Fig. 6.

Human epidermis shows higher levels of triHOME and HODE-EOS and reduced levels of epoxyHOME-EOS in upper layers. Tape strips were acquired from the volar forearm of healthy volunteers (n = 5 subjects, 30 strips per person, mean ± SEM). Strips were combined into groups of 3 and lipids extracted and analyzed using LC/MS/MS as described in Materials and methods for total levels of lipid present. A: LA-EOS is evenly distributed throughout the skin layers. B: Epoxy-HOME EOS increases with greater epidermal depth and is the highest in the stratum granulosum (SG)/stratum spinosum (SS) layers. C and D: TriHOME EOS and HODE EOS are increased in the upper layers of the epidermis and appear the highest in the stratum corneum (SC). EOS, esterified omega-hydroxy sphingosine; LA, linoleic acid.