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

Abstract

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.

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

“…STING pathway activation in macrophages can promote polarization toward a pro-inflammatory M1-like phenotype , with potential to drive disease pathology. For example, in inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis, macrophages in patient mucosa predominantly shift to an M1 phenotype; these highly present macrophages are thought to drive intestinal inflammation and are associated with patient nonresponse to IBD treatment. − Therefore, to test if SPINs could inhibit this M1-like polarization, we cotreated BMDMs with SPIN-RU 10% , free RU.521, or empty NP and HT DNA.…”

“…STING pathway activation in macrophages can promote polarization toward a pro-inflammatory M1-like phenotype 60,61 with potential to drive disease pathology. For example, in inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, macrophages in patient mucosa predom- 4F) and CD86 (Figure 4G) expression compared to HT DNA treatment alone, and these cells were not significantly different from unstimulated BMDMs.…”

STING inhibition alleviates bone resorption in apical periodontitis

“…As an important part of the immune response, macrophages could engulf pathogens, dead cells and debris, then secrete kinds of chemicals including complement proteins, inflammatory cytokines IL‐1, IL‐6 and TNF‐α and anti‐inflammatory cytokines IL‐4, IL‐10 and IL‐13 (Nagata, 2018). STING activation aggravating inflammation via promoting macrophages polarizing into M1 phenotype has been reported in neuroinflammation, pneumonia and arthritis (Ni et al., 2023; Ouyang et al., 2023; Peng et al., 2020). Macrophages could also increase the presentation of antigens by activating STING, which activates T lymphocytes Treg, Th1, Th2 and Th17, then promote cytokines like TGF‐β, IL‐2, IL‐4 and IL‐17 secretion (Ding et al., 2023).…”