Chemerin promotes angiogenesis in vivo

Synthetic retinoid-mediated preconditioning of cancer-associated fibroblasts and macrophages improves cancer response to immune checkpoint blockade

BACKGROUND

The proliferation of cancer-associated fibroblasts (CAFs) hampers drug delivery and anti-tumor immunity, inducing tumor resistance to immune checkpoint blockade (ICB) therapy. However, it has remained a challenge to develop therapeutics that specifically target or modulate CAFs.

METHODS

We investigated the involvement of Meflin+ cancer-restraining CAFs (rCAFs) in ICB efficacy in patients with clear cell renal cell carcinoma (ccRCC) and urothelial carcinoma (UC). We examined the effects of Am80 (a synthetic retinoid) administration on CAF phenotype, the tumor immune microenvironment, and ICB efficacy in cancer mouse models.

RESULTS

High infiltration of Meflin+ CAFs correlated with ICB efficacy in patients with ccRCC and UC. Meflin+ CAF induction by Am80 administration improved ICB efficacy in the mouse models of cancer. Am80 exerted this effect when administered prior to, but not concomitant with, ICB therapy in wild-type but not Meflin-deficient mice. Am80-mediated induction of Meflin+ CAFs was associated with increases in antibody delivery and M1-like tumor-associated macrophage (TAM) infiltration. Finally, we showed the role of Chemerin produced from CAFs after Am80 administration in the induction of M1-like TAMs.

CONCLUSION

Our data suggested that Am80 administration prior to ICB therapy increases the number of Meflin+ rCAFs and ICB efficacy by inducing changes in TAM phenotype.

Crosstalk between obesity and cancer: a role for adipokines

Adipose tissue is a complex organ that is increasingly being recognised as the largest endocrine organ in the body. Adipocytes among multiple cell types of adipose tissue can secrete a variety of adipokines, which are involved in signalling pathways and these can be changed by obesity and cancer. There are proposed mechanisms to link obesity/adiposity to cancer development including adipocytokine dysregulation. Among these adipokines, leptin acts through multiple pathways including the STAT3, MAPK, and PI3K pathways involved in cell growth. Adiponectin has the opposite action from leptin in tumour growth partly because of increased apoptotic responses of p53 and Bax. Visfatin increases cancer cell proliferation through ERK1/2, PI3K/AKT, and p38 which are stimulated by proinflammatory cytokines. Omentin through the PI3K/Akt-Nos pathway is involved in cancer-tumour development. Apelin might be involved through angiogenesis in tumour progressions. PAI-1 via its anti-fibrinolytic activity on cell adhesion and uPA/uPAR activity influence cancer cell growth.

Chemerin affects the expression of angiogenesis-related factors in the porcine endometrium during early pregnancy and the oestrous cycle: an in vitro study

CONTEXT

The appropriate course of angiogenesis in the endometrium is crucial for pregnancy establishment and maintenance. Very little is known about the factors linking vessel formation and immune system functioning.

AIMS

We hypothesised that chemerin, an adipokine known for its involvement in the regulation of energy balance and immunological functions, may act as a potent regulator of endometrial angiogenesis during early pregnancy in pigs.

METHODS

Porcine endometrial tissue explants were obtained from pregnant pigs on days 10-11, 12-13, 15-16 and 27-28, and on days 10-12 of the oestrous cycle. The explants were in vitro cultured for 24h in the presence of chemerin (100, 200ng/mL) or in medium alone (control). We evaluated the in vitro effect of chemerin on the secretion of vascular endothelial growth factors A-D (VEGF-A-D), placental growth factor (PlGF), basic fibroblast growth factor (bFGF) and angiopoietin 1 and 2 (ANG-1, ANG-2) with the ELISA method. The protein abundance of angiogenesis-related factor receptors, VEGF receptors 1-3 (VEGFR1-3), FGF receptors 1 and 2 (FGFR1-2) and ANG receptor (TIE2) was evaluated with the Western blot (WB) method. We also analysed the influence of chemerin on the phosphorylation of AMPK using WB.

KEY RESULTS

We found that in the studied endometrial samples, chemerin up-regulated the secretion of VEGF-A, VEGF-B and PlGF, and protein expression of VEGFR3. The adipokine caused a decrease in VEGF-C, VEGF-D and ANG-1 release. Chemerin effect on bFGF and ANG-2 secretion, and protein content of VEGFR1, VEGFR2, FGFR1, FGFR2 and TIE2 were dependent on the stage of pregnancy. Chemerin was found to down-regulate AMPK phosphorylation.

CONCLUSIONS

The obtained in vitro results suggest that chemerin could be an important factor in the early pregnant uterus by its influence on angiogenic factors' secretion and signalling.

IMPLICATIONS

The obtained results on the role of chemerin in the process of endometrial angiogenesis may, in the long term perspective, contribute to the elaboration of more effective methods of modifying reproductive processes and maintaining energy homeostasis in farm animals.

Single-Cell Transcriptomics Reveals Cellular Heterogeneity and Complex Cell-Cell Communication Networks in the Mouse Cornea

Purpose

To generate a single-cell RNA-sequencing (scRNA-seq) map and construct cell-cell communication networks of mouse corneas.

Methods

C57BL/6 mouse corneas were dissociated to single cells and subjected to scRNA-seq. Cell populations were clustered and annotated for bioinformatic analysis using the R package "Seurat." Differential expression patterns were validated and spatially mapped with whole-mount immunofluorescence staining. Global intercellular signaling networks were constructed using CellChat.

Results

Unbiased clustering of scRNA-seq transcriptomes of 14,732 cells from 40 corneas revealed 17 cell clusters of six major cell types: nine epithelial cell, three keratocyte, two corneal endothelial cell, and one each of immune cell, vascular endothelial cell, and fibroblast clusters. The nine epithelial cell subtypes included quiescent limbal stem cells, transit-amplifying cells, and differentiated cells from corneas and two minor conjunctival epithelial clusters. CellChat analysis provided an atlas of the complex intercellular signaling communications among all cell types.

Conclusions

We constructed a complete single-cell transcriptomic map and the complex signaling cross-talk among all cell types of the cornea, which can be used as a foundation atlas for further research on the cornea. This study also deepens the understanding of the cellular heterogeneity and heterotypic cell-cell interaction within corneas.

Neutrophils regulate tumor angiogenesis in oral squamous cell carcinoma and the role of Chemerin

Oral squamous cell carcinoma (OSCC) is the most common malignant tumor of the oral cavity. Tumor angiogenesis plays a crucial role in tumor progression. Studies have established the correlation between neutrophils and tumor angiogenesis in the tumor microenvironment. A previous study found that overexpression of Chemerin- in OSCC increased the infiltration of neutrophils in tumor tissues. This study aims to investigate the mechanisms underlying the regulation of the development and progression of OSCC, which have great significance in enhancing the postoperative survival of patients with OSCC. This study evaluated the accuracy of neutrophil count combined with MVD in predicting patients' survival time and its relationship with clinicopathological parameters and prognosis. Additionally, the study explored the effects of the Chemerin-neutrophil interaction on the angiogenic function of HUVECs. In OSCC, the overexpression of Chemerin promoted the angiogenesis of HUVECs through neutrophils. Moreover, Chemerin upregulated pro-angiogenic factors (e.g., VEGF-A, MMP-9, MMP-2, and S100A9) in neutrophils by activating MEK/ERK signaling pathway. In vivo experiments demonstrated that Chemerin may promote tumor growth by regulating tumor angiogenesis. In conclusion, the results suggest that neutrophil count and MVD serve as poor prognostic factors for patients with OSCC, and their combination is a more effective factor in predicting the survival time of OSCC patients. Neutrophils potentially contribute to angiogenesis through MEK/ERK signaling pathway via Chemerin and participate in the progression and metastasis of OSCC.

The Association between Serum Chemerin and Peritoneal Membrane Transport Function in Patients Undergoing Incident Peritoneal Dialysis: A Prospective Cohort Study

INTRODUCTION

Some biomarkers in drained dialyzate or peritoneal membrane have been found related to the dialyzate/plasma ratio of creatinine at 4 h (D/P Cr) in patients undergoing peritoneal dialysis (PD). But so far, there is no report on serum markers. Some biomarkers are associated with cardiovascular diseases (CVDs). Chemerin is a multifunctional chemoattractant adipokine which plays important roles in inflammation, adipogenesis, and metabolism. We intended to investigate the role of chemerin in the peritoneal membrane transport function and CVDs in incident PD patients.

METHODS

This prospective cohort study was conducted in our PD center. The patients underwent initial standardized peritoneal equilibration test after PD for 4-6 weeks. Level of serum chemerin was determined via enzyme-linked immunosorbent assay. The patients' CVDs were recorded during the follow-up period.

RESULTS

151 eligible patients with a mean age of 46.59 ± 13.52 years were enrolled, and the median duration of PD was 25.0 months. The median concentration of serum chemerin was 29.09 ng/mL. Baseline D/P Cr was positively correlated with serum chemerin (r = 0.244, p = 0.003). The multivariate analyses revealed that serum chemerin (p = 0.002), age (p = 0.041), albumin (p = 0.000), and high-density lipoprotein (p = 0.022) were independent factors of D/P Cr. The serum chemerin level was significantly higher in diabetes mellitus (DM) patients than that of patients without DM (36.45 ng/mL vs. 27.37 ng/mL, p = 0.000), and there was a significant statistical difference in CVDs between the high chemerin group (≥29.09 ng/mL) and low chemerin group (<29.09 ng/mL) (42 vs. 21%, p = 0.009).

CONCLUSIONS

Serum chemerin has a positive correlation with baseline D/P Cr in incident PD patients. It may be a biomarker that can predict the baseline transport function of the peritoneal membrane, and serum chemerin may be a risk factor of CVDs for incident PD patients. Multicenter studies with a larger sample size are warranted in the future.

The Role of Selected Adipocytokines in Ovarian Cancer and Endometrial Cancer

Due to their multidirectional influence, adipocytokines are currently the subject of numerous intensive studies. Significant impact applies to many processes, both physiological and pathological. Moreover, the role of adipocytokines in carcinogenesis seems particularly interesting and not fully understood. For this reason, ongoing research focuses on the role of these compounds in the network of interactions in the tumor microenvironment. Particular attention should be drawn to cancers that remain challenging for modern gynecological oncology-ovarian and endometrial cancer. This paper presents the role of selected adipocytokines, including leptin, adiponectin, visfatin, resistin, apelin, chemerin, omentin and vaspin in cancer, with a particular focus on ovarian and endometrial cancer, and their potential clinical relevance.

Understanding the Role of Chemerin in the Pathophysiology of Pre-Eclampsia

Chemerin is a multifaceted adipokine that is involved in multiple biological processes, including inflammation, angiogenesis, adipogenesis, and energy metabolism, as well as oxidative stress. There is a vast body of evidence for a crucial role of chemerin in the development of different cardiovascular diseases. Blood chemerin levels, as well as its placental expression, are elevated in patients with pre-eclampsia (PE) and correlate positively with the severity of the disease. This narrative review summarizes the current knowledge about the potential role of chemerin during PE development, with a particular focus on its involvement in oxidative stress and endothelial dysfunction.

Chemerin and Chemokine-like Receptor 1 Expression in Ovarian Cancer Associates with Proteins Involved in Estrogen Signaling

Chemerin, a pleiotropic adipokine coded by the RARRES2 gene, has been reported to affect the pathophysiology of various cancer entities. To further approach the role of this adipokine in ovarian cancer (OC), intratumoral protein levels of chemerin and its receptor chemokine-like receptor 1 (CMKLR1) were examined by immunohistochemistry analyzing tissue microarrays with tumor samples from 208 OC patients. Since chemerin has been reported to affect the female reproductive system, associations with proteins involved in steroid hormone signaling were analyzed. Additionally, correlations with ovarian cancer markers, cancer-related proteins, and survival of OC patients were examined. A positive correlation of chemerin and CMKLR1 protein levels in OC (Spearman's rho = 0.6, p < 0.0001) was observed. Chemerin staining intensity was strongly associated with the expression of progesterone receptor (PR) (Spearman´s rho = 0.79, p < 0.0001). Both chemerin and CMKLR1 proteins positively correlated with estrogen receptor β (ERβ) and estrogen-related receptors. Neither chemerin nor the CMKLR1 protein level was associated with the survival of OC patients. At the mRNA level, in silico analysis revealed low RARRES2 and high CMKLR1 expression associated with longer overall survival. The results of our correlation analyses suggested the previously reported interaction of chemerin and estrogen signaling to be present in OC tissue. Further studies are needed to elucidate to which extent this interaction might affect OC development and progression.

Biomarkers of haemodynamic severity of systemic sclerosis-associated pulmonary arterial hypertension by serum proteome analysis

OBJECTIVES

To mine the serum proteome of patients with systemic sclerosis-associated pulmonary arterial hypertension (SSc-PAH) and to detect biomarkers that may assist in earlier and more effective diagnosis and treatment.

METHODS

Patients with limited cutaneous SSc, no extensive interstitial lung disease and no PAH-specific therapy were included. They were classified as cases if they had PAH confirmed by right heart catheterisation (RHC) and serum collected on the same day as RHC; and as controls if they had no clinical evidence of PAH.

RESULTS

Patients were mostly middle-aged females with anticentromere-associated SSc. Among 1129 proteins assessed by a high-throughput proteomic assay (SOMAscan), only 2 were differentially expressed and correlated significantly with pulmonary vascular resistance (PVR) in SSc-PAH patients (n=15): chemerin (ρ=0.62, p=0.01) and SET (ρ=0.62, p=0.01). To validate these results, serum levels of chemerin were measured by ELISA in an independent cohort. Chemerin levels were confirmed to be significantly higher (p=0.01) and correlate with PVR (ρ=0.42, p=0.04) in SSc-PAH patients (n=24). Chemerin mRNA expression was detected in fibroblasts, pulmonary artery smooth muscle cells (PA-SMCs)/pericytes and mesothelial cells in SSc-PAH lungs by single-cell RNA-sequencing. Confocal immunofluorescence revealed increased expression of a chemerin receptor, CMKLR1, on SSc-PAH PA-SMCs. SSc-PAH serum seemed to induce higher PA-SMC proliferation than serum from SSc patients without PAH. This difference appeared neutralised when adding the CMKLR1 inhibitor α-NETA.

CONCLUSION

Chemerin seems an interesting surrogate biomarker for PVR in SSc-PAH. Increased chemerin serum levels and CMKLR1 expression by PA-SMCs may contribute to SSc-PAH pathogenesis by inducing PA-SMC proliferation.

The impact of adipokines on vascular networks in adipose tissue

Adipose tissue (AT) is a highly active and plastic endocrine organ. It secretes numerous soluble molecules known as adipokines, which act locally to AT control the remodel and homeostasis or exert pleiotropic functions in different peripheral organs. Aberrant production or loss of certain adipokines contributes to AT dysfunction associated with metabolic disorders, including obesity. The AT plasticity is strictly related to tissue vascularization. Angiogenesis supports the AT expansion, while regression of blood vessels is associated with AT hypoxia, which in turn mediates tissue inflammation, fibrosis and metabolic dysfunction. Several adipokines can regulate endothelial cell functions and are endowed with either pro- or anti-angiogenic properties. Here we address the role of adipokines in the regulation of angiogenesis. A better understanding of the link between adipokines and angiogenesis will open the way for novel therapeutic approaches to treat obesity and metabolic 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.

Role of Chemerin in Cardiovascular Diseases

(1) Background: Obesity is closely connected to the pathophysiology of cardiovascular diseases (CVDs). Excess fat accumulation is associated with metabolic malfunctions that disrupt cardiovascular homeostasis by activating inflammatory processes that recruit immune cells to the site of injury and reduce nitric oxide levels, resulting in increased blood pressure, endothelial cell migration, proliferation, and apoptosis. Adipose tissue produces adipokines, such as chemerin, that may alter immune responses, lipid metabolism, vascular homeostasis, and angiogenesis. (2) Methods: We performed PubMed and MEDLINE searches for articles with English abstracts published between 1997 (when the first report on chemerin identification was published) and 2022. The search retrieved original peer-reviewed articles analyzed in the context of the role of chemerin in CVDs, explicitly focusing on the most recent findings published in the past five years. (3) Results: This review summarizes up-to-date findings related to mechanisms of chemerin action, its role in the development and progression of CVDs, and novel strategies for developing chemerin-targeting therapeutic agents for treating CVDs. (4) Conclusions: Extensive evidence points to chemerin's role in vascular inflammation, angiogenesis, and blood pressure modulation, which opens up exciting perspectives for developing chemerin-targeting therapeutic agents for the treatment of CVDs.

Chemerin as a Potential Marker of Resolution of Inflammation in COVID-19 Infection

Chemerin is one of the specialized pro-resolving mediators that participate in the early phase of inflammation and contribute to the initiation of the pro-resolving response. There is a paucity of data regarding the time course of chemerin during acute infections. We aimed to evaluate the sequence of inflammatory responses in the acute COVID-19 phase throughout onset and resolution of inflammation. We evaluated changes in selected biomarkers in COVID-19 survivors on the 7-day and 28-day follow up. Chemerin was lower in patients with baseline moderate/severe disease at day 7 compared with asymptomatic patients and individuals with mild illness (7265 [5526−9448] vs. 8730 [6888−11,058] pg/mL; p = 0.03). Only in patients with moderate/severe disease, but not in those with mild symptoms, were chemerin concentrations decreased one week after infection onset compared with baseline (7265 [5526−9448] vs. 8866 [6383−10,690] pg/mL; p < 0.05) with a subsequent increase on the 28-day follow up (9313 [7353−11,033] pg/mL; p < 0.05). Resolution of inflammation in the group of moderate/severe SARS-CoV2 infection was associated with increasing serum concentrations of chemerin, contrary to pro-inflammatory cytokines and adipokines (pentraxin 3, TNFα, resistin, leptin). A similar pattern of angiopoietin-2 dynamics may suggest signs of enhanced vascularization as a consequence of acute SARS-CoV2 infection.

Anti-Tumoral Effect of Chemerin on Ovarian Cancer Cell Lines Mediated by Activation of Interferon Alpha Response

Simple Summary

Chemerin is a multifunctional protein with an important role in the immune system. Recent evidence showed that chemerin also regulates the development of cancer. Ovarian cancer is a common type of tumor in women. In this study, we observed that chemerin decreases the growth of ovarian cancer cell lines in vitro when cultivated in standard cell culture or in globular multicellular aggregates. When we examined the mechanisms involved in this process, we found that treatment of ovarian cancer cells with chemerin led to the activation of genes that are known to mediate the effects of interferon alpha (IFNα). The main effect of IFNα is to defend body cells against viral infections, but it is also able to defeat cancer cells. We observed that this activation of IFNα response by chemerin resulted from the increased production of IFNα protein in ovarian cancer cells, which then reduced cancer cells numbers. However, it remains to be investigated how exactly chemerin might be able to activate interferon alpha and its anti-tumoral actions.

Abstract

The pleiotropic adipokine chemerin affects tumor growth primarily as anti-tumoral chemoattractant inducing immunocyte recruitment. However, little is known about its effect on ovarian adenocarcinoma. In this study, we examined chemerin actions on ovarian cancer cell lines in vitro and intended to elucidate involved cell signaling mechanisms. Employing three ovarian cancer cell lines, we observed differentially pronounced effects of this adipokine. Treatment with chemerin (huChem-157) significantly reduced OVCAR-3 cell numbers (by 40.8% on day 6) and decreased the colony and spheroid growth of these cells by half. The spheroid size of SK-OV-3 ovarian cancer cells was also significantly reduced upon treatment. Transcriptome analyses of chemerin-treated cells revealed the most notably induced genes to be interferon alpha (IFNα)-response genes like IFI27, OAS1 and IFIT1 and their upstream regulator IRF9 in all cell lines tested. Finally, we found this adipokine to elevate IFNα levels about fourfold in culture medium of the employed cell lines. In conclusion, our data for the first time demonstrate IFNα as a mediator of chemerin action in vitro. The observed anti-tumoral effect of chemerin on ovarian cancer cells in vitro was mediated by the notable activation of IFNα response genes, resulting from the chemerin-triggered increase of secreted levels of this cytokine.

The Effect of TNF-α on CHD and the Relationship between TNF-α Antagonist and CHD in Rheumatoid Arthritis: A Systematic Review

Tumor necrosis factor-alpha (TNF-α) plays an important role in coronary heart disease (CHD), a chronic inflammatory process. Meanwhile, this pro-inflammatory factor is also involved in the pathogenesis of autoimmune diseases such as rheumatoid arthritis (RA). Patients with RA correspond to a higher risk of CHD. TNF-α antagonist, one of the main treatments for RA, may reduce the risk of CHD in patients with RA. This review summarizes the pathogenesis of TNF-α in CHD and discusses the relationship between TNF-α antagonist and CHD in patients with RA.

Role of Chemerin/ChemR23 axis as an emerging therapeutic perspective on obesity-related vascular dysfunction

Sufficient epidemiological investigations demonstrate that there is a close correlation between obesity and vascular dysfunction. Nevertheless, specific mechanisms underlying this link remain currently unclear. Given the crucial and decisive role of vascular dysfunction in multitudinous diseases, various hypotheses had been proposed and numerous experiments were being carried out. One recognized view is that increased adipokine secretion following the expanded mass of white adipose tissue due to obesity contributes to the regulation of vascular function. Chemerin, as a neo-adipokine, whose systemic level is elevated in obesity, is believed as a regulator of adipogenesis, inflammation, and vascular dysfunction via binding its cell surface receptor, chemR23. Hence, this review aims to focus on the up-to-date proof on chemerin/chemR23 axis-relevant signaling pathways, emphasize the multifarious impacts of chemerin/chemR23 axis on vascular function regulation, raise certain unsettled questions to inspire further investigations, and explore the therapeutic possibilities targeting chemerin/chemR23.

Chemerin Regulates the Proliferation and Migration of Pulmonary Arterial Smooth Muscle Cells via the ERK1/2 Signaling Pathway

Pulmonary arterial hypertension (PAH) is an incurable disease with high mortality. Chemerin has been found to be associated with pulmonary hypertension (PH). However, the specific role of chemerin in mediating PH development remains unclear. This study aimed to elucidate the regulatory effects and the underlying mechanism of chemerin on PH and to investigate the expression levels of chemerin protein in plasma in PAH patients. In vivo, two animal models of PH were established in rats by monocrotaline (MCT) injection and hypoxia. We found that the expression levels of chemerin and its receptor, chemokine-like receptor 1 (CMKLR1), were significantly upregulated in the lungs of PH rats. Primary cultured pulmonary arterial smooth muscle cells [(PASMCs) (isolated from pulmonary arteries of normal healthy rats)] were exposed to hypoxia or treated with recombinant human chemerin, we found that CMKLR1 expression was upregulated in PASMCs in response to hypoxia or chemerin stimulation, whereas the exogenous chemerin significantly promoted the migration and proliferation of PASMCs. Notably, the regulatory effects of chemerin on PASMCs were blunted by PD98059 (a selective ERK1/2 inhibitor). Using enzyme linked immunosorbent assay (ELISA), we found that the protein level of chemerin was also markedly increased in plasma from idiopathic pulmonary arterial hypertension (IPAH) patients compared to that from healthy controls. Moreover, the diagnostic value of chemerin expression in IPAH patients was determined through receiver operating characteristic (ROC) curve analysis and the result revealed that area under ROC curve (AUC) for plasma chemerin was 0.949. Taken together, these results suggest that chemerin exacerbates PH progression by promoting the proliferation and migration of PASMCs via the ERK1/2 signaling pathway, and chemerin is associated with pulmonary hypertension.

Chemerin - exploring a versatile adipokine

Chemerin is a small chemotactic protein and a key player in initiating the early immune response. As an adipokine, chemerin is also involved in energy homeostasis and the regulation of reproductive functions. Secreted as inactive prochemerin, it relies on proteolytic activation by serine proteases to exert biological activity. Chemerin binds to three distinct G protein-coupled receptors (GPCR), namely chemokine-like receptor 1 (CMKLR1, recently named chemerin₁), G protein-coupled receptor 1 (GPR1, recently named chemerin₂), and CC-motif chemokine receptor-like 2 (CCRL2). Only CMKLR1 displays conventional G protein signaling, while GPR1 only recruits arrestin in response to ligand stimulation, and no CCRL2-mediated signaling events have been described to date. However, GPR1 undergoes constitutive endocytosis, making this receptor perfectly adapted as decoy receptor. Here, we discuss expression pattern, activation, and receptor binding of chemerin. Moreover, we review the current literature regarding the involvement of chemerin in cancer and several obesity-related diseases, as well as recent developments in therapeutic targeting of the chemerin system.

CCRL2 Modulates Physiological and Pathological Angiogenesis During Retinal Development

Chemerin is a multifunctional protein involved in the regulation of inflammation, metabolism, and tumorigenesis. It binds to three receptors, CMKLR1, GPR1 and CCRL2. CMKLR1 is a fully functional receptor mediating most of the known activities of chemerin. CCRL2 does not seem to couple to any intracellular signaling pathway and is presently considered as an atypical receptor able to present the protein to cells expressing CMKLR1. CCRL2 is expressed by many cell types including leukocyte subsets and endothelial cells, and its expression is strongly upregulated by inflammatory stimuli. We recently reported that chemerin can negatively regulate the angiogenesis process, including during the development of the vascular network in mouse retina. The role of CCRL2 in angiogenesis was unexplored so far. In the present work, we demonstrate that mice lacking CCRL2 exhibit a lower density of vessels in the developing retina and this phenotype persists in adulthood, in a CMKLR1-dependent manner. Vascular sprouting was not affected, while vessel pruning, and endothelial cell apoptosis were increased. Pathological angiogenesis was also reduced in CCRL2^-/- mice in a model of oxygen-induced retinopathy. The phenotype closely mimics that of mice overexpressing chemerin, and the concentration of chemerin was found elevated in the blood of newborn mice, when the retinal vasculature develops. CCRL2 appears therefore to regulate the distribution and concentration of chemerin in organs, regulating thereby its bioactivity.

Monocyte biology conserved across species: Functional insights from cattle

Similar to human monocytes, bovine monocytes can be split into CD14^highCD16^- classical, CD14^highCD16^high intermediate and CD14^-/dimCD16^high nonclassical monocytes (cM, intM, and ncM, respectively). Here, we present an in-depth analysis of their steady-state bulk- and single-cell transcriptomes, highlighting both pronounced functional specializations and transcriptomic relatedness. Bulk gene transcription indicates pro-inflammatory and antibacterial roles of cM, while ncM and intM appear to be specialized in regulatory/anti-inflammatory functions and tissue repair, as well as antiviral responses and T-cell immunomodulation. Notably, intM stood out by high expression of several genes associated with antigen presentation. Anti-inflammatory and antiviral functions of ncM are further supported by dominant oxidative phosphorylation and selective strong responses to TLR7/8 ligands, respectively. Moreover, single-cell RNA-seq revealed previously unappreciated heterogeneity within cM and proposes intM as a transient differentiation intermediate between cM and ncM.

The Association of Serum Circulating Neuropeptide Q and Chemerin Levels with Cardiometabolic Risk Factors among Patients with Metabolic Syndrome

The potential involvement of neuropeptide Q (NPQ) and chemerin (CHEM) in metabolic disorders is yet to be fully elucidated. The aim of this study was to evaluate serum concentrations of NPQ and CHEM and to establish their relationship with cardiometabolic risk factors among individuals with metabolic syndrome. A total of 66 patients with metabolic syndrome (MetS) and 83 healthy volunteers (non-MetS) underwent biochemical, blood pressure, and anthropometric measurements. The concentration of NPQ in the MetS group was significantly lower (0.47 (0.34 ; 0.54) vs. 0.52 (0.43 ; 0.60) ng/mL, p = 0.015) than in non-MetS, while there were no differences in CHEM level. In the entire study population, we observed several negative correlations between NPQ concentration and waist-hip ratio (WHR), visceral adipose tissue, diastolic blood pressure (DBP), triglycerides (TG) along with a positive correlation with high-density lipoprotein (HDL), total muscle mass, and CHEM. Moreover, a negative correlation was observed in the MetS group between NPQ and glycemia. CHEM showed no significant correlations with cardiometabolic risk factors in the study population. In a multiple regression model, the total muscle mass proved to be an independent factor determining NPQ concentration in the population (p < 0.00000001, R²_adj = 28.6%). NPQ seems to protect against metabolic disorders correlated with obesity. Thus, it is worth considering NPQ level as a candidate protective biomarker of metabolic syndrome complications.

The Concentration of CMKLR1 Expression on Clinicopathological Parameters of Colorectal Cancer: A Preliminary Study

Background and Objectives: Colorectal cancer (CRC) is the second-most common cause of cancer-related deaths worldwide. Angiogenesis is crucial for cancer growth, infiltration of surrounding tissues, and metastasis and plays a key role in the pathogenesis of CRC. Chemerin/chemokine-like receptor 1 (CMKLR1) is one of the biochemical pathways involved in the regulation of angiogenesis in solid tumors. The aim of the study was to assess the CMKLR1 level in tumor and margin tissues of CRC in relation to histopathological parameters: microvessel density (MVD), budding, tumor-infiltrating lymphocytes (TILs), TNM scale, and grading. Materials and Methods: The study involved 43 samples of tumor and margin tissues obtained from CRC patients. To assess the concentration of CMKLR1 a commercially available enzyme-linked immunosorbent assay kit was used. For 35 cases, we performed CD34 immunostaining. The MVD, budding, and TILs were assessed using a light microscope. Results: The levels of CMKLR1 in both tumor and margin were negatively correlated with MVD and budding. CMKLR1 concentration in margin was higher in tissues with lymphocytic infiltration. Conclusions: Low vascularity and low budding are associated with higher CMKLR1 expression. CMKLR1 might play a multifunctional role in CRC pathogenesis by influencing tumor budding and peritumoral lymphocytic infiltration.

Expression of CCRL2 Inhibits Tumor Growth by Concentrating Chemerin and Inhibiting Neoangiogenesis

Simple Summary

Chemerin is a multifunctional protein regulating inflammation, immune responses, and metabolism. It was also shown to display anti-tumoral properties in various cancer models. CMKLR1 is the main functional receptor of chemerin. C-C motif chemokine receptor-like 2 (CCRL2) is another receptor binding chemerin with high affinity but failing to signal through any known signaling pathway. CCRL2 is strongly upregulated by inflammatory signals and was shown to regulate inflammatory reactions in diverse pathological conditions. Expression of CCRL2 was described in many types of human tumors such as melanoma, neuroblastoma, prostate, breast, and gastric cancer. However, its functional role in cancer has not been studied much so far. We investigate in this study how CCRL2 expression can influence the distribution of chemerin and thereby its biological activity in different tumoral contexts.

Abstract

CCRL2 belongs to the G protein-coupled receptor family and is one of the three chemerin receptors. It is considered as a non-signaling receptor, presenting chemerin to cells expressing the functional chemerin receptor ChemR23/CMKLR1 and possibly GPR1. In the present work, we investigate the role played by CCRL2 in mouse cancer models. Loss of function of Ccrl2 accelerated the development of papillomas in a chemical model of skin carcinogenesis (DMBA/TPA), whereas the growth of B16 and LLC tumor cell grafts was delayed. Delayed tumor growth was also observed when B16 and LLC cells overexpress CCRL2, while knockout of Ccrl2 in tumor cells reversed the consequences of Ccrl2 knockout in the host. The phenotypes associated with CCRL2 gain or loss of function were largely abrogated by knocking out the chemerin or Cmklr1 genes. Cells harboring CCRL2 could concentrate bioactive chemerin and promote the activation of CMKLR1-expressing cells. A reduction of neoangiogenesis was observed in tumor grafts expressing CCRL2, mimicking the phenotype of chemerin-expressing tumors. This study demonstrates that CCRL2 shares functional similarities with the family of atypical chemokine receptors (ACKRs). Its expression by tumor cells can significantly tune the effects of the chemerin/CMKLR1 system and act as a negative regulator of tumorigenesis.

The Adipokine Component in the Molecular Regulation of Cancer Cell Survival, Proliferation and Metastasis

A hormonal imbalance may disrupt the rigorously monitored cellular microenvironment by hampering the natural homeostatic mechanisms. The most common example of such hormonal glitch could be seen in obesity where the uprise in adipokine levels is in virtue of the expanding bulk of adipose tissue. Such aberrant endocrine signaling disrupts the regulation of cellular fate, rendering the cells to live in a tumor supportive microenvironment. Previously, it was believed that the adipokines support cancer proliferation and metastasis with no direct involvement in neoplastic transformations and tumorigenesis. However, the recent studies have reported discrete mechanisms that establish the direct involvement of adipokine signaling in tumorigenesis. Moreover, the individual adipokine profile of the patients has never been considered in the prognosis and staging of the disease. Hence, the present manuscript has focused on the reported extensive mechanisms that culminate the basis of poor prognosis and diminished survival rate in obese cancer patients.

Chemerin regulates normal angiogenesis and hypoxia-driven neovascularization

Chemerin is a multifunctional protein initially characterized in our laboratory as a chemoattractant factor for leukocyte populations. Its main functional receptor is CMKLR1. We identified previously chemerin as an anti-tumoral factor inhibiting the vascularization of tumor grafts. We show here that overexpression of bioactive chemerin in mice results in a reduction of the density of the retinal vascular network during its development and in adults. Chemerin did not affect vascular sprouting during the post-natal development of the network, but rather promoted endothelial cell apoptosis and vessel pruning. This phenotype was reversed to normal in CMKLR1-deficient mice, demonstrating the role of this receptor. Chemerin inhibited also neoangiogenesis in a model of pathological proliferative retinopathy, and in response to hind-limb ischemia. Mechanistically, PTEN and FOXO1 antagonists could almost completely restore the density of the retinal vasculature, suggesting the involvement of the PI3-kinase/AKT pathway in the chemerin-induced vessel regression process.

The antitumoral effects of chemerin are independent from leukocyte recruitment and mediated by inhibition of neoangiogenesis

Chemerin, a multifunctional protein acting through the receptor ChemR23/CMKLR1, is downregulated in various human tumors and was shown to display antitumoral properties in mouse models of cancer. In the present study, we report that bioactive chemerin expression by tumor cells delays the growth of B16 melanoma and Lewis lung carcinoma in vivo. A similar delay is observed when chemerin is not expressed by tumor cells but by keratinocytes of the host mice. The protective effect of chemerin is mediated by CMKLR1 and appears unrelated to the recruitment of leukocyte populations. Rather, tumors grown in the presence of chemerin display a much smaller number of blood vessels, hypoxic regions early in their development, and larger necrotic areas. These observations likely explain the slower growth of the tumors. The anti-angiogenic effects of chemerin were confirmed in a bead sprouting assay using human umbilical vein endothelial cells. These results suggest that CMKLR1 agonists might constitute therapeutic molecules inhibiting the neoangiogenesis process in solid tumors.

Chemerin promotes microangiopathy in diabetic retinopathy via activation of ChemR23 in rat primary microvascular endothelial cells

Purpose

The correlation between chemerin and diabetic retinopathy (DR) has been demonstrated previously. We aimed to investigate the potential inflammatory and angiogenic roles of chemerin in DR using rat primary retinal microvascular endothelial cells (RRMECs).

Methods

RRMECs were incubated in low- and high-glucose media, and stable chemerin receptor (ChemR23) knockdown in RRMECs was established by lentiviral infection. Real-time quantitative PCR (RT-qPCR), enzyme-linked immunosorbent assay (ELISA), and western blotting were employed to investigate the mRNA and protein expression of intercellular adhesion molecule-1 (ICAM-1), vascular endothelial growth factor (VEGF), tumor necrosis factor-α (TNF-α), and the interleukin-6 receptor (IL-6R) to explore the inflammatory and angiogenic effects of chemerin. A scratch assay was employed to evaluate the effect of chemerin on RRMEC migration.

Results

Chemerin and TNF-α markedly increased the mRNA and protein expression of ICAM-1 in RRMECs (p<0.001). ChemR23 knockdown may have decreased the ICAM-1 expression under low- and high-glucose conditions (p<0.001). Even in the ChemR23-knockdown group, TNF-α significantly increased the mRNA and protein levels of ICAM-1 under low- and high-glucose conditions (p<0.001). Chemerin promoted VEGF expression under low- and high-glucose conditions. ChemR23 knockdown markedly decreased VEGF levels under low- and high-glucose conditions (p<0.05) and significantly decreased RRMEC migration (p<0.001).

Conclusions

Chemerin promotes the expression of ICAM-1, the secretion of VEGF, and the migration of RRMECs via the activation of ChemR23.

Neuroprotective Effects of Chemerin on a Mouse Stroke Model: Behavioral and Molecular Dimensions

The present study was conducted to investigate the effects of different doses of recombinant human Chemerin (rhChemerin) on brain damage, spatial memory, blood-brain barrier (BBB) disruption and cellular and molecular mechanisms in a mouse stroke model. The mouse stroke model was developed by blocking the middle cerebral artery for 1 h and performing reperfusion for 23 h. Immediately, one and three hours after the stroke, 200, 400 and 800 ng/mouse of intranasal rhChemerin was administered. Neuronal and BBB damage, spatial memory and neurological performance were examined 24 h after the stroke. Western blotting and immunofluorescence were utilized to determine the effects of rhChemerin on the expressions of nuclear factor kappa B (NF-κB), pro-inflammatory cytokines such as TNF-α and IL-1β, anti-inflammatory cytokines such as IL-10 and TGF-β and vascular endothelial growth factor (VEGF). Administering 400 and 800 ng/mouse of rhChemerin in the mice immediately and one hour after ischemia minimized the infarct size, BBB opening, spatial memory and neurological impairment (P < 0.001). Furthermore, 800 ng/mouse of rhChemerin significantly diminished terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive (apoptotic) cells, suppressed the expressions of NF-kB, TNF-α and IL-1β and upregulated IL-10 and VEGF in the cortex and hippocampus of the mice. The present findings showed that rhChemerin administered immediately and one hour after stroke alleviates neuronal and BBB injures and improves spatial memory. These effects of rhChemerin may be mediated by inhibiting inflammatory pathways and apoptotic machinery.

Chemerin promotes the pathogenesis of preeclampsia by activating CMKLR1/p-Akt/CEBPɑ axis and inducing M1 macrophage polarization

A higher ratio of M1/M2 macrophages and an elevated chemerin level are both related to increased risk of preeclampsia. However, the crosstalk between these two events and their collective contribution to preeclampsia are not well understood. In this study, we assessed the impacts of chemerin chemokine-like receptor 1 (CMKLR1)/p-Akt/CEBPα axis in regulating macrophage polarization and mediating the pathogenic effects of chemerin on preeclampsia. We showed that chemerin, in a dose- and time-dependent manner, stimulated M1 macrophage polarization, inhibited macrophage-induced trophoblast invasion and migration, and suppressed macrophage-mediated angiogenesis. All these chemerin-induced phenotypes are essentially mediated by sequentially CMKLR1, Akt activation, and CEBPα. Mechanistically, CEBPα acted as a transcriptional activator for both IRF8 and chemerin. In vivo, chemerin aggravated preeclampsia, while α-NETA, an inhibitor for CMKLR1, significantly suppressed M1 macrophage polarization and alleviated preeclampsia. In summary, chemerin, by activating CMKLR1/Akt/CEBPα axis, forms a positive feedback loop, promotes M1 macrophage polarization, suppresses trophoblast migration/invasion and angiogenesis, and contributes to preeclampsia. Therefore, targeting chemerin signaling may benefit the prevention and/or treatment of preeclampsia.

Serum Chemerin Concentration Is Associated with Proinflammatory Status in Chronic Coronary Syndrome

Background: Chemerin is an adipokine and a chemoattractant for leukocytes. Increased chemerin levels were observed in patients with coronary artery disease (CAD). We investigated associations between chemerin and biochemical measurements or body composition in CAD patients. Methods: In the study, we included patients with stable CAD who had undergone percutaneous coronary intervention (PCI) in the past. All patients had routine blood tests, and their insulin and chemerin serum levels were routinely measured. Body composition was assessed with the DEXA method. Results: The study group comprised 163 patients (mean age 59.8 ± years, 26% of females, n = 43). There was no significant difference in serum chemerin concentrations between patients with diabetes and the remaining ones: 306.8 ± 121 vs. 274.15 ± 109 pg/mL, p = 0.1. Chemerin correlated positively with the white blood cell (WBC) count, the neutrophil to lymphocyte ratio, hsCRP, all fractions of cholesterol, triglycerides, platelet count, fasting insulin, and c-peptide. Chemerin levels were also correlated with total fat mass but only in a subgroup with normal glucose metabolism. Conclusion: In patients with CAD, serum chemerin levels are correlated with inflammation markers, insulin resistance, and an unfavorable lipid profile. Correlation with fat mass is dependent on glucose metabolism status. Depending on the presence of diabetes/prediabetes, the mechanisms regulating chemerin secretion may be different.

CHEMERIN as a modulator of angiogenesis and apoptosis processes in the corpus luteum of pigs: An in vitro study

The corpus luteum (CL) undergoes rapid changes, and its functional capabilities are influenced by processes such as angiogenesis and apoptosis. According to the literature, chemerin - a protein which participates in the regulation of energy homeostasis and the immune response, may also affect angiogenesis and apoptosis. Therefore, the aim of this study was to investigate the in vitro effect of chemerin on angiogenesis and apoptosis in porcine luteal cells (Lc) during specific phases related to CL physiology. Luteal cells were harvested from gilts during the early-, mid-, and late-luteal phases of the estrous cycle. The cells were preincubated for 48 h and incubated for 24 h with chemerin or a serum-free medium (controls). The abundance of angiogenesis- and apoptosis-related proteins was determined by ELISA in spent culture media, or by ELISA and Western Blot in protein extracts. The current study demonstrated that chemerin stimulates the production of VEGF-A and bFGF by porcine Lc and increases the protein abundance of angiogenic factors receptors (VEGFR1, VEGFR2, VEGFR3, FGFR1, FGFR2) in these cells. The study also revealed that chemerin exerts a modulatory effect (stimulatory/inhibitory, depending on the phase of the cycle) on the protein abundance of Fas, FasL, Bcl-2 and caspase-3 in porcine Lc. These results imply that chemerin may affect angiogenesis and apoptosis processes in the porcine CL, as evidenced by its modulatory effect of chemerin on the protein abundance of crucial angiogenesis- and apoptosis-related factors, observed in an in vitro study of porcine Lc.

Role of Atypical Chemokines and Chemokine Receptors Pathways in the Pathogenesis of COPD

Chronic obstructive pulmonary disease (COPD) represents a heightened inflammatory response in the lung generally resulting from tobacco smoking-induced recruitment and activation of inflammatory cells and/or activation of lower airway structural cells. Several mediators can modulate activation and recruitment of these cells, particularly those belonging to the chemokines (conventional and atypical) family. There is emerging evidence for complex roles of atypical chemokines and their receptors (such as high mobility group box 1 (HMGB1), antimicrobial peptides, receptor for advanced glycosylation end products (RAGE) or toll-like receptors (TLRs)) in the pathogenesis of COPD, both in the stable disease and during exacerbations. Modulators of these pathways represent potential novel therapies for COPD and many are now in preclinical development. Inhibition of only a single atypical chemokine or receptor may not block inflammatory processes because there is redundancy in this network. However, there are many animal studies that encourage studies for modulating the atypical chemokine network in COPD. Thus, few pharmaceutical companies maintain a significant interest in developing agents that target these molecules as potential antiinflammatory drugs. Antibody-based (biological) and small molecule drug (SMD)-based therapies targeting atypical chemokines and/or their receptors are mostly at the preclinical stage and their progression to clinical trials is eagerly awaited. These agents will most likely enhance our knowledge about the role of atypical chemokines in COPD pathophysiology and thereby improve COPD management.

Chemerin in atherosclerosis

Atherosclerosis (AS), a chronic arterial disease, is characterized by endothelial dysfunction, inflammatory reactions and lipid accumulation in parallel with aberrant angiogenesis and vascular smooth muscle cell (VSMC) proliferation. Adipose tissue has been suggested to have an integral influence on metabolism and endocrine secretion, while there have been increasing concerns about the possible involvement of adipokines in cardiovascular diseases, including AS. Here, we focused on chemerin, an adipokine highly expressed in adipose tissue, with strong evidence of an association with inflammation, endothelial dysfunction, metabolic disorder, aberrant angiogenesis, VSMC proliferation and calcification. In this review, we discuss chemerin and its receptors in the pathogenesis of AS. However, the existing data assign various, even contradictory, roles to chemerin in atherosclerosis, such as inhibiting vascular calcification and impairing endothelial function. Current studies focusing on its anti- and pro-atherogenic effects have pinpointed its distinct role in specific cell types and contexts in the pathogenesis of atherosclerosis. Therefore, the gaps in current knowledge regarding the specific role played by chemerin in the etiology of AS require additional future studies. It seems reasonable to suggest that targeted chemerin therapy can be developed as an innovative approach for treating AS.

Expression of antimicrobial peptide genes oscillates along day/night rhythm protecting mice skin from bacteria

Antimicrobial peptides (AMPs) are important components of the innate immune system and are involved in skin protection against environmental insults and in wound healing. Herein, we assessed the gene expression of chemerin (Rarres2), cathelicidin CRAMP (Camp), and three β-defensins (Defb1, Defb3, and Defb14) in mouse skin during light/dark cycle (LD 12:12) and constant darkness (DD). Next, we examined the survival of bacteria applied on the skin at specific times during the day. We found that the expression of Rarres2, Camp, and Defb1 was the highest at 4 h after the beginning of darkness, during high activity of mice. These rhythms, however, were not maintained under DD in the skin but were present in the liver. This indicated that in the case of skin, a circadian input was masked by daily changes of light in the environment. In contrast, Defb3 and Defb14 showed the highest mRNA levels when the mice slept, and these rhythmic mRNA oscillations were maintained under DD. This shows that Rarres2, Camp, and Defb1 levels in the skin are correlated with high locomotor activity in mice and they are controlled by daily changes of light and dark. Alternatively, oscillations in the mRNA levels of Defb3 and Defb14 seem to protect skin and heal wounds during sleep. These rhythms are maintained under DD, indicating that they are regulated by a circadian clock. Our study suggests that daily AMP expression affects the survival of bacteria on the surface of skin, which depends on the phase of AMP cycling.

Secreted Factors from Stem Cells of Human Exfoliated Deciduous Teeth Directly Activate Endothelial Cells to Promote All Processes of Angiogenesis

Diabetes is a major risk factor for atherosclerosis and ischemic vascular diseases. Recently, regenerative medicine is expected to be a novel therapy for ischemic diseases. Our previous studies have reported that transplantation of stem cells promoted therapeutic angiogenesis for diabetic neuropathy and ischemic vascular disease in a paracrine manner, but the precise mechanism is unclear. Therefore, we examined whether secreted factors from stem cells had direct beneficial effects on endothelial cells to promote angiogenesis. The soluble factors were collected as conditioned medium (CM) 48 h after culturing stem cells from human exfoliated deciduous teeth (SHED) in serum-free DMEM. SHED-CM significantly increased cell viability of human umbilical vein endothelial cells (HUVECs) in MTT assays and accelerated HUVECs migration in wound healing and Boyden chamber assays. In a Matrigel plug assay of mice, the migrated number of primary endothelial cells was markedly increased in the plug containing SHED-CM or SHED suspension. SHED-CM induced complex tubular structures of HUVECs in a tube formation assay. Furthermore, SHED-CM significantly increased neovascularization from the primary rat aorta, indicating that SHED-CM stimulated primary endothelial cells to promote comprehensive angiogenesis processes. The angiogenic effects of SHED-CM were the same or greater than the effective concentration of VEGF. In conclusion, SHED-CM directly stimulates vascular endothelial cells to promote angiogenesis and is promising for future clinical application.

The In Vitro Effect of Prostaglandin E2 and F2α on the Chemerin System in the Porcine Endometrium during Gestation

Chemerin belongs to the group of adipocyte-derived hormones known as adipokines, which are responsible mainly for the control of energy homeostasis. Adipokine exerts its influence through three receptors: Chemokine-like receptor 1 (CMKLR1), G protein-coupled receptor 1 (GPR1), and C-C motif chemokine receptor-like 2 (CCRL2). A growing body of evidence indicates that chemerin participates in the regulation of the female reproductive system. According to the literature, the expression of chemerin and its receptors in reproductive structures depends on the local hormonal milieu. The aim of this study was to investigate the in vitro effect of prostaglandins E2 (PGE2) and F2α (PGF2α) on chemerin and chemerin receptor (chemerin system) mRNAs (qPCR) and proteins (ELISA, Western blotting) in endometrial tissue explants collected from early-pregnant gilts. Both PGE2 and PGF2α significantly influenced the expression of the chemerin gene, hormone secretion, and the expression of chemerin receptor genes and proteins. The influence of both prostaglandins on the expression of the chemerin system varied between different stages of gestation. This is the first study to describe the modulatory effect of PGE2 and PGF2α on the expression of the chemerin system in the porcine uterus during early gestation.

Assessment of CMKLR1 level in colorectal cancer and its correlation with angiogenic markers

INTRODUCTION

Colorectal cancer (CRC) is the second most common malignant neoplasm in men and third in women. It is also the third leading cause of cancer-related death, killing annually >700,000 patients in the world. The global burden of CRC is expected to increase by 60% to >2.2 million new cases and 1.1 million deaths by 2030. The pathogenesis of cancer mainly depends on angiogenesis. This process plays a key role in the growth and infiltration of tumors which is essential for distant metastases. A large number of biochemical pathways is involved in the regulation of angiogenesis. As a subject of our study, we chose chemerin/chemokine-like receptor 1 (CMKLR1) pathway which is responsible for the angiogenic processes in malignant neoplasms.

AIM OF THE STUDY

To assess the CMKLR1 level and the concentrations of the two markers of angiogenesis, matrix metalloproteinase (MMP)-9 and vascular cell adhesion molecule (VCAM)-1, in tumor and margin tissues of CRC in relation to histological grade and TNM classification.

MATERIALS AND METHODS

The study used 47 samples of tumor and margin tissues derived from CRC patients. To determine the concentration of CMKLR1, MMP-9, and VCAM-1, we used the commercially available enzyme-linked immunosorbent assay kit.

RESULTS

We found a significantly higher concentration of CMKLR1 and MMP-9 in tumor tissue compared to margin. There was no difference in VCAM-1 concentration between tumor and margin. The margin concentration of CMKLR1 was significantly correlated with that of both MMP-9 and VCAM-1. The margin concentration of VCAM-1 was correlated with that of MMP-9. Additionally, we observed that the tumor levels of CMKLR1 and MMP-9 were positively correlated with the tumor size (T parameter).

CONCLUSION

CMKLR1 activity may be associated with the angiogenic process in CRC via MMP-9 activity. Further research, involving a larger sample, may verify whether chemerin/CMKLR1 axis could be considered as a suitable target in novel molecular therapies.

Correlation between adiponectin, chemerin, vascular endothelial growth factor and epicardial fat volume in patients with coronary artery disease

Epicardial fat, a local visceral fat depot surrounded by visceral pericardial sac, surrounds the coronary arteries for most of their course and may contribute to the development of coronary atherosclerosis by local production of inflammatory cytokines. Some studies on non-invasive measurement of epicardial fat mass have shown that epicardial fat mass is associated with the increased incidence of coronary artery disease (CAD), onset and progression of coronary plaque, mainly including major adverse cardiovascular events, myocardial ischemia, and atrial fibrillation. In the present study the correlation of adiponectin, chemerin, and vascular endothelial growth factor (VEGF) with the epicardial fat volume in patients with coronary artery disease was explored, and the risk factors for vascular remodeling of CAD patients were analyzed. A total of 50 CAD patients, treated in Chongzuo People's Hospital from August 2017 to September 2018, were enrolled as the observation group, and further 50 healthy individuals, who underwent physical examinations in the hospital at the same period, were enrolled as the control group. RT-qPCR was adopted to detect the expression levels of adiponectin, chemerin and VEGF in the two groups, a 64-slice dual-source CT to detect epicardial fat volume, and Pearson's correlation to analyze adiponectin, chemerin, VEGF and epicardial fat volume. Logistic regression analysis was performed to analyze the risk factors for vascular remodeling in CAD patients, and a receiver operating characteristic (ROC) curve analysis was used to analyze the value of indexes with multifactorial significance in vascular remodeling. The observation group showed obviously larger epicardial fat volume than the control group (P<0.001), lower adiponectin expression than the control group (P<0.001), and higher chemerin and VEGF expression than the control group (P<0.001). In the observation group, adiponectin expression decreased with the increase of epicardial fat volume (P<0.001), while the expression of chemerin and VEGF increased with the increase of epicardial fat volume (P<0.001). Remodeling occurred in 27 of the 50 patients. ROC curve analysis showed that the areas under the curves of adiponectin, chemerin, VEGF and epicardial fat volume were 0.697, 0.652, 0.696 and 0.689, respectively. Epicardial fat volume, adiponectin, chemerin and VEGF are independent risk factors for vascular remodeling and the expression of adiponectin, chemerin and VEGF can reflect epicardial fat volume.

Expression of Bioactive Chemerin by Keratinocytes Inhibits Late Stages of Tumor Development in a Chemical Model of Skin Carcinogenesis

Chemerin is a multifunctional protein acting mainly through the G protein-coupled receptor ChemR23/CMKLR1/Chemerin₁. Its expression is frequently downregulated in human tumors, including in melanoma and squamous cell carcinoma of the skin and anti-tumoral properties of chemerin were reported in mouse tumor graft models. In the present study, we report the development of spontaneous skin tumors in aged ChemR23-deficient mice. In order to test the potential therapeutic benefit of chemerin analogs, a transgenic model in which bioactive chemerin is over-expressed by basal keratinocytes was generated. These animals are characterized by increased levels of chemerin immunoreactivity and bioactivity in the skin and the circulation. In a chemical carcinogenesis model, papillomas developed later, were less numerous, and their progression to carcinomas was delayed. Temporal control of chemerin expression by doxycycline allowed to attribute its effects to late stages of carcinogenesis. The protective effects of chemerin were partly abrogated by ChemR23 invalidation. These results demonstrate that chemerin is able to delay very significantly tumor progression in a model that recapitulates closely the evolution of solid cancer types in human and suggest that the chemerin-ChemR23 system might constitute an interesting target for therapeutic intervention in the cancer field.

More Than an Adipokine: The Complex Roles of Chemerin Signaling in Cancer

Chemerin is widely recognized as an adipokine, with diverse biological roles in cellular differentiation and metabolism, as well as a leukocyte chemoattractant. Research investigating the role of chemerin in the obesity-cancer relationship has provided evidence both for pro- and anti-cancer effects. The tumor-promoting effects of chemerin primarily involve direct effects on migration, invasion, and metastasis as well as growth and proliferation of cancer cells. Chemerin can also promote tumor growth via the recruitment of tumor-supporting mesenchymal stromal cells and stimulation of angiogenesis pathways in endothelial cells. In contrast, the majority of evidence supports that the tumor-suppressing effects of chemerin are immune-mediated and result in a shift from immunosuppressive to immunogenic cell populations within the tumor microenvironment. Systemic chemerin and chemerin produced within the tumor microenvironment may contribute to these effects via signaling through CMKLR1 (chemerin₁), GPR1 (chemerin₂), and CCLR2 on target cells. As such, inhibition or activation of chemerin signaling could be beneficial as a therapeutic approach depending on the type of cancer. Additional studies are required to determine if obesity influences cancer initiation or progression through increased adipose tissue production of chemerin and/or altered chemerin processing that leads to changes in chemerin signaling in the tumor microenvironment.

Chemerin and Cancer

Chemerin is a multifunctional adipokine with established roles in inflammation, adipogenesis and glucose homeostasis. Increasing evidence suggest an important function of chemerin in cancer. Chemerin's main cellular receptors, chemokine-like receptor 1 (CMKLR1), G-protein coupled receptor 1 (GPR1) and C-C chemokine receptor-like 2 (CCRL2) are expressed in most normal and tumor tissues. Chemerin's role in cancer is considered controversial, since it is able to exert both anti-tumoral and tumor-promoting effects, which are mediated by different mechanisms like recruiting innate immune defenses or activation of endothelial angiogenesis. For this review article, original research articles on the role of chemerin and its receptors in cancer were considered, which are listed in the PubMed database. Additionally, we included meta-analyses of publicly accessible DNA microarray data to elucidate the association of expression of chemerin and its receptors in tumor tissues with patients' survival.

Chemerin Isoforms and Activity in Obesity

Overweight and adiposity are risk factors for several diseases, like type 2 diabetes and cancer. White adipose tissue is a major source for adipokines, comprising a diverse group of proteins exerting various functions. Chemerin is one of these proteins whose systemic levels are increased in obesity. Chemerin is involved in different physiological and pathophysiological processes and it regulates adipogenesis, insulin sensitivity, and immune response, suggesting a vital role in metabolic health. The majority of serum chemerin is biologically inert. Different proteases are involved in the C-terminal processing of chemerin and generate diverse isoforms that vary in their activity. Distribution of chemerin variants was analyzed in adipose tissues and plasma of lean and obese humans and mice. The Tango bioassay, which is suitable to monitor the activation of the beta-arrestin 2 pathway, was used to determine the ex-vivo activation of chemerin receptors by systemic chemerin. Further, the expression of the chemerin receptors was analyzed in adipose tissue, liver, and skeletal muscle. Present investigations assume that increased systemic chemerin in human obesity is not accompanied by higher biologic activity. More research is needed to fully understand the pathways that control chemerin processing and chemerin signaling.