期刊
PIGMENT CELL RESEARCH
卷 14, 期 2, 页码 103-109出版社
MUNKSGAARD INT PUBL LTD
DOI: 10.1034/j.1600-0749.2001.140205.x
关键词
UVA; tyrosinase; MAPK; normal human epidermal melanocytes
UV-induced melanogenesis is a well known physiological response of human skin exposed to solar radiation; however, the signaling molecules involved in the stimulation of melanogenesis in melanocytes following UV exposure remain unclear. In this study we induced melanogenesis in vitro in normal human epidermal melanocytes using a single irradiation with UVA at I kJ/m(2) and examined the potential involvement of mitogen-activated protein kinases (MAPK) as UVA-responsive signaling molecules in those cells, UVA irradiation did not affect the proliferation of melanocytes, but it did increase tyrosinase mRNA expression, which reached a maximum level 4 hr after UVA irradiation, The amount of tyrosinase protein, as quantitated by immunoblotting, was also increased at 24 hr following UVA irradiation. Among the MAPK examined, extracellular signal-related kinase (ERK) 1/2 was phosphorylated within 15 min of UVA irradiation, but no such phosphorylation was observed for c-Jun N-terminal kinases (JNK) or p38. Accordingly, the activity of ERK1/2 was also increased shortly after UVA irradiation, These responses of ERK1/2 to UVA irradiation were markedly inhibited when cells were pre-treated with N-acetyl-L-cysteine, an antioxidant, or with suramin, a tyrosine kinase receptor inhibitor, The formation of (6-4)photoproducts or cyclobutane pyrimidine dimers was not detected in cellular DNA after UVA irradiation. These findings suggest that a single UVA irradiation-induced melanogenesis is associated with the activation of ERK1/2 by upstream signals that originate from reactive oxygen species or from activated tyrosine kinase receptors, but not from damaged DNA.
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