Acute myocardial infarction (MI) provokes an inflammatory response in the heart that removes damaged tissues to facilitate tissue repair/regeneration. However, overactive and prolonged inflammation compromises healing, which may be counteracted by antiinflammatory mechanisms. A key regulatory factor in an inflammatory response is the antiinflammatory cytokine IL-10, which can be produced by a number of immune cells, including subsets of B lymphocytes. Here, we investigated IL-10–producing B cells in pericardial adipose tissues (PATs) and their role in the healing process following acute MI in mice. We found that IL-10–producing B cells were enriched in PATs compared to other adipose depots throughout the body, with the majority of them bearing a surface phenotype consistent with CD5+ B-1a cells (CD5+ B cells). These cells were detected early in life, maintained a steady presence during adulthood, and resided in fat-associated lymphoid clusters. The cytokine IL-33 and the chemokine CXCL13 were preferentially expressed in PATs and contributed to the enrichment of IL-10–producing CD5+ B cells. Following acute MI, the pool of CD5+ B cells was expanded in PATs. These cells accumulated in the infarcted heart during the resolution of MI-induced inflammation. B cell-specific deletion of IL-10 worsened cardiac function, exacerbated myocardial injury, and delayed resolution of inflammation following acute MI. These results revealed enrichment of IL-10–producing B cells in PATs and a significant contribution of these cells to the antiinflammatory processes that terminate MI-induced inflammation. Together, these findings have identified IL-10–producing B cells as therapeutic targets to improve the outcome of MI.
Acute myocardial infarction (MI) provokes an inflammatory response in the heart that removes damaged tissues to facilitate repair. However, exaggerated and/or persistent inflammation compromises healing, which may be counteracted by regulatory immune mechanisms. A key regulatory factor in an inflammatory response is the antiinflammatory cytokine IL-10, which can be produced by a number of immune cells including subsets of B lymphocytes. Here, we investigated IL-10-producing B cells in pericardial adipose tissues (PATs) and their role in the healing process following acute MI in mice. We found abundant IL-10-producing B cells in PATs under homeostatic conditions, with the majority of them bearing cell surface CD5 (CD5 + B cells). These cells were detected early in life, maintained a steady presence during adulthood, and resided in fat-associated lymphoid clusters (FALCs). The cytokine IL-33 was preferentially expressed in PATs under homeostatic conditions and contributed to enrichment of IL-10-producing CD5 + B cells in PATs. CD5 + B cells expanded in PATs following MI, and accumulated in the infarcted heart during the resolution of MI-induced inflammation. B cell-specific deletion of IL-10 worsened cardiac function after MI, exacerbated myocardial injury, and delayed resolution of inflammation. These findings reveal a significant contribution of IL-10-producing B cells to the anti-inflammatory mechanism that terminates MI-induced inflammation, and identify these cells as novel therapeutic targets to improve the outcome of MI. Significance StatementMyocardial infarction (MI) remains a leading cause of mortality and morbidity worldwide.Although it is now recognized that a balanced and timely terminated pro-inflammatory response following acute MI is essential in promoting tissue repair, the underlying regulatory mechanisms are poorly defined. In this report, we show that IL-10-producing B cells in mice 1) are enriched in pericardial adipose tissues (PATs) and influenced by cytokine IL-33 under homeostatic conditions; 2) expand in PATs following MI and accumulate in the infarcted heart during the resolution of MI-induced inflammation; and3) facilitate resolution of inflammation and reduce myocardial injury to preserve cardiac function after MI. These findings identify IL-10-producing B cells as novel therapeutic targets to improve the outcome of MI. 5
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