title: Zinc ion enhances GABA tea-mediated oxidative DNA damage.
abstract: GABA tea is a tea product that contains a high level of γ-aminobutyric acid (GABA). Previous study has demonstrated a synergistic effect of GABA tea and copper ions on DNA breakage. This study further explored whether zinc (Zn), a nonredox metal, modulated DNA cleavage induced by GABA tea extract. In a cell-free system, Zn(2+) significantly enhanced GABA tea extract and (-)-epigallocatechin-3-gallate (EGCG)- or H(2)O(2)-induced DNA damage at 24 h of incubation. Additionally, low dosages of GABA tea extract (1-10 μg/mL) possessed pro-oxidant activity to increase H(2)O(2)/Zn(2+)-induced DNA cleavage in a dose-dependent profile. By use of various reactive oxygen scavengers, it was observed that glutathione, catalase, and potassium iodide effectively inhibited DNA degradation caused by the GABA tea extract/H(2)O(2)/Zn(2+) system. Moreover, the data showed that the GABA tea extract itself (0.5-5 mg/mL) could induce DNA cleavage in a long-term exposure (48 h). EGCG, but not the GABA tea extract, enhanced H(2)O(2)-induced DNA cleavage. In contrast, GABA decreased H(2)O(2)- and EGCG-induced DNA cleavage, suggesting that GABA might contribute the major effect on the antioxidant activity of GABA tea extract. Furthermore, a comet assay revealed that GABA tea extract (0.25 mg/mL) and GABA had antioxidant activity on H(2)O(2)-induced DNA breakage in human peripheral lymphocytes. Taken together, these findings indicate that GABA tea has the potential of both pro-oxidant and antioxidant. It is proposed that a balance between EGCG-induced pro-oxidation and GABA-mediated antioxidation may occur in a complex mixture of GABA tea extract.
authors.affiliation: Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan, Republic of China.
authors.forename: Show-Mei
authors.initials: SM
authors.lastname: Chuang
authors.forename: Hsueh-Fang
authors.initials: HF
authors.lastname: Wang
authors.forename: Ching-Chuan
authors.initials: CC
authors.lastname: Hsiao
authors.forename: Shur-Hueih
authors.initials: SH
authors.lastname: Cherng
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D010584:Bacteriophage phi X 174 / Q000235:genetics; D002374:Catalase / Q000494:pharmacology; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects; D004279:DNA, Viral / Q000187:drug effects; D005978:Glutathione / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008214:Lymphocytes; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D011193:Potassium Iodide / Q000494:pharmacology; D013662:Tea / Q000737:chemistry*; D015032:Zinc / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000008:administration & dosage*
chemical_list: D000975:Antioxidants; D004279:DNA, Viral; D016877:Oxidants; D013662:Tea; D011193:Potassium Iodide; D005680:gamma-Aminobutyric Acid; D002392:Catechin; D006861:Hydrogen Peroxide; C045651:epigallocatechin gallate; D002374:Catalase; D005978:Glutathione; D015032:Zinc