Related Experiment Videos
Polymorphonuclear leukocyte-derived O2-reactive species activate primed platelets in human whole blood
D Praticò1, L Iuliano, C Alessandri
1University of Rome La Sapienza, Institute of 1st Clinical Medicine, Italy.
Abstract:
The activation of human platelets by polymorphonuclear leukocytes (PMN) was investigated in human whole blood challenged with "priming" concentrations of arachidonic acid or collagen in the presence or absence of N-formyl-Met-Leu-Phe (FMLP), a selective activator of PMN. With the use of arachidonic acid or collagen alone at priming concentrations or FMLP alone, no platelet response was observed. In contrast, FMLP in combination with arachidonic acid or collagen caused irreversible platelet aggregation with thromboxane A2 production. Platelet response to FMLP-activated PMN was enhanced by superoxide dismutase and blocked by catalase or the NADPH oxidase inhibitor diphenyliodonium, suggesting a role for the O2-.-H2O2 system in this cellular interaction. This was corroborated by experiments with exogenously added H2O2, which mimicked FMLP effects in the activation of primed platelets in whole blood. The present investigation indicates that platelets primed with minute amounts of arachidonic acid or collagen can be activated, in human whole blood, by oxygen-reactive species released by PMN.
Insights
Human platelets primed with arachidonic acid or collagen can be activated by polymorphonuclear leukocytes (PMN). This platelet activation involves reactive oxygen species generated by PMN.
Area of Science:
- Hematology
- Immunology
- Biochemistry
Background:
- Human platelets play a critical role in hemostasis and thrombosis.
- Polymorphonuclear leukocytes (PMN) are key immune cells involved in inflammation and host defense.
- Interactions between platelets and PMN can influence various physiological and pathological processes.
Purpose of the Study:
- To investigate the activation of human platelets by PMN in whole blood.
- To determine the role of reactive oxygen species in PMN-mediated platelet activation.
- To elucidate the signaling pathways involved in platelet activation by PMN.
Main Methods:
- Human whole blood was challenged with priming concentrations of arachidonic acid or collagen.
- N-formyl-Met-Leu-Phe (FMLP) was used to selectively activate PMN.
- Platelet aggregation and thromboxane A2 production were measured.
- The effects of superoxide dismutase, catalase, and diphenyliodonium were assessed.
- Exogenous hydrogen peroxide (H2O2) was used to mimic PMN-derived reactive oxygen species.
Main Results:
- Priming agents (arachidonic acid or collagen) alone or FMLP alone did not induce platelet response.
- FMLP in combination with priming agents induced irreversible platelet aggregation and thromboxane A2 production.
- PMN-activated platelet response was enhanced by superoxide dismutase and inhibited by catalase or NADPH oxidase inhibitor.
- Exogenously added H2O2 mimicked FMLP effects on primed platelets.
Conclusions:
- Platelets primed with low concentrations of arachidonic acid or collagen can be activated by PMN in whole blood.
- Reactive oxygen species, specifically the superoxide/hydrogen peroxide system, generated by PMN are crucial for this platelet activation.
- This study highlights a novel mechanism of platelet activation mediated by PMN-derived reactive oxygen species.