Abstract 2609: Mitochondrial Oxidative Stress Promotes Failure of the Pressure-Loaded Infant Right Ventricle
Background: Right ventricular hypertrophy (RVH) and failure induced by chronic RV pressure overload is a major problem in congenital heart disease. We have previously shown that mitochondrial (Mito) damage accompanied load-induced infant RV failure. Here we assessed Mito electron transport chain(ETC) dysfunction and Mito oxidative stress in the transition of infant RVH to failure.
Methods: Newborn rabbits underwent pulmonary artery banding (or sham) causing stable RV pressure load (~40 mmHg) and RVH by 2 weeks; RV contractile function (echocardiography) was preserved for ~4 weeks, followed by failure onset at ~8 weeks. Thus, RV free wall was assayed at 3, 4 and 8 weeks for ETC enzyme activities, high energy phosphates, Mito GSH/GSSH ratio (index of Mito ROS scavenging), Mito 8-hydroxy-2-deoxyguanosine (8-OHdG, oxidative Mito DNA damage), Mito protein carbonyls (oxidative Mito protein damage) and Mito ultrastructure (electron microscopy).
Results: By 4 weeks (RVH, preserved function), Mito 8-OHdG and protein carbonyl markedly increased, accompanied by decreased complex I and III activity. At 8 weeks (early failure), there were further increases in Mito 8-OHdG and protein carbonyls, significantly decreased GSH/GSSG ratio, further loss of complex I and III, and decreased activities of complexes IV and V; ATP content and ATP/ADP ratio were also significantly reduced. In parallel the number of abnormal disrupted RV mitochondria increased markedly.
Conclusion: Pressure-load of the infant RV rapidly induces Mito oxidative stress. Due to the limited Mito scavenging and repair systems, this results in a cycle of Mito DNA and protein damage, progressive loss of ETC enzyme activity and further oxidative stress, as well as loss of functional mitochondria. This load-induced oxidative stress may be a therapeutic target to preserve RV function and oxidative metabolism and prevent the transition of RVH to RV failure. Changes in banded and sham-operated hearts after surgery