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，在美国影响了大约3300万成年人。症状包括尿频、尿急、急迫性尿失禁或夜尿。当膀胱体积增大时，逼尿肌的不随意收缩常与膀胱过度活动有关。这些不自主收缩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，但由于通常使用抗毒蕈碱药物的不良反应，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能是治疗逼尿肌活性过强（DO）的另一个靶点。P2X受体介导收缩，P2Y受体参与松弛。P2X受体在平滑肌细胞中高表达，而P2Y受体表达有限。因此，我们假设嘌呤能松弛可能是由特定细胞中P2Y受体的激活介导的。P2Y受体是g蛋白偶联受体（GPCR）。GPCR调节离子通道的活性。P2Y受体对逼尿肌离子通道的激活尚未被研究。我们将描述P2Y受体的功能表达，随后细胞内Ca2+的增加和Ca2+激活的K+通道的调节，这些通道与逼尿肌松弛有关。小电导Ca2+激活的K+ (SK)通道在逼尿肌的功能表达已被报道。而在负膜电位下，逼尿肌平滑肌细胞内SK通道的电流密度几乎可以忽略不计。我们假设逼尿肌壁内特化细胞中SK通道的表达和激活参与了超极化和弛豫反应。最近，我们的实验室报道了膀胱中存在特定种类的间质细胞。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。这些细胞分布在整个逼尿肌，并与壁内神经纤维密切相关。PDGFR- +细胞已在胃肠道中被描述，并与嘌呤能抑制性神经传递有关。我们假设PDGFR- +细胞在逼尿肌嘌呤能松弛中起功能作用，PDGFR- +细胞异常诱导DO。总之，我们将描述一种新的细胞群，产生膀胱神经传递的嘌呤能抑制成分。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，并可能揭示控制逼尿肌运动的治疗新靶点。这一发现将为泌尿动力学生理学的研究开辟重要的新领域，并为膀胱过度活动的治疗开辟新的领域。

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.