IL-2 regulates tumor-reactive CD8+ T cell exhaustion by activating the aryl hydrocarbon receptor.

CD8+ T cell exhaustion dampens antitumor immunity. Although several transcription factors have been identified that regulate T cell exhaustion, the molecular mechanisms by which CD8+ T cells are triggered to enter an exhausted state remain unclear. Here, we show that interleukin-2 (IL-2) acts as an environmental cue to induce CD8+ T cell exhaustion within tumor microenvironments. We find that a continuously high level of IL-2 leads to the persistent activation of STAT5 in CD8+ T cells, which in turn induces strong expression of tryptophan hydroxylase 1, thus catalyzing the conversion to tryptophan to 5-hydroxytryptophan (5-HTP). 5-HTP subsequently activates AhR nuclear translocation, causing a coordinated upregulation of inhibitory receptors and downregulation of cytokine and effector-molecule production, thereby rendering T cells dysfunctional in the tumor microenvironment. This molecular pathway is not only present in mouse tumor models but is also observed in people with cancer, identifying IL-2 as a novel inducer of T cell exhaustion.

Interleukin-33 Induces the Enzyme Tryptophan Hydroxylase 1 to Promote Inflammatory Group 2 Innate Lymphoid Cell-Mediated Immunity.

Group 2 innate lymphoid cells (ILC2s) regulate immunity, inflammation, and tissue homeostasis. Two distinct subsets of ILC2s have been described: steady-state natural ILC2s and inflammatory ILC2s, which are elicited following helminth infection. However, how tissue-specific cues regulate these two subsets of ILC2s and their effector functions remains elusive. Here, we report that interleukin-33 (IL-33) promotes the generation of inflammatory ILC2s (ILC2INFLAM) via induction of the enzyme tryptophan hydroxylase 1 (Tph1). Tph1 expression was upregulated in ILC2s upon activation with IL-33 or following helminth infection in an IL-33-dependent manner. Conditional deletion of Tph1 in lymphocytes resulted in selective impairment of ILC2INFLAM responses and increased susceptibility to helminth infection. Further, RNA sequencing analysis revealed altered gene expression in Tph1 deficient ILC2s including inducible T cell co-stimulator (Icos). Collectively, these data reveal a previously unrecognized function for IL-33, Tph1, and ICOS in promoting inflammatory ILC2 responses and type 2 immunity at mucosal barriers.

Parallel pathways for serotonin biosynthesis and metabolism in C. elegans.

The neurotransmitter serotonin plays a central role in animal behavior and physiology, and many of its functions are regulated via evolutionarily conserved biosynthesis and degradation pathways. Here we show that in Caenorhabditis elegans, serotonin is abundantly produced in nonneuronal tissues via phenylalanine hydroxylase, in addition to canonical biosynthesis via tryptophan hydroxylase in neurons. Combining CRISPR-Cas9 genome editing, comparative metabolomics and synthesis, we demonstrate that most serotonin in C. elegans is incorporated into N-acetylserotonin-derived glucosides, which are retained in the worm body and further modified via the carboxylesterase CEST-4. Expression patterns of CEST-4 suggest that serotonin or serotonin derivatives are transported between different tissues. Last, we show that bacterial indole production interacts with serotonin metabolism via CEST-4. Our results reveal a parallel pathway for serotonin biosynthesis in nonneuronal cell types and further indicate that serotonin-derived metabolites may serve distinct signaling functions and contribute to previously described serotonin-dependent phenotypes.

Microbiota influence on behavior: Integrative analysis of serotonin metabolism and behavioral profile in germ-free mice.

Previous studies on germ-free (GF) animals have described altered anxiety-like and social behaviors together with dysregulations in brain serotonin (5-HT) metabolism. Alterations in circulating 5-HT levels and gut 5-HT metabolism have also been reported in GF mice. In this study, we conducted an integrative analysis of various behaviors as well as markers of 5-HT metabolism in the brain and along the GI tract of GF male mice compared with conventional (CV) ones. We found a strong decrease in locomotor activity, accompanied by some signs of increased anxiety-like behavior in GF mice compared with CV mice. Brain gene expression analysis showed no differences in HTR1A and TPH2 genes. In the gut, we found decreased TPH1 expression in the colon of GF mice, while it was increased in the cecum. HTR1A expression was dramatically decreased in the colon, while HTR4 expression was increased both in the cecum and colon of GF mice compared with CV mice. Finally, SLC6A4 expression was increased in the ileum and colon of GF mice compared with CV mice. Our results add to the evidence that the microbiota is involved in regulation of behavior, although heterogeneity among studies suggests a strong impact of genetic and environmental factors on this microbiota-mediated regulation. While no impact of GF status on brain 5-HT was observed, substantial differences in gut 5-HT metabolism were noted, with tissue-dependent results indicating a varying role of microbiota along the GI tract.

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.

Behavioural changes in young ovariectomized mice via GPR30-dependent serotonergic nervous system.

Fluctuations in estradiol levels at each stage of life in women are considered one of the causes of mental diseases through their effects on the central nervous system. During menopause, a decrease in estradiol levels has been reported to affect the serotonin nervous system and induce depression-like and anxiety symptoms. However, the regulation of brain and behaviour during childhood and adolescence is poorly understood. Moreover, the role of oestrogen receptors α and ß in the regulation of the serotonergic nervous system has been reported, but little is known about the involvement of G protein-coupled receptor 30. Therefore, in this study, we used an ovariectomized childhood mouse model to analyse behaviour and investigate the effects on the serotonin nervous system. We showed that ovariectomy surgery at 4 weeks of age, which is the weaning period, induced a decrease in spontaneous locomotor activity during the active period and a preference for novel mice over familiar mice in the three-chamber social test at 10 weeks of age. In addition, the administration of G-1, a protein-coupled receptor 30 agonist, to ovariectomized mice suppressed spontaneous locomotor activity and the preference for novel mice. Furthermore, we demonstrated that childhood ovariectomy induces increased tryptophan hydroxylase gene expression in the raphe nucleus and increased serotonin release in the amygdaloid nucleus, and administration of G-1 ameliorated these effects. Our study suggests that G protein-coupled receptor 30-mediated regulation of serotonin synthesis is involved in changes in activity and social-cognitive behaviour due to decreased estradiol levels during childhood.

Serotonin 2C receptor in a rat model of temporal lobe epilepsy: From brainstem expression to pharmacological blockade in relation to ventilatory function.

Because of its involvement in breathing control and neuronal excitability, dysregulation of the serotonin (5-HT) 2C receptor (5-HT2C) might play a key role in sudden unexpected death in epilepsy. Seizure-induced respiratory arrest is thus prevented by a 5-HT2B/C agonist in different seizure model. However, the specific contribution of 5-HT2C in chronic epilepsy-related respiratory dysfunction remains unknown. In a rat model of temporal lobe epilepsy (EPI rats), in which we previously reported interictal respiratory dysfunctions and a reduction of brainstem 5-HT tone, quantitative reverse transcriptase polymerase chain reaction showed overexpression of TPH2 (5-HT synthesis enzyme), SERT (5-HT reuptake transporter), and 5-HT2C transcript levels in the brainstem of EPI rats, and of RNA-specific adenosine deaminase (ADAR1, ADAR2) involved in the production of 5-HT2C isoforms. Interictal ventilation was assessed with whole-body plethysmography before and 2 h after administration of SB242084 (2 mg/kg), a specific antagonist of 5-HT2C. As expected, SB242084 administration induced a progressive decrease in ventilatory parameters and an alteration of breathing stability in both control and EPI rats. However, the size of the SB242084 effect was lower in EPI rats than in controls. Increased 5-HT2C gene expression in the brainstem of EPI rats could be part of a compensatory mechanism against epilepsy-related low 5-HT tone and expression of 5-HT2C isoforms for which 5-HT affinity might be lower.

Disfunction of dorsal raphe nucleus-hippocampus serotonergic-HTR3 transmission results in anxiety phenotype of Neuroplastin 65-deficient mice.

Anxiety disorders are the most common psychiatric condition, but the etiology of anxiety disorders remains largely unclear. Our previous studies have shown that neuroplastin 65 deficiency (NP65-/-) mice exhibit abnormal social and mental behaviors and decreased expression of tryptophan hydroxylase 2 (TPH2) protein. However, whether a causal relationship between TPH2 reduction and anxiety disorders exists needs to be determined. In present study, we found that replenishment of TPH2 in dorsal raphe nucleus (DRN) enhanced 5-HT level in the hippocampus and alleviated anxiety-like behaviors. In addition, injection of AAV-NP65 in DRN significantly increased TPH2 expression in DRN and hippocampus, and reduced anxiety-like behaviors. Acute administration of exogenous 5-HT or HTR3 agonist SR57227A in hippocampus mitigated anxiety-like behaviors in NP65-/- mice. Moreover, replenishment of TPH2 in DRN partly repaired the impairment of long-term potentiation (LTP) maintenance in hippocampus of NP65-/- mice. Finally, we found that loss of NP65 lowered transcription factors Lmx1b expression in postnatal stage and replenishment of NP65 in DRN reversed the decrease in Lmx1b expression of NP65-/- mice. Together, our findings reveal that NP65 deficiency induces anxiety phenotype by downregulating DRN-hippocampus serotonergic-HTR3 transmission. These studies provide a novel and insightful view about NP65 function, suggesting an attractive potential target for treatment of anxiety disorders.

Clarifying the Functional Role of Serotonin in Meloidogyne graminicola Host Plant Parasitism by Immunolocalization and RNA Interference.

Serotonin (5-hydroxytryptamine) is an essential neurotransmitter involved in regulating various behaviors in plant-parasitic nematodes, including locomotion, egg laying, feeding, and mating. However, the functional role of serotonin in root-knot nematode invasion of host plants and the molecular mechanisms underlying feeding behavior remain poorly understood. In this study, we tested the effects of exogenous serotonin and the pharmacological compounds fluoxetine and methiothepin on the feeding behaviors of Meloidogyne graminicola. Our results suggested that M. graminicola possesses an endogenous serotonin signaling pathway and that serotonin plays a crucial role in modulating feeding behaviors in M. graminicola second-stage juveniles. We also identified and cloned the serotonin synthesis enzyme tryptophan hydroxylase (Mg-tph-1) in M. graminicola and investigated the role of endogenous serotonin by generating RNA interference nematodes in Mg-tph-1. Silencing Mg-tph-1 substantially reduced nematode invasion, development, and reproduction. According to the immunostaining results, we speculated that these serotonin immunoreactive cells near the nerve ring in M. graminicola are likely homologous to Caenorhabditis elegans ADFs, NSMs, and RIH serotonergic neurons. Furthermore, we investigated the impact of phytoserotonin on nematode invasion and development in rice by overexpressing OsTDC-3 or supplementing rice plants with tryptamine and found that an increase in phytoserotonin increases nematode pathogenicity. Overall, our study provides insights into the essential role of serotonin in M. graminicola host plant parasitism and proposes that the serotonergic signaling pathway could be a potential target for controlling plant-parasitic nematodes.

Key Enzymes of the Serotonergic System - Tryptophan Hydroxylase 2 and Monoamine Oxidase A - In the Brain of Rats Selectively Bred for a Reaction toward Humans: Effects of Benzopentathiepin TC-2153.

At the Institute of Cytology and Genetics (Novosibirsk, Russia) for over 85 generations, gray rats have been selected for high aggression toward humans (aggressive rats) or its complete absence (tame rats). Aggressive rats are an interesting model for studying fear-induced aggression. Benzopentathiepin TC-2153 exerts an antiaggressive effect on aggressive rats and affects the serotonergic system: an important regulator of aggression. The aim of this study was to investigate effects of TC-2153 on key serotonergic-system enzymes - tryptophan hydroxylase 2 (TPH2) and monoamine oxidase A (MAOA) - in the brain of aggressive and tame rats. Either TC-2153 (10 or 20 mg/kg) or vehicle was administered once intraperitoneally to aggressive and tame male rats. TPH2 and MAOA enzymatic activities and mRNA and protein levels were assessed. The selection for high aggression resulted in upregulation of Tph2 mRNA in the midbrain, of the TPH2 protein in the hippocampus, and of proteins TPH2 and MAOA in the hypothalamus, as compared to tame rats. MAO enzymatic activity was higher in the midbrain and hippocampus of aggressive rats while TPH2 activity did not differ between the strains. The single TC-2153 administration decreased TPH2 and MAO activity in the hypothalamus and midbrain, respectively. The drug affected MAOA protein levels in the hypothalamus: upregulated them in aggressive rats and downregulated them in tame ones. Thus, this study shows profound differences in the expression and activity of key serotonergic system enzymes in the brain of rats selectively bred for either highly aggressive behavior toward humans or its absence, and the effects of benzopentathiepin TC-2153 on these enzymes may point to mechanisms of its antiaggressive action.

ERß activation improves nonylphenol-induced depression and neurotransmitter secretion disruption via the TPH2/5-HT pathway.

The aim of this study is to investigate the role of estrogen receptor ß (ERß) in nonylphenol (NP) - induced depression - like behavior in rats and its impact on the regulation of the TPH2/5-HT pathway. In the in vitro experiment, rat basophilic leukaemia cells (RBL-2H3) cells were divided into the four groups: blank group, NP group (20 µM), ERß agonist group (0.01 µM), and NP＋ERß agonist group (20 µM＋0.01 µM). For the in vivo experiment, 72 adult male Sprague-Dawley rats were randomly divided into following six groups: the Control, NP (40 mg/kg) group, ERß agonist (2 mg/kg, Diarylpropionitrile (DPN)) group, ERß inhibitor (0.1 mg/kg, 4-(2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl) phenol (PHTPP)) group, NP+ERß agonist (40 mg/kg NP ＋ 2 mg/kg DPN) group, and NP+ERß inhibitor (40 mg/kg NP + 0.1 mg/kg PHTPP) group, with 12 rats in each group. Each rat in drug group were given NP by gavage and/or received a single intraperitoneal injection of DPN 2 mg/kg or PHTPP 0.1 mg/kg. Both in vivo and in vitro, NP group showed a decrease in the expression levels of ERß, tryptophan hydroxylase (TPH1), and tryptophan hydroxylase-2 (TPH2) genes and proteins, and reduced levels of DA, NE, and 5-hydroxytryptophan (5-HT) neurotransmitters. RBL-2H3 cells showed signs of cell shrinkage, with rounded cells, increased suspension and more loosely arranged cells. The effectiveness of the ERß agonist stimulation exhibited an increase exceeding 60% in RBL-2H3 cells. The application of ERß agonist resulted in an alleviation the aforementioned alterations. ERß agonist activated the TPH2/5-HT signaling pathways. Compared to the control group, the NP content in the brain tissue of the NP group was significantly increased. The latency to eat for the rats was longer and the amount of food consumed was lower, and the rats had prolonged immobility time in the behavioral experiment of rats. The expression levels of ERß, TPH1, TPH2, 5-HT and 5-HITT proteins were decreased in the NP group, suggesting NP-induced depression-like behaviours as well as disturbances in the secretion of serum hormones and monoamine neurotransmitters. In the NP group, the midline raphe nucleus showed an elongated nucleus with a dark purplish-blue colour, nuclear atrophy, displacement and pale cytoplasm. ERß might ameliorate NP-induced depression-like behaviors, and secretion disorders of serum hormones and monoamine neurotransmitters via activating TPH2/5-HT signaling pathways.

Poor Decision Making and Sociability Impairment Following Central Serotonin Reduction in Inducible TPH2-Knockdown Rats.

Serotonin is an essential neuromodulator for mental health and animals' socio-cognitive abilities. However, we previously found that a constitutive depletion of central serotonin did not impair rat cognitive abilities in stand-alone tests. Here, we investigated how a mild and acute decrease in brain serotonin would affect rats' cognitive abilities. Using a novel rat model of inducible serotonin depletion via the genetic knockdown of tryptophan hydroxylase 2 (TPH2), we achieved a 20% decrease in serotonin levels in the hypothalamus after three weeks of non-invasive oral doxycycline administration. Decision making, cognitive flexibility, and social recognition memory were tested in low-serotonin (Tph2-kd) and control rats. Our results showed that the Tph2-kd rats were more prone to choose disadvantageously in the long term (poor decision making) in the Rat Gambling Task and that only the low-serotonin poor decision makers were more sensitive to probabilistic discounting and had poorer social recognition memory than other low-serotonin and control individuals. Flexibility was unaffected by the acute brain serotonin reduction. Poor social recognition memory was the most central characteristic of the behavioral network of low-serotonin poor decision makers, suggesting a key role of social recognition in the expression of their profile. The acute decrease in brain serotonin appeared to specifically amplify the cognitive impairments of the subgroup of individuals also identified as poor decision makers in the population. This study highlights the great opportunity the Tph2-kd rat model offers to study inter-individual susceptibilities to develop cognitive impairment following mild variations of brain serotonin in otherwise healthy individuals. These transgenic and differential approaches together could be critical for the identification of translational markers and vulnerabilities in the development of mental disorders.

Impact of Serotonin Deficiency on Circadian Dopaminergic Rhythms.

Physiology and behavior are structured temporally to anticipate daily cycles of light and dark, ensuring fitness and survival. Neuromodulatory systems in the brain-including those involving serotonin and dopamine-exhibit daily oscillations in neural activity and help shape circadian rhythms. Disrupted neuromodulation can cause circadian abnormalities that are thought to underlie several neuropsychiatric disorders, including bipolar mania and schizophrenia, for which a mechanistic understanding is still lacking. Here, we show that genetically depleting serotonin in Tph2 knockout mice promotes manic-like behaviors and disrupts daily oscillations of the dopamine biosynthetic enzyme tyrosine hydroxylase (TH) in midbrain dopaminergic nuclei. Specifically, while TH mRNA and protein levels in the Substantia Nigra (SN) and Ventral Tegmental Area (VTA) of wild-type mice doubled between the light and dark phase, TH levels were high throughout the day in Tph2 knockout mice, suggesting a hyperdopaminergic state. Analysis of TH expression in striatal terminal fields also showed blunted rhythms. Additionally, we found low abundance and blunted rhythmicity of the neuropeptide cholecystokinin (Cck) in the VTA of knockout mice, a neuropeptide whose downregulation has been implicated in manic-like states in both rodents and humans. Altogether, our results point to a previously unappreciated serotonergic control of circadian dopamine signaling and propose serotonergic dysfunction as an upstream mechanism underlying dopaminergic deregulation and ultimately maladaptive behaviors.

Cinnamic Acid, Perillic Acid, and Tryptophan Metabolites Differentially Regulate Ion Transport and Serotonin Metabolism and Signaling in the Mouse Ileum In Vitro.

Phytochemicals and tryptophan (Trp) metabolites have been found to modulate gut function and health. However, whether these metabolites modulate gut ion transport and serotonin (5-HT) metabolism and signaling requires further investigation. The aim of this study was to investigate the effects of selected phytochemicals and Trp metabolites on the ion transport and 5-HT metabolism and signaling in the ileum of mice in vitro using the Ussing chamber technique. During the in vitro incubation, vanillylmandelic acid (VMA) reduced (p < 0.05) the short-circuit current, and 100 µM chlorogenic acid (CGA) (p = 0.12) and perillic acid (PA) (p = 0.14) had a tendency to reduce the short-circuit current of the ileum. Compared with the control, PA and N-acetylserotonin treatment upregulated the expression of tryptophan hydroxylase 1 (Tph1), while 100 µM cinnamic acid, indolelactic acid (ILA), and 10 µM CGA or indoleacetaldehyde (IAld) treatments downregulated (p < 0.05) the mRNA levels of Tph1. In addition, 10 µM IAld or 100 µM ILA upregulated (p < 0.05) the expression of monoamine oxidase A (Maoa). However, 10 µM CGA or 100 µM PA downregulated (p < 0.05) Maoa expression. All selected phytochemicals and Trp metabolites upregulated (p < 0.05) the expression of Htr4 and Htr7 compared to that of the control group. VMA and CGA reduced (p < 0.05) the ratios of Htr1a/Htr7 and Htr4/Htr7. These findings may help to elucidate the effects of phytochemicals and Trp metabolites on the regulation of gut ion transport and 5-HT signaling-related gut homeostasis in health and disease.

Effect of (R)-2-Amino-6-(1R,2S)-1,2-Dihydroxypropyl)-5,6,7,8-Tetrahydropterin-4(3H)-One and Its Structural Analogues on the Temperature Stability of Tryptophan Hydroxylase 2 with the P447R Mutation.

The enzyme tryptophan hydroxylase 2 (TPH2) catalyzes the hydroxylation of L-tryptophan to L-5-hydroxytryptophan (5-HTP), the first and the key step in 5-HT synthesis in the mammalian brain. Mutations in the human Tph2 gene reducing enzyme activity increase the risk of psychopathology. Pharmacological chaperones are small molecules that can specifically bind to mutant protein molecules, restore their disturbed 3D structure to the native state, and increase their stability and functional activity. The chaperone activity of (R)-2-amino-6-(1R,2S)-1,2-dihydroxypropyl)-5,6,7,8-tetrahydropterin-4(3H)-one (BH4) is expressed by increasing the in vitro thermal stability of mutant tyrosine hydroxylase and phenylalanine hydroxylase molecules which are similar to TPH2 in their structure and characteristics. The P447R substitution in the mouse TPH2 molecule results in a 2-fold decrease in enzyme activity in their brains. We studied the effect of this mutation on the TPH2 thermal stability, as well as on the ability of BH4 and its 8 structural analogues to increase the thermal stability of the mutant TPH2 from midbrain extracts of BALB/C mice. Temperature stability was studied by the decrease in enzyme activity during its heating for 2 min at increasing temperatures and was evaluated by the T50 value that is the temperature at which the enzyme activity decreased by half. For the mutant TPH2, the T50 value was decreased compared to the wild type enzyme. BH4 and its closest structural analogue, 6-methyl-5,6,7,8-tetrahydropterin, increased the T50 value, i.e., exhibited chaperone activity. Other close BH4 analogs, 6,7-dimethyl-5,6,7,8-tetrahydropterin and folic acid, were not effective. It can be assumed that BH4 can be effective in the treatment of mental disorders caused by mutations in the Tph2 gene.

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.

The aromatic amino acid hydroxylases: Structures, catalysis, and regulation of phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase.

The aromatic amino acid hydroxylases phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase are non-heme iron enzymes that catalyze key physiological reactions. This review discusses the present understanding of the common catalytic mechanism of these enzymes and recent advances in understanding the relationship between their structures and their regulation.

Molecular signature of excessive female aggression: study of stressed mice with genetic inactivation of neuronal serotonin synthesis.

Aggression is a complex social behavior, critically involving brain serotonin (5-HT) function. The neurobiology of female aggression remains elusive, while the incidence of its manifestations has been increasing. Yet, animal models of female aggression are scarce. We previously proposed a paradigm of female aggression in the context of gene x environment interaction where mice with partial genetic inactivation of tryptophan hydroxylase-2 (Tph2+/- mice), a key enzyme of neuronal 5-HT synthesis, are subjected to predation stress resulting in pathological aggression. Using deep sequencing and the EBSeq method, we studied the transcriptomic signature of excessive aggression in the prefrontal cortex of female Tph2+/- mice subjected to rat exposure stress and food deprivation. Challenged mutants, but not other groups, displayed marked aggressive behaviors. We found 26 genes with altered expression in the opposite direction between stressed groups of both Tph2 genotypes. We identified several molecular markers, including Dgkh, Arfgef3, Kcnh7, Grin2a, Tenm1 and Epha6, implicated in neurodevelopmental deficits and psychiatric conditions featuring impaired cognition and emotional dysregulation. Moreover, while 17 regulons, including several relevant to neural plasticity and function, were significantly altered in stressed mutants, no alteration in regulons was detected in stressed wildtype mice. An interplay of the uncovered pathways likely mediates partial Tph2 inactivation in interaction with severe stress experience, thus resulting in excessive female aggression.

Interaction between childhood trauma experience and TPH2 rs7305115 gene polymorphism in brain gray matter volume.

BACKGROUND: Childhood trauma is one of the most extensively studied and well-supported environmental risk factors for the development of mental health problems. The human tryptophan hydroxylase 2 (TPH2) gene is one of the most promising candidate genes in numerous psychiatric disorders. However, it is now widely acknowledged that neither genetic variation nor environmental exposure alone can fully explain all the phenotypic variance observed in psychiatric disorders. Therefore, it is necessary to consider the interaction between the two factors in psychiatric research. METHODS: We enrolled a sizable nonclinical cohort of 786 young, healthy adults who underwent structural MRI scans and completed genotyping, the Childhood Trauma Questionnaire (CTQ) and behavioural scores. We identified the interaction between childhood trauma and the TPH2 rs7305115 gene polymorphism in the gray matter volume (GMV) of specific brain subregions and the behaviour in our sample using a multiple linear regression framework. We utilized mediation effect analysis to identify environment /gene-brain-behaviour relationships. RESULTS: We found that childhood trauma and TPH2 rs7305115 interacted in both behaviour and the GMV of brain subregions. Our findings indicated that the GMV of the right posterior parietal thalamus served as a significant mediator supporting relationship between childhood trauma (measured by CTQ score) and anxiety scores in our study population, and the process was partly modulated by the TPH2 rs7305115 gene polymorphism. Moreover, we found only a main effect of childhood trauma in the GMV of the right parahippocampal gyrus area, supporting the relationship between childhood trauma and anxiety scores as a significant mediator. CONCLUSIONS: Our findings suggest that early-life trauma may have a specific and long-term structural effect on brain GMV, potentially leading to altered cognitive and emotional processes involving the parahippocampal gyrus and thalamus that may also be modulated by the TPH2 gene polymorphism. This finding highlights the importance of considering genetic factors when examining the impact of early-life experiences on brain structure and function. Gene‒environment studies can be regarded as a powerful objective supplement for targeted therapy, early diagnosis and treatment evaluation in the future.

Synthesis and biological evaluation of xanthine derivatives with phenacyl group as tryptophan hydroxylase 1 (TPH1) inhibitors for obesity and fatty liver disease.

Tryptophan hydroxylase 1 (TPH1) has emerged as a target for the treatment of metabolic diseases including obesity and fatty liver disease. A series of xanthine derivatives were synthesized and evaluated for their TPH1 inhibition. Among the synthesized compounds, compound 40 showed good in vitro activity and liver microsomal stability. Docking studies revealed that compound 40 showed better binding to TPH1 via key intermolecular interactions involving the xanthine scaffold, imidazo-thiazolyl ring, and hydroxyl-containing phenacyl moiety. In addition, compound 40 effectively suppressed the adipocyte differentiation of 3 T3-L1 cells.