cAMP对大鼠颅脑损伤后神经功能及脑水肿的影响

目的 探讨蛋白激酶A（PKA）激活物cAMP对颅脑损伤（TBI）大鼠神经功能、脑水肿的影响。方法 选取120只成年雄性SD大鼠随机分为6组（每组20只）:假手术组（暴露硬脑膜而不给予液压打击）；高、中、低剂量cAMP组（TBI后1 h腹腔注射60、40、20 mg/kg PKA激活物8-Bromo-cAMP）；溶媒组（TBI后1 h腹腔注射cAMP溶媒二甲基亚砜10 μl）；模型组（液压打击处理）。TBI后48 h，采用神经损伤严重程度评分（NSS）评估神经功能，干湿重法测定脑含水量，免疫印迹法检查海马细胞外信号调节激酶1/2（ERK1/2）、非磷酸化缝隙连接蛋白43（NP-Cx43）、谷氨酸转运蛋白-1（GLT-1）及钠钾ATP酶的表达，高效液相色谱法检测海马谷氨酸（Glu）的含量。结果 TBI后，大鼠NSS明显增高（P<0.05），脑含水量明显增加（P<0.05），海马ERK1/2表达水平明显增加（P<0.05），海马Glu含量明显增加（P<0.05），而NP-Cx43、GLT-1、钠钾ATP酶表达水平明显降低（P<0.05）；cAMP干预后，显著逆转这些反应（P<0.05），而且呈剂量依赖性。结论 大鼠TBI后，给予cAMP干预，激活PKA，可通过门卫效应抑制ERK1/2，使NP-Cx43、GLT-1及钠钾ATP酶水平明显增高，进一步降低Glu等脑毒性代谢产物、缓解脑水肿，从而改善大鼠神经功能。

Role of inhibition of phosphorylated Cx43 by PKA pathway in treatment for traumatic brain injury

Objective To investigate the effect of inhibition of phosphorylated connexin (Cx)43 by protein kinase A (PKA) on the treatment of traumatic brain injury (TBI). Methods One hundred and twenty rats were randomly divided into 6 groups of 20 animal each, i.e. sham operation group, treatment groups, 1, 2 and 3 in which the rats received peritoneal injection of 20, 40 and 60 mg/kg 8-Bromo-cAMP respectively 1 hour after TBI, vehicle group in which the rats received peritoneal injection of dimethyl sulphoxide 1 hour after TBI and TBI group in which the rats underwent TBI only and did not receive any treatment. TBI models were established with fluid percussion device in the rats. Ten rates were sacrificed 48 hours after TBI and their brain water content was determined after the behavioral disordes were determined by Neurological Severity score (NSS) in all the groups. Another 10 rates were sacrificed 48 hours after TBI and their hippocampal astorcytes were obtained in order to determine the expressions of extracellular regulated protein kinase (ERK)1/2, nonphorylated (NP)-Cx43, glutamic transducin (GLT)-1 and Na-K-ATP determined by western blot and glutamic acid (Glu) by high pressure liquid chromatography. Result The levels of NP-Cx43, GLT-1 and Na-K-ATP expressions were significantly higher in all the treatment groups and sham operation group than those in other two groups (P<0.05). The levels of ERK1/2 and Glu expressions, brain water content and the scores of NSS were significantly lower in all the treatment groups and sham operation operation group than those in the TBI and vehicle groups (P<0.05). These changes were 8-Bromo-cAMP dose-dependent. Conclusions Activation of PKA pathway can inhibit ERK1/2 pathway, and up-regulate the levels of NP-Cx43, GLT-1 and Na-K-ATP protein expressions in the hippocampal astrocytes, which can reduce the contents of brain water and Glu on the brain in the rate with TBI.