疏肝饮通过肠道菌群调节肠易激综合征模型大鼠肠道五羟色胺合成的作用机制研究

The major clinical manifestation of Irritable bowel syndrome (IBS) is abdominal pain and altered defecation. Serotonin (5-HT) is a key signaling molecule that regulates visceral sensation and gastrointestinal motility in the brain-gut axis and plays an important role in the pathophysiology of IBS. More than 90% of the 5-HT in the body is synthesized in the gut. Increasing evidence suggested that gut microbiota is involved in regulating the synthesis of intestinal 5-HT, but the detailed mechanism remains unclarified. Chronic water avoidance stress (WAS) rat is a common IBS animal model. We found that the level of 5-HT was decreased in the colon of WAS rat, accompanied with the decrease of 5-HT transporter (SERT) expression and that Shugan decoction can improve the 5-HT content and SERT expression in WAS rat colon. In this study, we will explore the effect of Shugan decoction on the synthesis of 5-HT in gut via microbiota and the mechanisms involved by fecal microbiota transplantation and by measuring the levels of tryptophan, tryptophan hydroxylase (TPH) 1 and TPH2 and 5-HT, the expression of SERT, the numbers of intestinal chromaffin cells (EC) and mast cells (MC), the expression of THP1 on EC and MC, the content of 5-HT in EC and MC to elucidate the biological basis of "mediate liver and spleen" exerted by Shugan decoction.

肠易激综合征（IBS）以腹痛和排便异常为主要临床表现。5-羟色胺（5-HT）是脑-肠轴中调节内脏感觉和胃肠动力的关键信号分子，在IBS病理生理过程中发挥重要作用。体内超过90%的5-HT是在肠道合成的，越来越多的证据显示肠道菌群参与调节肠道5-HT合成，但详细机制有待阐明。慢性避水应激（WAS）大鼠是常用的IBS动物模型。我们在前期研究中发现WAS大鼠结肠中5-HT含量降低，伴随5-HT转运体（SERT）表达减少，疏肝饮可以提高WAS大鼠结肠中的5-HT含量和SERT表达。本研究拟通过粪菌移植并测定肠组织中色氨酸含量、色氨酸羟化酶（TPH）1和TPH2水平、5-羟色氨酸含量、SERT表达、肠嗜铬细胞（EC）和肥大细胞（MC）数量、EC和MC上TPH1表达、EC和MC中5-HT含量，探讨疏肝饮通过肠道菌群调节WAS大鼠肠道5-HT合成的作用机制，科学阐释疏肝饮“调和肝脾”的生物学基础。

本研究旨在探讨疏肝饮通过肠道菌群调节避水应激（water avoidance stress, WAS）大鼠肠道五羟色胺（5-hydroxytroptamin, 5-HT）合成的作用机制，科学阐释疏肝饮“调和肝脾”的生物学基础。主要从WAS引起的肠道菌群改变对肠道5-HT合成的影响及疏肝饮的调节作用、肠道菌群调节WAS大鼠肠道5-HT合成的作用机制和产芽孢菌对WAS大鼠肠道5-HT合成的调节作用及相关机制这三个方面进行研究。研究发现，与正常SPF大鼠相比，WAS会引起大鼠的排便异常以及内脏高敏感性，使大鼠结肠组织中5-HT含量增加及SERT蛋白表达减少。此外，我们研究发现WAS会引起大鼠肠道菌群的变化，SGD会恢复WAS大鼠的肠道菌群。给WAS大鼠肠内移植正常SPF大鼠粪菌会恢复WAS大鼠的排便异常和内脏高敏感性，引起大鼠结肠组织中5-HT含量减少及SERT蛋白表达增加。与WAS大鼠相比，疏肝饮可以恢复WAS大鼠的排便异常和内脏高敏感性，使大鼠结肠组织中5-HT含量减少及SERT蛋白表达增加。给未经疏肝饮处理的WAS大鼠肠内移植经疏肝饮处理的WAS大鼠粪菌也能恢复WAS大鼠排便异常和内脏高敏感性，使大鼠结肠组织中5-HT含量减少及SERT蛋白表达增加。进一步研究发现，给WAS大鼠肠内移植正常SPF大鼠粪菌或经疏肝饮处理的WAS大鼠粪菌后，其结肠组织中EC数量减少。最后一部分实验中我们发现，与WAS大鼠相比，补充枯草芽孢杆菌后的WAS大鼠VH得到改善，但排便量有所增加，结肠组织中5-HT含量和EC数量均增加。