Licochalcones extracted from Glycyrrhiza inflata inhibit platelet aggregation accompanied by inhibition of COX-1 activity

Abstract

Licochalcones extracted from Glycyrrhiza inflata are known to have a variety of biological properties such as anti-inflammatory, anti-bacterial, and anti-tumor activities, but their action on platelet aggregation has not yet been reported. Therefore, in this study we investigated the effects of licochalcones on platelet aggregation. Collagen and U46619, a thromboxane A2 receptor agonist, caused rabbit platelet aggregation, which was reversed by pretreatment with licochalcones A, C and D in concentration-dependent manners. Among these compounds, licochalcone A caused the most potent inhibitory effect on collagen-induced platelet aggregation. However, the licochalcones showed marginal inhibitory effects on thrombin or ADP-induced platelet aggregation. In addition to rabbit platelets, licochalcone A attenuated collagen-induced aggregation in human platelets. Because licochalcone A also inhibited arachidonic acid-induced platelet aggregation and production of thromboxane A2 induced by collagen in intact platelets, we further examined the direct interaction of licochalcone A with cyclooxygenase (COX)-1. As expected, licochalcone A caused an inhibitory effect on both COX-1 and COX-2 in vitro. Regarding the effect of licochalcone A on COX-1 enzyme reaction kinetics, although licochalcone A showed a stronger inhibition of prostaglandin E2 synthesis induced by lower concentrations of arachidonic acid, Vmax values in the presence or absence of licochalcone A were comparable, suggesting that it competes with arachidonic acid at the same binding site on COX-1. These results suggest that licochalcones inhibit collagen-induced platelet aggregation accompanied by inhibition of COX-1 activity.

Licochalcone A Prevents Platelet Activation and Thrombus Formation through the Inhibition of PLCγ2-PKC, Akt, and MAPK Pathways

“…In addition, only at a higher concentration of 80 µM did LA affect thrombin (0.01 U/mL)- or U46619 (1 µM)-mediated platelet aggregation ( Figure 1 B). These results are consistent with that Okuda-Tanino et al reported [ 15 ] and indicate that LA is more sensitive to the inhibition of collagen-mediated platelet activation. Accordingly, in the following experiments, we mainly evaluated the mechanism of LA at concentrations of 2–10 µM in collagen-mediated platelet activation events.…”

“…Therefore, we further systemically investigated its antiplatelet mechanism and for the first time determined whether LA prevents thrombus formation in in vivo studies. Our data reveal that LA is more sensitive to the inhibition of collagen-induced platelet aggregation in human platelets, as well as that which Okuda-Tanino et al reported [ 15 ]. Moreover, LA also inhibits collagen-mediated several activation events, such as granule release, calcium mobilization, and GPIIbIIIa activation.…”

“…; it possesses multiple biological activities, such as anti-inflammation, antioxidation, antibacteria, and antitumor effects [ 7 , 9 , 10 , 11 ]. Although, LA was recently reported to block rabbit and rat platelet aggregation through the inhibition of COX-1 activity [ 15 , 16 ], the role of LA on platelet activation and thrombosis remains unclear. Therefore, we further systemically investigated its antiplatelet mechanism and for the first time determined whether LA prevents thrombus formation in in vivo studies.…”

“…Although, recently, LA was also reported to reduce rabbit and rat platelet activation through the inhibition of cyclooxygenase-1 (COX-1) activity [ 15 , 16 ], its role in platelet activation and thrombosis remains unclear. In the present study, our preliminary data revealed that LA significantly inhibited collagen-induced platelet aggregation through PLCγ2–PKC pathway, suggesting that, in addition to inhibiting COX-1 activity, LA may attenuate platelet activation through other mechanisms.…”

Inhibition of human thrombin by the constituents of licorice: inhibition kinetics and mechanistic insights through in vitro and in silico studies

“…Therefore, it is conceivable that both pharmacokinetic and pharmacodynamics interactions may occur when anticoagulant or antiplatelet drugs are used in combination with licorice-containing products. It also has been reported that licochalcone A can block collageninduced platelet aggregation 59,60 and function as a inhibitor of clotting factor Xa, 61 suggesting that licorice constituents may regulate the blood coagulation cascade via multiple mechanisms. Therefore, the clinical consequences of licorice in combination with anticoagulant or antiplatelet agents should be carefully investigated from the views of both pharmacokinetic and pharmacodynamics interactions.…”