Serotonin Secretion Research Articles

Irritable Bowel Syndrome - current state of knowledge

Introduction and objective: Irritable bowel syndrome (IBS) is a common gastroenterological disorder affecting 9% to 23% of the population worldwide. The disease causes recurrent abdominal pain and abnormal bowel movements without visible anatomical or biochemical changes and diagnosis is often difficult. The purpose of this paper is to analyze the current knowledge of the pathophysiology, risk factors, diagnosis and treatment of IBS. Review methods: The literature available in the PubMed database was reviewed using the following key words: "irritable bowel syndrome," "constipation," "diarrhea", "abdominal pain", "diagnostics", "treatment". 49 articles were included in the review and 80% were from 2016-2024. Current state of knowledge: The pathophysiology of IBS is not fully understood, but it is recognized that the disease is a disorder of the gut-brain axis. It can lead to abnormal secretion of serotonin and dopamine, which affects symptoms. The diagnosis of IBS is based on the Rome IV Criteria, defining the characteristics and severity of symptoms. Summary: IBS is a disorder that significantly affects quality of life. Diagnosis is based on the exclusion of organic diseases and meeting certain criteria. Treatment includes both dietary modification and pharmacotherapy aimed at relieving symptoms. Despite advances in research, the pathophysiology of IBS is still not fully understood, making it difficult to develop effective treatments.

Assessment of Urinary Dopamine and Serotonin Metabolites in Relation to Dysbiosis Indicators in Patients with Functional Constipation.

The causes of functional constipation (FC) in adults are unclear, but changes in the gut microbiome may play an important role. The present study aimed to assess the relationship between urinary metabolites of dopamine and serotonin and some dysbiosis indicators in patients with FC. The study included 40 healthy women and 40 women with FC aged 21-46 years. Urinary levels of homovanillic acid (HVA), 5-hydoxyindoleacetic acid (5-HIAA), p-hydroxyphenylacetic acid (PhAc), and 3-indoxyl sulfate, as final metabolites of dopamine, serotonin, and indole pathway, respectively, were determined using the LC-Ms/Ms method. However, hydrogen-methane and ammonia breath tests were performed. The GA-map Dysbiosis Test was used to identify and characterize the dysbiosis index (DI). In patients with FC, the DI was significantly higher than in the control group: 4.05 ± 0.53 vs. 1.52 ± 0.81 points (p < 0.001), but the number of many types of bacteria varied among individuals. The levels of HVA were higher, while 5-HIAA levels were lower in patients. Moreover, the HVA/5-HIAA ratio had a positive correlation with DI as well as with the severity of symptoms. In patients with functional constipation, the balance in dopamine and serotonin secretion is disturbed, which is associated with changes in the gut microbiome.

Telotristat ethyl, a tryptophan hydroxylase inhibitor, enhances antitumor efficacy of standard chemotherapy in preclinical cholangiocarcinoma models.

Cholangiocarcinoma (CCA), an aggressive biliary tract cancer, carries a grim prognosis with a 5-year survival rate of 5%-15%. Standard chemotherapy regimens for CCA, gemcitabine plus cisplatin (GemCis) or its recently approved combination with durvalumab demonstrate dismal clinical activity, yielding a median survival of 12-14 months. Increased serotonin accumulation and secretion have been implicated in the oncogenic activity of CCA. This study investigated the therapeutic efficacy of telotristat ethyl (TE), a tryptophan hydroxylase inhibitor blocking serotonin biosynthesis, in combination with standard chemotherapies in preclinical CCA models. Nab-paclitaxel (NPT) significantly enhanced animal survival (60%), surpassing the marginal effects of TE (11%) or GemCis (9%) in peritoneal dissemination xenografts. Combining TE with GemCis (26%) or NPT (68%) further increased survival rates. In intrahepatic (iCCA), distal (dCCA) and perihilar (pCCA) subcutaneous xenografts, TE exhibited substantial tumour growth inhibition (41%-53%) compared to NPT (56%-69%) or GemCis (37%-58%). The combination of TE with chemotherapy demonstrated enhanced tumour growth inhibition in all three cell-derived xenografts (67%-90%). PDX studies revealed TE's marked inhibition of tumour growth (40%-73%) compared to GemCis (80%-86%) or NPT (57%-76%). Again, combining TE with chemotherapy exhibited an additive effect. Tumour cell proliferation reduction aligned with tumour growth inhibition in all CDX and PDX tumours. Furthermore, TE treatment consistently decreased serotonin levels in all tumours under all therapeutic conditions. This investigation decisively demonstrated the antitumor efficacy of TE across a spectrum of CCA preclinical models, suggesting that combination therapies involving TE, particularly for patients exhibiting serotonin overexpression, hold the promise of improving clinical CCA therapy.

Role of the circadian nuclear receptor REV-ERBα in dorsal raphe serotonin synthesis in mood regulation

Affective disorders are frequently associated with disrupted circadian rhythms. The existence of rhythmic secretion of central serotonin (5-hydroxytryptamine, 5-HT) pattern has been reported; however, the functional mechanism underlying the circadian control of 5-HTergic mood regulation remains largely unknown. Here, we investigate the role of the circadian nuclear receptor REV-ERBα in regulating tryptophan hydroxylase 2 (Tph2), the rate-limiting enzyme of 5-HT synthesis. We demonstrate that the REV-ERBα expressed in dorsal raphe (DR) 5-HTergic neurons functionally competes with PET-1—a nuclear activator crucial for 5-HTergic neuron development. In mice, genetic ablation of DR 5-HTergic REV-ERBα increases Tph2 expression, leading to elevated DR 5-HT levels and reduced depression-like behaviors at dusk. Further, pharmacological manipulation of the mice DR REV-ERBα activity increases DR 5-HT levels and affects despair-related behaviors. Our findings provide valuable insights into the molecular and cellular link between the circadian rhythm and the mood-controlling DR 5-HTergic systems.

Pengaruh Pemberian Baby Massage Lavender Essential Oil terhadap Peningkatan Kualitas Tidur pada Bayi Usia 3-12 Bulan

Background : poor sleep quality in babies will result in decreased immunity, impaired growth and physical development, and have an impact on the growth and development of the baby's brain. 1 year of age is a golden period for brain development. Baby Massage is a type of stimulation that will stimulate the development of the structure and function of cells in the brain. The improvement in the quality of baby's sleep during baby massage is due to an increase in the levels of serotonin secretion produced during massage. Apart from the Baby Massage method, adding Lavender Essential Oil also has an effect on improving the quality of baby's sleep because essential oil can influence brain function activities through the nervous system which is related to the sense of smell. Lavender contains esters which can calm and have a direct effect on the nervous system. Objective: to determine the effect of giving Baby Massage lavender essential oil on improving the sleep quality of babies aged 3-12. Method: Pre-Experiment with One Group Pretest Posttest design. Sample of 30 respondents. Respondents were given a massage once and then evaluated after 24 hours. Data analysis used the Wilcoxon test. Results: The quality of sleep before being given Baby Massage Lavender Essential was that all 30 respondents had poor sleep quality. The majority of sleep quality after being given Baby Massage Lavender Essential was good, namely 27 respondents (90%). The statistical test obtained a p-value of 0.000, &lt;0.05. Conclusion: There is an effect of giving Baby Massage lavender essential oil on improving the sleep quality of babies aged 3-12.

Morphine-Driven m6A Epitranscriptomic Neuroadaptations in Primary Cortical Cultures.

Opioid overdose is the leading cause of accidental death in the United States and remains a major public health concern, despite significant resources aimed at combating opioid misuse. Neurobiological research to elucidate molecular and cellular consequences of opioid exposure is required to define avenues to explore for reversal of opioid-induced neuroadaptations. Opioids impart well-documented regulation of the transcriptome and epigenetic modifications in the brain, but opioid-induced epitranscriptomic posttranscriptional regulation of RNA is vastly understudied. N6-methyladenosine (m6A) RNA methylation is significantly enriched in the brain and involved in learning, memory, and reward. m6A modifications have not been studied in opioid use disorder, despite being the most common RNA modification. We detected significant regulation of m6A-modifying enzymes in rat primary cortical cultures following morphine treatment, including AlkB Homolog 5 (Alkbh5). The m6a demethylaseALKBH5 functions as an m6A eraser, removing m6A modifications from mRNA. We hypothesized that chronic opioid treatment regulates m6A modifications through modulation of Alkbh5 and profiled m6A modifications in primary cortical cultures following chronic morphine treatment and Alkbh5 knock-down. We observed differential regulation of m6A modifications for a common set of transcripts following morphine or Alkbh5 knock-down, and the two treatments elicited concordant m6A epitranscriptomic profiles, suggesting that a subset of morphine-driven m6A modifications may be mediated through downregulation of Alkbh5 in cortical cultures. Gene Ontology terms of commonly regulated transcripts included serotonin secretion, synapse disassembly, neuron remodeling, and immune response. Thus, we conclude that morphine can drive epitranscriptomic changes, a subset of which may occur in an Alkbh5-dependent manner.

Purinergic Signaling Drives Multiple Aspects of Rotavirus Pathophysiology

Background: Rotavirus causes life-threatening diarrhea in children, resulting in ~200,000 deaths each year. Rotavirus infects a limited number of cells at the tips of the villi in the small intestine; however, rotavirus is known to dysregulate cells distant from the site of infection through paracrine signaling. We recently identified that rotavirus infected cells release the purinergic signaling molecule ADP, which binds to the P2Y1 receptor on nearby uninfected cells; causing a signaling cascade that affects distant uninfected cells. In vitro P2Y1 was found to contribute to chloride and serotonin secretion; suggesting P2Y1 may activate pathways responsible for diarrhea. Hypothesis: We hypothesize that P2Y1 orchestrates cell-cell communication involved in diarrhea and infection severity. Methods: To elucidate the role of purinergic signaling via P2Y1 receptors during rotavirus infection, we used the mouse-like rotavirus (rD6/2) to investigate the effects of purinergic signaling in the context of homologous murine rotavirus infection in vivo. C57Black6 mouse pups were orally gavaged rD6/2 rotavirus at day 4-6 of age and assessed over the course of 5 days. Beginning at day 1 post infection, infected pups were treated daily by oral gavage with saline or 4mg/kg MRS2500, a P2Y1-selective, competitive antagonist. Stool was collected and scored for diarrhea daily prior to each treatment. Pups were euthanized and small intestine tissue was collected at 3- and 5-days post infection for immunostaining, qRT-PCR and luminal contents. Intestinal organoids derived from Balb/C pup jejunum were inoculated with rD6/2 rotavirus, followed by supplementation with vehicle or MRS2500 to assess fluid secretion by organoid swelling over time. Results: Rotavirus-infected pups exhibited significant diarrhea incidence and high diarrhea scores on days 2, 3, and 4 post infection. Treatment of rotavirus-infected mouse pups with MRS2500 resulted in decreased severity and incidence of diarrhea compared to vehicle treated controls. This was consistent with in vitro, rD6/2-infected organoids exhibiting a significant increase in organoid swelling compared to uninfected organoids, which was significantly prevented by inhibition of P2Y1 signaling. Viral stool shedding from MRS2500 treated pups was significantly lower than saline-treated pups starting at day 4 post infection, which suggests P2Y1 signaling may amplify rotavirus replication in vivo. Finally, transmission experiments in litters with infected (but not treated) and pretreated MRS2500 uninfected pups show a decreased incidence in diarrhea suggesting that P2Y1 inhibition has a potential protective role in reducing the effects of transmission. Conclusion: Collectively these findings establish a conserved role of purinergic signaling in the pathophysiology of rotavirus infection. Additionally, our data indicates P2Y1 as a new candidate for host-targeted therapeutics that could have both antiviral and antidiarrheal effects against rotavirus pathophysiology. R01 DK115507 (Hyser) R01 AI158683 (Hyser)APS Postdoctoral Fellowship (Engevik) F32 DK130288 (Engevik). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Mucus-coated, magnetically-propelled fecal surrogate to mimic fecal shear forces on colonic epithelium

The relationship between the mechanical forces associated with bowel movement and colonic mucosal physiology is understudied. This is partly due to the limited availability of physiologically relevant fecal models that can exert these mechanical stimuli in in vitro colon models in a simple-to-implement manner. In this report, we created a mucus-coated fecal surrogate that was magnetically propelled to produce a controllable sweeping mechanical stimulation on primary intestinal epithelial cell monolayers. The mucus layer was derived from purified porcine stomach mucins, which were first modified with reactive vinyl sulfone (VS) groups followed by reaction with a thiol crosslinker (PEG-4SH) via a Michael addition click reaction. Formation of mucus hydrogel network was achieved at the optimal mixing ratio at 2.5 % w/v mucin-VS and 0.5 % w/v PEG-4SH. The artificial mucus layer possessed similar properties as the native mucus in terms of its storage modulus (66 Pa) and barrier function (resistance to penetration by 1-μm microbeads). This soft, but mechanically resilient mucus layer was covalently linked to a stiff fecal hydrogel surrogate (based on agarose and magnetic particles, with a storage modulus of 4600 Pa). The covalent bonding between the mucus and agarose ensured its stability in the subsequent fecal sliding movement when tested at travel distances as long as 203 m. The mucus layer served as a lubricant and protected epithelial cells from the moving fecal surrogate over a 1 h time without cell damage. To demonstrate its utility, this mucus-coated fecal surrogate was used to mechanically stimulate a fully differentiated, in vitro primary colon epithelium, and the physiological stimulated response of mucin-2 (MUC2), interleukin-8 (IL-8) and serotonin (5HT) secretion was quantified. Compared with a static control, mechanical stimulation caused a significant increase in MUC2 secretion into luminal compartment (6.4 × ), a small but significant increase in IL-8 secretion (2.5 × and 3.5 × , at both luminal and basal compartments, respectively), and no detectable alteration in 5HT secretion. This mucus-coated fecal surrogate is expected to be useful in in vitro colon organ-on-chips and microphysiological systems to facilitate the investigation of feces-induced mechanical stimulation on intestinal physiology and pathology.

Contrary effects of the gut metabolites deoxycholate and butyrate on the acetylcholine-evoked calcium response in an enteroendocrine cell model

The interaction of nutrients and bacterial-derived products and their enteroendocrine effects are still enigmatic. We used the human enteroendocrine tumour cell line P-STS isolated from the terminal ileum as cellular sentinel. In this model, P-STS cells react to acetylcholine or histamine with an increase in intracellular calcium mediated by T-type voltage-gated calcium channels followed by serotonin secretion. Incubation with the secondary bile acid deoxycholate inhibited the calcium response to acetylcholine but not to histamine. No response to other nutrients or bacterial products tested (i.e. palmitate, lactate, acetate, proprionate, butyrate, the OR51E1 ligand isovalerate and the HCA2 ligand β-hydroxybutyrate) could be observed. The bile acid receptor TGR5 agonist CCDC did not inhibit the acetylcholine-induced calcium response, and the free fatty acid receptor 2 agonist 4-CMTB had no enhancing effect on the calcium response to acetylcholine. Only butyrate had an enhancing effect on the calcium response in P-STS cells when added for short-time pre-incubation before challenge with acetylcholine. From our data we propose i) an inhibitory effect of deoxycholate at the muscarinic acetylcholine receptor M3 without involvement of TGR5, and that ii) high butyrate concentrations derived from bacterial metabolism of carbohydrates might increase intestinal release of serotonin and potentially also other gut hormones and satiety-inducing peptides independently of known butyrate receptors, thereby influencing intestinal motility and ion secretion.

Epidemiological, Clinical and Biological Hemogram Features in a Cohort of Neuroendocrine Tumor Patients.

We conducted a retrospective study based on 55 patients diagnosed with gastroenteropancreatic neuroendocrine tumors (GEP-NETs)-gastric (G-NET), small bowel (SB-NET) and colonic (C-NET), hospitalized and evaluated within the Surgical, Gastroenterology and Internal Medicine Clinics, in The Clinical Emergency County Hospital Craiova, between May 2016 and April 2024. We aimed in this study to analyze the epidemiological aspects and clinical characteristics of patients with GEP-NETs. In our study group, the patients' ages were between 39-82 years, with a mean of 66.40 (±12.46) years. The incidence of GEP-NETs cases in young patients was insignificant low-1 case. 45.46% of all patients lived in urban areas. 16.36% were G-NET, 14,54 were SB-NET and 69.09% were C-NET. The GEP-NETs diagnosis was established by immunohistochemistry features. Also, we observed that the most frequency localization was on the ascending colon, while the rarest on the colon it is located on the transverse colon and the rarest is on the small bowel, in spite of the generally literature data. From the C-NET group, 49.09% have been presented arterial hypertension probable explained by serotonin and dopamine secretion an inflammatory through phenotype expression and just one patient has been presented an erythematous psoriasis, which could be also explained by the same neurotransmitter's involvement as a possible purposed mechanism. The results obtained in our study demonstrate that could be a common profile of GEP-NETs patients through epidemiological general information and clinical characteristics. Also, we demonstrate that, in the last years, the incidence increased for the GEP-NETs.

Biochemical Properties and Antithrombotic Effect of a Serine Protease Isolated from the Medicinal Mushroom Pycnoporus coccineus (Agaricomycetes).

The purification of a fibrinolytic enzyme from the fruiting bodies of wild-growing medicinal mushroom, Pycnoporus coccineus was achieved through a two-step procedure, resulting in its homogeneity. This purification process yielded a significant 4.13-fold increase in specific activity and an 8.0% recovery rate. The molecular weight of P. coccineus fibrinolytic enzyme (PCFE) was estimated to be 23 kDa using sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. PCFE demonstrated its optimal activity at a temperature of 40 °C and pH 8. Notably, the enzymatic activity was inhibited by the presence of zinc or copper metal ions, as well as serine protease inhibitors, such as phenylmethylsulfonyl fluoride and 4-amidinophenylmethanesulfonyl fluoride. PCFE exhibited remarkable specificity towards a synthetic chromogenic substrate for thrombin. The enzyme demonstrated the Michaelis-Menten constant (Km), maximal velocity (V ), and catalytic rate constant (Kcat) values of 3.01 mM, 0.33 mM min-1 μg-1, and 764.1 s-1, respectively. In vitro assays showed PCFE's ability to effectively degrade fibrin and blood clots. The enzyme induced alterations in the density and structural characteristics of fibrin clots. PCFE exhibited significant effects on various clotting parameters, including recalcification time, activated partial thromboplastin time, prothrombin time, serotonin secretion from thrombin-activated platelets, and thrombin-induced acute thromboembolism. These findings suggest that P. coccineus holds potential as an antithrombotic biomaterials and resources for cardiovascular research.

Rapid electrochemical detection of L-lactate in Baijiu affecting serotonin and dopamine secretion in mice.

Baijiu, a traditional Chinese alcoholic beverage, carries China's rich historical and cultural heritage. Consumers experience varying levels of relaxation and pleasure after consuming different types of Baijiu, with the biological basis of delectation influenced by serotonin and dopamine. In this study, we prepared carbon fiber electrodes modified with surface decorated gold nanoparticles to directly measure the electrochemical response signals in the serum of mice before and after gavage with different types of Baijiu. It was observed that the serum signal change in mice after consuming Baijiu sample 1 (J1) was higher than that of the other two types of Baijiu. Consequently, trace flavor compounds in the Baijiu samples were detected using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS), revealing the highest content of L-lactic acid in J1. Mice were intraperitoneally injected with 200 mg kg-1 of L-lactic acid. The changes in dopamine and serotonin in the serum of the injected mice were monitored using a biosensor, and the results were compared with the results of high performance liquid chromatography-triple quadrupole mass spectrometry (HPLC-MS). The findings confirmed that L-lactic acid could indeed stimulate the secretion of both neurotransmitters in mice, suggesting that the trace components in J1 may even exhibit synergistic effects. This study contributes to a deeper understanding of the effects of Baijiu on the body and provides a scientific basis for the production and consumption of Baijiu.

Shatianyu (Citrus grandis L. Osbeck) whole fruit alleviated loperamide-induced constipation via enhancing gut microbiota-mediated intestinal serotonin secretion and mucosal barrier homeostasis.

This study aims to explore the effects of Shatianyu (Citrus grandis L. Osbeck) whole fruit powder (SWFP) enriched in flavonoids and dietary fiber on loperamide-induced constipation after a 4-week administration in the diet, together with possible microbiota-mediated mechanisms. The SWFP intervention shortened the first defecation time and increased defecation frequency; it also increased the serum serotonin (5-HT) level and decreased the LPS level in constipation mice. SWFP promoted the development of colonic enterochromaffin cells (ECs) and upregulated the expression of 5-HT synthetic rate-limiting enzyme (Tph1) in ECs. Furthermore, SWFP downregulated the expression of colonic TLR-4, TNF-α and IL-1β and upregulated the expression of tight junction proteins. Besides promoting 5-HT secretion in ECs, butyrate was proved to play a positive role in enhancing intestinal barrier homeostasis through FFAR2/3. Notably, SWFP increased both the fecal butyrate contents and colonic FFAR3 expression in a dose-related manner. Likewise, SWFP enriched butyrate-production related microbes, such as Ruminococcus_torques_group, Ruminococcus, Dubosiella and Parasutterella. Thus, SWFP might alleviate constipation by regulating the microbiota to produce butyrate, thereby enhancing colonic 5-HT secretion and the FFAR3-mediated anti-inflammatory pathway.

Molecular Dynamics Simulation of Serotonin Transport Protein Complex with 6-Hydroxy-1-Methyl-1,2,3,4-Tetrahydro-β-Carboline Ligand from Chocolate (Theobroma cacao L.) Isolate

6-hydroxy-1-methyl1,2,3,4-tetrahydro-β-carboline (6OHMTHβC) is a chocolate derivate that has antidepressant potency. It can increase dopamine and serotonin secretion, which leads to mood improvement. This method was carried out using computational molecular docking simulations (in silico). The research design was computational-based exploratory descriptive. The results of molecular docking showed the lowest energy score and the backbone RMSD value ≤2Å. The procedure performed was 6AWP receptor docking without ligand, with native ligand (6OHMTHβC), and with reference ligand (fluvoxamine). This study also performed molecular docking simulations of 6OHMTHβC towards 6AWP to find compounds in the receptor binding pocket. This study also performed dynamics simulations and identified the molecular determinants using PyPLIF-HIPPOS and YASARA Structure software 20.1.24.10 with the Windows 10 operating system. This study succeeded in determining the stability of the dynamics simulation of the serotonin transport protein complex with the reference ligand 6OHMTHβC for 50 ns, and this result corresponds to the RMSD value and binding energy. The determination of binding energy (BE) was calculated from the BE calculation available at YASARA and Ubuntu. The binding energy value of the original ligand was -11.6590 kJ/mol, and the reference ligand was -83880 kJ/mol. The highest RMSD value of the original ligand was 1.39292Å, while the RMSD value of the reference ligand was 1.71072Å. The essential amino acid carried out was 438Ser with hydrogen bond interactions, so 6OHMTHβC was considered a competent antidepressant candidate.

A comparative study of platelet storage lesion in platelet-rich plasma under cryopreservation.

Platelet-rich plasma (PRP) has significant potential for various applications and holds clinical value in regenerative medicine. Cryopreservation is used to extend the preservation period of PRP, facilitating its clinical application. However, the potential negative effects of long-term cryopreservation on platelet storage lesion are still uncertain. In this study, PRP was stored at - 30°C or - 80°C. Platelet count, apoptosis, reactive oxygen species (ROS) content, and CD62P expression were assessed on the 14th and 28th days. The study also evaluated platelet mitochondria morphology and function, serotonin (5-HT) secretion by platelets, and the inflammatory activating effect of cryopreserved platelets in PRP. The results showed that there were no significant differences in platelet count, the content of 5-HT, and inflammatory effects between fresh PRP and PRP cryopreserved at both - 30°C and - 80°C. However, there was an increase in ROS level, apoptosis, and CD62P level after cryopreservation at both temperatures. Additionally, the levels of ROS, apoptosis, and CD62P in platelets were similar after storage at - 30°C and - 80°C. The main difference observed was that the morphology and function of mitochondria were severely damaged after storage at - 30°C, while they were less affected at - 80°C. Based on these findings, it can be concluded that storing PRP at - 80°C is more suitable for achieving a better therapeutic effect in clinical applications, but cryopreservation could not replace the current standard.

Circadian rhythm regulation in the sea cucumber Apostichopus japonicus: Insights into clock gene expression, photoperiod susceptibility, and neurohormone signaling

Sea cucumber Apostichopus japonicus displays the typical circadian rhythms. This present study investigated the molecular regulation of clock genes, as well as monoamines and melatonin, in multiple tissues of A. japonicus, responding to the photoperiod. In order to determine their pivotal role in circadian rhythms, the crucial clock genes, namely AjClock, AjArnt1, AjCry1, and AjTimeless, were identified and a comprehensive analysis of their expressions across various tissues in adult A. japonicus was conducted, revealing the potential existence of central and peripheral oscillators. Results demonstrated that the tissues of polian vesicle and nerve ring exhibited significant clock gene expression associated with the orchestration of circadian regulation, and that environmental light fluctuations exerted influence on the expression of these clock genes. However, a number of genes, such as AjArnt1 and AjCry1, maintained their circadian rhythmicity even under continuous light conditions. Moreover, we further investigated the circadian patterns of melatonin (MT), serotonin (5-HT), and dopamine (DA) secretion in A. japonicus, data that underscored the tissue-specific regulatory differences and the inherent adaptability to dynamic light environments. Collectively, these findings will provide the molecular mechanisms controlling the circadian rhythm in echinoderms and the candidate tissues playing the role of central oscillators in sea cucumbers.

RET Signaling Persists in the Adult Intestine and Stimulates Motility by Limiting PYY Release From Enteroendocrine Cells

RET tyrosine kinase is necessary for enteric nervous system development. Loss-of-function RET mutations cause Hirschsprung disease (HSCR), in which infants are born with aganglionic bowel. Despite surgical correction, patients with HSCR often experience chronic defecatory dysfunction and enterocolitis, suggesting that RET is important after development. To test this hypothesis, we determined the location of postnatal RET and its significance in gastrointestinal (GI) motility. RetCFP/+ mice and human transcriptional profiling data were studied to identify the enteric neuronal and epithelial cells that express RET. To determine whether RET regulates gut motility invivo, genetic, and pharmacologic approaches were used to disrupt RET in all RET-expressing cells, a subset of enteric neurons, or intestinal epithelial cells. Distinct subsets of enteric neurons and enteroendocrine cells expressed RET in the adult intestine. RET disruption in the epithelium, rather than in enteric neurons, slowed GI motility selectively in male mice. RET kinase inhibition phenocopied this effect. Most RET+ epithelial cells were either enterochromaffin cells that release serotonin or L-cells that release peptide YY (PYY) and glucagon-like peptide 1 (GLP-1), both of which can alter motility. RET kinase inhibition exaggerated PYY and GLP-1 release in a nutrient-dependent manner without altering serotonin secretion in mice and human organoids. PYY receptor blockade rescued dysmotility in mice lacking epithelial RET. RET signaling normally limits nutrient-dependent peptide release from L-cells and this activity is necessary for normal intestinal motility in male mice. These effects could contribute to dysmotility in HSCR, which predominantly affects males, and uncovers a mechanism that could be targeted to treat post-prandial GI dysfunction.

The probiotic fermented milk of Lacticaseibacillus paracasei JY062 and Lactobacillus gasseri JM1 alleviates constipation via improving gastrointestinal motility and gut microbiota

Constipation is directly related to the intestinal microenvironment, in which the promotion of gastrointestinal (GI) motility and improvement of gut microbiota distribution are important for alleviating symptoms. Herein, after the intervention of probiotic fermented milk (FMMIX) containing Lacticaseibacillus paracasei JY062 and Lactobacillus gasseri JM1 for 14 d in Kunming mice with loperamide-induced constipation, the results indicated that FMMIX significantly increased the secretion of serum motilin, gastrin and 5-hydroxytryptamine, as well as decreased the secretion of peptide YY, vasoactive intestinal peptide, and nitric oxide in mice. As determined by immunohistochemical analysis, FMMIX promoted an augmentation in the quantity of Cajal interstitial cells. In addition, the mRNA and protein expression of c-kit and stem cell factor (SCF) were upregulated to facilitate intestinal motility. High-throughput sequencing and gas chromatography techniques revealed that FMMIX led to an increase in the relative abundance of beneficial bacteria (Lactobacillus, Oscillospira, Ruminococcus, Coprococcus, and Akkermansia), reduced the presence of harmful bacteria (Prevotella), and resulted in elevated levels of short-chain fatty acids (SCFA) with a superior improvement compared with unfermented milk. Untargeted metabolomics revealed significant upregulation of functional metabolites such as l-pipecolinic acid, dl-phenylalanine, and naringenin in FMMIX, presumably playing a potential role in constipation relief. Overall, our results showed that FMMIX had the potential to alleviate constipation symptoms in mice by improving the secretion of serum GI regulatory peptides and neurotransmitters, increasing the expression of c-kit and SCF proteins, and modulating the gut microbiota structure and SCFA levels, and may be associated with an increase in these functional metabolites. This suggested that FMMIX could be a promising adjunctive strategy for managing constipation symptoms and could contribute to the development of functional foods aimed at improving gut health.

Colon-Targeted Delivery of Indole Acetic Acid Helps Regulate Gut Motility by Activating the AHR Signaling Pathway.

Intestinal peristalsis is vital for gastrointestinal physiology and host homeostasis and is frequently dysregulated in intestinal disorders. Gut microbiota can regulate gut motility, especially through the tryptophan metabolism pathway. However, the role of indoles as microbial tryptophan metabolites in colonic function requires further exploration. Here, we show that the delivery of indole acetic acid (IAA) targeting the colon can improve gut motility by activating the aryl hydrocarbon receptor (AHR). To achieve colon-targeted delivery, Eudragit S-100 (ES) and chitosan (CS) were used as drug carriers. After optimisation, IAA-loaded ES-coated CS nanoparticles exhibited an encapsulation efficiency of 83% and a drug-loading capacity of 16%. These nanoparticles exhibited pH-dependent characteristics and remained stable in acidic conditions and the upper intestine. In simulated intestinal fluid (pH 7.4) and colonic lumen, considerable amounts of IAA were released after approximately 4 h. Compared with free IAA, the nanoparticles exerted enhanced therapeutic effects on gut movement disorders induced by loperamide. The efficacy of IAA treatment was attributable to the activation of the AHR signalling pathway and increased levels of AHR agonists. Furthermore, the oral administration of IAA-loaded nanoparticles promoted serotonin secretion and maintained the intestinal barrier function. The experimental outcomes demonstrate the efficiency of the proposed colon-specific delivery system and highlight the role of IAA, produced by gut microbiota metabolism, in regulating gut peristalsis through AHR activation.

Enteric Nervous System: Identification of a Novel Neuronal Sensory Network in the Duodenal Epithelium.

The communication between the intestinal epithelium and the enteric nervous system has been considered indirect. Mechanical or chemical stimuli activate enteroendocrine cells inducing hormone secretion, which act on sub-epithelial nerve ends, activating the enteric nervous system. However, we identified an epithelial cell that expresses NKAIN4, a neuronal protein associated with the β-subunit of Na+/K+-ATPase. This cell overexpresses Na+/K+-ATPase and ouabain-insensitive Na+-ATPase, enzymes involved in active sodium transport. NKAIN4-positive cells also express neuronal markers as NeuN, acetylcholine-esterase, acetylcholine-transferase, α3- and α7-subunits of ACh receptors, glutamic-decarboxylase, and serotonin-receptor-7, suggesting they are neurons. NKAIN4-positive cells show a polarized shape with an oval body, an apical process finished in a knob-like terminal in contact with the lumen, a basal cilia body at the base of the apical extension, and basal axon-like soma projections connecting sub-epithelial nerve terminals, lymphoid nodules, glial cells, and enterochromaffin cells, forming a network that reaches the epithelial surface. We also showed, using retrograde labeling and immunofluorescence, that these cells receive afferent signals from the enteric nervous system. Finally, we demonstrated that acetylcholine activates NKAIN4-positive cells inducing Ca2+ mobilization and probably serotonin secretion in enterochromaffin cells. NKAIN4-positive cells are neurons that would form a part of a duodenal sensory network for physiological or noxious luminal stimuli.