Abstract
The cause of enormous accumulation of arachidonic acid (AA) in the epidermis of psoriasis (a benign epidermal hyperproliferative disease) patients is unknown. As an initial step to elucidate the reason, the fatty acid composition in whole plasma lipid extract of psoriatic and normal subjects, male and female separately, was studied by gas chromatography. The results revealed a decrease in plasma linoleic acid (LA), a major component of whole plasma fatty acid, in both male and female psoriatic patients as the only statistically significant finding. A statistically significant decrease in AA in psoriatic plasma as reported previously was not confirmed in males. The results suggest that plasma LA in psoriatic patients is selectively incorporated into epidermis and transformed into AA there, so as to meet the great demand of psoriatic epidermis for AA. However, another possibility is also considered that a decrease in LA itself is the cause of psoriasis, since animals fed an essential fatty acid-deficient diet show psoriasis-like skin and their epidermal DNA synthesis is increased. Interestingly, increased tendency of plasma docosahexaenoic acid (DCHA) level in psoriatic patients was also found, which has not been reported before. Just as indomethacin exacerbates psoriasis, DCHA, which was shown to be a strong competitive inhibitor of AA conversion to prostaglandins, may be involved in the development of psoriasis.
