title: Splenic RNA and MicroRNA Mimics Promote Complement Factor B Production and Alternative Pathway Activation via Innate Immune Signaling.
abstract: Complement factor B (cfB) is an essential component of the alternative pathway (AP) and plays an important role in the pathogenesis of polymicrobial sepsis. However, the mechanism leading to cfB production and AP activation during sepsis remains poorly understood. In this study, we found that plasma cell-free RNA was significantly increased following cecal ligation and puncture (CLP), an animal model of polymicrobial sepsis, and was closely associated with sepsis severity. Quantitative RT-PCR and microRNA (miRNA) array analysis revealed an increase in bacterial RNA and multiple host miRNAs (miR-145, miR-146a, miR-122, miR-210) in the blood following CLP. Treatment with tissue RNA or synthetic miRNA mimics (miR-145, miR-146a, miR-122, miR-34a) induced a marked increase in cfB production in cardiomyocytes or macrophages. The newly synthesized cfB released into medium was biologically active because it participated in AP activation initiated by cobra venom factor. Genetic deletion of TLR7 or MyD88, but not TLR3, and inhibition of the MAPKs (JNK and p38) or NF-κB abolished miR-146a-induced cfB production. In vivo, CLP led to a significant increase in splenic cfB expression that correlated with the plasma RNA or miRNA levels. Peritoneal injection of RNA or miR-146a led to an increase in cfB expression in the peritoneal space that was attenuated in MyD88-knockout or TLR7-knockout mice, respectively. These findings demonstrate that host cellular RNA and specific miRNAs are released into the circulation during polymicrobial sepsis and may function as extracellular mediators capable of promoting cfB production and AP activation through specific TLR7 and MyD88 signaling.
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114; and Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, MD 21201.
authors.forename: Lin
authors.initials: L
authors.lastname: Zou
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114; and Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, MD 21201.
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114; and.
authors.forename: Ganqiong
authors.initials: G
authors.lastname: Xu
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114; and.
authors.forename: Wenling
authors.initials: W
authors.lastname: Jian
authors.affiliation: Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114; and Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, MD 21201 wchao@anes.umm.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Chao
mesh_terms: D000818:Animals; D032701:Biomimetics; D002432:Cecum / Q000601:surgery; D002478:Cells, Cultured; D011415:Complement Factor B / Q000235:genetics / Q000378:metabolism*; D003170:Complement Pathway, Alternative / Q000235:genetics; D004195:Disease Models, Animal; D004546:Elapid Venoms / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D035683:MicroRNAs / Q000008:administration & dosage* / Q000276:immunology; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors / Q000502:physiology; D012313:RNA / Q000008:administration & dosage* / Q000276:immunology; D051381:Rats; D018805:Sepsis / Q000276:immunology*; D015398:Signal Transduction / Q000235:genetics; D051199:Toll-Like Receptor 7 / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics
chemical_list: D004546:Elapid Venoms; D035683:MicroRNAs; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D051199:Toll-Like Receptor 7; C016310:cobra venom factor; C068686:Pax3 protein, mouse; D012313:RNA; D011415:Complement Factor B