Abstract
Despite combination antiretroviral therapies (cARTs), a significant proportion of HIV-infected patients develop HIV-associated neurocognitive disorders (HAND). Ongoing viral replication in the central nervous system (CNS) caused by poor brain penetration of cART may contribute to HAND. However, it has also been proposed that the toxic effects of long-term cART may contribute to HAND. A better understanding of the neurotoxic potential of cART is critically needed in light of the use of CNS-penetrating cARTs to contend with the virus reservoir in the brain. The efavirenz (EFV) metabolites 7-hydroxyefavirenz (7-OH-EFV) and 8-hydroxyefavirenz (8-OH-EFV) were synthesized and purified, and their chemical structures were confirmed by mass spectrometry and NMR. The effects of EFV, 7-OH-EFV, and 8-OH-EFV on calcium, dendritic spine morphology, and survival were determined in primary neurons. EFV, 7-OH-EFV, and 8-OH-EFV each induced neuronal damage in a dose-dependent manner. However, 8-OH-EFV was at least an order of magnitude more toxic than EFV or 7-OH-EFV, inducing considerable damage to dendritic spines at a 10 nM concentration. The 8-OH-EFV metabolite evoked calcium flux in neurons, which was mediated primarily by L-type voltage-operated calcium channels (VOCCs). Blockade of L-type VOCCs protected dendritic spines from 8-OH-EFV-induced damage. Concentrations of EFV and 8-OH-EFV in the cerebral spinal fluid of HIV-infected subjects taking EFV were within the range that damaged neurons in culture. These findings demonstrate that the 8-OH metabolite of EFV is a potent neurotoxin and highlight the importance of directly determining the effects of antiretroviral drugs and drug metabolites on neurons and other brain cells.
Footnotes
This work was supported by the National Institutes of Health National Institute on Alcohol Abuse and Alcoholism [Grant AA0017408], the National Institutes of Health National Institute of Mental Health [Grants MH077542, MH075673, MH075673, MH71150]; the National Institutes of Health National Institute on Aging [Grant AG034849]; and the National Institutes of Health National Institute of Neurological Disorders and Stroke [Grant NS049465].
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
ABBREVIATIONS:
- cART
- combination antiretroviral therapy
- AM
- acetoxymethyl ester
- AMPA
- α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid
- ANOVA
- analysis of variance
- ARV
- antiretroviral drug
- [Ca2+]c
- cytosolic calcium
- CNS
- central nervous system
- CSF
- cerebrospinal fluid
- EFV
- efavirenz
- 7-OH-EFV
- 7-hydroxyefavirenz
- 8-OH-EFV
- 8-hydroxyefavirenz
- F-EFV
- fluorinated analog of EFV
- HAND
- HIV-associated neurocognitive disorders
- HPLC
- high-performance liquid chromatography
- MK-801
- (5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine
- NBQX
- 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(f)quinoxaline
- NMDA
- N-methyl-d-aspartate
- P450
- cytochrome P450
- PBS
- phosphate-buffered saline
- PPADS
- 4-[(E)-{4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl]pyridin-2-yl}diazenyl]benzene-1,3-disulfonic acid
- VOCC
- voltage-operated calcium channel.
- Received April 16, 2012.
- Accepted September 10, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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