Uterine microvascular sensitivity to nanomaterial inhalation: An in vivo assessment

Single inhalation exposure to polyamide micro and nanoplastic particles impairs vascular dilation without generating pulmonary inflammation in virgin female Sprague Dawley rats

BACKGROUND

Exposure to micro- and nanoplastic particles (MNPs) in humans is being identified in both the indoor and outdoor environment. Detection of these materials in the air has made inhalation exposure to MNPs a major cause for concern. One type of plastic polymer found in indoor and outdoor settings is polyamide, often referred to as nylon. Inhalation of combustion-derived, metallic, and carbonaceous aerosols generate pulmonary inflammation, cardiovascular dysfunction, and systemic inflammation. Additionally, due to the additives present in plastics, MNPs may act as endocrine disruptors. Currently there is limited knowledge on potential health effects caused by polyamide or general MNP inhalation.

OBJECTIVE

The purpose of this study is to assess the toxicological consequences of a single inhalation exposure of female rats to polyamide MNP during estrus by means of aerosolization of MNP.

METHODS

Bulk polyamide powder (i.e., nylon) served as a representative MNP. Polyamide aerosolization was characterized using particle sizers, cascade impactors, and aerosol samplers. Multiple-Path Particle Dosimetry (MPPD) modeling was used to evaluate pulmonary deposition of MNPs. Pulmonary inflammation was assessed by bronchoalveolar lavage (BAL) cell content and H&E-stained tissue sections. Mean arterial pressure (MAP), wire myography of the aorta and uterine artery, and pressure myography of the radial artery was used to assess cardiovascular function. Systemic inflammation and endocrine disruption were quantified by measurement of proinflammatory cytokines and reproductive hormones.

RESULTS

Our aerosolization exposure platform was found to generate particles within the micro- and nano-size ranges (thereby constituting MNPs). Inhaled particles were predicted to deposit in all regions of the lung; no overt pulmonary inflammation was observed. Conversely, increased blood pressure and impaired dilation in the uterine vasculature was noted while aortic vascular reactivity was unaffected. Inhalation of MNPs resulted in systemic inflammation as measured by increased plasma levels of IL-6. Decreased levels of 17β-estradiol were also observed suggesting that MNPs have endocrine disrupting activity.

CONCLUSIONS

These data demonstrate aerosolization of MNPs in our inhalation exposure platform. Inhaled MNP aerosols were found to alter inflammatory, cardiovascular, and endocrine activity. These novel findings will contribute to a better understanding of inhaled plastic particle toxicity.

Maternal, placental, and fetal distribution of titanium after repeated titanium dioxide nanoparticle inhalation through pregnancy

Epidemiological studies have associated ambient engineered nanomaterials or ultrafine particulate matter (PM_0.1), collectively referred to as nanoparticles (NPs), with adverse pregnancy outcomes including miscarriage, preterm labor, and fetal growth restriction. Evidence from non-pregnant models demonstrate that NPs can cross the lung air-blood barrier and circulate systemically. Therefore, inhalation of NPs during pregnancy leading to fetoplacental exposure has garnered attention. The purpose of this study was to evaluate the distribution of inhaled titanium dioxide nanoparticles (nano-TiO₂) from the maternal lung to maternal and fetal systemic tissues. Pregnant Sprague Dawley rats were administered whole-body exposure to filtered air or of nano-TiO₂ aerosols (9.96 ± 0.06 mg/m³) between gestational day (GD) 4 and 19. On GD 20 maternal, placental, and fetal tissues were harvested then digested for ICP-MS analysis to measure concentrations of titanium (Ti). TEM was used to visualize particle internalization by the placental syncytium. The results demonstrate the extrapulmonary distribution of Ti to various maternal organs during pregnancy. Our study found Ti accumulation in the decidua/junctional and labyrinth zones of placentas embedded in all sections of uterine horns. Further, NPs deposited in the placenta, identified by TEM, were found intracellularly within nuclear, endoplasmic reticulum, and vesicle organelles. This study identified the systemic distribution and placental accumulation of Ti after nano-TiO₂ aerosol inhalation in a pregnancy model. These findings arouse concerns for poor air quality for pregnant women and possible contributions to adverse pregnancy outcomes.

Prenatal exposure to paraquat and nanoscaled TiO2 aerosols alters the gene expression of the developing brain

Nanopesticides are innovative pesticides involving engineered nanomaterials in their formulation to increase the efficiency of plant protection products, while mitigating their environmental impact. Despite the predicted growth of the nanopesticide use, no data is available on their inhalation toxicity and the potential cocktail effects between their components. In particular, the neurodevelopmental toxicity caused by prenatal exposures might have long lasting consequences. In the present study, we repeatedly exposed gestating mice in a whole-body exposure chamber to three aerosols, involving the paraquat herbicide, nanoscaled titanium dioxide particles (nTiO₂), or a mixture of both. Particle number concentrations and total mass concentrations were followed to enable a metrological follow-up of the exposure sessions. Based on the aerosols characteristics, the alveolar deposited dose in mice was then estimated. RNA-seq was used to highlight dysregulations in the striatum of pups in response to the in utero exposure. Modifications in gene expression were identified at post-natal day 14, which might reflect neurodevelopmental alterations in this key brain area. The data suggest an alteration in the mitochondrial function following paraquat exposure, which is reminiscent of the pathological process leading to Parkinson disease. Markers of different cell lineages were dysregulated, showing effects, which were not limited to dopaminergic neurons. Exposure to the nTiO₂ aerosol modulated the regulation of cytokines and neurotransmitters pathways, perhaps reflecting a minor neuroinflammation. No synergy was found between paraquat and nTiO₂. Instead, the neurodevelopmental effects were surprisingly lower than the one measured for each substance separately.

Adverse cardiovascular responses of engineered nanomaterials: Current understanding of molecular mechanisms and future challenges

Nanotechnology is spanning multiple fields of study from materials science to computer engineering and drug discovery. Since the early 21st century, nanotechnology and nano-enabled research have received great attention and governmental funding accompanied with interest to ensure human and environmental safety of engineered nanomaterials (ENMs). Optimal functioning of the cardiovascular (CV) system is of utmost importance for the overall health of the body. Following exposure, ENMs essentially end up in the circulation (at least partially) and hence it is key to assess any associated adverse CV consequences. Accumulating research suggests that exposure to ENMs (different compositions and physicochemical properties) has the capacity to directly and indirectly interact with CV components resulting in adverse events and worsening of CV complications. However, the underlying molecular mechanisms driving these events remain to be elucidated. In this article, we review state-of-art literature on ENM-associated adverse CV responses and discuss the potential underlying molecular mechanisms.

Uterine Vascular Control Preconception and During Pregnancy

Successful pregnancy and reproduction are dependent on adequate uterine blood flow, placental perfusion, and vascular responsivity to fetal demands. The ability to support pregnancy centers on systemic adaptation and endometrial preparation through decidualization, embryonic implantation, trophoblast invasion, arterial/arteriolar reactivity, and vascular remodeling. These adaptations occur through responsiveness to endocrine signaling and local uteroplacental mediators. The purpose of this article is to highlight the current knowledge associated with vascular remodeling and responsivity during uterine preparation for and during pregnancy. We focus on maternal cardiovascular systemic and uterine modifications, endometrial decidualization, implantation and invasion, uterine and spiral artery remodeling, local uterine regulatory mechanisms, placentation, and pathological consequences of vascular dysfunction during pregnancy. © 2021 American Physiological Society. Compr Physiol 11:1-23, 2021.

Developmental Toxicity of the Neural Tube Induced by Titanium Dioxide Nanoparticles in Mouse Embryos

Background:

This study investigated the potential effects of Titanium dioxide nanoparticles (Tio2NPs) followed by maternal gavage on fetal development and neural tube formation during pregnancy in mice.

Methods:

Thirty pregnant mice were randomly divided into five main study groups including the untreated control and 4 experimental groups (n=6 per group). The control group was treated with normal saline and the experimental groups were orally treated with doses of 30, 150, 300, and 500 mg/kg Body Weight (BW) of Tio2NPs during pregnancy. On gestational day 16 and 19 (n=3 per group), pregnant mice were euthanized and then examined for neural tube defects and compared with control. Serial transverse sections were prepared in both cranial region and in lumbar region of spinal cord.

Results:

Treatment with Tio2NPs resulted in low fetal weight and short length, dilation of lateral ventricle, thinning of cerebral cortex and spinal cord, spina bifida occulta and an increase in the number of apoptotic neurons in exposed embryos at doses of 300 and 500 mg/kg (p<0.05).

Conclusion:

It seems that exposure to nanoparticles of Tio2 during pregnancy induces growth retardation and for the first time, teratogenicity of this nanomaterial in neural tube development and induction of defects such as spinal bifida, reduction in cortical thickness and dilatation of lateral ventricles were verified which can be related to incidence of apoptosis in central nervous system.

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.

Group II innate lymphoid cells and microvascular dysfunction from pulmonary titanium dioxide nanoparticle exposure

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 μg 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-ĸB) 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- α 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-κB 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 α-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.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0280-2) contains supplementary material, which is available to authorized users.

Estrous cycle-dependent modulation of in vivo microvascular dysfunction after nanomaterial inhalation

Preconceptive health encompasses male and female reproductive capability. In females, this takes into account each of the stages of the estrous cycle. Microvascular reactivity varies throughout the estrous cycle in response to hormonal changes and in preparation for pregnancy. Microvascular alterations in response to engineered nanomaterial (ENM) exposure have been described within 24-h of inhalation; however, the impact upon the uterine vasculature at differing estrous stages and at late-stage pregnancy is unclear. Female Sprague Dawley (SD) rats (virgin and late stage pregnancy [GD 19]) were exposed to nano-TiO aerosols (173.2 ± 6.4 nm, 10.2 ± 0.46 mg/m³, 5 h) 24-h prior to experimentation leading to a single calculated deposition of 42.2 ± 1.9 µg nano- TiO₂ (exposed) or 0µg (control). Animals were anesthetized, estrous status verified, and prepared for in situ assessment of leukocyte trafficking and vascular function by means of intravital microscopy, Uterine basal arteriolar reactivity was stimulated using iontophoretically applied chemicals: acetylcholine (ACh, 0.025 M; 20, 40, 100, 200 nA), sodium nitroprusside (SNP, 0.05 M; 20, 40, 100 nA), phenylephrine (PE, 0.05 M; 20, 40, 100 nA). Finally, adenosine (ADO, 10⁻⁴ M) was superfused over the tissue to identify maximum diameter. In situ vessel reactivity after exposure was significantly blunted based on estrous stage, but not at late-stage pregnancy. Local uterine venular leukocyte trafficking and systemic inflammatory markers were also significantly affected during preparatory (proestrus), fertile (estrus), and infertile (diestrus) periods after ENM inhalation. Overall, these deficits in reactivity and increased inflammatory activity may impair female fertility after ENM exposure.

Inhalation exposure to three-dimensional printer emissions stimulates acute hypertension and microvascular dysfunction

Fused deposition modeling (FDM™), or three-dimensional (3D) printing has become routine in industrial, occupational and domestic environments. We have recently reported that 3D printing emissions (3DPE) are complex mixtures, with a large ultrafine particulate matter component. Additionally, we and others have reported that inhalation of xenobiotic particles in this size range is associated with an array of cardiovascular dysfunctions. Sprague-Dawley rats were exposed to 3DPE aerosols via nose-only exposure for ~3h. Twenty-four hours later, intravital microscopy was performed to assess microvascular function in the spinotrapezius muscle. Endothelium-dependent and -independent arteriolar dilation were stimulated by local microiontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP). At the time of experiments, animals exposed to 3DPE inhalation presented with a mean arterial pressure of 125±4mmHg, and this was significantly higher than that for the sham-control group (94±3mmHg). Consistent with this pressor response in the 3DPE group, was an elevation of ~12% in resting arteriolar tone. Endothelium-dependent arteriolar dilation was significantly impaired after 3DPE inhalation across all iontophoretic ejection currents (0-27±15%, compared to sham-control: 15-120±21%). Endothelium-independent dilation was not affected by 3DPE inhalation. These alterations in peripheral microvascular resistance and reactivity are consistent with elevations in arterial pressure that follow 3DPE inhalation. Future studies must identify the specific toxicants generated by FDM™ that drive this acute pressor response.

Heterogeneous Vascular Bed Responses to Pulmonary Titanium Dioxide Nanoparticle Exposure

A growing body of research links engineered nanomaterial (ENM) exposure to adverse cardiovascular endpoints. The purpose of this study was to evaluate the impact of ENM exposure on vascular reactivity in discrete segments so that we may determine the most sensitive levels of the vasculature where these negative cardiovascular effects are manifest. We hypothesized that acute nano-TiO₂ exposure differentially affects reactivity with a more robust impairment in the microcirculation. Sprague-Dawley rats (8–10 weeks) were exposed to nano-TiO₂via intratracheal instillation (20, 100, or 200 µg suspended per 250 µL of vehicle) 24 h prior to vascular assessments. A serial assessment across distinct compartments of the vascular tree was then conducted. Wire myography was used to evaluate macrovascular active tension generation specifically in the thoracic aorta, the femoral artery, and third-order mesenteric arterioles. Pressure myography was used to determine vascular reactivity in fourth- and fifth-order mesenteric arterioles. Vessels were treated with phenylephrine, acetylcholine (ACh), and sodium nitroprusside. Nano-TiO₂ exposure decreased endothelium-dependent relaxation in the thoracic aorta and femoral arteries assessed via ACh by 53.96 ± 11.6 and 25.08 ± 6.36%, respectively. Relaxation of third-order mesenteric arterioles was impaired by 100 and 20 µg nano-TiO₂ exposures with mean reductions of 50.12 ± 8.7 and 68.28 ± 8.7%. Cholinergic reactivity of fourth- and fifth-order mesenteric arterioles was negatively affected by nano-TiO₂ with diminished dilations of 82.86 ± 12.6% after exposure to 200 µg nano-TiO₂, 42.6 ± 12.6% after 100 µg nano-TiO₂, and 49.4 ± 12.6% after 20 µg nano-TiO₂. Endothelium-independent relaxation was impaired in the thoracic aorta by 34.05 ± 25% induced by exposure to 200 µg nano-TiO₂ and a reduction in response of 49.31 ± 25% caused by 100 µg nano-TiO₂. Femoral artery response was reduced by 18 ± 5%, while third-order mesenteric arterioles were negatively affected by 20 µg nano-TiO₂ with a mean decrease in response of 38.37 ± 10%. This is the first study to directly compare the differential effect of ENM exposure on discrete anatomical segments of the vascular tree. Pulmonary ENM exposure produced macrovascular and microvascular dysfunction resulting in impaired responses to endothelium-dependent, endothelium-independent, and adrenergic agonists with a more robust dysfunction at the microvascular level. These results provide additional evidence of an endothelium-dependent and endothelium-independent impairment in vascular reactivity.

Thrombospondin-1 mediates multi-walled carbon nanotube induced impairment of arteriolar dilation

Pulmonary exposure to multi-walled carbon nanotubes (MWCNT) has been shown to disrupt endothelium-dependent arteriolar dilation in the peripheral microcirculation. The molecular mechanisms behind these arteriolar disruptions have yet to be fully elucidated. The secreted matricellular matrix protein thrombospondin-1 (TSP-1) is capable of moderating arteriolar vasodilation by inhibiting soluble guanylate cyclase activity. We hypothesized that TSP-1 may be a link between nanomaterial exposure and observed peripheral microvascular dysfunction. To test this hypothesis, wild-type C57B6J (WT) and TSP-1 knockout (KO) mice were exposed via lung aspiration to 50 μg MWCNT or a Sham dispersion medium control. Following exposure (24 h), arteriolar characteristics and reactivity were measured in the gluteus maximus muscle using intravital microscopy (IVM) coupled with microiontophoretic delivery of acetylcholine (ACh) or sodium nitroprusside (SNP). In WT mice exposed to MWCNT, skeletal muscle TSP-1 protein increased > fivefold compared to Sham exposed, and exhibited a 39% and 47% decrease in endothelium-dependent and -independent vasodilation, respectively. In contrast, TSP-1 protein was not increased following MWCNT exposure in KO mice and exhibited no loss in dilatory capacity. Microvascular leukocyte-endothelium interactions were measured by assessing leukocyte adhesion and rolling activity in third order venules. The WT + MWCNT group demonstrated 223% higher leukocyte rolling compared to the WT + Sham controls. TSP-1 KO animals exposed to MWCNT showed no differences from the WT + Sham control. These data provide evidence that TSP-1 is likely a central mediator of the systemic microvascular dysfunction that follows pulmonary MWCNT exposure.

Maternal-engineered nanomaterial exposure disrupts progeny cardiac function and bioenergetics

Nanomaterial production is expanding as new industrial and consumer applications are introduced. Nevertheless, the impacts of exposure to these compounds are not fully realized. The present study was designed to determine whether gestational nano-sized titanium dioxide exposure impacts cardiac and metabolic function of developing progeny. Pregnant Sprague-Dawley rats were exposed to nano-aerosols (~10 mg/m³, 130- to 150-nm count median aerodynamic diameter) for 7-8 nonconsecutive days, beginning at gestational day 5-6 Physiological and bioenergetic effects on heart function and cardiomyocytes across three time points, fetal (gestational day 20), neonatal (4-10 days), and young adult (6-12 wk), were evaluated. Functional analysis utilizing echocardiography, speckle-tracking based strain, and cardiomyocyte contractility, coupled with mitochondrial energetics, revealed effects of nano-exposure. Maternal exposed progeny demonstrated a decrease in E- and A-wave velocities, with a 15% higher E-to-A ratio than controls. Myocytes isolated from exposed animals exhibited ~30% decrease in total contractility, departure velocity, and area of contraction. Bioenergetic analysis revealed a significant increase in proton leak across all ages, accompanied by decreases in metabolic function, including basal respiration, maximal respiration, and spare capacity. Finally, electron transport chain complex I and IV activities were negatively impacted in the exposed group, which may be linked to a metabolic shift. Molecular data suggest that an increase in fatty acid metabolism, uncoupling, and cellular stress proteins may be associated with functional deficits of the heart. In conclusion, gestational nano-exposure significantly impairs the functional capabilities of the heart through cardiomyocyte impairment, which is associated with mitochondrial dysfunction.NEW & NOTEWORTHY Cardiac function is evaluated, for the first time, in progeny following maternal nanomaterial inhalation. The findings indicate that exposure to nano-sized titanium dioxide (nano-TiO₂) during gestation negatively impacts cardiac function and mitochondrial respiration and bioenergetics. We conclude that maternal nano-TiO₂ inhalation contributes to adverse cardiovascular health effects, lasting into adulthood.

Metal Nanomaterial Toxicity Variations Within the Vascular System

Engineered nanomaterials (ENM) are anthropogenic materials with at least one dimension less than 100 nm. Their ubiquitous employment in biomedical and industrial applications in the absence of full toxicological assessments raises significant concerns over their safety on human health. This is a significant concern, especially for metal and metal oxide ENM as they may possess the greatest potential to impair human health. A large body of literature has developed that reflects adverse systemic effects associated with exposure to these materials, but an integrated mechanistic framework for how ENM exposure influences morbidity remains elusive. This may be due in large part to the tremendous diversity of existing ENM and the rate at which novel ENM are produced. In this review, the influence of specific ENM physicochemical characteristics and hemodynamic factors on cardiovascular toxicity is discussed. Additionally, the toxicity of metallic and metal oxide ENM is presented in the context of the cardiovascular system and its discrete anatomical and functional components. Finally, future directions and understudied topics are presented. While it is clear that the nanotechnology boom has increased our interest in ENM toxicity, it is also evident that the field of cardiovascular nanotoxicology remains in its infancy and continued, expansive research is necessary in order to determine the mechanisms via which ENM exposure contributes to cardiovascular morbidity.