Fig 1.
Structures of stratum corneum and formation of the corneocyte lipid envelope (CLE).
(a) An image of the cornified barrier obtained by electron microscopy [5]. In stratum corneum, the corneocytes are bound together by the fusion of three substructures: (i) polymerized proteins forming the corneocyte envelope (CE), (ii) extracellular lamellar lipids between cells, and (iii) a monolayer of covalently bound ceramides and fatty acids, the corneocyte lipid envelope (CLE), covering the CE and forming a scaffold for the extracellular lamellar lipids. (b) Our working hypothesis [9] requires the LOX-catalyzed oxidation of the linoleate in esterified omega-hydroxyacyl-sphingosine (EOS), ceramide, facilitating hydrolysis of the ester bond, separating ceramide OS for coupling to the CE protein by transglutaminase, finally forming the CLE. Trihydroxy-linoleic acid (triol) cleaved from ceramide EOS is produced as the final metabolite. (i) 9-hydroperoxy-11,12-octadecadienoate, (ii) 9,10-epoxy-11E-13-hydroxyoctadecenoate (iii) 9,10,13-trihydroxy-11E-octadecenoate.
Fig 2.
LC-MS analysis of triols. SIM chromatograms (m/z 329) of triols analyzed by reverse-phase LC-ESI-MS.
(a) Analysis of a mixture of authentic triols-1 to -8 (2 ng) as a standard, (b) triols of forehead skin in normal subjects and (c) atopic dermatitis patients, and (d) triols of forearm skin in normal subjects and (e) atopic dermatitis patients.
Table 1.
Baseline characteristics and comparison of TEWL and the quantity of trihydroxy-linoleic acids between normal subjects and atopic dermatitis patients.
Fig 3.
Correlation coefficients between trihydroxy-linoleic acid and TEWL.
(a) Forehead skin and (b) forearm skin of non-lesional area in atopic dermatitis.
Fig 4.
The mRNA expression of enzymes involved in CLE formation upon IL-4 stimulation.
ALOX12B, ALOXE3 and ABHD9 mRNA levels of primary normal human epidermal keratinocytes were measured by real-time RT-PCR. The mean values of threshold cycle were 27.5 ± 0.5 (ALOX12B), 22.4 ± 0.1 (ALOXE3), 23.1 ± 0.4 (ABHD9), 15.4 ± 0.4 (β-actin), respectively. The amount of mRNA was normalized to that of β-actin using the ΔCt method, as described in the manufacturer’s protocol. Data are expressed as mean ± SD (n = 6). One-way ANOVA with repeated measures was used for the comparison. Because the initial P value was less than 0.05, Scheffe’s test was used to determine the significance between groups. *p < 0.05 versus control.