ML355 Modulates Platelet Activation and Prevents ABT-737 Induced Apoptosis in Platelets

Abstract

is implicated in regulation of platelet activation processes and can be a new promising target for antiplatelet therapy. However, investigations of 12-LOX were restricted by the lack of specific and potent 12-LOX inhibitors and by controversial data concerning the role of 12-LOX metabolites in platelet functions. A novel specific 12-LOX inhibitor ML355 was shown to inhibit platelet aggregation without adverse side effects on hemostasis; however, the molecular mechanisms of its action on platelets are poorly understood. Here, we showed that ML355 inhibited platelet activation induced by thrombin or thromboxane A 2 , but not by collagenrelated peptide. ML355 blocked protein kinase B, phosphoinositide 3-kinase, and extracellular signal-regulated kinase, but not p38 kinase, spleen tyrosine kinase (Syk), or phospholipase Cc2 phosphorylation in activated platelets. The main inhibitory effect of low doses of ML355 (1-20 lM) on thrombin activated platelets was mediated by the decrease in reactive oxygen species level, whereas high doses of ML355 (50 lM) caused cyclic adenosine monophosphate activation. ML355 did not affect the activity of nitric oxide-dependent soluble guanylyl cyclase, nor did it affect the relaxation of preconstricted aortic rings in mice. ML355 itself did not affect platelet viability, but at 50 lM dose blocked caspase-dependent apoptosis induced by B-cell lymphoma II inhibitor ABT-737. SIGNIFICANCE STATEMENTThe current paper provides novel and original data concerning molecular mechanisms of 12-LOX inhibitor ML355 action on platelets. These data reveal antiplatelet and protective effects of ML355 on platelets and may be of importance for both antiplatelet and anticancer therapy.

Antiplatelet Effects of Flavonoid Aglycones Are Mediated by Activation of Cyclic Nucleotide-Dependent Protein Kinases

“…Then, the reaction was stopped by the addition of PBS (1:40). For positive control, platelets were incubated with gossypol (40 µM, 10 min), which can affect cell viability via inhibition of B-cell lymphoma II (Bcl-2) proteins [108].…”

Current Status and Future Direction of Antithrombotic Therapy for Patients with STEMI Undergoing Primary PCI

“…In a second tier with experimental data in humans and novel mechanism of action but not yet in clinical development we have ML355, that blocks Akt, PI3K and Erk1/2, but not p38, Syk or PLCγ2 phosphorylation in activated platelets. It is a selective 12-LOX inhibitor that blocks thrombosis with little effects on hemostasis [178,179]. are specific inhibitors of the PAR-4 receptor; SCH-28 is a synthetic small molecular heparin analogue that inhibits PAR-4 by blocking thrombin exosite II.…”

“…In a second tier with experimental data in humans and novel mechanism of action but not yet in clinical development we have ML355, that blocks Akt, PI3K and Erk1/2, but not p38, Syk or PLC 2 phosphorylation in activated platelets. It is a selective 12-LOX inhibitor that blocks thrombosis with little effects on hemostasis [ 178 , 179 ].…”