Leukocyte recruitment is a fundamental step in the inflammatory response during ischemia/reperfusion injury (IRI). Rolling and adhesion of leukocytes to activated endothelium promote tissue inflammation after IRI and require presentation of adhesion molecules E-selectin and ICAM-1 on the endothelial surface. Bone morphogenetic protein (BMP) 4 is a prominent member of the BMP family expressed and secreted by endothelial cells. BMP4 derived from endothelial cells has important functions in vascular disease but its influence on the leukocyte adhesion cascade during inflammation is incompletely understood. In the present study, we challenged mice with an inducible endothelial-specific BMP4 deletion (referred to as EC-BMP4^−/− mice) and their control littermates (EC-BMP4^+/+) with thioglycollate i.p. and assessed extravasation of different leukocyte subsets during peritonitis. Peritoneal lavages were performed and peritoneal cells were counted. Total cell count in lavages of EC-BMP4^−/− mice was markedly reduced compared with lavages of EC-BMP4^+/+ mice. FACS analyses of thioglycollate-elicited peritoneal cells revealed that diverse leukocyte subsets were reduced in EC-BMP4^−/− mice. Intravital microscopy of cremaster venules demonstrated that rolling and adhesion of leukocytes were significantly diminished in EC-BMP4^−/− mice in comparison with control mice in response to TNFα. These observations indicate that endothelial BMP4 is essential for rolling, adhesion, and extravasation of leukocytes in vivo. To understand the underlying mechanisms, levels of endothelial adhesion molecules E-selectin and ICAM-1 were quantified in EC-BMP4^−/− and EC-BMP4^+/+ mice by quantitative PCR and Western blotting. Interestingly, ICAM-1 and E-selectin expressions were reduced in the hearts of EC-BMP4^−/− mice. Next we confirmed pro-inflammatory properties of BMP4 in a gain of function experiments and found that administration of recombinant BMP4 in male C57BL/6 mice increased leukocyte rolling and adhesion in cremaster venules in vivo. To assess the regulation of BMP4 in inflammatory disease in humans, we collected plasma samples of patients from day 0 to day 7 after survived out-of-hospital cardiac arrest (OHCA, n = 42). Remarkably, plasma of OHCA patients contained significantly higher BMP4 protein levels compared with patients with coronary artery disease (CAD, n = 12) or healthy volunteers (n = 11). Subgroup analysis revealed that elevated plasma BMP4 levels after ROSC are associated with decreased survival and unfavorable neurological outcome. Collectively, endothelial BMP4 is a potent activator of inflammation in vivo that promotes rolling, adhesion, and extravasation of leukocyte subsets by induction of E-selectin and ICAM-1. Elevation of plasma BMP4 levels in the post-resuscitation period suggests that BMP4 contributes to pathophysiology and poor outcome of post-cardiac arrest syndrome.

白细胞募集是缺血/再灌注损伤 (IRI) 期间炎症反应的基本步骤。白细胞滚动和粘附到活化的内皮细胞会促进 IRI 后的组织炎症，并且需要在内皮表面上呈递粘附分子 E-选择素和 ICAM-1。骨形态发生蛋白 (BMP) 4 是由内皮细胞表达和分泌的 BMP 家族的重要成员。源自内皮细胞的 BMP4 在血管疾病中具有重要功能，但其对炎症期间白细胞粘附级联的影响尚不完全清楚。在本研究中，我们用可诱导的内皮特异性 BMP4 缺失（称为 EC-BMP4 ^-/-小鼠）及其对照同窝小鼠（EC-BMP4 ^+/+) 与硫乙醇酸盐 ip 并评估腹膜炎期间不同白细胞亚群的外渗。进行腹膜灌洗并计数腹膜细胞。^{与EC-BMP4 +/+小鼠的灌洗液相比，EC-BMP4 -/-}小鼠灌洗液中的总细胞计数显着减少。硫代乙醇酸盐引发的腹膜细胞的 FACS 分析显示，EC-BMP4 ^-/-小鼠中不同的白细胞亚群减少。提睾小静脉的活体显微镜检查表明，与响应 TNFα 的对照小鼠相比， EC-BMP4 ^{-/-小鼠的白细胞滚动和粘附显着减少。}这些观察结果表明，内皮 BMP4 对于白细胞的滚动、粘附和外渗至关重要在体内。为了解潜在机制，通过定量 PCR 和蛋白质印迹在 EC-BMP4 ^-/-和 EC-BMP4 ^+/+小鼠中定量内皮粘附分子 E-选择素和 ICAM-1 的水平。^{有趣的是，EC-BMP4 -/-}小鼠心脏中的 ICAM-1 和 E-选择素表达降低。接下来，我们在功能增益实验中证实了 BMP4 的促炎特性，并发现在雄性 C57BL/6 小鼠中施用重组 BMP4 可增加体内提睾小静脉中的白细胞滚动和粘附。为了评估 BMP4 在人类炎症性疾病中的调节作用，我们收集了在院外心脏骤停（OHCA，n= 42)。值得注意的是，与冠状动脉疾病患者（CAD，n = 12）或健康志愿者（n = 11）相比，OHCA 患者的血浆中 BMP4 蛋白水平显着升高。亚组分析显示，ROSC 后血浆 BMP4 水平升高与生存率降低和神经系统预后不良有关。总的来说，内皮 BMP4 是体内炎症的有效激活剂，通过诱导 E-选择素和 ICAM-1 促进白细胞亚群的滚动、粘附和外渗。复苏后血浆 BMP4 水平的升高表明 BMP4 有助于心脏骤停后综合征的病理生理学和不良结果。