Vascular Tissue Contractility Changes Following Late Gestational Exposure to Multi-Walled Carbon Nanotubes or their Dispersing Vehicle in Sprague Dawley Rats

Oral administration of TiO2 nanoparticles during early life impacts cardiac and neurobehavioral performance and metabolite profile in an age- and sex-related manner

BACKGROUND

Nanoparticles (NPs) are increasingly incorporated in everyday products. To investigate the effects of early life exposure to orally ingested TiO2 NP, male and female Sprague-Dawley rat pups received four consecutive daily doses of 10 mg/kg body weight TiO2 NP (diameter: 21 ± 5 nm) or vehicle control (water) by gavage at three different pre-weaning ages: postnatal day (PND) 2-5, PND 7-10, or PND 17-20. Cardiac assessment and basic neurobehavioral tests (locomotor activity, rotarod, and acoustic startle) were conducted on PND 20. Pups were sacrificed at PND 21. Select tissues were collected, weighed, processed for neurotransmitter and metabolomics analyses.

RESULTS

Heart rate was found to be significantly decreased in female pups when dosed between PND 7-10 and PND 17-20. Females dosed between PND 2-5 showed decrease acoustic startle response and when dosed between PND 7-10 showed decreased performance in the rotarod test and increased locomotor activity. Male pups dosed between PND 17-20 showed decreased locomotor activity. The concentrations of neurotransmitters and related metabolites in brain tissue and the metabolomic profile of plasma were impacted by TiO2 NP administration for all dose groups. Metabolomic pathways perturbed by TiO2 NP administration included pathways involved in amino acid and lipid metabolism.

CONCLUSION

Oral administration of TiO2 NP to rat pups impacted basic cardiac and neurobehavioral performance, neurotransmitters and related metabolites concentrations in brain tissue, and the biochemical profiles of plasma. The findings suggested that female pups were more likely to experience adverse outcome following early life exposure to oral TiO2 NP than male pups. Collectively the data from this exploratory study suggest oral administration of TiO2 NP cause adverse biological effects in an age- and sex-related manner, emphasizing the need to understand the short- and long-term effects of early life exposure to TiO2 NP.

Pulmonary delivery of the broad-spectrum matrix metalloproteinase inhibitor marimastat diminishes multiwalled carbon nanotube-induced circulating bioactivity without reducing pulmonary inflammation

BACKGROUND

Multiwalled carbon nanotubes (MWCNT) are an increasingly utilized engineered nanomaterial that pose the potential for significant risk of exposure-related health outcomes. The mechanism(s) underlying MWCNT-induced toxicity to extrapulmonary sites are still being defined. MWCNT-induced serum-borne bioactivity appears to dysregulate systemic endothelial cell function. The serum compositional changes after MWCNT exposure have been identified as a surge of fragmented endogenous peptides, likely derived from matrix metalloproteinase (MMP) activity. In the present study, we utilize a broad-spectrum MMP inhibitor, Marimastat, along with a previously described oropharyngeal aspiration model of MWCNT administration to investigate the role of MMPs in MWCNT-derived serum peptide generation and endothelial bioactivity.

RESULTS

C57BL/6 mice were treated with Marimastat or vehicle by oropharyngeal aspiration 1 h prior to MWCNT treatment. Pulmonary neutrophil infiltration and total bronchoalveolar lavage fluid protein increased independent of MMP blockade. The lung cytokine profile similarly increased following MWCNT exposure for major inflammatory markers (IL-1β, IL-6, and TNF-α), with minimal impact from MMP inhibition. However, serum peptidomic analysis revealed differential peptide compositional profiles, with MMP blockade abrogating MWCNT-derived serum peptide fragments. The serum, in turn, exhibited differential potency in terms of inflammatory bioactivity when incubated with primary murine cerebrovascular endothelial cells. Serum from MWCNT-treated mice led to inflammatory responses in endothelial cells that were significantly blunted with serum from Marimastat-treated mice.

CONCLUSIONS

Thus, MWCNT exposure induced pulmonary inflammation that was largely independent of MMP activity but generated circulating bioactive peptides through predominantly MMP-dependent pathways. This MWCNT-induced lung-derived bioactivity caused pathological consequences of endothelial inflammation and barrier disruption.

Fetotoxicity of Nanoparticles: Causes and Mechanisms

The application of nanoparticles in consumer products and nanomedicines has increased dramatically in the last decade. Concerns for the nano-safety of susceptible populations are growing. Due to the small size, nanoparticles have the potential to cross the placental barrier and cause toxicity in the fetus. This review aims to identify factors associated with nanoparticle-induced fetotoxicity and the mechanisms involved, providing a better understanding of nanotoxicity at the maternal–fetal interface. The contribution of the physicochemical properties of nanoparticles (NPs), maternal physiological, and pathological conditions to the fetotoxicity is highlighted. The underlying molecular mechanisms, including oxidative stress, DNA damage, apoptosis, and autophagy are summarized. Finally, perspectives and challenges related to nanoparticle-induced fetotoxicity are also discussed.

Recent insights on indirect mechanisms in developmental toxicity of nanomaterials

BACKGROUND

Epidemiological and animal studies provide compelling indications that environmental and engineered nanomaterials (NMs) pose a risk for pregnancy, fetal development and offspring health later in life. Understanding the origin and mechanisms underlying NM-induced developmental toxicity will be a cornerstone in the protection of sensitive populations and the design of safe and sustainable nanotechnology applications.

MAIN BODY

Direct toxicity originating from NMs crossing the placental barrier is frequently assumed to be the key pathway in developmental toxicity. However, placental transfer of particles is often highly limited, and evidence is growing that NMs can also indirectly interfere with fetal development. Here, we outline current knowledge on potential indirect mechanisms in developmental toxicity of NMs.

SHORT CONCLUSION

Until now, research on developmental toxicity has mainly focused on the biodistribution and placental translocation of NMs to the fetus to delineate underlying processes. Systematic research addressing NM impact on maternal and placental tissues as potential contributors to mechanistic pathways in developmental toxicity is only slowly gathering momentum. So far, maternal and placental oxidative stress and inflammation, activation of placental toll-like receptors (TLRs), impairment of placental growth and secretion of placental hormones, and vascular factors have been suggested to mediate indirect developmental toxicity of NMs. Therefore, NM effects on maternal and placental tissue function ought to be comprehensively evaluated in addition to placental transfer in the design of future studies of developmental toxicity and risk assessment of NM exposure during pregnancy.

Effect of Gestational Age on Maternofetal Vascular Function Following Single Maternal Engineered Nanoparticle Exposure

Normal pregnancy outcome is accomplished, in part, by rapid and expansive physiological adaptations to the systemic circulation, the extent of which is specific to gestational day (GD) and anatomical location. Pregnancy-related hemodynamic changes in uterine placental blood flow stimulate compensatory vascular signaling and remodeling that begins early and continues throughout gestation. Exposure of the maternal environment to engineered nanomaterials (ENM) during pregnancy has been shown to impact health of the dam, fetus, and adult offspring; however, the consequences of specific temporal (gestational age) and spatial (vascular location) considerations are largely undetermined. We exposed pregnant Sprague-Dawley rats to nano-TiO2 aerosols at three critical periods of fetal development (GD 4, 12, and 17) to identify vascular perturbations associated with ENM exposure at these developmental milestones. Vascular reactivity of the maternal thoracic aorta, the uterine artery, the umbilical vein, and the fetal thoracic aorta were evaluated using wire myography on GD 20. While impairments were noted at each level of the maternofetal vascular tree and at each exposure day, our results indicate the greatest effects may be identified within the fetal vasculature (umbilical vein and fetal aorta), wherein effects of a single maternal inhalational exposure to nano-TiO2 on GD 4 modified responses to cholinergic, NO, and α-adrenergic signaling.

Cardiopulmonary consequences of gestational toxicant exposure: Symposium overview at the 56th annual SOT meeting, Baltimore, MD

Xenobiotic exposures affect the maternal and/or in utero environment resulting in impairments in fetal development. During the period of rapid fetal growth, developing cardiovascular systems are especially vulnerable to their environment. Furthermore, fetal exposures can evoke changes in epigenetic signatures that result in permanent modifications in gene expression. This symposium focused on the intersection between maternal and fetal exposure and the developing cardiovascular system. The impact of maternal exposures on prenatal development is of major concern for regulatory agencies given the unique vulnerability of the embryo/fetus to environmental factors, the importance of vascular biology to maternal-fetal interactions, and the adverse consequences of vascular disruption to children's health. Speakers provided data from diverse exposures: nanomaterials, particulate matter or air pollution (PM_2.5), nicotine, and environmental chemicals. The current findings related to susceptible gestational windows for cardiovascular development and epigenetic, transcriptomic, toxicokinetic, and toxicodynamic changes in vascular physiology and cardiac function. In response to these concerns, new concepts in predictive modeling and risk assessment associated with in utero exposures were presented as future avenues of research within developmental toxicology. Finally, current applications using an Adverse Outcome Pathway framework for developmental toxicity were presented to integrate data from in vitro profiling of chemical libraries (e.g. ToxCast™) with computational models for in silico toxicology. In summary, this symposium addressed the significant threats to cardiovascular health that are associated with fetal/perinatal exposures, and offered new insights into the predictive, mechanistic, and risk assessment strategies in developmental toxicology.

Engineered nanomaterial applications in perinatal therapeutics

Engineered nanomaterials (ENM) are widely used in commercial, domestic, and more recently biomedical applications. While the majority of exposures to ENM are unintentional, biomedical platforms are being evaluated for use in individualized and/or tissue-targeted therapies. Treatments are often avoided during prenatal periods to reduce adverse effects on the developing fetus. The placenta is central to maternal-fetal medicine. Perturbation of placental functions can limit transfer of necessary nutrients, alter production of hormones needed during pregnancy, or allow undesired passage of xenobiotics to the developing fetus. The development of therapeutics to target specific maternal, placental, or fetal tissues would be especially important to reduce or circumvent toxicities. Therefore, this review will discuss the potential use of ENM in perinatal medicine, the applicable physiochemical properties of ENM in therapeutic use, and current methodologies of ENM testing in perinatal medicine, and identify maternal, fetal, and offspring concerns associated with ENM exposure during gestation. As potential nanoparticle-based therapies continue to develop, so does the need for thorough consideration and evaluation for use in perinatal medicine.

Acute intravenous exposure to silver nanoparticles during pregnancy induces particle size and vehicle dependent changes in vascular tissue contractility in Sprague Dawley rats

The use of silver nanoparticles (AgNP) raises safety concerns during susceptible life stages such as pregnancy. We hypothesized that acute intravenous exposure to AgNP during late stages of pregnancy will increase vascular tissue contractility, potentially contributing to alterations in fetal growth. Sprague Dawley rats were exposed to a single dose of PVP or Citrate stabilized 20 or 110nm AgNP (700μg/kg). Differential vascular responses and EC50 values were observed in myographic studies in uterine, mesenteric arteries and thoracic aortic segments, 24h post-exposure. Reciprocal responses were observed in aortic and uterine vessels following PVP stabilized AgNP with an increased force of contraction in uterine artery and increased relaxation responses in aorta. Citrate stabilized AgNP exposure increased contractile force in both uterine and aortic vessels. Intravenous AgNP exposure during pregnancy displayed particle size and vehicle dependent moderate changes in vascular tissue contractility, potentially influencing fetal blood supply.

Impact of pulmonary exposure to gold core silver nanoparticles of different size and capping agents on cardiovascular injury

BACKGROUND

The uses of engineered nanomaterials have expanded in biomedical technology and consumer manufacturing. Furthermore, pulmonary exposure to various engineered nanomaterials has, likewise, demonstrated the ability to exacerbate cardiac ischemia reperfusion (I/R) injury. However, the influence of particle size or capping agent remains unclear. In an effort to address these influences we explored response to 2 different size gold core nanosilver particles (AgNP) with two different capping agents at 2 different time points. We hypothesized that a pulmonary exposure to AgNP induces cardiovascular toxicity influenced by inflammation and vascular dysfunction resulting in expansion of cardiac I/R Injury that is sensitive to particle size and the capping agent.

METHODS

Male Sprague-Dawley rats were exposed to 200 μg of 20 or 110 nm polyvinylprryolidone (PVP) or citrate capped AgNP. One and 7 days following intratracheal instillation serum was analyzed for concentrations of selected cytokines; cardiac I/R injury and isolated coronary artery and aorta segment were assessed for constrictor responses and endothelial dependent relaxation and endothelial independent nitric oxide dependent relaxation.

RESULTS

AgNP instillation resulted in modest increase in selected serum cytokines with elevations in IL-2, IL-18, and IL-6. Instillation resulted in a derangement of vascular responses to constrictors serotonin or phenylephrine, as well as endothelial dependent relaxations with acetylcholine or endothelial independent relaxations by sodium nitroprusside in a capping and size dependent manner. Exposure to both 20 and 110 nm AgNP resulted in exacerbation cardiac I/R injury 1 day following IT instillation independent of capping agent with 20 nm AgNP inducing marginally greater injury. Seven days following IT instillation the expansion of I/R injury persisted but the greatest injury was associated with exposure to 110 nm PVP capped AgNP resulted in nearly a two-fold larger infarct size compared to naïve.

CONCLUSIONS

Exposure to AgNP may result in vascular dysfunction, a potentially maladaptive sensitization of the immune system to respond to a secondary insult (e.g., cardiac I/R) which may drive expansion of I/R injury at 1 and 7 days following IT instillation where the extent of injury could be correlated with capping agents and AgNP size.

Distribution and biomarker of carbon-14 labeled fullerene C60 ([(14) C(U)]C60 ) in pregnant and lactating rats and their offspring after maternal intravenous exposure

A comprehensive distribution study was conducted in pregnant and lactating rats exposed to a suspension of uniformly carbon-14 labeled C60 ([(14) C(U)]C60 ). Rats were administered [(14) C(U)]C60 (~0.2 mg [(14) C(U)]C60 kg(-1) body weight) or 5% polyvinylpyrrolidone (PVP)-saline vehicle via a single tail vein injection. Pregnant rats were injected on gestation day (GD) 11 (terminated with fetuses after either 24 h or 8 days), GD15 (terminated after 24 h or 4 days), or GD18 (terminated after 24 h). Lactating rats were injected on postnatal day 8 and terminated after 24 h, 3 or 11 days. The distribution of radioactivity in pregnant dams was influenced by both the state of pregnancy and time of termination after exposure. The percentage of recovered radioactivity in pregnant and lactating rats was highest in the liver and lungs. Radioactivity was quantitated in over 20 tissues. Radioactivity was found in the placenta and in fetuses of pregnant dams, and in the milk of lactating rats and in pups. Elimination of radioactivity was < 2% in urine and feces at each time point. Radioactivity remained in blood circulation up to 11 days after [(14) C(U)]C60 exposure. Biomarkers of inflammation, cardiovascular injury and oxidative stress were measured to study the biological impacts of [(14) C(U)]C60 exposure. Oxidative stress was elevated in female pups of exposed dams. Metabolomics analysis of urine showed that [(14) C(U)]C60 exposure to pregnant rats impacted the pathways of vitamin B, regulation of lipid and sugar metabolism and aminoacyl-tRNA biosynthesis. This study demonstrated that [(14) C(U)]C60 crosses the placenta at all stages of pregnancy examined, and is transferred to pups via milk.

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.

Cardiac Ischemia Reperfusion Injury Following Instillation of 20 nm Citrate-capped Nanosilver

BACKGROUND

Silver nanoparticles (AgNP) have garnered much interest due to their antimicrobial properties, becoming one of the most utilized nano-scale materials. However, any potential evocable cardiovascular injury associated with exposure has not been reported to date. We have previously demonstrated expansion of myocardial infarction after intratracheal (IT) instillation of carbon-based nanomaterials. We hypothesized pulmonary exposure to Ag core AgNP induces a measureable increase in circulating cytokines, expansion of cardiac ischemia-reperfusion (I/R) injury and is associated with depressed coronary constrictor and relaxation responses. Secondarily, we addressed the potential contribution of silver ion release on AgNP toxicity.

METHODS

Male Sprague-Dawley rats were exposed to 200 μl of 1 mg/ml of 20 nm citrate-capped Ag core AgNP, 0.01, 0.1, 1 mg/ml Silver Acetate (AgAc), or a citrate vehicle by intratracheal (IT) instillation. One and 7 days following IT instillation the lungs were evaluated for inflammation and the presence of silver; serum was analyzed for concentrations of selected cytokines; cardiac I/R injury and coronary artery reactivity were assessed.

RESULTS

AgNP instillation resulted in modest pulmonary inflammation with detection of silver in lung tissue and alveolar macrophages, elevation of serum cytokines: G-CSF, MIP-1α, IL-1β, IL-2, IL-6, IL-13, IL-10, IL-18, IL-17α, TNFα, and RANTES, expansion of I/R injury and depression of the coronary vessel reactivity at 1 day post IT compared to vehicle treated rats. Silver within lung tissue was persistent at 7 days post IT instillation and was associated with an elevation in cytokines: IL-2, IL-13, and TNFα and expansion of I/R injury. AgAc resulted in a concentration dependent infarct expansion and depressed vascular reactivity without marked pulmonary inflammation or serum cytokine response.

CONCLUSIONS

Based on these data, IT instillation of AgNP increases circulating levels of several key cytokines, which may contribute to persistent expansion of I/R injury possibly through an impaired vascular responsiveness.

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

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.

Distribution and biomarker of carbon-14 labeled fullerene C60 ([(14) C(U)]C60 ) in pregnant and lactating rats and their offspring after maternal intravenous exposure

A comprehensive distribution study was conducted in pregnant and lactating rats exposed to a suspension of uniformly carbon-14 labeled C60 ([(14) C(U)]C60 ). Rats were administered [(14) C(U)]C60 (~0.2 mg [(14) C(U)]C60 kg(-1) body weight) or 5% polyvinylpyrrolidone (PVP)-saline vehicle via a single tail vein injection. Pregnant rats were injected on gestation day (GD) 11 (terminated with fetuses after either 24 h or 8 days), GD15 (terminated after 24 h or 4 days), or GD18 (terminated after 24 h). Lactating rats were injected on postnatal day 8 and terminated after 24 h, 3 or 11 days. The distribution of radioactivity in pregnant dams was influenced by both the state of pregnancy and time of termination after exposure. The percentage of recovered radioactivity in pregnant and lactating rats was highest in the liver and lungs. Radioactivity was quantitated in over 20 tissues. Radioactivity was found in the placenta and in fetuses of pregnant dams, and in the milk of lactating rats and in pups. Elimination of radioactivity was < 2% in urine and feces at each time point. Radioactivity remained in blood circulation up to 11 days after [(14) C(U)]C60 exposure. Biomarkers of inflammation, cardiovascular injury and oxidative stress were measured to study the biological impacts of [(14) C(U)]C60 exposure. Oxidative stress was elevated in female pups of exposed dams. Metabolomics analysis of urine showed that [(14) C(U)]C60 exposure to pregnant rats impacted the pathways of vitamin B, regulation of lipid and sugar metabolism and aminoacyl-tRNA biosynthesis. This study demonstrated that [(14) C(U)]C60 crosses the placenta at all stages of pregnancy examined, and is transferred to pups via milk.