STING inhibitor ameliorates LPS-induced ALI by preventing vascular endothelial cells-mediated immune cells chemotaxis and adhesion

Targeting the smooth muscle cell KEAP1-Nrf2-STING axis with pterostilbene attenuates abdominal aortic aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) is a life-threatening aortic disease, and to date, there are currently no effective pharmacological treatments to address this condition. Activation of cytosolic DNA sensing adaptor stimulator of interferon genes (STING) signaling is a crucial mechanism in AAA formation.

PURPOSE

This study investigated pterostilbene (Pt), a naturally occurring polyphenol and resveratrol analogue, as a STING inhibitor for preventing AAA.

METHODS

We evaluated the effect of Pt on AAA formation in angiotensin II (AngII)-infused apolipoprotein E-deficient (ApoE-/-) mice. We used histological analysis, MMP activity measurement, western blot, and immunohistochemistry to detect AAA formation and development. We applied RNA sequencing, molecular docking, cellular thermal shift assay (CETSA) and functional studies to dissect the molecular mechanism of Pt-regulating KEAP1-Nrf2-STING signaling. We conditionally knocked down Nrf2 in vascular smooth muscle cells (VSMCs) in vivo to investigate its role in Pt-mediated protective effects on AAA.

RESULTS

Pt effectively blocked the formation of AAA in AngII-infused ApoE-/- mice. Whole transcriptome sequencing analysis revealed that nuclear factor erythroid 2-related factor 2 (Nrf2) and STING pathway in VSMCs were linked to the anti-AAA effects of pterostilbene. Mechanistically, Pt upregulated Nrf2 target genes (e.g., HO-1 and NQO1) through activation of the KEAP1/Nrf2 signaling, which restricted the immunostimulatory axis of mtDNA-STING-TBK1-NF-κB, thereby alleviating VSMC inflammation and preserving the VSMC contractile phenotype. Subsequently, molecular docking and CETSA revealed a binding mode between Pt and KEAP1/Nrf2. Intriguingly, the inhibitory effect of Pt on STING signaling and the protective role of Pt in AAA were largely abrogated by VSMC-specific Nrf2 knockdown in mice.

CONCLUSION

Collectively, naturally derived Pt shows promising efficacy for the treatment of AAA by targeting the KEAP1-Nrf2-STING axis in VSMCs.

A phytomedicine extract exerts an anti-inflammatory response in the lungs by reducing STING-mediated type I interferon release

BACKGROUND

Acute respiratory distress syndrome (ARDS) is an acute respiratory disease characterized by bilateral chest radiolucency and severe hypoxemia. Quzhou Fructus Aurantii ethyl acetate extract (QFAEE), which is prepared from the traditional Chinese respiratory anti-inflammatory natural herb Quzhou Fructus Arantii, has the potential to alleviate ARDS. In this work, we aimed to investigate the potential and mechanism underlying the action of QFAEE on ARDS and how QFAEE modulates the STING pathway to reduce type I interferon release to alleviate the inflammatory response.

METHODS

Lipopolysaccharide (LPS), a potential proinflammatory stimulant capable of causing pulmonary inflammation with edema after nasal drops, was employed to model ARDS in vitro and in vivo. Under QFAEE intervention, the mechanism of action of QFAEE to alleviate ARDS was explored in this study. TREX1-/- mice were sued as a research model for the activation of the congenital STING signaling pathway. The effect of QFAEE on TREX1-/- mice could explain the STING-targeted effect of QFAEE on alleviating the inflammatory response. Our explorations covered several techniques, Western blot, histological assays, immunofluorescence staining, transcriptomic assays and qRT-PCR to determine the potential mechanism of action of QFAEE in antagonizing the inflammatory response in the lungs, as well as the mechanism of action of QFAEE in targeting the STING signaling pathway to regulate the release of type I interferon.

RESULTS

QFAEE effectively alleviates ARDS symptoms in LPS-induced ARDS. We revealed that the mechanism underlying LPS-induced ARDS is the STING-TBK1 signaling pathway and further elucidated the molecular mechanism of QFAEE in the prevention and treatment of ARDS. QFAEE reduced the release of type I interferons by inhibiting the STING-TBK1-IRF3 axis, thus alleviating LPS-induced pneumonia and lung cell death in mice. Another key finding is that activation of the STING pathway by activators or targeted knockdown of the TREX1 gene can also induce ARDS. As expected, QFAEE was found to be an effective protective agent in alleviating ARDS and the antagonistic effect of QFAEE on ARDS was achieved by inhibiting the STING signaling pathway.

CONCLUSIONS

The main anti-inflammatory effect of QFAEE was achieved by inhibiting the STING signaling pathway and reducing the release of type I interferons. According to this mechanism of effect, QFAEE can effectively alleviate ARDS and can be considered a potential therapeutic agent. In addition, the STING pathway plays an essential role in the development and progression of ARDS, and it is a potential target for ARDS therapy.

Exocarpium Citri Grandis ameliorates LPS-induced acute lung injury by suppressing inflammation, NLRP3 inflammasome, and ferroptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Exocarpium Citri Grandis (ECG), the epicarp of C. grandis 'Tomentosa' which is also known as Hua-Ju-Hong in China, has been widely used for thousands of years to treat inflammatory lung disorders such as asthma, and cough as well as dispelling phlegm. However, its underlying pharmacological mechanisms in acute lung injury (ALI) remain unclear.

AIM OF THE STUDY

To explore the therapeutic effect of ECG on ALI and reveal the potential mechanisms based on experimental techniques in vivo and in vitro.

MATERIALS AND METHODS

Lipopolysaccharides (LPS) induced ALI in mice and induced RAW 264.7 cell inflammatory model were established to investigate the pharmacodynamics of ECG. ELISA kits, commercial kits, Western Blot, qPCR, Hematoxylin and Eosin (H&E) staining, immunohistochemistry, and immunofluorescence technologies were used to evaluate the pharmacological mechanisms of ECG in ameliorating ALI.

RESULTS

ECG significantly attenuated pulmonary edema in LPS-stimulated mice and decreased the levels of IL1β, IL6, and TNF-α in serum and BALF, reduced MDA and iron concentration as well as increased SOD and GSH levels in lung tissues, and also decreased the ROS level in BALF and Lung tissue. Further pharmacological mechanism studies showed that ECG significantly inhibited mRNA expression of inflammatory signaling factors and chemokines, and down-regulated the expression of TLR4, MyD88, NF-κB p65, NF-κB p-p65 (S536), COX2, iNOS, Txnip, NLRP3, ASC, Caspase-1, JAK1, p-JAK1 (Y1022), JAK2, STAT1, p-STAT1 (S727), STAT3, p-STAT3 (Y705), STAT4, p-STAT4 (Y693), and Keap1, and also up-regulated the expression of Trx-1, Nrf2, HO-1, NQO1, GPX4, PCBP1, and SLC40A1. In the LPS-induced RAW264.7 cell inflammatory model, ECG showed similar results to animal experiments.

CONCLUSIONS

Our results showed that ECG alleviated ALI by inhibiting TLR4/MyD88/NF-κB p65 and JAK/STAT signaling pathway-mediated inflammatory response, Txnip/NLRP3 signaling pathway-mediated inflammasome activation, and regulating Nrf2/GPX4 axis-mediated ferroptosis. Our findings provide an experimental basis for the application of ECG.

Anthrahydroquinone‑2,6‑disulfonate attenuates PQ‑induced acute lung injury through decreasing pulmonary microvascular permeability via inhibition of the PI3K/AKT/eNOS pathway

In paraquat (PQ)‑induced acute lung injury (ALI)/ acute respiratory distress syndrome, PQ disrupts endothelial cell function and vascular integrity, which leads to increased pulmonary leakage. Anthrahydroquinone‑2,6‑disulfonate (AH2QDS) is a reducing agent that attenuates the extent of renal injury and improves survival in PQ‑intoxicated Sprague‑Dawley (SD) rats. The present study aimed to explore the beneficial role of AH2QDS in PQ‑induced ALI and its related mechanisms. A PQ‑intoxicated ALI model was established using PQ gavage in SD rats. Human pulmonary microvascular endothelial cells (HPMECs) were challenged with PQ. Superoxide dismutase, malondialdehyde, reactive oxygen species and nitric oxide (NO) fluorescence were examined to detect the level of oxidative stress in HPMECs. The levels of TNF‑α, IL‑1β and IL‑6 were assessed using an ELISA. Transwell and Cell Counting Kit‑8 assays were performed to detect the migration and proliferation of the cells. The pathological changes in lung tissues and blood vessels were examined by haematoxylin and eosin staining. Evans blue staining was used to detect pulmonary microvascular permeability. Western blotting was performed to detect target protein levels. Immunofluorescence and immunohistochemical staining were used to detect the expression levels of target proteins in HPMECs and lung tissues. AH2QDS inhibited inflammatory responses in lung tissues and HPMECs, and promoted the proliferation and migration of HPMECs. In addition, AH2QDS reduced pulmonary microvascular permeability by upregulating the levels of vascular endothelial‑cadherin, zonula occludens‑1 and CD31, thereby attenuating pathological changes in the lungs in rats. Finally, these effects may be related to the suppression of the phosphatidylinositol‑3‑kinase (PI3K)/protein kinase B (AKT)/endothelial‑type NO synthase (eNOS) signalling pathway in endothelial cells. In conclusion, AH2QDS ameliorated PQ‑induced ALI by improving alveolar endothelial barrier disruption via modulation of the PI3K/AKT/eNOS signalling pathway, which may be an effective candidate for the treatment of PQ‑induced ALI.

Immunological alterations in the endothelial barrier: a new predictive and therapeutic paradigm for sepsis

INTRODUCTION

Despite the fact incidence and mortality vary widely among regions, sepsis remains a major cause of morbidity and cost worldwide. The importance of the endothelial barrier in sepsis and infectious diseases is increasingly recognized; however, the underlying pathophysiology of the endothelial barrier in sepsis remains poorly understood.

AREAS COVERED

Here we review the advances in basic and clinical research for relevant papers in PubMed database. We attempt to provide an updated overview of immunological alterations in endothelial dysfunction, discussing the central role of endothelial barrier involved in sepsis to provide new predictive and therapeutic paradigm for sepsis.

EXPERT OPINION

Given its physiological and immunological functions in infectious diseases, the endothelial barrier has been dramatically altered in sepsis, suggesting that endothelial dysfunction may play a critical role in the pathogenesis of sepsis. Although many reliable biomarkers have been investigated to monitor endothelial activation and injury in an attempt to find diagnostic and therapeutic tools, there are no specific therapies to treat sepsis due to its complex pathophysiology. Since sepsis is initiated by both hyperinflammation and immunoparalysis occurring simultaneously, a 'one-treatment-fits-all' strategy for sepsis-induced immune injury and immunoparalysis is bound to fail, and an individualized 'precision medicine' approach is required.

Focus on the cGAS-STING Signaling Pathway in Sepsis and Its Inflammatory Regulatory Effects

Sepsis is a severe systemic inflammatory response commonly occurring in infectious diseases, caused by infection with virulent pathogens. In the pathogenesis of sepsis, the cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase-stimulator of interferon genes (cGAS-STING) signaling pathway serves a crucial role as a fundamental immunoregulatory mechanism. This signaling pathway activates STING upon recognizing intracellular DNA damage and pathogen-derived DNA, subsequently inducing the production of numerous inflammatory mediators, including interferon and inflammatory cytokines, which in turn trigger an inflammatory response. The aim of this paper is to explore the activation mechanism of the cGAS-STING signaling pathway in sepsis and its impact on inflammatory regulation. By delving into the mechanism of action of the cGAS-STING signaling pathway in sepsis, we aim to identify new therapeutic strategies for the treatment and prevention of sepsis.

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

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

Icariside II alleviates lipopolysaccharide-induced acute lung injury by inhibiting lung epithelial inflammatory and immune responses mediated by neutrophil extracellular traps

AIMS

Acute lung injury (ALI) is a life-threatening lung disease characterized by inflammatory cell infiltration and lung epithelial injury. Icariside II (ICS II), one of the main active ingredients of Herba Epimedii, exhibits anti-inflammatory and immunomodulatory effects. However, the effect and mechanism of ICS II in ALI remain unclear. The purpose of the current study was to investigate the pharmacological effect and underlying mechanism of ICS II in ALI.

MAIN METHODS

Models of neutrophil-like cells, human peripheral blood neutrophils, and lipopolysaccharide (LPS)-induced ALI mouse model were utilized. RT-qPCR and Western blotting determined the gene and protein expression levels. Protein distribution and quantification were analyzed by immunofluorescence.

KEY FINDINGS

ICS II significantly reduced lung histopathological damage, edema, and inflammatory cell infiltration, and it reduced pro-inflammatory cytokines in ALI. There is an excessive activation of neutrophils leading to a significant production of NETs in ALI mice, a process mitigated by the administration of ICS II. In vivo and in vitro studies found that ICS II could decrease NET formation by targeting neutrophil C-X-C chemokine receptor type 4 (CXCR4). Further data showed that ICS II reduces the overproduction of dsDNA, a NETs-related component, thereby suppressing cGAS/STING/NF-κB signalling pathway activation and inflammatory mediators release in lung epithelial cells.

SIGNIFICANCE

This study suggested that ICS II may alleviate LPS-induced ALI by modulating the inflammatory response, indicating its potential as a therapeutic agent for ALI treatment.

Neutrophil extracellular traps induced by IL-1β promote endothelial dysfunction and aggravate limb ischemia

Vascular inflammation and endothelial dysfunction contribute to vascular diseases. While neutrophil extracellular traps (NETs) participate in some vascular pathologies, their roles in lower limb ischemia remain poorly defined. This study investigated the functional significance of NETs in vascular inflammation and remodeling associated with limb ischemia. Single-cell RNA sequencing (scRNA-seq) and flow cytometry revealed neutrophil activation and upregulated NETs formation in human limb ischemia, with immunofluorescence confirming IL-1β-induced release of NETs for vascular inflammation. Endothelial cell activation was examined via scRNA-seq and western blotting, indicating enhanced proliferation, expression of adhesion molecules (VCAM-1, ICAM-1), inflammatory cytokines (IL-1β, IL-6) and decreased expression of VE-cadherin, that could be mediated by NETs to exacerbate endothelial inflammation. Mechanistically, NETs altered endothelial cell function via increased pSTAT1/STAT1 signaling. Vascular inflammation and subsequent ischemia were alleviated in vivo by NETosis or IL-1β inhibition in ischemic mice. IL-1β-NETs induce endothelial activation and inflammation in limb ischemia by stimulating STAT1 signaling. Targeting NETs may thus represent a novel therapeutic strategy for inflammatory vascular diseases associated with limb ischemia. Graphical abstract of NETs regulation of the development of vascular inflammation in lower limb ischemia via pSTAT1/STAT1 signaling pathway.

Cytosolic DNA initiates a vicious circle of aging-related endothelial inflammation and mitochondrial dysfunction via STING: the inhibitory effect of Cilostazol

Endothelial senescence, aging-related inflammation, and mitochondrial dysfunction are prominent features of vascular aging and contribute to the development of aging-associated vascular disease. Accumulating evidence indicates that DNA damage occurs in aging vascular cells, especially in endothelial cells (ECs). However, the mechanism of EC senescence has not been completely elucidated, and so far, there is no specific drug in the clinic to treat EC senescence and vascular aging. Here we show that various aging stimuli induce nuclear DNA and mitochondrial damage in ECs, thus facilitating the release of cytoplasmic free DNA (cfDNA), which activates the DNA-sensing adapter protein STING. STING activation led to a senescence-associated secretory phenotype (SASP), thereby releasing pro-aging cytokines and cfDNA to further exacerbate mitochondrial damage and EC senescence, thus forming a vicious circle, all of which can be suppressed by STING knockdown or inhibition. Using next-generation RNA sequencing, we demonstrate that STING activation stimulates, whereas STING inhibition disrupts pathways associated with cell senescence and SASP. In vivo studies unravel that endothelial-specific Sting deficiency alleviates aging-related endothelial inflammation and mitochondrial dysfunction and prevents the development of atherosclerosis in mice. By screening FDA-approved vasoprotective drugs, we identified Cilostazol as a new STING inhibitor that attenuates aging-related endothelial inflammation both in vitro and in vivo. We demonstrated that Cilostazol significantly inhibited STING translocation from the ER to the Golgi apparatus during STING activation by targeting S162 and S243 residues of STING. These results disclose the deleterious effects of a cfDNA-STING-SASP-cfDNA vicious circle on EC senescence and atherogenesis and suggest that the STING pathway is a promising therapeutic target for vascular aging-related diseases. A proposed model illustrates the central role of STING in mediating a vicious circle of cfDNA-STING-SASP-cfDNA to aggravate age-related endothelial inflammation and mitochondrial damage.

Design, Synthesis, and Pharmacological Evaluation of Spiro[carbazole-3,3'-pyrrolidine] Derivatives as cGAS Inhibitors for Treatment of Acute Lung Injury

Overactivation of cyclic GMP-AMP synthase (cGAS) is implicated in the occurrence of many inflammatory and autoimmune diseases, and inhibition of cGAS with a specific inhibitor has been proposed as a potential therapeutic strategy. However, only a few low-potency cGAS inhibitors have been reported, and few are suitable for clinical investigation. As a continuation of our structural optimization on the reported cGAS inhibitor 6 (G140), we developed a series of spiro[carbazole-3,3'-pyrrolidine] derivatives bearing a unique 2-azaspiro[4.5]decane structural motif, among which compound 30d-S was identified with high cellular effects against cGAS. This compound showed improved plasma exposure, lower clearance, and an oral bioavailability of 35% in rats. Moreover, in the LPS-induced acute lung injury (ALI) mice model, oral administration of compound 30d-S at 30 mg/kg markedly reduced lung inflammation and alleviated histopathological changes. These results confirm that 30d-S is a new efficacious cGAS inhibitor and is worthy of further investigation.

STING-Pathway Inhibiting Nanoparticles (SPINs) as a Platform for Treatment of Inflammatory Diseases

Aberrant activation of the cyclic GMP-AMP synthase (cGAS)/Stimulator of Interferon Genes (STING) pathway has been implicated in the development and progression of a myriad of inflammatory diseases including colitis, nonalcoholic steatohepatitis, amyotrophic lateral sclerosis (ALS), and age-related macular degeneration. Thus, STING pathway inhibitors could have therapeutic application in many of these inflammatory conditions. The cGAS inhibitor RU.521 and the STING inhibitor H-151 have shown promise as therapeutics in mouse models of colitis, ALS, and more. However, these agents require frequent high-dose intraperitoneal injections, which may limit translatability. Furthermore, long-term use of systemically administered cGAS/STING inhibitors may leave patients vulnerable to viral infections and cancer. Thus, localized or targeted inhibition of the cGAS/STING pathway may be an attractive, broadly applicable treatment for a variety of STING pathway-driven ailments. Here we describe STING-Pathway Inhibiting Nanoparticles (SPINS)-poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with RU.521 and H-151-as a platform for enhanced and sustained inhibition of cGAS/STING signaling. We demonstrate that SPINs are equally or more effective at inhibiting type-I interferon responses induced by cytosolic DNA than free H-151 or RU.521. Additionally, we describe a SPIN formulation in which PLGA is coemulsified with poly(benzoyloxypropyl methacrylamide) (P(HPMA-Bz)), which significantly improves drug loading and allows for tunable release of H-151 over a period of days to over a week by varying P(HPMA-Bz) content. Finally, we find that all SPIN formulations were as potent or more potent in inhibiting cGAS/STING signaling in primary murine macrophages, resulting in decreased expression of inflammatory M1-like macrophage markers. Therefore, our study provides an in vitro proof-of-concept for nanoparticle delivery of STING pathway inhibitors and positions SPINs as a potential platform for slowing or reversing the onset or progression of cGAS/STING-driven inflammatory conditions.

Mitochondrial DNA-Activated cGAS-STING Signaling in Environmental Dry Eye

Purpose

The cGAS-STING pathway has been shown to be an important mediator of inflammation. There is emerging evidence of the importance of this signaling cascade in a variety of inflammatory diseases settings. Here, we present evidence that the mitochondrial DNA (mtDNA) damage-mediated cGAS-STING pathway plays an important role in the induction of inflammation in environmental dry eye (DE).

Methods

RT-qPCR and Western blot were used to assess the induction of the cGAS-STING pathway and inflammatory cytokines in environmental DE mouse model, primary human corneal epithelial cells (pHCECs), and patients with DE. RNA sequencing was used to determine mRNA expression patterns of high osmotic pressure (HOP)-stimulated pHCECs. mtDNA was detected with electron microscopy, flow cytometry, and immunofluorescent staining. mtDNA was isolated and transfected into pHCECs for evaluating the activation of the cGAS-STING pathway.

Results

The expression levels of cGAS, STING, TBK1, IRF3, and IFNβ were significantly increased in an environmental DE model and HOP-stimulated pHCECs. The STING inhibitor decreased the expression of inflammatory factors in DE. An upregulation of STING-mediated immune responses and IRF3 expression mediated by TBK1 were observed in the HOP group. HOP stimulation induced mitochondrial oxidative damage and the leakage of mtDNA into the cytoplasm. Then, mtDNA activated the cGAS-STING pathway and induced intracytoplasmic STING translocated to the Golgi apparatus. Finally, we also found activated cGAS-STING signaling in the human conjunctival blot cell of patients with DE.

Conclusions

Our findings suggest that the cGAS-STING pathway is activated by recognizing cytoplasmic mtDNA leading to STING translocation, further exacerbating the development of inflammation in environmental DE.

RIPK1 inhibitor ameliorates pulmonary injury by modulating the function of neutrophils and vascular endothelial cells

Acute lung injury (ALI) is an acute and progressive hypoxic respiratory failure that could progress to acute respiratory distress syndrome (ARDS) with a high mortality rate, thus immediate medical attention and supportive care are necessary. The pathophysiology of ALI is characterized by the disruption of the alveolar-capillary barrier and activation of neutrophils, leading to lung tissue damage. The receptor-interacting protein kinase 1 (RIPK1) has emerged as a promising target for the treatment of multiple inflammatory diseases, but the role of RIPK1 in the ALI remains poorly understood. In this study, we aimed to figure out the pathological role of RIPK1 in ALI, especially in the pulmonary immune microenvironment involving neutrophils and endothelial cells. In vivo experiments showed that RIPK1 inhibitor protected against lipopolysaccharide (LPS)-induced lung injury in mouse models, with reduced neutrophils and monocytes infiltration in the lungs. Further studies demonstrated that, besides the inhibitory action on necroptosis, RIPK1 inhibitor directly suppressed reactive oxygen species (ROS) generation and inflammatory cytokines secretion from neutrophils. Furthermore, RIPK1 inhibition maintains the barrier function in TNF-α-primed vascular endothelial cells and prevents their activation induced by the supernatant from LPS-stimulated neutrophils. Mechanistically, the aforementioned effects of RIPK1 inhibitor are associated with the NF-κB signaling pathway, which is partially independent of necroptosis inhibition. These results provide new evidence that RIPK1 inhibitor directly regulates the function of neutrophils and endothelial cells, as well as interferes with the interactions between these two cell types, therefore contributing to a better understanding of RIPK1 in ALI and providing a potential avenue for future therapeutic interventions.

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

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

Pyroptosis and polarization of macrophages in septic acute lung injury induced by lipopolysaccharide in mice

BACKGROUND

Pyroptosis and polarization are significant contributors to the onset and development of many diseases. At present, the relationship between pyroptosis and polarization in acute lung injury (ALI) caused by sepsis remains unclear.

METHODS

The ALI model for sepsis was created in mice and categorized into the blank control, lipopolysaccharide (LPS) group, LPS + low-dose Belnacasan group, LPS + high-dose Belnacasan group, LPS + low-dose Wedelolactone group, LPS + high-dose Wedelolactone group, and positive control group. The wet-dry specific gravity was evaluated to compare pulmonary edema. Hematoxylin-eosin, Masson, and terminal deoxynucleotidyl transferase dUTP nick end labeling staining techniques were conducted to observe and contrast the pathological changes in lung tissue. ELISA was utilized to identify M1 and M2 macrophages and correlated inflammatory factors. Immunohistochemical staining and flow cytometry were employed to identify markers of M1 and M2 macrophages in lung tissue. Propidium iodide staining, together with flow cytometry, was utilized to observe the degree and positive rate of pyroptosis of alveolar macrophages. Western blot analysis was conducted to detect the expression levels of Caspase 1, Caspase 11, GSDMD, and IL-18 in the lung tissues of each group. The real-time quantitative polymerase chain reaction method was used to ascertain relative expression levels of NLRP3, Caspase 1, Caspase 11, GSDMD, IL-18, iNOS, and Arg-1 in lung tissues of all groups.

RESULTS

In mice with sepsis-induced ALI, both classical and nonclassical pathways of pyroptosis are observed. Inhibiting pyroptosis has been found to ameliorate lung injury, pulmonary edema, and inflammation induced by LPS. Notably, the expression of NLRP3, Caspase 1, Caspase 11, GSDMD, IL-1β, IL-18, TGF-β, CD86, CD206, iNOS, and Arg-1 were all altered in this process. Additionally, alveolar macrophages were polarized along with pyroptosis in mice with ALI caused by sepsis.

CONCLUSION

Pyroptosis of alveolar macrophages in the context of ALI in mice infected with sepsis has been linked to the polarization of alveolar macrophages toward type M1.

FGF18 alleviates sepsis-induced acute lung injury by inhibiting the NF-κB pathway

BACKGROUND

Acute lung injury (ALI) is a devastating clinical disorder with a high mortality rate, and there is an urgent need for more effective therapies. Fibroblast growth factor 18 (FGF18) has potent anti-inflammatory properties and therefore has become a focus of research for the treatment of lung injury. However, the precise role of FGF18 in the pathological process of ALI and the underlying mechanisms have not been fully elucidated.

METHODS

A mouse model of ALI and human umbilical vein endothelial cells (HUVEC) stimulated with lipopolysaccharide (LPS) was established in vivo and in vitro. AAV-FGF18 and FGF18 proteins were used in C57BL/6J mice and HUVEC, respectively. Vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and p65 protein levels were determined by western blotting or immunofluorescent staining. Afterward, related inhibitors were used to explore the potential mechanism by which FGF18 relieves inflammation.

RESULTS

In this study, we found that FGF18 was significantly upregulated in LPS-induced ALI mouse lung tissues and LPS-stimulated HUVECs. Furthermore, our studies demonstrated that overexpressing FGF18 in the lung or HUVEC could significantly alleviate LPS-induced lung injury and inhibit vascular leakage.

CONCLUSIONS

Mechanically, FGF18 treatment dramatically inhibited the NF-κB signaling pathway both in vivo and in vitro. In conclusion, these results indicate that FGF18 attenuates lung injury, at least partially, via the NF-κB signaling pathway and therefore may be a potential therapeutic target for ALI.

Signaling pathways and potential therapeutic targets in acute respiratory distress syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) is a common condition associated with critically ill patients, characterized by bilateral chest radiographical opacities with refractory hypoxemia due to noncardiogenic pulmonary edema. Despite significant advances, the mortality of ARDS remains unacceptably high, and there are still no effective targeted pharmacotherapeutic agents. With the outbreak of coronavirus disease 19 worldwide, the mortality of ARDS has increased correspondingly. Comprehending the pathophysiology and the underlying molecular mechanisms of ARDS may thus be essential to developing effective therapeutic strategies and reducing mortality. To facilitate further understanding of its pathogenesis and exploring novel therapeutics, this review provides comprehensive information of ARDS from pathophysiology to molecular mechanisms and presents targeted therapeutics. We first describe the pathogenesis and pathophysiology of ARDS that involve dysregulated inflammation, alveolar-capillary barrier dysfunction, impaired alveolar fluid clearance and oxidative stress. Next, we summarize the molecular mechanisms and signaling pathways related to the above four aspects of ARDS pathophysiology, along with the latest research progress. Finally, we discuss the emerging therapeutic strategies that show exciting promise in ARDS, including several pharmacologic therapies, microRNA-based therapies and mesenchymal stromal cell therapies, highlighting the pathophysiological basis and the influences on signal transduction pathways for their use.

The possible role of Gremlin1 in inflammatory apical periodontitis

OBJECTIVE

In this study, we investigated the involvement of Gremlin1 on the pathological process of apical periodontitis and detect the underlying mechanisms preliminarily.

METHODS

Clinical healthy and inflamed periapical specimens were collected. Then, apical periodontitis (AP) animal models were established by consistent pulp exposure. In addition, AAV-shGremlin1 was injected into inflamed periapical lesions to inhibit the expression of Gremlin1. Alveolar bone loss was measured by Micro-CT. Furthermore, immunohistochemical or immunofluorescence staining of Gremlin1, phosphorylated-CREB, ICAM-1, VCAM-1, IL-1β were performed.

RESULTS

The expression of Gremlin1 is markedly increased in periapical lesions not only in clinic samples but also in animal models. Moreover, in rats' AP model, we uncovered that the Gremlin1 protein expression levels in apical lesions is positively correlated with those of IL-1β. Besides, the blockade of Gremlin1 in periapical lesions could substantially suppress the alveolar bone loss and restrains the inflammatory status by impacting the activation levels of phosphorylated-CREB, ICAM-1, VCAM-1, IL-1β.

CONCLUSIONS

Taken together, these results illustrated that Gremlin1 acts as a crucial mediator and possibly serves as a potential diagnostic marker for periapical periodontitis. Discovery of new factors involved in the pathophysiology of periapical periodontitis could contribute to the development of novel therapeutic treatment for the disease.

Microtubule-destabilizing agents enhance STING-mediated innate immune response via biased mechanism in human monocyte cells

The stimulator of the interferon gene (STING) signaling pathway acts as a primary defense system against DNA pathogens. Because of the crucial role of STING in type I interferon (IFN) response and innate immunity, extensive research has been conducted to elucidate the roles of various effector molecules involved in STING-mediated signal transduction. However, despite the substantial contribution of microtubules to the immune system, the association between the STING signaling pathway and microtubules remains unclear. In this study, we revealed that the modulation of STING via microtubule-destabilizing agents (MDAs) specifically induced type I IFN responses rather than inflammatory responses in human monocytes. Co-treatment of MDAs with STING agonists induced the elevation of phospho-TANK-binding kinase 1 (TBK1), amplifying the innate immune response. However, during the deficiency of TBK1, the non-canonical signaling pathway through nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) contributed to MDA-induced STING activation in type I IFN response which suggested the versatile regulation of MDA in STING-mediated immunity.

TRPC6 Deletion Enhances eNOS Expression and Reduces LPS-Induced Acute Lung Injury

Acute lung injury (ALI) is characterized by endothelial barrier disruption and associated inflammatory responses, and transient receptor potential cation channel 6 (TRPC6)-mediated Ca2+ influx is critical for endothelial hyperpermeability. In this study, we investigated the role of TRPC6 in LPS-induced ALI, analyzed gene expression in WT and TRPC6-/- lungs using RNA sequencing, and explored the effects of TRPC6 in the LPS-induced hyperpermeability in human umbilical vein endothelial cells (HUVECs) to elucidate the underlying mechanisms. Intratracheal instillation of LPS caused edema in the mouse lungs. Deletion of TRPC6 reduced LPS-induced lung edema and decreased cell infiltration. RNA sequencing analysis suggested that downregulated cell adhesion molecules in TRPC6-/- lungs may be responsible for their resistance to LPS-induced injury. In addition, downregulation of TRPC6 significantly alleviated the LPS-induced decrease in eNOS expression in lung tissue as well as in HUVECs. Moreover, inhibition of TRPC6 with the channel antagonist larixyl led to a decrease in LPS-induced hyperpermeability and ROS production in HUVECs, which could be reversed by blocking eNOS. Our findings suggest that inhibition of TRPC6 ameliorates LPS-induced ALI, which may be achieved by acting on the cell adhesion molecule signaling pathway and participating in the regulation of eNOS levels in endothelial cells.

Genetically Engineered Cellular Nanovesicle as Targeted DNase I Delivery System for the Clearance of Neutrophil Extracellular Traps in Acute Lung Injury

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are prevalent critical illnesses with a high mortality rate among patients in intensive care units. Neutrophil extracellular traps (NETs) are implicated in the pathogenesis of ALI/ARDS and represent a promising therapeutic target. However, the clinical application of deoxyribonuclease I (DNase I), the only drug currently available to clear NETs, is limited due to the lack of precise and efficient delivery strategies. Therefore, targeted delivery of DNase I to the inflamed lung remains a critical issue to be addressed. Herein, a novel biomimetic DNase I delivery system is developed (DCNV) that employs genetically and bioorthogonally engineered cellular nanovesicles for pulmonary NETs clearance. The CXC motif chemokine receptor 2 overexpressed cellular nanovesicles can mimic the inflammatory chemotaxis of neutrophils in ALI/ARDS, leading to enhanced lung accumulation. Furthermore, DNase I immobilized through bioorthogonal chemistry exhibits remarkable enzymatic activity in NETs degradation, thus restraining inflammation and safeguarding lung tissue in the lipopolysaccharide-induced ALI murine model. Collectively, the findings present a groundbreaking proof-of-concept in the utilization of biomimetic cellular nanovesicles to deliver DNase I for treating ALI/ARDS. This innovative strategy may usher in a new era in the development of pharmacological interventions for various inflammation-related diseases.

Targeting sting to reduce sepsis-induced acute intestinal injury

BACKGROUND

Sepsis is a dysregulated host response to infection syndrome leading to life-threatening organ dysfunction. Sepsis-induced intestinal dysfunction is a key element in the progression to multisystem organ failure. The stimulator of interferon genes is an intracellular protein implicated in intestinal injury in sepsis. H151, a small molecule inhibitor of stimulator of interferon genes, has not yet been studied as a potential therapeutic in sepsis. We hypothesize that H151 therapeutically reduces sepsis-induced acute intestinal injury.

METHODS

Male mice underwent cecal ligation and puncture and were treated with intraperitoneal H151 (10 mg/kg body weight) or vehicle. Intestines and serum were collected for analysis 20 hours after cecal ligation and puncture. Oral gavage of mice with FITC-dextran was performed 15 hours after cecal ligation and puncture. Five hours after gavage, serum was collected, and intestinal permeability was assessed. Mice were monitored for 10 days after cecal ligation and puncture to assess survival.

RESULTS

Zonula occludens 1 tight junctional protein expression was reduced after cecal ligation and puncture and recovered with H151 treatment. This was associated with a 62.3% reduction in intestinal permeability as assessed by fluorimetry. After cecal ligation and puncture, treatment with H151 was associated with a 58.7% reduction in intestinal histopathologic injury (P < .05) and a 56.6% reduction in intestinal apoptosis (P < .05). Intestinal myeloperoxidase activity was decreased by 70.8% after H151 treatment (P < .05). Finally, H151 improved 10-day survival from 33% to 80% after cecal ligation and puncture (P = .011).

CONCLUSION

H151, a novel stimulator of interferon genes inhibitor, reduces intestinal injury, inflammation, and permeability when administered as a treatment for cecal ligation and puncture-induced sepsis. Thus, targeting stimulator of interferon genes shows promise as a therapeutic strategy to ameliorate sepsis-induced acute intestinal injury.

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.

PCSK9 causes inflammation and cGAS/STING pathway activation in diabetic nephropathy

Our previous research revealed that an increase in PCSK9 is linked to aggravated inflammation in the kidneys of mice affected by a high-fat diet and streptozotocin (HFD/STZ) or in HGPA-induced HK-2 cells. Furthermore, the cGAS/STING pathway has been reported to be involved in diabetic nephropathy (DN). Therefore, in this study, we aimed to examine the correlation between the proinflammatory effect of PCSK9 and the cGAS/STING pathway in DN. We used PCSK9 mAbs to inhibit PCSK9 in vivo and PCSK9 siRNA in vitro and measured the inflammatory phenotype in HFD/STZ-treated mice or HGPA-induced HK-2 cells, and observed decreased blood urea nitrogen, creatinine, UACR, and kidney injury in response to the PCSK9 mAb in HFD/STZ-treated mice. Moreover, IL-1 β, MCP-1, and TNF-α levels were reduced by the PCSK9 mAb in vivo and PCSK9 siRNA in vitro. We observed increased mtDNA damage and activation of the cGAS-STING signaling pathway during DN, as well as the downstream targets p-TBK1, p-NF-κB p65, and IL-1β. In a further experiment with an HGPA-induced DN model in HK-2 cells, we revealed that mtDNA damage was increased, which led to the activation of the cGAS/STING system and its downstream targets. Notably, the cGAS-STING signaling pathway was inhibited by the PCSK9 mAb in vivo and PCSK9 siRNA in vitro. In addition, inhibition of STING with C-176 in HGPA-induced HK-2 cells markedly blocked inflammation. In conclusion, we report for the first time that PCSK9 triggers mitochondrial DNA damage and activates the cGAS-STING pathway in DN, which leads to a series of inflammation cascades. PCSK9-targeted intervention can effectively reduce DN inflammation and delay its progression. Moreover, the inhibition of STING significantly abrogated the inflammation triggered by HGPA in HK-2 cells.

Neutrophil extracellular traps contribute to immunothrombosis formation via the STING pathway in sepsis-associated lung injury

Neutrophil extracellular traps (NETs) are involved in the activation and dysfunction of multiple overlapping and interacting pathways, including the immune response to injury, inflammation, and coagulation, which contribute to the pathogenesis of sepsis-induced acute lung injury (SI-ALI). However, how NETs mediate the relationship between inflammation and coagulation has not been fully clarified. Here, we found that NETs, through stimulator of interferon genes (STING) activation, induced endothelial cell damage with abundant production of tissue factor (TF), which magnified the dysregulation between inflammatory and coagulant responses and resulted in poor prognosis of SI-ALI model mice. Disruption of NETs and inhibition of STING improved the outcomes of septic mice and reduced the inflammatory response and coagulation. Furthermore, Toll-like receptor 2 (TLR2) on the surface of endothelial cells was involved in the interaction between NETs and the STING pathway. Collectively, these findings demonstrate that NETs activate the coagulant cascade in endothelial cells in a STING-dependent manner in the development of SI-ALI.

The battle between the innate immune cGAS-STING signaling pathway and human herpesvirus infection

The incidence of human herpesvirus (HHVs) is gradually increasing and has affected a wide range of population. HHVs can result in serious consequences such as tumors, neonatal malformations, sexually transmitted diseases, as well as pose an immense threat to the human health. The cGAS-STING pathway is one of the innate immune pattern-recognition receptors discovered recently. This article discusses the role of the cGAS-STING pathway in human diseases, especially in human herpesvirus infections, as well as highlights how these viruses act on this pathway to evade the host immunity. Moreover, the author provides a comprehensive overview of modulators of the cGAS-STING pathway. By focusing on the small molecule compounds based on the cGAS-STING pathway, novel targets and concepts have been proposed for the development of antiviral drugs and vaccines, while also providing a reference for the investigation of disease models related to the cGAS-STING pathway. HHV is a double-stranded DNA virus that can trigger the activation of intracellular DNA sensor cGAS, after which the host cells initiate a cascade of reactions that culminate in the secretion of type I interferon to restrict the viral replication. Meanwhile, the viral protein can interact with various molecules in the cGAS-STING pathway. Viruses can evade immune surveillance and maintain their replication by inhibiting the enzyme activity of cGAS and reducing the phosphorylation levels of STING, TBK1 and IRF3 and suppressing the interferon gene activation. Activators and inhibitors of the cGAS-STING pathway have yielded numerous promising research findings in vitro and in vivo pertaining to cGAS/STING-related disease models. However, there remains a dearth of small molecule modulators that have been successfully translated into clinical applications, which serves as a hurdle to be overcome in the future.

Radiation Induces Bone Microenvironment Disruption by Activating the STING-TBK1 Pathway

Background and Objectives: Damage to normal bone tissue following therapeutic irradiation (IR) represents a significant concern, as IR-induced bone microenvironment disruption can cause bone loss and create a more favorable environment for tumor metastases. The aim of the present study was to explore the cellular regulatory mechanism of IR-induced bone microenvironment disruption to effectively prevent radiotherapy-associated adverse effects in the future. Materials and Methods: In this study, a mouse model of local IR was established via local irradiation of the left hind limb of BALB/c mice with 12 Gy X-rays, and an in vitro osteocyte (OCY) model was established by exposing osteocyte-like MLO-Y4 cells to 2, 4, and 8 Gy irradiation to analyze multicellular biological injuries and cellular senescence. Small interfering RNA (siRNA) transfection at the cellular level and a selective antagonist intervention C-176 at the animal level were used to explore the potential role of the stimulator of interferon genes (STING) on IR-induced bone microenvironment disruption. Results: The results showed that 12 Gy local IR induces multicellular dysfunction, manifested as ascension of OCYs exfoliation, activation of osteoclastogenesis, degeneration of osteogenesis and fate conversion of adipogenesis, as well as cellular senescence and altered senescence-associated secretory phenotype (SASP) secretion. Furthermore, the expression of STING was significantly elevated, both in the primary OCYs harvested from locally irradiated mice and in vitro irradiated MLO-Y4 cells, accompanied by the markedly upregulated levels of phosphorylated TANK-binding kinase 1 (P-TBK1), RANKL and sclerostin (SOST). STING-siRNA transfection in vitro restored IR-induced upregulated protein expression of P-TBK1 and RANKL, as well as the mRNA expression levels of inflammatory cytokines, such as IL-1α, IL-6 and NF-κB, accompanied by the alleviation of excessive osteoclastogenesis. Finally, administration of the STING inhibitor C-176 mitigated IR-induced activation of osteoclastogenesis and restraint of osteogenesis, ameliorating the IR-induced biological damage of OCYs, consistent with the inhibition of P-TBK1, RANKL and SOST. Conclusions: The STING-P-TBK1 signaling pathway plays a crucial role in the regulation of the secretion of inflammatory cytokines and osteoclastogenesis potential in IR-induced bone microenvironment disruption. The selective STING antagonist can be used to intervene to block the STING pathway and, thereby, repair IR-induced multicellular biological damage and mitigate the imbalance between osteoclastogenesis and osteoblastgenesis.

Licorice extract inhibits the cGAS-STING pathway and protects against non-alcoholic steatohepatitis

Background: Inflammation and fibrosis are typical symptoms of non-alcoholic steatohepatitis (NASH), which is one of the most common chronic liver diseases. The cGAS-STING signaling pathway has been implicated in the progression of NASH, and targeting this pathway may represent a new therapeutic strategy. Licorice is a widely used herb with anti-inflammatory and liver-protective properties. In this study, we assessed the effect of licorice extract on the cGAS-STING pathway.

Methods: Bone marrow-derived macrophages (BMDMs) were treated with licorice extract and then stimulated with HT-DNA, 2'3'-cGAMP, or other agonists to activate the cGAS-STING pathway. Quantitative real-time PCR and western blot were conducted to analyze whether licorice extract could affect the cGAS-STING pathway. Methionine and choline-deficient diet (MCD) was used to induce NASH in mice, which were treated with licorice extract (500 mg/kg) by gavage and/or c-176 (15 mg/kg) by intraperitoneal injection every 2 days. After 6 weeks of treatment, histological analysis of liver tissue was performed, along with measurements of plasma biochemical parameters.

Results: Licorice extract inhibits cGAS-STING pathway activation. Mechanistically, it might function by inhibiting the oligomerization of STING. Treatment with licorice extract reduced inflammation and fibrosis in MCD diet-induced NASH mice models. Furthermore, we found that the therapeutic effect of combination treatment with licorice extract and C-176 (STING inhibitor) on the pathology and fibrosis of MCD diet-induced NASH models was similar to that of licorice extract or C-176 administered alone.

Conclusion: Licorice extract can inhibit the cGAS-STING pathway and improve hepatic inflammation and fibrosis in NASH mice models. It strongly suggests that licorice extract may be a candidate therapeutic for NASH.

Downregulation of ROR2 attenuates LPS-induced A549 cell injury through JNK and ERK signaling pathways

BACKGROUND

We aimed to determine whether receptor tyrosine kinase-like orphan receptor 2 (ROR2) is involved in the occurrence of acute lung injury (ALI) by an animal study and explore the effect of ROR2 downregulation on lipopolysaccharide (LPS)-treated human lung carcinoma A549 cells by a cytological study.

METHODS

Murine models of ALI were successfully constructed by intratracheal instillation of LPS. Meanwhile, A549 cell line stimulated with LPS was used for a cytological study. The expression of ROR2 and its effect on proliferation, cell cycle, apoptosis, and inflammation were detected.

RESULTS

It was found that LPS administration markedly inhibited the cell proliferation, resulted in cell cycle arrest at G1 phage, elevated levels of pro-inflammatory cytokines and apoptosis rate of A549 cells. However, LPS-mediated adverse effects mentioned above were significantly ameliorated by downregulation of ROR2 in comparison with LPS treatment. In addition, administration of ROR2 siRNA notably decreased the phosphorylation level of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) in LPS-challenged A549 cells.

CONCLUSIONS

Thus, the present data indicate that downregulation of ROR2 may decrease LPS-induced inflammatory responses and cell apoptosis through inhibiting JNK and ERK signaling pathway, which attenuates ALI.

Potential Therapeutic Value of the STING Inhibitors

The stimulator of interferon genes (STING) is a critical protein in the activation of the immune system in response to DNA. It can participate the inflammatory response process by modulating the inflammation-preferred translation program through the STING-PKR-like endoplasmic reticulum kinase (PERK)-eIF2α pathway or by inducing the secretion of type I interferons (IFNs) and a variety of proinflammatory factors through the recruitment of TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3) or the regulation of the nuclear factor kappa-B (NF-κB) pathway. Based on the structure, location, function, genotype, and regulatory mechanism of STING, this review summarizes the potential value of STING inhibitors in the prevention and treatment of infectious diseases, psoriasis, systemic lupus erythematosus, non-alcoholic fatty liver disease, and other inflammatory and autoimmune diseases.

Flavonoids derived from licorice suppress LPS-induced acute lung injury in mice by inhibiting the cGAS-STING signaling pathway

In recent years, we have found that the dysregulation of the cyclic-GMP-AMP synthase (cGAS)‒stimulator of interferon genes (STING) pathway leads to the development of immune and inflammatory diseases, therefore, finding compounds that can specifically regulate this pathway is essential for effective regulation of the immune pathway for addressing inflammatory diseases. Licorice flavonoids (LFs), are active ingredients extracted from the Chinese herb licorice, which has been reported to have strong anti-inflammatory activity in previous studies. Here, we report that LFs inhibit the activation of the cGAS-STING pathway evidenced by the inhibition of the expression of type I interferons and related downstream genes such as interferon-stimulated gene 15 (ISG15) and C-X-C motif chemokine ligand 10 (CXCL10), as well as inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Notably, LFs markedly improve the LPS-induced acute lung injury by inhibiting the excessive activation of cGAS-STING signaling pathway. Mechanistically, LFs treatment leads to the blocking of 2'3'-cyclic GMP-AMP (cGAMP) synthesis resulting in an inhibition of the activation of the cGAS-STING pathway. Our results indicate that LFs is a specific inhibitor of the cGAS-STING pathway, which is suggested to be a potential candidate for the treatment of cGAS-STING pathway-mediated inflammatory diseases.

Targeting immunometabolism against acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening conditions triggered by multiple intra- and extra-pulmonary injury factors, characterized by complicated molecular mechanisms and high mortality. Great strides have been made in the field of immunometabolism to clarify the interplay between intracellular metabolism and immune function in the past few years. Emerging evidence unveils the crucial roles of immunometabolism in inflammatory response and ALI. During ALI, both macrophages and lymphocytes undergo robust metabolic reprogramming and discrete epigenetic changes after activated. Apart from providing ATP and biosynthetic precursors, these metabolic cellular reactions and processes in lung also regulate inflammation and immunity.In fact, metabolic reprogramming involving glucose metabolism and fatty acidoxidation (FAO) acts as a double-edged sword in inflammatory response, which not only drives inflammasome activation but also elicits anti-inflammatory response. Additionally, the features and roles of metabolic reprogramming in different immune cells are not exactly the same. Here, we outline the evidence implicating how adverse factors shape immunometabolism in differentiation types of immune cells during ALI and summarize key proteins associated with energy expenditure and metabolic reprogramming. Finally, novel therapeutic targets in metabolic intermediates and enzymes together with current challenges in immunometabolism against ALI were discussed.

Activation of the STING pathway induces peripheral sensitization via neuroinflammation in a rat model of bone cancer pain

BACKGROUND

Neuroinflammation in the peripheral nervous system has been linked to cancer metastasis-induced bone pain. The stimulator of interferon genes (STING), an innate immune sensor for cytosolic DNA, plays an important role in inflammation and cancer metastasis and is reported to be a critical regulator of nociception. Here, we examined the role of STING in primary nociceptive neurons and chronic pain to determine if it could be a new target for treating bone cancer pain (BCP).

METHODS

Walker 256 cancer cells were injected intratibially to induce bone cancer pain in rats. STING and its downstream inflammatory factors in dorsal root ganglia (DRG) were detected using western blotting and immunofluorescent staining. Transmission electron microscopy and the BCL2-associated X (Bax) expression were used to detect the mitochondrial stress in DRG neurons. C-176, a specific inhibitor of STING, was used to block STING activation and to test the pain behavior.

RESULTS

Mechanical hyperalgesia and spontaneous pain were observed in BCP rats, accompanied by the upregulation of the STING expression in the ipsilateral L4-5 DRG neurons which showed significant mitochondrion stress. The STING/TANK-binding kinase 1 (TBK1)/nuclear factor-kappa B (NF-κB) pathway activation was observed in the DRGs of BCP rats as well as increased IL-1β, IL-6, and TNF-α expression. C-176 alleviated bone cancer pain and reduced the STING and its downstream inflammatory pathway.

CONCLUSION

We provide evidence that STING pathway activation leads to neuroinflammation and peripheral sensitization. Pharmacological blockade of STING may be a promising novel strategy for preventing BCP.

The protective effect of natural medicines against excessive inflammation and oxidative stress in acute lung injury by regulating the Nrf2 signaling pathway

Acute lung injury (ALI) is a common critical disease of the respiratory system that progresses into acute respiratory distress syndrome (ARDS), with high mortality, mainly related to pulmonary oxidative stress imbalance and severe inflammation. However, there are no clear and effective treatment strategies at present. Nuclear factor erythroid 2-related factor 2(Nrf2) is a transcription factor that interacts with multiple signaling pathways and regulates the activity of multiple oxidases (NOX, NOS, XO, CYP) related to inflammation and apoptosis, and exhibits antioxidant and anti-inflammatory roles in ALI. Recently, several studies have reported that the active ingredients of natural medicines show protective effects on ALI via the Nrf2 signaling pathway. In addition, they are cheap, naturally available, and possess minimal toxicity, thereby having good clinical research and application value. Herein, we summarized various studies on the protective effects of natural pharmaceutical components such as polyphenols, flavonoids, terpenoids, alkaloids, and polysaccharides on ALI through the Nrf2 signaling pathway and demonstrated existing gaps as well as future perspectives.

STING Targeting in Lung Diseases

The cGAS-STING pathway displays important functions in the regulation of innate and adaptive immunity following the detection of microbial and host-derived DNA. Here, we briefly summarize biological functions of STING and review recent literature highlighting its important contribution in the context of respiratory diseases. Over the last years, tremendous progress has been made in our understanding of STING activation, which has favored the development of STING agonists or antagonists with potential therapeutic benefits. Antagonists might alleviate STING-associated chronic inflammation and autoimmunity. Furthermore, pharmacological activation of STING displays strong antiviral properties, as recently shown in the context of SARS-CoV-2 infection. STING agonists also elicit potent stimulatory activities when used as an adjuvant promoting antitumor responses and vaccines efficacy.

Ibrutinib Prevents Acute Lung Injury via Multi-Targeting BTK, FLT3 and EGFR in Mice

Ibrutinib has potential therapeutic or protective effects against viral- and bacterial-induced acute lung injury (ALI), likely by modulating the Bruton tyrosine kinase (BTK) signaling pathway. However, ibrutinib has multi-target effects. Moreover, immunity and inflammation targets in ALI treatment are poorly defined. We investigated whether the BTK-, FLT3-, and EGFR-related signaling pathways mediated the protective effects of ibrutinib on ALI. The intratracheal administration of poly I:C or LPS after ibrutinib administration in mice was performed by gavage. The pathological conditions of the lungs were assessed by micro-CT and HE staining. The levels of neutrophils, lymphocytes, and related inflammatory factors in the lungs were evaluated by ELISA, flow cytometry, immunohistochemistry, and immunofluorescence. Finally, the expression of proteins associated with the BTK-, FLT3-, and EGFR-related signaling pathways were evaluated by Western blotting. Ibrutinib (10 mg/kg) protected against poly I:C-induced (5 mg/kg) and LPS-induced (5 mg/kg) lung inflammation. The wet/dry weight ratio (W/D) and total proteins in the bronchoalveolar lavage fluid (BALF) were markedly reduced after ibrutinib (10 mg/kg) treatment, relative to the poly I:C- and LPS-treated groups. The levels of ALI indicators (NFκB, IL-1β, IL-6, TNF-α, IFN-γ, neutrophils, and lymphocytes) were significantly reduced after treatment. Accordingly, ibrutinib inhibited the poly I:C- and LPS-induced BTK-, FLT3-, and EGFR-related pathway activations. Ibrutinib inhibited poly I:C- and LPS-induced acute lung injury, and this may be due to its ability to suppress the BTK-, FLT3-, and EGFR-related signaling pathways. Therefore, ibrutinib is a potential protective agent for regulating immunity and inflammation in poly I:C- and LPS-induced ALI.

H151, A SMALL MOLECULE INHIBITOR OF STING AS A NOVEL THERAPEUTIC IN INTESTINAL ISCHEMIA-REPERFUSION INJURY

BACKGROUND

Intestinal ischemia-reperfusion (I/R) injury is a severe disease associated with high mortality. Stimulator of interferon genes (STING) is an intracellular protein that is activated by cytosolic DNA and is implicated in I/R injury, resulting in transcription of type I interferons (IFN-α and IFN-β) and other proinflammatory molecules. Extracellular cold-inducible RNA-binding protein (eCIRP), a damage-associated molecular pattern, induces STING activation. H151 is a small molecule inhibitor of STING that has not yet been studied as a potential therapeutic. We hypothesize that H151 reduces inflammation, tissue injury, and mortality after intestinal I/R. Methods: In vitro, RAW264.7 cells were pretreated with H151 then stimulated with recombinant murine (rm) CIRP, and IFN-β levels in the culture supernatant were measured at 24 hours after stimulation. In vivo, male C57BL/6 mice were subjected to 60-minute intestinal ischemia via superior mesenteric artery occlusion. At the time of reperfusion, mice were intraperitoneally instilled with H151 (10 mg/kg BW) or 10% Tween-80 in PBS (vehicle). Four hours after reperfusion, the small intestines, lungs, and serum were collected for analysis. Mice were monitored for 24 hours after intestinal I/R to assess survival. Results: In vitro, H151 reduced rmCIRP-induced IFN-β levels in a dose-dependent manner. In vivo, intestinal levels of pIRF3 were increased after intestinal I/R and decreased after H151 treatment. There was an increase in serum levels of tissue injury markers (lactate dehydrogenase, aspartate aminotransferase) and cytokine levels (interleukin 1β, interleukin 6) after intestinal I/R, and these levels were decreased after H151 treatment. Ischemia-reperfusion-induced intestinal and lung injury and inflammation were significantly reduced after H151 treatment, as evaluated by histopathologic assessment, measurement of cell death, chemokine expression, neutrophil infiltration, and myeloperoxidase activity. Finally, H151 improved the survival rate from 41% to 81% after intestinal I/R. Conclusions: H151, a novel STING inhibitor, attenuates the inflammatory response and reduces tissue injury and mortality in a murine model of intestinal I/R. H151 shows promise as a potential therapeutic in the treatment of this disease.

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.

New mechanism of nephrotoxicity of triptolide: Oxidative stress promotes cGAS-STING signaling pathway

Triptolide (TPL) is a bioactive component extracted from the traditional Chinese herb Tripterygium wilfordii Hook F., and has multiple pharmacological activities, such as anti-tumor activity. However, severe adverse effects and toxicity, especially nephrotoxicity, limit its clinical application. It has been demonstrated that mitochondrial defect is a major toxic effects of TPL. In this study, we show that triptolide activated the cGAS-STING signaling pathway in kidney tubular cells in vivo and in vitro. Renal injury models were established in BALB/c mice and human tubular epithelial cells using TPL. We found that TPL enhanced the phosphorylation levels of STING, TBK1 and IRF3, and upregulated the expression of IFNβ, which is the production of cGAS-STING signaling pathway. STING inhibitor C176 had protective effects in TPL-induced nephrocyte damage. STING siRNA down regulated the expression level of IFNβ. In addition, triptolide induced an increase in protein levels of the transcription factor BACH1, while transcriptional expression of the antioxidant enzyme HMOX1 was reduced due to the increased expression of BACH1. Furthermore, oxidative stress-induced mtDNA damage and DNA leakage caused activation of the cGAS-STING signaling pathway. Altogether, cGAS-STING signaling pathway involved in TPL induced nephrotoxicity. Inhibiting cGAS-STING over-activation may be a new strategy for alleviating renal injury of triptolide.

Post-Translational Modifications of STING: A Potential Therapeutic Target

Stimulator of interferon genes (STING) is an endoplasmic-reticulum resident protein, playing essential roles in immune responses against microbial infections. However, over-activation of STING is accompanied by excessive inflammation and results in various diseases, including autoinflammatory diseases and cancers. Therefore, precise regulation of STING activities is critical for adequate immune protection while limiting abnormal tissue damage. Numerous mechanisms regulate STING to maintain homeostasis, including protein-protein interaction and molecular modification. Among these, post-translational modifications (PTMs) are key to accurately orchestrating the activation and degradation of STING by temporarily changing the structure of STING. In this review, we focus on the emerging roles of PTMs that regulate activation and inhibition of STING, and provide insights into the roles of the PTMs of STING in disease pathogenesis and as potential targeted therapy.