Soluble TLR2 Is Present in Human Amniotic Fluid and Modulates the Intraamniotic Inflammatory Response to Infection

Abstract

TLRs are pattern recognition transmembrane receptors that play key roles in innate immunity. A recently discovered soluble truncated form of TLR2 (sTLR2) acts as a decoy receptor, down-regulating the host inflammatory response to bacteria. To identify the presence and functional role of sTLR2 in modulating the intraamniotic inflammatory response to infection, we studied 109 amniotic fluid samples of women with normal pregnancy outcomes (n ‫؍‬ 28) and women with (n ‫؍‬ 39) and without (n ‫؍‬ 42) intraamniotic infection. We sought to demonstrate a functional role of the amniotic fluid sTLR2 in modulating the TLR2 inflammatory signaling in vitro by using a villous explant system. Two sTLR2 forms were identified, and specificity was confirmed with neutralizing peptides. We showed that sTLR2 is present constitutively in amniotic fluid, its levels are gestational age dependent, and we determined that the sTLR2 quantity and functional engagement modulates the intensity of the intraamniotic inflammation elicited by Gram-positive bacteria. In vitro, we demonstrated that challenging placental villous explants with a specific TLR2 agonist (Pam3Cys) induced a significant cytokine response. Notably, preincubation of the preterm, but not near-term, amniotic fluid with Pam3Cys significantly inhibited the ability of this TLR2 agonist to elicit a cytokine reaction. Moreover, depletion of sTLR2 from preterm amniotic fluid removed its neutralizing property. Monensin significantly diminished sTLR2 immunoreactivity, indicating that sTLR2 is the result of intracellular posttranslational processing of TLR2. We conclude that sTLR2 is part of the amniotic fluid innate immune system and participates in regulating the inflammatory response to microbial pathogens. The Journal of Immunology, 2009, 182: 7244 -7253.T he innate immune system is an archaic defense mechanism, phylogenetically preserved to be at the forefront of resistance to microbial infections (1). The human TLRs are essential for triggering an inflammatory innate immune response (2). To date, 13 mammalian TLRs have been identified and 10 of these are present in humans (3). At the maternal-fetal interface, TLRs are expressed not only in immune cells, but also in the trophoblast and decidual cells (4, 5). Moreover, their expression pattern varies according to the stage of pregnancy (5). Such findings provide evidence that during pregnancy, placental TLRs may play a key role in modulating the inflammatory response triggered by infection.TLRs are transmembrane receptors that mediate host defense through the engagement of pathogen-associated molecular patterns (PAMPs) 3 , which are ubiquitous constituents of the bacterial wall (6). TLR2 was the first of 10 human TLRs, proven to be precisely involved in recognition of PAMPs (lipoproteins, peptidoglycan, glycolipids, nucleic acids), representing broad groups of microbial species such as Gram-positive bacteria, Mycobacteria, spirochetes, and Mycoplasmataceae (7,8,9). Traditionally, it has been thought that the extracellular recepto...

A proteomic analysis of human follicular fluid: comparison between fertilized oocytes and non-fertilized oocytes in the same patient

“…However, a limitation of this study is that we are unable to attribute fertilization to oocyte quality only, although we Fig. 2 Spectral counts of heparan sulfate proteoglycan perlecan in the follicular fluids containing fertilized oocytes (fFF) and non-fertilized oocytes (nfFF) in each patient (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) tried to minimize the influence of sperm quality using ICSI. An increased number of samples would enable the use of a proteomics analysis to identify distinctive biomarkers.…”

“…Proteomics is helpful not only for identifying new disease-related biomarkers, but also for improving understanding of the pathophysiology of diseases. The application of proteomic analyses in medical research is intended to enrich a targetsetofdisease-relatedproteins.Inthegynecologicfield,this technique has been applied in the analysis of amniotic [5,10] and follicular fluid [3,11,18].…”

Functional Screening of TLRs in Human Amniotic Epithelial Cells

“…Upregulation of both receptors was reported for amniotic mem- brane from women who delivered after spontaneous PTL and women with chorioamnionitis (16,21,29,30). Recently, the presence and functional role of a soluble truncated form of TLR2, which acts as a decoy receptor, was described in human amniotic fluid (31). Only activation by TLR5 and TLR6/2 by their cognate ligands (flagellin and MALP-2, respectively) induced proinflammatory responses in amniotic epithelial cells.…”

Increased production of soluble TLR2 by lamina propria mononuclear cells from ulcerative colitis patients

“…Soluble TLR2 is released by placental tissue (Dulay et al 2009). To evaluate the production of sTLR2 by intestinal mucosa, organ culture biopsies from IBD and control patients were incubated for 24 h in culture media and detected by ELISA in the supernatant.…”

“…Extracellularly, soluble TLR (sTLR) behaves as a decoy receptor that counteracts receptor activation. sTLR2 has been detected in human fluids, such as serum, plasma, breast milk, saliva and amniotic fluid (Dulay et al 2009;Kuroishi et al 2007;LeBouder et al 2003). In particular, sTLR2 variants have been shown to block inflammatory responses driven by TLR2 activation, through negative regulatory effects, by acting as a decoy receptor, and by disrupting the close proximity between the coreceptor (CD14) and the receptor (TLR2) that is crucial to highly efficient signaling (LeBouder et al 2003;Raby et al 2009).…”