title: Bacillus pasteurii urease shares with plant ureases the ability to induce aggregation of blood platelets.
abstract: Ureases (EC 3.5.1.5) are highly homologous enzymes found in plants, bacteria and fungi. Canatoxin, an isoform Canavalia ensiformis urease, has several biological properties unrelated to its ureolytic activity, like platelet-aggregating and pro-inflammatory effects. Here, we describe that Bacillus pasteurii urease (BPU) also induces aggregation of rabbit platelets, similar to the canatoxin-induced effect (ED(50) 0.4 and 0.015 mg/mL, respectively). BPU induced-aggregation was blocked in platelets pretreated with dexamethasone and esculetin, a phospholipase A(2) and a lipoxygenase inhibitor, respectively, while platelets treated with indomethacin, a cyclooxygenase inhibitor, showed increased response to BPU. Methoxyverapamil (Ca(2+) channel blocker) and AMP (ADP antagonist) abrogated urease-induced aggregation, whereas the PAF-acether antagonist Web2170 had no effect. We concluded that platelet aggregation induced by BPU is mediated by lipoxygenase-derived eicosanoids and secretion of ADP from the platelets through a calcium-dependent mechanism. Potential relevance of these findings for bacterium-plant interactions and pathogenesis of bacterial infections are discussed.
authors.affiliation: Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: D
authors.initials: D
authors.lastname: Olivera-Severo
authors.forename: G E
authors.initials: GE
authors.lastname: Wassermann
authors.forename: C R
authors.initials: CR
authors.lastname: Carlini
mesh_terms: D000818:Animals; D001407:Bacillus / Q000201:enzymology*; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D007887:Fabaceae / Q000201:enzymology*; D010940:Plant Proteins / Q000008:administration & dosage*; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D014510:Urease / Q000008:administration & dosage*
chemical_list: D010940:Plant Proteins; D014510:Urease