Honaker, A. | bioRxiv Science

bioRxiv2025

Developmental benzopyrene exposure alters stress hormones, neurotransmitters and behavioral responses of mice dependent on Cyp1 genotype

Benzo[a]pyrene (BaP) is a prototypical polycyclic aromatic hydrocarbon (PAH) produced during combustion processes and when grilling foods. Epidemiological studies indicate exposure to PAHs during pregnancy lead to learning and memory deficits as well as behavioral problems that persist into adolescence. Studies in rodents and zebrafish have frequently reported anxiolytic effects of BaP exposure in adult animals and in developmental studies. We conducted sequential experiments of Cyp1a1(-/-) and Cyp1b1(-/-) knockout mice compared with wild type C57BL/6J mice to determine if genotype changes the response to developmental BaP exposure. We treated pregnant dams from gestational day 10 to postnatal day 25 (P25) with BaP in corn oil-soaked cereal or the corn oil vehicle and tested one male and one female offspring beginning at P60. We found increased exploratory behavior in the elevated zero maze for Cyp1a1(-/-) knockout mice, but no significant differences in Cyp1b1(-/-) knockouts. In contrast, Cyp1b1(-/-) knockout mice buried fewer marbles in a second test of anxiety-like behavior. There were no significant differences when Cyp1a1(-/-) knockout mice were tested. BaP decreased immobility time in Cyp1a1(-/-) knockouts in the forced swim test, but increased immobility time in wild type and Cyp1b1(-/-) knockout mice. We measured plasma corticosterone levels at baseline and following the forced swim test and monoamine neurotransmitters at the end of behavioral testing. BaP treatment increased corticosterone in wild type mice, but decreased it in Cyp1a1(-/-) knockout mice. Both BaP-exposed and corn oil control Cyp1b1(-/-) knockout mice had higher corticosterone levels compared with wild type mice. Dopamine and serotonin signaling were altered in the hypothalamus dependent on genotype, treatment and sex. Together, these data suggest that both CYP1A1 and CYP1B1 have a normal role in brain functioning or development, and that CYP1 genotype alters the response to developmental BaP exposure in behavioral and biochemical tests related to stress, anxiety and depression. HighlightsO_LIBaP-exposed Cyp1a1(-/-) mice had lower corticosterone and decreased immobility in the forced swim test C_LIO_LIBaP exposure increased FST immobility in wild type and Cyp1b1(-/-) mice C_LIO_LICyp1a1(-/-) and Cyp1b1(-/-) knockout mice showed less anxiety-like behavior C_LIO_LIDevelopmental BaP exposure altered corticosterone levels dependent on Cyp1 genotype C_LIO_LIGenotype, treatment and sex all impacted neurotransmitter levels in the hypothalamus C_LIO_LIGenetic differences in CYP enzymes altered susceptibility to developmental BaP exposure C_LI

pharmacology and toxicology↗

bioRxiv2021

The behavioral effects of gestational and lactational benzopyrene exposure vary by sex and genotype in mice with differences at the Ahr and Cyp1a2 loci

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) and known carcinogen in the Top 10 on the United States list of priority pollutants. Humans are exposed through a variety of sources including tobacco smoke, grilled foods and fossil fuel combustion. Recent studies of children exposed to higher levels of PAHs during pregnancy and early life have identified numerous adverse effects on the brain and behavior that persist into school age and adolescence. Our studies were designed to look for genotype and sex differences in susceptibility to gestational and lactational exposure to BaP using a mouse model with allelic differences in the aryl hydrocarbon receptor and the xenobiotic metabolizing enzyme CYP1A2. Pregnant dams were exposed to 10 mg/kg/day of BaP in corn oil-soaked cereal or the corn oil vehicle alone from gestational day 10 until weaning at postnatal day 25. Neurobehavioral testing began at P60 using one male and one female per litter. We found main effects of sex, genotype and treatment as well as significant gene x treatment and sex x treatment interactions. BaP-treated female mice had shorter latencies to fall in the Rotarod test. High-affinity AhrbCyp1a2(-/-) mice had greater impairments in Morris water maze. Interestingly, poor-affinity AhrdCyp1a2(-/-) mice also had deficits in spatial learning and memory regardless of treatment. We believe our findings provide future directions in identifying human populations at highest risk of early life BaP exposure, because our model mimics known human variation in our genes of interest. Our studies also highlight the value of testing both males and females in all neurobehavioral studies. HighlightsO_LIGestational and lactational benzo[a]pyrene (BaP) exposure has sex and genotype-specific neurobehavioral effects in mice. C_LIO_LIFemale mice were more susceptible to motor deficits following developmental BaP exposure. Males were more susceptible to deficits in reversal learning and memory. C_LIO_LIAhrbCyp1a2(-/-) knockout mice were more susceptible to spatial learning and memory deficits following developmental BaP exposure. C_LIO_LIPoor-affinity AhrdCyp1a2(-/-) mice had deficits in spatial learning and memory regardless of treatment. C_LI

pharmacology and toxicology↗