Department of Neurology, University of Texas Health Science Center, Houston, TX, USA.
Department of Neurology, Henry Ford Hospital, Detroit, MI, USA.
Transl Stroke Res. 2018 Oct;9(5):506-514. doi: 10.1007/s12975-018-0611-5. Epub 2018 Feb 24.
Neurite plasticity is a critical aspect of brain functional recovery after stroke. Emerging data suggest that Ras-related C3 botulinum toxin substrate 1 (Rac1) plays a central role in axonal regeneration in the injured brain, specifically by stimulating neuronal intrinsic growth and counteracting the growth inhibitory signaling that leads to growth cone collapse. Therefore, we investigated the functional role of Rac1 in axonal regeneration after stroke.Delayed treatment with a specific Rac1 inhibitor, NSC 23766, worsened functional recovery, which was assessed by the pellet reaching test from day 14 to day 28 after stroke. It additionally reduced axonal density in the peri-infarct zone, assessed 28 days after stroke, with no effect on brain cavity size or on the number of newly formed cells. Accordingly, Rac1 overexpression using lentivirus promoted axonal regeneration and functional recovery after stroke from day 14 to day 28. Rac1 inhibition led to inactivation of pro-regenerative molecules, including mitogen-activated protein kinase kinase (p-MEK)1/2, LIM domain kinase (LIMK)1, and extracellular signal-regulated kinase (p-ERK)1/2 at 14 days after stroke. Inhibition of Rac1 reduced axonal length and number in cultured primary mouse cortical neurons using microfluidic chambers after oxygen-glucose deprivation (OGD) without affecting cell viability. In contrast, inhibition of Rac1 increased levels of glial fibrillary acidic protein, an extrinsic inhibitory signal for axonal growth, after stroke in vivo and in primary astrocytes after OGD.In conclusion, Rac1 signaling enhances axonal regeneration and improve post-stroke functional recovery in experimental models of stroke.
神经突可塑性是中风后大脑功能恢复的关键方面。新出现的数据表明，Ras 相关 C3 肉毒梭菌毒素底物 1（Rac1）在受损大脑中的轴突再生中起着核心作用，特别是通过刺激神经元内在生长并抵消导致生长锥塌陷的生长抑制信号。因此，我们研究了 Rac1 在中风后轴突再生中的功能作用。中风后第 14 天至第 28 天，特异性 Rac1 抑制剂 NSC 23766 的延迟治疗会加重功能恢复，该功能通过球粒到达测试进行评估。此外，它还降低了梗塞周围区的轴突密度，评估时间为中风后 28 天，对脑腔大小或新形成细胞的数量没有影响。因此，使用慢病毒进行 Rac1 过表达可促进中风后第 14 天至第 28 天的轴突再生和功能恢复。中风后第 14 天，Rac1 抑制导致促再生分子失活，包括丝裂原活化蛋白激酶激酶（p-MEK）1/2、LIM 结构域激酶（LIMK）1 和细胞外信号调节激酶（p-ERK）1/2。Rac1 抑制在体外氧葡萄糖剥夺（OGD）后使用微流控室减少了培养的原代小鼠皮质神经元中的轴突长度和数量，而不影响细胞活力。相比之下，在体内中风后和原发性星形胶质细胞在 OGD 后，Rac1 抑制增加了神经生长的外在抑制信号胶质纤维酸性蛋白的水平。总之，Rac1 信号增强了轴突再生，并改善了中风后实验模型中的功能恢复。
