Tom G.P. Saldeen

Neutrophil function in ischemic heart disease.

Neutrophils contribute to the healing of and scar formation in myocardium after ischemic injury. Many recent studies indicate that neutrophils may be involved in the genesis and propagation of myocardial ischemia. To characterize neutrophil function in ischemic heart disease, neutrophil chemotaxis, leukotriene B4 (LTB4) generation, and elastase release in plasma were measured in 20 patients with stable angina, 17 patients with unstable angina or acute myocardial infarction (AMI), and 20 age-matched control subjects. Neutrophils from patients with stable angina exhibited markedly increased chemotactic activity and LTB4 generation as compared with the age-matched control subjects (p less than 0.01). Neutrophils of nine of 17 patients with unstable angina or AMI clumped spontaneously ex vivo and exhibited marked pseudopod formation and granule extrusion on electron microscopy. Subsequent chemotactic activity and LTB4 generation by neutrophils from these patients was less than in patients with stable angina, suggesting previous in vivo activation. Plasma levels of peptide B beta, a product of fibrin degradation by human neutrophil elastase, were approximately 15-fold higher (p less than 0.001) in patients with unstable angina or AMI (588 +/- 171 pmol/l, mean +/- SEM) compared with those in patients with stable angina (37 +/- 25 pmol/l) or control subjects (40 +/- 22 pmol/l), confirming intense in vivo neutrophil activation. Our study shows enhanced neutrophil function in patients with ischemic heart disease. The increased neutrophil chemotactic activity and LTB4 generation may be markers of stable angina pectoris. Intense neutrophil activation in unstable angina or AMI, as manifested by morphologic changes in neutrophils and elastase release, may relate to ongoing in vivo cellular activation.

INCREASED NEUTROPHIL ELASTASE RELEASE IN UNSTABLE ANGINA PECTORIS AND ACUTE MYOCARDIAL INFARCTION

Neutrophils, a source of proteolytic enzymes and oxygen free radicals, have been shown to participate in animal models of myocardial ischemic injury. To characterize neutrophil activation in human ischemic heart disease, a specific neutrophil elastase-derived fibrinopeptide in plasma was measured in 25 patients with stable angina pectoris, 29 patients with unstable angina pectoris, 17 patients with acute myocardial infarction and 22 control subjects. Mean plasma levels (+/- standard error) of a neutrophil elastase-derived fibrinopeptide (B beta 30-43) measured by a specific radioimmunoassay were fivefold higher in patients with acute myocardial infarction (877 +/- 337 pmol/liter, p less than 0.02) and 13-fold higher in patients with unstable angina (2,277 +/- 613 pmol/liter, p less than 0.006) as compared with control subjects (172 +/- 74 pmol/liter). Mean plasma levels of peptide B beta 30-43 in patients with stable angina (676 +/- 334 pmol/liter), although higher than in control subjects, were not significantly increased (p = 0.64). Total leukocyte counts were 11.0 +/- 0.6 x 10(6)/ml in those with acute myocardial infarction, 9.2 +/- 0.7 x 10(6)/ml in those with unstable angina, 7.1 +/- 0.3 x 10(6)/ml in those with stable angina and 7.7 +/- 0.4 x 10(6)/ml in control subjects. Although total leukocyte counts in patients with unstable angina pectoris and acute myocardial infarction were higher (p less than 0.01) than in patients with stable angina or in control subjects, elevations in peptide B beta 30-43 levels were independent of the differences in both leukocyte count and absolute neutrophil count as well as in history of smoking, hypertension, diabetes mellitus or treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction in plasminogen activator inhibitor-1 (PAI-1) with omega-3 polyunsaturated fatty acid (PUFA) intake.

Activity of plasminogen activator inhibitor-1 (PAI-1) in human blood correlates with thrombotic tendency and with serum triglyceride concentrations. Since intake of fish-derived omega-3 polyunsaturated fatty acids (PUFA) decreases serum triglycerides, we examined the effects of omega-3 PUFA maximum eicosapentaenoic acid (Max EPA) intake on PAI-1 levels in eight patients with coronary artery disease and in four normal subjects. After 4 weeks of Max-EPA intake by coronary artery disease patients, serum triglyceride concentrations and PAI-1 levels decreased 43 +/- 8% and 21 +/- 5%, respectively (both p less than or equal to 0.01) without any change in tissue plasminogen activator (TPA) levels. No changes were noted at 1 week of Max EPA intake in normal subjects, but at 3 weeks serum triglyceride concentrations and PAI-1 levels decreased 32 +/- 13% and 22 +/- 4%, respectively (p less than or equal to 0.01) without any change in tissue plasminogen activator (TPA) levels. No changes were noted at 1 week of Max EPA intake in normal subjects, but at 3 weeks serum triglyceride concentrations and PAI-1 levels decreased 32 +/- 13% and 22 +/- 4%, respectively (p less than or equal to 0.02) without change in TPA. The magnitude of reduction in triglycerides was dependent on the initial serum concentration (r = 0.68, p less than or equal to 0.01). In addition, decrease in PAI-1 levels correlated with reduction in serum triglycerides (r = 0.79, p less than or equal to 0.01). This study shows that omega-3 PUFA intake reduces PAI-1 levels without change in TPA antigen. These observations may relate to decrease in thrombotic activity upon consumption of large amounts of fish or fish-derived products.

Long-term dietary fish oil supplementation protects against ischemia-reperfusion-induced myocardial dysfunction in isolated rat hearts

Dietary fish oil has been shown to exert protective effects against arrhythmias and myocardial infarction after coronary artery occlusion. However, the effects of fish oil on ischemia-reperfusion-induced cardiac dysfunction are not known. This study was designed to examine if long-term dietary fish oil protects against a rise in coronary perfusion pressure and myocardial contractile dysfunction following ischemia and reperfusion. Fifteen Sprague-Dawley rats (age 7 to 9 weeks) were fed fish oil-rich chow for 4 to 5 weeks and 11 rats from the same batch were fed ordinary chow. Three fish oil-fed rats were also fed ad libitum indomethacin for the last 2 days. Isolated hearts from both groups were perfused on a Langendorff apparatus and were subjected to 25 minutes of global ischemia and 20 minutes of reperfusion. Myocardial phospholipid acid content was also measured. After 4 to 5 weeks of dietary fish oil supplementation, myocardial content of long-chain polyunsaturated fatty acid (PUFA) (C20-C22) and omega-3 PUFA was increased and that of omega-6 PUFA was decreased in the fish oil-fed group (all p < 0.01). Following global ischemia and reoxygenation, there was a reduction in the force of cardiac contraction and an increase in coronary perfusion pressure. However, reduction in the force of cardiac contraction was less in the hearts of fish oil-fed rats than in the control hearts (49 +/- 9% vs 63 +/- 5%, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Prostacyclin analogue iloprost decreases thrombolytic potential of tissue-type plasminogen activator in canine coronary thrombosis.

Platelets play an important role in the formation of a coronary thrombus and reocclusion after thrombolysis. Therefore, we examined the thrombolytic potential of concomitant intravenous administration of potent platelet inhibitor iloprost, a prostacyclin analogue, with tissue-type plasminogen activator (t-PA; n = 8) and t-PA alone (n = 9) in dogs with an electrically induced occlusive coronary artery thrombus. t-PA (0.75 mg/kg) was given over 20 minutes, and iloprost (4 micrograms/kg) was given over 40 minutes. Reperfusion rate was 63% (five of eight dogs) in the t-PA plus iloprost group and 67% (six of nine dogs) in the t-PA alone group (p = NS). The time to thrombolysis (or reperfusion) in the t-PA plus iloprost group was almost twice as great as in the t-PA alone group (33.0 +/- 13.3 vs. 18.5 +/- 6.7 minutes, mean +/- SD, p less than 0.02), and the duration of reperfusion was much shorter (3.4 +/- 1.8 vs. 39.3 +/- 17.4 minutes, p less than 0.005). Peak coronary artery blood flow after reperfusion in the t-PA plus iloprost group was also less (20 +/- 17 ml/min) than in the t-PA alone group (58 +/- 21 ml/min, p less than 0.005). Reocclusion occurred in all dogs given t-PA with iloprost despite potent synergistic platelet inhibitory effects of t-PA and iloprost, whereas four of six dogs given t-PA alone reoccluded. Neither regimen exerted a significant beneficial effect on regional myocardial shortening during coronary reperfusion. Plasma levels of t-PA were lower when iloprost was given with t-PA (1,022 +/- 360 vs. 1,459 +/- 270 ng/ml in t-PA alone group, p less than 0.05). The detrimental effects of iloprost identified in this study may relate to the reduction in plasma t-PA concentrations by its degradation in the liver caused by the prostacyclin analogue iloprost.

Effects of fish oil on some parameters of fibrinolysis and lipoprotein(a) in healthy subjects

Abstract In summary, our studies show that (n-3) fatty acids consistently decrease triglyceride levels and increase PAI-1 activity and antigen levels without affecting t-PA levels. The reduction in lipoprotein(a) and fibrinogen levels with long-term intake of (n-3) fatty acids may have a bearing on their antiatherosclerotic and antithrombotic effects. The consistent increase in PAI-1 activity and antigen may be a nonspecific response to maintain vascular hemostasis. The addition of vitamin E may be important in overcoming the potentially deleterious oxidant effect of fish oil.

Leukocyte elastase inhibition and t-PA-induced coronary artery thrombolysis in dogs: Beneficial effects on myocardial histology

Leukocyte-derived elastase is released following coronary artery occlusion and reperfusion and may contribute to reperfusion-related myocardial injury. Leukocyte infiltration into the reperfused myocardium may also contribute to ischemic injury following reflow. In the present study, we examined the effects of tissue-plasminogen activator (t-PA, 1 mg/kg over 20 minutes) given intravenously with either saline or a leukocyte elastase inhibitor (ICI 200,880, 5 mg/kg) in dogs with electrically-induced coronary artery thrombosis. ICI 200,880 administration increased elastase inhibitory activity without affecting t-PA and plasminogen activator inhibitor (PAI-1) activities. Time to reflow, magnitude of peak coronary blood flow, and duration of reflow were not different in dogs given t-PA with saline or with the elastase inhibitor. However, administration of the elastase inhibitor decreased the histologically-determined leukocyte infiltration and severity of myocardial injury in dogs subjected to coronary artery thrombosis and subsequent thrombolysis. These early observations suggest that elastase release during reperfusion may be an important mediator of anoxia-reoxygenation-mediated tissue injury.

Increased production of thromboxane A2 by coronary arteries after thrombolysis

The coronary artery produces large amounts of prostacyclin (PGI2) and a small amount of thromboxane A2 (TXA2); this high PGI2/TXA2 ratio contributes to the antithrombotic properties of the coronary artery. This study was designed to determine whether this ratio changes after coronary artery thrombosis and thrombolysis and accounts for coronary artery reocclusion. Anesthetized dogs (N = 12) were subjected to electrically induced coronary artery thrombosis and tissue plasminogen activator-induced thrombolysis. Thrombolysis was achieved in 11 dogs, and the coronary artery reoccluded in five of these dogs after the initial reperfusion. Spontaneous and ionophore A23,187-stimulated PGI2 and TXA2 synthesis in normal circumflex and ischemic-reperfused left anterior descending coronary artery segments was measured by radioimmunoassay of thromboxane B2 and 6-keto-prostaglandin F1 alpha, respectively. Production of TXA2 was 413% to 656% greater in left anterior descending segments (from the region of thrombosis and sites proximal and distal to the thrombus) compared with normal circumflex segments (p < 0.001). Production of PGI2 was also increased but only by 46% to 80% in the left anterior descending segments compared with normal circumflex segments (p < 0.05). TXA2 production was greater in coronary artery segments that reocculded compared with segments that stayed open (p < 0.02). Scanning electron microscopy revealed platelet deposition in thrombosed left anterior descending segments but not in segments proximal or distal to the thrombus site, indicating that the vascular wall per se may be a source of increased production of TXA2.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant lys-plasminogen, but not glu-plasminogen, improves recombinant tissue-type plasminogen activator-induced coronary thrombolysis in dogs

OBJECTIVES This study examined the modification of recombinant tissue-type plasminogen activator (rt-PA)-induced thrombolysis by recombinant lys-plasminogen. BACKGROUND Recombinant tissue-type plasminogen activator restores flow in the thrombosed coronary artery, but the artery often reoccludes. The rt-PA-induced thrombolysis is a result of activation of plasminogen bound to fibrin in the thrombus and results in generation of the fibrinolytic enzyme plasmin. Small amounts of lys-plasminogen are formed when rt-PA is used. Lys-plasminogen binds to fibrin with a 10-fold greater affinity than the predominant native glu-plasminogen, leading to a loose fibrin structure. METHODS Dogs with electrically induced occlusive intracoronary thrombus were treated with saline solution (n = 9), glu-plasminogen (2 mg/kg body weight, n = 5) or lys-plasminogen (2 mg/kg, n = 5), followed by infusion of rt-PA (1 mg/kg over 20 min) 10 min later. RESULTS Reperfusion rates were similar in all groups of dogs, but the time to reflow was lowest in dogs given lys-plasminogen compared with those given saline solution or glu-plasminogen before rt-PA (mean [+/- SE] 14 +/- 2 vs. 22 +/- 2 and 23 +/- 3 min, respectively, p < 0.05). None of the reperfused coronary arteries reoccluded in the lys-plasminogen plus rt-PA group, whereas 75% reoccluded in dogs given saline solution plus rt-PA, and 50% reoccluded in those given glu-plasminogen plus rt-PA. Accordingly, duration of reflow was greater in the lys-plasminogen plus rt-PA group (> 120 vs. 39 +/- 7 and 82 +/- 21 min, respectively, p < 0.05). Plasminogen activator inhibitor-1 activity decreased during rt-PA infusion and thereafter increased in all dogs, but less so in dogs given lys-plasminogen (p < 0.05 vs. those given saline solution before rt-PA). CONCLUSIONS Treatment with recombinant lys-plasminogen before rt-PA reduces time to reflow and sustains reflow after thrombolysis, whereas glu-plasminogen has no such effect.

Failure of prostacyclin analog iloprost to sustain coronary blood flow after recombinant tissue-type plasminogen-induced thrombolysis in dogs

The coronary artery often reoccludes soon after the flow has been restored with recombinant tissue-type plasminogen activator (TPA) in dogs with electrically-induced thrombosis. The coronary artery reocclusion relates to intense in situ platelet activation and thrombin generation in the reperfused coronary artery. To determine the effect of a potent platelet inhibitor, the prostacyclin analog iloprost, in the prevention of coronary artery reocclusion, an occlusive thrombus was created in the left anterior descending coronary artery in 23 dogs. Coronary artery reflow occurred in 17 dogs after TPA (1 mg/kg over 20 minutes intravenously) administration. After the reflow was established, 10 dogs were given saline and 7 dogs were given iloprost (4 micrograms/kg over 40 minutes). In the saline-treated group, the coronary artery reoccluded in 8 of 10 dogs over 90 minutes (reocclusion rate 80%). In the iloprost-treated group, the coronary artery reoccluded in five of seven dogs (reocclusion rate 71%; p = NS vs TPA alone). The magnitude of peak coronary blood flow and duration of flow were similar in dogs given saline or iloprost after TPA-induced thrombolysis. Scanning electron microscopy showed residual thrombus and the appearance of coronary arterial narrowing distal to the thrombus in all dogs examined. Thus residual thrombus formation and coronary artery narrowing continue to occur after TPA-induced thrombolysis in dogs whether the animals are treated with saline or iloprost. Administration of iloprost after reflow does not modulate the frequency of coronary artery reocclusion.