| Summary: | 碩士 === 中山醫學院 === 生物化學研究所 === 86 ===
Hibiscus protocatechuic acid (PCA), a simple phenolic compound, isolated from Hibiscus sabdariffa L. was studied for its molecular mechanisms on 12-0-tetradecanoy 1phorbol 13-acetate (TPA)-induced promotion of skin tumors.
Topical application of 5 nmol TPA to the dorsal surface of CD-1 mice twice daily for 5 days caused epidermal hyperplasia, lipid peroxidation and the enhancement of the protein levels of the singaling proteins, such as c-Fos, MEK, ERK1, ERK2 and PKC were 2.39-, 2.34-2.26-,2.47-and 2.45-fold as compared to control on TPA-treated mice epidermis. Topical application of PCA briefly prior to the application of TPA not only inhibited the TPA-induced hyperplasia but also lipid peroxidation was markedly reduced. The TPA-induced expression of c-Fos, MEK1,ERK1,ERK2 and PKC were also significantly inhibited by PCA (5□mol) to the extent of 25,33,16,49, and 16% respectively. Higher dose of PCA (20□mol) showed even more marked inhibition on the TPA-induced expressions of these proteins described above, by 68, 66, 64, 65, and 68%, respectively , in mice epidermis.
These data and our previous results indicated that the TPA-induced enhancement of the expression of mitogenic signaling proteins plays an important role in the suppression of TPA-induced tumor promotions.
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