title: Complement activation: the missing link between ADAMTS-13 deficiency and microvascular thrombosis of thrombotic microangiopathies.
abstract: Endothelial injury is the central factor in the events leading to thrombotic microangiopathy (TMA); however, the mechanisms involved are not fully understood. Here we investigate the role of neutrophils (PMNs) and of complement activation in inducing microvascular damage and loss of thromboresistance in TMA associated with ADAMTS-13 deficiency. PMNs isolated during the acute phase of the disease released excessive amounts of reactive-oxygen species (ROS), N-derived oxidants and proteinases and induced damage and thromboresistance loss in human microvascular endothelial cell line (HMEC-1) ex vivo. Endothelial cytotoxicity and thromboresistance loss was also induced by TMA serum. Complement-derived products were responsible for the above effects: in fact, TMA serum caused C3 and Membrane Attack Complex (MAC) deposition on HMEC-1 and its cytotoxic effect was abolished by complement inhibition. TMA serum caused surface expression of P-selectin on HMEC-1 which may promote PMN adhesion and resulted in increased PMN cytotoxicity, indicating that complement may have a role in PMN activation. In addition, TMA serum stimulated control PMNs to release ROS and proteinases, and to cause endothelial cell cytotoxicity. All of the above effects were abrogated by complement inactivation. These data document for the first time that complement-initiated PMN activation and endothelial injury may have a crucial role in microvascular thrombosis of TMA associated with ADAMTS-13 deficiency.
authors.affiliation: Mario Negri Institute for Pharmacological Research, Center for Research on Organ Transplantation, Chiara Cucchi de Alessandri e Gilberto Crespi, Villa Camozzi-Ranica (BG), Italy.
authors.forename: Maria Piedad
authors.initials: MP
authors.lastname: Ruiz-Torres
authors.forename: Federica
authors.initials: F
authors.lastname: Casiraghi
authors.forename: Miriam
authors.initials: M
authors.lastname: Galbusera
authors.forename: Daniela
authors.initials: D
authors.lastname: Macconi
authors.forename: Sara
authors.initials: S
authors.lastname: Gastoldi
authors.forename: Marta
authors.initials: M
authors.lastname: Todeschini
authors.forename: Francesca
authors.initials: F
authors.lastname: Porrati
authors.forename: Daniela
authors.initials: D
authors.lastname: Belotti
authors.forename: Enrico Maria
authors.initials: EM
authors.lastname: Pogliani
authors.forename: Marina
authors.initials: M
authors.lastname: Noris
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Remuzzi
mesh_terms: D051722:ADAM Proteins / Q000172:deficiency*; D000071120:ADAMTS13 Protein; D002460:Cell Line; D003167:Complement Activation / Q000502:physiology*; D004730:Endothelium, Vascular / Q000473:pathology; D006463:Hemolytic-Uremic Syndrome / Q000209:etiology*; D006801:Humans; D018375:Neutrophil Activation / Q000276:immunology; D016877:Oxidants / Q000097:blood; D010447:Peptide Hydrolases / Q000097:blood; D011697:Purpura, Thrombotic Thrombocytopenic / Q000209:etiology*; D017382:Reactive Oxygen Species / Q000097:blood
chemical_list: D016877:Oxidants; D017382:Reactive Oxygen Species; D010447:Peptide Hydrolases; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human