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

Bethel-Brown C, Yao H, Hu G, Buch S - J Neuroinflammation (2012)

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA.

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.

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Mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt cell signaling pathways lie upstream of platelet-derived growth factor (PDGF)-BB induced nuclear factor κB (NFκB) in astrocytes. The nuclear fractions of A172 cells transfected with wild-type (WT) or dominant-negative (DN) forms of mitogen-activated protein (MAP) kinase kinase (MEK) and Akt were subjected to western blot analysis for NFκB. (A) Transfection with DN-MEK but not WT-MEK resulted in abrogation of PDGF-BB-mediated induction of NFκB phosphorylation. (B) Transduction with DN-Akt but not WT-Akt also resulted in abrogation of PDGF-BB-mediated induction of NFκB phosphorylation. All the data are presented as mean ± SD of three individual experiments. ***P <0.001 versus control group, ###P <0.001 versus PDGF-BB-treated group.
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Figure 7: Mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt cell signaling pathways lie upstream of platelet-derived growth factor (PDGF)-BB induced nuclear factor κB (NFκB) in astrocytes. The nuclear fractions of A172 cells transfected with wild-type (WT) or dominant-negative (DN) forms of mitogen-activated protein (MAP) kinase kinase (MEK) and Akt were subjected to western blot analysis for NFκB. (A) Transfection with DN-MEK but not WT-MEK resulted in abrogation of PDGF-BB-mediated induction of NFκB phosphorylation. (B) Transduction with DN-Akt but not WT-Akt also resulted in abrogation of PDGF-BB-mediated induction of NFκB phosphorylation. All the data are presented as mean ± SD of three individual experiments. ***P <0.001 versus control group, ###P <0.001 versus PDGF-BB-treated group.

Mentions: Having determined the involvement of ERK1/2, JNK and p38 MAPKs and NFκB in PDGF-BB-mediated MCP-1 the next logical step was to examine whether there existed a link that could tie together the activation of MAP kinase and Akt pathways with NFκB. Astrocytes were transfected with either the WT or DN constructs of MEK prior to PDGF-BB treatment as described before. Nuclear fractions were extracted and NFκB phosphorylation was assessed via western blotting. PDGF-BB-mediated induction of NFκB was attenuated by DN-MEK, but not by WT-MEK construct (Figure 7A). To confirm the role of PI3K/Akt in PDGF-BB-mediated NFκB, A172 cells were transduced with adenoviral constructs containing either WT or DN forms of Akt, treated with PDGF-BB and assessed for NFκB expression. As shown in Figure 7B, cells transduced with DN Akt construct failed to upregulate NFκB unlike the cells transduced with the WT Akt construct. These findings thus linked PDGF-BB-mediated activation of MAP kinase and Akt pathways to the downstream activation of NFκB.


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

Bethel-Brown C, Yao H, Hu G, Buch S - J Neuroinflammation (2012)

Mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt cell signaling pathways lie upstream of platelet-derived growth factor (PDGF)-BB induced nuclear factor κB (NFκB) in astrocytes. The nuclear fractions of A172 cells transfected with wild-type (WT) or dominant-negative (DN) forms of mitogen-activated protein (MAP) kinase kinase (MEK) and Akt were subjected to western blot analysis for NFκB. (A) Transfection with DN-MEK but not WT-MEK resulted in abrogation of PDGF-BB-mediated induction of NFκB phosphorylation. (B) Transduction with DN-Akt but not WT-Akt also resulted in abrogation of PDGF-BB-mediated induction of NFκB phosphorylation. All the data are presented as mean ± SD of three individual experiments. ***P <0.001 versus control group, ###P <0.001 versus PDGF-BB-treated group.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3526410&req=5

Figure 7: Mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt cell signaling pathways lie upstream of platelet-derived growth factor (PDGF)-BB induced nuclear factor κB (NFκB) in astrocytes. The nuclear fractions of A172 cells transfected with wild-type (WT) or dominant-negative (DN) forms of mitogen-activated protein (MAP) kinase kinase (MEK) and Akt were subjected to western blot analysis for NFκB. (A) Transfection with DN-MEK but not WT-MEK resulted in abrogation of PDGF-BB-mediated induction of NFκB phosphorylation. (B) Transduction with DN-Akt but not WT-Akt also resulted in abrogation of PDGF-BB-mediated induction of NFκB phosphorylation. All the data are presented as mean ± SD of three individual experiments. ***P <0.001 versus control group, ###P <0.001 versus PDGF-BB-treated group.
Mentions: Having determined the involvement of ERK1/2, JNK and p38 MAPKs and NFκB in PDGF-BB-mediated MCP-1 the next logical step was to examine whether there existed a link that could tie together the activation of MAP kinase and Akt pathways with NFκB. Astrocytes were transfected with either the WT or DN constructs of MEK prior to PDGF-BB treatment as described before. Nuclear fractions were extracted and NFκB phosphorylation was assessed via western blotting. PDGF-BB-mediated induction of NFκB was attenuated by DN-MEK, but not by WT-MEK construct (Figure 7A). To confirm the role of PI3K/Akt in PDGF-BB-mediated NFκB, A172 cells were transduced with adenoviral constructs containing either WT or DN forms of Akt, treated with PDGF-BB and assessed for NFκB expression. As shown in Figure 7B, cells transduced with DN Akt construct failed to upregulate NFκB unlike the cells transduced with the WT Akt construct. These findings thus linked PDGF-BB-mediated activation of MAP kinase and Akt pathways to the downstream activation of NFκB.

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA.

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.

Show MeSH
Related in: MedlinePlus