Mitochondrial NADP(þ)-dependent isocitrate dehydrogenase (IDH2) plays an essential role protecting
cells against oxidative stress-induced damage. A deficiency in IDH2 leads to mitochondrial dysfunction
and the production of reactive oxygen species (ROS) in cardiomyocytes and cancer cells. However, the
function of IDH2 in vascular endothelial cells is mostly unknown. In this study the effects of IDH2 de-
ficiency on mitochondrial and vascular function were investigated in endothelial cells. IDH2 knockdown
decreased the expression of mitochondrial oxidative phosphorylation (OXPHOS) complexes I, II and III,
which lead to increased mitochondrial superoxide. In addition, the levels of fission and fusion proteins
(Mfn-1, OPA-1, and Drp-1) were significantly altered and MnSOD expression also was decreased by IDH2
knockdown. Furthermore, knockdown of IDH2 decreased eNOS phosphorylation and nitric oxide (NO)
concentration in endothelial cells. Interestingly, treatment with Mito-TEMPO, a mitochondrial-specific
superoxide scavenger, recovered mitochondrial fission–fusion imbalance and blunted mitochondrial
superoxide production, and reduced the IDH2 knockdown-induced decrease in MnSOD expression, eNOS
phosphorylation and NO production in endothelial cells. Endothelium-dependent vasorelaxation was
impaired, and the concentration of bioavailable NO decreased in the aortic ring in IDH2 knockout mice.
These findings suggest that IDH2 deficiency induces endothelial dysfunction through the induction of
dynamic mitochondrial changes and impairment in vascular function.