Efavirenz Induced Suicidal Death of Human Erythrocytes

Abstract

Background/Aims: The reverse transcriptase inhibitor efavirenz utilized for the treatment of human immunodeficiency virus (HIV)-1 infection, triggers suicidal cell death or apoptosis, an effect in part due to interference with mitochondrial potential. Side effects of efavirenz include anemia. Causes of anemia include accelerated clearance of circulating erythrocytes. Even though lacking mitochondria, erythrocytes may enter suicidal erythrocyte death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include Ca²⁺ entry and increase of cytosolic Ca²⁺ activity ([Ca²⁺]_i), oxidative stress, ceramide, as well as activation of p38 kinase, casein kinase 1α and/or cyclooxygenase. The present study explored, whether and how efavirenz induces eryptosis. Methods: Phosphatidylserine exposure at the cell surface was estimated from annexin V binding, cell volume from forward scatter, [Ca²⁺]_i from Fluo3-fluorescence, ROS formation from DCFDA dependent fluorescence, and ceramide abundance utilizing selective antibodies. Results: A 48 hours exposure of human erythrocytes to efavirenz (≥ 2 µg/ml) significantly increased the percentage of annexin-V-binding cells, significantly decreased forward scatter (2 µg/ml), significantly increased Fluo3-fluorescence (≥ 2 µg/ml), but did not significantly modify DCFDA fluorescence or ceramide abundance. The effect of efavirenz on annexin-V-binding was significantly blunted, but not abolished by removal of extracellular Ca²⁺. The effect of efavirenz on annexin-V-binding was further significantly blunted by p38 kinase inhibitor SB203580 (2 µM) and casein kinase 1α inhibitor D4476 (10 µM), but not by cyclooxygenase inhibitor aspirin (50 µM). Conclusions: Efavirenz triggers cell shrinkage and phosphatidylserine translocation to the erythrocyte surface, an effect in part due to stimulation of Ca²⁺ entry as well as activation of p38 kinase and casein kinase 1α.