inflammation-in-pregnancy.at

Home

Faculty

Publications

 

Webmaster

Ute Panzenboeck, PhD:

Nuclear receptors regulating metabolism and inflammatory mediators in endothelial cells

Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Chair of Pathophysiology and Immunology, Medical University of Graz, Heinrichstraße 31a, A-8010 Graz;
phone: +43-316-380 1955, fax: +43-316-380 9640, ✉ e-mail
• Profile ⏬     • Curriculum vitae     • PhD students     • Grants     • Publications    

Keywords:

Fetoplacental endothelial barrier, cholesterol metabolism, oxysterols, liver-X receptors, cytokines, oxidative stress, high-density lipoproteins, gestational diabetes mellitus, metabolic syndrome

Research interest:

Rising evidence suggests that Gestational diabetes mellitus (GDM) modulates the placental endothelium to an altered metabolic state causing vascular dysfunction and altered fetal programming. GDM is associated with oxidative stress which may contribute to endothelial dysfunction. Oxysterols, generated from cholesterol oxidation either by CYP-450 reductase or by reactive oxygen species (ROS), are endogenous activators of liver-X receptors (LXRs), nuclear transcription factors centrally involved in important biological processes, including lipid / cholesterol and glucose metabolism (1).

LXRs promote high-density lipoprotein (HDL) formation by activating several target genes of reverse cholesterol transport. We reported earlier that LXR target genes (ABCA1, ABCG1 and PLTP) are centrally involved in HDL mediated cholesterol efflux from fetoplacental endothelial cells (HPEC) (2, 3, 4).

A current focus of our laboratory is to define the impact of oxysterols and pharmacological activators of LXRs on cholesterol-metabolic and inflammatory functions in the GDM feto-placental vasculature. Unpublished results of our group strongly suggest that the GDM environment modulates cholesterol homeostasis by enhancing cholesterol biosynthesis and cholesterol efflux in fetoplacental endothelial cells while cellular cholesterol homeostasis is largely maintained. Thus, GDM may affect placental cholesterol metabolism via LXR activation due to increased oxysterol levels in cells and /&harsp;or in the fetal circulation.

While HDL itself exerts anti-inflammatory actions on endothelial cells, LXRs are also involved in immune regulatory functions and can reduce inflammation by sumoylation-dependent and -independent mechanisms (1). Upon activation, LXRs can be sumoylated, and as a monomer, can stabilize repressor complexes present on the promoter sequence of proinflammatory pathways such as activator protein 1 (AP-1) and nuclear factor κB (NF-κB), thereby preventing the expression of proinflammatory factors. In brain endothelial cells, LXR activation by oxysterols or synthetic agonist TO901317 significantly reduced expression of inflammatory genes COX-II and TNFα along with modulating cellular cholesterol metabolism (5). We hypothesize that endogenous and /&harsp;or pharmacologic activation of LXRs may improve fetoplacental endothelial function in conditions of GDM and other pregnancy complications related to metabolic diseases.

Illustrations:

 
Fig. 1: A: Sequential steps in transplacental transfer of lipoprotein-derived cholesterol at the end of gestation. Overall maternal–fetal transfer likely encompasses an “uptake / nflux” component for maternal lipoproteins and / or their cholesterol into the syncytio­tropho­blast (STB), transport of lipoprotein-derived cholesterol (C) to the basal side of the STB, subsequent release into the villous core for passage through the extracellular matrix (ECM), uptake into HPECs, and, finally, an efflux component by which cholesterol is released from HPECs into the fetal circulation. To date, only the uptake and degradation of LDL and HDL in cultured trophoblasts have been described. However, other lipoproteins and their respective receptors have not been analyzed, and the subsequent intraplacental transport steps are still uncharacterized. B: Proposed pathway for cholesterol efflux from placental ECs into the fetal circulation at the end of gestation. The efflux of cholesterol (C) from HPECs into the fetal circulation involves an interactive role of ABCA1, ABCG1, and fetal apolipoproteins. ABCA1 promotes cholesterol efflux to lipid-free / poor apoA-I or apoE in the fetal circulation, thus initiating the formation of nascent, discoidal HDL, which will be further enriched with cholesterol by the cooperation of ABCA1 and ABCG1. ApoE-enriched HDL particles may facilitate cholesterol efflux via the ABCG1 pathway. Esterification of cholesterol by lecithin cholesterol acyl transferase will eventually result in the formation of mature spherical HDL. Oxysterols activate LXRs, which induce expression of ABCA1 and ABCG1, and, hence, will represent an effective mechanism regulating cholesterol efflux (dotted lines). [2]
 
Fig. 2: Localization of PLTP in term human placenta. A: The endothelial marker vonsrp;Willebrand factor (vWF) stains blood vessels and fibrin deposits but not cytotrophoblast (dotted arrows). B: PLTP is predominantly expressed in placental blood vessels (bv, black arrows). C: Cytokeratin 7 (KRT7) is expressed in placental trophoblast. D: Pltp mRNA expression levels (mean&8239;± sem of four different cell preparations) in HPEC (set to 100 %) and term trophoblast cells (TT). **p < 0.01 vs. HPEC. E–H: Immuno­histo­chemical staining of PLTP in blood vessels of healthy (E) and GDM placenta (F), vWF expression (G), and IgG control (H). All pictures are representative of at least three stainings from three different placentas and were taken with the same contrast settings. Scale bar: 50 µm. [4]

References:

  1. Guillemot-Legris O, Mutemberezi V, Muccioli GG: Oxysterols in metabolic syndrome: from bystander molecules to bioactive lipids. Trends Mol Med, 2016; 22(7):​594–614.
  2. Stefulj J, Panzenboeck U, Becker T, Hirschmugl B, Schweinzer C, Lang I, Marsche G, Sadjak A, Lang U, Desoye G, Wadsack C: Human endothelial cells of the placental barrier efficiently deliver cholesterol to the fetal circulation via ABCA1 and ABCG1. Circ Res, 2009; 104(5):​600–608.
  3. Scholler M, Wadsack C, Metso J, Chirackal Manavalan AP, Sreckovic I, Schweinzer C, Hiden U, Jauhiainen M, Desoye G, Panzenboeck U: Phospholipid transfer protein is differentially expressed in human arterial and venous placental endothelial cells and enhances cholesterol efflux to fetal HDL. J Clin Endocrinol Metab, 2012; 97(7):​2466–2474.
  4. Scholler M, Wadsack C, Lang I, Etschmaier K, Schweinzer C, Marsche G, Dieber-Rotheneder M, Desoye G, Panzenboeck U: Phospholipid transfer protein in the placental endothelium is affected by gestational diabetes mellitus. J Clin Endocrinol Metab, 2012; 97(2):​437–445.
  5. Schweinzer C, Kober A, Lang I, Etschmaier K, Scholler M, Kresse A, Sattler W, Panzenboeck U: Processing of endogenous AβPP in blood-brain barrier endothelial cells is modulated by liver-X receptor agonists and altered cellular cholesterol homeostasis. J Alzheimers Dis, 2011; 27(2):​341–360.

Collaborations within the DP-iDP:

  • G. Desoye will provide know-how and technology to perform in-depth epigenetic analyses of fetoplacental endothelial cells.
  • G. Marsche will provide equipment required for isolation of lipoproteins.
  • C. Wadsack will provide fetal and maternal plasma as well as clinically well-definded placental tissue obtained from healthy and GDM pregnancies.

Collaborating research groups where PhD students could perform their research stay abroad:

  • Ingemar Björkhem (Division of Clinical Chemistry, Karolinska University Hospital, Huddinge, Sweden) is one of the world leading experts in oxysterol/bile acid research with particular emphasis on cerebral cholesterol metabolism. The student will learn and perform sophisticated LC and GC-MS/MS methodology to analyze (oxy)sterols in plasma, cells and tissue samples.
  • Kerry-Anne Rye (Central Clinical School of Medicine, The Heart Research Institute, Sydney, Australia) is a leading expert in the field of HDL metabolism. Her current research covers novel functions of HDL in angiogenesis, HDL functionality in inflammatory diseases and in diabetes, including GDM. The student will study specific effects of HDL-associated proteins on endothelial function in vitro and in murine models of diabetes.
  • Jasminka Štefulj (Ruđer Bošković Institute, Zagreb, Croatia) is a molecular biologist focusing on serotonergic neurotransmission, genetics of neuropsychiatric disorders, and cholesterol metabolism and LXRs. The student will study epigenetic regulation of HDL-associated proteins in HPEC.
  • Matti Jauhiainen (Biomedicum Helsinki, Finland) is a leading expert in HDL metabolism and atherosclerosis research. Visiting his laboratory, the student will learn how to characterize HDL particles and HDL remodeling by plasma enzymes and lipid transfer proteins (native PAGE, 2D-immune-electrophoresis, size-exclusion chromatography, ELISA).

Know-how and infrastructure of the research group:

Ute Panzenboeck has profound research experience in the field of lipid and lipoprotein metabolism with a focus on anti-atherogenic and anti-neurodegenerative activities of HDL. She has established her own ‘Lipid Research’ group at the Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Chair of Pathophysiology and Immunology at the Medical University of Graz in 2006 and has been employing 2 post-docs and 11 PhD students from funded research projects since then. The principal recent findings of the research group include characterization of mechanisms of HDL- and apolipoprotein-mediated cholesterol transport at specific endothelial barriers, (i) the fetoplacental and (ii) the blood–brain barrier and highlight the role of nuclear receptors (in particular LXRs) as lipid sensors and regulators of (chole)sterol transport and generation of HDL-like particles. Expertise in Ute Panzenboeck’s group includes isolation and culture of primary EC (and other cells), in vitro models of the BBB consisting of polarized brain capillary EC cultured on Transwell filters, co-culture models, methods for isolation and qualitative and quantitative (lipid and protein) analysis of lipoproteins, standard molecular biological methods, real-time PCR, cloning and transfection, standard and special immunological methods, radiobio-chemical methods, in situ hybridization histochemistry, and experience with animal studies. The local infrastructure comprises cell culture facilities, a fluorescence microscopy facility, a fluorescence-activated cell sorting facility, HPLC laboratory, molecular biology and immunology laboratory, histology and laboratory, radionuclide laboratory, and an animal facility.

Scientific concepts and techniques that students will learn in this laboratory:

DP-iDP students students will gain specific knowledge on the important role of fetoplacental endothelial cells providing both a barrier as well as an exchange surface between the fetus and the maternal circulation. Specifically, they will learn about molecular and regulatory mechanisms of interaction of peripheral and placental lipid and lipoprotein metabolism under healthy conditions as well as during lipid-related metabolic (metabolic syndrome, gestational diabetes mellitus) and pregnancy disorders. By combining studies performed on in vitro models of the placental endothelial barrier with complementary clinical studies (in close collaboration with G. Desoye and C. Wadsack), DP-iDP students will contribute to establish the protective effects of HDL against lipid-related neurodegenerative diseases. The students will further acquire practical know-how in a broad array of laboratory techniques including biochemical, radiochemical, molecular biological and immunological techniques.

30.05.2018 DP-iDP Doctoral Programme “Inflammatory Disorders in Pregnancy”