Ceramide composition of the psoriatic scale.

This paper investigates the ceramide composition of the psoriatic scale compared with that of normal human SC. A method was optimalized, based on TLC separation followed by densitometry, allowing the provision of good resolution and quantification of ceramide fractions from both normal and pathological specimens. Seven ceramide fractions were isolated and submitted to compositional analysis. The obtained results suggested a revisitation of previous ceramide designation. Therefore a simple classification is suggested, based on grouping ceramides carrying structural similarities under common codes. According to these rules, ceramides were grouped into five classes designated as: (1) Cer[EOS], which contains ester-linked fatty acids, omega-OH fatty acids and sphingosines; (2) Cer[NS], which contains non-OH fatty acids and sphingosines; (3) Cer[NP], which contains non-OH fatty acids and phytosphingosines; (4) Cer[AS], which contains alpha-OH fatty acids and sphingosines; (5) Cer[AP], which contains alpha-OH fatty acids and phytosphingosines. Analysis of ceramides from the psoriatic scale, compared to those from normal human SC, resulted in an impairment of the Cer[EOS] content as well as of the ceramides containing phytosphingosine, with concurrent increase in ceramides containing sphingosine, being the total amount maintained identical. Since one of the suggested pathways for phytosphingosine biosynthesis involves the water addition to the corresponding sphingosine double bond, we can speculate that the observed alteration is due to a deranged water bioavailability, associated with psoriasis.

Abnormality of water barrier function in psoriasis. Role of ceramide fractions.

BACKGROUND AND DESIGN: In psoriasis the formation of the cornified layer is deranged and water flux is reportedly increased. We investigated three different forms of psoriasis: transepidermal water loss was measured on uninvolved skin and psoriatic plaques; lipids from plaques were extracted; and ceramide distribution in scale vs normal stratum corneum was compared. Moreover, the lipid biochemical results were compared with transepidermal water loss rates in the same lesions. To assess potential alteration in ceramide distribution, lipids from both psoriatic scale and normal stratum corneum were extracted by the Bligh-Dyer method, separated on high performance thin layer chromatography plates, and quantified by computerized densitometry. Water flux was measured as transepidermal water loss using an evaporimeter; results between uninvolved and involved psoriatic skin and age-matched control skin were statistically evaluated. RESULTS: In comparison with normal stratum corneum, psoriatic plaque ceramides showed a different distribution; in particular, ceramide 1 was significantly decreased. The increased transepidermal water loss values of psoriatic plaques vs control skin and between psoriatic involved vs uninvolved skin were significant. CONCLUSION: Our findings indicate that in psoriasis the altered ceramide distribution can be linked specifically to the defect in keratinocyte differentiation; the defect in skin barrier function may be attributed largely or in part to ceramide 1 reduction.

Interlamellar lipid differences between normal and psoriatic stratum corneum.

Intercellular lipids of the stratum corneum are involved in permeability barrier integrity and function. In psoriasis, desquamation and permeability barrier homeostasis are modified; these observations are consistent with an alteration in stratum corneum lipid production. Therefore, in the present study, we determined and compared the total content of the three main intercellular lipids in psoriatic scales and normal human stratum corneum. Our results showed that the relative free fatty acid content decreased remarkably (46%) in psoriatic scales, compared with normal human stratum corneum. This decrease may reflect a general state of emergency of keratinocytes, in which free fatty acids can be employed.

Cellular uptake of coumarin-6 as a model drug loaded in solid lipid nanoparticles.

The aim of present work was to elucidate the interaction of solid lipid nanoparticles (SLNs) with cellular plasma-membrane to gain insight of intracellular drug delivery. To this aim we followed the uptake of coumarin-6 (a drug model) either free in the extracellular medium or loaded on SLN (c-SLN). Alveolar epithelial cells were exposed to a biocompatible concentration of c-SLN (0.01 mg/ml of tripalmitin) prepared by warm microemulsion whose lipid matrix was constituted by low melting point molecules (fatty acids, triglycerides). Intracellular fluorescence and preferential accumulation in the perinuclear region were increased by 54.8% on comparing c-SLN to the same amount of free coumarin-6 in the medium. Lowering temperature from 37 ° to 4 °C decreased the intracellular signal intensity by about 48% equally for the free as well as for loaded drug, thus suggesting the inhibition of a similar non-endocytotic entrance pathway. No specific co-localization of the fluorescence with intracellular organelles was found. The c-SLN calorimetric profile obtained with differential scanning calorimetry (DSC), revealing transition within the range 58-62 °C, altered remarkably upon incubation with cells, suggesting a change in SLN structure after association with cells membranes. We propose that the uptake of the model drug loaded on SLN is only partly related to the endocytotic pathway; it occurs despite the loss of integrity of the original SLN structure and it appears to be more efficient when the drug is vehicled rather than being free in the culture medium.