@phdthesis{Seifert2019,
  author    = {Seifert, Daniel},
  title     = {Der Einfluss des Apelin/APJ-Systems auf die Sauerstoffradikalproduktion von glatten Gef{\"a}ßmuskelzellen},
  institution = {Kliniken und Polikliniken f{\"u}r Innere Medizin},
  year      = {2019},
  abstract  = {Introduction: The G protein-coupled receptor APJ and its endogenous ligand Apelin are widely expressed throughout the body. Within the human vasculature, APJ was found in vascular smooth muscle cells (VSMC) and Apelin is restricted to endothelial cells. Adjacent to their important role in regulation of the cardiovascular homeostasis, the Apelin-/APJ-system also takes part in the response of vascular injuries like the endothelial denudation by the percutaneous coronary intervention (PCI) with the following formation of a neointima. Majority of intimal VSMC are derived from resident medial VSMC that undergo phenotypic modulation and migration into the neointima. These VSMC show high levels of the APJ receptor that suggest a locally paracrine pathway in injured vessels to the endothelial derived Apelin. We suppose that the observed elevation of APJ expression in VSMC is due to the exposure to shear stress after endothelial denudation. Recent studies have shown that Apelin-13 can promote the VSMC proliferation by a NADPH Oxidase 4 (NOX4) depended increase of the reactive oxygen species (ROS). But there are no results to other Apelin-isoforms like Apelin-17. Because of that, we investigated the influence of shear stress on the APJ- and NOX- expression in human coronary arterial smooth muscle cells (HCASMC). Furthermore we are interested in the effect of Apelin-17 on the NOX dependent ROS production. Methods: A monolayer of HCASMC were exposed to hemodynamic shear stress (0.5 dyne/cm² for physiological and 20 dyne/cm² for pathophysiological conditions) for 3, 6 and 12 hours using a parallel plate flow chamber. Additionally, HCASMC were incubated with apelin-17. Static controls were kept under same conditions. On the one hand the cells were then prepared for real-time qRT-PCR- and Western Blot analysis or on the other hand for measuring the concentration of ROS by using the flow cytometry (FACS). Therefore, we pre-incubated the HCASMCs with 2',7' dichlorofluorescin diacetate (DCFDA). Results: The application of physiological shear stress to HCASMC didn`t influence the expression of the APJ receptor and all the NOX isoforms. There also was no alteration in ROS concentration. But after 3 hours under pathological flow we were able to show an initially significantly increase by 8-fold of the APJ expression. This effect was abolished after 12 hours of flow exposure. The apelin expression was shear-independent diminished. Furthermore the HCASMC showed a NOX dependent rise of the intracellular ROS concentration. Interestingly, static Apelin-17 stimulation reduced the production of ROS and we have only seen this effect after 3 hours incubation and not after 6 hours. Under dynamic conditions apelin-17 abolished the shear-dependent increase of ROS. Conclusion: Our results show a flow-dependent increase of the APJ expression only after three and six hours of pathophysiological flow-exposure. These data suggest that the apelin/APJ system only takes part in the acute phase of vascular injury. The early apelin-17 effect would confirm this suggestion. But the inhibition of intracellular ROS production by apelin-17 is in contrast to recent studies of Apelin-13. So further studies are required to understand the different cell signalling mechanism of both isoforms and their participation in vascular injuries like the formation of a neointima after a PCI.},
  subject      = {APJ-Rezeptor},
  language  = {de}
}