Inhibitory Effect of Thymol on Suicidal Erythrocyte Death

The antibacterial plant component thymol has antioxidant activity. Oxidative stress is known to activate Ca(2+)-permeable cation channels with subsequent Ca(2+) entry, activation of Ca(2+)-sensitive K(+) channels, cell shrinkage, cell membrane scrambling and phosphatidylserine exposure at the erythrocyte surface. Cell shrinkage and phosphatidylserine exposure are typical features of suicidal erythrocyte death or eryptosis. Eryptotic cells are cleared from circulating blood thus causing anemia and may adhere to the vascular wall thus interfering with the microcirculation. The present experiments explored whether thymol interacts with eryptosis. Annexin V-binding was utilized to determine phosphatidylserine exposure, forward scatter to detect alterations of cell volume and Fluo3 fluorescence to depict changes of the cytosolic Ca(2+) activity. Oxidative stress (30 min. 0.3 mM tert-butylhydroperoxide), energy depletion (48 h glucose removal) and isotonic cell shrinkage (48 h replacement of extracellular Cl(-) with gluconate) significantly increased annexin V-binding and decreased the forward scatter, effects significantly blunted in the presence of thymol 2.5 - 20 microg/ml. Thymol is a potent inhibitor of suicidal erythrocyte death particularly following oxidative stress. In conclusion, thymol may be useful incounteracting anemia and impairment of microcirculation.