Coffer P J, Schweizer R C, Dubois G R, Maikoe T, Lammers J W, Koenderman L
Department of Pulmonary Diseases, University Hospital Utrecht, Utrecht, The Netherlands.
Blood. 1998 Apr 1;91(7):2547-57.
Activation and recruitment of eosinophils in allergic inflammation is in part mediated by chemoattractants and T-helper 2 (Th2)-derived cytokines. However, little is known concerning the signal transduction mechanisms by which this activation occurs. We have investigated tyrosine kinase-mediated activation of phosphatidylinositol 3-kinase (PI3K) and compared this with the activation of the p21ras-ERK signaling pathway in human eosinophils. The related cytokines interleukin-3 (IL-3), IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF), all induced PI3K activity detected in antiphosphotyrosine immunoprecipitates. Furthermore, the chemoattractants platelet-activating factor (PAF), RANTES, and C5a were also able to induce phosphotyrosine-associated PI3K activity. Protein kinase B (PKB) is a downstream target of PI3K activation by growth factors. Induction of PKB phosphorylation in human eosinophils was transiently induced on activation with the cytokines IL-4 and IL-5, as well as the chemoattractants PAF, C5a, and RANTES showing a broad activation profile. Surprisingly, analysis of the activation of the mitogen-activated protein (MAP) kinases p44(ERK1) and p42(ERK2), showed that ERK2, but not ERK1, was transiently activated in human eosinophils after stimulation with IL-5 or PAF. Activation kinetics correlated with activation of p21ras by both cytokines and chemoattractants as measured by a novel assay for guanosine triphosphate (GTP)-loading. Finally, using specific inhibitors of both the p21ras-ERK and PI3K signaling pathways, a role was demonstrated for PI3K, but not p21ras-ERK, in activation of the serum-treated zymosan (STZ)-mediated respiratory burst in IL-5 and PAF-primed eosinophils. In summary, these data show that in human eosinophils, Th2-derived cytokines differentially activate both PI3K and MAP kinase signal transduction pathways with distinct functional consequences showing complex regulation of eosinophil effector functions.
嗜酸性粒细胞在过敏性炎症中的激活和募集部分是由趋化因子和辅助性T细胞2（Th2）衍生的细胞因子介导的。然而，关于这种激活发生的信号转导机制却知之甚少。我们研究了酪氨酸激酶介导的磷脂酰肌醇3激酶（PI3K）的激活，并将其与人类嗜酸性粒细胞中p21ras-ERK信号通路的激活进行了比较。相关细胞因子白细胞介素-3（IL-3）、IL-5和粒细胞-巨噬细胞集落刺激因子（GM-CSF），均能在抗磷酸酪氨酸免疫沉淀物中检测到诱导的PI3K活性。此外，趋化因子血小板活化因子（PAF）、调节激活正常T细胞表达和分泌的趋化因子（RANTES）和C5a也能够诱导与磷酸酪氨酸相关的PI3K活性。蛋白激酶B（PKB）是生长因子激活PI3K的下游靶点。用细胞因子IL-4和IL-5以及趋化因子PAF、C5a和RANTES激活人类嗜酸性粒细胞时，会短暂诱导PKB磷酸化，显示出广泛的激活谱。令人惊讶的是，对丝裂原活化蛋白（MAP）激酶p44（ERK1）和p42（ERK2）激活的分析表明，在用IL-5或PAF刺激后，人类嗜酸性粒细胞中ERK2而非ERK1被短暂激活。激活动力学与细胞因子和趋化因子对p21ras的激活相关，这通过一种新的三磷酸鸟苷（GTP）负载检测法进行测量。最后，使用p21ras-ERK和PI3K信号通路的特异性抑制剂，证明了PI3K而非p21ras-ERK在IL-5和PAF预处理的嗜酸性粒细胞中血清处理的酵母聚糖（STZ）介导的呼吸爆发激活中起作用。总之，这些数据表明，在人类嗜酸性粒细胞中，Th2衍生的细胞因子以不同方式激活PI3K和MAP激酶信号转导通路，具有不同的功能后果，显示出嗜酸性粒细胞效应功能的复杂调节。
