Diesel exhaust inhalation enhances airway hyperresponsiveness in mice

Ambient air pollution and thrombosis

Air pollution is a growing public health concern of global significance. Acute and chronic exposure is known to impair cardiovascular function, exacerbate disease and increase cardiovascular mortality. Several plausible biological mechanisms have been proposed for these associations, however, at present, the pathways are incomplete. A seminal review by the American Heart Association (2010) concluded that the thrombotic effects of particulate air pollution likely contributed to their effects on cardiovascular mortality and morbidity. The aim of the current review is to appraise the newly accumulated scientific evidence (2009-2016) on contribution of haemostasis and thrombosis towards cardiovascular disease induced by exposure to both particulate and gaseous pollutants.Seventy four publications were reviewed in-depth. The weight of evidence suggests that acute exposure to fine particulate matter (PM_2.5) induces a shift in the haemostatic balance towards a pro-thrombotic/pro-coagulative state. Insufficient data was available to ascertain if a similar relationship exists for gaseous pollutants, and very few studies have addressed long-term exposure to ambient air pollution. Platelet activation, oxidative stress, interplay between interleukin-6 and tissue factor, all appear to be potentially important mechanisms in pollution-mediated thrombosis, together with an emerging role for circulating microvesicles and epigenetic changes.Overall, the recent literature supports, and arguably strengthens, the contention that air pollution contributes to cardiovascular morbidity by promoting haemostasis. The volume and diversity of the evidence highlights the complexity of the pathophysiologic mechanisms by which air pollution promotes thrombosis; multiple pathways are plausible and it is most likely they act in concert. Future research should address the role gaseous pollutants play in the cardiovascular effects of air pollution mixture and direct comparison of potentially susceptible groups to healthy individuals.

Effects of 4-nitrophenol on expression of the ER-α and AhR signaling pathway-associated genes in the small intestine of rats

4-Nitrophenol (PNP) is a persistent organic pollutant that was proven to be an environmental endocrine disruptor. The aim of this study was to evaluate the role of the estrogen receptor-α (ER-α) and aryl hydrocarbon receptor (AhR) signaling pathway in regulating the damage response to PNP in the small intestine of rats. Wistar-Imamichi male rats (21 d) were randomly divided into two groups: the control group and PNP group. Each group had three processes that were gavaged with PNP or vehicle daily: single dose (1 d), repeated dose (3 consecutive days) (3 d), and repeated dose with recovery (3 consecutive days and 3 recovery days) (6 d). The weight of the body, the related viscera, and small intestine were examined. Histological parameters of the small intestine and the quantity of mucus proteins secreted by small goblet cells were determined using HE staining and PAS staining. The mRNA expression of AhR, ER-α, CYP1A1, and GST was measured by real-time qPCR. In addition, we also analyzed the AhR, ER-α, and CYP1A1 expression in the small intestine by immunohistochemical staining. The small intestines histologically changed in the PNP-treated rat and the expression of AhR, CYP1A1, and GST was increased. While ER-α was significantly decreased in the small intestine, simultaneously, when rats were exposed to a longer PNP treatment, the damages disappeared. Our results demonstrate that PNP has an effect on the expression of AhR signaling pathway genes, AhR, CYP1A1, and GST, and ER-α in the rat small intestine.

Diesel exhaust particulate increases the size and complexity of lesions in atherosclerotic mice

Objective

Diesel exhaust particulate (DEP), a major component of urban air pollution, has been linked to atherogenesis and precipitation of myocardial infarction. We hypothesized that DEP exposure would increase and destabilise atherosclerotic lesions in apolipoprotein E deficient (ApoE^−/−) mice.

Methods

ApoE^−/− mice were fed a ‘Western diet’ (8 weeks) to induce ‘complex’ atherosclerotic plaques, with parallel experiments in normal chow fed wild-type mice. During the last 4 weeks of feeding, mice received twice weekly instillation (oropharyngeal aspiration) of 35 μL DEP (1 mg/mL, SRM-2975) or vehicle (saline). Atherosclerotic burden was assessed by en-face staining of the thoracic aorta and histological examination of the brachiocephalic artery.

Results

Brachiocephalic atherosclerotic plaques were larger in ApoE^−/− mice treated with DEP (59±10%) than in controls (32±7%; P = 0.017). In addition, DEP-treated mice had more plaques per section of artery (2.4±0.2 vs 1.8±0.2; P = 0.048) and buried fibrous layers (1.2±0.2 vs 0.4±0.1; P = 0.028). These changes were associated with lung inflammation and increased antioxidant gene expression in the liver, but not with changes in endothelial function, plasma lipids or systemic inflammation.

Conclusions

Increased atherosclerosis is caused by the particulate component of diesel exhaust producing advanced plaques with a potentially more vulnerable phenotype. These results are consistent with the suggestion that removal of the particulate component would reduce the adverse cardiovascular effects of diesel exhaust.

Effects of exposure to nanoparticle-rich or -depleted diesel exhaust on allergic pathophysiology in the murine lung

Although it has been shown that exposure to diesel exhaust (DE) is linked to the induction or exacerbation of respiratory disorders, the major components responsible have not been fully identified. We examined the effects of airway exposure to nanoparticle-rich DE (NR-DE) or DE without particles on allergic pulmonary inflammation in mice. We also investigated the cellular responses to intratracheal instillation of NR-DE particles (NR-DEP). ICR mice inhaled one of four different mixtures (control air, low-concentration DE, high-concentration DE, and high-concentration DE without particles) for 8 weeks in the presence or absence of repeated intratracheal administration of ovalbumin (OVA). In a separate study, NR-DEP and/or OVA were repeatedly administrated intratracheally to mice. High-concentration NR-DE or DE without particles substantially exacerbated OVA-induced eosinophilic airway inflammation. This exacerbation was concomitant with increases in lung levels of Th2 cytokines such as interleukin (IL)-4, IL-5, and IL-13 and of chemokines such as monocyte chemotactic protein-1. Furthermore, in the presence of allergen, both DE without particles and high-concentration NR-DE strongly enhanced the production and release of myeloperoxidase into the alveolar spaces. Repeated administration of NR-DEP did not substantially affect the allergic asthma. These results strongly suggest that gaseous compounds in NR-DE aggravate murine allergic airway inflammation, mainly via amplification of the Th2 response.

Necrosis and apoptosis of renal tubular epithelial cells in rats exposed to 3-methyl-4-nitrophenol

The 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC) exists in diesel exhaust particles (DEP), and is also one of the degradation products of insecticide fenitrothion. To assess potential nephrotoxicity of PNMC, male Sprague-Dawley (SD) rats were subcutaneously dosed with PNMC at 1, 10, and 100 mg/kg/day for five consecutive days. No significant changes were detected in body weights and relative weights of kidneys by the treatment of PNMC. However, the extent of cellular necrosis was found to be severe in renal tubular epithelial cells of PNMC-treated rats. In addition, PNMC exposure significantly increased the number of terminal deoxynucleotidyle transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells compared to the control in renal tubule of PNMC-treated rats. Moreover, immunohistochemical results indicated that significant decrease in the B-cell lymphoma 2 (Bcl-2) expressions andincrease in the Bcl-2 associated × protein (Bax) expression were detected in PNMC-treated rats. The ratio of Bcl-2/Bax was also reduced significantly at PNMC-treated rats dosed at 10 or 100 mg kg(-1) . Furthermore, the significant increase of FAS (CD95/APO-1) expression was found in the groups dosed at 10 or 100 mg kg(-1) of PNMC. The expression of Caspase-3 was higher in PNMC-treated rats, compared to the control group. Our results indicated that activation of mitochondria and Caspase-3 protease may contribute to the PNMC-induced apoptosis, suggesting that PNMC could cause both necrosis and apoptosis resulting in cell death of renal epithelium cells and could induce renal toxicity.

The biological effects of subacute inhalation of diesel exhaust following addition of cerium oxide nanoparticles in atherosclerosis-prone mice

BACKGROUND

Cerium oxide (CeO(2)) nanoparticles improve the burning efficiency of fuel, however, little is known about health impacts of altered emissions from the vehicles.

METHODS

Atherosclerosis-prone apolipoprotein E knockout (ApoE(-/-)) mice were exposed by inhalation to diluted exhaust (1.7 mg/m(3), 20, 60 or 180 min, 5 day/week, for 4 weeks), from an engine using standard diesel fuel (DE) or the same diesel fuel containing 9 ppm cerium oxide nanoparticles (DCeE). Changes in hematological indices, clinical chemistry, atherosclerotic burden, tissue levels of inflammatory cytokines and pathology of the major organs were assessed.

RESULTS

Addition of CeO(2) to fuel resulted in a reduction of the number (30%) and surface area (10%) of the particles in the exhaust, whereas the gaseous co-pollutants were increased (6-8%). There was, however, a trend towards an increased size and complexity of the atherosclerotic plaques following DE exposure, which was not evident in the DCeE group. There were no clear signs of altered hematological or pathological changes induced by either treatment. However, levels of proinflammatory cytokines were modulated in a brain region and liver following DCeE exposure.

CONCLUSIONS

These results imply that addition of CeO(2) nanoparticles to fuel decreases the number of particles in exhaust and may reduce atherosclerotic burden associated with exposure to standard diesel fuel. From the extensive assessment of biological parameters performed, the only concerning effect of cerium addition was a slightly raised level of cytokines in a region of the central nervous system. Overall, the use of cerium as a fuel additive may be a potentially useful way to limit the health effects of vehicle exhaust. However, further testing is required to ensure that such an approach is not associated with a chronic inflammatory response which may eventually cause long-term health effects.

Diesel exhaust particulate induces pulmonary and systemic inflammation in rats without impairing endothelial function ex vivo or in vivo

Background

Inhalation of diesel exhaust impairs vascular function in man, by a mechanism that has yet to be fully established. We hypothesised that pulmonary exposure to diesel exhaust particles (DEP) would cause endothelial dysfunction in rats as a consequence of pulmonary and systemic inflammation.

Methods

Wistar rats were exposed to DEP (0.5 mg) or saline vehicle by intratracheal instillation and hind-limb blood flow, blood pressure and heart rate were monitored in situ 6 or 24 h after exposure. Vascular function was tested by administration of the endothelium-dependent vasodilator acetylcholine (ACh) and the endothelium-independent vasodilator sodium nitroprusside (SNP) in vivo and ex vivo in isolated rings of thoracic aorta, femoral and mesenteric artery from DEP exposed rats. Bronchoalveolar lavage fluid (BALF) and blood plasma were collected to assess pulmonary (cell differentials, protein levels & interleukin-6 (IL-6)) and systemic (IL-6), tumour necrosis factor alpha (TNFα) and C-reactive protein (CRP)) inflammation, respectively.

Results

DEP instillation increased cell counts, total protein and IL-6 in BALF 6 h after exposure, while levels of IL-6 and TNFα were only raised in blood 24 h after DEP exposure. DEP had no effect on the increased hind-limb blood flow induced by ACh in vivo at 6 or 24 h. However, responses to SNP were impaired at both time points. In contrast, ex vivo responses to ACh and SNP were unaltered in arteries isolated from rats exposed to DEP.

Conclusions

Exposure of rats to DEP induces both pulmonary and systemic inflammation, but does not modify endothelium-dependent vasodilatation. Other mechanisms in vivo limit dilator responses to SNP and these require further investigation.

Pollutant particles induce arginase II in human bronchial epithelial cells

Exposure to particulate matter (PM) is associated with adverse pulmonary effects, including induction and exacerbation of asthma. Recently arginase was shown to play an important role in the pathogenesis of asthma. In this study, it was postulated that PM exposure might induce arginase. Human bronchial epithelial cells (HBEC) obtained from normal individuals by endobronchial brushings cultured on an air-liquid interface were incubated with fine Chapel Hill particles (PM₂.₅, 100 μg/ml) for up to 72 h. Arginase activity, protein expression, and mRNA of arginase I and arginase II were measured. PM₂.₅ increased arginase activity in a time-dependent manner. The rise was primarily due to upregulation of arginase II. PD153035 (10 μM), an epidermal growth factor (EGF) receptor antagonist, attenuated the PM₂.₅-induced elevation in arginase activity and arginase II expression. Treatment of HBEC with human EGF increased arginase activity and arginase II expression. Pretreatment with catalase (200 U/ml), superoxide dismutase (100 U/ml), or apocynin (5 μg/ml), an NAD(P)H oxidase inhibitor, did not markedly affect arginase II expression. Treatment of HBEC with arginase II siRNA inhibited the expression of arginase II by 60% and increased IL-8 release induced by PM₂.₅. These results indicate that PM exposure upregulates arginase II activity and expression in human bronchial epithelial cells, in part via EGF-dependent mechanisms independent of oxidative stress. The elevated arginase II activity and expression may be a mechanism underlying adverse effects induced by PM exposure in asthma patients.

Mouse models to unravel the role of inhaled pollutants on allergic sensitization and airway inflammation

Air pollutant exposure has been linked to a rise in wheezing illnesses. Clinical data highlight that exposure to mainstream tobacco smoke (MS) and environmental tobacco smoke (ETS) as well as exposure to diesel exhaust particles (DEP) could promote allergic sensitization or aggravate symptoms of asthma, suggesting a role for these inhaled pollutants in the pathogenesis of asthma. Mouse models are a valuable tool to study the potential effects of these pollutants in the pathogenesis of asthma, with the opportunity to investigate their impact during processes leading to sensitization, acute inflammation and chronic disease. Mice allow us to perform mechanistic studies and to evaluate the importance of specific cell types in asthma pathogenesis. In this review, the major clinical effects of tobacco smoke and diesel exhaust exposure regarding to asthma development and progression are described. Clinical data are compared with findings from murine models of asthma and inhalable pollutant exposure. Moreover, the potential mechanisms by which both pollutants could aggravate asthma are discussed.

Effects of inhaled nanoparticle-rich diesel exhaust on regulation of testicular function in adult male rats

We investigated the effects of nanoparticle-rich diesel exhaust (NR-DE) on reproductive function. Eight-week-old male F344 rats were divided into 12 experimental groups and exposed to either whole NR-DE at low (15.37 microg/m(3), 2.27 x 10(5) particles/cm(3)), middle (36.35 microg/m(3), 5.11 x 10(5) particles/cm(3)), or high (168.84 microg/m(3), 1.36 x 10(6) particles/cm(3)) concentrations or clean air for 4, 8, or 12 weeks (5 hours/day, 5 days/week). NR-DE exposure for 4 or 8 weeks did not affect body weight; however, body weight was significantly decreased in rats exposed to low- or high- concentration NR-DE for 12 weeks compared to the control group. Relative weights of testes, epididymides, seminal vesicles, and prostate had increased non-significantly in all NR-DE-exposed rats at 4, 8, and 12 weeks. Adrenal gland relative weights were significantly increased at 4 weeks in rats exposed to low-concentration NR-DE. Plasma luteinizing hormone and follicle stimulating hormone concentrations did not change significantly. Plasma testosterone concentrations were significantly increased after exposure to low- or middle-concentration NR-DE for 4 or 8 weeks compared to controls. Plasma immunoreactive (ir-) inhibin concentrations were significantly increased after exposure to high-concentration NR-DE for 4 weeks or middle- or high-concentration NR-DE for 12 weeks compared to controls. Testicular testosterone concentrations were significantly increased at 4, 8, and 12 weeks after exposure to low-concentration NR-DE compared to controls. In contrast, with exposure to low- or high-concentration NR-DE, testicular ir-inhibin concentrations were significantly greater than in controls, but only at 4 weeks. These results suggest that NR-DE inhalation disrupts the endocrine activity of the male reproductive system.

Endocrine disruptive effect of 3-methyl-4-nitrophenol isolated from diesel exhaust particles in Hershberger assay using castrated immature rats

To examine the endocrine disruptive effects of 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC) in diesel exhaust particles (DEP), the rat Hershberger assay was carried out using castrated immature rats. Castrated 28-d-old immature male rats were implanted with a 5-mm-long silastic tube containing crystalline testosterone and injected with PNMC subcutaneously at doses 1, 10, or 100 mg/kg for 5 consecutive d. The weights of the livers significantly decreased in the 10 and 100 mg/kg PNMC treatment groups as compared with the control group. The weights of the seminal vesicles significantly increased in the 10 mg/kg PNMC treatment group as compared with the control group. The weights of the Cowper's glands were significantly increased in 1 mg/kg PNMC treatment group compared with the control group. The concentrations of plasma testosterone significantly increased in the 10 and 100 mg/kg PNMC treatment groups, indicating that PNMC induced accumulation of bioactive testosterone released from the implanted tube in circulation. Plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels significantly decreased under all the doses in the PNMC treatment groups, indicating that PNMC acts on the hypothalamus-pituitary axis.

4-Nitrophenol isolated from diesel exhaust particles disrupts regulation of reproductive hormones in immature male rats

In previous studies, we found that 4-nitrophenol (PNP) isolated from diesel exhaust particles exhibited both estrogenic and anti-androgenic activities. This compound is also a degradation product of the insecticide parathion. Here, we investigated the in vivo effect of PNP on reproductive function in immature male rats. Twenty-eight-day-old rats were injected subcutaneously with PNP (0.01, 0.1, 1, or 10 mg/kg) daily for 14 days. Plasma concentrations of luteinizing hormone (LH) were significantly lower in all PNP dosage groups than in the control group, and follicle-stimulating hormone (FSH) was significantly decreased in rats treated with 0.1, 1, or 10 mg/kg PNP. However, plasma concentrations of testosterone were significantly increased by 10 mg/kg PNP, and plasma concentrations of immunoreactive (ir)-inhibin were also significantly increased in the 0.1, 1, and 10 mg/kg PNP groups. Plasma concentrations of prolactin were significantly increased by 10 mg/kg PNP, and plasma concentrations of corticosterone were significantly increased in all treatment groups. These findings clearly show that PNP influences the hypothalamic-pituitary-gonadal axis in immature male rats, with decreased secretion of LH and FSH and increased secretion of testosterone and inhibin. PNP, therefore, appears to disrupt endocrine activity in the immature male reproductive system.

Optimization of Route of Administration for Coexposure to Ovalbumin and Particle Matter to Induce Adjuvant Activity in Respiratory Allergy in the Mouse

Epidemiological and experimental studies have not only shown that air pollution induces increased pulmonary morbidity, and mortality, but also that air pollution components may potentiate allergic responses. The respiratory allergy model to ovalbumin in the mouse has been shown a useful tool to characterize the adjuvant potency of air pollution components. However, the choice for the most effective route of administration for testing small amounts of air pollution component is hampered by the diversity of routes of administration used. To test the adjuvant activity of airborne particles (Ottawa dust EHC-93), we studied the optimal route of respiratory administration: intranasally (in) and aerosol (aero) in comparison with responses observed by intraperitoneal (ip) with diesel exhaust particles (DEP) as a positive control. Our results show that the combination of in/aero with ovalbumin caused almost similar immunoglobulin (Ig)E and inflammatory responses compared to the ip/aero. In/in application induced less responses for IgE, less inflammation in the lung, and less increased numbers of eosinophils in the bronchoalveolar lavage (BAL). This response increased dramatically when ovalbumin was coadministered with DEP. Subsequently, EHC-93, which is made up of airborne particles, was tested via the in/in route of administration. EHC-93 induced similar IgE responses, inflammation, and eosinophilic response in BAL compared to DEP. In addition, EHC-93 increased the airway responsiveness of the ovalbumin-sensitized mice measured in unrestrained condition and not in nonsensitized control mice. It is concluded that intranasal sensitization with intranasal challenge with airborne particles (EHC-93) is an effective route of administration to show potency of adjuvant activity of airborne particles.

Traffic-related air pollution and childhood respiratory symptoms, function and allergies

BACKGROUND

Urban air pollution can trigger asthma symptoms in children, but there is conflicting evidence on effects of long-term exposure on lung function, onset of airway disease and allergic sensitization.

METHODS

The spatial distribution of nitrogen oxides from traffic (traffic-NOx) and inhalable particulate matter from traffic (traffic-PM10) in the study area was assessed with emission databases and dispersion modeling. Estimated levels were used to assign first-year exposure levels for children in a prospective birth cohort (n = 4089), by linking to geocoded home addresses. Parents in 4 Swedish municipalities provided questionnaire data on symptoms and exposures when the children were 2 months and 1, 2, and 4-year-old. At 4 years, 73% of the children underwent clinical examination including peak expiratory flow and specific IgE measurements.

RESULTS

Exposure to air pollution from traffic during the first year of life was associated with an excess risk of persistent wheezing (odds ratio [OR] for 44 microg/m3 [5th-95th percentile] difference in traffic-NOx = 1.60; 95% confidence interval [CI] = 1.09-2.36). Similar results were found for sensitization (measured as specific IgE) to inhalant allergens, especially pollen (OR for traffic-NOx = 1.67; 95% CI = 1.10-2.53), at the age of 4 years. Traffic-related air pollution exposure during the first year of life was also associated with lower lung function at 4 years of age. Results were similar using traffic-NOx and traffic-PM10 as indicators.

CONCLUSIONS

Exposure to moderate levels of locally emitted air pollution from traffic early in life appears to influence the development of airway disease and sensitization in preschool children.

Nitrophenols isolated from diesel exhaust particles regulate steroidogenic gene expression and steroid synthesis in the human H295R adrenocortical cell line

Studies of nitrophenols isolated from diesel exhaust particles (DEPs), 3-methyl-4-nitrophenol (PNMC) and 4-nitro-3-phenylphenol (PNMPP) have revealed that these chemicals possess estrogenic and anti-androgenic activity in vitro and in vivo and that PNMC accumulate in adrenal glands in vivo. However, the impacts of exposure to these compounds on adrenal endocrine disruption and steroidogenesis have not been investigated. To elucidate the non-receptor mediated effects of PNMC and PNMPP, we investigated the production of the steroid hormones progesterone, cortisol, testosterone, and estradiol-17beta and modulation of nine major enzyme genes involved in the synthesis of steroid hormones (CYP11A, CYP11B1, CYP17, CYP19, 17betaHSD1, 17betaHSD4, CYP21, 3betaHSD2, StAR) in human adrenal H295R cells supplied with cAMP. Exposure to 10(-7) to 10(-5) M PNMC and 1 mM 8-Br-cAMP for 48 h decreased testosterone, cortisol, and estradiol-17beta levels and increased progesterone secretion. At 10(-5) M, PNMC with 1 mM 8-Br-cAMP significantly stimulated expression of the 17betaHSD4 and significantly suppressed expression of 3betaHSD2. In comparison, 10(-7) to 2 x 10(-5) M PNMPP with 1 mM 8-Br-cAMP for 48 h decreased concentrations of estradiol-17beta, increased progesterone levels, but did not affect testosterone and cortisol secretion due to the significant suppression of CYP17 and the non-significant but obvious suppression of CYP19. Our results clarified steroidogenic enzymes as candidates responsible for the inhibition or stimulation for the production of steroid hormones in the steroidogenic pathway, thus providing the first experimental evidence for multiple mechanisms of disruption of endocrine pathways by these nitrophenols.

Effects of 3-Methyl-4-Nitrophenol in Diesel Exhaust Particles on the Regulation of Reproductive Function in Immature Female Japanese Quail (Coturnix japonica)

In a previous study, we found that 3-methyl-4-nitrophenol (PNMC), a component of diesel exhaust particles and also a degradation product of the insecticide fenitrothion, exhibits reproductive toxicity in the adult male Japanese quail. The present study investigated the toxicity of PNMC in the female Japanese quail and its ability to influence reproduction in immature females. The quail (21-day-old) were injected intramuscularly (im) with PNMC at doses 0.1, 1 or 10 mg/kg body weight daily for 3 days. There was no significant difference in body growth between the PNMC-administered and control birds. However, the weights of the oviducts were significantly lower in the PNMC-treated birds at all doses. Furthermore, the plasma concentrations of luteinizing hormone (LH) and estradiol-17 beta were significantly decreased with 1 and 10 mg/kg of PNMC. These findings suggest that PNMC might influence the hypothalamo-pituitary-gonadal axis with decreasing in secretion of GnRH, LH and ovarian steroid hormones and subsequently disturb growth of the reproductive organs of immature female quail. This study indicates that PNMC induces reproductive toxicity at the central level and disrupts reproductive function in the immature female quail.

Estrogenic and anti-androgenic activities of 4-nitrophenol in diesel exhaust particles

A 4-nitrophenol (PNP) isolated from diesel exhaust particles (DEP) has been identified as a vasodilator. PNP is also a known degradation product of the insecticide parathion. We used uterotrophic and Hershberger assays to study the estrogenic and anti-androgenic activities of PNP in-vivo. In ovariectomized immature female rats injected subcutaneously with 1, 10, or 100 mg/kg PNP daily for 7 days, significant (P<0.05) increases in uterine weight were seen in only those receiving 10 or 100 mg/kg PNP. Furthermore, in castrated immature male rats implanted with a silastic tube (length, 5 mm) containing crystalline testosterone and injected subcutaneously with 0.01, 0.1, or 1 mg/kg PNP daily for 5 days, those receiving the doses of 0.1 mg/kg showed significant (P<0.05) weight decreases in seminal vesicles, ventral prostate, levator ani plus bulbocavernosus muscles, and glans penis. Plasma FSH and LH levels did not change in female rats but were significantly (P<0.05) increased in male rats treated with 0.1 mg/kg PNP. These results clearly demonstrated that PNP has estrogenic and anti-androgenic activities in-vivo. Our results therefore suggest that diesel exhaust emissions and the degradation of parathion can lead to accumulation of PNP in air, water, and soil and thus could have serious deleterious effects on wildlife and human health.

Anti-androgenic activity of 3-methyl-4-nitrophenol in diesel exhaust particles

In our continuing studies on nitrophenol derivatives as vasodilators in diesel exhaust particles, we have reported that nitrophenols in diesel exhaust particles possess not only vasodilatory activity but also estrogenic activity in vitro and in vivo, as well as anti-androgenic activity in vitro. Our efforts here were focused on the in vitro and in vivo anti-androgenic activity of 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC), known a degradation product of the insecticide fenitrothion, in diesel exhaust particles. We investigated its anti-androgenic activity using an in vitro recombinant yeast screen and in vivo Hershberger assays. Recombinant yeast screen assay showed that PNMC possesses anti-androgenic activity at low concentrations. Furthermore, castrated 28-day-old immature male rats each implanted with a 5-mm-long silastic tube containing crystalline testosterone and injected with PNMC subcutaneously at doses from as low as 0.01 and 0.1 mg/kg up to 1 mg/kg for 5 consecutive days showed significantly decreased weights of the seminal vesicles, ventral prostate, and glans penis. Plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were significantly increased in the 0.1 mg/kg PNMC treatment group. Our results demonstrate that PNMC in diesel exhaust particles clearly has anti-androgenic activity both in vitro and in vivo and can therefore be considered as an endocrine-disrupting chemical.

Use of a fluorescent phosphoprotein dye to characterize oxidative stress-induced signaling pathway components in macrophage and epithelial cultures exposed to diesel exhaust particle chemicals

A large body of evidence has shown that exposure to ambient particulate matter (PM) leads to asthma exacerbation through an excitation of allergic inflammation. Utilizing diesel exhaust particles (DEPs) as a model air pollutant, we and others have demonstrated that PM contains redox-active chemicals that generate inflammation through an oxidative stress mechanism. Recently, the strengths of proteomics have enabled us to demonstrate that organic DEP extracts induce a hierarchical expression pattern of oxidative stress-induced proteins in macrophages and epithelial cells. As a further extension of this work, we now employ a new phosphosensor fluorescent dye, Pro-Q Diamond, to elucidate the induction of phosphoproteins and intracellular signaling cascades that may play a role in DEP-induced inflammation. We demonstrate that DEPs induced the phosphorylation of several phosphoproteins that belong to a number of signaling pathways as well as other oxidative stress pathways. In combination with cytokine array, phosphoproteome analysis using Pro-Q Diamond allowed us to characterize the aromatic and polar chemicals of DEPs that are involved in the activation of three different mitogen-activated protein (MAP) kinase signaling pathways.

Effect of prolonged exposure to low concentrations of formaldehyde on the corticotropin releasing hormone neurons in the hypothalamus and adrenocorticotropic hormone cells in the pituitary gland in female mice

We examine the effect on the hypothalamus-pituitary-adrenal gland (HPA) axis of prolonged exposure to low levels of formaldehyde in female C3H/He mice, using immunocytochemical and RT-PCR methods. Two groups of female mice were exposed to differing concentrations (0, 80, 400, 2000 ppb) of formaldehyde inhalation for 16 h/day, 5 days/week, for 12 weeks. The corticotropin releasing hormone (CRH)-immunoreactive (ir) neurons in the hypothalamus were then examined, together with the adrenocorticotropin hormone (ACTH)-ir cells and ACTH mRNA in the pituitary. One group comprised sham control mice. The other group was made allergic by injection of ovalbumin (OVA) and alum prior to exposure to formaldehyde, since most sick building syndrome (SBS) sufferers are women with allergic disease. These animals were further exposed to aerosolized OVA as a booster four times during the exposure period. Our results showed a dose-dependent increase in the number of CRH-ir neurons in the non-allergy (NAG) group. A similar pattern was found in ACTH-ir cells and ACTH mRNA. The allergy (AG) model group showed an increase in basal levels of all markers of HPA activity. Moreover, the AG mice appeared to respond to the lowest concentration of formaldehyde, and all indices of HPA activity were reduced at the highest concentrations of formaldehyde. These results relate to an important clinical issue and also have implications in the broader area of HPA regulation. We conclude that our experimental system may be a suitable animal model for SBS and/or multiple chemical sensitivity (MCS).

Long-term exposure to low levels of formaldehyde increases the number of tyrosine hydroxylase-immunopositive periglomerular cells in mouse main olfactory bulb

Multiple chemical sensitivity (MCS) in response to a long-term low-level chemical exposure is as yet an unclarified disorder. To determine the role of olfactory function in the induction of MCS, immunocytochemical analysis of the main olfactory bulb (MOB) was performed after exposure of mice to low levels of formaldehyde. A long-term exposure resulted in an increase in the number of tyrosine hydroxylase-immunopositive periglomerular cells and may affect the neuronal function of the MOB.

Estrogenic Activities of Nitrophenols in Diesel Exhaust Particles1

We recently isolated 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC) and 4-nitro-3-phenylphenol (PNMPP) from diesel exhaust particles (DEP) and identified them as vasodilators. Because these compounds are alkylphenolic derivatives that might mimic hormones, we evaluated their estrogenic activity by using recombinant yeast screens, myometrial contractility assays, and in vivo uterotrophic assays. Recombinant yeast screen assays showed that both PNMC and PNMPP possess estrogenic activity. Furthermore, ovariectomized 25-day-old immature female rats injected with PNMC and PNMPP subcutaneously for 2 days showed significant increases in uterine weight among those receiving 100 mg/kg PNMC and 0.1 and 1.0 mg/kg PNMPP. To clarify further the estrogenic activity of PNMC and PNMPP, rat uterine horns were monitored in organ bath chambers for myometrial contractility in response to oxytocin (OT). Significant differences occurred in the initial and maximum contractilities to OT at 0.25 and 25 mIU/ml in uterine horns obtained from animals treated with 100 mg/kg PNMC and in the maximum contractilities to OT at 0.025, 0.25, and 25 mIU/ml in those from rats treated with 0.1 mg/kg PNMPP. These results clearly demonstrated that PNMC and PNMPP in DEP have estrogenic activity both in vitro and in vivo and might therefore be considered as endocrine-disrupting chemicals.

Size distribution and characterization of ultrafine particles in roadside atmosphere

The number concentration and number size distributions of ultrafine particles were measured with a Scanning Mobility Particle Sizer (SMPS) at a roadside in early autumn and winter, and the results are discussed with regard to the contribution of traffic activity and meteorological conditions. The number concentration of the <50 nm fraction increased in the morning under calm wind conditions, and this increase corresponded with the increase in total traffic volume and nitric oxide. The increase in ultrafine particles was influenced not only by the increase in total traffic but also by the high contribution of diesel engine vehicles. The number concentration decreased around noon as the wind speed increased, although the total traffic and the number of diesel engine vehicles were at the same level as in the morning. The number size distribution in the morning was bimodal, with a first peak diameter of around 30 nm and a second of around 90 nm in both periods. The volatility of ultrafine particles was investigated using a thermal denuder operating at 250 degrees C. The first peak consisted mainly of volatile components, whereas the second one consisted of solid materials plus some volatile components. These results were consistent with the mass size distribution of elemental and organic carbon. The number size distribution with a peak diameter of around 30 nm was also observed in the afternoon at a suburban site; however, it was produced not by vehicle emissions directly but by photochemical reactions. Although a relatively high number concentration was also observed in the morning at the suburban site due to vehicle emission, the peak diameter ranged from 40 to 90 nm, which was larger than at the roadside.

Use of proteomics to demonstrate a hierarchical oxidative stress response to diesel exhaust particle chemicals in a macrophage cell line

Epidemiological studies demonstrate an association between short term exposure to ambient particulate matter (PM) and cardiorespiratory morbidity and mortality. Although the biological mechanisms of these adverse effects are unknown, emerging data suggest a key role for oxidative stress. Ambient PM and diesel exhaust particles (DEP) contain redox cycling organic chemicals that induce pro-oxidative and pro-inflammatory effects in the lung. These responses are suppressed by N-acetylcysteine (NAC), which directly complexes to electrophilic DEP chemicals and exert additional antioxidant effects at the cellular level. A proteomics approach was used to study DEP-induced responses in the macrophage cell line, RAW 264.7. We demonstrate that in the dose range 10-100 microg/ml, organic DEP extracts induce a progressive decline in the cellular GSH/GSSG ratio, in parallel with a linear increase in newly expressed proteins on the two-dimensional gel. Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry and electrospray ionization-liquid chromatography/mass spectrometry/mass spectrometry analysis, 32 newly induced/NAC-suppressed proteins were identified. These include antioxidant enzymes (e.g. heme oxygenase-1 and catalase), pro-inflammatory components (e.g. p38MAPK and Rel A), and products of intermediary metabolism that are regulated by oxidative stress. Heme oxygenase-1 was induced at low extract dose and with minimal decline in the GSH/GSSG ratio, whereas MAP kinase activation required a higher chemical dose and incremental levels of oxidative stress. Moreover, at extract doses >50 microg/ml, there is a steep decline in cellular viability. These data suggest that DEP induce a hierarchical oxidative stress response in which some of these proteins may serve as markers for oxidative stress during PM exposures.

Effect of diesel on chemokines and chemokine receptors involved in helper T cell type 1/type 2 recruitment in patients with asthma

The objective of this study was to evaluate if diesel exhausts could favor helper T cell type (Th) 2-associated allergic reactions either through an increased production of Th2-associated chemokines and of their associated receptors or through a decrease of Th1-attracting chemokines and chemokine receptors. Diesel but not allergen exposure of peripheral blood mononuclear cells from subjects with allergy induced a release of I-309, whereas both diesel and Der p 1 induced an early but transient release of monokine induced by IFN-gamma and a late release of pulmonary and activation-regulated chemokine. Although both Th1- and Th2-attracting chemokines were induced, the resulting effect was an increased chemotactic activity on Th2 but not Th1 cells. Surprisingly, diesel induced a late increase in the expression of the Th1-associated CXC receptor 3 and CC receptor 5. T cell CXC receptor 3 upregulation was not associated with an increased migration to its ligands. These two antagonistic effects have been previously reported as a scavenger mechanism to clear chemokines. Altogether, these results suggest that diesel, even without allergen, may amplify a type 2 immune response but that it can also increase late Th1-associated chemokine receptor expression, perhaps as a scavenger mechanism to clear pro-Th1 chemokines and promote the Th2 pathway.

Murine strain differences in airway inflammation induced by diesel exhaust particles and house dust mite allergen

BACKGROUND

Differences in allergic airway inflammation induced by ovalbumin (OVA) + diesel exhaust particles (DEP) in various murine strains have already been reported. However, there is no report that different murine strains respond differently towards house dust mites or DEP, which are known to aggravate allergic asthma.

METHODS

The Dermatophagoides farinae allergens Der f (1 microg) or Der f (1 microg) + DEP (50 microg) were administered intratracheally to two different mouse strains (CBA/JN and C57BL/6N). Histological changes in the lung tissues, asthma-relevant cytokines in the lungs, and allergen-specific immunoglobulins in plasma were investigated.

RESULTS

Der f treatment led to the proliferation of goblet cells, production of mucus plugs, and the recruitment of eosinophils and lymphocytes to the airways of the mice. The manifestation of the airway inflammation in the C57BL/6N mouse was much greater than in the CBA/JN mouse. The protein levels of interleukin (IL)-4 and IL-5, regulated on activation, normal T cell expressed, and presumably secreted (RANTES), and eotaxin in the lung tissue of C57BL/6N mice were higher than those in CBA/JN mice by a factor of 1.26 (IL-4), 5.26 (IL-5), 2.07 (RANTES) and 3.27 (eotaxin). DEP aggravated the manifestations of the eosinophilic inflammation in CBA/JN mice through goblet cell proliferation. However, the exact effect of DEP could not be evaluated in C57BL/6N because of its severe enhancement of the inflammation. DEP enhanced the local expression of IL-5, RANTES, and eotaxin in the CBA/JN mouse, and consequently triggered an increased IgG1 production in both strains. Allergen-specific IgE antibodies were lower than 1 titer in both mice.

CONCLUSION

The murine strain differences in the pathogenesis of allergic airway disease caused by mite allergen might be related to the local expression of the cytokines we screened. The aggravating effect of DEP may be mediated by an increase in the local expression of IL-5, RANTES, eotaxin, and the production of an antigen specific to IgG1.

Lung macrophage-epithelial cell interactions amplify particle-mediated cytokine release

Interactions between alveolar macrophages (AMs) and epithelial cells may promote inflammatory responses to air pollution particles. Normal rat AMs, the alveolar type II epithelial cell line RLE-6TN (RLE), or cocultures of both cell types were incubated with various particles (0-50 microg/ml) for 24 h, followed by assay of released TNF-alpha and MIP-2. The particles used included titanium dioxide (TiO2), alpha-quartz (SiO2), residual oil fly ash (ROFA), or urban air particles (UAP). For all particles, a dose-dependent increase in TNF-alpha and MIP-2 release was observed in AM+RLE co-cultures but not in RLE or AM monoculture. AM+RLE co-culture also synergistically enhanced basal levels of tumor necrosis factor (TNF)-alpha and macrophage inflammatory protein (MIP)-2. In contrast, when AMs were co-cultured with fibroblasts, basal and particle-induced TNF-alpha and MIP-2 were similar to levels found in AM monoculture. Particle uptake by AMs was similar in mono- or AM+RLE co-culture. Increased basal and particle-induced cytokine release were not observed when the AMs were physically separated from the RLE. This contact-dependent cytokine potentiation could not be blocked with anti-CD18/anti-CD54, arginine-glycine-aspartate (RGD) peptide, or heparin. We conclude that in vitro inflammatory responses to particles are amplified by contact-dependent interactions between AMs and epithelial cells. AM-epithelial co-culture may provide a useful model of in vivo particle effects.

Is diesel the cause for the increase in allergic disease?

LEARNING OBJECTIVES

The purpose of this review is to objectively critique available data regarding the role of diesel exhaust particles (DEPs) in allergic disease. Readers of this review should understand the ways in which diesel particulates can affect human airways and the extent of the scientific data which are currently available.

DATA SOURCES

Data were obtained from published studies and reviews.

STUDY SELECTION

The specific reviewed studies selected for this review met the following criteria: human and animal in vivo, in vitro, and pulmonary dosimetry studies, as well as epidemiologic studies to examine the role of DEPs and particulates on the airways.

RESULTS

The results of the published studies show that although DEPs may play a role in the increased levels of allergic disorders through a number of immunologic mechanisms, it remains to be proven whether it is responsible for the recent rise in the prevalence of asthma and other allergic disorders.

CONCLUSIONS

Further studies in humans are needed to elucidate the mechanisms by which DEPs may be responsible for the increased prevalence of allergic disorders.

Induction of inflammatory response of mice exposed to diesel exhaust is modulated by CD4(+) and CD8(+) T cells

Exposure to diesel exhaust (DE) increased airway inflammatory responses and airway responsiveness to allergen challenge. To clarify the roles of T cells in DE exposure-induced early inflammation, we studied the effect of CD4 and CD8 cells on the effect DE might have on allergic inflammation by using monoclonal antibody-mediated cellular depletion assays. In the bronchoalveolar lavage (BAL) fluid, the numbers of inflammatory cells from 3 mg/m(3) DE-exposed and ovalbumin (OVA)-immunized mice markedly increased. Depletion of CD4(+) cells resulted in reduced accumulation of inflammatory cells. DE exposure to OVA-immunized mice significantly increased interleukin (IL)-1 beta production but decreased IL-12 production. DE exposure significantly enhanced production of the macrophage inflammatory proteins (MIP)-1 alpha and MIP-2, but not monocyte chemoattractant protein (MCP)-1 and regulated upon activation normal T cells expressed and secreted (RANTES). Treatment with anti-CD4 and anti-CD8 mAbs abrogated the adverse effect of DE exposure. In CLN cells from OVA + DE-exposed mice, CD45R/B220-, CD3-, CD4-, and CD8-positive cells were significantly increased, but the OVA-stimulated cytokine production remained at the same levels with OVA-immunized mice. These findings suggest that the induction of early inflammatory responses by DE exposure may initially be related to the modulated function of lymphocyte subpopulations.

Diesel exhaust enhances airway responsiveness in asthmatic subjects

Particulate matter (PM) pollution has been associated with negative health effects, including exacerbations of asthma following exposure to PM peaks. The aim of the present study was to investigate the effects of short-term exposure to diesel exhaust (DE) in asthmatics, by specifically addressing the effects on airway hyperresponsiveness, lung function and airway inflammation. Fourteen nonsmoking, atopic asthmatics with stable disease, on continuous treatment with inhaled corticosteroids, were included. All were hyperresponsive to methacholine. Each subject was exposed to DE (particles with a 50% cut-off aerodynamic diameter of 10 microm (PM10) 300 microg x m(-3)) and air during 1 h on two separate occasions. Lung function was measured before and immediately after the exposures. Sputum induction was performed 6 h, and methacholine inhalation test 24 h, after each exposure. Exposure to DE was associated with a significant increase in the degree of hyperresponsiveness, as compared to after air, of 0.97 doubling concentrations at 24 h after exposure (p < 0.001). DE also induced a significant increase in airway resistance (p=0.004) and in sputum levels of interleukin (IL)-6 (p=0.048). No changes were detected in sputum levels of methyl-histamine, eosinophil cationic protein, myeloperoxidase and IL-8. This study indicated that short-term exposure to diesel exhaust, equal to high ambient levels of particulate matter, is associated with adverse effects in asthmatic airways, even in the presence of inhaled corticosteroid therapy. The increase in airway responsiveness may provide an important link to epidemiological findings of exacerbations of asthma following exposure to particulate matter.

Induction of the imbalance of helper T-cell functions in mice exposed to diesel exhaust

Administration of diesel exhaust particles (DEP) increases antigen-specific IgE production and IgE-secreting cells, and induces Th2-type cytokine profiles in the airway in mice and humans. To determine the early effects of diesel exhaust (DE) inhalation on the cytokine production profile, BALB/c mice were exposed to 0 (controls) and 1.0 mg/m3 DE inhalation for 4 weeks. Intraperitoneal sensitization with ovalbumin (OVA) was conducted immediately before DE inhalation. Mice were treated with anti-CD4 or anti-CD8 mAb 1 day before and after the sensitization. On day 21, these mice were boosted with OVA and blood; bronchoalveolar lavage (BAL) fluid, and spleens were collected on day 28. In BAL fluid, both TNFalpha and IL-10 production in DE-exposed and control mice remained basically the same. IL-6 production in the anti-CD4 treatment group of DE-exposed mice, however, significantly increased compared with that of the controls. In vitro antigen-stimulated interleukin-4 (IL-4) and -10 (IL-10) production in spleen cells of exposed mice were not affected by low-dose DE inhalation. In vitro interferon (IFN)-gamma production in the anti-CD4 treated group of exposed mice decreased markedly. Although anti-OVA IgE production in the plasma of sham-treated mice exposed to DE was the same level as for controls, anti-CD4 mAb treatment in DE-exposed mice significantly reduced IgE production compared to controls. In anti-OVA IgG1 production, anti-CD4 or anti-CD8 mAb treatment in DE-exposed groups also significantly reduced. Anti-OVA IgG2a production was reduced by treatment with anti-CD4 mAb, but increased by anti-CD8 mAb treatment in DE-exposed mice. Low dose DE inhalation is thus shown to adversely affect the cytokine and antibody production in mice by altering CD4+ and CD8+ T-cell functions.

Health effects of diesel exhaust emissions

Epidemiological studies have demonstrated an association between different levels of air pollution and various health outcomes including mortality, exacerbation of asthma, chronic bronchitis, respiratory tract infections, ischaemic heart disease and stroke. Of the motor vehicle generated air pollutants, diesel exhaust particles account for a highly significant percentage of the particles emitted in many towns and cities. This review is therefore focused on the health effects of diesel exhaust, and especially the particular matter components. Acute effects of diesel exhaust exposure include irritation of the nose and eyes, lung function changes, respiratory changes, headache, fatigue and nausea. Chronic exposures are associated with cough, sputum production and lung function decrements. In addition to symptoms, exposure studies in healthy humans have documented a number of profound inflammatory changes in the airways, notably, before changes in pulmonary function can be detected. It is likely that such effects may be even more detrimental in asthmatics and other subjects with compromised pulmonary function. There are also observations supporting the hypothesis that diesel exhaust is one important factor contributing to the allergy pandemic. For example, in many experimental systems, diesel exhaust particles can be shown to act as adjuvants to allergen and hence increase the sensitization response. Much of the research on adverse effects of diesel exhaust, both in vivo and in vitro, has however been conducted in animals. Questions remain concerning the relevance of exposure levels and whether findings in such models can be extrapolated into humans. It is therefore imperative to further assess acute and chronic effects of diesel exhaust in mechanistic studies with careful consideration of exposure levels. Whenever possible and ethically justified, studies should be carried out in humans.

Synergistic effect of diesel organic extracts and allergen Der p 1 on the release of chemokines by peripheral blood mononuclear cells from allergic subjects: involvement of the map kinase pathway

The organic compounds of diesel exhaust particles (DEP-PAHs) have been shown to favor immunoglobulin production and bronchial hyperresponsiveness and to affect cytokine and chemokine productions. To evaluate if diesel exhaust could act in synergy with a house dust mite allergen (Der p 1), peripheral blood mononuclear cells from allergic patients were exposed to DEP-PAHs, with or without purified Der p 1. DEP-PAHs and Der p 1 separately induced an increase in interleukin (IL)-8, regulated on activation, normal T cells expressed and secreted (RANTES), and tumor necrosis factor-alpha concentrations. Interestingly, a synergy between the two stimuli was also observed. In the case of monocyte chemotactic protein (MCP)-1, DEP-PAHs reduced the release, whereas Der p 1 enhanced it. A simultaneous exposure led to reduced production as compared with allergen exposure alone, but still represented an increase as compared with the control exposure. Mitogen-activated protein (MAP) kinase Erk1/2 antagonist mainly inhibited the release of MCP-1, whereas MAP kinase p38 antagonist mainly suppressed the release of IL-8 and RANTES. Messenger RNA expression correlated with protein measurements. Moreover, supernatants from cells exposed to both DEP-PAHs and Der p 1 had a significant chemotactic activity on neutrophils and eosinophils. These findings suggest that simultaneous exposure of allergic patients to DEPs and allergens could result in high local chemokine levels via MAP kinase pathways activation, increasing the likelihood of reaching a critical threshold leading to the initiation of respiratory allergic symptoms.

Diesel exhaust particles activate p38 MAP kinase to produce interleukin 8 and RANTES by human bronchial epithelial cells and N-acetylcysteine attenuates p38 MAP kinase activation

Air pollutants including diesel exhaust particles (DEPs) have been shown to enhance allergic responses. DEPs stimulate airway epithelial cells to produce various cytokines; however, the intracellular signal transduction pathway and the involvement of reduction and oxidation (redox) control in DEP-activated signaling have not been determined. In the present study, we therefore examined the role of p38 mitogen-activated protein (MAP) kinase in DEP-induced interleukin 8 (IL-8) and RANTES production by human bronchial epithelial cells (BECs) in order to clarify the intracellular signal transduction pathway that regulates IL-8 and RANTES production. In addition, we also examined the effect of a thiol-reducing agent, N-acetylcysteine (NAC), on DEP-induced p38 MAP kinase activation and cytokine production in order to clarify the redox control mechanism in DEP-induced p38 MAP kinase activation and IL-8 and RANTES production. The results showed that DEP induced IL-8 and RANTES production and the threonine and tyrosine phosphorylation of p38 MAP kinase, reflecting the activation of p38 MAP kinase in BECs. SB 203580, as the specific inhibitor of p38 MAP kinase activity, inhibited DEP-induced IL-8 and RANTES production. NAC inhibited DEP-induced p38 MAP kinase activation and IL-8 and RANTES production. These results indicate that p38 MAP kinase plays an important role in the DEP-activated signaling pathway that regulates IL-8 and RANTES production by BECs and that the cellular redox state is critical for DEP-induced p38 MAP kinase activation leading to IL-8 and RANTES production.

Manipulation of the L-arginine-nitric oxide pathway in airway inflammation induced by diesel exhaust particles in mice

The role of the L-arginine-nitric oxide (NO) pathway in bronchial asthma that is characterized by eosinophilic airway inflammation has not yet been established. We investigated the effects of three different agents on eosinophilic airway inflammation induced by the intratracheal instillation of diesel exhaust particles (DEP) in mice: L-Arginine, the substrate for NO synthases; L-N(G)-nitro-L-arginine methyl ester (L-NAME), a relatively selective inhibitor of constitutive NO synthase; and aminoguanidine, a relatively selective inhibitor of inducible NO synthase. The mice received drinking water with or without added drug for a continuous period of 9 weeks plus 4 days. Lung histology showed that airway inflammation with goblet cell proliferation induced by DEP was aggravated by the administration of L-arginine or L-NAME, whereas it was reduced by aminoguanidine. The numbers of neutrophils around the airways in animals that received plain drinking water, L-arginine, L-NAME, and aminoguanidine were 0.98+/-0.26, 3.66+/-0.81, 1.64+/-0.31, and 0.12+/-0.04 (number/mm basement membrane), respectively. The numbers of eosinophils around the airways were 0.37+/-0.08, 16.1+/-6.47, 11.1+/-3.59, and 0.21+/-0.11, respectively. The numbers of goblet cells in the bronchial epithelium were 1.67+/-0.80, 16.5+/-7.33, 19.0+/-3.40, and 0.86+/-0.41, respectively. The cellular profiles of the bronchoalveolar lavage fluid also showed that airway inflammation induced by DEP was aggravated by the administration of L-arginine or L-NAME, whereas it was reduced by aminoguanidine. These results suggest that NO produced from inducible NO synthase may have a detrimental effect on the DEP-induced airway inflammation. A relatively selective inhibition of inducible NO synthase by aminoguanidine may have therapeutic value in the inhalant injury. NO derived from constitutive NO synthase may afford protection against the airway inflammation induced by DEP.

Particulate air pollution and asthma: a review of epidemiological and biological studies

The link between exposure to air pollution and exacerbation of asthma symptoms has been investigated by epidemiological study and by direct biological experimentation. In asthmatics, epidemiological studies generally show a positive correlation between the particulate fraction of air pollution and increased morbidity, although roles for other co-pollutants (for example, ozone) are implicated as well. Direct experimentation using air pollutants, especially particles, to investigate their effects on humans or on animal models of asthma provides corroboration of the epidemiology and has begun to identify the pathophysiological mechanisms involved. We begin this review with an overview of air pollution, followed by a survey of the epidemiological and experimental data regarding air pollution particles and asthma. We finish with a discussion of directions for future research.

Involvement of superoxide and nitric oxide on airway inflammation and hyperresponsiveness induced by diesel exhaust particles in mice

We previously demonstrated that chronic intratracheal instillation of diesel exhaust particles (DEP) induces airway inflammation and hyperresponsiveness in the mouse, and that these effects were partially reversed by the administration of superoxide dismutase (SOD). In the present study, we have investigated the involvement of superoxide in DEP-induced airway response by analyzing the localization and activity of two enzymes: (1) a superoxide producer, NADPH cytochrome P-450 reductase (P-450 reductase), and (2) a superoxide scavenger, SOD, in the lungs of the exposed mice and controls. P-450 reductase was detected mainly in ciliated cells and clara cells: its activity was increased by the repeated intratracheal instillation of DEP. While CuZn-SOD and Mn-SOD were also present in the airway epithelium, their activity was significantly decreased following DEP instillation. Exposure to DEP doubled the level of nitric oxide (NO) in the exhaled air. DEP exposure also increased the level of constitutive NO synthase (cNOS) in the airway epithelium and inducible NO synthase (iNOS) in the macrophages. Pretreatment with N-G-monomethyl L-arginine, a nonspecific inhibitor of NO synthase, significantly reduced the airway hyperresponsiveness induced by DEP. These results indicate that superoxide and NO may each contribute to the airway inflammation and hyperresponsiveness induced by the repeated intratracheal instillation of DEP in mice.