P. Görög

Elevated plasma lipid hydroperoxides in patients with coronary artery disease.

Sustained presence of lipid peroxides in the circulation and their plasma carrier is a controversial issue. Particularly, there is no firm evidence for an increased plasma lipid peroxide level in patients with atherosclerosis. In this study, a strong correlation was found between plasma total lipid hydroperoxide and lipid hydroperoxide content of LDL cholesterol (r = 0.882; p < 0.001; n = 16). Lipid hydroperoxides in plasma were carried almost exclusively (89%) in LDL. In 70 patients tested 3 months after coronary artery bypass graft surgery with a specific assay, plasma lipid hydroperoxide levels were significantly increased when compared with matched healthy controls (4.31 +/- 0.23 nmol/ml and 2.34 +/- 0.13 nmol/ml, p < 0.0001, patients vs controls, respectively). These concentrations are 10 times lower than those detected by the nonspecific thiobarbituric acid assay. However, considering the in vitro concentration range in which oxidized LDL exerts important atherogenic effects, the elevated plasma lipid hydroperoxide levels measured in atherosclerotic patients have pathologic significance.

Lipid peroxidation by activated platelets: A possible link between thrombosis and atherogenesis

Generation of reactive oxygen species (ROS) by platelets was detected by a cyano-tetrazolium dye (CTC) which forms fluorescent formazan on the cell surface upon reduction. Fluorescence was quantitated by a densitometric device. Resting platelets in plasma produced significant fluorescence (P < 0.0001), and addition of thrombin enhanced the fluorescence of the coagulated platelet mass even further (by 2 h, a 6- and 8-fold increase over fluorescence of platelet-free plasma was measured, respectively). Blood containing CTC was perfused through a glass capillary tubing and the action of shear forces resulted in the formation of an occlusive platelet thrombus. Such thrombi (formed either from whole blood or platelet-rich plasma) were intensely fluorescent, indicating formation of ROS in the platelet mass (a 10- and 8-fold increase in fluorescence over coagulated plasma, respectively). Lipid peroxide content of resting platelets in platelet-rich plasma was doubled over 24 h storage, while addition of thrombin caused a 7.4-fold increase (P < 0.0001) of lipid peroxides in the retracted platelet-rich plasma-clot. Transition metal chelator and antioxidant prevented lipid peroxidation by platelets in response to thrombin. Thrombin activation of (washed) platelets in plasma-free medium caused only 1.4-fold increase in oxidation of added low density lipoprotein (LDL). In contrast, thrombin activation of platelets suspended in de-lipidated autologous plasma resulted in a 5.25-fold increase (P < 0.0001) in LDL oxidation. Generation of ROS and lipid peroxides by platelets can be an important mechanism through which thrombotic events contribute to atherogenesis.

Laser-induced stimulation of the vascularization of the healing wound. An ear chamber experiment

In Ohrkammer Modellexperimenten konnten die Wundheilung wie auch die Gefässformation mittels Laserstrahlen wesentlich stimuliert werden.

Inhibition of Vascular Smooth Muscle Cell Migration by Intact Endothelium Is Nitric Oxide-Mediated: Interference by Oxidised Low Density Lipoproteins

Migration of vascular smooth muscle cells (SMCs) leading to neointimal hyperplasia is an early and cardinal feature of atherogenesis. Migration of rat aortic SMCs from an upper chamber towards a lower one has been studied in a microchemotaxis (Boyden) chamber. Spontaneous migration of SMCs was practically prevented by the presence of endothelium in the lower chamber and was reduced if endothelial cells were substituted with endothelial cell-conditioned medium. Endothelial cells which had been treated with either the inhibitor of protein synthesis cycloheximide or nitric oxide synthesis NG-nitro-L-arginine showed no inhibitory effect on SMC migration. Addition of a nitric oxide donor S-nitroso-N-acetylpenicillamine to cell-free medium in the lower chamber prevented SMC migration. Addition of native LDL to endothelial cells had no effect on SMC migration, while (UV light) oxidised LDL completely abolished the inhibitory effect of endothelial cells on SMC migration. It is concluded that via nitric oxide, endothelium exerts a powerful inhibitory effect on SMC migration. This effect of intact endothelium is completely abolished by oxidised LDL applied in a concentration, which is relevant to those measured in plasma of patients with severe coronary artery disease. It is suggested that oxidised LDL may contribute to the pathogenesis of atherogenesis by stimulating migration of SMCs from media to the intima via abolishing the physiological inhibitory effect of normal endothelium.

The inhibitory effect of non-steroidal anti-inflammatory agents on aggregation of red cells in vitro

Aggregation of red cells of rat in saline suspension was induced by gelatin, high molecular weight dextran and fibrinogen. Except chloroquine, non‐steroidal anti‐inflammatory agents (NAIA) inhibited macromolecule‐induced red cell aggregation in vitro. Glucocorticoids failed to inhibit red cell aggregation even in large concentrations. Of many drugs examined, only the NAIA and certain antihistamines, having experimental anti‐inflammatory effects proved to be effective inhibitors of gelatin‐induced red cell aggregation, in vitro.

Anti-inflammatory effect of sialic acid

Sialic acid was shown to possess anti-inflammatory properties as measured by carrageenan-induced rat paw oedema and pleurisy tests. As the number of leukocytes mobilized was significantly reduced it was concluded that the inhibitory effect of sialic acid on leukocyte accumulation is responsible for the inhibition of exudate/oedema formation.

Evidence against hypercoagulability in coronary artery disease

The strong epidemiological association between elevated plasma clotting factors and coronary artery disease is generally interpreted as evidence that patients with coronary atherosclerosis are in a procoagulant (hypercoagulable) state. A dynamic global test was used to assess the overall coagulation status of 761 patients with coronary artery disease scheduled for coronary artery bypass grafting and compared to healthy matched controls (n = 100). Platelet reactivity to shear-stress was simultaneously measured from identical, non-anticoagulated blood samples. Contrary to expectation, the overall coagulation in cardiac patients did not differ significantly from that of controls. Furthermore, the coagulation status of patients bore no relationship to the severity of coronary atherosclerosis. The latter is in contrast with platelet reactivities, which were significantly increased in patients with > or = 2 vessel disease as compared with single vessel disease. The present results do not necessarily conflict with the finding of elevated plasma clotting factors in cardiac patients. However, they do not support the claim that these markers are a reflection of a hypercoagulable state. Indeed, this study confirms that such patients are in a prothrombotic state, which is related to enhanced platelet reactivities, and not to a prothrombotic imbalance of the coagulation mechanism.

The biologic background to some therapeutic uses of aspirin

The therapeutic success of aspirin as an effective analgesic, antipyretic, and anti-inflammatory drug had been universally established for many decades before its mode of action was discovered in 1971. This mode of action is the prevention, or diminution, of prostaglandin biosynthesis through the inhibition of the enzyme, cyclo-oxygenase. Demonstrations of the major contributions of prostaglandins to pain, fever, and other cardinal features of inflammation provided rational explanations for the well-established therapeutic uses of aspirin. It had been shown earlier that aspirin antagonized two mediators of inflammation by an indirect process. While aspirins mode of action was being discovered, research on platelets in hemostasis and thrombosis was also being done. It was shown that aspirin inhibited an exocytotic reaction (the release reaction) of platelets. This reaction was regarded as essential for their aggregation as thrombi in, most importantly, coronary and cerebral arteries. This observation was the starting point of an enormous effort, still going on to determine through both fundamental and clinical investigations, the therapeutic potential of aspirin as an antithrombotic drug. Costly clinical trials have provided evidence in favor of aspirin preventing thrombotic events affecting the brain; its effectiveness against coronary thrombosis is not yet definitely established. Possible explanations for this situation will be considered on the basis of rapidly advancing biologic knowledge about the mechanism of thrombosis.

COAGULATION OF FLOWING NATIVE BLOOD: ADVANTAGES OVER STAGNANT (TUBE) CLOTTING TESTS

A broad-based, dynamic model of intrinsic coagulation is described. Non-anticoagulated whole blood was perfused through polyethylene tubing under standard conditions, and coagulation (cessation of flow) was monitored by pressure changes. The dynamic coagulation test (DCT) is a sequel to the shear-induced haemostasis, a platelet function test routinely performed prior to coagulation. DCT has two important advantages over stagnant overall clotting tests: i./DCT reflects platelet coagulant activities; selective activation by adenosine diphosphate or shear-stress or inhibition of platelets by prostacyclin greatly enhanced or prolonged dynamic coagulation, respectively. Furthermore, activation of platelets by plasminogen activators (streptokinase, t-PA) was manifested in a significantly shortened coagulation. ii./ DCT allows the rapid assessment of fibrin crosslinking, the mechanical stability of the clot formed. Antibody against factor XIIIa greatly prolonged the time until completion of clotting. In patients taking oral anticoagulant (n = 54), strong correlations were observed between DCT, the prothrombin time (INR) and the thrombelastograph measurements. It is concluded that this simple assay could be useful in the overall screening for coagulation abnormalities.

Effect of anti-inflammatory compounds on actomyosin-adenosinetriphosphate interaction

Abstract The influence of several non-steroid anti-inflammatory agents (NAIA) on the superprecipitation and adenosinetriphosphatase (ATP-ase) activity of natural actomyosin has been studied. Superprecipitation and the ATP-induced reduction of light-scattering of actomyosin solution have been significantly inhibited by some of the investigated compounds. Inhibitory action showed the following order: flufenamic acid > mefenamic acid > indomethacin > ibuprofen > ibufenac > acetylsalicylic acid > phenylbutazone > salicylic acid. Mg and Ca ion activated ATP-ase activity of actomyosin was inhibited with similar relative potencies. The compounds proved to be much stronger inhibitors of Ca than of Mg ion activated ATP-ase. Positive correlation has been found between the inhibitory effect of NAIA on vascular smooth muscle constriction and antagonism of actomyosin-ATP-interaction.