Diacylglycerol kinase epsilon modulates rapid kindling epileptogenesis.
OBJECTIVE
Diacylglycerol kinase epsilon (DGKepsilon) regulates seizure susceptibility and long-term potentiation through arachidonoyl-inositol lipid signaling. We studied the significance of arachidonoyl-diacylglycerol (20:4 DAG) in epileptogenesis in DGKepsilon-deficient mice undergoing rapid kindling epileptogenesis.


METHODS
Tripolar electrode units were implanted in right dorsal hippocampi of male DGKepsilon(+/+) and DGKepsilon(-/-) mice. Ten days after surgery, kindling was achieved by stimulating 6 times daily for 4 days with a subconvulsive electrical stimulation (10-s train of 50-Hz biphasic pulses, 75-200 muA amplitude) at 30-min intervals. After 1 week, mice were rekindled. EEGs were recorded and analyzed to characterize epileptogenic events as spikes, sharp waves, or abnormal amplitudes and rhythms. Right hippocampi were analyzed by histology [Timm's staining, neuropeptide Y (NPY) and glial fibrillary acidic protein immunoreactivity], and for DNA fragmentation (TUNEL).


RESULTS
DGKepsilon(-/-) mice had significantly fewer motor seizure and epileptic events compared with DGKepsilon(+/+) mice from the second day of stimulation. These differences were maintained during rekindling. DGKepsilon(-/-) mice also exhibited low-amplitude spike-wave complexes, short spreading depression, and predominant lower-frequency (1-4 Hz) bands throughout stimulation, whereas DGKepsilon(+/+) mice exhibited increased high-frequency bands (4-8 Hz; 8-15 Hz) from the second day of stimulation, as determined by power spectral analysis. DGKepsilon(-/-) mice displayed no sprouting in the supragranular area or NPY inmunoreactivity in the hilus and had weak astrocyte reactivation in all hippocampal areas. No TUNEL-positive cells were detected in any group of mice.


CONCLUSIONS
DGKepsilon modulates kindling epileptogenesis through inositol lipid signaling. Because arachidonate-containing diacylglycerol phosphorylation to phosphatidic acid is selectively blocked in DGKepsilon(-/-) mice, we postulate that the shortage of arachidonoyl-moiety inositol lipids and/or the messengers derived thereof is a key signaling event in epileptogenesis.
Musto
Alberto
A
LSU Neuroscience Center of Excellence, Louisiana State University School of Medicine, Health Sciences Center, 2020 Gravier Street, New Orleans, LA 70112, U.S.A.
Bazan
Nicolas G
NG
D000818:Animals; D019852:Diacylglycerol Kinase / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D004198:Disease Susceptibility / Q000503:physiopathology; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000378:metabolism / Q000503:physiopathology*; D006624:Hippocampus / Q000378:metabolism / Q000503:physiopathology*; D007150:Immunohistochemistry; D007294:Inositol / Q000502:physiology; D007696:Kindling, Neurologic / Q000378:metabolism / Q000502:physiology*; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010712:Phosphatidic Acids / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology; D013997:Time Factors
D010712:Phosphatidic Acids; D007294:Inositol; D019852:Diacylglycerol Kinase