Cardioprotective mechanisms of novel noncoding RNA in myocardial infarction

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PROJECT SUMMARY/ABSTRACT This proposal seeks to understand the cardioprotective effects of a new noncoding RNA (ncRNA) entity, TY4, that is bioinspired by the contents of exosomes. Our focus is on one class of small ncRNA, not previously recognized as particularly relevant to cardiac disease. Y RNAs captured our attention because molecules encoded by the YRNA4 gene are exceptionally plentiful in exosomes secreted by cardiosphere-derived cells. The predominant such ncRNA, EV-YF1, has salutary properties when delivered on its own: EV-YF1 increases IL-10 secretion, is cardioprotective and anti-hypertrophic. Here we present preliminary data on TY4, a new chemical entity (NCE) bioinspired by EV-YF1. TY4 exerts global transcriptomic changes involving inflammatory and fibrotic pathways, and exerts disease-modifying bioactivity in murine models of heart failure with preserved ejection fraction, Duchenne muscular dystrophy, and MI. Remarkably, TY4, when formulated with the breast milk protein casein, works orally in all three models. In terms of mechanism, preliminary data show that TY4 binds to TPR, a nuclear pore complex protein that acts as a gatekeeper for messenger RNA export from the nucleus. We have also found that macrophage depletion abrogates TY4-mediated cardioprotection. As a small chemically- modified mutant NCE, TY4 has key features desirable in a synthetic RNA drug. But other RNA drugs, whether FDA-approved or in development, all have known mechanisms of action: they are antisense oligos, small interfering RNAs, aptamers, or miR-modifiers. TY4 fits into none of those classes and thus is the prototype for a new class of RNA drugs. The focus here is on understanding the mechanism whereby TY4 limits infarct size. We will test the following mechanistic hypothesis: TY4 is cardioprotective against MI by binding to TPR and altering gene expression in target cells (and specifically, in macrophages). We will pursue the following Aims: 1: Investigate the mechanism(s) whereby TY4 alters gene expression in macrophages. Sub-aims seek to identify TY4 binding partners, characterize the transcriptomic changes induced by TY4, and prioritize biological targets for further interrogation. 2: Optimize in vivo efficacy of oral TY4 in murine MI. Sub-aims seek to optimize the dosage paradigm for oral TY4 in acute MI, measure biodistribution of TY4 after oral delivery in mice pre- and post- acute MI, determine the window of opportunity for TY4 efficacy post-MI in acute MI, test TY4 cardioprotective efficacy in aged mice, and characterize the effects of optimized oral TY4 delivery in a chronic MI model. 3: Test whether macrophages are necessary and sufficient to explain TY4 efficacy in acute MI. Sub-aims seek to compare MI outcomes +/- TY4 with and without prior macrophage depletion, probe the relative roles of tissue-resident versus circulating macrophages, and determine whether post-MI adoptive transfer of ex vivo TY4-conditioned macrophages reduces infarct size in macrophage-depleted mice. While highly mechanistic, our proposal, focusing on a synthetic ncRNA NCE bioinspired by exosomal cargo, also offers translational value in its development of a novel cardioprotective agent that is effective even when given after reperfusion.