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The Serotonin Precursor 5-Hydroxytryptophan Reinforces Intestinal Barrier Function
and α-TOC (i.e. membrane). CONCLUSION: NAC and α-TOC are able to reverse LPSinduced persistent HSMC alterations resulting possible tools in the therapeutic strategy of post-infective motor disorders.
syndrome (IBS). Changes in serotonergic metabolism have also been associated with IBS. The direct precursor of 5-HT, 5-hydroxytryptophan (5-HTP), is available as over-the-counter dietary supplement and is a potential substance to influence serotonin availability and possibly also intestinal barrier function. Aim: To assess the effect of an oral bolus of 5-HTP in comparison to placebo on intestinal barrier function and mucosal 5-HT metabolism. Methods: 15 healthy volunteers (7 male; 30±3 yrs) participated in this randomized doubleblind placebo-controlled crossover study. Intestinal permeability was measured by determining the plasma recovery of an orally ingested multi-sugar drink (lactulose, rhamnose, sucrose, sucralose, erythritol) on two separate occasions. Plasma samples were taken prior to, at 60, 90 and 120 min after intake of 100 mg 5-HTP or placebo. At the end of each of both test days, a gastroduodenoscopy was performed to obtain mucosal samples from the duodenum. Plasma concentrations of the sugars and mucosal concentrations of 5-HTP, 5-HT and 5hydroxyindoleacetic acid (5-HIAA, the main metabolite of 5-HT) were determined by HPLCMS. In mucosal samples, the expression of tight junction proteins occludin and ZO-1 was analyzed by qPCR and immunohistochemistry. Data are expressed as mean ± SEM. Results: Intestinal permeability as defined by the plasma recovery ratios of lactulose/rhamnose (L/ R) and sucralose/erythritol (S/E) was significantly reduced after 5-HTP (L/R 0.005±0.002 vs 0.006±0.002, p<0.05, S/E 0.004±0.001 vs 0.005±0.001, p<0.05; 5-HTP vs placebo). The mRNA expression of ZO-1 was significantly increased after 5-HTP (normalized expression ratios 1.27±0.24 vs 0.87±0.12; p<0.05), whereas the expression of occludin was not altered by 5-HTP. Immunohistochemical staining for the ZO-1 and occludin proteins showed that the proteins were located significantly closer to each other after 5-HTP. Administration of 5-HTP significantly increased mucosal 5-HTP levels (12.7±9.1 vs 1.6±1.5 pmol/mg; p= 0.001), but did not affect 5-HT levels (57±21 vs 47±18 pmol/mg; p=0.68), while 5-HIAA levels increased significantly (7.1±1.7 vs 2.5±0.7 pmol/mg; p<0.05). Conclusion: Oral administration of 5-HTP reinforces small intestinal barrier function by lowering intestinal sugar permeability, inducing the expression of the tight junction protein ZO-1 and rearranging tight junction proteins. These changes are associated with 5-HTP-induced alterations in mucosal serotonin metabolism. These data point to a role for serotonergic metabolism in reinforcing intestinal barrier function.
AGA Abstracts
Sa2018 Immunohistochemical Study Evaluating the Vagal Innervation of Intestinal Resident Macrophages Cathy Cailotto, Pedro J. Gomez Pinilla, Jan van der Vliet, Gianluca Matteoli, Guy E. Boeckxstaens BACKGROUND: The vagal cholinergic anti-inflammatory pathway inhibits cytokine release and prevents tissue injury in several inflammatory disorders. We previously demonstrated that electrical stimulation of the vagus nerve suppresses intestinal inflammation and normalizes gut motility in a mouse model of postoperative ileus. However, it is unclear whether the vagus nerve makes direct contact with intestinal resident macrophages or rather indirectly via enteric neurons. In the present study, we therefore analyzed the anatomical relationship between the vagal preganglionic/enteric postganglionic nerve fibers and resident macrophages within the small intestine. METHODS: Anterograde labeling of motor neurons in the dorsal motor nucleus of the vagus (DMV) was achieved by stereotactic injection of biotin-conjugated dextran amine (5%) in the DMV. 19 days after injection, brainstem sections were processed with DAB staining to check the exact localization of the injection site. Vagal nerve fibers were stained in cross sections and intestinal whole mounts using DAB-Nickel staining and were double stained with DAB and cuprolinic blue to evaluate the anatomical contact between enteric neurons and macrophages, respectively. Immunofluorescent labeling for neurofilaments (PGP 9.5), Tyrosine Hydroxylase (TH), Choline Acetyltransferase (ChAT), Vasoactive Intestinal Peptide (VIP), neural Nitric Oxide synthase (nNOS), substance P (SP) and Calcitonin Gene-Related Peptide (CGRP) was performed to identify the neurochemical phenotype of the vagal efferent fibers and the enteric neurons. F4/80 antibody was used to label resident macrophages. RESULTS: Biotin-labeled vagal nerve fibers were identified in the myenteric plexus, but not the submucosal plexus. These vagal preganglionic fibers were cholinergic (ChAT-positive) in nature and negative for TH, VIP, SP, nNOS or CGRP. Vagal nerve fibers were noted in close association with ChAT positive myenteric neurons. A dense network of F4/80-positive macrophages was identified between the circular and longitudinal smooth muscle layers with some macrophages surrounding myenteric ganglia. Vagal nerve fibers only sporadically came in close contact with macrophages. CONCLUSION: In the present study, we demonstrate that there is no close anatomical association between vagal preganglionic fibers and resident macrophages of the intestinal muscularis. Instead, the vagus nerve synapses with cholinergic myenteric neurons suggesting an amplification of the vagal signal through the enteric neuronal network.
Sa2021 Pathogen and Probiotic Bacteria Differentially Stimulate Nitric Oxide Production and S100B Protein Expression in Human Enteroglial Cells Fabio Turco, Giovanni Sarnelli, Carla Cirillo, Annamaria Mango, Alessandra D'Alessandro, Ilaria Palumbo, Rosario Cuomo Background and Aim: Enteric glial cells (EGCs) are involved in intestinal homeostasis and may contribute to regulate host-bacteria interaction. Astrocytes, the equivalent of enteroglial cells (EGCs) in Central Nervous System respond to bacteria releasing nitric oxide (NO), whether this does occur bacterial-EGCs interaction is yet not known. We aimed to investigate whether human EGC generate NO in response to pathogen and probiotic bacteria and whether thi is associated with S100B overexpression. Methods: Human EGCs were obtained according to a method previously described by our group. Briefly, myenteric plexus preparations were isolated from ileum of patients undergoing surgery and enzimatically dissociated. Ganglia were plated and cell cultures were grown to subconfluence. After 21 days, EGCs were purified by incubation with the anti-Thy-1.1 ab-coated magnetic beads and separated using a Dynal Magnet®. EGC were then incubated for 24 hours with the probiotic strain Lactobacillus Paracasei F19 (LP F19) and the pathogen Enteroinvasive Escherichia coli (EIEC). Two different bacteria/cells ratios were used (0.1/1 and 10/1, respectively). Nitrite assay and Western Blot analysis were respectively used to evaluate NO release and S100B expression in stimulated cells and compared to unstimulated cells, that served as controls. Data are expressed as mean±SD of 3 independent experiments. Results: Glial derived S100B protein expression was significantly higher in response to EIEC than to LP F19 (+2.9±0.2 and +0.9±0.3 fold increase vs control; p<0.05). EIEC induced a significantly higher NO release than LP F19 both at a 0.1/1 (17.7±0.7 vs 4.0±0.1 nmol x 10^6 cells; p<0.001) and at 10/ 1 ratio (20.7±2.1 vs 9.0±0.1 nmol x 10^6 cells; p<0.001). When compared to control conditions (3.7±0.1 nmol x 10^6 cells), EIEC and only high concentration of LP F19 induced a significant increase of nitric oxide release (all p<0.001). Conclusion: We show that enteroglial cells are able to release nitric oxide when challenged with bacteria and, that this is likely dependent on the different expression of S100B protein. As EGCs-released nitric oxide was different between pathogen and probiotic bacteria we suggest that human EGCs likely participate to host-bacteria interaction via a different NO release.
Sa2019 Validation of a Post-Infectious IBS Mouse Model Using Campylobacter Jejuni Mira M. Wouters, Nadine Kotman, Kathleen Lambaerts, Caroline L. Van Heijningen, Guy E. Boeckxstaens Background and Aim: Post-infectious irritable bowel syndrome (PI-IBS) occurs in 10 to 30% of patients who suffered from bacterial gastroenteritis. Insight in the underlying pathophysiological mechanisms of PI-IBS is however mainly based on studies using rodents infected with parasites or helminths. These infections trigger a different immune response compared to bacterial infections potentially leading to different pathophysiological mechanisms. Therefore, we developed a PI-IBS mouse model using C. jejuni to study the mechanisms underlying PI-IBS. Methods: Six weeks old balb/c were orally gavaged with 5x10E10 CFU Campylobacter jejuni. To study the inflammatory response, mice were killed at PI day 3 and 10. Quantitative PCR for inflammatory markers was performed on total RNA (RNeasy; Qiagen, reverse transcriptase using QuantaScript; Quanta) from jejunum, colon and mesenteric lymph nodes (MLN). To evaluate visceral pain, electrodes (Nichrome 80, Pelican Wire) were implanted in the abdominal muscularis and EMG was recorded. Colorectal distention (CRD) was performed by inflating a Fogarty probe 4.0 (0.02-0.1 ml) at 3 weeks post infection. EMG spikes were analyzed with Spike2. Statistical analysis was performed using a paired Student's t-test. Results: C. jejuni was cultured from stool samples up to 8 days post infection. At PI day 3, inflammatory markers (fold change in expression IL4 (3.01 ± 0.66; p<0.02), IFNγ (4.66 ± 0.64; p<0.02), TNFα (4.35 ± 0.87; p<0.02), MCP1 (3.78 ± 0.91; p<0.03), IL1b (3.18 ± 0.66; p<0.03), IL10 (3.14 ± 0.61; p<0.01) and IL6 (3.48 ± 0.75; p<0.02)) were increased in the jejunum of infected mice compared to controls. TGFβ, IL9 and IL17a and IL17f were unaffected. At PI day 10, all inflammatory markers in jejunum and MLN returned to normal. CRD in control balb/c resulted in a volume dependent increase in visceromotor response (0.02 ml 1.79±1.78; 0.04 ml 2.25±0.29; 0.06 ml 4.3±0.93; 0.08 ml 4.21±0.57; 0.1 ml 2.81±0.53 spikes per second). After infection, the pain response to CRD was increased (0.02 ml 0.4±0.36; 0.04 ml 4.31±1.30; 0.06 ml 12.95±1.72; 0.08 ml 29.53±5.94; 0.1 ml 38.45±3.91 spikes per second) compared to control animals. Seven out of 10 PI mice showed an increased pain response (threshold for hypersensitivity: 5 spikes/second at 0.1 ml) to colorectal distention . Conclusion: C. jejuni induced a weak and transient infection in balb/ c mice resulting in post infectious visceral hypersensitivity in 7 out of 10 animals at 3 weeks PI. These results demonstrate that C. jejuni infection in balb/c mice may be a useful model to unravel the mechanisms underlying bacterial PI-IBS.
Sa2022 Neuronal 5-HT is Anti-Inflammatory and Critical for GI Motility Kara G. Margolis, Korey D. Stevanovic, Zhishan Li, Ross Mazo, Alexander Diacou, Michael D. Gershon The luminal microbiome constitutively presents the bowel with a threat of invasion. The gut thus requires robust mechanisms maintain its integrity and prevent bacterial translocation. The gut contains most of the body's serotonin (5-HT), a versatile molecule that can act as a hormone, paracrine messenger, or neurotransmitter. 5-HT release from enterochromaffin (EC) cells initiates peristaltic and secretory reflexes, whereas synaptic release of 5-HT from enteric neurons mediates fast and slow excitatory transmission. The rate-limiting enzyme in 5-HT biosynthesis in EC cells is tryptophan hydroxylase 1 (TPH1), while in neurons it is TPH2. 5-HT is inactivated primarily by uptake, which in both enterocytes and neurons, is mediated by the serotonin transporter (SERT). Deletion of TPH1 selectively depletes 5HT from EC cells, while knockout of TPH2 depletes 5-HT from neurons. In contrast, knockout of SERT potentiates the actions of 5-HT in both the mucosa and the enteric nervous system (ENS). SERT KO increases the severity of inflammation associated with the knockout of IL-10 and that induced by TNBS or DSS. TPH1 KO exerts an opposite effect and decreases the severity of colitis induced either with TNBS or DSS. These observations are compatible with the idea that mucosal 5-HT is pro-inflammatory. Because neuronal 5HT is neuroprotective and important in propulsion, we postulated that neuronal 5-Ht protects the gut from inflammation. We tested this hypothesis in TPH2 KO mice, which lack neuronal 5-HT, but have normal levels of mucosal 5-HT. Colitis was induced with TNBS in 6-8 week
Sa2020 The Serotonin Precursor 5-Hydroxytryptophan Reinforces Intestinal Barrier Function Daniel Keszthelyi, Freddy Troost, Hans van Eijk, Esther Schaepkens, Patrick J. Lindsey, Daisy Jonkers, Wim A. Buurman, Jan Dekker, Ad Masclee Introduction: Tight junctions between intestinal epithelial cells form a selective barrier that contributes to gut homeostasis. Alterations in intestinal barrier function are considered to be early factors in the pathogenesis of gastrointestinal disorders such as irritable bowel
AGA Abstracts
S-370
syndrome (IBS). Changes in serotonergic metabolism have also been associated with IBS. The direct precursor of 5-HT, 5-hydroxytryptophan (5-HTP), is available as over-the-counter dietary supplement and is a potential substance to influence serotonin availability and possibly also intestinal barrier function. Aim: To assess the effect of an oral bolus of 5-HTP in comparison to placebo on intestinal barrier function and mucosal 5-HT metabolism. Methods: 15 healthy volunteers (7 male; 30±3 yrs) participated in this randomized doubleblind placebo-controlled crossover study. Intestinal permeability was measured by determining the plasma recovery of an orally ingested multi-sugar drink (lactulose, rhamnose, sucrose, sucralose, erythritol) on two separate occasions. Plasma samples were taken prior to, at 60, 90 and 120 min after intake of 100 mg 5-HTP or placebo. At the end of each of both test days, a gastroduodenoscopy was performed to obtain mucosal samples from the duodenum. Plasma concentrations of the sugars and mucosal concentrations of 5-HTP, 5-HT and 5hydroxyindoleacetic acid (5-HIAA, the main metabolite of 5-HT) were determined by HPLCMS. In mucosal samples, the expression of tight junction proteins occludin and ZO-1 was analyzed by qPCR and immunohistochemistry. Data are expressed as mean ± SEM. Results: Intestinal permeability as defined by the plasma recovery ratios of lactulose/rhamnose (L/ R) and sucralose/erythritol (S/E) was significantly reduced after 5-HTP (L/R 0.005±0.002 vs 0.006±0.002, p<0.05, S/E 0.004±0.001 vs 0.005±0.001, p<0.05; 5-HTP vs placebo). The mRNA expression of ZO-1 was significantly increased after 5-HTP (normalized expression ratios 1.27±0.24 vs 0.87±0.12; p<0.05), whereas the expression of occludin was not altered by 5-HTP. Immunohistochemical staining for the ZO-1 and occludin proteins showed that the proteins were located significantly closer to each other after 5-HTP. Administration of 5-HTP significantly increased mucosal 5-HTP levels (12.7±9.1 vs 1.6±1.5 pmol/mg; p= 0.001), but did not affect 5-HT levels (57±21 vs 47±18 pmol/mg; p=0.68), while 5-HIAA levels increased significantly (7.1±1.7 vs 2.5±0.7 pmol/mg; p<0.05). Conclusion: Oral administration of 5-HTP reinforces small intestinal barrier function by lowering intestinal sugar permeability, inducing the expression of the tight junction protein ZO-1 and rearranging tight junction proteins. These changes are associated with 5-HTP-induced alterations in mucosal serotonin metabolism. These data point to a role for serotonergic metabolism in reinforcing intestinal barrier function.
AGA Abstracts
Sa2018 Immunohistochemical Study Evaluating the Vagal Innervation of Intestinal Resident Macrophages Cathy Cailotto, Pedro J. Gomez Pinilla, Jan van der Vliet, Gianluca Matteoli, Guy E. Boeckxstaens BACKGROUND: The vagal cholinergic anti-inflammatory pathway inhibits cytokine release and prevents tissue injury in several inflammatory disorders. We previously demonstrated that electrical stimulation of the vagus nerve suppresses intestinal inflammation and normalizes gut motility in a mouse model of postoperative ileus. However, it is unclear whether the vagus nerve makes direct contact with intestinal resident macrophages or rather indirectly via enteric neurons. In the present study, we therefore analyzed the anatomical relationship between the vagal preganglionic/enteric postganglionic nerve fibers and resident macrophages within the small intestine. METHODS: Anterograde labeling of motor neurons in the dorsal motor nucleus of the vagus (DMV) was achieved by stereotactic injection of biotin-conjugated dextran amine (5%) in the DMV. 19 days after injection, brainstem sections were processed with DAB staining to check the exact localization of the injection site. Vagal nerve fibers were stained in cross sections and intestinal whole mounts using DAB-Nickel staining and were double stained with DAB and cuprolinic blue to evaluate the anatomical contact between enteric neurons and macrophages, respectively. Immunofluorescent labeling for neurofilaments (PGP 9.5), Tyrosine Hydroxylase (TH), Choline Acetyltransferase (ChAT), Vasoactive Intestinal Peptide (VIP), neural Nitric Oxide synthase (nNOS), substance P (SP) and Calcitonin Gene-Related Peptide (CGRP) was performed to identify the neurochemical phenotype of the vagal efferent fibers and the enteric neurons. F4/80 antibody was used to label resident macrophages. RESULTS: Biotin-labeled vagal nerve fibers were identified in the myenteric plexus, but not the submucosal plexus. These vagal preganglionic fibers were cholinergic (ChAT-positive) in nature and negative for TH, VIP, SP, nNOS or CGRP. Vagal nerve fibers were noted in close association with ChAT positive myenteric neurons. A dense network of F4/80-positive macrophages was identified between the circular and longitudinal smooth muscle layers with some macrophages surrounding myenteric ganglia. Vagal nerve fibers only sporadically came in close contact with macrophages. CONCLUSION: In the present study, we demonstrate that there is no close anatomical association between vagal preganglionic fibers and resident macrophages of the intestinal muscularis. Instead, the vagus nerve synapses with cholinergic myenteric neurons suggesting an amplification of the vagal signal through the enteric neuronal network.
Sa2021 Pathogen and Probiotic Bacteria Differentially Stimulate Nitric Oxide Production and S100B Protein Expression in Human Enteroglial Cells Fabio Turco, Giovanni Sarnelli, Carla Cirillo, Annamaria Mango, Alessandra D'Alessandro, Ilaria Palumbo, Rosario Cuomo Background and Aim: Enteric glial cells (EGCs) are involved in intestinal homeostasis and may contribute to regulate host-bacteria interaction. Astrocytes, the equivalent of enteroglial cells (EGCs) in Central Nervous System respond to bacteria releasing nitric oxide (NO), whether this does occur bacterial-EGCs interaction is yet not known. We aimed to investigate whether human EGC generate NO in response to pathogen and probiotic bacteria and whether thi is associated with S100B overexpression. Methods: Human EGCs were obtained according to a method previously described by our group. Briefly, myenteric plexus preparations were isolated from ileum of patients undergoing surgery and enzimatically dissociated. Ganglia were plated and cell cultures were grown to subconfluence. After 21 days, EGCs were purified by incubation with the anti-Thy-1.1 ab-coated magnetic beads and separated using a Dynal Magnet®. EGC were then incubated for 24 hours with the probiotic strain Lactobacillus Paracasei F19 (LP F19) and the pathogen Enteroinvasive Escherichia coli (EIEC). Two different bacteria/cells ratios were used (0.1/1 and 10/1, respectively). Nitrite assay and Western Blot analysis were respectively used to evaluate NO release and S100B expression in stimulated cells and compared to unstimulated cells, that served as controls. Data are expressed as mean±SD of 3 independent experiments. Results: Glial derived S100B protein expression was significantly higher in response to EIEC than to LP F19 (+2.9±0.2 and +0.9±0.3 fold increase vs control; p<0.05). EIEC induced a significantly higher NO release than LP F19 both at a 0.1/1 (17.7±0.7 vs 4.0±0.1 nmol x 10^6 cells; p<0.001) and at 10/ 1 ratio (20.7±2.1 vs 9.0±0.1 nmol x 10^6 cells; p<0.001). When compared to control conditions (3.7±0.1 nmol x 10^6 cells), EIEC and only high concentration of LP F19 induced a significant increase of nitric oxide release (all p<0.001). Conclusion: We show that enteroglial cells are able to release nitric oxide when challenged with bacteria and, that this is likely dependent on the different expression of S100B protein. As EGCs-released nitric oxide was different between pathogen and probiotic bacteria we suggest that human EGCs likely participate to host-bacteria interaction via a different NO release.
Sa2019 Validation of a Post-Infectious IBS Mouse Model Using Campylobacter Jejuni Mira M. Wouters, Nadine Kotman, Kathleen Lambaerts, Caroline L. Van Heijningen, Guy E. Boeckxstaens Background and Aim: Post-infectious irritable bowel syndrome (PI-IBS) occurs in 10 to 30% of patients who suffered from bacterial gastroenteritis. Insight in the underlying pathophysiological mechanisms of PI-IBS is however mainly based on studies using rodents infected with parasites or helminths. These infections trigger a different immune response compared to bacterial infections potentially leading to different pathophysiological mechanisms. Therefore, we developed a PI-IBS mouse model using C. jejuni to study the mechanisms underlying PI-IBS. Methods: Six weeks old balb/c were orally gavaged with 5x10E10 CFU Campylobacter jejuni. To study the inflammatory response, mice were killed at PI day 3 and 10. Quantitative PCR for inflammatory markers was performed on total RNA (RNeasy; Qiagen, reverse transcriptase using QuantaScript; Quanta) from jejunum, colon and mesenteric lymph nodes (MLN). To evaluate visceral pain, electrodes (Nichrome 80, Pelican Wire) were implanted in the abdominal muscularis and EMG was recorded. Colorectal distention (CRD) was performed by inflating a Fogarty probe 4.0 (0.02-0.1 ml) at 3 weeks post infection. EMG spikes were analyzed with Spike2. Statistical analysis was performed using a paired Student's t-test. Results: C. jejuni was cultured from stool samples up to 8 days post infection. At PI day 3, inflammatory markers (fold change in expression IL4 (3.01 ± 0.66; p<0.02), IFNγ (4.66 ± 0.64; p<0.02), TNFα (4.35 ± 0.87; p<0.02), MCP1 (3.78 ± 0.91; p<0.03), IL1b (3.18 ± 0.66; p<0.03), IL10 (3.14 ± 0.61; p<0.01) and IL6 (3.48 ± 0.75; p<0.02)) were increased in the jejunum of infected mice compared to controls. TGFβ, IL9 and IL17a and IL17f were unaffected. At PI day 10, all inflammatory markers in jejunum and MLN returned to normal. CRD in control balb/c resulted in a volume dependent increase in visceromotor response (0.02 ml 1.79±1.78; 0.04 ml 2.25±0.29; 0.06 ml 4.3±0.93; 0.08 ml 4.21±0.57; 0.1 ml 2.81±0.53 spikes per second). After infection, the pain response to CRD was increased (0.02 ml 0.4±0.36; 0.04 ml 4.31±1.30; 0.06 ml 12.95±1.72; 0.08 ml 29.53±5.94; 0.1 ml 38.45±3.91 spikes per second) compared to control animals. Seven out of 10 PI mice showed an increased pain response (threshold for hypersensitivity: 5 spikes/second at 0.1 ml) to colorectal distention . Conclusion: C. jejuni induced a weak and transient infection in balb/ c mice resulting in post infectious visceral hypersensitivity in 7 out of 10 animals at 3 weeks PI. These results demonstrate that C. jejuni infection in balb/c mice may be a useful model to unravel the mechanisms underlying bacterial PI-IBS.
Sa2022 Neuronal 5-HT is Anti-Inflammatory and Critical for GI Motility Kara G. Margolis, Korey D. Stevanovic, Zhishan Li, Ross Mazo, Alexander Diacou, Michael D. Gershon The luminal microbiome constitutively presents the bowel with a threat of invasion. The gut thus requires robust mechanisms maintain its integrity and prevent bacterial translocation. The gut contains most of the body's serotonin (5-HT), a versatile molecule that can act as a hormone, paracrine messenger, or neurotransmitter. 5-HT release from enterochromaffin (EC) cells initiates peristaltic and secretory reflexes, whereas synaptic release of 5-HT from enteric neurons mediates fast and slow excitatory transmission. The rate-limiting enzyme in 5-HT biosynthesis in EC cells is tryptophan hydroxylase 1 (TPH1), while in neurons it is TPH2. 5-HT is inactivated primarily by uptake, which in both enterocytes and neurons, is mediated by the serotonin transporter (SERT). Deletion of TPH1 selectively depletes 5HT from EC cells, while knockout of TPH2 depletes 5-HT from neurons. In contrast, knockout of SERT potentiates the actions of 5-HT in both the mucosa and the enteric nervous system (ENS). SERT KO increases the severity of inflammation associated with the knockout of IL-10 and that induced by TNBS or DSS. TPH1 KO exerts an opposite effect and decreases the severity of colitis induced either with TNBS or DSS. These observations are compatible with the idea that mucosal 5-HT is pro-inflammatory. Because neuronal 5HT is neuroprotective and important in propulsion, we postulated that neuronal 5-Ht protects the gut from inflammation. We tested this hypothesis in TPH2 KO mice, which lack neuronal 5-HT, but have normal levels of mucosal 5-HT. Colitis was induced with TNBS in 6-8 week
Sa2020 The Serotonin Precursor 5-Hydroxytryptophan Reinforces Intestinal Barrier Function Daniel Keszthelyi, Freddy Troost, Hans van Eijk, Esther Schaepkens, Patrick J. Lindsey, Daisy Jonkers, Wim A. Buurman, Jan Dekker, Ad Masclee Introduction: Tight junctions between intestinal epithelial cells form a selective barrier that contributes to gut homeostasis. Alterations in intestinal barrier function are considered to be early factors in the pathogenesis of gastrointestinal disorders such as irritable bowel
AGA Abstracts
S-370