Abstract
Astrocytes modify and maintain neural activity and functions via gliotransmitter release such as, glutamate. They also change their properties and functions in response to alterations of ion environment resulting from neurotransmission; however, the direct evidence for whether intracellular ion alteration in astrocytes triggers gliotransmitter release is not indicated. Recent studies have reported that channelrhodopsin-2 (ChR2) is useful for alteration of intracellular ion environment in several types of cells with blue light exposure. Here, we show that ChR2-expressing GL261 (GLChR2) cells, clonal astrocytes, change their properties by photo-activation. Increased intracellular sodium and calcium ion concentrations and an altered membrane potential were observed in GLChR2 cells with blue light exposure. Alterations in the intracellular ion environment caused intracellular acidification and the inhibition of proliferation. In addition, it triggered glutamate release from GLChR2 cells. Glutamate from GLChR2 cells acted on N18 cells, clonal neuronal cells, as both a transmitter and neurotoxin depending on photo-activation. Our results show that the properties of ChR2-expressing astrocytes can be controlled by blue light exposure, and cation influx through photo-activated ChR2 might trigger functional cation influx via endogenous channels and result in the increase of glutamate release. Further, our results suggest that ChR2-expressing glial cells could become a useful tool in understanding the roles of glial cell activation and neural communication in the regulation of brain functions.
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Abbreviations
- ChR2:
-
Channelrhodopsin-2
- GLChR2:
-
ChR2-expressing GL261
- EYFP:
-
Enhanced yellow fluorescent protein
- DMEM:
-
Dulbecco’s modified Eagle’s medium
- MEM:
-
Eagle’s minimum essential medium
- GAPDH:
-
Glyceraldehyde 3 phosphate dehydrogenase
- DIC:
-
Differential interference contrast
- RB:
-
Recording buffer
- Carboxy SNARF-1 AM:
-
5-(and-6)-Carboxy SNARF-1, acetoxymethyl ester, acetate
- PI:
-
Propidium iodide
- BL:
-
Blue light
- TTX:
-
Tetrodotoxin
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Acknowledgments
We thank Dr. Karl Deisseroth (Stanford University) for providing expression vectors. This study was supported by the Industrial Technology Research Grant Program from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, the Hori Information Science Promotion Foundation, and the Research Foundation for Opto-Science and Technology.
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Ono, K., Suzuki, H., Higa, M. et al. Glutamate release from astrocyte cell-line GL261 via alterations in the intracellular ion environment. J Neural Transm 121, 245–257 (2014). https://doi.org/10.1007/s00702-013-1096-8
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DOI: https://doi.org/10.1007/s00702-013-1096-8