Dulkys Y, Kluthe C, Buschermöhle T, Barg I, Knöss S, Kapp A, Proudfoot A E, Elsner J
Department of Dermatology and Allergology, Hannover Medical University, Hannover, Germany.
J Immunol. 2001 Sep 15;167(6):3443-53. doi: 10.4049/jimmunol.167.6.3443.
Cytokines and chemokines are responsible for the attraction and activation of eosinophils in allergic and inflammatory diseases. Whereas cytokines such as IL-3, IL-5, and GM-CSF activate eosinophils via heterodimeric receptors containing a distinct alpha-chain (binding domain) and a common beta-chain (signaling domain), chemokines such as eotaxin activate eosinophils via seven-transmembrane G(i) protein-coupled CCRs. Recent studies have demonstrated the importance of CCR3 on human eosinophils that undergo receptor recycling after chemokine activation, but the modulation of this receptor by cytokines has not yet been addressed. In this study, we demonstrate that IL-3 induces a dose- and time-dependent down-regulation of CCR3 from the surface of human eosinophils comparable to the CCR3-specific ligand eotaxin, whereas IL-5, GM-CSF, IL-4, IL-10, IL-13, IFN-gamma, and TNF-alpha had no effect. Maximal down-regulation of CCR3 in response to IL-3 was reached at 24 h. Reduction of CCR3 surface protein in response to IL-3 could be prevented by an anti-IL-3 mAb and was neither due to the release of CC chemokines nor to nonspecific binding of IL-3 to CCR3. Moreover, down-regulation was prevented by phenylarsine oxide, a nonspecific inhibitor of receptor internalization. After 24 h, IL-3-induced decrease of CCR3 surface expression correlated with diminished mRNA expression, suggesting a transcriptional regulation mechanism. Since wortmannin partially inhibited IL-3- but not eotaxin-induced CCR3 down-regulation, receptor down-modulation seems to underlie different signaling events. Therefore, these data suggest a novel role for the cytokine IL-3 in the activation process of eosinophils and its predominant chemokine receptor CCR3.
细胞因子和趋化因子在过敏性和炎性疾病中负责嗜酸性粒细胞的吸引和激活。诸如白细胞介素-3（IL-3）、白细胞介素-5（IL-5）和粒细胞-巨噬细胞集落刺激因子（GM-CSF）等细胞因子通过含有独特α链（结合结构域）和共同β链（信号传导结构域）的异二聚体受体激活嗜酸性粒细胞，而诸如嗜酸性粒细胞趋化因子等趋化因子通过七跨膜G(i)蛋白偶联的CCR受体激活嗜酸性粒细胞。最近的研究表明CCR3在趋化因子激活后经历受体再循环的人嗜酸性粒细胞上的重要性，但细胞因子对该受体的调节尚未得到研究。在本研究中，我们证明IL-3可诱导人嗜酸性粒细胞表面CCR3呈剂量和时间依赖性下调，其程度与CCR3特异性配体嗜酸性粒细胞趋化因子相当，而IL-5、GM-CSF、IL-4、IL-10、IL-13、干扰素-γ（IFN-γ）和肿瘤坏死因子-α（TNF-α）则无此作用。对IL-3反应的CCR3最大下调在24小时时达到。抗IL-3单克隆抗体可阻止IL-3诱导的CCR3表面蛋白减少，且这既不是由于CC趋化因子的释放，也不是由于IL-3与CCR3的非特异性结合。此外，受体内化的非特异性抑制剂氧化苯胂可阻止下调。24小时后，IL-3诱导的CCR3表面表达降低与mRNA表达减少相关，提示存在转录调节机制。由于渥曼青霉素部分抑制IL-3诱导的而非嗜酸性粒细胞趋化因子诱导的CCR3下调，受体下调似乎是不同信号事件的基础。因此，这些数据提示细胞因子IL-3在嗜酸性粒细胞及其主要趋化因子受体CCR3的激活过程中具有新作用。
