Blockade of P2X receptor prevents astroglial death in the dentate gyrus following pilocarpine-induced status epilepticus.
OBJECTIVE
The P(2) receptor is involved in diverse signal cascades, including the initiation of the rapid release and processing of proinflammatory cytokines, the induction of cytoskeletal rearrangements and transcription factor activation. Therefore, we investigated whether blocking the P(2) receptor would prevent the astroglial death induced by status epilepticus (SE).


METHODS
We performed seizure induction and drug treatments. After tissue processing, we executed immunoreactivities: mouse anti-glial fibrillary acidic protein (GFAP) IgG (diluted 1 : 200; Chemicon, Billerica, MA, USA rabbit anti-P(2)X(7) receptor IgG (diluted 1 : 200; Chemicon).


RESULTS
In control animals, P(2)X(7) receptor-immunoreactive (P(2)X(7)(+)) microglia had small cell bodies with thin ramified processes. Seven days after SE, P(2)X(7) receptor immunoreactivity in microglia was significantly elevated in the dentate gyrus, and the microglia appeared amoeboid or phagocytic. At this point, loss of GFAP immunoreactivity in the dentate gyrus was even more pronounced, indicating that the network of astrocytes was disrupted and a large empty zone was observed. Treatment with pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid and suramin (2, 20 and 200 mg/kg, i.p., respectively) markedly, but not completely, inhibited microglial activation following SE. The morphology of microglia was similar to that of the astrocytes in that they appeared hyper-ramified. In addition, P(2)X(7) receptor antagonist treatments effectively prevented astroglial degeneration.


CONCLUSIONS
These findings suggest that astroglial death induced by ATP-mediated microglia activation may be an important pathophysiological pathway in epileptogenesis.
Kim
Ji-Eun
JE
Department of Anatomy and Neurobiology, College of Medicine, Hallym University, Chunchon, Korea.
Kwak
Sung-Eun
SE
Jo
Seung-Mook
SM
Kang
Tae-Cheon
TC
D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity; D001253:Astrocytes / Q000187:drug effects* / Q000473:pathology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D048430:Cell Shape / Q000187:drug effects / Q000502:physiology; D003292:Convulsants / Q000494:pharmacology; D018891:Dentate Gyrus / Q000187:drug effects* / Q000473:pathology; D004195:Disease Models, Animal; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005911:Gliosis / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D008297:Male; D017628:Microglia / Q000187:drug effects / Q000473:pathology; D009410:Nerve Degeneration / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology*; D010862:Pilocarpine / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058469:Receptors, Purinergic P2X; D058486:Receptors, Purinergic P2X7; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013226:Status Epilepticus / Q000150:complications / Q000503:physiopathology*; D013498:Suramin / Q000633:toxicity
D000970:Antineoplastic Agents; D003292:Convulsants; D005904:Glial Fibrillary Acidic Protein; C546469:P2rx7 protein, mouse; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058486:Receptors, Purinergic P2X7; D010862:Pilocarpine; D013498:Suramin