Ultrasensitive cell-based bioassay for the measurement of global estrogenic activity of flavonoid mixtures revealing additive, restrictive, and enhanced actions in binary and higher order combinations.
Flavonoids present in food, botanicals, and body fluids occur as complex mixtures, and data on their combinatorial estrogenic effects are sparse. Human cell lines that permanently express estrogen receptor (ER) alpha and ERbeta proteins were developed for the measurement of the global estrogenicity of flavonoids in such complex mixtures. The presence of estrogenic ligands, known and unknown, in these mixtures can be detected by activation of an ER-driven luciferase reporter gene. We also examined the effect of hydroxylation on the estrogenic activities of four common flavonoids-apigenin, kaempferol, luteolin, and quercetin, alone and in combination. An inverse relationship was observed between the number of hydroxyl groups in flavonoids and ERalpha bioactivity. When submaximal doses of apigenin, luteolin, kaempferol, genistein, and estradiol were combined in binary and higher order mixtures, the experimental estrogenic effects matched those obtained by summing effects extrapolated from dose-response curves of individual compounds. The estrogenic activities of mixtures containing quercetin were observed to deviate from additivity, suggesting that it was a partial agonist/antagonist. Our assay reveals superagonistic, additive, and antagonistic ERalpha or ERbeta actions of flavonoids and adds to our understanding of the estrogenic effects of phytoestrogens in complex mixtures.
Wong
Shih Peng
SP
Department of Obstetrics and Gynecology, National University Hospital, Yong Loo Lin School of Medicine, National University of Singapore, Republic of Singapore.
Li
Jun
J
Shen
Ping
P
Gong
Yinhan
Y
Yap
Sook Peng
SP
Yong
Eu Leong
EL
D004357:Drug Synergism; D004359:Drug Therapy, Combination; D047628:Estrogen Receptor alpha / Q000187:drug effects; D047629:Estrogen Receptor beta / Q000187:drug effects; D004967:Estrogens / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D012680:Sensitivity and Specificity; D013329:Structure-Activity Relationship
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D004967:Estrogens; D005419:Flavonoids