Maternal nanomaterial exposure: a double threat to maternal uterine health and fetal development?

Distinct profiles of oxylipid mediators in liver, lung, and placenta after maternal nano-TiO2 nanoparticle inhalation exposure

Nano-titanium dioxide (nano-TiO2) is a widely used nanomaterial found in several industrial and consumer products, including surface coatings, paints, sunscreens and cosmetics, among others. Studies have linked gestational exposure to nano-TiO2 with negative maternal and fetal health outcomes. For example, maternal pulmonary exposure to nano-TiO2 during gestation has been associated not only with maternal, but also fetal microvascular dysfunction in a rat model. One mediator of this altered vascular reactivity and inflammation is oxylipid signaling. Oxylipids are formed from dietary lipids through several enzyme-controlled pathways as well as through oxidation by reactive oxygen species. Oxylipids have been linked to control of vascular tone, inflammation, pain and other physiological and disease processes. In this study, we use a sensitive UPLC-MS/MS based analysis to probe the global oxylipid response in liver, lung, and placenta of pregnant rats exposed to nano-TiO2 aerosols. Each organ presented distinct patterns in oxylipid signaling, as assessed by principal component and hierarchical clustering heatmap analysis. In general, pro-inflammatory mediators, such as 5-hydroxyeicosatetraenoic acid (1.6 fold change) were elevated in the liver, while in the lung, anti-inflammatory and pro-resolving mediators such as 17-hydroxy docosahexaenoic acid (1.4 fold change) were elevated. In the placenta the levels of oxylipid mediators were generally decreased, both inflammatory (e.g. PGE2, 0.52 fold change) and anti-inflammatory (e.g. Leukotriene B4, 0.49 fold change). This study, the first to quantitate the levels of these oxylipids simultaneously after nano-TiO2 exposure, shows the complex interplay of pro- and anti-inflammatory mediators from multiple lipid classes and highlights the limitations of monitoring the levels of oxylipid mediators in isolation.

Nanomaterial Inhalation During Pregnancy Alters Systemic Vascular Function in a Cyclooxygenase-Dependent Manner

Pregnancy requires rapid adaptations in the uterine microcirculation to support fetal development. Nanomaterial inhalation is associated with cardiovascular dysfunction, which may impair gestation. We have shown that maternal nano-titanium dioxide (nano-TiO2) inhalation impairs microvascular endothelial function in response to arachidonic acid and thromboxane (TXA2) mimetics. However, the mechanisms underpinning this process are unknown. Therefore, we hypothesize that maternal nano-TiO2 inhalation during gestation results in uterine microvascular prostacyclin (PGI2) and TXA2 dysfunction. Pregnant Sprague-Dawley rats were exposed from gestational day 10-19 to nano-TiO2 aerosols (12.17  ± 1.67 mg/m3) or filtered air (sham-control). Dams were euthanized on gestational day 20, and serum, uterine radial arterioles, implantation sites, and lungs were collected. Serum was assessed for PGI2 and TXA2 metabolites. TXB2, the stable TXA2 metabolite, was significantly decreased in nano-TiO2 exposed dams (597.3 ± 84.4 vs 667.6 ± 45.6 pg/ml), whereas no difference was observed for 6-keto-PGF1α, the stable PGI2 metabolite. Radial arteriole pressure myography revealed that nano-TiO2 exposure caused increased vasoconstriction to the TXA2 mimetic, U46619, compared with sham-controls (-41.3% ± 4.3% vs -16.8% ± 3.4%). Nano-TiO2 exposure diminished endothelium-dependent vasodilation to carbaprostacyclin, a PGI2 receptor agonist, compared with sham-controls (30.0% ± 9.0% vs 53.7% ± 6.0%). Maternal nano-TiO2 inhalation during gestation decreased nano-TiO2 female pup weight when compared with sham-control males (3.633 ± 0.064 vs 3.995 ± 0.124 g). Augmented TXA2 vasoconstriction and decreased PGI2 vasodilation may lead to decreased placental blood flow and compromise maternofetal exchange of waste and nutrients, which could ultimately impact fetal health outcomes.

Maternal Engineered Nanomaterial Inhalation During Gestation Disrupts Vascular Kisspeptin Reactivity

Maternal engineered nanomaterial (ENM) inhalation is associated with uterine vascular impairments and endocrine disruption that may lead to altered gestational outcomes. We have shown that nano-titanium dioxide (nano-TiO2) inhalation impairs endothelium-dependent uterine arteriolar dilation in pregnant rats. However, the mechanism underlying this dysfunction is unknown. Due to its role as a potent vasoconstrictor and essential reproductive hormone, we examined how kisspeptin is involved in nano-TiO2-induced vascular dysfunction and placental efficiency. Pregnant Sprague Dawley rats were exposed (gestational day [GD] 10) to nano-TiO2 aerosols (cumulative dose = 525 ± 16 μg; n = 8) or sham exposed (n = 6) and sacrificed on GD 20. Plasma was collected to evaluate estrogen (E2), progesterone (P4), prolactin (PRL), corticosterone (CORT), and kisspeptin. Pup and placental weights were measured to calculate placental efficiency (grams fetus/gram placental). Additionally, pressure myography was used to determine uterine artery vascular reactivity. Contractile responses were assessed via cumulative additions of kisspeptin (1 × 10-9 to 1 × 10-4 M). Estrogen was decreased at GD 20 in exposed (11.08 ± 3 pg/ml) versus sham-control rats (66.97 ± 3 pg/ml), whereas there were no differences in P4, PRL, CORT, or kisspeptin. Placental weights were increased in exposed (0.99 ± 0.03 g) versus sham-control rats (0.70 ± 0.04 g), whereas pup weights (4.01 ± 0.47 g vs 4.15 ± 0.15 g) and placental efficiency (4.5 ± 0.2 vs 6.4 ± 0.5) were decreased in exposed rats. Maternal ENM inhalation exposure augmented uterine artery vasoconstrictor responses to kisspeptin (91.2%±2.0 vs 98.6%±0.10). These studies represent initial evidence that pulmonary maternal ENM exposure perturbs the normal gestational endocrine vascular axis via a kisspeptin-dependent mechanism, and decreased placental, which may adversely affect health outcomes.

Identification and quantification of gold engineered nanomaterials and impaired fluid transfer across the rat placenta via ex vivo perfusion

Development and implementation of products incorporating nanoparticles are occurring at a rapid pace. These particles are widely utilized in domestic, occupational, and biomedical applications. Currently, it is unclear if pregnant women will be able to take advantage of the potential biomedical nanoproducts out of concerns associated with placental transfer and fetal interactions. We recently developed an ex vivo rat placental perfusion technique to allow for the evaluation of xenobiotic transfer and placental physiological perturbations. In this study, a segment of the uterine horn and associated placenta was isolated from pregnant (gestational day 20) Sprague-Dawley rats and placed into a modified pressure myography vessel chamber. The proximal and distal ends of the maternal uterine artery and the vessels of the umbilical cord were cannulated, secured, and perfused with physiological salt solution (PSS). The proximal uterine artery and umbilical artery were pressurized at 80 mmHg and 50 mmHg, respectively, to allow countercurrent flow through the placenta. After equilibration, a single 900 μL bolus dose of 20 nm gold engineered nanoparticles (Au-ENM) was introduced into the proximal maternal artery. Distal uterine and umbilical vein effluents were collected every 10 min for 180 min to measure placental fluid dynamics. The quantification of Au-ENM transfer was conducted via inductively coupled plasma mass spectrometry (ICP-MS). Overall, we were able to measure Au-ENM within uterine and umbilical effluent with 20 min of material infusion. This novel methodology may be widely incorporated into studies of pharmacology, toxicology, and placental physiology.

Maternal titanium dioxide nanomaterial inhalation exposure compromises placental hemodynamics

The fetal consequences of gestational engineered nanomaterial (ENM) exposure are unclear. The placenta is a barrier protecting the fetus and allowing transfer of substances from the maternal circulation. The purpose of this study was to determine the effects of maternal pulmonary titanium dioxide nanoparticle (nano-TiO₂) exposure on the placenta and umbilical vascular reactivity. We hypothesized that pulmonary nano-TiO₂ inhalation exposure increases placental vascular resistance and impairs umbilical vascular responsiveness. Pregnant Sprague-Dawley rats were exposed via whole-body inhalation to nano-TiO₂ with an aerodynamic diameter of 188 ± 0.36 nm. On gestational day (GD) 11, rats began inhalation exposures (6 h/exposure). Daily lung deposition was 87.5 ± 2.7 μg. Animals were exposed for 6 days for a cumulative lung burden of 525 ± 16 μg. On GD 20, placentas, umbilical artery and vein were isolated, cannulated, and treated with acetylcholine (ACh), angiotensin II (ANGII), S-nitroso-N-acetyl-DL-penicillamine (SNAP), or calcium-free superfusate (Ca²⁺-free). Mean outflow pressure was measured in placental units. ACh increased outflow pressure to 53 ± 5 mmHg in sham-controls but only to 35 ± 4 mmHg in exposed subjects. ANGII decreased outflow pressure in placentas from exposed animals (17 ± 7 mmHg) compared to sham-controls (31 ± 6 mmHg). Ca²⁺-free superfusate yielded maximal outflow pressures in sham-control (63 ± 5 mmHg) and exposed (30 ± 10 mmHg) rats. Umbilical artery endothelium-dependent dilation was decreased in nano-TiO₂ exposed fetuses (30 ± 9%) compared to sham-controls (58 ± 6%), but ANGII sensitivity was increased (-79 ± 20% vs -36 ± 10%). These results indicate that maternal gestational pulmonary nano-TiO₂ exposure increases placental vascular resistance and impairs umbilical vascular reactivity.

Developmental onset of cardiovascular disease-Could the proof be in the placenta?

The Barker Hypothesis states change to the maternal environment may have significant impacts on fetal development, setting the stage for adult disease to occur. The development of the maternofetal vasculature during implantation and maintenance during pregnancy is extremely precise, yet dynamic. Delays or dysfunction in the orchestration of anatomical remodeling, maintenance of blood pressure, or responsiveness to metabolic demand may have severe consequences to the developing fetus. While these intermissions may not be fatal to the developing fetus, an interruption, reduction, or an inability to meet fetal demand of blood flow during crucial stages of development may predispose young to disease later in life. Maternal inability to meet fetal demand can be attributed to improper placental development and vascular support through morphological change or physiological function will significantly limit nutrient delivery and waste exchange to the developing fetus. Therefore, we present an overview of the uteroplacental vascular network, maternal cardiovascular adaptations that occur during pregnancy, placental blood flow, and common maternal comorbidities and/or exposures that may perturb maternal homeostasis and affect fetal development. Overall, we examine uterine microvasculature pathophysiology contributing to a hostile gestational environment and fetal predisposition to disease as it relates to the Barker Hypothesis.

Disposition of intravenously or orally administered silver nanoparticles in pregnant rats and the effect on the biochemical profile in urine

Few investigations have been conducted on the disposition and fate of silver nanoparticles (AgNP) in pregnancy. The distribution of a single dose of polyvinylpyrrolidone (PVP)-stabilized AgNP was investigated in pregnant rats. Two sizes of AgNP, 20 and 110 nm, and silver acetate (AgAc) were used to investigate the role of AgNP diameter and particle dissolution in tissue distribution, internal dose and persistence. Dams were administered AgNP or AgAc intravenously (i.v.) (1 mg kg^-1 ) or by gavage (p.o.) (10 mg kg^-1 ), or vehicle alone, on gestation day 18 and euthanized at 24 or 48 h post-exposure. The silver concentration in tissues was measured using inductively-coupled plasma mass spectrometry. The distribution of silver in dams was influenced by route of administration and AgNP size. The highest concentration of silver (μg Ag g^-1 tissue) at 48 h was found in the spleen for i.v. administered AgNP, and in the lungs for AgAc. At 48 h after p.o. administration of AgNP, the highest concentration was measured in the cecum and large intestine, and for AgAc in the placenta. Silver was detected in placenta and fetuses for all groups. Markers of cardiovascular injury, oxidative stress marker, cytokines and chemokines were not significantly elevated in exposed dams compared to vehicle-dosed control. NMR metabolomics analysis of urine indicated that AgNP and AgAc exposure impact the carbohydrate, and amino acid metabolism. This study demonstrates that silver crosses the placenta and is transferred to the fetus regardless of the form of silver. Copyright © 2016 John Wiley & Sons, Ltd.

Knowledge gaps between nanotoxicological research and nanomaterial safety

With the wide research and application of nanomaterials in various fields, the safety of nanomaterials attracts much attention. An increasing number of reports in the literature have shown the adverse effects of nanomaterials, representing the quick development of nanotoxicology. However, many studies in nanotoxicology have not reflected the real nanomaterial safety, and the knowledge gaps between nanotoxicological research and nanomaterial safety remain large. Considering the remarkable influence of biological or environmental matrices (e.g., biological corona) on nanotoxicity, the situation of performing nanotoxicological experiments should be relevant to the environment and humans. Given the possibility of long-term and low-concentration exposure of nanomaterials, the reversibility of and adaptation to nanotoxicity, and the transgenerational effects should not be ignored. Different from common pollutants, the specific analysis methodology for nanotoxicology need development and exploration furthermore. High-throughput assay integrating with omics was highlighted in the present review to globally investigate nanotoxicity. In addition, the biological responses beyond individual levels, special mechanisms and control of nanotoxicity deserve more attention. The progress of nanotoxicology has been reviewed by previous articles. This review focuses on the blind spots in nanotoxicological research and provides insight into what we should do in future work to support the healthy development of nanotechnology and the evaluation of real nanomaterial safety.

Impacts of prenatal nanomaterial exposure on male adult Sprague-Dawley rat behavior and cognition

It is generally accepted that gestational xenobiotic exposures result in systemic consequences in the adult F1 generation. However, data on detailed behavioral and cognitive consequences remain limited. Using our whole-body nanoparticle inhalation facility, pregnant Sprague-Dawley rats (gestational day [GD] 7) were exposed 4 d/wk to either filtered air (control) or nano-titanium dioxide aerosols (nano-TiO2; count median aerodynamic diameter of 170.9 ± 6.4 nm, 10.4 ± 0.4 mg/m(3), 5 h/d) for 7.8 ± 0.5 d of the remaining gestational period. All rats received their final exposure on GD 20 prior to delivery. The calculated daily maternal deposition was 13.9 ± 0.5 µg. Subsequently, at 5 mo of age, behavior and cognitive functions of these pups were evaluated employing a standard battery of locomotion, learning, and anxiety tests. These assessments revealed significant working impairments, especially under maximal mnemonic challenge, and possible deficits in initial motivation in male F1 adults. Evidence indicates that maternal engineered nanomaterial exposure during gestation produces psychological deficits that persist into adulthood in male rats.

Gestational nanomaterial exposures: microvascular implications during pregnancy, fetal development and adulthood

Air pollution particulate matter and engineered nanomaterials are encompassed in the broad definition of xenobiotic particles. While the effects of perinatal air pollution exposure have been investigated, elucidation of outcomes associated with nanomaterial exposure, the focus of this review, is still in its infancy. As the potential uses of nanomaterials, and therefore exposures, increase exponentially so does the need for thorough evaluation. Up to this point, the majority of research in the field of cardiovascular nanotoxicology has focused on the coronary and vascular reactions to pulmonary exposures in young adult, healthy, male models; however, as intentional and unintentional contacts persist, the non-pulmonary risks to under-represented populations become a critical concern. Development of the maternal-fetal circulation during successful mammalian gestation is one of the most unusual complex, dynamic, and acutely demanding physiological systems. Fetal development in a hostile gestational environment can lead to systemic alterations, which may encourage adult disease. Therefore, the purpose of this review is to highlight the few knowns associated with gestational engineered nanomaterial exposure segmented by physiological periods of development or systemic targets: preconception and maternal, gestational, fetal and progeny (Abstract figure). Overall, the limited studies currently available provide compelling evidence of maternal, fetal and offspring dysfunctions after engineered nanomaterial exposure. Understanding the mechanisms associated with these multigenerational effects may allow pregnant women to safely reap the benefits of nanotechnology-enabled products and assist in the implementation of exposure controls to protect the mother and fetus allowing for development of safety by design for engineered nanomaterials.

Xenobiotic pulmonary exposure and systemic cardiovascular response via neurological links

The cardiovascular response to xenobiotic particle exposure has been increasingly studied over the last two decades, producing an extraordinary scope and depth of research findings. With the flourishing of nanotechnology, the term "xenobiotic particles" has expanded to encompass not only air pollution particulate matter (PM) but also anthropogenic particles, such as engineered nanomaterials (ENMs). Historically, the majority of research in these fields has focused on pulmonary exposure and the adverse physiological effects associated with a host inflammatory response or direct particle-tissue interactions. Because these hypotheses can neither account entirely for the deleterious cardiovascular effects of xenobiotic particle exposure nor their time course, the case for substantial neurological involvement is apparent. Indeed, considerable evidence suggests that not only is neural involvement a significant contributor but also a reality that needs to be investigated more thoroughly when assessing xenobiotic particle toxicities. Therefore, the scope of this review is several-fold. First, we provide a brief overview of the major anatomical components of the central and peripheral nervous systems, giving consideration to the potential biologic targets affected by inhaled particles. Second, the autonomic arcs and mechanisms that may be involved are reviewed. Third, the cardiovascular outcomes following neurological responses are discussed. Lastly, unique problems, future risks, and hurdles associated with xenobiotic particle exposure are discussed. A better understanding of these neural issues may facilitate research that in conjunction with existing research, will ultimately prevent the untoward cardiovascular outcomes associated with PM exposures and/or identify safe ENMs for the advancement of human health.

Uterine microvascular sensitivity to nanomaterial inhalation: An in vivo assessment

With the tremendous number and diverse applications of engineered nanomaterials incorporated in daily human activity, exposure can no longer be solely confined to occupational exposures of healthy male models. Cardiovascular and endothelial cell dysfunction have been established using in vitro and in situ preparations, but the translation to intact in vivo models is limited. Intravital microscopy has been used extensively to understand microvascular physiology while maintaining in vivo neurogenic, humoral, and myogenic control. However, a tissue specific model to assess the influences of nanomaterial exposure on female reproductive health has not been fully elucidated. Female Sprague Dawley (SD) rats were exposed to nano-TiO2 aerosols (171 ± 6 nm, 10.1 ± 0.39 mg/m(3), 5h) 24-hours prior to experimentation, leading to a calculated deposition of 42.0 ± 1.65 μg. After verifying estrus status, vital signs were monitored and the right horn of the uterus was exteriorized, gently secured over an optical pedestal, and enclosed in a warmed tissue bath using intravital microscopy techniques. After equilibration, significantly higher leukocyte-endothelium interactions were recorded in the exposed group. Arteriolar responsiveness was assessed using ionophoretically applied agents: muscarinic agonist acetylcholine (0.025 M; ACh; 20, 40, 100, and 200 nA), and nitric oxide donor sodium nitroprusside (0.05 M; SNP; 20, 40, and 100 nA), or adrenergic agonist phenylephrine (0.05 M; PE; 20, 40, and 100 nA) using glass micropipettes. Passive diameter was established by tissue superfusion with 10(-4)M adenosine. Similar to male counterparts, female SD rats present systemic microvascular dysfunction; however the ramifications associated with female health and reproduction have yet to be elucidated.