Department of Signal Processing, Tampere University of Technology, Tampere, Finland.
PLoS One. 2011 Mar 29;6(3):e17914. doi: 10.1371/journal.pone.0017914.
To better understand the complex molecular level interactions seen in the pathogenesis of Alzheimer's disease, the results of the wet-lab and clinical studies can be complemented by mathematical models. Astrocytes are known to become reactive in Alzheimer's disease and their ionic equilibrium can be disturbed by interaction of the released and accumulated transmitters, such as serotonin, and peptides, including amyloid- peptides (A). We have here studied the effects of small amounts of A25-35 fragments on the transmitter-induced calcium signals in astrocytes by Fura-2AM fluorescence measurements and running simulations of the detected calcium signals.
METHODOLOGY/PRINCIPAL FINDINGS: Intracellular calcium signals were measured in cultured rat cortical astrocytes following additions of serotonin and glutamate, or either of these transmitters together with A25-35. A25-35 increased the number of astrocytes responding to glutamate and exceedingly increased the magnitude of the serotonin-induced calcium signals. In addition to A25-35-induced effects, the contribution of intracellular calcium stores to calcium signaling was tested. When using higher stimulus frequency, the subsequent calcium peaks after the initial peak were of lower amplitude. This may indicate inadequate filling of the intracellular calcium stores between the stimuli. In order to reproduce the experimental findings, a stochastic computational model was introduced. The model takes into account the major mechanisms known to be involved in calcium signaling in astrocytes. Model simulations confirm the principal experimental findings and show the variability typical for experimental measurements.
CONCLUSIONS/SIGNIFICANCE: Nanomolar A25-35 alone does not cause persistent change in the basal level of calcium in astrocytes. However, even small amounts of A25-35, together with transmitters, can have substantial synergistic effects on intracellular calcium signals. Computational modeling further helps in understanding the mechanisms associated with intracellular calcium oscillations. Modeling the mechanisms is important, as astrocytes have an essential role in regulating the neuronal microenvironment of the central nervous system.
为了更好地理解阿尔茨海默病发病机制中观察到的复杂分子水平相互作用，湿实验室和临床研究的结果可以通过数学模型来补充。众所周知，星形胶质细胞在阿尔茨海默病中会变得活跃，其离子平衡会因释放和积累的递质（如血清素）以及包括淀粉样肽（A）在内的肽之间的相互作用而受到干扰。我们在这里通过 Fura-2AM 荧光测量研究了少量 A25-35 片段对星形胶质细胞中递质诱导的钙信号的影响，并对检测到的钙信号进行了模拟。
方法/主要发现：在培养的大鼠皮质星形胶质细胞中，通过加入血清素和谷氨酸，或这两种递质与 A25-35 一起加入，测量细胞内钙信号。A25-35 增加了对谷氨酸有反应的星形胶质细胞数量，并极大地增加了血清素诱导的钙信号幅度。除了 A25-35 诱导的作用外，还测试了细胞内钙库对钙信号的贡献。当使用更高的刺激频率时，初始峰后的后续钙峰幅度较低。这可能表明在刺激之间细胞内钙库的填充不足。为了再现实验结果，引入了一个随机计算模型。该模型考虑了已知参与星形胶质细胞钙信号的主要机制。模型模拟证实了主要的实验发现，并显示了实验测量的典型可变性。
结论/意义：单独的纳米摩尔 A25-35 不会导致星形胶质细胞基础钙水平持续变化。然而，即使是少量的 A25-35，与递质一起，也会对细胞内钙信号产生显著的协同作用。计算建模进一步有助于理解与细胞内钙振荡相关的机制。对机制进行建模很重要，因为星形胶质细胞在调节中枢神经系统神经元微环境方面起着至关重要的作用。
