Dynamics of Neutrophil Extracellular Trap (NET) Formation
von Elsa Neubert
Datum der mündl. Prüfung:2019-05-07
Erschienen:2019-12-03
Betreuer:Dr. Luise Erpenbeck
Betreuer:Dr. Sebastian Kruss
Gutachter:Prof. Dr. Michael P. Schön
Gutachter:Prof. Dr. Jürgen Wienands
Gutachter:Prof. Dr. Bastian Schilling
Zum Verlinken/Zitieren:
http://dx.doi.org/10.53846/goediss-7746
Dateien
Name:Neubert E, Dissertation.pdf
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Zusammenfassung
Englisch
Neutrophil granulocytes are the largest group of white blood cells and play a significant role in the innate immune system. With the discovery of a vast number of thus far unknown functions, neutrophil granulocytes became a focus in biomedical research. One of the most remarkable findings are neutrophil extracellular traps (NETs), fibril networks of decondensed chromatin with attached antimicrobial proteins that can be released as a response to various stimuli in order to defend pathogens. The process of NET formation (NETosis) is evolutionarily highly conserved and involved in many pathological conditions. A detailed analysis of NETosis can, therefore, contribute to a better understanding of such diseases and therapeutic strategies. So far, the biophysical forces driving the morphological alternations that underlie chromatin decondensation and subsequent NET release are poorly understood. This issue is addressed in the first manuscript of this thesis. The results of this study show that NETosis occurs in three distinct phases of which only the first depends on enzymatic activity and energy consumption. The second phase is primarily driven by material properties and entropic swelling of chromatin. Therefore, the start of chromatin decondensation with nuclear envelope breakdown (onset of phase 2) represents a point of no return in NETosis. Complete chromatin decondensation is followed by NET release through rupture of the plasma membrane at a predetermined breaking point (phase 3). This biophysical characterization facilitates our understanding of the precise mechanisms of NETosis and highlights the extent by which complex biological processes can be driven by material properties. In vitro NETosis studies are being conducted by an ever-increasing number of groups. They use highly diverse amounts of serum and serum albumin in their culture media. This is problematic, as these supplements interfere with NETosis depending on their concentration, used stimulus and neutrophil donor species (human vs. mouse). Details are analyzed in the second manuscript, which contributes to the comparability of research conditions. Furthermore, ultraviolet-visible (UV-Vis) light can massively alter cell functions. The third manuscript investigates the effect of UVA and blue light on NETosis. Light activates a neutrophil elastase (NE)- and myeloperoxidase (MPO)-dependent pathway of ‘suicidal’ NETosis, which requires the riboflavin-mediated generation of reactive oxygen species (ROS). External factors, therefore, have a crucial impact on NET formation, which has to be considered for in vitro studies. Additionally, light-induced NETosis may be of particular interest in the pathogeneses of light-sensitive disorders (“photodermatoses”) including autoimmune diseases such as lupus erythematosus. Together, these studies provide detailed insight into the mechanisms of NET formation and their regulation.
Keywords: Neutrophil extracellular trap (NET) formation; Neutrophil granulocytes; Innate immunity
