Skeletal Muscle Sirt3 Deficiency-Mediated Loxl2 Secretion in Remote Pulmonary Vascular Remodeling and Pulmonary Hypertension in Heart Failure with Preserved Ejection Fraction

Background: Pulmonary hypertension in the context of heart failure with preserved ejection fraction (PH-HFpEF) is the most common cause of PH worldwide. However, major pathways involved in the regulation of PH-HFpEF are still not well understood. We have recently reported on a role of skeletal muscle sirtuin-3 (SIRT3) in modulating PH-HFpEF. In this study, we attempted to define the processes by which skeletal muscle SIRT3 defects affect pulmonary vascular health in PH-HFpEF. Methods and Results: Skeletal muscle-specific Sirt3 knockout mice ( Sirt3 skm-/- ) exhibited drastically reduced pulmonary vascular density accompanied by pulmonary vascular proliferative remodeling and elevated pulmonary pressures. Using global mass spectrometry-based comparative secretome analysis, we found elevated secretion of lysyl oxidase homolog 2 (LOXL2) in SIRT3-deficeint skeletal muscle cells. Elevated circulation and protein expression levels of LOXL2 were also observed in plasma and skeletal muscle of Sirt3 skm-/- mice, rats with experimental PH-HFpEF (SU5416/Obese ZSF1, Ob-Su), and patients with PH-HFpEF. Interestingly, expression levels of the tumor suppressor WW domain-containing oxidoreductase (WWOX), which plays a housekeeping role in repressing cellular proliferation, were decreased in PASMCs from Sirt3 skm-/- mice. Reduced WWOX expression levels were also detected in PASMCs from Ob-Su rats and human subjects with obesity and diabetes. Treatment with LOXL2 recombinant protein resulted in reduced WWOX expression ex vivo in precision-cut lung slices (PCLS) and in vitro in PASMCs. Media conditioned by SIRT3-deficient skeletal muscle cells reduced WWOX expression in PASMCs, concomitant with increased PCNA levels and cellular proliferation. Finally, knockdown of both SIRT3 and LOXL2 in skeletal muscle cells or suppression of LOXL2 with β-aminopropionitrile (BAPN) restored WWOX and PCNA levels in PASMCs. Conclusions: These studies indicate a systemic pathogenic impact of skeletal muscle SIRT3 deficiency in remote pulmonary vascular remodeling and PH-HFpEF. These studies also reveal a new endocrine signaling axis that links skeletal muscle SIRT3 deficiency to remote WWOX regulation in the pulmonary vasculature through myokine LOXL2.