The effect of platelet activating factor on mucociliary regulation in airway epithelium cultured at airinterface

为了阐明血小板激活因子对呼吸道上皮细胞黏液纤毛运输的影响，我们研究了在空气界面培养的牛气管上皮细胞的生物电学特性。PAF剂量依赖性地增加短路电流和电导。这种作用可被氯通道阻滞剂DPAC所抑制，但不能被钠通道阻滞剂阿米洛利所抑制。此外，PAF拮抗剂BAPTA-AM和消炎痛可抑制PAF的这种作用，提示PAF通过PAF受体、钙和前列腺素依赖途径增加氯的分泌。因此，为了阐明PAF在气道上皮细胞中的信号转导，我们测量了第二信使。在Fura2负载的细胞中，PAF以剂量依赖的方式增加[Ca^&lt；2&gt；]i。这种反应由一过性升高和随后的持续升高组成。不含钙的培养液完全消除了持续性反应，但仅抑制了瞬时反应。此外，PAF还可增加肌醇三磷酸水平，其时间过程类似于瞬时钙反应。放射免疫分析显示，PAF还可使PGE2和PGF2α水平升高。这些结果表明，PAF诱导的上皮功能是通过钙离子和前列腺素的增加而实现的。

To elucidate the effect of platelet activating factor on mucociliary transport of airway epithelial cells, we studied bioelectric properties of cow tracheal epithelial cells cultured at an airinterface. PAF dose-dependently increased short-circuit current and conductance. This effect was inhibited by Cl channel blocker, DPAC,but not Na channel blocker, amiloride. In addition, this effect was inhibited by the pretreatment of PAF antagonist, BAPTA-AM,and indomethacin, suggesting that PAF increases Cl secretion via PAF receptor, calcium and prostaglandin dependent pathway. Therefore, to elucidate the signal transduction of PAF in the airway epithelial cells, we measured second messengers.In fura2-loaded cells, PAF increased [Ca^<2+>]i in a dose-dependent manner. This [Ca^<2+>]i response consisted of a transient increase and a subsequent sustained elevation. Ca^<2+>-free medium totally abolished the sustained response, but it only inhibited the transient response. Moreover, PAF increased inositol triphosphate level whose time course was similar to the transient calcium response. PAF also increased PGE2 and PGF2alpha by RIA assay.These results suggest that PAF-induced epithelial function is mediated by the increased calcium and prostaglandins.