Phosphoinositide 3-kinase inhibition reverses platelet aggregation triggered by the combination of the neutrophil proteinases elastase and cathepsin G without impairing alpha(IIb)beta(3) integrin activation.
Neutrophil elastase (NE) upregulates the fibrinogen binding activity of the platelet integrin alpha(IIb)beta(3) through proteolysis of the alpha(IIb) subunit. This cleavage allows a strong potentiation of platelet aggregation induced by low concentrations of cathepsin G (CG), another neutrophil serine proteinase. During this activation process, we observed a strong fibrinogen binding and aggregation-dependent phosphatidylinositol 3,4-bis-phosphate (PtdIns(3,4)P(2)) accumulation. PtdIns(3,4)P(2) has been suggested to play a role in the stabilization of platelet aggregation, possibly through the control of a maintained alpha(IIb)beta(3) integrin activation. Here we show that inhibition of phosphoinositide 3-kinase (PI 3-K) by very low concentrations of wortmannin or LY294002 transformed the irreversible platelet aggregation induced by a combination of NE and low concentrations of CG into a reversible aggregation. However, although inhibition of PI 3-K was very efficient in inducing platelet disaggregation, it did not modify the level of alpha(IIb)beta(3) activation as assessed by binding of an activation-dependent antibody. These results indicate that PI 3-K activity can control the irreversibility of platelet aggregation even under conditions where alpha(IIb)beta(3) integrin remains activated.
Trumel
C
C
Institut Fédératif de Recherche en Immunologie Cellulaire et Moléculaire, INSERM Unité, Hôpital Purpan, Toulouse, France.
Si-Tahar
M
M
Balloy
V
V
Chignard
M
M
Chap
H
H
Payrastre
B
B
Plantavid
M
M
Pidard
D
D
D000730:Androstadienes / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D056649:Cathepsin G; D002403:Cathepsins / Q000494:pharmacology / Q000502:physiology*; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005340:Fibrinogen / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D019272:Leukocyte Elastase / Q000494:pharmacology / Q000502:physiology*; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000097:blood*; D010716:Phosphatidylinositols / Q000097:blood; D000081082:Phosphoinositide-3 Kinase Inhibitors; D015539:Platelet Activation / Q000502:physiology; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000187:drug effects / Q000502:physiology*; D012697:Serine Endopeptidases; D000077191:Wortmannin
D000730:Androstadienes; D056649:Cathepsin G; D002403:Cathepsins; D002867:Chromones; D004791:Enzyme Inhibitors; D005340:Fibrinogen; D019272:Leukocyte Elastase; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D010716:Phosphatidylinositols; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D012697:Serine Endopeptidases; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C534094:CTSG protein, human