Chemerin and CMKLR1 expression in human arteries and periadventitial fat: a possible role for local chemerin in atherosclerosis?

Dynamic changes in proresolving lipid mediators and their receptors following acute vascular injury in male rats

Acute vascular injury provokes an inflammatory response, resulting in neointimal hyperplasia (NIH) and downstream pathologies. The resolution of inflammation is an active process in which specialized proresolving lipid mediators (SPM) and their receptors play a central role. We sought to examine the acute phase response of SPM and their receptors in both circulating blood and the arterial wall in a rat angioplasty model. We found that the ratio of proresolving to pro-inflammatory lipid mediators (LM) in plasma decreased sharply 1 day after vascular injury, then increased slightly by day 7, while that in arteries remained depressed. Granulocyte expression of SPM receptors ALX/FPR2 and DRV2/GPR18, and a leukotriene B4 receptor BLT1 increased postinjury, while ERV1/ChemR23 expression was reduced early and then recovered by day 7. Importantly, we show unique arterial expression patterns of SPM receptors in the acute setting, with generally low levels through day 7 that contrasted sharply with that of the pro-inflammatory CCR2 receptor. Overall, these data document acute, time-dependent changes of LM biosynthesis and SPM receptor expression in plasma, leukocytes, and artery walls following acute vascular injury. A biochemical imbalance between inflammation and resolution LM pathways appears persistent 7 days after angioplasty in this model. These findings may help guide therapeutic approaches to accelerate vascular healing and improve the outcomes of vascular interventions for patients with advanced atherosclerosis.

Chemokine receptor PET imaging: Bridging molecular insights with clinical applications

Chemokine receptors are important components of cellular signaling and play a critical role in directing leukocytes during inflammatory reactions. Their importance extends to numerous pathological processes, including tumor differentiation, angiogenesis, metastasis, and associations with multiple inflammatory disorders. The necessity to monitor the in vivo interactions of cellular chemokine receptors has been driven the recent development of novel positron emission tomography (PET) imaging agents. This imaging modality provides non-invasive localization and quantitation of these receptors that cannot be provided through blood or tissue-based assays. Herein, we provide a review of PET imaging of the chemokine receptors that have been imaged to date, namely CXCR3, CXCR4, CCR2, CCR5, and CMKLR1. The quantification of these receptors can aid in understanding various diseases, including cancer, atherosclerosis, idiopathic pulmonary fibrosis, and acute respiratory distress syndrome. The development of specific radiotracers targeting these receptors will be discussed, including promising results for disease diagnosis and management. However, challenges persist in fully translating these imaging advancements into practical therapeutic applications. Given the success of CXCR4 PET imaging to date, future research should focus on clinical translation of these approaches to understand their role in the management of a wide variety of diseases.

Inconsequential role for chemerin-like receptor 1 in the manifestation of ozone-induced lung pathophysiology in male mice

We executed this study to determine if chemerin-like receptor 1 (CMKLR1), a Gi/o protein-coupled receptor expressed by leukocytes and non-leukocytes, contributes to the development of phenotypic features of non-atopic asthma, including airway hyperresponsiveness (AHR) to acetyl-β-methylcholine chloride, lung hyperpermeability, airway epithelial cell desquamation, and lung inflammation. Accordingly, we quantified sequelae of non-atopic asthma in wild-type mice and mice incapable of expressing CMKLR1 (CMKLR1-deficient mice) following cessation of acute inhalation exposure to either filtered room air (air) or ozone (O3), a criteria pollutant and non-atopic asthma stimulus. Following exposure to air, lung elastic recoil and airway responsiveness were greater while the quantity of adiponectin, a multi-functional adipocytokine, in bronchoalveolar lavage (BAL) fluid was lower in CMKLR1-deficient as compared to wild-type mice. Regardless of genotype, exposure to O3 caused AHR, lung hyperpermeability, airway epithelial cell desquamation, and lung inflammation. Nevertheless, except for minimal genotype-related effects on lung hyperpermeability and BAL adiponectin, we observed no other genotype-related differences following O3 exposure. In summary, we demonstrate that CMKLR1 limits the severity of innate airway responsiveness and lung elastic recoil but has a nominal effect on lung pathophysiology induced by acute exposure to O3.

Progression of Arterial Vasa Vasorum from Regulator of Arterial Homeostasis to Promoter of Atherogenesis

The vasa vasorum (vessels of vessels) are a dynamic microvascular system uniquely distributed to maintain physiological homeostasis of the artery wall by supplying nutrients and oxygen to the outer layers of the artery wall, adventitia, and perivascular adipose tissue, and in large arteries, to the outer portion of the medial layer. Vasa vasorum endothelium and contractile mural cells regulate direct access of bioactive cells and factors present in both the systemic circulation and the arterial perivascular adipose tissue and adventitia to the artery wall. Experimental and human data show that proatherogenic factors and cells gain direct access to the artery wall via the vasa vasorum and may initiate, promote, and destabilize the plaque. Activation and growth of vasa vasorum occur in all blood vessel layers primarily by angiogenesis, producing fragile and permeable new microvessels that may cause plaque hemorrhage and fibrous cap rupture. Ironically, invasive therapies, such as angioplasty and coronary artery bypass grafting, injure the vasa vasorum, leading to treatment failures. The vasa vasorum function both as a master integrator of arterial homeostasis and, once perturbed or injured, as a promotor of atherogenesis. Future studies need to be directed at establishing reliable in vivo and in vitro models to investigate the cellular and molecular regulation of the function and dysfunction of the arterial vasa vasorum.

Endothelial CCRL2 induced by disturbed flow promotes atherosclerosis via chemerin-dependent β2 integrin activation in monocytes

AIMS

Chemoattractants and their cognate receptors are essential for leucocyte recruitment during atherogenesis, and atherosclerotic plaques preferentially occur at predilection sites of the arterial wall with disturbed flow (d-flow). In profiling the endothelial expression of atypical chemoattractant receptors (ACKRs), we found that Ackr5 (CCRL2) was up-regulated in an endothelial subpopulation by atherosclerotic stimulation. We therefore investigated the role of CCRL2 and its ligand chemerin in atherosclerosis and the underlying mechanism.

METHODS AND RESULTS

By analysing scRNA-seq data of the left carotid artery under d-flow and scRNA-seq datasets GSE131776 of ApoE-/- mice from the Gene Expression Omnibus database, we found that CCRL2 was up-regulated in one subpopulation of endothelial cells in response to d-flow stimulation and atherosclerosis. Using CCRL2-/-ApoE-/- mice, we showed that CCRL2 deficiency protected against plaque formation primarily in the d-flow areas of the aortic arch in ApoE-/- mice fed high-fat diet. Disturbed flow induced the expression of vascular endothelial CCRL2, recruiting chemerin, which caused leucocyte adhesion to the endothelium. Surprisingly, instead of binding to monocytic CMKLR1, chemerin was found to activate β2 integrin, enhancing ERK1/2 phosphorylation and monocyte adhesion. Moreover, chemerin was found to have protein disulfide isomerase-like enzymatic activity, which was responsible for the interaction of chemerin with β2 integrin, as identified by a Di-E-GSSG assay and a proximity ligation assay. For clinical relevance, relatively high serum levels of chemerin were found in patients with acute atherothrombotic stroke compared to healthy individuals.

CONCLUSIONS

Our findings indicate that d-flow-induced CCRL2 promotes atherosclerotic plaque formation via a novel CCRL2-chemerin-β2 integrin axis, providing potential targets for the prevention or therapeutic intervention of atherosclerosis.

The Role of Chemerin in Metabolic and Cardiovascular Disease: A Literature Review of Its Physiology and Pathology from a Nutritional Perspective

Chemerin is a novel adipokine that plays a major role in adipogenesis and lipid metabolism. It also induces inflammation and affects insulin signaling, steroidogenesis and thermogenesis. Consequently, it likely contributes to a variety of metabolic and cardiovascular diseases, including atherosclerosis, diabetes, hypertension and pre-eclampsia. This review describes its origin and receptors, as well as its role in various diseases, and subsequently summarizes how nutrition affects its levels. It concludes that vitamin A, fat, glucose and alcohol generally upregulate chemerin, while omega-3, salt and vitamin D suppress it. Dietary measures rather than drugs acting as chemerin receptor antagonists might become a novel tool to suppress chemerin effects, thereby potentially improving the aforementioned diseases. However, more detailed studies are required to fully understand chemerin regulation.

Up-regulation of CMKLR1 in endometriosis and its relationship with inflammatory responses

Inflammation plays a critical role in the pathogenesis of endometriosis. We aimed to study the proinflammatory effect of Chemerin chemokine-like receptor 1 (CMKLR1) in patients with endometriosis. Sixty patients with endometriosis and 50 healthy controls were recruited in this study for the collection of endometrial samples and peritoneal fluid. The expression levels of CMKLR1, IL-6, MCP-1, and TNF-α in peritoneal fluid and endometrial tissues were detected by ELISA, qRT-PCR, and immunohistochemical staining. Human endometrial stromal cells (HESCs) were used to measure the Chemerin-induced CMKLR1 activation and inflammatory responses. CMKLR1 level was significantly up-regulated in peritoneal fluid and endometrial tissues in patients with endometriosis. Interestingly, CMKLR1 overexpression positively correlated with pro-inflammatory cytokines and chemokine in both peritoneal fluid and ectopic endometrium. Chemerin treatment increased the expression of CMKLR1, and aggravated inflammatory responses in HESCs. CMKLR1 is up-regulated in peritoneal fluid and endometrial tissues, and promotes the inflammatory responses in of endometriosis.

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.

Prognostic value of plasma adipokine chemerin in patients with coronary artery disease

Background

Adipokine chemerin was proven to be associated with coronary artery disease (CAD), but its prognostic implications in CAD remain unclear.

Methods

This study consists of two parts, one is a basic study and the other is a clinical cohort study. First, we investigated the differential expression of six adipokines in the atherosclerotic mice model compared to mice with milder degrees of atherosclerosis and mice without atherosclerosis using microarray data. We then examined the potential of chemerin as a diagnostic and prognostic indicator in a CAD cohort. A total of 152 patients were enrolled in our study, including 77 patients with angiographically proven CAD and 75 control subjects without cardiovascular disease. Plasma adipokine chemerin levels were measured in all patients, and major adverse cardiovascular events (MACEs) were followed up, including ischemic stroke, non-fatal myocardial infarction, revascularization, and cardiovascular death.

Results

In the aortas of atherosclerotic mice, chemerin expression was up-regulated compared to control mice. The plasma chemerin levels of CAD patients were higher than those of non-CAD patients (128.93 ± 37.06 vs. 109.85 ± 27.47 mmol/L, respectively, P < 0.001). High chemerin levels were an independent predictor of CAD (β = 2.702, 95% CI, 1.344–5.431, P = 0.001). We followed up with patients for a median duration of 5.5 years (3.9–5.6). The Kaplan–Meier curves showed that patients in the high chemerin group had a significantly higher risk of MACEs than the low chemerin group in patients with CAD (log-rank P = 0.003), not with non-CAD (Log-rank P = 0.120). Furthermore, Cox multivariate analysis revealed that high chemerin levels were an independent predictor of MACEs (HR 2.267; 95% CI, 1.139–4.515; P = 0.020). Finally, the cellular study showed that chemerin is predominantly expressed in PBMC-derived macrophages.

Conclusion

Plasma chemerin levels were increased in the CAD patients, and a high chemerin level increased the risk of MACEs in CAD patients.

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.

Exploring the Relationship of Perivascular Adipose Tissue Inflammation and the Development of Vascular Pathologies

Initially thought to only provide mechanical support for the underlying blood vessels, perivascular adipose tissue (PVAT) has now emerged as a regulator of vascular function. A healthy PVAT exerts anticontractile and anti-inflammatory actions on the underlying vasculature via the release of adipocytokines such as adiponectin, nitric oxide, and omentin. However, dysfunctional PVAT produces more proinflammatory adipocytokines such as leptin, resistin, interleukin- (IL-) 6, IL-1β, and tumor necrosis factor-alpha, thus inducing an inflammatory response that contributes to the pathogenesis of vascular diseases. In this review, current knowledge on the role of PVAT inflammation in the development of vascular pathologies such as atherosclerosis and hypertension was discussed.

Chemokine-like Receptor 1 in Brain of Spontaneously Hypertensive Rats Mediates Systemic Hypertension

Adipocytokine chemerin is a biologically active molecule secreted from adipose tissue. Chemerin elicits a variety of functions via chemokine-like receptor 1 (CMKLR1). The cardiovascular center in brain that regulates blood pressure (BP) is involved in pathophysiology of systemic hypertension. Thus, we explored the roles of brain chemerin/CMKLR1 on regulation of BP in spontaneously hypertensive rats (SHR). For this aim, we examined effects of intracerebroventricular (i.c.v.) injection of CMKLR1 small interfering (si)RNA on both systemic BP as measured by tail cuff system and protein expression in paraventricular nucleus (PVN) of SHR as determined by Western blotting. We also examined both central and peripheral protein expression of chemerin by Western blotting. Systolic BP of SHR but not normotensive Wistar Kyoto rats (WKY) was decreased by CMKLR1 siRNA. The decrease of BP by CMKLR1 siRNA persisted for 3 days. Protein expression of CMKLR1 in PVN of SHR tended to be increased compared with WKY, which was suppressed by CMKLR1 siRNA. Protein expression of chemerin in brain, peripheral plasma, and adipose tissue was not different between WKY and SHR. In summary, we for the first time revealed that the increased protein expression of CMKLR1 in PVN is at least partly responsible for systemic hypertension in SHR.

Novel Cardioprotective Effect of L-Carnitine on Obese Diabetic Mice: Regulation of Chemerin and CMKLRI Expression in Heart and Adipose Tissues

Fundamentos

A L-carnitina (LC) tem muitos efeitos benéficos em animais diabéticos e humanos, mas seu efeito regulatório sobre a quemerina como uma citocina inflamatória e seu receptor no estado diabético são desconhecidos.

Objetivos

O presente estudo teve como objetivo investigar o efeito regulatório da LC na expressão do receptor semelhante ao de quimiocina 1 e quemerina (CMKLRI) em tecidos adiposo e cardíaco de camundongos diabéticos.

Métodos

Sessenta camundongos NMARI foram divididos em quatro grupos, incluindo controle, diabético, diabético + suplementação com LC e controle + suplementação com LC. O diabetes foi induzido pela alimentação dos animais com dieta hipercalórica por 5 semanas e injeção de estreptozotocina. Os animais foram tratados com 300 mg/kg de LC por 28 dias. Nos dias 7, 14 e 28 após o tratamento, os níveis de mRNA e proteína da quemerina e CMKLRI nos tecidos cardíacos e adiposos de animais foram determinados utilizando análise por qPCR e ELISA. Os índices de resistência à insulina também foram medidos em todos os grupos experimentais. A diferença com p<0,05 foi considerada significativa.

Resultados

A expressão de quemerina e CMKLRI aumentou nos tecidos cardíaco e adiposo de camundongos diabéticos nos dias 14 e 28 após a indução do diabetes, concomitantemente com a incidência de resistência à insulina e níveis aumentados de quemerina circulante (p<0,05). O tratamento com LC causou uma diminuição significativa na expressão de ambos os genes nos tecidos estudados e redução dos sintomas de resistência à insulina e dos níveis séricos de quemerina (p<0,05).

Conclusão

Os resultados sugerem que o tratamento com LC pode diminuir a expressão de quemerina e CKLR1 em tecidos cardíacos e adiposos de animais experimentais obesos e diabéticos.

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.

An Integrative Study of Aortic mRNA/miRNA Longitudinal Changes in Long-Term LVAD Support

Studying the long-term impact of continuous-flow left ventricular assist device (CF-LVAD) offers an opportunity for a complex understanding of the pathophysiology of vascular changes in aortic tissue in response to a nonphysiological blood flow pattern. Our study aimed to analyze aortic mRNA/miRNA expression changes in response to long-term LVAD support. Paired aortic samples obtained at the time of LVAD implantation and at the time of heart transplantation were examined for mRNA/miRNA profiling. The number of differentially expressed genes (Pcorr < 0.05) shared between samples before and after LVAD support was 277. The whole miRNome profile revealed 69 differentially expressed miRNAs (Pcorr < 0.05). Gene ontology (GO) analysis identified that LVAD predominantly influenced genes involved in the extracellular matrix and collagen fibril organization. Integrated mRNA/miRNA analysis revealed that potential targets of miRNAs dysregulated in explanted samples are mainly involved in GO biological process terms related to dendritic spine organization, neuron projection organization, and cell junction assembly and organization. We found differentially expressed genes participating in vascular tissue engineering as a consequence of LVAD duration. Changes in aortic miRNA levels demonstrated an effect on molecular processes involved in angiogenesis.

Adipokines and Arterial Stiffness in Obesity

Adipokines are active molecules with pleiotropic effects produced by adipose tissue and involved in obesity-related metabolic and cardiovascular diseases. Arterial stiffness, which is a consequence of arteriosclerosis, has been shown to be an independent predictor of cardiovascular morbidity and mortality. The pathogenesis of arterial stiffness is complex but incompletely understood. Adipokines dysregulation may induce, by various mechanisms, vascular inflammation, endothelial dysfunction, and vascular remodeling, leading to increased arterial stiffness. This article summarizes literature data regarding adipokine-related pathogenetic mechanisms involved in the development of arterial stiffness, particularly in obesity, as well as the results of clinical and epidemiological studies which investigated the relationship between adipokines and arterial stiffness.

Chemerin causes lipid metabolic imbalance and induces passive lipid accumulation in human hepatoma cell line via the receptor GPR1

AIMS

Chemerin is abundant in patients with high body mass index and metabolic syndrome possibly due to its activation in adipogenesis and glucose intolerance. It has reported that sera chemerin is positively associated with fatty liver with little known underlying mechanisms. Our aim is to study the role of chemerin in hepatic lipid metabolism.

MAIN METHODS

Oil Red O staining and TG quantitative assay were used to detect intracellular lipid accumulation. PCR, QPCR and western blot were applied to measure lipid metabolism-related genes, CMKLR1, GPR1 and inflammation marker genes. Luciferase reporter assay was employed to uncover the down-regulation of proximate promoter activities of CMKLR1 and GPR1 by SREBP1c. Antibody neutralization assay was used to address the effects of chemerin on hepatic lipid synthesis.

KEY FINDINGS

Over-expression of chemerin led to passive lipid accumulation, in human hepatoma cell line HepG2. The disable form of chemerin (chemerin 21-158) and active chemerin (chemerin 21-157) performed strongly effects on lipid metabolism in HepG2 cells. Heterologous expression of CMKLR1 or G-protein coupled receptor1 (GPR1) played similar roles in hepatocyte lipid metabolism as chemerin. Chemerin exerted its effects on lipid metabolism via GPR1 in HepG2 cells. Furthermore, free fatty acids and high concentration insulin inhibited chemerin expression. Consistently, the key lipogenic transcription factor Sterol regulatory element binding protein 1c suppressed chemerin mRNA expression and proximate promoter activities of CMKLR1 and GPR1.

SIGNIFICANCE

It implied the existence of negative feed-back regulation and further confirmed the involvement of chemerin in hepatic lipid metabolism.

Chemerin as a Driver of Hypertension: A Consideration

The protein chemerin (tazarotene-induced gene, TIG2; RARRES2) is a relatively new adipokine. Many studies support that circulating chemerin levels associate strongly and positively with body mass index, visceral fat, and blood pressure. Here, we focus on the specific relationship of chemerin and blood pressure with the goal of understanding whether and how chemerin drives (pathological) changes in blood pressure such that it could be interfered with therapeutically. We dissect the biosynthesis of chemerin and how current antihypertensive medications change chemerin metabolism. This is followed with a review of what is known about where chemerin is synthesized in the body and what chemerin and its receptors can do to the physiological function of organs important to blood pressure determination (e.g., brain, heart, kidneys, blood vessels, adrenal, and sympathetic nervous system). We synthesize from the literature our best understanding of the mechanisms by which chemerin modifies blood pressure, with knowledge that plasma/serum levels of chemerin may be limited in their pathological relevance. This review reveals several gaps in our knowledge of chemerin biology that could be filled by the collective work of protein chemists, biologists, pharmacologists, and clinicians.

Adipokines and Inflammation: Focus on Cardiovascular Diseases

It is well established that adipose tissue, apart from its energy storage function, acts as an endocrine organ that produces and secretes a number of bioactive substances, including hormones commonly known as adipokines. Obesity is a major risk factor for the development of cardiovascular diseases, mainly due to a low grade of inflammation and the excessive fat accumulation produced in this state. The adipose tissue dysfunction in obesity leads to an aberrant release of adipokines, some of them with direct cardiovascular and inflammatory regulatory functions. Inflammation is a common link between obesity and cardiovascular diseases, so this review will summarise the role of the main adipokines implicated in the regulation of the inflammatory processes occurring under the scenario of cardiovascular diseases.

Endogenous Chemerin from PVAT Amplifies Electrical Field-Stimulated Arterial Contraction: Use of the Chemerin Knockout Rat

Background: We previously reported that the adipokine chemerin, when added exogenously to the isolated rat mesenteric artery, amplified electrical field-stimulated (EFS) contraction. The Chemerin1 antagonist CCX832 alone inhibited EFS-induced contraction in tissues with but not without perivascular adipose tissue (PVAT). These data suggested indirectly that chemerin itself, presumably from the PVAT, facilitated EFS-induced contraction. We created the chemerin KO rat and now test the focused hypothesis that endogenous chemerin amplifies EFS-induced arterial contraction. Methods: The superior mesenteric artery +PVAT from global chemerin WT and KO female rats, with endothelium and sympathetic nerve intact, were mounted into isolated tissue baths for isometric and EFS-induced contraction. Results: CCX832 reduced EFS (2-20 Hz)-induced contraction in tissues from the WT but not KO rats. Consistent with this finding, the magnitude of EFS-induced contraction was lower in the tissues from the KO vs. WT rats, yet the maximum response to the adrenergic stimulus PE was not different among all tissues. Conclusion: These studies support that endogenous chemerin modifies sympathetic nerve-mediated contraction through Chemerin1, an important finding relative in understanding chemerin's role in control of blood pressure.

Acute intracerebroventricular injection of chemerin-9 increases systemic blood pressure through activating sympathetic nerves via CMKLR1 in brain

Chemerin is an adipocytokine involved in inflammation and lipid metabolism via G protein-coupled receptor, chemokine-like receptor (CMKLR)1. Since the important nuclei regulating pressure (BP) exist in the brain, we examined the effects of acute intracerebroventricular (i.c.v.) injection of chemerin-9 on systemic BP and explored underlying mechanisms. We examined the effects of acute i.c.v. injection of chemerin-9 (10 nmol/head) on systemic BP by a carotid cannulation method in the control or CMKLR1 small interfering (si) RNA-treated Wistar rats (0.04 nmol, 3 days, i.c.v.). We examined protein expression of CMKLR1 around brain ventricles by Western blotting. We examined the effects of acute i.c.v. injection of chemerin-9 on serum adrenaline by a high performance liquid chromatography. In the control siRNA-treated rats, chemerin-9 significantly increased mean BP, which reached a peak at 2 to 4 min after injection. On the other hand, in the CMKLR1 siRNA-treated rats, chemerin-9 did not affect the mean BP. Protein expression of CMKLR1 specifically in subfornical organ (SFO) and paraventricular nucleus (PVN) from the CMKLR1 siRNA-treated rats decreased compared with the control siRNA-treated rats. In the control siRNA-treated rats, chemerin-9 increased serum adrenaline level. On the other hand, in the CMKLR1 siRNA-treated rats, chemerin-9 did not affect the serum adrenaline level. Further, pretreatment with prazosin, an α-adrenaline receptor blocker, significantly prevented the pressor responses induced by chemerin-9. In summary, we for the first time demonstrated that chemerin-9 stimulates the sympathetic nerves via CMKLR1 perhaps expressed in SFO and PVN, which leads to an increase in systemic BP.

The Treponema pallidum outer membrane protein Tp92 activates endothelial cells via the chemerin/CMKLR1 pathway

Endothelium damage caused by Treponema pallidum is the key step in the systemic dissemination and pathophysiology of syphilis, particularly cardiovascular syphilis and neurosyphilis. However, the molecular mechanisms supporting endothelium damage of syphilis are undefined. The outer membrane proteins were thought to be involved. Tp92 was first identified as an outer membrane protein of T. pallidum. Homologous proteins to Tp92 play important roles in cell attachment, inflammation, and tissue destruction in other bacterial species. In this study, we investigated the effect of Tp92 on endothelial cells activation. The data showed that Tp92 induced chemerin production in activated endothelial cells. Endothelial cell-derived chemerin upregulated the expression of TNF-α and ICAM-1 in endothelial cells via CMKLR1. In addition, endothelial cell-derived chemerin promoted THP-1-derived macrophage migration towards endothelial cells. These findings suggest that Tp92 may play an important role in mediating endothelial cell activation by inducing the secretion of chemerin.

Inflammation and its resolution in atherosclerosis: mediators and therapeutic opportunities

Atherosclerosis is a lipid-driven inflammatory disease of the arterial intima in which the balance of pro-inflammatory and inflammation-resolving mechanisms dictates the final clinical outcome. Intimal infiltration and modification of plasma-derived lipoproteins and their uptake mainly by macrophages, with ensuing formation of lipid-filled foam cells, initiate atherosclerotic lesion formation, and deficient efferocytotic removal of apoptotic cells and foam cells sustains lesion progression. Defective efferocytosis, as a sign of inadequate inflammation resolution, leads to accumulation of secondarily necrotic macrophages and foam cells and the formation of an advanced lesion with a necrotic lipid core, indicative of plaque vulnerability. Resolution of inflammation is mediated by specialized pro-resolving lipid mediators derived from omega-3 fatty acids or arachidonic acid and by relevant proteins and signalling gaseous molecules. One of the major effects of inflammation resolution mediators is phenotypic conversion of pro-inflammatory macrophages into macrophages that suppress inflammation and promote healing. In advanced atherosclerotic lesions, the ratio between specialized pro-resolving mediators and pro-inflammatory lipids (in particular leukotrienes) is strikingly low, providing a molecular explanation for the defective inflammation resolution features of these lesions. In this Review, we discuss the mechanisms of the formation of clinically dangerous atherosclerotic lesions and the potential of pro-resolving mediator therapy to inhibit this process.

Hematopoietic ChemR23 (Chemerin Receptor 23) Fuels Atherosclerosis by Sustaining an M1 Macrophage-Phenotype and Guidance of Plasmacytoid Dendritic Cells to Murine Lesions-Brief Report

Objective- Expression of the chemokine-like receptor ChemR23 (chemerin receptor 23) has been specifically attributed to plasmacytoid dendritic cells (pDCs) and macrophages and ChemR23 has been suggested to mediate an inflammatory immune response in these cells. Because chemokine receptors are important in perpetuating chronic inflammation, we aimed to establish the role of ChemR23-deficiency on macrophages and pDCs in atherosclerosis. Approach and Results- ChemR23-knockout/knockin mice expressing eGFP (enhanced green fluorescent protein) were generated and after crossing with apolipoprotein E-deficient ( Apoe^-/- ChemR23 ^e/e) animals were fed a western-type diet for 4 and 12 weeks. Apoe^-/- ChemR23 ^e/e mice displayed reduced lesion formation and reduced leukocyte adhesion to the vessel wall after 4 weeks, as well as diminished plaque growth, a decreased number of lesional macrophages with an increased proportion of M2 cells and a less inflammatory lesion composition after 12 weeks of western-type diet feeding. Hematopoietic ChemR23-deficiency similarly reduced atherosclerosis. Additional experiments revealed that ChemR23-deficiency induces an alternatively activated macrophage phenotype, an increased cholesterol efflux and a systemic reduction in pDC frequencies. Consequently, expression of the pDC marker SiglecH in atherosclerotic plaques of Apoe^-/- ChemR23 ^e/e mice was declined. ChemR23-knockout pDCs also exhibited a reduced migratory capacity and decreased CCR (CC-type chemokine receptor)7 expression. Finally, adoptive transfer of sorted wild-type and knockout pDCs into Apoe^-/- recipient mice revealed reduced accumulation of ChemR23-deficient pDCs in atherosclerotic lesions. Conclusions- Hematopoietic ChemR23-deficiency increases the proportion of alternatively activated M2 macrophages in atherosclerotic lesions and attenuates pDC homing to lymphatic organs and recruitment to atherosclerotic lesions, which synergistically restricts atherosclerotic plaque formation and progression.

ERV1/ChemR23 Signaling Protects Against Atherosclerosis by Modifying Oxidized Low-Density Lipoprotein Uptake and Phagocytosis in Macrophages

Supplemental Digital Content is available in the text.

Background:

In addition to enhanced proinflammatory signaling, impaired resolution of vascular inflammation plays a key role in atherosclerosis. Proresolving lipid mediators formed through the 12/15 lipoxygenase pathways exert protective effects against murine atherosclerosis. n-3 Polyunsaturated fatty acids, including eicosapentaenoic acid (EPA), serve as the substrate for the formation of lipid mediators, which transduce potent anti-inflammatory and proresolving actions through their cognate G-protein–coupled receptors. The aim of this study was to identify signaling pathways associated with EPA supplementation and lipid mediator formation that mediate atherosclerotic disease progression.

Methods:

Lipidomic plasma analysis were performed after EPA supplementation in Apoe^−/− mice. Erv1/Chemr23^−/−xApoe^−/− mice were generated for the evaluation of atherosclerosis, phagocytosis, and oxidized low-density lipoprotein uptake. Histological and mRNA analyses were done on human atherosclerotic lesions.

Results:

Here, we show that EPA supplementation significantly attenuated atherosclerotic lesion growth induced by Western diet in Apoe^−/− mice and was associated with local cardiovascular n-3 enrichment and altered lipoprotein metabolism. Our systematic plasma lipidomic analysis identified the resolvin E1 precursor 18-monohydroxy EPA as a central molecule formed during EPA supplementation. Targeted deletion of the resolvin E1 receptor Erv1/Chemr23 in 2 independent hyperlipidemic murine models was associated with proatherogenic signaling in macrophages, increased oxidized low-density lipoprotein uptake, reduced phagocytosis, and increased atherosclerotic plaque size and necrotic core formation. We also demonstrate that in macrophages the resolvin E1–mediated effects in oxidized low-density lipoprotein uptake and phagocytosis were dependent on Erv1/Chemr23. When analyzing human atherosclerotic specimens, we identified ERV1/ChemR23 expression in a population of macrophages located in the proximity of the necrotic core and demonstrated augmented ERV1/ChemR23 mRNA levels in plaques derived from statin users.

Conclusions:

This study identifies 18-monohydroxy EPA as a major plasma marker after EPA supplementation and demonstrates that the ERV1/ChemR23 receptor for its downstream mediator resolvin E1 transduces protective effects in atherosclerosis. ERV1/ChemR23 signaling may represent a previously unrecognized therapeutic pathway to reduce atherosclerotic cardiovascular disease.

Chemerin-9, a potent agonist of chemerin receptor (ChemR23), prevents atherogenesis

Plasma levels of chemerin, an adipocytokine produced from the adipose tissues and liver, are associated with metabolic syndrome and coronary artery disease (CAD). Chemerin and its analog, chemerin-9, are known to bind to their receptor, ChemR23. However, whether chemerin and chemerin-9 affect atherogenesis remains to be elucidated. We investigated the expression of chemerin and ChemR23 in human coronary arteries and cultured human vascular cells. The effects of chemerin and chemerin-9 on atheroprone phenomena were assessed in human THP1 monocytes, human umbilical vein endothelial cells (HUVECs), and human aortic smooth muscle cells (HASMCs) and aortic lesions in Apoe−/− mice. In patients with CAD, a small amount of ChemR23, but not chemerin, was expressed within atheromatous plaques in coronary arteries. Chemerin and ChemR23 were expressed at high levels in THP1 monocytes, THP1-derived macrophages, and HUVECs; however, their expression in HASMCs was weak. Chemerin and chemerin-9 significantly suppressed the tumor necrosis factor-α (TNF-α)-induced mRNA expression of adhesion and pro-inflammatory molecules in HUVECs. Chemerin and chemerin-9 significantly attenuated the TNF-α-induced adhesion of THP1 monocytes to HUVECs and macrophage inflammatory phenotype. Chemerin and chemerin-9 suppressed oxidized low-density lipoprotein (oxLDL)-induced macrophage foam cell formation associated with down-regulation of CD36 and up-regulation of ATP-binding cassette transporter A1 (ABCA1). In HASMCs, chemerin and chemerin-9 significantly suppressed migration and proliferation without inducing apoptosis. In the Apoe−/− mice, a 4-week infusion of chemerin-9 significantly decreased the areas of aortic atherosclerotic lesions by reducing intraplaque macrophage and SMC contents. Our results indicate that chemerin-9 prevents atherosclerosis. Therefore, the development of chemerin analogs/ChemR23 agonists may serve as a novel therapeutic target for atherosclerotic diseases.

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.

Chemerin stimulates aortic smooth muscle cell proliferation and migration via activation of autophagy in VSMCs of metabolic hypertension rats

Vascular remodeling is a characteristic pathogenesis of hypertension and a main cause of abnormal construction and function of organs because of hypertension. Chemerin is a new adipokine that is elevated in states of obesity and metabolic syndrome (MS). However, the molecular mechanisms behind these pathological processes are not fully clarified. An animal model of metabolic hypertension was created to evaluate the role of metabolic chemerin in hypertension. In this study, the expression of chemerin/CMKLR-1 and autophagy in the arteries of metabolic hypertension rats undergoing vascular remodeling was investigated and the effect and mechanisms on the regulation of human aortic smooth muscle cells (HA-SMCs) were explored. The vascular remodeling in vivo was more serious in the metabolic hypertensive rat model, and the expression of chemerin and its receptor CMKLR1 were remarkably higher in the media layer of the thoracic aorta and the mesenteric artery in metabolic hypertension rats. In addition, there was an increased number of autophagosomes in SMCs and an up-regulation of the autophagy-related protein LC3 and beclin-1 levels in metabolic hypertension rats. In vitro, chemerin significantly stimulated HA-SMC proliferation and migration, as determined by MTT assay and scratch assay, respectively. Chemerin significantly increased LC3 and beclin-1 levels, as measured by western blot analysis, while this effect was inhibited by the autophagy inhibitor 3-MA. It is demonstrated that chemerin stimulates SMC proliferation and migration via autophagy, which may lead to vascular structural remodeling in metabolic hypertension.

Expression of chemerin correlates with a poor prognosis in female breast cancer patients

Objective

Chemerin was reported to regulate adipogenesis, metabolism, and immunity. But, its relation to cancer remains controversial. In breast cancer, chemerin expression has only been studied in serum, however, its expression in tissue, to our knowledge, has not been studied. The aim of this study was to investigate chemerin expression in breast cancer tissue in comparison to the adjacent normal tissue, and to assess its relationship to disease prognosis.

Methods

We examined chemerin expression in tissue with immunohistochemistry and analyzed the association of chemerin expression with the patients’ clinical and pathological characteristics to determine its role as a predictor of the disease and its relation to disease prognosis.

Results

We detected a significantly higher expression of chemerin in the malignant vs the non-cancerous tissue specimens in 30/53, (56%) patients, (P=0.001). Moreover, its expression was significantly higher in the metastatic lymph nodes in comparison to the tumor tissues, (P=0.01). Chemerin expression was significantly correlated with weight (r=0.256, P=0.04), body mass index (r=0.233, P=0.03), tumor size (r=0.235, P=0.03), lymph node metastasis (r=0.265, P=0.045), distant metastasis (r=0.267, P=0.02), and tumor grading, (r=0.421, P=0.004), while it was inversely significantly correlated with estrogen receptor and progesterone receptor expression in malignant breast tissues (P=0.038, r=−0.437, and P=0.047, r=–0.316), respectively. The area under the receiver operating characteristic curve for chemerin as a predictor of breast cancer was 0.82, (P<0.001, sensitivity 89%, and specificity 69%). The Kaplan–Meier survival curves revealed that patients with higher chemerin expression had worse overall survival in comparison to those with a lower chemerin expression, (P=0.001).

Conclusion

Our results revealed higher chemerin expression in malignant vs adjacent normal breast tissue and lend support to a presumable role of chemerin tissue expression as an independent predictor of poor prognosis in breast cancer patients.

The Effect of Chemerin on Cardiac Parameters and Gene Expressions in Isolated Perfused Rat Heart

Background:

Chemerin is a novel chemoattractant adipokine expressed in cardiovascular system, and its receptor has been detected in the epicardial adipose tissue.

Aims:

To determine the effects of chemerin on the cardiac parameters and gene expressions in the isolated perfused rat heart.

Study Design:

Animal experiment.

Methods:

The hearts were retrogradely perfused with Langendorff technique to measure the cardiac parameters. The experimental groups were acutely treated with 10, 100, and 1000 nM doses of chemerin. Another group was given 10 μM L-nitric oxide synthase inhibitor for 5 min before 1000 nM chemerin administration. The real-time polymerase chain reaction was performed for detecting the expression of target genes.

Results:

All doses of chemerin significantly decreased the left ventricular developed pressure (max 35.33 Δ%, p<0.001), and +dP/dt_max (max 31.3 Δ%, p<0.001), which are the indexes of cardiac contractile force. In addition, 1000 nM chemerin reduced the coronary flow (max 31 Δ%, p<0.001). N(W)-nitro-L-arginine methyl ester antagonized the negative inotropic effect of chemerin on contractility. Chemerin induced a 2.16-fold increase in endothelial nitric oxide synthase mRNA and increased the cyclic guanosine monophosphate levels (p<0.001) but decreased the PI3Kγ gene expression (1.8-fold, p<0.001). Furthermore, all doses of chemerin decreased the CaV1.2 gene expression (1.69-fold, p<0.001).

Conclusion:

Acute chemerin treatment induces a negative inotropic action with the involvement of nitric oxide pathway, CaV1.2, and PI3Kγ on isolated rat heart.

The chemerin knockout rat reveals chemerin dependence in female, but not male, experimental hypertension

Measures of the adipokine chemerin are elevated in multiple cardiovascular diseases, including hypertension, but little mechanistic work has been done to implicate chemerin as being causative in such diseases. The chemerin knockout (KO) rat was created to test the hypothesis that removal of chemerin would reduce pressure in the normal and hypertensive state. Western analyses confirmed loss of chemerin in the plasma and tissues of the KO vs. wild-type (WT) rats. Chemerin concentration in plasma and tissues was lower in WT females than in WT males, as determined by Western analysis. Conscious male and female KO rats had modest differences in baseline measures vs. the WT that included systolic, diastolic, mean arterial and pulse pressures, and heart rate, all measured telemetrically. The mineralocorticoid deoxycorticosterone acetate (DOCA) and salt water, combined with uninephrectomy as a hypertensive stimulus, elevated mean and systolic blood pressures of the male KO higher than the male WT. By contrast, all pressures in the female KO were lower than their WT throughout DOCA-salt treatment. These results revealed an unexpected sex difference in chemerin expression and the ability of chemerin to modify blood pressure in response to a hypertensive challenge.-Watts, S. W., Darios, E. S., Mullick, A. E., Garver, H., Saunders, T. L., Hughes, E. D., Filipiak, W. E., Zeidler, M. G., McMullen, N., Sinal, C. J., Kumar, R. K., Ferland, D. J., Fink, G. D. The chemerin knockout rat reveals chemerin dependence in female, but not male, experimental hypertension.

Association of Circulating Chemerin With Subclinical Parameters of Atherosclerosis: Results of a Population-Based Study

Supplemental Digital Content is available in the text.

Objective—

Chemerin has been shown to be associated with inflammation and metabolic syndrome, which are in turn leading risk factors for atherosclerosis. A few clinical studies have concentrated on the role of chemerin in atherosclerosis but revealed divergent findings. Therefore, we aimed to investigate the association of plasma chemerin levels with different subclinical measurements of atherosclerosis in a population-based sample.

Approach and Results—

Linear and logistic regression models with different atherosclerotic parameters as subclinical outcomes were applied to analyze data from 4003 subjects of the SHIP (Study of Health in Pomerania). After adjustment for metabolic and inflammatory parameters, these models revealed no association of chemerin with carotid intima-media thickness, carotid plaque, or carotid stenosis but a significant inverse association between chemerin and ankle-brachial index. In detail, logistic regression analysis showed that a 25-ng/mL increase in chemerin was associated with a 30% higher odd (95% confidence interval, 1.20–1.41) of having an ankle-brachial index value below the 25th age- and sex-specific quartile.

Conclusions—

Our analyses revealed a modest inverse association between chemerin and ankle-brachial index that remained consistent after adjustment for metabolic and inflammatory parameters. The association of chemerin with carotid intima-media thickness, carotid plaque, or carotid stenosis was not significant after adjustment for the same confounder set. The investigated subclinical atherosclerotic parameters are representative for the atherosclerotic burden of different arterial regions and different disease stages. Thus, our results might suggest that the value of chemerin as a marker of higher atherosclerotic risk differs depending on the affected arterial region and disease stage.

Increased circulating chemerin in patients with advanced carotid stenosis

Background

Chemerin is an adipokine which plays a crucial role in atherosclerosis. Here, we examined whether circulating chemerin is enhanced in patients with advanced carotid stenosis.

Methods

Chemerin was quantified in 178 patients prior to carotid end arterectomy (CEA) and in age- and gender-matched controls (n = 163). Chemerin levels were related to anthropometric, clinical and metabolic characteristics of the patients.

Results

Chemerin levels were higher in patients compared to controls (p <  0.001). Chemerin correlated to parameters associated with inflammation such as C-reactive protein (CRP, p <  0.001), leukocyte blood count (p <  0.001) and circulating TNF-α (p = 0.004) in the patients. Chemerin levels did not differ between asymptomatic (n = 93) and symptomatic patients who experienced an ischemic event within 6 months prior to CEA (n = 85). However, in the case of high-grade carotid stenosis (≥ 90%), chemerin levels were higher in symptomatic (n = 44) compared to asymptomatic patients (n = 41, p = 0.014). Chemerin was increased in patients with (n = 50) compared to patients without (n = 128) coronary artery disease (CAD, p = 0.002). A high level of chemerin increases the risk for CAD in patients (p = 0.0013).

Conclusions

Circulating chemerin is increased and correlates to inflammatory parameters in patients with advanced carotid stenosis.

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.

Increased serum chemerin level to predict early onset of aortic valve stenosis

Inflammation appears to be the cause of aortic valve (AoV) stenosis and identification of predictive biomarkers is therefore imperative. The aim of the current study was to evaluate the potential role of serum chemerin and fibroblast growth factor-21 (FGF-21) in the pathogenesis of the disease. A total of 102 patients were selected based on certain criteria and divided into an aortic stenosis group and a control group. Patients with AoV stenosis were subdivided into three groups depending on the severity according to the echocardiography criteria: Aortic jet velocity, Vmax (m/sec); mean pressure gradient, PG (mmHg); aortic valve area (AVA), cm²; and indexed AVA, cm²/m². Patients were graded as: Severe: Vmax >4 m/sec, PG >40 mmHg, AVA <1.0 cm², indexed AVA <0.6; moderate: Vmax 3.0–4.0 m/sec, PG 20–40 mmHg, AVA 1.0–1.5 cm², indexed AVA 0.60–0.85; mild: Vmax 2.5–2.9 m/sec, PG <20 mmHg, AVA >1.5 cm², indexed AVA >0.85. ELISA was used for the detection of chemerin and FGF-21. Post-hoc analysis with Tukey's correction was performed. The highest chemerin levels were found in mild and moderate AoV stenosis and decreased along with the grade of severity, compared with the control group. The FGF-21 level was increased in all the stenosis groups, reaching the highest level at severe stenosis. Receiver-operating characteristic analysis of chemerin in all the AoV stenosis groups without grading the severity included, area under the curve (AUC)=0.76; 0.70–0.80= fair; P<0.001 and for mild AoV stenosis was AUC=0.82; 0.80–0.90= good; P<0.001. In conclusion, chemerin is a good diagnostic biomarker for mild AoV stenosis, while FGF-21 is a moderate diagnostic marker.

Serum levels of chemerin, apelin, vaspin, and omentin-1 in obese type 2 diabetic Egyptian patients with coronary artery stenosis

Cardiovascular diseases (CVD) are the leading cause of death in the diabetic population. Obesity is a serious problem that has been linked with CVD and diabetes via a variety of adipokines. The aims of this study were to evaluate and correlate circulating chemerin, apelin, vaspin, and omentin-1 levels in obese type 2 diabetic Egyptian patients with coronary artery stenosis (CAS), and to assess their usefulness as noninvasive diagnostic biomarkers. Chemerin, apelin, vaspin, and omentin-1 levels were determined by enzyme immunoassay in coronary artery disease (CAD) I patients (45 non-obese, nondiabetic with CAS), CAD II patients (45 obese, diabetic with CAS), and 30 controls. Patients in CAD I and CAD II groups exhibited higher levels of chemerin and apelin together with lower levels of vaspin and omentin-1 than in controls. These alterations were more significant in CAD II than in CAD I patients. Additionally, adipokine levels were individually correlated with each other and with certain biochemical variables. Moreover, chemerin and vaspin levels could differentiate CAD II patients from CAD I and controls. Alterations of these adipokines may play a crucial role in the pathogenesis of CAS in obese type 2 diabetic Egyptian patients. Chemerin and vaspin could be used as markers to support diagnosis of CAS.

Adipokine Contribution to the Pathogenesis of Osteoarthritis

Recent studies have shown that overweight and obesity play an important role in the development of osteoarthritis (OA). However, joint overload is not the only risk factor in this disease. For instance, the presence of OA in non-weight-bearing joints such as the hand suggests that metabolic factors may also contribute to its pathogenesis. Recently, white adipose tissue (WAT) has been recognized not only as an energy reservoir but also as an important secretory organ of adipokines. In this regard, adipokines have been closely associated with obesity and also play an important role in bone and cartilage homeostasis. Furthermore, drugs such as rosuvastatin or rosiglitazone have demonstrated chondroprotective and anti-inflammatory effects in cartilage explants from patients with OA. Thus, it seems that adipokines are important factors linking obesity, adiposity, and inflammation in OA. In this review, we are focused on establishing the physiological mechanisms of adipokines on cartilage homeostasis and evaluating their role in the pathophysiology of OA based on evidence derived from experimental research as well as from clinical-epidemiological studies.

Chemerin Stimulates Vascular Smooth Muscle Cell Proliferation and Carotid Neointimal Hyperplasia by Activating Mitogen-Activated Protein Kinase Signaling

Vascular neointimal hyperplasia and remodeling arising from local inflammation are characteristic pathogeneses of proliferative cardiovascular diseases, such as atherosclerosis and post angioplasty restenosis. The molecular mechanisms behind these pathological processes have not been fully determined. The adipokine chemerin is associated with obesity, metabolism, and control of inflammation. Recently, chemerin has gained increased attention as it was found to play a critical role in the development of cardiovascular diseases. In this study, we investigated the effects of chemerin on the regulation of vascular smooth muscle cells and carotid neointimal formation after angioplasty. We found that circulating chemerin levels increased after carotid balloon injury, and that knockdown of chemerin significantly inhibited the proliferative aspects of vascular smooth muscle cells induced by platelet-derived growth factor-BB and pro-inflammatory chemokines in vitro as well as prohibited carotid neointimal hyperplasia and pro-inflammatory chemokines in vivo after angioplasty. Additionally, inhibition of chemerin down-regulated the expression of several proteins, including phosphorylated p38 mitogen-activated protein kinase, phosphorylated extracellular signal regulated kinase 1/2, nuclear factor-kappa B p65, and proliferation cell nuclear antigen. The novel finding of this study is that chemerin stimulated vascular smooth muscle cells proliferation and carotid intimal hyperplasia through activation of the mitogen-activated protein kinase signaling pathway, which may lead to vascular inflammation and remodeling, and is relevant to proliferative cardiovascular diseases.

Chemerin Elicits Potent Constrictor Actions via Chemokine-Like Receptor 1 (CMKLR1), not G-Protein-Coupled Receptor 1 (GPR1), in Human and Rat Vasculature

BACKGROUND

Circulating levels of chemerin are significantly higher in hypertensive patients and positively correlate with blood pressure. Chemerin activates chemokine-like receptor 1 (CMKLR1 or ChemR23) and is proposed to activate the "orphan" G-protein-coupled receptor 1 (GPR1), which has been linked with hypertension. Our aim was to localize chemerin, CMKLR1, and GPR1 in the human vasculature and determine whether 1 or both of these receptors mediate vasoconstriction.

METHODS AND RESULTS

Using immunohistochemistry and molecular biology in conduit arteries and veins and resistance vessels, we localized chemerin to endothelium, smooth muscle, and adventitia and found that CMKLR1 and GPR1 were widely expressed in smooth muscle. C9 (chemerin149-157) contracted human saphenous vein (pD2=7.30±0.31) and resistance arteries (pD2=7.05±0.54) and increased blood pressure in rats by 9.1±1.0 mm Hg at 200 nmol. Crucially, these in vitro and in vivo vascular actions were blocked by CCX832, which we confirmed to be highly selective for CMKLR1 over GPR1. C9 inhibited cAMP accumulation in human aortic smooth muscle cells and preconstricted rat aorta, consistent with the observed vasoconstrictor action. Downstream signaling was explored further and, compared to chemerin, C9 showed a bias factor=≈5000 for the Gi protein pathway, suggesting that CMKLR1 exhibits biased agonism.

CONCLUSIONS

Our data suggest that chemerin acts at CMKLR1, but not GPR1, to increase blood pressure. Chemerin has an established detrimental role in metabolic syndrome, and these direct vascular actions may contribute to hypertension, an additional risk factor for cardiovascular disease. This study provides proof of principle for the therapeutic potential of selective CMKLR1 antagonists.

The adipokine chemerin amplifies electrical field-stimulated contraction in the isolated rat superior mesenteric artery

The adipokine chemerin causes arterial contraction and is implicated in blood pressure regulation, especially in obese subjects with elevated levels of circulating chemerin. Because chemerin is expressed in the perivascular adipose tissue (PVAT) that surrounds the sympathetic innervation of the blood vessel, we tested the hypothesis that chemerin (endogenous and exogenous) amplifies the sympathetic nervous system in mediating electrical field-stimulated (EFS) contraction. The superior mesenteric artery, with or without PVAT and with endothelium and sympathetic nerve intact, was mounted into isolated tissue baths and used for isometric contraction and stimulation. Immunohistochemistry validated a robust expression of chemerin in the PVAT surrounding the superior mesenteric artery. EFS (0.3-20 Hz) caused a frequency-dependent contraction in isolated arteries that was reduced by the chemerin receptor ChemR23 antagonist CCX832 alone (100 nM; with, but not without, PVAT), but not by the inactive congener CCX826 (100 nM). Exogenous chemerin-9 (1 μM)-amplified EFS-induced contraction in arteries (with and without PVAT) was blocked by CCX832 and the α-adrenergic receptor antagonist prazosin. CCX832 did not directly inhibit, nor did chemerin directly amplify, norepinephrine-induced contraction. Whole mount immunohistochemical experiments support colocalization of ChemR23 with the sympathetic nerve marker tyrosine hydroxylase in superior mesenteric PVAT and, to a lesser extent, in arteries and veins. These studies support the idea that exogenous chemerin modifies sympathetic nerve-mediated contraction through ChemR23 and that ChemR23 may be endogenously activated. This is significant because of the well-appreciated role of the sympathetic nervous system in blood pressure control.

Chemerin as an independent predictor of cardiovascular event risk

Currently, coronary artery disease (CAD) is considered a major ailment in humans with widespread prevalence. CAD also accounts for high mortality rates around the world that involves several known risk factors. Chemerin is a novel adipokinine that is associated with inflammation and adipogenesis. Furthermore, experimental and clinical data indicate that localized as well as circulating chemerin expression and activation are elevated in numerous metabolic and inflammatory diseases including psoriasis, obesity, type 2 diabetes, metabolic syndrome and cardiovascular disease. Chemerin is accepted as being a strong marker because the serum chemerin levels are increased in a CAD condition. However, the chimeric characteristics of chemerin have not been fully investigated. Although chemerin is known to be responsible for CAD development among other factors, authors still investigate it at the marker level. This review focuses on chemerin expression, processing, biological function and relevance to human diseases, and on the role of chemerin in the maintenance of a cardiovascular disease.

Chemerin: A comprehensive review elucidating the need for cardiovascular research

When chemerin was discovered in 1997, it was relegated to being a protein associated with the normal skin function contrasting the setting of psoriasis. However, with the discovery of multiple receptors for the chemerin protein and a vast collection of associations with various pathologies, chemerin has global influence capable of regulating chemotactic, adipokine, autocrine/paracrine, adipogenic, angiogenic, and reproductive functions. These individual abilities of chemerin are important for understanding its basic pharmacology and physiology, but application of these principles to human pathology relies on the ability of scientists and physicians to view this protein from a much wider, all-encompassing angle. A global participant in the action of chemerin is the cardiovascular system (CVS). Although the CVS may not have as many direct interactions (e.g. smooth muscle in endothelium) with chemerin as it does indirect (e.g. chemerin activation in the lumen by proteases), our basic understanding of the CVS and its relation to chemerin is necessary to form a proper grasp of its individual actions and make the applications to pathology. This review provides a fundamental, yet comprehensive review of chemerin that inherently identifies the CVS as a necessary link between chemerin and its associated pathologies, but also calls for basic cardiovascular research as the solution to this chasm between knowledge and application.

Association of serum chemerin levels with the severity of coronary artery disease in patients with metabolic syndrome

OBJECTIVES

The newly identified adipokine chemerin has been shown to be associated with the components of MetS, inflammation and insulin resistance. In this study, the relationship between serum chemerin levels and the presence and severity of coronary artery disease (CAD) was evaluated in patients with MetS.

METHODS

The study population consisted of 84 MetS patients (43 patients with CAD and 41 without CAD), who had coronary angiography for suspected coronary artery disease, and 46 healthy individuals as a control group. Angiographic CAD was defined as ≥ 50% luminal diameter stenosis of at least one major epicardial coronary artery. The severity of CAD was determined by the Gensini score. Serum chemerin levels were measured with enzyme linked immunosorbent assay (ELISA).

RESULTS

Serum chemerin levels were significantly higher in patients with MetS (n=84) than those in the control group (120.47±25.32 vs. 90.4±11.4 ng/ml P < 0.001). In addition, MetS patients with CAD had higher chemerin levels than MetS patients without CAD (128.7±26.6 vs. 115.7±15.2 ng/ml, P < 0.001). Serum chemerin levels had a significant positive correlation with the Gensini score (r=0.58, P < 0.001). Multivariate logistic regression demonstrated that serum high-density lipoprotein cholesterol (HDL-C) and chemerin levels were significant and independent predictors for determining the presence of angiographic CAD (OR=1.009, 95% CI: 0.972-1.057; P=0.003 and OR=0.925, 95% CI: 0.896-0.922; P < 0.001, respectively).

CONCLUSION

This study demonstrated that in patients with MetS, chemerin levels were higher in patients with CAD than patients without CAD and also showed a significant positive correlation with CAD severity.