A Threshold Shear Force for Calcium Influx in an Astrocyte Model of Traumatic Brain Injury
A Threshold Shear Force for Calcium Influx in an Astrocyte Model of Traumatic Brain Injury
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DOI：
10.1089/neu.2014.3677
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发表时间：
2015-07-01
影响因子：
4.2
通讯作者：
Hua, Susan Z.
中科院分区：
文献类型：
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作者：
Maneshi, Mohammad Mehdi;Sachs, Frederick;Hua, Susan Z.
外伤性脑损伤（TBI）是指由爆炸或撞击等外部机械力造成的脑损伤。我们目前对创伤性脑损伤的理解主要来自体内研究，这些研究显示了创伤性脑损伤后神经元的可测量生物学效应。关于脑细胞在刺激过程中的早期反应，以及刺激的哪些特征对细胞损伤最关键，我们知之甚少。我们在微流体室中使用快速压力伺服产生定义的剪切应力，并检测了培养的成人星形胶质细胞的细胞内Ca2+水平。剪切应力增加细胞内Ca2+取决于刺激的幅度，持续时间和上升时间。快速上升时间（约2ms）的方脉冲引起细胞内Ca2+的短暂增加，但当上升时间延长到20ms时，响应要小得多。响应的阈值是由多个参数组成的矩阵。细胞可以整合来自重复挑战的剪切力的影响：10个窄脉冲（11.5dyn/cm(2)和10ms宽）的脉冲序列导致Ca2+相对于100ms宽的相同振幅的单个脉冲增加4倍。Ca2+的增加在Ca2+无介质中被消除，但在用thapsigargin耗尽细胞内Ca2+储存后观察到，这表明需要Ca2+内流。胞外Gd3+（一种机械敏感离子通道的非特异性抑制剂）可抑制Ca2+内流，但不受更特异性抑制剂GsMTx4的影响。电压门控通道阻滞剂硝苯地平、地尔硫卓和维拉帕米也无效。数据表明，机械诱导的Ca2+内流通常与脑损伤的神经元模型相关，也存在于星形胶质细胞中，并且剪切应力与Ca2+内流存在粘弹/塑性耦合。Ca2+内流的位置尚未确定。
Traumatic brain injury (TBI) refers to brain damage resulting from external mechanical force, such as a blast or crash. Our current understanding of TBI is derived mainly from in vivo studies that show measurable biological effects on neurons sampled after TBI. Little is known about the early responses of brain cells during stimuli and which features of the stimulus are most critical to cell injury. We generated defined shear stress in a microfluidic chamber using a fast pressure servo and examined the intracellular Ca2+ levels in cultured adult astrocytes. Shear stress increased intracellular Ca2+ depending on the magnitude, duration, and rise time of the stimulus. Square pulses with a fast rise time (approximate to 2ms) caused transient increases in intracellular Ca2+, but when the rise time was extended to 20ms, the response was much less. The threshold for a response is a matrix of multiple parameters. Cells can integrate the effect of shear force from repeated challenges: A pulse train of 10 narrow pulses (11.5dyn/cm(2) and 10ms wide) resulted in a 4-fold increase in Ca2+ relative to a single pulse of the same amplitude 100ms wide. The Ca2+ increase was eliminated in Ca2+-free media, but was observed after depleting the intracellular Ca2+ stores with thapsigargin suggesting the need for a Ca2+ influx. The Ca2+ influx was inhibited by extracellular Gd3+, a nonspecific inhibitor of mechanosensitive ion channels, but it was not affected by the more specific inhibitor, GsMTx4. The voltage-gated channel blockers, nifedipine, diltiazem, and verapamil, were also ineffective. The data show that the mechanically induced Ca2+ influx commonly associated with neuron models for TBI is also present in astrocytes, and there is a viscoelastic/plastic coupling of shear stress to the Ca2+ influx. The site of Ca2+ influx has yet to be determined.