SR-A deficiency reduces myocardial ischemia/reperfusion injury; involvement of increased microRNA-125b expression in macrophages |
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Authors: | Danyang Ren Xiaohui Wang Tuanzhu Ha Li Liu John Kalbfleisch Xiang Gao David Williams Chuanfu Li |
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Institution: | 1. Department of Surgery, East Tennessee State University, Johnson City, TN 37614, USA;2. Department of Geriatrics, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China;3. Department of Biometry and Medical Computing, East Tennessee State University, Johnson City, TN 37614, USA;4. Animal Model Research Center, Nanjing University, Nanjing, 210093 China |
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Abstract: | The macrophage scavenger receptor class A (SR-A) participates in the innate immune and inflammatory responses. This study examined the role of macrophage SR-A in myocardial ischemia/reperfusion (I/R) injury and hypoxia/reoxygenation (H/R)-induced cell damage. SR-A?/? and WT mice were subjected to ischemia (45 min) followed by reperfusion for up to 7 days. SR-A?/? mice showed smaller myocardial infarct size and better cardiac function than did WT I/R mice. SR-A deficiency attenuated I/R-induced myocardial apoptosis by preventing p53-mediated Bak-1 apoptotic signaling. The levels of microRNA-125b in SR-A?/? heart were significantly greater than in WT myocardium. SR-A is predominantly expressed on macrophages. To investigate the role of SR-A macrophages in H/R-induced injury, we isolated peritoneal macrophages from SR-A deficient (SR-A?/?) and wild type (WT) mice. Macrophages were subjected to hypoxia followed by reoxygenation. H/R markedly increased NF-κB binding activity as well as KC and MCP-1 production in WT macrophages but not in SR-A?/? macrophages. H/R induced caspase-3/7 and -8 activities and cell death in WT macrophages, but not in SR-A?/? macrophages. The levels of miR-125b in SR-A?/? macrophages were significantly higher than in WT macrophages. Transfection of WT macrophages with miR-125b mimics attenuated H/R-induced caspase-3/7 and -8 activities and H/R-decreased viability, and prevented H/R-increased p-53, Bak-1 and Bax expression. The data suggest that SR-A deficiency attenuates myocardial I/R injury by targeting p53-mediated apoptotic signaling. SR-A?/? macrophages contain high levels of miR-125b which may play a role in the protective effect of SR-A deficiency on myocardial I/R injury and H/R-induced cell damage. |
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