A synergistic effect of GABA tea and copper(II) on DNA breakage in human peripheral lymphocytes

Abstract

GABA tea is a tea product that contains a high level of γ-aminobutyric acid (GABA). The oxidant and antioxidant roles of GABA tea in DNA damage were investigated in this study. DNA cleavage was observed by GABA-tea extract in the presence of copper ions. Comet assay revealed that combination of GABA-tea extract, but not pure GABA, and Cu 2+ is capable of oxidatively degrading cellular DNA in human peripheral lymphocytes. Using various reactive oxygen scavengers, we found that catalase and sodium azide effectively inhibited GABA-tea extract/Cu(II)-induced DNA degradation, suggesting the essential role of singlet oxygen and H 2O 2 in the reaction. In addition, neocuproine inhibited the DNA degradation, confirming that Cu(I) is an intermediate in the DNA cleavage reaction. Therefore, we speculate that GABA-tea extract/Cu(II)-induced DNA damage is probably mediated through the formation of H 2O 2 and the reduction of copper. Furthermore, our data showed that GABA-tea extract was more genotoxic and pro-oxidant than its major catechin constituent, (−)-epigallocatechin-3-gallate (EGCG), leading to DNA cleavage in the presence of Cu 2+. These findings will provide implications for the potential of GABA-tea extract in anticancer property, which may involve copper ions and the consequent pro-oxidant action.