IL-4 and IL-13 Stimulate Human Bronchial Epithelial Cells to Release IL-8

Byline: I. StAiz (1), T. Mio (2), Y. Adachi (2), R. A. Robbins (3), D. J. Romberger (3), S. I. Rennard (2) Abstract: Cytokine networks are important in regulating the traffic of inflammatory cells in the airways. Interleukin-8 (IL-8) released by human bronchial epithelial cells (HBECs) is thought to be of particular importance in attracting neutrophils and monocytes to sites of inflammation. Increased release of IL-8 by HBECs in response to Th-1 cytokines such as TNF alpha and IL-1 beta may be an important pathophysiologic pathway. The present study was designed to explore the role of the Th2 cytokine IL-4 and the functionally related interleukins IL-10, and IL-13 on the regulation of IL-8 release by HBECs. HBECs (passage 4--6) were cultured in LHC9/RPMI and when confluent cells were stimulated in unsupplemented medium LHCD/RPMI by IL-4, IL-10, and IL-13 at 10 ng/ml concentration for all cytokines. TNF alpha stimulation was used as a positive control. After 24 hours supernatants were collected and tested for IL-8 by a sandwich ELISA. Unstimulated HBECs spontaneously released limited amounts of IL-8 (11 +- 1 pM) and significantly increased cytokine production in response to IL-4 (42 +- 1 pM), IL-13 (30 +- 1 pM) and TNF (128 +- 11 pM). Stimulation with IL-10 (11 +- 1 pM) did not change basal production of IL-8. When HBECs were co-stimulated with IL-4 plus TNF, the production of IL-8 was further increased (204 +- 5 pM). In contrast, IL-10 attenuated the effect of TNF during co-stimulation (82 +- 5 pM). IL-13 did not affect the release of IL-8 induced by TNF (111 +- 9 pM). Northern blot analysis of IL-8 mRNA levels showed the highest induction of IL-8 mRNA in HBECs co-stimulated with TNF and IL-4. We conclude from our study that IL-4 directly induces IL-8 release from HBECs and amplifies the release of IL-8 in response to TNF alpha. IL-13 is less active and IL-10 has an inhibitory effect. Airway epithelial cells are able to interact, therefore, with products of both Th1 and Th2 cells with respect to modulating release of IL-8. Author Affiliation: (1) Department of Immunology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic (2) Pulmonary and Critical Care Medicine Section, Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska (3) Veterans Administration Hospital, Omaha, Nebraska Article History: Registration Date: 30/09/2004