HIV and opiates dysregulate K⁺- Cl⁻ cotransporter 2 (KCC2) to cause GABAergic dysfunction in primary human neurons and Tat-transgenic mice

Highlights

• HIV-1 proteins, infective HIV, and morphine reduce KCC2 levels in primary human neurons.

• Viral factors reduced KCC2 via NMDAR and CCR5; morphine acted via μ-opioid receptors.

• The loss of KCC2 dysregulated GABA_AR-mediated hyperpolarization and inhibition.

• KCC2 and neuronal dysfunction were rescued by manipulating KCC2 or upstream pathways.

• HIV-Tat expression in vivo diminished KCC2 levels in the striatum.

Abstract

Approximately half of people infected with HIV (PWH) exhibit HIV-associated neuropathology (neuroHIV), even when receiving combined antiretroviral therapy. Opiate use is widespread in PWH and exacerbates neuroHIV. While neurons themselves are not infected, they incur sublethal damage and GABAergic disruption is selectively vulnerable to viral and inflammatory factors released by infected/affected glia. Here, we demonstrate diminished K⁺-Cl⁻ cotransporter 2 (KCC2) levels in primary human neurons after exposure to HIV-1 or HIV-1 proteins ± morphine. Resulting disruption of GABA_AR-mediated hyperpolarization/inhibition was shown using genetically-encoded voltage (Archon1) and calcium (GCaMP6f) indicators. The HIV proteins Tat (acting through NMDA receptors) and R5-gp120 (acting via CCR5) but not X4-tropic gp120 (acting via CXCR4), and morphine (acting through μ-opioid receptors) all induced KCC2 loss. We demonstrate that modifying KCC2 levels or function, or antagonizing NMDAR, CCR5 or MOR rescues KCC2 and GABA_AR-mediated hyperpolarization/inhibition in HIV, Tat, or gp120 ± morphine-exposed neurons. Using an inducible, Tat-transgenic mouse neuroHIV model, we found that chronic exposure to Tat also reduces KCC2. Our results identify KCC2 as a novel therapeutic target for ameliorating the pathobiology of neuroHIV, including PWH exposed to opiates.