Effects of Labor on Placental Expression of Superoxide Dismutases in Preeclampsia

Abstract 

A decreased antioxidant activity for superoxide dismutases (SODs) in the placenta was reported in preeclampsia (PE). However, it is unclear if this reduced enzymatic activity can be attributed to a specific SOD isoform. Moreover, the specific spatial SOD expression in the placenta and the impact of the mode of delivery on the latter are still lacking. There are three known SOD isoforms: SOD1 (cytosolic), SOD2 (mitochondrial) and SOD3 (extracellular). Our main objective was to characterize by RT-PCR, western blot and immunolocalization, the expression of SOD1, SOD2, and SOD3 in placentas of normotensive (n = 23) and PE pregnancies (n = 25) according to the presence or absence of labor, the sampling site (peri-insertion, mid-disc and periphery) and the placental layer: amnion-chorion, villi, and maternal side layer (MS). In absence of labor (cesarean), SOD1 expression in the placental villi and MS was lower in PE than in controls (p < 0.049). In presence of labor (vaginal deliveries), SOD1 expression in the amnion-chorion only was higher in PE than controls (p = 0.014). Additionally, SOD2 and SOD3 expression in presence of labor were higher in all three layers in PE than controls, with a strong positive correlation between these two SODs (mRNA; r > 0.65, p < 0.008). The sampling site and gestational age had no effect on SOD expression within the placenta. In this study, we showed that the reported decrease for SOD activity in PE may be attributed to SOD1 in absence of labor. Also, this is the first study characterizing specific SOD isoforms according to the mode of delivery. We demonstrated in PE that labor upregulates SOD1 in fetal membranes as well as SOD2 and SOD3 in the whole placenta.

Keywords: Oxidative stress, Amnion, Superoxide dismutase, Preeclampsia, Effect of labor, Human, Chorion, Villi