Abstracts

Rationale: Temporal lobe epilepsy is the most common form of epilepsy in humans. Caspase activation is a mechanism of cell death induced by seizures. Tellurium (IV) compounds present antitumoral, immunomodulatory and neuroprotective effects due to their ability to inhibit cysteine proteases. We studied the activity of caspase-1, -3 and -8 in the hippocampus of rats exhibiting status epilepticus induced by pilocarpine. All three caspases were activated. Methods: Four groups were studied: PILO, rats treated with pilocarpine (360 mg/Kg); RF+PILO, rats treated with the organotellurane compound RF-07 15 min prior pilocarpine; RF+Saline, rats treated with RF and saline instead of pilocarpine, and Saline group. All rats were pretreated with Methyl-scopolamine 30 min prior to pilocarpine to reduce peripheral effect of this cholinergic agonist. For caspase activity, rats of four groups (N=4/group) were decapited (1 hour 30 min after SE) under deep pentobarbital anaesthesia and their hippocampus were quickly dissected and washed in ice cold phosphate buffer. Rat hippocampus were lysed using a reaction mixture composed by 100 mM HEPES and 2 mM EDTA, pH 7.4, containing 0.2% CHAPS, 10% sucrose, 10 mM dithiothreitol (DTT), and proteases inhibitors: 0.1% PMSF, 0.1% benzamidin, 0.1% antipain, 0.1% TLCK, 0.1% chemostatin and 0,1% pepstatin. The mixture was added to the tissue samples that were frozen three times on dry-ice. The samples were centrifuged at 12000g for 40 min at 4C to remove cellular debris. The supernatants were collected for measure protein using Bradford method. Caspase activity was measured by fluorescence spectrophotometer. Effect in vitro of RF-07 in caspases activities in the rat hippocampus and in recombinant caspases activities were also determined using fluorimetric methods. Results: Tellurium (IV) compounds RF-07, RF-03 and AS-101 inhibited caspases in vitro, showing high second-order inhibition rate constants. The intraperitoneal injection of RF-07 prior to pilocarpine suppressed the behavioral and electroencephalographic seizure occurrence. Conclusions: According to our results, the caspases are activated as early as 90 min following SE. Tellurium (IV) compounds exerted anticonvulsant effects associated with the inhibition of caspases. These results suggest a promising therapeutic potential of organotellurium (IV) compounds as antiepileptogenic agents. Acknowledgements: Fapesp, CNPq, FAP-Unifesp