One-month diesel exhaust inhalation produces hypertensive gene expression pattern in healthy rats

Biological effects of diesel exhaust inhalation. III cardiovascular function

OBJECTIVE

Inhalation of diesel exhaust (DE) has been shown to be an occupational hazard in the transportation, mining, and gas and oil industries. DE also contributes to air pollution, and therefore, is a health hazard to the general public. Because of its effects on human health, changes have been made to diesel engines to reduce both the amounts of particulate matter and volatile fumes they generate. The goal of the current study was to examine the effects of inhalation of diesel exhaust.

MATERIALS AND METHODS

The study presented here specifically examines the effects of exposure to 0.2 and 1.0 mg/m3 DE or filtered air (6h/d for 4 d) on measures of peripheral and cardio-vascular function, and biomarkers of heart and kidney dysfunction in male rats. A Tier 2 engine used in oil and gas fracking operations was used to generate the diesel exhaust.

RESULTS

Exposure to 0.2 mg/m3 DE resulted in an increase in blood pressure 1d following the last exposure, and increases in dobutamine-induced cardiac output and stroke volume 1 and 27d after exposure. Changes in peripheral vascular responses to norepinephrine and acetylcholine were minimal as were changes in transcript expression in the heart and kidney. Exposure to 1.0 mg/m3 DE did not result in major changes in blood pressure, measures of cardiac function, peripheral vascular function or transcript expression.

DISCUSSION AND CONCLUSIONS

Based on the results of this study, we suggest that exposure to DE generated by a Tier 2 compliant diesel engine generates acute effects on biomarkers indicative of cardiovascular dysfunction. Recovery occurs quickly with most measures of vascular/cardiovascular function returning to baseline levels by 7d following exposure.

Effect Of Atmospheric Particulate Matter On The Functional State Of Mitochondria

The health risks associated with outdoor air pollution are of global concern. Atmospheric air pollution negatively affects a number of key aspects of human health, including the functioning of the respiratory, cardiovascular and central nervous systems, but many issues remain unresolved about the relationship between atmospheric air pollution and the development and course of pathologies. The review analyzes data from Russian and foreign sources on the effect of atmospheric particulate matter on the functional state of mitochondria. The effect of air pollution on structural changes in mitochondria, ATP synthesis, production of reactive oxygen species, damage to mitochondrial DNA, and mitochondrial membrane potential has been shown. The data presented in the review indicate the need for further studies of the functional state of mitochondria under the impact of solid particles in atmospheric air.

Environmental Stressors and the PINE Network: Can Physical Environmental Stressors Drive Long-Term Physical and Mental Health Risks?

Both psychosocial and physical environmental stressors have been linked to chronic mental health and chronic medical conditions. The psycho-immune-neuroendocrine (PINE) network details metabolomic pathways which are responsive to varied stressors and link chronic medical conditions with mental disorders, such as major depressive disorder via a network of pathophysiological pathways. The primary objective of this review is to explore evidence of relationships between airborne particulate matter (PM, as a concrete example of a physical environmental stressor), the PINE network and chronic non-communicable diseases (NCDs), including mental health sequelae, with a view to supporting the assertion that physical environmental stressors (not only psychosocial stressors) disrupt the PINE network, leading to NCDs. Biological links have been established between PM exposure, key sub-networks of the PINE model and mental health sequelae, suggesting that in theory, long-term mental health impacts of PM exposure may exist, driven by the disruption of these biological networks. This disruption could trans-generationally influence health; however, long-term studies and information on chronic outcomes following acute exposure event are still lacking, limiting what is currently known beyond the acute exposure and all-cause mortality. More empirical evidence is needed, especially to link long-term mental health sequelae to PM exposure, arising from PINE pathophysiology. Relationships between physical and psychosocial stressors, and especially the concept of such stressors acting together to impact on PINE network function, leading to linked NCDs, evokes the concept of syndemics, and these are discussed in the context of the PINE network.

Genome-wide evaluation of transcriptomic responses of human tissues to smoke: A systems biology study

The harmful compounds in various sources of smoke threaten human health. So far, many studies have investigated the effects of compounds of smoke on transcriptome changes in different human tissues. However, no study has been conducted on the effects of these compounds on transcriptome changes in different human tissues simultaneously. Hence, the present study was conducted to identify smoke-related genes (SRGs) and their response mechanisms to smoke in various human cells and tissues using systems biology based methods. A total of 6,484 SRGs were identified in the studied tissues, among which 4,095 SRGs were up-regulated and 2,389 SRGs were down-regulated. Totally, 459 SRGs were smoke-related transcription factors (SRTFs). Gene regulatory network analysis showed that the studied cells and tissues have different gene regulation and responses to compounds of smoke. The comparison of different tissues revealed no common SRG among the all studied tissues. However, the CYP1B1 gene was common among seven cells and tissues, and had the same expression trend. Network analysis showed that the CYP1B1 is a hub gene among SRGs in various cells and tissues. To the best of our knowledge, for the first time, our results showed that compounds of smoke induce and increase the expression of CYP1B1 key gene in all target and non-target tissues of human. Moreover, despite the specific characteristics of CYP1B1 gene and its identical expression trend in target and non-target tissues, it can be used as a biomarker for diagnosis and prognosis.

Diesel exhaust impairs TREM2 to dysregulate neuroinflammation

Background

Air pollution has been linked to neurodegenerative diseases, including Alzheimer’s disease (AD), and the underlying neuroimmune mechanisms remain poorly understood. TREM2 is a myeloid cell membrane receptor that is a key regulator of disease-associated microglia (DAM) cells, where loss-of-function TREM2 mutations are associated with an increased risk of AD. At present, the basic function of TREM2 in neuroinflammation is a point of controversy. Further, the impact of air pollution on TREM2 and the DAM phenotype is largely unknown. Using diesel exhaust (DE) as a model of urban air pollution exposure, we sought to address its impact on TREM2 expression, the DAM phenotype, the association of microglia with the neurovasculature, and the role of TREM2 in DE-induced neuroinflammation.

Methods

WYK rats were exposed for 4 weeks to DE (0, 50, 150, 500 μg/m³) by inhalation. DE particles (DEP) were administered intratracheally once (600 μg/mouse) or 8 times (100 μg/mouse) across 28 days to male mice (Trem2^+/+, Trem2^−/−, PHOX^+/+, and PHOX^−/−).

Results

Rats exposed to DE exhibited inverted-U patterns of Trem2 mRNA expression in the hippocampus and frontal cortex, while TREM2 protein was globally diminished, indicating impaired TREM2 expression. Analysis of DAM markers Cx3Cr1, Lyz2, and Lpl in the frontal cortex and hippocampus showed inverted-U patterns of expression as well, supporting dysregulation of the DAM phenotype. Further, microglial-vessel association decreased with DE inhalation in a dose-dependent manner. Mechanistically, intratracheal administration of DEP increased Tnf (TNFα), Ncf1 (p47^PHOX), and Ncf2 (p67^PHOX) mRNA expression in only Trem2^+/+ mice, where Il1b (IL-1β) expression was elevated in only Trem2^−/− mice, emphasizing an important role for TREM2 in DEP-induced neuroinflammation.

Conclusions

Collectively, these findings reveal a novel role for TREM2 in how air pollution regulates neuroinflammation and provides much needed insight into the potential mechanisms linking urban air pollution to AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-020-02017-7.

Effects of air pollution particles (ultrafine and fine particulate matter) on mitochondrial function and oxidative stress - Implications for cardiovascular and neurodegenerative diseases

Environmental pollution is a major cause of global mortality and burden of disease. All chemical pollution forms together may be responsible for up to 12 million annual excess deaths as estimated by the Lancet Commission on pollution and health as well as the World Health Organization. Ambient air pollution by particulate matter (PM) and ozone was found to be associated with an all-cause mortality rate of up to 9 million in the year 2015, with the majority being of cerebro- and cardiovascular nature (e.g. stroke and ischemic heart disease). Recent evidence suggests that exposure to airborne particles and gases contributes to and accelerates neurodegenerative diseases. Especially, airborne toxic particles contribute to these adverse health effects. Whereas it is well established that air pollution in the form of PM may lead to dysregulation of neurohormonal stress pathways and may trigger inflammation as well as oxidative stress, leading to secondary damage of cardiovascular structures, the mechanistic impact of PM-induced mitochondrial damage and dysfunction is not well established. With the present review we will discuss similarities between mitochondrial damage and dysfunction observed in the development and progression of cardiovascular disease and neurodegeneration as well as those adverse mitochondrial pathomechanisms induced by airborne PM.

Oxidative stress and the cardiovascular effects of air pollution

Cardiovascular causes have been estimated to be responsible for more than two thirds of the considerable mortality attributed to air pollution. There is now a substantial body of research demonstrating that exposure to air pollution has many detrimental effects throughout the cardiovascular system. Multiple biological mechanisms are responsible, however, oxidative stress is a prominent observation at many levels of the cardiovascular impairment induced by pollutant exposure. This review provides an overview of the evidence that oxidative stress is a key pathway for the different cardiovascular actions of air pollution.

Comparison of silver nanoparticle-induced inflammatory responses between healthy and metabolic syndrome mouse models

Silver nanoparticles (AgNPs) are utilized in surgical implants and medical textiles, thus providing access to the circulation. While research has been conducted primarily in healthy models, AgNP-induced toxicity evaluations in disease conditions are critical, as many individuals have preexisting conditions. Specifically, over 20% of United States adults suffer from metabolic syndrome (MetS). It was hypothesized that MetS may increase susceptibility to AgNP-mediated toxicity due to induction of differential inflammation and altered biodistribution. Mice were injected with 2 mg/kg AgNPs, and organs assessed for inflammatory gene expression (TNF-α, CXCL1, CXCL2, CCL2, TGF-β, HO-1, IL-4, IL-13), and Ag content. AgNPs were determined to induce differential inflammation in healthy and MetS mice. While AgNP exposure increased TNF-α, CXCL1, TGF-β, HO-1, and IL-4 expression within healthy mouse spleens, MetS-treated animals demonstrated decreased CXCL1, IL-4, and IL-13 expression. Healthy and MetS mice livers exhibited similar inflammatory responses to one another. AgNPs localized primarily to the liver and spleen, although Ag was present in all examined organs. In organs of minor AgNP deposition, such as kidney, gene expression was variable. Induction of inflammatory genes did not correspond with biodistribution, suggesting disease-related variations in AgNP-mediated adverse responses. These findings indicate that disease may influence inflammation and biodistribution, impacting AgNP clinical applications.

Susceptibility Variations in Air Pollution Health Effects: Incorporating Neuroendocrine Activation

Diverse host factors/phenotypes may exacerbate or diminish biological responses induced by air pollutant exposure. We lack an understanding of biological indicators of environmental exposures that culminate in a physiological response versus those that lead to adversity. Variations in response phenotype might arise centrally and/or at the local tissue level. In addition to genetic differences, the current evidence supports the roles of preexisting cardiopulmonary diseases, diabetes, diet, adverse prenatal environments, neurobehavioral disorders, childhood infections, microbiome, sex, and psychosocial stressors in modifying the susceptibility to air pollutant exposures. Animal models of human diseases, obesity, nutritional inadequacies, and neurobehavioral conditions have been compared with healthy controls to understand the causes of variations in susceptibility. Although psychosocial stressors have been associated with increased susceptibility to air pollutant effects, the contribution of neuroendocrine stress pathways in mediating these effects is just emerging. The new findings of neuroendocrine activation leading to systemic metabolic and immunological effects of air pollutants, and the potential contribution to allostatic load, emphasize the consideration of these mechanisms into susceptibility. Variations in susceptibility to air pollution health effects are likely to underlie host genetic and physiological conditions in concert with disrupted neuroendocrine circuitry that alters physiological stability under the influence of stressors.

Traffic-related particulate matter exposure induces nephrotoxicity in vitro and in vivo

Traffic emission is responsible for most small-sized particulate matter (PM) air pollution in urban areas. Several recent studies have indicated that traffic-related PM may aggravate kidney disease. Furthermore, exposure to particulate air pollution may be related to the risk of chronic kidney disease (CKD). However, the underlying molecular mechanisms have not been adequately addressed. In the present study, we studied the mechanisms of renal damage that might be associated with exposure to PM. In a real world of whole-body exposure to traffic-related PM model for 3-6 months, PM in urban ambient air can affect kidney function and induce autophagy, endoplasmic reticulum (ER) stress and apoptosis in kidney tissues. Exposure to traffic-related diesel particulate matter (DPM) led to a reduction in cell viability in human kidney tubular epithelial cells HK-2. DPM increased mitochondrial reactive oxygen species (ROS) and decreased the mitochondrial membrane potential. Furthermore, DPM induced ER stress and activated the unfolded protein response (UPR) pathway. Eventually, DPM exposure induced caspase pathways and triggered apoptosis. In addition, DPM induced autophagy through the inhibition of the Akt/mTOR pathway. Autophagy inhibition resulted in significantly increased cytotoxicity and apoptosis. These findings suggest that air pollution in urban areas may cause nephrotoxicity and autophagy as a protective role in PM-induced cytotoxicity.

Role of oxidative stress in cardiovascular disease outcomes following exposure to ambient air pollution

Exposure to ambient air pollution is associated with adverse cardiovascular outcomes. These are manifested through several, likely overlapping, pathways including at the functional level, endothelial dysfunction, atherosclerosis, pro-coagulation and alterations in autonomic nervous system balance and blood pressure. At numerous points within each of these pathways, there is potential for cellular oxidative imbalances to occur. The current review examines epidemiological, occupational and controlled exposure studies and research employing healthy and diseased animal models, isolated organs and cell cultures in assessing the importance of the pro-oxidant potential of air pollution in the development of cardiovascular disease outcomes. The collective body of data provides evidence that oxidative stress (OS) is not only central to eliciting specific cardiac endpoints, but is also implicated in modulating the risk of succumbing to cardiovascular disease, sensitivity to ischemia/reperfusion injury and the onset and progression of metabolic disease following ambient pollution exposure. To add to this large research effort conducted to date, further work is required to provide greater insight into areas such as (a) whether an oxidative imbalance triggers and/or worsens the effect and/or is representative of the consequence of disease progression, (b) OS pathways and cardiac outcomes caused by individual pollutants within air pollution mixtures, or as a consequence of inter-pollutant interactions and (c) potential protection provided by nutritional supplements and/or pharmacological agents with antioxidant properties, in susceptible populations residing in polluted urban cities.

Rat models of cardiometabolic diseases: baseline clinical chemistries, and rationale for their use in examining air pollution health effects

Individuals with cardiovascular and metabolic diseases (CVD) are shown to be more susceptible to adverse health effects of pollutants. Rodent models of CVD are used for examining susceptibility variations. CVD models developed by selective inbreeding are shown to represent the etiology of human disease and metabolic dysfunction. The goal of this article was to review the origin and the pathobiological features of rat models of varying CVD with or without metabolic syndrome and healthy laboratory rat strains to allow better interpretation of the data regarding their susceptibility to air pollutant exposures. Age-matched healthy Sprague-Dawley (SD), Wistar (WIS) and Wistar Kyoto (WKY), and CVD-prone spontaneously hypertensive (SH), Fawn-Hooded hypertensive (FHH), SH stroke-prone (SHSP), SHHF/Mcc heart failure obese (SHHF) and insulin-resistant JCR:LA-cp obese (JCR) rat models were considered for this study. The genetics and the underlying pathologies differ between these models. Normalized heart weights correlated with underlying cardiac disease while wide differences exist in the number of white blood cells and platelets within healthy strains and those with CVD. High plasma fibrinogen and low angiotensin converting enzyme activity in FHH might relate to kidney disease and associated hypertension. However, other obese strains with known kidney lesions do not exhibit decreases in ACE activity. The increased activated partial thromboplastin time only in SHSP correlates with their hemorrhagic stroke susceptibility. Increases plasma lipid peroxidation in JCR might reflect their susceptibility to acquire atherosclerosis. These underlying pathologies involving CVD and metabolic dysfunction are critical in interpretation of findings related to susceptibility variations of air pollution health effects.

Systemic metabolic derangement, pulmonary effects, and insulin insufficiency following subchronic ozone exposure in rats

Acute ozone exposure induces a classical stress response with elevated circulating stress hormones along with changes in glucose, protein and lipid metabolism in rats, with similar alterations in ozone-exposed humans. These stress-mediated changes over time have been linked to insulin resistance. We hypothesized that acute ozone-induced stress response and metabolic impairment would persist during subchronic episodic exposure and induce peripheral insulin resistance. Male Wistar Kyoto rats were exposed to air or 0.25ppm or 1.00ppm ozone, 5h/day, 3 consecutive days/week (wk) for 13wks. Pulmonary, metabolic, insulin signaling and stress endpoints were determined immediately after 13wk or following a 1wk recovery period (13wk+1wk recovery). We show that episodic ozone exposure is associated with persistent pulmonary injury and inflammation, fasting hyperglycemia, glucose intolerance, as well as, elevated circulating adrenaline and cholesterol when measured at 13wk, however, these responses were largely reversible following a 1wk recovery. Moreover, the increases noted acutely after ozone exposure in non-esterified fatty acids and branched chain amino acid levels were not apparent following a subchronic exposure. Neither peripheral or tissue specific insulin resistance nor increased hepatic gluconeogenesis were present after subchronic ozone exposure. Instead, long-term ozone exposure lowered circulating insulin and severely impaired glucose-stimulated beta-cell insulin secretion. Thus, our findings in young-adult rats provide potential insights into epidemiological studies that show a positive association between ozone exposures and type 1 diabetes. Ozone-induced beta-cell dysfunction may secondarily contribute to other tissue-specific metabolic alterations following chronic exposure due to impaired regulation of glucose, lipid, and protein metabolism.

Stretching the stress boundary: Linking air pollution health effects to a neurohormonal stress response

Inhaled pollutants produce effects in virtually all organ systems in our body and have been linked to chronic diseases including hypertension, atherosclerosis, Alzheimer's and diabetes. A neurohormonal stress response (referred to here as a systemic response produced by activation of the sympathetic nervous system and hypothalamus-pituitary-adrenal (HPA)-axis) has been implicated in a variety of psychological and physical stresses, which involves immune and metabolic homeostatic mechanisms affecting all organs in the body. In this review, we provide new evidence for the involvement of this well-characterized neurohormonal stress response in mediating systemic and pulmonary effects of a prototypic air pollutant - ozone. A plethora of systemic metabolic and immune effects are induced in animals exposed to inhaled pollutants, which could result from increased circulating stress hormones. The release of adrenal-derived stress hormones in response to ozone exposure not only mediates systemic immune and metabolic responses, but by doing so, also modulates pulmonary injury and inflammation. With recurring pollutant exposures, these effects can contribute to multi-organ chronic conditions associated with air pollution. This review will cover, 1) the potential mechanisms by which air pollutants can initiate the relay of signals from respiratory tract to brain through trigeminal and vagus nerves, and activate stress responsive regions including hypothalamus; and 2) the contribution of sympathetic and HPA-axis activation in mediating systemic homeostatic metabolic and immune effects of ozone in various organs. The potential contribution of chronic environmental stress in cardiovascular, neurological, reproductive and metabolic diseases, and the knowledge gaps are also discussed. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.

Cerium Dioxide Nanoparticle Exposure Improves Microvascular Dysfunction and Reduces Oxidative Stress in Spontaneously Hypertensive Rats

The elevated production of reactive oxygen species (ROS) in the vascular wall is associated with cardiovascular diseases such as hypertension. This increase in oxidative stress contributes to various mechanisms of vascular dysfunction, such as decreased nitric oxide bioavailability. Therefore, anti-oxidants are being researched to decrease the high levels of ROS, which could improve the microvascular dysfunction associated with various cardiovascular diseases. From a therapeutic perspective, cerium dioxide nanoparticles (CeO₂ NP) hold great anti-oxidant potential, but their in vivo activity is unclear. Due to this potential anti-oxidant action, we hypothesize that injected CeO₂ NP would decrease microvascular dysfunction and oxidative stress associated with hypertension. In order to simulate a therapeutic application, spontaneously hypertensive (SH) and Wistar-Kyoto (WKY) rats were intravenously injected with either saline or CeO₂ NP (100 μg suspended in saline). Twenty-four hours post-exposure mesenteric arteriolar reactivity was assessed via intravital microscopy. Endothelium-dependent and –independent function was assessed via acetylcholine and sodium nitroprusside. Microvascular oxidative stress was analyzed using fluorescent staining in isolated mesenteric arterioles. Finally, systemic inflammation was examined using a multiplex analysis and venular leukocyte flux was counted. Endothelium-dependent dilation was significantly decreased in the SH rats (29.68 ± 3.28%, maximal response) and this microvascular dysfunction was significantly improved following CeO₂ NP exposure (43.76 ± 4.33%, maximal response). There was also an increase in oxidative stress in the SH rats, which was abolished following CeO₂ NP treatment. These results provided evidence that CeO₂ NP act as an anti-oxidant in vivo. There were also changes in the inflammatory profile in the WKY and SH rats. In WKY rats, IL-10 and TNF-α were increased following CeO₂ NP treatment. Finally, leukocyte flux was increased in the SH rats (34 ± 4 vs. 17 ± 3 cells/min in the normotensive controls), but this activation was decreased following exposure (15 ± 2 vs. 34 ± 4 cells/min). These results indicated that CeO₂ NP may alter the inflammatory response in both SH and WKY rats. Taken together, these results provide evidence that CeO₂ NP act as an anti-oxidant in vivo and may improve microvascular reactivity in a model of hypertension.

Reduced gene expression levels after chronic exposure to high concentrations of air pollutants

We analyzed the ability of particulate matter (PM) and chemicals adsorbed onto it to induce diverse gene expression profiles in subjects living in two regions of the Czech Republic differing in levels and sources of the air pollution. A total of 312 samples from polluted Ostrava region and 154 control samples from Prague were collected in winter 2009, summer 2009 and winter 2010. The highest concentrations of air pollutants were detected in winter 2010 when the subjects were exposed to: PM of aerodynamic diameter <2.5μm (PM2.5) (70 vs. 44.9μg/m(3)); benzo[a]pyrene (9.02 vs. 2.56ng/m(3)) and benzene (10.2 vs. 5.5μg/m(3)) in Ostrava and Prague, respectively. Global gene expression analysis of total RNA extracted from leukocytes was performed using Illumina Expression BeadChips microarrays. The expression of selected genes was verified by quantitative real-time PCR (qRT-PCR). Gene expression profiles differed by locations and seasons. Despite lower concentrations of air pollutants a higher number of differentially expressed genes and affected KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways was found in subjects from Prague. In both locations immune response pathways were affected, in Prague also neurodegenerative diseases-related pathways. Over-representation of the latter pathways was associated with the exposure to PM2.5. The qRT-PCR analysis showed a significant decrease in expression of APEX, ATM, FAS, GSTM1, IL1B and RAD21 in subjects from Ostrava, in a comparison of winter 2010 and summer 2009. In Prague, an increase in gene expression was observed for GADD45A and PTGS2. In conclusion, high concentrations of pollutants in Ostrava were not associated with higher number of differentially expressed genes, affected KEGG pathways and expression levels of selected genes. This observation suggests that chronic exposure to air pollution may result in reduced gene expression response with possible negative health consequences.

A cross-sectional analysis of polycyclic aromatic hydrocarbons and diesel particulate matter exposures and hypertension among individuals of Mexican origin

BACKGROUND

Epidemiological studies have found that particulate matter is associated with increases in blood pressure. Yet, less is known about the effects of specific sources or constituents of particulate matter, such as diesel particulate matter or polycyclic aromatic hydrocarbons (PAHs). We evaluated associations between self-reported hypertension and residential air levels of diesel particulate matter and PAHs among individuals of Mexican origin living in a large inner city.

METHODS

The Mano a Mano cohort (established in 2001 by the University of Texas MD Anderson Cancer Center) is comprised of individuals of Mexican origin residing in Houston, Texas. Using geographical information systems, we linked modeled annual estimates of PAHs and diesel particulate matter at the census tract level from the 2002 and 2005 U.S. Environmental Protection Agency's National-Scale Air Toxics Assessment to baseline residential addresses of cohort members who enrolled from 2001 to 2003 or 2004 to 2006, respectively. For each enrollment period, we applied mixed-effects logistic regression models to determine associations between diesel particulate matter and PAHs, separately, and self-reported hypertension while adjusting for confounders and the clustering of observations within census tracts and households.

RESULTS

The study population consisted of 11218 participants of which 77% were women. The mean participant age at baseline was 41 years. Following adjustment for age, there was a dose-dependent, positive association between PAHs and hypertension (medium exposure, adjusted odds ratio (OR) = 1.09, 95% CI: 0.88-1.36; high exposure, OR = 1.40, 95% CI: 1.01-1.94) for individuals enrolled during 2001-2003; associations were generally similar in magnitude, but less precise, following adjustment for age, gender, smoking, and BMI. No association was detected for the later period. There was no evidence of an association between residential levels of diesel particulate matter and hypertension.

CONCLUSIONS

This study builds on a limited number of prior investigations of the association between ambient air levels of PAHs or diesel particulate matter and hypertension by focusing on a relatively young cohort of predominantly adult women of Mexican origin. Future analyses are warranted to explore associations in the cohort using incident hypertension when sufficient data become available and to further examine associations between specific chemical constituents of particulate matter and hypertension in this and other populations.

Comparative cardiopulmonary toxicity of exhausts from soy-based biofuels and diesel in healthy and hypertensive rats

Increased use of renewable energy sources raise concerns about health effects of new emissions. We analyzed relative cardiopulmonary health effects of exhausts from (1) 100% soy biofuel (B100), (2) 20% soy biofuel + 80% low sulfur petroleum diesel (B20), and (3) 100% petroleum diesel (B0) in rats. Normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats were exposed to these three exhausts at 0, 50, 150 and 500 μg/m(3), 4 h/day for 2 days or 4 weeks (5 days/week). In addition, WKY rats were exposed for 1 day and responses were analyzed 0 h, 1 day or 4 days later for time-course assessment. Hematological parameters, in vitro platelet aggregation, bronchoalveolar lavage fluid (BALF) markers of pulmonary injury and inflammation, ex vivo aortic ring constriction, heart and aorta mRNA markers of vasoconstriction, thrombosis and atherogenesis were analyzed. The presence of pigmented macrophages in the lung alveoli was clearly evident with all three exhausts without apparent pathology. Overall, exposure to all three exhausts produced only modest effects in most endpoints analyzed in both strains. BALF γ-glutamyl transferase (GGT) activity was the most consistent marker and was increased in both strains, primarily with B0 (B0 > B100 > B20). This increase was associated with only modest increases in BALF neutrophils. Small and very acute increases occurred in aorta mRNA markers of vasoconstriction and thrombosis with B100 but not B0 in WKY rats. Our comparative evaluations show modest cardiovascular and pulmonary effects at low concentrations of all exhausts: B0 causing more pulmonary injury and B100 more acute vascular effects. BALF GGT activity could serve as a sensitive biomarker of inhaled pollutants.

Systematic Omics Analysis Review (SOAR) tool to support risk assessment

Environmental health risk assessors are challenged to understand and incorporate new data streams as the field of toxicology continues to adopt new molecular and systems biology technologies. Systematic screening reviews can help risk assessors and assessment teams determine which studies to consider for inclusion in a human health assessment. A tool for systematic reviews should be standardized and transparent in order to consistently determine which studies meet minimum quality criteria prior to performing in-depth analyses of the data. The Systematic Omics Analysis Review (SOAR) tool is focused on assisting risk assessment support teams in performing systematic reviews of transcriptomic studies. SOAR is a spreadsheet tool of 35 objective questions developed by domain experts, focused on transcriptomic microarray studies, and including four main topics: test system, test substance, experimental design, and microarray data. The tool will be used as a guide to identify studies that meet basic published quality criteria, such as those defined by the Minimum Information About a Microarray Experiment standard and the Toxicological Data Reliability Assessment Tool. Seven scientists were recruited to test the tool by using it to independently rate 15 published manuscripts that study chemical exposures with microarrays. Using their feedback, questions were weighted based on importance of the information and a suitability cutoff was set for each of the four topic sections. The final validation resulted in 100% agreement between the users on four separate manuscripts, showing that the SOAR tool may be used to facilitate the standardized and transparent screening of microarray literature for environmental human health risk assessment.

Carbon black nanoparticle intratracheal instillation does not alter cardiac gene expression

Exposure to nanoparticles has been associated with inflammation-related progression of atherosclerosis. To examine nanoparticle-induced cardiac effects in more detail, we characterized heart gene expression profiles alongside plasma proteins associated with cardiovascular disease in C57BL/6 mice intratracheally instilled with vehicle or 0.162 mg Printex 90 carbon black nanoparticles (CBNPs). Mice were killed 1, 3, and 28 days after the exposure and expression profiles were derived using DNA microarrays. Cardiac gene expression was unperturbed by CBNP exposure in two independent experiments, despite substantive changes in pulmonary and hepatic gene expression. MicroRNAs were not affected. Plasma levels of cell adhesion molecules (sE-selectin, sICAM-1, sVCAM-1) and total PAI-1 were immediately increased up to day 3, whereas Apo-A1 and Apo-E were marginally decreased on day 1. These data suggest that though adverse cardiovascular effects are likely following CBNP exposure, these effects are unlikely to be mediated by major direct effects on cardiac gene expression.

Toxicological and epidemiological studies of cardiovascular effects of ambient air fine particulate matter (PM2.5) and its chemical components: coherence and public health implications

Recent investigations on PM2.5 constituents' effects in community residents have substantially enhanced our knowledge on the impacts of specific components, especially the HEI-sponsored National Particle Toxicity Component (NPACT) studies at NYU and UW-LRRI that addressed the impact of long-term PM2.5 exposure on cardiovascular disease (CVD) effects. NYU's mouse inhalation studies at five sites showed substantial variations in aortic plaque progression by geographic region that was coherent with the regional variation in annual IHD mortality in the ACS-II cohort, with both the human and mouse responses being primarily attributable to the coal combustion source category. The UW regressions of associations of CVD events and mortality in the WHI cohort, and of CIMT and CAC progression in the MESA cohort, indicated that [Formula: see text] had stronger associations with CVD-related human responses than OC, EC, or Si. The LRRI's mice had CVD-related biomarker responses to [Formula: see text]. NYU also identified components most closely associated with daily hospital admissions (OC, EC, Cu from traffic and Ni and V from residual oil). For daily mortality, they were from coal combustion ([Formula: see text], Se, and As). While the recent NPACT research on PM2.5 components that affect CVD has clearly filled some major knowledge gaps, and helped to define remaining uncertainties, much more knowledge is needed on the effects in other organ systems if we are to identify and characterize the most effective and efficient means for reducing the still considerable adverse health impacts of ambient air PM. More comprehensive speciation data are needed for better definition of human responses.

Bioassay-directed fractionation and sub-fractionation for mutagenicity and chemical analysis of diesel exhaust particles

Several types of diesel exhaust particles (DEPs) have been used for toxicology studies, including a high-organic automobile DEP (A-DEP) from Japan, and a low-organic forklift DEP developed by the National Institute of Standards and Technology (N-DEP). However, these DEPs were not characterized extensively for chemical composition or sub-fractionated and tested extensively for mutagenicity. We collected a compressor-generated DEP (C-DEP) and characterized it by conducting bioassay-directed fractionation of the extractable organics in Salmonella and correlating the results by hierarchical clustering with the concentrations of 32 polycyclic aromatic hydrocarbons (PAHs). Relative to A- and N-DEP, the mutagenic potency of C-DEP was intermediate in TA100 +S9 (PAH mutagenicity) but was lowest in TA98 -S9 (nitroarene mutagenicity). More than 50% of the mass of the extractable organics of C-DEP eluted in the nonpolar Fraction 1, and only ∼20% eluted in the moderately polar Fractions 2 and 3. However, most of the mutagenicity eluted in Fractions 2 and 3, similar to A-DEP but different from N-DEP. HPLC-derived mutagrams of 62 sub-fractions per fraction confirmed that most of the mutagenicity was due to moderately polar compounds. The diagnostic strains identified a strong role for PAHs, nitroarenes, aromatic amines, and oxy-PAHs in the mutagenicity of C-DEP. Hierarchical clustering confirmed the importance of oxy-PAHs but not that of nitroarenes. To our knowledge this is the first use of hierarchical clustering to correlate chemical composition with the mutagenicity of a complex mixture. The chemical analysis and mutagenicity of C-DEP described here makes C-DEP suitable for additional toxicological studies.

Diesel exhaust induced pulmonary and cardiovascular impairment: the role of hypertension intervention

Exposure to diesel exhaust (DE) and associated gases is linked to cardiovascular impairments; however, the susceptibility of hypertensive individuals is poorly understood. The objectives of this study were (1) to determine cardiopulmonary effects of gas-phase versus whole-DE and (2) to examine the contribution of systemic hypertension in pulmonary and cardiovascular effects. Male Wistar Kyoto (WKY) rats were treated with hydralazine to reduce blood pressure (BP) or l-NAME to increase BP. Spontaneously hypertensive (SH) rats were treated with hydralazine to reduce BP. Control and drug-pretreated rats were exposed to air, particle-filtered exhaust (gas), or whole DE (1500μg/m(3)), 4h/day for 2days or 5days/week for 4weeks. Acute and 4-week gas and DE exposures increased neutrophils and γ-glutamyl transferase (γ-GT) activity in lavage fluid of WKY and SH rats. DE (4weeks) caused pulmonary albumin leakage and inflammation in SH rats. Two-day DE increased serum fatty acid binding protein-3 (FABP-3) in WKY. Marked increases occurred in aortic mRNA after 4-week DE in SH (eNOS, TF, tPA, TNF-α, MMP-2, RAGE, and HMGB-1). Hydralazine decreased BP in SH while l-NAME tended to increase BP in WKY; however, neither changed inflammation nor BALF γ-GT. DE-induced and baseline BALF albumin leakage was reduced by hydralazine in SH rats and increased by l-NAME in WKY rats. Hydralazine pretreatment reversed DE-induced TF, tPA, TNF-α, and MMP-2 expression but not eNOS, RAGE, and HMGB-1. ET-1 was decreased by HYD. In conclusion, antihypertensive drug treatment reduces gas and DE-induced pulmonary protein leakage and expression of vascular atherogenic markers.

From particles to patients: oxidative stress and the cardiovascular effects of air pollution

Air pollution, especially airborne particulate matter (PM), is associated with an increase in both morbidity and mortality from cardiovascular disease, although the underlying mechanisms remain incompletely established. The one consistent observation that links the pulmonary and cardiovascular effects of inhaled PM is oxidative stress. This article examines the evidence for the role of oxidative stress in the cardiovascular effects of air pollution, beginning with observations from epidemiological and controlled exposure studies and then exploring potential mechanistic pathways involving free radical generation from PM itself, to effects of PM on cell cultures, isolated organs, healthy animals and animal models of disease. Particular emphasis is placed on the vascular and atherosclerotic effects of urban air pollution and diesel exhaust emissions as rich sources of environmental ultrafine particles.

Cardiovascular and thermoregulatory responses of unrestrained rats exposed to filtered or unfiltered diesel exhaust

Diesel exhaust has been associated with adverse cardiovascular and pulmonary health effects. The relative contributions of the gas phase and particulate components of diesel exhaust are less well understood. We exposed telemetered Wistar-Kyoto rats to air or diesel exhaust that was either filtered (F) or unfiltered [gas-phase plus diesel exhaust particles (DEP)], containing ~1.9 mg/m³ of particulate matter for 5 h/day; 5 days/week for 4 consecutive weeks. Blood pressure (BP), core temperature (T(c)), heart rate (HR), and cardiac contractility (CC) estimated by the QA interval were monitored by radiotelemetry during exposure as well as during a 2-week period of recovery. Pulmonary injury and inflammation markers were analysed after 2-day, and 4 weeks of exposure, and 2-week recovery. Exposure to F or DEP was associated with a trend for a reduction in BP during weeks 1, 2 and 4. A reduction in HR in the DEP group was apparent during week 4. Exposure to DEP but not F was associated with significant reduction in CC over weeks 1-4. There was also a slight elevation in T(c) during DEP exposure. All telemetry parameters were normal during recovery at night and a 2-week recovery period. Neutrophilic inflammation in bronchoalveolar lavage fluid was evident after 2 days and 4 weeks of exposure to F and DEP. There were no signs of inflammation after 2-week recovery. We found a significant decrease in CC and slight reduction in BP. Exposure to DEP and F is associated with pulmonary inflammation, and mild effects on HR, BP, and T(c) but there is a marked effect of DEP on CC.

Manufactured and airborne nanoparticle cardiopulmonary interactions: a review of mechanisms and the possible contribution of mast cells

Human inhalation exposures to manufactured nanoparticles (NP) and airborne ultrafine particles (UFP) continues to increase in both occupational and environmental settings. UFP exposures have been associated with increased cardiovascular mortality and morbidity, while ongoing research supports adverse systemic and cardiovascular health effects after NP exposures. Adverse cardiovascular health effects include alterations in heart rate variability, hypertension, thrombosis, arrhythmias, increased myocardial infarction, and atherosclerosis. Exactly how UFP and NP cause these negative cardiovascular effects is poorly understood, however a variety of mediators and mechanisms have been proposed. UFP and NP, as well as their soluble components, are known to systemically translocate from the lung. Translocated particles could mediate cardiovascular toxicity through direct interactions with the vasculature, blood, and heart. Recent study suggests that sensory nerve stimulation within the lung may also contribute to UFP- and NP-induced acute cardiovascular alterations. Activation of sensory nerves, such as C-fibers, within the lung may result in altered cardiac rhythm and function. Lastly, release of pulmonary-derived mediators into systemic circulation has been proposed to facilitate cardiovascular effects. In general, these proposed pulmonary-derived mediators include proinflammatory cytokines, oxidatively modified macromolecules, vasoactive proteins, and prothrombotic factors. These pulmonary-derived mediators have been postulated to contribute to the subsequent prothrombotic, atherogenic, and inflammatory effects after exposure. This review will evaluate the potential contribution of individual mediators and mechanisms in facilitating cardiopulmonary toxicity following inhalation of UFP and NP. Lastly, we will appraise the literature and propose a hypothesis regarding the possible role of mast cells in contributing to these systemic effects.

In vivo screening to determine neurological hazards of nitrogen dioxide (NO2) using Wistar rats

NO(2) is a well-known indoor and outdoor pollutant that may cause adverse health problems. Recently, accumulating but extremely limited evidences show that NO(2) possibly express neurotoxicity and is responsible for various neurological disorders. In the present study, neurological hazard of NO(2) and possible mechanisms were determined in rat pallium following a repetitive inhalation exposure with various concentrations (5, 10 and 20mg/m(3)). After 7-day exposure (6h/day), observable adverse effects were induced encompassing decreased ratio of brain to body weight, mild brain pathology, increased neuronal apoptosis, altered antioxidants (Cu/Zn-SOD, Mn-SOD, GPx and NO) activity and increasing formation of PCO. NO(2) inhalation also induced augment of oncogenes (c-fos, c-jun) levels, and deregulation of apoptosis-related genes (p53, bax and bcl-2) expression. With all above data, the present report provided essential information for the characterization of the neurotoxic hazard of NO(2) and related mechanisms, which is required in response to the general concern about the vulnerability of the neurological system to it.

Myocardial Mitochondrial Injury Induced by Pulmonary Exposure to Particulate Matter in Rats

Exposure to air pollution has been associated with acute myocardial ischemia, impaired myocardrial function, and ST-segment depression. Particulate matter (PM)–associated metals, especially vanadium and nickel, have been implicated in observed cardiovascular impairments. We aimed to assess the effect of single intratracheal pulmonary exposure to vanadium-rich respirable oil combustion PM (HP-10) on the intrinsic myocardial ischemic tolerance and mitochondrial integrity in rats. The authors subjected isolated heart tissue slices derived from saline or PM-exposed rats to low glucose low oxygen induced ischemia followed by oxygenated condition with glucose supplementation. Mitochondrial structural integrity was determined by TEM (transmission electron microscopy) and functionality by the 3-(4, 5 dimethylthiazol-2yl)-2, 5 diphenyltetrazolium bromide (MTT) assay. Rats exposed to PM exhibited no apparent inhibition of mitochondrial dehydrogenase activity in oxygenated conditions at 24 or 48 hr post–PM exposure. However, in conditions of simulated ischemia/reoxygenation, these heart slices showed a delayed but consistent and significant decrease in dehydrogenase activity compared to controls at 48 hr after exposure to PM. Electron microscopy revealed significant myocardial mitochondrial injury upon exposure to PM characterized by mitochondrial swelling and fusion. The authors conclude that exposure to soluble vanadium-rich PM induces mitochondrial functional impairment and structural abnormality, which compromises mitochondrial respiration and results in decreased tolerance to ischemia/reoxygenation in rats.

Diesel exhaust particulate induces pulmonary and systemic inflammation in rats without impairing endothelial function ex vivo or in vivo

Background

Inhalation of diesel exhaust impairs vascular function in man, by a mechanism that has yet to be fully established. We hypothesised that pulmonary exposure to diesel exhaust particles (DEP) would cause endothelial dysfunction in rats as a consequence of pulmonary and systemic inflammation.

Methods

Wistar rats were exposed to DEP (0.5 mg) or saline vehicle by intratracheal instillation and hind-limb blood flow, blood pressure and heart rate were monitored in situ 6 or 24 h after exposure. Vascular function was tested by administration of the endothelium-dependent vasodilator acetylcholine (ACh) and the endothelium-independent vasodilator sodium nitroprusside (SNP) in vivo and ex vivo in isolated rings of thoracic aorta, femoral and mesenteric artery from DEP exposed rats. Bronchoalveolar lavage fluid (BALF) and blood plasma were collected to assess pulmonary (cell differentials, protein levels & interleukin-6 (IL-6)) and systemic (IL-6), tumour necrosis factor alpha (TNFα) and C-reactive protein (CRP)) inflammation, respectively.

Results

DEP instillation increased cell counts, total protein and IL-6 in BALF 6 h after exposure, while levels of IL-6 and TNFα were only raised in blood 24 h after DEP exposure. DEP had no effect on the increased hind-limb blood flow induced by ACh in vivo at 6 or 24 h. However, responses to SNP were impaired at both time points. In contrast, ex vivo responses to ACh and SNP were unaltered in arteries isolated from rats exposed to DEP.

Conclusions

Exposure of rats to DEP induces both pulmonary and systemic inflammation, but does not modify endothelium-dependent vasodilatation. Other mechanisms in vivo limit dilator responses to SNP and these require further investigation.

Vascular and thrombogenic effects of pulmonary exposure to Libby amphibole

Exposure to Libby amphibole (LA) asbestos is associated with increased incidences of human autoimmune disease and mortality related to cardiovascular diseases. However, the systemic and vascular impacts are less well examined because of the dominance of pulmonary disease. It was postulated that regardless of the type of exposure scenario, LA exposure might produce systemic and vascular inflammogenic and thrombotic alterations in healthy and cardiovascular compromised rat models. Samples from three independent studies were examined. In the first study, male Wistar Kyoto (WKY), spontaneously hypertensive (SH), and SH heart failure (SHHF) rats were intratracheally instilled once with 0 (vehicle), 0.25, or 1 mg/rat of LA. In the second study, F344 rats were instilled with vehicle or LA at 0.5, 1.5, or 5 mg/rat. In the third study, F344 rats were instilled with the same mass concentrations of LA delivered by biweekly multiple instillations over 3 mo to simulate an episodic subchronic exposure. Complete blood count, platelet aggregation, serum cytokines, and biomarkers of systemic and aortic effects were examined. LA reduced adenosine diphosphate (ADP)-induced platelet aggregation and decreased circulating platelets in WKY (1 mg/rat) and F344 (5 mg/rat) at the 3-mo time point but did not do so in SH or SHHF rats. A decline in circulating lymphocytes with age appeared to be exacerbated by LA exposure in F344 rats but the differences were not significant. Aorta mRNA expression for biomarkers of oxidative stress (HO-1, LOX-1), inflammation (MIP-2), and thrombosis (tPA, PAI-1, vWf) were increased at baseline in SH and SHHF relative to WKY. LA exposure upregulated several of these biomarkers and also those involved in aortic contractility of WKY rats at 3 mo, suggesting thrombogenic, vasocontractile, and oxidative stress-mediated impairments. The aorta changes in F344 rats were less remarkable than changes noted in WKY following LA exposure. In conclusion, exposure to LA decreased circulating platelets and platelet coagulability while increasing the expression of oxidative stress, thrombosis, and vasoconstriction biomarkers in the aorta of healthy rats. These changes were similar to those noted at baseline in SH and SHHF rats, suggesting that LA-induced pulmonary injury might increase the risk of developing cardiovascular disease in healthy individuals.

Diesel exhaust activates and primes microglia: air pollution, neuroinflammation, and regulation of dopaminergic neurotoxicity

BACKGROUND

Air pollution is linked to central nervous system disease, but the mechanisms responsible are poorly understood.

OBJECTIVES

Here, we sought to address the brain-region-specific effects of diesel exhaust (DE) and key cellular mechanisms underlying DE-induced microglia activation, neuroinflammation, and dopaminergic (DA) neurotoxicity.

METHODS

Rats were exposed to DE (2.0, 0.5, and 0 mg/m3) by inhalation over 4 weeks or as a single intratracheal administration of DE particles (DEP; 20 mg/kg). Primary neuron-glia cultures and the HAPI (highly aggressively proliferating immortalized) microglial cell line were used to explore cellular mechanisms.

RESULTS

Rats exposed to DE by inhalation demonstrated elevated levels of whole-brain IL-6 (interleukin-6) protein, nitrated proteins, and IBA-1 (ionized calcium-binding adaptor molecule 1) protein (microglial marker), indicating generalized neuroinflammation. Analysis by brain region revealed that DE increased TNFα (tumor necrosis factor-α), IL-1β, IL-6, MIP-1α (macrophage inflammatory protein-1α) RAGE (receptor for advanced glycation end products), fractalkine, and the IBA-1 microglial marker in most regions tested, with the midbrain showing the greatest DE response. Intratracheal administration of DEP increased microglial IBA-1 staining in the substantia nigra and elevated both serum and whole-brain TNFα at 6 hr posttreatment. Although DEP alone failed to cause the production of cytokines and chemokines, DEP (5 μg/mL) pretreatment followed by lipopolysaccharide (2.5 ng/mL) in vitro synergistically amplified nitric oxide production, TNFα release, and DA neurotoxicity. Pretreatment with fractalkine (50 pg/mL) in vitro ameliorated DEP (50 μg/mL)-induced microglial hydrogen peroxide production and DA neurotoxicity.

CONCLUSIONS

Together, these findings reveal complex, interacting mechanisms responsible for how air pollution may cause neuroinflammation and DA neurotoxicity.

Vascular and cardiac impairments in rats inhaling ozone and diesel exhaust particles

BACKGROUND

Mechanisms of cardiovascular injuries from exposure to gas and particulate air pollutants are unknown.

OBJECTIVE

We sought to determine whether episodic exposure of rats to ozone or diesel exhaust particles (DEP) causes differential cardiovascular impairments that are exacerbated by ozone plus DEP.

METHODS AND RESULTS

Male Wistar Kyoto rats (10-12 weeks of age) were exposed to air, ozone (0.4 ppm), DEP (2.1 mg/m(3)), or ozone (0.38 ppm) + DEP (2.2 mg/m(3)) for 5 hr/day, 1 day/week for 16 weeks, or to air, ozone (0.51 or 1.0 ppm), or DEP (1.9 mg/m(3)) for 5 hr/day for 2 days. At the end of each exposure period, we examined pulmonary and cardiovascular biomarkers of injury. In the 16-week study, we observed mild pulmonary pathology in the ozone, DEP, and ozone + DEP exposure groups, a slight decrease in circulating lymphocytes in the ozone and DEP groups, and decreased platelets in the DEP group. After 16 weeks of exposure, mRNA biomarkers of oxidative stress (hemeoxygenase-1), thrombosis (tissue factor, plasminogen activator inhibitor-1, tissue plasminogen activator, and von Willebrand factor), vasoconstriction (endothelin-1, endothelin receptors A and B, endothelial NO synthase) and proteolysis [matrix metalloprotease (MMP)-2, MMP-3, and tissue inhibitor of matrix metalloprotease-2] were increased by DEP and/or ozone in the aorta, but not in the heart. Aortic LOX-1 (lectin-like oxidized low-density lipoprotein receptor-1) mRNA and protein increased after ozone exposure, and LOX-1 protein increased after exposure to ozone + DEP. RAGE (receptor for advanced glycation end products) mRNA increased in the ozone + DEP group. Exposure to ozone or DEP depleted cardiac mitochondrial phospholipid fatty acids (DEP > ozone). The combined effect of ozone and DEP exposure was less pronounced than exposure to either pollutant alone. Exposure to ozone or DEP for 2 days (acute) caused mild changes in the aorta.

CONCLUSIONS

In animals exposed to ozone or DEP alone for 16 weeks, we observed elevated biomarkers of vascular impairments in the aorta, with the loss of phospholipid fatty acids in myocardial mitochondria. We conclude that there is a possible role of oxidized lipids and protein through LOX-1 and/or RAGE signaling.

Antiretrovirals induce endothelial dysfunction via an oxidant-dependent pathway and promote neointimal hyperplasia

Human immunodeficiency virus-1 antiretroviral treatment is associated with an increased incidence of atherosclerosis. We hypothesized that antiretrovirals directly impair endothelial function after short-term exposure and that with chronic exposure, this dysfunction promotes a proliferative response, inducing neointimal hyperplasia, thus contributing to vascular lesion formation. To test this hypothesis, we treated mice with the nucleoside reverse transcriptase inhibitor azidothymidine (AZT), the protease inhibitor indinavir, or AZT + indinavir. Treatment with AZT or AZT + indinavir for 5 days impaired endothelium-dependent vessel relaxation. Though indinavir treatment alone did not alter vessel relaxation, it potentiated the impairment of endothelium-dependent relaxation induced by AZT. Coadministration of the antioxidant Mn (III) tetrakis (1-methyl-4-pyridyl) porphyrin attenuated antiretroviral-induced endothelial dysfunction, suggesting that oxidant production may have a causal role in the observed endothelial dysfunction. To test whether the antiretrovirals promote a proliferative response following endothelial dysfunction, we treated mice with antiretrovirals for 14 days and then induced a carotid endothelial injury. Two weeks later, we observed a dramatic increase in neointimal formation in all antiretroviral-treated animals, and the newly formed neointima was comprised mainly of proliferated smooth muscle cells. Although a functional endothelium surrounding the lesioned area and re-endothelialization across the area of injury is important in reducing proliferation in this model, we tested whether the neointimal hyperplasia was associated with endothelial dysfunction. Plasma levels of asymmetric dimethylarginine, a biomarker of endothelial dysfunction, increased after treatment with indinavir or AZT + indinavir. On the other hand, treatment with AZT or AZT + indinavir increased endothelial vascular cell adhesion molecule staining. We conclude that short-term treatment with antiretrovirals elicited a direct impairment in endothelial function, in part via an oxidant-dependent pathway. These antiretrovirals also exacerbated injury-induced vascular smooth muscle cell proliferation and neointimal hyperplasia, likely because of their inhibition of endothelial function.

Predicting environmental chemical factors associated with disease-related gene expression data

BACKGROUND

Many common diseases arise from an interaction between environmental and genetic factors. Our knowledge regarding environment and gene interactions is growing, but frameworks to build an association between gene-environment interactions and disease using preexisting, publicly available data has been lacking. Integrating freely-available environment-gene interaction and disease phenotype data would allow hypothesis generation for potential environmental associations to disease.

METHODS

We integrated publicly available disease-specific gene expression microarray data and curated chemical-gene interaction data to systematically predict environmental chemicals associated with disease. We derived chemical-gene signatures for 1,338 chemical/environmental chemicals from the Comparative Toxicogenomics Database (CTD). We associated these chemical-gene signatures with differentially expressed genes from datasets found in the Gene Expression Omnibus (GEO) through an enrichment test.

RESULTS

We were able to verify our analytic method by accurately identifying chemicals applied to samples and cell lines. Furthermore, we were able to predict known and novel environmental associations with prostate, lung, and breast cancers, such as estradiol and bisphenol A.

CONCLUSIONS

We have developed a scalable and statistical method to identify possible environmental associations with disease using publicly available data and have validated some of the associations in the literature.

Tungsten carbide cobalt nanoparticles exert hypoxia-like effects on the gene expression level in human keratinocytes

Background

Tungsten carbide (WC) and tungsten carbide cobalt (WC-Co) nanoparticles are of occupational health relevance because of the increasing usage in hard metal industries. Earlier studies showed an enhanced toxic potential for WC-Co compared to WC or cobalt ions alone. Therefore, we investigated the impact of these particles, compared to cobalt ions applied as CoCl₂, on the global gene expression level in human keratinocytes (HaCaT) in vitro.

Results

WC nanoparticles exerted very little effects on the transcriptomic level after 3 hours and 3 days of exposure. In contrast, WC-Co nanoparticles caused significant transcriptional changes that were similar to those provoked by CoCl₂. However, CoCl₂ exerted even more pronounced changes in the transcription patterns. Gene set enrichment analyses revealed that the differentially expressed genes were related to hypoxia response, carbohydrate metabolism, endocrine pathways, and targets of several transcription factors. The role of the transcription factor HIF1 (hypoxia inducible factor 1) is particularly highlighted and aspects of downstream events as well as the role of other transcription factors related to cobalt toxicity are considered.

Conclusions

This study provides extensive data useful for the understanding of nanoparticle and cobalt toxicity. It shows that WC nanoparticles caused low transcriptional responses while WC-Co nanoparticles are able to exert responses similar to that of free cobalt ions, particularly the induction of hypoxia-like effects via interactions with HIF1α in human keratinocytes. However, the enhanced toxicity of WC-Co particles compared to CoCl₂ could not be explained by differences in gene transcription.

Differential pulmonary retention of diesel exhaust particles in Wistar Kyoto and spontaneously hypertensive rats

Spontaneously hypertensive (SH) and normotensive Wistar Kyoto (WKY) rats have been used for understanding the mechanisms of variations in susceptibility to airborne pollutants. We examined the lung burden of diesel exhaust particles (DEP) following inhalation of diesel engine exhaust (DEE) in both strains. The kinetics of clearance was also examined after single intratracheal (IT) instillation of DEP. Lungs were analyzed for DEP elemental carbon (EC) after exposure to DEE (0, 500, or 2000 microg/m(3) 4 h/day, 5 days/week x 4 weeks). SH rats had 16% less DEP-EC at 500 and 32% less at 2000 microg/m(3) in the lungs, despite having 50% higher than the average minute volume. No strain-related differences were noted in number of alveolar macrophages or their average DEP load as evident from examining cells in bronchoalveolar lavage fluid (BALF). The kinetics of DEP clearance from lungs of male WKY and SH rats was studied following a single instillation at 0.0 or 8.33 mg/kg of DEP standard reference material (SRM 2975) from the National Institute of Standards Technology. SH rats cleared 60% DEP over 112 days while minimal clearance occurred from the lungs of WKY. The pattern of DEP-induced inflammatory response assessed by BALF analysis was similar in both strains, although the overall protein leak was slightly greater in SH rats. A time-dependent accumulation of DEP occurred in tracheal lymph nodes of both strains (SH > WKY). Thus, SH rats may clear DEP more efficiently from their lungs than normotensive WKY rats, with a small contribution of more effective lymphatic drainage.