title: Constitutive activation of phosphatidylinositol 3-kinase signaling pathway down-regulates TLR4-mediated tumor necrosis factor-alpha release in alveolar macrophages from asymptomatic HIV-positive persons in vitro.
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.
authors.affiliation: Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. stachado@bidmc.harvard.edu
authors.forename: Souvenir D
authors.initials: SD
authors.lastname: Tachado
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Katharine
authors.initials: K
authors.lastname: Swan
authors.forename: Naimish
authors.initials: N
authors.lastname: Patel
authors.forename: Henry
authors.initials: H
authors.lastname: Koziel
mesh_terms: D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D038362:Glycogen Synthase Kinase 3 / Q000276:immunology / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D015658:HIV Infections / Q000276:immunology / Q000378:metabolism*; D015497:HIV-1 / Q000276:immunology; D006801:Humans; D016753:Interleukin-10 / Q000276:immunology / Q000378:metabolism; D008050:Lipid A / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology; D016676:Macrophages, Alveolar / Q000276:immunology / Q000378:metabolism* / Q000821:virology; D019950:Mitogen-Activated Protein Kinase 1 / Q000276:immunology / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000276:immunology / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D051058:Oncogene Protein v-akt / Q000276:immunology / Q000378:metabolism; D051059:PTEN Phosphohydrolase / Q000276:immunology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000276:immunology / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000276:immunology / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism*; D020298:U937 Cells; D054311:nef Gene Products, Human Immunodeficiency Virus / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology
chemical_list: D002867:Chromones; D004791:Enzyme Inhibitors; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D016753:Interleukin-10; D008050:Lipid A; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D009025:Morpholines; D051058:Oncogene Protein v-akt; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D054311:nef Gene Products, Human Immunodeficiency Virus; C508609:IL10 protein, human; C495345:TLR4 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C000605506:GSK3B protein, human; C494929:PTEN protein, human