Related Experiment Videos
Defective aggregation in cirrhosis is independent of in vivo platelet activation
G Laffi1, S Cinotti, E Filimberti
1Istituto di Medicina Interna, Università Degli Studi di Firenze, Rome, Italy.
Insights
Platelets are not activated in cirrhosis patients, despite impaired aggregation. Defective platelet function likely stems from altered signaling, not in vivo activation. Increased thromboxane A2 metabolites may indicate intrasplenic platelet destruction.
Area of Science:
- Hepatology
- Hematology
- Thrombosis Research
Background:
- Platelet dysfunction is a hallmark of cirrhosis, contributing to bleeding risks.
- The precise mechanism behind defective platelet aggregation in cirrhosis remains unclear.
- This study investigates in vivo platelet activation as a potential cause.
Purpose of the Study:
- To evaluate in vivo platelet activation in patients with cirrhosis.
- To determine if platelet activation contributes to defective platelet aggregation.
- To explore the role of thromboxane A2 metabolites in cirrhosis.
Main Methods:
- Studied nine patients with severe cirrhosis (Child B-C) and controls.
- Assessed platelet activation using flow cytometry and plasma markers (beta-thromboglobulin, platelet factor 4).
- Measured urinary thromboxane A2 metabolites (11-dehydro-TXB2, 2,3-dinor-TXB2) via radioimmunoassay.
Main Results:
- Platelet activation markers (GMP 140, GP 53) were not different in unstimulated platelets.
- Activated antigen expression was lower in cirrhotic platelets after stimulation (ADP, epinephrine).
- Plasma markers of in vivo activation were comparable; urinary TXA2 metabolites were significantly higher in cirrhosis patients.
Conclusions:
- Circulating platelets are not activated in cirrhosis.
- Defective platelet aggregation is likely due to altered transmembrane signaling pathways.
- Elevated urinary TXA2 metabolites may be linked to increased intrasplenic platelet destruction.
Background/Aims:
Platelet function abnormalities contribute to the hemostatic defect in patients with cirrhosis. In this study we evaluated the occurrence of in vivo platelet activation as a possible mechanism of defective platelet aggregation in patients with cirrhosis.
Methods:
Nine patients with severe (Child B-C) cirrhosis and defective platelet aggregation were studied in comparison with age- and sex-matched healthy controls. The presence of activated platelets in the bloodstream was evaluated by fluorescence-activated flow cytometry using antibodies directed against activation-dependent platelet proteins and by measuring plasma levels of beta-thromboglobulin and platelet factor 4. Urinary levels of 11-dehydro-TXB2 and of 2,3-dinor-TXB2 were assayed by radioimmunoassay following chromatographic separation.
Results:
In unstimulated platelets, the expression of both GMP 140 and GP 53 was not significantly different in patients with cirrhosis and in controls. After stimulation with ADP and epinephrine, expression of activation-dependent antigens was lower in platelets from patients (GMP 140: 0.64 +/- 0.09 vs 0.73 +/- 0.04, p = 0.02; GP 53: 0.41 +/- 0.13 vs 0.54 +/- 0.14). Plasma levels of beta-thromboglobulin and platelet factor 4, as indexes of in vivo platelet activation, were also comparable in the two groups of subjects. Urinary levels of 11-dehydro-TXB2 and of 2,3-dinor-TXB2, the major systemic metabolites of TXA2, were significantly higher in patients with cirrhosis (1807 +/- 518 vs 341 +/- 121 ng/pg creatinine and 693 +/- 512 vs 205 (93 ng/pg creatinine, respectively, p < 0.001). However, increased excretion of TXB2 metabolites was also observed in three patients with chronic autoimmune thrombocytopenia.
Conclusions:
These data indicate that circulating platelets are not activated in cirrhosis, and that defective aggregation is most likely dependent on the alteration of the transmembrane signaling pathways. The increased urinary excretion of systemic TXA2 metabolites may be related to increased intrasplenic platelet destruction.