Loredana Poggesi

DIFFERENTIAL INHIBITION OF PROSTACYCLIN PRODUCTION AND PLATELET AGGREGATION BY ASPIRIN

Abstract The effect of aspirin ingestion on platelet aggregation, malondialdehyde (MDA) formation, and prostacyclin (PGI 2 ) production by the blood-vessel wall was investigated in twenty-five healthy young volunteers. PGI 2 production induced by ischaemia in the arm was assayed in venous blood. MDA formation and platelet aggregation induced by adenosine disphosphate (ADP), collagen, and adrenaline were inhibited by doses of aspirin smaller than those inhibiting prostacyclin production. The doses which inhibited 50% of platelet aggregation (ID 50) were 3·2 mg/kg for adrenaline, 3·4 for ADP, and 3·2 for collagen, whereas the ID 50 for prostacyclin production was 4·9 mg/kg. Inhibition of platelet aggregation increased only slightly with increasing doses, whereas inhibition of PGI 2 production increased linearly up to 8 mg/kg. Inhibition of platelet aggregation and MDA formation was still present after 72 h, whereas prostacyclin inhibition reversed within 24 h in all subjects after 2, 3·5, and 5 mg/kg and in 6 out of 9 subjects after 8 and 10 mg/kg. These findings indicate that inhibition of platelet cyclo-oxygenase occurs with smaller doses of aspirin and lasts longer than inhibition of vessel-wall cyclo-oxygenase. 3·5 mg/kg is the dose of aspirin most likely to produce a consistent inhibition of platelet aggregation and only a slight inhibition of prostacyclin production.

Transient intermittent lymphocyte activation is responsible for the instability of angina.

BackgroundBlood clotting activation is an important component of the inflammatory response; the outbursts of unstable angina are usually associated with increased thrombin formation and coronary mural thrombosis. Methods and ResultsTo investigate 1) whether monocyte activation is responsible for the enhanced thrombin formation during bursts of unstable angina and 2) what mechanism(s) might be responsible for monocyte activation, we studied patients with unstable angina (n=31), stable effort angina (n=23), left endoventricular thrombosis (n=8), and control subjects (n=44), measuring plasma fibrinopeptide A (FPA) levels and the capacity of monocytes to express procoagulant activity (PCA) and of lymphocytes to modulate this expression. Patients with unstable angina and patients with endoventricular thrombosis had significantly (p<0.0001) higher FPA plasma levels than patients with effort angina and control subjects. However, only monocytes from unstable angina patients expressed significantly increased PCA characterized as tissue factor-like activity (units/105 monocytes, median and range; 120, 1.1–463.2 versus 10.8, 0.8–39.1 in control subjects; p<0.0001 versus the other groups). When 14 patients with unstable angina were restudied 8–12 weeks later, they showed neither elevated plasma FPA levels nor monocyte PCA. In unstable angina patients, there was a correlation between FPA and PCA (r=0.56, p<0.001). For expression of PCA by monocytes, both an incubation of at least 2 hours with lymphocytes and direct monocyte-lymphocyte contact were needed. In reconstitution and cross-mixing experiments, only lymphocytes from patients with active unstable angina induced the expression ofPCA by monocytes from both control and patient groups. ConclusionsThe results demonstrate that the increased thrombin formation in unstable angina patients is due to the expression of tissue factor-like activity by activated monocytes. The monocyte activation appears to be a part of a lymphocytic cell-instructed response intermittently triggered by unknown factors.

Acute T-cell activation is detectable in unstable angina.

BACKGROUND Recent studies suggest a role for inflammation in the pathophysiology of unstable angina. This study was designed to investigate whether circulating lymphocytes are involved in the inflammatory reaction associated with the episodes of unstable angina. METHODS AND RESULTS Twenty-nine patients with proven unstable angina, 36 with stable angina, and 30 healthy subjects were studied. Both early and short-lived (interleukin-2 receptor [IL-2R], alpha-chain CD25, and transferrin receptor CD71) and late antigen (HLA-DR) expression were investigated by flow cytometric analysis. Soluble IL-2R (sIL-2R) was also measured in plasma by ELISA. Lymphocyte activation was studied at day 1 of hospital admission and after 7, 15, 30, 60, and 90 days. In patients with unstable angina, the number of HLA-DR+ CD3 lymphocytes and levels of sIL-2R were higher (P < .001) than in patients with stable angina and control subjects. Both CD4+ and CD8+ lymphocytes expressed HLA-DR antigens. No differences were found among the different groups of subjects in regard to the expression of CD25 and CD71. Lymphocyte activation was more marked in patients with urgent revascularization. No relationships were found between the number of HLA-DR+ lymphocytes and either the severity of coronary angiographic lesions or the number of ischemic episodes. Observations over time showed a gradual decrease in the number of HLA-DR+ lymphocytes and sIL-2R levels from weeks 3 through 8 to 12. CONCLUSIONS The present results indicate that (1) CD4+ and CD8+ circulating lymphocytes are activated in patients with unstable angina, and their activation state lasts 6 to 8 weeks; and (2) activation of lymphocytes is not a consequence of myocardial ischemia. These results support the immune system-mediated inflammatory nature of unstable angina.

Effect of heparin, aspirin, or alteplase in reduction of myocardial ischaemia in refractory unstable angina

399 out of 474 inpatients with unstable angina were monitored for 48 h and 97 of these were found to be refractory to conventional antianginal treatments and entered a randomised double-blind study. With the initial protocol heparin infusion or bolus were compared with aspirin; with a modified protocol, heparin infusion, the best of these three treatments, was compared with alteplase. Patients were monitored for 3 days after starting treatment and then observed clinically for 4 more days. On the first days of treatment heparin infusion significantly decreased the frequency of angina (by 84-94%), episodes of silent ischaemia (by 71-77%), and the overall duration of ischaemia (by 81-86%). Heparin bolus and aspirin were not effective. Alteplase caused small (non-significant) reductions on the first day only. Only minor bleeding complications occurred.

Evidence for the Existence of a Functional Cardiac Renin-Angiotensin System in Humans

BACKGROUND The presence of mRNA for the essential components of the renin-angiotensin system (RAS) has been found in animal and human hearts. The present study was designed to provide evidence for the existence of a (functional) cardiac RAS. METHODS AND RESULTS Twenty-four patients with atypical chest pain undergoing coronary angiography for diagnostic purposes were investigated. The cardiac production rate of angiotensins was estimated by measurement of the cardiac extraction of 125I-angiotensin I and 125I-angiotensin II associated with the determination of endogenous angiotensins in aortic and coronary sinus blood in normal, low, or high sodium diets. In a normal sodium diet, angiotensin I and II aorta-coronary sinus gradients were tendentially negative (-1.8 +/- 2.5 and -0.9 +/- 1.7 pg/mL, respectively), and the amounts of angiotensin I and II added by cardiac tissues were 6.5 +/- 3.1 and 2.7 +/- 1.3 pg/mL, respectively. The low sodium diet caused a significant increase in both plasma renin activity (PRA) and angiotensin I concentration in aortic but not in coronary sinus blood, resulting in a more negative aorta-coronary sinus gradient (-9.7 +/- 3.1 pg/mL, P < .01). Angiotensin formation by PRA in blood during transcardiac passage increased (P < .001), whereas angiotensin I formed by cardiac tissues decreased dramatically. Accordingly, in the low sodium diet, 125I-angiotensin II extraction did not change, the cardiac fractional conversion rate of 125I-angiotensin I to 125I-angiotensin II notably decreased (P < .01), and angiotensin II formation by cardiac tissues was undetectable. The high sodium diet caused a decrease in PRA and no changes in cardiac extraction of radiolabeled angiotensins; conversely, angiotensin I formed by cardiac tissues, cardiac Ang I fractional conversion rate, and angiotensin II formed during transcardiac passage significantly (P < .01 for all) increased. CONCLUSIONS These results provide evidence for the existence of a functional cardiac RAS independent of but related to the circulating RAS.

Human Vascular Renin-Angiotensin System and Its Functional Changes in Relation to Different Sodium Intakes

A growing body of evidence supports the existence of a tissue-based renin-angiotensin system (RAS) in the vasculature, but the functional capacity of vascular RAS was not investigated in humans. In 28 normotensive healthy control subjects, the metabolism of angiotensins through vascular tissue was investigated in normal, low, and high sodium diets by the measurement of arterial-venous gradient of endogenous angiotensin (Ang) I and Ang II in two different vascular beds (forearm and leg), combined with the study of 125I-Ang I and 125I-Ang II kinetics. In normal sodium diet subjects, forearm vascular tissue extracted 36+/-6% of 125I-Ang I and 30+/-5% of 125I-Ang II and added 14.9+/-5.1 fmol x 100 mL(-1) x min(-1) of de novo formed Ang I and 6.2+/-2.8 fmol x 100 mL(-1) x min(-1) of Ang II to antecubital venous blood. Fractional conversion of 125I-Ang I through forearm vascular tissue was about 12%. Low sodium diet increased (P<.01) plasma renin activity, whereas de novo Ang I and Ang II formation by forearm vascular tissue became undetectable. Angiotensin degradation (33+/-7% for Ang I and 30+/-7% for Ang II) was unchanged, and vascular fractional conversion of 125I-Ang I decreased from 12% to 6% (P<.01). In high sodium diet subjects, plasma renin activity decreased, and de novo Ang I and Ang II formation by forearm vascular tissue increased to 22 and 14 fmol x 100 mL(-1) x min(-1), respectively (P<.01). Angiotensin degradation did not significantly change, whereas fractional conversion of 125I-Ang I increased from 12% to 20% (P<.01). Leg vascular tissue functional activities of RAS paralleled those of forearm vascular tissue both at baseline and during different sodium intake. These results provide consistent evidence for the existence of a functional tissue-based RAS in vascular tissue of humans. The opposite changes of plasma renin activity and vascular angiotensin formation indicate that vascular RAS is independent from but related to circulating RAS.

Randomised comparison of subcutaneous heparin, intravenous heparin, and aspirin in unstable angina

Intravenous heparin has been used in the control of myocardial ischaemia in patients with unstable angina. We set out to assess the efficacy of subcutaneous heparin in reducing myocardial ischaemia in patients with unstable angina. 343 of 399 patients with unstable angina were monitored for 24 h and 108 were refractory to conventional antianginal treatment and were entered into a randomised multicentre trial. 37 patients were assigned to heparin infusion (partial thromboplastin time 1.5-2 times baseline), 35 to subcutaneous heparin (adjusted dose with partial thromboplastin time 1.5-2 times baseline), and 36 to aspirin (325 mg daily). All had additional conventional antianginal therapy. After the run-in patients were monitored for 3 days. The primary endpoint was reduced myocardial ischaemia assessed by the number of anginal attacks, silent ischaemic episodes, and duration of ischaemia per day. At 1 week and 1 month we accounted for anginal attacks and other clinical events (myocardial infarction, revascularisation procedures, and death). Aspirin did not significantly affect the incidence of myocardial ischaemia. On the first 3 days, infused and subcutaneous heparin significantly decreased the frequency of angina (on average by 91% and 86%, respectively), episodes of silent ischaemia (by 56% and 46%), and the overall duration of ischaemia (66% and 61%) versus run-in day and aspirin (p < 0.001 for all variables). The favourable effects of heparin therapy remained evident during follow-up. Only minor bleeding complications occurred. Subcutaneous heparin is effective in the control of myocardial ischaemia in patients with unstable angina.

Reduced prostacyclin production in patients with different manifestations of ischemic heart disease

Prostacyclin, a substance produced by vessel wall, has a sustained vasodilating and platelet antiaggregating activity and therefore the variations in its production in patients with ischemic heart disease are of interest. Prostacyclin production was assessed in 59 patients with ischemic heart disease and 59 control subjects matched for age, sex, body weight, smoking habits, blood pressure and serum cholesterol levels. Of the 59 patients examined, 23 had had a myocardial infarction 3 to 12 months earlier; 21 had had spontaneous angina and 15 effort angina for at least 3 months. Patients with myocardial infarction and spontaneous angina were also classified in subgroups with and without acute coronary insufficiency, according to the occurrence of ischemic attacks in the week preceding the study. Both circulating prostacyclin levels and prostacyclin produced after 3 minutes of ischemia were measured by bioassay. Circulating prostacyclin was significantly less in patients with ischemic heart disease than in matched control subjects independent of the clinical type of ischemic heart disease. Circulating prostacyclin was particularly reduced in patients with acute coronary insufficiency in comparison to patients without, both in the group with myocardial infarction (1.11 +/- 0.22 ng/ml and 2.09 +/- 1.32, respectively) and in the group with spontaneous angina (1.24 +/- 0.42 and 2.17 +/- 1.16, respectively). No differences could be found for prostacyclin produced after 3 minutes of ischemia in relation to the presence of acute coronary insufficiency. The lower level of prostacyclin production in patients with ischemic heart disease and especially in those with acute coronary insufficiency may be an important factor in the occurrence of coronary occlusion or spasm.

Renal resistive index early detects chronic tubulointerstitial nephropathy in normo- and hypertensive patients

Background: We studied whether the measurement of intrarenal vascular resistance by Doppler ultrasonography, capable of investigating renal interstitial compartment, allows the early detection of chronic tubulointerstitial nephropathy (TIN). Methods: 30 normotensive and 28 hypertensive (I-II OMS) patients with a clinical history suggestive of chronic TIN and normal renal function were enrolled. 40 healthy volunteers served as controls. Patients were considered TIN-negative or TIN-positive after investigating tubular function by urine concentrating and acidification tests. Renal sonographic parameters and renal resistive index (RRI) were obtained by duplex scanner. Glomerular filtration rate/effective renal plasmatic flow ratio was investigated by sequential renal scintigraphy in TIN-negative and TIN-positive patients; 99mTc-DMSA scintigraphy was also performed in TIN-positive patients. Results: RRI values of TIN-positive normotensive and hypertensive patients were significantly higher (p < 0.01 for both) than those of TIN-negative patients and of controls. RRI values resulted to be linearly related to uricemia (r = 0.88, p < 0.0001) only in normotensive patients. RRI values also resulted to be linearly related to filtration ratio values (r = 0.60, p < 0.0001). 99mTc-DMSA scintigraphy confirmed interstitial renal damage (grade 1 and 2). Conclusion: RRI measurement allows the early identification of both normotensive and hypertensive patients with chronic TIN and signs of tubular dysfunction, when renal function is still preserved.

Enhanced prostacyclin production by dipyridamole in man

SummaryThe effects of some phosphodiesterase (PDE) inhibitors (dipyridamole, theophylline, papaverine and SH-869) on prostacyclin (PGI2) production have been studied in vitro and in vivo. PGI2 was bioassayed by Vanes superfusion technique. In rabbit aortic rings, only dipyridamole in concentrations from 1 to 12 µM was able to stimulate PGI2 biosynthesis in a dose-dependent manner. This effect was also detected with so-called “exhausted” rabbit aortic rings. The other PDE inhibitors used, both in µM and mM concentration, did not affect PGI2 biosynthesis. Dipyridamole was found to increase PGI2 production in healthy volunteers, when given both by infusion (8 µg/kg/min × 2 h) and by oral administration (375 mg/day for seven days). Circulating PGI2 and PGI2 production induced by a 3-min period of ischaemia were increased by an average of 137% (p<0.001) and 30.8% (p<0.001) respectively. Saline and theophylline (as aminophylline) infusions used as controls did not affect PGI2 production.