P0106URINE COMPLEMENT FRAGMENTS ARE ASSOCIATED WITH KIDNEY FUNCTION AND DISEASE ETIOLOGY

Background and Aims Changes in complement factors have been associated with chronic kidney disease, most prominently in the context of C3 glomerulopathy. Based on these reports, the hypothesis was generated that specific urine complement fragments are associated with kidney disease etiologies, and progression of the disease may be reflected by changes in these proteins or peptides. In this study, we aimed at investigating the occurrence of complement fragments in urine, and their association with kidney function in general and disease etiology in particular. Methods Urine samples from patients with kidney disease of different etiologies and control subjects with normal kidney function were investigated using tandem mass spectrometry coupled with capillary electrophoresis and liquid chromatography to identify complement derived peptides based on their amino acid sequence. Subsequently, distribution of these peptides in the different kidney disease etiologies and normal kidney function was investigated via analysis of datasets recorded in the human proteome/peptidome database. All datasets, where eGFR was available and at least one of the complement peptides detected, were included. Results Twenty one different urinary peptides derived from complement could be identified. These peptide fragments originated from the complement factors C3, C4A and C4B, and CFB. Further investigation of 4557 datasets recorded in the urine proteome/peptidome database meeting the aforementioned inclusion requirements (eg available eGFR values and with at least one of the complement peptides detected), revealed, for most C3-derived peptides, an inverse, while for the majority of peptides derived from CFB, a positive association with eGFR. The table lists the detected complement derived peptides, the parental protein (Complement X), rho and p-value of the association with eGFR, and the number of samples (n) where the peptide was detected. When investigating the urine complement fragments, as a result of disease etiology, disease-specific distribution was detected, indicating a distinct association of complement factors and associated proteases, depending on disease etiology. As an example, the peptide distribution in AKI, IgA-Nephropathy (IgA-N) and vasculitis is shown in the Figure. Conclusion Multiple complement-derived peptides are significantly associated with kidney function, and with certain kidney disease etiologies, such as AKI, IgA-N or vasculitis. Proteomic screening of these complement factors may provide a basis, not only for non-invasively assessing kidney disease, but also for an opportunity to develop novel drugs; the latter, via targeting the associated proteases responsible for the release of these complement-derived peptides, in a specific kidney disease manner, in urine.