Increased placental phospholipase A2 gene expression and free F2-isoprostane levels in response to oxidative stress in preeclampsia

Vasoactive eicosanoids such as thromboxane (TX) A2 and F2-isoprostanes (F2-isoPs) were shown to be increased in the preeclamptic placenta. Only one of the 64 possible isomers of F2-isoPs derived from the oxidation of arachidonic acid was investigated in the placenta so far. F2-isoPs are released from membrane phospholipids by phospholipases A2 (PLA2) and were shown to act on the TXA2 receptor (TBXA2R). However, the PLA2 deregulated in preeclampsia (PE) remains to be determined. In this study, we analyzed the concentrations of six isomers of F2-isoPs; 8-iso-PGF2α, 8-iso-15(R)-PGF2α, 15(R)-PGF2α, iPF2α-IV, iPF2α-VI, 5-iPF2α-VI and the concentrations of the stable metabolites of TXA2, TXB2, by high performance liquid chromatography coupled with tandem mass spectrometry in placentas of PE (n = 17) and normotensive (n = 15) pregnancies according to the biopsy site: peri-insertion or periphery. In the same biopsies, relative mRNA expression of PLA2G2A, PLA2G4A, PLA2G5, PLA2G7, the PLA2 receptor (PLA2R1), the TXA2 synthase and TBXAR2 were measured by quantitative RT-PCR. We observed similar concentrations of total F2-isoP isomers between groups whereas higher concentrations (>40%) of free F2-isoP were observed for all isomers (p ≤ 0.033) in PE than normotensive controls. As expected, we also observed higher placental concentrations of TXB2 in PE (p = 0.005). Interestingly, we concomitantly found higher mRNA expression of secretory PLA2G2A (p = 0.010), PLA2G5 (p = 0.038) and TBXA2R (p = 0.023) in PE than normotensive placentas. In sum, deregulated PLA2 could potentially be implicated in freeing F2-isoP which could participate in local hypertension observed in the PE placenta through the TX pathway.