title: Narrow-band ultraviolet B radiation induces the expression of β-endorphin in human skin in vivo.
abstract: BACKGROUND
  Ultraviolet radiation (UVR) from the sun and solaria has addictive properties that may develop into dependence. In mice, UVR addiction was connected to β-endorphin (β-END) formed in the skin after UVR exposure. In humans, the formation of β-END in skin keratinocytes has not been confirmed in vivo.
  
  
  OBJECTIVE
  To determine with immunohistochemistry if sub-erythematous narrow-band UV-B (NB-UV-B) exposures stimulate p53 mediated expression of pro-opiomelanocortin (POMC), β-END and α-melanocyte stimulating hormone (α-MSH) in human skin keratinocytes in vivo.
  
  
  METHODS
  Within 12 healthy volunteers, 7 received a single 1 standard erythema dose (SED) of NB-UV-B on their whole body, and 5 volunteers received a cumulative dose of 3 SED delivered on two subsequent days i.e., 1+2 SED. Skin biopsies were taken immediately before the first exposure and at 24h from the last UV-B exposure to assess p53, β-END, POMC, and α-MSH expression.
  
  
  RESULTS
  Nuclear p53 expression increased in all samples taken at 24h after NB-UV-B exposure. UV-B irradiation also increased epidermal β-END expression in 11 out of 12 samples taken at 24h after UV-B exposure. The brownish staining was localized in the cytoplasm of keratinocytes and around the nuclei, being more pronounced in the basal cell layers. POMC and α-MSH staining showed no obvious meaningful increase since only one section of each showed any change compared with basal levels.
  
  
  CONCLUSIONS
  Our study is the first to show that UV-B exposures increase β-END expression in epidermal keratinocytes of human skin in vivo, which could be the link to proposed UVR addiction.
authors.affiliation: University of Tampere, Medical School, Department of Dermatology and Venereology, Finland; Tampere University Hospital, Department of Dermatology and Allergology, Finland. Electronic address: jussila.anna.k@student.uta.fi.
authors.forename: Anna
authors.initials: A
authors.lastname: Jussila
authors.affiliation: University of Tampere, Department of Pathology & Fimlab Laboratories, Finland. Electronic address: riitta.huotari-orava@staff.uta.fi.
authors.forename: Riitta
authors.initials: R
authors.lastname: Huotari-Orava
authors.affiliation: STUK - Radiation and Nuclear Safety Authority, Finland. Electronic address: lasse.ylianttila@stuk.fi.
authors.forename: Lasse
authors.initials: L
authors.lastname: Ylianttila
authors.affiliation: National Institute for Health and Welfare, Department of Health, Finland. Electronic address: timo.partonen@thl.fi.
authors.forename: Timo
authors.initials: T
authors.lastname: Partonen
authors.affiliation: University of Tampere, Medical School, Department of Dermatology and Venereology, Finland; Tampere University Hospital, Department of Dermatology and Allergology, Finland. Electronic address: erna.snellman@staff.uta.fi.
authors.forename: Erna
authors.initials: E
authors.lastname: Snellman
mesh_terms: D000328:Adult; D004817:Epidermis / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D011333:Pro-Opiomelanocortin / Q000378:metabolism; D012867:Skin / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014466:Ultraviolet Rays; D000521:alpha-MSH / Q000378:metabolism; D001615:beta-Endorphin / Q000378:metabolism*
chemical_list: D016159:Tumor Suppressor Protein p53; D000521:alpha-MSH; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin
keywords: Addiction; Neuropeptide; POMC; UV-B; p53; α-MSH