Schoerner 2014 Thesis University Giessen

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Schörner S (2014) Changes in function of mitochondrial respiratory chain in pulmonary artery smooth muscle cells under conditions of chronic hypoxia : measurements by respirometry and remission-spectrophotometry. Thesis University Giessen 130 pp.

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Schoerner S (2014) Thesis University Giessen

Abstract: Hypoxic pulmonary vasoconstriction (HPV) is a physiological response of the lung to hypoxia and is also known as von-Euler-Liljestrand-mechanism, which optimizes blood perfusion to ventilation. In contrast, chronic hypoxia (as occuring in COPD or high altitude) leads to pathological changes and can result in pulmonary hypertension (PH) and vascular remodeling. The precapillary pulmonary artery smooth muscle cells (PASMCs) could be identified as sensor- and effector cells as they contract and proliferate in response to hypoxia mediated by Ca2+-entry and transcription factors, e.g. HIF. Mitochondria take part in both, acute oxygen sensing and chronic remodeling processes. Mitochondrial ROS-production and metabolic changes are discussed to be essential for these alterations. Aim of this dissertation was to investigate, if mitochondrial respiration and cytochromal redox-state of the mitochondrial respiratory chain complexes in PASMCs show alterations under conditions of chronic hypoxia. These results were compared to aortal SMCs (ASCMs). The protocol consisted of a combination of respirometry and remissions-spectrophotometry to analyze mitochondrial oxygen affinity, oxygen consumption and cytochromal redox state. After establishment of a valid cell culture model, measurements in cells after 24 and 48 hours of hypoxic incubation (1 % O2) were performed. It could be shown that cell culture conditions with regard to passage or sowing did not have any effect on oxygen affinity (p 50) or oxygen consumption (Vmax). Cells incubated with 1 % FCS showed a decrease in both values compared to cells cultured with 10 % FCS. After hypoxic incubation (1 % O2), a decrease in Vmax after 24 hours could be detected, which was increased after 48 hours. In contrast, a decrease of oxygen affinity only could be seen after 48 hours of hypoxic incubation. During 24 hours hypoxic incubation, the number of mitochondria was constant, measured by citrate synthase activity. In comparison to pulmonary artery cells, in aortal cells oxygen affinity was more reduced after 24 hours of hypoxic incubation with similar values of oxygen consumption. In spectrophotometry, no significant difference in pO2-dependent reduction of cytochromes could be found. In conclusion, pulmonary artery smooth muscle cells showed a decrease in respiration and oxygen affinity after hypoxic incubation. This may affect proliferation and vascular remodeling in conditions of chronic hypoxia.

Keywords: Hypoxic pulmonary vasoconstriction, Pulmonary hypertension, Mitochondria, High-resolution respirometry, Spectrophotometry

O2k-Network Lab: DE_Giessen_Weissmann N

Labels: MiParea: Respiration 

Stress:Ischemia-reperfusion  Organism: Rabbit  Tissue;cell: Endothelial;epithelial;mesothelial cell 

Coupling state: LEAK, ROUTINE, ET  Pathway: ROX  HRR: Oxygraph-2k