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Biomedical subjects

F Mach

Publications and source records attributed to F Mach.

At least 37 records · Page 2Linked to original sources
PubMed2000

CD154 (CD40 ligand).

CD40 ligand, a type II transmembrane protein recently renamed CD154, was originally considered restricted to activated T lymphocytes, functioning as a mediator of T cell-dependent B cell activation, proliferation, and differentiation. However, the spectrum of CD154 expression and function has broadened considerably during recent years, establishing new roles as a central mediator of immunity and inflammation for this member of the tumor necrosis factor (TNF) gene superfamily. The emerging picture indicates that ligation of the receptor CD40 via CD154, most potently in its trimeric form, functions in two ways. CD154 modulates physiologic processes, such as T cell-mediated effector functions and general immune responses required for appropriate host defense, but also triggers the expression of pro-inflammatory mediators, such as cytokines, adhesion molecules, and matrix degrading activities, all of which are associated with the pathogenesis of chronic inflammatory diseases, e.g., autoimmune disorders, arthritis, atherosclerosis, and cancer. Accordingly, CD40/CD154 interactions have advanced as a potential therapeutic target for these diseases, whereby two opposing strategies, interruption as well as enhancement of CD40 signaling, are explored for beneficial outcomes.

Animals↗
PubMed2000

Statins as a newly recognized type of immunomodulator.

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, or statins, are effective lipid-lowering agents, extensively used in medical practice. Statins have never been shown to be involved in the immune response, although a report has indicated a better outcome of cardiac transplantation in patients under Pravastatin therapy. Major histocompatibility complex class II (MHC-II) molecules are directly involved in the activation of T lymphocytes and in the control of the immune response. Whereas only a limited number of specialized cell types express MHC-II constitutively, numerous other cells become MHC-II positive upon induction by interferon gamma (IFN-gamma). This complex regulation is under the control of the transactivator CIITA (refs 6,7). Here we show that statins act as direct inhibitors of induction of MHC-II expression by IFN-gamma and thus as repressors of MHC-II-mediated T-cell activation. This effect of statins is due to inhibition of the inducible promoter IV of the transactivator CIITA and is observed in several cell types, including primary human endothelial cells (ECs) and monocyte-macrophages (Mstraight phi). It is of note that this inhibition is specific for inducible MHC-II expression and does not concern constitutive expression of CIITA and MHC-II. In repressing induction of MHC-II, and subsequent T-lymphocyte activation, statins therefore provide a new type of immunomodulation. This unexpected effect provides a scientific rationale for using statins as immunosuppressors, not only in organ transplantation but in numerous other pathologies as well.

Adjuvants, Immunologic↗
PubMed2000

Role of the vascular endothelium in patients with angina pectoris or acute myocardial infarction with normal coronary arteries.

Chest pain with normal coronary angiograms is a relatively common syndrome. The mode of presentation of this syndrome includes patients with syndrome X and patients with an acute myocardial infarction and angiographically normal coronary arteries. Different mechanisms have been proposed to elucidate the exact cause and to explain the various clinical presentations in these patients. Abnormalities of pain perception and the presence of oesophageal dysmotility have all been reported in patients with syndrome X. In situ thrombosis or embolization with subsequent clot lysis and recanalization, coronary artery spasm, cocaine abuse, and viral myocarditis have been described as potential mechanisms responsible for an acute myocardial infarction in patients with angiographically normal coronary arteries. Recent data suggest that both microvascular and epicardial endothelial dysfunction may play an important role in the pathophysiological mechanism of the syndrome of stable angina or acute myocardial infarction with normal coronary arteries.

Cocaine-Related Disorders↗
PubMed1999

Expression of stromelysin-3 in atherosclerotic lesions: regulation via CD40-CD40 ligand signaling in vitro and in vivo.

Stromelysin-3 is an unusual matrix metalloproteinase, being released in the active rather than zymogen form and having a distinct substrate specificity, targeting serine proteinase inhibitors (serpins), which regulate cellular functions involved in atherosclerosis. We report here that human atherosclerotic plaques (n = 7) express stromelysin-3 in situ, whereas fatty streaks (n = 5) and normal arterial specimens (n = 5) contain little or no stromelysin-3. Stromelysin-3 mRNA and protein colocalized with endothelial cells, smooth muscle cells, and macrophages within the lesion. In vitro, usual inducers of matrix metalloproteinases such as interleukin-1, interferon-gamma, or tumor necrosis factor alpha did not augment stromelysin-3 in vascular wall cells. However, T cell-derived as well as recombinant CD40 ligand (CD40L, CD154), an inflammatory mediator recently localized in atheroma, induced de novo synthesis of stromelysin-3. In addition, stromelysin-3 mRNA and protein colocalized with CD40L and CD40 within atheroma. In accordance with the in situ and in vitro data obtained with human material, interruption of the CD40-CD40L signaling pathway in low density lipoprotein receptor-deficient hyperlipidemic mice substantially decreased expression of the enzyme within atherosclerotic plaques. These observations establish the expression of the unusual matrix metalloproteinase stromelysin-3 in human atherosclerotic lesions and implicate CD40-CD40L signaling in its regulation, thus providing a possible new pathway that triggers complications within atherosclerotic lesions.

Animals↗
PubMed1999

T lymphocytes induce endothelial cell matrix metalloproteinase expression by a CD40L-dependent mechanism: implications for tubule formation.

Neovascularization frequently accompanies chronic immune responses characterized by T cell infiltration and activation. Angiogenesis requires endothelial cells (ECs) to penetrate extracellular matrix, a process that involves matrix metalloproteinases (MMPs). We report here that activated human T cells mediate contact-dependent expression of MMPs in ECs through CD40/CD40 ligand signaling. Ligation of CD40 on ECs induced de novo expression of gelatinase B (MMP-9), increased interstitial collagenase (MMP-1) and stromelysin (MMP-3), and activated gelatinase A (MMP-2). Recombinant human CD40L induced expression of MMPs by human vascular ECs to a greater extent than did maximally effective concentrations of interleukin-1beta or tumor necrosis factor-alpha. Moreover, activation of human vascular ECs through CD40 induced tube formation in a three-dimensional fibrin matrix gel assay, an effect antagonized by a MMP inhibitor. These results demonstrated that activation of ECs by interaction with T cells induced synthesis and release of MMPs and promoted an angiogenic function of ECs via CD40L-CD40 signaling. As vascular cells at the sites of chronic inflammation, such as atherosclerotic plaques, express CD40 and its ligand, our findings suggest that ligation of CD40 on ECs can mediate aspects of vascular remodeling and neovessel formation during atherogenesis and other chronic immune reactions.

CD40 Antigens↗
PubMed1999

Differential expression of three T lymphocyte-activating CXC chemokines by human atheroma-associated cells.

Activated T lymphocytes accumulate early in atheroma formation and persist at sites of lesion growth and rupture, suggesting that they may play an important role in the pathogenesis of atherosclerosis. Moreover, atherosclerotic lesions contain the Th1-type cytokine IFN-gamma, a potentiator of atherosclerosis. The present study demonstrates the differential expression of the 3 IFN-gamma-inducible CXC chemokines--IFN-inducible protein 10 (IP-10), monokine induced by IFN-gamma (Mig), and IFN-inducible T-cell alpha chemoattractant (I-TAC)--by atheroma-associated cells, as well as the expression of their receptor, CXCR3, by all T lymphocytes within human atherosclerotic lesions in situ. Atheroma-associated endothelial cells (ECs), smooth muscle cells (SMCs), and macrophages (MO) all expressed IP-10, whereas Mig and I-TAC were mainly expressed in ECs and MO, as detected by double immunofluorescence staining. ECs of microvessels within lesions also expressed abundant I-TAC. In vitro experiments supported these results and showed that IL-1beta, TNF-alpha, and CD40 ligand potentiated IP-10 expression from IFN-gamma-stimulated ECs. In addition, nitric oxide (NO) treatment decreased IFN-gamma induction of IP-10. Our findings suggest that the differential expression of IP-10, Mig, and I-TAC by atheroma-associated cells plays a role in the recruitment and retention of activated T lymphocytes observed within vascular wall lesions during atherogenesis.

Animals↗
PubMed1998

Generation of biologically active IL-1 beta by matrix metalloproteinases: a novel caspase-1-independent pathway of IL-1 beta processing.

Biologic activity of IL-1 beta requires processing of the inactive precursor, a function generally ascribed to IL-1 beta-converting enzyme (caspase-1). However, alternative mechanisms of IL-1 beta activation have been postulated in local inflammatory reactions. Expression of IL-1 beta and matrix metalloproteinases (MMPs) frequently occurs simultaneously at sites of inflammation. We describe here that stromelysin-1 (MMP-3), as well as the gelatinases A (MMP-2) and B (MMP-9), processes recombinant human IL-1 beta precursor (pIL-1 beta) into biologically active forms. Detection of both pIL-1 beta processing and biologic IL-1 beta activity demonstrated different processing capacities of the respective MMPs. Conversion of pIL-1 beta by stromelysin-1 required coincubation for at least 1 h, and biologic activity faded after 8 h to 24 h. Gelatinase A was less effective in processing pIL-1 beta, requiring at least 24 h of coincubation. In contrast, gelatinase B processed pIL-1 beta within minutes, resulting in immunoreactive products as well as biologic activity stable for 72 h. In addition, prolonged incubation of mature IL-1 beta with stromelysin-1, and to a lesser extent also with gelatinases, but not with interstitial collagenase, resulted in the degradation of mature IL-1 beta. None of the MMPs processed the second isoform of IL-1, IL-1 alpha. The present study indicates a biphasic regulation of IL-1 beta activity by MMPs: a caspase-1-independent pathway of IL-1 beta activation and inhibition of IL-1 beta activity by degrading the mature cytokine. The balance of the respective MMPs and pIL-1 beta might regulate the long term appearance of IL-1 beta activity at sites of acute or chronic inflammation.

Animals↗
PubMed1998

Reduction of atherosclerosis in mice by inhibition of CD40 signalling.

Increasing amounts of evidence support the involvement of inflammation and immunity in atherogenesis, but mediators of communication between the major cell types in atherosclerotic plaques are poorly defined. Cells in human atherosclerotic lesions express the immune mediator CD40 and its ligand CD40L (also known as CD154 or gp39). The interaction of CD40 with CD40L figures prominently in both humoral and cell-mediated immune responses. CD40L-positive T cells accumulate in atheroma, and, by virtue of their early appearance, persistence and localization at sites of lesion growth and complication, activated T cells may coordinate important aspects of atherogenesis. Interruption of CD40L-CD40 signalling by administration of an anti-CD40L antibody limits experimental autoimmune diseases such as collagen-induced arthritis, lupus nephritis, acute or chronic graft-versus-host disease, multiple sclerosis and thyroiditis. Ligation of CD40 on atheroma-associated cells in vitro activates functions related to atherogenesis, including induction of proinflammatory cytokines, matrix metalloproteinases, adhesion molecules and tissue factor. However, the role of CD40 signalling in atherogenesis in vivo remains unknown. Here we determine whether interruption of CD40 signalling influences atherogenesis in vivo in hyperlipidaemic mice. Treatment with antibody against mouse CD40L limited atherosclerosis in mice lacking the receptor for low-density lipoprotein that had been fed a high-cholesterol diet for 12 weeks. This antibody reduces the size of aortic atherosclerotic lesions by 59% and their lipid content by 79%. Furthermore, atheroma of mice treated with anti-CD40L antibody contained significantly fewer macrophages (64%) and T lymphocytes (70%), and exhibited decreased expression of vascular cell adhesion molecule-1. These data support the involvement of inflammatory pathways in atherosclerosis and indicate a role for CD40 signalling during atherogenesis in hyperlipidaemic mice.

Animals↗
PubMed1998

Current concepts in cardiovascular pathology: the role of LDL cholesterol in plaque rupture and stabilization.

Emerging evidence is redefining traditional concepts of coronary atherosclerosis. Recent data indicate that severe stenoses, the traditional focus of attention, do not cause most coronary events. Rather, interest has increased in the often less stenotic but more vulnerable lesions that are characterized by thin fibrous caps, large lipid accumulations, large numbers of macrophages, and depletion of smooth muscle cells. Such lesions appear prone to rupture, which allows the blood to come into contact with the highly thrombogenic material in the lipid core of the plaque, thereby precipitating thrombosis. The fibrous cap may become weakened through decreased synthesis of the extracellular matrix or increased degradation of the matrix. The cytokine interferon-gamma, produced by T-lymphocytes, inhibits the ability of smooth muscle cells to synthesize collagen, a structurally important component of the fibrous cap. A family of enzymes known as matrix metalloproteinases can degrade all major constituents of the vascular extracellular matrix: collagen, elastin, and proteoglycans. Additional studies on the biochemical mechanisms of atherosclerosis may provide a fuller understanding of the ways in which lipid-lowering therapy can confer clinical benefit.

Cholesterol, LDL↗
PubMed1998

CD40 signaling in vascular cells: a key role in atherosclerosis?

Atherosclerosis is one of the most prevalent fatal diseases in Western societies, and results from an intricate interplay between diverse factors such as lipid metabolism, blood coagulation elements, cytokines, hemodynamic stress, and behavioral risk factors. Atherosclerotic lesions are characterized by the infiltration of immune competent cells such as macrophages and T-lymphocytes, the proliferation of intimal cells of the arterial wall, the accumulation of lipids and the deposition of extracellular matrix components. For some years, endothelial cells, smooth muscle cells, and macrophages have been accorded crucial roles in the process of atherosclerosis. The mechanisms by which these cells contribute to atherosclerosis include augmented expression of adhesion molecules, as well as secretion of proinflammatory cytokines, matrix metalloproteinases, and tissue factor within human and experimental atheroma. Much evidence supports the role of tissue factor in inciting the thrombosis that causes most acute coronary syndromes. Macrophage content and expression of tissue factor correlate with rupture and instability of the atherosclerotic plaque. Matrix metalloproteinases can digest the plaque's extracellular matrix, and thus impair its stability. Plaque rupture exposes circulating blood components to the tissue factor-rich lipid-core, inciting thrombosis. Despite the increasing appreciation that atherogenesis involves participation of inflammatory pathways within cellular interactions, mediators of local communication between the major cell types within atherosclerotic plaques remain incompletely defined. By early appearance, activated T-cells may act as the orchestrator of atherogenesis. Both soluble and contact-dependent mediators from T-cells may be crucial in the development of this prevalent disease. Recent reports have helped explain some of these questions by pointing to a role of contact dependent interaction between CD40 and CD40 ligand (CD40L, renamed CD154) as a stimulus for atheroma-associated cells. We and others have recently showed that activated T-lymphocytes within the atherosclerotic vessel wall express the CD40 ligand surface molecule, known to play a major role in several immunological pathways. In addition to activated T-lymphocytes, functional CD40 and CD40L are coexpressed by human vascular endothelial cells, smooth muscle cells and human macrophages in vitro as well as in situ in human atherosclerotic lesions. Recent studies indicate that CD40L activates atheroma-associated cells by promoting the expression of molecules thought to be involved in atherosclerosis, such as adhesion molecules, cytokines, matrix metalloproteinases, and tissue factor. Thus, CD40 ligation on these vascular wall cells may promote mononuclear cell recruitment, participate in the weakening of the plaque and set the stage for thrombosis, mechanisms of crucial importance in the process of atherosclerosis. The involvement of the CD40 signaling pathway may play major roles during atherogenesis by regulating antigen-specific T-cell responses to yield activation instead of tolerance, and the presence of functional CD40L on non-leukocytic cells associated with atherosclerotic lesion indicates a novel T-cell-independent route of inflammatory activation, a now well recognized component of atherogenesis. These findings establish a possible crucial role for CD40-CD40L interactions in a prevalent human disease.

Animals↗
PubMed1997

Ligation of CD40 activates interleukin 1beta-converting enzyme (caspase-1) activity in vascular smooth muscle and endothelial cells and promotes elaboration of active interleukin 1beta.

Inflammation contributes to a variety of arterial diseases including atherosclerosis. Interleukin 1beta (IL-1beta) in its activated mature 17-kDa form may mediate aspects of vascular inflammation. As shown previously, human vascular wall cells, such as smooth muscle cells (SMC), express the IL-1beta precursor upon stimulation and the IL-1beta-converting enzyme (ICE) constitutively but do not produce mature IL-1beta or express ICE activity. How SMC, the most numerous cell type in arteries, may release active IL-1beta has therefore remained a perplexing problem. We report here that stimulation of human vascular SMC and endothelial cells (EC) through CD40 ligand, a mediator recently localized in human atheroma, induced elaboration of the IL-1beta precursor as well as activation of cell-associated ICE. In addition to the constitutively expressed 45- and 30-kDa immunoreactive ICE proteins, vascular cells incubated with recombinant human CD40 ligand (rCD40L) (but not IL-1 or TNF) showed an increase of a 20-kDa immunoreactive ICE protein by Western blot analysis. Furthermore, SMC and EC stimulated through rCD40L processed recombinant human IL-1beta precursor (pIL-1beta), generating a cleavage product of approximately 17 kDa. Appearance of both the 20-kDa immunoreactive ICE protein and pIL-1beta processing activity required at least 6 h of stimulation with 0.3 or 1.0 microg/ml rCD40L, respectively, and was inhibited by pre-incubation of the ligand with an anti-CD40L antibody. Stimulation of vascular SMC and EC through rCD40L resulted in the release of biologically active IL-1beta, indicating processing of the native IL-1beta precursor induced by the ligand. These findings establish a novel mechanism of IL-1beta activation in human vascular cells and, moreover, indicate a new pathway of ICE-activation, which could participate in inflammatory aspects of atherogenesis and other disease states.

CD40 Antigens↗
PubMed1997

Activation of monocyte/macrophage functions related to acute atheroma complication by ligation of CD40: induction of collagenase, stromelysin, and tissue factor.

BACKGROUND: Plaque disruption with thrombosis commonly causes the acute coronary syndromes. Macrophages, abundant at sites of plaque rupture, release proteinases that weaken plaques and express tissue factor (TF), which initiates thrombosis. The signals that induce expression of these macrophage functions, particularly TF, remain obscure. Recent studies have localized the receptor CD40 and its ligand in human atheroma. This study tested the hypothesis that ligation of CD40 can activate key mononuclear phagocyte functions related to clinical manifestations of atheroma. METHODS AND RESULTS: Stimulation of human monocytes/macrophages through CD40 by either membranes from activated T cells or recombinant CD40L (rCD40L) induced expression of interstitial collagenase, stromelysin, and TF protein and activity. In contrast, the soluble cytokines interleukin-1 or tumor necrosis factor-alpha did not induce or weakly induced TF expression. Neutralization with anti-CD40L antibody markedly inhibited these actions of both T-cell membranes and rCD40L. CONCLUSIONS: By inducing the expression of matrix-degrading proteinases and of TF procoagulant, CD40 signaling may contribute to the triggering of acute coronary events.

Arteriosclerosis↗
PubMed1997

Functional CD40 ligand is expressed on human vascular endothelial cells, smooth muscle cells, and macrophages: implications for CD40-CD40 ligand signaling in atherosclerosis.

Increasing evidence supports involvement of inflammation and immunity in atherogenesis. We report here that CD40 ligand (CD40L), an immunoregulatory signaling molecule heretofore considered largely restricted to recently activated CD4+ T lymphocytes, is expressed by human vascular endothelial cells (EC), smooth muscle cells (SMC), and human macrophages in vitro, and is coexpressed with its receptor CD40 on all three cells types in human atherosclerotic lesions in situ. Cultured human vascular EC, SMC, and human macrophages all constitutively expressed CD40L mRNA as well as protein. Stimulation with interleukin 1beta, tumor necrosis factor alpha, or interferon gamma increased surface levels and de novo synthesis of CD40L on all three cell types. CD40L expressed on EC, SMC, and macrophages exhibited biological activity, as it induced B7.2 expression on B cells. Human vascular SMC also constitutively expressed CD40, the receptor for CD40L, and through CD40 signaling, human recombinant CD40L induced expression of proinflammatory cytokines in these cells, identifying SMC as a target for CD40L. Human atherosclerotic lesions (n = 8) showed expression of immunoreactive CD40L on EC, SMC, and macrophages, while normal arterial tissues (n = 5) contained no CD40L. In atheroma CD40L+ cells often also expressed CD40. These observations establish human vascular EC, SMC, and human macrophages as a novel source of CD40L, and point to T cell-independent CD40 signaling, and a broader function of this pathway in regulation of nonimmune cells, as illustrated here by potential autocrine and paracrine activation during atherogenesis.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1997

C-reactive protein as a marker for acute coronary syndromes.

BACKGROUND: For several years, acute coronary syndromes have been perceived as causing the most hospital admissions, and even hospital mortality. The syndrome of unstable angina frequently progresses to acute myocardial infarction but its pathogenesis is poorly understood, and prognosis determination is still problematic. We tested the hypothesis that measurement of the C-reactive protein in patients admitted for chest pain could be a marker for acute coronary syndromes. METHODS AND RESULTS: We studied 110 patients admitted with suspected ischaemic heart disease, but without elevated serum creatine-kinase levels at the time of hospital admission. Patients were subsequently divided into two groups based on their final diagnosis: group 1 comprised patients with unstable angina; group 2 patients with acute myocardial infarction. We measured the C-reactive protein at the time of hospital admission. The concentration of C-reactive protein was elevated in 59% of the patients with a final diagnosis of acute myocardial infarction, and in 5% of the patients with a final diagnosis of unstable angina, (P < 0.001). CONCLUSION: This study indicates that C-reactive protein levels measured at the time of admission in patients with suspected ischaemic heart disease could be a marker for acute coronary syndromes, and helpful in identifying patients at high risk for acute myocardial infarction. Measurement of C-reactive protein may have practical clinical significance in the management of patients hospitalized for suspected acute coronary syndromes.

Acute Disease↗
PubMed1997

Regulation of matrix metalloproteinase expression in human vascular smooth muscle cells by T lymphocytes: a role for CD40 signaling in plaque rupture?

Physical disruption of an atheromatous lesion often underlies acute coronary syndromes. Matrix-degrading enzymes, eg, matrix metalloproteinases (MMPs), may cause loss in mechanical integrity of plaque tissue that favors rupture. T lymphocytes accumulate at sites where atheromata rupture, but the mechanisms by which these immune cells may contribute to plaque destabilization are unknown. This study tested the hypothesis that the T-lymphocyte surface molecule CD40 ligand (CD40L), recently localized in atherosclerotic plaques, regulates the expression of MMPs in human vascular smooth muscle cells (SMCs), the most numerous cell type in arteries. We report here that stimulated human T lymphocytes induced the expression of the matrix-degrading enzymes, ie, interstitial collagenase (MMP-1), stromelysin (MMP-3), gelatinase B (MMP-9), and activated gelatinase A (MMP-2), in human vascular SMCs by cell contact via CD40 ligation, as demonstrated by Western blot analysis, zymography, and antibody neutralization. Recombinant human CD40L (rCD40L) induced de novo synthesis of MMP-1, MMP-3, and MMP-9 on vascular SMCs and stimulated the expression of these enzymes to a greater extent than did maximally effective concentrations of tumor necrosis factor-alpha or interleukin-1beta, established agonists of MMP expression. Interferon gamma, another T-lymphocyte- derived cytokine, inhibited the induction of MMPs by rCD40L. Immunohistochemical analysis of human coronary atheromata colocalized MMP-1 and MMP-3 with CD40-positive SMCs. These results demonstrated that CD40 ligand, expressed on T lymphocytes, promoted the expression of matrix-degrading enzymes in vascular SMCs and thus established a new pathway of immune-modulated destabilization in human atheromata.

Arteriosclerosis↗