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Kidney Week

Abstract: TH-PO092

Binding of Cell Surface Carboxypeptidase M Contributes to Tubulo-Protective Effects of Fibrinopeptide Bß15-42

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Soerensen-Zender, Inga, Hannover Medical School, Hannover, Germany
  • Rong, Song, Hannover Medical School, Hannover, Germany
  • David, Sascha, Hannover Medical School, Hannover, Germany
  • Haller, Hermann G., Hannover Medical School, Hannover, Germany
  • Schmitt, Roland, Hannover Medical School, Hannover, Germany
Background

Acute and chronic kidney disease is often associated with activation of the coagulation cascade and with parallel activation of the fibrinolytic system. During fibrinolysis the peptide Bβ15-42 is cleaved off the end of the fibrin Bβ chain. Previous studies have demonstrated a protective effect of Bβ15-42 in sepsis, myocardial infarction and renal ischemia/reperfusion. The responsible molecular mechanism was attributed to binding of Bβ15-42 to endothelial VE-cadherin. Our preliminary work had shown that Bβ15-42 also has a direct protective effect on renal tubular cells. It was the goal of the present study to clarify this VE-cadherin independent mechanism.

Methods

Repetitive doses of Bβ15-42 (3 mg / kg i.v.) or control peptide were tested in vivo in unilateral ureteral obstruction (UUO) and in aristolochic acid nephropathy (AAN). Kidneys were examined at different time points by histomorphology and damage marker expression. In vitro, renal tubular cells were stressed by AA or staurosporine before treatment with Bβ15-42 or control peptide. Target proteins were knocked-down by siRNA and cell damage was quantified by LDH release and qPCR. Bβ15-42 binding partners were identified by ligand-receptor capture (LRC) technology LRC-TriCEPS. Carboxypeptidase M activity was measured by Dansyl-Ala-Arg-OH trifluoroacetate assay.

Results

In vivo, Bβ15-42 improved the tubular damage pattern after induction of AAN and after UUO. To identify potential new Bβ15-42 interaction partners on tubular cells, we used LRC-TriCEPS and found the membrane protein carboxypeptidase M (CBPM) as a highly specific binding partner. Despite its strong tubular expression the physiological role of renal CBPM which modifies a variety of candidate signal peptides by C-terminal cleavage is unknown. CBPM enzymatic activity was significantly inhibited by Bβ15-42, both in vitro and in vivo. Knockdown of CBPM by siRNA resulted in a marked reduction in the protective effect of Bβ15-42.

Conclusion

The fibrinopeptide Bβ15-42 has a direct protective effect on tubular epithelial cells, which is largely determined by binding to CBPM and inhibition of CBPM enzymatic activity. Our results show a novel mode of action for Bβ15-42 and suggest that CBPM may represent a new target that can be used therapeutically for nephroprotection.