In vitro cytotoxicity of bisphenol A to human gingival epithelial S-G cells

In vitro cell culture studies have noted that bisphenol A (BPA), acting as a xenoestrogen, stimulated human breast cancer cell proliferation in vitro. BPA is the precursor of many monomers, including bisphenol A dimethacrylate (Bis-DMA), which is used widely hi resin-based dental composites and sealants. The detection of BPA in the saliva of patients in whom sealants had been applied 1 h earlier raised several health safety concerns. Studies on the in vitro response of normal human cells to BPA are lacking. By quantitating the in vitro cytotoxicity of BPA using cell culture assays combined with microscopy, the study presented herein provides a cytotoxicity profile of BPA toward normal human cells. The relative cytotoxicity of BPA, and, for comparative purposes, of other leachates from dental materials, toward human gingival epithelial (S-G) cells, gingival (GN) fibroblasts, and periodontal ligament (PDL) fibroblasts was evaluated with the neutral red (NR) assay. For the S-G and GN cells the sequence of potency was BPA, bisphenol glycidyl methacrylate (Bis-GMA) > Bis-DMA > triethylene glycol dimethacrylate (TEGDMA), but for the PDL fibroblasts the sequence was BPA, Bis-GMA. > TEGDMA > Bis-DMA. More extensive studies focused on BPA and SG cells. The midpoint NR cytotoxicity value of 0.2 mM BPA noted for a 24-h exposure of the S-G cells was similar to that noted with the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and AlamarBlue metabolic assays. The lack of cytotoxicity as assayed by the release of lactic acid dehydrogenase (LDH) after a 3-h exposure of the SG cells to BPA, indicated that the plasma membrane was not a prime target for BPA. Furthermore, the cytotoxicity of BPA was not potentiated in the presence of a P450 metabolic activating system. Subtoxic levels of BPA induced the formation of micronuclei and extensive vacuolization was noted upon exposure to highly toxic levels of BPA, induction of cell death by apoptosis was evident with EPA exposure in serum-limited. medium, with the extent of apoptosis dependent upon the concentration of BPA and the length of exposure.