On Endogenous Angiotensin II Antagonism in Hypertension: The Role of Dipeptidyl Peptidase III

Dipeptidylamino-tripeptidylcarboxypeptidase NEMP3 and DPP3 (DPP III) are the same protein

Earlier it was shown that a group of extracellular low-specific metallopeptidases is present in the mammalian brain Kropotova and Mosevitsky (2016) [1]. These enzymes are weakly connected to the axonal ends of neurons. They were named Neuron bound Extracellular MetalloPeptidases (NEMP). The enzyme named NEMP3 turned out to be a unique exopeptidase that exhibits two activities: it removes the dipeptide from the N-end of the peptide, and it can also remove the tripeptide from the C-end of the peptide. Therefore, NEMP3 possesses the activities of dipeptidylaminopeptidase and of tripeptidylcarboxypeptidase. Mass spectrometry has revealed a homology of NEMP3 with DPP3 (DPP III, EC3.4.14.4), known as cytosolic dipeptidylaminopeptidase. We isolated DPP3 from rat and bovine liver and brain by the procedures used for this purpose by other authors. The effect of DPP3 on test peptides is the same as that of NEMP3. In particular, all DPP3 samples delete the tripeptide (AKF) from the C-end of the test peptide blocked at the N-end. The data obtained show that NEMP3 and DPP3 are the same protein (enzyme). Thus, DPP3 has two exopeptidase activities: the previously known activity of dipeptidylaminopeptidase and the activity of tripeptidylcarboxypeptidase discovered in this study. Another discovery is the extracellular activity of DPP 3 in the mammalian brain near synapses, which controls neuropeptides. DPP3 is involved in various processes, but in many cases its role remains to be clarified. The results obtained in this study will be useful for solving these questions.

In-hospital mortality and organ failure after open and endovascular thoraco-abdominal aortic surgery can be predicted by increased levels of circulating dipeptidyl peptidase 3

OBJECTIVES

Endovascular and open thoraco-abdominal aortic aneurysm (TAAA) repair is associated with specific complications. Circulating dipeptidyl peptidase 3 (cDPP3) is a novel biomarker that shows a strong association with organ failure which has not been assessed in surgical settings. Therefore, the objective of this study was to assess the prognostic capabilities of cDPP3 for predicting patient survival and organ failure following open and endovascular TAAA repair.

METHODS

Thirty-three patients undergoing TAAA repair were assessed in this prospective observational single-centre study. cDPP3 levels were serially measured perioperatively until 72 h after admission to the intensive care unit (ICU). In-hospital mortality and any organ failure were the clinical end points.

RESULTS

Postoperative organ failure was detected in 17 patients (51.5%), and 6 patients died after surgery (18.2%). At 12 h after admission to the ICU, cDPP3 levels were significantly increased in patients who died or developed organ failure (P < 0.001). cDPP3 levels after surgery demonstrated a remarkable predictive accuracy for in-hospital mortality [12 h area under the receiver operating characteristic curve (AUC): 0.907 (P < 0.001), 24 h AUC: 0.815 (P = 0.016), 48 h AUC: 0.914 (P = 0.003)] and the development of organ failure [12 h AUC: 0.882 (P < 0.001), 24 h AUC: 0.850 (P < 0.001), 48 h AUC: 0.846 (P < 0.001)]. Additionally, a significant correlation between cDPP3, the sequential organ failure assessment score and procalcitonin, C-reactive protein and interleukin-6 levels (P < 0.001, P < 0.001, P = 0.011, P = 0.007, respectively) based on all available measurements and time points was observed.

CONCLUSIONS

The present findings highlight the role of cDPP3 as an early, highly specific postoperative biomarker for prediction of in-hospital mortality and organ failure after TAAA repair.

Targeting Endothelial Dysfunction in Eight Extreme-Critically Ill Patients with COVID-19 Using the Anti-Adrenomedullin Antibody Adrecizumab (HAM8101)

Recently, the stabilization of the endothelium has been explicitly identified as a therapeutic goal in coronavirus disease 2019 (COVID-19). Adrecizumab (HAM8101) is a first-in-class humanized monoclonal anti-Adrenomedullin (anti-ADM) antibody, targeting the sepsis- and inflammation-based vascular and capillary leakage. Within a "treatment on a named-patient basis" approach, Adrecizumab was administered to eight extreme-critically ill COVID-19 patients with acute respiratory distress syndrome (ARDS). The patients received a single dose of Adrecizumab, which was administered between 1 and 3 days after the initiation of mechanical ventilation. The SOFA (median 12.5) and SAPS-II (median 39) scores clearly documented the population at highest risk. Moreover, six of the patients suffered from acute renal failure, of whom five needed renal replacement therapy. The length of follow-up ranged between 13 and 27 days. Following the Adrecizumab administration, one patient in the low-dose group died at day 4 due to fulminant pulmonary embolism, while four were in stable condition, and three were discharged from the intensive care unit (ICU). Within 12 days, the SOFA score, as well as the disease severity score (range 0-16, mirroring critical resources in the ICU, with higher scores indicating more severe illness), decreased in five out of the seven surviving patients (in all high-dose patients). The PaO2/FiO2 increased within 12 days, while the inflammatory parameters C-reactive protein, procalcitonin, and interleukin-6 decreased. Importantly, the mortality was lower than expected and calculated by the SOFA score. In conclusion, in this preliminary uncontrolled case series of eight shock patients with life-threatening COVID-19 and ARDS, the administration of Adrecizumab was followed by a favorable outcome. Although the non-controlled design and the small sample size preclude any definitive statement about the potential efficacy of Adrecizumab in critically ill COVID-19 patients, the results of this case series are encouraging.

Perspectives on the Potential Benefits of Antihypertensive Peptides towards Metabolic Syndrome

In addition to the regulation of blood pressure, the renin-angiotensin system (RAS) also plays a key role in the onset and development of insulin resistance, which is central to metabolic syndrome (MetS). Due to the interplay between RAS and insulin resistance, antihypertensive compounds may exert beneficial effects in the management of MetS. Food-derived bioactive peptides with RAS blocking properties can potentially improve adipose tissue dysfunction, glucose intolerance, and insulin resistance involved in the pathogenesis of MetS. This review discusses the pathophysiology of hypertension and the association between RAS and pathogenesis of the MetS. The effects of bioactive peptides with RAS modulating effects on other components of the MetS are discussed. While the in vivo reports on the effectiveness of antihypertensive peptides against MetS are encouraging, the exact mechanism by which these peptides infer their effects on glucose and lipid handling is mostly unknown. Therefore, careful design of experiments along with standardized physiological models to study the effect of antihypertensive peptides on insulin resistance and obesity could help to clarify this relationship.

The vasoprotective axes of the renin-angiotensin system: Physiological relevance and therapeutic implications in cardiovascular, hypertensive and kidney diseases

The renin-angiotensin system (RAS) is undisputedly one of the most prominent endocrine (tissue-to-tissue), paracrine (cell-to-cell) and intracrine (intracellular/nuclear) vasoactive systems in the physiological regulation of neural, cardiovascular, blood pressure, and kidney function. The importance of the RAS in the development and pathogenesis of cardiovascular, hypertensive and kidney diseases has now been firmly established in clinical trials and practice using renin inhibitors, angiotensin-converting enzyme (ACE) inhibitors, type 1 (AT₁) angiotensin II (ANG II) receptor blockers (ARBs), or aldosterone receptor antagonists as major therapeutic drugs. The major mechanisms of actions for these RAS inhibitors or receptor blockers are mediated primarily by blocking the detrimental effects of the classic angiotensinogen/renin/ACE/ANG II/AT₁/aldosterone axis. However, the RAS has expanded from this classic axis to include several other complex biochemical and physiological axes, which are derived from the metabolism of this classic axis. Currently, at least five axes of the RAS have been described, with each having its key substrate, enzyme, effector peptide, receptor, and/or downstream signaling pathways. These include the classic angiotensinogen/renin/ACE/ANG II/AT₁ receptor, the ANG II/APA/ANG III/AT₂/NO/cGMP, the ANG I/ANG II/ACE2/ANG (1-7)/Mas receptor, the prorenin/renin/prorenin receptor (PRR or Atp6ap2)/MAP kinases ERK1/2/V-ATPase, and the ANG III/APN/ANG IV/IRAP/AT₄ receptor axes. Since the roles and therapeutic implications of the classic angiotensinogen/renin/ACE/ANG II/AT₁ receptor axis have been extensively reviewed, this article will focus primarily on reviewing the roles and therapeutic implications of the vasoprotective axes of the RAS in cardiovascular, hypertensive and kidney diseases.