Juntendo Itch Research Center (JIRC), Institute for Environmental and Gender Specific Medicine, Juntendo University Graduate School of Medicine, Chiba, Japan; Department of Cellular Physiology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan.
Juntendo Itch Research Center (JIRC), Institute for Environmental and Gender Specific Medicine, Juntendo University Graduate School of Medicine, Chiba, Japan; Department of Cellular Physiology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan.
Biochem Biophys Res Commun. 2024 Nov 12;733:150595. doi: 10.1016/j.bbrc.2024.150595. Epub 2024 Aug 26.
Mast cells are key effector cells that elicit immunoglobulin E (IgE)-mediated allergic inflammations. Allergen cross-linking of IgE bound to the high-affinity IgE receptor, FcεRI, on mast cells triggers signaling cascades that activate signal proteins and evoke extracellular Ca influx, which are crucial for cytokine production. The β2-adrenergic receptor (Adrb2) on mast cells negatively regulates FcεRI signaling, as demonstrated by the inhibition of IgE/antigen (Ag)-induced activation by Adrb2 agonists.
Although β2-adrenergic-related reagents are known to influence mast cell functions, the specific intrinsic role of Adrb2 in these cells is not fully understood, potentially because of off-target effects. In this study, the additional roles of Adrb2 in mast cells were investigated, specifically the involvement of Adrb2 in FcεRI signaling, using Adrb2 mice.
Adrb2 mice were used to investigate the roles of Adrb2 in mast cells by examining bone marrow-derived mast cells (BMMCs) for surface expression of mast cell markers, granule numbers, and gene expression of mast cell proteases. Cytokine production, Ca influx, and nuclear factor of activated T cells (NFAT) nuclear translocation were measured in Adrb2 and Adrb2 BMMCs upon IgE/Ag stimulation.
Adrb2 did not affect the generation of BMMCs, their surface expression of mast cell markers, granule numbers, or gene expression of mast cell proteases, indicating that the absence of Adrb2 had no adverse effect on mast cell development. However, Adrb2 BMMCs exhibited reduced tumor necrosis factor α (TNFα) production and diminished Ca⁺ influx upon IgE/Ag stimulation, which correlated with decreased NFAT translocation. Restoration of Adrb2 in Adrb2 BMMCs rescued cytokine production. Notably, FcεRI-mediated phosphorylation of the phospholipase PLCγ1 and mitogen-activated protein kinases (MAPKs) remained unchanged in the absence of Adrb2.
These results suggest that Adrb2 has a novel ligand-independent function, increasing Ca entry in mast cells when stimulated with IgE/Ag.
肥大细胞是引发免疫球蛋白 E（IgE）介导的过敏炎症的关键效应细胞。过敏原交联与高亲和力 IgE 受体 FcεRI 结合的 IgE 触发信号级联反应，激活信号蛋白并引发细胞外 Ca²⁺内流，这对于细胞因子的产生至关重要。肥大细胞上的β2-肾上腺素能受体（Adrb2）负调节 FcεRI 信号，这是由 Adrb2 激动剂抑制 IgE/抗原（Ag）诱导的激活所证明的。
虽然已知β2-肾上腺素能相关试剂会影响肥大细胞的功能，但 Adrb2 在这些细胞中的特定内在作用尚未完全了解，这可能是由于脱靶效应。在这项研究中，使用 Adrb2 小鼠研究了 Adrb2 在肥大细胞中的其他作用，特别是 Adrb2 在 FcεRI 信号中的参与。
使用 Adrb2 小鼠通过检查骨髓来源的肥大细胞（BMMC）表面肥大细胞标志物的表达、颗粒数量和肥大细胞蛋白酶的基因表达来研究 Adrb2 在肥大细胞中的作用。在 IgE/Ag 刺激下，测量 Adrb2 和 Adrb2 BMMC 中的细胞因子产生、Ca²⁺内流和活化 T 细胞核因子（NFAT）核易位。
Adrb2 不影响 BMMC 的产生、它们表面肥大细胞标志物的表达、颗粒数量或肥大细胞蛋白酶的基因表达，这表明 Adrb2 的缺失对肥大细胞的发育没有不利影响。然而，Adrb2 BMMC 在 IgE/Ag 刺激下表现出肿瘤坏死因子 α（TNFα）产生减少和 Ca²⁺内流减少，这与 NFAT 易位减少相关。在 Adrb2 BMMC 中恢复 Adrb2 可挽救细胞因子的产生。值得注意的是，在没有 Adrb2 的情况下，FcεRI 介导的磷脂酶 PLCγ1 和丝裂原活化蛋白激酶（MAPKs）的磷酸化保持不变。
这些结果表明，Adrb2 具有一种新的配体非依赖性功能，即在 IgE/Ag 刺激下增加肥大细胞中的 Ca²⁺内流。
