Hexabromocyclododecane facilitates FSH activation of ERK1/2 and AKT through epidermal growth factor receptor in rat granulosa cells

Long-term in vitro exposure of human granulosa cells to the mixture of endocrine disrupting chemicals found in human follicular fluid disrupts steroidogenesis

Most in vitro studies examine the effects of a single ED or a mixture of EDs on granulosa cells using short-term exposure; however, this approach is unlikely to reflect long-term, real-life exposures that are common in humans. We established an in vitro model that mimics long-term exposure of granulosa cells to real-life ED mixture. Human granulosa cells, HGrC1, were exposed to the mixture consisting of bisphenol A, polychlorinated biphenyl 153, benzo[a]pyrene, and perfluorooctanesulfonate in concentrations found in human follicular fluid (MIX) for 48 h and 4 weeks. Only long-term exposure to MIX decreased estradiol production after 2 and 3 weeks, and CYP19A1 protein after 2 weeks of exposure. By week 4, the cells restored estradiol production and CYP19A1 protein level. MIX increased basal progesterone production after 3 and 4 weeks of exposure but did not affect STAR and CYP11A1 mRNA. Cells that had been exposed to MIX for 4 weeks showed augmentation of forskolin-stimulated progesterone production. These results demonstrate that only long-term exposure to MIX alters steroidogenesis in HGrC1. This study also revealed that adverse effects of MIX on steroidogenesis in HGrC1 occurred a few weeks into MIX exposure and that this effect can be transient.

Characterization of the ERK1/2 phosphorylation profile in human and fish liver cells upon exposure to chemicals of environmental concern

We developed phospho-ERK1/2 ELISA for human and rainbow trout liver cells, employing HepG2 and RTL-W1 cell lines as models. The assay was applied to detect changes in ERK1/2 activity for nine chemicals, added over a wide concentration range and time points. Cell viability was measured to separate ERK1/2 regulation from cytotoxicity. Perfluorooctane sulfonate and carbendazim did not change ERK1/2 activity; influence on ERK1/2 due to cytotoxicity was indicated for tributyltin and cypermethrin. Mancozeb, benzo[a]pyrene, and bisphenol A stimulated ERK1/2 up to ∼2- (HepG2) and 1.5 (RTL-W1)-fold, though the kinetics differed between chemicals and cell lines. Bisphenol A and benzo[a]pyrene were the most potent concentration-wise, altering ERK1/2 activity in pM (HepG2) to nM (RTL-W1) range. While atrazine and ibuprofen increased ERK1/2 activity by ∼2-fold in HepG2, they did not initiate an appreciable response in RTL-W1. This assay proved to be a sensitive, medium- to high-throughput tool for detecting unrecognized ERK1/2-disrupting chemicals.

Update of the risk assessment of hexabromocyclododecanes (HBCDDs) in food

The European Commission asked EFSA to update its 2011 risk assessment on hexabromocyclododecanes (HBCDDs) in food. HBCDDs, predominantly mixtures of the stereoisomers α-, β- and γ-HBCDD, were widely used additive flame retardants. Concern has been raised because of the occurrence of HBCDDs in the environment, food and in humans. Main targets for toxicity are neurodevelopment, the liver, thyroid hormone homeostasis and the reproductive and immune systems. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour in mice can be considered the critical effects. Based on effects on spontaneous behaviour in mice, the Panel identified a lowest observed adverse effect level (LOAEL) of 0.9 mg/kg body weight (bw) as the Reference Point, corresponding to a body burden of 0.75 mg/kg bw. The chronic intake that would lead to the same body burden in humans was calculated to be 2.35 μg/kg bw per day. The derivation of a health-based guidance value (HBGV) was not considered appropriate. Instead, the margin of exposure (MOE) approach was applied to assess possible health concerns. Over 6,000 analytical results for HBCDDs in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary LB exposure to HBCDDs were fish meat, eggs, livestock meat and poultry. The CONTAM Panel concluded that the resulting MOE values support the conclusion that current dietary exposure to HBCDDs across European countries does not raise a health concern. An exception is breastfed infants with high milk consumption, for which the lowest MOE values may raise a health concern.

HBCDD-induced sustained reduction in mitochondrial membrane potential, ATP and steroidogenesis in peripubertal rat Leydig cells

Hexabromocyclododecane (HBCDD), a brominated flame retardant added to various consumer products, is a ubiquitous environmental contaminant. We have previously shown that 6-hour exposure to HBCDD disturbs basal and human chorionic gonadotropin (hCG)-induced steroidogenesis in rat Leydig cells. Reduction in mitochondrial membrane potential (ΔΨm) and cAMP production was also observed. Here, we further expanded research on the effect of HBCDD on Leydig cells by using a prolonged exposure scenario. Cells were incubated in the presence of HBCDD during 24h and then treated with HBCDD+hCG for additional 2h. Results showed that HBCDD caused a sustained reduction in ATP level after 24h of exposure, which persisted after additional 2-hour treatment with HBCDD+hCG. cAMP and androgen accumulations measured after 2h of HBCDD+hCG treatment were also inhibited. Real-time PCR analysis showed significant inhibition in the expression of genes for steroidogenic enzymes, luteinizing hormone receptor, regulatory and transport proteins, and several transcription factors under both treatment conditions. Western blot analysis revealed a decreased level of 30kDa steroidogenic acute regulatory protein (StAR) after HBCDD+hCG treatment. In addition, HBCDD decreased the conversion of 22-OH cholesterol to pregnenolone and androstenedione to testosterone, indicating loss of the activity of cytochrome P450C11A1 (CYP11A1) and 17β-hydroxysteroid dehydrogenase (HSD17β). Cell survival was not affected, as confirmed by cytotoxicity and trypan blue tests or DNA fragmentation analysis. In summary, our data showed that HBCDD inhibits ATP supply, most likely through a decrease in ΔΨm, and targets multiple sites in the steroidogenic pathway in Leydig cells.