t0901317 and 7-ketocholesterol

Oxygenated cholesterol metabolites known as oxysterols display potent biological activities ranging from regulation of lipid homeostasis to cytotoxicity. Oxysterols have previously been shown to inhibit the invasion of first trimester trophoblasts, an effect which involves activation of the nuclear liver X receptors (LXRs). In the present study, we investigated the effects of several oxysterols on syncytialisation (differentiation and fusion) in term placental trophoblasts. Treatment of cultured term primary trophoblast cells with oxysterols [25-hydroxycholesterol, 7-ketocholesterol, 22(R)-hydroxycholesterol] and the synthetic LXR agonist T0901317 at non-toxic doses decreased expression of GCM-1 and HERV-W mRNA and reduced hCG secretion and placental alkaline phosphatase activity, indicative of diminished trophoblast differentiation. Furthermore, treatment with these compounds also decreased cell fusion measured by E-cadherin immunostaining and quantification of syncytialised nuclei. Treatment with an LXR antagonist (geranylgeranyl diphosphate) abrogated the inhibitory effects of oxysterols and T0901317 on trophoblast syncytialisation indicating that these effects are mediated by LXR. These findings suggest that oxysterols impair differentiation and fusion of term trophoblast cells via an LXR-dependent mechanism.

Topics: Alkaline Phosphatase; Cell Differentiation; Cell Fusion; Chorionic Gonadotropin; DNA-Binding Proteins; Female; Gene Products, env; Humans; Hydrocarbons, Fluorinated; Hydroxycholesterols; Ketocholesterols; Liver X Receptors; Nuclear Proteins; Orphan Nuclear Receptors; Placenta; Pregnancy; Pregnancy Proteins; RNA, Messenger; Sulfonamides; Transcription Factors; Trophoblasts

Cholesterols are enriched in the brain and can be oxidized to oxysterols by several processes. Oxysterols are transport forms of cholesterols across cell membranes and the blood-brain barrier. Here, to elucidate the roles of oxysterols in brain inflammation, we treated lipopolysaccharide-stimulated rat brain astrocytes with two oxysterols, 7-ketocholesterol and 22(R)-hydroxycholesterol. Both oxysterols suppressed inducible nitric oxide synthase expression and nitric oxide release as well as upstream signaling molecules including interferon-beta, phosphorylated signal transducer and activator of transcription 1/3, and interferon regulatory factor-1. Oxysterols are known as liver X receptor agonists, and inhibitory effects were also observed with synthetic agonists of liver X receptor and retinoid X receptor. Thus, we conclude that it is most likely mediated by liver X receptor/retinoid X receptor heterodimers.

Topics: Animals; Animals, Newborn; Astrocytes; Benzoates; Benzylamines; Blotting, Western; Cells, Cultured; Cholesterol; Desmosterol; DNA-Binding Proteins; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Activation; Enzyme Inhibitors; Gene Expression Regulation; Hydrocarbons, Fluorinated; Interferon Regulatory Factor-1; Interferon-beta; Ketocholesterols; Lipopolysaccharides; Liver X Receptors; Models, Biological; Nitric Oxide Synthase Type II; Orphan Nuclear Receptors; Rats; Receptors, Cytoplasmic and Nuclear; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sulfonamides