ABNORMALITY OF WATER BARRIER FUNCTION IN PSORIASIS - ROLE OF CERAMIDEFRACTIONS

Background and Design: In psoriasis the formation of the cornified lay er is deranged and water flux is reportedly increased. We investigated three different forms of psoriasis: transepidermal water loss was mea sured on uninvolved skin and psoriatic plaques; lipids from plaques we re extracted; and ceramide distribution in scale vs normal stratum cor neum was compared. Moreover, the lipid biochemical results were compar ed with transepidermal water loss rates in the same lesions. To assess potential alteration in ceramide distribution, lipids from both psori atic scale and normal stratum corneum were extracted by the Bligh-Dyer method, separated on high performance thin layer chromatography plate s; and quantified by computerized densitometry. Water flux was measure d as transepidermal water loss using an evaporimeter; results between uninvolved and involved psoriatic skin and age-matched control skin we re statistically evaluated. Results: In comparison with normal stratum corneum, psoriatic plaque ceramides showed a different distribution; in particular, ceramide 1 was significantlydecreased. The increased tr ansepidermal water loss values of psoriatic plaques vs control skin an d between psoriatic involved vs uninvolved skin were significant. Conc lusion: Our findings indicate that in psoriasis the altered ceramide d istribution can be linked specifically to the defect in keratinocyte d ifferentiation; the defect in skin barrier function may be attributed largely or in part to ceramide 1 reduction.