Dexamethasone-induced apoptosis of freshly isolated human nasal epithelial cells concomitant with abrogation of IL-8 production* S. Bobic 1 , C.M. van Drunen 2 , I. Callebaut 1 , V. Hox 1 , M. Jorissen 3 , W.J. Fokkens 2 , P.W. Hellings 1,3 1 Laboratory of Experimental Immunology, Catholic University Hospitals, Leuven, Belgium 2 Department of Otorhinolaryngology, Academic Medical Center, Amsterdam, the Netherlands 3 Department of Otorhinolaryngology, Head and Neck Surgery, Catholic University Hospitals, Leuven, Belgium *Received for publication: February 3, 2010; accepted: April 12, 2010 DOI:10.4193/Rhino10.033 INTRODUCTION Epithelial cells lining the nasal cavity have a pivotal role in detecting and responding to various environmental stimuli. Nasal epithelial cells are more than just a physical barrier. They exert their immunological function by producing various cytokines and growth factors that enable the recruitment and effector function of immune cells (1) . In addition, supernatants from cultured nasal or airway epithelial cells have been shown to prolong the survival of neutrophils (2) and eosinophils (3) . Many authors have studied airway epithelial cell biology using either immortalized cell lines (1,4-6) or freshly isolated nasal/air- way epithelial cells. In most studies, primary epithelial cells obtained by positive selection are grown for 6-14 days in a medium rich in growth factors and mediators that stimulate growth of epithelial cells and apoptosis of other cell types (2,6-9) . Although these techniques yield 99,5% pure epithelial cell cul- tures, long term incubation might introduce immunological alterations in parallel with variations in phenotypical aspects of epithelial cells (10-12) . Here we build further on a recently reported novel technique of isolation and purification of pri- mary nasal epithelial cells (hNECs) using two negative selec- tions (13) . Epithelial cells were freshly isolated and incubated to study the contribution of human nasal epithelial cells (hNECs) to IL-8 production in chronic rhinosinusitis with nasal polyps (CRSwithNP). IL-8 is one of the major cytokines secreted by epithelial cells upon stimulation. It is mainly produced upon stimulation of the toll-like receptors (TLRs) on the surface of the epithelial cells by an antigen (14) or microbial products. Super-antigens Staphylococcus aureus enterotoxin A (SEA) and B (SEB) (15) Background: Human nasal epithelial cells (hNECs) are the first line of immune defense and are able to produce mediators that recruit, activate and prolong survival of immune cells, among which IL-8 takes an important place. This study investigates the contribution of freshly isolated hNECs to IL-8 production in chronic rhinosinusitis with nasal polyps (CRSwithNP). Secondly, the effects of dexamethasone treatment on hNEC apoptosis and IL-8 production are investigated. Methodology: hNECs were isolated from nasal polyps and healthy inferior turbinate of NP patients and from inferior turbinates of healthy donors by protease treatment and two negative selection procedures. hNECs were incubated with IL-1β, TNF-α or dexamethasone. After 24h, IL-8 levels were determined in the supernatants by ELISA. Finally, hNECs were incubated with increasing doses of dexamethasone and apoptosis was studied. Results: hNECs isolated from nasal turbinates of healthy and NP patients and polyp tissue from NP patients produced similar levels of IL-8. IL-1β induced higher levels of IL-8 produc- tion in all types of hNECs without differences between control and NP tissue. Dexamethasone induced apoptosis of hNECs concomitant with abrogation of IL-8 production by hNECs. Conclusions: IL-8 production by human nasal epithelial cells does not differ between NP and healthy tissue under baseline nor stimulatory conditions. Dexamethasone induces apoptosis of hNECs and abrogates IL-8 production. Key words: IL-8, human nasal epithelial cells (hNECs), chronic rhinosinusitis with nasal polyps (CRSwithNP) and dexamethasone SUMMARY ORIGINAL CONTRIBUTION Rhinology, 48, 401-407, 2010