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

项目概要 膀胱在充盈过程中必须避免过早收缩。该项目研究了一个内在的 小鼠和人类逼尿肌的机制，通过伸长来感知体积变化 平滑肌纤维。该机制归因于拉伸依赖性 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）的伸展会激活外向电流， 稳定这些细胞的兴奋性。拉伸激活 K 通道阻滞剂会导致显着激活 充盈期间膀胱壁的短暂收缩（TC），TC 是感觉的主要刺激物 骨盆传入神经传递的信息。我们发现 Kcnk2，它编码主导的拉伸依赖 逼尿肌 SMC 中的电导 TREK1 在卵巢切除术后雌性激素丧失后下调。 我们注意到，当 TREK1 水平下降时，TC 会随之增加。我们还发现雌激素可以 卵巢切除术后膀胱功能恢复接近正常。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影响的文献，我们将探讨 造成这种差异的可能原因。一种解释可能是雌激素替代的时机可能 对功效至关重要。因此，我们提出了实验来研究之间的延迟的影响 卵巢切除术和雌激素替代对雌激素恢复 Kcnk2 和 TREK1 表达能力的影响 膀胱对充盈的正常反应。我们在初步实验中还发现，有一个时间—— 卵巢切除术后雌激素受体α（ERα）的依赖性丧失。因此，我们将研究时间依赖性 雌激素受体的丧失以及受体丧失与有效性降低之间的相关性 雌激素替代。另一个需要研究的想法是 ERα 和 ERβ 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，而且还改变了反应 雌激素从有帮助到难以维持到正常膀胱功能。这个问题将用动物来探索 SMC 特异性敲除 ERα 和 ERβ。该项目将使用多种最先进的分子和 生理测定提供 TREK1 和可能的 TREK2 表达之间的严格关联 经络和膀胱功能。 ERα和ERβ表达以及雌激素变化的后果 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发生后的机制 更年期。

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.