Biomass fuels related-PM_2.5 promotes lung fibroblast-myofibroblast transition through PI3K/AKT/TRPC1 pathway

Emerging evidence has suggested that exposure to PM_2.5 is a significant contributing factor to the development of chronic obstructive pulmonary disease (COPD). However, the underlying biological effects and mechanisms of PM_2.5 in COPD pathology remain elusive. In this study, we aimed to investigate the implication and regulatory effect of biomass fuels related-PM_2.5 (BRPM_2.5) concerning the pathological process of fibroblast-to-myofibroblast transition (FMT) in the context of COPD. In vivo experimentation revealed that exposure to biofuel smoke was associated with airway inflammation in rats. After 4 weeks of exposure, there was inflammation in the small airways, but no significant structural changes in the airway walls. However, after 24 weeks, airway remodeling occurred due to increased collagen deposition, myofibroblast proliferation, and tracheal wall thickness. In vitro, cellular immunofluorescence results showed that with stimulation of BRPM_2.5 for 72 h, the cell morphology of fibroblasts changed significantly, most of the cells changed from spindle-shaped to star-shaped irregular, α-SMA stress fibers appeared in the cytoplasm and the synthesis of type I collagen increased. The collagen gel contraction experiment showed that the contractility of fibroblasts was enhanced. The expression level of TRPC1 in fibroblasts was increased. Specific siRNA-TRPC1 blocked BRPM_2.5-induced FMT and reduced cell contractility. Additionally, specific siRNA-TRPC1 resulted in a decrease in the augment of intracellular Ca²⁺ concentration ([Ca²⁺]_i) induced by BRPM_2.5. Notably, it was found that the PI3K inhibitor, LY294002, inhibited enhancement of AKT phosphorylation level, FMT occurrence, and elevation of TRPC1 protein expression induced by BRPM_2.5. The findings indicated that BRPM_2.5 is capable of inducing the FMT, with the possibility of mediation by PI3K/AKT/TRPC1. These results hold potential implications for the understanding of the molecular mechanisms involved in BRPM_2.5-induced COPD and may aid in the development of novel therapeutic strategies for pathological conditions characterized by fibrosis.