4,4'-(9-Fluorenylidene)dianiline (BAFL) is antiestrogenic and has adverse effects on female development in CD-1 mice

Many phenolic compounds have been found to have endocrine disrupting activities, but their arylamine analogs, the phenolic hydroxyl groups substituted by aniline amino groups, have rarely been reported. 4,4'-(9-Fluorenylidene)dianiline (BAFL) is an arylamine analog of fluorene-9-bisphenol (BHPF) and BHPF has been reported to be a strong antiestrogen which could cause endometrial atrophy, ovarian damage and adverse pregnancy outcomes in animals. BAFL has been widely used as material to synthetize polymers, such as polyimides, polyamide, and polyamine, for various uses since the 1970s. Here, we assessed the antiestrogenicity of BAFL using a variety of methods and looked into its impacts on the development of females in CD-1 mice. With the aid of a yeast estrogen screen assay, we found BAFL possessed obviously antiestrogenic activity (IC₅₀ = 8.15 × 10^-6 M), which close to that of tamoxifen and BHPF. Using a 10-d mouse uterotrophic assay, we found that BAFL obviously decreased uterine weight in a dose-dependent way. Histological analyses of mouse uteri revealed that BAFL induced marked endometrial atrophy and inhibited the uterine development. Immunohistochemical analyses showed that Sprr2d, an estrogen-responsive gene encoding protein, was mainly expressed in endometrial epithelial cells and BAFL decreased the areas and levels of Sprr2d staining in mouse uteri. It was clear from uterine transcriptome investigations that BAFL significantly downregulated the expressions of multiple genes responding to estrogen. Molecular docking showed that BAFL could effectively occupy the antagonist-binding pocket of hERα, and one of the amino groups of BAFL formed hydrogen bonds with the side chains of Arg394 and Glu353 in the receptor. These results indicated that BAFL exhibited clearly antiestrogenic characteristics and could interfere with normal female development in mice, which should be avoided using in commodities that come into direct contact with humans. Moreover, this study indicated that the arylamine analogs of phenolic endocrine disrupting chemicals might also have endocrine disrupting activities.