Kinase AKT1 Negatively Controls Neutrophil Recruitment and Function in Mice

Abstract

Neutrophils are critically involved in host defense and inflammatory injury. However, intrinsic signaling mechanisms controlling neutrophil recruitment and activities are poorly defined. In this article, we showed that protein kinase AKT1 (also known as PKBα) is the dominant isoform expressed in neutrophils and is downregulated upon bacterial infection and neutrophil activation. AKT1 deficiency resulted in severe disease progression accompanied by recruitment of neutrophils and enhanced bactericidal activity in the acute inflammatory lung injury (ALI) and the Staphylococcus aureus infection mouse models. Moreover, the depletion of neutrophils efficiently reversed the aggravated inflammatory response, but adoptive transfer of AKT1−/− neutrophils could potentiate the inflammatory immunity, indicating an intrinsic effect of the neutrophil in modulating inflammation in AKT1−/− mice. In the ALI model, the infiltration of neutrophils into the inflammatory site was associated with enhanced migration capacity, whereas inflammatory stimuli could promote neutrophil apoptosis. In accordance with these findings, neutralization of CXCR2 attenuated neutrophil infiltration and delayed the occurrence of inflammation. Finally, the enhanced bactericidal activity and inflammatory immunity of AKT-deficient neutrophils were mediated by a STAT1-dependent, but not a mammalian target of rapamycin–dependent, pathway. Thus, our findings indicated that the AKT1–STAT1 signaling axis negatively regulates neutrophil recruitment and activation in ALI and S. aureus infection in mice.

The Calcineurin-NFAT Axis Controls Allograft Immunity in Myeloid-Derived Suppressor Cells through Reprogramming T Cell Differentiation

“…Samples were also stained with CD11b and Gr1 to visualize MDSCs. Apoptosis of MDSCs in recipient mouse splenic cells was assayed by flow cytometry using annexin V (BD Pharmingen) staining with a gating strategy aligned to analyze CD11b ϩ Gr1 ϩ cells as described previously (33). The FCM data were acquired on a FACSCalibur cell analyzer, and data were analyzed using FlowJo software.…”

Targeting S1P1 Receptor Protects against Murine Immunological Hepatic Injury through Myeloid-Derived Suppressor Cells

“…Chemotaxis was evaluated, as previously described (40,41), in a 24-well microchemotaxis plate (Corning, Corning, NY) in which the chambers were separated by polycarbonate membrane. RPMI 1640 containing 0.01% BSA (Fluka-P5369) or CXCL1 (30 nM; SRP3216, both from SigmaAldrich) was placed in the lower chamber.…”

IL-17A Produced by Neutrophils Protects against Pneumonic Plague through Orchestrating IFN-γ–Activated Macrophage Programming

“…Isolation of neutrophils from bone marrow cells was accomplished according to our previously published procedures (16,30). Bone marrow CD11b + cells were isolated using anti-CD11b magnetic beads and positive selection columns (Miltenyi Biotec).…”