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Microglial proliferation and monocyte infiltration contribute to microgliosis following status epilepticus.

ABSTRACT: Microglial activation has been recognized as a major contributor to inflammation of the epileptic brain. Seizures are commonly accompanied by remarkable microgliosis and loss of neurons. In this study, we utilize the CX3CR1GFP/+ CCR2RFP/+ genetic mouse model, in which CX3CR1+ resident microglia and CCR2+ monocytes are labeled with GFP and RFP, respectively. Using a combination of time-lapse two-photon imaging and whole-cell patch clamp recording, we determined the distinct morphological, dynamic, and electrophysiological characteristics of infiltrated monocytes and resident microglia, and the evolution of their behavior at different time points following kainic acid-induced seizures. Seizure activated microglia presented enlarged somas with less ramified processes, whereas, infiltrated monocytes were smaller, highly motile cells that lacked processes. Moreover, resident microglia, but not infiltrated monocytes, proliferate locally in the hippocampus after seizure. Microglial proliferation was dependent on the colony-stimulating factor 1 receptor (CSF-1R) pathway. Pharmacological inhibition of CSF-1R reduced seizure-induced microglial proliferation, which correlated with attenuation of neuronal death without altering acute seizure behaviors. Taken together, we demonstrated that proliferation of activated resident microglia contributes to neuronal death in the hippocampus via CSF-1R after status epilepticus, providing potential therapeutic targets for neuroprotection in epilepsy.

SUBMITTER: Feng L

PROVIDER: S-EPMC6559368 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Microglial proliferation and monocyte infiltration contribute to microgliosis following status epilepticus.

Feng Lijie L Murugan Madhuvika M Bosco Dale B DB Liu Yong Y Peng Jiyun J Worrell Gregory A GA Wang Hai-Long HL Ta Lauren E LE Richardson Jason R JR Shen Yuxian Y Wu Long-Jun LJ

Glia 20190405 8

Microglial activation has been recognized as a major contributor to inflammation of the epileptic brain. Seizures are commonly accompanied by remarkable microgliosis and loss of neurons. In this study, we utilize the CX3CR1GFP/+ CCR2RFP/+ genetic mouse model, in which CX3CR1+ resident microglia and CCR2+ monocytes are labeled with GFP and RFP, respectively. Using a combination of time-lapse two-photon imaging and whole-cell patch clamp recording, we de ...[more]

PMID: 31179602

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Project description:Endothelial monocyte‑activating polypeptide II (EMAP II) is a sensitive marker of neurotoxic injury, the expression of which increases significantly under conditions of stress, such as hypoxia or apoptosis. Studies have confirmed the extensive apoptosis of nerve cells in the brain following status epilepticus (SE), and the occurrence of SE can confer a hypoxic state on cells. The purpose of the present study was to observe the changes in the expression of EMAP II, and in the numbers and tight junction protein levels of microvascular endothelial cells in the hippocampus of rats with pilocarpine‑induced SE. The protein expression levels of EMAP II, CD31, zonula occludens 1 (ZO‑1) and occludin in the hippocampus were determined by immunofluorescence and western blot analyses. It was found that almost 75.6% of the rats in the SE group developed Racine stage IV‑V seizures at approximately 44.7±18.8 min after the pilocarpine administration, and the 24‑h mortality rate was almost 10.4%. The weight of the rats in the SE group was significantly decreased within 24 h following SE. Immunofluorescence staining revealed a low EMAP II expression in the hippocampus of the rats in the control group; however, the numbers of EMAP II‑positive cells were significantly increased in the SE group from 2 h to 21 days. The trend of EMAP II protein expression was consistent with that obtained with immunofluorescence staining. The numbers of CD31‑positive microvascular endothelial cells were significantly increased from 24 h to 21 days compared with the levels in the control group. The protein expression of ZO‑1 and occludin was most significantly decreased in the SE group. On the whole, the present study demonstrated that the expression of EMAP II in the rat hippocampus was upregulated in the SE model, which may promote angiogenesis and alter the TJ integrity of brain microvascular endothelial cells, with an increased number of CD31‑positive microvascular endothelial cells and a decreased expression of ZO‑1 and occludin.

Project description:BackgroundHippocampal damage caused by status epilepticus (SE) can bring about cognitive decline and emotional disorders, which are common clinical comorbidities in patients with epilepsy. It is therefore imperative to develop a novel therapeutic strategy for protecting hippocampal damage after SE. Mitochondrial dysfunction is one of contributing factors in epilepsy. Given the therapeutic benefits of mitochondrial replenishment by exogenous mitochondria, we hypothesized that transplantation of mitochondria would be capable of ameliorating hippocampal damage following SE.MethodsPilocarpine was used to induced SE in mice. SE-generated cognitive decline and emotional disorders were determined using novel object recognition, the tail suspension test, and the open field test. SE-induced hippocampal pathology was assessed by quantifying loss of neurons and activation of microglia and astrocytes. The metabolites underlying mitochondrial transplantation were determined using metabonomics.ResultsThe results showed that peripheral administration of isolated mitochondria could improve cognitive deficits and depressive and anxiety-like behaviors. Exogenous mitochondria blunted the production of reactive oxygen species, proliferation of microglia and astrocytes, and loss of neurons in the hippocampus. The metabonomic profiles showed that mitochondrial transplantation altered multiple metabolic pathways such as sphingolipid signaling pathway and carbon metabolism. Among potential affected metabolites, mitochondrial transplantation decreased levels of sphingolipid (d18:1/18:0) and methylmalonic acid, and elevated levels of D-fructose-1,6-bisphosphate.ConclusionTo the best of our knowledge, these findings provide the first direct experimental evidence that artificial mitochondrial transplantation is capable of ameliorating hippocampal damage following SE. These new findings support mitochondrial transplantation as a promising therapeutic strategy for epilepsy-associated psychiatric and cognitive disorders.

Dataset Information

Microglial proliferation and monocyte infiltration contribute to microgliosis following status epilepticus.

Publications

Microglial proliferation and monocyte infiltration contribute to microgliosis following status epilepticus.

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