thromboxane-a2 and indobufen

We have previously reported aspirin failure in suppressing enhanced thromboxane (TX) biosynthesis in a subset of episodes of platelet activation during the acute phase of unstable angina. The recent discovery of a second prostaglandin H synthase (PGHS-2), inducible in response to inflammatory or mitogenic stimuli, prompted us to reexamine TXA2 biosynthesis in unstable angina as modified by two cyclooxygenase inhibitors differentially affecting PGHS-2 despite a comparable impact on platelet PGHS-1.. We randomized 20 patients (15 men and 5 women aged 59+/-10 years) with unstable angina to short-term treatment with aspirin (320 mg/d) or indobufen (200 mg BID) and collected 6 to 18 consecutive urine samples. Urinary 11-dehydro-TXB2 was extracted and measured by a previously validated radioimmunoassay as a reflection of in vivo TXA2 biosynthesis. Metabolite excretion averaged 102 pg/mg creatinine (median value; n=76) in the aspirin group and 55 pg/mg creatinine (median value; n=99) in the indobufen group (P<.001). There were 16 samples (21%) with 11-dehydro-TXB2 excretion >200 pg/mg creatinine among patients treated with aspirin versus 6 such samples (6%) among those treated with indobufen (P<.001). In vitro and ex vivo studies in healthy subjects demonstrated the capacity of indobufen to largely suppress monocyte PGHS-2 activity at therapeutic plasma concentrations. In contrast, aspirin could only inhibit monocyte PGHS-2 transiently at very high concentrations.. We conclude that in unstable angina, episodes of aspirin-insensitive TXA2 biosynthesis may reflect extraplatelet sources, possibly expressing the inducible PGHS in response to a local inflammatory milieu, and a selective PGHS-2 inhibitor would be an ideal tool to test the clinical relevance of this novel pathway of arachidonic acid metabolism in this setting.

Topics: Aged; Angina, Unstable; Aspirin; Cyclooxygenase 1; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Double-Blind Method; Female; Humans; Isoenzymes; Isoindoles; Male; Membrane Proteins; Middle Aged; Phenylbutyrates; Prostaglandin-Endoperoxide Synthases; Reference Values; Thromboxane A2; Thromboxane B2

To assess whether indobufen, a reversible inhibitor of platelet cyclooxygenase (Cox) activity, affects tissue factor (TF) in human monocytes and to investigate the relationship between Cox-derived products and TF.. TF was evaluated in isolated adherent monocytes, both resting and lipopolysaccharide (LPS)-stimulated, in terms of procoagulant activity, protein, and mRNA levels. The expression of TF surface antigen was determined in LPS-stimulated whole blood monocytes by flow cytometry. The levels of the stable thromboxane A2 (TxA2) metabolite, TxB2, and of prostaglandin E2 (PGE2) were measured in monocyte supernatant by immunoenzymatic techniques. Cox-1 and Cox-2 protein level, tyrosine phosphorylation, and mitogen-activated protein kinase (MAP-kinase) activation were determined by Western blot analysis.. Indobufen prevents TF expression and activity both in isolated and in whole blood monocytes. Reduction of TxA2 synthesis, coupled with a lack of effect on PGE2 levels and prevention of ERK1/2 phosphorylation are highlighted as the mechanisms through which indobufen negatively affects TF.. Data show that indobufen down-regulates TF in monocytes. This novel activity, coupled with the antiplatelet effect of the drug, may add benefit for its use in the management of atherothrombosis.

Topics: Cells, Cultured; Cyclooxygenase Inhibitors; Depression, Chemical; Dinoprostone; Flow Cytometry; Humans; Isoindoles; Lipopolysaccharides; Monocytes; Phenylbutyrates; Thromboplastin; Thromboxane A2; Thromboxane B2; Thromboxanes

16 patients with insulin-dependent diabetes mellitus (IDDM) lasting 8-19 years had pronounced diabetic nephropathy (proteinuria stage), retinopathy (stage I, II or III), disturbed circulation in the lower limbs detected at foot dopplerography. For 3 months these patients received ibustrin (inhibitor of cyclooxigenase, blocker of tromboxane A2 synthesis and platelet aggregation) before renal function underwent positive changes: glomerular filtration rate increased in 13 patients (81%), 24-h proteinuria decreased in 12 patients (75%). Retinal vascular condition improved in 5 of 6 patients with nonproliferative retinopathy and in 2 of 5 patients with preproliferative retinopathy, in 1 and 3 patients stabilization occurred, respectively. In proliferative retinopathy improvement and stabilization were registered in 1 and 3 of 5 patients, respectively. According to feet artery dopplerography the improvement, no changes and moderate aggravation occurred in 10(62%), 3(19%) and 3(19%) of patients, respectively The conclusion is made that ibustrin effectively inhibits progression of IDDM vascular complications, especially at early angiopathy stages.

Topics: Adolescent; Adult; Blood Coagulation; Chronic Disease; Cyclooxygenase Inhibitors; Diabetes Mellitus, Type 1; Diabetic Angiopathies; Diabetic Nephropathies; Diabetic Retinopathy; Drug Evaluation; Foot; Humans; Isoindoles; Middle Aged; Phenylbutyrates; Platelet Aggregation Inhibitors; Thromboxane A2

Topics: Animals; Aspirin; Blood Platelets; Blood Specimen Collection; Dipyridamole; Guinea Pigs; In Vitro Techniques; Indoles; Indomethacin; Isoindoles; Phenylbutyrates; Platelet Aggregation; Prostaglandins; Prothrombin Time; Serotonin; Thrombin; Thromboxane A2; Time Factors