Assessment for the mechanisms of anti-apoptotic effects of transcription factor MafB in alveolar macrophages of emphysematous lungs induced by cigarette smoke exposure

吸烟是慢性阻塞性肺疾病（COPD）最常见的危险因素，这是一个严重的世界性医学问题。COPD在生理上表现为不同程度的气流阻塞，在病理上表现为肺气肿。在吸烟者的肺部，由于自由基和氧化剂的增加，氧化应激升高。在这样的环境中，肺泡巨噬细胞（Ams）的功能发生了改变，它们在香烟烟雾（CS）毒性作用下的存活时间延长，其机制尚不清楚。我们之前证明了cs暴露小鼠的Ams中转录因子MafB上调。在这些小鼠的Ams中，mab对Maf识别元件的DNA结合能力也增加了。此外，我们建立了一个巨噬细胞系，可以过表达MafB，从而明确了MafB的作用。在cs提取物处理的细胞中，强制表达MafB可提高细胞活力，减少细胞凋亡的发生。CS暴露后，与对照细胞相比，MafB过表达细胞的Caspase-3活性受到抑制，而MafB过表达细胞的细胞色素c的释放与对照细胞没有差异。caspase-3 mRNA的表达未因MafB过表达而改变。另一方面，凋亡调节因子1 （Moap1）基因表达因MafB过表达而显著降低。其他调节caspase-3活性的基因，如活化因子1 （Apaf1）、p21^<CIP1/WAF1>、BclX_L和Bax的表达保持不变。这些结果表明，氧化应激增强的MafB表达通过caspase途径抑制AM细胞死亡，而不是通过线粒体途径。为了进一步评估MafB的作用，我们目前在人类清道夫受体启动子的控制下建立了只在巨噬细胞中特异性表达基因的显性阴性MafB表达小鼠（手稿正在准备中）。利用这只小鼠，我们正在评估mab在体内的作用。少

Cigarette smoking is the most common risk factor for the development of chronic obstructive pulmonary disease (COPD), a severe worldwide medical problem. COPD is characterized physiologically by various levels of airflow obstruction, and pathologically by findings of pulmonary emphysema. In the lungs of smokers, oxidative stress rises due to increase of free radicals and oxidants. The functions of alveolar macrophages (Ams) are altered in such an environment, and their survival is prolonged against toxicities of cigarette smoke (CS) by an unknown mechanism. We previously demonstrated that transcriptional factor MafB was upregulated in Ams from CS-exposed mice. DNA binding capacity of MafB for Maf recognition element was also increased in Ams from those mice. Furthermore, we established a macrophage cell line that can overexpress MafB, and thereby clarified the role of MafB. Forced expression of MafB heightened cell viability and attenuated the occurrence of apoptosis in cells treated w … More ith CS-extract. After CS exposure Caspase-3 activity was inhibited in MafB overexpressing cells compared to control cells, while the release of cytochrome c in MafB overexpressing cells was not different from those of control cells. mRNA expression of caspase-3 was not altered by MafB overexpression. On the other hand, modulator of apoptosis 1 (Moap1) gene expression was significantly reduced by MafB overexpression. The expressions of other genes which are regulating caspase-3 activity, such as activated factor 1 (Apaf1), p21^<CIP1/WAF1>, BclX_L, and Bax, remained unchanged. These results suggest that enhanced MafB expression by oxidative stress inhibits AM cell death through caspase pathway, not through mitochondrial pathway.In order to evaluate the role of MafB further, we currently establish dominant-negative MafB expressing mice under the control of human scavenger receptor promoter that enables specific gene expression only in macrophages (manuscript under preparation). Using this mouse, we are assessing the role of MafB in vivo. Less