title: Dihydrolipoyl dehydrogenase as a potential UVB target in skin epidermis; using an integrated approach of label-free quantitative proteomics and targeted metabolite analysis.
abstract: Photodamage is extrinsically induced by overexposure to ultraviolet (UV) radiation, and it increases the risk of various skin disorders. Therefore, discovery of novel biomarkers of photodamage is important. In this study, using LC-MS/MS analysis of epidermis from UVB-irradiated hairless mice, we identified 57 proteins whose levels changed after UVB exposure, and selected 7 proteins related to the tricarboxylic acid (TCA) cycle through pathway analysis. Dihydrolipoyl dehydrogenase (DLD) was the only TCA cycle-associated protein that showed a decreased expression after the UVB exposure. We also performed targeted analysis to detect intermediates and products of the TCA cycle using GC-TOF-MS. Interestingly, malic acid and fumaric acid levels significantly decreased in the UVB-treated group. Our results demonstrate that DLD and its associated metabolites, malic acid and fumaric acid, may be candidate biomarkers of UVB-induced skin photoaging. Additionally, we showed that Aloe vera, a natural skin moisturizer, regulated DLD, malic acid and fumaric acid levels in UVB-exposed epidermis. Our strategy to integrate the proteome and targeted metabolite to detect novel UVB targets will lead to a better understanding of skin photoaging and photodamage. Our study also supports that A. vera exerts significant anti-photodamage activity via regulation of DLD, a novel UVB target, in the epidermis.
  
  
  CONCLUSIONS
  This study is the first example of an integration of proteomic and metabolite analysis techniques to find new biomarker candidates for the regulation of the UVB-induced skin photoaging. DLD, malic acid, and fumaric acid can be used for development of cosmeceuticals and nutraceuticals regulating the change of skin metabolism induced by the UVB overexposure. Moreover, this is also the first attempt to investigate the role of the TCA cycle in photodamaged epidermis. Our integration of the proteomic and targeted metabolite analyses will lead to a better understanding of the unidentified photobiological results from UVB-irradiated models and can elicit new diagnostic and treatment strategies based on altered metabolism.
authors.affiliation: College of Pharmacy, Gachon University, Incheon, Republic of Korea. Electronic address: jubbi@hanmail.net.
authors.forename: Eunjung
authors.initials: E
authors.lastname: Moon
authors.affiliation: Department of Bioscience and Biotechnology, Konkuk University, Seoul, Republic of Korea. Electronic address: ramgee@naver.com.
authors.forename: Hye Min
authors.initials: HM
authors.lastname: Park
authors.affiliation: Department of Bioscience and Biotechnology, Konkuk University, Seoul, Republic of Korea. Electronic address: chlee123@konkuk.ac.kr.
authors.forename: Choong Hwan
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Life Science Research Institute, Univera, Inc., Seoul, Republic of Korea. Electronic address: sgildo@univera.com.
authors.forename: Seon-Gil
authors.initials: SG
authors.lastname: Do
authors.affiliation: College of Pharmacy, Gachon University, Incheon, Republic of Korea. Electronic address: bio4647@naver.com.
authors.forename: Jong-Moon
authors.initials: JM
authors.lastname: Park
authors.affiliation: College of Pharmacy, Gachon University, Incheon, Republic of Korea. Electronic address: ddasehan@nate.com.
authors.forename: Na-Young
authors.initials: NY
authors.lastname: Han
authors.affiliation: College of Pharmacy, Gachon University, Incheon, Republic of Korea. Electronic address: dvmoono@naver.com.
authors.forename: Moon Ho
authors.initials: MH
authors.lastname: Do
authors.affiliation: College of Pharmacy, Gachon University, Incheon, Republic of Korea. Electronic address: whdgkfl@naver.com.
authors.forename: Jong Ha
authors.initials: JH
authors.lastname: Lee
authors.affiliation: College of Pharmacy, Gachon University, Incheon, Republic of Korea; Gachon Medical Research Institute, Gil Medical Center, Incheon, Republic of Korea; Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Incheon, Republic of Korea. Electronic address: hklee@gachon.ac.kr.
authors.forename: Hookeun
authors.initials: H
authors.lastname: Lee
authors.affiliation: College of Pharmacy, Gachon University, Incheon, Republic of Korea; Gachon Medical Research Institute, Gil Medical Center, Incheon, Republic of Korea. Electronic address: sunnykim@gachon.ac.kr.
authors.forename: Sun Yeou
authors.initials: SY
authors.lastname: Kim
mesh_terms: D000504:Aloe / Q000737:chemistry; D000818:Animals; D002952:Citric Acid Cycle / Q000187:drug effects / Q000528:radiation effects; D008058:Dihydrolipoamide Dehydrogenase / Q000096:biosynthesis*; D004817:Epidermis / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000528:radiation effects*; D051379:Mice; D008812:Mice, Hairless; D040901:Proteomics; D015595:Skin Aging / Q000187:drug effects / Q000528:radiation effects*; D063465:Skin Cream / Q000737:chemistry / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D008058:Dihydrolipoamide Dehydrogenase
keywords: Aloe vera; Dihydrolipoyl dehydrogenase; Epidermis; Integration of proteomics and targeted metabolite analysis; Photoaging; UVB targets