Conclusions
Mitochondrial fission is an obligatory, early step in mammalian O2 sensing and offers a promising target for modulating DA patency.
Objective
The purpose of this study was to determine whether mitochondrial fission is crucial for O2-induced DA constriction and closure.
Results
Using DA harvested from 30 term infants during correction of congenital heart disease, as well as DA from term rabbits, we demonstrate that mitochondrial fission is crucial for O2-induced constriction and closure. O2 rapidly (<5 minutes) causes mitochondrial fission by a cyclin-dependent kinase- mediated phosphorylation of dynamin-related protein 1 (Drp1) at serine 616. Fission triggers a metabolic shift in the ductal smooth muscle cells that activates pyruvate dehydrogenase and increases mitochondrial H2O2 production. Subsequently, fission increases complex I activity. Mitochondrial-targeted catalase overexpression eliminates PO2-induced increases in mitochondrial-derived H2O2 and cytosolic calcium. The small molecule Drp1 inhibitor, Mdivi-1, and siDRP1 yield concordant results, inhibiting O2-induced constriction (without altering the response to phenylephrine or KCl) and preventing O2-induced increases in oxidative metabolism, cytosolic calcium, and ductal smooth muscle cells proliferation. Prolonged Drp1 inhibition reduces DA closure in a tissue culture model. Conclusions: Mitochondrial fission is an obligatory, early step in mammalian O2 sensing and offers a promising target for modulating DA patency.