Synergistic effects of S-adenosylhomocysteine and homocysteine on DNA damage in a murine microglial cell line

Abstract

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 Hey 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: Hey at 100 mu mol/l and SAH at 4 mu mol/l alone caused little DNA strand breaks, whereas 100 pmol/l Hcy in combination with 0.5 to 4 mu mol/l SAH led to marked DNA damage and uracil misincorporation. The combination of 100 mu mol/l Hcy with 4 mu mol/l SAH (SAH+Hcy) significantly increased intracellular H2O2, 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 mu mol/l) but was not affected by replacing Hcy with cysteine (100 mu mol/l). Conclusion: 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. (c) 2007 Elsevier B.V. All rights reserved.