FLUOROFENIDONE ATTENUATES PULMONARY INFLAMMATION AND FIBROSIS BY INHIBITING THE IL-11/MEK/ERK SIGNALING PATHWAY

Idiopathic pulmonary fibrosis is defined as a specific form of chronic, progressive fibrosing interstitial pneumonia of unknown cause. Interleukin (IL)-11 plays an important role in the pathogenesis of idiopathic pulmonary fibrosis. In this study, we explore whether a potential antifibrotic agent fluorofenidone (FD) exerts its anti-inflammatory and antifibrotic effects through suppressing activation of the IL-11/MEK/ERK signaling pathway in vivo and in vitro. Male C57BL/6 J mice were intratracheally injected with bleomycin or saline. Fluorofenidone was administered throughout the course of the experiment. Lung tissue sections were stained with hemotoxylin and eosin, and Masson trichrome. Cytokines were measured using the enzyme-linked immunosorbent assay. The α-smooth muscle actin (α-SMA), fibronectin, and collagen I were measured using immunohistochemistry, and the phosphorylated extracellular signal–regulated kinase, phosphorylated mitogen-activated protein kinase, IL-11RA, and gp130 were measured using Western blot. The RAW264.7 cells and the normal human lung fibroblasts were treated with IL-11 and/or FD, IL-11RA–siRNA, or MEK inhibitor. The expressions of phosphorylated extracellular signal–regulated kinase, phosphorylated mitogen-activated protein kinase, IL-11RA, gp130, α-SMA, fibronectin, and collagen I were measured using Western blot and/or real-time polymerase chain reaction, and the cytokines were measured using enzyme-linked immunosorbent assay. Results showed that FD markedly reduced the expressions of IL-8, IL-18, IL-11, monocyte chemotactic protein-1, α-SMA, fibronectin, and collagen I in mice lung tissues. In addition, FD attenuated IL-11–induced expressions of α-SMA, fibronectin, and collagen I and inhibited IL-11RA, gp130, and phosphorylation of the ERK and MEK protein expression, as well as reduced the expressions of IL-8, IL-18, and monocyte chemotactic protein-1 in vitro. This study demonstrated that FD attenuated bleomycin-induced pulmonary inflammation and fibrosis in mice by inhibiting the IL-11/MEK/ERK signaling pathway.