Offspring behavioral outcomes following maternal allergic asthma in the IL-4-deficient mouse

Abstract

Maternal allergic asthma (MAA) during pregnancy has been associated with increased risk of neurodevelopmental disorders in humans, and rodent studies have demonstrated that inducing a T helper-2-mediated allergic response during pregnancy leads to an offspring behavioral phenotype characterized by decreased social interaction and increased stereotypies. The interleukin (IL)-4 cytokine is hypothesized to mediate the neurobehavioral impact of MAA on offspring. Utilizing IL-4 knockout mice, this study assessed whether MAA without IL-4 signaling would still impart behavioral deficits. C57 and IL-4 knockout female mice were sensitized to ovalbumin, exposed to repeated MAA inductions, and their offspring performed social, cognitive, and motor tasks. Only C57 offspring of MAA dams displayed social and cognitive deficits, while IL-4 knockout mice showed altered motor activity compared with C57 mice. These findings highlight a key role for IL-4 signaling in MAA-induced behavioral deficits and more broadly in normal brain development.

Keywords: Allergic asthma; Behavior; Interleukin-4; Mouse; Offspring; Pregnancy.

Figure 1.

(A) Schematic of the experimental timeline for the maternal allergic asthma exposure paradigm. Four hours after the final aerosol indication, serum was collected from C57 and IL-4KO dams and assessed for (B) IgE and IgG2 antibodies using ELISA, and (C) cytokine concentrations using multiplex bead-based immunoassay. *p <0.05 Bars represent marginal means ±SE. ND: none detected. C57 PBS (n = 9-13), C57 OVA (n=7-14), IL-4 KO PBS (n=6-8), IL-4 KO OVA (n=5-7).

Figure 2.

Juvenile, 3-week-old, offspring were assessed for social behaviors in the reciprocal social interaction task. (A) Offspring were allowed to habituate for 20 minutes in an empty arena followed immediately by the introduction of a novel weight-, genotype-, and sex-matched C57 stimulus mouse. (B) Social sniffing, (C) close body contact, and (D) distance traveled were measured automatically using EthoVision XT 15 software over 20 minutes. *p < 0.05 as determined by linear mixed-effects modeling with treatment and genotype as fixed effects and litters as random effects. Plots represent individual mice; bars represent marginal means ± SE.

Figure 3.

At 8 weeks of age, offspring were assessed for approach/avoidance behaviors and locomotor activity in the elevated plus maze and open field task, respectively. (A) Mice were allowed to explore the elevated plus maze for 5 minutes and measured for time spent in the open and closed arms of the maze using EthoVision XT 15 software. (B) Percent time in the open arms was calculated as the time spent in the open arms divided by the total time spent in open and closed arms. (C) Latency to first enter the open arm was assessed as the first instance the mouse crossed into the open arms of the arena. (D) Locomotor activity during the elevated plus maze was assessed as total distance traveled. (E) In the open field task mice were allowed 20 minutes to explore a novel arena and measured for (F) the total time in the center of the arena, (G) the latency to first enter the center, and (H) total distance traveled. ^#p < 0.10 *p < 0.05 as determined by linear mixed-effects modeling with treatment and genotype as fixed effects and litters as random effects. Plots represent individual mice; bars represent marginal means ± SE.

Figure 4.

(A) Adult offspring underwent a 6-minute forced swim task and were assessed for (B) total time spent immobile. (C) Memory performance was measured using the novel object recognition (NOR) task. Following habituation, mice were given 10 minutes to freely explore 2 identical objects. Twenty-four hours later, mice were reintroduced to the arena with one object replaced by a novel object and allowed 10 minutes of exploration. (D) NOR score was calculated as the time spent sniffing the familiar object divided by the total time sniffing the familiar and novel objects. (E) Object memory was evaluated as spending significantly more time with the novel object compared with familiar object. *p < 0.05 as determined by linear mixed-effects modeling with treatment and genotype as fixed effects and litters as random effects. For object sniff measures, linear mixed-effects modeling included object, treatment, and genotype as fixed effects and litters and animal as random effects. Plots represent individual mice; bars represent marginal means ± SE.

Figure 5.

(A) Grooming behaviors were assessed during a 10-minute recorded observation. (B) Total time spent grooming was assessed by two researchers blinded to treatment condition and analyzed using linear mixed-effects modeling with treatment and genotype as fixed effects and litters and animal as random effects. (C) In the marble burying task, mice were allowed 10 minutes to habituate to a clean cage filled with corn cob bedding. After habituation, 15 marbles were lined up in 5 rows of 3 marbles and mice were given 10 minutes of free exploration. (D) The total number of marbles buried were counted by two observers blinded to treatment condition and analyzed using a negative binomial model to account for overdispersion. *p <0.05. Plots represent individual mice; bars represent marginal means ± SE, violin plots represent frequency densities.