Develpoment of allergic asthma model using rat airway smooth muscle

Choi, In Seon; Koh, Young Il; Jang, An Soo; Na, Hyun Ju; Lee, Hyun Chul; Lee, Mee Kyung; Lee, Jong Un

Abstract

Airway hyperresponsiveness is a consistent feature of asthma. Since the airway smooth muscle is hyperresponsive to a number of different stimuli operating through many different mechanisms, it is attractive to speculate that the abnormality may reside in the airway smooth muscle itself. Animal model of asthma is needed to unravel possible mechanisms underlying airway hyperresponsiveness and also to develop new therapeutic approaches. However, there are few reports showing that airway smooth muscle from animal asthma model is indeed hyperresponsive. In addition, sensitizing and provoking doses of allergen were different each other ambng the studies on animal asthma model. The aim of this study was to determine an appropriate sensitizing and provoking dose of allergen to induce a maximum airway hyperresponsiveness. Eighty-four male Sprague-Dawley rats were actively sensitized with a subcutaneous injection of 0, 10, or 1000/gg ovalbumin(OA) and 14 days later they were provoked with 0, 1, or 5 % OA aerosols. One day after the provocation, serum levels of OA-specific IgE, cell numbers in bronchoalveolar lavage fluid (BALF), and in vitro isometric contractile responses of the isolated tracheal smooth muscle(TSM) to 120 mM KC1, acetylcholine(ACh, 0.1~ 1000/micro meter), electrical field stimulation (EFS, 0.5~100Hz), serotonin(5-HT, 0.014 100/micro meter), and OA(10, 50, or 250 micro gram/ml) were measured. The results were as follows; 1) When 38 OA-sensitized rats were exposed to OA aerosols in vivo early asthmatic responses(EAR) were observed in 20(52.6%) rats. In vitro isometric contractile forces of TSM from rats with EAR were stronger than those from rats without EAR. 2) The maximal contractile responses to KC1 and EFS were significantly higher in rats only sensitized with OA compared with those in controls. The maximal response to ACh was significantly related to OA-specific serum IgE level(r=0.40, p%0.05), and the latter was in turn significantly related to the BALF eosinophil count(r=0.67, p<0.01). 3) When 10 microgram OA-sensitized rats were analyzed, the maximal response to KC1, ACh, EFS, and 250 micro gram/ml OA were lower in OA-provoked rats compared to those in saline-provoked control rats, in which 5% OA-provoked rats had a lower response than 1% OA-provoked rats. 4) The sensitivity of TSM to ACh was significantly higher in 10/micro gram OA-sensitized & OA-provoked rats, and the sensitivity to EFS was also significantly higher in 10/~g OA-sensitized & 5% OA-provoked rats compared to that in controls(p<0.05). 5) There was a significant correlation between the sensitivity of TSM to EFS and the counts of eosinophil or of lymphocytes in BALF(for eosinophil, r=-0.30; p<0.05, for lymphocyte, r=-0.35; p<0.05), or OA-specific serum IgE level(r=-0.46, p<0.01) in OA-sensitized & OA-provoked rats. This relationship was maintained in the data obtained only from 10 micro gram OA-sensitized & 5% OA-provoked rats. 6) The ratio of EFS-sensitivity to ACh-sensitivity was significantly lower in OA-sensitized & OA-provoked rats compared to that in controls or rats only sensitized with OA(p%0.05). 7) The Schultz-Dale phenomenon occurred in an in vitro dose-dependent manner. However, the inhaled provocation with OA in vivo resulted in a decrease in the contractile response to OA in vitro. There was a significant correlation between OA-specific serum IgE level and isometric response to 250 micro gram/ml OA(r=0.36, p<0.01). These results suggest that sensitization and provocation in vivo with OA in rats induces hypersensitivity of airway smooth muscle to cholinergic stimuli through an allergic inflammatory mechanism. The sensitivity was highest when sensitized to 10 micro gram OA and exposed to 5% OA aerosols.

Develpoment of allergic asthma model using rat airway smooth muscle

Abstract

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