Mixed Vehicle Emissions Induces Angiotensin II and Cerebral Microvascular Angiotensin Receptor Expression in C57Bl/6 Mice and Promotes Alterations in Integrity in a Blood-Brain Barrier Coculture Model

Abstract

Exposure to traffic-generated pollution is associated with alterations in blood-brain barrier (BBB) integrity and exacerbation of cerebrovascular disorders. Angiotensin (Ang) II signaling through the Ang II type 1 (AT1) receptor is known to promote BBB disruption. We have previously reported that exposure to a mixture of gasoline and diesel vehicle engine emissions (MVE) mediates alterations in cerebral microvasculature of C57Bl/6 mice, which is exacerbated through consumption of a high-fat (HF) diet. Thus, we investigated the hypothesis that inhalation exposure to MVE results in altered central nervous system microvascular integrity mediated by Ang II-AT1 signaling. Three-month-old male C57Bl/6 mice were placed on an HF or low-fat diet and exposed via inhalation to either filtered air (FA) or MVE (100 μg/m3 PM) 6 h/d for 30 days. Exposure to HF+MVE resulted in a significant increase in plasma Ang II and expression of AT1 in the cerebral microvasculature. Results from a BBB coculture study showed that transendothelial electrical resistance was decreased, associated with reduced expression of claudin-5 and occludin when treated with plasma from MVE+HF animals. These effects were attenuated through pretreatment with the AT1 antagonist, Losartan. Our BBB coculture showed increased levels of astrocyte AT1 and decreased expression of aryl hydrocarbon receptor and glutathione peroxidase-1, associated with increased interleukin-6 and transforming growth factor-β in the astrocyte media, when treated with plasma from MVE-exposed groups. Our results indicate that inhalation exposure to traffic-generated pollutants results in altered BBB integrity, mediated through Ang II-AT1 signaling and inflammation, which is exacerbated by an HF diet.

Exposure to diesel exhaust particles results in altered lung microbial profiles, associated with increased reactive oxygen species/reactive nitrogen species and inflammation, in C57Bl/6 wildtype mice on a high-fat diet

“…The concentration for DEP exposure chosen was higher than what would be expected for daily environmental human exposure (see Discussion section). This specific concentration for DEP exposure was chosen because it is similar to the concentration of total PM used in preliminary analysis containing mixtures of whole vehicle exhaust (PM + gases) [ 87 ]. OA was chosen as the preferred route for exposure for these studies since it stimulates the route PM would take from the oropharynx region into the lungs and ensures homogenous delivery to the respiratory system.…”

Vehicle emissions-exposure alters expression of systemic and tissue-specific components of the renin-angiotensin system and promotes outcomes associated with cardiovascular disease and obesity in wild-type C57BL/6 male mice

“…Male 6–8 week-old C57BL/6 mice (C57BL/6NTac, Taconic, Albany, NY) were fed either a low-fat (LF) standard chow or high-fat diet (HF: TD88137 Custom Research Diet, Harlan Teklad, Madison, WI; 42 % kcal from fat, 21.2 % fat content by weight) for 30 d. Mice on each diet were then randomly sorted to be exposed by inhalation to either a combined mixture of diesel engine and gasoline engine vehicle emissions (MVE: 70 μg PM/m 3 diesel engine exhaust + 30 μg PM/m 3 gasoline engine exhaust, n = 16; n = 8 HF diet, n = 8 LF diet) or filtered-air (FA: controls, n = 16; n = 8 HF diet, n = 8 LF diet) for 6 h/d, 7 d/wk, for 30 d. As previously detailed by our laboratory, the MVE was generated by combining the emissions from a Yanmar diesel generator system with those from a 1996 GM gasoline engine [ 45 ]. The resulting mixture was characterized daily for chemical composition throughout the exposures, as previously detailed (Lund et al 2011; [ 44 ]). While higher than average PM concentrations rates, 100 μg PM/m 3 is within the daily levels of PM 2.5 measured across heavily populated urban areas, as well as certain occupational settings [ 46 , 47 , 48 ].…”

“…While higher than average PM concentrations rates, 100 μg PM/m 3 is within the daily levels of PM 2.5 measured across heavily populated urban areas, as well as certain occupational settings [ 46 , 47 , 48 ]. Furthermore, this concentration was chosen for the current study for comparison of toxicological outcomes in C57BL/6 wild-type mice compared to those previously reported by our laboratory in atherosclerotic Apolipoprotein E null mice and human exposure models, as well as toxicological endpoints across organ systems [ 49 , 50 , 44 ]. For the exposures, mice were housed in an AAALC-approved facility, four to a cage, in standard shoebox cages within the 2 m 3 whole-body exposure chambers.…”

“…Briefly, a Qiagen AllPrep DNA/RNA/miRNA Universal Kit (Catalog #80224, Germantown, MD) was used to isolate RNA from kidney, vascular (aorta), and adipose tissue. A BIORAD CFX96 (Hercules, CA) was used for RT-qPCR reactions and analyses [ 50 , 44 ]. ΔΔC T results were analyzed (GAPDH controls) in the aorta, kidney, or adipose tissues from an n = 7–8 animals from each study group.…”

“…Understanding key mechanistic pathways by which traffic-generated air pollution exposure can promote inflammatory comorbid disease states such as CVD, metabolic syndrome, and obesity is necessary for preventative and therapeutic targets, and also environmental regulatory outcomes. Our laboratory has reported that inhalation exposure to a ubiquitous source of ambient air pollution, namely a mixture of diesel and gasoline vehicle engine exhaust (MVE), leads to elevated systemic Ang II plasma levels, associated with increased cerebrovascular expression of the AT1 receptor in C57BL/6 wild-type mice, which were further elevated in HF-diet fed animals [ 44 ]. These findings suggest that exposure to traffic-generated pollutants may alter RAS signaling.…”