The antioxidant butylated hydroxytoluene (BHT) inhibits the dioctanoylglycerol-evoked platelet response but potentiates that elicited by ionomycin.
Preincubation of aspirin-treated human platelets with butylated hydroxytoluene (BHT) inhibits secretion, aggregation, and protein phosphorylation induced by dioctanoylglycerol or phorbol 12-myristate 13-acetate (PMA). BHT alone elicits a rapid and transient phosphorylation of a 47-kDa protein, which is indistinguishable from the well-recognized major substrate of protein kinase C (PKC). Inhibition of diacylglycerol- or PMA-induced platelet activation is also observed after decay to the basal level of the BHT-evoked phosphorylation of the 47-kDa protein. By contrast BHT potentiates platelet responses elicited by the calcium ionophore ionomycin. In the presence of the PKC inhibitor staurosporine BHT fails to increase the ionomycin-promoted platelet aggregation, indicating that its effect occurs through a PKC activation, even if no correlation with the 47-kDa protein phosphorylation is observed. BHT does not significantly modify the affinity of protein kinase C purified from calf brain for Ca2+ or dioctanoylglycerol. It is concluded that: (a) a short exposure of platelets to BHT induces an activation, whereas a long exposure an inhibition of PKC, (b) at variance with diacylglycerols BHT decreases the platelet responses promoted by subsequent challenge with PKC activators themselves, and (c) similarly to other PKC activators BHT potentiates the cellular response elicited by calcium ionophores most likely by activating the phospholipase A2.
Ruzzene
M
M
Department of Biological Chemistry, University of Padova, Italy.
Francesconi
M
M
Donella-Deana
A
A
Alexandre
A
A
Deana
R
R
D000255:Adenosine Triphosphate / Q000097:blood*; D000470:Alkaloids / Q000494:pharmacology; D016718:Arachidonic Acid / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D002084:Butylated Hydroxytoluene / Q000494:pharmacology*; D004075:Diglycerides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004357:Drug Synergism; D006801:Humans; D066298:In Vitro Techniques; D015759:Ionomycin / Q000494:pharmacology*; D007700:Kinetics; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000097:blood*; D010750:Phosphoproteins / Q000096:biosynthesis / Q000302:isolation & purification; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000097:blood* / Q000302:isolation & purification; D019311:Staurosporine
D000470:Alkaloids; D004075:Diglycerides; D010750:Phosphoproteins; D010975:Platelet Aggregation Inhibitors; C044295:1,2-dioctanoylglycerol; D002084:Butylated Hydroxytoluene; D016718:Arachidonic Acid; D015240:Phorbol 12,13-Dibutyrate; D015759:Ionomycin; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D010749:Phosphoprotein Phosphatases; D019311:Staurosporine