Signaling through PI3K/Akt mediates stretch and PDGF-BB-dependent DNA synthesis in bladder smooth muscle cells
Signaling through PI3K/Akt mediates stretch and PDGF-BB-dependent DNA synthesis in bladder smooth muscle cells
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DOI：
10.1097/01.ju.0000063980.99368.35
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发表时间：
2003-06-01
影响因子：
6.6
通讯作者：
Freeman, MR
中科院分区：
文献类型：
--
作者：
Adam, RM;Roth, JA;Freeman, MR
目的：膀胱平滑肌细胞（SMC）在持续机械超负荷后会发生肥大和增生。尽管心脏和膀胱对肥大刺激的反应表面上相似，表明可能涉及相似的分子机制，但这仍有待证明。在这项研究中，我们比较了原代培养的膀胱 SMC 和心肌成纤维细胞响应循环拉伸的信号转导通路激活情况。还研究了生长因子刺激对膀胱 SMC 通路激活的影响。 材料和方法：在不存在或存在磷酸肌醇 3 激酶（PI3K）/Akt（细胞外信号调节激酶丝裂原）药物抑制剂的情况下，对原代培养的啮齿动物膀胱 SMC 或心肌成纤维细胞进行循环拉伸松弛 激活蛋白激酶 (Erk-MAPK) 或 p38 应激激活蛋白激酶-2 (SAPK2) 途径。在平行实验中，用血小板衍生生长因子-BB (PDGF-BB)、肝素结合 EGF 样生长因子 (HB-EGF) 或成纤维细胞生长因子-2 (FGF-2) 处理人膀胱 SMC。在每种情况下，DNA 合成的程度通过氚化胸苷的摄取来确定，并且使用针对 Akt、p38 和 Erk1/2 的非磷酸化和磷酸化（激活）形式的抗体通过免疫印迹分析来确定特定信号传导中间体的激活。结果：Akt 和 p38 在拉伸的膀胱 SMC 和心脏中快速磷酸化。 肌成纤维细胞和这些细胞中拉伸诱导的 DNA 合成被 PI3K 或 p38 抑制剂消除，但 Erk-MAPK 却没有。同样，PDGF-BB 以 p38 和 Akt 依赖性方式上调膀胱 SMC 中的 DNA 合成。结论：我们得出结论，不同的刺激（例如机械拉伸和 PDGF-BB）通过共享的下游信号通路促进膀胱 SMC 中的 DNA 合成。此外，来自膀胱和心脏的表型相似的细胞在拉伸反应中表现出类似的通路激活。这些发现表明，类似的分子机制是膀胱和心脏对机械超负荷的生长反应改变的基础。这项研究还提供了膀胱 SMC 中 Akt 激活的第一份报告，并表明 Akt 与其在心脏肥大中的关键作用一致，也可能是体内暴露于肥厚/增生刺激的膀胱 SMC 室重塑的关键调节因子。
Purpose: Smooth muscle cells (SMC) of the bladder undergo hypertrophy and hyperplasia following exposure to sustained mechanical overload. Although superficial similarities in the response of the heart and bladder to hypertrophic stimuli suggest that similar molecular mechanisms may be involved, this remains to be demonstrated. In this study we compared signal transduction pathway activation in primary culture bladder SMC and cardiac myofibroblasts in response to cyclic stretch. The effects of growth factor stimulation on pathway activation in bladder SMC were also investigated.Materials and Methods: Primary culture rodent bladder SMC or cardiac myofibroblasts were subjected to cyclic stretch-relaxation in the absence or presence of pharmacologic inhibitors of the phosphoinositide-3-kinase, (PI3K)/Akt, extracellular signal-regulated kinase-mitogen activated protein kinase (Erk-MAPK) or the p38 stress-activated protein kinase-2 (SAPK2) pathways. In parallel experiments human bladder SMC were treated with platelet-derived growth factor-BB (PDGF-BB), heparin-binding EGF-like growth factor (HB-EGF) or fibroblast growth factor-2 (FGF-2). In each case the extent of DNA synthesis was determined by uptake of tritiated thymidine, and activation of specific signaling intermediates was determined by immunoblot analysis using antibodies to the non-phosphorylated and phosphorylated (activated) forms of Akt, p38 and Erk1/2.Results: Akt and p38 were rapidly phosphorylated in stretched bladder SMC and cardiac myofibroblasts, and stretch-induced DNA synthesis in these cells was ablated with inhibitors of PI3K or p38 but not Erk-MAPK. Similarly, PDGF-BB up-regulated DNA synthesis in bladder SMC in a p38 and Akt-dependent manner.Conclusions: We conclude that distinct stimuli, such as mechanical stretch and PDGF-BB, promote DNA synthesis in bladder SMC through shared downstream signaling pathways. Furthermore, phenotypically similar cells from the bladder and heart show comparable pathway activation in response to stretch. These findings suggest that similar molecular mechanisms underlie the altered growth responses of the bladder and heart to mechanical overload. This study also provides the first report of Akt activation in bladder SMC and suggests that Akt, consistent with its pivotal role in cardiac hypertrophy, may also be a key regulator of remodeling in the SMC compartment of the bladder exposed to hypertrophic/hyperplastic stimuli in vivo.