DNA from macrophages induces fibrosis and vasculopathy through POLR3A/STING/type I interferon axis in systemic sclerosis

Association of serum interferon alpha-2a levels with disease severity and prognosis in systemic sclerosis

OBJECTIVE

To determine serum type I IFN (IFN-α2a) concentrations in SSc patients, explore its association with cytokine/chemokine expressions and evaluate correlation with the phenotype including the predictive value for interstitial lung disease (ILD) progression.

METHODS

Serum samples were obtained from 200 SSc patients and 29 healthy controls. IFN-α2a levels were measured by ultrasensitive electrochemiluminescence assay. Pro-inflammatory and chemokine panels were determined by Luminex® Discovery Assay multiplex kit. Baseline SSc disease characteristics were recorded together with longitudinal data for determining ILD progression after 2 years.

RESULTS

IFN-α2a concentrations were higher in SSc patients compared with controls, although not reaching significance [means ± SD of 49.20 ± 156.8 fg/ml vs 9.606 ± 4.399 fg/ml, respectively (P = 0.158)]. Using the cut-off of 15.9 fg/ml, we identified 62 patients as having a type 1 (T1) IFN signature in their circulation. Patients with an IFN signature had significantly higher levels of chemokines (CCL8, CCL19, CXCL10, CXCL11) and the cytokine IL-1α compared with those without an IFN signature. IFN-α2a concentrations strongly correlated with a T1 IFN-related chemokine score supporting activation of this pathway. Phenotyping association queries revealed association between IFN values and both skin and ILD involvements at baseline. Longitudinal data did not identify IFN as a predictive marker for ILD progression.

CONCLUSION

Using serum determinations, the activation of the T1 IFN pathway showed strong correlations with inflammatory mediators and associations with clinical manifestations, especially skin fibrosis and ILD in SSc patients. However, activated IFN pathway was not predictive of ILD progression.

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.

IFIT3 mediates TBK1 phosphorylation to promote activation of pDCs and exacerbate systemic sclerosis in mice

OBJECTIVE

To assess the impact of the IFIT3/TBK1 signalling pathway in activating plasmacytoid dendritic cells (pDCs) and its role in the development of SSc.

METHODS

Utilized single-cell RNA sequencing (scRNA-seq) and high-throughput transcriptome RNA sequencing to reveal the differential abundance of pDCs and the role of the key gene IFIT3 in SSc. Conducted in vitro cell experiments to evaluate the effect of IFIT3/TBK1 signalling pathway intervention on pDC activation cytokine release and fibroblast function. Constructed an IFIT3-/- mouse model using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene editing to assess the potential benefits of intervening in the IFIT3/TBK1 signalling pathway on skin and lung fibrosis in the SSc mouse model.

RESULTS

The IFIT3/TBK1 signalling pathway plays a crucial role in activating pDCs, with IFIT3 acting as an upstream regulator of TBK1. Intervention in the IFIT3/TBK1 signalling pathway can inhibit pDC activation cytokine release and impact fibroblast function. The IFIT3-/- mouse model shows potential benefits of targeting the IFIT3/TBK1 signalling pathway in reducing skin and lung fibrosis in the SSc mouse model.

CONCLUSION

This study provides new insights into potential therapeutic targets for SSc, highlighting the critical role of the IFIT3/TBK1 signalling pathway in SSc development.

HIGHLIGHTS

This study elucidates the pivotal role of plasmacytoid dendritic cells (pDCs) in systemic sclerosis (SSc). This study identified the key regulatory gene involved in systemic sclerosis (SSc) as IFIT3. This study has found that IFIT3 functions as an upstream regulatory factor, activating TBK1. This study provides Evidence of the regulatory effects of the IFIT3/TBK1 pathway on plasmacytoid dendritic cells (pDCs). This study validated the therapeutic potential using the IFIT3-/- mouse model.

Emerging therapeutic targets in systemic sclerosis

Systemic sclerosis is an autoimmune connective tissue disease which is characterised by vascular perturbations, inflammation, and fibrosis. Although huge progress recently into the underlying molecular pathways that are perturbed in the disease, currently no therapy exists that targets the fibrosis element of the disease and consequently there is a huge unmet medical need. Emerging studies reveal new dimensions of complexity, and multiple aberrant pathways have been uncovered that have shed light on disturbed signalling in the disease, primarily in inflammatory pathways that can be targeted with repurposed drugs. Pre-clinical animal models using these inhibitors have yielded proof of concept for targeting these signalling systems and progressing to clinical trials. This review will examine the recent evidence of new perturbed pathways in SSc and how these can be targeted with new or repurposed drugs to target a currently intractable disease.

STING signaling activation modulates macrophage polarization via CCL2 in radiation-induced lung injury

BACKGROUND

Radiation-induced lung injury (RILI) is a prevalent complication of thoracic radiotherapy in cancer patients. A comprehensive understanding of the underlying mechanisms of RILI is essential for the development of effective prevention and treatment strategies.

METHODS

To investigate RILI, we utilized a mouse model that received 12.5 Gy whole-thoracic irradiation. The evaluation of RILI was performed using a combination of quantitative real-time polymerase chain reaction (qRT-PCR), enzyme-linked immunosorbent assay (ELISA), histology, western blot, immunohistochemistry, RNA sequencing, and flow cytometry. Additionally, we established a co-culture system consisting of macrophages, lung epithelial cells, and fibroblasts for in vitro studies. In this system, lung epithelial cells were irradiated with a dose of 4 Gy, and we employed STING knockout macrophages. Translational examinations were conducted to explore the relationship between STING expression in pre-radiotherapy lung tissues, dynamic changes in circulating CCL2, and the development of RILI.

RESULTS

Our findings revealed significant activation of the cGAS-STING pathway and M1 polarization of macrophages in the lungs of irradiated mice. In vitro studies demonstrated that the deficiency of cGAS-STING signaling led to impaired macrophage polarization and RILI. Through RNA sequencing, cytokine profiling, and rescue experiments using a CCL2 inhibitor called Bindarit, we identified the involvement of CCL2 in the regulation of macrophage polarization and the development of RILI. Moreover, translational investigations using patient samples collected before and after thoracic radiotherapy provided additional evidence supporting the association between cGAS-STING signaling activity, CCL2 upregulation, and the development of radiation pneumonitis.

CONCLUSIONS

The cGAS-STING signaling pathway plays a crucial role in regulating the recruitment and polarization of macrophages, partly through CCL2, during the pathogenesis of RILI.

The effect of the cyclic GMP-AMP synthase-stimulator of interferon genes signaling pathway on organ inflammatory injury and fibrosis

The cyclic GMP-AMP synthase-stimulator of interferon genes signal transduction pathway is critical in innate immunity, infection, and inflammation. In response to pathogenic microbial infections and other conditions, cyclic GMP-AMP synthase (cGAS) recognizes abnormal DNA and initiates a downstream type I interferon response. This paper reviews the pathogenic mechanisms of stimulator of interferon genes (STING) in different organs, including changes in fibrosis-related biomarkers, intending to systematically investigate the effect of the cyclic GMP-AMP synthase-stimulator of interferon genes signal transduction in inflammation and fibrosis processes. The effects of stimulator of interferon genes in related auto-inflammatory and neurodegenerative diseases are described in this article, in addition to the application of stimulator of interferon genes-related drugs in treating fibrosis.