Chemokine CXCL12 uses CXCR4 and a signaling core formed by bifunctional Akt, extracellular signal-regulated kinase (ERK)1/2, and mammalian target of rapamycin complex 1 (mTORC1) proteins to control chemotaxis and survival simultaneously in mature dendritic cells

CAR-T cells are more affected than T lymphocytes by mechanical constraints: A microfluidic-based approach

AIMS

CAR-T cell therapy has attracted considerable attention in recent years owing to its well-known efficacy against haematopoietic malignancies. Nevertheless, this immunotherapy fails against solid tumours due to hostile conditions found in the tumour microenvironment. In this context, many relevant biochemical factors have been thoroughly studied, but crucial mechanical cues have been underestimated.

MAIN METHODS

We developed an innovative approach using microfluidic devices, which recreate the biomechanical aspects of solid tumours. Using these platforms, we quantified immune cell migration (T and CAR-T cells) under different confinement conditions.

KEY FINDINGS

We found that both CAR-T cell and T cell velocities are affected by the biomechanical and chemical cues studied, which are closely related to those found in solid tumours. Under biochemical stimulus-free conditions, the velocity of T cells is independent of the width of the microchannel, whereas the velocity of CAR-T cells is greatly reduced in the highest confinement channels. When chemoattractants or tumour cells are added, immune cells display increased confined migration velocity. However, in the presence of immunosuppressive chemokines, T cells become slower, whereas CAR-T cells significantly increase their velocity via a chimeric cytokine receptor.

SIGNIFICANCE

Our approach contributes to a better understanding of immune cell migration and the influence of mechanical constraints, which will allow the testing of new ways to improve CAR-T cell trafficking into solid tumours. Therefore, our study revealed that the migratory behaviour of CAR-T cells differs from that of T cells under confined conditions and that biomechanical cues, such as cell deformability caused by confinement, can influence the correct infiltration of immune cells into solid tumours during the immune response.

Stromal Cell Derived Factor-1 Promotes Hepatic Insulin Resistance via Inhibiting Hepatocyte Lipophagy

Saturated fatty acid (SFA) accumulation in liver decreases hepatocyte lipophagy, a type of selective autophagy that degrades intracellular lipid droplets, leading to hepatic insulin resistance (IR), which contributes to simultaneous increases in liver glucose production and fat synthesis, resulting in hyperglycemia and dyslipidemia traits of type 2 diabetes mellitus (T2DM). Stromal cell derived factor-1 (SDF-1), a cytokine produced by hepatocytes, inhibits autophagy. In this study, we evaluated the hypothesis that SDF-1 promoted hepatic IR via inhibiting hepatocyte lipophagy during T2DM. Furthermore, we probed the downstream pathway participating in the role of SDF-1. The results showed that the neutralising of SDF-1 improved hepatic IR via promoting hepatocyte lipophagy in a mouse high-fat and high sucrose diet (HFHSD)-induced T2DM model. In vitro, SDF-1 expression and release increased in palmitic acid (PA, a kind of SFA)-treated hepatocytes. Meanwhile, SDF-1 bound to up-regulated C-X-C chemokine receptor type 4 (CXCR4) and C-X-C chemokine receptor type 7 (CXCR7) on PA-treated hepatocytes. Subsequently, SDF-1 inhibited lipophagy in PA-treated hepatocytes via CXCR4, rather than CXCR7. Finally, SDF-1/CXCR4/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) pathway-inhibited lipophagy promotes PA-induced hepatocyte IR. Collectively, this study discovered that SDF-1 might inhibit lipophagy in SFA-treated hepatocytes to promote hepatic IR via CXCR4/AKT/mTOR pathway.

CXCL12/CXCR4 Axis Promotes the Chemotaxis and Phagocytosis of B Cells through the PI3K-AKT Signaling Pathway in an Early Vertebrate

Chemokines play crucial roles in the regulation of immune cell migration and development. The CXCL12/CXCR4 axis has been extensively studied in mammals, but its regulatory mechanism in teleost fish remains unclear. In this study, we used Nile tilapia (Oreochromis niloticus) as a teleost model to investigate the mediation of the CXCL12/CXCR4 axis in IgM+ B cells. Our findings demonstrate that the CXCL12/CXCR4 axis exhibits chemotactic activity on IgM+ B cells and promotes the phagocytosis of IgM+ B cells. Blocking CXCR4 severely impairs the chemotaxis and phagocytosis of IgM+ B cells in vitro and reduces the percentages and numbers of IgM+ B cells that migrate to peripheral blood after pathogen infection in vivo. This reduction in migration leads to a decrease in the inflammatory response, an increase in tissue bacterial load, and a decrease in survival rate. We also discovered that the evolutionarily conserved PI3K-AKT signaling pathway and Girdin are involved in the immune response during Streptococcus agalactiae infection. Inhibitors of the PI3K-AKT signaling pathway prevent the chemotaxis and phagocytosis of IgM+ B cells, impair the expression and phosphorylation levels of related proteins in vitro, and prevent IgM+ B cells chemotaxis into the peripheral blood after pathogen infection in vivo. Furthermore, CXCR4 blocking significantly downregulates the expression of AKT and Girdin. Overall, our study reveals the regulatory mechanism of the CXCL12/CXCR4 axis on IgM+ B cells via the PI3K-AKT signaling pathway in tilapia, suggesting that the functions of the CXCL12/CXCR4 axis in B cells may be conserved between mammals and teleost fish.

Bactericidal ability of target acidic phospholipids and phagocytosis of CDC42 GTPase-mediated cytoskeletal rearrangement underlie functional conservation of CXCL12 in vertebrates

Chemokine CXCL12 plays a crucial role in both direct bactericidal activity and phagocytosis in humans. However, the mechanisms and evolutionary functions of these processes in vertebrates remain largely unknown. In this study, we found that the direct bactericidal activity of CXCL12 is highly conserved across various vertebrate lineages, including Arctic lamprey (Lampetra japonica), Basking shark (Cetorhinus maximus), grass carp (Ctenopharyngodon idella), Western clawed frog (Xenopus tropicalis), Green anole (Anolis carolinensis), chicken (Gallus gallus), and human (Homo sapiens). CXCL12 also has been shown to promote phagocytosis in lower and higher vertebrates. We then employed C. idella CXCL12a (CiCXCL12a) as a model to further investigate its immune functions and underlying mechanisms. CiCXCL12a exerts direct broad-spectrum antibacterial activity by targeting bacterial acidic phospholipids, resulting in bacterial cell membrane perforation, and eventual lysis. Monocytes/macrophages are attracted to the infection sites for phagocytosis through the rapid production of CiCXCL12a during bacterial infection. CiCXCL12a induces CDC42 and CDC42 GTPase activation, which in turn mediates F-actin polymerization and cytoskeletal rearrangement. The interaction between F-actin and Aeromonas hydrophila facilitates bacterial internalization into monocytes/macrophages. Additionally, A. hydrophila is colocalized within early endosomes, late endosomes and lysosomes, ultimately degrading within phagolysosomes. CiCXCL12a also activates PI3K-AKT, JAK-STAT5 and MAPK-ERK signaling pathways. Notably, only the PI3K-AKT signaling pathway inhibits LPS-induced monocyte/macrophage apoptosis. Thus, CiCXCL12a plays key roles in reducing tissue bacterial loads, attenuating organ injury, and decreasing mortality rates. Altogether, our findings elucidate the conserved mechanisms underlying CXCL12-mediated bactericidal activity and phagocytosis, providing novel perspectives into the immune functions of CXCL12 in vertebrates.

Potential advantages of genetically modified mesenchymal stem cells in the treatment of acute and chronic liver diseases

Liver damage caused by toxicity can lead to various severe conditions, such as acute liver failure (ALF), fibrogenesis, and cirrhosis. Among these, liver cirrhosis (LC) is recognized as the leading cause of liver-related deaths globally. Unfortunately, patients with progressive cirrhosis are often on a waiting list, with limited donor organs, postoperative complications, immune system side effects, and high financial costs being some of the factors restricting transplantation. Although the liver has some capacity for self-renewal due to the presence of stem cells, it is usually insufficient to prevent the progression of LC and ALF. One potential therapeutic approach to improving liver function is the transplantation of gene-engineered stem cells. Several types of mesenchymal stem cells from various sources have been suggested for stem cell therapy for liver disease. Genetic engineering is an effective strategy that enhances the regenerative potential of stem cells by releasing growth factors and cytokines. In this review, we primarily focus on the genetic engineering of stem cells to improve their ability to treat damaged liver function. We also recommend further research into accurate treatment methods that involve safe gene modification and long-term follow-up of patients to increase the effectiveness and reliability of these therapeutic strategies.

A meta-analysis indicates that the regulation of cell motility is a non-intrinsic function of chemoattractant receptors that is governed independently of directional sensing

Chemoattraction, defined as the migration of a cell toward a source of a chemical gradient, is controlled by chemoattractant receptors. Chemoattraction involves two basic activities, namely, directional sensing, a molecular mechanism that detects the direction of a source of chemoattractant, and actin-based motility, which allows the migration of a cell towards it. Current models assume first, that chemoattractant receptors govern both directional sensing and motility (most commonly inducing an increase in the migratory speed of the cells, i.e. chemokinesis), and, second, that the signaling pathways controlling both activities are intertwined. We performed a meta-analysis to reassess these two points. From this study emerge two main findings. First, although many chemoattractant receptors govern directional sensing, there are also receptors that do not regulate cell motility, suggesting that is the ability to control directional sensing, not motility, that best defines a chemoattractant receptor. Second, multiple experimental data suggest that receptor-controlled directional sensing and motility can be controlled independently. We hypothesize that this independence may be based on the existence of separated signalling modules that selectively govern directional sensing and motility in chemotactic cells. Together, the information gathered can be useful to update current models representing the signalling from chemoattractant receptors. The new models may facilitate the development of strategies for a more effective pharmacological modulation of chemoattractant receptor-controlled chemoattraction in health and disease.

Innate Immune Cells in Pressure Overload-Induced Cardiac Hypertrophy and Remodeling

Pressure overload and heart failure are among the leading causes of cardiovascular morbidity and mortality. Accumulating evidence suggests that inflammatory cell activation and release of inflammatory mediators are of vital importance during the pathogenesis of these cardiac diseases. Yet, the roles of innate immune cells and subsequent inflammatory events in these processes remain poorly understood. Here, we outline the possible underlying mechanisms of innate immune cell participation, including mast cells, macrophages, monocytes, neutrophils, dendritic cells, eosinophils, and natural killer T cells in these pathological processes. Although these cells accumulate in the atrium or ventricles at different time points after pressure overload, their cardioprotective or cardiodestructive activities differ from each other. Among them, mast cells, neutrophils, and dendritic cells exert detrimental function in experimental models, whereas eosinophils and natural killer T cells display cardioprotective activities. Depending on their subsets, macrophages and monocytes may exacerbate cardiodysfunction or negatively regulate cardiac hypertrophy and remodeling. Pressure overload stimulates the secretion of cytokines, chemokines, and growth factors from innate immune cells and even resident cardiomyocytes that together assist innate immune cell infiltration into injured heart. These infiltrates are involved in pro-hypertrophic events and cardiac fibroblast activation. Immune regulation of cardiac innate immune cells becomes a promising therapeutic approach in experimental cardiac disease treatment, highlighting the significance of their clinical evaluation in humans.

Strict network analysis of evolutionary conserved and brain-expressed genes reveals new putative candidates implicated in Intellectual Disability and in Global Development Delay

OBJECTIVES

Intellectual Disability (ID) and Global Development Delay (GDD) are frequent reasons for referral to genetic services and although they present overlapping phenotypes concerning cognitive, motor, language, or social skills, they are not exactly synonymous. Aiming to better understand independent or shared mechanisms related to these conditions and to identify new candidate genes, we performed a highly stringent protein-protein interaction network based on genes previously related to ID/GDD in the Human Phenotype Ontology portal.

METHODS

ID/GDD genes were searched for reliable interactions through STRING and clustering analysis was applied to detect biological complexes through the MCL algorithm. Six coding hub genes (TP53, CDC42, RAC1, GNB1, APP, and EP300) were recognised by the Cytoscape NetworkAnalyzer plugin, interacting with 1625 proteins not yet associated with ID or GDD. Genes encoding these proteins were explored by gene ontology, associated diseases, evolutionary conservation, and brain expression.

RESULTS

One hundred and seventy-two new putative genes playing a role in enriched processes/pathways previously related to ID and GDD were revealed, some of which were already postulated to be linked to ID/GDD in additional databases.

CONCLUSIONS

Our findings expanded the aetiological genetic landscape of ID/GDD and showed evidence that both conditions are closely related at the molecular and functional levels.

Nile tilapia CXCR4, the receptor of chemokine CXCL12, is involved in host defense against bacterial infection and chemotactic activity

CXC chemokine receptor 4 (CXCR4), a member of seven-transmembrane (7-TM) G-protein-coupled receptor superfamily, is the receptor of the CXC chemokine ligand 12 (CXCL12), and plays important roles in host defense and inflammation. In the current study, we cloned and identified a homolog of CXCR4 from Nile tilapia (Oreochromis niloticus), designated as OnCXCR4. The open reading frame of OnCXCR4 is 1149 bp encoding a peptide of 382 amino acids, and the predicted molecular weight is 42.65 kDa OnCXCR4 shares common features of CXCR4 family, including a 7-TM domain and a characteristic CXC motif (containing CYC). Expression analysis showed that OnCXCR4 constitutively expresses in various tested tissues of Nile tilapia, with the highest level in the anterior kidney. When stimulated with Streptococcus agalactiae, Aeromonas hydrophila, Poly(I:C), or LPS in vivo and in vitro, the expression of OnCXCR4 was significantly regulated. AMD3100, a CXCR4 antagonist, could not only inhibit the chemotactic activity of the recombinant OnCXCL12 protein on the leukocytes from anterior kidney, but also reduce the expression of OnCXCR4 significantly. Taken together, these results of our study above indicate that OnCXCR4 may play important roles in host defense against bacterial infectionin in Nile tilapia, and being a receptor of OnCXCL12 to exert functions.

The CXCL12-CXCR4 Signaling Axis Plays a Key Role in Cancer Metastasis and is a Potential Target for Developing Novel Therapeutics against Metastatic Cancer

Metastasis is the main cause of death in cancer patients; there is currently no effective treatment for cancer metastasis. This is primarily due to our insufficient understanding of the metastatic mechanisms in cancer. An increasing number of studies have shown that the C-X-C motif chemokine Ligand 12 (CXCL12) is overexpressed in various tissues and organs. It is a key niche factor that nurtures the pre-metastatic niches (tumorigenic soil) and recruits tumor cells (oncogenic "seeds") to these niches, thereby fostering cancer cell aggression and metastatic capabilities. However, the C-X-C motif chemokine Receptor 4 (CXCR4) is aberrantly overexpressed in various cancer stem/progenitor cells and functions as a CXCL12 receptor. CXCL12 activates CXCR4 as well as multiple downstream multiple tumorigenic signaling pathways, promoting the expression of various oncogenes. Activation of the CXCL12-CXCR4 signaling axis promotes Epithelial-Mesenchymal Transition (EMT) and mobilization of cancer stem/progenitor cells to pre-metastatic niches. It also nurtures cancer cells with high motility, invasion, and dissemination phenotypes, thereby escalating multiple proximal or distal cancer metastasis; this results in poor patient prognosis. Based on this evidence, recent studies have explored either CXCL12- or CXCR4-targeted anti-cancer therapeutics and have achieved promising results in the preclinical trials. Further exploration of this new strategy and its potent therapeutics effect against metastatic cancer through the targeting of the CXCL12- CXCR4 signaling axis may lead to a novel therapy that can clean up the tumor microenvironment ("soil") and kill the cancer cells, particularly the cancer stem/progenitor cells ("seeds"), in cancer patients. Ultimately, this approach has the potential to effectively treat metastatic cancer.

The Chemokine Receptor CXCR4 in Cell Proliferation and Tissue Regeneration

The CXCR4 receptor upon binding its ligands triggers multiple signaling pathways that orchestrate cell migration, hematopoiesis and cell homing, and retention in the bone marrow. However, CXCR4 also directly controls cell proliferation of non-hematopoietic cells. This review focuses on recent reports pointing to its pivotal role in tissue regeneration and stem cell activation, and discusses the connection to the known role of CXCR4 in promoting tumor growth. The mechanisms may be similar in all cases, since regeneration often recapitulates developmental processes, and cancer often exploits developmental pathways. Moreover, cell migration and cell proliferation appear to be downstream of the same signaling pathways. A deeper understanding of the complex signaling originating from CXCR4 is needed to exploit the opportunities to repair damaged organs safely and effectively.

FtH-Mediated ROS Dysregulation Promotes CXCL12/CXCR4 Axis Activation and EMT-Like Trans-Differentiation in Erythroleukemia K562 Cells

The cell-microenvironment communication is essential for homing of hematopoietic stem cells in stromal niches. Recent evidences support the involvement of epithelial-to-mesenchymal (EMT) process in hematopoietic stem cell homeostasis as well as in leukemia cells invasiveness and migration capability. Here, we demonstrate that the alteration of iron homeostasis and the consequent increase of redox metabolism, mediated by the stable knock down of ferritin heavy chain (FtH), enhances the expression of CXCR4 in K562 erythroleukemia cells, thus promoting CXCL12-mediated motility. Indeed, addition of the CXCR4 receptor antagonist AMD3100 reverts this effect. Upon FtH knock down K562 cells also acquire an “EMT-like” phenotype, characterized by the increase of Snail, Slug and Vimentin with the parallel loss of E-cadherin. By using fibronectin as substrate, the cell adhesion assay further shows a reduction of cell adhesion capability in FtH-silenced K562 cells. Accordingly, confocal microscopy shows that adherent K562 control cells display a variety of protrusions while FtH-silenced K562 cells remain roundish. These phenomena are largely due to the reactive oxygen species (ROS)-mediated up-regulation of HIF-1α/CXCR4 axis which, in turn, promotes the activation of NF-κB and the enhancement of EMT features. These data are confirmed by treatments with either N-acetylcysteine (NAC) or AMD3100 or NF-κB inhibitor IκB-alpha which revert the FtH-silenced K562 invasive phenotype. Overall, our findings demonstrate the existence of a direct relationship among iron metabolism, redox homeostasis and EMT in the hematological malignancies. The effects of FtH dysregulation on CXCR4/CXCL12-mediated K562 cell motility extend the meaning of iron homeostasis in the leukemia cell microenvironment.

The Chemokine Receptor CCR7 Uses Distinct Signaling Modules With Biased Functionality to Regulate Dendritic Cells

Chemotaxis is a molecular mechanism that confers leukocytes the ability to detect gradients of chemoattractants. Chemokine receptors are well-known regulators of chemotaxis in leukocytes; however, they can regulate several other activities in these cells. This information has been often neglected, probably due to the paramount role of chemotaxis in the immune system and in biology. Therefore, the experimental data available on the mechanisms used by chemokine receptors to regulate other functions of leukocytes is sparse. The results obtained in the study of the chemokine receptor CCR7 in dendritic cells (DCs) provide interesting information on this issue. CCR7 guides the DCs from the peripheral tissues to the lymph nodes, where these cells control T cell activation. CCR7 can regulate DC chemotaxis, survival, migratory speed, cytoarchitecture, and endocytosis. Biochemical and functional analyses show: first, that CCR7 uses in DCs the PI3K/Akt pathway to control survival, the MAPK pathway to control chemotaxis, and the RhoA pathways to regulate actin dynamics, which in turn controls migratory speed, cytoarchitecture, and endocytosis; second, that these three signaling pathways behave as modules with a high degree of independence; and third, that although each one of these routes can regulate several functions in different settings, CCR7 promotes in DCs a functional bias in each pathway. The data uncover an interesting mechanism used by CCR7 to regulate the DCs, entailing multifunctional signaling pathways organized in modules with biased functionality. A similar mechanism could be used by other chemoattractant receptors to regulate the functions of leukocytes.

Constitutive and stimulated macropinocytosis in macrophages: roles in immunity and in the pathogenesis of atherosclerosis

Macrophages respond to several stimuli by forming florid membrane ruffles that lead to fluid uptake by macropinocytosis. This type of induced macropinocytosis, executed by a variety of non-malignant and malignant cells, is initiated by transmembrane receptors and is involved in nutrient acquisition and mTOR signalling. However, macrophages also perform a unique type of constitutive ruffling and macropinocytosis that is dependent on the presence of extracellular calcium. Calcium-sensing receptors are responsible for this activity. This distinct form of macropinocytosis enables macrophages to continuously sample their microenvironment for antigenic molecules and for pathogen- and danger-associated molecular patterns, as part of their immune surveillance functions. Interestingly, even within the monocyte lineage, there are differences in macropinocytic ability that reflect the polarized functional roles of distinct macrophage subsets. This review discusses the shared and distinct features of both induced and constitutive macropinocytosis displayed by the macrophage lineage and their roles in physiology, immunity and pathophysiology. In particular, we analyse the role of macropinocytosis in the uptake of modified low-density lipoprotein (LDL) and its contribution to foam cell and atherosclerotic plaque formation. We propose a combined role of scavenger receptors and constitutive macropinocytosis in oxidized LDL uptake, a process we have termed 'receptor-assisted macropinocytosis'. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.

Characterization of monocyte-derived dendritic cells used in immunotherapy for HIV-1-infected individuals

AIMS

A therapeutic vaccine based on monocyte-derived dendritic cells (MDDCs) has been shown to represent a promising strategy for the treatment of cancer and viral infections. Here, we characterized the MDDCs used as an immunogen in a clinical trial for an anti-HIV-1 therapeutic vaccine.

PATIENTS & METHODS

Monocytes obtained from 17 HIV-infected individuals were differentiated into MDDCs and, after loading with autologous HIV, the cells were characterized concerning surface molecule expression, migratory and phagocytosis capacity, cytokine production and the induction of an effective cell-mediated immune response.

RESULTS

The MDDCs were able to induce antigen-specific responses in autologous CD4+ and CD8+ T lymphocytes.

CONCLUSIONS

Despite a large interindividual variability, the results suggested that MDDCs present the potential to promote immune responses in vaccinated patients.

Inhibition of Dipeptidyl Peptidase-4 Accelerates Epithelial-Mesenchymal Transition and Breast Cancer Metastasis via the CXCL12/CXCR4/mTOR Axis

Dipeptidyl peptidase (DPP)-4 is a multifunctional glycoprotein involved in various biological and pathologic processes. DPP-4 has been widely recognized as a therapeutic target for type 2 diabetes mellitus but is also implicated in the development of human malignancies. Here, we show that inhibition of DPP-4 accelerates breast cancer metastasis via induction of CXCL12/CXCR4, which activates mTOR to promote epithelial-mesenchymal transition (EMT). In cultured cells, DPP-4 knockdown induced EMT and cell migration. Treatment with the DPP-4 inhibitor KR62436 (KR) promoted primary tumor growth and lung metastasis in a 4T1 tumor allograft mouse model; DPP-4 knockdown in 4T1 cells displayed similar phenotypes in vivo and in vitro. KR treatment enhanced the levels of CXCL12/CXCR4 and phosphorylated mTOR, which were associated with the induction of EMT in metastatic cancer cells. KR-induced EMT in cancer cells was inhibited by treatment with the CXCR4 inhibitor AMD3100 or the mTOR inhibitor rapamycin, and AMD3100 suppressed KR-induced metastasis in vivo. Our findings suggest that DPP-4 plays a significant role in cancer biology and that inhibition of DPP-4 promotes cancer metastasis via induction of the CXCL12/CXCR4/mTOR/EMT axis. SIGNIFICANCE: These findings reveal that inhibition of DPP-4 increases the metastatic potential of breast cancer. This is especially important given the potential use of DPP-4 inhibition as a therapeutic strategy for type 2 diabetes.

Deficiency of β-Arrestin 2 in Dendritic Cells Contributes to Autoimmune Diseases

Altered migration and immune responses of dendritic cells (DCs) lead to inflammatory and autoimmune diseases. Our studies demonstrated that β-arrestin 2 deficiency promoted migration and cytokine production of mouse bone marrow-derived DCs. We further found that β-arrestin 2 directly interacted with Zbtb46, a DC-specific transcription factor. What's more, our results suggested that the interaction between β-arrestin 2 and Zbtb46 might negatively regulate DC migration. Using RNA sequencing, we indicated that genes CD74, NR4A1, and ZFP36 might be the target genes regulated by the interaction between β-arrestin 2 and Zbtb46. Mice with selective deficiency of β-arrestin 2 in DCs developed severer experimental autoimmune encephalomyelitis with more DC infiltration in the CNS and increased IL-6 in serum. In the systemic lupus erythematosus mice model, Arrb2^fl/fl Itgax-cre⁺ mice were prone to exacerbation of lupus nephritis with a higher level of IL-6 and DC accumulation. Taken together, our study identified β-arrestin 2 as a new regulator of DC migration and immune properties, providing new insights into the mechanisms underlying the development of autoimmune disease.

Inflammatory cells and their non-coding RNAs as targets for treating myocardial infarction

Myocardial infarction triggers infiltration of several types of immune cells that coordinate both innate and adaptive immune responses. These play a dual role in post-infarction cardiac remodeling by initiating and resolving inflammatory processes, which needs to occur in a timely and well-orchestrated way to ensure a reestablishment of normalized cardiac functions. Thus, therapeutic modulation of immune responses might have benefits for infarct patients. While such strategies have shown great potential in treating cancer, applications in the post-infarction context have been disappointing. One challenge has been the complexity and plasticity of immune cells and their functions in cardiac regulation and healing. The types appear in patterns that are temporally and spatially distinct, while influencing each other and the surrounding tissue. A comprehensive understanding of the immune cell repertoire and their regulatory functions following infarction is sorely needed. Processes of cardiac remodeling trigger additional genetic changes that may also play critical roles in the aftermath of cardiovascular disease. Some of these changes involve non-coding RNAs that play crucial roles in the regulation of immune cells and may, therefore, be of therapeutic interest. This review summarizes what is currently known about the functions of immune cells and non-coding RNAs during post-infarction wound healing. We address some of the challenges that remain and describe novel therapeutic approaches under development that are based on regulating immune responses through non-coding RNAs in the aftermath of the disease.

Tobacco smoke and nicotine suppress expression of activating signaling molecules in human dendritic cells

Cigarette smoke has significant toxic effects on the immune system, and increases the risk of developing autoimmune diseases; one immunosuppressive effect of cigarette smoke is that it inhibits the T cell-stimulating, immunogenic properties of myeloid dendritic cells (DCs). As the functions of DCs are regulated by intra-cellular signaling pathways, we investigated the effects of cigarette smoke extract (CSE) and nicotine on multiple signaling molecules and other regulatory proteins in human DCs to elucidate the molecular basis of the inhibition of DC maturation and function by CSE and nicotine. Maturation of monocyte-derived DCs was induced with the TLR3-agonist poly I:C or with the TLR4-agonist lipopolysaccharide, in the absence or presence of CSE or nicotine. Reverse-phase protein microarray was used to quantify multiple signaling molecules and other proteins in cell lysates. Particularly in poly I:C-matured DCs, cigarette smoke constituents and nicotine suppressed the expression of signaling molecules associated with DC maturation and T cell stimulation, cell survival and cell migration. In conclusion, constituents of tobacco smoke suppress the immunogenic potential of DCs at the signaling pathway level.

Autoantibody against integrin αv β3 contributes to thrombocytopenia by blocking the migration and adhesion of megakaryocytes

Essentials The pathogenesis of immune thrombocytopenia (ITP) has not been fully clarified. We analyzed the role of anti-αvβ3 autoantibody in the pathogenesis of ITP in patients. Anti-αvβ3 autoantibody impeded megakaryocyte migration and adhesion to the vascular niche. Anti-αv β3 autoantibody potentially contributes to the pathogenesis of refractory ITP.

SUMMARY

Background The pathogenesis of immune thrombocytopenia (ITP) has not been fully clarified. Anti-αvβ3 integrin autoantibody is detected in chronic ITP patients, but its contribution to ITP is still unclear. Objectives To clarify the potential role of anti-αvβ3 integrin autoantibody in chronic ITP and the related mechanism. Methods Relationship between levels of anti-αvβ3 autoantibody and platelets in chronic ITP patients was evaluated. The influence of anti-αvβ3 antibody on megakaryocyte (MK) survival, differentiation, migration and adhesion was assessed, and the associated signal pathways were investigated. Platelet recovery and MKs' distribution were observed in an ITP mouse model pretreated with different antibodies. Result In this study, we showed that the anti-αvβ3 autoantibody usually coexists with anti-αIIbβ3 autoantibody in chronic ITP patients, and patients with both autoantibodies have lower platelets. In in vitro studies, we showed that the anti-αvβ3 antibody had no significant effect on the survival and proliferation of MKs, whereas it decreased formations of proplatelet significantly. Anti-αvβ3 antibody impeded stromal cell derived facor-1 alpha (SDF-1α)- mediated migration and inhibited the phosphorylation of protein kinase B. Anti-αvβ3 antibody significantly inhibited MKs' adhesion to endothelial cells and Fibrogen. The phosphorylation of focal adhesion kinase and proto-oncogene tyrosine-protein kinase Src induced by adhesion was inhibited when MKs were pretreated with anti-αvβ3 antibody. In in vivo studies, we showed that injection with anti-αv antibody delayed platelet recovery in a mouse model of ITP. Conclusions These findings demonstrate that the autoantibody against integrin αv β3 may aggravate thrombocytopenia in ITP patients by impeding MK migration and adhesion to the vascular niche, which provides new insights into the pathogenesis of ITP.

Beyond migration-Chemokines in lymphocyte priming, differentiation, and modulating effector functions

Chemokines and their receptors coordinate the positioning of leukocytes, and lymphocytes in particular, in space and time. Discrete lymphocyte subsets, depending on their activation and differentiation status, express various sets of chemokine receptors to be recruited to distinct tissues. Thus, the network of chemokines and their receptors ensures the correct localization of specialized lymphocyte subsets within the appropriate microenvironment enabling them to search for cognate antigens, to become activated, and to fulfill their effector functions. The chemokine system therefore is vital for the initiation as well as the regulation of immune responses to protect the body from pathogens while maintaining tolerance towards self. Besides the well investigated function of orchestrating directed cell migration, chemokines additionally act on lymphocytes in multiple ways to shape immune responses. In this review, we highlight and discuss the role of chemokines and chemokine receptors in controlling cell-to-cell contacts required for lymphocyte arrest on endothelial cells and immunological synapse formation, in lymphocyte priming and differentiation, survival, as well as in modulating effector functions.

Molecular mechanisms for enhancement of stromal cell-derived factor 1-induced chemotaxis by platelet endothelial cell adhesion molecule 1 (PECAM-1)

Platelet endothelial cell adhesion molecule 1 (PECAM-1) is a cell adhesion protein involved in the regulation of cell adhesion and migration. Interestingly, several PECAM-1-deficient hematopoietic cells exhibit impaired chemotactic responses to stromal cell-derived factor 1 (SDF-1), a chemokine essential for B lymphopoiesis and bone marrow myelopoiesis. However, whether PECAM-1 is involved in SDF-1-regulated chemotaxis is unknown. We report here that SDF-1 induces tyrosine phosphorylation of PECAM-1 at its immunoreceptor tyrosine-based inhibition motifs in several hematopoietic cell lines via the Src family kinase Lyn, Bruton's tyrosine kinase, and JAK2 and that inhibition of these kinases reduced chemotaxis. Overexpression and knockdown of PECAM-1 enhanced and down-regulated, respectively, SDF-1-induced Gα_i-dependent activation of the PI3K/Akt/mTORC1 pathway and small GTPase Rap1 in hematopoietic 32Dcl3 cells, and these changes in activation correlated with chemotaxis. Furthermore, pharmacological or genetic inhibition of the PI3K/Akt/mTORC1 pathway or Rap1, respectively, revealed that these pathways are independently activated and required for SDF-1-induced chemotaxis. When coexpressed in 293T cells, PECAM-1 physically associated with the SDF-1 receptor CXCR4. Moreover, PECAM-1 overexpression and knockdown reduced and enhanced SDF-1-induced endocytosis of CXCR4, respectively. Furthermore, when expressed in 32Dcl3 cells, an endocytosis-defective CXCR4 mutant, CXCR4-S324A/S325A, could activate the PI3K/Akt/mTORC1 pathway as well as Rap1 and induce chemotaxis in a manner similar to PECAM-1 overexpression. These findings suggest that PECAM-1 enhances SDF-1-induced chemotaxis by augmenting and prolonging activation of the PI3K/Akt/mTORC1 pathway and Rap1 and that PECAM-1, at least partly, exerts its activity by inhibiting SDF-1-induced internalization of CXCR4.

Leveraging the IncuCyte Technology for Higher-Throughput and Automated Chemotaxis Assays for Target Validation and Compound Characterization

Chemotaxis is the directional movement of cells in response to a chemical stimulus and is vital for many physiological processes, including immune responses, tumor metastasis, wound healing, and blood vessel formation. Therefore, modulation of chemotaxis is likely to be of therapeutic benefit. Hence, a high-throughput means to conduct chemotaxis assays is advantageous for lead evaluation and optimization in drug discovery. In this study, we have validated a novel approach for a higher-throughput, label-free, image-based IncuCyte chemotaxis assay encompassing various cell types, including T cells, B cells, mouse Th17, immature and mature dendritic cells, monocyte THP-1, CCRF-CEM, monocytes, neutrophils, macrophages, and MDA-MB-231. These assays enable us to visualize chemotactic cell migration in real time and perform kinetic cell motility studies on an automated platform, thereby allowing us to incorporate the quantitative studies of cell migration behavior into a routine drug discovery screening cascade.

Beyond Chemoattraction: Multifunctionality of Chemokine Receptors in Leukocytes

The word chemokine is a combination of the words chemotactic and cytokine, in other words cytokines that promote chemotaxis. Hence, the term chemokine receptor refers largely to the ability to regulate chemoattraction. However, these receptors can modulate additional leukocyte functions, as exemplified by the case of CCR7 which, apart from chemotaxis, regulates survival, migratory speed, endocytosis, differentiation and cytoarchitecture. We present evidence highlighting that multifunctionality is a common feature of chemokine receptors. Based on the activities that they regulate, we suggest that chemokine receptors can be classified into inflammatory (which control both inflammatory and homeostatic functions) and homeostatic families. The information accrued also suggests that the non-chemotactic functions controlled by chemokine receptors may contribute to optimizing leukocyte functioning under normal physiological conditions and during inflammation.

Epithelial-to-mesenchymal transition in FHC-silenced cells: the role of CXCR4/CXCL12 axis

Background

Ferritin plays a central role in the intracellular iron metabolism; the molecule is a nanocage of 24 subunits of the heavy and light types. The heavy subunit (FHC) is provided of a ferroxidase activity and thus performs the key transformation of iron in a non-toxic form. Recently, it has been shown that FHC is also involved in additional not iron-related critical pathways including, among the others, p53 regulation, modulation of oncomiRNAs expression and chemokine signalling. Epithelial to mesenchymal transition (EMT) is a cellular mechanism by which the cell acquires a fibroblast-like phenotype along with a decreased adhesion and augmented motility. In this work we have focused our attention on the role of the FHC on EMT induction in the human cell lines MCF-7 and H460 to elucidate the underlying molecular mechanisms.

Methods

Targeted silencing of the FHC was performed by lentiviral-driven shRNA strategy. Reconstitution of the FHC gene product was obtained by full length FHC cDNA transfection with Lipofectamine 2000. MTT and cell count assays were used to evaluate cell viability and proliferation; cell migration capability was assayed by the wound-healing assay and transwell strategy. Quantification of the CXCR4 surface expression was performed by flow cytometry.

Results

Experimental data indicated that FHC-silenced MCF-7 and H460 cells (MCF-7^shFHC, H460^shFHC) acquire a mesenchymal phenotype, accompanied by a significant enhancement of their migratory and proliferative capacity. This shift is coupled to an increase in ROS production and by an activation of the CXCR4/CXCL12 signalling pathway. We present experimental data indicating that the cytosolic increase in ROS levels is responsible for the enhanced proliferation of FHC-silenced cells, while the higher migration rate is attributable to a dysregulation of the CXCR4/CXCL12 axis.

Conclusions

Our findings indicate that induction of EMT, increased migration and survival depend, in MCF-7 and H460 cells, on the release of FHC control on two pathways, namely the iron/ROS metabolism and CXCR4/CXCL12 axis. Besides constituting a further confirmation of the multifunctional nature of FHC, this data also suggest that the analysis of FHC amount/function might be an important additional tool to predict tumor aggressiveness.

Harnessing CXCR4 antagonists in stem cell mobilization, HIV infection, ischemic diseases, and oncology

CXCR4 antagonists (e.g., Plerixafor^TM ) have been successfully validated as stem cell mobilizers for peripheral blood stem cell transplantation. Applications of the CXCR4 antagonists have heralded the era of cell-based therapy and opened a potential therapeutic horizon for many unmet medical needs such as kidney injury, ischemic stroke, cancer, and myocardial infarction. In this review, we first introduce the central role of CXCR4 in diverse cellular signaling pathways and discuss its involvement in several disease progressions. We then highlight the molecular design and optimization strategies for targeting CXCR4 from a large number of case studies, concluding that polyamines are the preferred CXCR4-binding ligands compared to other structural options, presumably by mimicking the highly positively charged natural ligand CXCL12. These results could be further justified with computer-aided docking into the CXCR4 crystal structure wherein both major and minor subpockets of the binding cavity are considered functionally important. Finally, from the clinical point of view, CXCR4 antagonists could mobilize hematopoietic stem/progenitor cells with long-term repopulating capacity to the peripheral blood, promising to replace surgically obtained bone marrow cells as a preferred source for stem cell transplantation.

Lung ischemia reperfusion injury: the therapeutic role of dipeptidyl peptidase 4 inhibition

Dipeptidyl peptidase 4 (DPP4) is a cell surface protease that has been reported to play a role in glucose homeostasis, cancer, HIV, autoimmunity, immunology and inflammation. A role for DPP4 in ischemia-reperfusion injury (IRI) in the heart has been established. Dipeptidyl peptidase 4 inhibition (DPP4i) appeared to decrease infarct size, improves cardiac function and promotes myocardial regeneration. Lung ischemia reperfusion injury is caused by a complex mechanism in which macrophages and neutrophils play an important role. Generation of reactive oxygen species (ROS), uncoupling of nitric oxide synthase (NOS), activation of nuclear factor-κB (NF-κB), activation of nicotinamide adenine dinucleotide phosphate metabolism, and generation of pro-inflammatory cytokines lead to acute lung injury (ALI). In this review we present the current knowledge on DPP4 as a target to treat IRI in the lung. We also provide evidence of the roles of the DPP4 substrates glucagon-like peptide 1 (GLP-1), vasoactive intestinal peptide (VIP) and stromal cell-derived factor-1α (SDF-1α) in protection against oxidative stress through activation of the mitogen-activated protein kinase (MAPK) 1/2 and phosphatidylinositol 3'-kinase (PI3K)/Akt signal transduction pathways.

Regulation of Chemokine Signal Integration by Activator of G-Protein Signaling 4 (AGS4)

Activator of G-protein signaling 4 (AGS4)/G-protein signaling modulator 3 (Gpsm3) contains three G-protein regulatory (GPR) motifs, each of which can bind Gαi-GDP free of Gβγ We previously demonstrated that the AGS4-Gαi interaction is regulated by seven transmembrane-spanning receptors (7-TMR), which may reflect direct coupling of the GPR-Gαi module to the receptor analogous to canonical Gαβγ heterotrimer. We have demonstrated that the AGS4-Gαi complex is regulated by chemokine receptors in an agonist-dependent manner that is receptor-proximal. As an initial approach to investigate the functional role(s) of this regulated interaction in vivo, we analyzed leukocytes, in which AGS4/Gpsm3 is predominantly expressed, from AGS4/Gpsm3-null mice. Loss of AGS4/Gpsm3 resulted in mild but significant neutropenia and leukocytosis. Dendritic cells, T lymphocytes, and neutrophils from AGS4/Gpsm3-null mice also exhibited significant defects in chemoattractant-directed chemotaxis and extracellular signal-regulated kinase activation. An in vivo peritonitis model revealed a dramatic reduction in the ability of AGS4/Gpsm3-null neutrophils to migrate to primary sites of inflammation. Taken together, these data suggest that AGS4/Gpsm3 is required for proper chemokine signal processing in leukocytes and provide further evidence for the importance of the GPR-Gαi module in the regulation of leukocyte function.

Macrophages confer survival signals via CCR1-dependent translational MCL-1 induction in chronic lymphocytic leukemia

Protective interactions with bystander cells in micro-environmental niches, such as lymph nodes (LNs), contribute to survival and therapy resistance of chronic lymphocytic leukemia (CLL) cells. This is caused by a shift in expression of B-cell lymphoma 2 (BCL-2) family members. Pro-survival proteins B-cell lymphoma-extra large (BCL-X_L), BCL-2-related protein A1 (BFL-1) and myeloid leukemia cell differentiation protein 1 (MCL-1) are upregulated by LN-residing T cells through CD40L interaction, presumably via nuclear factor (NF)-κB signaling. Macrophages (Mφs) also reside in the LN, and are assumed to provide important supportive functions for CLL cells. However, if and how Mφs are able to induce survival is incompletely known. We first established that Mφs induced survival because of an exclusive upregulation of MCL-1. Next, we investigated the mechanism underlying MCL-1 induction by Mφs in comparison with CD40L. Genome-wide expression profiling of in vitro Mφ- and CD40L-stimulated CLL cells indicated activation of the phosphoinositide 3-kinase (PI3K)-V-Akt murine thymoma viral oncogene homolog (AKT)-mammalian target of rapamycin (mTOR) pathway, which was confirmed in ex vivo CLL LN material. Inhibition of PI3K-AKT-mTOR signaling abrogated MCL-1 upregulation and survival by Mφs, as well as CD40 stimulation. MCL-1 can be regulated at multiple levels, and we established that AKT leads to increased MCL-1 translation, but does not affect MCL-1 transcription or protein stabilization. Furthermore, among Mφ-secreted factors that could activate AKT, we found that induction of MCL-1 and survival critically depended on C-C motif chemokine receptor-1 (CCR1). In conclusion, this study indicates that two distinct micro-environmental factors, CD40L and Mφs, signal via CCR1 to induce AKT activation resulting in translational stabilization of MCL-1, and hence can contribute to CLL cell survival.

Decreased Migration of Dendritic Cells into the Jugular-Nodose Ganglia by the CXCL12 Neutraligand Chalcone 4 in Ovalbumin-Sensitized Asthmatic Mice

OBJECTIVE

The chemokine CXCL12 interacting with the CXC receptor 4 (CXCR4) has been reported to play a role in the development and progression of bronchial asthma, but its mechanism of action is still unknown. The objective of this study was to assess the effect of the CXCL12 neutraligand chalcone 4 on the migration of dendritic cells (DCs) in a murine model of allergic airway inflammation.

METHODS

A 21-day ovalbumin (OVA)-induced allergic-airway TH2 inflammation model in BALB/c mice was used. Four groups were sensitized with OVA adsorbed on alum and challenged either with OVA or saline for 4 days. Mice were treated intranasally with chalcone 4 (300 nmol/kg body weight) or solvent 2 h before each OVA or saline challenge; 24 h after the last challenge, CD11c+F4/80- DCs were counted in the bronchoalveolar lavage. Jugular-nodose ganglion complex (JNC) sections were sampled, and for immunofluorescence staining, cryocut sections were prepared. MHC II+F4/80- DCs as well as calcitonin gene-related peptide (CGRP)- and substance P (SP)-positive neuronal cell bodies were analyzed.

RESULTS

In OVA-challenged mice, chalcone 4 caused a significantly decreased DC/neuron ratio in the JNC from 51.7% in solvent-treated to 32.6% in chalcone 4-treated mice. In parallel, chalcone 4 also decreased the DC population in BALF from 11.5 × 103 cells in solvent to 4.5 × 103 cells in chalcone 4-treated mice. By contrast, chalcone 4 had no effect on the expression of the neuropeptides CGRP and SP in JNC.

CONCLUSION

This study reported the CXCL12 neutraligand chalcone 4 to affect DC infiltration into the airways and airway ganglia as well as to decrease airway eosinophilic inflammation and, therefore, validated CXCL12 as a new target in allergic disease models of asthma.

Effect of Yi Guan Jian decoction on differentiation of bone marrow mesenchymalstem cells into hepatocyte-like cells in dimethylnitrosamine-induced liver cirrhosis in mice

Yi Guan Jian decoction (YGD) may induce the differentiation of bone marrow mesenchymal stem cells (BMSCs) into hepatocyte-like cells (HLCs); however, the underlying mechanisms remain to be elucidated. The present study aimed to investigate this process. To do this, a dimethylnitrosamine (DMN)-induced liver cirrhosis mouse model was established. The mice from the model group were randomly divided into three subgroups: i) Negative control, ii) hepatocyte growth factor and iii) YGD. The overall health, liver function and histological alterations were monitored. The expression of α‑smooth muscle actin (α‑SMA), C‑X‑C chemokine receptor type 4 (CXCR4), extracellular signal‑regulated kinase (ERK1/2), nuclear factor κB p65 subunit (NF‑κB p65) and β‑catenin were measured by immunohistochemistry, western blotting and reverse transcription‑quantitative polymerase chain reaction. Following administration of DMN, the overall health of the mice significantly decreased, with an increase in pathological developments and liver damage resulting in a decrease in liver function. Immunohistochemistry revealed that the expression of α‑SMA, CXCR4, ERK1/2, NF‑κB p65 and β‑catenin was upregulated. Following treatment with YGD, the overall health, liver function and pathology improved. The mRNA and protein expression levels of CXCR4 and ERK1/2 were upregulated, where as α‑SMA, NF‑κB p65 and β‑catenin levels were downregulated. The results demonstrated that YGD may induce the differentiation of BMSCs into HLCs to reverse DMN‑induced liver cirrhosis; this may be achieved via an upregulation of the SDF‑1/CXCR4 axis to activate the mitogen activated protein kinase/ERK1/2 signaling pathway.

CXCL12-induced macropinocytosis modulates two distinct pathways to activate mTORC1 in macrophages

Although growth factors and chemokines elicit different overall effects on cells-growth and chemotaxis, respectively-and activate distinct classes of cell-surface receptors, nonetheless, they trigger similar cellular activities and signaling pathways. The growth factor M-CSF and the chemokine CXCL12 both stimulate the endocytic process of macropinocytosis, and both activate the mechanistic target of rapamycin complex 1 (mTORC1), a protein complex that regulates cell metabolism. Recent studies of signaling by M-CSF in macrophages identified a role for macropinocytosis in the activation of mTORC1, in which delivery of extracellular amino acids into lysosomes via macropinocytosis was required for activation of mTORC1. Here, we analyzed the regulation of macropinosome (MP) formation in response to CXCL12 and identified 2 roles for macropinocytosis in the activation of mTORC1. Within 5 min of adding CXCL12, murine macrophages increased ruffling, macropinocytosis and amino acid-dependent activation of mTORC1. Inhibitors of macropinocytosis blocked activation of mTORC1, and various isoform-specific inhibitors of type 1 PI3K and protein kinase C (PKC) showed similar patterns of inhibition of macropinocytosis and mTORC1 activity. However, unlike the response to M-CSF, Akt phosphorylation (pAkt) in response to CXCL12 required the actin cytoskeleton and the formation of macropinocytic cups. Quantitative fluorescence microscopy showed that phosphatidylinositol (3,4,5)-trisphosphate (PIP₃), a product of PI3K and an upstream activator of Akt, localized to macropinocytic cups and that pAkt occurred primarily in cups. These results indicate that CXCL12 activates mTORC1 via 2 mechanisms: 1) that the macropinocytic cup localizes Akt signaling and 2) that MPs convey extracellular nutrients to lysosomes.

Modeling the Pro-inflammatory Tumor Microenvironment in Acute Lymphoblastic Leukemia Predicts a Breakdown of Hematopoietic-Mesenchymal Communication Networks

Lineage fate decisions of hematopoietic cells depend on intrinsic factors and extrinsic signals provided by the bone marrow microenvironment, where they reside. Abnormalities in composition and function of hematopoietic niches have been proposed as key contributors of acute lymphoblastic leukemia (ALL) progression. Our previous experimental findings strongly suggest that pro-inflammatory cues contribute to mesenchymal niche abnormalities that result in maintenance of ALL precursor cells at the expense of normal hematopoiesis. Here, we propose a molecular regulatory network interconnecting the major communication pathways between hematopoietic stem and progenitor cells (HSPCs) and mesenchymal stromal cells (MSCs) within the BM. Dynamical analysis of the network as a Boolean model reveals two stationary states that can be interpreted as the intercellular contact status. Furthermore, simulations describe the molecular patterns observed during experimental proliferation and activation. Importantly, our model predicts instability in the CXCR4/CXCL12 and VLA4/VCAM1 interactions following microenvironmental perturbation due by temporal signaling from Toll like receptors (TLRs) ligation. Therefore, aberrant expression of NF-κB induced by intrinsic or extrinsic factors may contribute to create a tumor microenvironment where a negative feedback loop inhibiting CXCR4/CXCL12 and VLA4/VCAM1 cellular communication axes allows for the maintenance of malignant cells.

Tolerogenic dendritic cells for reprogramming of lymphocyte responses in autoimmune diseases

Dendritic cells (DCs) control immune responses by driving potent inflammatory actions against external and internal threats while generating tolerance to self and harmless components. This duality and their potential to reprogram immune responses in an antigen-specific fashion have made them an interesting target for immunotherapeutic strategies to control autoimmune diseases. Several protocols have been described for in vitro generation of tolerogenic DCs (tolDCs) capable of modulating adaptive immune responses and restoring tolerance through different mechanisms that involve anergy, generation of regulatory lymphocyte populations, or deletion of potentially harmful inflammatory T cell subsets. Recently, the capacity of tolDCs to induce interleukin (IL-10)-secreting regulatory B cells has been demonstrated. In vitro assays and rodent models of autoimmune diseases provide insights to the molecular regulators and pathways enabling tolDCs to control immune responses. Here we review mechanisms through which tolDCs modulate adaptive immune responses, particularly focusing on their suitability for reprogramming autoreactive CD4⁺ effector T cells. Furthermore, we discuss recent findings establishing that tolDCs also modulate B cell populations and discuss clinical trials applying tolDCs to patients with autoimmune diseases.

Local CXCR4 Upregulation in the Injured Arterial Wall Contributes to Intimal Hyperplasia

CXCR4 is a stem/progenitor cell surface receptor specific for the cytokine stromal cell‐derived factor‐1 (SDF‐1α). There is evidence that bone marrow‐derived CXCR4‐expressing cells contribute to intimal hyperplasia (IH) by homing to the arterial subintima which is enriched with SDF‐1α. We have previously found that transforming growth factor‐β (TGFβ) and its signaling protein Smad3 are both upregulated following arterial injury and that TGFβ/Smad3 enhances the expression of CXCR4 in vascular smooth muscle cells (SMCs). It remains unknown, however, whether locally induced CXCR4 expression in SM22 expressing vascular SMCs plays a role in neointima formation. Here, we investigated whether elevated TGFβ/Smad3 signaling leads to the induction of CXCR4 expression locally in the injured arterial wall, thereby contributing to IH. We found prominent CXCR4 upregulation (mRNA, 60‐fold; protein, 4‐fold) in TGFβ‐treated, Smad3‐expressing SMCs. Chromatin immunoprecipitation assays revealed a specific association of the transcription factor Smad3 with the CXCR4 promoter. TGFβ/Smad3 treatment also markedly enhanced SDF‐1α‐induced ERK1/2 phosphorylation as well as SMC migration in a CXCR4‐dependent manner. Adenoviral expression of Smad3 in balloon‐injured rat carotid arteries increased local CXCR4 levels and enhanced IH, whereas SMC‐specific depletion of CXCR4 in the wire‐injured mouse femoral arterial wall produced a 60% reduction in IH. Our results provide the first evidence that upregulation of TGFβ/Smad3 in injured arteries induces local SMC CXCR4 expression and cell migration, and consequently IH. The Smad3/CXCR4 pathway may provide a potential target for therapeutic interventions to prevent restenosis. Stem Cells2016;34:2744–2757

Dendritic Cells and Their Role in Cardiovascular Diseases: A View on Human Studies

The antigen-presenting dendritic cells (DCs) are key to the immunological response, with different functions ascribed ranging from cellular immune activation to induction of tolerance. Such immunological responses are involved in the pathophysiological mechanisms of cardiovascular diseases, with DCs shown to play a role in atherosclerosis, hypertension, and heart failure and most notably following heart transplantation. A better understanding of the interplay between the immune system and cardiovascular diseases will therefore be critical for developing novel therapeutic treatments as well as innovative monitoring tools for disease progression. As such, the present review will provide an overview of DCs involvement in the pathophysiology of cardiovascular diseases and how targeting these cells may have beneficial effects for the prognosis of patients.

Genetic ablation of interleukin-18 does not attenuate hypobaric hypoxia-induced right ventricular hypertrophy

Interleukin-18 (IL-18), a proinflammatory cytokine, has been implicated in pathologic left ventricular hypertrophy and is elevated in plasma of heart failure patients. However, IL-18 blockade strategies have been conflicting. The purpose of these experiments was to determine whether genetic ablation of IL-18 would protect mice against hypobaric hypoxia (HH)-induced right ventricular (RV) hypertrophy, a condition in which chamber-specific inflammation is prominent. We hypothesized that IL-18 knockout (KO) mice would be protected while wild-type (WT) mice would demonstrate RV hypertrophy in response to HH exposure. KO and WT mice were exposed to HH for 7 wk, and control mice were exposed to normoxic ambient air. Following echocardiography, the RV was dissected and flash-frozen for biochemical analyses. HH exposure increased IL-18 mRNA (P = 0.08) in RV from WT mice. Genetic ablation of IL-18 mildly attenuated RV hypertrophy as assessed by myocyte size. However, IL-18 KO mice were not protected against HH-induced organ-level remodeling, as evidenced by higher RV weights, elevated RV systolic pressure, and increased RV anterior wall thickness compared with normoxic KO mice. These RV changes were similar to those seen in HH-exposed WT mice. Compensatory upregulation of other proinflammatory cytokines IL-2 and stromal cell-derived factor-1 was seen in the HH-KO animals, suggesting that activation of parallel inflammatory pathways might mitigate the effect of IL-18 KO. These data suggest targeted blockade of IL-18 alone is not a viable therapeutic strategy in this model.

mTOR and differential activation of mitochondria orchestrate neutrophil chemotaxis

Neutrophil chemotaxis is regulated by opposing autocrine purinergic signaling mechanisms, which are stimulated by mitochondrial ATP formation that is up-regulated via mTOR and P2Y2 receptors at the front and down-regulated via A2a receptors and cAMP/PKA signaling at the back of cells.

Neutrophils use chemotaxis to locate invading bacteria. Adenosine triphosphate (ATP) release and autocrine purinergic signaling via P2Y2 receptors at the front and A2a receptors at the back of cells regulate chemotaxis. Here, we examined the intracellular mechanisms that control these opposing signaling mechanisms. We found that mitochondria deliver ATP that stimulates P2Y2 receptors in response to chemotactic cues, and that P2Y2 receptors promote mTOR signaling, which augments mitochondrial activity near the front of cells. Blocking mTOR signaling with rapamycin or PP242 or mitochondrial ATP production (e.g., with CCCP) reduced mitochondrial Ca²⁺ uptake and membrane potential, and impaired cellular ATP release and neutrophil chemotaxis. Autocrine stimulation of A2a receptors causes cyclic adenosine monophosphate accumulation at the back of cells, which inhibits mTOR signaling and mitochondrial activity, resulting in uropod retraction. We conclude that mitochondrial, purinergic, and mTOR signaling regulates neutrophil chemotaxis and may be a pharmacological target in inflammatory diseases.

The presence of CXCR4+ CD1a+ cells at onset of Langerhans cell histiocytosis is associated with a less favorable outcome

PURPOSE

Langerhans Cell Histiocytosis (LCH) is a neoplastic disorder characterized by tissue accumulating CD1a⁺ histiocytes which frequently carry somatic mutations. Irrespective of mutation status, these LCH-cells display constitutively active kinases belonging to the MAPK pathway. We evaluated, in retrospect, the contribution of individual components of the MAPK-activating and chemotaxis-promoting TNF-CXCR4-CXCL12 axis to LCH manifestation and outcome.

EXPERIMENTAL DESIGN

CXCR4, CXCL12 and TNF protein expression was immunohistochemically analyzed in 70 LCH-affected biopsies. The presence of CXCR4⁺CD1a⁺ cells in peripheral blood (PB) and/or bone marrow (BM) samples was evaluated by flowcytometry in 13 therapy-naive LCH-patients.

RESULTS

CXCL12 was detected in 68/70 (97%) biopsies. CXCR4⁺LCH-cells were present in 50/70 (71%) biopsies; their presence was associated with higher levels of intralesional TNF. Circulating CD1a⁺CXCR4⁺ cells were detected in 4/13 (31%) therapy-naïve LCH-patients which displayed BRAF^V600E (2/4), MAP2K1 (1/4) or no (1/4) mutations in their tissues. These CD11c co-expressing CD1a⁺CXCR4⁺cells migrated to CXCL12 in chemotaxis assays. Lesional CXCR4⁺LCH-cells were detected in 18/20 cases who presented with LCH manifestation at multiple sites and in 5/23 (22%) patients who developed additional lesions after initially presenting with a single lesion. The CXCR4 status at onset proved to be an independent risk factor for LCH reactivation in multivariate analysis (odds ratio 10.4, p = 0.034).

CONCLUSIONS

This study provides the first evidence that CXCR4 is involved in the homing and retention of LCH-cells in CXCL12-expressing tissues and qualifies CXCR4 as a candidate prognostic marker for less favorable disease outcome.

Neuropeptide Y receptor mediates activation of ERK1/2 via transactivation of the IGF receptor

Neuropeptide Y binds to G-protein coupled receptors whose action results in inhibition of adenylyl cyclase activity. Using HEK293 cells stably expressing the native neuropeptide Y Y1 receptors, we found that the NPY agonist elicits a transient phosphorylation of the extracellular signal-regulated kinases (ERK1/2). We first show that ERK1/2 activation following Y1 receptor stimulation is dependent on heterotrimeric Gi/o since it is completely inhibited by pre-treatment with pertussis toxin. In addition, ERK1/2 activation is internalization-independent since mutant Y1 receptors unable to recruit β-arrestins, can still activate ERK signaling to the same extent as wild-type receptors. We next show that this activation of the MAPK pathway is inhibited by the MEK inhibitor U0126, is not dependent on calcium signaling at the Y1 receptor (no effect upon inhibition of phospholipase C, protein kinase C or protein kinase D) but instead dependent on Gβ/γ and associated signaling pathways that activate PI3-kinase. Although inhibition of the epidermal-growth factor receptor tyrosine kinase did not influence NPY-induced ERK1/2 activation, we show that the inhibition of insulin growth factor receptor IGFR by AG1024 completely blocks activation of ERK1/2 by the Y1 receptor. This Gβ/γ-PI3K-AG1024-sensitive pathway does not involve activation of IGFR through the release of a soluble ligand by metalloproteinases since it is not affected by the metalloproteinase inhibitor marimastat. Finally, we found that a similar pathway, sensitive to wortmannin-AG1024 but insensitive to marimastat, is implicated in activation of ERK signaling in HEK293 cells by endogenously expressed GPCRs coupled to Gq-protein (muscarinic M3 receptors) or coupled to Gs-protein (endothelin ETB receptors). Our analysis is the first to show that β-arrestin recruitment to the NPY Y1 receptor is not necessary for MAPK activation by this receptor but that transactivation of the IGFR receptor is required.

Skewing dendritic cell differentiation towards a tolerogenic state for recovery of tolerance in rheumatoid arthritis

To date, the available options to treat autoimmune diseases such as rheumatoid arthritis (RA) include traditional corticoids and biological drugs, which are not exempt of adverse effects. The development of cellular therapies based on dendritic cells with tolerogenic functions (TolDCs) has opened a new possibility to efficiently eradicate symptoms and control the immune response in the field of autoimmunity. TolDCs are an attractive tool for antigen-specific immunotherapy to restore self-tolerance in RA and other autoimmune disorders. A promising strategy is to inject autologous self-antigen-loaded TolDCs, which are able to delete or reprogram autoreactive T cells. Different protocols for the generation of stable human TolDCs have been established and the therapeutic effect of TolDCs has been investigated in multiple rodent models of arthritis. Pilot studies in humans confirmed that TolDC application is safe, encouraging clinical trials using self-antigen-loaded TolDCs in RA patients. Although an abundance of molecular regulators of DC functions has been discovered in the last decade, no master regulator of tolerogenicity has been identified yet. Further research is required to define biomarkers or key regulators of tolerogenicity that might facilitate the induction and monitoring of TolDCs.

The endosomal sorting complex required for transport pathway mediates chemokine receptor CXCR4-promoted lysosomal degradation of the mammalian target of rapamycin antagonist DEPTOR

G protein-coupled receptor (GPCR) signaling mediates many cellular functions, including cell survival, proliferation, and cell motility. Many of these processes are mediated by GPCR-promoted activation of Akt signaling by mammalian target of rapamycin complex 2 (mTORC2) and the phosphatidylinositol 3-kinase (PI3K)/phosphoinositide-dependent kinase 1 (PDK1) pathway. However, the molecular mechanisms by which GPCRs govern Akt activation by these kinases remain poorly understood. Here, we show that the endosomal sorting complex required for transport (ESCRT) pathway mediates Akt signaling promoted by the chemokine receptor CXCR4. Pharmacological inhibition of heterotrimeric G protein Gαi or PI3K signaling and siRNA targeting ESCRTs blocks CXCR4-promoted degradation of DEPTOR, an endogenous antagonist of mTORC2 activity. Depletion of ESCRTs by siRNA leads to increased levels of DEPTOR and attenuated CXCR4-promoted Akt activation and signaling, consistent with decreased mTORC2 activity. In addition, ESCRTs likely have a broad role in Akt signaling because ESCRT depletion also attenuates receptor tyrosine kinase-promoted Akt activation and signaling. Our data reveal a novel role for the ESCRT pathway in promoting intracellular signaling, which may begin to identify the signal transduction pathways that are important in the physiological roles of ESCRTs and Akt.

A novel MEK-ERK-AMPK signaling axis controls chemokine receptor CCR7-dependent survival in human mature dendritic cells

Chemokine receptor CCR7 directs mature dendritic cells (mDCs) to secondary lymph nodes where these cells regulate the activation of T cells. CCR7 also promotes survival in mDCs, which is believed to take place largely through Akt-dependent signaling mechanisms. We have analyzed the involvement of the AMP-dependent kinase (AMPK) in the control of CCR7-dependent survival. A pro-apoptotic role for AMPK is suggested by the finding that pharmacological activators induce apoptosis, whereas knocking down of AMPK with siRNA extends mDC survival. Pharmacological activation of AMPK also induces apoptosis of mDCs in the lymph nodes. Stimulation of CCR7 leads to inhibition of AMPK, through phosphorylation of Ser-485, which was mediated by G(i)/Gβγ, but not by Akt or S6K, two kinases that control the phosphorylation of AMPK on Ser-485 in other settings. Using selective pharmacological inhibitors, we show that CCR7-induced phosphorylation of AMPK on Ser-485 is mediated by MEK and ERK. Coimmunoprecipitation analysis and proximity ligation assays indicate that AMPK associates with ERK, but not with MEK. These results suggest that in addition to Akt-dependent signaling mechanisms, CCR7 can also promote survival of mDCs through a novel MEK1/2-ERK1/2-AMPK signaling axis. The data also suggest that AMPK may be a potential target to modulate mDC lifespan and the immune response.