Estrogenic and antiproliferative effects of 8-prenylnaringenin on the vascular system

Based on well described estrogenic effects of the phytoestrogen 8-prenylnaringenin (8PN) in vitro, its estrogen like actions on the uterus and on bone density in rats have been investigated recently, whereas information on potential effects of 8PN on the vascular system is missing. Therefore we studied mRNA expression of estrogen regulated genes in the vena cava in ovariectomized rats, following a time dependent treatment protocol (7h, 24h and 72h) with chemically synthesized 8PN by real time RT-PCR. The effects of 8PN (15mg/kg BW; s.c.) were comparatively assessed to the positive control 17β-estradiol (E2) (10µg/kg BW; s.c) and the negative control (castor oil). The mRNA expression of the following genes has been measured: estrogen receptor α, endothelial NO synthase, angiotensin converting enzyme, clusterin and vascular endothelial growth factor receptor 2. In addition in vitro experiments using human umbilical vein endothelial cells (HUVEC) have been performed. Effects on the proliferation of HUVECs have been investigated by determining protein levels after six days of treatment with the test substances using a BCA assay. Differentiation of endothelial cells has been studied by comparing the ability of HUVECs to form endothelial tubes on a reconstituted basal membrane (Matrigel) by microscopic examination in response to a 24h of treatment with test substances.

The time course of the mRNA expression of all genes studied in the vena cava follows a comparable pattern for 8PN and E2 treatment suggesting estrogen agonistic effects of 8PN on the vascular system. Differentiation of HUVECs was also promoted in an E2 like manner by 8PN and could be inhibited with the pure antiestrogen Fulvestrant suggesting an estrogen receptor dependent mode of action.

However, unlike E2, 8PN did not promote proliferation of HUVECs. In addition co-treatment with E2 and 8PN lead to an inhibition of E2 induced increase in proliferation by 8PN suggesting antiproliferative properties of 8PN in the vascular wall.