Elevated pre-activation basal level of nuclear NF-κB in native macrophages accelerates LPS-induced translocation of cytosolic NF-κB into the cell nucleus

Abstract

Signaling via Toll-like receptor 4 (TLR4) in macrophages constitutes an essential part of the innate immune response to bacterial infections. Detailed and quantified descriptions of TLR4 signal transduction would help to understand and exploit the first-line response of innate immune defense. To date, most mathematical modelling studies were performed on transformed cell lines. However, properties of primary macrophages differ significantly. We therefore studied TLR4-dependent activation of NF-κB transcription factor in bone marrow-derived and peritoneal primary macrophages. We demonstrate that the kinetics of NF-κB phosphorylation and nuclear translocation induced by a wide range of bacterial lipopolysaccharide (LPS) concentrations in primary macrophages is much faster than previously reported for macrophage cell lines. We used a comprehensive combination of experiments and mathematical modeling to understand the mechanisms of this rapid response. We found that elevated basal NF-κB in the nuclei of primary macrophages is a mechanism increasing native macrophage sensitivity and response speed to the infection. Such pre-activated state of macrophages accelerates the NF-κB translocation kinetics in response to low agonist concentrations. These findings enabled us to refine and construct a new model combining both NF-κB phosphorylation and translocation processes and predict the existence of a negative feedback loop inactivating phosphorylated NF-κB.

Visualization and Modeling of Inhibition of IL-1β and TNF-α mRNA Transcription at the Single-Cell Level

“…⋅" (1 − *+ " ⋅" ).C/EBP was assumed to exert a constant influence on the rate of switching from # to $ . This model of NF-kB activation is in general agreement with the literature on NF-kB nuclear localization [40]. The expression dynamics of different genes (IL-1β, TNFα) in response to different treatments (No inhibitors, with MG132, U0126, or both) were described by chemical master equations (CMEs) with the same reactions but different kinetic rate parameters.…”

Priming Is Dispensable for NLRP3 Inflammasome Activation in Human Monocytes In Vitro

“…Constitutive NF-κB activation by tonic signals, independent of IL-1R, TNFR, or TLR priming, occurs in the bone marrow ( 52 ) and has also been found in human monocytes as well as mouse peritoneal and bone marrow derived macrophages. However, the mechanisms that control this basal activation are not clear ( 53 ). High constitutive NF-κB levels are also a feature of acute myeloid leukemia (AML) ( 54 ) and hence this might be reflected in THP-1 cells.…”

Antioxidant Nanoparticles for Concerted Inhibition of α-Synuclein Fibrillization, and Attenuation of Microglial Intracellular Aggregation and Activation

“…Iba1 fluorescence quantification was performed using NIH-ImageJ software and normalized to the cell count within the field of view. A NF-κB nuclear translocation study was conducted as described in previous publications with slight modifications (Trask, 2004;Bagaev et al, 2019). Briefly, a set of ROIs were defined using Hoechst nuclear stain fluorescence and subsequently overlaid on NF-κB fluorescence images after applying same fluorescence threshold to all images.…”