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 μM) 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 μM; N = 9) occurred at 1 h (235±59 ng/mg protein), whereas maximum generation after PAF treatment (10 μM; N = 9) occurred at 6 h (153±48 ng/mg protein). Neither arachidonic acid nor PAF at concentrations up to 100 μM caused cell toxicity as determined by ⁵¹Cr release. 15-HETE at concentrations of ≥0.1 μM contracted isolated human bronchus. An initial small amplitude, short-lasting (< 15 min) contraction was followed by a much larger contraction beginning 30–60 min following 15-HETE challenge, reaching a maximum at ~ 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.