Upregulation of platelet CD40, CD40 ligand (CD40L) and P-Selectin expression in cigarette smokers: a flow cytometry study.

Cigarette smoking is a well known risk factor for cardiovascular disease with a great impact on mortality. Studies have linked smoking to inflammation, platelet activation and enhanced atherosclerosis. The present study investigated the activation and expression of proinflammatory markers on platelets obtained from smokers. The expression of P-selectin (CD62P) (as a marker of activation) and CD40/CD40L (as a marker for proinflammatory processes) were quantified in platelets by flow cytometry. Platelet-rich plasma was obtained from 34 apparent healthy volunteers (19 cigarette smokers, 15 age-matched control persons). Basal measurements and the response to stimulation with ADP and TRAP (10, 30, 100 micromol/l) were evaluated. Values given (mean fluorescence index, MFI) are mean +/- standard deviation. The basal values of platelet bound CD40 (3.20 +/- 0.50 vs. 2.71 +/- 0.28; P = 0.002), CD40L (1.10 +/- 0.12 vs. 0.95 +/- 0.12; P = 0.005) and P-selectin (0.70 +/- 0.21 vs. 0.55 +/- 0.11; P = 0.012) were significantly elevated in smokers as compared to controls. In addition, higher values were noted on stimulation with ADP or TRAP in smokers, although these different values were without statistical significance. According to our data cigarette smoking activates platelets (P-selectin expression) and stimulates the CD40-CD40L-pathway in otherwise healthy volunteers. These findings emphasize that cigarette smoking leads to a proinflammatory and prothrombotic state thus contributing to accelerated atherosclerosis.

Hormonal status modulates circulating endothelial progenitor cells.

OBJECTIVE: Endothelial progenitor cells (EPCs) may have an important role in vascular homeostasis and repair. METHODS: We examined the level of circulating EPCs in pre- (n = 22; mean age 28.7 years), and postmenopausal healthy females without (n = 30; mean age 61.6 years) or under current hormone replacement therapy (HRT) (n = 19; mean age 59.8 years). RESULTS: Premenopausal females had the highest level of circulating EPCs (0.147 +/- 0.076 per thousand of polymorphnuclear cells). The level of EPCs was lowest in postmenopausal females (0.094 +/- 0.058 per thousand), and increased significantly with HRT on average by 25.5%. In addition, the proliferative capacity of circulating EPCs was assessed under cell culture conditions. This capacity was significantly increased in EPCs isolated from postmenopausal subjects under current HRT as compared to corresponding samples obtained from postmenopausal females without HRT. CONCLUSIONS: This observation is in line with the hypothesis that the hormonal status in females modulates the cardiovascular risk and that circulating EPCs could be involved in this phenomenon.

Lipophilic statins interfere with the inhibitory effects of clopidogrel on platelet function--a flow cytometry study.

AIMS: Clopidogrel is a pro-drug which is converted to an active, unstable drug by cytochrome P450 (CYP). The active drug irreversibly blocks one specific platelet adenosine 5'-diphosphate (ADP) receptor (P2Y12). It has been recently suggested that the most abundant human CYP isoform, 3A4, activates clopidogrel. Since certain lipophilic statins (i.e. simvastatin, atorvastatin, lovastatin) are a substrate of CYP3A4, we were interested in potential drug interactions between clopidogrel and statins. METHODS: In patients with coronary artery disease (n=47) in whom clopidogrel treatment was initiated for balloon angioplasty and stent implantation, blood samples were taken at 0, 5 and 48 h after oral administration of clopidogrel (loading dose 300 mg, followed by 75 mg daily). ADP-stimulated (1, 10, 100 micromol/l) expression of P-selectin (CD62P) on platelets was measured by flow cytometry, and used as a marker for the antiplatelet effect of clopidogrel. RESULTS: Pre-treatment with statins (atorvastatin, simvastatin) reduced significantly (10 micromol/l ADP stimulation) the inhibitory effects of clopidogrel during the loading phase (relative reduction after 5 h 29.3%) and, to a lesser extent during the maintenance phase (relative reduction after 48 h 16.6%). In addition we found a considerable individual heterogeneity in the response and three patients (6%) were identified in whom clopidogrel exerted almost no effect. CONCLUSION: Certain statins which are substrates of the CYP3A4 isoform competitively inhibit the metabolic activation of clopidogrel. As a result the relative clopidogrel induced platelet inhibition (P-selectin-expression) is diminished--but still there is a relative clopidogrel effect of more than 80% in the maintenance phase. It may be reasonable to test the therapeutic efficacy of clopidogrel in those patients who require long-term treatment.