Caffeine Inhibits Suicidal Erythrocyte Death

Abstract

Eryptosis, the suicidal death of erythrocytes, is characterized by cell shrinkage and by cell membrane scrambling with phosphatidylserine exposure at the erythrocyte surface. Eryptosis is triggered by several stress conditions including isotonic cell shrinkage (Cl^- removal) and energy depletion (glucose removal). Both are effective through an increase in the cytosolic Ca²⁺ concentration. Phosphatidylserine-exposing erythrocytes are cleared from circulating blood. Enhanced eryptosis thus leads to anemia. Accordingly, drugs interfering with eryptosis may prove useful in the treatment of anemia. The present study explored, whether caffeine interferes with eryptosis. Erythrocyte phosphatidylserine exposure was estimated from annexin V-binding, cell volume from forward scatter and cytosolic Ca²⁺ activity from Fluo3 fluorescence. Under control conditions, eryptosis affected less than 5% of the erythrocytes and was not significantly modified by the presence of caffeine (50-500 µM).Glucose depletion (for 48 hours) significantly increased Fluo3 fluorescence and annexin V-binding and decreased forward scatter, effects partially reversed by caffeine (500 µM).Low Cl^- solution (Cl^- exchanged by gluconate for 48 hours) similarly increased annexin V-binding and decreased forward scatter, effects again reversed by caffeine (50-500 µM). In conclusion, caffeine inhibits Ca²⁺ entry following glucose depletion and thus counteracts eryptosis during isotonic cell shrinkage and energy depletion.

Suicide for Survival - Death of Infected Erythrocytes as a Host Mechanism to Survive Malaria

“…The molecular identity of those channels is incompletely understood but may include TRPC6 [67]. The cation channels are activated by osmotic shock [68,69], oxidative stress [70,71] [133][134][135][136][137][138][139][140] causes cell shrinkage [75].…”

“…The cation channels [68,69] and thus eryptosis [130] are further inhibited by amiloride [69] and ethylisopropylamiloride (EIPA) [130]. Additional inhibitors of eryptosis include flufenamic acid [131], adenosine [132], zidovudine [133] and caffeine [134]. The most powerful known inhibitor of eryptosis is nitric oxide [135], which could be released from erythrocytes [136][137][138], whereby oxygenated hemoglobin binds and desoxygenated hemoglobin releases NO [137,[139][140][141][142][143].…”

“…Cell Physiol Biochem 2009;24: [133][134][135][136][137][138][139][140] edly facilitates tissue sequestration of trophozoite-infected cells and, thus, contributes to the partial immune evasion of the late stages [150,157]. In addition to triggering phosphatidylserine exposure, the intraerythrocytic pathogen ages its host cell, i.e., it induces a dramatic, time-compressed acceleration of normal erythrocyte senescence which contributes to the clearance of infected cells [156,158].…”

“…Host cells may be forced to support the pathogen by increased nutrient supply and waste disposal across the cell membrane [1]. Altered transport across the cell membrane is particularly important during infection of 134 erythrocytes with the malaria pathogen Plasmodium [2], a disease causing 300-500 million clinical cases and 1-3 million deaths per year [3]. Substrate turnover of noninfected erythrocytes is low but very high in erythrocytes harbouring replicating Plasmodium with its extensive nutrient requirements [2].…”

Triggering of Suicidal Erythrocyte Death by Amphotericin B

“…Cellular depletion of ATP is further known to stimulate eryptosis [36]. The intracellular ATP concentration of erythrocytes was therefore determined upon incubation in the presence or absence of amphotericin B.…”