Obstruction-initiated mechanotranscription in colonic smooth muscle cells

描述（由申请人提供）：结肠平滑肌细胞中梗阻引发的机械转录（摘要）肠梗阻是影响儿童和成人的重大健康挑战。许多病理情况，包括粘连、癌和巨结肠病，都会导致肠道梗阻。不管梗阻的最初原因是什么，其结果基本上是相同的：肠道近端段因肠道内容物和气体的积累而过度伸展。随后，发生一系列功能和形态变化。这些症状包括运动功能改变、平滑肌收缩力下降和肌肉层厚度增加（肥大），并导致腹部腹胀、呕吐、腹部痉挛和便秘等症状，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，肠口到梗阻部位的机械拉伸激活了特定的信号通路，改变了平滑肌基因表达（机械转录），而基因表达的改变导致收缩性受损和肌肉肥大。部分梗阻大鼠模型的初步研究表明，结肠梗阻导致环氧化酶-2 （COX-2）表达急剧增加，特别是在梗阻近端结肠段平滑肌细胞（SMC）中，然后收缩性受损和肥厚发生。此外，我们发现诱导COX-2的初始触发因素是机械拉伸，因为COX-2的表达在梗阻远端未拉伸的节段中不会增加，而且在体外拉伸原代培养的结肠环状肌条或结肠SMCs诱导COX-2的显著表达和前列腺素（PG） PGE2的释放。众所周知，COX-2和COX-2生成的pg可以影响平滑肌收缩力并促进细胞增殖。因此，我们的具体目的是：1)研究拉伸诱导的结肠平滑肌细胞COX-2表达在梗阻性收缩性损伤和平滑肌肥厚中的作用；2)探讨拉伸诱导的结肠环状SMCs中COX-2表达的机械转录机制；3)确定COX-2抑制剂和机械转录阻滞剂是否能预防和/或减轻大鼠梗阻相关症状。进一步的研究表明，机械转录也可能参与其他与拉伸相关的运动障碍，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缺乏松弛分别与食管体和胃窦的扩张和动力低下有关。总之，我们关于机械转录调节肠道SMC功能并在阻塞性疾病的病理生理中起关键作用的假设是新颖的。我们的建议有望确立拉伸诱导的COX-2在梗阻时的低运动性和肥厚中的关键作用。这在临床上具有重要意义，因为COX-2抑制剂和机械转录阻滞剂在梗阻和其他与拉伸相关的运动障碍中具有治疗潜力。公共卫生相关性：肠梗阻可能由多种病理条件引起，是影响成人和儿童的重大健康挑战。我们发现，梗阻引发的机械拉伸导致肠道平滑肌细胞中COX-2分子的显著诱导，COX-2表达的增加解释了梗阻相关的运动性变化和肠道增厚。我们期望发现COX-2抑制剂的使用可能成为梗阻和其他与拉伸相关的运动障碍的新治疗靶点，如贲门失弛缓症、胃轻瘫、慢性便秘和先天性巨结肠病。

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.