Search

Cross-talks between toll-like receptors (TLRs) including various negative regulatory mechanisms are many unknown. We investigated the differential mechanism of IL-23 production in M1 macrophages by single immunoglobulin interleukin-1 receptor-related (SIGIRR) molecule through TLR4 or TLR7/8. IL-12p40 production by M1 macrophages pretreated with human neutrophil elastase (HNE) was synergistically enhanced IL-12p40, but not IL-23 production, after exposure to lipopolysaccharide (LPS). LPS (a TLR4 agonist) induced a slight increase of IL-23 production, while Resiquimod (a TLR7/8 agonist) significantly enhanced IL-23 production. Expression of SIGIRR protein, a negative regulator of TLR4, was higher in M1 macrophages than in monocytes. Interestingly, SIGIRR siRNA induced a slight increment of IL-23 production after exposure of macrophages to LPS, while IL-23 production in response to Resiquimod was significantly upregulated by SIGIRR siRNA. Silencing SIGIRR enhanced IRF4 protein level determined by western blotting or ELISA. IRF4 siRNA dramatically restored IL-23 production after exposure to Resiquimod in macrophages transfected with SIGIRR siRNA. In conclusion, production of IL-23 is differentially regulated in M1 macrophages by SIGIRR through TLR4- or TLR7/8-mediated signaling. SIGIRR is both a negative regulator of TLR4 and a positive regulator of TLR7/8. [ABSTRACT FROM AUTHOR]

Granulocyte-macrophage colony stimulating factor (GM-CSF) induces procoagulant activity of macrophages. Tissue factor (TF) is a membrane-bound glycoprotein and substance P (SP) is a pro-inflammatory neuropeptide involved in the formation of membrane blebs. This study investigated the role of SP in TF release by GM-CSF-dependent macrophages. SP significantly decreased TF levels in whole-cell lysates of GM-CSF-dependent macrophages. TF was detected in the culture supernatant by enzyme-linked immunosorbent assay after stimulation of macrophages by SP. Aprepitant (an SP/neurokinin 1 receptor antagonist) reduced TF release from macrophages stimulated with SP. Pretreatment of macrophages with a radical scavenger(pyrrolidinedithiocarbamate) also limited the decrease of TF in whole-cell lysates after stimulation with SP. A protein kinase C inhibitor (rottlerin) partially blocked this macrophage response to SP, while it was significantly inhibited by a ROCK inhibitor (Y-27632) or a dynamin inhibitor (dinasore). An Akt inhibitor (perifosine) also partially blocked this response. Furthermore, siRNA targeting p22phox, β-arrestin 2, or Rho A, blunted the release of TF from macrophages stimulated with SP. In other experiments, visceral adipocytes derived from cryopreserved preadipocytes were found to produce SP. In conclusion, SP enhances the release of TF from macrophages via the p22phox/β-arrestin 2/Rho A signaling pathway. [ABSTRACT FROM AUTHOR]

Neutrophil extracellular traps (NETs) have an important role in antimicrobial innate immunity and release substances that may modulate the immune response. We investigated the effects of soluble factors from NETs and neutrophil granule proteins on human monocyte function by using the Transwell system to prevent cell–cell contact. NET formation was induced by exposing human neutrophils to phorbol myristate acetate (PMA). When monocytes were incubated with PMA alone, expression of interleukin (IL)-4, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha mRNA was upregulated, but IL-10, IL-12, and interferon (IFN)-gamma mRNA were not detected. Incubation of monocytes with NETs enhanced the expression of IL-10 and IFN-gamma mRNA, but not IL-12 mRNA. Myeloperoxidase stimulated IFN-gamma production by monocytes in a dose-dependent manner. Both a nuclear factor-kappaB inhibitor (PDTC) and an intracellular calcium antagonist (TMB-8) prevented upregulation of IFN-gamma production. Neither a combined p38alpha and p38beta inhibitor (SB203580) nor an extracellular signal-regulated kinase inhibitor (PD98059) suppressed IFN-gamma production. Interestingly, a combined p38gamma and p38delta inhibitor (BIRB796) significantly decreased IFN-gamma production. These findings suggest that myeloperoxidase induces IFN-gamma production by monocytes via p38gamma/delta mitogen-activated protein kinase. [ABSTRACT FROM AUTHOR]

Background Granulocyte-macrophage colony-stimulating factor (GM-CSF) promotes classically activated M1 macrophages. GM-CSF upregulates protease-activated receptor-2 (PAR-2) protein expression and activation of PAR-2 by human neutrophil elastase (HNE) regulates cytokine production. Aim This study investigated the mechanism of PAR-2-mediated interleukin (IL)-13 production by GM-CSF-dependent macrophages stimulated with HNE. Methods Adherent macrophages were obtained from primary cultures of human mononuclear cells. After stimulation with HNE to activate the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling pathway, IL-13 mRNA and protein levels were assessed by the reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Results PAR-2 protein was detected in GM-CSF-dependent macrophages by Western blotting. Unexpectedly, PD98059 (an ERK1 inhibitor) increased IL-13 production, even at higher concentrations. Interestingly, U0126 (an ERK1/2 inhibitor) reduced IL-13 production in a concentration-dependent manner. Neither SB203580 (a p38alpha/p38beta inhibitor) nor BIRB796 (a p38gamma/p38delta inhibitor) affected IL-13 production, while TMB-8 (a calcium chelator) diminished IL-13 production. Discussion Stimulation with HNE promoted the production of IL-13 (a Th2 cytokine) by GM-CSF-dependent M1 macrophages. PAR-2-mediated IL-13 production may be dependent on the Ca 2 + /ERK2 signaling pathway. [ABSTRACT FROM AUTHOR]