STING is an endoplasmic reticulum adaptor that facilitates innate immune signalling. Nature. 2008;455:674-678. [PMID: 18724357 PMCID: PMC2804933 DOI: 10.1038/nature07317]

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.

Organellophagy regulates cell death:A potential therapeutic target for inflammatory diseases

BACKGROUND

Dysregulated alterations in organelle structure and function have a significant connection with cell death, as well as the occurrence and development of inflammatory diseases. Maintaining cell viability and inhibiting the release of inflammatory cytokines are essential measures to treat inflammatory diseases. Recently, many studies have showed that autophagy selectively targets dysfunctional organelles, thereby sustaining the functional stability of organelles, alleviating the release of multiple cytokines, and maintaining organismal homeostasis. Organellophagy dysfunction is critically engaged in different kinds of cell death and inflammatory diseases.

AIM OF REVIEW

We summarized the current knowledge of organellophagy (e.g., mitophagy, reticulophagy, golgiphagy, lysophagy, pexophagy, nucleophagy, and ribophagy) and the underlying mechanisms by which organellophagy regulates cell death.

KEY SCIENTIFIC CONCEPTS OF REVIEW

We outlined the potential role of organellophagy in the modulation of cell fate during the inflammatory response to develop an intervention strategy for the organelle quality control in inflammatory diseases.

African swine fever virus MGF505-6R attenuates type I interferon production by targeting STING for degradation

African swine fever (ASF) is an acute hemorrhagic and devastating infectious disease affecting domestic pigs and wild boars. It is caused by the African swine fever virus (ASFV), which is characterized by genetic diversity and sophisticated immune evasion strategies. To facilitate infection, ASFV encodes multiple proteins to antagonize host innate immune responses, thereby contributing to viral virulence and pathogenicity. The molecular mechanisms employed by ASFV-encoded proteins to modulate host antiviral responses have not been comprehensively elucidated. In this study, it was observed that the ASFV MGF505-6R protein, a member of the multigene family 505 (MGF505), effectively suppressed the activation of the interferon-beta (IFN-β) promoter, leading to reduced mRNA levels of antiviral genes. Additional evidence has revealed that MGF505-6R antagonizes the cGAS-STING signaling pathway by interacting with the stimulator of interferon genes (STING) for degradation in the autophagy-lysosomal pathway. The domain mapping revealed that the N-terminal region (1-260aa) of MGF505-6R is the primary domain responsible for interacting with STING, while the CTT domain of STING is crucial for its interaction with MGF505-6R. Furthermore, MGF505-6R also inhibits the activation of STING by reducing the K63-linked polyubiquitination of STING, leading to the disruption of STING oligomerization and TANK binding kinase 1 (TBK1) recruitment, thereby impairing the phosphorylation and nuclear translocation of interferon regulatory factor 3 (IRF3). Collectively, our study elucidates a novel strategy developed by ASFV MGF505-6R to counteract host innate immune responses. This discovery may offer valuable insights for further exploration of ASFV immune evasion mechanisms and antiviral strategies.

The STING agonist IMSA101 enhances chimeric antigen receptor T cell function by inducing IL-18 secretion

As a strategy to improve the therapeutic success of chimeric antigen receptor T cells (CART) directed against solid tumors, we here test the combinatorial use of CART and IMSA101, a newly developed stimulator of interferon genes (STING) agonist. In two syngeneic tumor models, improved overall survival is observed when mice are treated with intratumorally administered IMSA101 in addition to intravenous CART infusion. Transcriptomic analyses of CART isolated from tumors show elevated T cell activation, as well as upregulated cytokine pathway signatures, in particular IL-18, in the combination treatment group. Also, higher levels of IL-18 in serum and tumor are detected with IMSA101 treatment. Consistent with this, the use of IL-18 receptor negative CART impair anti-tumor responses in mice receiving combination treatment. In summary, we find that IMSA101 enhances CART function which is facilitated through STING agonist-induced IL-18 secretion.

The Interplay between KSHV Infection and DNA-Sensing Pathways

During viral infection, the innate immune system utilizes a variety of specific intracellular sensors to detect virus-derived nucleic acids and activate a series of cellular signaling cascades that produce type I IFNs and proinflammatory cytokines and chemokines. Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic double-stranded DNA virus that has been associated with a variety of human malignancies, including Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman disease. Infection with KSHV activates various DNA sensors, including cGAS, STING, IFI16, and DExD/H-box helicases. Activation of these DNA sensors induces the innate immune response to antagonize the virus. To counteract this, KSHV has developed countless strategies to evade or inhibit DNA sensing and facilitate its own infection. This review summarizes the major DNA-triggered sensing signaling pathways and details the current knowledge of DNA-sensing mechanisms involved in KSHV infection, as well as how KSHV evades antiviral signaling pathways to successfully establish latent infection and undergo lytic reactivation.

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.

Microglia and macrophages in glioblastoma: landscapes and treatment directions

Glioblastoma is the most common primary malignant tumour of the central nervous system and remains uniformly and rapidly fatal. The tumour-associated macrophage (TAM) compartment comprises brain-resident microglia and bone marrow-derived macrophages (BMDMs) recruited from the periphery. Immune-suppressive and tumour-supportive TAM cell states predominate in glioblastoma, and immunotherapies, which have achieved striking success in other solid tumours have consistently failed to improve survival in this 'immune-cold' niche context. Hypoxic and necrotic regions in the tumour core are found to enrich, especially in anti-inflammatory and immune-suppressive TAM cell states. Microglia predominate at the invasive tumour margin and express pro-inflammatory and interferon TAM cell signatures. Depletion of TAMs, or repolarisation towards a pro-inflammatory state, are appealing therapeutic strategies and will depend on effective understanding and classification of TAM cell ontogeny and state based on new single-cell and spatial multi-omic in situ profiling. Here, we explore the application of these datasets to expand and refine TAM characterisation, to inform improved modelling approaches, and ultimately underpin the effective manipulation of function.

Targeting STING elicits GSDMD-dependent pyroptosis and boosts anti-tumor immunity in renal cell carcinoma

While Stimulator-of-interferon genes (STING) is an innate immune adapter cruicial for sensing cytosolic DNA and modulating immune microenvironment, its tumor-promoting role in tumor survival and immune evasion remains largely unknown. Here we reported that renal cancer cells are exceptionally dependent on STING for survival and evading immunosurveillance via suppressing ER stress-mediated pyroptosis. We found that STING is significantly amplified and upregulated in clear cell renal cell carcinoma (ccRCC), and its elevated expression is associated with worse clinical outcomes. Mechanically, STING depletion in RCC cells specifically triggers activation of the PERK/eIF2α/ATF4/CHOP pathway and activates cleavage of Caspase-8, thereby inducing GSDMD-mediated pyroptosis, which is independent of the innate immune pathway of STING. Moreover, animal study revealed that STING depletion promoted infiltration of CD4+ and CD8+ T cells, consequently boosting robust antitumor immunity via pyroptosis-induced inflammation. From the perspective of targeted therapy, we found that Compound SP23, a PROTAC STING degrader, demonstrated comparable efficacy to STING depletion both in vitro and in vivo for treatment of ccRCC. These findings collectively unveiled an unforeseen function of STING in regulating GSDMD-dependent pyroptosis, thus regulating immune response in RCC. Consequently, pharmacological degradation of STING by SP23 may become an attractive strategy for treatment of advanced RCC.

STINGing away the pain: the role of interferon-stimulated genes

Pain and inflammation are biologically intertwined responses that warn the body of potential danger. In this issue of the JCI, Defaye, Bradaia, and colleagues identified a functional link between inflammation and pain, demonstrating that inflammation-induced activation of stimulator of IFN genes (STING) in dorsal root ganglia nociceptors reduced pain-like behaviors in a rodent model of inflammatory pain. Utilizing mice with a gain-of-function STING mutation, Defaye, Bradaia, and colleagues identified type I IFN regulation of voltage-gated potassium channels as the mechanism of this pain relief. Further investigation into mechanisms by which proinflammatory pathways can reduce pain may reveal druggable targets and insights into new approaches for treating persistent pain.

STING activator 2'3'-cGAMP enhanced HSV-1-based oncolytic viral therapy

Oncolytic viruses (OVs) can selectively replicate in tumor cells and remodel the microenvironment of immunologically cold tumors, making them a promising strategy to evoke antitumor immunity. Similarly, agonists of the stimulator of interferon genes (STING)-interferon (IFN) pathway, the main cellular antiviral system, provide antitumor benefits by inducing the activation of dendritic cells (DC). Considering how the activation of the STING-IFN pathway could potentially inhibit OV replication, the use of STING agonists alongside OV therapy remains largely unexplored. Here, we explored the antitumor efficacy of combining an HSV-1-based OV, C-REV, with a membrane-impermeable STING agonist, 2'3'-GAMP. Our results demonstrated that tumor cells harbor a largely defective STING-IFN pathway, thereby preventing significant antiviral IFN induction regardless of the permeability of the STING agonist. In vivo, the combination therapy induced more proliferative KLRG1-high PD1-low CD8+ T-cells and activated CD103+ DC in the tumor site and increased tumor-specific CD44+ CD8+ T-cells in the lymph node. Overall, the combination therapy of C-REV with 2'3'-cGAMP elicited antitumor immune memory responses and significantly enhanced systemic antitumor immunity in both treated and non-treated distal tumors.

The antiviral role of largemouth bass STING against iridovirus infection

Stimulator of interferon gene (STING) plays a crucial role in the innate immune response against viral and bacterial pathogens. However, its function in largemouth bass iridovirus (LMBV) infection remains uncertain. Here, a STING homolog (MsSTING) from largemouth bass (Micropterus salmoides) was cloned and characterized. MsSTING encoded a 407-amino-acid polypeptide, which shared 84.08% and 41.45% identity with golden perch (Perca flavescens) and human (Homo sapiens) homologs, respectively. MsSTING contained four transmembrane domains and a conserved C-terminal domain. The mRNA level of MsSTING was significantly increased in response to LMBV infection in vitro. Subcellular localization observation indicated that MsSTING encoded a cytoplasmic protein, which co-localized predominantly with endoplasmic reticulum (ER) and partially with mitochondria. Moreover, its accurate localization was dependent on the N-terminal transmembrane motif (TM) domains. MsSTING was able to activate interferon (IFN) response, evidenced by the activation of IFN1, IFN3 and ISRE promoters by its overexpression in vitro. Mutant analysis showed that both the N-terminal and C-terminal domain of MsSTING were essential for its activation on IFN response. In addition, overexpression of MsSTING inhibited the transcription and protein levels of viral core genes, indicating that MsSTING exerted antiviral action against LMBV. Consistently, the inhibitory effects were significantly attenuated when the N-terminal or C-terminal domains of MsSTING was deleted. Furthermore, MsSTING overexpression upregulated the transcriptions of interferon-related genes and pro-inflammatory factors, including TANK-binding kinase 1(TBK1), interferon regulatory factor 3 (IRF3), interferon regulatory factor 7 (IRF7), interferon stimulated exonuclease gene 20 (ISG20), interferon-induced transmembrane protein 1(IFITM1), interferon γ (IFN-γ), tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and interleukin 6 (IL-6). Together, MsSTING exerted antiviral action upon LMBV infection through positive regulation the innate immune response.

Second messenger 2'3'-cyclic GMP-AMP (2'3'-cGAMP): the cell autonomous and non-autonomous roles in cancer progression

Cytosolic double-stranded DNA (dsDNA) is frequently accumulated in cancer cells due to chromosomal instability or exogenous stimulation. Cyclic GMP-AMP synthase (cGAS) acts as a cytosolic DNA sensor, which is activated upon binding to dsDNA to synthesize the crucial second messenger 2'3'-cyclic GMP-AMP (2'3'-cGAMP) that in turn triggers stimulator of interferon genes (STING) signaling. The canonical role of cGAS-cGAMP-STING pathway is essential for innate immunity and viral defense. Recent emerging evidence indicates that 2'3'-cGAMP plays an important role in cancer progression via cell autonomous and non-autonomous mechanisms. Beyond its role as an intracellular messenger to activate STING signaling in tumor cells, 2'3'-cGAMP also serves as an immunotransmitter produced by cancer cells to modulate the functions of non-tumor cells especially immune cells in the tumor microenvironment by activating STING signaling. In this review, we summarize the synthesis, transmission, and degradation of 2'3'-cGAMP as well as the dual functions of 2'3'-cGAMP in a STING-dependent manner. Additionally, we discuss the potential therapeutic strategies that harness the cGAMP-mediated antitumor response for cancer therapy.

ACE mRNA (Additional Chimeric Element incorporated IVT mRNA) for Enhancing Protein Expression by Modulating Immunogenicity

The development of in vitro transcribed mRNA (IVT mRNA)-based therapeutics/vaccines depends on the management of IVT mRNA immunogenicity. IVT mRNA, which is used for intracellular protein translation, often triggers unwanted immune responses, interfering with protein expression and leading to reduced therapeutic efficacy. Currently, the predominant approach for mitigating immune responses involves the incorporation of costly chemically modified nucleotides like pseudouridine (Ψ) or N1-methylpseudouridine (m1Ψ) into IVT mRNA, raising concerns about expense and the potential misincorporation of amino acids into chemically modified codon sequences. Here, an Additional Chimeric Element incorporated mRNA (ACE mRNA), a novel approach incorporating two segments within a single IVT mRNA structure, is introduced. The first segment retains conventional IVT mRNA components prepared with unmodified nucleotides, while the second, comprised of RNA/DNA chimeric elements, aims to modulate immunogenicity. Notably, ACE mRNA demonstrates a noteworthy reduction in immunogenicity of unmodified IVT mRNA, concurrently demonstrating enhanced protein expression efficiency. The reduced immune responses are based on the ability of RNA/DNA chimeric elements to restrict retinoic acid-inducible gene I (RIG-I) and stimulator of interferon genes (STING)-mediated immune activation. The developed ACE mRNA shows great potential in modulating the immunogenicity of IVT mRNA without the need for chemically modified nucleotides, thereby advancing the safety and efficacy of mRNA-based therapeutics/vaccines.

The regulation of cGAS-STING signaling by RNA virus-derived components

The Cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) serves as a key innate immune signaling axis involved in the regulation of various human diseases. It has been found that cGAS-STING pathway can recognize a variety of cytosolic double-stranded DNA (dsDNA), contributing to cause a robust type I interferon response thereby affecting the occurrence and progression of viral infection. Accumulating evidence indicates RNA virus-derived components play an important role in regulating cGAS-STING signaling, either as protective or pathogenic factors in the pathogenesis of diseases. Thus, a comprehensive understanding of the function of RNA virus-derived components in regulating cGAS-STING signaling will provide insights into developing novel therapies. Here, we review the existing literature on cGAS-STING pathway regulated by RNA virus-derived components to propose insights into pharmacologic strategies targeting the cGAS-STING pathway.

An updated patent review of stimulator of interferon genes agonists (2021 - present)

INTRODUCTION

Stimulator of Interferon Genes (STING) is an innate immune sensor. Activation of STING triggers a downstream response that results in the expression of proinflammatory cytokines (TNF-α, IL-1β) via nuclear factor kappa-B (NF-κB) or the expression of type I interferons (IFNs) via an interferon regulatory factor 3 (IRF3). IFNs can eventually result in promotion of the adaptive immune response including activation of tumor-specific CD8+ T cells to abolish the tumor. Consequently, activation of STING has been considered as a potential strategy for cancer treatment.

AREAS COVERED

This article provides an overview on structures and pharmacological data of CDN-like and non-nucleotide STING agonists acting as anticancer agents (January 2021 to October 2023) from a medicinal chemistry perspective. The data in this review come from EPO, WIPO, RCSB PDB, CDDI.

EXPERT OPINION

In recent years, several structurally diverse STING agonists have been identified. As an immune enhancer, they are used in the treatment of tumors, which has received extensive attention from scientific community and pharmaceutical companies. Despite the multiple challenges that have appeared, STING agonists may offer opportunities for immunotherapy.

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.

Role of the STING pathway in myeloid neoplasms: a prospero-registered systematic review of principal hurdles of STING on the road to the clinical practice

Myeloid neoplasms are a group of bone marrow diseases distinguished by disruptions in the molecular pathways that regulate the balance between hematopoietic stem cell (HSC) self-renewal and the generation of specialized cells. Cytokines and chemokines, two important components of the inflammatory process, also influence hematological differentiation. In this scenario, immunological dysregulation plays a pivotal role in the pathogenesis of bone marrow neoplasms. The STING pathway recognizes DNA fragments in the cell cytoplasm and triggers an immune response by type I interferons. The role of STING in cancer has not yet been established; however, both actions, as an oncogene or tumor suppressor, have been documented in other types of cancer. Therefore, we performed a systematic review (registered in PROSPERO database #CRD42023407512) to discuss the role of STING pathway in the advancement of pathogenesis and/or prognosis for different myeloid neoplasms. In brief, scientific evidence supports investigations that primarily use cell lines from myeloid neoplasms, such as leukemia. More high-quality research and clinical trials are needed to understand the role of the STING pathway in the pathology of hematological malignancies. Finally, the STING pathway suggests being a promising therapeutic molecular target, particularly when combined with current drug therapies.

Endothelial cell expression of a STING gain-of-function mutation initiates pulmonary lymphocytic infiltration

Patients afflicted with Stimulator of interferon gene (STING) gain-of-function mutations frequently present with debilitating interstitial lung disease (ILD) that is recapitulated in mice expressing the STINGV154M mutation (VM). Prior radiation chimera studies revealed an unexpected and critical role for non-hematopoietic cells in initiating ILD. To identify STING-expressing non-hematopoietic cell types required for the development of ILD, we use a conditional knockin (CKI) model and direct expression of the VM allele to hematopoietic cells, fibroblasts, epithelial cells, or endothelial cells. Only endothelial cell-targeted VM expression results in enhanced recruitment of immune cells to the lung associated with elevated chemokine expression and the formation of bronchus-associated lymphoid tissue, as seen in the parental VM strain. These findings reveal the importance of endothelial cells as instigators of STING-driven lung disease and suggest that therapeutic targeting of STING inhibitors to endothelial cells could potentially mitigate inflammation in the lungs of STING-associated vasculopathy with onset in infancy (SAVI) patients or patients afflicted with other ILD-related disorders.

Dual modifying of MAVS at lysine 7 by SIRT3-catalyzed deacetylation and SIRT5-catalyzed desuccinylation orchestrates antiviral innate immunity

To effectively protect the host from viral infection while avoiding excessive immunopathology, the innate immune response must be tightly controlled. However, the precise regulation of antiviral innate immunity and the underlying mechanisms remain unclear. Here, we find that sirtuin3 (SIRT3) interacts with mitochondrial antiviral signaling protein (MAVS) to catalyze MAVS deacetylation at lysine residue 7 (K7), which promotes MAVS aggregation, as well as TANK-binding kinase I and IRF3 phosphorylation, resulting in increased MAVS activation and enhanced type I interferon signaling. Consistent with these findings, loss of Sirt3 in mice and zebrafish renders them more susceptible to viral infection compared to their wild-type (WT) siblings. However, Sirt3 and Sirt5 double-deficient mice exhibit the same viral susceptibility as their WT littermates, suggesting that loss of Sirt5 in Sirt3-deficient mice may counteract the increased viral susceptibility displayed in Sirt3-deficient mice. Thus, we not only demonstrate that SIRT3 positively regulates antiviral immunity in vitro and in vivo, likely via MAVS, but also uncover a previously unrecognized mechanism by which SIRT3 acts as an accelerator and SIRT5 as a brake to orchestrate antiviral innate immunity.

MAVS promotes interferon signaling in RNA virus infection by ZUFSP-mediated chromatin regulation

Mitochondria serve as a platform for innate immune signaling transduction, and mitochondrial antiviral signaling protein (MAVS) is essential for interferon-β (IFN-β) production and innate antiviral immunity against RNA viruses. Here, we identified zinc finger-containing ubiquitin peptidase 1 (ZUFSP/ZUP1) as a MAVS-interacting protein by using proximity-based labeling technology in HEK293T and found it could act as a positive regulator of the retinoic acid-inducible gene-I (RIG-I)-like receptors(RLRs), including RIG-I and interferon-induced helicase C domain-containing protein 1 (MDA5). ZUFSP deficiency markedly inhibited RNA virus-triggered induction of downstream antiviral genes, and Zufsp-deficient mice were more susceptible to RNA virus infection. After RNA virus infection,ZUFSP was translocated from cytoplasm to nucleus and interacted with chromatin remodeling complex to facilitate the opening of IFN-stimulated gene (ISG) loci for transcription. This study provides a critical mechanistic basis for MAVS-regulated chromatin remodeling to promote interferon signaling.

Novel nucleotide-packaging vaccine delivers antigen and poly(I:C) to dendritic cells and generate a potent antibody response in vivo

An issue with many current vaccines is the dependency on broadly inflammatory adjuvants, such as aluminum hydroxide or aluminum salts that affect many immune- and non-immune cells. These adjuvants are not necessarily activating all antigen-presenting cells (APCs) that take up the antigen and most likely they also activate APCs with no antigen uptake, as well as many non-immune cells. Conjugation of antigen and adjuvant would enable the use of smaller amounts of adjuvant and avoid unnecessary tissue damage and activation of bystander cells. It would ensure that all APCs that take up the antigen would also become activated and avoid that immature and non-activated APCs present the antigen to T cells without a co-stimulatory signal, leading to tolerogenesis. We have developed a novel vaccine that co-deliver antigen and a nucleotide adjuvant to the same APC and lead to a strong activation response in dendritic cells and macrophages. The vaccine is constructed as a fusion-protein with an antigen fused to the DNA/RNA-binding domain from the Hc2 protein from Chlamydia trachomatis. We have found that the fusion protein is able to package polyinosinic:polycytidylic acid (poly(I:C)) or dsDNA into small particles. These particles were taken up by macrophages and dendritic cells and led to strong activation and maturation of these cells. Immunization of mice with the fusion protein packaged poly(I:C) led to a stronger antibody response compared to immunization with a combination of poly(I:C) and antigen without the Hc2 DNA/RNA-binding domain.

Sequential administration of delta-tocotrienol ameliorates radiation-induced myelosuppression in mice and non-human primates through inducing G-CSF production

To date only four recombinant growth factors, including Filgrastim (rhG-CSF), have been approved by FDA as radiomitigators to ameliorate hematopoietic acute radiation syndrome (H-ARS). These approved agents are not stable under room-temperature, needing to be stored at 2-8 °C, and would not be feasible in a mass casualty scenario where rapid and cost-effective intervention is crucial. Delta-tocotrienol (δ-T3H), the most potent G-CSF-inducing agent among vitamin E isoforms, exhibited efficiency and selectivity on G-CSF production in comparison with TLR and STING agonists in mice. Five-dose δ-T3H was utilized as the optimal therapeutic regimen due to long-term G-CSF production and the best peripheral blood (PB) recovery of irradiated mice. Comparable with rhG-CSF, sequential administration of δ-T3H post-irradiation improved hematologic recovery and accelerated the regeneration of hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) in the bone marrow (BM) and spleen of 6.5Gy irradiated mice; and consistently enhanced repopulation of BM-HSCs. In 4.0Gy irradiated nonhuman primates, δ-T3H exhibited comparable efficacy as rhG-CSF to promote PB recovery and colony-formation of BM-HPCs. Altogether, we demonstrated that sequential administration of delta-tocotrienol ameliorates radiation-induced myelosuppression in mice and non-human primates through inducing G-CSF production, indicated δ-T3H as a promising radiomitigator for the management of H-ARS, particularly in a mass casualty scenario.

Inhibition of spinal BRD4 alleviates pyroptosis and M1 microglia polarization via STING-IRF3 pathway in morphine-tolerant rats

BACKGROUND

Morphine tolerance has been a challenging medical issue. Neuroinflammation is considered as a critical mechanism for the development of morphine tolerance. Bromodomain-containing protein 4 (BRD4), a key regulator in cell damage and inflammation, participates in the development of chronic pain. However, whether BRD4 is involved in morphine tolerance and the underlying mechanisms remain unknown.

METHODS

The morphine-tolerant rat model was established by intrathecal administration of morphine twice daily for 7 days. Behavior test was assessed by a tail-flick latency test. The roles of BRD4, pyroptosis, microglia polarization and related signaling pathways in morphine tolerance were elucidated by Western blot, real-time quantitative polymerase chain reaction, and immunofluorescence.

RESULTS

Repeated morphine administration upregulated BRD4 level, induced pyroptosis, and promoted microglia M1-polarization in spinal cord, accompanied by the release of proinflammatory cytokines, such as TNF-α and IL-1β. JQ-1, a BRD4 antagonist, alleviated the development of morphine tolerance, diminished pyroptosis and induced the switch of microglia from M1 to M2 phenotype. Mechanistically, stimulator of interferon gene (STING)- interferon regulatory factor 3 (IRF3) pathway was activated and the protective effect of JQ-1 against morphine tolerance was at least partially mediated by inhibition of STING-IRF3 pathway.

CONCLUSION

This study demonstrated for the first time that spinal BRD4 contributes to pyroptosis and switch of microglia polarization via STING-IRF3 signaling pathway during the development of morphine tolerance, which extend the understanding of the neuroinflammation mechanism of morphine tolerance and provide an alternative strategy for the precaution against of this medical condition.

Azobenzene-Based Linker Strategy for Selective Activation of Antibody-Drug Conjugates

Existing antibody-drug conjugate (ADC) linkers, whether cleavable or non-cleavable, are designed to release highly toxic payloads or payload derivatives upon internalisation of the ADCs into cells. However, clinical studies have shown that only <1 % of the dosed ADCs accumulate in tumour cells. The remaining >99 % of ADCs are nonspecifically distributed in healthy tissue cells, thus inevitably leading to off-target toxicity. Herein, we describe an intelligent tumour-specific linker strategy to address these limitations. A tumour-specific linker is constructed by introducing a hypoxia-activated azobenzene group as a toxicity controller. We show that this azobenzene-based linker is non-cleavable in healthy tissues (O2 >10 %), and the corresponding payload derivative, cysteine-appended azobenzene-linker-monomethyl auristatin E (MMAE), can serve as a safe prodrug to mask the toxicity of MMAE (switched off). Upon exposure to the hypoxic tumour microenvironment (O2<1 %), this linker is cleaved to release MMAE and fully restores the high cytotoxicity of the ADC (switched on). Notably, the azobenzene linker-containing ADC exhibits satisfactory antitumour efficacy in vivo and a larger therapeutic window compared with ADCs containing traditional cleavable or non-cleavable linkers. Thus, our azobenzene-based linker sheds new light on the development of next-generation ADC linkers.

Effect of Regulation of Chemerin/Chemokine-like Receptor 1/Stimulator of Interferon Genes Pathway on Astrocyte Recruitment to Aβ Plaques

Recruitment and accumulation of reactive astrocytes around senile plaques are common pathological features of Alzheimer's disease (AD), with unclear mechanisms. Chemerin, an adipokine implicated in neuroinflammation, acts through its receptor, chemokine-like receptor 1 (CMKLR1), which also functions as a receptor for amyloid β (Aβ). The impact of the chemerin/CMKLR1 axis on astrocyte migration towards Aβ plaques is unknown. Here we investigated the effect of CMKLR1 on astrocyte migration around Aβ deposition in APP/PS1 mice with Cmklr1 knockout (APP/PS1-Cmklr1-/-). CMKLR1-expressed astrocytes were upregulated in the cortices and hippocampi of 9-month-old APP/PS1 mice. Chemerin mainly co-localized with neurons, and its expression was reduced in the brains of APP/PS1 mice, compared to WT mice. CMKLR1 deficiency decreased astrocyte colocalization with Aβ plaques in APP/PS1-Cmklr1-/- mice, compared to APP/PS1 mice. Activation of the chemerin/CMKLR1 axis promoted the migration of primary cultured astrocytes and U251 cells, and reduced astrocyte clustering induced by Aβ42. Mechanistic studies revealed that chemerin/CMKLR1 activation induced STING phosphorylation. Deletion of STING attenuated the promotion of the chemerin/CMKLR1 axis relative to astrocyte migration and abolished the inhibitory effect of chemerin on Aβ42-induced astrocyte clustering. These findings suggest the involvement of the chemerin/CMKLR1/STING pathway in the regulation of astrocyte migration and recruitment to Aβ plaques/Aβ42.

Tracing the STING exocytosis pathway during herpes viruses infection

The STimulator of INterferon Genes (STING) constitutes a major DNA-sensing pathway that restricts HSV-1 infection in different models by activating type I interferon and pro-inflammatory responses. To counteract STING, HSV-1 has evolved numerous strategies including mechanisms to interfere with its oligomerization, post-translational modifications, and downstream signaling. Previously, we demonstrated that STING is packaged in extracellular vesicles (EVs) produced from HSV-1-infected cells. These EVs activated antiviral responses in uninfected recipient cells and suppressed a subsequent HSV-1 infection in a STING-dependent manner. Here, we provide information on the packaging of STING in EVs and its exocytosis. We found that STING exocytosis did not occur in CD63 knockdown cells supporting that STING follows the CD63 exocytosis pathway. Consistently, we found that STING co-localized with CD63 in cytoplasmic globular structures and exosomal STING and CD63 co-fractionated. Both golgicide A and brefeldin A prevented STING exocytosis during HSV-1 infection suggesting that STING trafficking through the Golgi is required. A STING ligand was insufficient for STING exocytosis, and downstream signaling through TBK1 was not required. However, STING palmitoylation and tethering to the ER by STIM1 were required for STING exocytosis. Finally, we found that HSV-1 replication/late gene expression triggered CD63 exocytosis that was required for STING exocytosis. Surprisingly, HSV-2 strain G did not trigger CD63 or STING exocytosis as opposed to VZV and HCMV. Also, EVs from HSV-1(F)- and HSV-2(G)-infected cells displayed differences in their ability to restrict these viruses. Overall, STING exocytosis is induced by certain viruses and shapes the microenvironment of infection.IMPORTANCEExtracellular vesicles (EVs) are released by all types of cells as they constitute a major mechanism of intercellular communication. The packaging of specific cargo in EVs and the pathway of exocytosis are not fully understood. STING is a sensor of a broad spectrum of pathogens and a key component of innate immunity. STING exocytosis during HSV-1 infection has been an intriguing observation, raising questions of whether this is a virus-induced process, the purpose it serves, and whether it is observed after infection with other viruses. Here, we have provided insights into the pathway of STING exocytosis and determined factors involved. STING exocytosis is a virus-induced process and not a response of the host to the infection. Besides HSV-1, other herpes viruses triggered STING exocytosis, but HSV-2(G) did not. HSV-1 EVs displayed different restriction capabilities compared with HSV-2(G) EVs. Overall, STING exocytosis is triggered by viruses to shape the microenvironment of infection.

The interplay between autophagy and cGAS-STING signaling and its implications for cancer

Autophagy is an intracellular process that targets various cargos for degradation, including members of the cGAS-STING signaling cascade. cGAS-STING senses cytosolic double-stranded DNA and triggers an innate immune response through type I interferons. Emerging evidence suggests that autophagy plays a crucial role in regulating and fine-tuning cGAS-STING signaling. Reciprocally, cGAS-STING pathway members can actively induce canonical as well as various non-canonical forms of autophagy, establishing a regulatory network of feedback mechanisms that alter both the cGAS-STING and the autophagic pathway. The crosstalk between autophagy and the cGAS-STING pathway impacts a wide variety of cellular processes such as protection against pathogenic infections as well as signaling in neurodegenerative disease, autoinflammatory disease and cancer. Here we provide a comprehensive overview of the mechanisms involved in autophagy and cGAS-STING signaling, with a specific focus on the interactions between the two pathways and their importance for cancer.

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

The cGAS-STING intracellular DNA-sensing pathway has emerged as a key element of innate antiviral immunity and a promising therapeutic target. The existence of an innate immune sensor that can be activated by any double-stranded DNA (dsDNA) of any origin raises fundamental questions about how cGAS is regulated and how it responds to "foreign" DNA while maintaining tolerance to ubiquitous self-DNA. In this review, we summarize recent evidence implicating important roles for cGAS in the detection of foreign and self-DNA. We describe two recent and surprising insights into cGAS-STING biology: that cGAS is tightly tethered to the nucleosome and that the cGAMP product of cGAS is an immunotransmitter acting at a distance to control innate immunity. We consider how these advances influence our understanding of the emerging roles of cGAS in the DNA damage response (DDR), senescence, aging, and cancer biology. Finally, we describe emerging approaches to harness cGAS-STING biology for therapeutic benefit.

Classification and functional characterization of regulators of intracellular STING trafficking identified by genome-wide optical pooled screening

STING is an innate immune sensor that traffics across many cellular compartments to carry out its function of detecting cyclic di-nucleotides and triggering defense processes. Mutations in factors that regulate this process are often linked to STING-dependent human inflammatory disorders. To systematically identify factors involved in STING trafficking, we performed a genome-wide optical pooled screen and examined the impact of genetic perturbations on intracellular STING localization. Based on subcellular imaging of STING protein and trafficking markers in 45 million cells perturbed with sgRNAs, we defined 464 clusters of gene perturbations with similar cellular phenotypes. A higher-dimensional focused optical pooled screen on 262 perturbed genes which assayed 11 imaging channels identified 73 finer phenotypic clusters. In a cluster containing USE1, a protein that mediates Golgi to ER transport, we found a gene of unknown function, C19orf25. Consistent with the known role of USE1, loss of C19orf25 enhanced STING signaling. Other clusters contained subunits of the HOPS, GARP and RIC1-RGP1 complexes. We show that HOPS deficiency delayed STING degradation and consequently increased signaling. Similarly, GARP/RIC1-RGP1 loss increased STING signaling by delaying STING exit from the Golgi. Our findings demonstrate that genome-wide genotype-phenotype maps based on high-content cell imaging outperform other screening approaches, and provide a community resource for mining for factors that impact STING trafficking as well as other cellular processes observable in our dataset.

STINGing Defenses: Unmasking the Mechanisms of DNA Oncovirus-Mediated Immune Escape

DNA oncoviruses represent an intriguing subject due to their involvement in oncogenesis. These viruses have evolved mechanisms to manipulate the host immune response, facilitating their persistence and actively contributing to carcinogenic processes. This paper describes the complex interactions between DNA oncoviruses and the innate immune system, with a particular emphasis on the cGAS-STING pathway. Exploring these interactions highlights that DNA oncoviruses strategically target and subvert this pathway, exploiting its vulnerabilities for their own survival and proliferation within the host. Understanding these interactions lays the foundation for identifying potential therapeutic interventions. Herein, we sought to contribute to the ongoing efforts in advancing our understanding of the innate immune system in oncoviral pathogenesis.

Chloride Homeostasis Regulates cGAS-STING Signaling

The cGAS-STING signaling pathway has emerged as a key mediator of inflammation. However, the roles of chloride homeostasis on this pathway are unclear. Here, we uncovered a correlation between chloride homeostasis and cGAS-STING signaling. We found that dysregulation of chloride homeostasis attenuates cGAS-STING signaling in a lysosome-independent manner. Treating immune cells with chloride channel inhibitors attenuated 2'3'-cGAMP production by cGAS and also suppressed STING polymerization, leading to reduced cytokine production. We also demonstrate that non-selective chloride channel blockers can suppress the NPC1 deficiency-induced, hyper-activated STING signaling in skin fibroblasts derived from Niemann Pick disease type C (NPC) patients. Our findings reveal that chloride homeostasis majorly affects cGAS-STING pathway and suggest a provocative strategy to dampen STING-mediated inflammation via targeting chloride channels.

The Golgi Apparatus: A Key Player in Innate Immunity

The Golgi apparatus, long recognized for its roles in protein processing and vesicular trafficking, has recently been identified as a crucial contributor to innate immune signaling pathways. This review discusses our expanding understanding of the Golgi apparatus's involvement in initiating and activating these pathways. It highlights the significance of membrane connections between the Golgi and other organelles, such as the endoplasmic reticulum, mitochondria, endosomes, and autophagosomes. These connections are vital for the efficient transmission of innate immune signals and the activation of effector responses. Furthermore, the article delves into the Golgi apparatus's roles in key immune pathways, including the inflammasome-mediated activation of caspase-1, the cGAS-STING pathway, and TLR/RLR signaling. Overall, this review aims to provide insights into the multifunctional nature of the Golgi apparatus and its impact on innate immunity.

Dysfunction of STING Autophagy Degradation in Senescent Nucleus Pulposus Cells Accelerates Intervertebral Disc Degeneration

The pathogenesis of Intervertebral Disc Degeneration (IDD) is complex and multifactorial, with cellular senescence of nucleus pulposus (NP) cells and inflammation playing major roles in the progression of IDD. The stimulator of interferon genes (STING) axis is a key mediator of inflammation during infection, cellular stress, and tissue damage. Here, we present a progressive increase in STING in senescent NP cells with the degradation disorder. The STING degradation function in normal NP cells can prevent IDD. However, the dysfunction of STING degradation through autophagy causes the accumulation and high expression of STING in senescent NP cells as well as inflammation continuous activation together significantly promotes IDD. In senescent NP cells and intervertebral discs (IVDs), we found that STING autophagy degradation was significantly lower than that of normal NP cells and IVDs when STING was activated by 2'3'-cGAMP. Also, the above phenomenon was found in STINGgt/gt, cGAS-/- mice with models of age-induced, lumbar instability-induced IDD as well as found in the rat caudal IVD puncture models. Taken together, we suggested that the promotion of STING autophagy degradation in senescent NP Cells demonstrated a potential therapeutic modality for the treatment of IDD.

STING pathway as a cancer immunotherapy: Progress and challenges in activating anti-tumor immunity

The stimulator of the interferon genes (STING) signaling pathway plays a crucial role in innate immunity by detecting cytoplasmic DNA and initiating antiviral host defense mechanisms. The STING cascade is triggered when the enzyme cyclic GMP-AMP synthase (cGAS) binds cytosolic DNA and synthesizes the secondary messenger cGAMP. cGAMP activates the endoplasmic reticulum adaptor STING, leading to the activation of kinases TBK1 and IRF3 that induce interferon production. Secreted interferons establish an antiviral state in infected and adjacent cells. Beyond infections, aberrant DNA in cancer cells can also activate the STING pathway. Preclinical studies have shown that pharmacological STING agonists like cyclic dinucleotides elicit antitumor immunity when administered intratumorally by provoking innate and adaptive immunity. Combining STING agonists with immune checkpoint inhibitors may improve outcomes by overcoming tumor immunosuppression. First-generation STING agonists encountered challenges like poor pharmacokinetics, limited tumor specificity, and systemic toxicity. The development of the next-generation STING-targeted drugs to realize the full potential of engaging this pathway for cancer treatment can be a solution to overcome the current challenges, but further studies are required to determine optimal applications and combination regimens for the clinic. Notably, the controlled activation of STING is needed to preclude adverse effects. This review explores the mechanisms and effects of STING activation, its role in cancer immunotherapy, and current challenges.

Deoxyuridine-rich cytoplasmic DNA antagonizes STING-dependent innate immune responses and sensitizes resistant tumors to anti-PD-L1 therapy

DNA damage and cytoplasmic DNA induce type-1 interferon (IFN-1) and potentiate responses to immune checkpoint inhibitors. Our prior work found that inhibitors of the DNA damage response kinase ATR (ATRi) induce IFN-1 and deoxyuridine (dU) incorporation by DNA polymerases, akin to antimetabolites. Whether and how dU incorporation is required for ATRi-induced IFN-1 signaling is not known. Here, we show that ATRi-dependent IFN-1 responses require uracil DNA glycosylase (UNG)-initiated base excision repair and STING. Quantitative analyses of nine distinct nucleosides reveals that ATRi induce dU incorporation more rapidly in UNG wild-type than knockout cells, and that induction of IFN-1 is associated with futile cycles of repair. While ATRi induce similar numbers of micronuclei in UNG wild-type and knockout cells, dU containing micronuclei and cytoplasmic DNA are increased in knockout cells. Surprisingly, DNA fragments containing dU block STING-dependent induction of IFN-1, MHC-1, and PD-L1. Furthermore, UNG knockout sensitizes cells to IFN-γ in vitro , and potentiates responses to anti-PD-L1 in resistant tumors in vivo . These data demonstrate an unexpected and specific role for dU-rich DNA in suppressing STING-dependent IFN-1 responses, and show that UNG-deficient tumors have a heightened response to immune checkpoint inhibitors.

STATEMENT OF SIGNIFICANCE

Antimetabolites disrupt nucleotide pools and increase dU incorporation by DNA polymerases. We show that unrepaired dU potentiates responses to checkpoint inhibitors in mouse models of cancer. Patients with low tumor UNG may respond to antimetabolites combined with checkpoint inhibitors, and patients with high tumor UNG may respond to UNG inhibitors combined with checkpoint inhibitors.

Non-apoptotic regulated cell death mediates reprogramming of the tumour immune microenvironment by macrophages

Tumour immune microenvironment (TIME) plays an indispensable role in tumour progression, and tumour-associated macrophages (TAMs) are the most abundant immune cells in TIME. Non-apoptotic regulated cell death (RCD) can avoid the influence of tumour apoptosis resistance on anti-tumour immune response. Specifically, autophagy, ferroptosis, pyroptosis and necroptosis mediate the crosstalk between TAMs and tumour cells in TIME, thus reprogram TIME and affect the progress of tumour. In addition, although some achievements have been made in immune checkpoint inhibitors (ICIs), there is still defect that ICIs are only effective for some people because non-apoptotic RCD can bypass the apoptosis resistance of tumour. As a result, ICIs combined with targeting non-apoptotic RCD may be a promising solution. In this paper, the basic molecular mechanism of non-apoptotic RCD, the way in which non-apoptotic RCD mediates crosstalk between TAMs and tumour cells to reprogram TIME, and the latest research progress in targeting non-apoptotic RCD and ICIs are reviewed.

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.

Harnessing anti-inflammatory pathways and macrophage nano delivery to treat inflammatory and fibrotic disorders

Targeting specific organs and cell types using nanotechnology and sophisticated delivery methods has been at the forefront of applicative biomedical sciences lately. Macrophages are an appealing target for immunomodulation by nanodelivery as they are heavily involved in various aspects of many diseases and are highly plastic in their nature. Their continuum of functional "polarization" states has been a research focus for many years yielding a profound understanding of various aspects of these cells. The ability of monocyte-derived macrophages to metamorphose from pro-inflammatory to reparative and consequently to pro-resolving effectors has raised significant interest in its therapeutic potential. Here, we briefly survey macrophages' ontogeny and various polarization phenotypes, highlighting their function in the inflammation-resolution shift. We review their inducing mediators, signaling pathways, and biological programs with emphasis on the nucleic acid sensing-IFN-I axis. We also portray the polarization spectrum of macrophages and the characteristics of their transition between different subtypes. Finally, we highlighted different current drug delivery methods for targeting macrophages with emphasis on nanotargeting that might lead to breakthroughs in the treatment of wound healing, bone regeneration, autoimmune, and fibrotic diseases.

Evolution of innate immunity: lessons from mammalian models shaping our current view of insect immunity

The innate immune system, a cornerstone for organismal resilience against environmental and microbial insults, is highly conserved across the evolutionary spectrum, underpinning its pivotal role in maintaining homeostasis and ensuring survival. This review explores the evolutionary parallels between mammalian and insect innate immune systems, illuminating how investigations into these disparate immune landscapes have been reciprocally enlightening. We further delve into how advancements in mammalian immunology have enriched our understanding of insect immune responses, highlighting the intertwined evolutionary narratives and the shared molecular lexicon of immunity across these organisms. Therefore, this review posits a holistic understanding of innate immune mechanisms, including immunometabolism, autophagy and cell death. The examination of how emerging insights into mammalian and vertebrate immunity inform our understanding of insect immune responses and their implications for vector-borne disease transmission showcases the imperative for a nuanced comprehension of innate immunity's evolutionary tale. This understanding is quintessential for harnessing innate immune mechanisms' potential in devising innovative disease mitigation strategies and promoting organismal health across the animal kingdom.

DNA Damage-driven Inflammatory Cytokines: Reprogramming of Tumor Immune Microenvironment and Application of Oncotherapy

DNA damage occurs across tumorigenesis and tumor development. Tumor intrinsic DNA damage can not only increase the risk of mutations responsible for tumor generation but also initiate a cellular stress response to orchestrate the tumor immune microenvironment (TIME) and dominate tumor progression. Accumulating evidence documents that multiple signaling pathways, including cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) and ataxia telangiectasia-mutated protein/ataxia telangiectasia and Rad3-related protein (ATM/ATR), are activated downstream of DNA damage and they are associated with the secretion of diverse cytokines. These cytokines possess multifaced functions in the anti-tumor immune response. Thus, it is necessary to deeply interpret the complex TIME reshaped by damaged DNA and tumor-derived cytokines, critical for the development of effective tumor therapies. This manuscript comprehensively reviews the relationship between the DNA damage response and related cytokines in tumors and depicts the dual immunoregulatory roles of these cytokines. We also summarize clinical trials targeting signaling pathways and cytokines associated with DNA damage and provide future perspectives on emerging technologies.

18F-Labeled Amidobenzimidazole Analogue for Visualizing STING Expression in Tumor

The stimulator of interferon genes (STING) is pivotal in mediating STING-dependent type I interferon production, which is crucial for enhancing tumor rejection. Visualizing STING within the tumor microenvironment is valuable for STING-related treatments, yet the availability of suitable STING imaging probes is limited. In this study, we developed [18F]AlF-ABI, a novel 18F-labeled agent featuring an amidobenzimidazole core structure, for positron emission tomography (PET) imaging of STING in B16F10 and CT26 tumors. [18F]AlF-ABI was synthesized with a decay-corrected radiochemical yield of 38.0 ± 7.9% and radiochemical purity exceeding 97%. The probe exhibited a nanomolar STING binding affinity (KD = 35.6 nM). Upon administration, [18F]AlF-ABI rapidly accumulated at tumor sites, demonstrating significantly higher uptake in B16F10 tumors compared to CT26 tumors, consistent with STING immunofluorescence patterns. Specificity was further validated through in vitro cell experiments and in vivo blocking PET imaging. These findings suggest that [18F]AlF-ABI holds promise as an effective agent for visualizing STING in the tumor microenvironment.

HERC5-catalyzed ISGylation potentiates cGAS-mediated innate immunity

The cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) is essential to elicit type I interferon cascade response; thus, the activity of cGAS must be strictly regulated to boost the antiviral innate immunity. Here, we report that cGAS is responsible for the DNA-induced ISG15 conjugation system. The E3 HERC5 catalyzes the ISGylation of cytoplasmic cGAS at lysine 21, 187, 219, and 458, whereas Ubl carboxy-terminal hydrolase 18 removes the ISGylation of cGAS. The interaction of cGAS and HERC5 depends on the cGAS C-terminal domain and the RRC1-4 and RRC1-5 domains of HERC5. Mechanically, HERC5-catalyzed ISGylation promotes DNA-induced cGAS oligomerization and enhances cGAS enzymatic activity. Deficiency of ISGylation attenuates the downstream inflammatory gene expression induced by the cGAS-STING axis and the antiviral ability in mouse and human cells. Mice deficient in Isg15 or Herc6 are more vulnerable to herpes simplex virus 1 infection. Collectively, our study shows a positive feedback regulation of the cGAS-mediated innate immune pathway by ISGylation.

Non-canonical isoforms of the mRNA polyadenylation factor WDR33 regulate STING-mediated immune responses

The human WDR33 gene encodes three major isoforms. The canonical isoform WDR33v1 (V1) is a well-characterized nuclear mRNA polyadenylation factor, while the other two, WDR33v2 (V2) and WDR33v3 (V3), have not been studied. Here, we report that V2 and V3 are generated by alternative polyadenylation, and neither protein contains all seven WD (tryptophan-aspartic acid) repeats that characterize V1. Surprisingly, V2 and V3 are not polyadenylation factors but localize to the endoplasmic reticulum and interact with stimulator of interferon genes (STING), the immune factor that induces the cellular response to cytosolic double-stranded DNA. V2 suppresses interferon-β induction by preventing STING disulfide oligomerization but promotes autophagy, likely by recruiting WIPI2 isoforms. V3, on the other hand, functions to increase STING protein levels. Our study has not only provided mechanistic insights into STING regulation but also revealed that protein isoforms can be functionally completely unrelated, indicating that alternative mRNA processing is a more powerful mechanism than previously appreciated.

Cordyceps sinensis extract protects against acute kidney injury by inhibiting perforin expression in NK cells via the STING/IRF3 pathway

Acute kidney injury (AKI) is associated with immune cell activation and inflammation. However, the putative pathogenic mechanisms of this injury have not been thoroughly investigated. Natural killer (NK) cells play an important role in immune regulation; however, whether NK cells regulate AKI remains unclear. Cordyceps sinensis (CS), a modern Chinese patented medicine preparation, has been widely used in treating patients with chronic kidney disease (CKD) owing to its anti-inflammatory effects and maintenance of immune homeostasis. Whether 2'-deoxyadenosine, a major active component in CS, can ameliorate renal AKI by regulating immunity, particularly in NK cells, has not been reported. This study is the first to demonstrate how NK cells promote AKI by releasing perforin, interferon-gamma (IFN-γ) and other inflammatory factors in vivo and in vitro. Differential gene expression between AKI and normal tissues was assessed using bioinformatic analyses. Quantitative real-time PCR, western blotting, and immunohistochemical staining were used to detect target protein mRNA and protein expression. Levels of inflammatory factors were measured using enzyme-linked immunosorbent assay. We found the high doses of the 2'-deoxyadenosine treatment significantly alleviated FA-induced renal damage in vivo, and alleviated the NK cells of renal injury by activating the STING/IRF3 pathway to inhibit perforin release in vitro. The results showed that 2'-deoxyadenosine could mitigate AKI by downregulating the activity of NK cells (by decreasing the expressions of perforin and IFN-γ) and inhibiting the stimulator of interferon genes and phosphorylated IFN regulatory factor 3. This may provide valuable evidence supporting the clinical use of CS in treating patients with AKI.

cGAS-STING pathway mediates activation of dendritic cell sensing of immunogenic tumors

Type I interferons (IFN-I) play pivotal roles in tumor therapy for three decades, underscoring the critical importance of maintaining the integrity of the IFN-1 signaling pathway in radiotherapy, chemotherapy, targeted therapy, and immunotherapy. However, the specific mechanism by which IFN-I contributes to these therapies, particularly in terms of activating dendritic cells (DCs), remains unclear. Based on recent studies, aberrant DNA in the cytoplasm activates the cyclic GMP-AMP synthase (cGAS)- stimulator of interferon genes (STING) signaling pathway, which in turn produces IFN-I, which is essential for antiviral and anticancer immunity. Notably, STING can also enhance anticancer immunity by promoting autophagy, inflammation, and glycolysis in an IFN-I-independent manner. These research advancements contribute to our comprehension of the distinctions between IFN-I drugs and STING agonists in the context of oncology therapy and shed light on the challenges involved in developing STING agonist drugs. Thus, we aimed to summarize the novel mechanisms underlying cGAS-STING-IFN-I signal activation in DC-mediated antigen presentation and its role in the cancer immune cycle in this review.

Induction of antiviral interferon-stimulated genes by neuronal STING promotes the resolution of pain in mice

Inflammation and pain are intertwined responses to injury, infection, or chronic diseases. While acute inflammation is essential in determining pain resolution and opioid analgesia, maladaptive processes occurring during resolution can lead to the transition to chronic pain. Here we found that inflammation activates the cytosolic DNA-sensing protein stimulator of IFN genes (STING) in dorsal root ganglion nociceptors. Neuronal activation of STING promotes signaling through TANK-binding kinase 1 (TBK1) and triggers an IFN-β response that mediates pain resolution. Notably, we found that mice expressing a nociceptor-specific gain-of-function mutation in STING exhibited an IFN gene signature that reduced nociceptor excitability and inflammatory hyperalgesia through a KChIP1-Kv4.3 regulation. Our findings reveal a role of IFN-regulated genes and KChIP1 downstream of STING in the resolution of inflammatory pain.

Neuronal STING activation in amyotrophic lateral sclerosis and frontotemporal dementia

The stimulator of interferon genes (STING) pathway has been implicated in neurodegenerative diseases, including Parkinson's disease and amyotrophic lateral sclerosis (ALS). While prior studies have focused on STING within immune cells, little is known about STING within neurons. Here, we document neuronal activation of the STING pathway in human postmortem cortical and spinal motor neurons from individuals affected by familial or sporadic ALS. This process takes place selectively in the most vulnerable cortical and spinal motor neurons but not in neurons that are less affected by the disease. Concordant STING activation in layer V cortical motor neurons occurs in a mouse model of C9orf72 repeat-associated ALS and frontotemporal dementia (FTD). To establish that STING activation occurs in a neuron-autonomous manner, we demonstrate the integrity of the STING signaling pathway, including both upstream activators and downstream innate immune response effectors, in dissociated mouse cortical neurons and neurons derived from control human induced pluripotent stem cells (iPSCs). Human iPSC-derived neurons harboring different familial ALS-causing mutations exhibit increased STING signaling with DNA damage as a main driver. The elevated downstream inflammatory markers present in ALS iPSC-derived neurons can be suppressed with a STING inhibitor. Our results reveal an immunophenotype that consists of innate immune signaling driven by the STING pathway and occurs specifically within vulnerable neurons in ALS/FTD.

The activation of the adaptor protein STING depends on its interactions with the phospholipid PI4P

Activation of the endoplasmic reticulum (ER)-resident adaptor protein STING, a component of a cytosolic DNA-sensing pathway, induces the transcription of genes encoding type I interferons (IFNs) and other proinflammatory factors. Because STING is activated at the Golgi apparatus, control of the localization and activation of STING is important in stimulating antiviral and antitumor immune responses. Through a genome-wide CRISPR interference screen, we found that STING activation required the Golgi-resident protein ACBD3, which promotes the generation of phosphatidylinositol 4-phosphate (PI4P) at the trans-Golgi network, as well as other PI4P-associated proteins. Appropriate localization and activation of STING at the Golgi apparatus required ACBD3 and the PI4P-generating kinase PI4KB. In contrast, STING activation was enhanced when the lipid-shuttling protein OSBP, which removes PI4P from the Golgi apparatus, was inhibited by the US Food and Drug Administration-approved antifungal itraconazole. The increase in the abundance of STING-activating phospholipids at the trans-Golgi network resulted in the increased production of IFN-β and other cytokines in THP-1 cells. Furthermore, a mutant STING that could not bind to PI4P failed to traffic from the ER to the Golgi apparatus in response to a STING agonist, whereas forced relocalization of STING to PI4P-enriched areas elicited STING activation in the absence of stimulation with a STING agonist. Thus, PI4P is critical for STING activation, and manipulating PI4P abundance may therapeutically modulate STING-dependent immune responses.