Mammalian target of rapamycin inhibition in macrophages of asymptomatic HIV+ persons reverses the decrease in TLR-4-mediated TNF-α release through prolongation of MAPK pathway activation.
TLR-4-mediated signaling is significantly impaired in macrophages from HIV(+) persons, predominantly owing to altered MyD88-dependent pathway signaling caused in part by constitutive activation of PI3K. In this study we assessed in these macrophages if the blunted increase in TLR-4-mediated TNF-α release induced by lipid A (LA) is associated with PI3K-induced upregulation of mammalian target of rapamycin (mTOR) activity. mTOR inhibition with rapamycin enhanced TLR-4-mediated TNF-α release, but suppressed anti-inflammatory IL-10 release. Targeted gene silencing of mTOR in macrophages resulted in LA-induced TNF-α and IL-10 release patterns similar to those induced by rapamycin. Rapamycin restored MyD88/IL-1R-associated kinase interaction in a dose-dependent manner. Targeted gene silencing of MyD88 (short hairpin RNA) and mTOR (RNA interference) inhibition resulted in TLR-4-mediated 70-kDa ribosomal protein S6 kinase activation and enhanced TNF-α release, whereas IL-10 release was inhibited in both silenced and nonsilenced HIV(+) macrophages. Furthermore, mTOR inhibition augmented LA-induced TNF-α release through enhanced and prolonged phosphorylation of ERK1/2 and JNK1/2 MAPK, which was associated with time-dependent MKP-1 destabilization. Taken together, impaired TLR-4-mediated TNF-α release in HIV(+) macrophages is attributable in part to mTOR activation by constitutive PI3K expression in a MyD88-dependent signaling pathway. These changes result in MAPK phosphatase 1 stabilization, which shortens and blunts MAPK activation. mTOR inhibition may serve as a potential therapeutic target to upregulate macrophage innate immune host defense responsiveness in HIV(+) persons.
Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA.
Xin
X
Li
Xinbing
X
Han
Juliana
J
Llano
Medhavi
M
Bole
Xiuqin
X
Zhou
Katharine
K
Swan
Asha
A
Anandaiah
Benjamin
B
Nelson
Naimish R
NR
Patel
Peter S
PS
Reinach
Henry
H
Koziel
Souvenir D
SD
Tachado
D015153:Blotting, Western; D004789:Enzyme Activation / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D055785:Gene Knockdown Techniques; D015658:HIV Infections / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D020935:MAP Kinase Signaling System / Q000276:immunology*; D008264:Macrophages / Q000276:immunology / Q000378:metabolism* / Q000821:virology; D058570:TOR Serine-Threonine Kinases / Q000276:immunology / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism*
C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases