Cardiovascular and blood coagulative effects of pulmonary zinc exposure

Heavy metals controlling cardiovascular diseases risk factors in myocardial infarction patients in critically environmentally heavy metal-polluted steel industrial town Mandi-Gobindgarh (India)

Heavy metals (HMs) have a very significant clinical role in the pathogenesis, progression and management of cardiovascular diseases (CVDs). The prevalence of CVDs was reported to be higher in critically environmentally HM-polluted (EHMP) steel industrial town Mandi-Gobindgarh (India) for the last more than a decade. To ascertain the role of HMs in the onset of CVDs, the present study was chosen to investigate HMs content in myocardial infarction (MI) patients from EHMP steel industrial town Mandi-Gobindgarh. Total of 110 MI patients along with number- and age-matched healthy volunteers were recruited in the present investigation. The CVDs risk factors estimated in MI patients were overweight (higher body mass index), hypertension (higher systolic and diastolic blood pressures), dyslipidaemia (higher serum cholesterol, triglycerides and lower HDL cholesterol), inflammation (higher-serum C reactive protein and aldosterone) and elevated oxidative stress (higher urinary 8-hydroxydeoxyguanosine). An imbalance of serum electrolyte concentrations including Na (hypernatremia), Ca (hypercalcaemia) and K (hypokalaemia) was also observed in MI patients in which CVDs risk factors were found to correlate positively with serum Na and Ca and negatively with serum K, respectively. Hair HM analysis was used as a bio-indicator for monitoring body HM status from past environmental HM exposure in which CVDs risk factors were observed to correlate positively with higher hair concentrations of Zn, Fe, Mo, Pb, As, Ca and Na and negatively with lower hair concentrations of Cu, Mg, Mn and K in MI patients, respectively. Thus, higher hair concentrations of Zn and Pb indicate their higher environmental exposure and possible cause of higher CVDs risk factors in MI patients from Mandi-Gobindgarh.

A critical review of approaches and limitations of inhalation bioavailability and bioaccessibility of metal(loid)s from ambient particulate matter or dust

Inhalation of metal(loid)s in ambient particulate matter (APM) represents a significant exposure pathway to humans. Although exposure assessment associated with this pathway is currently based on total metal(loid) content, a bioavailability (i.e. absorption in the systemic circulation) and/or bioaccessibility (i.e. solubility in simulated lung fluid) based approach may more accurately quantify exposure. Metal(loid) bioavailability-bioaccessibility assessment from APM is inherently complex and lacks consensus. This paper reviews the discrepancies that impede the adoption of a universal protocol for the assessment of inhalation bioaccessibility. Exposure assessment approaches for in-vivo bioavailability, in-vitro cell culture and in-vitro bioaccessibility (composition of simulated lungs fluid, physico-chemical and methodological considerations) are critiqued in the context of inhalation exposure refinement. An important limitation of bioavailability and bioaccessibility studies is the use of considerably higher than environmental metal(loid) concentration, which diminishing their relevance to human exposure scenarios. Similarly, individual metal(loid) studies have been criticised due to complexities of APM metal(loid) mixtures which may impart synergistic or antagonistic effects compared to single metal(loid) exposure. Although a number of different simulated lung fluid (SLF) compositions have been used in metal(loid) bioaccessibility studies, information regarding the comparative leaching efficiency among these different SLF and comparisons to in-vivo bioavailability data is lacking. In addition, the particle size utilised is often not representative of what is deposited in the lungs while assay parameters (extraction time, solid to liquid ratio, temperature and agitation) are often not biologically relevant. Research needs are identified in order to develop robust in-vitro bioaccessibility protocols for the assessment or prediction of metal(loid) bioavailability in APM for the refinement of inhalation exposure.

Individual PM2.5 exposure is associated with the impairment of cardiac autonomic modulation in general residents

Fine particulate matter (PM2.5) is one of the major pollutants in metropolitan areas. The current study was conducted to observe the effects of PM2.5 on cardiac autonomic modulation. The participants included 619 men and women aged from 35-75 in a residential area in Shanghai, China. All the participants were divided into four categories according to the distance between their apartments and major road. In addition, individual PM2.5 was measured using SIDEPAKTM AM510 (TSI, USA) from 8:00 am to 6:00 pm. At the end of the individual PM2.5 measurement, the systolic pressure, diastolic pressure, heart rate (HR), low-frequency (LF), high-frequency (HF), and LF/HF were determined. The association between individual PM2.5 level and the above health effects was analyzed using generalized linear regression. The results showed that the average concentration of individual PM2.5 was 95.5 and 87.0 μg/m(3) for men and women. Residential distance to major road was negatively correlated with the individual PM2.5. The results indicated that per 1.0 μg/m(3) increase of individual PM2.5 was associated with a 2.3 % increase for systolic pressure, 0.3 % increase for diastolic pressure, 0.4 % decrease for LF, and 0.4 % decrease for HF. Nevertheless, there was no statistical association between individual PM2.5 and heart rate and LF/HF in the total model. In addition, the similar results were found in men and women excluding a significant association between PM2.5 and the heart rate in men. The alterations of cardiac autonomic modulation hinted that PM2.5 exposure might be associated with the potential occurrence of cardiovascular disease, such as arrhythmia and ischemic heart diseases.

Zinc compound air releases from Toxics Release Inventory facilities and cardiovascular disease mortality rates

BACKGROUND

Inhaled zinc has been found in association with cardiopulmonary toxicity. However, limited human epidemiologic studies are available. This study analyzed the association between covariate-adjusted cardiovascular (CVD) mortality rates and zinc compound air releases in the United States.

METHODS

We conducted an ecological analysis on the association between zinc compound air releases for 1991-2000 using the Toxics Release Inventory database and average age-adjusted CVD mortality for 2006-2010, adjusting for race/ethnicity composition and several health and socioeconomic factors. Models were estimated for males and females and for metropolitan and nonmetropolitan counties.

RESULTS

Zinc compound air releases were positively associated with increased adjusted CVD mortality rates in all four models (β=0.0085, p<0.0001 for males in nonmetropolitan counties; β=0.0093, p<0.0001 for males in metropolitan counties; β=0.0145, p<0.0001 for females in nonmetropolitan counties; and β=0.0098, p<0.0001 for females in metropolitan counties). Results were largely robust to various sensitivity analyses.

CONCLUSION

This study provides epidemiological evidence for possible CVD health impacts of inhaled zinc in the United States. Although the strongest effect was found for females in nonmetropolitan counties, the associations were consistent in nonmetropolitan or metropolitan counties for both genders.

Respiratory and cardiovascular effects of metals in ambient particulate matter: a critical review

In this review, we critically evaluated the epidemiological and toxicological evidence for the role of specific transition metals (As. Cr. Cu. Fe. Mn. Ni. Sc. Ti. V and Zn) in causing or contributing to the respiratory and cardiovascular health effects associated with ambient PM. Although the epidemiologic studies arc suggestive. and both the in vivo and in vitro laboratory studies document the toxicity of specific metals (Fe. Ni. V and Zn). the overall weight of evidence does not convincingly implicate metals as major contributors to health effects. None of the epidemiology studies that we reviewed conclusively implicated specific transition metals as having caused the respiratory and cardiovascular effects associated with ambient levels of PM. However, the studies reviewed tended to be internal ly consistent in identifying some metals (Fe, Ni, V and Zn) more frequently than others (As, Cu, Mn and Sc) as having positive associations wi th health effects. The major problem wi th which the epidemiological studies were faced was classifying and quantifying exposure. Community and population exposures to metals or other components of ambient PM were inferred from centrally- located samplers that may not accurately represent individual level exposures. Only a few authors reported findings that did not support the stated premise of the study; indeed, statistic ally significant associations are not necessarily biologically significant. It is likely that ·'negative studies" are under-represented in the published literature, making it a challenge to achieve a balanced evaluation of the role of metals in causing health effects associated with ambient PM. Both the in vivo and in vitro study results demonstrated that individual metals (Cu. Fe. Ni. V and Zn) and extracts of metals from ambient PM sources can produce acute inflammatory responses. However. the doses administered to laboratory animals were many orders of magnitude greater than what humans experience from breathing ambient air. The studies that used intratracheal instillation have the advantage of delivering a known dose to a specific anatomical location. but arc not analogous to an inhaled dose that is distributed over the surface area of the respiratory tract. Studies. in which laboratory animals or human volunteers inhaled CAPs best represent exposures to the general human population. The in vivo and in vitro studies reviewed provide indications that the probable mechanisms involved in the respiratory and cardiac effects from high metal exposures include: an inflammatory response mediated by formation of ROS, upregulation of genes coding for inflammatory cytokines, altered expression of genes involved in cell signaling pathways and maintenance of metals homeostasis.The fact that doses of metals many orders of magnitude greater than those existing in ambient air were required to produce measurable adverse effects in animals makes it doubtful that metals play any major role in respiratory and cardiovascular effects produced from human exposure to ambient PM. We suggest that future research priorities should focus on testing at more environmentally relevant exposure levels and that any new toxicological studies be written to include dosages in units that can be easily compared to human exposure levels.

Ultrafine carbon particle mediated cardiovascular impairment of aged spontaneously hypertensive rats

Background

Studies provide compelling evidences for particulate matter (PM) associated cardiovascular health effects. Elderly individuals, particularly those with preexisting conditions like hypertension are regarded to be vulnerable. Experimental data are warranted to reveal the molecular pathomechanism of PM related cardiovascular impairments among aged/predisposed individuals. Thus we investigated the cardiovascular effects of ultrafine carbon particles (UfCP) on aged (12–13 months) spontaneously hypertensive rats (SHRs) and compared the findings with our pervious study on adult SHRs (6–7 months) to identify age related predisposition events in cardiovascular compromised elderly individuals.

Methods

Aged SHRs were inhalation exposed to UfCP for 24 h (~180 μg/m³) followed by radio-telemetric assessment for blood pressure (BP) and heart rate (HR). Bronchoalveolar lavage (BAL) fluid cell differentials, interleukin 6 (IL-6) and other proinflammatory cytokines; serum C-reactive protein (CRP) and haptoglobin (HPT); and plasma fibrinogen were measured. Transcript levels of hemeoxygenase 1 (HO-1), endothelin 1 (ET1), endothelin receptors A, B (ETA, ETB), tissue factor (TF), and plasminogen activator inhibitor-1 (PAI-1) were measured in the lung and heart to assess oxidative stress, endothelial dysfunction and coagulation cascade.

Result

UfCP exposed aged SHRs exhibited increased BP (4.4%) and HR (6.3%) on 1^st recovery day paralleled by a 58% increase of neutrophils and 25% increase of IL-6 in the BAL fluid. Simultaneously higher CRP, HPT and fibrinogen levels in exposed SHRs indicate systemic inflammation. HO-1, ET1, ET-A, ET-B, TF and PAI-1 were induced by 1.5-2.0 folds in lungs of aged SHRs on 1^st recovery day. However, in UfCP exposed adult SHRs these markers were up-regulated (2.5-6 fold) on 3^rd recovery day in lung without detectable pulmonary/systemic inflammation.

Conclusions

The UfCP induced pulmonary and systemic inflammation in aged SHRs is associated with oxidative stress, endothelial dysfunction and disturbed coagulatory hemostasis. UfCP exposure increased BP and HR in aged SHRs rats which was associated with lung inflammation, and increased expression of inflammatory, vasoconstriction and coagulation markers as well as systemic changes in biomarkers of thrombosis in aged SHRs. Our study provides further evidence for potential molecular mechanisms explaining the increased risk of particle mediated cardiac health effects in cardiovascular compromised elderly individuals.

Extracellular histones mediate the effects of metal-rich air particles on blood coagulation

BACKGROUND

Epidemiological studies have shown associations of particulate matter (PM) exposure with hypercoagulability and thrombosis. Extracellular circulating histones have recently been identified as novel mediators of inflammatory and procoagulant responses. The potential roles of extracellular histones in PM-related hypercoagulability have yet not been investigated.

OBJECTIVES

In 63 steel workers, we evaluated the effects of exposure to PM and PM metal components on two extracellular histone modifications (H3K4me3 and H3K9ac); and the association of H3K4me3 and H3K9ac with coagulation markers.

METHODS

Extracellular H3K4me3 and H3K9ac were determined in plasma through enzyme-linked immunosorbent assays. Coagulation markers included endogenous thrombin potentials (ETPs), tissue-type plasminogen activator antigen (t-PA) and D-dimer. Exposure to PM with aerodynamic diameters <1 μm (PM1) or <10 μm (PM10) and PM10 metal components were estimated for each participant.

RESULTS

The coagulation marker ETP, measured in the presence of soluble thrombomodulin (ETP TM+), showed significant positive associations with PM1 (β=107.84, p=0.03), PM10 (β=83.06, p=0.02), and zinc (β=75.14, p=0.03); and a marginal association with iron (β=122.58, p=0.07). Additional PM effects were observed on t-PA, D-dimer, and ETP TM+. PM1 exposure was associated with increased plasma H3K4me3 and H3K9ac (β=0.20, p=0.02; β=0.16, p=0.05, respectively). H3K4me3, but not H3K9ac, was associated with zinc (β=0.13, p=0.03) and iron (β=0.32, p=0.01) contained in PM. ETP TM+ was increased in association with higher plasma H3K4me3 (β=0.50, p=0.05) and H3K9ac (β=0.54, p=0.05).

CONCLUSIONS

This observational study suggests potential roles of extracellular histones in PM-induced hypercoagulability. Experimental studies are warranted to further characterize these findings.

Cardiopulmonary toxicity of pulmonary exposure to occupationally relevant zinc oxide nanoparticles

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/m(3) 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.

Evaluation of potential for toxicity from subacute inhalation of tire and road wear particles in rats

Tire and road wear particles (TRWP) are a component of ambient particulate matter (PM) produced from the interaction of tires with the roadway. Inhalation of PM has been associated with cardiopulmonary morbidities and mortalities thought to stem from pulmonary inflammation. To determine whether TRWP may contribute to these events, the effects of subacute inhalation of TRWP were evaluated in rats. TRWP were collected at a road simulator laboratory, aerosolized, and used to expose male and female Sprague-Dawley rats (n = 10/treatment group) at ~10, 40, or 100 μg/m³ TRWP via nose-only inhalation for 6 h/day for 28 days. Particle size distribution of the aerosolized TRWP was found to be within the respirable range for rats. Toxicity was assessed following OECD guidelines (TG 412). No TRWP-related effects were observed on survival, clinical observations, body or organ weights, gross pathology, food consumption, immune system endpoints, serum chemistry, or biochemical markers of inflammation or cytotoxicity. Rare to few focal areas of subacute inflammatory cell infiltration associated with TWRP exposure were observed in the lungs of one mid and four high exposure animals, but not the low-exposure animals. These alterations were minimal, widely scattered and considered insufficient in extent or severity to have an impact on pulmonary function. Furthermore, it is expected that these focal lesions would remain limited and may undergo resolution without long-term or progressive pulmonary alterations. Therefore, from this study we identified a no-observable-adverse-effect-level (NOAEL) of 112 μg/m³ of TRWP in rats for future use in risk assessment of TRWP.

Blood hypomethylation of inflammatory genes mediates the effects of metal-rich airborne pollutants on blood coagulation

OBJECTIVES

Recent investigations have associated airborne particulate matter (PM) with increased coagulation and thrombosis, but underlying biological mechanisms are still incompletely characterised. DNA methylation is an environmentally sensitive mechanism of gene regulation that could potentially contribute to PM-induced hypercoagulability. We aimed to test whether altered methylation mediates environmental effects on coagulation.

METHODS

We investigated 63 steel workers exposed to a wide range of PM levels, as a work-related condition with well-characterised prothrombotic exposure. We measured personal PM10 (PM≤10 µm in aerodynamic diameter), PM1 (≤1 µm) and air metal components. We determined leukocyte DNA methylation of NOS3 (nitric-oxide-synthase-3) and EDN1 (endothelin-1) through bisulfite-pyrosequencing and we measured ETP as a global coagulation-activation test after standardised triggers.

RESULTS

ETP increased in association with PM10 (β=20.0, 95% CI 3.0 to 37.0), PM1 (β=80.8 95% CI 14.9 to 146.7) and zinc (β=51.3, 95% CI 0.01 to 111.1) exposures. NOS3 methylation was negatively associated with PM10 (β=-0.2, 95% CI -0.4 to -0.03), PM1 (β=-0.8, 95% CI -1.4 to -0.1), zinc (β=-0.9, 95% CI -1.4 to -0.3) and iron (β=-0.7, 95% CI -1.4 to -0.01) exposures. Zinc exposure was negatively associated with EDN1 (β=-0.3, 95% CI -0.8 to -0.1) methylation. Lower NOS3 (β=-42.3; p<0.001) and EDN1 (β=-14.5; p=0.05) were associated with higher ETP. Statistical mediation analysis formally confirmed NOS3 and EDN1 hypomethylation as intermediate mechanisms for PM-related coagulation effects.

CONCLUSIONS

Our study showed for the first time, that gene hypomethylation contributes to environmentally induced hypercoagulability.

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.

Zinc toxicology following particulate inhalation

The current mini-review describes the toxic effects of zinc inhalation principally in the workplace and associated complications with breathing and respiration. The International Classification of Functioning, Disability and Health Criteria were used to specifically select articles. Most of the commercial production of zinc involves the galvanizing of iron and the manufacture of brass. The recommended daily allowance for adults is 15 mg zinc/day. Metal fume fever associated with inhalation of fumes of ZnO is characterized by fatigue, chills, fever, myalgias, cough, dyspnea, leukocytosis, thirst, metallic taste and salivation. ZnCl₂ inhalation results in edema in the alveolar surface and the protein therein the lavage fluid is elevated. Particular pathological changes associated with zinc intoxication include: pale mucous membranes; jaundice; numerous Heinz bodies; and marked anemia. Adequate ambient air monitors for permissible exposure limits, excellent ventilation and extraction systems, and approved respirators are all important in providing adequate protection.

Metals in air pollution particles decrease whole-blood coagulation time

The mechanism underlying procoagulative effects of air pollution particle exposure is not known. The authors tested the postulate that (1) the water-soluble components of an air pollution particle could affect whole-blood coagulation time and (2) metals included in this fraction were responsible for this effect. Exposure to the water-soluble fraction of particulate matter (PM), at doses as low as 50 ng/ml original particle, significantly diminished the whole-blood coagulation time. Inclusion of deferoxamine prolonged coagulation time following the exposures to the water-soluble fraction, whereas equivalent doses of ferroxamine had no effect. Except for nickel, all metal sulfates shortened the whole-blood coagulation time. Iron and zinc were two metals with the greatest capacity to reduce the coagulation time, with an effect observed at 10 ng/ml. Finally, in contrast to the anticoagulants citrate and EDTA, their iron complexes were found to be procoagulative. The authors conclude that metals in the water-soluble fraction of air pollution particles decrease whole-blood coagulation time. These metals can potentially contribute to procoagulative effects observed following human exposures to air pollution particles.

Cardiovascular and inflammatory effects of intratracheally instilled ambient dust from Augsburg, Germany, in spontaneously hypertensive rats (SHRs)

Rationale

Several epidemiological studies associated exposure to increased levels of particulate matter in Augsburg, Germany with cardiovascular mortality and morbidity. To elucidate the mechanisms of cardiovascular impairments we investigated the cardiopulmonary responses in spontaneously hypertensive rats (SHR), a model for human cardiovascular diseases, following intratracheal instillation of dust samples from Augsburg.

Methods

250 μg, 500 μg and 1000 μg of fine ambient particles (aerodynamic diameter <2.5 μm, PM_2.5-AB) collected from an urban background site in Augsburg during September and October 2006 (PM_2.5 18.2 μg/m³, 10,802 particles/cm³) were instilled in 12 months old SHRs to assess the inflammatory response in bronchoalveolar lavage fluid (BALF), blood, lung and heart tissues 1 and 3 days post instillation. Radio-telemetric analysis was performed to investigate the cardiovascular responses following instillation of particles at the highest dosage based on the inflammatory response observed.

Results

Exposure to 1000 μg of PM_2.5-AB was associated with a delayed increase in delta mean blood pressure (ΔmBP) during 2^nd-4^th day after instillation (10.0 ± 4.0 vs. -3.9 ± 2.6 mmHg) and reduced heart rate (HR) on the 3^rd day post instillation (325.1 ± 8.8 vs. 348.9 ± 12.5 bpm). BALF cell differential and inflammatory markers (osteopontin, interleukin-6, C-reactive protein, and macrophage inflammatory protein-2) from pulmonary and systemic level were significantly induced, mostly in a dose-dependent way. Protein analysis of various markers indicate that PM_2.5-AB instillation results in an activation of endothelin system (endothelin1), renin-angiotensin system (angiotensin converting enzyme) and also coagulation system (tissue factor, plasminogen activator inhibitor-1) in pulmonary and cardiac tissues during the same time period when alternation in ΔmBP and HR have been detected.

Conclusions

Our data suggests that high concentrations of PM_2.5-AB exposure triggers low grade PM mediated inflammatory effects in the lungs but disturbs vascular homeostasis in pulmonary tissues and on a systemic level by affecting the renin angiotensin system, the endothelin system and the coagulation cascade. These findings are indicative for promotion of endothelial dysfunction, atherosclerotic lesions, and thrombogeneis and, thus, provide plausible evidence that susceptible-predisposed individuals may develop acute cardiac events like myocardial infarction when repeatedly exposed to high pollution episodes as observed in epidemiological studies in Augsburg, Germany.

Differential pulmonary and cardiac effects of pulmonary exposure to a panel of particulate matter-associated metals

Biological mechanisms underlying the association between particulate matter (PM) exposure and increased cardiovascular health effects are under investigation. Water-soluble metals reaching systemic circulation following pulmonary exposure are likely exerting a direct effect. However, it is unclear whether specific PM-associated metals may be driving this. We hypothesized that exposure to equimolar amounts of five individual PM-associated metals would cause differential pulmonary and cardiac effects. We exposed male WKY rats (14 weeks old) via a single intratracheal instillation (IT) to saline or 1 micromol/kg body weight of zinc, nickel, vanadium, copper, or iron in sulfate form. Responses were analyzed 4, 24, 48, or 96 h after exposure. Pulmonary effects were assessed by bronchoalveolar lavage fluid levels of total cells, macrophages, neutrophils, protein, albumin, and activities of lactate dehydrogenase, gamma-glutamyl transferase, and n-acetyl glucosaminidase. Copper induced earlier pulmonary injury/inflammation, while zinc and nickel produced later effects. Vanadium or iron exposure induced minimal pulmonary injury/inflammation. Zinc, nickel, or copper increased serum cholesterol, red blood cells, and white blood cells at different time points. IT of nickel and copper increased expression of metallothionein-1 (MT-1) in the lung. Zinc, nickel, vanadium, and iron increased hepatic MT-1 expression. No significant changes in zinc transporter-1 (ZnT-1) expression were noted in the lung or liver; however, zinc increased cardiac ZnT-1 at 24 h, indicating a possible zinc-specific cardiac effect. Nickel exposure induced an increase in cardiac ferritin 96 h after IT. This data set demonstrating metal-specific cardiotoxicity is important in linking metal-enriched anthropogenic PM sources with adverse health effects.

Exposure to ultrafine carbon particles at levels below detectable pulmonary inflammation affects cardiovascular performance in spontaneously hypertensive rats

BACKGROUND

Exposure to particulate matter is a risk factor for cardiopulmonary disease but the underlying molecular mechanisms remain poorly understood. In the present study we sought to investigate the cardiopulmonary responses on spontaneously hypertensive rats (SHRs) following inhalation of UfCPs (24 h, 172 mug.m-3), to assess whether compromised animals (SHR) exhibit a different response pattern compared to the previously studied healthy rats (WKY).

METHODS

Cardiophysiological response in SHRs was analyzed using radiotelemetry. Blood pressure (BP) and its biomarkers plasma renin-angiotensin system were also assessed. Lung and cardiac mRNA expressions for markers of oxidative stress (hemeoxygenase-1), blood coagulation (tissue factor, plasminogen activator inhibitor-1), and endothelial function (endothelin-1, and endothelin receptors A and B) were analyzed following UfCPs exposure in SHRs. UfCPs-mediated inflammatory responses were assessed from broncho-alveolar-lavage fluid (BALF).

RESULTS

Increased BP and heart rate (HR) by about 5% with a lag of 1-3 days were detected in UfCPs exposed SHRs. Inflammatory markers of BALF, lung (pulmonary) and blood (systemic) were not affected. However, mRNA expression of hemeoxygenase-1, endothelin-1, endothelin receptors A and B, tissue factor, and plasminogen activator inhibitor showed a significant induction (~2.5-fold; p < 0.05) with endothelin 1 being the maximally induced factor (6-fold; p < 0.05) on the third recovery day in the lungs of UfCPs exposed SHRs; while all of these factors - except hemeoxygenase-1 - were not affected in cardiac tissues. Strikingly, the UfCPs-mediated altered BP is paralleled by the induction of renin-angiotensin system in plasma.

CONCLUSION

Our finding shows that UfCPs exposure at levels which does not induce detectable pulmonary neutrophilic inflammation, triggers distinct effects in the lung and also at the systemic level in compromised SHRs. These effects are characterized by increased activity of plasma renin-angiotensin system and circulating white blood cells together with moderate increases in the BP, HR and decreases in heart rate variability. This systemic effect is associated with pulmonary, but not cardiac, mRNA induction of biomarkers reflective of oxidative stress; activation of vasoconstriction, stimulation of blood coagulation factors, and inhibition of fibrinolysis. Thus, UfCPs may cause cardiovascular and pulmonary impairment, in the absence of detectable pulmonary inflammation, in individuals suffering from preexisting cardiovascular diseases.

A hyperlipidemic rabbit model provides new insights into pulmonary zinc exposure effects on cardiovascular health

This study ascertains the effects of zinc, a major component of particulate matter, on pulmonary and systemic endpoints using hyperlipidemic rabbits to model diet-induced human atherosclerosis. New Zealand White rabbits were fed a normal or cholesterol-enriched diet and then were intratracheally instilled 1x/week for 4 weeks with saline or 16 microg/kg of zinc, equal parts sulfate and oxide. Physiologic responses, blood after each exposure, and terminal bronchoalveolar lavage (BAL) were assessed. Rabbits fed a cholesterol-rich diet developed hyperlipidemia and had consistently higher circulating leukocyte counts than rabbits fed normal chow. Within minutes after zinc instillation, saturation of peripheral oxygen was decreased in hyperlipidemic rabbits and heart rate was increased in hyperlipidemic rabbits with total serum cholesterol levels greater than 200 mg/dl. Total circulating leukocytes levels were increased 24 h after the first zinc instillation, but upon repeated exposures this effect was attenuated. After repeated zinc exposures, BAL fluid (BALF) N-acetylglucosaminidase activity was increased regardless of hyperlipidemic state. Hyperlipidemic rabbits had an increase in BALF-oxidized glutathione and a decrease in serum nitrite. The study elucidates mechanisms by which the zinc metal component of PM drives cardiovascular health effects, as well as the possible susceptibility induced by hyperlipidemia. Furthermore, the study exemplifies the benefits of monitoring circulatory physiology during exposure as well as after exposure.

Systemic translocation of (70)zinc: kinetics following intratracheal instillation in rats

Mechanisms of particulate matter (PM)-induced cardiotoxicity are not fully understood. Direct translocation of PM-associated metals, including zinc, may mediate this effect. We hypothesized that following a single intratracheal instillation (IT), zinc directly translocates outside of the lungs, reaching the heart. To test this, we used high resolution magnetic sector field inductively coupled plasma mass spectrometry to measure levels of five stable isotopes of zinc ((64)Zn, (66)Zn, (67)Zn, (68)Zn, (70)Zn), and copper in lungs, plasma, heart, liver, spleen, and kidney of male Wistar Kyoto rats (13 weeks old, 250-300 g), 1, 4, 24, and 48 h following a single IT or oral gavage of saline or 0.7 micromol/rat (70)Zn, using a solution enriched with 76.6% (70)Zn. Natural abundance of (70)Zn is 0.62%, making it an easily detectable tracer following exposure. In IT rats, lung (70)Zn was highest 1 h post IT and declined by 48 h. Liver endogenous zinc was increased 24 and 48 h post IT. (70)Zn was detected in all extrapulmonary organs, with levels higher following IT than following gavage. Heart (70)Zn was highest 48 h post IT. Liver, spleen and kidney (70)Zn peaked 4 h following gavage, and 24 h following IT. (70)Zn IT exposure elicited changes in copper homeostasis in all tissues. IT instilled (70)Zn translocates from lungs into systemic circulation. Route of exposure affects (70)Zn translocation kinetics. Our data suggests that following pulmonary exposure, zinc accumulation and subsequent changes in normal metal homeostasis in the heart and other organs could induce cardiovascular injury.

Cardiopulmonary responses of intratracheally instilled tire particles and constituent metal components

Tire and brake wear particles contain transition metals, and contribute to near-road PM. We hypothesized that acute cardiopulmonary injury from respirable tire particles (TP) will depend on the amount of soluble metals. Respirable fractions of two types of TP (TP1 and TP2) were analyzed for water and acid-leachable metals using ICP-AES. Both TP types contained a variety of transition metals, including zinc (Zn), copper (Cu), aluminum, and iron. Zn and Cu were detected at high levels in water-soluble fractions (TP2 > TP1). Male Wistar Kyoto rats (12-14 wk) were intratracheally instilled, in the first study, with saline, TP1 or TP2 (5 mg/kg), and in the second study, with soluble Zn, Cu (0.5 micromol/kg), or both. Pulmonary toxicity and cardiac mitochondrial enzymes were analyzed 1 d, 1 wk, or 4 wk later for TP and 4 or 24 h later for metals. Increases in lavage fluid markers of inflammation and injury were observed at d 1 (TP2 > TP1), but these changes reversed by wk 1. No effects on cardiac enzymes were noted with either TP. Exposure of rats to soluble Zn and Cu caused marked pulmonary inflammation and injury but temporal differences were apparent (Cu effects peaked at 4 h and Zn at 24 h). Instillation of Zn, Cu, and Zn + Cu decreased the activity of cardiac aconitase, isocitrate dehydrogenase, succinate dehydrogenase, cytochrome-c-oxidase and superoxide dismutase suggesting mitochondrial oxidative stress. The observed acute pulmonary toxicity of TP could be due to the presence of water soluble Zn and Cu. At high concentrations these metals may induce cardiac oxidative stress.

Subchronic inhalation of zinc sulfate induces cardiac changes in healthy rats

Zinc is a common metal in most ambient particulate matter (PM), and has been proposed to be a causative component in PM-induced adverse cardiovascular health effects. Zinc is also an essential metal and has the potential to induce many physiological and nonphysiological changes. Most toxicological studies employ high levels of zinc. We hypothesized that subchronic inhalation of environmentally relevant levels of zinc would cause cardiac changes in healthy rats. To address this, healthy male WKY rats (12 weeks age) were exposed via nose only inhalation to filtered air or 10, 30 or 100 microg/m(3) of aerosolized zinc sulfate (ZnSO(4)), 5 h/day, 3 days/week for 16 weeks. Necropsies occurred 48 h after the last exposure to ensure effects were due to chronic exposure rather than the last exposure. No significant changes were observed in neutrophil or macrophage count, total lavageable cells, or enzyme activity levels (lactate dehydrogenase, n-acetyl beta-D-glucosaminidase, gamma-glutamyl transferase) in bronchoalveolar lavage fluid, indicating minimal pulmonary effect. In the heart, cytosolic glutathione peroxidase activity decreased, while mitochondrial ferritin levels increased and succinate dehydrogenase activity decreased, suggesting a mitochondria-specific effect. Although no cardiac pathology was seen, cardiac gene array analysis indicated small changes in genes involved in cell signaling, a pattern concordant with known zinc effects. These data indicate that inhalation of zinc at environmentally relevant levels induces cardiac effects. While changes are small in healthy rats, these may be especially relevant in individuals with pre-existent cardiovascular disease.

The role of particulate matter-associated zinc in cardiac injury in rats

BACKGROUND

Exposure to particulate matter (PM) has been associated with increased cardiovascular morbidity; however, causative components are unknown. Zinc is a major element detected at high levels in urban air.

OBJECTIVE

We investigated the role of PM-associated zinc in cardiac injury.

METHODS

We repeatedly exposed 12- to 14-week-old male Wistar Kyoto rats intratracheally (1x/week for 8 or 16 weeks) to a) saline (control); b) PM having no soluble zinc (Mount St. Helens ash, MSH); or c) whole-combustion PM suspension containing 14.5 microg/mg of water-soluble zinc at high dose (PM-HD) and d ) low dose (PM-LD), e) the aqueous fraction of this suspension (14.5 microg/mg of soluble zinc) (PM-L), or f ) zinc sulfate (rats exposed for 8 weeks received double the concentration of all PM components of rats exposed for 16 weeks).

RESULTS

Pulmonary inflammation was apparent in all exposure groups when compared with saline (8 weeks > 16 weeks). PM with or without zinc, or with zinc alone caused small increases in focal subepicardial inflammation, degeneration, and fibrosis. Lesions were not detected in controls at 8 weeks but were noted at 16 weeks. We analyzed mitochondrial DNA damage using quantitative polymerase chain reaction and found that all groups except MSH caused varying degrees of damage relative to control. Total cardiac aconitase activity was inhibited in rats receiving soluble zinc. Expression array analysis of heart tissue revealed modest changes in mRNA for genes involved in signaling, ion channels function, oxidative stress, mitochondrial fatty acid metabolism, and cell cycle regulation in zinc but not in MSH-exposed rats.

CONCLUSION

These results suggest that water-soluble PM-associated zinc may be one of the causal components involved in PM cardiac effects.

Cardiopulmonary responses of Wistar Kyoto, spontaneously hypertensive, and stroke-prone spontaneously hypertensive rats to particulate matter (PM) exposure

Humans with underlying cardiovascular disease, including stroke, are more susceptible to ambient particulate matter (PM)-induced morbidity and mortality. We hypothesized that stroke-prone spontaneously hypertensive rats (SHRSP) would be more susceptible than healthy Wistar Kyoto (WKY) rats to PM-induced cardiac oxidative stress and pulmonary injury. We further postulated that PM-induced injury would be greater in SHRSP than in spontaneously hypertensive rats (SHR) based on the greater disease severity in SHRSP than SHR. First, male WKY and SHRSP were intratracheally (IT) instilled with saline or 1.11, 3.33, or 8.33 mg/kg of oil combustion PM and responses were analyzed 4 or 24 h later. Second, SHR and SHRSP were IT instilled with saline or 3.33 or 8.33 mg/kg of the same PM and responses were analyzed 24 h later. Pulmonary injury and inflammation were assessed in bronchoalveolar lavage fluid (BALF) and cardiac markers in cytosolic and mitochondrial fractions. BALF neutrophilic inflammatory response was induced similarly in all strains following PM exposure. BALF protein leakage, gamma-glutamyl transferase, and N-acetylglucosaminidase activities, but not lactate dehydrogenase activity, were exacerbated in SHRSP compared to WKY or SHR. Pulmonary cytosolic and cardiac mitochondrial ferritin levels decreased, and cardiac cytosolic superoxide dismutase (SOD) activity increased in SHRSP only. Pulmonary SOD activity decreased in WKY and SHRSP. Cardiac mitochondrial isocitrate dehydrogenase (ICDH) activity decreased in PM-exposed WKY and SHR; control levels were lower in SHRSP than SHR or WKY. In summary, strain-related differences exist in pulmonary protein leakage and oxidative stress markers. PM-induced changes in cardiac oxidative stress sensitive enzymes are small, and appear only slightly exacerbated in SHRSP compared to WKY or SHR. Multiple biological markers may be differentially affected by PM in genetic models of cardiovascular diseases. Preexisting cardiovascular disease may influence susceptibility to PM pulmonary and cardiac health effects in a disease-specific manner.

Effect of fly ash inhalation on biochemical and histomorphological changes in rat liver

The effect of fly ash inhalation (4h daily, 5 days a week) for 28 days on the deposition of metal ions and histopathological changes in the liver and serum clinical enzymes has been studied. The results showed an increase in the concentration of metals such as cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), and lead (Pb) in the tissues of exposed rats. The level of metals varied from metal to metal and from organ to organ. Level of serum enzymes such as serum glutamate oxaloacetate transaminase, serum glutamate pyruvate transaminase, and alkaline phosphatase were increased in fly ash exposed rats using whole body inhalation exposure as compared to sham controls. Histopathological studies of rat liver exposed to fly ash revealed infiltration of mononuclear cells in and around the portal triads, which seems to be laden with fly ash particles. Hepatocytes showed necrotic changes such as pyknotic nuclei, karyorrhexis, and karyolytic. These changes were more towards the centrolobular areas than the midzonal and periportal areas. These findings demonstrate that the toxic metals of inhaled fly ash in rats may get translocated into extrapulmonary organs, become deposited and hence may manifest their toxic effects on different tissues.

Coagulation markers in healthy human subjects exposed to diesel exhaust

BACKGROUND

Ambient particulate matter (PM) is associated with cardiovascular morbidity and mortality. It has been proposed that PM induces a pro-thrombotic process, increasing the risk of cardiovascular events, with some support from epidemiological and laboratory-based models. Diesel exhaust is a major contributor to urban PM, and we conducted a controlled human exposure of diesel exhaust in healthy subjects.

OBJECTIVE

To evaluate diesel exhaust exposure effects on fibrinolytic burden (D-dimer), platelet number, and endothelial injury (von Willebrand's factor, VWF), inhibition of the fibrinolytic pathway (plasminogen activator inhibitor-1 [PAI-1]), and inflammation (C-reactive protein, CRP).

MATERIALS AND METHODS

Randomized, crossover, double-blinded design, with 13 healthy participants exposed on three different days (>or=2 weeks washout) to diesel exhaust at 0 (filtered air), 100 microg PM(2.5)/m(3) and 200 microg PM(2.5)/m(3). We assessed diesel exhaust-associated changes in D-dimer, VWF, PAI-1 and platelets at 3, 6 and 22 h, and CRP at 22 h, after exposure initiation.

RESULT

Significant changes did not occur in any primary endpoints. Among secondary endpoints, diesel exhaust (200 microg PM(2.5)/m(3)) effect on PAI-1 levels at 22 h was of borderline significance, with a 1.32-fold decrease after exposure to diesel exhaust (200 microg PM(2.5)/m(3)), relative to filtered air (CI 1.00 to 1.54). Diurnal patterns in D-dimer and PAI-1 were observed.

CONCLUSIONS

In healthy individuals, exposure to 200 microg PM(2.5)/m(3) diesel exhaust did not affect primary pro-thrombotic endpoints. Thus, these data do not support a diesel exhaust-induced pro-thrombotic phenomenon. Replication of these studies should be carried out to ascertain whether or not they inform our mechanistic understanding of air pollution's cardiovascular effects.

Systemic imbalance of essential metals and cardiac gene expression in rats following acute pulmonary zinc exposure

It was recently demonstrated that particulate matter (PM) containing water-soluble zinc produces cardiac injury following pulmonary exposure. To investigate whether pulmonary zinc exposure produces systemic metal imbalance and direct cardiac effects, male Wistar Kyoto (WKY) rats (12-14 wk age) were intratracheally (IT) instilled with saline or 2 micromol/kg zinc sulfate. Temporal analysis was performed for systemic levels of essential metals (zinc, copper, and selenium), and induction of zinc transporter-2 (ZT-2) and metallothionein-1 (MT-1) mRNA in the lung, heart, and liver. Additionally, cardiac gene expression profile was evaluated using Affymetrix GeneChips (rat 230A) arrays to identify zinc-specific effects. Pulmonary zinc instillation produced an increase in plasma zinc to approximately 20% at 1 and 4 h postexposure with concomitant decline in the lung levels. At 24 and 48 h postexposure, zinc levels rose significantly (approximately 35%) in the liver. At these time points, plasma and liver levels of copper and selenium also increased significantly, suggesting systemic disturbance in essential metals. Zinc exposure was associated with marked induction of MT-1 and ZT-2 mRNA in lung, heart, and liver, suggesting systemic metal sequestration response. Given the functional role of zinc in hundreds of proteins, the gene expression profiles demonstrated changes that are expected based on its physiological role. Zinc exposure produced an increase in expression of kinases and inhibition of expression of phosphatases; up- or downregulation of genes involved in mitochondrial function; changes in calcium regulatory proteins suggestive of elevated intracellular free calcium and increases in sulfotransferases; upregulation of potassium channel genes; and changes in free radical-sensitive proteins. Some of these expression changes are reflective of a direct effect of zinc on myocardium following pulmonary exposure, which may result in impaired mitochondrial respiration, stimulated cell signaling, altered Ca2+ homeostasis, and increased transcription of sulfotransferases. Cardiotoxicity may be an outcome of acute zinc toxicosis and occupational exposures to metal fumes containing soluble zinc. Imbalance of systemic metal homeostasis as a result of pulmonary zinc exposure may underlie the cause of extrapulmonary effects.