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 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 the 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. qRT-PCR and miRNA array analysis revealed an increase in bacterial RNA and multiple host microRNAs (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 as it participated in the AP activation initiated by cobra venom factor. Genetic deletion of TLR7 or MyD88, but not TLR3, and inhibition of the MAP kinases (JNK and p38) or NF-κB abolished miR-146a-induced cfB production. In vivo, CLP led to a significant increase in splenic cfB expression, which was correlated with the plasma RNA or miRNA levels. Peritoneal injection of RNA or miR-146a led to a rise in cfB expression in the peritoneal space, which was attenuated in MyD88-KO or TLR7-KO 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 the specific TLR7 and MyD88 signaling.

Toll‐like receptors 2 and 7 mediate coagulation activation and coagulopathy in murine sepsis

“…TLR7 is a sensor for single‐stranded RNA virus, and plays a pivotal role in inflammation . We have found that the levels of plasma miRNAs such as miR‐146a‐5p are increased following polymicrobial infection . To test whether miRNA is capable of activating coagulant production, we challenged WT and TLR7 −/− BMDMs with miR‐146a or its mutant.…”

“…Polymicrobial sepsis was created by cecal ligation and puncture (CLP) as previously described. 16,18 The operator (B.W.) was blinded to the animal strain and group information.…”

“…5 We have recently discovered that significant amounts of host cellular microRNAs (miRNAs) and extracellular vesicles are released into the blood circulation during sepsis, and that certain extracellular miRNAs, including miR-146a-5p, can function as DAMPs and drive inflammation via a TLR7-dependent pathway. [15][16][17][18] Finally, stimulation of TLR2 induces PAI-1 expression and increased fibrin deposition in the lung microvasculature, 19 and bacterial DNA (CpG)-activated TLR9 signaling induces TF expression in endothelial cells. 20 In this study, we tested the hypothesis that TLRs play a pivotal role in host procoagulant responses and contribute to SIC.…”

The involvement of regulatory non-coding RNAs in sepsis: a systematic review

“…Upregulation of miR-181 enhances TNF-α mRNA degradation [60]. In a THP-1 human promonocytic cell model, miR-146a increased in a time-dependent manner on LPS/TLR4 stimulation, suppressing the production of proinflammatory cytokines in a feed-forward loop [63, 64]. …”

Theranostic Nucleic Acid Binding Nanoprobe Exerts Anti-inflammatory and Cytoprotective Effects in Ischemic Injury

“…NA levels are elevated in the serum of patients with sepsis, shock, autoimmune disease, stroke, and acute ischemia, and correlate with the severity of injury 1-6. The released NAs exacerbate the degree of injury by stimulating an inflammatory response in immune cells 7-9, cardiomyocytes 8, 9, fibroblasts 10 and epithelial cells 11, 12. This effect is mediated by pattern-recognition receptors, such as Toll-like receptors (TLRs) on immune cells, and plays a central role in innate immunity.…”