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Regulation of CCAAT/Enhancer-Binding Protein-β Is Altered in Primary Lung Fibroblasts Obtained From Patients With Idiopathic Pulmonary Fibrosis* FREE TO VIEW

Roberto A. Cruz-Gervis, MD; Arlene A. Stecenko, MD; Timothy S. Blackwell, MD, FCCP; Linda Sealy, PhD; James E. Loyd, MD; Gayle King; Kenneth L. Brigham, MD
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*From the Center for Lung Research, Vanderbilt University Medical Center, Nashville, TN.

Correspondence to: Roberto A. Cruz-Gervis, MD, Division of Pulmonary and Critical Care Medicine, Vanderbilt University Medical Center, MCN T-1217, Nashville TN 37232-2650

Chest. 2001;120(1_suppl):S9. doi:10.1378/chest.120.1_suppl.S9
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Since BAL fluid interleukin (IL)-6 levels are elevated in multiple chronic inflammatory and fibrotic lung diseases, and since stimulated lung fibroblasts produced large amounts of IL-6 in vitro, these cells may represent a major source of this cytokine. Nuclear factor (NF)-κB and CCAAT/enhancer-binding protein-β (C/EBP-β) are necessary for maximal transcription of IL-6, and the latter has also been shown to induce gene expression of profibrotic factors, namely insulin-like growth factor-1 and collagen I. For those reasons, we asked whether primary lung fibroblasts obtained from lung of patients with idiopathic pulmonary fibrosis (HF-IPF) could have an altered regulation of these transcription factors compared with fibroblasts obtained from normal human lungs (HF-NL).

We stimulated HF-IPF from two different patients and HF-NL from two different control subjects with IL-1β (10 pg/mL) for 4 h and measured NF-κB and C/EBP-β activity by electrophoretic mobility shift assay. We found that NF-κB activation was increased by IL-1β and to a similar extent in HF-IPF and HF-NL. C/EBP-β activity was also increased by IL-1β, but to a greater degree in HF-IPF. Since C/EBP-β can regulate its own activity by producing a truncated transcription-repressor isoform (p20), which cannot be differentiated from the full-length transcription-activator isoform (p42) on gel shift, we subjected nuclear extracts from the above experiments to Western blot and used densitometry of the blot to quantify levels of p20 and p42. We found that baseline p42 and p20 production were similar between HF-IPF (4.1 relative densitometric units [RDU] and 1.4 RDU, respectively) and HF-NL (4.2 RDU and 1.8 RDU, respectively). Likewise, IL-1β-stimulated p42 production was similar in HF-IPF and HF-NL (1.5-fold and 1.2-fold increase over baseline, respectively). In contrast, IL-1β–induced p20 production was higher in HF-NL compared to HF-IPF (3.0-fold and 1.4-fold increase over baseline, respectively). This resulted in a lower repressor:activator (p20:p42) ratio in HF-IPF (0.38), compared to HF-NL (1.01) [Fig 1].

We conclude that HF-IPF have an altered C/EBP-β regulation, which could account for greater capacity to produce proinflammatory and profibrotic cytokines.

Abbreviations: C/EBPβ = CCAAT/enhancer-binding protein-β; HF-NL = fibroblasts obtained from normal human lung; HF-IPF = fibroblasts obtained from lung of patients with idiopathic pulmonary fibrosis; IL = interleukin; NF = nuclear factor; RDU = relative densitometric units



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