Activation of platelet caspases by TNF and its consequences for kinetics.
TNF is known to induce a thrombocytopenia, due to a reduced platelet life span. Injection of TNF (10 microg) to mice did markedly increase the number of platelet-derived microparticles in plasma, most pronounced 1h after injection. Injection of TNF induced a transient activation of platelet caspases, -1, -3, -6, -8, -9, as seen by the binding of caspases probes detected by flow cytometry, most pronounced 1h after injection. Activation of caspase-3 was also evidenced by antibodies. Injection of the caspases inhibitor ZVAD-fmk decreased TNF-induced generation of microparticles and thrombocytopenia, indicating a causal role of caspases in platelet fragmentation. Activation of platelet caspases was also evident in platelets exposed to TNF in vitro, indicating that TNF acts on platelets directly. Comparison of platelets from +/+, TNFR1 -/- and TNFR2 -/- mice showed that caspases are activated mainly by the TNFR1. These observations indicate that TNF activates platelet caspases via the TNFR1, which results in platelet fragmentation and thrombocytopenia.
Department of Pathology, University of Geneva, CH 1211, Switzerland. pierre.piguet@medecine.unige.ch
Pierre Francois
PF
Piguet
Christian
C
Vesin
Chen
C
Da Kan
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D000081242:B-Cell Lymphoma 3 Protein; D001792:Blood Platelets / Q000201:enzymology*; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000097:blood / Q000378:metabolism*; D002469:Cell Separation; D004789:Enzyme Activation; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D010455:Peptides / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013921:Thrombocytopenia / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D000590:Amino Acid Chloromethyl Ketones; D000081242:B-Cell Lymphoma 3 Protein; C000631345:Bcl3 protein, mouse; D005456:Fluorescent Dyes; D010455:Peptides; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases