title: Cystatin A suppresses ultraviolet B-induced apoptosis of keratinocytes.
abstract: BACKGROUND
  Cystatin A is a cysteine proteinase inhibitor abundantly expressed in keratinocytes. Although cystatin A is one of the cornified cell envelope constituents and expressed in the upper epidermis, its precise function is still unknown. Ultraviolet B irradiation (UVB) induces apoptosis accompanied with the activation of cysteine proteinases, caspases.
  
  
  OBJECTIVE
  We investigated the effect of cystatin A on UVB-induced apoptosis of keratinocytes.
  
  
  METHODS
  We assessed the caspase activities and apoptotic cell numbers induced by UVB ittadiation in cystatin A gene transfected keratinocytes.
  
  
  RESULTS
  UVB-induced pro-caspase 3 cleavage and caspase 3 activation were suppressed in cystatin A expression vector-transfected SV40-transformed human keratinocytes (SVHK). Furthermore, the transfected SVHK cells were resistant to UVB-induced apoptosis. In contrast neither caspase 8 nor caspase 9 activities were affected by UVB irradiation in cystatin A-transfected SVHK cells. The effects were also observed in cystatin A expression adenovirus vector-transfected cultured normal human keratinocytes (NHK). Conversely knockdown of cystatin A by si-RNA induced marked apoptosis of NHK cells following UVB irradiation accompanied with increased caspase 3 activity. In order to confirm the antiapoptotic effect of cystatin A in vivo UVB irradiation was performed on cystatin A transgenic mice (cystatin A-tg). The epidermis from cystatin A-tg was resistant to UVB-induced apoptosis compared to control mice epidermis.
  
  
  CONCLUSIONS
  These results indicate that cystatin A suppresses UVB-induced apoptosis of keratinocytes by the inhibition of caspase 3 activation.
authors.affiliation: Department of Dermatology, Asahikawa Medical College, 2-1-1-1 Midorigaokaminami, Asahikawa 078-8510, Japan. ht@asahikawa-med.ac.jp
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Takahashi
authors.forename: Naritsuna
authors.initials: N
authors.lastname: Komatsu
authors.forename: Masaki
authors.initials: M
authors.lastname: Ibe
authors.forename: Akemi
authors.initials: A
authors.lastname: Ishida-Yamamoto
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: Hajime
authors.initials: H
authors.lastname: Iizuka
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology* / Q000528:radiation effects*; D053148:Caspase 3 / Q000378:metabolism*; D002478:Cells, Cultured; D015891:Cystatins / Q000235:genetics / Q000502:physiology*; D015853:Cysteine Proteinase Inhibitors / Q000235:genetics / Q000502:physiology; D004789:Enzyme Activation; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D051379:Mice; D008822:Mice, Transgenic; D034741:RNA, Small Interfering / Q000494:pharmacology; D013539:Simian virus 40 / Q000235:genetics; D014162:Transfection; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D034741:RNA, Small Interfering; D053148:Caspase 3