Influência da epilepsia na expressão de transportadores

Abstract

Epilepsy is a pathology spread worldwide, but prevalent in developing countries; about fifty million people in the world are affected by this pathology. The disease is characterized by recurrent seizures, which are brief episodes of involuntary movement named as seizures, and occur due to excessive electrical discharges that affect the brain cells. Patients who have epilepsy, in some cases, are not successfully at treatment. Some carriers, such as the Pglycoprotein (Pg-P), present in the blood brain barrier may be involved in resistance mechanisms to antiepileptic drugs, which are substrates of Pg-P. Therefore, the evaluation of Pg-P expression and its activity may help to understand the pathological mechanisms of epilepsy. The evaluation was performed comparing healthy animals and others presenting genetic background susceptible to the development of epilepsy, wistar audiogenic rats (WAR with temporal lobe epilepsy and WAR resistant to seizures) who received fexofenadine (dose of 10mg/kg, oral gavage), a Pg-P substrate, collecting blood, from 0 until 12 hours after administration. The concentrations of fexofenadine were determined by ultra-high performance liquid chromatography coupled to mass spectrometry; sample preparation was performed by protein precipitation with acetonitrile. Chromatographic conditions were: C18column, with mobile phase of methanol:acetonitrile:ammonium acetate 10mM (45:45:10, v:v), with flow of 0.4mL/min, and monitoring the following transitions from fexofenadine: precursor ion m/z 502 and product ions 484, 466 and 171; and internal standard (losartan), following transitions m/z 423 for the precursor and ions products 207, 192 and 235. The developed and validated analitical method validated according to brazilian legislation, being accurate, exact, stable and suitable to the pharmacokinetic study. The results of pharmacokinetic analysis, showed an increase in fexofenadine bioavailability (AUC) and half-life due to a clearance reduction in WAR-resistant to seizures (p<0,05). Immunohistochemical analysis of the brain tissue showed an increase in Pg-P expression on the WAR groups with ELT and WAR resistant in the blood-brain barrier, when compared to control group. The change in Pg-P expression may be responsible for pharmacokinetic alterations on the WAR resistant group, once the drug delivery into the CNS was reduced, and this finding may be one of failure at pharmacological treatment observed in the patients.