whole-body-nanoparticle-aerosol-inhalation-exposures

Whole-Body Nanoparticle Aerosol Inhalation Exposures

Inhalation is the most likely exposure route for individuals working with aerosolizable engineered nano-materials (ENM). To properly perform nanoparticle ...

Epidemiological evidence indicates that environmental air pollutants are positively associated with the development of chronic vascular disease; however, the mechanisms involved have not been fully elucidated. In the present study we examined molecular pathways associated with chronic vascular disease in atherosclerosis-prone apolipoprotein E-deficient (ApoE(-/-)) mice, including markers of vascular remodeling and oxidative stress, in response to exposure to the ubiquitous environmental pollutant, gasoline engine emissions. ApoE(-/-) mice, on a high-fat diet, were exposed by inhalation to either filtered air; 8, 40, or 60 mug/m(3) particulate matter whole exhaust; or filtered exhaust with gases matching the 60-mug/m(3) concentration, for 7 weeks. Aortas and plasma were collected and assayed for changes in histochemical markers, real-time reverse transcriptase-polymerase chain reaction, and indicators of oxidative damage. Inhalational exposure to gasoline engine emissions resulted in increased aortic mRNA expression of matrix metalloproteinase-3 (MMP-3), MMP-7, and MMP-9, tissue inhibitor of metalloproteinases-2, endothelin-1 and heme oxygenase-1 in ApoE(-/-) mice; increased aortic MMP-9 protein levels were confirmed through immunohistochemistry. Elevated reactive oxygen species were also observed in arteries from exposed animals, despite absence of plasma markers. Similar findings were also observed in the aortas of ApoE(-/-) mice exposed to particle-filtered atmosphere, implicating the gaseous components of the whole exhaust in mediating the expression of markers associated with the vasculopathy. These findings demonstrate that exposure to gasoline engine emissions results in the transcriptional upregulation of factors associated with vascular remodeling, as well as increased markers of vascular oxidative stress, which may contribute to the progression of atherosclerosis and reduced stability of vulnerable plaques.

Gasoline exhaust emissions induce vascular remodeling pathways involved in atherosclerosis.

Epidemiological studies have shown a positive association between exposure to air particulate matter (PM) pollution and adverse cardiovascular health effects in susceptible subpopulations such as those with pre-existing cardiovascular disease. The mechanism(s) through which pulmonary deposited PM, particularly fine PM2.5, PM with mass median aerodynamic diameter <2.5 microm, affects the cardiovascular system is currently not known and remains a major focus of investigation. In the present study, the transcriptosome and transcription factor proteome were examined in rat neonatal cardiomyocyte (RCM) cultures, following an acute exposure to bioavailable constituents of PM2.5 oil combustion particles designated residual oil fly ash leachate (ROFA-L). Out of 3924 genes examined, 38 genes were suppressed and 44 genes were induced following a 1-h exposure to 3.5 microg/ml of a particle-free leachate of ROFA (ROFA-L). Genomic alterations in pathways related to IGF-1, VEGF, IL-2, PI3/AKT, cardiovascular disease, and free radical scavenging, among others, were detected 1 h postexposure to ROFA-L. Global gene expression was altered in a manner consistent with cardiac myocyte electrophysiological remodeling, cellular oxidative stress, and apoptosis. ROFA-L altered the transcription factor proteome by suppressing activity of 24 and activating 40 transcription factors out of a total of 149. Genomic alterations were found to correlate with changes in transcription factor proteome. These acute changes indicate pathological molecular alterations, which may lead to possible chronic alterations to the cardiac myocyte. These data also potentially relate underlying cardiovascular effects from occupational exposure to ROFA and identify how particles from specific emission sources may mediate ambient PM cardiac effects.

Fine oil combustion particle bioavailable constituents induce molecular profiles of oxidative stress, altered function, and cellular injury in cardiomyocytes.

Environmental air pollution is associated with adverse cardiovascular events, including increased hospital admissions due to heart failure and myocardial infarction. The exact mechanism(s) by which air pollution affects the heart and vasculature is currently unknown. Recent studies have found that exposure to air pollution enhances arterial vasoconstriction in humans and animal models. Work in our laboratory has shown that diesel emissions (DE) enhance vasoconstriction of mouse coronary arteries. Thus, we hypothesized that DE could enhance vasoconstriction in arteries and veins through uncoupling of endothelial nitric oxide synthase (eNOS). To test this hypothesis, we first bubbled DE through a physiological saline solution and exposed isolated mesenteric veins. Second, we exposed animals, whole body, to DE at 350 microg/m(3) for 4 h, after which mesenteric arteries and veins were isolated. Results from these experiments show that saline bubbled with DE as well as inhaled DE enhances vasoconstriction in veins but not arteries. Exposure to several representative volatile organic compounds found in the DE-exposed saline did not enhance arterial constriction. L-nitro-arginine-methyl-ester (L-NAME), an eNOS inhibitor, normalized the control vessels to the DE-exposed vessels implicating an uncoupling of eNOS as a mechanism for enhanced vasoconstriction. The principal conclusions of this research are 1) veins exhibit endothelial dysfunction following in vivo and ex vivo exposures to DE, 2) veins appear to be more sensitive to DE effects than arteries, and 3) DE components most likely induce endothelial dysfunction through the uncoupling of eNOS.

Diesel exhaust exposure enhances venoconstriction via uncoupling of eNOS.

Mechanisms of air pollution-induced exacerbation of cardiovascular disease are currently unknown, thus we examined the roles of vascular endothelin-1 (ET-1) and reactive oxygen species (ROS) in regulating mediators of vascular remodeling, namely matrix metalloproteinases (MMPs), after exposure to vehicle engine emissions.

Vehicular emissions induce vascular MMP-9 expression and activity associated with endothelin-1-mediated pathways.

Air pollutant levels positively correlate with increases in both acute and chronic cardiovascular disease. The pollutant diesel exhaust (DE) increases endothelin (ET) levels, suggesting that this peptide may contribute to DE-induced cardiovascular disease. We hypothesized that acute exposure to DE also enhances ET-1-mediated coronary artery constrictor sensitivity. Constrictor responses to KCl, U-46619, and ET-1 were recorded by videomicroscopy in pressurized intraseptal coronary arteries from rats exposed for 5 h to DE (300 microg/m(3)) or filtered air (Air). ET-1 constriction was augmented in arteries from DE-exposed rats. Nitric oxide synthase (NOS) inhibition [N(omega)-nitro-L-arginine (L-NNA), 100 microM] and endothelium inactivation augmented ET-1 responses in arteries from Air but not DE rats so that after either treatment responses were not different between groups. DE exposure did not affect KCl and U-46619 constrictor responses, while NOS inhibition augmented KCl constriction equally in both groups. Thus basal NOS activity does not appear to be affected by DE exposure. The endothelin type B (ET(B)) receptor antagonist BQ-788 (10 microM) inhibited ET-1 constriction in DE but not Air arteries, and constriction in the presence of the antagonist was not different between groups. Cytokine levels were not different in plasma from DE and AIR rats, suggesting that acute exposure to DE does not cause an immediate inflammatory response. In summary, a 5-h DE exposure selectively increases constrictor sensitivity to ET-1. This augmentation is endothelium-, NOS-, and ET(B) receptor dependent. These data suggest that DE exposure diminishes ET(B) receptor activation of endothelial NOS and augments ET(B)-dependent vasoconstriction. This augmented coronary vasoreactivity to ET-1 after DE, coupled with previous reports that DE induces production of ET-1, suggests that ET-1 may contribute to the increased incidence of cardiac events during acute increases in air pollution levels.

Impairment of coronary endothelial cell ET(B) receptor function after short-term inhalation exposure to whole diesel emissions.

Recent epidemiological studies suggest that traffic-related air pollution may have detrimental effects on cardiovascular health. Previous studies reveal that gasoline emissions can induce several enzyme pathways involved in the formation and development of atherosclerotic plaques. As a direct comparison, the present study examined the impact of diesel engine emissions on these pathways, and further examined the effects on vascular lesion pathology. Apolipoprotein E-null mice were simultaneously placed on a high-fat chow diet and exposed to four concentrations, plus a high concentration exposure with particulates (PM) removed by filtration, of diesel emissions for 6 h/day for 50 days. Aortas were subsequently assayed for alterations in matrix metalloproteinase-9, endothelin-1, and several other biomarkers. Diesel induced dose-related alterations in gene markers of vascular remodeling and aortic lipid peroxidation; filtration of PM did not significantly alter these vascular responses, indicating that the gaseous portion of the exhaust was a principal driver. Immunohistochemical analysis of aortic leaflet sections revealed no net increase in lesion area, but a significant decrease in lipid-rich regions and increasing trends in macrophage accumulation and collagen content, suggesting that plaques were advanced to a more fragile, potentially more vulnerable state by diesel exhaust exposure. Combined with previous studies, these results indicate that whole emissions from mobile sources may have a significant role in promoting chronic vascular disease.

Inhaled diesel emissions alter atherosclerotic plaque composition in ApoE(-/-) mice.

Emerging evidence suggests that the systemic vasculature may be a target of inhaled pollutants of vehicular origin. We have identified several murine markers of vascular toxicity that appear sensitive to inhalation exposures to combustion emissions.

A comparison of vascular effects from complex and individual air pollutants indicates a role for monoxide gases and volatile hydrocarbons.

Epidemiological studies have associated traffic-related airborne pollution with adverse cardiovascular outcomes. Nitric oxide (NO) is a common component of fresh diesel and gasoline engine emissions that rapidly transforms both in the atmosphere and once inhaled. Because of this rapid transformation, limited information is available in terms of potential human exposures and adverse health effects. Young rats were exposed to whole diesel emissions (DE) adjusted to 300 Î¼g/m(3) of particulate matter (containing 3.5 ppm NO) or 0, 3, or 10 ppm NO as a positive control. Animals were also pre-injected (ip) with either saline or N-acetylcysteine (NAC), a precursor of glutathione. Predictably, pure NO exposures led to a concentration-dependent increase in plasma nitrates compared to controls, which lasted for roughly 4 h postexposure. Whole DE exposure for 1 h also led to a doubling of plasma NOx. NAC injection increased the levels of plasma nitrates and nitrites (NOx) in the DE exposure group. Inhibition of nitric oxide symthase (NOS) by N(G)-nitro-L-arginine (L-NNA) did not block the rise in plasma NOx, demonstrating that the increase was entirely due to exogenous sources. Both DE and pure NO exposures paradoxically led to elevated eNOS expression in aortic tissue. Furthermore, coronary arterioles from NO-exposed animals exhibited greater constriction to endothelin-1 compared to controls, consistent with a derangement of the NOS system. Thus, NO may be an important contributor to traffic-related cardiovascular morbidity, although further research is necessary for proper hazard identification.

Formation of vascular S-nitrosothiols and plasma nitrates/nitrites following inhalation of diesel emissions.

The widespread increase in the production and use of nanomaterials has increased the potential for nanoparticle exposure; however, the biological effects of nanoparticle inhalation are poorly understood. Rats were exposed to nanosized titanium dioxide aerosols (10 Î¼g lung burden); at 24 h post-exposure, the spinotrapezius muscle was prepared for intravital microscopy. Nanoparticle exposure did not alter perivascular nerve stimulation (PVNS)-induced arteriolar constriction under normal conditions; however, adrenergic receptor inhibition revealed a more robust effect. Nanoparticle inhalation reduced arteriolar dilation in response to active hyperaemia (AH). In both PVNS and AH experiments, nitric oxide synthase (NOS) inhibition affected only controls. Whereas cyclooxygenase (COX) inhibition only attenuated AH-induced arteriolar dilation in nanoparticle-exposed animals. This group displayed an enhanced U46619 constriction and attenuated iloprost-induced dilation. Collectively, these studies indicate that nanoparticle exposure reduces microvascular NO bioavailability and alters COX-mediated vasoreactivity. Furthermore, the enhanced adrenergic receptor sensitivity suggests an augmented sympathetic responsiveness.

Nanoparticle inhalation alters systemic arteriolar vasoreactivity through sympathetic and cyclooxygenase-mediated pathways.

Xenobiotic particles can be considered in two genres: air pollution particulate matter and engineered nanoparticles. Particle exposures can occur in the greater environment, the workplace, and our homes. The majority of research in this field has, justifiably, focused on pulmonary reactions and outcomes. More recent investigations indicate that cardiovascular effects are capable of correlating with established mortality and morbidity epidemiological data following particle exposures. While the preliminary and general cardiovascular toxicology has been defined, the mechanisms behind these effects, specifically within the microcirculation, are largely unexplored. Therefore, the purpose of this review is several fold: first, a historical background on toxicological aspects of particle research is presented. Second, essential definitions, terminology, and techniques that may be unfamiliar to the microvascular scientist will be discussed. Third, the most current concepts and hypotheses driving cardiovascular research in this field will be reviewed. Lastly, potential future directions for the microvascular scientist will be suggested. Collectively speaking, microvascular research in the particle exposure field represents far more than a "niche." The immediate demand for basic, translational, and clinical studies is high and diverse. Microvascular scientists at all career stages are strongly encouraged to expand their research interests to include investigations associated with particle exposures.

Xenobiotic particle exposure and microvascular endpoints: a call to arms.

Air pollution PM is associated with cardiovascular morbidity and mortality. In Appalachia, PM from mining may represent a health burden to this sensitive population that leads the nation in cardiovascular disease, among others. Cardiovascular consequences following inhalation of PM(MTM) are unclear, but must be identified to establish causal effects.

Article	Year
Gasoline exhaust emissions induce vascular remodeling pathways involved in atherosclerosis. Toxicological sciences : an official journal of the Society of Toxicology\| PubMed ID: 17065432	2007
Fine oil combustion particle bioavailable constituents induce molecular profiles of oxidative stress, altered function, and cellular injury in cardiomyocytes. Journal of toxicology and environmental health. Part A\| PubMed ID: 17934955	2007
Diesel exhaust exposure enhances venoconstriction via uncoupling of eNOS. Toxicology and applied pharmacology\| PubMed ID: 18455212	2008
Vehicular emissions induce vascular MMP-9 expression and activity associated with endothelin-1-mediated pathways. Arteriosclerosis, thrombosis, and vascular biology\| PubMed ID: 19150882	2009
Impairment of coronary endothelial cell ET(B) receptor function after short-term inhalation exposure to whole diesel emissions. American journal of physiology. Regulatory, integrative and comparative physiology\| PubMed ID: 19535675	2009
Inhaled diesel emissions alter atherosclerotic plaque composition in ApoE(-/-) mice. Toxicology and applied pharmacology\| PubMed ID: 19891982	2010
A comparison of vascular effects from complex and individual air pollutants indicates a role for monoxide gases and volatile hydrocarbons. Environmental health perspectives\| PubMed ID: 20197249	2010
Formation of vascular S-nitrosothiols and plasma nitrates/nitrites following inhalation of diesel emissions. Journal of toxicology and environmental health. Part A\| PubMed ID: 21598168	2011
Nanoparticle inhalation alters systemic arteriolar vasoreactivity through sympathetic and cyclooxygenase-mediated pathways. Nanotoxicology\| PubMed ID: 21830860	2012
Xenobiotic particle exposure and microvascular endpoints: a call to arms. Microcirculation (New York, N.Y. : 1994)\| PubMed ID: 21951337	2012
Air pollution particulate matter collected from an appalachian mountaintop mining site induces microvascular dysfunction. Microcirculation (New York, N.Y. : 1994)\| PubMed ID: 22963349	2013

Travis L. Knuckles

Biography

JoVE Journal Publications

Other Publications