Signal relay by CC chemokine receptor 2 (CCR2) and formylpeptide receptor 2 (Fpr2) in the recruitment of monocyte-derived dendritic cells in allergic airway inflammation

Developmental and homeostatic signaling transmitted by the G-protein coupled receptor FPR2

Formyl peptide receptor 2 (FPR2) and its mouse counterpart Fpr2 are the members of the G protein-coupled receptor (GPCR) family. FPR2 is the only member of the FPRs that interacts with ligands from different sources. FPR2 is expressed in myeloid cells as well as epithelial cells, endothelial cells, neurons, and hepatocytes. During the past years, some unusual properties of FPR2 have attracted intense attention because FPR2 appears to possess dual functions by activating or inhibiting intracellular signal pathways based on the nature, concentration of the ligands, and the temporal and spatial settings of the microenvironment in vivo, the cell types it interacts with. Therefore, FPR2 controls an abundant array of developmental and homeostatic signaling cascades, in addition to its "classical" capacity to mediate the migration of hematopoietic and non-hematopoietic cells including malignant cells. In this review, we summarize recent development in FPR2 research, particularly in its role in diseases, therefore helping to establish FPR2 as a potential target for therapeutic intervention.

Strategy and application of manipulating DCs chemotaxis in disease treatment and vaccine design

As the most versatile antigen-presenting cells (APCs), dendritic cells (DCs) function as the cardinal commanders in orchestrating innate and adaptive immunity for either eliciting protective immune responses against canceration and microbial invasion or maintaining immune homeostasis/tolerance. In fact, in physiological or pathological conditions, the diversified migratory patterns and exquisite chemotaxis of DCs, prominently manipulate their biological activities in both secondary lymphoid organs (SLOs) as well as homeostatic/inflammatory peripheral tissues in vivo. Thus, the inherent mechanisms or regulation strategies to modulate the directional migration of DCs even could be regarded as the crucial cartographers of the immune system. Herein, we systemically reviewed the existing mechanistic understandings and regulation measures of trafficking both endogenous DC subtypes and reinfused DCs vaccines towards either SLOs or inflammatory foci (including neoplastic lesions, infections, acute/chronic tissue inflammations, autoimmune diseases and graft sites). Furthermore, we briefly introduced the DCs-participated prophylactic and therapeutic clinical application against disparate diseases, and also provided insights into the future clinical immunotherapies development as well as the vaccines design associated with modulating DCs mobilization modes.

Gastric alarmin release: A warning signal in the development of gastric mucosal diseases

Alarmins exist outside cells and are early warning signals to the immune system; as such, alarmin receptors are widely distributed on various immune cells. Alarmins, proinflammatory molecular patterns associated with tissue damage, are usually released into the extracellular space, where they induce immune responses and participate in the damage and repair processes of mucosal diseases.In the stomach, gastric alarmin release has been shown to be involved in gastric mucosal inflammation, antibacterial defense, adaptive immunity, and wound healing; moreover, this release causes damage and results in the development of gastric mucosal diseases, including various types of gastritis, ulcers, and gastric cancer. Therefore, it is necessary to understand the role of alarmins in gastric mucosal diseases. This review focuses on the contribution of alarmins, including IL33, HMGB1, defensins and cathelicidins, to the gastric mucosal barrier and their role in gastric mucosal diseases. Here, we offer a new perspective on the prevention and treatment of gastric mucosal diseases.

A Stable Chemokine Gradient Controls Directional Persistence of Migrating Dendritic Cells

Navigation of dendritic cells (DCs) from the site of infection to lymphoid organs is guided by concentration gradients of CCR7 ligands. How cells interpret chemokine gradients and how they couple directional sensing to polarization and persistent chemotaxis has remained largely elusive. Previous experimental systems were limited in the ability to control fast de novo formation of the final gradient slope, long-lasting stability of the gradient and to expose cells to dynamic stimulation. Here, we used a combination of microfluidics and quantitative in vitro live cell imaging to elucidate the chemotactic sensing strategy of DCs. The microfluidic approach allows us to generate soluble gradients with high spatio-temporal precision and to analyze actin dynamics, cell polarization, and persistent directional migration in both static and dynamic environments. We demonstrate that directional persistence of DC migration requires steady-state characteristics of the soluble gradient instead of temporally rising CCL19 concentration, implying that spatial sensing mechanisms control chemotaxis of DCs. Kymograph analysis of actin dynamics revealed that the presence of the CCL19 gradient is essential to stabilize leading edge protrusions in DCs and to determine directionality, since both cytoskeletal polarization and persistent chemotaxis are abrogated in the range of seconds when steady-state gradients are perturbed. In contrast to Dictyostelium amoeba, DCs are unable to decode oscillatory stimulation of soluble chemokine traveling waves into a directional response toward the wave source. These findings are consistent with the notion that DCs do not employ adaptive temporal sensing strategies that discriminate temporally increasing and decreasing chemoattractant concentrations in our setting. Taken together, in our experimental system DCs do not depend on increasing absolute chemokine concentration over time to induce persistent migration and do not integrate oscillatory stimulation. The observed capability of DCs to migrate with high directional persistence in stable gradients but not when subjected to periodic temporal cues, identifies spatial sensing as a key requirement for persistent chemotaxis of DCs.

A Scoping Analysis of Cathelicidin in Response to Organic Dust Exposure and Related Chronic Lung Illnesses

Over two billion people worldwide are exposed to organic dust, which can cause respiratory disorders. The discovery of the cathelicidin peptide provides novel insights into the lung's response to organic dust; however, its role in the lung's response to organic dust exposure and chronic lung diseases remains limited. We conducted a scoping review to map the current evidence on the role of cathelicidin LL-37/CRAMP in response to organic dust exposure and related chronic lung diseases: hypersensitivity pneumonitis (HP), chronic obstructive pulmonary disease (COPD) and asthma. We included a total of n = 53 peer-reviewed articles in this review, following the process of (i) a preliminary screening; (ii) a systematic MEDLINE/PubMed database search; (iii) title, abstract and full-text screening; (iv) data extraction and charting. Cathelicidin levels were shown to be altered in all clinical settings investigated; its pleiotropic function was confirmed. It was found that cathelicidin contributes to maintaining homeostasis and participates in lung injury response and repair, in addition to exerting a positive effect against microbial load and infections. In addition, LL-37 was found to sustain continuous inflammation, increase mucus formation and inhibit microorganisms and corticosteroids. In addition, studies investigated cathelicidin as a treatment modality, such as cathelicidin inhalation in experimental HP, which had positive effects. However, the primary focus of the included articles was on LL-37's antibacterial effect, leading to the conclusion that the beneficial LL-37 activity has not been adequately examined and that further research is required.

Dynamic Urinary Proteome Changes in Ovalbumin-Induced Asthma Mouse Model Using Data-Independent Acquisition Proteomics

Background

In this work, we aim to investigate dynamic urinary proteome changes during asthma development and to identify potential urinary protein biomarkers for the diagnosis of asthma.

Methods

An ovalbumin (OVA)-induced mouse model was used to mimic asthma. The urinary proteome from asthma and control mice was determined using data-independent acquisition combined with high-resolution tandem mass spectrometry.

Results

Overall, 331 proteins were identified, among which 53 were differentially expressed (26, 24, 14 and 20 on days 2, 8, 15 and 18, respectively; 1.5-fold change, adjust P<0.05). Gene Ontology annotation of the differential proteins showed that the acute-phase response, innate immune response, B cell receptor signaling pathway, and complement activation were significantly enriched. Protein–protein interaction network revealed that these differential proteins were partially biologically connected in OVA-induced asthma, as a group. On days 2 and 8, after two episodes of OVA sensitization, six differential proteins (CRAMP, ECP, HP, F2, AGP1, and CFB) were also reported to be closely associated with asthma. These proteins may hold the potential for the early screening of asthma. On days 15 and 18, after challenged with 1% OVA by inhalation, seven differential proteins (VDBP, HP, CTSE, PIGR, AAT, TRFE, and HPX) were also reported to be closely associated with asthma. Thus, these proteins hold the potential to be biomarkers for the diagnosis of asthma attack.

Conclusion

Our results indicate that the urinary proteome could reflect dynamic pathophysiological changes in asthma progression.

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 T_H 1 and T_H 17 cells in the spleens of CIA mice. WKYMVm attenuated T_H 1 and T_H 17 differentiation in a dendritic cell (DC)-dependent manner. WKYMVm-induced beneficial effects against CIA and WKYMVm-attenuated T_H 1 and T_H 17 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 T_H 1 and T_H 17 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 T_H 1 and T_H 17 cells via IL-10 production, providing novel insight into the function of FPR1 in regulating CIA pathogenesis.

PTX3 Deficiency Promotes Enhanced Accumulation and Function of CD11c+CD11b+ DCs in a Murine Model of Allergic Inflammation

PTX3 is a unique member of the long pentraxins family and plays an indispensable role in regulating the immune system. We previously showed that PTX3 deletion aggravates allergic inflammation via a Th17 -dominant phenotype and enhanced CD4 T cell survival using a murine model of ovalbumin (OVA) induced allergic inflammation. In this study, we identified that upon OVA exposure, increased infiltration of CD11c⁺CD11b⁺ dendritic cells (DCs) was observed in the lungs of PTX3^-/- mice compared to wild type littermate. Further analysis showed that a short-term OVA exposure led to an increased number of bone marrow common myeloid progenitors (CMP) population concomitantly with increased Ly6C^high CCR2^high monocytes and CD11c⁺CD11b⁺ DCs in the lungs. Also, pulmonary CD11c⁺CD11b⁺ DCs from OVA-exposed PTX3^-/- mice exhibited enhanced expression of maturation markers, chemokines receptors CCR2, and increased OVA uptake and processing compared to wild type controls. Taken together, our data suggest that PTX3 deficiency heightened lung CD11c⁺CD11b⁺DC numbers and function, hence exacerbating airway inflammatory response.

Requirement of CRAMP for mouse macrophages to eliminate phagocytosed E. coli through an autophagy pathway

Host-derived antimicrobial peptides play an important role in the defense against extracellular bacterial infections. However, the capacity of antimicrobial peptides derived from macrophages as potential antibacterial effectors against intracellular pathogens remains unknown. In this study, we report that normal (wild-type, WT) mouse macrophages increased their expression of cathelin-related antimicrobial peptide (CRAMP, encoded by Camp) after infection by viable E. coli or stimulation with inactivated E. coli and its product lipopolysaccharide (LPS), a process involving activation of NF-κB followed by protease-dependent conversion of CRAMP from an inactive precursor to an active form. The active CRAMP was required by WT macrophages for elimination of phagocytosed E. coli, with participation of autophagy-related proteins ATG5, LC3-II and LAMP-1, as well as for aggregation of the bacteria with p62 (also known as SQSTM1). This process was impaired in CRAMP-/- macrophages, resulting in retention of intracellular bacteria and fragmentation of macrophages. These results indicate that CRAMP is a critical component in autophagy-mediated clearance of intracellular E. coli by mouse macrophages.

Distinct contributions of cathelin-related antimicrobial peptide (CRAMP) derived from epithelial cells and macrophages to colon mucosal homeostasis

The cathelin‐related antimicrobial peptide CRAMP protects the mouse colon from inflammation, inflammation‐associated carcinogenesis, and disrupted microbiome balance, as shown in systemic Cnlp^−/− mice (also known as Camp^−/− mice). However, the mechanistic basis for the role and the cellular source of CRAMP in colon pathophysiology are ill defined. This study, using either epithelial or myeloid conditional Cnlp^−/−mice, demonstrated that epithelial cell‐derived CRAMP played a major role in supporting normal development of colon crypts, mucus production, and repair of injured mucosa. On the other hand, myeloid cell‐derived CRAMP potently supported colon epithelial resistance to bacterial invasion during acute inflammation with exacerbated mucosal damage and higher rate of mouse mortality. Therefore, a well concerted cooperation of epithelial‐ and myeloid‐derived CRAMP is essential for colon mucosal homeostasis. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Formyl peptide receptors in the mucosal immune system

Formyl peptide receptors (FPRs) belong to the G protein-coupled receptor (GPCR) family and are well known as chemotactic receptors and pattern recognition receptors (PRRs) that recognize bacterial and mitochondria-derived formylated peptides. FPRs are also known to detect a wide range of ligands, including host-derived peptides and lipids. FPRs are highly expressed not only in phagocytes such as neutrophils, monocytes, and macrophages but also in nonhematopoietic cells such as epithelial cells and endothelial cells. Mucosal surfaces, including the gastrointestinal tract, the respiratory tract, the oral cavity, the eye, and the reproductive tract, separate the external environment from the host system. In mucosal surfaces, the interaction between the microbiota and host cells needs to be strictly regulated to maintain homeostasis. By sharing the same FPRs, immune cells and epithelial cells may coordinate pathophysiological responses to various stimuli, including microbial molecules derived from the normal flora. Accumulating evidence shows that FPRs play important roles in maintaining mucosal homeostasis. In this review, we summarize the roles of FPRs at mucosal surfaces.

Role of Chemokines in the Biology of Cholangiocarcinoma

Cholangiocarcinoma (CCA), a heterogeneous tumor with poor prognosis, can arise at any level in the biliary tree. It may derive from epithelial cells in the biliary tracts and peribiliary glands and possibly from progenitor cells or even hepatocytes. Several risk factors are responsible for CCA onset, however an inflammatory milieu nearby the biliary tree represents the most common condition favoring CCA development. Chemokines play a key role in driving the immunological response upon liver injury and may sustain tumor initiation and development. Chemokine receptor-dependent pathways influence the interplay among various cellular components, resulting in remodeling of the hepatic microenvironment towards a pro-inflammatory, pro-fibrogenic, pro-angiogenic and pre-neoplastic setting. Moreover, once tumor develops, chemokine signaling may influence its progression. Here we review the role of chemokines in the regulation of CCA development and progression, and the modulation of angiogenesis, metastasis and immune control. The potential role of chemokines and their receptors as possible biomarkers and/or therapeutic targets for hepatobiliary cancer is also discussed.

The Contribution of Chemoattractant GPCRs, Formylpeptide Receptors, to Inflammation and Cancer

A hallmark of inflammatory responses is leukocyte mobilization, which is mediated by pathogen and host released chemotactic factors that activate Gi-protein-coupled seven-transmembrane receptors (GPCRs) on host cell surface. Formylpeptide receptors (FPRs, Fprs in mice) are members of the chemoattractant GPCR family, shown to be critical in myeloid cell trafficking during infection, inflammation, immune responses, and cancer progression. Accumulating evidence demonstrates that both human FPRs and murine Fprs are involved in a number of patho-physiological processes because of their expression on a wide variety of cell types in addition to myeloid cells. The unique capacity of FPRs (Fprs) to interact with numerous structurally unrelated chemotactic ligands enables these receptors to participate in orchestrated disease initiation, progression, and resolution. One murine Fpr member, Fpr2, and its endogenous agonist peptide, Cathelicidin-related antimicrobial peptide (CRAMP), have been demonstrated as key mediators of colon mucosal homeostasis and protection from inflammation and associated tumorigenesis. Recent availability of genetically engineered mouse models greatly expanded the understanding of the role of FPRs (Fprs) in pathophysiology that places these molecules in the list of potential targets for therapeutic intervention of diseases.

Exploring the complex role of chemokines and chemoattractants in vivo on leukocyte dynamics

Chemotaxis is fundamental for leukocyte migration in immunity and inflammation and contributes to the pathogenesis of many human diseases. Although chemokines and various other chemoattractants were initially appreciated as important mediators of acute inflammation, in the past years they have emerged as critical mediators of cell migration during immune surveillance, organ development, and cancer progression. Such advances in our knowledge in chemokine biology have paved the way for the development of specific pharmacological targets with great therapeutic potential. Chemoattractants may belong to different classes, including a complex chemokine system of approximately 50 endogenous molecules that bind to G protein-coupled receptors, which are expressed by a wide variety of cell types. Also, an unknown number of other chemoattractants may be generated by pathogens and damaged/dead cells. Therefore, blocking chemotaxis without causing side effects is an extremely challenging task. In this review, we focus on recent advances in understanding how the chemokine system orchestrates immune cell migration and positioning at the whole organ level in homeostasis, inflammation, and infection.

Formyl peptide receptor 2 regulates monocyte recruitment to promote intestinal mucosal wound repair

Mucosal wound repair is coordinated by dynamic crosstalk between endogenous and exogenous mediators and specific receptors on epithelial cells and infiltrating immune cells. One class of such receptor-ligand pairs involves formyl peptide receptors (FPRs) that have been shown to influence inflammatory response and repair. Here we explored the role of murine Fpr2/3, an ortholog of human FPR2/receptor for lipoxin A4 (ALX), in orchestrating intestinal mucosal repair. Compared with wild-type (WT) mice, Fpr2/3-/- mice exhibited delayed recovery from acute experimental colitis and perturbed repair after biopsy-induced colonic mucosal injury. Decreased numbers of infiltrating monocytes were observed in healing wounds from Fpr2/3-/- mice compared with WT animals. Bone marrow transplant experiments revealed that Fpr2/3-/- monocytes showed a competitive disadvantage when infiltrating colonic wounds. Moreover, Fpr2/3-/- monocytes were defective in chemotactic responses to the chemokine CC chemokine ligand (CCL)20, which is up-regulated during early phases of inflammation. Analysis of Fpr2/3-/- monocytes revealed altered expression of the CCL20 receptor CC chemokine receptor (CCR)6, suggesting that Fpr2/3 regulates CCL20-CCR6-mediated monocyte chemotaxis to sites of mucosal injury in the gut. These findings demonstrate an important contribution of Fpr2/3 in facilitating monocyte recruitment to sites of mucosal injury to influence wound repair.-Birkl, D., O'Leary, M. N., Quiros, M., Azcutia, V., Schaller, M., Reed, M., Nishio, H., Keeney, J., Neish, A. S., Lukacs, N. W., Parkos, C. A., Nusrat, A. Formyl peptide receptor 2 regulates monocyte recruitment to promote intestinal mucosal wound repair.

Formyl peptide receptor-2 is decreased in foetal growth restriction and contributes to placental dysfunction

STUDY QUESTION

What is the association between placental formyl peptide receptor 2 (FPR2) and trophoblast and endothelial functions in pregnancies affected by foetal growth restriction (FGR)?

SUMMARY ANSWER

Reduced FPR2 placental expression in idiopathic FGR results in significantly altered trophoblast differentiation and endothelial function in vitro.

WHAT IS KNOWN ALREADY

FGR is associated with placental insufficiency, where defective trophoblast and endothelial functions contribute to reduced feto-placental growth.

STUDY DESIGN, SIZE, DURATION

The expression of FPR2 in placental tissues from human pregnancies complicated with FGR was compared to that in gestation-matched uncomplicated control pregnancies (n = 25 from each group). Fpr2 expression was also determined in placental tissues obtained from a murine model of FGR (n = 4). The functional role of FPR2 in primary trophoblasts and endothelial cells in vitro was assessed in diverse assays in a time-dependent manner.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Placentae from third-trimester pregnancies complicated by idiopathic FGR (n = 25) and those from gestation-matched pregnancies with appropriately grown infants as controls (n = 25) were collected at gestation 27-40 weeks. Placental tissues were also collected from a spontaneous CBA/CaH × DBA/2 J murine model of FGR. Placental FPR2/Fpr2 mRNA expression was determined by real-time PCR, while protein expression was examined by immunoblotting and immunohistochemistry. siRNA transfection was used to silence FPR2 expression in primary trophoblasts and in human umbilical vein endothelial cells (HUVEC), and the quantitation of cytokines, chemokines and apoptosis was performed following a cDNA array analyses. Functional effects of trophoblast differentiation were measured using HCGB/β-hCG and syncytin-2 expression as well as markers of apoptosis, tumour protein 53 (TP53), caspase 8, B cell lymphoma 2 (BCL2) and BCL associated X (BAX). Endothelial function was assessed by proliferation, network formation and permeability assays.

MAIN RESULTS AND THE ROLE OF CHANCE

Placental FPR2/Fpr2 expression was significantly decreased in FGR placentae (n = 25, P < 0.05) as well as in murine FGR placentae compared to controls (n = 4, P < 0.05). FPR2 siRNA (siFPR2) in term trophoblasts significantly increased differentiation markers, HCGB and syncytin-2; cytokines, interleukin (IL)-6, CXCL8; and apoptotic markers, TP53, caspase 8 and BAX, but significantly reduced the expression of the chemokines CXCL12 and its receptors CXCR4 and CXCR7; CXCL16 and its receptor, CXCR6; and cytokine, IL-10, compared with control siRNA (siCONT). Treatment of HUVECs with siFPR2 significantly reduced proliferation and endothelial tube formation, but significantly increased permeability of HUVECs.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Reduced expression of placental FPR2/Fpr2 was observed in the third trimester at delivery after development of FGR, suggesting that FPR2 is associated with FGR pregnancies. However, there is a possibility that the decreased placental FPR2 observed in FGR may be a consequence rather than a cause of FGR, although our in vitro functional analyses using primary trophoblasts and endothelial cells suggest that FPR2 may have a direct or indirect regulatory role on trophoblast differentiation and endothelial function in FGR.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study linking placental FPR2 expression with changes in the trophoblast and endothelial functions that may explain the placental insufficiency observed in FGR.

STUDY FUNDING/COMPETING INTERESTS

P.M. and P.R.E. received funding from the Australian Institute of Musculoskeletal Science, Western Health, St. Albans, Victoria 3021, Australia. M.L. is supported by a Career Development Fellowship from the National Health and Medical Research Council (NHMRC; Grant no. 1047025). Monash Health is supported by the Victorian Government's Operational Infrastructure Support Programme. The authors declare that there is no conflict of interest in publishing this work.

The Critical Role of the Antimicrobial Peptide LL-37/ CRAMP in Protection of Colon Microbiota Balance, Mucosal Homeostasis, Anti-Inflammatory Responses, and Resistance to Carcinogenesis

Mouse cathelin-related antimicrobial peptide (CRAMP) and its homologue human cathelicidin (LL-37) play active roles in innate immune responses, angiogenesis, and wound healing. In addition, LL-37/CRAMP fends off microbes and protects against infections in the colon, where the epithelium is exposed to myriad of enteric pathogens. It is increasingly recognized that LL-37/CRAMP maintains colon mucosal barrier integrity, shapes the composition of microbiota, and protects the host from tumorigenesis. In this review, we discuss the importance of LL-37/CRAMP in the homeostasis of the host, with novel findings derived from mice deficient in CRAMP that support the proposition for this natural antimicrobial peptide and an immune modulator as a drug lead for therapeutic development.

Ca2+ and innate immune pathways are activated and differentially expressed in childhood asthma phenotypes

BACKGROUND

Asthma is the most common chronic disease in children. Underlying immunologic mechanisms-in particular of different phenotypes-are still just partly understood. The objective of the study was the identification of distinct cellular pathways in allergic asthmatics (AA) and nonallergic asthmatics (NA) vs healthy controls (HC).

METHODS

Peripheral blood mononuclear cells (PBMCs) of steroid-naïve children (n(AA/NA/HC) = 35/13/34)) from the CLARA study (n = 275) were stimulated (anti-CD3/CD28, LpA) or kept unstimulated. Gene expression was investigated by transcriptomics and quantitative RT-PCR. Differentially regulated pathways between phenotypes were assessed after adjustment for sex and age (KEGG pathways). Networks based on correlations of gene expression were built using force-directed graph drawing.

RESULTS

Allergic asthmatics vs NA and asthmatics overall vs HC showed significantly different expression of Ca²⁺ and innate immunity-associated pathways. PCR analysis confirmed significantly increased Ca²⁺ -associated gene regulation (ORMDL3 and ATP2A3) in asthmatics vs HC, most prominent in AA. Innate immunity receptors (LY75, TLR7), relevant for virus infection, were also upregulated in AA and NA compared to HC. AA and NA could be differentiated by increased ATP2A3 and FPR2 in AA, decreased CLEC4E in AA, and increased IFIH1 expression in NA following anti-CD3/28 stimulation vs unstimulated (fold change).

CONCLUSIONS

Ca²⁺ regulation and innate immunity response pattern to viruses were activated in PBMCs of asthmatics. Asthma phenotypes were differentially characterized by distinct regulation of ATP2A3 and expression of innate immune receptors (FPR2, CLEC4E, IFIH1). These genes may present promising targets for future in-depth investigation with the long-term goal of more phenotype-specific therapeutic interventions in asthmatics.

Deficiency in Fpr2 results in reduced numbers of Lin-cKit+Sca1+ myeloid progenitor cells

The Lin-c-Kit+ Sca-1+ cell population in the bone marrow (BM) serves as the direct precursor for differentiation of myeloid cells. In this study, we report that deficiency in Fpr2, a G protein-coupled chemoattractant receptor in mice, is associated with reduced BM nucleated cells, including CD31+Ly6C+ (granulocytes and monocytes), CD31-/Ly6Cint (granuloid cells), and CD31-/Ly6Chigh (predominantly monocytes) cells. In particular, the number of Lin-c-Kit+Sca-1+ (LKS) cells was reduced in Fpr2-/- mouse BM. This was supported by observations of the reduced incorporation of intraperitoneally injected bromodeoxyuridine by cells in the c-Kit+ population from Fpr2-/- mouse BM. Purified c-Kit+ cells from Fpr2-/- mice showed reduced expansion when cultured in vitro with stem cell factor (SCF). SCF/c-Kit-mediated phosphorylation of P38, STAT1, Akt (Thr-308), and Akt (Ser-473) was also significantly reduced in c-Kit+ cells from Fpr2-/- mice. Furthermore, Fpr2 agonists enhanced SCF-induced proliferation of c-Kit+ cells. Colony-forming unit assays revealed that CFU-granulocyte-macrophage formation of BM cells from Fpr2-/- mice was significantly reduced. After heat-inactivated bacterial stimulation in the airway, the expansion of c-kit+ Sca-1+ cells in BM and recruitment of Ly6G+ cells to the lungs and CD11b+Ly6C+TNFα+ cells to the spleen of Fpr2-/- mice was significantly reduced. These results demonstrate an important role for Fpr2 in the development of myeloid lineage precursors in mouse BM.

Oleoylethanolamide treatment reduces neurobehavioral deficits and brain pathology in a mouse model of Gulf War Illness

There are nearly 250,000 Gulf War (GW) veterans who suffer from Gulf War Illness (GWI), a multi-symptom condition that remains untreatable. The main objective was to determine if targeting peroxisomal function could be of therapeutic value in GWI. We performed a pilot study that showed accumulation of very long chain fatty acids (VLCFA), which are metabolized in peroxisomes, in plasma from veterans with GWI. We then examined if targeting peroxisomal β-oxidation with oleoylethanolamide (OEA) restores these lipids to the normal levels and mitigates neuroinflammation and neurobehavioral deficits in a well-established mouse model of GWI. In GWI mice, treatment with OEA corresponded with cognitive benefits and reduced fatigue and disinhibition-like behavior in GWI mice. Biochemical and molecular analysis of the brain tissue showed reduced astroglia and microglia staining, decreased levels of chemokines and cytokines, and decreased NFκB phosphorylation. Treatment with OEA reduced accumulation of peroxisome specific VLCFA in the brains of GWI mice. These studies further support the translational value of targeting peroxisomes. We expect that OEA may be a potential therapy for treating neurobehavioral symptoms and the underlying lipid dysfunction and neuroinflammation associated with GWI. Oleoylethanolamide is available as a dietary supplement, making it appealing for human translational studies.

Chemokines in homeostasis and diseases

For the past twenty years, chemokines have emerged as a family of critical mediators of cell migration during immune surveillance, development, inflammation and cancer progression. Chemokines bind to seven transmembrane G protein-coupled receptors (GPCRs) that are expressed by a wide variety of cell types and cause conformational changes in trimeric G proteins that trigger the intracellular signaling pathways necessary for cell movement and activation. Although chemokines have evolved to benefit the host, inappropriate regulation or utilization of these small proteins may contribute to or even cause diseases. Therefore, understanding the role of chemokines and their GPCRs in the complex physiological and diseased microenvironment is important for the identification of novel therapeutic targets. This review introduces the functional array and signals of multiple chemokine GPCRs in guiding leukocyte trafficking as well as their roles in homeostasis, inflammation, immune responses and cancer.

Chemokine and chemotactic signals in dendritic cell migration

Dendritic cells (DCs) are professional antigen-presenting cells responsible for the activation of specific T-cell responses and for the development of immune tolerance. Immature DCs reside in peripheral tissues and specialize in antigen capture, whereas mature DCs reside mostly in the secondary lymphoid organs where they act as antigen-presenting cells. The correct localization of DCs is strictly regulated by a large variety of chemotactic and nonchemotactic signals that include bacterial products, DAMPs (danger-associated molecular patterns), complement proteins, lipids, and chemokines. These signals function both individually and in concert, generating a complex regulatory network. This network is regulated at multiple levels through different strategies, such as synergistic interactions, proteolytic processing, and the actions of atypical chemokine receptors. Understanding this complex scenario will help to clarify the role of DCs in different pathological conditions, such as autoimmune diseases and cancers and will uncover new molecular targets for therapeutic interventions.

Chemokine expression in the early response to injury in human airway epithelial cells

Basal airway epithelial cells (AEC) constitute stem/progenitor cells within the central airways and respond to mucosal injury in an ordered sequence of spreading, migration, proliferation, and differentiation to needed cell types. However, dynamic gene transcription in the early events after mucosal injury has not been studied in AEC. We examined gene expression using microarrays following mechanical injury (MI) in primary human AEC grown in submersion culture to generate basal cells and in the air-liquid interface to generate differentiated AEC (dAEC) that include goblet and ciliated cells. A select group of ~150 genes was in differential expression (DE) within 2-24 hr after MI, and enrichment analysis of these genes showed over-representation of functional categories related to inflammatory cytokines and chemokines. Network-based gene prioritization and network reconstruction using the PINTA heat kernel diffusion algorithm demonstrated highly connected networks that were richer in differentiated AEC compared to basal cells. Similar experiments done in basal AEC collected from asthmatic donor lungs demonstrated substantial changes in DE genes and functional categories related to inflammation compared to basal AEC from normal donors. In dAEC, similar but more modest differences were observed. We demonstrate that the AEC transcription signature after MI identifies genes and pathways that are important to the initiation and perpetuation of airway mucosal inflammation. Gene expression occurs quickly after injury and is more profound in differentiated AEC, and is altered in AEC from asthmatic airways. Our data suggest that the early response to injury is substantially different in asthmatic airways, particularly in basal airway epithelial cells.

The G-Protein-Coupled Chemoattractant Receptor Fpr2 Exacerbates High Glucose-Mediated Proinflammatory Responses of Müller Glial Cells

In proliferative diabetic retinopathy (PDR), activated Müller glial cells (MGCs) exhibit increased motility and a fibroblast-like proliferation phenotype that contribute to the formation of fibrovascular membrane. In this study, we investigated the capacity of high glucose (HG) to regulate the expression of cell surface receptors that may participate in the proinflammatory responses of MGCs. We found that MGCs express a G-protein coupled chemoattractant receptor formyl peptide receptor 2 (Fpr2) and fibroblast growth factor receptor 1 (FGFR1), which mediated MGC migration and proliferation in response to corresponding ligands. HG upregulated Fpr2 through an NF-κB pathway in MGCs, increased the activation of MAPKs coupled to Fpr2 and FGFR1, which also further enhanced the production of vascular endothelial growth factor by MGCs in the presence of HG. In vivo, Fpr2 was more highly expressed by retina MGCs of diabetic mice and the human counterpart FPR2 was detected in the retina MGCs in fibrovascular membrane of PDR patients. To support the potential pathological relevance of Fpr2, an endogenous Fpr2 agonist cathelin-related antimicrobial peptide was detected in mouse MGCs and the retina, which was upregulated by HG. These results suggest that Fpr2, together with FGFR1, may actively participate in the pathogenesis of PDR thus may be considered as one of the potential therapeutic targets.

Regulation of inflammation by members of the formyl-peptide receptor family

Inflammation is associated with a variety of diseases. The hallmark of inflammation is leukocyte infiltration at disease sites in response to pathogen- or damage-associated chemotactic molecular patterns (PAMPs and MAMPs), which are recognized by a superfamily of seven transmembrane, Gi-protein-coupled receptors (GPCRs) on cell surface. Chemotactic GPCRs are composed of two major subfamilies: the classical GPCRs and chemokine GPCRs. Formyl-peptide receptors (FPRs) belong to the classical chemotactic GPCR subfamily with unique properties that are increasingly appreciated for their expression on diverse host cell types and the capacity to interact with a plethora of chemotactic PAMPs and MAMPs. Three FPRs have been identified in human: FPR1-FPR3, with putative corresponding mouse counterparts. FPR expression was initially described in myeloid cells but subsequently in many non-hematopoietic cells including cancer cells. Accumulating evidence demonstrates that FPRs possess multiple functions in addition to controlling inflammation, and participate in the processes of many pathophysiologic conditions. They are not only critical mediators of myeloid cell trafficking, but are also implicated in tissue repair, angiogenesis and protection against inflammation-associated tumorigenesis. A series recent discoveries have greatly expanded the scope of FPRs in host defense which uncovered the essential participation of FPRs in step-wise trafficking of myeloid cells including neutrophils and dendritic cells (DCs) in host responses to bacterial infection, tissue injury and wound healing. Also of great interest is the FPRs are exploited by malignant cancer cells for their growth, invasion and metastasis. In this article, we review the current understanding of FPRs concerning their expression in a vast array of cell types, their involvement in guiding leukocyte trafficking in pathophysiological conditions, and their capacity to promote the differentiation of immune cells, their participation in tumor-associated inflammation and cancer progression. The close association of FPRs with human diseases and cancer indicates their potential as targets for the development of therapeutics.

Exogenous murine antimicrobial peptide CRAMP significantly exacerbates Ovalbumin-induced airway inflammation but ameliorates oxazolone-induced intestinal colitis in BALB/c mice

Cathelicidin has been reported to be multifunctional. The current study aimed to investigate the influences of exogenous cathelicidin-related antimicrobial peptide (CRAMP) on inflammatory responses in different disease models. In OVA-induced allergic airway inflammation, CRAMP significantly enhanced the infiltration of inflammatory cells and accumulation of proinflammatory Th2 cytokine IL-13 and IL-33 in bronchial alveolar lavage fluid (BALF), exacerbated lung tissue inflammation and airway goblet cell hyperplasia, and elevated OVA-specific IgE level in serum. In oxazolone-induced intestinal colitis, the expression levels of CRAMP and its receptor FPR2 significantly increased in comparison with those of TNBS-induced mice, vesicle and normal controls. Exogenous CRAMP significantly prevented the development of ulcerative colitis, evidenced by improved body weight regain, decreased colons weight/length ratio, elevated epithelial integrity, and ameliorated colon tissue inflammation. In addition, pro-inflammatory cytokines TNF-α, IL-1β, IL-4 and IL-13, as well as chemokines CXCL2 and CXCL5 for neutrophils recruitment were significantly decreased in CRAMP-treated mice, and epithelial repair-related factors MUC2 and Claudin1 were increased, determined by real time-PCR and ELISAs. The results indicated that although CRAMP has pro-inflammatory effects in airway, local application of exogenous CRAMP might be a potential approach for the treatment of ulcerative colitis.

CRAMP deficiency leads to a pro-inflammatory phenotype and impaired phagocytosis after exposure to bacterial meningitis pathogens

BACKGROUND

Antimicrobial peptides are important components of the host defence with a broad range of functions including direct antimicrobial activity and modulation of inflammation. Lack of cathelin-related antimicrobial peptide (CRAMP) was associated with higher mortality and bacterial burden and impaired neutrophil granulocyte infiltration in a model of pneumococcal meningitis. The present study was designed to characterize the effects of CRAMP deficiency on glial response and phagocytosis after exposure to bacterial stimuli.

METHODS

CRAMP-knock out and wildtype glial cells were exposed to bacterial supernatants from Streptococcus pneumoniae and Neisseria meningitides or the bacterial cell wall components lipopolysaccharide and peptidoglycan. Cell viability, expression of pro- and anti-inflammatory mediators and activation of signal transduction pathways, phagocytosis rate and glial cell phenotype were investigated by means of cell viability assays, immunohistochemistry, real-time RT-PCR and Western blot.

RESULTS

CRAMP-deficiency was associated with stronger expression of pro-inflammatory and weakened expression of anti-inflammatory cytokines indicating a higher degree of glial cell activation even under resting-state conditions. Furthermore, increased translocation of nuclear factor 'kappa-light-chain-enhancer' of activated B-cells was observed and phagocytosis of S. pneumoniae was reduced in CRAMP-deficient microglia indicating impaired antimicrobial activity.

CONCLUSIONS

In conclusion, the present study detected severe alterations of the glial immune response due to lack of CRAMP. The results indicate the importance of CRAMP to maintain and regulate the delicate balance between beneficial and harmful immune response in the brain.

Resolution Agonist 15-epi-Lipoxin A4 Programs Early Activation of Resolving Phase in Post-Myocardial Infarction Healing

Following myocardial infarction (MI), overactive inflammation remodels the left ventricle (LV) leading to heart failure coinciding with reduced levels of 15-epi-Lipoxin A₄ (15-epi LXA₄). However, the role of 15-epi LXA₄ in post-MI acute inflammatory response and resolving phase is unclear. We hypothesize that liposomal fusion of 15-epi-LXA₄ (Lipo-15-epi-LXA₄) or free 15-epi-LXA₄ will expedite the resolving phase in post-MI inflammation. 8 to 12-week-old male C57BL/6 mice were subjected to permanent coronary artery ligation. Lipo-15-epi-LXA₄ or 15-epi-LXA₄ (1 µg/kg/day) was injected 3 hours post-MI for (d)1 or continued daily till d5. 15-epi-LXA₄ activated formyl peptide receptor (FPR2) and GPR120 on alternative macrophages but inhibited GPR40 on classical macrophages in-vitro. The 15-epi-LXA₄ injected mice displayed reduced LV and lung mass to body weight ratios and improved ejection fraction at d5 post-MI. In the acute phase of inflammation-(d1), 15-epi-LXA₄ primes neutrophil infiltration with a robust increase of Ccl2 and FPR2 expression. During the resolving phase-(d5), 15-epi-LXA₄ initiated rapid neutrophils clearance with persistent activation of FPR2 in LV. Compared to MI-control, 15-epi-LXA₄ injected mice showed reduced renal inflammation along with decreased levels of ngal and plasma creatinine. In summary, 15-epi-LXA₄ initiates the resolving phase early to discontinue inflammation post-MI, thereby reducing LV dysfunction.

PGI2 Controls Pulmonary NK Cells That Prevent Airway Sensitization to House Dust Mite Allergen

In allergic asthma, inhalation of airborne allergens such as the house dust mite (HDM) effectively activates both innate and adaptive immunity in the lung mucosa. To determine the role of the eicosanoid PGI₂ and its receptor IP during allergic airway sensitization, HDM responses in mice lacking a functional IP receptor (i.e., PGI₂ IP receptor-deficient [IP^-/-]) were compared with wild type (WT) mice. Surprisingly, IP^-/- mice had increased numbers of pulmonary CD3^-NK1.1⁺Ly49b⁺ NK cells producing IFN-γ that was inversely associated with the number of type 2 innate lymphoid cells (ILC2s) expressing IL-33Rα and IL-13 compared with WT animals. This phenomenon was associated with elevated CX₃CL1 levels in the airways of IP^-/- mice and treatment with a neutralizing Ab to CX₃CL1 reduced IFN-γ production by the lung NK cells. Remarkably, IP^-/- mice were less responsive to HDM challenge than WT counterparts because intranasal instillation of the allergen induced markedly reduced levels of airway eosinophils, CD4⁺ lymphocyte infiltration, and mucus production, as well as depressed levels of CCL2 chemokine and Th2 cytokines. NK cells were responsible for such attenuated responses because depletion of NK1.1⁺ cells in IP^-/- mice restored both the HDM-induced lung inflammation and ILC2 numbers, whereas transfer of CD3^-NK1.1⁺ NK cells into the airways of WT hosts suppressed the inflammatory response. Collectively, these data demonstrate a hitherto unknown role for PGI₂ in regulating the number and properties of NK cells resident in lung tissue and reveal a role for NK cells in limiting lung tissue ILC2s and preventing allergic inflammatory responses to inhaled HDM allergen.

Innate Allorecognition Results in Rapid Accumulation of Monocyte-Derived Dendritic Cells

Although the mechanisms governing the innate recognition of pathogen-associated molecular patterns have been well defined, how allogeneic cellular stimuli evoke innate responses remains less so. In this article, we report that upon i.v. transfer (to avoid major iatrogenic interference), allogeneic but not syngeneic leukocytes could induce a rapid (after 1 d) accumulation of host monocyte-derived dendritic cells (moDCs) without any increase in conventional DCs. This occurred in various donor-host strain combinations, did not require MHC mismatch, and could be induced by various donor cell types including B cells, T cells, or NK cells. Using RAG(-/-)γc(-/-) and scid γc(-/-)mice with different MHC, we found that the presence of either donor or host lymphoid cells was required. Alloinduced moDC accumulation was significantly reduced when splenocytes from mice deficient in NK cells by genetic ablation were used as donors. A major component of this moDC accumulation appears to be recruitment. Our findings provide new insights into how the innate and adaptive immune system may interact during allogeneic encounters and thus transplant rejection.

Alarmins and Antitumor Immunity

PURPOSE

Alarmins are constitutively present endogenous molecules that essentially act as early warning signals for the immune system. We provide a brief overview of major alarmins and highlight their roles in tumor immunity.

METHODS

We searched PubMed up to January 10, 2016, using alarmins and/or damage-associated molecular patterns (DAMPs), as key words. We selected and reviewed articles that focused on the discovery and functions of alarmin and their roles in tumor immunity.

FINDINGS

Alarmins are essentially endogenous immunostimulatory DAMP molecules that are exposed in response to danger (eg, infection or tissue injury) as a result of degranulation, cell death, or induction. They are sensed by chemotactic receptors and pattern recognition receptors to induce immune responses by promoting the recruitment and activation of leukocytes, particularly antigen-presenting cells.

IMPLICATIONS

Accumulating data suggest that certain alarmins, High-mobility group nucleosome-binding protein 1 (HMGN1) in particular, contribute to the generation of antitumor immunity. Some alarmins can also be used as cancer biomarkers. Therefore, alarmins can potentially be applied for our fight against cancers.

Tissue-resident dendritic cells and diseases involving dendritic cell malfunction

Dendritic cells (DCs) control immune responses and are central to the development of immune memory and tolerance. DCs initiate and orchestrate immune responses in a manner that depends on signals they receive from microbes and cellular environment. Although DCs consist mainly of bone marrow-derived and resident populations, a third tissue-derived population resides the spleen and lymph nodes (LNs), different subsets of tissue-derived DCs have been identified in the blood, spleen, lymph nodes, skin, lung, liver, gut and kidney to maintain the tolerance and control immune responses. Tissue-resident DCs express different receptors for microbe-associated molecular patterns (MAMPs) and damage-associated molecular patterns (DAMPs), which were activated to promote the production of pro- or anti-inflammatory cytokines. Malfunction of DCs contributes to diseases such as autoimmunity, allergy, and cancer. It is therefore important to update the knowledge about resident DC subsets and diseases associated with DC malfunction.

Origin, Localization, and Immunoregulatory Properties of Pulmonary Phagocytes in Allergic Asthma

Allergic asthma is a chronic inflammatory disease of the airways that is driven by maladaptive T helper 2 (Th2) and Th17 immune responses against harmless, airborne substances. Pulmonary phagocytes represent the first line of defense in the lung where they constantly sense the local environment for potential threats. They comprise two distinct cell types, i.e., macrophages and dendritic cells (DC) that differ in their origins and functions. Alveolar macrophages quickly take up most of the inhaled allergens, yet do not deliver their cargo to naive T cells sampling in draining lymph nodes. In contrast, pulmonary DCs instruct CD4(+) T cells develop into Th2 and Th17 effectors, initiating the maladaptive immune responses toward harmless environmental substances observed in allergic individuals. Unraveling the mechanisms underlying this mistaken identity of harmless, airborne substances by innate immune cells is one of the great challenges in asthma research. The identification of different pulmonary DC subsets, their role in antigen uptake, migration to the draining lymph nodes, and their potential to instruct distinct T cell responses has set the stage to unravel this mystery. However, at this point, a detailed understanding of the spatiotemporal resolution of DC subset localization, allergen uptake, processing, autocrine and paracrine cellular crosstalk, and the humoral factors that define the activation status of DCs is still lacking. In addition to DCs, at least two distinct macrophage populations have been identified in the lung that are either located in the airway/alveolar lumen or in the interstitium. Recent data suggest that such populations can exert either pro- or anti-inflammatory functions. Similar to the DC subsets, detailed insights into the individual roles of alveolar and interstitial macrophages during the different phases of asthma development are still missing. Here, we will provide an update on the current understanding of the origin, localization, and function of the diverse pulmonary antigen-presenting cell subsets, in particular with regard to the development and regulation of allergic asthma. While most data are from mouse models of experimental asthma, we have also included available human data to judge the translational value of the findings obtained in experimental asthma models.

New development in studies of formyl-peptide receptors: critical roles in host defense

Formyl-peptide receptors are a family of 7 transmembrane domain, Gi-protein-coupled receptors that possess multiple functions in many pathophysiologic processes because of their expression in a variety of cell types and their capacity to interact with a variety of structurally diverse, chemotactic ligands. Accumulating evidence demonstrates that formyl-peptide receptors are critical mediators of myeloid cell trafficking in the sequential chemotaxis signal relays in microbial infection, inflammation, and immune responses. Formyl-peptide receptors are also involved in the development and progression of cancer. In addition, one of the formyl-peptide receptor family members, Fpr2, is expressed by normal mouse-colon epithelial cells, mediates cell responses to microbial chemotactic agonists, participates in mucosal development and repair, and protects against inflammation-associated tumorigenesis. These novel discoveries greatly expanded the current understanding of the role of formyl-peptide receptors in host defense and as potential molecular targets for the development of therapeutics.

Monocyte-Derived Dendritic Cells Promote Th Polarization, whereas Conventional Dendritic Cells Promote Th Proliferation

Monocyte-derived dendritic cells (moDCs) dramatically increase in numbers upon infection and inflammation; accordingly, we found that this also occurs during allogeneic responses. Despite their prominence, how emergent moDCs and resident conventional DCs (cDCs) divide their labor as APCs remain undefined. Hence, we compared both direct and indirect presentation by murine moDCs versus cDCs. We found that, despite having equivalent MHC class II expression and in vitro survival, moDCs were 20-fold less efficient than cDCs at inducing CD4(+) T cell proliferation through both direct and indirect Ag presentation. Despite this, moDCs were more potent at inducing Th1 and Th17 differentiation (e.g., 8-fold higher IFN-γ and 2-fold higher IL-17A in T cell cocultures), whereas cDCs induced 10-fold higher IL-2 production. Intriguingly, moDCs potently reduced the ability of cDCs to stimulate T cell proliferation in vitro and in vivo, partially through NO production. We surmise that such division of labor between moDCs and cDCs has implications for their respective roles in the immune response.

Migration of blood cells to β-amyloid plaques in Alzheimer's disease

Alzheimer’s disease (AD) is a neurodegenerative disease that leads to the progressive deterioration of cognitive and memory functions. The deposition of extracellular beta-amyloid (Aβ) senile plaques and intracellular tau neurofibrillary tangles are considered the cardinal pathological hallmarks of AD, however, accumulating evidence indicates that immune cells may also play an important role in disease pathogenesis. Among these immune cells, blood-derived cells and their infiltration into the CNS towards Aβ plaques have been implicated in therapeutic strategies against AD. Here, we review the current literature on blood cell migration into the AD brain and the important players involved in this selective migration towards Aβ plaques.

6-shogaol, an active constituent of dietary ginger, impairs cancer development and lung metastasis by inhibiting the secretion of CC-chemokine ligand 2 (CCL2) in tumor-associated dendritic cells

This study has two novel findings: it is not only the first to demonstrate that tumor-associated dendritic cells (TADCs) facilitate lung and breast cancer metastasis in vitro and in vivo by secreting inflammatory mediator CC-chemokine ligand 2 (CCL2), but it is also the first to reveal that 6-shogaol can decrease cancer development and progression by inhibiting the production of TADC-derived CCL2. Human lung cancer A549 and breast cancer MDA-MB-231 cells increase TADCs to express high levels of CCL2, which increase cancer stem cell features, migration, and invasion, as well as immunosuppressive tumor-associated macrophage infiltration. 6-Shogaol decreases cancer-induced up-regulation of CCL2 in TADCs, preventing the enhancing effects of TADCs on tumorigenesis and metastatic properties in A549 and MDA-MB-231 cells. A549 and MDA-MB-231 cells enhance CCL2 expression by increasing the phosphorylation of signal transducer and activator of transcription 3 (STAT3), and the activation of STAT3 induced by A549 and MDA-MB-231 is completely inhibited by 6-shogaol. 6-Shogaol also decreases the metastasis of lung and breast cancers in mice. 6-Shogaol exerts significant anticancer effects on lung and breast cells in vitro and in vivo by targeting the CCL2 secreted by TADCs. Thus, 6-shogaol may have the potential of being an efficacious immunotherapeutic agent for cancers.

Lack of formyl peptide receptor 1 and 2 leads to more severe inflammation and higher mortality in mice with of pneumococcal meningitis

Bacterial meningitis is, despite progress in research and the development of new treatment strategies, still a cause of severe neuronal sequelae. The brain is protected from penetrating pathogens by both the blood-brain barrier and the innate immune system. The invading pathogens are recognized by pattern recognition receptors including the G-protein coupled formyl peptide receptors (FPRs), which are expressed by immune cells of the central nervous system. The expression of FPRs is up-regulated during bacterial meningitis, but the consequence on the progression of inflammation and impact on mortality are far from clear. Therefore, we used mFPR1 and mFPR2-deficient mice to investigate the effects on inflammation, bacterial growth and mortality in a mouse model of pneumococcal meningitis. Our results revealed increased bacterial burden, increased neutrophil infiltration and higher mortality in mFPR1/2-deficient mice in comparison to wild-type mice. The mFPR1- or mFPR2-deficient mice also showed significantly increased glial cell density, whereas the immune responses including the expression of anti-inflammatory cytokines and antimicrobial peptides were decreased in bacterial meningitis. Taken together, the results suggest that FPR1 and FPR2 play an important role in the innate immune responses against Streptococcus pneumoniae within the central nervous system and the lack of the receptors leads to a dysregulation of the inflammatory response compared with wild-type mice.

The formylpeptide receptor 2 (Fpr2) and its endogenous ligand cathelin-related antimicrobial peptide (CRAMP) promote dendritic cell maturation

Mouse formylpeptide receptor 2 (Fpr2) is a homologue of the human G-protein coupled chemoattractant receptor FPR2, which interacts with pathogen and host-derived chemotactic agonists. Our previous studies revealed reduced allergic airway inflammation and immune responses in Fpr2-deficient (Fpr2(-/-)) mice in association with diminished dendritic cell (DC) recruitment into the airway and draining lymph nodes. These defects prompted us to investigate the potential changes in the differentiation and maturation of DCs caused by Fpr2 deficiency. Bone marrow monocytes from Fpr2(-/-) mouse mice incubated with GM-CSF and IL-4 in vitro showed normal expression of markers of immature DCs. However, upon stimulation with the TLR4 agonist LPS, Fpr2(-/-) mouse DCs failed to express normal levels of maturation markers with reduced production of IL-12 and diminished chemotaxis in response to the DC homing chemokine CCL21. Fpr2(-/-) DCs also failed to induce allogeneic T-cell proliferation in vitro, and their recruitment into the T-cell zones of the spleen was reduced after antigen immunization. The capacity of Fpr2 to sustain normal DC maturation was dependent on its interaction with an endogenous ligand CRAMP expressed by DCs, because neutralization of either Fpr2 or CRAMP inhibited DC maturation in response to LPS. We additionally observed that the presence of exogenous CRAMP in culture increased the sensitivity of WT mouse DCs to LPS stimulation. The importance of CRAMP for DC maturation was further demonstrated by the observations that DCs from CRAMP(-/-) mice expressed lower levels of costimulatory molecules and MHC II and exhibited poor chemotaxis in response to CCL21 after LPS stimulation. Our observations indicate a nonredundant role for Fpr2 and its agonist CRAMP in DC maturation in immune responses.

Formylpeptide receptors mediate rapid neutrophil mobilization to accelerate wound healing

Wound healing is a multi-phased pathophysiological process requiring chemoattractant receptor-dependent accumulation of myeloid cells in the lesion. Two G protein-coupled formylpeptide receptors Fpr1 and Fpr2 mediate rapid neutrophil infiltration in the liver of Listeria-infected mice by sensing pathogen-derived chemotactic ligands. These receptors also recognize host-derived chemotactic peptides in inflammation and injury. Here we report the capacity of Fprs to promote the healing of sterile skin wound in mice by initiating neutrophil infiltration. We found that in normal miceneutrophils rapidly infiltrated the dermis in the wound before the production of neutrophil-specific chemokines by the injured tissue. In contrast, rapid neutrophil infiltration was markedly reduced with delayed wound closure in mice deficient in both Fprs. In addition, we detected Fpr ligand activity that chemoattracted neutrophils into the wound tissue. Our study thus demonstrates that Fprs are critical for normal healing of the sterile skin wound by mediating the first wave of neutrophil infiltration.