Li Hong, Wang Yu-sheng
Department of Ophthalmology, Eye Institute of Chinese PLA, Xijing Hospital, Fourth Military Medical University, Xi'an, PR China.
Mol Vis. 2013 May 29;19:1107-21. Print 2013.
Stromal-derived factor (SDF)-1 is a chemokine that recruits bone marrow-derived endothelial precursor cells (EPCs) for choroidal neovascularization (CNV) development. Angiotensin-converting enzyme (ACE) inhibitors mediate the compensatory effects of ACE and CD26/dipeptidyl peptidase IV (DPP IV), which results in the degradation and inactivation of SDF-1 in vivo. ACE inhibitors, such as imidapril, exhibit potential antiangiogenic effects on laser-induced CNV in mice. The role that this imidapril-mediated effect plays in modulating SDF-1 signals has not been defined. The present study assessed the effect of the CD26/SDF-1 signaling pathway on the inhibitory effect of imidapril in CNV development.
CNV was induced in C57BL/6J mice by focally rupturing Bruch's membrane using a 532-nm diode laser. The animals were pretreated with PBS, imidapril, diprotin-A (a DPP IV antagonist), or imidapril plus diprotin-A for 5 days before photocoagulation. Treatments were continued daily for 14 days following the laser induction. The normal control group did not undergo laser rupture or receive treatment. CD26 activity was measured using a substrate conversion assay and flow cytometry. SDF-1 levels in both the blood and the bone marrow were measured using an enzyme-linked immunosorbent assay, and the number of circulating endothelial progenitor cells (EPCs) and leukocytes was quantified. Functional analyses of circulating SDF-1 were performed using actin polymerization blood biomarker assays, and the CNV-related responses were evaluated using fluorescein angiography and isolectin-B4-labeled flatmounts.
Imidapril directly amplified CD26 activity and had a minor effect on the number of CD26+ cells in the bone marrow. However, decreased CD26 activity in the plasma was secondary to a decrease in the number of circulating CD26+ cells and blood leukocytes. Furthermore, imidapril increased SDF-1 concentrations in the peripheral circulation via CD26-induced degradation of SDF-1 in the bone marrow, an effect that coincided with elevated numbers of circulating EPCs. CD26-mediated SDF-1 inactivation was demonstrated by a decrease in SDF-1-induced actin polymerization in the whole blood of imidapril-treated mice. Imidapril markedly decreased angiographic leakage and CNV size. CD26 inhibition completely blocked the CD26/SDF-1 signaling pathway in vivo and reduced the antiangiogenic effect of imidapril.
These results strongly suggest that the antiangiogenic effects of imidapril on laser-induced CNV partially involve the modulation of the CD26/SDF-1 signaling pathway.
基质衍生因子（SDF）-1是一种趋化因子，可募集骨髓来源的内皮祖细胞（EPC）以促进脉络膜新生血管（CNV）的形成。血管紧张素转换酶（ACE）抑制剂可介导ACE和CD26/二肽基肽酶IV（DPP IV）的代偿作用，从而导致SDF-1在体内降解和失活。诸如咪达普利等ACE抑制剂对小鼠激光诱导的CNV具有潜在的抗血管生成作用。尚未明确这种咪达普利介导的效应在调节SDF-1信号中所起的作用。本研究评估了CD26/SDF-1信号通路对咪达普利抑制CNV形成作用的影响。
使用532nm二极管激光局部破坏C57BL/6J小鼠的 Bruch膜以诱导CNV。在光凝前5天，动物分别用磷酸盐缓冲液（PBS）、咪达普利、二肽基肽酶A（DPP IV拮抗剂）或咪达普利加二肽基肽酶A进行预处理。激光诱导后每天持续治疗14天。正常对照组未进行激光破坏或接受治疗。使用底物转化测定法和流式细胞术测量CD26活性。使用酶联免疫吸附测定法测量血液和骨髓中的SDF-1水平，并对循环内皮祖细胞（EPC）和白细胞的数量进行定量。使用肌动蛋白聚合血液生物标志物测定法对循环SDF-1进行功能分析，并使用荧光素血管造影和异凝集素B4标记的平铺标本评估与CNV相关的反应。
咪达普利直接增强了CD26活性，对骨髓中CD26+细胞的数量影响较小。然而，血浆中CD26活性的降低继发于循环CD26+细胞和血液白细胞数量的减少。此外，咪达普利通过CD26诱导骨髓中SDF-1的降解，增加了外周循环中SDF-1的浓度，这一效应与循环EPC数量的增加相一致。在咪达普利治疗的小鼠全血中，SDF-1诱导的肌动蛋白聚合减少，证明了CD26介导的SDF-1失活。咪达普利显著降低了血管造影渗漏和CNV大小。CD26抑制在体内完全阻断了CD26/SDF-1信号通路，并降低了咪达普利的抗血管生成作用。
这些结果强烈表明，咪达普利对激光诱导的CNV的抗血管生成作用部分涉及CD26/SDF-1信号通路的调节。
