Inhibition of DNA methylase activity by acrolein

Abstract

Acrolein, a reactive metabolite of cyclophosphamide, may be responsible for bladder cancer induced by cyclophosphamide. DNA methylase was isolated from the liver and urothelium of rats by high salt extraction of purified nuclei. Acrolein at 10 microM inhibited liver and bladder DNA methylase activity by 30-50%. Kinetic studies with the liver enzyme showed a competitive type of inhibition with a Ki of 6.7 microM. Both dithiothreitol and glutathione afforded protection to the enzyme when added to the assay. At near equimolar concentrations of glutathione to acrolein, the methylase retained 80-90% activity. An increase in DNA had no effect on the inhibition by acrolein, whereas increased amounts of protein protected against acrolein inhibition, suggesting that acrolein reacted with the DNA methylase protein. On the other hand, DNA that had been reacted with acrolein was unable to serve as a substrate for DNA methylase. As the DNA adducts increased the methylation of the DNA decreased. Thus, acrolein has the ability to react with DNA and the DNA methylase protein, either of which results in inhibition of DNA methylation.

Ethanol Consumption Inhibits Fetal DNA Methylation in Mice: Implications for the Fetal Alcohol Syndrome

“…I3 DNA methyltransferase has been shown to be inhibited by another aldehyde, acrolein, over a concentration range similar to that shown here for a~etaldehyde.~~ The inhibition of DNA methyltransferase activity by acrolein, which is a metabolite of cyclophosphamide, is blocked by dithiothreitol and glutathione and is thought to be due to reaction of this unsaturated aldehyde with critical sulfhydry1 or amino groups. 43 While acetaldehyde has been reported to react with free thiol and amino groups in hepatic micro some^,^^ the inhibition of DNA methyltransferase activity reported here was not blocked by dithiothreitol, which protects thiol groups (data not shown). The acetaldehyde-mediated inhibition of DNA methyltransferase activity is similar to the inhibition we have seen with the DNA repair enzyme, 06-alkylguanine transferase, which removes methyl groups from guaninine bases.…”

Alterations inDNAMethylation Resulting from Exposure to Chemical Carcinogens

“…More importantly, CpG methylation greatly increases the acrolein-induced G to T and G to A mutation frequency in human lung fibroblasts to levels similar to those found at CpG sites in the p53 gene in tobacco smoke-related lung cancer . Additionally, it has been demonstrated that acrolein inhibits DNMT activity and may cause demethylation of DNA (Cox et al, 1988).…”

2‐Propenal (Acrolein) [MAK Value Documentation in German language, 1997]

“…Die DNA-(Cytosin-5-)methyltransferase, die bei der Regulation der Genexpression eine Rolle spielt, wird durch Acrolein gehemmt (K i : 6,7 VM) (Cox et al 1988). Die DNA-(Cytosin-5-)methyltransferase, die bei der Regulation der Genexpression eine Rolle spielt, wird durch Acrolein gehemmt (K i : 6,7 VM) (Cox et al 1988).…”