title: Pulmonary vascular inflammation: effect of TLR signalling on angiopoietin/TIE regulation.
abstract: Increased pulmonary vascular resistance is a critical complication in sepsis. Toll-like receptor (TLR) as well as angiopoietin (ANG) signalling both contribute to the emergence of pulmonary arterial hypertension. We hypothesized that TLR stimulation by bacterial ligands directly affects expression and secretion of ligands and receptors of the angiopoietin/TIE axis. Microvascular endothelial (HPMEC) and smooth muscle cells (SMC) of pulmonary origin were incubated with thrombin and with ligands for TLR2, -4, -5, and -9. Expression and secretion of ANG1, -2, TIE2 and IL-8 were determined using quantitative real-time PCR and ELISA. TLR stimulation had no impact either on the expression of ANG2 and TIE2 in HPMEC or on that of ANG1 in SMC. However, overall levels of both released ANG1 and -2 were halved upon stimulation with the TLR9 ligand CpG, and ANG2 release was significantly enhanced by TLR4 activation when initially provoked by sequentially performed stimulation. Furthermore, enhanced ANG2 activity increased endothelial permeability, as demonstrated in an in vitro transwell assay. We conclude that sole TLR stimulation by bacterial ligands plays no significant role for altered expression and secretion of ANG1, -2 and TIE2 in human pulmonary vascular cells. The interplay between various stimuli is required to induce imbalances between ANG1 and -2.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Hilbert
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Dornbusch
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Johanniter Hospital Bonn, Bonn, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Baumgarten
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hoeft
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany.
authors.forename: Stilla
authors.initials: S
authors.lastname: Frede
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Klaschik
mesh_terms: D042683:Angiopoietin-1 / Q000096:biosynthesis*; D042702:Angiopoietin-2 / Q000096:biosynthesis*; D042682:Angiopoietins / Q000096:biosynthesis; D002478:Cells, Cultured; D005408:Flagellin / Q000633:toxicity; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism; D055806:Microvessels / Q000187:drug effects / Q000378:metabolism; D011014:Pneumonia / Q000139:chemically induced / Q000378:metabolism; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism*; D042787:Receptor, TIE-2 / Q000096:biosynthesis*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D051193:Toll-Like Receptors / Q000096:biosynthesis*
chemical_list: C467630:ANGPT1 protein, human; C586513:ANGPT2 protein, human; D042683:Angiopoietin-1; D042702:Angiopoietin-2; D042682:Angiopoietins; D018836:Inflammation Mediators; D051193:Toll-Like Receptors; D005408:Flagellin; D042787:Receptor, TIE-2
keywords: Tie2 receptor; acute lung injury; angiopoietins; endothelial dysfunction; pulmonary hypertension; sepsis; vascular resistance