Plasminogen deficiency differentially affects recruitment of inflammatory cell populations in mice

It is widely held that the plasminogen (Plg) system plays a role in inflammation through plasmin-mediated directional cell migration. However, substantial evidence for its involvement in the inflammatory response has been obtained from indirect studies and lacks firm biological confirmation. To directly characterize plasminogen's involvement in the inflammatory response, we used thioglycollate to induce a peritoneal inflammatory reaction in Plg(+/+), Plg(+/-), and Plg(-/-) mice. At 6 hours poststimulation, neutrophil recruitment into the peritoneum was maximal and similar between Plg(+/+), Plg(+/-), and Plg(-/-) mice. In contrast, monocyte recruitment was significantly diminished after 24 hours poststimulation in Plg(-/-) mice relative to Plg(+/+) mice. Lymphocyte recruitment also was blunted. Blood monocyte levels in these mice indicated that diminished recruitment into the peritoneum was not the result of a diminished source of cells in the circulation. Macrophage phagocytic function was similar between Plg(+/+) and Plg(-/-) mice. This study establishes a direct involvement of plasminogen in monocyte recruitment during a representative inflammatory response.     

Is atherosclerosis an arginine deficiency disease?

To conclude, an impairment of the NO synthase pathway may be one of the earliest events in atherogenesis. A reduction in NO synthesis and/or activity may contribute to the initiation and progressive of atherosclerosis. Derangement of the NO synthase pathway may occur by several mechanisms, including lipoproptein-induced alterations in signal transduction; increases in superoxide anion elaboration (and degradation of NO); reduced affinity of NOS for L-arginine; and/or elevated levels of circulating antagonists. NO is a potent vasodilator, a regulator of vascular structure, and an inhibitor of endothelial interactions and circulating blood elements. A loss of endothelial NO activity may contribute to the abnormal vasomotion observed in coronary artery disease, as well as the progression of atherosclerosis. Strategies to enhance NO synthesis and/or activity may be useful in maintaining cardiovascular health.     

Hepatic lipase deficiency increases plasma cholesterol but reduces susceptibility to atherosclerosis in apolipoprotein E-deficient mice

The effect of hepatic lipase (HL) deficiency on the susceptibility to atherosclerosis was tested using mice with combined deficiencies in HL and apoE. Mice lacking both HL and apoE (hhee) have a plasma total cholesterol of 917 +/- 252 mg/dl (n = 24), which is 184% that of mice lacking only apoE (HHee; 497 +/- 161 mg/dl, n = 20, p < 0. 001). The increase in cholesterol was mainly in beta-migrating very low density lipoproteins, although high density lipoprotein cholesterol (HDLc) was also increased (53 +/- 37 versus 20 +/- 13 mg/dl, p < 0.01). Despite the increase in plasma cholesterol, we found that HL deficiency significantly decreased aortic plaque sizes in female mice fed normal chow (31 x 10(3) +/- 22 x 10(3) microm2 in hhee versus 115 x 10(3) +/- 69 x 10(3) microm2 in HHee, p < 0.001). Reduction of plaque sizes was also observed in female heterozygous apoE-deficient mice fed an atherogenic diet (2 x 10(3) +/- 2.5 x 10(3) microm2 in hhEe versus 56 x 10(3) +/- 49 x 10(3) microm2 in HHEe, p < 0.01). Changes in aortic lesion size were not apparent in the small number of male mice studied. In HHee females, both HDLc and the capacity of high density lipoprotein (HDL) particles to promote cholesterol efflux from cultured cells were 26% of the wild type. The absence of HL in hhee females partially restored HDLc levels to 57% and cholesterol efflux to 55% of the wild type. Circulating pre-beta1-migrating HDL were present in all mutants, suggesting that there are alternative pathways in the formation of these pre-beta-HDL not involving apoE, HL, or cholesteryl ester transfer protein. The improved capacity to promote cholesterol efflux, together with increased HDL, may explain why these animals can overcome the increase in atherogenic lipoproteins.     

Force acting on spheres adhered to a vessel wall

To evaluate the force and torque acting on leukocytes attached to the vessel wall, we numerically study the flow field around the leukocytes by using rigid spherical particles adhered to the wall of a circular cylindrical tube as a model of adherent leukocytes. The adherent particles are assumed to be placed regularly in the flow direction with equal spacings, in one row or two rows. The flow field of the suspending fluid is analyzed by a finite element method applied to the Stokes equations, and the drag force and torque acting on each particle, as well as the apparent viscosity, are evaluated as a function of the particle to tube diameter ratio and the particle arrangements. For two-row arrangements of adhered particles where neighboring particles are placed alternately on opposite sides of the vessel, the drag and the torque exerted on each particle are higher than those for single-row arrangements, for constant particle to tube diameter ratio and axial spacing between neighboring particles. This is enhanced for larger particles and smaller axial spacings. The apparent viscosity of the flow through vessels with adhered particles is found to be significantly higher than that without adhered particles or when the particles are freely floating through the vessels.     

Damage to the vessel wall by the Fogarty balloon catheter

Thromboembolectomy with the Fogarty balloon-catheter is a well-established surgical therapy for the treatment of acute ischemia with generally good results. However, arterial injuries caused by balloon embolectomy occur in up to 6%. The different types of injury are mentioned, the role of myointimal hyperplasia as a result of endothelial denudation is discussed. We conclude that after balloon-catheter thromboembolectomy an early angiographic control should be performed and repeated 3 months postoperatively.     

Plasminogen activator inhibitor 1 in thrombotic disease

Impaired fibrinolytic function, mainly due to an elevation of plasma plasminogen activator inhibitor 1 concentration, is a common finding in patients with thrombotic disease. In patients subjected to hip surgery, preoperatively increased levels of plasminogen activator inhibitor 1 seem to be predictive of postoperative deep venous thrombosis. Several prospective studies of patients with angina pectoris or a past myocardial infarction have shown strong correlation between plasmatic plasminogen activator inhibitor 1 elevation and future cardiovascular events. However, before plasminogen activator inhibitor 1 can be regarded as a risk factor in the conventional epidemiologic sense, its relationship to myocardial infarction must be demonstrated in prospective studies of healthy populations. The regulation of plasminogen activator inhibitor 1 concentration in plasma is complex and at present not well understood. Multiple interactions with disturbances of both carbohydrate and lipoprotein metabolism are evident. Studies performed in cultured cells, transformed or natural, can be translated into human pathophysiology only with great caution. Both environmental and genetic factors seem to be of importance for the plasma plasminogen activator inhibitor 1 concentration. Platelet plasminogen activator inhibitor 1 seems to play a role in the resistance of platelet-rich thrombi to thrombolytic treatment.     

Studies of the vessel wall properties in hemodialysis patients

Compliance is an important property of the arterial system and abnormalities in compliance can greatly affect cardiovascular function. The elastic properties of the common carotid artery were therefore studied in 24 normotensive hemodialysis patients and 24 healthy normotensives using a noninvasive technique. The hemodialysis patients and the control subjects were matched for blood pressure. Arterial distension was measured by Doppler analysis of the vessel wall movements and blood pressure was recorded by finger-phlethysmography (Finapres). The vessel wall distensibility (DC: 2.49 +/- 0.23 10(-3)/mm Hg; mean +/- SEM) was significantly reduced and the end diastolic diameter (d: 7.3 +/- 0.3 mm) was significantly increased in younger hemodialysis patients (36.3 +/- 2.0 years) when compared with age-related controls (DC: 3.44 +/- 0.24 10(-3)/mm Hg; d: 6.3 +/- 0.3 mm; mean +/- SEM). In older hemodialysis patients (60.2 +/- 2.3 years), there was no significant difference in vessel wall distensibility (DC: 1.55 +/- 0.15 10(-3)/mm Hg) and vessel diameter (d: 7.8 +/- 0.3 mm) as compared with age-matched controls (DC: 1.77 +/- 0.14 10(-3)/mm Hg; d: 7.2 +/- 0.3 mm). The results show that vessel wall distensibility of the common carotid artery is decreased in younger hemodialysis patients as compared with age-matched healthy subjects. The volume expanded state in hemodialysis patients cannot account for the decreased arterial distensibility, since volume depletion by hemodialysis was not associated with a significant change of arterial distensibility (DC 2.14 +/- 0.44 10(-3)/mm Hg before, DC 2.26 +/- 0.45 10(-3)/mm Hg after ultrafiltration, NS).(ABSTRACT TRUNCATED AT 250 WORDS)     

Loss of vessel wall viability in cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is a neuropathological feature of Alzeheimer's disease and an important cause of cerebral haemorrhage in the elderly. CAA is characterized by the deposition of Alzheimer amyloid beta protein (A beta) in cerebral and leptomeningeal vessel walls. In order to study the effect of cerebrovascular A beta deposits in vivo, living canine leptomeninges obtained from old dogs affected by CAA were analysed by confocal laser scanning microscopy after immunofluorescence staining for A beta and viability staining with fluorescein diacetate (FDA). Simultaneous detection of the two signals showed a segmental loss of leptomeningeal vessel wall viability at some site of A beta deposition. Many of the non-viable vessels segments were also dilated, suggesting that A beta-induced vascular cell death creates the loci minores resistentiae for the development of cerebral haemorrhage in CAA.     

Genetically obese (ob/ob) mice are predisposed to gastric stress ulcers.

In Exp I, 20 adult male genetically obese (ob/ob) mice and 20 lean littermate controls were food deprived and subsequently physically restrained at normal room temperatures. Obese Ss became hypothermic and developed gastric stress ulcers. Lean Ss maintained normal body temperatures and did not form gastric ulcers. In Exp II, 5 male obese and 4 lean littermates were used to test the effects of noradrenaline (NA) during restraint, and 5 obese and 5 lean mice were used to test the effects of NA alone. It was expected that in lean, but not in obese, Ss that NA would induce an increase in O? consumption beyond that induced by initial restraint. O? consumption was measured during food deprivation and restraint. Obese and lean Ss had parallel metabolic responses, with obese Ss using significantly less O? at all times. The predisposition to formation of gastric ulcers is a new phenotypic expression of the ob/ob genotype. The pathogenesis of this susceptibility appears to be related to a genetic disturbance in heat production. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adherent leukocytes to the aortic wall promotes atherosclerosis in the Watanabe heritable hyperlipidemic rabbits

It is well known that leukocytes adherence to the endothelium of arterial wall occurs in diet-induced hypercholesterolemic animals. We examined the relationship between leukocytes adherence and atherosclerosis in the thoratic aorta of the Watanabe heritable hyperlipidemic rabbits (WHHL rabbits). Five of 2 or 3 months old WHHL rabbits were sacrificed and after perfusion fixation with 2.5% gulutaraldehyde, thoratic aorta was taken out carefully and divided into the 4 portions: Portion 1; cranial side of aortic arch, Portion 2; caudal side of aortic arch, Portion 3; upper side of thoratic aorta except aortic arch, Portion 4; lower side of thoratic aorta except aortic arch. Three to 6 samples from each portion except branching sites were examined using electron microscopy, and the counts of adherent leukocytes (LC) in each portion were calculated. Seven of 6 to 12 months old WHHL rabbits were sacrificed and the internal side of thoratic aorta was cut opened from the ventral side and the atherosclerotic lesions were copied. From these copies, the % area of atherosclerotic plaques (%AT) in each 4 portions as described was calculated using microcomputer. LC in Portion 1 to 4 was 265 +/- 62, 234 +/- 46, 53 +/- 8 and 41 +/- 13/mm2 respectively. LC in Portion 1 or 2 was significantly larger than that in Portion 3 or 4 (p < 0.05). The endothelium to which leukocytes adhered was intact. %AT in Portion 1 to 4 was 68 +/- 8, 63 +/- 8, 40 +/- 8 and 34 +/- 8% respectively. %AT in Portion 1 or 2 was significantly larger than that in Portion 3 or 4 (p < 0.05). It is concluded that leukocytes adherence to the intact endothelium of the arterial wall was one of the geneses and promoters of atherosclerosis in WHHL rabbits.     

Urokinase-type plasminogen activator-deficient mice are predisposed to staphylococcal botryomycosis, pleuritis, and effacement of lymphoid follicles

Urokinase-type plasminogen activator (uPA) is thought to be an important mediator in the proteolytic degradation of extracellular matrix components observed in a wide variety of normal physiological and pathological conditions. However, the phenotype of a recently developed strain of urokinase-deficient (uPA-/-) mice appears to be normal when maintained under ideal nonstressful conditions. We report an outbreak of botryomycosis, an unusual staphylococcal infection, in a colony of uPA-deficient mice. A detailed histological examination of these uPA-deficient animals also revealed a variety of previously unreported phenotypic abnormalities such as pleuritis and the effacement of lymphoid follicles in the regional lymph nodes and spleen. Additional phenotypic abnormalities such as dystrophic calcifications and rectal prolapse were also observed in the uPA-deficient population. These abnormalities were also noted in ostensibly healthy uPA-deficient animals. Botryomycosis did not affect a colony of wild-type (uPA+/+) animals maintained concurrently under identical conditions in the same room. The peculiar predisposition of the uPA-deficient animals to this rare bacterial infection and the development of phenotypic abnormalities associated with the targeted disruption the uPA gene suggests that uPA contributes significantly to the cutaneous microenvironment and is additional evidence of the extensive involvement of the plasminogen activators in mammalian physiology.     

Complement C6 deficiency protects against diet-induced atherosclerosis in rabbits

Low-density lipoprotein (LDL) can be transformed to an atherogenic moiety by nonoxidative, enzymatic degradation. Enzymatically degraded LDL induces macrophage foam cell formation, provokes release of cytokines, and also activates complement. To determine whether complement activation may contribute to atherogenesis, 6 pairs of homozygous C6-deficient rabbits and their non-C6-deficient heterozygous siblings were fed a cholesterol-rich diet for 14 weeks. Cholesterol levels and plasma lipoprotein profiles of the animals in the C6-competent and C6-deficient groups did not significantly differ, and the high density lipoprotein and LDL cholesterol ratios at the end of the experiment were 0.07+/-0.01 and 0.08+/-0.01 (SEM), respectively. However, differences in atherosclerotic plaque formation were discernible macroscopically, with extensive aortic lesions being visible in all C6-competent animals and absent in all C6-deficient animals. Aortas were sectioned from thorax to abdomen, and 10 sections were stained from each aorta. Quantification of atherosclerotic lesions and lumen stenosis with the use of computer-based morphometry documented a dramatic protective effect of C6 deficiency on the development of diet-induced atherosclerosis. We conclude that the terminal complement sequence is centrally involved in atherosclerotic lesion progression.     

Monocyte diapedesis through an in vitro vessel wall construct: inhibition with monoclonal antibodies to thrombospondin

Human peripheral blood monocytes were examined for migration across an endothelial cell monolayer in an in vitro vessel wall construct. Few monocytes invaded in the absence of a chemotactic gradient, despite significant adhesion to the endothelial monolayer. However, the addition of zymosan-activated human plasma to the lower compartment, to create a chemotactic gradient across the vessel wall, resulted in significantly enhanced monocyte migration. Pretreatment of the monocytes with monoclonal antibodies to thrombospondin (TSP) dramatically inhibited monocyte diapedesis into the vessel wall. The same treatment inhibited monocyte adhesion to endothelial cells in two-dimensional monolayer cultures as well as in vessel wall constructs (no chemotactic gradient). Of interest, however, the monoclonal antibodies had no inhibitory effect on monocyte migration into collagen gels devoid of endothelial cells in response to the same chemotactic gradient, suggesting the importance of TSP in monocyte-endothelial cell interactions. Monoclonal antibodies to fibronectin and normal mouse immunoglobulin G did not inhibit migration in this model of a vessel wall. Furthermore, monoclonal antibodies to TSP showed no inhibition of human peripheral blood neutrophil migration. Previous studies have shown that monocytes synthesize TSP and express this moiety on their surface. The present data suggest that monocytes may utilize TSP to interact with endothelial cells lining the vessel wall during diapedesis.     

Using genetically engineered mice to understand apolipoprotein-B deficiency syndromes in humans

Several human diseases are characterized by defects in the synthesis and secretion of the apolipoprotein (apo) B-containing lipoproteins. Familial hypobetalipoproteinemia is caused by mutations in the apo-B gene and is characterized by abnormally low plasma concentrations of apo-B and low-density lipoprotein (LDL) cholesterol. Another apo-B deficiency syndrome, abetalipoproteinemia, is caused by mutations in the gene for microsomal triglyceride transfer protein (MTP). MTP is a microsomal protein that is thought to transfer lipids to the apo-B protein as it is translated, allowing it to attain the proper conformation for lipoprotein assembly. A third apo-B deficiency syndrome, Anderson's disease (or chylomicron retention disease), is characterized by the inability to secrete apo-B-containing chylomicrons from the intestine but an apparently normal capacity to secrete lipoproteins from the liver. To more fully understand these human apo-B deficiency syndromes, our laboratory has generated and characterized gene-targeted mouse models. This review summarizes what has been learned from these animal models.     

Fibrinogen deficiency reduces vascular accumulation of apolipoprotein(a) and development of atherosclerosis in apolipoprotein(a) transgenic mice

To test directly whether fibrin(ogen) is a key binding site for apolipoprotein(a) [apo(a)] in vessel walls, apo(a) transgenic mice and fibrinogen knockout mice were crossed to generate fibrin(ogen)-deficient apo(a) transgenic mice and control mice. In the vessel wall of apo(a) transgenic mice, fibrin(ogen) deposition was found to be essentially colocalized with focal apo(a) deposition and fatty-streak type atherosclerotic lesions. Fibrinogen deficiency in apo(a) transgenic mice decreased the average accumulation of apo(a) in vessel walls by 78% and the average lesion (fatty streak type) development by 81%. Fibrinogen deficiency in wild-type mice did not significantly reduce lesion development. Our results suggest that fibrin(ogen) provides one of the major sites to which apo(a) binds to the vessel wall and participates in the generation of atherosclerosis.     

Immunoglobulin treatment reduces atherosclerosis in apo E knockout mice

Atherosclerosis is associated with immune activation. T cells and macrophages infiltrate atherosclerotic plaques and disease progression is associated with formation of autoantibodies to oxidized lipoproteins. In the apo E knockout mouse, a genetic model of cholesterol-induced atherosclerosis, congenital deficiency of macrophages, lymphocytes, or interferon-gamma receptors result in reduced lesion formation. We have now evaluated whether immune modulation in the adult animal affects disease development. Injections of 7-wk-old male apo E knockout mice with polyclonal immunoglobulin preparations (ivIg) during a 5-d period reduced fatty streak formation over a 2-mo period on cholesterol diet by 35%. Fibrofatty lesions induced by diet treatment for 4 mo were reduced by 50% in mice receiving ivIg after 2 mo on the diet. ivIg treatment also reduced IgM antibodies to oxidized LDL and led to inactivation of spleen and lymph node T cells. These data indicate that ivIg inhibits atherosclerosis, that it is effective both during the fatty streak and plaque phases, and that it may act by modulating T cell activity and/or antibody production. Therefore, immunomodulation may be an effective way to prevent and/or treat atherosclerosis.