The two formyl peptide receptors differently regulate GPR84-mediated neutrophil NADPH-oxidase activity

Abstract

Neutrophils express many G protein-coupled receptors (GPCRs) including the two formyl peptide receptors (FPR1 and FPR2) and the medium chain fatty acid receptor GPR84. The FPRs are known to define a hierarchy among neutrophil GPCRs, i.e., the GPCR-mediated response can be either suppressed or amplified by signals generated by FPRs. In this study, we investigated the position of GPR84 in the FPR-defined hierarchy regarding the activation of neutrophil NADPH-oxidase, an enzyme system designed to generate reactive oxygen species (ROS). When naïve neutrophils are activated by GPR84 agonists a modest ROS release was induced. However, vast amounts of ROS production was induced by these GPR84 agonists in FPR2-desensitized neutrophils, and the response is inhibited not only by a GPR84 antagonist but also by an FPR2 specific antagonist. This suggests that the amplified GPR84 agonist response is achieved through a reactivation of the desensitized FPR2. In addition, the GPR84-mediated FPR2 reactivation was independent of β-arrestin recruitment and sensitive to a protein phosphatase inhibitor. In contrast, the modest ROS production induced by GPR84 agonists was primarily suppressed in FPR1-desensitized neutrophils through hierarchical desensitization of GPR84 by FPR1 generated signals.In summary, our data show that FPRs control the NADPH-oxidase activity mediated through GPR84 in human neutrophils. While an amplified ROS generation is achieved by GPR84 agonists through reactivation of desensitized FPR2, FPR1 heterologously desensitizes GPR84 and by that suppresses the release of ROS induced by GPR84 agonists.

Selective phosphorylation of threonine residues defines GPR84–arrestin interactions of biased ligands

“…1B). Activation of GPR84 with certain, but not all, ligands is reported to promote interaction with arrestin isoforms (21,28). When hGPR84-eYFP was transiently coexpressed in human embryonic kidney (HEK) 293T cells with arrestin-3 fused to nanoluciferase, 2-HTP effectively promoted proximity and potential interactions between the receptor and this arrestin construct (Fig.…”

Resolution of inflammation via RvD1/FPR2 signaling mitigates Nox2 activation and ferroptosis of macrophages in experimental abdominal aortic aneurysms

“…Future studies will be focused on delineating the RvD1‐stimulated macrophages in preventing p47 phox phosphorylation to culminate in proteolysis of MerTK. Additionally, FPR1 and FPR2 receptor signaling on neutrophils has been shown to modulate chemotaxis and Nox2 activation causing oxidative stress and neutrophil activation in various diseases 46,47 . Our previous study has shown that FPR1 receptors on activated neutrophils in AAA can be used as an SPECT imaging tool using a radiolabeled peptide, c‐FLFLF 48 .…”

“…Additionally, FPR1 and FPR2 receptor signaling on neutrophils has been shown to modulate chemotaxis and Nox2 activation causing oxidative stress and neutrophil activation in various diseases. 46,47 Our previous study has shown that FPR1 receptors on activated neutrophils in AAA can be used as an SPECT imaging tool using a radiolabeled peptide, c-FLFLF. 48 Therefore, RvD1/FPR2 signaling on other pertinent immune cells like neutrophils, as well as resident cells such as aortic smooth muscle cells and endothelial cells, could also play a significant role in the pathogenesis of AAA and remains to be delineated.…”