γ-Tocotrienol prevents cell cycle arrest in aged human fibroblast cells through p16INK4a pathway

Human diploid fibroblasts (HDFs) proliferation in culture has been used as a model of aging at the cellular level. Growth arrest is one of the most important mechanisms responsible for replicative senescence. Recent researches have been focusing on the function of vitamin E in modulating cellular signaling and gene expression. Therefore, the aim of this study was to elucidate the effect of palm γ-tocotrienol (vitamin E) in modulating cellular aging through p16INK4a pathway in HDF cells. Primary culture of senescent HDFs was incubated with 70 μM of palm γ-tocotrienol for 24 hours. Silencing of p16INK4a was carried out by siRNA transfection. RNA was extracted from the different treatment groups and gene expression analysis was carried out by real-time reverse transcription polymerase chain reaction. Proteins that were regulated by p16INK4a were determined by western blot technique. The finding of this study showed that p16INK4a mRNA was overexpressed in senescent HDFs, and hypophosphorylated-pRb and cyclin D1 protein expressions were increased (p