Aged garlic extract may inhibit aggregation in human platelets by suppressing calcium mobilization

Cardiovascular disease is associated with multiple factors including the increased ability of platelets to aggregate. Aged garlic extract (AGE) was shown to inhibit platelet aggregation; however, the underlying mechanisms have yet to be established. Because calcium mobilization plays an important role in platelet aggregation, the effect of AGE was investigated in this preliminary study. ADP and the calcium ionophore A23187 both stimulated platelet aggregation with a concomitant increase in intracellular calcium ion concentration. When these experiments were repeated in the presence of AGE, both platelet aggregation and calcium mobilization were suppressed. In addition, when platelets were preincubated with AGE, the initial concentration of intracellular calcium was significantly reduced compared with platelets without AGE, confirming the metal-chelating properties of AGE. Platelets loaded with fura-2 acetoxymethyl ester (fura-2 AM) also displayed a reduction in platelet aggregation, and the addition of external calcium did not alter this observation. Although variable data were obtained in this study, these results taken together imply that AGE probably exerts its inhibitory effect on platelet aggregation either by suppressing the influx of calcium ions by chelating calcium within platelet cytosol or by altering other intracellular second messengers within the platelets.