2010 Volume 33 Issue 9 Pages 1471-1476
In the present study, we investigated the dose-dependent effect of δ-tocotrienol long term (48, 72 h) on the melanin content of cells treated with δ-tocotrienol, and whether cells treated with δ-tocotrienol for long a time show cytotoxicity. We also examined whether other enzymes responsible for melanin biosynthesis, tyrosinase-related protein-1 (TRP-1) and -2 (TRP-2), are involved in the decrease in melanin levels. Protein levels in cells treated with 25 or 50 μM δ-tocotrienol for 48 h or 72 h were similar to those in control cells. Melanin content decreased by 44 (25 μM δ-tocotrienol) to 50% (50 μM) at 48 h, and by 14 to 21% at 72 h, compared to control levels. Tyrosinase activity, amounts of tyrosinase and TRP-1 decreased dependent on dose : by 50 (25 μM δ-tocotrienol) to 75% (50 μM), 20 to 45% and 42 to 82% at 48 h, and by 25 to 50%, 75 to 80% and 78 to 77% at 72 h, respectively. Although the amount of TRP-2 increased by 20% on treatment with 25 μM δ-tocotrienol for 48 h, it decreased by 52% on treatment with 50 μM δ-tocotrienol for 48 h. The amount of TRP-2 dose-dependently decreased by 55% and 75% on 72 h by treatment with 25 and 50 μM δ-tocotrienol, respectively. From these findings, δ-tocotrienol at up to 50 μM dose-dependently caused a reduction in melanin content by the decrease of TRP-1 and TRP-2 as well as tyrosinase, and no cytotoxicity.
