Perinatal exposure to concentrated ambient particulates results in autism-like behavioral deficits in adult mice

Abstract

Exposure to fine ambient particulates (PM_2.5) during gestation or neonatally has potent neurotoxic effects. While biological and behavioral data indicate a vulnerability to environmental pollutants across distinct neurodevelopmental windows, the behavioral consequences following exposure across the entire developmental period remain unknown. Moreover, several epidemiological studies support a link between developmental exposure to air pollution and an increased risk of later receiving a diagnosis of autism spectrum disorders (ASD), a neurodevelopmental disorder that persists throughout life. In the current study we sought to determine whether perinatal exposure to PM_2.5 would reduce sociability and increase repetitive deficits in mice, two hallmark characteristics of ASD. Pregnant female B₆C₃F₁ mice were exposed daily to concentrated ambient PM_2.5 (CAPs) (135.8μg/m³) or filtered air (3.1μg/m³) throughout gestation followed by additional exposures to both dams and their litters from days 2-10 postpartum. Adult offspring were subsequently assessed for social and repetitive behaviors at 20 weeks of age. Daily perinatal exposure to CAPs significantly decreased sociability in male and female mice as measured by the social approach task; however, reductions in reciprocal social interaction and increased grooming behavior were only present in male offspring exposed to CAPs. These findings demonstrate that exposure to particulate air pollutants throughout early neurodevelopment induces long lasting behavioral deficits in a sex-dependent manner and may be an underlying cause of neurodevelopmental disorders such as ASD.

Keywords: ASD; Animal model; Autism; Particulate matter; Translational.

Figure 1

Maternal Weight and Pup Growth Curves. (A) Pregnant dams of both FA and CAPs groups showed similar weight gains throughout gestation. (B) There were no differences in average pup growth (i.e. weight) during the first nine days of postnatal development. Linear mixed-effects modeling with treatment and time as fixed effects. Data shown as mean ± SEM. Sample size: FA n = 26 pups (13M/13F; 13 dams), CAPs n = 31 pups (15M/16F; 12 dams).

Figure 2

Offspring born to CAPs-exposed dams show reductions in social approach, but not in social recognition. (A) While both FA- and CAPs-exposed mice spent significantly more time in the novel mouse chamber compared to the novel object chamber, CAPs mice showed significantly reduced preference for the novel mouse compared to FA-treated controls. (B) Calculation of sociability score (time with mouse – time with object) further revealed CAPs mice had significantly decreased social motivation compared to sex- and age-matched FA controls. (C) FA- and CAPs exposed mice spent significantly more time sniffing the novel mouse compared to novel object, however CAPs mice displayed significantly decreased time sniffing the novel mouse compared to FA controls. (D) In the social recognition phase, mice in both exposure groups spent significantly more time in the chamber with the novel mouse compared to the chamber with the familiar mouse. Data were compared using a linear mixed-effects model with chamber, maternal treatment, and offspring sex as fixed effects and dam as the random effect (* p < 0.05 treatment; # p < 0.05 chamber). Data shown are means ± SEM. Sample size: FA n = 26 (13M/13F; 13 litters), CAPs n = 31 (15M/16F; 12 litters).

Figure 3

CAPs exposure results in sex-dependent reductions in reciprocal social interactions. (A) Perinatal CAPs reduced social interaction time in male but not female offspring compared to FA controls. Female FA-exposed mice displayed reduced social interaction time compared to FA-treated males. (B) Male CAPs and female FA offspring displayed a significant reduction in anogenital sniffing behavior compared to FA male mice. (C) CAPs-exposure significantly decreased body sniffing in males compared to FA controls. (D) There were no differences in the total time spent in nose-to-nose sniffs between treatment conditions. Data were compared using a linear mixed-effects model with treatment and sex as fixed effects and dam as the random effect (* p < 0.05 treatment; + p < 0.05 sex). Data are means ± SEM. Sample size: FA n = 26 (13M/13F; 13 litters), CAPs n = 31 (15M/16F; 12 litters).

Figure 4

Perinatal CAPs exposure increased grooming behavior in male offspring compared to FA-exposed controls. No differences in grooming were observed in females between treatment groups. Linear mixed-effects modeling with treatment and sex as fixed effects and litter as random effects (* p < 0.05). Data shown as mean ± SEM. Sample size: FA n = 26 (13M/13F; 13 litters), CAPs n = 31 (15M/16F; 12 litters).

Figure 5

Mice exposed to CAPs showed no differences in non-ASD associated anxiety and locomotor behaviors. Perinatal CAPs exposure did not affect (A) open arm exploration in the elevated plus maze or (B) distance traveled in the open field task when compared to FA-exposed controls. Linear mixed-effects modeling with treatment and sex as fixed effects and litter as random effects. Data shown as mean ± SEM. Sample size: FA n = 26 (13M/13F; 13 litters), CAPs n = 31 (15M/16F; 12 litters).