A Theoretical Model of the Mechanism by which Dietary Lipid Variance and Increased Oxysterols Allow Increased Formation of Soluble Endoglin in Preeclampsia

Abstract

Endoglin (TGF‐β receptor III), an accessory receptor necessary for transforming growth factor‐β (TGF‐β) signaling, is essential during angiogenesis. Cleavage of endoglin by matrix metalloproteinase‐14 (MMP‐14) creates a soluble receptor (sEng) which is elevated in the sera of people with preeclampsia. Similarly to sflts which bind VEGF, sEng binds TGF‐β and impairs functions ranging from endothelial nitric oxide synthesis, vasodilation, and modulation of vascular permeability, to regulation of immune homeostasis, trophoblastic invasion and differentiation.Cleavage of endoglin to form sEng is upregulated in the presence of oxysterols. Initially, oxysterols were believed to upregulate MMP‐14 and down regulate its inhibiter TIMP3. However, in placental explants, expression MMP14 and TIMP3 mRNA were not altered by oxysterols and pravastatin did not decrease oxysterol‐induced upregulation of sEng. Membrane raft domains negatively regulate TGF‐β signaling, and aspirin, which disperses membrane rafts, induces TGF‐β signaling.This perspective considers the known changes in dietary lipids over the last 100 years, the possible effects of these changes on membrane raft formation, oxidative stress, and oxysterol formation, as well as the known effects of oxysterols on membrane thickness and fluidity and proposes an alternate mechanism by which oxysterols might increase sEng formation.