Polymorphonuclear leukocyte-platelet interaction: role of P-selectin in thromboxane B2 and leukotriene C4 cooperative synthesis
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N Maugeri1, V Evangelista, A Celardo
1Giulio Bizzozero Laboratory of Platelet and Leukocyte Pharmacology, Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy.
Abstract:
In PMN/platelet suspensions stimulated by fMLP giant mixed aggregates are formed and TxB2 and LTC4 are synthesized as the result of the cooperation in the arachidonic acid (AA) metabolism during cell/cell contact. PMN-derived cathepsin G induced the expression of P-selectin on platelet surface. GE12, an antibody against P-selectin, significantly reduced mixed cell aggregates. GE12 did not affect platelet aggregation induced by PMN-derived supernatants, indicating that the inhibitory effect of GE12 on mixed cell aggregation depends on inhibition of PMN/platelet adhesion. GE12 significantly reduced TxB2 and LTC4 production in PMN/platelet mixed cell suspensions stimulated by fMLP. As previously reported, synthesis of 3H-TxB2 in 3H-AA-labeled PMN/unlabeled platelets indicates that platelets utilize 3H-AA from PMN. 3H-LTC4 production in unlabeled PMN/3H-AA-labeled platelets indicates that bidirectional routes are utilized in this system for LTC4 synthesis. GE12 significantly reduced 3H-TxB2 and 3H-LTC4 synthesis. These results show that cathepsin G released by activated PMN induces the expression of P-selectin on platelet membrane: this adhesive glycoprotein modulates cell-cell contact and transcellular metabolism of AA.
Insights
Neutrophil cathepsin G triggers P-selectin on platelets, forming aggregates and influencing arachidonic acid metabolism. Blocking P-selectin (GE12) inhibits these interactions and reduces key inflammatory mediators.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Neutrophils and platelets interact during inflammation.
- Cell-cell contact influences arachidonic acid (AA) metabolism and mediator synthesis.
- Cathepsin G is released by activated neutrophils.
Purpose of the Study:
- To investigate the role of neutrophil-derived cathepsin G in PMN/platelet aggregate formation.
- To determine the involvement of P-selectin in PMN/platelet adhesion and AA metabolism.
- To elucidate the mechanisms of TxB2 and LTC4 synthesis during PMN/platelet interactions.
Main Methods:
- Stimulation of PMN/platelet suspensions with fMLP.
- Measurement of TxB2 and LTC4 synthesis.
- Use of anti-P-selectin antibody (GE12) to block P-selectin.
- Tracing arachidonic acid metabolism using radiolabeled compounds.
- Assessment of PMN/platelet adhesion and aggregate formation.
Main Results:
- PMN/platelet suspensions formed aggregates and synthesized TxB2 and LTC4 upon fMLP stimulation.
- Neutrophil cathepsin G induced P-selectin expression on platelets.
- GE12 significantly reduced mixed cell aggregates, PMN/platelet adhesion, and TxB2/LTC4 production.
- GE12 did not inhibit platelet aggregation induced by PMN supernatants, confirming its effect on adhesion.
Conclusions:
- Neutrophil-derived cathepsin G induces platelet P-selectin expression, mediating PMN/platelet adhesion.
- P-selectin plays a crucial role in regulating cell-cell contact and transcellular arachidonic acid metabolism.
- Blocking P-selectin effectively inhibits inflammatory mediator synthesis in PMN/platelet interactions.