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PlGF enhances TLR-dependent inflammatory responses in human mononuclear phagocytes.

ABSTRACT: PROBLEM:Levels of placental growth factor (PlGF) peak during third trimester of pregnancy, a time when women are at increased risk of virus-induced morbidity. We hypothesized PlGF might contribute to an exaggerated inflammatory response to Toll-like receptor (TLR) activation. METHOD OF STUDY:Primary human adult and cord blood CD14+ cells were cultured in the presence of TLR ligands and/or PlGF. RESULTS:PlGF significantly enhanced the magnitude and duration of TNF messenger RNA and protein production by TLR-7/8-activated monocytes, and increased subsequent production of TNF-independent inflammatory cytokines. This PlGF/TLR effect involved multiple inflammatory cytokines/chemokines and was seen with the majority of TLR agonists. PlGF enhanced phosphorylation of IkappaB kinase (IKK) in monocytes stimulated with the TLR-7/8 agonist R848, and IKK inhibition completely suppressed the PlGF effect. CONCLUSION:PlGF enhances TLR-signaling upstream of IKK and contributes to an exaggerated pathologic pro-inflammatory state in response to activation of maternal and fetal mononuclear phagocytes by specific TLR agonists.

SUBMITTER: Newell LF

PROVIDER: S-EPMC5915625 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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PlGF enhances TLR-dependent inflammatory responses in human mononuclear phagocytes.

Newell Laura F LF Holtan Shernan G SG Yates Jane E JE Pereira Leonardo L Tyner Jeffrey W JW Burd Irina I Bagby Grover C GC

American journal of reproductive immunology (New York, N.Y. : 1989) 20170620 4

<h4>Problem</h4>Levels of placental growth factor (PlGF) peak during third trimester of pregnancy, a time when women are at increased risk of virus-induced morbidity. We hypothesized PlGF might contribute to an exaggerated inflammatory response to Toll-like receptor (TLR) activation.<h4>Method of study</h4>Primary human adult and cord blood CD14<sup>+</sup> cells were cultured in the presence of TLR ligands and/or PlGF.<h4>Results</h4>PlGF significantly enhanced the magnitude and duration of TNF ...[more]

PMID: 28635072

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Project description:BackgroundHypoxia is a hallmark of the tumor microenvironment (TME) and in addition to altering metabolism in cancer cells, it transforms tumor-associated stromal cells. Within the tumor stromal cell compartment, tumor-associated macrophages (TAMs) provide potent pro-tumoral support. However, TAMs can also be harnessed to destroy tumor cells by monoclonal antibody (mAb) immunotherapy, through antibody dependent cellular phagocytosis (ADCP). This is mediated via antibody-binding activating Fc gamma receptors (FcγR) and impaired by the single inhibitory FcγR, FcγRIIb.MethodsWe applied a multi-OMIC approach coupled with in vitro functional assays and murine tumor models to assess the effects of hypoxia inducible factor (HIF) activation on mAb mediated depletion of human and murine cancer cells. For mechanistic assessments, siRNA-mediated gene silencing, Western blotting and chromatin immune precipitation were utilized to assess the impact of identified regulators on FCGR2B gene transcription.ResultsWe report that TAMs are FcγRIIbbright relative to healthy tissue counterparts and under hypoxic conditions, mononuclear phagocytes markedly upregulate FcγRIIb. This enhanced FcγRIIb expression is transcriptionally driven through HIFs and Activator protein 1 (AP-1). Importantly, this phenotype reduces the ability of macrophages to eliminate anti-CD20 monoclonal antibody (mAb) opsonized human chronic lymphocytic leukemia cells in vitro and EL4 lymphoma cells in vivo in human FcγRIIb+/+ transgenic mice. Furthermore, post-HIF activation, mAb mediated blockade of FcγRIIb can partially restore phagocytic function in human monocytes.ConclusionOur findings provide a detailed molecular and cellular basis for hypoxia driven resistance to antitumor mAb immunotherapy, unveiling a hitherto unexplored aspect of the TME. These findings provide a mechanistic rationale for the modulation of FcγRIIb expression or its blockade as a promising strategy to enhance approved and novel mAb immunotherapies.

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PlGF enhances TLR-dependent inflammatory responses in human mononuclear phagocytes.

Publications

PlGF enhances TLR-dependent inflammatory responses in human mononuclear phagocytes.

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