Interactive comorbidity between opioid drug abuse and HIV-1 Tat: chronic exposure augments spine loss and sublethal dendritic pathology in striatal neurons.
HIV-1 infection predisposes the central nervous system to damage by opportunistic infections and environmental insults. Such maladaptive plasticity may underlie the exaggerated comorbidity seen with HIV-1 infection and opioid abuse. Although morphine and HIV-1 Tat synergize at high concentrations to increase neuronal death in vitro, we questioned whether chronic low Tat exposure in vivo might contribute to the spectrum of neuropathology through sublethal neuronal injury. We used a doxycycline-driven, inducible, HIV-1 Tat transgenic mouse, in which striatal neuron death was previously shown to be absent, to examine effects of differential Tat expression, alone and combined with morphine. Low constitutive Tat expression caused neurodegeneration; higher levels induced by 7 days of doxycycline significantly reduced dendritic spine numbers. Moreover, Tat expression widely disrupted the endogenous opioid system, altering mu and kappa, but not delta, opioid receptor and proopiomelanocortin, proenkephalin, and prodynorphin transcript levels in cortex, hippocampus, and striatum. In addition to markedly reducing spine density by itself, morphine amplified the effect of higher levels of Tat on spines, and also potentiated Tat-mediated dendritic pathology, thus contributing to maladaptive neuroplasticity at multiple levels. The dendritic pathology and reductions in spine density suggest that sustained Tat +/- morphine exposure underlie key aspects of chronic neurodegenerative changes in neuroAIDS, which may contribute to the exacerbated neurological impairment in HIV patients who abuse opioids.
Fitting
Sylvia
S
Department Pharmacology and Toxicology, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA 23298, USA.
Xu
Ruqiang
R
Bull
Cecilia
C
Buch
Shreya K
SK
El-Hage
Nazira
N
Nath
Avindra
A
Knapp
Pamela E
PE
Hauser
Kurt F
KF
D000818:Animals; D015153:Blotting, Western; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D049229:Dendritic Spines / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D004745:Enkephalins / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D007150:Immunohistochemistry; D051379:Mice; D008822:Mice, Transgenic; D009020:Morphine / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D011333:Pro-Opiomelanocortin / Q000235:genetics / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D017473:Receptors, Opioid, kappa / Q000235:genetics / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
D004745:Enkephalins; D009294:Narcotics; D011498:Protein Precursors; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; C029992:proenkephalin; D054322:tat Gene Products, Human Immunodeficiency Virus; D011333:Pro-Opiomelanocortin; D009020:Morphine; C033660:preproenkephalin