Go Y M, Boo Y C, Park H, Maland M C, Patel R, Pritchard K A, Fujio Y, Walsh K, Darley-Usmar V, Jo H
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30322, USA.
J Appl Physiol (1985). 2001 Oct;91(4):1574-81. doi: 10.1152/jappl.2001.91.4.1574.
Laminar shear stress activates c-Jun NH(2)-terminal kinase (JNK) by the mechanisms involving both nitric oxide (NO) and phosphatidylinositide 3-kinase (PI3K). Because protein kinase B (Akt), a downstream effector of PI3K, has been shown to phosphorylate and activate endothelial NO synthase, we hypothesized that Akt regulates shear-dependent activation of JNK by stimulating NO production. Here, we examined the role of Akt in shear-dependent NO production and JNK activation by expressing a dominant negative Akt mutant (Akt(AA)) and a constitutively active mutant (Akt(Myr)) in bovine aortic endothelial cells (BAEC). As expected, pretreatment of BAEC with the PI3K inhibitor (wortmannin) prevented shear-dependent stimulation of Akt and NO production. Transient expression of Akt(AA) in BAEC by using a recombinant adenoviral construct inhibited the shear-dependent stimulation of NO production and JNK activation. However, transient expression of Akt(Myr) by using a recombinant adenoviral construct did not induce JNK activation. This is consistent with our previous finding that NO is required, but not sufficient on its own, to activate JNK in response to shear stress. These results and our previous findings strongly suggest that shear stress triggers activation of PI3K, Akt, and endothelial NO synthase, leading to production of NO, which (along with O(2-), which is also produced by shear) activates Ras-JNK pathway. The regulation of Akt, NO, and JNK by shear stress is likely to play a critical role in its antiatherogenic effects.
层流切应力通过涉及一氧化氮（NO）和磷脂酰肌醇3激酶（PI3K）的机制激活c-Jun氨基末端激酶（JNK）。由于PI3K的下游效应分子蛋白激酶B（Akt）已被证明可磷酸化并激活内皮型一氧化氮合酶，我们推测Akt通过刺激NO生成来调节切应力依赖的JNK激活。在此，我们通过在牛主动脉内皮细胞（BAEC）中表达显性负性Akt突变体（Akt(AA)）和组成型活性突变体（Akt(Myr)），研究了Akt在切应力依赖的NO生成和JNK激活中的作用。正如预期的那样，用PI3K抑制剂（渥曼青霉素）预处理BAEC可阻止切应力对Akt和NO生成的刺激。使用重组腺病毒构建体在BAEC中瞬时表达Akt(AA)可抑制切应力对NO生成和JNK激活的刺激。然而，使用重组腺病毒构建体瞬时表达Akt(Myr)并未诱导JNK激活。这与我们之前的发现一致，即NO是响应切应力激活JNK所必需的，但仅靠其自身并不充分。这些结果以及我们之前的发现强烈表明，切应力触发PI3K、Akt和内皮型一氧化氮合酶的激活，导致NO生成，而NO（连同同样由切应力产生的O(2-)）激活Ras-JNK途径。切应力对Akt、NO和JNK的调节可能在其抗动脉粥样硬化作用中起关键作用。
