Department of Physiology, Loma Linda University of Medicine, Loma Linda, CA 92354, USA.
Ann Neurol. 2010 Nov;68(5):650-60. doi: 10.1002/ana.22102.
Osteopontin (OPN), a pleiotropic extracellular matrix glycoprotein, has been reported to be protective against ischemic lesions, but effects of OPN on vascular functions have not been investigated. The aim of this study was to assess whether recombinant OPN (r-OPN) could prevent cerebral vasospasm after subarachnoid hemorrhage (SAH) in rats.
r-OPN was administered intraventricularly to rats undergoing SAH by endovascular perforation, and its protective effects were evaluated by measuring the diameter of cerebral arteries and neurobehavioral testing. Western blotting and immunofluorescence were performed to explore the underlying mechanisms. An integrin receptor antagonist GRGDSP or mitogen-activated protein kinase (MAPK) phosphatase (MKP)-1 small interfering RNA (siRNA) was also administered to r-OPN-treated SAH rats, and those effects were evaluated.
Pre-SAH administration of r-OPN prevented vasospasm and neurological impairments at 24-72 hours post-SAH. r-OPN enhanced an endogenous MAPK inhibitor, MKP-1, and suppressed the phosphorylation of MAPKs, caldesmon, and heat shock protein 27 in the spastic cerebral arteries at 24 hours post-SAH. Immunofluorescence revealed that MKP-1 was induced in the arterial smooth muscle layer. GRGDSP prevented r-OPN-induced MKP-1 upregulation, and MKP-1 siRNA abolished both MAPK inactivation and anti-vasospastic effects by r-OPN. Post-SAH r-OPN treatment also prevented vasospasm.
r-OPN induced MKP-1 in the spastic cerebral arteries via binding to L-arginyl-glycyl-L-aspartate-dependent integrin receptors and prevented vasospasm after SAH. Therapeutic induction of MKP-1 may be a novel approach for the prevention and treatment of cerebral vasospasm.
骨桥蛋白（OPN）是一种多功能细胞外基质糖蛋白，已被报道对缺血性病变具有保护作用，但 OPN 对血管功能的影响尚未得到研究。本研究旨在评估重组 OPN（r-OPN）是否可以预防大鼠蛛网膜下腔出血（SAH）后的脑血管痉挛。
通过血管内穿孔使大鼠发生 SAH，然后脑室注射 r-OPN，通过测量脑动脉直径和神经行为测试来评估其保护作用。进行 Western blot 和免疫荧光实验以探索潜在机制。GRGDSP（一种整合素受体拮抗剂）或丝裂原活化蛋白激酶（MAPK）磷酸酶（MKP-1）小干扰 RNA（siRNA）也被给予 r-OPN 治疗的 SAH 大鼠，并评估其作用。
SAH 前给予 r-OPN 可预防 SAH 后 24-72 小时的血管痉挛和神经损伤。r-OPN 增强了内源性 MAPK 抑制剂 MKP-1，并抑制了 SAH 后 24 小时痉挛性脑动脉中的 MAPK、钙调蛋白和热休克蛋白 27 的磷酸化。免疫荧光显示 MKP-1 诱导于动脉平滑肌层。GRGDSP 阻止 r-OPN 诱导的 MKP-1 上调，MKP-1 siRNA 消除 r-OPN 对 MAPK 失活和抗血管痉挛作用。SAH 后 r-OPN 治疗也可预防血管痉挛。
r-OPN 通过与 L-精氨酰-甘氨酰-L-天冬氨酸依赖性整合素受体结合诱导痉挛性脑动脉中的 MKP-1，从而预防 SAH 后的血管痉挛。诱导 MKP-1 的治疗可能是预防和治疗脑血管痉挛的新方法。
