Nerve growth factor secretion by human lung epithelial A549 cells in pro- and anti-inflammatory conditions

Nerve growth factor (NGF) has recently been presented as a possible effecto r of inflammation and bronchial hyperresponsiveness. However, the productio n of NGF in human airways as well as the regulation of its expression by in flammatory cytokines and glucacorticoids have received little attention. A5 49 epithelial cells were cultured in Dulbecco's modified Eagle's medium sup plemented with 10% foetal bovine serum, and starved for 24 h. The effect of the pro-inflammatory cytokine interleukin-1 beta (1-30 U/ml), and of the g lucocorticoid dexamethasone (1 muM) on NGF secretion was studied and quanti fied by enzyme-linked immunosorbent assay (ELISA). In addition, NGF product ion within the cells was visualized by immunocytochemistry. Under basal con ditions, A549 cells produced and secreted NGF (12.6 +/- 2.0 pg/ml). Stimula tion by interleukin-1 beta for 24 h induced a dose-dependent increase in NG F production (maximal at 10 U/ml with 59.6 +/- 3.5% increase, P < 0.05). De xamethasone (1 muM) markedly reduced the constitute NGF secretion by 44.9% (7.0 +/- 2.1 pg/ml, P < 0.001). In addition, the interleuk-in-1 beta -stimu lated NGF secretion was inhibited to approximately the same low level (8.5 +/- 2.5 pg/ml, P < 0.001). In conclusion, we here report that human airway A549 epithelia] cells are capable of producing NGF. This production is posi tively regulated by the pro-inflammatory interleukin-1 beta, and negatively regulated by dexamethasone. (C) 2001 Published by Elsevier Science B.V.