THE EFFECT OF ULTRAVIOLET-B INDUCED ADULT T-CELL LEUKEMIA-DERIVED FACTOR THIOREDOXIN (ADF TRX) ON SURVIVAL AND GROWTH OF HUMAN MELANOCYTES/

Ultraviolet B (UVB) radiation is known to induce reactive oxygen speci es (ROS) in the skin. The skin, however counteracts ROS by both consti tutional and newly produced antioxidants. One such antioxidant, adult T cell leukemia-derived factor (ADF), a human homologue of thioredoxin (TRX), was shown to be efficiently produced in and released from cult ured normal human keratinocytes after UVB irradiation by Northern and Western blot analyses and enzyme-linked immunoabsorbent assay (ELISA). Recombinant ADF (rADF) did not rescue UVB-induced melanocyte death, e ither when added pre- or post-UV irradiation. However, further additio n of neutralizing antibody caused cell death of both keratinocytes and melanocytes. rADF was shown to induce higher expression in melanocort in-1 receptor (MC1-R) mRNA accompanied by increased binding activity u sing I-125 labeled [Nle(4), D-Phe(7)]-alpha-MSH in melanocytes, leadin g to the enhanced increment of DNA synthesis. Taken together it was sh own that released ADF from UVB-irradiated keratinocytes acts as a surv ival factor for both keratinocytes and melanocytes but does not rescue UV-induced melanocyte death. Further, it may work as one of the stimu latory factors for UVB-induced melanogenesis by upregulating MSH-R bin ding activity in combination with the enhanced DNA synthesis by alpha- MSH.