Estrogenic/Antiestrogenic activities of polycyclic aromatic hydrocarbons and their monohydroxylated derivatives by yeast two-hybrid assay

Estrogenic/antiestrogenic activities of 14 polycyclic aromatic hydrocarbons (PAHs) and 63 monohydroxylated PAHs (OHPAHs) having 2 to 6 rings were evaluated by yeast two-hybrid assay expressing human estrogen receptor a. Relative effective potencies of estrogenic and antiestrogenic activities were calculated as the inverse values of the relative concentration of the test compound that gave the same activities of E-2 and 4-hydroxytamoxifen, respectively. PAHs did not show any estrogenic/antiestrogenic activity, but several OHPAHs having 3 to 5 rings showed activities. Especially, OHPAHs having 4 rings such as 3-, 4- and 10-hydroxybenz[a]anthracenes (3-, 4- and 10-OHBaAs) and 2-hydroxychrysene (2-OHCh) showed strongly estrogenic activity. Several other OHPAHs having 4 rings such as 2- and 3-hydroxybenzo[c]phenanthrenes (2-, 3-OHBcPhs), 2-OHBaA and 3-OHCh showed strongly antiestrogenic activity. The length-to-breadth (L/B) ratios of the rectangular van der Walls planes surrounding the ring molecules of estrogenic OHPAHs were in the narrow range from 1.599 to 1.734. The distances between the oxygen atom of the phenol group and farthest hydrogen atom (O-H distance) of the estrogenic OHPAHs ranged from 10.825,angstrom to 11.738 angstrom. The L/B ratios and O-H distances of antiestrogenic OHPAHs were in the wider ranges from 1.277 to 1.734 and from 8.47 angstrom to 11.681 A, respectively. The partial charges (atomic unit) of the phenol Group of both estrogenic and antiestrogenic OHPAHs were in the range from -0.250 atmic unit (an) to -0.253 an. The similarity of these values to those of E-2 and diethylstilbestrol suggested that the compositions of estrogenic OHPAHs were similar to them and that the compositional conditions of estrogenic OHPAHs were much smaller than those of antiestrogenic OHPAHs. These results raise the possibility of predicting the estrogenic/antiestrogenic activities of OHPAHs from their structural characteristics, although using only the above three parameters might not be enough for accurate estimations.