LINE‐1 hypomethylation induced by reactive oxygen species is mediated via depletion of S‐adenosylmethionine |
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| Authors: | Chiraphat Kloypan Monpicha Srisa‐art Apiwat Mutirangura Chanchai Boonla |
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| Affiliation: | 1. Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand;2. Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand;3. Department of Anatomy, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand |
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| Abstract: | Whether long interspersed nuclear element‐1 (LINE‐1) hypomethylation induced by reactive oxygen species (ROS) was mediated through the depletion of S‐adenosylmethionine (SAM) was investigated. Bladder cancer (UM‐UC‐3 and TCCSUP) and human kidney (HK‐2) cell lines were exposed to 20 μM H2O2 for 72 h to induce oxidative stress. Level of LINE‐1 methylation, SAM and homocysteine (Hcy) was measured in the H2O2‐exposed cells. Effects of α‐tocopheryl acetate (TA), N‐acetylcysteine (NAC), methionine, SAM and folic acid on oxidative stress and LINE‐1 methylation in the H2O2‐treated cells were explored. Viabilities of cells treated with H2O2 were not significantly changed. Intracellular ROS production and protein carbonyl content were significantly increased, but LINE‐1 methylation was significantly decreased in the H2O2‐treated cells. LINE‐1 methylation was restored by TA, NAC, methionine, SAM and folic acid. SAM level in H2O2‐treated cells was significantly decreased, while total glutathione was significantly increased. SAM level in H2O2‐treated cells was restored by NAC, methionine, SAM and folic acid; while, total glutathione level was normalized by TA and NAC. Hcy was significantly decreased in the H2O2‐treated cells and subsequently restored by NAC. In conclusion, in bladder cancer and normal kidney cells exposed to H2O2, SAM and Hcy were decreased, but total glutathione was increased. Treatments with antioxidants (TA and NAC) and one‐carbon metabolites (SAM, methionine and folic acid) restored these changes. This pioneer finding suggests that exposure of cells to ROS activates glutathione synthesis via the transsulfuration pathway leading to deficiency of Hcy, which consequently causes SAM depletion and eventual hypomethylation of LINE‐1. Copyright © 2015 John Wiley & Sons, Ltd. |
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| Keywords: | DNA methylation epigenetics oxidative stress LINE‐1 SAM bladder cancer |
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