Stimulation of the adenosine A3 receptor, not the A1 or A2 receptors, promote neurite outgrowth of retinal ganglion cells
Stimulation of the adenosine A3 receptor, not the A1 or A2 receptors, promote neurite outgrowth of retinal ganglion cells
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DOI：
10.1016/j.exer.2018.02.019
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发表时间：
2018-05-01
影响因子：
3.4
通讯作者：
Tanihara, Hidenobu
中科院分区：
文献类型：
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作者：
Nakashima, Kei-Ichi;Iwao, Keiichiro;Tanihara, Hidenobu
在候选神经保护剂中，腺苷被认为是治疗中枢神经系统疾病的可能方法。腺苷通过四种 G 蛋白偶联受体（A；、A(2A)、A(2B) 和 A(3)）引发生物效应。 A(2A) 和 A(2B) 受体刺激腺苷酸环化酶 (AC) 并增加环磷酸腺苷 (cAMP) 水平，而 A(1) 和 A(3) 受体抑制 AC 并降低 cAMP 水平。多项研究调查了腺苷受体 (AdoR) 在青光眼中的作用，因为 A(1)、A(2A) 或 A(3) 受体的调节可调节眼内压。此外，AdoR 相关现象可能会诱导视网膜神经元的神经保护作用。值得注意的是，A(1,)、A(2A,) 和 A(3) 受体激动剂据报道可在体外和体内青光眼模型中抑制视网膜神经节细胞 (RGC) 死亡。然而，关于 AdoR 激活对神经突生长或 RGC 再生的影响的了解有限。在本报告中，我们描述了 AdoR 亚型在神经突生长和 RGC 轴突再生中的作用。通过免疫组织化学分析评估 AdoRs 在视网膜中的分布。使用体外原代培养的大鼠 RGC 和体内视神经挤压模型，在以下 AdoR 激动剂刺激后评估神经突伸长：CHA，一种 A(1) 受体激动剂； CGS21680，一种 A(2A) 受体激动剂； BAY60-6583，一种 A(2B) 受体激动剂；和 2-C1-IB-MECA，一种 A(3) 受体激动剂。为了确定神经突促进的机制，分别通过酶联免疫吸附测定（ELISA）和蛋白质印迹分析评估与AdoRs神经突伸长相关的信号转导候选分子。所有四种 AdoR（A(1)、A(2A)、A(2B) 和 A(3)）均存在于视网膜内层中。在 AdoR 激动剂中，只有 2-C1-IB-MECA 显着促进原代培养的 RGC 中的神经突生长。信号通路分析表明，2-C1-IB-MECA 导致培养的 RGC 中 Akt 磷酸化上调。此外，LY294002（一种 Akt 抑制剂）可抑制 RGC 中 A(3) 受体激动剂的神经促进作用。此外，2-C1-IB-MECA 增加了视神经挤压模型中再生轴突的数量。总之，这些数据表明，在大鼠 RGC 再生过程中，A(3) 受体的激活，而不是 A(3) 或 A(2) 受体，促进体外和体内神经突的生长，这是由 Akt 依赖性信号通路的激活引起的。因此，AdoR 激活可能是开发治疗青光眼和其他视神经病变的新型再生方式的有希望的候选者。
Among candidate neuroprotective agents, adenosine is thought to be a possible treatment for central nervous system disorders. Adenosine elicits biological effects through four G protein-coupled receptors (A;, A(2A), A(2B,) and A(3)). The A(2A) and A(2B) receptors stimulate adenylyl cyclase (AC) and increase cyclic adenosine monophosphate (cAMP) levels, whereas A(1) and A(3) receptors inhibit AC and decrease cAMP levels. Several studies have investigated the effects of adenosine receptors (AdoRs) in glaucoma, because modulation of A(1),A(2A,) or A(3) receptor regulates intraocular pressure. In addition, AdoR-related phenomena may induce neuroprotective effects in retinal neurons. Notably, A(1,) A(2A,) and A(3) receptor agonists reportedly inhibit retinal ganglion cell (RGC) death in m vitro and in vivo glaucoma models. However, there is limited knowledge of the effects of AdoR activation on neurite outgrowth or the regeneration of RGCs. In this report, we described the role of an AdoR subtype in neurite outgrowth and RGC axonal regeneration. The distribution of AdoRs in the retina was evaluated by lmmunohistochemical analysis. Using primary cultured rat RGCs in vitro and an optic nerve crush model m vivo, neurite elongation was evaluated after stimulation by the following AdoR agonists: CHA, an A(1) receptor agonist; CGS21680, an A(2A) receptor agonist; BAY60-6583, an A(2B) receptor agonist; and 2-C1-IB-MECA, an A(3) receptor agonist. To determine the mechanism of neunte promotion, the candidate molecules of signal transduction associated with the neurite elongation of AdoRs were evaluated by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis, respectively. All four AdoRs (A(1), A(2A) A(2B), and A(3)) were present in the inner retinal layers. Among the agonists for AdoR, only 2-C1-IB-MECA significantly promoted neurite outgrowth m primary cultured RGCs. Signaling pathway analyses showed that 2-C1-IB-MECA caused upregulated phosphorylation of Akt in cultured RGCs. Additionally, LY294002, an inhibitor of Akt, suppressed the neunte-promoting effects of the A(3) receptor agonist in RGCs. Moreover, 2-C1-IB-MECA increased the number of regenerating axons in the optic nerve crush model. Taken together, these data indicate that activation of the A(3) receptor, not the A(3) or A(2) receptors, promotes in vitro and in vivo neurite outgrowth during the regeneration of rat RGCs, which is caused by the activation of an Akt-dependent signaling pathway. Therefore, AdoR activation may be a promising candidate for the development of novel regenerative modalities for glaucoma and other optic neuropathies.