The Effects of Exosomes from Latent HIV‐1 Infected Cells on Mitophagy and Mitochondrial Fusion in Brain Microvasculature
Authors: Chandra Partha K. , Cikic Sinisa , Rutkai Ibolya , Kim Hogyoung , Abdel-Mageed Asim B. , Busija David W. 
Published: April 2020

Background

HIV‐1‐associated neurocognitive disorders (HAND) combined with opportunistic infections and malignancies comprise the conditional term: neuroAIDS. Insufficient removal of dysfunctional mitochondria, due to a defective mitophagy pathway, is a trigger in the pathogenesis of various neurodegenerative diseases, but its role in neuroAIDS has not been examined. Using in vitro and ex vivo models, we investigated the uptake of exosomes isolated from latent HIV‐1 infected cells (HIV‐exosome), induction of mitophagy, and mitochondrial fusion in brain microvasculature to study the role of HIV‐exosome in neuropathogenesis.

Methods

Exosomes were isolated by ultracentrifugation from uninfected and latent HIV‐1 infected T‐cells (Jurkat Exo and J‐Lat(9.2) Exo, respectively) and monocytes (U937 Exo and U1 Exo, respectively) and characterized exosomes by the qNano‐IZON system. For in vitro studies, we used primary human brain microvascular endothelial cells (HBMVEC) and primary human brain astrocytes (HBAC). For ex vivo studies, we isolated large basilar artery and microvessels (MVs) from mice brain expressing mito‐Dendra2+ fluorescence protein (Green) in endothelial mitochondria.

Results

The uptake of DiD‐tagged (Red) HIV‐exosomes (J‐Lat(9.2) Exo and U1 Exo) were significantly higher than control exosomes (Jurkat Exo and U937 Exo) in primary HBMVECs. In our ex vivo studies, the uptake of HIV‐exosome (Red) by basilar artery endothelium in mito‐Dendra2+ mice was notable. Also, the affinity of HIV‐exosome uptake was higher in brain MVs (diameter < 70 μm) that were isolated from mito‐Dendra2+ mice. Moreover, we observed co‐localization of DiD‐HIV‐exosomes (Red) with mitochondria (Green) in the endothelium of the isolated MVs. Exposure of HBMVEC to HIV‐exosome resulted in time‐ and dose‐dependent increases of Parkin, indicating induction of mitophagy. HIV‐exosome increased the expression of p62, and decreased proteolytic activity, suggesting possible inhibition of mitophagy, thus leading to the accumulation of mitophagosomes in HBMVEC. HIV‐exosome increased mitochondrial hyper‐fusion, possibly due to loss of pDrp1 in HBMVEC. Inversely, dose‐dependent increases of pDrp1 and gradual decreases of total Drp1 were observed in primary HBAC exposed to U1 Exo. Detection of CD31 indicated the presence of endothelium in isolated brain MVs. The ex vivo exposure of brain MVs to HIV‐exosome (U1 Exo) showed increased expression of Parkin and LC3B‐II, suggesting the induction of mitophagy. It also revealed increased expression of pDrp1, indicating mitochondrial fragmentation by U1 Exo.

Conclusions

Our results suggest that latent‐HIV‐1 exosome dysregulates mitophagy and mitochondrial fusion in brain microvasculature. Mitophagy and mitochondrial fusion/fission are key pathogenic mechanisms common to cancer and neurodegenerative diseases. Our findings may explain the role of HIV‐exosome in the development of neuroAIDS.

Support or Funding Information

HL‐093554, U54 GM104940 and AHA 17SDG33410366