The aspirin metabolite sodium salicylate causes focal cerebral hemorrhage and cell death in rats with kainic acid-induced seizures

• Published in: Neuroscience 2000-01, Vol.99 (1), p.107-117
• Main Authors: Najbauer, J., Schuman, E.M., Mamelak, A.N.
• Format: Article
• Language: English
• Subjects: Animals; Anti-Inflammatory Agents, Non-Steroidal - pharmacology; aspirin; Aspirin - metabolism; Biological and medical sciences; cell death; Cell Death - drug effects; Cell Death - physiology; Cerebral Hemorrhage - chemically induced; Contraindications; epilepsy; Excitatory Amino Acid Agonists; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; hippocampus; Hippocampus - cytology; Hippocampus - drug effects; Hippocampus - injuries; Kainic Acid; Male; Medical sciences; Microglia - drug effects; Microglia - physiology; Nervous system (semeiology, syndromes); Neurology; Neurons - drug effects; Neurons - physiology; Neuroprotective Agents; neurotoxicity; Rats; Rats, Sprague-Dawley; Seizures - chemically induced; sodium salicylate; Sodium Salicylate - pharmacology
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(00)00158-5

Aspirin (acetylsalicylic acid), and its main metabolite sodium salicylate, have been shown to protect neurons from excitotoxic cell death in vitro. The objective of our study was to investigate the possible neuroprotective effects of sodium salicylate in vivo in rats with kainic acid-induced seizures, a model for temporal lobe epilepsy in human patients. Male Sprague–Dawley rats received intraperitoneal injections of kainic acid either alone, or with sodium salicylate given before and for 40 h after kainic acid injections. The control group received either phosphate-buffered saline or sodium salicylate without co-administration of kainic acid. Animals developed status epilepticus, which was aborted 1.5–2 h later with diazepam. On day 3 following kainic acid-induced seizures, animals received bromodeoxyuridine to measure cellular proliferation, and were killed under anesthesia 24 h later. Brains were removed, sectioned, and analysed for gross histological changes, evidence of hemorrhage, DNA fragmentation, cellular proliferation, and microglial immunohistochemistry. We report that sodium salicylate did not protect neurons from seizure-induced cell death, and to the contrary, it caused focal hemorrhage and cell death in the hippocampal formation and the entorhinal/piriform cortex of rats with kainic acid-induced seizures. Hemorrhage was never observed in animals that received vehicle, kainic acid or sodium salicylate only, which indicated that sodium salicylate exerted its effect only in animals with seizures, and was confined to select regions of the brain that undergo seizure activity. Large numbers of cells displaying DNA fragmentation were detected in the hippocampal formation, entorhinal/piriform cortex and the dorsomedial thalamic nucleus of rats that received kainic acid or kainic acid in combination with sodium salicylate. Bromodeoxyuridine immunohistochemistry revealed large numbers of proliferating cells in and around the areas with most severe neural injury induced by kainic acid or kainic acid co-administered with sodium salicylate. These same brain regions displayed intense staining with a microglia-specific marker, an indication of microglial activation in response to brain damage. In all cases, the degree of cell death, cell proliferation and microglia staining was more severe in animals that received the combination of kainic acid and sodium salicylate when compared to animals that received kainic acid alone. We hypothesize that our findings