Effects of Toxicants on Blood‐Brain Barrier Function in Resilient Versus Non‐resilient Mice

Abstract

Environmental toxicants such as perfluorooctane sulfonate (PFOS), benzo‐a‐pyrene (BaP) and 2, 3, 7, 8‐tetrachlorodibenzo‐p‐dioxin (TCDD) can damage brain microvascular endothelial cells (BMECs), the primary component of the blood‐brain barrier (BBB). It is largely unknown whether differences in BBB phenotype contribute to people’s susceptibility to the neurological effects of environmental toxicants. We used a mouse model of psychological resilience to investigate effects of environmental toxicants on BBB function. In this model, C57BL/6 and Balb/c mice display “resilient” and “non‐resilient” phenotypes, respectively. We hypothesized that BaP, TCDD, and PFOS will affect BMECs of C57BL/6 mice differently than the BMECs of the Balb/c mice.BBB permeability was assessed by measuring transendothelial electrical resistance (TEER; ohms cm2) of primary adult mouse BMECs derived from C57BL/6 (cBMECs) or Balb/c (bBMECs) mice. Cells were treated with BaP (2, 10, 50 uM), TCDD (1.5, 15, 150 nM), PFOS (3, 30, 300 uM). After 24 hours, gene expression of occludin (Ocln), tight junction protein‐1 (Tjp‐1), claudin‐5 (Cldn‐5), and vascular cell adhesion molecule 1 (Vcam‐1) was measured by RT‐qPCR. Tetrazolium salt assay was used to measure cell viability. One‐ and two‐way ANOVA followed by Holm‐Sidak post‐hoc tests were performed to detect differences in TEER and cell viability (absorbance, nm). T‐tests were performed to compare RT‐qPCR data. Statistical significance was reached at p<0.05. Experiments were performed with technical triplicates on 3 different days to obtain N=3/group.cBMECs displayed higher maximal TEER than bBMECs (1194±149 versus 628±64 ohms cm2; p<0.01), and were significantly more sensitive to the TEER‐reducing effects of BaP (10 and 50 uM) after 1 hour of exposure (Holm‐Sidak, t’s>5.24, p’s<0.0002). This difference was maintained for 24 hours after treatment. After 1 hour of PFOS treatment (3 and 300 uM), TEER of bBMECs was significantly lower than that of the cBMECs (Holm‐Sidak, t’s>3.173, p’s<0.017). However, there was no difference in TEER between cell types at any other PFOS concentrations or time points. TCDD treatment induced a significant increase in TEER in both cBMECs and bBMECs over the course of 24 hours (ANOVA, p’s<0.02), with no significant difference in TEER response to treatment between cell types. Although cell viability was higher in bBMECs, treatment with BaP, PFOS or TCDD did not differentially affect viability of the two cell types after 24 hours. Gene expression of Ocln, Cldn‐5, and Vcam‐1 were reduced only by the highest concentration of PFOS in both cell types (p’s<0.04), while Tjp‐1 expression was not affected by any of the treatments across both cell types.Our study demonstrates that the BBB’s response to toxicants is dependent on the phenotype (resilient versus non‐resilient) of the individual, and that the difference in direction and magnitude of the response is toxicant‐specific. This suggests that the variability in BBB phenotype associated with psychological resilience may determine an individual’s susceptibility to the effects of environmental toxicants.