Nearly one−half of people infected with Human immunodeficiency virus type 1 (HIV−1) experience HIV-associated neurocognitive disorder (HAND) despite antiretroviral therapy. Mechanisms underlying HAND development remain unclear, but neuroinflammation is a major contributing factor. HIV-1 viral Tat protein and morphine have both been independently implicated in exacerbation of brain inflammation. Tat produced by astrocytes can inhibit Dicer endoribonuclease cleavage necessary for microRNA (miRNA) maturation. We found that Tat binds and inhibits miRNAs to downregulate Wnt/β−catenin signaling, a pathway shown to be protective against HIV brain inflammation. The direct mechanism behind Tat-miRNA and β-catenin downregulation is unknown. With combined Tat and morphine treatment, we hypothesize worsening HAND outcomes mediated by miRNA changes.
Primary human and U87MG astrocytes were cultured, transfected with Tat mutant plasmids informed by the Drexel Medicine CNS AIDS Research and Eradication Study (CARES) cohort neurocognitive status, and treated with morphine. Luciferase reporter assay and western blot were used to quantify expression levels of β-catenin. The population of miRNA changes were profiled by RT-qPCR from Tat and morphine treated cells and their extracellular vesicles (EVs). Moreover, conditioned EVs were exposed to non−infected bystander cells to observe biological impact.
β-catenin signaling showed significant suppression in Tat and morphine combined treatments compared to Tat alone. Tat mutants differentially suppressed β-catenin signaling. Certain Tat mutants associated with neurocognitive impairment had a greater ability to suppress β-catenin compared to wildtype, while Tat mutants associated with non-impairment could not suppress β-catenin as effectively as wildtype. Astrocytes showed synergistic miRNA changes with combined Tat and morphine treatment compared to single treatments. Tat mutant K51A abrogated miRNA aberrations both intra- and extracellularly. Moreover, isolated Tat-EVs biologically activated HIV LTR in noninfected bystander TZMbl cells.
We found that morphine potentiated the suppressive function of Tat on β-catenin signaling, suggesting worsening HAND in morphine use. Unique miRNA disturbances in both cell and EVs suggests that combination of infection and morphine initiates a new pathology in the CNS. This data could influence management and treatment development in morphine use patients. MiRNA changes give insight to miRNA-directed β-catenin pathway downregulation and other neuroinflammatory pathways. These findings suggest that these cellular aberrations can influence non-infected bystander cells through Tat-EVs as a mechanism for HAND progression.
|Advisor:||Klase, Zachary A.|
|Commitee:||Adams, Jessica, Appelt, Denah, Montie, Heather, Nonnemacher, Michael|
|School:||University of the Sciences in Philadelphia|
|Department:||Cell & Molecular Biology|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 80/11(E), Dissertation Abstracts International|
|Subjects:||Molecular biology, Neurosciences|
|Keywords:||Astrocytes, Hiv, Mirna, Morphine, Neuroinflammation, Tat|
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