CYLD Proteolysis Protects Macrophages from TNF-Mediated Auto-necroptosis Induced by LPS and Licensed by Type I IFN

Exploring necroptosis: mechanistic analysis and antitumor potential of nanomaterials

Necroptosis, a non-apoptotic mode of programmed cell death, is characterized by the disintegration of the plasma membrane, ultimately leading to cell perforation and rupture. Recent studies have disclosed the mechanism of necroptosis and its intimate link with nanomaterials. Nanomedicine represents a novel approach in the development of therapeutic agents utilizing nanomaterials to treat a range of cancers with high efficacy. This article provides an overview of the primary mechanism behind necroptosis, the current research progress in nanomaterials, their potential use in various diseases-notably cancer, safety precautions, and prospects. The goal is to aid in the development of nanomaterials for cancer treatment.

The role of hydrogen sulfide in the regulation of necroptosis across various pathological processes

Necroptosis is a programmed cell death form executed by receptor-interacting protein kinase (RIPK) 1, RIPK3 and mixed lineage kinase domain-like protein (MLKL), which assemble into an oligomer called necrosome. Accumulating evidence reveals that necroptosis participates in many types of pathological processes. Hence, clarifying the mechanism of necroptosis in pathological processes is particularly important for the prevention and treatment of various diseases. For over 300 years, hydrogen sulfide (H2S) has been widely known in the scientific community as a toxic and foul-smelling gas. However, after discovering the important physiological and pathological functions of H2S, human understanding of this small molecule changed, believing that H2S is the third gas signaling molecule after carbon monoxide (CO) and nitric oxide (NO). H2S plays an important role in various diseases, but the related mechanisms are not yet fully understood. In recent years, more and more studies have shown that H2S regulation of necroptosis is involved in various pathological processes. Herein, we focus on the recent progress on the role of H2S regulation of necroptosis in different pathological processes and profoundly analyze the related mechanisms.

Bacterial indole-3-propionic acid inhibits macrophage IL-1β production through targeting methionine metabolism

The gut microbiota plays key roles in host health by shaping the host immune responses through their metabolites, like indole derivatives from tryptophan. However, the direct role of these indole derivatives in macrophage fate decision and the underlying mechanism remains unknown. Here, we found that bacterial indole-3-propionic acid (IPA) downregulates interleukin-1beta (IL-1β) production in M1 macrophages through inhibition of nuclear factor-kappa B (NF-κB) signaling. Mechanistically, IPA binds specifically with methionine adenosyl-transferase 2A (MAT2A) to promote S-adenosylmethionine (SAM) synthesis, which facilitates the DNA methylation of ubiquitin-specific peptidase 16 (USP16, a deubiquitinase), and in turn promotes Toll-like receptor 4 (TLR4) ubiquitination and NF-κB inhibition. Furthermore, IPA administration attenuates sepsis in mouse models induced by lipopolysaccharides (LPS), showcasing its potential as a microbial-derived adjunct in alleviating inflammation. Collectively, our findings reveal a newly found microbial metabolite-immune system regulatory pathway mediated by IPA.

VPO1 Promotes Programmed Necrosis of Cardiomyocytes in Rats with Chronic Heart Failure by Upregulating CYLD

BACKGROUND

Chronic heart failure (CHF) is a serious cardiovascular condition. Vascular peroxidase 1 (VPO1) is associated with various cardiovascular diseases, yet its role in CHF remains unclear. This research aims to explore the involvement of VPO1 in CHF.

METHODS

CHF was induced in rats using adriamycin, and the expression levels of VPO1 and cylindromatosis (CYLD) were assessed. In parallel, the effects of VPO1 on programmed necrosis in H9c2 cells were evaluated through cell viability assays, lactate dehydrogenase (LDH) level measurements, and analysis of receptor-interacting protein kinase 1/receptor-interacting protein kinase 3/mixed lineage kinase domain-like protein (RIPK1/RIPK3/MLKL) pathway-related proteins. The impact of CYLD on RIPK1 protein stability and ubiquitination was also investigated, along with the interaction between VPO1 and CYLD. Additionally, cardiac structure and function were assessed using echocardiography, Hematoxylin-eosin (HE) staining, Masson staining, and measurements of myocardial injury-related factors, including N-terminal prohormone of brain natriuretic peptide (NT-proBNP), Aspartate aminotransferase (AST), LDH, and creatine kinase-myocardial band (CK-MB).

RESULTS

VPO1 expression was upregulated in CHF rats and in H9c2 cells treated with adriamycin. In cellular experiments, VPO1 knockdown improved cell viability, inhibited necrosis and the expression of proteins associated with the RIPK1/RIPK3/MLKL pathway. Mechanistically, VPO1 promoted cardiomyocyte programmed necrosis by interacting with the deubiquitinating enzyme CYLD, which enhanced RIPK1 ubiquitination and degradation, leading to activation of the RIPK1/RIPK3/MLKL signaling pathway. At animal level, overexpression of CYLD counteracted the cardiac failure, cardiac hypertrophy, myocardial injury, myocardial fibrosis, and tissue necrosis caused by VPO1 knockdown.

CONCLUSIONS

VPO1 exacerbates cardiomyocyte programmed necrosis in CHF rats by upregulating CYLD, which activates the RIPK1/RIPK3/MLKL signaling pathway. Thus, VPO1 may represent a potential therapeutic target for CHF.

Necroptosis and autoimmunity

Autoimmunity is a normal physiological state that requires immunological homeostasis and surveillance, whereas necroptosis is a type of inflammatory cell death. When necroptosis occurs, various immune system cells must perform their appropriate duties to preserve immunological homeostasis, whether the consequence is expanding or limiting the inflammatory response and the pathological condition is cleared or progresses to the autoimmune disease stage. This article discusses necroptosis based on RIP homotypic interaction motif (RHIM) interaction under various physiological and pathological situations, with the RIPK1-RIPK3-MLKL necrosome serving as the regulatory core. In addition, the cell biology of necroptosis involved in autoimmunity and its application in autoimmune diseases were also reviewed.

Influenza A virus infection activates caspase-8 to enhance innate antiviral immunity by cleaving CYLD and blocking TAK1 and RIG-I deubiquitination

Caspase-8, an aspartate-specific cysteine protease that primarily functions as an initiator caspase to induce apoptosis, can downregulate innate immunity in part by cleaving RIPK1 and IRF3. However, patients with caspase-8 mutations or deficiency develop immunodeficiency and are prone to viral infections. The molecular mechanism underlying this controversy remains unknown. Whether caspase-8 enhances or suppresses antiviral responses against influenza A virus (IAV) infection remains to be determined. Here, we report that caspase-8 is readily activated in A549 and NL20 cells infected with the H5N1, H5N6, and H1N1 subtypes of IAV. Surprisingly, caspase-8 deficiency and two caspase-8 inhibitors, Z-VAD and Z-IETD, do not enhance but rather downregulate antiviral innate immunity, as evidenced by decreased TBK1, IRF3, IκBα, and p65 phosphorylation, decreased IL-6, IFN-β, MX1, and ISG15 gene expression; and decreased IFN-β production but increased virus replication. Mechanistically, caspase-8 cleaves and inactivates CYLD, a tumor suppressor that functions as a deubiquitinase. Caspase-8 inhibition suppresses CYLD cleavage, RIG-I and TAK1 ubiquitination, and innate immune signaling. In contrast, CYLD deficiency enhances IAV-induced RIG-I and TAK1 ubiquitination and innate antiviral immunity. Neither caspase-3 deficiency nor treatment with its inhibitor Z-DEVD affects CYLD cleavage or antiviral innate immunity. Our study provides evidence that caspase-8 activation in two human airway epithelial cell lines does not silence but rather enhances innate immunity by inactivating CYLD.

TBK1 and IKKε protect target cells from IFNγ-mediated T cell killing via an inflammatory apoptotic mechanism

Cytotoxic T cells produce interferon gamma (IFNγ), which plays a critical role in anti-microbial and anti-tumor responses. However, it is not clear whether T cell-derived IFNγ directly kills infected and tumor target cells, and how this may be regulated. Here, we report that target cell expression of the kinases TBK1 and IKKε regulate IFNγ cytotoxicity by suppressing the ability of T cell-derived IFNγ to kill target cells. In tumor targets lacking TBK1 and IKKε, IFNγ induces expression of TNFR1 and the Z-nucleic acid sensor, ZBP1, to trigger RIPK1-dependent apoptosis, largely in a target cell-autonomous manner. Unexpectedly, IFNγ, which is not known to signal to NFκB, induces hyperactivation of NFκB in TBK1 and IKKε double-deficient cells. TBK1 and IKKε suppress IKKα/β activity and in their absence, IFNγ induces elevated NFκB-dependent expression of inflammatory chemokines and cytokines. Apoptosis is thought to be non-inflammatory, but our observations demonstrate that IFNγ can induce an inflammatory form of apoptosis, and this is suppressed by TBK1 and IKKε. The two kinases provide a critical connection between innate and adaptive immunological responses by regulating three key responses: (1) phosphorylation of IRF3/7 to induce type I IFN; (2) inhibition of RIPK1-dependent death; and (3) inhibition of NFκB-dependent inflammation. We propose that these kinases evolved these functions such that their inhibition by pathogens attempting to block type I IFN expression would enable IFNγ to trigger apoptosis accompanied by an alternative inflammatory response. Our findings show that loss of TBK1 and IKKε in target cells sensitizes them to inflammatory apoptosis induced by T cell-derived IFNγ.

Regulation of Zfp36 by ISGF3 and MK2 restricts the expression of inflammatory cytokines during necroptosis stimulation

Necrosome activation following TLR- or cytokine receptor-signaling results in cell death by necroptosis which is characterized by the rupture of cell membranes and the consequent release of intracellular contents to the extracellular milieu. While necroptosis exacerbates various inflammatory diseases, the mechanisms through which the inflammatory responses are regulated are not clear. We show that the necrosome activation of macrophages results in an upregulation of various pathways, including the mitogen-activated protein kinase (MAPK) cascade, which results in an elevation of the inflammatory response and consequent expression of several cytokines and chemokines. Programming for this upregulation of inflammatory response occurs during the early phase of necrosome activation and proceeds independently of cell death but depends on the activation of the receptor-interacting protein kinase-1 (RipK1). Interestingly, necrosome activation also results in an upregulation of IFNβ, which in turn exerts an inhibitory effect on the maintenance of inflammatory response through the repression of MAPK-signaling and an upregulation of Zfp36. Activation of the interferon-induced gene factor-3 (ISGF3) results in the expression of ZFP36 (TTP), which induces the post-transcriptional degradation of mRNAs of various inflammatory cytokines and chemokines through the recognition of AU-rich elements in their 3'UTR. Furthermore, ZFP-36 inhibits IFNβ-, but not TNFα- induced necroptosis. Overall, these results reveal the molecular mechanism through which IFNβ, a pro-inflammatory cytokine, induces the expression of ZFP-36, which in turn inhibits necroptosis and halts the maintenance of the inflammatory response.

Necroptosis in bacterial infections

Necroptosis, a recently discovered form of cell-programmed death that is distinct from apoptosis, has been confirmed to play a significant role in the pathogenesis of bacterial infections in various animal models. Necroptosis is advantageous to the host, but in some cases, it can be detrimental. To understand the impact of necroptosis on the pathogenesis of bacterial infections, we described the roles and molecular mechanisms of necroptosis caused by different bacterial infections in this review.

Acute lung injury: a view from the perspective of necroptosis

BACKGROUND

ALI/ARDS is a syndrome of acute onset characterized by progressive hypoxemia and noncardiogenic pulmonary edema as the primary clinical manifestations. Necroptosis is a form of programmed cell necrosis that is precisely regulated by molecular signals. This process is characterized by organelle swelling and membrane rupture, is highly immunogenic, involves extensive crosstalk with various cellular stress mechanisms, and is significantly implicated in the onset and progression of ALI/ARDS.

METHODS

The current body of literature on necroptosis and ALI/ARDS was thoroughly reviewed. Initially, an overview of the molecular mechanism of necroptosis was provided, followed by an examination of its interactions with apoptosis, pyroptosis, autophagy, ferroptosis, PANOptosis, and NETosis. Subsequently, the involvement of necroptosis in various stages of ALI/ARDS progression was delineated. Lastly, drugs targeting necroptosis, biomarkers, and current obstacles were presented.

CONCLUSION

Necroptosis plays an important role in the progression of ALI/ARDS. However, since ALI/ARDS is a clinical syndrome caused by a variety of mechanisms, we emphasize that while focusing on necroptosis, it may be more beneficial to treat ALI/ARDS by collaborating with other mechanisms.

The dance of macrophage death: the interplay between the inevitable and the microenvironment

Macrophages are highly plastic cells ubiquitous in various tissues, where they perform diverse functions. They participate in the response to pathogen invasion and inflammation resolution following the immune response, as well as the maintenance of homeostasis and proper tissue functions. Macrophages are generally considered long-lived cells with relatively strong resistance to numerous cytotoxic factors. On the other hand, their death seems to be one of the principal mechanisms by which macrophages perform their physiological functions or can contribute to the development of certain diseases. In this review, we scrutinize three distinct pro-inflammatory programmed cell death pathways - pyroptosis, necroptosis, and ferroptosis - occurring in macrophages under specific circumstances, and explain how these cells appear to undergo dynamic yet not always final changes before ultimately dying. We achieve that by examining the interconnectivity of these cell death types, which in macrophages seem to create a coordinated and flexible system responding to the microenvironment. Finally, we discuss the complexity and consequences of pyroptotic, necroptotic, and ferroptotic pathway induction in macrophages under two pathological conditions - atherosclerosis and cancer. We summarize damage-associated molecular patterns (DAMPs) along with other microenvironmental factors, macrophage polarization states, associated mechanisms as well as general outcomes, as such a comprehensive look at these correlations may point out the proper methodologies and potential therapeutic approaches.

Baicalin ameliorates deficient decidualization in URSA by regulating mitochondrial fission induced necroptosis

Unexplained recurrent spontaneous abortion (URSA) is a common complication of pregnancy that affects the health of pregnant women. Deficient endometrial decidualization has been associated with URSA. However, the underlying mechanism is poorly understood. This study aims to explore the mechanisms of mitochondrial fission induced necroptosis in deficient decidualization in URSA, and explore the regulation of baicalin on this mechanism. Initially, decidual tissues were collected from patients with URSA and health controls. Subsequently, in vitro induced decidualization model of Telomerase-Immortalized Human Endometrial Stromal Cells (T-hESCs) was constructed. Additionally, murine models of URSA (CBA/J × DBA/2) and normal pregnancy (CBA/J × BALB/c) were established, respectively. The level of decidualization, necroptosis, and mitochondrial fission of decidual tissues from clinical samples were detected. The function of mitochondrial fission on necroptosis during decidualization in T-hESCs was assessed by enhancing or inhibiting mitochondrial fission or necroptosis. Finally, CBA/J × DBA/2 pregnant mice were administrated with different doses of baicalin or saline, and the expression of mitochondrial fission, necroptosis, and decidualization markers were verified. The results of the study demonstrated a significant decrease in decidualization markers in the decidual tissues of URSA patients (P < 0.05), along with an increase in the incidence of cell necroptosis (P < 0.05) and hyperactive mitochondrial fission (P < 0.05). In vitro experiments, LPS was induced to trigger necroptosis of T-hESCs during induced decidualization, and decidualization markers IGFBP1 and PRL were subsequently decreased (P < 0.05). Besides, the mitochondrial fission agonist Tyrphostin A9 was found to promote the level of necroptosis (P < 0.05) and induced deficient decidualization (P < 0.05), which could be rescued by mitochondrial fission inhibitor Mdivi-1 and necroptosis inhibitor Nec-1 (P < 0.05). In addition, baicalin was shown to reduce hyperactive mitochondrial fission (P < 0.05), necroptosis (P < 0.05) and ameliorate deficient decidualization in vitro and in URSA murine models (P < 0.05). Collectively, baicalin shows potential in ameliorating deficient decidualization in URSA by inhibiting mitochondrial fission-triggered necroptosis.

Necroptosis does not drive disease pathogenesis in a mouse infective model of SARS-CoV-2 in vivo

Necroptosis, a type of lytic cell death executed by the pseudokinase Mixed Lineage Kinase Domain-Like (MLKL) has been implicated in the detrimental inflammation caused by SARS-CoV-2 infection. We minimally and extensively passaged a single clinical SARS-CoV-2 isolate to create models of mild and severe disease in mice allowing us to dissect the role of necroptosis in SARS-CoV-2 disease pathogenesis. We infected wild-type and MLKL-deficient mice and found no significant differences in viral loads or lung pathology. In our model of severe COVID-19, MLKL-deficiency did not alter the host response, ameliorate weight loss, diminish systemic pro-inflammatory cytokines levels, or prevent lethality in aged animals. Our in vivo models indicate that necroptosis is dispensable in the pathogenesis of mild and severe COVID-19.

ZBP1 activation triggers hematopoietic stem and progenitor cell death resulting in bone marrow failure in mice

Human bone marrow failure (BMF) syndromes result from the loss of hematopoietic stem and progenitor cells (HSPC), and this loss has been attributed to cell death; however, the cell death triggers, and mechanisms remain unknown. During BMF, tumor necrosis factor-α (TNFα) and interferon-γ (IFNγ) increase. These ligands are known to induce necroptosis, an inflammatory form of cell death mediated by RIPK1, RIPK3, and MLKL. We previously discovered that mice with a hematopoietic RIPK1 deficiency (Ripk1HEM KO) exhibit inflammation, HSPC loss, and BMF, which is partially ameliorated by a RIPK3 deficiency; however, whether RIPK3 exerts its effects through its function in mediating necroptosis or other forms of cell death remains unclear. Here, we demonstrate that similar to a RIPK3 deficiency, an MLKL deficiency significantly extends survival and like Ripk3 deficiency partially restores hematopoiesis in Ripk1HEM KO mice revealing that both necroptosis and apoptosis contribute to BMF in these mice. Using mouse models, we show that the nucleic acid sensor Z-DNA binding protein 1 (ZBP1) is up-regulated in mouse RIPK1-deficient bone marrow cells and that ZBP1's function in endogenous nucleic acid sensing is necessary for HSPC death and contributes to BMF. We also provide evidence that IFNγ mediates HSPC death in Ripk1HEM KO mice, as ablation of IFNγ but not TNFα receptor signaling significantly extends survival of these mice. Together, these data suggest that RIPK1 maintains hematopoietic homeostasis by preventing ZBP1 activation and induction of HSPC death.

Necroptosis in Pneumonia: Therapeutic Strategies and Future Perspectives

Pneumonia remains a major global health challenge, necessitating the development of effective therapeutic approaches. Recently, necroptosis, a regulated form of cell death, has garnered attention in the fields of pharmacology and immunology for its role in the pathogenesis of pneumonia. Characterized by cell death and inflammatory responses, necroptosis is a key mechanism contributing to tissue damage and immune dysregulation in various diseases, including pneumonia. This review comprehensively analyzes the role of necroptosis in pneumonia and explores potential pharmacological interventions targeting this cell death pathway. Moreover, we highlight the intricate interplay between necroptosis and immune responses in pneumonia, revealing a bidirectional relationship between necrotic cell death and inflammatory signaling. Importantly, we assess current therapeutic strategies modulating necroptosis, encompassing synthetic inhibitors, natural products, and other drugs targeting key components of the programmed necrosis pathway. The article also discusses challenges and future directions in targeting programmed necrosis for pneumonia treatment, proposing novel therapeutic strategies that combine antibiotics with necroptosis inhibitors. This review underscores the importance of understanding necroptosis in pneumonia and highlights the potential of pharmacological interventions to mitigate tissue damage and restore immune homeostasis in this devastating respiratory infection.

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.

Deubiquitylating Enzymes in Cancer and Immunity

Deubiquitylating enzymes (DUBs) maintain relative homeostasis of the cellular ubiquitome by removing the post-translational modification ubiquitin moiety from substrates. Numerous DUBs have been demonstrated specificity for cleaving a certain type of ubiquitin linkage or positions within ubiquitin chains. Moreover, several DUBs perform functions through specific protein-protein interactions in a catalytically independent manner, which further expands the versatility and complexity of DUBs' functions. Dysregulation of DUBs disrupts the dynamic equilibrium of ubiquitome and causes various diseases, especially cancer and immune disorders. This review summarizes the Janus-faced roles of DUBs in cancer including proteasomal degradation, DNA repair, apoptosis, and tumor metastasis, as well as in immunity involving innate immune receptor signaling and inflammatory and autoimmune disorders. The prospects and challenges for the clinical development of DUB inhibitors are further discussed. The review provides a comprehensive understanding of the multi-faced roles of DUBs in cancer and immunity.

Mechanisms underlying linear ubiquitination and implications in tumorigenesis and drug discovery

Linear ubiquitination is a distinct type of ubiquitination that involves attaching a head-to-tail polyubiquitin chain to a substrate protein. Early studies found that linear ubiquitin chains are essential for the TNFα- and IL-1-mediated NF-κB signaling pathways. However, recent studies have discovered at least sixteen linear ubiquitination substrates, which exhibit a broader activity than expected and mediate many other signaling pathways beyond NF-κB signaling. Dysregulation of linear ubiquitination in these pathways has been linked to many types of cancers, such as lymphoma, liver cancer, and breast cancer. Since the discovery of linear ubiquitin, extensive effort has been made to delineate the molecular mechanisms of how dysregulation of linear ubiquitination causes tumorigenesis and cancer development. In this review, we highlight newly discovered linear ubiquitination-mediated signaling pathways, recent advances in the role of linear ubiquitin in different types of cancers, and the development of linear ubiquitin inhibitors. Video Abstract.

A1 is induced by pathogen ligands to limit myeloid cell death and NLRP3 inflammasome activation

Programmed cell death pathways play an important role in innate immune responses to infection. Activation of intrinsic apoptosis promotes infected cell clearance; however, comparatively little is known about how this mode of cell death is regulated during infections and whether it can induce inflammation. Here, we identify that the pro-survival BCL-2 family member, A1, controls activation of the essential intrinsic apoptotic effectors BAX/BAK in macrophages and monocytes following bacterial lipopolysaccharide (LPS) sensing. We show that, due to its tight transcriptional and post-translational regulation, A1 acts as a molecular rheostat to regulate BAX/BAK-dependent apoptosis and the subsequent NLRP3 inflammasome-dependent and inflammasome-independent maturation of the inflammatory cytokine IL-1β. Furthermore, induction of A1 expression in inflammatory monocytes limits cell death modalities and IL-1β activation triggered by Neisseria gonorrhoeae-derived outer membrane vesicles (NOMVs). Consequently, A1-deficient mice exhibit heightened IL-1β production in response to NOMV injection. These findings reveal that bacteria can induce A1 expression to delay myeloid cell death and inflammatory responses, which has implications for the development of host-directed antimicrobial therapeutics.

Identification of PANoptosis-related biomarkers and immune infiltration characteristics in psoriasis

BACKGROUND

PANoptosis may play a vital role in psoriasis. We investigated the relationship between PANoptosis in psoriasis.

METHODS

Genes information was mainly obtained from GeneCards and the gene expression omnibus database. Genefunctions identification was based on gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses. Gene set enrichment analysis was used to identify enriched signaling pathways in psoriasis. We constructed PPI networks using the search tool for the retrieval of interacting genes database and Cytoscape and explored mRNA-miRNA, mRNA-TF, and mRNA-drug interaction networks. Receiver operating characteristic curves were performed to screen potential biomarkers among these hub genes. Immune cell infiltration was analyzed using the Pearson algorithm, and the correlation between immune-cell abundance and PANoptosis-related differentially expressed gene (PDGs) was investigated.

RESULTS

We identified 10 PDGs, which were mainly involved in pyroptosis, cytokine-mediated signaling pathways, Salmonella infection and NOD-like receptor signaling pathway. The activated pathways were mostly proinflammatory and immunoregulatory pathways between immune cells. BAK1, CASP4, IL18, and IRF1 were identified as hub genes in the mRNA-miRNA network, and BAK1, IRF1, and PYCARD were hub genes in the mRNA-TF network. CASP1 was found to be the most targeted gene by drugs or molecular compounds. We found PDGs were positively associated with proinflammatory immune cell infiltration and negatively associated with anti-inflammatory or regulatory immune cells.

CONCLUSION

We confirmed the role of PANoptosis in psoriasis for the first time and predicted hub genes and immune characteristics, which provides new ideas for further investigation of psoriasis on pathogenic mechanisms and therapeutic strategies.

Inflammation-related mRNA expression in patients with multiple myeloma undergoing hematopoietic stem cell mobilization

Mobilization of CD34+ cells is a key element in the therapy of patients with multiple myeloma undergoing autologous stem cell transplantation. The use of chemotherapy and the granulocyte colony-stimulating factor can significantly affect the expression of inflammation-related proteins and the migration of hematopoietic stem cells. We assessed the mRNA expression of selected proteins involved in the inflammatory landscape in MM patients (n=71). The aim of the study was to evaluate C-C motif chemokine ligand 3, 4, 5 (CCL3, CCL4, CCL5), leukocyte cell-derived chemotaxin 2 (LECT2), tumor necrosis factor (TNF), and formyl peptide receptor 2 (FPR2) levels in the course of mobilization and their role in the CD34+ collection efficacy. mRNA expression from peripheral blood plasma was evaluated by RT-PCR. We observed a deep decline in CCL3, CCL4, LECT2, and TNF mRNA expression on the day of the first apheresis (day A) as compared to baseline. A negative correlation was observed between CCL3, FPR2, LECT2, TNF level, and the CD34+ cells count in peripheral blood on day A, and the number of CD34+ cells obtained at first apheresis . Our results indicate that the investigated mRNAs significantly alter and may regulate the migration of CD34+ cells during mobilization. Moreover, in case of FPR2 and LECT2, the results obtained in patients differ from the murine models.

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.

Expansion of interferon inducible gene pool via USP18 inhibition promotes cancer cell pyroptosis

While immunotherapy has emerged as a breakthrough cancer therapy, it is only effective in some patients, indicating the need of alternative therapeutic strategies. Induction of cancer immunogenic cell death (ICD) is one promising way to elicit potent adaptive immune responses against tumor-associated antigens. Type I interferon (IFN) is well known to play important roles in different aspects of immune responses, including modulating ICD in anti-tumor action. However, how to expand IFN effect in promoting ICD responses has not been addressed. Here we show that depletion of ubiquitin specific protease 18 (USP18), a negative regulator of IFN signaling, selectively induces cancer cell ICD. Lower USP18 expression correlates with better survival across human selected cancer types and delays cancer progression in mouse models. Mechanistically, nuclear USP18 controls the enhancer landscape of cancer cells and diminishes STAT2-mediated transcription complex binding to IFN-responsive elements. Consequently, USP18 suppression not only enhances expression of canonical IFN-stimulated genes (ISGs), but also activates the expression of a set of atypical ISGs and NF-κB target genes, including genes such as Polo like kinase 2 (PLK2), that induce cancer pyroptosis. These findings may support the use of targeting USP18 as a potential cancer immunotherapy.

Pseudomonas aeruginosa Cytotoxins: Mechanisms of Cytotoxicity and Impact on Inflammatory Responses

Pseudomonas aeruginosa is one of the most virulent opportunistic Gram-negative bacterial pathogens in humans. It causes many acute and chronic infections with morbidity and mortality rates as high as 40%. P. aeruginosa owes its pathogenic versatility to a large arsenal of cell-associated and secreted virulence factors which enable this pathogen to colonize various niches within hosts and protect it from host innate immune defenses. Induction of cytotoxicity in target host cells is a major virulence strategy for P. aeruginosa during the course of infection. P. aeruginosa has invested heavily in this strategy, as manifested by a plethora of cytotoxins that can induce various forms of cell death in target host cells. In this review, we provide an in-depth review of P. aeruginosa cytotoxins based on their mechanisms of cytotoxicity and the possible consequences of their cytotoxicity on host immune responses.

SIRPα maintains macrophage homeostasis by interacting with PTK2B kinase in Mycobacterium tuberculosis infection and through autophagy and necroptosis

Background

To determine whether SIRPα can be a diagnostic marker of pulmonary tuberculosis (PTB) and the molecular mechanism of SIRPα regulating macrophages to kill Mycobacterium tuberculosis (MTB).

Methods

Meta-analysis combined with subsequent qRT-PCR, western-blotting and flow cytometry assay were used to detect SIRPα expression in PTB patients. Cell-based assays were used to explore the regulation of macrophage function by SIRPα. SIRPα^−/- and wide type macrophages transplanted C57BL/6J mice were used to determine the function of SIRPα on MTB infection in vivo.

Findings

SIRPα levels are closely correlated with the treatment outcomes among PTB patients. Cell-based assay demonstrated that MTB significantly induces the expression of SIRPα on macrophages. SIRPα deficiency enhances the killing ability of macrophages against MTB through processes that involve enhanced autophagy and reduced necroptosis of macrophages. Mechanistically, SIRPα forms a direct interaction with PTK2B through its intracellular C-terminal domain, thus inhibiting PTK2B activation in macrophages. Necroptosis inhibition due to SIRPα deficiency requires PTK2B activity. The transfer of SIRPα-deficient bone marrow-derived macrophages (BMDMs) into wild type mice resulted in a drop of bacterial load in the lungs but an enhancement of inflammatory lung damage, and the combination of ulinastatin and SIRPα^−/−→WT treatment could decrease the inflammation and maintain the bactericidal capacity.

Interpretation

Our data define SIRPα a novel biomarker for tuberculosis infection and underlying mechanisms for maintaining macrophage homeostasis.

Funding

This work was financially supported by the Chinese National Natural Science Foundation project (No.81401635). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

The resurrection of RIP kinase 1 as an early cell death checkpoint regulator-a potential target for therapy in the necroptosis era

Receptor-interacting serine threonine protein kinase 1 (RIPK1) has emerged as a central molecular switch in controlling the balance between cell survival and cell death. The pro-survival role of RIPK1 in maintaining cell survival is achieved via its ability to induce NF-κB-dependent expression of anti-apoptotic genes. However, recent advances have identified the pro-death function of RIPK1: posttranslational modifications of RIPK1 in the tumor necrosis factor receptor 1 (TNFR1)-associated complex-I, in the cytosolic complex-IIb or in necrosomes regulate the cytotoxic potential of RIPK1, forming an early cell death checkpoint. Since the kinase activity of RIPK1 is indispensable in RIPK3- and MLKL-mediated necroptosis induction, while it is dispensable in apoptosis, a better understanding of this early cell death checkpoint via RIPK1 might lead to new insights into the molecular mechanisms controlling both apoptotic and necroptotic modes of cell death and help develop novel therapeutic approaches for cancer. Here, we present an emerging view of the regulatory mechanisms for RIPK1 activity, especially with respect to the early cell death checkpoint. We also discuss the impact of dysregulated RIPK1 activity in pathophysiological settings and highlight its therapeutic potential in treating human diseases.

Improved understanding of the molecular mechanisms that allow a protein to control the balance between cell survival or early death could reveal new approaches to treating conditions including chronic inflammatory disease and cancer. Gang Min Hur and colleagues at Chungnam National University in Daejeon, South Korea, with Han-Ming Shen at the University of Macau in China, review emerging evidence about how the protein called receptor-interacting serine/threonine-protein kinase 1 (RIPK1) influences whether cells move towards death or survival at a key ‘checkpoint’ in cell development. Cells can undergo a natural process of programmed cell death called apoptosis, die abnormally in a disease process called necroptosis, or survive. RIPK1 appears able to influence which path is chosen depending on which genes it regulates and which proteins it interacts with. Many details are still unclear, and need further investigation.

The regulation of necroptosis by ubiquitylation

Necroptosis is a programmed necrosis that is mediated by receptor-interacting protein kinases RIPK1, RIPK3 and the mixed lineage kinase domain-like protein, MLKL. Necroptosis must be strictly regulated to maintain normal tissue homeostasis, and dysregulation of necroptosis leads to the development of various inflammatory, infectious, and degenerative diseases. Ubiquitylation is a widespread post-translational modification that is essential for balancing numerous physiological processes. Over the past decade, considerable progress has been made in the understanding of the role of ubiquitylation in regulating necroptosis. Here, we will discuss the regulatory functions of ubiquitylation in necroptosis signaling pathway. An enhanced understanding of the ubiquitylation enzymes and regulatory proteins in necroptotic signaling pathway will be exploited for the development of new therapeutic strategies for necroptosis-related diseases.

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.

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.

Pleural Resident Macrophages and Pleural IRA B Cells Promote Efficient Immunity Against Pneumonia by Inducing Early Pleural Space Inflammation

Airway infection is a major cause of mortality worldwide. The identification of new mechanisms aiding in effective host immune response is therefore required. Here, we show that the specific depletion of the pleural immune cell compartment during bacterial pneumonia resulted in a reduced pulmonary immune response and increased mortality in mice. Bacterial airway infection provoked early pleural space (PS) inflammation characterized by innate response activator (IRA) B cell development and pleural large resident macrophage (LRM) necroptosis, the repopulation of LRMs being driven by cellular proliferation in situ. Necroptotic LRMs amplified PS inflammation by stimulating pleural Mincle-expressing macrophages whereas IRA B cells contributed partially to GM-CSF-induced PS inflammation. Upon pulmonary infection, the induction of PS inflammation resulted in reduced bacterial burden whereas the specific depletion of pleural resident macrophages led to increased mortality and bacterial burden and reduced pulmonary immunity. Moreover, mice in which B cells were unable to produce GM-CSF exhibited reduced CD103⁺ dendritic cells and reduced CD4⁺ T cell numbers in the draining lymph node. Altogether, our results describe a previously unrecognized mechanism of pleural space inflammation necessary for effective protection against bacterial airway infection.

Caspase-8 has dual roles in regulatory T cell homeostasis balancing immunity to infection and collateral inflammatory damage

Targeting the potent immunosuppressive properties of FOXP3⁺ regulatory T cells (T_regs) has substantial therapeutic potential for treating autoimmune and inflammatory diseases. Yet, the molecular mechanisms controlling T_reg homeostasis, particularly during inflammation, remain unclear. We report that caspase-8 is a central regulator of T_reg homeostasis in a context-specific manner that is decisive during immune responses. In mouse genetic models, targeting caspase-8 in T_regs led to accumulation of effector T_regs resistant to apoptotic cell death. Conversely, inflammation induced the MLKL-dependent necroptosis of caspase-8-deficient lymphoid and tissue T_regs, which enhanced immunity to a variety of chronic infections to promote clearance of viral or parasitic pathogens. However, improved immunity came at the risk of lethal inflammation in overwhelming infections. Caspase-8 inhibition using a clinical-stage compound revealed that human T_regs have heightened sensitivity to necroptosis compared with conventional T cells. These findings reveal a fundamental mechanism in T_regs that could be targeted to manipulate the balance between immune tolerance versus response for therapeutic benefit.

Application of Regulatory Cell Death in Cancer: Based on Targeted Therapy and Immunotherapy

The development of cancer treatment methods is constantly changing. For common cancers, our treatment methods are still based on conventional treatment methods, such as chemotherapy, radiotherapy, and targeted drug therapy. Nevertheless, the emergence of tumor resistance has a negative impact on treatment. Regulated cell death is a gene-regulated mode of programmed cell death. After receiving specific signal transduction, cells change their physical and chemical properties and the extracellular microenvironment, resulting in structural destruction and decomposition. As research accumulates, we now know that by precisely inducing specific cell death patterns, we can treat cancer with less collateral damage than other treatments. Many newly discovered types of RCD are thought to be useful for cancer treatment. However, some experimental results suggest that some RCDs are not sensitive to cancer cell death, and some may even promote cancer progression. This review summarizes the discovered types of RCDs, reviews their clinical efficacy in cancer treatment, explores their anticancer mechanisms, and discusses the feasibility of some newly discovered RCDs for cancer treatment in combination with the immune and tumor microenvironment.

Immune dysregulation in SHARPIN-deficient mice is dependent on CYLD-mediated cell death

SHARPIN, together with RNF31/HOIP and RBCK1/HOIL1, form the linear ubiquitin chain assembly complex (LUBAC) E3 ligase that catalyzes M1-linked polyubiquitination. Mutations in RNF31/HOIP and RBCK/HOIL1 in humans and Sharpin in mice lead to autoinflammation and immunodeficiency, but the mechanism underlying the immune dysregulation remains unclear. We now show that the phenotype of the Sharpincpdm/cpdm mice is dependent on CYLD, a deubiquitinase previously shown to mediate removal of K63-linked polyubiquitin chains. Dermatitis, disrupted splenic architecture, and loss of Peyer's patches in the Sharpincpdm/cpdm mice were fully reversed in Sharpincpdm/cpdm Cyld-/- mice. We observed enhanced association of RIPK1 with the death-signaling Complex II following TNF stimulation in Sharpincpdm/cpdm cells, a finding dependent on CYLD since we observed reversal in Sharpincpdm/cpdm Cyld-/- cells. Enhanced RIPK1 recruitment to Complex II in Sharpincpdm/cpdm cells correlated with impaired phosphorylation of CYLD at serine 418, a modification reported to inhibit its enzymatic activity. The dermatitis in the Sharpincpdm/cpdm mice was also ameliorated by the conditional deletion of Cyld using LysM-cre or Cx3cr1-cre indicating that CYLD-dependent death of myeloid cells is inflammatory. Our studies reveal that under physiological conditions, TNF- and RIPK1-dependent cell death is suppressed by the linear ubiquitin-dependent inhibition of CYLD. The Sharpincpdm/cpdm phenotype illustrates the pathological consequences when CYLD inhibition fails.

miR-130-CYLD Axis Is Involved in the Necroptosis and Inflammation Induced by Selenium Deficiency in Pig Cerebellum

Selenium (Se) is an essential trace element in creatures which deficiency can cause necroptosis and inflammation of multiple tissues. MicroRNAs (miRNAs) have been identified to participate multiple biological processes by regulating the expression of target genes. In the present study, the Se-deficient pig cerebellar model was established and conducted by light microscopy, qRT-PCR, and Western blot. Morphological observation exhibited necrosis-like lesions and inflammatory infiltration in the cerebellum of the Se-deficient group. Quantitative analysis result showed that Se deficiency significantly suppressed miR-130 expression, which in turn disinhibited the expression of CYLD. Meanwhile, in comparison to the control group, the expression levels of TNF-α pathway genes (TNF-α, TNFR1, and NF-κB p65) and necroptosis-related genes (RIPK1, RIPK3, and MLKL) in Se deficiency group were obviously increased (P < 0.05). Moreover, Se deficiency induced the occurrence of inflammation by upregulating the expression of inflammatory cytokines (IL-1β, IL-2, IL-8, IL-18, IFN-γ, COX-2, PTGEs, and NLRP3). In conclusion, we proved Se deficiency could induce the deregulation of miR-130-CYLD axis to cause RIPK3-dependent necroptosis and inflammation in pig cerebellum.

Cullin Deneddylation Suppresses the Necroptotic Pathway in Cardiomyocytes

Cardiomyocyte death in the form of apoptosis and necrosis represents a major cellular mechanism underlying cardiac pathogenesis. Recent advances in cell death research reveal that not all necrosis is accidental, but rather there are multiple forms of necrosis that are regulated. Necroptosis, the earliest identified regulated necrosis, is perhaps the most studied thus far, and potential links between necroptosis and Cullin-RING ligases (CRLs), the largest family of ubiquitin E3 ligases, have been postulated. Cullin neddylation activates the catalytic dynamic of CRLs; the reverse process, Cullin deneddylation, is performed by the COP9 signalosome holocomplex (CSN) that is formed by eight unique protein subunits, COPS1/CNS1 through COPS8/CNS8. As revealed by cardiomyocyte-restricted knockout of Cops8 (Cops8-cko) in mice, perturbation of Cullin deneddylation in cardiomyocytes impairs not only the functioning of the ubiquitin-proteasome system (UPS) but also the autophagic-lysosomal pathway (ALP). Similar cardiac abnormalities are also observed in Cops6-cko mice; and importantly, loss of the desmosome targeting of COPS6 is recently implicated as a pathogenic factor in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). Cops8-cko causes massive cardiomyocyte death in the form of necrosis rather than apoptosis and rapidly leads to a progressive dilated cardiomyopathy phenotype as well as drastically shortened lifespan in mice. Even a moderate downregulation of Cullin deneddylation as seen in mice with Cops8 hypomorphism exacerbates cardiac proteotoxicity induced by overexpression of misfolded proteins. More recently, it was further demonstrated that cardiomyocyte necrosis caused by Cops8-cko belongs to necroptosis and is mediated by the RIPK1-RIPK3 pathway. This article reviews these recent advances and discusses the potential links between Cullin deneddylation and the necroptotic pathways in hopes of identifying potentially new therapeutic targets for the prevention of cardiomyocyte death.

MLKL in cancer: more than a necroptosis regulator

Mixed lineage kinase domain-like protein (MLKL) emerged as executioner of necroptosis, a RIPK3-dependent form of regulated necrosis. Cell death evasion is one of the hallmarks of cancer. Besides apoptosis, some cancers suppress necroptosis-associated mechanisms by for example epigenetic silencing of RIPK3 expression. Conversely, necroptosis-elicited inflammation by cancer cells can fuel tumor growth. Recently, necroptosis-independent functions of MLKL were unraveled in receptor internalization, ligand-receptor degradation, endosomal trafficking, extracellular vesicle formation, autophagy, nuclear functions, axon repair, neutrophil extracellular trap (NET) formation, and inflammasome regulation. Little is known about the precise role of MLKL in cancer and whether some of these functions are involved in cancer development and metastasis. Here, we discuss current knowledge and controversies on MLKL, its structure, necroptosis-independent functions, expression, mutations, and its potential role as a pro- or anti-cancerous factor. Analysis of MLKL expression patterns reveals that MLKL is upregulated by type I/II interferon, conditions of inflammation, and tissue injury. Overall, MLKL may affect cancer development and metastasis through necroptosis-dependent and -independent functions.

Deubiquitinases: Modulators of Different Types of Regulated Cell Death

The mechanisms and physiological implications of regulated cell death (RCD) have been extensively studied. Among the regulatory mechanisms of RCD, ubiquitination and deubiquitination enable post-translational regulation of signaling by modulating substrate degradation and signal transduction. Deubiquitinases (DUBs) are involved in diverse molecular pathways of RCD. Some DUBs modulate multiple modalities of RCD by regulating various substrates and are powerful regulators of cell fate. However, the therapeutic targeting of DUB is limited, as the physiological consequences of modulating DUBs cannot be predicted. In this review, the mechanisms of DUBs that regulate multiple types of RCD are summarized. This comprehensive summary aims to improve our understanding of the complex DUB/RCD regulatory axis comprising various molecular mechanisms for diverse physiological processes. Additionally, this review will enable the understanding of the advantages of therapeutic targeting of DUBs and developing strategies to overcome the side effects associated with the therapeutic applications of DUB modulators.

Positive regulation of TNFR1 signaling via SH3 recognition motif

TNF is a pleiotropic cytokine and shows its biological function by binding to its receptors called TNFR1 and TNFR2. While TNFR1 induces apoptosis by activation of caspase-8 via the “death domain”, it also activates IKKα/β, MKK3/6, MKK4/7 by activation of TAK1. Although the TNFR1 signaling pathway is known by in large, it is not known how AKT and MAPKs p38, ERK1/2, and JNK1/2 are activated. The presence of a proline-rich PPAP region, (P448PAP451, a binding site for the SH3 domain-containing proteins) very close to the C-terminus promoted us to determine whether this region has any role in the TNFR1 signal transduction. To test this, the codons of P448 and P451 were changed to that of Alanin, GCG, via site-directed mutagenesis, and this plasmid was named as TNFR1-SH3-P/A. Subsequently, ectopically expressed the wild type TNFR1 and TNFR1-SH3-P/A in 293T cells and determined the levels of TNF-α-mediated phosphorylations of ERK, p38, JNK and AKT, NF-kB, and caspase-8 activation. While ectopic expression of our mutant diminished TNFα-mediated phosphorylations of p38, JNK, ERK and AKT, it increased NF-kB, and caspase-8 activations. In conclusion, TNFα-mediated ERK, AKT, JNK, p38 activations are affected by TNFR1 SH3 domain modifications.

Down-regulation of cylindromatosis protein phosphorylation by BTK inhibitor promotes apoptosis of non-GCB-diffuse large B-cell lymphoma

BACKGROUND

Non-germinal center B-cell-like diffuse large B-cell lymphoma (non-GCB-DLBCL) has worse clinical outcome than GCB-DLBCL, and some relapsed/refractory non-GCB-DLBCL (R/R non-GCB-DLBCL) are even resistant to CD20 monoclonal antibody (rituximab). Bruton's tyrosine kinase inhibitors (BTKis) are new drugs for B-cell lymphoma. BTKis can promote apoptosis of DLBCL by inactivating nuclear transcription factor κB (NFκB) signaling pathway. Cylindromatosis (CYLD) is a tumor suppressor and ubiquitinase. CYLD can inactivate NFκB signaling pathway through ubiquitination and regulate the apoptosis of hematological tumors. The ubiquitination of CYLD can be regulated by phosphorylation, suggesting that the regulation of CYLD phosphorylation can be a potential mechanism to promote the apoptosis of hematological tumors. Therefore, we hypothesized that BTKis could promote the apoptosis of non-GCB-DLBCL by regulating the phosphorylation of CYLD, especially in rituximab resistant cases, and we proved this hypothesis through both in vivo and in vitro experiments.

METHODS

The baseline expression levels of CYLD phosphorylation in non-GCB-DLBCL patients and cell lines were detected by Western Blotting. The non-GCB-DLBCL cell lines were treated with BTKis, and apoptosis induced by BTKis treatment was detected by Western blotting, cell viability assay and Annexin V assay. To verify whether the effect of BTKis on apoptosis in non-GCN-DLBCL cells is CYLD dependent, the expression of CYLD was knocked down by lentiviral shRNAs. To verify the effect of BTKis on the phosphorylation of CYLD and the apoptosis in vivo and in rituximab resistant non-GCB-DLBCL, the xeograft model and rituximab resistant non-GCB-DLBCL cells were generated by tumor cell inoculation and escalation of drug concentrations, respectively.

RESULTS

BTKis induced apoptosis by down-regulating CYLD phosphorylationin in non GCB-DLBCL, xenograft mouse model, and rituximab-resistant cells, and this effect could be enhanced by rituximab. Knocking-down CYLD reversed apoptosis which was induced by BTKis. BTKis induced CYLD-dependent apoptosis in non-GCB-DLBCL including in rituximab-resistant cells.

CONCLUSIONS

The present results indicated that CYLD phosphorylation is a potential clinical therapeutic target for non-GCB-DLBCL, especially for rituximab-resistant relapsed/refractory cases.

The regulation of necroptosis by post-translational modifications

Necroptosis is a caspase-independent, lytic form of programmed cell death whose errant activation has been widely implicated in many pathologies. The pathway relies on the assembly of the apical protein kinases, RIPK1 and RIPK3, into a high molecular weight cytoplasmic complex, termed the necrosome, downstream of death receptor or pathogen detector ligation. The necrosome serves as a platform for RIPK3-mediated phosphorylation of the terminal effector, the MLKL pseudokinase, which induces its oligomerization, translocation to, and perturbation of, the plasma membrane to cause cell death. Over the past 10 years, knowledge of the post-translational modifications that govern RIPK1, RIPK3 and MLKL conformation, activity, interactions, stability and localization has rapidly expanded. Here, we review current knowledge of the functions of phosphorylation, ubiquitylation, GlcNAcylation, proteolytic cleavage, and disulfide bonding in regulating necroptotic signaling. Post-translational modifications serve a broad array of functions in modulating RIPK1 engagement in, or exclusion from, cell death signaling, whereas the bulk of identified RIPK3 and MLKL modifications promote their necroptotic functions. An enhanced understanding of the modifying enzymes that tune RIPK1, RIPK3, and MLKL necroptotic functions will prove valuable in efforts to therapeutically modulate necroptosis.

An intestinal organoid-based platform that recreates susceptibility to T-cell-mediated tissue injury

A goal in precision medicine is to use patient-derived material to predict disease course and intervention outcomes. Here, we use mechanistic observations in a preclinical animal model to design an ex vivo platform that recreates genetic susceptibility to T-cell-mediated damage. Intestinal graft-versus-host disease (GVHD) is a life-threatening complication of allogeneic hematopoietic cell transplantation. We found that intestinal GVHD in mice deficient in Atg16L1, an autophagy gene that is polymorphic in humans, is reversed by inhibiting necroptosis. We further show that cocultured allogeneic T cells kill Atg16L1-mutant intestinal organoids from mice, which was associated with an aberrant epithelial interferon signature. Using this information, we demonstrate that pharmacologically inhibiting necroptosis or interferon signaling protects human organoids derived from individuals harboring a common ATG16L1 variant from allogeneic T-cell attack. Our study provides a roadmap for applying findings in animal models to individualized therapy that targets affected tissues.

Deubiquitylases in developmental ubiquitin signaling and congenital diseases

Metazoan development from a one-cell zygote to a fully formed organism requires complex cellular differentiation and communication pathways. To coordinate these processes, embryos frequently encode signaling information with the small protein modifier ubiquitin, which is typically attached to lysine residues within substrates. During ubiquitin signaling, a three-step enzymatic cascade modifies specific substrates with topologically unique ubiquitin modifications, which mediate changes in the substrate's stability, activity, localization, or interacting proteins. Ubiquitin signaling is critically regulated by deubiquitylases (DUBs), a class of ~100 human enzymes that oppose the conjugation of ubiquitin. DUBs control many essential cellular functions and various aspects of human physiology and development. Recent genetic studies have identified mutations in several DUBs that cause developmental disorders. Here we review principles controlling DUB activity and substrate recruitment that allow these enzymes to regulate ubiquitin signaling during development. We summarize key mechanisms of how DUBs control embryonic and postnatal differentiation processes, highlight developmental disorders that are caused by mutations in particular DUB members, and describe our current understanding of how these mutations disrupt development. Finally, we discuss how emerging tools from human disease genetics will enable the identification and study of novel congenital disease-causing DUBs.

The deubiquitinase CYLD controls protective immunity against helminth infection by regulation of Treg cell plasticity

BACKGROUND

Type 2 immunity can be modulated by regulatory T (Treg) cell activity. It has been suggested that the deubiquitinase cylindromatosis (CYLD) plays a role in the development or function of Treg cells, implying that it could be important for normal protective immunity, where type 2 responses are prevalent.

OBJECTIVE

We sought to investigate the role of CYLD in Treg cell function and T_H2 cell immune responses under steady-state conditions and during helminth infection.

METHODS

Foxp3-restricted CYLD conditional knockout (KO) mice were examined in mouse models of allergen-induced airway inflammation and Nippostrongylus brasiliensis infection. We performed multiplex magnetic bead assays, flow cytometry, and quantitative PCR to understand how a lack of CYLD affected cytokine production, homing, and suppression in Treg cells. Target genes regulated by CYLD were identified and validated by microarray analysis, coimmunoprecipitation, short hairpin RNA knockdown, and transfection assays.

RESULTS

Treg cell-specific CYLD KO mice showed severe spontaneous pulmonary inflammation with increased migration of Treg cells into the lung. CYLD-deficient Treg cells furthermore produced high levels of IL-4 and failed to suppress allergen-induced lung inflammation. Supporting this, the conditional KO mice displayed enhanced protection against N brasiliensis infection by contributing to type 2 immunity. Treg cell conversion into IL-4-producing cells was due to augmented mitogen-activated protein kinase and nuclear factor κB signaling. Moreover, Scinderin, a member of the actin-binding gelsolin family, was highly upregulated in CYLD-deficient Treg cells, and controlled IL-4 production through forming complexes with mitogen-activated protein kinase kinase/extracellular receptor kinase. Correspondingly, both excessive IL-4 production in vivo and the protective role of CYLD-deficient Treg cells against N brasiliensis were reversed by Scinderin ablation.

CONCLUSIONS

Our findings indicate that CYLD controls type 2 immune responses by regulating Treg cell conversion into T_H2 cell-like effector cells, which potentiates parasite resistance.

Necroptotic movers and shakers: cell types, inflammatory drivers and diseases

The necroptotic cell death pathway has received significant attention for its ability to trigger inflammatory responses and its potential involvement in related conditions. Recent insights into the essential membrane damaging necroptotic pseudokinase effector, Mixed lineage kinase domain like (MLKL), have revealed a number of diverse MLKL functions that contribute to the inflammatory nature of necroptosis. Here we review distinct MLKL signalling roles and document the immunogenic molecules released by necroptosis. We discuss specific in vivo MLKL-driven responses, the activation of inflammasome complexes and innate lymphoid cells, which have been documented to drive disease. Finally, we list necroptotic competent cell types and their involvement in MLKL-driven cell death-associated and inflammatory-associated conditions.

Importance of Deubiquitination in Macrophage-Mediated Viral Response and Inflammation

Ubiquitination and deubiquitination play a fundamental role in the signaling pathways associated with innate and adaptive immune responses. Macrophages are key sentinels for the host defense, triggering antiviral and inflammatory responses against various invading pathogens. Macrophages recognize the genetic material of these pathogens as pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) through the activation of its pattern recognition receptors (PRRs), initiating the cascade of immune signaling, which leads to the production of pro- and anti-inflammatory cytokines that initiates the appropriate immune response. Macrophage-mediated immune response is highly regulated and tightly controlled by the ubiquitin system since its abnormal activation or dysregulation may result in the severe pathogenesis of numerous inflammatory and autoimmune diseases. Deubiquitinating enzymes (DUBs) play a crucial role in reversing the ubiquitination and controlling the magnitude of the immune response. During infection, pathogens manipulate the host defense system by regulating DUBs to obtain nutrients and increase proliferation. Indeed, the regulation of DUBs by small molecule inhibitors has been proposed as an excellent way to control aberrant activation of immune signaling molecules. This review is focused on the complex role of DUBs in macrophage-mediated immune response, exploring the potential use of DUBs as therapeutic targets in autoimmune and inflammatory diseases by virtue of small molecule DUB inhibitors.

Crosstalk between cGAS-STING signaling and cell death

Cytosolic nucleic acid sensors have a critical role in detecting endogenous nucleic acids to initiate innate immune responses during microbial infections and/or cell death. Several seminal studies over the past decade have delineated the conserved mechanism of cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) and the downstream signaling adapter stimulator of interferon genes (STING) in mediating innate immune signaling pathways as a host defense mechanism. Besides the predominant role in microbial infections and inflammatory diseases, there is an increased attention on alternative functional responses of cGAS-STING-mediated signaling. Here we review the complexity of interactions between the cGAS-STING signaling and cell death pathways. A better understanding of molecular mechanisms of this interplay is important with regard to the development of new therapeutics targeting cGAS-STING signaling in cancer, infectious, and chronic inflammatory diseases.

CYLD expression in dendritic cells involved in the immunoregulation of pulmonary adenocarcinoma via NF-κB pathway

Our previous study found that IL33 repressed the growth of pulmonary adenocarcinoma (PA) via regulation of dendritic cells (DCs). However, the molecular mechanism of DCs in PA is still unclear. The present work showed that CYLD^-/- mice have a shorter survival rate of PA, and knockout CYLD in DCs also repress the progression of PA in mice. Subsequently, we found that decreased expression and reduced the nuclear translocation of NF-κB signalling was observed in CYLD knockout DCs, and inhibiting NF-κB pathway repressed DCs-induced proliferation and function of CD4⁺ T cells. These results indicated that CYLD function as a tumour suppresser in PA via regulates the function of DCs through NF-κB signalling pathway. Our findings support that CYLD serves as a potential target for immunotherapy in PA.

RIPK1 polymorphisms alter the susceptibility to cervical Cancer among the Uyghur population in China

Background

RIPK1 (receptor-interacting protein kinase-1) plays a role in cancer development, whereas no clear studies focused on the cervical cancer. The objective of this study was to evaluate the relationship between RIPK1 polymorphisms and cervical cancer risk among the Uyghur population.

Methods

We performed a case-control study including 342 cervical cancer patients and 498 age-matched healthy controls. Four RIPK1 genetic variants (rs6907943, rs2077681, rs9503400 and rs17548629) were genotyped with Agena MassARRAY platform. The associations between RIPK1 polymorphisms and cervical cancer risk were assessed under Binary logistic regression models. False discovery rate (FDR) was used to improve the results reliability.

Results

The results showed rs2077681 was significantly associated with cervical cancer risk under various genetic models (codominant: OR = 3.14, 95% CI = 1.40–7.07, p = 0.006, FDR-p = 0.018; recessive: OR = 3.20, 95% CI = 1.43–7.16, p = 0.005, FDR-0.018). The stratified analysis indicated that the relationships of rs6907946, rs9503400 and rs17548629 with cervical cancer risk were statistically significant in the subgroup of clinical stage (p < 0.05).

Conclusion

Our findings demonstrated that RIPK1 polymorphisms were associated with cervical cancer susceptibility among the Uyghur population in China, and RIPK1 polymorphisms might be involved in the development of cervical cancer.

Negative Regulation of TNFR1 Signaling Via PKA-Mediated Phosphorylation of TNFR1

Tumor necrosis factor alpha (TNF-α) plays a paramount role in homeostasis by inducing tumor cytotoxicity and activating immune system. The signaling complexes formed by TNFR1 to activate JNK, p38, and nuclear factor-kappa B pathways and to subsequently induce apoptosis and necroptosis are well known. However, this "canonical TNF-α signaling" does not explain how ERK, AKT, and STAT3 can be activated by TNF-α. In addition, little to nothing is known about negative regulation of TNFR1 signaling. Because cyclic AMP-activated kinase (PKA) shows anti-TNF and anti-inflammatory activities, we postulated that PKA might affect TNF-α signaling by directly phosphorylating TNFR1. In line with this, we identified 2 putative PKA-phosphorylation motifs RRRT₄₁₁ and REAT₄₁₇ within the death domain of TNFR1, and investigated whether "canonical" and "noncanonical" TNFR1 signaling is regulated by modifications of T411 and T417. In this study, we demonstrate for the first time that PKA directly binds to and phosphorylates TNFR1 after TNF-α stimulation. To further support our hypothesis, we generated alanine and phosphomimetic (aspartic acid) mutants of TNFR1 at positions T411 and T417, ectopically expressed these mutants, and determined their influence on TNF-α-induced activations of ERKs, AKT, STAT3, p38α, and JNK1/2. Our results clearly showed that phosphomimetic mutants significantly suppressed and alanine mutants augmented TNF-α-induced phosphorylations of ERKs, AKT, Stat3, p38α, and JNKs. These findings strongly suggest that PKA-mediated phosphorylation of T411 and T417 of TNFR1 interferes with both "canonical" and "noncanonical" TNF-α signaling. [Figure: see text].