Oxysterols exert proinflammatory effects in placental trophoblasts via TLR4-dependent, cholesterol-sensitive activation of NF-κB.

Abstract

Oxidized cholesterol metabolites (oxysterols) promote inflammation in a variety of cell types and are thought to be involved in a number of disease pathologies. Oxysterol concentrations are increased in pregnancy, together with systemic oxidative stress and inflammation. We tested the hypothesis that oxysterols 25-hydroxycholesterol (25-OHC) and 7-ketocholesterol (7-ketoC) promote placental trophoblast inflammation, and determined the mechanisms involved. Treatment of primary trophoblasts in culture with 25-OHC and 7-ketoC increased the production of proinflammatory cytokines (interleukin-6, macrophage inflammatory protein-1β and tumour necrosis factor-α) in a concentration-dependent fashion. Inhibition of TLR4 activation using selective inhibitors of TLR4 complex formation (OxPAPC) or signalling transmission (CLI095) prevented lipopolysaccharide (LPS)- and oxysterol-induced inflammatory cytokine production. Pretreatment of trophoblasts with selective inhibitors of I-kB kinase activity (parthenolide and TPCA-1) reduced oxysterol- and LPS-stimulated inflammatory responses, consistent with the involvement of the nuclear factor kappa B (NF-κB) pathway downstream of TLR4 signalling. Both oxysterols also increased the phosphorylation and nuclear localization of NF-κB subunit p65/RelA. Oxysterols are also known to activate liver X receptors (LXRs) which can inhibit inflammatory signalling, either directly or indirectly via membrane cholesterol reduction. Treatment with the LXR agonist, T0901317, exerted significant anti-inflammatory effects, reducing LPS- and oxysterol-driven cytokine production. Treatment with methyl-β-cyclodextrin to deplete membrane microdomain cholesterol and thereby disrupt TLR4 signalling, similarly abrogated their effects. Together, these findings indicate that although oxysterols likely activate both pro- and anti-inflammatory pathways in the placenta, the predominant effect is the promotion of placental inflammation via TLR4-dependent activation of NF-κB.

• Authors: Irving L M H Aye, Brendan J Waddell, Peter J Mark, Jeffrey A Keelan
• Journal: Molecular human reproduction (Mol Hum Reprod) Vol. 18 Issue 7 Pg. 341-53 (Jul 2012) ISSN: 1460-2407 [Electronic] England
• PMID: 22238372 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Chemokine CCL4
• Hydroxycholesterols
• Interleukin-6
• Ketocholesterols
• Lipopolysaccharides
• NF-kappa B
• Tumor Necrosis Factor-alpha
• 25-hydroxycholesterol
• 7-ketocholesterol

Topics

• Cells, Cultured
• Chemokine CCL4 (metabolism)
• Female
• Humans
• Hydroxycholesterols (pharmacology)
• Immunohistochemistry
• Interleukin-6 (metabolism)
• Ketocholesterols (pharmacology)
• Lipopolysaccharides (pharmacology)
• NF-kappa B (metabolism)
• Pregnancy
• Trophoblasts (drug effects, metabolism)
• Tumor Necrosis Factor-alpha (metabolism)