BPS2026 – Proteomics analysis reveals ETC assembly and mitochondrial proteostasis pathways are more deranged in the RV than LV and associate with degree of dysfunction in explanted failing human hearts

RV dysfunction associated with group II pulmonary hypertension significantly increases mortality in left heart failure. However, signaling changes associated with progression of RV dysfunction remains poorly understood. We performed a DIA proteomic analysis of explanted left-heart failure patient RV and LV tissue and compared patients with mild and severe RV dysfunction to unused donor hearts. Explanted transplant hearts ( n = 22) were obtained at transplant and unused donor hearts (controls) ( n = 16, 7M/7F) were provided by the Gill Cardiovascular Biorepository, University of Kentucky. All transplant patients exhibited left heart failure and pulmonary hypertension. Right atrial pressure to pulmonary wedge pressure ratio (RAP/PCWP) from right heart catheterization defined RV mild (RAP/PCWP0.55, n = 11, 7M/4F). Total protein was isolated for DIA-MS analysis and mitochondria for isolated frozen mitochondrial respiration assessment. DIA-MS analysis reliably measured ∼4000 proteins/group. Mild RV dysfunction showed 221 up- and 213 downregulated proteins vs. donors; severe dysfunction had 319 up- and 254 downregulated proteins (B-H adj p < 0.05). LV changes were less pronounced. Enriched pathways downregulated in RV included mitochondrial translation, respiratory electron transport, oxidative phosphorylation, complex I biogenesis, and complex IV assembly, with greater enrichment in severe dysfunction. LV tissue showed minimal changes in these cascades but increased inflammatory signaling. 302 RV proteins correlated with CI-dependent and 532 with CII-dependent respiration, enriched for oxidative phosphorylation, RV cardiomyopathy, and mitochondrial disease signatures. Our findings show significant downregulation of mitochondrial proteostasis pathways and ETC assembly in the RV compared to LV of left heart failure patients and these changes associated with impairment in respiration and disease severity. This highlights a heightened bioenergetic vulnerability in the RV vs. LV in HF.