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，COPD是一个严重的世界性医学问题。COPD的生理特征是不同程度的气流阻塞，病理特征是肺气肿。在吸烟者的肺部，由于自由基和氧化剂的增加，氧化应激增加。在这种环境中，肺泡巨噬细胞(Ams)的功能发生了变化，并通过一种未知的机制延长了它们的存活时间。我们先前证明了转录因子MafB在CS暴露的小鼠AM中上调。小鼠AM中MafB与Maf识别元件的DNA结合能力也增强。此外，我们建立了一个能过表达MafB的巨噬细胞系，从而阐明了MafB的作用。强制表达MafB可提高…诱导的细胞存活率并减少细胞凋亡更多使用CS-提取液。CS作用后，MafB高表达细胞的Caspase-3活性较对照细胞受到抑制，而细胞色素c的释放与对照细胞无明显差异。MafB过表达不影响caspase-3mRNA的表达。另一方面，MafB过表达显著降低了Moap1基因的表达。其他调控caspase-3活性的基因如激活因子1(Apaf1)、p21^-lt、CIP1/WAF1&gt；bclx_L和bax的表达没有变化。这些结果表明，氧化应激增强MafB的表达是通过caspase途径而不是通过线粒体途径来抑制AM细胞的死亡。为了进一步评估MafB的作用，我们目前建立了在人类清道夫受体启动子的控制下表达MafB的显性负性小鼠，该启动子仅能在巨噬细胞中实现特异性基因的表达(手稿正在准备中)。利用这只小鼠，我们正在评估MafB在体内的作用。较少

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