尼古丁在呼吸道上皮細胞A549及BEAS-2B藉由Toll-like receptor 3 調控與表現及路徑之探討

Abstract

Nicotine is a major component of cigarette smoke and has been postulated to play an important role in malignancy. There is overwhelming evidence that an association exists between cigarette smoking and a number of pathological conditions. Among the smoke effects on respiratory system, we can identify two main mechanisms: inducing inflammation and mutagen if-carcinogenic effect. Lung cancer is the single most common cause of death, and almost all of it is due to tobacco smoking. Tobacco smoke is a complex mixture of numerous mutagens and carcinogens. The respiratory epithelium is an important interface between the body and the environment and is constantly exposed to invading pathogens. Recent studies have shown that airway epithelial cells express a family of pattern recognition receptors called Toll-like receptors (TLRs) and that the expression of TLRs can be regulated by cytokines, corticosteroids or microbes. We attempted to determine whether nicotine could regulate the expression of TLRs and IL-6, 8 secrete from two pulmonary tumor cell lines in the present study. Establish an in vitro cell culture model for evaluation of nicotine influence cellular response in airway epithelial cells and characterize the mechanism of nicotine acting of airway epithelial cells. In the present study, effects of nicotine on expression of TLRs in both human A549 and BEAS-2B cell lines were examined by using reverse transcription PCR analysis. The results revealed that both cell types constitutively expressed mRNAs for TLR2-4. Nicotine up-regulated the expression of TLR3 mRNA in both cell types. The time course showed that up-regulated expression of TLR3 mRNA induced by nicotine in both A549 and BEAS-2B cells was initiated at 30min, nearly reached peak values after 2h and started declined after 4h. However, the maximum expression of TLR3 protein in both A549 and BEAS-2B cells induced by nicotine occurs at 4h. We also showed the up- regulated secretion of IL-6 and IL-8 in the nicotine treated time course study in A549 and BEAS-2B cells. In conclusion, nicotine not only by itself stimulates IL-6 and IL-8 released, but also through selective up-regulation of TLR3 expression in both A549 and BEAS-2B cells. The potentiation of induced IL-6 and IL-8 secretion by nicotine appeared to associate with NF-kB activation through the up-regulation of TLR3 pathway via TRIF, RIP1. These findings may have implications for our understanding of the role of nicotine induced inflammation and the pathway.