Sarabi A, Chang C F, Wang Y, Tomac A C, Hoffer B J, Morales M
National Institute on Drug Abuse, IRP Department, Cellular Neurophysiology Section, NIH, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA.
Neurosci Lett. 2003 May 8;341(3):241-5. doi: 10.1016/s0304-3940(03)00195-2.
Exogenous administration of glial cell line-derived neurotrophic factor (GDNF) reduces ischemia-induced cerebral infarction. Cerebral ischemia induces gene expression of GDNF, GDNF-receptor alpha-1 (GFRalpha-1) and c-Ret, suggesting that a GDNF signaling cascade mechanism may be involved in endogenous neuroprotection during ischemia. In the present study, we examined if this endogenous neuroprotective pathway was altered in Gfralpha-1 deficient mice. Since mice homozygous for the Gfralpha-1 deletion (-/-) die within 24 h of birth, stroke-induced changes in the levels of Gfralpha-1 mRNA were studied in Gfralpha-1 heterozygous (+/-) mice and their wild-type (+/+) littermates. The right middle cerebral artery was transiently ligated for 45 min in anesthetized mice. Animals were killed at 0, 6, 12 and 24 h after the onset of reperfusion and levels of Gfralpha-1 mRNA were measured by in situ hybridization histochemistry. Previously, we showed that Gfralpha-1 (+/-) mice are more vulnerable to focal cerebral ischemia. In the present study, we found that basal levels of GFRalpha-1 mRNA were at similar low levels in cortex and striatum in adult Gfralpha-1 (+/+) and Gfralpha-1 (+/-) mice and that ischemia/reperfusion induced up-regulation of Gfralpha-1 mRNA in the lesioned and contralateral sides of cortex and striatum in both Gfralpha-1 (+/+) and GFRalpha-1 (+/-) mice. However, the ischemia/reperfusion induction of Gfralpha-1 mRNA was significantly higher in the cortex of wild type mice, as compared to Gfralpha-1 (+/-) mice. Moreover, the increased expression of Gfralpha-1 in striatum after reperfusion occurred earlier in the GFRalpha-1 (+/+) than in the Gfralpha-1 (+/-) mice. These results indicate that after ischemia, there is a differential up-regulation of Gfralpha-1 expression in Gfralpha-1 (+/+) and Gfralpha-1 (+/-) mice. Since GDNF has neuroprotective effects, the reduced up-regulation of Gfralpha-1 in Gfralpha-1 (+/-) mice at early time points after ischemia suggests that the responsiveness to GDNF and GDNF receptor mediated neuroprotection is attenuated in these genetically modified animals and may underlie their greater vulnerability.
外源性给予胶质细胞源性神经营养因子（GDNF）可减少缺血性脑梗死。脑缺血可诱导GDNF、GDNF受体α-1（GFRα-1）和c-Ret的基因表达，提示GDNF信号级联机制可能参与缺血期间的内源性神经保护。在本研究中，我们检测了这种内源性神经保护途径在Gfralpha-1基因敲除小鼠中是否发生改变。由于Gfralpha-1基因纯合缺失（-/-）的小鼠在出生后24小时内死亡，因此我们在Gfralpha-1基因杂合（+/-）小鼠及其野生型（+/+）同窝小鼠中研究了中风诱导的Gfralpha-1 mRNA水平变化。在麻醉的小鼠中，将右侧大脑中动脉短暂结扎45分钟。在再灌注开始后的0、6、12和24小时处死动物，并通过原位杂交组织化学法检测Gfralpha-1 mRNA水平。此前，我们发现Gfralpha-1（+/-）小鼠更容易发生局灶性脑缺血。在本研究中，我们发现成年Gfralpha-1（+/+）和Gfralpha-（+/-）小鼠的皮质和纹状体中GFRα-1 mRNA的基础水平相似且较低，并且缺血/再灌注可诱导Gfralpha-1（+/+）和GFRα-1（+/-）小鼠皮质和纹状体损伤侧及对侧的Gfralpha-1 mRNA上调。然而，与Gfralpha-1（+/-）小鼠相比，野生型小鼠皮质中缺血/再灌注诱导的Gfralpha-1 mRNA水平显著更高。此外，再灌注后纹状体中Gfralpha-1的表达增加在GFRα-1（+/+）小鼠中比在Gfralpha-1（+/-）小鼠中出现得更早。这些结果表明，缺血后，Gfralpha-1（+/+）和Gfralpha-1（+/-）小鼠中Gfralpha-1的表达上调存在差异。由于GDNF具有神经保护作用，缺血后早期Gfralpha-1（+/-）小鼠中Gfralpha-1上调减少表明，这些基因修饰动物对GDNF和GDNF受体介导的神经保护的反应性减弱可能是其更易发生脑缺血的原因。
