cytochrome-c-t 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

Topics: Acute Disease; Apoptosis; Child, Preschool; Cytochromes c; E-Selectin; Humans; Infant; Prognosis; Status Epilepticus

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

Status epilepticus results in preferential neuronal cell loss in the hippocampus. We evaluated the hypothesis that the repertoire of intracellular events in the vulnerable hippocampal CA3 subfield after induction of experimental temporal lobe status epilepticus entails upregulation of nitric oxide synthase II (NOS II), followed by the release of mitochondrial cytochrome c that triggers the cytosolic caspase-3 cascade, leading to apoptotic cell death. In Sprague-Dawley rats, significant and temporally correlated upregulation of NOS II (3-24h), but not NOS I or II expression, enhanced cytosolic translocation of cytochrome c (days 1 and 3), augmented activated caspase-3 in cytosol (days 1, 3 and 7) and DNA fragmentation (days 1, 3 and 7) was detected bilaterally in the hippocampal CA3 subfield after elicitation of sustained seizure activity by microinjection of kainic acid into the unilateral CA3 subfield. Application bilaterally into the hippocampal CA3 subfield of a selective NOS II inhibitor, S-methylisothiourea, significantly blunted these apoptotic events; a selective NOS I inhibitor, N(omega)-propyl-l-arginine or a potent NOS III inhibitor, N(5)-(1-iminoethyl)-l-ornithine was ineffective. We conclude that upregulation of NOS II contributes to apoptotic cell death in the hippocampal CA3 subfield via a cytochrome c/caspase-3 signaling cascade following the induction of experimental temporal lobe status epilepticus.

Topics: Animals; Apoptosis; Blotting, Western; Caspase 3; Cytochromes c; Cytosol; DNA Fragmentation; Electroencephalography; Enzyme Inhibitors; Epilepsy, Temporal Lobe; Fluorescent Antibody Technique; Functional Laterality; Hippocampus; In Situ Nick-End Labeling; Male; Microscopy, Confocal; Nitric Oxide; Nitric Oxide Synthase Type II; Rats; Rats, Sprague-Dawley; Signal Transduction; Status Epilepticus; Up-Regulation

Experimentally evoked seizures can activate the intrinsic mitochondrial cell death pathway, components of which are modulated in the hippocampus of patients with temporal lobe epilepsy. Bcl-2 family proteins are critical regulators of mitochondrial dysfunction, but their significance in this setting remains primarily untested. Presently, we investigated the mitochondrial pathway and role of anti-apoptotic Bcl-2 proteins using a mouse model of seizure-induced neuronal death. Status epilepticus was evoked in mice by intra-amygdala kainic acid, causing cytochrome c release, processing of caspases 9 and 7, and death of ipsilateral hippocampal pyramidal neurons. Seizures caused a rapid decline in hippocampal Bcl-w levels not seen for either Bcl-2 or Bcl-xl. To test whether endogenous Bcl-w was functionally significant for neuronal survival, we investigated hippocampal injury after seizures in Bcl-w-deficient mice. Seizures induced significantly more hippocampal CA3 neuronal loss and DNA fragmentation in Bcl-w-deficient mice compared with wild-type mice. Quantitative electroencephalography analysis also revealed that Bcl-w-deficient mice display a neurophysiological phenotype whereby there was earlier polyspike seizure onset. Finally, we detected higher levels of Bcl-w in hippocampus from temporal lobe epilepsy patients compared with autopsy controls. These data identify Bcl-w as an endogenous neuroprotectant that may have seizure-suppressive functions.

Topics: Animals; Apoptosis; Apoptosis Regulatory Proteins; Bcl-2-Like Protein 11; Caspase 7; Caspase 9; Cytochromes c; DNA Fragmentation; Electroencephalography; Electrophysiology; gamma-Aminobutyric Acid; Hippocampus; Humans; Kainic Acid; Membrane Proteins; Mice; Mice, Mutant Strains; Mitochondria; Neurons; Proteins; Proto-Oncogene Proteins; Seizures; Status Epilepticus

We examined the mechanism of neuronal necrosis induced by hypoxia in dentate gyrus cultures or by status epilepticus (SE) in adult mice. Our observations showed that hypoxic necrosis can be an active process starting with early mitochondrial swelling and loss of the mitochondrial membrane potential, followed by cytochrome c release and caspase-9-dependent activation of caspase-3. This sequence of events (or program) was independent of protein synthesis and may be induced by energy failure and/or calcium overloading of mitochondria. We called this form of necrosis "programmed necrosis." After SE in adult mice, CA1 and CA3 pyramidal neurons displayed a necrotic morphology, associated with caspase-3 immunoreactivity and with double-stranded DNA breaks, suggesting that "programmed necrosis" may be involved in SE-induced neuronal loss.

Topics: Animals; Brain; Caspase 3; Caspase 9; Caspases; Cell Death; Cell Hypoxia; Cytochromes c; Dentate Gyrus; DNA; Mice; Mitochondria; Mitochondrial Swelling; Necrosis; Neurons; Pyramidal Cells; Status Epilepticus

Status epilepticus (SE) increases neurogenesis in the subgranular zone (SGZ) of the adult dentate gyrus, but many of the newborn cells die, partly through caspase-induced apoptosis. Here we provide immunohistochemical evidence indicating that the caspase-evoked death of the new neurons involves the mitochondrial but not the death-receptor-mediated pathway. Cytochrome c released from mitochondria was found in a subset of progenitor cell progeny, while Fas ligand and tumor necrosis factor 1 receptor-associated domain as well as the mitochondria-related, caspase-independent apoptosis-inducing factor were not detected. We also show that additional seizures, induced at different stages during neuronal differentiation of progenitor cell progeny following SE, neither potentiate cell death mechanisms in the SGZ nor compromise the survival of the new cells. Thus, we found similar expression of cytochrome c, active caspase-3, caspase-cleaved PARP, and TUNEL/Hoechst-positive DNA fragmentation, as well as numbers of new cells in the SGZ in rats exposed to additional seizures at days 6 and 7 or days 33 and 34 following SE as in control animals only subjected to SE. We propose that the degree of survival of newly generated neurons is determined primarily by the initial SE insult and the ensuing pathology in the tissue environment, whereas spontaneous seizures play a minor role.

Topics: Animals; Antigens, CD; Apoptosis; Caspases; Cell Differentiation; Cell Survival; Cytochromes c; Dentate Gyrus; Disease Models, Animal; Epilepsy; Fas Ligand Protein; Male; Membrane Glycoproteins; Mitochondria; Neurons; Rats; Rats, Sprague-Dawley; Receptors, Tumor Necrosis Factor; Receptors, Tumor Necrosis Factor, Type I; Signal Transduction; Status Epilepticus; Stem Cells