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Untersuchungen zum Vorkommen gastrointestinaler Nematoden und zur Wirksamkeit anthelminthischer Behandlungen bei kleinen Wiederkäuern in Deutschland
Get PDFExploring new photocatalytic applications with covalent organic frameworks: oxygen evolution, water-gas shift, and photoredox catalysis
Get PDFDevelopment of efficient and low-scaling coupled cluster and algebraic diagrammatic construction methods
Get PDFMolecular electronic structure theory attempts to find approximate solutions to the electronic Schrödinger equation for molecules, and decades of research provided scientists with a plethora of methods of increasing accuracy and cost. Coupled cluster linear response (LR-CC) and algebraic diagrammatic construction (ADC) scheme for the polarization propagator are among the most accurate and hence successful methods for the in silico study of excited state properties.
However, the steep scaling in the computational and storage demands are prohibitive and limit their application to small molecules. Even in the most cost-effective variants of LR-CC and ADC, i.e., LR-CC2 and ADC(2), the computational effort and the storage demands scale with the fifth and fourth power of the system size, respectively. In the past two decades, several approximations have been made to mitigate the drawbacks of LR-CC2 and ADC(2) and to extend their application to molecular systems of interest. Rank-reduction techniques for the electron-repulsion integrals (ERIs) paved the way for efficient implementations based on the canonical molecular orbitals (MOs), and their combination with the Laplace transformation
technique as well as the semi-empirical scaled opposite-spin (SOS) approximation allowed for a diminution of the computational scaling to quartic or even cubic. More recently, local excited state implementations based on spatially confined orbital representations have been proposed showing low-scaling behavior. Nowadays, state-specific local molecular orbitals (LMOs), natural orbitals (NOs), natural transition orbitals (NTOs), or combinations thereof are employed. However, the localization procedures yielding these orbitals increase the prefactor and make the methods less robust. In this thesis, we present efficient and low-scaling reformulations of SOS-LR-CC2 and SOS-ADC(2) that, contrary to the current local excited state methods, do not require expensive localization techniques. Inspired by the preceding low-scaling second-order Møller-Plesset (MP2) energy approaches, we reformulate the SOS-LR-CC2 and SOS-ADC(2) methods in the local atomic orbitals (AO) basis and derive expressions for the excitation energies based on Cholesky decomposed density matrices (CDD). For systems with a significant HOMO-LUMO gap, the computational effort, I/O effort, memory and storage demands, as well as their scaling, are reduced by block-sparse linear algebra that takes advantage of the sparsity manifested by the density matrices and the AO-based ERIs decomposed within the resolution of the identity (RI) and tensor hypercontraction (THC) ansatz. For systems with a local electronic structure and local excitations, the presented local ω-CDD-RI-SOS-LR-CC2/ADC(2) implementations show asymptotical linear scaling computational behavior and memory demands when a local metric is used. On the other hand, the CDD-THC-SOS-LR-CC2/ADC(2) implementations show a quadratic scaling behavior in the asymptotic limit and exhibit considerably reduced computational effort and memory demands with respect to the RI-based variants. Finally, low-scaling reformulations for computing the one-particle reduced density matrix of excited states and transition density matrix are provided enabling, e.g., the analysis of the electronic structure of excited states and transition properties for molecules with hundreds of atoms at the ADC(2) level of theory
Exploiting RIG-I-targeted therapy as a strategy to overcome CAR T cell therapy limitations in the treatment of solid tumors
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The role of MIF-2 in obesity-induced wound healing disorder
Get PDFWounds that do not undergo sufficient healing or even become chronic wounds represent a major challenge for medicine. Obese individuals are prone to non-healing wounds. In this context, the adipose tissue can become chronically inflamed, causing a pathological alteration at the molecular and cellular level. This results in impaired cell migration, proliferation and differentiation, as well as a reduced angiogenesis. Since the adipose tissue is located in immediate vicinity of cutaneous wounds and is involved in wound healing, the obesity-induced cellular and molecular changes also negatively influence the wound healing process. Although obesity-induced chronic wounds have been studied for a long time and a lot is known, there our understanding of the mechanisms is still limited.
One pathologically altered protein family is the macrophage migration inhibitor factor (MIF) family, in human encompassing MIF and MIF-2. While MIF has been well studied, MIF 2 was only recently discovered as a homologue of MIF. Both bind to the same receptor, CD74, while only MIF interacts with CXCR2, and they differ in various systemic conditions e.g. in obesity, in which MIF is increased and MIF 2 is decreased. In inflammation, MIF polarizes macrophages towards a pro-inflammatory M1-like phenotype and MIF-2 towards an anti-inflammatory M2-like subtype. The role of MIF in wound healing is still controversially discussed, but it seems that its function differs in distinct phases and tissue types. MIF-2 was recently reported to exhibit a positive effect on wound healing.
Thus, in this thesis, the role of MIF-2 in wound healing was investigated in a murine wound healing model employing Mif-2–/– mice, accompanied by mechanistic in vitro experiments. Both mice groups, the obese wild type as well as the Mif-2–/– mice showed a delayed wound healing when compared to the control lean wild type mice. Their wound sizes became even wider during the first days. Immunohistochemical analysis confirmed the impaired healing process in obese and Mif-2–/– mice. Furthermore, tissue examinations and genetic analysis showed reduced collagen production and granulation tissue formation as well as a diminished myofibroblast differentiation, which was most pronounced in the Mif-2–/– mice. In in vitro experiments, NIH/3T3 cells were differentiated into myofibroblasts when treated with recombinant MIF 2 or a MIF 2 inhibitor. When MIF 2 was inhibited, differentiation potential decreased sharply even at low doses. At higher concentrations of recombinant MIF 2, cell differentiation was also partially reduced.
My experiments revealed that MIF-2 is crucial for the differentiation from “wound fibroblasts” into myofibroblasts, which are primarily responsible for collagen production and formation of granulation tissue. In an in vivo wound model characterized by obese and Mif 2–/– mice as well as applying in vitro pathway analyses, the deletion of MIF-2 resulted in an impaired differentiation and wound closure. It appeared that MIF-2 influenced the canonical TGF-β/Smad pathway, the main pathway for myofibroblasts differentiation, via an ERK1/2-MAPK downstream cascade and a so far unknown key protein. However, I also obtained evidence in my thesis that an excess of MIF-2 leads to a partial inhibition of the differentiation, most likely also via ERK1/2, suggestive of a differential dose behavior.
In conclusion, the obesity-induced downregulation of MIF 2 seems to be one major reason for a delayed and insufficient wound healing process in obese individuals. Furthermore, my results indicates that this impairment is caused by diminished myofibroblast differentiation resulting in delayed granulation tissue formation.Nicht ausreichend heilende Wunden und chronische Wunden stellen eine große Herausforderung für die Medizin dar. Übergewichtige Personen sind anfälliger für nicht heilende Wunden. Ihr Fettgewebe ist chronisch entzündet, was eine pathologische Veränderung auf molekularer und zellulärer Ebene zur Folge hat. Dies führt zu einer beeinträchtigten Zellmigration, -proliferation und -differenzierung sowie einer verminderten Angiogenese. Da sich das Fettgewebe in unmittelbarer Nähe zu kutanen Wunden befindet und an der Wundheilung beteiligt ist, beeinflussen durch Fettleibigkeit bedingte zelluläre und molekulare Veränderungen auch die Wundheilung negativ. Obwohl Adipositas-induzierte chronische Wunden seit langem untersucht werden und bereits einiges darüber bekannt ist, fehlt noch viel, um den gesamten Mechanismus zu verstehen.
Eine pathologisch veränderte Protein Gruppe ist die Makrophagen Migration Inhibition Faktor (MIF) Familie, MIF und MIF-2. Während MIF seit langem gut erforscht ist, wurde MIF-2 erst kürzlich als MIF-Homolog entdeckt. Beide binden an denselben Rezeptor, CD74, unterscheiden sich jedoch in verschiedenen systemischen Zuständen wie bei Fettleibigkeit, MIF ist erhöht und MIF-2 erniedrigt. Bei Entzündungen polarisiert MIF Makrophagen zum pro-inflammatorischen M1 und MIF-2 zum anti-inflammatorischen M2 Phänotypen. Die Rolle von MIF in der Wundheilung wird noch kontrovers diskutiert, aber seine Funktion scheint sich in verschiedenen Phasen und Gewebetypen zu unterscheiden. Kürzlich gab es Hinweise für einen positiven Effekt von MIF-2 auf die Wundheilung.
Daher wurde in dieser Arbeit die Rolle von MIF-2 bei der Wundheilung in einem murinen Wundheilungsmodel mit Mif-2–/– Mäusen untersucht und mit in-vitro Experimenten zum Mechanismus untermauert. Sowohl die adipösen Wildtypen als auch die Mif-2–/– Mäuse wiesen eine verzögerte Wundheilung auf im Vergleich zu den normalgewichtigen Kontrollmäusen. Während den ersten Tagen hat sich das Wundareal sogar erweitert. Immunhistologische Analysen bestätigten den verschlechterten Heilungsprozess in der adipösen und in der Mif-2–/– Gruppe. Zusätzlich wiesen Gewebeanalysen und genetische Untersuchungen eine reduzierte Produktion von Kollagen und des Granulationsgewebes auf, sowie eine verminderte Myofibroblastendifferenzierung, welche am stärksten bei den Mif-2–/– Mäusen vorhanden war. NIH/3T3 Zellen wurden in in-vitro Experimenten zu Myofibroblasten differenziert unter der Behandlung von rekombinantem MIF-2 oder einem MIF-2 Inhibitor. Wenn die Zellen mit dem MIF-2 Inhibitor behandelt wurden, sank das Differenzierungspotential bereits bei geringer Konzentration rapide ab. Ebenso hatten hohe Dosen vom rekombinantem MIF-2 eine partielle Reduzierung der Differenzierbarkeit zufolge
In meiner Arbeit konnte ich zeigen, dass MIF-2 eine zentrale Rolle für die Differenzierung von “Wund-Fibroblasten” zu Myofibroblasten hat, welche hauptverantwortlich sind für die Kollagenproduktion und für die Bildung des Granulationsgewebes. Sowohl in dem in-vivo Wundheilungsmodel als auch in den in-vitro Mechanismusanalysen führte die Deletion von MIF-2 zu einer beeinträchtigen Differenzierung und Wundschliessung. Es scheint, dass MIF-2 den kanonischen TGF β/Smad-Weg, den Hauptweg für die Differenzierung von Myofibroblasten, über die ERK1/2-MAPK-Downstream-Kaskade beeinflusst und ein bisher unbekanntes Schlüsselprotein ist. Allerdings wurde in der Dissertation auch gezeigt, dass ein Überschuss an MIF-2 auch zu einer teilweisen Hemmung der Differenzierung führt, höchstwahrscheinlich auch über ERK1/2.
Zusammengefasst scheint die durch Fettleibigkeit induzierte Herunterregulation von MIF-2 ein Hauptfaktor für die verzögerte und unzureichende Wundheilung zu sein, welche bei Adipositas beobachtet werden kann. Weiterhin geben meine Ergebnisse Hinweise darauf, dass die Beeinträchtigung durch eine verminderte Differenzierung von Myofibroblasten herführt, wodurch die Bildung von Granulationsgewebe verzögert wird
