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  • Title: Extracellular regulation of interleukin (IL)-1beta through lung epithelial cells and defective IL-1 type II receptor expression.
    Author: Coulter KR, Wewers MD, Lowe MP, Knoell DL.
    Journal: Am J Respir Cell Mol Biol; 1999 May; 20(5):964-75. PubMed ID: 10226066.
    Abstract:
    Interleukin (IL)-1beta is produced primarily by activated mononuclear phagocytic cells in the lung airway and functions as a potent proinflammatory cytokine. Release of IL-1beta in the airway microenvironment induces the production of proinflammatory factors from parenchymal airway cells, including IL-8. To study the regulation of lung epithelial cell responsiveness to IL-1beta, the human type II-like airway epithelial cell line A549 and primary normal human bronchial epithelial (NHBE) cells were assayed for IL-1-specific response modifiers. Specifically, the IL-1 type I receptor (IL-1RI), IL-1 type II receptor (IL-1RII), IL-1 receptor accessory protein (IL-1RAcP), and IL-1 receptor antagonist (IL-1Ra) were analyzed. Constitutive expression of IL-1RI, IL-1RAcP, and IL-1Ra was detected in both immortalized and primary human airway epithelial cells. Interestingly, a complete absence of IL-1RII expression was demonstrated under all study conditions in both A549 and NHBE cells. Both cell types were responsive to IL-1beta at concentrations as low as 50 to 500 pg/ml when measured by IL-8 release into cell supernatants. IL-1beta-induced chemokine production and release were inhibited by a 10- to 1,000-fold molar excess of recombinant IL-1RII or IL-1Ra, whereas IL-1RI was a less effective inhibitor. On the basis of our results, we propose that human lung epithelial cells lack the ability to downregulate IL-1beta activity extracellularly because of an inability to express IL-1RII. Release of extracellular IL-1 inhibitors, including soluble IL-1Ra and soluble IL-1RII, by other inflammatory cells present in the airway may be critical for regulation of IL-1beta activity in the airway microenvironment.
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