Lipoxygenase activity of Pityrosporum in vitro and in vivo.

Lipid peroxidation has been investigated both in cultures of Pityrosporum supplemented with different lipid classes and in skin surface lipids from patients affected with pityriasis versicolor. Thin-layer chromatography (TLC) and 2 spectrophotometric methods were used: the indirect thiobarbituric acid test and the direct N,N-diethyl-1,4-phenylene-diammonium sulfate (DEPD) test. The coupling of the DEPD test with the TLC technique performed by different eluent systems allowed the detection of the specific lipoperoxides deriving from the oxidation of the different lipid classes. In the cultures, Pityrosporum was capable of peroxidating not only unsaturated free fatty acids, but also unsaturated triglycerides, cholesterol, and squalene. A similar lipid peroxidation was observed in patients with pityriasis versicolor in skin lipids from areas positive for fungal hyphae and spores and fluorescent under the UV lamp (366 nm). The lipoperoxide values were significantly higher (p less than 0.05) than in skin lipids from normal controls. Hyphae and spore-negative areas of patients with pityriasis versicolor, whether apparently normal or achromic, showed no evidence of a significant lipid peroxidation and neither did skin areas of patients with pityriasis alba. Though further investigations are necessary, it seems reasonable to suggest, in analogy with other biologic systems, that the presence in skin lipids of a significant amount of highly reactive and cytotoxic lipoperoxides may play a role in the pathogenesis of skin alterations in pityriasis versicolor, including damage to melanocytes and resulting achromia.