Accumulating evidence suggests that opioid drug abuse per se directly exacerbates the neuropathology of HIV-1. Neuronal death is preceded by a prolonged period of synaptic culling and functional losses, and dendritic pathology that are presumably reversible. Opiate abuse potentiates the neuropathogenesis of HIV by synergistically increasing dendritic pathology (varicosity formation &pruning), while promoting spine losses (plasticity) in the striatum and hippocampal CA1 pyramidal neurons. Moreover, behavioral defects in both Morris water maze and rotarod performance coincide with synaptic losses and dendritic pathology in the absence of neuronal death, suggesting that neuronal injury and reduced synaptic connectivity underlie comorbid increases in HIV-associated neurological disorders (HAND). This represent a fundamental shift in our understanding of opioid drug action and propel the grant in novel directions. While death per se is significant, the interruption of events preceding neuron death may be more strategic therapeutically. We hypothesize that opioid-HIV interactive increases in neuron death are preceded by cumulative insults to synaptic organization and function that are non-lethal and assumed reversible.
Aim 1 will characterize the events underlying opioid and HIV-1-dependent neuronal dysfunction and/or injury in hippocampal neurons.
Aim 2 shall define the excitotoxic mechanisms by which opioids exacerbate HIV-1 Tat and gp120-induced neuronal dysfunction, injury, and/or death. Opioid and HIV-1-dependent alterations in synaptic function (altered membrane properties, EPSPs) spine morphology, and dendritic pathology (altered Na+, Ca2+, and ATP homeostasis) will be assessed. Lastly, aim 3 will identify the MOPr-expressing cellular sites of opioid action that exacerbate HIV-1-induced hippocampal neuronal injury, dysfunction and behavioral deficits in vivo. Cellular sites where opioids exacerbate Tat and gp120 actions in the hippocampus will be identified using floxed MOPr mice bred to astroglial specific GFAP, myeloid (microglial) specific lysozyme 2, and GABAergic forebrain neuron expressing Cre recombinase mice. Conditionally deleting MOPr at key sites will define the targets and associated mechanisms by which opioids exacerbate neuronal injury (including synaptic and dendritic pathology) and death, and neurocognitive defects (spatial learning-Morris water maze) in the hippocampus. Our long-term goal is to define the mechanisms by which opiate drug abuse exacerbates neurodegenerative and neurocognitive defects, and to identify the underlying signaling events that could be targeted therapeutically.

Public Health Relevance

Emerging evidence suggests opioid drug abuse exacerbates the neurodegenerative effects of HIV-1 through cumulative insults that limit neuronal function long before the neuron is fatally injured. The grant proposes to examine the mechanisms underlying the functional decline of opioid-HIV-exposed hippocampal neurons involved in learning and memory. Events underlying early functional damage are likely to be reversible and may be excellent therapeutic targets.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
5R01DA018633-08
Application #
8298188
Study Section
NeuroAIDS and other End-Organ Diseases Study Section (NAED)
Program Officer
Sorensen, Roger
Project Start
2004-10-01
Project End
2015-07-31
Budget Start
2012-08-01
Budget End
2013-07-31
Support Year
8
Fiscal Year
2012
Total Cost
$359,038
Indirect Cost
$116,538
Name
Virginia Commonwealth University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
105300446
City
Richmond
State
VA
Country
United States
Zip Code
23298
Fitting, Sylvia; Stevens, David L; Khan, Fayez A et al. (2016) Morphine Tolerance and Physical Dependence Are Altered in Conditional HIV-1 Tat Transgenic Mice. J Pharmacol Exp Ther 356:96-105
Guedia, Joy; Brun, Paola; Bhave, Sukhada et al. (2016) HIV-1 Tat exacerbates lipopolysaccharide-induced cytokine release via TLR4 signaling in the enteric nervous system. Sci Rep 6:31203
Marks, William D; Paris, Jason J; Schier, Christina J et al. (2016) HIV-1 Tat causes cognitive deficits and selective loss of parvalbumin, somatostatin, and neuronal nitric oxide synthase expressing hippocampal CA1 interneuron subpopulations. J Neurovirol 22:747-762
Hahn, Yun K; Paris, Jason J; Lichtman, Aron H et al. (2016) Central HIV-1 Tat exposure elevates anxiety and fear conditioned responses of male mice concurrent with altered mu-opioid receptor-mediated G-protein activation and β-arrestin 2 activity in the forebrain. Neurobiol Dis 92:124-36
Hahn, Yun Kyung; Podhaizer, Elizabeth M; Farris, Sean P et al. (2015) Effects of chronic HIV-1 Tat exposure in the CNS: heightened vulnerability of males versus females to changes in cell numbers, synaptic integrity, and behavior. Brain Struct Funct 220:605-23
Fitting, S; Ngwainmbi, J; Kang, M et al. (2015) Sensitization of enteric neurons to morphine by HIV-1 Tat protein. Neurogastroenterol Motil 27:468-80
Fitting, Sylvia; Knapp, Pamela E; Zou, Shiping et al. (2014) Interactive HIV-1 Tat and morphine-induced synaptodendritic injury is triggered through focal disruptions in Na⁺ influx, mitochondrial instability, and Ca²⁺ overload. J Neurosci 34:12850-64
Sorrell, Mary E; Hauser, Kurt F (2014) Ligand-gated purinergic receptors regulate HIV-1 Tat and morphine related neurotoxicity in primary mouse striatal neuron-glia co-cultures. J Neuroimmune Pharmacol 9:233-44
Fitting, Sylvia; Zou, Shiping; El-Hage, Nazira et al. (2014) Opiate addiction therapies and HIV-1 Tat: interactive effects on glial [Ca²⁺]i, oxyradical and neuroinflammatory chemokine production and correlative neurotoxicity. Curr HIV Res 12:424-34
Ngwainmbi, Joy; De, Dipanjana D; Smith, Tricia H et al. (2014) Effects of HIV-1 Tat on enteric neuropathogenesis. J Neurosci 34:14243-51

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