Is diesel exhaust a cause for increasing allergies?

Indoor and outdoor air quality in street corner kiosks in a large metropolitan area

Poor air quality in workplaces constitutes a great concern on human health as a good fraction of our time is spent at work. In Greece, very unique workplaces are the street corner kiosks, which are freestanding boxes placed on sidewalks next to city streets and vehicular traffic, where one can find many consumer goods. As such, its employees are exposed to both outdoor and indoor air pollutants. Very few studies have examined the occupational exposure of kiosk workers to air pollutants, and thus the magnitude of this unique indoor and outdoor exposure remains unknown. The objective of this study is to investigate and compare the levels of indoor and outdoor particulate matter (PM10 and PM2.5), ultrafine particles (UFPs) and black carbon (BC) in different kiosks located in Athens, Greece, in urban-traffic and urban-background environments. Continuous measurements of the above-mentioned pollutants were carried out on a 24-h basis over 7 consecutive days at three kiosks from September to October 2019. Indoor PM10 concentrations in the urban kiosk ranged from 19.0 to 44.0 μg/m3, PM2.5 values ranged from 14.0 to 33.0 μg/m3, whereas BC concentrations ranged from 1.2 to 7.0 μg/m3 and UFPs from almost 9.5 to 47.0 × 103 pt/cm3. Outdoor PM10 and PM2.5 measurements ranged from 29.0 to 59.0 μg/m3 and from 22.0 to 39.0 μg/m3, respectively. BC outdoor concentrations ranged from 1.1 to 2.2 μg/m3. The mean hazard quotient (HQ) for PM10 (4.9) and PM2.5 (4.7) among all participants was >1. The health risk of exposure to PM10 and PM2.5 was found to be at moderate hazard levels, although in some cases we observed HQ values higher than 10 due to high PM10 and PM2.5 concentrations in the kiosks. Overall our study indicates that people working at kiosks can be exposed to very high concentrations on particulate pollution depending on a number of factors including the traffic that strongly depends on location and the time of the day.

ROS-independent cytotoxicity of 9,10-phenanthrenequinone inhibits cell cycle progression and spindle assembly during meiotic maturation in mouse oocytes

Diesel exhaust particles (DEPs) are major components of ambient particulate matter and are associated with various adverse health effects. Typically, DEPs contain a vast number of organic compounds, among which 9,10-phenanthrenequinone (9,10-PQ), the quinone derivative of the polycyclic aromatic hydrocarbon phenanthrene, is one of the most abundant and toxic. 9,10-PQ can produce excessive reactive oxygen species (ROS) via redox cycling and exhibit cytotoxicity in various cells. However, the underlying mechanisms involved in cytotoxicity of 9,10-PQ remain elusive. In this study, we investigated the effects of exposure to 9,10-PQ using mouse oocytes as a model system. We found that 9,10-PQ compromised meiotic maturation by impairing acentriolar microtubule organizing center (MTOC) assembly and subsequent spindle formation during meiotic maturation. Moreover, 9,10-PQ exposure prevented cell cycle progression by inhibiting Cdk1 activation via disturbance of cyclin B1 accumulation. Importantly, meiotic defects induced by 9,10-PQ exposure were not rescued by decreasing ROS levels, revealing that 9,10-PQ has ROS-independent activity that regulates cell cycle progression and spindle assembly. Therefore, our findings reveal that 9,10-PQ has novel activity that regulates cell-cycle progression and spindle formation in an ROS-independent manner during meiotic maturation in mouse oocytes.

Cytotoxicity of 9,10-Phenanthrenequinone Impairs Mitotic Progression and Spindle Assembly Independent of ROS Production in HeLa Cells

The polycyclic aromatic hydrocarbon quinone derivative 9,10-phenanthrenequinone (9,10-PQ) is one of the most abundant and toxic components found in diesel exhaust particles (DEPs). These DEPs are created during diesel fuel combustion and are considered the main source of urban air pollution. As 9,10-PQ can produce excessive reactive oxygen species (ROS) through redox cycling, it has been shown to exert potent cytotoxic effects against various cell types. However, the mechanisms underlying this cytotoxicity remain unclear. In this study, we showed that 9,10-PQ exerts cytotoxicity by impairing mitotic progression and spindle assembly in HeLa cells. Exposure to 9,10-PQ impaired spindle assembly and chromosome alignment, resulting in delayed mitotic entry and progression in HeLa cells. Furthermore, 9,10-PQ exposure decreased the CEP192 and p-Aurora A levels at the spindle poles. Notably, these mitotic defects induced by 9,10-PQ were not rescued by scavenging ROS, implying the ROS-independent activity of 9,10-PQ. Therefore, our results provide the first evidence that 9,10-PQ exerts its cytotoxicity through specific inhibition of mitotic progression and spindle assembly, independent of ROS.

Comparison of inflammatory cytokine release from nasal epithelial cells of non-atopic non-rhinitic, allergic rhinitic and polyp subjects and effects of diesel exhaust particles in vitro

BACKGROUND

Although studies have reported an association between air pollutants and increased allergic airway diseases, such as allergic rhinitis and nasal polyposis, the underlying mechanisms are not fully understood. A limited number of studies have suggested that diesel exhaust particles (DEP) play a role in atopy and the pathogenesis of allergic upper airway diseases. The aim of this study was to investigate the effect of DEP on inflammatory cytokine release, and mRNA expression of transcription factors such as JNK and NF-β in primary nasal epithelial cells (NECs), in vitro.

METHODS

NECs from non-atopic, non-rhinitic subjects (controls) and patients with allergic rhinitis and nasal polyps were cultured and incubated with 0-100μg/ml DEP for 24h. ELISA and RT-PCR were used to assess the release of IL-8, GM-CSF, and RANTES, and mRNA expression for JNK and NF-κB, respectively.

RESULTS

Compared to control cells, NECs from subjects with atopic polyps released significantly greater amounts of IL-8 (median=887 vs. 176.6pg/μg cellular protein; p<0.0001) and RANTES (median=0.191 vs. 0.02pg/μg cellular protein; p<0.001). While 50μg/ml DEP induced release of RANTES in NECs from patients with allergic rhinitis, 100μg/ml DEP decreased IL-8 levels in NECs from both control and allergic rhinitic subjects. DEP did not affect mRNA expression for JNK and NF-κB from NECs of subjects with polyps.

CONCLUSIONS

NECs from subjects with various pathologies may respond differently to DEP.

Particulate matter-mediated release of long pentraxin 3 (PTX3) and vascular endothelial growth factor (VEGF) in vitro: Limited importance of endotoxin and organic content

Exposure to particulate matter (PM) is associated with adverse health effects, but it is still relatively unknown which role PM sources and physicochemical properties play in the observed effects. It was postulated that PM in vitro induces release of long pentraxin 3 (PTX3) and vascular endothelial growth factor (VEGF) and that endotoxin and organic compounds present in the PM regulate this release. A contact coculture of THP-1 human leukemia monocytes and A549 human adenocarcinoma alveolar pneumocytes was exposed to PM from Traffic, Wood, Diesel, and Quartz (10-40 µg/cm²) for 12-64 h to determine release of PTX3 and VEGF. The role of endotoxin and the organic fraction in the mediator release was assessed using polymyxin B sulfate and organic extracts, respectively. Finally, antagonists were used to investigate whether the early proinflammatory cytokines interleukin (IL)-1 and tumor necrosis factor (TNF)-α affected the PTX3 and VEGF release. All PM samples induced a time-dependent release of both PTX3 and VEGF. Traffic mediated the greatest release of PTX3, whereas Wood and Diesel were more potent inducers of VEGF. The endotoxin content did not markedly affect release of either mediator, while the organic fraction exerted no significant effect on VEGF release and limited influence on PTX3 release. In addition, the IL-1 and TNF-α agonists affected PTX3 release more strongly than VEGF release. In conclusion, the current data show a limited impact of endotoxin and organic compounds on PTX3 and VEGF release. Further, the observed differences in response patterns may point toward differential regulation of PM-mediated release of PTX3 and VEGF.

Latex Allergy and Sensitization in Cities: A Survey in a Population at Risk

The constant increase in allergic diseases in western countries is correlated with changes in lifestyle and with the deterioration of the air inhaled by the inhabitants because of the growing concentrations of pollutant substances present. Within a population at risk, i.e., the inhabitants of cities, a group of subjects at even higher risk was selected, whose job exposes them to automobile exhaust fumes for many hours a day. All the study subjects underwent allergological screening and spirometry. The results obtained show an overall increase of respiratory allergic diseases but no increased sensitisation to latex. It therefore seems plausible that, besides social and lifestyle changes, the deterioration of the quality of the air could be considered responsible, at least in part, for the growing numbers of allergic subjects. This study offers an opportunity to reconsider the validity of the “hygiene hypothesis” as an explanation for the increase of allergic disease in western countries, although recent reports have indicated that a sedentary lifestyle may also contribute, together with environmental degradation, to the notably increased prevalence of allergic diseases in large cities in industrialized nations.

Autocrine ligands of the epithelial growth factor receptor mediate inflammatory responses to diesel exhaust particles

Background

Diesel exhaust is associated with cardiovascular and respiratory mortality and morbidity. Acute exposure leads to increased IL-8 expression and airway neutrophilia, however the mechanism of this response is unknown. Objectives: As cigarette smoke-induced IL-8 expression by epithelial cells involves transactivation of the epidermal growth factor receptor (EGFR), we studied the effects of diesel exhaust particles (DEP) on IL-8 release and the role of the EGFR.

Methods

Primary bronchial epithelial cells (PBEC) were exposed to DEPs or carbon black. IL-8 and EGFR ligand expression (transforming growth factor alpha (TGFα), heparin-binding EGF-like growth factor, and amphiregulin (AR)) were assessed by quantitative RT-PCR and ELISA.

Results

DEP, but not carbon black, caused a dose-dependent increase in mitogen-activated protein kinase (MAPK) activation and IL-8 expression, however above 50 μg/ml there was an increase in cytotoxicity. At 50 μg/ml, DEPs stimulated transcription and release of IL-8 and EGFR ligands. IL-8 release was blocked by EGFR neutralizing antibodies, an EGFR-selective tyrosine kinase inhibitor and by the metalloprotease inhibitor, GM6001, which blocks EGFR ligand shedding. Neutralizing antibodies to AR, TGFα and heparin-binding (HB)-EGF reduced DEP-induced IL-8 by >50%. Conclusion Expression of IL-8 in response to DEPs is dependent on EGFR activation and that autocrine production of EGFR ligands makes a substantial contribution to this response. Capsule Summary: This study identifies a mechanism whereby diesel particles stimulates IL-8 release from bronchial epithelial cells. This mechanism may help to explain the recruitment of neutrophils into the airways of people exposed to particulate air pollution.

Effect of serum on diesel exhaust particles (DEP)-induced apoptosis of airway epithelial cells in vitro

Patients with chronic airway diseases may be more susceptible to adverse effects of air pollutants including diesel exhaust particles (DEP). We investigated effects of foetal calf serum (FCS) on DEP-induced changes in airway epithelial cell apoptosis and inflammation. DEP (50-200 μg/ml) increased A549 cell viability in the absence of FCS. In the presence of 3.3%FCS, DEP (50-400 μg/ml) decreased A549 cell viability. N-acetylcysteine (NAC, 33 mM) and the c-jun N-terminal kinase (JNK) inhibitor (SP600125, 33 μM) further decreased the viability in the presence of DEP (200 μg/ml) and 3.3% FCS. Under serum-free (SF) condition, DEP (50 μg/ml) reduced apoptotic cells; however, when 3.3% FCS added to the culture medium, this effect was abolished. DEP (200 μg/ml) induced mRNA expression of p21(CIP1/WAF1) both in absence or presence of 3.3% FCS and enhanced JNK2 mRNA expression only in the presence of 3.3% FCS. Under SF condition, DEP (50 μg/ml) induced mRNA expression for p27 and p53, whereas cyclin E mRNA expression was inhibited by DEP (50 and 200 μg/ml). Furthermore, DEP (200 μg/ml) decreased the release of interleukin (IL)-8 in the absence of FCS. In conclusion, FCS modulates effects of DEP on cell death, cell cycle and apoptosis regulating proteins, and IL-8 release by activating oxidant stress pathways, JNK and NF-κB. Extravasation of serum, as occurs in the inflamed airways of patients with chronic airway diseases such as asthma and COPD, may render airway epithelial cells more susceptible to the deleterious effects of DEP.

Household chemicals, immune function, and allergy: a commentary

In recent decades, in the US and in Western and Northern Europe, there has been a significant increase in the prevalence of atopic allergic disease. Although that increase may now be slowing, or have already reached a plateau, there remains considerable interest in the factor or factors that may have caused this increased susceptibility to allergy and asthma. Certainly, the changes recorded have been too rapid to implicate a change in the gene pool, and for that reason attention has focused on the possible impact of environmental, dietary, and lifestyle factors. Although the hygiene hypothesis proposes that increased susceptibility to allergic sensitization is associated with changes in childhood exposure pathogenic microorganisms, other factors have been considered also. Among these is exposure to chemicals and atmospheric pollutants. There is some evidence that exposure to certain chemicals may elicit or exacerbate respiratory reactions in those who are already sensitized, or who already have existing airway disease. However, a recent article has proposed that exposure to specific household cleaning products may be one factor that is able to affect susceptibility to allergic sensitization. In the light of that article it is timely now to consider again the ability of chemical exposure to influence sensitization to common antigens.

Exposure to diesel exhaust up-regulates iNOS expression in ApoE knockout mice

Traffic related particulate matter air pollution is a risk factor for cardiovascular events; however, the biological mechanisms are unclear. We hypothesize that diesel exhaust (DE) inhalation induces up-regulation of inducible nitric oxide synthase (iNOS), which is known to contribute to vascular dysfunction, progression of atherosclerosis and ultimately cardiovascular morbidity and mortality.

METHODS

ApoE knockout mice (30-week) were exposed to DE (at 200 μg/m³ of particulate matter) or filtered-air (control) for 7 weeks (6 h/day, 5 days/week). iNOS expression in the blood vessels and heart was evaluated by immunohistochemistry and western blotting analysis. To examine iNOS activity, thoracic aortae were mounted in a wire myograph, and vasoconstriction stimulated by phenylephrine (PE) was measured with and without the presence of the specific inhibitor for iNOS (1400 W). NF-κB (p65) activity was examined by ELISA. The mRNA expression of iNOS and NF-κB (p65) was determined by real-time PCR.

RESULTS

DE exposure significantly enhanced iNOS expression in the thoracic aorta (4-fold) and heart (1.5 fold). DE exposure significantly attenuated PE-stimulated vasoconstriction by ~20%, which was partly reversed by 1400 W. The mRNA expression of iNOS and NF-κB was significantly augmented after DE exposure. NF-κB activity was enhanced 2-fold after DE inhalation, and the augmented NF-κB activity was positively correlated with iNOS expression (R²=0.5998).

CONCLUSIONS

We show that exposure to DE increases iNOS expression and activity possibly via NF-κB-mediated pathway. We suspect that DE exposure-caused up-regulation of iNOS contributes to vascular dysfunction and atherogenesis, which could ultimately lead to urban air pollution-associated cardiovascular morbidity and mortality.

An assessment of the ability of phthalates to influence immune and allergic responses

It has been suggested that one possible contributor to the increasing prevalence of atopic (IgE-mediated) allergic diseases and asthma in Europe and the US is exposure to chemicals that may act as adjuvants. Certain commonly used phthalate plasticisers, such as di-(2-ethylhexyl) phthalate, have been implicated in this regard. The evidence for the ability of phthalates to impact on immune and allergic responses has been examined, encompassing epidemiological investigations and results deriving from studies using experimental animals and from analyses in vitro. The epidemiological data provide some evidence that exposure to phthalates may be associated with increased risk of development of allergies and asthma, however, the lack of objective exposure information limits the interpretation. A variety of studies have been performed in mice to examine the influence of phthalate (delivered via various routes of exposure) to impact on immune responses. Measurement of antibody responses is the commonest read out, although other parameters of inflammation such as eosinophil infiltration and cytokine production have been used also. Although certain phthalates, when delivered at appropriate doses, and via an appropriate route, have been reported to impact on immune and inflammatory function in rodents, as yet no consistent pattern has emerged. Results ranged from potentiation of immune or inflammatory responses, to the absence of any effect, to inhibitory or immunosuppressive activity. In addition, comparatively low doses of phthalates have been associated with immune effects only when routes of administration (subcutaneous or intraperitoneal) are used that do not reflect, and are much less relevant for, opportunities for human contact with phthalates. There is clearly a case to be made for the design of more definitive animal studies that will allow development of a more detailed understanding of whether and to what extent, and under what conditions, phthalates are able to effect meaningful changes in immune function that may in turn impact on human health.

Chemical pollution, respiratory allergy and asthma: a perspective

The European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) convened a workshop in June 2005 to address the speculation that exposure to specific chemicals, and/or chemical pollutants in general, may play an important role in the increased prevalence of allergy and asthma in 'westernized' societies. This paper summarises one perspective arrived at during this workshop. It was acknowledged that certain chemicals and certain types of pollution might trigger or exacerbate asthmatic reactions in sensitised subjects. However, overall levels of pollution appear not to have had a major impact upon the prevalence of atopic allergy. Epidemiological studies suggest that pollution may in some circumstances protect from acquisition of sensitisation. Increasing exposure to household chemicals may enhance pre-existing allergies, but evidence for their causation of allergy is lacking. Other risk factors considered included societal dietary changes and exposure to endotoxins. Future research needs were identified which included epidemiological studies employing exposure and biomonitoring data, studies on domestic exposure to chemicals and their association with the incidence of allergy and asthma, and prospective birth cohort studies employing well-defined aspects of lifestyle, diet, chemical and endotoxin exposure as factors that may drive susceptibility to allergy and asthma.

Combustion-generated nanoparticulates in the El Paso, TX, USA / Juarez, Mexico Metroplex: their comparative characterization and potential for adverse health effects

In this paper we report on the collection of fine (PM₁) and ultrafine (PM_0.1), or nanoparticulate, carbonaceous materials using thermophoretic precipitation onto silicon monoxide/formvar-coated 3 mm grids which were examined in the transmission electron microscope (TEM). We characterize and compare diesel particulate matter (DPM), tire particulate matter (TPM), wood burning particulate matter, and other soot (or black carbons (BC)) along with carbon nanotube and related fullerene nanoparticle aggregates in the outdoor air, as well as carbon nanotube aggregates in the indoor air; and with reference to specific gas combustion sources. These TEM investigations include detailed microstructural and microdiffraction observations and comparisons as they relate to the aggregate morphologies as well as their component (primary) nanoparticles. We have also conducted both clinical surveys regarding asthma incidence and the use of gas cooking stoves as well as random surveys by zip code throughout the city of El Paso. In addition, we report on short term (2 day) and longer term (2 week) in vitro assays for black carbon and a commercial multiwall carbon nanotube aggregate sample using a murine macrophage cell line, which demonstrate significant cytotoxicity; comparable to a chrysotile asbestos nanoparticulate reference. The multi-wall carbon nanotube aggregate material is identical to those collected in the indoor and outdoor air, and may serve as a surrogate. Taken together with the plethora of toxic responses reported for DPM, these findings prompt concerns for airborne carbonaceous nanoparticulates in general. The implications of these preliminary findings and their potential health effects, as well as directions for related studies addressing these complex issues, will also be examined.

Intima-media thickness of the common carotid artery in highway toll collectors

PURPOSE

To assess the effects of exposure to exhaust particles on intima-media thickness of the common carotid artery in highway toll collectors.

METHODS

Sixty-one highway toll collectors (HTCs) between 24 and 56 years of age (mean, 36.2 +/- 7.3) and 48 controls between 24 and 64 years of age (mean, 42.6 +/- 10.6) were evaluated with gray-scale sonography to measure intima-media thickness (IMT) of the common carotid artery (CCA). Subgroups were categorized according to duration of exhaust exposure and further divided according to tobacco use.

RESULTS

CCA IMT was higher (0.8 +/- 0.2 mm) in HTCs than in the control group (0.6 +/- 0.1 mm; p < 0.001) and remained higher when subgroups with similar smoking habits were compared. In HTCs, IMT was greater when the number of years working in tollbooths was greater (p = 0.023). IMT was lower in HTCs with an exposure duration of < 10 years compared with a duration of 10-20 years (p = 0.017) or > 20 years (p value not significant).

CONCLUSION

Air pollution has a widely acknowledged negative effect on humans. This study confirms that exposure to exhaust particles might cause wall thickening of carotid arteries.

[Bronchial asthma. Update 2006]

Bronchial asthma, with a prevalence in Germany of 5% among adults and 10% among children, remains a frequent disease. Newer cell biological data show a separate regulation of the allergy (interleukin 4, IL-4, pathway) and of the eosinophilic inflammation in asthma (IL-5 pathway). Both conditions require a therapeutic approach. To prevent irreversible bronchial remodeling, early diagnosis and targeted therapy are decisive. Bronchial asthma is regarded as evident when the paroxysmal character of the disease is confirmed and an-at least intermittent-obstructive ventilation disorder is apparent which responds well to short-acting beta2-adrenergic agents. Current asthma treatment has been assured in many studies (evidence level A) and is based on therapy in stages which classifies therapeutic measures depending on four grades of severity. Accordingly, most patients are largely without complaints, and nocturnal attacks are now rare. New medications are intended to overcome any remaining therapeutic weak points. Antileukotrienes and anti-IgE antibodies can contribute to reducing the necessary corticosteroids. Pharmaceutical agents that intervene in the IL-4 or IL-5 regulation or prevent remodeling are being developed.

Immunization with soot from a non-combustion process provokes formation of antibodies against polycyclic aromatic hydrocarbons

The emission of soot during combustion processes used in transportation, manufacturing, and power generation is of increasing concern because of its serious adverse health effects. In particular, the ability to modulate the immune system has recently been established. In the present investigation, an artificial soot sample that was prepared by fragmentation of acetylene in a laser-induced plasma was used as an antigen for the immunization of a rabbit. A highly sensitive competition curve in an indirect competitive ELISA using a benzo[a]pyrene-BSA conjugate as a coating antigen could be constructed for benzo[a]pyrene with an IC50 of 2.94 mug/l (11.65 nmol/l). In contrast to the high affinity, the soot antiserum dilution (antibody titer) of 1:750 was rather low. The cross-reactivity was tested with 16 parent polycyclic aromatic hydrocarbons, 7 nitrated polycyclic aromatics, and 3 methylated, hydroxylated or butyric acid derivatives. The results obtained suggest that the vertebrate immune system can respond to an immunization with soot by the generation of high affinity IgG class antibodies against polycyclic aromatics. It is likely that antibodies are raised against the molecular structures which form the framework of the soot particles and not against adsorbed and extractable polyaromatic compounds. The experiments suggest that if soot is considered a T-independent antigen, the isotype switch, essentially from IgM to IgG, could have been caused by co-inoculation with a T-dependent antigen, i.e., mycobacteria contained in Freunds complete adjuvant. However, at the cellular level the mechanism remains to be uncovered.

Induction of nuclear factor-kappaB activation through TAK1 and NIK by diesel exhaust particles in L2 cell lines

Diesel exhaust particles (DEPs) are known to induce allergic responses in airway epithelial cells, such as the production of various cytokines via nuclear factor-kappa B (NF-kappaB). However, the intracellular signal transduction pathways underlying this phenomenon have not been fully examined. This study showed that DEP induced NF-kappaB activity via transforming growth factor-beta activated kinase 1 (TAK1) and NF-kappaB-inducing kinase (NIK) in L2 rat lung epithelial cells. DEP induced the NF-kB dependent reporter activity approximately two- to three-fold in L2 cells. However, this effect was abolished by the expression of the dominant negative forms of TAK1 or NIK. Furthermore, it was shown that DEP induced TAK1 phosphorylation in the L2 cells. These results suggest that TAK1 and NIK are important mediators of DEP-induced NF-kappaB activation.

The diesel exhaust component pyrene induces expression of IL-8 but not of eotaxin

Environmental pollutants can influence the expression of immunoregulatory molecules and, in this way, promote allergies. The local synthesis of proinflammatory chemokines is an important aspect in the development of allergic airway inflammation. We have characterized the influence of pyrene, a polycyclic aromatic hydrocarbon (PAH) contained, for example, in diesel exhaust particles (DEP), on transcription and secretion of the chemokines interleukin-8 (IL-8) and eotaxin. Reporter genes under control of the respective promoters were tested in the human cell lines A549 and HeLa, mRNA production was assayed in A549 cells and protein production was measured by ELISA in cell supernatants from primary human fibroblasts. Pyrene content of cell supernatants was measured by analytical HPLC. Promoter activity, mRNA production and protein expression of IL-8 were increased by pyrene. The activating effect in reporter gene studies was abolished by mutating either an NF-kappaB or an AP-1 binding site in the IL-8 promoter. In contrast, pyrene showed no effect on transcription from the eotaxin promoter, despite the important role of this chemokine in asthma. Our data show that pyrene has specific effects on chemokine synthesis, which are not restricted to mediators primarily associated with atopic diseases. Pyrene also affected cells not derived from lung tissue, which suggests a broader immunoregulatory influence for this pollutant.

Diesel exhaust particle extracts and associated polycyclic aromatic hydrocarbons inhibit Cox-2-dependent prostaglandin synthesis in murine macrophages and fibroblasts

Diesel exhaust particles (DEP) and their organic constituents modulate the immune system and exacerbate allergic airway inflammation. We investigated the role of DEP extract and associated polycyclic aromatic hydrocarbons (PAHs) on prostaglandin synthesis in endotoxin-activated murine macrophages and in mitogen-stimulated fibroblasts. In both macrophages and fibroblasts, DEP extract, phenanthrene, anthracene, phenanthrenequinone, and beta-napthoflavone inhibit prostaglandin production from endogenous arachidonic acid in response to ligand stimulation. However, DEP extract and PAHs do not block ligand induction of cyclooxygenase-2 (COX-2) protein, either in mitogen-stimulated fibroblasts or endotoxin-treated macrophages. Release of total arachidonic acid and total lipid products is not reduced by DEP or PAHs following ligand stimulation of macrophages or fibroblasts. DEP extract and the PAHs inhibit the activity of purified COX-2 enzyme in vitro but do not inhibit COX-1 activity. Thus, DEP and PAHs do not affect ligand-induced COX-2 gene expression, phospholipase activation, or arachidonic acid release in macrophages and fibroblasts but exert their inhibitory effect on prostaglandin production by preferentially blocking COX-2 enzyme activity.

Effects of fractions of traffic particulate matter on TH2-cytokines, IgE levels, and bronchial hyperresponsiveness in mice

In recent decades an increased prevalence of allergic conditions has been observed in developed countries. Although lifestyles, exposure to infection, and diet are all likely important factors, many studies have also shown a strong link between industrialization and allergy. The aim of this study was to investigate which extract fractions from traffic particulate matter (TPM, collected in a tunnel in Prague) have the greatest impact on different inflammatory and immunological parameters, such as cytokine production, levels of immunoglobulin E (IgE) antibodies, and bronchial hyperresponsiveness (BHR) in mice, when the extracts are used together with birch pollen for immunization. BP2 mice were immunized with birch pollen and different fractions of TPM (fractions 1-8). They were provoked intranasally with a mixture of pollen and TPM or pollen alone before they were challenged with methacholine. The BHR was evaluated in a whole-body plethysmograph. Th2 cytokines and fibronectin concentrations were measured, and differential cell counts were performed in the bronchioalveolar lavage (BAL) fluid. Sera were collected for determination of antibody titers. The highest titers of IgE and the highest BHR were found in the positive control mice (immunized and provoked with a mixture of pollen and TPM), followed by mice immunized with pollen and fraction 2 (which contains organic acids). Fraction 2 also induced the highest number of eosinophils and increased levels of interleukin 5 (IL-5) in the BAL fluid. The highest levels of IL-5, in BAL fluid and sera, were obtained in mice immunized with fraction 6 (moderately polar compounds), a somewhat surprising result since those mice did not produce any IgE, did not have any eosinophils in their BAL, or showed almost no BHR. Our data demonstrate that fractions 2 (organic acids) and 7 (highly polar compounds) seem to contain potential adjuvants stimulating the IL-5 production, the IgE synthesis, the eosinophil recruitment, and the bronchial hyperreactivity. Further characterization at the molecular level is now necessary to be able to identify the exact nature of those potential adjuvants. This will be of help in the future to improve the quality of the urban air aerosol.

Allergic susceptibility associated with diesel exhaust particle exposure: clear as mud

Exposure to elevated levels of particulate air pollution from motor vehicles is frequently associated with increased morbidity and mortality from cardiovascular conditions, lung cancer, and nonmalignant respiratory illnesses (e.g., asthma, bronchitis, respiratory tract infections). It appears, however, that less attention has been paid to the potential role of road traffic fumes in the induction of allergic conditions. Laboratory studies in humans and animals have shown that particulate toxic pollutants-particularly diesel exhaust particulates-can enhance allergic inflammation and can induce allergic immune responses. Most of these immune responses are mediated by the carbon core of diesel exhaust particulates. Polyaromatic hydrocarbons (e.g., anthracene, fluoranthene, pyrene, phenanthrene) are major chemical components of diesel exhaust particulates, and they have enhanced the production of immunoglobulin E. Although several large epidemiological studies have demonstrated a strong association between exposure to motor vehicle traffic emissions and allergic symptoms and reduced lung function, the evidence for the development of allergic sensitization from diesel exhaust particulates is less abundant than for the aforementioned associations. Recent comparisons of the prevalence of hay fever, as well as positive skin-prick tests, between citizens of former West and East Germany and between Hong Kong and China civilians, have demonstrated marked differences. Crucial variations in the level of particulate air pollution from motor vehicles in these countries may account for the observed increased prevalence of atopy. Although road-traffic pollution from automobile exhausts may be a risk factor for atopic sensitization, the evidence in support of this view remains conflictive. Some investigators have reported a clear association between the prevalence of allergy and road-traffic-related air pollution, whereas such a difference was not observed in other studies. Most discrepancies have been related to important variations in study design and methodology. In addition, inasmuch as exposure to ambient particles differs substantially in worldwide urban environments, perhaps qualitative-rather than quantitative-variations in particulate air pollution at different locations account for differences in the prevalence and/or severity of respiratory allergies.

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.

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.

Higher occurrence of asthma-related symptoms in an urban than a suburban area in adults, but not in children

In young adults, a higher occurrence of asthma-related symptoms was found in an urban than an adjacent suburban area in a survey performed in 1991. The authors now wondered whether such differences could be established in other age groups. The present study (in 1996) included 14,299 subjects, aged 5-75 yrs, of a random sample of the general population in the same two adjacent areas: the centre of Antwerp (Belgium) and its south suburban border. The standardized European Community Respiratory Health Survey (ECRHS) and International Study of Asthma and Allergies in Childhood (ISAAC) questionnaires were used to assess the occurrence of asthma-related symptoms. Higher rates were confirmed in urban compared to suburban Antwerp in adults (20-75 yrs), but no such area differences were found in children (5-8 and 12-15 yrs). Adjustment for a number of recorded risk factors did not seem to affect the area differences in asthma-related symptoms. Comparing the survey results of 1991 and 1996 in 20-44 yr old adults, the findings suggest a slight increase in reported respiratory symptoms in both areas. A higher occurrence of asthma symptoms was observed in the urban than suburban area in adults, but not in children. This might be explained by a progressive effect of long-term exposure to the "urban environment". However, longitudinal studies are necessary to further clarify the factors accounting for these age-related area differences.

The interaction between particulate air pollution and allergens in enhancing allergic and airway responses

Although the detrimental effects of air pollution on human health have been brought widely to public notice, it appears that less attention has been given to the potential role of toxic air pollutants in the induction of allergic conditions such as asthma, rhinoconjunctivitis, and atopic eczema. A number of large epidemiologic studies have shown that people exposed to intense motor vehicle traffic and its associated emissions are at major risk for allergic symptoms, reduced lung function, and increased sensitization to common airborne allergens. Several laboratory-based studies have demonstrated that particulate air pollutants emitted from motor vehicles can induce allergic inflammation, enhance IgE responses, and increase airway hyperresponsiveness, which could provide an underlying mechanism for the increasing prevalence of allergic diseases. This article reviews the evidence that supports the causative link between particulate air pollution and the sharp increase in the prevalence of type I allergies in developed countries.

Traffic exposure and allergic sensitization against latex in children

BACKGROUND

Latex antigens have been found in urban air samples and in debris deposited near freeways.

OBJECTIVE

We investigated whether exposure to road traffic in a large city is associated with allergic sensitization against latex in children.

METHODS

A population-based sample of 2505 children aged 5 to 11 years was examined in a cross-sectional study in the city of Dresden, Germany. Specific IgE levels against latex and a panel of common aeroallergens (timothy grass, rye, birch, mugwort, Cladosporium herbarum, Dermatophagoides pteronyssinus, cat dander, and dog dander) was determined by using a fluorescence immunoassay (CAP Pharmacia). Traffic exposure was assessed by (1) parental self-report on traffic frequency and truck traffic in the street of residence, (2) traffic counts, and (3) measurements of benzene at 182 points on a 1-km(2) grid for 1 year, which were used to estimate the children's individual exposure at the home address.

RESULTS

Eight hundred fifty-four (34.1%) of the children were sensitized against any of the allergens, and 150 (6.0%) had specific IgE (>0.35 kU/L) against latex. The prevalence of latex sensitization was not positively associated with self-reported traffic exposure, traffic counts in the street of residence (adjusted prevalence odds ratio for >5000 vs < or =5000 cars/d, 0.7; 95% confidence interval, 0.4-1.3), or benzene exposure (adjusted prevalence odds ratio for an increase of 1 microg/m(3) air, 0.8; 95% confidence interval, 0.7-1.05).

CONCLUSION

The data suggest that exposure to road traffic is not associated with allergic sensitization to latex in children.

Urbanization and childhood asthma: an African perspective

The increasing prevalence of childhood asthma in the developed world is a cause for concern. Much research is currently being conducted in an attempt to identify possible reasons for this occurrence. A so-called Western lifestyle has been the factor most commonly cited to explain this worrying increase in asthma prevalence. In essence, this implies a way of life where children are exposed from early infancy to a wide range of foods, infections, indoor and outdoor allergens, and irritants and to the effects of motor vehicle pollution. Until fairly recently, children in many African countries lived mainly in rural areas and were not exposed to the effects of a Western lifestyle. Early studies in a limited number of African countries showed a very low rural prevalence of childhood asthma, especially where children lived according to a traditional lifestyle. These same studies showed that asthma was not uncommon in urbanized African children. There has been an increasing tendency over the past 20 years for those in rural communities to move to the large urban centers. More recent childhood asthma prevalence studies, especially those from Kenya and Ghana, have confirmed the urban-rural differences but have shown a much narrower gap. In part this may be the result of exposure of rural children to agricultural pesticides and irritants as well as of an increasing tendency to adopt a more Westernized lifestyle such as the use of beds with mattresses, pillows, and blankets. These circumstances on the African continent provide a natural laboratory in the quest for factors that influence the development of asthma in susceptible children. Once more fully elucidated, it is possible that much valuable information will be available to combat the relentless increase in childhood asthma both here as well as in the developed world.

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.

The environmental predictors of allergic disease

The prevalence of allergic diseases has been on the rise for the last 200 years, when hay fever, an easy and obvious-to-recognize illness, was virtually unknown in Europe and North America. Genetic factors are unlikely to explain these rapid increases. Among the potential environmental factors, exposure to ambient air pollution has been intensely debated. Besides passive smoking, which has convincingly been shown to increase the risk for asthma and bronchial hyperresponsiveness among exposed children, the evidence to suggest that outdoor pollution to sulfur dioxide, particulate matter, diesel exhaust, and ozone is causally related with the inception of allergic diseases is poor. Rather, factors associated with the lifestyle of populations or families, such as socioeconomic status, allergen exposure, sibship size, early childhood infections, dietary habits, and growing up in anthroposophic families or a farming environment, may prove to be of greater relevance. The future challenge is to tackle the complex interplay between environmental factors and genetic determinants that will eventually contribute to a better understanding and to better prevention strategies for such multifactorial conditions as asthma and allergies.