Notch signaling regulates the responses of lipopolysaccharide-stimulated macrophages in the presence of immune complexes

Abstract

Macrophages exhibit diverse effector phenotypes depending on the stimuli and their microenvironment. Classically activated macrophages are primed with interferon (IFN)γ and stimulated with pathogen-associated molecular patterns. They produce inflammatory mediators and inflammatory cytokines, such as IL-12. In the presence of immune complexes (ICs), activated macrophages have decreased IL-12 production and increased IL-10 production and presumably act as regulatory macrophages. Notch signaling has been shown to regulate the effector functions of classically activated macrophages. In this study, we investigated whether Notch signaling is active in lipopolysaccharide (LPS)-stimulated macrophages in the presence of ICs. LPS/IC stimulation increased the level of cleaved Notch1 in murine macrophages, while IC stimulation alone did not. Delta-like 4, but not Jagged1, was responsible for generating cleaved Notch1. The activation of Notch signaling by LPS/ICs depended upon NF-κB and MEK/Erk pathway activation. Macrophages with the targeted deletion of Rbpj, which encodes a DNA-binding protein central to canonical Notch signaling, produced significantly less IL-10 upon LPS/IC stimulation. A similar impact on IL-10 production was observed when Notch signaling was inhibited with a gamma-secretase inhibitor (GSI). Defects in NF-κB p50 nuclear localization were observed in GSI-treated macrophages and in Rbpj-/- macrophages, suggesting cross-regulation between the Notch and NF-κB pathways. Transcriptomic analysis revealed that Notch signaling regulates the transcription of genes involved in the cell cycle, macrophage activation, leukocyte migration and cytokine production in LPS/IC-stimulated macrophages. Taken together, these results suggest that the Notch signaling pathway plays an important role in regulating the functions of macrophages activated by LPS and ICs.

The Use of Nutraceuticals to Counteract Atherosclerosis: The Role of the Notch Pathway

“…These data have been confirmed by Xu and collaborators that showed in macrophages isolated from Notch-1 -/mice a decreased basal and LPS-induced NF-κB and HIF-1α activation, indicative that induction of the M1 pathway is dependent on Notch signaling [274]. Defects in NF-κB p50 nuclear localization were observed in DAPT-treated macrophages and in RBP-Jκ-deficent macrophages, indicative of crosstalk between Notch and NF-κB pathways [275]. Lastly, DAPT treatment during MI diminished the number of macrophages in the infarcted area and significantly increased the M2 macrophage polarization [276], data resembling those obtained by Singla et al that confirmed reduction of the proinflammatory M1 phenotype following monocyte treatment with DAPT or Notch-1 siRNA [277].…”

Weighted Gene Co-expression Network Analysis Identifies CALD1 as a Biomarker Related to M2 Macrophages Infiltration in Stage III and IV Mismatch Repair-Proficient Colorectal Carcinoma

“…Our results revealed that stromal score was strongly and positively correlated with CALD1 (cor = 0.85 and 0.82, P < 0.001) and CCL2 (cor = 0.81 and 0.79, P < 0.001) expressions in the two datasets, indicating that signals from intricate CALD1 , CCL2 , and stromal interactions might drive M2 macrophage activation and polarization. Furthermore, GSEA disclosed that high expression of CALD1 was correlated with several immunoregulation pathways associated with M2 macrophage activation and recruitment, such as cytokine–cytokine receptor interaction, leukocyte transendothelial migration, vascular smooth muscle contraction, TGF-beta signaling pathway, and MAPK signaling pathway ( Jiang et al, 2017 ; Wongchana et al, 2018 ).…”

Immunomodulatory Effects of (24R)-Pseudo-Ginsenoside HQ and (24S)-Pseudo-Ginsenoside HQ on Cyclophosphamide-Induced Immunosuppression and Their Anti-Tumor Effects Study

“…They modulate the balance between humoral and cell-based immune responses and regulate the maturation, growth, and responsiveness of particular cell populations. Interleukin 1 beta (IL-1β) promotes antimicrobial immunity in macrophages, interferon gamma (IFNγ) and tumor necrosis factor alpha (TNF-α) participate in cell-mediated immune responses, and IL-4 and IL-6 promote humoral or allergic responses [ 26 ]. As shown in Figure 5 , the levels of IL-1β, IL-4, IL-6, IFN-γ, and TNF-α in serum were significantly decreased in the CTX group compared with the normal group ( p < 0.01).…”