Effects of folate cycle disruption by the green tea polyphenol epigallocatechin-3-gallate.
We demonstrate that the tea polyphenol, epigallocatechin-3-gallate, is an efficient inhibitor of human dihydrofolate reductase. Like other antifolate compounds, epigallocatechin-3-gallate acts by disturbing folic acid metabolism in cells, causing the inhibition of DNA and RNA synthesis and altering DNA methylation. Epigallocatechin-3-gallate was seen to inhibit the growth of a human colon carcinoma cell line in a concentration and time dependent manner. Rescue experiments using leucovorin and hypoxanthine-thymine medium were the first indication that epigallocatechin-3-gallate could disturb the folate metabolism within cells. Epigallocatechin-3-gallate increased the uptake of [(3)H]-thymidine and showed synergy with 5-fluorouracil, while its inhibitory action was strengthened after treatment with hypoxanthine, which indicates that epigallocatechin-3-gallate decreases the cellular production of nucleotides, thus, disturbing DNA and RNA synthesis. In addition to its effects on nucleotide biosynthesis, antifolate treatment has been linked to a decrease in cellular methylation. Here, we observed that epigallocatechin-3-gallate altered the p16 methylation pattern from methylated to unmethylated as a result of folic acid deprivation. Finally, we demonstrate that epigallocatechin-3-gallate causes adenosine to be released from the cells because it disrupts the purine metabolism. By binding to its specific receptors, adenosine can modulate different signalling pathways. This proposed mechanism should help us to understand most of the molecular and cellular effects described for this tea polyphenol.
Departamento de Bioquímica y Biología Molecular A, Facultad de Biología, Universidad de Murcia, E-30100 Espinardo, Murcia, Spain.
Enma
E
Navarro-Perán
Juan
J
Cabezas-Herrera
Luis Sánchez Del
LS
Campo
José Neptuno
JN
Rodríguez-López
D000241:Adenosine / Q000378:metabolism / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D018938:Caco-2 Cells; D028241:Camellia sinensis / Q000737:chemistry*; D053148:Caspase 3 / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D019175:DNA Methylation / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects; D005472:Fluorouracil / Q000494:pharmacology; D005493:Folic Acid Antagonists / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D019271:Hypoxanthine / Q000494:pharmacology; D002955:Leucovorin / Q000494:pharmacology; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism; D011485:Protein Binding; D043684:Receptor, Adenosine A3 / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D013941:Thymine / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
D019941:Cyclin-Dependent Kinase Inhibitor p16; D005493:Folic Acid Antagonists; D016328:NF-kappa B; D043684:Receptor, Adenosine A3; D019271:Hypoxanthine; D002392:Catechin; C045651:epigallocatechin gallate; D013762:Tetrahydrofolate Dehydrogenase; D053148:Caspase 3; D000241:Adenosine; D002955:Leucovorin; D013941:Thymine; D005472:Fluorouracil