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.     

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

In this study, we investigated the effects of ozone (O3) exposure on expression of cell-surface molecules associated with antigen presentation and on accessory activity of bronchoalveolar lavage cells (BAL cells). Rats were exposed to 1 ppm O3 for 3 days. Expression of cell-surface molecules was measured by flow cytometry. Accessory activity of BAL cells was assessed by the allogeneic mixed lymphocyte reaction (MLR) and specific antigen-presenting activity. O3 exposure increased the expression of Ia, B7.1, B7.2, and CD11b/c on BAL cells. Morphological and immunological studies showed the Ia-positive cells to have monocyte-like features. Peripheral blood monocytes expressed Ia, B7.1, B7.2, and CD11b/c. The Ia expression on the monocytes was further increased by treatment of them with BAL fluid from O3-exposed rats (O3-BALF). Resident alveolar macrophages, however, did not express Ia antigen, and the Ia expression was not increased by O3-BALF. Neutrophils, which also infiltrated in response to O3 exposure, did not express Ia, B7.1, and B7.2. Therefore, infiltrating monocytes may have caused the increased expression of Ia and B7 molecules on BAL cells exposed to O3. The accessory activity of BAL cells in terms of MLR and specific antigen-presenting activity was also enhanced by O3 exposure. The present study suggests that monocytes infiltrating in response to O3 exposure caused enhancements of the expression of Ia and costimulatory molecules on and the accessory activity of BAL cells.     

Organic extract of diesel exhaust particles stimulates expression of Ia and costimulatory molecules associated with antigen presentation in rat peripheral blood monocytes but not in alveolar macrophages

We hypothesized that diesel exhaust particles (DEP) induce the activation of antigen-presenting cells (APC) in lung. The present study was designed to clarify the following about DEP: (1) whether it affects the expression of Ia and B7 molecules in alveolar macrophages (AM) as a mature cell or in peripheral blood monocytes (PBM) as an immature cell, (2) if it affects the antigen-presenting (AP) activity of PBM, (3) what component of DEP is responsible for the effects, and (4) whether the effect of DEP is related to oxidative stress. DEP was extracted with methylene chloride. Cells were exposed to whole DEP, organic extract, or residual particles for 24 h. Cell-surface molecules were measured by flow cytometry. AP activity was assessed by antigen-specific T cell proliferation. Whole DEP or organic extract significantly increased the expression of Ia and B7 molecules on PBM but not on AM. No significant effect of residual particles was observed. A low concentration of organic extract also increased the AP activity of PBM. When the induction of an antioxidative enzyme was assessed, heme oxygenase-1 protein was found to be significantly increased by exposure to whole DEP, and the organic extract was more effective than the residual particles. Furthermore, the organic extract-induced expression of Ia antigen on PBM was reduced by the addition of an antioxidative agent. These results suggest that DEP may act on immature APC and enhance their AP activity and that the action contributing to oxidative stress may be mediated by organic compounds of DEP.     

Lung injury, inflammation, and inflammatory stimuli in rats exposed to ozone

The effects of ozone (O3) on airway epithelia, inflammation, and expression of inflammatory stimuli were investigated to delineate the mechanisms of inflammatory reactions relevant to lung injury. Because the airway responses to O3 develop gradually, this investigation included a time-sequence analysis. Rats exposed for 3 h to 1 ppm O3 were studied at 4-h intervals up to 20 h postexposure. Bronchoalveolar lavage fluid (BAL) was analyzed for albumin as an indicator of increased permeability, polymorphonuclear leukocytes (PMNs) to assess the inflammatory status, macrophage inflammatory protein-2 (MIP-2, an inflammatory chemokine), and cell adhesion molecules for their role in inflammation and PMN functions. The time-related increase in albumin was matched by a similar significant increase for PMNs, MIP-2, and intercellular adhesion molecule-1 (ICAM-1). However, no marked change occurred for beta-2 integrin (CD-18) and leukotriene B4 (LTB4). The results establish a temporal correlation of epithelial permeability with changes in inflammatory activity and stimuli responsible for PMN recruitment in the lung. The observations of elevated MIP-2 and ICAM-1 levels are consistent with their role in injury and inflammation. An early expression of MIP-2 mRNA in BAL cells, that is, immediately post O3 exposure, and the peak increase in BAL MIP-2 levels 4 h later support the chemotactic role of MIP-2 in PMN recruitment at 4- and 12-h time points. The rapid drop in MIP-2 and ICAM-1 levels appears to signal the termination of inflammatory cell recruitment, which is accompanied by an onset of recovery.     

Differences in pulmonary biochemical and inflammatory responses of rats and guinea pigs resulting from daytime or nighttime, single and repeated exposure to ozone.

Rats and guinea pigs were exposed to 0.8 mg ozone (O3)/m3 (approximately 0.4 ppm) for 12 hr during the daytime, 12 hr during the nighttime, or continuously to investigate circadian variation in O3-induced pulmonary toxicity during single and repeated O3 exposures. Biomarkers in bronchoalveolar lavage (BAL) fluid and lung tissues were measured as indicators of biochemical and inflammatory responses. Nighttime O3 exposure of rats resulted in larger increases of protein, albumin, and inflammatory cells in BAL fluid compared to those after daytime O3 exposure and this daytime-nighttime difference was statistically significant (p < 0.05). Single daytime or nighttime O3 exposure of guinea pigs resulted in comparable increases of BAL fluid proteins and inflammatory cells without a daytime-nighttime difference. Nighttime and continuous O3 exposure of rats for 3 days resulted in comparable increases in lung antioxidant enzyme activities, both of which differed statistically from effects from daytime O3 exposures (p < 0.05). Continuous O3 exposure of guinea pigs for 3 days caused, in general, statistically larger increases in lung tissue parameters compared to nighttime O3 exposures (p < 0.05). These results suggest that the extent of O3-induced acute pulmonary biochemical and inflammatory responses is directly related to the level of physical and respiratory activity. For rats, effects from continuous O3 exposure appear to be controlled by the nighttime, physically active period. In guinea pigs, the comparable responses following daytime or nighttime O3 exposure seem in accordance with their random behavioral daily activity pattern. This study supports the view that physical activity-related increases in inhaled dose significantly enhance the pulmonary O3 responses.     

The Role of IgG1 and IgG2 in Trimellitic Anhydride-Induced Allergic Response in the Guinea Pig Lung

Trimellitic anhydride (TMA) is a small molecular weight chemical used in the paint and plastics industry that can cause asthma-like symptoms in humans. Guinea pigs sensitized intradermally with TMA will respond to antigen challenge with asthma-like symptoms, including an immediate bronchoconstriction and a delayed cellular infiltration into the lung, particularly eosinophil infiltration. Sensitized guinea pigs produce TMA-specific IgG1, which is thought to be important in asthmatic reactions in this animal model; however, they also produce TMA-specific IgG2 antibody. The purpose of the present study was to determine the role of IgG1 and IgG2 in the TMA-induced immediate bronchoconstriction and delayed cellular infiltration in the guinea pig. Guinea pigs were passively sensitized by intratracheal instillation of TMA-specific IgG2, an antibody preparation enriched with TMA-specific IgG1, or a combination of the two. The allergic response was induced by intratracheal instillation of TMA conjugated to guinea pig serum albumin (TMA–GPSA). A significantly greater bronchoconstrictor response was observed in animals sensitized with a combination of the IgG2 and IgG1 preparation compared to those sensitized with IgG2 or the IgG1 preparation alone. Cellular infiltration was quantified 24 h after antigen challenge by differential cell counts of bronchoalveolar lavage (BAL) cells as well as by using eosinophil peroxidase (EPO) and myeloperoxidase (MPO) activity as a measure of the numbers of eosinophils and neutrophils, respectively. In the BAL, passively sensitizing with IgG2 alone resulted in an increase in both TMA-induced MPO and EPO activity. In contrast, in the lung, passively sensitizing with a partially purified preparation of TMA-specific IgG1 alone resulted in a significant increase in TMA-induced EPO activity. Passively sensitizing with IgG2 in conjunction with the IgG1 preparation resulted in an enhanced cellular infiltration and lung injury over that seen with either antibody preparation alone. These data demonstrate an augmentation of IgG1-mediated responses by the addition of IgG2 and suggest a significant role for both subclasses of IgG antibodies in this guinea pig model of TMA-induced occupational asthma.     

Differential effects of female sex hormones on cellular recruitment and tracheal reactivity after formaldehyde exposure

Female sex hormones (FSHs) exert profound regulatory effects on the course of lung inflammation due to allergic and non-allergic immune responses. As pollution is one of the pivotal factors to induce lung dysfunction, in this study we investigated the modulatory role of FSHs on lung inflammation after a formaldehyde (FA) exposure. For this purpose, lung and systemic inflammatory responses were evaluated in terms of leukocytes countings in bronchoalveolar lavage (BAL), peripheral blood and bone marrow lavage from 7-day ovariectomized (OVx) and Sham-OVx rats subjected to FA inhalation for 3 consecutive days. The hypothesized link between effects of FSHs on expression of adhesion molecules and mast cells degranulation was also studied. Once exposed to FA, Sham-OVx rats increased the number of total cells recovered in BAL and of leukocytes in peripheral blood, and decreased the counts in bone marrow. By contrast, in OVx rats upon FA exposure there was a reduction of the total cells counts in BAL and of blood leukocytes; lung expressions of ICAM-1 and Mac-1 were depressed, but the number of bone marrow cells did not vary. Estradiol treatment of OVx rats increased the total cells in BAL and decreased the number of blood leukocytes, whereas the number of bone marrow cell remained unaltered. Progesterone treatment, in turn increased the total cells in BAL and blood leukocytes, but decreased the number of bone marrow cells. OVx rats exposed to FA developed tracheal hyperresponsiveness to methacholine (MCh). A similarly altered response was found between the tracheal segments of Sham-OVx rats after FA exposure and that found in tracheae of naïve rats. Estradiol treatment prevented FA-induced tracheal hyperresponsiveness to MCh whereas progesterone was ineffective in this regard. In addition, OVx rats upon FA exposure significantly increased both, the ability of mast cell degranulation and serum corticosterone levels. In conclusion, it was found that FSHs act by distinct control mechanisms on FA-induced lung inflammation and tracheal hyperresponsiveness, since at low circulating levels of FSHs (such as those after OVx) there is some resistance to the development of a lung inflammatory response, but the cholinergic tracheal responsiveness is exacerbated. Our data also help to understand the involvement of FSHs on mast cells activity after pollutants exposure and add information regarding the role of FSHs on the mechanisms related to endothelium-leukocyte interactions.     

ALTERATION OF EPITHELIAL INTEGRITY,ALKALINE PHOSPHATASE ACTIVITY,AND FIBRONECTIN EXPRESSION IN LUNGS OF RATS EXPOSED TO OZONE

The deleterious effects of ozone (O3), an oxidant air pollutant, in the lung are dependent on dose and exposure duration and generally evolve with time postexposure. This study characterized the time sequence of epithelial injury and fibronectin expression in the lungs of rats exposed to O3. Bronchoalveolar lavage (BAL) fluid was analyzed for alkaline phosphatase and total protein as markers of epithelial injury and increased permeability, and fibronectin for its role in inflammation and lung injury. The results revealed a time-related increase in total protein in the BAL fluid following a 3-h exposure of rats to 1 ppm O3. The increased protein concentrations peaked at 12 h and then declined, but remained significantly higher than control at 24 h postexposure. A similar time-related significant increase also occurred for BAL fibronectin and alkaline phosphatase activity. However, the return of alkaline phosphatase levels to baseline prior to a comparable reduction in protein levels suggests repair of injured cells, but a delay in the formation of epithelial junctions that limit the transfer of serum proteins to air spaces. By cytochemistry, alkaline phosphatase activity was detected in association with lung type II epithelial cells and in BAL polymorphonuclear leukocytes (PMNs), but not in macrophages. While a significant increase in cytochemically detectable alkaline phosphatase resulted from the increase in PMN number following O3 exposure, mononuclear cells constituted the primary cell type responsible for fibronectin mRNA upregulation. While the cytochemical observations support the role of inflammatory cells in the injury process, the comparability of temporal changes in BAL protein, fibronectin, and alkaline phosphatase suggests a mechanistic role for fibronectin in lung injury.     

Alteration of epithelial integrity, alkaline phosphatase activity, and fibronectin expression in lungs of rats exposed to ozone.

The deleterious effects of ozone (O3), an oxidant air pollutant, in the lung are dependent on dose and exposure duration and generally evolve with time postexposure. This study characterized the time sequence of epithelial injury and fibronectin expression in the lungs of rats exposed to O3. Bronchoalveolar lavage (BAL) fluid was analyzed for alkaline phosphatase and total protein as markers of epithelial injury and increased permeability, and fibronectin for its role in inflammation and lung injury. The results revealed a time-related increase in total protein in the BAL fluid following a 3-h exposure of rats to 1 ppm O3. The increased protein concentrations peaked at 12 h and then declined, but remained significantly higher than control at 24 h postexposure. A similar time-related significant increase also occurred for BAL fibronectin and alkaline phosphatase activity. However, the return of alkaline phosphatase levels to baseline prior to a comparable reduction in protein levels suggests repair of injured cells, but a delay in the formation of epithelial junctions that limit the transfer of serum proteins to air spaces. By cytochemistry, alkaline phosphatase activity was detected in association with lung type II epithelial cells and in BAL polymorphonuclear leukocytes (PMNs), but not in macrophages. While a significant increase in cytochemically detectable alkaline phosphatase resulted from the increase in PMN number following O3 exposure, mononuclear cells constituted the primary cell type responsible for fibronectin mRNA upregulation. While the cytochemical observations support the role of inflammatory cells in the injury process, the comparability of temporal changes in BAL protein, fibronectin, and alkaline phosphatase suggests a mechanistic role for fibronectin in lung injury.     

Flt3 ligand: a novel cytokine prevents allergic asthma in a mouse model

Flt-3 ligand (FL), a recently described growth factor affecting early hematopoietic progenitor cells, can also support the expansion of dendritic cells secreting IL-12. Since type 2 T cells predominate in asthma and IL-12 prevents the differentiation of naive T lymphocytes to a type 2 phenotype, we hypothesized that FL could prevent the development of asthma-like conditions in the ovalbumin mouse model. We found that co-administration of FL during ovalbumin sensitization abrogated late allergic responses, but had no effect on early allergic responses. Airway hyperresponsiveness to methacholine was also blocked by FL treatment. Analysis of bronchoalveolar lavage (BAL) fluid demonstrated a significant reduction in eosinophils, with concomitant decreases in IL-5 and increases in IFN-gamma levels. However, there was no change in BAL fluid IL-4 and serum IgE levels. These data suggest that FL treatment prevents ovalbumin-induced asthma in the mouse and may provide a useful adjuvant in the treatment of human asthma.     

Effects of MK-801 and amphetamine treatments on allergic lung inflammatory response in mice

Glutamate acts as a neurotransmitter within the Central Nervous System (CNS) and modifies immune cell activity. In lymphocytes, NMDA glutamate receptors regulate intracellular calcium, the production of reactive oxygen species and cytokine synthesis. MK-801, a NMDA receptor open-channel blocker, inhibits calcium entry into mast cells, thereby preventing mast cell degranulation. Several lines of evidence have shown the involvement of NMDA glutamate receptors in amphetamine (AMPH)-induced effects. AMPH treatment has been reported to modify allergic lung inflammation. This study evaluated the effects of MK-801 (0.25 mg/kg) and AMPH (2.0 mg/kg), given alone or in combination, on allergic lung inflammation in mice and the possible involvement of NMDA receptors in this process. In OVA-sensitized and challenged mice, AMPH and MK-801 given alone decreased cellular migration into the lung, reduced IL-13 and IL10 levels in BAL supernatant, reduced ICAM-1 and L-selectin expression in granulocytes in the BAL and decreased mast cell degranulation. AMPH treatment also decreased IL-5 levels. When both drugs were administered, treatment with MK-801 reversed the decrease in the number of eosinophils and neutrophils induced by AMPH in the BAL of OVA-sensitized and challenged mice as well as the effects on the expression of L-selectin and ICAM-1 in granulocytes, the IL-10, IL-5 and IL-13 levels in BAL supernatants and increased mast cell degranulation. At the same time, treatment with MK-801, AMPH or with MK-801 + AMPH increased corticosterone serum levels in allergic mice. These results are discussed in light of possible indirect effects of AMPH and MK-801 via endocrine outflow from the CNS (i.e., HPA-axis activity) to the periphery and/or as a consequence of the direct action of these drugs on immune cell activity, with emphasis given to mast cell participation in the allergic lung response of mice.     

LUNG INJURY,INFLAMMATION, AND INFLAMMATORY STIMULI IN RATS EXPOSED TO OZONE

The effects of ozone (O₃) on airway epithelia, inflammation, and expression of inflammatory stimuli were investigated to delineate the mechanisms of inflam matory reactions relevant to lung injury. Because the airway responses to O₃ develop gradually, this investigation included a time-sequence analysis. Rats exposed for 3 h to 1 ppm O₃ were studied at 4-h intervals up to 20 h postexposure. Bronchoalveolar lavage fluid (BAL) was analyzed for albumin as an indicator of increased permeability, polymorphonuclear leukocytes (PMNs) to assess the inflammatory status, macrophage inflammatory protein-2 (MIP-2, an inflammatory chemokine), and cell adhesion molecules for their role in inflammation and PMN functions. The time-related increase in album in was matched by a similar significant increase for PMNs, MIP-2, and intercellular adhesion molecule-1 (ICAM-1). However, no marked change occurred for b-2 integrin (CD-18) and leukotriene B₄ (LTB₄). The results establish a temporal correlation of epithelial permeability with changes in inflammatory activity and stimuli responsible for PMN recruitment in the lung. The observations of elevated MIP-2 and ICAM-1 levels are consistent with their role in injury and inflammation. An early expression of MIP-2 mRNA in BAL cells, that is, immediately post O₃ exposure, and the peak increase in BAL MIP-2 levels 4 h later support the chem otactic role of MIP-2 in PMN recruitm ent at 4- and 12-h time points. The rapid drop in MIP-2 and ICAM-1 levels appears to signal the termination of inflammatory cell recruitment, which is accompanied by an onset of recovery.     

Complement 3 is involved with ventilator-induced lung injury

Humoral molecules can trigger injury on mechanically stressed and damaged tissue. We have studied the role of complement 3 (C3) in a mouse model of ventilator-induced lung injury (VILI). Compared with sham-treated wild type (WT) mice, ventilated WT mice have reduced total bronchoalveolar lavage (BAL) cells; and elevated activities of thrombin and matrix metalloproteinases (MMPs), such as gelatinase/collagenase in the BAL fluid. In contrast, these parameters in ventilated C3 null mice are not significantly different from sham-treated WT and C3 null mice. In mechanically ventilated mice, thrombin activity and MMPs are lower in C3 null mice than in WT mice and are inversely correlated with total single BAL cells. C3 activation is associated with MMP activation in vitro. Pretreatment of WT mice with humanized cobra venom factor, which inactivates C3, reduces C3 deposition in the lung and increases total BAL cells in VILI. We propose that C3 is involved with VILI and inhibition of complement activation may be a potential therapeutic strategy.     

Complement 3 is involved with ventilator-induced lung injury

Humoral molecules can trigger injury on mechanically stressed and damaged tissue. We have studied the role of complement 3 (C3) in a mouse model of ventilator-induced lung injury (VILI). Compared with sham-treated wild type (WT) mice, ventilated WT mice have reduced total bronchoalveolar lavage (BAL) cells; and elevated activities of thrombin and matrix metalloproteinases (MMPs), such as gelatinase/collagenase in the BAL fluid. In contrast, these parameters in ventilated C3 null mice are not significantly different from sham-treated WT and C3 null mice. In mechanically ventilated mice, thrombin activity and MMPs are lower in C3 null mice than in WT mice and are inversely correlated with total single BAL cells. C3 activation is associated with MMP activation in vitro. Pretreatment of WT mice with humanized cobra venom factor, which inactivates C3, reduces C3 deposition in the lung and increases total BAL cells in VILI. We propose that C3 is involved with VILI and inhibition of complement activation may be a potential therapeutic strategy.     

Inhibitory effect of acetamide-45 on airway inflammation and phosphodiesterase 4 in allergic rats

AIM: To determine the effects of acetamide-45 on respiratory function, airway inflammation, and the activity of phosphodiesterase 4 (PDE4) in allergic rats. METHODS: Rats were sensitized by a single intramuscular injection with ovalbumin (OVA) and were challenged with ovalbumin applied by using an aerosol repeatedly for 7 d after 2 weeks. Acetamide-45 at concentrations of 5, 10, or 30 mg/kg was then administered by intraperitoneal injection. Changes in dynamic lung compliance and lung resistance, the accumulation of inflammatory cells in bronchoalveolar lavage, PDE4 activity, and the concentration of interleukin-4 in rat lung tissue were determined. RESULTS: Seven days of treatment with acetamide-45 prevented eosinophil accumulation in allergic rats. At doses of 5, 10, and 30 mg/kg, acetamide-45 decreased lung resistance to 0.20+/-0.04, 0.25+/-0.07, and 0.22+/-0.05 cmH2O.s(-1).mL(-1), respectively (P<0.05 vs OVA), and it also increased dynamic lung compliance to 0.41+/-0.07, 0.39+/-0.06, and 0.42+/-0.09 mL/cmH2O (P<0.05 vs OVA). After being treated with different doses of acetamide-45, the PDE4 activities in lung tissue were 281+/-55, 273+/-57, and 238+/-36 nmol.g(-1).min( -1) (P<0.05 vs OVA), and the concentrations of interleukin-4 in lung tissue were 6.22+/-1.13, 5.95+/-1.20, and 5.68+/-2.20 microg/protein (P<0.05 vs OVA). CONCLUSIONS: Acetamide-45 was found to improve respiratory function and inhibit airway inflammation in this animal model, and the PDE4 activity of lung tissue was obviously inhibited. Acetamide-45 was an effective anti-inflammatory agent in respiratory inflammation, and the mechanism of its action might depend on inhibition of PDE4.     

OZONE-INDUCED DNA SINGLE STRAND BREAKS IN HUMAN AND GUINEA PIG LUNG CELLS IN VIVO

Ozone O3 has been postulated to induce DNA damage and has been shown to be mildly tumorigenic in some studies utilizing long-term rodent exposures. We investigated lung DNA damage induced by controlled O3 exposure in vivo in guinea pigs and human subjects. We specifically examined DNA single-strand breaks SSB using the single-cell gel electrophoresis assay. Guinea pigs were exposed for 2 h to air, 0.4 ppm O3, or 1.0 ppm O3, and lung cells were collected by bronchoalveolar lavage BAL and bronchial scraping within 1 h after exposure. Both the 0.4 and 1.0 ppm O3 exposures induced significant increases in SSB in both the BAL cells and tracheal cells as indicated by an increased cell DNA length in electrophoresized agarose gel. The increase in DNA SSB was a more sensitive biomarker of exposure compared to more traditional biomarkers BAL total protein and lactate dehydrogenase, alterations in BAL cell differential, which changed only at the 1.0 ppm exposure. In an initial study with human volunteers, BAL and bronchial epithelial cells were collected from human volunteers 1-2 h after an air or 0.4 ppm O3 exposure in vivo without exercise. BAL cells primarily macrophages and bronchial epithelial cells showed no change in DNA SSB compared to the air-exposed controls. In a second study, DNA SSB in bronchial epithelial cells and BAL cells collected from exercising subjects exposed to 0.4 ppm O3 were not altered by steroid prednisone, beclomethasone pre- treatment compared to placebo treatment. However the bronchial epithelial cell DNA SSB values in the O3-exposed, placebo-pretreated group were significantly increased compared to values air or O3 exposed, no exercise in the first study. The dosimetry of O3 deposi- tion in the guinea pig and human subjects appeared similar based on the amount of 18O derived from 18O-labeled O3 found in the BAL cell fraction. These data suggest that O3 exposure at 0.4 ppm induces DNA SSB in rodent and human lung cells, although the effect of exercise on the increase of human lung cell SSB is unclear. Formation of DNA SSB may be an indicator of the tumorigenic potential of O3. Additionally, DNA SSB can potentially be a good biomarker of O3 exposure in humans and animal model systems. 3     

维甲酸对肺纤维化大鼠肺成纤维细胞胶原表达的调控机制

目的　研究维甲酸 (RA)对肺纤维化大鼠肺成纤维细胞胶原表达的影响及机制。方法　正常组、纤维化组和RA治疗组 3组大鼠分别于肺纤维化模型制备后d 2 8处死 ,取肺组织进行肺成纤维细胞的原代培养。用Northernblot方法检测原代培养肺成纤维细胞前胶原α1(Ⅰ )mRNA表达 ,[3 H] 脯氨酸参入法测定胶原蛋白合成 ,凝胶迁移率法检测核因子AP 1活性 ,RT PCR方法测维甲酸受体的mRNA表达。结果　RA可诱导肺成纤维细胞RXRαmRNA的表达 ,使肺纤维化时增高的AP 1活性下调 ,并抑制前胶原α1(Ⅰ )mRNA表达及胶原蛋白合成。结论　肺纤维化时肺成纤维细胞AP 1活性增高可能是导致胶原过度表达的重要机制。RA可能通过诱导肺成纤维细胞RXRα的表达使增高的AP 1活性得以抑制 ,从而下调胶原基因的表达。     

Effects of inhaled ozone on pulmonary immune cells critical to antibacterial responses in situ

The goal of this study was to examine effects from repeated exposure to ozone (O3) on immune cells involved in cell-mediated antibacterial responses in the lungs. Rats exposed to 0.1 or 0.3 ppm O3 for 4 h/day, 5 days/wk, for 1 or 3 wk were analyzed for the ability to clear an intrapulmonary challenge with Listeria monocytogenes or had their lungs processed to obtain pulmonary alveolar macrophages (PAM) and lung-associated lymphocytes for analyses of select cell functions and surface marker expression. The results indicate that repeated inhalation exposure to O3 affected local cell-mediated immunity (CMI) responses as evidenced by effects on clearance of Listeria. However, this modulation was not consistently dependent on exposure concentration or duration. Short-term repeat exposures had more effect on host resistance than did the more prolonged regimen, with rats exposed to 0.1 ppm O3 most adversely impacted. Clearance patterns suggest modifications in innate resistance following 1 wk of exposure to 0.1 ppm O3, but no similar effect following a 3-wk regimen. Exposure to 0.3 ppm O3 appeared to affect both innate and acquired resistance after a 1-wk regimen, but mainly the former after an additional 2 wk of exposure. We conclude that these two mechanisms of resistance are differentially affected by O3 and that distinct time- and O3 concentration-dependent adaptation phenomena evolve for each; that is, in situ adaptation to higher levels of O3 may occur more readily with acquired than with innate/PAM-dependent resistance. A similar pattern of inconsistent effect on PAM and lung-associated lymphocytes was also evident. For example, while 3-wk exposures had a greater effect on PAM reactive oxygen intermediate ROI production, evidence for a significant effect on antibacterial activity was only notable among PAM from rats exposed for 1 wk. Among lung lymphocytes, while 3-wk exposure to 0.1 ppm O3 led to a significant increase in CD25 expression, there was no corresponding increase in responsivity to concanavalin A (ConA); only among cells from 1-wk-exposed rats did lymphoproliferative responses increase. Though investigations of altered immune cell cytokine receptor expression/binding activity are ongoing, results herein provide further evidence to support our longstanding hypothesis that some well-documented effects of O3 exposure on human health are quite likely linked to changes in local immune cell (i.e., PAM and lung-associated lymphocytes) functions, with the latter being related to changes in the capacities of these cells to interact with immunoregulatory cytokines.     

EFFECTS OF INHALED OZONE ON PULMONARY IMMUNE CELLS CRITICAL TO ANTIBACTERIAL RESPONSES IN SITU

The goal of this study was to examine effects from repeated exposure to ozone (O 3) on immune cells involved in cell-mediated antibacterial responses in the lungs. Rats exposed to 0.1 or 0.3 ppm O 3 for 4 h/day, 5 days/wk, for 1 or 3 wk were analyzed for the ability to clear an intrapulmonary challenge with Listeria monocytogenes or had their lungs processed to obtain pulmonary alveolar macrophages (PAM) and lung-associated lymphocytes for analyses of select cell functions and surface marker expression. The results indicate that repeated inhalation exposure to O 3 affected local cell-mediated immunity (CMI) responses as evidenced by effects on clearance of Listeria. However, this modulation was not consistently dependent on exposure concentration or duration. Short-term repeat exposures had more effect on host resistance than did the more prolonged regimen, with rats exposed to 0.1 ppm O 3 most adversely impacted. Clearance patterns suggest modifications in innate resistance following 1 wk of exposure to 0.1 ppm O 3, but no similar effect following a 3-wk regimen. Exposure to 0.3 ppm O 3 appeared to affect both innate and acquired resistance after a 1-wk regimen, but mainly the former after an additional 2 wk of exposure. We conclude that these two mechanisms of resistance are differentially affected by O 3 and that distinct time- and O 3 concentration-dependent adaptation phenomena evolve for each; that is, in situ adaptation to higher levels of O 3 may occur more readily with acquired than with innate/PAM-dependent resistance. A similar pattern of inconsistent effect on PAM and lung-associated lymphocytes was also evident. For example, while 3-wk exposures had a greater effect on PAM reactive oxygen intermediate ROI production, evidence for a significant effect on antibacterial activity was only notable among PAM from rats exposed for 1 wk. Among lung lymphocytes, while 3-wk exposure to 0.1 ppm O 3 led to a significant increase in CD25 expression, there was no corresponding increase in responsivity to concanavalin A (ConA); only among cells from 1-wk-exposed rats did lymphoproliferative responses increase. Though investigations of altered immune cell cytokine receptor expression/binding activity are ongoing, results herein provide further evidence to support our longstanding hypothesis that some well-documented effects of O 3 exposure on human health are quite likely linked to changes in local immune cell (i.e., PAM and lung-associated lymphocytes) functions, with the latter being related to changes in the capacities of these cells to interact with immunoregulatory cytokines.