Pirfenidone exerts antifibrotic effects through inhibition of GLI transcription factors

Abstract

Pirfenidone is an antifibrotic drug, recently approved for the treatment of patients with idiopathic pulmonary fibrosis (IPF). Although pirfenidone exhibits anti-inflammatory, antioxidant, and antifibrotic properties, the molecular mechanism underlying its protective effects remains unknown. Here, we link pirfenidone action with the regulation of the profibrotic hedgehog (Hh) signaling pathway. We demonstrate that pirfenidone selectively destabilizes the glioma-associated oncogene homolog (GLI)2 protein, the primary activator of Hh-mediated gene transcription. Consequently, pirfenidone decreases overall Hh pathway activity in patients with IPF and in patient-derived primary lung fibroblasts and leads to diminished levels of Hh target genes, such as GLI1, Hh receptor Patched-1, α-smooth muscle actin, and fibronectin, and to reduced cell migration and proliferation. Interestingly, Hh-triggered TGF-β1 expression potentiated Hh responsiveness of primary lung fibroblasts by elevating the available pool of glioma-associated oncogene homolog (GLI)1/GLI2, thus creating a vicious cycle of amplifying fibrotic processes. Because GLI transcription factors are not only crucial for Hh-mediated changes but are also required as mediators of TGF-β signaling, our findings suggest that pirfenidone exerts its clinically beneficial effects through dual Hh/TGF-β inhibition by targeting the GLI2 protein.-Didiasova, M., Singh, R., Wilhelm, J., Kwapiszewska, G., Wujak, L., Zakrzewicz, D., Schaefer, L., Markart, P., Seeger, W., Lauth, M., Wygrecka, M. Pirfenidone exerts antifibrotic effects through inhibition of GLI transcription factors.

Pirfenidone reduces subchondral bone loss and fibrosis after murine knee cartilage injury

“…Therefore, if PFD reduces the deposition of fibrotic tissues during the proliferative phase, remodeling of that temporary matrix into chondrophytic tissue is likewise reduced, a reduction that would be reflected in both the lower Col2a1 expression observed and the prevention of cortical bone loss at the site of injury. The corresponding PFD-driven depression of pro-fibrotic genes in the proliferative phase is consistent with reports that PFD reduces collagen expression 30; 31 and blocks fibroblast proliferation and migration by destabilizing GLI2 and suppressing both TGF-β and Hh signaling pathways 32 . Moreover, inhibition of the GLI2/Hh axis by PFD 54 might underlie the pro-chondrogenic effect in both genotypes (Figures 3–5) on the growth plate ECM 55; 56 and the anabolic effect on the subchondral bone 57 .…”

“…The corresponding PFD-driven depression of pro-fibrotic genes in the proliferative phase is consistent with reports that PFD reduces collagen expression 30,31 and blocks fibroblast proliferation and migration by destabilizing GLI2 and suppressing both TGF-b and Hh signaling pathways. 32 Moreover, inhibition of the GLI2/Hh axis by PFD 54 might underlie the pro-chondrogenic effect in both genotypes ( Figs. 3-5) on the growth plate ECM 55,56 and the anabolic effect on the subchondral bone.…”

“…For example, PFD inhibits the non-canonical hedgehog (Hh) pathway by shortening the half-life of endogenous full-length glioma-associated oncogene homolog 2 (GLI2), a transcription factor, by more than 3-fold, and thereby reduces Hh/TGF-β signaling and expression of collagen type I 32 . PFD has also been shown to reduce IL-1β-induced hyaluronan production in orbital fibroblasts 33 .…”

“…30,31 For example, PFD inhibits the non-canonical hedgehog (Hh) pathway by shortening the half-life of endogenous full-length gliomaassociated oncogene homolog 2 (GLI2), a transcription factor, by more than threefold, and thereby reduces Hh/TGF-b signaling and expression of collagen type I. 32 PFD has also been shown to reduce IL-1b-induced hyaluronan production in orbital fibroblasts. 33 PFD has shown pain relief in RA 34 and may also be able to block nitric oxide release in articular chondrocytes, 35 but PFD has not yet been tested in vivo against posttraumatic OA.…”

Effect of Pirfenidone on cough in patients with Idiopathic Pulmonary Fibrosis

“…Pirfenidone's anti-fibrotic effect was thought to be enigmatic, but has recently been linked to the inhibition of GLI transcription factors [5,11]. Whether this inhibition relates to the antitussive effect of pirfenidone is unclear.…”