Abstract
Lipids are important structural and functional components of the skin. Alterations in the lipid composition of the epidermis are associated with inflammation and can affect the barrier function of the skin. SHARPIN-deficient cpdm mice develop a chronic dermatitis with similarities to atopic dermatitis in humans. Here, we used a recently-developed approach named multiple reaction monitoring (MRM)-profiling and single ion monitoring to rapidly identify discriminative lipid ions. Shorter fatty acyl residues and increased relative amounts of sphingosine ceramides were observed in cpdm epidermis compared to wild type mice. These changes were accompanied by downregulation of the Fasn gene which encodes fatty acid synthase. A profile of diverse lipids was generated by fast screening of over 300 transitions (ion pairs). Tentative attribution of the most significant transitions was confirmed by product ion scan (MS/MS), and the MRM-profiling linear intensity response was validated with a C17-ceramide lipid standard. Relative quantification of sphingosine ceramides CerAS(d18:1/24:0)2OH, CerAS(d18:1/16:0)2OH and CerNS(d18:1/16:0) discriminated between the two groups with 100% accuracy, while the free fatty acids cerotic acid, 16-hydroxy palmitic acid, and docosahexaenoic acid (DHA) had 96.4% of accuracy. Validation by liquid chromatography tandem mass spectrometry (LC-MS/MS) of the above-mentioned ceramides was in agreement with MRM-profiling results. Identification and rapid monitoring of these lipids represent a tool to assess therapeutic outcomes in SHARPIN-deficient mice and other mouse models of dermatitis and may have diagnostic utility in atopic dermatitis.
Highlights
Lipids play an important role in maintaining the integrity of the skin and in inflammatory skin diseases, phototoxicity, and wound healing [1]
Since each phospholipid contains two fatty acids esterified to a glycerol, lipids are attributed by their class abbreviation (PS, PI, PE, principal components (PC)) followed by the number of carbon atoms in the esterified fatty acid, a colon, and the number of carbon-carbon double bonds in Profiling of epidermal lipids in dermatitis parentheses, such as PC(34:1)
Based on the results from multiple reaction monitoring (MRM) profiling, we examined the expression levels of two enzymes involved in biosynthesis and elongation of fatty acids, namely fatty acid synthase (FASN) and elongation of very long fatty acids-like 1 (ELOVL1), and two enzymes of the sphingolipid pathway, phosphodiesterase 12 (PDE12) and beta acid glucosidase (GBA)
Summary
Lipids play an important role in maintaining the integrity of the skin and in inflammatory skin diseases, phototoxicity, and wound healing [1]. Profiling of epidermal lipids in dermatitis design, data collection and analysis, decision to publish, or preparation of the manuscript
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