Antioxidant effects of dimethyl fumarate in SIV-infected rhesus macaques may indicate its use as a neuroprotective adjunct in HIV treatment

Philadelphia, PA

INTRODUCTION: Dimethyl fumarate (DMF) is an oral prodrug that is FDA approved for the treatment of multiple sclerosis. DMF is metabolized to monomethyl fumarate and able to cross the blood-brain barrier to illicit its central nervous system (CNS) affects. DMF is an antioxidant/anti-inflammatory that acts at the level of gene transcription through the Nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. We assessed the potential neuroprotective effects of DMF in HIV infection by using the rhesus macaque simian immunodeficiency virus (SIV) infection model. We hypothesized that DMF would increase the expression of antioxidant enzymes and subsequently reduce central nervous system oxidative stress in the setting of SIV-infection.

METHODS: Twelve rhesus macaques were used in this study and each was immunologically depleted of their CD8+ T lymphocytes to accelerate immunodeficiency and AIDS development. Ten of the twelve macaques were infected with SIV, while the remaining two acted as uninfected controls. Additionally, of the ten SIV-infected macaques, six received DMF a week prior to SIV-infection through the animals’ date of necropsy (development of terminal AIDS). Collected frozen and paraffin embedded tissues were used for western blotting and quantitative immunohistochemistry (IHC) analysis. Western blotting was done for antioxidant enzymes, NAD(P)H quinone dehydrogenase 1 (NQO1) and glutathione peroxidase (GPX1), across eleven brain regions. IHC staining looked at markers of protein and DNA oxidation, 3-nitrotyrosine (3-NT) and 8-hydroxy-2’-deoxyguanosine (8-OHdG) respectively, a lipid peroxidation enzyme, lysophosphatidylcholine acyltransferase 3 (LPCAT3), and a lipid peroxidation end product, malondialdehyde (MDA).

RESULTS: In DMF-treated, SIV-infected rhesus macaques compared to untreated, SIV-infected rhesus macaques: i) western blotting analysis revealed an overall increase in the expression of the antioxidant enzymes NQO1 and GPX1 (paired t-test) and an increase of GPX1 in specific regions (unpaired t-test) (p< .05); ii) quantitative IHC analysis of oxidation markers showed a decrease in both protein (3-NT) and DNA (8-OHdG) oxidation in the cortex and brainstem, via unpaired t-test (p< .05), an increase in lipid peroxidation enzyme (LPCAT3) expression in the cortex and spinal cord, via unpaired t-test (p< .05), and a decrease in lipid peroxidation end product (MDA) in the cortex and spinal cord (no statistical significance).

DISCUSSION: DMF’s increase in antioxidant enzyme expression, and decrease in protein and DNA oxidation in the setting of SIV-infection suggest that the drug is effective at reducing oxidative stress within the CNS. Additionally, the inverse relationship in relative detection of lipid peroxidation enzyme and end product levels may be also indicative of DMF’s affect at limiting oxidative stress in regions more susceptible to oxidative injury. Given these findings we propose that in HIV-infected individuals, DMF may have a use as a neuroprotective adjunct to anti-retroviral therapy to help protect against CNS injury.