Synergistic effects of S-adenosylhomocysteine and homocysteine on DNA damage in a murine microglial cell line.
BACKGROUND
Homocysteine (Hcy) and S-adenosylhomocysteine (SAH) are 2 major metabolites of methionine. However, little is known about their interactions in human diseases.


METHODS
We determined the interaction of Hcy with SAH on DNA damage (measured as comet formation) and DNA hypomethylation (assayed as 5-methyldeoxycytidine, 5-mdc) in BV-2 cells (immortalized murine microglia).


RESULTS
Hcy at 100 micromol/l and SAH at 4 micromol/l alone caused little DNA strand breaks, whereas 100 micromol/l Hcy in combination with 0.5 to 4 micromol/l SAH led to marked DNA damage and uracil misincorporation. The combination of 100 micromol/l Hcy with 4 micromol/l SAH (SAH+Hcy) significantly increased intracellular H(2)O(2), and the DNA damage induced by SAH+Hcy was strongly inhibited by addition of superoxide dismutase, catalase or desferrioxamine, suggesting the involvement of reactive oxygen species. DNA damage induced by SAH+Hcy may also involve DNA hypomethylation (i.e., decreased %5-mdc) because of the high correlation between them. The effects induced by SAH+Hcy were specific to SAH but not to Hcy because they were markedly decreased by replacing SAH with adenosine (4.0 micromol/l) but was not affected by replacing Hcy with cysteine (100 micromol/l).


CONCLUSIONS
SAH in combination with Hcy can cause synergistic DNA damage in BV-2 cells. It remains to be seen whether some of the Hcy-related diseases may be caused by a collaborative action of Hcy with SAH.
Lin
Pei-Ying
PY
Department of Food Science and Biotechnology, National Chung-Hsing University, 250 Kuo-Kuang Road, Taichung, 402, Taiwan, ROC.
Yang
Tsai-Hsiu
TH
Lin
Hung-Gi
HG
Hu
Miao-Lin
ML
D000818:Animals; D002460:Cell Line; D004247:DNA / Q000187:drug effects*; D004249:DNA Damage; D019175:DNA Methylation / Q000187:drug effects; D004357:Drug Synergism; D016166:Free Radical Scavengers / Q000494:pharmacology; D006710:Homocysteine / Q000633:toxicity*; D006861:Hydrogen Peroxide / Q000378:metabolism; D051379:Mice; D017628:Microglia / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D012435:S-Adenosylhomocysteine / Q000633:toxicity*; D014498:Uracil / Q000378:metabolism
D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D006710:Homocysteine; D014498:Uracil; D004247:DNA; D012435:S-Adenosylhomocysteine; D006861:Hydrogen Peroxide