Dexamethasone-induced apoptosis of freshly isolated human nasal epithelial cells concomitant with abrogation of IL-8 production

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. Studies on IL-8 and effects of dexamethasone on hNECs have been hampered by methodological shortcomings. The purpose of the study is to investigate 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 freshly isolated from nasal polyp tissue and healthy inferior turbinate of NP patients (n=12) and from inferior turbinates of healthy donors (n=19) by protease treatment and two negative selection procedures. hNECs were incubated with IL-1β (10ng/ml), TNFα (10ng/ml) or dexamethasone (10, 100 and 1000 Amicrog/ml). After 24h, IL-8 levels were determined in the supernatants by ELISA. Finally, hNECs were incubated with increasing doses of dexamethasone and stained with trypan-blue and annexin-FITC/PI to study apoptosis. 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 production 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.