Bestimmung der mitochondrialen Atmungskettenfunktion im Rett-Syndrom mittels hochauflösender Respirometrie
by Verena Maria Husemann
Date of Examination:2023-06-13
Date of issue:2023-06-05
Advisor:Prof. Dr. Michael Müller
Referee:Prof. Dr. Ralph Kehlenbach
Referee:Prof. Dr. Ralf Dressel
Persistent Address:
http://dx.doi.org/10.53846/goediss-9924
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Abstract
English
Rett syndrome is a disorder frequently caused by pathological changes in the MECP2 gene, an essential transcription factor. It results in various morphological and biochemical alterations in mitochondria, which affect a variety of intracellular processes such as ATP and ROS production, as well as apoptosis regulation. The disruption of the redox balance in Rett syndrome alters physiological processes in neurons of affected patients. Given that this influence may play a significant role in the manifestation of symptoms in affected individuals, manipulating and correcting the redox balance has been pursued as a therapeutic approach. In my work, I am investigating the impact on transgenic mice of a Rett mouse model through the administration of antioxidant feed or the expression of mitochondrial catalase to potentially restore a physiological redox balance. In my study, wild-type mice and Mecp2-/y mice, which serve as an animal model for Rett syndrome, were examined. The oxygen consumption of isolated mitochondria from the cerebellum and brainstem was analyzed using the Oroboros respirometer. For this purpose, the individual complexes of the respiratory chain were selectively targeted with substrates and inhibitors. Furthermore, before each of these measurements, the weight, body length, blood glucose, and hematocrit of these mice were determined and compared with regard to the influence of the absence of the MeCP2 protein on these phenotypic characteristics. Our results showed no difference in oxygen consumption between wild-type and Mecp2-/y mice isolated from the cerebellum or brainstem. This is interesting in light of previous findings which in contrast demonstrated increased consumption in samples from the cortex and hippocampus. Additionally, I showed that neither the use of antioxidant feed nor the application of mitochondrial catalase had an impact on oxygen consumption. Therefore, at first sight these interventions do not seem to be a promising therapeutic approach to improving mitochondrial efficiency in Rett syndrome, at least in relation to the cerebellum and brainstem. Interestingly, they also did not have any negative effects on wild-type mice. The analysis of phenotypic characteristics showed that Mecp2-/y mice are significantly lighter and smaller, have an increased hematocrit, and exhibit partially reduced blood glucose levels which is in line with previously published data. In summary, mitochondrial oxygen consumption as a measure of respiratory chain efficiency showed no differences between animals of the Rett mouse model and wild-type mice in the cerebellum or brainstem. This contrasts with previous publications where increased oxygen consumption was observed in mitochondria samples from the cortex and hippocampus. Further studies are needed to investigate the reasons for these differences between brain regions. Furthermore, it can be concluded that neither the administration of antioxidant feed nor the expression of mitochondrial catalase had a positive or negative effect on mitochondrial oxygen consumption.
Keywords: rett syndrome; mitochondrial oxygen consumption; respirometry; Oroboros; redox imbalance; mecp2 knockout mouse model; mitochondrial catalase; antioxidant feed