Inhibition and induction of aromatase (CYP19) activity by brominated flame retardants in H295R human adrenocortical carcinoma cells.
Brominated flame retardants (BFRs) are persistent and ubiquitous chemicals in the environment, and they are found at increasing levels in tissues of wildlife and humans. Previous in vitro studies with the BFR class of polybrominated diphenyl ethers (BDEs) have shown endocrine-disrupting properties. Our study assessed the potential effects of nineteen BDEs, five hydroxylated BDEs (OH-BDEs), one methoxylated BDE (CH(3)O-BDE), tetrabromobisphenol-A (TBBPA), its dibromopropane ether derivative (TBBPA-DBPE), and the brominated phenols/anisols 2,4,6-tribromophenol (TBP), 4-bromophenol (4BP) and 2,4,6-tribromoanisole (TBA) on the catalytic activity of the steroidogenic enzyme aromatase (CYP19) in H295R human adrenocortical carcinoma cells. Effects were studied in the concentration range from 0.5 to 7.5 microM; exposures were for 24 h. Both 6-OH-BDE47 and 6-OH-BDE99 showed an inhibitory effect on aromatase activity at concentrations >2.5 microM and >5 microM, respectively. However, 6-OH-BDE47 also caused a statistically significant increase in cytotoxicity (based on mitochondrial MTT reduction and lactate dehydrogenase-leakage [LDH]) at concentrations >2.5 microM that could explain in part the apparent inhibitory effect on aromatase activity. Compared to 6-OH-BDE47, the methoxy analog (6-CH(3)O-BDE47) did not elicit a cytotoxic effect, whereas significant inhibition of aromatase remained. TBP caused a concentration-dependent induction of aromatase activity between 0.5 and 7.5 microM (with a maximum of 3.8-fold induction at 7.5 microM). This induction was not observed when a OH- group replaced the CH(3)O- group or when bromine atoms adjacent to this OH- group were absent. These in vitro results provide a basis for studies of more detailed structure-activity relationships between these brominated compounds and the modulation of aromatase activity.
Cantón
Rocío F
RF
Institute for Risk Assessment Sciences, IRAS Utrecht University, The Netherlands. r.fernandezcanton@iras.uu.nl
Sanderson
J Thomas
JT
Letcher
Robert J
RJ
Bergman
Ake
A
van den Berg
Martin
M
D000306:Adrenal Cortex Neoplasms / Q000188:drug therapy / Q000201:enzymology*; D018268:Adrenocortical Carcinoma / Q000188:drug therapy / Q000201:enzymology*; D001141:Aromatase / Q000096:biosynthesis*; D047072:Aromatase Inhibitors / Q000633:toxicity*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity*; D004790:Enzyme Induction; D005411:Flame Retardants / Q000633:toxicity*; D006801:Humans; D011075:Polybrominated Biphenyls / Q000633:toxicity*
D047072:Aromatase Inhibitors; D004785:Environmental Pollutants; D005411:Flame Retardants; D011075:Polybrominated Biphenyls; D001141:Aromatase