Intermittent Hypoxia Preconditioning-Induced Epileptic Tolerance by Upregulation of Monocarboxylate Transporter 4 Expression in Rat Hippocampal Astrocytes

Noxious stimuli applied at doses close to but below the threshold of cell injury induce adaptive responses that provide a defense against additional stress. Epileptic preconditioning protects neurons against status epilepticus and ischemia; however, it is not known if the converse is true. During hypoxia/ischemia (H/I), lactate released from astrocytes is taken up by neurons and is stored for energy, a process mediated by monocarboxylate transporter 4 (MCT4) in astroglia. The present study investigated whether H/I preconditioning can provide protection to neurons against epilepsy through upregulation of MCT4 expression in astrocytes in vitro and in vivo. An oxygen/glucose deprivation protocol was used in primary astrocyte cultures, while rats were subjected to an intermittent hypoxia preconditioning (IHP) paradigm followed by lithium-pilocarpine-induced epilepsy as well as lactate transportation inhibitor injection, with a subsequent evaluation of protein expression as well as behavior. H/I induced an upregulation of MCT4 expression, while an IHP time course of 5 days provided the greatest protection against epileptic seizures, which was most apparent by 3 days after IHP. However, lactate transport function disturbances can block the protective effect induced by IHP. These findings provide a potential basis for the clinical treatment of epilepsy.