thromboxane-a2 and Cystic-Fibrosis

Cystic fibrosis (CF) is caused by a mutation of the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). We examined platelet function in CF patients because lung inflammation is part of this disease and platelets contribute to inflammation. CF patients had increased circulating leukocyte-platelet aggregates and increased platelet responsiveness to agonists compared with healthy controls. CF plasma caused activation of normal and CF platelets; however, activation was greater in CF platelets. Furthermore, washed CF platelets also showed increased reactivity to agonists. CF platelet hyperreactivity was incompletely inhibited by prostaglandin E(1) (PGE(1)). As demonstrated by Western blotting and reverse-transcriptase-polymerase chain reaction (RT-PCR), there was neither CFTR nor CFTR-specific mRNA in normal platelets. There were abnormalities in the fatty acid composition of membrane fractions of CF platelets. In summary, CF patients have an increase in circulating activated platelets and platelet reactivity, as determined by monocyte-platelet aggregation, neutrophil-platelet aggregation, and platelet surface P-selectin. This increased platelet activation in CF is the result of both a plasma factor(s) and an intrinsic platelet mechanism via cyclic adenosine monophosphate (cAMP)/adenylate cyclase, but not via platelet CFTR. Our findings may account, at least in part, for the beneficial effects of ibuprofen in CF.

Topics: Adenylyl Cyclases; Adolescent; Adult; Alprostadil; Anti-Inflammatory Agents, Non-Steroidal; Arachidonic Acid; Blood Platelets; Blotting, Western; Case-Control Studies; Cell Membrane; Child; Cyclic AMP; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Fatty Acids; Genotype; Humans; Ibuprofen; Inflammation; Leukocytes; Monocytes; Neutrophils; P-Selectin; Platelet Activation; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Thromboxane A2; Time Factors; Vitamin E

The urinary excretion rate (ng/h/1.73 m2) of prostanoids was determined with a capillary gas-liquid chromatographic mass spectrometric method in 19 patients with cystic fibrosis (CF) aged 1-29 years. Patients with CF showed an increased excretion of prostaglandin E2 metabolites (PGE-M) and thromboxane B2 and its metabolites at all ages. An imbalance in the excretion pattern of thromboxane B2 metabolites also suggested a relative impairment of beta-oxidation. There was no increased excretion of dinor-6-keto-PGF1 alpha, indicating normal prostacyclin biosynthesis. No correlation was found to genotype, clinical score, lung function or bacterial colonization but a significant negative relation was found between the main prostanoids in the urine and serum phospholipid levels of essential fatty acids. The results show that, contrary to the generally accepted decrease of prostanoid excretion in essential fatty acid deficiency, patients with CF increase their production parallel to the development of the deficiency. Since prostanoid synthesis is rate limited by arachidonic acid release, our data support a previously presented hypothesis about a pathological regulation of the release of arachidonic acid in CF.

Topics: Adolescent; Adult; Age Factors; Child; Child, Preschool; Cystic Fibrosis; Dinoprostone; Epoprostenol; Fatty Acids; Female; Humans; Infant; Linoleic Acid; Linoleic Acids; Male; Phospholipids; Prostaglandins; Thromboxane A2; Thromboxane B2

Platelet function was investigated in 15 patients with cystic fibrosis (CF) and in ten age-matched controls. Marked hyperaggregability of platelets to adrenaline, collagen and arachidonic acid was observed in platelet rich plasma (PRP) prepared from patients with cystic fibrosis. Thromboxane A2 (TXA2) release from these platelets was also markedly enhanced. Hyperaggregability and increased TXA2 release observed in patients with CF was not due to the higher platelet counts in these patients since hyperaggregability was observed even in those patients whose platelet counts were similar to those in controls. Platelet hyperaggregability and increased thromboxane release in these patients were also independent of their body weight and occurred despite supplementation with vitamin E. Hyperaggregability of platelets in CF may be clinically relevant since it may contribute to the pathogenesis of bronchoconstriction through the release of TXA2 and other bronchoconstrictor platelet products such as serotonin.

Topics: Adolescent; Adult; Blood Platelets; Cystic Fibrosis; Fatty Acids, Essential; Female; Humans; In Vitro Techniques; Male; Platelet Aggregation; Platelet Count; Thromboxane A2; Vitamin E Deficiency