A key component of cardiac remodeling after acute myocardial infarction (MI) is the inflammatory response, which modulates cardiac tissue repair. The purpose of this study was to investigate the relationship between the monocytic inflammatory response and left ventricular remodeling after MI using mice deficient in CC chemokine receptor 2 (CCR2), the primary receptor for the critical regulator of CC chemokine ligand 2. Immunohistochemical analysis revealed rapid infiltration of macrophages into infarcted tissue within 7 days in wild-type (WT) mice. However, this process was greatly impaired in CCR2-deficient (CCR2(-/-)) mice. Echocardiography demonstrated beneficial effects of CCR2 deficiency on left ventricular remodeling at 7 and 28 days after MI. In situ zymography showed augmented gelatinolytic activity in WT mice within 7 days after MI, whereas gelatinolytic activity was barely detectable in CCR2(-/-) mice. Moreover, the distribution of gelatinolytic activity in serial sections was very similar to the distribution of macrophages rather than neutrophils. Expression of matrix metalloproteinases and tumor necrosis factor-alpha mRNAs was up-regulated in infarcted regions from WT mice compared to CCR2(-/-) mice at 3 days after MI. Direct inhibition of CCR2 functional pathway might contribute to the attenuation of left ventricular remodeling after MI.

arly coronary reperfusion limits myocardial damage and improves survival after myocardial infarction. However, growing evidence indicates that reperfusion itself can cause damage to the ischemic myocardium; this damage is known as post-ischemic myocardial reperfusion injury. 1 Local and systemic inflammatory reactions play a key role in the extension of myocardial tissue injury and adverse effects during left ventricular (LV) recovery. 2 Some experimental studies have demonstrated the importance of monocyte/macrophage infiltration after myocardial infarction. 3,4 Monocyte chemoattractant protein-1 (MCP-1) belongs to the CC chemokine subfamily with 2 adjacent cysteine residues, and serves as a chemotactic and activating factor for the recruitment of monocytes. 5 MCP-1 is secreted by various types of cells, such as monocytes/macrophages, T lymphocytes, endothelial cells, vascular smooth muscle cells and myocytes. [5][6][7] Many experimental and clinical studies have demonstrated up-regulation of MCP-1 after myocardial infarction, with recruitment of monocytes/macrophages to the ischemic myocardium. 8,9 CC chemokine receptor 2 (CCR2) is a major receptor for MCP-1 and MCP-1 appears to bind solely to CCR2. 5 We have previously reported improvement in LV remodeling after myocardial infarction in mice deficient in the gene encoding CCR2 by inhibiting matrix metalloproteinase (MMP) activity. 10 Recently, Dewald et al also reported that MCP-1 -/-mice attenuated LV remodeling after myocardial ischemia followed by reperfusion. 11 In addition to the effects on MMP activity and the release of pro-inflammatory cytokines, macrophages may cause oxidative stress. 12-14 Increased oxidative stress has been implicated in the cell death associated with cardiovascular diseases including ischemia-reperfusion injury. 15 Macrophages have been shown to produce peroxynitrite (ONOO -), a highly reactive oxygen species that can cause cell injury. 16 Several studies have implicated peroxynitrite as a major cause of injury in the heart subjected to ischemiareperfusion or cytokines. 17,18 However, it is not clear whether the inhibition of the CCR2 pathway may attenuate oxidative stress induced by myocardial ischemia-reperfusion in mice. We hypothesized that the inhibition of the MCP-1/CCR2 pathway may contribute to the attenuation of infarct size after myocardial ischemia-reperfusion via inhibition of macrophage-related oxidative stress and MMP.Thus, the purpose of the present study was to investigate the relationship between the monocytic inflammatory response and myocardial ischemia-reperfusion injury by using mice deficient in the CCR2 gene. Background Monocyte chemoattractant protein-1 (MCP-1) and its major receptor, CC chemokine receptor 2 (CCR2), have been shown to contribute to left ventricular remodeling after myocardial infarction. However, it is unknown whether CCR2 deficiency protects the myocardium after myocardial ischemia-reperfusion. The purpose of the present study was to investigate the effects of CCR2 deficiency on myocardial...

The development of microsurgical techniques has facilitated the establishment of fully vascularized cardiac transplantation models in small mammals. A particularly useful model that has evolved for the study of cardiac allograft vasculopathy (CAV) is a heterotopic (abdominal) vascularized murine cardiac transplantation model. Using this model has permitted the elucidation of genetic, immune and non-immune factors contributing to the development of this inexorable pathological condition, which compromises half of all human cardiac transplants. This protocol details methods for performing the transplant, histomorphometric assessment of the graft vasculature and functional evaluation of the transplanted heart. In experienced hands, the surgical procedure requires approximately 75 min to complete, and vasculopathy results are obtained at 2 months. This model entails a fully vascularized implantation technique in which the donor ascending aorta and pulmonary artery are sutured end-to-side to the recipient abdominal aorta and inferior vena cava, respectively. As this model reliably reproduces immunological and non-immunological features of CAV, investigators can thoroughly explore contributory mechanisms, diagnostic modalities and therapeutic approaches to its mitigation.

Ectoenzymes expressed on the surface of vascular cells and leukocytes modulate the ambient nucleotide milieu. CD73 is an ecto-5’ nucleotidase that catalyzes the terminal phosphohydrolysis of AMP and resides in the brain on glial cells, cells of the choroid plexus, and leukocytes. Though CD73 tightens epithelial barriers, its role in the ischemic brain remains undefined. When subjected to photothrombotic arterial occlusion, CD73−/− mice exhibited significantly larger (49%) cerebral infarct volumes than wild type (WT)4 mice, with concordant increases in local accumulation of leukocyte subsets (neutrophils, T lymphocytes, macrophages, microglia). CD73−/− mice were rescued from ischemic neurological injury by soluble 5’ nucleotidase. In situ, CD73−/− macrophages upregulated expression of costimulatory molecules far more than WT macrophages, with a sharp increase of the CD80:CD86 ratio. To define the CD73-bearing cells responsible for ischemic cerebroprotection, mice were subjected to irradiative myeloablation, marrow reconstitution, and then stroke following engraftment. Chimeric mice lacking CD73 in tissue had larger cerebral infarct volumes and more tissue leukosequestration than did mice lacking CD73 on circulating cells. These data show for the first time a cardinal role for CD73 in suppressing ischemic tissue leukosequestration. This underscores a critical role for CD73 as a modulator of brain inflammation and immune function.

Background— Class A macrophage scavenger receptor (SR-A) is a macrophage-restricted multifunctional molecule that optimizes the inflammatory response by modulation of the activity of inflammatory cytokines. This study was conducted with SR-A–deficient (SR-A −/− ) mice to evaluate the relationship between SR-A and cardiac remodeling after myocardial infarction. Methods and Results— Experimental myocardial infarction (MI) was produced by ligation of the left coronary artery in SR-A −/− and wild-type (WT) male mice. The number of mice that died within 4 weeks after MI was significantly greater in SR-A −/− mice than in WT mice ( P =0.03). Importantly, death caused by cardiac rupture within 1 week after MI was 31% (17 of 54 mice) in SR-A −/− mice and 12% (6 of 51 mice) in WT mice ( P =0.01). In situ zymography demonstrated augmented gelatinolytic activity in the infarcted myocardium in SR-A −/− mice compared with WT mice. Real-time reverse transcription–polymerase chain reaction at day 3 after MI showed that the expression of matrix metalloproteinase-9 mRNA increased significantly in the infarcted myocardium in SR-A −/− mice compared with WT mice. Furthermore, SR-A −/− mice showed augmented expression of tumor necrosis factor-α and reduction of interleukin-10 in the infarcted myocardium at day 3 after MI. In vitro experiments also demonstrated increased tumor necrosis factor-α and decreased interleukin-10 expression in activated SR-A −/− macrophages. Conclusions— The present findings suggest that SR-A deficiency might cause impairment of infarct remodeling that results in cardiac rupture via insufficient production of interleukin-10 and enhanced expression of tumor necrosis factor-α and of matrix metalloproteinase-9. SR-A might contribute to the prevention of cardiac rupture after MI.

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Summary To clarify the role of the monocyte chemoattractant protein‐1 (MCP‐1)/C–C chemokine receptor 2 (CCR2) signalling pathway in hyperoxia‐induced acute lung injury, CCR2‐deficient (CCR2−/−) and wild‐type (CCR2+/+) mice were exposed to 85% O2 for up to 6 days. At day 3, body weight significantly decreased and total protein concentration in bronchoalveolar lavage fluid (BALF) was higher in CCR2−/− mice compared with CCR2+/+ mice. Cumulative survivals were significantly lower in CCR2−/− mice than in CCR2+/+ mice. However, the two groups showed no significant differences in both histological changes and number of macrophages in BALF. Real‐time reverse transcriptase‐polymerase chain reaction revealed increased mRNA levels of MCP‐1, interleukin‐1β thioredoxin‐1, and inducible nitric oxide synthase (iNOS) in lung tissues in CCR2−/− mice compared with CCR2+/+ mice. Increased iNOS mRNA levels in alveolar macrophages exposed to 85% O2 for 48 h in vivo or in vitro were significantly higher in CCR2−/− mice than in CCR2+/+ mice. These results suggest that the MCP‐1/CCR2 signalling pathway is protective against hyperoxia‐induced tissue injury by suppressing induction of iNOS and consequent production of reactive oxygen species by activated alveolar macrophages.

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