Presentation Title
Enzymatic Pathways Involved in Serotonin Breakdown in the GI Tract
Abstract
Serotonin (5-hydroxytryptamine; 5-HT) is a crucial biological signaling molecule that has been shown to play a critical role in gut functions including secretion, motility and sending signals to the central nervous system. Alterations in 5-HT signaling have been implicated in gut dysfunction associated with gastrointestinal (GI) disorders including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). While 5-HT release, receptor activation, and reuptake have been extensively studied, it is not clear how 5-HT is degraded in the intestine. This is important as breakdown products may be bioactive. Thus, my aim was to investigate the distribution along the GI tract, and comparative expression, of enzymes that could break down 5-HT. To accomplish this, full-thickness tissue sections (stomach, duodenum, jejunum, ileum, cecum, proximal) were collected from male B6 mice. RNA extraction and RT-PCR were conducted to obtain cDNA samples from the collected tissue. q-PCR was run on the cDNA samples with selective primer sets for 5-HT-degredative enzymes and other 5-HT-related proteins (MAO-A; MAO-B; IDO; NAT-2; AR; ALDH1, TPH1, SERT). Additionally, q-PCR was conducted on total human RNA (stomach, small intestine, colon) to compare overall distribution trend to the mouse model. The results demonstrate that MAO-A, SERT and TPH1 show the largest levels of expression overall. In the mouse tissues, MAO-A, TPH-1 show higher expression in the distal portion of the GI tract. whereas SERT, NAT-2, MAO-B and IDO exhibited higher expression in the proximal colon. Considerable variation amongst the samples was observed, especially in the colon. Furthermore, a comparison of trends across mouse GI tissues shows a relatively similar distribution to that in humans. However, based on the previously established research that demonstrates significantly higher levels of SERT in the small intestine than in the colon, more research may be needed to verify normal tissue-specific quantification of SERT in human tissues.
Primary Faculty Mentor Name
Gary M. Mawe, PhD.
Status
Undergraduate
Student College
College of Arts and Sciences
Second Student College
Larner College of Medicine
Program/Major
Neuroscience
Primary Research Category
Biological Sciences
Enzymatic Pathways Involved in Serotonin Breakdown in the GI Tract
Serotonin (5-hydroxytryptamine; 5-HT) is a crucial biological signaling molecule that has been shown to play a critical role in gut functions including secretion, motility and sending signals to the central nervous system. Alterations in 5-HT signaling have been implicated in gut dysfunction associated with gastrointestinal (GI) disorders including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). While 5-HT release, receptor activation, and reuptake have been extensively studied, it is not clear how 5-HT is degraded in the intestine. This is important as breakdown products may be bioactive. Thus, my aim was to investigate the distribution along the GI tract, and comparative expression, of enzymes that could break down 5-HT. To accomplish this, full-thickness tissue sections (stomach, duodenum, jejunum, ileum, cecum, proximal) were collected from male B6 mice. RNA extraction and RT-PCR were conducted to obtain cDNA samples from the collected tissue. q-PCR was run on the cDNA samples with selective primer sets for 5-HT-degredative enzymes and other 5-HT-related proteins (MAO-A; MAO-B; IDO; NAT-2; AR; ALDH1, TPH1, SERT). Additionally, q-PCR was conducted on total human RNA (stomach, small intestine, colon) to compare overall distribution trend to the mouse model. The results demonstrate that MAO-A, SERT and TPH1 show the largest levels of expression overall. In the mouse tissues, MAO-A, TPH-1 show higher expression in the distal portion of the GI tract. whereas SERT, NAT-2, MAO-B and IDO exhibited higher expression in the proximal colon. Considerable variation amongst the samples was observed, especially in the colon. Furthermore, a comparison of trends across mouse GI tissues shows a relatively similar distribution to that in humans. However, based on the previously established research that demonstrates significantly higher levels of SERT in the small intestine than in the colon, more research may be needed to verify normal tissue-specific quantification of SERT in human tissues.