Molecular and Functional Mechanisms of Purinergic Relaxation in Detrusor Muscle

描述(由申请人提供)：膀胱过度活动是一种非常普遍的疾病，在美国大约有3300万成年人受到影响。症状包括频率、紧迫感、急迫性尿失禁或夜尿。随着膀胱容量的增加，逼尿肌的不自主收缩通常与膀胱过度活动有关。这些非自愿收缩背后的机制尚未完全阐明。尽管这种情况对患者的生活质量有相当大的影响，但由于常用的抗毒扁豆碱药物的不良反应，膀胱过度活动的药物治疗仍然存在争议。嘌呤能介导的反应可以成为治疗逼尿肌过度活动(DO)的另一个靶点。P2X受体介导收缩，而P2Y受体参与松弛。P2X受体在血管内皮细胞高表达，而P2Y受体表达有限。因此，我们推测，嘌呤能松弛可能是通过激活特定细胞中的P2Y受体来实现的。P2Y受体是G蛋白偶联受体。GPCR3调节离子通道的活性。在逼尿肌中，还没有发现P2Y受体对离子通道的激活作用。我们将研究与逼尿肌松弛有关的P2Y受体的功能表达、随后细胞内钙离子的增加以及钙激活的钾通道的调节。小电导钙激活钾(SK)通道在逼尿肌中的功能表达已有报道。然而，在负膜电位下，逼尿肌细胞SK通道的电流密度几乎可以忽略不计。我们推测，逼尿肌壁内的特化细胞中SK通道的表达和激活参与了超极化和松弛反应。最近，我们的实验室报告说，膀胱中存在特定类型的间质细胞。这些间质细胞是用抗血小板衍生生长因子受体(PDGFR-)的抗体鉴定的。这些细胞分布于逼尿肌各处，与肌壁内神经纤维紧密相连。PDGFR~+细胞存在于胃肠道中，与嘌呤能抑制性神经传递有关。我们推测PDGFR~+细胞在PDGFR~+细胞引起的DO的逼尿肌嘌呤能松弛和异常中起作用。综上所述，我们将描述产生膀胱神经传递的嘌呤能抑制成分的一组新的细胞。PDGFR~+细胞的分离和PDGFR~+细胞的功能研究将有助于更详细地了解嘌呤能神经传递，并可能为控制逼尿肌运动的治疗提供新的靶点。这些信息将开辟尿流动力学生理学研究的重要新领域，并拓展治疗膀胱过度活动的新场所。

DESCRIPTION (provided by applicant): Overactive bladder is a highly prevalent condition, affecting approximately 33 million adults in the United States. Symptoms include frequency, urgency, urge incontinence, or nocturia. As bladder volume increases, involuntary contractions of the detrusor muscle are often associated with overactive bladder. The mechanisms underlying these involuntary contractions have not yet been fully elucidated. Despite the considerable impact this condition has on patients' quality of life, the pharmacological treatment of overactive bladder still remains controversial because of the adverse effects of commonly using anti-muscarinic agents. The purinergic- mediated responses can be another targeting for the treatment of detrusor over activity (DO). P2X receptors mediate contraction and P2Y receptors involve relaxation. P2X receptors are highly expressed in smooth muscle cells but limited expression of P2Y receptors. Thus, we hypothesize that purinergic relaxation might be mediated by activation of P2Y receptors in specialized cells. P2Y receptors are G-protein coupled receptors (GPCR). GPCR modulate the activity of ion channels. The activation of ion channels by P2Y receptors has not been explored in detrusor muscle. We will characterize the functional expression of P2Y receptors, the subsequent increase in intracellular Ca2+ and modulation of Ca2+- activated K+ channels which are involved in detrusor relaxation. Functional expression of small conductance Ca2+-activated K+ (SK) channels in the detrusor muscle has been reported. However the current density of SK channels in detrusor smooth muscle cell was almost negligible at negative membrane potentials. We hypothesize that the expression and activation of SK channels in specialized cells within the detrusor wall are involved in the hyperpolarization and relaxation responses. Recently, our lab reported that specific classes of interstitial cells exist in the bladder. These interstitial cells are identified using antibodies aainst platelet-derived growth factor receptor-¿ (PDGFR-¿+). These cells were distributed throughout detrusor muscle, and were in close apposition with intramural nerve fibers. PDGFR-¿+ cells have been described in the gastrointestinal tract and are implicated in purinergic inhibitory neurotransmission. We hypothesize that PDGFR-¿+ cells have functional roles on the detrusor purinergic relaxation and abnormality of PDGFR-¿+ cells induces DO. In summary, we will characterize a novel population of cells that generate the purinergic inhibitory component of bladder neurotransmission. Isolation of PDGFR-¿+ cells and functional study of PDGFR-¿+ cells will allow more detailed understanding of purinergic neurotransmission and may reveal new targets for therapies to control detrusor motility. This information will open up important novel areas of investigation in urodynamics physiology and expand new venue of treatment of bladder over activity.