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). 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.
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). 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.
Authors: Preethi S Ganapathy; Brent Moister; Penny Roon; Barbara A Mysona; Jennifer Duplantier; Ying Dun; Tracy K V E Moister; Marlena J Farley; Puttur D Prasad; Kebin Liu; Sylvia B Smith Journal: Invest Ophthalmol Vis Sci Date: 2009-04-08 Impact factor: 4.799