Dual pathways for nuclear factor kappaB activation by angiotensin II in vascular smooth muscle: phosphorylation of p65 by IkappaB kinase and ribosomal kinase.

Activation of nuclear factor (NF)-kappaB by angiotensin II (Ang II) plays an essential role in stimulating expression of vascular adhesion molecules, which are essential for vascular inflammation. We report that Ang II activates NF-kappaB by phosphorylating its p65 subunit via a pathway mediated partially by ribosomal S6 kinase (RSK). In investigating other pathway(s) that may be involved, we found that the ability of Ang II to activate NF-kappaB in mouse embryonic fibroblast is suppressed (approximately 70%) either by deletion of IkappaB Kinase (IKK) or by inhibiting or knocking down IKK in vascular smooth muscle cells using a dominant-negative IKK adenovirus or small interference RNA to IKKbeta. Thus, Ang II also stimulates NF-kappaB via IKK. In vitro, we found that Ang II stimulates IKK to phosphorylate myelin basic protein and the p65 subunit of NF-kappaB. The mechanism by which Ang II activates IKK is to increase phosphorylation of IKKbeta in its activation loop (Ser181) rather than IkappaB phosphorylation. Inhibiting both the RSK and IKK pathways completely blocks the Ang II-induced p65 phosphorylation and NF-kappaB activation. These 2 pathways are independent: inhibiting IKK does not block Ang II-induced phosphorylation of RSK, whereas inhibiting mitogen-activated protein kinase 1 does not affect phosphorylation of IKK. Finally, we found that Ang II can induce expression of vascular adhesion molecules by 2 pathways; both IKK and RSK lead to phosphorylation of the p65 subunit of NF-kappaB to increase vascular cell adhesion molecule-1 transcription. The 2 pathways are functionally important because inhibiting IKK and RSK in vascular smooth muscle cells blocks Ang II-induced expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 to limit vascular inflammation.

血管平滑肌中血管紧张素II激活核因子κb的双重途径:IkappaB激酶和核糖体激酶磷酸化p65。

血管紧张素II (Ang II)对核因子(NF)-kappaB的激活在刺激血管粘附分子的表达中起着至关重要的作用，血管粘附分子对于血管炎症是必不可少的。我们报道Ang II通过核糖体S6激酶(RSK)部分介导的途径磷酸化其p65亚单位来激活NF-kappaB。在研究可能涉及的其他途径时，我们发现，通过删除IkappaB激酶(IKK)或通过使用显性阴性IKK腺病毒或ikkβ小干扰RNA抑制或敲除血管平滑肌细胞中的IKK，Ang II激活小鼠胚胎成纤维细胞中NF-κb的能力受到抑制(约70%)。因此，Ang II也通过IKK刺激NF-kappaB。在体外，我们发现Ang II刺激IKK磷酸化髓鞘碱性蛋白和NF-κb的p65亚单位。Ang II激活IKK的机制是增加其激活环(Ser181)中IKKbeta的磷酸化，而不是IkappaB的磷酸化。抑制RSK和IKK途径完全阻断Ang II诱导的p65磷酸化和NF-κb活化。这两条途径是独立的:抑制IKK不能阻断Ang II诱导的RSK磷酸化，而抑制丝裂原活化蛋白激酶1不能影响IKK的磷酸化。最后，我们发现Ang II可以通过两条途径诱导血管粘附分子的表达；IKK和RSK都导致NF-κb的p65亚单位磷酸化，从而增加血管细胞粘附分子-1的转录。这两种途径在功能上非常重要，因为抑制血管平滑肌细胞中的IKK和RSK可以阻断血管紧张素ⅱ诱导的血管细胞粘附分子-1和细胞间粘附分子-1的表达，从而限制血管炎症。