Exp Neurobiol.  2019 Aug;28(4):529-536. 10.5607/en.2019.28.4.529.

Calpain-2 as a Treatment Target in Prenatal Stress-induced Epileptic Spasms in Infant Rats

• Kwon HH
• Neupane C
• Shin J
• Gwon DH
• Yin Y
• Shin N
• Shin HJ
• Hong J
• Park JB
• Yi Y
• Kim DW
• Kang JW

• KMID: 2458550
• DOI: http://doi.org/10.5607/en.2019.28.4.529

Abstract

Stress can induce a serious epileptic encephalopathy that occurs during early infancy. Recent studies have revealed that prenatal stress exposure is a risk factor for the development of infantile spasms. Our previous work demonstrates that prenatal stress with betamethasone-induced alterations to the expression of the K⁺/Cl⁻ co-transporter (KCC2) in gamma-aminobutyric acid (GABA) interneurons lowers the seizure threshold in exposed animals. Here, we further investigated the mechanisms involved in this KCC2 dysfunction and explored possible treatment options. We stressed Sprague-Dawley rats prenatally and further treated dams with betamethasone on gestational day 15, which increases seizure susceptibility and NMDA (N-Methyl-D-aspartate)-triggered spasms on postnatal day 15. In this animal model, first, we evaluated baseline calpain activity. Second, we examined the cleavage and dephosphorylation of KCC2. Finally, we checked the effect of a calpain inhibitor on seizure occurrence. The phosphorylated-N-methyl-D-aspartate Receptor 2B (NR2B):non-phosphorylated NR2B ratio was found to be higher in the cortex of the prenatally stressed beta-methasone model. We further found that the betamethasone model exhibited increased phosphorylation of calpain-2 and decreased phosphorylation of KCC2 and Glutamic acid decarboxylase 67 (GAD67). After using a calpain inhibitor in prenatal-stress rats, the seizure frequency decreased, while latency increased. GABAergic depolarization was further normalized in prenatal-stress rats treated with the calpain inhibitor. Our study suggests that calpain-dependent cleavage and dephosphorylation of KCC2 decreased the seizure threshold of rats under prenatal stress. Calpain-2 functions might, thus, be targeted in the future for the development of treatments for epileptic spasms.

Keyword

Epilepsy; Calpain; KCC2; NMDA; Glutamate decarboxylase 67; K⁺/Cl⁻ co-transporter

MeSH Terms

Animals
Betamethasone
Brain Diseases
Calpain
Epilepsy
gamma-Aminobutyric Acid
Glutamate Decarboxylase
Humans
Infant*
Infant, Newborn
Interneurons
Models, Animal
N-Methylaspartate
Phosphorylation
Rats*
Rats, Sprague-Dawley
Risk Factors
Seizures
Spasm*
Spasms, Infantile
Betamethasone
Calpain
Glutamate Decarboxylase
N-Methylaspartate
gamma-Aminobutyric Acid