Abstract 14299: MicroRNAs are Released During Myocardial Ischemia Reperfusion Injury and Induce Inflammation via Toll-like Receptor 7 in vitro
Introduction: We have reported that cardiac RNA elicits a robust cytokine response in both cardiomyocyte (CM) and immune cells and promotes leukocyte peritoneal recruitment, but the type of RNA responsible for the effect is unknown. We test the hypothesis that microRNAs (miRs) mediate the pro-inflammatory response.
Methods: I/R model: mice were subjected to thoracotomy (sham) or coronary occlusion for 45 min followed by reperfusion (I/R). miR array: 68 miRs in the plasma were quantified. Cytokine detection: CM and macrophage (Mφ) were treated with synthetic miRs for 18 h and cytokines in media measured by ELISA. Leukocyte migration assay: mice were i.p. injected with 20 μg miRs or mutant. The peritoneal lavage was harvested at 20 h and tested for leukocytes by flow cytometry (neutrophil as Ly-6G+, monocyte as F4/80low, and Mφ as F4/80high). miR inhibition: 6 specific inhibitors complementary to the target miRs were mixed as anti-miR combo.
Results: Among 68 cardiac disease-related miRs, 38 were significantly increased in the plasma 4 h following myocardial I/R. Eight miR mimics were selected to treated CM and Mφ and 6 of them (miR-34a, -122, -133a, 142a, -146a, -208a) found to induce robust cytokine response. The effects were abolished by pre-treatment of RNase (but not DNase) or by U - A mutation. miR-induced cytokine response was completely diminished in TLR7-/- or MyD88-/-, but not in TLR3-/- or Trif-/- Mφ, and markedly inhibited by a specific TLR7 inhibitor in CM. Importantly, the anti-miR combo significantly inhibited the cardiac cellular RNA-induced cytokine production in both Mφ and CM. In vivo, compared to the control group (lipofectamine or the mutant), i.p. injection of miRs (-133a or -146a) led to neutrophil and monocyte recruitment into the peritoneal cavity, but promoted Mφ efflux. The migration of the leukocytes were markedly decreased in TLR7-/-, abolished in MyD88-/-, but not affected in Trif-/- mice.
Conclusions: We demonstrate that 1) a group of miRs are released to circulation during I/R, 2) specific miR mimics induce cytokine production and leukocyte migration via TLR7-MyD88 signaling, 3) endogenous miRs mediate, in part, the cellular RNA-induced cytokine response. These data suggest that certain miRNAs are potent pro-inflammatory TLR7 ligand.
Author Disclosures: Y. Feng: None. L. Zou: None. D. Yan: None. H. Chen: None. G. Xu: None. W. Chao: None.
- © 2016 by American Heart Association, Inc.