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Electric pulse stimulation induces NMDA glutamate receptor mRNA in NIH3T3 mouse fibroblasts.

Electric pulse stimulation induces NMDA glutamate receptor mRNA in NIH3T3 mouse fibroblasts.

Okutsu S, Hatakeyama H, Kanzaki M, Tsubokawa H, Nagatomi R


Excess glutamate and Ca(2+) influx into neurons exacerbate brain damage such as ischemia. Astrocytes at the site of damage proliferate and attenuate the glutamate- and Ca(2+)-induced neuronal damage by removing excess glutamate and Ca(2+) through the N-methyl-D-aspartate (NMDA) glutamate receptor and the L-type Ca(2+) channel, respectively. Fibroblasts are commonly mobilized to the site of damage, probably supporting the restoration process. Notably, fibroblasts express the L-type voltage-sensitive Ca(2+) channel, but not central nervous system-specific NMDA glutamate receptor. We examined if electric pulse stimulation (EPS) was capable of inducing NMDA receptor on fibroblasts by way of Ca(2+) channel activation, so that they could potentially have a neuroprotective role. To activate L-type Ca(2+) channel, we delivered electric pulse to cultured NIH3T3 mouse fibroblasts. EPS of 20 V with a pulse duration of 2 msec at a frequency of 1 Hz for more than 1 h up to 24 h successfully introduced Ca(2+) into NIH3T3 fibroblasts as detected by Fluo-4AM calcium imaging, which was totally inhibited by a L-type Ca(2+) channel inhibitor, verapamil. Remarkable expression of NMDA receptor mRNA in the fibroblasts after 24-h EPS was demonstrated by RT-PCR. Verapamil treatment during EPS totally abrogated the EPS-induced NMDA receptor mRNA expression. To the best of our knowledge, this is the first report showing that electric pulse is able to induce sustained Ca(2+) influx via L-type Ca(2+) channel in a non-excitatory fibroblast, which leads to the expression CNS-specific NMDA receptor mRNA. Neuroprotective role of NMDA receptor induced in fibroblasts needs to be further examined.


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