Elevation of thromboxane B2 levels in patients with classic and variant angina Pectoris

Apolipoprotein (a)/Lipoprotein(a)-Induced Oxidative-Inflammatory α7-nAChR/p38 MAPK/IL-6/RhoA-GTP Signaling Axis and M1 Macrophage Polarization Modulate Inflammation-Associated Development of Coronary Artery Spasm

Objective. Apolipoprotein (a)/lipoprotein(a) (Lp(a)), a major carrier of oxidized phospholipids, and α7-nicotinic acetylcholine receptor (α7-nAChR) may play an important role in the development of coronary artery spasm (CAS). In CAS, the association between Lp(a) and the α7-nAChR-modulated inflammatory macrophage polarization and activation and smooth muscle cell dysfunction remains unknown. Methods. We investigated the relevance of Lp(a)/α7-nAChR signaling in patient monocyte-derived macrophages and human coronary artery smooth muscle cells (HCASMCs) using expression profile correlation analyses, fluorescence-assisted cell sorting flow cytometry, immunoblotting, quantitative real-time polymerase chain reaction, and clinicopathological analyses. Results. There are increased serum Lp(a) levels (3.98-fold, $p=0.011$ ) and macrophage population (3.30-fold, $p=0.013$ ) in patients with CAS compared with patients without CAS. Serum Lp(a) level was positively correlated with high-sensitivity C-reactive protein ( $r^2=0.48$ , $p<0.01$ ), IL-6 ( $r^2=0.38$ , $p=0.03$ ), and α7-nAChR ( $r^2=0.45$ , $p<0.01$ ) in patients with CAS, but not in patients without CAS. Compared with untreated or low-density lipoprotein- (LDL-) treated macrophages, Lp(a)-treated macrophages exhibited markedly enhanced α7-nAChR mRNA expression ( $p<0.01$ ) and activity ( $p<0.01$ ), in vitro and ex vivo. Lp(a) but not LDL preferentially induced CD80+ macrophage (M1) polarization and reduced the inducible nitric oxide synthase expression and the subsequent NO production. While shRNA-mediated loss of α7-nAChR function reduced the Lp(a)-induced CD80+ macrophage pool, both shRNA and anti-IL-6 receptor tocilizumab suppressed Lp(a)-upregulated α7-nAChR, p-p38 MAPK, IL-6, and RhoA-GTP protein expression levels in cultures of patient monocyte-derived macrophages and HCASMCs. Conclusions. Elevated Lp(a) levels upregulate α7-nAChR/IL-6/p38 MAPK signaling in macrophages of CAS patients and HCASMC, suggesting that Lp(a)-triggered inflammation mediates CAS through α7-nAChR/p38 MAPK/IL-6/RhoA-GTP signaling induction, macrophage M1 polarization, and HCASMC activation.

Coronary Artery Spasm: New Insights

Coronary artery spasm (CAS) defined by a severe reversible diffuse or focal vasoconstriction is the most common diagnosis among INOCA (ischemia with no obstructive coronary artery disease) patients irrespective to racial, genetic, and geographic variations. However, the prevalence of CAS tends to decrease in correlation with the increasing use of medicines such as calcium channel blockers, angiotensin converting enzyme inhibitor, and statins, the controlling management of atherosclerotic risk factors, and the decreased habitude to perform a functional reactivity test in highly active cardiac catheterization centers. A wide spectrum of clinical manifestations from silent disease to sudden cardiac death was attributed to this complex entity with unclear pathophysiology. Multiple mechanisms such as the autonomic nervous system, endothelial dysfunction, chronic inflammation, oxidative stress, and smooth muscle hypercontractility are involved. Regardless of the limited benefits proffered by the newly emerged cardiac imaging modalities, the provocative test remains the cornerstone diagnostic tool for CAS. It allows to reproduce CAS and to evaluate reactivity to nitrates. Different invasive and noninvasive therapeutic approaches are approved for the management of CAS. Long-acting nondihydropyridine calcium channel blockers are recommended for first line therapy. Invasive strategies such as PCI (percutaneous coronary intervention) and CABG (coronary artery bypass graft) have shown benefits in CAS with significant atherosclerotic lesions. Combination therapies are proposed for refractory cases.

Myocardial Ischemic Syndromes, Heart Failure Syndromes, Electrocardiographic Abnormalities, Arrhythmic Syndromes and Angiographic Diagnosis of Coronary Artery Spasm: Literature Review

In coronary artery spasm (CAS), an excess coronary vasoconstriction causing total or subtotal vessel occlusion could lead to syncope, heart failure syndromes, arrhythmic syndromes, and myocardial ischemic syndromes including asymptomatic myocardial ischemia, stable and unstable angina, acute myocardial infarction, and sudden cardiac death. Although the clinical significance of CAS has been underrated because of the frequent absence of symptoms, affected patients appear to be at higher risk of syncope, serious arrhythmias, and sudden death than those with classic Heberden's angina pectoris. Therefore, a prompt diagnosis has important therapeutic implications, and is needed to avoid CAS-related complications. While a definitive diagnosis is based mainly on coronary angiography and provocative testing, clinical features may help guide decision-making. We perform a literature review to assess the past and current state of knowledge regarding the clinical features, electrocardiographic abnormalities and angiographic diagnosis of CAS, while a discussion of mechanisms is beyond the scope of this review.

Dietary modulation of oxylipins in cardiovascular disease and aging

Oxylipins are a group of fatty acid metabolites generated via oxygenation of polyunsaturated fatty acids and are involved in processes such as inflammation, immunity, pain, vascular tone, and coagulation. As a result, oxylipins have been implicated in many conditions characterized by these processes, including cardiovascular disease and aging. The best characterized oxylipins in relation to cardiovascular disease are derived from the ω-6 fatty acid arachidonic acid. These oxylipins generally increase inflammation, hypertension, and platelet aggregation, although not universally. Similarly, oxylipins derived from the ω-6 fatty acid linoleic acid generally have more adverse than beneficial cardiovascular effects. Alternatively, most oxylipins derived from 20- and 22-carbon ω-3 fatty acids have anti-inflammatory, antiaggregatory, and vasodilatory effects that help explain the cardioprotective effects of these fatty acids. Much less is known regarding the oxylipins derived from the 18-carbon ω-3 fatty acid α-linolenic acid, but clinical trials with flaxseed supplementation have indicated that these oxylipins can have positive effects on blood pressure. Normal aging also is associated with changes in oxylipin levels in the brain, vasculature, and other tissues, indicating that oxylipin changes with aging may be involved in age-related changes in these tissues. A small number of trials in humans and animals with interventions that contain either 18-carbon or 20- and 22-carbon ω-3 fatty acids have indicated that dietary-induced changes in oxylipins may be beneficial in slowing the changes associated with normal aging. In summary, oxylipins are an important group of molecules amenable to dietary manipulation to target cardiovascular disease and age-related degeneration.NEW & NOTEWORTHY Oxylipins are an important group of fatty acid metabolites amenable to dietary manipulation. Because of the role they play in cardiovascular disease and in age-related degeneration, oxylipins are gaining recognition as viable targets for specific dietary interventions focused on manipulating oxylipin composition to control these biological processes.

Specific plasma oxylipins increase the odds of cardiovascular and cerebrovascular events in patients with peripheral artery disease

Oxylipins and fatty acids may be novel therapeutic targets for cardiovascular disease. The objective was to determine if plasma oxylipins or fatty acids can influence the odds of cardiovascular/cerebrovascular events. In 98 patients (25 female, 73 male) with peripheral artery disease, the prevalence of transient ischemic attacks, cerebrovascular accidents, stable angina, and acute coronary syndrome was n = 16, 10, 16, and 24, respectively. Risk factors such as being male, diagnosed hypertension, diabetes mellitus, and hyperlipidemia were not associated with events. Plasma fatty acids and oxylipins were analyzed with gas chromatography and HPLC-MS/MS, respectively. None of 24 fatty acids quantified were associated with events. In contrast, 39 plasma oxylipins were quantified, and 8 were significantly associated with events. These 8 oxylipins are known regulators of vascular tone. For example, every 1 unit increase in Thromboxane B₂/Prostaglandin F_1α and every 1 nmol/L increase in plasma 16-hydroxyeicosatetraenoic acid, thromboxane B2, or 11,12-dihydroxyeicosatrienoic acid (DiHETrE) increased the odds of having had ≥2 events versus no event (p < 0.05). The greatest predictor was plasma 8,9-DiHETrE, which increased the odds of acute coronary syndrome by 92-fold. In conclusion, specific oxylipins were highly associated with clinical events and may represent specific biomarkers and (or) therapeutic targets of cardiovascular disease.

Coronary artery spasm: review and update

Coronary artery spasm (CAS), an intense vasoconstriction of coronary arteries that causes total or subtotal vessel occlusion, plays an important role in myocardial ischemic syndromes including stable and unstable angina, acute myocardial infarction, and sudden cardiac death. Coronary angiography and provocative testing usually is required to establish a definitive diagnosis. While the mechanisms underlying the development of CAS are still poorly understood, CAS appears to be a multifactorial disease but is not associated with the traditional risk factors for coronary artery disease. The diagnosis of CAS has important therapeutic implications, as calcium antagonists, not β-blockers, are the cornerstone of medical treatment. The prognosis is generally considered benign; however, recurrent episodes of angina are frequently observed. We provide a review of the literature and summarize the current state of knowledge regarding the pathogenesis of CAS.

Airway hyperresponsiveness in patients with coronary spastic angina: relationship between coronary spasticity and airway responsiveness

BACKGROUND

Several reports have suggested a possible link between bronchial asthma and coronary spasm, but the possibility of a relationship in coronary spastic angina (CSA) has not been clarified.

METHODS AND RESULTS

Airway responsiveness to methacholine and coronary spasticity to acetylcholine were examined in 42 patients with CSA and 36 patients with chest pain syndrome (CP). Furthermore, 18 control subjects were examined and their airway responsiveness compared with that of the CSA and CP patients. The incidence of airway hyperresponsiveness was significantly higher in the CSA group (74%) than in the CP (19%) and control (17%) groups (p<0.0001). The geometric mean of the log minimum dose (Dmin), defined as the cumulative dose at the point at which respiratory conductance began to decrease, was significantly lower in the CSA group (0.75 log units) than in the CP (1.20 log units) and control (1.38 log units) groups (p=0.004).

CONCLUSION

These results demonstrate that acetylcholine-induced coronary spasticity is significantly related to methacholine-induced airway responsiveness in patients with CSA. A generalized hyperresponsiveness of the vascular and nonvascular smooth muscles, including that through cholinergic mechanisms, may exist in patients with CSA.

Assessment of anti-migraine potential of a novel alpha-adrenoceptor agonist S19014: effects on porcine carotid and regional haemodynamics and human coronary artery

Taking into account the drawbacks associated with the use of triptans, attempts are being made to explore other avenues for the treatment of migraine. Recently, it has been shown that both alpha1- and alpha2-adrenoceptors mediate the constriction of porcine carotid arteriovenous anastomoses, which has effectively served as an experimental model predictive of anti-migraine activity. The present study investigated the effects of a novel alpha-adrenoceptor agonist S19014 (spiro[(1,3-diazacyclopent-1-ene)-5 : 2'-(4',5'-dimethylindane)] fumarate) on carotid and systemic haemodynamics in anaesthetized pigs, and on human isolated coronary arteries. Increasing doses of S19014 (1-30 micro g/kg, i.v.) produced a dose-dependent initial short-lasting vasopressor response and a decrease of total carotid blood flow and conductance. The carotid blood flow and conductance changes were exclusively due to constriction of carotid arteriovenous anastomoses (capillary blood flow increased) and were accompanied by an increase in arterio-jugular venous oxygen saturation difference. Whereas prazosin (100 micro g/kg, i.v.) was ineffective, rauwolscine (300 micro g/kg, i.v.) attenuated the responses to S19014. The compound did not much affect the distribution of cardiac output to peripheral organs when compared with the vehicle group. Furthermore, S19014 only slightly contracted the human isolated coronary artery and its contractions, contrary to those of sumatriptan, were not increased in blood vessels pre-contracted with U46619. These results suggest that (i) the systemic and carotid vascular effects of S19014 are mainly mediated by alpha2-adrenoceptors, and (ii) S19014 could be effective in the treatment of migraine with an improved cardiovascular tolerance.

Amplification of sumatriptan-induced contraction in rabbit saphenous vein but not in basilar artery

The modulation of serotonin (5-HT(1B/1D)) receptor-induced vascular contractility by histamine and U-46619 was compared in the rabbit basilar artery and saphenous vein. In the saphenous vein, histamine (5 x 10(-7) M) significantly increased the potency (from pEC(50) of 6.0 to 6.8) and efficacy (from 52.3% to 88.2%) of sumatriptan. Likewise, U-46619 (5 x 10(-9) M) also increased the potency (from pEC(50) of 5.9 to 6.6) and efficacy (from 51.8% to 92.1%) of sumatriptan in the saphenous vein. In contrast, equieffective concentrations of histamine (10(-7) M) and U-46619 (3 x 10(-9) M) failed to amplify contraction to sumatriptan in the basilar artery. Contraction to sumatriptan was inhibited by nitrendipine (10(-7) M) in the basilar artery but not in the saphenous vein, suggesting that different contractile signaling mechanisms are operating in these tissues. Furthermore, U-46619- and thrombin-induced contractility in the basilar artery were also not amplified by histamine, suggesting that lack of amplification of contraction in the basilar artery was not restricted to sumatriptan but was rather a characteristic of this cerebral vessel. These data suggest that in the in vivo plasma milieu sumatriptan will more markedly contract the peripheral saphenous vein than the basilar artery, a cerebral blood vessel.

Myocardial Bridge: a clinical review

Human coronary arteries occasionally course intramyocardially--a condition termed Myocardial Bridge. We review the anatomic and pathophysiological basis of the Myocardial Bridge and discuss clinical presentations, prognoses and the current treatment options for this interesting coronary angiographic variant.

Intracoronary administration of a thromboxane A2 synthase inhibitor relieves acetylcholine-induced coronary spasm

This study sought to clarify the effectiveness of intracoronary administration of a thromboxane (TX) A2 synthase inhibitor, Ozagrel Na, to relieve coronary spasms induced by intracoronary injection of acetylcholine (ACh). An ACh spasm provocation test was performed in 92 consecutive patients with coronary spastic angina using incremental doses of 20, 50, and 80 microg into the right coronary artery, and 20, 50, and 100 microg into the left coronary artery within 20s. A coronary spasm was defined as TIMI 0 or 1 flow and an intracoronary injection of 20 mg Ozagrel Na was administered when it was provoked. Within 2 min of the administration of the TXA2 synthase inhibitor, ACh-induced coronary spasms were relieved (TIMI 3 flow) in 88.1% of procedures without complications. In only 4 cases (4.3%), it took more than 3 min to relieve the coronary spasms. Intracoronary administration of 20mg Ozagrel Na when ACh-induced spasms occurred, shortened the spasm relief time in all 7 patients (200 +/- 59s vs 111 +/- 23s, p < 0.01), improved the maximal ST segment elevation in 5 of them (3.9 +/- 3.7 mm vs 0.7 +/- 1.5 mm, p < 0.05), and stopped chest pain in 4 patients. In 4 patients who had ACh-induced coronary spasm of the left anterior descending artery, the TXB2 concentration in the coronary sinus decreased after intracoronary administration of Ozagrel Na into the left coronary artery (463 +/- 562 vs 96 +/- 45, p < 0.01). In conclusion, intracoronary administration of a TXA2 synthase inhibitor can relieve ACh-induced coronary spasms by inhibiting TXA2 synthesis in the local coronary circulation.

Transcardiac 8-iso-prostaglandin F(2 alpha)generation from acute myocardial infarction heart: insight into abrupt reperfusion and oxidant stress

8-iso-prostaglandin F(2 alpha)(8-iso-PGF(2 alpha)), a representative isoprostane, has been reported to be a reliable marker for oxidant stress in vivo. To examine if 8-iso-PGF(2 alpha)is generated in patients with acute myocardial infarction (AMI), we measured the level of immunoreactive 8-iso PGF(2 alpha)in the great cardiac vein as well as classical eicosanoids, 6-keto-prostaglandin F(1 alpha)(6-keto-PGF(1 alpha)) and thromboxane B(2)(TXB(2)) in the process of urgent coronary balloon angioplasty. Fourteen patients with anterior AMI were divided into two groups: the totally occluded (n=7) and the already perfused groups (n=7). In the former, transient elevation of 8-iso-PGF(2 alpha)was observed immediately after the angioplasty, i.e. the ratio of post-angioplasty level to pre-level was approximately 2.4 for 8-iso-PGF(2 alpha), 14 for 6-keto-PGF(1 alpha), and 5 for TXB(2). In the already perfused group, the levels of these eicosanoids were unchanged. In the totally occluded group, peak creatine phosphokinase in a peripheral vein was correlated with the level of 8-iso-PGF(2 alpha)(r(2)=0.841, P<0.01), but not with those of the other two eicosanoids. In conclusion, transcardiac 8-iso-PGF(2 alpha)generation is a reliable marker for the size of myocardium exposed to oxidant stress.

Modulation of contractions to ergonovine and methylergonovine by nitric oxide and thromboxane A2 in the human coronary artery

This study explored the modulatory effects of nitric oxide and thromboxane A2 on contractions to ergonovine and methylergonovine in human coronary arteries. To elucidate the different role of nitric oxide synthase in the response to the ergot alkaloids, the serotonin (5-HT) receptors involved in nitric oxide synthase in the response to the ergot alkaloids, the 5-HT receptors involved in nitric oxide release and the contraction of the vascular smooth muscle were characterized with more selective 5-HT-receptor agonists and antagonists. Rings of human coronary arteries from explanted hearts were suspended in organ chambers for isometric tension recording. After testing for contractile (potassium chloride, 60 mM) and endothelial function (substance P, 10(-8) M), respectively, they were exposed to ergot alkaloids or other agonists in the absence or presence of U 46619 (10(-9) M), or nitro-L-arginine (10(-4) M), or both. Ergonovine and methylergonovine were comparable, weak vasoconstrictors in untreated preparations. Contractions to ergonovine were augmented by U 46619, but not by nitro-L-arginine. Contractions to methylergonovine were augmented only by combining U 46619 and nitro-L-arginine. Serotonin and methylergonovine, but not ergonovine, elicited endothelium-dependent, nitric oxide-mediated relaxations. Nonselective 5-HT(1B/1D)-receptor stimulation caused both contractions and relaxations; selective 5-HT1B stimulation caused relaxations only. In the human coronary artery, contractions to ergonovine are not dependent on NO release but are synergistically augmented by thromboxane. Methylergonovine causes similar effects on the vascular smooth muscle, but contractions are inhibited by the release of NO from the endothelium. The 5-HT receptor on the endothelium appears to be different from the receptor on the vascular smooth muscle, which mediates the contractile response to the ergot alkaloids.

Changes in endothelium-derived vascular regulatory factors during dobutamine-stress-induced silent myocardial ischemia in patients with Kawasaki disease

The changes in endothelium-derived vascular regulatory factors during dobutamine (DOB)-induced myocardial ischemia (MI) were investigated in 21 patients with Kawasaki disease aged from 11 months to 18 years. They were classified into an ischemia group (8 patients) and a non-ischemia group (13 patients) based on the results of 99mTc myocardial scintigraphy and DOB stress 99mTc myocardial scintigraphy. In the ischemia group, MI was relatively mild, because there were ischemic changes on the electrocardiogram and no significant symptoms during DOB stress. Catheters were positioned near the orifice of the coronary artery (Ao) and at the coronary sinus (CS). Hemodynamics and the blood concentrations of lactic acid and endothelin-1, as well as NO3-, 6-keto-prostaglandin F1alpha, and thromboxane B2, (which are inactive metabolites of nitric oxide, prostaglandin I2 and thromboxane A2, respectively), were measured at rest and after DOB stress (maximum dose: 30 microg x kg(-1) x min(-1)). The CS/Ao ratio was determined for all parameters. The rate-pressure product, an index of work load, and the cardiac index were significantly increased by DOB stress in both groups. Coronary angiography showed no vasospasm of the epicardial coronary arteries before or after DOB stress in either group. The plasma concentrations of endothelin-1 and 6-keto-prostaglandin F1alpha were significantly increased after DOB stress in the ischemia group, but the serum concentration of NO did not increase. The lack of an increase in NO production during DOB stress may have contributed to the worsening of MI in patients with Kawasaki disease.

Interferon-alpha elevates pulmonary blood pressure in sheep--the role of thromboxane cascade

We tested the effect of interferon-alpha on lung function to examine whether interferon-alpha causes some pathophysiological change in the lung. We prepared awake sheep with chronic lung lymph fistula, and measured the pulmonary hemodynamics, lung fluid balance and concentrations of prostanoid products. At 1 h after intravenous interferon-alpha administration (18 x 10(6) I.U.), pulmonary arterial pressure and pulmonary vascular resistance were significantly increased compared to the baseline values. The levels of thromboxane B2 in both plasma and lung lymph were increased concomitant with early elevation on pulmonary arterial pressure. In addition, OKY-046 [sodium-3[4-(1-imidazolylmethyl)phenyl]-2-propenoic acid] (10 mg kg(-1)), a selective thromboxane synthase inhibitor, significantly prevented the interferon-alpha-induced pulmonary hypertension and thromboxane B2 production. While no evidence of increased pulmonary vascular leakage was observed. These findings suggest that a single infusion of interferon-alpha stimulates a thromboxane cascade and causes transient pulmonary hypertension. However, interferon-alpha itself or increased thromboxane A2 might not affect the pulmonary vascular permeability in sheep.

Impairment of serotonin-mediated nitric oxide release across the coronary bed in patients with coronary spastic angina

Simultaneous assessment of plasma nitrate/nitrite and serotonin levels revealed possible impairment of serotonin-mediated nitric oxide release in patients with coronary spastic angina.

Transcardiac 5-hydroxytryptamine release and impaired coronary endothelial function in patients with vasospastic angina

1. The present study was designed to test the hypotheses whether platelet degranulation across the coronary bed is detectable during non-ischaemic periods in patients with vasospastic angina (VSA) and whether the exogenous nitric oxide (NO) donor nitroglycerin (GTN) is able to modify platelet degranulation, reflecting an impaired endothelial production of NO. 2. We studied 13 patients with VSA and 10 controls. The time course of coronary sinus (CS) plasma 5-hydroxytryptamine (5-HT) levels was evaluated every 4 h before and after intravenous infusion of GTN over a period of 40 h. Coronary sinus plasma 5-HT levels were significantly higher at any measured time point in patients with VSA compared with control and were significantly decreased in patients with VSA following treatment with GTN, but not in controls. Femoral artery plasma 5-HT levels remained almost constant throughout the study. The ratio of CS:aorta 6-keto-prostaglandin F1 alpha was significantly and inversely correlated with the transcardiac plasma 5-HT difference only in patients with VSA (r = -0.68; P < 0.02; n = 13). 3. The time course of CS 5-HT levels confirmed significant platelet degranulation across the coronary bed supplied by the spasming artery in patients with VSA and this was modified by GTN. The present data suggest that platelet degranulation occurs during non-ischaemic periods in patients with VSA and that prostacyclin biosynthesis may be a compensatory response to an impaired endothelial release of NO, limiting the degree of the effects of platelet degranulation.

Chemically induced platelet lysis causes vasoconstriction by release of serotonin

Our previous studies have shown that menadione is cytotoxic to platelets, leading to substantial release of vasoactive substances. To test whether platelet lysis induced by menadione could cause vasoconstriction, we investigated the effect of platelet lysate induced by menadione on rat aorta in organ bath system. We showed that menadione-induced platelet lysate caused vasoconstriction in a dose- and time-dependent manner. These effects were seen in aortic rings both with and without endothelium, but it was much greater in rings without intact endothelium. The time course of vasoconstriction was well correlated with the time courses of platelet lysis (assessed by lactate dehydrogenase release) as well as serotonin release. The vasoconstriction by platelet lysate was blocked by serotonin antagonists, ketanserin, and LY53,857, but not by thromboxane A2 (TXA2) receptor antagonist, SQ29,548, suggesting that vasoconstriction mainly occurred secondary to the release of serotonin in our in vitro system. However, potentiation of vasoconstriction by combined treatment of serotonin and a stable TXA2 mimic, U46619, suggests the possibility of the increased risk for vasoconstriction in vivo. In addition, the serotonin-induced vasoconstriction was potentiated by residual menadione present in the organ bath. These results suggest that chemically induced platelet cytotoxicity can provoke alteration in vasomotor tone by release of serotonin.

Effect of post-treatment with granulocyte colony-stimulating factor on endotoxin-induced lung injury in sheep

We administered a bolus of G-CSF (250 micrograms/body) just after the infusion of endotoxin (1 microgram/kg) in awake sheep with chronic lung lymph fistula to examine the effect of post-treatment with G-CSF on endotoxin-induced lung injury. We measured pulmonary hemodynamics, lung lymph flow, and concentrations of thromboxane B2 and 6-keto-prostaglandin F1 alpha in plasma and lung lymph. In the G-CSF post-treated group, the pulmonary arterial pressure, pulmonary vascular resistance, and lung lymph flow did not significantly increase in the late period (3-5 h after endotoxin infusion). The arterial oxygen gas tension in the late period was higher in the G-CSF post-treated sheep than in those that received only endotoxin. Although the level of thromboxane B2 in plasma significantly increased at 1 h after endotoxin, the lung lymph flow did not increase much in the G-CSF post-treated group. We conclude that post-treatment with G-CSF instead attenuates the degree of pulmonary vascular leakage on endotoxin-induced lung injury and increased thromboxane B2, the principle metabolite of thromboxane A2, may not exacerbate the injury in awake sheep.

Stent placement for recurrent vasospastic angina resistant to medical treatment

The successful stent placement for treatment of recurrent vasospastic angina in a patient with nonstenotic coronary arteries is described. Use of the Palmaz-Schatz stent resulted in successful vasodilation that completely prevented anginal attacks. This procedure represents an alternative treatment for patients with vasospastic angina refractory to aggressive medical therapy.

Expression of Prostacyclin Receptor in Human Megakaryocytes

Prostacyclin (prostaglandin I2, PGI2) is a potent vasodilator and inhibitor of platelet aggregation. Although it is well known that the specific receptor for prostacyclin (PGI2-R) is abundantly expressed on platelets, PGI2-R expression in megakaryocytes is poorly understood. In this study, we examined its expression in leukemic or normal megakaryocytes. PGI2-R mRNA was expressed in human leukemic cell lines of megakaryocytic nature as evaluated by Northern blot analysis. Phorbol 12-myristate 13-acetate (PMA), interleukin-1 (IL-1), IL-3, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF ), thrombopoietin (TPO), and tumor necrosis factor-α (TNF-α) enhanced PGI2-R mRNA expression. The enhancement of PGI2-R expression by PMA and TPO was associated with the upregulation of platelet factor 4 or glycoprotein IIb mRNA expression. Iloprost, an agonist of prostacyclin, induced significant cyclic (c)AMP synthesis in these leukemic cells indicating that interaction of PGI2-R and its ligand can induce postreceptor signal transduction. Furthermore, iloprost-induced cAMP synthesis was enhanced by the pretreatment with PMA or the cytokines that promoted PGI2-R expression. PMA and TPO also increased the specific binding of [3H]iloprost to these cells. Pooled normal megakaryocytic colonies from TPO-containing semisolid culture of purified human CD34+ cells expressed PGI2-R, which were increased as the megakaryocytes matured with the peak expression before proplatelet formation, as evaluated by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). These results indicate that PGI2-R is expressed in human megakaryocytes and is upregulated by cytokines involved in thrombopoiesis or inflammation. Also, it was indicated that megakaryocytic maturation accompanies enhancement of PGI2-R expression.

Expression of Prostacyclin Receptor in Human Megakaryocytes

Prostacyclin (prostaglandin I2, PGI2) is a potent vasodilator and inhibitor of platelet aggregation. Although it is well known that the specific receptor for prostacyclin (PGI2-R) is abundantly expressed on platelets, PGI2-R expression in megakaryocytes is poorly understood. In this study, we examined its expression in leukemic or normal megakaryocytes. PGI2-R mRNA was expressed in human leukemic cell lines of megakaryocytic nature as evaluated by Northern blot analysis. Phorbol 12-myristate 13-acetate (PMA), interleukin-1 (IL-1), IL-3, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF ), thrombopoietin (TPO), and tumor necrosis factor-α (TNF-α) enhanced PGI2-R mRNA expression. The enhancement of PGI2-R expression by PMA and TPO was associated with the upregulation of platelet factor 4 or glycoprotein IIb mRNA expression. Iloprost, an agonist of prostacyclin, induced significant cyclic (c)AMP synthesis in these leukemic cells indicating that interaction of PGI2-R and its ligand can induce postreceptor signal transduction. Furthermore, iloprost-induced cAMP synthesis was enhanced by the pretreatment with PMA or the cytokines that promoted PGI2-R expression. PMA and TPO also increased the specific binding of [3H]iloprost to these cells. Pooled normal megakaryocytic colonies from TPO-containing semisolid culture of purified human CD34+ cells expressed PGI2-R, which were increased as the megakaryocytes matured with the peak expression before proplatelet formation, as evaluated by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). These results indicate that PGI2-R is expressed in human megakaryocytes and is upregulated by cytokines involved in thrombopoiesis or inflammation. Also, it was indicated that megakaryocytic maturation accompanies enhancement of PGI2-R expression.

Augmented contraction of the human isolated coronary artery by sumatriptan: a possible role for endogenous thromboxane

1. The antimigraine drug, sumatriptan, contracts the human coronary artery and, in some patients, elicits chest symptoms (e.g. pressure and pain), particularly after subcutaneous administration. We studied the effects of the thromboxane A2 (TxA2) analogue, U46619 and endothelin-1 on contractile responses to sumatriptan in the human isolated coronary artery as well as the role of endogenously produced TxA2 and endothelin-1 in contractions evoked by sumatriptan. 2. In the presence of U46619 (1 and 3 nM), mean concentration-response curves to sumatriptan in the human coronary artery were shifted vertically due to the initial contraction by U46619, but when this initial contraction was subtracted from the response to sumatriptan, no significant augmentation was observed. However, analysis of the degree of augmentation in individual arterial segments revealed that the augmentation was variable and related inversely to the Emax of sumatriptan in the absence of U46619 (r = 0.78 and 0.81 for 1 and 3 nM, respectively; P < 0.05). 3. Treatment with the TxA2 receptor antagonist, SQ30741 (100 nM), or incubation of vessel segments with aspirin (10 microM), significantly reduced responses to sumatriptan; in aspirin-treated vessel segments, SQ30741 failed to decrease further the contractions to sumatriptan. The decrease in Emax of sumatriptan by both SQ30741 and aspirin correlated significantly with the Emax of sumatriptan without SQ30741 (r = 0.74; P < 0.01) or aspirin (r = 0.94; P < 0.01). In aspirin-treated vessel segments, responses to sumatriptan were significantly augmented in the presence of U46619 (3 nM; P < 0.05). 4. The specificity of SQ30741 was demonstrated by its ability to antagonize coronary artery contractions to U46619 (pA2: 7.54 +/- 0.30), but not endothelin-1. Similarly, incubation with aspirin (10 microM) did not affect contractile responses to endothelin-1, but significantly reduced TxA2 production in coronary artery segments as judged by a decrease in thromboxane B2 (TxB2) from 4.77 +/- 0.98 to 1.38 +/- 0.36 ng g-1 2 h-1. 5. Endothelin-1 (1 nM) did not significantly augment contractions to sumatriptan; there was also no relationship between the degree of augmentation and the control Emax of sumatriptan in the absence of endothelin-1. Furthermore, unlike SQ30741 or aspirin, a high concentration (100 nM) of the non-selective ETA/ETB receptor antagonist, SB 209670, failed to affect contractile responses to sumatriptan. However, SB 209670 potently antagonized coronary artery contractions induced by endothelin-1 with a pA2 of 8.84 +/- 0.32. 6. Compared to control vascular segments, endothelial denudation did not reduce TxA2 production (with endothelium = 2.56 +/- 1.38 vs. without endothelium = 12.32 +/- 4.94 ng TxB2 g-1 2 h-1), suggesting that the production of TxA2 is not confined to the endothelium. The sumatriptan-induced contractions were also unaffected by endothelial denudation. 7. The results of the present study suggest that endogenously produced TxA2 enhances contractions to sumatriptan in the human isolated coronary artery. Such a mechanism may play a role in causing chest symptoms after sumatriptan by potentiating coronary vascular contraction by sumatriptan in vivo.

Action of neurotransmitters: acetylcholine, adrenaline and serotonin on arterial thrombosis induced by a laser beam

The releasing of catecholamines is increased in stress situation which promotes the formation of circulating platelet aggregates, and could participate in the arterial thrombosis formation in coronary diseases. The purpose of this study is to evaluate the thrombogenic action of some neurotransmitters, and their participation through the vessel's vasomotoricity, in the growth of an arteriolar thrombosis. Endothelial cells destruction, induced by a laser beam in mesenteric arteriole of the rat were observed to determine changes in thrombus growth, through the embolization and variation of vessel diameter. It is desirable to get insight into the interrelation of thrombus formation and local vasomotoricity in the presence of acetylcholine, adrenaline and serotonin. The administration of acetylcholine (5mg/kg) increases the number of emboli which detached from thrombus, and decreases the thrombus area. Therefore, acetylcholine induces a variation of the vessel's diameter, a vasodilation in the intact vessel and a vasoconstriction when the endothelium is removed. Two vasoconstrictor agents are used: adrenaline and serotonin which increase the number of laser injuries required to induce thrombus formation, decrease the number of emboli and the duration of embolization (p < 0.05). They cause a potent vasoconstriction. These neurotransmitters seem to be involved in the arterial thrombosis induced by laser beam, promoting or not the platelet aggregation, and modulating the vascular tone by the endothelium.

Increased serotonin release across the coronary bed during a nonischemic interval in patients with vasospastic angina

BACKGROUND

Platelet activation and coagulation abnormality have been observed during coronary spasm. It is crucial whether platelet activation occurs even during a nonischemic period.

HYPOTHESIS

This study was designed to determine whether platelets might be activated across the coronary bed during a nonischemic interval in patients with vasospastic angina.

METHODS

Plasma levels of serotonin, 6-keto-prostaglandin F1 alpha, and catecholamines in the aorta and the coronary sinus were simultaneously measured in 16 patients with vasospastic angina and 13 control patients with nonischemic heart disease.

RESULTS

None of these patients showed myocardial ischemia during sampling. The difference in transcardiac plasma levels of serotonin in patients with vasospastic angina was significantly higher than that in controls (1.48 +/- 1.08 ng/ml vs. 0.07 +/- 0.12 ng/ml, respectively, p < 0.001). Coronary sinus plasma norepinephrine levels in these two groups were almost the same (204.8 +/- 110.8 pg/ml vs. 190.4 +/- 131.6 pg/ml, respectively). The ratio of 6-keto-prostaglandin F1 alpha in the coronary sinus and the aorta was not different between the two groups (1.17 +/- 0.96 in patients with vasospastic angina vs. 1.15 +/- 0.68 in controls).

CONCLUSIONS

These data suggest that platelet activation across the coronary bed should be ascribed to endothelial dysfunction. Lack of compensatory enhancement of prostacyclin production might be concerned with dysfunction of coronary endothelial cells in these patients.

Elevation of the plasma histamine concentration in the coronary circulation in patients with variant angina

In the present study plasma histamine was found to be elevated in the great cardiac vein in 8 of 11 patients with variant angina but in none of 8 control patients. Although further investigation is required to determine the exact cause-and-effect relation between histamine release and provocation of spontaneous variant anginal attacks, the present study presents clinical evidence that histamine may well be related to episodes of variant angina as suggested in animal studies.

Effects of gallopamil on epinephrine and norepinephrine plasmatic levels and on TxB2 and beta-tg release in patients with coronary artery disease during adrenergic stimulus with cold pressor test

We investigated the effect of gallopamil administration during a cold pressor test (CPT) in 18 patients suffering from chronic angina (CA) and in 21 healthy subjects. CA patients showed increased basal levels of beta-thromboglobulin and thromboxane B2 compared to control patients and normal plasma levels of catecholamines. CPT caused plasma catecholamines, beta-thromboglobulin and TxB2 levels to rise. This rise was greater in CA patients than in control patients. Administration of gallopamil (50 mg kg-1 three times a day for 30 days) reduced plasma levels of catecholamines, beta-thromboglobulin and TxB2 blood concentrations either under basal conditions or after CPT. Our data suggest that gallopamil is able to modulate the response induced by adrenergic stress.

Enhanced insulin response relates to acetylcholine-induced vasoconstriction in vasospastic angina

OBJECTIVES

This study investigated whether insulin response to an oral glucose load correlates to acetylcholine-induced coronary vasoconstriction in subjects with vasospastic angina.

BACKGROUND

It has been suggested that coronary vasospasm is caused by augmented vascular responsiveness possibly exerted by atherosclerosis. Recently, insulin resistance syndrome has been proposed as a major promotor of atherosclerotic disease, potentially enhancing vascular smooth muscular tone.

METHODS

Among subjects with angiographically smooth coronary arteries, we selected 14 subjects with vasospastic angina and 14 age- and gender-matched subjects with atypical chest pain. We compared coronary vasomotor response to acetylcholine infusion, glucose and insulin responses to an oral glucose load (75 g), serum lipid concentrations, obesity, heart rate, blood pressure and smoking habits in both groups.

RESULTS

Fasting serum insulin concentrations and insulin response were higher in subjects with vasospastic angina than in those with atypical chest pain; however, glucose tolerance, obesity, heart rate, blood pressure and smoking habits did not differ between groups. In subjects with vasospastic angina, nearly all coronary segments, except distal segments of the left circumflex coronary artery, were constricted at peak acetylcholine infusion (20 to 100 micrograms), whereas all segments were dilated in subjects with atypical chest pain. Regression analysis for both groups demonstrated a correlation between coronary vasoconstriction and fasting serum insulin concentrations (r = 0.52, p < 0.01), insulin response (r = 0.71, p < 0.001), serum triglyceride concentrations (r = 0.51, p < 0.05) and atherogenic index (r = 0.44, p < 0.05).

CONCLUSIONS

Results show that acetylcholine-induced coronary vasoconstriction in subjects with vasospastic angina correlates with hyperinsulinemia and enhanced insulin response, suggesting insulin resistance syndrome as a feature of vasospastic angina.

Pathogenesis of acute myocardial infarction. Novel regulatory systems of bioactive substances in the vessel wall

Rupture of the lipid-rich atheromatous plaque, intraplaque hemorrhage, and intraluminal thrombus are three pathological hallmarks most commonly recognized in the infarct-related coronary artery at the site of acute myocardial infarction. Rupture of the atheromatous plaque is closely related to but does not fully explain the genesis of occlusive intracoronary thrombus formation and thus the development of acute myocardial infarction. Besides a variety of hematologic disorders, one should emphasize the role of the platelet-derived mediators that promote an environment where thrombosis and vasoconstriction occur, including TXA2, serotonin, ADP, platelet-derived growth factor, tissue factor, and the diminished availability of those natural endogenous substances that inhibit platelet aggregation, such as EDRF, tissue plasminogen activator, and PGI2. PGI2 released from vascular endothelial cells is extremely unstable. Our group provided the first evidence that HDL stabilizes PGI2 through the newly discovered function of Apo A-I, which is associated with the surface of HDL particles and identified as PGI2 stabilizing factor. Decrease in HDL-associated Apo A-I in patients with unstable angina and during the acute phase of myocardial infarction indicates that HDL plays an important role in preventing coronary atherosclerosis and intracoronary thrombus formation by stabilizing PGI2 in addition to the generally accepted biochemical property of HDL to prevent the accumulation of cholesterol by mobilizing free cholesterol from tissues or macrophages. There is also a PGI2 synthesis-stimulating factor in serum that has not yet been identified chemically. EDRF or nitric oxide provides another important regulating system in the vessel wall. Lipoproteins are inhibitors of endothelium-dependent relaxation of rabbit aorta.(ABSTRACT TRUNCATED AT 250 WORDS)

Eicosanoid biosynthesis in patients with stable angina: beneficial effects of very low dose aspirin

OBJECTIVE

We assessed the production of eicosanoids and the effects of very low dose aspirin in patients with stable angina under basal conditions and during rapid atrial pacing.

BACKGROUND

Platelet activation occurs in acute ischemic syndromes but is still controversial in stable angina. Very low dose aspirin is known to be platelet selective and can be used to test the hypothesis of the platelet origin of increased thromboxane production in stable angina.

METHODS

Urinary excretion of eicosanoids was measured in 42 patients, including 24 patients with and 18 patients without coronary artery disease. The effects of 50 mg/day of aspirin were measured at rest and during pacing-induced ischemia in 10 patients with stable angina and were compared with a similar group of patients not treated by aspirin.

RESULTS

Excretion of 11-dehydro-thromboxane B2 was 2.6 times higher in patients with stable angina than in healthy subjects (mean [+/- SEM] 74.8 +/- 13.0 [24 patients] vs. 29.0 +/- 5.4 [18 patients] ng/mmol of creatinine, p < 0.01). Urinary prostacyclin metabolite levels did not differ between the two groups. Treatment for 8 days with 50 mg/day of aspirin inhibited platelet cyclooxygenase, as reflected by the 97% reduction of in vitro serum thromboxane production. This aspirin regimen normalized the level of urinary thromboxane metabolites in patients with angina (17.3 +/- 3.4 ng/mmol of creatinine [10 patients], p < 0.001 from baseline level before treatment) and did not change prostacyclin metabolite levels. Atrial pacing in patients with angina not treated with aspirin caused lactate and thromboxane release into the coronary sinus. In patients with very low dose aspirin therapy, pacing did not cause thromboxane release despite inducing myocardial ischemia. However, fractional lactate extraction decreased less sharply in patients with than without aspirin therapy.

CONCLUSIONS

Thromboxane production is greatly increased in patients with stable angina. Very low dose aspirin administered to these patients reduces thromboxane synthesis to normal levels, preserves prostacyclin biosynthesis and prevents acute thromboxane release into the coronary circulation during pacing-induced ischemia. Our data suggest that platelets (not monocytes/macrophages) are activated in stable angina to produce thromboxane.

Effects of bepridil on silent myocardial ischemia and eicosanoid metabolism in chronic stable angina pectoris after healing of myocardial infarction

To investigate the effects of bepridil on silent myocardial ischemia and on eicosanoid metabolism, 10 patients with chronic stable angina underwent exercise treadmill testing and 48-hour ambulatory electrocardiographic monitoring both before and after 4 weeks of bepridil administration (150 mg/day). Fasting venous levels of thromboxane B2, 6-keto-prostaglandin F1 alpha, and leukotriene C4 were measured by radioimmunoassay. Bepridil decreased heart rate responses to daily activities during ambulatory monitoring, and significantly (p < 0.05) reduced the median frequency and duration of silent myocardial ischemic episodes (from 5.5 to 0 events/48 hours and from 86 to 0 minutes/48 hours respectively). Bepridil significantly decreased the blood pressure heart rate product at peak exercise and significantly prolonged the mean exercise tolerance time (from 456.6 to 527.0 second). Bepridil also significantly decreased the plasma levels of thromboxane B2 and leukotriene C4 at rest. These results suggest that bepridil may reduce silent myocardial ischemic episodes either by the reduction of cardiac oxygen demand during daily activities and exercise stress, or by controlling coronary and systemic vasomotor tone. The drug also has a salutary effect on eicosanoid metabolism, to which its efficacy on silent myocardial ischemic episodes may be related.

Beneficial effects of smoking cessation on the short-term prognosis for variant angina--validation of the smoking status by urinary cotinine measurements

To examine whether smoking cessation would improve the short-term prognosis for patients with variant angina, 37 smokers with variant angina who were discharged after the complete disappearance of angina by medical treatment with calcium blockers were advised to stop smoking and were followed-up for 1 year. Urinary cotinine radioimmunoassay was used to evaluate their current smoking status. Patients with a urinary cotinine concentration above 50 ng/ml were classified as current smokers. The prevalence of smokers was underestimated by self-reports (11% by self-reports vs. 35% by urinary cotinine measurements after 3 months; 17% by self-reports vs. 36% by urinary cotinine measurements after 1 year). The presence of angina during the first 3 months was significantly (P < 0.05) more prevalent in those who continued to smoke (8/13, 62%) than in those who succeeded in smoking cessation (5/24, 21%) when the current smoking status was determined by urinary cotinine measurements. Smoking cessation definitely improved the prognosis for variant angina even during a relatively short follow-up period.

Low-dose aspirin inhibits platelet-induced contraction of the human isolated coronary artery. A role for additional 5-hydroxytryptamine receptor antagonism against coronary vasospasm?

BACKGROUND

The beneficial effect of low-dose aspirin in the prevention of coronary vasospasm is well documented. In this study, we investigated the contractile effect of human washed platelets on the human isolated coronary artery. We concentrated on the effect of low-dose aspirin (40 mg/d) taken by the platelet donor and on the efficacy of thromboxane A2 (TXA2) and 5-hydroxytryptamine (5-HT) receptor antagonists.

METHODS AND RESULTS

Human coronary artery segments were suspended in an organ bath set-up for isometric tension measurement. Platelets (10(9) to 3 x 10(10)/L) elicited concentration-dependent contractile responses of the coronary artery segments, reaching 28.4 +/- 7.1% of contractions induced by 100 mmol/L K+. The contractile response tended to be decreased in vessel segments with histological signs of early atherosclerosis. Contraction was significantly attenuated after pretreatment of the vessel segments with ketanserin (5-HT2 receptor antagonist, 1 mumol/L) or SQ30741 (TXA2 receptor antagonist, 0.01 mumol/L), reaching 8.8 +/- 2.3% and 3.2 +/- 2.2% of contraction to 100 mmol/L K+, respectively. Platelets obtained from the same platelet donors after they had taken aspirin (40 mg/d for 7 to 13 days) caused significantly lower contractile responses (7.6 +/- 2.7% of 100 mmol/L K+) associated with an almost selective inhibition of the synthesis of thromboxane measured in the organ bath solution (untreated platelets, 2.19 +/- 0.43 nmol/L; aspirin-treated platelets, 0.66 +/- 0.05 nmol/L). The amount of 5-HT secreted in the organ bath remained unaltered (65.17 +/- 9.94 and 64.03 +/- 8.98 nmol/L, respectively). This explains why ketanserin significantly attenuated the residual contractile responses caused by platelets obtained from aspirin-treated subjects, whereas SQ30741 caused minor, nonsignificant additional attenuation.

CONCLUSIONS

The results of the present study therefore suggest that additional antagonism of the contractile 5-HT receptors in the coronary artery may increase the efficacy of low-dose aspirin in vivo.

Bronchial hyperresponsiveness to acetylcholine in patients with vasospastic angina pectoris

STUDY OBJECTIVE

To investigate the similarity between coronary vasospasm and bronchial spasm.

DESIGN

Nonrandomized, case-control study.

SETTING

Referral-based clinics for cardiac and pulmonary disease at one secondary care center.

PATIENTS

Seventeen patients with vasospastic angina pectoris (VSAP) and 14 patients with chest pain syndrome (CPS).

INTERVENTIONS

Medications prohibited: those with known effects on bronchial responsiveness.

MEASUREMENT

Induction of coronary vasospasm: ergonovine maleate (10, 20, 40 micrograms) injection into coronary arteries during coronary angiography. Bronchial responsiveness to acetylcholine (ACh): acetylcholine chloride (0.08 to 20 mg/ml) inhalation and calculation of the provocative concentration of ACh (PC20-ACh) that revealed 20 percent fall in FEV1.

RESULTS

The median value for PC20-ACh in patients with VSAP, 7.80 mg/ml, was significantly lower than that in patients with CPS, > 20.0 mg/ml (p < 0.01 by Mann-Whitney U test). The PC20-ACh in patients with VSAP, however, was correlated neither with the responsive threshold of ergonovine maleate, which induced coronary vasospasm, nor with the duration from the latest angina attack.

CONCLUSION

These results suggest that bronchial responsiveness was increased in most patients with VSAP, but not with CPS. We therefore speculate that patients with VSAP may also have hypercontractibility to ACh of noncoronary systemic smooth muscles.

Granulocyte colony-stimulating factor does not exacerbate endotoxin-induced lung injury in sheep

Because it has been suggested that neutrophils play a role in endotoxin-induced lung injury, we examined the effects of increased peripheral blood-neutrophils induced by recombinant human granulocyte-colony-stimulating factor (rhG-CSF) on the lung dysfunction when induced by endotoxin in awake sheep. We prepared chronically instrumented awake sheep with lung lymph fistulae and catheters for hemodynamic monitoring. We compared alterations of pulmonary hemodynamics, lung lymph balance, circulating leukocytes, plasma and lung lymph concentrations of thromboxane B2 and 6-keto-prostaglandin F1 alpha, and arterial blood gases in sheep that received Escherichia coli endotoxin infusion intravenously (1 microgram/kg) in the following two groups: Group 1 (n = 6) received endotoxin alone, and Group 2 (n = 7) received rhG-CSF (125 micrograms/day) intravenously for 3 days before endotoxin was administered in the same manner as in Group 1. The rhG-CSF remarkably increased circulating neutrophils to 24,600 +/- 2,500/microliters in Group 2 sheep at baseline when compared with the level in Group 1 (5,700 +/- 550 microliters). After endotoxin infusion, we observed significant decreases in circulating neutrophils in both groups. There were no differences between the two groups in the time course of changes in pulmonary hemodynamics, arterial blood gases, or arachidonate products after endotoxemia. However, lung lymph flow and lung lymph protein clearance during the late phase were lower in rhG-CSF-treated sheep than in those that received only endotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of diltiazem on silent ischemic episodes, plasma bradykinin and prostaglandin metabolism

Plasma bradykinin and prostaglandin metabolism are related to the anginal pain modulating system in patients with ischemic heart disease. We carried out a placebo controlled single blind test of diltiazem (30 mg three times a day) in 15 patients with chronic stable angina. The effect of diltiazem was evaluated by exercise treadmill testing and 48-h ambulatory electrocardiographic monitoring. Plasma bradykinin, thromboxane B2, and 6-keto-prostaglandin F1 alpha levels were determined by radioimmunoassay prior to and during diltiazem therapy. Diltiazem significantly increased the exercise time and reduced episodes of angina. Diltiazem, however, did not appreciably improve either the frequency of silent myocardial ischemic episodes or the total duration of the silent myocardial ischemic episodes. Diltiazem also tended to decrease plasma bradykinin, thromboxane B2, and 6-keto-prostaglandin F1 alpha levels. When ischemic episodes on ambulatory electrocardiographic monitoring are categorized according to heart rate change at the onset of episode (type A, preceded by heart rate increase > or = 5 beats/min; type B, no preceding heart rate increase), diltiazem was only effective on type A ischemic episodes as well as on symptomatic ischemia. Further, bradykinin was significantly decreased by diltiazem only in patients with exercise-induced silent ischemia or no exercise-induced ischemia, while the thromboxane B2/6-keto-prostaglandin F1 alpha ratio was unaffected by the administration of diltiazem. Thus, silent and symptomatic ischemia may be associated with different bradykinin and prostaglandin responses.

Statistical analysis of clinical risk factors for coronary artery spasm: identification of the most important determinant

Coronary artery spasm plays an important role in acute ischemic events, and it has a close relationship with coronary atherosclerosis. Thus we attempted to determine the most significant risk factor for coronary artery spasm. Among 3000 consecutive patients who underwent coronary cineangiography with ergonovine maleate testing, 330 with typical angina pectoris (group 1) and 294 with old myocardial infarction (group 2) were studied. We divided each group into three or four subgroups according to the presence of fixed organic stenosis (FOS+) or a positive reaction to ergonovine maleate (coronary artery spasm [CAS]+). We examined the relationship between coronary artery spasm and eight coronary risk factors: age, sex, hypertension, diabetes mellitus, smoking, and serum cholesterol, uric acid, and high-density lipoprotein cholesterol levels. The proportion of smokers in the subgroups with CAS(+) was significantly higher than in the subgroups with CAS(-)(p less than 0.01). There was no correlation between smoking and fixed organic stenosis. According to the results of multiple regression analysis, there was a positive correlation between smoking and CAS(+) and between serum high-density lipoprotein cholesterol levels and CAS(+)(p less than 0.01). Thus we concluded that smoking is the most significant risk factor in discriminating between patients with and without coronary artery spasm.

A novel loop diuretic, torasemide, inhibits thromboxane A2-induced contraction in the isolated canine coronary artery

We examined the effect of a novel antihypertensive diuretic, torasemide, on the vasoconstriction induced by TXA2 in the isolated canine coronary artery. Carbocyclic thromboxane A2 (CTA2), a stable analogue of the potent coronary vasoconstrictor thromboxane A2, exhibited a slow onset and progressive contraction of isolated canine coronary arteries at 2 x 10(-8) M. Torasemide (10(-7) approximately 10(-4) M) elicited a dose-dependent vasodilating action in the isolated canine coronary arteries contracted by CTA2, whereas indapamide or furosemide had little effect on this preparation. The maximum vasodilating response to torasemide was 45 +/- 12% of vasodilating effect induced by 10(-4) M papaverine. These results suggest that torasemide is a promising antihypertensive agent with a coronary protective effect.

Evaluation of thromboxane production and complement activation during myocardial ischemia in patients with angina pectoris

BACKGROUND

The complement system and arachidonic acid metabolites are involved in severe myocardial ischemia such as myocardial infarction. Furthermore, there is experimental evidence for C5a participation in thromboxane production.

METHODS AND RESULTS

We examined whether C5a and thromboxane are produced during brief and reversible episodes of myocardial ischemia induced in patients with stable angina. Twenty-five patients underwent either atrial pacing or percutaneous transluminal coronary angioplasty associated with arterial and coronary sinus blood sampling. Rapid atrial stimulation of patients with effort angina caused significant ST segment depression (delta ST = -1.7 +/- 0.2 mm), decreased fractional lactate extraction (from +12.8 +/- 2.5% baseline to -13.7 +/- 4.6% at peak ischemia, n = 13, p less than 0.001), and increased coronary sinus plasma thromboxane B2 levels (from 345 +/- 85 pg/ml baseline to 1,684 +/- 64 pg/ml at peak ischemia, p less than 0.01). Changes of fractional lactate extraction correlated significantly with changes of coronary sinus plasma levels of thromboxane B2. There was no change of coronary sinus 6-keto-PGF1 alpha levels. Similar pacing of control subjects (n = 6) did not cause release of lactate or thromboxane. Seventeen other patients underwent exercise testing with noninvasive measurements of thromboxane and prostacyclin metabolites in urinary samples collected before and after the test. No detectable increase of urinary 11-dehydrothromboxane B2 was measured in patients with stable angina after exercise-induced myocardial ischemia. However, basal 11-dehydrothromboxane B2 levels were significantly higher in patients with angina (105 +/- 25 pg/mmol creatinine, n = 9) than in control patients (45 +/- 8 pg/mmol creatinine, n = 8, p less than 0.05 between groups). Coronary sinus plasma levels of the anaphylatoxin C5a always remained below 4 ng/ml in patients undergoing pacing. More severe myocardial ischemia after coronary angioplasty (percent lactate extraction decreased from +24.8 +/- 2.7% baseline to -41.6 +/- 22.4% at peak ischemia, p less than 0.05) was not associated with C3a or C5b-9 generation. In all patients, there was neither platelet sequestration nor platelet alpha-granule release (no changes of beta-thromboglobulin/platelet factor 4 levels) into the coronary sinus plasma.

CONCLUSIONS

Patients with stable angina have chronically increased thromboxane synthesis as assessed by excretion of urinary metabolites. Thromboxane is acutely released into the coronary sinus during pacing-induced ischemia without significant intracoronary platelet aggregation. Complement does not appear to be activated in stable angina during brief and reversible episodes of myocardial ischemia and does not contribute to thromboxane production.

Plasma 11-dehydrothromboxane B2: a reliable indicator of platelet hyperfunction in patients with ischemic stroke

The plasma level of 11-dehydrothromboxane B2 (11-dehydroTXB2) is free from artifactual increase during blood sampling, and it can be reliable indicator of TXA2 production in vivo. We have estimated plasma 11-dehydroTXB2 in patients with ischemic stroke. Subjects studied were 29 patients with cerebral thrombosis (62 +/- 9 years old) and 41 healthy controls (61 +/- 7 years old). Plasma 11-dehydroTXB2 and TXB2 were determined by radioimmunoassay. Plasma 11-dehydroTXB2 levels in patients and controls were 5.4 +/- 2.5 and 1.8 +/- 0.9 pg ml, respectively, and the difference was significant (p less than 0.001). Plasma TXB2 also was higher in patients than in controls: 401 +/- 61 vs 311 +/- 51 pg/ml (p less than 0.05). However, the 11-dehydroTXB2 was found to be a more effective parameter to distinguish between stroke patients and controls. Estimation of plasma 11-dehydroTXB2 levels is a reliable method to detect platelet hyperfunction in stroke patients.

Fibrinopeptide A is released into the coronary circulation after coronary spasm

To examine whether acute myocardial ischemia activates the coagulation system and platelet activation in the coronary circulation, we measured plasma levels of fibrinopeptide A and beta-thromboglobulin in the coronary sinus and the aortic root simultaneously in 15 patients with coronary spastic angina before and after the left coronary spasm induced by intracoronary injection of acetylcholine and in 15 patients with stable exertional angina before and after acute myocardial ischemia induced by rapid atrial pacing. Fifteen patients with chest pain but normal coronary arteries and no coronary spasm served as controls. The coronary sinus-arterial difference of fibrinopeptide A increased markedly (p less than 0.001) from 0.1 +/- 0.2 to 4.3 +/- 0.7 ng/ml after the anginal attacks in the coronary spastic angina group. However, fibrinopeptide A levels remained unchanged after the attacks in the stable exertional angina group and after intracoronary injection of acetylcholine in the control group. Plasma beta-thromboglobulin levels remained unchanged after the attacks in both patient groups and after acetylcholine in the control group. Our data indicate that coronary spasm induces thrombin generation and may lead to thrombus formation in the coronary artery involved, but pacing-induced ischemia does not activate the coagulation system.

The role of serotonin in cardiovascular diseases and their treatment

Serotonin (5HT), discovered in the 1950s, has been the subject of renewed interest for several years, in particular due to the subdivision of 5HT receptors into various types. Concomitantly, several more or less selective agonists and antagonists for these various receptor subtypes have been developed. Although the physiologic relevance of 5HT remains largely unknown, its role in certain pathologic processes is widely accepted. Certain symptoms of the carcinoid syndrome, thromboembolic processes at the level of the microcirculation, and possibly also coronary spasm and peripheral vascular disease are likely to be associated, at least in part, with endogenous 5HT and serotonergic mechanisms. However, a primary and causative role for such mechanisms in essential hypertension seems unlikely. The blockade of peripheral 5HT2 receptors with drugs may offer advantages, in particular in those disorders where an interaction between predamaged blood vessels and platelets is involved. Such a therapeutic approach seems to be a more generally applicable principle than the lowering of blood pressure as such, which appears not to be a general phenomenon provoked by 5HT2-receptor blockade.