Placental Production of Eicosanoids and Sphingolipids in Women Who Developed Preeclampsia on Low-Dose Aspirin

Abstract

Low-dose aspirin, which selectively inhibits thromboxane synthesis, is now standard of care for the prevention of preeclampsia in at risk women, but some women still develop preeclampsia despite an aspirin regimen. To explore the "aspirin failures," we undertook a comprehensive evaluation of placental lipids to determine if abnormalities in non-aspirin sensitive lipids might help explain why some women on low-dose aspirin develop preeclampsia. We studied placentas from women with normal pregnancies and women with preeclampsia. Placental villous explants were cultured and media analyzed by mass spectrometry for aspirin-sensitive and non-aspirin-sensitive lipids. In women who developed severe preeclampsia and delivered preterm, there were significant elevations in non-aspirin-sensitive lipids with biologic actions that could cause preeclampsia. There were significant increases in 15- and 20-hydroxyeicosatetraenoic acids and sphingolipids: D-e-C_18:0 ceramide, D-e-C_18:0 sphingomyelin, D-e-sphingosine-1-phosphate, and D-e-sphinganine-1-phosphate. With regard to lipids sensitive to aspirin, there was no difference in placental production of thromboxane or prostacyclin, but prostaglandins were lower. There was no difference for isoprostanes, but surprisingly, anti-inflammatory omega 3 and 6 PUFAs were increased. In total, 10 of 30 eicosanoids and 5 of 42 sphingolipids were abnormal in women with severe early onset preeclampsia. Lipid changes in women with mild preeclampsia who delivered at term were of lesser magnitude with few significant differences. The placenta produces many aspirin-sensitive and non-aspirin-sensitive lipids. Abnormalities in eicosanoids and sphingolipids not sensitive to aspirin might explain why some aspirin-treated women develop preeclampsia.

Keywords: Eicosanoids; Low-dose aspirin; Placenta; Preeclampsia; Sphingolipids.

Fig.1

Increases in sphingolipids related to the development of preeclampsia. Placental production of sphingolipids would not be affected by low-dose aspirin therapy. D-e-C_18:0 ceramide, D-e-C_18:0 sphingomyelin, D-e-sphingosine-1-phosphate (S1P), and D-e- sphinganine-1-phosphate were significantly increased in SPE ASA as compared to NP. There were no differences among NP, NP ASA and MPE ASA for any of the sphingolipids. (*P < 0.05; NP - normal pregnancy without aspirin and no risk factors; NP ASA - normal pregnancy with risk factors and aspirin; MPE ASA - mild preeclampsia with risk factors and aspirin; SPE ASA - severe preeclampsia with risk factors and aspirin)

Fig.2

Increases in HETEs related to the development of preeclampsia. Placental production of lipoxygenase metabolites would not be affected by low-dose aspirin. There were no differences for 5-HETE or 12-HETE among groups and there were no differences among NP, NP ASA and MPE ASA for 15-HETE and 20-HETE, however 15-HETE and 20-HETE were significantly increased in women with SPE ASA as compared to women with NP. (*P < 0.05; ** P < 0.01, HETE, hydroxyeicosatetraenoic acid)

Fig.3

Alterations in placental metabolism of eicosanoids with anti-inflammatory properties. 11, 12 DHET and 14, 15 DHET were significantly increased in women with SPE ASA as compared to NP. There were no significant differences among NP, NP ASA and MPE ASA for DHETs. (*P < 0.05; DHET, dihydroxyeicosatrienoic acids)

Fig.4

Placental production of cyclooxygenase metabolites and isoprostanes. Cyclooxygenase metabolites are aspirin-sensitive lipids. There were no differences among groups for 6-keto PGF1a, TXB2, 8-iso PGF2a or 5-iPF2a. PGE1, PGE2 and PGF2a were significantly lower than NP for SPE ASA and PGE1 and PGF2a were significantly lower than NP for NP ASA as well. (*P < 0.05; TXB2, thromboxane B2; 6- keto PGF1a, 6-keto prostaglandin F1a; 8-iso PGF2a, 8-isoprostane; 5-iPF2a, 5- isoprostane; PGE1, prostaglandin E1; PGE2, prostaglandin E2; PGF2a, prostaglandin F2α)

Fig.5

Anti-inflammatory omega-3 and omega-6 PUFAs in the placenta. There were no significant differences among NP, NP ASA and MPE ASA for EPA, DHA or DHGLA, however the SPE ASA group was significantly higher than NP for all three PUFAs. There were no significant differences for arachidonic acid. (*P < 0.05; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid; DHGLA, dihomo-gamma-linolenic acid)

Fig.6

Radar graphs showing percent changes of selected eicosanoids and sphingolipids in women with SPE (red long dashed line) as compared to women with normal pregnancies (blue inner circle solid line) and women with MPE (green short dashed line). Women with MPE showed changes similar to SPE, but the changes were not as great. PE (tan medium dashed line) is the average of SPE and MPE. Prostaglandins and thromboxane on the right-hand side of the eicosanoid plot for PE patients were less than or no different than NP, whereas HETEs, EPA, DHA and DHGLA on the left-hand side were greater than NP. All sphingolipids that were abnormal in SPE were significantly elevated as compared to normal pregnancy. Placental S1P, which would be secreted into the maternal circulation, was over 5-fold higher for SPE than NP. (PE, preeclampsia; MPE, mild preeclampsia; SPE, severe preeclampsia; NP, normal pregnancy; 6-keto PGF1α, 6-keto prostaglandin F1α; 8-iso PGF2α, 8-isoprostane; TXB2, thromboxane B2; PGE2, prostaglandin E2; PGF2a, prostaglandin F2a; PGE1, prostaglandin E1; PGA2, prostaglandin A2; DHET, dihydroxyeicosatrienoic acids; HETE, hydroxyeicosatetraenoic acid; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid; DHGLA, dihomo-gamma-linolenic acid; S1P, sphingosine-1-phosphate)