Obstruction-initiated mechanotranscription in colonic smooth muscle cells

描述(申请人提供)：梗阻启动的结肠平滑肌细胞的机械转录(摘要)肠梗阻是一个重大的健康挑战，影响儿童和成人。许多病理情况，包括粘连、癌症和先天性巨结肠，都会导致肠梗阻。不管最初的梗阻原因如何，后果基本相同：肠腔内容物和气体的积聚使肠管近端过度伸展。随后，发生了一系列的功能和形态变化。这些症状包括运动功能改变，平滑肌收缩能力降低，肌肉层厚度增加(肥大)，并导致腹胀、呕吐、腹部痉挛和便秘等症状，并可能导致肠道衰竭。不幸的是，这些变化背后的分子机制尚不清楚。我们的假说是，机械牵拉到肠梗阻部位会激活特定的信号通路，改变平滑肌基因的表达(机械转录)，而改变的基因表达会导致收缩能力受损和肌肉肥大。在部分梗阻大鼠模型上的初步研究表明，结肠梗阻导致环氧合酶-2(COX-2)的表达显著增加，尤其是在肠梗阻近端的平滑肌细胞(SMC)，在收缩功能受损和肥大开始之前。此外，我们发现机械牵张是诱导COX-2的最初触发因素，因为COX-2在梗阻远端的非牵张节段没有增加，而且在体外牵拉结肠环状肌条或原代培养的结肠SMC可以诱导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产生的前列腺素能影响平滑肌收缩和促进细胞增殖。因此，我们的具体目标是：1)研究牵张诱导的结肠平滑肌细胞COX-2表达在梗阻引起的收缩功能损害和平滑肌肥大中的作用；2)探讨牵张诱导的结肠环状SMC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够预防和/或缓解大鼠梗阻相关症状。进一步的研究表明，机械转录也可能参与其他牵张相关的运动障碍，如失弛缓症和胃轻瘫，在这些疾病中，下食道括约肌和幽门括约肌松弛不足分别与食管体和胃窦的扩张和动力低下有关。总之，我们的假设是，机械转录调节肠道SMC功能，并在阻塞性疾病的病理生理学中发挥关键作用是新的。我们的建议有望确定牵张诱导的COX-2在梗阻的运动功能减退和肥大中起关键作用。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对梗阻和其他牵张相关的运动障碍具有治疗潜力。公共卫生相关性：肠梗阻可能由多种病理情况引起，是影响成人和儿童的重大健康挑战。我们发现机械牵张导致肠梗阻引起的肠平滑肌细胞中COX-2分子的显著诱导，COX-2表达的增加是梗阻相关的运动改变和肠壁增厚的原因。我们有望发现，COX-2抑制剂的使用可能成为治疗梗阻和其他牵张相关运动障碍的新靶点，如失弛缓症、胃瘫、慢性便秘和先天性巨结肠。

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.