Tsun-Jen Cheng

ZINC OXIDE NANOPARTICLES INTERFERE WITH ZINC ION HOMEOSTASIS TO CAUSE CYTOTOXICITY

The toxicological effects of zinc oxide nanoparticles (ZnO-NPs) are attracting increasing concern as the field of nanotechnology progresses. Although the literature suggests that toxicity of ZnO-NPs may be related to their dissolution, the mechanism for ZnO-NP perturbation of cytosolic zinc concentration ([Zn(2+)](c)) homeostasis remains obscure. Using FluoZin-3 and RhodZin-3, this study investigated changes in both [Zn(2+)](c) and mitochondrial free Zn(2+) concentration ([Zn(2+)](m)) under conditions of ZnO-NP treatment in vivo and in vitro. In human leukemia Jurkat cells and human lung carcinoma H1355 cells, ZnO-NP treatment resulted in an elevation of both [Zn(2+)](c) and [Zn(2+)](m). In H1355 cells, ZnO-NP treatment induced depolarization of mitochondrial membrane potential, as well as caspase-3 activation and lactic dehydrogenase (LDH) release. In our in vivo experiments, when rats were exposed to ZnO-NPs, higher [Zn(2+)](c) and [Zn(2+)](m) were recorded in both broncho-alveolar lavage (BAL) cells and white blood cells isolated from ZnO-NP-exposed rats, compared with high efficiency particulate air-filter-protected controls LDH levels were also elevated in the BAL of ZnO-NP-exposed rats compared with controls. A mechanical toxicological pathway for ZnO-NP toxicity is suggested by these results: an elevation in [Zn(2+)](c) resulting from ZnO-NP dissolution in the intracellular endosome; cytosolic Zn(2+) sequestration by mitochondria; and elevated [Zn(2+)](m) leading to mitochondrial dysfunction, caspase activation, and cell apoptosis. We conclude that exposure to ZnO-NPs interferes with the homeostasis of [Zn(2+)](c,) and that elevated [Zn(2+)](c) results in cell apoptosis.

Long-term air pollution exposure and risk factors for cardiovascular diseases among the elderly in Taiwan.

Objectives To investigate changes in blood pressure, blood lipids, blood sugar and haematological markers of inflammation associated with changes in long-term exposure to ambient air pollutants. Methods We conducted secondary analyses of data on blood pressure and blood biochemistry markers from the Social Environment and Biomarkers of Aging Study in Taiwan and air pollution data from the Taiwan Environmental Protection Administration in 2000. Associations of 1-year averaged criteria air pollutants (particulate matter with aerodynamic diameters <10 μm (PM10) and <2.5 μm (PM2.5), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide and carbon monoxide) with systolic blood pressure, diastolic blood pressure, total cholesterol, triglycerides, high-density lipoprotein cholesterol, fasting glucose, haemoglobin A1c (HbA1c), interleukin 6 (IL-6) and neutrophils were explored by applying generalised additive models. Results After controlling for potential confounders, we observed that increased 1-year averaged particulate air pollutants (PM10 and PM2.5) and NO2 were associated with elevated blood pressure, total cholesterol, fasting glucose, HbA1c, IL-6 and neutrophils. Associations of increased 1-year averaged O3 with elevated blood pressure, total cholesterol, fasting glucose, HbA1c and neutrophils were also observed. In particular, our two-pollutant models showed that PM2.5 was more significantly associated with end-point variables than two gaseous pollutants, O3 and NO2. Conclusions Changes in blood pressure, blood lipids, blood sugar and haematological markers of inflammation are associated with long-term exposure to ambient air pollutants. This might provide a link between air pollution and atherosclerotic cardiovascular diseases.

Global magnitude of reported and unreported mesothelioma.

Background Little is known about the global magnitude of mesothelioma. In particular, many developing countries, including some with extensive historical use of asbestos, do not report mesothelioma. Objectives We estimated the global magnitude of mesothelioma accounting for reported and unreported cases. Methods For all countries with available data on mesothelioma frequency and asbestos use (n = 56), we calculated the 15-year cumulative number of mesotheliomas during 1994–2008 from data available for fewer years and assessed its relationship with levels of cumulative asbestos use during 1920–1970. We used this relationship to predict the number of unreported mesotheliomas in countries for which no information on mesothelioma is available but which have recorded asbestos use (n = 33). Results Within the group of 56 countries with data on mesothelioma occurrence and asbestos use, the 15-year cumulative number of mesothelioma was approximately 174,300. There was a statistically significant positive linear relation between the log-transformed national cumulative mesothelioma numbers and the log-transformed cumulative asbestos use (adjusted R2 = 0.83, p < 0.0001). Extrapolated to the group of 33 countries without reported mesothelioma, a total of approximately 38,900 (95% confidence interval, 36,700–41,100) mesothelioma cases were estimated to have occurred in the 15-year period (1994–2008). Conclusions We estimate conservatively that, globally, one mesothelioma case has been overlooked for every four to five reported cases. Because our estimation is based on asbestos use until 1970, the many countries that increased asbestos use since then should anticipate a higher disease burden in the immediate decades ahead.

Effects on sister chromatid exchange frequency of polymorphisms in DNA repair gene XRCC1 in smokers

The association between metabolic polymorphisms and cigarette smoking-induced cancers has been documented. However, the role of DNA repair polymorphism in carcinogenesis is less clear. To investigate if the polymorphisms of metabolic traits and DNA repair modulate smoking-related DNA damage, we used sister chromatid exchange (SCE) as a marker of genetic damage to explore the relationship of microsomal epoxide hydrolase (mEH), glutathione S-transferase M1 (GSTM1), and X-ray cross-complementing group 1 (XRCC1) and cigarette smoking-induced SCE. Sixty-one workers without significant exposure to mutagens were recruited. Questionnaires were completed to obtain detailed occupational, smoking, and medical histories. SCE frequency in peripheral lymphocytes was determined using a standard cytogenetic assay and GSTM1, mEH (exons 3 and 4), XRCC1 (codon 399) genotypes were determined using polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP). Smokers had higher SCE frequency than non-smokers (8.4 versus 7.1, P<0.05). Among workers who had smoked equal to or greater than 10 cigarettes each day, those with XRCC1 Arg/Gln+Gln/Gln had higher SCE frequency than those with XRCC1 Arg/Arg after adjusting for potential confounders (9.0 versus 7.9, P<0.05). The interaction of XRCC1 and cigarettes smoked per day on SCE frequency was also observed (P=0.02). There was no significant interaction between cigarettes smoked per day with GSTM1 and mEH on SCE frequency. Our results support previous epidemiological studies that XRCC1 may play a role in cigarette smoking-induced lung cancer.

Effects of Asian dust event particles on inflammation markers in peripheral blood and bronchoalveolar lavage in pulmonary hypertensive rats

The health impact of dust events from China has become a concern within China and in its neighboring countries. Previous epidemiological studies have demonstrated an association between particulate matter exposure and cardiopulmonary mortality. Here, we use pulmonary hypertensive rat models to examine inflammation markers in the lung and in peripheral blood after exposure to Asian dust storm particles. Using a nose-only inhalation system, eight pulmonary hypertensive rats were exposed to concentrated ambient particles (CAPs) from an actual Asian dust storm that took place between March 18 and 19, 2002; four control rats were also exposed to room air. Four rats exposed to CAPs of 315.6 g/m3 for 6 h were classified as the low-exposure group, and another four rats exposed to CAPs of 684.5 g/m3 for 4.5 h were classified as the high-exposure group. The animals were sacrificed 36 h after exposure. Inflammation markers in the peripheral blood and in the bronchoalveolar lavage (BAL) were analyzed, and IL-6 in BAL was also determined using ELISA. White blood cell counts in peripheral blood increased with increased CAP exposure levels (P<0.001, test for trend). In BAL analysis, total cell numbers and the proportion of neutrophil also increased with increased CAP levels (P<0.001, test for trend for both markers). Positive dose-response relationships between CAP exposure and total protein (P<0.05) and between CAPs and LDH activity (P<0.05) were also observed. Moreover, IL-6 protein in BAL increasing with CAP levels (P<0.05, test for trend) was demonstrated. Our results revealed that exposure to particulate matters during an Asian dust storm could increase lung inflammation and injury in pulmonary hypertensive rats. Further studies are needed to determine the components of dust storm particles that may contribute to the particle toxicity.

Effect of air pollution on blood pressure, blood lipids, and blood sugar: A population-based approach

Objective: To investigate changes in blood pressure, lipids, and sugar associated with changes in exposure to ambient air pollution. Methods: We conducted secondary analyses of blood pressure and biochemistry markers from Taiwanese Survey on Prevalence of Hyperglycemia, Hyperlipidemia, and Hypertension and air pollution monitoring data in 2002 by applying generalized additive models. Results: We observed increased particulate matter with aerodynamic diameters <10 &mgr;m was associated with elevated systolic blood pressure (an interquartile range, 34 &mgr;g/m3, for 0.47 mmHg; 95% CI, −0.09 to 1.02), triglyceride, apolipoprotein B, hemoglobin A1c, and reduced high-density lipoprotein cholesterol. Elevated ozone was associated with increased diastolic blood pressure, apolipoprotein B, and hemoglobin A1c. Conclusions: Alterations of atherosclerotic indicators are associated with particulate matter with aerodynamic diameters <10 &mgr;m and ozone changes. This might provide a link between air pollution and progression of atherosclerotic cardiovascular diseases.

Pulmonary toxicity of inhaled nanoscale and fine zinc oxide particles: Mass and surface area as an exposure metric

The total surface area is known to be an effective exposure metric for predicting the lung toxicity of low solubility nanoparticles (NPs). However, if NPs are dissolved quickly enough in the lungs, the mass may be correlated with the toxicity. Recent studies have found that the toxicity of zinc oxide (ZnO) NPs was caused by the release of zinc ions. Thus, we hypothesized that mass could be used as an exposure metric for the toxicity of ZnO NPs. Healthy Sprague-Dawley rats were exposed to a low, moderate, or high dose of 35 and 250 nm ZnO particles or filtered air. Bronchoalveolar lavage fluid was collected to determine lung inflammation, injury and oxidative stress. The lung inflammation induced by ZnO particles according to different concentration metrics, including number, mass and surface area, was compared. The mass concentration was significantly correlated with the percentage of neutrophils (R2 = 0.84), number of neutrophils (R2 = 0.84) and total cells (R2 = 0.73). Similarly, surface area concentration was significantly correlated with the percentage of neutrophils (R2 = 0.94), number of neutrophils (R2 = 0.81) and total cells (R2 = 0.76). There was no correlation between the number and lung inflammation. We found that both mass and surface area were effective as metrics for the toxicity of ZnO NPs, although only surface area was previously indicated to be an effective metric. Our results are also consistent with recent study results that ZnO NPs and released zinc ions may play a role mediating the toxicity of NPs.

Cardiopulmonary toxicity of pulmonary exposure to occupationally relevant zinc oxide nanoparticles.

Abstract Exposure to zinc oxide (ZnO) metal fumes is linked to adverse human health effects; however, the hazards of ZnO nanoparticles (ZnONPs) remain unclear. To determine pulmonary exposure to occupationally relevant ZnONPs cause cardiopulmonary injury, Sprague-Dawley rats were exposed to ZnONPs via intratracheal (IT) instillation and inhalation. The relationship between intrapulmonary zinc levels and pulmonary oxidative-inflammatory responses 72 h after ZnONP instillation was determined in bronchoalveolar lavage fluid (BALF). Instilled ZnONPs altered zinc balance and increased the levels of total cells, neutrophils, lactate dehydrogenase (LDH) and total protein in BALF and 8-hydroxy-2′-deoxyguanosine (8-OHdG) in blood after 72 h. The ZnONPs accumulated predominantly in the lungs over 24 h, and trivial amounts of zinc were determined in the heart, liver, kidneys and blood. Furthermore, the inflammatory-oxidative responses induced by occupationally relevant levels of 1.1 and 4.9 mg/m3 of ZnONP inhalation for 2 weeks were determined in BALF and blood at 1, 7 and 30 days post-exposure. Histopathological examinations of the rat lungs and hearts were performed. Inhalation of ZnONP caused an inflammatory cytological profile. The total cell, neutrophil, LDH and total protein levels were acutely increased in the BALF, and there was an inflammatory pathology in the lungs. There were subchronic levels of white blood cells, granulocytes and 8-OHdG in the blood. Cardiac inflammation and the development of fibrosis were detected 7 days after exposure. Degeneration and necrosis of the myocardium were detected 30 days after exposure. The results demonstrate that ZnONPs cause cardiopulmonary impairments. These findings highlight the occupational health effects for ZnONP-exposed workers.

The GST T1 and CYP2E1 genotypes are possible factors causing vinyl chloride induced abnormal liver function

Abstract Vinyl chloride monomer (VCM) is hepatotoxic as well as carcinogenic in humans. There are reports that exposure to VCM seems to induce abnormal liver function, liver fibrosis, cirrhosis, portal hypertension, and angiosarcoma of the liver. In vivo, VCM is metabolized by cytochrome P450 2E1 (CYP2E1) to form the electrophilic metabolites, chloroethylene oxide (CEO) and chloroacetaldehyde (CAA), which may either cause cell damage or be further metabolized and detoxified by glutathione S-transferases (GSTs). This study investigated whether or not the genotypes CYP2E1, glutathione S-transferase θ (GST T1) and μ (GST M1) correlated with abnormal liver function found in vinyl chloride exposed workers. For this study, 251 workers from five polyvinyl chloride plants were enrolled. The workers were classified into two exposure groups (high and low) and the degree of exposure was determined based on their job titles and airborne VCM concentration. The activity of serum alanine aminotransferase (ALT) was used as the parameter of liver function. The genotypes CYP2E1, GST T1 and GST M1 were determined by polymerase chain reaction and restriction fragment length polymorphism on peripheral white blood cell DNA. Other potential risk factors were also ascertained and the confounding effect was adjusted accordingly. Stratified analyses were used to explore the correlation between the alteration of liver function and the genotypes CYP2E1, GST T1 and GST M1 among the workers exposed to different levels of VCM. The following results were obtained (1) at low VCM exposure, the odds ratio (OR) of positive GST T1 on abnormal ALT was 3.8 (95% CI 1.2–14.5) but the CYP2E1 genotype was not associated with abnormal ALT. (2) At high VCM exposure, a c2c2 CYP2E1 genotype was associated with increased OR on abnormal ALT (OR 5.4, 95% CI 0.7–35.1) and positive GST T1 was significantly associated with decreased OR on abnormal ALT (OR 0.3, 95% CI 0.1–0.9). (3) Multiple linear and logistic regression also showed strong interactions of the VCM exposure to CYP2E1 as well as to the GST T1 genotype. These observations suggest that the two genotypes, CYP2E1 and GST T1, may play important roles in the biotransformation of VCM, the effect of which leads to liver damage.

Effects of Concentrated Ambient Particles on Heart Rate, Blood Pressure, and Cardiac Contractility in Spontaneously Hypertensive Rats

Epidemiological studies have shown that particulate matter (PM) air pollution is associated with cardiovascular mortality and morbidity, especially for particles with aerodynamic diameters under 2.5 μm (PM2.5). Recent studies have revealed an association between PM pollution and autonomic functions including heart rate (HR), blood pressure (BP), and heart-rate variability. However, the association and linking mechanisms have not been clearly demonstrated in animal studies. Utilizing a novel approach that employs a mixed-effects model to overcome the problems of variations in diseased animals and circadian cycles, we have previously demonstrated an association between concentrated PM2.5 and changes of HR and BP in pulmonary hypertensive rats. The objective of this study is to test the plausibility of this methodology and to demonstrate the particle effects under different pathophysiology. The feasibility of cardiac contractility (measured as QA interval, QAI) as an indicator for PM toxicology was also explored. Four spontaneously hypertensive (SH) rats were repeatedly exposed to concentrated PM2.5 during spring and summer. The mass concentration of particles during the 5 h of exposure was 202.0 ± 68.8 (mean ± SE) and 141.0 ± 54.9 μg/m3 for spring and summer experiments, respectively. During spring exposures, the maximum increase of HR and mean BP noted at the end of exposure were 51.6 bpm (p < .001) and 8.7 mm Hg (p = .002), respectively. The maximum decrease of QAI noted at the same time was 1.6 ms (p = .001). Though a similar pattern was demonstrated during summer exposures, the responses were less prominent. We conclude that concentrated PM2.5 may increase HR and mean BP and decrease QAI in SH rats. Our results also show that QAI may be used as an indicator in PM toxicology.