Tohoku J. Exp. Med., 2008, 215(2)

Electric Pulse Stimulation Induces NMDA Glutamate Receptor mRNA in NIH3T3 Mouse Fibroblasts

SAEKO OKUTSU,¹ HIROYASU HATAKEYAMA,² MAKOTO KANAZAKI,³ HIROSHI TSUBOKAWA⁴ and RYOICHI NAGATOMI¹

¹Department of Medicine and Science in Sports and Exercise, Tohoku University Graduate School of Medicine, Sendai, Japan
²Center for Research Strategy and Support, Tohoku University, Sendai, Japan
³TUBERO/Tohoku University Biomedical Engineering Research Organization, School of Medicine, Sendai, Japan
⁴Graduate School of Information Science, Tohoku University, Sendai, Japan

Excess glutamate and Ca²⁺ influx into neurons exacerbate brain damage such as ischemia. Astrocytes at the site of damage proliferate and attenuate the glutamate- and Ca²⁺-induced neuronal damage by removing excess glutamate and Ca²⁺ through the N-methyl-D-aspartate (NMDA) glutamate receptor and the L-type Ca²⁺ channel, respectively. Fibroblasts are commonly mobilized to the site of damage, probably supporting the restoration process. Notably, fibroblasts express the L-type voltage-sensitive Ca²⁺ 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 Ca²⁺ channel activation, so that they could potentially have a neuroprotective role. To activate L-type Ca²⁺ 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 Ca²⁺ into NIH3T3 fibroblasts as detected by Fluo-4AM calcium imaging, which was totally inhibited by a L-type Ca²⁺ 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 Ca²⁺ influx via L-type Ca²⁺ 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.

keywords —— NIH3T3; fibroblasts; electric pulse stimulation (EPS); Ca²⁺ influx; NMDA receptor.

© 2008 Tohoku University Medical Press

===============================

Tohoku J. Exp. Med., 2008, 215, 181-187

Correspondence to: Ryoichi Nagatomi, Department of Medicine and Exercise in Sports and Exercise, Tohoku University, Graduate School of Medicine, Seiryo-machi 2-1, Aoba-ku, Sendai 980-8575, Japan.

e-mail: nagatomi@mail.tains.tohoku.ac.jp