, coagulopathy, and multi-system organ failure. In response to SARS-CoV-2 infection, the airway epithelium can mount a maladaptive immune response which can delay viral clearance, perpetuate excessive inflammation, and contribute to the pathogenesis of severe COVID-19. In this article, we will review the barrier and immune functions of the airway epithelium, how SARS-CoV-2 can interact with the epithelium, and epithelial-derived cytokines and chemokines and their roles in COVID-19 and as biomarkers. Finally, we will discuss these immune mediators and their potential as therapeutic targets in COVID-19.

The Molecular Mechanisms of Neuroinflammation in Alzheimer's Disease, the Consequence of Neural Cell Death

Alzheimer's disease (AD) is accompanied by neural cell loss and memory deficit. Neural cell death, occurring via apoptosis and autophagy, is widely observed in the AD brain in addition to neuroinflammation mediated by necroptosis and the NLRP3 inflammasome. Neurotoxicity induced by amyloid-beta (Aβ) and tau aggregates leads to excessive neural cell death and neuroinflammation in the AD brain. During AD progression, uncontrolled neural cell death results in the dysregulation of cellular activity and synaptic function. Apoptosis mediated by pro-apoptotic caspases, autophagy regulated by autophagy-related proteins, and necroptosis controlled by the RIPK/MLKL axis are representative of neural cell death occurred during AD. Necroptosis causes the release of cellular components, contributing to the pro-inflammatory environment in the AD brain. Inordinately high levels of neural cell death and pro-inflammatory events lead to the production of pro-inflammatory cytokines and feed-forward hyper neuroinflammation. Thus, neural cell death and neuroinflammation cause synaptic dysfunction and memory deficits in the AD brain. In this review, we briefly introduce the mechanisms of neural cell death and neuroinflammation observed in the AD brain. Combined with a typical strategy for targeting Aβ and tau, regulation of neural cell death and neuroinflammation may be effective for the amelioration of AD pathologies.

PTRF-IL33-ZBP1 signaling mediating macrophage necroptosis contributes to HDM-induced airway inflammation

Polymerase 1 and transcript release factor (PTRF, encoding by Cavin-1) regulates interleukin 33 (IL-33) release, which is implicated in asthma development. Z-DNA binding protein 1 (ZBP1)-sensing Z-RNAs induces necroptosis which causes inflammatory diseases. House dust mite (HDM) is the major source of allergen in house dust and is strongly associated with the development of asthma. Whether PTRF via IL-33 and ZBP1 mediates HDM-induced macrophage necroptosis and airway inflammation remains unclear. Here, we found that deficiency of PTRF could reduce lung IL-33, ZBP1, phosphor-receptor-interacting protein kinase 3 (p-RIPK3), and phosphor-mixed lineage kinase domain-like (p-MLKL) (necroptosis executioner), and airway inflammation in an HDM-induced asthma mouse model. In HDM-treated macrophages, ZBP1, p-RIPK3, and p-MLKL levels were markedly increased, and these changes were reversed by deletion of Cavin-1. Deletion of Il33 also reduced expression of ZBP1, p-RIPK3, and p-MLKL in HDM-challenged lungs. Moreover, IL-33 synergizing with HDM boosted expression of ZBP1, p-RIPK3, and p-MLKL in macrophages. In bronchial epithelial cells rather than macrophages and vascular endothelial cells, PTRF positively regulates IL-33 expression. Therefore, we conclude that PTRF mediates HDM-induced macrophage ZBP1/necroptosis and airway inflammation, and this effect could be boosted by bronchial epithelial cell-derived IL-33. Our findings suggest that PTRF-IL33-ZBP1 signaling pathway might be a promising target for dampening airway inflammation.

Viral-induced neuronal necroptosis: Detrimental to brain function and regulation by necroptosis inhibitors

Neuronal necroptosis (programmed necrosis) in the CNS naturally occurs through a caspase-independent way and, especially in neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD), Parknson's disease (PD), Amyotrophic Lateral Sclerosis (ALS) and viral infections. Understanding necroptosis pathways (death receptor-dependent and independent), and its connections with other cell death pathways could lead to new insights into treatment. Receptor-interacting protein kinase (RIPK) mediates necroptosis via mixed-lineage kinase-like (MLKL) proteins. RIPK/MLKL necrosome contains FADD, procaspase-8-cellular FLICE-inhibitory proteins (cFLIPs), RIPK1/RIPK3, and MLKL. The necrotic stimuli cause phosphorylation of MLKL and translocate to the plasma membrane, causing an influx of Ca2+ and Na+ ions and, the immediate opening of mitochondrial permeability transition pore (mPTP) with the release of inflammatory cell damage-associated molecular patterns (DAMPs) like mitochondrial DNA (mtDNA), high-mobility group box1 (HMGB1), and interleukin1 (IL-1). The MLKL translocates to the nucleus to induce transcription of the NLRP3 inflammasome complex elements. MLKL-induced NLRP3 activity causes caspase-1 cleavage and, IL-1 activation which promotes neuroinflammation. RIPK1-dependent transcription increases illness-associated microglial and lysosomal abnormalities to facilitate amyloid plaque (Aβ) aggregation in AD. Recent research has linked neuroinflammation and mitochondrial fission with necroptosis. MicroRNAs (miRs) such as miR512-3p, miR874, miR499, miR155, and miR128a regulate neuronal necroptosis by targeting key components of necroptotic pathways. Necroptosis inhibitors act by inhibiting the membrane translocation of MLKL and RIPK1 activity. This review insights into the RIPK/MLKL necrosome-NLRP3 inflammasome interactions during death receptor-dependent and independent neuronal necroptosis, and clinical intervention by miRs to protect the brain from NDDs.

Programmed Cell Death in Asthma: Apoptosis, Autophagy, Pyroptosis, Ferroptosis, and Necroptosis

Bronchial asthma is a complex heterogeneous airway disease, which has emerged as a global health issue. A comprehensive understanding of the different molecular mechanisms of bronchial asthma may be an efficient means to improve its clinical efficacy in the future. Increasing research evidence indicates that some types of programmed cell death (PCD), including apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis, contributed to asthma pathogenesis, and may become new targets for future asthma treatment. This review briefly discusses the molecular mechanism and signaling pathway of these forms of PCD focuses on summarizing their roles in the pathogenesis and treatment strategies of asthma and offers some efficient means to improve clinical efficacy of therapeutics for asthma in the near future.

Symbiotic microbiome Staphylococcus epidermidis restricts IL-33 production in allergic nasal epithelium via limiting the cellular necroptosis

BACKGROUND

Allergic rhinitis (AR) is characterized by airway inflammation in nasal mucosa from inhaled allergens and interleukin (IL)-33 is the potent inducer of Th2 inflammation in allergic nasal epithelium. Staphylococcus epidermidis is one of the most abundant colonizers of the healthy human nasal mucosa and might impact the allergen-induced inflammatory responses in the nasal epithelium. Thus, we sought to characterize the mechanism of S. epidermidis regulating Th2 inflammation and IL-33 production in AR nasal mucosa.

RESULTS

The AR symptoms were alleviated and eosinophilic infiltration, serum IgE levels, and Th2 cytokines were significantly decreased in OVA-sensitized AR mice in response to human nasal commensal S. epidermidis. The inoculation of S. epidermidis to normal human nasal epithelial cells reduced IL-33 and GATA3 transcriptions and also reduced IL-33 and GATA3 expression in AR nasal epithelial (ARNE) cells and the nasal mucosa of AR mice. Our data exhibited that the cellular necroptosis of ARNE cells might be involved in IL-33 production and inoculation of S. epidermidis decreased the phosphorylation of necroptosis enzymes in ARNE cells, which was related to the reduction of IL-33 production.

CONCLUSIONS

We present that human nasal commensal S. epidermidis reduces allergic inflammation by suppressing IL-33 production in nasal epithelium. Our findings indicate that S. epidermidis serves a role in blocking allergen-induced cellular necroptosis in allergic nasal epithelium which might be a key mechanism of reduction of IL-33 and Th2 inflammation.

"Under Pressure" - How fungi evade, exploit, and modulate cells of the innate immune system

The human immune system uses an arsenal of effector mechanisms to prevent and counteract infections. Yet, some fungal species are extremely successful as human pathogens, which can be attributed to a wide variety of strategies by which these fungi evade, exploit, and modulate the immune system. These fungal pathogens normally are either harmless commensals or environmental fungi. In this review we discuss how commensalism, but also life in an environmental niche without human contact, can drive the evolution of diverse and specialized immune evasion mechanisms. Correspondingly, we discuss the mechanisms contributing to the ability of these fungi to cause superficial to life-threatening infections.

Scavenger receptor BI attenuates oxidized phospholipid-induced pulmonary inflammation

Damage associated molecular patterns (DAMPs) are molecules released from dead/dying cells following toxicant and/or environmental exposures that activate the immune response through binding of pattern recognition receptors (PRRs). Excessive production of DAMPs or failed clearance leads to chronic inflammation and delayed inflammation resolution. One category of DAMPs are oxidized phospholipids (oxPLs) produced upon exposure to high levels of oxidative stress, such as following ozone (O3) induced inflammation. OxPLs are bound by multiple classes of PRRs that include scavenger receptors (SRs) such as SR class B-1 (SR-BI) and toll-like receptors (TLRs). Interactions between oxPLs and PRRs appear to regulate inflammation; however, the role of SR-BI in oxPL-induced lung inflammation has not been defined. Therefore, we hypothesize that SR-BI is critical in protecting the lung from oxPL-induced pulmonary inflammation/injury. To test this hypothesis, C57BL/6J (WT) female mice were dosed with oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphatidylcholine (oxPAPC) by oropharyngeal aspiration which increased pulmonary SR-BI expression. Following oxPAPC exposure, SR-BI deficient (SR-BI-/-) mice exhibited increased lung pathology and inflammatory cytokine/chemokine production. Lipidomic analysis revealed that SR-BI-/- mice had an altered pulmonary lipidome prior to and following oxPAPC exposure, which correlated with increased oxidized phosphatidylcholines (PCs). Finally, we characterized TLR4-mediated activation of NF-κB following oxPAPC exposure and discovered that SR-BI-/- mice had increased TLR4 mRNA expression in lung tissue and macrophages, increased nuclear p65, and decreased cytoplasmic IκBα. Overall, we conclude that SR-BI is required for limiting oxPAPC-induced lung pathology by maintaining lipid homeostasis, reducing oxidized PCs, and attenuating TLR4-NF-κB activation, thereby preventing excessive and persistent inflammation.

Initiation of type 2 immunity at barrier surfaces

Although seemingly unrelated, parasitic worms, venoms, and allergens all induce a type 2 immune response. The effector functions and clinical features of type 2 immunity are well-defined, but fundamental questions about the initiation of type 2 immunity remain unresolved. How are these enormously diverse type 2 stimuli first detected? How are type 2 helper T cells primed and regulated? And how do mechanisms of type 2 initiation vary across tissues? Here, we review the common themes governing type 2 immune sensing and explore aspects of T cell priming and effector reactivation that make type 2 helper T cells a unique T helper lineage. Throughout the review, we emphasize the importance of non-hematopoietic cells and highlight how the unique anatomy and physiology of each barrier tissue shape mechanisms of type 2 immune initiation.

Full-length IL-33 augments pulmonary fibrosis in an ST2- and Th2-independent, non-transcriptomic fashion

Mature IL-33 (MIL33) acting through its receptor, ST2, is known to regulate fibrosis. The precursor, full-length IL-33 (FLIL33), may function differently from MIL33 and independently of ST2. Here we report that genetic deletion of either IL-33 or ST2 attenuates pulmonary fibrosis in the bleomycin model, as does Cre-induced IL-33 deficiency in response to either acute or chronic bleomycin challenge. However, adenovirus-mediated gene delivery of FLIL33, but not MIL33, to the lungs of either wild-type or ST2-deficient mice potentiates the profibrotic effect of bleomycin without inducing a Th2 phenotype. In cultured mouse lung cells, FLIL33 overexpression induces moderate and distinct transcriptomic changes compared with a robust response induced by MIL33, whereas ST2 deletion abrogates the effects of both IL-33 forms. Thus, FLIL33 may contribute to fibrosis in an ST2-independent, Th2-independent, non-transcriptomic fashion, suggesting that pharmacological targeting of both FLIL33 and MIL33 may prove efficacious in patients with pulmonary fibrosis.

Resolution Potential of Necrotic Cell Death Pathways

During tissue damage caused by infection or sterile inflammation, not only damage-associated molecular patterns (DAMPs), but also resolution-associated molecular patterns (RAMPs) can be activated. These dying cell-associated factors stimulate immune cells localized in the tissue environment and induce the production of inflammatory mediators or specialized proresolving mediators (SPMs). Within the current prospect of science, apoptotic cell death is considered the main initiator of resolution. However, more RAMPs are likely to be released during necrotic cell death than during apoptosis, similar to what has been observed for DAMPs. The inflammatory potential of many regulated forms of necrotic cell death modalities, such as pyroptosis, necroptosis, ferroptosis, netosis, and parthanatos, have been widely studied in necroinflammation, but their possible role in resolution is less considered. In this review, we aim to summarize the relationship between necrotic cell death and resolution, as well as present the current available data regarding the involvement of certain forms of regulated necrotic cell death in necroresolution.

RIPK1 and RIPK3 in antibacterial defence

Upon sensing pathogenic bacterial infection, host cells activate a multitude of inflammatory and immunogenic responses to promote bacterial clearance and restore tissue homeostasis. RIPK1 and RIPK3 are two key players in antimicrobial defence, by either driving inflammatory signalling or inducing programmed cell death activation, ranging from apoptosis, pyroptosis to necroptosis. In this review, we first discuss the mechanisms by which RIPK1 and RIPK3 promote the assembly of death-inducing complexes and how these cell death pathways are activated as host responses to counteract pathogenic bacteria. We further outline the immunological importance of cell death in antibacterial defence and highlight outstanding questions in the field.

Examination of the role of necroptotic damage-associated molecular patterns in tissue fibrosis

Fibrosis is defined as the abnormal and excessive deposition of extracellular matrix (ECM) components, which leads to tissue or organ dysfunction and failure. However, the pathological mechanisms underlying fibrosis remain unclear. The inflammatory response induced by tissue injury is closely associated with tissue fibrosis. Recently, an increasing number of studies have linked necroptosis to inflammation and fibrosis. Necroptosis is a type of preprogrammed death caused by death receptors, interferons, Toll-like receptors, intracellular RNA and DNA sensors, and other mediators. These activate receptor-interacting protein kinase (RIPK) 1, which recruits and phosphorylates RIPK3. RIPK3 then phosphorylates a mixed lineage kinase domain-like protein and causes its oligomerization, leading to rapid plasma membrane permeabilization, the release of cellular contents, and exposure of damage-associated molecular patterns (DAMPs). DAMPs, as inflammatory mediators, are involved in the loss of balance between extensive inflammation and tissue regeneration, leading to remodeling, the hallmark of fibrosis. In this review, we discuss the role of necroptotic DAMPs in tissue fibrosis and highlight the inflammatory responses induced by DAMPs in tissue ECM remodeling. By summarizing the existing literature on this topic, we underscore the gaps in the current research, providing a framework for future investigations into the relationship among necroptosis, DAMPs, and fibrosis, as well as a reference for later transformation into clinical treatment.

Cell death in skin function, inflammation, and disease

Cell death is an essential process that plays a vital role in restoring and maintaining skin homeostasis. It supports recovery from acute injury and infection and regulates barrier function and immunity. Cell death can also provoke inflammatory responses. Loss of cell membrane integrity with lytic forms of cell death can incite inflammation due to the uncontrolled release of cell contents. Excessive or poorly regulated cell death is increasingly recognised as contributing to cutaneous inflammation. Therefore, drugs that inhibit cell death could be used therapeutically to treat certain inflammatory skin diseases. Programmes to develop such inhibitors are already underway. In this review, we outline the mechanisms of skin-associated cell death programmes; apoptosis, necroptosis, pyroptosis, NETosis, and the epidermal terminal differentiation programme, cornification. We discuss the evidence for their role in skin inflammation and disease and discuss therapeutic opportunities for targeting the cell death machinery.

Immunogenic Cell Death and Role of Nanomaterials Serving as Therapeutic Vaccine for Personalized Cancer Immunotherapy

Immunogenic cell death (ICD) is a rapidly growing research area representing one of the emerging therapeutic strategies of cancer immunotherapy. ICD is an umbrella term covering several cell death modalities including apoptosis, necroptosis, ferroptosis and pyroptosis, and is the product of a balanced combination of adjuvanticity (damage-associated molecular patterns and chemokines/cytokines) and antigenicity (tumor associated antigens). Only a limited number of anti-cancer therapies are available to induce ICD in experimental cancer therapies and even much less is available for clinical use. To overcome this limitation, nanomaterials can be used to increase the immunogenicity of cancer cells killed by anti-cancer therapy, which in themselves are not necessarily immunogenic. In this review, we outline the current state of knowledge of ICD modalities and discuss achievements in using nanomaterials to increase the immunogenicity of dying cancer cells. The emerging trends in modulating the immunogenicity of dying cancer cells in experimental and translational cancer therapies and the challenges facing them are described. In conclusion, nanomaterials are expected to drive further progress in their use to increase efficacy of anti-cancer therapy based on ICD induction and in the future, it is necessary to validate these strategies in clinical settings, which will be a challenging research area.

Types of necroinflammation, the effect of cell death modalities on sterile inflammation

Distinct types of immune responses are activated by infections, which cause the development of type I, II, or III inflammation, regulated by Th1, Th2, Th17 helper T cells and ILC1, ILC2 and ILC3 cells, respectively. While the classification of immune responses to different groups of pathogens is widely accepted, subtypes of the immune response elicited by sterile inflammation have not yet been detailed. Necroinflammation is associated with the release of damage-associated molecular patterns (DAMP) from dying cells. In this review, we present that the distinct molecular mechanisms activated during apoptosis, necroptosis, pyroptosis, and ferroptosis lead to the release of different patterns of DAMPs and their suppressors, SAMPs. We summarize the currently available data on how regulated cell death pathways and released DAMPs and SAMPs direct the differentiation of T helper and ILC cells. Understanding the subtypes of necroinflammation can be crucial in developing strategies for the treatment of sterile inflammatory diseases caused by cell death processes.

Necrotic reshaping of the glioma microenvironment drives disease progression

Glioblastoma is the most common primary brain tumor and has a dismal prognosis. The development of central necrosis represents a tipping point in the evolution of these tumors that foreshadows aggressive expansion, swiftly leading to mortality. The onset of necrosis, severe hypoxia and associated radial glioma expansion correlates with dramatic tumor microenvironment (TME) alterations that accelerate tumor growth. In the past, most have concluded that hypoxia and necrosis must arise due to "cancer outgrowing its blood supply" when rapid tumor growth outpaces metabolic supply, leading to diffusion-limited hypoxia. However, growing evidence suggests that microscopic intravascular thrombosis driven by the neoplastic overexpression of pro-coagulants attenuates glioma blood supply (perfusion-limited hypoxia), leading to TME restructuring that includes breakdown of the blood-brain barrier, immunosuppressive immune cell accumulation, microvascular hyperproliferation, glioma stem cell enrichment and tumor cell migration outward. Cumulatively, these adaptations result in rapid tumor expansion, resistance to therapeutic interventions and clinical progression. To inform future translational investigations, the complex interplay among environmental cues and myriad cell types that contribute to this aggressive phenotype requires better understanding. This review focuses on contributions from intratumoral thrombosis, the effects of hypoxia and necrosis, the adaptive and innate immune responses, and the current state of targeted therapeutic interventions.

Porphyromonas gingivalis lipopolysaccharide induced RIPK3/MLKL-mediated necroptosis of oral epithelial cells and the further regulation in macrophage activation

Necroptosis, a new type of regulated cell death with massive release of damage-associated molecular patterns (DAMPs), is involved in the pathogenesis of periodontitis. However, the role of necroptosis in oral epithelial cells and the following effect on macrophages activation remain unknown.

Human immortalized oral epithelial cells were stimulated with Porphyromonas gingivalis lipopolysaccharide (LPS). Cell death was assessed while expressions of RIPK3/MLKL and toll-like receptors (TLRs) were evaluated. Necrosulfonamide (NSA), an inhibitor of MLKL was applied to block necroptosis. The expression of DAMPs and the epithelial connection protein were evaluated by qPCR and immunofluorescence, respectively. Immortalized human monocytes U937 were induced into the M0 or M2 subset, and influences of HIOECs-derived DAMPs on macrophage polarization as well as activation of the Mincle/SYK axis were assessed.

P. gingivalis LPS could be recognized by TLR2 and regulates necroptosis of HIOECs by activating RIPK3/MLKL. NSA inhibited cell death of HIOECs, alleviated impaired epithelial connection, and inhibited expressions of DAMPs. Low dose of DAMPs derived from HIOECs promoted M2-like polarization by activating the Mincle/SYK axis, which was significantly suppressed with increased doses of DAMPs.

P. gingivalis LPS destructed oral epithelial cells via RIPK3/MLKL-mediated necroptosis, which further regulated macrophage activation via DAMPs from oral epithelial cells.

The role of necroptosis in common respiratory diseases in children

Studies have shown that necroptosis (NEC) relies on a unique gene-regulated molecular pathway to cause cell death. With the development of knockout mouse models and specific molecular inhibitors of necrotic proteins, this cell death pathway has been considered one of the important causes of the pathogenesis of human diseases. In this review, we explored the possible roles and mechanisms of NEC in common respiratory diseases in children, such as acute lung injury, acute respiratory distress syndrome, pulmonary infection, childhood asthma, pulmonary hypertension, etc., in order to provide new ideas for the prevention and treatment of such diseases.

Could Interleukin-33 (IL-33) Govern the Outcome of an Equine Influenza Virus Infection? Learning from Other Species

Influenza A viruses (IAVs) are important respiratory pathogens of horses and humans. Infected individuals develop typical respiratory disorders associated with the death of airway epithelial cells (AECs) in infected areas. Virulence and risk of secondary bacterial infections vary among IAV strains. The IAV non-structural proteins, NS1, PB1-F2, and PA-X are important virulence factors controlling AEC death and host immune responses to viral and bacterial infection. Polymorphism in these proteins impacts their function. Evidence from human and mouse studies indicates that upon IAV infection, the manner of AEC death impacts disease severity. Indeed, while apoptosis is considered anti-inflammatory, necrosis is thought to cause pulmonary damage with the release of damage-associated molecular patterns (DAMPs), such as interleukin-33 (IL-33). IL-33 is a potent inflammatory mediator released by necrotic cells, playing a crucial role in anti-viral and anti-bacterial immunity. Here, we discuss studies in human and murine models which investigate how viral determinants and host immune responses control AEC death and subsequent lung IL-33 release, impacting IAV disease severity. Confirming such data in horses and improving our understanding of early immunologic responses initiated by AEC death during IAV infection will better inform the development of novel therapeutic or vaccine strategies designed to protect life-long lung health in horses and humans, following a One Health approach.

The role of necroptosis in disease and treatment

Necroptosis, a distinctive type of programmed cell death different from apoptosis or necrosis, triggered by a series of death receptors such as tumor necrosis factor receptor 1 (TNFR1), TNFR2, and Fas. In case that apoptosis process is blocked, necroptosis pathway is initiated with the activation of three key downstream mediators which are receptor-interacting serine/threonine protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like protein (MLKL). The whole process eventually leads to destruction of the cell membrane integrity, swelling of organelles, and severe inflammation. Over the past decade, necroptosis has been found widely involved in life process of human beings and animals. In this review, we attempt to explore the therapeutic prospects of necroptosis regulators by describing its molecular mechanism and the role it played in pathological condition and tissue homeostasis, and to summarize the research and clinical applications of corresponding regulators including small molecule inhibitors, chemicals, Chinese herbal extracts, and biological agents in the treatment of various diseases.

Proteomic analysis of necroptotic extracellular vesicles

Necroptosis is a regulated and inflammatory form of cell death. We, and others, have previously reported that necroptotic cells release extracellular vesicles (EVs). We have found that necroptotic EVs are loaded with proteins, including the phosphorylated form of the key necroptosis-executing factor, mixed lineage kinase domain-like kinase (MLKL). However, neither the exact protein composition, nor the impact, of necroptotic EVs have been delineated. To characterize their content, EVs from necroptotic and untreated U937 cells were isolated and analyzed by mass spectrometry-based proteomics. A total of 3337 proteins were identified, sharing a high degree of similarity with exosome proteome databases, and clearly distinguishing necroptotic and control EVs. A total of 352 proteins were significantly upregulated in the necroptotic EVs. Among these were MLKL and caspase-8, as validated by immunoblot. Components of the ESCRTIII machinery and inflammatory signaling were also upregulated in the necroptotic EVs, as well as currently unreported components of vesicle formation and transport, and necroptotic signaling pathways. Moreover, we found that necroptotic EVs can be phagocytosed by macrophages to modulate cytokine and chemokine secretion. Finally, we uncovered that necroptotic EVs contain tumor neoantigens, and are enriched with components of antigen processing and presentation. In summary, our study reveals a new layer of regulation during the early stage of necroptosis, mediated by the secretion of specific EVs that influences the microenvironment and may instigate innate and adaptive immune responses. This study sheds light on new potential players in necroptotic signaling and its related EVs, and uncovers the functional tasks accomplished by the cargo of these necroptotic EVs.

Necroptosis in Pulmonary Diseases: A New Therapeutic Target

In the past decades, apoptosis has been the most well-studied regulated cell death (RCD) that has essential functions in tissue homeostasis throughout life. However, a novel form of RCD called necroptosis, which requires receptor-interacting protein kinase-3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL), has recently been receiving increasing scientific attention. The phosphorylation of RIPK3 enables the recruitment and phosphorylation of MLKL, which oligomerizes and translocates to the plasma membranes, ultimately leading to plasma membrane rupture and cell death. Although apoptosis elicits no inflammatory responses, necroptosis triggers inflammation or causes an innate immune response to protect the body through the release of damage-associated molecular patterns (DAMPs). Increasing evidence now suggests that necroptosis is implicated in the pathogenesis of several human diseases such as systemic inflammation, respiratory diseases, cardiovascular diseases, neurodegenerative diseases, neurological diseases, and cancer. This review summarizes the emerging insights of necroptosis and its contribution toward the pathogenesis of lung diseases.

Pulmonary Macrophage Cell Death in Lung Health and Disease

Over the last several decades, our understanding of regulated-cell-death (RCD) pathways has increased dramatically. In addition to apoptosis and accidental cell death (primary necrosis), a diverse spectrum of RCD pathways has been delineated. In the lung, airway macrophages are critical for maintaining the functionality of airways via the clearance of inhaled particles, cell debris, and infectious agents. Exposure of these cells to pathogenic organisms or particles can induce a variety of RCD pathways that promote the release of danger signals into the lung. These responses have evolved to trigger the innate and adaptive arms of the immune system and thus offer protection against pathogens; yet they can also contribute to the development of lung injury and pathogenic immune responses. In this review, we discuss recent studies that suggest a critical role for airway-macrophage RCD pathways in promoting the release of pulmonary danger signals in health and disease.

Targeting RIP Kinases in Chronic Inflammatory Disease

Chronic inflammatory disorders are characterised by aberrant and exaggerated inflammatory immune cell responses. Modes of extrinsic cell death, apoptosis and necroptosis, have now been shown to be potent drivers of deleterious inflammation, and mutations in core repressors of these pathways underlie many autoinflammatory disorders. The receptor-interacting protein (RIP) kinases, RIPK1 and RIPK3, are integral players in extrinsic cell death signalling by regulating the production of pro-inflammatory cytokines, such as tumour necrosis factor (TNF), and coordinating the activation of the NOD-like receptor protein 3 (NLRP3) inflammasome, which underpin pathological inflammation in numerous chronic inflammatory disorders. In this review, we firstly give an overview of the inflammatory cell death pathways regulated by RIPK1 and RIPK3. We then discuss how dysregulated signalling along these pathways can contribute to chronic inflammatory disorders of the joints, skin, and gastrointestinal tract, and discuss the emerging evidence for targeting these RIP kinases in the clinic.

The central role of IL-33/IL-1RL1 pathway in asthma: From pathogenesis to intervention

Interleukin-33 (IL-33), a member of the IL-1 family, and its cognate receptor, Interleukin-1 receptor like-1 (IL-1RL1 or ST2), are susceptibility genes for childhood asthma. In response to cellular damage, IL-33 is released from barrier tissues as an 'alarmin' to activate the innate immune response. IL-33 drives type 2 responses by inducing signalling through its receptor IL-1RL1 in several immune and structural cells, thereby leading to type 2 cytokine and chemokine production. IL-1RL1 gene transcript encodes different isoforms generated through alternative splicing. Its soluble isoform, IL-1RL1-a or sST2, acts as a decoy receptor by sequestering IL-33, thereby inhibiting IL1RL1-b/IL-33 signalling. IL-33 and its receptor IL-1RL1 are therefore considered as putative biomarkers or targets for pharmacological intervention in asthma. This review will provide an overview of the genetics and biology of the IL-33/IL-1RL1 pathway in the context of asthma pathogenesis. It will discuss the potential and complexities of targeting the cytokine or its receptor, how genetics or biomarkers may inform precision medicine for asthma targeting this pathway, and the possible positioning of therapeutics targeting IL-33 or its receptor in the expanding landscape of novel biologicals applied in asthma management.

The potential role of necroptosis in clinical diseases (Review)

As an important type of programmed cell death in addition to apoptosis, necroptosis occurs in a variety of pathophysiological processes, including infections, liver diseases, kidney injury, neurodegenerative diseases, cardiovascular diseases, and human tumors. It can be triggered by a variety of factors, such as tumor necrosis factor receptor and Toll‑like receptor families, intracellular DNA and RNA sensors, and interferon, and is mainly mediated by receptor‑interacting protein kinase 1 (RIP1), RIP3, and mixed lineage kinase domain‑like protein. A better understanding of the mechanism of necroptosis may be useful in the development of novel drugs for necroptosis‑related diseases. In this review, the focus is on the molecular mechanisms of necroptosis, exploring the role of necroptosis in different pathologies, discussing their potential as a novel therapeutic target for disease therapy, and providing suggestions for further study in this area.

Fungal-Induced Programmed Cell Death

Fungal infections are a cause of morbidity in humans, and despite the availability of a range of antifungal treatments, the mortality rate remains unacceptably high. Although our knowledge of the interactions between pathogenic fungi and the host continues to grow, further research is still required to fully understand the mechanism underpinning fungal pathogenicity, which may provide new insights for the treatment of fungal disease. There is great interest regarding how microbes induce programmed cell death and what this means in terms of the immune response and resolution of infection as well as microbe-specific mechanisms that influence cell death pathways to aid in their survival and continued infection. Here, we discuss how programmed cell death is induced by fungi that commonly cause opportunistic infections, including Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans, the role of programmed cell death in fungal immunity, and how fungi manipulate these pathways.

Cell death in head and neck cancer pathogenesis and treatment

Many cancer therapies aim to trigger apoptosis in cancer cells. Nevertheless, the presence of oncogenic alterations in these cells and distorted composition of tumour microenvironment largely limit the clinical efficacy of this type of therapy. Luckily, scientific consensus describes about 10 different cell death subroutines with different regulatory pathways and cancer cells are probably not able to avoid all of cell death types at once. Therefore, a focused and individualised therapy is needed to address the specific advantages and disadvantages of individual tumours. Although much is known about apoptosis, therapeutic opportunities of other cell death pathways are often neglected. Molecular heterogeneity of head and neck squamous cell carcinomas (HNSCC) causing unpredictability of the clinical response represents a grave challenge for oncologists and seems to be a critical component of treatment response. The large proportion of this clinical heterogeneity probably lies in alterations of cell death pathways. How exactly cells die is very important because the predominant type of cell death can have multiple impacts on the therapeutic response as cell death itself acts as a second messenger. In this review, we discuss the different types of programmed cell death (PCD), their connection with HNSCC pathogenesis and possible therapeutic windows that result from specific sensitivity to some form of PCD in some clinically relevant subgroups of HNSCC.

Rapid seroconversion and persistent functional IgG antibodies in severe COVID-19 patients correlates with an IL-12p70 and IL-33 signature

Despite ongoing efforts to characterize the host response toward SARS-CoV-2, a major gap in our knowledge still exists regarding the magnitude and duration of the humoral response. Analysis of the antibody response in mild versus moderate/severe patients, using our new developed quantitative electrochemiluminescent assay for detecting IgM/IgA/IgG antibodies toward SARS-CoV-2 antigens, revealed a rapid onset of IgG/IgA antibodies, specifically in moderate/severe patients. IgM antibodies against the viral receptor binding domain, but not against nucleocapsid protein, were detected at early stages of the disease. Furthermore, we observed a marked reduction in IgM/IgA antibodies over-time. Adapting our assay for ACE2 binding-competition, demonstrated that the presence of potentially neutralizing antibodies is corelated with IgG/IgA. Finally, analysis of the cytokine profile in COVID-19 patients revealed unique correlation of an IL-12p70/IL33 and IgG seroconversion, which correlated with disease severity. In summary, our comprehensive analysis has major implications on the understanding and monitoring of SARS-CoV-2 infections.