Abstract 11673: Neuroprotective Mechanisms of Mefenamic Acid in an in vitro Model of Stroke

Abstract

Introduction: Fenamates are classical non-steroidal anti-inflammatory drugs but they are also modulators of GABA A receptors, activators of potassium channels and antagonists of non-selective cation channels. Previous data from our lab has demonstrated that the fenamate, mefenamic acid (MFA), has neuroprotective effects both in vitro and in vivo . Hypothesis: We hypothesized that the neuroprotective actions of mefenamic acid result from its diverse pharmacological properties. To test this hypothesis, we have investigated four pharmacological properties of MFA, namely cyclooxygenase (COX) inhibition, GABA A receptor modulation, potassium channel activation and reactive oxygen species (ROS) inhibition against glutamate neurotoxicity in vitro . Methods: Neurotoxicity was induced by exposure of embryonic rodent hippocampal neurons, 9 days in vitro, to 10 mins of Na-glutamate (5μM). 24 hours after exposure to Na-glutamate, cell death was quantified by measuring the levels of lactate dehydrogenase (LDH) in the media using a CytoTox-96 non-radioactive assay kit. Generation of ROS was measured using Carboxy-H2DCFDA dye. Results: MFA and the non-fenamate COX inhibitors, ibuprofen, indomethacin and Na-salicylate were examined against glutamate neurotoxicity at 10 or 100μM. Cell death was significantly (p<0.01) reduced by 79%, (100μM) and 65% (100μM) by MFA and Na-salicylate, respectively, but not with ibuprofen and indomethacin. Generation of ROS was also decreased significantly when treated with MFA at 30μM and 100μM by 38% and 36% (p<0.05) respectively.The effects of co-application of MFA with either picrotoxin (a GABA A channel blocker) or bicuculline (a competitive GABA A receptor antagonist) or TEA (a K + channel blocker) were examined. Co-application of MFA (100μM) with picrotoxin (100μM), bicuculline (10μM) or TEA (30mM) all reduced cell death but neuroprotection was not significant. Conclusion: Collectively, these data suggest that COX inhibition and reduction of ROS generation significantly contribute to the neuroprotective actions of MFA against glutamate neurotoxicity. GABA modulation and potassium channel inhibition of MFA may also contribute but they are not the primary mechanism of its neuroprotective actions.