Friedberg, M. K. | bioRxiv Science

bioRxiv2025

NDUFS2 (NADH:Ubiquinone oxidoreductase core subunit S2) in Mitochondrial Electron Transport Chain Complex I is Critical to Oxygen Responsiveness of Human Ductus Arteriosus Smooth Muscle Cells

BackgroundMitochondria in ductus arteriosus smooth muscle cells (DASMCs) are oxygen sensors triggering vasoconstriction at birth; however, the oxygen sensing mechanisms are incompletely understood. Given the conserved role of mitochondrial Complex I subunit NDUFS2 in other oxygen-sensing tissues, we examined its role in DASMC oxygen sensing, comparing it to other Complex I subunits (NDUFS1 and NDUFS7) and putative O2-sensor subunits (UQCRFS1 and COX4I2). MethodsHuman DASMCs were grown in hypoxia (pO2=41mmHg). Oxygen responsiveness was assessed, measuring changes in intracellular calcium, [Ca2+]i, cell length, and mitochondrial reactive oxygen species (mROS). DASMCs were treated for 48-hours with control siRNA versus siRNA targeting NDUFS2, NDUFS1, NDUFS7, UQCRFS1, or COX4I2. qPCR and immunoblotting confirmed knockdown. 3RNA sequencing assessed transcriptional changes following siRNA. ResultsOxygen increased mitochondrial fission, [Ca2+]i, and constricted DASMCs. 48-hours post-treatment, siNDUFS2 selectively depressed oxygen-induced increase in [Ca2+]i (siControl +18.6{+/-}2.3%, siNDUFS2 +5.5{+/-}1.5%, p<0.0001), DASMC shortening (from 18.4{+/-}1.1% to 8.9{+/-}0.8%, p<0.0001), and mROS (+24{+/-}4.9% untreated, -6.6{+/-}5.4% post-siNDUFS2, p<0.0001), without altering the KCl response or depressing respiration. The mitochondrial antioxidant MitoTEMPO reduced mROS (2.9{+/-}4.5%, p=0.001) and attenuated oxygen-induced DASMC shortening (8.4{+/-}0.9%, p=0.0003). Transcriptomics revealed unique changes in mitochondrial pathways post siNDUFS2. ConclusionsNDUFS2 regulates mROS and is a mitochondrial oxygen sensor in human DASMCs. ImpactO_LIWe demonstrated a unique role of Complex I subunit NDUFS2 (NADH:Ubiquinone Oxidoreductase Core Subunit S2), amongst putative oxygen-sensing electron transport chain subunits, in the responsiveness of human ductus arteriosus (DA) smooth muscle cells (DASMCs) to oxygen. C_LIO_LINDUFS2 knockdown inhibited oxygen-induced DASMC constriction and generation of mitochondrial reactive oxygen species, at a timepoint prior to inhibition of mitochondrial respiration and without inhibition of KCl-induced constriction. C_LIO_LIWhile mitochondria are known DA oxygen sensors, this work identifies NDUFS2 as a molecular mediator of human DA oxygen sensing within the mitochondria, enhancing our understanding of a vital physiologic phenomenon and providing a novel potential therapeutic target to modulate ductal patency. C_LI

molecular biology↗

bioRxiv2024

Adverse structural and mechanical remodelling of main pulmonary artery in experimental pulmonary arterial hypertension is associated with impaired right ventricle-pulmonary artery coupling and function

RationaleCoupling between right ventricular function and the pulmonary vasculature determines outcomes in pulmonary arterial hypertension. The mechanics of the main pulmonary artery is an important but understudied determinant of right ventricular-pulmonary artery coupling. ObjectivesTo investigate the histology and mechanics of the pulmonary artery in relationship to right ventricular remodeling, mechanics, hemodynamics and coupling in experimental pulmonary arterial hypertension. MethodsIn a sugen+hypoxia rat model of pulmonary arterial hypertension, right ventricular hemodynamics were assessed by conductance catheters. Active tension-strain curves were generated using echocardiography. Main pulmonary artery and right ventricle free-wall were harvested to determine their macro- and micro-structure, composition, and mechanical properties. Comprehensive multivariate analyses elucidated relationships between pulmonary artery and right ventricle mechanics, structure and coupling. Measurements and Main ResultsPulmonary hypertensive main pulmonary arteries developed fibrosis relative to healthy controls, as did right ventricles, which also hypertrophied, with re-orientation of muscle fibres toward a tri-layer architecture reminiscent of normal left ventricular architecture. Increased glycosaminoglycan deposition and increased collagen-to-elastin ratio in the pulmonary artery; and increased collagen, as well as hypertrophy and reorganization of myofibers in the right ventricle, led to increased stiffness. This increase in stiffness was more pronounced in the longitudinal direction in the high- and low-strain regime for the pulmonary artery and right ventricle, respectively, causing increased mechanical anisotropy. Main pulmonary artery stiffening correlated significantly with right ventricular tissue mechanical remodelling and reduced systolic performance, cardiac output and right ventricle-pulmonary artery coupling. ConclusionsCompositional, structural, and mechanical changes in the main pulmonary artery correlate with adverse right ventricular remodeling, mechanics, function and coupling in pulmonary arterial hypertension. Therefore, increasing mechanical compliance of the large pulmonary arteries may be an important and novel therapeutic strategy for mitigating right ventricular failure.

physiology↗