Polarized release of lipid mediators derived from phospholipase A2 activity in a human bronchial cell line

The release of arachidonic acid (AA) and platelet activating factor (PAF) from airway epithelial cells may be an important mediating factor in lung physiological and inflammatory processes. The type of lung response may be determined by the directional release of AA and PAF. We used the human bronchial epithelial cell line, BEAS2B (S6 subclone; BEAS), to investigate the polarized release of AA and PAF from lung epithelial cells. BEAS, grown on Transwell filters, were prelabeled with either 3H-AA or 3H-lyso-PAF. 3H-AA products and 3H-PAF were analyzed by high performance liquid chromatography and thin layer chromatography, respectively. BEAS incubated with melittin (2-4 micrograms/ml for 15 min) had an increased release (compared to vehicle-incubated cells) of both free 3H-AA and 3H-PAF into the apical compartment but not into the basolateral compartment. Treatment of the BEAS cells with the phospholipase A2 (PLA2) inhibitor mepacrine (1 mM) prior to, and during, incubation with melittin inhibited the increase in 3H-AA and 3H-PAF release into the apical compartment by 65% and 100%, respectively. Exposure of BEAS cells to ozone (O3; 1.0 ppm for 15 min) increased the release of polar 3H-AA products as well as 3H-PAF into both the apical and basolateral compartments. Mepacrine did not significantly inhibit the O3-induced release of polar 3H-AA products or 3H-PAF into either the apical or basolateral compartments. These data suggest the direction of the release of 3H-AA (or 3H-AA products) and 3H-PAF is stimulus-specific and that PLA2 involvement in the release of the lipids is also dependent on the stimulus. The directional release of AA, AA products, and PAF may be important in the airways responses to various agonists and oxidants.