Petri MH, etal., Cardiovasc Res. 2015 Jan 1;105(1):65-74. doi: 10.1093/cvr/cvu224. Epub 2014 Oct 23.
AIMS: The formyl peptide receptor (FPR) subtype FPR2/ALX transduces pro-inflammatory responses and participates in the resolution of inflammation depending on activation. The aim of the present study was to unravel the role of FPR2
2/ALX signalling in atherosclerosis. METHODS AND RESULTS: Expression of FPR2/ALX was analysed in 127 human carotid atherosclerotic lesions and revealed that this receptor was expressed on macrophages, smooth muscle cells (SMCs), and endothelial cells. Furthermore, FPR2/ALX mRNA levels were significantly up-regulated in atherosclerotic lesions compared with healthy vessels. In multiple regression, age, creatinine, and clinical signs of increased cerebral ischaemia were independent predictors of FPR2/ALX expression. To provide mechanistic insights into these observations, we generated Ldlr(-/-)xFpr2(-/-) mice, which exhibited delayed atherosclerosis development and less macrophage infiltration compared with Ldlr(-/-)xFpr2(+/+) mice. These findings were reproduced by transplantation of Fpr2(-/-) bone marrow into Ldlr(-/-) mice and further extended by in vitro experiments, demonstrating a lower inflammatory state in Fpr2(-/-) macrophages. FPR2/ALX expression correlated with chemo- and cytokines in human atherosclerotic lesions and leucocytes. Finally, atherosclerotic lesions in Ldlr(-/-)xFpr2(-/-) mice exhibited decreased collagen content, and Fpr2(-/-) SMCs exhibited a profile of increased collagenase and decreased collagen production pathways. CONCLUSION: FPR2/ALX is proatherogenic due to effects on bone marrow-derived cells, but promoted a more stable plaque phenotype through effects on SMCs. Taken together, these results suggest a dual role of FPR2/ALX signalling in atherosclerosis by way of promoting disease progression and but increasing plaque stability.
Gabl M, etal., Biochim Biophys Acta. 2016 Jun;1863(6 Pt A):1228-37. doi: 10.1016/j.bbamcr.2016.03.014. Epub 2016 Mar 18.
Several G-protein-coupled receptors (GPCRs) can be activated or inhibited in a specific manner by membrane-permeable pepducins, which are short palmitoylated peptides with amino acid sequences identical to an intracellular domain of the receptor to be targeted. Unlike the endogenous P2Y2R agonist AT
P, the P2Y2PalIC2 pepducin, which has an amino acid sequence corresponding to the second intracellular loop of the human ATP receptor (P2Y2R), activated the superoxide anion-generating NADPH-oxidase in neutrophils. In addition to having a direct effect on neutrophils, the P2Y2R pepducin converted naive neutrophils to a primed state, which secondarily responded to ATP by producing superoxide. A pepducin with a peptide identical to the third intracellular loop of P2Y2R (P2Y2PalIC3) exhibited the same basic functions as P2Y2PalIC2, whereas one with a peptide that was identical to the first intracellular loop (P2Y2PalIC1) lacked these functions. The responses induced in neutrophils by the P2Y2R pepducins were not inhibited by the P2Y2R antagonist AR-C118925, and the receptor desensitization profile suggested the involvement of FPR2 rather than P2Y2R. Accordingly, antagonists/inhibitors of FPR2 attenuated the activities of the P2Y2R pepducins, which also selectively activated FPR2-overexpressing cells. In summary, we show that pepducins supposed to target P2Y2R activate human neutrophils through FPR2. We also show that the P2Y2PalIC2 pepducin can convert ATP from a non-activating agent to a potent neutrophil NADPH-oxidase activator. The molecular basis of this phenomenon involves cross-talk between the receptor/ligand pairs of P2Y2R/ATP and FPR2/P2Y2-pepducin.
Unregulated inflammation underlies many diseases, including sepsis. Much interest lies in targeting anti-inflammatory mechanisms to develop new treatments. One such target is the anti-inflammatory protein annexin A1 (AnxA1) and its receptor, FPR2/ALX. Using intr
avital videomicroscopy, we investigated the role of AnxA1 and FPR2/ALX in a murine model of endotoxin-induced cerebral inflammation [intraperitoneal injection of lipopolysaccharide (LPS)]. An inflammatory response was confirmed by elevations in proinflammatory serum cytokines, increased cerebrovascular permeability, elevation in brain myeloperoxidase, and increased leukocyte rolling and adhesion in cerebral venules of wild-type (WT) mice, which were further exacerbated in AnxA1-null mice. mRNA expression of TLR2, TLR4, MyD-88, and Ly96 was also assessed. The AnxA1-mimetic peptide, AnxA1(Ac2-26) (100 mug/mouse, approximately 33 mumol) mitigated LPS-induced leukocyte adhesion in WT and AnxA1-null animals without affecting leukocyte rolling, in comparison to saline control. AnxA1(Ac2-26) effects were attenuated by Boc2 (pan-FPR antagonist, 10 mug/mouse, approximately 12 nmol), and by minocycline (2.25 mg/mouse, approximately 6.3 nmol). The nonselective Fpr agonists, fMLP (6 mug/mouse, approximately 17 nmol) and AnxA1(Ac2-26), and the Fpr2-selective agonist ATLa (5 mug/mouse, approximately 11 nmol) were without effect in Fpr2/3(-/-) mice. In summary, our novel results demonstrate that the AnxA1/FPR2 system has an important role in effecting the resolution of cerebral inflammation in sepsis and may, therefore, provide a novel therapeutic target.
Sinniah A, etal., Int Immunopharmacol. 2016 Mar;32:87-95. doi: 10.1016/j.intimp.2016.01.003. Epub 2016 Jan 21.
1.We investigated the role of Annexin (ANX)-A1 and its receptor, ALX/FPR2, in the regulation of mast cell degranulation produced by compound 48/80. 2.Both human cord-blood derived mast cells (CBDMCs) and murine bone marrow derived mast cells (BMDMCs) release ph
osphorylated ANX-A1 during treatment with glucocorticoids or the mast cell 'stabilising' drugs ketotifen and nedocromil. 3.Compound 48/80 also stimulated ANX-A1 phosphorylation and release and this was also potentiated by nedocromil. Anti-ANX-A1 neutralising monoclonal antibodies (Mabs) enhanced the release of pro-inflammatory mediators in response to compound 48/80. 4.Nedocromil and ketotifen potently inhibited the release of histamine, PGD2, tryptase and beta-hexosaminidase from mast cells challenged with compound 48/80. Anti-ANX-A1 neutralising Mabs prevented the inhibitory effect of these drugs. 5.BMDMCs derived from Anx-A1-/- mice were insensitive to the inhibitory effects of nedocromil or ketotifen but cells retained their sensitivity to the inhibitory action of hu-r-ANX-A1. 6.The fpr2/3 antagonist WRW4 blocked the action of nedocromil on PGD2, but not histamine, release. BMDMCs derived from fpr2/3-/- mice were insensitive to the inhibitory effects of nedocromil on PGD2, but not histamine release. 7.Compound 48/80 stimulated both p38 and JNK phosphorylation in CBDMCs and this was inhibited by nedocromil. Inhibition of p38 phosphorylation was ANX-A1 dependent. 8.We conclude that ANX-A1 is an important regulator of mast cell reactivity to compound 48/80 exerting a negative feedback effect through a mechanism that depends at least partly on the FPR receptor.
