Molecular pathophysiology of pulmonary fibrosis in oxygen poisoning

8周龄小鼠(C57BL/6J)按如下方法饲养。在100%吸氧实验中，重复上述参数。雄性小鼠20只，体重21~24g，随机分为4组：(1)对照组5只，置于常压氧气中；(2)高氧暴露组15只，分别在以0.8L/min的速度充氧的金属舱中饲养1天、2天、3天。与氧气室相连的血氧仪(JKO-25LJII，日本JIKCO株式会社)显示95%-100%的氧气浓度。在75%氧气暴露实验中，10只雄性小鼠随机分为两组：(1)对照组，5只；(2)另5只作为高氧暴露组，分别在金属舱中饲养9天。在60%和40%氧气暴露实验中，10只雄性小鼠随机分为两组：…组另设对照组5只，高氧暴露组5只，分别在金属舱内饲养4周。在6%氧气暴露实验中，10只雄性小鼠随机分为两组：(1)对照组5只，在常压氧气中饲养；(2)另5只作为低氧暴露组，分别在金属舱内饲养3天。在这些实验中，我们不能在小鼠身上建立明显的肺纤维化。我们已经阐明了高氧暴露引起的小鼠弥漫性肺泡损伤(DAD)的转录谱，并显示表面活性物质相关蛋白C(SP-C)的mRNA水平显著下调，而c-Myc的mRNA水平显著上调(Int J Legal Med 2008；122：373-83)。为了更准确地确定这种肺泡功能障碍的分子病理生理机制，本研究还对其他表面活性物质相关基因和细胞凋亡相关基因进行了检测。我们的研究表明：(1)高氧诱导4-羟基-2-壬烯醛(HNE)氨基酸Michael加合物和c-Myc蛋白水平显著升高；(2)高氧暴露下肺表面活性物质相关蛋白A(SP-A)和表面活性物质相关蛋白C(SP-C)的mRNA水平显著下调，而c-Myc和Bax的mRNA水平显著上调。这些结果提示：(1)c-Myc和Bax的过表达意味着细胞凋亡的进展，从而导致活性氧(ROS)产生的恶性循环；(2)多条凋亡途径似乎参与了SP-A和SP-C的mRNAs水平的降低，进而导致肺衰竭的严重风险。较少

Eight-week-old mice (C57BL/6J) were bred as follows. In the 100 % oxygen-exposure experiment, the parameters were duplicated. Twenty male mice weighing 21-24 g were randomly divided into four groups as follows: (1) five mice for the control group were kept in atmospheric oxygen; (2) another fifteen mice to be used as the hyperoxia-exposure group were kept in a metallic chamber for 1 day, 2 days, and 3 days, respectively, into which oxygen flowed at a rate of 0.8 liter / min. The oximeter (JKO-25LJII, JIKCO Ltd, Japan), which was connected with the chamber, indicated 95-100 % oxygen concentration. In the 75 % oxygen-exposure experiment, ten male mice were randomly divided into two groups as follows: (1) five mice for the control group were kept in atmospheric oxygen; (2) another five mice to be used as the hyperoxia-exposure group were kept in a metallic chamber for 9 days, respectively.In the 60 % oxygen- and 40 % oxygen-exposure experiments, ten male mice were randomly divided into tw … More o groups as follows: (1) five mice for the control group were kept in atmospheric oxygen; (2) another five mice to be used as the hyperoxia-exposure group were kept in a metallic chamber for 4 weeks, respectively. In the 6 % oxygen-exposure experiment, ten male mice were randomly divided into two groups as follows: (1) five mice for the control group were kept in atmospheric oxygen; (2) another five mice to be used as the hypoxia-exposure group were kept in a metallic chamber for 3 days, respectively. In these experiment, we could not establish marked pulmonary fibrosis in mice. We have already elucidated transcript profiling of diffuse alveolar damage (DAD) induced by hyperoxia exposure in mice and showed that the mRNA level of surfactant-associated protein C (SP-C) is significantly down-regulated, while that of c-Myc is significantly up-regulated (Int J Legal Med 2008;122:373-83). To confirm the molecular pathophysiology of this alveolar dysfunction more precisely, other surfactant-associated genes and apoptosis-related genes were examined in this Grants-in-Aid for Scientific Research (C). Our study showed that: (1) hyperoxia induces a marked increase in protein levels of 4-hydroxy-2-nonenal (HNE)-amino acid Michael adduct and c-Myc; and (2) mRNA levels of surfactant-associated protein A (SP-A) and surfactant-associated protein C (SP-C) are significantly down-regulated, while those of c-Myc and Bax are significantly up-regulated in hyperoxia exposure. These results suggest that: (1) c-Myc and Bax overexpression means progression of apoptosis, which brings about a malignant cycle of reactive oxygen species (ROS) production; and (2) multiple apoptotic pathways seem to be involved in decreases in levels of mRNAs for SP-A and SP-C, in turn causing the serious risk for pulmonary collapse. Less