Department of Cellular Biology, Division of Molecular and Cellular Neurobiology, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria.
Brain Res. 2011 Aug 17;1407:1-12. doi: 10.1016/j.brainres.2011.06.050. Epub 2011 Jun 26.
Endogenous noradrenaline presumably prohibits neuroinflammation by stimulation of β-adrenergic receptor-dependent suppression of the production of inflammatory mediators. Using the microglial cell line, BV-2, as well as primary murine microglial cells, we show here that the β-adrenergic agonist, isoproterenol, suppresses uptake of hydrophobic polystyrene microspheres. The number of cells showing a specific number of engulfed microspheres followed a Poisson distribution. Isoproterenol decreased the number of engulfed particles per cell and the number of cells showing at least one incorporated particle. Elevation of intracellular cAMP by activation of adenylyl cyclase activity with forskolin, suppression of phosphodiesterase activity with 3-isobutyl-1-methylxanthine (IBMX), or application of the membrane-permeable cAMP analog, 8-bromo-cAMP, suppressed particle uptake. The protein kinase A inhibitor, H-89, did not prevent isoproterenol-dependent suppression of particle engulfment. However, activation of exchange protein activated by cAMP (Epac), specific guanine nucleotide exchange factors for the Ras GTPase homologues, Rap1 and Rap2, with the Epac1-specific cAMP analog, 8-pCPT-2'-O-Me-cAMP, mimicked the suppressive effect of isoproterenol on particle uptake. Our results suggest that β-adrenergic receptor stimulation suppresses particle uptake in microglia by cAMP-dependent activation of Epac.
内源性去甲肾上腺素可能通过刺激β-肾上腺素能受体依赖性抑制炎症介质的产生来抑制神经炎症。在这里，我们使用小胶质细胞系 BV-2 以及原代小鼠小胶质细胞表明，β-肾上腺素能激动剂异丙肾上腺素抑制疏水性聚苯乙烯微球的摄取。显示吞噬特定数量微球的细胞数量遵循泊松分布。异丙肾上腺素降低了每个细胞吞噬的颗粒数量和显示至少一个掺入颗粒的细胞数量。通过用佛波醇酯激活腺苷酸环化酶活性来升高细胞内 cAMP、用 3-异丁基-1-甲基黄嘌呤 (IBMX) 抑制磷酸二酯酶活性，或应用膜可渗透的 cAMP 类似物 8-溴-cAMP，抑制颗粒摄取。蛋白激酶 A 抑制剂 H-89 不能防止异丙肾上腺素依赖性吞噬颗粒的抑制。然而，通过 cAMP 激活的交换蛋白激活 (Epac) 激活，特异性鸟嘌呤核苷酸交换因子对于 Ras GTPase 同源物 Rap1 和 Rap2，用 Epac1 特异性 cAMP 类似物 8-pCPT-2'-O-Me-cAMP 模拟异丙肾上腺素对颗粒摄取的抑制作用。我们的结果表明，β-肾上腺素能受体刺激通过 cAMP 依赖性 Epac 激活抑制小胶质细胞中的颗粒摄取。
