Cyclopia extracts act as ERα antagonists and ERβ agonists, in vitro and in vivo

dc.contributor.authorVisser, Koch
dc.contributor.authorMortimer, Morne
dc.contributor.authorLouw, Ann
dc.identifier.citationVisser, K., Mortimer, M. & Louw, A. 2013. Cyclopia Extracts Act as ERα Antagonists and ERβ Agonists, In Vitro and In Vivo. PLoS ONE 8(11), e79223, doi:10.1371/journal.pone.0079223en_ZA
dc.identifier.issn1932-6203 (online)
dc.descriptionThe original publication is available at http:/www.plosone.orgen_ZA
dc.descriptionPublication of this article was funded by the Stellenbosch University Open Access Fund.
dc.description.abstractHormone replacement therapy associated risks, and the concomitant reluctance of usage, has instigated the search for new generations of estrogen analogues that would maintain estrogen benefits without associated risks. Furthermore, if these analogues display chemo-preventative properties in breast and endometrial tissues it would be of great value. Both the selective estrogen receptor modulators as well as the selective estrogen receptor subtype modulators have been proposed as estrogen analogues with improved risk profiles. Phytoestrogen containing extracts of Cyclopia, an indigenous South African fynbos plant used to prepare Honeybush tea may serve as a source of new estrogen analogues. In this study three extracts, P104, SM6Met, and cup-of-tea, from two species of Cyclopia, C. genistoides and C. subternata, were evaluated for ER subtype specific agonism and antagonism both in transactivation and transrepression. For transactivation, the Cyclopia extracts displayed ERα antagonism and ERβ agonism when ER subtypes were expressed separately, however, when co-expressed only agonism was uniformly observed. In contrast, for transrepression, this uniform behavior was lost, with some extracts (P104) displaying uniform agonism, while others (SM6Met) displayed antagonism when subtypes were expressed separately and agonism when co-expressed. In addition, breast cancer cell proliferation assays indicate that extracts antagonize cell proliferation in the presence of estrogen at lower concentrations than that required for proliferation. Furthermore, lack of uterine growth and delayed vaginal opening in an immature rat uterotrophic model validates the ERα antagonism of extracts observed in vitro and supports the potential of the Cyclopia extracts as a source of estrogen analogues with a reduced risk profile.en_ZA
dc.format.extent22 p. : ill. (some col.)
dc.publisherPublic Library of Science (PLOS)en_ZA
dc.subjectEstrogen -- Receptorsen_ZA
dc.subjectEstrogen -- Antagonistsen_ZA
dc.subjectHormone replacement therapyen_ZA
dc.titleCyclopia extracts act as ERα antagonists and ERβ agonists, in vitro and in vivoen_ZA
dc.description.versionPublishers' Versionen_ZA
dc.rights.holderAuthors retain copyrighten_ZA

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