Circulating dipeptidyl peptidase 3 is a myocardial depressant factor: dipeptidyl peptidase 3 inhibition rapidly and sustainably improves haemodynamics.

AIMS: Acute heart failure is a high mortality disease and its pathophysiology is not completely understood. Dipeptidyl peptidase 3 (DPP3) is a cytosolic enzyme involved in angiotensin II and enkephalins cleavage. The aim of this study was to investigate the association of circulating DPP3 (cDPP3) levels and mortality in cardiogenic shock patients and to determine the effects of high cDPP3 on organ function in a heart failure (HF) model in mice. METHODS AND RESULTS: cDPP3 was measured in 174 patients in cardiogenic shock and high cDPP3 levels were associated with an increased short-term mortality risk (standardized hazard ratio: 1.4 (1.1-1.8)) and severe organ dysfunction. Additionally, a rapid decrease in cDPP3 in cardiogenic shock patients within 24 h of admission was associated with a favourable outcome. This study showed that injection of DPP3 induced myocardial depression (-10 ± 2% of shortening fraction) and impaired kidney haemodynamics (+0.30 ± 0.02 of renal resistive index) in healthy mice. cDPP3 inhibition by Procizumab, a specific antibody directed against cDPP3, promptly normalized cardiac function and kidney haemodynamics in an acute heart failure mouse model, with a marked reduction in oxidative stress and inflammatory signalling. CONCLUSION: Our study demonstrated cDPP3 is a newly discovered myocardial depressant factor, the levels of which at admission are associated with mortality in severe HF patients. Furthermore, inhibition of cDPP3 by Procizumab improved haemodynamics in a mouse model of HF. Our results suggest that DPP3 could be a new biomarker and biotarget for severe HF.

Novel Methods for the Quantification of Dipeptidyl Peptidase 3 (DPP3) Concentration and Activity in Human Blood Samples.

BACKGROUND: The ubiquitously expressed dipeptidyl peptidase 3 (DPP3) is involved in protein metabolism, blood pressure regulation, and pain modulation. These diverse functions of DPP3 are attributed to the degradation of bioactive peptides like angiotensin II. However, because of limitations in currently available assays for determination of active DPP3 in plasma, the exact physiological function of DPP3 and its role in the catabolism of bioactive peptides is understudied. Here, we developed 2 assays to specifically detect and quantify DPP3 protein and activity in plasma and validated DPP3 quantification in samples from critically ill patients. METHODS: Assay performance was evaluated in a sandwich-type luminometric immunoassay (LIA) and an enzyme capture activity assay (ECA). DPP3 plasma concentrations and activities were detected in a healthy, population-based cohort and in critically ill patients suffering from severe sepsis and septic shock. RESULTS: The DPP3-LIA and DPP3-ECA show an almost ideal correlation and very similar and robust performance characteristics. DPP3 activity is detectable in plasma of predominantly healthy subjects with a mean (±SD) of 58.6 (±20.5) U/L. Septic patients show significantly increased DPP3 plasma activity at hospital admission. DPP3 activities further increase in patients with more severe conditions and high mortality risk. CONCLUSION: We developed 2 highly specific assays for the detection of DPP3 in plasma. These assays allow the use of DPP3 as a biomarker for the severity of acute clinical conditions and will be of great value for future investigations of DPP3's role in bioactive peptide degradation in general and the angiotensin II pathway in specific.

A novel and highly efficient purification procedure for native human dipeptidyl peptidase 3 from human blood cell lysate.

Dipeptidyl amino-peptidase 3 (DPP3) is an aminopeptidase involved in peptide degradation, including hormone peptides as angiotensin II and enkephalins. DPP3 plasma activity increases in septic patients and correlates with mortality risk. However, the exact physiological role of DPP3 remains unclear and animal studies are necessary to reveal the function of DPP3 in vivo. To this demand, we developed a two-step purification procedure for isolation of native human DPP3 from blood cell lysate (BCL) that is suitable for in vivo applications. With the use of monoclonal antibodies coupled to beads in combination with an ion-exchange chromatography, we recovered 68% of human DPP3 activity from BCL with a purity of ≥ 95%. Purified human DPP3 was assayed for activity and protein concentration using recently published DPP3-activity- and immunoassays. Additionally, protein stability and storage in relevant buffers were tested. Our results provide a promising strategy for fast and efficient isolation of human DPP3. The purified human DPP3 represents the native state of DPP3, suitable for future in vivo applications to investigate the physiological role of DPP3 and its involvement in pathophysiological conditions.