Gao Yuansheng, Dhanakoti Srinivas, Trevino Earleen M, Wang Xiaohua, Sander Fred C, Portugal Ada D, Raj J Usha
Harbor-UCLA Medical Center, Research and Education Institute, 1124 W. Carson St., RB-1, Torrance, CA 90502, USA.
Am J Physiol Lung Cell Mol Physiol. 2004 Apr;286(4):L786-92. doi: 10.1152/ajplung.00314.2003. Epub 2003 Dec 5.
Continuous exposure to nitrovasodilators and nitric oxide induces tolerance to their vasodilator effects in vascular smooth muscle. This study was done to determine the role of cGMP-dependent protein kinase (PKG) in the development of tolerance to nitric oxide. Isolated fourth-generation pulmonary veins of newborn lambs were studied. Incubation of veins for 20 h with DETA NONOate (DETA NO; a stable nitric oxide donor) significantly reduced their relaxation response to the nitric oxide donor and to beta-phenyl-1,N2-etheno-8-bromo-cGMP (8-Br-PET-cGMP, a cell-permeable cGMP analog). Incubation with DETA NO significantly reduced PKG activity and protein and mRNA levels in the vessels. These effects were prevented by 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (an inhibitor of soluble guanylyl cyclase) and Rp-8-Br-PET-cGMPS (an inhibitor of PKG). A decrease in PKG protein and mRNA levels was also observed after continuous exposure to cGMP analogs. The PKG inhibitor abrogated these effects. The decrease in cGMP-mediated relaxation and in PKG activity caused by continuous exposure to DETA NO was not affected by KT-5720, an inhibitor of cAMP-dependent protein kinase. Prolonged exposure to 8-Br-cAMP (a cell-permeable cAMP analog) did not affect PKG protein level in the veins. These results suggest that continuous exposure to nitric oxide or cGMP downregulates PKG by a PKG-dependent mechanism. Such a negative feedback mechanism may contribute to the development of tolerance to nitric oxide in pulmonary veins of newborn lambs.
持续暴露于硝基血管扩张剂和一氧化氮会导致血管平滑肌对其血管扩张作用产生耐受性。本研究旨在确定环鸟苷酸依赖性蛋白激酶（PKG）在一氧化氮耐受性形成中的作用。对新生羔羊分离的第四代肺静脉进行了研究。用DETA NONOate（DETA NO；一种稳定的一氧化氮供体）孵育静脉20小时，显著降低了它们对一氧化氮供体和β-苯基-1,N2-乙烯基-8-溴-cGMP（8-Br-PET-cGMP，一种可透过细胞的cGMP类似物）的舒张反应。用DETA NO孵育显著降低了血管中的PKG活性、蛋白质和mRNA水平。这些作用被1H-(1,2,4)恶二唑并(4,3-a)喹喔啉-1-酮（一种可溶性鸟苷酸环化酶抑制剂）和Rp-8-Br-PET-cGMPS（一种PKG抑制剂）所阻断。持续暴露于cGMP类似物后，也观察到PKG蛋白质和mRNA水平的下降。PKG抑制剂消除了这些作用。持续暴露于DETA NO导致的cGMP介导的舒张和PKG活性的降低不受cAMP依赖性蛋白激酶抑制剂KT-5720的影响。长时间暴露于8-Br-cAMP（一种可透过细胞的cAMP类似物）对静脉中的PKG蛋白质水平没有影响。这些结果表明，持续暴露于一氧化氮或cGMP通过一种PKG依赖性机制下调PKG。这种负反馈机制可能有助于新生羔羊肺静脉中一氧化氮耐受性的形成。
