From the Department of Neurology, Juntendo University Faculty of Medicine, Tokyo, Japan (K.H., Y.U., R.T., N.M., K.Y., N.H.).
Stroke Center, Jichi Medical University Hospital, Shimotsuke, Japan (R.T.).
Stroke. 2018 Oct;49(10):2483-2494. doi: 10.1161/STROKEAHA.118.021272.
Background and Purpose- Exosomes play a pivotal role in neurogenesis. In the peri-infarct area after stroke, axons begin to regenerate but are inhibited by astrocyte scar formation. The direct effect and underlying molecular mechanisms of astrocyte-derived exosomes on axonal outgrowth after ischemia are not known. Methods- Using a semaphorin 3A (Sema3A) inhibitor, we explored neuronal signaling during axonal outgrowth after ischemia in rats subjected to middle cerebral artery occlusion and in cultured cortical neurons challenged with oxygen-glucose deprivation. Furthermore, we assessed whether this inhibitor suppressed astrocyte activation and regulated astrocyte-derived exosomes to enhance axonal outgrowth after ischemia. Results- In rats subjected to middle cerebral artery occlusion, we administered a Sema3A inhibitor into the peri-infarct area from 7 to 21 days after occlusion. We found that phosphorylated high-molecular weight neurofilament-immunoreactive axons were increased, glial fibrillary acidic protein-immunoreactive astrocytes were decreased, and functional recovery was promoted at 28 days after middle cerebral artery occlusion. In cultured neurons, the Sema3A inhibitor decreased Rho family GTPase 1, increased R-Ras, which phosphorylates Akt and glycogen synthase kinase 3β (GSK-3β), selectively increased phosphorylated GSK-3β in axons, and thereby enhanced phosphorylated high-molecular weight neurofilament-immunoreactive axons after oxygen-glucose deprivation. In cultured astrocytes, the Sema3A inhibitor suppressed activation of astrocytes induced by oxygen-glucose deprivation. Exosomes secreted from ischemic astrocytes treated with the Sema3A inhibitor further promoted axonal elongation and increased prostaglandin D synthase expression on microarray analysis. GSK-3β and prostaglandin D synthase neurons were robustly increased after treatment with the Sema3A inhibitor in the peri-infarct area. Conclusions- Neuronal Rho family GTPase 1/R-Ras/Akt/GSK-3β signaling, axonal GSK-3β expression, and astrocyte-derived exosomes with prostaglandin D synthase expression contribute to axonal outgrowth and functional recovery after stroke.
背景与目的-外泌体在神经发生中起着关键作用。在中风后的梗死周边区，轴突开始再生，但被星形胶质细胞瘢痕形成所抑制。星形胶质细胞来源的外泌体对缺血后轴突生长的直接作用及其潜在的分子机制尚不清楚。方法-我们使用一种 semaphorin 3A（Sema3A）抑制剂，在大脑中动脉闭塞大鼠和氧葡萄糖剥夺培养的皮质神经元中，探讨缺血后轴突生长过程中的神经元信号。此外，我们评估了这种抑制剂是否抑制星形胶质细胞激活并调节星形胶质细胞来源的外泌体，以增强缺血后轴突的生长。结果-在大脑中动脉闭塞大鼠中，我们从闭塞后 7 至 21 天将 Sema3A 抑制剂注入梗死周边区。我们发现，磷酸化高分子量神经丝免疫反应性轴突增加，胶质纤维酸性蛋白免疫反应性星形胶质细胞减少，大脑中动脉闭塞后 28 天功能恢复得到促进。在培养的神经元中，Sema3A 抑制剂降低了 Rho 家族 GTPase 1，增加了 R-Ras，其磷酸化 Akt 和糖原合酶激酶 3β（GSK-3β），选择性地增加了轴突中磷酸化的 GSK-3β，从而增强了氧葡萄糖剥夺后的磷酸化高分子量神经丝免疫反应性轴突。在培养的星形胶质细胞中，Sema3A 抑制剂抑制了氧葡萄糖剥夺诱导的星形胶质细胞激活。在 Sema3A 抑制剂处理的缺血星形胶质细胞分泌的外泌体进一步促进了轴突伸长，并在微阵列分析中增加了前列腺素 D 合酶的表达。在梗死周边区用 Sema3A 抑制剂处理后，GSK-3β 和前列腺素 D 合酶神经元大量增加。结论-神经元 Rho 家族 GTPase 1/R-Ras/Akt/GSK-3β 信号、轴突 GSK-3β 表达和具有前列腺素 D 合酶表达的星形胶质细胞来源的外泌体有助于中风后的轴突生长和功能恢复。
