Abstract 291: The Type I Interferon Receptor Amplifies Innate Immune Responses After Myocardial Infarction

Abstract

Ischemic heart disease (IHD), the leading cause of death in the world, begins with myocardial infarction (MI). Overly exuberant innate immune responses are detrimental to post-MI healing and repair. Efforts to achieve post-MI cardioprotection focused on blocking NFκB-mediated inflammation have been largely unsuccessful. We recently discovered that MI leads to cytosolic DNA sensing in leukocytes and triggers the interferon regulatory factor 3 (IRF3)-dependent expression of interferon stimulated genes (ISGs). We found that genetic inhibition of IRF3 after MI reduces inflammation, limits ventricular dilation and contractile dysfunction, and improves survival. In this work, we test two hypotheses. 1) Type I interferons (IFNs), secreted by a few DNA-sensing/IRF3-activated leukocytes, signal via type I interferon alpha/beta receptors (IFNARs), to amplify ISG expression after MI. 2) Pharmacologic inhibition of type I IFN/IFNAR signaling blocks response amplification and significantly reduces ISG expression. We established DNA-stimulated bone marrow derived macrophages (BMDMs) as an in vitro model of the post-MI type I IFN response and measured the expression of ISGs ( Cxcl10 , Irf7 , Ifit1 , and Ifit3 ) by qPCR. We quantified and compared changes in ISG expression caused by direct DNA stimulation, incubation with conditioned media containing secreted factors from DNA-stimulated cells, and treatment with an IFNAR neutralizing antibody. Compared to unstimulated BMDMs, ISG expression was amplified by >35-fold in BMDMs stimulated by either DNA or conditioned media. However, there was no significant amplification when the experiments were performed in the presence of an IFNAR neutralizing antibody. In a mouse model of MI, single cell RNA-Seq revealed that IFNAR-deficient mice have reduced numbers of ISG-expressing leukocytes compared to wild type controls, which indicates that IFNAR-dependent amplification of innate immune responses occurs after MI in vivo . Collectively, these results demonstrate that IFNAR ligands are important amplifiers of DNA-induced innate immune responses after MI and suggest that anti-interferon therapy should be further investigated in vivo to improve clinical outcomes after MI.