Tyrosine phosphorylation regulates RIPK1 activity to limit cell death and inflammation

Geniposide protects against cerebral ischemic injury by targeting SOX2/RIPK1 axis

Convincing evidence has indicated that geniposide possesses neuroprotective effects in ischemic stroke. This study is designed to explore the potential molecular mechanism of geniposide in oxygen-glucose deprivation/reoxygenation (OGD/R)-treated BV-2 microglial cells and middle cerebral artery occlusion (MCAO) mice. OGD/R model in BV2 microglial cells was established in this research. Cell viability and apoptosis were determined using Cell Counting Kit-8 (CCK-8) and flow cytometry assays. Protein levels of B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), microtubule-associated protein light chain 3 (LC3)-II/LC3-I, Beclin-1, inducible nitric oxide synthase (iNOS), CD86, sex determining region Y-box 2 (SOX2), receptor-interacting serine/threonine-protein kinase 1 (RIPK1), TNF-α, IL-1β, ARG1, and CD163 were detected by western blot assay. RIPK1 mRNA level was determined using real-time quantitative polymerase chain reaction (RT-qPCR). TNF-α and IL-1β levels were analyzed using ELISA kits. After JASPAR analysis, binding between SOX2 and RIPK1 promoter was predicted and verified using chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays. The effects of geniposide on cerebral ischemic injury were assessed using MCAO mice in vivo. Geniposide treatment relieved OGD/R-triggered BV-2 cell viability promotion and apoptosis, autophagy, inflammatory response, and M1 polarization inhibition in vitro. SOX2 and RIPK1 expression was decreased in OGD/R-treated BV-2 cells. In mechanism, SOX2 upregulated RIPK1 transcription by binding to the RIPK1 promoter region. Geniposide administration significantly alleviated cerebral ischemic injury in MCAO mice in vivo. Geniposide administration protects against cerebral ischemic injury through regulating the SOX2/RIPK1 axis, providing a potential direction for the application of geniposide in the treatment of ischemic stroke.

The Role of Post-Translational Modifications in Necroptosis

Necroptosis, a distinct form of regulated necrosis implicated in various human pathologies, is orchestrated through sophisticated signaling pathways. During this process, cells undergoing necroptosis exhibit characteristic necrotic morphology and provoke substantial inflammatory responses. Post-translational modifications (PTMs)-chemical alterations occurring after protein synthesis that critically regulate protein functionality-constitute essential regulatory components within these complex signaling cascades. This intricate crosstalk between necroptotic pathways and PTM networks presents promising therapeutic opportunities. Our comprehensive review systematically analyzes the molecular mechanisms underlying necroptosis, with particular emphasis on the regulatory roles of PTMs in signal transduction. Through systematic evaluation of key modifications including ubiquitination, phosphorylation, glycosylation, methylation, acetylation, disulfide bond formation, caspase cleavage, nitrosylation, and SUMOylation, we examine potential therapeutic applications targeting necroptosis in disease pathogenesis. Furthermore, we synthesize current pharmacological strategies for manipulating PTM-regulated necroptosis, offering novel perspectives on clinical target development and therapeutic intervention.

Phosphorylation of PA at serine 225 enhances viral fitness of the highly pathogenic H5N1 avian influenza virus in mice

Currently, there is increasing spillover of highly pathogenic H5N1 avian influenza virus (AIV) to mammals, raising a concern of pandemic threat about this virus. Although the function of PA protein of the influenza virus is well understood, the understanding of how phosphorylation regulates this protein and influenza viral life cycle is still limited. We previously identified PA S225 as the phosphorylation site in the highly pathogenic H5N1 AIV. In this study, we investigated the role of phosphorylation in regulating PA function and viral fitness through dephosphorylation (PA S225A) or continuous phosphorylation (PA S225E)-mimetic mutation of PA S225. Structure analysis revealed that PA S225A or PA S225E mutation had no obvious effect on the structure of PA protein. Replication assay in vitro showed that PA S225A phosphorylation-ablative mutation significantly inhibited virus replication both in mammalian and avian-derived cells, while PA S225E enhanced viral replication in these cells. Correspondingly, PA S225A dephosphorylation significantly attenuated viral replication and virulence in mice, while PA S225E enhanced these aspects in mice. Mechanistically, PA S225A mutation significantly decreased viral polymerase activity, disabled viral ribonucleoprotein complex (vRNP) assembly and attenuated PA nuclear accumulation. Altogether, our study directly suggested that phosphorylation of PA protein at site S225 enhances viral fitness of the highly pathogenic H5N1 virus in mammals by assuring effective vRNP activity, providing a framework for further study of phosphorylation events in influenza virus life cycle.

Neuronal Injury after Ischemic Stroke: Mechanisms of Crosstalk Involving Necroptosis

Ischemic stroke is a leading cause of disability and death worldwide, largely due to its increasing incidence associated with an aging population. This condition results from arterial obstruction, significantly affecting patients' quality of life and imposing a substantial economic burden on healthcare systems. While current treatments primarily focus on the rapid restoration of blood flow through thrombolytic therapy or surgical interventions, a limited understanding of neuronal injury mechanisms hampers the development of more effective treatments.This article explores the interplay among various cell death pathways-necroptosis, apoptosis, autophagy, ferroptosis, and pyroptosis-in the context of ischemic stroke to identify novel therapeutic targets. Each mode of cell death displays unique characteristics and roles post-stroke, and the activation of these pathways may vary across different animal models, complicating the translation of therapeutic strategies to clinical settings. Notably, the interaction between apoptosis and necroptosis is highlighted; inhibiting apoptosis might heighten the risk of necroptosis. Therefore, a balanced regulation of these pathways could promote enhanced neuronal survival.Additionally, we introduce PANoptosis, a form of cell death that encompasses pyroptosis, apoptosis, and necroptosis, emphasizing the complexity and potential therapeutic implications of these interactions. In summary, understanding the relationships among these cell death mechanisms in ischemic stroke is vital for developing new neuroprotective agents. Future research should aim for combinatorial interventions targeting multiple pathways to optimize treatment strategies and improve patient outcomes.

Tear Fluid-Based Metabolomics Profiling in Chronic Dacryocystitis Patients

Chronic dacryocystitis (CD) can result in severe complications and vision impairment due to ongoing microbial infections and persistent tearing. Tear fluid, which contains essential components vital for maintaining ocular surface health, has been investigated for its potential in the noninvasive identification of ocular biomarkers through metabolomics analysis. In this study, we employed UHPLC-MS/MS to analyze the tear metabolome of CD patients. UHPLC-MS/MS analysis of tear samples from CD patients revealed significant metabolic alterations. Compared with the control group, 298 metabolites were elevated, while 142 were decreased. KEGG pathway analysis suggested that these changes primarily affected arginine and proline metabolism, biosynthesis of amino acids, and phenylalanine biosynthesis in CD. Notably, 3-dehydroquinic acid, anthranilic acid, citric acid, and l-isoleucine emerged as potential biomarker candidates of CD with high diagnostic accuracy (AUC = 0.94). These findings suggest that tear fluid metabolism, particularly amino acid biosynthesis, plays a significant role in the pathogenesis of CD. Uncovering these metabolic products and pathways provides valuable insights into the mechanisms underlying CD and paves the way for the development of diagnostic tools and targeted therapies.

Osteoblast-Derived ECM1 Promotes Anti-Androgen Resistance in Bone Metastatic Prostate Cancer

Acquired resistance to hormonal therapy, particularly enzalutamide (ENZ), remains a significant obstacle in the treatment of advanced bone metastatic prostate cancer. Here, it is demonstrated that under ENZ treatment, osteoblasts in the bone microenvironment secrete increased levels of extracellular matrix protein 1 (ECM1), which affects surrounding prostate cancer cells, promoting tumor cell proliferation and anti-androgen resistance. Mechanistically, ECM1 interacts with the enolase 1 (ENO1) receptor on the prostate cancer cell membrane, leading to its phosphorylation at the Y189 site. This event further recruits adapter proteins including growth factor receptor-bound protein 2 (GRB2) and son of sevenless homolog 1 (SOS1), which activates the downstream mitogen-activated protein kinase (MAPK) signaling pathway to induce anti-androgen resistance. Furthermore, inhibiting ECM1 or utilizing the ENO1-targeting inhibitor phosphonoacetohydroxamate (PhAH) significantly restores tumor cell sensitivity to ENZ. Taken together, a potential mechanism is identified through which osteoblast-derived ECM1 drives resistance in bone metastatic prostate cancer under ENZ treatment. Additionally, the findings indicate that ECM1 and ENO1 may serve as potential targets for developing therapies for bone metastatic castration-resistant prostate cancer.

Diverse perspectives on proteomic posttranslational modifications to address EGFR-TKI resistance in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the main histological subtype of lung cancer. For locally advanced and advanced NSCLC, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI)-targeted therapy has been the first choice for NSCLC patients with EGFR mutations. TKIs, as targeted drugs, inhibit kinase activity and autophosphorylation by competitively binding to the ATP binding site of the EGFR tyrosine kinase domain, which blocks the signal transduction mediated by EGFR and thus inhibits the proliferation of tumor cells. However, drug resistance to TKIs is inevitable. EGFR is also a highly glycosylated receptor tyrosine kinase, and a wide range of crosstalk occurs between phosphorylation and glycosylation. Therefore, can the phosphorylation state be altered by glycosylation to improve drug resistance? In this review, we summarize phosphorylation, glycosylation and the crosstalk between these processes as well as the current research status and methods. We also summarize the autophosphorylation and glycosylation sites of the EGFR protein and their crosstalk. By exploring the relationship between EGFR glycosylation and autophosphorylation in targeted TKI therapy, we find that research on EGFR glycosylation is crucial for targeted NSCLC treatment and will become a research direction for identifying potential targets related to regulating TKI drug sensitivity.

SHP2-Triggered Endothelial Cell Activation Fuels Estradiol-Independent Endometrial Sterile Inflammation

Sterile inflammation occurs in various chronic diseases due to many nonmicrobe factors. Examples include endometrial hyperplasia (EH), endometriosis, endometrial cancer, and breast cancer, which are all sterile inflammation diseases induced by estrogen imbalances. However, how estrogen-induced sterile inflammation regulates EH remains unclear. Here, a single-cell RNA-Seq is used to show that SHP2 upregulation in endometrial endothelial cells promotes their inflammatory activation and subsequent transendothelial macrophage migration. Independent of the initial estrogen stimulation, IL1β and TNFα from macrophages then create a feedforward loop that enhances endothelial cell activation and IGF1 secretion. This endothelial cell-macrophage interaction sustains sterile endometrial inflammation and facilitates epithelial cell proliferation, even after estradiol withdrawal. The bulk RNA-Seq results and phosphoproteomic analysis show that endothelial SHP2 mechanistically enhances RIPK1 activity by dephosphorylating RIPK1Tyr380. This event activates downstream activator protein 1 (AP-1) and instigates the inflammation response. Furthermore, targeting SHP2 using SHP099 (an allosteric inhibitor) or endothelial-specific SHP2 deletion alleviates endothelial cell activation, macrophage infiltration, and EH progression in mice. Collectively, the findings demonstrate that SHP2 mediates the transition of endothelial activation from estradiol-driven acute inflammation to macrophage-amplified chronic inflammation. Targeting sterile inflammation mediated by endothelial cell activation is a promising strategy for nonhormonal intervention in estrogen-related diseases.

Mechanisms of Zhixiao Tang on Anti-Inflammatory Multiple Targets and Multiple Components: Metabonomics Combined with Database Mining Technology

Purpose

Zhixiao Tang (ZXT), a traditional Chinese compound prescription, has been used clinically to treat pneumonia in China. However, the underlying mechanism of ZXT treatment in pneumonia is still unclear. The present study aimed to reveal the potential mechanism of ZXT in pneumonia using a strategy combining metabolomics and network pharmacology.

Methods

Initially, the chemical compositions were identified by UPLC-QE-Orbitrap-MS, while the prediction of potential signal pathways was performed through network pharmacology. To assess the anti-inflammatory properties of ZXT in the context of pneumonia, models of 16HBE cells induced by LPS and zebrafish induced by CuSO4 were established to measure levels of inflammatory markers and apoptosis. Subsequently, the differential changes of endogenous metabolites in cells caused by ZXT were examined using metabolomics technology, and the molecular docking analysis of key targets was carried out using Autodock Vina software. Ultimately, the validation of the primary pathways and targets was conducted through quantitative RT-PCR and Western blot techniques.

Results

A total of 75 compounds were identified through UPLC-QE-Orbitrap-MS analyses. Network pharmacological analysis shows that it plays an anti-inflammatory role in C-type lectin receptor signaling pathway. After ZXT intervention, the inflammatory factors and apoptosis in cells were significantly reduced. Metabonomics analysis showed that 18 metabolites changed significantly. Four key genes were identified, which exhibited partial compatibility with the findings of network pharmacology. Molecular docking analysis confirmed the substantial affinity of the primary targets for ZXT. Furthermore, ZXT exerted a suppressive effect on neutrophil migration, down-regulated the expression of pro-inflammatory cytokine genes, and inhibited the up-regulation of the Dectin-1/SYK/NF-κB signaling pathway. In vivo cell experiments also yielded consistent experimental outcomes.

Conclusion

This study enhances comprehension of the pharmacological mechanism underlying ZXT's efficacy in pneumonia treatment, thereby establishing a scholarly basis for future research and clinical utilization of ZXT in pneumonia management.

Regulation of RIPK1 Phosphorylation: Implications for Inflammation, Cell Death, and Therapeutic Interventions

Receptor-interacting protein kinase 1 (RIPK1) plays a crucial role in controlling inflammation and cell death. Its function is tightly controlled through post-translational modifications, enabling its dynamic switch between promoting cell survival and triggering cell death. Phosphorylation of RIPK1 at various sites serves as a critical mechanism for regulating its activity, exerting either activating or inhibitory effects. Perturbations in RIPK1 phosphorylation status have profound implications for the development of severe inflammatory diseases in humans. This review explores the intricate regulation of RIPK1 phosphorylation and dephosphorylation and highlights the potential of targeting RIPK1 phosphorylation as a promising therapeutic strategy for mitigating human diseases.

Identification of necroptosis-related genes in ankylosing spondylitis by bioinformatics and experimental validation

The pathogenesis of ankylosing spondylitis (AS) remains unclear, and while recent studies have implicated necroptosis in various autoimmune diseases, an investigation of its relationship with AS has not been reported. In this study, we utilized the Gene Expression Omnibus database to compare gene expressions between AS patients and healthy controls, identifying 18 differentially expressed necroptosis-related genes (DENRGs), with 8 upregulated and 10 downregulated. Through the application of three machine learning algorithms-least absolute shrinkage and selection operation, support vector machine-recursive feature elimination and random forest-two hub genes, FASLG and TARDBP, were pinpointed. These genes demonstrated high specificity and sensitivity for AS diagnosis, as evidenced by receiver operating characteristic curve analysis. These findings were further supported by external datasets and cellular experiments, which confirmed the downregulation of FASLG and upregulation of TARDBP in AS patients. Immune cell infiltration analysis suggested that CD4+ T cells, CD8+ T cells, NK cells and neutrophils may be associated with the development of AS. Notably, in the group with high FASLG expression, there was a significant infiltration of CD8+ T cells, memory-activated CD4+ T cells and resting NK cells, with relatively less infiltration of memory-resting CD4+ T cells and neutrophils. Conversely, in the group with high TARDBP expression, there was enhanced infiltration of naïve CD4+ T cells and M0 macrophages, with a reduced presence of memory-resting CD4+ T cells. In summary, FASLG and TARDBP may contribute to AS pathogenesis by regulating the immune microenvironment and immune-related signalling pathways. These findings offer new insights into the molecular mechanisms of AS and suggest potential new targets for therapeutic strategies.

Cell death shapes cancer immunity: spotlighting PANoptosis

PANoptosis represents a novel type of programmed cell death (PCD) with distinctive features that incorporate elements of pyroptosis, apoptosis, and necroptosis. PANoptosis is governed by a newly discovered cytoplasmic multimeric protein complex known as the PANoptosome. Unlike each of these PCD types individually, PANoptosis is still in the early stages of research and warrants further exploration of its specific regulatory mechanisms and primary targets. In this review, we provide a brief overview of the conceptual framework and molecular components of PANoptosis. In addition, we highlight recent advances in the understanding of the molecular mechanisms and therapeutic applications of PANoptosis. By elucidating the complex crosstalk between pyroptosis, apoptosis and necroptosis and summarizing the functional consequences of PANoptosis with a special focus on the tumor immune microenvironment, this review aims to provide a theoretical basis for the potential application of PANoptosis in cancer therapy.

Based on Network Pharmacology and Molecular Docking, the Active Components, Targets, and Mechanisms of Flemingia philippinensis in Improving Inflammation Were Excavated

Flemingia philippinensis, a polyphenol-rich plant, holds potential for improving inflammation, but its mechanisms are not well understood. Therefore, this study employed network pharmacology and molecular docking to explore the mechanism by which Flemingia philippinensis ameliorates inflammation. In this study, 29 kinds of active ingredients were obtained via data mining. Five main active components were screened out for improving inflammation, which were flemichin D, naringenin, chrysophanol, genistein and orobol. In total, 52 core targets were identified, including AKT serine/threonine kinase 1 (AKT1), tumor necrosis factor (TNF), B-cell lymphoma-2 (BCL2), serum albumin (ALB), and estrogen receptor 1 (ESR1). Gene ontology (GO) enrichment analysis identified 2331 entries related to biological processes, 98 entries associated with cellular components, and 203 entries linked to molecular functions. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis yielded 149 pathways, including those involved in EGFR tyrosine kinase inhibitor resistance, endocrine resistance, and the PI3K-Akt signaling pathway. Molecular docking results showed strong binding effects between the main active components and the core targets, with binding energies less than -5 kcal/mol. In summary, this study preliminarily elucidated the underlying mechanisms by which Flemingia philippinensis, through a multi-component, multi-target, and multi-pathway approach, ameliorates inflammation. This provides a theoretical foundation for the subsequent application of Flemingia philippinensis in inflammation amelioration.

Protein phosphorylation and kinases: Potential therapeutic targets in necroptosis

Necroptosis is a pivotal contributor to the pathogenesis of various human diseases, including those affecting the nervous system, cardiovascular system, pulmonary system, and kidneys. Extensive investigations have elucidated the mechanisms and physiological ramifications of necroptosis. Among these, protein phosphorylation emerges as a paramount regulatory process, facilitating the activation or inhibition of specific proteins through the addition of phosphate groups to their corresponding amino acid residues. Currently, the targeting of kinases has gained recognition as a firmly established and efficacious therapeutic approach for diverse diseases, notably cancer. In this comprehensive review, we elucidate the intricate role of phosphorylation in governing key molecular players in the necroptotic pathway. Moreover, we provide an in-depth analysis of recent advancements in the development of kinase inhibitors aimed at modulating necroptosis. Lastly, we deliberate on the prospects and challenges associated with the utilization of kinase inhibitors to modulate necroptotic processes.

RIPK1 inhibitors: A key to unlocking the potential of necroptosis in drug development

Within the field of medical science, there is a great deal of interest in investigating cell death pathways in the hopes of discovering new drugs. Over the past two decades, pharmacological research has focused on necroptosis, a cell death process that has just been discovered. Receptor-interacting protein kinase 1 (RIPK1), an essential regulator in the cell death receptor signalling pathway, has been shown to be involved in the regulation of important events, including necrosis, inflammation, and apoptosis. Therefore, researching necroptosis inhibitors offers novel ways to treat a variety of disorders that are not well-treated by the therapeutic medications now on the market. The research and medicinal potential of RIPK1 inhibitors, a promising class of drugs, are thoroughly examined in this study. The journey from the discovery of Necrostatin-1 (Nec-1) to the recent advancements in RIPK1 inhibitors is marked by significant progress, highlighting the integration of traditional medicinal chemistry approaches with modern technologies like high-throughput screening and DNA-encoded library technology. This review presents a thorough exploration of the development and therapeutic potential of RIPK1 inhibitors, a promising class of compounds. Simultaneously, this review highlights the complex roles of RIPK1 in various pathological conditions and discusses potential inhibitors discovered through diverse pathways, emphasizing their efficacy against multiple disease models, providing significant guidance for the expansion of knowledge about RIPK1 and its inhibitors to develop more selective, potent, and safe therapeutic agents.

Study on the mechanism of puerarin against osteoarthritis from ferroptosis based on network pharmacology and bioinformatics

Network pharmacology and bioinformatics were used to study puerarin's molecular mechanism in treating osteoarthritis from the perspective of ferroptosis, revealing a new treatment target. Ferroptosis-related targets were obtained from FerrDb. Puerarin action targets were retrieved from TCMSP, Pharmmappe, SwissTargetPrediction, and Targetnet databases, and supplemented with PubMed. The gene expression profiles of GSE12021, GSE55235, and GSE82107 were obtained using "Osteoarthritis" as the search term in the GEO database, and the differential expression gene screening analysis was performed for osteoarthritis. The intersection targets between puerarin, iron death, and osteoarthritis were obtained using Venn diagrams. GO and KEGG analyses were conducted with R software. Molecular docking and visualization of puerarin and core targets were performed using Autodock Vina and PyMol software. The effects of puerarin on the cell viability and the TNFα, IL6, and Ilβ levels of human inflammation articular chondrocytes were tested in vitro experiments. Puerarin, ferroptosis, and osteoarthritis share four targets: PLIN2, PTGS2, VEGFA, and IL6. GO enrichment analysis showed that puerarin maintained the blood-brain barrier, regulated peptide serine phosphorylation, and had anti-inflammatory effects. KEGG analysis showed that puerarin's anti-inflammatory effects were mainly through VEGF, IL-17, C-type lectin receptor, HIF-1, TNF, and other signaling pathways. Puerarin closely bound PLIN2, PTGS2, VEGFA, and IL6 targets in molecular docking. In vitro, puerarin prevented osteoarthritis. Network pharmacology and bioinformatics explained puerarin's multi-target and multi-pathway treatment of OA, which may be related to ferroptosis, and confirmed its anti-inflammatory effect.

Roles of RIPK1 as a stress sentinel coordinating cell survival and immunogenic cell death

Cell death and inflammation are closely linked arms of the innate immune response to combat infection and tissue malfunction. Recent advancements in our understanding of the intricate signals originating from dying cells have revealed that cell death serves as more than just an end point. It facilitates the exchange of information between the dying cell and cells of the tissue microenvironment, particularly immune cells, alerting and recruiting them to the site of disturbance. Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is emerging as a critical stress sentinel that functions as a molecular switch, governing cellular survival, inflammatory responses and immunogenic cell death signalling. Its tight regulation involves multiple layers of post-translational modifications. In this Review, we discuss the molecular mechanisms that regulate RIPK1 to maintain homeostasis and cellular survival in healthy cells, yet drive cell death in a context-dependent manner. We address how RIPK1 mutations or aberrant regulation is associated with inflammatory and autoimmune disorders and cancer. Moreover, we tease apart what is known about catalytic and non-catalytic roles of RIPK1 and discuss the successes and pitfalls of current strategies that aim to target RIPK1 in the clinic.

5-Iodotubercidin sensitizes cells to RIPK1-dependent necroptosis by interfering with NFκB signaling

Receptor-interacting protein kinases (RIPK)-1 and -3 play crucial roles in cell fate decisions and are regulated by multiple checkpoint controls. Previous studies have identified IKK1/2- and p38/MK2-dependent checkpoints that phosphorylate RIPK1 at different residues to inhibit its activation. In this study, we investigated TNF-induced death in MAPK-activated protein kinase 2 (MK2)-deficient cells and found that MK2 deficiency or inactivation predominantly leads to necroptotic cell death, even without caspase inhibition. While RIPK1 inhibitors can rescue MK2-deficient cells from necroptosis, inhibiting RIPK3 seems to switch the process to apoptosis. To understand the underlying mechanism of this switch, we screened a library of 149 kinase inhibitors and identified the adenosine analog 5-Iodotubercidin (5-ITu) as the most potent compound that sensitizes MK2-deficient MEFs to TNF-induced cell death. 5-ITu also enhances LPS-induced necroptosis when combined with MK2 inhibition in RAW264.7 macrophages. Further mechanistic studies revealed that 5-ITu induces RIPK1-dependent necroptosis by suppressing IKK signaling in the absence of MK2 activity. These findings highlight the role for the multitarget kinase inhibitor 5-ITu in TNF-, LPS- and chemotherapeutics-induced necroptosis and its potential implications in RIPK1-targeted therapies.

Cell death checkpoints in the TNF pathway

Tumor necrosis factor (TNF) plays a central role in orchestrating mammalian inflammatory responses. It promotes inflammation either directly by inducing inflammatory gene expression or indirectly by triggering cell death. TNF-mediated cell death-driven inflammation can be beneficial during infection by providing cell-extrinsic signals that help to mount proper immune responses. Uncontrolled cell death caused by TNF is instead highly detrimental and is believed to cause several human autoimmune diseases. Death is not the default response to TNF sensing. Molecular brakes, or cell death checkpoints, actively repress TNF cytotoxicity to protect the organism from its detrimental consequences. These checkpoints therefore constitute essential safeguards against inflammatory diseases. Recent advances in the field have revealed the existence of several new and unexpected brakes against TNF cytotoxicity and pathogenicity.

Breaking bad: necroptosis in the pathogenesis of gastrointestinal diseases

A delicate balance between programmed cell death and proliferation of intestinal epithelial cells (IEC) exists in the gut to maintain homeostasis. Homeostatic cell death programs such as anoikis and apoptosis ensure the replacement of dead epithelia without overt immune activation. In infectious and chronic inflammatory diseases of the gut, this balance is invariably disturbed by increased levels of pathologic cell death. Pathological forms of cell death such as necroptosis trigger immune activation barrier dysfunction, and perpetuation of inflammation. A leaky and inflamed gut can thus become a cause of persistent low-grade inflammation and cell death in other organs of the gastrointestinal (GI) tract, such as the liver and the pancreas. In this review, we focus on the advances in the molecular and cellular understanding of programmed necrosis (necroptosis) in tissues of the GI tract. In this review, we will first introduce the reader to the basic molecular aspects of the necroptosis machinery and discuss the pathways leading to necroptosis in the GI system. We then highlight the clinical significance of the preclinical findings and finally evaluate the different therapeutic approaches that attempt to target necroptosis against various GI diseases. Finally, we review the recent advances in understanding the biological functions of the molecules involved in necroptosis and the potential side effects that may occur due to their systemic inhibition. This review is intended to introduce the reader to the core concepts of pathological necroptotic cell death, the signaling pathways involved, its immuno-pathological implications, and its relevance to GI diseases. Further advances in our ability to control the extent of pathological necroptosis will provide better therapeutic opportunities against currently intractable GI and other diseases.