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Updated: Oct 2, 2025
Comprehensive Analysis of Procoagulant Platelets Exhibiting Features of Necrosis, Apoptosis and Platelet Activation
Published on: May 23, 2025
ML355 Modulates Platelet Activation and Prevents ABT-737 Induced Apoptosis in Platelets
Valentina Shpakova1, Natalia Rukoyatkina1, Nada Al Arawe1
1Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Saint Petersburg, Russia (V.S., N.R., S.G.); Saint Petersburg State University, Saint Petersburg, Russia (N.A.A., A.P., A.K.); and Department of Internal Medicine, Division of Cardiology, University of Texas Houston Medical School, Houston, Texas (I.S., E.M.).
Abstract:
12-lipoxigenase (12-LOX) 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 A2, but not by collagen-related peptide. ML355 blocked protein kinase B, phosphoinositide 3-kinase, and extracellular signal-regulated kinase, but not p38 kinase, spleen tyrosine kinase (Syk), or phospholipase Cγ2 phosphorylation in activated platelets. The main inhibitory effect of low doses of ML355 (1-20 μM) on thrombin activated platelets was mediated by the decrease in reactive oxygen species level, whereas high doses of ML355 (50 μM) 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 μM dose blocked caspase-dependent apoptosis induced by B-cell lymphoma II inhibitor ABT-737. SIGNIFICANCE STATEMENT: The 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.
Insights
The 12-lipoxygenase (12-LOX) inhibitor ML355 reduces platelet activation and offers protective effects against apoptosis. This study elucidates ML355
Area of Science:
- Biochemistry
- Pharmacology
- Hematology
Background:
- 12-lipoxygenase (12-LOX) plays a role in platelet activation, making it a potential target for antiplatelet therapies.
- Research on 12-LOX has been limited by a lack of specific inhibitors and conflicting data on its metabolites' functions in platelets.
- The specific 12-LOX inhibitor ML355 shows antiplatelet activity but its precise molecular mechanisms in platelets require further investigation.
Purpose of the Study:
- To investigate the molecular mechanisms underlying the action of the 12-LOX inhibitor ML355 on platelet activation and function.
- To determine the signaling pathways affected by ML355 in activated platelets.
- To evaluate the protective effects of ML355 on platelet viability and apoptosis.
Main Methods:
- Platelet aggregation assays were performed using various agonists (thrombin, thromboxane A2, collagen-related peptide).
- Western blotting was used to assess the phosphorylation status of key signaling proteins (PKB, PI3K, ERK, p38, Syk, PLCγ2).
- Reactive oxygen species (ROS) levels, cyclic adenosine monophosphate (cAMP) production, and apoptosis were measured in platelets treated with ML355.
Main Results:
- ML355 inhibited platelet activation induced by thrombin and thromboxane A2, but not by collagen-related peptide.
- ML355 blocked the phosphorylation of PKB, PI3K, and ERK, while not affecting p38, Syk, or PLCγ2.
- Low ML355 doses reduced ROS levels, whereas high doses increased cAMP. ML355 also inhibited apoptosis without affecting platelet viability.
Conclusions:
- ML355 exhibits antiplatelet effects by modulating specific signaling pathways and reducing ROS levels.
- High doses of ML355 can induce cAMP activation and provide protection against platelet apoptosis.
- ML355 demonstrates potential as a therapeutic agent for both antiplatelet and anticancer strategies.
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