Abstract 12635: Mitochondria-Targeted NOX4 Overexpression Causes Restrictive Diastolic Dysfunction in a “Two-Hit” Mouse Model of HFpEF

Abstract

Heart failure with preserved ejection fraction (HFpEF) prevalence increases with age. However, the pathophysiologic mechanisms of HFpEF are unknown and no specific treatment is available. NOX4 NADPH oxidase levels, particularly in mitochondria, increase with age and induce mitochondrial dysfunction. We previously showed that diastolic dysfunction patients’ hearts had higher NOX4, ROS levels and mitochondrial damage whereas mice with mitochondria-targeted NOX4 overexpression ( Nox4 TG) had impaired mitochondrial function and pronounced diastolic dysfunction. Here we investigated the effects of increased mitochondrial NOX4 levels on the pathophysiology of HFpEF using Nox4 TG mice in a “two-hit” model. The “two-hit” mouse HFpEF model is a combination of metabolic stress from high-fat diet and dysregulation of NO after treatment with L-NAME. Compared to wild-type, Nox4 TG mice had significantly lower ATP-linked and maximal oxygen consumption rates in ventricular cardiomyocytes and showed a trend towards reduced exercise tolerance. Echocardiography analysis showed that both strains in “two-hit” model had increased E/E' versus controls, whereas Nox4 TG mice had significantly prolonged isovolumic relaxation and mitral valve deceleration time. In addition, NOX4 overexpression significantly reduced cardiac output, suggesting restrictive diastolic dysfunction. MCP1 expression was significantly higher in left ventricle (LV) lysates and the percentage of CD11b + cells was higher in LV sections of Nox4 TG mice. Myocardium flow cytometry analysis showed higher percentage of Ly6C hi macrophages with elevated TNFα expression in Nox4 TG mice. TGFβ1 and osteopontin expression was also higher in the LV lysates. Picrosirius red and collagen I staining showed increased interstitial fibrosis in Nox4 TG mice as in LV sections of patients with diastolic dysfunction. Congruently, percentage of periostin + and ACTA2 + cells was significantly higher in Nox4 TG mice, recapitulating findings in human LV sections. Together, our data show that mitochondrial dysfunction leads to restrictive diastolic dysfunction through inflammation and fibrosis, suggesting that preserving mitochondrial function in aging is a potential therapeutic strategy for HFpEF.