Title

Harmine, a natural beta-carboline alkaloid, upregulates astroglial glutamate transporter expression

Document Type

Article

Abstract

Glutamate is the predominant excitatory amino acid neurotransmitter in the mammalian central nervous system (CNS). Glutamate transporter EAAT2/GLT-1 is the physiologically dominant astroglial protein that inactivates synaptic glutamate. Previous studies have shown that EAAT2 dysfunction leads to excessive extracellular glutamate and may contribute to various neurological disorders including amyotrophic lateral sclerosis (ALS). The recent discovery of the neuroprotective properties of ceftriaxone, a beta lactam antibiotic, suggested that increasing EAAT2/GLT-1 gene expression might be beneficial in ALS and other neurological/psychiatric disorders by augmenting astrocytic glutamate uptake. Here we report our efforts to develop a new screening assay for identifying compounds that activate EAAT2 gene expression. We generated fetal derived-human immortalized astroglial cells that are stably expressing a firefly luciferase reporter under the control of the human EAAT2 promoter. When screening a library of 1040 FDA approved compounds and natural products, we identified harmine, a naturally occurring beta-carboline alkaloid, as one of the top hits for activating the EAAT2 promoter. We further tested harmine in our in vitro cell culture systems and confirmed its ability to increase EAAT2/GLT1 gene expression and functional glutamate uptake activity. We next tested its efficacy in both wild type animals and in an ALS animal model of disease and demonstrated that harmine effectively increased GLT-1 protein and glutamate transporter activity in vivo. Our studies provide potential novel neurotherapeutics by modulating the activity of glutamate transporters via gene activation. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.

Medical Subject Headings

Alkaloids (pharmacology); Amino Acid Transport System X-AG (genetics, metabolism); Animals; Astrocytes (metabolism); Cell Culture Techniques; Drug Discovery; Excitatory Amino Acid Transporter 2 (genetics, metabolism); Gene Expression (drug effects); Glutamic Acid (metabolism); Harmine (pharmacology); Humans; Mice; Mice, Inbred C57BL; Peganum; Phytotherapy; Plant Preparations (pharmacology); Promoter Regions, Genetic (physiology); RNA, Messenger (metabolism); Stem Cells; Up-Regulation (drug effects)

Publication Date

6-1-2011

Publication Title

Neuropharmacology

E-ISSN

1873-7064

Volume

60

Issue

7-8

First Page

1168

Last Page

75

PubMed ID

21034752

Digital Object Identifier (DOI)

10.1016/j.neuropharm.2010.10.016

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