Degree of STING activation is associated with disease outcomes

The cGAS-STING pathway as a novel therapeutic strategy for pancreatic diseases

The Cyclic GMP-AMP synthase (cGAS)-Stimulator of interferon genes [1] signaling pathway has emerged as a pivotal immune response mechanism, activating immune defenses upon detection of both exogenous and endogenous DNA within cells. Its activation is intricately linked to various diseases and inflammatory processes, spanning autoimmune disorders, infectious ailments, and malignancies. Among pancreatic diseases, encompassing acute pancreatitis, chronic pancreatitis, and pancreatic cancer, current clinical treatment efficacy remains suboptimal. Here, we elucidate the molecular intricacies of the cGAS-STING signaling pathway and delineate its therapeutic potential in acute pancreatitis, chronic pancreatitis, and pancreatic cancer. Additionally, we offer an overview of recent advancements in STING agonists and antagonists, assessing their therapeutic potential in pancreatic-related disorders. In summary, by exploring the multifaceted roles of the cGAS-STING signaling pathway and its implications in pancreatic diseases, we aim to shed light on potential avenues for therapeutic intervention and management in these challenging clinical contexts.

Targeting the cGAS-STING pathway as an inflammatory crossroad in coronavirus disease 2019 (COVID-19)

CONTEXT AND OBJECTIVE

The emerging pandemic of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has imposed significant mortality and morbidity on the world. An appropriate immune response is necessary to inhibit SARS-CoV-2 spread throughout the body.

RESULTS

During the early stages of infection, the pathway of stimulators of interferon genes (STING), known as the cGAS-STING pathway, has a significant role in the induction of the antiviral immune response by regulating nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and Interferon regulatory factor 3 (IRF3), two key pathways responsible for proinflammatory cytokines and type I IFN secretion, respectively.

DISCUSSION

During the late stages of COVID-19, the uncontrolled inflammatory responses, also known as cytokine storm, lead to the progression of the disease and poor prognosis. Hyperactivity of STING, leading to elevated titers of proinflammatory cytokines, including Interleukin-I (IL-1), IL-4, IL-6, IL-18, and tissue necrosis factor-α (TNF-α), is considered one of the primary mechanisms contributing to the cytokine storm in COVID-19.

CONCLUSION

Exploring the underlying molecular processes involved in dysregulated inflammation can bring up novel anti-COVID-19 therapeutic options. In this article, we aim to discuss the role and current studies targeting the cGAS/STING signaling pathway in both early and late stages of COVID-19 and COVID-19-related complications and the therapeutic potential of STING agonists/antagonists. Furthermore, STING agonists have been discussed as a vaccine adjuvant to induce a potent and persistent immune response.

The Role and Potential Regulatory Mechanism of STING Modulated Macrophage Apoptosis and Differentiation in Severe Acute Pancreatitis-Associated Lung Injury

This study aims to investigate the role of STING in promoting macrophage apoptosis and regulating macrophage polarization in severe acute pancreatitis (SAP)-associated lung injury in vitro and in vivo. A murine model was established by intraperitoneal injection of caerulein and lipopolysaccharide (LPS). Meanwhile, ANA-1 cells were stimulated with LPS to induce apoptosis in vitro. More primary alveolar macrophages underwent apoptosis and M1 macrophage polarization in the SAP group compared with the control group, which was reversed by inhibiting STING. When ANA-1 cells were induced into M2-type macrophages, the reduction of M1 macrophage markers was accompanied by a decrease of LPS-induced apoptosis. Finally, the inhibitory effect of C-176 on STING ameliorates lung injury and inflammation by adjusting macrophage polarization and rescuing apoptosis. Therefore, inhibiting STING could be a new therapeutic strategy for treating acute pancreatitis-associated lung injury.

A novel 18F-labeled agonist for PET imaging of stimulator of interferon gene expression in tumor-bearing mice

PURPOSE

Stimulator of interferon genes (STING) protein plays a vital role in the immune surveillance of tumor microenvironment. Monitoring STING expression in tumors benefits the relevant STING therapy. This study aimed to develop a novel 18F-labeled agonist, dimeric amidobenzimidazole (diABZI), and firstly evaluate the feasibility of noninvasive positron emission tomography (PET) imaging of STING expression in the tumor microenvironment.

METHODS

An analog of the STING agonist NOTA-DABI was synthesized and labeled with 18F via Al18F-NOTA complexation (denoted as [18F]F-DABI). Physicochemical properties, STING protein-binding affinity, and specificity of [18F]F-DABI were evaluated using cell uptake and docking assays. In vivo small-animal PET imaging and biodistribution studies of [18F]F-DABI in tumor-bearing mice were performed to verify the pharmacokinetics and tumor targeting ability. The correlation between tumor uptake and STING expression was also analyzed.

RESULTS

[18F]F-DABI was produced conveniently with high radiochemical yield (44 ± 15%), radiochemical purity (> 97%) and molar activity (15-30 GBq/μmol). In vitro binding assays demonstrated that [18F]F-DABI has a favorable affinity and specificity for STING with a KD of 12.98 ± 2.07 nM. In vivo studies demonstrated the specificity of [18F]F-DABI for PET imaging of STING expression with B16F10 tumor uptake of 10.93 ± 0.93%ID/g, which was significantly different from that of blocking groups (3.13 ± 0.88%ID/g, ***p < 0.0001). Furthermore, tumor uptake of [18F]F-DABI was well positively correlated with STING expression in different tumor types. Biodistribution results demonstrated that [18F]F-DABI was predominately uptaken in the liver and intestines, indicating its hepatobiliary elimination.

CONCLUSION

This proof-of-concept study demonstrated a STING-binding radioligand for PET imaging, which could be used as a potential companion diagnostic tool for related STING-agonist therapies.

Role of released mitochondrial DNA in acute lung injury

Acute lung injury(ALI)/acute respiratory distress syndrome(ARDS) is a form of acute-onset hypoxemic respiratory failure characterised by an acute, diffuse, inflammatory lung injury, and increased alveolar-capillary permeability, which is caused by a variety of pulmonary or nonpulmonary insults. Recently, aberrant mitochondria and mitochondrial DNA(mtDNA) level are associated with the development of ALI/ARDS, and plasma mtDNA level shows the potential to be a promising biomarker for clinical diagnosis and evaluation of lung injury severity. In mechanism, the mtDNA and its oxidised form, which are released from impaired mitochondria, play a crucial role in the inflammatory response and histopathological changes in the lung. In this review, we discuss mitochondrial outer membrane permeabilisation (MOMP), mitochondrial permeability transition pore(mPTP), extracellular vesicles (EVs), extracellular traps (ETs), and passive release as the principal mechanisms for the release of mitochondrial DNA into the cytoplasm and extracellular compartments respectively. Further, we explain how the released mtDNA and its oxidised form can induce inflammatory cytokine production and aggravate lung injury through the Toll-like receptor 9(TLR9) signalling, cytosolic cGAS-stimulator of interferon genes (STING) signalling (cGAS-STING) pathway, and inflammasomes activation. Additionally, we propose targeting mtDNA-mediated inflammatory pathways as a novel therapeutic approach for treating ALI/ARDS.

Chemical and Biomolecular Strategies for STING Pathway Activation in Cancer Immunotherapy

The stimulator of interferon genes (STING) cellular signaling pathway is a promising target for cancer immunotherapy. Activation of the intracellular STING protein triggers the production of a multifaceted array of immunostimulatory molecules, which, in the proper context, can drive dendritic cell maturation, antitumor macrophage polarization, T cell priming and activation, natural killer cell activation, vascular reprogramming, and/or cancer cell death, resulting in immune-mediated tumor elimination and generation of antitumor immune memory. Accordingly, there is a significant amount of ongoing preclinical and clinical research toward further understanding the role of the STING pathway in cancer immune surveillance as well as the development of modulators of the pathway as a strategy to stimulate antitumor immunity. Yet, the efficacy of STING pathway agonists is limited by many drug delivery and pharmacological challenges. Depending on the class of STING agonist and the desired administration route, these may include poor drug stability, immunocellular toxicity, immune-related adverse events, limited tumor or lymph node targeting and/or retention, low cellular uptake and intracellular delivery, and a complex dependence on the magnitude and kinetics of STING signaling. This review provides a concise summary of the STING pathway, highlighting recent biological developments, immunological consequences, and implications for drug delivery. This review also offers a critical analysis of an expanding arsenal of chemical strategies that are being employed to enhance the efficacy, safety, and/or clinical utility of STING pathway agonists and lastly draws attention to several opportunities for therapeutic advancements.

Circulating mitochondrial DNA-triggered autophagy dysfunction via STING underlies sepsis-related acute lung injury

The STING pathway and its induction of autophagy initiate a potent immune defense response upon the recognition of pathogenic DNA. However, this protective response is minimal, as STING activation worsens organ damage, and abnormal autophagy is observed during progressive sepsis. Whether and how the STING pathway affects autophagic flux during sepsis-induced acute lung injury (sALI) are currently unknown. Here, we demonstrate that the level of circulating mtDNA and degree of STING activation are increased in sALI patients. Furthermore, STING activation was found to play a pivotal role in mtDNA-mediated lung injury by evoking an inflammatory storm and disturbing autophagy. Mechanistically, STING activation interferes with lysosomal acidification in an interferon (IFN)-dependent manner without affecting autophagosome biogenesis or fusion, aggravating sepsis. Induction of autophagy or STING deficiency alleviated lung injury. These findings provide new insights into the role of STING in the regulatory mechanisms behind extrapulmonary sALI.

Insight into the dichotomous regulation of STING activation in immunotherapy

Cyclic GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING) signaling pathway (cGAS-STING) is a hub linking innate immunity and adaptive immunity against pathogen infection by inducing the production of type I interferon (IFN-I). It also plays pivotal roles in modulating tumorigenesis by ensuring the antigen presentation, T cell priming, activation, and tumor regression. Given its antitumor immune properties, cGAS-STING has attracted intense focus and several STING agonists have entered into clinical trials. However, some problems still exist when activating STING for use in oncological indications. It is remarkable that multiple downstream cytokines such as TNF-α, IL-6 may lead to inflammatory disease and even tumor metastasis in practical trials. Besides, there is a synergistic effect when STING agonists are combined with other immunotherapies. In this review, we discussed the advanced understanding between STING and anti-tumor immunity, as well as a variety of promising clinical treatment strategies.

STING-dependent induction of lipid peroxidation mediates intestinal ischemia-reperfusion injury

Stimulator of interferon genes (STING) is essential for the type I interferon response against DNA pathogens. Recent evidence has indicated that STING also plays a critical role in various diseases such as systemic lupus erythematous, nonalcoholic fatty liver disease, and cancer. However, the exact function and mechanism of STING in ischemia/reperfusion (I/R) injury, especially in the intestine, remains unknown. In the current study, we evaluated the contribution of STING to the intestinal I/R progression. The data indicate a robust STING activation, specifically in the reperfusion period, with the evidence of interferon response and NF-κB pathway activation. The intestinal I/R injury and distant organ damage was absent in STING-/- mice. Mechanically, this detrimental effect relies on excess level of lipid peroxidation, which was proved by the level of 4-hydroxynonenal (4-HNE) and the malondialdehyde (MDA). Additionally, bone marrow derived macrophage (BMDM) was stimulated with mtDNA or STING agonist showed a dose- and time-dependent lipid peroxidation and cell death, which could be reverse by STING-/- or pretreatment of lipid peroxidation inhibitor. Liproxstatin-1 could also ameliorate injury I/R induced multiple-organ damage. Similar results were also identified in the GSE96733 database, which indicated that STING activation was associated with the disbalance of lipid peroxidation and antioxidant system. Collectively, our results indicate a novel role for STING activation in the regulation of lipid peroxidation is closely associated with intestinal I/R injury, and that anti-lipid peroxidation is a unique and effective mechanistic approach for intestinal I/R injury and STING activation associated damage prevention and treatment.

Cytosolic sensor STING in mucosal immunity: a master regulator of gut inflammation and carcinogenesis

The stimulator of interferon genes (STING) connects microbial cytosolic sensing with host cell effector functions. STING signaling plays a central role in cyclic dinucleotides (CDNs) and DNA sensing to induce secretion of interferons and pro-inflammatory mediators. Although activated STING signaling favors antimicrobial progress and facilitates mucosal would healing, its role in mucosal immunity and gut homeostasis is paradoxical, ranging from positive and negative effects within the gut. In our review, we summarize recent advance of STING signaling in gut homeostasis and inflammation, especially focusing on its molecular basis in mucosal immune response. Deep understanding of the regulatory mechanisms of intestinal STING pathway could promote clinical manipulation of this fundamental signaling as a promising immunomodulatory therapy.

Computational study on new natural compound agonists of stimulator of interferon genes (STING)

Objective

This study aimed to screen lead compounds and medication candidates from drug library (ZINC database) which has potential agonist effect targeting STING protein.

Methods and materials

A series of computer-aided virtual screening techniques were utilized to identify potential agonists of STING. Structure-based screening using Libdock was carried out followed by ADME (absorption, distribution, metabolism, excretion) and toxicity prediction. Molecular docking was performed to demonstrate the binding affinity and mechanism between ligands and STING dimers. Molecular dynamic simulation was utilized to evaluate the stability of ligand-receptor complex. Finally, animal experiment was conducted to validate the effectiveness of selected compounds.

Results

Three novel natural compounds 1,2,3 (ZINC000015149223, ZINC000011616633 and ZINC000001577210, respectively) from the ZINC15 database were found binding to STING with more favorable interaction energy. Also, they were predicted with less ames mutagenicity, rodent carcinogenicity, non-developmental toxic potential and tolerant with cytochrome P450 2D6 (CYP2D6). The ligand chemical structure analysis showed the three compounds were inborn axisymmetric, such chemical structures account for combining and activating process of STING protein dimers. The dynamic simulation analysis demonstrated that ZINC000015149223-, ZINC000011616633- and ZINC000001577210-STING dimer complex had more favorable potential energy compared with amidobenzimidazole (ABZI) and they can exist in natural environments stably. Animal experiments also demonstrated that these three compounds could suppress tumor growth.

Conclusion

This study demonstrates that ZINC000015149223, ZINC000011616633 and ZINC000001577210 are potential agonists targeting STING protein. These compounds are safe drug candidates and have a great significance in STING agonists development.