Ca2+ Sparks and Urinary Bladder Smooth Muscle Excitability

描述（由申请人提供）：许多疾病和病理与尿失禁和勃起功能障碍（艾德）相关，包括糖尿病、良性前列腺增生、高血压和高脂血症。膀胱和勃起功能障碍的共同发生表明存在机械共性。一个这样的会聚点是大电导Ca 2+激活的K+（BK）通道，如通过以下事实所证明的：孔形成BKa亚基的靶向破坏导致逼尿肌过度活动、尿失禁和ED。第二个潜在的共同点是NO/cGMP/PKG途径，其直接以及通过调节BK通道功能的钙信号传导元件间接调节BK通道功能。NO/cGMP/PKG通路几乎普遍与平滑肌（SM）松弛相关。然而，与海绵体（CC）SM相反，其中通过PKG途径的氮能信号传导是SM松弛和勃起功能的公认介质，NO在膀胱（UB）SM中的作用是一个未解决的问题。在目标1中，UBSM和CCSM将在分子和细胞水平上进行研究，以建立NO/cGMP/PKG信号转导调节SM功能的潜力，重点是BK通道通路的作用。BK通道功能和PKG的调节机制，在完整的膀胱和身体组织将在目标2，这也将考虑cGMP特异性磷酸二酯酶，PDE 5和Ca 2+敏感的氯电流（ClCa）的作用，作为潜在的贡献者组织特异性差异的NO敏感性。最后，目标3试图整合目标1和2的发现，并使用离体全膀胱模型来说明BK通道和cGMP/PKG通路在膀胱充盈期间调节功能的作用。此外，这些途径在调节膀胱充盈过程中的海绵体内压力和尿动力学特性的作用将在vivo. cGMP特异性磷酸二酯酶-5（PDE 5）抑制剂西地那非（万艾可）和相关化合物在治疗勃起功能障碍中的临床成功证明了cGMP依赖性蛋白激酶（PKG）途径在调节海绵体平滑肌松弛和勃起功能中的明确作用。尽管存在的神经元和尿路上皮来源的NO在膀胱，和NO反应性cGMP/PKG信号通路成分在肌细胞中的表达的证据，cGMP/PKG通路在膀胱生理学的意义仍然是一个悬而未决的问题。大电导钙激活钾（BK）通道在松弛下尿路平滑肌中具有中心作用，是PKG途径的靶点，并且代表了治疗西地那非耐药艾德和尿失禁的有前景的治疗靶点。

DESCRIPTION (provided by applicant): A number of diseases and pathologies are associated with both urinary incontinence and erectile dysfunction (ED), including diabetes, benign prostate hyperplasia, hypertension, and hyperlipidemia. The co-occurrence of urinary bladder and erectile dysfunction suggests the existence of mechanistic commonalities. One such point of convergence is the large conductance Ca2+-activated K+ (BK) channel, as evidenced by the fact that targeted disruption of the pore-forming BKa-subunit leads to overactive detrusor, urinary incontinence, and ED. A second potential common denominator is the NO/cGMP/PKG pathway, which regulates BK channel function directly as well as indirectly through calcium signaling elements that modulate BK channel function. The NO/cGMP/PKG pathway is nearly universally associated with smooth muscle (SM) relaxation. Yet, in contrast to corpus cavernosum (CC) SM, where nitrergic signaling through the PKG pathway is a well-established mediator of SM relaxation and erectile function, the role of NO in urinary bladder (UB) SM is an unsettled issue. In Aim 1, UBSM and CCSM will be investigated at the molecular and cellular levels to establish the potential of NO/cGMP/PKG signaling to regulate SM function, with an emphasis on the role of the BK channel pathway. BK channel function and PKG regulatory mechanisms in intact bladder and corpus tissue will be addressed in Aim 2, which will also consider the role of the cGMP-specific phosphodiesterase, PDE5, and Ca2+-sensitive chloride currents (ClCa) as potential contributors to tissue-specific differences in NO sensitivity. Finally, Aim 3 seeks to integrate the findings of Aim 1 and 2 and address the roles of the BK channel and cGMP/PKG pathways in regulating function during bladder filling using an ex vivo whole bladder model. Additionally, the role of these pathways in regulating intracavernous pressure and urodynamic properties during bladder filling will be addressed in vivo.The clinical success of the cGMP-specific phosphodiesterase-5 (PDE5) inhibitor sildenafil (Viagra) and related compounds in treating erectile dysfunction demonstrates a clear role for the cGMP-dependent protein kinase (PKG) pathway in regulating corpus cavernosum smooth muscle relaxation and erectile function. Despite the existence of both neuronal and urothelial sources of NO in the urinary bladder, and evidence for the expression of NO-responsive cGMP/PKG signaling pathway components in myocytes, the significance of the cGMP/PKG pathway in bladder physiology remains an unsettled question. The large conductance, calcium activated potassium (BK) channel, which has a central role in relaxing smooth muscle in the lower urinary tract, is a target of the PKG pathway, and represents a promising therapeutic target in the treatment of sildenafil-resistant ED and urinary incontinence.