Despite increasing knowledge about molecular pathways in pathogenesis of chronic liver disease, selective therapeutic options are scarce, especially in advanced diseases characterized by scarring of the liver (termed fibrosis) or even complete cirrhosis. Sustained hepatic inflammation as a result to various types of injury (e.g., hepatitis C, nonalcoholic steatohepatitis) is generally accepted to represent the key prerequisite for fibrogenesis. Liver inflammation is characterized by an activation of distinct chemokine pathways in the liver and the circulation allowing distinct immune cell populations to enter the liver via sinusoids and postsinusoidal venules. Recent investigations have shed light on the intimate interactions between the fibrogenic hepatic stellate cell (HSC) and infiltrating immune cells, which fundamentally drive liver scarring. Experimental fibrosis and inflammation models have demonstrated that disruption of chemokine pathways such as CCL2 (MCP-1) or its receptor CCR2, CCL5 (RANTES) or CCR1 / CCR5 and others may efficiently prevent collagen deposition, by targeting monocytes and macrophages, T-cell populations or NKT cells. However, immigration of certain mononuclear cells may even be beneficial in the course of fibrosis. Infiltrating NK cells and monocyte-derived macrophage subsets can promote resolution of extracellular matrix. This emphasizes that hepatic fibrosis is not a unidirectional process, but can be reverted up to a certain point. The present review aims at summarizing the contribution of immune cell infiltration as well as related chemokine systems to experimental liver fibrosis and will discuss possible therapeutic applications in humans, with a special emphasis on the monocyte/macrophage lineage and their related chemokine pathways.

OBJECTIVE

Single-nucleotide polymorphisms (SNPs) that alter immune function, inflammatory responses, and disease susceptibility have been identified in several genes encoding Toll-like receptors (TLRs). The TLR SNPs with the best evidence of an effect on immune function are those in TLR1 (1805GG), TLR2 (2258GA), and TLR5 (1174CT). This study was undertaken to assess the frequency and functional outcomes of these polymorphisms in patients with Lyme disease.

METHODS

SNP frequencies and functional outcomes were assessed in 248 patients with Lyme disease. Cytokine and chemokine levels were determined using multiplex assays in the serum of patients with erythema migrans (EM), joint fluid of patients with Lyme arthritis, and supernatants of Borrelia burgdorferi-stimulated peripheral blood mononuclear cells (PBMCs) from patients with Lyme arthritis.

RESULTS

The frequency of the TLR1-1805GG polymorphism was greater in patients with antibiotic-refractory arthritis compared with patients with EM or those with antibiotic-responsive arthritis. Early in the illness, patients with EM carrying 1805GG, primarily those infected with B burgdorferi 16S-23S ribosomal spacer RNA intergenic type 1 (RST1) strains, had higher serum levels of interferon-γ (IFNγ), CXCL9, and CXCL10 and had more severe infection than EM patients carrying the 1805TG/TT polymorphism. These inflammatory responses were amplified in patients with Lyme arthritis, and the highest responses were observed in patients with 1805GG in the antibiotic-refractory group who had been infected with RST1 strains. When PBMCs from patients with Lyme arthritis were stimulated with a B burgdorferi RST1 strain, the 1805GG group had a significantly larger fold increase in the levels of IFNγ, CCL2, CXCL9, and CXCL10 compared to the 1805TG/TT group. In contrast, the TLR2 and TLR5 polymorphisms did not vary in frequency or function among the groups.

CONCLUSIONS

The TLR1-1805GG polymorphism in B burgdorferi RST1-infected patients was associated with stronger Th1-like inflammatory responses, an environment that may set the stage for antibiotic-refractory arthritis.

Inflammatory leukocytes infiltrate the CNS parenchyma in neuroinflammation. This involves cellular migration across various structures associated with the blood-brain barrier: the vascular endothelium, the glia limitans, and the perivascular space between them. Leukocytes accumulate spontaneously in the perivascular space in brains of transgenic (Tg) mice that overexpress CCL2 under control of a CNS-specific promoter. The Tg mice show no clinical symptoms, even though leukocytes have crossed the endothelial basement membrane. Pertussis toxin (PTx) given i.p. induced encephalopathy and weight loss in Tg mice. We used flow cytometry, ultra-small superparamagnetic iron oxide-enhanced magnetic resonance imaging, and immunofluorescent staining to show that encephalopathy involved leukocyte migration across the glia limitans into the brain parenchyma, identifying this as the critical step in inducing clinical symptoms. Metalloproteinase (MPs) enzymes are implicated in leukocyte infiltration in neuroinflammation. Unmanipulated Tg mice had elevated expression of tissue inhibitor of metalloproteinase-1, matrix metalloproteinase (MMP)-10, and -12 mRNA in the brain. PTx further induced expression of tissue inhibitor of metalloproteinase-1, metalloproteinase disintegrins-12, MMP-8, and -10 in brains of Tg mice. Levels of the microglial-associated MP MMP-15 were not affected in control or PTx-treated Tg mice. PTx also up-regulated expression of proinflammatory cytokines IL-1beta and TNF-alpha mRNA in Tg CNS. Weight loss and parenchymal infiltration, but not perivascular accumulation, were significantly inhibited by the broad-spectrum MP inhibitor BB-94/Batimastat. Our finding that MPs mediate PTx-induced parenchymal infiltration to the chemokine-overexpressing CNS has relevance for the pathogenesis of human diseases involving CNS inflammation, such as multiple sclerosis.

Chronic myocarditis is the main pathological finding associated with Chagas disease-related morbidity. Concentrations of CCL2, CCL3, tumor necrosis factor (TNF)-alpha, and brain natriuretic peptide (BNP) were evaluated in plasma samples obtained from patients with different clinical forms of chronic chagasic cardiomyopathy. Patients with more-severe Chagas disease had elevated plasma concentrations of TNF-alpha, CCL2, and BNP, and there was a good correlation between levels of these proteins (especially TNF-alpha ) and the degree of heart dysfunction. Indeed, TNF-alpha level was an excellent predictor of heart failure. Peripheral blood mononuclear cell samples obtained from patients with mild or severe chagasic cardiomyopathy produced greater amounts of TNF-alpha and CCL2 than did those obtained from noninfected individuals. The elevation of TNF-alpha and CCL2 levels in the plasma of patients appears to be secondary to the degree of heart dysfunction, whereas spontaneous production of TNF-alpha and CCL2 by mononuclear cells is secondary not only to heart dysfunction, but also to the underlying inflammation in the heart of chagasic patients. Measurement of the TNF-alpha level could be a useful tool in the identification of patients with heart dysfunction who may benefit from further investigation and treatment.

The parasitic protozoan Giardia lamblia is a worldwide cause of diarrhea, but the mechanism of disease remains elusive. The parasite colonizes the small intestinal epithelium, known to be a sensor for the presence of enteric pathogens, without invading or causing severe inflammation. In this study we investigated the epithelial cell response to G. lamblia. Differentiated Caco-2 cells were infected with G. lamblia isolate WB-A11, and the transcriptome of the intestinal cells was analyzed after 1.5, 6, and 18 h of interaction, using oligonucleotide microarrays. A large number of genes displayed changed expression patterns, showing the complexity of the interaction between G. lamblia and intestinal cells. A novel chemokine profile (<em>CCL2</em>, <em>CCL2</em>0, CXCL1, CXCL2, and CXCL3) was induced that was different from the response induced by enteric pathogens causing intestinal inflammation. Several genes involved in stress regulation changed their expression. These findings indicate that the intestinal epithelium senses the G. lamblia infection, and this is important for induction of innate and adaptive immunity. The induced stress response can be important in the pathogenesis.

OBJECTIVE

To investigate whether high-density lipoproteins (HDLs) suppress chemokine (CCL2, CCL5, and CX(3)CL1) and chemokine receptor (CCR2 and CX(3)CR1) expression, a mechanism for the atheroprotective properties of HDLs.

RESULTS

Apolipoprotein (apo) E(-/-) mice were fed a high-fat diet for 12 weeks. Before being euthanized, the mice received 5 consecutive daily injections of lipid-free apoA-I, 40 mg/kg, or saline (control). The injection of apoA-I reduced CCR2 and CX(3)CR1 expression in plaques compared with controls (P<0.05). ApoA-I-injected mice had lower plasma CCL2 and CCL5 levels. Hepatic CCL2, CCL5, and CX(3)CL1 levels were also reduced (P<0.05). In vitro studies found that reconstituted HDL (rHDL) reduced monocyte CCR2 and CX(3)CR1 expression and inhibited their migration toward CCL2 and CX(3)CL1 (P<0.05). Preincubation with rHDL reduced CCL2, CCL5, and CX(3)CL1 expression in monocytes and human coronary artery endothelial cells. The stimulation of CX(3)CR1 with peroxisome proliferator-activated receptor gamma agonist CAY10410 was suppressed by preincubation with rHDL but did not affect the peroxisome proliferator-activated receptor gamma antagonist (GW9664)-mediated increase in CCR2. In monocytes and human coronary artery endothelial cells, rHDL reduced the expression of the nuclear p65 subunit, IkappaB kinase activity, and the phosphorylation of IkappaBalpha (P<0.05).

CONCLUSIONS

Lipid-free apoA-I and rHDL reduce the expression of chemokines and chemokine receptors in vivo and in vitro via modulation of nuclear factor kappaB and peroxisome proliferator-activated receptor gamma.

OBJECTIVE

Mechanical joint loading is critical for the development of osteoarthritis (OA). Although once regarded as a disease of cartilage attrition, OA is now known to be controlled by the expression and activity of key proteases, such as ADAMTS-5, that drive matrix degradation. This study was undertaken to investigate the link between protease expression and mechanical joint loading in vivo.

METHODS

We performed a microarray analysis of genes expressed in the whole joint following surgical induction of murine OA (by cutting the medial meniscotibial ligament). Gene expression changes were validated by reverse transcriptase-polymerase chain reaction in whole joints and microdissected tissues of the joint, including the articular cartilage, meniscus, and epiphysis. Following surgery, mouse joints were immobilized, either by prolonged anesthesia or by sciatic neurectomy.

RESULTS

Many genes were regulated in the whole joint within 6 hours of surgical induction of OA in the mouse. These included Arg1, Ccl2, Il6, Tsg6, Mmp3, Il1b, Adamts5, Adamts4, and Adamts1. All of these were significantly regulated in the articular cartilage. When joints were immobilized by prolonged anesthesia, regulation of the vast majority of genes was abrogated. When joints were immobilized by sciatic neurectomy, regulation of selected genes was abrogated, and OA was prevented up to 12 weeks postsurgery.

CONCLUSIONS

These findings indicate that gene expression in the mouse joint following the induction of OA is rapid and highly mechanosensitive. Regulated genes include the known pathogenic protease ADAMTS-5. Targeting the mechanosensing mechanisms of joint tissue may offer new strategies for disease modification.

Inflammatory monocytes are key early responders to infection that contribute to pathogen-host interactions in diverse ways. Here, we report that the murine cytomegalovirus-encoded CC chemokine, MCK2, enhanced CCR2-dependent recruitment of these cells to modulate antiviral immunity, impairing virus-specific CD8(+) T cell expansion and differentiation into effector cytotoxic T lymphocytes, thus reducing the capacity to eliminate viral antigen-bearing cells and slowing viral clearance. Adoptive transfer of inflammatory monocytes into Ccr2(-/-)Ccl2(-/-) mice impaired virus antigen-specific clearance. Cytomegalovirus therefore enhances a natural CCR2-dependent immune regulatory network to modulate adaptive immunity via nitric oxide production, reminiscent of the monocytic subtype of myeloid-derived suppressor cells primarily implicated in cancer immunomodulation.

BACKGROUND

The chemokine (C-C motif) ligand 2 (CCL2) is a monocyte chemoattractant protein that mediates macrophage recruitment and migration during peripheral and central nervous system (CNS) inflammation.

METHODS

To determine the impact of CCL2 in inflammation in vivo and to elucidate the CCL2-induced polarization of activated brain microglia, we delivered CCL2 into the brains of wild-type mice via recombinant adeno-associated virus serotype 9 (rAAV-9) driven by the chicken β-actin promoter. We measured microglial activation using histological and chemical measurement and recruitment of monocytes using histology and flow cytometry.

RESULTS

The overexpression of CCL2 in the CNS induced significant activation of brain resident microglia. CD45 and major histocompatibility complex class II immunoreactivity significantly increased at the sites of CCL2 administration. Histological characterization of the microglial phenotype revealed the elevation of "classically activated" microglial markers, such as calgranulin B and IL-1β, as well as markers associated with "alternative activation" of microglia, including YM1 and arginase 1. The protein expression profile in the hippocampus demonstrated markedly increased levels of IL-6, GM-CSF and eotaxin (CCL-11) in response to CCL2, but no changes in the levels of other cytokines, including TNF-α and IFN-γ. Moreover, real-time PCR analysis confirmed increases in mRNA levels of gene transcripts associated with neuroinflammation following CCL2 overexpression. Finally, we investigated the chemotactic properties of CCL2 in vivo by performing adoptive transfer of bone marrow-derived cells (BMDCs) isolated from donor mice that ubiquitously expressed green fluorescent protein. Flow cytometry and histological analyses indicated that BMDCs extravasated into brain parenchyma and colabeled with microglial markers.

CONCLUSIONS

Taken together, our results suggest that CCL2 strongly activates resident microglia in the brain. Both pro- and anti-inflammatory activation of microglia were prominent, with no bias toward the M1 or M2 phenotype in the activated cells. As expected, CCL2 overexpression actively recruited circulating monocytes into the CNS. Thus, CCL2 expression in mouse brain induces microglial activation and represents an efficient method for recruitment of peripheral macrophages.

OBJECTIVE

Biomarkers of progression of interstitial lung disease (ILD) are needed to allow early therapeutic intervention in patients with scleroderma-associated disease (SSc-ILD).

METHODS

A panel of 8 serum cytokines [interleukin 6 (IL-6), IL-8, IL-10, CCL2, CXCL10, vascular endothelial growth factor, fibroblast growth factor 2, and CX3CL1] was assessed by Luminex bead technology in exploratory cohorts of 74 patients with SSc and 58 patients with idiopathic pulmonary fibrosis (IPF). Mortality and significant lung function decline [forced vital capacity (FVC) ≥ 10%; DLCO ≥ 15%] from date of serum collection were evaluated by proportional hazards analysis. Based on these findings, the prognostic value of serum IL-6, evaluated by ELISA, was assessed in a larger test cohort of 212 patients with SSc-ILD.

RESULTS

In the exploratory cohort, only serum IL-6 was an independent predictor of DLCO decline in both IPF and SSc-ILD. The IL-6 threshold level most predictive of DLCO decline within a year was 7.67 pg/ml. In the larger test cohort, serum IL-6>> 7.67 pg/ml was predictive of decline in FVC (HR 2.58 ± 0.98, p = 0.01) and in DLCO (HR 3.2 ± 1.7, p = 0.02) within the first year, and predictive of death within the first 30 months (HR 2.69 ± 0.96, p = 0.005). When stratified according to severity (FVC < 70%), serum IL-6>> 7.67 pg/ml was predictive of functional decline or death within the first year in patients with milder disease (OR 3.1, 95% CI 1.4-7.2, p = 0.007), but not in those with severe ILD.

CONCLUSIONS

In SSc-ILD, serum IL-6 levels appear to be predictive of early disease progression in patients with mild ILD, and could be used to target treatment in this group, if confirmed by prospective studies.

Herpes simplex virus type 1 (HSV-1) is the leading cause of corneal blindness in the developed world due to reactivation of infectious virus and the subsequent immune response. The innate response that facilitates viral control in the cornea is currently unknown. In the present study using a mouse chimera model, we found that a bone marrow component is crucial in inhibiting viral replication and identified inflammatory monocytes (F4/80(+) Gr1(+)) as the responsible cell. CCL2 was critical for recruiting inflammatory monocytes, and a loss of this chemokine in CCL2(-/-) mice resulted in a loss of viral containment and inflammatory monocyte recruitment. To confirm these results, clodronate depletion of inflammatory monocytes resulted in elevated viral titers. Furthermore, siRNA targeting the innate sensor p204/IFI-16 resulted in a loss of CCL2 production. In conclusion, CCL2 expression driven by IFI-16 recognition of HSV-1 facilitates the recruitment of inflammatory monocytes into the cornea proper to control viral replication.

Chondrosarcoma is a type of highly malignant tumor with a potent capacity to invade locally and cause distant metastasis. Chondrosarcoma shows a predilection for metastasis to the lungs. Chemokine ligand 2 (CCL2), also known as monocyte chemoattractant protein-1 (MCP-1), belongs to the CC chemokine family that is associated with the disease status and outcomes of cancers. However, the effect of CCL2 on migration activity in human chondrosarcoma cells is mostly unknown. Here we found that CCL2 increased the migration and expression of matrix metalloproteinase (MMP)-9 in human chondrosarcoma cells. CCL2-mediated migration and MMP-9 up-regulation were attenuated by CCR2, Ras, Raf-1, and MEK inhibitor. Activation of the Ras, Raf-1, MEK, ERK, and NF-κB signaling pathway after CCL2 treatment was demonstrated, and CCL2-induced expression of MMP-9 and migration activity were inhibited by the specific inhibitor, and mutant of Ras, Raf-1, MEK, ERK, and NF-κB cascades. Taken together, our results indicated that CCL2 enhances the migration of chondrosarcoma cells by increasing MMP-9 expression through the CCR2 receptor, Ras, Raf-1, MEK, ERK, and NF-κB signal transduction pathway.

OBJECTIVE

While various monocyte chemokine systems are increased in expression in osteoarthritis (OA), the hierarchy of chemokines and chemokine receptors in mediating monocyte/macrophage recruitment to the OA joint remains poorly defined. Here, we investigated the relative contributions of the CCL2/CCR2 versus CCL5/CCR5 chemokine axes in OA pathogenesis.

METHODS

Ccl2-, Ccr2-, Ccl5- and Ccr5-deficient and control mice were subjected to destabilisation of medial meniscus surgery to induce OA. The pharmacological utility of blocking CCL2/CCR2 signalling in mouse OA was investigated using bindarit, a CCL2 synthesis inhibitor, and RS-504393, a CCR2 antagonist. Levels of monocyte chemoattractants in synovial tissues and fluids from patients with joint injuries without OA and those with established OA were investigated using a combination of microarray analyses, multiplexed cytokine assays and immunostains.

RESULTS

Mice lacking CCL2 or CCR2, but not CCL5 or CCR5, were protected against OA with a concomitant reduction in local monocyte/macrophage numbers in their joints. In synovial fluids from patients with OA, levels of CCR2 ligands (CCL2, CCL7 and CCL8) but not CCR5 ligands (CCL3, CCL4 and CCL5) were elevated. We found that CCR2+ cells are abundant in human OA synovium and that CCR2+ macrophages line, invade and are associated with the erosion of OA cartilage. Further, blockade of CCL2/CCR2 signalling markedly attenuated macrophage accumulation, synovitis and cartilage damage in mouse OA.

CONCLUSIONS

Our findings demonstrate that monocytes recruited via CCL2/CCR2, rather than by CCL5/CCR5, propagate inflammation and tissue damage in OA. Selective targeting of the CCL2/CCR2 system represents a promising therapeutic approach for OA.

Valpha24-invariant natural killer T (NKT) cells are potentially important for antitumor immunity. We and others have previously demonstrated positive associations between NKT cell presence in primary tumors and long-term survival in distinct human cancers. However, the mechanism by which aggressive tumors avoid infiltration with NKT and other T cells remains poorly understood. Here, we report that the v-myc myelocytomatosis viral related oncogene, neuroblastoma derived (MYCN), the hallmark of aggressive neuroblastoma, repressed expression of monocyte chemoattractant protein-1/CC chemokine ligand 2 (MCP-1/CCL2), a chemokine required for NKT cell chemoattraction. MYCN knockdown in MYCN-amplified neuroblastoma cell lines restored CCL2 production and NKT cell chemoattraction. Unlike other oncogenes, MYCN repressed chemokine expression in a STAT3-independent manner, requiring an E-box element in the CCL2 promoter to mediate transcriptional repression. MYCN overexpression in neuroblastoma xenografts in NOD/SCID mice severely inhibited their ability to attract human NKT cells, T cells, and monocytes. Patients with MYCN-amplified neuroblastoma metastatic to bone marrow had 4-fold fewer NKT cells in their bone marrow than did their nonamplified counterparts, indicating that the MYCN-mediated immune escape mechanism, which we believe to be novel, is operative in metastatic cancer and should be considered in tumor immunobiology and for the development of new therapeutic strategies.

Macrophage migration inhibitory factor (MIF) promotes leukocyte recruitment to sites of inflammation. However, whether this stems from a direct effect on leukocyte migration is unknown. Furthermore, the role of the MIF-binding protein CD74 in this response has not been investigated. Therefore, the aim of this study was to examine the contributions of MIF and CD74 to chemokine-induced macrophage recruitment. Intravital microscopy studies demonstrated that CCL2-induced leukocyte adhesion and transmigration were reduced in MIF(-/-) and CD74(-/-) mice. MIF(-/-) and CD74(-/-) macrophages also exhibited reduced chemotaxis in vitro, although CD74(-/-) macrophages showed increased chemokinesis. Reduced CCL2-induced migration was associated with attenuated MAPK phosphorylation, RhoA GTPase activity, and actin polymerization in MIF(-/-) and CD74(-/-) macrophages. Furthermore, in MIF(-/-) macrophages, MAPK phosphatase-1 was expressed at elevated levels, providing a potential mechanism for the reduction in MAPK phosphorylation in MIF-deficient cells. No increase in MAPK phosphatase-1 expression was observed in CD74(-/-) macrophages. In in vivo experiments assessing the link between MIF and CD74, combined administration of MIF and CCL2 increased leukocyte adhesion in both MIF(-/-) and CD74(-/-) mice, showing that CD74 was not required for this MIF-induced response. Additionally, although leukocyte recruitment induced by administration of MIF alone was reduced in CD74(-/-) mice, consistent with a role for CD74 in leukocyte recruitment induced by MIF, MIF-treated CD74(-/-) mice displayed residual leukocyte recruitment. These data demonstrate that MIF and CD74 play previously unappreciated roles in CCL2-induced macrophage adhesion and migration, and they indicate that MIF and CD74 mediate this effect via both common and independent mechanisms.

OBJECTIVE

To examine whether chemokine antagonists inhibit the initiation and progression of lupus nephritis in MRL/lpr mice.

METHODS

NH(2)-terminal-truncated monocyte chemoattractant protein 1 (MCP-1)/CCL2 or thymus and activation-regulated chemokine (TARC)/CCL17 analogs were inserted into the pCXN2 expression vector and transfected into a nonmetastatic fibroblastoid cell line, MRL/N-1, established from an MRL/gld mouse.

RESULTS

MCP-1 antagonist- or TARC antagonist-transfected MRL/N-1 cells were injected subcutaneously into MRL/lpr mice ages 7 weeks (before the onset of lupus nephritis) and 12 weeks (at the early stage of the disease). After 8 weeks, mice bearing the MCP-1 antagonist showed markedly diminished infiltration of macrophages and T cells, glomerular hypercellularity, glomerulosclerosis, crescent formation, and vasculitis compared with control mice. This seemed to be due to decreased production of interferon-gamma and interleukin-2 in the kidney. In contrast, there was no significant difference in renal damage between mice bearing TARC antagonist and control mice.

CONCLUSIONS

We established a new system using MRL/N-1 cells that allows long-term observation of the effects of chemokine antagonists on lupus nephritis in MRL/lpr mice. We also showed that the MCP-1 antagonist ameliorated the initiation and progression of lupus nephritis and of renal vasculitis, which might provide a new approach to the treatment of the disease.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is known for specifically killing cancer cells, whereas in resistant cancers, TRAIL/TRAIL-R can promote metastasis via Rac1 and PI3K. It remains unknown, however, whether and to what extent TRAIL/TRAIL-R signaling in cancer cells can affect the immune microenvironment. Here we show that TRAIL-triggered cytokine secretion from TRAIL-resistant cancer cells is FADD dependent and identify the TRAIL-induced secretome to drive monocyte polarization to myeloid-derived suppressor cells (MDSCs) and M2-like macrophages. TRAIL-R suppression in tumor cells impaired CCL2 production and diminished both lung MDSC presence and tumor growth. In accordance, the receptor of CCL2, CCR2, is required to facilitate increased MDSC presence and tumor growth. Finally, TRAIL and CCL2 are co-regulated with MDSC/M2 markers in lung adenocarcinoma patients. Collectively, endogenous TRAIL/TRAIL-R-mediated CCL2 secretion promotes accumulation of tumor-supportive immune cells in the cancer microenvironment, thereby revealing a tumor-supportive immune-modulatory role of the TRAIL/TRAIL-R system in cancer biology.

During malaria infection, high levels of proinflammatory molecules (e.g., cytokines, chemokines) correlate with disease severity. Even if their role as activators of the host immune response has been studied, the direct contribution of hemozoin (HZ), a parasite metabolite, to such a strong induction is not fully understood. Previous in vitro studies demonstrated that both Plasmodium falciparum HZ and synthetic HZ (sHZ), beta-hematin, induce macrophage/monocyte chemokine and proinflammatory cytokine secretion. In the present study, we investigated the proinflammatory properties of sHZ in vivo. To this end, increasing doses of sHZ were injected either i.v. or into an air pouch generated on the dorsum of BALB/c mice over a 24-h period. Our results showed that sHZ is a strong modulator of leukocyte recruitment and more specifically of neutrophil and monocyte populations. In addition, evaluation of chemokine and cytokine mRNA and protein expression revealed that sHZ induces the expression of chemokines, macrophage-inflammatory protein (MIP)-1alpha/CCL3, MIP-1beta/CCL4, MIP-2/CXCL2, and monocyte chemoattractant protein-1/CCL2; chemokine receptors, CCR1, CCR2, CCR5, CXCR2, and CXCR4; cytokines, IL-1beta and IL-6; and myeloid-related proteins, S100A8, S100A9, and S100A8/A9, in the air pouch exudates. Of interest, chemokine and cytokine mRNA up-regulation were also detected in the liver of i.v. sHZ-injected mice. In conclusion, our study demonstrates that sHZ is a potent proinflammatory agent in vivo, which could contribute to the immunopathology related to malaria.

In areas where schistosomiasis is endemic, a negative correlation is observed between atopy and helminth infection, associated with a low prevalence of asthma. We investigated whether Schistosoma mansoni infection or injection of parasite eggs can modulate airway allergic inflammation in mice, examining the mechanisms of such regulation. We infected BALB/c mice with 30 S. mansoni cercariae or intraperitoneally injected 2,500 schistosome eggs, and experimental asthma was induced by ovalbumin (OVA). The number of eosinophils in bronchoalveolar lavage fluid was higher in the asthmatic group than in asthmatic mice infected with S. mansoni or treated with parasite eggs. Reduced Th2 cytokine production, characterized by lower levels of interleukin-4 (IL-4), IL-5, and immunoglobulin E, was observed in both S. mansoni-treated groups compared to the asthmatic group. There was a reduction in the number of inflammatory cells in lungs of S. mansoni-infected and egg-treated mice, demonstrating that both S. mansoni infection and the egg treatment modulated the lung inflammatory response to OVA. Only allergic animals that were treated with parasite eggs had increased numbers of CD4(+) CD25(+) Foxp3(+) T cells and increased levels of IL-10 and decreased production of CCL2, CCL3, and CCL5 in the lungs compared to the asthmatic group. Neutralization of IL-10 receptor or depletion of CD25(+) T cells in vivo confirmed the critical role of CD4(+) CD25(+) Foxp3(+) regulatory T cells in experimental asthma modulation independent of IL-10.

The causes of age-related macular degeneration (AMD) are not well understood. Due to demographic shifts in the industrialized world a growing number of people will develop AMD in the coming decades. To develop treatments it is essential to characterize the disease's pathogenic process. Over the past few years, numerous studies have focused on the role of chemotactic cytokines, also known as chemokines. Certain chemokines, such as CCL2 and CX3CL1, appear to be crucial in subretinal microglia and macrophage accumulation observed in AMD, and participate in the development of retinal degeneration as well as in choroidal neovascularization. This paper reviews the possible implications of CCL2 and CX3CL1 signaling in AMD. Expression patterns, single nucleotide polymorphisms (SNPs) association studies, chemokine and chemokine receptor knockout models are discussed. Future AMD treatments could target chemokines and/or their receptors.

The therapeutic efficacy of anthracyclines relies, at least partially, on the induction of a dendritic cell- and T-lymphocyte-dependent anticancer immune response. Here, we show that anthracycline-based chemotherapy promotes the recruitment of functional CD11b(+)CD11c(+)Ly6C(high)Ly6G(-)MHCII(+) dendritic cell-like antigen-presenting cells (APC) into the tumor bed, but not into lymphoid organs. Accordingly, draining lymph nodes turned out to be dispensable for the proliferation of tumor antigen-specific T cells within neoplastic lesions as induced by anthracyclines. In addition, we found that tumors treated with anthracyclines manifest increased expression levels of the chemokine Ccl2. Such a response is important as neoplasms growing in Ccl2(-/-) mice failed to accumulate dendritic cell-like APCs in response to chemotherapy. Moreover, cancers developing in mice lacking Ccl2 or its receptor (Ccr2) exhibited suboptimal therapeutic responses to anthracycline-based chemotherapy. Altogether, our results underscore the importance of the CCL2/CCR2 signaling axis for therapeutic anticancer immune responses as elicited by immunogenic chemotherapy.

OBJECTIVE

Chronic inflammation in type 2 diabetes is proposed to affect islets as well as insulin target organs. However, the nature of islet inflammation and its effects on islet function in type 2 diabetes remain unclear. Moreover, the immune cell profiles of human islets in healthy and type 2 diabetic conditions are undefined. We aimed to investigate the correlation between proinflammatory cytokine expression, islet leucocyte composition and insulin secretion in type 2 diabetic human islets.

METHODS

Human islets from organ donors with or without type 2 diabetes were studied. First and second phases of glucose-stimulated insulin secretion were determined by perifusion. The expression of inflammatory markers was obtained by quantitative PCR. Immune cells within human islets were analysed by FACS.

RESULTS

Type 2 diabetic islets, especially those without first-phase insulin secretion, displayed higher CCL2 and TNFa expression than healthy islets. CD45(+) leucocytes were elevated in type 2 diabetic islets, to a greater extent in moderately functional type 2 diabetic islets compared with poorly functional ones, and corresponded with elevated ALOX12 but not with CCL2 or TNFa expression. T and B lymphocytes and CD11c(+) cells were detectable within both non-diabetic and type 2 diabetic islet leucocytes. Importantly, the proportion of B cells was significantly elevated within type 2 diabetic islets.

CONCLUSIONS

Elevated total islet leucocyte content and proinflammatory mediators correlated with islet dysfunction, suggesting that heterogeneous insulitis occurs during the development of islet dysfunction in type 2 diabetes. In addition, the altered B cell content highlights a potential role for the adaptive immune response in islet dysfunction.

Immune and inflammatory responses to SARS-CoV-2 contribute to disease severity of COVID-19. However, the utility of specific immune-based biomarkers to predict clinical outcome remains elusive. Here, we analyzed levels of 66 soluble biomarkers in 175 Italian patients with COVID-19 ranging from mild/moderate to critical severity, and assessed type-I IFN-, type-II IFN-, and NF-κB-dependent whole blood transcriptional signatures. A broad inflammatory signature was observed, implicating activation of various immune and non-hematopoietic cell subsets. Discordance between IFN-α2a protein and IFNA2 transcript levels in blood suggests that type-I IFNs during COVID-19 may be primarily produced by tissue-resident cells. Multivariable analysis of patients' first samples revealed 12 biomarkers (CCL2, IL-15, sST2, NGAL, sTNFRSF1A, ferritin, IL-6, S100A9, MMP-9, IL-2, sVEGFR1, IL-10) that when increased were independently associated with mortality. Multivariate analyses of longitudinal biomarker trajectories identified 8 of the aforementioned biomarkers (IL-15, IL-2, NGAL, CCL2, MMP-9, sTNFRSF1A, sST2, IL-10) and two additional biomarkers (lactoferrin, CXCL9) that were significantly associated with mortality when increased, while IL-1α was associated with mortality when decreased. Among these, sST2, sTNFRSF1A, IL-10, and IL-15 were consistently higher throughout the hospitalization in patients who died versus those who recovered, suggesting that these biomarkers may provide an early warning of eventual disease outcome.

Keywords: COVID-19; Chemokines; Cytokines; Immunology.

BACKGROUND

Chemokines are emerging as important mediators of CNS inflammation capable of activating leukocyte integrins and directing the migration of leukocyte subsets to sites of antigenic challenge. In this study we investigated the expression, release and binding of CCL2 (MCP-1) and CCL3 (MIP-1alpha) in an in vitro model of the human blood-brain barrier.

METHODS

The kinetics of expression and cytokine upregulation and release of the beta-chemokines CCL2 and CCL3 were studied by immunocytochemistry and enzyme-linked immunosorbent assay in primary cultures of human brain microvessel endothelial cells (HBMEC). In addition, the differential binding of these chemokines to the basal and apical endothelial cell surfaces was assessed by immunoelectron microscopy.

RESULTS

Untreated HBMEC synthesize and release low levels of CCL2. CCL3 is minimally expressed, but not released by resting HBMEC. Treatment with TNF-alpha, IL-1beta, LPS and a combination of TNF-alpha and IFN-gamma, but not IFN-gamma alone, significantly upregulated the expression and release of both chemokines in a time-dependent manner. The released CCL2 and CCL3 bound to the apical and basal endothelial surfaces, respectively. This distribution was reversed in cytokine-activated HBMEC resulting in a predominantly basal localization of CCL2 and apical distribution of CCL3.

CONCLUSIONS

Since cerebral endothelial cells are the first resident CNS cells to contact circulating leukocytes, expression, release and presentation of CCL2 and CCL3 on cerebral endothelium suggests an important role for these chemokines in regulating the trafficking of inflammatory cells across the BBB in CNS inflammation.