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Investigation of the Quality of Essential Medicines in African Countries and of Medicine Quality Screening Technologies for Use in Low-Resource Settings
No full textWithin their Sustainable Development Goals (SDGs), the United Nations aim to achieve “access to safe, effective, quality and affordable essential medicines for all.” However, the occurrence of substandard and falsified (SF) medicines threatens the achievement of this goal, especially in low- and middle-income countries (LMICs). Often, the data on the occurrence of SF medicines in LMICs, like Nigeria, are very heterogeneous. Therefore, a study on the quality of 13 essential medicines in Enugu and Anambra states, Nigeria, was carried out in collaboration with the Nigerian partner organization Faith-Based Central Medical Foundation (FBCMF). In total, 260 samples were collected from licensed vendors and markets with unclear licensing status. They were investigated according to the United States Pharmacopeia (USP) for content and dissolution of their active pharmaceutical ingredient (API). Of all 260 samples, 25.4% did not comply with the USP specifications. Unexpectedly, no difference was observed in the proportions of out-of-specification medicines for samples collected from licensed vendors compared to markets. Four samples (1.5%), all collected in markets, were found to be falsified, as they did not contain any of the stated APIs. However, the percentage of falsified medicines found in this study is lower than previously reported in the media.
To fight SF medicines, the World Health Organization (WHO) promotes a “prevention, detection and response” strategy. The detection of these harmful products, which is particularly challenging in low-resource settings, can be improved through rapid, inexpensive and easy-to-use screening technologies. Therefore, the possibilities and limitations of detecting the API in tablets using a low-cost near-infrared (NIR) spectrometer were investigated. Spectra of 170 products were collected, comprising 41 different APIs, API combinations, placebos or falsified products. Chemometric models were built for 10 APIs using data-driven soft independent modelling of class analogy (DD-SIMCA) and subsequently tested with all other APIs and placebos, as well as the 20 falsified medicines. All developed models correctly identified samples containing a different API from the stated one, no API or grossly incorrect API amounts with 100% specificity, suggesting that the studied method is a promising technology for screening medicines for their quality in low-resource settings.
A widely used screening technology is the Global Pharma Health Fund (GPHF)-Minilab. Medicines collected during the medicine quality study in Nigeria were thus analyzed according to the GPHF-Minilab monographs with visual inspection, disintegration and TLC testing. The four falsified samples were flagged as suspicious during visual inspection and were readily identifiable with TLC analysis. However, only seven (35%) out of all 20 medicines deviating by more than 20% in USP assay analysis, which is the possible GPHF-Minilab detection limit, were detected as non-compliant in TLC analysis. To improve the quantitative evaluation of these TLC-analyses, a smartphone-based imaging software (TLCyzer) was developed in cooperation with the group of Hendrik Lensch (department of computer science, University of Tuebingen). The TLCyzer had shown promising results in a laboratory performance evaluation for 14 APIs and was subsequently tested in the course of this doctoral research in a real-life setting in Nigeria. Compared to analyzing the TLC plates visually, the detection of SF medicines was improved with the TLCyzer, but good quality samples were often incorrectly detected as non-compliant, indicating that the application needs further improvements before it is ready for field-use.
Since 2022, there has been an increase in the occurrence of pediatric medicines contaminated with diethylene glycol and ethylene glycol, leading to at least 300 fatalities in children worldwide. To improve the availability of suitable screening technologies to detect such contaminations, a target product profile (TPP) for screening devices to detect medicines contaminated with diethylene glycol and ethylene glycol was developed during this doctoral thesis and is in the process of being officially adopted by the WHO. The developed TPP may also be used as a template for further urgently needed TPPs for screening devices.
There is a general public opinion that higher costs for a medicine equate to better quality, yet there is little evidence on the relationship between prices and quality of medical products in LMICs. To address this research gap, the relationship between prices and quality of essential medicines collected in Cameroon, the Democratic Republic of the Congo and Nigeria was investigated. The 70 originator medicines and SRA generics (generic medicines manufactured in countries with stringent regulatory authorities [SRA]) were all within the pharmacopeial specifications for content and dissolution, whereas 21.1% of the 626 non-SRA generics (generic medicines manufactured in countries without an SRA) were outside the pharmacopeial specifications. Originators were thrice as expensive, and SRA generics twice as expensive, as non-SRA generics. Among the non-SRA generics, no positive correlation between medicine quality and medicine prices was established. Some criteria could be defined for the selection of manufacturers of good-quality medicines at affordable prices.Die Dissertation ist gesperrt bis zum 08. Dezember 2026
Women in Religious Positions of Contemporary Shrine and Imperial Court Shinto: An Ethnographic Perspective on the Identity and Agency of Female Priests, Miko and Naishōten
No full textDie Dissertation ist gesperrt bis zum 05. September 2026
Translational regulation of plant arginine decarboxylases by an ancient cis element and development of tools to study its role in bacterial wilt disease.
No full textPolyamines (PAs) are small cationic metabolites, essential for eukaryotic organisms and many prokaryotes. In plants, PAs are important for growth, development, gene expression, and abiotic and biotic stress responses, and their levels are finetuned through transcriptional and translational regulation of PA synthesis and catabolic enzymes (Chen et al., 2019). Synthesis of the most abundant PAs in plants, putrescine, spermidine, and spermine, predominantly starts with decarboxylation of arginine to agmatine by arginine decarboxylase (ADC, typically encoded by two genes, ADC1 and ADC2). Interestingly, all examined land plant ADC transcripts contain a highly conserved GC-rich ~50 bp sequence in their 5’ untranslated region (5’UTRs), termed the “ADC-box” (Wu et al., 2019). Using transient reporter assays, the ADC- box was found to inhibit translation of the downstream coding sequence, possibly by forming an RNA secondary structure that prevents ribosomal scanning. In addition to the ADC-box, ADC 5’UTRs contain a small uORF ~150 bp 5’ to the ADC-box; however, no clear role for this uORF was found (Wu et al., 2019).
This work aimed to determine if the ADC-box and uORF regulate ADC translation in planta and investigate how the ADC-box translational regulatory mechanism functions. CRISPR/Cas9 mutagenesis of ADC-boxes in tomato, Arabidopsis thaliana, and Marchantia polymorpha (relative of the first land plants) was conducted. As a proxy for measuring in planta ADC protein levels, a previously established liquid chromatography-mass spectrometry (LCMS)- based ADC activity assay (Wu et al., 2019) was further optimised, improving sensitivity ~600- fold and number of measured PA-related metabolites. Increased ADC activity and levels of some PA-related metabolites were found in tomato, A. thaliana, and M. polymorpha adc-box mutants, demonstrating that the ADC-box is a repressor of ADC translation in planta and that its role has likely been conserved throughout land plant evolution. The tomato ADC-box RNA secondary structures were experimentally and computationally determined using SHAPE analysis, finding a triple hairpin ADC-box structure. Through analysing ADC activity levels across adc-box mutants, it seems that the central hairpin, which is conserved across vascular and early non-vascular land plants, is essential for ADC-box functionality. CRISPR/Cas9 mutagenesis of the tomato ADC uORFs resulted in reduced ADC activity compared to wildtype (WT) and a shorter plant phenotype with fewer leaves and flowers, suggesting that this uORF not only positively regulates ADC translation but is also essential for plant development. Overall, these findings suggest that plant ADC translation is both negatively and positively regulated by two highly conserved 5’UTR elements that finetune ADC protein levels and maintain PA homeostasis under various conditions.
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In addition to influencing PA levels, ADC activity also correlated with levels of phenolamides, compounds made from PA conjugation to hydroxycinnamic acids (HCAs), which are both antimicrobial compounds and substrates for the formation of physical barriers in roots (i.e., lignin and suberin). Interestingly, the broad-host bacterial pathogen Ralstonia solanacearum, which infects plants via their roots, injects a conserved effector protein (RipTAL) into host cells to transcriptionally activate plant ADC genes and boost PA levels (Wu et al., 2019). Through this work, we hypothesise that R. solanacearum uses RipTALs to manipulate host phenolamide levels to either alter the plant microbiome or production of physical barriers in the roots. In brief, through expanding our capabilities of PA measurement by LCMS and our understanding of how ADCs influence the PA network, new experimental approaches and hypotheses as to how R. solanacearum benefits from a RipTAL-induced PA boost have been developed.Dissertation ist gesperrt bis 10. Juli 2026
γδ T Cells: Friend or Foe in Melanoma under Immune Checkpoint Blockade?
Full text linkImmune checkpoint blockade was the first treatment to significantly prolong the survival of melanoma patients with distant metastases and nowadays has become standard of care. Therapeutic antagonistic antibodies targeting PD-1 block binding to its ligands and are able to reinvigorate exhausted T cells. However, PD-1 expression is not limited to αβ T cells, but can also be found on γδ T cells making this heterogeneous population of unconventional T cells a further target of anti-PD-1 therapy.
Since γδ T cells are a less-well-studied T cell population, we looked into the pitfalls one might encounter when investigating these cells using polychromatic flow or mass cytometry, applying commercially available kits for magnetic cell isolation or when performing immunohistochemical staining. In this context, a careful selection of the utilized antibodies is of particular importance in order to avoid bias in the phenotypic or functional characterization and the drawn conclusions. Furthermore, we adapted an assay developed for αβ T cells to the γδ T cell subset, allowing a more rapid detection of functional Vδ1 and Vδ2 T cells based on the assessment of integrin activation. In addition to that we implemented the identification of γδ T cells in a high dimensional in situ imaging approach. This enables in-depth investigation of the phenotypic profile of tissue-resident and tumor-infiltrating innate-like Vγ9Vδ2 and adaptive-like Vδ1 T cells and their microenvironment. Building on this, future studies might elucidate the role and interplay of γδ T cells in solid malignancies and uncover potential targets of immunotherapy.
In parallel, we examined the role of γδ T cells in late-stage melanoma patients undergoing anti-PD-1 therapy, since a durable response is only achieved in a fraction of patients. Peripheral blood mononuclear cells and tumor-infiltrating lymphocytes were used to study the phenotype, functionality and TCR repertoire of Vδ1 and Vδ2 T cells. High frequencies of peripheral Vδ1 T cells were linked to poor overall survival and a late-differentiated potentially senescent-like phenotype that is presumably not responsive to immune checkpoint blockade. However, the abundance of Vδ1 T cells in the tumor was linked to prolonged overall survival and the senescent-like phenotype showed a lower prevalence at the tumor site. This supports the currently ongoing endeavors taking advantage of Vδ1 T cells for cancer immunotherapy
Bruton’s tyrosine kinase in NLRP3 inflammasome: An insight into its activation, interaction and downstream effects on NLRP3
No full textThe NLRP3 inflammasome comprises a sensor NLRP3, an adaptor ASC and an effector caspase-1 which together form a multiprotein complex that enables maturation of the inflammatory cytokines IL-1β and IL-18 and executes an inflammatory type of cell death called pyroptosis. NLRP3 is strictly regulated during its priming and activation phases, and several post-translational modifiers of NLRP3 contribute to its activation and regulation. Previous studies have identified Bruton tyrosine kinase (BTK) as a post- translational activator of NLRP3 that interacts and phosphorylates multiple tyrosine residues in the central NLRP3 NACHT linker domain. In this study we have aimed at analysing BTK’s activation and interaction with NLRP3, and the downstream effects of BTK-mediated phosphorylation on NLRP3 oligomerization. We observed that BTK was phosphorylated, a common indication of BTK activation, during the early TLR priming phase using immunoblotting analysis. We further hypothesized that Syk, a tyrosine kinase known to phosphorylate BTK in B cells to be upstream of BTK activation. Indeed, pharmacological Syk inhibition abolished BTK phosphorylation in primary mouse macrophages. Furthermore, confocal microscopy in primary mouse macrophages revealed that within 20 mins of TLR4 stimulation, BTK was recruited transiently to the plasma membrane, in good agreement with findings that the BTK Pleckstrin homology (PH) domain is known to interact with phospho inositol (PIP3) in the plasma membrane in B cells. However, Xid BTK with a point mutant in its PH domain (R28C), did not show plasma membrane localization upon TLR priming in mouse macrophages. As Xid BTK macrophages did not show plasma membrane recruitment, we speculated if the Xid mutation would affect the interaction of NLRP3 and BTK. Proximity ligation assays of the NLRP3 and Xid BTK interaction indicated that the interaction was indeed reduced compared to the WT BTK, possibly due to reduced BTK activation or aberrant localization in this phenotype. Using co-immunoprecipitation, we further established that BTK interacts with proline residues P199 and P202 in the NLRP3 NACHT linker which, when substituted to alanine or glycine, showed reduced interaction with BTK. In the publicly available cryo-EM structures of NLRP3, the Pro sites were in proximity to the BTK-modified Tyr residues in the NACHT linker. Finally, analysing the downstream effect of BTK on NLRP3 oligomerization, we observed a significant decrease in NLRP3 specks in Btk KO vs WT murine macrophages using immunofluorescence staining which corresponded to a decrease in IL-1β. Altogether, we have endeavoured to address the mechanisms of BTK activation and interaction with NLRP3 in the inflammasome cascade. Although the interaction sites of BTK and NLRP3 and the role of Syk in NLRP3 inflammasome requires further investigation, our results highlight the requirement for precise targeting of specific interaction interfaces of BTK and NLRP3. Additionally, the involvement of Syk raises the possibility that Syk inhibitors could be potential and attractive alternate targets for inflammasome inhibition in NLRP3 related diseases
Towards a better understanding of human-AI relationship perception
No full textDie Dissertation ist gesperrt bis zum 20. April 2026 !Zuerst haben wir getippt, dann haben wir gewischt, und heute sprechen wir mit Computern. Künstliche Intelligenz (KI) ermöglicht es Nutzer:innen, mit Computern in natürlicher Sprache zu kommunizieren. Konversationelle KI, wie Amazons Alexa, sind lediglich Werkzeuge, die die Nutzer:innen bei vielen Aufgaben unterstützen (Kulkarni et al., 2019). Menschen anthropomorphisieren jedoch häufig Technologien und reagieren auf soziale Art und Weise (Gambino et al., 2020; Nass & Moon, 2000b). Darüber hinaus haben die jüngsten Fortschritte im Bereich der künstlichen Intelligenz dazu geführt, dass die Interaktionen zwischen Mensch und KI nicht nur sozial sind, sondern in gewissem Sinne mit Intentionen oder Emotionen angereichert werden. Dadurch wurde auch das Potenzial erweitert, Beziehungen zu diesen Agenten aufzubauen (Pentina et al., 2023). Es gibt jedoch nur wenige empirische Untersuchungen, die die Beziehungen zwischen Menschen und KI direkt untersucht haben, die über relationale Substitute wie Vertrauen hinausgehen. Unabhängig von der ontologischen Frage, ob Menschen Beziehungen haben können (Evans et al., 2023), besteht das Ziel meiner Dissertation darin, das gegenwärtige Verständnis darüber zu verbessern, wie Menschen ihre Beziehung zu konversationeller KI wahrnehmen und wie diese Wahrnehmung mit dem Nutzerverhalten zusammenhängt.
In meiner Dissertation löse ich mich von der vorherrschenden Annahme, dass soziale Beziehungen eine Domäne sind, die ausschließlich dem Menschen vorbehalten ist (Guzman & Lewis, 2020). Zum ersten Mal wurde die Theorie der Beziehungsmodelle von A.P. Fiske (Fiske, 1992) herangezogen, um zu bewerten, wie Menschen ihre Beziehung zur Technologie wahrnehmen. Fiskes Theorie der Beziehungsmodelle geht von vier Beziehungsdimensionen aus, die die menschliche Interaktion prägen (authority ranking, market pricing, communal sharing, und equality matching). Ich habe den relationalen Ansatz in vier Online-Querschnitts-studien getestet (Gesamt N=1568). Die Ergebnisse zeigten durchweg, dass die Beziehungsmodi, die Menschen verwenden, um ihre Beziehungen zu konversationeller KI zu konstruieren, denen ähneln, die in Beziehungen zu anderen Menschen verwendet werden, sich aber dennoch etwas davon unterscheiden. Anstelle der ursprünglichen vier Dimensionen nehmen die Nutzer:innen ihre konversationelle KI entlang dreier verschiedener Beziehungs-modi wahr: Authority ranking (d. h. eine hierarchische Diener-Meister Beziehung), market pricing (d. h. eine gleichberechtigte, rationale Beziehung auf “Augenhöhe”) und peer bonding (diese Dimension stellt eine neue, eher emotionale Dimension dar, kollegial). Die ersten beiden Studien unterstrichen den Wert des multidimensionalen Ansatzes, wobei jede
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Beziehungsdimension distinkte Assoziationen mit Systemwahrnehmungsvariablen (z. B. Vertrauen) und Nutzereigenschaften (z. B. Nutzungszwecke) zeigte.
Nachdem ich eine robuste Methodik zur Untersuchung entwickelt hatte, wie Menschen ihre Beziehung zu konversationeller KI wahrnehmen, führte ich zwei Studien durch, um die Auswirkungen auf das Verhalten zu untersuchen und ihren praktischen Wert im Kontext des Voice Commerce (d. h. Einkaufen mit konversationeller KI). Die Ergebnisse zeigten, dass die Beziehungsmodi zwischen Menschen und KI in unterschiedlichem Maße mit Ergebnisvariab-len verbunden sind, die für Voice Shopping relevant sind. Insbesondere war Voice Shopping stark mit peer bonding verbunden, was die Bedeutung sozio-emotionaler Elemente beim Voice Shopping unterstreicht. Daher konzentrierte sich die anschließende experimentelle Studie auf die Rolle sozio-emotionaler Designelemente, indem sie einen Human-AI-Fit-Ansatz verfolgte (d. h. die Anpassung der Benutzeroberfläche an Benutzereigenschaften zur Optimierung der Benutzererfahrung, Liu et al., 2011). Ich untersuchte die Auswirkungen verschiedener Konversationsdesigns in Bezug auf die Beziehungswahrnehmung der Nutzer:innen beim Voice Shopping. Die Ergebnisse zeigten, dass ein emotionaleres Gesprächsdesign Personen in autho-rity ranking Beziehungen vom Voice Shopping abhielt. Daher ist eine sorgfältige Betrachtung der Wechselwirkung zwischen Design und Beziehungswahrnehmung von entscheidender Be-deutung für das Verständnis von Faktoren, die Voice Shopping behindern oder erleichtern kön-nen.
Trotz verschiedener Einschränkungen bietet diese Dissertation eine stark theorie- geleitete, leicht reproduzierbare Messung der Wahrnehmung der Beziehung zwischen Menschen und KI. Nachdem die praktische Relevanz des mehrdimensionalen Ansatzes im Voice Commerce veranschaulicht wurde, ist es mein Ziel, zukünftige Forscher:innen und Fach-leute zu inspirieren, diesen Ansatz für die Mensch-KI-Beziehung in verschiedenen Kontexten anzuwenden. Ganz gleich, ob es sich um konversationelle KI, konventionelle Systeme oder zukünftige, noch zu realisierende Technologien handelt, in jeder Situation, in der die Wahrnehmung der Beziehung als relevant erachtet wird, bin ich optimistisch, dass sich der hier entwickelte Rahmenwerk der Mensch-KI-Beziehung als nützlich erweisen wird, um ihre po-tenziell positiven oder negativen Auswirkungen auf Mensch-Computer-Interaktionen zu er-gründen
Real-Time In-Situ Investigations of [6]Phenacene Organic-Inorganic Structures with Organic Molecular Beam Deposition
No full textOrganic semiconductors (OSCs) that consist of fused benzene rings are promising candidates for high-performance electronic devices like organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaics (OPV). Compared to their inorganic counterparts, OSCs have a different charge transfer mechanism that depends on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). OSCs offer mechanical flexibility, stretchability as well as optical transparency and are low-cost alternatives for their inorganic counterpart that are suitable for mass production. A vast amount of different OSCs are available, which are under constant development and research. Especially the study of growth, structure and molecular packing is important due to its influence on the electronic properties of prepared devices. Devices made of OSCs consist of several layers where multiple materials are combined into a complex organic-inorganic interface or so-called hybrid system. Two parts of this interface were under investigation in this work. Alkali metal doped layers are used to manipulate the electronic properties of the original material and gold-organic interfaces that are used for electrical contacting. Both methods can lead to changes in the growth, structure and morphology of the original material and were therefore investigated in this thesis. This was achieved by utilizing preliminary work in the home laboratory as well as real-time in-situ measurements performed at state-of-the-art synchrotrons. Thin films were characterized by using various X-ray scattering methods combined with optical methods. The evaluation was done by examining the in-plane and out-of-plane structure during growth and calculating the unit cell structure, orientation and molecular packing. The molecule used for this study was [6]Phenacene deposited as a thin film by using organic molecular beam deposition (OMBD) under ultra-high vacuum (UHV) conditions. These results were also compared to other phenacenes. [6]Phenacene shows a Stranski-Krastanov growth behaviour which leads to wedding cake islands with a well-defined transition between the terraces. The unit cell parameters and molecular packing was calculated by assuming four molecules inside a unit cell. The molecular stacking is influenced by the parity of used molecules, which depends on the number of benzene rings of the used phenacene. Organic-inorganic interfaces of [6]Phenacene were investigated by using the alkali metals: potassium, rubidium and caesium. They were either deposited on top of a [6]Phenacene thin film or co-evaporated during growth leading to various changes in crystallinity and intercalation into the thin film. Further experiments with gold as a common contacting material were performed by depositing the metal on top of [6]Phenacene thin films. The results of this thesis showed various changes in structure and morphology for organic-inorganic systems which can lead to a further understanding of growth processes in thin films. This is especially important for the further development of OSCs
Einfluss von Netrin-4 auf die Neutrophilen-Endothel-Interaktion
No full textDie Dissertation ist gesperrt bis zum 12. Juli 2026
Gentechnische Modifizierung des Pacidamycin-Genclusters zur Produktion von Mureidomycinen
No full textDie Dissertation ist gesperrt bis zum 17. Mai 2026 !Der Erreger Pseudomonas aeruginosa ist aufgrund seiner schnellen Resistenzausbildung von hoher klinischer Relevanz. In dieser Arbeit wurden Naturstoffe aus Streptomyceten isoliert, die eine antipseudomonale Aktivität besitzen. Diese Naturstoffe gehören zu der Klasse der Uridyl-Peptid-Antibiotika. Durch gentechnische Modifikationen konnte sowohl die Struktur optimiert werden als auch die Produktionsrate dieser Antibiotikaklasse erhöht werden
Pathophysiological and Pharmacological Relevance of NO/cGMP Signaling in Atherosclerosis
No full textAtherosclerosis leads to heart attack and stroke, the most common causes of death worldwide. This disease is characterized by chronic inflammation of the blood vessel walls, accompanied by the formation of atherosclerotic plaques. Vascular smooth muscle cells (VSMCs) play a crucial role in this process. VSMCs significantly contribute to the plaque formation through migration, clonal expansion, and phenotypic modulation. The molecular mechanisms leading to the alteration of VSMC behavior in atherogenesis are not fully understood. The cyclic gua-nosine monophosphate (cGMP) signaling pathway, synthesized by the nitric oxide (NO)-sen-sitive guanylyl cyclase (NO-GC) is a key factor in the (patho-)physiology of VSMCs. It is assumed that a disruption of the NO/cGMP signaling pathway in VSMCs impact phenotypic mod-ulation and plaque growth. However, it remains unclear whether pharmacological stimulation/activation of the NO/cGMP pathway in VSMCs exerts pro- or anti-atherogenic effects.
This study aimed to further elucidate the pathophysiological and pharmacological relevance of the NO/cGMP pathway in VSMCs in a mouse model of atherosclerosis and investigate its potential effects on atherosclerotic plaque growth and composition. To modulate the activity of the NO/cGMP signaling pathway in vivo, NO-GC modulating drugs or cell specific genetic in-activation of NO-GC in VSMCs (NO-GCsmko) were used. A novel aspect of this study was the comparison of the effects of a NO-GC activator (BAY Activator) and a NO-GC stimulator (Vericiguat). Both compounds induce cGMP generation by binding to NO-GC but differ in their mode of action. NO-GC stimulators enhance NO-GC activity independently or synergistically with endogenous NO. In contrast, NO-GC activators activate the dysfunctional heme-oxidized NO-GC. Particularly under conditions of increased oxidative stress, as observed in atheroscle-rosis, NO-GC activators are assumed to have high therapeutic potential.
Various biochemical, immunological, and histochemical methods were combined for analysis. Initially, the expression of NO-GC as a potential drug target was demonstrated by in situ im-munofluorescence staining in VSMCs and macrophage antigen-2 (MAC2)-positive cells in ath-erosclerotic plaques, indicating the possibility of pharmacological modulation of the enzyme. MAC2 was used as a cellular marker for VSMC-derived transdifferentiated macrophage-like cells or macrophages. Interestingly, en face analysis of atherosclerotic aortas showed that BAY Activator treatment led to a significant increase in the atherosclerotic lesion area, while Vericiguat did not exhibit this pro-atherosclerotic effect. Comprehensive analyses revealed that the administered drugs were detectable in the blood plasma and that various parameters that could influence atherosclerosis, such as blood pressure, plasma lipid profile and complete blood count, were not significantly changed by the BAY Activator treatment. To investigate the functional relevance of the NO/cGMP signaling pathway in VSMCs for the pro-atherosclerotic effect of the BAY Activator, in vitro experiments were performed with primary VSMCs isolated from mouse aortas. First, the effects of NO-GC modulators on intracellular cGMP concentration were visualized in real-time under normal and oxidative conditions using a Förster/fluorescence resonance energy transfer (FRET)-based cGMP biosensor. Additionally, the effects on VSMC growth were examined using the xCELLigence system. These experiments demon-strated that both the BAY Activator and Vericiguat increased cGMP levels and promoted VSMC growth. As expected, the BAY Activator showed higher efficacy in increasing intracellular cGMP levels under conditions of oxidative stress, which may also imply an enhanced efficacy under atherosclerotic conditions. Based on the results of the present study and the existing literature, we postulate that the growth-promoting effects of NO-GC modulators are likely as-sociated with the role of NO-GC in the phenotypic modulation of VSMCs. Interestingly, our in vivo study revealed that the increased atherosclerotic lesion area caused by the BAY Activator treatment was accompanied by an accumulation of MAC2-positive cells. This indicates that activation of the NO/cGMP signaling pathway led to an enrichment of VSMC-derived transdifferentiated macrophage-like cells or macrophages.
It was also planned to validate the target specificity of the effects of NO-GC modulators and the pathophysiological role of the NO/cGMP signaling cascade in VSMCs using an NO-GCsmko mouse model. Although we successfully generated the NO-GCsmko mouse model, the preliminary data suggested that the induction of NO-GCsmko led to a hypertensive phenotype and elevated plasma lipid levels, which complicated the interpretation of the data regarding the effects on atherosclerosis. Thus, no further conclusions were drawn from these data at this time.
In summary, our results suggest a pro-atherosclerotic effect of activation of the NO/cGMP sig-naling pathway by BAY Activator treatment. We hypothesize that this is closely related to the increased efficacy of BAY Activator under the oxidative conditions prevalent in atherosclerotic plaques and the impact on the phenotypic modulation of VSMCs in the plaque. These findings provide the basis for further research to deepen our understanding of the pathophysiological and pharmacological relevance of the NO/cGMP signaling pathway in atherosclerosis.Die Dissertation ist gesperrt bis zum 11. April 2026