Stimulation of human airway epithelial cells by platelet activating factor (PAF) and arachidonic acid produces 15-hydroxyeicosatetraenoic acid (15-HETE) capable of contracting bronchial smooth muscle.

Human airway epithelial cells grown to confluence were incubated with varying concentrations (10-100 microM) of arachidonic acid or platelet activating factor (PAF) for periods of 30 min to 24 h. Both stimuli caused the production of 15-hydroxyeicosatetraenoic acid (15-HETE) by epithelial cells as determined by HPLC. Neither stimulus caused the production of leukotrienes, thromboxane or prostaglandins aside from minimal amounts of PGE2. Maximal production of 15-HETE after arachidonic acid (10 microM; N = 9) occurred at 1 h (235 +/- 59 ng/mg protein), whereas maximum generation after PAF treatment (10 microM; N = 9) occurred at 6 h (153 +/- 48 ng/mg protein). Neither arachidonic acid nor PAF at concentrations up to 100 microM caused cell toxicity as determined by 51Cr release. 15-HETE at concentrations of greater than or equal to 0.1 microM contracted isolated human bronchus. An initial small amplitude, short-lasting (less than 15 min) contraction was followed by a much larger contraction beginning 30-60 min following 15-HETE challenge, reaching a maximum at approximately 2 hr. These results demonstrate that PAF may induce delayed airway smooth muscle contraction by the generation of 15-HETE from epithelial cells. The kinetics of 15-HETE generation and its contractile activity are compatible with it being a mediator of the late asthmatic reaction.