101. Neuroprotective Role of Na+/myo-Inositol Cotransporter Against Veratridine Cytotoxicity.
- Author
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Yamashita, Toshihide, Yamauchi, Atsushi, Miyai, Akiko, Taniguchi, Masaaki, Yoshimine, Toshiki, and Tohyama, Masaya
- Subjects
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INOSITOL , *SODIUM channels , *GENES - Abstract
Na+/myo-inositol cotransporter has been shown to protect cells from the perturbing effects of hypertonic stress by the accumulation of myo-inositol. Here we report a regulatory mechanism for the cotransporter. Induction of myo-inositol cotransporter mRNA was observed after exposure to veratridine, a voltage-gated sodium channel opener. The veratridine-elicited induction was inhibited when Na+ was eliminated from the bath, although calcium chelation failed to modify the gene expression. Veratridine evoked an accumulation of Na+ in the cells, which paralleled the abundance of the mRNA. These results strongly suggested that an increase in Na+ influx due to sodium channel opening affected transcription of the cotransporter gene. Activity of the myo-inositol cotransporter was also up-regulated after veratridine exposure. To clarify the possible roles of myo-inositol accumulation under veratridine exposure, we next examined the neurotoxic effects of veratridine when myo-inositol uptake was blocked. Neither 30 μM veratridine nor 500 μM 2-O,C-methylene myo-inositol, a competitive inhibitor of myo-inositol, elicited apparent cytotoxicity. However, a combination of these agents markedly increased cytotoxicity in culture, suggesting that an adequate amount of myo-inositol was necessary when the cells were stimulated with veratridine. [ABSTRACT FROM AUTHOR]
- Published
- 1999
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