Division of Tumor and Cellular Biochemistry, Department of Medical Sciences, Faculty of Medicine, Miyazaki University, Miyazaki, Japan.
Int Arch Allergy Immunol. 2013;161 Suppl 2:44-51. doi: 10.1159/000350359. Epub 2013 May 29.
Zinc (Zn) affects many aspects of immune function, including thymic development and the activities of immune cells. Zn is also involved in many steps of high-affinity IgE receptor (FcεRI)-induced mast cell (MC) activation, which is required for degranulation and cytokine production. Intracellular Zn levels increase in mouse MCs after FcεRI stimulation. We previously reported that Zn distribution in a human MC line, LAD2, changed dramatically following FcεRI aggregation with synchrotron radiation microbeams. However, the kinetics of Zn distribution and the underlying mechanisms following FcεRI cross-linking remain unknown.
We used cord-blood-derived MCs and LAD2 cells. Degranulation was assessed by β-hexosaminidase (β-hex) release. Extracellular Zn levels were determined by inductively coupled plasma atomic emission spectrometry or based on the fluorescence intensity of a Zn indicator. We also used RNAi to knockdown ZnT1 expression. mRNA expression levels were determined by real-time RT-PCR.
Zn was rapidly released from human MCs after FcεRI aggregation. The kinetics and optimal conditions for FcεRI cross-linking for Zn release were different from those for degranulation. Treating LAD2 cells with an intracellular Ca(2+) chelator significantly inhibited IgE-mediated β-hex release but not Zn release. We investigated IgE-mediated β-hex and Zn release with specific inhibitors of signaling pathways. Zn and β-hex release were partly correlated with but also partly independent of IgE. Knockdown of the Zn efflux transporter, ZnT1, significantly inhibited Zn release from human MCs.
Our results indicate that IgE-dependent Zn release from human MCs involves signaling cascades that are distinct from those of degranulation. Thus, Zn may have a unique function as a mediator of allergic inflammation.
锌（Zn）影响免疫功能的许多方面，包括胸腺发育和免疫细胞的活性。Zn 还参与高亲和力 IgE 受体（FcεRI）诱导的肥大细胞（MC）激活的许多步骤，这些步骤是脱颗粒和细胞因子产生所必需的。FcεRI 刺激后，小鼠 MC 中的细胞内 Zn 水平增加。我们之前报道过，在 FcεRI 聚集后，人 MC 系 LAD2 中的 Zn 分布发生了剧烈变化，使用同步辐射微束。然而，FcεRI 交联后 Zn 分布的动力学和潜在机制仍不清楚。
我们使用脐血衍生的 MC 和 LAD2 细胞。脱颗粒通过β-己糖（β-hex）释放来评估。通过电感耦合等离子体原子发射光谱或基于 Zn 指示剂的荧光强度来测定细胞外 Zn 水平。我们还使用 RNAi 敲低 ZnT1 的表达。通过实时 RT-PCR 测定 mRNA 表达水平。
FcεRI 聚集后，Zn 迅速从人 MC 中释放出来。FcεRI 交联的动力学和最佳条件与脱颗粒不同。用细胞内 Ca(2+)螯合剂处理 LAD2 细胞显著抑制 IgE 介导的β-hex 释放，但不抑制 Zn 释放。我们用信号通路的特异性抑制剂研究了 IgE 介导的β-hex 和 Zn 释放。Zn 和β-hex 的释放与 IgE 部分相关，但也部分独立。Zn 外排转运蛋白 ZnT1 的敲低显著抑制人 MC 中 Zn 的释放。
我们的结果表明，IgE 依赖性人 MC 中 Zn 的释放涉及与脱颗粒不同的信号级联。因此，Zn 作为过敏炎症的介质可能具有独特的功能。
