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In situ fluorescence imaging of glutamate-evoked mitochondrial Na+ responses in astrocytes.
Glia 2006; 54(5):460-70GLIA

Abstract

Astrocytes can experience large intracellular Na+ changes following the activation of the Na+-coupled glutamate transport. The present study investigated whether cytosolic Na+ changes are transmitted to mitochondria, which could therefore influence their function and contribute to the overall intracellular Na+ regulation. Mitochondrial Na+ (Na+(mit)) changes were monitored using the Na+-sensitive fluorescent probe CoroNa Red (CR) in intact primary cortical astrocytes, as opposed to the classical isolated mitochondria preparation. The mitochondrial localization and Na+ sensitivity of the dye were first verified and indicated that it can be safely used as a selective Na+(mit) indicator. We found by simultaneously monitoring cytosolic and mitochondrial Na+ using sodium-binding benzofuran isophthalate and CR, respectively, that glutamate-evoked cytosolic Na+ elevations are transmitted to mitochondria. The resting Na+(mit) concentration was estimated at 19.0 +/- 0.8 mM, reaching 30.1 +/- 1.2 mM during 200 microM glutamate application. Blockers of conductances potentially mediating Na+ entry (calcium uniporter, monovalent cation conductances, K+(ATP) channels) were not able to prevent the Na+(mit) response to glutamate. However, Ca2+ and its exchange with Na+ appear to play an important role in mediating mitochondrial Na+ entry as chelating intracellular Ca2+ with BAPTA or inhibiting Na+/Ca2+ exchanger with CGP-37157 diminished the Na+(mit) response. Moreover, intracellular Ca2+ increase achieved by photoactivation of caged Ca2+ also induced a Na+(mit) elevation. Inhibition of mitochondrial Na/H antiporter using ethylisopropyl-amiloride caused a steady increase in Na+(mit) without increasing cytosolic Na+, indicating that Na+ extrusion from mitochondria is mediated by these exchangers. Thus, mitochondria in intact astrocytes are equipped to efficiently sense cellular Na+ signals and to dynamically regulate their Na+ content.

Authors+Show Affiliations

Department of Physiology, University of Lausanne, Switzerland.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16886210

Citation

Bernardinelli, Yann, et al. "In Situ Fluorescence Imaging of Glutamate-evoked Mitochondrial Na+ Responses in Astrocytes." Glia, vol. 54, no. 5, 2006, pp. 460-70.
Bernardinelli Y, Azarias G, Chatton JY. In situ fluorescence imaging of glutamate-evoked mitochondrial Na+ responses in astrocytes. Glia. 2006;54(5):460-70.
Bernardinelli, Y., Azarias, G., & Chatton, J. Y. (2006). In situ fluorescence imaging of glutamate-evoked mitochondrial Na+ responses in astrocytes. Glia, 54(5), pp. 460-70.
Bernardinelli Y, Azarias G, Chatton JY. In Situ Fluorescence Imaging of Glutamate-evoked Mitochondrial Na+ Responses in Astrocytes. Glia. 2006;54(5):460-70. PubMed PMID: 16886210.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - In situ fluorescence imaging of glutamate-evoked mitochondrial Na+ responses in astrocytes. AU - Bernardinelli,Yann, AU - Azarias,Guillaume, AU - Chatton,Jean-Yves, PY - 2006/8/4/pubmed PY - 2006/11/2/medline PY - 2006/8/4/entrez SP - 460 EP - 70 JF - Glia JO - Glia VL - 54 IS - 5 N2 - Astrocytes can experience large intracellular Na+ changes following the activation of the Na+-coupled glutamate transport. The present study investigated whether cytosolic Na+ changes are transmitted to mitochondria, which could therefore influence their function and contribute to the overall intracellular Na+ regulation. Mitochondrial Na+ (Na+(mit)) changes were monitored using the Na+-sensitive fluorescent probe CoroNa Red (CR) in intact primary cortical astrocytes, as opposed to the classical isolated mitochondria preparation. The mitochondrial localization and Na+ sensitivity of the dye were first verified and indicated that it can be safely used as a selective Na+(mit) indicator. We found by simultaneously monitoring cytosolic and mitochondrial Na+ using sodium-binding benzofuran isophthalate and CR, respectively, that glutamate-evoked cytosolic Na+ elevations are transmitted to mitochondria. The resting Na+(mit) concentration was estimated at 19.0 +/- 0.8 mM, reaching 30.1 +/- 1.2 mM during 200 microM glutamate application. Blockers of conductances potentially mediating Na+ entry (calcium uniporter, monovalent cation conductances, K+(ATP) channels) were not able to prevent the Na+(mit) response to glutamate. However, Ca2+ and its exchange with Na+ appear to play an important role in mediating mitochondrial Na+ entry as chelating intracellular Ca2+ with BAPTA or inhibiting Na+/Ca2+ exchanger with CGP-37157 diminished the Na+(mit) response. Moreover, intracellular Ca2+ increase achieved by photoactivation of caged Ca2+ also induced a Na+(mit) elevation. Inhibition of mitochondrial Na/H antiporter using ethylisopropyl-amiloride caused a steady increase in Na+(mit) without increasing cytosolic Na+, indicating that Na+ extrusion from mitochondria is mediated by these exchangers. Thus, mitochondria in intact astrocytes are equipped to efficiently sense cellular Na+ signals and to dynamically regulate their Na+ content. SN - 0894-1491 UR - https://www.unboundmedicine.com/medline/citation/16886210/In_situ_fluorescence_imaging_of_glutamate_evoked_mitochondrial_Na+_responses_in_astrocytes_ L2 - https://doi.org/10.1002/glia.20387 DB - PRIME DP - Unbound Medicine ER -