Mitochondrial Dysfunction in Obstructed Bladder: Role of Desmin and Vimentin

 描述（由申请方提供）：下尿路功能障碍（LUTD）与继发于良性前列腺增生（BPH）诱导的部分膀胱出口梗阻（PBOO）、神经源性膀胱和糖尿病的膀胱平滑肌（BSM）肥大相关，其发病率和患病率随着人群年龄的增长而增加。现有的治疗干预措施既不高效也不持久，而且本身也有副作用。生物化学研究表明，在梗阻性膀胱的肥大BSM中，线粒体ATP减少，活性氧（ROS）产生增加，这与中间丝（IF）蛋白、结蛋白和波形蛋白的过度表达有关，这些蛋白对肌肉和线粒体功能很重要。线粒体和肌肉病理生理学，包括ATP减少，ROS产生增加和LUTD中平滑肌收缩性降低，表明结蛋白和波形蛋白过表达在诱导线粒体和肌肉功能障碍中的作用。然而，这些IF蛋白介导BSM功能障碍的潜在机制仍有待研究。我们的初步数据表明，结蛋白和波形蛋白在人类和小鼠BSM条和细胞中的过表达显著降低了线粒体ATP合成;增加了ROS的产生并抑制了卡巴胆碱和KCl介导的收缩，这也见于BSM与PBOO。IF蛋白在BSM条和细胞中的过表达增强丝裂原活化蛋白激酶（MAPK）/JNK 2磷酸化，这与其增加的线粒体定位和结蛋白和波形蛋白的磷酸化一致，如在具有PBOO的BSM中也看到的。线粒体结蛋白和波形蛋白可能通过线粒体JNK 2抑制线粒体电压依赖性阴离子通道（VDAC）的通透性。基于我们的初步数据，我们假设JNK 2的激活及其增加的线粒体定位参与结蛋白和波形蛋白诱导的BSM收缩和线粒体功能障碍。我们进一步假设JNK 2磷酸化的线粒体结蛋白和波形蛋白与VDAC相互作用，这种相互作用抑制ATP合成并增加ROS产生。我们设计了三个具体目标来解决这些假设。在目标1中，我们将建立IF表达增加在诱导BSM收缩功能障碍中的稳健性，并阐明JNK 2作为关键效应子。在目标2中，我们将确定IF蛋白过表达诱导的BSM收缩和线粒体功能障碍是否是由于结蛋白和波形蛋白与VDAC的JNK 2依赖性相互作用。在目的3中，我们将确定线粒体JNK 2在PBOO诱导的BSM收缩和线粒体功能障碍中的作用。我们希望我们的研究能够描述由线粒体JNK 2信号传导介导的收缩功能障碍的机制，促进VDAC与结蛋白和波形蛋白的相互作用，从而确定治疗PBOO/LUTD的新的治疗靶点。

 DESCRIPTION (provided by applicant): Lower urinary tract dysfunction (LUTD) is associated with bladder smooth muscle (BSM) hypertrophy secondary to benign prostatic hyperplasia (BPH)-induced partial bladder outlet obstruction (PBOO), neurogenic bladder, and diabetes, and its incidence and prevalence are increasing as the population ages. Existing therapeutic interventions are neither highly effective nor durable and have side effects of their own. Biochemical studies have shown reduced mitochondrial ATP and increased reactive oxygen species (ROS) production in the hypertrophied BSM of obstructed bladders and this is associated with overexpression of the intermediate filament (IF) proteins, desmin and vimentin which are important for muscle and mitochondrial function. Mitochondrial and muscle pathophysiology, including decreased ATP, increased ROS production and diminished contractility of smooth muscle in LUTD suggests a role for desmin and vimentin overexpression in inducing mitochondrial and muscle dysfunction. However, potential mechanisms by which these IF proteins mediate BSM dysfunction remain unexplored. Our preliminary data demonstrate that desmin and vimentin overexpression in human and murine BSM strips and cells significantly reduces mitochondrial ATP synthesis; increases ROS production and inhibits carbachol-and KCl-mediated contraction as also seen in BSM with PBOO. Overexpression of IF proteins in BSM strips and cells enhances mitogen-activated protein kinase (MAPK)/JNK2 phosphorylation which coincides with its increased mitochondrial localization and phosphorylation of desmin and vimentin as also seen in BSM with PBOO. Mitochondrial desmin and vimentin could potentially function to inhibit the mitochondrial voltage-dependent anion channel (VDAC) permeability via mitochondrial JNK2. Based on our preliminary data, we hypothesize that the activation of JNK2 and its increased mitochondrial localization is involved in desmin- and vimentin-induced BSM contractile and mitochondrial dysfunction. we further hypothesize that JNK2 phosphorylated mitochondrial desmin and vimentin interacts with the VDAC and this interaction inhibits ATP synthesis and increases ROS production. We designed three Specific Aims to address these hypotheses. In Aim 1, we will establish the robustness of increased IF expression in inducing BSM contractile dysfunction, and clarify JNK2 as a critical effector. In Aim 2, we will determine whether IF protein overexpression-induced BSM contractile and mitochondrial dysfunction is due to JNK2 dependent interaction of desmin and vimentin with VDAC. In Aim 3, we will ascertain the role of mitochondrial JNK2 in PBOO- induced BSM contractile and mitochondrial dysfunction. We expect our studies to delineate a mechanism of contractile dysfunction mediated by mitochondrial JNK2 signaling promoting the VDAC interaction with desmin and vimentin, and thus identify novel therapeutic targets for the treatment of PBOO/LUTD.