calpain-inhibitor-iii and Status-Epilepticus

We comment this manuscript recently published in Brain Res. Bull.: S. Wang, S. Wang, P. Shan, Z. Song, T. Dai, R. Wang, Z. Chi, Mu-calpain mediates hippocampal neuron death in rats after lithium-pilocarpine-induced status epilepticus. Brain Res. Bull. 76(1-2) (2008) 90-96.

Topics: Animals; Antipsychotic Agents; Apoptosis; Apoptosis Inducing Factor; BH3 Interacting Domain Death Agonist Protein; Calpain; Caspase 3; Cysteine Proteinase Inhibitors; Cytochromes c; Dipeptides; Enzyme Activation; Hippocampus; Lithium Compounds; Mitochondria; Muscarinic Agonists; Neurons; Pilocarpine; Rats; Spectrin; Status Epilepticus

Evidence for increased calpain activity has been described in the hippocampus of rodent models of temporal lobe epilepsy. However, it is not known whether calpains are involved in the cell death that accompanies seizures. In this work, we characterized calpain activation by examining the proteolysis of calpain substrates and in parallel we followed cell death in the hippocampus of epileptic rats. Male Wistar rats were injected with kainic acid (10 mg/kg) intraperitoneally and killed 24 h later, after development of grade 5 seizures. We observed a strong Fluoro-Jade labeling in the CA1 and CA3 areas of the hippocampus in the rats that received kainic acid, when compared with saline-treated rats. Immunohistochemistry and western blot analysis for the calpain-derived breakdown products of spectrin showed evidence of increased calpain activity in the same regions of the hippocampus where cell death is observed. No evidence was found for caspase activation, in the same conditions. Treatment with the calpain inhibitor MDL 28170 significantly prevented the neurodegeneration observed in CA1. Taken together, our data suggest that early calpain activation, but not caspase activation, is involved in neurotoxicity in the hippocampus after status epilepticus.

Topics: Animals; Calpain; Caspases; Convulsants; Dipeptides; Disease Models, Animal; Enzyme Activation; Enzyme Inhibitors; Epilepsy; Fluoresceins; Hippocampus; Kainic Acid; Male; Nerve Degeneration; Organic Chemicals; Rats; Rats, Wistar; Spectrin; Status Epilepticus; Time Factors

Status epilepticus (SE) is a severe clinical manifestation of epilepsy which causes brain damage. The pathological process and underlying mechanisms involved in the programmed cell death (PCD) are still not fully clear. In the current study, rats were induced SE by lithium-pilocarpine administration. Our data showed hippocampal neurons death appeared at 6h after SE and sustained for 7 days. By blotting the activation of mu-calpain and its specific cleavage of nonerythroid alpha-spectrin (alphaSpII) (145 kDa) was evident at 1 and 3 days after SE, which coincided with Bid activation, apoptosis inducing factor (AIF) translocation and cytochrome c release from mitochondria, whereas, activated caspase-3 and caspase-3-specific fragments of alphaSpII (120 kDa) predominantly appeared at 5 and 7 days after SE. Moreover, MDL-28170, a calpain inhibitor, partially rescued the neuron death and attenuated the expression of activated mu-calpain, cleavage of Bid (15 kDa), AIF translocation and cytochrome c release. Taken together, our study indicated that mu-calpain mediated hippocampal neuron PCD is prior to caspase-3 activation. It functioned via translocation of Bid, AIF and cytochrome c release.

Topics: Animals; Antipsychotic Agents; Apoptosis Inducing Factor; BH3 Interacting Domain Death Agonist Protein; Calpain; Cell Death; Cysteine Proteinase Inhibitors; Cytochromes c; Dipeptides; Hippocampus; Humans; Lithium; Male; Muscarinic Agonists; Neurons; Pilocarpine; Random Allocation; Rats; Rats, Wistar; Spectrin; Status Epilepticus