Proposal Summary Treatments for pediatric heart failure (HF) have not improved outcomes significantly over the last 30 years using evidence-based therapies derived from adult trials. Our previous work and that of others suggests that age-based mechanistic differences in HF physiology underlie this failure to effectively treat pediatric HF due to dilated cardiomyopathy (DCM). We show here that mitochondrial energy production is disrupted in pediatric DCM, with total tissue ATP and phosphocreatine being depleted. DMC hearts have lower mitochondrial copy number and depleted content of the critical mitochondrial phospholipid, cardiolipin (CL), with associated derangement of mitochondrial respiratory capacity and metabolism. Quantitative assessment of CL has shown that there is no alteration in the relative content of the cardiac-specific form of CL, which has four linoleic acid side-chains (L4CL). Additionally we see evidence that mitochondrial biogenesis and mitophagy are both upregulated in pediatric DCM. These observations suggest that there is upregulated mitochondrial turnover in the pediatric DCM, with preservation of L4CL-rich mitochondria, but with lower total tissue mitochondrial content and disrupted respiration. Preliminary experiments presented in this grant show that oxidized-CL species are significantly higher in pediatric but not in adult DCM, and additionally that peroxidized CLs (peroxCL) are very elevated in anthracycline-induced cardiomyopathy which is known to be in part caused by mitochondrial oxidative stress. Other investigations have correlated oxCL and peroxCL, and translocation of CL from the inner to the outer mitochondrial membrane with apoptosis and mitophagy. Based on these observations and our preliminary data, we hypothesize that oxCL and peroxCL are critical signals for recruitment of mitophagy machinery in the failing cardiomyocyte. We additionally expect to see age-related differences in response to oxidative stress with younger age conferring increased susceptibility to oxidation of CL species. Our central hypothesis is that increased oxCL and peroxCL are critical for mitochondrial signaling in the setting of mitochondrial oxidative stress. We expect that oxCL and peroxCL are important mediators of mitophagy and apoptotic cell death. In addition, we hypothesize that there are age-dependent mechanisms that explain differences in mitochondrial response to oxidative stress between pediatric and adult DCM. The focus of this work is to validate this hypothesis by a translational approach using tissue from DCM patients to assess mitochondrial response to oxCL/peroxCL, and utilizing a rat ventricular myocyte culture model of oxidative stress using doxorubicin (Dox) to elucidate the mechanisms CL oxidative events as a function of age and age-related CL profiles. Finally we propose to use dietary intervention in Dox-treated juvenile rats to show that oxidation of myocardial CL is dependent on content of specific CL species that can be altered by diet.

R56HL153740

2020-09-17

2021-08-31