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Original Article

Korean J Physiol Pharmacol 2020; 24(1): 81-88

Published online January 1, 2020 https://doi.org/10.4196/kjpp.2020.24.1.81

Copyright © The Korean Journal of Physiology & Pharmacology.

Spatiotemporal expression of RCAN1 and its isoform RCAN1-4 in the mouse hippocampus after pilocarpine-induced status epilepticus

Kyung-Ok Cho1,2, Kyoung Hoon Jeong1, Jung-Ho Cha3, and Seong Yun Kim1,*

1Department of Pharmacology, Department of Biomedicine & Health Sciences, Catholic Neuroscience Institute, College of Medicine, The Catholic University of Korea, 2Institute of Aging and Metabolic Diseases, College of Medicine, The Catholic University of Korea, 3Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea

Correspondence to:*Seong Yun Kim
E-mail: syk@catholic.ac.kr

Received: September 21, 2019; Revised: October 17, 2019; Accepted: November 22, 2019

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Regulator of calcineurin 1 (RCAN1) can be induced by an intracellular calcium increase and oxidative stress, which are characteristic features of temporal lobe epilepsy. Thus, we investigated the spatiotemporal expression and cellular localization of RCAN1 protein and mRNA in the mouse hippocampus after pilocarpine-induced status epilepticus (SE). Male C57BL/6 mice were given pilocarpine hydrochloride (280 mg/kg, i.p.) and allowed to develop 2 h of SE. Then the animals were given diazepam (10 mg/kg, i.p.) to stop the seizures and sacrificed at 1, 3, 7, 14, or 28 day after SE. Cresyl violet staining showed that pilocarpine-induced SE resulted in cell death in the CA1 and CA3 subfields of the hippocampus from 3 day after SE. RCAN1 immunoreactivity showed that RCAN1 was mainly expressed in neurons in the sham-manipulated hippocampi. At 1 day after SE, RCAN1 expression became detected in hippocampal neuropils. However, RCAN1 signals were markedly enhanced in cells with stellate morphology at 3 and 7 day after SE, which were confirmed to be reactive astrocytes, but not microglia by double immunofluorescence. In addition, realtime reverse transcriptase?polymerase chain reaction showed a significant upregulation of RCAN1 isoform 4 (RCAN1-4) mRNA in the SE-induced hippocampi. Finally, in situ hybridization with immunohistochemistry revealed astrocytic expression of RCAN1-4 after SE. These results demonstrate astrocytic upregulation of RCAN1 and RCAN1-4 in the mouse hippocampus in the acute and subacute phases of epileptogenesis, providing foundational information for the potential role of RCAN1 in reactive astrocytes during epileptogenesis.

Keywords: Epilepsy, Hippocampus, Regulator of calcineurin 1, Regulator of calcineurin 1-4, Status epilepticus