Effects And Mechanisms Of Aspergillus Fumigatus Spores On Lung Pathophysiology In Asthmatic Rats

Aspergillus fumigatus (A. fumigatus) is a uniquitous fungus and an important indoor and outdoor allergen. Its spore is so small that it can be easy to disperse in the airway. After colonizing into respiratory tract, spores will release of allergens and enzymes during germination of spores or after cell death. Because of itself allergenicity and released enzymes, more and more peoples think highly of A. fumigatus that may play an important role in the development of asthma, especially severe asthma. TLR2 is one of innate-immunity receptor family. It can recognize and bind A. fumigatus, and then produce many biological consequences. Therefore, it shows that the TLR2 on the bronchial epithelial is very important. However, effects of A. fumigatus spores on asthma and the changes of TLR2 on bronchial epithelial of animal asthma model treated with A. fumigatus remain obscure. Thus, in order to evaluate this issue in details, we decided to investigate the effect of A. fumigatus spores exposure on rat model of asthma and changes of TLR2 expression on bronchial epithelial in the present study.Part 1 Effects of Aspergillus fumigatus spores on airway construction and airway resistance in an asthmatic rat model Objective: we explored changes in airway construction and airway resistance in asthmatic rats treated with A. fumigatus spores before or after aerosol challenged.Method: Male Wistar rats were sensitized to ovalbumin (OVA) and challenged with aerosol OVA. All rats were divided into A and B groups. A or B group was to investigate the effects of A. fumigatus spores on asthmatic rats before or after undergoing OVA aerosol challenged, respectively. The parameters associated with airway inflammation,the percentage of goblet cell hyperplasia in the lumens, the amount of collagen deposition around bronchus , bronchial epithelial damage, total protein concentration in BALF and variation of airway resistances to Ach in all rats were measured. The total cells and differential cells count in BALF were also counted.Results: Asthmatic rats treated with A. fumigatus spores before or after OVA challenged have significantly increased percentage of goblet cell hyperplasia in the lumens, the enhanced variation of airway resistances to Ach compared with asthmatic rats without treatment of A. fumigatus spores. Furthermore, in contrast to asthmatic rats without treatment of A. fumigatus spores, asthmatic rats treated with A. fumigatus spores before OVA challenged had remarkably increased total protein concentration in BALF and the amount of collagen deposition around bronchus, and increased damages of bronchial epithelial cell junction, but A. fumigatus spores did not change airway inflammation of those rats significantly. However, asthmatic rats treated with A. fumigatus spores after OVA challenged had obviously increased neutrophilic leukocyte count in BALF compared with asthmatic rats without treatment of A. fumigatus spores.Conclusion: These data indicated that exposure to A. fumigatus spores aggravates epithelial damage, increases mucin expression, and enhances airway reactivity in an asthmatic rat model. Taken together, A. fumigatus spores may induce development of asthma and aggravate the symptoms of asthma.Part 2 Effects of Aspergillus fumigatus spores on expression of Toll-like receptor 2 on bronchial epithelial in asthmatic ratsObjective: we investigated the effects of A. fumigatus on expression of TLR2 on bronchial epithelial in asthmatic rat model.Method: Male Wistar rats were sensitized to OVA and were challenged with aerosol OVA. All rats were divided into A and B groups. A or B group was to investigate the effects of A. fumigatus spores on expression of TLR2 on bronchial epithelial in asthmatic rats before or after undergoing OVA aerosol challenged, respectively. The expression of TLR2 mRNA and protein of TLR2 on bronchial epithelial were detected by semi-quantitative RT-PCR and immunohistochemical analysis, respectively. And the IL-5 in BALF of all rats were measured by ELISA.Results: A. fumigatus not only leads to up-regulation of TLR2 mRNA(0.742±0.050) and IL-5 in BALF[(624.12±60.2)pg/ml] in asthma rats with A. fumigatus spores before challenged compared with those of asthma rats without A. fumigatus spores｛TLR2:(0.571±0.041, P﹤0.05),IL-5:[(436.65±41.2)pg/ml, P﹤0.05]｝, but also results in significantly changes in TLR2 protein expression on the bronchial epithelial between two groups. Howere, A. fumigatus spores do not increase TLR2 mRNA of lung and TLR2 protein expression on the bronchial epithelial in asthma rats with A. fumigatus spores after challenged.Conclusion: The up-regulation of TLR2 in the asthmatic rats supports the idea of a role for TLR2 in asthmatic rat model. More interestingly, TLR2 may play an important role in on bronchial epithelial damage and further mediating aggravations of physiopathological changes which are involved in effects by A. fumigatus on the asthmatic rats.