MicroRNA-138 and MicroRNA-25 Down-regulate Mitochondrial Calcium Uniporter, Causing the Pulmonary Arterial Hypertension Cancer Phenotype.

RATIONALE: Pulmonary 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.

OBJECTIVES: To determine how changes in mitochondrial calcium uniporter (MCU) complex (MCUC) function influence mitochondrial dynamics and contribute to PAH's cancer-like phenotype.

METHODS: PASMCs 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 RESULTS: Impaired 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.

CONCLUSIONS: These results highlight miR-mediated MCUC dysfunction as a unifying mechanism in PAH that can be therapeutically targeted.