Leucocyte chemotaxis: Examination of mitogen-activated protein kinase and phosphoinositide 3-kinase activation by Monocyte Chemoattractant Proteins-1, -2, -3 and -4

C-C Motif Chemokine 2 Regulates Macrophage Polarization and Contributes to Myocardial Infarction Healing

Macrophages are crucial immune cells that play essential roles in the healing of myocardial infarction (MI), undergoing continuous polarization throughout this process. C-C motif chemokine 2 (CCL2) is a chemokine that regulates inflammatory responses during MI. However, the extent to which CCL2 influences macrophage polarization and MI healing remains incompletely understood. In this study, we investigate the role of CCL2 in macrophage polarization and MI healing. Our findings reveal that CCL2 is differentially expressed in lipopolysaccharide (LPS)-induced M1 and interleukin (IL)-4-induced M2 RAW264.7 macrophages. Knockdown of CCL2 attenuates TNF-α secretion stimulated by LPS, while overexpression of CCL2 mitigates IL-10 production triggered by IL-4 in these macrophages. Moreover, CCL2 deficiency disrupts LPS-induced M1 polarization, whereas CCL2 overexpression reduces M2 polarization of RAW264.7 macrophages induced by IL-4. Further exploration indicates that the promotion of M1 polarization by CCL2 is significantly impaired by inhibition of the p38-mediated MAPK pathway and NF-κB pathway. In a MI mouse model, CCL2 knockdown remarkably reduces infarct size, collagen synthesis, and the expression of cardiac fibrosis and hypertrophy markers. The activity of the p38-mediated MAPK pathway and NF-κB pathway is downregulated by CCL2 knockdown as well. Additionally, the number of total macrophages and M1 macrophages in the infarct decreases, while the number of M2 macrophages increases upon CCL2 deficiency. In conclusion, these results suggest that CCL2 is a key regulator of macrophage polarization, controlling MI healing in vivo.

Adipokines and Bacterial Metabolites: A Pivotal Molecular Bridge Linking Obesity and Gut Microbiota Dysbiosis to Target

Adipokines are essential mediators produced by adipose tissue and exert multiple biological functions. In particular, adiponectin, leptin, resistin, IL-6, MCP-1 and PAI-1 play specific roles in the crosstalk between adipose tissue and other organs involved in metabolic, immune and vascular health. During obesity, adipokine imbalance occurs and leads to a low-grade pro-inflammatory status, promoting insulin resistance-related diabetes and its vascular complications. A causal link between obesity and gut microbiota dysbiosis has been demonstrated. The deregulation of gut bacteria communities characterizing this dysbiosis influences the synthesis of bacterial substances including lipopolysaccharides and specific metabolites, generated via the degradation of dietary components, such as short-chain fatty acids, trimethylamine metabolized into trimethylamine-oxide in the liver and indole derivatives. Emerging evidence suggests that these bacterial metabolites modulate signaling pathways involved in adipokine production and action. This review summarizes the current knowledge about the molecular links between gut bacteria-derived metabolites and adipokine imbalance in obesity, and emphasizes their roles in key pathological mechanisms related to oxidative stress, inflammation, insulin resistance and vascular disorder. Given this interaction between adipokines and bacterial metabolites, the review highlights their relevance (i) as complementary clinical biomarkers to better explore the metabolic, inflammatory and vascular complications during obesity and gut microbiota dysbiosis, and (ii) as targets for new antioxidant, anti-inflammatory and prebiotic triple action strategies.

Neighborhood socioeconomic deprivation and individual-level socioeconomic status are associated with dopamine-mediated changes to monocyte subset CCR2 expression via a cAMP-dependent pathway

Social determinants of health (SDoH) include socioeconomic, environmental, and psychological factors that impact health. Neighborhood socioeconomic deprivation (NSD) and low individual-level socioeconomic status (SES) are SDoH that associate with incident heart failure, stroke, and cardiovascular mortality, but the underlying biological mechanisms are not well understood. Previous research has demonstrated an association between NSD, in particular, and key components of the neural-hematopoietic-axis including amygdala activity as a marker of chronic stress, bone marrow activity, and arterial inflammation. Our study further characterizes the role of NSD and SES as potential sources of chronic stress related to downstream immunological factors in this stress-associated biologic pathway. We investigated how NSD, SES, and catecholamine levels (as proxy for sympathetic nervous system activation) may influence monocytes which are known to play a significant role in atherogenesis. First, in an ex vivo approach, we treated healthy donor monocytes with biobanked serum from a community cohort of African Americans at risk for CVD. Subsequently, the treated monocytes were subjected to flow cytometry for characterization of monocyte subsets and receptor expression. We determined that NSD and serum catecholamines (namely dopamine [DA] and norepinephrine [NE]) associated with monocyte C-C chemokine receptor type 2 (CCR2) expression (p < 0.05), a receptor known to facilitate recruitment of monocytes towards arterial plaques. Additionally, NSD associated with catecholamine levels, especially DA in individuals of low SES. To further explore the potential role of NSD and the effects of catecholamines on monocytes, monocytes were treated in vitro with epinephrine [EPI], NE, or DA. Only DA increased CCR2 expression in a dose-dependent manner (p < 0.01), especially on non-classical monocytes (NCM). Furthermore, linear regression analysis between D2-like receptor surface expression and surface CCR2 expression suggested D2-like receptor signaling in NCM. Indicative of D2-signaling, cAMP levels were found to be lower in DA-treated monocytes compared to untreated controls (control 29.78 pmol/ml vs DA 22.97 pmol/ml; p = 0.038) and the impact of DA on NCM CCR2 expression was abrogated by co-treatment with 8-CPT, a cAMP analog. Furthermore, Filamin A (FLNA), a prominent actin-crosslinking protein, that is known to regulate CCR2 recycling, significantly decreased in DA-treated NCM (p < 0.05), indicating a reduction of CCR2 recycling. Overall, we provide a novel immunological mechanism, driven by DA signaling and CCR2, for how NSD may contribute to atherogenesis. Future studies should investigate the importance of DA in CVD development and progression in populations disproportionately experiencing chronic stress due to SDoH.

Role of CCL2/CCR2 axis in the pathogenesis of COVID-19 and possible Treatments: All options on the Table

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is cause of the novel coronavirus disease (COVID-19). In the last two years, SARS-CoV-2 has infected millions of people worldwide with different waves, resulting in the death of many individuals. The evidence disclosed that the host immune responses to SARS-CoV-2 play a pivotal role in COVID-19 pathogenesis and clinical manifestations. In addition to inducing antiviral immune responses, SARS-CoV-2 can also cause dysregulated inflammatory responses characterized by the noticeable release of proinflammatory mediators in COVID-19 patients. Among these proinflammatory mediators, chemokines are considered a subset of cytokines that participate in the chemotaxis process to recruit immune and non-immune cells to the site of inflammation and infection. Researchers have demonstrated that monocyte chemoattractant protein-1 (MCP-1/CCL2) and its receptor (CCR2) are involved in the recruitment of monocytes and infiltration of these cells into the lungs of patients suffering from COVID-19. Moreover, elevated levels of CCL2 have been reported in the bronchoalveolar lavage fluid (BALF) obtained from patients with severe COVID-19, initiating cytokine storm and promoting CD163⁺ myeloid cells infiltration in the airways and further alveolar damage. Therefore, CCL2/CCR axis plays a key role in the immunopathogenesis of COVID-19 and targeted therapy of involved molecules in this axis can be a potential therapeutic approach for these patients. This review discusses the biology of the CCL2/CCR2 axis as well as the role of this axis in COVID-19 immunopathogenesis, along with therapeutic options aimed at inhibiting CCL2/CCR2 and modulating dysregulated inflammatory responses in patients with severe SARS-CoV-2 infection.

Thromboinflammatory Processes at the Nexus of Metabolic Dysfunction and Prostate Cancer: The Emerging Role of Periprostatic Adipose Tissue

Simple Summary

As overweight and obesity increase among the population worldwide, a parallel increase in the number of individuals diagnosed with prostate cancer was observed. There appears to be a relationship between both diseases where the increase in the mass of fat tissue can lead to inflammation. Such a state of inflammation could produce many factors that increase the aggressiveness of prostate cancer, especially if this inflammation occurred in the fat stores adjacent to the prostate. Another important observation that links obesity, fat tissue inflammation, and prostate cancer is the increased production of blood clotting factors. In this article, we attempt to explain the role of these latter factors in the effect of increased body weight on the progression of prostate cancer and propose new ways of treatment that act by affecting how these clotting factors work.

Abstract

The increased global prevalence of metabolic disorders including obesity, insulin resistance, metabolic syndrome and diabetes is mirrored by an increased incidence of prostate cancer (PCa). Ample evidence suggests that these metabolic disorders, being characterized by adipose tissue (AT) expansion and inflammation, not only present as risk factors for the development of PCa, but also drive its increased aggressiveness, enhanced progression, and metastasis. Despite the emerging molecular mechanisms linking AT dysfunction to the various hallmarks of PCa, thromboinflammatory processes implicated in the crosstalk between these diseases have not been thoroughly investigated. This is of particular importance as both diseases present states of hypercoagulability. Accumulating evidence implicates tissue factor, thrombin, and active factor X as well as other players of the coagulation cascade in the pathophysiological processes driving cancer development and progression. In this regard, it becomes pivotal to elucidate the thromboinflammatory processes occurring in the periprostatic adipose tissue (PPAT), a fundamental microenvironmental niche of the prostate. Here, we highlight key findings linking thromboinflammation and the pleiotropic effects of coagulation factors and their inhibitors in metabolic diseases, PCa, and their crosstalk. We also propose several novel therapeutic targets and therapeutic interventions possibly modulating the interaction between these pathological states.

FcER1: A Novel Molecule Implicated in the Progression of Human Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a key microvascular complication of diabetes, with few therapies for targeting renal disease pathogenesis and progression. We performed transcriptional and protein studies on 103 unique blood and kidney tissue samples from patients with and without diabetes to understand the pathophysiology of DKD injury and its progression. The study was based on the use of 3 unique patient cohorts: peripheral blood mononuclear cell (PBMC) transcriptional studies were conducted on 30 patients with DKD with advancing kidney injury; Gene Expression Omnibus (GEO) data was downloaded, containing transcriptional measures from 51 microdissected glomerulous from patients with DKD. Additionally, 12 independent kidney tissue sections from patients with or without DKD were used for validation of target genes in diabetic kidney injury by kidney tissue immunohistochemistry and immunofluorescence. PBMC DKD transcriptional analysis, identified 853 genes (p < 0.05) with increasing expression with progression of albuminuria and kidney injury in patients with diabetes. GEO data was downloaded, normalized, and analyzed for significantly changed genes. Of the 325 significantly up regulated genes in DKD glomerulous (p < 0.05), 28 overlapped in PBMC and diabetic kidney, with perturbed FcER1 signaling as a significantly enriched canonical pathway. FcER1 was validated to be significantly increased in advanced DKD, where it was also seen to be specifically co-expressed in the kidney biopsy with tissue mast cells. In conclusion, we demonstrate how leveraging public and private human transcriptional datasets can discover and validate innate immunity and inflammation as key mechanistic pathways in DKD progression, and uncover FcER1 as a putative new DKD target for rational drug design.

Tumor-Associated Macrophages as Multifaceted Regulators of Breast Tumor Growth

Breast cancer is the most commonly occurring cancer in women of Western countries and is the leading cause of cancer-related mortality. The breast tumor microenvironment contains immune cells, fibroblasts, adipocytes, mesenchymal stem cells, and extracellular matrix. Among these cells, macrophages or tumor-associated macrophages (TAMs) are the major components of the breast cancer microenvironment. TAMs facilitate metastasis of the breast tumor and are responsible for poor clinical outcomes. High TAM density was also found liable for the poor prognosis of breast cancer. These observations make altering TAM function a potential therapeutic target to treat breast cancer. The present review summarizes the origin of TAMs, mechanisms of macrophage recruitment and polarization in the tumor, and the contributions of TAMs in tumor progression. We have also discussed our current knowledge about TAM-targeted therapies and the roles of miRNAs and exosomes in re-educating TAM function.

Nanoparticles Interfere with Chemotaxis: An Example of Nanoparticles as Molecular "Knockouts" at the Cellular Level

Engineered colloidal nanoparticles show great promise in biomedical applications. While much of the work of assessing nanoparticle impact on living systems has been focused on the direct interactions of nanoparticles with cells/organisms, indirect effects via the extracellular matrix have been observed and may provide deeper insight into nanoparticle fate and effects in living systems. In particular, the large surface area of colloidal nanoparticles may sequester molecules from the biological milieu, make these molecules less bioavailable, and therefore function indirectly as "molecular knockouts" to exert effects at the cellular level and beyond. In this paper, the hypothesis that molecules that control cellular behavior (in this case, chemoattract molecules that promote migration of a human monocytic cell line, THP-1) will be less bioavailable in the presence of appropriately functionalized nanoparticles, and therefore the cellular behavior will be altered, was investigated. Three-dimensional chemotaxis assays for the characterization and comparison of THP-1 cell migration upon exposure to a gradient of monocyte chemoattractant protein-1 (MCP-1), with and without gold nanoparticles with four different surface chemistries, were performed. By time-lapse microscopy, characteristic parameters for chemotaxis, along with velocity and directionality of the cells, were quantified. Anionic poly(sodium 4-styrenesulfonate)-coated gold nanoparticles were found to significantly reduce THP-1 chemotaxis. Enzyme-linked immunosorbent assay results show adsorption of MCP-1 on the poly(sodium 4-styrenesulfonate)-coated gold nanoparticle surface, supporting the hypothesis that adsorption of chemoattractants to nanoparticle surfaces interferes with chemotaxis. Free anionic sulfonated polyelectrolytes also interfered with cell migrational behavior, showing that nanoparticles can also act as carriers of chemotactic-interfering molecules.

Does C-C Motif Chemokine Ligand 2 (CCL2) Link Obesity to a Pro-Inflammatory State?

The mechanisms of how obesity contributes to the development of cardio-metabolic diseases are not entirely understood. Obesity is frequently associated with adipose tissue dysfunction, characterized by, e.g., adipocyte hypertrophy, ectopic fat accumulation, immune cell infiltration, and the altered secretion of adipokines. Factors secreted from adipose tissue may induce and/or maintain a local and systemic low-grade activation of the innate immune system. Attraction of macrophages into adipose tissue and altered crosstalk between macrophages, adipocytes, and other cells of adipose tissue are symptoms of metabolic inflammation. Among several secreted factors attracting immune cells to adipose tissue, chemotactic C-C motif chemokine ligand 2 (CCL2) (also described as monocyte chemoattractant protein-1 (MCP-1)) has been shown to play a crucial role in adipose tissue macrophage infiltration. In this review, we aimed to summarize and discuss the current knowledge on CCL2 with a focus on its role in linking obesity to cardio-metabolic diseases.

Osteoblastic monocyte chemoattractant protein-1 (MCP-1) mediation of parathyroid hormone's anabolic actions in bone implicates TGF-β signaling

Parathyroid hormone (PTH) is necessary for the regulation of calcium homeostasis and PTH (1-34) was the first approved osteoanabolic therapy for osteoporosis. It is well established that intermittent PTH increases bone formation and that bone remodeling and several cytokines and chemokines play an essential role in this process. Earlier, we had established that the chemokine, monocyte chemoattractant protein-1 (MCP-1/CCL2), was the most highly stimulated gene in rat bone after intermittent PTH injections. Nevertheless, MCP-1 function in bone appears to be complicated. To identify the primary cells expressing MCP-1 in response to PTH, we performed in situ hybridization of rat bone sections after hPTH (1-34) injections and showed that bone-lining osteoblasts are the primary cells that express MCP-1 after PTH treatment. We previously demonstrated MCP-1's importance by showing that PTH's anabolic effects are abolished in MCP-1 null mice, further implicating a role for the chemokine in this process. To establish whether rhMCP-1 peptide treatment could rescue the anabolic effect of PTH in MCP-1 null mice, we treated 4-month-old wild-type (WT) mice with hPTH (1-34) and MCP-1^-/- mice with rhMCP-1 and/or hPTH (1-34) for 6 weeks. Micro-computed tomography (μCT) analysis of trabecular and cortical bone showed that MCP-1 injections for 6 weeks rescued the PTH anabolic effect in MCP-1^-/- mice. In fact, the combination of rhMCP-1 and hPTH (1-34) has a synergistic anabolic effect compared with monotherapies. Mechanistically, PTH-enhanced transforming growth factor-β (TGF-β) signaling is abolished in the absence of MCP-1, while MCP-1 peptide treatment restores TGF-β signaling in the bone marrow. Here, we have shown that PTH regulates the transcription of the chemokine MCP-1 in osteoblasts and determined how MCP-1 affects bone cell function in PTH's anabolic actions. Taken together, our current work indicates that intermittent PTH stimulates osteoblastic secretion of MCP-1, which leads to increased TGF-β signaling, implicating it in PTH's anabolic actions.

Sex specific effect of alcohol on hepatic plasmacytoid dendritic cells

Alcoholic liver disease includes a spectrum of clinical and histological entities. They result from the combined direct effect of alcohol and its metabolites on immune cells and resident tissue cells. In humans and mice, females are more susceptible to alcoholic liver injury than males. Despite being involved in sex specific differences of immune mediated tissue injury, plasmacytoid dendritic cells (pDCs) have not been thoroughly assessed as a cellular target of alcohol in humans or mice. Therefore, Meadows-Cook diet was used to study alcohol effect on hepatic dendritic cells. Alcohol consumption for 12 weeks increased hepatic pDCs in female mice. The expression of the C-C chemokine receptor type 2 (CCR2) increased in hepatic pDC of alcohol-fed female mice. Bone marrow transplant chimera showed CCR2 dependent bone marrow egress of pDCs. Chronic alcohol exposure has a sex specific effect on hepatic pDCs population that may explain sex differences to alcoholic liver disease.

MCP-1 Priming Enhanced the Therapeutic Effects of Human Mesenchymal Stromal Cells on Contact Hypersensitivity Mice by Activating the COX2-PGE2/STAT3 Pathway

Mesenchymal stromal cells (MSCs) have become a promising treatment for inflammation-related diseases, and their therapeutic efficacy mainly depends on crosstalk between MSCs and inflammation. However, methods to improve the immunosuppressive efficiency of MSCs in different diseases still need to be developed. In this study, we investigated whether preconditioning MSCs with a disease-related inflammatory cytokine could increase their immunosuppressive properties and improve therapeutic efficacy. In a contact hypersensitivity (CHS) mouse model, inflammatory profile screening revealed that among all tested cytokines, monocyte chemotactic protein-1 (MCP-1) exhibited the most significantly increased level in the local microenvironment. As expected, MSCs preconditioned with MCP-1 (P-MSCs) exhibited an enhanced ability to downregulate proinflammatory cytokine secretion, induce regulatory T cells, inhibit T cell proliferation, and polarize M2-type macrophages. In vivo experiments showed that P-MSCs alleviated ear swelling and local proinflammatory cytokine production more effectively than control MSCs. Mechanistically, MCP-1 could significantly activate the signal transducer and activator of transcription 3 (STAT3) signaling pathway and induce the expression of cyclooxygenase-2 (COX2) and prostaglandin E2 (PGE2) in MSCs. STAT3 inhibitor reversed the MCP-1-mediated enhancing of their immunosuppressive ability. Collectively, our findings demonstrate that CHS-related MCP-1 preconditioning enhanced the immunomodulatory effects of MSCs and improved their therapeutic efficacy in CHS. Enhancing the immunosuppressive efficacy of MSCs by preconditioning with certain disease-related inflammatory cytokines may provide a new strategy for MSC-based therapies for inflammatory diseases.

More Than Just Attractive: How CCL2 Influences Myeloid Cell Behavior Beyond Chemotaxis

Monocyte chemoattractant protein-1 (MCP-1/CCL2) is renowned for its ability to drive the chemotaxis of myeloid and lymphoid cells. It orchestrates the migration of these cell types both during physiological immune defense and in pathological circumstances, such as autoimmune diseases including rheumatoid arthritis and multiple sclerosis, inflammatory diseases including atherosclerosis, as well as infectious diseases, obesity, diabetes, and various types of cancer. However, new data suggest that the scope of CCL2's functions may extend beyond its original characterization as a chemoattractant. Emerging evidence shows that it can impact leukocyte behavior, influencing adhesion, polarization, effector molecule secretion, autophagy, killing, and survival. The direction of these CCL2-induced responses is context dependent and, in some cases, synergistic with other inflammatory stimuli. The involvement of CCL2 signaling in multiple diseases renders it an interesting therapeutic target, although current targeting strategies have not met early expectations in the clinic. A better understanding of how CCL2 affects immune cells will be pivotal to the improvement of existing therapeutic approaches and the development of new drugs. Here, we provide an overview of the pleiotropic effects of CCL2 signaling on cells of the myeloid lineage, beyond chemotaxis, and highlight how these actions might help to shape immune cell behavior and tumor immunity.

CCL2 But Not CCR2 Is Required for Spontaneous Articular Cartilage Regeneration Post-Injury

The role of the inflammatory response in articular cartilage degeneration and/or repair is often debated. Chemokine networks play a critical role in directing the recruitment of immune cells to sites of injury and have been shown to regulate cell behavior. In this study, we investigated the role of the CCL2/CCR2 signaling axis in cartilage regeneration and degeneration. CCL2^-/- , CCR2^-/- , CCL2^-/- CCR2^-/- , and control (C57) mice were subjected to full-thickness cartilage defect (FTCD) injuries (n = 9/group) within the femoral groove. Cartilage regeneration at 4 and 12 weeks post-FTCD was assessed using a 14-point histological scoring scale. Mesenchymal stem cells (MSCs) (Sca-1⁺ , CD140a⁺ ), macrophages (M1:CD38⁺ , M2:CD206⁺ , and M0:F4/80⁺ ) and proliferating cells (Ki67⁺ ) were quantified within joints using immunofluorescence. The multi-lineage differentiation capacity of Sca1⁺ MSCs was determined for all mouse strains. ACL transection (ACL-x) was employed to determine if CCL2^-/- CCR2^-/- mice were protected against osteoarthritis (OA) (n  = 6/group). Absence of CCR2, but not CCL2 nor both (CCL2 and CCR2), enhanced spontaneous articular cartilage regeneration by 4 weeks post-FTCD. Furthermore, increased chondrogenesis was observed in MSCs derived from CCR2^-/- mice. CCL2 deficiency promoted MSC homing to the adjacent synovium and FTCD at both 4 and 12 weeks post-injury; with no MSCs present at the surface of the FTCD in the remaining strains. Lower OA scores were observed in CCL2^-/- CCR2^-/- mice at 12 weeks post-ACL-x compared with C57 mice. Our findings demonstrate an inhibitory role for CCR2 in cartilage regeneration after injury, while CCL2 is required for regeneration, acting through a CCR2 independent mechanism. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2561-2574, 2019.

Ethanol and Cytokines in the Central Nervous System

The innate immune system plays a critical role in the ethanol-induced neuroimmune response in the brain. Ethanol initiates the innate immune response via activation of the innate immune receptors Toll-like receptors (TLRs, e.g., TLR4, TLR3, TLR7) and NOD-like receptors (inflammasome NLRs) leading to a release of a plethora of chemokines and cytokines and development of the innate immune response. Cytokines and chemokines can have pro- or anti-inflammatory properties through which they regulate the immune response. In this chapter, we will focus on key cytokines (e.g., IL-1, IL-6, TNF-α) and chemokines (e.g., MCP-1/CCL2) that mediate the ethanol-induced neuroimmune responses. In this regard, we will use IL-1β, as an example cytokine, to discuss the neuromodulatory properties of cytokines on cellular properties and synaptic transmission. We will discuss their involvement through a set of evidence: (1) changes in gene and protein expression following ethanol exposure, (2) association of gene polymorphisms (humans) and alterations in gene expression (animal models) with increased alcohol intake, and (3) modulation of alcohol-related behaviors by transgenic or pharmacological manipulations of chemokine and cytokine systems. Over the last years, our understanding of the molecular mechanisms mediating cytokine- and chemokine-dependent regulation of immune responses has advanced tremendously, and we review evidence pointing to cytokines and chemokines serving as neuromodulators and regulators of neurotransmission.

Role of MCP-1 and CCR2 in alcohol neurotoxicity

Alcohol abuse causes profound damage to both the developing brain and the adult brain. Prenatal exposure to alcohol results in a wide range of deficits known as fetal alcohol spectrum disorders (FASD). Alcohol abuse in adults is associated with brain shrinkage, memory and attention deficits, communication disorders and physical disabilities. Monocyte chemoattractant protein-1 (MCP-1/CCL2) is one of the key chemokines that regulate the recruitment and activation of monocytes and microglia. Both MCP-1 and its receptor C-C chemokine receptor type 2 (CCR2) expressed in the brain are involved in various neuroinflammatory disorders, such as multiple sclerosis (MS), Alzheimer's disease (AD) and Parkinson's disease (PD). However, the role of MCP-1/CCR2 in alcohol-induced brain damage is unclear. Recent evidence indicates that alcohol exposure increased the activity of MCP-1/CCR2 in both mature and developing central nervous systems (CNS). MCP-1/CCR2 signaling in the brain was involved in alcohol drinking behavior. MCP-1/CCR2 inhibition alleviated alcohol neurotoxicity by reducing microglia activation/neuroinflammation in the developing brain and spinal cord. In this review, we discussed the role of MCP-1/CCR2 signaling in alcohol-induced neuroinflammation and brain damage. We also discussed the signaling cascades that are involved in the activation of MCP-1/CCR2 in response to alcohol exposure.

One microenvironment does not fit all: heterogeneity beyond cancer cells

Human cancers exhibit formidable molecular heterogeneity, to a large extent accounting for the incomplete and transitory efficacy of current anti-cancer therapies. However, neoplastic cells alone do not manifest the disease, but conscript a battery of non-tumor cells to enable and sustain hallmark capabilities of cancer. Escaping immunosurveillance is one of such capabilities. Tumors evolve immunosuppressive microenvironment to subvert anti-tumor immunity. In this review, we will focus on tumor-associated myeloid cells, which constitute an essential part of the immune microenvironment and reciprocally interact with cancer cells to establish malignancy toward metastasis. The diversity and plasticity of these cells constitute another layer of heterogeneity, beyond the heterogeneity of cancer cells themselves. We envision that immune microenvironment co-evolves with the genetic heterogeneity of tumor. Addressing the question of how genetically distinct tumors shape and are shaped by unique immune microenvironment will provide an attractive rationale to develop novel immunotherapeutic modalities. Here, we discuss the complex nature of tumor microenvironment, with an emphasis on the cellular and functional heterogeneity among tumor-associated myeloid cells as well as immune environment heterogeneity in the context of a full spectrum of human breast cancers.

CCL2 nitration is a negative regulator of chemokine-mediated inflammation

Chemokines promote leukocyte recruitment during inflammation. The oxidative burst is an important effector mechanism, this leads to the generation of reactive nitrogen species (RNS), including peroxynitrite (ONOO). The current study was performed to determine the potential for nitration to alter the chemical and biological properties of the prototypical CC chemokine, CCL2. Immunofluorescence was performed to assess the presence of RNS in kidney biopsies. Co-localisation was observed between RNS-modified tyrosine residues and the chemokine CCL2 in diseased kidneys. Nitration reduced the potential of CCL2 to stimulate monocyte migration in diffusion gradient chemotaxis assays (p < 0.05). This was consistent with a trend towards reduced affinity of the nitrated chemokine for its cognate receptor CCR2b. The nitrated chemokine was unable to induce transendothelial monocyte migration in vitro and failed to promote leukocyte recruitment when added to murine air pouches (p < 0.05). This could potentially be attributed to reduced glycosaminoglycan binding ability, as surface plasmon resonance spectroscopy showed that nitration reduced heparan sulphate binding by CCL2. Importantly, intravenous administration of nitrated CCL2 also inhibited the normal recruitment of leukocytes to murine air pouches filled with unmodified CCL2. Together these data suggest that nitration of CCL2 during inflammation provides a mechanism to limit and resolve acute inflammation.

Identification of Motile Sperm Domain-Containing Protein 2 as Regulator of Human Monocyte Migration

Binding of chemokines to their cognate receptors on monocytes instigates a cascade of events that directs these cells to migrate to sites of inflammation and cancerous tissues. Although targeting of selected chemokine receptors on monocytes exhibited preclinical efficacy, attempts to translate these studies to the clinic have failed thus far, possibly due to redundancy of the target receptor. We reveal that motile sperm domain-containing protein 2 (MOSPD2), a protein with a previously unknown function, regulates monocyte migration in vitro. This protein was found to be expressed on the cytoplasmic membrane of human monocytes. Silencing or neutralizing MOSPD2 in monocytes restricted their migration when induced by different chemokines. Mechanistically, silencing MOSPD2 inhibited signaling events following chemokine receptor ligation. When tested for expression in other immune cell subsets, MOSPD2 was apparent also, though less abundantly, in neutrophils, but not in lymphocytes. Thus, in the presence of neutralizing Abs, neutrophil migration was inhibited to some extent whereas lymphocyte migration remained intact. In view of these results, we suggest MOSPD2 as a potential target protein for treating diseases in which monocyte and neutrophil accumulation is correlated with pathogenesis.

CCL2/Monocyte Chemoattractant Protein 1 and Parathyroid Hormone Action on Bone

Chemokines are small molecules that play a crucial role as chemoattractants for several cell types, and their components are associated with host immune responses and repair mechanisms. Chemokines selectively recruit monocytes, neutrophils, and lymphocytes and induce chemotaxis through the activation of G protein-coupled receptors. Two well-described chemokine families (CXC and CC) are known to regulate the localization and trafficking of immune cells in cases of injury, infection, and tumors. Monocyte chemoattractant protein 1 (MCP-1/CCL2) is one of the important chemokines from the CC family that controls migration and infiltration of monocytes/macrophages during inflammation. CCL2 is profoundly expressed in osteoporotic bone and prostate cancer-induced bone resorption. CCL2 also regulates physiological bone remodeling in response to hormonal and mechanical stimuli. Parathyroid hormone (PTH) has multifaceted effects on bone, depending on the mode of administration. Intermittent PTH increases bone in vivo by increasing the number and activity of osteoblasts, whereas a continuous infusion of PTH decreases bone mass by stimulating a net increase in bone resorption. CCL2 is essential for both anabolic and catabolic effects of PTH. In this review, we will discuss the pharmacological role of PTH and involvement of CCL2 in the processes of PTH-mediated bone remodeling.

Expression Profile of Immune-Associated Genes in Nasal Polyps

Objectives:

We performed this study to investigate the expression profile of immune-associated genes and to probe the role of related genes in the immune pathogenesis of nasal polyps.

Methods:

Microarray analysis was used to find the expression profile of 491 immune-associated genes in nasal polyps. In validation studies, immunohistochemical staining and Western blot analysis were used to detect interleukin (IL)–17 and IL-17 receptor (IL-17R) in nasal polyps and controls.

Results:

Eighty-seven genes were differentially expressed in the immune-associated gene profile of nasal polyps, and 15 genes showed differential expression in both chips. In nasal polyp tissues, IL-17 was expressed mainly in the cytoplasm of plasma cells and to a lesser degree in the prickle cell layer of the epithelium and the acinus of the serous gland. In turbinates, IL-17 was also expressed in the same location, but the expression of IL-17 in nasal polyps and that in turbinates differed significantly (p > .05). Both IL-17 and IL-17R displayed specific bands in nasal polyps and turbinates, but the bands of IL-17 and IL-17R in nasal polyps were stronger than those in turbinates.

Conclusions:

The differentially expressed genes in immune-associated gene chips will provide clues about, and a theoretical foundation for, the pathogenesis of nasal polyps. Furthermore, IL-17 may play an important role in the occurrence of nasal polyps by overexpression.

Modulating the Innate Immune Response to Influenza A Virus: Potential Therapeutic Use of Anti-Inflammatory Drugs

Infection by influenza A viruses (IAV) is frequently characterized by robust inflammation that is usually more pronounced in the case of avian influenza. It is becoming clearer that the morbidity and pathogenesis caused by IAV are consequences of this inflammatory response, with several components of the innate immune system acting as the main players. It has been postulated that using a therapeutic approach to limit the innate immune response in combination with antiviral drugs has the potential to diminish symptoms and tissue damage caused by IAV infection. Indeed, some anti-inflammatory agents have been shown to be effective in animal models in reducing IAV pathology as a proof of principle. The main challenge in developing such therapies is to selectively modulate signaling pathways that contribute to lung injury while maintaining the ability of the host cells to mount an antiviral response to control virus replication. However, the dissection of those pathways is very complex given the numerous components regulated by the same factors (i.e., NF kappa B transcription factors) and the large number of players involved in this regulation, some of which may be undescribed or unknown. This article provides a comprehensive review of the current knowledge regarding the innate immune responses associated with tissue damage by IAV infection, the understanding of which is essential for the development of effective immunomodulatory drugs. Furthermore, we summarize the recent advances on the development and evaluation of such drugs as well as the lessons learned from those studies.

Effect and possible mechanism of monocyte-derived VEGF on monocyte-endothelial cellular adhesion after electrical burns

OBJECTIVE

One of the major obstacles in the treatment of severe electrical burns is properly handling the resulting uncontrolled inflammation. Such inflammation often causes secondary injury and necrosis, thus complicating patient outcomes. Vascular endothelial grow factor (VEGF) has emerged as an important mediator for the recruitment of monocytes to the site inflammation. This study was designed to explore the effects and possible mechanism of VEGF on monocyte-endothelial cellular adhesion. To do so, we used a cultured human monocytic cell line (THP-1) that was stimulated with serum derived from rats that had received electrical burns.

METHODS

Serum was obtained from rats that had received electrical burns. Both the VEGF and soluble flt-1 (sflt-1) concentrations of the serum were determined by double-antibody sandwich ELISA. The concentrations of VEGF, sflt-1, and TNF-α obtained from the cell-free cultured supernatant of THP-1 cells that had been exposed to the serum were then determined by double-antibody sandwich ELISA. Serum-stimulated THP-1 cells were added to wells with a monolayer of endothelial cells to detect the level of monocyte-endothelial cells adhesion. Finally, the state of phosphorylation of AKT was determined by Western blotting.

RESULTS

Both in vivo and in vitro studies showed that compared to controls, the levels of VEGF were significantly increased after electrical burns. This increased was accompanied by a reduction of sflt-1 levels. Furthermore, the serum of rats that had received electrical burns was able to both activate monocytes to secrete TNF-α and enhance monocyte-endothelial cell adhesion. Treatment with the serum also resulted in an up-regulation of the phosphorylation of AKT, but had no effect on the total levels of AKT. Phosphatidylinositide 3-kinases (PI3K) inhibition decreased the number of THP-1 cells that were adhered to endothelial cells. Finally, sequestering VEGF with sflt-1 was able to reduce the effect on monocyte-endothelial cells adhesion by blocking the PI3K signaling pathway.

CONCLUSION

Our results indicate that VEGF is implicated in the pathogenesis of inflammation after electrical burns. Inhibition of VEGF activity could attenuate monocyte-endothelial cells adhesion by suppressing the state of phosphorylation of AKT, which is downstream of the PI3K signaling pathway.

Anti-donor HLA class I antibodies: pathways to endothelial cell activation and cell-mediated allograft rejection

BACKGROUND

The development of donor-specific human leukocyte antigen (HLA) class I antibodies after organ transplantation is associated with subsequent acute and chronic rejection. The aim of this study was to examine the role of anti-HLA class I antibody in modulating endothelium-leukocyte interaction.

METHODS

Human microvascular endothelial cells (HMEC-1) stimulated with HLA class I antibody (W6/32) or allospecific antibodies from sensitized patients (n=6) were examined for activation of transcription factor CREB by Western blotting. Up-regulation of endothelial adhesion molecules and chemokines was measured by flow cytometry and quantitative polymerase chain reaction, respectively. Leukocyte adhesion was evaluated by chemotaxis and in vitro flow-based assays.

RESULTS

Treatment of HMEC-1 cells with HLA class I antibody resulted in the phosphorylation of CREB in protein kinase A-dependent pathway. Furthermore, there was a significant increase in the expression of cell surface VCAM-1 (Akt-dependent) and ICAM-1 in Akt-dependent and extracellular signal-regulated kinase-dependent manner (P<0.001). Additionally, exposure to W6/32 antibody induced significant expression of interleukin-6, CXCL8, CXCL10, and CCL5. Knockdown of CREB produced a reduction in W6/32-induced CXCL8 expression (P<0.001). Media from W6/32-treated endothelial cells induced a significant monocyte chemotaxis (P<0.001) and flow-based adhesion assay demonstrated an increase in monocyte adhesion to endothelial cells compared with the control group (P<0.001). Importantly, allospecific antibodies from sensitized patients also activated endothelial CREB and significantly up-regulated VCAM-1, ICAM-1, and CXCL8.

CONCLUSION

These findings suggest that donor-specific HLA class I antibodies directly activate endothelial cells leading to an increase in their potential to recruit and bind recipient leukocytes, thereby increasing the potential for allograft inflammation.

Monocyte chemoattractant protein-1 and the blood-brain barrier

The blood-brain barrier (BBB) is a dynamic structure that maintains the homeostasis of the brain and thus proper neurological functions. BBB compromise has been found in many pathological conditions, including neuroinflammation. Monocyte chemoattractant protein-1 (MCP1), a chemokine that is transiently and significantly up-regulated during inflammation, is able to disrupt the integrity of BBB and modulate the progression of various diseases, including excitotoxic injury and hemorrhage. In this review, we first introduce the biochemistry and biology of MCP1, and then summarize the effects of MCP1 on BBB integrity as well as individual BBB components.

Chemokine CCL2 induces apoptosis in cortex following traumatic brain injury

The chemokine C-C motif ligand 2 (CCL2) is an important mediator of neuroinflammation. Released in response to acute injury, ischemia, and neurodegenerative disease, CCL2 binds primarily to the G-protein-coupled chemokine C-C motif receptor 2 (CCR2) to recruit inflammatory cells to sites of tissue damage. Inflammation is thought to have both beneficial and deleterious consequences following traumatic brain injury (TBI), so we investigated CCL2-CCR2 signaling during the post-TBI period to assess possible neurodegenerative and protective actions. Local TBI in adult rat cortex was induced by Feeney's weight-drop method, and the expression of CCL2 and CCR2 in the tissue around the contusion site was measured by real-time quantitative PCR. Both CCL2 and CCR2 mRNA levels were increased markedly for at least 10 days after injury, peaking on day 3. The CCL2 protein was mainly co-localized with the astroglial marker glial fibrillary acidic protein and CCR2 protein with the neuronal nuclear marker NeuN as revealed by double immunofluorescence staining. A selective CCR2 antagonist, RS504393, reduced TUNEL staining, a marker of apoptosis, and improved performance in the Morris water maze 3 days post-TBI, suggesting that CCL2-CCR2 signaling has deleterious effects on neuronal survival and learning. Targeting the CCL2-CCR2 pathway may provide a novel therapeutic approach for the treatment of TBI.

Inhibition of monocyte chemotaxis by VB-201, a small molecule lecinoxoid, hinders atherosclerosis development in ApoE⁻/⁻ mice

OBJECTIVE

Monocytes are motile cells which sense inflammatory stimuli and subsequently migrate to sites of inflammation. Key players in host defense, monocytes have nevertheless been implicated as requisite mediators of several chronic inflammatory diseases. Inhibition of monocyte chemotaxis is therefore an attractive anti-inflammatory strategy. Oxidized phospholipids (OxPL) are native regulators of inflammation, yet their direct effect on monocyte chemotaxis is poorly defined. In this study, we investigated the direct effect of natural and synthetic phospholipids on monocyte chemotaxis.

METHODS

Exploring various phospholipids using in vitro chemotaxis assays, we found that the natural phospholipid 1-palmitoyl-2-glutaryl phosphatidylcholine (PGPC) can decrease monocyte chemotaxis by 50%, while other tested OxPL had no effect. We generated a library of synthetic OxPL designated lecinoxoids, which was screened for anti-inflammatory properties.

RESULTS AND CONCLUSIONS

VB-201, a small-molecule lecinoxoid, exhibited up to 90% inhibition of monocyte chemotaxis in vitro. Molecular analysis revealed that the effect of VB-201 was not restricted to a specific chemotactic ligand or receptor, and resulted from inhibition of signaling pathways required for monocyte chemotaxis. Interestingly, VB-201 did not inhibit monocyte adhesion or phagocytosis and had no effect on chemotaxis of CD4(+) T-cells or neutrophils. In vivo, oral treatment with VB-201 reduced monocyte migration in a peritonitis model and inhibited atheroma development in ApoE(-/-) mice, without affecting cholesterol or triglyceride levels. Our findings highlight a novel role played by native and synthetic phospholipids in regulation of monocyte chemotaxis. The data strengthen the involvement of phospholipids as key signaling molecules in inflammatory settings and demonstrate their potential therapeutic applicability.

Role of chemokine CCL2 and its receptor CCR2 in neurodegenerative diseases

Chemokines are members of the chemoattractant cytokine family. They play key roles in the trafficking of leukocytes and in the induction of chemotaxis through the activation of G protein-coupled receptor. Considerable interest has been paid to these molecules to elucidate their roles in the unique inflammatory responses elicited in the central nervous system (CNS). Chemokine CCL2 (also known as monocyte chemoattractant protein-1, MCP-1) is one of the vital chemokines that control the migration and infiltration of monocytes/macrophages. CCL2 and its receptor CCR2 have been shown to be induced and involved in various neurodegenerative disorders including Alzheimer's disease, multiple sclerosis, and ischemic brain injury. The present review will focus on the biological and pathophysiological aspects of CCL2 and CCR2 in the CNS and the possible therapeutic approaches for targeting these two proteins to combat neurodegenerative diseases.

The role of tumor-associated macrophages in breast cancer progression (review)

It is well established that the tumor microenvironment plays a major role in the aggressive behavior of malignant solid tumors. Among cell types associated with tumor microenvironment, tumor-associated macrophages (TAMs) are the most influential for tumor progression. Breast cancer is characterized by having a large population of TAMs, and experimental models have exposed multiple mechanisms by which TAMs interact with and influence the surrounding tumor cells. The process of metastasis involves tumor cells gaining access to the tissue outside the immediate tumor environment and invading the confining extracellular matrix (ECM). Supporting this process, TAMs secrete proangiogenic factors such as VEGF to build a network of vessels that provide nutrition for tumor cells, but also function as channels of transport into the ECM. Additionally, TAMs release factors to decrease the local pro-inflammatory antitumor response, suppressing it and providing a means of escape of the tumor cells. Similarly, hypoxia in the tumor microenvironment stimulates macrophages to further produce VEGF and suppress the T-cell immune responses, thus, enhancing the evasion of tumor cells and ultimately metastasis. Given the multiple roles of TAMS in breast cancer progression and metastasis, therapies targeting these cells are in development and demonstrate promising results.

Both macrophages and hypoxia play critical role in regulating invasion of gastric cancer in vitro

BACKGROUND

As previously demonstrated, tumor associated macrophages (TAMs) infiltration is associated with some cancers invasion and metastasis. However, the role of TAMs in the gastric cancer remains unclear.

METHODS

Three- dimensional dynamic migration imaging system and real time RT-PCR were used to quantitatively investigate the effect of macrophages on the cancer cell mobility and gene expression related to cancer invasion and metastasis, including ADAM8, ADAM9, MMP9, TIMP3, VEGF-A and IL8 genes, in AGS, HGC-27, Hs-746T and NCI-N87 gastric cancer cell lines under normal or hypoxic conditions.

RESULTS

Under normal conditions, the cancer cell invasion rate was increased significantly and all six gene expressions were upregulated in all four cancer cell lines by macrophages. Under hypoxia the changes in the cancer cell invasion rate induced by macrophages was negatively correlated to the TIMP3 expression. In non- metastatic cell line AGS, the increase in migration rate induced by macrophages was further elevated under hypoxia with increased ADAM8 and ADAM9 expression and decreased MMP9 and TIMP3 expressions. Under hypoxia, the induction by macrophages for IL-8 expression was increased significantly in distant metastatic cell lines NCI-N87 and HS-746T, VEGF-A was increased in HGC-27 cell line.

CONCLUSIONS

Both macrophages and hypoxia play an indispensable role in regulating the invasion of gastric cancer cells in vitro; ADAMs, MMP9 and TIMP3 might be involved in TAM induced invasive power of gastric cancer cells.

MCP-1 impacts RCT by repressing ABCA1, ABCG1, and SR-BI through PI3K/Akt posttranslational regulation in HepG2 cells

Monocyte chemoattractant protein-1 (MCP-1) plays crucial roles at multiple stages of atherosclerosis. We hypothesized that MCP-1 might impair the reverse cholesterol transport (RCT) capacity of HepG2 cells by decreasing the cell-surface protein expression of ATP binding cassette A1 (ABCA1), ATP binding cassette G1 (ABCG1), and scavenger receptor class B type I (SR-BI). MCP-1 reduced the total protein and mRNA levels of ABCA1 and SR-BI, but not of ABCG1. MCP-1 decreased the cell-surface protein expression of ABCA1, ABCG1, and SR-BI in dose-dependent and time-dependent manners, as measured using cell-surface biotinylation. We further studied the phosphoinositide 3-kinase (PI3K)/serine/threonine protein kinase Akt pathway in regulating receptor trafficking. Both the translation and transcription of ABCA1, ABCG1, and SR-BI were not found to be regulated by the PI3K/Akt pathway. However, the cell-surface protein expression of ABCA1, ABCG1, and SR-BI could be regulated by PI3K activity, and PI3K activation corrected the MCP-1-induced decreases in the cell-surface protein expression of ABCA1, ABCG1, and SR-BI. Moreover, we found that MCP-1 decreased the lipid uptake by HepG2 cells and the ABCA1-mediated cholesterol efflux to apoA-I, which could be reversed by PI3K activation. Our data suggest that MCP-1 impairs RCT activity in HepG2 cells by a PI3K/Akt-mediated posttranslational regulation of ABCA1, ABCG1, and SR-BI cell-surface expression.

Metabolic products of soluble epoxide hydrolase are essential for monocyte chemotaxis to MCP-1 in vitro and in vivo

Monocyte chemoattractant protein-1 (MCP-1)-induced monocyte chemotaxis is a major event in inflammatory disease. Our prior studies have demonstrated that MCP-1-dependent chemotaxis requires release of arachidonic acid (AA) by activated cytosolic phospholipase A(2) (cPLA(2)). Here we investigated the involvement of AA metabolites in chemotaxis. Neither cyclooxygenase nor lipoxygenase pathways were required, whereas pharmacologic inhibitors of both the cytochrome-P450 (CYP) and the soluble epoxide hydrolase (sEH) pathways blocked monocyte chemotaxis to MCP-1. To verify specificity, we demonstrated that the CYP and sEH products epoxyeiscosatrienoic acids (EETs) and dihydroxyeicosatrienoic acids (DHETs), respectively, restored chemotaxis in the presence of the inhibitors, indicating that sEH-derived products are essential for MCP-1-driven chemotaxis. Importantly, DHETs also rescued chemotaxis in cPLA(2)-deficient monocytes and monocytes with blocked Erk1/2 activity, because Erk controls cPLA(2) activation. The in vitro findings regarding the involvement of CYP/sEH pathways were further validated in vivo using two complementary approaches measuring MCP-1-dependent chemotaxis in mice. These observations reveal the importance of sEH in MCP-1-regulated monocyte chemotaxis and may explain the observed therapeutic value of sEH inhibitors in treatment of inflammatory diseases, cardiovascular diseases, pain, and even carcinogenesis. Their effectiveness, often attributed to increasing EET levels, is probably influenced by the impairment of DHET formation and inhibition of chemotaxis.

CCR2 Antagonists for the Treatment of Diseases Associated with Inflammation

The CCR2 and MCP-1 pathway has become one of the most-studied chemokine systems for therapeutic use in inflammatory diseases and conditions. It plays a pivotal role in inflammatory diseases, especially those that are characterized by monocyte-rich infiltration. This chapter reviews the biology of CCR2 and MCP-1, and their roles in diseases and conditions related to inflammation such as rheumatoid arthritis, multiple sclerosis, asthma, obesity, type 2 diabetes, atherosclerosis, nephropathy, cancer, pulmonary fibrosis and pain. Intense drug-discovery efforts over the past 15 years have generated a large number of CCR2 antagonists in diverse structural classes. Mutagenesis studies have elucidated important residues on CCR2 that interact with many classes of these CCR2 antagonists. To facilitate understanding of CCR2 antagonist SAR, a simple pharmacophore model is used to summarize the large number of diverse chemical structures. The majority of published compounds are classified based on their central core structures using this model. Key SAR points in the published literature are briefly discussed for most of the series. Lead compounds in each chemical series are highlighted where information is available. The challenges in drug discovery and development of CCR2 antagonists are briefly discussed. Clinical candidates in various diseases in the public domain are summarized with a brief discussion about the clinical challenges.

Chemokine CCL2 and its receptor CCR2 in the medullary dorsal horn are involved in trigeminal neuropathic pain

Background

Neuropathic pain in the trigeminal system is frequently observed in clinic, but the mechanisms involved are largely unknown. In addition, the function of immune cells and related chemicals in the mechanism of pain has been recognized, whereas few studies have addressed the potential role of chemokines in the trigeminal system in chronic pain. The present study was undertaken to test the hypothesis that chemokine C-C motif ligand 2 (CCL2)-chemokine C-C motif receptor 2 (CCR2) signaling in the trigeminal nucleus is involved in the maintenance of trigeminal neuropathic pain.

Methods

The inferior alveolar nerve and mental nerve transection (IAMNT) was used to induce trigeminal neuropathic pain. The expression of ATF3, CCL2, glial fibrillary acidic protein (GFAP), and CCR2 were detected by immunofluorescence histochemical staining and western blot. The cellular localization of CCL2 and CCR2 were examined by immunofluorescence double staining. The effect of a selective CCR2 antagonist, RS504393 on pain hypersensitivity was checked by behavioral testing.

Results

IAMNT induced persistent (>21 days) heat hyperalgesia of the orofacial region and ATF3 expression in the mandibular division of the trigeminal ganglion. Meanwhile, CCL2 expression was increased in the medullary dorsal horn (MDH) from 3 days to 21 days after IAMNT. The induced CCL2 was colocalized with astroglial marker GFAP, but not with neuronal marker NeuN or microglial marker OX-42. Astrocytes activation was also found in the MDH and it started at 3 days, peaked at 10 days and maintained at 21 days after IAMNT. In addition, CCR2 was upregulated by IAMNT in the ipsilateral medulla and lasted for more than 21 days. CCR2 was mainly colocalized with NeuN and few cells were colocalized with GFAP. Finally, intracisternal injection of CCR2 antagonist, RS504393 (1, 10 μg) significantly attenuated IAMNT-induced heat hyperalgesia.

Conclusion

The data suggest that CCL2-CCR2 signaling may be involved in the maintenance of orofacial neuropathic pain via astroglial–neuronal interaction. Targeting CCL2-CCR2 signaling may be a potentially important new treatment strategy for trigeminal neuralgia.

Chemokines in CNS injury and repair

Recruitment of inflammatory cells is known to drive the secondary damage cascades that are common to injuries of the central nervous system (CNS). Cell activation and infiltration to the injury site is orchestrated by changes in the expression of chemokines, the chemoattractive cytokines. Reducing the numbers of recruited inflammatory cells by the blocking of the action of chemokines has turned out be a promising approach to diminish neuroinflammation and to improve tissue preservation and neovascularization. In addition, several chemokines have been shown to be essential for stem/progenitor cell attraction, their survival, differentiation and cytokine production. Thus, chemokines might indirectly participate in remyelination, neovascularization and neuroprotection, which are important prerequisites for CNS repair after trauma. Moreover, CXCL12 promotes neurite outgrowth in the presence of growth inhibitory CNS myelin and enhances axonal sprouting after spinal cord injury (SCI). Here, we review current knowledge about the exciting functions of chemokines in CNS trauma, including SCI, traumatic brain injury and stroke. We identify common principles of chemokine action and discuss the potentials and challenges of therapeutic interventions with chemokines.

Chemokines and their receptors in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating clinical event which results in a high rate of disability and death. At present, no effective treatment is available for ICH. Accumulating evidence suggests that inflammatory responses contribute significantly to the ICH-induced secondary brain outcomes. During ICH, inflammatory cells accumulate at the ICH site attracted by gradients of chemokines. This review summarizes recent progress in ICH studies and the chemoattractants that act during the injury and focuses on and introduces the basic biology of the chemokine monocyte chemoattractant protein-1 (MCP1) and its role in the progression of ICH. Better understanding of MCP1 signaling cascade and the compensation after its inhibition could shed light on the development of effective treatments for ICH.

Suppression and regression of choroidal neovascularization in mice by a novel CCR2 antagonist, INCB3344

PURPOSE

To investigate the effect of an intravitreally administered CCR2 antagonist, INCB3344, on a mouse model of choroidal neovascularization (CNV).

METHODS

CNV was induced by laser photocoagulation on Day 0 in wild type mice. INCB3344 or vehicle was administered intravitreally immediately after laser application. On Day 14, CNV areas were measured on retinal pigment epithelium (RPE)-choroid flat mounts and histopathologic examination was performed on 7 µm-thick sections. Macrophage infiltration was evaluated by immunohistochemistry on RPE-choroid flat mounts and quantified by flow cytometry on Day 3. Expression of vascular endothelial growth factor (VEGF) protein in RPE-choroid tissue was examined by immunohistochemistry and ELISA, VEGF mRNA in sorted macrophages in RPE-choroid tissue was examine by real-time PCR and expression of phosphorylated extracellular signal-regulated kinase (p-ERK 1/2) in RPE-choroid tissue was measured by Western blot analysis on Day 3. We also evaluated the efficacy of intravitreal INCB3344 to spontaneous CNV detected in Cu, Zn-superoxide dismutase (SOD1) deficient mice. Changes in CNV size were assessed between pre- and 1week post-INCB3344 or vehicle administration in fundus photography and fluorescence angiography (FA).

RESULTS

The mean CNV area in INCB3344-treated mice decreased by 42.4% compared with the vehicle-treated control mice (p<0.001). INCB3344 treatment significantly inhibited macrophage infiltration into the laser-irradiated area (p<0.001), and suppressed the expression of VEGF protein (p = 0.012), VEGF mRNA in infiltrating macrophages (p<0.001) and the phosphorylation of ERK1/2 (p<0.001). The area of spontaneous CNV in Sod1⁻/⁻ mice regressed by 70.35% in INCB3344-treated animals while no change was detected in vehicle-treated control mice (p<0.001).

CONCLUSIONS

INCB3344 both inhibits newly forming CNV and regresses established CNV. Controlling inflammation by suppressing macrophage infiltration and angiogenic ability via the CCR-2/MCP-1 signal may be a useful therapeutic strategy for treating CNV associated with age-related macular degeneration.

Development of a mathematical model to describe the transport of monocyte chemoattractant protein-1 through a three-dimensional collagen matrix

INTRODUCTION

Monocyte chemoattractant protein-1 is a bioactive molecule that is expressed in significant amounts in all stages of atherosclerosis. The role of monocyte chemoattractant protein-1 in this disease is to recruit monocytes across the endothelium and into the arterial tissue. Eventually, the monocytes differentiate into cholesterol-engorged macrophages called "foam cells" that result in atherosclerotic plaque formation. The mechanism that monocyte chemoattractant protein-1 uses to mediate monocyte transendothelial migration is believed to be via its concentration gradient. However, the formation of the monocyte chemoattractant protein-1 concentration gradient in the extracellular matrix is still poorly understood.

METHODS

A three-dimensional in vitro vascular tissue model has been developed to study the cellular mechanisms involved in the early stages of atherosclerosis. In the present study, a mathematical model is used to determine the gradient of monocyte chemoattractant protein-1 in the collagen matrix of the three-dimensional in vitro vascular tissue model. Experiments were performed to investigate the stability of monocyte chemoattractant protein-1 and the interaction between monocyte chemoattractant protein-1 and the collagen matrix.

RESULTS AND CONCLUSIONS

Monocyte chemoattractant protein-1 is stable for at least 24 h under experimental conditions and monocyte chemoattractant protein-1 interacts with the collagen matrix. The diffusion coefficient for the transport of monocyte chemoattractant protein-1 in the collagen matrix and the rate constant for the binding of monocyte chemoattractant protein-1 to collagen were determined to be 0.108 mm(2) h(-1) and 0.858 h(-1), respectively. Numerical results from the model indicate that the concentration gradients of both soluble and matrix-bound (or static) monocyte chemoattractant protein-1 are formed inside the collagen matrix.

Experimental Swine lung autotransplant model to study lung ischemia-reperfusion injury

INTRODUCTION

Ischemia-reperfusion (IR) lung injury has been investigated extensively on clinical and experimental models of cold ischemia. However, relatively few studies examine the detailed biochemical changes occurring during normothermic (warm) IR. The objective of this work was to establish an experimental lung autotransplant model to be carried out on pigs in order to study the early stages of normothermic lung IR. ANIMALS Y METHODS: Six Large-White pigs underwent a lung autotransplant which entailed left pneumonectomy, ex situ cranial lobectomy, caudal lobe reimplantation and its reperfusion for 30 min. Throughout the procedure, several parameters were measured in order to identify hemodynamic, gasometric and biochemical changes. Non-parametric statistical analyses were used to compare differences between periods.

RESULTS

After ischemia, a significant increase (P < 0.05) in lipid peroxidation metabolites, proinflammatory cytokines and chemokines (TNF-α, IL-1β y MCP-1), neutrophil activation, inducible nitric oxide synthase activity and protein-kinase MAPK p38 levels were observed in lung tissue. However, constitutive nitric oxide synthase activity in lung tissue and carbon monoxide plasma levels were decrease. The same held true throughout the reperfusion period, when an increase in the constitutive heme-oxygenase activity was also shown.

CONCLUSIONS

An experimental model of normothermic lung IR injury is presented and detailed changes in hemodynamic, gasometric and biochemical parameters are shown. Both the model and the studied parameters may be clinically useful in future investigations testing new therapies to prevent normothermic IR induced lung injury.

Effect of storage conditions on the stability of recombinant human MCP-1/CCL2

Monocyte chemoattractant protein-1 (MCP-1) is commercially available in a form of recombinant protein. This makes it more convenient to study the functions of MCP-1 and its involvement in many cell functions. However, when using MCP-1 in experimental studies, if the analysis is not performed immediately, the stability of recombinant MCP-1 may become an issue. In this study, the stability of recombinant MCP-1 at different concentrations and storage conditions was investigated. Results show that no significant loss of MCP-1 is observed when MCP-1 solutions were stored at non-freezing condition (4 °C) for seven days. However, for storage at freezing conditions (-20 °C or -81 °C), it appears that the first freeze-thaw cycle may contribute to some loss of MCP-1 in the solutions, and such loss may be concentration and time dependent. The effect of multiple freeze-thaw cycles for storage at freezing conditions was also examined. Data reveal that the second freeze-thaw cycle causes approximately 50% loss of MCP-1 in the solutions. This finding confirms that multiple freeze-thaw cycles should be avoided. The findings of this study provide an outline of how storage can affect the stability of recombinant proteins and should be taken into account during the evaluation of the concentration of recombinant proteins.

Patients with acute pancreatitis complicated by organ failure show highly aberrant monocyte signaling profiles assessed by phospho-specific flow cytometry

OBJECTIVES

To outline signaling profiles and transmigration capacity of monocytes of patients with severe acute pancreatitis.

DESIGN

Prospective study.

SETTING

University hospital intensive care unit.

PATIENTS

Thirteen patients with severe acute pancreatitis. All patients had organ dysfunction (acute respiratory distress syndrome in 12, renal dysfunction in eight). Healthy volunteers served as reference subjects.

INTERVENTIONS

Blood samples were collected after admission to the intensive care unit.

MEASUREMENTS AND MAIN RESULTS

Phosphorylation of nuclear factor-kappaB and p38, signal transducers and activators of transcription (STATs) 1, 3, 5, and extracellular signal-regulated kinases 1/2 in appropriately stimulated and nonstimulated samples were studied using phospho-specific whole-blood flow cytometry. Monocyte chemotactic protein-1-induced transmigration of monocytes among mononuclear cells obtained by density gradient centrifugation was studied using Transwell cell culture inserts covered with confluent layer of endothelial EA-HY cells. Phosphorylation levels of nuclear factor-kappaB induced by tumor necrosis factor, bacterial lipopolysaccharide, muramyl dipeptide, Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis were significantly lower in patients' monocytes than monocytes of healthy reference subjects, whereas mitogen-activated protein kinase p38 phosphorylation levels were normal. Phosphorylation levels induced by interleukin-6 in STAT1 and STAT3 and by combination of phorbol 12-myristate 13-acetate and calcium ionophore A23187 in extracellular signal-regulated kinases 1/2, members of a mitogen-activated protein kinase family, were depressed in patients' monocytes, whereas phosphorylation levels induced by granulocyte-macrophage colony-stimulating factor in STAT5 was normal. In nonstimulated samples, phosphorylation levels were normal. The transmigration percentage of patients' monocytes was significantly lower than that of reference monocytes.

CONCLUSIONS

In severe acute pancreatitis, monocytes show impaired nuclear factor kappaB and STAT1 activation, which may increase susceptibility to secondary infections. p38 activation is normal and STAT3 activation is depressed, which may contribute to maintenance of systemic inflammation. Extracellular signal-regulated kinases 1/2 activation is impaired, which may depress monocytes' transmigration and may consequently increase risk of infection. Monitoring of monocyte signaling profiles may aid in finding new therapeutic approaches and predictors of outcome of severe acute pancreatitis.

MCP-1: chemoattractant with a role beyond immunity: a review

BACKGROUND

Monocyte Chemoattractant Protein (MCP)-1, a potent monocyte attractant, is a member of the CC chemokine subfamily. MCP-1 exerts its effects through binding to G-protein-coupled receptors on the surface of leukocytes targeted for activation and migration. Role of MCP-1 and its receptor CCR2 in monocyte recruitment during infection or under other inflammatory conditions is well known.

METHOD

A comprehensive literature search was conducted from the websites of the National Library of Medicine (http://www.ncbl.nlm.nih.gov) and Pubmed Central, the US National Library of Medicine's digital archive of life sciences literature (http://www.pubmedcentral.nih.gov/). The data was assessed from books and journals that published relevant articles in this field.

RESULT

Recent and ongoing research indicates the role of MCP-1 in various allergic conditions, immunodeficiency diseases, bone remodelling, and permeability of blood - brain barrier, atherosclerosis, nephropathies and tumors.

CONCLUSION

MCP-1 plays an important role in pathogenesis of various disease states and hence MCP-1 inhibition may have beneficial effects in such conditions.

Role of chemokines in CNS health and pathology: a focus on the CCL2/CCR2 and CXCL8/CXCR2 networks

Chemokines and their receptors have crucial roles in the trafficking of leukocytes, and are of particular interest in the context of the unique immune responses elicited in the central nervous system (CNS). The chemokine system CC ligand 2 (CCL2) with its receptor CC receptor 2 (CCR2), as well as the receptor CXCR2 and its multiple ligands CXCL1, CXCL2 and CXCL8, have been implicated in a wide range of neuropathologies, including trauma, ischemic injury and multiple sclerosis. This review aims to overview the current understanding of chemokines as mediators of leukocyte migration into the CNS under neuroinflammatory conditions. We will specifically focus on the involvement of two chemokine networks, namely CCL2/CCR2 and CXCL8/CXCR2, in promoting macrophage and neutrophil infiltration, respectively, into the lesioned parenchyma after focal traumatic brain injury. The constitutive brain expression of these chemokines and their receptors, including their recently identified roles in the modulation of neuroprotection, neurogenesis, and neurotransmission, will be discussed. In conclusion, the value of evidence obtained from the use of Ccl2- and Cxcr2-deficient mice will be reported, in the context of potential therapeutics inhibiting chemokine activity which are currently in clinical trial for various inflammatory diseases.

Upregulation of plasma CCL8 in mouse model of graft-vs-host disease

OBJECTIVE

Using a proteomic approach, we recently identified plasma CCL8 as a potential biomarker for diagnosis of graft-vs-host-disease (GVHD) in mice as well as humans. Because mass spectrometric analysis is only semi-quantitative, a quantitative method of measuring plasma CCL8 levels in mice is needed.

MATERIALS AND METHODS

We established an enzyme-linked immunosorbent assay for the quantitative measurement of CCL8 concentrations in mouse plasma.

RESULTS

Our newly established enzyme-linked immunosorbent assay revealed that the plasma CCL8 concentrations (mean +/- standard error; n=12) were 1287+/-55.7 ng/mL and 1604+/-110.8 ng/mL on days 7 and 14 after allogeneic bone marrow transplantation (BMT), respectively, while the plasma concentrations was 316.6+/-16.3 ng/mL on day 7 after syngeneic BMT. A Western blotting analysis also showed a difference in the plasma CCL8 levels between the allogeneic and syngeneic BMT groups, as did clinical GVHD scores. Neither lipopolysaccharide nor poly(I:C) elevated the plasma CCL8 concentrations, although a dramatic increase in interleukin-6 was detected after both treatments.

CONCLUSION

An elevated plasma CCL8 concentration may be a promising plasma marker for GVHD in mouse models.