[Show abstract][Hide abstract] ABSTRACT: The effects of palm gamma-tocotrienol (GGT) on oxidative stress-induced cellular ageing was investigated in normal human skin fibroblast cell lines derived from different age groups; young (21-year-old, YF), middle (40-year-old, MF) and old (68-year-old, OF). Fibroblast cells were treated with gamma-tocotrienol for 24 hours before or after incubation with IC50 dose of H2O2 for 2 hours. Changes in cell viability, telomere length and telomerase activity were assessed using the MTS assay (Promega, USA), Southern blot analysis and telomere repeat amplification protocol respectively. Results showed that treatment with different concentrations of gamma-tocotrienol increased fibroblasts viability with optimum dose of 80 microM for YF and 40 microM for both MF and OF. At higher concentrations, gamma-tocotrienol treatment caused marked decrease in cell viability with IC50 value of 200 microM (YF), 300 microM (MF) and 100 microM (OF). Exposure to H2O2 decreased cell viability in dose dependent manner, shortened telomere length and reduced telomerase activity in all age groups. The IC50 of H2O2 was found to be; YF (700 microM), MF (400 microM) and OF (100 microM). Results showed that viability increased significantly (p < 0.05) when cells were treated with 80 microM and 40 microM gamma-tocotrienol prior or after H2O2-induced oxidative stress in all age groups. In YF and OF, pretreatment with gamma-tocotrienol prevented shortening of telomere length and reduction in telomerase activity. In MF, telomerase activity increased while no changes in telomere length was observed. However, post-treatment of gamma-tocotrienol did not exert any significant effects on telomere length and telomerase activity. Thus, these data suggest that gamma-tocotrienol protects against oxidative stress-induced cellular ageing by modulating the telomere length possibly via telomerase.
Preview · Article · Jan 2010 · Oxidative Medicine and Cellular Longevity
[Show abstract][Hide abstract] ABSTRACT: Stress-induced premature senescence (SIPS) model is in vitro model of cellular aging. In this study, apoptosis was evaluated in SIPS model and in replicative senescent fibroblasts. We also compared the activity of senescence-associated beta-galactosidase (SA-beta gal) as a biomarker of cellular aging. Our results suggested that SIPS model and senescent fibroblasts might share similar mechanism of aging and apoptosis pathway.
No preview · Article · Aug 2008 · The Medical journal of Malaysia
[Show abstract][Hide abstract] ABSTRACT: Vitamin E extracted from palm oil consists of 70% tocotrienols and 30% tocopherols. In the present study we investigated the effects of γ-tocotrienol and α-tocopherol extracted from palm oil on the arachidonic acid-induced cytotoxicity and apoptosis in transfected Hep G2 cell line expressing human cytochrome P4502E1 (CYP2E1). Arachidonic acid as a representative of polyunsaturated fatty acid was used to induce the CYP2E1 gene. CYP2E1 is a xenobiotic-metabolizing enzyme which is actives in catalyzing lipid peroxidation than several other forms of cytochrome P450 enzymes. Two types of cells ie. Hep G2 E47 and Hep G2 C34 were used in this study. E47 is a transfected HepG2 cell line that expresses human CYP2E1 whereas C34 does not express this enzyme. Both E47 and C34 cells were treated with palm oil γ-tocotrienol and a-tocopherol at three different doses ie. 50 μM, 150 μM and 300 μM. In order to evaluate the effects of γ-tocotrienol and α-tocopherol on the cytotoxicity and apoptosis after CYP2E1 induction, both types of cells were treated with arachidonic acid at 0.03 mM before treatment with γ-tocotrienol and α-tocopherol. Cytotoxicity was determined using Lactate dehydrogenase Leakage method and apoptosis was determined using ELISA Cellular DNA Fragmentation kit. The results of the study showed that arachidonic acid increased the cytotoxicity and apoptosis in both E47 and C34 cell lines significantly (p<0.05). However arachidonic acid was found to be more cytotoxic to E47 cells that express CYP2E1 compared to C34 cells (p<0.05). Treatment with different doses of γ-tocotrienol and α-tocopherol caused a marked reduction (p<0.05) in the cytotoxicity of both cell lines with or without CYP2E1 induction. However treatment with α-tocopherol did not cause any changes to the percentage of apoptosis in C34 and E47 cell lines. In contrast, treatment with γ-tocotrienol significantly increased the percentage of apoptosis in both C34 and E47 cell lines. It was also indicated that γ-tocotrienol and α-tocopherol possessed the same antioxidant activity in reducing the cytotoxicity in both cell lines. Therefore we concluded that γ-tocotrienol and α-tocopherol are protective against arachidonic acid-induced cytotoxicity in Hep G2 cells transfected with CYP2E1 gene.