Modulation of phospholipase A activity in psoriatic skin.

The activity of phospholipase A2 was tested both in rat skin and human psoriatic skin before and after systemic treatment with a retinoic acid derivative: RO 10-9359. An increase of activity was found in the rat skin homogenates when the animals were treated with 3 mg/kg/day of the drug for 8 days, while no effect was found following treatment with 1.5 mg/kg/day for 10 days. On the contrary a decrease of this activity was found in homogenates from both involved and uninvolved skin of psoriatic patients after systemic treatment with 1-1.5 mg/kg/day for 10 days. These different results are discussed also in the light of the clinical effect of RO 10-9359 on psoriasis.