NEUROPROTECTIVE EFFECTS OF ETHYL PYRUVATE ON ENERGY METABOLISM OF RAT BRAIN AFTER ISCHEMIA: A 31P-NMR STUDY

简介：丙酮酸不仅是一种能量代谢的中间代谢物，也是一种神经保护剂，是一种有效的抗氧化剂和自由基清除剂。据报道，丙酮酸可改善失血性休克时的脑代谢和功能状态，减少脑缺血后的神经元死亡。采用磷核磁共振（^<31>P-NMR）研究了丙酮酸酯稳定的亲脂衍生物丙酮酸乙酯（EP）对缺血大鼠脑能量代谢的神经保护作用。方法：取雄性Wistar大鼠（6周龄）脑切片，用标准人工脑脊液（ACSF）与2mM EP或仅ACSF（对照组）在25℃下孵育。停止灌注1小时，使脑切片缺血。用^<31>P-NMR测定再灌注后高能磷酸盐、磷酸肌酸（PCr）水平的恢复情况。结果：有EP时ACSF缺血后PCr水平的恢复明显高于无EP时（分别为78.2±3.3% vs 60.8±1.9%,p = 0.001）。仅在恢复期应用EP效果较差（71.9±4.6%;p = 0.059）。用1001μM氟柠檬酸盐（FC）处理脑切片后，PCr水平降至未处理水平的92.0±3.3%。富神经元脑切片经FC预处理后，缺血后PCr水平恢复无差异（69.8±6.4% vs 70.0±4.5%;p = 0.66）。结论：提示在缺血暴露前给药EP对缺血有保护作用。我们的研究结果还表明，EP在经FC预处理的富含神经元的切片中没有明显的神经保护作用。提示在缺血前给药EP和神经胶质细胞的存在是EP发挥神经保护作用的必要条件。

Introduction : Pyruvate is not only an intermediary metabolite of energy metabolism but also a neuro-protectant as a potent antioxidant and free radical scavenger. It was reported that administration of pyruvate improved cerebral metabolic and functional status during hemorrhagic shock and reduced neuronal death after cerebral ischemia.Neuroprotective effects of ethyl pyruvate (EP), a stable and lipophilic derivative of pyruvate, on energy metabolism of rat brain exposed to ischemia were investigated by phosphorous nuclear magnetic resonance (^<31>P-NMR) spectroscopy.Methods : Brain slices prepared from a male Wistar rat (6 week-old) were incubated in standard artificial cerebrospinal fluid (ACSF) with 2mM EP or ACSF only (control) at 25℃. The brain slices were exposed to ischemia by halting the perfusion for 1 hr. Recovery of the levels of high-energy phosphates, phosphocreatine (PCr), after reperfusion were measured by ^<31>P-NMR.Results : Recovery of the level of PCr after ischemia was significantly greater when EP was present in ACSF than in its absence (78.2 ± 3.3% vs 60.8 ± 1.9%, respectively; p = 0.001). EP was less effective when it was administered only during the recovery period (71.9 ± 4.6%; p = 0.059). When the brain slices were treated with 1001μM fluorocitrate (FC), a selective glial poison, PCr level was decreased to 92.0 ± 3.3% of the untreated level. In neuron-rich brain slices pretreated with FC, difference in recovery of the PCr level after ischemia was not detected (69.8 ± 6.4% vs 70.0 ± 4.5%; p = 0.66).Conclusions : These results indicated that EP is neuroprotective against ischemia when administered before the ischemic exposure. Our results also showed that EP did not show significant neuroprotective effects in neuron-rich slices pretreated with FC. It was suggested that the administration of EP before ischemia and the presence of glial cells are required for EP to exert neuroprotective effects.