Chun-Kai Huang1,2, Daopeng Dai1,2, Hongyang Xie1,2, Zhengbin Zhu1,2, Jian Hu1,2, Min Su3, Mingyao Liu4, Lin Lu1, Weifeng Shen1,2, Guang Ning5, Jiqiu Wang5, Ruiyan Zhang1,2, Xiaoxiang Yan1,2. 1. From the Department of Cardiology (C.-K.H., D.D., H.X., Z.Z., J.H., L.L., W.S., R.Z., X.Y.), Shanghai Jiao Tong University School of Medicine, Shanghai, PR China. 2. Ruijin Hospital, Institute of Cardiovascular Diseases (C.-K.H., D.D., H.X., Z.Z., J.H., L.L., W.S., R.Z., X.Y.), Shanghai Jiao Tong University School of Medicine, Shanghai, PR China. 3. Department of Pathology, Institute of Clinical Pathology, Shantou University Medical College, Guangdong, PR China (M.S.). 4. Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, PR China (M.L.). 5. Department of Endocrinology and Metabolism (G.N., J.W.), Shanghai Jiao Tong University School of Medicine, Shanghai, PR China.
Abstract
RATIONALE: Macrophages are critically involved in wound healing following myocardial infarction (MI). Lgr4, a member of LGR (leucine-rich repeat-containing G protein-coupled receptor) family, is emerging as a regulator of macrophage-associated immune responses. However, the contribution of Lgr4 to macrophage phenotype and function in the context of MI remains unclear. OBJECTIVE: To determine the role of macrophage Lgr4 in MI and to dissect the underlying mechanisms. METHODS AND RESULTS: During early inflammatory phase of MI, infarct macrophages rather than neutrophils expressed high level of Lgr4. Macrophage-specific Lgr4 knockout mice had no baseline cardiovascular defects but manifested improved heart function, modestly reduced infarct size, decreased early mortality due to cardiac rupture, and ameliorated adverse remodeling after MI. Improved outcomes in macrophage-specific Lgr4 knockout mice subjected to MI were associated with mitigated ischemic injury and optimal infarct healing, as determined by reduction of cardiac apoptosis in the peri-infarct zone, attenuation of local myocardial inflammatory response, decrease of matrix metalloproteinase expression in the infarct, enhancement of angiogenesis, myofibroblast proliferation, and collagen I deposition in reparative granulation tissue as well as formation of collagen-rich scar. More importantly, macrophage-specific Lgr4 knockout infarcts had reduced numbers of infiltrating leukocytes and inflammatory macrophages but harbored abundant reparative macrophage subsets. Lgr4-null infarct macrophages exhibited a less inflammatory transcriptional signature. These findings were further supported by transcriptomic profiling data showing repression of multiple pathways and broad-spectrum genes associated with proinflammatory responses in macrophage-specific Lgr4 knockout infarcts. Notably, we discovered that Lgr4-mediated functional phenotype programing in infarct macrophages was at least partly attributed to regulation of AP (activator protein)-1 activity. We further demonstrated that the synergistic effects of Lgr4 on AP-1 activation in inflammatory macrophages occurred via enhancing CREB (cAMP response element-binding protein)-mediated c-Fos, Fosl1, and Fosb transactivation. CONCLUSIONS: Together, our data highlight the significance of Lgr4 in governing proinflammatory phenotype of infarct macrophages and postinfarction repair.
RATIONALE: Macrophages are critically involved in wound healing following myocardial infarction (MI). Lgr4, a member of LGR (leucine-rich repeat-containing G protein-coupled receptor) family, is emerging as a regulator of macrophage-associated immune responses. However, the contribution of Lgr4 to macrophage phenotype and function in the context of MI remains unclear. OBJECTIVE: To determine the role of macrophage Lgr4 in MI and to dissect the underlying mechanisms. METHODS AND RESULTS: During early inflammatory phase of MI, infarct macrophages rather than neutrophils expressed high level of Lgr4. Macrophage-specific Lgr4 knockout mice had no baseline cardiovascular defects but manifested improved heart function, modestly reduced infarct size, decreased early mortality due to cardiac rupture, and ameliorated adverse remodeling after MI. Improved outcomes in macrophage-specific Lgr4 knockout mice subjected to MI were associated with mitigated ischemic injury and optimal infarct healing, as determined by reduction of cardiac apoptosis in the peri-infarct zone, attenuation of local myocardial inflammatory response, decrease of matrix metalloproteinase expression in the infarct, enhancement of angiogenesis, myofibroblast proliferation, and collagen I deposition in reparative granulation tissue as well as formation of collagen-rich scar. More importantly, macrophage-specific Lgr4 knockout infarcts had reduced numbers of infiltrating leukocytes and inflammatory macrophages but harbored abundant reparative macrophage subsets. Lgr4-null infarct macrophages exhibited a less inflammatory transcriptional signature. These findings were further supported by transcriptomic profiling data showing repression of multiple pathways and broad-spectrum genes associated with proinflammatory responses in macrophage-specific Lgr4 knockout infarcts. Notably, we discovered that Lgr4-mediated functional phenotype programing in infarct macrophages was at least partly attributed to regulation of AP (activator protein)-1 activity. We further demonstrated that the synergistic effects of Lgr4 on AP-1 activation in inflammatory macrophages occurred via enhancing CREB (cAMP response element-binding protein)-mediated c-Fos, Fosl1, and Fosb transactivation. CONCLUSIONS: Together, our data highlight the significance of Lgr4 in governing proinflammatory phenotype of infarct macrophages and postinfarction repair.
Authors: Mediha Becirovic-Agic; Upendra Chalise; Mira Jung; Jocelyn R Rodriguez-Paar; Shelby R Konfrst; Elizabeth R Flynn; Jeffrey D Salomon; Michael E Hall; Merry L Lindsey Journal: Am J Physiol Heart Circ Physiol Date: 2022-01-28 Impact factor: 4.733