engleski

Determination of free fatty acids of different chain lengths in the stratum corneum as a biomarker of skin barrier

Exposure to skin irritants like wet work or organic solvents can lead to changes in the composition and organization of the skin lipids which are the principal barrier of the skin. In addition to environmental insults, alteration of the skin lipids can be caused by genetic factors or inflammation. E.g. recently it has been shown that individuals with atopic dermatitis have higher proportion of shorter chain free fatty acids (FFAs) and ceramides which was directly associated with reduced skin barrier (Janssens et al. Journal of Lipid Research 2013). Therefore, relative composition of FFAs might be a relevant biomarker of the skin barrier function. The purpose of this work was to develop feasible and reliable LC-ESI-MS method for the determination of saturated (C16:0, C18:0, C22:0, C24:0, C26:0, C28:0) and monounsaturated (C18:1, C18:2) FFAs in the stratum corneum obtained by tape stripping technique. Human stratum corneum samples were obtained from the inner forearm by tape stripping technique. After extraction with the mixture of solvents FFAs were subsequently converted to their 3-acyloxymethyl-1-methylpyridinium iodide derivatives by reaction with in-house synthesized reagents. All FAA derivatives were detected in positive ionization mode using RP-LC-ESI-MS and multiple reaction monitoring (MRM). The content of some shorter chain fatty acids (C16 and C18) originated from the adhesive tape were calculated from the correlation with C12:0 signal, which was not detected in the stratum corneum. To overcome the matrix effect, FAAs in the human stratum corneum were quantified by “surrogate analyte” method and internal standardization using isotope labelled derivatives of FAAs. Developed LC-ESI-MS method showed to be reproducible and sensitive enough for simultaneous detection and quantification of eight long and very long chain FFAs in the human stratum corneum. The method also showed good recovery, precision and large linear range for all FFAs. So far we have applied the method to investigate the differences in the composition and levels of FFA in the stratum corneum between control subjects and AD patients. We intend, in cooperation with other STANDERM members to apply this method to study the role of the relative composition of FFA for individual susceptibility to common skin irritants.

free fatty acids; skin barrier function; LC-MS/MS

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