Li Qi, Zhou Xiang-Dong, Kolosov Victor P, Perelman Juliy M
Department of Respiratory Medicine, Second Affiliated Hospital, Chongqing Medical University, Chongqing, P.R. China.
Cell Physiol Biochem. 2011;27(5):605-12. doi: 10.1159/000329982. Epub 2011 Jun 15.
To explore the signaling mechanism associated with the inhibitory effect of nicotine on tumor necrosis factor (TNF)- α expression in human airway epithelial cells.
HBE16 airway epithelial cells were cultured and incubated with either nicotine or cigarette smoke extract (CE). Cells were then transfected with α1, α5, or α7 nicotinic acetylcholine receptor (nAChR)-specific small interfering RNAs (siRNAs). The effects of nicotine on the production of proinflammatory factors TNF-α, in transfected cells were analyzed. Furthermore, we assayed the expression levels of myeloid differentiation primary response gene 88 (MyD88) protein, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 protein, NF-κB activity and NF-κB inhibitor alpha (I-κBα) expression in cells after treatment with nicotine or α7 nAChR inhibitor, α -bungarotoxin (α-BTX).
The production of TNF-α was lower in cells pretreated with nicotine before lipopolysaccharide (LPS) stimulation, compared with LPS-only-treated cells. In contrast, in α7 siRNA-transfected cells incubated with nicotine and LPS, TNF-α expression was higher than that in non-transfected cells or in α1 or α5 siRNA-transfected cells. Addition of MyD88 siRNA or the NF-κB inhibitor pyridine-2,6-dithiocarboxylic acid (PDTC) also reduced TNF-α expression. Furthermore, we found that nicotine decreased MyD88 protein, NF-κB p65 protein, NF-κB activity and phospho-I-κBα expression induced by CE or LPS. The inhibitor α-BTX could reverse these effects.
Nicotine reduces TNF-α expression in HBE16 airway epithelial cells, mainly through an α7 nAChR/MyD88/NF-κB pathway.
探讨尼古丁对人气道上皮细胞肿瘤坏死因子（TNF）-α表达的抑制作用相关的信号传导机制。
培养HBE16气道上皮细胞，并用尼古丁或香烟烟雾提取物（CE）进行孵育。然后用α1、α5或α7烟碱型乙酰胆碱受体（nAChR）特异性小干扰RNA（siRNAs）转染细胞。分析尼古丁对转染细胞中促炎因子TNF-α产生的影响。此外，我们检测了用尼古丁或α7 nAChR抑制剂α-银环蛇毒素（α-BTX）处理后细胞中髓样分化初级反应基因88（MyD88）蛋白、活化B细胞核因子κB轻链增强子（NF-κB）p65蛋白、NF-κB活性和NF-κB抑制剂α（I-κBα）的表达水平。
与仅用脂多糖（LPS）处理的细胞相比，在LPS刺激前用尼古丁预处理的细胞中TNF-α的产生较低。相反，在与尼古丁和LPS孵育的α7 siRNA转染细胞中，TNF-α表达高于未转染细胞或α1或α5 siRNA转染细胞。添加MyD88 siRNA或NF-κB抑制剂吡啶-2,6-二硫代羧酸（PDTC）也降低了TNF-α的表达。此外，我们发现尼古丁降低了CE或LPS诱导的MyD88蛋白、NF-κB p65蛋白、NF-κB活性和磷酸化I-κBα的表达。抑制剂α-BTX可以逆转这些作用。
尼古丁主要通过α7 nAChR/MyD88/NF-κB途径降低HBE16气道上皮细胞中TNF-α的表达。
