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Abstract: PO1416

The Proteinase 3-Alpha1-Antitrypsin Connection in PR3-ANCA Vasculitis

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Ebert, Maximilian, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin and Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
  • Jerke, Uwe, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin and Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
  • Eulenberg-Gustavus, Claudia, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin and Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
  • Jenne, Dieter E., Institute of Lung Biology and Disease (ILBD), Comprehensive Pneumology Center (CPC), Helmholtz Zentrum, Munich, Germany
  • Bieringer, Markus, Department of Nephrology, Helios Klinikum Berlin-Buch, Berlin, Germany
  • Elitok, Saban, Department of Nephrology and Endocrinology, Ernst von Bergmann Klinikum, Potsdam, Potsdam, Germany
  • Eckardt, Kai-Uwe, Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin, Berlin, Germany
  • Schreiber, Adrian, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin and Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
  • Salama, Alan D., Department of Renal Medicine , University College London, Royal Free Hospital, London, United Kingdom
  • Kettritz, Ralph, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin and Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
Background

PR3 is a major autoantigen in ANCA-associated vasculitis (AAV) and a neutrophil serine protease inhibited by alpha1-antitrypsin (AAT). Increased PR3 and decreased AAT were suggested as disease mechanism for PR3- but not MPO-AAV

Methods

We assessed PR3 and AAT in 100 AAV patients and 50 healthy controls (HC) and produced recombinant wt- and mut-AAT to study the effect on proteolytic PR3 activity, membrane PR3 (mPR3) by flow cytometry and surface plasmon resonance (SPR), and neutrophil activation.

Results

In active PR3- and MPO-AAV, plasma PR3 concentration increased approximately 5-fold and plasma AAT 1.8-fold shifting the PR3:AAT ratio significantly towards PR3. Both parameters normalized with remission. Notably, only one PR3-AAV remission patient showed strongly decreased plasma AAT. The PR3 neutrophil content was approximately 50% higher in active PR3- and MPO-AAV accompanied by increased PR3 transcription. The resulting total PR3 pool (plasma PR3 concentration x plasma volume + neutrophil PR3 x neutrophil number) was approximately 3-fold larger in active AAV and normalized with disease remission. In active PR3-AAV but not MPO-AAV, the total PR3 pool correlated with kidney injury, hemoglobin, and PR3-ANCA ELISA. Membrane-PR3 (mPR3) correlated negatively with plasma AAT in HC, was increased in AAV patients with a compromised plasma AAT correlation. Mechanistically, extracellular AAT dose-dependently reduced mPR3 by competing with PR3 for the PR3-presenting CD177 receptor. Consequently, AAT reduced neutrophil activation by PR3- but not MPO-ANCA. Neutrophils from AAV patients and HC showed similar mPR3 reduction with AAT. However, in contrast to HC plasma, neutrophil incubation in active AAV plasma increased the AAT concentrations required to lower mPR3, an effect that was recapitulated by adding inflammatory mediators to HC plasma. Finally, oxidative AAT modification resulted in less PR3 interaction and diminished mPR3 reduction

Conclusion

We found a strongly increased PR3 pool in active PR3-AAV and exclude decreased plasma AAT as the general underlying disease mechanism, as previously proposed. However, AAT controls mPR3 expression and subsequently PR3-ANCA induced neutrophil activation, suggesting adjunctive AAT administration may have beneficial effects in acute PR3-AAV

Funding

  • Government Support – Non-U.S.