Abstract 20517: MicroRNA-155: A New Player in Sepsis-Induced Cardiac Dysfunction

Abstract

Introduction: Cardiac dysfunction is an important outcome predictor in patients with septic shock and lacks effective and targeted therapies. MicroRNA-155 (miR-155) is a multifunctional microRNA with important target genes in inflammation, immunity and cardiovascular system. Hypothesis: The present study assessed the role of miR-155 in experimental and human sepsis-induced cardiac dysfunction. Methods: Experimental sepsis was induced using endotoxin injection (LPS) or cecal ligation and puncture (CLP) models. Genetic loss (miR-155 KO) and pharmacological inhibition (LNA-anti-miR; AM) of miR-155 were evaluated. Cardiac function was assessed through echocardiography; mortality analysis was also performed. Quantification of myocardial miR-155, pro-inflammatory cytokine mRNA profile, miR-155 targets, apoptosis, cellular adhesion proteins and activation of pro-inflammatory intracellular signaling pathways were assessed. In another experiment, myocardial miR-155 expression, cellular localization and associations between its levels and other clinical variables were evaluated using post-mortem samples from septic shock (SS) patients. Results: Myocardial miR-155 levels were increased in experimental and human septic myocardium. This was associated with a decreased ejection fraction (EF) and cardiac output (CO) and increased diastolic LV diameter (LVDd) in septic WT animals. Knockout and anti-miR-155 treated animals and presented with preserved EF, CO and LVDd, compared with WT; this was accompanied by ~50% mortality reduction. Experimental sepsis induced downregulation of SOCS1 and CD47, myocardial cytokine upregulation, increased apoptosis and adhesion protein expression as well as pro-inflammatory kinase and transcription factor activation, all of which were attenuated in KO and AM. In human myocardium, miR-155 expression was positively associated with 24h antemortem period plasma troponin I levels. Conclusions: miR-155 is upregulated in experimental and human septic myocardium. Loss or inhibition of miR-155 attenuated sepsis-induced cardiac dysfunction, blunted proinflammatory activation and reduced mortality. This suggests miR-155 as a potential target in human sepsis-associated cardiac dysfunction.