Thermoregulatory effects following exposure to particulate matter in healthy and cardiopulmonary-compromised rats

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

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

Cardiovascular effects of nickel in ambient air

BACKGROUND

Fine particulate matter (FPM) in ambient air causes premature mortality due to cardiac disease in susceptible populations.

OBJECTIVE

Our objective in this study was to determine the most influential FPM components.

METHODS

A mouse model of atherosclerosis (ApoE-/-) was exposed to either filtered air or concentrated FPM (CAPs) in Tuxedo, New York (85 microg/m3 average, 6 hr/day, 5 days/week, for 6 months), and the FPM elemental composition was determined for each day. We also examined associations between PM components and mortality for two population studies: National Mortality and Morbidity Air Pollution Study (NMMAPS) and Hong Kong.

RESULTS

For the CAPs-exposed mice, the average of nickel was 43 ng/m3, but on 14 days, there were Ni peaks at approximately 175 ng/m3 and unusually low FPM and vanadium. For those days, back-trajectory analyses identified a remote Ni point source. Electrocardiographic measurements on CAPs-exposed and sham-exposed mice showed Ni to be significantly associated with acute changes in heart rate and its variability. In NMMAPS, daily mortality rates in the 60 cities with recent speciation data were significantly associated with average Ni and V, but not with other measured species. Also, the Hong Kong sulfur intervention produced sharp drops in sulfur dioxide, Ni, and V, but not other components, corresponding to the intervention-related reduction in cardiovascular and pulmonary mortality.

CONCLUSIONS

Known biological mechanisms cannot account for the significant associations between Ni with the acute cardiac function changes in the mice or with cardiovascular mortality in people at low ambient air concentrations; therefore, further research is needed.

Cardiac and thermoregulatory responses to inhaled pollutants in healthy and compromised rodents: modulation via interaction with environmental factors

Rodents often demonstrate a profound depression in physiological function following acute exposure to toxic xenobiotic agents. This effect, termed the hypothermic response, is primarily characterized by significant decreases in core temperature and heart rate and is generally accompanied by similar deficits in other important functional parameters. This response appears to be remarkably consistent across a wide variety of toxic agents and exposure regimens; however, the magnitude and duration of the induced effects may be modulated by changes in dose, animal mass, and environmental conditions. While the initiating stimulus and underlying mechanism(s) remains elusive, this response may represent an inherent reflexive pattern that is unique to the rodent and serves to attenuate the induced toxicity. Given that rodents are the primary animal species used in toxicological studies, it is important to consider this hypothermic response and its modulatory factors when interpreting the results of such studies and extrapolating those results to man.

Cardiac and thermoregulatory effects of instilled particulate matter-associated transition metals in healthy and cardiopulmonary-compromised rats

Particulate matter air pollution has been associated with cardiopulmonary morbidity and mortality in many recent epidemiological studies. Previous toxicological research has demonstrated profound cardiac and thermoregulatory changes in rats following exposure to residual oil fly ash (ROFA), a combustion-derived particulate. The response to ROFA appeared biphasic, consisting of both immediate (0-6 h) and delayed (24-96 h) bradycardia and hypothermia. Other studies have demonstrated that much of the pulmonary toxicity of ROFA was caused by its constitutive transition metals, namely, Fe, Ni, and V. This study examined the contributions of these metals to the observed cardiac and thermoregulatory changes caused by ROFA in conscious, unrestrained rats. Prior to exposure, each animal was surgically implanted with a radiotelemetry device capable of continuously monitoring heart rate, electrocardiographic, and core temperature data. Individual metals were intratracheally instilled in healthy rats (n = 4 per metal species) and in rats with monocrotaline (MCT; 60 mg/kg)-induced pulmonary hypertension (n = 10 per metal species); combinations of metals were instilled in MCT-treated rats only (n = 6 per combination of metal species). Metals were administered in doses equivalent to those found in the highest dose of ROFA used in previous studies, that is, 105 microg Fe(2)(SO(4))(3), 263 microg NiSO(4), and 245 microg VSO(4). Healthy and MCT-treated rats demonstrated similar responses to metals. Fe caused little response, whereas V caused marked bradycardia, arrhythmogenesis, and hypothermia immediately following instillation and lasting approximately 6 h. Ni caused no immediate response, but induced a delayed bradycardia, arrhythmogenesis, and hypothermia that began approximately 24 h after instillation and lasted for several days. When instilled in combination, Ni appeared to exacerbate the immediate effects of V, whereas Fe attenuated them. These data suggest that the biphasic response to instilled ROFA may result from a summation of the temporally different effects of V and Ni.

The spontaneously hypertensive rat as a model of human cardiovascular disease: evidence of exacerbated cardiopulmonary injury and oxidative stress from inhaled emission particulate matter

Cardiovascular disease is considered a probable risk factor of particulate matter (PM)-related mortality and morbidity. It was hypothesized that rats with hereditary systemic hypertension and underlying cardiac disease would be more susceptible than healthy normotensive rats to pulmonary injury from inhaled residual oil fly ash (ROFA) PM. Eight spontaneously hypertensive (SH) and eight normotensive Wistar-Kyoto (WKY) rats (12-13 weeks old) were implanted with radiotelemetry transmitters on Day -10 for measurement of electrocardiographic (ECG) waveforms. These and other nonimplanted rats were exposed to filtered air or ROFA (containing leachable toxic levels of metals) on Day 0 by nose-only inhalation (ROFA, 15 mg/m(3) x 6 h/day x 3 days). ECGs were monitored during both exposure and nonexposure periods. At 0 or 18 h post-ROFA exposure, rats were assessed for airway hyperreactivity, pulmonary and cardiac histological lesions, bronchoalveolar lavage fluid (BALF) markers of lung injury, oxidative stress, and cytokine gene expression. Comparisons were made in two areas: (1) underlying cardiopulmonary complications of control SH rats in comparison to control WKY rats; and (2) ROFA-induced cardiopulmonary injury/inflammation and oxidative burden. With respect to the first area, control air-exposed SH rats had higher lung and left ventricular weights when compared to age-matched WKY rats. SH rats had hyporeactive airways to acetylcholine challenge. Lung histology revealed the presence of activated macrophages, neutrophils, and hemorrhage in control SHrats. Consistently, levels of BALF protein, macrophages, neutrophils, and red blood cells were also higher in SH rats. Thiobarbituric acid-reactive material in the BALF of air-exposed SH rats was significantly higher than that of WKY rats. Lung inflammation and lesions were mirrored in the higher basal levels of pulmonary cytokine mRNA expression. Cardiomyopathy and monocytic cell infiltration were apparent in the left ventricle of SH rats, along with increased cytokine expression. ECG demonstrated a depressed ST segment area in SH rats. With regard to the second area of comparison (ROFA-exposed rats), pulmonary histology indicated a slightly exacerbated pulmonary lesions including inflammatory response to ROFA in SH rats compared to WKY rats and ROFA-induced increases in BALF protein and albumin were significantly higher in SH rats than in WKY rats. In addition, ROFA caused an increase in BALF red blood cells in SH rats, indicating increased hemorrhage in the alveolar parenchyma. The number of alveolar macrophages increased more dramatically in SH rats following ROFA exposure, whereas neutrophils increased similarly in both strains. Despite greater pulmonary injury in SH rats, ROFA-induced increases in BALF GSH, ascorbate, and uric acid were attenuated when compared to WKY rats. ROFA inhalation exposure was associated with similar increases in pulmonary mRNA expression of IL-6, cellular fibronectin, and glucose-6-phosphate dehydrogenase (relative to that of beta-actin) in both rat strains. The expression of MIP-2 was increased in WKY but attenuated in SH rats. Thus, SH rats have underlying cardiac and pulmonary complications. When exposed to ROFA, SH rats exhibited exacerbated pulmonary injury, an attenuated antioxidant response, and acute depression in ST segment area of ECG, which is consistent with a greater susceptibility to adverse health effects of fugitive combustion PM. This study shows that the SH rat is a potentially useful model of genetically determined susceptibility with pulmonary and cardiovascular complications.