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  • Title: Cystatin A suppresses ultraviolet B-induced apoptosis of keratinocytes.
    Author: Takahashi H, Komatsu N, Ibe M, Ishida-Yamamoto A, Hashimoto Y, Iizuka H.
    Journal: J Dermatol Sci; 2007 Jun; 46(3):179-87. PubMed ID: 17412564.
    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. CONCLUSION: These results indicate that cystatin A suppresses UVB-induced apoptosis of keratinocytes by the inhibition of caspase 3 activation.
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