Morita Mitsuhiro, Kozuka Nagisa, Itofusa Rurika, Yukawa Masashi, Kudo Yosihisa
Laboratory of Cellular Neurobiology, School of Life Science, Tokyo University of Pharmacy and Life Science, Tokyo, Japan.
J Neurochem. 2005 Nov;95(3):871-9. doi: 10.1111/j.1471-4159.2005.03430.x. Epub 2005 Aug 31.
We previously reported that astrocytes cultured for more than 2 days in a defined medium containing epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) showed calcium oscillation in response to glutamate, whereas the response pattern was transient in the absence of the exogenous growth factors. In the present study, we found that astrocytes showed glutamate-induced calcium oscillation, even in growth factor-free medium, if the cells had been cultured for more than 5 days. The calcium oscillation promoted by the prolonged culture period was suppressed by an inhibitor of EGF receptor tyrosine kinase, but not by a neutralizing antibody to bFGF, indicating that the accumulation of an autocrine factor that activates the EGF receptor leads to calcium oscillation. Astrocytes in our culture system expressed EGF, transforming growth factor alpha (TGFalpha), bFGF and acidic fibroblast growth factor (aFGF). Exogenous aFGF, which induced astrocyte immediate early gene expression to the same extent as EGF or bFGF, did not affect calcium oscillation. Exogenous EGF and bFGF promoted astrocyte hypertrophic morphology and proliferation, as well as calcium oscillation. In contrast, these properties did not accompany calcium oscillation induced by the prolonged culture period. These results suggest that astrocytes possess the ability to promote their own calcium oscillation, which is independent of hypertrophic changes to reactive astrocytes.
我们之前报道过，在含有表皮生长因子（EGF）和碱性成纤维细胞生长因子（bFGF）的限定培养基中培养超过2天的星形胶质细胞，对谷氨酸会产生钙振荡，而在没有外源性生长因子的情况下，反应模式是短暂的。在本研究中，我们发现，如果细胞培养超过5天，即使在无生长因子的培养基中，星形胶质细胞也会出现谷氨酸诱导的钙振荡。延长培养时间所促进的钙振荡被EGF受体酪氨酸激酶抑制剂抑制，但不被bFGF中和抗体抑制，这表明激活EGF受体的自分泌因子的积累导致了钙振荡。我们培养系统中的星形胶质细胞表达EGF、转化生长因子α（TGFα）、bFGF和酸性成纤维细胞生长因子（aFGF）。外源性aFGF诱导星形胶质细胞立即早期基因表达的程度与EGF或bFGF相同，但不影响钙振荡。外源性EGF和bFGF促进星形胶质细胞肥大形态和增殖以及钙振荡。相比之下，这些特性并不伴随延长培养时间诱导的钙振荡。这些结果表明，星形胶质细胞具有促进自身钙振荡的能力，这与反应性星形胶质细胞的肥大变化无关。
