Chemokine-like Receptor Research Articles

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.

Chemerin/CMKLR1 axis influences pulmonary arterial pressure and the NO signaling pathway

Pulmonary arterial hypertension (PAH) is a clinical condition associated with sustained elevations in pulmonary arterial pressure, leading to right ventricular failure. The adipokines leptin and adiponectin have shown respectively deleterious and protective effects in animal models of PAH. Chemerin is a novel adipokine implicated in blood pressure regulation and recently associated with atherosclerosis, essential hypertension and obesity-induced hypertension. In this context, we aimed to determine whether the chemerin/CMKLR1 axis could influence pulmonary arterial pressure and the severity of pulmonary hypertension. Age-matched wild-type (WT) and CMKLR1 knockout (KO) mice were used. We localized chemerin and the chemokine-like receptor-1 (CMKLR1) in lung sections, pulmonary artery and thoracic aorta. WT and KO mice were exposed to normoxia (21% O2) or hypoxia (10% O2) for 3 weeks ( N = 6 per group). Right ventricular systolic pressure (RVSP) was measured with a micro-tip catheter. Segments of pulmonary artery and thoracic aorta were incubated, immediately after sacrifice, with recombinant mouse chemerin (10–8 mol/L, 1 hour) or vehicle, then stimulated or not with acetylcholine (ACH) (10–4 mol/L, 5 min) to measure NO production in supernatants by determination of nitrites. RVSP was higher in KO than in WT mice in normoxia (26.6 ± 0.4 vs. 22.2 ± 1 mmHg, P = 0.001) and in hypoxia (37.8 ± 0.5 vs. 31.4 ± 1.2 mmHg, P = 0.001). Hypoxia reduced NO production in WT and KO mice. In WT, ACH-induced NO production was abolished by chemerin pre-incubation. In normoxia and hypoxia, basal NO production was lower in KO than WT mice and ACH-stimulated NO production was totally inhibited in KO mice. These observations provide support for a role of the chemerin/CMKLR1 axis as regulator of pulmonary vascular homeostasis and as a disease-modifier in the context of pulmonary hypertension by the negative modulation of pulmonary vascular NO production.

Possible involvement of the RARRES2/CMKLR1-system in metabolic and reproductive parameters in Holstein dairy cows

BackgroundIn dairy cows, the energy cost of milk yield results in a negative energy balance (EB) and body fat mobilization that impairs reproductive efficiency. Emerging evidence suggests that the novel adipokines, Retinoic acid receptor responder protein 2 (RARRES2), and its main receptor, Chemokine-like receptor 1 (CMKLR1) are involved in the regulation of metabolic and ovarian functions. So, we investigated in a first experiment the plasma RARRES2, and RARRES2 and CMKLR1 mRNA expression levels in subcutaneous adipose tissue (SAT) and granulosa cells (GC) at different times of body fat mobilization in dairy cows (4, 8, 20 and 44 weeks postpartum, wk. pp. for SAT and 8, 20 and 44 wk. pp. for GC). Then, in a second experiment we examined the effect of high (HE) and low energy (LE) diets on the RARRES2 system and its links with metabolic and reproductive parameters.MethodsThe first experiment included 9 animals fed with HE diet from 4 to 44 wk. pp. and the second one included animals fed either a HE diet (n = 8) or a LE diet (n = 8) from − 4 to 16 wk. peripartum. In both experiments, various metabolic and reproductive parameters were determined and associated with plasma RARRES2 as measured by bovine ELISA. RARRES2 and CMKLR1 mRNA expression levels were analyzed by RT-qPCR in SAT after biopsy and GC after aspiration of follicles.ResultsPlasma RARRES2 levels were higher at 4 wk. pp. as compared to 20 and 44 wk. pp. and they were positively correlated with body fat mobilization and milk yield. RARRES2 and CMKLR1 mRNA expression levels increased from 4 to 8 wk. pp. (fat mobilization, EB < 0) and remained unchanged at 20 and 44 wk. pp. (fat reconstitution, EB > 0) as compared to 4 wk. pp. in SAT. RARRES2 and CMKLR1 mRNA levels decreased from 8 to 44 wk. pp. in GC from small follicles. In the second experiment, plasma RARRES2 increased from − 4 to 8 wk. peripartum similarly in both LE and HE cows. In addition, the area under of plasma RARRES2 curve was highly negatively associated with the number of small follicles obtained in HE animals during the cycle before the first artificial insemination. In SAT of HE cows, RARRES2 mRNA expression decreased at 1 wk. pp. compared to − 4 and 16 wk. peripartum whereas opposite expression patterns were obtained for CMKLR1. Similar results were observed for CMKLR1 mRNA expression in LE cows while there was no variation in RARRES2 mRNA expression. Moreover, RARRES2 mRNA was higher expressed in LE than in HE cows at 1 wk. pp.ConclusionsThe lactation-induced fat and energy mobilization influenced plasma RARRES2 profile and mRNA expression pattern of RARRES2 and CMKLR1 similarly in both SAT and GC. In addition, the energy content of the diet did not affect plasma RARRES2 but it altered RARRES2 mRNA expression in SAT and the area under the curve of plasma RARRES2 that was negatively associated to the number of small follicles in HE animals. Thus, RARRES2 could be a metabolic or ovarian signal involved in the interactions between metabolic and reproductive functions in dairy cows.

Dermal mesenchymal stem cells: a resource of migration-associated function in psoriasis?

BackgroundPsoriasis is a chronic and systemic, immune-mediated, inflammatory disease. Mesenchymal stem cells have effects on the inflammatory microenvironment, including regulating the proliferation, differentiation, recruitment, and migration of immunocytes.MethodsTo investigate whether dermal mesenchymal stem cells (DMSCs) may act on migration of immunocytes in psoriasis patients, 22 patients with psoriasis and 22 matching healthy controls (age and sex in this study) were recruited. Seven migration-associated genes including chemokine like receptor-1 (CMKLR-1), collagen type VIII alpha1 (COL8A-1), neuropilin and tolloid-like 2 (NETO-2), nik-related kinase (NRK), secreted frizzled-related protein (SFRP), sulfate 6-O-endosulfatase 2 (SULF-2), and synaptotagmin-like protein 2 (SYTL-2) were analyzed by quantitative real-time reverse transcription PCR and western blot. Peripheral blood-derived mononuclear cells (PBMCs) migration to MSCs was measured using a Thanswell chamber system.ResultsWe observed the upregulation of CMKLR-1, COL8A-1, NETO-2, NRK, SYTL-2, and SULF-2 in dermal mesenchymal stem cells derived from patients with psoriasis at both mRNA and protein level, however, a significant downregulation of SFRP-2 between two groups. By contrast, there were no significant between-group differences at the mRNA and protein expression level of NETO-2 and SULF-2. The migration assay showed that in vitro the normal PBMC migration to psoriatic DMSC group was a 6.3 ± 0.7-fold increase compared with the control group.ConclusionsThe results may suggest a potential pathogenetic involvement of DMSCs on migration of monocytes in psoriasis. Immune responses are regulated at the level of DMSCs, which probably represent the cells primarily involved in the “psoriatic march.”

Chemerin acts via CMKLR1 and GPR1 to stimulate migration and invasion of gastric cancer cells: putative role of decreased TIMP-1 and TIMP-2.

The chemokine-like peptide, chemerin, stimulates chemotaxis in several cell types. In this study we examined the expression of putative chemerin receptors in gastric cancer and the action of chemerin on cancer cell migration and invasion. Immunohistochemical studies of gastric tumors identified expression of two putative receptors, chemokine-like receptor-1 (CMKLR1) and G-protein coupled receptor 1(GPR1), in cancer cells; there was also some expression in stromal myofibroblasts although generally at a lower intensity. The expression of both receptors was detected in a gastric cancer cell line, AGS; chemerin itself was expressed in cultured gastric cancer myofibroblasts but not AGS cells. Chemerin stimulated (a) morphological transformation of AGS cells characterized by extension of processes and cell scattering, (b) migration in scratch wound assays and (c) both migration and invasion in Boyden chamber chemotaxis assays. These responses were inhibited by two putative receptor antagonists CCX832 and α-NETA. Inhibition of receptor expression by siRNA selectively reduced CMKLR1 or GPR1 and inhibited the action of chemerin indicating that both receptors contributed to the functional response. Using a proteomic approach employing stable isotope dynamic labeling of secretomes (SIDLS) to selectively label secreted proteins, we identified down regulation of tissue inhibitors of metalloproteinease (TIMP)1 and TIMP2 in media in response to chemerin. When cells were treated with chemerin and TIMP1 or TIMP2 the migration response to chemerin was reduced. The data suggest a role for chemerin in promoting the invasion of gastric cancer cells via CMKLR1 and GPR1at least partly by reducing TIMP1 and TIMP2 expression. Chemerin receptor antagonists have potential in inhibiting gastric cancer progression.

CMKLR1-targeting peptide tracers for PET/MR imaging of breast cancer.

Background: Molecular targeting remains to be a promising approach in oncology. Overexpression of G protein-coupled receptors (GPCRs) in human cancer is offering a powerful opportunity for tumor-selective imaging and treatment employing nuclear medicine. We utilized novel chemerin-based peptide conjugates for chemokine-like receptor 1 (CMKLR1) targeting in a breast cancer xenograft model.Methods: By conjugation with the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), we obtained a family of five highly specific, high-affinity tracers for hybrid positron emission tomography/magnetic resonance (PET/MR) imaging. A xenograft model with target-positive DU4475 and negative A549 tumors in immunodeficient nude mice enabled CMKLR1-specific imaging in vivo. We acquired small animal PET/MR images, assessed biodistribution by ex vivo measurements and investigated the tracer specificity by blocking experiments.Results: Five CMKLR1-targeting peptide tracers demonstrated high biological activity and affinity in vitro with EC50 and IC50 values below 2 nM. Our target-positive (DU4475) and target-negative (A549) xenograft model could be validated by ex vivo analysis of CMKLR1 expression and binding. After preliminary PET imaging, the three most promising tracers [68Ga]Ga-DOTA-AHX-CG34, [68Ga]Ga-DOTA-KCap-CG34 and [68Ga]Ga-DOTA-ADX-CG34 with best tumor uptake were further analyzed. Hybrid PET/MR imaging along with concomitant biodistribution studies revealed distinct CMKLR1-specific uptake (5.1% IA/g, 3.3% IA/g and 6.2% IA/g 1 h post-injection) of our targeted tracers in DU4475 tumor tissue. In addition, tumor uptake was blocked by excess of unlabeled peptide (6.4-fold, 5.5-fold and 3.4-fold 1 h post-injection), further confirming CMKLR1 specificity. Out of five tracers, we identified these three tracers with moderate, balanced hydrophilicity to be the most potent in receptor-mediated tumor targeting.Conclusion: We demonstrated the applicability of 68Ga-labeled peptide tracers by visualizing CMKLR1-positive breast cancer xenografts in PET/MR imaging, paving the way for developing them into theranostics for tumor treatment.

Chemokine-like receptor 1 deficiency leads to lower bone mass in male mice.

The adipokine Chemerin and its receptor, chemokine-like receptor 1 (CMKLR1), are associated with osteoblastogenic differentiation of mesenchymal stem cells (MSCs) and osteoclastogenic differentiation of osteoclast precursors in vitro, suggesting that CMKLR1 would affect the bone mineral density (BMD). However, the role of CMKLR1 on BMD in vivo remains unknown. Here, using CMKLR1 knockout mouse model, we unveiled that CMKLR1 effected the amount of Leydig cells in testis and regulated androgen-dependent bone maintenance in male mice, which exhibited lower serum testosterone levels, thereby reducing the trabecular bone mass. Correspondingly, the mRNA expression of testosterone synthesis enzymes in testis decreased. The bone tissue also showed decreased mRNAs expression of osteogenic markers and increased mRNA levels for osteoclast markers. Furthermore, by in vitro differentiation models, we found CMKLR1-deficiency could break the balance between osteoblastogenesis and osteoclastogenesis that caused a shift from osteogenic to adipogenic differentiation in MSCs and enhanced osteoclast formation. In addition, bone mass increase in CMKLR1 KO male mice can be promoted by treatment with 5α-dihydrotestosterone (DHT), and the inactivation of CMKLR1 in male wild-type (WT) mice with antagonist treatment can lead to low bone mass. Taken together, these data indicate that CMKLR1 positively regulates bone metabolism through mediating testosterone production and the balance between osteoblast and osteoclast formation.

PO-206 Effects of chemerin/CMKLR1 on aerobic exercise-induced improvement of glycolipid metabolism in atherosclerosis rats

Objective As an adipokine and inflammatory cytokines, chemerin plays an vital role in the occurrence and severity of obesity and its related disease such as atherosclerosis (AS), type 2 diabetes and coronary artery disease, among which the regulation of chemerin on glycolipid metabolism is of great important. Chemerin exerts its main biological functions through binding to its receptor: G protein-coupled receptor chemokine-like receptor (CMKLR1). Chemerin/CMKLR1 has become potential targets for diabetes treatment. For AS, the serum level of chemerin is also related to the disorders of glycolipid metabolism as well as the size and fibrous cap maturity of AS plaques. Exercise decreased the serum level of chemerin in AS, accompanied with the improvement of glucose and lipid metabolism, which indicated the possible relation between decrease of chemerin and improvement of glycolipid metabolism. However, it is still unclear whether exercise-induced improvements of glycolipid metabolism is associated with the changes of chemerin and CMKLR1 in tissue such as livers and gastrocnemius (play key roles in the modulation of glycolipid metabolism) and the mechanism by which chemerin/CMKLR1 modulated glycolipid metabolism. Recent studies reported that chemerin is a target gene of nuclear transcription factor- peroxisome proliferator activated receptor γ (PPARγ). PPARγ links glycolipid metabolism and inflammation through its target gene-adipose triglyceride lipase (ATGL) and lipoprotein lipase (LPL), gate-keeping enzymes hydrolyzing lipids in intracellular triglyceride and plasma lipoproteins respectively. Our previous work has found that aerobic exercise decreased the level of chemerin/CMKLR1 in serum and tissues of type 2 diabetes rats by the mediation of PPARγ-ATGL and LPL. So the purposes of this study were to clarify if exercise-modulated improvement of glycolipid metabolism of atherosclerosis rats was also associated with the changes of chemerin and CMKLR1 in serum and tissues (liver and gastrocnemius), similar as in diabetes, and further its mechanisms. &#x0D; Methods Twenty-seven male Sprague-Dawley (SD) rats aged 6 weeks were randomly divided into control group (Con, n=9) and atherosclerosis (AS, n=18) model rats. AS model rats were established by intraperitoneal injection of Vitamin D3 (600,000 IU/kg body weight in the first week, 100,000 IU/kg body weight in the third week and six week) in combination with 8-week high fat diet feeding. For verifying the successful establishment of AS rats, one rat from Con group and two rats from AS model group were taken randomly to determine the levels of blood glucose and lipid as well as the morphological and pathological alterations of the aorta. Then, 16 successfully established AS rats were randomly divided into AS group (n=8) and exercised AS group (EAS, n=8). EAS group rats experience 4-week moderate intensity aerobic exercise on treadmill with gradually increasing intensity, while the Con and AS rats were kept sedentary life, with all of the rats were fed with common diet during the experiments. Before and after 4-week exercise, the blood sample of the three group rats were drawn to measure the circulating levels of fasting blood glucose (FBG), triglyceride (TC), total cholesterol (TG), LDL and HDL. The serum fasting insulin (FINS) and serum chemerin were measured by ELISA. The protein levels of chemerin, CMKLR1, PPARγ, ATGL and LPL in livers and gastrocnemius were detected by Western blot. And the full-length aorta of the rats were separated to determine AS arteriosclerosis plaques with oil red O staining and histopathological examination with HE staining.&#x0D; &#x0D; Results 1) Compared with AS rats, the disorder of glycolipid metabolism (reflected&#x0D; by increases in TC, TG, LDL and FINS as well as decrease in HDL in blood although no difference in serum level of FBG) were all improved in EAS rats. 2) Compared with AS rats, the atherosclerotic plaque in the aoras and the enhanced proliferation and arrangement disorder of smooth muscle cells in aorta membrane were all alleviated in EAS rats. 3) Compared with AS rats, the increased chemerin in serum and the enhancements of chemerin and CMKLR1 in liver and gastrocnemius at protein levels were all significantly decreased in EAS rats. 4) Compared with AS rats, the protein levels of PPARγ, ATGL and LPL in the livers and gastrocnemius were all increased in EAS rats.&#x0D; Conclusions This study verified that: 1) the exercise-induced improvement of glycolipid metabolism in AS rats was likely to be associated with the decreases of chemerin in serum as well as of chemerin and CMKLR1 in tissues (liver and gastrocnemius). To our knowledge, it is the first report that exercise down-regulated chemerin/CMKLR1 in tissues in AS rats, and the decreases of chemerin/CMKLR1 might be related to the improvement of glycolipid metabolism in AS rats. 2) the exercise-induced decreases of chemerin/CMKLR1 in AS rats might be mediated by PPARγ and its target genes- ATGL and LPL, which need further investigations.

Regulation of Chemerin and CMKLR1 Expression by Nutritional Status, Postnatal Development, and Gender.

Chemerin (also known as tazarotene-induced gene 2 and retinoic acid receptor responder 2) has been identified as an adipokine that exerts effects on many biological processes, including adipogenesis, angiogenesis, inflammation, immune responses, and food intake. This variety of effects has led to its implication in obesity and co-morbidities including diabetes and a risk of cardiovascular disease. The biological effects are mostly mediated by a so-called G protein-coupled receptor, chemokine-like receptor 1 (CMKLR1). Given the association of chemerin with obesity and related diseases, we decided to study in detail the regulation of chemerin and CMKLR1 expression in white adipose tissue (WAT). Specifically, we focused on their expression levels in physiological and pathophysiological settings involved in energy balance: e.g., fasting, postnatal development, and gender. We used Sprague Dawley rats with different nutritional statuses, levels of hormonal deficiency, and states of development as well as ob/ob (leptin-deficient) mice. We analysed the protein expression of both the ligand and receptor (chemerin and CMKLR1) in gonadal WAT by western blotting. We found that chemerin and CMKLR1 protein levels were regulated in WAT by different conditions associated with metabolic changes such as nutritional status, sex steroids, pregnancy, and food composition. Our data indicate that regulation of the expression of this new adipokine and its receptor by nutritional status and gonadal hormones may be a part of the adaptive mechanisms related to altered fat mass and its metabolic complications.

The impact of chemerin or chemokine-like receptor 1 loss on the mouse gut microbiome

Chemerin is an adipocyte derived signalling molecule (adipokine) that serves as a ligand activator of Chemokine-like receptor 1(CMKLR1). Chemerin/CMKLR1 signalling is well established to regulate fundamental processes in metabolism and inflammation. The composition and function of gut microbiota has also been shown to impact the development of metabolic and inflammatory diseases such as obesity, diabetes and inflammatory bowel disease. In this study, we assessed the microbiome composition of fecal samples isolated from wildtype, chemerin, or CMKLR1 knockout mice using Illumina-based sequencing. Moreover, the knockout mice and respective wildtype mice used in this study were housed at different universities allowing us to compare facility-dependent effects on microbiome composition. While there was no difference in alpha diversity within samples when compared by either facility or genotype, we observed a dramatic difference in the presence and abundance of numerous taxa between facilities. There were minor differences in bacterial abundance between wildtype and chemerin knockout mice, but significantly more differences in taxa abundance between wildtype and CMKLR1 knockout mice. Specifically, CMKLR1 knockout mice exhibited decreased abundance of Akkermansia and Prevotella, which correlated with body weight in CMKLR1 knockout, but not wildtype mice. This is the first study to investigate a linkage between chemerin/CMKLR1 signaling and microbiome composition. The results of our study suggest that chemerin/CMKLR1 signaling influences metabolic processes through effects on the gut microbiome. Furthermore, the dramatic difference in microbiome composition between facilities might contribute to discrepancies in the metabolic phenotype of CMKLR1 knockout mice reported by independent groups. Considered altogether, these findings establish a foundation for future studies to investigate the relationship between chemerin signaling and the gut microbiome on the development and progression of metabolic and inflammatory disease.

The expression of chemerin and the influence of sitagliptin on its expression in non-alcoholic fatty liver disease rats complicated with prediabetes

Objective: To study the role of chemerin in the development and progression of non-alcoholic fatty liver disease (NAFLD) rats complicated with prediabetes and explore the effect of sitagliptin on the expression of chemerin. Methods: The model of NAFLD and prediabetic rats was established. The rats were then randomly divided into normal group, model group and intervention group. Sitagliptin intervention was performed for 8 weeks after 8 weeks's feeding with high-fat diet. After that, the level of blood glucose, insulin and chemerin was measured. Cytological changes of liver, omentum and epididymal adipose tissue were observed by HE staining. The distribution of chemerin in the tissues was observed by immunohistochemistry. The mRNA and protein expression of chemerin and chemokine-like receptor 1 (chemR23) in liver and adipose tissue were detected by RT-PCR and Western blotting. Results: After 8 weeks of sitagliptin treatment, compared with the normal group(n=8), serum chemerin in the model group (n=6) increased[(35.19±3.86) ng/L vs (29.90±2.17) ng/L, P=0.046)]. Serum chemerin in the intervention group (n=6) was lower than that of the normal group[(23.20±1.89) ng/L vs (29.90±2.17) ng/L, P=0.013)]. Compared with the normal group, the mRNA and protein expression of chemerin in the liver and omentum adipose tissue of the model group increased (P<0.05). The expression amount of the omental adipose tissue was more than that of the liver(P<0.05). The mRNA expression of chemR23 both in liver and omental adipose tissue increased (P<0.05), and the expression amount of the liver was more than that of omental adipose tissue. The levels of fasting blood glucose[(5.72 ±1.36)mmol/L vs(3.77±0.77)mmol/L, P=0.002], total cholesterol[(1.53±0.09)mmol/L vs (1.23±0.17)mmol/L, P=0.032], aspartate aminotransferase[(319.8±104.4)U/L vs (195.0±25.0) U/L, P=0.016]in the model group were significantly higher than those in the normal group. The differences between the intervention group and the normal group was not significant. But the level of fasting blood glucose[(4.33±0.39)mmol/L vs (5.72±1.36)mmol/L, P=0.019], total cholesterol[(1.23±0.17)mmol/L vs (1.53±0.09)mmol/L, P=0.047]and aspartate aminotransferase[(198.4±22.8)U/L vs (319.8±104.4)U/L, P=0.014)]of the intervention group was significantly lower than those of the model group. Conclusions: Increasing expression of serum chemerin is consistent with hepatic steatosis, suggesting that chemerin can serve as a serological warning indicator for NAFLD complicated with pre-diabetes. Sitagliptin affects the mRNA and protein expression of chemerin and its receptor chemR23 in steatosis liver. This may provide a research direction for the pathophysiology and treatment of NAFLD.

Polycystic ovary syndrome: possible involvement of androgen-induced, chemerin-mediated ovarian recruitment of monocytes/macrophages.

Polycystic ovary syndrome (PCOS) is a continuum of endocrine and reproductive disorders characterized by hyperandrogenism, antral follicle growth arrest, and chronic inflammation. Macrophages play key role in inflammation, and the balance between M1 (inflammatory) and M2 (anti-inflammatory) macrophages determines physiological/pathological outcomes. Here, we investigated if hyperandrogenism increases ovarian chemerin altering the balance of M1 and M2 macrophages and the granulosa cell death. Ovarian chemerin was upregulated by 5α-dihydrotestosterone (DHT) in lean and overweight rats; while increased serum chemerin levels were only evident in overweight rats, suggesting that the serum chemerin may be reflective of a systemic response and associated with obesity, whereas increased ovarian chemerin expression is a localized response independent of the metabolic status. DHT altered follicle dynamics while increased the M1: M2 macrophages ratio in antral and pre-ovulatory follicles. While ovarian M1 macrophages expressing chemokine-like receptor 1 (CMKLR1) were increased, CMKLR1+ monocytes, which migrated toward chemerin-rich environment, were markedly decreased after 15 days of DHT. Androgen-induced granulosa cell apoptosis was dependent on the presence of macrophages. In humans, chemerin levels in follicular fluid, but not in serum, were higher in lean PCOS patients compared to BMI-matched controls and were associated with increased M1: M2 ratio. Our results support the concept that in PCOS, hyperandrogenemia increases chemerin expression while promotes CMKLR1+ monocytes recruitment and deregulates the immunological niche of ovaries. This study established a new immunological perspective in PCOS at the ovarian level. Hyperandrogenism is associated with upregulation of chemerin and macrophage unbalance in the ovaries.

Role of chemerin/CMKLR1 in the maintenance of early pregnancy

Chemerin is a cytokine that attracts much attention in the reproductive process. This study aimed to explore the effects of chemerin and its receptor chemokine-like receptor 1 (CMKLR1) on the maintenance of early pregnancy. The expression levels of chemerin and CMKLR1 in the decidua tissues of 20 early normal pregnant women and 20 early spontaneous abortion women were examined by Western blot and real-time polymerase chain reaction analyses. CMKLR1 receptor antagonist (α-NETA) was then intrauterinely injected into normal pregnant mice model to assess its effect on the outcome of pregnancy and the phosphorylation rate of ERK1/2 in decidua tissues.We found that the expression level of chemerin in women who had experienced early spontaneous abortion was lower than in those who had experienced normal early pregnancy (P < 0.01); conversely, CMKLR1 expression was higher in the former than in the latter (P < 0.01). In a pregnant-mouse model, the embryo resorption rate of α-NETA group was higher than that in the negative control group (61.5% vs. 10.8%) (P < 0.001). Compared with the control group, ERK1/2 phosphorylation in decidua tissues decreased in the α-NETA-treated group (P < 0.01). These results suggested that the inhibition of the chemerin/CMKLR1 signaling pathway can lead to the abortion of mouse embryos, and that chemerin/CMKLR1 may play an important role in the maintenance of early pregnancy possibly by regulating ERK1/2 phosphorylation.

Specialized Pro-Resolving Lipid Mediators Regulate Ozone-Induced Pulmonary and Systemic Inflammation.

Exposure to ozone (O3) induces lung injury, pulmonary inflammation, and alters lipid metabolism. During tissue inflammation, specialized pro-resolving lipid mediators (SPMs) facilitate the resolution of inflammation. SPMs regulate the pulmonary immune response during infection and allergic asthma; however, the role of SPMs in O3-induced pulmonary injury and inflammation is unknown. We hypothesize that O3 exposure induces pulmonary inflammation by reducing SPMs. To evaluate this, male C57Bl/6J mice were exposed to filtered air (FA) or 1 ppm O3 for 3 h and necropsied 24 h after exposure. Pulmonary injury/inflammation was determined by bronchoalveolar lavage (BAL) differentials, protein, and lung tissue cytokine expression. SPMs were quantified by liquid chromatography tandem mass spectrometry and SPM receptors leukotriene B4 receptor 1 (BLT-1), formyl peptide receptor 2 (ALX/FPR2), chemokine-like receptor 1 (ChemR23), and SPM-generating enzyme (5-LOX and 12/15-LOX) expression were measured by real time PCR. 24 h post-O3 exposure, BAL PMNs and protein content were significantly increased compared to FA controls. O3-induced lung inflammation was associated with significant decreases in pulmonary SPM precursors (14-HDHA, 17-HDHA), the SPM PDX, and in pulmonary ALX/FPR2, ChemR23, and 12/15-LOX expression. Exogenous administration of 14-HDHA, 17-HDHA, and PDX 1 h prior to O3 exposure rescued pulmonary SPM precursors/SPMs, decreased proinflammatory cytokine and chemokine expression, and decreased BAL macrophages and PMNs. Taken together, these data indicate that O3-mediated SPM reductions may drive O3-induced pulmonary inflammation.

Ex vivo analysis of serum chemerin activity in murine models of obesity

ObjectivesChemerin is an adipokine with established roles in inflammation, adipogenesis and the regulation of glucose and lipid homeostasis. Extracellular proteolytic processing of chemerin generates a spectrum of isoforms that differ significantly with respect to the ability to activate the cognate receptors chemokine-like receptor 1 (CMKLR1) and G-protein-coupled receptor 1 (GPR1). Increased total serum chemerin has been widely reported in obese humans as well as in preclinical rodent models of adiposity. However, very little information is available regarding the correspondence, if any, of changes in total serum chemerin protein with chemerin bioactivity. MethodsTotal serum chemerin and ex vivo CMKLR1 and GPR1 activation was compared using two widely used murine obesity models: high fat diet feeding (HFD) and leptin deficiency (ob/ob). ResultsTotal serum chemerin levels and ex vivo CMKLR1 and GPR1 activation were significantly induced in HFD. The bioactivity ratio (bioactive chemerin/total chemerin) was also increased when measured with CMKLR1, but not GPR1. In contrast, while ob/ob mice exhibited increased total serum chemerin protein, ex vivo receptor activation was observed with GPR1, but not CMKLR1. There was no change in bioactivity ratio for either receptor. Of note, GPR1 but not CMKLR1 bioactivity positively correlated with adipose tissue inflammation. ConclusionsWhile increased total serum chemerin is a consistent finding among rodent obesity models, this may not accurately reflect changes in chemerin bioactivity which is the major determinant of biological effects.

Alleviation of Diet-Induced Fat Accumulation by a Small Molecule CMKLR1 Antagonist in Mice

Objective: Non-alcoholic Fatty Liver Disease (NAFLD) is believed to be correlated with chemerin and its receptor, Chemokine-like Receptor 1 (CMKLR1). We analyse the role of CMKLR1 in NAFLD by using a novel small molecule CMKLR1 antagonist-NETA (2-naphthoyl ethyl trimethyl ammonium) in vitro and in vivo. Methods: We assessed the effects of -NETA on a mouse model of high-fat-diet-induced fat accumulation in liver and adipose tissue and an analogous cell model established by culturing Hepa 1-6 and 3T3-L1 cells. Results: We found that chemerin and CMKLR1 mRNA were significantly increased in the livers and fat tissue of the mice fed the high fat diet relative to those in mice fed the normal diet. α-NETA administration suppressed serum TC, TG, AST and ALT levels and hepatic TG content as well as inhibited lipid metabolism-associated factors in the livers and fat of high fat diet mice. Furthermore, in the cell model, α-NETA suppressed oleic acid induction of Hepa 1-6 cell steatosis, 3T3-L1 adipogenesis and the expression of mRNAs for related lipid metabolism-associated factors. Conclusions: Chemerin/CMKLR1 signaling plays an important role in the progression of NAFLD.

Elevated Chemerin Induces Insulin Resistance in Human Granulosa-Lutein Cells from Polycystic Ovary Syndrome Patients

Background: The insulin resistance (IR) of the ovarian granulosa cells from polycystic ovary syndrome (PCOS) aggravates the abnormalities in steroidogenesis and anovulation, and chemerin is an adipokine involved in regulating adipogenesis and glucose homeostasis. The underlying mechanism of IR and the role of chemerin in the development of IR remain to be demonstrated. Methods: The granulosa-lutein cells (hGLs) and follicular fluid from PCOS and non-PCOS patients with or without IR were collected to determine the chemerin levels and molecules pertinent to insulin signaling. The effects and molecular mechanism of chemerin on the insulin signaling were investigated in cultured hGLs with immunofluorescence staining, special enzyme-linked immunosorbent assay (ELISA), quantitative real-time PCR (qRT-PCR), western blotting, [18F]-Fluorodeoxyglucose ([18F]-FDG) incorporation and siRNA transfection respectively. Findings: The chemerin levels were elevated in both follicular fluid and hGLs samples obtained from PCOS with IR patients and the hGLs obtained from PCOS with IR patients showed decreased insulin sensitivity and impaired glucose uptake capacity. Moreover, treatment of chemerin attenuated insulin-stimulated glucose uptake by decreasing phosphorylation of Akt and membrane translocation of glucose transporter type 4 (GLUT4) through increasing Ser307 phosphorylation of insulin receptor substrate 1 (IRS1) in cultured hGLs. These effects could be abolished by siRNA-mediated knockdown of chemokine-like receptor 1 (CMKLR1). Furthermore, insulin induced the expression of chemerin in hGLs. Interpretation: Our findings demonstrate a novel role of chemerin in the metabolic dysfunction of PCOS, which suggested that chemerin and its receptor can be further implicated as potential therapeutic targets in the future treatment of PCOS. Funding Statement: This work was supported by the National Natural Science Foundation of China [grant numbers 81771648, 81571499]; the National Key RD the Shanghai Commission of Science and Technology [grant number 17DZ2271100]; the Shanghai Municipal Education Commission-Gaofeng Clinical Medicine Grant [grant number 20161413]; the Program of Shanghai Academic Research Leader in Shanghai Municipal Commission of Health and Family Planning [grant number 2017BR015]; and the Clinical Skills Improvement Project of Major Disorders, Hospital Development Center of Shanghai [grant number 16CR1022A] and Shanghai Technological Innovation Plan [grant number 18140902400]. Declaration of Interests: The authors report no conflicts of interest in this work. Ethics Approval Statement: All samples were collected with written informed consent under a protocol approved by the Ethics Committee of Renji Hospital.

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 Gi/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.

The Atypical Receptor CCRL2 (C-C Chemokine Receptor-Like 2) Does Not Act As a Decoy Receptor in Endothelial Cells.

C-C chemokine receptor-like 2 (CCRL2) is a non-signaling seven-transmembrane domain (7-TMD) receptor related to the atypical chemokine receptor (ACKR) family. ACKRs bind chemokines but do not activate G protein-dependent signaling or cell functions. ACKRs were shown to regulate immune functions in vivo by their ability to scavenge chemokines from the local environment. This study was performed to investigate whether CCRL2 shares two of the main characteristics of ACKRs, namely the ability to internalize and scavenge the ligands. Cell membrane analysis of CCRL2-transfected cells revealed a weak, constitutive, ligand-independent internalization, and recycling of CCRL2, with a kinetics that was slower than those observed with ACKR3, a prototypic ACKR, or other chemotactic signaling receptors [i.e., chemokine-like receptor 1 and C-X-C motif chemokine receptor 2]. Intracellularly, CCRL2 colocalized with early endosome antigen 1-positive and Rab5-positive vesicles and with recycling compartments mainly characterized by Rab11-positive vesicles. CCRL2-transfected cells and activated mouse blood endothelial cells, that endogenously express CCRL2, were used to investigate the scavenging ability of CCRL2. These experiments confirmed the ability of CCRL2 to bind chemerin, the only recognized ligand, but excluded the ability of CCRL2 to perform scavenging. Collectively, these results identify unique functional properties for this member of the non-signaling 7-TMD receptor family.

Chemokine Like Receptor-1 (CMKLR-1) Receptor: A Potential Therapeutic Target in Management of Chemerin Induced Type 2 Diabetes Mellitus and Cancer.

Chemerin is an adipokine that induces insulin resistance by the mechanism of inflammation in adipose tissue but these are still unclear. A high level of chemerin in humans is considered as a marker of inflammation in insulin resistance and obesity as well as in type 2 diabetes mellitus. Despite the role of chemerin in insulin resistance progression, chemerin as one of the novel adipokines is proposed to be involved in high cancer risk and mortality. The aim of this paper was to review the role of CMKLR-1 receptor and the potential therapeutic target in the management of chemerin induced type 2 diabetes mellitus and cancer. Increased chemerin secretion activates an inflammatory response. The inflammatory response will increase the oxidative stress in adipose tissue and consequently results in an insulin-resistant state. The occurrence of inflammation, oxidative stress and insulin resistance leads to the progression of cancers. Chemerin is one of the markers that may involve in development of both cancer and insulin resistance. Chemokine like receptor- 1 (CMKLR-1) receptor that regulates chemerin levels exhibits a potential therapeutic target for insulin resistance, type 2 diabetes and cancer treatment.