C Ma1, L-F Li, X Chen. 1. Department of Dermatology, Peking University Third Hospital, Haidian District, Beijing, China.
Abstract
BACKGROUND: Metallothioneins (MT) are important antioxidants involved in the ageing process of many tissues and organs. To our knowledge, the role of MT in skin ageing has not been reported. OBJECTIVES: To investigate the expression of MT in ageing skin. METHODS: The protein levels of MT-I and MT-II in sun-exposed and sun-protected skin specimens obtained from healthy individuals were detected by immunohistochemistry using tissue microarray and expressed as average integrated optical density (AIOD). Proliferating cell nuclear antigen (PCNA) and Ki-67 protein levels in these specimens were also detected to study the possible link between the proliferation of keratinocytes and expression of MT. RESULTS: The protein levels of MT-I and MT-II decreased significantly with increasing age of sun-exposed and sun-protected skin (r = -0·73 and -0·98, respectively, P < 0·01) but was more prominent in sun-exposed skin. In sex- and age-matched specimens, the intensity of MT-I and MT-II in sun-exposed skin was much lower than in sun-protected skin (9·46 ± 2·39 vs. 22·25 ± 8·04, mean ± SD of AIOD, P < 0·01, Student's t-test). The expression of PCNA and Ki-67 showed the same trend. CONCLUSIONS: The expression of MT-I and MT-II declined with the decrease of keratinocyte proliferation in the process of skin ageing, and this decline was more significant in sun-exposed skin. Whether MT-I and MT-II supplementation could inhibit skin ageing, especially photoageing, merits further study.
BACKGROUND: Metallothioneins (MT) are important antioxidants involved in the ageing process of many tissues and organs. To our knowledge, the role of MT in skin ageing has not been reported. OBJECTIVES: To investigate the expression of MT in ageing skin. METHODS: The protein levels of MT-I and MT-II in sun-exposed and sun-protected skin specimens obtained from healthy individuals were detected by immunohistochemistry using tissue microarray and expressed as average integrated optical density (AIOD). Proliferating cell nuclear antigen (PCNA) and Ki-67 protein levels in these specimens were also detected to study the possible link between the proliferation of keratinocytes and expression of MT. RESULTS: The protein levels of MT-I and MT-II decreased significantly with increasing age of sun-exposed and sun-protected skin (r = -0·73 and -0·98, respectively, P < 0·01) but was more prominent in sun-exposed skin. In sex- and age-matched specimens, the intensity of MT-I and MT-II in sun-exposed skin was much lower than in sun-protected skin (9·46 ± 2·39 vs. 22·25 ± 8·04, mean ± SD of AIOD, P < 0·01, Student's t-test). The expression of PCNA and Ki-67 showed the same trend. CONCLUSIONS: The expression of MT-I and MT-II declined with the decrease of keratinocyte proliferation in the process of skin ageing, and this decline was more significant in sun-exposed skin. Whether MT-I and MT-II supplementation could inhibit skin ageing, especially photoageing, merits further study.