Background We previously demonstrated that ischemically injured cardiomyocytes release cell-free DNA and HMGB1 (high mobility group box 1 protein) into circulation during reperfusion, activating proinflammatory responses and ultimately exacerbating reperfusion injury. We hypothesize that cell-free DNA and HMGB1 mediate myocardial ischemia-reperfusion injury by stimulating plasmacytoid dendritic cells (pDCs) to secrete type I interferon (IFN-I). Methods and Results C57BL/6 and interferon alpha receptor-1 knockout mice underwent 40 minutes of left coronary artery occlusion followed by 60 minutes of reperfusion (40'/60' IR) before infarct size was evaluated by 2,3,5-Triphenyltetrazolium chloride-Blue staining. Cardiac perfusate was acquired in ischemic hearts without reperfusion by antegrade perfusion of the isolated heart. Flow cytometry in pDC-depleted mice treated with multiple doses of plasmacytoid dendritic cell antigen-1 antibody via intraperitoneal injection demonstrated plasmacytoid dendritic cell antigen-1 antibody treatment had no effect on conventional splenic dendritic cells but significantly reduced splenic pDCs by 60%. pDC-depleted mice had significantly smaller infarct size and decreased plasma interferon-α and interferon-β compared with control. Blockade of the type I interferon signaling pathway with cyclic GMP-AMP synthase inhibitor, stimulator of interferon genes antibody, or interferon regulatory factor 3 antibody upon reperfusion similarly significantly attenuated infarct size by 45%. Plasma levels of interferon-α and interferon-β were significantly reduced in cyclic GMP-AMP synthase inhibitor-treated mice. Infarct size was significantly reduced by >30% in type I interferon receptor monoclonal antibody-treated mice and interferon alpha receptor-1 knockout mice. In splenocyte culture, 40'/0' cardiac perfusate treatment stimulated interferon-α and interferon-β production; however, this effect disappeared in the presence of cyclic GMP-AMP synthase inhibitor. Conclusions Type I interferon production is stimulated following myocardial ischemia by cardiogenic cell-free DNA/HMGB1 in a pDC-dependent manner, and subsequently activates type I interferon receptors to exacerbate reperfusion injury. These results identify new potential therapeutic targets to attenuate myocardial ischemia-reperfusion injury.
Keywords: cell signaling; infarct size; ischemia reperfusion injury.