Mazzoni I E, Kenigsberg R L
Department of Physiology, University of Montreal, Quebec, Canada.
Neuroscience. 1997 Jan;76(1):147-57. doi: 10.1016/s0306-4522(96)00235-7.
The normal development of the central nervous system is regulated by glia. In this regard, we have reported that astrocytes, stimulated by epidermal growth factor or transforming growth factor alpha, suppress the biochemical differentiation of rat medial septal cholinergic neurons in vitro, as evidenced by a decrease in choline acetyltransferase activity. In this study, we found that, in contrast to astrocytes, microglia enhance rather than suppress this aspect of cholinergic cell expression. When in excess, microglia can revert the effects of epidermal growth factor on the septal cholinergic neurons without altering the astroglial proliferative response to this growth factor. In the absence of growth factors or other glial cell types, microglia increase choline acetyltransferase activity above control levels and thus, may be a source of cholinergic differentiating activity. The increase in enzyme activity induced by microglia is rapid in onset, detected as early as 2 h after their addition to the septal neurons and maintained up to six or seven days in vitro. Furthermore, in the absence or presence of other glial cell types, microglia also influence septal GABAergic neurons by significantly increasing glutamate decarboxylase activity. As microglia affect neither septal cholinergic nor GABAergic neuronal cell survival, they appear to enhance the biochemical differentiation of these two neuronal cell types. Specific immunoneutralizing antibodies were used to identify the microglia-derived factors affecting these two neuronal types. In this regard, we found that the microglia-derived cholinergic differentiating activity is significantly suppressed by antibodies raised against interleukin-3. Furthermore, interleukin-3 was detected in both conditioned media and cell homogenates from septal neuronal-microglial co-cultures by western blotting. Finally, although basic fibroblast growth factor and interleukin-3 significantly increase septal glutamate decarboxylase activity, neither appears to be implicated in the GABAergic cell response to the microglia. In conclusion, these results demonstrate that microglia can enhance the biochemical differentiation of developing cholinergic and GABAergic neurons in vitro.
中枢神经系统的正常发育受神经胶质细胞调节。在这方面，我们已经报道，表皮生长因子或转化生长因子α刺激的星形胶质细胞在体外可抑制大鼠内侧隔区胆碱能神经元的生化分化，胆碱乙酰转移酶活性降低即证明了这一点。在本研究中，我们发现，与星形胶质细胞相反，小胶质细胞增强而非抑制胆碱能细胞表达的这一方面。当小胶质细胞过量时，它可逆转表皮生长因子对隔区胆碱能神经元的作用，而不改变星形胶质细胞对该生长因子的增殖反应。在没有生长因子或其他胶质细胞类型的情况下，小胶质细胞可使胆碱乙酰转移酶活性高于对照水平，因此，可能是胆碱能分化活性的一个来源。小胶质细胞诱导的酶活性增加起效迅速，早在将其添加到隔区神经元后2小时即可检测到，并在体外维持长达六七天。此外，在没有或存在其他胶质细胞类型的情况下，小胶质细胞还通过显著增加谷氨酸脱羧酶活性来影响隔区γ-氨基丁酸能神经元。由于小胶质细胞既不影响隔区胆碱能神经元也不影响γ-氨基丁酸能神经元的细胞存活，它们似乎增强了这两种神经元细胞类型的生化分化。使用特异性免疫中和抗体来鉴定影响这两种神经元类型的小胶质细胞衍生因子。在这方面，我们发现，针对白细胞介素-3产生的抗体可显著抑制小胶质细胞衍生的胆碱能分化活性。此外，通过蛋白质印迹法在隔区神经元-小胶质细胞共培养物的条件培养基和细胞匀浆中均检测到了白细胞介素-3。最后，尽管碱性成纤维细胞生长因子和白细胞介素-3可显著增加隔区谷氨酸脱羧酶活性，但两者似乎均与小胶质细胞对γ-氨基丁酸能细胞的反应无关。总之，这些结果表明，小胶质细胞在体外可增强发育中的胆碱能和γ-氨基丁酸能神经元的生化分化。
