Suppression of von Hippel-Lindau Protein in Fibroblasts Protects against Bleomycin-Induced Pulmonary Fibrosis.

Abstract

We have reported that von Hippel-Lindau protein (pVHL) expression is elevated in human and mouse fibrotic lungs and that overexpression of pVHL stimulates fibroblast proliferation. We sought to determine whether loss of pVHL in fibroblasts prevents injury and fibrosis in mice that are treated with bleomycin. We generated heterozygous fibroblast-specific pVHL (Fsp-VHL) knockdown mice (Fsp-VHL(+/-)) and homozygous Fsp-VHL knockout mice (Fsp-VHL(-/-)) by crossbreeding vhlh 2-lox mice (VHL(fl/fl)) with Fsp-Cre recombinase mice. Our data show that Fsp-VHL(-/-) mice, but not Fsp-VHL(+/-) mice, have elevated red blood cell counts, hematocrit, hemoglobin content, and expression of hypoxia-inducible factor (HIF) targets, indicating HIF activation. To examine the role of pVHL in bleomycin-induced lung injury and fibrosis in vivo, we administered PBS or bleomycin to age-, sex-, and strain-matched 8-week-old VHL(fl/fl), Fsp-VHL(+/-), and Fsp-VHL(-/-) mice. In Fsp-VHL(+/-) and Fsp-VHL(-/-) mice, bleomycin-induced collagen accumulation, fibroblast proliferation, differentiation, and matrix protein dysregulation were markedly attenuated. Suppression of pVHL also decreased bleomycin-induced Wnt signaling and prostaglandin E2 signaling but did not affect bleomycin-induced initial acute lung injury and lung inflammation. These results indicate that pVHL has a pivotal role in bleomycin-induced pulmonary fibrosis, possibly via an HIF-independent pathway. Paradoxically, pVHL does not affect bleomycin-induced lung injury and inflammation, indicating a separation of the mechanisms involved in injury/inflammation from those involved in pulmonary fibrosis.

• Authors: Qiyuan Zhou, Tianji Chen, Wei Zhang, Melike Bozkanat, Yongchao Li, Lei Xiao, Richard B van Breemen, John W Christman, Jacob I Sznajder, Guofei Zhou
• Journal: American journal of respiratory cell and molecular biology (Am J Respir Cell Mol Biol) Vol. 54 Issue 5 Pg. 728-39 (05 2016) ISSN: 1535-4989 [Electronic] United States
• PMID: 26488390 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Extracellular Matrix Proteins
• Hypoxia-Inducible Factor 1, alpha Subunit
• Bleomycin
• Von Hippel-Lindau Tumor Suppressor Protein
• VHL protein, mouse
• Dinoprostone
• Prostaglandin D2

Topics

• Animals
• Bleomycin
• Cell Differentiation
• Cell Proliferation
• Dinoprostone (metabolism)
• Extracellular Matrix (metabolism)
• Extracellular Matrix Proteins (metabolism)
• Fibroblasts (metabolism, pathology)
• Hypoxia-Inducible Factor 1, alpha Subunit (metabolism)
• Lung Injury (metabolism, pathology)
• Mice, Knockout
• Models, Biological
• Pneumonia (pathology)
• Prostaglandin D2 (metabolism)
• Pulmonary Fibrosis (chemically induced, metabolism, pathology)
• Von Hippel-Lindau Tumor Suppressor Protein (metabolism)
• Wnt Signaling Pathway