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LINE‐1 hypomethylation induced by reactive oxygen species is mediated via depletion of S‐adenosylmethionine
Author(s) -
Kloypan Chiraphat,
Srisaart Monpicha,
Mutirangura Apiwat,
Boonla Chanchai
Publication year - 2015
Publication title -
cell biochemistry and function
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 61
eISSN - 1099-0844
pISSN - 0263-6484
DOI - 10.1002/cbf.3124
Subject(s) - glutathione , methionine , oxidative stress , homocysteine , reactive oxygen species , methylation , acetylcysteine , chemistry , cell culture , biochemistry , transsulfuration , microbiology and biotechnology , cystathionine beta synthase , antioxidant , biology , amino acid , enzyme , genetics , gene
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 H 2 O 2 for 72 h to induce oxidative stress. Level of LINE‐1 methylation, SAM and homocysteine (Hcy) was measured in the H 2 O 2 ‐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 H 2 O 2 ‐treated cells were explored. Viabilities of cells treated with H 2 O 2 were not significantly changed. Intracellular ROS production and protein carbonyl content were significantly increased, but LINE‐1 methylation was significantly decreased in the H 2 O 2 ‐treated cells. LINE‐1 methylation was restored by TA, NAC, methionine, SAM and folic acid. SAM level in H 2 O 2 ‐treated cells was significantly decreased, while total glutathione was significantly increased. SAM level in H 2 O 2 ‐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 H 2 O 2 ‐treated cells and subsequently restored by NAC. In conclusion, in bladder cancer and normal kidney cells exposed to H 2 O 2 , 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.