Inhibition of PADI2-mediated vimentin citrullination alleviates silica-induced pulmonary fibrosis in mice

Silicosis remains a critical occupational health concern worldwide, lacking effective treatments due to unclear mechanisms. In this study, we investigated the citrullinated proteomic profile and its effects in mice exposed to silica. Our findings demonstrated elevated levels of citrullinated peptides and citrullinated vimentin (Cit-Vim) in silicotic mice and silica-treated macrophages, regulated by peptidylarginine deiminase (PADI2). Unlike vimentin, Cit-Vim amplified the production of tumor necrosis factor-α (TNF-α), Interleukin-6 (IL-6), and IL-1β in silica-treated macrophages through interaction with Toll-like receptor 4 (TLR4) signaling. RNA sequencing revealed that early growth response protein 1 (EGR1) is a target of PADI2, with Cit-Vim inducing lung inflammation via EGR1 signaling. Pharmacological inhibition or genetic knockout of Padi2 attenuated silica-induced lung inflammation and fibrosis. These findings suggest that targeting PADI2 may represent a novel therapeutic strategy of silicosis.