A lipidomic platform establishment for structural identification of skin ceramides with non-hydroxyacyl chains.
The stratum corneum (SC) is the outermost layer of skin that functions as a barrier and protects against environmental influences and transepidermal water loss. Its unique morphology consists of keratin-enriched corneocytes embedded in a distinctive mixture of lipids containing mainly ceramides, free fatty acids, and cholesterol. Ceramides are sphingolipids consisting of sphingoid bases, which are linked to fatty acids by an amide bond. Typical sphingoid bases in the skin are composed of dihydrosphingosine (dS), sphingosine (S), phytosphingosine (P), and 6-hydroxysphingosine (H), and the fatty acid acyl chains are composed of non-hydroxy fatty acid (N), α-hydroxy fatty acid (A), ω-hydroxy fatty acid (O), and esterified ω-hydroxy fatty acid (E). The 16 ceramide classes include several combinations of sphingoid bases and fatty acid acyl chains. Among them, N-type ceramides are the most abundant in the SC. Mass spectrometry (MS)/MS analysis of N-type ceramides using chip-based direct infusion nanoelectrospray-ion trap mass spectrometry generated the characteristic fragmentation pattern of both acyl and sphingoid units, which could be applied to structural identification of ceramides. Based on the MS/MS fragmentation patterns of N-type ceramides, comprehensive fragmentation schemes were proposed. In addition, mass fragmentation patterns, which are specific to the sphingoid backbone of N-type ceramides, were found in higher m/z regions of tandem mass spectra. These characteristic and general fragmentation patterns were used to identify N-type ceramides in human SC. Based on established MS/MS fragmentation patterns of N-type ceramides, 52 ceramides (including different classes of NS, NdS, NP, and NH) were identified in human SC. The MS/MS fragmentation patterns of N-type ceramides were characterized by interpreting their product ion scan mass spectra. This information may be used to identify N-type ceramides in the SC of human, rat, and mouse skin.
College of Pharmacy and Research Institute of Pharmaceutical Sciences, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu, 702-701, South Korea.
Jung-Hoon
JH
Shin
Jong Cheol
JC
Shon
Kyohoon
K
Lee
Sunki
S
Kim
Chang Seo
CS
Park
Eung Ho
EH
Choi
Choong Hwan
CH
Lee
Hye Suk
HS
Lee
Kwang-Hyeon
KH
Liu
D002518:Ceramides / Q000032:analysis* / Q000737:chemistry; D002784:Cholesterol / Q000032:analysis / Q000737:chemistry; D005227:Fatty Acids / Q000032:analysis* / Q000737:chemistry; D006801:Humans; D015394:Molecular Structure; D012867:Skin / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
D002518:Ceramides; D005227:Fatty Acids; D002784:Cholesterol