Activation Of Formyl Peptide Receptors Research Articles

Formyl peptide enhances cancer immunotherapy by activating antitumoral neutrophils, and T cells

Neutrophils are heterogeneous and plastic, with the ability to polarize from antitumour to protumour phenotype and modulate tumour microenvironment components. While some advances have been made, the neutrophil-targeting therapy remains underexplored. Activation of formyl peptide receptors (FPRs) by formylated peptides is needed for local control of infection through the recruitment of activated neutrophils while the potential contribution of antitumour activity remains underexplored. Here, we demonstrate that neutrophils can be harnessed to suppress tumour growth through the action of the formyl peptide (FP) on the formyl peptide receptor (FPR). Mechanistically, FP efficiently recruits neutrophils to produce reactive oxygen species production (ROS), resulting in the direct killing of tumours. Antitumour functions disappeared when neutrophils were depleted by anti-Ly6G antibodies. Interestingly, extensive T-cell activation was observed in mouse tumours treated with FP, showing the potential to alter the immune suppressed tumour microenvironment (TME) and further sensitize mice to anti-PD1 therapy. Transcriptomic and flow cytometry analyses revealed the mechanisms of FP-sensitized anti-PD1 therapy, mainly including stimulated neutrophils and an altered immune-suppressed tumour microenvironment. Collectively, these data establish FP as an effective combination partner for sensitizing anti-PD1 therapy by stimulating tumour-infiltrated neutrophils.

Formyl peptide receptor 1 mitigates colon inflammation and maintains mucosal homeostasis through the inhibition of CREB-C/EBPβ-S100a8 signaling

Excessive inflammatory responses are the main characteristic of ulcerative colitis (UC). Activation of formyl peptide receptor 1 (FPR1) has been found to promote the proliferation and migration of epithelial cells, but its role and therapeutic potential in UC remain unclear. This study observed an increased expression of FPR1 in a mouse model of colitis. Interestingly, FPR1 deficiency exacerbated UC and increased the secretion of the pro-inflammatory mediator from immune cells (e.g., macrophages), S100a8, a member of the damage-associated molecular patterns (DAMPs). Notably, the administration of the FPR agonist Cmpd43 ameliorated colon injury in a preclinical mice model of UC, likely via inhibiting phosphorylation of CREB and expression of C/EBPβ, which in turn suppressed the secretion of S100a8. In conclusion, these findings discovered a novel role of FPR1 in the development of colitis and will facilitate the development of FPR1-based pharmacotherapy to treat UC.

Peripheral Activation of Formyl Peptide Receptor 2/ALX by Electroacupuncture Alleviates Inflammatory Pain by Increasing Interleukin-10 Levels and Catalase Activity in Mice.

In the context of the electroacupuncture (EA) neurobiological mechanisms, we have previously demonstrated the involvement of formyl peptide receptor 2 (FPR2/ALX) in the antihyperalgesic effect of EA. The present study investigated the involvement of peripheral FPR2/ALX in the antihyperalgesic effect of EA on inflammatory cytokines levels, oxidative stress markers and antioxidant enzymes in an animal model of persistent inflammatory pain. Male Swiss mice underwent intraplantar (i.pl.) injection with complete Freund's adjuvant (CFA). Mechanical hyperalgesia was assessed with von Frey monofilaments. Animals were treated with EA (2/10Hz, ST36-SP6, 20 minutes) for 4 consecutive days. From the first to the fourth day after CFA injection, animals received i.pl. WRW4 (FPR2/ALX antagonist) or saline before EA. Levels of inflammatory cytokines (TNF, IL-6, IL-4 and IL-10), antioxidant enzymes (catalase and superoxide dismutase), oxidative stress markers (TBARS, protein carbonyl, nitrite/nitrate ratio), and myeloperoxidase activity were measured in paw tissue samples. As previously demonstrated, i.pl. injection of the FPR2/ALX antagonist prevented the antihyperalgesic effect induced by EA. Furthermore, animals treated with EA showed higher levels of IL-10 and catalase activity in the inflamed paw, and these effects were prevented by the antagonist WRW4. EA did not change levels of TNF and IL-6, SOD and MPO activity, and oxidative stress markers. Our work demonstrates that the antihyperalgesic effect of EA on CFA-induced inflammatory pain could be partially associated with higher IL-10 levels and catalase activity, and that these effects may be dependent, at least in part, on the activation of peripheral FPR2/ALX.

Dynamic Evolution of Bacterial Ligand Recognition by Formyl Peptide Receptors.

The detection of invasive pathogens is critical for host immune defense. Cell surface receptors play a key role in the recognition of diverse microbe-associated molecules, triggering leukocyte recruitment, phagocytosis, release of antimicrobial compounds, and cytokine production. The intense evolutionary forces acting on innate immune receptor genes have contributed to their rapid diversification across plants and animals. However, the functional consequences of immune receptor divergence are often unclear. Formyl peptide receptors (FPRs) comprise a family of animal G protein-coupled receptors which are activated in response to a variety of ligands including formylated bacterial peptides, pathogen virulence factors, and host-derived antimicrobial peptides. FPR activation in turn promotes inflammatory signaling and leukocyte migration to sites of infection. Here we investigate patterns of gene loss, diversification, and ligand recognition among FPRs in primates and carnivores. We find that FPR1, which plays a critical role in innate immune defense in humans, has been lost in New World primates. Amino acid variation in FPR1 and FPR2 among primates and carnivores is consistent with a history of repeated positive selection acting on extracellular domains involved in ligand recognition. To assess the consequences of FPR divergence on bacterial ligand interactions, we measured binding between primate FPRs and the FPR agonist Staphylococcus aureus enterotoxin B, as well as S. aureus FLIPr-like, an FPR inhibitor. We found that few rapidly evolving sites in primate FPRs are sufficient to modulate recognition of bacterial proteins, demonstrating how natural selection may serve to tune FPR activation in response to diverse microbial ligands.

Antibiotic-chemoattractants enhance neutrophil clearance of Staphylococcus aureus

The pathogen Staphylococcus aureus can readily develop antibiotic resistance and evade the human immune system, which is associated with reduced levels of neutrophil recruitment. Here, we present a class of antibacterial peptides with potential to act both as antibiotics and as neutrophil chemoattractants. The compounds, which we term ‘antibiotic-chemoattractants’, consist of a formylated peptide (known to act as chemoattractant for neutrophil recruitment) that is covalently linked to the antibiotic vancomycin (known to bind to the bacterial cell wall). We use a combination of in vitro assays, cellular assays, infection-on-a-chip and in vivo mouse models to show that the compounds improve the recruitment, engulfment and killing of S. aureus by neutrophils. Furthermore, optimizing the formyl peptide sequence can enhance neutrophil activity through differential activation of formyl peptide receptors. Thus, we propose antibiotic-chemoattractants as an alternate approach for antibiotic development.

Activation of formyl peptide receptor 1 elicits therapeutic effects against collagen-induced arthritis.

Rheumatoid arthritis (RA) is an autoimmune disorder which shows production of autoantibodies, inflammation, bone erosion, swelling and pain in joints. In this study, we examined the effects of an immune‐modulating peptide, WKYMVm, that is an agonist for formyl peptide receptors (FPRs). Administration of WKYMVm into collagen‐induced arthritis (CIA) mice, an animal model for RA, attenuated paw thickness, clinical scores, production of type II collagen‐specific antibodies and inflammatory cytokines. WKYMVm treatment also decreased the numbers of TH1 and TH17 cells in the spleens of CIA mice. WKYMVm attenuated TH1 and TH17 differentiation in a dendritic cell (DC)‐dependent manner. WKYMVm‐induced beneficial effects against CIA and WKYMVm‐attenuated TH1 and TH17 differentiation were reversed by cyclosporin H but not by WRW4, indicating a crucial role of FPR1. We also found that WKYMVm augmented IL‐10 production from lipopolysaccharide‐stimulated DCs and WKYMVm failed to suppress TH1 and TH17 differentiation in the presence of anti‐IL‐10 antibody. The therapeutic administration of WKYMVm also elicited beneficial outcome against CIA. Collectively, we demonstrate that WKYMVm stimulation of FPR1 in DCs suppresses the generation of TH1 and TH17 cells via IL‐10 production, providing novel insight into the function of FPR1 in regulating CIA pathogenesis.

The selective activation of formyl peptide receptor 2 prevents the inflammatory and pro-calcific differentiation of interstitial aortic valve cells

Background and Aims: To date, no effective pharmacological therapy has proven to halt or delay the progression of calcific aortic valve disease (CAVD). We aimed to investigate the effects of the activation of Formyl Peptide Receptor 2 (FPR2), a known receptor for lipoxins, resolvins and anti-inflammatory molecules, on interstitial aortic valve cells (VICs) calcification.

Annexin A1 Released in Extracellular Vesicles by Pancreatic Cancer Cells Activates Components of the Tumor Microenvironment, through Interaction with the Formyl-Peptide Receptors.

Pancreatic cancer (PC) is one of the most aggressive cancers in the world. Several extracellular factors are involved in its development and metastasis to distant organs. In PC, the protein Annexin A1 (ANXA1) appears to be overexpressed and may be identified as an oncogenic factor, also because it is a component in tumor-deriving extracellular vesicles (EVs). Indeed, these microvesicles are known to nourish the tumor microenvironment. Once we evaluated the autocrine role of ANXA1-containing EVs on PC MIA PaCa-2 cells and their pro-angiogenic action, we investigated the ANXA1 paracrine effect on stromal cells like fibroblasts and endothelial ones. Concerning the analysis of fibroblasts, cell migration/invasion, cytoskeleton remodeling, and the different expression of specific protein markers, all features of the cell switching into myofibroblasts, were assessed after administration of wild type more than ANXA1 Knock-Out EVs. Interestingly, we demonstrated a mechanism by which the ANXA1-EVs complex can stimulate the activation of formyl peptide receptors (FPRs), triggering mesenchymal switches and cell motility on both fibroblasts and endothelial cells. Therefore, we highlighted the importance of ANXA1/EVs-FPR axes in PC progression as a vehicle of intercommunication tumor cells-stroma, suggesting a specific potential prognostic/diagnostic role of ANXA1, whether in soluble form or even if EVs are captured in PC.

The Novel Small-molecule Annexin-A1 Mimetic, Compound 17b, Elicits Vasoprotective Actions in Streptozotocin-induced Diabetic Mice.

The formyl peptide receptor (FPR) family are a group of G-protein coupled receptors that play an important role in the regulation of inflammatory processes. It is well-established that activation of FPRs can have cardioprotective properties. Recently, more stable small-molecule FPR1/2 agonists have been described, including both Compound 17b (Cmpd17b) and Compound 43 (Cmpd43). Both agonists activate a range of signals downstream of FPR1/2 activation in human-engineered FPR-expressing cells, including ERK1/2 and Akt. Importantly, Cmpd17b (but not Cmpd43) favours bias away from intracellular Ca2+ mobilisation in this context, which has been associated with greater cardioprotection in response to Cmpd17b over Cmpd43. However, it is unknown whether these FPR agonists impact vascular physiology and/or elicit vasoprotective effects in the context of diabetes. First, we localized FPR1 and FPR2 receptors predominantly in vascular smooth muscle cells in the aortae of male C57BL/6 mice. We then analysed the vascular effects of Cmpd17b and Cmpd43 on the aorta using wire-myography. Cmpd17b but not Cmpd43 evoked a concentration-dependent relaxation of the mouse aorta. Removal of the endothelium or blockade of endothelium-derived relaxing factors using pharmacological inhibitors had no effect on Cmpd17b-evoked relaxation, demonstrating that its direct vasodilator actions were endothelium-independent. In aortae primed with elevated K+ concentration, increasing concentrations of CaCl2 evoked concentration-dependent contraction that is abolished by Cmpd17b, suggesting the involvement of the inhibition of Ca2+ mobilisation via voltage-gated calcium channels. Treatment with Cmpd17b for eight weeks reversed endothelial dysfunction in STZ-induced diabetic aorta through the upregulation of vasodilator prostanoids. Our data indicate that Cmpd17b is a direct endothelium-independent vasodilator, and a vasoprotective molecule in the context of diabetes.

The Contribution of Formyl Peptide Receptor Dysfunction to the Course of Neuroinflammation: A Potential Role in the Brain Pathology.

Chronic inflammatory processes within the central nervous system (CNS) are in part responsible for the development of neurodegenerative and psychiatric diseases. These processes are associated with, among other things, the increased and disturbed activation of microglia and the elevated production of proinflammatory factors. Recent studies indicated that the disruption of the process of resolution of inflammation (RoI) may be the cause of CNS disorders. It is shown that the RoI is regulated by endogenous molecules called specialized pro-resolving mediators (SPMs), which interact with specific membrane receptors. Some SPMs activate formyl peptide receptors (FPRs), which belong to the family of seven-transmembrane G protein-coupled receptors. These receptors take part not only in the proinflammatory response but also in the resolution of the inflammation process. Therefore, the activation of FPRs might have complex consequences.This review discusses the potential role of FPRs, and in particular the role of FPR2 subtype, in the brain under physiological and pathological conditions and their involvement in processes underlying neurodegenerative and psychiatric disorders as well as ischemia, the pathogenesis of which involves the dysfunction of inflammatory processes.

Structure of formylpeptide receptor 2-Gi complex reveals insights into ligand recognition and signaling

Formylpeptide receptors (FPRs) as G protein-coupled receptors (GPCRs) can recognize formylpeptides derived from pathogens or host cells to function in host defense and cell clearance. In addition, FPRs, especially FPR2, can also recognize other ligands with a large chemical diversity generated at different stages of inflammation to either promote or resolve inflammation in order to maintain a balanced inflammatory response. The mechanism underlying promiscuous ligand recognition and activation of FPRs is not clear. Here we report a cryo-EM structure of FPR2-Gi signaling complex with a peptide agonist. The structure reveals a widely open extracellular region with an amphiphilic environment for ligand binding. Together with computational docking and simulation, the structure suggests a molecular basis for the recognition of formylpeptides and a potential mechanism of receptor activation, and reveals conserved and divergent features in Gi coupling. Our results provide a basis for understanding the molecular mechanism of the functional promiscuity of FPRs.

Formyl-Peptide Receptor Activation Enhances Phagocytosis of Community-Acquired Methicillin-Resistant Staphylococcus aureus.

Formyl-peptide receptors (FPRs) are important pattern recognition receptors that sense specific bacterial peptides. Formyl-peptide receptors are highly expressed on neutrophils and monocytes, and their activation promotes the migration of phagocytes to sites of infection. It is currently unknown whether FPRs may also influence subsequent processes such as bacterial phagocytosis and killing. Staphylococcus aureus, especially highly pathogenic community-acquired methicillin-resistant S aureus strains, release high amounts of FPR2 ligands, the phenol-soluble modulins. We demonstrate that FPR activation leads to upregulation of complement receptors 1 and 3 as well as FCγ receptor I on neutrophils and, consequently, increased opsonic phagocytosis of S aureus and other pathogens. Increased phagocytosis promotes killing of S aureus and interleukin-8 release by neutrophils. We show here for the first time that FPRs govern opsonic phagocytosis. Manipulation of FPR2 activation could open new therapeutic opportunities against bacterial pathogens.

Extracellular annexin-A1 promotes myeloid/granulocytic differentiation of hematopoietic stem/progenitor cells via the Ca2+/MAPK signalling transduction pathway

Annexin A1 (AnxA1) modulates neutrophil life span and bone marrow/blood cell trafficking thorough activation of formyl-peptide receptors (FPRs). Here, we investigated the effect of exogenous AnxA1 on haematopoiesis in the mouse. Treatment of C57BL/6 mice with recombinant AnxA1 (rAnxA1) reduced the granulocyte–macrophage progenitor (GMP) population in the bone marrow, enhanced the number of mature granulocytes Gr-1+Mac-1+ in the bone marrow as well as peripheral granulocytic neutrophils and increased expression of mitotic cyclin B1 on hematopoietic stem cells (HSCs)/progenitor cells (Lin−Sca-1+c-Kit+: LSK). These effects were abolished by simultaneous treatment with Boc-2, an FPR pan-antagonist. In in vitro studies, rAnxA1 reduced both HSC (LSKCD90lowFLK-2−) and GMP populations while enhancing mature cells (Gr1+Mac1+). Moreover, rAnxA1 induced LSK cell proliferation (Ki67+), increasing the percentage of cells in the S/G2/M cell cycle phases and reducing Notch-1 expression. Simultaneous treatment with WRW4, a selective FPR2 antagonist, reversed the in vitro effects elicited by rAnxA1. Treatment of LSK cells with rAnxA1 led to phosphorylation of PCLγ2, PKC, RAS, MEK, and ERK1/2 with increased expression of NFAT2. In long-term bone marrow cultures, rAnxA1 did not alter the percentage of LSK cells but enhanced the Gr-1+Mac-1+ population; treatment with a PLC (U73122), but not with a PKC (GF109203), inhibitor reduced rAnxA1-induced phosphorylation of ERK1/2 and Elk1. Therefore, we identify here rAnxA1 as an inducer of HSC/progenitor cell differentiation, favouring differentiation of the myeloid/granulocytic lineage, via Ca2+/MAPK signalling transduction pathways.

Transformable Nanoparticle‐Enabled Synergistic Elicitation and Promotion of Immunogenic Cell Death for Triple‐Negative Breast Cancer Immunotherapy

AbstractAlthough cisplatin‐based neoadjuvant chemotherapy is an efficient therapy approach for triple‐negative breast cancer (TNBC), it has dismal prognosis and modestly improved survival benefit. Here, a synergistic immunotherapy of TNBC premised on the elicitation and promotion of immunogenic cell death (ICD) response, through a transformable nanoparticle‐enabled approach for contemporaneous delivery of cisplatin, adjudin, and WKYMVm is reported. The nanoparticles can sequentially respond to matrix metalloproteinases‐2, pH, and glutathione to achieve structural transformation with the advantages of optimal size change, efficient drug delivery, and well‐controlled release. Cisplatin and adjudin can synergistically amplify reactive oxygen species (ROS) cascade and eventually increase the formation of hydrogen peroxide and downstream highly toxic ROS like •OH, which can elicit ICD response by mechanisms of endoplasmic reticulum stress, apoptotic cell death, and autophagy. WKYMVm can further promote anti‐TNBC immunity by activation of formyl peptide receptor 1 to build stable interactions between dendritic cells and dying cancer cells. Thus, the nanoparticles achieve significant primary tumor regression and pulmonary metastasis inhibition as well as a remarkable survival benefit, with boosting of the innate and adaptive anti‐TNBC immunity.

Activation of Formyl Peptide Receptor Precedes the Onset of Hypertension in Dahl Salt Sensitive Rats: Effects of Microbiota and Salt

AimsChronic activation of the immune system contributes to kidney injury and hypertension. Mitochondria carry hallmarks of their bacterial ancestry and thus have emerged as a significant source of inflammatogenic damage‐associated molecular patterns. One of these hallmarks is that they still use formylated peptides (NFPs) as an initiator of protein synthesis. NFPs activate formyl peptide receptor (FPR), a G‐protein coupled receptor, and leads to receptor internalization and desensitization. We have observed that mitochondrial NFPs are elevated in the circulation of spontaneously hypertensive rats (SHR) and FPR blockage decreases blood pressure in this strain. Also, we and others observed that FPR downregulates upon activation in immune and non‐immune cells. Given that cell death and gut dysbiosis are present in salt sensitive hypertension, we hypothesized that Dahl sensitive rats would have decreased FPR expression, and that the decrease could be attributed to increased plasma levels of circulating mitochondria and/or bacteria NFPs from the cell death and leaky gut, respectively, and contributes to hypertension. Sex differences were also investigated.MethodsMale and Female Dahl Sensitive (S) and Resistant (R) rats (6‐week old) were given a low (0.3% NaCl) or high salt diet (2% NaCl) for 38 days. Rats received normal drinking water or water supplemented with neomycin (0.5 g/l, GIBCO) for 3 weeks. Kidney samples were taken from all rats and used for mRNA extraction and purification. The mRNA was made into cDNA to test gene expression for FPR. Blood was collected to measure mitochondrial NFPs. T‐test *p<0.05; n= 8–11 for Dahl S and R; n=7 for Dahl + neomycin.Results and ConclusionFPR expression was downregulated 4‐fold from male and female Dahl S when compared to Dahl R (AU: FPR mRNA: Dahl R 4.5 ± 1.3 vs. Dahl S: 0.7 ± 0.2*) (Figure 1). This phenomenon was independent of salt and sex differences. Antibiotic treatment partially restored FPR expression from Dahl S animals when compared to Dahl S treated with neomycin (AU FPR mRNA: Dahl S 4.5 ± 1.3 vs. Dahl S‐neomycin treated: 2.74 ± 0.99*). ND6, a mitochondrial protein, is 1.7‐fold higher in plasma from Dahl S compared to Dahl R. Unexpected, salt diet did not change this parameter. We have observed for the first time that FPR is downregulated in Dahl animals independent of salt probably due to overstimulation of this receptor. Therefore, FPR activation due to increased levels of bacterial (NFPs) could be associated with the development of renal injury at an early age independently of salt and elevations in arterial pressure.Support or Funding InformationAmerican Heart Association (18POST34060003) and National Institutes of Health (K99GM118885 and R01HL143082)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract 114: Increased Circulating Levels of Mitochondrial N-Formyl Peptides Leads to Vascular Dysfunction and High Blood Pressure in Spontaneously Hypertensive Rats

Aims: The most powerful signaling pathway that induces actin polymerization and movement in neutrophils is due to formyl peptide receptor (FPR) activation. FPR was originally identified by its ability to bind bacterial N-formyl peptides. Mitochondria carry hallmarks of their bacterial ancestry and one of these hallmarks is that this organelle uses an N-formyl-methionyl-tRNA as an initiator of protein synthesis. Consequently, mitochondrial N-formyl peptides (F-MITs) are recognized by FPR. Recently, we have observed that FPR is expressed in endothelial and vascular smooth muscle cells (VSMC). We hypothesized that increased plasma levels of F-MITs activates FPR and contributes to microvascular damage and hypertension. Methods: Male SHR (12-week old) were treated for 10 days with FPR antagonist cocktail: Cyclosporin H (CsH, 0.1 mg/kg/day i.p. ) and WRW4 (0.1 mg/kg/day i.p. ) or vehicle. Blood pressure (BP) was measured by telemetry. We also treated Wistar rats (12 week old) with F-MITs (formylated peptide corresponding to the NH2-terminus of mitochondria ND6; 0.02 mg/rat/day i.p. ) or non-formylated peptides (control) for 10 days. Blood was collected to measure F-MITs. Intrarenal arteries and mesenteric resistance arteries (MRA) were isolated and mounted in a wire myograph. Wistar VSMCs were treated with F-MITs (20 min, 10 μM) or control in the presence or absence of FPR antagonists to evaluate actin polymerization. T-test *p<0.05; n=5-6. Results and Conclusion: F-MITs plasma levels were increased in SHR (1.7-fold* vs. Wistar). FPR blockade decreased BP (SHR + vehicle: 151 ± 7.2 vs. SHR+CsH+WRW4: 138 ± 0.4* mmHg) and ameliorated acetylcholine-induced relaxation (Intrarenal; Emax: SHR+vehicle: 10 ± 5 vs. SHR+CsH+WRW4: 28 ± 6* %); (MRA; Emax: SHR+vehicle: 74±10 vs. SHR+CsH+WRW4: 99±0.6* %). F-MITs infusion increased BP in Wistar rats (Control: 133 ± 1.9 vs. F-MITs: 145 ± 4.7* mmHg) and decreased acetylcholine-induced relaxation (EC50; MRA: Control: -8.765 ± 0.05 vs. F-MIT: -8.348 ± 0.08*) (Emax; Intrarenal: Control: 63±4 vs. F-MIT: 46 ± 3* %). F-MITs induced VSMCs actin polymerization (1.8 fold* vs. control) and FPR blockers abolished this result. In conclusion, FMITs play a role in vascular dysfunction and hypertension via FPR activation.

Activation of formyl peptide receptor 2 by WKYMVm enhances emergency granulopoiesis through phospholipase C activity

Emergency granulopoiesis is a very important strategy to supply efficient neutrophil number in response to infection. However, molecular mechanism involved in this process remains unclear. Here, we found that administration of WKYMVm, an immune modulating peptide, to septic mice strongly increased neutrophil number through augmented emergency granulopoiesis. WKYMVm-induced emergency granulopoiesis was blocked not only by a formyl peptide receptor 2 (FPR2) antagonist (WRW4), but also by FPR2 deficiency. As progenitors of neutrophils, Lin−c-kit+Sca-1− cells expressed FPR2. WKYMVm-induced emergency granulopoiesis was also blocked by a phospholipase C inhibitor (U-73122). These results suggest that WKYMVm can stimulate emergency granulopoiesis via FPR2 and phospholipase C enzymatic activity.

Formyl peptide receptor activation inhibits the expansion of effector T cells and synovial fibroblasts and attenuates joint injury in models of rheumatoid arthritis

AbstractThe effects of formyl peptide receptors (FPRs) on effector T cells and inflammation-causing tissue-resident cells are not well known. Here, we explored the effect of FPR activation on efferent T cell responses in models of rheumatoid arthritis (RA) and on the expansion of fibroblast-like synoviocytes (FLS). Compound 43 (Cpd43; FPR1/2 agonist) was administered to mice with collagen-induced arthritis (CIA) or antigen-induced arthritis (AIA) after disease onset. Joint inflammation/damage and immunity were assessed. FLS were cultured with Cpd43 to test its effects on cell apoptosis and proliferation. To explore the effects of endogenous FPR2 ligands on FLS proliferation, FLS FPR2 was blocked or Annexin A1 (AnxA1) expression silenced. Cpd43 reduced arthritis severity in both models. In CIA, Cpd43 decreased CD4 T cell proliferation and survival and increased the production of the protective cytokine, IFNγ, in lymph nodes. In AIA, Cpd43 increased CD4 apoptosis and production of the anti-inflammatory IL-4, while augmenting the proportion of splenic regulatory T cells and their expression of IL-2Rα. In both models, Cpd43 increased CD4 IL-17A production, without affecting humoral immunity. FPR2 inhibitors reversed Cpd43-mediated effects on AIA and T cell immunity. Cpd43 decreased TNF-induced FLS proliferation and augmented FLS apoptosis in association with intracellular FPR2 accumulation, while endogenous AnxA1 and FPR2 reduced FLS proliferation via the ERK and NFκB pathways. Overall, FPR activation inhibits the expansion of arthritogenic effector CD4 T cells and FLS, and reduces joint injury in experimental arthritis. This suggests the therapeutic potential of FPR ligation for the treatment of RA.

Abstract P286: Circulating Lipoxin A4 Causes Resolution of Inflammation via Estrogen Receptor Activation, While Mitochondria N-Formyl Peptides Induce Inflammation via Formyl Peptide Receptor in Hypertension

Recently, we observed that mitochondrial components have inflammatogenic proprieties and that their fragments are elevated in the circulation of spontaneously hypertensive rats (SHR). Also, infusion of mitochondrial N-formyl peptides (F-MITs) into rats induces inflammation and vascular dysfunction via formyl peptide receptor (FPR) activation. In contrast, Lipoxin A4 (LXA4), a mediator of resolution of inflammation, also binds FPR. However, LXA4-FPR-dependent effects seem to be opposite from F-MITs. We first hypothesized that LXA4 is decreased in SHR. We collected plasma from male SHR and Wistar Kyoto rats (WKY) (12 weeks old) and LXA4 was extracted via hydrophobic, reverse-phase, silica-based column. Our initial hypothesis was refuted, since LXA4 was increased in SHR (WKY: 0.33±0.05 vs. SHR: 0.79±0.08 ng/ml, p<0.05). As a result, we inhibited LXA4 synthesis in SHR with a 5-lipoxygenase (5-LOX) inhibitor Zileuton (10mg/kg/day i.p.) for 10 days. 5-LOX blockade did not change blood pressure (BP), but did cause a deterioration of vascular function in intrarenal and mesenteric resistance arteries in SHR. On the other hand, the blockade of FPR in SHR for 10 days with Cyclosporin H (CsH) and WRW4 (0.1 mg/kg/day) reduced BP (telemetry: SHR+control: 151±7.2 vs. SHR+CsH+WRW4: 138±0.4 mmHg, p<0.05) and left ventricle mass. FPR blockade also ameliorated acetylcholine-induced relaxation of intrarenal (Emax: SHR+control: 10±5 vs. SHR+CsH+WRW4: 28±6 %, p<0.05) and mesenteric resistance arteries (Emax: SHR+vehicle: 74±10 vs. SHR+CsH+WRW4: 99±0.6 %, p<0.05). From these data, we suggest that LXA4 does not act on FPR to promote resolution of inflammation. We believe that another factor binds FPR (e.g., F-MITs) and leads to vascular damage in SHR. In support of this, we observed that LXA4 phosphorylates estrogen receptor (ER) alpha Ser118 in aortic vascular smooth muscle cells (VSMC) and ER antagonist ICI-182 (100nM), but not FPR antagonist, abolishes these responses. On the other hand, FMITs increased phosphoERK 1/2 in VSMC and FPR antagonists blocked this increase. In conclusion, FMITs and LXA4 have opposite effects in SHR. LXA4 induces resolution of inflammation, possibly via ER activation, and F-MITs lead to damage via FPR activation.

Formyl peptide receptors promotes neural differentiation in mouse neural stem cells by ROS generation and regulation of PI3K-AKT signaling

This study aimed to determine whether formyl peptide receptors (FPRs) regulated the differentiation of neural stem cells (NSCs). FPRs promote the migration of NSCs both in vitro and in vivo. However, the role of FPRs during differentiation of NSCs is unknown. Analysis by Western blot showed significantly increased expression of FPR1 and FPR2 during differentiation of NSCs. The activation of FPRs promotes NSCs to differentiate into neurons with more primary neurites and branch points and longer neurites per cell. Meanwhile, this activation also inhibits the differentiation of NSC into astrocytes. This bidirectional effect can be inhibited by the FPRs-specific inhibitor. Moreover, it was found that the activation of FPRs increased the generation of reactive oxygen species (ROS) and phosphorylation of AKT in the NSCs, while N-acetylcysteine and LY294002 inhibited the FPRs-stimulated increase in ROS generation and AKT phosphorylation, and blocked the FPRs-stimulated neural differentiation into neurons. Therefore, FPRs-stimulated neural differentiation was mediated via ROS and PI3K-AKT signaling pathways. Collectively, the present findings provided a novel insight into the functional role of FPRs in neurogenesis, with important implications for its potential use as a candidate for treating brain or spinal cord injury.