钾通道Kv4.2、Kv1.4在硫化氢后处理对大鼠短暂全脑缺血神经保护中的作用研究

目的研究硫氢化钠(sodium hydrosulfide,Na HS)后处理对短暂全脑缺血大鼠海马中钾通道Kv4.2和Kv1.4 mRNA表达变化的影响及其脑保护作用,从而探讨Na HS对大鼠短暂全脑缺血神经保护作用的机制。方法用4VO方法建立大鼠短暂性全脑缺血(transient global cerebral ischemia,t GCI)模型,大鼠被随机分配到3组,分别为:假手术组(sham)、t GCI组、Na HS后处理组。Na HS后处理组为t GCI之后1 d,给予大鼠腹腔注射Na HS 24μmmol/kg或者180μmmol/kg。通过尼氏染色与Neu N免疫染色确定海马神经元的死亡,通过RT-PCR方法检测海马组织Kv4.2和Kv1.4mRNA水平的表达变化。结果 (1)与t GCI组比较,在t GCI之后1 d给予24μmol/kg Na HS后处理使海马CA1区存活细胞数目显著增加,而高剂量的Na HS(180μmol/kg)后处理对t GCI大鼠海马CA1区则无明显的保护作用。(2)在Re 26 h和Re 48 h,海马组织中Kv4.2、Kv1.4的mRNA表达水平均明显低于假手术组(P<0.05)。在Re 26 h+Na HS组,kv4.2(1.24±0.08)和kv1.4(1.11±0.07)的mRNA表达水平均分别高于Re 26 h组的kv4.2(0.75±0.04)和kv1.4(0.79±0.06),差异均有显著性(P<0.05)。结论外源性Na HS可能通过上调大鼠t GCI后海马区Kv4.2和Kv1.4 mRNA的表达,从而导致膜电位超极化,降低神经元兴奋性和氧耗,继而保护神经元免受脑缺血损伤。

Effect of potassium channels Kv4.2 and Kv1.4 in neuroprotection of NaHS Postconditioning against Transient Global Cerebral Ischemia in Rats

Objective We intend to study the effects of sodium hydrosulfide postconditioning on the Kv4.2 and Kv1.4 potassium channel mRNA expression of hippocampus after transient global cerebral ischemia in rats and its role in brain protection,so as to explore the neuroprotective mechanism of NaHS against Transient Global Cerebral Ischemia model in Adult Rats.Methods Transient global ischemia was produced in adult Wistar rats using the 4-vessel occlusion method.The rats were randomly assigned into 3 groups:sham group,tGCI group,and tGCI+NaHS groups.NaHS postconditioning was carried out by intraperitoneal injection of 24 μmol/kg or 180 μmol/kg of NaHS at 1d post-tGCI.The neuronal death in the hippocampal CA1 subregion was determined by Nissl staining and NeuN staining.The mRNA expression levels of Kv4.2 and Kv1.4 potassium channels were analyzed by RT-PCR.Results (1)Compared with the tGCI group,24 μmol/kg NaHS Postconditioning significantly increased the number of surviving cells in hippocampus.However,higher concentration of exogenous NaHS (180 μmol/kg) didn't offer a protection against the neuronal injury induced by global cerebral ischemia-reperfusion.(2)The mRNA expression of Kv4.2 and Kv1.4 in hippocampus in the tGCI group were lower than that in Sham group (P<0.05).The mRNA expression of KV4.2 (1.24±0.08)、Kv1.4 (1.11±0.07) in hippocampus of NaHS treatment group was markedly higher than the tGCI group at 26 hours after reperfusion(0.75±0.04)、(0.79±0.06) respectively.(P<0.05).Conclusion Exogenous NaHS postconditioning may lead to membrane potential hyperpolarization by increasing Kv4.2 and Kv1.4 mRNA expression level,which inhibit the excitability of neurons and reduce oxygen consumption,protect neurons against cerebral ischemic injury.