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Updated: Mar 30, 2026
Microglia as a Surrogate Biosensor to Determine Nanoparticle Neurotoxicity
Published on: October 25, 2016
Glutaminase-containing microvesicles from HIV-1-infected macrophages and immune-activated microglia induce
Beiqing Wu1, Yunlong Huang2,3, Alexander L Braun4
1Laboratory of Neuroimmunology and Regenerative Therapy, Departments of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, 68198-5930, USA. beiqing.wu2@unmc.edu.
Background:
HIV-1-infected and/or immune-activated microglia and macrophages are pivotal in the pathogenesis of HIV-1-associated neurocognitive disorders (HAND). Glutaminase, a metabolic enzyme that facilitates glutamate generation, is upregulated and may play a pathogenic role in HAND. Our previous studies have demonstrated that glutaminase is released to the extracellular fluid during HIV-1 infection and neuroinflammation. However, key molecular mechanisms that regulate glutaminase release remain unknown. Recent advances in understanding intercellular trafficking have identified microvesicles (MVs) as a novel means of shedding cellular contents. We posit that during HIV-1 infection and immune activation, microvesicles may mediate glutaminase release, generating excessive and neurotoxic levels of glutamate.
Results:
MVs isolated through differential centrifugation from cell-free supernatants of monocyte-derived macrophages (MDM) and BV2 microglia cell lines were first confirmed in electron microscopy and immunoblotting. As expected, we found elevated number of MVs, glutaminase immunoreactivities, as well as glutaminase enzyme activity in the supernatants of HIV-1 infected MDM and lipopolysaccharide (LPS)-activated microglia when compared with controls. The elevated glutaminase was blocked by GW4869, a neutral sphingomyelinase inhibitor known to inhibit MVs release, suggesting a critical role of MVs in mediating glutaminase release. More importantly, MVs from HIV-1-infected MDM and LPS-activated microglia induced significant neuronal injury in rat cortical neuron cultures. The MV neurotoxicity was blocked by a glutaminase inhibitor or GW4869, suggesting that the neurotoxic potential of HIV-1-infected MDM and LPS-activated microglia is dependent on the glutaminase-containing MVs.
Conclusions:
These findings support MVs as a potential pathway/mechanism of excessive glutamate generation and neurotoxicity in HAND and therefore MVs may serve as a novel therapeutic target.
Insights
Microglia and macrophages release glutaminase via microvesicles (MVs) during HIV-1 infection, causing neurotoxicity. Inhibiting MVs may offer a new therapeutic strategy for HIV-1-associated neurocognitive disorders (HAND).
Area of Science:
- Neuroscience
- Cell Biology
- Virology
Background:
- Microglia and macrophages are key players in HIV-1-associated neurocognitive disorders (HAND) pathogenesis.
- Glutaminase, an enzyme producing glutamate, is upregulated in HAND and released extracellularly during HIV-1 infection and neuroinflammation.
- The mechanisms regulating glutaminase release, particularly via intercellular trafficking like microvesicles (MVs), are not well understood.
Purpose of the Study:
- To investigate the role of microvesicles (MVs) in mediating glutaminase release from HIV-1-infected and immune-activated microglia and macrophages.
- To determine if MVs carrying glutaminase contribute to neuronal injury in the context of HAND.
- To explore MVs as a potential therapeutic target for HAND.
Main Methods:
- Isolation and characterization of MVs from cell-free supernatants of monocyte-derived macrophages (MDMs) and BV2 microglia cell lines using differential centrifugation, electron microscopy, and immunoblotting.
- Quantification of MV numbers, glutaminase immunoreactivity, and enzyme activity in supernatants from HIV-1 infected/LPS-activated cells versus controls.
- Assessment of neurotoxicity induced by MVs in rat cortical neuron cultures, with and without treatment with a sphingomyelinase inhibitor (GW4869) or a glutaminase inhibitor.
Main Results:
- Elevated numbers of MVs, glutaminase immunoreactivities, and enzyme activity were observed in supernatants of HIV-1 infected MDMs and LPS-activated microglia compared to controls.
- Inhibition of MV release using GW4869 significantly reduced extracellular glutaminase levels, indicating MVs mediate glutaminase release.
- MVs isolated from HIV-1 infected/LPS-activated cells induced significant neuronal injury, which was abrogated by glutaminase inhibition or GW4869, confirming the neurotoxic role of glutaminase-containing MVs.
Conclusions:
- Microvesicles (MVs) represent a significant pathway for excessive glutamate generation and subsequent neurotoxicity in HAND.
- Glutaminase-containing MVs released by infected/activated immune cells are directly implicated in neuronal damage.
- Targeting MVs presents a promising novel therapeutic strategy for mitigating neurotoxicity in HAND.
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