Effects of combined prenatal exposure to air pollution and maternal stress on immune and dopaminergic gene expression in the gut-brain axis.

Abstract

Air pollution and maternal stress during pregnancy are both risk factors for neurodevelopmental disorders and often converge on the same communities. Epidemiological and animal studies suggest that maternal psychosocial stress may worsen the effects of air pollutants on neurodevelopmental outcomes. Previous work utilizing a mouse model of combined prenatal exposure to diesel exhaust particles (DEP) and maternal stress (MS) has found numerous sex-specific effects of DEP/MS exposure on neuroimmune outcomes, dopamine receptors, the gut-brain axis, and social behavior. However, it is unclear how broadly the immune landscape is shifted in the brain and intestinal epithelium following DEP/MS. Here, we analyzed immune gene expression in 5 brain regions important for social behavior and in 3 regions of the intestinal epithelium in both male and female offspring at ∼postnatal day 50, following either DEP/MS or control exposure. We found several interesting overall patterns. First, changes in expression of immune genes such as <i>CD11b</i> and <i>Tlr4</i> were concentrated in the nucleus accumbens and hippocampus. <i>Tlr4</i> and <i>Il-17ra</i> mRNA also increased in the jejunum and colon following DEP/MS, but only in females. Second, in the nucleus accumbens, catecholamine-O-methyltransferase (<i>Comt</i>) and dopamine transporter 1 (<i>Slc6a3</i>) gene expression were increased following DEP/MS, indicating increased dopamine degradation at and reuptake from the synapse, respectively. Additionally, dopamine D2 receptor (<i>Drd2</i>) mRNA was decreased following DEP/MS in males. Finally, we observed numerous sex differences in immune gene expression regardless of treatment in both the brain and gut. Together, these findings suggest the nucleus accumbens is a key site for neuroimmune and dopaminergic changes following DEP/MS exposure and indicate female-specific changes in intestinal immunity in young adulthood following these prenatal exposures.