title: Suicidal death of erythrocytes in recurrent hemolytic uremic syndrome.
abstract: Hemolytic uremic syndrome (HUS) is characterized by hemolytic anemia with fragmented erythrocytes, thrombocytopenia, and acute renal failure. Lack of complement inactivating factor H predisposes to the development of atypical HUS. Little is known about mechanisms linking complement activation with loss of erythrocyte integrity during HUS. Recent studies disclosed that increased cytosolic Ca2+ activity and cellular ceramide trigger programmed erythrocyte death or eryptosis, characterized by cell shrinkage and phosphatidylserine exposure at the erythrocyte surface. In the present study, we investigated whether eryptosis occurs during the course of HUS. To this end, erythrocytes from healthy volunteers were exposed to plasma from a patient with severe idiopathic recurrent HUS secondary to factor H depletion. Phosphatidylserine exposure (Annexin binding), cell volume (forward scatter), cytosolic Ca2+ activity (Fluo3 fluorescence), and ceramide formation [anti-ceramide antibody and enzymatic (diacylgycerol kinase) analysis] were determined. Exposure of erythrocytes to plasma from the patient, but not to plasma from healthy individuals, triggered Annexin binding. The effect of plasma on erythrocyte Annexin binding was abolished by plasmapheresis or filtration at 30 kDa. It was paralleled by formation of ceramide and increase of cytosolic Ca2+ activity. Enhanced Annexin binding of erythrocytes from healthy individuals was observed after exposure to plasma from three other patients with HUS. The proeryptotic effect of patient plasma was mimicked by exposure to the Ca2+ ionophore ionomycin, and eryptosis was potentiated in the presence of cell membrane-permeable C6-ceramide. Furthermore, in vitro complement activation similarly triggered erythrocyte phosphatidylserine exposure, an effect which was blunted by the addition of factor H. In conclusion, our present observations disclose a novel, pathophysiological, factor-H dependent mechanism leading to injury of erythrocytes during the course of hemolytic uremic syndrome.
authors.affiliation: Department of Physiology, University of Tübingen, Gmelinstr. 5, 72076 Tübingen, Germany.
authors.forename: Philipp A
authors.initials: PA
authors.lastname: Lang
authors.forename: Ortraud
authors.initials: O
authors.lastname: Beringer
authors.forename: Jan P
authors.initials: JP
authors.lastname: Nicolay
authors.forename: Oliver
authors.initials: O
authors.lastname: Amon
authors.forename: Daniela S
authors.initials: DS
authors.lastname: Kempe
authors.forename: Tobias
authors.initials: T
authors.lastname: Hermle
authors.forename: Philipp
authors.initials: P
authors.lastname: Attanasio
authors.forename: Ahmad
authors.initials: A
authors.lastname: Akel
authors.forename: Richard
authors.initials: R
authors.lastname: Schäfer
authors.forename: Björn
authors.initials: B
authors.lastname: Friedrich
authors.forename: Teut
authors.initials: T
authors.lastname: Risler
authors.forename: Matthias
authors.initials: M
authors.lastname: Baur
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Olbricht
authors.forename: Lothar Bernd
authors.initials: LB
authors.lastname: Zimmerhackl
authors.forename: Peter F
authors.initials: PF
authors.lastname: Zipfel
authors.forename: Thomas
authors.initials: T
authors.lastname: Wieder
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000368:Aged; D017302:Annexins / Q000097:blood / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D016923:Cell Death; D002518:Ceramides / Q000378:metabolism / Q000494:pharmacology; D003167:Complement Activation; D017242:Complement Factor H / Q000378:metabolism* / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D006463:Hemolytic-Uremic Syndrome / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D006801:Humans; D007223:Infant; D008875:Middle Aged; D010718:Phosphatidylserines / Q000097:blood; D010956:Plasmapheresis; D012016:Reference Values
chemical_list: D017302:Annexins; D002518:Ceramides; D010718:Phosphatidylserines; D017242:Complement Factor H; C504327:N-(alpha-hydroxyoctadecanoyl)phytosphingosine; D002118:Calcium