Obstruction-initiated mechanotranscription in colonic smooth muscle cells

结肠平滑肌细胞中阻塞启动的机械转录（摘要） 肠梗阻是影响儿童和成人的重大健康挑战。许多 病理状态，包括粘连、癌和先天性巨结肠，导致肠梗阻， 内脏不管梗阻的最初原因是什么，其后果在很大程度上是相同的： 肠段过度拉伸，管腔内容物和气体积聚。随后 发生了一系列的功能和形态变化。这些包括运动功能改变， 平滑肌收缩性和增加的肌肉层厚度（肥大），并负责 症状如腹胀、呕吐、腹部绞痛和便秘，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 一种假说是，肠口到阻塞部位机械拉伸激活了特定的信号传导 改变平滑肌基因表达（机械转录）的途径，以及改变的基因表达 导致收缩力受损和肌肉肥大。大鼠部分脑缺血模型的初步研究 梗阻表明，结肠梗阻导致环氧合酶-2（考克斯-2）显著增加， 表达特异性地在梗阻前近端结肠段的平滑肌细胞（SMC）中， 收缩力受损和肥大的开始。此外，我们发现， 考克斯-2的诱导是机械拉伸，因为在未拉伸的组织中考克斯-2的表达没有增加。 段远端梗阻，并因为在体外拉伸结肠环形肌条或结肠平滑肌细胞 诱导考克斯-2的显著表达和前列腺素（PG）PGE 2的释放。考克斯-2 和考克斯-2产生的PG影响平滑肌收缩性和促进细胞增殖是众所周知的。 因此，我们的具体目标是：1）研究牵张诱导的考克斯-2表达在结肠癌中的作用， 阻塞引起的收缩性损伤和平滑肌肥大中的平滑肌细胞; 2） 探讨牵张诱导考克斯-2在结肠环表达的机制 SMC; 3）确定考克斯-2抑制剂和机械转录阻断剂是否预防和/或减轻 大鼠的阻塞相关症状。进一步的研究表明，机械转录也可能参与 在其他牵张相关的运动性疾病中，例如贲门失弛缓症和胃轻瘫，其中下肌缺乏松弛， 食管括约肌和幽门括约肌与食管扩张和低动力有关 体部和窦部。总之，我们假设机械转录调节肠道平滑肌细胞， 功能，并在阻塞性疾病的病理生理学中起关键作用是新的。我们的建议是 预期建立牵张诱导的考克斯-2在梗阻中的低运动性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将 在阻塞和其他牵张相关运动障碍中的治疗潜力。

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.