Related Experiment Videos
Cyclic AMP-elevating agents prevent oligodendroglial excitotoxicity
A Yoshioka1, Y Shimizu, G Hirose
1Department of Neurology, Kanazawa Medical University, Uchinada, Ishikawa, Japan.
Abstract:
Previously, we have demonstrated that cells of the oligodendroglial lineage express non-NMDA glutamate receptor genes and are damaged by kainate-induced Ca2+ influx via non-NMDA glutamate receptor channels, representing oligodendroglial excitotoxicity. We find in the present study that agents that elevate intracellular cyclic AMP prevent oligodendroglial excitotoxicity. After oligodendrocyte-like cells, differentiated from the CG-4 cell line established from rat oligodendrocyte type-2 astrocyte progenitor cells, were exposed to 2 mM kainate for 24 h, cell death was evaluated by measuring activity of lactate dehydrogenase released into the culture medium. Released lactate dehydrogenase increased about threefold when exposed to 2 mM kainate. Kainate-induced cell death was prevented by one of the following agents: adenylate cyclase activator (forskolin), cyclic AMP analogues (dibutyryl cyclic AMP and 8-bromo-cyclic AMP), and cyclic AMP phosphodiesterase inhibitors (3-isobutyl-1-methylxanthine, pentoxifylline, propentofylline, and ibudilast). Simultaneous addition of both forskolin and phosphodiesterase inhibitors prevented the kainate-induced cell death in an additive manner. A remarkable increase in Ca2+ influx (approximately 5.5-fold) also was induced by kainate. The cyclic AMP-elevating agents caused a partial suppression of the kainate-induced increase in Ca2+ influx, leading to a less prominent response of intracellular Ca2+ concentration to kainate. The suppressing effect of forskolin on the kainate-induced Ca2+ influx was partially reversed by H-89, an inhibitor of cyclic AMP-dependent protein kinase. In contrast to this, okadaic acid, an inhibitor of protein phosphatases 1 and 2A, brought about a decrease in the kainate-induced Ca2+ influx. We therefore concluded that cyclic AMP-elevating agents prevented oligodendroglial excitotoxicity by cyclic AMP-dependent protein kinase-dependent protein phosphorylation, resulting in decreased kainate-induced Ca2+ influx.
Insights
Agents that increase cyclic AMP levels protect oligodendroglial cells from excitotoxicity. This protection involves reducing calcium influx through non-NMDA glutamate receptors, mediated by protein phosphorylation.
Area of Science:
- Neuroscience
- Cell Biology
- Neuropharmacology
Background:
- Oligodendroglial cells are vulnerable to excitotoxicity mediated by non-NMDA glutamate receptors.
- Kainate-induced calcium influx damages these cells, impacting central nervous system function.
Purpose of the Study:
- To investigate whether agents elevating intracellular cyclic AMP can prevent oligodendroglial excitotoxicity.
- To elucidate the mechanisms underlying the protective effects of cyclic AMP.
Main Methods:
- Utilized CG-4 cell line for oligodendrocyte-like cells.
- Exposed cells to kainate and measured cell death via lactate dehydrogenase release.
- Assessed the impact of cyclic AMP-elevating agents (forskolin, cyclic AMP analogues, phosphodiesterase inhibitors) on cell death and calcium influx.
- Investigated the role of cyclic AMP-dependent protein kinase and protein phosphatases using specific inhibitors (H-89, okadaic acid).
Main Results:
- Kainate exposure significantly increased cell death and calcium influx.
- Agents that elevated cyclic AMP effectively prevented kainate-induced cell death.
- These agents partially suppressed kainate-induced calcium influx.
- The protective effect was linked to cyclic AMP-dependent protein kinase activity and protein phosphorylation.
Conclusions:
- Elevating intracellular cyclic AMP levels protects oligodendrocytes from excitotoxicity.
- This protection is achieved by reducing kainate-induced calcium influx via a mechanism involving cyclic AMP-dependent protein kinase-mediated phosphorylation.