Abstract 528: ApoA-I Mimetic Peptide Treatment Improves Left Ventricular Diastolic Dysfunction and Decreases Iron Content in Coronary Plaques in Rabbits

Introduction: Left ventricular diastolic dysfunction (LVDD) is characterized by the disturbance of ventricle’s performance due to its abnormal relaxation or to its increased stiffness. Hypertrophy, inflammation, fibrosis and oxidative stress are often associated with LVDD. Hypothesis: Given the reported anti-inflammatory and anti-oxidant properties of HDL, we assessed the potential of an apoA-I mimetic peptide to improve LVDD in a recently developed rabbit model. Methods: Forty-two rabbits were fed a normal diet (n=7) or a 0.5% cholesterol-enriched diet supplemented with vitamin D2 (n=35) for an average of 16 weeks. The hypercholesterolemic rabbits were randomised to receive 6 infusions of saline (n=11), 10 mg/kg (n=12) or 30 mg/kg of an apoA-I mimetic peptide over a period of 2 weeks. Serial echocardiography was used to assess LVDD. RT-qPCR and histological staining were performed on left ventricular homogenates and sections, respectively. Results: LVDD was improved in treated groups compared to saline as shown by decreased E/Em and increased Em/Am ratio assessed by echocardiography (p≤0.05). The apoA-I mimetic decreased transferrin receptor mRNA expression (p=0.039 for 10 mg/kg group) and increased ferritin heavy chain mRNA (p=0.053 for 30 mg/kg group) compared to saline. These changes were associated with a large decrease of non-heme iron content in LV sections of the treated groups (-90% in 10 mg/kg group, p≤0.01; -72% in 30 mg/kg group, p=0.1) compared to the saline-treated group as detected by Prussian blue staining. Significant reduction of RAM-11 macrophage staining was observed in treated groups compared to saline. A correlation was observed between iron and macrophage contents in LV (R=0.59 and p=0.0002). Most of the non-heme iron and macrophage stainings were seen in coronary arteries and plaques. Anti-oxidant enzyme (SOD2) mRNA was numerically increased in the 30 mg/kg group compared to saline (p=0.08). Conclusion: ApoA-I mimetic treatment improves LVDD. The observed decrease of left ventricular iron content may lead to reduce oxidative stress as iron contributes to reactive oxygen species formation. Further work is ongoing to validate whether decreased iron-mediated toxicity is a new benefit of apoA-I mimetic therapy.