Zhu Chong-Bin, Blakely Randy D, Hewlett William A
Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232-8645, USA.
Neuropsychopharmacology. 2006 Oct;31(10):2121-31. doi: 10.1038/sj.npp.1301029. Epub 2006 Feb 1.
Proinflammatory cytokines and serotonergic homeostasis have both been implicated in the pathophysiology of major psychiatric disorders. We have demonstrated that activation of p38 mitogen-activated protein kinase (MAPK) induces a catalytic activation of the serotonin transporter (SERT) arising from a reduction in the SERT Km for 5-hydroxytryptamine (5-HT). As inflammatory cytokines can activate p38 MAPK, we hypothesized that they might also activate neuronal SERT. Indeed, Interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) stimulated serotonin uptake in both the rat embryonic raphe cell line, RN46A, and in mouse midbrain and striatal synaptosomes. In RN46A cells, IL-1beta stimulated 5-HT uptake in a dose- and time-dependent manner, peaking in 20 min at 100 ng/ml. This was abolished by IL-1ra (20 ng/ml), an antagonist of the IL-1 receptor, and by SB203580 (5 microM), a p38 MAPK inhibitor. TNF-alpha also dose- and time-dependently stimulated 5-HT uptake that was only partially blocked by SB203580. Western blots showed that IL-1beta and TNF-alpha activated p38 MAPK, in an SB203580-sensitive manner. IL-1beta induced an SB203580-sensitive decrease in 5-HT Km with no significant change in Vmax. In contrast, TNF-alpha stimulation decreased 5-HT Km and increased SERT Vmax. SB203580 selectively blocked the TNF-alpha-induced change in SERT Km. In mouse midbrain and striatal synaptosomes, maximal stimulatory effects on 5-HT uptake occurred at lower concentrations (IL-1beta, 10 ng/ml; TNF-alpha, 20 ng/ml), and over shorter incubation times (10 min). As with RN46A cells, the effects of IL-1beta and TNF-alpha were completely (IL-1beta) or partially (TNF-alpha) blocked by SB203580. These results provide the first evidence that proinflammatory cytokines can acutely regulate neuronal SERT activity via p38 MAPK-linked pathways.
促炎细胞因子和血清素能稳态均与主要精神疾病的病理生理学有关。我们已经证明，p38丝裂原活化蛋白激酶（MAPK）的激活会诱导血清素转运体（SERT）的催化激活，这是由于SERT对5-羟色胺（5-HT）的米氏常数（Km）降低所致。由于炎性细胞因子可激活p38 MAPK，我们推测它们也可能激活神经元SERT。事实上，白细胞介素-1β（IL-1β）和肿瘤坏死因子-α（TNF-α）在大鼠胚胎中缝细胞系RN46A以及小鼠中脑和纹状体突触体中均刺激了血清素摄取。在RN46A细胞中，IL-1β以剂量和时间依赖性方式刺激5-HT摄取，在100 ng/ml时20分钟达到峰值。这被IL-1受体拮抗剂IL-1ra（20 ng/ml）和p38 MAPK抑制剂SB203580（5 μM）消除。TNF-α也以剂量和时间依赖性方式刺激5-HT摄取，仅被SB203580部分阻断。蛋白质免疫印迹显示，IL-1β和TNF-α以对SB203580敏感的方式激活p38 MAPK。IL-1β诱导5-HT Km以对SB203580敏感的方式降低，而最大反应速度（Vmax）无显著变化。相比之下，TNF-α刺激降低了5-HT Km并增加了SERT的Vmax。SB203580选择性地阻断了TNF-α诱导的SERT Km变化。在小鼠中脑和纹状体突触体中，对5-HT摄取的最大刺激作用在较低浓度（IL-1β为10 ng/ml；TNF-α为20 ng/ml）和较短孵育时间（10分钟）时出现。与RN46A细胞一样，IL-1β和TNF-α的作用被SB203580完全（IL-1β）或部分（TNF-α）阻断。这些结果提供了首个证据，表明促炎细胞因子可通过p38 MAPK相关途径急性调节神经元SERT活性。
