Department of Pharmacology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan.
Department of Surgery, Kitasato University School of Medicine, Kanagawa, Japan.
Cardiovasc Res. 2015 Sep 1;107(4):509-21. doi: 10.1093/cvr/cvv139. Epub 2015 May 1.
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.
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(-/-).
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.
血栓烷 A2（TXA2）通过血栓烷前列腺素（TP）受体诱导血小板黏附。血小板含有许多促血管生成因子，并被募集到血管损伤部位。然而，血小板依赖性血管生成的细胞和分子机制，特别是 TP 信号的参与，尚未完全阐明。本研究假设 TP 依赖性血小板黏附将有助于小鼠后肢缺血模型中的血管生成。
与对照组小鼠相比，TXA2 受体拮抗剂（S-1452）和 TXA2 合酶抑制剂（OKY-046）抑制了血流恢复。与野生型（WT）和前列环素受体敲除（IP(-/-)）小鼠相比，TP 敲除（TP(-/-)）小鼠的缺血后血流恢复延迟，血管生成受损。通过体内显微镜观察到 WT 和 IP(-/-)中血小板通过 P-选择素选择性黏附于缺血内皮细胞（ECs），但在 TP(-/-)中则没有。IF 分析显示，在 WT 和 IP(-/-)中，P-选择素糖蛋白配体-1（PSGL-1）与缺血肌肉中的内皮 CD31 共定位，但在 TP(-/-)中则没有减少。WT 缺血后血小板富含血浆中的基质细胞衍生因子-1 和 VEGF 水平增加，WT 中用抗 P-选择素抗体抑制，但在 TP(-/-)中则没有抑制。此外，WT 和 IP(-/-)中的 VEGF 或 C-X-C 趋化因子受体 4 的中和抗体抑制了血流恢复，但在 TP(-/-)中则没有抑制。
这些结果表明，TP 信号通过 P-选择素介导的血小板黏附到 PSGL-1 上，促进了缺血诱导的血管生成，从而促进了血小板对缺血部位 ECs 的黏附，并供应了促血管生成因子。
