背景:创伤性脑损伤(TBI)是一个复杂的病理生理过程,突触后密度(PSD)蛋白的重要作用日益受到重视,如谷氨酸受体。我们先前的研究表明,PSD蛋白Arc/Arg3.1(Arc)在体外调节内质网(ER)应激和神经元坏死。
目的:在本研究中,我们调查了表达式,Arc在体内和体外实验TBI模型中的调节和生物学功能。
结果:创伤性神经元损伤(TNI)诱导了皮质神经元中电弧的时间上调,而TBI导致大鼠Arc表达持续增加直至24小时。Arc表达的增加是由代谢型谷氨酸受体5(mGluR5)的活性介导的,但不依赖于细胞内钙(Ca2+)的释放。通过使用抑制剂和拮抗剂,我们发现TNI通过Gq蛋白和蛋白周转调节Arc表达。此外,Arc的过表达在体内和体外保护TBI诱导的神经元损伤和运动功能障碍,而长期认知功能没有改变。为了确定电弧在mGluR5诱导的保护中的作用,进行慢病毒介导的短发夹RNA(shRNA)转染以敲低Arc表达。通过Arc敲低部分阻止了mGluR5激动剂(RS)-2-氯-5-羟基苯基甘氨酸(CHPG)诱导的对TBI的保护作用。此外,TNI后CHPG诱导的Ca2内流衰减依赖于Arc激活和AMPAR亚基的调节。Co-IP和Ca2成像结果表明,Arc-Homer1相互作用有助于CHPG诱导的细胞内Ca2释放调节。
结论:总之,目前的数据表明,mGluR5介导的Arc激活是一种保护机制,可以通过调节细胞内Ca2止血来减轻TBI后的神经毒性。Homer1-IP3R途径诱导的AMPAR相关的Ca2流入和ERCa2释放可能参与了这种保护。
BACKGROUND: Traumatic brain injury (TBI) is a complex pathophysiological process, and increasing attention has been paid to the important role of post-synaptic density (PSD) proteins, such as glutamate receptors. Our previous study showed that a PSD protein Arc/Arg3.1 (Arc) regulates endoplasmic reticulum (ER) stress and neuronal necroptosis in traumatic injury in vitro.
OBJECTIVE: In this study, we investigated the expression, regulation and biological function of Arc in both in vivo and in vitro experimental TBI models.
RESULTS: Traumatic neuronal injury (TNI) induced a temporal upregulation of Arc in cortical neurons, while TBI resulted in sustained increase in Arc expression up to 24 h in rats. The increased expression of Arc was mediated by the activity of metabotropic glutamate receptor 5 (mGluR5), but not dependent on the intracellular calcium (Ca2+) release. By using inhibitors and antagonists, we found that TNI regulates Arc expression via Gq protein and protein turnover. In addition, overexpression of Arc protects against TBI-induced neuronal injury and motor dysfunction both in vivo and in vitro, whereas the long-term cognitive function was not altered. To determine the role of Arc in mGluR5-induced protection, lentivirus-mediated short hairpin RNA (shRNA) transfection was performed to knockdown Arc expression. The mGluR5 agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG)-induced protection against TBI was partially prevented by Arc knockdown. Furthermore, the CHPG-induced attenuation of Ca2+ influx after TNI was dependent on Arc activation and followed regulation of AMPAR subunits. The results of Co-IP and Ca2+ imaging showed that the Arc-Homer1 interaction contributes to the CHPG-induced regulation of intracellular Ca2+ release.
CONCLUSIONS: In summary, the present data indicate that the mGluR5-mediated Arc activation is a protective mechanism that attenuates neurotoxicity following TBI through the regulation of intracellular Ca2+ hemostasis. The AMPAR-associated Ca2+ influx and ER Ca2+ release induced by Homer1-IP3R pathway might be involved in this protection.