title: Non-invasive monitoring of oxidative skin stress by ultraweak photon emission measurement. II: biological validation on ultraviolet A-stressed skin.
abstract: OBJECTIVE
  Several physical or chemical environmental stressors generate reactive oxygen species, which trigger oxidation reactions of cells or tissues and thereby induce a correlated ultraweak photon emission (UPE) signal. The present study was designed to qualify and validate UPE measurement following ultraviolet (UV) excitation of porcine and human skin as an analytical method to assess the potency of topical antioxidants in vivo.
  
  
  METHODS
  UPE of porcine skin in vitro and human skin in vivo following excitation with UVA was recorded using sensitive photomultiplier systems. For validation purposes, the effects of variation of extrinsic and intrinsic parameters encompassing skin thickness, humidity, temperature, pH, and composition of the surrounding atmosphere were assessed. Signals were analyzed with regard to overall signal intensity and spectral distribution. In two clinical trials enrolling 20 volunteers each, the effects of topical antioxidant treatment on UVA-induced UPE were validated.
  
  
  RESULTS
  Different stressors encompassing exposition to ozone, UVA irradiation, or even cigarette smoke induced UPE of skin. Critical parameters affecting the quality and quantity of the UPE signal were the spectral composition of the exciting UV light, skin temperature, skin humidity, and the O(2) concentration of the surrounding atmosphere. Generally, UVA-induced UPE decreased with increasing temperature, humidity, and O(2) concentration. Skin pH had no significant effect on UPE with regard to signal quality and quantity over a pH range of 2.8-8.2. In a clinical study UPE measurement following UVA excitation could precisely reflect a dose-dependent antioxidant effect of topically applied vitamin C and alpha-glucosylrutin.
  
  
  CONCLUSIONS
  Our data indicate that UVA irradiation induces UPE especially in deeper (living) skin layers, where antioxidants must be active in order to interfere with accelerated skin ageing. Based on the clinical data, and with knowledge of modulating external variables, UPE measurement following UV excitation can be qualified as a reliable and valid method for the non-invasive measurement of antioxidant efficacy on the skin.
authors.affiliation: F&E cosmed, Beiersdorf AG, Hamburg, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Hagens
authors.forename: Faryar
authors.initials: F
authors.lastname: Khabiri
authors.forename: Volker
authors.initials: V
authors.lastname: Schreiner
authors.forename: Horst
authors.initials: H
authors.lastname: Wenck
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Wittern
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Duchstein
authors.forename: Weiping
authors.initials: W
authors.lastname: Mei
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D001703:Biophysics / Q000379:methods*; D005260:Female; D005990:Glycerol / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008875:Middle Aged; D018384:Oxidative Stress; D010100:Oxygen; D017785:Photons; D011829:Radiation Dosage; D012431:Rutin / Q000031:analogs & derivatives / Q000494:pharmacology; D012867:Skin / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D012879:Skin Physiological Phenomena; D018709:Statistics, Nonparametric; D013552:Swine; D014312:Trisaccharides / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D014312:Trisaccharides; C069037:4(G)-alpha-glucopyranosyl-rutin; D012431:Rutin; D005990:Glycerol; D001205:Ascorbic Acid; D010100:Oxygen