Potential participation of calpain in platelet activation studied by use of a cell penetrating calpain inhibitor (calpeptin).
Employing a cell penetrating calpain inhibitor (calpeptin), the role of calpain in platelet activation was examined. In washed platelets (WPs) both thrombin and collagen-induced platelet aggregation were dose-dependently inhibited by calpeptin. The addition of plasma to WPs interfered with the action of calpeptin, however more than 3 min preincubation of calpeptin with WPs completely abolished the influence of plasma. In thrombin-activated WPs with calcium, the increase of intracellular calcium concentration, [Ca2+]i, and the production of inositol triphosphate (IP3) were dose-dependently inhibited by calpeptin. The generation of thromboxane B2 (TxB2) was inhibited by calpeptin in collagen and thrombin-activated WPs. In [3H]-arachidonic acid (AA)-labelled platelets, calpeptin increased the amount of [3H]-AA liberated by inhibiting [3H]-AA degradation after collagen or thrombin stimulation. When [14C]-AA degradation by the platelet suspension was observed, calpeptin inhibited TxB2 and hydroxyheptadecatrienoic acid (HHT) generation but increased prostaglandin (PG) E1, E2, 12-hydroxyeicosatetraenoic acid (12HETE) and AA. Based on these findings, calpain may be involved in the activation phospholipase C and thromboxane synthetase.
Tsujinaka
T
T
Second Department of Surgery, Osaka University Medical School, Japan.
Ariyoshi
H
H
Uemura
Y
Y
Sakon
M
M
Kambayashi
J
J
Mori
T
T
D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006023:Glycoproteins / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D015539:Platelet Activation / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects; D010976:Platelet Count; D013929:Thromboxane B2 / Q000378:metabolism
D001095:Arachidonic Acids; D006023:Glycoproteins; C039304:calpain inhibitors; D016718:Arachidonic Acid; D013929:Thromboxane B2; D015544:Inositol 1,4,5-Trisphosphate; D002154:Calpain; D002118:Calcium