Sex-associated protective effect of early bisphenol-A exposure during enteric infection with Trichinella spiralis in mice

Abstract

Bisphenol A (BPA) is an endocrine disruptor compound with estrogenic activity, possessing affinity for both nuclear (ERα and ERβ) and membrane estrogen receptors. The main source of BPA exposure comes from the contamination of food and water by plastic storage containers or disposable bottles, among others, in which case BPA is easily ingested. Exposure to BPA during early pregnancy leads to lifelong effects; however, its effect on the immune system has not been fully studied. Since endocrine and immune systems interact in a bidirectional manner, the disruption of the former may cause permanent alterations of the latter, thus affecting a future anti-parasitic response. In this study, neonate BALB/c mice were exposed to a single dose of BPA (250 μg/kg); once sexual maturity was reached, they were orally infected with Trichinella spiralis (T. spiralis). The analyses performed after 5 days of infection revealed a decreased parasitic load in the duodenum of mice in the BPA-treated group. Flow cytometry analyses also revealed changes in the immune cell subpopulations of the infected animals when compared to the BPA-treated group. RT-PCR analyses of duodenum samples showed an increased expression of TNF-α, IFN-γ, IL-4, IL-5, and IL-9 in the BPA-treated group. These findings show a new aspect whereby early-life exposure to BPA contributes to the protection against T. spiralis by modulating the anti-parasitic immune response.

Fig 1. Parasitic burden in the small intestine.

Treatment with BPA significantly decreased the number of parasites in male and female mice. The animals were infected with T. spiralis larvae and sacrificed after 5 days. Bars represent female and male mice from the three infected groups: control infected (C-I), vehicle infected (VH-I) and BPA infected (BPA-I). Data are shown as mean ± standard deviation. *** P<0.05.

Fig 2. Histological evaluation of the duodenal inflammatory infiltrate associated with T. spiralis infection.

Photomicrograph of longitudinal sections of the proximal duodenum of male and female control infected (C-I) mice (a, c, respectively), and male and female BPA infected (BPA-I) mice (b, d, respectively). The black arrow indicates T. spiralis larvae, red arrow indicates eosinophils attached to the parasite, and blue arrows indicate encysted larvae.

Fig 3. Histological analysis of the duodenal inflammatory infiltrate associated with T. spiralis infection.

Photomicrograph of longitudinal sections of proximal duodenum of male and female control infected (C-I) mice (a, c, respectively), and male and female BPA infected (BPA-I) mice (b, d, respectively). Goblet cells (arrow) are stained red to purple.

Fig 4. Analysis of the inflammatory infiltrate in the mesenteric lymph nodes.

Analysis of immune subpopulations frequencies by flow cytometry, (a) and (b) are representative dot-plots of cytometric analysis algorithm of T cells (CD3⁺), and CD4⁺ or CD8⁺cells, respectively. The graphs represent the frequencies of (c) T cells, (d) CD4⁺T cells, (e) CD8⁺ T cells. Literals-ANOVA 1way/Tukey between groups P<0.05 Asterisks- ANOVA 2 way/Bonferroni * P<0.05, ** P<0.01, *** P<0.001.

Fig 5

Analysis of B cell subpopulations frequencies by flow cytometry, (a) Representative dot-plot of cytometric analysis algorithm of B cells (CD3^-CD19⁺). The graph represents the frequencies of B cells (b). The levels of anti T. spiralis antibodies are depicted in (c). Literals-ANOVA 1 way/Tukey between groups P<0.05 Asterisks- ANOVA 2 way/Bonferroni * P<0.05, ** P<0.01, *** P<0.001.