Regulation of mechanosensitive K+ channels in detrusor smooth muscle by estrogen

项目摘要 膀胱在充盈期间必须避免过早收缩。这个项目调查了一个内在的 小鼠和人类逼尿肌的一种机制，它通过膀胱肌的伸长来感知膀胱容量的变化。 平滑肌纤维其机制是由于牵张依赖性K+通道的表达和功能。 先前的研究表明，逼尿肌平滑肌细胞（SMC）的伸展激活了外向电流， 稳定这些细胞的兴奋性。牵张激活的K+通道的阻断剂引起显著的激活 在充盈期间膀胱壁的短暂收缩（TC），TC是感觉的主要刺激物， 由骨盆传入神经传递的信息。我们发现Kcnk 2编码了显性的拉伸依赖性蛋白， 逼尿肌SMC中的TREK1传导，在卵巢切除术后雌性激素丧失后下调。 我们注意到当TREK1水平降低时TC伴随增加。我们还发现雌激素可以 在卵巢切除术后挽救了几乎正常的膀胱功能。这些发现并不完全符合 关于激素替代疗法对膀胱过度活动症的影响的文献，我们将探讨 这一差异的可能原因。一种解释可能是雌激素替代的时机可能 对疗效至关重要。因此，我们提出了实验来研究延迟之间的影响， 卵巢切除术和雌激素替代对雌激素恢复Kcnk 2和TREK 1表达的能力的影响， 正常的膀胱充盈反应我们在初步实验中也发现有一个时间- 卵巢切除术后雌激素受体α（ER α）依赖性丢失。因此，我们将研究时间依赖性 雌激素受体的损失和受体损失与有效性降低之间的相关性， 雌激素替代品另一个有待研究的观点是ER α和ER β之间的平衡可能会改变 卵巢切除术后，不仅导致雌激素替代的有效性丧失， 从有益到有害再到正常膀胱功能。我们将用动物来探讨这个问题 SMC特异性敲除ER α和ER β。该项目将使用几种最先进的分子和 提供TREK 1和可能的TREK 2表达之间严格关联的生理学测定 通道和膀胱功能。ER α和ER β表达变化与雌激素水平的关系 Kcnk2和Kcnk10的调节将提供有关拉伸依赖性K+作用的新信息。 膀胱功能的电导，并提出了膀胱过度活动症的发展机制， 绝经

Project Summary The bladder must refrain from premature contraction during filling. This project investigates an intrinsic mechanism of detrusor muscles in mouse and humans that senses volume changes through the elongation of smooth muscle fibers. The mechanism is due to the expression and function of stretch-dependent K+ channels. Previous studies have shown that stretch of detrusor smooth muscle cells (SMCs) activates outward current that stabilizes the excitability of these cells. Blockers of the stretch-activated K+ channels cause significant activation of transient contractions (TCs) in the bladder wall during filling, and TCs are a primary stimulant of sensory information conveyed by pelvic afferents. We found that Kcnk2, which encodes the dominant stretch-dependent conductance TREK1 in detrusor SMCs, is down-regulated after loss of female hormones following ovariectomy. We noted a concomitant increase in TCs when TREK1 levels decreased. We also found that estrogen can rescue nearly normal bladder function after ovariectomy. Such findings do not completely agree with the literature regarding the effects of hormone replacement therapy on overactive bladder, and we will explore possible reasons for this discrepancy. One explanation could be that the timing of estrogen replacement could be critical for efficacy. Thus, we have proposed experiments to study the effects of the delay between ovariectomy and estrogen replacement on the ability of estrogen to restore Kcnk2 and TREK1 expression and normal bladder responses to filling. We have also found in preliminary experiments that there is a time- dependent loss of estrogen receptor α (ERα) after ovariectomy. Thus, we will investigate the time-dependence of the loss of estrogen receptors and the correlation between receptor loss and reduction in the effectiveness of estrogen replacement. Another idea to be investigated is that the balance between ERα and ERβ might change after ovariectomy, causing not only loss of effectiveness of estrogen replacement but also shifting the responses to estrogen from helpful to eleterious to normal bladder function. This question will be explored using animals with SMC-specific knockouts of ERα and ERβ. The project will use several state-of-the-art molecular and physiological assays to provide rigorous associations between expression of TREK1 and possibly TREK2 channels and bladder function. The consequences of changes in ERα and ERβ expression and estrogen regulation of Kcnk2 and Kcnk10 will provide new information about the role of stretch-dependent K+ conductances in bladder function and suggest a mechanism for the development of overactive bladder after menopause.