Oxidatively damaged DNA and inflammation in the liver of dyslipidemic ApoE-/- mice exposed to diesel exhaust particles

Air pollutants and the risk of incident hepatobiliary diseases: A large prospective cohort study in the UK Biobank

The association between air pollutants and hepatobiliary pancreatic diseases remains inconclusive. This study analyzed up to 247,091 participants of White European ancestry (aged 37 to 73 years at recruitment) from the UK Biobank, a large-scale prospective cohort with open access. An air pollution score was utilized to assess the combined effect of PM2.5, PM2.5-10, PM10, NO2, and NOX on total hepatobiliary pancreatic diseases, liver diseases, cholecyst diseases, and pancreatic diseases. Cox proportional hazard models were employed to evaluate the relationships between air pollutants and the incidence of these diseases. Restricted cubic spline regressions were used to examine the dose-response association between air pollutants and the risk of hepatobiliary pancreatic diseases. We identified 4865 cases of total hepatobiliary pancreatic diseases, over a median follow-up of 10.86 years. The air pollution scores were moderately associated with increased liver disease risk (HR = 1.009, 95 % CI: 1.004, 1.014), but not with cholecyst and pancreatic diseases. Among the individual air pollutants, PM2.5 (HR = 1.069, 95 % CI: 1.025, 1.115) and PM10 (HR = 1.036, 95 % CI: 1.011, 1.061) significantly increased liver disease risk. Males showed a higher risk of liver diseases with PM2.5 (HR = 1.075, 95 % CI: 1.015, 1.139). Additionally, individuals with overweight (HR = 1.125, 95 % CI: 1.052, 1.203), age ≥ 60 and ≤73 (HR = 1.098, 95 % CI: 1.028, 1.172), and alcohol intake ≥ 14 unit/week (HR = 1.078, 95 % CI: 1.006, 1.155) had a higher risk of developing liver diseases at high expose to PM2.5. This study suggests that prolonged exposure to ambient air pollutants may elevate the risk of liver diseases.

Traditional lifestyle factors partly mediate the association of socioeconomic position with intrahepatic lipid content: The Maastricht study

Background & Aims

Recent studies have unveiled an association between socioeconomic position (SEP) and intrahepatic lipid (IHL) content. The aim of this study was to examine to what extent traditional lifestyle factors mediate the relationship between SEP and IHL content, independent of aetiology, and non-alcoholic fatty liver disease (NAFLD).

Methods

We used cross-sectional data derived from The Maastricht Study (N = 4,001; mean age: 60 years, 49% women, 32% low education level, 21% diabetes, 21% NAFLD). Education, income, and occupation were used as indicators of SEP. Physical activity (accelerometer), intake of total energy, alcohol, saturated fat, protein, vitamin E, dietary fibre, and fructose from sugar-sweetened beverages (SSBs) and fruit juice (food frequency questionnaires) were potential mediators. IHL content was quantified by magnetic resonance imaging. Age, sex, and type 2 diabetes were covariates. Multiple parallel mediation analyses (bootstraps = 10,000) were performed.

Results

Individuals with a low education level had a 1.056-fold higher IHL content (95% CI: 1.03-1.08) and a 44% greater NAFLD risk (OR:1.44; 95% CI:1.18-1.77) compared with those with higher education levels. Approximately 8.9% of educational disparity in risk of IHL content was attributable to moderate-to-vigorous physical activity; 6.3% to fructose intake from SSBs; 5.5% to dietary fibre; and -23% to alcohol. Approximately 8.7% of educational disparity in risk of NAFLD was attributable to moderate-to-vigorous physical activity; and 7.7% to fructose intake from SSBs. However, the indirect effect of these mediators was small (0.998 for IHL content and 1.045 for NAFLD) in comparison to the total effect. Similar results were found when income and occupation were used as SEP indicators.

Conclusions

Societal measures may alleviate the burden of NAFLD and further studies that identify mediators other than traditional lifestyle factors are warranted to define the relationship underlying SEP and IHL content.

Impact and implications

Individuals with a low or medium level of education, income, or occupational status had more fat accumulation in their livers than individuals with a higher education, income, or occupational status. This difference may be attributed to the influence of unhealthy lifestyle factors, such as reduced physical activity and a higher intake of sugar-sweetened beverages among individuals with lower socioeconomic position. Nevertheless, other yet unknown factors may also play a role.

Long-term exposure to air pollution and incident non-alcoholic fatty liver disease and cirrhosis: A cohort study

BACKGROUND AND AIMS

Epidemiological evidence regarding the association of air pollution with the risk of non-alcoholic fatty liver disease (NAFLD) is limited. This study was to examine the associations of long-term exposure to various air pollutants and overall air pollution with risk of incident NAFLD as well as cirrhosis, a major liver-related morbidity for NAFLD.

METHODS

Included were 456 687 UK residents. Air pollution data included PM_2.5 , PM_2.5-10 , PM₁₀ , NO₂ and NO_x . A weighted air pollution score was also generated from PM₁₀ and NO_x . Cox proportional hazard models were employed to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

We identified 4978 cases of NAFLD and 1575 cases of incident cirrhosis, over a median follow-up of 11.9 years. PM_2.5 , PM₁₀ , NO₂ and NO_x exposures contributed to the excess risk of NAFLD associated with air pollution score; and the corresponding adjusted HRs (95% CI) were 1.10 (1.05, 1.14), 1.14 (1.09, 1.20), 1.19 (1.13, 1.24) and 1.11 (1.07, 1.15), respectively, for each interquartile range increase in the above specific air pollutants. Similar patterns were also indicated for cirrhosis risk. Alcohol consumption was an effect modifier for the association between air pollution score and NAFLD risk, whereas body mass index modified the association for cirrhosis risk.

CONCLUSION

Long-term exposure to air pollution was associated with risks of NAFLD and cirrhosis among the UK population.

Mining biomarkers from routine laboratory tests in clinical records associated with air pollution health risk assessment

Clinical laboratory in hospital can produce amounts of health data every day. The purpose of this study was to mine biomarkers from clinical laboratory big data associated with the air pollution health risk assessment using clinical records. 13, 045, 629 clinical records of all 27 routine laboratory tests in Changsha Central Hospital, including ALB, TBIL, ALT, DBIL, AST, TP, UREA, UA, CREA, GLU, CK, CKMB, LDL-C, TG, TC, HDL-C, CRP, WBC, Na, K, Ca, Cl, APTT, PT, FIB, TT, RBC and those daily air pollutants concentration monitoring data of Changsha, including PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃ from 2014 to 2016, were retrieved. The moving average method was used to the biological reference interval was established. The tests results were converted into daily abnormal rate. After data cleaning, GAM statistical model construction and data analysis, a concentration-response relationship between air pollutants and daily abnormal rate of routine laboratory tests was observed. Our study found that PM_2.5 had a stable association with TP (lag07), ALB (lag07), ALT (lag07), AST (lag07), TBIL (lag07), DBIL (lag07), UREA (lag07), CREA (lag07), UA (lag07), CK (lag 06), GLU (lag07), WBC (lag07), Cl (lag07) and Ca (lag07), (P < 0.05); O₃ had a stable association with AST (lag01), CKMB (lag06), TG (lag07), TC (lag05), HDL-C (lag07), K (lag05) and RBC (lag07) (P < 0.05); CO had a stable association with UREA (lag07), Na (lag7) and PT (lag07) (P < 0.05); SO₂ had a stable association with TP (lag07) and LDL-C (lag0) (P < 0.05); NO₂ had a stable association with APTT (lag7) (P < 0.05). These results showed that different air pollutants affected different routine laboratory tests and presented different pedigrees. Therefore, biomarkers mined from routine laboratory tests may potentially be used to low-cost assess the health risks associated with air pollutants.

The links of fine airborne particulate matter exposure to occurrence of cardiovascular and metabolic diseases in Michigan, USA

Air pollutants, particularly airborne particulate matter with aerodynamic diameter < 2.5μm (PM2.5), have been linked to the increase in mortality and morbidity associated with cardiovascular and metabolic diseases. In this study, we investigated the dose-risk relationships between PM2.5 concentrations and occurrences of cardiovascular and metabolic diseases as well as the confounding socioeconomic factors in Michigan, USA, where PM2.5 levels are generally considered acceptable. Multivariate linear regression analyses were performed to investigate the relationship between health outcome and annual ground-level PM2.5 concentrations of 82 counties in Michigan. The analyses revelated significant linear dose-response associations between PM2.5 concentrations and cardiovascular disease (CVD) hospitalization. A 10 μg/m3 increase in PM2.5 exposure was found to be associated with a 3.0% increase in total CVD, 0.45% increase in Stroke, and a 0.3% increase in Hypertension hospitalization rates in Medicare beneficiaries. While the hospitalization rates of Total Stroke, Hemorrhagic Stroke, and Hypertension in urbanized counties were significantly higher than those of rural counties, the death rates of coronary heart disease and ischemic stroke in urbanized counties were significantly lower than those of rural counties. These results were correlated with the facts that PM2.5 levels in urbanized counties were significantly higher than that in rural counties and that the percentage of the population with health insurance and the median household income in rural counties were significantly lower. While obesity prevalence showed evidence of a weak positive correlation (ρ = 0.20, p-value = 0.078) with PM2.5 levels, there was no significant dose-response association between county diabetes prevalence rates and PM2.5 exposure in Michigan. In summary, this study revealed strong dose-response associations between PM2.5 concentrations and CVD incidence in Michigan, USA. The socioeconomic factors, such as access to healthcare resources and median household income, represent important confounding factors that could override the impact of PM2.5 exposure on CVD mortality.

Non-Alcoholic Fatty Liver Disease: Metabolic, Genetic, Epigenetic and Environmental Risk Factors

Non-alcoholic fatty liver disease (NAFLD) is one of the most frequent causes of chronic liver disease in the Western world, probably due to the growing prevalence of obesity, metabolic diseases, and exposure to some environmental agents. In certain patients, simple hepatic steatosis can progress to non-alcoholic steatohepatitis (NASH), which can sometimes lead to liver cirrhosis and its complications including hepatocellular carcinoma. Understanding the mechanisms that cause the progression of NAFLD to NASH is crucial to be able to control the advancement of the disease. The main hypothesis considers that it is due to multiple factors that act together on genetically predisposed subjects to suffer from NAFLD including insulin resistance, nutritional factors, gut microbiota, and genetic and epigenetic factors. In this article, we will discuss the epidemiology of NAFLD, and we overview several topics that influence the development of the disease from simple steatosis to liver cirrhosis and its possible complications.

Association between fine particle exposure and common test items in clinical laboratory: A time-series analysis in Changsha, China

Most studies on the health effects of PM_2.5 (fine particulate matter with diameter smaller than 2.5 μm) use indirect indicators, such as mortality and number of hospital visits. Recent research shows that biomarkers can also be used to evaluate the health effects of PM_2.5; however, these biomarkers are not very common. Clinical laboratories can provide a significant amount of test data that have been proven to have important diagnostic value. Therefore, we use big data analysis methods to find the associations between clinical laboratory common test items and PM_2.5 exposure. Data related to air pollution and meteorological information between 2014 and 2016 were obtained from the China National Environmental Monitoring Centre and the China National Meteorological Information Center. Additionally, data of 27 common test items from the same period were collected from Changsha Central Hospital. Primary analyses included a generalized additive model to analyze the associations between PM_2.5 concentration and common test items; the model was adjusted for time trends, weather conditions (temperature and humidity), and days of the week. Furthermore, we adjusted the effects of other air pollutants, such as PM₁₀, SO₂, NO₂, CO, and O₃. 17 items such as TP, ALB, ALT, AST, TBIL, DBIL, UREA, CREA, UA, GLU, LDL, WBC, K, Cl, Ca, TT, and FIB were significantly positively associated with PM_2.5 concentration (P< 0.05) and have concentration-response relationship. After adjusting the effect of PM₁₀+SO₂+NO₂+CO+O₃, TP, ALB, ALT, AST, TBIL, DBIL, UREA, CREA, UA, GLU, WBC, Cl, and Ca were still significantly associated with PM_2.5 concentration (P< 0.05). This current study suggested that clinical laboratory common test items may be used to assess and predict the health effects of PM_2.5 on the population.

The impact of polar fraction of the fine particulate matter on redox responses in different rat tissues

Particulate matter (PM) contains different chemical substances that have been associated with health effects and an increased risk of mortality due to their toxicity. In this study, fine particulate matter (PM_2.5) samples were collected in a region with rural characteristics (Seropédica (Se)) and another with some industries (Duque de Caxias (DC)) (Brazil, RJ). Rats were exposed to PM_2.5 extracts daily for 25 days at different dilutions: 10×, 5×, and a concentrated solution (CS). Biochemical analyses were investigated for total antioxidant capacity (ACAP), lipid peroxidation (LPO) levels, reduced glutathione (GSH) concentration, activity of glutamate cysteine ligase (GCL), and activity of glutathione S-transferase (GST). The liver showed a significant increase in GCL (DC-5×, DC-CS and Se-CS) and GST activities (DC-CS and Se-CS) in both regions when compared to the control group. In the renal cortex, GCL activity decreased in most of the tested groups while GST activity increased only in the 5× groups of both regions (DC and Se). In the renal medulla, GCL activity decreased for Se-10× and DC-CS but increased for Se-5×, and GST activity increased in the Se-10×, DC-5×, and DC-CS groups. Lung GCL increased in all groups for both regions. Moreover, this organ also showed an increase in GST activity when higher metal concentrations were present (5× and CS). TBARS levels were increased for all tissues in most tested concentrations. These data indicate that soluble compounds (e.g., metals) from PM_2.5 sampled in areas with different pollution indexes can change the redox status and cause damage to different tissues.

Outdoor Ambient Air Pollution and Neurodegenerative Diseases: the Neuroinflammation Hypothesis

PURPOSE OF REVIEW

Accumulating research indicates that ambient outdoor air pollution impacts the brain and may affect neurodegenerative diseases, yet the potential underlying mechanisms are poorly understood.

RECENT FINDINGS

The neuroinflammation hypothesis holds that elevation of cytokines and reactive oxygen species in the brain mediates the deleterious effects of urban air pollution on the central nervous system (CNS). Studies in human and animal research document that neuroinflammation occurs in response to several inhaled pollutants. Microglia are a prominent source of cytokines and reactive oxygen species in the brain, implicated in the progressive neuron damage in diverse neurodegenerative diseases, and activated by inhaled components of urban air pollution through both direct and indirect pathways. The MAC1-NOX2 pathway has been identified as a mechanism through which microglia respond to different forms of air pollution, suggesting a potential common deleterious pathway. Multiple direct and indirect pathways in response to air pollution exposure likely interact in concert to exert CNS effects.

Estimating Causal Effects of Local Air Pollution on Daily Deaths: Effect of Low Levels

BACKGROUND

Although many time-series studies have established associations of daily pollution variations with daily deaths, there are fewer at low concentrations, or focused on locally generated pollution, which is becoming more important as regulations reduce regional transport. Causal modeling approaches are also lacking.

OBJECTIVE

We used causal modeling to estimate the impact of local air pollution on mortality at low concentrations.

METHODS

Using an instrumental variable approach, we developed an instrument for variations in local pollution concentrations that is unlikely to be correlated with other causes of death, and examined its association with daily deaths in the Boston, Massachusetts, area. We combined height of the planetary boundary layer and wind speed, which affect concentrations of local emissions, to develop the instrument for particulate matter ≤ 2.5 μm (PM2.5), black carbon (BC), or nitrogen dioxide (NO2) variations that were independent of year, month, and temperature. We also used Granger causality to assess whether omitted variable confounding existed.

RESULTS

We estimated that an interquartile range increase in the instrument for local PM2.5 was associated with a 0.90% increase in daily deaths (95% CI: 0.25, 1.56). A similar result was found for BC, and a weaker association with NO2. The Granger test found no evidence of omitted variable confounding for the instrument. A separate test confirmed the instrument was not associated with mortality independent of pollution. Furthermore, the association remained when all days with PM2.5 concentrations > 30 μg/m3 were excluded from the analysis (0.84% increase in daily deaths; 95% CI: 0.19, 1.50).

CONCLUSIONS

We conclude that there is a causal association of local air pollution with daily deaths at concentrations below U.S. EPA standards. The estimated attributable risk in Boston exceeded 1,800 deaths during the study period, indicating that important public health benefits can follow from further control efforts. Citation: Schwartz J, Bind MA, Koutrakis P. 2017. Estimating causal effects of local air pollution on daily deaths: effect of low levels. Environ Health Perspect 125:23-29; http://dx.doi.org/10.1289/EHP232.

Tributyltin chloride induces renal dysfunction by inflammation and oxidative stress in female rats

Tributyltin chloride (TBT) is an organometallic pollutant that is used as a biocide in antifouling paints. TBT induces several toxic and endocrine-disrupting effects. However, studies evaluating the effects of TBT on renal function are rare. This study demonstrates that TBT exposure is responsible for improper renal function as well as the development of abnormal morphophysiology in mammalian kidneys. Female rats were treated with TBT, and their renal morphophysiology was assessed. Morphophysiological abnormalities such as decreased glomerular filtration rate and increased proteinuria levels were observed in TBT rats. In addition, increases in inflammation, collagen deposition and α-smooth muscle actin (α-SMA) protein expression were observed in TBT kidneys. A disrupted cellular redox balance and apoptosis in kidney tissue were also observed in TBT rats. TBT rats demonstrated reduced serum estrogen levels and estrogen receptor-α (ERα) protein expression in renal cortex. Together, these data provide in vivo evidence that TBT is toxic to normal renal function and that these effects may be associated with renal histopathology complications, such as inflammation and fibrosis.

The Apoe(-/-) mouse model: a suitable model to study cardiovascular and respiratory diseases in the context of cigarette smoke exposure and harm reduction

Atherosclerosis-prone apolipoprotein E-deficient (Apoe(-/-)) mice display poor lipoprotein clearance with subsequent accumulation of cholesterol ester-enriched particles in the blood, which promote the development of atherosclerotic plaques. Therefore, the Apoe(-/-) mouse model is well established for the study of human atherosclerosis. The systemic proinflammatory status of Apoe(-/-) mice also makes them good candidates for studying chronic obstructive pulmonary disease, characterized by pulmonary inflammation, airway obstruction, and emphysema, and which shares several risk factors with cardiovascular diseases, including smoking. Herein, we review the results from published studies using Apoe(-/-) mice, with a particular focus on work conducted in the context of cigarette smoke inhalation studies. The findings from these studies highlight the suitability of this animal model for researching the effects of cigarette smoking on atherosclerosis and emphysema.

Applications of the comet assay in particle toxicology: air pollution and engineered nanomaterials exposure

Exposure to ambient air particles is associated with elevated levels of DNA strand breaks (SBs) and endonuclease III, formamidopyrimidine DNA glycosylase (FPG) and oxoguanine DNA glycosylase-sensitive sites in cell cultures, animals and humans. In both animals and cell cultures, increases in SB and in oxidatively damaged DNA are seen after exposure to a range of engineered nanomaterials (ENMs), including carbon black, carbon nanotubes, fullerene C60, ZnO, silver and gold. Exposure to TiO2 has generated mixed data with regard to SB and oxidatively damaged DNA in cell cultures. Nanosilica does not seem to be associated with generation of FPG-sensitive sites in cell cultures, while large differences in SB generation between studies have been noted. Single-dose airway exposure to nanosized carbon black and multi-walled carbon nanotubes in animal models seems to be associated with elevated DNA damage levels in lung tissue in comparison to similar exposure to TiO2 and fullerene C60. Oral exposure has been associated with augmented DNA damage levels in cells of internal organs, although the doses have been typically very high. Intraveneous and intraperitoneal injection of ENMs have shown contradictory results dependent on the type of ENM and dose in each set of experiments. In conclusion, the exposure to both combustion-derived particles and ENMs is associated with increased levels of DNA damage in the comet assay. Particle size, composition and crystal structure of ENM are considered important determinants of toxicity, whereas their combined contributions to genotoxicity in the comet assay are yet to be thoroughly investigated.

Petroleum coke in the urban environment: a review of potential health effects

Petroleum coke, or petcoke, is a granular coal-like industrial by-product that is separated during the refinement of heavy crude oil. Recently, the processing of material from Canadian oil sands in U.S. refineries has led to the appearance of large petcoke piles adjacent to urban communities in Detroit and Chicago. The purpose of this literature review is to assess what is known about the effects of petcoke exposure on human health. Toxicological studies in animals indicate that dermal or inhalation petcoke exposure does not lead to a significant risk for cancer development or reproductive and developmental effects. However, pulmonary inflammation was observed in long-term inhalation exposure studies. Epidemiological studies in coke oven workers have shown increased risk for cancer and chronic obstructive pulmonary diseases, but these studies are confounded by multiple industrial exposures, most notably to polycyclic aromatic hydrocarbons that are generated during petcoke production. The main threat to urban populations in the vicinity of petcoke piles is most likely fugitive dust emissions in the form of fine particulate matter. More research is required to determine whether petcoke fine particulate matter causes or exacerbates disease, either alone or in conjunction with other environmental contaminants.

Amorphous silica nanoparticles impair vascular homeostasis and induce systemic inflammation

Amorphous silica nanoparticles (SiNPs) are being used in biomedical, pharmaceutical, and many other industrial applications entailing human exposure. However, their potential vascular and systemic pathophysiologic effects are not fully understood. Here, we investigated the acute (24 hours) systemic toxicity of intraperitoneally administered 50 nm and 500 nm SiNPs in mice (0.5 mg/kg). Both sizes of SiNPs induced a platelet proaggregatory effect in pial venules and increased plasma concentration of plasminogen activator inhibitor-1. Elevated plasma levels of von Willebrand factor and fibrinogen and a decrease in the number of circulating platelets were only seen following the administration of 50 nm SiNPs. The direct addition of SiNPs to untreated mouse blood significantly induced in vitro platelet aggregation in a dose-dependent fashion, and these effects were more pronounced with 50 nm SiNPs. Both sizes of SiNPs increased lactate dehydrogenase activity and interleukin 1β concentration. However, tumor necrosis factor α concentration was only increased after the administration of 50 nm SiNPs. Nevertheless, plasma markers of oxidative stress, including 8-isoprostane, thiobarbituric acid reactive substances, catalase, and glutathione S-transferase, were not affected by SiNPs. The in vitro exposure of human umbilical vein endothelial cells to SiNPs showed a reduced cellular viability, and more potency was seen with 50 nm SiNPs. Both sizes of SiNPs caused a decrease in endothelium-dependent relaxation of isolated small mesenteric arteries. We conclude that amorphous SiNPs cause systemic inflammation and coagulation events, and alter vascular reactivity. Overall, the effects observed with 50 nm SiNPs were more pronounced than those with 500 nm SiNPs. These findings provide new insight into the deleterious effect of amorphous SiNPs on vascular homeostasis.

Perspectives on neuroinflammation and excitotoxicity: a neurotoxic conspiracy?

Emerging evidences underline the ability of several environmental contaminants to induce an inflammatory response within the central nervous system, named neuroinflammation. This can occur as a consequence of a direct action of the neurotoxicant to the CNS and/or as a response secondary to the activation of the peripheral inflammatory response. In both cases, neuroinflammation is driven by the release of several soluble factors among which pro-inflammatory cytokines. IL-1β and TNF-α have been extensively studied for their effects within the CNS and emerged for their role in the modulation of the neuronal response, which allow the immune response to integrate with specific neuronal functions, as neurotransmission and synaptic plasticity. In particular, it has been evidenced a potential detrimental link between these cytokines and the glutamatergic system that seems to be part of increased brain excitability and excitotoxicity occurring in different pathological conditions. Aim of this mini-review will be to present experimental evidence on the way IL-1β and TNF-α impact neurons, focusing on the glutamatergic signalling, to provide a perspective on novel pathways possibly involved in environmental contaminants neurotoxicity.

Involvement of oxidative stress and inflammation in liver injury caused by perfluorooctanoic acid exposure in mice

Perfluorooctanoic acid (PFOA) is widely present in the environment and has been reported to induce hepatic toxicity in animals and humans. In this study, mice were orally administered different concentrations of PFOA (2.5, 5, or 10 mg/kg/day). Histological examination showed that the exposure to PFOA for 14 consecutive days led to serious hepatocellular injury and obvious inflammatory cell infiltration. In addition, malondialdehyde formation and hydrogen peroxide generation, indicators of oxidative stress, were significantly induced by PFOA treatment in the liver of mice. Furthermore, hepatic levels of interleukin-6, cyclooxygenase-2, and C-reactive protein, markers of inflammatory response, were markedly increased by exposure to PFOA in mice. These results demonstrated that PFOA-induced hepatic toxicity may be involved in oxidative stress and inflammatory response in mice.

Sildenafil ameliorates oxidative stress and DNA damage in the stenotic kidneys in mice with renovascular hypertension

Background

Oxidative stress and DNA damage have been implicated in the pathogenesis of renovascular hypertension induced by renal artery stenosis in the two-kidney, one-clip (2K1C) Goldblatt model. Considering our previous report indicating that the chronic blockade of phosphodiesterase 5 with sildenafil (Viagra®) has marked beneficial effects on oxidative stress and DNA damage, we tested the hypothesis that sildenafil could also protect the stenotic kidneys of 2K1C hypertensive mice against oxidative stress and genotoxicity.

Methods

The experiments were performed with C57BL6 mice subjected to renovascular hypertension by left renal artery clipping. Two weeks after clipping, the mice were treated with sildenafil (40 mg/kg/day for 2 weeks, 2K1C-sildenafil group) or the vehicle (2K1C). These mice were compared with control mice not subjected to renal artery clipping (Sham). After hemodynamic measurements, the stenotic kidneys were assessed using flow cytometry to evaluate cell viability and the comet assay to evaluate DNA damage. Measurements of intracellular superoxide anions and hydrogen peroxide levels as well as nitric oxide bioavailability were also obtained.

Results

Sildenafil treatment significantly reduced mean arterial pressure (15%), heart rate (8%), intrarenal angiotensin II (50%) and renal atrophy (36%). In addition, it caused a remarkable decrease of reactive oxygen species production. On the other hand, sildenafil increased nitric oxide levels relative to those in the nontreated 2K1C mice. Sildenafil treatment also significantly reduced the high level of kidney DNA damage that is a characteristic of renovascular hypertensive mice.

Conclusions

Our data reveal that sildenafil has a protective effect on the stenotic kidneys of 2K1C mice, suggesting a new use of phosphodiesterase 5 inhibitors for protection against the DNA damage observed in the hypoperfused kidneys of individuals with renovascular hypertension. Further translational research is necessary to delineate the mechanisms involved in the prevention of renal stenosis in the clinical setting.

Sildenafil ameliorates biomarkers of genotoxicity in an experimental model of spontaneous atherosclerosis

BACKGROUND

It is well known that enhanced production of reactive oxygen species (ROS) leads to oxidative stress observed in atherosclerosis and that ROS can also cause damage in cellular macromolecules, including DNA. Considering previous report that sildenafil, an inhibitor of phosphodiesterase 5 (PDE5), has antioxidant effects, in the present study we evaluated the effect of this drug on genotoxicity of blood mononuclear cells (MNC) and liver cells from atherosclerotic apolipoprotein E knockout mice (apoE(-/-)).

METHODS

ROS production in MNC was evaluated by flow cytometry with the fluorescent dye dihydroethidium (DHE), a method that has been used to quantify the production of superoxide anion, and DNA damage was evaluated in both MNC and liver cells using the alkaline comet assay. Sildenafil-administered apoE(-/-) mice were compared with strain-matched mice administered with vehicle and with C57BL/6 wild-type (WT) mice.

RESULTS

MNC from apoE(-/-) vehicle exhibited a 2-fold increase in production of superoxide anion in comparison with WT. In contrast, sildenafil-administered apoE(-/-) mice showed superoxide anion levels similar to those observed in WT mice. Similarly, MNC and liver cells from apoE(-/-) vehicle mice showed a 4-fold and 2-fold augmented DNA fragmentation compared with WT, respectively, and sildenafil-administered apoE(-/-) mice exhibited minimal DNA damage in those cells similar to WT mice.

CONCLUSIONS

ApoE(-/-) mice chronically administered with sildenafil exhibited reduced levels of superoxide anion in MNC and less DNA fragmentation in MNC and liver cells, which are biomarkers of genotoxicity. Therefore, sildenafil may offer a new perspective to the use of PDE5 inhibitors to protect against DNA damage, in cells involved in the inflammatory and dyslipidemic processes that accompany atherosclerosis.

Exposure to ambient air particulate matter and non-alcoholic fatty liver disease

The present study was designed to alert the public opinion and policy makers on the supposed enhancing effects of exposure to ambient air particulate matter with aerodynamic diameters < 2.5 mm (PM2.5) on non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease in Western countries. For far too long literature data have been fixated on pulmonary diseases and/or cardiovascular disease, as consequence of particulate exposure, ignoring the link between the explosion of obesity with related syndromes such as NAFLD and air pollution, the worst characteristics of nowadays civilization. In order to delineate a clear picture of this major health problem, further studies should investigate whether and at what extent cigarette smoking and exposure to ambient air PM2.5 impact the natural history of patients with obesity-related NAFLD, i.e., development of non alcoholic steatohepatitis, disease characterized by a worse prognosis due its progression towards fibrosis and hepatocarcinoma.

Oxidatively damaged DNA in animals exposed to particles

Exposure to combustion-derived particles, quartz and asbestos is associated with increased levels of oxidized and mutagenic DNA lesions. The aim of this survey was to critically assess the measurements of oxidatively damaged DNA as marker of particle-induced genotoxicity in animal tissues. Publications based on non-optimal assays of 8-oxo-7,8-dihydroguanine by antibodies and/or unrealistically high levels of 8-oxo-7,8-dihydroguanine (suggesting experimental problems due to spurious oxidation of DNA) reported more induction of DNA damage after exposure to particles than did the publications based on optimal methods. The majority of studies have used single intracavitary administration or inhalation with dose rates exceeding the pulmonary overload threshold, resulting in cytotoxicity and inflammation. It is unclear whether this is relevant for the much lower human exposure levels. Still, there was linear dose-response relationship for 8-oxo-7,8-dihydroguanine in lung tissue without obvious signs of a threshold. The dose-response function was also dependent on chemical composition and other characteristics of the administered particles, whereas dependence on species and strain could not be equivocally determined. Roles of cytotoxicity or inflammation for oxidatively induced DNA damage could not be documented or refuted. Studies on exposure to particles in the gastrointestinal tract showed consistently increased levels of 8-oxo-7,8-dihydroguanine in the liver. Collectively, there is evidence from animal experimental models that both pulmonary and gastrointestinal tract exposure to particles are associated with elevated levels of oxidatively damaged DNA in the lung and internal organs. However, there is a paucity of studies on pulmonary exposure to low doses of particles that are relevant for hazard/risk assessment.

Statins attenuate the development of atherosclerosis and endothelial dysfunction induced by exposure to urban particulate matter (PM10)

Exposure to ambient air particulate matter (particles less than 10μm or PM10) has been shown to be an independent risk factor for the development and progression of atherosclerosis. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have well-established anti-inflammatory properties. The aim of this study was to determine the impact of statins on the adverse functional and morphological changes in blood vessels induced by PM10. New Zealand White rabbits fed with a high fat diet were subjected to balloon injury to their abdominal aorta followed by PM10/saline exposure for 4weeks±lovastatin (5mg/kg/day) treatment. PM10 exposure accelerated balloon catheter induced plaque formation and increased intimal macrophages and lipid accumulation while lovastatin attenuated these changes and promoted smooth muscle cell recruitment into plaques. PM10 impaired vascular acetylcholine (Ach) responses and increased vasoconstriction induced by phenylephrine as assessed by wire myograph. Supplementation of nitric oxide improved the impaired Ach responses. PM10 increased the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in blood vessels and increased the plasma levels of endothelin-1 (ET-1). Incubation with specific inhibitors for iNOS, COX-2 or ET-1 in the myograph chambers significantly improved the impaired vascular function. Lovastatin decreased the expression of these mediators in atherosclerotic lesions and improved endothelial dysfunction. However, lovastatin was unable to reduce blood lipid levels to the baseline level in rabbits exposed to PM10. Taken together, statins protect against PM10-induced cardiovascular disease by reducing atherosclerosis and improving endothelial function via their anti-inflammatory properties.

Pulmonary exposure to particles from diesel exhaust, urban dust or single-walled carbon nanotubes and oxidatively damaged DNA and vascular function in apoE(-/-) mice

This study compared the oxidative stress level and vasomotor dysfunction after exposure to urban dust, diesel exhaust particles (DEP) or single-walled carbon nanotubes (SWCNT). DEP and SWCNT increased the production of reactive oxygen species (ROS) in cultured endothelial cells and acellullarly, whereas the exposure to urban dust did not generate ROS. The apoE(-/-) mice, which were exposed twice to 0.5 mg/kg of the particles by intratracheal (i.t.) instillation, had unaltered acetylcholine-elicited vasorelaxation in aorta segments. There was unaltered pulmonary expression level of Vcam-1, Icam-1, Hmox-1 and Ogg1. The levels of oxidatively damaged DNA were unchanged in lung tissue. The exposure to SWCNT significantly increased the expression of Ccl-2 in the lung tissue of the mice. The exposure to DEP and SWCNT was associated with elevated ROS production in cultured cells, whereas i.t. instillation of the same particles had no effect on biomarkers of pulmonary oxidative stress and dilatory dysfunction in the aorta.

Carbon black nanoparticles and vascular dysfunction in cultured endothelial cells and artery segments

Exposure to small size particulates is regarded as a risk factor for cardiovascular disease. We investigated effects of exposure to nanosized carbon black (CB) in human umbilical vein endothelial cells (HUVECs) and segments of arteries from rodents. The CB exposure was associated with increased surface expression of intercellular cell adhesion molecule 1 (ICAM-1) and vascular adhesion molecule 1 (VCAM-1) in HUVECs at 100μg/ml. CB exposure was also associated with increased reactive oxygen species production and damage to the cell membranes in the form of increased lactate dehydrogenase leakage, whereas it did not alter the mitochondrial enzyme activity (WST-1) or the nitric oxide level in HUVECs. Incubation of aorta segments with 10μg/ml of CB increased the endothelial-dependent vasorelaxation, induced by acetylcholine, and shifted the endothelium-independent vasorelaxation, induced by sodium nitroprusside, towards a decreased sensitivity. In mesenteric arteries, the exposure to 10μg/ml was associated with a reduced pressure-diameter relationship. Incubation with 100μg/ml CB significantly decreased both acetylcholine and sodium nitroprusside responses as well as decreased the receptor-dependent vasoconstriction caused by phenylephrine. In conclusion, nanosized CB exposure activates endothelial cells and generates oxidative stress, which is associated with vasomotor dysfunction.

Elevated serum liver enzymes and fatty liver changes associated with long driving among taxi drivers

BACKGROUND

Previous studies suggested increased morbidities and mortalities of liver diseases in drivers.

METHODS

To examine whether driving (monthly driving distance; tenure) is associated with elevated alanine aminotransferase (ALT), aspartate aminotransferase (AST), or chronic fatty liver (FL) changes, we performed a cross-sectional, secondary analysis of the Taxi Drivers' Health Study (n = 1,355), adjusting for clinical, demographic, and lifestyle factors.

RESULTS

Prevalence of elevated ALT, elevated AST, and fatty liver changes were 22.0%, 5.1%, and 9.3%, respectively. Driving distance had a positive association with elevated ALT with a prevalence ratio of 1.35 (95% CI: 0.98, 1.89) comparing the highest versus lowest driving quartile. This association differed by alcohol use, with a corresponding prevalence ratio of 2.08 (95% CI: 1.30, 3.33) among "past/current" drinkers but no association among "never" drinkers. Similar patterns were found for AST, but estimates were less stable. We found a curvilinear response pattern for fatty liver changes; prevalence first increased with years as a taxi driver and then receded in the highest ranges of driving tenure, regardless of the alcohol history.

CONCLUSIONS

Our results provide evidence that long driving is associated with both short-term and chronic liver insults, although alcohol use appears to modify this putative effect.

Oxidative stress, inflammation, and DNA damage in rats after intratracheal instillation or oral exposure to ambient air and wood smoke particulate matter

Wood combustion is a significant source of ambient particulate matter (PM) in many regions of the world. Exposure occurs through inhalation or ingestion after deposition of wood smoke particulate matter (WSPM) on crops and food. We investigated effects of ambient PM and WSPM by intragastric or intratracheal exposure in terms of oxidative stress, inflammation, genotoxicity, and DNA repair after 24 h in liver and lung tissue of rats. Rats were exposed to WSPM from high or low oxygen combustion and ambient PM collected in areas with and without many operating wood stoves or carbon black (CB) at the dose of 0.64 mg/kg body weight. The levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine, 1,N(6)-etheno-2'-deoxyadenosine, and 1-N(2)-etheno-2'-deoxyguanosine (εdG) were significantly increased with 23% (95% confidence interval [CI]: 0.1-45%), 54% (95% CI:18-90%), and 73% (95% CI: 31-134%) in the liver of rats exposed orally to CB, respectively. Rats orally exposed to PM from the wood stove area and low oxygen combustion WSPM (LOWS) had 35% (95% CI: 0.1-71%) and 45% (95% CI: 10-82%) increased levels of εdG in the liver, respectively. No significant differences were observed for bulky DNA adducts. Increased gene expression of proinflammatory cytokines, heme oxygenase-1, and oxoguanine DNA glycosylase 1 was observed in the liver following intragastric exposure and in the lung following instillation in particular of LOWS. Exposure to LOWS also increased the proportion of neutrophils in BAL fluid. These results indicate that WSPM and CB exert the strongest effect in terms of oxidative stress-induced response, inflammation, and genotoxicity in the organ closest to the port of entry.

Role of oxidative damage in toxicity of particulates

Particulates are small particles of solid or liquid suspended in liquid or air. In vitro studies show that particles generate reactive oxygen species, deplete endogenous antioxidants, alter mitochondrial function and produce oxidative damage to lipids and DNA. Surface area, reactivity and chemical composition play important roles in the oxidative potential of particulates. Studies in animal models indicate that particles from combustion processes (generated by combustion of wood or diesel oil), silicate, titanium dioxide and nanoparticles (C60 fullerenes and carbon nanotubes) produce elevated levels of lipid peroxidation products and oxidatively damaged DNA. Biomonitoring studies in humans have shown associations between exposure to air pollution and wood smoke particulates and oxidative damage to DNA, deoxynucleotides and lipids measured in leukocytes, plasma, urine and/or exhaled breath. The results indicate that oxidative stress and elevated levels of oxidatively altered biomolecules are important intermediate endpoints that may be useful markers in hazard characterization of particulates.

Kupffer cell activation by ambient air particulate matter exposure may exacerbate non-alcoholic fatty liver disease

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.

Kupffer cell activation by ambient air particulate matter exposure may exacerbate non-alcoholic fatty liver disease

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.

The immune effects of naturally occurring and synthetic nanoparticles

Ultrafine particles and engineered nanoparticles have unique aerodynamic and biochemical properties that affect the immune system and human health in ways that are different from or exceed those seen with gases or larger particulates. These effects result from a unique set of physical characteristics and surface moieties, which generate an ability of UFPs to enter tissues and cells, interact with proteins and DNA at a molecular level and directly and indirectly modulate the immune system by novel mechanisms. In recent years, a new field known as nanotechnology has impacted multiple industries by taking advantage of the special qualities of these small "atomic-sized" particles. Nanomedicine has already opened up a new avenue of research in cancer therapy, drug delivery and immune regulation. While the benefits of this new science to human civilization are seemingly immeasurable, it is also important to appreciate that these particles can also lead to harmful effects on human health. In vitro and animal studies are showing that nanoparticles and UFPs are capable of activating proinflammatory cytokines, chemokines and adhesion molecules, with recruitment of inflammatory cells including basophils, macrophages, dendritic cells, T cells, neutrophils and eosinophils. These changes may have an impact on immune defense, but also on the Th1/Th2 balance, and even on non-immunologic function. Resulting immune system derangement can lead to increases in incidence of autoimmune, allergic and even neoplastic diseases. Cardiorespiratory effects have been observed to occur in humans. Much further research is needed to establish safe exposure levels for this important new class of particulates.

Air pollution: mechanisms of neuroinflammation and CNS disease

Air pollution has been implicated as a chronic source of neuroinflammation and reactive oxygen species (ROS) that produce neuropathology and central nervous system (CNS) disease. Stroke incidence and Alzheimer's and Parkinson's disease pathology are linked to air pollution. Recent reports reveal that air pollution components reach the brain; systemic effects that impact lung and cardiovascular disease also impinge upon CNS health. While mechanisms driving air pollution-induced CNS pathology are poorly understood, new evidence suggests that microglial activation and changes in the blood-brain barrier are key components. Here we summarize recent findings detailing the mechanisms through which air pollution reaches the brain and activates the resident innate immune response to become a chronic source of pro-inflammatory factors and ROS, culminating in CNS disease.

Air pollution as a potential contributor to the 'epidemic' of autoimmune disease

There has been remarkable progress over the past 20 years in pushing forward our understanding of many facets of autoimmune disease. Indeed, knowledge of the genetic basis of autoimmunity and the molecular and cellular pathways involved in its pathogenesis has reached an unprecedented level. Yet this knowledge has not served to prevent autoimmune disease nor to curtail the dramatic rise in its incidence over the same interval. Population-level genetic changes cannot explain this trend; thus, environmental factors are strongly implicated. Among the possible environmental contributors to autoimmune disease, air pollution exposure has received very little attention. Although there is only a small amount of published data directly examining a possible causal relationship between air pollution exposure and autoimmunity, data from related fields suggests that it could facilitate autoimmunity as well. If correct, this hypothesis could prove to have sizeable public health implications.

Oxidative potential of semi-volatile and non volatile particulate matter (PM) from heavy-duty vehicles retrofitted with emission control technologies

Advanced exhaust after-treatment devices for diesel vehicles are less effective in controlling semivolatile species than the refractory PM fractions. This study investigated the oxidative potential (OP) of PM from vehicles with six retrofitted technologies (vanadium and zeolite based selective catalytic reduction (V-SCRT, Z-SCRT), Continuously regenerating technology (CRT), catalyzed DPX filter, catalyzed continuously regenerating trap (CCRT), and uncatalyzed Horizon filter) in comparison to a "baseline" vehicle (without any control device). Vehicles were tested on a chassis dynamometer atthree driving conditions, i.e., cruise, transient urban dynamometer driving schedule (UDDS), and idle. The consumption rate of dithiothreitol (DTT), one of the surrogate measures of OP, was determined for PM samples collected at ambient and elevated temperatures (thermally denuded of semivolatile species). Control devices reduced the OP expressed per vehicle distance traveled by 60-98%. The oxidative potential per unit mass of PM however, was highest for the Horizon followed by CRT, DPX -Idle, SCRTs, and baseline vehicles. Significant reduction in OP (by 50-100%) was observed forthermally denuded PM from vehicles with retrofitted technologies (PM with significant semivolatile fraction), whereas particles emitted bythe baseline vehicle (with insignificant semivolatile fraction) did not demonstrate any measurable changes in oxidative activity. This suggests that the semivolatile fraction of particles are far more oxidative in nature than refractory particles-a conclusion further supported by previous tunnel and ambient studies, demonstrating a decline in PM oxidative activity with increasing atmospheric dilution. Correlation analysis performed between all the species, showed that OP is moderately associated (R = 0.76) with organic carbon (OC) and strongly associated (R = 0.94) with the water-soluble organic carbon (WSOC).

Lack of acute phase response in the livers of mice exposed to diesel exhaust particles or carbon black by inhalation

BACKGROUND

Epidemiologic and animal studies have shown that particulate air pollution is associated with increased risk of lung and cardiovascular diseases. Although the exact mechanisms by which particles induce cardiovascular diseases are not known, studies suggest involvement of systemic acute phase responses, including C-reactive protein (CRP) and serum amyloid A (SAA) in humans. In this study we test the hypothesis that diesel exhaust particles (DEP) - or carbon black (CB)-induced lung inflammation initiates an acute phase response in the liver.

RESULTS

Mice were exposed to filtered air, 20 mg/m3 DEP or CB by inhalation for 90 minutes/day for four consecutive days; we have previously shown that these mice exhibit pulmonary inflammation (Saber AT, Bornholdt J, Dybdahl M, Sharma AK, Loft S, Vogel U, Wallin H. Tumor necrosis factor is not required for particle-induced genotoxicity and pulmonary inflammation., Arch. Toxicol. 79 (2005) 177-182). As a positive control for the induction of an acute phase response, mice were exposed to 12.5 mg/kg of lipopolysaccharide (LPS) intraperitoneally. Quantitative real time RT-PCR was used to examine the hepatic mRNA expression of acute phase proteins, serum amyloid P (Sap) (the murine homologue of Crp) and Saa1 and Saa3. While significant increases in the hepatic expression of Sap, Saa1 and Saa3 were observed in response to LPS, their levels did not change in response to DEP or CB. In a comprehensive search for markers of an acute phase response, we analyzed liver tissue from these mice using high density DNA microarrays. Globally, 28 genes were found to be significantly differentially expressed in response to DEP or CB. The mRNA expression of three of the genes (serine (or cysteine) proteinase inhibitor, clade A, member 3C, apolipoprotein E and transmembrane emp24 domain containing 3) responded to both exposures. However, these changes were very subtle and were not confirmed by real time RT-PCR.

CONCLUSION

Our findings collectively suggest that Sap, Saa1 and Saa3 are not induced in livers of mice exposed to DEP or CB. Despite pulmonary inflammation in these mice, global transcriptional profiling of liver did not reveal any hepatic response following exposure by inhalation.

An intratracheal instillation bioassay system for detection of lung toxicity due to fine particles in f344 rats

It is an urgent priority to establish in vivo bioassays for detection of hazards related to fine particles, which can be inhaled into deep lung tissue by humans. In order to establish an appropriate bioassay for detection of lung damage after particle inhalation, several experiments were performed in rats using quartz as a typical lung toxic particle. The results of pilot experiments suggest that Days 1 and 28 after intratracheal instillation of 2 mg of fine test particles in vehicle are most appropriate for detection of acute and subacute inflammatory changes, respectively. Furthermore, the BrdU incorporation on Day 1 and the iNOS level on Day 28 proved to be suitable end-point markers for this purpose. An examination of the toxicity of a series of particles was performed with the developed bioassay. Although some materials, including nanoparticles, demonstrated toxicity that was too strong for sensitive assessment, a ranking order could be clarified. The bioassay thus appears suitable for rapid hazard identification with a possible ranking of the toxicity of various particles at single concentrations.

Direct impairment of vascular function by diesel exhaust particulate through reduced bioavailability of endothelium-derived nitric oxide induced by superoxide free radicals

BACKGROUND

Diesel exhaust particulate (DEP) is a key arbiter of the adverse cardiovascular effects of air pollution.

OBJECTIVES

We assessed the in vitro effects of DEP on vascular function, nitric oxide (NO) availability, and the generation of oxygen-centered free radicals.

METHODS

We assessed the direct vascular effects of DEP (10-100 microg/mL) in isolated rat aortic rings using myography. We investigated NO scavenging and oxygen-centered free radical generation using an NO electrode and electron paramagnetic resonance (EPR) with the Tempone-H (1-hydroxyl-2,2,6,6-tetramethyl-4-oxo-piperidine) spin trap, respectively.

RESULTS

Acetylcholine-induced relaxation was attenuated by DEP (maximum relaxation reduced from 91 +/- 4% to 49 +/- 6% with 100 microg/mL DEP; p < 0.001) but was restored by superoxide dismutase (SOD; maximum relaxation, 73 +/- 6%; p < 0.001). DEP caused a modest inhibition of relaxation to NO donor drugs, an effect that could be reversed by SOD (p < 0.01). At 10 microg/mL, DEP did not affect verapamil-induced relaxation (p = 0.73), but at 100 microg/mL DEP inhibited relaxation (p < 0.001) by a mechanism independent of SOD. NO concentrations generated by 2-(N,N-diethylamino)-diazenolate-2-oxide (DEA/NO; 10 microM) were reduced by DEP (100 microg/mL; from 5.2 +/- 0.4 to 3.3 +/- 0.4 microM; p = 0.002). Free radical generation was increased by DEP (10 microg/mL; 9-fold increase in EPR spectra; p = 0.004) in a manner that could be attenuated by SOD (p = 0.015).

CONCLUSIONS

DEP caused oxidative stress through the generation of oxygen-centered free radicals that reduced the bioavailability of endothelium-derived NO without prior interaction with the lung or vascular tissue. These findings provide a mechanism for the adverse cardiovascular effects of particulate air pollution.

Modest vasomotor dysfunction induced by low doses of C60 fullerenes in apolipoprotein E knockout mice with different degree of atherosclerosis

Background

Exposure to small size particulate matter in urban air is regarded as a risk factor for cardiovascular effects, whereas there is little information about the impact on the cardiovascular system by exposure to pure carbonaceous materials in the nano-size range. C₆₀ fullerenes are nano-sized particles that are expected to have a widespread use, including cosmetics and medicines.

Methods

We investigated the association between intraperitoneal injection of pristine C₆₀ fullerenes and vasomotor dysfunction in the aorta of 11–13 and 40–42 weeks old apolipoprotein E knockout mice (apoE^-/-) with different degree of atherosclerosis.

Results

The aged apoE^-/-mice had lower endothelium-dependent vasorelaxation elicited by acetylcholine in aorta segments mounted in myographs and the phenylephrine-dependent vasoconstriction response was increased. One hour after an intraperitoneal injection of 0.05 or 0.5 mg/kg of C₆₀ fullerenes, the young apoE^-/- mice had slightly reduced maximal endothelium-dependent vasorelaxation. A similar tendency was observed in the old apoE^-/- mice. Hampered endothelium-independent vasorelaxation was also observed as slightly increased EC₅₀ of sodium nitroprusside-induced vasorelaxation response in young apoE^-/- mice.

Conclusion

Treatment with C₆₀ fullerenes affected mainly the response to vasorelaxation in young apoE^-/- mice, whereas the vasomotor dysfunction in old apoE^-/- mice with more advanced atherosclerosis was less affected by acute C₆₀ fullerene treatment. These findings represent an important step in the hazard characterization of C₆₀ fullerenes by showing that intraperitoneal administration is associated with a moderate decrease in the vascular function of mice with atherosclerosis.

Effects of particulate matter on genomic DNA methylation content and iNOS promoter methylation

BACKGROUND

Altered patterns of gene expression mediate the effects of particulate matter (PM) on human health, but mechanisms through which PM modifies gene expression are largely undetermined.

OBJECTIVES

We aimed at identifying short- and long-term effects of PM exposure on DNA methylation, a major genomic mechanism of gene expression control, in workers in an electric furnace steel plant with well-characterized exposure to PM with aerodynamic diameters < 10 microm (PM(10)).

METHODS

We measured global genomic DNA methylation content estimated in Alu and long interspersed nuclear element-1 (LINE-1) repeated elements, and promoter DNA methylation of iNOS (inducible nitric oxide synthase), a gene suppressed by DNA methylation and induced by PM exposure in blood leukocytes. Quantitative DNA methylation analysis was performed through bisulfite PCR pyrosequencing on blood DNA obtained from 63 workers on the first day of a work week (baseline, after 2 days off work) and after 3 days of work (postexposure). Individual PM(10) exposure was between 73.4 and 1,220 microg/m(3).

RESULTS

Global methylation content estimated in Alu and LINE-1 repeated elements did not show changes in postexposure measures compared with baseline. PM(10) exposure levels were negatively associated with methylation in both Alu [beta = -0.19 %5-methylcytosine (%5mC); p = 0.04] and LINE-1 [beta = -0.34 %5mC; p = 0.04], likely reflecting long-term PM(10) effects. iNOS promoter DNA methylation was significantly lower in postexposure blood samples compared with baseline (difference = -0.61 %5mC; p = 0.02).

CONCLUSIONS

We observed changes in global and gene specific methylation that should be further characterized in future investigations on the effects of PM.

Lung inflammation and genotoxicity following pulmonary exposure to nanoparticles in ApoE-/- mice

BACKGROUND

The toxic and inflammatory potential of 5 different types of nanoparticles were studied in a sensitive model for pulmonary effects in apolipoprotein E knockout mice (ApoE-/-). We studied the effects instillation or inhalation Printex 90 of carbon black (CB) and compared CB instillation in ApoE-/- and C57 mice. Three and 24 h after pulmonary exposure, inflammation was assessed by mRNA levels of cytokines in lung tissue, cell composition, genotoxicity, protein and lactate dehydrogenase activity in broncho-alveolar lavage (BAL) fluid.

RESULTS

Firstly, we found that intratracheal instillation of CB caused far more pulmonary toxicity in ApoE-/- mice than in C57 mice. Secondly, we showed that instillation of CB was more toxic than inhalation of a presumed similar dose with respect to inflammation in the lungs of ApoE-/- mice. Thirdly, we compared effects of instillation in ApoE-/- mice of three carbonaceous particles; CB, fullerenes C60 (C60) and single walled carbon nanotubes (SWCNT) as well as gold particles and quantum dots (QDs). Characterization of the instillation media revealed that all particles were delivered as agglomerates and aggregates. Significant increases in Il-6, Mip-2 and Mcp-1 mRNA were detected in lung tissue, 3 h and 24 h following instillation of SWCNT, CB and QDs. DNA damage in BAL cells, the fraction of neutrophils in BAL cells and protein in BAL fluid increased statistically significantly. Gold and C60 particles caused much weaker inflammatory responses.

CONCLUSION

Our data suggest that ApoE-/- model is sensitive for evaluating particle induced inflammation. Overall QDs had greatest effects followed by CB and SWCNT with C60 and gold being least inflammatory and DNA-damaging. However the gold was used at a much lower mass dose than the other particles. The strong effects of QDs were likely due to Cd release. The surface area of the instilled dose correlated well the inflammatory response for low toxicity particles.

Lung Toxicity of 16 Fine Particles on Intratracheal Instillation in a Bioassay Model Using F344 Male Rats

We have developed a bioassay model to estimate toxicity of fine particles in the lungs at an early stage after intratracheal instillation ( Yokohira et al. 2005 ; Yokohira et al. 2007 ). The present experiment was conducted to improve the model by estimating appropriate doses based on dose-dependent toxicity of instilled quartz (4 mg to 0 mg) as a positive control and assessing the impact of powdered particles without suspension (Experiment 1). In addition, examination of the toxicity of a series of particles was performed with the developed bioassay (Experiments 2A, 2B, and 2C). The materials chosen were sixteen particles, including nanoparticles and diesel powder. Histopathological and immunohistochemical analysis of bromodeoxyuridine (BrdU) incorporation and inducible nitric oxide synthase (iNOS) were performed after exposure of the lungs.

A dose of 2 mg quartz suspended in 0.2 mL saline was suggested to be most appropriate for sensitive detection of acute and subchronic inflammatory changes. Although some materials, including nanoparticles, demonstrated toxicity that was too strong for sensitive assessment, the ranking order could be given as follows: CuO > quartz > neutralized Na2PdCl4 > NiO > hydrotalcite > MnO2 > diesel > titanium dioxide (in Experiment 2B) > β-cyclodextrin > diesel standard > titanium dioxide (in Experiment 2A) > CaCO3.

Comet assay: a reliable tool for the assessment of DNA damage in different models

New chemicals are being added each year to the existing burden of toxic substances in the environment. This has led to increased pollution of ecosystems as well as deterioration of the air, water, and soil quality. Excessive agricultural and industrial activities adversely affect biodiversity, threatening the survival of species in a particular habitat as well as posing disease risks to humans. Some of the chemicals, e.g., pesticides and heavy metals, may be genotoxic to the sentinel species and/or to non-target species, causing deleterious effects in somatic or germ cells. Test systems which help in hazard prediction and risk assessment are important to assess the genotoxic potential of chemicals before their release into the environment or commercial use as well as DNA damage in flora and fauna affected by contaminated/polluted habitats. The Comet assay has been widely accepted as a simple, sensitive, and rapid tool for assessing DNA damage and repair in individual eukaryotic as well as some prokaryotic cells, and has increasingly found application in diverse fields ranging from genetic toxicology to human epidemiology. This review is an attempt to comprehensively encase the use of Comet assay in different models from bacteria to man, employing diverse cell types to assess the DNA-damaging potential of chemicals and/or environmental conditions. Sentinel species are the first to be affected by adverse changes in their environment. Determination of DNA damage using the Comet assay in these indicator organisms would thus provide information about the genotoxic potential of their habitat at an early stage. This would allow for intervention strategies to be implemented for prevention or reduction of deleterious health effects in the sentinel species as well as in humans.