Epileptiform discharge upregulates p-ERK1/2, growth-associated protein 43 and synaptophysin in cultured rat hippocampal neurons.
Extracellular signal-regulated protein kinase, ERK1/2 is activated by phosphorylation (p-ERK1/2) during environmental stress such as epileptiform discharge. We investigated the role of ERK1/2 in abnormal axon growth and synapse reorganization in cultured neurons displaying epileptiform activity. The cultured neurons displaying epileptiform activity were treated with magnesium-free extracellular fluid for 3h and monitored epileptiform discharges using whole-cell patch clamp. Two study groups, neurons displaying epileptiform activity and the same neurons treated with ERK1/2 inhibitor U0126, were studied at six time points, 0 min, 30 min, 2h, 6h, 12h, and 24h following discharge. The expressions of p-ERK1/2, C-fos, growth-associated protein 43 (GAP-43) and synaptophysin (SYP), as markers of axon growth and synapse reorganization, were investigated by double-label immunofluorescence and western blotting. In the neurons displaying epileptiform activity, p-ERK1/2 was detected immediately following discharge, and expression peaked at 30 min. The expression of C-fos, GAP-43 and SYP followed the same pattern as p-ERK1/2. In the treated group, p-ERK1/2 was inhibited completely, and C-fos, GAP-43 and SYP were reduced. These findings indicate that epileptiform discharge activates ERK1/2 which regulates C-fos in cultured neurons displaying epileptiform activity, and this cascade may upregulate GAP-43 and SYP to contribute to axon growth and synapse reorganization to potentiate epileptic activities.
Xu
Zu-Cai
ZC
Department of Neurology, the Second Affiliated Hospital, Chongqing Medical University, Chongqing 400010, China.
Chen
Yang-Mei
YM
Xu
Ping
P
Liu
Hua
H
Xie
Yun-Lan
YL
Zeng
Ke-Bin
KB
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D019922:GAP-43 Protein / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology*; D008274:Magnesium / Q000378:metabolism; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D016708:Synaptophysin / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*
D004791:Enzyme Inhibitors; D019922:GAP-43 Protein; D016708:Synaptophysin; D048049:Extracellular Signal-Regulated MAP Kinases; D008274:Magnesium