STING-dependent sensing of self-DNA drives silica-induced lung inflammation

Complement system is activated in acute inflammatory response to environmental particulates in the lungs

Short-term exposure (typically ranging from a few hours to 7 days) to particulate matter (PM) elicits acute inflammatory responses with significant activation of complement component C5. However, the relationship between PM-induced complement system activation, acute inflammation, and the contributing factors remains unclear. In this study, we aimed to investigate the intensity of acute inflammatory responses, as well as the activation levels of complement C5 and its related products, C5aR1 and C5b-9, following exposure to different types of PM. Acute inflammatory responses and complement activation were assessed in mice intratracheally administered four types of PM: titanium dioxide (TiO₂), diesel exhaust particles (DEP), Asian sand dust (ASD), and ambient PM with an aerodynamic diameter ≤ 2.5 μm (PM2.5). Complement system and inflammatory markers were evaluated by analyzing increased C5 protein levels, C5b-9 deposition, and C5aR1 expression. Additionally, dark-field microscopy and Raman microscopy were used to detect PM components adjacent to infiltrating neutrophils, and elemental composition was quantified using ICP-MS and EDXRF. ASD, DEP, and PM2.5 exposure significantly increased C5b-9 deposition in lung tissues. All PM-exposed groups exhibited substantial upregulation of C5aR1 expression, primarily in neutrophils. Raman spectroscopic analysis revealed Si, K, Mg, Al, and Fe adjacent to infiltrating neutrophils in ASD-exposed lungs. Furthermore, elemental analysis identified Si, Mg, Al, and K as the most potent contributors to complement activation and inflammatory responses. Of the four types of PM, ASD induced the most severe acute inflammatory response and complement system activation. Therefore, ASD-induced complement system activation, driven at least partly by its mineral components, may play a critical role in neutrophil activation and acute pulmonary inflammation. These findings highlight the differential impact of PM types on complement system activation and underscore the importance of PM composition in the evaluation of air pollution-related health risks, particularly acute pulmonary inflammation.

Calprotectin inhibition attenuates silica-induced lung fibrosis

Respirable silica exposure adversely affects lung tissue immunopathology, triggering oxidative bursts in macrophages and neutrophils, releasing Damage-associated molecular patterns (DAMPs), including calprotectin proteins, S100A8, and S100A9. Calprotectin constitutes up to 45% of these innate immune cells, and serum levels of these alarmins correlate with inflammation, fibrosis, remodelling, and drug response in chronic diseases, including inflammatory bowel disease, asthma, and cystic fibrosis. The consequence of releasing calprotectin protein could trigger the pro-fibrotic effect of silicosis. This study aimed to investigate the role of calprotectin (S100A8/S100A9) as a pro-inflammatory and pro-fibrotic mediator in silica-induced lung fibrosis and evaluated the therapeutic potential of the calprotectin inhibitor, paquinimod. Using a mouse model of silicosis, silica exposure significantly elevated calprotectin expression, lung inflammation, and fibrosis, as evidenced by increased levels of epithelial-to-mesenchymal transition (EMT) markers, collagen deposition, and matrix metalloproteinases (MMPs). In vitro, stimulation of human bronchial fibroblasts with S100A8/S100A9 upregulated fibrotic markers (COL1A1 and α-SMA), which were reduced by inhibitors of TLR4 and RAGE receptors, as well as by paquinimod. Treatment with paquinimod effectively reduced these pathological changes, normalized calprotectin levels, decreased fibrosis scores, and attenuated NF-κB activation. These findings highlighted calprotectin's pivotal role in silica-induced lung fibrosis and inflammation, suggesting that its inhibition could be a promising therapeutic approach for silicosis and other fibro-inflammatory lung diseases. Further research is warranted to explore the precise mechanisms linking calprotectin to lung fibrosis and its potential as a biomarker and therapeutic target.

Marine-derived STING inhibitors, excavatolide B promote wound repair in full-thickness-incision rats

The process of wound healing encompasses both inflammatory and proliferative stages. Excessive inflammation is known to impede the healing of chronic wounds. Activation of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway causes inflammation during cellular stress and tissue damage. Herein, we examined the anti-inflammatory effects of the marine-derived STING antagonist excavatolide B (EXCB) and its derivatives, EXCB-61 and EXCB-79, in full-thickness-incision rats. Wound area measurements, histopathological observations, and immunohistochemical analyses were performed to evaluate the roles of these compounds in wound healing. These three compounds were found to have low toxicity, with EXCB promoting Hs68 human dermal fibroblast migration and proliferation. EXCB and EXCB61 treatments, but not EXCB79, reduced the wound area. The histopathological results showed a significant decrease in immune cell infiltration and mast cell accumulation in all compound-treated groups. Immunohistochemical analysis revealed that EXCB and its derivatives reduced cGAS-STING pathway factors such as STING, phosphorylated TANK-binding kinase 1, nuclear factor kappa-light-chain-enhancer of activated B cells, and M1 macrophages while increasing the expression of angiogenic factors vascular endothelial growth factor and CD31, as well as M2 macrophages and collagen I/III deposition. We conclude that marine-derived STING antagonists can attenuate inflammatory responses by inhibiting the cGAS-STING pathway and promoting angiogenesis, thereby aiding wound healing.

Dihydroartemisinin Attenuates Radiation-Induced Lung Injury by Inhibiting the cGAS/STING/NF-κB Signaling Pathway

Dihydroartemisinin (DHA) is a derivative of artemisinin, which affects inflammation, oxidative stress, and immune regulation. However, the mechanism underlying its effects remains largely unknown. This study aims to explore the mechanism by which DHA affects radiation-induced lung injury (RILI), providing new insights for lung radiotherapy. To elucidate its mechanism of action, C57BL/6 J mice were irradiated with 15 Gy whole chest. RILI was evaluated by qRT-PCR, ELISA, histology, Western blot analysis, immunohistochemistry, and RILI signaling cascade studies. In addition, small interfering RNAs were employed to knockdown cGAS proteins in the cGAS-STING signaling pathway in the human bronchial epithelium cell line (BEAS-2B). Both In Vivo and Vitro experiments were conducted to investigate the specific mechanism by which DHA alleviated RILI. We observed the activation of the cGAS-STING pathway, along with the phosphorylation of the downstream target NF-κB and an increase in inflammatory factor levels in the mouse model following radiation exposure. In the cell model, irradiation also triggered the activation of the cGAS-STING signaling pathway and its downstream targets, leading to elevated levels of inflammatory factors. Notably, knocking down the cGAS using small interfering RNA in the BEAS-2B cells significantly alleviated RILI in the cell model. Our study elucidated the mechanism of DHA reducing RILI through the cGAS/STING/NF-κB signaling pathway, and revealed that the GAS/STING/NF-κB axis may be a potential therapeutic target for RILI.

The emerging concept of ANCA-associated vasculitis related to inborn errors of immunity

ANCA-associated vasculitis (AAV) is a group of rare small vessels vasculitis that preferentially affect the kidneys, lungs and upper airways. Although the detailed pathophysiology remains unclear, genetic background has been shown to play a role in sporadic forms of AAV. The discovery of these susceptibility genes (and associated biological pathways) involved in AAV have shaped the current understanding of AAV pathophysiology. In addition to common genetic polymorphisms, specific rare inborn errors of immunity (IEI) have been described with a high frequency of ANCA (antineutrophil cytoplasmic antibodies) positivity and vasculitis features in young individuals (in addition to other manifestations). A systematic literature search revealed that patients with pathogenic variants in COPA, STING1, DNASE1L3, and PIK3CD are at increased risk of developing ANCA and AAV features, including alveolar hemorrhage, interstitial lung disease, pauciimmune glomerulonephritis, and upper airways involvement (septum perforation, saddle-nose deformity, chronic nasal/sinuses ulceration). Some of these IEI may also present with a mixed phenotype and/or auto-antibodies profile associating features of AAV and other autoimmune diseases (in particular systemic lupus erythematosus). Notably, a proportion of reports and series lack serological (ANCA specificity and titers) and/or histopathological data, making challenging to assess the likelihood for ANCA pathogenicity in some patients with IEI (as opposed to unspecific signs of biologic autoimmunity). This point is nonetheless essential to make appropriate therapeutic decisions. In addition, since most of the genes mentioned above are involved in the type 1 interferon signaling, the role of this pathway in AAV etiopathogenesis deserves further investigation. In this review, we will describe these IEI, their overlap with sporadic AAV, and their evocative features. Next, we will discuss how these monogenic conditions might inform our general understanding of AAV pathophysiology. We also propose some directions for future research in order to better define the link between ANCA and IEI. Finally, we will consider how making the diagnosis of an IEI in a patient with AAV features might impact individual management.

Mitochondrial DNA signals driving immune responses: Why, How, Where?

There has been a recent expansion in our understanding of DNA-sensing mechanisms. Mitochondrial dysfunction, oxidative and proteostatic stresses, instability and impaired disposal of nucleoids cause the release of mitochondrial DNA (mtDNA) from the mitochondria in several human diseases, as well as in cell culture and animal models. Mitochondrial DNA mislocalized to the cytosol and/or the extracellular compartments can trigger innate immune and inflammation responses by binding DNA-sensing receptors (DSRs). Here, we define the features that make mtDNA highly immunogenic and the mechanisms of its release from the mitochondria into the cytosol and the extracellular compartments. We describe the major DSRs that bind mtDNA such as cyclic guanosine-monophosphate-adenosine-monophosphate synthase (cGAS), Z-DNA-binding protein 1 (ZBP1), NOD-, LRR-, and PYD- domain-containing protein 3 receptor (NLRP3), absent in melanoma 2 (AIM2) and toll-like receptor 9 (TLR9), and their downstream signaling cascades. We summarize the key findings, novelties, and gaps of mislocalized mtDNA as a driving signal of immune responses in vascular, metabolic, kidney, lung, and neurodegenerative diseases, as well as viral and bacterial infections. Finally, we define common strategies to induce or inhibit mtDNA release and propose challenges to advance the field.

Genetic deficiency or pharmacological inhibition of cGAS-STING signalling suppresses kidney inflammation and fibrosis

BACKGROUND AND PURPOSE

Chronic kidney disease (CKD) is characterised by inflammation, which can lead to tubular atrophy and fibrosis. The molecular mechanisms are not well understood. In this study, we investigated the functional role of the cyclic GMP-AMP synthase (cGAS)- stimulator of interferon genes (STING) signalling in renal inflammation and fibrosis.

EXPERIMENTAL APPROACH

Mice with global cGAS deficiency or global or myeloid cell-specific STING deficiency or wild-type mice treated with RU.521, a selective cGAS inhibitor, were used to examine the role of cGAS-STING signalling in renal inflammation and fibrosis in a preclinical model of obstructive nephropathy in vivo. Bone marrow-derived macrophages were used to determine whether tubular epithelial cell-derived DNA can activate cGAS-STING signalling in vitro.

KEY RESULTS

Following obstructive injury, cGAS-STING signalling was activated in the kidneys during the development of renal fibrosis. Mice with deficiency of cGAS or STING exhibited significantly less macrophage proinflammatory activation, myofibroblast formation, total collagen deposition, and extracellular matrix (ECM) protein production in the kidneys following obstructive injury. Pharmacological inhibition of cGAS with RU.521 reduced macrophage proinflammatory activation, suppressed myofibroblast formation, and attenuated kidney fibrosis following obstructive injury. Mechanistically, cGAS-STING signalling in macrophages is activated by double-stranded DNA released from damaged tubular epithelial cells, which induces inflammatory responses.

CONCLUSIONS AND IMPLICATIONS

Our study identifies the cGAS-STING signalling pathway as a critical regulator of macrophage proinflammatory activation during the development of renal fibrosis. Therefore, inhibition of cGAS-STING signalling may represent a novel therapeutic strategy for CKD.

CircHOMER1 promotes silica-induced pulmonary fibrosis by binding to HuR and stabilizing NOX4 mRNA

BACKGROUND

Silicosis, one of the serious occupational diseases, is mainly manifested by pulmonary fibrosis induced by long-term exposure to silica particles in workplace. Evidence demonstrates that circular RNAs (circRNAs) are interesting regulators of pulmonary fibrosis process. So, further elucidation of the role of circRNAs may provide a new perspective into mechanisms driving pulmonary fibrosis and silicosis.

METHODS

The characteristics of circRNA homer scaffold protein 1 (hsa_circ_0006916, circHOMER1) was assessed using Actinomycin D, RNase R, and nucleoplasmic separation assay. The histopathological examination and Enzyme-linked immunosorbent assay (ELISA) were used to confirm circHOMER1 function in mouse lung tissues under silica particle exposure. The expression of circHOMER1, human antigen R (HuR) and NADPH oxidase 4 (NOX4) was identified by western blot or RT-qPCR assay. The RNA immunoprecipitation (RIP) assay and plasmid co-transfection were used to analyze the interaction between circHOMER1, HuR and NOX4.

RESULTS

We confirmed an upregulated circHOMER1 in silicosis fibrosis. Functional assays showed that the knockdown of circHOMER1 suppressed the viability of fibroblasts and the production of fibrotic molecules and alleviated the histology fibrotic changes in lung tissues from mouse exposed to silica particles. Mechanistically, we found that circHOMER1 directly bound to HuR and promoted its protein expression in fibroblasts. And, circHOMER1 further regulated HuR/NOX4 signaling axis through HuR to stabilize NOX4 mRNA, which enhanced the production of reactive oxygen species (ROS), thereby promoting the silicosis fibrosis process.

CONCLUSION

This study revealed the role of circHOMER1 in silica-induced pulmonary fibrosis, suggesting that the inhibition of circHOMER1 may be a potential therapeutic approach to relieve the pathological process of silicosis.

NLRP3 deficiency abrogates silica-induced neutrophil infiltration, pulmonary damage and fibrosis

BACKGROUND

Silicosis is a progressive and often fatal occupational lung disease. The NLRP3 inflammasome is an innate immune sensor that is activated by silica. Accumulating evidence has implicated a role for NLRP3 in silicosis pathogenesis. In this study, we mechanistically elucidated the contribution of NLRP3 to silica-induced pulmonary disease.

METHODS

The in vivo role of NLRP3 was investigated following intranasal delivery of 2 mg of silica or diluent alone to wildtype, NLRP3 reporter, and NLRP3-deficient mice. Protein expression, inflammation, and histopathology were analyzed in the lung.

RESULTS

Intranasal administration of silica recapitulated the key pathological features of human silicosis, including nonresolving inflammation, the formation of silicotic nodules, and diffuse lung fibrosis. A reporter mouse placed under the native NLRP3 promoter revealed silica rapidly upregulated NLRP3 expression throughout the lung. NLRP3-deficient mice displayed marked early reductions in silica-induced IL-1β and IL-18 levels in the airways. Additionally, NLRP3 deficiency impaired the rapid infiltration of conventional Siglec-F- and fibrotic Siglec-F+ neutrophils, which correlated with reduced levels of neutrophil elastase. Deficiency in acute NLRP3-mediated inflammation correlated with significantly reduced pulmonary transforming growth factor beta and alpha smooth muscle actin expression, tissue damage, and fibrosis in the chronic phase of disease progression. Importantly, this included reduced silicotic nodule size and cellularity.

CONCLUSIONS

These findings highlight a major detrimental role for the NLRP3 inflammasome in driving silica-induced pulmonary neutrophil infiltration, TGFβ-mediated myofibroblast activation, tissue damage, and fibrosis.

Silica-induced ferroptosis activates retinoic acid signaling in dendritic cells to drive inflammation and fibrosis in silicosis

Silicosis, a chronic lung disease caused by inhalation of silica (SiO2) particles from environmental contamination or industrial exposure, is characterized by persistent inflammation and fibrosis. This study elucidates a novel mechanism where SiO2 exposure triggers ferroptosis, a lipid peroxidation-dependent form of cell death, in dendritic cells (DCs), thereby activating retinoic acid (RA) signaling. The RA response amplifies inflammatory pathways, including cGAS-STING-IFN-I and IL-1β signaling, exacerbating lung inflammation and fibrosis. The study uses murine models to demonstrate that ferroptosis inhibitors, such as ferrostatin-1, mitigate SiO2-induced inflammation and collagen deposition. Furthermore, systemic administration of the synthetic retinoid AM80 reduces pulmonary damage by modulating immune cell distribution and promoting lymphocyte homing. These findings reveal the interplay between ferroptosis and RA signaling as a pivotal driver of silicosis pathology and suggest therapeutic avenues targeting ferroptosis and RA modulation for disease management.

cGAS-STING mediates neutrophil extracellular traps-induced EMT in myositis-associated interstitial lung disease: STING as a potential therapeutic target

OBJECTIVE

Neutrophil extracellular traps (NETs) play crucial roles in idiopathic inflammatory myositis-associated interstitial lung disease (IIM-ILD) pathogenesis. The involvement and mechanism of alveolar epithelial cells in the pathogenesis of IIM-ILD remain unclear. This study aimed to clarify the hypothesis that NETs promote alveolar epithelial-mesenchymal transition (EMT), which contributes to IIM-ILD.

METHODS

Lung biopsy puncture tissue from three IIM-ILD patients was used for pathological analysis. An experimental mouse model of autoimmune myositis with ILD (EAM-ILD) was used for mechanism validation in vivo. A549 cells were treated with NETs and assessed using Western blotting, immunofluorescence, and RNA sequencing techniques. STING inhibitors were employed to assess the efficacy of stimulator of interferon gene (STING) as a therapeutic target for EAM-ILD.

RESULT

There was a marked EMT and the activation of cGAS-STING pathway found in the lung samples of IIM-ILD patients (N = 3) and in A549 cells in vitro (P < 0.05). RNA sequencing indicates that NETs induce an upregulation of inflammation and fibrosis-related pathways in A549 cells, with high expression of the STING-related pathway. The STING inhibitor can prevent EMT in alveolar epithelial cells both in vivo and in vitro, and reduce the inflammatory response in the lung tissue of the EAM-ILD mouse (P < 0.05).

CONCLUSION

These in vitro and ex vivo experiments demonstrate that NETs promote EAM-ILD by inducing EMT in alveolar epithelial cells and that the cGAS-STING signaling pathway is one of the potential mechanisms of action. Targeting STING is a potential therapeutic strategy for treating IIM-ILD.

cGAS/STING pathway modulation in polyhexamethyleneguanidine phosphate-induced immune dysregulation and pulmonary fibrosis using human monocytic cells (THP-1) and male C57BL/6 mice

Polyhexamethyleneguanidine phosphate (PHMG), a widely used antimicrobial agent, has been implicated in humidifier disinfectant-associated lung injuries (HDLI). PHMG exposure suppressed interferon regulatory factor 3 (IRF3) activation and interferon-β (IFN-β) expression induced by a cGAS agonist or a STING agonist in human monocytic cells (THP-1), which are known to transition to alveolar macrophages during pulmonary fibrosis development. However, the mechanisms underlying PHMG-induced pulmonary toxicity in lung remain unclear. Thus, it was of interest to investigate the effects of PHMG on the innate immune system in male C57BL/6 mouse, focusing on the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway and potential role in pulmonary fibrosis. Intratracheal administration of PHMG (1 or 2 mg/kg) in mice resulted in lung fibrosis, as evidenced by H&E staining with Szapiel scoring, Masson's trichrome staining with Ashcroft scoring, and increased mRNA levels of TGF-β and collagen type I. Interestingly, lower dose of PHMG enhanced IFN-β production in the lungs, whereas higher dose decreased IFN-β levels, indicating a biphasic effect that initially promotes inflammation but ultimately impairs host defense mechanisms, leading to pulmonary fibrosis. Our findings demonstrate the critical role of the cGAS/STING pathway in PHMG-induced mouse lung injury and suggest that targeting this pathway might serve as a potential therapeutic strategy for treating pulmonary fibrosis.

Engineering the physical characteristics of biomaterials for innate immune-mediated cancer immunotherapy

It has recently been recognized that the physical characteristics of biomaterials - such as size, structure, shape, charge, mechanical strength, hydrophobicity, and multivalency - regulate immunological functions in innate immune cells. In immuno-oncology applications, biomaterials are engineered with distinct physical properties to achieve desired innate immune responses. In this review, we discuss how physical characteristics influence effector functions and innate immune signaling pathways in distinct innate immune cell subtypes. We highlight how physical properties of biomaterials impact phagocytosis regulation, biodistribution, and innate immune cell targeting. We outline the recent advances in physical engineering of biomaterials that directly or indirectly induce desired innate immune responses for cancer immunotherapy. Lastly, we discuss the challenges in current biomaterial approaches that need to be addressed to improve clinical applicability.

cGAS-STING targeting offers therapy choice in lung diseases

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

DKN-01 Suppresses Gastric Cancer Progression Through Activating cGAS-STING Pathway to Block Macrophage M2 Polarization

Dickkopf-1 (DKK1) is a secretory antagonist that can bind with the Wnt coreceptor to desensitize cells to canonical Wnt ligands. DKN-01 is a specific antibody targeting secreted DKK1, which has been investigated as a monotherapy or combination therapy for various malignant tumors, including gastric cancer (GC). Tumor-associated macrophages (TAMs) with high plasticity usually present M2 phenotype, which can promote tumor progression. The aim of this study was to investigate the effect of DKN-01 on macrophage polarization in GC and the underlying molecular mechanism. To ascertain the effect of DKN-01 on GC tumor growth, we established a tumor-bearing mouse model and found that DKN-01 treatment suppressed tumor growth efficiently. Through RNA-seq and pathway enrichment analysis, we identified that the differentially expressed genes after DKN-01 treatment are associated with tumor immune-related pathways. Macrophage polarization was assessed using immunohistochemistry and quantitative real-time polymerase chain reaction. DKN-01 and knockdown of DKK1 promoted M1 polarization and inhibited M2 polarization of macrophages, while DKK1 overexpression got the opposite results. Moreover, DKN-01 activated the cGAS/STING pathway, while the inactivation of cGAS-STING pathway using RU.521 reversed the inhibition of tumor growth in vivo and macrophage M2 polarization caused by DKN-01. This study reveals that DKN-01 suppresses GC tumor growth through activating cGAS-STING pathway to block macrophage M2 polarization.

A mechanistic review-regulation of silica-induced pulmonary inflammation by IL-10 and exacerbation by Type I IFN

Occupational exposure to crystalline silica (CS) is known to induce silicosis, a chronic lung disease characterized by the formation of granulomas and severe lung fibrosis. Specifically, individuals exposed to low doses of CS may develop silicosis after a decade or more of exposure. Similarly, in rat silicosis models exposed to occupationally relevant doses of α-quartz, there is an initial phase characterized by minimal and well-controlled pulmonary inflammation, followed by the development of robust and persistent inflammation. During the initial phase, the inflammation provoked by α-quartz is subdued by two mechanisms. Firstly, α-quartz particles are engulfed by alveolar macrophages (AMs) of the alternatively activated (M2) subtype and interstitial macrophages (IMs), limiting their interaction with other lung cells. Secondly, the anti-inflammatory cytokine, interleukin (IL)-10, is constitutively expressed by these macrophages, further dampening the inflammatory response. In the later inflammatory phase, IL-10-dependent anti-inflammatory state is disrupted by Type I interferons (IFNs), leading to the production of pro-inflammatory cytokines in response to α-quartz, aided by lipopolysaccharides (LPS). This review delves into the complex pathways involving IL-10, LPS, and Type I IFNs in α-quartz-induced pulmonary inflammation, offering a detailed analysis of the underlying mechanisms and identifying areas for future research.

Honokiol ameliorates silica-induced lung fibrosis by inhibiting macrophage pyroptosis via modulating cGAS/STING signaling

Silicosis is a life-threatening occupational disease because of inhaling silica dust, leading to chronic inflammation, pyroptosis, and fibrosis. Unfortunately, it is still lacking effective pharmacological intervention currently. Honokiol (HKL), a natural extract with biological activity from Magnolia bark, is known for its antioxidant and anti-inflammatory biological effects. The current work aimed to investigate the therapeutic potential of HKL in mitigating silica-induced lung fibrosis and pyroptosis, particularly focusing on the cGAS/STING signaling pathway. The pulmonary pathological results shown in H&E and Masson's trichrome staining images confirmed the protective effects of HKL on lung tissue structure. In addition, HKL significantly reduced lung inflammation, collagen deposition, and oxidative stress compared to mice in the silicosis group. HKL treatment also alleviated silica-induced pyroptosis by suppressing the activation of the cGAS/STING signaling pathway in lung tissues. Moreover, the in vitro experiments using J774A.1 macrophages demonstrated that HKL reduced pyroptosis and improved cell viability under exposure to silica combined lipopolysaccharide (LPS). These were attributed to HKL downregulating the activation of the cGAS/STING signaling pathway in pyroptotic J774A.1 cells induced by silica combined with LPS. Meanwhile, inhibition of STING signaling induced by DNase I significantly enhanced the protective effects of HKL on the inflammatory and pyroptotic processes induced by silica. Overall, HKL could attenuate silica-induced pyroptosis by modulating the cGAS/STING signaling pathway against pulmonary fibrosis. The current study offers a promising approach for treating silicosis and related inflammatory responses.

The role of cGAS-STING pathway in the development of radiation-induced lung injury

BACKGROUND AND PURPOSE

Radiation-induced lung injury (RILI) limits the efficacy of thoracic radiotherapy. However, the underlying mechanism of RILI remains unclear. cGAS-STING pathway is reported to be involved in the recognization of cytosolic dsDNA and various inflammatory diseases. This study aimed to investigate the role of cGAS-STING pathway in the development of RILI.

MATERIALS AND METHODS

A pre-clinical mouse model of RILI was established by whole thorax irradiation and confirmed using H&E and Masson's trichrome staining. STING agonist (DMXAA) and antagonist(C-176) were administrated to modulate cGAS-STING pathway in vivo. Western blot and ELISA were used to determine the expression levels of different proteins.

RESULTS

Quantitation analysis showed dsDNA accumulation in lung tissue and western blot showed the up-regulation of cGAS and STING protein level post-irradiation, indicating pathway activation. Histological evaluation showed that C-176 administration ameliorated radiation-induced pulmonary inflammation and fibrosis, while DMXAA exhibited contrary effects. In further in vitro study, the release of dsDNA induced by radiation led to the activation of cGAS-STING pathway in RAW 264.7 cells, resulting in the polarization into M1 phenotype and pro-inflammatory production.

CONCLUSION

In summary, our data demonstrated a link between cGAS-STING pathway and the development of RILI, indicating its potential application in clinic.

A comprehensive retrospect on the current perspectives and future prospects of pneumoconiosis

Pneumoconiosis is a widespread occupational pulmonary disease caused by inhalation and retention of dust particles in the lungs, is characterized by chronic pulmonary inflammation and progressive fibrosis, potentially leading to respiratory and/or heart failure. Workers exposed to dust, such as coal miners, foundry workers, and construction workers, are at risk of pneumoconiosis. This review synthesizes the international and national classifications, epidemiological characteristics, strategies for prevention, clinical manifestations, diagnosis, pathogenesis, and treatment of pneumoconiosis. Current research on the pathogenesis of pneumoconiosis focuses on the influence of autophagy, apoptosis, and pyroptosis on the progression of the disease. In addition, factors such as lipopolysaccharide and nicotine have been found to play crucial roles in the development of pneumoconiosis. This review provides a comprehensive summary of the most fundamental achievements in the treatment of pneumoconiosis with the purpose of indicating the future direction of its treatment and control. New technologies of integrative omics, artificial intelligence, systemic administration of mesenchymal stromal cells have proved useful in solving the conundrum of pneumoconiosis. These directional studies will provide novel therapeutic targets for the treatment of pneumoconiosis.

KAE ameliorates LPS-mediated acute lung injury by inhibiting PANoptosis through the intracellular DNA-cGAS-STING axis

Background

Acute lung injury (ALI) is a severe condition characterized by inflammation, tissue damage, and persistent activation of the cyclic GMP-AMP (cGAS)-stimulator of interferon genes (STING) pathway, which exacerbates the production of pro-inflammatory mediators and promotes the progression of ALI. Specific inhibition of this pathway has been shown to alleviate ALI symptoms. Kaempferol-3-O-α-L-(4″-E-p-coumaroyl)-rhamnoside (KAE), an active compound found in the flowers of Angelica acutiloba Kitagawa, exhibits anti-inflammatory and antioxidant properties. This study aimed to investigate the molecular mechanisms through which KAE regulates the cGAS-STING pathway in the context of ALI.

Methods

ALI was induced using LPS. Lung damage and anti-inflammatory/antioxidant effects were assessed by H&E staining, lung edema index, and SOD, MDA, and ELISA assays. NO release and mitochondrial membrane potential (MMP) were measured by JC-1 and Griess methods. The impact of KAE on the cGAS-STING pathway and PANoptosis was analyzed using flow cytometry, Western blot, and immunofluorescence.

Results

KAE significantly alleviated lipopolysaccharide-induced pulmonary injury by reducing inflammatory cell infiltration, alleviating pulmonary edema, enhancing antioxidant capacity, and decreasing levels of inflammatory cytokines in mouse lung tissues. In both in vitro and in vivo analyses, KAE downregulated the expression of key components of the cGAS-STING pathway, including cGAS, STING, p-TBK1, and nuclear factor-κB. KAE also reduced the assembly and activation of the PANoptosome, thereby attenuating apoptosis, necroptosis, and pyroptosis. Additionally, KAE inhibited cGAS activation by restoring the MMP, which reduced the release of cytosolic DNA.

Conclusion

KAE improve ALI by inhibiting the release of cytosolic DNA and suppressing cGAS-STING pathway activation, thereby protecting cells from PANoptosis. Our findings provide valuable insights for the development and application of novel therapeutic strategies for ALI.

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

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

Occupational and Hobby Exposures Associated With Myositis Phenotypes in a National Myositis Patient Registry

OBJECTIVE

The objective of this study was to investigate occupational and hobby exposures to silica, solvents, and heavy metals and the odds of having the idiopathic inflammatory myopathy (IIM) phenotypes dermatomyositis (DM) and polymyositis (PM) versus inclusion body myositis (IBM), lung disease plus fever or arthritis (LD+), and systemic autoimmune rheumatic disease-associated overlap myositis (OM).

METHODS

The sample included 1,390 patients (598 with DM, 409 with PM, and 383 with IBM) aged ≥18 years from a national registry. Of these, 218 (16%) were identified with LD+, and 166 (12%) with OM. Of these, 218 (16%) were identified with LD+, and 166 (12%) with OM. We calculated adjusted odds ratios (ORs) and 95% confidence intervals (CIs) and explored joint effects with smoking.

RESULTS

High silica exposure was associated with increased odds of having DM (OR 2.02, 95% CI 1.18-3.46, compared to no exposure; P trend = 0.004), LD+ (OR 1.75, 95% CI 1.10-2.78, vs no LD; P trend = 0.005), and OM (OR 2.07, 95% CI 1.19-3.61, P trend = 0.020). Moderate to high heavy metals exposure was associated with greater odds of having LD+ (OR 1.49, 95% CI 1.00-2.14, P trend = 0.026) and OM (OR 1.59, 95% CI 0.99-2.55, P trend = 0.051). Greater odds of having LD+ were seen among smokers with moderate to high silica exposure versus nonsmokers with low or no exposure (high-certainty assessment OR 2.53, 95% CI 1.31-4.90, P interaction = 0.061).

CONCLUSION

These findings, based on a systematic exposure assessment, suggest that occupational and hobby exposures to silica and heavy metals contribute to adult IIM phenotypes, including DM, OM, and LD+, a possible marker for antisynthetase syndrome or other autoantibody-associated lung diseases.

Fantastic proteins and where to find them - histones, in the nucleus and beyond

Animal genomes are packaged into chromatin, a highly dynamic macromolecular structure of DNA and histone proteins organised into nucleosomes. This accommodates packaging of lengthy genomic sequences within the physical confines of the nucleus while also enabling precise regulation of access to genetic information. However, histones existed before chromatin and have lesser-known functions beyond genome regulation. Most notably, histones are potent antimicrobial agents, and the release of chromatin to the extracellular space is a defence mechanism nearly as ancient and widespread as chromatin itself. Histone sequences have changed very little throughout evolution, suggesting the possibility that some of their 'non-canonical' functions are at play in parallel or in concert with their genome regulatory functions. In this Review, we take an evolutionary perspective of histone, nuclear chromatin and extracellular chromatin biology and describe the known extranuclear and extracellular functions of histones. We detail molecular mechanisms of chromatin release and extracellular chromatin sensing, and we discuss their roles in physiology and disease. Finally, we present evidence and give a perspective on the potential of extracellular histones to act as bioactive, cell modulatory factors.

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

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

Graphical abstract

Supplementary Information

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

Treating acute lung injury through scavenging of cell-free DNA by cationic nanoparticles

Acute lung injury (ALI) and acute respiratory distress syndrome are life-threatening conditions induced by inflammatory responses, in which cell-free DNA (cfDNA) plays a pivotal role. This study investigated the therapeutic potential of biodegradable cationic nanoparticles (cNPs) in alleviating ALI. Using a mouse model of lipopolysaccharide-induced ALI, we examined the impact of intravenously administered cNPs. Our findings indicate that cNPs possess robust DNA binding capability, enhanced accumulation in inflamed lungs, and a favorable safety profile in vivo. Furthermore, cNPs attenuate the inflammatory response in LPS-induced ALI mice by scavenging cfDNA, mainly derived from neutrophil extracellular traps, and activating the macrophage-mediated cGAS-STING pathway. The findings suggest a potential treatment for ALI by targeting cfDNA with cNPs. This approach has demonstrated efficacy in mitigating lung injury and merits further exploration.

Unexpected Inhibitory Role of Silica Nanoparticles on Lung Cancer Development by Promoting M1 Polarization of Macrophages

Introduction

Inhalation exposure to silica nanoparticles (SiNPs) is frequently inevitable in modern times. Although the impact of SiNPs on the ecological niche of the lungs has been extensively explored, the role and mechanism of SiNPs in the microenvironment of lung tumors remain elusive.

Methods

In this investigation, Lewis lung carcinoma (LLC) was implanted into the left lung in situ after 28 days of intratracheal SiNPs injection into the lungs of mice. This study evaluates the effects of SiNPs on the tumor immune microenvironment both in vitro and in vivo. Our findings indicate that SiNPs can suppress lung cancer by modulating the immune microenvironment of tumors.

Results

SiNPs treatment promotes macrophage M1 polarization by activating both NF-κB pathway and glycolytic mechanisms. This phenomenon may be associated with lung inflammation and fluctuation in the pre-metastatic and metastatic microenvironments induced by SiNPs exposure in mice. Additionally, we have shown for the first time that SiNPs have an inhibitory effect on lung carcinogenesis and its progression.

Conclusion

This study uniquely demonstrates that SiNPs suppress lung cancer by promoting M1 polarization of macrophages in the immune microenvironment of lung tumors. Our findings are critical in exploring the interaction between SiNPs and lung cancer.

Pulmonary fibrosis in patients with autoimmune pulmonary alveolar proteinosis: a retrospective nationwide cohort study

Background

Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare disease that may progress towards pulmonary fibrosis. Data about fibrosis prevalence and risk factors are lacking.

Methods

In this retrospective multicentre nationwide cohort, we included patients newly diagnosed with aPAP between 2008 and 2018 in France and Belgium. Data were collected from medical records using a standardised questionnaire.

Results

61 patients were included in the final analysis. We identified 5 patients (8%) with fibrosis on initial computed tomography (CT) and 16 patients (26%) with fibrosis on final CT after a median time of 3.6 years. Dust exposure was associated with pulmonary fibrosis occurrence (OR 4.3; p=0.038). aPAP patients treated with whole-lung lavage, rituximab or granulocyte-monocyte colony-stimulating factor therapy did not have more fibrotic evolution than patients who did not receive these treatments (n=25 out of 45, 57% versus n=10 out of 16, 62%; p=0.69). All-cause mortality was significantly higher in fibrotic than in nonfibrotic cases (n=4 out of 16, 25% versus n=2 out of 45, 4.4%; p=0.036, respectively).

Conclusion

In our population, a quarter of aPAP patients progressed towards pulmonary fibrosis. Dust exposure seems to be an important factor associated with this complication. More studies are needed to analyse precisely the impact of dust exposure impact, especially silica, in patients with aPAP.

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

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

Review of Excessive Cytosolic DNA and Its Role in AIM2 and cGAS-STING Mediated Psoriasis Development

In psoriasis, keratinocytes are triggered by factors, such as infection or tissue damage, to release DNA, which thereby activates plasmacytoid dendritic cells and macrophages to induce inflammation, thickened epidermis, and parakeratosis. The recognition of double-stranded (ds)DNA facilitates the activation of cytoplasmic DNA sensors absent in melanoma 2 (AIM2) inflammasome assembly and cyclic guanosine monophosphate adenosine monophosphate (cGAMP) synthase (cGAS) - stimulator of interferon gene (STING) pathway, both of which play a pivotal role in mediating the inflammatory response and driving the progression of psoriasis. Additionally, secreted proinflammatory cytokines can stimulate further DNA release from keratinocytes. Notably, the activation of AIM2 and cGAS-STING signaling pathways also mediates programmed cell death, potentially enhancing DNA overproduction. As a result, excessive DNA can activate these pathways, amplifying persistent inflammatory responses that contribute to the maintenance of psoriasis. Several studies have validated that targeting DNA and its mediated activation of AIM2 and cGAS-STING offers promising therapeutic strategies for psoriasis. Here, we postulate a hypothesis that excessive cytosolic DNA can activate AIM2 and cGAS-STING, mediating inflammation and programmed cell death, ultimately fostering DNA accumulation and contributing to the development of psoriasis.

Nasal instillation of polystyrene nanoplastics induce lung injury via mitochondrial DNA release and activation of the cyclic GMP-AMP synthase-stimulator of interferon genes-signaling cascade

Nanoplastics (NPs) are a common type of degraded plastic material associated with adverse health effects such as pulmonary injury. However, the molecular mechanism(s) underlying lung injury as caused by NPs remains uncertain. Thus, we herein investigated the pulmonary toxicity of NPs on RAW264.7 cells and C57BL/6 mice. Our in vitro study indicated that NPs induced oxidative stress, cell death, inflammation, and the activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)-signaling pathway. Mice in our in vivo study displayed significant pulmonary fibrosis, inflammation, apoptosis, necrosis, and excessive double-stranded DNA release into serum and bronchoalveolar lavage fluid. Our mechanistic exploration uncovered cGAS-STING-signaling activation as the leading cause of NPs-induced pulmonary fibrosis. The current study opens an avenue toward elucidating the role of the cGAS-STING-signaling pathway in NPs-induced pulmonary injury.

Postinfectious Pulmonary Complications: Establishing Research Priorities to Advance the Field: An Official American Thoracic Society Workshop Report

Continued improvements in the treatment of pulmonary infections have paradoxically resulted in a growing challenge of individuals with postinfectious pulmonary complications (PIPCs). PIPCs have been long recognized after tuberculosis, but recent experiences such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic have underscored the importance of PIPCs following other lower respiratory tract infections. Independent of the causative pathogen, most available studies of pulmonary infections focus on short-term outcomes rather than long-term morbidity among survivors. In this document, we establish a conceptual scope for PIPCs with discussion of globally significant pulmonary pathogens and an examination of how these pathogens can damage different components of the lung, resulting in a spectrum of PIPCs. We also review potential mechanisms for the transition from acute infection to PIPC, including the interplay between pathogen-mediated injury and aberrant host responses, which together result in PIPCs. Finally, we identify cross-cutting research priorities for the field to facilitate future studies to establish the incidence of PIPCs, define common mechanisms, identify therapeutic strategies, and ultimately reduce the burden of morbidity in survivors of pulmonary infections.

The glycyl-l-histidyl-l-lysine-Cu2+ tripeptide complex attenuates lung inflammation and fibrosis in silicosis by targeting peroxiredoxin 6

Silicosis is the most common type of pneumoconiosis, having a high incidence in workers chronically exposed to crystalline silica (CS). No specific medication exists for this condition. GHK, a tripeptide naturally occurring in human blood and urine, has antioxidant effects. We aimed to investigate the therapeutic effect of GHK-Cu on silicosis and its potential underlying molecular mechanism. An experimental silicosis mouse model was established to observe the effects of GHK-Cu on lung inflammation and fibrosis. Moreover, the effects of GHK-Cu on the alveolar macrophages (AM) were examined using the RAW264.7 cell line. Its molecular target, peroxiredoxin 6 (PRDX6), has been identified, and GHK-Cu can bind to PRDX6, thus attenuating lung inflammation and fibrosis in silicosis mice without significant systemic toxicity. These effects were partly related to the inhibition of the CS-induced oxidative stress in AM induced by GHK-Cu. Thus, our results suggest that GHK-Cu acts as a potential drug by attenuating alveolar macrophage oxidative stress. This, in turn, attenuates the progression of pulmonary inflammation and fibrosis, which provides a reference for the treatment of silicosis.

mtDNA amplifies beryllium sulfate-induced inflammatory responses via the cGAS-STING pathway in 16HBE cells

Beryllium sulfate (BeSO4) can cause inflammation through the mechanism, which has not been elucidated. Mitochondrial DNA (mtDNA) is a key contributor of inflammation. With mitochondrial damage, released mtDNA can bind to specific receptors (e.g., cGAS) and then activate related pathway to promote inflammatory responses. To investigate the mechanism of mtDNA in BeSO4-induced inflammatory response in 16HBE cells, we established the BeSO4-induced 16HBE cell inflammation model and the ethidium bromide (EB)-induced ρ016HBE cell model to detect the mtDNA content, oxidative stress-related markers, mitochondrial membrane potential, the expression of the cGAS-STING pathway, and inflammation-related factors. Our results showed that BeSO4 caused oxidative stress, decline of mitochondrial membrane potential, and the release of mtDNA into the cytoplasm of 16HBE cells. In addition, BeSO4 induced inflammation in 16HBE cells by activating the cGAS-STING pathway. Furthermore, mtDNA deletion inhibited the expression of cGAS-STING pathway, IL-10, TNF-α, and IFN-β. This study revealed a novel mechanism of BeSO4-induced inflammation in 16HBE cells, which contributes to the understanding of the molecular mechanism of beryllium and its compounds-induced toxicity.

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

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

Activation of Sirtuin3 by honokiol ameliorates alveolar epithelial cell senescence in experimental silicosis via the cGAS-STING pathway

BACKGROUND

Silicosis, characterized by interstitial lung inflammation and fibrosis, poses a significant health threat. ATII cells play a crucial role in alveolar epithelial repair and structural integrity maintenance. Inhibiting ATII cell senescence has shown promise in silicosis treatment. However, the mechanism behind silica-induced senescence remains elusive.

METHODS

The study employed male C57BL/6 N mice and A549 human alveolar epithelial cells to investigate silicosis and its potential treatment. Silicosis was induced in mice via intratracheal instillation of crystalline silica particles, with honokiol administered intraperitoneally for 14 days. Silica-induced senescence in A549 cells was confirmed, and SIRT3 knockout and overexpression cell lines were generated. Various analyses were conducted, including immunoblotting, qRT-PCR, histology, and transmission electron microscopy. Statistical significance was determined using one-way ANOVA with Tukey's post-hoc test.

RESULTS

This study elucidates how silica induces ATII cell senescence, emphasizing mtDNA damage. Notably, honokiol (HKL) emerges as a promising anti-senescence and anti-fibrosis agent, acting through sirt3. honokiol effectively attenuated senescence in ATII cells, dependent on sirt3 expression, while mitigating mtDNA damage. Sirt3, a class III histone deacetylase, regulates senescence and mitochondrial stress. HKL activates sirt3, protecting against pulmonary fibrosis and mitochondrial damage. Additionally, HKL downregulated cGAS expression in senescent ATII cells induced by silica, suggesting sirt3's role as an upstream regulator of the cGAS/STING signaling pathway. Moreover, honokiol treatment inhibited the activation of the NF-κB signaling pathway, associated with reduced oxidative stress and mtDNA damage. Notably, HKL enhanced the activity of SOD2, crucial for mitochondrial function, through sirt3-mediated deacetylation. Additionally, HKL promoted the deacetylation activity of sirt3, further safeguarding mtDNA integrity.

CONCLUSIONS

This study uncovers a natural compound, HKL, with significant anti-fibrotic properties through activating sirt3, shedding light on silicosis pathogenesis and treatment avenues.

The effects of cGAS-STING inhibition in liver disease, kidney disease, and cellular senescence

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway is one of the fundamental mechanisms of the body's defense, which responds to the abnormal presence of double-stranded DNA in the cytoplasm to establish an effective natural immune response. In addition to detecting microbial infections, the cGAS pathway may be triggered by any cytoplasmic DNA, which is absent from the normal cytoplasm, and only conditions such as senescence and mitochondrial stress can lead to its leakage and cause sterile inflammation. A growing body of research has shown that the cGAS-STING pathway is strongly associated with sterile inflammation. In this study, we reviewed the regulatory mechanisms and biological functions of the cGAS-STING pathway through its involvement in aseptic inflammation in liver disease, kidney disease, and cellular senescence.

Systemic sclerosis, silica exposure and cellular therapies: The sand in the gears?

Systemic sclerosis (SSc) is a chronic orphan autoimmune disease with the highest mortality rate among rheumatic diseases. SSc-related interstitial-lung disease (ILD) remains among the leading causes of SSc-related mortality with still few therapeutic effective strategies. In patients with crystallin silica exposure, SSc is recognized as an occupational disease according to the French social security system (Table 25A of the general insurance regimen). Lympho-ablative or myeloablative immunosuppression followed by autologous hematopoietic stem-cell transplantation (aHSCT) is the only therapeutic approach with demonstrated efficacy, improved survival with disease modifying effects on SSc-fibrotic manifestations (skin disease and ILD) and quality of life. A documented past and/or present occupational silica exposure, with extensive exposure and/or silica-related ILD and/or with persistent silica content in the broncho-alveolar lavage fluid are contra-indications to aHSCT in SSc patients, due to the risk of silica-related malignancy or of SSc relapse. This article aims to discuss alternative options in SSc patients with a history of silica exposure, and how innovative cellular therapies (mesenchymal stromal cells, CAR cells) could represent new therapeutic options for these patients.

The value of single biomarkers in the diagnosis of silicosis: A meta-analysis

This study aims to establish a scientific foundation for early detection and diagnosis of silicosis by conducting meta-analysis on the role of single biomarkers in independent diagnosis. The combined sensitivity (Sen), specificity (Spe), positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic score, and diagnostic odds ratio (DOR) were 0.84 (95% confidence interval (CI): 0.77-0.90), 0.83 (95% CI: 0.78-0.88), 5.08 (95% CI: 3.92-6.59), 0.19 (95% CI: 0.13-0.27), 3.31 (95% CI: 2.88-3.74) and 27.29 (95% CI: 17.77-41.91), respectively. The area under the curve (AUC) was 0.90 (95% CI: 0.88-0.93). The Fagan plot shows a positive posterior probability of 82% and a negative posterior probability of 15%. This study establishes an academic basis for the swift identification, mitigation, and control of silicosis through scientific approaches. The assessed biomarkers offer precision and dependability in silicosis diagnosis, opening novel paths for early detection and intervention, thereby mitigating the disease burden associated with silicosis.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Pharmacological potential of cyclic nucleotide signaling in immunity

Cyclic nucleotides are important signaling molecules that play many critical physiological roles including controlling cell fate and development, regulation of metabolic processes, and responding to changes in the environment. Cyclic nucleotides are also pivotal regulators in immune signaling, orchestrating intricate processes that maintain homeostasis and defend against pathogenic threats. This review provides a comprehensive examination of the pharmacological potential of cyclic nucleotide signaling pathways within the realm of immunity. Beginning with an overview of the fundamental roles of cAMP and cGMP as ubiquitous second messengers, this review delves into the complexities of their involvement in immune responses. Special attention is given to the challenges associated with modulating these signaling pathways for therapeutic purposes, emphasizing the necessity for achieving cell-type specificity to avert unintended consequences. A major focus of the review is on the recent paradigm-shifting discoveries regarding specialized cyclic nucleotide signals in the innate immune system, notably the cGAS-STING pathway. The significance of cyclic dinucleotides, exemplified by 2'3'-cGAMP, in controlling immune responses against pathogens and cancer, is explored. The evolutionarily conserved nature of cyclic dinucleotides as antiviral agents, spanning across diverse organisms, underscores their potential as targets for innovative immunotherapies. Findings from the last several years have revealed a striking diversity of novel bacterial cyclic nucleotide second messengers which are involved in antiviral responses. Knowledge of the existence and precise identity of these molecules coupled with accurate descriptions of their associated immune defense pathways will be essential to the future development of novel antibacterial therapeutic strategies. The insights presented herein may help researchers navigate the evolving landscape of immunopharmacology as it pertains to cyclic nucleotides and point toward new avenues or lines of thinking about development of therapeutics against the pathways they regulate.

Qingfei xieding prescription ameliorates mitochondrial DNA-initiated inflammation in bleomycin-induced pulmonary fibrosis through activating autophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Qingfei Xieding prescription was gradually refined and produced by Hangzhou Red Cross Hospital. The raw material includes Ephedra sinica Stapf, Morus alba L., Bombyx Batryticatus, Gypsum Fibrosum, Prunus armeniaca L. var. ansu Maxim., Houttuynia cordata Thunb. , Pueraria edulis Pamp. Paeonia L., Scutellaria baicalensis Georgi and Anemarrhena asphodeloides Bge. It is effective in clinical adjuvant treatment of patients with pulmonary diseases.

AIM OF THE STUDY

To explore the efficacy and underlying mechanism of Qingfei Xieding (QF) in the treatment of bleomycin-induced mouse model.

MATERIALS AND METHODS

TGF-β induced fibrotic phenotype in vitro. Bleomycin injection induced lung tissue fibrosis mouse model in vivo. Flow cytometry was used to detect apoptosis, cellular ROS and lipid oxidation. Mitochondria substructure was observed by transmission electron microscopy. Autophagolysosome and nuclear entry of P65 were monitored by immunofluorescence. Quantitative real-time PCR was performed to detect the transcription of genes associated with mtDNA-cGAS-STING pathway and subsequent inflammatory signaling activation.

RESULTS

TGF-β induced the expression of α-SMA and Collagen I, inhibited cell viability in lung epithelial MLE-12 cells that was reversed by QF-containing serum. TGF-β-mediated downregulation in autophagy, upregulation in lipid oxidation and ROS contents, and mitochondrial damage were rescued by QF-containing serum treatment, but CQ exposure, an autophagy inhibitor, prevented the protective role of QF. In addition to that, the decreased autophagolysosome in TGF-β-exposed MLE-12 cells was reversed by QF and restored to low level in the combination treatment of QF and CQ. Mechanistically, QF-containing serum treatment significantly inhibited mtDNA-cGAS-STING pathway and subsequent inflammatory signaling in TGF-β-challenged cells, which were abolished by CQ-mediated autophagy inhibition. In bleomycin-induced mouse model, QF ameliorated pulmonary fibrosis, reduced mortality, re-activated autophagy in lung tissues and restrained mtDNA-cGAS-STING inflammation pathway. However, the protective effects of QF in bleomycin-induced model mice were also abrogated by CQ.

CONCLUSION

QF alleviated bleomycin-induced pulmonary fibrosis by activating autophagy, inhibiting mtDNA-cGAS-STING pathway-mediated inflammation. This research recognizes the protection role of QF on bleomycin-induced mouse model, and offers evidence for the potentiality of QF in clinical application for pulmonary fibrosis treatment.

The aging lung: microenvironment, mechanisms, and diseases

With the development of global social economy and the deepening of the aging population, diseases related to aging have received increasing attention. The pathogenesis of many respiratory diseases remains unclear, and lung aging is an independent risk factor for respiratory diseases. The aging mechanism of the lung may be involved in the occurrence and development of respiratory diseases. Aging-induced immune, oxidative stress, inflammation, and telomere changes can directly induce and promote the occurrence and development of lung aging. Meanwhile, the occurrence of lung aging also further aggravates the immune stress and inflammatory response of respiratory diseases; the two mutually affect each other and promote the development of respiratory diseases. Explaining the mechanism and treatment direction of these respiratory diseases from the perspective of lung aging will be a new idea and research field. This review summarizes the changes in pulmonary microenvironment, metabolic mechanisms, and the progression of respiratory diseases associated with aging.

Mitochondrial (mt)DNA-cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling promotes pyroptosis of macrophages via interferon regulatory factor (IRF)7/IRF3 activation to aggravate lung injury during severe acute pancreatitis

BACKGROUND

Macrophage proinflammatory activation contributes to the pathology of severe acute pancreatitis (SAP) and, simultaneously, macrophage functional changes, and increased pyroptosis/necrosis can further exacerbate the cellular immune suppression during the process of SAP, where cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) plays an important role. However, the function and mechanism of cGAS-STING in SAP-induced lung injury (LI) remains unknown.

METHODS

Lipopolysaccharide (LPS) was combined with caerulein-induced SAP in wild type, cGAS -/- and sting -/- mice. Primary macrophages were extracted via bronchoalveolar lavage and peritoneal lavage. Ana-1 cells were pretreated with LPS and stimulated with nigericin sodium salt to induce pyroptosis in vitro.

RESULTS

SAP triggered NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome activation-mediated pyroptosis of alveolar and peritoneal macrophages in mouse model. Knockout of cGAS/STING could ameliorate NLRP3 activation and macrophage pyroptosis. In addition, mitochondrial (mt)DNA released from damaged mitochondria further induced macrophage STING activation in a cGAS- and dose-dependent manner. Upregulated STING signal can promote NLRP3 inflammasome-mediated macrophage pyroptosis and increase serum interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α levels and, thus, exacerbate SAP-associated LI (SAP-ALI). Downstream molecules of STING, IRF7, and IRF3 connect the mtDNA-cGAS-STING axis and the NLRP3-pyroptosis axis.

CONCLUSIONS

Negative regulation of any molecule in the mtDNA-cGAS-STING-IRF7/IRF3 pathway can affect the activation of NLRP3 inflammasomes, thereby reducing macrophage pyroptosis and improving SAP-ALI in mouse model.

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.

Exposure to polystyrene nanoplastics induces abnormal activation of innate immunity via the cGAS-STING pathway

Endogenous immune defenses provide an intrinsic barrier against external entity invasion. Microplastics in the environment, especially those at the nanoscale (nanoplastics or NPs), may pose latent health risks through direct exposure. While links between nanoplastics and inflammatory processes have been established, detailed insights into how they may perturb the innate immune mechanisms remain uncharted. Employing murine and macrophage (RAW264.7) cellular models subjected to polystyrene nanoplastics (PS-NPs), our investigative approach encompassed an array of techniques: Cell Counting Kit-8 assays, flow cytometric analysis, acridine orange/ethidium bromide (AO/EB) fluorescence staining, cell transfection, cell cycle scrutiny, genetic manipulation, messenger RNA expression profiling via quantitative real-time PCR, and protein expression evaluation through western blotting. The results showed that PS-NPs caused RAW264.7 cell apoptosis, leading to cell cycle arrest, and activated the cGAS-STING pathway. This resulted in NF-κB signaling activation and increased pro-inflammatory mediator expression. Importantly, PS-NPs-induced activation of NF-κB and its downstream inflammatory cascade were markedly diminished after the silencing of the STING gene. Our findings highlight the critical role of the cGAS-STING pathway in the immunotoxic effects induced by PS-NPs. We outline a new mechanism whereby nanoplastics may trigger dysregulated innate immune and inflammatory responses via the cGAS/STING pathway.

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.

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.

The role of inflammation in silicosis

Silicosis is a chronic illness marked by diffuse fibrosis in lung tissue resulting from continuous exposure to SiO2-rich dust in the workplace. The onset and progression of silicosis is a complicated and poorly understood pathological process involving numerous cells and molecules. However, silicosis poses a severe threat to public health in developing countries, where it is the most prevalent occupational disease. There is convincing evidence supporting that innate and adaptive immune cells, as well as their cytokines, play a significant role in the development of silicosis. In this review, we describe the roles of immune cells and cytokines in silicosis, and summarize current knowledge on several important inflammatory signaling pathways associated with the disease, aiming to provide novel targets and strategies for the treatment of silicosis-related inflammation.

Mediation of PM2.5-induced cytotoxicity: the role of P2X7 receptor in NR8383 cells

Ambient fine particulate matter (PM2.5) is a threat to public health. The P2 X 7purinergic receptor (P2X7R) is a modulator that responds to inflammation. Yet the role of P2X7R in the mediation of PM2.5-induced pulmonary cytotoxicity is rarely investigated. In this study, the expression of P2X7R and its effect on cell viability, oxidative damage, apoptosis, mitochondrial dysfunction and underlying mechanism following PM2.5 treatment in rat alveolar macrophages (NR8383) were analyzed. The outcome indicated that PM2.5 exposure significantly increased the expression of P2X7R, while P2X7R antagonist oATP markedly alleviate the production of reactive oxygen species (ROS), Nitrite Oxidation (NO), mitochondrial membrane potential, apoptosis rate, and release of inflammatory cytokines. In contrast, P2X7 agonist BzATP showed opposite effect in PM2.5-treated NR8383 cells. Therefore, these results demonstrated that P2X7R participated in PM2.5-induced pulmonary toxicity, while the blockade of P2X7R is a promising therapeutic approach of treating PM2.5-induced lung diseases.

Results from omic approaches in rat or mouse models exposed to inhaled crystalline silica: a systematic review

BACKGROUND

Crystalline silica (cSiO2) is a mineral found in rocks; workers from the construction or denim industries are particularly exposed to cSiO2 through inhalation. cSiO2 inhalation increases the risk of silicosis and systemic autoimmune diseases. Inhaled cSiO2 microparticles can reach the alveoli where they induce inflammation, cell death, auto-immunity and fibrosis but the specific molecular pathways involved in these cSiO2 effects remain unclear. This systematic review aims to provide a comprehensive state of the art on omic approaches and exposure models used to study the effects of inhaled cSiO2 in mice and rats and to highlight key results from omic data in rodents also validated in human.

METHODS

The protocol of systematic review follows PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Eligible articles were identified in PubMed, Embase and Web of Science. The search strategy included original articles published after 1990 and written in English which included mouse or rat models exposed to cSiO2 and utilized omic approaches to identify pathways modulated by cSiO2. Data were extracted and quality assessment was based on the SYRCLE's Risk of Bias tool for animal studies.

RESULTS

Rats and male rodents were the more used models while female rodents and autoimmune prone models were less studied. Exposure of animals were both acute and chronic and the timing of outcome measurement through omics approaches were homogeneously distributed. Transcriptomic techniques were more commonly performed while proteomic, metabolomic and single-cell omic methods were less utilized. Immunity and inflammation were the main domains modified by cSiO2 exposure in lungs of mice and rats. Less than 20% of the results obtained in rodents were finally verified in humans.

CONCLUSION

Omic technics offer new insights on the effects of cSiO2 exposure in mice and rats although the majority of data still need to be validated in humans. Autoimmune prone model should be better characterised and systemic effects of cSiO2 need to be further studied to better understand cSiO2-induced autoimmunity. Single-cell omics should be performed to inform on pathological processes induced by cSiO2 exposure.