Prostaglandin F2α receptor signaling facilitates bleomycin-induced pulmonary fibrosis independently of transforming growth factor-β.

Idiopathic pulmonary fibrosis (IPF) is a progressive disease characterized by fibroblast proliferation and excess deposition of collagen and other extracellular matrix (ECM) proteins, which lead to distorted lung architecture and function. Given that anti-inflammatory or immunosuppressive therapy currently used for IPF does not improve disease progression therapies targeted to blocking the mechanisms of fibrogenesis are needed. Although transforming growth factor-β (TGF-β) functions are crucial in fibrosis, antagonizing this pathway in bleomycin-induced pulmonary fibrosis, an animal model of IPF, does not prevent fibrosis completely, indicating an additional pathway also has a key role in fibrogenesis. Given that the loss of cytosolic phospholipase A₂ (cPLA₂) suppresses bleomycin-induced pulmonary fibrosis, we examined the roles of prostaglandins using mice lacking each prostoaglandin receptor. Here we show that loss of prostaglandin F (PGF) receptor (FP) selectively attenuates pulmonary fibrosis while maintaining similar levels of alveolar inflammation and TGF-β stimulation as compared to wild-type (WT) mice, and that FP deficiency and inhibition of TGF-β signaling additively decrease fibrosis. Furthermore, PGF_2α is abundant in bronchoalveolar lavage fluid (BALF) of subjects with IPF and stimulates proliferation and collagen production of lung fibroblasts via FP, independently of TGF-β. These findings show that PGF_2α-FP signaling facilitates pulmonary fibrosis independently of TGF-β and suggests this signaling pathway as a therapeutic target for IPF. [ABSTRACT FROM AUTHOR]