Oxygen sensing, mitochondrial biology and experimental therapeutics for pulmonary hypertension and cancer

Danchen Wu, Asish Dasgupta, Austin D. Read, Rachel E.T. Bentley, Mehras Motamed, Kuang-Hueih Chen, Ruaa Al-Qazazi, Jeffrey D. Mewburn, Kimberly J. Dunham-Snary, Elahe Alizadeh, Lian Tian, Stephen L. Archer

Research output: Contribution to journalArticlepeer-review

Abstract

The homeostatic oxygen sensing system (HOSS) optimizes systemic oxygen delivery. Specialized tissues utilize a conserved mitochondrial sensor, often involving NDUFS2 in complex I of the mitochondrial electron transport chain, as a site of pO2-responsive production of reactive oxygen species (ROS). These ROS are converted to a diffusible signaling molecule, hydrogen peroxide (H2O2), by superoxide dismutase (SOD2). H2O2 exits the mitochondria and regulates ion channels and enzymes, altering plasma membrane potential, intracellular Ca2+ and Ca2+-sensitization and controlling acute, adaptive, responses to hypoxia that involve changes in ventilation, vascular tone and neurotransmitter release. Subversion of this O2-sensing pathway creates a pseudohypoxic state that promotes disease progression in pulmonary arterial hypertension (PAH) and cancer. Pseudohypoxia is a state in which biochemical changes, normally associated with hypoxia, occur despite normal pO2. Epigenetic silencing of SOD2 by DNA methylation alters H2O2 production, activating hypoxia-inducible factor 1α, thereby disrupting mitochondrial metabolism and dynamics, accelerating cell proliferation and inhibiting apoptosis. Other epigenetic mechanisms, including dysregulation of microRNAs (miR), increase pyruvate dehydrogenase kinase and pyruvate kinase muscle isoform 2 expression in both diseases, favoring uncoupled aerobic glycolysis. This Warburg metabolic shift also accelerates cell proliferation and impairs apoptosis. Disordered mitochondrial dynamics, usually increased mitotic fission and impaired fusion, promotes disease progression in PAH and cancer. Epigenetic upregulation of dynamin-related protein 1 (Drp1) and its binding partners, MiD49 and MiD51, contributes to the pathogenesis of PAH and cancer. Finally, dysregulation of intramitochondrial Ca2+, resulting from impaired mitochondrial calcium uniporter complex (MCUC) function, links abnormal mitochondrial metabolism and dynamics. MiR-mediated decreases in MCUC function reduce intramitochondrial Ca2+, promoting Warburg metabolism, whilst increasing cytosolic Ca2+, promoting fission. Epigenetically disordered mitochondrial O2-sensing, metabolism, dynamics, and Ca2+ homeostasis offer new therapeutic targets for PAH and cancer. Promoting glucose oxidation, restoring the fission/fusion balance, and restoring mitochondrial calcium regulation are promising experimental therapeutic strategies.
Original languageEnglish
Number of pages29
JournalFree Radical Biology and Medicine
Early online date12 Jan 2021
DOIs
Publication statusE-pub ahead of print - 12 Jan 2021

Keywords

  • ABT-263 (Navitoclax)
  • ABT-199 (Venetoclax)
  • B-Cell lymphoma 2 (BCL-2)
  • DNA methylation
  • DNA methyltransferase (DNMT)
  • dynamin-related protein 1 (Drp1)
  • group 1 pulmonary hypertension
  • hypoxia-inducible factor 1α (HIF-1α)
  • hypoxia-inducible factor 2α (HIF-2α)
  • hypoxic pulmonary vasoconstriction
  • mammalian target of rapamycin (mTOR
  • microRNA (miRNA)
  • miR-138miR-25
  • mitochondrial calcium uniporter (MCU)
  • mitochondrial dynamics protein of 49 kDa (MiD49)
  • mitochondrial dynamics protein of 51 kDa (MiD51)
  • Mitofusin 2 (Mfn2)
  • mitophagy
  • monocrotaline
  • oxygen sensing
  • Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α)
  • Pyruvate dehydrogenase (PDH)
  • Pyruvate dehydrogenase kinase (PDK)
  • Pyruvate kinase muscle isoform 2 (PKM2
  • Reactive oxygen species (ROS)
  • Sugen5416
  • Survivin
  • von hippel-lindau protein (VHL)

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