Introduction: During pre-eclampsia the compensatory properties regulating the placental oxidative state are aggravated, leading to increased production of pathogenic factors and subsequent vascular dysfunction. Endothelial cells are the primary targets of deleterious circulating factors in pre-eclampsia. There is significant circumstantial evidence demonstrating that mitochondrial dysfunction is a pathogenic mediator of oxidative stress in pre-eclampsia, with increased mitochondrial lipid peroxidation and enhanced susceptibility to oxidation evident in placental mitochondria in pre-eclampsia. Excessive production of mitochondrial-ROS is intrinsically linked to mitochondrial dysfunction. Recently mitochondria-targeted antioxidants (Mito-Tempo) alleviated endothelial dysfunction, reduced mitochondrial superoxide and subsequent hypertension in in vivo models of hypertension.
Aim: To investigate if pre-eclampsia plasma mediators distort vascular mitochondrial function.
To determine the role of mitochondrial-targeted antioxidants in alleviating endothelial dysfunction in pre-eclampsia.
Methods: Human umbilical vein endothelial cells were cultured for 4 hours with 3% pooled plasma from women with pre-eclampsia (n=9) and matched controls with uncomplicated pregnancies (n=9) from the SCOPE (www.scopestudy.net) biobank. Alternatively, cells were pre-treated with 5μM Mito-Tempo, 5uM N-acetylcysteine (NAC), or DMSO control for 2hours and incubated with 3% plasma for 4hours. Mitochondrial-specific superoxide was detected by fluorescent microscopy of MitoSOX probe upon its oxidation by mitochondrial O2−. Additionally, mitochondrial respiration was determined by measuring oxygen consumption (OCR) in plasma-treated HUVEC’s using the MitoXpress assay. The expression profile of markers of inflammation and endothelial dysfunction were evaluated by real-time PCR. Markers of mitochondrial redox signalling were determined by real-time PCR.
Results: This research showed for the first time that the magnitude of plasma-induced mitochondrial-specific superoxide production was significantly increased in endothelial cells incubated with plasma from women with pre-eclampsia (191.82%±25%, n=10, P< 0.05). compared with matched controls(127.65%±24%, n=10). Furthermore, pre-eclampsia plasma mediators significantly reduced OCR (40.61±18.10 RFU, n=5, P<0.05) when compared with with matched controls (94.12±34.9 RFU, n=5). Pre-eclampsia plasma mediators significantly increased TNF-α gene expression (2.67±0.26 fold, n=8, P<0.01)and ICAM-1 gene expression (1.76±0.17 fold, n=8, P<0.01) in HUVECs respectively, compared with matched controls. Pre-treatment with MitoTempo significantly reduced mROS generation compared to untreated cells (61.23%±15.42% vs 100%±0%, n=9, P<0.01) and with a greater proficiency than non-targeted antioxidant (NAC) treatment. MitoTempo administration also reduced the expression of pro-inflammatory markers in pre-eclampsia plasma treated cells.
Conclusion: Mitochondrial superoxide regulates plasma mediator-induced endothelial dysfunction in pre-eclampsia. Mitochondrial-targeted antioxidants modulate mitochondrial dysfunction by restraining the aberrant generation of mitochondrial reactive oxygen species (mROS) and the consequent mROS-mediated deleterious signalling pathways.