title: Epidermal photoprotection: comparative study of narrowband ultraviolet B minimal erythema doses with and without stratum corneum stripping in normal and vitiligo skin.
abstract: BACKGROUND
  Recent accumulating data in the literature have indicated a complex photoprotective role of the epidermis, and the role of melanin as the major epidermal photoprotective mechanism has become debatable.
  
  
  OBJECTIVE
  Comparative assessment of the photoprotective roles played by different epidermal structures and compounds.
  
  
  METHODS
  In total, 64 participants, comprising patients with vitiligo (n = 32) and healthy volunteers (n = 32), with skin phototypes (SPTs) II to V, were enrolled in the study. Areas of skin were delineated; for both lesional and nonlesional skin, the stratum corneum (the SC) was stripped, followed 24 h later by exposure to narrowband ultraviolet B (NB-UVB) irradiation, to measure the minimal erythema dose (MED) in normal, stripped normal, vitiliginous and stripped vitiliginous skin models. These MED values were used to assess the photoprotective role of epidermal structures: melanin, viable epidermis (VE) and the SC.
  
  
  RESULTS
  In the vitiligo group, the MED values were significantly (P < 0.05) different between the skin models, being highest in normal skin, followed by stripped normal, vitiliginous and stripped vitiliginous skin. A similar significance level was found within each SPT for almost all comparisons. There was also a significant (P < 0.001) positive correlation between MED and SPTs. There were also significant (P < 0.05) differences in MED values calculated for epidermal structures, being highest for VE, followed by melanin and then the SC, and there was a significant (P < 0.05) positive correlation between MED and SPTs.
  
  
  CONCLUSIONS
  Epidermal photoprotection may extend beyond melanin production, involving several factors such as epidermal layer thickness, optical properties and chromophores. Such a role was perceived to be reactive to UV irradiation, and more efficient in those with higher SPTs.
authors.affiliation: Department of Dermatology, Venereology and Andrology, Ain Shams University, Cairo, Egypt. ekramy.elkhateeb@med.asu.edu.eg
authors.forename: E A
authors.initials: EA
authors.lastname: El-Khateeb
authors.forename: N F
authors.initials: NF
authors.lastname: Ragab
authors.forename: S A
authors.initials: SA
authors.lastname: Mohamed
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D004307:Dose-Response Relationship, Radiation; D004817:Epidermis / Q000502:physiology / Q000528:radiation effects*; D004890:Erythema / Q000209:etiology; D006801:Humans; D008543:Melanins / Q000502:physiology / Q000528:radiation effects*; D008875:Middle Aged; D012880:Skin Pigmentation / Q000502:physiology / Q000528:radiation effects*; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014820:Vitiligo / Q000503:physiopathology*; D055815:Young Adult
chemical_list: D008543:Melanins