M.B. Donati

HÆMOLYTIC-URÆMIC SYNDROME: DEFICIENCY OF PLASMA FACTOR(S) REGULATING PROSTACYCLIN ACTIVITY?

It is suggested that patients with the haemolytic-uraemic syndrome and related disorders (such as thrombotic thrombocytopenic purpura) lack a plasma factor which stimulates prostacyclin (P.G.I2) activity. Normal plasma would supply the missing factor and is a rational treatment for some life-threatening symptoms (thrombocytopenia, haemolytic anaemia, hypertension) of this syndrome.

Reduced umbilical and placental vascular prostacyclin in severe pre-eclampsia

Prostacyclin production was significantly depressed in foetal and placental vascular tissues from five patients with severe pre-eclampsia in comparison to vascular tissues from women with uncomplicated pregnancy. Such an abnormality may be responsible for a reduced blood flow and defective fetal nutrition thus playing a major role in the pathogenesis of this syndrome.

Human polymorphonuclear leukocytes produce and express functional tissue factor upon stimulation

Summary.  Background: Blood‐borne tissue factor (TF) plays a crucial role in thrombogenesis. Aim: To study whether polymorphonuclear leukocytes (PMN) are a source of TF. Methods and Results: Human PMN were carefully separated from other blood cells and stimulated for 3 min with purified P‐selectin or the chemotactic peptide formyl‐MetLeuPhe (fMLP): they expressed both TF procoagulant activity, as identified by specific TF MoAb and inactivated factor VIIa blockade; and TF:Ag (four to six times), as shown by flow‐cytometry and immunocytochemistry. About 40% of permeabilized PMN, both resting and stimulated, contained TF:Ag, indicating that stimulation only modifies the location of TF:Ag within PMN. By real time‐polymerase chain reaction (RT‐PCR), a very low amount of TF mRNA was detectable in resting PMN, but a 3‐ to 5‐fold increase was observed after 1‐h stimulation with P‐selectin or fMLP, respectively. Conclusions: These findings suggest that TF is not constitutively expressed in peripheral PMN, but can be up‐regulated and produced upon stimulation and specific gene transcription, as for instance during contact with activated platelets or endothelium. The stored TF is rapidly expressed in vitro as a functional molecule on the surface of activated PMN. The availability of PMN TF supports the relevance of inflammatory cells and their interaction with platelets for fibrin deposition and thrombus formation.

Polymorphisms of the Interleukin-1β Gene Affect the Risk of Myocardial Infarction and Ischemic Stroke at Young Age and the Response of Mononuclear Cells to Stimulation In Vitro

Objectives— To investigate the role of interleukin-1&bgr; (IL-1&bgr;) gene polymorphisms as a link between inflammation, coagulation, and risk of ischemic vascular disease at young age. Methods and Results— A total of 406 patients with myocardial infarction (MI) at young age, frequency-matched for age, sex, and recruitment center, with 419 healthy population-based controls and 134 patients with ischemic stroke at young age, matched by age and sex, with 134 healthy population-based controls, were studied. Subjects carrying the TT genotype of the −511C/T IL-1&bgr; polymorphism showed a decreased risk of MI (odds ratio [OR], 0.36; 95% CI, 0.20 to 0.64) and stroke (OR, 0.32; 95% CI, 0.13 to 0.81) after adjustment for conventional risk factors. In both studies, the T allele showed a codominant effect (P=0.0020 in MI; P=0.021 in stroke). Mononuclear cells from volunteers carrying the T allele showed a decreased release of IL-1&bgr; and a decreased expression of tissue factor after stimulation with lipopolysaccharide compared with CC homozygotes. The presence of a monoclonal antibody against IL-1&bgr; during cell stimulation resulted in a marked reduction of tissue factor activity expression. Conclusions— −511C/T IL-1&bgr; gene polymorphism affects the risk of MI and ischemic stroke at young age and the response of mononuclear cells to inflammatory stimulation.

PROSTACYCLIN-LIKE ACTIVITY AND BLEEDING IN RENAL FAILURE

Specimens of venous tissue from three normal subjects and three patients with renal failure and very prolonged bleeding-times showed prostacyclin-like activity (inhibition of platelet aggregation) during incubation at room temperature. The specimens from all three uraemic patients showed more prostacyclin-like activity than those from the controls. After repeated washings, when this activity could hardly be detected in the controls, pronounced inhibitory activity was still evident in samples containing venous tissue from the three uraemic patients. These findings may be relevant to the pathogenesis of bleeding in renal failure.

Prostacyclin and human foetal circulation.

Tissues from human umbilical cord arteries and placental veins generated much greater prostacyclin activity than vessels from normal adults. High prostacyclin generation could contribute to maintaining the low peripheral vascular resistance typical of foetal circulation in which blood pressure is low despite very high cardiac output.

Bcl I Polymorphism in the Fibrinogen β-Chain Gene Is Associated With the Risk of Familial Myocardial Infarction by Increasing Plasma Fibrinogen Levels A Case-Control Study in a Sample of GISSI-2 Patients

The aim of this study was to investigate the association of the Bcl I beta-chain fibrinogen polymorphism with the risk of acute myocardial infarction (AMI) and its relationship with fibrinogen levels in the Italian population. We studied 102 AMI patients, selected within the framework of the GISSI-2 trial, who had a familial history of arterial thrombosis (at least one first-degree relative suffering from AMI or stroke before 65 years) and 173 control subjects (with neither AMI nor personal or familial history of arterial thrombosis). All subjects were Italian. Patients showed fibrinogen levels higher than control subjects. There was a highly significant difference in allele frequency in cases versus control subjects, the B2 allele frequencies being respectively 0.28 versus 0.17 (P = .002). In multivariate analysis, adjusted for sex, age, smoking habits, and history of hyperlipidemia, hypertension, or diabetes, the (B1B2 + B2B2) genotype was associated with a higher risk of AMI (odds ratio 2.4, 95% confidence interval, 1.2 to 4.6). The Bcl I genotype was also associated with fibrinogen levels, independently of gender and smoking habits, the (B1B2 + B2B2) subjects showing the highest levels in both cases and control subjects. The difference in fibrinogen levels between cases and control subjects was significantly influenced by the genotype (significant interaction, P = .042). The B2 allele of the Bcl I polymorphism in the beta-chain of the fibrinogen gene is a new factor associated with the risk of familial AMI through its association with fibrinogen levels. These data provide evidence for a causal role of fibrinogen in familial AMI.

A high‐score Mediterranean dietary pattern is associated with a reduced risk of peripheral arterial disease in Italian patients with Type 2 diabetes

Summary.  Background: The ‘Mediterranean diet’ is considered to exert protective effects on cardiovascular disease, although a wide range of dietary patterns exists among subjects living even in the same Mediterranean country. Objective: To investigate the association between specific dietary patterns and peripheral arterial disease (PAD) in Italian Type 2 diabetes patients. Design: From a cohort of 944 patients with Type 2 diabetes, 144 patients with PAD were selected, and matched for age and sex with 288 Type 2 diabetic control patients without macrovascular complications. A dietary score was elaborated from a semiquantitative food frequency questionnaire. The higher the final score, the healthier the eating habit. Results: In multivariate analysis, a higher score was independently associated with a significant reduction in PAD risk [odds ratio (OR) = 0.44; 95% confidence interval (CI) 0.24, 0.83]. Diabetes duration (OR > 15 years = 2.49; 95% CI 1.45, 4.25), hypertension (OR = 2.12; 95% CI 1.31, 3.45) and butter consumption (OR = 2.6; 95% CI 1.15, 3.68) were also significantly associated with PAD. The dietary score significantly improved the predictive value of models based on duration of diabetes and hypertension. (LSR = 2.19, DF = 7, P < 0.001). The effect of a high dietary score on the risk of PAD was independent of diabetes duration and hypertension. Conclusions: In Italian Type 2 diabetics, a higher dietary score has a protective role against PAD. The use of butter increases the risk of PAD even in patients regularly consuming olive oil. Dietary advice may be helpful for the prevention of PAD in diabetics even in populations traditionally accustomed to a Mediterranean dietary habit.

Inhibition of tissue factor expression by hydroxyurea in polymorphonuclear leukocytes from patients with myeloproliferative disorders: a new effect for an old drug?

Summary.  Background: Polymorphonuclear leukocytes (PMN) from healthy subjects can produce and store tissue factor (TF), which is expressed on PMN surface upon in vitro stimulation with P‐selectin. Results: We report here that platelets and PMN from 12 patients with myeloproliferative disorders (MPD) (six with polycythemia vera, six with essential thrombocythemia) show up regulation of P‐selectin and TF, respectively, in the absence of any in vitro challenge. The number of circulating mixed platelet‐PMN aggregates was also increased. PMN TF expression as well as mixed platelet‐PMN aggregates, but not platelet P‐selectin, were significantly reduced in six MPD patients after treatment with hydroxyurea (HU). In vitro studies performed on PMN separated from healthy donors confirmed HU effects (0–1400 μm). HU prevented both P‐selectin‐induced TF expression and mixed cell aggregate formation. The inhibitory effect of HU was specific for P‐selectin‐induced PMN activation, as it did not affect formyl‐methionyl‐leucyl‐phenylalanine‐induced PMN TF expression. Conclusions: In MPD patients, platelet P‐selectin‐mediated TF expression on circulating PMN may play a role in thrombus formation and represents a novel target for the antithrombotic activity of HU.

Glucose and insulin independently reduce the fibrinolytic potential of human vascular smooth muscle cells in culture

Summary Hyperglycaemia and hyperinsulinaemia have both been related to accelerated atherosclerosis in non-insulin-dependent diabetes mellitus (NIDDM). Plasma fibrinolytic potential is reduced in NIDDM and it is known that glucose and insulin can modulate plasminogen activator inhibitor (PAI-1) and tissue-plasminogen activator (t-PA) secretion and can therefore regulate local fibrinolysis. Vascular smooth muscle cells (vSMC) play an important role in the development of atherosclerotic lesions; however, the role of insulin and glucose in regulating PAI-1 and t-PA production in vSMC is presently not known. Therefore, we cultured arterial vSMC explanted from human umbilical cords and exposed them to increasing concentrations of glucose (5, 12, 20, 27, 35 mmol/l) or insulin (0.1, 0.5, 1, 10 nmol/l) in a serum free medium. After 24 h, PAI-1 and t-PA antigens and activity were evaluated in the culture medium; in cells exposed to 20 mmol/l glucose and to 0.5 nmol/l insulin PAI-1 gene expression was also evaluated. An increase in PAI-1 antigen was observed at each glucose concentration (by 138, 169, 251 and 357 % as compared to 5 mmol/l glucose) which was paralleled by an increase in PAI-1 activity. t-PA concentration was also increased by glucose but its activity was sharply reduced. An increase in PAI-1 antigen was detected at each insulin level (by 121, 128, 156 and 300 % as compared to no insulin). PAI-1 activity was slightly increased at the lowest insulin concentrations but markedly increased by 10 nmol/l insulin. t-PA antigen was also increased by insulin; however, its activity was markedly reduced at each concentration. As compared to control cells, PAI-1 mRNA was increased by 2.5 and 2.0 fold by 20 mmol/l glucose and 0.5 nmol/l insulin, respectively. We conclude that in human vSMC both glucose and insulin can affect the fibrinolytic balance so as to reduce fibrinolytic potential. This might contribute to decreased local fibrinolysis and thereby might accelerate the atherothrombotic process in NIDDM subjects. [Diabetologia (1996) 39: 1425–1431]