Effect of anandamide on erythrocyte survival

Abstract

The endocannabinoid anandamide (Arachidonylethanolamide, AEA) is known to induce apoptosis in a wide variety of nucleated cells. The present study explored whether anandamide induces suicidal death of erythrocytes or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the erythrocyte surface. Eryptotic cells are phagocytosed and thus cleared from circulating blood. Triggers of eryptosis include increase of cytosolic Ca 2+ activity, formation of PGE 2 , oxidative stress and excessive cell shrinkage. Erythrocyte Ca 2+ activity was estimated from Fluo3 fluorescence, phosphatidylserine exposure from annexin V binding, and erythrocyte volume from forward scatter in FACS analysis. Exposure of erythrocytes to anandamide (= 2.5 μM) increased cytosolic Ca 2+ activity, enhanced the percentage of annexin V binding erythrocytes and decreased erythrocyte forward scatter, effects significantly blunted in the presence of cycloxygenase inhibitors acetylsalicylic acid (50 μM) or ibuprofen 100 μM) and in the nominal absence of extracellular Ca 2+ . Anandamide further enhanced the stimulating effects of hypertonic (addition of 550 mM sucrose) or isotonic (isosmotic replacement of Cl - with gluconate) cell shrinkage on annexin V binding. The present observations demonstrate that anandamide increases cytosolic Ca 2+ activity, thus leading to cell shrinkage and cell membrane scrambling of mature erythrocytes. Copyright © 2007 S. Karger AG.