Abstract
Ets-2 is a ubiquitous transcription factor activated after phosphorylation at threonine-72. Previous studies highlighted the importance of phosphorylated ets-2 in lung inflammation and extracellular matrix remodeling, two pathways involved in pulmonary fibrosis. We hypothesized that phosphorylated ets-2 played an important role in pulmonary fibrosis, and we sought to determine the role of ets-2 in its pathogenesis. We challenged ets-2 (A72/A72) transgenic mice (harboring a mutated form of ets-2 at phosphorylation site threonine-72) and ets-2 (wild-type/wild-type [WT/WT]) control mice with sequential intraperitoneal injections of bleomycin, followed by quantitative measurements of lung fibrosis and inflammation and primary cell in vitro assays. Concentrations of phosphorylated ets-2 were detected via the single and dual immunohistochemical staining of murine lungs and lung sections from patients with idiopathic pulmonary fibrosis. Ets-2 (A72/A72) mice were protected from bleomycin-induced pulmonary fibrosis, compared with ets-2 (WT/WT) mice. This protection was characterized by decreased lung pathological abnormalities and the fibrotic gene expression of Type I collagen, Type III collagen, α-smooth muscle actin, and connective tissue growth factor. Immunohistochemical staining of lung sections from bleomycin-treated ets-2 (WT/WT) mice and from patients with idiopathic pulmonary fibrosis demonstrated increased staining of phosphorylated ets-2 that colocalized with Type I collagen expression and to fibroblastic foci. Lastly, primary lung fibroblasts from ets-2 (A72/A72) mice exhibited decreased expression of Type I collagen in response to stimulation with TGF-β, compared with fibroblasts from ets-2 (WT/WT) mice. These data indicate the importance of phosphorylated ets-2 in the pathogenesis of pulmonary fibrosis through the expression of Type I collagen and (myo)fibroblast activation.