Ozone exposure enhances expression of cell-surface molecules associated with antigen-presenting activity on bronchoalveolar lavage cells in rats

Ozone inhalation induces exacerbation of eosinophilic airway inflammation and Th2-skew immune response in a rat model of AR

BACKGROUND

Ozone (O3) exposure elicits allergic rhinitis (AR) exacerbations by mechanisms that remain poorly understood. We used a rat model to investigate the effects of O3 on eosinophilic airway inflammation and Th2-related response.

METHODS

Sprague-Dawley (SD) rats were sensitized and challenged with ovalbumin (OVA) to make AR models. Three groups of AR rats were exposed respectively to 0.5, 1.0, 2.0 ppm of O3 for 2 h daily over 6 weeks consecutively and studied 24 h later. Normal rats exposed to O3 alone were used as controls. Nasal symptoms and OVA-specific immunoglobulin E (OVA-sIg E) in the serum were evaluated. Inflammatory cells in nasal lavage fluid (NLF) were classified and counted. Cytokines protein levels in NLF were assessed by ELISA. The pathological changes in the nasal mucosa were examined by histology.

RESULTS

The combination of allergen and repeated O3 exposure in rats induced a significant increase of the number of sneezes, nasal rubs, amount of nasal secretion and OVA-sIgE in the serum, accompanied by enhancement of eosinophils in NLF and nasal mucosa. The increase of interleukin-5 (IL-5), IL-13, Eotaxin and decrease of INF-γ protein levels in NLF were detected in AR rats after O3 inhalation. Hematoxylin and eosin staining showed disordered arrangement of the nasal mucosa epithelium and eosinophilic infiltration in a concentration-dependent manner.

CONCLUSIONS

O3 inhalation deteriorated symptoms in AR rats, and the possible mechanism is that ozone co-exposure could enhance the expression of Th2 cytokines, eosinophilic airway inflammation dose-dependently. The observation is helpful for us to understand the synergistic effect of O3 in the air pollution and allergen on aggravating allergic rhinitis.

Macrophage phagocytosis: effects of environmental pollutants, alcohol, cigarette smoke, and other external factors

The ability of a pathogen to evade host immunity successfully, in contrast to the host's capacity to defend itself against a foreign invader, is a complex struggle, in which eradication of infection is dictated by a robust immunologic response. Often, there are external factors that can alter the outcome by tipping the scale to benefit pathogen establishment rather than resolution by the host's defense system. These external sources, such a cigarettes, alcohol, or environmental pollutants, can negatively influence the effectiveness of the immune system's response to a pathogen. The observed suppression of immune function can be attributed to dysregulated cytokine and chemokine production, the loss of migratory potential, or the inability to phagocytose pathogens by immune cells. This review will focus on the mechanisms involved during the toxin-induced suppression of phagocytosis. The accumulated data support the importance of studying the mechanisms of phagocytosis following exposure to these factors, in that this effect alone cannot only leave the host susceptible to infection but also promote alterations in many other macrophage functions necessary for pathogen clearance and restoration of homeostasis.

Protective role of interleukin-10 in ozone-induced pulmonary inflammation

BACKGROUND

The mechanisms underlying ozone (O₃)-induced pulmonary inflammation remain unclear. Interleukin-10 (IL-10) is an anti-inflammatory cytokine that is known to inhibit inflammatory mediators.

OBJECTIVES

We investigated the molecular mechanisms underlying interleuken-10 (IL-10)-mediated attenuation of O₃-induced pulmonary inflammation in mice.

METHODS

Il10-deficient (Il10(-/-)) and wild-type (Il10(+/+)) mice were exposed to 0.3 ppm O₃ or filtered air for 24, 48, or 72 hr. Immediately after exposure, differential cell counts and total protein (a marker of lung permeability) were assessed from bronchoalveolar lavage fluid (BALF). mRNA and protein levels of cellular mediators were determined from lung homogenates. We also used global mRNA expression analyses of lung tissue with Ingenuity Pathway Analysis to identify patterns of gene expression through which IL-10 modifies O₃-induced inflammation.

RESULTS

Mean numbers of BALF polymorphonuclear leukocytes (PMNs) were significantly greater in Il10(-/-) mice than in Il10(+/+) mice after exposure to O₃ at all time points tested. O₃-enhanced nuclear NF-κB translocation was elevated in the lungs of Il10(-/-) compared with Il10(+/+) mice. Gene expression analyses revealed several IL-10-dependent and O₃-dependent mediators, including macrophage inflammatory protein 2, cathepsin E, and serum amyloid A3.

CONCLUSIONS

Results indicate that IL-10 protects against O₃-induced pulmonary neutrophilic inflammation and cell proliferation. Moreover, gene expression analyses identified three response pathways and several genetic targets through which IL-10 may modulate the innate and adaptive immune response. These novel mechanisms of protection against the pathogenesis of O₃-induced pulmonary inflammation may also provide potential therapeutic targets to protect susceptible individuals.

An in vitro study of the effect of size and timing of administration of titanium dioxide particles on antigen presenting activity of alveolar macrophages and peripheral blood monocytes

Previous studies have shown that inhaled particles exacerbate asthma and allergic rhinitis. Several factors related to the particle may play a role in immune-stimulating activity; however, the underlying mechanisms remain unclear. We carried out in vitro studies to investigate the effects of TiO(2) particle exposure on antigen presenting activity and expression of the associated cell-surface molecules (Ia, B7.1, B7.2) in rat derived monocytes and alveolar macrophages, in terms of two aspects of the particles: (1) size (59 nm (ST) and 350 nm (LT) particles), and (2) the timing of particle exposure (before antigen exposure or co-administered). Results indicated that particle exposure prior to antigen exposure led to decreased antigen presenting activity in both types of cell. This decrease was greater with ST particles. In monocytes, the expression of cell surface molecules decreased similarly with both particles. Conversely, alveolar macrophages showed greater expression of Ia with ST than with LT exposures. Ia expression was confirmed to be functionally active by a mixed lymphocyte reaction. It is possible that particle exposure might result in poor antigen processing, thereby leading to decreased antigen presenting activity. Co-exposure of particles and antigen induced an increase in antigen presenting activity with both types of particle; however, ST exposure induced greater antigen presenting activity. The expression of Ia also increased similarly with both particle sizes. This suggests that, in a co-exposure situation, antigen may be processed without intensive retardation by particles, and factors other than Ia may affect antigen presenting activity. In conclusion, both size and timing of exposure to TiO(2) particles affect antigen presenting activity of monocytes and alveolar macrophages.

Inhibition of immunological function mediated DNA damage of alveolar macrophages caused by cigarette smoke in mice

Exposure to cigarette smoke impairs the pulmonary immune system, including alveolar macrophage function, although the mechanisms by which this occurs are not fully elucidated. This study investigates the effect of cigarette smoke exposure on the antigen-presenting activity of alveolar macrophages, which is required for antigen-specific response to T cells. C57BL/6 mice were exposed to cigarette smoke for 10 days using a Hamburg II smoking machine, and alveolar macrophages were obtained by bronchoalveolar lavage. The antigen-presenting activity of alveolar macrophages was significantly inhibited in mice exposed to cigarette smoke compared with mice not exposed to cigarette smoke. Major histocompatibility complex class II cell surface molecule-positive cells, B7-1 molecule-positive cells, and interleukin-1beta messenger RNA gene expression in alveolar macrophages were significantly decreased in mice exposed to cigarette smoke compared with mice not exposed to cigarette smoke. In contrast, DNA damage and generation of superoxide and hydrogen peroxide in alveolar macrophages were significantly increased by cigarette smoke exposure. These results suggest that inhibition of the antigen-presenting activity of alveolar macrophages may result from decreased expression of major histocompatibility complex class II and B7-1 molecules and interleukin-1beta messenger RNA gene expression following cigarette smoke exposure. Furthermore, inhibition of antigen presentation in alveolar macrophage may result from DNA damage induced by excessive amounts of reactive oxygen species being generated by alveolar macrophages following cigarette smoke exposure. These findings suggest that cigarette smoke impairs the immunological function of alveolar macrophages and, as a result, increases the risk for pulmonary infection.

Pulmonary exposure to carbon black nanoparticles increases the number of antigen-presenting cells in murine lung

Particulate matters can enhance antigen-related airway inflammation and immunoglobulin production. The present study was designed to determine the effects of different sizes of nanoparticles on the antigen-presenting cells (APC) in the lung. ICR mice were exposed to vehicle, carbon black (CB) nanoparticles (14 nm or 56 nm), ovalbumin (OVA), or OVA + nanoparticles intratracheally. The expression of major histocompatibility complex (MHC) class II, costimulatory molecules (CD80, CD86, CD11c), and DEC205 (dendritic cell marker), F4/80 (macrophage marker), and CD19 (B-cell marker) in the lung cells was measured by flow cytometry. 14 nm nanoparticles, but not 56 nm nanoparticles, increased the number of the total lung cells. Combination of OVA and 14 nm or 56 nm nanoparticles increased the total lung cells. The expression of MHC class II and/or costimulatory molecules and the number of APC in the lung were increased by 14 nm nanoparticles in the presence or absence of OVA. The increases were more prominent with combination of OVA and 14 nm nanoparticles. 56 nm nanoparticles did not show any significant effects. 14 nm CB nanoparticles can increase the expression of MHC class II and costimulatory molecules and the number of APC in the lung, especially in the presence of antigen, which can result in subsequent antigen-related airway inflammation and immunoglobulin production.

Effects of ozone exposure on inactivation of intra- and extracellular enterovirus 71

In this study, the potential of ozone in inactivating enterovirus 71 (EV71) free particles was investigated using either various ozone flow rates of 100, 80 or 60 mg/h or a constant flow rate of 80 mg/h, given to culture medium or various pH culture media containing EV71, respectively. Results demonstrated that EV71 inactivation by ozone was related to the kinetics of ozone solubility, approximately 99% inactivation being obtained in the exponential phase of ozone solubility. However, the inactivation rate was dependent on the ozone input flow rate and positively enhanced at acidic pH. Inactivation of intracellular EV71 was also studied. At a constant ozone supply of 60 mg/h, a significant reduction of intracellular virus titer (> or =99%, p < 0.01) was obtained after 45 or 60 min exposure but with low cell viability. Upon 30 min exposure, however, 45% cell viability was retained. The results indicate that the inactivating effect of ozone on intracellular EV71 virus is dependent on exposure duration.

Nasal allergy-like symptoms aggravated by ozone exposure in a concentration-dependent manner in guinea pigs

Our previous study revealed that exposure to 0.4 ppm ozone (O(3)) enhanced nasal allergy-like reactions in guinea pigs. In the present study, we investigated the concentration-dependency of the effects of exposure to O(3) on the aggravation of nasal allergy-like reactions induced by repeated nasal administration of antigen. Guinea pigs were exposed to filtered air or 0.1-0.6 ppm O(3) for 5 weeks. After each weekly administration of ovalbumin (OVA), sneezes and nasal secretions were measured. The number of eosinophils infiltrating the nasal septum and the titers of OVA-specific antibody were measured 24h after the last administration. Ozone increased sneezing and nasal secretion induced by OVA, nasal responsiveness to physical stimuli, and the number of infiltrating eosinophils in a concentration-dependent manner. The titer of anti-OVA-IgG was increased in animals exposed to 0.6 ppm O(3). Thus, exposure to O(3) aggravated nasal allergy-like symptoms concentration dependently. The aggravation was caused by induction of nasal hyperresponsiveness, the infiltration of eosinophils, and the increase in the production of anti-OVA-IgG. The estimated maximum likelihood estimation concentrations (MLECs) and bench mark concentrations (BMCs) of O(3) for these indices were in the range of 0.09-0.18 and 0.02-0.06 ppm, respectively.

Exposure to ozone enhances antigen-presenting activity concentration dependently in rats

The effect of ozone (O(3)) on the symptoms of allergic asthma and the mechanisms underlying have not yet been fully elucidated. Antigen presentation is one of the factors contributing to the allergic reaction. Therefore, we investigated the effects of repeated exposure to O(3) on antigen-presenting (AP) activity, on the expression of cell-surface molecules associated with antigen presentation (Ia, B7.1, B7.2 and CD11b/c) in bronchoalveolar lavage cells (BAL cells), and on allergic asthma-like symptoms. Rats were exposed to 0.3, 0.56, 1ppm O(3) or filtered air for a 3-day period every 2 weeks, this was replicated three times. AP activity was assessed by measuring antigen-specific T-cell proliferation; and the expression of cell-surface molecules, by flow cytometry. Rats were also made to inhale aerosolized 1% ovalbumin (OVA) or saline for 10min post-exposure to O(3), and allergic asthma-like symptoms were measured by determining the increase in enhanced pause (Penh), which correlates well with lung resistance. O(3) increased both AP activity and expression of Ia and costimulatory molecules in BAL cells concentration dependently. It also increased lung resistance, and the increase in lung resistance after O(3) exposure was significantly higher in the OVA-inhaled group than in the saline-inhaled group. The present results show that O(3) increased AP activity concentration dependently and suggest that O(3) might aggravate allergy symptoms by enhancing AP activity.

Ozone exposure enhances antigen-presenting activity of interstitial lung cells in rats

Ozone (O(3)) as a major component of photochemical air pollutants can increase the levels of allergen-specific antibody and may aggravate allergic symptoms. Antigen presentation is one of the factors contributing to allergic symptoms. Our present study is designed to clarify whether O(3) may increase the antigen-presenting (AP) activity of whole lung cells and its mechanisms. Male Wistar rats were exposed to 1 ppm O(3) for 3 days. The AP activity of whole lung cells and dendritic cells (DC) was measured by proliferation of T-cells. The expression of Ia and costimulatory molecules (B7.1, B7.2, CD11b/c) in lung cells was measured by flow cytometry, and the number of Ia-bearing cells, DC, macrophages, and B-cells in lung interstitum was examined immunohistochemically. The results show that O(3) increases AP activity of whole lung cells and DC, the expression of molecules associated with antigen presentation, and the number of AP cells (APC) in lung. Our results suggest that O(3) may enhance AP activity of lung cells caused by increases in the expression of cell-surface molecules and the number of APC in lung. The increase in the AP activity might contribute to subsequent antibody production, airway hyperresponsiveness and aggravation of allergic responses.