Comparison of apolipoprotein E isoform-specific effects after experimental cerebral ischemia.

本研究利用人载脂蛋白E2（apoE 2）（2/2）、apoE 3（3/3）和apoE 4（4/4）基因敲入（KI）小鼠，从以下四个方面进行了研究：（1）比较apoE亚型对局灶性脑缺血后早期梗死扩展发生的特异性;（ii）比较apoE亚型对局灶性脑缺血后迟发性梗死扩展发生的特异性;（iii）分析apoE 4亚型特异性加重脑损伤的可能机制;在2002年，发现在局灶性脑缺血后24小时，4/4-KI小鼠的梗死体积和神经功能缺损比2/2-和3/3-KI小鼠显著更差，表明apoE 4同种型加重急性梗死扩展。结果表明，在局灶性脑梗死的亚急性期（1 - 7天）， ...更多信息 在4/4-KI小鼠中，以同种型特异性方式（apoE 4> apoE 3 = apoE 2），血症显著加重。在2004年和2005年，进行了本研究，以探索增强的星形胶质细胞活化和4/4-KI小鼠脑损伤恶化之间的假定因果关系，使用反应性星形胶质细胞的调节剂，（R）-（-）-2-丙基辛酸（通过S-100蛋白合成的负调节抑制星形胶质细胞活化）。此外，本研究的目的是扩大可能的临床应用的代理对apoE 4亚型特异性加重脑损伤。结果清楚地表明，胡萝卜酸的有益作用在4/4-KI小鼠中最明显，其中延迟的梗塞扩展连同神经功能缺损的恶化被显著减轻。4/4-KI小鼠脑梗死灶周围S100/GFAP免疫反应负荷的减弱程度明显大于2/2-或3/3-KI小鼠。4/4-KI小鼠迟发性梗死扩展的加重伴随着梗死周围区域中显著的星形胶质细胞活化（如S100 B/GFAP免疫反应性负荷的增加所证明的），与KI小鼠的其他两个遗传系相比。上述结果表明，apoE 4亚型通过增强星形胶质细胞的活化而加重了局灶性脑缺血亚急性期的脑损伤。（2002 - 2005），本研究证实了（i）apoE 4亚型特异性脑损伤加重的实验证据;（ii）增强的星形胶质细胞激活和脑损伤加重之间的因果关系，这种现象的发病机制;（iii）一种新的治疗策略，通过药理学调节星形胶质细胞激活对apoE 4亚型特异性神经元脆弱性中风后。少

Using homozygous human apolipoprotein E2 (apoE2) (2/2)-, apoE3 (3/3)-, or apoE4 (4/4)-knock-in (KI) mice, the present study was undertaken to examine the following four aspects : (i)comparison of the apoE isoform specificity on the occurrence of early infarct expansion after focal cerebral ischemia ; (ii)comparison of the apoE isoform specificity on the occurrence of delayed infarct expansion after focal cerebral ischemia ; (iii)the analysis on the possible mechanisms underlying the apoE4 isoform-specific exacerbation of brain damage ; and (iv)the possible therapeutic intervention for this pathology.In 2002, infarct volume and neurologic deficits were found to be significantly worse in 4/4-KI mice than in 2/2- and 3/3-KI mice at 24 hours after focal cerebral ischemia, indicating that the apoE4 isoform exacerbates acute infarct expansion.In 2003, the results demonstrated that delayed infarct expansion and astrocytic activation during the subacute phase (1 to 7 days) of focal cerebral is … More chemia were markedly exacerbated in 4/4-KI mice in an isoform-specific fashion (apoE4>apoE3=apoE2). The above data indicated that the apoE4 isoform acts to augment reactive astrocytosis and the associated inflammatory responses, leading to exacerbation of delayed infarct expansion.In 2004 and 2005, the present study was performed to probe the putative causal relationship between enhanced astrocytic activation and exacerbation of brain damage in 4/4-KI mice using a modulating agent of reactive astrocytes, (R)-(-)-2-propyloctanoic acid (suppression of astrocytic activation through the negative regulation of S-100 protein synthesis). In addition, the present study was aimed to extend the possible clinical application of the agent against apoE4 isoform-specific exacerbation of brain damage. The results clearly showed that the beneficial effects of arundic acid were most pronounced in 4/4-KI mice, wherein delayed infarct expansion together with deterioration of neurologic deficits was significantly mitigated. The attenuation of the S100/GFAP immunoreactive burden in the peri-infarct area induced by arundic acid in 4/4-KI mice was much greater than that in 2/2- or 3/3-KI mice. The aggravation of delayed infarct expansion in 4/4-KI mice was accompanied by pronounced astrocytic activation in the peri-infarct area (as evidenced by an increase in the S100B/GFAP immunoreactive burden) as compared with the other two genetic lines of KI mice. The above results indicate that the apoE4 isoform exacerbates brain injury during the subacute phase of focal cerebral ischemia through augmentation of astrocytic activation.Based on the above data obtained from the consecutive studies during the past four years (2002 to 2005), the present study demonstrated (i)experimental evidence of the apoE4 isoform-specific exacerbation of brain damage ; (ii)causal relationship between enhanced astrocytic activation and exacerbation of brain damage in the pathogenesis of this phenomenon ; (iii)a novel therapeutic strategy by pharmacological modulation of astrocytic activation against apoE4 isoform-specific neuronal vulnerability after stroke. Less