Stratum corneum lipids in disorders of cornification: increased cholesterol sulfate content of stratum corneum in recessive x-linked ichthyosis.

Abstract

A B S T R A C T Activity of the microsomal enzyme, steroid sulfatase, is absent in keratinocytes, fibroblasts, and leukocytes of patienits with recessive xlinked ichthyosis. This study was uiidertaken to determine if cholesterol sulfate, a substrate of this enzyme, accumulates in the pathological scale of these patients.Scales from 8 patients with recessive x-linked ichthyosis, 10 patienits with other fornms of ichthyosis, and normal human outer stratum corneum were extracted with chloroform/water (1:2:0.8 by vol) and lipids were fractionated by quantitative, sequential thin-layer chromatography. Cholesterol sulfate was identified by cochromatography in several solvent systemns, by its staining characteristics, by biochemical analysis, and by mass spectrometry. The mean cholesterol sulfate content of recessive x-linked ichthyotic scale was 12.5+0.8% of the total lipid, a fivefold increase over normal (P < 0.0025), whereas the cholesterol sulfate content of other ichthyotic scale was normal. This increase in cholesterol sulfate content was accompanied by a decrease in total neutral lipids (P < 0.0025) and free sterols (P < 0.025) but no change in sterol esters or total sterols. These results demonstrate that deficiency of steroid sulfatase in recessive x-linked ichthyosis results in excessive accumulation of a substrate, cholesterol sulfate, in the pathologic scale, which may underly the pathogenesis of the scaling in this disorder. Measurement of cholesterol sulfate content in scale provides an alternative method to enzymatic assay for the diagnosis of this form of ichthyosis.

Stratum corneum lipids in disorders of cornification. Steroid sulfatase and cholesterol sulfate in normal desquamation and the pathogenesis of recessive X-linked ichthyosis.

“…Previous studies have demonstrated that absence of the enzyme, steroid sulfatase, in RXLI is associated with accumulation of cholesterol sulfate in erythrocytes (7), serum (8), and stratum corneum (9). The possibility that the increased cholesterol sulfate in RXLI stratum corneum results from passive accumulation of circulating cholesterol sulfate seems unlikely, since the concentration of cholesterol sulfate in serum and erythrocyte membranes in RXLI are an order of magnitude less than the levels encountered in normal epidermis, and two orders of (26).…”

“…The cholesterol sulfate content of portions of the stratum basale/spinosum, stratum granulosum, and the stratum corneum fractions from eight normals and five RXLI patients was assessed by sequential, quantitative thin-layer chromatography (TLC) as described recently (9,11). Because of its limited lipid solubility, cholesterol sulfate is found not only in the organic phase, but also in the aqueous-methanol phase unless 0.1 M KCI is added to the extraction mixture, which drives all of the cholesterol sulfate into the lipidcontaining infranatants (9).…”

“…The cholesterol sulfate content of portions of the stratum basale/spinosum, stratum granulosum, and the stratum corneum fractions from eight normals and five RXLI patients was assessed by sequential, quantitative thin-layer chromatography (TLC) as described recently (9,11). Because of its limited lipid solubility, cholesterol sulfate is found not only in the organic phase, but also in the aqueous-methanol phase unless 0.1 M KCI is added to the extraction mixture, which drives all of the cholesterol sulfate into the lipidcontaining infranatants (9). After fractionation of lipid extracts in tetrahydrofuran/methylal/methanol:4 M ammonium hydroxide (60:30:10:4, vol), the cholesterol sulfate-containing fraction from the normal skin samples, visualized by black light fluorescence after spraying with the fluorophore, 8-anilino-I-naphthalene sulfonic acid, was excised, extracted in Bligh-Dyer solvents (19,20) that contained 0.1 M KCl, and measured colorimetrically by the Franey-Amador method (21).…”

“…Previously characterized by inheritance pattern and clinical presentation (1), this disorder can now be diagnosed biochemically because of the recent discovery that patients with RXLI lack the enzyme steroid sulfatase (2,3). Presumably, as a consequence of steroid sulfatase deficiency in skin and other tissues (4)(5)(6), one substrate, cholesterol sulfate, accumulates in red blood cells (7), serum (7,8), and stratum corneum (9). In contrast, sulfated steroid hormones, such as dehydroepiandrosterone sulfate, that are also substrates of this enzyme in vitro, do not accumulate in either blood or urine (8,10).…”

Filaggrin Genotype in Ichthyosis Vulgaris Predicts Abnormalities in Epidermal Structure and Function

“…Using the water-soluble, low molecular weight tracer colloidal lanthanum, 62 we determined whether there was increased permeability due to leaky corneocytes, resulting in increased transcellular water movement (fragility), or an abnormality due to enhanced extracellular permeability (normal SC excludes lanthanum movement). Skin fragments prepared as described above were immersed in 4% lanthanum nitrate in 0.05 mol/L Tris buffer (pH 7.4) containing 2% glutaraldehyde and 1% paraformaldehyde for 1 hour at room temperature.…”