Urothelial ATP Signaling and Diabetic Bladder Dysfunction

描述(申请人提供)：三磷酸腺苷在膀胱的感觉和运动功能中起着重要作用。副交感神经纤维释放的三磷酸腺苷可兴奋逼尿肌，膀胱扩张时尿路上皮释放的三磷酸腺苷可通过激活传入纤维、刺激上皮下肌纤维母细胞和诱导尿路上皮释放其他信号分子来间接调节逼尿肌收缩。病理条件可以增加神经源性逼尿肌收缩的嘌呤能成分，也可以增加尿路上皮细胞ATP的释放。糖尿病患者会出现各种尿流动力学异常，包括膀胱活动增强。我们提出，糖尿病膀胱对嘌呤能刺激的敏感性增加与逼尿肌中特定的嘌呤能受体(P2R)亚型上调有关，而ATP信号的放大可能直接参与糖尿病膀胱过度活动的发生。根据最近的发现，我们现在有证据表明，在糖尿病的膀胱尿路上皮细胞中，ATP信号也被放大。STZ糖尿病大鼠膀胱尿路上皮细胞中的P2R，尤其是P2X7R和P2X3R亚型的表达显著增加，且对ATP的反应性更高。这些发现结合P2X7R的激活可以诱导ATP和前列腺素(PGE2)的释放，表明糖尿病膀胱不仅对ATP的敏感性增加，而且从尿路上皮细胞释放的ATP和PGE2也增加。在此背景下，来自膀胱的传入信号以及尿路上皮细胞、尿路上皮下肌纤维母细胞和平滑肌细胞的沟通能力将显著增强，并可能有助于糖尿病患者膀胱活动的增加。为了验证以下假设，即糖尿病增加尿路上皮ATP信号和膀胱腔之间的通讯，以及膀胱内和膀胱内增强的ATP信号有助于糖尿病患者膀胱功能障碍的发展，我们将结合分子生物学、生物化学、药理学、体外亚细胞成像和整体动物生理学方法。这些研究有望对参与尿路上皮和膀胱平滑肌细胞间信号转导的特定膜受体和通道蛋白之间的相互作用有新的认识，并揭示改善糖尿病患者膀胱功能障碍症状的新的治疗靶点和策略。公共卫生相关性：在这项RO1申请中提出的研究有望进一步加深我们对膀胱尿路上皮、尿路上皮下和平滑肌之间的相互作用以及尿路上皮ATP信号主要成分的表达变化如何促进糖尿病患者膀胱功能障碍的认识。

DESCRIPTION (provided by applicant): ATP plays important roles in the sensory and motor functions of the urinary bladder. ATP released from parasympathetic fibers can excite the detrusor muscle, and ATP released from the urothelium in response to bladder distension can indirectly modulate detrusor contractility by activating afferent fibers, stimulating suburothelial myofibroblasts and inducing release of other signaling molecules from the urothelium. Pathological conditions can increase the purinergic component of the neurogenic detrusor contraction and also augment urothelial ATP release. In diabetes various urodynamic abnormalities can develop, including increased bladder activity. We have proposed that increased sensitivity of diabetic bladders to purinergic stimulation was related to upregulation of specific purinergic receptor (P2R) subtypes in the detrusor muscle, and that amplification of ATP signaling would directly contribute to the development of bladder overactivity in diabetes. Based on recent findings we have now evidence that ATP signaling in also amplified in the diabetic bladder urothelium. Expression of P2Rs, particularly the P2X7R and P2X3R subtypes, is markedly increased in the urothelium of STZ-diabetic rat bladders and responses to ATP are higher in STZ-diabetic urothelial cells. These findings combined with demonstrations that P2X7R activation can induce release of both ATP and prostaglandin (PGE2), suggest that not only the sensitivity to ATP but also ATP and PGE2 release from urothelial cells is increased in diabetic bladders. In this context, afferent signaling from the bladder as well as ability of urothelial cells, suburothelial myofibroblast and smooth muscle cells to communicate would be significantly enhanced and likely contribute to increase bladder activity in diabetes. To test the hypotheses that diabetes increases urothelial ATP signaling and communication between bladder compartments, and that enhanced ATP signaling within and from the bladder contributes to the development of bladder dysfunction in diabetes we will use a combination of molecular biology, biochemistry, pharmacology, in vitro subcellular imaging and whole animal physiology approaches. These studies are expected to lead to novel understanding of the interplay among specific membrane receptors and channel proteins involved in intercellular signaling between urothelium and bladder smooth muscle, and reveal novel therapeutic targets and strategies to ameliorate the symptoms of bladder dysfunction in diabetes. PUBLIC HEALTH RELEVANCE: The studies proposed in this RO1 application are expected to further our understanding of the interactions between the bladder urothelial, suburothelial and smooth muscle compartments and of how changes in the expression of main components of the urothelial ATP signaling contribute to the development of bladder dysfunction in diabetes.