With the introduction of reperfusion therapy, mortality from AMI has decreased markedly, from 20% in 1980 to 5% in 2008, but has plateaued despite the fact that our time to reperfusion has progressively declined. Now, post MI chronic heart failure (CHF) is increasing and is directly related to infarct size. Microvascular obstruction (MVO) is a major obstacle to complete reperfusion and limits myocardial salvage. It results in lower post MI ejection fraction and is felt to be the single most important contributor to post MI CHF. In his first R01, the PI demonstrated that ultrasound targeted microbubble cavitation (UTMC) therapy physically relieves MVO and that specific mechanical mechanisms underly this phenomenon. While UTMC may address the physical obstruction of MVO, the associated inflammation and ischemia-reperfusion injury remain and can be significantly deleterious to the myocardial environment. It is proposed herein to apply a nitro-fatty acid (NFA)-based therapeutic strategy, in combination with UTMC. NFA are endogenously-produced electrophilic fatty acids having a nitroalkene substituent that is critical in mediating the modulation of pleiotropic anti-inflammatory signaling responses. Currently, NFA can be safely administered in humans (orally and intravenously) and have advanced to Phase 2 clinical trials. However, there is no method for concentrating at specific sites of pathology. Due to an amphipathic nature, NFA have favorable intermolecular interactions with the phospholipids present in most current MB compositions. Thus, we intend to synthesize novel nitro-fatty acid MBs (NFABs) for use with UTMC in an animal model of MVO. Incorporation into MBs, which release their shell contents when ruptured, allows for rapid and targeted release at the site of MVO. The advantages of a NFAB-UTMC therapeutic strategy, include (a) rapid, targeted delivery, (b) initial NO donor actions, and (c) pleiotropic modulation of both the acute and chronic inflammatory responses found in MVO. We hypothesize that nitro-fatty acid microbubbles, delivered via ultrasound-targeted microbubble cavitation, facilitates the targeted delivery of nitro-fatty acid to sites of microvascular obstruction and can improve therapeutic treatment. This will be tested in the following Specific Aims:
Aim 1 : Synthesize and characterize novel nitro-fatty acid microbubbles for ultrasound-targeted microbubble cavitation. In vitro characterization entails analysis of nitro-fatty acid MBs chemical composition and acoustic behavior.
Aim 2 : Determine the efficacy of ultrasound-targeted microbubble cavitation with nitro-fatty acid microbubbles for the treatment of microvascular obstruction. Application of this strategy, along with control conditions, will test the hypothesis that UTMC with NFABs results in increased local delivery and actions of NFA in a healthy rodent hindlimb model, compared against systemic NFA delivery (Aim 2A). This model will also test the hypothesis that UTMC with NFABs can lessen both the duration and severity of MVO (Aim 2B).

Public Health Relevance

Microembolization occurs during coronary stenting, when debris from a coronary narrowing in the vessel wall blocks the downstream microvessel, causing heart damage. There are 600,000 stenting cases annually. We developed a novel treatment using ultrasound to vibrate gas filled antioxidant microbubbles to clear the debris.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Exploratory/Developmental Grants (R21)
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Imaging Guided Interventions and Surgery Study Section (IGIS)
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Danthi, Narasimhan
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University of Pittsburgh
Internal Medicine/Medicine
Schools of Medicine
United States
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