Obstruction-initiated mechanotranscription in colonic smooth muscle cells

描述（由申请人提供）：结肠平滑肌细胞中阻塞启动的机械转录（摘要）肠阻塞是影响儿童和成人的重大健康挑战。许多病理状况，包括粘连、癌和先天性巨结肠，导致肠梗阻。无论梗阻的最初原因是什么，其后果在很大程度上是相同的：肠道的近端部分由于管腔内容物和气体的积聚而过度拉伸。随后，发生一系列功能和形态变化。这些包括运动功能改变、平滑肌收缩性降低和肌肉层厚度增加（肥大），并导致腹胀、呕吐、腹部绞痛和便秘等症状，并可能导致肠衰竭。不幸的是，这些变化背后的分子机制尚不清楚。我们的假设是，机械拉伸在肠道口阻塞的网站激活特定的信号通路，以改变平滑肌基因表达（mechanotranscriptions），和改变的基因表达导致收缩力受损和肌肉肥大。在大鼠部分梗阻模型中的初步研究表明，结肠梗阻导致环氧化酶-2（考克斯-2）表达显著增加，特别是在收缩力受损和肥大发生之前，在梗阻近端的结肠段的平滑肌细胞（SMC）中。此外，我们确定诱导考克斯-2的初始触发因素是机械牵拉，因为考克斯-2表达在梗阻远端的未牵拉段中没有增加，并且因为在原代培养中结肠环形肌条或结肠SMC的体外牵拉诱导考克斯-2的显著表达和前列腺素（PG）PGE 2的释放。众所周知，考克斯-2和考克斯-2产生的PG影响平滑肌收缩性并促进细胞增殖。因此，本研究的具体目的是：1）探讨牵张诱导的结肠平滑肌细胞考克斯-2表达在梗阻性收缩障碍和平滑肌肥大中的作用; 2）探讨牵张诱导的结肠平滑肌细胞考克斯-2表达的机械转录机制; 3）确定考克斯-2抑制剂和机械转录阻滞剂是否预防和/或缓解大鼠的阻塞相关症状。进一步的研究表明，机械转录也可能涉及其他牵张相关的运动障碍，如贲门失弛缓症和胃轻瘫，其中食管下括约肌和幽门括约肌松弛的缺乏分别与食管体和胃窦的扩张和运动不足相关。总之，我们的假设，机械转录调节肠道平滑肌细胞的功能，并在梗阻性疾病的病理生理学中发挥关键作用是新颖的。我们的建议有望建立牵张诱导的考克斯-2在梗阻性肠梗阻中的运动功能减退和肥大中的关键作用。这在临床上是重要的，因为考克斯-2抑制剂和机械转录阻断剂在阻塞和其他牵张相关的运动障碍中具有治疗潜力。公共卫生相关性：肠梗阻可能由许多病理条件引起，并且代表影响成人和儿童的重大健康挑战。我们发现，梗阻引发的机械牵张导致肠平滑肌细胞中考克斯-2分子的显著诱导，并且考克斯-2表达的增加解释了梗阻相关的运动变化和肠增厚。我们期望发现，使用考克斯-2抑制剂可能是一个新的治疗目标，在梗阻和其他牵拉相关的动力障碍，如贲门失弛缓症，胃轻瘫，慢性便秘，和先天性巨结肠症。

DESCRIPTION (provided by applicant): Obstruction-initiated mechanotranscription in colonic smooth muscle cells (Abstract) Bowel obstruction is a significant health challenge that affects children as well as adults. Numerous pathological conditions, including adhesions, carcinomas, and Hirschsprung's disease, result in obstruction in the gut. Regardless of the initial cause of obstruction, the consequences are largely the same: the proximal segment of the gut is over-stretched with the accumulation of the luminal contents and gas. Subsequently, a series of functional and morphological changes occurs. These include altered motility function, decreased smooth muscle contractility and increased thickness of muscle layer (hypertrophy), and are responsible for symptoms such as abdominal bloating, vomiting, abdominal cramps, and constipation, and may lead to intestinal failure. Unfortunately, the molecular mechanisms underlying these changes are not known. Our hypothesis is that mechanical stretch in the gut oral to the site of obstruction activates specific signaling pathways to alter smooth muscle gene expression (mechanotranscription), and the altered gene expression leads to impaired contractility and muscular hypertrophy. Preliminary studies in a rat model of partial obstruction demonstrated that colon obstruction leads to a dramatic increase of cyclooxygenase-2 (COX-2) expression specifically in the smooth muscle cells (SMC) of the colon segment proximal to obstruction before the onset of impaired contractility and hypertrophy. Furthermore, we identified that the initial trigger for the induction of COX-2 is mechanical stretch because COX-2 expression is not increased in the un-stretched segment distal to obstruction, and because in vitro stretch of the colonic circular muscle strips or colonic SMCs in primary culture induces marked expression of COX-2 and release of prostaglandin (PG) PGE2. The COX-2 and COX-2-generated PGs are well known to affect smooth muscle contractility and promote cell proliferation. Therefore, our specific aims are to: 1) investigate the role of stretch-induced COX-2 expression in the colonic smooth muscle cells in obstruction-initiated contractility impairments and smooth muscle hypertrophy; 2) investigate the mechanotranscription mechanism of stretch-induced COX-2 expression in the colonic circular SMCs; 3) determine whether COX-2 inhibitors and the mechanotrancription blockers prevent and/or alleviate obstruction-related symptoms in rats. Further studies indicate that mechanotranscription may also be involved in other stretch-related motility disorders such as achalasia and gastroparesis, where lack of relaxation of lower esophageal sphincter and pylorus sphincter is associated with distension and hypomotility in the esophageal body and antrum, respectively. In summary, our hypothesis that mechanotranscription regulates gut SMC function, and plays a critical role in the pathophysiology of obstructive disorders is novel. Our proposal is expected to establish a critical role of stretch-induced COX-2 in hypo-motility and hypertrophy in obstruction. This is clinically significant because COX-2 inhibitors and mechanotranscription blockers would have therapeutic potentials in obstruction and other stretch-related motility disorders. PUBLIC HEALTH RELEVANCE: Bowel obstruction may be caused by numerous pathological conditions, and represents a significant health challenge affecting adults and children. We find that obstruction-initiated mechanical stretch leads to marked induction of COX-2 molecule in gut smooth muscle cells, and the increased COX-2 expression accounts for obstruction-related motility changes and bowel thickening. We are expected to find that the use of COX-2 inhibitors may be a novel therapeutic target in obstruction and other stretch-related motility disorders, such as achalasia, gastroparesis, chronic constipation, and Hirschsprung's disease.