title: Highly abundant defense proteins in human sweat as revealed by targeted proteomics and label-free quantification mass spectrometry.
abstract: BACKGROUND
  The healthy human skin with its effective antimicrobial defense system forms an efficient barrier against invading pathogens. There is evidence suggesting that the composition of this chemical barrier varies between diseases, making the easily collected sweat an ideal candidate for biomarker discoveries.
  
  
  OBJECTIVE
  Our aim was to provide information about the normal composition of the sweat, and to study the chemical barrier found at the surface of skin.
  
  
  METHODS
  Sweat samples from healthy individuals were collected during sauna bathing, and the global protein panel was analysed by label-free mass spectrometry. SRM-based targeted proteomic methods were designed and stable isotope labelled reference peptides were used for method validation.
  
  
  RESULTS
  Ninety-five sweat proteins were identified, 20 of them were novel proteins. It was shown that dermcidin is the most abundant sweat protein, and along with apolipoprotein D, clusterin, prolactin-inducible protein and serum albumin, they make up 91% of secreted sweat proteins. The roles of these highly abundant proteins were reviewed; all of which have protective functions, highlighting the importance of sweat glands in composing the first line of innate immune defense system, and maintaining the epidermal barrier integrity.
  
  
  CONCLUSIONS
  Our findings with regard to the proteins forming the chemical barrier of the skin as determined by label-free quantification and targeted proteomics methods are in accordance with previous studies, and can be further used as a starting point for non-invasive sweat biomarker research.
authors: Department of Biochemistry and Molecular Biology, Proteomics Core Facility, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors: É
authors: É
authors: Csősz
authors: Department of Dermatology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors: G
authors: G
authors: Emri
authors: Department of Biochemistry and Molecular Biology, Proteomics Core Facility, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors: G
authors: G
authors: Kalló
authors: Center for Toxicology, University of Arizona, Tucson, AZ, USA.
authors: G
authors: G
authors: Tsaprailis
authors: Department of Biochemistry and Molecular Biology, Proteomics Core Facility, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors: J
authors: J
authors: Tőzsér
mesh_terms: D000328:Adult; D000418:Albumins / Q000032:analysis; D053399:Apolipoproteins D / Q000032:analysis; D002352:Carrier Proteins / Q000032:analysis; D051152:Clusterin / Q000032:analysis; D005260:Female; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D007113:Immunity, Innate; D008297:Male; D013058:Mass Spectrometry; D026901:Membrane Transport Proteins; D010455:Peptides / Q000032:analysis; D011506:Proteins / Q000032:analysis*; D040901:Proteomics; D012879:Skin Physiological Phenomena / Q000276:immunology*; D013542:Sweat / Q000737:chemistry*; D055815:Young Adult
chemical_list: D000418:Albumins; D053399:Apolipoproteins D; D002352:Carrier Proteins; D051152:Clusterin; D006023:Glycoproteins; D026901:Membrane Transport Proteins; C488892:PIP protein, human; D010455:Peptides; D011506:Proteins; C442243:dermcidin