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H R Lijnen

Publications and source records attributed to H R Lijnen.

At least 19 recordsLinked to original sources
PubMed2006

No functional role of plasminogen activator inhibitor-1 in murine adipogenesis or adipocyte differentiation.

OBJECTIVE: To substantiate a potential role of plasminogen activator inhibitor-1 (PAI-1) in adipogenesis, we have studied its effects on in vitro adipocyte differentiation and on in vivo adipose tissue formation. RESULTS: Our in vitro data do not support a functional role of PAI-1, as substantiated by our findings that: (i) inhibition of PAI-1 with a neutralizing antibody did not affect differentiation of 3T3-F442A preadipocytes; (ii) overexpression of murine PAI-1 in 3T3-F442A cells had no effect on differentiation; and (iii) differentiation of PAI-1-deficient murine embryonic fibroblasts into mature adipocytes was comparable to wild-type (WT) cells. Furthermore, our in vivo studies did not reveal an important role for PAI-1, as suggested by our findings that: (i) de novo fat pad formation in NUDE mice following injection of 3T3-F442A cells was not affected by a PAI-1 neutralizing antibody; and (ii) adipose tissue formation following combined injection of Matrigel and basic fibroblast growth factor was comparable in WT and in PAI-1 deficient mice. CONCLUSION: Taken together, these in vitro and in vivo studies in murine model systems do not support an important functional role of PAI-1 in adipogenesis.

3T3 Cells↗
PubMed2006

Haemostasis.

When the continuity of the vascular endothelium is disrupted, platelets and fibrin seal off the defect. Haemostatic processes are classified as primary (mainly involving platelets) and secondary (mainly related to fibrin formation or blood coagulation). When the blood clot is no longer required for haemostasis, the fibrinolytic system will dissolve it. The pivotal ligand for initial platelet recruitment to injured vessel wall components is von Willebrand factor (vWF), a multimeric protein present in the subendothelium and in plasma, where it is conformationally activated by shear forces. Adhering activated platelets recruit additional platelets, which are in turn activated and form a platelet aggregate. Coagulation is initiated by a reaction, activating factors IX and X. Once critical amounts of factor Xa are generated, thrombin generation is initiated and soluble fibrinogen is converted into insoluble fibrin. Excessive thrombin generation is prevented via inhibition by antithrombin and also via downregulation of its further generation by activation of the protein C pathway. Activation of the fibrinolytic system results from conversion of the proenzyme plasminogen into the active serine proteinase plasmin by tissue-type or urokinase-type plasminogen activators. Plasmin digests the fibrin component of a blood clot. Inhibition of the fibrinolytic system occurs at the level of the plasminogen activator (by plasminogen activator inhibitors) or at the level of plasmin (by alpha2-antiplasmin). Together, these physiological processes act to maintain normal functioning blood vessels and a non-thrombotic state.

Animals↗
PubMed2006

Plasminogen activation: a mediator of vascular smooth muscle cell apoptosis in atherosclerotic plaques.

BACKGROUND: Apoptosis of vascular cells is considered to be a major determinant of atherosclerotic plaque vulnerability and potential rupture. Plasmin can be generated in atherosclerotic plaques and recent in vitro data suggest that plasminogen activation may trigger vascular smooth muscle cell (VSMC) apoptosis. AIM: To determine whether plasminogen activation may induce aortic VSMC apoptosis ex vivo and in vivo. METHODS AND RESULTS: Mice with single or combined deficiencies of apolipoprotein E (ApoE) and plasminogen activator inhibitor-1 (PAI-1) were used. Ex vivo incubation with plasminogen of isolated aortic tunica media from PAI-1-deficient mice induced plasminogen activation and VSMC apoptosis, which was inhibited by alpha2-antiplasmin. In vivo, levels of plasmin, active caspase 3 and VSMC apoptotic index were significantly higher in atherosclerotic aortas from mice with combined ApoE and PAI-1 deficiencies than in those from littermates with single ApoE deficiency. A parallel decrease in VSMC density was observed. CONCLUSIONS: These data strongly suggest that plasminogen activation may contribute to VSMC apoptosis in atherosclerotic plaques.

Animals↗
PubMed2005

Pleiotropic functions of plasminogen activator inhibitor-1.

Plasminogen activator inhibitor-1 (PAI-1), a 45-kDa serine proteinase inhibitor with reactive site peptide bond Arg345-Met346, is the main physiological plasminogen activator inhibitor. It occurs in human plasma at an antigen concentration of about 20 ng mL(-1). Besides the active inhibitory form of PAI-1 that spontaneously converts to a latent form, also a substrate form exists that is cleaved at the P1-P1' site by its target enzymes, but does not form stable complexes. Besides its role in regulating hemostasis, PAI-1 plays a role in several biological processes dependent on plasminogen activator or plasmin activity. Studies with transgenic mice have revealed a functional role for PAI-1 in wound healing, atherosclerosis, metabolic disturbances such as obesity and insulin resistance, tumor angiogenesis, chronic stress, bone remodeling, asthma, rheumatoid arthritis, fibrosis, glomerulonephritis and sepsis. It is not always clear if these functions depend on the antiproteolytic activity of PAI-1, on its binding to vitronectin or on its intereference with cellular migration or matrix binding.

Animals↗
PubMed2005

The role of plasminogen activator inhibitor type 1 in the inflammatory response to local tissue injury.

BACKGROUND: The plasma levels of the plasminogen activator-inhibitor type 1 (PAI-1) are consistently elevated in patients with sterile tissue injury, often accompanied by a systemic acute phase protein response. It remains unknown, however, whether and to what extent PAI-1 affects the host response to trauma. METHODS AND RESULTS: By using the well-established murine model of turpentine-induced tissue injury we compared local and systemic inflammatory responses in PAI-1 gene-deficient (PAI-1-/-) and normal wild-type (Wt) mice. Subcutaneous turpentine injection elicited strong increases in PAI-1 protein concentration in plasma and at the site of injury, but not in liver. PAI-1 mRNA was locally increased and expressed mainly by macrophages and endothelial cells. PAI-1 deficiency greatly enhanced the early influx of neutrophils to the site of inflammation, which was associated with increased edema and necrosis at 8 h after injection. Furthermore, PAI-1-/- mice showed a reduced early interleukin (IL)-6 induction with subsequently lower acute phase protein levels and a much slower recovery of body weight loss. CONCLUSION: These findings suggest that PAI-1 is not merely a marker of tissue injury but plays a functional role in the local and systemic host response to trauma.

Acute-Phase Proteins↗
PubMed2005

On the role of plasminogen activator inhibitor-1 in adipose tissue development and insulin resistance in mice.

OBJECTIVES: To investigate the role of plasminogen activator inhibitor-1 (PAI-1) in adipose tissue development and insulin metabolism. METHODS: Aged male wild-type (WT) or transgenic mice with adipose tissue overexpression of PAI-1 (45-55 weeks) in 50% C57Bl/6: 50% Friend Virus B-strain (FVB) genetic background, kept on normal chow, were used without or with administration of a synthetic low molecular weight PAI-1 inhibitor (PAI-039) to the food (1 mg g(-1)) for 4 weeks. RESULTS: The PAI-1 transgenic mice showed somewhat lower body weight and adipose tissue mass than WT mice, whereas fasting insulin levels were higher. Glucose and insulin tolerance tests did not reveal significant differences between both genotypes. Addition of PAI-039 to the food did not significantly affect total body fat, weight of the isolated s.c. and gonadal fat territories or their adipocyte size and blood vessel composition in either genotype. Fasting glucose levels and glucose tolerance tests were, for both genotypes, comparable with those without inhibitor treatment. Insulin levels and insulin tolerance tests in WT, but not in PAI-1 transgenic mice, suggested a higher insulin sensitivity after inhibitor treatment (insulin level 30 min after glucose injection of 2.0 +/- 0.17 ng mL(-1) vs. 3.2 +/- 0.48 ng mL(-1) without inhibitor treatment; P = 0.028). CONCLUSIONS: In this model, overexpression of PAI-1 moderately impaired adipose tissue formation without affecting glucose or insulin tolerance. Administration of a synthetic PAI-1 inhibitor for 4 weeks did not affect adipose tissue development in WT or PAI-1 transgenic mice, but induced a higher insulin sensitivity in WT mice.

Acetates↗
PubMed2005

Effects of plasminogen activator inhibitor-1 on ischemic brain injury in permanent and thrombotic middle cerebral artery occlusion models in mice.

BACKGROUND AND OBJECTIVES: Tissue plasminogen activator (t-PA) improves the outcome of ischemic stroke by recanalization of occluded vessels, but has neurotoxic side effects in experimental stroke models. Here, the effect of plasminogen activator inhibitor-1 (PAI-1), an endogenous inhibitor of t-PA, on ischemic infarct volume was studied. METHODS: After either permanent ligation or thrombotic occlusion of the middle cerebral artery (MCA), infarct volume, spontaneous reperfusion of thrombosed MCA, t-PA/PAI-1 complex level, and blood-brain barrier (BBB) permeability in the ischemic region was studied in transgenic mice with overexpression of PAI-1 and wild-type littermate controls and in mice with intracerebroventricular injection of human PAI-1. RESULTS: Infarct volume was smaller in PAI-1 transgenic mice (2.9 +/- 3.7 mm3, mean +/- SD) than in controls (8.9 +/- 5.0 mm3, P < 0.05) after permanent MCA ligation (plasma PAI-1 level 39 +/- 23 ng mL(-1) in transgenic mice vs. 1.5 +/- 0.6 ng mL(-1) in controls), whereas after MCA thrombosis it was larger in transgenics (13.1 +/- 3.1 mm3) than in controls (8.0 +/- 3.2 mm3, P < 0.05). Spontaneous reperfusion of the thrombosed MCA was significantly delayed in transgenic vs. control mice. In the ligation model, t-PA/PAI-1 complex levels were higher and BBB disruption was more pronounced in the ischemic region. Human PAI-1 injection reduced infarct volume by about 50% in wild-type mice but not in t-PA gene deficient mice. CONCLUSIONS: High PAI-1 levels reduced infarct volume in the permanent MCA ligation model, but enhanced it in the MCA thrombosis model.

Adipocytes↗
PubMed2004

Neointima formation and thrombosis after vascular injury in transgenic mice overexpressing plasminogen activator inhibitor-1 (PAI-1).

The controversial role of plasminogen activator inhibitor-1 (PAI-1) in neointima formation and restenosis was studied with the use of a vascular injury model in transgenic mice overexpressing murine PAI-1 (PAI-1 Tg) and in wild-type (WT) controls. Despite the high circulating PAI-1 levels in the PAI-1 Tg mice (52 +/- 9.8 ng mL-1 vs. 0.76 +/- 0.17 ng mL-1 in WT mice), no significant fibrin deposition was observed in non-injured femoral arteries of 8- to 12-week-old mice. Two weeks after severe electric injury, extensive and comparable fibrin deposition was observed in both genotypes, despite a significantly reduced in situ fibrinolytic activity in arterial sections of the PAI-1 Tg mice. The neointimal and medial areas were similar in WT and PAI-1 Tg mice, resulting in comparable intima/media ratios (e.g. 0.94 +/- 0.25 and 1.04 +/- 0.17 at the center of the injury). Nuclear cell counts in cross-sectional areas of the neointima of the injured region were also comparable in arteries from WT and PAI-1 Tg mice (224 +/- 63, 233 +/- 20), and the distribution pattern of alpha-actin-positive smooth muscle cells was similar. These findings indicate that in a vascular injury model that induces extensive and persistent fibrin deposition in femoral arteries of mice, overexpression of PAI-1 does not affect neointima formation.

Animals↗
PubMed2004

Influence of membrane-bound tumor necrosis factor (TNF)-alpha on obesity and glucose metabolism.

OBJECTIVES: To investigate the influence of transmembrane tumor necrosis factor (TNF)-alpha on adipose tissue development and insulin-mediated glucose metabolism. METHODS AND RESULTS: TNF-alpha and lymphotoxin-alpha-deficient mice expressing non-cleavable transmembrane TNF-alpha (Tg-tmTNF-alpha) and TNF-alpha/lymphotoxin-alpha double knockout (control) mice were kept on high-fat diet for 15 weeks. The food intake and feeding efficiency of Tg-tmTNF-alpha mice were significantly higher compared with control mice. At the end of the study, Tg-tmTNF-alpha mice had a significantly higher total body weight, as well as subcutaneous and gonadal adipose tissue mass. Histological analysis revealed that the expression of Tg-tmTNF-alpha resulted in a significantly increased adipocyte area and blood vessel density. Plasma leptin levels correlated positively with adipose tissue mass. The plasma levels of total cholesterol and HDL-cholesterol were significantly increased and LDL-cholesterol levels significantly decreased in Tg-tmTNF-alpha mice. Fasting blood glucose and plasma insulin levels were not different between the two genotypes and intraperitoneal glucose and insulin tolerance tests did not show significant differences. CONCLUSIONS: Transmembrane TNF-alpha enhances adipose tissue formation without altering insulin-mediated glucose metabolism in mice with nutritionally induced obesity.

Adipose Tissue↗
PubMed2004

Tissue-type plasminogen activator: a historical perspective and personal account.

Over the past two decades tissue-type plasminogen activator (t-PA), the main physiological plasminogen activator, has been developed as a fibrin-specific thrombolytic agent for the treatment of various thromboembolic diseases. Milestones in this development include: first purification of human t-PA from uterine tissue, elucidation of the interactions regulating physiological fibrinolysis, thus providing a molecular basis for the concept of fibrin-specific plasminogen activation, first animal models of thrombosis and pilot studies in patients supporting the therapeutic potential of t-PA, cloning and expression of recombinant t-PA providing sufficient amounts for large scale clinical use, and demonstration of its therapeutic benefit in large multicenter clinical trials, mainly in patients with acute myocardial infarction (AMI), but also in patients with massive pulmonary embolism, ischemic stroke, deep vein thrombosis and peripheral arterial occlusion. Genetically modified variants of t-PA have been developed for bolus administration in patients with AMI.

Animals↗
PubMed2003

Endogenous alpha2-antiplasmin does not enhance glomerular fibrin deposition or injury in glomerulonephritis.

BACKGROUND: Fibrin deposition is an important mechanism of glomerular injury in crescentic glomerulonephritis (GN), a severe form of immune renal injury. Both coagulation and fibrinolysis (via the plasminogen-plasmin system) are important in net glomerular fibrin accumulation in GN. alpha2-Antiplasmin (alpha2-AP) is the major circulating inhibitor of plasmin and is expressed in the renal tubulointerstitium. OBJECTIVE: To determine whether endogenous alpha2-AP contributes to glomerular fibrin accumulation in GN. METHODS: Crescentic autologous phase antiglomerular basement membrane GN was induced in mice with intact and deficient endogenous alpha2-AP (alpha2-AP+/+ and alpha2-AP-/- mice). RESULTS: In mice with crescentic GN, alpha2-AP was detected in the tubulointerstitium and in segmental deposits within some glomeruli. alpha2-AP+/+ mice developed crescentic GN (38 +/- 9% glomeruli affected) with glomerular fibrin deposition and renal impairment (serum creatinine 30 +/- 1 micro mol L-1, normal without GN 11 +/- 1 micro mol L-1). Genetic deficiency of alpha2-AP did not result in attenuated glomerular fibrin deposition, crescent formation (39 +/- 8% glomeruli affected), glomerular leukocyte infiltration or renal impairment (serum creatinine 33 +/- 7 micro mol L-1). alpha2-AP was unmeasurable in kidneys from alpha2-AP-/- mice, which did not develop compensatory changes in plasminogen, tissue type plasminogen activator (tPA), urokinase type PA (uPA) or plasminogen activator inhibitor-1 proteins, or changes in tPA or uPA activity. alpha2-AP-/- mice did have enhanced total renal fibrinolytic capacity as assessed by in situ fibrin overlay (alpha2-AP+/+ 0.19 +/- 0.01, alpha2-AP-/- 0.36 +/- 0.03 lyzed area/total area). CONCLUSIONS: alpha2-AP is not important to net glomerular fibrin deposition, crescent formation or renal impairment in crescentic GN.

Animals↗
PubMed2002

Reduced atherosclerotic plaque but enhanced aneurysm formation in mice with inactivation of the tissue inhibitor of metalloproteinase-1 (TIMP-1) gene.

Development and progression of atherosclerotic lesions and aneurysm formation were investigated in mice with single or combined deficiency of apolipoprotein E (ApoE) and tissue inhibitor of metalloproteinase-1 (TIMP-1) kept on a cholesterol-rich diet for 30 weeks. Atherosclerotic lesions throughout the thoracic aorta were significantly (P<0.001) larger in mice wild-type for TIMP-1 (ApoE-/-:TIMP-1+/+) than in mice deficient in TIMP-1 (ApoE-/-:TIMP-1-/-). Aneurysms in the thoracic and abdominal aortas were less frequent in ApoE-/-:TIMP-1+/+ mice than in ApoE-/-:TIMP-1-/- mice (11+/-3.0 versus 23+/-5.1 aneurysms per 100 sections analyzed, mean+/-SD, P<0.001). Immunocytochemistry revealed enhanced accumulation of Oil red O-stained lipids, colocalizing with macrophages in atherosclerotic lesions of ApoE-/-:TIMP-1-/- mice (P<0.05). In situ zymography using a casein substrate showed enhanced lysis in plaques of ApoE-/-:TIMP-1-/- mice as compared with ApoE-/-:TIMP-1+/+ mice (P<0.01). MMP activity was most pronounced at sites where degradation of the elastic lamina occurred. These data suggest that enhanced MMP activity, as a result of TIMP-1 deficiency, contributes to a reduction of atherosclerotic plaque size but promotes aneurysm formation.

Animals↗
PubMed2002

Matrix metalloproteinase inhibition impairs adipose tissue development in mice.

The effect of galardin, a broad-spectrum matrix metalloproteinase (MMP) inhibitor, was studied in mice kept on a high fat diet (HFD). Five-week-old male wild-type mice were fed the HFD (42% fat) for up to 12 weeks and were daily injected intraperitoneally with the inhibitor (100 mg/kg) or with vehicle. After 12 weeks of the HFD, the body weights of both groups were comparable, but the weight of the isolated subcutaneous (SC) or gonadal (GON) fat deposits was significantly lower in the inhibitor-treated group than in the control group (88 +/- 11 versus 251 +/- 66 mg, respectively, for SC fat [P<0.05]; 90 +/- 24 versus 217 +/- 30 mg, respectively, for GON fat [P<0.02]). The number of adipocytes was somewhat higher and the diameter was somewhat smaller (but not significantly) in adipose tissues of the inhibitor-treated group. Adipose tissue of the inhibitor-treated mice contained more collagen than did that of the vehicle-treated mice (Sirius red-stained area of 42 +/- 2.6% versus 22 +/- 4.4%, respectively, for SC fat [P<0.05]; 21 +/- 5.1% versus 4.7 +/- 0.92%, respectively, for GON fat [P<0.01]); a distinct collagen-rich cap was formed around the inhibitor-treated tissue. In situ zymography with casein- or gelatin-containing gels confirmed a reduced MMP activity in SC and GON adipose tissues of inhibitor-treated mice. Thus, in this model, growth and development of adipose tissue appears to be limited by the formation of a collagen-rich matrix cap around the inhibitor-treated tissue. These data suggest a functional role for MMPs in the development of adipose tissue.

Adipocytes↗
PubMed2002

Influence of t-pA and u-PA on adipose tissue development in a murine model of diet-induced obesity.

To investigate the potential role of tissue-type plasminogen activator (t-PA) or urokinase-type plasminogen activator (u-PA) in development of adipose tissue, we have used a nutritionally induced obesity model in t-PA (t-PA-/-) and u-PA (u-PA-/-) deficient mice. Five week old male wild-type (WT), t-PA-/- or u-PA-/- mice (n = 9 to 16) were fed a high fat diet (HFD, 42% fat). After 16 weeks of HFD, the body weight of t-PA-/- mice was significantly higher than that of WT mice (48 +/- 1.1 g vs. 39 +/- 2.2 g, p = 0.004). The total weight of the isolated subcutaneous (sc) fat deposit was higher in t-PA-/- than in WT mice (2.4 +/- 0.22 g vs. 1.2 +/- 0.29 g, p = 0.002). accompanied with higher adipocyte diameters (80 +/- 1.7 microm vs. 61 +/- 4.7 microm, p < 0.01). These differences were not observed in the intra-abdominal fat deposit. The number of stroma cells in both adipose tissue territories was increased in t-PA-/- as compared to WT mice (2.0 +/- 0.13 vs. 1.5 +/- 0.10, p = 0.2 and 3.0 +/- 0.17 vs 1.6 +/- 0.17, p = 0.0001, stroma cells/adipocytes in sc and intra-abdominal tissue, respectively), partly as a result of an increased number of endothelial cells (192 +/- 9 vs. 154 +/-18, p = 0.06 and 108 +/- 13 vs. 69 +/- 8, p = 0.04 CD31 stained/adipocyte area). In contrast the weight gain and adipose tissue development in u-PA-/- mice was not different from that in WT mice. These data suggest that t-PA but not u-PA plays a role in adipose tissue development.

Adipocytes↗
PubMed2002

Adipocyte hypertrophy in stromelysin-3 deficient mice with nutritionally induced obesity.

Several matrix metalloproteinases (MMPs), including the stromelysins MMP-3 and MMP-11, are expressed in adipose tissue. To investigate a potential role of MMP-11 (stromelysin-3) in adipose tissue development, five-week-old male wild-type mice (MMP-11+/+) or mice with deficiency of MMP-11 (MMP-11-/-) were fed a high fat diet (HFD, 42% fat) for 15 weeks. Haematologic parameters, including white and red blood cells, platelets, haemoglobin and haematocrit, and metabolic parameters including glucose, triglycerides and total cholesterol were not different for both genotypes. At the time of sacrifice, the body weight of the MMP-11-/- mice was higher than that of the MMP-11+/+ mice (36+/-1.4 g versus 29+/-0.9 g, p = 0.0002). The weight of the isolated subcutaneous (SC) and gonadal (GON) fat deposits was also higher in MMP-11-/- mice (620+/-150 mg versus 280+/-28 mg for SC fat, and 970+/-180 mg versus 430+/-62 mg, p < 0.05, for GON fat). Adipocytes in MMP-11-/- adipose tissue were hypertrophic as compared to MMP-11+/+ adipocytes (volume of 57+/-12 x 10(3) microm3 versus 31+/-2.4 x 10(3) microm3 for SC fat, and 100+/-18 x 10(3) microm3 versus 57+/-7.6 x 10(3) microm3 for GON fat; both p < 0.06). In nutritionally induced obesity models in mice a potential role of the fibrinolytic system was suggested in adipocyte hypertrophy. The hypertrophy observed in this model is, however, not related to changes in fibrinolytic parameters, as suggested by our finding that levels of t-PA, u-PA and PAI-1 antigen as well as t-PA and u-PA activity were not different in SC or GON adipose tissue extracts of both genotypes. As the main biological function of MMP-11 remains unknown, it is not clear whether the adipocyte hypertrophy in MMP-11-/- adipose tissue is directly related to the deficiency or to other pathways affected by MMP-11.

Adipocytes↗