Homocysteine induces cytotoxicity and proliferationinhibition in neural stem cells via DNA methylation in vitro

摘要

Mild to moderate hyperhomocysteinemia has been implicated in neurodevelopmentaldisorders and neurodegenerative diseases in human studies.Although the molecular mechanisms underlying the effects of homocysteine(Hcy) neurotoxicity on the nervous system are not yet fully understood,inhibition of neural stem cell (NSC) proliferation and alterations in DNAmethylation may be involved. The aim of the present study was to characterizethe effects of Hcy on DNA methylation in NSCs, and to explorehow Hcy-induced changes in DNA methylation patterns affect NSC proliferation.We found that D,L-Hcy (30–1000 lM) but not L-cysteine inhibitedcell proliferation and reduced levels of global DNA methylation in NSCsfrom neonatal rat hippocampus and increased cell injury. High levels ofHcy also induced an increase in S-adenosylhomocysteine (SAH), a decreasein the ratio of S-adenosylmethionine (SAM) to SAH, and a reduction inprotein expression of the DNA methyltransferases DNMT1, DNMT3a andDNMT3b and their enzymatic activity. Moreover, the DNMT inhibitorzebularine reduced the global DNA methylation level and inhibited NSCproliferation. Our results suggest that alterations in DNA methylation maybe an important mechanism by which high levels of Hcy inhibit NSC viabilityin vitro. Hcy-induced DNA hypomethylation may be caused by areduction in the DNMT activity which is regulated by the cellular concentrationsof SAM and SAH, or their protein expression levels. Our resultsalso suggest that Hcy may play a role in the pathogenesis of certain nervoussystem diseases via a molecular mechanism that involves negative regulationof NSC proliferation and alterations in DNA methylation.