title: A segment of Staphylococcus aureus clumping factor A with fibrinogen-binding activity (ClfA221-550) inhibits platelet-plug formation in mice.
abstract: We previously reported that the fibrinogen-binding segment (residues 221-550) of Staphylococcus aureus clumping factor A (ClfA), which binds to fibrinogen gamma chain C-terminus, exerted inhibitory effects on platelet aggregation and fibrin clot formation in vitro. Here, we further demonstrated the effectiveness of using ClfA221-550 to inhibit platelet-rich thrombus formation in vivo. Platelet-rich thrombi were formed in the mesenteric venules of fluorescein-loaded mice by filtered light illumination. It grew rapidly and ultimately resulted in the cessation of blood flow due to vessel occlusion. Given by intravenous bolus injection, ClfA221-550 delayed occlusive thrombi formation in a dose-dependent manner: 2-, 3- and 4.5-fold prolongations of vessel occlusion time were attained with 0.69, 6.9 and 34.5 mg/kg of ClfA221-550, respectively. Reduced fibrin clot formation at the late phase with plasmas, which were prepared from ClfA221-550-treated mice, was also dose-dependent. The suppression of fibrin formation ex vivo coincided with the delay of occlusive thrombus formation in vivo, suggesting that the antithrombotic effect of ClfA221-550 may result from the blockade of fibrinogen gamma chain C-terminal functions, in mediating platelet aggregation and fibrin clot formation. Administration of ClfA221-550 also lengthened the tail bleeding of mice; however, significant effect was achieved only with a higher dosage, namely 34.5 mg/kg. These results together showed that blockade of fibrinogen gamma chain C-terminus with ClfA221-550 preferentially affected platelet-rich thrombus formation rather than normal haemostasis, thus providing a rationale for selecting fibrinogen gamma chain C-terminus as a new target for thrombotic intervention.
authors.affiliation: Department of Pharmacology, College of Medicine, Tzu Chi University, 701, Chung-Yang Road, Sec. 3, Hualien 970, Taiwan. czliu33@mail.tcu.edu.tw
authors.forename: Chao-Zong
authors.initials: CZ
authors.lastname: Liu
authors.forename: Tur-Fu
authors.initials: TF
authors.lastname: Huang
authors.forename: Po-Jun
authors.initials: PJ
authors.lastname: Tsai
authors.forename: Pei-Jane
authors.initials: PJ
authors.lastname: Tsai
authors.forename: Ling-Ya
authors.initials: LY
authors.lastname: Chang
authors.forename: Mei-Chi
authors.initials: MC
authors.lastname: Chang
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D003029:Coagulants / Q000494:pharmacology*; D003030:Coagulase / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005340:Fibrinogen / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010974:Platelet Aggregation / Q000187:drug effects* / Q000502:physiology; D011485:Protein Binding; D013211:Staphylococcus aureus / Q000502:physiology*; D013927:Thrombosis / Q000378:metabolism
chemical_list: C515944:ClfA protein, Staphylococcus aureus; D003029:Coagulants; D003030:Coagulase; D005340:Fibrinogen