4-Octyl itaconate restricts STING activation by blocking its palmitoylation

STING inhibitors and degraders: Potential therapeutic agents in inflammatory diseases

The regulation of the STING (stimulator of interferon genes) pathway represents a promising target for a range of inflammatory diseases. This review provides an overview of the structure of STING and discusses the mechanisms by which the cyclic GMP-AMP synthase (cGAS)-STING pathway is associated with various autoinflammatory and autoimmune diseases. We explore how targeting STING inhibition or degradation can alleviate excessive inflammatory signaling and improve efficacy. Emerging strategies include inhibiting STING expression by covalently binding compounds or using ligands that target the binding pocket. In addition, selective degradation of STING via the ubiquitin-proteasome system or the lysosomal pathway shows promise. In addition, we explore the implications of modulating the cGAS-STING pathway in the context of various inflammatory diseases. Finally, we summarize the chemical properties of recently developed STING compounds and their potential clinical applications. By comprehensively reviewing the current understanding of the role of STING in inflammation and the therapeutic potential of targeting STING, we aim to identify new avenues of intervention that could improve outcomes for patients with inflammatory diseases. This review highlights the important role of STING in the regulation of inflammation and its potential as a target for innovative therapeutic strategies.

Insights into the itaconate family: Immunomodulatory mechanisms and therapeutic potentials

The itaconate family, comprising itaconate derivatives, endogenous isomers, and other related compounds, has demonstrated substantial immunoregulatory properties. These compounds exhibit significant therapeutic potential in various disease models by modulating metabolic pathways, signal transduction cascades, and post-translational modifications. In this review, we delineate the structural characteristics and biological functions of the members of the itaconate family and elucidate their immunomodulatory mechanisms. Additionally, we summarize the immunomodulatory effects of the itaconate family across various disease categories, including cardiovascular, liver, respiratory, bone and cartilage, neurological, and autoimmune diseases. This review aims to deepen our understanding of the itaconate family and its potential applications, providing new perspectives and therapeutic strategies for inflammatory disorders and autoimmune diseases.

Acyl post-translational modification of proteins by metabolites in cancer cells

The relationship between metabolism and cancer is a major focus of current research, with an increasing number of studies highlighting the significant role of various metabolites in tumor cells, such as lactate, acetic acid, lysine, serine, tryptophan, palmitic acid, succinate, etc. These metabolites are involved in numerous biological processes within tumor cells, including transcription, translation, post-translational modification (PTM) of proteins, cell cycle regulation, and metabolism, thereby modulating tumor proliferation, migration, and drug resistance. Metabolite-mediated PTMs of proteins undoubtedly play a vital role in tumor cells, affecting both histones and non-histone proteins, covering modifications such as lactylation, crotonylation, acetylation, palmitoylation, and succinylation. Therefore, this review aims to elaborate on the abnormal levels of some major metabolites, related metabolic pathways, and the latest protein acyl PTMs they mediate in tumor cells, providing new insights for diagnosis and therapy in the field of oncology.

BAG2 Inhibits Cervical Cancer Progression by Modulating Type I Interferon Signaling through Stabilizing STING

Cervical cancer possesses high morbidity and mortality rates, and a comprehensive understanding of its molecular underpinnings is essential for advancing clinical management strategies. The innate immune sensor STING, which activates type I interferon signaling, plays a pivotal role in enhancing anti-tumor activity. Despite increased attention to STING's involvement in cervical cancer, the regulatory mechanisms governing its protein homeostasis remain poorly understood. In this study, it is found that the BAG2-STUB1 complex regulates ubiquitin proteasomal degradation of STING, which affects the development of cervical cancer. Mechanistically, BAG2 inhibits ubiquitination of STING and stabilizes it by interacting with STING. Specifically, BAG2 inhibits STUB1 from attaching the K48-linked ubiquitin chains at K338 and K370 of STING by forming a complex with STUB1. Functionally, enhanced BAG2 expression suppresses cervical cancer progression by activating the type I interferon pathway in a STING-dependent manner. Notably, clinical cervical cancer samples revealed a positive correlation between BAG2 and STING levels, with low BAG2 expression is strongly linked to advanced disease and poor prognosis in cervical cancer. Collectively, these findings elucidate the molecular mechanism by which the BAG2-STUB1 complex regulates STING homeostasis, underscoring BAG2's potential as a diagnostic biomarker and therapeutic target in cervical cancer.

STING: a multifaced player in cellular homeostasis

The stimulator of interferon gene (STING) is an important innate immune mediator of the cytoplasmic DNA sensing pathway. As a mediator known for its role in the immune response to infections, STING is also surprisingly at the center of a variety of non-infectious human diseases, including cancer, autoimmune diseases and neurodegenerative diseases. Recent studies have shown that STING has many signaling activities, including type I interferon (IFN-I) and other IFN-independent activities, many of which are poorly understood. STING also has the unique property of being continuous transported from the ER to the Golgi then to the lysosome. Mutations of STING or trafficking cofactors are associated with human diseases affecting multiple immune and non-immune organs. Here, we review recent advances in STING trafficking and signaling mechanisms based in part on studies of STING-associated monogenic inborn error diseases.

The cGAS-STING pathway in atherosclerosis

Atherosclerosis (AS), a chronic inflammatory disease, remains a leading contributor to cardiovascular morbidity and mortality. Recent studies highlight the critical role of the cGAS-STING pathway-a key innate immune signaling cascade-in driving AS progression. This pathway is activated by cytoplasmic DNA from damaged cells, thereby triggering inflammation and accelerating plaque formation. While risk factors such as aging, obesity, smoking, hypertension, and diabetes are known to exacerbate AS, emerging evidence suggests that these factors may also enhance cGAS-STING pathway, which amplifies inflammatory responses. Targeting this pathway offers a promising therapeutic strategy to reduce the burden of cardiovascular diseases (CVD). In this review, we summarize the mechanisms of the cGAS-STING pathway, explore its role in AS, and evaluate potential inhibitors as future therapeutic candidates. By integrating current knowledge, we aim to provide insights for developing novel treatments to mitigate AS and CVD burden.

Discovery of Potent STING Inhibitors Bearing a Difluorobenzodioxol Structural Motif as Potent Anti-Inflammatory Agents

Given the critical role of STING in autoimmune and inflammatory disorders, the development of targeted small-molecule inhibitors has been a promising strategy for the treatment of these diseases. Nevertheless, the currently reported STING inhibitors suffer from limited structural diversity, species sensitivity, and poor activity; therefore, none are suitable for clinical investigation. Herein, we performed a structural modification campaign on the tool compound 6 (H-151) based on its potential metabolic hotspots. Compound 66, bearing a difluorobenzodioxol moiety, was identified as one of the most potent STING inhibitors with IC50 values of 116 and 96.3 nM for h- and m-STING, respectively. This compound exhibited a notable enhancement in metabolic properties, especially in terms of metabolic stability. A mechanism study verified that 66 engaged with STING in a covalent manner akin to that of 6. In both the cisplatin-induced acute kidney injury and TREX1 D18N mouse models, 66 significantly alleviated tissue injury and inflammation.

Itaconate modulates immune responses via inhibition of peroxiredoxin 5

The immunoregulatory metabolite itaconate accumulates in innate immune cells upon Toll-like receptor stimulation. In response to macrophage activation by lipopolysaccharide, itaconate inhibits inflammasome activation and boosts type I interferon signalling; however, the molecular mechanism of this immunoregulation remains unclear. Here, we show that the enhancement of type I interferon secretion by itaconate depends on the inhibition of peroxiredoxin 5 and on mitochondrial reactive oxygen species. We find that itaconate non-covalently inhibits peroxiredoxin 5, leading to the modulation of mitochondrial peroxide in activating macrophages. Through genetic manipulation, we confirm that peroxiredoxin 5 modulates type I interferon secretion in macrophages. The non-electrophilic itaconate mimetic 2-methylsuccinate inhibits peroxiredoxin 5 and phenocopies immunoregulatory action of itaconate on type I interferon and inflammasome activation, providing further support for a non-covalent inhibition of peroxiredoxin 5 by itaconate. Our work provides insight into the molecular mechanism of actions and biological rationale for the predominantly immune specification of itaconate.

Preclinical insights into the potential of itaconate and its derivatives for liver disease therapy

Annually, approximately 3.5 % of the world's population dies of cirrhosis or liver cancer, and the burden of liver disease is steadily expanding owing to multiple factors such as alcohol consumption, irrational diets, viral transmission, and exposure to drugs and toxins. However, the lack of effective therapies and the adverse effects of some medications remain a threat to the management of liver disease. Recently, immunometabolism, as an emerging discipline, appears to be the focus of unprecedented research. As a natural metabolite that regulates cellular functions, itaconate is a crucial bridge connecting metabolism and immune response. Remodeling immune function through metabolic modulation may be a promising alternative for disease intervention strategies. In this review, we first briefly describe the historical origin of itaconate and the development of its derivatives. This was followed by a review of the molecular mechanisms by which itaconate regulated immune-metabolic responses. Furthermore, we analyzed the effects of itaconate regulation on immune cells of the hepatic system. Finally, we summarized the experimental evidence for itaconate and its derivatives in the therapeutic application of liver diseases. Itaconate is potentially an invaluable component of emerging therapeutic strategies for liver disease.

A Self-Assembled Metabolic Regulator Reprograms Macrophages to Combat Cytokine Storm and Boost Sepsis Immunotherapy

Sepsis, a life-threatening inflammatory disorder characterized by multiorgan failure, arises from a dysregulated immune response to infection. Modulating macrophage polarization has emerged as a promising strategy to control sepsis-associated inflammation. The endogenous metabolite itaconate has shown anti-inflammatory potential by suppressing the stimulator of interferon genes (STING) pathway, but its efficacy is inhibited by hyperactive glycolysis, which sustains macrophage overactivation. Here, we revealed a critical crosstalk between the itaconate-STING axis and glycolysis in macrophage-mediated inflammation. Building on this interplay, we developed a novel nanoparticle LDO (lonidamine disulfide 4-octyl-itaconate), a self-assembled metabolic regulator integrating an itaconate derivative with the glycolysis inhibitor Lonidamine. By concurrently targeting glycolysis and STING pathways, LDO reprograms macrophages to restore balanced polarization. In sepsis models, LDO effectively attenuates CCL2-driven cytokine storms, alleviates acute lung injury, and significantly enhances survival via metabolic reprogramming. This study offers a cytokine-regulatory strategy rooted in immunometabolism, providing a foundation for the translational development of immune metabolite-based sepsis therapies.

Pharmacological inhibition of STING-mediated GPX4 autophagic degradation by 4-octyl itaconate ameliorates sepsis-induced acute kidney injury

The precise pathogenic mechanisms underlying sepsis-induced acute kidney injury (AKI) remain elusive. Emerging evidence suggests a link between tubular ferroptosis and the pathogenesis of AKI, though the regulatory pathways are not fully understood. Stimulator of interferon genes (STING), previously recognized as a pivotal mediator of innate immunity via DNA-sensing pathways, is increasingly associated with lipid peroxidation, a hallmark of ferroptosis, and 4-octyl itaconate (4-OI) has been shown to inhibit STING activation, exerting anti-inflammatory effects. This study investigates the protective mechanisms of 4-OI in sepsis-AKI. Following cecal ligation and puncture (CLP), inflammation, oxidative stress, and ferroptosis levels in kidney tissue increased. Both 4-OI and ferrostatin-1 (Fer-1) mitigated renal ferroptosis, exerting anti-inflammatory and antioxidant stress effects, and improved renal function. Consistently, in vitro experiments demonstrated that 4-OI reduced ferroptosis in human renal proximal tubule (HK-2) cells induced by lipopolysaccharide (LPS). Mechanistically, 4-OI suppressed LPS-induced activation of the STING pathway and reduced levels of inflammatory cytokines in a manner independent of NF-E2-related factor 2 (Nrf2). Additionally, 4-OI inhibited STING transcription through the activation of Nrf2. These dual actions effectively suppressed LPS-induced STING pathway activation, thereby inhibiting STING-mediated autophagic degradation of glutathione peroxidase 4 (GPX4), reducing reactive oxygen species (ROS) accumulation, and alleviating ferroptosis. In summary, 4-OI is a promising therapeutic candidate, functioning both as a STING inhibitor and a ferroptosis inhibitor, with potential applications in the treatment of sepsis.

Orally Bioavailable and Site-Selective Covalent STING Inhibitor Derived from a Macrocyclic Marine Diterpenoid

Pharmacological inhibition of the cGAS-STING-controlled innate immune pathway is an emerging therapeutic strategy for a myriad of inflammatory diseases. Here, we report GHN105 as an orally bioavailable covalent STING inhibitor. Late-stage diversification of the briarane-type diterpenoid excavatolide B allowed the installation of solubility-enhancing functional groups while enhancing its activity as a covalent STING inhibitor against multiple human STING variants, including the S154 variant responsible for a genetic autoimmune disease. Selectively engaging the membrane-proximal Cys91 residue of STING, GHN105 dose-dependently inhibited cGAS-STING signaling and type I interferon responses in cells and in vivo. Moreover, orally administered GHN105 exhibited on-target engagement in vivo and markedly reversed key pathological features in a delayed treatment of the acute colitis mouse model. Our study provided proof of concept that the synthetic briarane analog GHN105 serves as a safe, site-selective, and orally active covalent STING inhibitor and devises a regimen that allows long-term systemic administration.

Regulation and Function of the cGAS-STING Pathway: Mechanisms, Post-Translational Modifications, and Therapeutic Potential in Immunotherapy

Autoimmune diseases arise when the immune system attacks healthy tissues, losing tolerance for self-tissues. Normally, the immune system recognizes and defends against pathogens like bacteria and viruses. The cGAS-STING pathway, activated by pattern-recognition receptors (PRRs), plays a key role in autoimmune responses. The cGAS protein senses pathogenic DNA and synthesizes cGAMP, which induces conformational changes in STING, activating kinases IKK and TBK1 and leading to the expression of interferon genes or inflammatory mediators. This pathway is crucial in immunotherapy, activating innate immunity, enhancing antigen presentation, modulating the tumor microenvironment, and integrating into therapeutic strategies. Modulation strategies include small molecule inhibitors, oligonucleotide therapies, protein and antibody therapies, genetic and epigenetic regulation, cytokine and metabolite modulation, and nanoscale delivery systems. Post-translational modifications (PTMs) of the cGAS-STING pathway, such as phosphorylation, acetylation, ubiquitination, methylation, palmitoylation, and glycosylation, fine-tune immune responses by regulating protein activity, stability, localization, and interactions. These modifications are interconnected and collectively influence pathway functionality. We summarize the functions of cGAS-STING and its PTMs in immune and non-immune cells across various diseases, and explore potential clinical applications.

Suppression of cGAS/STING pathway-triggered necroptosis in the hippocampus relates H2S to attenuate cognitive dysfunction of Parkinson's disease

BACKGROUND

Cognitive dysfunction is the most severe non-motor symptom of Parkinson's disease (PD). Our previous study revealed that hydrogen sulfide (H2S) ameliorates cognitive dysfunction in PD, but the underlying mechanisms remain unclear. Hippocampal necroptosis plays a vital role in cognitive dysfunction, while the cGAS/STING pathway triggers necroptosis. To understand the mechanism underlying the inhibitory role of H2S in cognitive dysfunction of PD, we explored whether H2S reduces the enhancement of necroptosis and the activation of the cGAS/STING pathway in the hippocampus of the rotenone (ROT)-induced PD rat model.

METHOD

Adult Sprague-Dawley (SD) rats were pre-treated with NaHS (30 or 100 μmol/kg/d, i.p.) for 7 days and then co-treated with ROT (2 mg/kg/d, s.i.) for 35 days. The Y-maze and Morris water maze (MWM) tests were used to assess the cognitive function. Hematoxylin-eosin (H&E) staining was used to detect the hippocampal pathological morphology. Western blotting analysis was used to measure the expressions of proteins. Enzyme-linked immunosorbent assay was used to determine the levels of inflammatory factors.

RESULT

NaHS (a donor of H2S) mitigated cognitive dysfunction in ROT-exposed rats, according to the Y-maze and MWM tests. NaHS treatment also markedly down-regulated the expressions of necroptosis-related proteins (RIPK1, RIPK3, and MLKL) and decreased the levels of necroptosis-related inflammatory factors (IL-6 and IL-1β) in the hippocampus of ROT-exposed rats. Furthermore, NaHS treatment reduced the expressions of cGAS/STING pathway-related proteins (cGAS, STING, p-TBK1Ser172, p-IRF3Ser396, and p-P65Ser536) and decreased the contents of pro-inflammation factors (INF-β and TNF-α) in the hippocampus of ROT-exposed rats.

CONCLUSION

H2S attenuates the cGAS/STING pathway-triggered necroptosis in the hippocampus, which is related to H2S to attenuate cognitive dysfunction in PD.

Activation of Nrf2 pathway by 4-Octyl itaconate enhances donor lung function in cold preservation settings

BACKGROUND

Lung transplantation is the primary treatment for end-stage lung diseases. However, ischemia-reperfusion injury (IRI) significantly impacts transplant outcomes. 4-Octyl itaconate (4-OI) has shown potential in mitigating organ IRI, although its effects in lung transplantation require further exploration.

METHODS

BEAS-2B cells were used to model transplantation, assessing the effects of 4-OI through viability, apoptosis, and ROS assays. qRT-PCR analyzed cytokine transcription post-cold ischemia/reperfusion (CI/R). RNA sequencing and Gene Ontology analysis elucidated 4-OI's mechanisms of action, confirmed by Western blotting. ALI-airway and lung transplantation organoid models evaluated improvements in bronchial epithelial morphology and function due to 4-OI. ELISA measured IL-6 and IL-8 levels. Rat models of extended cold preservation and non-heart-beating transplantation assessed 4-OI's impact on lung function, injury, and inflammation.

RESULTS

Our findings indicate that 4-OI (100 µM) during cold preservation effectively maintained cell viability, decreased apoptosis, and reduced ROS production in BEAS-2B cells under CI/R conditions. It also downregulated pro-inflammatory cytokine transcription, including IL1B, IL6, and TNF. Inhibition of Nrf2 partially reversed these protective effects. In cold preservation solutions, 4-OI upregulated Nrf2 target genes such as NQO1, HMOX1, and SLC7A11. In ALI airway models, 4-OI enhanced bronchial epithelial barrier integrity and ciliary beat function after CI/R. In rat models, 4-OI administration improved lung function and reduced pulmonary edema, tissue injury, apoptosis, and systemic inflammation following extended cold preservation or non-heart-beating lung transplantation.

CONCLUSIONS

Incorporating 4-OI into cold preservation solutions appears promising for alleviating CI/R-induced bronchial epithelial injury and enhancing lung transplant outcomes via Nrf2 pathway activation.

Regulation of pattern recognition receptor signaling by palmitoylation

Pattern recognition receptors (PRRs), consisting of Toll-like receptors, RIG-I-like receptors, cytosolic DNA sensors, and NOD-like receptors, sense exogenous pathogenic molecules and endogenous damage signals to maintain physiological homeostasis. Upon activation, PRRs stimulate the sensitization of nuclear factor κB, mitogen-activated protein kinase, TANK-binding kinase 1-interferon (IFN) regulatory factor, and inflammasome signaling pathways to produce inflammatory factors and IFNs to activate Janus kinase/signal transducer and activator of transcription signaling pathways, resulting in anti-infection, antitumor, and other specific immune responses. Palmitoylation is a crucial type of post-translational modification that reversibly alters the localization, stability, and biological activity of target molecules. Here, we discuss the available knowledge on the biological roles and underlying mechanisms linked to protein palmitoylation in modulating PRRs and their downstream signaling pathways under physiological and pathological conditions. Moreover, recent advances in the use of palmitoylation as an attractive therapeutic target for disorders caused by the dysregulation of PRRs were summarized.

Discovery of an Orally Bioavailable STING Inhibitor with In Vivo Anti-Inflammatory Activity in Mice with STING-Mediated Inflammation

The cyclic GMP-AMP synthase (cGAS)-stimulator of the interferon genes (STING) pathway plays a key role in triggering interferon and inflammatory responses against microbial invasion or tumor. However, aberrant activation of the cGAS-STING pathway is associated with a variety of inflammatory and autoimmune diseases, and thus inhibition of STING is regarded as a potential new approach to treating these diseases. Herein, we report a series of novel indolyl-urea derivatives as STING inhibitors. The representative compound 42 exhibited potent STING inhibitory activity, acceptable pharmacokinetic properties, and good in vivo safety profiles. Mechanistically, 42 could block the palmitoylation of the STING protein and STING downstream signaling. Importantly, oral administration of 42 could effectively suppress STING-mediated inflammation in 10-carboxymethyl-9-acridanone (CMA)-treated mouse and Trex1-/- mouse. Together, compound 42 represents a promising STING inhibitor for treating STING-associated inflammatory and autoimmune diseases.

Itaconate and its derivatives as anti-pathogenic agents

Pathogenic microorganisms and viruses cause outbreaks and pandemics that affect millions of people worldwide. Despite recent advances in pharmacology and medicine, the ability of infectious diseases to spread in the modern era is accelerating due to various factors contributing to increased human-to-human and human-animal contacts. With the global rise of drug resistance among pathogens and frequently occurring viral outbreaks, alternative drugs and therapies that specifically inhibit microbial virulence or regulate immune responses are attracting growing interest. The present review focuses on itaconate and its derivatives as potential anti-pathogenic agents. It summarizes the current state of research on itaconate metabolism in bacteria, fungi and mammals. This is followed by a comprehensive review of recent advances studying itaconate and its derivatives as anti-inflammatory, immunoregulatory, antimicrobial and antiviral compounds, along with their mechanisms of action. Finally, the review emphasises the existing challenges and future research directions for the application of itaconate and its derivatives as anti-pathogenic agents.

Aberrant fumarate metabolism links interferon release in diffuse systemic sclerosis

BACKGROUND

Systemic Sclerosis (SSc) is an idiopathic rheumatic inflammatory disease that is characterised by inflammation and skin fibrosis. Type I interferon is significantly elevated in the disease.

OBJECTIVE

The objective of this study is to determine the role of the TCA cycle metabolite fumarate in SSc.

METHODS

CD14 + cells were isolated from 12 SSc patients and healthy controls. Fumarate hydratase and Interferon dependant genes were quantified by qPCR. In vitro inhibition of STING using a small molecule STING inhibitor and enforced mitophagy was induced in vitro and IFN-β release was quantified. VDAC1 inhibitor was used to determine the role of mt DNA release in IFN-β induction. In whole skin biopsies fumarate and succinate was quantified.

RESULTS

Fumarate Hydratase is significantly reduced in SSc monocytes. Type I interferon is also elevated in monocytes from SSc donors compared to controls. The mitochondrial-specific stress marker GDF-15 was significantly elevated in SSc monocytes. Blockade of the cGAS-STING pathway chemically reduced interferon-β release and induced mitophagy also retarded release of the cytokine in response to LPS stimulation. Inhibition of VDAC1 mitigated IFN-β, as did the depletion of mitochondria in cells. Furthermore, the itaconate derivative 4-octyl itaconate reduced IFN-β induction in SSc monocytes, that was downstream of mitochondrial nucleic acid release. Fumarate, but not succinate was elevated in whole skin biopsies.

CONCLUSION

Fumarate metabolism links interferon release in SSc and may underlie the aberrant expression of interferon in SSc via cytosolic DNA released from mitochondria.

The cell autonomous and non-autonomous roles of itaconate in immune response

Itaconate which is discovered as a mammalian metabolite possessing antimicrobial and immunoregulatory activity has attracted much attention in the field of immunometabolism. Itaconate is synthesized by myeloid cells under conditions of pathogen infection and sterile inflammation. In addition to regulating immune response of myeloid cells, itaconate secreted from myeloid cells can also be taken up by non-myeloid cells to exert immunoregulatory effects in a cell non-autonomous manner. In this review, we recap the discovery of itaconate as a distinct immunologic regulator and effector, describe the development of itaconate biosensor, and detail the recent findings that decipher the mechanism underlying intercellular transport of itaconate. Based on these knowledges, we propose itaconate is a messenger transmitting immunologic signals from myeloid cells to other types of cells during host inflammation and immune defense.

Palmitoylation-related gene ZDHHC22 as a potential diagnostic and immunomodulatory target in Alzheimer's disease: insights from machine learning analyses and WGCNA

BACKGROUND

The mechanism of palmitoylation in the pathogenesis of Alzheimer's disease (AD) remains unclear.

METHODS

This study retrieved AD data sets from the GEO database to identify palmitoylation-associated genes (PRGs). This study applied WGCNA along with three machine learning algorithms-random forest, LASSO regression, and SVM-RFE-to further select key PRGs (KPRGs). The diagnostic performance of KPRGs was evaluated using Receiver Operating Characteristic (ROC) curve analysis. Immune cell infiltration analysis was conducted to assess correlations between KPRGs and immune cell types, and a competing endogenous RNA (ceRNA) regulatory network was constructed to explore their potential regulatory mechanisms.

RESULTS

17 PRGs were identified from the AD data sets, with 7 genes showing increased expression and 10 showing decreased expression. Through WGCNA and machine learning analyses, ZDHHC22 was selected as a KPRG. The ROC curve analysis demonstrated that ZDHHC22 had an area under the curve value of 0.659, indicating moderate diagnostic potential. Immune cell infiltration analysis revealed significant associations between ZDHHC22 expression and the infiltration of several immune cell types, including naïve B cells, CD8 + T cells, and M1 macrophages. In addition, 25 miRNAs and 55 lncRNAs were predicted to potentially target ZDHHC22, forming the basis for a lncRNA-miRNA-mRNA ceRNA network.

CONCLUSIONS

This study is the first to use bioinformatics methods to identify ZDHHC22 as a key KPRG in AD, highlighting its potential role in disease diagnosis and immune regulation. The regulatory network of ZDHHC22 provides new insights into the molecular mechanisms of AD and lays the foundation for future targeted therapeutic strategies.

Regulation of cGAS-STING signalling and its diversity of cellular outcomes

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signalling pathway, which recognizes both pathogen DNA and host-derived DNA, has emerged as a crucial component of the innate immune system, having important roles in antimicrobial defence, inflammatory disease, ageing, autoimmunity and cancer. Recent work suggests that the regulation of cGAS-STING signalling is complex and sophisticated. In this Review, we describe recent insights from structural studies that have helped to elucidate the molecular mechanisms of the cGAS-STING signalling cascade and we discuss how the cGAS-STING pathway is regulated by both activating and inhibitory factors. Furthermore, we summarize the newly emerging understanding of crosstalk between cGAS-STING signalling and other signalling pathways and provide examples to highlight the wide variety of cellular processes in which cGAS-STING signalling is involved, including autophagy, metabolism, ageing, inflammation and tumorigenesis.

Exploring the landscape of post-translational modification in drug discovery

Post-translational modifications (PTMs) play a crucial role in regulating protein function, and their dysregulation is frequently associated with various diseases. The emergence of epigenetic drugs targeting factors such as histone deacetylases (HDACs) and histone methyltransferase enhancers of zeste homolog 2 (EZH2) has led to a significant shift towards precision medicine, offering new possibilities to overcome the limitations of traditional therapeutics. In this review, we aim to systematically explore how small molecules modulate PTMs. We discuss the direct targeting of enzymes involved in PTM pathways, the modulation of substrate proteins, and the disruption of protein-enzyme interactions that govern PTM processes. Additionally, we delve into the emerging strategy of employing multifunctional molecules to precisely regulate the modification levels of proteins of interest (POIs). Furthermore, we examine the specific characteristics of these molecules, evaluating their therapeutic benefits and potential drawbacks. The goal of this review is to provide a comprehensive understanding of PTM-targeting strategies and their potential for personalized medicine, offering a forward-looking perspective on the evolution of precision therapeutics.

Itaconate facilitates viral infection via alkylating GDI2 and retaining Rab GTPase on the membrane

Metabolic reprogramming of host cells plays critical roles during viral infection. Itaconate, a metabolite produced from cis-aconitate in the tricarboxylic acid cycle (TCA) by immune responsive gene 1 (IRG1), is involved in regulating innate immune response and pathogen infection. However, its involvement in viral infection and underlying mechanisms remain incompletely understood. Here, we demonstrate that the IRG1-itaconate axis facilitates the infections of VSV and IAV in macrophages and epithelial cells via Rab GTPases redistribution. Mechanistically, itaconate promotes the retention of Rab GTPases on the membrane via directly alkylating Rab GDP dissociation inhibitor beta (GDI2), the latter of which extracts Rab GTPases from the membrane to the cytoplasm. Multiple alkylated residues by itaconate, including cysteines 203, 335, and 414 on GDI2, were found to be important during viral infection. Additionally, this effect of itaconate needs an adequate distribution of Rab GTPases on the membrane, which relies on Rab geranylgeranyl transferase (GGTase-II)-mediated geranylgeranylation of Rab GTPases. The single-cell RNA sequencing data revealed high expression of IRG1 primarily in neutrophils during viral infection. Co-cultured and in vivo animal experiments demonstrated that itaconate produced by neutrophils plays a dominant role in promoting viral infection. Overall, our study reveals that neutrophils-derived itaconate facilitates viral infection via redistribution of Rab GTPases, suggesting potential targets for antiviral therapy.

Click-chemistry-based protocol for detecting 4-octyl-itaconate-alkylated proteins in primary mouse macrophages

4-Octyl itaconate (4-OI), a derivative of itaconate, inhibits inflammation by alkylating its target proteins. Here, we present a click-chemistry-based protocol for detecting 4-OI-alkylated proteins in mouse primary bone-marrow-derived macrophages (BMDMs) by using an itaconate-alkyne (ITalk) probe. We describe steps for culturing and treating BMDMs and details on using click chemistry in the cell lysate. We also detail procedures for detecting alkylated proteins by western blot. For complete details on the use and execution of this protocol, please refer to Su et al.1.

ROS responsive nanozyme loaded with STING silencing for the treatment of sepsis-induced acute lung injury

Acute lung injury (ALI) is a common complication of sepsis and a leading cause of mortality in septic patients. Studies indicate that STING may play a crucial role in the pathogenesis of sepsis-induced ALI by interacting with the PARP-1/NLRP3 pathway. Therefore, targeting STING inhibition has potential as a novel therapeutic strategy for ALI. However, effective inhibition remains challenging due to the widespread expression of STING across various tissues. In this study, we developed a nanozyme-based drug delivery system, DSPE-TK-mPEG-MnO2@siSTING (abbreviated as DTmM@siSTING), using DSPE-TK-mPEG-MnO2 as the carrier, and characterized it via scanning electron microscopy, dynamic light scattering, nanoparticle size analysis, and gel electrophoresis. To evaluate the therapeutic effects of DTmM@siSTING, an in vitro ALI cell model and an in vivo ALI mouse model were established, assessing the nanozyme's impact on ROS levels, inflammatory responses, and the PARP-1/NLRP3 pathway in sepsis-induced ALI. Results demonstrated that DTmM@siSTING exhibited good physiological stability. In vitro, DTmM@siSTING significantly reduced ROS levels, myeloperoxidase activity, and expression of inflammatory cytokines, while also inhibiting PARP-1/NLRP3 pathway activation. In vivo experiments further revealed that DTmM@siSTING effectively delivered siSTING to the lungs, mitigating sepsis-induced ALI and associated inflammatory responses. Additionally, DTmM@siSTING displayed excellent biocompatibility. In summary, our findings suggest that DTmM@siSTING significantly enhances the therapeutic efficacy of siSTING, alleviating ALI by inhibiting ROS production, inflammatory responses, and activation of the PARP-1/NLRP3 pathway. This novel approach presents a promising therapeutic avenue for sepsis-induced ALI.

Itaconate uptake via SLC13A3 improves hepatic antibacterial innate immunity

Itaconate is an immunoregulatory metabolite produced by the mitochondrial enzyme immune-responsive gene 1 (IRG1) in inflammatory macrophages. We recently identified an important mechanism by which itaconate is released from inflammatory macrophages. However, it remains unknown whether extracellular itaconate is taken up by non-myeloid cells to exert immunoregulatory functions. Here, we used a custom-designed CRISPR screen to identify the dicarboxylate transporter solute carrier family 13 member 3 (SLC13A3) as an itaconate importer and to characterize the role of SLC13A3 in itaconate-improved hepatic antibacterial innate immunity. Functionally, liver-specific deletion of Slc13a3 impairs hepatic antibacterial innate immunity in vivo and in vitro. Mechanistically, itaconate uptake via SLC13A3 induces transcription factor EB (TFEB)-dependent lysosomal biogenesis and subsequently improves antibacterial innate immunity in mouse hepatocytes. These findings identify SLC13A3 as a key itaconate importer in mouse hepatocytes and will aid in the development of potent itaconate-based antibacterial therapeutics.

Cyclopeptide Inhibitors Target the N-Terminal Tail of STING and Alleviate Autoinflammation

Cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway is a crucial component of innate immunity that plays a vital role in protecting against pathogen infections and cellular stress. However, aberrant activation of cGAS-STING pathway is related to inflammatory and autoimmune diseases. Here, we developed cyclopeptide STING inhibitors by cyclizing the N-terminal tail (NTT) of STING. These cyclopeptides selectively inhibited the activation of STING pathway in human or murine cell lines. Mechanistically, the inhibitors directly bound to STING, and subsequently blocked the aggregation and activation of STING. In addition, the optimal inhibitor STi-2 significantly suppressed proinflammatory cytokine production and systemic inflammation in Trex1-/- mice. Overall, our work facilitates the development of specific inhibitors of STING as potential therapies for cGAS-STING associated autoinflammatory diseases.

Exploring Protein S-Palmitoylation: Mechanisms, Detection, and Strategies for Inhibitor Discovery

S-palmitoylation is a reversible and dynamic process that involves the addition of long-chain fatty acids to proteins. This protein modification regulates various aspects of protein function, including subcellular localization, stability, conformation, and biomolecular interactions. The zinc finger DHHC (ZDHHC) domain-containing protein family is the main group of enzymes responsible for catalyzing protein S-palmitoylation, and 23 members have been identified in mammalian cells. Many proteins that undergo S-palmitoylation have been linked to disease pathogenesis and progression, suggesting that the development of effective inhibitors is a promising therapeutic strategy. Reducing the protein S-palmitoylation level can target either the PATs directly or their substrates. However, there are rare clinically effective S-palmitoylation inhibitors. This review aims to provide an overview of the S-palmitoylation field, including the catalytic mechanism of ZDHHC, S-palmitoylation detection methods, and the functional impact of protein S-palmitoylation. Additionally, this review focuses on current strategies for expanding the chemical toolbox to develop novel and effective inhibitors that can reduce the level of S-palmitoylation of the target protein.

Metabolic Messengers: itaconate

The metabolite itaconate has emerged as an important immunoregulator with roles in antibacterial defence, inhibition of inflammation and, more recently, as an inhibitory factor in obesity. Itaconate is one of the most upregulated metabolites in inflammatory macrophages. It is produced owing to the disturbance of the tricarboxylic acid cycle and the diversion of aconitate to itaconate via the enzyme aconitate decarboxylase 1. In immunology, initial studies concentrated on the role of itaconate in inflammatory macrophages where it was shown to be inhibitory, but this has expanded as the impact of itaconate on other cell types is starting to emerge. This review focuses on itaconate as a key immunoregulatory metabolite and describes its diverse mechanisms of action and its many impacts on the immune and inflammatory responses and in cancer. We also examine the clinical relevance of this immunometabolite and its therapeutic potential for immune and inflammatory diseases.

The anti-inflammatory effects of itaconate and its derivatives in neurological disorders

Almost 16 % of the global population is affected by neurological disorders, including neurodegenerative and cerebral neuroimmune diseases, triggered by acute or chronic inflammation. Neuroinflammation is recognized as a common pathogenic mechanism in a wide array of neurological conditions including Alzheimer's disease, Parkinson's disease, postoperative cognitive dysfunction, stroke, traumatic brain injury, and multiple sclerosis. Inflammatory process in the central nervous system (CNS) can lead to neuronal damage and neuronal apoptosis, consequently exacerbating these diseases. Itaconate, an immunomodulatory metabolite from the tricarboxylic acid cycle, suppresses neuroinflammation and modulates the CNS immune response. Emerging human studies suggest that itaconate levels in plasma and cerebrospinal fluid may serve as biomarkers associated with inflammatory responses in neurological disorders. Preclinical studies have shown that itaconate and its highly cell-permeable derivatives are promising candidates for preventing and treating neuroinflammation-related neurological disorders. The underlying mechanism may involve the regulation of immune cells in the CNS and neuroinflammation-related signaling pathways and molecules including Nrf2/KEAP1 signaling pathway, reactive oxygen species, and NLRP3 inflammasome. Here, we introduce the metabolism and function of itaconate and the synthesis and development of its derivatives. We summarize the potential impact and therapeutic potential of itaconate and its derivatives on brain immune cells and the associated signaling pathways and molecules, based on preclinical evidence via various neurological disorder models. We also discuss the challenges and potential solutions for clinical translation to promote further research on itaconate and its derivatives for neuroinflammation-related neurological disorders.

Itaconate in host inflammation and defense

Immune cells undergo rapid and extensive metabolic changes during inflammation. In addition to contributing to energetic and biosynthetic demands, metabolites can also function as signaling molecules. Itaconate (ITA) rapidly accumulates to high levels in myeloid cells under infectious and sterile inflammatory conditions. This metabolite binds to and regulates the function of diverse proteins intracellularly to influence metabolism, oxidative response, epigenetic modification, and gene expression and to signal extracellularly through binding the G protein-coupled receptor (GPCR). Administration of ITA protects against inflammatory diseases and blockade of ITA production enhances antitumor immunity in preclinical models. In this article, we review ITA metabolism and its regulation, discuss its target proteins and mechanisms, and conjecture a rationale for developing ITA-based therapeutics to treat inflammatory diseases and cancer.

IRG1/itaconate alleviates acute liver injury in septic mice by suppressing NLRP3 expression and its mediated macrophage pyroptosis via regulation of the Nrf2 pathway

Sepsis, a systemic inflammatory response triggered by infection, has a considerably high mortality rate. However, effective prevention and intervention measures against sepsis remain insufficient. Therefore, this study aimed to investigate the mechanisms underlying the protective properties of immune response gene-1 (IRG1) and 4-Octyl itaconate (OI) during acute liver damage in mice with sepsis. A sepsis mouse model was established to compare wild-type and IRG1-/- groups. The impact of IRG1/Itaconate on pro- and anti-inflammatory cytokines was evaluated using J774A.1 cells. IRG1/Itaconate substantially reduced pro-inflammatory cytokines and increased the release of anti-inflammatory cytokines. It reduced pathological damage to liver tissues, preserved normal liver function, decreased the release of reactive oxygen species (ROS) and LDH, and enhanced the GSH/GSSG ratio. Moreover, IRG1 and itaconic acid activated the Nrf2 signaling pathway, regulating the expression of its downstream antioxidative stress-related proteins. Additionally, they inhibited the activity of NLRP3 inflammatory vesicles to suppress the expression of macrophage-associated pyroptosis signaling molecules. Our findings demonstrate that IRG1/OI inhibits NLRP3 inflammatory vesicle activation and macrophage pyroptosis by modulating the Nrf2 signaling pathway, thereby attenuating acute liver injury in mice with sepsis. These findings could facilitate the clinical application of IRG1/Itaconate to prevent sepsis-induced acute liver injury.

Agonists and Inhibitors of the cGAS-STING Pathway

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway is pivotal in immunotherapy. Several agonists and inhibitors of the cGAS-STING pathway have been developed and evaluated for the treatment of various diseases. The agonists aim to activate STING, with cyclic dinucleotides (CDNs) being the most common, while the inhibitors aim to block the enzymatic activity or DNA binding ability of cGAS. Meanwhile, non-CDN compounds and cGAS agonists are also gaining attention. The omnipresence of the cGAS-STING pathway in vivo indicates that its overactivation could lead to undesired inflammatory responses and autoimmune diseases, which underscores the necessity of developing both agonists and inhibitors of the cGAS-STING pathway. This review describes the molecular traits and roles of the cGAS-STING pathway and summarizes the development of cGAS-STING agonists and inhibitors. The information is supposed to be conducive to the design of novel drugs for targeting the cGAS-STING pathway.

When pyro(ptosis) meets palm(itoylation)

Pyroptosis, a programmed cell death process, is vital for the immune response against microbial infections and internal danger signals. Recent studies have highlighted the importance of protein palmitoylation, a modification that involves attaching palmitate to cysteine residues, in regulating key proteins involved in pyroptosis. Palmitoylation of cGAS at residue C474 by ZDHHC18 affects its enzymatic activity and DNA binding ability. Similarly, ZDHHC9 promotes cGAS activity through palmitoylation at residues C404/405. NLRP3 palmitoylation at residue C844, mediated by ZDHHC12, impacts its stability and interactions with other proteins, crucial for activating the NLRP3 inflammasome and triggering inflammation. However, the role of ZDHHC5 in NLRP3 palmitoylation remains uncertain due to conflicting findings. Palmitoylation at C88/91 is essential for STING activation and induction of type I interferons. It modulates the formation of multimeric complexes and downstream signaling pathways. GSDMD palmitoylation at C191 is necessary for pore formation and membrane translocation, while GSDME palmitoylation at C407/408 is associated with drug-induced pyroptosis. Moreover, palmitoylation of NOD1 and NOD2 influences their membrane recruitment and immune signaling pathways in response to bacterial peptidoglycans, acting as upstream regulators of pyroptosis. This review summarizes the important roles for palmitoylation in regulating the function of key pyroptosis-related proteins, shedding light on the intricate mechanisms governing immune responses and inflammation.

Itaconate alleviates diet-induced obesity via activation of brown adipocyte thermogenesis

Despite medical advances, there remains an unmet need for better treatment of obesity. Itaconate, a product of the decarboxylation of the tricarboxylic acid cycle intermediate cis-aconitate, plays a regulatory role in both metabolism and immunity. Here, we show that itaconate, as an endogenous compound, counteracts high-fat-diet (HFD)-induced obesity through leptin-independent mechanisms in three mouse models. Specifically, itaconate reduces weight gain, reverses hyperlipidemia, and improves glucose tolerance in HFD-fed mice. Additionally, itaconate enhances energy expenditure and the thermogenic capacity of brown adipose tissue (BAT). Unbiased proteomic analysis reveals that itaconate upregulates key proteins involved in fatty acid oxidation and represses the expression of lipogenic genes. Itaconate may provoke a major metabolic reprogramming by inducing fatty acid oxidation and suppression of fatty acid synthesis in BAT. These findings highlight itaconate as a potential activator of BAT-mediated thermogenesis and a promising candidate for anti-obesity therapy.

Octyl itaconate enhances VSVΔ51 oncolytic virotherapy by multitarget inhibition of antiviral and inflammatory pathways

The presence of heterogeneity in responses to oncolytic virotherapy poses a barrier to clinical effectiveness, as resistance to this treatment can occur through the inhibition of viral spread within the tumor, potentially leading to treatment failures. Here we show that 4-octyl itaconate (4-OI), a chemical derivative of the Krebs cycle-derived metabolite itaconate, enhances oncolytic virotherapy with VSVΔ51 in various models including human and murine resistant cancer cell lines, three-dimensional (3D) patient-derived colon tumoroids and organotypic brain tumor slices. Furthermore, 4-OI in combination with VSVΔ51 improves therapeutic outcomes in a resistant murine colon tumor model. Mechanistically, we find that 4-OI suppresses antiviral immunity in cancer cells through the modification of cysteine residues in MAVS and IKKβ independently of the NRF2/KEAP1 axis. We propose that the combination of a metabolite-derived drug with an oncolytic virus agent can greatly improve anticancer therapeutic outcomes by direct interference with the type I IFN and NF-κB-mediated antiviral responses.

Black carp ATG16L1 negatively regulates STING-mediated antiviral innate immune response

The precise control of interferon (IFN) production is indispensable for the host to eliminate invading viruses and maintain a homeostatic state. In mammals, stimulator of interferon genes (STING) is a prominent adaptor involved in antiviral immune signaling pathways. However, the regulatory mechanism of piscine STING has not been thoroughly investigated. Here, we report that autophagy related 16 like 1 (bcATG16L1) of black carp (Mylopharyngodon piceus) is a negative regulator in black carp STING (bcSTING)-mediated signaling pathway. Initially, we substantiated that knockdown of bcATG16L1 increased the transcription of IFN and ISGs and enhanced the antiviral activity of the host cells. Subsequently, we identified that bcATG16L1 inhibited the bcSTING-mediated IFN promoter activation and proved that bcATG16L1 suppressed bcSTING-mediated antiviral ability. Furthermore, we revealed that bcATG16L1 interacted with bcSTING and the two proteins shared a similar subcellular distribution. Mechanically, we found that bcATG16L1 attenuated the oligomerization of bcSTING, which was a key step for bcSTING activation. Taken together, our results indicate that bcATG16L1 interacts with bcSTING, dampens the oligomerization of bcSTING, and negatively regulates bcSTING-mediated antiviral activity.

IUPHAR ECR review: The cGAS-STING pathway: Novel functions beyond innate immune and emerging therapeutic opportunities

Stimulator of interferon genes (STING) is a crucial innate immune sensor responsible for distinguishing pathogens and cytosolic DNA, mediating innate immune signaling pathways to defend the host. Recent studies have revealed additional regulatory functions of STING beyond its innate immune-related activities, including the regulation of cellular metabolism, DNA repair, cellular senescence, autophagy and various cell deaths. These findings highlight the broader implications of STING in cellular physiology beyond its role in innate immunity. Currently, approximately 10 STING agonists have entered the clinical stage. Unlike inhibitors, which have a maximum inhibition limit, agonists have the potential for infinite amplification. STING signaling is a complex process that requires precise regulation of STING to ensure balanced immune responses and prevent detrimental autoinflammation. Recent research on the structural mechanism of STING autoinhibition and its negative regulation by adaptor protein complex 1 (AP-1) provides valuable insights into its different effects under physiological and pathological conditions, offering a new perspective for developing immune regulatory drugs. Herein, we present a comprehensive overview of the regulatory functions and molecular mechanisms of STING beyond innate immune regulation, along with updated details of its structural mechanisms. We discuss the implications of these complex regulations in various diseases, emphasizing the importance and feasibility of targeting the immunity-dependent or immunity-independent functions of STING. Moreover, we highlight the current trend in drug development and key points for clinical research, basic research, and translational research related to STING.

Regulation of cardiomyocyte intracellular trafficking and signal transduction by protein palmitoylation

Despite the well-established functions of protein palmitoylation in fundamental cellular processes, the roles of this reversible post-translational lipid modification in cardiomyocyte biology remain poorly studied. Palmitoylation is catalyzed by a family of 23 zinc finger and Asp-His-His-Cys domain-containing S-acyltransferases (zDHHC enzymes) and removed by select thioesterases of the lysophospholipase and α/β-hydroxylase domain (ABHD)-containing families of serine hydrolases. Recently, studies utilizing genetic manipulation of zDHHC enzymes in cardiomyocytes have begun to unveil essential functions for these enzymes in regulating cardiac development, homeostasis, and pathogenesis. Palmitoylation co-ordinates cardiac electrophysiology through direct modulation of ion channels and transporters to impact their trafficking or gating properties as well as indirectly through modification of regulators of channels, transporters, and calcium handling machinery. Not surprisingly, palmitoylation has roles in orchestrating the intracellular trafficking of proteins in cardiomyocytes, but also dynamically fine-tunes cardiomyocyte exocytosis and natriuretic peptide secretion. Palmitoylation has emerged as a potent regulator of intracellular signaling in cardiomyocytes, with recent studies uncovering palmitoylation-dependent regulation of small GTPases through direct modification and sarcolemmal targeting of the small GTPases themselves or by modification of regulators of the GTPase cycle. In addition to dynamic control of G protein signaling, cytosolic DNA is sensed and transduced into an inflammatory transcriptional output through palmitoylation-dependent activation of the cGAS-STING pathway, which has been targeted pharmacologically in preclinical models of heart disease. Further research is needed to fully understand the complex regulatory mechanisms governed by protein palmitoylation in cardiomyocytes and potential emerging therapeutic targets.