Preeclampsia (PE) is associated with exaggerated systemic inflammatory response (ESIR). Having shown that monocyte (Mo) subtypes in PE demonstrate a pro-inflammatory phenotype and increased expression of Toll like receptors (TLR) 2 and 4, we postulated that ESIR may be triggered by endogenous ligand(s) of these TLRs, and investigated the expression of markers of angiogenesis, chemotaxis and migration in monocytes from normal pregnant (NP, n=14), PE (n=14), and non-pregnant (n=9) women. Monocytes were labelled with antibodies to TLR2, TLR4, CD14, CD16, HLA-DR a MHC class II cell surface receptor, or isotypes; Tie2 (a receptor of angiopoietin), CCR2 (a receptor of the monocyte chemo-attractant protein-1), and CCR5 (a receptor of the macrophage inflammatory proteins, MIP-1α) or isotypes, and analysed by flow cytometry. Plasma endogenous TLR4 ligands- heparan sulfate, hyaluronan, fibronectin, fibrinogen and High mobility group box-1(HMGB1) - were measured by ELISA. Mo was stimulated by LPS, peptidoglycan and endogenous ligands, and cytokines measured by cytometric array. Compared to NP, CD14+CD16+ monocytes was higher in PE (P<0.001) while CD14++CD16- was lower; TLR2 and 4 were higher (P<0.001), differing between subpopulations; HLA-DR and Tie2 were lower (P<0.01); CCR2 and 5 were higher (P<0.01). Heparan sulfate, hyaluronan, fibronectin and fibrinogen did not differ, but HMGB1 was higher. Stimulation PE monocytes with peptidoglycan, LPS and fibrinogen exaggerated the release of TNF-α and IL-6, consistent with ESIR. Upregulation of TLR-2 and 4 and the migration factors CCR2 and 5, and downregulation of the angiogenic marker Tie 2, are key modulatory events of vascular injury in preeclampsia.
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