探討兩種腸躁症動物模式中內臟高敏感性及
腸道蠕動性的表現

背景：腸躁症(Irritable bowel syndrome, IBS)為功能性腸胃道疾病之一，患者出現反覆性腹痛和排便習慣的改變, 但在內視鏡及糞便篩檢中無腸道結構損傷或病原體。罹患IBS之風險因子包括精神壓力、腸道病原感染、慢性腸道炎等。目前已知腸道中血清素(5-HT)的改變為IBS的表徵之一。本篇利用兩種類腸躁症動物模式，探討第七型血清素受體(5-HT7 receptor, 5-HT7R)在內臟高敏感性與腸道蠕動性變化扮演的角色，以及評估新合成5-HT7R配體之止痛效果。方法：建立兩種類腸躁症模式，包括利用梨形蟲(Giardia)感染後排除期加上避水壓力(WAS)稱之後感染性腸躁症（GW）小鼠、利用三硝基苯黃酸誘發結腸炎復原後稱之後發炎性腸躁症（TNBS）小鼠。透過結直腸撐張刺激引起的內臟動器反應，評估內臟高敏感性。進行活性碳試驗，評估腸道蠕動性。藉由西方轉漬法、反轉錄酶連鎖反應與免疫螢光染色觀察腸道中5-HT7R的表現。此外在內臟動器試驗前經口給予小鼠5-HT7R配體與標準品，評估其改善內臟痛覺與腸道蠕動。結果：在後感染性腸躁症小鼠中確認梨形蟲在腸道中的感染狀況與避水壓力後血清中腎上腺皮質酮的增加，以及內臟痛覺相較對照組有敏感性的表現但無腸道黏膜型態改變。在後發炎性腸躁症小鼠中確認於灌輸三硝基苯黃酸後第2天腸道組織骨髓過氧化酶增加、組織型態受損，至第7天為發炎緩和復原期；第14、24天完全復原階段仍有持續的內臟痛覺表現；而在第57天痛覺消失。兩種類腸躁症小鼠的5-HT7R表現量在腸道肌肉層、黏膜層中均有提高的現象。腹腔注射SB-269970 (5-HT7R拮抗劑)能降低兩種類腸躁症小鼠的腸道痛覺。相較於Alosetron (臨床用5-HT3R拮抗劑)與Loperamide (臨床用止瀉劑)，經口給予CYY1005（新合成之5-HT7R 配體）更能顯著降低內臟高敏感性的表現。結論：本篇論文證實，腸道中5-HT7R的表現增加和類腸躁症小鼠的內臟高敏感性有關；此外，新合成之5-HT7R配體能有效減緩腸道痛覺。

關鍵字

腸躁症；精神壓力；梨形蟲；結腸炎；內臟高敏感性；腸道蠕動性；血清素第七型受體

並列摘要

Background：Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder of which patients experience recurrent abdominal pain or discomfort with changes in bowel habit but neither apparent structural lesion nor presence of pathogen. Risk factors related to the onset of IBS include psychological stress, pathogen infection and chronic gut inflammation. One of the hallmark of IBS is the altered intestinal levels of serotonin (5-HT). The aim is to evaluate the role of 5-HT7 receptor (5-HT7R) in visceral hypersensitivity and gut motility, and to test the antinociceptive effects of newly synthesized 5-HT7R ligands in two IBS-like mouse models. Method：Two mouse models were used, including post-giardiasis combined with water avoidance stress (GW) and post resolution of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. Visceromotor response (VMR) to colorectal distension and intestinal transit by charcoal meal test were measured. The expression of 5-HT7R protein and mRNA levels were examined in colonic tissue by Western blotting, RT-PCR and immunofluorescent staining. Moreover, 5-HT7R ligands and reference standards were orally administered prior to VMR and charcoal meal test. Result：In the first model, Giardia infection was confirmed by trophozoite counts in the intestine, and increased serum corticosterone were observed following stress. Elevated visceral pain with normal gut morphology was observed in GW mice compared to normal controls. In the second model, increased colonic myeloperoxidase activity and histopathological score were observed 2 days after TNBS administration and resolved by day 7. Sustained visceral pain was seen on day 14 and 24 but was absent on day 57 after TNBS administration. In the two mouse models, expression levels of 5-HT7R were elevated in colonic muscle/nerve and mucosal layers. Intraperitoneal injection of SB-269970 (a 5-HT7R inhibitor) reduced visceral pain in GW and TNBS mice. Oral administration of a novel 5-HT7R ligand, CYY1005, significantly reduced visceral hypersensitivity compared to Alosetron (a clinically used 5-HT3R antagonist), or Loperamide (a clinically use μ-opioid receptor agonist). Conclusion：Increased colonic 5-HT7R is involved in visceral hypersensitivity in IBS model. In addition, newly synthesized 5-HT7R ligands showed strong antinociceptive effect.

並列關鍵字

Irritable bowel syndrome ； stress ； Giardia lamblia ； colitis ； visceral hypersensitivity ； gut motility, ； 5-HT7 receptor

參考文獻

1. Furness, J.B., et al., Intrinsic primary afferent neurons of the intestine. Prog Neurobiol, 1998. 54(1): p. 1-18.

Google Scholar

2. Furness, J.B., et al., Intrinsic primary afferent neurons and nerve circuits within the intestine. Prog Neurobiol, 2004. 72(2): p. 143-64.

Google Scholar

3. Nezami, B.G. and S. Srinivasan, Enteric nervous system in the small intestine: pathophysiology and clinical implications. Curr Gastroenterol Rep, 2010. 12(5): p. 358-65.