The Cyclopeptide Astin C Specifically Inhibits the Innate Immune CDN Sensor STING

Inhibition of the cGAS-STING pathway: contributing to the treatment of cerebral ischemia-reperfusion injury

The cGAS-STING pathway plays an important role in ischemia-reperfusion injury in the heart, liver, brain, and kidney, but its role and mechanisms in cerebral ischemia-reperfusion injury have not been systematically reviewed. Here, we outline the components of the cGAS-STING pathway and then analyze its role in autophagy, ferroptosis, cellular pyroptosis, disequilibrium of calcium homeostasis, inflammatory responses, disruption of the blood-brain barrier, microglia transformation, and complement system activation following cerebral ischemia-reperfusion injury. We further analyze the value of cGAS-STING pathway inhibitors in the treatment of cerebral ischemia-reperfusion injury and conclude that the pathway can regulate cerebral ischemia-reperfusion injury through multiple mechanisms. Inhibition of the cGAS-STING pathway may be helpful in the treatment of cerebral ischemia-reperfusion injury.

Bidirectional regulation of the cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon gene pathway and its impact on hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) ranks as the fourth leading cause of cancer-related deaths in China, and the treatment options are limited. The cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) activates the stimulator of interferon gene (STING) signaling pathway as a crucial immune response pathway in the cytoplasm, which detects cytoplasmic DNA to regulate innate and adaptive immune responses. As a potential therapeutic target, cGAS-STING pathway markedly inhibits tumor cell proliferation and metastasis, with its activation being particularly relevant in HCC. However, prolonged pathway activation may lead to an immunosuppressive tumor microenvironment, which fostering the invasion or metastasis of liver tumor cells.

AIM

To investigate the dual-regulation mechanism of cGAS-STING in HCC.

METHODS

This review was conducted according to the PRISMA guidelines. The study conducted a comprehensive search for articles related to HCC on PubMed and Web of Science databases. Through rigorous screening and meticulous analysis of the retrieved literature, the research aimed to summarize and elucidate the impact of the cGAS-STING pathway on HCC tumors.

RESULTS

All authors collaboratively selected studies for inclusion, extracted data, and the initial search of online databases yielded 1445 studies. After removing duplicates, the remaining 964 records were screened. Ultimately, 55 articles met the inclusion criteria and were included in this review.

CONCLUSION

Acute inflammation can have a few inhibitory effects on cancer, while chronic inflammation generally promotes its progression. Extended cGAS-STING pathway activation will result in a suppressive tumor microenvironment.

Mitochondrial DAMPs: Key mediators in neuroinflammation and neurodegenerative disease pathogenesis

Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) are increasingly linked to mitochondrial dysfunction and neuroinflammation. Central to this link are mitochondrial damage-associated molecular patterns (mtDAMPs), including mitochondrial DNA, ATP, and reactive oxygen species, released during mitochondrial stress or damage. These mtDAMPs activate inflammatory pathways, such as the NLRP3 inflammasome and cGAS-STING, contributing to the progression of neurodegenerative diseases. This review delves into the mechanisms by which mtDAMPs drive neuroinflammation and discusses potential therapeutic strategies targeting these pathways to mitigate neurodegeneration. Additionally, it explores the cross-talk between mitochondria and the immune system, highlighting the complex interplay that exacerbates neuronal damage. Understanding the role of mtDAMPs could pave the way for novel treatments aimed at modulating neuroinflammation and slowing disease progression, ultimately improving patient outcome.

Mailuoning oral liquid ameliorates vasculitis in thromboangiitis obliterans rats via inactivating cGAS-STING-IRF3 and TLR4-MAPKs/NF-κB signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Mailuoning oral liquid (MLN O), one traditional Chinese patent medicine, has a good therapeutic effect on thromboangiitis obliterans (TAO) in clinical practice. However, the underlying mechanism remains unclear.

AIM OF THE STUDY

This study aimed to explore the effects and potential mechanisms of MLN O against TAO based on network pharmacology and experimental verification.

MATERIALS AND METHODS

Network pharmacology was used to identify the intersectional targets and signaling pathways of MLN O and TAO. In vivo, the TAO model was established by injecting sodium laurate and dihydrotestosterone (DHT) into the femoral arteries of Wistar rats. Rats were given the indicated drugs by intragastric administration (i.g.), intravenous injection (i.v.), or subcutaneous injection (s.c.) per day for 21 days since a week before surgery. In vitro, HUVECs, RAW264.7, and THP-1 cells were stimulated by LPS and DHT to simulate the pathological changes of TAO. The anti-inflammatory, anticoagulant, and immunomodulatory effects of MLN O were evaluated by histological observation, blood biochemical indexes detection, H&E staining, immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), qRT-PCR, western blotting and immunofluorescence assays. Furthermore, the vascular ring test was applied to explore the vasodilatory activity of MLN O.

RESULTS

MLN O significantly improved the pathological signs in TAO rats through its excellent anti-inflammatory, anticoagulant, immunomodulatory, and vasodilatory effects. Specifically, MLN O alleviated the gangrene and reduced the thrombosis in TAO rats, meanwhile, suppressed the expressions of inflammatory factors and clotting factors, which is related to the inactivations of cGAS-STING-IRF3 and TLR4-MAPKs/NF-κB signaling pathways. However, the superphysiological dose of DHT deteriorated the pathological development of TAO in vitro and in vivo. Moreover, the results of network pharmacology are consistent with the experimental verification.

CONCLUSION

Collectively, this study indicates for the first time that MLN O could alleviate TAO by inhibiting cGAS-STING-IRF3 and TLR4-MAPKs/NF-κB signaling pathways, which sheds light on a novel clinical therapeutic strategy for TAO.

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.

Discovery and Total Synthesis of Anhydrotuberosin as a STING Antagonist for Treating Autoimmune Diseases

Excessive activation of the stimulator of the interferon gene (STING) pathway has been identified as a significant contributor to various autoimmune diseases, such as STING-associated vasculopathy with infantile-onset (SAVI) and inflammatory bowel disease (IBD). However, discovering effective STING antagonists for treating STING-mediated autoimmune disorders remains challenging. Herein, we identified the natural product anhydrotuberosin (ATS) as a potent STING antagonist by a high-throughput chemical screen and follow-up biological validations. However, the limited supply from natural product isolation impeded the pharmacological evaluations of ATS. Accordingly, we developed a concise and scalable total synthesis of ATS in 6 steps. Enabled by total synthesis, we further extensively investigated ATS's mode of action and evaluated its therapeutic potential. Remarkably, ATS inhibits STING signaling in PBMCs derived from three SAVI patients. ATS showed decent pharmacokinetic parameters and strongly alleviated tissue inflammation in DSS-induced IBD colitis and Trex1-/- autoimmune animal models with low toxicity. Collectively, this research lays the foundation for developing novel STING antagonists as an effective therapy for autoinflammatory and autoimmune diseases.

Progress of cGAS-STING signaling pathway-based modulation of immune response by traditional Chinese medicine in clinical diseases

The cGAS-STING signaling pathway is a critical component of the innate immune response, playing a significant role in various diseases. As a central element of this pathway, STING responds to both endogenous and exogenous DNA stimuli, triggering the production of interferons and pro-inflammatory cytokines to enhance immune defenses against tumors and pathogens. However, dysregulated activation of the STING pathway is implicated in the pathogenesis of multiple diseases, including autoinflammation, viral infections, and cancer. Traditional Chinese Medicines (TCMs), which have a long history of use, have been associated with positive effects in disease prevention and treatment. TCM formulations (e.g., Lingguizhugan Decoction, Yi-Shen-Xie-Zhuo formula) and active compounds (e.g., Glabridin, Ginsenoside Rd) can modulate the cGAS-STING signaling pathway, thereby influencing the progression of inflammatory, infectious, or oncological diseases. This review explores the mechanisms by which TCMs interact with the cGAS-STING pathway to regulate immunity, focusing on their roles in infectious diseases, malignancies, and autoimmune disorders.

Inhibition of IRF3-STING axis interaction in silicosis using natural compounds: an in-silico study using molecular docking, ADMET, molecular dynamics and MMPBSA approach

Silicosis is a chronic occupational lung disease characterized by persistent inflammation driven by the activation of the cGAS-STING pathway, leading to the downstream activation of IRF3. To develop a natural compound library of COCONUT database for this investigation, Lipinski's rule of five was used and we explored the potential of these compounds to disrupt the IRF3-STING interaction, thereby mitigating the inflammatory response. Molecular docking and molecular dynamics (MD) simulations were employed to assess the binding stability and interaction dynamics of these compounds with IRF3. The stable RMSD values indicate that the protein-ligand complexes maintained structural integrity throughout the simulation period. The compounds also demonstrated drug-like characteristics, a promising safety profile, and formed stable complexes with the target protein. Further, decomposition of binding free energy highlighted the key contributions of IRF3 residues VAL295, ASP308, PRO324, and ARG338 interacting with the selected compounds, potentially inhibiting the IRF3-STING interaction. The origin of the selected compounds was determined using ClassyFire, classifying compound CNP0310627 as a burfenolide and compound CNP0200121 as a psoralen. Both classes are recognized for their anti-inflammatory properties, reinforcing the therapeutic potential of these compounds in reducing inflammation associated with silicosis. Our findings suggest that these compounds could serve as promising candidates for further investigation in the development of anti-inflammatory therapeutic molecules in the cGAS-STING-IRF3 signaling pathway. However, to fully assess the therapeutic potential of these compounds, further in vitro and in vivo studies are required to validate their efficacy and safety in modulating the STING-IRF3 pathway.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-024-00290-5.

Targeting STING oligomerization with licochalcone D ameliorates STING-driven inflammatory diseases

The development of STING inhibitors for the treatment of STING-related inflammatory diseases continues to encounter significant challenges. The activation of STING is a multi-step process that includes binding with cGAMP, self-oligomerization, and translocation from the endoplasmic reticulum to the Golgi apparatus, ultimately inducing the expression of IRF3 and NF-κB-mediated interferons and inflammatory cytokines. It has been demonstrated that disruption of any of these steps can effectively inhibit STING activation. Traditional structure-based drug screening methodologies generally focus on specific binding sites. In this study, a TransformerCPI model based on protein primary sequences and independent of binding sites is employed to identify compounds capable of binding to the STING protein. The natural product Licochalcone D (LicoD) is identified as a potent and selective STING inhibitor. LicoD does not bind to the classical ligand-binding pocket; instead, it covalently modifies the Cys148 residue of STING. This modification inhibits STING oligomerization, consequently suppressing the recruitment of TBK1 and the nuclear translocation of IRF3 and NF-κB. LicoD treatment ameliorates the inflammatory phenotype in Trex1-1- mice and inhibits the progression of DSS-induced colitis and AOM/DSS-induced colitis-associated colon cancer (CAC). In summary, this study reveals the potential of LicoD in treating STING-driven inflammatory diseases. It also demonstrates the utility of the TransformerCPI model in discovering allosteric compounds beyond the conventional binding pockets.

The crucial roles and research advances of cGAS‑STING pathway in liver diseases

Inflammation responses have identified as a key mediator of in various liver diseases with high morbidity and mortality. cGAS-STING signalling is essential in innate immunity since it triggers release of type I interferons and various of proinflammatory cytokines. The potential connection between cGAS-STING pathway and liver inflammatory diseases has recently been reported widely. In our review, the impact of cGAS-STING on liver inflammation and regulatory mechanism are summarized. Furthermore, many inhibitors of cGAS-STING signalling as promising agents to cure liver inflammation are also explored in detail. A comprehensive knowledge of molecular mechanisms of cGAS-STING signalling in liver inflammation is vital for exploring novel treatments and providing recommendations and perspectives for future utilization.

The cross-talk between the cGAS-STING signaling pathway and chronic inflammation in the development of musculoskeletal disorders

Musculoskeletal disorders (MSDs) comprise diverse conditions affecting bones, joints, and muscles, leading to pain and loss of function, and are one of the most prevalent and major global health concerns. One of the hallmarks of MSDs is DNA damage. Once accumulated in the cytoplasm, the damaged DNA is sensed by the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway, which triggers the induction of type I interferons and inflammatory cytokines. Thus, this pathway connects the musculoskeletal and immune systems. Inhibitors of cGAS or STING have shown promising therapeutic effects in the pre-clinical models of several MSDs. Systemic, chronic, low-grade inflammation (SCLGI) underlies the development and maintenance of many MSDs. Failure to resolve SCLGI has been hypothesized to play a critical role in the development of chronic diseases, suggesting that the successful resolution of SCLGI will result in the alleviation of their related symptomatology. The process of inflammation resolution is feasible by specialized pro-resolving mediators (SPMs), which are enzymatically generated from dietary essential polyunsaturated fatty acids (PUFAs). The supplementation of SPMs or their stable, small-molecule mimetics and receptor agonists has revealed beneficial effects in inflammation-related animal models, including arthropathies, osteoporosis, and muscle dystrophy, suggesting a translational potential in MSDs. In this review, we substantiate the hypothesis that the use of cGAS-STING signaling pathway inhibitors together with SCLG-resolving compounds may serve as a promising new therapeutic approach for MSDs.

Acacetin targets STING to alleviate the destabilization of the medial meniscus-induced osteoarthritis in mice

Osteoarthritis (OA) is a common joint disorder affecting about 7% of the global population, primarily characterized by the gradual loss of articular cartilage. This degeneration results from local inflammation, matrix depletion, and direct cartilage damage. A critical element in this process is the activation of the stimulator of the interferon genes (STING) pathway. Emerging evidence highlights its potential as a therapeutic target, with natural products showing promise as inhibitors. Our study centers on Acacetin, a basic unit of polyketides known for its anti-inflammatory properties. Prior research has highlighted its potential interaction with STING based on the structure. Thus, this study aimed to assess the effectiveness of Acacetin as a STING inhibitor and its protective role against OA. In vitro experiments showed that Acacetin pretreatment not only mitigated interleukin-1β (IL-1β)-induced cytotoxicity but also decreased the inflammatory response and degeneration in chondrocytes stimulated IL-1β. In vivo studies revealed that Acacetin administration significantly reduced articular cartilage destruction, abnormal bone remodeling, and osteophyte formation in a model of OA induced by destabilization of the medial meniscus (DMM). Mechanistically, Acacetin was found to interact directly with STING, and inhibit IL-1β-induced activation of STING, along with the subsequent phosphorylation of the TBK1/NF-κB pathway in chondrocytes. In conclusion, our findings establish Acacetin as an effective inhibitor of STING that protects chondrocytes from IL-1β-induced damage and slows the progression of OA in mice.

cGAS/STING signalling pathway in senescence and oncogenesis

The cGAS/STING signaling pathway is a crucial component of the innate immune system, playing significant roles in sensing cytosolic DNA, regulating cellular senescence, and contributing to oncogenesis. Recent advances have shed new lights into the molecular mechanisms governing pathway activation in multiple pathophysiological settings, the indispensable roles of cGAS/STING signaling in cellular senescence, and its context-dependent roles in cancer development and suppression. This review summarizes current knowledge related to the biology of cGAS/STING signaling pathway and its participations into senescence and oncogenesis. We further explore the clinical implications and therapeutic potential for cGAS/STING targeted therapies, and faced challenges in the field. With a focus on molecular mechanisms and emerging pharmacological targets, this review underscores the importance of future studies to harness the therapeutic potential of the cGAS/STING pathway in treating senescence-related disorders and cancer. Advanced understanding of the regulatory mechanisms of cGAS/STING signaling, along with the associated deregulations in diseases, combined with the development of new classes of cGAS/STING modulators, hold great promises for creating novel and effective therapeutic strategies. These advancements could address current treatment challenges and unlock the full potential of cGAS/STING in treating senescence-related disorders and oncogenesis.

DNA-sensing pathways in health, autoinflammatory and autoimmune diseases

Detection of microbial DNA is a primary means of host defense. In mammalian cells, DNA-sensing pathways induce robust anti-microbial responses and initiation of adaptive immunity, leading to the eventual clearance of the infectious agent. However, while conferring the advantage of broad detection capability, the sequence-independent recognition mechanisms of most DNA sensors pose a significant challenge for mammalian cells to maintain ignorance to self-DNA under homeostatic conditions. In this Review, we summarize the fundamentals of DNA-sensing pathways and the intricate regulatory networks that keep these pathways in check. In addition, we describe how regulatory restraints can be defective and underlie human autoinflammatory and autoimmune diseases. Further, we discuss therapies in development that limit inflammation fueled by self-DNA or inappropriate activation of DNA-sensing pathways.

The role of the cGAS-STING pathway in chronic pulmonary inflammatory diseases

The innate immune system plays a vital role in the inflammatory process, serving as a crucial mechanism for the body to respond to infection, cellular stress, and tissue damage. The cGAS-STING signaling pathway is pivotal in the onset and progression of various autoimmune diseases and chronic inflammation. By recognizing cytoplasmic DNA, this pathway initiates and regulates inflammation and antiviral responses within the innate immune system. Consequently, the regulation of the cGAS-STING pathway has become a prominent area of interest in the treatment of many diseases. Chronic inflammatory lung diseases, such as chronic obstructive pulmonary disease (COPD), asthma, and pulmonary fibrosis, are characterized by persistent or recurrent lung inflammation and tissue damage, leading to diminished respiratory function. This paper explores the mechanism of action of the cGAS-STING signaling pathway in these diseases, examines the development of STING inhibitors and nanomaterial applications, and discusses the potential clinical application prospects of targeting the cGAS-STING pathway in chronic inflammatory lung diseases.

cGAS-STING DNA-sensing in inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are chronic, incurable pathologies with unknown causes, affecting millions of people. Pediatric-onset IBD, starting before the age of 18 years, are increasing, with more aggressive and extensive features than adult-onset IBD. These differences remain largely unexplained. Intestinal mucosal damage, cell death, DNA release from nuclear, mitochondrial, or microbiota sources, and DNA-sensing activating the cGAS-STING pathway may contribute to disease evolution. Increased colonic cGAS and STING are increasingly reported in experimental and human IBD. However, limited knowledge of the mechanisms involved hinders the development of new therapeutic options. Here, we discuss recent advances and unresolved questions regarding DNA release, DNA sensor activation, and the role and therapeutic potential of the cGAS-STING pathway in inflammatory colitis.

Orally bioavailable STING antagonist synthesized via multi-component Povarov-Doebner type reaction

Aberrant activation of the cGAS-STING signaling results in innate immune response induction. Herein, we report HSKB142, an orally bioavailable compound containing the 3H-pyrazolo [4,3-f]quinoline synthesized via a Povarov-Doebner MCR. HSKB142 is non-cytotoxic towards immune cells and suppresses type-1 interferon expression in human THP-1 monocytes upon treatment with 2'3'-cGAMP.

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.

The role of the cGAS-STING signaling pathway in viral infections, inflammatory and autoimmune diseases

Pattern recognition receptors are an essential part of the immune system, which detect pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) and help shape both innate and adaptive immune responses. When dsDNA is present, cyclic GMP-AMP Synthase (cGAS) produces a second messenger called cyclic GMP-AMP (cGAMP), which then triggers an adaptor protein called STING, and eventually activates the expression of type I interferon (IFN) and pro-inflammatory cytokines in immune cells. The cGAS-STING signaling pathway has been receiving a lot of attention lately as a key immune-surveillance mediator. In this review, we summarize the present circumstances of the cGAS-STING signaling pathway in viral infections and inflammatory diseases, as well as autoimmune diseases. Modulation of the cGAS-STING signaling pathway provides potential strategies for treating viral infections, inflammatory diseases, and autoimmune diseases.

Pentagalloylglucose alleviates acetaminophen-induced acute liver injury by modulating inflammation via cGAS-STING pathway

BACKGROUND

The cGAS-STING pathway is an important component of the innate immune system and plays significant role in acetaminophen-induced liver injury (AILI). Pentagalloylglucose (PGG) is a natural polyphenolic compound with various beneficial effects, including anti-cancer, antioxidant, anti-inflammatory, and liver-protective properties; however, whether it can be used for the treatment of AILI and the specific mechanism remain unclear.

MATERIALS AND METHODS

A cell culture model was created to study the effect of PGG on cGAS-STING pathway activation using various techniques including western blotting (WB), real-time quantitative polymerase chain reaction (RT-qPCR), immunofluorescence (IF), and immunoprecipitation (IP). The effect of PGG was investigated in vivo by establishing a dimethylxanthenone acetic acid (DMXAA)-mediated activation model. An AILI model was used to evaluate the hepatoprotective and therapeutic effects of PGG by detecting liver function indicators, liver histopathology, and cGAS-STING pathway-related indicators in mice with AILI.

RESULTS

PGG blocked cGAS-STING pathway activation in bone marrow-derived macrophages (BMDMs), THP-1 cells, and peripheral blood mononuclear cells (PBMCs) in vitro. Furthermore, PGG inhibited the generation of type I interferons (IFN-I) and the secretion of inflammatory factors in DMXAA-induced in vivo experiments. In addition, PGG also reduced serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP), improved liver tissue damage and apoptosis, and inhibited the cGAS-STING pathway activation caused by acetaminophen. In terms of the mechanism, PGG disrupted the connection between STING and TBK1.

CONCLUSIONS

PGG exerts a protective effect against AILI by blocking the cGAS-STING pathway, offering a promising treatment strategy.

The role of cGAS-STING signaling in rheumatoid arthritis: from pathogenesis to therapeutic targets

Rheumatoid arthritis (RA) is a systemic autoimmune disease primarily characterized by erosive and symmetric polyarthritis. As a pivotal axis in the regulation of type I interferon (IFN-I) and innate immunity, the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling pathway has been implicated in the pathogenesis of RA. This pathway mainly functions by regulating cell survival, pyroptosis, migration, and invasion. Therefore, understanding the sources of cell-free DNA and the mechanisms underlying the activation and regulation of cGAS-STING signaling in RA offers a promising avenue for targeted therapies. Early detection and interventions targeting the cGAS-STING signaling are important for reducing the medical burden on individuals and healthcare systems. Herein, we review the existing literature pertaining to the role of cGAS-STING signaling in RA, and discuss current applications and future directions for targeting the cGAS-STING signaling in RA treatments.

cGAS activation in classical dendritic cells causes autoimmunity in TREX1-deficient mice

Detection of cytosolic DNA by the cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulator of interferon genes (STING) pathway provides immune defense against pathogens and cancer but can also cause autoimmunity when overactivated. The exonuclease three prime repair exonuclease 1 (TREX1) degrades DNA in the cytosol and prevents cGAS activation by self-DNA. Loss-of-function mutations of the TREX1 gene are linked to autoimmune diseases such as Aicardi-Goutières syndrome, and mice deficient in TREX1 develop lethal inflammation in a cGAS-dependent manner. In order to determine the type of cells in which cGAS activation drives autoinflammation, we generated conditional cGAS knockout mice on the Trex1-/- background. Here, we show that genetic ablation of the cGAS gene in classical dendritic cells (cDCs), but not in macrophages, was sufficient to rescue Trex1-/- mice from all observed disease phenotypes including lethality, T cell activation, tissue inflammation, and production of antinuclear antibodies and interferon-stimulated genes. These results show that cGAS activation in cDC causes autoinflammation in response to self-DNA accumulated in the absence of TREX1.

An updated and comprehensive review of the morphology, ethnomedicinal uses, phytochemistry, and pharmacological activity of Aster tataricus L. f

Ethnopharmacological relevance

Aster tataricus L.f., an extensively used herb in traditional Chinese medicine for more than 2000 years, is known as "Zi wan" or "Fan huncao". Its dried root and rhizome hold great promise in the treatment of cough, asthma, tumor, inflammation, etc.Aim of the study: This literature review summarizes the morphology characteristics, ethnopharmacological use, phytochemical properties, pharmacological effects, and potential applications of Aster tataricus. Furthermore, this review will discuss the future research trends and development prospects of this plant.

Materials and methods

Using "Aster tataricus L.f.", "Traditional medicinal usage", "Phytochemistry", "Pharmacological effects" as the keywords and gathered relevant data on Aster tataricus L.f. using electronic databases (Elsevier, PubMed, ACS, CNKI, Google Scholar, Baidu Scholar, Web of Science), relevant books, and classic literature about Chinese herb.

Result

A total of 186 compounds have been isolated and identified from Aster tataricus, including terpenes, organic acids, peptides, and flavonoids. And Aster tataricus has been widely used as a natural cough suppressant and has anti-oxidative, anti-inflammatory, anti-depressive, and anti-tumor effects. In addition, Aster tataricus has also been reported to have damaging effects on the liver as well as other toxicities were discussed in this review.

Conclusions

Aster tataricus is an ancient herbal medicine with a broad spectrum of pharmaco logical activities that has been used for thousands of years in China, and has shown remarkable effectiveness in the treatment of various diseases, especially cough, asthma, inflammation. Although its rich chemical constituents have various pharmacological activities, the underlying mechanisms, as well as its toxicity and safety, remains unclear and warrant further investigation.

The cGAS-STING pathway in COPD: targeting its role and therapeutic potential

Chronic obstructive pulmonary disease(COPD) is a gradually worsening and fatal heterogeneous lung disease characterized by airflow limitation and increasingly decline in lung function. Currently, it is one of the leading causes of death worldwide. The consistent feature of COPD is airway inflammation. Several inflammatory factors are known to be involved in COPD pathogenesis; however, anti-inflammatory therapy is not the first-line treatment for COPD. Although bronchodilators, corticosteroids and roflumilast could improve airflow and control symptoms, they could not reverse the disease. The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling pathway plays an important novel role in the immune system and has been confirmed to be a key mediator of inflammation during infection, cellular stress, and tissue damage. Recent studies have emphasized that abnormal activation of cGAS-STING contributes to COPD, providing a direction for new treatments that we urgently need to develop. Here, we focused on the cGAS-STING pathway, providing insight into its molecular mechanism and summarizing the current knowledge on the role of the cGAS-STING pathway in COPD. Moreover, we explored antagonists of cGAS and STING to identify potential therapeutic strategies for COPD that target the cGAS-STING pathway.

Role of interferon dependent and independent signaling pathways: Implications in cancer

Interferons (IFNs) are a class of cytokines with potent antiviral and immunomodulatory properties that regulate the immune system through multiple signaling pathways. In cancer, IFNs are vital to both tumor-intrinsic and extrinsic mechanisms that affect the quality of antitumor immunity as well as response to cancer treatments, including immunotherapy. However, there is a need for a deeper and better understanding of the mechanisms by which IFNs elicit immune signalling in cancerous cells. In this review, we focus on the IFN- dependent and independent axes in cancer as targetable hubs for new immunotherapeutic approaches to boost the treatment efficacy and to circumvent cancer resistance leading to improved clinical outcomes.

The cGAS-STING Pathway: A New Therapeutic Target for Ischemia-Reperfusion Injury in Acute Myocardial Infarction?

The innate immune system is the body's natural defense system, which recognizes a wide range of microbial molecules (such as bacterial DNA and RNA) and abnormal molecules within cells (such as misplaced DNA, self-antigens) to play its role. DNA released into the cytoplasm activates the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway to initiate an immune response. Ischemia-reperfusion injury (IRI) after acute myocardial infarction refers to the phenomenon where myocardial tissue suffers further damage upon the restoration of blood flow. This issue is a significant clinical problem in the treatment of myocardial infarction, as it can diminish the effectiveness of reperfusion therapy and lead to further deterioration of cardiac function. Studies have found that the cGAS-STING signaling pathway is closely related to this phenomenon. Therefore, this review aims to describe the role of the cGAS-STING signaling pathway in ischemia-reperfusion injury after myocardial infarction and summarize the current development status of cGAS-STING pathway inhibitors and the application of nanomaterials to further elucidate the potential of this pathway as a therapeutic target.

Cyclic-di-GMP induces inflammation and acute lung injury through direct binding to MD2

BACKGROUND

Severe bacterial infections can trigger acute lung injury (ALI) and acute respiratory distress syndrome, with bacterial pathogen-associated molecular patterns (PAMPs) exacerbating the inflammatory response, particularly in COVID-19 patients. Cyclic-di-GMP (CDG), one of the PAMPs, is synthesized by various Gram-positve and Gram-negative bacteria. Previous studies mainly focused on the inflammatory responses triggered by intracellular bacteria-released CDG. However, how extracellular CDG, which is released by bacterial autolysis or rupture, activates the inflammatory response remains unclear.

METHODS

The interaction between extracellular CDG and myeloid differentiation protein 2 (MD2) was investigated using in vivo and in vitro models. MD2 blockade was achieved using specific inhibitor and genetic knockout mice. Site-directed mutagenesis, co-immunoprecipitation, SPR and Bis-ANS displacement assays were used to identify the potential binding sites of MD2 on CDG.

RESULTS

Our data show that extracellular CDG directly interacts with MD2, leading to activation of the TLR4 signalling pathway and lung injury. Specific inhibitors or genetic knockout of MD2 in mice significantly alleviated CDG-induced lung injury. Moreover, isoleucine residues at positions 80 and 94, along with phenylalanine at position 121, are essential for the binding of MD2 to CDG.

CONCLUSION

These results reveal that extracellular CDG induces lung injury through direct interaction with MD2 and activation of the TLR4 signalling pathway, providing valuable insights into bacteria-induced ALI mechanisms and new therapeutic approaches for the treatment of bacterial co-infection in COVID-19 patients.

Proline Analogues

Within the canonical repertoire of the amino acid involved in protein biogenesis, proline plays a unique role as an amino acid presenting a modified backbone rather than a side-chain. Chemical structures that mimic proline but introduce changes into its specific molecular features are defined as proline analogues. This review article summarizes the existing chemical, physicochemical, and biochemical knowledge about this peculiar family of structures. We group proline analogues from the following compounds: substituted prolines, unsaturated and fused structures, ring size homologues, heterocyclic, e.g., pseudoproline, and bridged proline-resembling structures. We overview (1) the occurrence of proline analogues in nature and their chemical synthesis, (2) physicochemical properties including ring conformation and cis/trans amide isomerization, (3) use in commercial drugs such as nirmatrelvir recently approved against COVID-19, (4) peptide and protein synthesis involving proline analogues, (5) specific opportunities created in peptide engineering, and (6) cases of protein engineering with the analogues. The review aims to provide a summary to anyone interested in using proline analogues in systems ranging from specific biochemical setups to complex biological systems.

Harnessing cGAS-STING axis for therapeutic benefits in systemic lupus erythematosus

The cyclic GMP-AMP synthase (cGAS), a prominent intracellular DNA sensor in mammalian cells, controls the innate immune response and the stimulator of interferon genes (STING)-mediated synthesis of pro-inflammatory cytokines, such as type-I interferon (IFN-I). For decades, IFN-I has been hypothesized to be essential in the development of systemic lupus erythematosus (SLE), a chronic multisystem autoimmunity characterized by immune complex (IC) deposition in small vessels. Recent findings revealed that the activation of the cGAS-STING pathway by self-DNA would propagate the autoimmune responses via upregulating IFN-I production in SLE. In this review, we aimed to provide a comprehensive outlook of the role of the cGAS-STING pathway in SLE pathobiology, as well as, a better understanding of current therapeutic opportunities targeting this axis.

The emerging role of adaptor proteins in regulating innate immunity of sepsis

Sepsis is a life-threatening syndrome caused by a dysregulated immune response. A large number of adaptor proteins have been found to play a pivotal role in sepsis via protein-protein interactions, thus participating in inflammatory cascades, leading to the generation of numerous inflammatory cytokines, as well as oxidative stress and regulated cell death. Although available strategies for the diagnosis and management of sepsis have improved, effective and specific treatments are lacking. This review focuses on the emerging role of adaptor proteins in regulating the innate immunity of sepsis and evaluates the potential value of adaptor protein-associated therapeutic strategy for sepsis.

The role of the cGAS-STING pathway in metabolic diseases

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway is a critical innate immune pathway primarily due to its vital DNA sensing mechanism in pathogen defence. Recent research advances have shown that excessive activation or damage to the cGAS-STING pathway can exacerbate chronic inflammatory responses, playing a significant role in metabolic dysfunction and aging, leading to the development of related diseases such as obesity, osteoporosis, and neurodegenerative diseases. This article reviews the structure and biological functions of the cGAS-STING signaling pathway and discusses in detail how this pathway regulates the occurrence and development of metabolic and age-related diseases. Additionally, this article introduces potential small molecule drugs targeting cGAS and STING, aiming to provide new research perspectives for studying the pathogenesis and treatment of metabolic-related diseases.

Glycyrrhiza uralensis polysaccharides ameliorates cecal ligation and puncture-induced sepsis by inhibiting the cGAS-STING signaling pathway

Ethnopharmacological relevance: G. uralensis Fisch. (Glycyrrhiza uralensis) is an ancient and widely used traditional Chinese medicine with good efficacy in clearing heat and detoxifying action. Studies suggest that Glycyrrhiza Uralensis Polysaccharides (GUP), one of the major components of G. uralensis, has anti-inflammatory, anti-cancer and hepatoprotective effects., but its exact molecular mechanism has not been explored in depth. Aim of the study: Objectives of our research are about exploring the anti-inflammatory role of GUP and the mechanisms of its action. Materials and methods: ELISA kits, Western blotting, immunofluorescence, quantitative real-time PCR, immunoprecipitation and DMXAA-mediated STING activation mice models were performed to investigate the role of GUP on the cGAS-STING pathway. To determine the anti-inflammatory effects of GUP, cecal ligation and puncture (CLP) sepsis models were employed. Results: GUP could effectively inhibit the activation of the cGAS-STING signaling pathway accompany by a decrease the expression of type I interferon-related genes and inflammatory factors in BMDMs, THP-1, and human PBMCs. Mechanistically, GUP does not affect the oligomerization of STING, but affects the interaction of STING with TBK1 and TBK1 with IRF3. Significantly, GUP had great therapeutic effects on DMXAA-induced agonist experiments in vivo as well as CLP sepsis in mice. Conclusion: Our studies suggest that GUP is an effective inhibitor of the cGAS-STING pathway, which may be a potential medicine for the treatment of inflammatory diseases mediated by the cGAS-STING pathway.

Compound Danshen Dripping Pill effectively alleviates cGAS-STING-triggered diseases by disrupting STING-TBK1 interaction

BACKGROUND

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon (IFN) genes (STING) pathway is critical in the innate immune system and can be mobilized by cytosolic DNA. The various inflammatory and autoimmune diseases progression is highly correlated with aberrant cGAS-STING pathway activation. While some cGAS-STING pathway inhibitor were identified, there are no drugs that can be applied to the clinic. Compound Danshen Dripping Pill (CDDP) has been successfully used in clinic around the world, but the most common application is limited to cardiovascular disease. Therefore, the purpose of the present investigation was to examine whether CDDP inhibits the cGAS-STING pathway and could be used as a therapeutic agent for multiple cGAS-STING-triggered diseases.

METHODS

BMDMs, THP1 cells or Trex1-/- BMDMs were stimulated with various cGAS-STING-agonists after pretreatment with CDDP to detect the function of CDDP on IFN-β and ISGs productionn. Next, we detect the influence on IRF3 and P65 nuclear translocation, STING oligomerization and STING-TBK1-IRF3 complex formation of CDDP. Additionally, the DMXAA-mediated activation mice model of cGAS-STING pathway was used to study the effects of CDDP. Trex1-/- mice model and HFD-mediated obesity model were established to clarify the efficacy of CDDP on inflammatory and autoimmune diseases.

RESULTS

CDDP efficacy suppressed the IRF3 phosphorylation or the generation of IFN-β, ISGs, IL-6 and TNF-α. Mechanistically, CDDP did not influence the STING oligomerization and IRF3-TBK1 and STING-IRF3 interaction, but remarkably eliminated the STING-TBK1 interaction, ultimately blocking the downstream responses. In addition, we also clarified that CDDP could suppress cGAS-STING pathway activation triggered by DMXAA, in vivo. Consistently, CDDP could alleviate multi-organ inflammatory responses in Trex1-/- mice model and attenuate the inflammatory disorders, incleding obesity-induced insulin resistance.

CONCLUSION

CDDP is a specifically cGAS-STING pathway inhibitor. Furthermore, we provide novel mechanism for CDDP and discovered a clinical agent for the therapy of cGAS-STING-triggered inflammatory and autoimmune diseases.

Flavonoid extracted from Epimedium attenuate cGAS-STING-mediated diseases by targeting the formation of functional STING signalosome

Hyperactivation of the cyclic-GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signalling pathway has been shown to be associated with the development of a variety of inflammatory diseases, and the discovery of an inhibitor of the cGAS-STING signalling pathway holds great promise in the therapeutic interventions. Epimedium flavonoid (EF), a major active ingredient isolated from the medicinal plant Epimedium, has been reported to have good anti-inflammatory activity, but its exact mechanism of action remains unclear. In the present study, we found that EF in mouse bone marrow-derived macrophages (BMDMs), THP-1 (Tohoku Hospital Pediatrics-1) as well as in human peripheral blood mononuclear cells (hPBMC) inhibited the activation of the cGAS-STING signalling pathway, which subsequently led to a decrease in the expression of type I interferon (IFN-β, CXCL10 and ISG15) and pro-inflammatory cytokines (IL-6 and TNF-α). Mechanistically, EF does not affect STING oligomerization, but inhibits the formation of functional STING signalosome by attenuating the interaction of interferon regulatory factor 3 (IRF3) with STING and TANK-binding kinase 1 (TBK1). Importantly, in vivo experiments, EF has shown promising therapeutic effects on inflammatory diseases mediated by the cGAS-STING pathway, which include the agonist model induced by DMXAA stimulation, the autoimmune inflammatory disease model induced by three prime repair exonuclease 1 (Trex1) deficiency, and the non-alcoholic steatohepatitis (NASH) model induced by a pathogenic amino acid and choline deficiency diet (MCD). To summarize, our study suggests that EF is a potent potential inhibitor component of the cGAS-STING signalling pathway for the treatment of inflammatory diseases mediated by the cGAS-STING signalling pathway.

Therapeutic landscape in systemic lupus erythematosus: mtDNA activation of the cGAS-STING pathway

Mitochondrial DNA (mtDNA) serves as a pivotal immune stimulus in the immune response. During stress, mitochondria release mtDNA into the cytoplasm, where it is recognized by the cytoplasmic DNA receptor cGAS. This activation initiates the cGAS-STING-IRF3 pathway, culminating in an inflammatory response. The cGAS-STING pathway has emerged as a critical mediator of inflammatory responses in microbial infections, stress, autoimmune diseases, chronic illnesses, and tissue injuries. Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by connective tissue involvement across various bodily systems. Its hallmark is the production of numerous autoantibodies, which prompt the immune system to target and damage the body's own tissues, resulting in organ and tissue damage. Increasing evidence implicates the cGAS-STING pathway as a significant contributor to SLE pathogenesis. This article aims to explore the role of the mtDNA-triggered cGAS-STING pathway and its mechanisms in SLE, with the goal of providing novel insights for clinical interventions.

C-176 reduces inflammation-induced pain by blocking the cGAS-STING pathway in microglia

OBJECTIVE

Inflammatory pain, is caused by lesions or diseases of the somatosensory tissue, is a prevalent chronic condition that profoundly impacts the quality of life. However, clinical treatment for this type of pain remains limited. Traditionally, the stimulation of microglia and subsequent inflammatory reactions are considered crucial elements to promote the worsening of inflammatory pain. Recent research has shown the crucial importance of the cGAS-STING pathway in promoting inflammation. It is still uncertain if the cGAS-STING pathway plays the role in the fundamental cause of inflammatory pain. We aim to explore the treatment of inflammatory pain by interfering with cGAS-STING signaling pathway.

METHODS

In this study, we established an inflammatory pain model by CFA into the plantar of mice. Activation of microglia, various inflammatory factors and cGAS-STING protein in the spinal dorsal horn were evaluated. Immunofluorescence staining was used to observe the cellular localization of cGAS and STING. The cGAS-STING pathway proteins expression and mRNA expression of indicated microglial M1/M2 phenotypic markers in the BV2 microglia were detected. STING inhibitor C-176 was intrathecal injected into mice with inflammatory pain, and the pain behavior and microglia were observed.

RESULTS

This research showed that injecting CFA into the left hind paw of mice caused mechanical allodynia and increased inflammation in the spine. Our research results suggested that the cGAS-STING pathway had a function in the inflammation mediated by microglia in the spinal cord dorsal horn. Blocking the cGAS-STING pathway using STING antagonists (C-176) led to reduced release of inflammatory factors and prevented M1 polarization of BV2 microglia in a laboratory setting. Additionally, intrathecal administration of C-176 reduced the allodynia in CFA treated mice.

CONCLUSION

Our results suggest that inhibiting microglial polarization through the cGAS-STING pathway represents a potential novel therapeutic strategy for inflammatory pain.

cGAS-STING signaling in cardiovascular diseases

Sterile inflammation, characterized by a persistent chronic inflammatory state, significantly contributes to the progression of various diseases such as autoimmune, metabolic, neurodegenerative, and cardiovascular disorders. Recent evidence has increasingly highlighted the intricate connection between inflammatory responses and cardiovascular diseases, underscoring the pivotal role of the Stimulator of Interferon Genes (STING). STING is crucial for the secretion of type I interferon (IFN) and proinflammatory cytokines in response to cytosolic nucleic acids, playing a vital role in the innate immune system. Specifically, research has underscored the STING pathway involvement in unregulated inflammations, where its aberrant activation leads to a surge in inflammatory events, enhanced IFN I responses, and cell death. The primary pathway triggering STING activation is the cyclic GMP-AMP synthase (cGAS) pathway. This review delves into recent findings on STING and the cGAS-STING pathways, focusing on their regulatory mechanisms and impact on cardiovascular diseases. It also discusses the latest advancements in identifying antagonists targeting cGAS and STING, and concludes by assessing the potential of cGAS or STING inhibitors as treatments for cardiovascular diseases.

Salvianolic acid A prevents UV-induced skin damage by inhibiting the cGAS-STING pathway

DNA damage resulting from UV irradiation on the skin has been extensively documented in numerous studies. In our prior investigations, we demonstrated that UVB-induced DNA breakage from keratinocytes can activate the cGAS-STING pathway in macrophages. The cGAS-STING signaling pathway serves as the principal effector for detecting and responding to abnormal double-stranded DNA in the cytoplasm. Expanding on our previous findings, we have further validated that STING knockout significantly diminishes UVB-induced skin damage, emphasizing the critical role of cGAS-STING activation in this context. Salvianolic acid A, a principal active constituent of Salvia miltiorrhiza Burge, has been extensively studied for its therapeutic effects in conditions such as coronary heart disease, angina pectoris, and diabetic peripheral neuropathy. However, its effect on cGAS-STING pathway and its ability to alleviate skin damage have not been previously reported. In a co-culture system, supernatant from UVB-treated keratinocytes induced IRF3 activation in macrophages, and this activation was inhibited by salvianolic acid A. Our investigation, employing photodamage and photoaging models, establishes that salvianolic acid A effectively mitigates UV-induced epidermal thickening and collagen degeneration. Treatment with salvianolic acid A significantly reduced skin damage, epidermal thickness increase, and keratinocyte hyperproliferation compared to the untreated photo-damage and photoaging model groups. In summary, salvianolic acid A emerges as a promising candidate for preventing UV-induced skin damage by inhibiting cGAS-STING activation. This research enhances our understanding of the intricate mechanisms underlying skin photodamage and provides a potential avenue for the development of therapeutic interventions.

The cGAS-STING pathway in cardiovascular diseases: from basic research to clinical perspectives

The cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase-stimulator of interferon genes (cGAS-STING) signaling pathway, an important component of the innate immune system, is involved in the development of several diseases. Ectopic DNA-induced inflammatory responses are involved in several pathological processes. Repeated damage to tissues and metabolic organelles releases a large number of damage-associated molecular patterns (mitochondrial DNA, nuclear DNA, and exogenous DNA). The DNA fragments released into the cytoplasm are sensed by the sensor cGAS to initiate immune responses through the bridging protein STING. Many recent studies have revealed a regulatory role of the cGAS-STING signaling pathway in cardiovascular diseases (CVDs) such as myocardial infarction, heart failure, atherosclerosis, and aortic dissection/aneurysm. Furthermore, increasing evidence suggests that inhibiting the cGAS-STING signaling pathway can significantly inhibit myocardial hypertrophy and inflammatory cell infiltration. Therefore, this review is intended to identify risk factors for activating the cGAS-STING pathway to reduce risks and to simultaneously further elucidate the biological function of this pathway in the cardiovascular field, as well as its potential as a therapeutic target.

Mitochondrial dynamics, quality control, and mtDNA in alcohol-associated liver disease and liver cancer

Mitochondria are intracellular organelles responsible for energy production, glucose and lipid metabolism, cell death, cell proliferation, and innate immune response. Mitochondria are highly dynamic organelles that constantly undergo fission, fusion, and intracellular trafficking, as well as degradation and biogenesis. Mitochondrial dysfunction has been implicated in a variety of chronic liver diseases including alcohol-associated liver disease, metabolic dysfunction-associated steatohepatitis, and HCC. In this review, we provide a detailed overview of mitochondrial dynamics, mitophagy, and mitochondrial DNA-mediated innate immune response, and how dysregulation of these mitochondrial processes affects the pathogenesis of alcohol-associated liver disease and HCC. Mitochondrial dynamics and mitochondrial DNA-mediated innate immune response may thereby represent an attractive therapeutic target for ameliorating alcohol-associated liver disease and alcohol-associated HCC.

Design, synthesis, and evaluation of thiazolecarboxamide derivatives as stimulator of interferon gene inhibitors

Stimulator of interferon gene (STING) plays critical roles in the cytoplasmic DNA-sensing pathway and in the induction of inflammatory response. Aberrant cytoplasmic DNA accumulation and STING activation are implicated in numerous inflammatory and autoimmune diseases. Here, we reported the discovery of a series of thiazolecarboxamide-based STING inhibitors through a molecular planarity/symmetry disruption strategy. The privileged compound 15b significantly inhibited STING signaling and suppressed immune-inflammatory cytokine levels in both human and murine cells. In vivo experiments demonstrated 15b effectively ameliorated immune-inflammatory cytokines upregulation in MSA-2-stimulated and Trex1-D18N mice. Furthermore, compound 15b exhibited enhanced efficacy in suppressing interferon-stimulated gene 15 (ISG15), a critical positive feedback regulator of STING. Overall, compound 15b deserves further development for the treatment of STING-associated inflammatory and autoimmune diseases.

cGAS-STING, an important signaling pathway in diseases and their therapy

Since cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway was discovered in 2013, great progress has been made to elucidate the origin, function, and regulating mechanism of cGAS-STING signaling pathway in the past decade. Meanwhile, the triggering and transduction mechanisms have been continuously illuminated. cGAS-STING plays a key role in human diseases, particularly DNA-triggered inflammatory diseases, making it a potentially effective therapeutic target for inflammation-related diseases. Here, we aim to summarize the ancient origin of the cGAS-STING defense mechanism, as well as the triggers, transduction, and regulating mechanisms of the cGAS-STING. We will also focus on the important roles of cGAS-STING signal under pathological conditions, such as infections, cancers, autoimmune diseases, neurological diseases, and visceral inflammations, and review the progress in drug development targeting cGAS-STING signaling pathway. The main directions and potential obstacles in the regulating mechanism research and therapeutic drug development of the cGAS-STING signaling pathway for inflammatory diseases and cancers will be discussed. These research advancements expand our understanding of cGAS-STING, provide a theoretical basis for further exploration of the roles of cGAS-STING in diseases, and open up new strategies for targeting cGAS-STING as a promising therapeutic intervention in multiple diseases.

Development of STING degrader with double covalent ligands

Stimulator of interferon genes (STING), a homodimeric membrane receptor localized in the endoplasmic reticulum, plays a pivotal role in signaling innate immune responses. Inhibitors and proteolysis-targeting chimeras (PROTACs) targeting STING are promising compounds for addressing autoinflammatory and autoimmune disorders. In this study, we used a minimal covalent handle recently developed as the ligand portion of an E3 ligase. The engineered STING degrader with a low molecular weight compound covalently binds to STING and E3 ligase. Degrader 2 showed sustained STING degradation activity at lower concentrations (3 µM, 48 h, about 75 % degradation) compared to a reported STING PROTAC, SP23. This discovery holds significance for its potential in treating autoinflammatory and autoimmune diseases, offering promising avenues for developing more efficacious STING-targeted therapies.

Apigenin Suppresses Innate Immune Responses and Ameliorates Lipopolysaccharide-Induced Inflammation via Inhibition of STING/IRF3 Pathway

The stimulator of interferon genes (STING) signaling pathway is crucial for the pathogenesis of autoimmune and inflammatory disorders, including acute lung injury (ALI). Apigenin (4[Formula: see text],5,7-trihydroxyflavone) is a natural flavonoid widely found in fruits, vegetables, and Chinese medicinal herbs that exhibits a range of pharmacological effects, such as antibacterial and anti-inflammatory activities. However, the efficacy of apigenin in STING pathway-mediated diseases remains unclear. Accordingly, this study screened Chinese medicines to identify potent agents that reduced the synthesis of type I interferons (IFNs). The results revealed apigenin as a potent compound with low cytotoxicity that markedly reduced the synthesis of type I IFNs in response to STING pathway agonists. Besides, apigenin markedly suppressed innate immune responses triggered by the STING agonist SR-717. Mechanistically, apigenin downregulated IFN beta 1 (IFNB1) expression mediated by the STING pathway via dose-dependent inhibition of STING expression, reduction of dimerization, nuclear translocation of phosphorylated IRF3, and disruption of the association between STING and IRF3. Moreover, apigenin effectively mitigated pathological pulmonary inflammation and lung edema in lipopolysaccharide (LPS)-induced ALI in mice. Apigenin further strongly attenuated the hallmarks of immoderate inflammation (interleukin (IL)-6, IL-1[Formula: see text], and tumor necrosis factor [Formula: see text]) and innate immune responses (IFNB1, C-X-C motif chemokine ligand 10, and IFN-stimulated gene 15) by preventing the activation of the STING/IRF3 pathway both in vitro and in vivo. Importantly, SR-717 significantly reversed the inhibitory effects of apigenin in LPS-induced THP1-BlueTM ISG macrophages. Collectively, apigenin effectively alleviated innate immune responses and mitigated inflammation in LPS-induced ALI via inhibition of the STING/IRF3 pathway. These findings suggest the potential of apigenin as a prophylactic and therapeutic candidate for managing STING-mediated diseases.

The cytosolic DNA-sensing cGAS-STING pathway in neurodegenerative diseases

BACKGROUND

With the widespread prevalence of neurodegenerative diseases (NDs) and high rates of mortality and disability, it is imminent to find accurate targets for intervention. There is growing evidence that neuroimmunity is pivotal in the pathology of NDs and that interventions targeting neuroimmunity hold great promise. Exogenous or dislocated nucleic acids activate the cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS), activating the stimulator of interferon genes (STING). The activated STING triggers innate immune responses and then the cGAS-STING signaling pathway links abnormal nucleic acid sensing to the immune response. Recently, numerous studies have shown that neuroinflammation regulated by cGAS-STING signaling plays an essential role in NDs.

AIMS

In this review, we summarized the mechanism of cGAS-STING signaling in NDs and focused on inhibitors targeting cGAS-STING.

CONCLUSION

The cGAS-STING signaling plays an important role in the pathogenesis of NDs. Inhibiting the cGAS-STING signaling may provide new measures in the treatment of NDs.

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.

LicochalconeB inhibits cGAS-STING signaling pathway and prevents autoimmunity diseases

Cytosolic DNA activates the STING (stimulator of interferon genes) signaling pathway to trigger interferon and inflammatory responses that protect against microbial infections and cancer. However, Aicardi-Goutières syndrome (AGS) persistently activates the STING signaling pathway, which can lead to severe autoimmune diseases. We demonstrate herein that Licochalcone B (LicoB), the main component of traditional licorice, is an inhibitor of the STING signaling pathway. We observed that LicoB inhibited the activation of the STING signaling pathway in macrophages. Mechanically, LicoB affected the STING-TBK1-IRF3 signal axis and inhibited the activation of the STING downstream signaling pathway. Furthermore, LicoB inhibited the increase in type I interferon levels in mice induced by the STING agonist CMA. LicoB significantly reduced systemic inflammation in Trex1-/- mice. Our results show that LicoB, a STING signaling pathway inhibitor, is a promising candidate for the treatment of diseases related to STING signaling pathway activation.

Update on the STING Signaling Pathway in Developing Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a prevalent chronic liver condition with limited treatment options. Inflammation caused by metabolic disturbances plays a significant role in NAFLD development. Stimulator of interferon gene (STING), a critical regulator of innate immunity, induces the production of interferons and other pro-inflammatory factors by recognizing cytoplasmic DNA to defend against pathogen infection. The STING-mediated signaling pathway appears to play a vital role in hepatic inflammation, metabolic disorders, and even carcinogenesis. Promisingly, pharmacological interventions targeting STING have shown improvements in the pathological state of NAFLD. Macrophages, dendritic cells, natural killer cells, and T cell pathways regulated by STING present potential novel druggable targets for NAFLD treatment. Further research and development in this area may offer new therapeutic options for managing NAFLD effectively.

Production of Plant Proteins and Peptides with Pharmacological Potential

The use of plant proteins or peptides in biotechnology is based on their identification as possessing bioactive potential in plants. This is usually the case for antimicrobial, fungicidal, or insecticidal components of the plant's defense system. They function in addition to a large number of specialized metabolites. Such proteins can be classified according to their sequence, length, and structure, and this has been tried to describe for a few examples here. Even though such proteins or peptides can be induced during plant-pathogen interaction, they are still present in rather small amounts that make the system not suitable for the production in large-scale systems. Therefore, a suitable type of host needs to be identified, such as cell cultures or adult plants. Bioinformatic predictions can also be used to add to the number of bioactive sequences. Some problems that can occur in production by the plant system itself will be discussed, such as choice of promoter for gene expression, posttranslational protein modifications, protein stability, secretion of proteins, or induction by elicitors. Finally, the plant needs to be set up by biotechnological or molecular methods for production, and the product needs to be enriched or purified. In some cases of small peptides, a direct chemical synthesis might be feasible. Altogether, the process needs to be considered marketable.

Glabridin improves autoimmune disease in Trex1-deficient mice by reducing type I interferon production

BACKGROUND

The cGAS-STING signaling pathway is an essential section of the natural immune system. In recent years, an increasing number of studies have shown a strong link between abnormal activation of the cGAS-STING signaling pathway, a natural immune pathway mediated by the nucleic acid receptor cGAS, and the development and progression of autoimmune diseases. Therefore, it is important to identify an effective compound to specifically downregulate this pathway for disease.

METHODS

The effect of Glabridin (Glab) was investigated in BMDMs and Peripheral blood mononuclear cell (PBMC) by establishing an in vitro model of cGAS-STING signaling pathway activation. An activation model stimulated by DMXAA was also established in mice to study the effect of Glab. On the other hand, we investigated the possible mechanism of action of Glab and the effect of Glab on Trex1-deficient mice.

RESULTS

In this research, we report that Glab, a major component of licorice, specifically inhibits the cGAS-STING signaling pathway by inhibiting the level of type I interferon and inflammatory cytokines (IL-6 and TNF-α). In addition, Glab has a therapeutic effect on innate immune diseases caused by abnormal cytoplasmic DNA in Trex1-deficient mice. Mechanistically, Glab can specifically inhibit the interaction of STING with IRF3.

CONCLUSION

Glab is a specific inhibitor of the cGAS-STING signaling pathway and may be used in the clinical therapy of cGAS-STING pathway-mediated autoimmune diseases.