METHAMPHETAMINE (METH) REGULATES ASTROCYTE EXCITATORY AMINO ACID TRANSPORTER-2 (EAAT-2) VIA ACTIVATION OF TRACE AMINE ASSOCIATED RECEPTOR (TAAR1) AND DOWNSTREAM CAMP SIGNALING

Methamphetamine (METH) abuse has prevailed as a drug epidemic within the United States and worldwide with an estimated 27.4 million users.Short-term side effect of METH abuse include a heightened libido and impaired judgment increasing the users chances of contracting Human immunodeficiency virus-1 (HIV-1). HIV-1 associated dementia (HAD), is the most severe manifestation of HIV-1-associated neurocognitive disorders and is an important neurological complication of HIV-1 infection characterized by cognitive, behavioral and motor dysfunction. Long-term METH users share characterized neurocognitive defects and disorders as HIV-1 infected individuals.Molecular outcomes of METH/HIV-1-induced neurotoxicity include Excitotoxicity, oxidative stress, glial cell activation, inflammation, and hyperthermia. Astrogliosis is a key pathological feature of METH exposure and HAD, however, the molecular mechanisms remain unclear. The current studies investigate METH-induced TAAR1 activation and will uncover molecular mechanisms associated with glutamate transporter (EAAT-2) dysregulation. Purpose (a): Glutamate is an excitatory neurotransmitter that is highly regulated in the central nervous system (CNS). High concentrations of extracellular glutamate result in excitotoxicity and can exacerbate neurodegenerative disorders, including human immunodeficiency virus-1 (HIV-1)-associated neurocognitive disorders (HAND). Additionally, drugs of abuse such as methamphetamine (METH) can increase the severity of excitotoxicity and can accelerate HAND. Excitatory amino acid transporter-2 (EAAT-2) is responsible for approximately 90% of extracellular glutamate uptake from the synapse and is primarily localized in astrocytes. Dysregulation of EAAT-2 leads to astrocytes decreased ability to clear glutamate. Methods (b): It is established that METH leads to excitotoxicity in neurons, however, in astrocytes the molecular mechanisms resulting in METH-mediated EAAT-2 dysregulation are unclear. Previously we showed that HIV-1ADA, METH and transient hyperthermia regulates localization and expression of astrocyte trace amine associated receptor 1 (TAAR1). Results (c): Our data shows METH-induced activation of astrocyte TAAR1 increases intracellular cAMP levels in astrocytes that is significantly decreased in siTAAR1-transfected astrocytes. Further, METH treatment downregulates EAAT-2 mRNA levels. We propose downstream cAMP signaling pathways of METH-induced astrocyte TAAR1 activation result in EAAT-2 dysregulation. Conclusions (d): The results of this study will uncover novel molecular mechanism of METH-induced astrocyte TAAR1 activation and the downstream effects of cAMP signaling on astrocyte EAAT-2 levels in the context of HAND.