The effects of HIV-associated extracellular vesicles on mitochondrial dysfunction in brain microvessels - Combined antiretroviral therapy (cART) suppresses HIV replication, but 30-60% of infected patients suffer from severe HIV-1 associated neurocognitive disorders (HAND). However, the mechanisms underlying HAND are unclear and this lack of information has prevented the development of effective science-driven treatments. Our data have provided key information connecting etiology, especially by showing that pathogenic contents of plasma extracellular vesicles (EVs) from either chronic SHIV-infected and cART treated rhesus macaque (RM) or HIV(+)–cART treated patients play a key role in the development and progression of HAND. Moreover, our novel findings provide the first evidence that EVs released by HIV-replication defective cells (HIV-EVs) cause dysfunction and damage to the primary human brain microvascular endothelial cells (HBMECs) and disrupt blood-brain barrier (BBB) function via a mitochondrial-dependent mechanism. These results are consistent with our non-human primates and mice studies, which shown that brain microvessels (MVs: end arterioles, capillaries, and venules) composed primarily of endothelial cells, are more vulnerable due to SIV-infection and exposure to HIV-EVs, respectively. Additionally, our data suggest that neuroinflammatory protein fibrinogen (Fgn) and HIV- Tat are abundant in HIV-associated EVs, which impairs mitochondrial function and ATP production in BMECs by preventing normal mitochondrial fission/fusion events via direct inhibition of dynamin-related protein 1 (DRP1), thereby reducing energy production and increasing oxidative stress. These detrimental mitochondrial effects lead to endothelial cell damage, disruption of the BBB, impaired blood flow regulation, and cognitive impairment. Interestingly, we observed that EVs released by mesenchymal stem cells (MSC-EVs) rescued the HIV-EV/Fgn- mediated mitochondrial dysregulation and BBB leakage in HBMECs. Our focus on cerebral MVs is appropriate since this segment of the circulation is increasingly recognized as an initiation site for the progression of many neurological diseases, including HAND. Our overall hypothesis is that HIV verion free EVs accelerate cerebral microvascular endothelial and BBB dysfunction by inducing mitochondrial dysregulation. Moreover, we propose that MSC-EVs could protect endothelial mitochondria in live mice. We will explore EV-mediated BMEC/BBB dysregulation in cerebral MVs of humanized NOD/SCID/IL2Rγnull (NSG) mice. In Aim 1, we will determine the effects of HIV-free EVs on mitochondrial and BBB dysfunction in brain microvasculature of NSG mice. In Aim 2, we will establish the EV-containing fibrinogen and HIV-Tat dependent mechanism for mitochondrial and BBB dysregulation in cerebral MVs of NSG mice. In Aim 3, we will establish the therapeutic potential of MSC-EVs to reverse the EV-mediated mitochondrial and BBB dysfunction in cerebral MVs of NSG mice. Vascular contributions to cognitive impairment and dementia (VCID) are an integral part of HAND. The NIH has designated VCID as a critical research area and our application is highly relevant for this research area. 1
