Toxicol Lett. 2026 Apr 8:111887. doi: 10.1016/j.toxlet.2026.111887. Online ahead of print.
ABSTRACT
BACKGROUND: Fine particulate matter (PM2.5) exposure is a major environmental risk factor for pulmonary inflammation and injury, in which alveolar macrophages (AMs) play a central role. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is recognized for its role in cholesterol metabolism and cardiovascular inflammation; however, its involvement in PM2.5-induced lung injury remains unexplored.
AIM: This study aims to elucidate the role of PCSK9 in mediating AMs M1 polarization and lung injury following low-dose systemic PM2.5 exposure.
METHODS: Using in vitro PM2.5-exposed AMs (MH-S cell line) models and in vivo mouse whole-body exposure systems (56-day subacute injury and 112-day chronic fibrosis models), we employed genetic knockdown (shRNA, AAV-shPCSK9) and pharmacological inhibition (SBC-115076) approaches to validate PCSK9 function. Conditioned medium co-culture experiments were performed to assess alveolar epithelial cell (MLE-12) injury. M1 polarization was evaluated by flow cytometry (CD86), western blot (iNOS), and ELISA (TNF-α, IL-1β, IL-6). NF-κB pathway activation was assessed by phosphorylation of p65 and IκBα.
RESULTS: PM2.5 exposure (20μg/mL, 24h) upregulated PCSK9 expression by 4.7-fold and increased the proportion of CD86⁺ M1 macrophages from 3.38% ± 0.52% in controls to 33.41% ± 3.63%. Genetic knockdown of PCSK9 reduced the CD86⁺ population to 15.75% ± 1.45% (P < 0.01 vs. PM2.5 alone) and suppressed secretion of TNF-α, IL-1β, and IL-6 by 68%, 55%, and 62%, respectively (all P < 0.01). Pharmacological inhibition with SBC-115076 (10μM) similarly attenuated M1 polarization, with CD86⁺ cells reduced to 8.69% ± 1.34% (P < 0.01), and decreased TNF-α, IL-1β, and IL-6 levels by 66.94%, 58.73%, and 60.24%, respectively (all P < 0.01). Mechanistically, PCSK9 knockdown reduced phosphorylation of p65 and IκBα by 77.76% and 87.85% (P < 0.01), effects partially reversed by an NF-κB agonist. Conditioned medium from PM2.5-primed AMs decreased MLE-12 cell viability by 50.9% (P < 0.01) and increased apoptosis, with TUNEL⁺ cells rising from 3.62% ± 1.09% to 43.03% ± 5.24% (P < 0.01); these effects were abrogated by PCSK9 knockdown. In vivo, intranasal AAV-shPCSK9 reduced PM2.5-induced lung injury and decreased BALF levels of TNF-α, IL-1β, and IL-6. In the 112-day chronic model, SBC-115076 (10mg/kg) reduced collagen deposition, with Masson's trichrome-positive area decreasing from 25.02% ± 3.71% in the PM2.5 group to 8.98% ± 1.26% (P < 0.01), and downregulated fibrotic markers α-SMA and fibronectin by 60% and 55%, respectively (P < 0.01).
CONCLUSION: PCSK9 acts as a critical mediator of low-dose PM2.5-induced lung injury by driving AMs M1 polarization via NF-κB activation, highlighting its potential as a therapeutic target for mitigating air-pollution-related respiratory diseases.
PMID:41962642 | DOI:10.1016/j.toxlet.2026.111887