Adenoviral E1A Suppresses Secretory Leukoprotease Inhibitor and Elafin Secretion in Human Alveolar Epithelial Cells and Bronchial Epithelial Cells

Abstract

Background: An imbalance between neutrophil protease and surrounding antiprotease levels has been shown to be important in the pathogenesis of chronic obstructive pulmonary disease (COPD). Adenoviral E1A DNA and protein are frequently detected in the lungs of COPD patients. As secretory leukoprotease inhibitor (SLPI) and elafin/skin-derived antileukoproteinase (SKALP) are locally produced in the lung and inhibit neutrophil elastase activity, we hypothesized that adenoviral E1A might affect the production of these antiproteases. Objectives: To examine the effect of E1A on SLPI and elafin/SKALP secretion in A549 (alveolar epithelial) cells and primary human bronchial epithelial (HBE) cells. Methods: SLPI and elafin/SKALP were quantitated from cell culture supernatants using an ELISA. SLPI mRNA expression was examined by Northern blotting, and SLPI promoter activity was measured using a reporter gene assay. Results: E1A significantly suppressed SLPI and elafin/SKALP secretion by A549 cells upon interleukin (IL)-1β stimulation. E1A also suppressed SLPI and elafin/SKALP secretion by HBE cells. SLPI mRNA expression in A549 cells was suppressed by E1A regardless of IL-1β stimulation. IL-1β-induced SLPI promoter activity was suppressed by E1A gene transfection into A549 cells. Conclusions: Our findings of adenoviral E1A-mediated suppression of SLPI and elafin/SKALP secretion suggest that E1A may be involved in the enhancement of alveolar damage and play a role in the COPD process.