Gene Expression Profiles of Acute Exacerbations of Idiopathic Pulmonary Fibrosis

Abstract

Rationale: The molecular mechanisms underlying acute exacerbations of idiopathic pulmonary fibrosis (IPF) are poorly understood. We studied the global gene expression signature of acute exacerbations of IPF. Objectives: To understand the gene expression patterns of acute exacerbations of IPF. Methods: RNA was extracted from 23 stable IPF lungs, 8 IPF lungs with acute exacerbation (IPF-AEx), and 15 control lungs and used for hybridization on Agilent gene expression microarrays. Functional analysis of genes was performed with Spotfire and Genomica. Gene validations for MMP1, MMP7, AGER, DEFA1-3, COL1A2, and CCNA2 were performed by real-time quantitative reverse transcriptionpolymerase chain reaction. Immunohistochemistry and in situ terminal deoxynucleotidyltransferase dUTP nick end-labeling assays were performed on the same tissues used for the microarray. ELISA for adefensins was performed on plasma from control subjects, patients with stable IPF, and patients with IPF-AEx. Measurements and Main Results: Gene expression patterns in IPF-AEx and IPF samples were similar for the genes that distinguish IPF from control lungs. Five hundred and seventy-nine genes were differentially expressed (false discovery rate , 5%) between stable IPF and IPF-AEx. Functional analysis of these genes did not indicate any evidence of an infectious or overwhelming inflammatory etiology. CCNA2 and a-defensins were among the most up-regulated genes. CCNA2 and a-defensin protein levels were also higher and localized to the epithelium of IPF-AEx, where widespread apoptosis was also detected. a-Defensin protein levels were increased in the peripheral blood of patients with IPF-AEx. Conclusions: Our results indicate that IPF-AEx is characterized by enhanced epithelial injury and proliferation, as reflected by increases in CCNA2 and a-defensins and apoptosis of epithelium. The concomitant increase in a-defensins in the peripheral blood and lungs may suggest their use as biomarkers for this disorder.

Influenza Promotes Collagen Deposition via αvβ6 Integrin-mediated Transforming Growth Factor β Activation

“…The results described herein suggest a novel mechanism by which influenza infection can induce epithelial cell death and promote collagen deposition, which are critical steps in exacerbations of pulmonary fibrosis (25). This further raises the possibility that TLR3 activation by multiple RNA viruses may increase TGF␤ activity in epithelial cells and define a mechanism through which viral infection may initiate acute exacerbations of fibrotic lung disease.…”

“…Our data suggest that lung collagen can be deposited in the lung of virally infected mice as early as 5 days post-infection. Although we are not proposing that influenza infection causes pulmonary fibrosis, it is evident that key mechanisms involved in the development of fibrosis, including ␣v␤6-mediated TGF␤ activation (4,68), epithelial apoptosis (25), and lung collagen deposition (69), are triggered by influenza infection and may thus promote fibrogenesis in an appropriately susceptible host. In conclusion, the results described herein provide a novel mechanism through which pulmonary infection with influenza virus can result in the activation of TGF␤ via a Smad3-, TLR3-, and ␣v␤6 integrin-dependent pathway.…”

Serum heat shock protein 47 levels are elevated in acute exacerbation of idiopathic pulmonary fibrosis

“…Recent data have suggested that AE-IPF may be due to an acceleration of the underlying fibroproliferative disease process (Konishi et al 2009;Collard et al 2007). Finding higher pulmonary expression of HSP47, a collagen-specific molecular chaperone, in DAD than in UIP tissues in this study is consistent with that hypothesis.…”

“…Recent data have suggested that AE-IPF may be due to an acceleration of the underlying fibroproliferative disease process (Konishi et al 2009;Collard et al 2007); it is therefore assumed that HSP47 is also involved in its pathogenesis. Previous studies in several experimental animal fibrosis models have shown that downregulation of HSP47 expression reduces production of collagen and subsequently diminishes progression of fibrosis (Sunamoto et al 1998;Nishino et al 2003;Hagiwara et al 2007a, b, c;Obata et al 2012).…”

Matrix Metalloproteinase 3 Is a Mediator of Pulmonary Fibrosis

“…MMP-3 gene expression was further assessed by real-time quantitative PCR as described previously. 14 Total protein from the lung tissue was extracted with Pierce T-PER tissue protein extraction reagent (Thermo Fisher Scientific, Rockford, IL) according to the manufacturer's protocol. Western blot analysis of human tissue specimens for MMP-3 was performed as described previously.…”