King J M, Srivastava K D, Stefano G B, Bilfinger T V, Bahou W F, Magazine H I
Department of Biology, Queens College and Graduate School of the City University of New York, Flushing 11367, USA.
J Immunol. 1997 Jan 15;158(2):880-6.
Human monocytes have the capacity to produce both endothelin 1 (ET-1) and nitric oxide (NO), yet the roles of these mediators in monocyte function remain unclear. The relationship of ET-1 and NO release to monocyte adhesion was explored using peripheral blood monocytes (PBM) and the human monocytic cell lines THP-1 and U937. Specific binding of 125I-labeled ET-1 to THP-1 was abrogated by pretreatment with the endothelin B (ET(B)) receptor antagonist, BQ-788, but not by the endothelin A (ET(A)) receptor antagonist, BQ-123, consistent with predominant ET(B) receptor expression. Direct measurement of NO with an amperometric probe demonstrated the production of nanomolar concentrations of NO by PBM and THP-1 cells upon treatment with ET-1, which was abrogated by BQ-788, but not BQ-123, pretreatment, suggesting functional coupling of ET(B) receptors to NO release. Indeed, the presence of ET(B) receptor mRNA transcripts was detected in THP-1 and is consistent with previous reports that have demonstrated functional coupling of ET(B) receptors to constitutive NO synthase activation. In contrast, U937 cells did not release NO in response to ET-1 treatment, and mRNA transcripts were not detected in these cells, consistent their failure to bind 125I-labeled ET-1, as previously determined. Exposure of PBM to ET-1 markedly reduced the adhesion of these cells to human saphenous vein, whereas PBM adhesion in the presence of BQ-788 was restored to control levels. These data demonstrate that PBM interactions with the vascular wall can be reduced by autocrine production of NO and suggest that ET(B) receptors may attenuate monocyte activity at sites of inflammation.
人类单核细胞有能力产生内皮素1（ET-1）和一氧化氮（NO），然而这些介质在单核细胞功能中的作用仍不清楚。使用外周血单核细胞（PBM）以及人类单核细胞系THP-1和U937，探讨了ET-1和NO释放与单核细胞黏附之间的关系。用内皮素B（ET(B)）受体拮抗剂BQ-788预处理可消除125I标记的ET-1与THP-1的特异性结合，但内皮素A（ET(A)）受体拮抗剂BQ-123则不能，这与主要表达ET(B)受体一致。用安培探针直接测量NO表明，ET-1处理后PBM和THP-1细胞产生了纳摩尔浓度的NO，而BQ-788预处理可消除这种现象，BQ-123预处理则不能，这表明ET(B)受体与NO释放存在功能偶联。事实上，在THP-1中检测到了ET(B)受体mRNA转录本，这与先前报道的ET(B)受体与组成型NO合酶激活的功能偶联一致。相比之下，U937细胞在ET-1处理后不释放NO，且在这些细胞中未检测到mRNA转录本，这与之前确定的它们不能结合125I标记的ET-1一致。将PBM暴露于ET-1可显著降低这些细胞与人隐静脉的黏附，而在存在BQ-788的情况下，PBM的黏附恢复到对照水平。这些数据表明，自分泌产生的NO可减少PBM与血管壁的相互作用，并提示ET(B)受体可能在炎症部位减弱单核细胞活性。
