Relationship of Chlamydia pneumoniae infection to severity of human coronary atherosclerosis.

BACKGROUND: Infection with Chlamydia pneumoniae has been postulated to play a pathogenic role in atherosclerosis. We examined the role of infection with C pneumoniae in relation to the extent of coronary atherosclerosis. METHODS AND RESULTS: Coronary atherosclerosis was graded microscopically on a postmortem basis in a blinded fashion in 60 subjects as mild (n=18) or severe (n=42) atherosclerosis. Serum antibodies to C pneumoniae were measured by microimmunofluorescence test. Paraffin-embedded coronary artery specimens were examined for the presence of chlamydia by use of a genus-specific direct immunofluorescence monoclonal antibody. Frozen coronary artery specimens were examined by immunoperoxidase for the presence of C pneumoniae by use of a specific monoclonal antibody RR-402. Direct immunofluorescence was reactive in 86% of cases with severe atherosclerosis but in only 6% of cases with mild atherosclerosis (P<0.01), whereas immunoperoxidase staining was reactive in 80% and 38% of cases with severe and mild atherosclerosis, respectively (P<0. 01). Elevated IgG and IgA levels against C pneumoniae were not different in cases with severe and mild atherosclerosis (61% and 30% for severe atherosclerosis and 67% and 42% for mild atherosclerosis, respectively). CONCLUSIONS: This study supports the hypothesis that intracellular infection with C pneumoniae may relate to the severity of atherosclerosis in some subjects. Serum antibody titers against C pneumoniae do not differentiate between severe and mild atherosclerosis.

Seropositivity against Chlamydia pneumoniae in patients with coronary atherosclerosis.

BACKGROUND: Results of therapy in patients with unstable coronary syndromes with antibiotics directed against Chlamydia pneumoniae have been variable, perhaps due to the heterogeneity of patients in these trials. HYPOTHESIS: The aim of the present study was to correlate the severity of coronary artery disease (CAD) with seropositivity against C. pneumoniae prospectively. METHODS: We measured the frequency of seropositivity (IgG levels > or = 1/64 and IgA levels > or = 1/16 against Chlamydia pneumoniae) in 110 patients with CAD and in 49 controls. RESULTS: As expected, traditional CAD risk factors were seen more often in patients with CAD than in controls. Mean values of total cholesterol (184 +/- 52 and 166 +/- 44 mg/dl, respectively) and triglyceride (143 +/- 60 and 112 +/- 63 mg/dl, respectively) in serum were significantly higher in patients with CAD than in controls (both p < 0.04). There were no significant differences between the two groups in serum high-density lipoprotein cholesterol (34 +/- 13 and 32 +/- 14 mg/dl, respectively) and lipoprotein (a) (Lp(a):241 +/- 247 and 223 +/- 263 mg/l, respectively) levels. The rate of IgG seropositivity was 52% (28/54) in patients with stable CAD, 41% (23/56) in patients with unstable CAD, and 35% in controls (p = NS). The rate of IgA seropositivity was 25% (14/54) in patients with stable CAD, 12% (6/49) in patients with unstable angina, and 12% (6/49) in controls (all p = NS). CONCLUSIONS: Only a small percentage of patients with CAD demonstrate seropositivity against Chlamydia pneumoniae. Antibiotic therapy in these selected patients, but not in the remaining patients, may be considered rational. These considerations may underlie the failure to see consistent benefits of antibiotic therapy in patients with CAD.

Interactive role of infection, inflammation and traditional risk factors in atherosclerosis and coronary artery disease.

Although first suggested at the turn of the 20th century, there is a renewed interest in the infectious theory of atherosclerosis. Studies done in many laboratories around the world over the past several years have shown an association between markers of inflammation and coronary atherosclerosis with an exacerbation of the inflammatory process during acute myocardial ischemia, particularly in the early stages of reperfusion. It is also being recognized that the traditional risk factors, such as smoking, dyslipidemia, hypertension and diabetes mellitus, do not explain the presence of coronary atherosclerosis in a large proportion of patients. We believe that in certain genetically susceptible people, infection with very common organisms, such as Chlamydia pneumoniae or cytomegalovirus, may lead to a localized infection and a chronic inflammatory reaction. Persistence of infection may relate to the degree of inflammation and severity of atherosclerosis. Early trials with appropriate antibiotic agents in some patients with a recent history of acute myocardial infarction have led to very salutary results. If patients with an infectious basis of atherosclerosis can be identified, a therapy directed at eradication of the offending organism may be appropriate.

Melagatran, an oral active-site inhibitor of thrombin, prevents or delays formation of electrically induced occlusive thrombus in the canine coronary artery.

Intravenous administration of thrombin inhibitors, such as hirudin, has been shown to decrease the frequency of coronary artery reocclusion after thrombolysis. However, recent findings in large clinical trials in patients with unstable angina and myocardial infarction have failed to demonstrate a sustained antithrombotic effect after cessation of drug treatment. These findings indicate a need for a prolonged antithrombotic regimen, preferably an orally active thrombin inhibitor. To test the hypothesis that a regimen consisting of oral thrombin inhibitor will delay or prevent the formation of occlusive clot, anesthetized dogs were given saline (n = 9) or a single dose of a novel active site low-molecular-weight thrombin inhibitor melagatran by nasogastric tube (1.5 mg/kg, n = 6; 2.5 mg/kg, n = 6), and 15 min later, a potent thrombogenic stimulus in the form of anodal current (100 microA) was applied to the intimal surface of the narrowed left anterior descending coronary artery (LAD). All saline-treated dogs developed stable thrombus, indicated by zero flow at 34 +/- 7 min after initiation of direct current. On the other hand, one of the six dogs given high-dose melagatran did not develop thrombotic occlusion of the LAD during the entire 4 h of observation. Mean time to occlusive thrombus formation in 11 other dogs was prolonged 4-5 times as compared with that in the saline-treated dogs (p < 0.001). Spontaneous thrombolysis was observed in three of 11 dogs after initial clot formation. Overall, the coronary artery was patent for 68% (low dose) and 75% (high dose) of the observation period in melagatran-treated dogs (vs. 14% of observation period in saline-treated dogs). Peak plasma concentration was 0.87 +/- 0.22 microM in dogs given low-dose and 1.38 +/- 0.30 microM in dogs given high-dose melagatran. The activated partial thromboplastin time (aPTT) increased 1.5-fold at peak plasma concentration of melagatran. These observations imply (a) thrombin generation plays a critical role in thrombus formation in narrowed coronary arteries, (b) oral melagatran prevents or delays thrombus formation, whereas the aPTT is only modestly prolonged, and (c) the thrombus formed in the presence of melagatran is prone to spontaneous lysis in this canine model of coronary thrombosis.

Preservation of endogenous antioxidant activity and inhibition of lipid peroxidation as common mechanisms of antiatherosclerotic effects of vitamin E, lovastatin and amlodipine.

OBJECTIVES: We sought to document the common mechanisms of the antiatherogenic effects of the cholesterol-lowering hydroxy-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor lovastatin, the dihydropyridine Ca2+ blocker amlodipine and the antioxidant vitamin E. BACKGROUND: Vitamin E, HMG-CoA reductase inhibitors and Ca2+ blockers each inhibit atherosclerosis in hypercholesterolemic animals. METHODS: New Zealand White rabbits were fed regular chow (Group A), chow with 1% cholesterol (Group B), 1% cholesterol diet plus lovastatin (Group C), 1% cholesterol diet plus vitamin E (Group D) or 1% cholesterol diet plus amlodipine (Group E) for 12 weeks. The extent of aortic atherosclerosis was measured by planimetry of the sudanophilic area. Malondialdehyde (MDA) and superoxide dismutase (SOD) in blood were measured as indexes of lipid peroxidation and antioxidant activity, respectively. RESULTS: Group A rabbits showed no atherosclerosis, whereas Group B rabbits had 17.4 +/- 9.3% (mean +/- SD) of the aorta covered with atherosclerosis, and Groups C, D and E rabbits had significantly less atherosclerosis. Plasma SOD activity was lower in Group B than in Group A (6.9 +/- 1.1 vs. 12.8 +/- 1.5 U/ml, p < 0.01) and was preserved in the groups given lovastatin, vitamin E or amlodipine with a high cholesterol diet. The serum MDA level was higher in Group B rabbits than Group A rabbits (12.1 +/- 2.6 vs. 1.2 +/- 0.1 nmol/ml, p < 0.01) and increased minimally in rabbits given lovastatin, vitamin E or amlodipine with a high cholesterol diet. In in vitro experiments, both lovastatin and amlodipine preserved SOD activity and reduced the oxidizability of low density lipoproteins by rabbit leukocytes. CONCLUSIONS: This study suggests that a reduction in lipid peroxidation and preservation of SOD may be common mechanisms of antiatherosclerotic effects of lovastatin, vitamin E and amlodipine.

Reperfusion injury in the endotoxin-treated rat heart: reevaluation of the role of nitric oxide.

1. The role of nitric oxide (NO) in ischaemia-reperfusion injury to the heart continues to be debated. 2. The role of NO released during endotoxemia on myocardial reperfusion injury was examined in rats given saline or lipopolysaccharide (LPS, 10 mg. kg-1). 3. Aortic rings from LPS-treated rats showed a markedly decreased contractile response to both noradrenaline (NA) and U46619, and a diminished relaxation response to acetylcholine, thrombin and aggregating platelets. Treatment of rat aortic rings from LPS-treated rats with the NO synthesis inhibitor N omega-nitro-L-arginine (L-NOARG) reversed the diminished contractile response to NE and U46619. 4. Before ischaemia-reperfusion, baseline force of cardiac contraction (FCC) and coronary perfusion pressure (CPP) were lower and coronary flow was higher in hearts from LPS-treated rats (all P < 0.05 vs. saline-treated group). Treatment of hearts from LPS-treated rats with L-NOARG increased baseline FCC and CPP. 5. After ischaemia-reperfusion, hearts from saline-treated rats showed a 36 +/- 5% fall in FCC, a 38 +/- 6% rise in CPP and a 38 +/- 5% fall in coronary flow, whereas hearts from LPS-treated rats revealed only a 16 +/- 9% fall in FCC, a 10 +/- 3% rise in CPP and a 20 +/- 4% fall in coronary flow (all P < 0.05 vs. changes in saline-treated group). Fewer hearts from LPS-treated rats developed reperfusion arrhythmias (6% vs. 60% hearts from saline-treated rats, P < 0.02). Myocardial superoxide dismutase activity was higher in the LPS-treated group (P < 0.05). 6. NO synthesis, measured as formation of nitrite, was higher (P < 0.05) in cardiac and aortic tissues from LPS-treated rats. Prostacyclin (PGI2) release in coronary effluent was greater in LPS-treated rat hearts (P < 0.05 vs. saline-treated rats). 7. Thus LPS-treated hearts demonstrate a basal decrease in FCC and coronary vascular resistance. These hearts demonstrate a modest protection from reperfusion injury. Induction of NO synthesis, and possibly PGI2 release, may underlie cardioprotection from ischaemia-reperfusion.

Inogatran, a novel direct low molecular weight thrombin inhibitor, given with, but not after, tissue-plasminogen activator, improves thrombolysis.

Coronary artery often reoccludes after therapy of acute myocardial infarction with recombinant tissue plasminogen activator rt-PA, most likely due to in situ thrombin generation during thrombolysis. Previous studies with high molecular weight thrombin inhibitors, such as hirudin, have shown variable improvement in the frequency of sustained thrombolysis. This study was conducted to examine the modulation of thrombolysis, indices of thrombin generation and activated partial thromboplastin time (APTT) by a novel low molecular weight direct thrombin inhibitor, inogatran. A stable occlusive intracoronary thrombus was created in 19 dogs. Nine dogs were given an intravenous bolus of saline (group A), and 5 dogs were given inogatran (group B) followed by rapid infusion of rt-PA (1 mg/kg over 20 min), whereas saline or inogatran was continuously infused for 2 hr. Five other dogs were given inogatran (bolus and continuous infusion) only after thrombolysis by rt-PA was obtained (group C). Time to reflow was similar in all dogs. None of the reperfused coronary arteries reoccluded in group B dogs (vs. 75% and 40% reocclusion rates in groups A and C, respectively, P < .02). Accordingly, the mean duration of reflow was > 120 min in group B dogs (vs. 39 +/- 7 and 44 +/- 14 min in group A and C dogs, respectively, P < .05). After infusion of inogatran, APTT was increased to 1.6 to 1.9 times the base-line value, and the changes in APTT were similar in group B and C dogs. Thrombin generation and activity, assessed by thrombin-antithrombin complex and fibrinopeptide A levels, increased in all dogs during thrombus formation. The increase in thrombin-antithrombin complex and fibrinopeptide A levels during thrombolysis was not evident in group B dogs. These data show that direct thrombin inhibition with inogatran, when initiated before rt-PA, results in sustained thrombolysis and only a modest increase in APTT. However, inogatran given after thrombolysis only partially prevents reocclusion because large amounts of thrombin generation occur during the early stages of thrombolysis.

Recombinant lys-plasminogen given before, but not after, recombinant tissue-type plasminogen activator markedly improves coronary thrombolysis in dogs: relationship of thrombolytic efficacy with parameters of fibrinolysis.

Recombinant tissue-type plasminogen activator (rt-PA) administration rapidly restores blood flow in thrombosed coronary arteries, but coronary arteries often reocclude after initial thrombolysis. This occurs because of the short half-life of rt-PA and rapid increase in plasminogen activator inhibitor (PAI-1) and alpha2-antiplasmin levels in plasma. We hypothesized that administration of lys-plasminogen, which binds to fibrin with 10 times greater affinity and results in a loose fibrin structure (as compared with native glu-plasminogen), before rt-PA would enhance the thrombolytic efficacy of rt-PA and modulate parameters of fibrinolysis. To examine this hypothesis, dogs with electrically induced stable thrombus in the left anterior descending coronary artery (LAD) were treated with saline (group A, n = 9) or lys-plasminogen (group B, 2 mg/kg, n = 5), followed 10 min later by rt-PA (1 mg/kg in 20 min). Four other dogs with occlusive LAD thrombus were first given rt-PA, followed by lys-plasminogen (2 mg/kg) 50 min later (group C). Lys-plasminogen given before rt-PA restored flow in all dogs in 14 +/- 4 min (vs. 22 +/- 9 min in group A, p < 0.05), continuing > 2 h (vs. 41 +/- 15 min in group A, p < 0.02). Lys-plasminogen given after rt-PA did not potentiate the effect of rt-PA. Plasma t-PA antigen concentrations were highest in group B dogs at 2 h after rt-PA infusion. PAI-1 and alpha2-antiplasmin plasma levels were suppressed in all dogs receiving lys-plasminogen whether it was given before or after rt-PA. Therefore, lys-plasminogen given before rt-PA markedly potentiates the effect of rt-PA and alters the parameters of fibrinolysis. In contrast, lys-plasminogen given after rt-PA does not influence the thrombolytic effect of rt-PA, whereas it suppresses PAI-1 and alpha2-antiplasmin levels in plasma. This study also suggests that binding of plasminogen to the clot is more important than the plasma levels of PAI-1 and alpha2-antiplasmin.

Aspirin does not potentiate effect of suboptimal dose of the thrombin inhibitor inogatran during coronary thrombolysis.

OBJECTIVES: Coronary artery often reoccludes after thrombolytic therapy with recombinant tissue-plasminogen activator (rt-PA). This reocclusion is thought to be due to in situ platelet activation mediated by thromboxane (Tx) A2 and thrombin; hence, aspirin and thrombin inhibitors are often used in patients with acute myocardial infarction. This study was designed to examine the modulation of coronary artery reocclusion by a novel low molecular weight direct thrombin inhibitor inogatran with or without aspirin. METHODS: 22 dogs with electrically-induced occlusive intracoronary thrombus were treated with saline (n = 7, group A), or high dose inogatran (0.25 mg/kg bolus followed by 0.6 mg/kg per h for 2 h, n = 5, group B), or low dose inogatran (0.125 mg/kg bolus followed by 0.3 mg/kg per h for 2 h, n = 5, group C), or aspirin+low dose inogatran (n = 5, Group D). Recombinant tissue-plasminogen activator (rt-PA) was infused for 20 min starting 2 min after the bolus in all dogs. Coronary artery blood flow was monitored for 120 min after rt-PA administration. RESULTS: Reperfusion rates were similar in all groups, but the time to reperfusion was shortest in group B dogs (18 +/- 2 min vs. 32 +/- 7 min in group A dogs, P < 0.05). Reocclusion rates were 80%, 0%, 50%, and 60% in groups A, B, C, and D dogs, respectively. The restored blood flow persisted for 19 +/- 10, > 120 min, 71 +/- 30 and 54 +/- 26 min in groups A, B, C, and D dogs, respectively. At the end of rt-PA infusion, prothrombin time (PT) and activated partial thromboplastin time (APTT) were increased 1.3-2 times the control value, and the changes in PT and APTT were similar in all groups. Thrombin generation and activity, assessed by rise in thrombin-antithrombin complex and fibrinopeptide A levels, and decrease in fibrinogen levels were most marked in group A dogs, and less so in group B, C and D dogs. CONCLUSIONS: These data show that high dose of direct thrombin inhibitor inogatran shortens time to reflow and abolishes coronary artery reocclusion. However, aspirin does not potentiate the effect of suboptimal doses of inogatran.

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.

Attenuation of coronary flow reserve and myocardial function after temporary subtotal coronary artery occlusion and increased myocardial oxygen demand in dogs.

OBJECTIVES: We examined whether subtotal coronary artery occlusion and reperfusion alter coronary flow reserve and regional myocardial function. BACKGROUND: Total coronary artery occlusion followed by reperfusion results in decreased coronary flow reserve and regional myocardial dysfunction. METHODS: Thirteen anesthetized dogs were subjected to subtotal occlusion of the left anterior descending coronary artery for 1 h, followed by reperfusion for 1 h. During subtotal left anterior descending occlusion, heart rate was increased by atrial pacing. After reperfusion, coronary flow reserve, indicated by reactive hyperemia, as well as coronary flow responses to acetylcholine and nitroglycerin, regional myocardial function and myocardial leukocyte accumulation were measured. RESULTS: After reperfusion, coronary flow reserve was decreased in the ischemic left anterior descending but not the nonischemic circumflex coronary artery region. Myocardial function was also depressed in the left anterior descending coronary region and did not improve on reperfusion. Histologic study showed no leukocyte infiltration in the ischemic left anterior descending coronary region. Myeloperoxidase, an index of myocardial leukocyte accumulation, was similar in the left anterior descending and circumflex coronary regions. Sensitivity of epicardial left anterior descending coronary artery rings to the thromboxane A2 analog U46,619 was enhanced, and relaxation of these rings in response to endothelium-dependent relaxants was decreased. CONCLUSIONS: Coronary flow reserve is reduced and regional myocardial function depressed after subtotal coronary artery occlusion and increased heart rate. A decreased synthesis or increased breakdown of endothelium-derived relaxing factor may be related to a decrease in coronary flow reserve. However, the reduction in coronary flow reserve appears to be unrelated to leukocyte accumulation in the reperfused region.

Neutrophil elastase inhibitor ICI 200,880 protects against attenuation of coronary flow reserve and myocardial dysfunction following temporary coronary artery occlusion in the dog.

OBJECTIVE: Diminished coronary flow reserve and myocardial dysfunction following coronary artery occlusion and reperfusion have been attributed to neutrophil infiltration into the reperfused regions. Release of free radicals and elastase during reperfusion may also contribute to ischaemia-reperfusion induced changes. The aim of this study was to determine the effect of an elastase inhibitor on reperfusion induced attenuated coronary flow reserve and myocardial dysfunction. METHODS: Anaesthetised dogs were subjected to 1 h of left anterior descending coronary artery occlusion and 2 h of reperfusion. Ten minutes before reperfusion, dogs were randomly given saline or the neutrophil elastase inhibitor ICI 200,880 (10 mg.kg-1) and treatment was continued for the next 70 min. While the regional myocardial shortening fraction and coronary blood flow responses to acetylcholine and glyceryl trinitrate were attenuated following coronary reperfusion in saline treated dogs, similar reductions were not observed in the ICI 200,880 treated dogs (p < 0.01). Histopathology showed myocardial injury and extensive neutrophil infiltration in the reperfused regions in saline treated animals. In contrast, neutrophil infiltration was minimal in the ICI 200,880 treated dogs, in spite of myocardial injury. Myeloperoxidase, an index of neutrophil infiltration, was increased (p < 0.02 v control regions) in the reperfused regions in saline treated dogs, but not in the ICI 200,880 treated dogs. Flow cytometry also showed diminished neutrophil infiltration and oxidative burst in reperfused myocardium of ICI 200,880 treated (v saline treated) dogs. CONCLUSIONS: The elastase inhibitor ICI 200,880 protects against ischaemia-reperfusion induced attenuated coronary flow reserve and myocardial dysfunction, and this protective effect is associated with decreased neutrophil infiltration into the reperfused regions.

Replacement of L-Lys by D-Lys(NH2) in peptide Ala-Arg-Pro-Ala-Lys (peptide 6A) increases its coronary blood flow-promoting properties.

Peptide 6A, a degradation of B beta chain of fibrinogen, is known to increase coronary and femoral blood flow. In this study, we examined the effects of peptide 32, an analogue of peptide 6A on coronary blood flow in anesthetized dogs. Intracoronary administration of equimolar amounts of peptide 32 and peptide 6A showed a greater (p < 0.05) increase in blood flow with peptide 32. Intravenous administration of peptide 32 also resulted in greater and longer-lasting increase in coronary blood flow. The greater blood flow enhancing effect of peptide 32 than that of peptide 6A may relate to absence of its degradation by angiotensin converting enzyme.

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)

Dietary fish oil supplementation attenuates myocardial dysfunction and injury caused by global ischemia and reperfusion in isolated rat hearts.

To determine the effect of dietary fish oil supplementation on myocardial dysfunction following ischemia-reperfusion, independent of plasma and blood cells, Sprague-Dawley rats were fed fish oil-rich nonpurified diet or butter-enriched diet for 5 d. Myocardial content of long-chain and (n-3) polyunsaturated fatty acids was greater in the fish oil-fed rats (P < 0.01), whereas (n-6) fatty acid content was lower compared with controls (P < 0.01). Platelet aggregation in fish oil-fed rats was also inhibited. Hearts from all rats were subjected to 15 min of global ischemia and 10 min of reperfusion. In hearts of control rats, ischemia-reperfusion resulted in a marked decrease in force of cardiac contraction, increase in coronary perfusion pressure, appearance of ventricular arrhythmias and release of creatine kinase and thromboxane B2 in the coronary effluent. Dietary fish oil supplementation attenuated myocardial dysfunction induced by ischemia-reperfusion, as indicated by smaller change in force of cardiac contraction (-77% vs. -89%, P < 0.05) and coronary perfusion pressure (+37% vs. +71%, P < 0.001). Concomitantly, release of creatine kinase as well as thromboxane B2 in coronary effluent was lower (P < 0.01). Ventricular arrhythmias occurred less frequently in hearts from fish oil-fed rats. Thus, short-term dietary fish oil supplementation attenuates myocardial dysfunction caused by ischemia-reperfusion by a direct effect on the heart independent of blood and plasma components.

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.

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)

Adjunctive therapy with low molecular weight heparin with recombinant tissue-type plasminogen activator causes sustained reflow in canine coronary thrombosis.

Rethrombosis of the infarct-related artery after pharmacologic thrombolysis is a major limitation of the thrombolytic therapy. Platelet and fibrin deposition in the coronary artery after recombinant tissue-type plasminogen activator (rTPA) may play a leading role in reformation of thrombus. Therefore we examined the effect of low molecular weight heparin (LMWH) as adjunctive treatment with rTPA in a dog model of electrically induced intracoronary thrombus. Fourteen dogs, in which a stable coronary thrombus was induced with delivery of 100 microA of anodal direct current, were randomly given an intravenous bolus of LMWH, 75 IU/kg (n = 6), or saline (n = 8), followed by intravenous rTPA, 1 mg/kg over 20 minutes. LMWH (75 IU/kg) or saline was continuously infused over 90 minutes after rTPA-induced thrombolysis. Reperfusion occurred at 29 +/- 7 minutes in six of eight dogs receiving rTPA plus saline (reperfusion rate 75%), while reperfusion occurred at 18 +/- 3 minutes in all six dogs receiving rTPA plus LMWH (both p = NS versus rTPA plus saline group). Coronary reocclusion occurred in 83% of dogs given rTPA plus saline, but only in one dog (17%) given rTPA plus LMWH (p less than 0.05). Magnitude of reflow at 60 minutes of reperfusion was higher in the rTPA plus LMWH group than in the rTPA plus saline group (51 +/- 14 ml/min versus 10 +/- 9 ml/min; p less than 0.05). As expected, partial thromboplastin time was greater in rTPA plus LMWH than in rTPA plus saline-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Sustained reflow in dogs with coronary thrombosis with K2P, a novel mutant of tissue-plasminogen activator.

Coronary artery reocclusion after thrombolysis with human recombinant tissue-type plasminogen activator (rt-PA) is related to the short half-life of this agent in plasma. K2P, a mutant of rt-PA lacking the fibronectin fingerlike, epidermal growth factor-like and first kringle domains (amino acids 6 to 173) and having the glycosylation site Asn184 mutagenized to Gln, has been produced in Chinese hamster ovary cells. In this study we compared the thrombolytic effect of K2P and rt-PA in dogs with electrically induced coronary artery thrombosis. Both agents were given intravenously in equimolar amounts over 20 min after the occlusive thrombus was stable for 30 min; dogs were monitored for 1 h after reperfusion if flow occurred. Coronary blood flow was restored by rt-PA in 6 (60%) of 10 dogs. The restored flow lasted for 49 +/- 12 min and mean flow at 60 min from the start of reperfusion was 7 +/- 3 ml/min. The reocclusion rate was 50% (three of six dogs). Flow was restored in five (100%) of five dogs by K2P. The restored blood flow lasted during the entire 1-h observation period in all but one dog and mean flow at 60 min was 49 +/- 16 ml/min (p less than 0.02 vs. flow in rt-PA-treated dogs). Restored coronary blood flow showed marked cyclic flow variations in rt-PA-treated but not in K2P-treated dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

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.