Roles of astrocytes and microglia in seizure-induced aberrant neurogenesis in the hippocampus of adult rats.
Recent evidence showed that epileptic seizures increase hippocampal neurogenesis in the adult rat, but prolonged seizures result in the aberrant hippocampal neurogenesis that often leads to a recurrent excitatory circuitry and thus contributes to epileptogenesis. However, the mechanism underlying the aberrant neurogenesis after prolonged seizures remains largely unclear. In this study, we examined the role of activated astrocytes and microglia in the aberrant hippocampal neurogenesis induced by status epilepticus. Using a lithium-pilocarpine model to mimic human temporal lobe epilepsy, we found that status epilepticus induced a prominent activation of astrocytes and microglia in the dentate gyrus 3, 7, 14, and 20 days after the initial seizures. Then, we injected fluorocitrate stereotaxicly into the dentate hilus to inhibit astrocytic metabolism and found that fluorocitrate failed to prevent the seizure-induced formation of ectopic hilar basal dendrites but instead promoted the degeneration of dentate granule cells after seizures. In contrast, a selective inhibitor of microglia activation, minocycline, inhibited the aberrant migration of newborn neurons at 14 days after status epilepticus. Furthermore, with stereotaxic injection of lipopolysaccharide into the intact dentate hilus to activate local microglia, we found that lipopolysaccharide promoted the development of ectopic hilar basal dendrites in the hippocampus. These results indicate that the activated microglia in the epileptic hilus may guide the aberrant migration of newborn neurons and that minocycline could be a potential drug to impede seizure-induced aberrant migration of newborn neurons.
Department of Neurology, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
Fang
F
Yang
Zhi-Rong
ZR
Liu
Jing
J
Chen
Shi-Jun
SJ
Zhang
Qing-Yun
QY
Quan
Yuan-Gui
YG
Huang
Wen
W
Jiang
D000375:Aging; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D003712:Dendrites / Q000187:drug effects / Q000502:physiology; D018891:Dentate Gyrus / Q000187:drug effects / Q000503:physiopathology*; D004195:Disease Models, Animal; D004833:Epilepsy, Temporal Lobe / Q000139:chemically induced / Q000503:physiopathology; D008297:Male; D017628:Microglia / Q000187:drug effects / Q000502:physiology*; D009410:Nerve Degeneration / Q000139:chemically induced / Q000503:physiopathology; D055495:Neurogenesis / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012640:Seizures / Q000139:chemically induced / Q000503:physiopathology*; D013226:Status Epilepticus / Q000139:chemically induced / Q000503:physiopathology; D013997:Time Factors