Targeting the leukocyte activation cascade: getting to the site of inflammation using microfabricated assays

This paper describes the use of microfabricated devices to study the leukocyte activation cascade (LAC). The devices consist of microchannels fabricated in polydimethylsiloxane using soft lithography. Microfluidics, used to generate physiologically relevant levels of shear flow, was achieved by the simple attachment of a syringe pump. Microchannel surfaces were modified by self-assembled monolayer (SAM) chemistries. The devices were adapted to standard 96-well tissue culture format with microchannels that could accommodate either a monolayer of endothelial cells or a SAM with immobilized chemokines. Chemotaxis was performed using linear gradients of chemokine set in a 3D matrix. Using this approach, we demonstrated robust chemotaxis of primary human leukocytes (PHLs) in response to a gradient of the chemokine CCL2. Rolling and adhesion assays performed under shear flow demonstrated that leukocyte recruitment to the substrate was highly sensitive to both biological and physical forces. CCL2 and CXCL12 treatment of PHLs dose dependently increased activation and adhesion. These actions could be inhibited by the use of peptide or small molecule antagonists. These devices provide a robust platform to perform LAC assays under in vivo-like conditions.

Cytotoxic T lymphocyte trafficking and survival in an augmented fibrin matrix carrier

Cell-based therapies have intriguing potential for the treatment of a variety of neurological disorders. One such example is genetically engineered cytotoxic T lymphocytes (CTLs) that are being investigated in brain tumor clinical trials. The development of methods for CTL delivery is critical to their use in the laboratory and clinical setting. In our study, we determined whether CTLs can migrate through fibrin matrices and if their migration, survival, and function could be modulated by adding chemokines to the matrix. Our results indicated that CTLs can freely migrate through fibrin matrices. As expected, the addition of the monocyte chemotactic protein-1 (MCP-1), also known as chemokine C-C motif ligand 2 (CCL2), to the surrounding media increased egress of the CTLs out of the fibrin clot. Interleukin (IL) -2 and/or IL-15 embedded in the matrix enhanced T cell survival and further promoted T cell migration. The interleukin-13 receptor alpha 2 specific (IL-13R alpha2) T cells that traveled out of the fibrin clot retained the capacity to kill U251 glioma cells. In summary, CTLs can survive and migrate robustly in fibrin matrices. These processes can be influenced by modification of matrix constituents. We conclude that fibrin matrices may be suitable T cell carriers and can be used to facilitate understanding of T cell interaction with the surrounding microenvironment.

Contractile activity of human skeletal muscle cells prevents insulin resistance by inhibiting pro-inflammatory signalling pathways

AIMS/HYPOTHESIS

Obesity is closely associated with muscle insulin resistance and is a major risk factor for the pathogenesis of type 2 diabetes. Regular physical activity not only prevents obesity, but also considerably improves insulin sensitivity and skeletal muscle metabolism. We sought to establish and characterise an in vitro model of human skeletal muscle contraction, with a view to directly studying the signalling pathways and mechanisms that are involved in the beneficial effects of muscle activity.

METHODS

Contracting human skeletal muscle cell cultures were established by applying electrical pulse stimulation. To induce insulin resistance, skeletal muscle cells were incubated with human adipocyte-derived conditioned medium, monocyte chemotactic protein (MCP)-1 and chemerin.

RESULTS

Similarly to in exercising skeletal muscle in vivo, electrical pulse stimulation induced contractile activity in human skeletal muscle cells, combined with the formation of sarcomeres, activation of AMP-activated protein kinase (AMPK) and increased IL-6 secretion. Insulin-stimulated glucose uptake was substantially elevated in contracting cells compared with control. The incubation of skeletal muscle cells with adipocyte-conditioned media, chemerin and MCP-1 significantly reduced the insulin-stimulated phosphorylation of Akt. This effect was abrogated by concomitant pulse stimulation of the cells. Additionally, pro-inflammatory signalling by adipocyte-derived factors was completely prevented by electrical pulse stimulation of the myotubes.

CONCLUSIONS/INTERPRETATION

We showed that the effects of electrical pulse stimulation on skeletal muscle cells were similar to the effect of exercise on skeletal muscle in vivo in terms of enhanced AMPK activation and IL-6 secretion. In our model, muscle contractile activity eliminates insulin resistance by blocking pro-inflammatory signalling pathways. This novel model therefore provides a unique tool for investigating the molecular mechanisms that mediate the beneficial effects of muscle contraction.

Down-modulation of TNFSF15 in ovarian cancer by VEGF and MCP-1 is a pre-requisite for tumor neovascularization

Persistent inflammation and neovascularization are critical to cancer development. In addition to upregulation of positive control mechanisms such as overexpression of angiogenic and inflammatory factors in the cancer microenvironment, loss of otherwise normally functioning negative control mechanisms is likely to be an important attribute. Insights into the down-modulation of such negative control mechanisms remain largely unclear, however. We show here that tumor necrosis factor superfamily-15 (TNFSF15), an endogenous inhibitor of neovascularization, is a critical component of the negative control mechanism that operates in normal ovary but is missing in ovarian cancer. We show in clinical settings that TNFSF15 is present prominently in the vasculature of normal ovary but diminishes in ovarian cancer as the disease progresses. Vascular endothelial growth factor (VEGF) produced by cancer cells and monocyte chemotactic protein-1 (MCP-1) produced mainly by tumor-infiltrating macrophages and regulatory T cells effectively inhibits TNFSF15 production by endothelial cells in vitro. Using a mouse syngeneic tumor model, we demonstrate that silencing TNFSF15 by topical shRNA treatments prior to and following mouse ovarian cancer ID8 cell inoculation greatly facilitates angiogenesis and tumor growth, whereas systemic application of recombinant TNFSF15 inhibits angiogenesis and tumor growth. Our findings indicate that downregulation of TNFSF15 by cancer cells and tumor infiltrating macrophages and lymphocytes is a pre-requisite for tumor neovascularization.

Tumour tissue microenvironment can inhibit dendritic cell maturation in colorectal cancer

Inflammatory mediators in the tumour microenvironment promote tumour growth, vascular development and enable evasion of anti-tumour immune responses, by disabling infiltrating dendritic cells. However, the constituents of the tumour microenvironment that directly influence dendritic cell maturation and function are not well characterised. Our aim was to identify tumour-associated inflammatory mediators which influence the function of dendritic cells. Tumour conditioned media obtained from cultured colorectal tumour explant tissue contained high levels of the chemokines CCL2, CXCL1, CXCL5 in addition to VEGF. Pre-treatment of monocyte derived dendritic cells with this tumour conditioned media inhibited the up-regulation of CD86, CD83, CD54 and HLA-DR in response to LPS, enhancing IL-10 while reducing IL-12p70 secretion. We examined if specific individual components of the tumour conditioned media (CCL2, CXCL1, CXCL5) could modulate dendritic cell maturation or cytokine secretion in response to LPS. VEGF was also assessed as it has a suppressive effect on dendritic cell maturation. Pre-treatment of immature dendritic cells with VEGF inhibited LPS induced upregulation of CD80 and CD54, while CXCL1 inhibited HLA-DR. Interestingly, treatment of dendritic cells with CCL2, CXCL1, CXCL5 or VEGF significantly suppressed their ability to secrete IL-12p70 in response to LPS. In addition, dendritic cells treated with a combination of CXCL1 and VEGF secreted less IL-12p70 in response to LPS compared to pre-treatment with either cytokine alone. In conclusion, tumour conditioned media strongly influences dendritic cell maturation and function.

Host-derived MCP-1 and MIP-1α regulate protective anti-tumor immunity to localized and metastatic B16 melanoma

Leukocytic infiltration into malignant melanoma lesions is tightly regulated by chemokines. To assess the role of the CC chemokines monocyte chemotactic protein-1 (MCP-1/chemokine ligand 2) and macrophage inflammatory protein-1α (MIP-1α/chemokine ligand 3) in this process, s.c. primary and metastatic B16 F10 melanoma tumor growth levels were examined in mice lacking MCP-1 or MIP-1α. Primary s.c. B16 F10 melanoma growth was augmented by loss of MCP-1 or MIP-1α. Similarly, lung metastasis was enhanced by the deficiency of MCP-1 or MIP-1α. Enhanced tumor outgrowth was associated with decreased percentages of infiltrating CD4(+) T cells, CD8(+) T cells, and natural killer cells. In the absence of MCP-1 or MIP-1α, melanoma outgrowth was correlated with reduced local expression of interferon-γ, IL-6, tumor necrosis factor-α, and transforming growth factor-β. Among these cytokines, reduced expression levels of interferon-γ and tumor necrosis factor-α on leukocytes from the spleen were associated with the development of lung metastasis in chemokine-deficient mice. The local s.c. administration of these four cytokines significantly augmented another chemokine's expression and suppressed primary melanoma growth in mice deficient for MCP-1 or MIP-1α. The s.c. injection of MCP-1 or MIP-1α significantly inhibited the primary tumor growth in wild-type mice. These results indicate that host-derived MCP-1 and MIP-1α regulate protective anti-tumor immunity to B16 F10 melanoma by promoting lymphocyte infiltration into the tumor and subsequent cytokine production.

Intracerebral administration of recombinant rabies virus expressing GM-CSF prevents the development of rabies after infection with street virus

Recently it was found that prior immunization with recombinant rabies virus (RABV) expressing granulocyte-macrophage colony-stimulating factor (GM-CSF) (LBNSE-GM-CSF) resulted in high innate/adaptive immune responses and protection against challenge with virulent RABV (Wen et al., JVI, 2011). In this study, the ability of LBNSE-GM-CSF to prevent animals from developing rabies was investigated in mice after infection with lethal doses of street RABV. It was found that intracerebral administration of LBNSE-GM-CSF protected more mice from developing rabies than sham-treated mice as late as day 5 after infection with street RABV. Intracerebral administration of LBNSE-GM-CSF resulted in significantly higher levels of chemokine/cytokine expression and more infiltration of inflammatory and immune cells into the central nervous system (CNS) than sham-administration or administration with UV-inactivated LBNSE-GM-CSF. Enhancement of blood-brain barrier (BBB) permeability and increases in virus neutralizing antibodies (VNA) were also observed in mice treated with LBNSE-GM-CSF. On the other hand, intracerebral administration with UV-inactivated LBNSE-GM-CSF did not increase protection despite the fact that VNA were induced in the periphery. However, intracerebral administration with chemoattractant protein-1 (MCP-1, also termed CCL2) increased significantly the protective efficacy of UV-inactivated LBNSE-GM-CSF. Together these studies confirm that direct administration of LBNSE-GM-CSF can enhance the innate and adaptive immunity as well as the BBB permeability, thus allowing infiltration of inflammatory cells and other immune effectors enter into the CNS to clear the virus and prevent the development of rabies.

Chemokines and inflammatory mediators interact to regulate adult murine neural precursor cell proliferation, survival and differentiation

Adult neural precursor cells (NPCs) respond to injury or disease of the CNS by migrating to the site of damage or differentiating locally to replace lost cells. Factors that mediate this injury induced NPC response include chemokines and pro-inflammatory cytokines, such as tumor necrosis factor-α (TNFα) and interferon-γ (IFNγ), which we have shown previously promotes neuronal differentiation. RT-PCR was used to compare expression of chemokines and their receptors in normal adult mouse brain and in cultured NPCs in response to IFNγ and TNFα. Basal expression of many chemokines and their receptors was found in adult brain, predominantly in neurogenic regions, with OB≫SVZ>hippocampus and little or no expression in non-neurogenic regions, such as cortex. Treatment of SVZ-derived NPCs with IFNγ and TNFα (alone and in combination) resulted in significant upregulation of expression of specific chemokines, with CXCL1, CXCL9 and CCL2 most highly upregulated and CCL19 downregulated. Unlike IFNγ, chemokine treatment of NPCs in vitro had little or no effect on survival, proliferation or migration. Neuronal differentiation was promoted by CXCL9, CCL2 and CCL21, while astrocyte and total oligodendrocyte differentiation was not affected. However, IFNγ, CXCL1, CXCL9 and CCL2 promoted oligodendrocyte maturation. Therefore, not only do NPCs express chemokine receptors, they also produce several chemokines, particularly in response to inflammatory mediators. This suggests that autocrine or paracrine production of specific chemokines by NPCs in response to inflammatory mediators may regulate differentiation into mature neural cell types and may alter NPC responsiveness to CNS injury or disease.

Upregulation of pancreatic derived factor (FAM3B) expression in pancreatic β-cells by MCP-1 (CCL2)

Pancreatic derived factor (PANDER, FAM3B) is a peptide mainly synthesized and secreted by pancreatic β-cells. PANDER is proposed to be involved in regulation of β-cell function under physiological conditions and impairment of β-cell function under pathological conditions. MCP-1 (CCL2) is expressed by normal pancreatic islets and has been implicated in inflammation related pancreatic disorders. We examined the effect of MCP-1 on PANDER expression by using murine pancreatic β-cell line MIN6 and pancreatic islets. We found that MCP-1 induced PANDER mRNA transcription and protein synthesis in MIN6 cells and islets. By using calcium chelator (EGTA); inhibitors for PKC (Go6976), MEK1/2 (PD98059) or c-Jun-N-terminal kinase (JNK) (SP600125); c-Jun dominant-negative construct; PANDER promoter luciferase constructs; and islets isolated from Fos knockout mice; we demonstrated that MCP-1 induced PANDER gene expression in β-cells through Ca(2+)-ERK1/2-AP-1 and PKC-JNK-AP-1 signaling pathways. Our findings suggest a new link between the endocrine and immune systems and provide useful information for further investigating the physiological functions of PANDER and its involvement in inflammation-related pancreatic disorders.

Peroxisome proliferator-activated receptor-γ agonist rosiglitazone prevents albuminuria but not glomerulosclerosis in experimental diabetes

BACKGROUNDS/AIMS

Renal inflammation and nephrin downregulation contribute to albuminuria in diabetes. We studied, in streptozotocin-induced diabetic rats, the effect of rosiglitazone (RSG), a peroxisome proliferator-activated receptor-γ agonist, on renal macrophage infiltration, MCP1, and nephrin expression in relation to albuminuria.

METHODS

We investigated control and diabetic rats treated or untreated with RSG. Animals were sacrificed at 1, 3, and 9 months. Renal MCP1 and nephrin expression were studied by immunoblotting, renal macrophage infiltration by immunohistochemistry, and albuminuria by ELISA. Electron microscopy was used to assess glomerular ultrastructural morphology. In vitro experiments were conducted in isolated cultured rat glomeruli.

RESULTS

Glycaemic control was similar in diabetic rats treated and untreated with RSG, and blood pressure was comparable in all groups. RSG prevented diabetes-induced albuminuria at 9 months, and renal macrophage infiltration and MCP1 upregulation at 3 and 9 months. Diabetes-mediated nephrin downregulation was abolished by RSG. Diabetes-induced glomerulosclerosis, glomerular basement membrane thickening, and foot process fusion were not affected by RSG. In isolated glomeruli, MCP1 directly induced nephrin downregulation and this was prevented by RSG. RSG had no effect on nephrin expression.

CONCLUSION

RSG prevents albuminuria and nephrin downregulation in experimental diabetes independently of glycaemic and blood pressure control. This effect likely occurs via correction of diabetes-induced inflammatory processes.

[Experimental study on effect of monocyte chemoattractant protein 1 on migration of induced and differentiated mouse bone marrow mesenchymal stem cells in vitro]

OBJECTIVE

To investigate the effect of monocyte chemoattractant protein 1 (MCP-1) on the migration of the induced and differentiated mouse bone marrow mesenchymal stem cells (BMSCs) for raising the efficacy of intravenous transplantation of BMSCs.

METHODS

The BMSCs were cultured with the method of differential adhesion and density gradient centrifugation of C57/BL10 mice, and were identified by alkaline phosphatase Gomori modified staining after osteogenic inducing. At the 3rd passage, the BMSCs were induced to the myoblasts with 5-azacytidine (5-Aza). The chemotaxis of MCP-1 in the induced and differentiated BMSCs in vitro at concentrations of 25, 50, 100, 200, and 400 ng/mL was observed through the migration test, by counting the number of the migrated cells. The expression of the chemokine receptor 2 (CKR-2) in the induced and differentiated BMSCs was detected with the flow cytometry.

RESULTS

The cells could be cultured with the methods of differential adhesion and density gradient centrifugation and still had higher proliferative and differentiative potency; the induced cells at the 3rd passage could differentiate to the osteoblasts, confirming that the cells were BMSCs; the myogenic induced BMSCs possessed the sarcotubule structure. The number of the migrating BMSCs at MCP-1 concentrations of 25-400 ng/mL were respectively 35.066 7 +/- 6.584 2, 43.200 0 +/- 6.460 8, 44.466 7 +/- 4.823 5, 45.600 0 +/- 8.650 3, and 50.733 3 +/- 7.582 5; showing significant difference when compared with control group (28.333 3 +/- 8.917 6, P < 0.05), and presenting significant difference among 25, 50, 400 ng/mL groups compared with each other (P < 0.05). The expression of CKR-2 in the mouse BMSCs (48.0%) was significantly higher (P < 0.001) than those of blank control (0.6%) and negative control (17.0%).

CONCLUSION

The results indicate that the MCP-1 can induce the migration of mouse BMSCs by MCP-1/CKR-2 pathway.

CCL2 is induced by chemotherapy and protects prostate cancer cells from docetaxel-induced cytotoxicity

BACKGROUND

Metastatic prostate cancer is either inherently resistant to chemotherapy or rapidly acquires this phenotype after chemotherapy exposure. In this study, we identified a docetaxel-induced resistance mechanism centered on CCL2.

METHODS

We compared the gene expression profiles in individual human prostate cancer specimens before and after exposure to chemotherapy collected from previously untreated patients who participated in a clinical trial of preoperative chemotherapy. Subsequently, we used the gain- and loss-of-function approach in vitro to identify a potential mechanism underlying chemotherapy resistance.

RESULTS

Among the molecular signatures associated with treatment, several genes that regulate the inflammatory response and chemokine activity were upregulated including a significant increase in transcripts encoding the CC chemokine CCL2. Docetaxel increased CCL2 expression in prostate cancer cell lines in vitro. CCL2-specific siRNA inhibited LNCaP and LAPC4 cell proliferation and enhanced the growth inhibitory effect of low-dose docetaxel. In contrast, overexpression of CCL2 or recombinant CCL2 protein stimulated prostate cancer cell proliferation and rescued cells from docetaxel-induced cytotoxicity. This protective effect of CCL2 was associated with activation of the ERK/MAP kinase and PI3K/AKT, inhibition of docetaxel-induced Bcl2 phosphorylation at serine 70, phosphorylation of Bad, and activation of caspase-3. The addition of a PI3K/AKT inhibitor Ly294002 reversed the CCL2 protection and was additive to docetaxel-induced toxicity.

CONCLUSION

These results support a mechanism of chemotherapy resistance mediated by cellular stress responses involving the induction of CCL2 expression and suggest that inhibiting CCL2 activity could enhance therapeutic responses to taxane-based therapy.

Regulation of adiponectin secretion by adipocytes in the polycystic ovary syndrome: role of tumor necrosis factor-{alpha}

CONTEXT

Adipose tissue dysfunction associated with low-grade chronic inflammation and dysregulation of adipokine secretion might significantly contribute to the pathogenesis of polycystic ovary syndrome (PCOS).

OBJECTIVE

The objective of the study was to determine whether the effect of TNF-alpha, IL-6, monocyte chemoattractant protein-1, or coculture of adipocytes and adipose tissue macrophages (ATMs), on the secretion of adiponectin by adipocytes, differs in PCOS compared with controls.

DESIGN AND PARTICIPANTS

Primary cultures of sc adipocytes and coculture of adipocytes and ATMs from overweight and obese patients with PCOS and healthy control women were used.

MAIN OUTCOME MEASURES

Adiponectin secretion by adipocytes was measured.

RESULTS

The baseline secretion of adiponectin by isolated adipocytes did not differ between PCOS and control samples. The net change in adiponectin secretion in response to IL-6, monocyte chemoattractant protein-1, and TNF-alpha differed between PCOS (decreasing) and control (increasing) adipocytes, although the difference reached significance only for TNF-alpha (P < 0.04). Coculture of isolated adipocytes and ATMs resulted in a decrease in adiponectin secretion by PCOS (P < 0.05) but not control adipocytes, and the difference between the net change in adiponectin secretion in PCOS vs. control samples was significant (P < 0.03).

CONCLUSIONS

Our results suggest that adiponectin secretion by adipocytes in response to cytokines/chemokines and most notably in response to coculturing with ATMs differs between PCOS and control women, favoring greater suppression of adiponectin in PCOS. The mechanisms underlying these defects and the role of concurrent obesity remain to be determined.

OmpA-like protein Loa22 from Leptospira interrogans serovar Lai is cytotoxic to cultured rat renal cells and promotes inflammatory responses

Leptospirosis renal disease is one of the common clinical manifestations of leptospirosis, including acute renal failure and tubulointerstitial nephritis. Outer membrane protein A-like protein Loa22 is a lipoprotein from Leptospira interrogans and has been suggested to be a corresponding virulence factor. However, the role of Loa22 in leptospiral nephropathy is not yet understood. In the present study, we constructed a vector and artificially expressed Loa22 in Escherichia coli BL21(DE)pLysS cells. After extensive purification, along with a GST tag protein control, Loa22 protein was used to test the cytotoxicity in cultured rat proximal tubule cells (NRK52E) and examine its effects on the induction of inflammatory responses. Using morphological examination, 2,3-bis(2-methoxy-4- nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazoium hydrixide absorbance, lactate dehydrogenase assays and an analysis of apoptosis via flow cytometry, it was found that Loa22 protein mediates a direct cytotoxic effect on NRK52E cells in a dose-dependent manner. Using real-time PCR, western blotting and immunofluorescence, it was found that Loa22 protein upregulates the expression of toll-like receptor 2 (TLR2), induces nitric oxide synthase and promotes the production of nitric oxide (NO) and monocyte chemoattractant protein-1 (MCP-1) by NRK52E cells. Additionally, using a TLR2 blocking antibody, it was found that enhanced NO and MCP-1 production by NRK52E cells after Loa22 stimulation requires the activation of TLR2. Collectively, our data suggested that Loa22 is a critical virulence factor of L. interrogans and is involved in the leptospiral nephropathy through mediating direct cytotoxicity and enhancing inflammatory responses.

Effect of the monocyte chemoattractant protein-1/CC chemokine receptor 2 system on nephrin expression in streptozotocin-treated mice and human cultured podocytes

OBJECTIVE

Monocyte chemoattractant protein-1 (MCP-1), a chemokine binding to the CC chemokine receptor 2 (CCR2) and promoting monocyte infiltration, has been implicated in the pathogenesis of diabetic nephropathy. To assess the potential relevance of the MCP-1/CCR2 system in the pathogenesis of diabetic proteinuria, we studied in vitro if MCP-1 binding to the CCR2 receptor modulates nephrin expression in cultured podocytes. Moreover, we investigated in vivo if glomerular CCR2 expression is altered in kidney biopsies from patients with diabetic nephropathy and whether lack of MCP-1 affects proteinuria and expression of nephrin in experimental diabetes.

RESEARCH DESIGN AND METHODS

Expression of nephrin was assessed in human podocytes exposed to rh-MCP-1 by immunofluorescence and real-time PCR. Glomerular CCR2 expression was studied in 10 kidney sections from patients with overt nephropathy and eight control subjects by immunohistochemistry. Both wild-type and MCP-1 knockout mice were made diabetic with streptozotocin. Ten weeks after the onset of diabetes, albuminuria and expression of nephrin, synaptopodin, and zonula occludens-1 were examined by immunofluorescence and immunoblotting.

RESULTS

In human podocytes, MCP-1 binding to the CCR2 receptor induced a significant reduction in nephrin both mRNA and protein expression via a Rho-dependent mechanism. The MCP-1 receptor, CCR2, was overexpressed in the glomerular podocytes of patients with overt nephropathy. In experimental diabetes, MCP-1 was overexpressed within the glomeruli and the absence of MCP-1 reduced both albuminuria and downregulation of nephrin and synaptopodin.

CONCLUSIONS

These findings suggest that the MCP-1/CCR2 system may be relevant in the pathogenesis of proteinuria in diabetes.

Monocytes and neutrophils exhibit both distinct and common mechanisms in penetrating the vascular basement membrane in vivo

OBJECTIVE

Leukocyte migration through venular walls is a fundamental event during inflammation, but many aspects of this response, including the mechanisms associated with leukocyte migration through the vascular basement membrane (BM) in vivo, are poorly understood. Here we investigated and compared the means by which neutrophils and monocytes migrate through the venular BM. Specifically, as we have previously reported on the existence of neutrophil permissive sites (termed matrix protein low expression regions; LERs) within the venular BM, we have now investigated the role of these sites in monocyte transmigration in vivo.

METHODS AND RESULTS

Analysis of CCL2-stimulated mouse cremaster muscles by immunofluorescent staining and confocal microscopy demonstrated that both neutrophils and monocytes use LERs for penetrating venular walls, but independent and distinct mechanisms are used by the 2 cell types. Collectively, (1) neutrophil but not monocyte transmigration led to enlargement of LERs, (2) monocytes showed a greater extent of deformability in migrating through the venular BM, and (3) only extravasated neutrophils were associated with the carriage of laminin fragments.

CONCLUSIONS

The findings provide novel insights into mechanisms of leukocyte transmigration by presenting the first in vivo evidence for distinct modes used by neutrophils and monocytes in penetrating the vascular BM.

Synergy-inducing chemokines enhance CCR2 ligand activities on monocytes

The migration of monocytes to sites of inflammation is largely determined by their response to chemokines. Although the chemokine specificities and expression patterns of chemokine receptors are well defined, it is still a matter of debate how cells integrate the messages provided by different chemokines that are concomitantly produced in physiological or pathological situations in vivo. We present evidence for one regulatory mechanism of human monocyte trafficking. Monocytes can integrate stimuli provided by inflammatory chemokines in the presence of homeostatic chemokines. In particular, migration and cell responses could occur at much lower concentrations of the CCR2 agonists, in the presence of chemokines (CCL19 and CCL21) that per se do not act on monocytes. Binding studies on CCR2(+) cells showed that CCL19 and CCL21 do not compete with the CCR2 agonist CCL2. Furthermore, the presence of CCL19 or CCL21 could influence the degradation of CCL2 and CCL7 on cells expressing the decoy receptor D6. These findings disclose a new scenario to further comprehend the complexity of chemokine-based monocyte trafficking in a vast variety of human inflammatory disorders.

Suppression of the lipopolysaccharide-induced expression of MARCKS-related protein (MRP) affects transmigration in activated RAW264.7 cells

The molecular action mechanism of MRP, one of the protein kinase C (PKC) substrates, has been under intense investigation, but reports on its role in macrophage function remain controversial. The treatment of macrophage cell lines with bacterial lipopolysaccharide (LPS) induced a high level of MRP expression suggesting that MRP plays a role in the function of activated macrophages. In order to investigate the role of MRP in activated RAW264.7 cells, we stably transfected MRP-specific shRNA expression constructs and tested for alterations in macrophage-related functions. The down-regulation of MRP expression resulted in a marked reduction in chemotaxis toward MCP-1 or extracellular matrix proteins. Furthermore, pharmacological inhibitors of PKC significantly inhibited the chemotaxis in RAW264.7 cells. These data reveals the pivotal role of MRP in the transmigration of activated RAW264.7 cells.

Effects of synthetic monocyte chemotactic protein-1 fragment 65-76 on neointima formation after carotid artery balloon injury in rats

The effects of the synthetic monocyte chemotactic protein-1 (MCP-1) peptide fragment 65-76 (peptide X) on the development of neointima after balloon injury to the carotid artery were studied. The agent was given i.m. at a dose of 33 microg/kg once daily for 28 days after balloon injury. Animals given peptide showed significant suppression of neointima growth 4 and 7 days after lesioning, as indicated by morphometric analysis of sections of lesioned arteries. On days 14 and 28, there were no significant differences in neointima formation in rats given and not given peptide. Peptide administration was not accompanied by any changes in C-reactive peptide concentrations, leukocyte counts, or the population composition of peripheral blood lymphocytes. Use of synthetic peptide X as an inhibitor of leukocyte migration during angioplasty may, along with traditional treatments, decrease the risk of restenosis.

An engineered monomer of CCL2 has anti-inflammatory properties emphasizing the importance of oligomerization for chemokine activity in vivo

We demonstrated recently that P8A-CCL2, a monomeric variant of the chemokine CCL2/MCP-1, is unable to induce cellular recruitment in vivo, despite full activity in vitro. Here, we show that this variant is able to inhibit CCL2 and thioglycollate-mediated recruitment of leukocytes into the peritoneal cavity and recruitment of cells into lungs of OVA-sensitized mice. This anti-inflammatory activity translated into a reduction of clinical score in the more complex inflammatory model of murine experimental autoimmune encephalomyelitis. Several hypotheses for the mechanism of action of P8A-CCL2 were tested. Plasma exposure following s.c. injection is similar for P8A-CCL2 and wild-type (WT) CCL2, ruling out the hypothesis that P8A-CCL2 disrupts the chemokine gradient through systemic exposure. P8A-CCL2 and WT induce CCR2 internalization in vitro and in vivo; CCR2 then recycles to the cell surface, but the cells remain refractory to chemotaxis in vitro for several hours. Although the response to P8A-CCL2 is similar to WT, this finding is novel and suggests that despite the presence of the receptor on the cell surface, coupling to the signaling machinery is retarded. In contrast to CCL2, P8A-CCL2 does not oligomerize on glycosaminoglycans (GAGs). However, it retains the ability to bind GAGs and displaces endogenous JE (murine MCP-1) from endothelial surfaces. Intravital microscopy studies indicate that P8A-CCL2 prevents leukocyte adhesion, while CCL2 has no effect, and this phenomenon may be related to the mechanism. These results suggest that oligomerization-deficient chemokines can exhibit anti-inflammatory properties in vivo and may represent new therapeutic modalities.

SPARC ameliorates ovarian cancer-associated inflammation

We have recently identified that the role of secreted protein acidic and rich in cysteine (SPARC) in amelioration of peritoneal ovarian carcinomatosis is mediated, at least in part, through mesothelial cell/lysophosphatidic acid-induced inflammatory response in ovarian cancer cells. The aim of this study was to elucidate the molecular mechanisms of the interactions between tumor cells and the cellular components of the ovarian cancer peritoneal microenvironment, specifically, mesothelial cells and macrophages. We found that SPARC not only significantly reduced macrophage chemoattractant protein-1 production and its macrophage chemotactic effect, but also attenuated the response of ovarian cancer cells to the mitogenic and proinvasive effects of macrophage chemo-attractant protein-1 and decreased macrophage-induced cancer cell invasiveness. Overexpression of SPARC in ovarian cancer cells significantly attenuated macrophage- and mesothelial cell-induced production and activity of interleukin-6, prostanoids (prostaglandins E2 and 8-isoprostanes) as well as matrix metalloproteinases and urokinase plasminogen activator. Moreover, the effects of SPARC overexpression in ovarian cancer cells were mediated, in part, through inhibition of nuclear factor-kappaB promoter activation. These results indicate, for the first time, that the effects of tumor SPARC as a negative regulator of ovarian cancer are mediated through decreased recruitment of macrophages and downregulation of the associated inflammation.

CCL2 protects prostate cancer PC3 cells from autophagic death via phosphatidylinositol 3-kinase/AKT-dependent survivin up-regulation

Resistance to cell death is a hallmark of cancer. Autophagy is a survival mechanism activated in response to nutrient deprivation; however, excessive autophagy will ultimately induce cell death in a nonapoptotic manner. The present study demonstrates that CCL2 protects prostate cancer PC3 cells from autophagic death, allowing prolonged survival in serum-free conditions. Upon serum starvation, CCL2 induced survivin up-regulation in PC3, DU 145, and C4-2B prostate cancer cells. Both cell survival and survivin expression were stunted in CCL2-stimulated PC3 cells when treated either with the phosphatidylinositol 3-kinase inhibitor LY294002 (2 microm) or the Akt-specific inhibitor-X (Akti-X; 2.5 microm). Furthermore, CCL2 significantly reduced light chain 3-II (LC3-II) in serum-starved PC3; in contrast, treatment with LY294002 or Akti-X reversed the effect of CCL2 on LC3-II levels, suggesting that CCL2 signaling limits autophagy in these cells. Upon serum deprivation, the analysis of LC3 localization by immunofluorescence revealed a remarkable reduction in LC3 punctate after CCL2 stimulation. CCL2 treatment also resulted in a higher sustained mTORC1 activity as measured by an increase in phospho-p70S6 kinase (Thr389). Rapamycin, an inducer of autophagy, both down-regulated survivin and decreased PC3 cell viability in serum-deprived conditions. Treatment with CCL2, however, allowed cells to partially resist rapamycin-induced death, which correlated with survivin protein levels. In two stable transfectants expressing survivin-specific short hairpin RNA, generated from PC3, survivin protein levels controlled both cell viability and LC3 localization in response to CCL2 treatment. Altogether, these findings indicate that CCL2 protects prostate cancer PC3 cells from autophagic death via the phosphatidylinositol 3-kinase/Akt/survivin pathway and reveal survivin as a critical molecule in this survival mechanism.

Regulation of mammary parenchymal growth by the fat pad in prepubertal dairy heifers: role of inflammation-related proteins

In prepubertal heifers, the mammary parenchyma consists of epithelial and myoepithelial cells growing within a mammary fat pad (MFP). The MFP produces IGF-I that stimulates epithelial cell proliferation. In other species, adipose tissue expansion induces inflammation-related proteins (IRP), such as tumor necrosis factor alpha (TNFalpha), interleukin (IL)-6, IL-1beta transforming growth factor beta, monocyte chemoattractant protein 1 (MCP-1), and plasminogen activator inhibitor-1 (PAI-1). The MFP production of IRP may influence mammary development because they impair not only insulin but also IGF-I actions. Moreover, the MFP expansion seen with development and increased nutrition coincides with reduced parenchymal growth. Our first objective was to identify IRP capable of altering proliferation of bovine mammary epithelial cells. TNFalpha, but neither IL-6, IL-1beta MCP-1 nor PAI-1, inhibited basal and IGF-I-stimulated proliferation in MAC-T cells and primary cells isolated from heifers. Our second objective was to determine whether MFP expression of IRP changed in a manner consistent with inhibition of parenchymal growth. MFP expression was measured from 100 to 350 kg body weight (experiment 1) or at 240 kg body weight (experiment 2) in dairy heifers offered restricted or high planes of nutrition. In experiment 1, neither nutrition nor development altered MFP expression of TNFalpha. Nutrition increased MCP-1 and PAI-1 but only before MFP expansion and after cessation of allometric parenchymal growth. In experiment 2, nutrition increased TNFalpha and PAI-1, but not MCP-1. Thus, MFP expansion increases IRP production in cattle, but this is unlikely to contribute to reduced parenchymal growth observed with development or increased nutrition.

[Effects of induction of tubular epithelial-myofibroblast transition by monocyte chemoattractant protein-1 and mechanism thereof: an in vitro experiment]

OBJECTIVE

To examine the effects of monocyte chemoattractant protein-1 (MCP-1) on epithelial-myofibroblast transition (EMT) of renal proximal tubular epithelial cells and the possible mechanism involved.

METHODS

Human renal proximal tubular epithelial cells of the line HK-2 were cultured and divided into three groups: negative control group; positive control group, treated with transforming growth factor (TGF)-beta1 5 microg/L, and MPC-1 group, treated with MCP-1 0.1, 1, 10, and 100 microg/L for 24 h, 36 h, 48 h, and 72 h respectively. The expressions of alpha-smooth muscle actin (alpha-SMA) mRNA and protein of cells were detected by s. Western blotting and RT-PCR were used to detect the expression of P-Erk1/2, Erk1/2, P-P38MAPK, P38MAPK, and RhoA protein levels of the HK-2 cells, and RT-PCR was used to detect the expression of RhoC and Snail mRNA. Specific inhibitors of the Erk, P38MAPK, and Rho signal transduction pathways PD98059, SB203580, and Y27632 were added into the culture fluid of HK-2 cells respectively, 1 h later MCP-1 microg/L was added for 48 h, and Western blotting was used to detect the protein expression of alpha-small muscle actin (SMA).

RESULTS

The expression levels of alpha-SMA protein and mRNA significantly increased in the MCP-1 treated HK-2 cells,and these expression levels were the highest in the HK-2 cells treated with MCP-1 1 microg/L for 48 h. The ratios of (P-Erk1/2)/ (Erk1/2) and P-P38MAPK/P38MAPK were significantly increased (all P < 0.05) in the MCP-1 treated HK-2 cells with the highest ratios seen in the HK-2 cells treated by 100 microg/L of MCP-1. The expression levels of RhoA protein and RhoC mRNA of the HK-2 cells stimulated with MCP-1 of different concentrations were not significantly different (all P > 0.05). MCP-1 induced expression of a-SMA was only partly inhibited by PD98059 but not by SB203587 or Y27632. MCP-1 dose-dependently increased the expression of Snail mRNA of the HK-2 cells compared with those of the negative control cells. The level of Snail mRNA was the highest in the HK-2 cells treated with 100 microg/L MCP-1.

CONCLUSION

MCP-1 may induce the EMT of renal proximal tubular epithelial cells in vitro, and this effect may involve upregulation of Erk1/2 Map kinase signal pathways and Snail mRNA expression. P38MAPK or Rho kinase signal pathways can not be proven to be involved in MCP-1 induced EMT.

Role of astrocytes and chemokine systems in acute TNFalpha induced demyelinating syndrome: CCR2-dependent signals promote astrocyte activation and survival via NF-kappaB and Akt

Chemotactic factors known as chemokines play an important role in the pathogenesis of multiple sclerosis (MS). Transgenic expression of TNFalpha in the central nervous system (CNS) leads to the development of a demyelinating phenotype (TNFalpha-induced demyelination; TID) that is highly reminiscent of MS. Little is known about the role of chemokines in TID but insights derived from studying this model might extend our current understanding of MS pathogenesis and complement data derived from the classic autoimmune encephalomyelitis (EAE) model system. Here we show that in TID, chemokines and their receptors were significantly increased during the acute phases of disease. Notably, the CCL2 (MCP-1)-CCR2 axis and the closely related ligand-receptor pair CCR1-CCL3 (MIP-1alpha) were among the most up-regulated during disease. On the other hand, receptors like CCR3 and CCR4 were not elevated. This significant increase in the levels of chemokines/receptors correlated with robust immune infiltration of the CNS by inflammatory cells, i.e., macrophages, and immune cells particularly T and B cells. Immunostaining and confocal microscopy, along with in vitro studies revealed that astrocytes were a major source of locally produced chemokines and expressed functional chemokine receptors such as CCR2. Using an in vitro system we demonstrate that expression of CCR2 was functional in astrocytes and that signaling via this receptor lead to activation of NF-kB and Akt and was associated with increased astrocyte survival. Collectively, our data suggests that transgenic murine models of MS are useful to dissect mechanisms of disease and that in these models, up-regulation of chemokines and their receptors may be key determinants in TID.