Overexpression of Apoptotic Cell Removal Receptor MERTK in Alveolar Macrophages of Cigarette Smokers
Overexpression of Apoptotic Cell Removal Receptor MERTK in Alveolar Macrophages of Cigarette Smokers
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DOI：
10.1165/rcmb.2007-0306oc
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发表时间：
2008-12-01
影响因子：
6.4
通讯作者：
Crystal, Ronald G.
中科院分区：
文献类型：
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作者：
Kazeros, Angeliki;Harvey, Ben-Gary;Crystal, Ronald G.
单核细胞吞噬细胞通过表达识别和清除凋亡细胞的细胞表面受体，在清除凋亡细胞中发挥重要作用。基于吸烟与肺细胞更新增加相关的知识，我们假设正常吸烟者的肺泡巨噬细胞（AM）可能表现出凋亡细胞清除受体基因的表达增强。通过支气管肺泡灌洗正常非吸烟者（n = 11）和表型正常吸烟者（n = 13; 36 +/-6包-年）获得的AM，使用经TaqMan RT-PCR确认的Affytek HG-U133 Plus 2.0微阵列芯片筛选所有已知凋亡细胞清除受体的mRNA表达。在14种已知的凋亡受体表达中，只有MER酪氨酸激酶（MERTK），一种跨膜酪氨酸激酶受体，在吸烟者中显著上调。然后通过TaqMan RT-PCR、免疫细胞化学、Western分析和流式细胞仪分析评估吸烟者与非吸烟者AM中MERTK表达。吸烟者AM具有MERTK mRNA水平的上调（吸烟者与非吸烟者：通过微阵列的3.6倍，P <0.003;通过TaqMan RTPCR的9.5倍，P <0.02）。免疫细胞化学显示吸烟者AM上MERTK蛋白表达的定性增加。Western和flow分析证实吸烟者AM上MERTK蛋白表达增加（分别为P <0.007和P <0.0002）。MERTK是一种识别凋亡细胞的细胞表面受体，在人AM上表达，并且其表达在吸烟者的AM中上调。MERTK的这种上调可能反映了吸烟者对清除凋亡细胞的需求增加，这一观察结果对慢性阻塞性肺疾病（一种与肺实质细胞凋亡失调相关的疾病）的发生具有影响。
Mononuclear phagocytes play an important role in the removal of apoptotic cells by expressing cell surface receptors that recognize and remove apoptotic cells. Based on the knowledge that cigarette smoking is associated with increased lung cell turnover, we hypothesized that alveolar macrophages (AMs) of normal cigarette smokers may exhibit enhanced expression of apoptotic cell removal receptor genes. AMs obtained by bronchoalveolar lavage of normal nonsmokers (n = 11) and phenotypic normal smokers (n = 13; 36 +/- 6 pack-years) were screened for mRNA expression of all known apoptotic cell removal receptors using Affymetrix HG-U133 Plus 2.0 microarray chips with TaqMan RT-PCR confirmation. Of the 14 known apoptotic receptors expressed, only MER tyrosine kinase (MERTK), a transmembrane tyrosine kinase receptor, was significantly up-regulated in smokers. MERTK expression was then assessed in AMs of smokers versus nonsmokers by TaqMan RT-PCR, immunocytochemistry, Western analysis, and flow analysis. Smoker AMs had up-regulation of MERTK mRNA levels (smoker vs. nonsmoker: 3.6-fold by microarray, P < 0.003; 9.5-fold by TaqMan RTPCR, P < 0.02). Immunocytochemistry demonstrated a qualitative increase in MERTK protein expression on AMs of smokers. Increased protein expression of MERTK on AMs of smokers was confirmed by Western and flow analyses (P < 0.007 and P < 0.0002, respectively). MERTK, a cell surface receptor that recognizes apoptotic cells, is expressed on human AMs, and its expression is up-regulated in AMs of cigarette smokers. This up-regulation of MERTK may reflect an increased demand for removal of apoptotic cells in smokers, an observation with implications for the development of chronic obstructive pulmonary disease, a disorder associated with dysregulated apoptosis of lung parenchymal cells.