Regulation of mitochondrial fragmentation in microvascular endothelial cells isolated from the SU5416/hypoxia model of pulmonary arterial hypertension

Am J Physiol Lung Cell Mol Physiol. 2019 Nov 1;317(5):L639-L652. doi: 10.1152/ajplung.00396.2018. Epub 2019 Aug 28.


Pulmonary arterial hypertension (PAH) is a morbid disease characterized by progressive right ventricle (RV) failure due to elevated pulmonary artery pressures (PAP). In PAH, histologically complex vaso-occlusive lesions in the pulmonary vasculature contribute to elevated PAP. However, the mechanisms underlying dysfunction of the microvascular endothelial cells (MVECs) that comprise a significant portion of these lesions are not well understood. We recently showed that MVECs isolated from the Sugen/hypoxia (SuHx) rat experimental model of PAH (SuHx-MVECs) exhibit increases in migration/proliferation, mitochondrial reactive oxygen species (ROS; mtROS) production, intracellular calcium levels ([Ca2+]i), and mitochondrial fragmentation. Furthermore, quenching mtROS with the targeted antioxidant MitoQ attenuated basal [Ca2+]i, migration and proliferation; however, whether increased mtROS-induced [Ca2+]i entry affected mitochondrial morphology was not clear. In this study, we sought to better understand the relationship between increased ROS, [Ca2+]i, and mitochondrial morphology in SuHx-MVECs. We measured changes in mitochondrial morphology at baseline and following inhibition of mtROS, with the targeted antioxidant MitoQ, or transient receptor potential vanilloid-4 (TRPV4) channels, which we previously showed were responsible for mtROS-induced increases in [Ca2+]i in SuHx-MVECs. Quenching mtROS or inhibiting TRPV4 attenuated fragmentation in SuHx-MVECs. Conversely, inducing mtROS production in MVECs from normoxic rats (N-MVECs) increased fragmentation. Ca2+ entry induced by the TRPV4 agonist GSK1017920A was significantly increased in SuHx-MVECs and was attenuated with MitoQ treatment, indicating that mtROS contributes to increased TRPV4 activity in SuHx-MVECs. Basal and maximal respiration were depressed in SuHx-MVECs, and inhibiting mtROS, but not TRPV4, improved respiration in these cells. Collectively, our data show that, in SuHx-MVECs, mtROS production promotes TRPV4-mediated increases in [Ca2+]i, mitochondrial fission, and decreased mitochondrial respiration. These results suggest an important role for mtROS in driving MVEC dysfunction in PAH.

Keywords: PAH; calcium; endothelium; mitochondria.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiogenesis Inhibitors / toxicity
  • Animals
  • Calcium / metabolism
  • Cells, Cultured
  • Endothelial Cells / metabolism
  • Endothelial Cells / pathology*
  • Hypoxia / complications*
  • Indoles / toxicity*
  • Lung / metabolism
  • Lung / pathology*
  • Male
  • Mitochondria / metabolism
  • Mitochondria / pathology*
  • Oxygen Consumption
  • Pulmonary Arterial Hypertension / etiology
  • Pulmonary Arterial Hypertension / metabolism
  • Pulmonary Arterial Hypertension / pathology*
  • Pyrroles / toxicity*
  • Rats
  • Rats, Wistar
  • Reactive Oxygen Species / metabolism*
  • Vascular Remodeling


  • Angiogenesis Inhibitors
  • Indoles
  • Pyrroles
  • Reactive Oxygen Species
  • Semaxinib
  • Calcium