Deletion of puma protects hippocampal neurons in a model of severe status epilepticus

• Published in: Neuroscience 2010-06, Vol.168 (2), p.443-450
• Main Authors: Engel, T, Hatazaki, S, Tanaka, K, Prehn, J.H.M, Henshall, D.C
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Apoptosis Regulatory Proteins - genetics; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Hippocampus - metabolism; Hippocampus - pathology; Kainic Acid; Medical sciences; Mice; Mice, Knockout; Nervous system (semeiology, syndromes); Neurology; Neurons - metabolism; Neurons - pathology; Status Epilepticus - chemically induced; Status Epilepticus - metabolism; Status Epilepticus - pathology; Tumor Suppressor Proteins - genetics; Vertebrates: nervous system and sense organs
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2010.03.057

Abstract Prolonged seizures ( status epilepticus ) can activate apoptosis-associated signaling pathways. The extent to which such pathways contribute to cell death might depend on the insult intensity, whereby the programmed or apoptotic cell death component is reduced when seizures are more severe or protracted. We recently showed that mice lacking the pro-apoptotic Bcl-2 homology domain 3-only protein Puma (Bbc3) were potently protected against damage caused by status epilepticus . In the present study we examined whether Puma deficiency was protective when the seizure episode was more severe. Intra-amygdala microinjection of 1 μg kainic acid (KA) into C57BL/6 mice triggered status epilepticus that lasted about twice as long as with 0.3 μg KA prior to lorazepam termination. Hippocampal damage was also significantly greater in the higher-dose group. Over 80% of degenerating neurons after seizures were positive for DNA fragmentation assessed by terminal deoxynucleotidyl dUTP nick end labeling (TUNEL). Microscopic analysis of neuronal nuclear morphology in TUNEL-positive cells revealed the proportion displaying large rounded clumps of condensed chromatin was ∼50% lower in the high-dose versus low-dose KA group. Nevertheless, compared to heterozygous and wild-type mice subject to status epilepticus by high-dose KA, neuronal death was reduced by ∼50% in the hippocampus of Puma-deficient mice. These data suggest aspects of the apoptotic component of seizure-induced neuronal death are insult duration- or severity-dependent. Moreover, they provide further genetic evidence that seizure-induced neuronal death is preventable by targeting so-called apoptosis-associated signaling pathways and Puma loss likely disrupts caspase-independent or non-apoptotic seizure-induced neuronal death.