title: Stimulation of erythrocyte cell membrane scrambling by methyldopa.
abstract: Methyldopa is used for treatment of hypertension in pregnancy. Side effects of methyldopa include anemia, which could result from decreased formation or accelerated death of circulating erythrocytes. Several drugs cause anemia by triggering of suicidal erythrocyte death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling, the latter leading to phosphatidylserine exposure at the erythrocyte surface. Stimulators of erythrocyte membrane scrambling include increased cytosolic Ca(2+) concentration ([Ca(2+)](i)) and ceramide. Phosphatidylserine-exposing cells are rapidly cleared from circulating blood. The present study explored whether eryptosis could be triggered by methyldopa. Erythrocytes from healthy volunteers were exposed to methyldopa, and phosphatidylserine exposure (annexin A5 binding), cell volume (forward scatter), [Ca(2+)](i) (Fluo3-dependent fluorescence), and ceramide formation (anti-ceramide-fluorescein isothiocyanate antibody) were determined by flow cytometry. Methyldopa (6 microg/ml) did not increase [Ca(2+)](i) but led to stimulation of ceramide formation resulting in significant phosphatidylserine exposure and, at higher concentrations, to cell shrinkage. Methyldopa further decreased the GSH/GSSG ratio, pointing to oxidative stress. The scavenger N-acetyl-L-cysteine significantly blunted methyldopa-induced eryptosis. Clearance of erythrocytes from circulating blood was significantly accelerated by treatment with methyldopa. The present observations disclose a novel action of methyldopa, which may well contribute to drug-induced anemia.
authors.affiliation: Department of Physiology, University of Tubingen, Tubingen, Germany.
authors.forename: Hasan
authors.initials: H
authors.lastname: Mahmud
authors.forename: Michael
authors.initials: M
authors.lastname: Föller
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000316:Adrenergic alpha-Agonists; D000740:Anemia / Q000139:chemically induced* / Q000209:etiology; D000959:Antihypertensive Agents; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects*; D048429:Cell Size; D002478:Cells, Cultured; D004912:Erythrocytes / Q000648:ultrastructure*; D005434:Flow Cytometry; D006801:Humans; D008750:Methyldopa / Q000009:adverse effects*; D018384:Oxidative Stress; D010718:Phosphatidylserines / Q000378:metabolism
chemical_list: D000316:Adrenergic alpha-Agonists; D000959:Antihypertensive Agents; D010718:Phosphatidylserines; D008750:Methyldopa; D002118:Calcium