title: Effect of parathyroid-hormone-related protein on human platelet activation.
abstract: Evidence suggests that PTHrP [PTH (parathyroid hormone)-related protein] can act as an inflammatory mediator in several pathological settings including cardiovascular disease. The aim of the present study was to determine whether PTHrP might be involved in human platelet activation. We used a turbidimetric method to determine platelet aggregation. The expression of PTH1R (PTH type 1 receptor) in human platelets was analysed by Western blot and flow cytometry analyses. PTHrP-(1-36) (10(-7) mol/l) by itself failed to modify the activation of platelets. However, it significantly enhanced ADP-induced platelet activation, and also increased the ability of other agonists (thrombin, collagen and arachidonic acid) to induce platelet aggregation. H89 (10(-6) mol/l) and 25 x 10(-6) mol/l Rp-cAMPS (adenosine 3',5'-cyclic monophosphorothioate Rp-isomer), two protein kinase A inhibitors, and 25 x 10(-9) mol/l bisindolylmaleimide I, a protein kinase C inhibitor, partially decreased the enhancing effect of PTHrP-(1-36) on ADP-induced platelet activation. Meanwhile, 10(-6) mol/l PTHrP-(7-34), a PTH1R antagonist, as well as 10(-5) mol/l PD098059, a MAPK (mitogen-activated protein kinase) inhibitor, or a farnesyltransferase inhibitor abolished this effect of PTHrP-(1-36). Moreover, 10(-7) mol/l PTHrP-(1-36) increased (2-fold over control) MAPK activation in human platelets. PTH1R was detected in platelets, and the number of platelets expressing it on their surface in patients during AMI (acute myocardial infarction) was not different from that in a group of patients with similar cardiovascular risk factors without AMI. Western blot analysis showed that total PTH1R protein levels were markedly higher in platelets from control than those from AMI patients. PTH1R was found in plasma, where its levels were increased in AMI patients compared with controls. In conclusion, human platelets express the PTH1R. PTHrP can interact with this receptor to enhance human platelet activation induced by several agonists through a MAPK-dependent mechanism.
authors.affiliation: Bone and Mineral Metabolism Laboratory, Fundación Jiménez Díaz, Madrid, Spain.
authors.forename: Arantxa
authors.initials: A
authors.lastname: Ortega
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Pérez de Prada
authors.forename: Petra J
authors.initials: PJ
authors.lastname: Mateos-Cáceres
authors.forename: Priscila
authors.initials: P
authors.lastname: Ramos Mozo
authors.forename: Juan J
authors.initials: JJ
authors.lastname: González-Armengol
authors.forename: Juan M
authors.initials: JM
authors.lastname: González Del Castillo
authors.forename: Javier
authors.initials: J
authors.lastname: Martín Sánchez
authors.forename: Pedro
authors.initials: P
authors.lastname: Villarroel
authors.forename: José L
authors.initials: JL
authors.lastname: Santiago
authors.forename: Ricardo J
authors.initials: RJ
authors.lastname: Bosch
authors.forename: Carlos
authors.initials: C
authors.lastname: Macaya
authors.forename: Pedro
authors.initials: P
authors.lastname: Esbrit
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: López-Farré
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001792:Blood Platelets / Q000378:metabolism; D015153:Blotting, Western; D005434:Flow Cytometry; D006801:Humans; D007211:Indoles / Q000378:metabolism; D008301:Maleimides / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009203:Myocardial Infarction / Q000503:physiopathology*; D044162:Parathyroid Hormone-Related Protein / Q000494:pharmacology* / Q000502:physiology; D015539:Platelet Activation / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects
chemical_list: D007211:Indoles; D008301:Maleimides; D044162:Parathyroid Hormone-Related Protein; D020928:Mitogen-Activated Protein Kinases; C088060:bisindolylmaleimide