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Abstract
Abstract: Multidrug resistance-associated protein 1 (MRP1), an efflux multidrug transporter, was shown to be elevated in both glia and neurons in seizure focus in refractory epilepsy patients. Up-regulation of MRP1 and other multidrug transporters in perivascular astrocytes was suggested to cause resistance to antiepileptic drugs (AEDs) by reducing the concentration of AEDs at the epileptogenic areas. However, it is not known whether the up-regulation of MRP1 in neurons can cause resistance to AEDs, such as sodium phenytoin (PHT) and valproic acid (VPA). PHT inhibits voltage-gated sodium channel (VGSC) by occluding it, but whether PHT enters the channel through its inner or outer pore is not known. The authors overexpressed human MRP1 protein only in neurons in a Drosophila genetic seizure model, bang senseless (bss) mutants. The authors found that overexpression of MRP1 blocked the attenuation of the seizure behavior of bss mutants by acute and chronic application of PHT, and by chronic application of VPA. Conversely, overexpression of MRP1 in neurons increased the tolerance of bss flies to high-dosage PHT and VPA. Thus, up-regulation of MRP1 expression only in neurons causes resistance to AED in seizure flies. Moreover, the current data suggest that PHT enters VGSC through its inner pore.
ACKNOWLEDGMENTS
We thank Dr. Susan Cole (Queen's University at Kingston) for pcDNA3.1(−)-MRP1k vector. Drosophila Bloomington stock center for providing stocks. This work was supported by the National Natural Science Foundation of China (grant no. 81071026) and the 973 program 2011CBA00408 (grant no. 81071025).
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.