Ozone, airways and allergic airways disease

Allergic rhinitis and genetic components: focus on Toll-like receptors (TLRs) gene polymorphism

Allergic rhinitis represents a global health issue affecting 10% to 25% of the population worldwide. Over the years, studies have found that allergic diseases, including allergic rhinitis, are associated with immunological responses to antigens driven by a Th2-mediated immune response. Because Toll-like receptors (TLRs) are involved in both innate and adaptive immune responses to a broad variety of antigens, the association between polymorphisms of TLRs and allergic diseases has been the focus in many animal and human studies. Although the etiology of allergic rhinitis is still unknown, extensive research over the years has confirmed that the underlying causes of allergic diseases are due to many genetic and environmental factors, along with the interactions among them, which include gene-environment, gene-gene, and environment-environment interactions. Currently, there is great inconsistency among studies mainly due to differences in genetic background and unique gene-environment interactions. This paper reviews studies focusing on the association between TLR polymorphisms and allergic diseases, including allergic rhinitis, which would help researchers better understand the role of TLR polymorphisms in the development of allergic rhinitis, and ultimately lead to more efficient therapeutic interventions being developed.

Ozone-induced Nasal Hyperresponsiveness to Tachykinins in Guinea Pigs

Objective

To assess role of hydroxyl radials in the ozone-induced upper airway hyperresponsiveness to tachykinins.

Methods

A prospective, controlled, animal model (n = 96) was performed. Half of them exposed to air (A-group, placebo) and the other half exposed to 3 ppm ozone (O-group) for 2 h. Two hours post air/ozone exposure, animals were anesthetized and equally randomized to be pretreated with one of the three treatments, including saline vehicle, dimethylthiourea (DMTU; 500 mg/kg m, a hydroxyl radical scavenger), or phosphoramidon (Phos; 2 μg/kg, an inhibitor for neutral endopeptidase). Ten minutes after pretreatment, half of the animals in each group were i.v. injected with capsaicin (2 μg/kg), and the other half were i.v. injected with substance P (10 μg/kg) to produce Evans blue dye extravasation.

Results

Nasal exudative response to capsaicin or substance P in O-group was found to be significantly greater than that in A-group. This ozone-induced nasal airway hyperresponsiveness was largely prevented by DMTU. Phosphoramidon produced a similar nasal airway hyperresponsiveness in the A-group, but failed to alter ozone-induced nasal airway hyperresponsiveness in O-group. In sharp contrast, only substance P, but not capsaicin, produced a laryngeal exudative response in the A-group, which was similar to that in the O-group. The laryngeal exudative response to substance P was not significantly affected by DMTU or Phos.

Conculsion

In the guinea-pig model, hydroxyl radicals play a vital role in the development of ozone-induced nasal airway hyperresponsiveness to tachykinins. It is possibly mediated through the suppressive action of ozone on the tachykinin degradation.

Asthma

Asthma has been recognized as a disease since the earliest times. In the Corpus Hippocraticum, Hippocrates used the term “ασθμα” to indicate any form of breathing difficulty manifesting itself by panting. Aretaeus of Cappadocia, a well-known Greek physician (second century A.D.), is credited with providing the first detailed description of an asthma attack [13], and to Celsus it was a disease with wheezing and noisy, violent breathing. In the history of Rome, we find many members of the Julio-Claudian family affected with probable atopic respiratory disorders: Caesar Augustus suffered from bronchoconstriction, seasonal rhinitis as well as a highly pruritic skin disease. Claudius suffered from rhinoconjunctivitis and Britannicus was allergic to horse dander [529]. Maimonides (1136–1204) warned that to neglect treatment of asthma could prove fatal, whereas until the 19th century, European scholars defined it as “nervous asthma,” a term that was given to mean a defect of conductivity of the ninth pair of cranial nerves.

The incidence of respiratory symptoms and diseases among pulp mill workers with peak exposures to ozone and other irritant gases

OBJECTIVES

Pulp mills in Sweden started to use ozone as a bleaching agent in the early 1990s. The goal of this study was to investigate whether the incidence of selected respiratory outcomes was associated with peak exposures to ozone or other irritant gases (ie, chlorine dioxide [ClO2] or sulfur dioxide [SO2]) used in these mills.

METHODS

Bleachery workers (n = 245) from three pulp mills where ozone was used participated in surveys in the mid- to late-1990s. Comparison workers (n = 80) were from two adjacent paper mills. The person-time at risk was calculated for each participant, covering the period of employment when ozone was used. Data were collected by questionnaire, and a peak exposure was defined as a self-reported exposure to an irritant gas resulting in acute respiratory symptoms. The outcomes analyzed were self-reports of physician-diagnosed asthma, attacks of wheeze, and chronic bronchitis (ie, chronic cough with phlegm). Participants also reported when the peak exposures and outcomes occurred.

RESULTS

Based on proportional hazards regression (controlling for gender, age, cigarette smoking, atopy, and peak irritant exposures that occurred before follow-up), workers who reported both ozone and ClO2/SO2 peak exposures had elevated hazard ratios (HRs) for all three outcomes. Those who reported only ozone peak exposures had elevated HRs of 6.5 (95% confidence interval [CI], 1.2 to 36.3) for asthma and 3.3 (95% CI, 1.1 to 10.2) for attacks of wheeze but no increase in risk for chronic bronchitis. Workers with only ClO2/SO2 peak exposures had elevated HRs for attacks of wheeze (HR, 7.5; 95% CI, 1.9 to 29.3) and chronic bronchitis (HR, 22.9; 95% CI, 4.5 to 118.2) but not for asthma.

CONCLUSIONS

These findings suggest the need for additional efforts to prevent peak exposures in pulp-bleaching operations.

Risk factors of allergic rhinitis: genetic or environmental?

Allergic diseases such as allergic rhinitis represent a global health problem, affecting 10%-25% of the world population. There is clear evidence to support the concept that allergic diseases are influenced by genetic predisposition and environmental exposure. Polymorphisms of candidate genes have been associated with clinical expression of these diseases. However, characterization of these susceptibility markers in discriminating an "allergic individual" from the general population has not yet been achieved, and the value of how this genetic insight leading to recognition of specific subtypes of these disorders still needs to be confirmed. Environmental factors (eg, air pollution and bacterial/viral infection) also play an important role in the development of the diseases. A number of epidemiologic studies have supported the "hygiene hypothesis", which is based on the observations that Th1 responses induced by microbial stimulation can counterbalance allergen-induced Th2 responses. Future studies are needed to identify the key genes or their haplotypes for atopic phenotypes and to investigate the interactions between genetic and environmental factors that influence the complex trait of allergic diseases. This will help us to further understand the etiology of the diseases and develop new avenues for genetically oriented diagnosis and more effective measures of prevention and intervention.

An in vitro evaluation of the ability of ozone to kill a strain of Enterococcus faecalis

AIM

To evaluate the potential of ozone as an antibacterial agent using Enterococcus faecalis as the test species.

METHODOLOGY

Ozone was produced by a custom-made bench top generator and its solubility in water determined by ultraviolet (258 nm) spectrophotometric analysis of solutions through which ozone was sparged for various time-periods. The antibacterial efficacy of ozone was tested against both broth and biofilm cultures. Ozone was sparged for 30, 60, 120 and 240 s, through overnight broth cultures of a strain of E. faecalis (E78.2) and compared with those that were centrifuged, washed and resuspended in water. Enterococcus faecalis (E78.2) biofilms were grown on cellulose nitrate membrane filters for 48 h and suspended in water through which ozone gas was sparged with stirring for 60, 120 and 240 s in a standard fashion. In a separate test, biofilms were also exposed to gaseous ozone. Sodium hypochlorite (NaOCl) was used as a positive control. All experiments were repeated four times.

RESULTS

There were significant (P < 0.05) reductions of bacteria in the unwashed (2 log(10) reductions) and washed (5 log(10) reductions) broth cultures following 240 s applications. Biofilms incubated for 240 s with ozonated water showed no significant reduction in cell viability attributable to ozone alone, whereas with NaOCl no viable cells were detected over the same time. Gaseous ozone applied for 300 s had no effect on these biofilms.

CONCLUSIONS

Ozone had an antibacterial effect on planktonic E. faecalis cells and those suspended in fluid, but little effect when embedded in biofilms. Its antibacterial efficacy was not comparable with that of NaOCl under the test conditions used.

Pulmonary epithelial integrity in children: relationship to ambient ozone exposure and swimming pool attendance

Airway irritants such as ozone are known to impair lung function and induce airway inflammation. Clara cell protein (CC16) is a small anti-inflammatory protein secreted by the nonciliated bronchiolar Clara cells. CC16 in serum has been proposed as a noninvasive and sensitive marker of lung epithelial injury. In this study, we used lung function and serum CC16 concentration to examine the pulmonary responses to ambient O3 exposure and swimming pool attendance. The measurements were made on 57 children 10-11 years of age before and after outdoor exercise for 2 hr. Individual O3 exposure was estimated as the total exposure dose between 0700 hr until the second blood sample was obtained (mean O3 concentration/m3 times symbol hours). The maximal 1-hr value was 118 microg/m3 (59 ppb), and the individual exposure dose ranged between 352 and 914 microg/m3hr. These O3 levels did not cause any significant changes in mean serum CC16 concentrations before or after outdoor exercise, nor was any decrease in lung function detected. However, children who regularly visited chlorinated indoor swimming pools had significantly lower CC16 levels in serum than did nonswimming children both before and after exercise (respectively, 57 +/- 2.4 and 53 +/- 1.7 microg/L vs. 8.2 +/- 2.8 and 8.0 +/- 2.6 microg/L; p < 0.002). These results indicate that repeated exposure to chlorination by-products in the air of indoor swimming pools has adverse effects on the Clara cell function in children. A possible relation between such damage to Clara cells and pulmonary morbidity (e.g., asthma) should be further investigated.

Effect of ozone exposure on allergic sensitization and airway inflammation induced by dendritic cells

BACKGROUND

Epidemiological studies suggest that ozone exposure is related to increased asthma symptoms. Dendritic cells (DCs) are the principal antigen-presenting cells in the airways.

OBJECTIVE

We have examined whether ambient doses of ozone (100 ppb for 2 h) enhance allergic sensitization and/or airway inflammation in a mouse model.

METHODS

C57BL/6 mice were sensitized to inhaled ovalbumin (OVA) by intratracheal instillation of OVA-pulsed DCs on day 0. Daily exposure to OVA aerosol on days 14-20 resulted in an eosinophilic airway inflammation, as reflected in bronchoalveolar lavage fluid and lung histology. In a first experiment, mice were exposed to ozone or room air immediately prior to and following sensitization. Subsequently, we tested the effect of ozone exposure during antigen challenge in DC-sensitized mice.

RESULTS

Exposure to ozone during sensitization did not influence airway inflammation after subsequent allergen challenge. In contrast, in sensitized mice, challenge with OVA together with ozone (days 14-20) resulted in enhanced airway eosinophilia and lymphocytosis, as compared with mice exposed to OVA and room air (1.91 x 106 +/- 0.46 x 106 vs. 0.16 x 106 +/- 0.06 x 106 eosinophils/mL lavage fluid; P = 0.015; 0.49 x 106 +/- 0.11 x 106 vs. 0.08 x 106 +/- 0.03 x 106 lymphocytes/mL lavage fluid; P = 0.004). Ozone exposure without subsequent OVA exposure did not cause airway inflammation.

CONCLUSION

Ozone exposure does not increase allergic sensitization but enhances antigen-induced airway inflammation in mice that are sensitized via the airways.

Cigarette smoking, but not sensitization to Alternaria, is associated with severe asthma in urban patients

Hereditary susceptibility and allergen exposure have been identified as general risk factors for asthma. However, risk factors for severe asthma still remain to be identified. To further assess and quantify risk factors associated with severe asthma in adult patients apart from clinical exacerbations, 306 randomly selected subjects (mean age 40+/-17 years, 46% males) presenting to an inner city pulmonary practice between 1995 and 1996 were retrospectively investigated. Of these, 117 patients were atopic, 112 had current asthma, and 22 asthmatics had severe asthma. Risk factors associated with atopy were family history of atopy and any domestic pet ownership (OR: 3.1, 95% CI: 1.64-6.1). Asthma was generally associated with atopy (OR: 4.2, CI: 2.4-7.4) and pet ownership (OR: 2.4, CI: 1.2-4.6). Severe asthma was strongly associated with current smoking (OR: 4.8, CI: 1.3-18.3), and lung function was negatively correlated with the amount of consumed cigarettes per day (r = -0.61, p = 0.04). However, no association with sensitization to Alternaria was found in severe asthma. Cigarette smoking is an independent risk factor associated with severe asthma in urban patients, whereas sensitization to Alternaria is of less importance in these patients.

The prevalence of allergic rhinosinusitis: a review

A review of the literature indicates that there is an increase in the prevalence of self-reported symptoms suggestive of seasonal allergic rhinitis over the last 70 years. The reason for this remains unclear. Epidemiological studies which relate to the effect of pollution suggest that while pollution can exacerbate respiratory tract symptoms, there is no consistent evidence that high levels result in an increase in the prevalence of allergic rhinitis. The increased prevalence of house-dust mite, an alteration in immunity--possibly related to the number of childhood respiratory tract infections, and increased disease awareness, are all factors which may influence the reported prevalence of allergic rhinitis. At present the inconsistencies which exist in the literature mean that it is possible to 'pick' publications which support one view and ignore the rest, so that a variety of views may be held, each with apparently well referenced endorsement. The criteria defined by Bradford Hill (1965) to establish causation and not mere association between any of these factors and allergic rhinitis have, as yet, not been met (see Table V).

Investigation of gaseous ozone for MRSA decontamination of hospital side-rooms

A domestic, gaseous ozone generator was investigated for use in the decontamination of hospital side-rooms that have housed patients colonized with methicillin-resistant Staphylococcus aureus (MRSA). Three models of bacterial contamination were used. These were exposed to ozone generation in a standard hospital side-room for 4 and 7 h. A methicillin-sensitive and a methicillin-resistant strain of S. aureus were compared. Ozone concentrations of 0.14 ppm were reached, levels which are sufficient to cause mild pulmonary toxicity. Bacterial counts were reduced in the vicinity of the gas generator in most instances, but the effect elsewhere in the room was, at best, limited. MRSA appeared more resistant to the effects of ozone than methicillin-sensitive S. aureus. We conclude that the device tested would be inadequate for the decontamination of such hospital side-rooms.

Differential depletion of human respiratory tract antioxidants in response to ozone challenge

The toxicity of ozone, the major component of photochemical smog, is related to its powerful oxidising ability, and many of its deleterious effects are mediated through free radical reactions. As the majority of ozone oxidation events are thought to be confined to the pulmonary epithelial lining fluid, we studied the interaction of ozone with a range of small molecular weight antioxidants found within this compartment: ascorbic acid (AH2), uric acid (UA), and reduced glutathione (GSH). Epithelial lining fluid obtained as bronchoalveolar lavage (BAL) fluid, was taken from 16 male subjects and the antioxidant concentrations determined for each subject. BAL fluid samples from nine of these subjects were then exposed, using an interfacial exposure system, to a range (50-1000 ppb) of ozone concentrations. Both AH2 and UA were consumed by ozone in a time and ozone concentration dependent manner, with mean consumption rates of 1.7 +/- 0.8 and 1.0 +/- 0.5 pmol L-1 s-1 ppb-1, respectively. Considerable intersubject variation was however observed. The individual rates of consumption for each antioxidant were significantly correlated with the respective initial antioxidant concentration. In contrast, although GSH was consumed at 50 ppb ozone, the rate of consumption did not change with increasing ozone concentration. We conclude that there is differential depletion of BAL fluid antioxidants, suggesting a reactivity hierarchy toward ozone in human ELF of AH2 > UA > > GSH.