Department of Physiology, School of Medicine, Nantong University, Nantong, Jiangsu Province, China.
PLoS One. 2013 Jun 14;8(6):e65860. doi: 10.1371/journal.pone.0065860. Print 2013.
Dopamine (DA), a neurotransmitter in the nervous system, has been shown to modulate immune function. We have previously reported that five subtypes of DA receptors, including D1R, D2R, D3R, D4R and D5R, are expressed in T lymphocytes and they are involved in regulation of T cells. However, roles of these DA receptor subtypes and their coupled signal-transduction pathway in modulation of natural killer (NK) cells still remain to be clarified. The spleen of mice was harvested and NK cells were isolated and purified by negative selection using magnetic activated cell sorting. After NK cells were incubated with various drugs for 4 h, flow cytometry measured cytotoxicity of NK cells against YAC-1 lymphoma cells. NK cells expressed the five subtypes of DA receptors at mRNA and protein levels. Activation of D1-like receptors (including D1R and D5R) with agonist SKF38393 enhanced NK cell cytotoxicity, but activation of D2-like receptors (including D2R, D3R and D4R) with agonist quinpirole attenuated NK cells. Simultaneously, SKF38393 elevated D1R and D5R expression, cAMP content, and phosphorylated cAMP-response element-binding (CREB) level in NK cells, while quinpirole reduced D3R and D4R expression, cAMP content, and phosphorylated CREB level in NK cells. These effects of SKF38393 were blocked by SCH23390, an antagonist of D1-like receptors, and quinpirole effects were abolished by haloperidol, an antagonist of D2-like receptors. In support these results, H89, an inhibitor of phosphokinase A (PKA), prevented the SKF38393-dependent enhancement of NK cells and forskolin, an activator of adenylyl cyclase (AC), counteracted the quinpirole-dependent suppression of NK cells. These findings show that DA receptor subtypes are involved in modulation of NK cells and suggest that D1-like receptors facilitate NK cells by stimulating D1R/D5R-cAMP-PKA-CREB signaling pathway and D2-like receptors suppress NK cells by inhibiting D3R/D4R-cAMP-PKA-CREB signaling pathway. The results may provide more targets of therapeutic strategy for neuroimmune diseases.
多巴胺（DA）是神经系统中的一种神经递质，已被证明可调节免疫功能。我们之前曾报道过，五种 DA 受体亚型，包括 D1R、D2R、D3R、D4R 和 D5R，在 T 淋巴细胞中表达，并参与 T 细胞的调节。然而，这些 DA 受体亚型及其偶联的信号转导途径在调节自然杀伤（NK）细胞中的作用仍有待阐明。从小鼠脾脏中采集 NK 细胞，使用磁性激活细胞分选法通过阴性选择进行分离和纯化。将 NK 细胞与各种药物孵育 4 小时后，通过流式细胞术测量 NK 细胞对 YAC-1 淋巴瘤细胞的细胞毒性。NK 细胞在 mRNA 和蛋白质水平上表达五种 DA 受体亚型。激动剂 SKF38393 激活 D1 样受体（包括 D1R 和 D5R）可增强 NK 细胞的细胞毒性，但激动剂喹吡罗激活 D2 样受体（包括 D2R、D3R 和 D4R）则减弱 NK 细胞。同时，SKF38393 可提高 NK 细胞中 D1R 和 D5R 的表达、cAMP 含量和磷酸化 cAMP 反应元件结合蛋白（CREB）水平，而喹吡罗则降低 NK 细胞中 D3R 和 D4R 的表达、cAMP 含量和磷酸化 CREB 水平。这些 SKF38393 的作用被 D1 样受体拮抗剂 SCH23390 阻断，而喹吡罗的作用被 D2 样受体拮抗剂氟哌啶醇消除。这些结果得到了以下结果的支持：PKA 抑制剂 H89 可防止 SKF38393 依赖性增强 NK 细胞，而 AC 激活剂 forskolin 则拮抗了喹吡罗依赖性抑制 NK 细胞。这些发现表明，DA 受体亚型参与了 NK 细胞的调节，并表明 D1 样受体通过刺激 D1R/D5R-cAMP-PKA-CREB 信号通路促进 NK 细胞，而 D2 样受体通过抑制 D3R/D4R-cAMP-PKA-CREB 信号通路抑制 NK 细胞。这些结果可能为神经免疫疾病的治疗策略提供更多的靶点。
