Differential Mitochondrial Function in Remodeled Right and Nonremodeled Left Ventricles in Pulmonary Hypertension

Right ventricular failure is the primary reason for mortality in pulmonary hypertension (PH), but little is understood about the energetics of the failing right myocardium. Our aim was to examine mitochondrial function and proteomic signatures in paired remodeled right (RM-RV) and non-remodeled left (NRM-LV) ventricular tissue samples procured during heart-lung transplantation.

Contractile dysfunction in RM-RV and preserved contractile function in NRM-LV were determined clinically and by echocardiography. Mitochondria were isolated from fresh paired RV and LV wall specimens of explanted hearts. Respiratory states in response to 4 substrates and an uncoupler were analyzed. Proteomic analysis on the mitochondrial isolates was performed with the use of liquid chromatography-mass spectrometry. The RM-RV mitochondria exhibited higher succinate state 4 levels with lower respiratory control ratio (RCR) compared with state 4 levels for pyruvate-malate (PM) and glutamate-malate (GM). RM-RV mitochondria also exhibited lower state 3 for palmitoyl-carnitine (PC) and state 4 for all complex I substrates compared with NRM-LV. The mean RCR were greater in RM-RVs than in NRM-LVs for PM and GM, which is consistent with tight coupling (low state 4 rates, higher RCRs); however, low RM-RV state 3 rates suggest concurrent substrate-dependent impairment in respiratory capacity. Mitochondrial proteomics revealed greater levels of mitochondrial ADP-ATP translocase and proteins of ATP synthesis, mitochondrial pyruvate and short branched chain acyl-CoA metabolism in RM-RV.

The mitochondrial respiration and proteomics in RM-RV are different from NRM-LV. These results have important implications in expanding our understanding of RV metabolism and future management of RV failure.