Oliver Faass

Developmental toxicity of UV filters and environmental exposure: a review

Several ultraviolet (UV) filters exhibit estrogenic, some also anti-androgenic activity. They are present in waste water treatment plants, surface waters and biosphere including human milk, suggesting potential exposure during development. Developmental toxicity was studied in rats for the UV filters 4-methylbenzylidene camphor (4-MBC, 0.7, 7, 24, 47 mg/kg/day) and 3-benzylidene camphor (3-BC, 0.07, 0.24, 0.7, 2.4, 7 mg/kg/day) administered in chow to the parent generation before mating, during pregnancy and lactation, and to the offspring until adulthood. Neonates exhibited enhanced prostate growth after 4-MBC and altered uterine gene expression after both chemicals. 4-MBC and 3-BC delayed male puberty and affected reproductive organ weights of adult offspring. Effects on the thyroid axis were also noted. Expression and oestrogen sensitivity of oestrogen-regulated genes and nuclear receptor coregulator levels were altered at mRNA and protein levels in adult uterus, prostate and brain regions involved in gonadal control and sexual behaviour. Female sexual behaviour was impaired by both filters; 3-benzylidene camphor caused irregular cycles. Classical endpoints exhibited lowest observed adverse effect levels (LOAELs) and no observed adverse effect levels (NOAELs) of 7/0.7 mg/kg for 4-MBC and 0.24/0.07 mg/kg for 3-BC. Molecular endpoints were affected by the lowest doses studied. Our data indicate that the potential risk posed by endocrine active UV filters warrants further investigations.

Female sexual behavior, estrous cycle and gene expression in sexually dimorphic brain regions after pre- and postnatal exposure to endocrine active UV filters

The developing female brain represents a potential target for estrogenic environmental chemicals because it depends on estrogen but is exposed to low endogenous estrogen levels, thus facilitating competition by exogenous estrogen receptor (ER) agonists. We investigated effects of two estrogenic UV filters, 4-methylbenzylidene camphor (4-MBC) and 3-benzylidene camphor (3-BC). 4-MBC has been detected in human milk, indicating potential exposure of fetus and infant. The two chemicals were administered in chow to rats of the parent generation before mating, during pregnancy and lactation, and to their offspring until adulthood. Female sexual behavior was recorded on videotape in adult female offspring on proestrus evening at the beginning of the dark phase. 4-MBC (7 and 24mg/kg bw/day) and 3-BC (2.4 and 7mg/kg bw/day) reduced proceptive behavior (jump and ear wiggling) and receptive behavior (lordosis quotient), and increased rejection behavior towards the male. Estrous cycles were not affected by 4-MBC but disturbed by 3-BC. mRNAs encoding for genes involved in female sexual behavior, ERalpha, ERbeta, progesterone receptor (PR) and steroid receptor coactivator-1 (SRC-1), were measured by real-time RT-PCR in ventromedial hypothalamic nucleus (VMH) and medial preoptic area of adult male and female offspring (studied in diestrus) after pre- and postnatal exposure to 3-BC (0.24, 0.7, 2.4 and 7mg/kg bw/day). Gene expression was affected in a sex- and region-specific manner. PR mRNA in female VMH was reduced to male levels at dose levels of 2.4 and 7mg/kg bw/day 3-BC. Our data demonstrate that female sexual behavior represents a sensitive target of endocrine disrupters and point to an involvement of PR in VMH.

Differential Gene Expression Patterns in Developing Sexually Dimorphic Rat Brain Regions Exposed to Antiandrogenic, Estrogenic, or Complex Endocrine Disruptor Mixtures: Glutamatergic Synapses as Target

The study addressed the question whether gene expression patterns induced by different mixtures of endocrine disrupting chemicals (EDCs) administered in a higher dose range, corresponding to 450×, 200×, and 100× high-end human exposure levels, could be characterized in developing brain with respect to endocrine activity of mixture components, and which developmental processes were preferentially targeted. Three EDC mixtures, A-Mix (anti-androgenic mixture) with 8 antiandrogenic chemicals (di-n-butylphthalate, diethylhexylphthalate, vinclozolin, prochloraz, procymidone, linuron, epoxiconazole, and DDE), E-Mix (estrogenic mixture) with 4 estrogenic chemicals (bisphenol A, 4-methylbenzylidene camphor, 2-ethylhexyl 4-methoxycinnamate, and butylparaben), a complex mixture, AEP-Mix, containing the components of A-Mix and E-Mix plus paracetamol, and paracetamol alone, were administered by oral gavage to rat dams from gestation day 7 until weaning. General developmental endpoints were not affected by EDC mixtures or paracetamol. Gene expression was analyzed on postnatal day 6, during sexual brain differentiation, by exon microarray in medial preoptic area in the high-dose group, and by real-time RT-PCR in medial preoptic area and ventromedial hypothalamus in all dose groups. Expression patterns were mixture, sex, and region specific. Effects of the analgesic drug paracetamol, which exhibits antiandrogenic activity in peripheral systems, differed from those of A-Mix. All mixtures had a strong, mixture-specific impact on genes encoding for components of excitatory glutamatergic synapses and genes controlling migration and pathfinding of glutamatergic and GABAergic neurons, as well as genes linked with increased risk of autism spectrum disorders. Because development of glutamatergic synapses is regulated by sex steroids also in hippocampus, this may represent a general target of ECD mixtures.