Pathogenesis of gut dysfunction in bowel obstruction and after obstruction is resolved

 描述(由申请人提供)：肠梗阻(BO)是成人和儿童面临的重大健康挑战，在美国每年有超过30万人入院治疗。腹痛和运动功能障碍是BO保守治疗中的两个主要问题，尤其是在不可手术和恶性BO中。约57%的BO患者接受手术治疗。目前的手术方法是松解阻塞或移除远端狭窄段，而不是扩张的肠段。然而，手术后，许多患者会出现腹部不适、疼痛和便秘等长期的肠道功能障碍。BO及其释放后的肠道功能障碍的发病机制尚不清楚。这种影响数百万患者的疾病没有有效的治疗方法。我们推测，机械应激诱导BO时扩张段肠平滑肌细胞(SMC)的基因表达(机械转录)不仅在BO时腹痛和运动功能障碍中起关键作用，而且通过其对结肠感觉神经元和SMC基因表达的次级影响而对肠功能产生持久的影响。为了验证这一假说，我们将重点研究肠道功能障碍的两个方面，即AIM 1的腹痛和AIM 2的运动功能障碍。在目标1中，我们提出机械应激诱导疼痛介质神经生长因子(NGF)和脑源性神经营养因子(BDNF)在结肠SMC中的表达，使结肠感觉神经元敏感，并参与BO时的疼痛。NGF上调结肠感觉神经元瞬时受体电位阳离子通道亚型V1(TRPV1)和电压门控性Na+通道的表达和功能，而BDNF下调电压门控性K+通道的表达和功能。感觉神经元的一些继发性变化(即TRPV1的上调)是长期的，并解释了BO释放后持续的内脏高敏感性。在目标2中，我们将探讨BO期间和BO解决后运动功能障碍的机制。我们首次发现蛋白激酶D(PKD)与细胞对机械应力的反应密切相关。我们将检验这一工作假设，即结肠SMC中的机械转录不仅在BO期间通过依赖PKD诱导环氧合酶-2(COX-2)发挥关键作用，而且在BO通过依赖前列腺素E2(PGE2)上调微粒体PGE合成酶-1(mPGES-1)来缓解BO后也发挥关键作用。我们将使用体内和体外模型来定义这些新的机制。综上所述，我们的研究表明，BO中曾经膨胀的口腔段是机械转录发生的地方，也是长期肠道功能障碍的原因。拟议的研究将确定针对这种功能障碍的潜在预防和治疗方法。抑制BO过程中的机械转录(即NGF抗血清和PKD1抑制剂)不仅可以改善BO的疼痛和运动功能，还可以预防长期的肠道功能障碍，而靶向BO释放后的次要效应(即TRPV1和mPGES-1)是治疗长期肠道功能障碍的潜在方法。

 DESCRIPTION (provided by applicant): Bowel obstruction (BO) is a significant health challenge in adults and children, and accounts for more than 300,000 hospital admissions in the US per year. Abdominal pain and motility dysfunction are two main concerns in the conservative management of BO, especially in inoperable and malignant BO. About 57% of BO patients are treated by surgery. The current surgical approach is to release blockage or remove the distal constrictive segment, but to leave alone the distended segment in the gut. However, after the surgery, many patients suffer long-term gut dysfunction such as abdominal discomfort, pain and constipation. The pathogenesis of gut dysfunction in BO and after its release remains poorly understood. There is no effective treatment for the condition that impacts millions of patients. We hypothesize that mechanical stress-induced gene expression (mechano-transcription) in gut smooth muscle cells (SMC) in the distended segment not only plays a critical role in abdominal pain and motility dysfunction during BO, but exerts prolonged effects on bowel function through its secondary effects on gene expression in colonic sensory neurons and SMC. To test the hypothesis, we will focus on two aspects of gut dysfunction, i.e., abdominal pain in Aim 1 and motility dysfunction in Aim 2. In Aim 1, we propose that mechanical stress-induced expression of pain mediators nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in colonic SMC sensitize colonic sensory neurons and contribute to pain during BO. NGF increases the expression and function of transient receptor potential cation channel subtype V1 (TRPV1) and voltage-gated Na+ channel, whereas BDNF down-regulates the expression and function of voltage-gated K+ channel in colonic sensory neurons. Some of the secondary changes (i.e., up-regulation of TRPV1) in sensory neurons are long-lasting, and account for persistent visceral hypersensitivity after BO is released. In Aim 2, we will investigate the mechanisms of motility dysfunction during BO and after BO is resolved. We found for the first time that protein kinase D (PKD) is profoundly involved in the cellular response to mechanical stress. We will test the working hypothesis that mechano-transcription in colonic SMC plays a critical role in motility dysfunction not only during BO via PKD1-dependent induction of cyclooxygenase-2 (COX-2), but also after BO is resolved through prostaglandin E2 (PGE2)- dependent up-regulation of microsomal PGE synthase-1 (mPGES-1). We will use in vivo and in vitro models to define these novel mechanisms. In summary, our study suggests that the once distended oral segment in BO is where mechano-transcription occurs, and is the cause of long-term gut dysfunction. Proposed studies will identify potential prophylactic and therapeutic treatments towards the dysfunction. Inhibition of mechano-transcription during BO (i.e. NGF antiserum and PKD1 inhibitor) may not only improve pain and motility function in BO, but also prevent long-term gut dysfunction, whereas targeting secondary effects (i.e. TRPV1 and mPGES-1) following the release of BO is a potential treatment for long-term gut dysfunction.