Preventive CCL2/CCR2 Axis Blockade Suppresses Osteoclast Activity in a Mouse Model of Rheumatoid Arthritis by Reducing Homing of CCR2hi Osteoclast Progenitors to the Affected Bone

Detailed characterization of medullary and extramedullary reservoirs of osteoclast progenitors (OCPs) is required to understand the pathophysiology of increased periarticular and systemic bone resorption in arthritis. In this study, we focused on identifying the OCP population specifically induced by arthritis and the role of circulatory OCPs in inflammatory bone loss. In addition, we determined the relevant chemokine axis responsible for their migration, and targeted the attraction signal to reduce bone resorption in murine collagen-induced arthritis (CIA). OCPs were expanded in periarticular as well as circulatory compartment of arthritic mice, particularly the CCR2hi subset. This subset demonstrated enhanced osteoclastogenic activity in arthritis, whereas its migratory potential was susceptible to CCR2 blockade in vitro. Intravascular compartment of the periarticular area contained increased frequency of OCPs with the ability to home to the arthritic bone, as demonstrated in vivo by intravascular staining and adoptive transfer of splenic LysMcre/Ai9 tdTomato-expressing cells. Simultaneously, CCL2 levels were increased locally and systemically in arthritic mice. Mouse cohorts were treated with the small-molecule inhibitor (SMI) of CCR2 alone or in combination with methotrexate (MTX). Preventive CCR2/CCL2 axis blockade in vivo reduced bone resorption and OCP frequency, whereas combining with MTX treatment also decreased disease clinical score, number of active osteoclasts, and OCP differentiation potential. In conclusion, our study characterized the functional properties of two distinct OCP subsets in CIA, based on their CCR2 expression levels, implying that the CCR2hi circulatory-like subset is specifically induced by arthritis. Signaling through the CCL2/CCR2 axis contributes to OCP homing in the inflamed joints and to their increased osteoclastogenic potential. Therefore, addition of CCL2/CCR2 blockade early in the course of arthritis is a promising approach to reduce bone pathology.

Adult, but Not Neonatal, Platelet Transfusions Drive a Monocyte Trafficking Phenotype in Vitro and In Vivo

Although, thrombocytopenia can affect all age groups, neonates, especially pre-term, have an increased incidence of thrombocytopenia. Platelet transfusions may reduce the bleeding risk in neonates, but are also associated with adverse short and long-term immune and inflammatory outcomes. A randomized trial of platelet transfusions in neonates found that transfusion was associated with an increased risk of necrotizing enterocolitis, unilateral/bilateral retinopathy, and bronchopulmonary dysplasia. Past work from our research team found that neonatal platelets expressed lower levels of mRNA for many immune related molecules compared to adult platelets. We therefore sought to determine whether the transfusion of adult platelets to neonates resulted in developmental immune dysregulation, with a focus on platelet and monocyte interactions. To explore the interactions between monocytes and platelets, we isolated monocytes from adult mouse bone marrow and co-incubated monocytes with adult (>8 weeks old) or neonatal mouse platelets (7 days old mice) and determined inflammatory and trafficking monocyte phenotypes by flow cytometry and qRT-PCR. Monocytes treated with adult platelets had an increased inflammatory (Ly6C hi) and trafficking phenotype (CCR2 hi), while monocytes treated with neonatal platelets adopted an inflammatory, but not trafficking phenotype. As expected, adult platelets increased the expression of monocyte inflammatory (Nos2, Cxcl1, Ccl2) and trafficking (Ccr2) mRNA, while neonatal platelets also increased inflammatory mRNA expression, but did not increase Ccr2 expression. Adult platelets express more Selp (P-selectin) than neonatal platelets and P-selectin is a major mediator of platelet and monocyte interactions. We confirmed that adult platelets expressed more P-selectin protein compared to neonatal platelets, and found that blocking P-selectin decreased adult platelet induced CCR2 expression to levels similar to monocytes treated with neonatal platelets. Using a transwell chamber we assessed adult and neonatal platelet effects on monocyte migration towards the CCR2 ligand CCL2. Monocytes were treated with adult platelets had significantly greater monocyte migration compared to monocytes co-incubated with neonatal platelets. To model platelet transfusions in the setting of thrombocytopenia, we used 14d old thrombopoietin receptor knockout mice (TPOR -/-) that have low platelet counts, and infused adult or neonatal platelets. We observed a significant increase in inflammatory and trafficking monocytes in mice transfused with adult platelets compared to those transfused with neonatal platelets. Using an in vivo model of monocyte chemotaxis, mice were treated with CCL2 intraperitoneal after platelet transfusion. Adult platelet transfusions, but not neonatal, increased monocyte peritoneal trafficking to CCL2. These data provide comparative insights as to how adult and neonatal platelet transfusions regulate monocyte functions. Adult platelet transfusions to neonates are associated with an inflammatory and trafficking monocyte phenotype that is platelet P-selectin dependent and may have a major impact on neonatal platelet transfusion complications. Disclosures Palis: Rubius Therapeutics: Consultancy.

CCR2 Expression Promotes Diffuse Large B Lymphoma Cell Survival and Invasion

Objective: Diffuse large B cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma world wide. It is a phenotypically and genetically heterogeneous disease, accounting for 30-40% of all cases. 50%-70% of patients can be cured by the R-CHOP regimen, but nearly one-third of patients develop relapsed or refractory disease. CC chemokine receptor 2 (CCR2), the high affinity receptor of CC-Chemokine Ligand 2 (CCL2), which is the most representative of the CC chemokine family members, has be regarded to involve in tumor growth, angiogenesis, epithelial mesenchymal transition, metastasis and immune escape etc.. In recent years, the role and mechanism in DLBCL has not been reported yet. Our preliminary study showed that high expression of CCR2 was correlated with clinicopathological characteristics, and an adverse prognostic factor for overall survival (OS) and progression-free survival (PFS) of DLBCL patients. The purpose of this study is to investigate the role of CCR2 expression in DLBCL cells proliferation and migration by in vitro and in vivo. Methods: CCR2 expression were analyzed in human DLBCL cell lines (SUDHL-2, SUDHL-4, SUDHL-6, OCI-Ly8 and OCI-Ly10) by Western blot (WB). SUDHL-2 and OCI-Ly8 cells were incubated with CCR2 antagonist SC-202525 (Santa Crutz Biotechnology), and control cells were left untreated. The proliferation, migration, apoptosis and signaling pathway were detected by CCK8, transwell, flow cytometry (FC) and WB, respectively in vitro. The engraftment, tumor growth, dissemination and survival time were observed in BALB/c nude mice. Results: CCR2 were expressed in all human DLBCL cell lines (relative CCR2 expression was higher in SUDHL-2, SUDHL-4 and OCI-Ly8 than in SUDHL-6 and OCI-Ly10 cell lines). Blockade of CCR2 expression signaling with CCR2 antagonist inhibited tumor cell proliferation, migration and anti-apoptosis ability. The signaling involved in the proliferation and migration of DLBCL cells by activating PI3K/Akt signaling pathway, and induced apoptosis through activation of P38MARK signaling pathway. Expression of CCR2 was also associated with increased engraftment, tumor growth and dissemination, and decreased survival time in xenograft mice. Furthermore, administration of CCR2 antagonist decreased tumor growth and dissemination of DLBCL cells, and increased survival time in the xenograft model. Conclusions: Our study demonstrates that CCR2 plays an important role in the development of DLBCL by stimulating cell proliferation, migration and anti-apoptosis. The inhibition of CCR2 may, therefore, be a potential target for anticancer therapy in DLBCL. Disclosures No relevant conflicts of interest to declare.

The immunological profile of maternal obesity at 28 weeks of gestation underpins common negative pregnancy outcomes

Healthy pregnancy is accompanied by various immunological and metabolic adaptations. Maternal obesity has been implicated in adverse pregnancy outcomes such as miscarriage, preeclampsia, and gestational diabetes mellitus (GDM), while posing a risk to the neonate. There is a lack of knowledge surrounding obesity and the maternal immune system. The objective of this study was to consider if immunological changes in pregnancy are sabotaged by maternal obesity. Peripheral blood was collected from fasted GDM-negative pregnant women at 26-28 weeks of gestation. Analysis was done using immunoassay, flow cytometry, bioenergetics analysis and cell culture. The plasma profile was significantly altered with increasing BMI, specifically leptin (r=0.7635), MCP-1 (r=0.3024) and IL-6 (r=0.4985). Circulating leukocyte populations were also affected with changes in the relative abundance of intermediate monocytes (r=-0.2394), CD4:CD8 T cell ratios (r=0.2789), and NKT cells (r=-0.2842). Monocytes analysed in more detail revealed elevated CCR2 expression and decreased mitochondrial content. However, LPS-stimulated cytokine production and bioenergetic profile of MNCs was not affected by maternal BMI. The Th profile skews towards Th17 with increasing BMI; Th2 (r=-0.3202) and Th9 (r=-0.3205) cells were diminished in maternal obesity, and CytoStimTM-stimulation exacerbates IL-6 (r=0.4166), IL-17A (r=0.2753), IL-17F (r=0.2973) and IL-22 (r=0.2257) production with BMI, while decreasing IL-4 (r=-0.2806). Maternal obesity during pregnancy creates an inflammatory microenvironment. Successful pregnancy requires Th2-biased responses yet increasing maternal BMI favours a Th17 response that could be detrimental to pregnancy. Further research should investigate key populations of cells identified here to further understand the immunological challenges that beset pregnant women with obesity.

CX3CR1 But Not CCR2 Expression Is Required for the Development of Autoimmune Peripheral Neuropathy in Mice

One hallmark of Guillain-Barre syndrome (GBS), a prototypic autoimmune peripheral neuropathy (APN) is infiltration of leukocytes (macrophages and T cells) into peripheral nerves, where chemokines and their receptors play major roles. In this study, we aimed to understand the potential contribution of chemokine receptors CCR2 and CX3CR1 in APN by using a well-established mouse model, B7.2 transgenic (L31) mice, which possesses a predisposed inflammatory background. We crossbred respectively CCR2KO and CX3CR1KO mice with L31 mice. The disease was initiated by partial ligation on one of the sciatic nerves. APN pathology and neurological function were evaluated on the other non-ligated sciatic nerve/limb. Our results revealed that L31/CX3CR1KO but not L31/CCR2KO mice were resistant to APN. CX3CR1 is needed for maintaining circulating monocyte and CD8+ T cell survival. While migration of a significant number of activated CD8+ T cells to peripheral nerves is essential in autoimmune response in nerve, recruitment of monocytes into PNS seems optional. Disease onset is independent of CCR2 mediated blood-derived macrophage recruitment, which can be replaced by compensatory proliferation of resident macrophages in peripheral nerve. CX3CR1 could also contribute to APN via its critical involvement in maintaining nerve macrophage phagocytic ability. We conclude that blockade of CX3CR1 signaling may represent an interesting anti-inflammatory strategy to improve therapeutic management for GBS patients.

CCR2 Contributes to the Homing of MSCs and Liver Regeneration

Objective: Mesenchymal stem cells (MSCs) are emerging as a new therapeutic strategy for liver diseases.However, the inability of stem cells to efficiently return to the target tissue is a major obstacle to repair.The chemokine family and its receptors play an important role in the homing of mesenchymal stem cells.This study was conducted to verify that the overexpression of chemokine receptor CCR2 can contribute to the homing of MSCs, improve the therapeutic effect, and clarify the mechanism of action.Methods: A mouse model of partial hepatectomy was established. Transcriptome sequencing was used to detect the expression of CCl2 in liver tissue.CCR2 was transfected with lentivirus into BMSCs, and the expression of CCR2 in BMSCs was detected by qRT-PCR. The effect of BMSCs overexpressing CCR2 on liver regeneration in mice with partial hepatectomy was detected by liver index, HE staining and serum ALT and AST content. The migration ability of BMSCs modified by CCR2 was observed by Transwell test and PKH26 staining. The influence of CCl2-CCR2 on the homing signaling pathway of BMSCs was detected by Western blot and scratch experiments.Results: The expression of CCl2 was up-regulated during the whole process of liver regeneration.BMSCs can express CCR2 receptor, but lentivirus transfected BMSCs can express more CCR2.The BMSCs modified by CCR2 showed stronger migration ability. At 72 hours after partial hepatectomy, the liver index of BMSCS-CCR2 group was higher than that of BMSCs group, the liver tissue structure tended to be normal, and ALT and AST content decreased significantly. Expression of Rho/ROCK signaling pathway protein was increased in the liver of BMSCS-CCR2 group, while cell migration was decreased after treatment with the ROCK inhibitor Y-27632.Conclusion: In summary, this study suggests that CCR2 expression on BMSCs enhances their targeted migration to the liver of partial hepatectomy mice and promotes liver regeneration. The Rho/ROCK signaling pathway plays an important role in the homing of BMSCs.

Regulatory B cells improve ventricular remodeling after myocardial infarction by modulating monocyte migration

Overactivated inflammatory responses contribute to adverse ventricular remodeling after myocardial infarction (MI). Regulatory B cells (Bregs) are a newly discovered subset of B cells with immunomodulatory roles in many immune and inflammation-related diseases. Our study aims to determine whether the expansion of Bregs exerts a beneficial effect on ventricular remodeling and explore the mechanisms involved. Here, we showed that adoptive transfer of Bregs ameliorated ventricular remodeling in a murine MI model, as demonstrated by improved cardiac function, decreased scar size and attenuated interstitial fibrosis without changing the survival rate. Reduced Ly6Chi monocyte infiltration was found in the hearts of the Breg-transferred mice, while the infiltration of Ly6Clo monocytes was not affected. In addition, the replenishment of Bregs had no effect on the myocardial accumulation of T cells or neutrophils. Mechanistically, Bregs reduced the expression of C–C motif chemokine receptor 2 (CCR2) in monocytes, which inhibited proinflammatory monocyte recruitment to the heart from the peripheral blood and mobilization from the bone marrow. Breg-mediated protection against MI was abrogated by treatment with an interleukin 10 (IL-10) antibody. Finally, IL-10 neutralization reversed the effect of Bregs on monocyte migration and CCR2 expression. The present study suggests a therapeutic value of Bregs in limiting ventricular remodeling after MI through decreasing CCR2-mediated monocyte recruitment and mobilization.

CD73 Overexpression in Podocytes: A Novel Marker of Podocyte Injury in Human Kidney Disease

The CD73 pathway is an important anti-inflammatory mechanism in various disease settings. Observations in mouse models suggested that CD73 might have a protective role in kidney damage; however, no direct evidence of its role in human kidney disease has been described to date. Here, we hypothesized that podocyte injury in human kidney diseases alters CD73 expression that may facilitate the diagnosis of podocytopathies. We assessed the expression of CD73 and one of its functionally important targets, the C-C chemokine receptor type 2 (CCR2), in podocytes from kidney biopsies of 39 patients with podocytopathy (including focal segmental glomerulosclerosis (FSGS), minimal change disease (MCD), membranous glomerulonephritis (MGN) and amyloidosis) and a control group. Podocyte CD73 expression in each of the disease groups was significantly increased in comparison to controls (p < 0.001–p < 0.0001). Moreover, there was a marked negative correlation between CD73 and CCR2 expression, as confirmed by immunohistochemistry and immunofluorescence (Pearson r = −0.5068, p = 0.0031; Pearson r = −0.4705, p = 0.0313, respectively), thus suggesting a protective role of CD73 in kidney injury. Finally, we identify CD73 as a novel potential diagnostic marker of human podocytopathies, particularly of MCD that has been notorious for the lack of pathological features recognizable by light microscopy and immunohistochemistry.

Impact of the rs1024611 Polymorphism of CCL2 on the Pathophysiology and Outcome of Primary Myelofibrosis

Single nucleotide polymorphisms (SNPs) can modify the individual pro-inflammatory background and may therefore have relevant implications in the MPN setting, typified by aberrant cytokine production. In a cohort of 773 primary myelofibrosis (PMF), we determined the contribution of the rs1024611 SNP of CCL2—one of the most potent immunomodulatory chemokines—to the clinical and biological characteristics of the disease, demonstrating that male subjects carrying the homozygous genotype G/G had an increased risk of PMF and that, among PMF patients, the G/G genotype is an independent prognostic factor for reduced overall survival. Functional characterization of the SNP and the CCL2-CCR2 axis in PMF showed that i) homozygous PMF cells are the highest chemokine producers as compared to the other genotypes; ii) PMF CD34+ cells are a selective target of CCL2, since they uniquely express CCR2 (CCL2 receptor); iii) activation of the CCL2-CCR2 axis boosts pro-survival signals induced by driver mutations via Akt phosphorylation; iv) ruxolitinib effectively counteracts CCL2 production and down-regulates CCR2 expression in PMF cells. In conclusion, the identification of the role of the CCL2/CCR2 chemokine system in PMF adds a novel element to the pathophysiological picture of the disease, with clinical and therapeutic implications.