Effect of the calcineurin inhibitor FK506 on K+–Cl− cotransporter 2 expression in the mouse hippocampus after kainic acid-induced status epilepticus

Abstract

Calcineurin (CaN)-mediated excitotoxicity impairs γ-aminobutyric acid (GABA) transmission and induces neuronal apoptosis. Ca(2+)-dependent K(+)-Cl(-) cotransporter 2 (KCC2) participates in GABAergic inhibitory transmission. However, the mechanism by which CaN mediates GABA receptor-mediated KCC2 in seizures is not fully understood. In the present study, we investigated the altered expression of KCC2 and the effects of the CaN inhibitor FK506 on KCC2 expression in the mouse hippocampus following kainic acid (KA) treatment. FK506 was injected twice 24 h and 30 min before KA treatment and then mice were treated with KA and killed 2 days later. FK506 had anticonvulsant effect on KA-induced seizure activities. CaN cleavage was evident in the hippocampus 24 h after KA treatment. FK506 pretreatment blocked the truncation of CaN in the KA-treated hippocampus. Cresyl violet and TUNEL staining showed that FK506 prevented KA-induced hippocampal cell death. In particular, Western blot analysis showed that KCC2 expression was time dependent, with a peak at 6 h and a return to decreased levels at 48 h, whereas FK506 pretreatment inhibited the KA-induced decrease in KCC2 expression in the hippocampus. Immunofluorescence showed that FK506 pretreatment protected the loss of inhibitory GABAergic KCC2-expressing neurons following KA treatment. Taken together, these results provide evidence that altered KCC2 expression may be associated with Ca(2+)-mediated seizure activity and indicate that neuron-specific KCC2 may be involved in neuroprotection after seizures.

Possible alterations in GABAA receptor signaling that underlie benzodiazepine‐resistant seizures

“…In the chemically induced models of SE, there is some disagreement in the literature at time points greater than 1 h after SE induction. Kainate‐induced SE in mice caused a marked increase in KCC2 total protein levels at 2, 6, and 24 h prior to returning to basal levels at the 48‐h time point in the hippocampus (Shin et al., 2012). This study also found a small decrease in the expression of NKCC1 at 6 h. Similarly, pilocarpine‐induced SE caused a transient up‐regulation of KCC2 mRNA levels at the 6‐h time point (Zhu et al., 2012).…”

Atorvastatin pretreatment attenuates kainic acid-induced hippocampal neuronal death via regulation of lipocalin-2-associated neuroinflammation

“…KA injection activates both astrocytes and microglia related to cell apoptosis and increases inflammatory cytokines in damaged hippocampal neuronal cells [ 3 ]. KA-induced blood-brain barrier (BBB) leakage is associated with ionic imbalance and nuclear factor-κB (NF-κB) activation [ 4 5 ]. Thus, inhibition of neuroinflammation and neurovascular breakdown may be critical to protect against seizures-induced neuronal death.…”

Tonicity-responsive enhancer binding protein haplodeficiency attenuates seizure severity and NF-κB-mediated neuroinflammation in kainic acid-induced seizures

“…6,7 Recent papers showed that the brain edema induced by BBB leakage in seizures is associated with nuclear factor-kB (NF-kB) activation and ionic imbalance. 8,9 Thus, controlling the severity of neuroinflammation and BBB leakage may be critical to protect against seizure-induced neuronal death.…”