Microvascular and mitochondrial dysfunction in the female F1 generation after gestational TiO2 nanoparticle exposure

Abstract

Due to the ongoing evolution of nanotechnology, there is a growing need to assess the toxicological outcomes in under-studied populations in order to properly consider the potential of engineered nanomaterials (ENM) and fully enhance their safety. Recently, we and others have explored the vascular consequences associated with gestational nanomaterial exposure, reporting microvascular dysfunction within the uterine circulation of pregnant dams and the tail artery of fetal pups. It has been proposed (via work derived by the Barker Hypothesis) that mitochondrial dysfunction and subsequent oxidative stress mechanisms as a possible link between a hostile gestational environment and adult disease. Therefore, in this study, we exposed pregnant Sprague-Dawley rats to nanosized titanium dioxide aerosols after implantation (gestational day 6). Pups were delivered, and the progeny grew into adulthood. Microvascular reactivity, mitochondrial respiration and hydrogen peroxide production of the coronary and uterine circulations of the female offspring were evaluated. While there were no significant differences within the maternal or litter characteristics, endothelium-dependent dilation and active mechanotransduction in both coronary and uterine arterioles were significantly impaired. In addition, there was a significant reduction in maximal mitochondrial respiration (state 3) in the left ventricle and uterus. These studies demonstrate microvascular dysfunction and coincide with mitochondrial inefficiencies in both the cardiac and uterine tissues, which may represent initial evidence that prenatal ENM exposure produces microvascular impairments that persist throughout multiple developmental stages.

Keywords: Barker Hypothesis; engineered nanomaterials; nanotoxicology; pregnancy; prenatal.

Figure 1

Chemical agonists of arteriolar dilation. Endothelium-dependent dilation via an acetylcholine dose response curve for (A) coronary (N = 7 (sham) and 12 (gestationally exposed) rats; n = 11(sham) and 16 (gestationally exposed) vessels) and (B) uterine (N = 7 (sham) and 12 (gestationally exposed) rats; n = 12 (sham) and 19 (gestationally exposed) vessels) arterioles. Endothelium-independent dilation via a spermine-NONOate dose response curve for (C) coronary (N = 7 (sham) and 13 (exposed in utero) rats; n = 11 (sham) and 15 (exposed in utero) vessels) and (D) uterine (N = 6 (sham) and 11 (exposed in utero) rats; n = 11 (sham) and 19 (exposed in utero) vessels) arterioles. Values are means ± SE. *p ≤ 0.05 sham regression line vs. exposed regression line.

Figure 2

Mechanical initiators arteriolar responsiveness. Myogenic index calculations for (A) coronary (N = 8 (sham) and 13 (prenatally exposed) rats; n = 11 (sham) and 15 (prenatally exposed) vessels) and (B) uterine (N = 7 (sham) and 10 (prenatally exposed) rats; n = 8 (sham) and 11 (prenatally exposed) vessels) arterioles. Values are means ± SE. *p ≤ 0.05 two-way ANOVA; arteriolar dilation as a function of shear stress of the (C) coronary (N = 7 (sham) and 8 (exposed in utero) rats; n = 11 (sham) and 15 (exposed in utero) vessels) and (D) uterine (N = 7 (sham) and 11 (exposed in utero) rats; n = 11 (sham) and 11 (exposed in utero) vessels) arterioles. *p ≤ 0.05 sham regression line vs. gestational exposure regression line for both the coronary and uterine arterioles.

Figure 3

Mitochondrial dysfunction and reactive oxygen species production. (A) Cardiac subsarcolemmal (SSM) and intramyofibril (IFM) mitochondrial populations and (B) uterine mitochondrial dysfunction of state 3 and/or state 4 respiration. (C) Hydrogen peroxide production within the SSM, IFM and uterine tissues of female progeny after gestational ENM exposure (N = 11–16 rats from 8 to 10 differing litters per group). *Data were analyzed using Student’s t-test with p≤0.05.