Dissertations / Theses on the topic 'Cd3As2'

In this work we exploit the unique characteristics of a Dirac semimetal material to be symmetry-protected, to investigate dierent topological phase transitions provided by chemical dopings, focusing in particular on the electronic, magnetic and topological properties of the doped systems, studied by the mean of rst-principles methods based on density functional theory (DFT) approach. In particular these doped systems, besides being of interest for investigating the role of topology in solid state physics, could have a great potential for practical application since the dierent topological phases that come along with the chemical dopings allow one to exploit the unique properties of topological materials. The starting point for our study will be the material called cadmium-arsenide (Cd3As2), an example of a topological Dirac semimetal, which is chemically stable at ambient conditions. Chapter I presents a general introduction to topology, especially in condensed matter physics, and to the main physical properties of the topological materials we mentioned. Then, in chapter II, we briey present the methods and the computational tools that we used for our study. In chapter III a more detailed introduction to our work is given, along with a schemetic view of the path we followed, together with the results that we obtained for pristine Cd3As2, which we use as bench mark for our computational methods. Finally, in chapter IV and V, the results for the doped systems are presented and discussed, respectevely for the non-magnetic (IV) and magnetic (V) dopings. Our study has enabled us to discern how doping can give rise to see dierent topological phase transitions. Specically our work shows that dierent realizations of non-magnetic doping gives rise to dierent topological phases: the topological Weyl semimetal phase, which is of great interest since it can support a robust quantum spin Hall eect, and a very special mixed Dirac + Weyl phase, where surprisingly both a Dirac and a Weyl phase can coexist in the same system. Furthermore, magnetically doped systems show the emergence of a magnetic Weyl phase, which can support a quantum anomalous Hall eect. Our work can be the starting point for future studies, both theoretical and experimental, in which the unique physical properties we found in the doped Cd3As2 systems can be further investigated, in order to exploit them for practical applications.

O CD30 solúvel (CD30s) é uma glicoproteína transmembrana da família do fator de necrose tumoral expressa na superfície das células T. Quando este marcador é clivado ele torna-se solúvel, sendo detectado na circulação. Atualmente, o valor de CD30s pré-transplante vem sido demonstrado como um bom preditor de rejeição aguda (RA) e perda do enxerto. Poucos estudos foram realizados para sua avaliação no pós-transplante e sua correlação com sobrevida e TFG. Avaliar a eficácia da determinação dos marcadores laboratoriais CD30 solúvel (CD30s) e anticorpos reativos contra painel HLA (PRA) em seis meses, um ano e seis anos pós-transplante renal em receptores de doadores vivos, correlacionando estes marcadores com episódios de rejeição aguda, eventos infecciosos no pós-transplante, perda do enxerto e óbito do paciente transplantado. E, avaliar a correlação destes marcadores com a sobrevida do enxerto renal nestes períodos. Os pacientes estudados foram transplantados renais com doadores vivos no Hospital Federal de Bonsucesso (HFB) do Rio de Janeiro no ano de 2006 e do período de agosto de 2010 a maio de 2011, sendo uma extensão de um trabalho realizado previamente. CD30s e PRA foram analisados nas amostras coletadas no pré-transplante e com 7, 14, 21 dias, 1, 3, 6, 12 meses após o transplante e nos pacientes transplantados em 2006 amostras após 6 anos de transplante. A taxa de filtração glomerular (TFG) foi estimada utilizando MDRD e CKD-epi e 6 meses, 1 ano e 6 anos após o transplante. Os pacientes foram agrupados em 5 grupos: sem eventos, com perda do enxerto, óbito, rejeição aguda e pacientes com quadros infecciosos. Estes grupos foram avaliados com relação ao CD30s, PRA I e II e comparados dois a dois. O teste qui quadrado foi utilizado. Quando necessário aplicou-se a correção de Yates, o teste de Fisher, o teste de Kruskal-wallis. Foi considerado estatisticamente significante p<0,05. As análises foram feitas pelo programa EPI-Info (versão 3.5.3). Setenta e seis pacientes com doadores vivos foram incluídos no estudo 47 pacientes não tiveram nenhum evento (grupo 1), 7 pacientes perderam o enxerto (grupo 2), 3 pacientes faleceram (grupo 3), 11 pacientes ficaram no grupo de rejeição aguda (grupo 4) e oito pacientes tiveram infecção por CMV e herpes (grupo 5). Os pacientes do grupo de RA tiveram correlação positiva com os valores tanto de CD30s Pré-transplante (p=0,01), quanto do CD30s pós-transplante (p=0,002) e PRA I e II (p<0,001), respectivamente, quando comparados com pacientes sem eventos. A TFG tanto com MDRD e CKD-Epi não mostrou correlação com CD30s pré e pós-transplante e nem PRA I e II. A TFG com as duas fórmulas foi menor no grupo com RA comparado com o grupo sem evento após 6 anos de transplante (p=0,006). CD30s é um bom preditor de RA, assim como PRAI e II. E, também mais uma ferramenta que pode ser utilizada no acompanhamento pós-transplante Renal. A RA é um preditor isolado para diminuição de TFG no transplante.

C-type lectin receptors (CLR) play important roles in immune cell interactions with the environment. We described CD302 as the simplest type I CLR, which is restricted to myeloid cells in human blood. CD302 colocalised with cell migratory structures including podosomes and lamellopodia, leading us to hypothesise that this CLR contributes to cell migration. This thesis describes the use of mouse models to obtain further insights into CD302 expression and immunological function. Akin to humans, mouse CD302 transcripts were highest in liver, lungs, lymph nodes (LN), spleen, and bone marrow. Detailed analysis of CD302 transcription in immune cells revealed high expression by macrophage (Mϕ), granulocytes and myeloid dendritic cells (mDC). Greater CD302 expression was found in migratory compared to resident mDC. We generated the first CD302 knockout (CD302KO) mouse and revealed a decrease in migratory mDC within LN of these animals. CD302KO migratory DC exhibited reduced in vivo migration into LN interfollicular channels, establishing a role for CD302 in mDC migration. CD169+ Mϕ in LN subcapsular sinus also showed irregular distribution. Monoclonal antibodies have been shown effective in the treatments of different haematological malignancies. However, acute myeloid leukaemia (AML) targets are currently limited so discovery of new targets would be beneficial to patients. We found expression of CD302 on the surface of blasts in the vast majority of AML patients. More importantly, CD302 was positive on leukaemic stem cells, the population responsible for relapse of the disease. Monoclonal antibodies targeting human CD302 were effective in mediating antibody dependent cell cytotoxicity and were internalised, making them amenable to toxin conjugation. Targeting CD302 with antibodies also limited in vivo engraftment of the leukaemic cell line HL-60 in NOD/SCID mice. These studies provide the foundation for studies examining CD302 as a potential therapeutic target for AML.

Um die Wirkung herpesviral-kodierter FcgammaRezeptoren auf wirtskodierte zelluläre FcgammaRezeptoren und IgG-vermittelten Effektorfunktionen untersuchen zu können, einen methodisch neuen Ansatz wurde entwickelt, der die Detektion FcgammaR-aktivierender Antikörper ermöglicht. Dieses neuartige Assay beinhaltet die Kokultivierung virusinfizierter Zellen, die mit virusspezifischen IgG-Antikörpern opsoniert sind, mit FcgammaR-zeta BW5147-Transfektanten als Reporterzellen. Diese stabilen Transfektanten exprimieren chimäre Rezeptoren, die aus der extrazellulären Domäne der zellulären FcgammaRezeptoren bestehen, welche mit der TM und intrazellulären Domäne der murinen CD3zeta-Kette fusioniert wurden. Die Aktivierung der CD3zeta-Kette führt zu einer IgG-dosisabhängigen mIL-2 Sekretion, die im ELISA gemessen werden kann. Die FcgammaR-spezifische immune IgG könnte eine wichtige biologische Rolle in der antiviralen Immunabwehr spielen. Herpesviren exprimieren auf der Oberfläche infizierter Zellen viral-kodierte Fc-bindende Glykoproteine. Um zu bestimmen, ob virale FcgammaRezeptoren die IgG-abhängige Aktivierung von wirtskodierten FcgammaRezeptoren beeinflussen können, wurde das oben beschriebene Assay angewandt. Es wurde festgestellt, dass der HCMV-kodierte FcgammaR gp68 die Aktivierung und die nachfolgende Signalkaskade von CD16>CD32=CD64 inhibiert, während der HCMV-kodierte FcgammaR gp34 die Aktivierung von CD16>CD64>CD32 inhibiert. In klarem Kontrast dazu wirkt der HSV-kodierte FcgammaR gE, der CD16 Aktivierung vermindert, CD32 hingegen nur sehr schwach und CD64 gar nicht beeinflußt. Der MCMV-kodierte FcgammaR m138/fcr-1 vermindert die Aktivierung des murinenCD16. Zusammenfassend betrachtet zeigen die ermittelten Daten, dass es sich bei den herpesviral-kodierten FcgammaRezeptoren um hierarchische und redundante Antagonisten der wirtskodierten zellulären FcgammaRezeptoren handelt. Herpesviral-kodierte FcgammaRezeptoren wirken somit der Aktivierung des Immunsystems entgegen.
To study the possible interference of the herpesviral vFcgammaRs with the host FcgammaRs and IgG-mediated effector functions, a new methodological approach to detect FcgammaR activating antibodies was developed. The novel assay comprises the co-cultivation of virus infected cells upon opsonization with immune IgG antibodies and the stably transfected FcgammaR-zeta BW5147 transfectants as responder cells. The transfectants express chimeric receptors bearing the extracellular domain of the host FcgammaRs fused to the transmembrane and tail domains of the murine CD3zeta chain. Triggering the CD3zeta chain is sufficient to elicit IL-2 secretion in a dose dependent manner which is measured in an ELISA. The setup of the new assay provides a defined effector cell population bearing one Fcgamma receptor on the surface, which becomes activated in the presence of immune IgG antibodies bound to the native viral antigens displayed on the surface of infected cells. The assay system allows us to detect and quantify Fc gamma receptor-activating immune IgG in an FcgammaR-specific way, which is thought to have an important biological function in antiviral defense. Several alpha- and beta- herpesviruses express on the surface of infected cells virally encoded Fc binding glycoproteins. The assay described above was applied to determine if the viral FcgammaRs are able to impair IgG-mediated activation of host FcgammaRs. In a systematic approach, the effect on each host FcgammaR by each of the herpesviral FcgammaR was investigated. It was found that HCMV FcgammaR gp68 affects activation and downstream signaling of CD16 > CD32 = CD64, while gp34 attenuates CD16 > CD64 > CD32. In clear contrast, HSV gE impairs CD16 activation and weakly CD32, but has no effect on CD64. Furthemore, MCMV m138/fcr-1 diminishes activation of mouse CD16. Taken together, this data uncover herpesviral FcgammaRs as hierarchical and redundant antagonists precluding host FcgammaRs from triggering immune responses.

This thesis presents Raman studies of Sodium iridates (Na2IrO3 and Na4Ir3O8), VO2, black phosphorus, Weyl (TaAs, TaP, NbP and NbAs) and Dirac (Cd3As2) semimetals under ex-treme conditions like low temperature (upto 4K), ultra high pressures (upto 30 GPa) and electrochemical top gating of nanodevices. Temperature-dependent Raman studies were car-ried out to look for Raman signatures of Kitaev quantum spin liquid state in sodium iridates. In-situ Raman measurements were done on electrochemically top-gated field effect transistor devices fabricated on phosphorene and VO2 nanofilms to show symmetry-dependent phonon renormalization in phosphorene and microscopic origin of insulator to metal transition in VO2 nanofilms. High pressure studies were carried out to look for electronic topological as well as structural phase transitions in black phosphorus, Weyl and Dirac semimetals. For structural characterization as a function of pressure, x-ray diffraction measurements using synchrotron source have been pursued. We provide an overview of our work on these systems chapter-wise. In Chapter 1, we give a brief introduction of the systems studied in this thesis, i.e. Sodium iridates (Na2IrO3 and Na4Ir3O8), VO2, black phosphorus, Weyl (TaAs, TaP, NbP and NbAs) and Dirac (Cd3As2) semimetals. A summary of main results is given at the end of this chapter. Chapter 2 gives a brief introduction to Raman scattering and Synchrotron x-ray diffrac-tion, followed by the effect of temperature and pressure on the lattice. Further, the experi-mental setups and techniques used in this thesis are discussed. In Chapter 3, we discuss our Raman results on Sodium iridates (Na2IrO3 and Na4Ir3O8). This chapter is divided into two parts. In Part 3.1, we present temperature dependent Raman results on single crystals of (Na1−xLix)2IrO3 (x = 0, 0.05 and 0.15) in the temperature range from 4K to 300K. Our study shows a polarization independent broad band at ∼ 2750 cm−1 with a large band-width of ∼ 1800 cm−1. For Na2IrO3 the broad band is seen for temperatures ≤ 200 K and persists inside the magnetically ordered state. For Li-doped samples, the intensity of this mode increases, shifts to lower energy, and persists to higher temperatures. Such a mode has been predicted recently as a signature of the Kitaev quantum spin liquid (QSL). We assign the observed broad band to be a signature of strong Kitaev-exchange correlations. The fact that the broad band persists even inside the magnetically ordered state (with Neel temperature TN ) suggests that dynamically fluctuating moments survive even below TN . This is further supported by our mean field calculations of our collaborators. The Raman response calculated in mean field theory shows that the broad band predicted for the QSL state survives in the magnetically ordered state near the zigzag-spin liquid phase boundary. A comparison with the theoretical model gives an estimate of the Kitaev exchange interaction parameter to be JK ≈ 57 meV. In Part 3.2, we present temperature dependent Raman scattering on hyperkagome iri-date Na4Ir3O8 in the temperature range from 77K to 300K. Combining Raman scattering measurements with mean field calculations of the Raman response, we show that Kitaev-like magnetic exchange is dominant in the hyperkagome iridate Na4Ir3O8. In the measurements, we observe a broad Raman band at ∼ 3500 cm−1 with a band-width of ∼ 1700 cm−1. Calcu-lations of the Raman response of the Kitaev-Heisenberg model on the hyperkagome lattice by our collaborators show that the experimental observations are consistent with calculated Raman response where Kitaev exchange interaction (JK ) is much larger than the Heisenberg term J1 (J1/JK ∼ 0.1). A comparison with the theoretical model gives an estimate of the Kitaev exchange interaction parameter. In Chapter 4, in-situ Raman scattering studies of electrochemically top-gated VO2 ultra thin film are presented to address metal-insulator transition (MIT) under gating. The room temperature monoclinic insulating phase goes to a metallic state at a gate voltage of 2.6 V. However, the number of Raman modes do not change with electrolyte gating, showing that the metallic phase under gating is still monoclinic. The high frequency Raman mode Ag(7) −1 ˚ near 616 cm ascribed to V-O vibrations of bond length 2.06 A in VO6 octahedra hardens with increasing gate voltage and the Bg(3) mode near 654 cm−1 softens. This shows that the distortion of the VO6 octahedra in the monoclinic phase decreases with gating. The time dependent Raman data at fixed gate voltages of 1 V (for 50 minute, showing enhancement of conductivity by a factor of 50) and 2 V (for 130 minute, showing further increase in conductivity by a factor of 5) show similar changes in high frequency Raman modes Ag(7) and Bg(3) as observed in gating. This slow change in conductance together with Raman frequency changes show that the governing mechanism for metalization is more likely to be the diffusion controlled oxygen vacancy formation due to the applied electric field, rather than the carrier doping effect. In Chapter 5, we discuss our Raman studies on black phosphorus. This chapter has two parts. Part 5.1: We investigated an electrochemically top-gated field effect transistor of phos-phorene using in-situ Raman scattering. Our experiments show that the phonons with Ag symmetry depend much more strongly on the concentration of electrons than that of holes, while the phonons with Bg symmetry are insensitive to doping. With first-principles theo-retical analysis, we show that the observed electon-hole asymmetry arises from the radically different constitution of its conduction and valence bands involving π and σ bonding states respectively, whose symmetry permits coupling with only the phonons that preserve the lattice symmetry. Thus, Raman spectroscopy is shown to be a non-invasive tool for mea-suring electron concentration in phosphorene-based nanoelectronic devices, like in other 2D nanomaterials. Part 5.2: We discuss high pressure Raman experiments of Black phosphorus (BP) up to 24 GPa. The linewidths of first order Raman modes A1g, B2g and A2g of the orthorhombic phase show a minimum at 1.1 GPa. Our first-principles density functional analysis reveals that this is associated with the anomalies in electron-phonon coupling at the semiconduc-tor to topological insulator transition through inversion of valence and conduction bands, marking a change from trivial to nontrivial electronic topology. The frequencies of B2g and A2g modes become anomalous in the rhombohedral phase at 7.4 GPa, and new modes ap-pearing in the rhombohedral phase show anomalous softening with pressure. This is shown to originate from unusual structural evolution of black phosphorous with pressure, based on first-principles theoretical analysis. In Chapter 6, we describe our studies on Weyl semimetals. This chapter is divided into three parts. Part 6.1: We present high pressure Raman, synchrotron x-ray diffraction and electri-cal transport studies on Weyl semimetals NbP and TaP along with first-principles density functional theoretical (DFT) analysis. The frequencies of first-order Raman modes of NbP harden with increasing pressure and exhibit a slope change at Pc ∼ 9 GPa. The pressure dependent resistivity exhibits a minimum at Pc. The temperature coefficient of resistivity below Pc is positive as expected for semimetals but changes significantly in the high pressure phase. Using DFT calculations, we show that these anomalies are associated with pressure induced Lifshitz transition which involves appearance of electron and hole pockets in elec-tronic structure. In contrast, results of Raman and synchrotron x-ray diffraction experiments on TaP and DFT calculations show that TaP is quite robust under pressure and does not undergo any phase transition. Part 6.2: High pressure Raman, resistivity and synchrotron x-ray diffraction studies on Weyl semimetals NbAs and TaAs have been carried out along with density functional theoretical (DFT) analysis to explain pressure induced structural and electronic topologi-cal phase transitions. The frequencies of first order Raman modes harden with increasing pressure, exhibiting a slope change at PNbc∼15 GPa for NbAs and PTc a∼16 GPa for TaAs. The resistivities of NbAs and TaAs exhibit a minimum at pressures close to these transition pressures and also a change in the bulk modulus is observed. Our first-principles calculations reveal that the transition is associated with a Lifshitz transition at PNbc for NbAs while it is a structural phase transition from body centered tetragonal to hexagonal phase at PTc a for TaAs. Part 6.3: We report temperature dependent Raman study on Weyl semimetals NbAs, TaAs, TaP and NbP in the temperature range from 4K to 300K. Our study reveals phonon anomalies in the Raman frequencies of all the Raman modes in all the four systems at low temperatures. These anomalies in phonon frequencies were attributed to the addi-tional electron-phonon coupling, which gets suppressed at higher temperatures due to Pauli-blocking of interband transitions across the Weyl node. In Chapter 7, we present our Raman results on Cd3As2. This chapter has two parts. Part 7.1: We discuss high pressure Raman study of Cd3As2, a three dimensional Dirac semimetal, upto 19 GPa at room temperature. Our study shows that light scattering by in-tervalley and intravalley density fluctuations give rise to electronic Raman scattering (ERS), with Lorentzian like lineshape at low frequency. The strength and linewidth of the ERS are pressure dependent and exhibit a significant drop at Pc1 = 2.5 GPa, signifying a breakdown of the Dirac semimetal to a semiconducting phase. The first phase transition at Pc1 is also clearly identified by the significant changes in the pressure derivatives of the Raman phonon frequencies and their linewidths. Pressure dependence of phonon parameters also reveal a second phase transition at Pc2=9.5 GPa, being reported for the first time. This semicon-ductor to semiconductor transition coincides with the abrupt changes seen in the reported activation energy (band gap) of the semiconductor phase. Part 7.2: We present temperature dependent Raman study on single crystals of Cd3As2 in the temperature range from 300K to 77K. Here also, we see a broad electronic background on top of which Raman modes are superimposed. This electronic background decreases with decreasing temperature. The phonon frequencies of all the Raman modes exhibit anoma-lous behavior above 150K: T<150K, the slope of the frequency dω/dT<0, whereas above T>150K, dω/dT is close to zero or slightly positive. These phonon anomalies may be asso-ciated with the breakdown of Wiedemann-Franz law at higher temperatures. Chapter 8 summarizes our main results on different systems studied in this thesis.

No
Cd3P2 quantum dots (QDs) have been synthesized in both aqueous and high boiling point surfactant solutions via a gas-bubbling method. The synthesized QDs exhibit photoluminescent wavelengths spanning across the visible red to the near-infrared (NIR) spectral region. Two types of shell materials, SiO2 nanobeads and PS micro-spheres, have been employed to encapsulate the Cd3P2 QDs which provide protecting layers against physiological solutions. The coating layers are proven to enhance the optical and chemical stability of Cd3P2 QDs, and make the fluorescent particles capable of sustaining long-term photo-oxidation. To demonstrate the applicability of the bio-labelling, the fluorescent composite particles (PS@QDs, SiO2@QDs) were injected into a culture medium of colorectal carcinoma (LoVo) cells. The results demonstrated that the PS@QDs exhibited a brighter fluorescence, but the SiO2@QDs provided a better photostability which consequently led to long-term cancer cell detection as well as a much lower release of toxic Cd2+ into the PBS solutions.

No
A method for measuring the evaporation kinetics of pure solvents and solutions containing Cd3P2 quantum dots (QDs) in SiO/SiO2 rolled-up microtube (RUT) resonators is reported. The QDs serve as wavelength-tunable fluorescent sources for the RUT resonator. The first-order kinetic constant (295 K) of the evaporation of toluene embedded in a RUT (D = 9.10 μm) is evaluated (0.055 min−1).
Doctoral Program Education of China. Grant Number: 20110111120008; Alexander von Humboldt Foundation

Arteriosklerose mit ihren Folgeerkrankungen ist weltweit die Erkrankung mit der höchsten Mortalität und einer hohen Morbidität. Chronische Inflammationsprozesse spielen eine zentrale Rolle in der Atherogenese. Akutphaseproteinen, insbesondere dem C-reaktiven Protein (CRP) kommen als Marker chronischer Inflammationsprozesse in der Prädiktion kardiovaskulärer Ereignisse eine besondere Bedeutung zu. Erhöhte CRP-Spiegel wurden in zahlreichen Studien als Risikofaktor für Arteriosklerose und ihre Folgeerkrankungen identifiziert. Inzwischen gibt es auch einige Hinweise, die eine Rolle von CRP über die Rolle als passiver Indikator hinaus als aktiven Teilnehmer in der Arteriosklerose aufzeigen. Oxidiertes LDL ist ebenso als Risikofaktor anerkannt, die Aufnahme in Endothelzellen ist ein wichtiger Teilschritt in der Pathogenese der Arteriosklerose. Acetyliertes LDL (acLDL) wurde als Modell für oxLDL gewählt. Wir konnten nun in der FACS-Analyse zeigen dass, sich die verschiedenen Konfigurationen von CRP, monomeres CRP (mCRP) und pentameres CRP(nCRP) in der Beeinflussung der Aufnahme von acLDL in Endothelzellen unterscheiden. M-CRP führt zur Erniedrigung der Aufnahme, nCRP nicht. Dies bestätigte sich auch in der Immunfluoreszenzfärbung, die auch eine deutlichen Abnahme der acLDLAufnahme unter Einfluss von mCRP in den Endothelzellen zeigte, nCRP bewirkte dies nach 1 und 8 Stunden Inkubation nicht. Es konnte hier also gezeigt werden, dass sich die beiden CRP-Konfigurationen in der Beeinflussung des oxLDL-Metabolismus unterscheiden. Um diesen Effekt näher zu charakterisieren, untersuchten wir die Rolle der mutmaßlichen CRP-Rezeptoren auf Endothelzellen, CD16 und CD32. Sie konnten in Endothelzellen nicht nachgewiesen werden und Antikörper gegen CD16 und CD32 hatten keinen Einfluss auf die LDL-Aufnahme in Endothelzellen. Wir konnten so zeigen, dass CD16 und CD32 (mit den Isoformen a,b und c), die als Rezeptoren für mCRP und nCRP gesehen werden, nicht exprimiert wurden und so nicht an den inhibitorischen Effekten von mCRP auf die acLDLAufnahme beteiligt sind. Wir schlagen daher vor, dass andere Rezeptoren und/oder nichtrezeptorvermittelte Signalwege, wie eine Interaktion mit der Zellmembran (wie beispielsweise mit Lipid rafts), an der Entstehung des mCRP-Effektes in Endothelzellen beteiligt sind. Weitere Untersuchungen sind noch nötig, um den Effekt und seine Bedeutung in der Pathogenese der Arteriosklerose besser zu verstehen. Ansatzpunkte für zukünftige Forschungen sind beispielsweise die Signalkaskade von CRP mit seinen Konfigurationen, die Rezeptoren von CRP und die Herkunft von mCRP in vivo
Arteriosclerosis and its associated diseases is the disease with the highest mortality worldwide and a high morbidity. Chronic Inflammation has a crucial role in Atherogenesis. Acute-phase proteins, especially C-reactive Protein (CRP) are important predictors for cardiovascular endpoints. Elevated CRP-Levels have been identified by various studies as independent risk factor for cardiovascular endpoints. There is emerging evidence for an active Role of CRP in Atherogenesis surpassing its role as a marker. Oxidized LDL (oxLDL) is well known as risk factor for arteriosclerosis, its uptake into endothelial cells is an important step in Atherogenesis. Acetylated LDL (acLDL) was chosen as model for oxLDL. We could show in FACS-Analysis, that the distinct configurations of CRP, monomeric CRP (mCRP) and pentameric CRP (nCRP) have different effects on the uptake of acLDL in endothelial cells. M-CRP decreases the uptake significantly, nCRP has no effect. This was confirmed in Immunofluorescence, where also a significant decrease in the uptake of acLDL under the influence of mCRP was seen. To further investigate this effect, we examined the role of the putative CRP-Receptors on endothelial cells, CD16 and CD32. In RT-PCR there was no mRNA expressed in the endothial cells, and function-blocking antibodies directed against CD16 and CD32 had no influence on the uptake of acLDL. We conclude, that CD16 and CD32 (with its isoforms a,b and c) are not expressed in endothelial cells and do not take part in the inhibitory effects of mCRP on the uptake of acLDL. We suggest that other receptors and/or non-receptormediated signalpathways, like an interaction with the cell membrane (e.g. lipid rafts) mediate this effect. Further investigations are needed to better understand this effect and its role in Atherogenesis, the signaling cascade of CRP and its configurations, the receptors for CRP and the origin of mCRP in vivo

博士
國立中正大學
化學工程研究所
104
Atherosclerosis is a chronic inflammatory disease of the arteries. C-reactive protein (CRP) and oxidized low-density lipoprotein (oxLDL) play a significant role in the pro-inflammatory response observed in various types of vascular disease. CRP is capable of binding to various molecules including oxLDL and may bind to the receptor other than CD32 and lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1). However, how CRP/oxLDL complexes are formed, as well as their effect and corresponding receptors on endothelial cells, remains unknown. Here, we identified keratin 1 (KRT1) on endothelial cells as a novel protein for CRP binding by affinity chromatography and mass spectrometry. The interaction between KRT1 and CRP was also confirmed by the antibody blockade of KRT1 that decreased the CRP uptake and CRP-mediated reduction in nitric oxide (NO) release in human aortic endothelial cells (HAECs). Similar to CD32 and LOX-1 induced by oxdative stress, KRT1 was induced by CRP. Additionally, an increased KRT1 expression by transfection of plasmid pcDNA3.1-KRT1 enhanced but a reduced KRT1 expression by KRT1 small hairpin RNAs reversed the CRP antagonism in NO release. On the other hand, we found that the induction of NO release by CRP and oxLDL co-incubates was dependent on the ratio of CRP and oxLDL. Specifically, the concentration ratio of ~1:20 (CRP/oxLDL-1:20) resulted in the greatest inhibition of endothelial NO secretion. Pretreatment of neutralizing antibodies for CD32, LOX-1, or KRT1 abolished the effect of CRP/oxLDL-1:20 on NO production. Furthermore, we found that CD32, LOX-1, and KRT1 mediated the cellular uptake of CRP/oxLDL complexes, in which LOX-1 co-localized with KRT1, but not CD32. These results provide a novel mechanism by which the multifaceted effects of CRP/oxLDL complexes on endothelial cells can be targeted for the treatment of vasculature diseases.