HIV-1 Tat and opiate-induced changes in astrocytes promote chemotaxis of microglia through the expression of MCP-1 and alternative chemokines.
Opiates exacerbate human immunodeficiency virus type 1 (HIV-1) Tat(1-72)-induced release of key proinflammatory cytokines by astrocytes, which may accelerate HIV neuropathogenesis in opiate abusers. The release of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), in particular, is potentiated by opiate-HIV Tat interactions in vitro. Although MCP-1 draws monocytes/macrophages to sites of CNS infection, and activated monocytes/microglia release factors that can damage bystander neurons, the role of MCP-1 in neuro-acquired immunodeficiency syndrome (neuroAIDS) progression in opiate abusers, or nonabusers, is uncertain. Using a chemotaxis assay, N9 microglial cell migration was found to be significantly greater in conditioned medium from mouse striatal astrocytes exposed to morphine and/or Tat(1-72) than in vehicle-, mu-opioid receptor (MOR) antagonist-, or inactive, mutant Tat(delta31-61)-treated controls. Conditioned medium from astrocytes treated with morphine and Tat caused the greatest increase in motility. The response was attenuated using conditioned medium immunoneutralized with MCP-1 antibodies, or medium from MCP-1(-/-) astrocytes. In the presence of morphine (time-release, subcutaneous implant), intrastriatal Tat increased the proportion of neural cells that were astroglia and F4/80+ macrophages at 7 days post-injection. This was not seen after treatment with Tat alone, or with morphine plus inactive Tat(delta31-61) or naltrexone. Glia displayed increased MOR and MCP-1 immunoreactivity after morphine and/or Tat exposure. The findings indicate that MCP-1 underlies most of the response of microglia, suggesting that one way in which opiates exacerbate neuroAIDS is by increasing astroglial-derived proinflammatory chemokines at focal sites of CNS infection and promoting macrophage entry and local microglial activation. Importantly, increased glial expression of MOR can trigger an opiate-driven amplification/positive feedback of MCP-1 production and inflammation.
El-Hage
Nazira
N
Department of Anatomy and Neurobiology, University of Kentucky Chandler Medical Center, Lexington, Kentucky 40536-0298, USA.
Wu
Guanghan
G
Wang
Juan
J
Ambati
Jayakrishna
J
Knapp
Pamela E
PE
Reed
Janelle L
JL
Bruce-Keller
Annadora J
AJ
Hauser
Kurt F
KF
D000818:Animals; D001253:Astrocytes / Q000187:drug effects*; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism*; D018925:Chemokines / Q000378:metabolism*; D002633:Chemotaxis / Q000187:drug effects; D017077:Culture Media, Conditioned; D004343:Drug Implants; D015696:Gene Products, tat / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D017628:Microglia / Q000187:drug effects*; D009020:Morphine / Q000494:pharmacology; D009294:Narcotics / Q000008:administration & dosage / Q000494:pharmacology*; D017072:Neostriatum / Q000502:physiology
C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D018925:Chemokines; D017077:Culture Media, Conditioned; D004343:Drug Implants; D015696:Gene Products, tat; D009294:Narcotics; D009020:Morphine