Abstract
Alveolar macrophages represent critical effector cells of innate immunity to infectious challenge in the lungs and recognize bacterial pathogens through pattern recognition receptors such as Toll-like receptors (TLRs). Phosphatidylinositol 3-kinase (PI3K) regulates TLR-mediated cytokine release, but whether HIV infection influences PI3K signaling pathway and alters TLR4-mediated macrophage response has not been investigated. In the current study, surface TLR4 expression were similar but TLR4 activation (lipid A, 10 microg/ml) resulted in lower TNF-alpha release by HIV+ human macrophages compared with healthy cells. Pharmacological inhibition of PI3K (LY294002) normalized TNF-alpha release in HIV+ macrophages and augments ERK1/2 mitogen-activated protein kinase phosphorylation in response to lipid A. Importantly, HIV+ macrophages demonstrated increased constitutive phosphatidylinositol 3,4,5-trisphosphate formation, increased phosphorylation of downstream signaling molecules Akt and glycogen synthase kinase-3beta (GSK-3beta) at Ser9, and reduced PTEN protein expression. As a functional assessment of GSK-3beta phosphorylation, TLR4-mediated interleukin-10 release was significantly higher in HIV+ human macrophages compared with healthy cells. Incubation of human macrophages with exogenous HIV Nef protein induced phosphorylation of Akt and GSK-3beta (whereas phosphorylation was reduced by PI3K inhibition) and promoted interleukin-10 release. Taken together, these data demonstrate increased constitutive activation of the PI3K signaling pathway in HIV+ macrophages and support the concept that PI3K activation (by HIV proteins such as Nef) may contribute to reduced TLR4-mediated TNF-alpha release in HIV+ human macrophages and impair host cell response to infectious challenge.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Chromones / pharmacology
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Enzyme Activation / drug effects
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Enzyme Activation / immunology
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Enzyme Inhibitors / pharmacology
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Gene Expression Regulation, Enzymologic
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Glycogen Synthase Kinase 3 / immunology
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Glycogen Synthase Kinase 3 / metabolism
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Glycogen Synthase Kinase 3 beta
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HIV Infections / immunology
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HIV Infections / metabolism*
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HIV-1* / immunology
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Humans
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Interleukin-10 / immunology
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Interleukin-10 / metabolism
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Lipid A / pharmacology
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MAP Kinase Signaling System* / drug effects
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MAP Kinase Signaling System* / immunology
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Macrophages, Alveolar / immunology
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Macrophages, Alveolar / metabolism*
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Macrophages, Alveolar / virology
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Mitogen-Activated Protein Kinase 1 / immunology
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Mitogen-Activated Protein Kinase 1 / metabolism
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Mitogen-Activated Protein Kinase 3 / immunology
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Mitogen-Activated Protein Kinase 3 / metabolism
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Morpholines / pharmacology
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Oncogene Protein v-akt / immunology
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Oncogene Protein v-akt / metabolism
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PTEN Phosphohydrolase / immunology
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PTEN Phosphohydrolase / metabolism
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Phosphatidylinositol 3-Kinases / immunology
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Phosphatidylinositol 3-Kinases / metabolism*
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Phosphatidylinositol Phosphates / immunology
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Phosphatidylinositol Phosphates / metabolism
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Phosphoinositide-3 Kinase Inhibitors
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Phosphorylation / drug effects
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Phosphorylation / immunology
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Toll-Like Receptor 4 / immunology
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Toll-Like Receptor 4 / metabolism*
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Tumor Necrosis Factor-alpha / immunology
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Tumor Necrosis Factor-alpha / metabolism*
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U937 Cells
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nef Gene Products, Human Immunodeficiency Virus / immunology
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nef Gene Products, Human Immunodeficiency Virus / metabolism
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nef Gene Products, Human Immunodeficiency Virus / pharmacology
Substances
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Chromones
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Enzyme Inhibitors
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IL10 protein, human
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Lipid A
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Morpholines
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Phosphatidylinositol Phosphates
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Phosphoinositide-3 Kinase Inhibitors
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TLR4 protein, human
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Toll-Like Receptor 4
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Tumor Necrosis Factor-alpha
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nef Gene Products, Human Immunodeficiency Virus
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Interleukin-10
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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GSK3B protein, human
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Glycogen Synthase Kinase 3 beta
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Oncogene Protein v-akt
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Glycogen Synthase Kinase 3
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PTEN Phosphohydrolase
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PTEN protein, human