The Effects Of Gaseous Formaldehyde Exposure On Mice Asthma Model With Ovalbumin Immunization

Asthma is a popular public disease with specific pathological feature of "airway allergic inflammation", which needs both allergen and atopy. Nowadays, environmental factors attract interests for their potential strong affection of asthma, even though it is not substantiated. Formaldehyde (FA) is a regular indoor air pollutant, which is reported that it is harmful for human health and it could cause human asthma and syndrome like asthma. In order to explore whether formaldehyde could involve in asthma and its function in the process of asthma, experiments in vivo and vitro were employed.In vivo experiment, B/c mice were randomly divided into 6 groups to establish the asthma animal model:saline group, OVA-immunized group, gaseous FA (0.5mg/m3, 3.0mg/m3) exposed OVA-immunized group and only FA (0.5mg/m3,3.0mg/m3) exposure group,6 mice for each. And then, MCH experiment was used to detect the lung function, including inspiratory resistance, expiratory resistance and dynamic lung compliance. Then bronchoalveolar lavage fluid was collected to count eosinophils. After that, lung was extract to prepare slices for histological observation with one side of it, and cytokines were measured with another side of the lung. Results showed that:airway hyperresponsiveness, airway remolding, pulmonary interleukin-4 and interleukin-6 secretion and eosinophil infiltration were significantly increased in the FA exposed OVA-immunized group, indicating that FA may involve in inducing and deteriorating asthma. In addition, compared with saline group, eosinophil infiltration in FA exposure groups, especially higher FA exposure group also showed significant increase.In vitro experiment, airway smooth muscle cells (ASMC) were cultured originally to detect activity by MTT method. At first, ASMC were exposed in a series of FA with different concentrations to choose a proper dose of FA, which could decrease ASMC's activity but could not induce irreversible fetal destroy. Then ASMC was exposed in both FA of the certain dose and IL-4. Results presented that FA exposure alone could decrease ASMC's activity, whereas single IL-4 exposure could increase ASMC's activity significantly, and the combined exposure still could irritant the increase of activity.Therefore, based on the previous results, it is found that FA, as a small molecular environmental factor, it could effect the process of asthma. Concerned the mechanism, we concluded that FA may involve in the process of asthma through two pathways. On the one side, FA may aggravate asthma's symptoms as an adjuvant-like, which is supported by the results of FA exposure and OVA immunization groups. On the other side, in the FA exposure alone groups, especially in the higher concentration group, the ratio of eosinophils and total white cells, the content of IL-4 and IL-6 reflected significant increase even without dramatic changes of airway hyperresponsiveness and histological slices. It affirmed that FA played its inflammatory function to smooth the process of asthma. Meantime, the content of IFN-γdid not show obvious changes, proving the balance of Th1/Th2 populations was broken and tended to Th2 populations. In vitro experiment, IL-4 could strongly increase activity of ASMC even this increase was inhibited a little with combine exposure of IL-4 and FA. However, FA may incite airway or other cells to release IL-4, inflammatory factors or cytokines, in order to increase ASMC's increment, and then the risk of asthma.