Platelet-derived growth factor (PDGF)-BB-mediated induction of monocyte chemoattractant protein 1 in human astrocytes: implications for HIV-associated neuroinflammation

J Neuroinflammation. 2012 Dec 1:9:262. doi: 10.1186/1742-2094-9-262.

Abstract

Chemokine (C-C motif) ligand 2, also known as monocyte chemoattractant protein 1 (MCP-1) is an important factor for the pathogenesis of HIV-associated neurocognitive disorders (HAND). The mechanisms of MCP-1-mediated neuropathogenesis, in part, revolve around its neuroinflammatory role and the recruitment of monocytes into the central nervous system (CNS) via the disrupted blood-brain barrier (BBB). We have previously demonstrated that HIV-1/HIV-1 Tat upregulate platelet-derived growth factor (PDGF)-BB, a known cerebrovascular permeant; subsequently, the present study was aimed at exploring the regulation of MCP-1 by PDGF-BB in astrocytes with implications in HAND. Specifically, the data herein demonstrate that exposure of human astrocytes to HIV-1 LAI elevated PDGF-B and MCP-1 levels. Furthermore, treating astrocytes with the human recombinant PDGF-BB protein significantly increased the production and release of MCP-1 at both the RNA and protein levels. MCP-1 induction was regulated by activation of extracellular-signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein (MAP) kinases and phosphatidylinositol 3-kinase (PI3K)/Akt pathways and the downstream transcription factor, nuclear factor κB (NFκB). Chromatin immunoprecipitation (ChIP) assays demonstrated increased binding of NFκB to the human MCP-1 promoter following PDGF-BB exposure. Conditioned media from PDGF-BB-treated astrocytes increased monocyte transmigration through human brain microvascular endothelial cells (HBMECs), an effect that was blocked by STI-571, a tyrosine kinase inhibitor (PDGF receptor (PDGF-R) blocker). PDGF-BB-mediated release of MCP-1 was critical for increased permeability in an in vitro BBB model as evidenced by blocking antibody assays. Since MCP-1 is linked to disease severity, understanding its modulation by PDGF-BB could aid in understanding the proinflammatory responses in HAND. These results suggest that astrocyte activation by PDGF-BB exaggerates monocyte recruitment into the brain via MCP-1 and underscores the critical role astrocytes play in HAND.

MeSH terms

  • Analysis of Variance
  • Antibodies / pharmacology
  • Astrocytes / drug effects*
  • Astrocytes / virology
  • Becaplermin
  • Blood Vessels / cytology
  • Cell Movement
  • Cells, Cultured
  • Chemokine CCL2 / genetics
  • Chemokine CCL2 / metabolism*
  • Chromatin Immunoprecipitation
  • Endothelial Cells / drug effects
  • Endothelial Cells / pathology
  • Enzyme Inhibitors / pharmacology
  • Enzyme-Linked Immunosorbent Assay
  • Flow Cytometry
  • Gene Expression Regulation, Viral / drug effects
  • Gene Expression Regulation, Viral / physiology*
  • HIV Infections
  • HIV-1 / metabolism
  • Humans
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Monocytes / drug effects
  • Monocytes / metabolism
  • Monocytes / virology
  • Mutation / genetics
  • Proto-Oncogene Proteins c-sis / genetics
  • Proto-Oncogene Proteins c-sis / immunology
  • Proto-Oncogene Proteins c-sis / metabolism
  • Proto-Oncogene Proteins c-sis / pharmacology*
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / genetics
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Time Factors
  • Transcription Factor RelA / genetics
  • Transcription Factor RelA / metabolism
  • Transduction, Genetic
  • Transfection

Substances

  • Antibodies
  • Chemokine CCL2
  • Enzyme Inhibitors
  • Proto-Oncogene Proteins c-sis
  • RNA, Messenger
  • RNA, Small Interfering
  • Transcription Factor RelA
  • Becaplermin
  • Mitogen-Activated Protein Kinase Kinases