Department of Pediatrics, University of California, San Francisco, San Francisco, California;
Department of Surgery, University of California, Davis, Davis, California.
Am J Physiol Heart Circ Physiol. 2016 Jul 1;311(1):H137-45. doi: 10.1152/ajpheart.00649.2015. Epub 2016 May 13.
Associated abnormalities of the lymphatic circulation are well described in congenital heart disease. However, their mechanisms remain poorly elucidated. Using a clinically relevant ovine model of a congenital cardiac defect with chronically increased pulmonary blood flow (shunt), we previously demonstrated that exposure to chronically elevated pulmonary lymph flow is associated with: 1) decreased bioavailable nitric oxide (NO) in pulmonary lymph; and 2) attenuated endothelium-dependent relaxation of thoracic duct rings, suggesting disrupted lymphatic endothelial NO signaling in shunt lambs. To further elucidate the mechanisms responsible for this altered NO signaling, primary lymphatic endothelial cells (LECs) were isolated from the efferent lymphatic of the caudal mediastinal node in 4-wk-old control and shunt lambs. We found that shunt LECs (n = 3) had decreased bioavailable NO and decreased endothelial nitric oxide synthase (eNOS) mRNA and protein expression compared with control LECs (n = 3). eNOS activity was also low in shunt LECs, but, interestingly, inducible nitric oxide synthase (iNOS) expression and activity were increased in shunt LECs, as were total cellular nitration, including eNOS-specific nitration, and accumulation of reactive oxygen species (ROS). Pharmacological inhibition of iNOS reduced ROS in shunt LECs to levels measured in control LECs. These data support the conclusion that NOS signaling is disrupted in the lymphatic endothelium of lambs exposed to chronically increased pulmonary blood and lymph flow and may contribute to decreased pulmonary lymphatic bioavailable NO.
在先天性心脏病中，已经很好地描述了与淋巴循环相关的异常。然而，它们的机制仍未得到很好的阐明。使用具有慢性增加肺血流量（分流）的先天性心脏病的临床相关绵羊模型，我们先前证明，暴露于慢性升高的肺淋巴流量与：1）肺淋巴中生物可利用的一氧化氮（NO）减少；2）胸导管环的内皮依赖性松弛减弱，表明分流羔羊的淋巴内皮细胞一氧化氮信号传导受损。为了进一步阐明导致这种改变的 NO 信号传导的机制，从 4 周龄对照和分流羔羊的尾侧纵隔淋巴结的输出淋巴管中分离出初级淋巴管内皮细胞（LEC）。我们发现，与对照 LEC（n = 3）相比，分流 LEC（n = 3）的生物可利用的 NO 减少，内皮型一氧化氮合酶（eNOS）mRNA 和蛋白表达减少。分流 LEC 的 eNOS 活性也较低，但有趣的是，分流 LEC 中的诱导型一氧化氮合酶（iNOS）表达和活性增加，总细胞硝化包括 eNOS 特异性硝化和活性氧（ROS）的积累也增加。iNOS 的药理学抑制将分流 LEC 中的 ROS 降低到与对照 LEC 中测量的水平。这些数据支持这样的结论，即在暴露于慢性增加的肺血液和淋巴流量的羔羊的淋巴内皮细胞中，NOS 信号传导被破坏，这可能导致肺淋巴生物可利用的 NO 减少。
