Plasminogen activator inhibitor type 1 in platelets induces thrombogenicity by increasing thrombolysis resistance under shear stress in an in-vitro flow chamber model.
BACKGROUND
Despite the proven benefits of thrombolytic therapy with tissue plasminogen activator (t-PA) for peripheral thromboembolism, perfusion failure frequently occurs, particularly in arterial circulation. We evaluated how the modification of fibrinolytic activity affects thrombus formation under flow and static conditions.


METHODS
t-PA-treated human whole-blood samples (n=6) were perfused over a microchip coated with collagen and tissue thromboplastin at different shear rates, and thrombus formation was quantified by measuring flow pressure changes. For comparison, rotational thromboelastometry (ROTEM) was used to evaluate fibrinolytic activity under static conditions.


RESULTS
At a shear rate of 240s-1, t-PA (200-800IU/ml) concentration-dependently delayed capillary occlusion, whereas at 600s-1, capillary occlusion was significantly faster and t-PA had limited effects, even at a supra-pharmacological concentration (800IU/ml). In contrast, 200IU/ml t-PA efficiently prevented clot formation in the ROTEM assay. The combined treatment of blood with a specific PAI-1 inhibitor (PAI-039) moderately enhanced the efficacy of t-PA, but only under flow conditions. In addition, 1:1-diluted blood samples of PAI-1-deficient (-/-) mice showed a significant delay of capillary occlusion at 240s-1, compared with those from wild-type mice (1.55 fold; P<0.001). This delayed occlusion was reproduced in samples containing platelets from PAI-1-/- and plasma from wild type, but was not observed by the opposite combination of blood components.


CONCLUSIONS
The present results suggest that the anti-thrombotic efficacy of t-PA is sensitive to arterial shear flow, and that PAI-1 secreted from activated platelets plays an essential role in thrombolytic resistance.
Research Institute, Fujimori Kogyo Co., Ltd., 1-10-1, Sachiura, Kanazawa-ku, Yokohama, Kanagawa 236-0003, Japan.
Kazuya
K
Hosokawa
Research Institute, Fujimori Kogyo Co., Ltd., 1-10-1, Sachiura, Kanazawa-ku, Yokohama, Kanagawa 236-0003, Japan.
Tomoko
T
Ohnishi-Wada
Research Institute, Fujimori Kogyo Co., Ltd., 1-10-1, Sachiura, Kanazawa-ku, Yokohama, Kanagawa 236-0003, Japan.
Hisayo
H
Sameshima-Kaneko
Research Institute, Fujimori Kogyo Co., Ltd., 1-10-1, Sachiura, Kanazawa-ku, Yokohama, Kanagawa 236-0003, Japan; Department of System Biology in Thromboregulation, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1, Sakuragaoka, Kagoshima 890-8544, Japan.
Tomoka
T
Nagasato
Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24, Koorimoto, Kagoshima 890-0065, Japan.
Naoki
N
Miura
Department of Physiology, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan; Department of Neurosurgery, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan.
Kiyoshi
K
Kikuchi
Department of System Biology in Thromboregulation, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1, Sakuragaoka, Kagoshima 890-8544, Japan.
Takehiko
T
Koide
Department of System Biology in Thromboregulation, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1, Sakuragaoka, Kagoshima 890-8544, Japan.
Ikuro
I
Maruyama
Department of Medical Physiology, Hamamatsu University School of Medicine, 1-20-1, Handa-yama, Higashi-ku, Hamamatsu, Shizuoka 431-3192, Japan. Electronic address: uranot@hama-med.ac.jp.
Tetsumei
T
Urano
D000328:Adult; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D017395:Plasminogen Activator Inhibitor 1 / Q000172:deficiency*; D015912:Thrombolytic Therapy / Q000379:methods*; D013927:Thrombosis / Q000188:drug therapy*
D017395:Plasminogen Activator Inhibitor 1
Flow chamber; Platelets; Thrombolysis; Tissue plasminogen activator