Decreased level of mitochondrial RNA by glutamate in cultured cortical neurons.

Mitochondrial injury is induced by a decline in mitochondrial function as well as by damaged mitochondrial DNA. In this study, we evaluate the effects of glutamate exposure on the level of mitochondrial mRNA in cultured cortical neurons of mice. Glutamate exposure for 15 min significantly reduced cell viability 24 h later. Under these experimental conditions, glutamate was effective in reducing the level of mitochondrial mRNAs, especially the mRNAs of NADH-ubiquinone oxidoreductase subunits (nd1 and nd6), 6 h after the exposure. Southern blot analysis, however, revealed no significant change in that of the mitochondrial DNA at any time after glutamate exposure. These results suggest that the activation of glutamate signals negatively regulated the expression of mitochondrial mRNA, without affecting the level of mitochondrial DNA.