BACKGROUND: Ultraviolet radiation (UVR) from the sun and solaria has addictive properties that may develop into @entity734 . In @entity19 , UVR addiction was connected to b-endorphin (b-END) formed in the skin after UVR exposure. In @entity1 , the formation of b-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 @entity876 mediated expression of @entity4545 ( @entity4545 ), b-END and a-melanocyte stimulating hormone (a-MSH) in @entity1 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 @entity876 , b-END, @entity4545 , and a-MSH expression. RESULTS: Nuclear @entity876 expression increased in all samples taken at 24h after NB-UV-B exposure. UV-B irradiation also increased epidermal b-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. @entity4545 and a-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 b-END expression in epidermal keratinocytes of @entity1 skin in vivo, which could be the link to proposed UVR addiction.

Narrow-band ultraviolet B radiation induces the expression of b-endorphin in XXXX skin in vivo.

@entity1 :: ('9606', 'Species') :: ['humans', 'human'] @entity4545 :: ('5443', 'Gene') :: ['POMC', 'pro-opiomelanocortin'] @entity19 :: ('10090', 'Species') :: ['mice'] @entity876 :: ('7157', 'Gene') :: ['p53'] @entity734 :: ('MESH:D019966', 'Disease') :: ['dependence']
@entity1 :: (9606,Species) :: ['human']
