甲醛预暴露与微生物气溶胶吸入对大鼠呼吸系统的协同损伤效应研究

摘要

目的 探讨甲醛预暴露与微生物气溶胶吸入对大鼠呼吸系统的协同损伤效应.方法 6周龄雄性Wistar大鼠25只(购自中国科学院实验动物中心),体质量(160±10)g,按数字表法随机分为正常对照组(6只)、甲醛吸入组(6只)、微生物气溶胶吸入组(6只)、甲醛与微生物气溶胶联合吸入组(7只).正常对照组:普通室内环境中饲养生长28 d.甲醛吸入组:以舱内(3.1 ±0.2) mg/m3为稳定暴露浓度,每天吸入2h,连续吸入28 d.微生物气溶胶吸入组:吸入舱内微生物气溶胶浓度稳定在(0.5～1.0)×107 cfu/m3,每天吸入2h,连续吸入暴露28 d.甲醛与微生物气溶胶联合吸入组:每天甲醛暴露2h后,暴露舱通新鲜空气45 min,再行微生物暴露2h,连续暴露28 d.采用动态气溶胶染毒暴露系统建立大鼠染毒暴露模型,用ELISA方法测血清免疫球蛋白M,发光比色法检测血清超氧化物歧化酶活性,HE染色法检测肺组织结构损伤,TUNNEL原位显色法检测肺组织细胞凋亡情况,Gram染色检测大鼠各级支气管及肺泡腔细菌残留情况.结果 与对照组相比,微生物气溶胶吸入组,大鼠血清IgM水平升高明显,甲醛和微生物联合吸入组升高更显著[(0.35 ±0.09) g/L];3个实验组大鼠血清SOD活性增加,其中甲醛和微生物联合吸入组SOD活性[(2.22 ±0.25)×106 U/L]明显高于其他两单因素暴露组[(1.50±0.37) ×106 U/L与(1.58 ±0.34)×106 U/L].形态学观察结果显示,3个实验组大鼠肺泡间隔增宽、肺间质水肿、肺组织内炎性细胞侵润,以甲醛和微生物联合吸入组病理学改变最明显.TUNNEL检测结果表明,甲醛和微生物联合吸入组大鼠肺组织内凋亡细胞数明显增加.Gram染色结果显示,甲醛和微生物联合暴露后经2h正常通气停留,大鼠细支气管及肺泡腔内残留细菌数较微生物单因素暴露组明显增多.结论 甲醛预暴露明显促进微生物气溶胶吸入暴露后对大鼠肺组织的损伤效应,并降低肺组织对异源性污染物的清除能力.%Objective To investigate the synergistic effect of formaldehyde pre-exposure on the damage to the respiratory system in rats after microbial aerosol inhalation.Methods The intoxication model was established in rats by the dynamic aerosol exposure system.Serum IgM concentration and SOD activity were measured by ELISA and luminescence assay respectively.Morphologic injury of the lung tissue was detected by HE staining.Tunnel chromogenic in-situ detection was used to detect the apoptosis of lung epithelial cells and Gram staining was performed to detect the capacity of lung epithelial cells in bacterial clearance.Results Serum IgM levels in rats increased significantly,after microbial aerosol inhalation,when compared with that of the control group,with the serum IgM levels of the formaldehyde combined with microbial aerosol inhalation group increased more significantly [(0.35 ±0.09) g/L].The serum SOD activity of the experimental groups all increased,with the level of the formaldehyde combined with microbial aerosol inhalation group [(2.22 ± 0.25) × 106 U/L] being significantly higher than that of the 2 other groups [(1.50 ±0.37) × 106 U/L] and [(1.58 ± 0.34) × 106 U/L].Morphological observation showed that widened alveolar septum,interstitial edema and inflammatory cell infiltration could be clearly noted in the lung tissue of the 3 experimental groups,with the pathological changes in the formaldehyde combined with microbial aerosol inhalation group being most significant.Tunnel detection also indicated that the nnmber of apoptotic cells in the lung tissue for the formaldehyde combined with microbial aerosol inhalation group increased significantly.Gram staining showed that the number of residue bacteria in the rat bronchiole for the rats of the formaldehyde combined with microbial aerosol inhalation group after 2-hour air intervention was significantly more than that of the simple bacteria exposure group.Conclusions Formaldehyde pre-exposure combined with microbial aerosol inhalation could induce synergistic damage to the rat lung tissue and decrease the capacity of the lung tissue to clear out heterogeneous pollutants.