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

项目摘要 膀胱在充盈过程中必须避免过早收缩。本项目研究的是一个内在的 小鼠和人逼尿肌通过延长肌张力感受体积变化的机制 平滑的肌肉纤维。其机制是由于张力性K通道的表达和功能。 先前的研究表明，伸展的逼尿肌平滑肌细胞(SMC)激活外向电流，从而 稳定这些细胞的兴奋性。牵张激活的K通道阻断剂引起显著的激活 充盈过程中膀胱壁的一过性收缩(TCS)，TCS是感觉的主要刺激物 由骨盆传入传递的信息。我们发现，编码主要依赖于拉伸的Kcnk2 在卵巢切除后女性激素丢失后，逼尿肌平滑肌细胞的TREK1电导被下调。 我们注意到，当TREK1水平降低时，TCS随之增加。我们还发现雌激素可以 卵巢切除后挽救近乎正常的膀胱功能。这些发现并不完全与 有关激素替代治疗对膀胱过度活动的影响的文献，我们将探索 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 对疗效至关重要。因此，我们提出了一些实验来研究两国之间的延迟 卵巢切除和雌激素替代对雌激素恢复Kcnk2和TREK1表达能力的影响 正常的膀胱充盈反应。我们还在初步实验中发现，有一段时间- 卵巢切除后雌激素受体α依赖性丢失(ER-α)。因此，我们将研究时间依赖关系 雌激素受体缺失以及受体缺失与降压疗效降低之间的相关性 雌激素替代疗法。另一个需要研究的想法是，ERα和ERβ之间的平衡可能会改变 卵巢切除后，不仅导致雌激素替代效果的丧失，而且还改变了反应 从有益到兴奋再到正常的膀胱功能。这个问题将用动物来探索。 通过SMC特异性的ERα和ERβ基因敲除。该项目将使用几种最先进的分子和 提供TREK1和可能的TREK2表达之间严格关联的生理学分析 经络和膀胱功能。雌激素受体α和雌激素受体β表达变化与雌激素的关系 对Kcnk2和Kcnk10的调节将提供有关拉伸依赖K的作用的新信息 电导在膀胱功能中的作用，并提示膀胱过度活动的发生机制 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.