Dirk Hendriks - Academia.edu (original) (raw)

Papers by Dirk Hendriks

Pharmaceutics, 2021

Statins (hydroxymethyl-glutaryl-CoA-reductase inhibitors) lower procarboxypeptidase U (proCPU, TA... more Statins (hydroxymethyl-glutaryl-CoA-reductase inhibitors) lower procarboxypeptidase U (proCPU, TAFI, proCPB2). However, it is challenging to prove whether this is a lipid or non-lipid-related pleiotropic effect, since statin treatment decreases cholesterol levels in humans. In apolipoprotein E-deficient mice with a heterozygous mutation in the fibrillin-1 gene (ApoE−/−Fbn1C1039G+/−), a model of advanced atherosclerosis, statins do not lower cholesterol. Consequently, studying cholesterol-independent effects of statins can be achieved more straightforwardly in these mice. Female ApoE −/−Fbn1C1039G+/− mice were fed a Western diet (WD). At week 10 of WD, mice were divided into a WD group (receiving WD only) and a WD + atorvastatin group (receiving 10 mg/kg/day atorvastatin +WD) group. After 15 weeks, blood was collected from the retro-orbital plexus, and the mice were sacrificed. Total plasma cholesterol and C-reactive protein (CRP) were measured with commercially available kits. Plasm...

Journal of Thrombosis and Haemostasis, 2020

This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Journal of Biological Chemistry, 1994

A novel basic carboxypeptidase clearly different from carboxypeptidase N has been isolated from h... more A novel basic carboxypeptidase clearly different from carboxypeptidase N has been isolated from human plasma. It circulates as an enzymatically inactive precursor enzyme bound to plasminogen. During fibrinolysis, it can be converted to its active form, carboxypeptidase U, through the action of plasmin. The active enzyme has an apparent molecular weight of 63,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It hydrolyzes the synthetic peptides hippuryl-L-arginine and hippuryl-L-lysine but, in contrast to other human basic carboxypeptidases, has only a limited esterase activity. After its activation, carboxypeptidase U tends to be very unstable. The role of basic carboxypeptidases, i.e. enzymes that cleave COOH-terminal basic amino acids lysine and arginine, has gained renewed interest in medical science since it became evident that this type of enzyme can be involved in peptide hormone maturation. Most peptide hormones are initially synthesized as precursor proteins that are frequently cleaved at pairs of basic amino acids such as Arg-Arg or Lys-Arg, and carboxypeptidase B-like enzymes working in concert can generate the correct product from some of these precursors (1). In the plasma compartment, this family of enzymes is represented by carboxypeptidase N (arginine carboxypeptidase, kininase I, anaphylatoxin inactivator, serum carboxypeptidase B, EC 3.4.17.31, which is synthesized in the liver (2) and circulates in plasma as an M, 280,000 tetrameric complex. It is composed of two identical high molecular weight subunits (M, 83,0001, which are heavily glycosylated and lack enzymatic activity, and two identical low molecular weight subunits (M, 55,000), which lack carbohydrate but contain the active center (3,4). The high molecular weight subunit functions to stabilize the active subunit at body temperature and keep it in the circulation (4). Physiologically interesting substrates for this enzyme are the kinins bradykinin and kallidin (2), the anaphylatoxins C,, and C,, (5,6), the fibrinopeptides 6Aand 6D (7), the creatine kinase MM isoenzyme (8, 9), the hexapeptide enkephalins (lo), and the atrial natriuretic peptide atriopeptin I1 (11). Its most likely physiological function is to protect the organism from the actions of potent peptides that may escape from tissues or be released in the circulation. Recently, we have described the important differences in arginine carboxypeptidase activities between fresh serum and older serum or heparinized plasma, depending on the substrate * This work was supported in part by the Belgian National Fund for Scientific Research, Brussels, Belgium and the Belgian Program on Interuniversity Poles of Attraction. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "aduertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Clinical Chemistry, 1999

Background: Procarboxypeptidase U (proCPU) is a novel proenzyme found in human plasma. The active... more Background: Procarboxypeptidase U (proCPU) is a novel proenzyme found in human plasma. The active form, carboxypeptidase U (CPU; EC 3.4.17.20), retards the rate of fibrinolysis through its ability to cleave C-terminal lysine residues on fibrin partially degraded by plasmin. This reduces the number of high-affinity plasminogen-binding sites on fibrin.Methods: We developed an assay to determine the proCPU concentration in human plasma. The assay involved quantitative conversion of proCPU to active CPU by thrombin-thrombomodulin, a very efficient activator of proCPU, followed by determination of the enzymatic activity of CPU with the substrate hippuryl-l-arginine, using an HPLC-assisted determination of the released hippuric acid. Using this method, we established a reference interval based on 490 healthy individuals.Results: The mean proCPU concentration, determined after activation of the zymogen in diluted plasma and expressed as CPU activity, was 964 U/L, with a SD of 155 U/L. The ...

Journal of Thrombosis and Haemostasis, 2018

B2, activated thrombin-activatable fibrinolysis inhibitor) inhibition stimulates the fibrinolytic... more B2, activated thrombin-activatable fibrinolysis inhibitor) inhibition stimulates the fibrinolytic rate in different in vitro models.

Journal of Thrombosis and Haemostasis, 2019

Translational stroke research, Apr 26, 2016

Dipeptidyl peptidase IV (DPPIV) inhibition may be a promising therapeutic strategy for acute stro... more Dipeptidyl peptidase IV (DPPIV) inhibition may be a promising therapeutic strategy for acute stroke treatment, given its potential to prolong the biological half-life of neuroprotective substrates. A related protease, fibroblast activation protein (FAP), was recently shown to inactivate the same substrates. Therefore, it should also be investigated as a potential target in stroke. The study aimed to investigate whether stroke severity and outcome correlate with DPPIV and FAP activities and their kinetics shortly after acute ischemic stroke. DPPIV and FAP activities were analyzed in the serum of 50 hyperacute stroke patients at admission, 1 day, 3 days, and 7 days after stroke onset and in 50 age-matched healthy controls. This was done as part of the Middelheim's Interdisciplinary Stroke Study. DPPIV activity tended to increase shortly after stroke compared to the control population. DPPIV and FAP activities steadily decreased in the first week after stroke onset. Higher infarct ...

Neurochemical research, 2015

Prolyl carboxypeptidase (PRCP) is an enzyme associated with cerebrovascular risk factors such as ... more Prolyl carboxypeptidase (PRCP) is an enzyme associated with cerebrovascular risk factors such as hypertension, diabetes mellitus, obesity and hyperlipidemia. We aim to evaluate the relation between serum PRCP activity and severity, evolution and outcome of acute ischemic stroke. We used a specific RP-HPLC activity assay to measure PRCP activity in serum of 50 stroke patients at admission, and at 24 h, 72 h and 7 days after stroke onset to assess correlations with stroke severity based on the National Institutes of Health Stroke scale score (NIHSS), infarct volume on brain MRI scan, stroke outcome based on the modified Rankin scale (mRS) and mortality at 3 months after stroke. The average PRCP activity in serum decreased significantly the first 24 h after stroke onset and returned to baseline values at day 7. High NIHSS scores and infarct volumes at admission were related with a more pronounced decrease of PRCP in the first 24 h after stroke (ΔPRCP24, r = 0.31, P < 0.05; r = 0.30,...

Urologia Internationalis, 1987

Fibrinolysis and Proteolysis, 1997

Journal of Histochemistry & Cytochemistry, 2012

Although the kidney generally has been regarded as an excellent source of carboxypeptidase M (CPM... more Although the kidney generally has been regarded as an excellent source of carboxypeptidase M (CPM), little is known about its renal-specific expression level and distribution. This study provides a detailed localization of CPM in healthy and diseased human kidneys. The results indicate a broad distribution of CPM along the renal tubular structures in the healthy kidney. CPM was identified at the parietal epithelium beneath the Bowman's basement membrane and in glomerular mesangial cells. Capillaries, podocytes, and most interstitial cells were CPM negative. Tumor cells of renal cell carcinoma subtypes lose CPM expression upon dedifferentiation. Tissue microarray analysis demonstrated a correlation between low CPM expression and tumor cell type. CPM staining was intense on phagocytotic tumor-associated macrophages. Immunoreactive CPM was also detected in the tumor-associated vasculature. The absence of CPM in normal renal blood vessels points toward a role for CPM in angiogenesis. Coexistence of CPM and the epidermal growth factor receptor (EGFR) was detected in papillary renal cell carcinoma. However, the different subcellular localization of CPM and EGFR argues against an interaction between these h proteins. The description of the distribution of CPM in human kidney forms the foundation for further study of the (patho)physiological activities of CPM in the kidney.

Clinical Chemistry and Laboratory Medicine, 1989

Arginine carboxypeptidase activity in human serum, measured with the hippuryl-L-arginine substrat... more Arginine carboxypeptidase activity in human serum, measured with the hippuryl-L-arginine substrate, is about three times higher than in human plasma. This difference is much smaller when hippuryl-Llysine is used äs the Substrate. When fresh serum is incubated at 30 °C, the arginine and lysine carboxypeptidase activity decreases until a stable activity, close to the plasma activity, is reached. This stable carboxypeptidase activity is attributed to carboxypeptidase N. The unstable carboxypeptidase differs from carboxypeptidase N in pH-optimum, esterase activity, Substrate specifity, Co 2+-activation and dithiotreitol activation. Blood cells are not responsible for the release of this enzyme during coagulation. No activator of carboxypeptidase N was detectable in human serum.-exchange chromatography on DEAE-cellulose confirms the presence of two different molecular forms of arginine carboxypeptidase activity.

Clinical Chemistry and Laboratory Medicine, 1986

Clinical and Applied Thrombosis/Hemostasis, 2001

In 1988, Hendricks et al. first reported on the presence of carboxypeptidase U (U refers to the u... more In 1988, Hendricks et al. first reported on the presence of carboxypeptidase U (U refers to the unstable nature of the enzyme) in human serum. One decade later, the importance of carboxypeptidase U (CPU) in the regulation of fibrin clot dissolution is well documented. CPU circulates in plasma as an inactive zymogen, proCPU, that is converted to its active form during coagulation and fibrinolysis. CPU cleaves off C-terminal lysine residues exposed on fibrin partially degraded by the action of plasmin. Because these C-terminal lysine residues are important for upregulating the fibrinolytic rate, CPU thus slows down fibrinolysis.

Clinica Chimica Acta, 1992

The membrane-bound dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5) has been purified 5,400-fold fro... more The membrane-bound dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5) has been purified 5,400-fold from human peripheral blood mononuclear cells. The purification procedure included detergent solubilization and successive chromatography on DEAE Sepharose Fast Flow, Con A Sepharose, Cu2+ loaded metal-chelating Sepharose, Sephacryl S-300 High Resolution and Q Sepharose Hiload. The molecular mass of the native, detergent solubilized enzyme estimated by gel filtration was 264.kDa. Chromatofocusing indicated a pI of approximately 5.0. The pI optimum was 8.7. The enzymatic activity of the purified preparation was irreversibly inhibited by N-(H-Phe-Pro)-O-(4-nitrobenzoyl)hydroxylamine hydrochloride in the micromolar range. The binding of purified DPP IV to CD26 monoclonal antibodies confirmed the identity between CD26 and dipeptidyl peptidase IV. The purification and characterization of lymphocytic dipeptidyl peptidase IV is of great value for the identification of its natural substrates and for the study of its physiological significance in the T-lymphocyte function.

Clinica Chimica Acta, 2004

Carboxypeptidase U (EC 3.4.17.20, TAFIa) is a new member of the metallocarboxypeptidase family ci... more Carboxypeptidase U (EC 3.4.17.20, TAFIa) is a new member of the metallocarboxypeptidase family circulating in human plasma as a zymogen. It is activated during coagulation and is considered as an important player in the regulation of fibrinolysis. Heterologous expression of human plasma procarboxypeptidase U (proCPU, TAFI) was obtained in mammalian cells (C127 and DON) and in insect cells (Sf21 and H5 cells). Conditioned media were purified by cation-exchange chromatography and plasminogen affinity chromatography to yield an essentially pure protein. All systems gave high expression levels (6-20 mg/l). Due to differences in glycosylation of the activation peptide, the recombinant variants of proCPU migrated differently on SDS-PAGE (52-65 kDa). However, after activation, all active recombinant enzymes migrated at 35 kDa, similar to native CPU and no evidence for post-translational modification of the catalytic domains could be detected. For the mammalian cell produced variants, activation was more efficient after desialylation. After activation, CPU showed low solubility (0.2 mg/ml) but was inhibited similarly as native CPU. Mammalian cell systems were the most efficient for the production of human plasma recombinant proCPU. The obtained zymogen differs with respect to the extent and the heterogeneity of glycosylation but, after activation, the experiments did not reveal any alteration between the recombinant and native protein.

Arteriosclerosis, Thrombosis, and Vascular Biology, 2003

Objective— A Thr/Ile polymorphism at position 325 in the coding region of proCPU has been reporte... more Objective— A Thr/Ile polymorphism at position 325 in the coding region of proCPU has been reported. Immunological assays, fully characterized (including genotype dependency), are required for the quantitation of proCPU levels. Methods and Results— We have generated a panel of monoclonal antibodies against human, plasma-derived proCPU. Two combinations exhibiting distinct reactivities were selected for measurement of proCPU in plasma. T12D11/T28G6-HRP yielded values of 10.1±3.1 μg/mL (mean±SD, n=86; normal donors), and T32F6/T9G12-HRP yielded values of 5.4±3.0 μg/mL. Grouping according to the 325 genotype demonstrated that T12D11/T28G6-HRP was independent to this polymorphism whereas T32F6/T9G12-HRP revealed a complete lack of reactivity with the Ile/Ile genotype (ie, 0.0±0.0, 4.2±1.7, and 7.3±2.9 μg/mL for the Ile/Ile, Ile/Thr, and Thr/Thr isoforms, respectively). Commercially available antigen assays appeared to be partially dependent on the 325 genotype (eg, 44±8.9% and 100±30% fo...

Applied Biochemistry and Biotechnology, 1994

Carboxypeptidase N-Sepharose was prepared by covalent immobilization of purified human plasma car... more Carboxypeptidase N-Sepharose was prepared by covalent immobilization of purified human plasma carboxypeptidase N. More than 98% of the carboxypeptidase N was immobilized; 42% of the applied activity can be detected on the support. The column has excellent capabilities to quantitatively remove carboxy-terminal basic amino acids from peptides, as is demonstrated using the synthetic peptide substrate hippuryl-L-arginine and the nonapeptide bradykinin, and remains stable for several months. In contrast with apocarboxypeptidase B-Sepharose, apocarboxypeptidase N-Sepharose poorly binds its substrates.

Clinica Chimica Acta, Mar 1, 2008