Focal Myocardial Delivery of Small Molecule Nitroalkenes using Ultrasound Targeted Microbubble Cavitation to Improve Ventricular Recovery Following Myocardial Infarction - Myocardial infarction (MI) causes two major problems, microvascular obstruction (MVO) and myocardial fibrosis. MVO occurs after downstream embolization during percutaneous coronary intervention for MI in most patients and is a strong independent predictor of major adverse events, including mortality. Post MI myocardial fibrosis is a maladaptive response causing left ventricular dysfunction; it causes an increase in congestive heart failure (CHF), the leading cause of death. No consistently effective therapy for either condition exists. Ultrasound-targeted microbubble cavitation (UTMC) provides a means for myocardial reperfusion and targeted drug delivery. This technique involves external ultrasound stimulation to intravenously injected lipid microbubble (MB) contrast agents, which oscillate to generate shear forces, and then release their contents at the ultrasound site. We have successfully developed UTMC to cause mechanical disruption of microthrombi, relieving MVO and restoring perfusion. However, persistent inflammation and maladaptive signaling responses in the microcirculation remains and can be significantly deleterious to the myocardial environment. Therefore, we propose a nitro-fatty acid (NFA)-based MB (NFAB) UTMC therapeutic strategy. NFA are endogenously produced electrophilic fatty acids having a nitroalkene substituent, critical in modulating pleiotropic anti-inflammatory and anti-fibrotic responses. Currently, NFA are safely administered systemically in humans and have advanced to Phase 2 clinical trials. Yet, there is no method for concentrating at specific sites of pathology. Due to their amphipathic nature, NFA have favorable intermolecular interactions with the phospholipids present in most MBs. In our current R21, we synthesized a novel nitro-fatty acid MB (NFAB) with a high loading efficiency and demonstrated the UTMC with this NFAB enhances perfusion and markedly suppresses inflammatory gene expression during ischemia reperfusion. Incorporation into MBs, which release their shell contents during ultrasound exposure, allows for rapid and targeted release at the site of MVO. The advantages of an NFAB-UTMC strategy include (a) initial NO donor actions, (b) pleiotropic modulation of both the acute and chronic inflammatory responses found in MVO and (b) potent anti-fibrotic activity via suppression of TGF-B signaling. Therefore, it is hypothesized that UTMC with NFABs will facilitate targeted delivery of NFA to (1) sites of MVO and (2) sites of myocardial fibrosis to preserve post MI LV function. Aim 1: Determine the efficacy of UTMC with NFABs for the treatment of reperfusion injury and MVO. We will test the hypothesis that UTMC with NFABs enhances flow and reduces inflammation during myocardial ischemia reperfusion (rat model) and MVO (pig model). Aim 2: Determine the anti-fibrotic efficacy of UTMC with NFABs for post MI fibrosis. We will test the hypothesis that UTMC with NFABs reduces fibrosis in both a rodent model and in a clinically relevant porcine model of MI.
