title: Release of matrix metalloproteinases-1 and -2, but not -9, from activated platelets measured by enzyme-linked immunosorbent assay.
abstract: Matrix metalloproteinases (MMPs), in particular MMP-9, have been introduced as novel biomarkers in coronary artery disease. Activated platelets are considered to be a major source of the highly elevated levels of MMPs that are detected in serum compared to plasma. The aim of this study was to clarify if activated platelets release MMPs-1, -2 and -9 as measured by enzyme-linked immunosorbent assays (ELISA). Isolated platelets (separated by several procedures) or platelet-rich plasma (PRP) were stimulated by collagen, thrombin or the TLR2 agonist Pam(3)CSK(4). The concentrations of MMPs-1,-2 and -9 in supernatants were determined by ELISA. In addition, a MMP-9 enzyme activity assay was used as well as immunofluorescent staining of MMPs-1,-2 and 9 in platelets. Isolated platelets stimulated by collagen, thrombin or Pam(3)CSK(4) released significant amounts of MMP-1 to the supernatant measured as either pro- or total-MMP-1. However, there was no detectable release of MMP-2 or -9 from isolated platelets. Collagen-stimulated platelets in PRP released MMP-2, but not -9. Before stimulation; platelets were positive for MMPs-1 and -2, but not -9, as assessed by immunofluorescence. Acting as positive controls, neutrophils were found to release significant amounts of MMP-9. Our findings indicate that activated platelets may be a major source of MMP-1 and to a minor extent MMP-2, in peripheral blood. However, in contrast to what has been argued in previous literature, platelets appear to be only negligible contributors to circulating MMP-9.
authors.affiliation: Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Sweden. hanna.kalvegren@lio.se
authors.forename: Hanna
authors.initials: H
authors.lastname: Kälvegren
authors.forename: Simon
authors.initials: S
authors.lastname: Jönsson
authors.forename: Lena
authors.initials: L
authors.lastname: Jonasson
mesh_terms: D001792:Blood Platelets / Q000201:enzymology*; D003094:Collagen / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D015539:Platelet Activation; D013917:Thrombin / Q000378:metabolism
chemical_list: D003094:Collagen; D013917:Thrombin; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D020781:Matrix Metalloproteinase 1