Thromboxane A2 induces blood flow recovery via platelet adhesion to ischaemic regions.
OBJECTIVE
Thromboxane A2 (TXA2) induces platelet adhesion through thromboxane prostanoid (TP) receptor. Platelets contain many pro-angiogenic factors and are recruited to the site of vascular injury. However, the cellular and molecular mechanisms of platelet-dependent angiogenesis, especially the involvement of TP signalling, have not been fully elucidated. The present study hypothesized that TP-dependent platelet adhesion would contribute to angiogenesis in a mouse hindlimb ischaemic model.


RESULTS
Blood flow recovery was suppressed by the TXA2 receptor antagonist (S-1452) and the TXA2 synthase inhibitor (OKY-046) compared with control mice. TP knockout mice (TP(-/-)) showed delayed blood flow recovery from ischaemia and impaired angiogenesis compared with wild-type (WT) mice and prostacyclin receptor knockout mice (IP(-/-)). Selective platelet adhesion to ischaemic endothelial cells (ECs) via P-selectin was identified in WT and IP(-/-), but not in TP(-/-), via in vivo microscopy. IF analysis showed that P-selectin glycoprotein ligand-1 (PSGL-1) co-localized with endothelial CD31 in ischaemic muscle in WT and IP(-/-) but not diminished in TP(-/-). Platelet-rich plasma levels of stromal cell-derived factor-1 and VEGF were increased after ischaemia in WT, and suppressed by antibody against P-selectin in WT but not in TP(-/-). Furthermore, the blood flow recovery was suppressed by neutralizing antibodies against VEGF or C-X-C chemokine receptor type 4 in WT and IP(-/-) but not in TP(-/-).


CONCLUSIONS
These results indicated that TP signalling facilitates ischaemia-induced angiogenesis via P-selectin-mediated platelet adhesion to PSGL-1 on the ECs at ischaemic sites and the supply of pro-angiogenic factors by the adherent platelets.
Department of Pharmacology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan.
Hideki
H
Amano
Department of Surgery, Kitasato University School of Medicine, Kanagawa, Japan.
Yoshiya
Y
Ito
Department of Immunology, Kitasato University School of Medicine, Kanagawa, Japan.
Koji
K
Eshima
Department of Pharmacology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan Department of Cardiology, Kitasato University School of Medicine, Kanagawa, Japan.
Shintaro
S
Kato
Department of Pharmacology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan.
Fumihiro
F
Ogawa
Department of Pharmacology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan.
Kanako
K
Hosono
Department of Pharmacology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan.
Kazuhito
K
Oba
Department of Anatomy, Kitasato University School of Medicine, Kanagawa, Japan.
Hideaki
H
Tamaki
Department of Anatomy, Kitasato University School of Medicine, Kanagawa, Japan.
Hiroyuki
H
Sakagami
Gakubunkan Institute of Physiology and Medicine, Jobu University, Gunma, Japan.
Masabumi
M
Shibuya
Innovation Center for Immunoregulation Technologies and Drugs (AK Project), Kyoto University Graduate School of Medicine, Kyoto City, Kyoto, Japan.
Shuh
S
Narumiya
Department of Pharmacology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan mmajima@med.kitasto-u.ac.jp.
Masataka
M
Majima
D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects*; D042783:Endothelial Cells / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D018345:Mice, Knockout; D017202:Myocardial Ischemia / Q000378:metabolism*; D010973:Platelet Adhesiveness / Q000187:drug effects* / Q000235:genetics; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013928:Thromboxane A2 / Q000494:pharmacology*
D008562:Membrane Glycoproteins; C084882:P-selectin ligand protein; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D013928:Thromboxane A2
Angiogenesis; P-selectin; PSGL-1; Platelets; Thromboxane receptor