Repeated subacute ozone exposure of inbred mice: airway inflammation and ventilation

Pulmonary inflammation induced by subacute ozone is augmented in adiponectin-deficient mice: role of IL-17A

Pulmonary responses to ozone, a common air pollutant, are augmented in obese individuals. Adiponectin, an adipose-derived hormone that declines in obesity, has regulatory effects on the immune system. To determine the role of adiponectin in the pulmonary inflammation induced by extended (48-72 h) low-dose (0.3 parts per million) exposure to ozone, adiponectin-deficient (Adipo(-/-)) and wild-type mice were exposed to ozone or to room air. In wild-type mice, ozone exposure increased total bronchoalveolar lavage (BAL) adiponectin. Ozone-induced lung inflammation, including increases in BAL neutrophils, protein (an index of lung injury), IL-6, keratinocyte-derived chemokine, LPS-induced CXC chemokine, and G-CSF were augmented in Adipo(-/-) versus wild-type mice. Ozone also increased IL-17A mRNA expression to a greater extent in Adipo(-/-) versus wild-type mice. Moreover, compared with control Ab, anti-IL-17A Ab attenuated ozone-induced increases in BAL neutrophils and G-CSF in Adipo(-/-) but not in wild-type mice, suggesting that IL-17A, by promoting G-CSF release, contributed to augmented neutrophilia in Adipo(-/-) mice. Flow cytometric analysis of lung cells revealed that the number of CD45(+)/F4/80(+)/IL-17A(+) macrophages and γδ T cells expressing IL-17A increased after ozone exposure in wild-type mice and further increased in Adipo(-/-) mice. The IL-17(+) macrophages were CD11c(-) (interstitial macrophages), whereas CD11c(+) macrophages (alveolar macrophages) did not express IL-17A. Taken together, the data are consistent with the hypothesis that adiponectin protects against neutrophil recruitment induced by extended low-dose ozone exposure by inhibiting the induction and/or recruitment of IL-17A in interstitial macrophages and/or γδ T cells.

Mouse strain modulates the role of the ciliated cell in acute tracheobronchial airway injury-distal airways

Understanding cellular repair mechanisms in vivo has been advanced through the use of well-defined injury and repair models and their application to knockout and transgenic animals, primarily mice generated in a variety of background strains. However, little is known concerning the effect that mouse strain itself has on the interpretation and comparability of observations when the strain used for genetic manipulation is not the strain used to develop the model. We compared acute bronchiolar injury and repair in three strains of mice used in knockout mouse development (C57BL/6, 129/TerSv, and 129/SvEv) to the model strain (Swiss Webster) after treatment with the same dose of naphthalene and sacrificed at 1, 2, 4, 7, and 14 days after treatment. Extent of Clara cell toxicity and exfoliation was identical in the distal airways of all strains. There were significant strain-related differences in ciliated cell squamation, initiation and duration of proliferation, epithelial differentiation, and time to completion of epithelial repair. We conclude that ciliated cells play a prominent role in repair of distal airway injury, but that all phases of the repair process differ by strain. In addition, our findings reinforce that control animals must be of the same strain, ideally litter mates, when transgenic or knockout mice are used for the study of airway repair processes and mechanisms.

Urban air particulate inhalation alters pulmonary function and induces pulmonary inflammation in a rodent model of chronic bronchitis

Epidemiological studies have reported increased morbidity in human populations following inhalation of elevated levels of urban particulate matter. These responses are especially prevalent in populations with chronic obstructive pulmonary diseases, including chronic bronchitis. Toxicological studies have reported altered pulmonary function and increased pulmonary inflammation following particulate inhalation in the laboratory setting. However, most of these studies have utilized artificial particles that may not accurately mimic outdoor air pollutant conditions. Few studies have utilized actual urban air particle samples in inhalation studies. In the present study, the effects of inhaled concentrated urban air particulates on pulmonary function and pulmonary inflammation are addressed. Normal rats and rats with chronic bronchitis induced by approximately 200 ppm SO(2) for 6 wk were subsequently subjected to filtered air or concentrated air particles (CAPs). Twelve rats per group in 4 groups (48 rats total) were exposed for 5 h/day for 3 consecutive days. The CAPs aerosol levels were 206, 733, and 607 microg/m(3) (MMAD = 0.18 microm, sigma(g) = 2.9) on days 1, 2, and 3, respectively. Following the final day of exposure, pulmonary function parameters, including peak expiratory flow (PEF), tidal volume (TV), respiratory frequency (RF), and minute volume (MV), were measured and compared to preexposure baseline levels. Twenty-four hours following the final day of exposure, bronchoalveolar lavage was performed for total cell counts, differential cell counts, and total lavage protein levels. Pulmonary responses to CAPs in chronic bronchitic animals indicated a significant increase in tidal volume as well as peak expiratory flow. In CAPs-exposed animals without underlying bronchitis, significantly increased tidal volume was observed. Significant pulmonary inflammation was observed in the CAPs-exposed animals, particularly those with chronic bronchitis. Significant increases in neutrophils, lymphocytes, and total lavage protein were observed. These results suggest two distinct mechanistic responses to inhaled particles: a stress-type pulmonary function response marked by increases in flow and volume, that is, deeper breathing; and acute pulmonary inflammation marked by cellular influx, particularly neutrophils. From these data it is concluded that inhaled urban air particles alter pulmonary breathing parameters and increase pulmonary inflammation.

Inhibition of airway inflammation in rDer f 2-sensitized mice by oral administration of recombinant der f 2

Recombinant Der f 2 (rDer f 2) is a promising new allergen expected to improve the diagnosis and immunotherapy of house dust mite allergy and to further immunological studies. To evaluate the hyposensitizing activity of rDer f 2 to mite allergy, we examined the effect of its oral administration on allergic inflammation in A/J mice immunized with mite allergens. A/J mice immunized with rDer f 2 alone or rDer f 2 + crude mite extract were orally given 0 (control), 0.01, 0.1, or 1 mg/day of rDer f 2 for 4 weeks, followed by an antigen inhalation challenge. Twenty-four hours after rDer f 2 inhalation, control animals experienced severe leukocyte influx into the airway. The infiltrating cells were mainly neutrophils, with some eosinophils and lymphocytes. The concentrations of IL4, IFNgamma, and soluble ICAM-1 in the bronchial alveolar lavage fluid increased twofold compared with values before rDer f 2 inhalation. In contrast, inflammation was significantly suppressed in mice given 1 mg/day of rDer f 2 orally for 4 weeks and partially suppressed in those fed 0.1 mg/day of the antigen. Plasma anti-rDer f 2 antibody levels were unchanged by oral rDer f 2 treatment. Mite extract inhalation challenge provoked neutophilia in rDer f 2 + mite-sensitized control mice, and this allergic reaction tended to decrease in sensitized mice fed 1 mg/day of rDer f 2 orally for 4 weeks. We conclude that rDer f 2 has hyposensitizing activities and may be useful in immunotherapy for house dust mite allergy.

Ozone-induced inflammation and altered ventilation in genetically susceptible mice: a comparison of acute and subacute exposures

We have examined whether the effects of acute (2 ppm/3 h) and subacute (0.3 ppm/72 h) ozone (O3) exposures on airways are mutually predictive. Inbred C57BL/6J (susceptible) and C3H/HeJ (resistant) mice are differentially responsive to inflammation induced by the 2 exposures. Breeding experiments and cosegregation analysis indicated that 2 separate genes control inflammatory responses: Inf (acute), Inf-2 (subacute). The genetic model was also used to examine the effects of both exposures on the magnitude and pattern of breathing. Results imply that mechanisms that control susceptibility to the 2 exposures are not the same, and that one response is not necessarily predictive of the other.