DOI
https://doi.org/10.25772/59TK-4D03
Defense Date
2020
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Neuroscience
First Advisor
Pamela E. Knapp
Abstract
With adherence to combined antiretroviral therapy (cART), HIV infection can be considered a controllable chronic condition, but quality of life issues remain. The preeminent of which, HIV-associated neurocognitive disorders (HAND), encompasses an array of neurological complications and has persisted despite cART implementation. The symptoms of HAND can be exacerbated by opiate use, a common comorbidity for people infected with HIV (PWH). While neurons are not infected by HIV, they incur sublethal damage, with γ-amino butyric acid- (GABA)ergic function being particularly vulnerable to viral and inflammatory factors released by infected/affected glia. This dissertation presents studies on novel organoid and dissociated primary human CNS models of HAND, the latter of which showed diminished levels of K+ - Cl- cotransporter 2 (KCC2), a neuronal transporter that maintains low intracellular Cl-, after exposure to HIV-1 and HIV proteins ± morphine. GABAAR-mediated hyperpolarization is predicated upon activity of KCC2 and functional examination of these neurons revealed decreased hyperpolarization and disinhibition in response to GABAAR activation due KCC2 loss. Additionally, we identified the mechanisms through which HIV-1 mediates KCC2 reduction: the HIV protein, transactivator of transcription (Tat), through activation of N-methyl-D-aspartate receptor (NMDAR), and the HIV protein, glycoprotein 120 (gp120), through a novel mechanism involving CCR5 activation. We also found that morphine acts through the µ opioid receptor (MOR) to dysregulate KCC2. Pharmacological maintenance of KCC2 with the KCC2 enhancer, CLP257, rescued HIV, Tat, and morphine effects on KCC2 and GABAAR activity.
Common neurological deficits in PWH include memory and motor dysfunction which are likely the manifestations of HIV-induced hippocampal and striatal degeneration. Thus, we expanded our in vitro results to the glial fibrillary acidic protein (GFAP)-driven, doxycycline(DOX)-inducible Tat-transgenic mouse model of HAND. No changes in KCC2 in the hippocampus were seen, but we did find significant Tat-induced loss of KCC2 in the striatum which was associated with locomotor abnormalities in these mice. We also rescued phosphorylation of serine 940-KCC2 leading to increased KCC2 membrane localization and restoration of baseline motor activity with oral gavage of the prodrug of CLP257, CLP290. Overall, our in vitro and in vivo results demonstrate KCC2 as a promising, novel therapeutic target to alleviate the symptoms associated with HAND ± opiate use.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
4-28-2020