黄芩素对人野生型CFTR氯离子通道的激活作用

Activation effect of natural flavonoid compound baicalein on human wild cystic fibrosis transmembrane conductance regulator chloride channel

目的:研究天然黄酮类化合物黄芩素对囊性纤维化跨膜电导调节因子(CFTR)氯离子通道的激活作用。方法:利用稳定共表达人CFTR与一种对卤族元素敏感的荧光绿蛋白突变体(EYFP-H148Q)的FRT细胞模型,测定黄芩素(0.18、0.55、1.65、5、15、44、133及400μmol.L-1)对CFTR介导的I-内流速度[d[I-]/dt(mmol.L-1.s-1)]的影响。结果:黄芩素对CFTR的亲和力Ka≈16μmol.L-1,其对CFTR氯离子通道的激活作用10 min之内能达到最大活力的1/2,并且激活作用能够在其被去除后20 min内就迅速消失。不同浓度(0、20、50及100 nmol.L-1)的Forskolin对黄芩素的激活作用无明显影响,黄芩素对CFTR的激活作用能被CFTR特异性抑制剂CFTRinh-172抑制。结论:首次发现了黄芩素能够以剂量依赖方式激活CFTR,其激活作用具有迅速、可逆的特点。并且初步确定了黄芩素通过提高CFTR磷酸化水平及其直接与CFTR结合发挥作用。

Objective To study activation effect of a natural compound baicalein on cystic fibrosis transmembrane conductance regulator （CFTR） chloride channel. Methods A cell-based fluorescence assay was used to determine CFTR-mediate iodide influx rate [d [I^-] /dt （mmol·L^-1·s^-1）] activated by baicalein （the concentrations were 0.18, 0.55, 1.65, 5, 15, 44, 133 and 400 μmol ·L^-1） .Results The Ka of flavonoid baicalein stimulating CFTR was about 16 μmol·L^-1. The half of maximal activity was reached in ten minutes and the activation disappeared in 20 rain after baicalein was washed out. The activation of baicalein was not affected obviously under different concentrations of Forsklin （0, 20, 50 and 100 nmol·L^-1） and the activation could be totally inhibited by CFTRinh-172. Conclusion Baicalein can stimulate CFTR-mediated iodide influx in a dose-dependent way and its activity manifests a rapid and reversible characteristic. It might work in both elevating CFTR protein phosphorylation and direct binding way.