Reversal of P-glycoprotein overexpression by Ginkgo biloba extract in the brains of pentylenetetrazole-kindled and phenytoin-treated mice

Kaohsiung J Med Sci. 2015 Aug;31(8):398-404. doi: 10.1016/j.kjms.2015.05.007. Epub 2015 Jun 29.

Abstract

The purpose of this study was to investigate the combined effects of Ginkgo biloba extract and phenytoin (PHT) sodium as a dose regimen simulating the clinical treatment of patients with epilepsy, on P-glycoprotein (P-GP) overexpression in a pentylenetetrazole-kindled mouse model of epilepsy. Epilepsy was induced by intraperitoneal administration of pentylenetetrazole (40 mg/kg) for 7 days followed by intragastric administration of PHT (40 mg/kg) for 14 days. Thirty mice that developed seizures were randomly divided into three groups and administered PHT as well as the following treatments: saline (negative control); verapamil (20 mg/kg, positive control); and G. biloba (30 mg/kg). Seizure severity was recorded 30 minutes after treatment on Day 4 of drug administration, after which the mice were euthanized, and their brains isolated. Western blots and immunohistochemistry were performed to analyze the expression of P-GP and caspase-3, respectively, in the brain tissue. High-performance liquid chromatography was used to measure the concentrations of PHT in the brains of the treated mice. After 4 consecutive days of treatment, the seizure severity in the mice in the G. biloba extract group was more significantly reduced than the seizure severity in the saline control group, and a significant difference was observed between the G. biloba extract and verapamil control groups (p < 0.05). P-GP expression in the brain more significantly decreased in the mice treated with G. biloba extract and verapamil than it did in the saline-treated control group (p < 0.05). Compared with the saline-treated control group, the mice treated with G. biloba extract and verapamil showed significantly increased brain PHT concentrations (p < 0.05). Furthermore, caspase-3 expression in the brain tissue of the G. biloba extract group was significantly lower than that in the vehicle control group (p < 0.05); this finding demonstrated the neuroprotective effects of G. biloba. Therefore, this study showed that treatment with G. biloba extract in combination with PHT prevented the upregulation of P-GP expression in mice. Moreover, G. biloba extract decreased seizure severity in pentylenetetrazole-kindled/PHT-treated mice through a mechanism that might be related to the reduction of P-GP expression in the brain.

Keywords: Caspase-3; Drug resistance; Ginkgo biloba; P-glycoprotein; Phenytoin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism*
  • Animals
  • Brain / drug effects*
  • Brain / enzymology
  • Brain / metabolism*
  • Brain / pathology
  • Caspase 3 / metabolism
  • Disease Models, Animal
  • Ginkgo biloba / chemistry*
  • Kindling, Neurologic*
  • Male
  • Mice
  • Pentylenetetrazole
  • Phenytoin / pharmacology
  • Phenytoin / therapeutic use*
  • Plant Extracts / pharmacology*
  • Plant Extracts / therapeutic use
  • Seizures / chemically induced
  • Seizures / enzymology
  • Seizures / pathology
  • Verapamil / pharmacology

Substances

  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Plant Extracts
  • Phenytoin
  • Verapamil
  • Caspase 3
  • Pentylenetetrazole