Interactions between cGMP- and cAMP-pathways are involved in the regulation of penile smooth muscle tone
Interactions between cGMP- and cAMP-pathways are involved in the regulation of penile smooth muscle tone
复制标题
DOI：
10.1007/s00345-003-0394-4
复制
发表时间：
2004-08-01
影响因子：
3.4
通讯作者：
Stief, CG
中科院分区：
文献类型：
--
作者：
Ückert, S;Hedlund, P;Stief, CG
一氧化氮 (NO)/环鸟苷酸 (cGMP) 介导的机制在降低正常勃起反应期间阴茎平滑肌组织张力方面具有关键功能。环磷酸腺苷 (cAMP) 信号通路也参与平滑肌收缩力的调节，并且已经提出了 cGMP 和 cAMP 介导机制之间相互作用的建议。使用 cGMP 或 cAMP 途径的激活剂，以及蛋白激酶 A（PKA；cAMP 依赖性激酶）和蛋白激酶 G（PKG；cGMP 依赖性激酶）的抑制剂，本研究旨在进一步描述阴茎中这些途径之间的功能关系。此外，还研究了人勃起组织中 PKA 和一些 cAMP 结合磷酸二酯酶 (cAMP-PDE) 的分布。在分离的人海绵体（HCC）上进行功能实验。研究了 PKA 抑制剂 Rp-8CPT-cAMPS (10 μM) 或 PKG Rp-8-pCPT-cGMPS (10 μM) 对硝普钠 (SNP)、毛喉素、西地那非或他达拉非 (IC351) 累积给药引起的松弛的影响，在用 1 μM 预收缩的 HCC 制剂中进行了研究 去甲肾上腺素（NE）。使用免疫组织化学方法，在 HCC 样本中研究了 cAMP-PDEs PDE3、PDE4 和 PDE4A 以及 PKA 免疫反应性的存在，其中的制剂也用于功能实验。 Forskolin、SNP、西地那非和 IC 351 剂量依赖性地逆转 NE 诱导的分离 HCC 制剂的张力。 Rp-8-pCPT-cGMPS 显着减弱了 SNP 的松弛作用，但 Rp-8CPT-cAMPS 则没有显着减弱。相反，Rp-8-pCPT-cGMPS 和 Rp-8CPT-cAMPS 均显着逆转毛喉素、西地那非和他达拉非诱导的松弛。在海绵体平滑肌细胞中观察到丰富的 PDE3 和 PKA 免疫反应性。在平滑肌组织和海绵窦内皮细胞的细胞质中，以及散布在小梁基质中的神经纤维中也检测到了 PDE4 的免疫反应性。目前的结果支持 HCC 中 cGMP 和 cAMP 介导的信号之间相互作用的假设，并表明 PDE5 抑制剂对分离的勃起组织的影响也可能部分或间接包括 cAMP 第二信使系统的作用。这种相互作用发生的确切机制尚不清楚，但它可能涉及 cGMP 抑制的 PDE3 的活性改变，这是由于 PDE5 的抑制导致细胞内 cGMP 水平的变化。这反过来会导致 cAMP 水平增加，促进 cAMP 与 PKA 的相互作用。 HCC 切片中记录的 PDE3、PDE4、PDE4A 和 PKA 特异性免疫反应性也支持 cAMP/PKA 系统对阴茎平滑肌功能的重要作用。
Nitric oxide (NO)/cyclic GMP (cGMP)-mediated mechanisms have a pivotal function in reducing the tone of the penile smooth musculature during normal erectile responses. The cyclic AMP ( cAMP) signaling pathway is also involved in the adjustment of smooth muscle contractility, and suggestions for interactions between cGMP- and cAMP-mediated mechanisms have been presented. Using activators of the cGMP- or the cAMP-pathway, as well as inhibitors of protein kinase A (PKA; cAMP-dependent kinase) and protein kinase G (PKG; cGMP- dependent kinase), the present study was undertaken to further delineate the functional relation between these pathways in the penis. In addition, the distribution of PKA and some cAMP-binding phosphodiesterases (cAMP-PDEs) were investigated in human erectile tissue. Functional experiments were performed on isolated human corpus cavernosum (HCC). The effects of an inhibitor of the PKA, Rp-8CPT-cAMPS ( 10 muM), or the PKG, Rp-8-pCPT-cGMPS ( 10 muM), on relaxation induced by the cumulative administration of sodium nitroprusside ( SNP), forskolin, sildenafil or tadalafil (IC351) were studied in preparations of HCC precontracted with 1 muM norepinephrine ( NE). Using immunohistochemical procedures, the presence of immunoreactivity for cAMP-PDEs PDE3, PDE4, and PDE4A, as well as for PKA was investigated in specimens of HCC from which preparations were also used in the functional experiments. Forskolin, SNP, sildenafil, and IC 351 dose-dependently reversed NE-induced tension of isolated HCC preparations. The relaxing effects of SNP were significantly attenuated by Rp-8-pCPT-cGMPS, but not by Rp-8CPT-cAMPS. In contrast, relaxation induced by forskolin, sildenafil and tadalafil were significantly reversed by both Rp-8-pCPT-cGMPS and Rp-8CPT-cAMPS. Abundant immunoreactivity for PDE3 and PKA was observed in the corpus cavernosum smooth muscle cells. Immunoreactivity for PDE4 was also detected in the smooth musculature and in the cytoplasm of endothelial cells lining the cavernous sinusoids, as well as in nerve fibres interspersing the trabecular stroma. The present results support the hypothesis of interactions between cGMP- and cAMP-mediated signals in the HCC, and suggest that the effects of inhibitors of PDE5 on isolated erectile tissue may also partly or indirectly include actions of the cAMP second messenger system. The exact mechanism by which such an interaction occurs is not clear, but it may involve altered activity of the cGMP- inhibited PDE3 brought about by a change in the intracellular levels of cGMP by the inhibition of PDE5. This will in turn lead to increasing levels of cAMP, facilitating the interaction of cAMP with the PKA. The immunoreactivity specific for PDE3, PDE4, PDE4A and PKA registered in HCC section is also in support of an important role for the cAMP/PKA-system for penile smooth muscle function.