Inhibitor(s) of prostaglandin synthesis in psoriatic plaque

Abstract

IN 1926, Woronoff¹ described an area of blanched skin surrounding psoriatic lesions. The mechanisms of this reaction were unknown but were thought to be a consequence of vasoconstriction. In considering the probable explanation of the blanched area, we have noted that the blanched area is approximately the same width (1 cm) around the psoriatic lesion irrespective, of the size of the lesion (suggesting that a substance diffuses out of the lesion), and the whitened area does not become red during ultraviolet light therapy. Snyder and Eaglstein reported that the redness following exposure to ultraviolet light can be aborted by treatment with indomethacin, which is known to inhibit the synthesis of prostaglandins (PGs^2,3). We have also found that: (1) PGE₂ levels in whole skin removed from the blanched area are one-third of those in normal skin; (2) injection of PGE₂ into the blanched area produced redness, and (3) an inhibitor(s) of PG synthesis was present in this blanched area (our unpublished results). These observations suggested that a diffusable inhibitor of PG synthesis was present within the psoriatic lesion. We now report the detection of an inhibitor(s) of PG synthesis in psoriatic plaque that is not present in extracts of uninvolved skin obtained from either psoriatic patients or normal volunteers.