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Biomedical subjects

I De Meester

Publications and source records attributed to I De Meester.

At least 19 recordsLinked to original sources
PubMed2006

Ischemia/reperfusion injury: The role of CD26/dipeptidyl-peptidase-IV-inhibition in lung transplantation.

UNLABELLED: CD26/Dipeptidyl peptidase (DPP) IV is an integral membrane protein of lymphocytes that modulates the activities of chemokines, interleukins, and neuropeptides. We investigated the effect of enzymatic DPP IV inhibition on ischemia/reperfusion injury after extended ischemia prior to transplantation. MATERIALS AND METHODS: We used a syngeneic rat (Lewis) orthotopic left lung transplantation model. In the control group (group I), donor lungs were flushed and preserved in Perfadex for 18 hours at 4 degrees C, then transplanted and reperfused for 2 hours. Group II donor lungs were perfused with and stored in Perfadex +25mol/L AB192 (bis(4-acetamidophenyl) 1-(S)-prolylpyrrolidine-2(R,S)-phosphonate), a small molecular weight DPP IV inhibitor. After 2-hour reperfusion, we measured blood gas, peak airway pressure, and thiobarbituric acid reactive substances. RESULTS: Grafts from group II versus group I showed a significantly increased oxygenation capacity (II: 298.4 +/- 87.6 mm Hg vs 120.9 +/- 48.0, P < .01), lower peak airway pressure (11.8 +/- 0.9 mm Hg vs 16.0 +/- 1.4, P < .01), and less lipid peroxidation (9.3 +/- 2.0 micromol/L vs 13.8 +/- 1.8, P < .01). CONCLUSION: Inhibition of intragraft DPP IV enzymatic activity significantly reduced ischemia/reperfusion-associated pulmonary injury, allowing for successful transplantation after 18 hours of ischemia.

Animals↗
PubMed2001

Kinetic study of the processing by dipeptidyl-peptidase IV/CD26 of neuropeptides involved in pancreatic insulin secretion.

Dipeptidyl-peptidase IV (DPPIV/CD26) metabolizes neuropeptides regulating insulin secretion. We studied the in vitro steady-state kinetics of DPPIV/CD26-mediated truncation of vasoactive intestinal peptide (VIP), pituitary adenylyl cyclase-activating peptide (PACAP27 and PACAP38), gastrin-releasing peptide (GRP) and neuropeptide Y (NPY). DPPIV/CD26 sequentially cleaves off two dipeptides of VIP, PACAP27, PACAP38 and GRP. GRP situates between the best DPPIV/CD26 substrates reported, comparable to NPY. Surprisingly, the C-terminal extension of PACAP38, distant from the scissile bond, improves both PACAP38 binding and turnover. Therefore, residues remote from the scissile bond can modulate DPPIV/CD26 substrate selectivity as well as residues flanking it.

Dipeptidyl Peptidase 4↗
PubMed2001

Kinetic investigation of chemokine truncation by CD26/dipeptidyl peptidase IV reveals a striking selectivity within the chemokine family.

Chemokines coordinate many aspects of leukocyte migration. As chemoattractants they play an important role in the innate and acquired immune response. There is good experimental evidence that N-terminal truncation by secreted or cell surface proteases is a way of modulating chemokine action. The localization of CD26/dipeptidyl peptidase IV on cell surfaces and in biological fluids, its primary specificity, and the type of naturally occurring truncated chemokines are consistent with such a function. We determined the steady-state catalytic parameters for a relevant selection of chemokines (CCL3b, CCL5, CCL11, CCL22, CXCL9, CXCL10, CXCL11, and CXCL12) previously reported to alter their chemotactic behavior due to CD26/dipeptidyl peptidase IV-catalyzed truncation. The results reveal a striking selectivity for stromal cell-derived factor-1alpha (CXCL12) and macrophage-derived chemokine (CCL22). The kinetic parameters support the hypothesis that CD26/dipeptidyl peptidase IV contributes to the degradation of certain chemokines in vivo. The data not only provide insight into the selectivity of the enzyme for specific chemokines, but they also contribute to the general understanding of CD26/dipeptidyl peptidase IV secondary substrate specificity.

Amino Acid Sequence↗
PubMed2001

Ectopeptidases in pathophysiology.

Ectopeptidases are transmembrane proteins present in a wide variety of tissues and cell types. Dysregulated expression of certain ectopeptidases in human malignancies suggests their value as clinical markers. Ectopeptidase interaction with agonistic antibodies or their inhibitors has revealed that these ectoenzymes are able to modulate bioactive peptide responses and to influence growth, apoptosis and differentiation, as well as adhesion and motility, all functions involved in normal and tumoral processes. There is evidence that ectopeptidase-mediated signal transduction frequently involves tyrosine phosphorylation. Combined analyses of gene organization and regulation of ectopeptidases by various physiological factors have provided insights into their structure-function relationships. Understanding the roles of ectopeptidases in pathophysiology may have implications in considering them as therapeutic targets.

Cell Transformation, Neoplastic↗
PubMed2001

Reference values for plasma dipeptidyl-peptidase IV activity and their association with other laboratory parameters.

In blood, the exopeptidase dipeptidyl-peptidase IV (DPPIV; EC 3.4.14.5) is predominantly present in a soluble form in plasma/serum and as an activation antigen on the membrane of lymphocytes (CD26). It modifies some important biologically active peptides (neuropeptides, chemokines), and a regulatory role for DPPIV/CD26 in immune and endocrine processes has been demonstrated. The aim of this study was to determine reference values for plasma/serum DPPIV activity and to study the association of this activity with a series of biochemical and hematological parameters and baseline characteristics such as age, gender, blood pressure and body mass index. We studied 481 healthy subjects aged between 19 and 61 years. The group consisted of 213 men and 268 women equally divided between the different categories of age. Among the women, 127 were taking hormone therapy (contraception/hormone replacement) and 141 were not. A multiple regression model shows that DPPIV activity decreases significantly with age. The activity in women is slightly lower than in men. We observed an important association with liver, muscle and lipid metabolism-related parameters. In this model, no significant contribution of body mass index, blood pressure or hormone therapy could be stated.

Adult↗
PubMed2001

Peptide truncation by dipeptidyl peptidase IV: a new pathway for drug discovery?

Membrane peptidases are a group of ectoenzymes with a broad functional repertoire. In protein metabolism, their importance is well known, especially in peptide degradation and amino acid scavenging at the intestinal and renal brush border. However, they also perform more subtle tasks; not only do they provide or extinguish signals by cleaving exterior peptide mediators, but they also may function as receptors or participate in signal transduction or in adhesion. Dipeptidyl peptidase IV (DPPIV), which is identical to the lymphocyte surface glycoprotein CD26, is unique among these peptidases because of its ability to liberate Xaa-Pro and less efficiently Xaa-Ala dipeptides from the N-terminus of regulatory peptides. It occurs in the plasma membrane as a homodimer with a total molecular mass of 22-240 KdA and the C-terminal domain probably forms on alpha/beta hydrolase fold. In addition to, but independent of its serine type catalytic activity, DPPIV binds closely to the soluble extracellular enzyme adenosine deaminase. The in vivo expression on epithelial, endothelial and lymphoid cells of DPPIV is compatible with a role as physiological regulator of a number of peptides that serve as biochemical reporters between and within the immune and neuroendocrine system. Surprisingly, not cytokines with a N-terminal Xaa-Pro motif, but a number of chemokines have recently been identified as substrates. Despite DPPIV mediates only a minimal N-terminal truncation, important alterations in chemokine activities and receptor specificitIes were observed in vitro together with modified inflammatory and antiviral responses. Most probably the great flexibility of the N-terminus of a number of chemokines facilitates the accessibIlity to the catalytic site of DPPIV. Other known substrates which are subject in vitro to receptor-specific changes induced by DPPIV truncation include neuropeptides such as substance P, peptidE YY and neuropeptide Y. On the other hand, DPPIV mediated cleavage of the N-terminal His-Ala or Tyr-Ala dipeptides from circulating incretin hormones like, glucagon-like peptides (GLP)-1 and -2, gastric inhibitory polypeptide (GIP), all members of the enteroglucagon/GRF superfamily, results in their biological inactivation in vitro and in vivo. Administration of specific DPPIV inhibitors closes this pathway of incretin degradation and greatly enhances insulin secretion. The improved glucose tolerance in several animal models for type II diabetes points to specific DPPIV inhibition as a pharmaceutical approach for type 2 diabetes drug development.

Alcohol Oxidoreductases↗
PubMed2000

Cleavage by CD26/dipeptidyl peptidase IV converts the chemokine LD78beta into a most efficient monocyte attractant and CCR1 agonist.

Chemokines are proinflammatory cytokines that play a role in leukocyte migration and activation. Recent reports showed that RANTES (regulated on activation normal T-cell expressed and secreted chemokine), eotaxin, macrophage-derived chemokine (MDC), and stromal cell-derived factor-1 (SDF-1) are NH(2)-terminally truncated by the lymphocyte surface glycoprotein and protease CD26/dipeptidyl peptidase IV (CD26/DPP IV). Removal of the NH(2)-terminal dipeptide resulted in impaired inflammatory properties of RANTES, eotaxin, MDC, and SDF-1. The potential CD26/DPP IV substrate macrophage inflammatory protein-1beta (MIP-1beta) and the related chemokine, LD78alpha (ie, one of the MIP-1alpha isoforms), were not affected by this protease. However, CD26/DPP IV cleaved LD78beta, a most potent CCR5 binding chemokine and inhibitor of macrophage tropic human immunodeficiency virus-1 (HIV-1) infection, into LD78beta(3-70). Naturally truncated LD78beta(3-70), but not truncated MIP-1beta, was recovered as an abundant chemokine form from peripheral blood mononuclear cells. In contrast to all other chemokines processed by CD26/DPP IV, LD78beta(3-70) had increased chemotactic activity in comparison to intact LD78beta. With a minimal effective concentration of 30 pmol/L, LD78beta(3-70) became the most efficient monocyte chemoattractant. LD78beta(3-70) retained its high capacity to induce an intracellular calcium increase in CCR5-transfected cells. Moreover, on CCR1 transfectants, truncated LD78beta(3-70) was 30-fold more potent than intact LD78beta. Thus, CD26/DPP IV can exert not only a negative but also a positive feedback during inflammation by increasing the specific activity of LD78beta. CD26/DPP IV-cleaved LD78beta(3-70) is the most potent CCR1 and CCR5 agonist that retains strong anti-HIV-1 activity, indicating the importance of the chemokine-protease interaction in normal and pathologic conditions. (Blood. 2000;96:1674-1680)

Animals↗
PubMed2000

Lowered serum dipeptidyl peptidase IV activity in patients with anorexia and bulimia nervosa.

The aim of this study was to examine whether anorexia nervosa and bulimia nervosa are accompanied by lower serum activity of dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5), a membrane-bound serine protease that catalyses the cleavage of dipeptides from the amino-terminus of oligo- and polypeptides. Substrates of DPP IV are, amongst others, neuroactive eptides, such as substance P, growth hormone releasing hormone, neuropeptide Y, and peptide YY. DPP IV activity was measured in the serum of 21 women with anorexia nervosa, 21 women with bulimia nervosa and 18 normal women. Serum DPP IV activity was significantly lower in patients with anorexia nervosa and bulimia nervosa than in the normal controls. In the total study group, there were significant and inverse relationships between serum DPP IV activity and the total scores on the Bulimic Investigatory Test, Edinburgh, the Eating Disorder Inventory (EDI) and the Hamilton Depression Rating Scale. In the total study group no significant correlations between DPP IV and age, body weight or body mass index could be found. It is concluded that lowered serum DPP IV activity takes part in the pathophysiology of anorexia and bulimia nervosa. It is hypothesised that a combined dysregulation of DPP IV and neuroactive peptides, which are substrates of DPP IV, e.g. neuropeptide Y and peptide YY, could be an integral component of eating disorders.

Adult↗
PubMed2000

Molecular characterization of dipeptidyl peptidase activity in serum: soluble CD26/dipeptidyl peptidase IV is responsible for the release of X-Pro dipeptides.

Dipeptidyl peptidase IV (DPPIV, EC 3.4.14.5) is a serine type protease with an important modulatory activity on a number of chemokines, neuropeptides and peptide hormones. It is also known as CD26 or adenosine deaminase (ADA; EC 3.5.4.4) binding protein. DPPIV has been demonstrated on the plasmamembranes of T cells and activated natural killer or B cells as well as on a number of endothelial and differentiated epithelial cells. A soluble form of CD26/DPPIV has been described in serum. Over the past few years, several related enzymes with similar dipeptidyl peptidase activity have been discovered, raising questions on the molecular origin(s) of serum dipeptidyl peptidase activity. Among them attractin, the human orthologue of the mouse mahogany protein, was postulated to be responsible for the majority of the DPPIV-like activity in serum. Using ADA-affinity chromatography, it is shown here that 95% of the serum dipeptidyl peptidase activity is associated with a protein with ADA-binding properties. The natural protein was purified in milligram quantities, allowing molecular characterization (N-terminal sequence, glycosylation type, CD-spectrum, pH and thermal stability) and comparison with CD26/DPPIV from other sources. The purified serum enzyme was confirmed as CD26.

Amino Acid Sequence↗
PubMed1999

CD26/dipeptidyl-peptidase IV down-regulates the eosinophil chemotactic potency, but not the anti-HIV activity of human eotaxin by affecting its interaction with CC chemokine receptor 3.

Chemokines attract and activate distinct sets of leukocytes. The CC chemokine eotaxin has been characterized as an important mediator in allergic reactions because it selectively attracts eosinophils, Th2 lymphocytes, and basophils. Human eotaxin has a penultimate proline, indicating that it might be a substrate for dipeptidyl-peptidase IV (CD26/DPP IV). In this study we demonstrate that eotaxin is efficiently cleaved by CD26/DPP IV and that the NH2-terminal truncation affects its biological activity. CD26/DPP IV-truncated eotaxin(3-74) showed reduced chemotactic activity for eosinophils and impaired binding and signaling properties through the CC chemokine receptor 3. Moreover, eotaxin(3-74) desensitized calcium signaling and inhibited chemotaxis toward intact eotaxin. In addition, HIV-2 infection of CC chemokine receptor 3-transfected cells was inhibited to a similar extent by eotaxin and eotaxin(3-74). Thus, CD26/DPP IV differently regulates the chemotactic and antiviral potencies of eotaxin by the removal of two NH2-terminal residues. This physiological processing may be an important down-regulatory mechanism, limiting eotaxin-mediated inflammatory responses.

Anti-HIV Agents↗
PubMed1999

Structure-activity relationship of diaryl phosphonate esters as potent irreversible dipeptidyl peptidase IV inhibitors.

The previously reported diphenyl 1-(S)-prolylpyrrolidine-2(R, S)-phosphonate (5) was used as a lead compound for the development of potent and irreversible inhibitors of dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5). The synthesis of a series of diaryl 1-(S)-prolylpyrrolidine-2(R,S)-phosphonates with different substituents on the aryl rings (hydroxyl, methoxy, acylamino, sulfonylamino, ureyl, methoxycarbonyl, and alkylaminocarbonyl) started from the corresponding phosphites. A good correlation was found between the electronic properties of the substituent and the inhibitory activity and stability. The most striking divergence of this correlation was the high potency combined with a high stability of the 4-acetylamino-substituted derivative 11e. This compound shows low cytotoxicity in human peripheral blood mononuclear cells and also has favorable properties in vivo. Therefore bis(4-acetamidophenyl) 1-(S)-prolylpyrrolidine-2(R,S)-phosphonate (11e) is considered as a major improvement and will be a highly valuable DPP IV inhibitor for further studies on the biological function of the enzyme and the therapeutic value of its inhibition.

Animals↗
PubMed1999

Truncation of macrophage-derived chemokine by CD26/ dipeptidyl-peptidase IV beyond its predicted cleavage site affects chemotactic activity and CC chemokine receptor 4 interaction.

The serine protease CD26/dipeptidyl-peptidase IV (CD26/DPP IV) and chemokines are known key players in immunological processes. Surprisingly, CD26/DPP IV not only removed the expected Gly1-Pro2 dipeptide from the NH2 terminus of macrophage-derived chemokine (MDC) but subsequently also the Tyr3-Gly4 dipeptide, generating MDC(5-69). This second cleavage after a Gly residue demonstrated that the substrate specificity of this protease is less restricted than anticipated. The unusual processing of MDC by CD26/DPP IV was confirmed on the synthetic peptides GPYGANMED (MDC(1-9)) and YGANMED (MDC(3-9)). Compared with intact MDC(1-69), CD26/DPP IV-processed MDC(5-69) had reduced chemotactic activity on lymphocytes and monocyte-derived dendritic cells, showed impaired mobilization of intracellular Ca2+ through CC chemokine receptor 4 (CCR4), and was unable to desensitize for MDC-induced Ca2+-responses in CCR4 transfectants. However, MDC(5-69) remained equally chemotactic as intact MDC(1-69) on monocytes. In contrast to the reduced binding to lymphocytes and CCR4 transfectants, MDC(5-69) retained its binding properties to monocytes and its anti-HIV-1 activity. Thus, NH2-terminal truncation of MDC by CD26/DPP IV has profound biological consequences and may be an important regulatory mechanism during the migration of Th2 lymphocytes and dendritic cells to germinal centers and to sites of inflammation.

Binding, Competitive↗
PubMed1999

Study of the enzymatic degradation of vasostatin I and II and their precursor chromogranin A by dipeptidyl peptidase IV using high-performance liquid chromatography/electrospray mass spectrometry.

The interaction of dipeptidyl peptidase IV with structurally related proteins differing in chain length, namely vasostatin I and II and their precursor protein chromogranin A, was examined using high-performance liquid chromatography in combination with electrospray mass spectrometry. Suitable analytical procedures were developed involving the use of reversed-phase high-performance liquid chromatography for purification of the enzymatic degradation products and a peptide mapping procedure for evaluating the enzymatic degradation of the large precursor protein chromogranin A. While vasostatin I was found to be a substrate for dipeptidyl peptidase IV, no N-terminal cleavage of Leu-Pro could be noted for chromogranin A. With respect to vasostatin II, N-terminal degradation was only observed after degradation in the C-terminal domain to proteins containing < or = 78 amino acids. The specificity of the N-terminal release of Leu-Pro was proved by addition of a DPP IV specific inhibitor.

Amino Acid Sequence↗
PubMed1999

CD26, let it cut or cut it down.

The costimulatory properties of CD26 have been studied extensively and significant progress has been made in unravelling the complex nature of this molecule. Here, we summarize recent findings on molecular and functional characteristics of CD26. We argue that a multidisciplinary approach might reveal the molecular events underlying the role of CD26 in HIV infection and immune, inflammatory and endocrine responses.

Chemokines↗
PubMed1999

Lower activity of serum peptidases in abstinent alcohol-dependent patients.

This study examines i) the activity of serum prolyl endopeptidase (PEP) and dipeptidlyl peptidase IV (DPP IV) in detoxified alcohol-dependent patients without liver disease versus normal controls, and ii) the relationships between serum DPP IV and PEP activity and the production of cytokines or cytokine receptors, such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), interferon-y (IFN-y), IL-1 receptor antagonist (IL-1RA), and IL-10, and granulocyte-macrophage colony stimulatory factor (GM-CSF). Alcohol-dependent patients had significantly lower serum PEP and DPP IV activity than normal controls. We found that 58.3% and 50.0% of the alcohol-dependent patients, respectively, had PEP and DPP IV activities, which were lower than the mean control values minus 2 SD. There were significant inverse correlations between lowered serum DPP IV and PEP activity and the increased production of IL-6, INF-gamma, IL-IRA, IL-10, and GM-CSF. These results show that lower serum DPP IV and PEP activity may be related to the pathophysiology of alcohol dependence.

Adult↗
PubMed1999

Constitutive expression of CD26/dipeptidylpeptidase IV on peripheral blood B lymphocytes of patients with B chronic lymphocytic leukaemia.

We have investigated the expression of the ectoenzyme dipeptidylpeptidase IV (DPP IV)/CD26 on lymphocytes obtained from patients with B chronic lymphocytic leukaemia (B-CLL) and compared it with healthy subjects. Using two-colour immunofluorescence analysis with CD26 and CD20 or CD23 monoclonal antibodies, CD26 was found undetectable on peripheral resting B-cells (CD20+ CD23-) from normal donors whereas it was expressed on B-cells activated in vitro with interleukin (IL)-4 and Staphylococcus aureus strain cowan I (CD20+ CD23+). The expression of CD26 on leukaemic B-cells (CD20+ CD23+) was clearly induced in 22 out of 25 patients examined. Consequently, induced levels of CD26 cell surface expression on either normal activated and malignant B-cells coincided with the enhancement of DPP IV activity detected on the surface of these cells. Reverse transcription polymerase chain reaction analyses showed that the transcript levels of the CD26 gene was higher in normal activated B-cells and B-CLL cells than in resting B-cells, suggesting that CD26 was expressed at the level of transcriptional activation. These observations provide evidence of the abnormal expression of DPPIV/CD26 in B-CLL which, therefore, may be considered as a novel marker for B-CLL. Further investigation in relation to CD26 expression and other B malignancies needs to be defined.

Adult↗