Hypoxia causes perinuclear mitochondrial clustering and nuclear oxidant stress in pulmonary artery endothelial cells (PAECS) via a dynein‐dependent molecular motor

Accumulating evidence suggests that mitochondria are motile, and may be recruited to subcellular domains where they participate in signal transduction. Mitochondria respond to hypoxia in PAECs by increasing oxygen radical generation, but whether hypoxia alters the disposition of mitochondria in PAECs is unknown, and if so, the molecular mechanism remains to be clarified. Accordingly, we mapped the disposition of Mitotracker‐stained mitochondria in cultured PAECs, and found that hypoxia caused a time‐dependent decrease in mitochondrial density near the plasma membrane and an increase in the perinuclear region. Interruption of the dynein‐dependent molecular motor using a specific siRNA prevented both the perinuclear mitochondrial clustering and, importantly, a hypoxia‐induced nuclear oxidant stress as detected by nuclear DCF fluorescence and by the level of oxidative base modifications in the VEGF promoter. Mitochondria were the source of the DNA‐modifying oxidants as evidenced by the finding that the respiratory chain inhibitor, myxothiazol, prevented the hypoxia‐induced nuclear DCF fluorescence without altering mitochondrial perinuclear clustering. These data suggest that hypoxia causes dynein‐dependent mitochondrial translocation to the perinuclear domain in PAECs that serves to create a nuclear oxidant stress important for hypoxic signaling. Supported by NIH