LINE-1 hypomethylation induced by reactive oxygen species is mediated via depletion of S-adenosylmethionine.
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.
['Kloypan|Chiraphat|C|', 'Srisa-art|Monpicha|M|', 'Mutirangura|Apiwat|A|', 'Boonla|Chanchai|C|']
D000975:Antioxidants D002460:Cell Line D019175:DNA Methylation D005978:Glutathione D006710:Homocysteine D006801:Humans D006861:Hydrogen Peroxide D007668:Kidney D020084:Long Interspersed Nucleotide Elements D016877:Oxidants D018384:Oxidative Stress D017382:Reactive Oxygen Species D012436:S-Adenosylmethionine D019459:Urothelium
LINE-1 SAM bladder cancer oxidative stress DNA methylation epigenetics