Formyl peptide receptor 2 regulates dendritic cell metabolism and Th17 cell differentiation during neuroinflammation.

Formyl peptide receptor 2 (FPR2) is a receptor for formylated peptides and specific pro-resolving mediators, and is involved in various inflammatory processes. Here, we aimed to elucidate the role of FPR2 in dendritic cell (DC) function and autoimmunity-related central nervous system (CNS) inflammation by using the experimental autoimmune encephalomyelitis (EAE) model. EAE induction was accompanied by increased Fpr2 mRNA expression in the spinal cord. FPR2-deficient (Fpr2 KO) mice displayed delayed onset of EAE compared to wild-type (WT) mice, associated with reduced frequencies of Th17 cells in the inflamed spinal cord at the early stage of the disease. However, FPR2 deficiency did not affect EAE severity after the disease reached its peak. FPR2 deficiency in mature DCs resulted in decreased expression of Th17 polarizing cytokines IL6, IL23p19, IL1ß, and thereby diminished the DC-mediated activation of Th17 cell differentiation. LPS-activated FPR2-deficient DCs showed upregulated Nos2 expression and nitric oxide (NO) production, as well as reduced oxygen consumption rate and impaired mitochondrial function, including decreased mitochondrial superoxide levels, lower mitochondrial membrane potential and diminished expression of genes related to the tricarboxylic acid cycle and genes related to the electron transport chain, as compared to WT DCs. Treatment with a NO inhibitor reversed the reduced Th17 cell differentiation in the presence of FPR2-deficient DCs. Together, by regulating DC metabolism, FPR2 enhances the production of DC-derived Th17-polarizing cytokines and hence Th17 cell differentiation in the context of neuroinflammation.

Implication of the Annexin 1/FPR axis in leishmanial exosome-mediated Leishmania major skin hyperpathogenesis.

Introduction: Exosomes produced by the protozoan parasite Leishmania (LeishEXO) are well-established drivers of virulence, though mechanisms underlying their exacerbation of experimental leishmaniasis remain elusive. Expression of Annexin A1 (ANXA1), a protein implicated in exosome-mediated pathologies and viral internalization, has been shown to correlate with cutaneous leishmaniasis severity. Given ANXA1's regulation of myeloid cells - the canonical hosts for Leishmania - we studied the potential role of ANXA1 and its receptors FPR1/2 in exerting LeishEXO's effects. Methods: Murine and in vitro ANXA1-/- models were used to study the generation of protective TH1 responses during experimental L. major infection with and without LeishEXO. Recruitment of inflammatory cells was assessed using a peritoneal cell recruitment assay and immunophenotyping, and production of inflammatory mediators was measured using a cytokine and chemokine array. Treatment of experimental models with FPR2 antagonist WRW4 and FPR1/2 agonist WKYMVm was used to delineate the role of the FPR/ANXA1 axis in LeishEXO-mediated hyperpathogenesis. Results: We established that ANXA1 deficiency prohibits LeishEXO-mediated pathogenesis and myeloid cell infection, with minimal alterations to adaptive and innate immune phenotypes. FPR2 blockade with WRW4 similarly inhibited leishmanial hyperpathogenesis, while direct activation of FPRs with WKYMVm enhanced infection and recapitulated the LeishEXO-mediated phenotype. This research describes LeishEXO's utilization of the ANXA1/FPR axis to facilitate parasitic internalization and pathogenesis, which may be leveraged in the development of therapeutics for leishmaniasis.

Post-treatment with Resolvin D1 attenuates pulmonary hypertension by inhibiting endothelial-to-mesenchymal transition.

Pulmonary hypertension (PH) is a life-threatening disease characterized by pulmonary vascular remodeling. Endothelial-to-mesenchymal transition (EndMT) is an important manifestation and mechanism of pulmonary vascular remodeling. Resolvin D1 (RvD1) is an endogenous lipid mediator promoting the resolution of inflammation. However, the role of RvD1 on EndMT in PH remains unknown. Here, we aimed to investigate the effect and mechanisms of RvD1 on the treatment of PH. We showed that RvD1 and its receptor FPR2 expression were markedly decreased in PH patients and both chronic hypoxia-induced PH (CH-PH) and sugen 5416/hypoxia-induced PH (SuHx-PH) mice models. RvD1 treatment decreased right ventricular systolic pressure (RVSP) and alleviated right ventricular function, and reduced pulmonary vascular remodeling and collagen deposition in the perivascular of both two PH mice models. Then, RvD1 inhibited EndMT in both the lungs of PH mice models and primary cultured human umbilical vein endothelial cells (HUVECs) treated with TGF-ß and IL-1ß. Moreover, RvD1 inhibited EndMT by downregulating Smad2/3 phosphorylation in vivo and in vitro via FPR2. In conclusion, our date suggest that RvD1/FPR2 axis prevent experimental PH by inhibiting endothelial-mensenchymal-transition and may be a therapeutic target for PH.

LL37/FPR2 regulates neutrophil mPTP promoting the development of neutrophil extracellular traps in diabetic retinopathy.

Diabetic retinopathy (DR) is characterized by chronic, low-grade inflammation. This state may be related to the heightened production of neutrophil extracellular traps (NETs) induced by high glucose (HG). Human cathelicidin antimicrobial peptide (LL37) is an endogenous ligand of G protein-coupled chemoattractant receptor formyl peptide receptor 2 (FPR2), expressed on neutrophils and facilitating the formation and stabilization of the structure of NETs. In this study, we detected neutrophils cultured under different conditions, the retinal tissue of diabetic mice, and fibrovascular epiretinal membranes (FVM) samples of patients with proliferative diabetic retinopathy (PDR) to explore the regulating effect of LL37/FPR2 on neutrophil in the development of NETs during the process of DR. Specifically, HG or NG with LL37 upregulates the expression of FPR2 in neutrophils, induces the opening of mitochondrial permeability transition pore (mPTP), promotes the increase of reactive oxygen species and mitochondrial ROS, and then leads to the rise of NET production, which is mainly manifested by the release of DNA reticular structure and the increased expression of NETs-related markers. The PI3K/AKT signaling pathway was activated in neutrophils, and the phosphorylation level was enhanced by FPR2 agonists in vitro. In vivo, increased expression of NETs markers was detected in the retina of diabetic mice and in FVM, vitreous fluid, and serum of PDR patients. Transgenic FPR2 deletion led to decreased NETs in the retina of diabetic mice. Furthermore, in vitro, inhibition of the LL37/FPR2/mPTP axis and PI3K/AKT signaling pathway decreased NET production induced by high glucose. These results suggested that FPR2 plays an essential role in regulating the production of NETs induced by HG, thus may be considered as one of the potential therapeutic targets.

Advances in the Chemistry and Biology of Specialised Pro-Resolving Mediators (SPMs).

This review article assembles key recent advances in the synthetic chemistry and biology of specialised pro-resolving mediators (SPMs). The major medicinal chemistry developments in the design, synthesis and biological evaluation of synthetic SPM analogues of lipoxins and resolvins have been discussed. These include variations in the top and bottom chains, as well as changes to the triene core, of lipoxins, all changes intended to enhance the metabolic stability whilst retaining or improving biological activity. Similar chemical modifications of resolvins are also discussed. The biological evaluation of these synthetic SPMs is also described in some detail. Original investigations into the biological activity of endogenous SPMs led to the pairing of these ligands with the FPR2/LX receptor, and these results have been challenged in more recent work, leading to conflicting results and views, which are again discussed.

Mitigation of acute lung injury by human bronchial epithelial cell-derived extracellular vesicles via ANXA1-mediated FPR signaling.

Acute lung injury (ALI) is characterized by respiratory failure resulting from the disruption of the epithelial and endothelial barriers as well as immune system. In this study, we evaluated the therapeutic potential of airway epithelial cell-derived extracellular vesicles (EVs) in maintaining lung homeostasis. We isolated human bronchial epithelial cell-derived EVs (HBEC-EVs), which endogenously express various immune-related surface markers and investigated their immunomodulatory potential in ALI. In ALI cellular models, HBEC-EVs demonstrated immunosuppressive effects by reducing the secretion of proinflammatory cytokines in both THP-1 macrophages and HBECs. Mechanistically, these effects were partially ascribed to nine of the top 10 miRNAs enriched in HBEC-EVs, governing toll-like receptor-NF-κB signaling pathways. Proteomic analysis revealed the presence of proteins in HBEC-EVs involved in WNT and NF-κB signaling pathways, pivotal in inflammation regulation. ANXA1, a constituent of HBEC-EVs, interacts with formyl peptide receptor (FPR)2, eliciting anti-inflammatory responses by suppressing NF-κB signaling in inflamed epithelium, including type II alveolar epithelial cells. In a mouse model of ALI, intratracheal administration of HBEC-EVs reduced lung injury, inflammatory cell infiltration, and cytokine levels. Collectively, these findings suggest the therapeutic potential of HBEC-EVs, through their miRNAs and ANXA1 cargo, in mitigating lung injury and inflammation in ALI patients.

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.

Role of formyl peptide receptor 2 in steatosis of L02 cells exposed to Mono-(2-ethylhexyl) phthalate.

Mono-(2-ethylhexyl) phthalate (MEHP) can accumulate in the liver and then lead to hepatic steatosis, while the underlying mechanism remains unclear. Inflammation plays an important role in the disorder of hepatic lipid metabolism. This study aims to clarify the role of the inflammatory response mediated by formyl peptide receptor 2 (FPR2) in steatosis of L02 cells exposed to MEHP. L02 cells were exposed to MEHP of different concentrations and different time. A steatosis model of L02 cells was induced with oleic acid and the cells were exposed to MEHP simultaneously. In addition, L02 cells were incubated with FPR2 antagonist and then exposed to MEHP. Lipid accumulation was determined by oil red O staining and extraction assay. The indicators related to lipid metabolism and inflammatory response were measured with appropriate kits. The relative expression levels of FPR2 and its ligand were determined by Western blot, and the interaction of them was detected by co-immunoprecipitation. As a result, MEHP exposure could promote the occurrence and progression of steatosis and the secretion of chemokines and inflammatory factors in L02 cells. MEHP could also affect the expression and activation of FPR2 and the secretion of FPR2 ligands. In addition, the promotion effect of MEHP on the secretion of total cholesterol and interleukin 1ß in L02 cells could be significantly inhibited by the FPR2 antagonist. We concluded that FPR2 might affect the promotion effect of MEHP on steatosis of L02 cells by mediating inflammatory response.

FPR3 reprograms glycolytic metabolism and stemness in gastric cancer via calcium-NFATc1 pathway.

Aerobic glycolysis accelerates tumor proliferation and progression, and inhibitors or drugs targeting abnormal cancer metabolism have been developing. Cancer stem-like cells (CSCs) significantly contribute to tumor initiation, metastasis, therapy resistance, and recurrence. Formyl peptide receptor 3 (FPR3), a member of FPR family, involves in inflammation, tissue repair, and angiogenesis. However, studies in exploring the regulatory mechanisms of aerobic glycolysis and CSCs by FPR3 in gastric cancer (GC) remain unknown. Here, we demonstrated that overexpressed FPR3 suppressed glycolytic capacity and stemness of tumor cells, then inhibited GC cells proliferation. Mechanistically, FPR3 impeded cytoplasmic calcium ion flux and hindered nuclear factor of activated T cells 1 (NFATc1) nuclear translocation, leading to the transcriptional inactivation of NFATc1-binding neurogenic locus notch homolog protein 3 (NOTCH3) promoter, subsequently obstructing NOTCH3 expression and the AKT/mTORC1 signaling pathway, and ultimately downregulating glycolysis. Additionally, NFATc1 directly binds to the sex determining region Y-box 2 (SOX2) promoter and modifies stemness in GC. In conclusion, our work illustrated that FPR3 played a negative role in GC progression by modulating NFATc1-mediated glycolysis and stemness in a calcium-dependent manner, providing potential insights into cancer therapy.

Formyl peptide receptor 1 mitigates colon inflammation and maintains mucosal homeostasis through the inhibition of CREB-C/EBPß-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 proinflammatory mediator from immune cells (e.g. macrophages), S100a8, a member of the damage-associated molecular patterns. Notably, the administration of the FPR agonist Cmpd43 ameliorated colon injury in a preclinical mice model of UC, likely via inhibiting phosphorylation of cyclic adenosine monophosphate-response element-binding protein and expression of CCAAT/enhancer-binding protein ß, 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.

Knockout of formyl peptide receptor 1 reduces osteogenesis and bone healing.

AIMS: Formyl peptide receptor 1 (FPR1), from a G-protein coupled receptor family, was previously well-characterized in immune cells. But the function of FPR1 in osteogenesis and fracture healing was rarely reported. This study, using the FPR1 knockout (KO) mouse, is one of the first studies that try to investigate FPR1 function to osteogenic differentiation of bone marrow-derived stem cells (BMSCs) in vitro and bone fracture healing in vivo. MATERIALS AND METHODS: Primary BMSCs were isolated from both FPR1 KO and wild type (WT) mice. Cloned mouse BMSCs (D1 cells) were used to examine role of FoxO1 in FPR1 regulation of osteogenesis. A closed, transverse fracture at the femoral midshaft was created to compare bone healing between KO and WT mice. Biomechanical and structural properties of femur were compared between healthy WT and KO mice. KEY FINDINGS: FPR1 expression increased significantly during osteogenesis of both primary and cloned BMSCs. Compared to BMSCs from FPR1 KO mice, WT BMSCs displayed considerably higher levels of osteogenic markers as well as mineralization. Osteogenesis by D1 cells was inhibited by either an FPR1 antagonist cFLFLF or a specific inhibitor of FoxO1, AS1842856. In addition, the femur from WT mice had better biomechanical properties than FPR1 KO mice. Furthermore, bone healing in WT mice was remarkably improved compared to FPR1 KO mice analyzed by X-ray and micro-CT. SIGNIFICANCE: These findings indicated that FPR1 played a vital role in osteogenic differentiation and regenerative capacity of fractured bone, probably through the activation of FoxO1 related signaling pathways.

The Crosstalk between N-Formyl Peptide Receptors and uPAR in Systemic Sclerosis: Molecular Mechanisms, Pathogenetic Role and Therapeutic Opportunities.

Systemic Sclerosis (SSc) is a heterogeneous autoimmune disease characterized by widespread vasculopathy, the presence of autoantibodies and the progressive fibrosis of skin and visceral organs. There are still many questions about its pathogenesis, particularly related to the complex regulation of the fibrotic process, and to the factors that trigger its onset. Our recent studies supported a key role of N-formyl peptide receptors (FPRs) and their crosstalk with uPAR in the fibrotic phase of the disease. Here, we found that dermal fibroblasts acquire a proliferative phenotype after the activation of FPRs and their interaction with uPAR, leading to both Rac1 and ERK activation, c-Myc phosphorylation and Cyclin D1 upregulation which drive cell cycle progression. The comparison between normal and SSc fibroblasts reveals that SSc fibroblasts exhibit a higher proliferative rate than healthy control, suggesting that an altered fibroblast proliferation could contribute to the initiation and progression of the fibrotic process. Finally, a synthetic compound targeting the FPRs/uPAR interaction significantly inhibits SSc fibroblast proliferation, paving the way for the development of new targeted therapies in fibrotic diseases.

FPR1: A critical gatekeeper of the heart and brain.

G protein-coupled receptors (GPCRs) are currently the most widely focused drug targets in the clinic, exerting their biological functions by binding to chemicals and activating a series of intracellular signaling pathways. Formyl-peptide receptor 1 (FPR1) has a typical seven-transmembrane structure of GPCRs and can be stimulated by a large number of endogenous or exogenous ligands with different chemical properties, the first of which was identified as formyl-methionine-leucyl-phenylalanine (fMLF). Through receptor-ligand interactions, FPR1 is involved in inflammatory response, immune cell recruitment, and cellular signaling regulation in key cell types, including neutrophils, neural stem cells (NSCs), and microglia. This review outlines the critical roles of FPR1 in a variety of heart and brain diseases, including myocardial infarction (MI), ischemia/reperfusion (I/R) injury, neurodegenerative diseases, and neurological tumors, with particular emphasis on the milestones of FPR1 agonists and antagonists. Therefore, an in-depth study of FPR1 contributes to the research of innovative biomarkers, therapeutic targets for heart and brain diseases, and clinical applications.

Microglial uptake of hADSCs-Exo mitigates neuroinflammation in ICH.

Intracerebral hemorrhage (ICH) is associated with secondary neuroinflammation, leading to severe central nervous system damage. Exosomes derived from human adipose-derived mesenchymal stem cells (hADSCs-Exo) have shown potential therapeutic effects in regulating inflammatory responses in ICH. This study aims to investigate the role of hADSCs-Exo in ICH and its underlying mechanism involving miRNA-mediated regulation of formyl peptide receptor 1 (FPR1). Flow cytometry was used to identify hADSCs and extract exosomes. Transmission electron microscopy and Western blot were performed to confirm the characteristics of the exosomes. In vitro experiments were conducted to explore the uptake of hADSCs-Exo by microglia cells and their impact on inflammatory responses. In vivo, an ICH mouse model was established, and the therapeutic effects of hADSCs-Exo were evaluated through neurological function scoring, histological staining, and immunofluorescence. Bioinformatics tools and experimental validation were employed to identify miRNAs targeting FPR1. hADSCs-Exo were efficiently taken up by microglia cells and exhibited anti-inflammatory effects by suppressing the release of inflammatory factors and promoting M1 to M2 transition. In the ICH mouse model, hADSCs-Exo significantly improved neurological function, reduced hemorrhage volume, decreased neuronal apoptosis, and regulated microglia polarization. miR-342-3p was identified as a potential regulator of FPR1 involved in the neuroprotective effects of hADSCs-Exo in ICH. hADSCs-Exo alleviate neuroinflammation in ICH through miR-342-3p-dependent targeting of FPR1, providing a new therapeutic strategy for ICH.

Enhancement of LC3-associated efferocytosis for the alleviation of intestinal inflammation.

LC3-associated phagocytosis (LAP) is an instrumental machinery for the clearance of extracellular particles including apoptotic cells for the alleviation of inflammation. While pharmacological approaches to modulate LAP for inflammation regulation have been poorly explored, in our study we identified a novel compound, columbamine (COL), which can trigger LAP and enhance efferocytosis in an animal model of colitis to attenuate inflammation. We found that COL directly binds to and biasedly activates FPR2 (formyl peptide receptor 2) to promote efferocytosis and alleviate colitis. Biochemically, COL induces an interaction between RAC1 and the PIK3C3/VPS34-RUBCN/RUBICON complex, stimulating LC3-associated efferocytosis. These findings provide a novel interpretation of the potential roles of LAP in regulating inflammatory bowel disease (IBD), reveal the relationship between G protein-coupled receptors (GPCRs) and LAP, and highlight the role of RAC1 in regulating the PIK3C3/VPS34-RUBCN complex in LAP.

FPR1 Antagonist (BOC-MLF) Inhibits Amniotic Epithelial-mesenchymal Transition.

OBJECTIVE: Premature rupture of membranes (PROM) is a common pregnancy disorder that is closely associated with structural weakening of fetal membranes. Studies have found that formyl peptide receptor 1 (FPR1) activates inflammatory pathways and amniotic epithelialmesenchymal transition (EMT), stimulates collagen degradation, and leads to membrane weakening and membrane rupture. The purpose of this study was to investigate the anti-inflammatory and EMT inhibitory effects of FPR1 antagonist (BOC-MLF) to provide a basis for clinical prevention of PROM. METHODS: The relationship between PROM, FPR1, and EMT was analyzed in human fetal membrane tissue and plasma samples using Western blotting, PCR, Masson staining, and ELISA assays. Lipopolysaccharide (LPS) was used to establish a fetal membrane inflammation model in pregnant rats, and BOC-MLF was used to treat the LPS rat model. We detected interleukin (IL)-6 in blood from the rat hearts to determine whether the inflammatory model was successful and whether the anti-inflammatory treatment was effective. We used electron microscopy to analyze the structure and collagen expression of rat fetal membrane. RESULTS: Western blotting, PCR and Masson staining indicated that the expression of FPR1 was significantly increased, the expression of collagen was decreased, and EMT appeared in PROM. The rat model indicated that LPS caused the collapse of fetal membrane epithelial cells, increased intercellular gaps, and decreased collagen. BOC-MLF promoted an increase in fetal membrane collagen, inhibited EMT, and reduced the weakening of fetal membranes. CONCLUSION: The expression of FPR1 in the fetal membrane of PROM was significantly increased, and EMT of the amniotic membrane was obvious. BOC-MLF can treat inflammation and inhibit amniotic EMT.

Larixol is not an inhibitor of Gαi containing G proteins and lacks effect on signaling mediated by human neutrophil expressed formyl peptide receptors.

Neutrophils express several G protein-coupled receptors (GPCRs) connected to intracellular Gαi or Gαq containing G proteins for down-stream signaling. To dampen GPCR mediated inflammatory processes, several inhibitors targeting the receptors and/or their down-stream signals, have been developed. Potent and selective inhibitors for Gαq containing G proteins are available, but potent and specific inhibitors of Gαi containing G proteins are lacking. Recently, Larixol, a compound extracted from the root of Euphorbia formosana, was shown to abolish human neutrophil functions induced by N-formyl-methionyl-leucyl-phenylalanine (fMLF), an agonist recognized by formyl peptide receptor 1 (FPR1) which couple to Gαi containing G proteins. The inhibitory effect was suggested to be due to interference with/inhibition of signals transmitted by ßγ complexes of the Gαi containing G proteins coupled to FPR1. In this study, we applied Larixol, obtained from two different commercial sources, to determine the receptor- and G protein- selectivity of this compound in human neutrophils. However, our data show that Larixol not only lacks inhibitory effect on neutrophil responses mediated through FPR1, but also on responses mediated through FPR2, a Gαi coupled GPCR closely related to FPR1. Furthermore, Larixol did not display any features as a selective inhibitor of neutrophil responses mediated through the Gαq coupled GPCRs for platelet activating factor and ATP. Hence, our results imply that the inhibitory effects described for the root extract of Euphorbia formosana are not mediated by Larixol and that the search for a selective inhibitor of G protein dependent signals generated by Gαi coupled neutrophil GPCRs must continue.

Lipoxin-mediated signaling: ALX/FPR2 interaction and beyond.

In the aftermath of tissue injury or infection, an efficient resolution mechanism is crucial to allow tissue healing and preserve appropriate organ functioning. Pro-resolving bioactive lipids prevent uncontrolled inflammation and its consequences. Among these mediators, lipoxins were the first described and their pro-resolving actions have been mainly described in immune cells. They exert their actions mostly through formyl-peptide receptor 2 (ALX/FPR2 receptor), a G-protein-coupled receptor whose biological function is tremendously complex, primarily due to its capacity to mediate variable cellular responses. Moreover, lipoxins can also interact with alternative receptors like the cytoplasmic aryl hydrocarbon receptor, the cysteinyl-leukotrienes receptors or GPR32, triggering different intracellular signaling pathways. The available information about this complex response mediated by lipoxins is addressed in this review, going over the different mechanisms used by these molecules to stop the inflammatory reaction and avoid the development of dysregulated and chronic pathologies.

Microglia Depletion Attenuates the Pro-Resolving Activity of the Formyl Peptide Receptor 2 Agonist AMS21 Related to Inhibition of Inflammasome NLRP3 Signalling Pathway: A Study of Organotypic Hippocampal Cultures.

Microglial cells have been demonstrated to be significant resident immune cells that maintain homeostasis under physiological conditions. However, prolonged or excessive microglial activation leads to disturbances in the resolution of inflammation (RoI). Formyl peptide receptor 2 (FPR2) is a crucial player in the RoI, interacting with various ligands to induce distinct conformational changes and, consequently, diverse biological effects. Due to the poor pharmacokinetic properties of endogenous FPR2 ligands, the aim of our study was to evaluate the pro-resolving effects of a new ureidopropanamide agonist, compound AMS21, in hippocampal organotypic cultures (OHCs) stimulated with lipopolysaccharide (LPS). Moreover, to assess whether AMS21 exerts its action via FPR2 specifically located on microglial cells, we conducted a set of experiments in OHCs depleted of microglial cells using clodronate. We demonstrated that the protective and anti-inflammatory activity of AMS21 manifested as decreased levels of lactate dehydrogenase (LDH), nitric oxide (NO), and proinflammatory cytokines IL-1ß and IL-6 release evoked by LPS in OHCs. Moreover, in LPS-stimulated OHCs, AMS21 treatment downregulated NLRP3 inflammasome-related factors (CASP1, NLRP3, PYCARD) and this effect was mediated through FPR2 because it was blocked by the FPR2 antagonist WRW4 pre-treatment. Importantly this beneficial effect of AMS21 was only observed in the presence of microglial FPR2, and absent in OHCs depleted with microglial cells using clodronate. Our results strongly suggest that the compound AMS21 exerts, at nanomolar doses, protective and anti-inflammatory properties and an FPR2 receptor located specifically on microglial cells mediates the anti-inflammatory response of AMS21. Therefore, microglial FPR2 represents a promising target for the enhancement of RoI.

Development of potent isoflavone-based formyl peptide receptor 1 (FPR1) antagonists and their effects in gastric cancer cell models.

Formyl peptide receptor-1 (FPR1) is a G protein-coupled chemoattractant receptor that plays a crucial role in the trafficking of leukocytes into the sites of bacterial infection and inflammation. Recently, FPR1 was shown to be expressed in different types of tumor cells and could play a significant role in tumor growth and invasiveness. Starting from the previously reported FPR1 antagonist 4, we have designed a new series of 4H-chromen-2-one derivatives that exhibited a substantial increase in FPR1 antagonist potency. Docking studies identified the key interactions for antagonist activity. The most potent compounds in this series (24a and 25b) were selected to study the effects of the pharmacological blockade of FPR1 in NCl-N87 and AGS gastric cancer cells. Both compounds potently inhibited cell growth through a combined effect on cell proliferation and apoptosis and reduced cell migration, while inducing an increase in angiogenesis, thus suggesting that FPR1 could play a dual role as oncogene and onco-suppressor.