Thymoquinone‐induced platelet apoptosis

Abstract

Thymoquinone (TQ) is a nutrient with anticarcinogenic activity that stimulates suicidal death of tumor cells. Moreover, TQ triggers suicidal death of erythrocytes or eryptosis, an effect at least partially due to increase in cytosolic Ca(2+) activity and ceramide formation. The present experiments explored whether TQ influences apoptosis of blood platelets. Cell membrane scrambling was determined utilizing Annexin V binding to phosphatidylserine exposing platelets, cytosolic Ca(2+) activity utilizing Fluo 3-AM fluorescence, caspase activity utilizing immunofluorescence and Western blotting of active caspase-3 and inactive procaspase-3, mitochondrial potential utilizing DiOC(6) fluorescence and ceramide by FACS analysis of ceramide-binding antibodies. A 30 min exposure to TQ (≥5 µM) was followed by Annexin V binding, paralleled by caspase activation, increase of cytosolic Ca(2+) activity, mitochondrial depolarization, and ceramide formation. P-selectin exposure and integrin α(IIb) β(3) activation did not increase in response to TQ. Nominal absence of extracellular Ca(2+) blunted but did not fully abolish the TQ-induced activation of caspase-3. The effects of TQ on platelets are significantly abolished with phosphoinositide-3 kinase (PI3K) inhibitor wortmannin and G-protein coupled receptor (GPCR) inhibitor pertussis toxin treatment prior to TQ stimulation. In conclusion, TQ triggers suicidal death of blood platelets in a PI3K-dependent manner, possibly through a GPCR family receptor; an effect paralleled by increase of cytosolic Ca(2+) activity, ceramide formation, mitochondrial depolarization, and caspase-3 activation.

Sesamol induces apoptosis in human platelets via reactive oxygen species-mediated mitochondrial damage

“…Previously, studies have explored the pro-apoptotic effects of therapeutic compounds such as resveratrol and thymoquinone [7,34]. The current piece of work stresses upon the pro-apoptotic effects of yet another therapeutic compound sesamol, at concentrations higher than 0.25 mM on human platelets.…”

“…Human platelets reportedly undergo apoptosis upon stimulation with a suitable agonist or under stress and are very sensitive to nutritional and therapeutic components in the circulatory system [7]. There are numerous studies of therapeutic compounds influencing platelet functions.…”

Protein kinase A activation by the anti-cancer drugs ABT-737 and thymoquinone is caspase-3-dependent and correlates with platelet inhibition and apoptosis

“…28 In platelets, TQ induces apoptosis by increase of cytosolic calcium concentration, phosphoinositide 3-kinase and caspase-3 activation, ceramide formation, and mitochondrial depolarization. 29 …”

Biologicals, platelet apoptosis and human diseases: An outlook

“…1) [3]. Recent reports suggest the involvement of cell signaling pathways such as, p38 MAPK/cPLA2, PI3K, extracellular signal-regulated protein kinase (ERK) and c-Jun NH2-terminal kinase (JNK) in apoptotic platelets [4][5][6][7]. Further, there are various lines of evidence suggesting the existence of extrinsic apoptotic pathway in platelets, but none decisively prove it.…”