title: Cardiac RNA induces inflammatory responses in cardiomyocytes and immune cells via Toll-like receptor 7 signaling.
abstract: We have recently reported that extracellular RNA (exRNA) released from necrotic cells induces cytokine production in cardiomyocytes and immune cells and contributes to myocardial ischemia/reperfusion injury. However, the signaling mechanism by which exRNA exhibits its pro-inflammatory effect is unknown. Here we hypothesize that exRNA directly induces inflammation through specific Toll-like receptors (TLRs). To test the hypothesis, we treated rat neonatal cardiomyocytes, mouse bone marrow-derived macrophages (BMDM), or mouse neutrophils with RNA (2.5-10 μg/ml) isolated from rat cardiomyocytes or the hearts from mouse, rat, and human. We found that cellular RNA induced production of several cytokines such as macrophage inflammatory protein-2 (MIP-2), ILs, TNFα, and the effect was completely diminished by RNase, but not DNase. The RNA-induced cytokine production was partially inhibited in cells treated with TLR7 antagonist or genetically deficient in TLR7. Deletion of myeloid differentiation primary response protein 88 (MyD88), a downstream adapter of TLRs including TLR7, abolished the RNA-induced MIP-2 production. Surprisingly, genetic deletion of TLR3 had no impact on the RNA-induced MIP-2 response. Importantly, extracellular RNA released from damaged cardiomyocytes also induced cytokine production. Finally, mice treated with 50 μg of RNA intraperitoneal injection exhibited acute peritonitis as evidenced by marked neutrophil and monocyte migration into the peritoneal space. Together, these data demonstrate that exRNA of cardiac origin exhibits a potent pro-inflammatory property in vitro and in vivo and that exRNA induces cytokine production through TLR7-MyD88 signaling.
authors.affiliation: From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114 yfeng@mgh.harvard.edu.
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.affiliation: From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Hongliang
authors.initials: H
authors.lastname: Chen
authors.affiliation: From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Jiayan
authors.initials: J
authors.lastname: Cai
authors.affiliation: From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Lin
authors.initials: L
authors.lastname: Zou
authors.affiliation: From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Dan
authors.initials: D
authors.lastname: Yan
authors.affiliation: From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Ganqiong
authors.initials: G
authors.lastname: Xu
authors.affiliation: From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114 wchao@mgh.harvard.edu wchao@anes.umm.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Chao
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D054426:Chemokine CXCL2 / Q000096:biosynthesis / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007378:Interleukins / Q000096:biosynthesis / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology / Q000473:pathology; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D032383:Myocytes, Cardiac / Q000737:chemistry* / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D009336:Necrosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009504:Neutrophils / Q000187:drug effects* / Q000276:immunology / Q000473:pathology; D010538:Peritonitis / Q000139:chemically induced / Q000235:genetics / Q000276:immunology / Q000473:pathology; D061251:Primary Cell Culture; D012313:RNA / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D015398:Signal Transduction; D051196:Toll-Like Receptor 3 / Q000172:deficiency / Q000235:genetics / Q000276:immunology; D051199:Toll-Like Receptor 7 / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000378:metabolism
chemical_list: D054426:Chemokine CXCL2; C404915:Cxcl2 protein, mouse; D007378:Interleukins; D008562:Membrane Glycoproteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C519703:TLR3 protein, mouse; C477038:Tlr7 protein, mouse; D051196:Toll-Like Receptor 3; D051199:Toll-Like Receptor 7; D014409:Tumor Necrosis Factor-alpha; D012313:RNA
keywords: RNA; extracellular RNA; inflammation; innate immunity; signal transduction; toll-like receptor (TLR)