The Role of Interleukin-1β in Direct and Toll-Like Receptor 4-Mediated Neutrophil Activation and Survival

Abstract

The regulation of systemic and local neutrophil activation is crucial to the clearance of infections and the successful resolution of inflammation without progress to tissue damage or disseminated inflammatory reactions. Using purified lipopolysaccharide (pLPS) and highly purified neutrophils, we have previously shown that Toll-like receptor 4 signaling is a potent neutrophil activator, but a poor stimulator of survival. In the presence of peripheral blood mononuclear cells (PBMCs), however, pLPS becomes a potent neutrophil survival factor. Interleukin (IL)-1beta has been identified as an important neutrophil activator and prosurvival cytokine, and is produced in abundance by LPS-stimulated PBMCs. We now show that IL-1beta fails to activate highly purified neutrophils or enhance their survival, but in the presence of PBMCs, IL-1beta induces neutrophil survival. We hypothesized that LPS-primed neutrophils might become responsive to IL-1beta, but were unable to demonstrate this. Moreover, IL-1ra failed to prevent pLPS + PBMC-dependent neutrophil survival. In studies of IL-1R1(-/-) mice, we found that LPS was still able to mediate neutrophil survival, and neutrophil survival was enhanced by the addition of monocytic cells. Thus an important paradigm of neutrophil regulation needs to be viewed in the context of a cellular network in which actions of IL-1beta on neutrophils are indirect and mediated by other cells.

Enhanced Neutrophil Longevity and Recruitment Contribute to the Severity of Oviduct Pathology during Chlamydia muridarum Infection

“…Although we determined that D/UW-3/Cx and CTD153 were equally efficient at delaying the apoptosis of highly purified neutrophils after 20 h of incubation, we determined that partially purified preparations of neutrophils containing a population of ϳ1% monocytes exhibited delayed apoptosis upon incubation with D/UW-3/Cx relative to results with CTD153. Thus, it is possible that differences in monocyte production of cytokines such as IL-1␤, TNF-␣, and G-CSF were responsible for the differential ability of D/UW-3/Cx and CTD153 to delay neutrophil apoptosis (4,6,36,46). Differences in apoptosis were not due to discrepancies in the bacterial burden, since we verified equivalent bacterial loading by titration of Chlamydia after 1 and 3 h of incubation.…”

“…For example, when neutrophils were flow sorted from the cervices of mice infected with C. muridarum, they were determined to produce IL-1␤ at levels equivalent to those for macrophages (35). In addition, proinflammatory cytokines have been demonstrated to augment neutrophil expression of TLRs and to promote neutrophil activation (14,22,36,39).…”

Inhibition of Neutrophil Apoptosis by TLR Agonists in Whole Blood: Involvement of the Phosphoinositide 3-Kinase/Akt and NF-κB Signaling Pathways, Leading to Increased Levels of Mcl-1, A1, and Phosphorylated Bad

“…However, our data do not rule out a contribution of PBMC to the kinetics of spontaneous PMN apoptosis and to the TLR agonist-induced delay in PMN apoptosis. Release of survival factors such as cytokines by activated monocytes (22,38) could contribute to the stronger agonist-induced inhibition of PMN apoptosis that we observed in whole blood as compared with highly purified PMN.…”

NR4A orphan nuclear receptor family members, NR4A2 and NR4A3, regulate neutrophil number and survival

“…9,10 In selected experiments, neutrophils and monocytes were further purified by negative magnetic selection by using either a custom mixture from StemCell Technologies containing antibodies to CD36, CD2, CD3, CD9 CD19, CD56 and glycophorin A, or the Monocyte Isolation Kit II (Miltenyl Biotech, Bergisch Gladbach, Germany), respectively. Following negative selection, neutrophil and monocyte purity was .99%.…”

“…Nuclear morphology was assessed on Giemsa-stained cytocentrifuge slides by counting .300 cells per slide. 10 Apoptosis was also measured by Annexin V/ToPro-3 viability staining. In brief, cells were washed in phosphate-buffered saline and stained with 2.5 ml Annexin V-PE (BD Biosciences, San Jose, CA) and ToPro3 iodide (1:10 000 dilution, Molecular Probes, Eugene, OR), and samples were analyzed by using a FACS Calibur flow cytometer (BD Biosciences) and FlowJo software (Tree Star, Ashland, OR).…”