Elucidating molecular mechanisms of TAAR1-dependent astrocyte regulation during HIV-associated neurocognitive disorders and methamphetamine exposure

Elucidating molecular mechanisms of TAAR1-dependent astrocyte regulation during HIV-associated neurocognitive disorders and methamphetamine exposure Shannon Mythen and Anuja Ghorpade Department of Microbiology, Immunology and Genetics, UNT Health Science Center, Fort Worth, TX Purpose: A study conducted in 2012 estimated that 1.2 million people in the U.S. reported the use of methamphetamine (METH) in the previous year, with 133,000 new users age 12 or older. METH is a highly addictive substance that leads to an imbalance in dopamine and norepinephrine release causing euphoric effects. Long term METH use has been linked to many central nervous system (CNS) abnormalities including deficits in memory, executive function, anxiety and depression. METH use is associated with risky sexual behavior, lowered inhibitions and increased likelihood for acquiring HIV. METH abuse exacerbates the onset of HIV-associated neurocognitive disorders (HAND) and promotes a neurotoxic environment by increasing oxidative stress and excitotoxicity. Our lab previously identified trace amine associated receptor 1 (TAAR1) as a novel stimulatory G protein coupled receptor in primary human astrocytes. The expression of TAAR1 is modulated by METH and HAND-relevant stimuli. We hypothesize that TAAR1 dysregulates astrocyte intracellular signaling during HAND and METH exposure thus contributing to disease pathogenesis. Methods: To mimic upregulation of TAAR1 during HIV CNS disease, TAAR1 overexpression was studied in human astrocytes. We then used a physiologically relevant model of extended METH exposure and low level HIV-associated activation. First, exogenous TAAR1 expression and intracellular localization were characterized. Next, TAAR1 localization with HAND relevant stimuli and METH exposure were assessed. Finally, TAAR1-dependent signaling and activation of downstream modulators were evaluated. We used a TAAR1 selective antagonist, EPPTB, to determine TAAR1-dependent changes in astrocyte function. Results: The overexpression model was standardized for TAAR1 levels in astrocytes. TAAR1 function mirrored expression levels in transfected astrocytes. Exposure to METH and HAND-relevant stimuli altered astrocyte functional responses, including proliferation and reactive morphological phenotype. Conclusions: Our study aims to delineate therapeutically targetable mechanisms that regulate astrocytes during neuroinflammation in HAND and METH exposure. Therefore, we propose astrocyte TAAR1 as a potential target to combat neurocognitive decline.