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This study detailed the sequence of recurring inflammatory events associated with episodic allergen exposures of mice resulting in airway hyperreactivity, sustained inflammation, goblet-cell hyperplasia, and fibrogenesis that characterize a lung with chronic asthma. Ovalbumin (OVA)-sensitized female BALB/cmice were exposed to saline-control or OVA aerosols for 1 h per day for episodes of 3 d/wk for up to 8 wk. Lung inflammation was assessed by inflammatory cell recoveries using bronchoalveolar lavages (BAL) and tissue collagenase dispersions. Cell accumulations were observed within airway submucosal and associated perivascular spaces using immunohistochemical and tinctorial staining methods. Airway responsiveness to methacholine aerosols were elevated after 2 wk and further enhanced to a sustained level after wk 4 and 8. Although by wk 8 diminished OVA-induced accumulations of eosinophils, neutrophils, and monocyte-macrophages were observed, suggesting diminished responsiveness, the BAL recovery of lymphocytes remained elevated. Airway but not perivascular lesions persisted with a proliferating cell population, epithelial goblet-cell hyperplasia, and evidence of enhanced collagen deposition. Examination of lung inflammatory cell content before the onset of the first, second, and fourth OVA exposure episodes demonstrated enhancements in residual BAL lymphocyte and BAL and tissue eosinophil recoveries with each exposure episode. Although tissue monocyte-macrophage numbers returned to baseline prior to each exposure episode, the greatest level of accumulation was observed after wk 4. These results provide the basis for establishing the inflammatory and exposure criteria by which episodic environmental exposures to allergen might result in the development of a remodeled lung in asthma. [ABSTRACT FROM AUTHOR]

Short-term exposure of rats to ozone results in lung inflammation characterized by increased permeability damage and the infiltration of neutrophils into the airways. The present study compared these ozone-induced inflammatory responses in different strains of male rat, Brown Norway rats from Charles River Laboratories, Inc. (BN-CRL), and Harlan Sprague Dawley, Inc. (BN-HSD), and Fischer 344 (F344), Sprague-Dawley (SPD), and Wistar (WSTR) male rats from Hilltop Lab Animals, Inc. Ozone-induced permeability damage was indicated by recoveries of bronchoalveolar lavage fluid (BALF) albumin 20 h following single exposures of 6 h to either air or 1 ppm or 2 ppm O [sub 3]. Although BALF albumin recoveries from air-exposed rats were not significantly different between strains, ozone exposures resulted in a range of enhancements of BALF albumin of 2-, 9-, 17-, 7-, and 20-fold following exposures of BN-CRL, BN-HSD, F344, SPD, and WSTR rats to 2 ppm ozone, respectively. Concomitant strain differences in the number of ozone-induced BAL-recoverable neutrophils were not observed, except for BN-CRL rats, which demonstrated significantly lower numbers. However, the degree of ozoneinduced permeability damage did directly correspond to differences observed in the numbers of neutrophils and eosinophils in the peripheral blood and collagenase tissue digest of lavaged and perfused lungs prior to ozone exposure. Ozone-resistant BN-CRL rats exhibited the highest numbers of blood and lung tissue neutrophils and eosinophils when compared with ozone-susceptible WSTR rats exhibiting the lowest number of these granulocytes. These data suggested that the presence of high numbers of blood and tissue granulocytes at the onset of short-term ozone exposures might provide a certain degree of protection against subsequent pathological events. [ABSTRACT FROM AUTHOR]