Autocrine activation of EGF receptor promotes oscillation of glutamate-induced calcium increase in astrocytes cultured in rat cerebral cortex.
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.
Morita
Mitsuhiro
M
Laboratory of Cellular Neurobiology, School of Life Science, Tokyo University of Pharmacy and Life Science, Tokyo, Japan. moritam@ls.toyaku.ac.jp
Kozuka
Nagisa
N
Itofusa
Rurika
R
Yukawa
Masashi
M
Kudo
Yosihisa
Y
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019898:Autocrine Communication / Q000187:drug effects / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D003470:Culture Media / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000235:genetics / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D016220:Fibroblast Growth Factor 1 / Q000235:genetics / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000235:genetics / Q000494:pharmacology; D015870:Gene Expression; D018698:Glutamic Acid / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D016211:Transforming Growth Factor alpha / Q000235:genetics
D003470:Culture Media; D016211:Transforming Growth Factor alpha; D016222:Fibroblast Growth Factor 2; D016220:Fibroblast Growth Factor 1; D018698:Glutamic Acid; D004815:Epidermal Growth Factor; D066246:ErbB Receptors