Background-Inflammation plays a key role in the pathophysiology of myocardial ischemia/reperfusion (I/R) injury; however, the mechanism by which myocardial I/R induces inflammation remains unclear. Recent evidence indicates that a sterile inflammatory response triggered by tissue damage is mediated through a multiple-protein complex called the inflammasome. Therefore, we hypothesized that the inflammasome is an initial sensor for danger signal(s) in myocardial I/R injury. Methods and Results-We demonstrate that inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes, is crucially involved in the initial inflammatory response after myocardial I/R injury. We found that inflammasomes are formed by I/R and that its subsequent activation of inflammasomes leads to interleukin-1␤ production, resulting in inflammatory responses such as inflammatory cell infiltration and cytokine expression in the heart. In mice deficient for apoptosis-associated speck-like adaptor protein and caspase-1, these inflammatory responses and subsequent injuries, including infarct development and myocardial fibrosis and dysfunction, were markedly diminished. Bone marrow transplantation experiments with apoptosis-associated speck-like adaptor protein-deficient mice revealed that inflammasome activation in bone marrow cells and myocardial resident cells such as cardiomyocytes or cardiac fibroblasts plays an important role in myocardial I/R injury. In vitro experiments revealed that hypoxia/reoxygenation stimulated inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes, and that hypoxia/reoxygenation-induced activation was mediated through reactive oxygen species production and potassium efflux. Conclusions-Our results demonstrate the molecular basis for the initial inflammatory response after I/R and suggest that the inflammasome is a potential novel therapeutic target for preventing myocardial I/R injury. (Circulation. 2011;123:594-604.)Key Words: cytokine Ⅲ heart Ⅲ hypoxia Ⅲ inflammation Ⅲ leukocyte I ncreasing evidence indicates that inflammation is involved in the pathophysiology of myocardial ischemia/reperfusion (I/R) injury. 1 One prominent and early mediator for inflammation in I/R injury is interleukin-1␤ (IL-1␤). 2,3 I/R induces IL-1␤ expression in the heart, and the inhibition of IL-1␤ prevents myocardial injury after I/R, 3 suggesting that the deleterious effects of myocardial I/R are mediated, at least in part, by IL-1␤. In the generation of IL-1␤, pro-IL-1␤, an inactive precursor, undergoes proteolysis by the converting enzyme caspase-1. Caspase-1 is activated within a cytosolic multiprotein complex, the inflammasome. The inflammasome contains cytoplasmic receptors of the NACHT leucine-rich-repeat protein family that are associated with the apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), which in turn recruits and activates caspase-1. 4,5 Increasing evidence indicates that several sterile inflammatory responses triggered by tissue damage are mediated by th...

Abstract-Myocardial infarction (MI) is accompanied by inflammatory responses that lead to the recruitment of leukocytes and subsequent myocardial damage, healing, and scar formation. Because monocyte chemoattractant protein-1 (MCP-1) (also known as CCL2) regulates monocytic inflammatory responses, we investigated the effect of cardiac MCP-1 overexpression on left ventricular (LV) dysfunction and remodeling in a murine MI model. Transgenic mice expressing the mouse JE-MCP-1 gene under the control of the ␣-cardiac myosin heavy chain promoter (MHC/MCP-1 mice) were used for this purpose. MHC/MCP-1 mice had reduced infarct area and scar formation and improved LV dysfunction after MI. These mice also showed induction of macrophage infiltration and neovascularization; however, few bone marrow-derived endothelial cells were detected in MHC/MCP-1 mice whose bone marrow was replaced with that of Tie2/LacZ transgenic mice. Flow cytometry analysis showed no increase in endothelial progenitor cells (CD34 ϩ /Flk-1 ϩ cells) in MHC/MCP-1 mice. Marked myocardial interleukin (IL)-6 secretion, STAT3 activation, and LV hypertrophy were observed after MI in MHC/MCP-1 mice. Furthermore, cardiac myofibroblasts accumulated after MI in MHC/MCP-1 mice. In vitro experiments revealed that a combination of IL-6 with MCP-1 synergistically stimulated and sustained STAT3 activation in cardiomyocytes. MCP-1, IL-6, and hypoxia directly promoted the differentiation of cardiac fibroblasts into myofibroblasts. Our results suggest that cardiac overexpression of MCP-1 induced macrophage infiltration, neovascularization, myocardial IL-6 secretion, and accumulation of cardiac myofibroblasts, thereby resulting in the prevention of LV dysfunction and remodeling after MI. They also provide a new insight into the role of cardiac MCP-1 in the pathophysiology of MI. Key Words: cytokines Ⅲ heart failure Ⅲ hypertrophy Ⅲ inflammation Ⅲ myocardial infarction M yocardial infarction (MI) is accompanied by inflammatory responses that lead to the recruitment of leukocytes and subsequent myocardial damage, healing, and scar formation. 1 Recruitment and activation of monocytes/macrophages in the infarcted myocardium have been shown to contribute importantly to the processes that occur after MI. The activated macrophages lead to the release of cytokines and proteinases, which can induce further inflammation and left ventricular (LV) remodeling. Meanwhile, recent evidence indicates that some endothelial progenitor cells (EPCs) are derived from monocytic lineage cells and participate in neovascularization in ischemic tissues. [2][3][4] Moreover, monocytic-derived EPCs secrete a large amount of angiogenic factors such as the vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF), 4 thereby suggesting that monocytes/macrophages could improve LV dysfunction and remodeling after MI.Chemokines are a family of potent chemotactic cytokines that regulate locomotion and trafficking of leukocytes in basal and inflammatory processes; however, it has been rece...

Background-Inflammatory cytokines such as interleukin (IL)-1␤ and IL-18 play an important role in the development of atherosclerosis and restenosis. Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is an adaptor protein that regulates caspase-1-dependent IL-1␤ and IL-18 generation; however, the role of ASC in vascular injury remains undefined. Here, we investigated the contribution of ASC to neointimal formation after vascular injury in ASC-deficient (ASC Ϫ/Ϫ ) mice. Methods and Results-Wire-mediated vascular injury was produced in the femoral artery of ASC Ϫ/Ϫ and wild-type mice. Immunohistochemical analysis revealed that ASC was markedly expressed at the site of vascular injury. Neointimal formation was significantly attenuated in ASC Ϫ/Ϫ mice after injury. IL-1␤ and IL-18 were expressed in the neointimal lesion in wild-type mice but showed decreased expression in the lesion of ASC Ϫ/Ϫ mice. To investigate the contribution of bone marrow-derived cells, we developed bone marrow-transplanted mice and found that neointimal formation was significantly decreased in wild-type mice in which bone marrow was replaced with ASC Ϫ/Ϫ bone marrow cells. Furthermore, in vitro experiments showed that the proliferation activity of ASC Ϫ/Ϫ vascular smooth muscle cells was not impaired. Conclusions-These findings suggest that bone marrow-derived ASC is critical for neointimal formation after vascular injury and identify ASC as a novel therapeutic target for atherosclerosis and restenosis. (Circulation. 2008;117: 3079-3087.)

G-CSF treatment accelerated reendothelialization and decreased neointimal formation following vascular injury, although there was little contribution of bone marrow-derived EPCs to the reendothelialization of the artery. These results suggest that G-CSF pretreatment has a therapeutic potential for prevention of restenosis following PCI.

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Objective-Since the macrophage colony-stimulating factor (M-CSF) has been shown to stimulate differentiation and proliferation of monocyte/macrophage lineage and to be involved in the process of neointimal formation after vascular injury, we tested the effects of M-CSF on the recruitment of bone marrow-derived progenitor cells in neointimal formation after vascular injury in mice. Methods and Results-Wire-mediated vascular injury was produced in the femoral artery of C57BL/6 mice. Recombinant human M-CSF [500 g/(kg⅐day)] or saline (control) was administered for 10 consecutive days, starting 4 days before the injury. Treatment with M-CSF accelerated neointimal formation in the early phase after injury, and this neointimal lesion mainly consisted of bone marrow-derived cells. M-CSF treatment had no effect on the mobilization of endothelial progenitor cells (EPCs: CD34 ϩ /Flk-1 ϩ ) and reendothelialization after injury. The stromal cell-derived factor-1 (SDF-1) was markedly expressed in the neointima and media after injury, whereas CXCR4 ϩ cells were observed in the neointima. Further, a novel CXCR4 antagonist, AMD3100, significantly attenuated the M-CSF-induced neointimal formation. Conclusions-These findings suggest that M-CSF accelerated neointimal formation after vascular injury via the SDF-1-CXCR4 system, and the inhibition of this system has therapeutic potential for the treatment of cardiovascular diseases. Key Words: angioplasty Ⅲ cytokines Ⅲ inflammation Ⅲ restenosis Ⅲ vascular biology T he vascular endothelium forms a biological interface between circulating blood components and various tissues in the body. This monolayer of endothelial cells locally monitors systemically generated stimuli, and alters the functional state of the vessels. This adaptive mechanism contributes to normal homeostasis; however, nonadaptive changes in the endothelial structure and function, provoked by pathophysiological stimuli, may induce "endothelial dysfunction," which plays an important role in the initiation and progression of cardiovascular diseases. In particular, the loss of endothelial cells because of vascular injury leads to the migration and proliferation of vascular smooth muscle cells (SMCs), resulting in neointimal formation. Further, the vascular injury initiates an inflammatory healing response that involves the expression of growth factors and cytokines and promotes neointimal formation. The resultant neointimal formation is the pathological basis of atherosclerosis and restenosis following percutaneous coronary intervention (PCI) such as angioplasty and stenting. See page 263The recruitment, activation, and proliferation of monocytes/macrophages in the vessel wall make important contribution to the process of atherosclerosis and restenosis. The presence of activated monocytes/macrophages at the site of the vascular injury leads to the release of vasoactive molecules, cytokines, and growth factors, which can induce the migration and proliferation of SMCs. However, recent evidence indicates that a part of the po...

These findings suggest that cardiac MCP-1 prevented LV dysfunction after global I/R through a reactive oxygen species-dependent but K(ATP) channel-independent pathway; this provides new insight into the beneficial role of MCP-1 in the pathophysiology of ischaemic heart diseases.

Abstract. To construct a non-clinical database for drug-induced QT interval prolongation, the electrophysiological effects of 11 positive and 10 negative compounds on action potentials (AP) in guinea-pig papillary muscles were investigated in a multi-site study according to a standard protocol. Compounds with a selective inhibitory effect on the rapidly activated delayed rectifier potassium current (I Kr ) prolonged action potential duration at 90% repolarization (APD 90 ) in a concentration-dependent manner, those showing Ca 2+ current (I Ca ) inhibition shortened APD 30 , and those showing Na + current (I Na ) inhibition decreased action potential amplitude (APA) and V max . Some of the mixed ion-channel blockers showed a bell-shaped concentration-response curve for APD 90 , probably due to their blockade of I Na and / or I Ca , sometimes leading to a falsenegative result in the assay. In contrast, all positive compounds except for terfenadine and all negative compounds with I Kr -blocking activity prolonged APD 30-90 regardless of their I Na -and / or I Ca -blocking activities, suggesting that APD 30-90 is a useful parameter for evaluating the I Krblocking activity of test compounds. Furthermore, the assay is highly informative regarding the modulation of cardiac ion channels by test compounds. Therefore, when APD 90 and APD 30-90 are both measured, the action potential assay can be considered a useful method for assessing the risk of QT interval prolongation in humans in non-clinical safety pharmacology studies. Supplementary material (Appendix): available only at http://dx