Department of Pharmacology, College of Pharmacy, Seoul National University, Shillim-Dong, Kwanak-Gu, Seoul, Korea.
Neuroimmunomodulation. 2009;16(6):365-76. doi: 10.1159/000228911. Epub 2009 Jul 17.
Neural progenitor cells (NPC) are self-renewing multipotent cells that generate neurons and glial cells in the brain. NPCs generate neurons and glia not only during development but also after neural injury. Recent studies have shown that endogenous NPCs are activated after brain injury and migrate toward damaged areas where astrocyte activation occurs. Considering the massive proliferation of astrocytes as well as the production of several kinds of cytoactive molecules after brain injury, such as NO, growth factors and cytokines, it is tempting to think that cytoactive molecules released by activated glial cells regulate neural progenitor differentiation and proliferation through inflammatory mediators. To test this hypothesis, we stimulated rat primary astrocytes with lipopolysaccharide (LPS) to induce the activation of astrocytes. After addition of the conditioned media from LPS-stimulated astrocytes to NPC culture, proliferation was examined by MTT assay and bromodeoxyuridine (BrdU) incorporation. The differentiation of NPC into neurons and astrocytes was examined by Western blot, ELISA and immunocytochemical staining with cell-type-specific markers. Conditioned media from LPS-stimulated astrocytes increased NPC proliferation as well as gliogenesis as compared with control conditioned media from astrocytes without LPS stimulation. In contrast, neurogenesis was decreased by LPS-conditioned media. To investigate the molecular mechanism mediating glial differentiation and proliferation of NPC by reactive astrocytes, we added inhibitors of the Erk and JNK pathways during LPS stimulation. These inhibitors - except for a p38 inhibitor - decreased NPC proliferation and glial differentiation. These results suggest that LPS stimulated astrocytes generate factors regulating NPC proliferation and gliogenesis via the Erk and JNK pathways.
神经祖细胞（NPC）是具有自我更新能力的多能细胞，可在大脑中生成神经元和神经胶质细胞。NPC 不仅在发育过程中产生神经元和神经胶质细胞，而且在神经损伤后也会产生。最近的研究表明，内源性 NPC 在脑损伤后被激活，并向发生星形胶质细胞激活的受损区域迁移。考虑到星形胶质细胞的大量增殖以及脑损伤后产生的多种细胞活性分子，如 NO、生长因子和细胞因子，很容易想到激活的神经胶质细胞释放的细胞活性分子通过炎症介质调节神经祖细胞的分化和增殖。为了验证这一假设，我们用脂多糖（LPS）刺激大鼠原代星形胶质细胞以诱导星形胶质细胞的激活。在将 LPS 刺激的星形胶质细胞的条件培养基添加到 NPC 培养物后，通过 MTT 测定和溴脱氧尿苷（BrdU）掺入来检查增殖。通过 Western blot、ELISA 和细胞类型特异性标志物的免疫细胞化学染色检查 NPC 向神经元和星形胶质细胞的分化。与未经 LPS 刺激的星形胶质细胞的对照条件培养基相比，LPS 刺激的星形胶质细胞的条件培养基增加了 NPC 的增殖和神经胶质发生，但减少了神经发生。为了研究反应性星形胶质细胞通过 Erk 和 JNK 途径介导 NPC 胶质分化和增殖的分子机制，我们在 LPS 刺激期间添加了 Erk 和 JNK 途径的抑制剂。这些抑制剂（除了 p38 抑制剂）减少了 NPC 的增殖和神经胶质分化。这些结果表明，LPS 刺激的星形胶质细胞通过 Erk 和 JNK 途径产生调节 NPC 增殖和神经胶质发生的因子。
