Platelet activating factor stimulates arachidonic acid release in differentiated keratinocytes via arachidonyl non-selective phospholipase A2.

Platelet activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is known to be present in excess in psoriatic skin, but its exact role is uncertain. In the present study we demonstrate for the first time the role of group VI PLA(2) in PAF-induced arachidonic acid release in highly differentiated human keratinocytes. The group IValpha PLA(2) also participates in the release, while secretory PLA(2)s play a minor role. Two anti-inflammatory synthetic fatty acids, tetradecylthioacetic acid and tetradecylselenoacetic acid, are shown to interfere with signalling events upstream of group IValpha PLA(2) activation. In summary, our major novel finding is the involvement of the arachidonyl non-selective group VI PLA(2) in PAF-induced inflammatory responses.