Pulmonary and systemic effects of zinc-containing emission particles in three rat strains: multiple exposure scenarios.

As a common component of ambient particulate matter (PM), zinc has been proposed to play a role in PM-induced adverse health effects. Although occupational exposures to high levels of zinc-fume have been associated with metal-fume fever accompanied by pulmonary inflammation and injury, the effects of PM-associated zinc are unclear. We hypothesized that an oil combustion emission PM (EPM) containing bioavailable zinc would induce pulmonary injury and systemic hematological changes attributable to the leachable zinc following acute as well as longer-term exposures in a rat strain-specific manner. In order to initially characterize the pulmonary response to EPM, male Sprague-Dawley (SD) rats were intratracheally (IT) instilled with 0.0, 0.8, 3.3, or 8.3 mg/kg EPM in saline. To further determine if the pulmonary injury was associated with the EPM leachable zinc, subsequent studies included IT instillation of SD rats with either saline, whole EPM suspension, the saline leachable fraction of EPM, the particulate fraction of EPM (all at 8.3 mg/kg, soluble Zn = 14.5 microg/mg EPM), or ZnSO(4) (0.0, 33.0, or 66.0 microg/kg Zn). Finally, to ascertain the cumulative impact of inhaled EPM in the causation of acute pulmonary and systemic effects as well as long-term fibrotic responses, we exposed three rat strains of differential susceptibility to PM. Male SD, normotensive Wistar-Kyoto (WKY), and spontaneously hypertensive (SH) rats (90 days old) were exposed nose-only to either filtered air or EPM: 2, 5, or 10 mg/m(3) (6 h/day x 4 days/week x 1 week); or 10 mg/m(3) (6 h/day x 1 day/week for 1, 4, or 16 weeks) and assessed at 2 days postexposure. IT exposures to whole EPM suspensions were associated with a dose-dependent increase in protein/albumin permeability and neutrophilic inflammation. Pulmonary protein/albumin leakage and neutrophilic inflammation caused by the leachable fraction of EPM and ZnSO(4) were comparable to the effect of whole suspension. However, protein/albumin leakage was not associated with the particulate fraction, although significant neutrophilic inflammation did occur following instillation. With EPM nose-only inhalation, acute exposures (10 mg/m(3) only) for 4 days resulted in small increases in bronchoalveolar lavage fluid (BALF) protein and n-acetyl glucosaminidase activities (approximately 50% above control). Surprisingly, unlike IT exposures, no neutrophilic influx was detectable in BALF from any of the inhalation groups. The only major effect of acute and long-term EPM inhalation was a dose- and time-dependent increase in alveolar macrophages (AM) regardless of the rat strain. Histological evidence also showed dose- and time-dependent accumulations of particle-loaded AM. Particles were also evident in interstitial spaces, and in the lung-associated lymph nodes following the inhalation exposures (SH > WKY = SD). There were strain-related differences in peripheral white blood cell counts and plasma fibrinogen with no major EPM inhalation effect. The present study demonstrated the critical differences in pulmonary responsiveness to EPM between IT and inhalation exposures, probably attributable to the dose of bioavailable zinc. EPM IT exposures, but not acute and long-term inhalation of up to 10 mg/m(3), caused neutrophilic inflammation. Inhalation exposures may result in particle accumulation and macrophage recruitment with potential strain differences in EPM clearance.     

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.     

TEMPORAL ASSOCIATION BETWEEN PULMONARY AND SYSTEMIC EFFECTS OF PARTICULATE MATTER IN HEALTHY AND CARDIOVASCULAR COMPROMISED RATS

Exposure to particulate matter (PM) has been associated with increased morbidity and mortality among individuals with cardiovascular disease. It is hypothesized that systemic alterations occur concurrent to pulmonary injury/inflammation, and contribute to cardiac events in compromised hosts. We explored this hypothesis using a rat model for human hypertension and cardiovascular disease (spontaneously hypertensive, SH), and normotensive Wistar Kyoto (WKY) rats. SH and WKY rats (12-13 wk old) were exposed either intratracheally (IT; 0.0, 1.0, or 5.0 mg/kg in saline) or nose-only (15 mg/m 3 2 6 h/d 2 3 d/wk 2 1, 2 or 4 wk) to combustion source residual oil fly ash (ROFA) with low metal content, and examined 1, 2 or 4 d later. Bronchoalveolar lavage fluid (BALF) albumin and neutrophils increased (SH WKY) at d 1 following ROFA IT. With inhalation exposure, both strains experienced progressive histological lung damage and increases in BALF albumin and neutrophils during 1 to 4 wk (SH > WKY). Acute lung injury from ROFA IT was temporally associated with increases in plasma fibrinogen in both strains, but only the SH rats responded to the acute 1-wk ROFA inhalation. Longer term (2 or 4 wk) ROFA caused progressive lung injury (SH > WKY), but did not sustain the increase in fibrinogen. BALF glutathione increased in a temporal fashion similar to fibrinogen; however, only WKY rats demonstrated this response. There was a small but consistent decrease in blood lymphocytes and an increase in blood neutrophils in SH rats exposed to ROFA acutely. In conclusion, acute PM exposure can provoke an acute systemic thrombogenic response associated with pulmonary injury/inflammation and oxidative stress in cardiovascular compromised rats. This evidence is consistent with greater cardiovascular events during acute PM episodes in compromised humans.     

Temporal association between pulmonary and systemic effects of particulate matter in healthy and cardiovascular compromised rats

Exposure to particulate matter (PM) has been associated with increased morbidity and mortality among individuals with cardiovascular disease. It is hypothesized that systemic alterations occur concurrent to pulmonary injury/inflammation, and contribute to cardiac events in compromised hosts. We explored this hypothesis using a rat model for human hypertension and cardiovascular disease (spontaneously hypertensive, SH), and normotensive Wistar Kyoto (WKY) rats. SH and WKY rats (12-13 wk old) were exposed either intratracheally (IT; 0.0, 1.0, or 5.0 mg/kg in saline) or nose-only (15 mg/m(3) x 6 h/d x 3 d/wk x 1, 2 or 4 wk) to combustion source residual oil fly ash (ROFA) with low metal content, and examined 1, 2 or 4 d later. Bronchoalveolar lavage fluid (BALF) albumin and neutrophils increased (SH approximately equal WKY) at d 1 following ROFA IT. With inhalation exposure, both strains experienced progressive histological lung damage and increases in BALF albumin and neutrophils during 1 to 4 wk (SH > WKY). Acute lung injury from ROFA IT was temporally associated with increases in plasma fibrinogen in both strains, but only the SH rats responded to the acute 1-wk ROFA inhalation. Longer term (2 or 4 wk) ROFA caused progressive lung injury (SH > WKY), but did not sustain the increase in fibrinogen. BALF glutathione increased in a temporal fashion similar to fibrinogen; however, only WKY rats demonstrated this response. There was a small but consistent decrease in blood lymphocytes and an increase in blood neutrophils in SH rats exposed to ROFA acutely. In conclusion, acute PM exposure can provoke an acute systemic thrombogenic response associated with pulmonary injury/inflammation and oxidative stress in cardiovascular compromised rats. This evidence is consistent with greater cardiovascular events during acute PM episodes in compromised humans.     

Clinical and pathological manifestations of cardiovascular disease in rat models: the influence of acute ozone exposure

Abstract

Rodent models of cardiovascular diseases (CVD) and metabolic disorders are used for examining susceptibility variations to environmental exposures. However, cross-model organ pathologies and clinical manifestations are often not compared. We hypothesized that genetic CVD rat models will exhibit baseline pathologies and will thus express varied lung response to acute ozone exposure. Male 12–14-week-old healthy Wistar Kyoto (WKY), Wistar (WIS), and Sprague–Dawley (SD) rats and CVD-compromised spontaneously hypertensive (SH), fawn-hooded hypertensive (FHH), stroke-prone SH (SHSP), obese SH heart-failure (SHHF), obese diabetic JCR (JCR) rats were exposed to 0.0, 0.25, 0.5, or 1.0?ppm ozone for 4?h and clinical biomarkers, and lung, heart and kidney pathologies were compared immediately following (0–h) or 20-h later. Strain differences were observed between air-exposed CVD-prone and WKY rats in clinical biomarkers and in kidney and heart pathology. Serum cholesterol was higher in air-exposed obese SHHF and JCR compared to other air-exposed strains. Ozone did not produce lesions in the heart or kidney. CVD-prone and SD rats demonstrated glomerulopathy and kidney inflammation (WKY?=?WIS?=?SH?<?SD?=?SHSP?<?SHHF?<?JCR?=?FHH) regardless of ozone. Cardiac myofiber degeneration was evident in SH, SHHF, and JCR, while only JCR tends to have inflammation in coronaries. Lung pathology in air-exposed rats was minimal in all strains except JCR. Ozone induced variable alveolar histiocytosis and bronchiolar inflammation; JCR and SHHF were less affected. This study provides a comparative account of the clinical manifestations of disease and early-life organ pathologies in several rat models of CVD and their differential susceptibility to lung injury from air pollutant exposure.     

Divergent electrocardiographic responses to whole and particle-free diesel exhaust inhalation in spontaneously hypertensive rats

Diesel exhaust (DE) is a major contributor to traffic-related fine particulate matter (PM)(2.5). Although inroads have been made in understanding the mechanisms of PM-related health effects, DE's complex mixture of PM, gases, and volatile organics makes it difficult to determine how the constituents contribute to DE's effects. We hypothesized that exposure to particle-filtered DE (fDE; gases alone) will elicit less cardiac effects than whole DE (wDE; particles plus gases). In addition, we hypothesized that spontaneously hypertensive (SH) rats will be more sensitive to the electrocardiographic effects of DE exposure than Wistar Kyoto rats (WKY; background strain with normal blood pressure). SH and WKY rats, implanted with telemeters to monitor electrocardiogram and heart rate (HR), were exposed once for 4 h to 150 μg/m(3) or 500 μg/m(3) of wDE (gases plus PM) or fDE (gases alone) DE, or filtered air. Exposure to fDE, but not wDE, caused immediate electrocardiographic alterations in cardiac repolarization (ST depression) and atrioventricular conduction block (PR prolongation) as well as bradycardia in SH rats. Exposure to wDE, but not fDE, caused postexposure ST depression and increased sensitivity to the pulmonary C fiber agonist capsaicin in SH rats. The only notable effect of DE exposure in WKY rats was a decrease in HR. Taken together, hypertension may predispose to the potential cardiac effects of DE and components of DE may have divergent effects with some eliciting immediate irritant effects (e.g., gases), whereas others (e.g., PM) trigger delayed effects potentially via separate mechanisms.     

The role of cardiovascular disease-associated iron overload in Libby amphibole-induced acute pulmonary injury and inflammation

Pulmonary toxicity induced by asbestos is thought to be mediated through redox-cycling of fiber-bound and bioavailable iron (Fe). We hypothesized that Libby amphibole (LA)-induced cute lung injury will be exacerbated in rat models of cardiovascular disease (CVD)-associated Fe-overload and oxidative stress. Healthy male Wistar Kyoto (WKY), spontaneously hypertensive (SH) and SH heart failure (SHHF) rats were intratracheally instilled with 0.0, 0.25 or 1.0?mg/rat LA and examined at 1 day, 1 week or 1 month. Although histologically it was not possible to distinguish severity differences between strains in LA-induced initial inflammation and later fibrosis, quantitative assessment of biomarkers showed strain-related differences. LA-induced neutrophilic inflammation was reversible in WKY but persisted more in SH and SHHF. Lung MIP-2 mRNA increased only in WKY at 1 day in response to LA but not in SH and SHHF. Bronchoalveolar lavage fluid (BALF) protein increased in SH but not WKY at 1 week and 1 month, while γ-glutamyltransferase and N-acetyl-β-D-glucosaminidase activities increased in all strains (WKY>SH=SHHF). BALF ferritin levels were high at baseline and increased following LA exposure only in SH and SHHF. Ferritin heavy chain mRNA increased only in SHHF at 1 day. At 1 month ferritin light chain mRNA declined from already high baseline levels in SHHF but increased in WKY and SH suggesting its differential involvement in LA-induced injury in Fe-overload. Unlike WKY, both SHHF and SH failed to increase the lung lining antioxidant, ascorbate, in response to LA. We conclude that underlying CVD-associated Fe-overload is likely linked to persistent lung injury, inflammation and antioxidant decompensation following LA exposure in rats.     

The role of cardiovascular disease-associated iron overload in Libby amphibole-induced acute pulmonary injury and inflammation

Pulmonary toxicity induced by asbestos is thought to be mediated through redox-cycling of fiber-bound and bioavailable iron (Fe). We hypothesized that Libby amphibole (LA)-induced cute lung injury will be exacerbated in rat models of cardiovascular disease (CVD)-associated Fe-overload and oxidative stress. Healthy male Wistar Kyoto (WKY), spontaneously hypertensive (SH) and SH heart failure (SHHF) rats were intratracheally instilled with 0.0, 0.25 or 1.0 mg/rat LA and examined at 1 day, 1 week or 1 month. Although histologically it was not possible to distinguish severity differences between strains in LA-induced initial inflammation and later fibrosis, quantitative assessment of biomarkers showed strain-related differences. LA-induced neutrophilic inflammation was reversible in WKY but persisted more in SH and SHHF. Lung MIP-2 mRNA increased only in WKY at 1 day in response to LA but not in SH and SHHF. Bronchoalveolar lavage fluid (BALF) protein increased in SH but not WKY at 1 week and 1 month, while γ-glutamyltransferase and N-acetyl-β-D-glucosaminidase activities increased in all strains (WKY>SH=SHHF). BALF ferritin levels were high at baseline and increased following LA exposure only in SH and SHHF. Ferritin heavy chain mRNA increased only in SHHF at 1 day. At 1 month ferritin light chain mRNA declined from already high baseline levels in SHHF but increased in WKY and SH suggesting its differential involvement in LA-induced injury in Fe-overload. Unlike WKY, both SHHF and SH failed to increase the lung lining antioxidant, ascorbate, in response to LA. We conclude that underlying CVD-associated Fe-overload is likely linked to persistent lung injury, inflammation and antioxidant decompensation following LA exposure in rats.     

Hypertensive rats are susceptible to TLR4-mediated signaling following exposure to combustion source particulate matter

Toll-like receptor 4 (TLR4) has been shown to play a role in cell signaling that results in neutrophilic inflammation in response to lipopolysaccharide and respiratory syncytial virus infection. TLR4 also interacts with CD14, which upon complex formation triggers TLR4-associated signaling pathways to produce a proinflammatory response. This mechanism results in the activation of NF-kappa B and subsequent inflammatory gene induction. In order to determine the effect of combustion source particle matter (PM), rich in zinc and nickel but with negligible endotoxin, on a possible activation of TLR4-mediated cell signaling and inflammation, we intratracheally (IT) instilled 3.3 mg/kg of PM into 12-w-old healthy male Wistar Kyoto (WKY) and susceptible spontaneously hypertensive (SH) rats. Inflammation, inflammatory-mediator gene expression, bronchoalveolar lavage fluid (BALF) protein and LDH, TLR4 and CD14 protein, and NF-kappa B activation in the lung were determined after 24 h. Dose-response data (0.0, 0.83, 3.33, and 8.3 mg/kg PM) for BALF LDH were obtained as a marker of lung cell injury in SH rats. BALF neutrophils, but not macrophages, were significantly increased in the PM-exposed WKY and SH rats. SH rats showed a greater PMN increase than WKY rats. Similarly, BALF protein and LDH levels were also increased following PM exposure but to a significantly greater extent in SH rats. Plasma fibrinogen was increased only in SH rats exposed to PM. The increased inflammation seen in PM-exposed SH rats was accompanied by a significant increase in TLR4 protein in the lung tissue, which was primarily localized in alveolar macrophages and epithelial cells. CD14 was also increased by PM exposure in both SH and WKY rats but was significantly greater in the SH rats. These increases were associated with greater translocation of NF-kappa B in the lungs of SH rather than WKY rats. This was accompanied by increased macrophage inhibitory protein (MIP)-2 mRNA expression at 24 h of exposure. These data suggest that the increased inflammation in the lungs of PM-exposed SH rats compared to WKY rats is accompanied by an increase in TLR4-mediated cell signaling. Thus, one of the mechanisms for greater susceptibility of SH rats to PM exposure may involve an increased activation of the TLR4 signaling pathway.     

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.     

Variability in ozone-induced pulmonary injury and inflammation in healthy and cardiovascular-compromised rat models

Abstract

The molecular bases for variability in air pollutant-induced pulmonary injury due to underlying cardiovascular (CVD) and/or metabolic diseases are unknown. We hypothesized that healthy and genetic CVD-prone rat models will exhibit exacerbated response to acute ozone exposure dependent on the type and severity of disease. Healthy male 12–14-week-old Wistar Kyoto (WKY), Wistar (WS) and Sprague Dawley (SD); and CVD-compromised spontaneously hypertensive (SH), Fawn-Hooded hypertensive (FHH), stroke-prone spontaneously hypertensive (SHSP), obese spontaneously hypertensive heart failure (SHHF) and obese JCR (JCR) rats were exposed to 0.0, 0.25, 0.5, or 1.0?ppm ozone for 4?h; pulmonary injury and inflammation were analyzed immediately following (0-h) or 20-h later. Baseline bronchoalveolar lavage fluid (BALF) protein was higher in CVD strains except for FHH when compared to healthy. Ozone-induced increases in protein and inflammation were concentration-dependent within each strain but the degree of response varied from strain to strain and with time. Among healthy rats, SD were least affected. Among CVD strains, lean rats were more susceptible to protein leakage from ozone than obese rats. Ozone caused least neutrophilic inflammation in SH and SHHF while SHSP and FHH were most affected. BALF neutrophils and protein were poorly correlated when considering the entire dataset (r?=?0.55). The baseline and ozone-induced increases in cytokine mRNA varied markedly between strains and did not correlate with inflammation. These data illustrate that the degree of ozone-induced lung injury/inflammation response is likely influenced by both genetic and physiological factors that govern the nature of cardiovascular compromise in CVD models.     

Ambient Particulate Matter Affects Cardiac Recovery in a Langendorff Ischemia Model

Exposure to ambient particulate matter (PM) is associated with increased mortality and morbidity among subjects with cardiovascular impairment. We hypothesized that exposure of spontaneously hypertensive (SH) rats to PM impairs the recovery of cardiovascular performance after coronary occlusion and reperfusion-ischemia. SH rats were exposed by intratracheal instillation to saline, standard urban PM (Ottawa dust EHC-93, 10 mg/kg body weight) or endotoxin (lipopolysaccharides LPS, 350 EU/animal) to induce a similar pulmonary inflammation. At 4 h postexposure, hearts were isolated and retrograde perfused in a Langendorff model. The experimental protocol included 35 min of coronary occlusion followed by 120 min of reperfusion, during which left ventricular developing pressure (LDVP), coronary flow (CF), and heart rate (HR) were measured. Baseline LVDP in particle-instilled SH rats was significantly decreased compared to saline-instilled animals. In addition, after ischemia the recovery of LDVP was much slower in rats pretreated with PM or LPS compared to saline instilled rats. The direct effects of the soluble PM fraction and the role of Zn²⁺ were also tested cardiomyocytes (H9C2 cells). Both particle-free filtrate and Zn²⁺ inhibited ATP or ionophore-stimulated calcium influx in cardiomyocytes. This inhibitory effect was related to an effect on calcium channels, as shown with Nifedipine. This study provides evidence that exposure to instillation of PM has reversible acute effects on the recovery of cardiac physiological parameters after ischemia. The effect may be caused by a direct action of soluble metals on calcium homeostasis in heart, but pulmonary inflammation may also play a significant role.     

Ambient particulate matter affects cardiac recovery in a Langendorff ischemia model

Exposure to ambient particulate matter (PM) is associated with increased mortality and morbidity among subjects with cardiovascular impairment. We hypothesized that exposure of spontaneously hypertensive (SH) rats to PM impairs the recovery of cardiovascular performance after coronary occlusion and reperfusion-ischemia. SH rats were exposed by intratracheal instillation to saline, standard urban PM (Ottawa dust EHC-93, 10 mg/kg body weight) or endotoxin (lipopolysaccharides LPS, 350 EU/animal) to induce a similar pulmonary inflammation. At 4 h postexposure, hearts were isolated and retrograde perfused in a Langendorff model. The experimental protocol included 35 min of coronary occlusion followed by 120 min of reperfusion, during which left ventricular developing pressure (LDVP), coronary flow (CF), and heart rate (HR) were measured. Baseline LVDP in particle-instilled SH rats was significantly decreased compared to saline-instilled animals. In addition, after ischemia the recovery of LDVP was much slower in rats pretreated with PM or LPS compared to saline instilled rats. The direct effects of the soluble PM fraction and the role of Zn2+ were also tested cardiomyocytes (H9C2 cells). Both particle-free filtrate and Zn2+ inhibited ATP or ionophore-stimulated calcium influx in cardiomyocytes. This inhibitory effect was related to an effect on calcium channels, as shown with Nifedipine. This study provides evidence that exposure to instillation of PM has reversible acute effects on the recovery of cardiac physiological parameters after ischemia. The effect may be caused by a direct action of soluble metals on calcium homeostasis in heart, but pulmonary inflammation may also play a significant role.     

Sex and strain-based inflammatory response to repeated tobacco smoke exposure in spontaneously hypertensive and Wistar Kyoto rats

Context: Approximately four million people die every year from chronic obstructive pulmonary disease (COPD), with more than 80% of the cases attributed to smoking.

Object: The purpose of this study was to examine the rat strain and sex-related differences and the extended tobacco smoke exposure to induce lung injury and inflammation with the goal of finding a suitable rodent model to study COPD.

Methods: Male and female spontaneously hypertensive (SH) and male Wistar Kyoto (WKY) rats were exposed to filtered air (FA) or to tobacco smoke (TS: 90?mg/m³ particulate concentration) for 6?h/day, three days/week for 4 or 12 weeks.

Results: Male SH rats demonstrated an enhanced, persistent inflammatory response compared to female SH and male WKY rats with extended TS exposure. Following four weeks of TS exposure, male SH rats had significantly increased total leukocytes and macrophage numbers, levels of TNF-alpha and elevated lactate dehydrogenase activity in bronchoalveolar lavage fluid compared with female SH, male WKY rats and corresponding controls. After 12 weeks of TS exposure, male SH rats continued to show significant increase in inflammatory cells and TNF-alpha, as well as IL-6 mRNA lung expression. In addition, the alveolar airspace of male SH rats exposed to TS was significantly enlarged compared to their FA controls, female SH and WKY rats.

Conclusion: The male SH rat demonstrates greater cellular, inflammatory and structural changes highly reminiscent of COPD compared to female SH and male WKY rats, suggesting that the male SH rat is an optimal rodent model to study COPD.     

Acute lung injury from intratracheal exposure to fugitive residual oil fly ash and its constituent metals in normo- and spontaneously hypertensive rats

We have recently shown that the spontaneously hypertensive (SH) rats with underlying cardiovascular disease exhibited greater pulmonary vascular leakage and oxidative stress than healthy normotensive (Wistar Kyoto, WKY) rats after a 3-day inhalation exposure to residual oil fly ash (ROFA) particles (Kodavanti et al., 2000). Since host responsiveness to a 3-day episodic ROFA inhalation could be different from a single acute exposure, we examined ROFA and its constituent metal (vanadium, V; nickel, Ni)-induced lung injury after a single intratracheal (IT) exposure. Male SH and WKY rats (12-13 wk) were IT instilled with either saline or ROFA (0.0, 0.83 or 3.33 mg/kg). The bronchoalveolar lavage fluid (BALF) was analyzed for lung injury markers at 24 and 96 h post-IT. Rats were also IT instilled with 0.0 or 1.5 micromol/kg of either VSO(4) or NiSO(4).6H(2)O in saline (equivalent to a dose of 2-3 mg ROFA), and assessed at 6 and 24 h post-IT. Basal levels of BALF protein, macrophages, and neutrophils, but not lactate dehydrogenase (LDH), were higher in control SH compared to control WKY rats. Lung histology of control SH rats exhibited mild focal alveolitis and perivascular inflammation; these changes were minimal in control WKY rats. ROFA-induced increases in BALF protein, and to a lesser extent in LDH, were greater in SH compared to WKY rats. ROFA IT was associated with the increases in BALF total cells in both strains (SH > WKY). BALF neutrophils increased at 24 h and macrophages at 96 h in a dose-dependent manner (SH > WKY). The increase in BALF neutrophils was largely reversed by 96 h in both rat strains. The V-induced increases in BALF protein and LDH peaked at 6 h post-IT and returned to control by 24 h in WKY rats. In SH rats, BALF protein and LDH were not affected by V. Ni caused BALF protein to increase in both strains at 6 and 24 h; however, the control values at 24 h were high in SH rats, and were not distinguishable from exposed rats. The Ni-induced increase in LDH activity was progressive over a 24-h time period (WKY > SH). The number of macrophages decreased following V and Ni exposure at 6 h, and this decrease was reversed by 24 h in both strains. V caused BALF neutrophils to increase only in WKY rats. The Ni-induced increase in BALF neutrophils was more dramatic and progressive than that of V, but was similar in both strains. Lung histology similarly revealed more severe and persistent edema, perivascular and peribronchiolar inflammation, and hemorrhage in Ni- than in V-exposed rats. This effect of Ni appeared slightly more severe in SH than in WKY rats. In summary, the acute single IT exposure to ROFA resulted in greater pulmonary protein leakage and inflammation in SH rats than in WKY rats. The metallic constituents of ROFA produced these effects in a strain-specific manner such that, at the dose level used, V caused pulmonary injury only in WKY rats, whereas Ni was toxic to both strains.     

Acute phase response, inflammation and metabolic syndrome biomarkers of Libby asbestos exposure

Identification of biomarkers assists in the diagnosis of disease and the assessment of health risks from environmental exposures. We hypothesized that rats exposed to Libby amphibole (LA) would present with a unique serum proteomic profile which could help elucidate epidemiologically-relevant biomarkers. In four experiments spanning varied protocols and temporality, healthy (Wistar Kyoto, WKY; and F344) and cardiovascular compromised (CVD) rat models (spontaneously hypertensive, SH; and SH heart failure, SHHF) were intratracheally instilled with saline (control) or LA. Serum biomarkers of cancer, inflammation, metabolic syndrome (MetS), and the acute phase response (APR) were analyzed. All rat strains exhibited acute increases in α-2-macroglobulin, and α1-acid glycoprotein. Among markers of inflammation, lipocalin-2 was induced in WKY, SH and SHHF and osteopontin only in WKY after LA exposure. While rat strain- and age-related changes were apparent in MetS biomarkers, no LA effects were evident. The cancer marker mesothelin was increased only slightly at 1 month in WKY in one of the studies. Quantitative Intact Proteomic profiling of WKY serum at 1 day or 4 weeks after 4 weekly LA instillations indicated no oxidative protein modifications, however APR proteins were significantly increased. Those included serine protease inhibitor, apolipoprotein E, α-2-HS-glycoprotein, t-kininogen 1 and 2, ceruloplasmin, vitamin D binding protein, serum amyloid P, and more 1 day after last LA exposure. All changes were reversible after a short recovery regardless of the acute or long-term exposures. Thus, LA exposure induces an APR and systemic inflammatory biomarkers that could have implications in systemic and pulmonary disease in individuals exposed to LA.     

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 microm (PM(2.5)). 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 PM(2.5) 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 PM(2.5) 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 microg/m(3) 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 PM(2.5) 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.     

Whole body plethysmography reveals differential ventilatory responses to ozone in rat models of cardiovascular disease

Abstract

To elucidate key factors of host susceptibility to air pollution, healthy and cardiovascular (CV)-compromised rats were exposed to air or ozone (O₃) at 0.25, 0.5, or 1.0?ppm for 4?h. We hypothesized that rat strains with the least cardiac reserve would be most prone to develop significant health effects. Using flow whole body plethysmography (FWBP), ventilatory responses in healthy 3-month-old male rats [i.e. Wistar–Kyoto (WKY), Wistar (WIS), and Sprague–Dawley (SD) strains] were compared with hypertensive [i.e. spontaneously hypertensive (SH), fawn-hooded-hypertensive (FHH), and SH-stroke-prone (SHSP)] strains and obese [i.e. SH-heart failure-prone (SHHF) and JCR:LA-cp, atherosclerosis-prone (JCR)] strains. SH were slower to acclimate to the FWBP chambers. At 0-h post-air-exposure, SHSP and SHHF exhibited hyperpnea, indicative of cardiopulmonary insufficiency. At 0-h-post-O₃, all but one strain showed significant concentration-dependent decreases in minute volume [MV?=?tidal volume (TV)?×?breathing frequency]. Comparing air with 1.0?ppm responses, MV declined 20–27% in healthy, 21–42% in hypertensive, and 33% in JCR rats, but was unchanged in SHHF rats. Penh increased significantly in all strains, with disproportionate increases in “responder” WKY and FHH strains. By 20?h, most changes had resolved, although Penh remained elevated in WKY, SH, and SHSP. Based on the effective dose estimates (O₃?ppm?×?h?×?MV), the most CV-compromised (SHSP and SHHF) strains received significantly greater O₃ lung deposition (25% and 40%, respectively). Data support epidemiologic associations that individuals with cardiopulmonary insufficiency are at greater risk for urban pollutant exposure due, in part, to enhanced lung deposition and exacerbation of hypoxia and pathophysiologic processes of heart failure.