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Electroconvulsive Seizures in Rats and Fractionation of Their Hippocampi to Examine Seizure-induced Changes in Postsynaptic Density Proteins
Published on: August 15, 2017
Enhanced hippocampal miR-32-5p promotes neuronal hyperexcitability and epileptic seizures by targeting KCC2
Xiaolin Zhong1, Ling Chen1, Shixi Zhou2
1The First Affiliated Hospital, Department of Endocrinology and Metabolism, Hengyang Medical School, University of South China, Hengyang, Hunan, 421001, China; The First Affiliated Hospital, Clinical Medicine Research Center, Hengyang Medical School, University of South China, Hengyang, Hunan, 421001, China.
Abstract:
MicroRNAs (miRNAs) are small noncoding RNAs that control gene expression at the post-transcriptional level and are involved in the pathogenesis of epilepsy. Although miRNA-32-5p (miR-32-5p) is known to be significantly upregulated at seizure onset in patients, its function and mechanism in neuron hyperexcitability and epileptic seizures remain unclear. In this study, we demonstrated elevated levels of miR-32-5p in the plasma of patients with temporal lobe epilepsy and in the hippocampus and plasma of pentylenetetrazol (PTZ)-induced seizure mice. Systemic knockout (KO) and hippocampal-specific knockdown of miR-32-5p mitigated acute seizure discharge and neuronal spiking in the experimental mice. Additionally, miR-32-5p KO attenuated chronic seizure severity and hippocampal neuronal loss of epileptic mice. Furthermore, miR-32-5p KO reversed the expression of immediate early genes (IEGs), which are neuronal activity markers significantly upregulated during acute seizure in mice. Mechanically, we found that potassium-chloride transporter 2 (KCC2), a main cation-chloride cotransporter involved in neuronal circuit excitation/inhibition (E/I) balance, is the key direct target of miR-32-5p. We further verified that miR-32-5p KO re-balanced hippocampal neuronal E/I imbalance underlying epilepsy. Gain-of-function experiment further revealed that the anti-seizure effect of miR-32-5p KO was abolished by hippocampal KCC2 knockdown. Taken together, our findings showed that hippocampal miR-32-5p promotes neuron hyperexcitability and epileptic seizures, and specifically identified miR-32-5p as a putative biomarker and therapeutic target for hippocampus-related epilepsy.
Insights
MicroRNA-32-5p (miR-32-5p) promotes epilepsy by disrupting neuronal excitation/inhibition balance. Inhibiting miR-32-5p in the hippocampus offers a potential therapeutic strategy for epilepsy.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- MicroRNAs (miRNAs) are key regulators of gene expression involved in epilepsy pathogenesis.
- MicroRNA-32-5p (miR-32-5p) is upregulated during seizures, but its role in epilepsy remains unclear.
Purpose of the Study:
- To investigate the function and mechanism of miR-32-5p in neuronal hyperexcitability and epileptic seizures.
- To identify miR-32-5p as a potential biomarker and therapeutic target for epilepsy.
Main Methods:
- Measured miR-32-5p levels in epilepsy patients and PTZ-induced seizure mouse models.
- Utilized systemic knockout and hippocampal-specific knockdown of miR-32-5p in mice.
- Assessed seizure activity, neuronal spiking, gene expression (IEGs), and KCC2 levels.
- Performed gain-of-function experiments with KCC2 knockdown.
Main Results:
- Elevated miR-32-5p levels were found in plasma of epilepsy patients and in the hippocampus/plasma of seizure mice.
- miR-32-5p knockout/knockdown reduced seizure activity, neuronal hyperexcitability, and hippocampal damage.
- miR-32-5p regulates the expression of immediate early genes (IEGs) and directly targets KCC2.
- Restoring KCC2 expression re-balanced neuronal excitation/inhibition (E/I) in the hippocampus.
Conclusions:
- Hippocampal miR-32-5p promotes neuronal hyperexcitability and epilepsy by targeting KCC2 and disrupting E/I balance.
- miR-32-5p is a potential biomarker and therapeutic target for hippocampus-related epilepsy.
