Na Channels in Afferents after Bladder Obstruction

描述(由申请人提供)：每四名男性中就有一人患有良性前列腺增生症。超过10亿美元被用于缓解由于膀胱过度活跃(OAB)而导致的BPH令人烦恼的症状。这些症状可能包括紧迫感、频发率、夜尿和急迫性尿失禁。症状可以通过局部麻醉剂和微创手术来缓解，这些手术削弱了来自膀胱和尿路的感觉输入，但未能通畅。使用啮齿类动物的部分尿路结扎模型，研究人员假设OAB可能起源于下尿路肌肉和神经的变化。梗阻(OBS)大鼠表现出尿频和逼尿肌过度活动，与传入肥厚的发展、脊髓反射增强和神经生长因子(NGF)升高有关。对NGF的免疫可阻止神经可塑性和OAB。因此，NGF被认为作为一种细胞因子参与了这些事件，NGF影响传入兴奋性的能力被认为部分源于改变钠电导，而钠电导又依赖于钠通道亚型的表达。数据表明，来自OBS大鼠的传入神经表现出Nay1.8亚型的免疫组织化学(IHC)染色减少。这个Naα亚基在C纤维传入纤维中产生河豚毒素抗性(TTX-R)钠(Na)电流。此外，针对该异构体的反义(AS)但不错配的寡核苷酸(ODN)可降低OAB。我们推测OBS大鼠1)传入兴奋性增加，2)OAB和传入兴奋性是由于钠(Na)电导的改变，3)鞘内反义寡核苷酸下调Na通道异构体(S)可降低传入兴奋性和OAB，4)神经生长因子参与传入兴奋性增强、Na通道功能改变和/或异构体表达的发生。这些假说将通过确定梗阻与假手术相比是否1)改变基于膜片钳分析的标记的膀胱传入神经元的电特性，2)使用IHC和Western blotting改变Na通道亚型的表达，以及3)兴奋性或蛋白表达的改变是否随着结扎和排尿行为的正常化而可逆来检验这些假说。NGF协调这些事件的能力将通过观察NGF免疫或TrkA拮抗剂是否阻止与对照组相比OBS的电特性和蛋白质表达的变化来阐明。对这些细胞过程的深入了解可以被用来开发基于传入的OAB治疗方法，采用基于药理学、分子或基因的策略。

DESCRIPTION (provided by applicant): Benign prostatic hyperplasia (BPH) develops in one out of four men. In excess of $1 billion is spent to relieve bothersome symptoms of BPH due to an overactive bladder (OAB). These symptoms may include urgency, frequency, nocturia and urge incontinence. Symptoms can be relieved by local anesthetics and minimally invasive procedures that blunt sensory input from the bladder and urethra yet fail to un-obstruct. Using the partial urethral ligation model in rodents, investigators postulate that OAB may originate from changes in muscle and nerves in the lower urinary tract. Obstructed (OBS) rats exhibit urinary frequency and detrusor overactivity temporally correlated to the development of afferent hypertrophy, an enhanced spinal reflex, and a rise in nerve growth factor (NGF). Immunity to NGF prevents both neural plasticity and OAB. Therefore, NGF acting as a cytokine is thought to participate in these events, NGF's ability to influence afferent excitability is thought to derive, in part, from altering Na conductances, which in turn depends on Na channel isoform expression. Data suggests that afferents from OBS rats exhibit decreased immunohistochemical (IHC) staining for the Nay1.8 isoform. This Na alpha subunit gives rise to tetrodotoxin resistant (TTX-R) sodium (Na) currents in C-fiber afferents. Moreover, an antisense (AS) but not mismatch oligodeoxynucleotide (ODN) against this isoform reduces OAB. We postulate that in OBS rats 1) increased afferent excitability exists, 2) OAB and afferent excitability are due to an alteration in sodium (Na) conductance, 3) knockdown of Na channel isoform(s) using intrathecal AS ODN reduces afferent hyperexcitability and OAB, and 4) NGF participates in the genesis of enhanced afferent excitability, alterations in Na channel function and/or isoform expression. These hypotheses will be tested by determining whether obstruction compared to sham surgery 1) alters electrical properties of labeled afferent bladder neurons based on patch clamp analysis, 2) changes expression of Na channel isoforms using IHC and Western blotting, and 3) whether alterations in excitability or protein expression are reversible with deligation and normalization of voiding behavior. The ability of NGF to orchestrate these events will be elucidated by noting if NGF immunity or trkA antagonists prevent changes in electrical properties and protein expression in OBS compared to controls. Insight into these cellular processes could be exploited to develop afferent based treatments for OAB employing pharmacologic, molecular or gene based strategies.