PGE2 induces COX-2 expression in podocytes via the EP4 receptor through a PKA-independent mechanism
PGE2 induces COX-2 expression in podocytes via the EP4 receptor through a PKA-independent mechanism
复制标题
DOI：
10.1016/j.cellsig.2008.08.007
复制
发表时间：
2008-11-01
影响因子：
4.8
通讯作者：
Kennedy, Christopher R. J.
中科院分区：
文献类型：
--
作者：
Faour, Wissam H.;Gomi, Kaede;Kennedy, Christopher R. J.
环氧合酶-2（考克斯-2）依赖性前列腺素E-2（PGE（2））合成与蛋白尿和肾小球毛细血管压（P-gc）升高的肾小球疾病模型的发生相关。我们先前发现，体外P-gc（周期性机械拉伸）替代物可上调培养小鼠足细胞中考克斯-2和PGE（2）响应性E-前列腺素受体EP 4的表达。在本研究中，我们进一步阐明了调节足细胞考克斯-2诱导的信号通路。在条件永生化小鼠足细胞中进行的时间过程实验显示，PGE（2）在10 min时瞬时增加磷酸化p38 MAPK水平，并在4 h时诱导考克斯-2蛋白表达。与用EP 1受体拮抗剂SC 19220处理不同，siRNA介导的EP 4受体表达的敲低完全消除了PGE（2）诱导的p38磷酸化和考克斯-2上调，表明EP 4受体亚型的参与。PGE（2）诱导的考克斯-2诱导可通过抑制p38 MAPK或AMP激活的蛋白激酶（AMPK）而消除，并可被AICAR（一种选择性AMPK激活剂）和cAMP升高剂forskolin（FSK）和IBMX模拟。令人惊讶的是，PGE（2）和FSK/IBMX依赖性p38激活和考克斯-2表达均未被PKA抑制剂阻断或被选择性EPAC激活剂8-cPT-cAMP模拟，而是被化合物C消除，表明AMPK参与。这些结果表明，除了机械牵拉，PGE（2）在足细胞中启动了一个正反馈回路，通过cAMP/AMPK依赖性但PKA非依赖性信号级联驱动p38 MAPK活性和考克斯-2表达。这种PGE（2）诱导的信号网络被增加的Pc激活，可能对足细胞的健康和肾小球滤过屏障的完整性有害。(C)2008年爱思唯尔公司All rights reserved.
Cyclooxygenase-2 (COX-2)-dependent prostaglandin E-2 (PGE(2)) synthesis correlates with the onset of proteinuria and increased glomerular capillary pressure (P-gc) glomerular disease models. We previously showed that an in vitro surrogate for P-gc (cyclical mechanical stretch) upregulates the expression of both COX-2 and the PGE(2) responsive E-Prostanoid receptor, EP4 in cultured mouse podocytes. In the present study we further delineate the signaling pathways regulating podocyte COX-2 induction. Time course experiments carried out in conditionally-immortalized mouse podocytes revealed that PGE(2) transiently increased phosphorylated p38 MAPK levels at 10 min, and induced COX-2 protein expression at 4 h. siRNA-mediated knockdown of EP4 receptor expression, unlike treatment with the EP1 receptor antagonist SC 19220, completely abrogated PGE(2)-induced p38 phosphorylation and COX-2 upregulation suggesting the involvement of the EP4 receptor subtype. PGE(2)-induced COX-2 induction was abrogated by inhibition of either p38 MAPK or AMP activated protein kinase (AMPK), and was mimicked by AICAR, a selective AMPK activator, and by the cAMP-elevating agents, forskolin (FSK) and IBMX. Surprisingly, neither PGE(2) nor FSK/IBMX-dependent p38 activation and COX-2 expression were blocked by PKA inhibitors or mimicked by 8-cPT-cAMP a selective EPAC activator, but were instead abrogated by Compound C, suggesting the involvement of AMPK. These results indicate that in addition to mechanical stretch, PGE(2) initiates a positive feedback loop in podocytes that drives p38 MAPK activity and COX-2 expression through a cAMP/AMPK-dependent, but PKA-independent signaling cascade. This PGE(2)-induced signaling network activated by increased Pc could be detrimental to podocyte health and glomerular filtration barrier integrity. (C) 2008 Elsevier Inc. All rights reserved.