title: Mobilization of Nuclear Copper by Green Tea Polyphenol Epicatechin-3-Gallate and Subsequent Prooxidant Breakage of Cellular DNA: Implications for Cancer Chemotherapy.
abstract: Epidemiological as well as experimental evidence exists in support of chemopreventive and anticancer properties of green tea and its constituents. The gallocatechin, epicatechin-3-gallate is a major polyphenol present in green tea, shown responsible for these effects. Plant-derived polyphenolic compounds are established natural antioxidants which are capable of catalyzing oxidative DNA degradation of cellular DNA, alone as well as in the presence of transition metal ions, such as copper. Here we present evidence to support that, similar to various other polyphenoic compounds, epicatechin-3-gallate also causes oxidative degradation of cellular DNA. Single cell alkaline gel electrophoresis (Comet assay) was used to assess DNA breakage in lymphocytes that were exposed to various concentrations of epicatechin-3-gallate. Inhibition of DNA breakage in the presence of scavengers of reactive oxygen species (ROS) suggested involvement of ROS generation. Addition of neocuproine (a cell membrane permeable Cu(I) chelator) inhibited DNA degradation, dose-dependently, in intact lymphocytes. In contrast, bathocuproine, which does not permeate cell membrane, was observed to be ineffective. We further show that epicatechin-3-gallate degrades DNA in cell nuclei, which can also be inhibited by neocuproine, suggesting mobilization of nuclear copper in this reaction as well. Our results are indicative of ROS generation, possibly through mobilization of endogenous copper ions, and support our long-standing hypothesis of a prooxidant activity of plant-derived polyphenols as a mechanism for their documented anticancer properties.
authors.affiliation: Department of Biochemistry, Faculty of Life Sciences, AMU, Aligarh 202001, India. farhan@mohdfarhan.com.
authors.forename: Mohd
authors.initials: M
authors.lastname: Farhan
authors.affiliation: Center of Excellence in Environmental Studies, King Abdulaziz University, Jeddah 21589, Saudi Arabia. owais.micro@gmail.com.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Oves
authors.affiliation: Department of Biochemistry, Faculty of Life Sciences, AMU, Aligarh 202001, India. sandeshchibber@gmail.com.
authors.forename: Sandesh
authors.initials: S
authors.lastname: Chibber
authors.affiliation: Department of Biochemistry, Faculty of Life Sciences, AMU, Aligarh 202001, India. smhadi1946@gmail.com.
authors.forename: Sheikh Mumtaz
authors.initials: SM
authors.lastname: Hadi
authors.affiliation: Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, 1660 Springhill Avenue, Mobile, AL 36604-1405, USA. aahmad@health.southalabama.edu.
authors.forename: Aamir
authors.initials: A
authors.lastname: Ahmad
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003300:Copper / Q000378:metabolism*; D053938:DNA Fragmentation / Q000187:drug effects*; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013662:Tea / Q000737:chemistry
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D017382:Reactive Oxygen Species; D013662:Tea; D003300:Copper; D002392:Catechin; C062669:epicatechin gallate
keywords: DNA damage; anticancer; comet assay; copper; epicatechin-3-gallate; prooxidant; reactive oxygen species