Department of Biopathology and Image Diagnostics, Anatomic Pathology, Tor Vergata University of Rome, Via Montpellier, Rome 00133, Italy.
Cardiovasc Res. 2010 Jan 1;85(1):214-23. doi: 10.1093/cvr/cvp288.
Flt-1 is an fms-like tyrosine kinase receptor which binds to vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). Ligand activation and blocking of flt-1 influence several vascular smooth muscle cell (SMC) functions, including apoptotic susceptibility. However, downstream signal transduction pathways by which flt-1 regulates SMC apoptosis have still to be investigated.
Flt-1 expression and apoptosis in Wistar rat aortic intimal cells 15 days after ballooning were studied by immunohistochemistry, cytometry, cell sorting, western blotting, and PCR. Anti-flt1 blocking antibody effects were compared with those of anti-PlGF and anti-VEGF antibodies. Rat aortic intimal cells 15 days after injury exhibited increased flt-1 protein and mRNA and lower smooth muscle markers compared with normal media SMCs. Immunoreactivity for flt-1 protein was also observed in apoptotic intimal cells. Anti-flt-1 (EC(50) = 16.5 ng/mL) and anti-PlGF (EC(50) = 20.5 ng/mL) antibodies added to intimal cultures reduced serum-deprived apoptosis but not serum- and PDGF-BB-induced proliferation; the anti-VEGF antibody was ineffective. Sorted flt-1(+) cells were more clonogenic than flt-1(-) and whole intimal SMC populations. Increased nuclear factor-kappaB (NF-kappaB) and inhibitor of apoptosis protein-1 (IAP-1) and reduced bax levels associated with the anti-flt-1-induced increase of intimal SMC survival; the latter was prevented by NF-kappaB activity inhibitor and IAP-1 interfering RNA (RNAi). Blocking of NF-kappaB activity reduced IAP-1 expression and prevented IAP-1 RNAi effects. Increased flt-1 immunoreaction was also documented in human atheromatous lesions.
Our results show that anti-flt-1 blocking reduces apoptosis through NF-kappaB and the downstream IAP-1 pathway. The close link between flt-1, PlGF, and apoptotic susceptibility of intimal SMCs suggests new potential strategies aimed at influencing post-injury arterial remodelling.
Flt-1 是一种与血管内皮生长因子（VEGF）和胎盘生长因子（PlGF）结合的 fms 样酪氨酸激酶受体。配体激活和 flt-1 阻断会影响多种血管平滑肌细胞（SMC）功能，包括凋亡易感性。然而，flt-1 调节 SMC 凋亡的下游信号转导途径仍有待研究。
通过免疫组织化学、细胞计数、细胞分选、Western blot 和 PCR 研究了球囊扩张后 15 天 Wistar 大鼠主动脉内膜细胞中的 Flt-1 表达和凋亡。比较了抗 flt-1 阻断抗体与抗 PlGF 和抗 VEGF 抗体的作用。损伤后 15 天的大鼠主动脉内膜细胞表现出较高的 flt-1 蛋白和 mRNA，以及较低的平滑肌标志物，与正常培养基中的 SMC 相比。凋亡的内膜细胞中也观察到 flt-1 蛋白的免疫反应性。添加到内膜培养物中的抗 flt-1（EC(50) = 16.5 ng/mL）和抗 PlGF（EC(50) = 20.5 ng/mL）抗体减少了血清剥夺诱导的凋亡，但不减少血清和 PDGF-BB 诱导的增殖；抗 VEGF 抗体无效。分选的 flt-1(+)细胞比 flt-1(-)和整个内膜 SMC 群体具有更强的克隆形成能力。与抗 flt-1 诱导的内膜 SMC 存活增加相关的核因子-κB（NF-κB）和凋亡抑制蛋白-1（IAP-1）增加和 bax 水平降低；NF-κB 活性抑制剂和 IAP-1 干扰 RNA（RNAi）可预防后者。NF-κB 活性的阻断减少了 IAP-1 的表达，并防止了 IAP-1 RNAi 的作用。在人动脉粥样硬化病变中也记录到了增加的 flt-1 免疫反应。
我们的结果表明，抗 flt-1 阻断通过 NF-κB 和下游 IAP-1 途径减少凋亡。flt-1、PlGF 和内膜 SMC 凋亡易感性之间的紧密联系表明了新的潜在策略，旨在影响损伤后的动脉重塑。
