• Zhigang Hong, Kuang-Hueih Chen, Asish DasGupta, Francois Potus, Kimberly Dunham-Snary, Sebastien Bonnet, Lian Tian, Jennifer Fu, Sandra Breuils-Bonnet, Steeve Provencher, Danchen Wu, Jeffrey Mewburn, Mark L Ormiston, and Stephen L Archer.
• 1 Department of Medicine, Queen's University, Kingston, Ontario, Canada; and.
• Am. J. Respir. Crit. Care Med. 2017 Feb 15; 195 (4): 515-529.

RationalePulmonary arterial hypertension (PAH) is an obstructive vasculopathy characterized by excessive pulmonary artery smooth muscle cell (PASMC) proliferation, migration, and apoptosis resistance. This cancer-like phenotype is promoted by increased cytosolic calcium ([Ca2+]cyto), aerobic glycolysis, and mitochondrial fission.ObjectivesTo determine how changes in mitochondrial calcium uniporter (MCU) complex (MCUC) function influence mitochondrial dynamics and contribute to PAH's cancer-like phenotype.MethodsPASMCs were isolated from patients with PAH and healthy control subjects and assessed for expression of MCUC subunits. Manipulation of the pore-forming subunit, MCU, in PASMCs was achieved through small interfering RNA knockdown or MCU plasmid-mediated up-regulation, as well as through modulation of the upstream microRNAs (miRs) miR-138 and miR-25. In vivo, nebulized anti-miRs were administered to rats with monocrotaline-induced PAH.Measurements And Main ResultsImpaired MCUC function, resulting from down-regulation of MCU and up-regulation of an inhibitory subunit, mitochondrial calcium uptake protein 1, is central to PAH's pathogenesis. MCUC dysfunction decreases intramitochondrial calcium ([Ca2+]mito), inhibiting pyruvate dehydrogenase activity and glucose oxidation, while increasing [Ca2+]cyto, promoting proliferation, migration, and fission. In PAH PASMCs, increasing MCU decreases cell migration, proliferation, and apoptosis resistance by lowering [Ca2+]cyto, raising [Ca2+]mito, and inhibiting fission. In normal PASMCs, MCUC inhibition recapitulates the PAH phenotype. In PAH, elevated miRs (notably miR-138) down-regulate MCU directly and also by decreasing MCU's transcriptional regulator cAMP response element-binding protein 1. Nebulized anti-miRs against miR-25 and miR-138 restore MCU expression, reduce cell proliferation, and regress established PAH in the monocrotaline model.ConclusionsThese results highlight miR-mediated MCUC dysfunction as a unifying mechanism in PAH that can be therapeutically targeted.

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