title: γ-Tocotrienol prevents cell cycle arrest in aged human fibroblast cells through p16INK4apathway.
abstract: 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 p16INK4apathway in HDF cells. Primary culture of senescent HDFs was incubated with 70 μM of palm γ-tocotrienol for 24 hours. Silencing of p16INK4awas 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 p16INK4awere determined by western blot technique. The finding of this study showed that p16INK4amRNA was overexpressed in senescent HDFs, and hypophosphorylated-pRb and cyclin D1 protein expressions were increased (p < 0.05). However, downregulation of p16INK4aand hypophosphorylated-pRb and cyclin D1 protein expressions (p < 0.05) by γ-tocotrienol led to modulation of the cell cycle regulation during cellular aging. In conclusion, senescent HDFs showed change in biological process specifically in cell cycle regulation with elevated expression of genes and proteins which may contribute to cell cycle arrest. Palm γ-tocotrienol may delay cellular senescence of HDFs by regulating cell cycle through downregulation of p16INK4aand hypophosphorylated-pRb and cyclin D1 protein expressions.
authors.affiliation: Department of Chemical Pathology, School of Medical Sciences, Universiti Sains Malaysia, Kota Bharu, Kelantan, Malaysia.
authors.forename: Azalina
authors.initials: A
authors.lastname: Zainuddin
authors.affiliation: Department of Physiology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia.
authors.forename: Kien-Hui
authors.initials: KH
authors.lastname: Chua
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Level 17, Preclinical Building, Universiti Kebangsaan Malaysia Medical Centre, Jalan Yaacob Latif, Bandar Tun Razak, 56000 Cheras, Kuala Lumpur, Malaysia.
authors.forename: Jen-Kit
authors.initials: JK
authors.lastname: Tan
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Level 17, Preclinical Building, Universiti Kebangsaan Malaysia Medical Centre, Jalan Yaacob Latif, Bandar Tun Razak, 56000 Cheras, Kuala Lumpur, Malaysia.
authors.forename: Faizul
authors.initials: F
authors.lastname: Jaafar
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Level 17, Preclinical Building, Universiti Kebangsaan Malaysia Medical Centre, Jalan Yaacob Latif, Bandar Tun Razak, 56000 Cheras, Kuala Lumpur, Malaysia. suzanamakpol@ppukm.ukm.edu.my.
authors.forename: Suzana
authors.initials: S
authors.lastname: Makpol
mesh_terms: D002453:Cell Cycle; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence; D002648:Child; D002839:Chromans / Q000378:metabolism*; D019938:Cyclin D1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D052816:Foreskin / Q000166:cytology; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D034741:RNA, Small Interfering; D056286:Retinoblastoma Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: C530104:CCND1 protein, human; C000614131:CDKN2A protein, human; D002839:Chromans; D019941:Cyclin-Dependent Kinase Inhibitor p16; C000606393:RB1 protein, human; D034741:RNA, Small Interfering; D056286:Retinoblastoma Binding Proteins; D019938:Cyclin D1; D014810:Vitamin E; C013649:plastochromanol 8; D044767:Ubiquitin-Protein Ligases
keywords: Cell cycle aging; Gene and protein expression; Tocotrienol; p16INK4a