Molecular mechanism of alveolar epithelial healing process in acute lung injury : roles of KGF and transcription factor on lung repair

1.肺泡II型细胞生长因子对肺损伤的影响：我们已经证明，角质细胞生长因子（KGF）是肺泡II型细胞增殖和分化的有效因子。我们已经研究了KGF是否会预防博莱霉素诱导的肺损伤和纤维化。重组人KGF（rhKGF）分别于博莱霉素注射前48 h和注射后24 h行气管内注射。KGF治疗可防止博莱霉素诱导的大鼠肺中（1）体重减轻，（2）肺总容量降低，（3）I型和III型胶原及其mRNA的积累，以及（4）表面活性蛋白A（SP-A）、SP-B和SP-C mRNA的放射自显影银颗粒减少。KGF在酸（0.1N HCl）滴注前72小时预处理也可预防酸滴注所致的肺损伤，但后处理无效。2.为了阐明预防机制，我们检测了转录因子、C/EBP家族成员和表面活性蛋白在急性肺损伤和C/EBP缺陷小鼠肺中的表达。C/EBP家族成员在急性肺损伤中的差异表达。特别是，C/EBPdδ在一些肺泡II型细胞中表达，这表明存在细胞亚型。此外，C/EBPα缺陷小鼠出现类似肺泡蛋白沉积症的肺部异常。分子生物学研究表明，C/EBPα基因缺陷小鼠肺组织中SP-C mRNA表达增加，提示C/EBPα可能对SP-C基因具有抑制性调节作用。3.为了探讨KGF预防肺损伤的机制，我们检测了KGF是否预防另一种器官损伤，脑缺血诱导的沙土鼠海马区神经元死亡。组织学和TUNEL研究显示其对神经元死亡有抑制作用。4.未来计划：我们将研究腺病毒介导的KGF基因转染对肺损伤和肺纤维化的预防作用。

1. Effect of growth factor for alveolar type II cells on lung injury: We have demonstrated that keratinocyte growth factor (KGF) is a potent factor for proliferation and differentiation of alveolar type II cells. We have examined whether KGF would prevent bleomycin-induced lung injury and fibrosis. Recombinant human KGF(rhKGF) was injected intratracheally at 48h before and 24h after bleomycin. KGF treatment prevents (1)loss of body weight, (2)reduced total lung capacity, (3)accumulation of collagen type I & III and their mRNAs, and (4)decreased autoradiographic silver grains for surfactant protein A(SP-A), SP-B and SP-C mRNAs in the rat lungs induced by bleomycin. Lung injury due to acid instillation was also prevented by KGF pretreatment at 72h before acid (0.1N HCl) instillation, but not by posttreatment. 2. To clarify the mechanisms of prevention, we were examining the expression of the transcription factor, C/EBP family members, and the surfactant proteins in acute lung injury and in lungs of C/EBP deficient mice. C/EBP family members are differentially expressed in the lung with acute injury. Especially, C/EBPdδ is expressed in some of alveolar type II cells, which suggests the presence of a subtype of the cell. Further C/EBPα-deficient mice had a pulmonary abnormality resembling pulmonary alveolar proteinosis. Molecular study demonstrated overexpression of SP-C mRNA in the lungs of C/EBPα-deficient mice, which suggests C/EBPα may have an inhibitory regulation on SP-C gene. 3. To investigate the mechanism of preventing lung injury by KGF, we have examined whether KGF prevents another organ injury, brain ischemia-induced neuronal death in hippocampal region in gerbils. Histological and TUNEL studies showed its inhibition on neuronal death. 4. Future project: We are going to study gene transfer of KGF using adeno-virus intratracheally for preventing lung injury and fibrosis.