New frontiers in the cGAS-STING intracellular DNA-sensing pathway

Endothelia-targeting eye drops deliver a STING inhibitor to effectively reduce retinal neovascularization in ischemic retinopathy

Retinal neovascularization is the main pathologic feature of ischemic retinopathy, which eventually leads to vision loss and even blindness. Current treatments like laser photocoagulation and intravitreal injection of anti-vascular endothelial growth factor A drugs are invasive, expensive, and incompetent. Therefore, it is urgent to explore optimized therapies, particularly eye drops, to improve treatment effects. Our recent study reported that abnormal up-regulation of stimulator of interferon genes (STING) is closely associated with retinal vascular diseases, and it is highly enriched in retinal endothelial cells with retinopathy. Thus, we evaluated whether endothelial STING affects retinal neovascularization. In addition, we constructed iRGD- and TAT-decorated nanoparticles (NPs) loaded with C-176 (I/T-C-NP), capable of penetrating the cornea and targeting retinal endothelial cells. The I/T-C-NP eye drops were applied to the eyes of oxygen-induced retinopathy mice, resulting in attenuated activation of the STING pathway. Consequently, retinal neovascularization and vascular tortuosity were effectively reduced, astrocyte activation was prohibited, and pericyte coverage was improved. These observations suggest that I/T-C-NP eye drops can be a potential solution for the treatment of retinal neovascularization.

MINT3 promotes STING activation and facilitates antiviral immune responses

Stimulator-of-interferon genes (STING) translocation is the rate-limiting step in the cGAS-STING signaling which detects cytosolic DNA and produces type I interferons. However, the mechanism by which this process is modulated remains to be further clarified. In the present study, we identified munc18-1-interacting protein 3 (MINT3) as a positive regulator of STING signaling. MINT3 promotes type I interferons production induced by herpes simplex virus-1 (HSV-1) infection and ISD or cGAMP stimulation in mouse peritoneal macrophages. Deficiency of Mint3 greatly inhibited STING and IRF3 activation in macrophages. Mint3 knockdown also attenuated STING and IRF3 activation in macrophages, human THP-1 cells, and RAW264.7 cells. Mechanistically, MINT3 interacted with STING, selectively enhanced its K63-linked polyubiquitination and facilitated STING translocation to the Golgi, resulting in the enhancement of the STING and TBK1 interaction. Furthermore, MINT3 also facilitated HSV-1-induced innate antiviral immune responses and impaired HSV-1 replication in vitro and in vivo. Interestingly, we showed that the expression of MINT3 was dramatically elevated during HSV-1 infection, and ISD stimulation in macrophages. Thus, we have revealed a feedback mechanism for the regulation of the cGAS-STING pathway, providing a promising therapeutic target for the treatment of disorders triggered by aberrant STING activity.

Repurposing oxiconazole to inhibit STING trafficking via OSBP and alleviate autoimmune pathology in Trex1-/- mice

The cGAS-STING pathway is a critical component of the innate immune response to cytosolic DNA, driving the production of type I interferons (IFNs) and pro-inflammatory cytokines. However, excessive activation of this pathway is associated with various autoimmune and inflammatory diseases. In this study, we evaluated the regulation of FDA-approved azole antifungal drugs on the cGAS-STING pathway. Among these drugs, oxiconazole, miconazole, and itraconazole demonstrate significant inhibitory effects, with oxiconazole showing the strongest activity. Our data demonstrates that oxiconazole significantly suppressed type I IFN production and downstream inflammatory responses in macrophages and fibroblasts stimulated with synthetic DNA or infected with HSV-1. Mechanistically, oxiconazole hindered STING trafficking via oxysterol-binding protein OSBP. Using the Listeria monocytogenes infection model and the Trex1-/- mouse disease model, both representing in vivo models of inflammation driven by excessive cGAS-STING activation, we demonstrate that oxiconazole enhanced bacterial clearance and reduced tissue damage in the Listeria monocytogenes infection model. Moreover, oxiconazole treatment significantly alleviated multi-organ inflammation and normalized aberrant IFN responses in the Trex1-/- autoimmune disease mouse model. These findings highlight the potential of oxiconazole as a promising therapeutic agent for STING-driven autoimmune and inflammatory diseases.

Saturated fatty acid-induced neutrophil extracellular traps contribute to exacerbation and biologic therapy resistance in obesity-related psoriasis

Psoriasis patients who are obese tend to have serious clinical manifestations and poor responses to various biological agents in most cases. However, the mechanisms by which obesity exacerbates psoriasis remain enigmatic. In this study, we found that the abundance of systemic and localized cutaneous neutrophil extracellular traps (NETs) associated with the obesity-induced aggravation of psoriasis was positively correlated with disease severity and that the inhibition of NETs alleviated psoriatic dermatitis in obese mice. Mechanistically, we found that changes in fatty acid composition in obese subjects resulted in the deposition of saturated fatty acids (SFAs), which promoted the release of NETs via the TLR4-MD2/ROS signaling pathway. We further revealed that NETs potentiate IL-17 inflammation, especially γδT17-mediated immune responses, in obesity-exacerbated psoriasis patients. Moreover, SFAs induced a decreased response to anti-IL17A treatment in psoriasis-like mice, whereas the inhibition of NETs improved the beneficial effects of anti-IL17A in psoriasis-like mice with lipid metabolism disorders. Our findings collectively suggest that SFA-induced NETs play a critical role in the exacerbation of obesity-related psoriasis and provide potential new strategies for the clinical treatment of refractory psoriasis patients with lipid metabolism disorders.

SESN1 negatively regulates STING1 to maintain innate immune homeostasis

STING1 is a central hub protein of CGAS-STING1 signaling which is important signaling axis to sense DNA for the host against pathogens infection through regulating type I interferon (IFN-I) production. However, excessive STING1 activation-induced overproduced IFN-I triggers tissue damage and autoimmune disorders. Thus, the activity of STING1 must be precisely regulated for immune homeostasis. Here, we discovered SESN1 (sestrin 1) as an essential negative regulator of STING1 to maintain immune homeostasis. Upon herpes simplex virus-1 (HSV-1) infection, the expression of SESN1 was downregulated, which enhanced potentiality to virus defense for host. Consistently, SESN1-deficient mice exhibited stronger ability against HSV-1 infection compared to wild-type littermates. Additionally, we found the expression of SESN1 was decreased in systemic lupus erythematosus (SLE) patients and trex1 KO mouse model of autoimmune disease. Intriguingly, the replenishment of SESN1 effectively impressed IFN-I production and autoimmune responses in the PBMCs of human SLE specimens and the trex1 KO mouse model both in vitro and in vivo. Mechanistically, SESN1 targeted STING1 and promoted STING1 autophagic degradation by facilitating the interaction of SQSTM1/p62 and STING1. Together, our study uncovers a crucial role of SESN1 for immune homeostasis to balance anti-virus and autoimmunity by regulating STING1. SESN1 might be a potential therapeutic target for infectious and autoimmune diseases.Abbreviations: BMDMs: bone marrow-derived macrophages; cGAMP: cyclic GMP-AMP; CGAS: cyclic GMP-AMP synthase; HTDNA: herring testes DNA; IFNA4: interferon alpha 4; IFNB: interferon beta; IRF3: interferon regulatory factor 3; ISD: interferon stimulatory DNA; ISGs: IFN-stimulated genes; PBMCs: peripheral blood mononuclear cells; RSAD2: radical S-adenosyl methionine domain containing 2; SLE: systemic lupus erythematosus; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK binding kinase 1.

Neoantigens combined with in situ cancer vaccination induce personalized immunity and reshape the tumor microenvironment

Neoantigen (nAg) vaccines can induce anti-tumor specific immunity, and tumor killing promotes further antigen diffusion, which is expected to improve prognosis. However, the mutation of cancer cells under the selective pressure of vaccines and the immunosuppressive tumor microenvironment make the therapeutic effect unsatisfactory. Here, we develop a nanovaccine (nAg-MRDE/Mn) that can deliver nAg and induce in situ cancer vaccination to synergistically promote a personalized immune response, enhance antigen diffusion, and improve the microenvironment by modulating immunosuppressive cells and activating the innate immune response. Experiments show that nAgs are presented by dendritic cells and expressed by T cells, which cooperate with in situ vaccination to stimulate specific immunity. Cells involved in immunosuppression, such as M2 macrophages and regulatory T cells, are down-regulated, while M1 macrophages and natural killer cells are increased. In addition, the hydrogel loaded with chemokines and nAg-MRDE/Mn inhibits postoperative tumor recurrence, and the combination of nAg-MRDE/Mn and αPD-1 improves the therapeutic effect of αPD-1. This study validates the clinical potential of this strategy and provides ideas for improving neoantigen vaccines.

Design, synthesis, and in-vitro/in-vivo pharmacodynamic studies of novel aza-fused heterocyclic compounds against herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1) is a prevalent pathogen that can lead to severe diseases, including herpes labialis, keratitis, and encephalitis. The development of novel antiviral therapies is significant due to the limited number of available treatments and the emergence of drug-resistant strains. In this study, a series of aza-fused heterocyclic derivatives were synthesized and evaluated for antiviral efficacy. Compound 5i demonstrated notable antiviral activity in vitro with an EC50 (Effective Concentration 50 %) of 1.95 ± 0.07 μM. This effect was achieved by inhibiting viral replication and targeting viral ICP4 and gD proteins. In addition, the expression of STING and NF-κB signaling pathways was down-regulated, cytokine storm was reduced, and the multi-targeted activity of compound 5i inhibited apoptosis. The high efficacy of compound 5i was demonstrated in a mouse herpes encephalitis model. Infected mice's survival significantly improved, and viral load in brain tissue was substantially reduced in the presence of compound 5i. Furthermore, compound 5i demonstrated favorable safety in preliminary in vivo evaluations, with no adverse effects on major organs observed. In conclusion, the aza-fused heterocyclic derivative 5i has substantial potential as a therapeutic agent for HSV-1 infection, providing a valuable foundation for further drug development and clinical translation.

Genomic context influences translesion synthesis DNA polymerase-dependent mechanisms of micronuclei induction by G-quadruplexes

Guanine quadruplexes (G4s) are non-canonical DNA structures that can trigger micronuclei (MNi). Mechanisms of micronuclei formation by G4s are not fully understood. Here, we show that G4 stabilization can trigger cell-cycle-phase-specific mechanisms of replication fork stalling and DNA synthesis restart dependent on translesion synthesis (TLS) DNA polymerases (Pols). Fork stalling is caused by G-loops and high transcription during early S only. Moreover, while induction of micronuclei is dependent on DNA Pol η throughout S phase, primase and DNA-directed polymerase (PrimPol) is required in late S only. DNA breakage is not an immediate response to stabilized G4s but rather a consequence of persistent G4-mediated replication stress. Thus, different modes of fork stalling and restart, based on genomic context and TLS Pols, avoid immediate DNA breakage at stalled forks but at the expense of a risk of later mitotic chromosomal instability. The insights can lead to the development of more effective therapies for cancer and neurological diseases.

cGAS/STING signalling in macrophages aggravates obliterative bronchiolitis via an IFN-α-dependent mechanism after orthotopic tracheal transplantation in mice

BACKGROUND

Our previous findings have underscored the role of innate immunity in obliterative bronchiolitis (OB). However, despite the central importance of the cyclic GMP‒AMP synthase (cGAS)/stimulator of interferon genes (STING) signalling pathway in innate immune responses, its specific contribution to OB progression remains largely unexplored.

METHODS

A murine orthotopic tracheal transplantation model was established to replicate OB pathogenesis. RNA sequencing and single-cell RNA sequencing data were analysed to investigate mechanisms underlying OB. Key molecules of the cGAS/STING pathway were assessed using immunofluorescence staining. Macrophage-specific Sting1 knockout mice were generated to investigate the role of the cGAS/STING pathway in OB. Haematoxylin and eosin staining and Masson's trichrome staining were utilised to evaluate allograft stenosis and fibrosis. Immune cell infiltration and cytokine expression were analysed using immunofluorescence staining and qRT-PCR. Flow cytometry was used to characterise splenic T-cell subsets and assess co-stimulatory molecule expression in macrophages.

RESULTS

The cGAS/STING pathway was upregulated in macrophages infiltrating allografts. Macrophage-specific Sting1 knockout significantly attenuated alloreactive T-cell responses and alleviated OB. Furthermore, Sting1 deletion reduced the expression of inflammatory marker NOS2, antigen-presenting molecule MHC class II and co-stimulatory molecules (CD80 and CD86) in macrophages. Mechanistically, Sting1 knockout inhibited the production of interferon-α2 (IFN-α2), while the protective effect of macrophage-specific Sting knockout was reversed by IFN-α2 administration. Importantly, STING inhibition enhanced the allograft tolerance-promoting effects of cytotoxic T-lymphocyte-associated antigen 4-Ig (CTLA4-Ig), leading to the preservation of the airway epithelium.

CONCLUSIONS

Our study demonstrated that cGAS/STING signalling pathway exacerbated allograft rejection in an IFN-α2-dependent manner. These findings provide insights into potential novel strategies for prolonging allograft survival.

KEY POINTS

cGAS/STING signalling pathway was activated in macrophages infiltrating allografts. cGAS/STING signalling pathway in macrophages exacerbated allograft rejection, promoted antigen-presenting ability of macrophages and enhanced alloreactive T-cell responses in an IFN-α2-dependent manner. STING inhibition potentiated the therapeutic efficacy of CTLA4-Ig in OB.

The fucoidan delivery system enhanced the anti-cervical cancer effect of caffeic acid

Cervical cancer remains one of the leading causes of mortality among women, and immunotherapy targeting the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway holds promise for its treatment. This study has developed nanoparticles based on fucoidan (Fu/CA NPs), successfully loading them with caffeic acid (CA) for application in cervical cancer therapy. In vitro experiments revealed that Fu/CA NPs significantly inhibited the proliferation of cervical cancer HeLa cells (by 65.73 ± 4.06 %) and induced apoptosis through the accumulation of reactive oxygen species and mitochondrial damage. Furthermore, treatment with Fu/CA NPs activated the cGAS-STING pathway, attributed to the cytoplasmic release of mitochondrial DNA (mtDNA) and the induction of DNA double-strand breaks (dsDNA) by Fu/CA NPs. In vivo results confirmed that Fu/CA NPs suppressed solid tumor growth (by 67.8 %), with even more pronounced antitumor effects observed when combined with cisplatin (96.5 %), a phenomenon also associated with the activation of the cGAS-STING pathway. Excitingly, the combination of Fu/CA NPs and cisplatin alleviated cisplatin-induced nephrotoxicity, as indicated by a decrease in blood urea nitrogen (BUN) by 53.27 % and serum creatinine (SCr) by 74.93 %. In summary, our research presents a potential therapeutic avenue for cervical cancer treatment, particularly highlighting the synergistic benefits of combining Fu/CA NPs with cisplatin.

Targeting KMT5C Suppresses Lung Cancer Progression and Enhances the Efficacy of Immunotherapy

The immune evasion is one major challenge for cancer immunotherapy. Despite considerable advancements in immune checkpoint blockade (ICB) therapies for the advanced non-small cell lung cancer (NSCLC) patients, only a minority of patients receive long-term survival benefit. Here, this work demonstrates that lysine methyltransferase 5C (KMT5C) is a crucial promoter of the NSCLC progression and immune evasion. This work first observes that upregulation of KMT5C in NSCLC correlated with cancer progression and poor patient prognosis. Notably, KMT5C knockdown in NSCLC cells suppress tumor growth and metastasis in mice. Mechanistically, this work demonstrates that KMT5C activated the DNA repair response to inhibit the STING-IRF3 pathway, downstream type I IFN signaling, and CCL5 secretion, leading to the downregulation of CD8+ T cell infiltration and function in NSCLC, ultimately facilitating tumor immune evasion and tumor progression. Importantly, both the pharmacological inhibitor A196 and the genetic inhibition of KMT5C could synergize with anti-PD-1 therapy in the lung cancer mouse model. Clinically, high expression levels of KMT5C in patients with NSCLC are associated with a lower response rate and worse clinical outcomes to ICB therapy. Therefore, these findings identify a previously unknown functional link between KMT5C and tumor immune evasion, and demonstrate that targeting KMT5C may be a potential therapeutic approach for enhancing the efficacy of NSCLC patients to ICB therapy.

Effect and mechanism of the miR-1284/EIF4A1 axis on the cGAS-STING pathway under radiotherapy

Background

Gastric cancer (GC) remains a major global health concern, with limited treatment options, especially in advanced stages. Radiotherapy (RT) plays a vital role in GC management, but resistance to DNA damage impedes its effectiveness. MicroRNA-1284 (miR-1284), a tumor suppressor, regulates eukaryotic translation initiation factor 4A1 (EIF4A1), which is involved in DNA damage repair through homologous recombination (HR). This axis has been implicated in enhancing GC cell survival following RT. Additionally, the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway, activated by DNA damage, plays a key role in triggering an anti-tumor immune response. However, the interaction between the miR-1284/EIF4A1 axis, DNA repair, and the cGAS-STING pathway in GC under RT conditions remains unclear. This study aims to investigate how the miR-1284/EIF4A1 axis influences DNA repair and its role in activating the cGAS-STING pathway to enhance RT efficacy in GC.

Methods

A stably expressed messenger miR-1284 cell line was established. Quantitative reverse transcription and western blot were used to examine the expression of miR-1284 and EIF4A1, and the effect of blocking the miR-1284/EIF4A1 axis on the cGAS-STING pathway and interferon-β (IFN-β) in GC cells after RT; cytotoxicity experiments were conducted to explore the mechanism of the miR-1284/EIF4A1 axis in radiation-induced DNA damage repair; animal experiments were conducted to explore the translational application of rocaglamide (RocA) combined with the programmed cell death-ligand 1 (PD-L1) antibody in RT.

Results

The miR-1284/EIF4A1 axis in the GC cells promoted the repair of radiation-induced DNA damage and was associated with the prognosis of GC patients. Blocking this axis delayed the C-terminal binding protein interacting protein (CtIP)-mediated DNA repair, enhanced RT effectiveness, and activated the cGAS-STING pathway, while increasing the rate of apoptosis. In vivo experiments based on RocA binding to PD-L1 antibodies under RT had good biological safety, and thus provide a potential therapeutic strategy for the treatment of GC.

Conclusions

The miR-1284/EIF4A1 axis promotes the repair of DNA damage caused by RT, promotes the activation of the cGAS-STING pathway in GC, and has good biological safety. Our findings provide an important experimental basis for enhancing the anti-tumor immune effect of RT in the treatment of GC.

STING aggravates ferroptosis-dependent myocardial ischemia-reperfusion injury by targeting GPX4 for autophagic degradation

Despite advancements in interventional coronary reperfusion technologies following myocardial infarction, a notable portion of patients continue to experience elevated mortality rates as a result of myocardial ischemia-reperfusion (MI/R) injury. An in-depth understanding of the mechanisms underlying MI/R injury is crucial for devising strategies to minimize myocardial damage and enhance patient survival. Here, it is discovered that during MI/R, double-stranded DNA (dsDNA)-cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signal accumulates, accompanied by high rates of myocardial ferroptosis. The specific deletion of cgas or Sting in cardiomyocytes, resulting in the inhibition of oxidative stress, has been shown to mitigate ferroptosis and I/R injury. Conversely, activation of STING exacerbates ferroptosis and I/R injury. Mechanistically, STING directly targets glutathione peroxidase 4 (GPX4) to facilitate its degradation through autophagy, by promoting the fusion of autophagosomes and lysosomes. This STING-GPX4 axis contributes to cardiomyocyte ferroptosis and forms a positive feedback circuit. Blocking the STING-GPX4 interaction through mutations in T267 of STING or N146 of GPX4 stabilizes GPX4. Therapeutically, AAV-mediated GPX4 administration alleviates ferroptosis induced by STING, resulting in enhanced cardiac functional recovery from MI/R injury. Additionally, the inhibition of STING by H-151 stabilizes GPX4 to reverse GPX4-induced ferroptosis and alleviate MI/R injury. Collectively, a novel autophagy-dependent ferroptosis mechanism is identified in this study. Specifically, STING autophagy induced by anoxia or ischemia-reperfusion leads to GPX4 degradation, thereby presenting a promising therapeutic target for heart diseases associated with I/R.

Opportunities and Challenges for Nanomaterials as Vaccine Adjuvants

Adjuvants, as a critical component of vaccines, are capable of eliciting more robust and sustained immune responses. Nanomaterials have shown unique advantages and broad application prospects in adjuvant development due to their high adjustability and distinctive physicochemical properties. This review focuses on nanoadjuvants and their immunological mechanisms. First, various types of adjuvants are introduced with an emphasis on metal and metal oxide nanoparticles, coordination polymers, liposomes, polymer nanoparticles, and other inorganic nanoparticles that can serve as vaccine adjuvants. Second, this review describes the current status of the clinical applications of nanoadjuvants. Next, the mechanisms of action for nanoadjuvants have been thoroughly elucidated, including the depot effect, NLRP3 inflammasome activation, targeting C-type lectin receptors, activation of toll-like receptors, and activation of the cGAS-STING signaling pathway. Finally, the challenges and opportunities associated with the development of nanoadjuvants have also been addressed.

Death domain-associated protein (Daxx) impairs colon cancer chemotherapy by inhibiting the cGAS-STING pathway

Background

Colorectal cancer (CRC) holds the third position in global cancer prevalence mortality. Although chemotherapy is a conventional treatment, recent investigations have shed light on the therapeutic potential of the cGAS cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway in CRC management. Despite the primary role of the death domain-associated protein (Daxx) in cellular apoptosis, its influence on the regulation of cGAS-STING activation remains elusive.

Methods

The Daxx degradation and speck formation were conducted using immunofluorescence and Western blotting. The Daxx knock-down and over-expression in CRC cells were performed to detect in vivo and in vitro migration, proliferation, cGAS-STING activation, and immune responses.

Results

Our study reveals that treatment with irinotecan (CPT-11) and oxaliplatin (OXA) significantly accelerated the Daxx degradation and diminished the formation of Daxx specks within the nucleus of CRC cells. Genetic elimination of Daxx enhanced the irinotecan and oxaliplatin-induced suppression of proliferation and migration in CRC cells, and overexpression of Daxx resulted in similar results. Mechanistically, Daxx overexpression reduced DNA damage repair by restraining homologous recombination (HR) over non-homologous end-joining (NHEJ), which suppressed TBK1 and IRF3 phosphorylation downstream of the cGAS-STING signal. In a murine model of CT-26 tumors, Daxx knockdown amplified the OXA-mediated tumor growth inhibition by promoting STING activation and immune responses.

Conclusions

Our findings show that the degradation of nuclear Daxx potentiates the cGAS-STING pathway, thereby bolstering the efficacy of chemotherapy.

A non-canonical cGAS-STING pathway drives cellular and organismal aging

Accumulation of cytosolic DNA has emerged as a hallmark of aging, inducing sterile inflammation. STING (Stimulator of Interferon Genes) protein translates the sensing of cytosolic DNA by cGAS (cyclic-GMP-AMP synthase) into an inflammatory response. However, the molecular mechanisms whereby cytosolic DNA-induced cGAS-STING pathway leads to aging remain poorly understood. We show that STING does not follow the canonical pathway of activation in human fibroblasts passaged (aging) in culture, senescent fibroblasts, or progeria fibroblasts (from Hutchinson Gilford Progeria Syndrome patients). Despite cytosolic DNA buildup, features of the canonical cGAS-STING pathway like increased cGAMP production, STING phosphorylation, and STING trafficking to perinuclear compartment are not observed in progeria/senescent/aging fibroblasts. Instead, STING localizes at endoplasmic reticulum, nuclear envelope, and chromatin. Despite the non-conventional STING behavior, aging/senescent/progeria cells activate inflammatory programs such as the senescence-associated secretory phenotype (SASP) and the interferon (IFN) response, in a cGAS and STING-dependent manner, revealing a non-canonical pathway in aging. Importantly, progeria/aging/senescent cells are hindered in their ability to activate the canonical cGAS-STING pathway with synthetic DNA, compared to young cells. This deficiency is rescued by activating vitamin D receptor signaling, unveiling new mechanisms regulating the cGAS-STING pathway in aging. Significantly, in HGPS, inhibition of the non-canonical cGAS-STING pathway ameliorates cellular hallmarks of aging, reduces tissue degeneration, and extends the lifespan of progeria mice. Our study reveals that a new feature of aging is the progressively reduced ability to activate the canonical cGAS-STING pathway in response to cytosolic DNA, triggering instead a non-canonical pathway that drives senescence/aging phenotypes.

Significance Statement

Our study provides novel insights into the mechanisms driving sterile inflammation in aging and progeria. We reveal a previously unrecognized characteristic of aging cells: the progressive loss of ability to activate the canonical response to foreign or self-DNA at the cytoplasm. Instead, aging, senescent, and progeria cells activate inflammatory programs via a non-conventional pathway driven by cGAS and the adaptor protein STING. Importantly, pharmacological inhibition of the non-canonical cGAS-STING pathway ameliorates cellular, tissue and organismal decline in a devastating accelerated aging disease (Hutchinson Gilford Progeria Syndrome), highlighting it as a promising therapeutic target for age-related pathologies.

Dendritic cell maturation in cancer

Dendritic cells (DCs) are specialized antigen-presenting cells that are present at low abundance in the circulation and tissues; they serve as crucial immune sentinels by continually sampling their environment, migrating to secondary lymphoid organs and shaping adaptive immune responses through antigen presentation. Owing to their ability to orchestrate tolerogenic or immunogenic responses to a specific antigen, DCs have a pivotal role in antitumour immunity and the response to immune checkpoint blockade and other immunotherapeutic approaches. The multifaceted functions of DCs are acquired through a complex, multistage process called maturation. Although the role of inflammatory triggers in driving DC maturation was established decades ago, less is known about DC maturation in non-inflammatory contexts, such as during homeostasis and in cancer. The advent of single-cell technologies has enabled an unbiased, high-dimensional characterization of various DC states, including mature DCs. This approach has clarified the molecular programmes associated with DC maturation and also revealed how cancers exploit these pathways to subvert immune surveillance. In this Review, we discuss the mechanisms by which cancer disrupts DC maturation and highlight emerging therapeutic opportunities to modulate DC states. These insights could inform the development of DC-centric immunotherapies, expanding the arsenal of strategies to enhance antitumour immunity.

Environmental low-dose nanosized carbon black exposure aggravates lung fibrosis-induced by radiation in vivo and in vitro

The question of whether the emerging nano-material, nanosized carbon black (CB) could influence the lung damage-induced by radiation exposure in cancer patients or in acute nuclear accident population remains incompletely uncovered. Therefore, our study investigated potential health risk from environmental low-dose CB exposure level (0.1 mg/kg/d, once per three days, for 12 weeks) via nasal instillation using a lung fibrosis mouse model induced by radiation. Compared to either CB or radiation single exposure, low-dose CB plus radiation exposure showed an aggravated risk of lung damage in mice, which was embodied in more increased collagen, reactive oxygen species (ROS) concentrations, and inflammation cytokines levels including IL-1β and TNF-α, as well as promoted epithelial-mesenchymal transition (EMT) progress through increasing relative biomarkers such as N-cadherin and α-SMA. Mechanistically, CB triggered the cGAS-STING signaling pathway to aggravation of radiation-induced lung injury. Furthermore, knocking down the GAS or STING expression would suppress the EMT process and inflammation reaction, resulting in significantly attenuating the combination effects of low-dose CB plus radiation on lung damage. Overall, our study indicates that environmental CB exposure may increase the lung damage in certain special population cannot be ignored. It sheds light on possible molecular mechanisms from cGAS-STING inflammation perspective and providing valuable basic understanding for future study on radiation-induced lung damage. Synopsis State of exposure of environmentally relevant nanosized carbon black may exacerbate the lung injury among cancer patients undergoing radiotherapy.

Unintegrated HIV-1 DNA recruits cGAS via its histone-binding domain to escape innate immunity

To ensure optimal replication and spread, viruses have evolved countermeasures to evade type 1 IFN-mediated antiviral activity. During the early viral replication cycle steps until uncoating, the HIV-1 core protects viral pathogen associated molecular patterns (viral RNA and reverse transcription products) from recognition by innate immune sensors, including cGAS. However, after capsid uncoating, unintegrated viral DNA (uvDNA) becomes accessible. Here, we show that HIV-1 uses chromatin-mediated cGAS inactivation as a mechanism to protect its uvDNA from innate immune activation.

Discovery of a Novel CRBN-Recruiting cGAS PROTAC Degrader for the Treatment of Ulcerative Colitis

Cyclic GMP-AMP synthase (cGAS), a critical cytosolic DNA sensor initiating innate immune responses in the presence of cytosolic DNA, is increasingly recognized as a promising therapeutic target for ulcerative colitis (UC). Here, we reported the design, synthesis, structure-activity relationship exploration and biological evaluation of a novel class of CRBN-recruiting cGAS-targeting PROTAC degraders. Among them, TH35 exhibited the most favorable degradation profile, achieving potent and selective degradation of cGAS, and markedly attenuated dsDNA-induced activation of cGAS signaling in both human and murine cells, with minimal cytotoxic effects. In vivo, TH35 demonstrated superior therapeutic efficacy in a dextran sulfate sodium (DSS)-induced mouse model of UC compared to the corresponding cGAS inhibitor, while also displaying acceptable pharmacokinetic properties. Collectively, TH35 as the first CRBN-recruiting cGAS PROTAC holds promise for augmenting anti-inflammatory responses and offers a new avenue for treating cGAS-driven inflammatory diseases.

Targeting cGAS-STING pathway for reprogramming tumor-associated macrophages to enhance anti-tumor immunotherapy

The cyclic GMP-AMP synthase (cGAS)-stimulator interferon genes (STING) signaling pathway plays a crucial role in activating innate and specific immunity in anti-tumor immunotherapy. As the major infiltrating cells in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) could be polarized into either anti-tumor M1 or pro-tumor M2 types based on various stimuli. Accordingly, targeted reprogramming TAMs to restore immune balance shows promise as an effective anti-tumor strategy. In this review, we aim to target cGAS-STING pathway for reprogramming TAMs to enhance anti-tumor immunotherapy. We investigated the double-edged sword effects of cGAS-STING in regulating TME. The regulative roles of cGAS-STING pathway in TAMs and its impact on the TME were further revealed. More importantly, several strategies of targeting cGAS-STING for reprogramming TAMs were designed for enhancing anti-tumor immunotherapy. Taken together, targeting cGAS-STING pathway for reprogramming TAMs in TME might be a promising strategy to enhance anti-tumor immunotherapy.

The cGAS-STING pathway in cancer immunity: dual roles, therapeutic strategies, and clinical challenges

The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway is a crucial component of the host's innate immunity and plays a central role in detecting cytosolic double-stranded DNA from endogenous and exogenous sources. Upon activation, cGAS synthesizes cGAMP, which binds to STING, triggering a cascade of immune responses, including the production of type I interferons and pro-inflammatory cytokines. In the context of cancers, the cGAS-STING pathway can exert dual roles: on the one hand, it promotes anti-tumor immunity by enhancing antigen presentation, stimulating T-cell responses, and inducing direct tumor cell apoptosis. On the other hand, chronic activation, particularly in tumors with chromosomal instability, can lead to immune suppression and tumor progression. Persistent cGAS-STING signaling results in the up-regulation of immune checkpoint molecules such as PD-L1, contributing to immune evasion and metastasis. Consequently, anti-tumor strategies targeting the cGAS-STING pathway have to consider the balance of immune activation and the immune tolerance caused by chronic activation. This review explores the mechanisms underlying both the anti-tumor and protumor roles of the cGAS-STING pathway, with a focus on potential therapeutic approaches, and the challenges faced in their clinical application, along with corresponding solutions.

Integrative bioinformatics analysis reveals CGAS as a ferroptosis-related signature gene in sepsis and screens the potential natural inhibitors of CGAS

Sepsis is a fatal organ dysfunction characterized by the simultaneous hyperinflammation and immunosuppression. Nowadays, the early precision intervention of sepsis is challenging. Ferroptosis is involved in the development of sepsis. The current study aimed to find out the signature genes of sepsis with network topology analysis and machine learning, and further provide the potential natural compounds for sepsis with virtual screening and in vitro validation. In this study, five genes namely CGAS, DPP4, MAPK14, PPARG and TXN were identified as ferroptosis-related signature genes for sepsis by network topological analysis, machine learning algorithms, and external datasets verification. The results of immune infiltration analysis confirmed these genes were significantly associated with the infiltration abundance of some immune cells including neutrophil, macrophage, plasmacytoid dendritic cell and activated dendritic cell. Moreover, coniferin, 5-O-caffeoylshikimic acid, and psoralenoside were initially identified as the natural inhibitors of CGAS by virtual screening. However, further in vitro study on macrophages revealed coniferin and psoralenoside had better inhibitory activities on CGAS. In summary, the present study pointed out the importance of CGAS in sepsis, and discovered novel natural inhibitors of CGAS.

A Single-Atom Mn/MoO3- x Nanoagonist for Cascade cGAS/STING Activation in Tumor-Specific Catalytic Metalloimmunotherapy

The cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway plays a crucial role in initiating anti-tumor immunity. Despite the development of various STING agonists, their effectiveness is often limited by suboptimal activation efficiency and poor sustainability. To address this, a Mn/MoO3- x nanoagonist featuring Mn single-atom sites is presented, designed for cascade cGAS/STING activation in tumor-specific catalytic metalloimmunotherapy. The single-atom nanoagonist (SANA) is meticulously crafted by doping Mn atoms into defective molybdenum oxide (MoO3- x), enabling robust peroxidase-mimicking catalysis and inducing severe double-stranded DNA (dsDNA) damage in tumors. Of note, Mn2+ and MoO4 2- can be responsively released from Mn/MoO3- x SANA and enhance the sensitivity of cGAS to dsDNA. Importantly, MoO4 2- with a relatively slow-release profile and facile cellular accumulation compensates for Mn2+ that has poor cellular accumulation due to continuous efflux, thus continuatively triggering the secretion of type I interferon for beyond 72 h. Remarkably, Mn/MoO3- x SANA significantly inhibits tumor growth and metastasis without supplementary STING agonists or external stimulation. This study offers a promising cascade cGAS/STING activation approach to enhance the efficacy and sustainability of catalytic metalloimmunotherapy.

cGAS-STING targeting offers novel therapeutic opportunities in neurological diseases

Cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) (cGAMP) synthase (cGAS) is a cytosolic DNA sensor that produces the secondary messenger cGAMP. cGAMP activates the endoplasmic reticulum-associated adaptor stimulator of interferon genes (STING) and activates the innate immune system to produce a type I interferon response. Besides sensing microbial DNA, cGAS can also be activated by self-DNA or endogenous DNA, including that derived from genotoxic extranuclear chromatin and mitochondrially released DNA, indicating that cGAS-STING is an important mechanism in sterile inflammatory responses, autoimmunity, and cellular senescence. However, aberrant activation of the cGAS-STING pathway results in inflammatory and autoimmune diseases. cGAS-STING has emerged as a vital mechanism driving the pathogenesis of inflammation, implicating cGAS-STING signaling in neurological diseases. In this review, we first outline the principal elements of the cGAS-STING signaling cascade, summarizing recent research highlighting how cGAS-STING activation contributes to the pathogenesis of neurological diseases, including various autoimmune, autoinflammatory, and neurodegenerative diseases. Next, we outline selective small-molecule modulators that function as cGAS-STING inhibitors and summarize their mechanisms for treating multiple neurological diseases. Finally, we discuss key limitations of the current therapeutic paradigm and generate possible strategies to overcome them.

Liver-Secreted Extracellular Vesicles Promote Cirrhosis-Associated Skeletal Muscle Injury Through mtDNA-cGAS/STING Axis

Skeletal muscle atrophy (sarcopenia) is a serious complication of liver cirrhosis, and chronic muscle inflammation plays a pivotal role in its pathologenesis. However, the detailed mechanism through which injured liver tissues mediate skeletal muscle inflammatory injury remains elusive. Here, it is reported that injured hepatocytes might secrete mtDNA-enriched extracellular vesicles (EVs) to trigger skeletal muscle inflammation by activating the cGAS-STING pathway. Briefly, injured liver secreted increased amounts of EVs into circulation, which are then engulfed primarily by macrophages in skeletal muscle and subsequently induce cGAS-STING signaling and its-mediated inflammatory response in muscles. In contrast, suppression of hepatic EV secretion or STING signaling significantly alleviated cirrhosis-induced skeletal muscle inflammation and muscle atrophy in vivo. Circulating EVs from cirrhotic patients showed higher levels of mtDNA, and the levels of EV-mtDNA positively correlated with the severity of liver injury. In injured hepatocytes, mitochondrial damage promoted the release of cytosolic mtDNA and the subsequent secretion of mtDNA-enriched EVs. This study reveals that injured hepatocyte-derived EVs induce skeletal muscle inflammation via the mtDNA‒STING axis, while targeted blockade of liver EV secretion or STING signaling represents a potential therapeutic approach for preventing cirrhosis-associated skeletal muscle atrophy.

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.

The role of cGAS-STING pathway ubiquitination in innate immunity and multiple diseases

The cGAS-STING pathway is essential in innate immunity, especially in antiviral responses and cellular stress management. cGAS acts as a cytoplasmic DNA sensor by initiating the synthesis of the second messenger cyclic GMP-AMP synthase (cGAMP), which subsequently activates the STING pathway, leading to the production of type I interferons and other cytokines, as well as the activation of inflammatory mediators. Recent studies have demonstrated that ubiquitination changes closely regulate the function of the cGAS-STING pathway. Ubiquitination modifications influence the stability and activity of cGAS and STING, while also influencing the accuracy of the immune response by adjusting their degradation and signal intensity. E3 ubiquitin ligase specifically facilitates the degradation or modulates the signaling of cGAS-STING-associated proteins via ubiquitination alterations. Furthermore, the ubiquitination of the cGAS-STING pathway serves distinct functions in various cell types and engages with NF-κB, IRF3/7, autophagy, and endoplasmic reticulum stress. This ubiquitin-mediated regulation is crucial for sustaining the balance of innate immunity, while excessive or inadequate ubiquitination can result in autoimmune disorders, cancers, and viral infections. An extensive examination of the ubiquitination process within the cGAS-STING pathway elucidates its specific regulatory mechanisms in innate immunity and identifies novel targets for the intervention of associated diseases.

Profile of STING agonist and inhibitor research: a bibliometric analysis

Background

STING is a core signaling hub molecule in the innate immune system, involved in various diseases, including infectious diseases, autoimmune diseases, tumors, aging, organ fibrosis, and neurodegenerative diseases. Its activation has shown great potential in anti-tumor and anti-infective therapies, with STING agonists emerging as a promising approach in cancer immunotherapy in recent years. This study identifies research trends and potential directions in the field by collecting and analyzing relevant literature.

Methods

A total of 527 publications regarding STING agonists and 107 about inhibitors were retrieved from the WOS Core Collection database. Bibliometric information was extracted with CiteSpace and VOSviewer software for visualization.

Results

It shows that research on both STING agonists and inhibitors is burgeoning rapidly. The United States and China are leading contributors in this field. Application of STING agonists primarily focuses on cancer immunotherapy, while STING inhibitors target inflammation, particularly neuroinflammation and acute lung injury.

Conclusion

Current research emphasizes optimizing STING agonists for permeability, efficacy, and safety, with nanotechnology and lipid nanoparticles being prominent delivery techniques. Future research is expected to focus on drug development and clinical applications. This comprehensive bibliometric analysis provides clinical insights and a guide for further investigation to STING agonist/inhibitor.

Short 5' UTRs serve as a marker for viral mRNA translation inhibition by the IFIT2-IFIT3 antiviral complex

Recognition of "non-self" nucleic acids, including cytoplasmic dsDNA, dsRNA, or mRNAs lacking proper 5' cap structures, is critical for the innate immune response to viruses. Here, we demonstrate that short 5' untranslated regions (UTRs), a characteristic of many viral mRNAs, can also serve as a molecular pattern for innate immune recognition via the interferon-induced proteins IFIT2 and IFIT3. The IFIT2-IFIT3 heterodimer, formed through an intricate domain swap structure resolved by cryo-EM, mediates viral mRNA 5' end recognition, translation inhibition, and ultimately antiviral activity. Critically, 5' UTR lengths <50 nucleotides are necessary and sufficient to sensitize an mRNA to translation inhibition by the IFIT2-IFIT3 complex. Accordingly, diverse viruses whose mRNAs contain short 5' UTRs, such as vesicular stomatitis virus and parainfluenza virus 3, are sensitive to IFIT2-IFIT3-mediated antiviral activity. Our work thus reveals a pattern of antiviral nucleic acid immune recognition that takes advantage of the inherent constraints on viral genome size.

Mitochondrial DNA leakage: underlying mechanisms and therapeutic implications in neurological disorders

Mitochondrial dysfunction is a pivotal instigator of neuroinflammation, with mitochondrial DNA (mtDNA) leakage as a critical intermediary. This review delineates the intricate pathways leading to mtDNA release, which include membrane permeabilization, vesicular trafficking, disruption of homeostatic regulation, and abnormalities in mitochondrial dynamics. The escaped mtDNA activates cytosolic DNA sensors, especially cyclic gmp-amp synthase (cGAS) signalling and inflammasome, initiating neuroinflammatory cascades via pathways, exacerbating a spectrum of neurological pathologies. The therapeutic promise of targeting mtDNA leakage is discussed in detail, underscoring the necessity for a multifaceted strategy that encompasses the preservation of mtDNA homeostasis, prevention of membrane leakage, reestablishment of mitochondrial dynamics, and inhibition the activation of cytosolic DNA sensors. Advancing our understanding of the complex interplay between mtDNA leakage and neuroinflammation is imperative for developing precision therapeutic interventions for neurological disorders.

cGAS-STING targeting offers therapy choice in lung diseases

Cyclic GMP/AMP (cGAMP) synthase (cGAS), along with the endoplasmic reticulum (ER)-associated stimulator of interferon genes (STING), are crucial elements of the type 1 interferon response. cGAS senses microbial DNA and self-DNA, labeling cGAS-STING as a crucial mechanism in autoimmunity, sterile inflammatory responses, and cellular senescence. However, chronic and aberrant activation of the cGAS-STING axis results in inflammatory and autoimmune diseases. cGAS-STING has emerged as a vital mechanism driving inflammation-related diseases, including lung diseases. Insights into the biology of the cGAS-STING pathway have enabled the discovery of small-molecule agents which have the potential to inhibit the cGAS-STING axis in lung diseases. In this review, we first outline the principal components of the cGAS-STING signaling cascade. Then, we discuss recent research that highlights general mechanisms by which cGAS-STING contributes to lung diseases. Then, we focus on summarizing a list of bioactive small-molecule compounds which inhibit the cGAS-STING pathway, reviewing their potential mechanisms.These review highlights a novel groundbreaking therapeutic possibilities through targeting cGAS-STING in lung diseases.

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.

Dendrimer-Mediated Generation of a Metal-Phenolic Network for Antibody Delivery to Elicit Improved Tumor Chemo/Chemodynamic/Immune Therapy

To simplify the composition and improve the efficacy of metal-phenolic network (MPN)-based nanomedicine, herein, we designed an MPN platform to deliver programmed death ligand-1 (PD-L1) antibody (anti-PD-L1) for combined tumor chemo/chemodynamic/immune therapy. Here, generation 5 poly(amidoamine) dendrimers conjugated with gossypol (Gos) through boronic ester bonds were used as a synthetic polyphenol to coordinate Mn2+, and then complexed with anti-PD-L1 to obtain the nanocomplexes (for short, DPGMA). The prepared DPGMA exhibited good water dispersibility with a hydrodynamic size of 166.3 nm and tumor-microenvironment-responsive drug release behavior. The integration of Gos and Mn2+ within the DPGMA resulted in significant tumor inhibition and immunogenic cell death activation through Gos-mediated chemotherapy and Mn2+-catalyzed chemodynamic therapy, respectively, thereby leading to significant dendritic cell maturation due to the role of Mn2+ played to mediate the activation of the stimulator of interferon genes (STING) pathway. Moreover, the complexed anti-PD-L1 promoted the recognition and uptake of nanocomplexes by PD-L1-overexpressed tumors through antibody targeting, thereby achieving combinational chemo/chemodynamic/immune therapy in a mouse melanoma model, where the immunotherapy modes combined three parts of activation via chemotherapy/CDT-mediated ICD, Mn2+-mediated STING activation, and antibody-mediated immune checkpoint blockade. With the Mn2+-endowed r1 relaxivity (1.38 mM-1 s-1), the DPGMA nanocomplexes can also be used for tumor MR imaging. The designed dendrimer-mediated MPN platform may be developed as an advanced nanomedicine to tackle other cancer types.

MicroSphere 3D Structures Delay Tissue Senescence through Mechanotransduction

The extracellular matrix (ECM) stores signaling molecules and facilitates mechanical and biochemical signaling in cells. However, the influence of biomimetic "rejuvenation" ECM structures on aging- and degeneration-related cellular activities and tissue repair is not well understood. We combined physical extrusion and precise "on-off" alternating cross-linking methods to create anisotropic biomaterial microgels (MicroRod and MicroSphere) and explored how they regulate the cell activities of the nucleus pulposus (NP) and their potential antidegenerative effects on intervertebral discs. NP cells exhibited aligned growth along the surface of the MicroRod, enhanced proliferation, and reduced apoptosis. This suggests an adaptive cellular response involving adhesion and mechanosensing, which causes cytoskeletal extension via environmental cues. NP cells maintain nuclear membrane integrity through the YAP/TAZ pathway, which activates the cGAS-STING pathway to rectify the aging mechanisms. In vivo, MicroRod carries NP cells and reduces inflammatory factor and protease secretion in degenerated intervertebral discs, inhibiting degeneration and promoting NP tissue regeneration. Our findings highlight the role of mechanical stress in maintaining cellular activity and antiaging effects in harsh environments, providing a foundation for further research and development of antidegenerative biomaterials.

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.

Macrophage STING signaling promotes fibrosis in benign airway stenosis via an IL6-STAT3 pathway

Acute and chronic inflammation are important pathologies of benign airway stenosis (BAS) fibrosis, which is a frequent complication of critically ill patients. cGAS-STING signalling has an important role in inflammation and fibrosis, yet the function of STING in BAS remains unclear. Here we demonstrate using scRNA sequencing that cGAS‒STING signalling is involved in BAS, which is accompanied by increased dsDNA, expression and activation of STING. STING inhibition or deficiency effectively alleviates tracheal fibrosis of BAS mice by decreasing both acute and chronic inflammation. Macrophage depletion also effectively ameliorates BAS. Mechanistically, dsDNA from damaged epithelial cells activates the cGAS-STING pathway of macrophages and induces IL-6 to activate STAT3 and promote fibrosis. In summary, the present results suggest that cGAS-STING signalling induces acute inflammation and amplifies the chronic inflammation and tracheal fibrosis associated with benign airway stenosis, highlighting the mechanism and potential drug target of BAS.

Elucidating the expression and role of cGAS in pan-cancer using integrated bioinformatics and experimental approaches

cGAS plays an important role in regulating both tumor immune responses and DNA damage repair. Nevertheless, there was little research that comprehensively analyzed the correlation between cGAS and the tumor microenvironment, immune cell infiltration, and DNA damage repair in different cancers. In this study, The Cancer Genome Atlas (TCGA) and Cancer Cell Line Encyclopedia (CCLE) data were used to analyze the mRNA expression and genomic alterations of cGAS in pan-cancer. The HPA database was used to explore the protein levels of cGAS in normal tissues and cancers. Correlation analysis were performed to explore the role of cGAS in interferon expression, immune cell infiltrations, DNA damage repair, and predictive immune markers. The prognostic value of cGAS was analyzed using survival data from the TCGA, Kaplan-Meier plotter database, and PrognoScan database. Lastly, the role of cGAS in DNA damage repair signaling and interferon signaling was validated in NSCLC cell lines. The results showed that cGAS was widely expressed in human normal tissues and various cancers, and the expression of cGAS was significantly upregulated in almost all of the solid cancers. Genomic analysis indicated that the expression of cGAS was positively correlated with copy number levels, while negatively correlated with the methylation levels of cGAS promoter. In addition, the level of cGAS was positively correlated with type I interferons expression, infiltration levels of most immune cell types, TMB and MSI levels, stromal and immune scores, and DNA damage repair gene sets including nonhomologous end joining and homologous recombination pathway. Survival analysis indicated that cGAS levels were associated with patient prognosis in several cancers. Lastly, in vitro study showed knockdown of cGAS expression inhibits the DNA damage repair signaling pathway and interferon signaling in NSCLC. In conclusions, cGAS is wildly activated in human cancers, which might participate in regulating cancer immunity and DNA damage repair. cGAS could be used as an effective target for cancer treatment and might be a potential predictive immune marker.

Mitochondria-Associated Endoplasmic Reticulum Membranes in Microglia: One Contact Site to Rule Them all

Microglia, the resident immune cells of the central nervous system (CNS), play a crucial role in maintaining tissue homeostasis by monitoring and responding to environmental changes through processes such as phagocytosis, cytokine production or synapse remodeling. Their dynamic nature and diverse functions are supported by the regulation of multiple metabolic pathways, enabling microglia to efficiently adapt to fluctuating signals. A key aspect of this regulation occurs at mitochondria-associated ER membranes (MAM), specialized contact sites between the ER and mitochondria. These structures facilitate the exchange of calcium, lipids, and metabolites and serve as metabolic and signaling hubs. This review synthesizes current research on how MAM influence microglial physiology, with an emphasis on their role in immunometabolism, offering new insights into the integration of metabolic and immune functions in the CNS and its impact in the context of neurodegeneration.

Homogeneous and bioluminescent biochemical and cellular assay for monitoring cGAMP and enzymes that generate and degrade cGAMP

The cyclic GMP-AMP synthase-stimulator of the interferon gene (cGAS-STING) signaling pathway is considered an essential pattern recognition and effector pathway in the natural immune system and is mainly responsible for recognizing DNA molecules present in the cytoplasm and activating downstream signaling pathways to generate type I interferons (IFN-I) and other inflammatory factors. STING, a crucial junction protein in the innate immune system, exerts an essential role in host resistance to external pathogen invasion. The DNA introduced by pathogens or tumors is recognized by the cytoplasmic nucleic acid receptor cGAS, and a second messenger, cGAMP, is generated using intracellular guanosine triphosphate (GTP) and adenosine triphosphate (ATP). Furthermore, cellular and extracellular cGAMP concentrations are also controlled by ENPP1, an enzyme that breaks down cGAMP to AMP and GMP. Therefore, the role of the cGAS-STING signaling pathway has generated great interest in inflammatory and cancer research. To advance our understanding of innate immune system and in particular the STING pathway, we have developed a homogeneous, bioluminescent cGAMP detection assay that is very sensitive and highly selective against other nucleotides, cyclic nucleotides, and dicyclic nucleotides. The assay can be also used to monitor the activity of cGAS and ENPP1 to enable the development of inhibitors of both enzymes which might be used for therapeutic applications.

The role of cGAS-STING signaling pathway in colorectal cancer immunotherapy: Mechanism and progress

Colorectal cancer (CRC) is a common malignant tumor in the gastrointestinal tract, it is known as the "silent killer", which poses a serious threat to the lives of patients. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING) signaling pathway responds to DNA by sensing, which plays an important role in anti-infection, autoimmune diseases and anti-tumor immunity. Recent studies have found that the activation of cGAS-STING pathway in CRC can induce the expression and secretion of type I interferon (IFN-I) and a variety of inflammatory factors, further activate anti-tumor CD8+ T cells, exert anti-tumor immune response, and inhibit the progression of CRC. Therefore, targeting the cGAS-STING pathway and developing drugs that can regulate the cGAS-STING pathway are of great significance for improving the therapeutic effect and prognosis of CRC patients. In this review, we introduce the cGAS-STING signaling pathway and the regulatory role of this signaling pathway in CRC immune microenvironment. In addition, we discussed the research progress of cGAS-STING pathway in CRC immunotherapy and the clinical research status of STING agonists developed against this pathway, emphasizing the clinical potential of CRC immunotherapy based on the cGAS-STING signaling pathway.

Nanomedicines harnessing cGAS-STING pathway: sparking immune revitalization to transform 'cold' tumors into 'hot' tumors

cGAS-STING pathway stands at the forefront of innate immunity and plays a critical role in regulating adaptive immune responses, making it as a key orchestrator of anti-tumor immunity. Despite the great potential, clinical outcomes with cGAS-STING activators have been disappointing due to their unfavorable in vivo fate, signaling an urgent need for innovative solutions to bridge the gap in clinical translation. Recent advancements in nanotechnology have propelled cGAS-STING-targeting nanomedicines to the cutting-edge of cancer therapy, leveraging precise drug delivery systems and multifunctional platforms to achieve remarkable region-specific biodistribution and potent therapeutic efficacy. In this review, we provide an in-depth exploration of the molecular mechanisms that govern cGAS-STING signaling and its potential to dynamically modulate the anti-tumor immune cycle. We subsequently introduced several investigational cGAS-STING-dependent anti-tumor agents and summarized their clinical trial progress. Additionally, we provided a comprehensive review of the unique advantages of cGAS-STING-targeted nanomedicines, highlighting the transformative potential of nanotechnology in this field. Furthermore, we comprehensively reviewed and comparatively analyzed the latest breakthroughs cGAS-STING-targeting nanomedicine, focusing on strategies that induce cytosolic DNA generation via exogenous DNA delivery, chemotherapy, radiotherapy, or dynamic therapies, as well as the nanodelivery of STING agonists. Lastly, we discuss the future prospects and challenges in cGAS-STING-targeting nanomedicine development, offering new insights to bridge the gap between mechanistic research and drug development, thereby opening new pathways in cancer treatment.

The cGAS-STING pathway in ischemia-reperfusion injury in acute cerebral infarction: a new therapeutic opportunities?

The innate immune response is the body's first line of defense against external pathogens and endogenous damage signals. The cGAS-STING pathway is a crucial component of the innate immune response, playing a key role in initiating antiviral and anti-infective immune responses by recognizing cytosolic DNA. Acute cerebral infarction is one of the leading causes of death and disability worldwide, with the primary treatment approach being the restoration of blood flow to ischemic brain tissue. However, reperfusion injury remains a significant challenge during treatment. The overactivation of the cGAS-STING pathway and its association with ischemia-reperfusion injury have been confirmed in numerous studies. This article will systematically elucidate the mechanisms of the cGAS-STING pathway, its role in ischemia-reperfusion injury in acute cerebral infarction, the current research status of cGAS-STING inhibitors, and the application of nanomaterials in this context, evaluating the therapeutic potential of this pathway.

Taking the STING out of radiotherapy: STING checkpoints mediate radiation resistance

The cyclic GMP-AMP synthase/stimulator of interferon genes (cGAS/STING) pathway is a critical driver of type I interferon (IFN-I) and antitumor CD8+ T cell responses after radiotherapy (RT). In this issue of the JCI, two reports describe mechanisms that restrained STING signaling and abrogated antitumor immunity after RT. Wen, Wang, and colleagues discovered that IFN-I mediated the induction of YTHDF1, an RNA N6-methyladenosine-binding protein, in DCs after RT promoted cathepsin-mediated STING degradation. Zhang, Deng, Wu, and colleagues discovered that hemeoxygenase 1 (HO-1) was induced and proteolytically cleaved after RT to suppress cGAS cytoplasmic export as well as STING oligomerization at the ER. Blocking the STING-suppressive functions of YTHDF1 and HO-1, respectively, improved antitumor T cell immunity and tumor control after RT. Together, these studies support the development of clinical avenues to sustain STING signaling during RT, a standard treatment for approximately 50% of malignancies.

Ccl2-Induced Regulatory T Cells Balance Inflammation Through Macrophage Polarization During Liver Reconstitution

Inflammation is highlighted as an initial factor that helps orchestrate liver reconstitution. However, the precise mechanisms controlling inflammation during liver reconstitution have not been fully elucidated. In this study, a clear immune response is demonstrated during hepatic reconstitution. Inhibition of the hepatic inflammatory response retards liver regeneration. During this process, Ccl2 is primarily produced by type 1 innate lymphoid cells (ILC1s), and ILC1-derived Ccl2 recruits peripheral ILC1s and regulatory T cells (Tregs) to the liver. Deletion of Ccl2 or Tregs exacerbates hepatic injury and inflammatory cytokine release, accelerating liver proliferation and regeneration. The adoption of Tregs and IL-10 injection reversed these effects on hepatocyte regenerative proliferation. Additionally, Treg-derived IL-10 can directly induce macrophage polarization from M1 to M2, which alleviated macrophage-secreted IL-6 and TNF-α and balanced the intrahepatic inflammatory milieu during liver reconstitution. This study reveals the capacity of Tregs to modulate the intrahepatic inflammatory milieu and liver reconstitution through IL-10-mediated macrophage polarization, providing a potential opportunity to improve hepatic inflammation and maintain homeostasis.

STING facilitates the development of radiation-induced lung injury via regulating the PERK/eIF2α pathway

Background

Radiation-induced lung injury (RILI) is one of the serious adverse reactions of thoracic radiotherapy, which largely limits the dose and therapeutic effect of radiotherapy. The underlying mechanism has not been elucidated. RILI is characterized by an acute inflammatory response, and stimulator of interferon genes (STING) has been reported to play an important role in regulating inflammation and innate immune activation. However, its role in RLLI, remains unclear. Here, we reported the potential therapeutic effect of STING inhibitor H-151 on RILI.

Methods

C57BL/6J mice were exposed to 20 Gy whole-thorax irradiation and H-151 was injected intraperitoneally from the day of irradiation for 4 weeks. The degree of RILI was then assessed. To further explore the mechanism of STING in RILI, the supernatant of irradiated lung epithelial cell MLE-12 was co-cultured with embryonic fibroblast cell NIH/3T3.

Results

The cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-STING pathway is abnormally activated in irradiated mouse lung tissues. The early application of STING inhibitor significantly alleviated radiation-induced inflammatory cell infiltration and pro-inflammatory cytokine release in lung tissue, as well as the degree of fibrosis in the late stage. The amount of double-stranded DNA (dsDNA) in the supernatant of irradiated MLE-12 cells was abnormally increased, and the epithelial-derived dsDNA could promote the transformation of fibroblasts into myofibroblasts. Mechanistically, STING could mediate the activation of fibroblasts to myofibroblasts via the PKR-like endoplasmic reticulum kinase (PERK)-eukaryotic initiation factor 2α (eIF2α) pathway.

Conclusions

Our study focused on the activation of cGAS-STING signaling pathway in RILI, and inhibition of STING significantly ameliorated RILI in mice. STING mediated the effect of radiation-induced dsDNA release to stimulate the activation of inflammatory response, and STING restriction significantly delayed the fibrosis process through the PERK-eIF2α pathway, suggesting that STING intervention may pave a new avenue for the treatment of RILI.

The cGAS-STING pathway drives neuroinflammation and neurodegeneration via cellular and molecular mechanisms in neurodegenerative diseases

Neurodegenerative diseases (NDs) are a type of common chronic progressive disorders characterized by progressive damage to specific cell populations in the nervous system, ultimately leading to disability or death. Effective treatments for these diseases are still lacking, due to a limited understanding of their pathogeneses, which involve multiple cellular and molecular pathways. The triggering of an immune response is a common feature in neurodegenerative disorders. A critical challenge is the intricate interplay between neuroinflammation, neurodegeneration, and immune responses, which are not yet fully characterized. In recent years, the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING) pathway, a crucial immune response for intracellular DNA sensing, has gradually gained attention. However, the specific roles of this pathway within cellular types such as immune cells, glial and neuronal cells, and its contribution to ND pathogenesis, remain not fully elucidated. In this review, we systematically explore how the cGAS-STING signaling links various cell types with related cellular effector pathways under the context of NDs for multifaceted therapeutic directions. We emphasize the discovery of condition-dependent cellular heterogeneity in the cGAS-STING pathway, which is integral for understanding the diverse cellular responses and potential therapeutic targets. Additionally, we review the pathogenic role of cGAS-STING activation in Parkinson's disease, ataxia-telangiectasia, and amyotrophic lateral sclerosis. We focus on the complex bidirectional roles of the cGAS-STING pathway in Alzheimer's disease, Huntington's disease, and multiple sclerosis, revealing their double-edged nature in disease progression. The objective of this review is to elucidate the pivotal role of the cGAS-STING pathway in ND pathogenesis and catalyze new insights for facilitating the development of novel therapeutic strategies.

cGAS regulates metabolic reprogramming independently of STING pathway in colorectal cancer

BACKGROUND

Cyclic GMP-AMP synthase (cGAS) is widely acknowledged for detecting cytosolic chromatin fragments and triggering innate immune responses through the production of the second messenger cGAMP, which subsequently activates the adaptor protein STING. However, the role of cGAS in regulating metabolic reprogramming independently of STING activation has not yet been explored.

METHODS

Gene set enrichment pathway analysis (GSEA) based on TCGA transcriptomics, combined with Seahorse metabolic analysis of CRC cell lines and human normal colonic mucosa cell line FHC, was performed to profile the metabolic features in CRC. cGAS doxycycline- (dox) inducible knockout (iKO) CRC sublines were generated to investigate the role of cGAS in CRC. Transcriptome and proteome data from COAD cohorts were utilized to evaluate the RNA and protein expression levels of cGAS in COAD tissues and normal colon tissues. Overall survival information of patients with COAD was used to evaluate the prognostic value of cGAS expression. Colony formation assays were conducted to evaluate the clonogenicity of CRC cells under different situations. Flow cytometry detecting the signal of fluorogenic reactive oxygen species (ROS) probes was performed to evaluate the total cellular and mitochondrial oxidative stress level in CRC cells. A propidium iodide (PI) staining assay was used to evaluate the cell death level in CRC cells. Quantitative PCR (qPCR) was conducted to detect the RNA level of STING pathway downstream target genes. Mass spectrometry was used for the identification of novel binding partners of cGAS in CRC cells. Co-immunoprecipitation (co-IP) was conducted to confirm the interaction between cGAS and NDUFA4L2.

RESULTS

By integrating metabolic pathway analysis based on TCGA transcriptomics with Seahorse metabolic analysis of a panel CRC cell lines and the human normal colonic mucosa cell line FHC, we demonstrated that CRC cells exhibit typical characteristics of metabolic reprogramming, characterized by a shift from oxidative phosphorylation (OXPHOS) to glycolysis. We found that cGAS is critical for CRC cells to maintain this metabolic switch. Specifically, the suppression of cGAS through siRNA-mediated knockdown or doxycycline-inducible knockout reversed this metabolic switch, resulting in increased OXPHOS activity, elevated production of OXPHOS byproduct reactive oxygen species (ROS), and consequently caused oxidative stress. This disruption induced oxidative stress, ultimately resulting in cell death and reduced cell viability. Moreover, significant upregulation of cGAS in CRC tissues and cell lines and its association with poor prognosis in CRC patients was observed. Subsequently, we demonstrated that the role of cGAS in regulating metabolic reprogramming does not rely on the canonical cGAS-STING pathway. Co-immunoprecipitation combined with mass spectrometry identified NDUFA4L2 as a novel interactor of cGAS. Subsequent functional experiments, including mitochondrial respiration and oxidative stress assays, demonstrated that cGAS plays a crucial role in sustaining elevated levels of NDUFA4L2 protein expression. The increased expression of NDUFA4L2 is essential for cGAS-mediated regulation of metabolic reprogramming and cell survival in CRC cells.

CONCLUSION

cGAS regulates metabolic reprogramming and promotes cell survival in CRC cells through its interaction with NDUFA4L2, independently of the canonical cGAS-STING pathway.

Apoptotic Caspases Suppress Expression of Endogenous Retroviruses in HPV31+ Cells That Are Associated with Activation of an Innate Immune Response

Avoidance of an immune response is critical to completion of the human papillomavirus (HPV) life cycle, which occurs in the stratified epithelium and is linked to epithelial differentiation. We previously demonstrated that high-risk HPVs use apoptotic caspases to suppress an antiviral innate immune response during the productive phase of the life cycle. We found that caspase-8 and caspase-3 suppress a type I IFN-β and type III IFN-λ response by disabling the MDA5/MAVS double-stranded RNA (dsRNA) sensing pathway, indicating that immunogenic RNAs increase upon differentiation in HPV+ cells. In this study, we demonstrate that caspase inhibition results in aberrant transcription of a subset of endogenous retroviruses (ERVs) that have been shown to activate an IFN response through dsRNA-sensing pathways. We show that the increase in ERV transcription is accompanied by an enrichment in dsRNA formation. Additionally, we demonstrate that the robust increase in ERV expression requires activation of the JAK/STAT-signaling pathway, indicating that this subset of ERVs is IFN-inducible. Overall, these results suggest a model by which caspase activity blocks the reactivation of ERVs through the JAK/STAT pathway, protecting HPV+ cells from an increase in immunogenic dsRNAs that otherwise would trigger an IFN response that inhibits productive viral replication.

Signaling Mechanism of Cuproptosis Activating cGAS-STING Immune Pathway

Copper-mediated programmed cell death, which influences the regulation of tumor progression, is an effective approach for antitumor molecular therapy. Unlike apoptosis, copper complex-induced cuproptosis by lipid-acylated protein aggregation triggers the mitochondrial proteotoxic stress response, which could be associated with immunomodulation. However, it remains a great challenge to understand the distinctive molecular mechanisms that presumably activate immunity by cuproptosis. Here, the new nonlabeling fluorescent molecular tools of Cu-DPPZ-Py+ and Cu-DPPZ-Ph are synthesized and used to investigate the differential immune signaling mechanisms induced by copper-mediated cuproptosis or apoptosis. With Cu-DPPZ-Py+ and Cu-Elesclomol, there is strong evidence that the triggering cuproptosis significantly drives mitochondrial DNA (mtDNA) release to activate innate immunity via cyclic GMP-AMP synthase-stimulation of interferon genes (cGAS-STING), which can improve T cell antitumor immunity in vivo. By contrast, it is observed that Cu-DPPZ-Ph treated tumor cells could release intracellular caspase-3, resulting in apoptosis-associated immunosuppression. This study supports insights into how cuproptosis bridges cGAS-STING immune pathways, contributing to the development of cuproptosis-based antitumor immunotherapy.