Institute for Neurosurgical Pathophysiology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz 55131, Germany.
Neuroscience. 2013 Jul 9;242:1-10. doi: 10.1016/j.neuroscience.2013.03.018. Epub 2013 Mar 21.
Glutamate transporter-1 (GLT-1) maintains low concentrations of extracellular glutamate by removing glutamate from the extracellular space. It is controversial, however, whether upregulation of GLT-1 is neuroprotective under all ischemic/hypoxic conditions. Recently, a neuroprotective effect of preconditioning with a β-lactam antibiotic ceftriaxone (CTX) that increases expression of GLT-1 has been reported in animal models of focal ischemia. On the other hand, it is said that CTX does not play a neuroprotective role in an in vitro study. Thus, we examined the effect of CTX on ischemic injury in a rat model of two-vein occlusion (2VO). This model mimics venous ischemia during, e.g. tumor surgery, a clinical situation that is best suitable for pretreatment with CTX.
CTX (100mg/kg, 200mg/kg per day) or vehicle (0.9% NaCl) was intraperitoneally injected into Wistar rats for 5days before venous ischemia (n=57). Then, animals were prepared for occlusion of two adjacent cortical veins (2VO) by photothrombosis with rose bengal that was followed by KCl-induced cortical spreading depression (CSD). Infarct volume was evaluated with hematoxylin and eosin (H&E) staining 2days after venous occlusion. [(3)H]MK-801, [(3)H]AMPA and [(3)H]Muscimol ligand binding were examined autoradiographically in additional two groups without 2VO (n=5/group). Animals were injected either with NaCl (vehicle) or CTX 200mg/kg for 5days in order to evaluate whether NMDA, AMPA and GABAA ligand binding densities were affected.
CTX pretreatment reduced infarct volume compared to vehicle pretreatment (p<0.05). The effect of CTX pretreatment was attenuated by administration of the GLT-1 inhibitor, dihydrokainate (DHK) 30min before 2VO. CTX had no effect on the number of spontaneous spreading depressions after 2VO. Analysis of quantitative receptor autoradiography showed no statistically significant difference between rats after administration with CTX compared to control rats.
Pretreatment with CTX has neuroprotective potential without effect on NMDA, AMPA and GABAA receptor density and spontaneous spreading depression. This effect can be abolished by GLT-1 inhibition, indicating that upregulation of GLT-1 is an important mechanism for neuroprotective action in penumbra-like conditions, e.g. if neurosurgeons plan to occlude cerebral veins during tumor surgery.
谷氨酸转运体-1（GLT-1）通过将谷氨酸从细胞外间隙中移除，从而维持细胞外谷氨酸的低浓度。然而，在所有缺血/缺氧情况下，GLT-1 的上调是否具有神经保护作用仍存在争议。最近，有研究报道，β-内酰胺抗生素头孢曲松（CTX）预处理可增加 GLT-1 的表达，从而发挥对局灶性缺血动物模型的神经保护作用。另一方面，据说 CTX 在一项体外研究中没有发挥神经保护作用。因此，我们在两静脉闭塞（2VO）大鼠模型中研究了 CTX 对缺血损伤的影响。该模型模拟了肿瘤手术期间等情况下的静脉缺血，这种临床情况最适合 CTX 预处理。
CTX（100mg/kg、200mg/kg/天）或载体（0.9%NaCl）腹腔注射至 Wistar 大鼠 5 天，然后用玫瑰红进行光血栓形成以闭塞两条相邻的皮质静脉（2VO），随后用 KCl 诱导皮质扩散性抑制（CSD）。静脉闭塞后 2 天，用苏木精和伊红（H&E）染色评估梗死体积。在没有 2VO 的另外两组（每组 n=5）中，通过放射自显影检查[3H]MK-801、[3H]AMPA 和[3H]Muscimol 配体结合。为了评估 NMDA、AMPA 和 GABAA 配体结合密度是否受到影响，动物分别用 NaCl（载体）或 CTX 200mg/kg 注射 5 天。
与载体预处理相比，CTX 预处理可减少梗死体积（p<0.05）。2VO 前 30 分钟给予 GLT-1 抑制剂二氢奎宁酸（DHK）可减弱 CTX 预处理的作用。CTX 对 2VO 后自发性扩散性抑制的次数无影响。定量受体放射自显影分析显示，CTX 处理组与对照组大鼠之间无统计学差异。
CTX 预处理具有神经保护作用，而对 NMDA、AMPA 和 GABAA 受体密度及自发性扩散性抑制无影响。GLT-1 抑制可消除这种作用，表明 GLT-1 的上调是在类似半影区的情况下发挥神经保护作用的重要机制，例如神经外科医生计划在肿瘤手术期间闭塞脑静脉。
