Tumor Necrosis Factor-alpha and Transforming Growth Factor-beta Synergistically Upregulate Endothelin-1 Expression in Human Bronchial Epithelial Cells BEAS-2B

Abstract

: Endothelin-1 is a peptide with many functions including bronchoconstriction and the stimulation of fibroblasts, and myofibroblasts, and airway smooth muscle cell proliferation. These functions are related to airway remodeling and endothelin-1 is known to be upregulated in the epithelium of patients with severe asthma. We thus sought to elucidate the mechanisms underlying endothelin-1 expression in bronchial epithelial cells in vitro. The human bronchial epithelial cell line BEAS-2B was grown in culture and then treated with tumor necrosis factoralpha TNF-, interleukin-4 IL-4 , interleukin-13 IL-13 , and transforming growth factor-beta TGF-. Expression of endothelin-1 mRNA and protein was quantified by real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. We also repressed expression of the key transcription factor in the pathogenesis of severe asthma, nuclear factor-kappa B NF-B , using small interfering RNA siRNA . TNF-and TGF-signi cantly increased the release of endothelin-1 protein into the culture medium of BEAS-2B cells at 24 h after treatment compared to untreated cells ; however, the Th2 cytokines, IL-4 and IL-13, had no effect. Endothelin-1 mRNA expression was also upregulated by TNFand TGFwith a peak time point at 4 h after stimulation. Finally, the combination of TNF-and TGF-synergistically increased both endothelin-1 protein secretion and mRNA expression, and this upregulation was signi cantly suppressed in cells transfected with siRNA to repress NF-B expression. TNF-and TGF-synergistically upregulate the expression of endothelin-1 in human bronchial epithelial cells, possibly via the activity of NF-B. Our ndings thus suggest NFBa as a potential therapeutic target for the regulation of airway remodeling.