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.

Inflammatory and Vasoactive Effects of Serum Following Inhalation of Varied Complex Mixtures.

Chronic cardiovascular disease is associated with air pollution exposure in epidemiology and toxicology studies. Inhaled toxicants can induce changes in serum bioactivity that impact endothelial inflammatory gene expression in vitro and impair vasorelaxation ex vivo, which are common precursors to atherosclerosis. Comparisons between single pollutants and common combustion mixtures, in terms of driving such serum inflammatory and vasoactive effects, have not been characterized. Healthy C57BL/6 mice were exposed to a single 6-h period of contrasting pollutant atmospheres: road dust, mixed vehicle emissions (MVE; a combination of gasoline and diesel engine emissions) particulate matter, mixed vehicle emissions gases, road dust plus ozone, road dust plus MVE, and hardwood smoke. Serum obtained from mice 24 h after these exposures was used as a stimulus to assess inflammatory potential in two assays: incubated with primary murine cerebrovascular endothelial cells for 4 h to measure inflammatory gene expression or applied to naïve aortic rings in an ex vivo myographic preparation. Road dust and wood smoke exposures were most potent at inducing inflammatory gene expression, while MVE atmospheres and wood smoke were most potent at impairing vasorelaxation to acetylcholine. Responses are consistent with recent reports on MVE toxicity, but reveal novel serum bioactivity related to wood smoke and road dust. These studies suggest that the compositional changes in serum and resultant bioactivity following inhalation exposure to pollutants may be highly dependent on the composition of mixtures.

Characterization of a novel endothelial biosensor assay reveals increased cumulative serum inflammatory potential in stabilized coronary artery disease patients.

BACKGROUND: Vascular disease is promoted by systemic inflammation that can arise from sites distal to the affected vessels. We sought to characterize the net inflammatory potential of serum from patients with coronary artery disease (CAD) using cultured endothelial cells as a cumulative biosensor. METHODS AND RESULTS: Serum samples from CAD patients (N = 45) and healthy control subjects (N = 48) were incubated with primary human coronary artery endothelial cells at a 1:10 dilution for 4 h, followed by isolation of the cellular RNA. Alteration of inflammation-responsive elements (adhesion molecules and cytokines) was assessed by gene expression. Specific indicators included intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and interleukin-8 (IL-8). Additionally, the cytokine levels in serum samples from all subjects were quantified. Serum from CAD subjects induced greater endothelial ICAM-1, VCAM-1, and IL-8 expression compared to healthy control serum (p < 0.001 for each analysis). The three indicators of inflammatory potential (ICAM-1, VCAM-1, and IL-8 mRNA) trended independently of each other and also of serum inflammatory biomarkers. IL-8 expression correlated negatively with serum HDL levels but positively correlated with VLDL, plasminogen activator inhibitor-1 and C-reactive protein. Interestingly, serum levels of cytokines in CAD patients were not statistically different from healthy control subjects. A year of follow-up in a sub-group of CAD subjects revealed relatively stable measures. CONCLUSIONS: As yet unidentified circulating factors in the serum of CAD patients appear to activate endothelial cells, leading to upregulation of adhesion molecules and chemokines. This cumulative assay performed well in terms of discriminating patients with CAD compared to healthy subjects, with greater range and specificity than specific inflammatory markers.