title: Pneumolysin Mediates Platelet Activation In Vitro.
abstract: This study has explored the role of the pneumococcal toxin, pneumolysin (Ply), in activating human platelets. Following exposure to Ply (10-80 ng/ml), platelet activation and cytosolic Ca(2+) concentrations were measured flow cytometrically according to the level of expression of CD62P (P-selectin) and spectrofluorimetrically, respectively. Exposure to Ply resulted in marked upregulation of expression of platelet CD62P, achieving statistical significance at concentrations of 40 ng/ml and higher (P < 0.05), in the setting of increased influx of Ca(2+). These potentially pro-thrombotic actions of Ply were attenuated by depletion of Ca(2+) from the extracellular medium or by exposure of the cells to a pneumolysoid devoid of pore-forming activity. These findings are consistent with a mechanism of Ply-mediated platelet activation involving sub-lytic pore formation, Ca(2+) influx, and mobilization of CD62P-expressing α-granules, which, if operative in vivo, may contribute to the pathogenesis of associated acute lung and myocardial injury during invasive pneumococcal disease.
authors.affiliation: Department of Haematology, Faculty of Health Sciences, University of Pretoria and Tshwane Academic Division of the National Health Laboratory Service, PO Box 2034, Pretoria, 0001, South Africa. jan.nel@up.ac.za.
authors.forename: Jan Gert
authors.initials: JG
authors.lastname: Nel
authors.affiliation: Institute for Cellular and Molecular Medicine, and SAMRC Extramural Unit for Stem Cell Research and Therapy, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Chrisna
authors.initials: C
authors.lastname: Durandt
authors.affiliation: Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Mitchell
authors.affiliation: Division of Pulmonology, Department of Internal Medicine, Faculty of Health Sciences, and Charlotte Maxeke Academic Hospital, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Charles
authors.initials: C
authors.lastname: Feldman
authors.affiliation: Institute for Cellular and Molecular Medicine, and SAMRC Extramural Unit for Stem Cell Research and Therapy, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Ronald
authors.initials: R
authors.lastname: Anderson
authors.affiliation: Department of Internal Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Tintinger
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D001426:Bacterial Proteins / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D065096:Calcium Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D019007:P-Selectin / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000494:pharmacology; D015539:Platelet Activation / Q000187:drug effects*; D013301:Streptolysins / Q000494:pharmacology*; D015854:Up-Regulation
chemical_list: D001426:Bacterial Proteins; D065096:Calcium Chelating Agents; D019007:P-Selectin; D010972:Platelet Activating Factor; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae; D004533:Egtazic Acid; D000244:Adenosine Diphosphate; D002118:Calcium
keywords: CD62P; Calcium; Community-acquired pneumonia; P-selectin; Pneumococcus; Streptococcus pneumoniae