Faculty Bibliography

Owing to increased obesity, non-alcoholic fatty liver disease (NAFLD) is now the most prevalent liver disease in the United States. NAFLD is considered a component of metabolic syndrome, a cluster of disorders that also includes diabetes mellitus, dyslipidemia, arteriosclerosis, and hypertension. Exposure to ambient air particulate matter with aerodynamic diameters < 2.5 microm (PM(2.5)) is a risk factor for arteriosclerosis and lung disease, but its effect on NAFLD is unknown. PM(2.5) induces pulmonary dysfunction via Toll-like receptor (TLR) activation on alveolar macrophages. TLR activation of Kupffer cells, resident hepatic macrophages, and subsequent pro-inflammatory cytokine production have been shown to play a key role in NAFLD progression. We hypothesized that PM(2.5) exposure is a significant risk factor for the progression of NAFLD. Thus, following exposure of male C57BL/6 mice fed high fat chow (HFC) to concentrated air particulate matter (CAPs) or filtered air for 6 weeks, progression of NAFLD was evaluated by standardized histological assessment of hepatic inflammation and fibrosis. In mice fed HFC, the hepatic inflammatory grade (3.00 +/- 0.00 vs. 1.50 +/- 0.71, P < 0.001) and fibrosis stage (1.00 +/- 0.00 vs. 0.60 +/- 0.52, P = 0.023) were both significantly higher in mice exposed to CAPs versus filtered air, respectively. Increased numbers of Kupffer cells contained PM in CAPs-exposed mice scores of (2.00 +/- 0.94 vs. 0.20 +/- 0.42, respectively, P < 0.001). PM exposure increased IL-6 secretion up to seven-fold in a dose-dependent manner by isolated wild-type but not TLR4(-/-) Kupffer cells (P < 0.050). In conclusion, ambient PM(2.5) exposure may be a significant risk factor for NAFLD progression

We review literature that provides insights on health-related effects observed in laboratory-based inhalation studies in humans and laboratory animals using concentrated ambient air particulate matter (CAPs) in the fine, thoracic coarse, and ultrafine size ranges. The CAPs studies are highly informative on the health effects of ambient air particulate matter (PM) because they represent realistic PM exposure mixtures. When PM components are also analyzed and regressed against the effects, they can sometimes be used to identify influential individual components or source-related mixtures responsible for the effects. Such CAPs inhalation studies are analogous to epidemiological studies of human populations for which both health-related effects were observed and PM composition data were available for multi-pollutant regression analyses or source apportionment. Various acute and chronic health-related effects have occurred in short- and long-term CAPs inhalation studies in the cardiovascular, nervous, hepatic, and pulmonary systems, as well as changes in markers of the metabolic syndrome, and many correspond to effects associated with ambient air PM exposures in epidemiological studies. In addition, many CAPs studies have been conducted in coordination with in vitro studies that have identified biomarkers indicative of the underlying biological mechanisms that account for the responses

Epidemiology studies have reported associations between increased mortality and morbidity with exposure to particulate air pollution, particularly within individuals with preexisting cardiovascular disease (CVD). Clinical and toxicological studies have provided evidence that exposure to ambient air particulate matter (PM) impacts CVD by increasing plaque size. It is unclear whether PM-induced increased plaque size is associated with molecular disease progression. This study examines molecular profiles within plaques recovered from ApoE(-/-) mice exposed to concentrated ambient air particles (CAPs) to determine whether pulmonary deposition of PM contributes to molecular alterations leading to vascular disease progression. Laser capture microdissection was used to recover atherosclerotic plaques from ApoE(-/-) male mice exposed daily for 5 mo to filtered air or CAPs. Alterations in mRNA expression was assessed in microdissected plaques of CAPs-exposed and air controls using the Affymetrix microarray platform. Bioinformatic analysis indicated alterations in 611 genes: 395 genes downregulated and 216 genes upregulated. Gene ontology revealed CAPs-induced changes to inflammation, proliferation, cell cycle, hematological system, and cardiovascular pathways. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) verified microarray data also revealing gene expression alterations undetected by the microarray analysis, i.e., decreased expression of alpha-actin for smooth muscle cells, and increased expression of the macrophage marker Cd68 and of beta-actin. Comparison of CAPs-induced gene expression profiles demonstrated consistency with previously published gene expression profiles in the ApoE(-/-) mouse model and humans associated with plaque progression. These results indicate that exposure to fine PM induces molecular alterations associated with vascular disease progression and provides insight into potential biological pathways responsible for this effect

Exposure to ambient air pollution has been associated with increases in blood pressure. We have previously demonstrated activation of the Rho/Rho kinase pathway in experimental hypertension in rats. In this investigation, we evaluated the effects of particulate matter of < 2.5 microm (PM(2.5)) exposure on cardiovascular responses and remodeling and tested the effect of Rho kinase inhibition on these effects. C57BL/6 mice were exposed to concentrated ambient PM(2.5) or filtered air for 12 wk followed by a 14-day ANG II infusion in conjunction with fasudil, a Rho kinase antagonist, or placebo treatment. Blood pressure was monitored, followed by analysis of vascular function and ventricular remodeling indexes. PM(2.5) exposure potentiated ANG II-induced hypertension, and this effect was abolished by fasudil treatment. Cardiac and vascular RhoA activation was enhanced by PM(2.5) exposure along with increased expression of the guanine exchange factors (GEFs) PDZ-RhoGEF and p115 RhoGEF in PM(2.5)-exposed mice. Parallel with increased RhoA activation, PM(2.5) exposure increased ANG II-induced cardiac hypertrophy and collagen deposition, with these increases being normalized by fasudil treatment. In conclusion, PM(2.5) potentiates cardiac remodeling in response to ANG II through RhoA/Rho kinase-dependent mechanisms. These findings have implications for the chronic cardiovascular health effects of air pollution

Previous studies have shown a link between inhaled particulate matter (PM) exposure in urban areas and susceptibility to cardiovascular diseases. Although an oxidative stress pathway is strongly implicated, the locus of generation of reactive oxygen species (ROS) and the mechanisms by which these radicals exert their effects remain to be characterized. To test the hypothesis that exposure to environmentally relevant inhaled concentrated ambient PM (CAPs) enhances atherosclerosis through induction of vascular ROS and reactive nitrogen species. High-fat chow fed apolipoprotein E(-/-) mice were exposed to CAPs of less than 2.5 microm (PM(2.5)) or filtered air (FA), for 6 h/day, 5 days/week, for 4 months in Manhattan, NY. Atherosclerotic lesions were analyzed by histomorphometricly. Vascular reactivity, superoxide generation, mRNA expression of NADPH (nicotinamide adenine dinucleotide phosphate, reduced) oxidase subunits, inducible nitric oxide synthase, endothelial nitric oxide synthase, and GTP cyclohydrolase I were also assessed. Manhattan PM(2.5) CAPs were characterized by higher concentrations of organic and elemental carbon. Analysis of vascular responses revealed significantly decreased phenylephrine constriction in CAPs-exposed mice, which was restored by a soluble guanine cyclase inhibitor 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one. Vascular relaxation to A23187, but not to acetylcholine, was attenuated in CAPs mice. Aortic expression of NADPH oxidase subunits (p47(phox) and rac1) and iNOS were markedly increased, paralleled by increases in superoxide generation and extensive protein nitration in the aorta. The composite plaque area of thoracic aorta was significantly increased with pronounced macrophage infiltration and lipid deposition in the CAPs mice. CAPs exposure in Manhattan alters vasomotor tone and enhances atherosclerosis through NADPH oxidase dependent pathways

BACKGROUND: There is a strong link between urbanization and type 2 diabetes mellitus. Although a multitude of mechanisms have been proposed, there are no studies evaluating the impact of ambient air pollutants and the propensity to develop type 2 diabetes mellitus. We hypothesized that exposure to ambient fine particulate matter (<2.5 mum; PM(2.5)) exaggerates diet-induced insulin resistance, adipose inflammation, and visceral adiposity. METHODS AND RESULTS: Male C57BL/6 mice were fed high-fat chow for 10 weeks and randomly assigned to concentrated ambient PM(2.5) or filtered air (n=14 per group) for 24 weeks. PM(2.5)-exposed C57BL/6 mice exhibited marked whole-body insulin resistance, systemic inflammation, and an increase in visceral adiposity. PM(2.5) exposure induced signaling abnormalities characteristic of insulin resistance, including decreased Akt and endothelial nitric oxide synthase phosphorylation in the endothelium and increased protein kinase C expression. These abnormalilties were associated with abnormalities in vascular relaxation to insulin and acetylcholine. PM(2.5) increased adipose tissue macrophages (F4/80(+) cells) in visceral fat expressing higher levels of tumor necrosis factor-alpha/interleukin-6 and lower interleukin-10/N-acetyl-galactosamine specific lectin 1. To test the impact of PM(2.5) in eliciting direct monocyte infiltration into fat, we rendered FVBN mice expressing yellow fluorescent protein (YFP) under control of a monocyte-specific promoter (c-fms, c-fms(YFP)) diabetic over 10 weeks and then exposed these mice to PM(2.5) or saline intratracheally. PM(2.5) induced YFP cell accumulation in visceral fat and potentiated YFP cell adhesion in the microcirculation. CONCLUSIONS: PM(2.5) exposure exaggerates insulin resistance and visceral inflammation/adiposity. These findings provide a new link between air pollution and type 2 diabetes mellitus

Recent studies have suggested a link between inhaled particulate matter (PM) exposure and atherogenesis. We investigated tissue factor (TF) expression with ambient fine particulate matter (diameter < 2.5 microm, PM(2.5)) exposure and in response to in vitro exposure to fine and ultrafine PM in cultured human bronchial epithelial cells, vascular smooth muscle cells (hSMCs), and monocytes. ApoE-/- mice, fed with normal chow (NC) or high-fat chow (HFC), were exposed to concentrated PM(2.5) or filtered air (FA) for 6 mo (6 h/day, 5 day/wk, n = 28). Following in vivo ultrasound bio-microscopy (UBM) assessment of plaque area, macrophage infiltration (CD68) and TF expression in the aorta were quantified. Cultured cells were incubated with size-fractionated PM from cascade impactors, or with standard reference PM material (SRM, number 1649a) and assayed for TF protein, mRNA, and activity. UBM-derived plaque areas were 7 +/- 1% larger in the PM(2.5)-HFC than the FA-HFC group (p = .04), but not significantly different between the PM(2.5)-NC and FA-NC groups (p = .07). Immunohistochemistry revealed increased TF (15 +/- 3% vs. 8 +/- 2%, p < .01) and macrophage infiltration (19 +/- 2% vs. 14 +/- 3%, p < .01) in the plaques of PM(2.5)-HFC compared with FA-HFC groups. Impactor-collected PM(2.5) and ultrafine particles consistently increased TF protein in bronchial epithelial cells, monocytes, and hSMCs. TF mRNA expression increased rapidly (within 1 h) in response to SRM PM. We conclude that in vivo and in vitro exposure to ambient air PM(2.5) induces TF expression

OBJECTIVE: Fine particulate matter <2.5 microm (PM(2.5)) has been implicated in vasoconstriction and potentiation of hypertension in humans. We investigated the effects of short-term exposure to PM(2.5) in the angiotensin II (AII) infusion model. METHODS AND RESULTS: Sprague-Dawley rats were exposed to PM(2.5) or filtered air (FA) for 10 weeks. At week 9, minipumps containing AII were implanted and the responses studied over a week. Mean concentration of PM(2.5) inside the chamber was 79.1+/-7.4 microg/m(3). After AII infusion, mean arterial pressure was significantly higher in PM(2.5)-AII versus FA-AII group. Aortic vasoconstriction to phenylephrine was potentiated with exaggerated relaxation to the Rho-kinase (ROCK) inhibitor Y-27632 and increase in ROCK-1 mRNA levels in the PM(2.5)-AII group. Superoxide (O(2).(-)) production in aorta was increased in the PM(2.5)-AII compared to the FA group, inhibitable by apocynin and L-NAME with coordinate upregulation of NAD(P)H oxidase subunits p22(phox) and p47(phox) and depletion of tetrahydrobiopterin. In vitro exposure to ultrafine particles (UFP) and PM(2.5) was associated with an increase in ROCK activity, phosphorylation of myosin light chain, and myosin phosphatase target subunit (MYPT1). Pretreatment with the nonspecific antioxidant N-acetylcysteine and the Rho kinase inhibitors (Fasudil and Y-27632) prevented MLC and MYPT-1 phosphorylation by UFP suggesting a O(2)(.-)-mediated mechanism for PM(2.5) and UFP effects. CONCLUSIONS: Short-term air pollution exaggerates hypertension through O(2)(.-)-mediated upregulation of the Rho/ROCK pathway