Role of Sonic Hedgehog in idiopathic pulmonary fibrosis

Abstract

Idiopathic pulmonary fibrosis (IPF) is a progressive and lethal disease of unknown etiology and uncertain pathogenic mechanisms. Recent studies indicate that the pathogenesis of the disease may involve the abnormal expression of certain developmental pathways. Here we evaluated the expression of Sonic Hedgehog (SHH), Patched-1, Smoothened, and transcription factors glioma-associated oncogene homolog (GLI)1 and GLI2 by RT-PCR, as well as their localization in IPF and normal lungs by immunohistochemistry. The effects of SHH on fibroblast proliferation, migration, collagen and fibronectin production, and apoptosis were analyzed by WST-1, Boyden chamber chemotaxis, RT-PCR, Sircol, and annexin V-propidium iodide binding assays, respectively. Our results showed that all the main components of the Sonic signaling pathway were overexpressed in IPF lungs. With the exception of Smoothened, they were also upregulated in IPF fibroblasts. SHH and GLI2 localized to epithelial cells, whereas Patched-1, Smoothened, and GLI1 were observed mainly in fibroblasts and inflammatory cells. No staining was detected in normal lungs. Recombinant SHH increased fibroblast proliferation (P < 0.05), collagen synthesis, (2.5 ± 0.2 vs. 4.5 ± 1.0 μg of collagen/ml; P < 0.05), fibronectin expression (2-3-fold over control), and migration (190.3 ± 12.4% over control, P < 0.05). No effect was observed on α-smooth muscle actin expression. SHH protected lung fibroblasts from TNF-α/IFN-γ/Fas-induced apoptosis (14.5 ± 3.2% vs. 37.3 ± 7.2%, P < 0.0001). This protection was accompanied by modifications in several apoptosis-related proteins, including increased expression of X-linked inhibitor of apoptosis. These findings indicate that the SHH pathway is activated in IPF lungs and that SHH may contribute to IPF pathogenesis by increasing the proliferation, migration, extracellular matrix production, and survival of fibroblasts.

Small molecule-mediated inhibition of myofibroblast transdifferentiation for the treatment of fibrosis

“…In agreement with our observation that Hh and VEGF signaling components are up-regulated upon MFB differentiation, the increased expression of Hh and VEGF-related factors has been demonstrated as a salient feature of fibroblasts and tissue derived from patients of multiple fibrotic disease backgrounds (30)(31)(32). Additionally, the exogenous expression of either Hh or VEGF has been shown to additively contribute to TGF-β-driven fibrotic disease progression in animal models (33)(34)(35)).…”

Sonic hedgehog signaling in kidney fibrosis: a master communicator

“…Shh signaling is upregulated in animal models and patients with idiopathic pulmonary fibrosis (IPF), other interstitial lung diseases and nonalcoholic fatty liver disease (NAFLD), with nuclear accumulation of Gli1, Gli2 in the fibrotic areas and an increased expression of the Shh downstream target genes. In lung, Shh is predominantly expressed in type II like epithelial cells of terminal bronchioles and alveoli (Bolanos et al, 2012). Shh activation causes aberrant epithelium-fibroblast interactions and directly triggers pulmonary fibrosis after injury (Hu et al, 2015; McGowan and McCoy, 2013).…”

Tissue remodelling in chronic bronchial diseases: from the epithelial to mesenchymal phenotype

“…Furthermore, in Ptch+/-mice, the over-activation of the Hh pathway parallels an increase in EMT and an aggravated liver fibrosis [108]. In the lung, expression of the Shh ligand is increased in patients with usual interstitial pneumonia, nonspecific interstitial pneumonia [109], cryptogenic pneumonia [110] or IPF [111,112]. Recent studies in IPF lungs have revealed distinct expression of Hh-related proteins in IPF tissues [111,112].…”

“…In the lung, expression of the Shh ligand is increased in patients with usual interstitial pneumonia, nonspecific interstitial pneumonia [109], cryptogenic pneumonia [110] or IPF [111,112]. Recent studies in IPF lungs have revealed distinct expression of Hh-related proteins in IPF tissues [111,112]. Shh is expressed in bronchial and alveolar epithelial cells in fibrotic areas while Ptch1 is observed in fibroblasts, interstitial inflammatory cells and the hyperplastic epithelium.…”