SPRINGER Stephanie

Defining the Role of the Tissue-Specific Renin-Angiotensin-System

The Renin-Angiotensin-System (RAS) is a proteolytic peptide cascade, which is ubiquitously present and primarily responsible for salt retention and implicated in the regulation of blood pressure and fluid homeostasis. As dysregulated RAS has been proposed to be an essential pathogenetic factor in various disease states including arterial hypertension, heart and kidney failure, diabetes and even cancer making the system also an attractive target for several drugs.

One of the major problems in the fields of RAS research is the biochemical background of the RAS that is only incompletely understood, since the majority of publications reporting effector peptide levels, the so called angiotensins, are very heterogeneous with fluctuation ranges of up to ± 10.000 pg/ml while physiological levels of angiotensin II range between 10 and 20 pg/ml. The lack of reliable and reproducible methods to accurately quantify angiotensins is the principal cause of hitherto reported inconsistencies of angiotensin research and can therefore be considered as one of the central drawbacks in RAS research in general.

During recent years the so-called tissue localized RAS moved increasingly into the focus of RAS research as the expression of angiotensin processing enzymes and the presence of distinct angiotensin metabolites has been reported for multiple tissues, however, with hitherto unclarified biological significance. Nevertheless, further progress in this special field is not possible unless the methodological caveats for the analysis of the RAS that also apply for tissue samples are not resolved. Hence, in order to understand and interpret the physiological consequences of the tissue RAS, a solid and reproducible assay with high sensitivity is essential.

The central theme of this PhD thesis will be the establishment of a novel method that allows for the exact quantification of the RAS at the tissue level. This would provide a tool that allows the analysis of tissue biopsies, which shall be proved in clinical samples and a rodent study. By means of a recently established mass-spectrometry-based (also LC-MS/MS-based) method, the so-called “RAS-Fingerprint-assay” which allows for the solid and reproducible quantification of angiotensin levels with a lower detection limit of 1 pg/ml, further methodological optimization to enable the analysis of angiotensin-peptides levels will be pursued. With the help of such a method, a versatile tool to investigate the biological role of the RAS under different physiologic and pathological conditions will be available. Hence, for the first time it would be possible to set into relation the circulating with the local RAS, allowing the investigation of the interaction between both systems leading to an improved and integrated understanding of the physiology of the human RAS.

Methods and Skills:

ultrasound examination; clinical studies; ELISA