Receptor-mediated tobacco toxicity:: acceleration of sequential expression of α5 and α7 nicotinic receptor subunits in oral keratinocytes exposed to cigarette smoke
Receptor-mediated tobacco toxicity:: acceleration of sequential expression of α5 and α7 nicotinic receptor subunits in oral keratinocytes exposed to cigarette smoke
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DOI：
10.1096/fj.07-9965.com
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发表时间：
2008-05-01
期刊：
影响因子：
4.8
通讯作者：
Grando, Sergei A.
中科院分区：
文献类型：
--
作者：
Arredondo, Juan;Chernyavsky, Alexander I.;Grando, Sergei A.
烟草制品和尼古丁会改变细胞周期，导致口腔角质形成细胞 (KC) 鳞状化和鳞状细胞癌。烟碱乙酰胆碱受体 (nAChR) 的激活会引起 Ca(2+) 内流，不同 nAChR 亚型的大小不同。 KC 的正常分化与具有增加的 Ca(2+) 通透性的 nAChR 亚型的顺序表达相关，例如含有 α 5 的 α 3 nAChR 和 α 7 nAChR。暴露于环境烟草烟雾（ETS）或同等浓度的尼古丁使KCs中α5和α7的表达加速几倍，美加明和et-银环蛇毒素可以消除这种表达，但效果不同，表明nAChR亚型表达的自动调节顺序如下：α3（β2/β4）>α 3(β 2/β 4)α 5 > α 7 > α 7。使用 nAChR 特异性药理学拮抗剂和小干扰 RNA 对亚基 mRNA 和蛋白质水平进行定量测定的结果证实了这一猜想。 ETS 和尼古丁的基因组效应涉及转录因子 GATA-2，在暴露的 KC 中，转录因子 GATA-2 的数量和活性成倍增加。使用蛋白激酶抑制剂和显性失活和组成型活性构建体，我们表征了介导 nAChR 亚型转换的主要信号级联。累积结果表明，α 3(β 2/β 4)至α 3(β 2/β 4)α 5 nAChR转变主要涉及蛋白激酶C、α 3(β 2/β 4)α 5至α 7 nAChR转变-Ca(2+)/钙调蛋白依赖性蛋白激酶II和p38 MAPK以及α 7 自我上调 - p38 MAPK/Akt 途径和 JAK-2。这些结果提供了 ETS 和尼古丁对 KC 的基因组效应的机制见解，并表征了介导 nAChR 亚型逐步过表达的自动调节以及暴露细胞中 Ca(2+) 通透性增加的信号通路。这些观察结果具有显着的临床意义，因为 nAChR 亚基组成的改变可以引起受体功能的相应改变，从而导致在暴露于烟草产品的 KC 中观察到深刻的病理生物学效应。
Tobacco products and nicotine alter the cell cycle and lead to squamatization of oral keratinocytes (KCs) and squamous cell carcinoma. Activation of nicotinic acetylcholine receptors (nAChRs) elicits Ca(2+) influx that varies in magnitude between different nAChR subtypes. Normal differentiation of KCs is associated with sequential expression of the nAChR subtypes with increasing Ca(2+) permeability, such as alpha 5-containing alpha 3 nAChR and alpha 7 nAChR. Exposure to environmental tobacco smoke (ETS) or an equivalent concentration of nicotine accelerated by severalfold the alpha 5 and alpha 7 expression in KCs, which could be abolished by mecamylamine and et-bungarotoxin with different efficacies, suggesting the following sequence of autoregulation of the expression of nAChR subtypes: alpha 3(beta 2/beta 4) > alpha 3(beta 2/beta 4)alpha 5 > alpha 7 > alpha 7. This conjecture was corroborated by results of quantitative assays of subunit mRNA and protein levels, using nAChR-specific pharmacologic antagonists and small interfering RNAs. The genomic effects of ETS and nicotine involved the transcription factor GATA-2 that showed a multifold increase in quantity and activity in exposed KCs. Using protein kinase inhibitors and dominant negative and constitutively active constructs, we characterized the principal signaling cascades mediating a switch in the nAChR subtype. Cumulative results indicated that the alpha 3(beta 2/beta 4) to alpha 3(beta 2/beta 4)alpha 5 nAChR transition predominantly involved protein kinase C, alpha 3(beta 2/beta 4)alpha 5 to alpha 7 nAChR transition-Ca(2+)/calmodulin-dependent protein kinase II and p38 MAPK, and alpha 7 self-up-regulation-the p38 MAPK/Akt pathway, and JAK-2. These results provide a mechanistic insight into the genomic effects of ETS and nicotine on KCs and characterize signaling pathways mediating autoregulation of stepwise overexpression of nAChR subtypes with increasing Ca(2+) permeability in exposed cells. These observations have salient clinical implications, because a switch in the nAChR subunit composition can bring about a corresponding switch in receptor function, leading to profound pathobiologic effects observed in KCs exposed to tobacco products.