Rudolf-Boehm Institute of Pharmacology and Toxicology, Clinical Pharmacology, University Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany.
Chem Biol Interact. 2013 Dec 5;206(3):462-71. doi: 10.1016/j.cbi.2013.08.012. Epub 2013 Aug 30.
The cation channel TRPA1 functions as a chemosensory protein and is directly activated by a number of noxious inhalants. A pulmonary expression of TRPA1 has been described in sensory nerve endings and its stimulation leads to the acceleration of inflammatory responses in the lung. Whereas the function of TRPA1 in neuronal cells is well defined, only few reports exist suggesting a role in epithelial cells. The aim of the present study was therefore (1) to evaluate the expression of TRPA1 in pulmonary epithelial cell lines, (2) to characterize TRPA1-promoted signaling in these cells, and (3) to study the extra-neuronal expression of this channel in lung tissue sections. Our results revealed that the widely used alveolar type II cell line A549 expresses TRPA1 at the mRNA and protein level. Furthermore, stimulating A549 cells with known TRPA1 activators (i.e., allyl isothiocyanate) led to an increase in intracellular calcium levels, which was sensitive to the TRPA1 blocker ruthenium red. Investigating TRPA1 coupled downstream signaling cascades it was found that TRPA1 activation elicited a stimulation of ERK1/2 whereas other MAP kinases were not affected. Finally, using epithelial as well as neuronal markers in immunohistochemical approaches, a non-neuronal TRPA1 protein expression was detected in distal parts of the porcine lung epithelium, which was also found examining human lung sections. TRPA1-positive staining co-localized with both epithelial and neuronal markers underlining the observed epithelial expression pattern. Our findings of a functional expression of TRPA1 in pulmonary epithelial cells provide causal evidence for a non-neuronal TRPA1-mediated control of inflammatory responses elicited upon TRPA1-mediated registration of toxic inhalants in vivo.
阳离子通道 TRPA1 作为一种化学感觉蛋白，可被多种有害吸入物直接激活。在感觉神经末梢已描述了 TRPA1 的肺表达，其刺激导致肺中炎症反应的加速。虽然 TRPA1 在神经元细胞中的功能已得到很好的定义，但仅有少数报道表明其在上皮细胞中具有作用。因此，本研究的目的是：（1）评估 TRPA1 在肺上皮细胞系中的表达；（2）表征这些细胞中 TRPA1 促进的信号转导；（3）研究该通道在肺组织切片中的非神经元表达。我们的结果表明，广泛使用的肺泡 II 型细胞系 A549 在 mRNA 和蛋白质水平上表达 TRPA1。此外，用已知的 TRPA1 激活剂（即丙烯基异硫氰酸酯）刺激 A549 细胞会导致细胞内钙离子水平增加，该增加对 TRPA1 阻断剂钌红敏感。研究 TRPA1 偶联的下游信号转导级联反应发现，TRPA1 激活可刺激 ERK1/2，而其他 MAP 激酶不受影响。最后，使用上皮和神经元标记物进行免疫组织化学方法研究，在猪肺上皮的远端部分检测到非神经元 TRPA1 蛋白表达，在检查人肺切片时也发现了这种表达。TRPA1 阳性染色与上皮和神经元标记物共定位，强调了观察到的上皮表达模式。我们在肺上皮细胞中功能性表达 TRPA1 的发现为体内通过 TRPA1 介导的有毒吸入物登记来非神经元 TRPA1 介导的炎症反应控制提供了因果证据。
