Intestinal 5-HT Transporter: A novel therapeutic target for GI disorders

5-羟色胺转运体（SLC 6A 4; SERT）是调节肠道5-HT利用率的主要机制 粘膜大量证据支持SERT与各种GI疾病的联系，然而， 机制还不太清楚。我们最近的研究和初步数据表明， SERT和细胞内5-HT在新认识的芳烃受体（AhR）激活中的作用 IBD易感基因有趣的是，用AhR激动剂（β-萘啶酮）喂养的SERT KO小鼠显示， CYP 1A 1（典型AhR基因靶点）诱导受损。我们的初步数据进一步表明，SERT 对于维持健康的肠道微生物群至关重要，因为小鼠中SERT的缺失与 放线菌的减少和群落结构的改变可能会影响已知配体的可用性， 激活AhR由于AhR途径调节肠道免疫，SERT的减少可能有助于肠道免疫。 通过抑制基础和激动剂诱导的AhR活性来研究肠道炎症的病理生理学。然而，在这方面， 将这种新的模式的β-肾上腺素能机制的作用，在生态失调和激动剂， 诱导的AhR活化是未知的。有趣的是，膳食AhR配体，如那些存在于十字花科植物中的配体， 蔬菜对改善肠道炎症有保护作用。然而，SERT的下降 与炎症相关的表达可能会抑制它们的作用，并降低治疗过程中的有效性。 IBD。我们假设SERT介导的5-HT摄取对于AhR的激活是至关重要的， 饮食配体。我们还假设激活SERT和/或抵消其下降的药物 调节将通过AhR依赖性机制赋予新的抗炎作用。拟定研究 具体目标1将：a）研究细胞特异性机制，5-HT通过该机制激活肠AhR， 小鼠和人肠类; B）检查SERT的丧失是否使对以下有益作用的抗性： TNBS回肠炎模型中的饮食AhR配体;和; c）阐明微生物群在AhR活化中的作用 利用粪便转移的途径，并研究SERT与微生物群产生 AhR配体。鉴于SERT在所有炎症模型中一致显示下降， 对于IBD患者，Specific Aim 2中提出的研究将检查天然AhR配体的疗效 在预防肠道炎症发作的饮食中存在，当与上调 SERT，如益生菌短双歧杆菌。此外，SERT上调在AhR机制中的作用 将利用最先进的上皮细胞特异性可诱导的小鼠模型来研究激活。 SERT的过度表达。拟议研究的结果应通过以下方式确定分子机制： 其中5-HT激活AhR，并应建立这种新的联系，宿主的多巴胺能机制， 通过AhR和肠道微生物群/代谢物的肠道炎症。这些研究还应确定 SERT上调作为IBD的新干预策略的有益作用。

Serotonin transporter (SLC6A4; SERT) represents a primary mechanism to regulate 5-HT availability in the gut mucosa. A large body of evidence supports linkage of SERT to various GI disorders, however, the mechanisms are not well understood. Our recent studies and preliminary data demonstrated an entirely novel role of SERT and intracellular 5-HT in the activation of Aryl hydrocarbon receptor (AhR), a newly recognized IBD susceptibility gene. Interestingly, SERT KO mice fed with AhR agonist (β-naphthoflavone) showed impaired induction of CYP1A1, the canonical AhR gene target. Our preliminary data further showed that SERT was essential for the maintenance of healthy gut microbiota, as deletion of SERT in mice was associated with a reduction in actinobacteria, and altered community structure that may affect the availability of ligands known to activate AhR. Since AhR pathways regulate gut immunity, the decrease in SERT may contribute to the pathophysiology of intestinal inflammation by suppressing basal and agonist-induced AhR activity. However, the mechanisms linking this novel paradigm of the role of serotonergic machinery in dysbiosis and agonist induced AhR activation are not known. Interestingly, dietary AhR ligands such as those present in cruciferous vegetables have protective roles in ameliorating intestinal inflammation. However, a decrease in SERT expression associated with inflammation may dampen their effects and reduce effectiveness in the course of IBD. We hypothesize that SERT-mediated uptake of 5-HT is crucial for the activation of AhR in response to dietary ligands. We also hypothesize that agents which activate SERT and/or counteract its down regulation will confer novel anti-inflammatory effects via AhR dependent mechanisms. Proposed studies in Specific Aim 1 will: a) investigate cell specific mechanisms by which 5-HT activates intestinal AhR utilizing mouse and human enteroids; b) examine whether loss of SERT renders resistance to the beneficial effects of dietary AhR ligands in TNBS ileitis model; and; c) elucidate the effects of microbiota in the activation of AhR pathways utilizing fecal transfer and investigate the link between SERT and the ability of microbiota to produce AhR ligands. Given that SERT is consistently shown to be decreased in all models of inflammation and patients with IBD, proposed studies in Specific Aim 2 will examine the efficacy of natural AhR ligands present in the diet in preventing the onset of gut inflammation, when combined with agents that upregulate SERT, such as probiotic Bifidobacteria breve. In addition, the role of SERT upregulation on mechanisms of AhR activation will be investigated utilizing state-of-the-art mouse model of epithelial cell- specific inducible overexpression of SERT. Outcome of the proposed studies should define the molecular mechanisms by which 5-HT activates AhR and should establish this novel link of the host serotonergic machinery with gut inflammation via AhR and gut microbiota/metabolites. These studies should also establish the beneficial role of SERT up regulation as a novel interventional strategy for IBD.