Chemerin15 inhibits neutrophil-mediated vascular inflammation and myocardial ischemia-reperfusion injury through ChemR23

Sphingosine-1-Phosphate Receptor Targeted PLGA Nanobubbles for Inflammatory Vascular Endothelial Cell Catching

Vascular inflammation is an early manifestation and common pathophysiological basis of numerous cardiovascular and cerebrovascular diseases. However, effective surveillance methods are lacking. In this study, sulfur hexafluoride (SF6 )-loaded polylactic acid-co-glycolic acid (PLGA) nanobubbles (NBs) with a surface assembly of cyclodextrin (CD) and sphingosine-1-phosphate (S1P) (S1P@CD-PLGA NBs) are designed. The characterization results show that S1P@CD-PLGA NBs with diameters of ≈200 nm have good stability, biosafety, and ultrasound imaging-enhancement effects. When interacting with inflammatory vascular endothelial cells, S1P molecules encapsulated in cyclodextrin cavities exhibit a rapid, excellent, and stable targeting effect owing to their specific interaction with the highly expressed S1P receptor 1 (S1PR1) on the inflammatory vascular endothelial cells. Particularly, the S1P-S1PR1 interaction further activates the downstream signaling pathway of S1PR1 to reduce the expression of tumor necrosis factor-α (TNF-α) to protect endothelial cells. Furthermore, mouse models of carotid endothelial injuries and mesenteric thrombosis demonstrate that S1P@CD-PLGA NBs have excellent capabilities for in vivo targeting imaging. In summary, this study proposes a new strategy of using S1P to target inflammatory vascular endothelial cells while reducing the expression of TNF-α, which has the potential to be utilized in the targeted surveillance and treatment of vascular inflammatory diseases.

A dual functional polypeptide with antibacterial and anti-inflammatory properties for the treatment of periodontitis

Periodontitis has been reported as the sixth most prevalent disease in human beings. This destructive disease is closely related to systemic diseases. Existing local drug delivery systems for periodontitis suffer from poor antibacterial effect and drug resistance. Inspired by the pathogenesis of periodontitis, we implemented a strategy to construct a dual functional polypeptide LL37-C15, which exhibited remarkable antibacterial effect against P. gingivalis and A. actinomycetemcomitans. In addition, LL37-C15 inhibits the release of pro-inflammatory cytokines by controlling the inflammatory pathway and reversing macrophage M1. Furthermore, the anti-inflammatory effect of LL37-C15 was also verified in vivo in a periodontitis rat model through the morphometry and histological observations of alveolar bone, hematoxylin-eosin, and Trap staining in gingival tissue. The results of molecular dynamics simulations showed that LL37-C15 could selectively destroy the bacterial cell membrane and protect the animal cell membrane in a self-destructive manner. The results showed that the polypeptide LL37-C15, as a novel promising therapeutic agent, exhibited a great potential for the periodontitis management. What's more, this dual functional polypeptide provides a promising strategy for building a multifunctional therapeutic platform against the inflammation and other diseases.

Targeting the chemerin/CMKLR1 axis by small molecule antagonist α-NETA mitigates endometriosis progression

Endometriosis is a common gynecological disease, characterized by the presence of endometrial-like lesions outside the uterus. This debilitating disease causes chronic pelvic pain and infertility with limited therapeutics. Chemerin is a secretory protein that acts on CMKLR1 (Chemokine-Like Receptor 1) to execute functions vital for immunity, adiposity, and metabolism. Abnormal chemerin/CMKLR1 axis underlies the pathological mechanisms of certain diseases including cancer and inflammatory diseases, but its role in endometriosis remains unknown. Herein, our results showed that chemerin and CMKLR1 are up-regulated in endometriotic lesions by analyzing the human endometriosis database and murine model. Knockdown of chemerin or CMKLR1 by shRNA led to mesenchymal-epithelial transition (MET) along with compromised viability, migration, and invasion of hEM15A cells. Most importantly, 2-(α-naphthoyl) ethyltrimethylammonium iodide (α-NETA), a small molecule antagonist for CMKLR1, was evidenced to exhibit profound anti-endometriosis effects (anti-growth, anti-mesenchymal features, anti-angiogenesis, and anti-inflammation) in vitro and in vivo. Mechanistically, α-NETA exhibited a dual inhibition effect on PI3K/Akt and MAPK/ERK signaling pathways in hEM15A cells and murine endometriotic grafts. This study highlights that the chemerin/CMKLR1 signaling axis is critical for endometriosis progression, and targeting this axis by α-NETA may provide new options for therapeutic intervention.

Formylpeptide receptor 2: Nomenclature, structure, signalling and translational perspectives: IUPHAR review 35

We discuss the fascinating pharmacology of formylpeptide receptor 2 (FPR2; often referred to as FPR2/ALX since it binds lipoxin A₄ ). Initially identified as a low-affinity 'relative' of FPR1, FPR2 presents complex and diverse biology. For instance, it is activated by several classes of agonists (from peptides to proteins and lipid mediators) and displays diverse expression patterns on myeloid cells as well as epithelial cells and endothelial cells, to name a few. Over the last decade, the pharmacology of FPR2 has progressed from being considered a weak chemotactic receptor to a master-regulator of the resolution of inflammation, the second phase of the acute inflammatory response. We propose that exploitation of the biology of FPR2 offers innovative ways to rectify chronic inflammatory states and represents a viable avenue to develop novel therapies. Recent elucidation of FPR2 structure will facilitate development of the anti-inflammatory and pro-resolving drugs of next decade.

Chemerin Forms: Their Generation and Activity

Chemerin is the product of the RARRES2 gene which is secreted as a precursor of 143 amino acids. That precursor is inactive, but proteases from the coagulation and fibrinolytic cascades, as well as from inflammatory reactions, process the C-terminus of chemerin to first activate it and then subsequently inactivate it. Chemerin can signal via two G protein-coupled receptors, chem1 and chem2, as well as be bound to a third non-signaling receptor, CCRL2. Chemerin is produced by the liver and secreted into the circulation as a precursor, but it is also expressed in some tissues where it can be activated locally. This review discusses the specific tissue expression of the components of the chemerin system, and the role of different proteases in regulating the activation and inactivation of chemerin. Methods of identifying and determining the levels of different chemerin forms in both mass and activity assays are reviewed. The levels of chemerin in circulation are correlated with certain disease conditions, such as patients with obesity or diabetes, leading to the possibility of using chemerin as a biomarker.

Molecular Pharmacology of Inflammation Resolution in Atherosclerosis

Atherosclerosis is one of the most important problems of modern medicine as it is the leading cause of hospitalizations, disability, and mortality. The key role in the development and progression of atherosclerosis is the imbalance between the activation of inflammation in the vascular wall and the mechanisms of its control. The resolution of inflammation is the most important physiological mechanism that is impaired in atherosclerosis. The resolution of inflammation has complex, not fully known mechanisms, in which lipid mediators derived from polyunsaturated fatty acids (PUFAs) play an important role. Specialized pro-resolving mediators (SPMs) represent a group of substances that carry out inflammation resolution and may play an important role in the pathogenesis of atherosclerosis. SPMs include lipoxins, resolvins, maresins, and protectins, which are formed from PUFAs and regulate many processes related to the active resolution of inflammation. Given the physiological importance of these substances, studies examining the possibility of pharmacological effects on inflammation resolution are of interest.

Chemerin-9 stimulates migration in rat cardiac fibroblasts in vitro

Since chemerin is an adipocytokine whose concentration in blood increases in the subjects with various cardiac diseases, chemerin may be involved in pathogenesis of cardiac diseases. In the present study, we examined the effects of chemerin-9, an active fragment of chemerin, on functions of cardiac fibroblasts, which are involved in pathophysiology of cardiac diseases. Primary cardiac fibroblasts were enzymatically isolated from adult male Wistar rats. Migration of cardiac fibroblasts was measured by a Boyden chamber assay and a scratch assay. Phosphorylation of Akt and extracellular signal-regulated kinase (ERK) was measured by Western blotting. Reactive oxygen species (ROS) production was measured by 2',7'-dichlorodihydrofluoresein staining. Chemerin-9 significantly stimulated migration in cardiac fibroblasts. Chemerin-9 significantly stimulated phosphorylation of Akt and ERK as well as ROS production. An Akt pathway inhibitor, LY294002, an ERK pathway inhibitor, PD98059, an antagonist of chemokine-like receptor 1 (CMKLR1), 2-(α-Napththoyl) ethyltrimethylammonium iodide, or an antioxidant, N-acetyl-L-cysteine prevented the migration induced by chemerin-9. In summary, we for the first time revealed that chemerin-9 stimulates migration perhaps through the ROS-dependent activation of Akt and ERK via CMKLR1 in cardiac fibroblasts. It is proposed that chemerin plays a role in the pathogenesis of cardiac diseases.

Anti-Inflammatory Function of Fatty Acids and Involvement of Their Metabolites in the Resolution of Inflammation in Chronic Obstructive Pulmonary Disease

Lipid metabolism plays an important role in many lung functions. Disorders of lipid metabolism are part of the pathogenesis of chronic obstructive pulmonary disease (COPD). Lipids are involved in numerous cross-linkages with inflammation. Recent studies strongly support the involvement of fatty acids as participants in inflammation. They are involved in the initiation and resolution of inflammation, including acting as a substrate for the formation of lipid mediators of inflammation resolution. Specialized pro-inflammatory mediators (SPMs) belonging to the classes of lipoxins, resolvins, maresins, and protectins, which are formed enzymatically from unsaturated fatty acids, are now described. Disorders of their production and function are part of the pathogenesis of COPD. SPMs are currently the subject of active research in order to find new drugs. Short-chain fatty acids are another important participant in metabolic and immune processes, and their role in the pathogenesis of COPD is of great clinical interest.

Curcumin inhibits the proliferation and migration of vascular smooth muscle cells by targeting the chemerin / CMKLR1 / LCN2 axis

Atherosclerosis (AS) is a chronic progressive inflammatory disease and a leading cause of death worldwide. Being a novel adipokine, chemerin is reported to be positively correlated with the severity of AS, yet its underlying mechanisms in AS remains elusive. It is well-known that AS development is significantly attributed to abnormal proliferation and migration of vascular smooth muscle cells (VSMCs). Therefore, we investigated the role of the chemerin / chemokine-like receptor 1 (CMKLR1, chemerin receptor) signaling, and the potential therapeutic effect of curcumin in VSMCs proliferation and migration during AS by establishing a high fat diet (HFD) mouse model. We found that CMKLR1 was highly expressed in HFD-induced AS tissues and that its expression level was positively correlated with aortic proliferation. Knockdown of CMKLR1 significantly inhibited VSMCs proliferation and migration, as evidenced by the EdU-incorporation assay, wound healing assay, and the induction of proliferating cell nuclear antigen (PCNA) and matrix metalloproteinase-9 (MMP-9) expression. Furthermore, we discovered that Lipocalin-2 (LCN2) acts as a key factor involved in CMKLR1-mediated VSMCs proliferation and migration via the p38 / MAPK and Wnt / β-catenin signaling pathways, and we demonstrated that curcumin inhibits VSMCs proliferation and migration by inhibiting chemerin / CMKLR1 / LCN2, thereby reducing AS progression. Our findings suggest that chemerin / CMKLR1 activation promotes the development of AS; hence, targeting the chemerin / CMKLR1 / LCN2 signaling pathway may be a reasonable treatment modality for AS.

Agonist anti-ChemR23 mAb reduces tissue neutrophil accumulation and triggers chronic inflammation resolution

Resolution of inflammation is elicited by proresolving lipids, which activate GPCRs to induce neutrophil apoptosis, reduce neutrophil tissue recruitment, and promote macrophage efferocytosis. Transcriptional analyses in up to 300 patients with Inflammatory Bowel Disease (IBD) identified potential therapeutic targets mediating chronic inflammation. We found that ChemR23, a GPCR targeted by resolvin E1, is overexpressed in inflamed colon tissues of severe IBD patients unresponsive to anti-TNFα or anti-α4β7 therapies and associated with significant mucosal neutrophil accumulation. We also identified an anti-ChemR23 agonist antibody that induces receptor signaling, promotes macrophage efferocytosis, and reduces neutrophil apoptosis at the site of inflammation. This ChemR23 mAb accelerated acute inflammation resolution and triggered resolution in ongoing chronic colitis models, with a significant decrease in tissue lesions, fibrosis and inflammation-driven tumors. Our findings suggest that failure of current IBD therapies may be associated with neutrophil infiltration and that ChemR23 is a promising therapeutic target for chronic inflammation.

Targeting inflammation in atherosclerosis - from experimental insights to the clinic

Atherosclerosis, a dominant and growing cause of death and disability worldwide, involves inflammation from its inception to the emergence of complications. Targeting inflammatory pathways could therefore provide a promising new avenue to prevent and treat atherosclerosis. Indeed, clinical studies have now demonstrated unequivocally that modulation of inflammation can forestall the clinical complications of atherosclerosis. This progress pinpoints the need for preclinical investigations to refine strategies for combatting inflammation in the human disease. In this Review, we consider a gamut of attractive possibilities for modifying inflammation in atherosclerosis, including targeting pivotal inflammatory pathways such as the inflammasomes, inhibiting cytokines, manipulating adaptive immunity and promoting pro-resolution mechanisms. Along with lifestyle measures, pharmacological interventions to mute inflammation could complement traditional targets, such as lipids and hypertension, to make new inroads into the management of atherosclerotic risk.

ATP-Sensitive Potassium Channels Mediate the Cardioprotective Effect of Panax notoginseng Saponins against Myocardial Ischaemia-Reperfusion Injury and Inflammatory Reaction

Inflammatory response during myocardial ischemia reperfusion injury (MIRI) is essential for cardiac healing, while excessive inflammation extends the infarction and promotes adverse cardiac remodeling. Understanding the mechanism of these uncontrolled inflammatory processes has a significant impact during the MIRI therapy. Here, we found a critical role of ATP-sensitive potassium channels (K_ATP) in the inflammatory response of MIRI and its potential mechanism and explored the effects of Panax Notoginseng Saponins (PNS) during this possess. Rats underwent 40 min ischemia by occlusion of the left anterior descending (LAD) coronary artery and 60 min of reperfusion. PNS was treated at the corresponding time point before operation; 5-hydroxydecanoate (5-HD) and glybenclamide (Gly) (or Nicorandil (Nic)) were used as pharmacological blocker (or nonselective opener) of K_ATP. Cardiac function and pathomorphology were evaluated and a set of molecular signaling experiments was tested. K_ATP current density was measured by patch-clamp. Results revealed that in MIRI, PNS pretreatment restored cardiac function, reduced infarct size, and ameliorated inflammation through K_ATP. However, inhibiting K_ATP by 5-HD and Gly significantly reversed the effects, including NLRP3 inflammasome and inflammatory mediators IL-6, MPO, TNF-α, and MCP-1. Moreover, PNS inhibited the phosphorylation and nuclear translocation of NF-κB in I/R myocardium when the K_ATP was activated. Importantly, PNS promoted the expression of subunits and activation of K_ATP. The study uncovered K_ATP served as a new potential mechanism during PNS modulating MIRI-induced inflammation and promoting injured heart recovery. The manipulation of K_ATP could be a potential therapeutic approach for MIRI and other inflammatory diseases.

The GPR40 Agonist GW9508 Enhances Neutrophil Function to Aid Bacterial Clearance During E. coli Infections

G-protein-coupled receptor 40 (GPR40) is known to play a role in the regulation of fatty acids, insulin secretion, and inflammation. However, the function of this receptor in human neutrophils, one of the first leukocytes to arrive at the site of infection, remains to be fully elucidated. In the present study, we demonstrate that GPR40 is upregulated on activated human neutrophils and investigated the functional effects upon treatment with a selective agonist; GW9508. Interestingly, GPR40 expression was up-regulated after neutrophil stimulation with platelet-activating factor (10 nM) or leukotriene B₄ (LTB₄, 10 nM) suggesting potential regulatory roles for this receptor during inflammation. Indeed, GW9508 (1 and 10 μM) increased neutrophil chemotaxis in response to the chemokine IL-8 (30 ng/ml) and enhanced phagocytosis of Escherichia coli by approximately 50% when tested at 0.1 and 1 μM. These results were translated in vivo whereby administration of GW9508 (10 mg/kg, i.p.) during E. coli infections resulted in elevated peritoneal leukocyte infiltration with a higher phagocytic capacity. Importantly, GW9508 administration also modulated the lipid mediator profile, with increased levels of the pro-resolving mediators resolvin D3 and lipoxins. In conclusion, GPR40 is expressed by activated neutrophils and plays an important host protective role to aid clearance of bacterial infections.

A review of myocardial ischaemia/reperfusion injury: Pathophysiology, experimental models, biomarkers, genetics and pharmacological treatment

Cardiovascular diseases are known to be the most fatal diseases worldwide. Ischaemia/reperfusion (I/R) injury is at the centre of the pathology of the most common cardiovascular diseases. According to the World Health Organization estimates, ischaemic heart disease is the leading global cause of death, causing more than 9 million deaths in 2016. After cardiovascular events, thrombolysis, percutaneous transluminal coronary angioplasty or coronary bypass surgery are applied as treatment. However, after restoring coronary blood flow, myocardial I/R injury may occur. It is known that this damage occurs due to many pathophysiological mechanisms, especially increasing reactive oxygen types. Besides causing cardiomyocyte death through multiple mechanisms, it may be an important reason for affecting other cell types such as platelets, fibroblasts, endothelial and smooth muscle cells and immune cells. Also, polymorphonuclear leukocytes are associated with myocardial I/R damage during reperfusion. This damage may be insufficient in patients with co-morbidity, as it is demonstrated that it can be prevented by various endogenous antioxidant systems. In this context, the resulting data suggest that optimal cardioprotection may require a combination of additional or synergistic multi-target treatments. In this review, we discussed the pathophysiology, experimental models, biomarkers, treatment and its relationship with genetics in myocardial I/R injury. SIGNIFICANCE OF THE STUDY: This review summarized current information on myocardial ischaemia/reperfusion injury (pathophysiology, experimental models, biomarkers, genetics and pharmacological therapy) for researchers and reveals guiding data for researchers, especially in the field of cardiovascular system and pharmacology.

Neutrophils Enhance Cutaneous Vascular Dilation and Permeability to Aggravate Psoriasis by Releasing Matrix Metallopeptidase 9

Neutrophil infiltration and papillary vessel dilation are hallmarks of the initiation phase of psoriatic lesions. However, how neutrophils aggravate psoriasis development during transendothelial migration and the interaction between neutrophils and cutaneous vascular endothelial cells are less well-understood. In this study, we reported that neutrophils and cutaneous vascular endothelial cells activated each other when neutrophils migrated through the cutaneous endothelial barrier. In addition, neutrophil infiltration into skin lesions caused vascular remodeling including cutaneous vasodilation and enhanced vascular permeability in vivo and in vitro. Microarray gene profile data showed that matrix metallopeptidase (MMP)-9 was overexpressed in psoriatic neutrophils, and zymography assay further validated the bioactivity of MMP-9 secreted by psoriatic neutrophils. Moreover, MMP-9 activated vascular endothelial cells through the extracellular signal‒regulated kinase 1/2 and p38-MAPK signaling pathways, enhancing CD4⁺ T-cell transmigration in vitro. Correspondingly, an MMP-9 inhibitor significantly reduced cutaneous vasodilation, vascular permeability, and psoriatic symptoms in an imiquimod- or IL-23‒induced psoriasiform mouse model. Overall, our study demonstrates that neutrophil-derived MMP-9 induces cutaneous vasodilation and hyperpermeability by activating cutaneous vascular endothelial cells, thus facilitating psoriatic lesion development, which increases our knowledge on the role of neutrophils in the pathogenesis of psoriasis.

Immune Cell Therapies to Improve Regeneration and Revascularization of Non-Healing Wounds

With the increased prevalence of chronic diseases, non-healing wounds place a significant burden on the health system and the quality of life of affected patients. Non-healing wounds are full-thickness skin lesions that persist for months or years. While several factors contribute to their pathogenesis, all non-healing wounds consistently demonstrate inadequate vascularization, resulting in the poor supply of oxygen, nutrients, and growth factors at the level of the lesion. Most existing therapies rely on the use of dermal substitutes, which help the re-epithelialization of the lesion by mimicking a pro-regenerative extracellular matrix. However, in most patients, this approach is not efficient, as non-healing wounds principally affect individuals afflicted with vascular disorders, such as peripheral artery disease and/or diabetes. Over the last 25 years, innovative therapies have been proposed with the aim of fostering the regenerative potential of multiple immune cell types. This can be achieved by promoting cell mobilization into the circulation, their recruitment to the wound site, modulation of their local activity, or their direct injection into the wound. In this review, we summarize preclinical and clinical studies that have explored the potential of various populations of immune cells to promote skin regeneration in non-healing wounds and critically discuss the current limitations that prevent the adoption of these therapies in the clinics.

Chemerin: A Potential Regulator of Inflammation and Metabolism for Chronic Obstructive Pulmonary Disease and Pulmonary Rehabilitation

Chronic obstructive pulmonary disease (COPD) features chronic inflammatory reactions of both intra- and extrapulmonary nature. Moreover, COPD is associated with abnormal glucose and lipid metabolism in patients, which influences the prognosis and chronicity of this disease. Abnormal glucose and lipid metabolism are also closely related to inflammation processes. Further insights into the interactions of inflammation and glucose and lipid metabolism might therefore inspire novel therapeutic interventions to promote lung rehabilitation. Chemerin, as a recently discovered adipokine, has been shown to play a role in inflammatory response and glucose and lipid metabolism in many diseases (including COPD). Chemerin recruits inflammatory cells to sites of inflammation during the early stages of COPD, leading to endothelial barrier dysfunction, early vascular remodeling, and angiogenesis. Moreover, it supports the recruitment of antigen-presenting cells that guide immune cells as part of the body's inflammatory responses. Chemerin also regulates metabolism via activation of its cognate receptors. Glucose homeostasis is affected via effects on insulin secretion and sensitivity, and lipid metabolism is changed by increased transformation of preadipocytes to mature adipocytes through chemerin-binding receptors. Controlling chemerin signaling may be a promising approach to improve various aspects of COPD-related dysfunction. Importantly, several studies indicate that chemerin expression in vivo is influenced by exercise. Although available evidence is still limited, therapeutic alterations of chemerin activity may be a promising target of therapeutic approaches aimed at the rehabilitation of COPD patients based on exercises. In conclusion, chemerin plays an essential role in COPD, especially in the inflammatory responses and metabolism, and has a potential to become a target for, and a biomarker of, curative mechanisms underlying exercise-mediated lung rehabilitation.

Effect of weight loss on neutrophil resolvins in the metabolic syndrome

BACKGROUND

Non-resolving inflammation associates with obesity and insulin resistance, and may be dependent on the balance of inflammatory substances and specialised pro-resolving mediators of inflammation (SPM) that act to halt the inflammatory response. This controlled trial examined the effect of weight loss on neutrophil synthesis of SPM in volunteers with the metabolic syndrome (MetS).

METHODS

Volunteers with MetS (n = 42) were matched for age and gender and randomly assigned to a 12-wk weight loss program followed by 4-wk weight stabilization or a 16-wk weight maintenance program. At baseline and 16 weeks, isolated neutrophils were stimulated with calcium ionophore and the released SPM were measured by LC-MS/MS.

RESULTS

At baseline the SPM resolvin (Rv) E1, 18R-RvE3, RvD2 and Maresin-1 (MaR-1) were detected from stimulated neutrophils. The concentration of released RvE1 was at least 6-fold that of other detected SPM. Weight loss of 4.7 ± 0.8 kg, led to a 2-fold increase in RvE1, P = 0.013, relative to the weight maintenance group. The increase in RvE1 after weight loss was related to, but independent of leukotriene B_4. CONCLUSION: Following weight loss, human neutrophils from individuals with the metabolic syndrome are capable of releasing larger amounts of RvE1 upon stimulation.

G-Protein Coupled Receptor Targeting on Myeloid Cells in Atherosclerosis

Atherosclerosis, the underlying cause of the majority of cardiovascular diseases (CVDs), is a lipid-driven, inflammatory disease of the large arteries. Gold standard therapy with statins and the more recently developed proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have improved health conditions among CVD patients by lowering low density lipoprotein (LDL) cholesterol. Nevertheless, a substantial part of these patients is still suffering and it seems that 'just' lipid lowering is insufficient. The results of the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) have now proven that inflammation is a key driver of atherosclerosis and that targeting inflammation improves CVD outcomes. Therefore, the identification of novel drug targets and development of novel therapeutics that block atherosclerosis-specific inflammatory pathways have to be promoted. The inflammatory processes in atherosclerosis are facilitated by a network of immune cells and their subsequent responses. Cell networking is orchestrated by various (inflammatory) mediators which interact, bind and induce signaling. Over the last years, G-protein coupled receptors (GPCRs) emerged as important players in recognizing these mediators, because of their diverse functions in steady state but also and specifically during chronic inflammatory processes - such as atherosclerosis. In this review, we will therefore highlight a selection of these receptors or receptor sub-families mainly expressed on myeloid cells and their role in atherosclerosis. More specifically, we will focus on chemokine receptors, both classical and atypical, formyl-peptide receptors, the chemerin receptor 23 and the calcium-sensing receptor. When information is available, we will also describe the consequences of their targeting which may hold promising options for future treatment of CVD.

Antiinflammatory peptides: current knowledge and promising prospects

BACKGROUND

Inflammation is part of the regular host reaction to injury or infection caused by toxic factors, pathogens, damaged cells, irritants, and allergens. Antiinflammatory peptides (AIPs) are present in all living organisms, and many peptides from herbal, mammalian, bacterial, and marine origins have been shown to have antimicrobial and/or antiinflammatory properties.

METHODS

In this study, we investigated the effects of antiinflammatory peptides on inflammation, and highlighted the underlying mechanisms responsible for these effects.

RESULTS

In multicellular organisms, including humans, AIPs constitute an essential part of their immune system. In addition, numerous natural and synthetic AIPs are effective immunomodulators and can interfere with signal transduction pathways involved in inflammatory cytokine expression. Among them, some peptides such as antiflammin, N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), and those derived from velvet antler proteins, bee venom, horse fly salivary gland, and bovine β-casein have received considerable attention over the past few years.

CONCLUSION

This article presents an overview on the major properties and mechanisms of action associated with AIPs as immunomodulatory, chemotactic, antioxidant, and antimicrobial agents. In addition, the results of various studies dealing with effects of AIPs on numerous classical models of inflammation are reviewed and discussed.

Chemerin suppresses neuroinflammation and improves neurological recovery via CaMKK2/AMPK/Nrf2 pathway after germinal matrix hemorrhage in neonatal rats

Chemerin, an adipokine, has been reported to reduce the production of pro-inflammatory cytokines and neutrophil infiltration. This study investigated the role of Chemerin and its natural receptor, ChemR23, as well as its downstream mediator calmodulin-dependent protein kinase kinase 2 (CAMKK2)/adenosine monophosphate-activated protein kinase (AMPK) /Nuclear factor erythroid 2-related factor 2 (Nrf2) following germinal matrix hemorrhage (GMH) in neonatal rats, with a specific focus on inflammation. GMH was induced by intraparenchymal injection of bacterial collagenase (0.3U) in P7 rat pups. The results demonstrated that human recombinant Chemerin (rh-Chemerin) improved neurological and morphological outcomes after GMH. Rh-Chemerin promoted accumulation and proliferation of M2 microglia in periventricular regions at 72 h. Rh-Chemerin increased phosphorylation of CAMKK2, AMPK and expression of Nrf2, and decreased IL-1beta, IL-6 and TNF-alpha levels. Selective inhibition of ChemR23/CAMKK2/AMPK signaling in microglia via intracerebroventricular delivery of liposome-encapsulated specific ChemR23 (Lipo-alpha-NETA), CAMKK2 (Lipo-STO-609) and AMPK (Lipo-Dorsomorphin) inhibitor increased the expression levels of IL-1beta, IL-6 and TNF- alpha, demonstrating that ChemR23/CAMKK2/AMPK signaling in microglia suppressed inflammatory response after GMH. Cumulatively, these data showed that rh-Chemerin ameliorated GMH-induced inflammatory response by promoting ChemR23/CAMKK2/AMPK/Nrf2 pathway, and M2 microglia may be a major mediator of this effect. Thus, rh-Chemerin can serve as a potential agent to reduce the inflammatory response following GMH.

International Union of Basic and Clinical Pharmacology CIII: Chemerin Receptors CMKLR1 (Chemerin1) and GPR1 (Chemerin2) Nomenclature, Pharmacology, and Function

Chemerin, a chemoattractant protein and adipokine, has been identified as the endogenous ligand for a G protein–coupled receptor encoded by the gene CMKLR1 (also known as ChemR23), and as a consequence the receptor protein was renamed the chemerin receptor in 2013. Since then, chemerin has been identified as the endogenous ligand for a second G protein–coupled receptor, encoded by the gene GPR1. Therefore, the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification recommends that the official name of the receptor protein for chemokine-like receptor 1 (CMKLR1) is chemerin receptor 1, and G protein–coupled receptor 1 is chemerin receptor 2 to follow the convention of naming the receptor protein after the endogenous ligand. Chemerin receptor 1 and chemerin receptor 2 can be abbreviated to Chemerin₁ and Chemerin₂, respectively. Chemerin requires C-terminal processing for activity, and human chemerin21–157 is reported to be the most active form, with peptide fragments derived from the C terminus biologically active at both receptors. Small-molecule antagonist, CCX832, selectively blocks CMKLR1, and resolvin E1 activation of CMKLR1 is discussed. Activation of both receptors by chemerin is via coupling to G_i/o, causing inhibition of adenylyl cyclase and increased Ca²⁺ flux. Receptors and ligand are widely expressed in humans, rats, and mice, and both receptors share ∼80% identity across these species. CMKLR1 knockout mice highlight the role of this receptor in inflammation and obesity, and similarly, GPR1 knockout mice exhibit glucose intolerance. In addition, the chemerin receptors have been implicated in cardiovascular disease, cancer, steroidogenesis, human immunodeficiency virus replication, and neurogenerative disease.

Armed for destruction: formation, function and trafficking of neutrophil granules

Neutrophils respond nearly instantly to infection, rapidly deploying a potent enzymatic and chemical arsenal immediately upon entering an infected site. This capacity for rapid and potent responses is endowed by stores of antimicrobial proteins contained in readily mobilizable granules. These granules contain the proteins necessary to mediate the recruitment, chemotaxis, antimicrobial function and NET formation of neutrophils. Four granule types exist, and are sequentially deployed as neutrophils enter infected sites. Secretory vesicles are released first, enabling recruitment of neutrophils out of the blood. Next, specific and gelatinase granules are released to enable neutrophil migration and begin the formation of an antimicrobial environment. Finally, azurophilic granules release potent antimicrobial proteins at the site of infection and into phagosomes. The step-wise mobilization of these granules is regulated by calcium signaling, while specific trafficking regulators and membrane fusion complexes ensure the delivery of granules to the correct subcellular site. In this review, we describe neutrophil granules from their formation through to their deployment at the site of infection, focusing on recent developments in our understanding of the signaling pathways and vesicular trafficking mechanisms which mediate neutrophil degranulation.

Absence of the Non-Signalling Chemerin Receptor CCRL2 Exacerbates Acute Inflammatory Responses In Vivo

Chemerin is a chemotactic protein that induces migration of several immune cells including macrophages, immature dendritic cells, and NK cells. Chemerin binds to three G protein-coupled receptors (GPCRs), including CCRL2. The exact function of CCRL2 remains unclear. CCRL2 expression is rapidly upregulated during inflammation, but it lacks the intracellular DRYLAIV motif required for classical GPCR downstream signalling pathways, and it has not been reported to internalise chemerin upon binding. The aim of this study was to investigate what role if any CCRL2 plays during acute inflammation. Using the zymosan- and thioglycollate-induced murine models of acute inflammation, we report that mice deficient in the Ccrl2 gene display exaggerated local and systemic inflammatory responses, characterised by increased myeloid cell recruitment. This amplified myeloid cell recruitment was associated with increased chemerin and CXCL1 levels. Furthermore, we report that the inflammatory phenotype observed in these mice is dependent upon elevated levels of endogenous chemerin. Antibody neutralisation of chemerin activity in Ccrl2-/- mice abrogated the amplified inflammatory responses. Importantly, chemerin did not directly recruit myeloid cells but rather increased the production of other chemotactic proteins such as CXCL1. Administration of recombinant chemerin to wild-type mice before inflammatory challenge recapitulated the increased myeloid cell recruitment and inflammatory mediator production observed in Ccrl2-/- mice. We have demonstrated that the absence of CCRL2 results in increased levels of local and systemic chemerin levels and exacerbated inflammatory responses during acute inflammatory challenge. These results further highlight the importance of chemerin as a therapeutic target in inflammatory diseases.

Bronchoprotective mechanisms for specialized pro-resolving mediators in the resolution of lung inflammation

Bronchi are exposed daily to irritants, microbes and allergens as well as extremes of temperature and acid. The airway mucosal epithelium plays a pivotal role as a sentinel, releasing alarmins when danger is encountered. To maintain homeostasis, an elaborate counter-regulatory network of signals and cellular effector mechanisms are needed. Specialized pro-resolving mediators (SPMs) are chemical mediators that enact resolution programs in response to injury, infection or allergy. SPMs are enzymatically derived from essential polyunsaturated fatty acids with potent cell-type specific immunoresolvent properties. SPMs signal by engaging cell-based receptors to turn off acute inflammatory responses and restore tissue homeostasis. Several common lung diseases involving the airways, including asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF), are characterized by unresolved bronchial inflammation. In preclinical murine models of lung disease, SPMs carry potent bronchoprotective actions. Here, we review cellular and molecular effects for SPM-initiated catabasis in the lung and their human translation.

Neutrophil Resolvin E1 Receptor Expression and Function in Type 2 Diabetes

Unresolved inflammation is key in linking metabolic dysregulation and the immune system in type 2 diabetes. Successful regulation of acute inflammation requires biosynthesis of specialized proresolving lipid mediators, such as E-series resolvin (RvE) 1, and activation of cognate G protein-coupled receptors. RvE1 binds to leukotriene B4 (BLT-1) on neutrophils and to ERV-1/ChemR23 on monocyte/macrophages. We show novel actions of RvE1 and expression patterns of neutrophil receptors in type 2 diabetes. Neutrophils from healthy subjects express functional BLT-1, low levels of minimally functional ERV-1, and inversed coexpression when compared to neutrophils from type 2 diabetes subjects. Stimulation with TNF-α or LPS increased the expression of ERV-1 by healthy and diabetic neutrophils. RvE1 counteracted LPS and TNF-α induction of ERV-1 overexpression and endogenous diabetic overexpression, activating phagocytosis and resolution signals. Functional ERV-1 was determined by phosphorylation of the signaling protein ribosomal S6. Receptor-antagonism experiments revealed that the increase in phosphorylation of ribosomal S6 was mediated by BLT-1 in healthy subject neutrophils and by ERV-1 in diabetes. Metabololipidomics reveal a proinflammatory profile in diabetic serum. Cell phagocytosis is impaired in type 2 diabetes and requires RvE1 for activation. The dose of RvE1 required to activate resolution signals in type 2 diabetic neutrophils was significantly higher than in healthy controls. RvE1 rescues the dysregulation seen on neutrophil receptor profile and, following a therapeutic dosage, activates phagocytosis and resolution signals in type 2 diabetes. These findings reveal the importance of resolution receptors in health, disease, and dysregulation of inflammation in type 2 diabetes.

A soluble receptor for advanced glycation end-products inhibits myocardial apoptosis induced by ischemia/reperfusion via the JAK2/STAT3 pathway

sRAGE can protect cardiomyocytes from apoptosis induced by ischemia/reperfusion (I/R). However, the signaling mechanisms in cardioprotection by sRAGE are currently unknown. We investigated the cardioprotective effect and potential molecular mechanisms of sRAGE inhibition on apoptosis in the mouse myocardial I/R as an in vivo model and neonatal rat cardiomyocyte subjected to ischemic buffer as an in vitro model. Cardiac function and myocardial infarct size following by I/R were evaluated with echocardiography and Evans blue/2,3,5-triphenyltetrazolium chloride. Apoptosis was detected by TUNEL staining and caspase-3 activity. Expression of the apoptosis-related proteins p53, Bax, Bcl-2, JAK2/p-JAK2, STAT3/p-STAT3, AKT/p-AKT, ERK/p-ERK, STAT5A/p-STAT5A and STAT6/p-STAT6 were detected by western blot analysis in the presence and absence of the JAK2 inhibitor AG 490. sRAGE (100 µg/day) improved the heart function in mice with I/R: the left ventricular ejection fraction and fractional shortening were increased by 42 and 57%, respectively; the infarct size was decreased by 52%, the TUNEL-positive myocytes by 66%, and activity of caspase-3 by 24%, the protein expression of p53 and ratio of Bax to Bcl-2 by 29 and 88%, respectively; protein expression of the p-JAK2, p-STAT3 and p-AKT were increased by 92, 280 and 31%, respectively. sRAGE have no effect on protein expression of p-ERK1/2, p-STAT5A and p-STAT6 following by I/R. sRAGE (900 nmol/L) exhibited anti-apoptotic effects in cardiomyocytes by decreasing TUNEL-positive myocytes by 67% and caspase-3 activity by 20%, p53 protein level and the Bax/Bcl-2 ratio by 58 and 86%, respectively; increasing protein expression of the p-JAK2 and p-STAT3 by 26 and 156%, respectively, p-AKT protein level by 33%. The anti-apoptotic effects of sRAGE following I/R were blocked by JAK2 inhibitor AG 490. The effect of sRAGE reduction on TUNEL-positive myocytes and caspase-3 activity were abolished by PI3K inhibitor LY294002, but not ERK 1/2 inhibitor PD98059. These results suggest that sRAGE protects cardiomyocytes from apoptosis induced by I/R in vitro and in vivo by activating the JAK2/STAT3 signaling pathway.

CMKLR1 and GPR1 mediate chemerin signaling through the RhoA/ROCK pathway

Chemerin is an adipose-derived hormone that regulates immunity and energy homesotasis. To date, all known chemerin functions have been attributed to activation of the G protein-coupled receptor chemokine-like receptor-1 (CMKLR1). Chemerin is also the only known ligand for a second receptor, G protein-coupled receptor-1 (GPR1), whose signaling and function remains unknown. This study investigated the in vitro signal transduction mechanisms of CMKLR1 and GPR1 using a panel of luciferase-reporters and pathway-specific inhibitors. Herein we report the novel finding that chemerin signals through a RhoA and rho-associated protein kinase (ROCK)-dependent pathway for activation of the transcriptional regulator serum-response factor (SRF). Despite similarities in RhoA/ROCK, Gαi/o, and MAPK signaling, we also demonstrate species-specific and receptor-dependent variations in GPR1 and CMKLR1 signaling and expression of the SRF target genes EGR1, FOS and VCL. Moreover, we demonstrate that signaling through p38, Gαi/o, RhoA, and ROCK is required for chemerin-mediated chemotaxis of L1.2 lymphocytes and AGS gastric adenocarcinoma cells. These results provide, to our knowledge, the first empirical evidence that GPR1 is a functional chemerin receptor and identify RhoA/SRF as a novel chemerin-signaling axis via both CMKLR1 and GPR1.

In the eye of the neutrophil swarm-navigation signals that bring neutrophils together in inflamed and infected tissues

Neutrophils are sentinel cells that express in higher vertebrates >30 chemokine and chemoattractant receptors to sense and quickly react to tissue damage signals. Intravital microscopy studies in mouse models of wounding, inflammation, and infection have revealed that neutrophils form cell swarms at local sites of tissue injury and cell death. This swarming response is choreographed by chemokines, lipids, and other chemoattractants, controlling sequential phases of highly coordinated chemotaxis, intercellular signal relay, and cluster formation among neutrophils. This review will give a brief overview about the basic principles and key molecules that have led to the refined multistep model of how neutrophils come together to isolate sites of tissue injury and microbial invasion from healthy tissue. Whereas auto- and paracrine signaling among neutrophils during later phases of swarming can provide a level of self-organization for robust navigation in diverse inflammatory settings, guidance factors from primary tissue lesions, resident bystander cells, and dying cells regulate the initial phases of the swarming response. This review will discuss how the specific environmental context and mixture of attractants at the locally inflamed site can lead to variants of the multistep attraction model and influence the extent of neutrophil swarming, ranging from accumulations of only few individual cells to the aggregation of several hundreds of neutrophils, as found in abscesses. Given the critical roles of neutrophils in both host protection and tissue destruction, novel insights on neutrophil swarming might provide useful for the therapeutic modulation of neutrophil-dependent inflammatory processes.

Wound repair: role of immune-epithelial interactions

The epithelium serves as a highly selective barrier at mucosal surfaces. Upon injury, epithelial wound closure is orchestrated by a series of events that emanate from the epithelium itself as well as by the temporal recruitment of immune cells into the wound bed. Epithelial cells adjoining the wound flatten out, migrate, and proliferate to rapidly cover denuded surfaces and re-establish mucosal homeostasis. This process is highly regulated by proteins and lipids, proresolving mediators such as Annexin A1 protein and resolvins released into the epithelial milieu by the epithelium itself and infiltrating innate immune cells including neutrophils and macrophages. Failure to achieve these finely tuned processes is observed in chronic inflammatory diseases that are associated with non-healing wounds. An improved understanding of mechanisms that mediate repair is important in the development of therapeutics aimed to promote mucosal wound repair.

Chemerin15-Ameliorated Cardiac Ischemia-Reperfusion Injury Is Associated with the Induction of Alternatively Activated Macrophages

Chemerin15 (C15), an endogenous anti-inflammatory component, inhibits the activity of neutrophils and macrophages through G protein-coupled receptor ChemR23; however, its role as well as functional mechanism in mouse myocardial ischemia/reperfusion (I/R) injury remains unknown. Methods. Sham or I/R operations were performed on C57BL/6J mice. The I/R mice received an injection of C15 immediately before reperfusion. Serum troponin T levels, infarct size, cardiomyocyte apoptosis, reactive oxygen species (ROS) production, and infiltration of neutrophils were assessed 24 h after reperfusion, while the macrophage phenotypes, macrophage infiltration, and inflammatory cytokine levels were assessed 48 h after reperfusion. Results. Compared with the control group, the C15-treated mice showed an obvious amelioration of I/R injury and displayed less ROS, accompanied by reduced neutrophil recruitment. C15 decreased the tumor necrosis factor- (TNF-) α and interleukin- (IL-) 6 levels and increased the IL-10 levels in the serum of the I/R mice, which suggested a suppressed inflammatory response that could be related to elevated alternatively activated M2 macrophages with characteristic skewed expression of M2 markers and inhibition of classically activated M1 marker expression. Conclusion. C15 may induce alternatively activated M2 macrophage polarization and suppress the inflammatory response to protect against myocardial I/R injury in mice.

Atherosclerosis - A matter of unresolved inflammation

Atherosclerosis is commonly looked upon as a chronic inflammatory disease of the arterial wall arising from an unbalanced lipid metabolism and a maladaptive inflammatory response. However, atherosclerosis is not merely an inflammation of the vessel wall. In fact, the cardinal signs of unstable atherosclerotic lesions are primarily characteristics of failed resolution of a chronic inflammation. In contrast to acute inflammatory events which are typically self-limiting, atherosclerosis is an unresolved inflammatory condition, lacking the switch from the pro-inflammatory to the pro-resolving phase, the latter characterized by termination of inflammatory cell recruitment, removal of inflammatory cells from the site of inflammation by apoptosis and dead cell clearance, reprogramming of macrophages toward an anti-inflammatory, regenerative phenotype, and finally egress of effector cells and tissue regeneration. Here we present an overview on mechanisms of failed resolution contributing to atheroprogression and deliver a summary of novel therapeutic strategies to restore resolution in inflamed arteries.

Chemerin/chemR23 axis in inflammation onset and resolution

Chemerin is an adipokine secreted by adipocytes and associated with obesity, insulin resistance and metabolic syndrome. Different chemerin fragments with pro- or anti-inflammatory action can be produced, depending on the class of proteases predominating in the microenvironment. Chemerin binds to three receptors, especially to chemR23, expressed on various cells, as dendritic cells, macrophages and natural killer cells, regulating chemotaxis towards the site of inflammation and activation status. Recently, the chemerin/chemR23 axis has attracted particular attention for the multiple roles related to the control of inflammation, metabolism and cancerogenesis in different organs and systems as lung (allergy and cancer), skin (psoriasis, lupus, cancer, wound repair), cardiovascular system (lipid profile and atherosclerosis), reproductive apparatus (polycystic ovary syndrome, follicular homoeostasis), and digestive tract (inflammatory bowel diseases and cancer). This pathway may regulate immune responses by contributing both to the pathogenesis of inflammatory diseases and to the resolution of acute inflammation. Thus, chemerin-derived peptides or other substances that may affect the chemerin/chemR23 axis could be used in the future for the treatment of many diseases, including cancer at different sites.

Impact of resolvin E1 on murine neutrophil phagocytosis in type 2 diabetes

Diabetic complications involve inflammation-mediated microvascular and macrovascular damage, disruption of lipid metabolism, glycosylation of proteins, and abnormalities of neutrophil-mediated events. Resolution of inflamed tissues to health and homeostasis is an active process mediated by endogenous lipid agonists, including lipoxins and resolvins. This proresolution system appears to be compromised in type 2 diabetes (T2D). The goal of this study was to investigate unresolved inflammation in T2D. Wild-type (WT) and genetically engineered mice, including T2D mice (db/db), transgenic mice overexpressing the human resolvin E1 (RvE1) receptor (ERV1), and a newly bred strain of db/ERV1 mice, were used to determine the impact of RvE1 on the phagocytosis of Porphyromonas gingivalis in T2D. Neutrophils were isolated and incubated with fluorescein isothiocyanate-labeled P. gingivalis, and phagocytosis was measured in a fluorochrome-based assay by flow cytometry. Mitogen-activated protein kinase (MAPK) (p42 and p44) and Akt (Thr308 and Ser473) phosphorylation was analyzed by Western blotting. The mouse dorsal air pouch model was used to evaluate the in vivo impact of RvE1. Results revealed that RvE1 increased the neutrophil phagocytosis of P. gingivalis in WT animals but had no impact in db/db animals. In ERV1-transgenic and ERV1-transgenic diabetic mice, phagocytosis was significantly increased. RvE1 decreased Akt and MAPK phosphorylation in the transgenic animals. In vivo dorsal air pouch studies revealed that RvE1 decreases neutrophil influx into the pouch and increases neutrophil phagocytosis of P. gingivalis in the transgenic animals; cutaneous fat deposition was reduced, as was macrophage infiltration. The results suggest that RvE1 rescues impaired neutrophil phagocytosis in obese T2D mice overexpressing ERV1.

Resolution mediator chemerin15 reprograms the wound microenvironment to promote repair and reduce scarring

Disorders of cutaneous repair can cause disability or death given that skin functions as a protective barrier against the external environment. The inflammatory response triggered by tissue damage is thought to play both positive (e.g., pathogen-killing) and negative (e.g., scarring) roles in repair [1–3]. Inflammatory resolution mediators such as chemerin15 (C15) control the magnitude and duration of the inflammatory response; however, their role in wound repair and scarring is unknown [4–8]. Here, we show that the C15 precursor, chemerin, and its receptor, ChemR23, are both upregulated after skin damage and that the receptor is expressed by macrophages, neutrophils, and keratinocytes. Dynamic live-imaging studies of murine cutaneous wounds demonstrate that C15 delivery dampens the immediate intravascular inflammatory events, including platelet adhesion to neutrophils, an important event in driving leukocyte recruitment. C15 administration indirectly accelerates wound closure while altering fibroblast-mediated collagen deposition and alignment to reduce scarring. Macrophage recruitment is restricted to the immediate wound site rather than spilling extensively into the adjacent tissue as in control wounds, and macrophage phenotype in C15-treated wounds is skewed toward a less inflammatory phenotype with reduced iNOS, increased Arginase-1, and lower wound tumor necrosis factor α (TNF-α) expression. Modulation of inflammatory resolution pathways in acute and chronic wounds may therefore provide a novel therapeutic avenue to improve repair and reduce scarring.

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C15 inhibits the earliest intravascular inflammatory events after wounding

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C15 skews wound macrophage phenotype

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C15 treatment reduces wound collagen fiber alignment and thus scarring

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Resolution pathways could be targeted to improve repair and reduce scarring