PLATELET-ACTIVATING-FACTOR (PAF) AND LYSO-PAF IN PSORIASIS

Previous studies have shown that scale from lesional psoriatic skin co ntains substantial amounts of platelet activating factor (PAF). In thi s study, PAF and its immediate precursor lyso-PAF, were measured in ex udates from abrasions on lesional and uninvolved psoriatic skin, and f rom skin of healthy subjects. The mean amounts of PAF recovered from l esional and uninvolved psoriatic skin (n = 13) and from healthy skin ( n = 14) were not significantly different (range 0.05-2.14 pmol/sample) . Mean recoveries of lyso-PAF from lesional psoriatic skin (n = 9) and skin of healthy subjects (n = 13) were also similar (9.5 +/- 1.9 and 11.0 +/- 1.9 pmol/sample, respectively), but significantly less lyso-P AF was found in exudates from the uninvolved psoriatic skin (n = 9; 3. 1 +/- 0.4 pmol/sample; P < 0.01 relative to both lesional psoriasis an d healthy skin). The finding of reduced lyso-PAF in uninvolved psoriat ic skin was unexpected because increased phospholipase-A(2) activity i s associated with psoriasis. These results do not support the hypothes is that extracellular PAF contributes significantly to the inflammatio n associated with psoriasis.