Ann Gils

The pro- or antiangiogenic effect of plasminogen activator inhibitor 1 is dose dependent

Plasminogen activator inhibitor 1 (PAI‐1) is believed to control proteolytic activity and cell migration during angiogenesis. We previously demonstrated in vivo that this inhibitor is necessary for optimal tumor invasion and vascularization. We also showed that PAI‐1 angiogenic activity is associated with its control of plasminogen activation but not with the regulation of cell‐matrix interaction. To dissect the role of the various components of the plasminogen activation system during angiogenesis, we have adapted the aortic ring assay to use vessels from gene‐inactivated mice. The single deficiency of tPA, uPA, or uPAR, as well as combined deficiencies of uPA and tPA, did not dramatically affect microvessel formation. Deficiency of plasminogen delayed microves‐sel outgrowth. Lack of PAI‐1 completely abolished angio‐genesis, demonstrating its importance in the control of plasmin‐mediated proteolysis. Microvessel outgrowth from PAI‐1‐/‐ aortic rings could be restored by adding exogenous PAI‐1 (wild‐type serum or purified recombi‐nant PAI‐1). Addition of recombinant PAI‐1 led to a bell‐shaped angiogenic response clearly showing that PAI‐1 is proangiogenic at physiological concentrations and antiangiogenic at higher levels. Using specific PAI‐1 mutants, we could demonstrate that PAI‐1 promotes an‐giogenesis at physiological (nanomolar) concentrations through its antiproteolytic activity rather than by interacting with vitronectin.—Devy, L., Blacher, S., Grignet‐Debrus, C., Bajou, K., Masson, V., Gerard, R. D., Gils, A., Carmeliet, G., Carmeliet, P., Declerck, P. J., Noèl, A., Foidart, J. M. The pro‐ or antiangiogenic effect of plasminogen activator inhibitor 1 is dose dependent. FASEB J. 16, 147–154 (2002)

Host-derived plasminogen activator inhibitor-1 (PAI-1) concentration is critical for in vivo tumoral angiogenesis and growth

Plasminogen activator inhibitor type 1 (PAI-1) plays a key role in tumor progression and is believed to control proteolytic activity and cell migration during angiogenesis. We report here that host PAI-1, at physiological concentration, promotes in vivo tumor invasion and angiogenesis. In sharp contrast, inhibition of tumor vascularization was observed when PAI-1 was produced at supraphysiologic levels, either by host cells (transgenic mice overexpressing PAI-1) or by tumor cells (after transfection with murine PAI-1 cDNA). This study provides for the first time in vivo evidence for a dose-dependent effect of PAI-1 on tumor angiogenesis. Of great interest is the finding that PAI-1 produced by tumor cells, even at high concentration, did not overcome the absence of PAI-1 in the host, emphasizing the importance of the cellular source of PAI-1.

The relationship between infliximab concentrations, antibodies to infliximab and disease activity in Crohn's disease

Objective Although low infliximab trough concentrations and antibodies to infliximab (ATI) are associated with poor outcomes in patients with Crohns disease (CD), the clinical relevance of ATI in patients with adequate infliximab concentrations is uncertain. We evaluated this question using an assay sensitive for identification of ATI in the presence of infliximab. Design In an observational study, 1487 trough serum samples from 483 patients with CD who participated in four clinical studies of maintenance infliximab therapy were analysed using a fluid phase mobility shift assay. Infliximab and ATI concentrations most discriminant for remission, defined as a C-reactive protein concentration of ≤5 mg/L, were determined by receiver operating characteristic curves. A multivariable regression model evaluated these factors as independent predictors of remission. Results Based upon analysis of 1487 samples, 77.1% of patients had detectable and 22.9% had undetectable infliximab concentrations, of which 9.5% and 71.8%, respectively, were positive for ATI. An infliximab concentration of >2.79 μg/mL (area under the curve (AUC)=0.681; 95% CI 0.632 to 0.731) and ATI concentration of <3.15 U/mL (AUC=0.632; 95% CI 0.589 to 0.676) were associated with remission. Multivariable analysis showed that concentrations of both infliximab trough (OR 1.8; 95% CI 1.3 to 2.5; p<0.001) and ATI (OR 0.57; 95% CI 0.39 to 0.81; p=0.002) were independent predictors of remission. Conclusions The development of ATI increases the probability of active disease even at low concentrations and in the presence of a therapeutic concentration of drug during infliximab maintenance therapy. Evaluation of strategies to prevent ATI formation, including therapeutic drug monitoring with selective infliximab dose intensification, is needed.

Detection of infliximab levels and anti-infliximab antibodies: a comparison of three different assays

Formation of antibodies to infliximab (ATI) inversely correlates with functional drug levels and clinical outcome. Comparison of drug levels and anti‐drug antibody monitoring is hampered by lack of standardisation.

Plasminogen activator inhibitor-1.

Plasminogen activator inhibitor-1 (PAI-1) is an important component of the plasminogen/plasmin system as it is the main inhibitor of tissue-type and urokinase-type plasminogen activator. Consequently, PAI-1 plays an important role in cardiovascular diseases (mainly through inhibition of t-PA) and in cell migration and tumor development (mainly through inhibition of u-PA). As a member of the serpin superfamily, PAI-1 shares important structural properties with other serpins. However, PAI-1 also exhibits unique conformational and functional properties. The current paper provides an overview of the knowledge on PAI-1 gathered since its discovery two decades ago. We are discussing (a) its structural properties and their subsequent association with the functional properties, (b) its role in a wide variety of (patho)physiological processes and (c) a number of strategies to interfere with its functional properties eventually aiming at pharmacological modulation of this risk factor.

Development of a Genotype 325–Specific proCPU/TAFI ELISA

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 &mgr;g/mL (mean±SD, n=86; normal donors), and T32F6/T9G12-HRP yielded values of 5.4±3.0 &mgr;g/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 &mgr;g/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% for the Ile/Ile and Thr/Thr isoforms, respectively). Conclusions—Our data demonstrate that great care should be taken when evaluating proCPU antigen values as a putative causative agent or as a diagnostic risk marker for cardiovascular events.

Switch to adalimumab in patients with Crohn's disease controlled by maintenance infliximab: prospective randomised SWITCH trial

Background Elective switching between anti-tumour necrosis factor (TNF) agents not necessarily dictated by efficacy or tolerability occurs in clinical practice. A study was undertaken to evaluate prospectively the impact of elective switching of patients with Crohns disease well controlled with intravenous infliximab to subcutaneous adalimumab in a controlled trial. Methods An open-label randomised single-centre trial recruited 73 patients with ongoing response to at least 6 months of scheduled maintenance infliximab. Patients were randomised to continue intravenous 5 mg/kg infliximab or to switch to subcutaneous adalimumab 80 mg at baseline followed by 40 mg every other week for 1 year. Dose optimisation was allowed for intermittent flares, and patients with loss of response or intolerance could cross over to the alternative treatment group. Tolerability, patient preference and efficacy of both treatment options were the primary outcomes. Results Dose optimisation or interruption of treatment occurred in 17/36 patients (47%) in the adalimumab group and in 6/37 patients (16%) in the infliximab group (p=0.006). One patient interrupted infliximab treatment and 10 patients interrupted adalimumab treatment (p=0.003), mostly for loss of tolerance. Overall, patients preferred adalimumab treatment. All five serious adverse events were related to complicated Crohns disease and occurred in patients randomised to adalimumab. Injection site reactions were more frequent than infusion reactions (8 vs 1, p=0.01), but only the latter caused cessation of further dosing. Anti-TNF serum levels were stable throughout the 1-year period in both groups. Conclusion Elective switching from infliximab to adalimumab is associated with loss of tolerance and loss of efficacy within 1 year. Adherence to the first anti-TNF agent is recommended.

The structural basis for the pathophysiological relevance of PAI-1 in cardiovascular diseases and the development of potential PAI-1 inhibitors

Plasminogen activator inhibitor-I (PAI-I) is an important component of the plasminogen/plasmin system as it is the main inhibitor of tissue-type and urokinase-type plasminogen activator. Consequently, PAI-I plays an important role in cardiovascular diseases (mainly through inhibition of t-PA), and in cell migration and tumor development (mainly through inhibition of u-PA and interaction with vitronectin). As a member of the serpin superfamily, PAI-I shares important structural properties with other serpins. However, PAI-I also exhibits unique conformational and functional properties. The current review provides an overview of the knowledge on PAI-I gathered since its discovery two decades ago. We discuss (a) its structural properties of the protein and their subsequent relation to functional activities, (b) its role in a wide variety of (patho)physiological processes and (c) a number of strategies to interfere with its functional properties eventually aiming at pharmacological modulation of this risk factor.

Three decades of research on plasminogen activator inhibitor-1: a multifaceted serpin.

Plasminogen activator inhibitor 1 (PAI-1) is the main inhibitor of tissue-type (t-PA) and urokinase-type (u-PA) plasminogen activator and therefore plays an important role in the plasminogen-plasmin system. PAI-1 is involved in a variety of cardiovascular diseases (mainly through inhibition of t-PA) as well as in cell migration and tumor development (mainly through inhibition of u-PA and interaction with vitronectin). PAI-1 is a unique member of the serpin superfamily, exhibiting particular unique conformational and functional properties. Because of its involvement in various biologic and pathophysiologic processes, PAI-1 has been the subject of many studies, including extensive structural investigations, in vitro cell biologic studies, in vivo animal studies, and epidemiologic studies. The review provides an overview on the current knowledge on PAI-1.

The Biochemistry, Physiology and Pathological roles of PAI-1 and the requirements for PAI-1 inhibition in vivo

Plasminogen activator inhibitor-1 (PAI-1) is the primary physiological inhibitor of both tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) and is consequently one the most important inhibitors of the plasminogen/plasmin system. PAI-1 attenuates fibrinolysis and increased levels of active PAI-1 have been associated with an increased risk for cardiovascular diseases. PAI-1 knock-out mice as well as PAI-1 overexpressing mice have been generated and characterized to study the role of PAI-1 in vivo. A number of PAI-1 inhibitors have been generated to study the pharmacological effect of PAI-1 inhibition in vitro and in vivo. The current review provides an overview of 1) the biochemical features of PAI-1, 2) the role of PAI-1 in diverse pathologies, 3) the in vitro and in vivo data obtained with PAI-1 inhibitors and 4) the vitronectin, glycosylation and species dependency of PAI-1 inhibition.