Integrative single‑cell and bulk transcriptomic profiling reveals MMP1 as a core effector and CTSB as a putative...

Acetyl tributyl citrate (ATBC) is a widely used environmentally friendly plasticizer, and exposure via the respiratory tract is common in the general population. However, its pulmonary toxicity and underlying molecular mechanisms remain poorly understood.

An integrative strategy combining compound target prediction, IPF transcriptome screening, Bootstrap LASSO stability selection, and protein‑protein interaction network topological analysis was used to identify core targets. Single-cell transcriptomics was applied to dissect the cellular localization and functional roles of these targets. A bleomycin‑induced mouse pulmonary fibrosis model was employed to assess the effects of intratracheal instillation exposure to ATBC.

Two core targets, MMP1(matrix metalloproteinase-1) and CTSB(cathepsin B), were identified from 17 candidate genes. Single-cell analysis revealed that MMP1 exhibits an "off-on" regulatory pattern in airway epithelial club cells-it is not expressed under steady‑state conditions but is specifically induced upon activation. In contrast, CTSB is highly expressed in macrophages and enhances pro‑fibrotic communication. The two targets exert complementary functions: MMP1⁺club cells enter a translationally hyperactive state involved in basement membrane remodeling, while CTSB⁺ macrophages amplify pro‑fibrotic signaling. Animal experiments showed that ATBC dose‑dependently exacerbates pulmonary fibrosis and upregulates MMP1 protein expression.

Intratracheal instillation exposure to ATBC may aggravate fibrosis progression on the basis of pre‑existing lung injury, with MMP1 serving as a core effector molecule. These findings offer preliminary experimental support for the safety assessment of plasticizers following respiratory tract exposure.