Melanogenesis Inhibition by Palm Tocotrienol Rich Fraction in Cellular Ageing
Tocotrienol rich fraction inhibits melanin synthesis
Abstract
Melanin is the pigment that determines skin color. Melanin synthesis is catalysed by the enzyme tyrosinase and is controlled by TYR, TYRP1 and TYRP2 genes. In this study, tocotrienol rich fraction (TRF) was used to inhibit melanin synthesis. TRF contains 75% a-tocotrienol and 25% tocopherol. The objective of this study was to determine the effect of tocotrienol rich fraction (TRF) on melanin synthesis by determining melanin content and expression of genes involved in the regulation of melanin synthesis in skin melanocytes. Melanin synthesis was studied by determining melanin level and tyrosinase enzyme activity, while expression of TYR, TYRP1 and TYRP2 genes was determined by quantitative real time reverse transcriptase polymerase chain reaction (real time RT-PCR). Primary culture of skin melanocytes were divided into two groups; control and cells that were treated with 500 µg/ml tocotrienol rich fraction for 24 hours. Our results showed that there was a reduction in melanin content and tyrosinase activity in skin melanocytes treated with tocotrienol rich fraction compared to the control (p<0.05). Expression of TYRP2 gene in melanocytes treated with tocotrienol rich fraction was also decreased (p<0.05) compared to the control. In conclusion, palm tocotrienol rich fraction has anti pigmentation property that inhibits melanin synthesis in cellular aging by inhibiting tyrosinase activity and down regulating TYRP2 gene expression.
Keywords :
gene expression,
melanin synthesis,
skin mela¬nocytes,
tocotrienol rich fraction,
Abstrak
Melanin merupakan pigmen yang menentukan warna kulit. Sintesis melanin dimangkinkan oleh enzim tirosinase dan melibatkan pengawalaturan oleh gen TYR, TYRP1 danTYRP2. Dalam kajian ini, fraksi kaya tokotrienol (TRF) telah digunakan sebagai perencat sintesis melanin. TRF mengandungi 75% alfa-tokotrienol dan 25% tokoferol. Objektif kajian ini adalah untuk menentukan kesan fraksi kaya tokotrienol sawit terhadap sintesis melanin melalui penentuan kandungan aras melanin, aktiviti enzim tirosinase dan ekspresi gen yang mengawalatur sintesis melanin di dalam melanosit kulit iaitu TYR, TYRP1 danTYRP2. Sintesis melanin ditentukan melalui pengukuran kandungan melanin dan asai aktiviti tirosinase. Ekspresi gen diukur dengan menggunakan kaedah kuantitatif PCR transkripsi berbalik (real time RT-PCR). Kultur primer sel melanosit kulit dibahagikan kepada dua kumpulan iaitu kumpulan kawalan dan kumpulan perlakuan dengan TRF pada dos 500 µg/ml selama 24 jam. Hasil kajian menunjukkan terdapat penurunan kandungan melanin dan aktiviti tirosinase pada sel melanosit kulit yang diperlakukan dengan TRF berbanding sel kawalan (p<0.05). Ekspresi gen TYRP2menunjukkan penurunan apabila melanosit diperlakukan dengan TRF berbanding dengan sel kawalan (p<0.05) . Oleh itu, dapat disimpulkan bahawa fraksi kaya tokotrienol sawit bertindak sebagai agen anti pigmentasi semasa penuaan kulit iaitu ia merencat sintesis melanin melalui perencatan aktiviti tirosinase dan menurunkan ekspresi gen TYRP2.
Kata Kunci :
ekpresi gen,
fraksi kaya tokotrienol,
melanosit kulit,
sintesis melanin,
Correspondance Address
Assoc Prof Dr. Suzana Makpol, Department of Biochemistry, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abd. Aziz, 50300 Kuala Lumpur. Tel: 603-92897296/7222. Fax: 603-26938037. Email: suzana@medic.ukm.my
