Multiple pathways for elevating extracellular adenosine in the rat hippocampal CA1 region characterized by adenosine sensor cells.
Multiple pathways for elevating extracellular adenosine in the rat hippocampal CA1 region characterized by adenosine sensor cells.
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DOI：
10.1111/jnc.13888
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发表时间：
2017-01
影响因子：
4.7
通讯作者：
Morita M
中科院分区：
文献类型：
--
作者：
Yamashiro K;Fujii Y;Maekawa S;Morita M
脑细胞外腺苷调节多种生理和病理过程，其波动方式复杂，反映了昼夜周期、神经元活动、代谢和疾病状态。细胞外腺苷在大脑中的动态尚不完全清楚，主要是因为缺乏简单可靠的方法来测量组织腺苷分布的时间依赖性变化。本研究描述了一种生物传感器的开发，称为腺苷传感器细胞，表达腺苷A1受体和基因修饰的G蛋白。这种生物传感器通过测量细胞内钙对腺苷的反应来表征脑组织中细胞外腺苷的升高。将腺苷传感器细胞放置在海马片下，通过常规钙成像成功地检测到腺苷释放对神经元活动和星形胶质细胞肿胀的反应。药理学分析表明，高频电刺激诱导突触后腺苷释放依赖于l型钙通道和钙诱导的钙释放。治疗后引起星形胶质细胞肿胀的腺苷释放与钙通道无关，但依赖于水通道蛋白4，一种星形胶质细胞特异性水通道亚型。外核苷酶抑制剂抑制星形胶质细胞肿胀后腺苷释放的能力，而不是电刺激，表明前者反映了星形胶质细胞ATP释放和随后的酶分解，而后者反映了神经元直接释放腺苷。这些结果表明，神经元和星形胶质细胞的胞外腺苷升高有不同的机制，从而可以对大脑中的胞外腺苷进行精细调节。腺苷是一种具有多种生理和病理功能的神经调节剂，利用一种新型的生物传感器对细胞外腺苷进行成像，分析了海马切片中腺苷分布的时间依赖性变化。电刺激后组织腺苷的增加归因于突触后神经元释放l型钙通道依赖性腺苷，而星形胶质细胞肿胀通过释放ATP和随后的酶分解代谢增加腺苷。
Extracellular adenosine in the brain, which modulates various physiological and pathological processes, fluctuates in a complicated manner that reflects the circadian cycle, neuronal activity, metabolism and disease states. The dynamics of extracellular adenosine in the brain are not fully understood, largely because of the lack of simple and reliable methods of measuring time-dependent changes in tissue adenosine distribution. This study describes the development of a biosensor, designated an adenosine sensor cell, expressing adenosine A1 receptor and a genetically-modified G protein. This biosensor was used to characterize extracellular adenosine elevation in brain tissue by measuring intracellular calcium elevation in response to adenosine. Placement of adenosine sensor cells below hippocampal slices successfully detected adenosine releases from these slices in response to neuronal activity and astrocyte swelling by conventional calcium imaging. Pharmacological analyses indicated that high-frequency electrical stimulation induced postsynaptic adenosine release in a manner dependent on L-type calcium channels and calcium-induced calcium release. Adenosine release following treatments that cause astrocyte swelling is independent of calcium channels, but dependent on aquaporin 4, an astrocyte-specific water channel subtype. The ability of ectonucleotidase inhibitors to inhibit adenosine release following astrocyte swelling, but not electrical stimulation, suggests that the former reflects astrocytic ATP release and subsequent enzymatic breakdown, whereas the latter reflects direct adenosine release from neurons. These results suggest that distinct mechanisms are responsible for extracellular adenosine elevations by neurons and astrocytes, allowing exquisite regulation of extracellular adenosine in the brain. Time-dependent changes in the distribution of adenosine, a neuromodulator with various physiological and pathological functions, were analyzed in hippocampal slices using a novel biosensor that images extracellular adenosine. Increases in tissue adenosine following electrical stimulation were attributed to L-type calcium channel dependent adenosine release from postsynaptic neurons, whereas astrocyte swelling increased adenosine by releasing ATP and subsequent enzymatic catabolism.