Possible defects in triacylglycerol and phosphatidylcholine metabolism in psoriatic epidermis.

Biopsies of normal skin, psoriatic lesions and the adjacent psoriatic skin were incubated with I-14C-acetate, 32P-orthophosphate and U-14C-glycerol. Total incorporation of I-14C-acetate into psoriatic lesions (17 samples) was 50% higher than in the adjacent uninvolved epidermis (9 samples) and 120% higher than into normal epidermis (10 samples). In the psoriatic lesion a much higher proportion of the total incorporation was into the neutral lipids and was due mainly to a very high incorporation of I-14C-acetate into the triacylglycerols. The I-14C-acetate incorporated into the phospholipids and especially phosphatidylcholine was proportionally much less in the psoriatic lesion and uninvolved psoriatic epidermis than in normal epidermis even though the incorporation of 32P-orthophosphate and U-14C-glycerol, both representing de novo synthesis, into the phospholipids in the psoriatic lesions and uninvolved epidermis were higher (four-fold in lesion) than in normal epidermis. Our findings (1) are evidence for a much increased triacylglycerol synthesis in psoriatic epidermis which would account for the long-known observation of lipid droplet accumulation in psoriatic cells; (2) suggest that in psoriatic epidermis there is a defect in phospholipid metabolism mainly involving phosphatidycholine and the deacylation (phospholipase A)-reacylation (phospholipid acyltransferase) cycle for fatty acid transfer.