Effects of combined prenatal exposure to air pollution and maternal stress on social behavior and oxytocin and vasopressin systems in male and female mice

Prenatal exposures to air pollution and maternal psychosocial stress are each associated with increased risk of neurodevelopmental disorders, including autism spectrum disorder (ASD) and epidemiological work suggests that concurrent exposure to these risk factors may be particularly harmful. This is important given that the same populations often bear the brunt of both toxicant and psychosocial stress burdens. Social impairments are a defining symptom in ASD. Previous work modeling combined prenatal exposure to diesel exhaust particles (DEP) and maternal stress (MS) in rodents has found male-biased social deficits in offspring, as well as changes to neuroimmune processes and the gut microbiome. However, the precise neural circuits on which these exposures converge to impact social behavior is unclear. Oxytocin (OXT) and vasopressin (AVP) are neuropeptides critical to the regulation of social behavior across species, signaling primarily at the oxytocin receptor (Oxtr) and vasopressin V1a receptor (V1aR) in the brain. Here, we hypothesized that OXT and/or AVP expression would be reduced in the brain following DEP/MS exposure. Following prenatal exposure to DEP/MS or the vehicle/control condition (VEH/CON), we measured maternal and offspring outcomes during the perinatal period, social and anxiety-like behavior during adolescence, OXT and AVP cell/fiber density and Oxtr and Avpr1a mRNA expression in early adulthood in several brain regions in both males and females. We observed a decrease in interaction time in DEP/MS males as compared to VEH/CON in the sociability assay and a decrease in social novelty preference in DEP/MS females as compared to VEH/CON. No effects of sex or treatment were observed on OXT or AVP cell number or fiber density in the hypothalamic regions assessed. However, numerous sex differences were observed in Oxtr and Avpr1a mRNA. Moreover, Avpr1a mRNA was significantly increased following DEP/MS exposure in the nucleus accumbens in both sexes and tended to increase in the dorsal hippocampus. Conversely, Avpr1a mRNA tended to decrease in the amygdala in both sexes following DEP/MS exposure. Together, these findings suggest that DEP/MS exposure has a stronger impact on female social behavior than previously observed. Moreover, while DEP/MS exposure does not appear to impact OXT or AVP expression in the brain, V1aR expression is modulated by DEP/MS exposure in several brain regions.