Tayeh M A, Scicli A G
Division of Hypertension and Vascular Research, Heart and Vascular Institute, Henry Ford Hospital, Detroit, MI 48202-3450, USA.
Proc Assoc Am Physicians. 1998 Sep-Oct;110(5):412-21.
Cell-surface expression of endothelial P-selectin increases adhesion and migration of leukocytes and thus may participate in the pathogenesis of reperfusion injury and atherosclerosis. Angiotensin II (Ang II) is also thought to be involved in such disease states. Nitric oxide (NO) downregulates P-selectin expression, and bradykinin (BK) is known to stimulate NO release from endothelial cells. The objective of this study was to determine the effects of 10-min stimulation of cultured human umbilical endothelial cells (HUVECs) with Ang II, BK, or both on P-selectin expression. Ang II (10(-9)-10(-5) M) stimulated P-selectin expression in a concentration-dependent manner, exhibiting a significant effect at 10(-7) M and reaching a plateau at 5 x 10(-5) M. Pretreatment of HUVECs with the AT1 antagonist losartan and the AT1/AT2 antagonist saralasin but not the AT2 antagonist PD123319 (all at 10(-5) M) markedly attenuated the effect of 10(-7) M Ang II. The effects of Ang II on P-selectin expression were not affected by the presence of the NO synthase inhibitor nitro-L-arginine (L-NA, 5 x 10(-4) M) but were abolished by pretreatment with superoxide dismutase (SOD). BK (10(-6) M) abolished the effects of 10(-7) M Ang II on P-selectin expression but did not affect P-selectin expression induced by desmopressin (0.01-10 microM). L-NA obliterated the blunting effect of BK on the Ang II-induced P-selectin membrane expression. BK alone slightly stimulated P-selectin expression, but in the presence of L-NA, BK markedly enhanced P-selectin expression. The effects of BK in the presence of NA were not altered by SOD, indicating that at difference with Ang II, it acts by a mechanism other than superoxide generation. Thus, Ang II acting on AT1 receptors stimulates superoxide generation, which, in turn, induces expression of P-selectin on the endothelial cell surface. BK inhibits the effects of Ang II, likely acting via NO. We conclude that the balance between Ang II, BK, and NO can regulate P-selectin expression on the endothelial cell membrane, an important component of the cascade leading to leukocyte adhesion to the vascular endothelium.
内皮细胞P-选择素的细胞表面表达增加白细胞的黏附和迁移，因此可能参与再灌注损伤和动脉粥样硬化的发病机制。血管紧张素II（Ang II）也被认为与这些疾病状态有关。一氧化氮（NO）下调P-选择素的表达，而缓激肽（BK）已知可刺激内皮细胞释放NO。本研究的目的是确定用Ang II、BK或两者对培养的人脐静脉内皮细胞（HUVECs）进行10分钟刺激对P-选择素表达的影响。Ang II（10^(-9)-10^(-5) M）以浓度依赖性方式刺激P-选择素表达，在10^(-7) M时表现出显著作用，在5×10^(-5) M时达到平台期。用AT1拮抗剂氯沙坦和AT1/AT2拮抗剂沙拉新（均为10^(-5) M）预处理HUVECs，但用AT2拮抗剂PD123319（10^(-5) M）预处理则不能显著减弱10^(-7) M Ang II的作用。Ang II对P-选择素表达的影响不受NO合酶抑制剂硝基-L-精氨酸（L-NA，5×10^(-4) M）存在的影响，但超氧化物歧化酶（SOD）预处理可消除该影响。BK（10^(-6) M）消除了10^(-7) M Ang II对P-选择素表达的影响，但不影响去氨加压素（0.01-10 microM）诱导的P-选择素表达。L-NA消除了BK对Ang II诱导的P-选择素膜表达的抑制作用。单独的BK轻微刺激P-选择素表达，但在L-NA存在下，BK显著增强P-选择素表达。在NA存在下BK的作用不受SOD影响，表明与Ang II不同，它通过超氧化物生成以外的机制起作用。因此，作用于AT1受体的Ang II刺激超氧化物生成，进而诱导内皮细胞表面P-选择素的表达。BK抑制Ang II的作用，可能通过NO起作用。我们得出结论，Ang II、BK和NO之间的平衡可以调节内皮细胞膜上P-选择素的表达，这是导致白细胞黏附于血管内皮的级联反应的一个重要组成部分。
