Juric D M, Carman-Krzan M
Department of Pharmacology, Faculty of Medicine, Korytkova 2, SI-1000 Ljubljana, Slovenia.
Int J Dev Neurosci. 2001 Nov;19(7):675-83. doi: 10.1016/s0736-5748(01)00044-2.
In astrocytes, nerve growth factor (NGF) synthesis and secretion is stimulated by the cytokine interleukin-1 beta (IL-1 beta). In the present study, the role of IL-1 receptor binding sites in the regulation of NGF release was evaluated by determining the pharmacological properties of astroglially localized IL-1 receptors, and, by comparing the effects of both the agonists (IL-1 alpha and IL-1 beta) and the antagonist (IL-1ra)-members of the IL-1 family on NGF secretion from rat neonatal cortical astrocytes in primary culture. Using receptor-binding studies, binding of [(125)I] IL-1 beta to cultured astrocytes was saturable and of high affinity. Mean values for the K(D) and B(max) were calculated to be 60.7+/-7.4 pM and 2.5+/-0.1 fmol mg(-1) protein, respectively. The binding was rapid and readily reversible. IL-1 receptor agonists IL-1 alpha (K(i) of 341.1 pM) and IL-1 beta (K(i) 59.9 pM), as well as the antagonist IL-1ra (K(i) 257.6 pM), displaced specific [(125)I] IL-1 beta binding from cultured astrocytes in a monophasic manner. Anti-IL-1RI antibody completely blocked specific [(125)I] IL-1 beta binding while anti-IL-1RII antibody had no inhibitory effect. Exposure of cultured astrocytes to IL-1 alpha and IL-1 beta revealed the functional difference between the agonists in influencing NGF release. In contrast to IL-1 beta (10 U/ml), which caused a 3-fold increase in NGF secretion compared to control cells, IL-1 alpha by itself had no stimulatory action on NGF release. The simultaneous application of IL-1 alpha and IL-1 beta elicited no additive response. IL-1ra had no effect on basal NGF release but dose-dependently inhibited the stimulatory response induced by IL-1 beta. We concluded that IL-1 beta-induced NGF secretion from cultured rat cortical astrocytes is mediated by functional type I IL-1 receptors, whereas IL-1 alpha and IL-1ra, in spite of their affinity for IL-1RI, have no effect on NGF secretion from these cells. Type II IL-1R is not present on rat neonatal cortical astrocytes.
在星形胶质细胞中，细胞因子白细胞介素-1β（IL-1β）可刺激神经生长因子（NGF）的合成与分泌。在本研究中，通过测定星形胶质细胞定位的IL-1受体的药理学特性，并比较IL-1家族的激动剂（IL-1α和IL-1β）和拮抗剂（IL-1ra）对原代培养的新生大鼠皮质星形胶质细胞分泌NGF的影响，评估了IL-1受体结合位点在NGF释放调节中的作用。利用受体结合研究，[(125)I] IL-1β与培养的星形胶质细胞的结合具有饱和性且亲和力高。计算得出的K(D)和B(max)平均值分别为60.7±7.4 pM和2.5±0.1 fmol mg(-1)蛋白质。结合迅速且易于逆转。IL-1受体激动剂IL-1α（K(i)为341.1 pM）和IL-1β（K(i) 59.9 pM）以及拮抗剂IL-1ra（K(i) 257.6 pM）以单相方式取代了培养的星形胶质细胞中特异性[(125)I] IL-1β的结合。抗IL-1RI抗体完全阻断了特异性[(125)I] IL-1β的结合，而抗IL-1RII抗体没有抑制作用。将培养的星形胶质细胞暴露于IL-1α和IL-1β显示了激动剂在影响NGF释放方面的功能差异。与对照组细胞相比，IL-1β（10 U/ml）使NGF分泌增加了3倍，而IL-1α本身对NGF释放没有刺激作用。同时应用IL-1α和IL-1β未引起相加反应。IL-1ra对基础NGF释放没有影响，但剂量依赖性地抑制了IL-1β诱导的刺激反应。我们得出结论，培养的大鼠皮质星形胶质细胞中IL-1β诱导的NGF分泌是由功能性I型IL-1受体介导的，而IL-1α和IL-1ra尽管对IL-1RI有亲和力，但对这些细胞的NGF分泌没有影响。II型IL-1R不存在于新生大鼠皮质星形胶质细胞上。
