Prostaglandin E₂ attenuates lung fibroblast differentiation via inactivation of yes-associated protein signaling

Prostaglandin E-2 (PGE(2)) has been implicated in counteracting fibroblast differentiation by TGF beta 1 during pulmonary fibrosis. However, the precise mechanism is not well understood. We show here that PGE(2) via EP2R and EP4R inhibits the expression of mechanosensory molecules Lysyl Oxidase Like 2 (LOXL2), myocardin-related transcription factor A (MRTF-A), ECM proteins, plasminogen activation inhibitor 1 (PAI-1), fibronectin (FN), alpha-smooth muscle actin (alpha-SMA), and redox sensor (nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4)) required for TGF beta 1-mediated fibroblast differentiation. We further demonstrate that PGE(2) inhibits fibrotic signaling via Yes-associated protein (YAP) but does so independently from its actions on SMAD phosphorylation and conserved cylindromatosis (CYLD; deubiquitinase) expression. Mechanistically, PGE(2) phosphorylates/inactivates YAP downstream of EP2R/Gas and restrains its translocation to the nucleus, thus inhibiting its interaction with TEA domain family members (TEADs) and transcription of fibrotic genes. Importantly, pharmacological or siRNA-mediated inhibition of YAP significantly downregulates TGF beta 1-mediated fibrotic gene expression and myofibroblast formation. Notably, YAP expression is upregulated in the lungs of D. farinae-treated wild type (WT) mice relative to saline-treated WT mice. Our results unravel a unique role for PGE(2)-YAP interactions in fibroblast differentiation, and that PGE(2)/YAP inhibition can be used as a novel therapeutic target in the treatment of pathological conditions associated with myofibroblasts like asthma.