MMP-9-Dependent Serum-Borne Bioactivity Caused by Multiwalled Carbon Nanotube Exposure Induces Vascular Dysfunction via the CD36 Scavenger Receptor

Noise and Air Pollution as Risk Factors for Hypertension: Part II-Pathophysiologic Insight

Traffic noise and air pollution are environmental stressors found to increase risk for cardiovascular events. The burden of disease attributable to environmental stressors and cardiovascular disease globally is substantial, with a need to better understand the contribution of specific risk factors that may underlie these effects. Epidemiological observations and experimental evidence from animal models and human controlled exposure studies suggest an essential role for common mediating pathways. These include sympathovagal imbalance, endothelial dysfunction, vascular inflammation, increased circulating cytokines, activation of central stress responses, including hypothalamic and limbic pathways, and circadian disruption. Evidence also suggests that cessation of air pollution or noise through directed interventions alleviates increases in blood pressure and intermediate surrogate pathways, supporting a causal link. In the second part of this review, we discuss the current understanding of mechanisms underlying and current gaps in knowledge and opportunities for new research.

Aging influence on pulmonary and systemic inflammation and neural metabolomics arising from pulmonary multi-walled carbon nanotube exposure in apolipoprotein E-deficient and C57BL/6 female mice

OBJECTIVE

Environmental exposures exacerbate age-related pathologies, such as cardiovascular and neurodegenerative diseases. Nanoparticulates, and specifically carbon nanomaterials, are a fast-growing contributor to the category of inhalable pollutants, whose risks to health are only now being unraveled. The current study assessed the exacerbating effect of age on multiwalled-carbon nanotube (MWCNT) exposure in young and old C57BL/6 and ApoE-/- mice.

MATERIALS AND METHODS

Female C57BL/6 and apolipoprotein E-deficient (ApoE-/-) mice, aged 8 weeks and 15 months, were exposed to 0 or 40 µg MWCNT via oropharyngeal aspiration. Pulmonary inflammation, inflammatory bioactivity of serum, and neurometabolic changes were assessed at 24 h post-exposure.

RESULTS

Pulmonary neutrophil infiltration was induced by MWCNT in bronchoalveolar lavage fluid in both C57BL/6 and ApoE-/-. Macrophage counts decreased with MWCNT exposure in ApoE-/- mice but were unaffected by exposure in C57BL/6 mice. Older mice appeared to have greater MWCNT-induced total protein in lavage fluid. BALF cytokines and chemokines were elevated with MWCNT exposure, but CCL2, CXCL1, and CXCL10 showed reduced responses to MWCNT in older mice. However, no significant serum inflammatory bioactivity was detected. Cerebellar metabolic changes in response to MWCNT were modest, but age and strain significantly influenced metabolite profiles assessed. ApoE-/- mice and older mice exhibited less robust metabolite changes in response to exposure, suggesting a reduced health reserve.

CONCLUSIONS

Age influences the pulmonary and neurological responses to short-term MWCNT exposure. However, with only the model of moderate aging (15 months) in this study, the responses appeared modest compared to inhaled toxicant impacts in more advanced aging models.

Lung-Based, Exosome Inhibition Mediates Systemic Impacts Following Particulate Matter Exposure

Particulate matter (PM) exposure is a global health issue that impacts both urban and rural communities. Residential communities in the Southwestern United States have expressed concerns regarding the health impacts of fugitive PM from rural, legacy mine-sites. In addition, the recent literature suggests that exosomes may play a role in driving toxicological phenotypes following inhaled exposures. In this study, we assessed exosome-driven mechanisms and systemic health impacts following inhaled dust exposure, using a rodent model. Using an exosome inhibitor, GW4869 (10 μM), we inhibited exosome generation in the lungs of mice via oropharyngeal aspiration. We then exposed mice to previously characterized inhaled particulate matter (PM) from a legacy mine-site and subsequently assessed downstream behavioral, cellular, and molecular biomarkers in lung, serum, and brain tissue. Results indicated that CCL-2 was significantly upregulated in the lung tissue and downregulated in the brain (p < 0.05) following PM exposure. Additional experiments revealed cerebrovascular barrier integrity deficits and increased glial fibrillary acidic protein (GFAP) staining in the mine-PM exposure group, mechanistically dependent on exosome inhibition. An increased stress and anxiety response, based on the open-field test, was noted in the mine-PM exposure group, and subsequently mitigated with GW4869 intervention. Exosome lipidomics revealed 240 and eight significantly altered positive-ion lipids and negative-ion lipids, respectively, across the three treatment groups. Generally, phosphatidylethanolamine (PE) and phosphatidylcholine (PC) lipids were significantly downregulated in the PM group, compared to FA. In conclusion, these data suggest that systemic, toxic impacts of inhaled PM may be mechanistically dependent on lung-derived, circulating exosomes, thereby driving a systemic, proinflammatory phenotype.

Biological effects of crude oil vapor. IV. Cardiovascular effects

Workers in the oil and gas extraction industry are at risk of inhaling volatile organic compounds. Epidemiological studies suggest oil vapor inhalation may affect cardiovascular health. Thus, in this hazard identification study we investigated the effects of inhalation of crude oil vapor (COV) on cardiovascular function. Male rats were exposed to air or COV (300 ppm) for 6 h (acute), or 6 h/day × 4 d/wk. × 4 wk. (sub-chronic). The effects of COV inhalation were assessed 1, 28, and 90 d post-exposure. Acute exposure to COV resulted in reductions in mean arterial and diastolic blood pressures 1 and 28 d after exposure, changes in nitrate-nitrite and H₂O₂ levels, and in the expression of transcripts and proteins that regulate inflammation, vascular remodeling, and the synthesis of nitric oxide (NO) in the heart and kidneys. The sub-chronic exposure resulted in a reduced sensitivity to α₁-adrenoreceptor-mediated vasoconstriction in vitro 28 d post-exposure, and a reduction in oxidative stress in the heart. Sub-chronic COV exposure led to alterations in the expression of NO synthases and anti-oxidant enzymes, which regulate inflammation and oxidative stress in the heart and kidneys. There seems to be a balance between changes in the expression of transcripts associated with the generation of reactive oxygen species (ROS) and antioxidant enzymes. The ability of antioxidant enzymes to reduce or inhibit the effects of ROS may allow the cardiovascular system to adapt to acute COV exposures. However, sub-chronic exposures may result in longer-lasting negative health consequences on the cardiovascular system.

Indirect mediators of systemic health outcomes following nanoparticle inhalation exposure

The growing field of nanoscience has shed light on the wide diversity of natural and anthropogenic sources of nano-scale particulates, raising concern as to their impacts on human health. Inhalation is the most robust route of entry, with nanoparticles (NPs) evading mucociliary clearance and depositing deep into the alveolar region. Yet, impacts from inhaled NPs are evident far outside the lung, particularly on the cardiovascular system and highly vascularized organs like the brain. Peripheral effects are partly explained by the translocation of some NPs from the lung into the circulation; however, other NPs largely confined to the lung are still accompanied by systemic outcomes. Omic research has only just begun to inform on the complex myriad of molecules released from the lung to the blood as byproducts of pulmonary pathology. These indirect mediators are diverse in their molecular make-up and activity in the periphery. The present review examines systemic outcomes attributed to pulmonary NP exposure and what is known about indirect pathological mediators released from the lung into the circulation. Further focus was directed to outcomes in the brain, a highly vascularized region susceptible to acute and longer-term outcomes. Findings here support the need for big-data toxicological studies to understand what drives these health outcomes and better predict, circumvent, and treat the potential health impacts arising from NP exposure scenarios.

Neuroinflammatory and Neurometabolomic Consequences From Inhaled Wildfire Smoke-Derived Particulate Matter in the Western United States

Utilizing a mobile laboratory located >300 km away from wildfire smoke (WFS) sources, this study examined the systemic immune response profile, with a focus on neuroinflammatory and neurometabolomic consequences, resulting from inhalation exposure to naturally occurring wildfires in California, Arizona, and Washington in 2020. After a 20-day (4 h/day) exposure period in a mobile laboratory stationed in New Mexico, WFS-derived particulate matter (WFPM) inhalation resulted in significant neuroinflammation while immune activity in the peripheral (lung, bone marrow) appeared to be resolved in C57BL/6 mice. Importantly, WFPM exposure increased cerebrovascular endothelial cell activation and expression of adhesion molecules (VCAM-1 and ICAM-1) in addition to increased glial activation and peripheral immune cell infiltration into the brain. Flow cytometry analysis revealed proinflammatory phenotypes of microglia and peripheral immune subsets in the brain of WFPM-exposed mice. Interestingly, endothelial cell neuroimmune activity was differentially associated with levels of PECAM-1 expression, suggesting that subsets of cerebrovascular endothelial cells were transitioning to resolution of inflammation following the 20-day exposure. Neurometabolites related to protection against aging, such as NAD+ and taurine, were decreased by WFPM exposure. Additionally, increased pathological amyloid-beta protein accumulation, a hallmark of neurodegeneration, was observed. Neuroinflammation, together with decreased levels of key neurometabolites, reflect a cluster of outcomes with important implications in priming inflammaging and aging-related neurodegenerative phenotypes.

VCAM-1 Is Upregulated in Uranium Miners Compared to Other Miners

The United States has a rich history of mining including uranium (U)-mining, coal mining, and other metal mining. Cardiovascular diseases (CVD) are largely understudied in miners and recent literature suggests that when compared to non-U miners, U-miners are more likely to report CVD. However, the molecular basis for this phenomenon is currently unknown. In this pilot study, a New Mexico (NM)-based occupational cohort of current and former miners (n = 44) were recruited via a mobile screening clinic for miners. Serum- and endothelial-based endpoints were used to assess circulating inflammatory potential relevant to CVD. Non-U miners reported significantly fewer pack years of smoking than U-miners. Circulating biomarkers of interest revealed that U-miners had significantly greater serum amyloid A (SAA), soluble intercellular adhesion molecule 1 (ICAM-1, ng/mL), soluble vascular cell adhesion molecule 1 (VCAM-1, ng/mL), and VCAM-1 mRNA expression, as determined by the serum cumulative inflammatory potential (SCIP) assay, an endothelial-based assay. Even after adjusting for various covariates, including age, multivariable analysis determined that U-miners had significantly upregulated VCAM-1 mRNA. In conclusion, VCAM-1 may be an important biomarker and possible contributor of CVD in U-miners. Further research to explore this mechanism may be warranted.

Serum peptidome: diagnostic window into pathogenic processes following occupational exposure to carbon nanomaterials

BACKGROUND

Growing industrial use of carbon nanotubes and nanofibers (CNT/F) warrants consideration of human health outcomes. CNT/F produces pulmonary, cardiovascular, and other toxic effects in animals along with a significant release of bioactive peptides into the circulation, the augmented serum peptidome. While epidemiology among CNT/F workers reports on few acute symptoms, there remains concern over sub-clinical CNT/F effects that may prime for chronic disease, necessitating sensitive health outcome diagnostic markers for longitudinal follow-up.

METHODS

Here, the serum peptidome was assessed for its biomarker potential in detecting sub-symptomatic pathobiology among CNT/F workers using label-free data-independent mass spectrometry. Studies employed a stratified design between High (> 0.5 µg/m3) and Low (< 0.1 µg/m3) inhalable CNT/F exposures in the industrial setting. Peptide biomarker model building and refinement employed linear regression and partial least squared discriminant analyses. Top-ranked peptides were then sequence identified and evaluated for pathological-relevance.

RESULTS

In total, 41 peptides were found to be highly discriminatory after model building with a strong linear correlation to personal CNT/F exposure. The top-five peptide model offered ideal prediction with high accuracy (Q2 = 0.99916). Unsupervised validation affirmed 43.5% of the serum peptidomic variance was attributable to CNT/F exposure. Peptide sequence identification reveals a predominant association with vascular pathology. ARHGAP21, ADAM15 and PLPP3 peptides suggest heightened cardiovasculature permeability and F13A1, FBN1 and VWDE peptides infer a pro-thrombotic state among High CNT/F workers.

CONCLUSIONS

The serum peptidome affords a diagnostic window into sub-symptomatic pathology among CNT/F exposed workers for longitudinal monitoring of systemic health risks.

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.

Carbon Nanotube Exposure Triggers a Cerebral Peptidomic Response: Barrier Compromise, Neuroinflammation, and a Hyperexcited State

The unique physicochemical properties of carbon nanomaterials and their ever-growing utilization generate a serious concern for occupational risk. Pulmonary exposure to these nanoparticles induces local and systemic inflammation, cardiovascular dysfunction, and even cognitive deficits. Although multiple routes of extrapulmonary toxicity have been proposed, the mechanism for and manner of neurologic effects remain minimally understood. Here, we examine the cerebral spinal fluid (CSF)-derived peptidomic fraction as a reflection of neuropathological alterations induced by pulmonary carbon nanomaterial exposure. Male C57BL/6 mice were exposed to 10 or 40 µg of multiwalled carbon nanotubes (MWCNT) by oropharyngeal aspiration. Serum and CSFs were collected 4 h post exposure. An enriched peptide fraction of both biofluids was analyzed using ion mobility-enabled data-independent mass spectrometry for label-free quantification. MWCNT exposure induced a prominent peptidomic response in the blood and CSF; however, correlation between fluids was limited. Instead, we determined that a MWCNT-induced peptidomic shift occurred specific to the CSF with 292 significant responses found that were not in serum. Identified MWCNT-responsive peptides depicted a mechanism involving aberrant fibrinolysis (fibrinopeptide A), blood-brain barrier permeation (homeobox protein A4), neuroinflammation (transmembrane protein 131L) with reactivity by astrocytes and microglia, and a pro-degradative (signal transducing adapter molecule, phosphoglycerate kinase), antiplastic (AF4/FMR2 family member 1, vacuolar protein sorting-associated protein 18) state with the excitation-inhibition balance shifted to a hyperexcited (microtubule-associated protein 1B) phenotype. Overall, the significant pathologic changes observed were consistent with early neurodegenerative disease and were diagnostically reflected in the CSF peptidome.

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.

Mine-site derived particulate matter exposure exacerbates neurological and pulmonary inflammatory outcomes in an autoimmune mouse model

The Southwestern United States has a legacy of industrial mining due to the presence of rich mineral ore deposits. The relationship between environmental inhaled particulate matter (PM) exposures and neurological outcomes within an autoimmune context is understudied. The aim of this study was to compare two regionally-relevant dusts from high-priority abandoned mine-sites, Claim 28 PM, from Blue Gap Tachee, AZ and St. Anthony mine PM, from the Pueblo of Laguna, NM and to expose autoimmune-prone mice (NZBWF1/J). Mice were randomly assigned to one of three groups (n = 8/group): DM (dispersion media, control), Claim 28 PM, or St. Anthony PM, subjected to oropharyngeal aspiration of (100 µg/50 µl), once per week for a total of 4 consecutive doses. A battery of immunological and neurological endpoints was assessed at 24 weeks of age including: bronchoalveolar lavage cell counts, lung gene expression, brain immunohistochemistry, behavioral tasks and serum autoimmune biomarkers. Bronchoalveolar lavage results demonstrated a significant increase in number of polymorphonuclear neutrophils following Claim 28 and St. Anthony mine PM aspiration. Lung mRNA expression showed significant upregulation in CCL-2 and IL-1ß following St. Anthony mine PM aspiration. In addition, neuroinflammation was present in both Claim 28 and St. Anthony mine-site derived PM exposure groups. Behavioral tasks resulted in significant deficits as determined by Y-maze new arm frequency following Claim 28 aspiration. Neutrophil elastase was significantly upregulated in the St. Anthony mine exposure group. Interestingly, there were no significant changes in serum autoantigens suggesting systemic inflammatory effects may be mediated through other molecular mechanisms following low-dose PM exposures.

Bioactivity of Circulatory Factors After Pulmonary Exposure to Mild or Stainless Steel Welding Fumes

Studies suggest that alterations in circulating factors are a driver of pulmonary-induced cardiovascular dysfunction. To evaluate, if circulating factors effect endothelial function after a pulmonary exposure to welding fumes, an exposure known to induce cardiovascular dysfunction, serum collected from Sprague Dawley rats 24 h after an intratracheal instillation exposure to 2 mg/rat of 2 compositionally distinct metal-rich welding fume particulates (manual metal arc welding using stainless steel electrodes [MMA-SS] or gas metal arc welding using mild steel electrodes [GMA-MS]) or saline was used to test molecular and functional effects of in vitro cultures of primary cardiac microvascular endothelial cells (PCMEs) or ex vivo organ cultures. The welding fumes elicited significant pulmonary injury and inflammation with only minor changes in measured serum antioxidant and cytokine levels. PCME cells were challenged for 4 h with serum collected from exposed rats, and 84 genes related to endothelial function were analyzed. Changes in relative mRNA patterns indicated that serum from rats exposed to MMA-SS, and not GMA-MS or PBS, could influence several functional aspects related to endothelial cells, including cell migration, angiogenesis, inflammation, and vascular function. The predictions were confirmed using a functional in vitro assay (scratch assay) as well as an ex vivo multicellular environment (aortic ring angiogenesis assay), validating the concept that endothelial cells can be used as an effective screening tool of exposed workers for determining bioactivity of altered circulatory factors. Overall, the results indicate that pulmonary MMA-SS fume exposure can cause altered endothelial function systemically via altered circulating factors.

Serum-borne factors alter cerebrovascular endothelial microRNA expression following particulate matter exposure near an abandoned uranium mine on the Navajo Nation

Background

Commercial uranium mining on the Navajo Nation has subjected communities on tribal lands in the Southwestern United States to exposures from residual environmental contamination. Vascular health effects from these ongoing exposures are an active area of study. There is an association between residential mine-site proximity and circulating biomarkers in residents, however, the contribution of mine-site derived wind-blown dusts on vascular and other health outcomes is unknown. To assess neurovascular effects of mine-site derived dusts, we exposed mice using a novel exposure paradigm, the AirCARE1 mobile inhalation laboratory, located 2 km from an abandoned uranium mine, Claim 28 in Blue Gap Tachee, AZ. Mice were exposed to filtered air (FA) (n = 6) or concentrated ambient particulate matter (CAPs) (n = 5) for 2 wks for 4 h per day.

Results

To assess miRNA differential expression in cultured mouse cerebrovascular cells following particulate matter (PM) exposure (average: 96.6 ± 60.4 μg/m³ for all 4 h exposures), the serum cumulative inflammatory potential (SCIP) assay was employed. MiRNA sequencing was then performed in cultured mouse cerebrovascular endothelial cells (mCECs) to evaluate transcriptional changes. Results indicated 27 highly differentially expressed (p < 0.01) murine miRNAs, as measured in the SCIP assay. Gene ontology (GO) pathway analysis revealed notable alterations in GO enrichment related to the cytoplasm, protein binding and the cytosol, while significant KEGG pathways involved pathways in cancer, axon guidance and Wnt signaling. Expression of these 27 identified, differentially expressed murine miRNAs were then evaluated in the serum. Nine of these miRNAs (~ 30%) were significantly altered in the serum and 8 of those miRNAs demonstrated the same directional change (either upregulation or downregulation) as cellular miRNAs, as measured in the SCIP assay. Significantly upregulated miRNAs in the CAPs exposure group included miRNAs in the let-7a family. Overexpression of mmu-let-7a via transfection experiments, suggested that this miRNA may mediate mCEC barrier integrity following dust exposure.

Conclusions

Our data suggest that mCEC miRNAs as measured in the SCIP assay show similarity to serum-borne miRNAs, as approximately 30% of highly differentially expressed cellular miRNAs in the SCIP assay were also found in the serum. While translocation of miRNAs via exosomes or an alternative mechanism is certainly possible, other yet-to-be-identified factors in the serum may be responsible for significant miRNA differential expression in endothelium following inhaled exposures. Additionally, the most highly upregulated murine miRNAs in the CAPs exposure group were in the let-7a family. These miRNAs play a prominent role in cell growth and differentiation and based on our transfection experiments, mmu-let-7a may contribute to cerebrovascular mCEC alterations following inhaled dust exposure.

Vehicular Particulate Matter (PM) Characteristics Impact Vascular Outcomes Following Inhalation

Roadside proximity and exposure to mixed vehicular emissions (MVE) have been linked to adverse pulmonary and vascular outcomes. However, because of the complex nature of the contribution of particulate matter (PM) versus gases, it is difficult to decipher the precise causative factors regarding PM and the copollutant gaseous fraction. To this end, C57BL/6 and apolipoprotein E knockout mice (ApoE-/-) were exposed to either filtered air (FA), fine particulate (FP), FP+gases (FP+G), ultrafine particulate (UFP), or UFP+gases (UFP+G). Two different timeframes were employed: 1-day (acute) or 30-day (subchronic) exposures. Examined biological endpoints included aortic vasoreactivity, aortic lesion quantification, and aortic mRNA expression. Impairments in vasorelaxation were observed following acute exposure to FP+G in C57BL/6 animals and FP, UFP, and UFP+G in ApoE-/- animals. These effects were completely abrogated or markedly reduced following subchronic exposure. Aortic lesion quantification in ApoE-/- animals indicated a significant increase in atheroma size in the UFP-, FP-, and FP+G-exposed groups. Additionally, ApoE-/- mice demonstrated a significant fold increase in TNFα expression following FP+G exposure and ET-1 following UFP exposure. Interestingly, C57BL/6 aortic gene expression varied widely across exposure groups. TNFα decreased significantly following FP exposure and CCL-5 decreased in the UFP-, FP-, and FP+G-exposed groups. Conversely, ET-1, CCL-2, and CXCL-1 were all significantly upregulated in the FP+G group. These findings suggest that gas-particle interactions may play a role in vascular toxicity, but the contribution of surface area is not clear.

Telomere length and genotoxicity in the lung of rats following intragastric exposure to food-grade titanium dioxide and vegetable carbon particles

Vegetable carbon (E153) and titanium dioxide (E171) are widely used as black and white food colour additives. The aim of this study was to assess gastrointestinal tight junction and systemic genotoxic effects in rats following exposure to E153 and E171 for 10 weeks by oral gavage once a week. The expression of tight junction proteins was assessed in intestinal tissues. Levels of DNA strand breaks, oxidatively damaged DNA and telomere length were assessed in secondary organs. Hydrodynamic suspensions of E153 and E173 indicated mean particles sizes of 230 and 270 nm, respectively, and only E153 gave rise to intracellular production of reactive oxygen species in colon epithelial (Caco-2) cells. Rats exposed to E153 (6.4 mg/kg/week) or E171 (500 mg/kg/week) had decreased gene expression of the tight junction protein TJP1 (P < 0.05). E153 (6.4 mg/kg/week) also decreased OCLN (P < 0.05) in the colon and occludin protein expression in the small intestine (P < 0.05). Furthermore, E153 or E171 exposed rats had shorter telomeres in the lung (P < 0.05). Plasma from particle-exposed rats also produced telomere shortening in cultured lung epithelial cells. There were unaltered levels of oxidatively damaged DNA in the liver and lung and no changes in the DNA repair activity of oxidatively damaged DNA in the lung. Altogether, these results indicate that intragastric exposure to E153 and E171 is associated with reduced tight junction protein expression in the intestinal barrier and telomere length shortening in the lung in rats.

Toxic Effects of Particulate Matter Derived from Dust Samples Near the Dzhidinski Ore Processing Mill, Eastern Siberia, Russia

Ambient particulate matter (PM) is associated with increased mortality and morbidity, an effect influenced by the metal components of the PM. We characterized five sediment samples obtained near a tungsten-molybdenum ore-processing complex in Zakamensk, Russia for elemental composition and PM toxicity with regard to pulmonary, vascular, and neurological outcomes. Elemental and trace metals analysis of complete sediment and PM₁₀ (the respirable fraction, < 10 µm mass mean aerodynamic diameter) were performed using inductively coupled plasma optical emission spectrometry (ICP-OES) and mass spectrometry (ICP-MS). Sediment samples and PM₁₀ consisted largely of silicon and iron and silicon and sodium, respectively. Trace metals including manganese and uranium in the complete sediment, as well as copper and lead in the PM₁₀ were observed. Notably, metal concentrations were approximately 10 × higher in the PM₁₀ than in the sediment. Exposure to 100 µg of PM₁₀ via oropharyngeal aspiration in C56BL/6 mice resulted in pulmonary inflammation across all groups. In addition, mice exposed to three of the five PM₁₀ samples exhibited impaired endothelial-dependent relaxation, and correlative analysis revealed associations between pulmonary inflammation and levels of lead and cadmium. A tendency for elevated cortical ccl2 and Tnf-α mRNA expression was induced by all samples and significant upregulation was noted following exposure to PM₁₀ samples Z3 and Z4, respectively. Cortical Nqo1 mRNA levels were significantly upregulated in mice exposed to PM₁₀ Z2. In conclusion, pulmonary exposure to PM samples from the Zakamensk region sediments induced varied pulmonary and systemic effects that may be influenced by elemental PM composition. Further investigation is needed to pinpoint putative drivers of neurological outcomes.

Association of occupational exposures with ex vivo functional immune response in workers handling carbon nanotubes and nanofibers

The objective of this study was to evaluate the association between carbon nanotube and nanofiber (CNT/F) exposure and ex vivo responses of whole blood challenged with secondary stimulants, adjusting for potential confounders, in a cross-sectional study of 102 workers. Multi-day exposure was measured by CNT/F structure count (SC) and elemental carbon (EC) air concentrations. Demographic, lifestyle and other occupational covariate data were obtained via questionnaire. Whole blood collected from each participant was incubated for 18 hours with and without two microbial stimulants (lipopolysaccharide/LPS and staphylococcal enterotoxin type B/SEB) using TruCulture technology to evaluate immune cell activity. Following incubation, supernatants were preserved and analyzed for protein concentrations. The stimulant:null response ratio for each individual protein was analyzed using multiple linear regression, followed by principal component (PC) analysis to determine whether patterns of protein response were related to CNT/F exposure. Adjusting for confounders, CNT/F metrics (most strongly, the SC-based) were significantly (p < 0.05) inversely associated with stimulant:null ratios of several individual biomarkers: GM-CSF, IFN-γ, interleukin (IL)-2, IL-4, IL-5, IL-10, IL-17, and IL-23. CNT/F metrics were significantly inversely associated with PC1 (a weighted mean of most biomarkers, explaining 25% of the variance in the protein ratios) and PC2 (a biomarker contrast, explaining 14%). Among other occupational exposures, only solvent exposure was significant (inversely related to PC2). CNT/F exposure metrics were uniquely related to stimulant responses in challenged whole blood, illustrating reduced responsiveness to a secondary stimulus. This approach, if replicated in other exposed populations, may present a relatively sensitive method to evaluate human response to CNT/F or other occupational exposures.

Airway Exposure to Modified Multi-walled Carbon Nanotubes Perturbs Cardiovascular Adenosinergic Signaling in Mice

The broad list of commercial applications for multi-walled carbon nanotubes (MWCNT) can be further expanded with the addition of various surface chemistry modifications. For example, standard commercial grade MWCNT (C-grade) can be carboxylated (COOH) or nitrogen-doped (N-doped) to suite specific utilities. We previously reported dose-dependent expansions of cardiac ischemia/reperfusion (I/R) injury, 24 h after intratracheal instillation of C-grade, COOH, or N-doped MWCNT in mice. Here, we have tested the hypothesis that airway exposure to MWCNT perturbs cardiovascular adenosinergic signaling, which could contribute to exacerbation of cardiac I/R injury. 100 µL of Vehicle or identical suspension volumes containing 100 µg of C-grade, COOH, or N-doped MWCNT were instilled into the trachea of CD-1 ICR mice. 1 day later, we measured cyclic adenosine monophosphate (cAMP) concentrations in cardiac tissue and evaluated arterial adenosinergic smooth muscle signaling mechanisms related to nitric oxide synthase (NOS) and cyclooxygenase (COX) in isolated aortic tissue. We also verified cardiac I/R injury expansion and examined both lung histology and bronchoalveolar lavage fluid cellularity in MWCNT exposed mice. Myocardial cAMP concentrations were reduced (p < 0.05) in the C-grade group by 17.4% and N-doped group by 13.7% compared to the Vehicle group. Curve fits to aortic ring 2-Cl-Adenosine concentration responses were significantly greater in the MWCNT groups vs. the Vehicle group. Aortic constrictor responses were more pronounced with NOS inhibition and were abolished with COX inhibition. These findings indicate that addition of functional chemical moieties on the surface of MWCNT may alter the biological responses to exposure by influencing cardiovascular adenosinergic signaling and promoting cardiac injury.

Multi-Walled Carbon Nanotube-Induced Gene Expression Biomarkers for Medical and Occupational Surveillance

As the demand for multi-walled carbon nanotube (MWCNT) incorporation into industrial and biomedical applications increases, so does the potential for unintentional pulmonary MWCNT exposure, particularly among workers during manufacturing. Pulmonary exposure to MWCNTs raises the potential for development of lung inflammation, fibrosis, and cancer among those exposed; however, there are currently no effective biomarkers for detecting lung fibrosis or predicting the risk of lung cancer resulting from MWCNT exposure. To uncover potential mRNAs and miRNAs that could be used as markers of exposure, this study compared in vivo mRNA and miRNA expression in lung tissue and blood of mice exposed to MWCNTs with in vitro mRNA and miRNA expression from a co-culture model of human lung epithelial and microvascular cells, a system previously shown to have a higher overall genome-scale correlation with mRNA expression in mouse lungs than either cell type grown separately. Concordant mRNAs and miRNAs identified by this study could be used to drive future studies confirming human biomarkers of MWCNT exposure. These potential biomarkers could be used to assess overall worker health and predict the occurrence of MWCNT-induced diseases.

Nanoparticle exposure driven circulating bioactive peptidome causes systemic inflammation and vascular dysfunction

Background

The mechanisms driving systemic effects consequent pulmonary nanoparticle exposure remain unclear. Recent work has established the existence of an indirect process by which factors released from the lung into the circulation promote systemic inflammation and cellular dysfunction, particularly on the vasculature. However, the composition of circulating contributing factors and how they are produced remains unknown. Evidence suggests matrix protease involvement; thus, here we used a well-characterized multi-walled carbon nanotube (MWCNT) oropharyngeal aspiration model with known vascular effects to assess the distinct contribution of nanoparticle-induced peptide fragments in driving systemic pathobiology.

Results

Data-independent mass spectrometry enabled the unbiased quantitative characterization of 841 significant MWCNT-responses within an enriched peptide fraction, with 567 of these factors demonstrating significant correlation across animal-paired bronchoalveolar lavage and serum biofluids. A database search curated for known matrix protease substrates and predicted signaling motifs enabled identification of 73 MWCNT-responsive peptides, which were significantly associated with an abnormal cardiovascular phenotype, extracellular matrix organization, immune-inflammatory processes, cell receptor signaling, and a MWCNT-altered serum exosome population. Production of a diverse peptidomic response was supported by a wide number of upregulated matrix and lysosomal proteases in the lung after MWCNT exposure. The peptide fraction was then found bioactive, producing endothelial cell inflammation and vascular dysfunction ex vivo akin to that induced with whole serum. Results implicate receptor ligand functionality in driving systemic effects, exemplified by an identified 59-mer thrombospondin fragment, replete with CD36 modulatory motifs, that when synthesized produced an anti-angiogenic response in vitro matching that of the peptide fraction. Other identified peptides point to integrin ligand functionality and more broadly to a diversity of receptor-mediated bioactivity induced by the peptidomic response to nanoparticle exposure.

Conclusion

The present study demonstrates that pulmonary-sequestered nanoparticles, such as multi-walled carbon nanotubes, acutely upregulate a diverse profile of matrix proteases, and induce a complex peptidomic response across lung and blood compartments. The serum peptide fraction, having cell-surface receptor ligand properties, conveys peripheral bioactivity in promoting endothelial cell inflammation, vasodilatory dysfunction and inhibiting angiogenesis. Results here establish peptide fragments as indirect, non-cytokine mediators and putative biomarkers of systemic health outcomes from nanoparticle exposure.

Respirable Uranyl-Vanadate-Containing Particulate Matter Derived From a Legacy Uranium Mine Site Exhibits Potentiated Cardiopulmonary Toxicity

Exposure to windblown particulate matter (PM) arising from legacy uranium (U) mine sites in the Navajo Nation may pose a human health hazard due to their potentially high metal content, including U and vanadium (V). To assess the toxic impact of PM derived from Claim 28 (a priority U mine) compared with background PM, and consider the putative role of metal species U and V. Two representative sediment samples from Navajo Nation sites (Background PM and Claim 28 PM) were obtained, characterized in terms of chemistry and morphology, and fractioned to the respirable (≤ 10 μm) fraction. Mice were dosed with either PM sample, uranyl acetate, or vanadyl sulfate via aspiration (100 µg), with assessments of pulmonary and vascular toxicity 24 h later. Particulate matter samples were also examined for in vitro effects on cytotoxicity, oxidative stress, phagocytosis, and inflammasome induction. Claim 28 PM10 was highly enriched with U and V and exhibited a unique nanoparticle ultrastructure compared with background PM10. Claim 28 PM10 exhibited enhanced pulmonary and vascular toxicity relative to background PM10. Both U and V exhibited complementary pulmonary inflammatory potential, with U driving a classical inflammatory cytokine profile (elevated interleukin [IL]-1β, tumor necrosis factor-α, and keratinocyte chemoattractant/human growth-regulated oncogene) while V preferentially induced a different cytokine pattern (elevated IL-5, IL-6, and IL-10). Claim 28 PM10 was more potent than background PM10 in terms of in vitro cytotoxicity, impairment of phagocytosis, and oxidative stress responses. Resuspended PM10 derived from U mine waste exhibit greater cardiopulmonary toxicity than background dusts. Rigorous exposure assessment is needed to gauge the regional health risks imparted by these unremediated sites.

Current state of knowledge on the health effects of engineered nanomaterials in workers: a systematic review of human studies and epidemiological investigations

Objectives The widespread application of nano-enabled products and the increasing likelihood for workplace exposures make understanding engineered nanomaterial (ENM) effects in exposed workers a public and occupational health priority. The aim of this study was to report on the current state of knowledge on possible adverse effects induced by ENM in humans to determine the toxicological profile of each type of ENM and potential biomarkers for early detection of such effects in workers. Methods A systematic review of human studies and epidemiological investigations of exposed workers relative to the possible adverse effects for the most widely used ENM was performed through searches of major scientific databases including Web of Science, Scopus, and PubMed. Results Twenty-seven studies were identified. Most of the epidemiological investigations were cross-sectional. The review found limited evidence of adverse effects in workers exposed to the most commonly used ENM. However, some biological alterations are suggestive for possible adverse impacts. The primary targets of some ENM exposures were the respiratory and cardiovascular systems. Changes in biomarker levels compared with controls were also observed; however, limited exposure data and the relatively short period since the first exposure may have influenced the incidence of adverse effects found in epidemiological studies. Conclusions There is a need for longitudinal epidemiologic investigations with clear exposure characterizations for various ENM to discover potential adverse health effects and identify possible indicators of early biological alterations. In this state of uncertainty, precautionary controls for each ENM are warranted while further study of potential health effects continues.

Comparison of multi-wall carbon nanotube and nitrogen-doped multi-wall carbon nanotube effects on lung function and airway reactivity in rats

Incorporation of multi-wall carbon nanotubes (MWCNT) into materials has raised concerns about their potential hazards to manufacturing workers. In animal models, airway inflammation and lung fibrosis follow aspiration, instillation, and inhalation exposures to MWCNT. However, the effects of MWCNT on pulmonary function, airway reactivity and airway epithelium function following inhalation exposure has not been studied. We investigated whether inhaled MWCNT affects lung resistance (R_L) and dynamic compliance (C_dyn), reactivity to inhaled methacholine (MCh), epithelial regulation of airway reactivity to MCh in vitro, and airway epithelial ion transport. Male rats were exposed by whole body inhalation for 6 h to air or aerosolized MWCNT (0.5, 1 or 5 mg/m³) for one or nine days. Eighteen h after 1 d exposure to 5 mg/m³ MWCNT, basal R_L was increased and basal C_dyn was decreased; changes did not persist for 7 d. Reactivity to MCh (R_L) was increased and C_dyn responses were decreased at 18 h, but not 7 d after exposure to 1 and 5 mg/m³ MWCNT. The effects of i.t.-instilled MWCNT and nitrogen-doped MWCNT (N-MWCNT) on pulmonary function and reactivity to MCh at doses comparable to deposition after inhalation of 5 mg/m³ at 1 d and 0.5, 1, and 5 mg/m³ MWCNT 9 d-exposures were compared. Both nanoparticles increased airway reactivity (R_L); N-MWCNT did not affect C_dyn responses. Lung function and airway reactivity are altered following a single MWCNT inhalation and generally subside over time. Given i.t., MWCNT's and N-MWCNT's effects were comparable, but N-MWCNT evoke smaller changes in C_dyn responses.

Microvascular Dysfunction Following Multiwalled Carbon Nanotube Exposure Is Mediated by Thrombospondin-1 Receptor CD47

Pulmonary exposure to multiwalled carbon nanotubes (MWCNTs) disrupts peripheral microvascular function. Thrombospondin-1 (TSP-1) is highly expressed during lung injury and has been shown to alter microvascular reactivity. It is unclear exactly how TSP-1 exerts effects on vascular function, but we hypothesized that the TSP-1 receptor CD47 may mediate changes in vasodilation. Wildtype (WT) or CD47 knockout (CD47 KO) C57B6/J-background animals were exposed to 50 µg of MWCNT or saline control via pharyngeal aspiration. Twenty-four hours postexposure, intravital microscopy was performed to assess arteriolar dilation and venular leukocyte adhesion and rolling. To assess tissue redox status, electron paramagnetic resonance and NOx measurements were performed, while inflammatory biomarkers were measured via multiplex assay.Vasodilation was impaired in the WT + MWCNT group compared with control (57 ± 9 vs 90 ± 2% relaxation), while CD47 KO animals showed no impairment (108 ± 8% relaxation). Venular leukocyte adhesion and rolling increased by >2-fold, while the CD47 KO group showed no change. Application of the antioxidant apocynin rescued normal leukocyte activity in the WT + MWCNT group. Lung and plasma NOx were reduced in the WT + MWCNT group by 47% and 32%, respectively, while the CD47 KO groups were unchanged from control. Some inflammatory cytokines were increased in the CD47 + MWCNT group only. In conclusion, TSP-1 is an important ligand mediating MWCNT-induced microvascular dysfunction, and CD47 is a component of this dysregulation. CD47 activation likely disrupts nitric oxide (•NO) signaling and promotes leukocyte-endothelial interactions. Impaired •NO production, signaling, and bioavailability is linked to a variety of cardiovascular diseases in which TSP-1/CD47 may play an important role.

The effects of subacute inhaled multi-walled carbon nanotube exposure on signaling pathways associated with cholesterol transport and inflammatory markers in the vasculature of wild-type mice

Exposure to multi-walled carbon nanotubes (MWCNTs) has been associated with detrimental cardiovascular outcomes; however, underlying mechanisms have not yet been fully elucidated. Thus, we investigated alterations in proatherogenic and proinflammatory signaling pathways in C57Bl6/ mice exposed to MWCNTs (1 mg/m³) or filtered air (FA-Controls), via inhalation, for 6 h/day, 14d. Expression of mediators of cholesterol transport, namely the lectin-like oxidized low-density lipoprotein receptor (LOX)-1 and ATP-binding cassette transporter (ABCA)-1, inflammatory markers tumor necrosis factor (TNF)-α and interleukin (IL)-1β/IL-6, nuclear-factor kappa-light-chain-enhancer of activated B cells (NF-κB), intracellular/vascular adhesion molecule(s) (VCAM-1, ICAM-1), and miRNAs (miR-221/-21/-1), associated with cardiovascular disease (CVD), were analyzed in cardiac tissue and coronary vasculature. Cardiac fibrotic deposition, matrix-metalloproteinases (MMP)-2/9, and reactive oxygen species (ROS) were also assessed. MWCNT-exposure resulted in increased coronary ROS production with concurrent increases in expression of LOX-1, VCAM-1, TNF-α, and MMP-2/9 activity; while ABCA-1 expression was downregulated, compared to FA-Controls. Additionally, trends in fibrotic deposition and induction of cardiac TNF-α, MMP-9, IκB Kinase (IKK)-α/β, and miR-221 mRNA expression were observed. Analysis using inhibitors for nitric oxide synthase or NADPH oxidase resulted in attenuated coronary ROS production. These findings suggest that subacute inhalation MWCNT-exposure alters expression of cholesterol transporter/receptors, and induces signaling pathways associated with inflammation, oxidative stress, and CVD in wild-type mice.

Carbon nanotube and nanofiber exposure and sputum and blood biomarkers of early effect among U.S. workers

BACKGROUND

Carbon nanotubes and nanofibers (CNT/F) are increasingly used for diverse applications. Although animal studies suggest CNT/F exposure may cause deleterious health effects, human epidemiological studies have typically been small, confined to single workplaces, and limited in exposure assessment.

OBJECTIVES

We conducted an industrywide cross-sectional epidemiological study of 108 workers from 12 U.S. sites to evaluate associations between occupational CNT/F exposure and sputum and blood biomarkers of early effect.

METHODS

We assessed CNT/F exposure via personal breathing zone, filter-based air sampling to measure background-corrected elemental carbon (EC) (a CNT/F marker) mass and microscopy-based CNT/F structure count concentrations. We measured 36 sputum and 37 blood biomarkers. We used factor analyses with varimax rotation to derive factors among sputum and blood biomarkers separately. We used linear, Tobit, and unconditional logistic regression models to adjust for potential confounders and evaluate associations between CNT/F exposure and individual biomarkers and derived factors.

RESULTS

We derived three sputum and nine blood biomarker factors that explained 78% and 67%, respectively, of the variation. After adjusting for potential confounders, inhalable EC and total inhalable CNT/F structures were associated with the most sputum and blood biomarkers, respectively. Biomarkers associated with at least three CNT/F metrics were 72 kDa type IV collagenase/matrix metalloproteinase-2 (MMP-2), interleukin-18, glutathione peroxidase (GPx), myeloperoxidase, and superoxide dismutase (SOD) in sputum and MMP-2, matrix metalloproteinase-9, metalloproteinase inhibitor 1/tissue inhibitor of metalloproteinases 1, 8-hydroxy-2'-deoxyguanosine, GPx, SOD, endothelin-1, fibrinogen, intercellular adhesion molecule 1, vascular cell adhesion protein 1, and von Willebrand factor in blood, although directions of associations were not always as expected.

CONCLUSIONS

Inhalable rather than respirable CNT/F was more consistently associated with fibrosis, inflammation, oxidative stress, and cardiovascular biomarkers.

Thrombospondin-1, Free Radicals, and the Coronary Microcirculation: The Aging Conundrum

SIGNIFICANCE

Successful matching of cardiac metabolism to perfusion is accomplished primarily through vasodilation of the coronary resistance arterioles, but the mechanism that achieves this effect changes significantly as aging progresses and involves the contribution of reactive oxygen species (ROS). Recent Advances: A matricellular protein, thrombospondin-1 (Thbs-1), has been shown to be a prolific contributor to the production and modulation of ROS in large conductance vessels and in the peripheral circulation. Recently, the presence of physiologically relevant circulating Thbs-1 levels was proven to also disrupt vasodilation to nitric oxide (NO) in coronary arterioles from aged animals, negatively impacting coronary blood flow reserve.

CRITICAL ISSUES

This review seeks to reconcile how ROS can be successfully utilized as a substrate to mediate vasoreactivity in the coronary microcirculation as "normal" aging progresses, but will also examine how Thbs-1-induced ROS production leads to dysfunctional perfusion and eventual ischemia and why this is more of a concern in advancing age.

FUTURE DIRECTIONS

Current therapies that may effectively disrupt Thbs-1 and its receptor CD47 in the vascular wall and areas for future exploration will be discussed. Antioxid. Redox Signal. 27, 785-801.

Thrombospondin-1 and microRNA-1 expression in response to multiwalled carbon nanotubes in alveolar epithelial cells

Thrombospondin-1 (TSP-1) is a glycoprotein that plays a role in extracellular matrix (ECM) remodeling. Previously, we have shown that multiwalled carbon nanotubes (MWCNT) regulate ECM components TGFβ and its target Col3A1 in alveolar epithelial cells. In this study, we investigated the effect of MWCNT on TSP-1 and microRNA-1 (miR-1) in the regulation of TGFβ in ECM remodeling using alveolar epithelial A549 cells. A549 cells were treated with MWCNT (20 or 50 µg/mL) for 6 or 24 h and the expression of TSP-1 and miR-1, and the exogenous miR-1 effect on cell morphology were analyzed. MWCNT induced in a time- and dose-dependent manner the expression of TSP-1. miR-1 was suppressed by MWCNT after 6 or 24 h of treatment regardless of the dose. TSP-1 and miR-1 negatively correlated with each other, r = -0.58. Exogenous administration of miR-1 induced alveolar epithelial cell morphology changes including cell clustering, whereas inhibition of miR-1 induced less cell to cell contact, cell rounding, and cellular projections. IntAct molecular network interactions analysis revealed that TSP-1 interacts with 21 molecular factors including ECM genes, and molecules. These results indicate a relationship between that TSP-1, MWCNT, and TGFβ, and suggest TSP-1 may play a role in MWCNT-induced TGFβ and ECM remodeling. Moreover, these data also suggest an inverse relationship between TSP-1 and miR-1 and a potential role of miR-1 in MWCNT-induced fibrotic signaling. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1596-1606, 2017.

Serum-borne bioactivity caused by pulmonary multiwalled carbon nanotubes induces neuroinflammation via blood-brain barrier impairment

Pulmonary exposure to multiwalled carbon nanotubes (MWCNTs) causes indirect systemic inflammation through unknown pathways. MWCNTs translocate only minimally from the lungs into the systemic circulation, suggesting that extrapulmonary toxicity may be caused indirectly by lung-derived factors entering the circulation. To assess a role for MWCNT-induced circulating factors in driving neuroinflammatory outcomes, mice were acutely exposed to MWCNTs (10 or 40 µg/mouse) via oropharyngeal aspiration. At 4 h after MWCNT exposure, broad disruption of the blood-brain barrier (BBB) was observed across the capillary bed with the small molecule fluorescein, concomitant with reactive astrocytosis. However, pronounced BBB permeation was noted, with frank albumin leakage around larger vessels (>10 µm), overlain by a dose-dependent astroglial scar-like formation and recruitment of phagocytic microglia. As affirmed by elevated inflammatory marker transcription, MWCNT-induced BBB disruption and neuroinflammation were abrogated by pretreatment with the rho kinase inhibitor fasudil. Serum from MWCNT-exposed mice induced expression of adhesion molecules in primary murine cerebrovascular endothelial cells and, in a wound-healing in vitro assay, impaired cell motility and cytokinesis. Serum thrombospondin-1 level was significantly increased after MWCNT exposure, and mice lacking the endogenous receptor CD36 were protected from the neuroinflammatory and BBB permeability effects of MWCNTs. In conclusion, acute pulmonary exposure to MWCNTs causes neuroinflammatory responses that are dependent on the disruption of BBB integrity.

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.