Front Pharmacol. 2026 Aug 6;17:1902928. doi: 10.3389/fphar.2026.1902928. eCollection 2026.
ABSTRACT
BACKGROUND: Exposure to fine particulate matter (PM2.5) is a well-established risk factor for lung inflammation and injury. Macrophages are key innate immune cells in the lung and play critical roles in maintaining pulmonary immune homeostasis and orchestrating inflammatory responses following environmental insults. However, the precise mechanisms by which PM2.5 modulates macrophage function and contributes to lung injury remain incompletely understood. This study aimed to investigate the role of macrophage phenotypic polarization in PM2.5-induced lung injury and the underlying molecular mechanisms.
METHODS: A subacute exposure (21-day) PM2.5 mouse model and bone marrow-derived macrophages (BMDMs) were used in vivo and in vitro to evaluate the effects of PM2.5 on pulmonary inflammation, macrophage polarization, mitochondrial injury, and cGAS-STING signaling activation. Pharmacological inhibition of cGAS was performed using RU.521 to assess the functional role of the cGAS-STING pathway in PM2.5-induced macrophage activation and lung injury. Statistical analyses were conducted to compare differences between experimental groups.
RESULTS: PM2.5 exposure triggered pulmonary inflammation and tissue injury, accompanied by increased pulmonary macrophage accumulation and polarization toward the pro-inflammatory M1 phenotype. Mechanistically, PM2.5 induced mitochondrial damage in macrophages, leading to mtDNA release and subsequent activation of cGAS-STING signaling. Pharmacological inhibition of cGAS with RU.521 attenuated STING pathway activation, macrophage M1 polarization, and PM2.5-induced pulmonary inflammation and lung injury in mice.
CONCLUSIONS: Our study indicates that PM2.5 promotes lung injury by driving macrophage M1 polarization through an mtDNA-cGAS-STING axis, highlighting cGAS-STING signaling as a potential therapeutic target for PM2.5-related lung injury.
PMID:42625593 | PMC:PMC13489883 | DOI:10.3389/fphar.2026.1902928
