Chang Fumin, Flavahan Sheila, Flavahan Nicholas A
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD, USA.
J Physiol. 2016 Sep 1;594(17):4933-44. doi: 10.1113/JP272176. Epub 2016 Jun 16.
Endothelial expression and the release of endothelin-1 (ET-1) in levels sufficient to initiate vasoconstriction is considered to be a hallmark feature of pathological endothelial dysfunction. During the immediate postnatal period, arterial endothelial cells undergo remarkable structural and functional changes as they transition to a mature protective cell layer, which includes a marked increase in NO dilator activity. The present study demonstrates that endothelial cells lining newborn central arteries express high levels of ET-1 peptides and, in response to endothelial stimulation, rapidly release ET-1 and initiate powerful ET-1-mediated constriction. This activity is lost as the endothelium matures in the postnatal period. Heightened activity of ET-1 in the neonatal endothelium might contribute to inappropriate responses of immature arteries to stress or injury. Indeed, the immature endothelium resembles dysfunctional endothelial cells, and retention or re-emergence of this phenotype may contribute to the development of vascular disease.
Endothelial cells lining fetal and newborn arteries have an unusual phenotype, including reduced NO activity, prominent actin stress fibres and poorly developed cellular junctions. Experiments were performed to determine whether the immature endothelium of newborn arteries also expresses and releases endothelin-1 (ET-1) and initiates endothelium-dependent constriction. Carotid arteries were isolated from newborn (postnatal day 1; P1), postnatal day 7 (P7) and postnatal day 21 (P21) mice and assessed in a pressure myograph system. Endothelial stimulation with A23187 or thrombin caused constriction in P1 arteries, no significant change in diameter of P7 arteries, and dilatation in P21 arteries. In P1 arteries, constriction to thrombin or A23187 was inhibited by endothelial-denudation, by ET-1 receptor antagonists (BQ123 plus BQ788) or by inhibition of endothelin-converting enzyme (phosphoramidon or SM19712). ET-1 receptor antagonism did not affect responses to thrombin or A23187 in more mature arteries. Exogenous ET-1 caused similar concentration-dependent constrictions of P1, P7 and P21 arteries. Endothelial stimulation with thrombin rapidly increased the endothelial release of ET-1 from P1 but not P21 aortas. Endothelial expression of ET-1 peptides, as assessed by immunofluorescence analysis, was increased in P1 compared to P21 arteries. Therefore, newborn endothelial cells express high levels of ET-1 peptides, rapidly release ET-1 in response to endothelial stimulation, and initiate ET-1-mediated endothelium-dependent constriction. This activity is diminished as the endothelium matures in the immediate postnatal period. Heightened activity of ET-1 in neonatal endothelium probably reflects an early developmental role of the peptide, although this might contribute to inappropriate responses of immature arteries to stress or injury.
内皮素 -1（ET-1）在内皮细胞中的表达及释放达到足以引发血管收缩的水平，被认为是病理性内皮功能障碍的标志性特征。在出生后的即刻阶段，动脉内皮细胞向成熟的保护细胞层转变时会经历显著的结构和功能变化，其中包括一氧化氮（NO）舒张活性的显著增加。本研究表明，新生中枢动脉的内皮细胞表达高水平的ET-1肽，并且在内皮细胞受到刺激时，会迅速释放ET-1并引发强大的ET-1介导的血管收缩。随着内皮细胞在出生后逐渐成熟，这种活性会丧失。新生儿内皮细胞中ET-1活性增强可能导致未成熟动脉对应激或损伤产生不适当反应。实际上，未成熟的内皮细胞类似于功能失调的内皮细胞，这种表型的保留或再次出现可能会促进血管疾病的发展。
胎儿和新生动脉的内皮细胞具有异常表型，包括NO活性降低、明显的肌动蛋白应激纤维和发育不良的细胞连接。进行实验以确定新生动脉未成熟的内皮细胞是否也表达和释放内皮素 -1（ET-1）并引发内皮依赖性血管收缩。从出生后第1天（P1）、出生后第7天（P7）和出生后第21天（P21）的小鼠中分离出颈动脉，并在压力肌动描记系统中进行评估。用A23187或凝血酶刺激内皮细胞会导致P1动脉收缩，P7动脉直径无显著变化，P21动脉扩张。在P1动脉中，对凝血酶或A23187的收缩反应可被内皮剥脱、ET-1受体拮抗剂（BQ123加BQ788）或抑制内皮素转换酶（磷酰胺素或SM19712）所抑制。ET-1受体拮抗作用对更成熟动脉对凝血酶或A23187的反应没有影响。外源性ET-1对P1、P7和P21动脉引起类似的浓度依赖性收缩。用凝血酶刺激内皮细胞会使P1主动脉内皮ET-1的释放迅速增加，但P21主动脉则不会。通过免疫荧光分析评估，与P21动脉相比，P1动脉中ET-1肽的内皮表达增加。因此，新生内皮细胞表达高水平的ET-1肽，在内皮细胞受到刺激时迅速释放ET-1，并引发ET-1介导的内皮依赖性血管收缩。随着内皮细胞在出生后即刻阶段逐渐成熟，这种活性会减弱。新生儿内皮细胞中ET-1活性增强可能反映了该肽在早期发育中的作用，尽管这可能会导致未成熟动脉对应激或损伤产生不适当反应。
