An investigation into the potential toxicological effects of fracking sand dust (FSD), collected from unconventional gas drilling sites, has been undertaken, along with characterization of their chemical and biophysical properties. Using intratracheal instillation of nine FSDs in rats and a whole body 4-d inhalation model for one of the FSDs, i.e., FSD 8, and related in vivo and in vitro experiments, the effects of nine FSDs on the respiratory, cardiovascular and immune systems, brain and blood were reported in the preceding eight tandem papers. Here, a summary is given of the key observations made in the organ systems reported in the individual studies. The major finding that inhaled FSD 8 elicits responses in extra-pulmonary organ systems is unexpected, as is the observation that the pulmonary effects of inhaled FSD 8 are attenuated relative to forms of crystalline silica more frequently used in animal studies, i.e., MIN-U-SIL®. An attempt is made to understand the basis for the extra-pulmonary toxicity and comparatively attenuated pulmonary toxicity of FSD 8.

Hydraulic fracturing creates fissures in subterranean rock to increase the flow and retrieval of natural gas. Sand ("proppant") in fracking fluid injected into the well bore maintains fissure patency. Fracking sand dust (FSD) is generated during manipulation of sand to prepare the fracking fluid. Containing respirable crystalline silica, FSD could pose hazards similar to those found in work sites where silica inhalation induces lung disease such as silicosis. This study was performed to evaluate the possible toxic effects following inhalation of a FSD (FSD 8) in the lung and airways. Rats were exposed (6 h/d × 4 d) to 10 or 30 mg/m(3) of a FSD, i.e., FSD 8, collected at a gas well, and measurements were performed 1, 7, 27 and, in one series of experiments, 90 d post-exposure. The following ventilatory and non-ventilatory parameters were measured in vivo and/or in vitro: 1) lung mechanics (respiratory system resistance and elastance, tissue damping, tissue elastance, Newtonian resistance and hysteresivity); 2) airway reactivity to inhaled methacholine (MCh); airway epithelium integrity (isolated, pefused trachea); airway efferent motor nerve activity (electric field stimulation in vitro); airway smooth muscle contractility; ion transport in intact and cultured epithelium; airway effector and sensory nerves; tracheal particle deposition; and neurogenic inflammation/vascular permeability. FSD 8 was without large effect on most parameters, and was not pro-inflammatory, as judged histologically and in cultured epithelial cells, but increased reactivity to inhaled MCh at some post-exposure time points and affected Na(+) transport in airway epithelial cells.

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 mug; 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 x 10-9 to 1 x 10-4 M). Estrogen was decreased at GD 20 in exposed (11.08+/-3 pg/mL) vs. 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) vs. 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.

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+/-0.36nm. On gestational day (GD) 11, rats began inhalation exposures (6h/exposure). Daily lung deposition was 87.5+/-2.7mug. Animals were exposed for 6days for a cumulative lung burden of 525+/-16mug. 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 (Ca(2+)-free). Mean outflow pressure was measured in placental units. ACh increased outflow pressure to 53+/-5mmHg in sham-controls but only to 35+/-4mmHg in exposed subjects. ANGII decreased outflow pressure in placentas from exposed animals (17+/-7mmHg) compared to sham-controls (31+/-6mmHg). Ca(2+)-free superfusate yielded maximal outflow pressures in sham-control (63+/-5mmHg) and exposed (30+/-10mmHg) 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.

BACKGROUND: The cardiovascular effects of pulmonary exposure to engineered nanomaterials (ENM) are poorly understood, and the reproductive consequences are even less understood. Inflammation remains the most frequently explored mechanism of ENM toxicity. However, the key mediators and steps between lung exposure and uterine health remain to be fully defined. The purpose of this study was to determine the uterine inflammatory and vascular effects of pulmonary exposure to titanium dioxide nanoparticles (nano-TiO2). We hypothesized that pulmonary nano-TiO2 exposure initiates a Th2 inflammatory response mediated by Group II innate lymphoid cells (ILC2), which may be associated with an impairment in uterine microvascular reactivity. METHODS: Female, virgin, Sprague-Dawley rats (8-12 weeks) were exposed to 100 mug of nano-TiO2 via intratracheal instillation 24 h prior to microvascular assessments. Serial blood samples were obtained at 0, 1, 2 and 4 h post-exposure for multiplex cytokine analysis. ILC2 numbers in the lungs were determined. ILC2s were isolated and phosphorylated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) levels were measured. Pressure myography was used to assess vascular reactivity of isolated radial arterioles. RESULTS: Pulmonary nano-TiO2 exposure was associated with an increase in IL-1ss, 4, 5 and 13 and TNF- alpha 4 h post-exposure, indicative of an innate Th2 inflammatory response. ILC2 numbers were significantly increased in lungs from exposed animals (1.66 +/- 0.19%) compared to controls (0.19 +/- 0.22%). Phosphorylation of the transactivation domain (Ser-468) of NF-kappaB in isolated ILC2 and IL-33 in lung epithelial cells were significantly increased (126.8 +/- 4.3% and 137 +/- 11% of controls respectively) by nano-TiO2 exposure. Lastly, radial endothelium-dependent arteriolar reactivity was significantly impaired (27 +/- 12%), while endothelium-independent dilation (7 +/- 14%) and alpha-adrenergic sensitivity (8 +/- 2%) were not altered compared to control levels. Treatment with an anti- IL-33 antibody (1 mg/kg) 30 min prior to nano-TiO2 exposure resulted in a significant improvement in endothelium-dependent dilation and a decreased level of IL-33 in both plasma and bronchoalveolar lavage fluid. CONCLUSIONS: These results provide evidence that the uterine microvascular dysfunction that follows pulmonary ENM exposure may be initiated via activation of lung-resident ILC2 and subsequent systemic Th2-dependent inflammation.