TPH1 inhibits bladder tumorigenesis by targeting HIF-1α pathway in bladder cancer.

Background: BCa is the most common cancer of the urinary system. TPH1 has been reported to be associated with distinct tumorigenesis. However, the role of TPH1 in BCa remains to be clarified. Objectives: Our aim is to demonstrate the molecular mechanism of TPH1 in BCa carcinogenesis and development. Methods: In research, we explored the effect of TPH1 on T24 cells. Colony formation, soft agar, and cell proliferation assays were used to determine the survival and proliferative capacity of cells. Moreover, TPH1-/- cell lines were analyzed using CRISP-CAS9, and the recovery experiment was conducted. Realtime fluorescence quantitative PCR (qPCR) and Western blot were used to detect HIF-1α mRNA levels and TPH1 protein. Results: The TPH1 expression is lower in tumor tissues than in normal tissues. Colony formation, soft agar, and cell proliferation assays revealed that the overexpression of TPH1 declined cells survival. Moreover, the deficiency of TPH1 increased the number of clones. These results suggested that survival rate of TPH1 overexpression was repressed in cells. In addition, we found that HIF-1α activity was significantly downregulated with an increase in TPH1. The transcriptional activity of survivin was increased with TPH1-/- cells. Then, the proliferative ability of TPH1-/- cells was almost similar to the wild type levels with the treatment of LW6, TPH1 might play a major role to repress HIF-1α activity. Conclusions: Taken together, these results suggested that increasing TPH1 activity could inhibit survival and proliferation of cells via HIF-1α pathway. TPH1 may be a potential target for human BCa therapy.

Unraveling the hierarchical structure of posture and muscle activity changes during mating of Caenorhabditis elegans.

One goal of neurobiology is to explain how decision-making in neuromuscular circuits produces behaviors. However, two obstacles complicate such efforts: individual behavioral variability and the challenge of simultaneously assessing multiple neuronal activities during behavior. Here, we circumvent these obstacles by analyzing whole animal behavior from a library of Caenorhabditis elegans male mating recordings. The copulating males express the GCaMP calcium sensor in the muscles, allowing simultaneous recording of posture and muscle activities. Our library contains wild type and males with selective neuronal desensitization in serotonergic neurons, which include male-specific posterior cord motor/interneurons and sensory ray neurons that modulate mating behavior. Incorporating deep learning-enabled computer vision, we developed a software to automatically quantify posture and muscle activities. By modeling, the posture and muscle activity data are classified into stereotyped modules, with the behaviors represented by serial executions and transitions among the modules. Detailed analysis of the modules reveals previously unidentified subtypes of the male's copulatory spicule prodding behavior. We find that wild-type and serotonergic neurons-suppressed males had different usage preferences for those module subtypes, highlighting the requirement of serotonergic neurons in the coordinated function of some muscles. In the structure of the behavior, bi-module repeats coincide with most of the previously described copulation steps, suggesting a recursive "repeat until success/give up" program is used for each step during mating. On the other hand, the transition orders of the bi-module repeats reveal the sub-behavioral hierarchy males employ to locate and inseminate hermaphrodites.

Diversity and evolution of serotonergic cells in taste buds of elasmobranchs and ancestral actinopterygian fish.

A subset of gustatory cells are serotonin immunoreactive (ir) in the mammalian taste bud. In the taste bud of lamprey, elongated gustatory-like cells are also serotonin-ir. In contrast, flattened serotonin-ir cells are located only in the basal region of the taste buds in the teleosts and amphibians. These serotonin-ir cells are termed as basal cells. To evaluate the evolution and diversity of serotonergic cells in the taste bud of amniote animals, we explored the distribution and morphology of serotonin-ir cells in the taste buds of ancestral actinopterygian fish (spotted gar, sturgeon, Polypterus senegalus) and elasmobranch (stingray). In all examined animals, the taste buds contained serotonin-ir cells in their basal part. The number of serotonin-ir basal cells in each taste bud was different between these fish species. They were highest in the stingray and decreased in the order of the Polypterus, sturgeon, and gar. While serotonin immunoreactivity was observed only in the basal cells in the taste buds of the ancestral actinopterygian fish, some elongated cells were also serotonin-ir in addition to the basal cells in the stingray taste buds. mRNA of tryptophan hydroxylase 1 (tph1), a rate-limiting enzyme of the serotonin synthesis, is expressed in both the elongated and basal cells of stingray taste buds, indicating that these cells synthesize the serotonin by themselves. These results suggest that the serotonin-ir basal cells arose from the ancestor of the cartilaginous fish, and serotonin-ir cells in the elasmobranch taste bud exhibit an intermediate aspect between the lamprey and actinopterygian fish.

Increased tryptophan, but not increased glucose metabolism, predict resistance of pembrolizumab in stage III/IV melanoma.

Clinical trials of combined IDO/PD1 blockade in metastatic melanoma (MM) failed to show additional clinical benefit compared to PD1-alone inhibition. We reasoned that a tryptophan-metabolizing pathway other than the kynurenine one is essential. We immunohistochemically stained tissues along the nevus-to-MM progression pathway for tryptophan-metabolizing enzymes (TMEs; TPH1, TPH2, TDO2, IDO1) and the tryptophan transporter, LAT1. We assessed tryptophan and glucose metabolism by performing baseline C11-labeled α-methyl tryptophan (C11-AMT) and fluorodeoxyglucose (FDG) PET imaging of tumor lesions in a prospective clinical trial of pembrolizumab in MM (clinicaltrials.gov, NCT03089606). We found higher protein expression of all TMEs and LAT1 in melanoma cells than tumor-infiltrating lymphocytes (TILs) within MM tumors (n = 68). Melanoma cell-specific TPH1 and LAT1 expressions were significantly anti-correlated with TIL presence in MM. High melanoma cell-specific LAT1 and low IDO1 expression were associated with worse overall survival (OS) in MM. Exploratory optimal cutpoint survival analysis of pretreatment 'high' vs. 'low' C11-AMT SUVmax of the hottest tumor lesion per patient revealed that the 'low' C11-AMT SUVmax was associated with longer progression-free survival in our clinical trial (n = 26). We saw no such trends with pretreatment FDG PET SUVmax. Treatment of melanoma cell lines with telotristat, a TPH1 inhibitor, increased IDO expression and kynurenine production in addition to suppression of serotonin production. High melanoma tryptophan metabolism is a poor predictor of pembrolizumab response and an adverse prognostic factor. Serotoninergic but not kynurenine pathway activation may be significant. Melanoma cells outcompete adjacent TILs, eventually depriving the latter of an essential amino acid.

Tryptophan Hydroxylase-2-Mediated Serotonin Biosynthesis Suppresses Cell Reprogramming into Pluripotent State.

The monoamine neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) has important functions both in the neural system and during embryonic development in mammals. In this study, we set out to investigate whether and how endogenous serotonin affects reprogramming to pluripotency. As serotonin is synthesized from tryptophan by the rate limiting enzymes tryptophan hydroxylase-1 and -2 (TPH1 and TPH2), we have assessed the reprogramming of TPH1- and/or TPH2-deficient mouse embryonic fibroblasts (MEFs) to induced pluripotent stem cells (iPSCs). The reprogramming of the double mutant MEFs showed a dramatic increase in the efficiency of iPSC generation. In contrast, ectopic expression of TPH2 alone or in conjunction with TPH1 reverted the rate of reprogramming of the double mutant MEFs to the wild-type level and besides, TPH2 overexpression significantly suppressed reprogramming of wild-type MEFs. Our data thus suggest a negative role of serotonin biosynthesis in the reprogramming of somatic cells to a pluripotent state.

Mechanism of action and promising clinical application of melatonin from a dermatological perspective.

Melatonin is the main neuroendocrine product in the pineal gland. Melatonin can regulate circadian rhythm-related physiological processes. Evidence indicates an important role of melatonin in hair follicles, skin, and gut. There appears to be a close association between melatonin and skin disorders. In this review, we focus on the latest research of the biochemical activities of melatonin (especially in the skin) and its promising clinical applications.

Effect of Yinchenhao Decoction on"Intestinal TPH1-Hepatic HTR2A Axis"in Mice with Metabolic Associated Fatty Liver Disease / 世界科学技术-中医药现代化

Objective To explore the mechanism of Yinchenhao Decoction in preventing and treating MAFLD based on"Intestinal TPH1-hepatic HTR2A axis".Methods Twenty-four C57BL/6J mice were arbitrarily splited up into control group,model group and Yinchenhao decoction group,eight in each group.Mice in the Yinchenhao decoction group and model group were fed with high-fat diet.After 12 weeks,the Yinchenhao decoction group was given Yinchenhao decoction by gavage,once a day for 4 consecutive weeks.Histopathological changes were observed by HE staining and oil red O staining.Serum HDL-C,LDL-C,TC,TG,AST,ALT and 5-HT contents,liver TC,TG,DAG,PLC contents were detected.Intestinal TPH1,SERT and liver HTR2A,SREBP-1c,GPAT1,FASN mRNA levels;Intestinal TPH1,SERT and liver HTR2A,SREBP-1c,GPAT1,FASN,P-PI3K,PKC-ε,P-AKT,P-mTOR protein expression level were detected.Results In the control group,the hepatocytes were arranged neatly without significant steatosis;In the model group,the hepatocytes were swollen in volume with significant steatosis;Compared with the control group,hepatocyte steatosis was significantly reduced in the Yinchenhao decoction group.Compared with the control group,liver lipid deposition was significantly higher in the model group,and the Yinchenhao decoction group significantly improved liver lipid deposition.Compared with the control group,the liver TG,TC levels in the model group were significantly increased(P<0.05);the serum AST,ALT,HDL-C,LDL-C,TG,TC levels were significantly increased(P<0.05);the serum 5-HT and liver DAG,PLC was significantly increased(P<0.05);the mRNA expression levels of HTR2A,SREBP-1c,GPAT1,FASN in the liver and TPH1 in the Intestinal were significantly increased,SERT in the Intestinal were significantly decreased(P<0.05);the protein expression levels of HTR2A,SREBP-1c,GPAT1,FASN,P-PI3K,P-AKT,P-mTOR,PKC-ε in the liver were significantly increased,and TPH1 in the Intestinal were significantly increased,SERT in the Intestinal were significantly decreased(P<0.05).Compared with the model group,the liver TG,TC levels in Yinchenhao decoction group were significantly decreased(P<0.05);the serum AST,ALT,LDL-C and TG levels were significantly decreased(P<0.05);the serum 5-HT and liver DAG,PLC level was significantly decreased;The mRNA expression levels of HTR2A,SREBP-1c,GPAT1,FASN in the liver and TPH1 in the Intestinal were significantly decreased,SERT in the Intestinal were significantly increased(P<0.05);the protein expression levels of HTR2A,SREBP-1c,GPAT1,FASN,P-PI3K,P-AKT,P-mTOR,PKC-ε in the liver were significantly decreased and TPH1 in the Intestinal were significantly increased,SERT in the Intestinal were significantly increased(P<0.05).Conclusion Yinchenhao decoction may regulate liver TG synthesis through Intestinal TPH1-hepatic HTR2A axis,thereby inhibiting the occurrence and development of MAFLD.

The Lignan-Rich Fraction from Sambucus williamsii Hance Exerts Bone Protective Effects via Altering Circulating Serotonin and Gut Microbiota in Rats.

Our previous study revealed that the bone anabolic effects of the lignan-rich fraction (SWCA) from Sambucus williamsii Hance was involved in modulating the metabolism of tryptophan in vivo and inhibiting serotonin (5-HT) synthesis in vitro. This study aimed to determine how SWCA modulates bone metabolism via serotonin in vivo. The effects of SWCA were evaluated by using 4-month-old Sprague-Dawley (SD) ovariectomized rats. The serum levels of 5-HT and kynurenine, the protein expressions of tryptophan hydroxylase 1 (TPH-1) and TPH-2, the genes and proteins related to the 5-HT signaling pathway as well as gut microbiota composition were determined. SWCA treatment alleviated bone loss and decreased serum levels of serotonin, which was negatively related to bone mineral density (BMD) in rats. It suppressed the protein expression of TPH-1 in the colon, and reversed the gene and protein expressions of FOXO1 and ATF4 in the femur in OVX rats, while it did not affect the TPH-2 protein expression in the cortex. SWCA treatment escalated the relative abundance of Antinobacteria and modulated several genera relating to BMD. These findings verified that the bone protective effects of lignans were mediated by serotonin, and provided evidence that lignans might be a good source of TPH-1 inhibitors.

Peptide OM-LV20 protects astrocytes against oxidative stress via the 'PAC1R/JNK/TPH1' axis.

Stroke can lead to severe nerve injury and debilitation, resulting in considerable social and economic burdens. Due to the high complexity of post-injury repair mechanisms, drugs approved for use in stroke are extremely scarce, and thus, the discovery of new antistroke drugs and targets is critical. Tryptophan hydroxylase 1 (TPH1) is involved in a variety of mental and neurobehavioral processes, but its effects on stroke have not yet been reported. Here, we used primary astrocyte culture, quantitative real-time PCR, double immunofluorescence assay, lentiviral infection, cell viability analysis, Western blotting, and other biochemical experiments to explore the protective mechanism of peptide OM-LV20, which previously exhibited neuroprotective effects in rats after ischemic stroke via a mechanism that may involve TPH1. First, we showed that TPH1 was expressed in rat astrocytes. Next, we determined that OM-LV20 impacted expression changes of TPH1 in CTX-TNA2 cells and exhibited a protective effect on the decrease in cell viability and catalase (CAT) levels induced by hydrogen peroxide. Importantly, we also found that TPH1 expression induced by OM-LV20 may be related to the level of change in the pituitary adenylate cyclase-activating peptide type 1 receptor (PAC1R) and to the JNK signaling pathways, thereby exerting a protective effect on astrocytes against oxidative stress. The protective effects of OM-LV20 likely occur via the 'PAC1R/JNK/TPH1' axis, thus highlighting TPH1 as a novel antistroke drug target.

Peripheral Serotonin Deficiency Affects Anxiety-like Behavior and the Molecular Response to an Acute Challenge in Rats.

Serotonin is synthetized through the action of tryptophan hydroxylase (TPH) enzymes. While the TPH2 isoform is responsible for the production of serotonin in the brain, TPH1 is expressed in peripheral organs. Interestingly, despite its peripheral localization, alterations of the gene coding for TPH1 have been related to stress sensitivity and an increased susceptibility for psychiatric pathologies. On these bases, we took advantage of newly generated TPH1-/- rats, and we evaluated the impact of the lack of peripheral serotonin on the behavior and expression of brain plasticity-related genes under basal conditions and in response to stress. At a behavioral level, TPH1-/- rats displayed reduced anxiety-like behavior. Moreover, we found that neuronal activation, quantified by the expression of Bdnf and the immediate early gene Arc and transcription of glucocorticoid responsive genes after 1 h of acute restraint stress, was blunted in TPH1-/- rats in comparison to TPH1+/+ animals. Overall, we provided evidence for the influence of peripheral serotonin levels in modulating brain functions under basal and dynamic situations.

Tryptophan hydroxylase 1 drives glioma progression by modulating the serotonin/L1CAM/NF-κB signaling pathway.

BACKGROUND: Glioma is one of the main causes of cancer-related mortality worldwide and is associated with high heterogeneity. However, the key players determining the fate of glioma remain obscure. In the present study, we shed light on tumor metabolism and aimed to investigate the role of tryptophan hydroxylase 1 (TPH-1) in the advancement of glioma. METHOD: Herein, the levels of TPH-1 expression in glioma tissues were evaluated using The Cancer Genome Atlas (TCGA) database. Further, the proliferative characteristics and migration ability of TPH-1 overexpressing LN229/T98G cells were evaluated. Additionally, we performed a cytotoxicity analysis using temozolomide (TMZ) in these cells. We also examined the tumor growth and survival time in a mouse model of glioma treated with chemotherapeutic agents and a TPH-1 inhibitor. RESULTS: The results of both clinical and experimental data showed that excess TPH-1 expression resulted in sustained glioma progression and a dismal overall survival in these patients. Mechanistically, TPH-1 increased the production of serotonin in glioma cells. The elevated serotonin levels then augmented the NF-κB signaling pathway through the upregulation of the L1-cell adhesion molecule (L1CAM), thereby contributing to cellular proliferation, invasive migration, and drug resistance. In vivo experiments demonstrated potent antitumor effects, which benefited further from the synergistic combination of TMZ and LX-1031. CONCLUSION: Taken together, these data suggested that TPH-1 facilitated cellular proliferation, migration, and chemoresistance in glioma through the serotonin/L1CAM/NF-κB pathway. By demonstrating the link of amino acid metabolic enzymes with tumor development, our findings may provide a potentially viable target for therapeutic manipulation aimed at eradicating glioma.

The Regulatory Role of the Central and Peripheral Serotonin Network on Feeding Signals in Metabolic Diseases.

Central and peripheral serotonin (5-hydroxytryptamine, 5-HT) regulate feeding signals for energy metabolism. Disruption of central 5-HT signaling via 5-HT2C receptors (5-HT2CRs) induces leptin-independent hyperphagia in mice, leading to late-onset obesity, insulin resistance, and impaired glucose tolerance. 5-HT2CR mutant mice are more responsive than wild-type mice to a high-fat diet, exhibiting earlier-onset obesity and type 2 diabetes. High-fat and high-carbohydrate diets increase plasma 5-HT and fibroblast growth factor-21 (FGF21) levels. Plasma 5-HT and FGF21 levels are increased in rodents and humans with obesity, type 2 diabetes, and non-alcohol fatty liver diseases (NAFLD). The increases in plasma FGF21 and hepatic FGF21 expression precede hyperinsulinemia, insulin resistance, hyperglycemia, and weight gain in mice fed a high-fat diet. Nutritional, pharmacologic, or genetic inhibition of peripheral 5-HT synthesis via tryptophan hydroxylase 1 (Tph1) decreases hepatic FGF21 expression and plasma FGF21 levels in mice. Thus, perturbing central 5-HT signaling via 5-HT2CRs alters feeding behavior. Increased energy intake via a high-fat diet and/or high-carbohydrate diet can upregulate gut-derived 5-HT synthesis via Tph1. Peripheral 5-HT upregulates hepatic FGF21 expression and plasma FGF21 levels, leading to metabolic diseases such as obesity, insulin resistance, type 2 diabetes, and NAFLD. The 5-HT network in the brain-gut-liver axis regulates feeding signals and may be involved in the development and/or prevention of metabolic diseases.

Effect of process parameters and surfactant additives on the obtained activity of recombinant tryptophan hydroxylase (TPH1) for enzymatic synthesis of 5-hydroxytryptophan (5-HTP).

5-hydroxytryptophan (5-HTP) is an intermediate molecule in the biosynthesis of serotonin, an important neurotransmitter, regulating a series of metabolic and psychological functions in humans. In this work, we studied the heterologous production of Human tryptophan hydroxylase (TPH1) in Escherichia coli, for the synthesis of 5-hydroxytryptophan (5-HTP) from Tryptophan (Trp). To quantify TPH1 activity, a simple fluorescence-based microtiter plate assay was established, based on the changes in fluorescence emission at 340 nm between substrate and product when excited at 310 nm, allowing quick and reliable quantification of released 5-HTP. To increase enzyme production, heterologous TPH1 production was studied in stirred tank bioreactor scale. The effect of rate of aeration (0.25, 0.50 and 0.75 vvm) and agitation (150, 250 and 500 rpm) was evaluated for biomass production, pH, volumetric oxygen transfer coefficient (kLa) and volumetric TPH1 activity. We determined that high agitation and low aeration allowed reaching the maximum measured enzyme activity. Under such conditions, we observed a 90% substrate conversion, obtaining 90 µM (~0.02 g/L) 5-HTP from a 100 µM Tryptophan substrate solution. Finally, we observed that the addition of Tween 20 (0.1%) in the culture broth under production conditions expanded the pH operation range of TPH1. Our results establish a base for a biocatalytic approach as a potential alternative process for the synthesis of 5-HTP using recombinant TPH1.

TPH1 gene polymorphism rs211105 is associated with serotonin and tryptophan hydroxylase 1 concentrations in acute pancreatitis patients.

BACKGROUND: The role of serotonin and its metabolic pathway in proper functioning of the pancreas has not been thoroughly investigated yet in acute pancreatitis (AP) patients. Tryptophan hydroxylase (TPH) as the rate-limiting enzyme of serotonin synthesis has been considered for possible associations in various diseases. Single-nucleotide polymorphisms (SNPs) in TPH genes have been already described in associations with psychiatric and digestive system disorders. This study aimed to explore the association of a rs211105 (T/G) polymorphism in TPH1 gene with tryptophan hydroxylase 1 concentrations in blood serum in a population of acute pancreatitis patients, and to investigate this association with acute pancreatitis susceptibility. RESULTS: Our data showed an association between the presence of the T allele at the position rs211105 (OR = 2.47, 95 % CI 0.94-6.50, p = 0.06) under conditions of a decreased AP incidence. For TT and GT genotypes in the control group, the lowest concentration of TPH was associated with higher serotonin levels (TT: Rs = - 0.415, p = 0.0018; GT: Rs = - 0.457, p = 0.0066), while for the AP group the highest levels of TPH among the TT genotype were associated with lower levels of serotonin (TT: Rs = - 0.749, p < 0.0001, and in the GG genotype higher levels of TPH were associated with higher levels of serotonin (GG: Rs = - 0.738, p = 0.037). CONCLUSIONS: Here, a new insight in the potential role of a selected genetic factor in pancreatitis development was shown. Not only the metabolic pathway of serotonin, but also factors affecting serotonin synthesis may be interesting and important points in acute pancreatitis.

Relationships of Ischemic Stroke Occurrence and Outcome with Gene Variants Encoding Enzymes of Tryptophan Metabolism.

Ischemic stroke is among the leading causes of mortality and long-term disability worldwide. Among stroke risk factors the importance of genetic background is gaining interest. There is a growing body of evidence of changes of metabolite levels and enzyme activities involved in the conversion of Trp during the course of cerebral ischemia. We compared the frequencies of ten SNPs of five genes related to Trp metabolism between groups of 122 ischemic stroke patients and 120 control individuals. Furthermore, we examined the mRNA levels of TPH1, IDO1 and KYAT1 genes in peripheral venous blood with the aim of assessing (i) whether there are changes in their expression during the course of stroke and (ii) does any of their investigated SNPs have an impact on gene expression. In seven cases out of ten studied polymorphisms we detected significant differences in frequencies in relation to ischemic stroke occurrence, etiology, and clinical parameters. We also detected changes in the expression of TPH1 and IDO1 genes during the course of the disease. We found that those IDO1 variants which show a trend towards elevated mRNA level are more frequent in stroke patients than in controls. Our results are important novel observations which suggest a causal relationship between elevated IDO1 expression and stroke etiology.

Tryptophan Catabolism and Response to Therapy in Locally Advanced Rectal Cancer (LARC) Patients.

In locally advanced rectal cancer patients (LARC), preoperative chemoradiation improves local control and sphincter preservation. The response rate to treatment varies substantially between 20 and 30%, and it is an important prognostic factor. Indeed, nonresponsive patients are subjected to higher rates of local and distant metastases, and worse survival compared to patients with complete response. In the search of predictive biomarkers for response prediction to therapy in LARC patients, we found increased plasma tryptophan levels in nonresponsive patients. On the basis of plasma levels of 5-hydroxy-tryptophan and kynurenine, the activities of tryptophan 5-hydroxylase 1 (TPH1) and indoleamine-2,3-dioxygenases 1 (IDO1)/tryptophan-2,3-dioxygenase (TDO2) have been obtained and data have been correlated with gene expression profiles. We demonstrated that TDO2 overexpression in nonresponsive patients correlates with kynurenine plasma levels. Finally, through the gene expression and targeted metabolomic analysis in paired healthy mucosa-rectal cancer tumor samples, we evaluated the impact of tryptophan catabolism at tissue level in responsive and nonresponsive patients.

Poricoic acid A as a modulator of TPH-1 expression inhibits renal fibrosis via modulating protein stability of ß-catenin and ß-catenin-mediated transcription.

BACKGROUND: Renal fibrosis is the common feature of chronic kidney disease (CKD). However, few drugs specifically target fibrogenesis due to the lack of an effective therapeutic target. Hence, it is urgent to find a therapeutic strategy that inhibits renal fibrosis. Here, we identified that poricoic acid A (PAA) as the modulator of tryptophan hydroxylase-1 (TPH-1), the key enzyme in tryptophan metabolism, exerted potent anti-fibrotic effects in the kidney. METHODS: Lentiviral vector, luciferase reporter activity assay and co-immunoprecipitation were used. The animal model of unilateral ureteral obstruction and adenine-induced chronic renal failure as well as transforming growth factor (TGF)-ß1-treated epithelial cells NRK-52E and fibroblasts NRK-49F were used. RESULTS: TPH-1 was gradually decreased during CKD progression, while PAA treatment significantly increased TPH-1 expression to suppress renal fibrosis. Pharmacological overexpression of TPH-1 by PAA treatment exhibited anti-fibrosis and was linked to Wnt/ß-catenin signaling activity. TPH-1 exhibited anti-fibrotic effects by suppressing epithelial cell injury and fibroblast activation, and PAA promoted TPH-1 expression and then suppressed the Wnt/ß-catenin signaling pathway via regulating the protein stability of ß-catenin and ß-catenin-mediated transcription. TPH-1 overexpression enhanced the anti-fibrotic effects of PAA, while TPH-1 deficiency weakened the anti-fibrotic effects of PAA, indicating that TPH-1 was required for the anti-fibrotic effects of PAA. CONCLUSION: PAA as a modulator of TPH-1 expression attenuated renal fibrosis through regulating the Wnt/ß-catenin signaling pathway by acting on the protein stability of ß-catenin and ß-catenin-mediated transcription. TPH-1 was required for PAA to exert anti-fibrosis.

Discovery and biological characterization of a novel scaffold for potent inhibitors of peripheral serotonin synthesis.

Aim: Tryptophan hydroxylase 1 (TPH1) catalyzes serotonin synthesis in peripheral tissues. Selective TPH1 inhibitors may be useful for treating disorders related to serotonin dysregulation. Results & methodology: Screening using a thermal shift assay for TPH1 binders yielded Compound 1 (2-(4-methylphenyl)-1,2-benzisothiazol-3(2H)-one), which showed high potency (50% inhibition at 98 ± 30 nM) and selectivity for inhibiting TPH over related aromatic amino acid hydroxylases in enzyme activity assays. Structure-activity relationships studies revealed several analogs of 1 showing comparable potency. Kinetic studies suggested a noncompetitive mode of action of 1, with regards to tryptophan and tetrahydrobiopterin. Computational docking studies and live cell assays were also performed. Conclusion: This TPH1 inhibitor scaffold may be useful for developing new therapeutics for treating elevated peripheral serotonin.

Protein acetylation derepresses Serotonin Synthesis to potentiate Pancreatic Beta-Cell Function through HDAC1-PKA-Tph1 signaling.

Rationale: Protein acetylation is tightly linked to transcriptional control and energy metabolism. However, the role of protein acetylation in islet function remains enigmatic. This study aims to determine how protein acetylation controls ß-cell function and explore the underlying mechanism. Methods: The gene-expression profiles were analyzed for rat islets in response to two histone deacetylase (HDAC) inhibitors. Insulin secretion, tryptophan hydroxylase 1 (Tph1) expression, and serotonin synthesis of rat islets were detected after HDAC inhibitor treatment both in vivo and ex vivo. ß-cell-specific Tph1-overexpressing transgenic rats and ß-cell-specific Tph1 knockout mice were constructed to evaluate the role of Tph1 in ß-cell function. The deacetylation of PKA in ß-cells by HDAC1 was investigated by adenoviral infection, immunoprecipitation, and western blot. Results: Inhibition of HDACs greatly potentiated pancreatic ß-cell function and reprogrammed transcriptional landscape of islets. Among the commonly up-regulated genes by two pan-HDAC inhibitors, Tph1 displayed the most prominent change. Specifically, inhibition of HDAC1 and HDAC3 by MS-275 strongly promoted Tph1 expression and endogenous serotonin synthesis in rat islets, concomitantly with enhanced insulin secretory capacity in vivo and ex vivo. ß-cell-specific Tph1-overexpressing transgenic rats exhibited improved glucose tolerance and amplified glucose-stimulated insulin secretion. On the contrary, ß-cell-specific Tph1 knockout mice displayed glucose intolerance and impaired insulin secretion with aging. Moreover, depletion of Tph1 in ß-cells abrogated MS-275-induced insulin hypersecretion. Overexpression of HDAC1, not HDAC3, inhibited Tph1 transcriptional activity and decreased MS-275-stimulated Tph1 expression. Mechanistically, HDAC1 deacetylated PKA catalytic subunit and decreased its activity, resulting in Tph1 transcriptional repression. The acetylation mimetic K62Q mutant of PKA increased its catalytic activity. HDAC1 inhibition exerted a synergistic effect with cAMP/PKA signal on Tph1 expression. Conclusions: The present findings highlight a novel role of HDAC1-PKA-Tph1 signaling in governing ß-cell functional compensation by derepressing serotonin synthesis.

The ever-changing roles of serotonin.

Serotonin (5-HT) has traditional roles as a key neurotransmitter in the central nervous system and as a regulatory hormone controlling a broad range of physiological functions. Perhaps the most classically-defined functions of 5-HT are centrally in the control of mood, sleep and anxiety and peripherally in the modulation of gastrointestinal motility. A more recently appreciated role for 5-HT has emerged, however, as an important metabolic hormone contributing to glucose homeostasis and adiposity, with a causal relationship existing between circulating 5-HT levels and metabolic diseases. Almost all peripheral 5-HT is derived from specialised enteroendocrine cells, called enterochromaffin (EC) cells, located throughout the length of the lining of the gastrointestinal tract. EC cells are important luminal sensory cells that can detect and respond to an array of ingested nutrients, as well as luminal gut microbiota and their associated metabolites. Intriguingly, the interaction between gut microbiota and EC cells is dynamic in nature and has strong implications for host physiology. In this review, we discuss the traditional and modern functions of 5-HT and highlight an emerging pathway by which gut microbiota influences host health. Serotonin, also known as 5-hydroxytryptamine (5-HT), is an important neurotransmitter, growth factor and hormone that mediates a range of physiological functions. In mammals, serotonin is synthesized from the essential amino acid tryptophan by the rate-limiting enzyme tryptophan hydroxylase (TPH), for which there are two isoforms expressed in distinct cell types throughout the body. Tph1 is mainly expressed by specialized gut endocrine cells known as enterochromaffin (EC) cells and by other non-neuronal cell types such as adipocytes (Walther et al., 2003). Tph2 is primarily expressed in neurons of the raphe nuclei of the brain stem and a subset of neurons in the enteric nervous system (ENS) (Yabut et al., 2019). As 5-HT cannot readily cross the blood-brain barrier, the central and peripheral pools of 5-HT are anatomically separated and as such, act in their own distinct manners (Martin et al., 2017c). In this review we discuss the peripheral roles of serotonin, with particular focus on the interaction of gut-derived serotonin with the gut microbiota, and address emerging evidence linking this relationship with host homeostasis.