In vitro and Ex vivo Neurotoxic Effects of Efavirenz are Greater than Those of Other Common Antiretrovirals

Abstract

Although antiretroviral (ARV) therapy has reduced the incidence of severe dementia associated with HIV infection, there has been a rise in milder neurocognitive complaints. Data from HIV patients taking ARVs have shown measurable neurocognitive improvements during drug cessation, suggesting a neurotoxic role of the therapy itself. Mechanisms underlying potential ARV neurotoxicity have not been thoroughly investigated, however pathologic oxidative stress and mitochondrial dysfunction have been suspected. Using DIV 16 primary rat cortical neuron culture, we tested eight ARVs from the three most commonly prescribed ARV classes: nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs/NtRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), and protease inhibitors (PIs) for effects on neuron viability and morphology after 24 h of drug exposure. Of the tested NRTIs, only stavudine at nearly 100 times the target plasma concentration affected neuron viability with no appreciable change in morphology. Dideoxyinosine induced dendritic simplification at 100 times target plasma concentrations, but did not adversely affect viability. The sole NtRTI, tenofovir, induced dendritic simplification at approximately 3-4 times target plasma concentration, but did not affect viability. Of the tested PIs, only amprenavir decreased neuron viability at nearly 100 times the target plasma concentration. The non-nucleoside reverse transcriptase inhibitor, efavirenz, consistently reduced viability (at 50 µM) and induced dendritic simplification (at 20 µM) nearest the target plasma concentration. Probing mitochondrial energetics of DIV16 cortical neurons after exposure to 20 µM efavirenz showed rapid diminution of mitochondrial-dependent oxygen consumption. Further, 20 µM efavirenz decreased excitability in ex vivo slice culture whereas 2 µM had no effect.

Cerebral Vascular Toxicity of Antiretroviral Therapy

“…Additionally, a comparison of these findings to the aforementioned studies that reported OCR alternations suggests that there are multiple mechanisms in which electron transport chain function can be affected by ART. Indeed, no changes in viability were found in cells exposed to selected anti-retroviral drugs through the reductivedependent reagent, CTB (Ciavatta et al 2017). These results suggest the existence of a non-mitochondrial mechanism compensating for the lost mitochondrial reductive capacity.…”

“…A commonly used research method to estimate electron transport chain function is measuring the oxygen consumption rate (OCR), and we (and others) have shown that ART drug combinations induce alternations of OCR (Apostolova et al 2015a;Cohen et al 2017;Velichkovska et al 2018). An interesting observation also indicates that the inhibition of Complex I and alterations to the electron transport chain function may occur without any changes in the OCR levels (Ciavatta et al 2017). The explanation for this phenomenon was suggested to arise from the activation of Complex II to act as a bypass and substituting for the Complex I electronpumping function.…”

“…Exposure to ART can also induce alternations of mitochondrial dynamics. For example, exposure to Efavirenz as well as Tenofovir and Dideoxyinosine resulted in a significant decrease in MAP2 staining (Ciavatta et al 2017). The microtubule-associated protein 2 (MAP2) is important for neurite maintenance, growth, and extension; hence, it is primarily used to track morphological and developmental alternations of dendrites, which were also reported to occur as a result of several different ART drugs exposures (Robertson et al 2012;Akay et al 2014).…”

High-content analysis and Kinetic Image Cytometry identify toxic and epigenotoxic effects of HIV antiretrovirals on human iPSC-neurons and primary neural precursor cells

“…In a seminal study 36 toxic effects on MAP-2 expression (biomarker for neurons) were found for abacavir, EFV, etravirine, nevaripine, and atazanavir, whereas darunavir, FTC, tenofovir, and maraviroc were nontoxic; also, doravirine+abacavir+lamivudine strongly increased calcium responses to glutamate (potentially increasing excitotoxicity) and didanosine strongly affected mitochondria. Similarly, EFV strongly decreased neuronal viability, reduced neurites and synapses, and reduced excitability of brain slices while tenofovir was less toxic 37 . Akay et al 2014 38 , compared in vivo and in vitro effects of ARVs; in vivo, cART reduced neuronal and synaptic markers in the CNS of SIV-infected monkeys, while cART in uninfected adult rats reduced MAP2 and upregulated proteins associated with anti-oxidation (NQO-1 and HO-1); in vitro (rat neurons), the HIV protease inhibitors ritonavir and saquinovir, alone or in combination, reduced MAP2, increased ROS, and upregulated NQO-1 and HO-1, implicating oxidative effects in the neurotoxicity of ARVs.…”

High efavirenz levels but not neurofilament light plasma levels are associated with poor neurocognitive functioning in asymptomatic HIV patients

“…For instance, a neurotoxic effect of efavirenz and its major metabolite Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13365-020-00860-1) contains supplementary material, which is available to authorized users. 8-hydroxy-efavirenz was found in neuronal cultures, affecting dendrites and dendritic processes (Robertson et al 2012;Tovar-y-Romo et al 2012;Ciavatta et al 2017). Moreover, studies have shown a detrimental effect of efavirenz on the bloodbrain barrier and on neuronal action potential thresholds (Bertrand and Toborek 2015;Ciavatta et al 2017).…”