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Birgbauer E, Rao TS, Webb M. Lysolecithin induces demyelination in vitro in a cerebellar slice culture system. J Neurosci Res 2004; 78:157-66. [PMID: 15378614 DOI: 10.1002/jnr.20248] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Demyelination is a hallmark of several human diseases, including multiple sclerosis. To understand better the process of demyelination and remyelination, we explored the use of an in vitro organotypic cerebellar slice culture system. Parasagittal slices of postnatal Day 10 (P10) rat cerebella cultured in vitro demonstrated significant myelination after 1 week in culture. Treatment of the cultures at 7 days in vitro (DIV) with the bioactive lipid lysolecithin (lysophosphatidylcholine) for 15-17 hr in vitro produced marked demyelination. This demyelination was observed by immunostaining for the myelin components myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG), and 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase). After a transient demyelinating insult with lysolecithin in vitro, the cultures recovered with oligodendrocyte differentiation recapitulating a normal time course; there was initially re-expression of CNPase and MBP during this recovery, and this was followed by MOG. In addition, there seemed to be some limited remyelination during the recovery phase. Lysolecithin thus induces demyelination in an in vitro organotypic cerebellar slice culture system, providing a model system for studying myelination, demyelination, and remyelination in vitro.
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Affiliation(s)
- Eric Birgbauer
- Department of Neurobiology, Merck Research Laboratories, San Diego, California, USA.
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52
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Schecter AD, Berman AB, Yi L, Ma H, Daly CM, Soejima K, Rollins BJ, Charo IF, Taubman MB. MCP-1-dependent signaling in CCR2(-/-) aortic smooth muscle cells. J Leukoc Biol 2004; 75:1079-85. [PMID: 15020650 DOI: 10.1189/jlb.0903421] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Monocyte chemoattractant protein-1 (MCP-1, CCL2) is a mediator of inflammation that has been implicated in the pathogenesis of a wide variety of human diseases. CCR2, a heterotrimeric G-coupled receptor, is the only known receptor that functions at physiologic concentrations of MCP-1. Despite the importance of CCR2 in mediating MCP-1 responses, several recent studies have suggested that there may be another functional MCP-1 receptor. Using arterial smooth muscle cells (SMC) from CCR2(-/-) mice, we demonstrate that MCP-1 induces tissue-factor activity at physiologic concentrations. The induction of tissue factor by MCP-1 is blocked by pertussis toxin and 1,2-bis(O-aminophenyl-ethane-ethan)-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, suggesting that signal transduction through the alternative receptor is G(alphai)-coupled and dependent on mobilization of intracellular Ca(2+). MCP-1 induces a time- and concentration-dependent phosphorylation of the mitogen-activated protein kinases p42/44. The induction of tissue factor activity by MCP-1 is blocked by PD98059, an inhibitor of p42/44 activation, but not by SB203580, a selective p38 inhibitor. These data establish that SMC possess an alternative MCP-1 receptor that signals at concentrations of MCP-1 that are similar to those that activate CCR2. This alternative receptor may be important in mediating some of the effects of MCP-1 in atherosclerotic arteries and in other inflammatory processes.
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MESH Headings
- Animals
- Aorta
- Calcium/metabolism
- Cells, Cultured
- Chemokine CCL2/pharmacology
- Enzyme Inhibitors/pharmacology
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Homozygote
- Mice
- Mice, Knockout
- Mitogen-Activated Protein Kinase 1/antagonists & inhibitors
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3
- Mitogen-Activated Protein Kinases/antagonists & inhibitors
- Mitogen-Activated Protein Kinases/metabolism
- Monocytes/drug effects
- Monocytes/metabolism
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Pertussis Toxin/pharmacology
- Phosphorylation
- Receptors, CCR2
- Receptors, Chemokine/genetics
- Receptors, Chemokine/metabolism
- Receptors, Chemokine/physiology
- Recombinant Proteins/metabolism
- Signal Transduction
- Thromboplastin/metabolism
- p38 Mitogen-Activated Protein Kinases
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Affiliation(s)
- Alison D Schecter
- The Cardiovascular Institute, Department of Medicine, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA.
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53
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Dobreva I, Waeber G, Mooser V, James RW, Widmann C. LDLs induce fibroblast spreading independently of the LDL receptor via activation of the p38 MAPK pathway. J Lipid Res 2003; 44:2382-90. [PMID: 12951358 DOI: 10.1194/jlr.m300266-jlr200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Because adventitial fibroblasts play an important role in the repair of blood vessels, we assessed whether elevation in LDL concentrations would affect fibroblast function and whether this depended on activation of intracellular signaling pathways. We show here that in primary human fibroblasts, LDLs induced transient activation of the p38 mitogen-activated protein kinase (MAPK) pathway, but not the c-Jun N-terminal kinase MAPK pathway. This activation did not require the recruitment of the LDL receptor (LDLR), because LDLs efficiently stimulated the p38 MAPK pathway in human and mouse fibroblasts lacking functional LDLR, and because receptor-associated protein, an LDLR family antagonist, did not block the LDL-induced p38 activation. LDL particles also induced lamellipodia formation and cell spreading. These effects were blocked by SB203580, a specific p38 inhibitor. Our data demonstrate that LDLs can regulate the shape of fibroblasts in a p38 MAPK-dependent manner, a mechanism that may participate in wound healing or vessel remodeling as in atherosclerosis.
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Affiliation(s)
- Iveta Dobreva
- Institut de Biologie Cellulaire et de Morphologie, Université de Lausanne, Switzerland
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54
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Morita T, Imai T, Yamaguchi T, Sugiyama T, Katayama S, Yoshino G. Induction of heme oxygenase-1 in monocytes suppresses angiotensin II-elicited chemotactic activity through inhibition of CCR2: role of bilirubin and carbon monoxide generated by the enzyme. Antioxid Redox Signal 2003; 5:439-47. [PMID: 13678532 DOI: 10.1089/152308603768295186] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Monocyte chemoattractant protein 1 (MCP-1) and the receptor for MCP-1, CCR2, play a pivotal role in the recruitment of monocytes to the subendothelium, which is the initial event in atherosclerosis. Heme oxygenase (HO) is a microsomal enzyme that catalyzes the degradation of heme into biliverdin, which is subsequently reduced to bilirubin, free iron, and carbon monoxide, and induction of HO-1 is potentially associated with cellular protection, especially against oxidative insults. The present study was designed to examine the role of HO-1 in monocytes in angiotensin II (Ang II)-induced chemotactic response. Ang II significantly stimulated superoxide formation in monocytes, as measured by nitro blue tetrazolium reduction assay, as well as the chemotactic response to MCP-1 with the increased expression of CCR2 determined by RT-PCR and western blotting analysis. Hemin-treated monocytes displayed an enhanced HO activity with the increased accumulation of bilirubin determined by immunostaining, when compared with control monocytes. The induction of HO-1 in monocytes suppresses not only Ang II-stimulated superoxide formation, but also Ang II-enhanced chemotactic activity. Exogenously applied bilirubin and carbon monoxide mimicked the inhibitory effect of HO-1 on the chemotactic response. These findings suggest that monocytic HO-1 might be a new therapeutic target for atherosclerosis.
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Affiliation(s)
- Toshisuke Morita
- Department of Laboratory Medicine, Toho University, School of Medicine, Tokyo, Japan.
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55
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Lin P, Ye RD. The lysophospholipid receptor G2A activates a specific combination of G proteins and promotes apoptosis. J Biol Chem 2003; 278:14379-86. [PMID: 12586833 DOI: 10.1074/jbc.m209101200] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
G2A, a G protein-coupled receptor for which lysophosphatidylcholine (LPC) is a high affinity ligand, belongs to a newly defined lysophospholipid receptor subfamily. Expression of G2A is transcriptionally up-regulated by stress-inducing and cell-damaging agents, and ectopic expression of G2A leads to growth inhibition. However, the G proteins that functionally couple to G2A have not been elucidated in detail. We report here that G2A ligand independently stimulates the accumulation of both inositol phosphates and cAMP. LPC does not further enhance inositol phosphate accumulation but dose-dependently augments intracellular cAMP concentration. Expression of G alpha(q) and G alpha(13) with G2A potentiates G2A-mediated activation of a NF-kappa B-luciferase reporter. These results demonstrate that G2A differentially couples to multiple G proteins including G alpha(s), G alpha(q), and G alpha(13), depending on whether it is bound to ligand. G2A-transfected HeLa cells display apoptotic signs including membrane blebbing, nuclear condensation, and reduction of mitochondrial membrane potential. Furthermore, G2A-induced apoptosis can be rescued by the caspase inhibitors, z-vad-fmk and CrmA. Although apoptosis occurs without LPC stimulation, LPC further enhances G2A-mediated apoptosis and correlates with its ability to induce cAMP elevation in both HeLa cells and primary lymphocytes. Rescue from G2A-induced apoptosis was achieved by co-expression of a G alpha(12/13)-specific inhibitor, p115RGS (regulator of G protein signaling), in combination with 2',5'-dideoxyadenosine treatment. These results demonstrate the ability of G2A to activate a specific combination of G proteins, and that G2A/LPC-induced apoptosis involves both G alpha(13)- and G alpha(s)-mediated pathways.
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Affiliation(s)
- Phoebe Lin
- Department of Pharmacology, College of Medicine, University of Illinois, Chicago 60612, USA
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56
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Drobnik W, Liebisch G, Audebert FX, Frohlich D, Gluck T, Vogel P, Rothe G, Schmitz G. Plasma ceramide and lysophosphatidylcholine inversely correlate with mortality in sepsis patients. J Lipid Res 2003; 44:754-61. [PMID: 12562829 DOI: 10.1194/jlr.m200401-jlr200] [Citation(s) in RCA: 243] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent data indicate that ceramide (Cer) and lysophosphatidylcholine (LPC) regulate immune cell functions. Since these bioactive lipids are generated in blood plasma by inflammatory lipases, we hypothesized that they may be involved in the process of acute systemic sepsis. In order to provide support for this hypothesis, we analyzed the plasma levels of Cer and LPC by quantitative tandem mass spectrometry in 102 sepsis patients starting with the day at which the sepsis criteria were fulfilled for the first time, as well as on day 4 and day 11. The values were compared with 56 healthy controls and correlated with sepsis-related mortality within 30 days of study entry. Most Cer species were increased in sepsis patients, while all LPC species were markedly decreased. In addition, we determined the molar ratios with their precursor molecules sphingomyelin (SPM) and phosphatidylcholine (PC), which reflect the enzymatic reactions responsible for their formation. Species-specific as well as total Cer-SPM ratios were increased, whereas LPC-PC ratios were decreased in sepsis patients. The increased Cer-SPM ratios as well as the decreased LPC-PC ratios showed a strong predictive power for sepsis-related mortality. Together with existing data from in vitro experiments and animal models, the results provide the first ex vivo indication for the role of Cer and lysophospholipids in systemic inflammation in humans.
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Affiliation(s)
- Wolfgang Drobnik
- Institute for Clinical Chemistry, University of Regensburg, Germany
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57
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Sun Y, Cheng Z, Ma L, Pei G. Beta-arrestin2 is critically involved in CXCR4-mediated chemotaxis, and this is mediated by its enhancement of p38 MAPK activation. J Biol Chem 2002; 277:49212-9. [PMID: 12370187 DOI: 10.1074/jbc.m207294200] [Citation(s) in RCA: 309] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Chemotaxis mediated by chemokine receptors such as CXCR4 plays a key role in lymphocyte homing and hematopoiesis as well as in breast cancer metastasis. We have demonstrated previously that beta-arrestin2 functions to attenuate CXCR4-mediated G protein activation and to enhance CXCR4 internalization. Here we show further that the expression of beta-arrestin2 in both HeLa and human embryonic kidney 293 cells significantly enhances the chemotactic efficacy of stromal cell-derived factor 1alpha, the specific agonist of CXCR4, whereas the suppression of beta-arrestin2 endogenous expression by antisense or RNA-mediated interference technology considerably attenuates stromal cell-derived factor 1alpha-induced cell migration. Expression of beta-arrestin2 also augmented chemokine receptor CCR5-mediated but not epidermal growth factor receptor-mediated chemotaxis, indicating the specific effect of beta-arrestin2. Further analysis reveals that expression of beta-arrestin2 strengthened CXCR4-mediated activation of both p38 MAPK and ERK, and the suppression of beta-arrestin2 expression blocked the activation of two kinases. Interestingly, inhibition of p38 MAPK activation (but not ERK activation) by its inhibitors or by expression of a dominant-negative mutant of p38 MAPK effectively blocked the chemotactic effect of beta-arrestin2. Expression of a dominant-negative mutant of ASK1 also exerted the similar blocking effect. The results of our study suggest that beta-arrestin2 can function not only as a regulator of CXCR4 signaling but also as a mediator of stromal cell-derived factor 1alpha-induced chemotaxis and that this activity probably occurs via the ASK1/p38 MAPK pathway.
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Affiliation(s)
- Yue Sun
- Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, People's Republic of China
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58
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Salomonsson L, Pettersson S, Englund MCO, Wiklund O, Ohlsson BG. Post-transcriptional regulation of VEGF expression by oxidised LDL in human macrophages. Eur J Clin Invest 2002; 32:767-74. [PMID: 12406026 DOI: 10.1046/j.1365-2362.2002.01072.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Accumulation of oxidised low density lipoproteins (oxLDL) in macrophages and their subsequent transformation into lipid-filled foam cells is generally considered an early event in atherosclerosis. Vascular Endothelial Growth Factor (VEGF) may contribute to atherogenesis through increased vascular permeability, chemoattraction towards monocytes and intraplaque vessel formation. In this study we investigate the effect and regulation of VEGF expression in human macrophages stimulated with oxLDL. MATERIALS AND METHODS Vascular Endothelial Growth Factor mRNA and protein expression was assayed using RT-PCR and ELISA, respectively. The activity of mitogen-activated protein kinases (MAPKs) was investigated using Western blots. RESULTS In human monocyte-derived macrophages, oxLDL significantly increased VEGF mRNA expression and subsequent protein secretion in a concentration-dependent manner after 6 h and 18 h, respectively. Using an in vitro mRNA decay assay, we show that this oxLDL-induced VEGF expression partly is regulated through increased stability of the VEGF mRNA. Involvement of MAPKs has previously been implicated in the stabilisation of VEGF mRNA. Activity of the p38 MAPK, but not the c-jun-N-terminal kinase (JNK), increased in macrophages stimulated with oxLDL (50 micro g mL-1) for 5-15 min. Preincubation with SB202190 (20 micro M), a specific inhibitor of p38 MAPK, significantly decreased the oxLDL-induced VEGF mRNA expression by 40%. The prolonged half-life of VEGF mRNA, induced by oxLDL, was not inhibited by SB202190. CONCLUSIONS OxLDL increases VEGF expression and p38 MAPK activity in human macrophages. The increased VEGF mRNA expression by oxLDL is mediated through at least two intracellular pathways, one involving p38 MAPK and another that independently of p38 MAPK activity increases VEGF mRNA stability.
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Affiliation(s)
- L Salomonsson
- Wallenberg Laboratory, Sahlgrenska Academy, Göteborg, Sweden.
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59
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Koul HK, Menon M, Chaturvedi LS, Koul S, Sekhon A, Bhandari A, Huang M. COM crystals activate the p38 mitogen-activated protein kinase signal transduction pathway in renal epithelial cells. J Biol Chem 2002; 277:36845-52. [PMID: 12121971 DOI: 10.1074/jbc.m200832200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interaction of calcium oxalate monohydrate (COM) crystals with renal cells has been shown to result in altered gene expression, DNA synthesis, and cell death. In the current study the role of a stress-specific p38 MAP kinase-signaling pathway in mediating these effects of COM crystals was investigated. Exposure of cells to COM crystals (20 microg/cm(2)) rapidly stimulated strong phosphorylation and activation of p38 mitogen-activated protein kinase (p38 MAP kinase) and re-initiation of DNA synthesis. Inhibition of COM crystal binding to the cells by heparin blocked the effects of COM crystals on p38 MAPK activation. We also show that specific inhibition of p38 MAPK by 4-(4-fluorophenyl)-2-(4-methylsulfonylphenyl)-5-(4-pyridyl) imidazole (SB203580) or by overexpression of a dominant negative mutant of p38 MAP kinase abolishes COM crystal-induced re-initiation of DNA synthesis. The inhibition is dose-dependent and correlates with in situ activity of native p38 MAP kinase, determined as mitogen-activated protein kinase-activated protein kinase-2 (MAPKAP kinase-2) activity in cell extracts. In summary, inhibiting activation of p38 MAPK pathway abrogated the DNA synthesis in response to COM crystals. These data are the first demonstrations of activation of the p38 MAPK signaling pathway by COM crystals and suggest that, in response to COM crystals, this pathway transduces critical signals governing the re-initiation of DNA synthesis in renal epithelial cells.
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Affiliation(s)
- Hari K Koul
- Biochemistry and Molecular Biology Laboratory, Vattikuti Urology Institute, Henry Ford Health Sciences Center, Detroit, Michigan 48202, USA.
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60
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Burysek L, Syrovets T, Simmet T. The serine protease plasmin triggers expression of MCP-1 and CD40 in human primary monocytes via activation of p38 MAPK and janus kinase (JAK)/STAT signaling pathways. J Biol Chem 2002; 277:33509-17. [PMID: 12093796 DOI: 10.1074/jbc.m201941200] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanism of proinflammatory activation of human monocytes by plasmin is unknown. Here we demonstrate that in human primary monocytes, plasmin stimulates mitogen-activated protein kinase (MAPK) signaling via phosphorylation of MAPK kinase 3/6 (MKK3/6) and p38 MAPK that triggers subsequent DNA binding of transcription factor activator protein-1 (AP-1). The AP-1 complex contained phosphorylated c-Jun and ATF2, and its DNA binding activity was blocked by the p38 MAPK inhibitor SB203580. In addition, plasmin elicits Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling, as detected by phosphorylation of JAK1 tyrosine kinase and STAT1 and STAT3 proteins. Plasmin-induced DNA binding of STAT1 and STAT3 was blocked by SB203580 and AG490, inhibitors of p38 MAPK and JAK, respectively, but not by U0126, an inhibitor of MKK1/2. DNA binding of NF-kappaB remained unaffected by any of these inhibitors. The plasmin-induced signaling led to expression of monocyte chemoattractant protein-1 (MCP-1) and CD40, which required activation of both p38 MAPK and JAK/STAT signaling pathways. Additionally, signaling through both p38 MAPK and JAK is involved in the plasmin-mediated monocyte migration, whereas the formylmethionylleucylphenylalanine-induced chemotaxis remained unaffected. Taken together, our data demonstrate a novel function of the serine protease plasmin in a proinflammatory signaling network.
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Affiliation(s)
- Ladislav Burysek
- Department of Pharmacology of Natural Products and Clinical Pharmacology, University of Ulm, D-89081 Ulm, Germany
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61
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Goncharova EA, Vorotnikov AV, Gracheva EO, Wang CLA, Panettieri RA, Stepanova VV, Tkachuk VA. Activation of p38 MAP-kinase and caldesmon phosphorylation are essential for urokinase-induced human smooth muscle cell migration. Biol Chem 2002; 383:115-26. [PMID: 11930938 DOI: 10.1515/bc.2002.012] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We have explored intracellular pathways involved in the urokinase type plasminogen activator (urokinase or uPA)-stimulated migration of human airway smooth muscle cells (hAWSMC). Using a set of uPA mutants we found that protease activity, growth factor-like and kringle domains of uPA differentially contribute to activation of p42/p44erk1,2 and p38 MAP-kinases. Consistent with our earlier data [Mukhina et al., J. Biol. Chem. 275 (2000), 16450-16458], the kringle domain of uPA was sufficient and required to stimulate cell motility. Here we report that uPA mutants containing the kringle domain specifically activate the p38 MAP-kinase pathway and actomyosin by increasing phosphorylation of the critical Ser-19 on the myosin regulatory light chain and MAP-kinase sites of the actin-associated regulatory protein caldesmon. While pharmacological inhibition of p38 MAP-kinase activation did not affect myosin light chain phosphorylation, it blocked the increase in caldesmon phosphorylation and uPA-stimulated migration of hAWSMC on a collagen-coated surface. We conclude that activation of p38 MAP-kinase and downstream phosphorylation of non-muscle caldesmon is essential for urokinase-stimulated smooth muscle cell migration.
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Affiliation(s)
- Elena A Goncharova
- Laboratory of Cell Motility, Institute of Experimental Cardiology, Russian Cardiology Research Center, Moscow
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62
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Kabarowski JH, Zhu K, Le LQ, Witte ON, Xu Y. Lysophosphatidylcholine as a ligand for the immunoregulatory receptor G2A. Science 2001; 293:702-5. [PMID: 11474113 DOI: 10.1126/science.1061781] [Citation(s) in RCA: 246] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Although the biological actions of the cell membrane and serum lipid lysophosphatidylcholine (LPC) in atherosclerosis and systemic autoimmune disease are well recognized, LPC has not been linked to a specific cell-surface receptor. We show that LPC is a high-affinity ligand for G2A, a lymphocyte-expressed G protein-coupled receptor whose genetic ablation results in the development of autoimmunity. Activation of G2A by LPC increased intracellular calcium concentration, induced receptor internalization, activated ERK mitogen-activated protein kinase, and modified migratory responses of Jurkat T lymphocytes. This finding implicates a role for LPC-G2A interaction in the etiology of inflammatory autoimmune disease and atherosclerosis.
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Affiliation(s)
- J H Kabarowski
- Department of Microbiology, Immunology, and Molecular Genetics, Lerner Research Institute, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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63
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Wang G, O K. Homocysteine stimulates the expression of monocyte chemoattractant protein-1 receptor (CCR2) in human monocytes: possible involvement of oxygen free radicals. Biochem J 2001; 357:233-40. [PMID: 11415454 PMCID: PMC1221946 DOI: 10.1042/0264-6021:3570233] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Homocysteinaemia is an independent risk factor for atherosclerosis. The development of atherosclerosis involves monocyte chemoattractant protein 1 (MCP-1)-mediated monocyte recruitment to the lesion site. The action of MCP-1 is mostly via its interaction with MCP-1 receptor (CCR2), which is the major receptor for MCP-1 on the surface of monocytes. The objective of the present study was to investigate the effect of homocysteine on CCR2 expression in human THP-1 monocytes. Cells were incubated with various concentrations of homocysteine for 6, 12, 24 and 48 h. The expression of CCR2 mRNA was determined by nuclease protection assay and the CCR2 protein was measured by Western immunoblotting analysis. The binding of MCP-1 to CCR2 as a functional receptor on the monocyte surface was determined by flow cytometry. Homocysteine (0.05-0.2 mM) significantly enhanced the expression of CCR2 mRNA (129-209% of the control) and CCR2 protein (up to 183% of control) in these cells after 24 h of incubation. Stimulation of CCR2 expression was associated with a parallel increase in the binding activity of CCR2 (129-191% of control) as well as an enhanced chemotactic response of homocysteine-treated monocytes. Further investigation revealed that the levels of superoxide were significantly elevated in cells incubated with homocysteine for 12-48 h. The addition of superoxide dismutase, a scavenger of superoxide, to the culture medium abolished the stimulatory effect of homocysteine on CCR2 expression as well as the binding activity of the receptor. The stimulatory effect of homocysteine on the expression of CCR2 mRNA and the levels of CCR2 protein was also observed in human peripheral blood monocytes. In conclusion, the present study has clearly demonstrated that homocysteine stimulates CCR2 expression in monocytes, leading to an enhanced binding activity and chemotatic response. Homocysteine-induced superoxide formation might serve as one of the underlying mechanisms for this effect.
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Affiliation(s)
- G Wang
- Department of Pharmacology, Institute of Cardiovascular Science and Medicine, Faculty of Medicine, University of Hong Kong, 1/F, Li Shu Fan Building, 5 Sassoon Road, Pokfulam, Hong Kong, People's Republic of China
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64
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Wang G, Siow YL, O K. Homocysteine induces monocyte chemoattractant protein-1 expression by activating NF-kappaB in THP-1 macrophages. Am J Physiol Heart Circ Physiol 2001; 280:H2840-7. [PMID: 11356643 DOI: 10.1152/ajpheart.2001.280.6.h2840] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Homocysteinemia is an independent risk factor for cardiovascular disorders. The recruitment of monocytes is an important event in atherogenesis. Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that stimulates monocyte migration into the intima of arterial walls. The objective of the present study was to investigate the effect of homocysteine on MCP-1 expression in macrophages and the underlying mechanism of such effect. Human monocytic cell (THP-1)-derived macrophages were incubated with homocysteine. By nuclease protection assay and ELISA, homocysteine (0.05-0.2 mM) was shown to significantly enhance the expression of MCP-1 mRNA (up to 2.6-fold) and protein (up to 4.8-fold) in these cells. Homocysteine-induced MCP-1 expression resulted in increased monocyte chemotaxis. The increase in MCP-1 expression was associated with activation of nuclear factor (NF)-kappaB due to increased phosphorylation of the inhibitory protein (IkappaB-alpha) as well as reduced expression of IkappaB-alpha mRNA in homocysteine-treated cells. In conclusion, our results demonstrate that homocysteine, at pathological concentration, stimulates MCP-1 expression in THP-1 macrophages via NF-kappaB activation.
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Affiliation(s)
- G Wang
- Department of Pharmacology and Institute of Cardiovascular Science and Medicine, Faculty of Medicine, University of Hong Kong, Hong Kong, China
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65
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Bruyninckx WJ, Comerford KM, Lawrence DW, Colgan SP. Phosphoinositide 3-kinase modulation of beta(3)-integrin represents an endogenous "braking" mechanism during neutrophil transmatrix migration. Blood 2001; 97:3251-8. [PMID: 11342456 DOI: 10.1182/blood.v97.10.3251] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During episodes of inflammation, neutrophils (polymorphonuclear leukocytes [PMNs]) encounter subendothelial matrix substrates that may require additional signaling pathways as directives for movement through the extracellular space. Using an in vitro endothelial and epithelial model, inhibitors of phosphoinositide 3-kinase (PI3K) were observed to promote chemoattractant-stimulated migration by as much as 8 +/- 0.3-fold. Subsequent studies indicated that PMNs respond in a similar manner to RGD-containing matrix substrates and that PMN-matrix interactions are potently inhibited by antibodies directed against beta(3)- but not beta(1)-integrin antibodies, and that PI3K inhibitors block beta(3)-integrin dependence. Biochemical analysis of intracellular beta(3)-integrin uncoupling by PI3K inhibitors revealed diminished beta(3)-integrin tyrosine phosphorylation and decreased association with p72(syk). Similarly, the p72(syk) inhibitor piceatannol promoted PMN transmatrix migration, whereas HIV-tat peptide-facilitated loading of peptides corresponding to the beta(3)-integrin cytoplasmic tail identified the functional tyrosine residues for this activity. These data indicate that PI3K-regulated beta(3)-integrin represents a natural "braking" mechanism for PMNs during transit through the extracellular matrix.
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Affiliation(s)
- W J Bruyninckx
- Center for Experimental Therapeutics and Reperfusion Injury, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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Ashida N, Arai H, Yamasaki M, Kita T. Distinct signaling pathways for MCP-1-dependent integrin activation and chemotaxis. J Biol Chem 2001; 276:16555-60. [PMID: 11278464 DOI: 10.1074/jbc.m009068200] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Transmigration of monocytes to the subendothelial space is the initial step of atherosclerotic plaque formation and inflammation. Integrin activation and chemotaxis are two important functions involved in monocyte transmigration. To delineate the signaling cascades leading to integrin activation and chemotaxis by monocyte chemoattractant protein-1 (MCP-1), we have investigated the roles of MAPK and Rho GTPases in THP-1 cells, a monocytic cell line. MCP-1 stimulated beta1 integrin-dependent, but not beta2 integrin-dependent cell adhesion in a time-dependent manner. MCP-1-mediated cell adhesion was inhibited by a MEK inhibitor but not by a p38-MAPK inhibitor. In contrast, MCP-1-mediated chemotaxis was inhibited by the p38-MAPK inhibitor but not by the MEK inhibitor. The inhibitor of Rho GTPase, C3 exoenzyme, and a Rho kinase inhibitor abrogated MCP-1-dependent chemotaxis but not integrin-dependent cell adhesion. Further, C3 exoenzyme and the Rho kinase inhibitor blocked MCP-1-dependent p38-MAPK activation. These data indicate that ERK is responsible for integrin activation, that p38-MAPK and Rho are responsible for chemotaxis mediated by MCP-1, and that Rho and the Rho kinase are upstream of p38-MAPK in MCP-1-mediated signaling. This study demonstrates that two distinct MAPKs regulate two dependent signaling cascades leading to integrin activation and chemotaxis induced by MCP-1 in THP-1 cells.
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Affiliation(s)
- N Ashida
- Department of Geriatric Medicine, Kyoto University Graduate School of Medicine, Kyoto, 606-8507, Japan
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Rikitake Y, Hirata K, Kawashima S, Takeuchi S, Shimokawa Y, Kojima Y, Inoue N, Yokoyama M. Signaling mechanism underlying COX-2 induction by lysophosphatidylcholine. Biochem Biophys Res Commun 2001; 281:1291-7. [PMID: 11243876 DOI: 10.1006/bbrc.2001.4510] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Lysophosphatidylcholine, a component of oxidized low density lipoprotein, is critical for pathological conditions including atherosclerosis. However, the signaling mechanism of lysophosphatidylcholine remains poorly understood. Here we reported that lysophosphatidylcholine induces phosphorylation of p38 and the transcription factors, CREB and ATF-1 with concomitant up-regulation of cyclooxygenase-2 expression in cultured vascular endothelial cells. Lysophosphatidylcholine induced p38 phosphorylation in a time- and concentration-dependent manner partly via pathway depending on protein tyrosine kinase. Both lysophosphatidylcholine-stimulated phosphorylation of CREB and ATF-1 and lysophosphatidylcholine-increased expression of cyclooxygenase-2 mRNA and protein were effectively inhibited by a combination of SB203580 and PD98059, specific inhibitors of p38 and MEK1, respectively, as well as Ro31-8220 and H89, potent inhibitors of MSK1. These results suggest that both p38 and ERK may function as upstream signaling pathways capable of activating CREB and ATF-1 with subsequent induction of cyclooxygenase-2 expression by lysophosphatidylcholine.
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Affiliation(s)
- Y Rikitake
- First Department of Internal Medicine, Kobe University School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
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