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.     

Orthotopic liver transplantation in a patient with carbamyl phosphate synthetase deficiency and cystic fibrosis

A 15-year-old female with carbamyl phosphate synthetase deficiency, cystic fibrosis, and cystic fibrosis-related diabetes underwent orthotopic cadaveric liver transplantation. Metabolic control was maintained during the procedure with nutritional support and the use of intravenous sodium phenylacetate and benzoate. Her postoperative course was complicated by seizures and a transient decline in her pulmonary function tests, which returned to preoperative levels within one year of the transplant. Now, four years post-transplant, her quality of life has dramatically improved. There are only four Canadian centres with paediatric liver transplantation programs. However, expert medical care for adults with inborn error of metabolism is even more limited, suggesting that access to adult medical care is one of the many factors to be considered when liver transplantation is contemplated for patients with metabolically unstable conditions.     

Studies on some kinetic parameters of aldolases in selected tissues of the freshwater fish (Tilapia mossambica) under the toxic impact of methyl parathion

Kinetic parameters of aldolases in muscle, gill, liver and brain tissues of the teleost Tilapia mossambica were studied at sublethal concentrations with methyl parathion (MP). The pH activity profiles were optimal at pH 7.0 and 9.0 in gill, liver and brain tissues, whereas only a single peak at pH 7.0 was observed in muscle tissue of both control and MP-exposed fish. The pH 7.0-specific peak was confirmed as aldolase A and the pH 9.0-specific peak represents the tissue-specific aldolases: aldolase B in liver, aldolase C in brain and aldolase B-C in gill. It is further confirmed with the inhibitor sensitivity of aldolases at two peaks with 6 x 10(-3) M ATP or AMP. The pH-based substrate-dependent kinetics of aldolases showed a variable trend. The tissue-specific activity of pH 7.0-specific aldolases showed low Km values for gill followed by muscle, liver and brain tissues, suggestive of its high enzyme-substrate affinity. During MP exposure, the Vmax values of pH 7.0-specific aldolases in muscle, gill and brain were unchanged compared to controls, but Km values were decreased. The pH 9.0-specific aldolases of gill and liver from MP-exposed fish showed decreased Km values with a slight increase in Vmax values. Effectors such as lysine, arginine and Ca2+ inhibited, while histidine, cysteine, aspartic acid and alpha-ketoglutaric acid elevated the activity levels of aldolases.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pulmonary Structural and Extracellular Matrix Alterations in Fischer 344 Rats Following Subchronic Phosgene Exposure

Phosgene, an acylating agent, is a very potent inducer of pulmonaryedema. Subchronic effects of phosgene in laboratory animalsare not well characterized. The purpose of the study was toelucidate potential long-term effects on collagen and elastinmetabolism during pulmonary injury/recovery and obtain informationabout the concentration x time (C x T) behavior of low levelsof phosgene. Male Fischer 344 rats (60 days old) were exposedeither to clean air or phosgene, 6 hr/day: 0.1 ppm (5 days/week),0.2 ppm (5 days/week), 0.5 ppm (2 days/week), and 1.0 ppm (1day/week), for 4 or 12 weeks. A group of rats was allowed cleanair recovery for 4 weeks after 12 weeks of phosgene exposure.This exposure scenario was designed to provide equal C x T productfor all concentrations at one particular time point except for0.1 ppm (50% C x T). Phosgene exposure for 4 or 12 weeks increasedlung to body weight ratio and lung displacement volume in aconcentration-dependent manner. The increase in lung displacementvolume was significant even at 0.1 ppm phosgene at 4 weeks.Light microscopic level histopathology examination of lung wasconducted at 0.0, 0.1, 0.2, and 1.0 ppm phosgene following 4and 12 and 16 weeks (recovery). Small but clearly apparent terminalbronchiolar thickening and inflammation were evident with 0.1ppm phosgene at both 4 and 12 weeks. At 0.2 ppm phosgene, terminalbronchiolar thickening and inflammation appeared to be moreprominent when compared to the 0.1 ppm group and changes inalveolar parenchyma were minimal. At 1.0 ppm, extensive inflammationand thickening of terminal bronchioles as well as alveolar wallswere evident. Concentration rather than C x T seems to drivepathology response. Trichrome staining for collagen at the terminalbronchiolar sites indicated a slight increase at 4 weeks andmarked increase at 12 weeks in both 0.2 and 1.0 ppm groups (0.5ppm was not examined), 1.0 ppm being more intense. Wholelungprolyl hydroxylase activity and hydroxyproline, taken as anindex of collagen synthesis, were increased following 1.0 ppmphosgene exposure at 4 as well as 12 weeks, respectively. Desmosinelevels, taken as an index of changes in elastin, were increasedin the lung after 4 or 12 weeks in the 1.0 ppm phosgene group.Following 4 weeks of air recovery, lung hydroxyproline was furtherincreased in 0.5 and 1.0 ppm phosgene groups. Lung weight alsoremained significantly higher than the controls; however, desmosineand lung displacement volume in phosgene-exposed animals weresimilar to controls. In summary, terminal bronchiolar and lungvolume displacement changes occurred at very low phosgene concentrations(0.1 ppm). Phosgene concentration, rather than C x T productappeared to drive toxic responses. The changes induced by phosgene(except of collagen) following 4 weeks were not further amplifiedat 12 weeks despite continued exposure. Phosgene-induced alterationsof matrix were only partially reversible after 4 weeks of cleanair exposure.     

Effects of Acute and Repeated Exposures to Aroclor 1254 in Adult Rats: Motor Activity and Flavor Aversion Conditioning

While considerable research has focused on the neurotoxicityof developmental exposures to polychlorinated biphenyls, includingAroclor 1254, relatively little is known about exposures inadult animals. This study investigated the behavioral effectsof acute and repeated Aroclor 1254 exposures to adult rats onmotor activity and flavor aversion conditioning. Male Long-Evansrats (60 days old) were tested for motor activity in a photocelldevice after acute (0, 100, 300, or 1000 mg/kg, po) or repeated(0, 1, 3, 10, 30 or 100 mg/kg/day, po, 5 days/week for 4 to6 weeks) exposure to Aroclor 1254. Motor activity was decreaseddose-dependently at doses of 300 mg/kg or more after acute exposure.Severe body weight loss and deaths occurred at 1000 mg/kg. Recoveryof activity occurred over 9 weeks but was incomplete. Afterrepeated exposure, motor activity was decreased dose-dependentlyat doses of 30 mg/kg or more, and severe weight loss and deathsoccurred at 100 mg/kg. In contrast to acute exposure, completerecovery of activity occurred 3 weeks after exposure. Additionalrats were water deprived (30 mm/day) and received acute po administrationof Aroclor 1254 (0, 10, 15, 25, 30, 100, or 300 mg/kg) shortlyafter consuming a saccharin solution. Three days later theywere given the choice between consuming saccharin or water,and saccharin preferences were recorded. Saccharin preferencewas decreased at doses of 25 mg/kg or more. Additional experimentsdetermined the effect of repeated saccharin-Aroclor 1254 pairings(0, 3.75, 7.5, or 15 mg/kg/day, 14 days) followed by a choicetest 1 day after the last dose. Repeated exposure to 15 mg/kgproduced robust flavor aversion conditioning. Repeated exposureto 7.5 mg/kg produced flavor aversion conditioning in four of12 rats. These results demonstrate that Aroclor 1254 causeshypoactivlty and flavor aversions in adult rats; the no observableeffect level (NOEL) for motor activity was 100 mg/kg for acuteexposure and 10 mg/kg for repeated exposure for a period ofup to 6 weeks. The acute NOEL for flavor aversion conditioningwas 15 mg/kg while the repeated NOEL was 7.5 mg/kg.     

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.     

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.     

Workshop summary: phosgene-induced pulmonary toxicity revisited: appraisal of early and late markers of pulmonary injury from animal models with emphasis on human significance

A workshop was held February 14, 2007, in Arlington, VA, under the auspices of the Phosgene Panel of the American Chemistry Council. The objective of this workshop was to convene inhalation toxicologists and medical experts from academia, industry and regulatory authorities to critically discuss past and recent inhalation studies of phosgene in controlled animal models. This included presentations addressing the benefits and limitations of rodent (mice, rats) and nonrodent (dogs) species to study concentration x time (C x t) relationships of acute and chronic types of pulmonary changes. Toxicological endpoints focused on the primary pulmonary effects associated with the acute inhalation exposure to phosgene gas and responses secondary to injury. A consensus was reached that the phosgene-induced increased pulmonary extravasation of fluid and protein can suitably be probed by bronchoalveolar lavage (BAL) techniques. BAL fluid analyses rank among the most sensitive methods to detect phosgene-induced noncardiogenic, pulmonary high-permeability edema following acute inhalation exposure. Maximum protein concentrations in BAL fluid occurred within 1 day after exposure, typically followed by a latency period up to about 15 h, which is reciprocal to the C x t exposure relationship. The C x t relationship was constant over a wide range of concentrations and single exposure durations. Following intermittent, repeated exposures of fixed duration, increased tolerance to recurrent exposures occurred. For such exposure regimens, chronic effects appear to be clearly dependent on the concentration rather than the cumulative concentration x time relationship. The threshold C x t product based on an increased BAL fluid protein following single exposure was essentially identical to the respective C x t product following subchronic exposure of rats based on increased pulmonary collagen and influx of inflammatory cells. Thus, the chronic outcome appears to be contingent upon the acute pulmonary threshold dose. Exposure concentrations high enough to elicit an increased acute extravasation of plasma constituents into the alveolus may also be associated with surfactant dysfunction, intra-alveolar accumulation of fibrin and collagen, and increased recruitment and activation of inflammatory cells. Although the exact mechanisms of toxicity have not yet been completely elucidated, consensus was reached that the acute pulmonary toxicity of phosgene gas is consistent with a simple, irritant mode of action at the site of its initial deposition/retention. The acute concentration x time mortality relationship of phosgene gas in rats is extremely steep, which is typical for a local, directly acting pulmonary irritant gas. Due to the high lipophilicity of phosgene gas, it efficiently penetrates the lower respiratory tract. Indeed, more recent published evidence from animals or humans has not revealed appreciable irritant responses in central and upper airways, unless exposure was to almost lethal concentrations. The comparison of acute inhalation studies in rats and dogs with focus on changes in BAL fluid constituents demonstrates that dogs are approximately three to four times less susceptible to phosgene than rats under methodologically similar conditions. There are data to suggest that the dog may be useful particularly for the study of mechanisms associated with the acute extravasation of plasma constituents because of its size and general morphology and physiology of the lung as well as its oronasal breathing patterns. However, the study of the long-term sequelae of acute effects is experimentally markedly more demanding in dogs as compared to rats, precluding the dog model to be applied on a routine base. The striking similarity of threshold concentrations from single exposure (increased protein in BAL fluid) and repeated-exposure 3-mo inhalation studies (increased pulmonary collagen deposition) in rats supports the notion that chronic changes depend on acute threshold mechanisms.     

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.