Tryptophan hydroxylase-1 regulates immune tolerance and inflammation

Host-microbe serotonin metabolism

As a result of a long evolutionary history, serotonin plays a variety of physiological roles, including neurological, cardiovascular, gastrointestinal, and endocrine functions. While many of these activities can be accommodated within the serotoninergic activity, recent findings have revealed an unsuspected role of serotonin in orchestrating host and microbial dialogue at the tryptophan dining table, to the benefit of local and systemic homeostasis. Herein we review the dual role of serotonin at the host-microbe interface and discuss how unraveling the interconnections among the host and microbial pathways of tryptophan degradation may help to accommodate the versatility of serotonin in physiology and pathology.

Novel applications of Yinhua Miyanling tablets in ulcerative colitis treatment based on metabolomics and network pharmacology

BACKGROUND

Yinhua Miyanling tablets (YMT), comprising 10 Chinese medicinal compounds, is a proprietary Chinese medicine used in the clinical treatment of urinary tract infections. Medicinal compounds, extracts, or certain monomeric components in YMT all show good effect on ulcerative colitis (UC). However, no evidence supporting YMT as a whole prescription for UC treatment is available.

PURPOSE

To evaluate the anti-UC activity of YMT and elucidate the underlying mechanisms. The objective of the study was to provide evidence for the add-on development of YMT to treat UC.

METHODS

First, YMT's protective effect on the intestinal barrier was evaluated using a lipopolysaccharide (LPS)-induced Caco-2 intestinal injury model. Second, the UC mouse model was established using dextran sodium sulfate (DSS) to determine YMT's influence on symptoms, inflammatory factors, intestinal barrier, and histopathological changes in the colon. Third, an integrated method combining metabolomics and network pharmacology was employed to screen core targets and key metabolic pathways with crucial roles in YMT's therapeutic effect on UC. Molecular docking was employed to identify the key targets with high affinity. Finally, western blotting was performed to validate the mechanism of YMT action against UC.

RESULTS

YMT enhanced the transepithelial electrical resistance value and improved the expression of proteins of the tight junctions dose-dependently in LPS-induced Caco-2 cells. UC mice treated with YMT exhibited alleviated pathological lesions of the colon tissue in the in vivo pharmacodynamic experiments. The colonic lengths tended to be normal, and the levels of inflammatory factors (TNF-α, IL-6, and iNOS) along with those of the core enzymes (MPO, MDA, and SOD) improved. YMT effectively ameliorated DSS-induced colonic mucosal injury; pathological changes along with ultrastructure damage were significantly alleviated (evidenced by a relatively intact colon tissue, recovery of epithelial damage, repaired gland, reduced infiltration of inflammatory cells and epithelial cells arranged closely with dense microvilli). Seven key targets (IL-6, TNF-α, MPO, COX-2, HK2, TPH, and CYP1A2) and four key metabolic pathways (arachidonic acid metabolism, linoleate metabolism, glycolysis, and gluconeogenesis and tyrosine biosynthesis) were identified to play vital roles in the treatment on UC using YMT.

CONCLUSIONS

YMT exerts beneficial therapeutic effects on UC by regulating multiple endogenous metabolites, targets, and metabolic pathways, suggestive of its potential novel application in UC treatment.

A microbially produced AhR ligand promotes a Tph1-driven tolerogenic program in multiple sclerosis

Multiple sclerosis is a debilitating autoimmune disease, characterized by chronic inflammation of the central nervous system. While the significance of the gut microbiome on multiple sclerosis pathogenesis is established, the underlining mechanisms are unknown. We found that serum levels of the microbial postbiotic tryptophan metabolite indole-3-carboxaldehyde (3-IAld) inversely correlated with disease duration in multiple sclerosis patients. Much like the host-derived tryptophan derivative L-Kynurenine, 3-IAld would bind and activate the Aryl hydrocarbon Receptor (AhR), which, in turn, controls endogenous tryptophan catabolic pathways. As a result, in peripheral lymph nodes, microbial 3-IAld, affected mast-cell tryptophan metabolism, forcing mast cells to produce serotonin via Tph1. We thus propose a protective role for AhR-mast-cell activation driven by the microbiome, whereby natural metabolites or postbiotics will have a physiological role in immune homeostasis and may act as therapeutic targets in autoimmune diseases.

The potential influence of melatonin on mitochondrial quality control: a review

Mitochondria are critical for cellular energetic metabolism, intracellular signaling orchestration and programmed death regulation. Therefore, mitochondrial dysfunction is associated with various pathogeneses. The maintenance of mitochondrial homeostasis and functional recovery after injury are coordinated by mitochondrial biogenesis, dynamics and autophagy, which are collectively referred to as mitochondrial quality control. There is increasing evidence that mitochondria are important targets for melatonin to exert protective effects under pathological conditions. Melatonin, an evolutionarily conserved tryptophan metabolite, can be synthesized, transported and metabolized in mitochondria. In this review, we summarize the important role of melatonin in the damaged mitochondria elimination and mitochondrial energy supply recovery by regulating mitochondrial quality control, which may provide new strategies for clinical treatment of mitochondria-related diseases.

Bridging of host-microbiota tryptophan partitioning by the serotonin pathway in fungal pneumonia

The aromatic amino acid L-tryptophan (Trp) is essentially metabolized along the host and microbial pathways. While much is known about the role played by downstream metabolites of each pathways in intestinal homeostasis, their role in lung immune homeostasis is underappreciated. Here we have examined the role played by the Trp hydroxylase/5-hydroxytryptamine (5-HT) pathway in calibrating host and microbial Trp metabolism during Aspergillus fumigatus pneumonia. We found that 5-HT produced by mast cells essentially contributed to pathogen clearance and immune homeostasis in infection by promoting the host protective indoleamine-2,3-dioxygenase 1/kynurenine pathway and limiting the microbial activation of the indole/aryl hydrocarbon receptor pathway. This occurred via regulation of lung and intestinal microbiota and signaling pathways. 5-HT was deficient in the sputa of patients with Cystic fibrosis, while 5-HT supplementation restored the dysregulated Trp partitioning in murine disease. These findings suggest that 5-HT, by bridging host-microbiota Trp partitioning, may have clinical effects beyond its mood regulatory function in respiratory pathologies with an inflammatory component.

Serum Tryptophan Metabolites are Associated with Erosive Hand Osteoarthritis and Pain: Results from the DIGICOD Cohort

OBJECTIVE

To investigate host and gut-microbiota related Tryptophan metabolism in hand osteoarthritis (HOA).

METHODS

The baseline serum concentration of 20 Tryptophan metabolites was measured in 416 HOA patients in a cross-sectional analysis of the DIGICOD cohort. Tryptophan metabolites levels, metabolite-ratios and metabolism pathway activation were compared between erosive (N=141) and non-erosive HOA (N=275) by multiple logistic regressions adjusted on age, BMI and sex. The association between Tryptophan metabolite levels and HOA symptoms was investigated by a Spearman's rank correlation analysis.

RESULTS

Four serum Tryptophan metabolites, eight metabolite ratios and one metabolism pathway were associated with erosive HOA. Erosive HOA was negatively associated with Tryptophan (odds ratio (OR)=0.41, 95% confidence interval [0.24-0.70]), indole-3-aldehyde (OR=0.67 [0.51-0.90]) and 3-OH-anthranilic acid (OR=1.32 [1.13-1.54]) and positively with 5-OH-Tryptophan levels (OR=1.41 [1.13-1.77]). The pro-inflammatory kynurenine-indoleamine 2,3-dioxygenase pathway was upregulated in erosive HOA (OR=1.60 [1.11-2.29]). Eleven metabolites were correlated with HOA symptoms and were mostly pain-related. Serotonin and N-acetyl serotonin levels were negatively correlated with number of tender joints. Indole-3-aldehyde level was negatively correlated and 3-OH-anthranilic acid, 3-OH-kynurenine and 5-OH-Tryptophan levels were positively correlated with number of patients-reported painful joints. Quinolinic acid and 3-OH-kynurenine levels correlated positively with AUSCAN pain.

CONCLUSIONS

Tryptophan metabolites disturbance is associated with erosive HOA and pain and emphasize the role of low-grade inflammation and gut dysbiosis in HOA.

Dietary tryptophan deficiency promotes gut RORγt+ Treg cells at the expense of Gata3+ Treg cells and alters commensal microbiota metabolism

Micronutrient deficiency is a major cause of disease throughout the world. Yet, how perturbations influence the immune-microbiome interface remains poorly understood. Here, we report that loss of dietary tryptophan (Trp) reshapes intestinal microbial communities, including the depletion of probiotic L. reuteri, drives transcriptional changes to immune response genes in the intestinal ileum, and reshapes the regulatory T cell (Treg) compartment. Dietary Trp deficiency promotes expansion of RORγt⁺ Treg cells and the loss of Gata3⁺ Tregs in a microbiota-dependent manner. In the absence of dietary Trp, provision of the AhR ligand indole-3-carbinol is sufficient to restore the Treg compartment. Together, these data show that dietary Trp deficiency perturbs the interaction between the host and its bacterial symbionts to regulate Treg homeostasis via the deprivation of bacterially derived Trp metabolites. Our findings highlight an essential role for immune-microbiome crosstalk as a key homeostatic regulator during nutrient deficiency.

Probiotics as a Tool for Regulating Molecular Mechanisms in Depression: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Depression is one of the main mental disorders. Pharmacological treatment of depression is often associated with delayed effects or insufficient efficacy. Consequently, there is a need to discover new therapeutic methods to cope with depression faster and more effectively. Several lines of evidence indicate that the use of probiotic therapy reduces depressive symptoms. Nonetheless, the exact mechanisms linking the gut microbiota and the central nervous system, as well as the potential mechanisms of action for probiotics, are still not entirely clarified. The aim of this review was to systematically summarize the available knowledge according to PRISMA guidelines on the molecular mechanisms linking probiotics and healthy populations with subclinical depression or anxiety symptoms, as well as depressed patients with or without comorbid somatic illnesses. The standardized mean difference (SMD) with 95% confidence intervals (CI) was calculated. Twenty records were included. It has been found that probiotic administration is linked to a significant increase in BDNF levels during probiotic treatment compared to the placebo (SMD = 0.37, 95% CI [0.07, 0.68], p = 0.02) when considering the resolution of depressive symptoms in depressed patients with or without comorbid somatic illnesses. CRP levels were significantly lower (SMD = -0.47, 95% CI [0.75, -0.19], p = 0.001), and nitric oxide levels were significantly higher (SMD = 0.97, 95% CI [0.58, 1.36], p < 0.0001) in probiotic-treated patients compared to the placebo, however, only among depressed patients with somatic co-morbidities. There were no significant differences in IL-1β, IL-6, IL-10, TNF-α, and cortisol levels after probiotic administration between the intervention and control groups (all p > 0.05). Firm conclusions on the effectiveness of probiotics and their possible association with inflammatory markers in the healthy population (only with subclinical depressive or anxiety symptoms) cannot be drawn. The advent of clinical trials examining the long-term administration of probiotics could evaluate the long-term effectiveness of probiotics in treating depression and preventing its recurrence.

The exploitation of enzyme-based cancer immunotherapy

Cancer immunotherapy utilizes the immune system and its wide-ranging components to deliver anti-tumor responses. In immune escape mechanisms, tumor microenvironment-associated soluble factors and cell surface-bound molecules are mainly accountable for the dysfunctional activity of tumor-specific CD8⁺ T cells, natural killer (NK) cells, tumor associated macrophages (TAMs) and stromal cells. The myeloid-derived suppressor cells (MDSCs) and Foxp3⁺ regulatory T cells (Tregs), are also key tumor-promoting immune cells. These potent immunosuppressive networks avert tumor rejection at various stages, affecting immunotherapies' outcomes. Numerous clinical trials have elucidated that disruption of immunosuppression could be achieved via checkpoint inhibitors. Another approach utilizes enzymes that can restore the body's potential to counter cancer by triggering the immune system inhibited by the tumor microenvironment. These immunotherapeutic enzymes can catalyze an immunostimulatory signal and modulate the tumor microenvironment via effector molecules. Herein, we have discussed the immuno-metabolic roles of various enzymes like ATP-dephosphorylating ectoenzymes, inducible Nitric Oxide Synthase, phenylamine, tryptophan, and arginine catabolizing enzymes in cancer immunotherapy. Understanding the detailed molecular mechanisms of the enzymes involved in modulating the tumor microenvironment may help find new opportunities for cancer therapeutics.

Role of neurotransmitters in immune-mediated inflammatory disorders: a crosstalk between the nervous and immune systems

Immune-mediated inflammatory diseases (IMIDs) are a group of common heterogeneous disorders, characterized by an alteration of cellular homeostasis. Primarily, it has been shown that the release and diffusion of neurotransmitters from nervous tissue could result in signaling through lymphocyte cell-surface receptors and the modulation of immune function. This finding led to the idea that the neurotransmitters could serve as immunomodulators. It is now manifested that neurotransmitters can also be released from leukocytes and act as autocrine or paracrine modulators. Increasing data indicate that there is a crosstalk between inflammation and alterations in neurotransmission. The primary goal of this review is to demonstrate how these two pathways may converge at the level of the neuron and glia to involve in IMID. We review the role of neurotransmitters in IMID. The different effects that these compounds exert on a variety of immune cells are also reviewed. Current and future developments in understanding the cross-talk between the immune and nervous systems will undoubtedly identify new ways for treating immune-mediated diseases utilizing agonists or antagonists of neurotransmitter receptors.

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 SUV_max of the hottest tumor lesion per patient revealed that the 'low' C11-AMT SUV_max was associated with longer progression-free survival in our clinical trial (n = 26). We saw no such trends with pretreatment FDG PET SUV_max. 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.

Identification of an Amino Acid Metabolism Signature Participating in Immunosuppression in Ovarian Cancer

Ovarian cancer is one of the most fatal gynecologic cancer types, and its heterogeneity in the microenvironment limited the efficacy of the current treatment. In this study, we aimed at building a risk score to predict patient survival based on the amino acid metabolic genes and TCGA RNA-seq dataset (n = 376). We first used univariate analysis and PCA to select and test the survival-related genes, and the LASSO regression was applied to build the risk score signature with prediction accuracy estimation by survival analysis and ROC. We then conducted GSEA and GSVA to investigate the biological roles of the signature and run ESTIMATE and 4 different immunocyte infiltration algorithms to investigate the immunological diversity between the risk groups. Furthermore, the immune checkpoint expression was compared. We finally explored the cMap and PRISM database to screen out sensitive drugs for high-risk patients and analyzed the oncogenic role of TPH1 by clone formation and transwell migration assays. As a result, the risk score predicted patients' survival and stage with high accuracy. We found that the signature mainly affected the extracellular activities and cancer immunity by functional enrichment. We further discovered that the high-risk OV harbored a high level of stromal cell infiltration and was associated with highly infiltrated fibroblasts and decreased CD8+ T cells. The immune checkpoint analyses showed that TGFB1 and CD276 were upregulated. Finally, we screened out 4 PRISM drugs with lower IC₅₀ in the high-risk group and validated the oncogenic role of TPH1 in OV cancers. We believe this research offered a novel understanding of the interplay between amino acid metabolism and immunity in OV and will benefit patients with better prognostic management and therapeutic strategy development.

Clinical significance of plasma-free amino acids and tryptophan metabolites in patients with non-small cell lung cancer receiving PD-1 inhibitor: a pilot cohort study for developing a prognostic multivariate model

Background

Amino acid metabolism is essential for tumor cell proliferation and regulation of immune cell function. However, the clinical significance of free amino acids (plasma-free amino acids (PFAAs)) and tryptophan-related metabolites in plasma has not been fully understood in patients with non-small cell lung cancer (NSCLC) who receive immune checkpoint inhibitors.

Methods

We conducted a single cohort observational study. Peripheral blood samples were collected from 53 patients with NSCLC before treatment with PD-1 (Programmed cell death-1) inhibitors. The plasma concentrations of 21 PFAAs, 14 metabolites, and neopterin were measured by liquid chromatography–mass spectrometry. Using Cox hazard analysis with these variables, a multivariate model was established to stratify patient overall survival (OS). Gene expression in peripheral blood mononuclear cells (PBMCs) was compared between the high-risk and low-risk patients by this multivariate model.

Results

On Cox proportional hazard analysis, higher concentrations of seven PFAAs (glycine, histidine, threonine, alanine, citrulline, arginine, and tryptophan) as well as lower concentrations of three metabolites (3h-kynurenine, anthranilic acid, and quinolinic acid) and neopterin in plasma were significantly correlated with better OS (p<0.05). In particular, the multivariate model, composed of a combination of serine, glycine, arginine, and quinolinic acid, could most efficiently stratify patient OS (concordance index=0.775, HR=3.23, 95% CI 2.04 to 5.26). From the transcriptome analysis in PBMCs, this multivariate model was significantly correlated with the gene signatures related to immune responses, such as CD8 T-cell activation/proliferation and proinflammatory immune responses, and 12 amino acid-related genes were differentially expressed between the high-risk and low-risk groups.

Conclusions

The multivariate model with PFAAs and metabolites in plasma might be useful for stratifying patients who will benefit from PD-1 inhibitors.

GPR35 promotes neutrophil recruitment in response to serotonin metabolite 5-HIAA

Rapid neutrophil recruitment to sites of inflammation is crucial for innate immune responses. Here, we reveal that the G-protein-coupled receptor GPR35 is upregulated in activated neutrophils, and it promotes their migration. GPR35-deficient neutrophils are less recruited from blood vessels into inflamed tissue, and the mice are less efficient in clearing peritoneal bacteria. Using a bioassay, we find that serum and activated platelet supernatant stimulate GPR35, and we identify the platelet-derived serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) as a GPR35 ligand. GPR35 function in neutrophil recruitment is strongly dependent on platelets, with the receptor promoting transmigration across platelet-coated endothelium. Mast cells also attract GPR35+ cells via 5-HIAA. Mice deficient in 5-HIAA show a loss of GPR35-mediated neutrophil recruitment to inflamed tissue. These findings identify 5-HIAA as a GPR35 ligand and neutrophil chemoattractant and establish a role for platelet- and mast cell-produced 5-HIAA in cell recruitment to the sites of inflammation and bacterial clearance.

Construction of a "Bacteria-Metabolites" Co-Expression Network to Clarify the Anti-Ulcerative Colitis Effect of Flavonoids of Sophora flavescens Aiton by Regulating the "Host-Microbe" Interaction

Ulcerative colitis (UC) is considered an immune disease, which is related to the dysbiosis of intestinal microbiota and disorders of the host immune system and metabolism. Sophora flavescens Aiton has been used for the clinical treatment of UC in China and East Asia for thousands of years. It has many traditional prescriptions and modern preparations, and its curative effects are definite. We are the first to report that the flavonoids in Sophora flavescens (S. flavescens) Aiton EtOAc extract (SFE) could potentially attenuate the dextran sodium sulfate–induced UC in mice, which changed the current understanding of considering alkaloids as the only anti-UC pharmacological substances of S. flavescens Aiton. Based on the 16S rRNA gene sequencing and metabolomic analysis, it was found that the anti-UC effects of SFE were due to the regulation of gut microbiota, reversing the abnormal metabolisms, and regulation of the short-chain fatty acids synthesis. Notably, according to the interaction networks of specific bacteria and “bacteria and metabolites” co-expression network, the SFE could enrich the abundance of the commensal bacterium Lactobacillus, Roseburia, norank_f__Muribaculaceae, Anaerotruncus, Candidatus_Saccharimona, and Parasutterella, which are proposed as potentially beneficial bacteria, thereby playing vital roles in the treatment of UC.

Tapping into 5-HT3 Receptors to Modify Metabolic and Immune Responses

5-hydroxytryptamine type 3 (5-HT₃) receptors are ligand gated ion channels, which clearly distinguish their mode of action from the other G-protein coupled 5-HT or serotonin receptors. 5-HT₃ receptors are well established targets for emesis and gastrointestinal mobility and are used as adjunct targets in treating schizophrenia. However, the distribution of these receptors is wider than the nervous system and there is potential that these additional sites can be targeted to modulate inflammatory and/or metabolic conditions. Recent progress in structural biology and pharmacology of 5-HT₃ receptors have provided profound insights into mechanisms of their action. These advances, combined with insights into clinical relevance of mutations in genes encoding 5-HT₃ subunits and increasing understanding of their implications in patient's predisposition to diseases and response to the treatment, open new avenues for personalized precision medicine. In this review, we recap on the current status of 5-HT₃ receptor-based therapies using a biochemical and physiological perspective. We assess the potential for targeting 5-HT₃ receptors in conditions involving metabolic or inflammatory disorders based on recent findings, underscoring the challenges and limitations of this approach.

Zebrafish intestinal transcriptome highlights subdued inflammatory responses to dietary soya bean and efficacy of yeast β-glucan

Anti-nutritional factors in dietary components can have a negative impact on the intestinal barrier. Here, we present soya bean-induced changes in the intestine of juvenile zebrafish and the effect of yeast β-glucan through a transcriptomic approach. The inclusion of soya bean meal affected the expression of several intestinal barrier function-related genes like arl4ca, rab25b, rhoub, muc5ac, muc5d, clcn2c and cltb in zebrafish. Several metabolic genes like cyp2x10.2, cyp2aa2, aldh3a2b, crata, elovl4, elovl6, slc51a, gpat2 and ATP-dependent peptidase activity (lonrf, clpxb) were altered in the intestinal tissue. The expression of immune-related genes like nlrc3, nlrp12, gimap8, prdm1 and tph1a, and genes related to cell cycle, DNA damage and DNA repair (e.g. spo11, rad21l1, nabp1b, spata22, tdrd9) were also affected in the soya bean fed group. Furthermore, our study suggests the plausible effect of yeast β-glucan through the modulation of several genes that regulate immune responses and barrier integrity. Our findings indicate a subdued inflammation in juvenile zebrafish fed soya bean meal and the efficacy of β-glucan to counter these subtle inflammatory responses.

Overproduction of Gastrointestinal 5-HT Promotes Colitis-Associated Colorectal Cancer Progression via Enhancing NLRP3 Inflammasome Activation

Chronic inflammation is a key driver for colitis-associated colorectal cancer. 5-hydroxytryptamine (5-HT), a neurotransmitter, has been reported to promote inflammation in the gastrointestinal tract. However, the mechanism behind this remains unclear. In this study, we found that 5-HT levels, as well as the expression of tryptophan hydroxylase 1 (TPH1), the 5-HT biosynthesis rate-limiting enzyme, were significantly upregulated in colorectal tumor tissues from patients with colorectal cancer, colorectal cancer mouse models, and colorectal cancer cell lines when compared with normal colorectal tissues or epithelial cell lines. Colorectal cancer cell-originated 5-HT enhanced NLRP3 inflammasome activation in THP-1 cells and immortalized bone marrow-derived macrophages (iBMDM) via its ion channel receptor, HTR3A. Mechanistically, HTR3A activation led to Ca²⁺ influx, followed by CaMKIIα phosphorylation (Thr286) and activation, which then induced NLRP3 phosphorylation at Ser198 (mouse: Ser194) and inflammasome assembling. The NLRP3 inflammasome mediated IL1β maturation, and release upregulated 5-HT biosynthesis in colorectal cancer cells by inducing TPH1 transcription, revealing a positive feedback loop between 5-HT and NLRP3 signaling. Silencing TPH1 or HTR3A by short hairpin RNA slowed down tumor growth in an established CT26 and iBMDM coimplanted subcutaneous allograft colorectal cancer mouse model, whereas treatment with TPH1 inhibitor 4-chloro-DL-phenylalanine or HTR3A antagonist tropisetron alleviated tumor progression in an azoxymethane/dextran sodium sulfate-induced colorectal cancer mouse model. Addressing the positive feedback loop between 5-HT and NLRP3 signaling could provide potential therapeutic targets for colorectal cancer.

Fluorine-18-Labeled PET Radiotracers for Imaging Tryptophan Uptake and Metabolism: a Systematic Review

Due to its metabolism via the serotonin and kynurenine pathways, tryptophan plays a key role in multiple disease processes including cancer. Imaging tryptophan uptake and metabolism in vivo can be achieved with tryptophan derivative positron emission tomography (PET) radiotracers. While human studies with such tracers have been confined to C-11-labeled compounds, preclinical development of F-18-labeled tryptophan-based radiotracers has surged in recent years. We performed a systematic review of studies reporting on such F-18-labeled tryptophan tracers to summarize and compare their biological characteristics and their potential for tumor imaging, with a particular focus on key enzymes of the kynurenine pathway (indoleamine 2,3-dioxygenase [IDO] and tryptophan 2,3-dioxygenase [TDO]), which play an important role in tumoral immune resistance. From a PubMed search, English language articles including data on the preparation and radiochemical and/or biological characteristics of F-18-labeled tryptophan derivative radiotracers were reviewed. A total of 19 original papers included data on 15 unique radiotracers, the majority of which were synthesized with an adequate radiochemical yield. Automated synthesis was reported for 1-(2-[¹⁸F]fluoroethyl)-L-tryptophan, the most extensively evaluated tracer thus far. Biodistribution studies showed high uptake in the pancreas, while the L-type amino acid transporter was the dominant transport mechanism for most of the reviewed tracers. Tracers tested for tumor uptake showed accumulation in tumor cell lines in vitro and in xenografts in vivo, often with favorable tumor-to-background uptake ratios in comparison with clinically used F-18-labeled radiotracers. Five tracers showed promise for imaging IDO activity, including 1-(2-[¹⁸F]fluoroethyl)-L-tryptophan and a F-18-labeled analog of alpha-[¹¹C]methyl-L-tryptophan tested clinically in previous studies. Two radiotracers were metabolized by TDO but showed defluorination in vivo. In summary, most F-18-labeled tryptophan derivative PET tracers share common transport mechanisms and biodistribution characteristics. Several reported tracers could be candidates for further testing and validation toward PET imaging applications in a variety of human diseases.

Transcription Factors in the Development and Pro-Allergic Function of Mast Cells

Mast cells (MCs) are innate immune cells of hematopoietic origin localized in the mucosal tissues of the body and are broadly implicated in the pathogenesis of allergic inflammation. Transcription factors have a pivotal role in the development and differentiation of mast cells in response to various microenvironmental signals encountered in the resident tissues. Understanding the regulation of mast cells by transcription factors is therefore vital for mechanistic insights into allergic diseases. In this review we summarize advances in defining the transcription factors that impact the development of mast cells throughout the body and in specific tissues, and factors that are involved in responding to the extracellular milieu. We will further describe the complex networks of transcription factors that impact mast cell physiology and expansion during allergic inflammation and functions from degranulation to cytokine secretion. As our understanding of the heterogeneity of mast cells becomes more detailed, the contribution of specific transcription factors in mast cell-dependent functions will potentially offer new pathways for therapeutic targeting.

Regulatory T cells and transplantation tolerance: Emerging from the darkness?

The field of tissue transplantation has revolutionized the treatment of patients with failing organs. Its success, thus far, has depended on combinations of immunosuppressive drugs that damp host immunity, while also imposing numerous unwanted side-effects. There is a longstanding recognition that better treatment outcomes, will come from replacing these drugs, fully or in part, by taking advantage of tractable physiological mechanisms of self-tolerance. The past 50 years have seen many advances in the field of self-tolerance, but perhaps, the most tractable of these has been the more recent discovery of a subset T-cells (Treg) whose role is to regulate or damp immunity. This article is intended to first provide the reader with some historical background to explain why we have been slow to identify these cells, despite numerous clues to their existence, and also to indicate how little we know about how they achieve their regulatory function in averting transplant rejection. However, as is often the case in immunology, the therapeutic needs often dictate that our advances move to translation even before detailed explanations of the science are available. The final part of the article will briefly summarize how Treg are being harnessed as agents to interface with or perhaps, replace current drug combinations.

Nicotinamide adenine dinucleotide metabolism in the immune response, autoimmunity and inflammageing

Metabolism is dynamically regulated to accompany immune cell function, and altered immunometabolism can result in impaired immune responses. Concomitantly, the pharmacological manipulation of metabolic processes offers an opportunity for therapeutic intervention in inflammatory disorders. The nicotinamide adenine dinucleotide (NAD⁺) is a critical metabolic intermediate that serves as enzyme cofactor in redox reactions, and is also used as a co‐substrate by many enzymes such as sirtuins, adenosine diphosphate ribose transferases and synthases. Through these activities, NAD⁺ metabolism regulates a broad spectrum of cellular functions such as energy metabolism, DNA repair, regulation of the epigenetic landscape and inflammation. Thus, the manipulation of NAD⁺ availability using pharmacological compounds such as NAD⁺ precursors can have immune‐modulatory properties in inflammation. Here, we discuss how the NAD⁺ metabolism contributes to the immune response and inflammatory conditions, with a special focus on multiple sclerosis, inflammatory bowel diseases and inflammageing.

International Union of Basic and Clinical Pharmacology. CX. Classification of Receptors for 5-hydroxytryptamine; Pharmacology and Function

5-HT receptors expressed throughout the human body are targets for established therapeutics and various drugs in development. Their diversity of structure and function reflects the important role 5-HT receptors play in physiologic and pathophysiological processes. The present review offers a framework for the official receptor nomenclature and a detailed understanding of each of the 14 5-HT receptor subtypes, their roles in the systems of the body, and, where appropriate, the (potential) utility of therapeutics targeting these receptors. SIGNIFICANCE STATEMENT: This review provides a comprehensive account of the classification and function of 5-hydroxytryptamine receptors, including how they are targeted for therapeutic benefit.

Short-Term Lincomycin Exposure Depletion of Murine Microbiota Affects Short-Chain Fatty Acids and Intestinal Morphology and Immunity

Lincomycin, as one of the most commonly used antibiotics, may cause intestinal injury, enteritis and other side effects, but it remains unknown whether these effects are associated with microbial changes and the effects of different doses of lincomycin on infants. Here, 21-day old mice were exposed to 1 and 5 g/L lincomycin to explore the effects of lincomycin on the gut microbiota, metabolites and inflammation. Compared to the control mice, 1 g/L lincomycin exposure decreased the body weight gain of mice (p < 0.05). Both 1 and 5 g/L lincomycin exposure reduced the diversity and microbial composition of mice (p < 0.05). Furthermore, 1 and 5 g/L lincomycin reduced the relative concentrations of acetate, propionate, butyrate, valerate, isobutyric acid and isovaleric acid in the colon chyme of mice (p < 0.05). In addition, 5 g/L lincomycin exposure reduced the villus height, crypt depth, and relative expression of TLR2, TLR3, TLR4, IL-18, TNF-α, and p65 in the jejunum of mice (p < 0.05), while 1 g/L lincomycin exposure reduced the relative expression of TLR2, TLR3, TNF-α, and p65 (p < 0.05). Collectively, these results highlight the depletion effect of short-term lincomycin exposure on microbiota and the further regulatory effect on intestinal morphology and immunosuppression in infant mice.

Modulation of Crustacean Innate Immune Response by Amino Acids and Their Metabolites: Inferences From Other Species

Aquaculture production of crustaceans (mainly shrimp and crabs) has expanded globally, but disease outbreaks and pathogenic infections have hampered production in the last two decades. As invertebrates, crustaceans lack an adaptive immune system and mainly defend and protect themselves using their innate immune system. The immune system derives energy and metabolites from nutrients, with amino acids constituting one such source. A growing number of studies have shown that amino acids and their metabolites are involved in the activation, synthesis, proliferation, and differentiation of immune cells, as well as in the activation of immune related signaling pathways, reduction of inflammatory response and regulation of oxidative stress. Key enzymes in amino acid metabolism have also been implicated in the regulation of the immune system. Here, we reviewed the role played by amino acids and their metabolites in immune-modulation in crustaceans. Information is inferred from mammals and fish where none exists for crustaceans. Research themes are identified and the relevant research gaps highlighted for further studies.

CD4 T cells differentially express cellular machinery for serotonin signaling, synthesis, and metabolism

CD4 T cells play a major role to orchestrate the immune response. Upon activation, CD4 T cells differentiate into effector T cell (Teff) or regulatory T cell (Treg) subsets that promote or suppress the immune response, respectively. Along with these unique immunological roles, CD4 T cell subsets have specific metabolic requirements and programs that can influence the immune response. We therefore examined the metabolite levels of Teff and Treg in detail. Surprisingly, the metabolite showing the largest difference between Teff and Treg was serotonin (5-HT), revealing a potentially distinct role for serotonin in CD4 T cell function. 5-HT is well known as a neurotransmitter and recently has been recognized to play a role in the immune response; however, little is known about the immune cell type-specific expression of the serotonergic machinery and receptors. We therefore examined the serotonergic-related machinery in Teff and Treg and found differential expression of the serotonin transporter SERT and 5-HT1a and 5-HT2 receptors. We also found that Treg express tryptophan hydroxylase, which converts tryptophan to serotonin, suggesting for the first time that Treg synthesize serotonin. Our results in this study expand the potential immunomodulatory role of serotonin in CD4 T cell biology and could ultimately aid the development of novel immunomodulatory targets for treatment of autoimmune and neuropsychiatric disorders.

Pyridoxal 5'-Phosphate-Dependent Enzymes at the Crossroads of Host-Microbe Tryptophan Metabolism

The chemical processes taking place in humans intersects the myriad of metabolic pathways occurring in commensal microorganisms that colonize the body to generate a complex biochemical network that regulates multiple aspects of human life. The role of tryptophan (Trp) metabolism at the intersection between the host and microbes is increasingly being recognized, and multiple pathways of Trp utilization in either direction have been identified with the production of a wide range of bioactive products. It comes that a dysregulation of Trp metabolism in either the host or the microbes may unbalance the production of metabolites with potential pathological consequences. The ability to redirect the Trp flux to restore a homeostatic production of Trp metabolites may represent a valid therapeutic strategy for a variety of pathological conditions, but identifying metabolic checkpoints that could be exploited to manipulate the Trp metabolic network is still an unmet need. In this review, we put forward the hypothesis that pyridoxal 5′-phosphate (PLP)-dependent enzymes, which regulate multiple pathways of Trp metabolism in both the host and in microbes, might represent critical nodes and that modulating the levels of vitamin B6, from which PLP is derived, might represent a metabolic checkpoint to re-orienteer Trp flux for therapeutic purposes.

Albumin is a secret factor involved in multidirectional interactions among the serotoninergic, immune and endocrine systems that supervises the mechanism of CYP1A and CYP3A regulation in the liver

This review focuses on albumin, which is involved in multidirectional interactions among the immune, endocrine and serotoninergic systems and supervises the regulation of cytochrome P450 (CYP) isoforms under conditions of both normal liver function and liver insufficiency. Special attention is paid to albumin, thyroid hormones, testosterone and tryptophan hydroxylase in these interactions as well as their potential roles in liver regeneration. The association of these factors with inflammation and the modification of the mechanism of hepatic drug-metabolizing CYP isoform regulation are also presented because changes in the expression of CYP isoforms in the liver may result in subsequent changes to a marker substance used for testing CYP activity, thus providing a simple way to control the liver regeneration process or the dangerous stimulation of hepatocarcinogenesis.

An untargeted metabolomics approach to investigate the wine-processed mechanism of Scutellariae radix in acute lung injury

ETHNOPHARMACOLOGICAL RELEVANCE

Scutellariae radix (SR) is one of the most popular traditional Chinese medicines (TCM). Crude SR (CSR) and wine-processed SR (WSR) are the two most common commercial specifications. According to the theories of TCM, wine-processing increases the inclination and direction of SR's actions, thereby strengthening its efficacy in clearing the upper-energizer lung damp heat. The pharmacological mechanism-related research on WSR for the treatment of lung disease is limited and needs to be expanded.

AIM OF THE STUDY

The aim of this report was to identify the relevant biological pathways by assessing changes in plasma metabolites between CSR and WSR in a lipopolysaccharide (LPS)-induced acute lung injury (ALI) model, and thus, revealed the potential mechanism of wine processing in SR.

MATERIALS AND METHODS

Rats with LPS-induced ALI were treated with CSR and WSR. The contents of inflammatory cytokines and histopathological examination were determined to explore the effects of CSR and WSR. Next, the metabolic profiling of rat plasma samples was performed by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS). Then, principal component analysis (PCA) were used to provide an overview for all of the groups and orthogonal partial least squares-discriminant analysis (OPLS-DA) was utilized to maximize the discrimination and present the differences in the metabolite between all of the groups.

RESULTS

WSR exhibited a more remarkable effect on improving ALI than CSR by reducing the levels of inflammatory factors, including nitric oxide (NO), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8). On the basis of UPLC-QTOF-MS technology, an unequal curative effect was revealed by nontargeting metabolomics. Sixteen biomarkers were discovered in the plasma of LPS-induced rats. Pathway analysis indicated that CSR acted on ALI by regulating the abnormal sphingolipid metabolism pathways; however, an WSR-mediated cure of ALI was linked primarily to reversing the abnormality of retinol metabolism pathways and tryptophan metabolism pathways.

CONCLUSIONS

This report examined the underlying wine-processing mechanism of SR from the perspective of plasma metabolites. In addition, this work provided a novel and valuable insight into interpretation of the processing mechanisms of TCM in a holistic way.

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 (ILC2^INFLAM) 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 ILC2^INFLAM 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.

Induction of tryptophan hydroxylase in the liver of s.c. tumor model of prostate cancer

Enhanced degradation of tryptophan (Trp) and thus decreased plasma Trp levels are common in several types of cancers. Although it is well known that Trp catabolism is induced in the tumor microenvironment by the enzymes expressed in cancer cells, immune cells, or both, few studies have examined systemic Trp catabolism in cancer pathophysiology. The present study aimed to evaluate Trp catabolism in both tumor and peripheral tissues using tumor‐engrafted Copenhagen rats that were s.c. inoculated with AT‐2 rat prostate cancer cells negative for expression of Trp catabolic enzymes. Liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) metabolomics showed significantly decreased plasma Trp levels in AT‐2 engrafted rats, accompanied by increased kynurenine/Trp ratios in spleen and thymus and serotonin levels in liver and thymus. Quantitative PCR and enzymatic activity assays showed indoleamine‐2, 3‐dioxygenase, an inducible enzyme that catalyzes Trp to kynurenine, was increased in tumor tissues, whereas tryptophan‐2,3‐dioxygenase, a major Trp catabolic enzyme that regulates systemic level of Trp, tended to be increased in the liver of AT‐2 engrafted rats. Furthermore, tryptophan hydroxylase‐1 (TPH1), an enzyme that catalyzes the reaction of Trp to serotonin, was significantly increased in liver and spleen of AT‐2 engrafted rats. Further histochemical analysis revealed that the induction of TPH1 in the liver could be attributed to infiltration of mast cells. A similar phenomenon was observed with nonneoplastic liver samples from colorectal cancer patients. These results suggested that Trp catabolism toward serotonin synthesis might be induced in peripheral remote tissues in cancer, which could have a pathophysiological effect on cancer.

Genetic deletion of mast cell serotonin synthesis prevents the development of obesity and insulin resistance

Obesity is linked with insulin resistance and is characterized by excessive accumulation of adipose tissue due to chronic energy imbalance. Increasing thermogenic brown and beige adipose tissue futile cycling may be an important strategy to increase energy expenditure in obesity, however, brown adipose tissue metabolic activity is lower with obesity. Herein, we report that the exposure of mice to thermoneutrality promotes the infiltration of white adipose tissue with mast cells that are highly enriched with tryptophan hydroxylase 1 (Tph1), the rate limiting enzyme regulating peripheral serotonin synthesis. Engraftment of mast cell-deficient mice with Tph1^−/− mast cells or selective mast cell deletion of Tph1 enhances uncoupling protein 1 (Ucp1) expression in white adipose tissue and protects mice from developing obesity and insulin resistance. These data suggest that therapies aimed at inhibiting mast cell Tph1 may represent a therapeutic approach for the treatment of obesity and type 2 diabetes.

Serotonin inhibits adipose tissue thermogenesis. Here the authors show that obese mice housed in thermoneutrality have increased mast cell serotonin synthesis, and that inhibiting this pathway through deletion of mast cell Tph1 increases white adipose tissue browning and protects against diet-induced obesity, insulin resistance and liver steatosis.

IL-9 and Mast Cells Are Key Players of Candida albicans Commensalism and Pathogenesis in the Gut

Candida albicans is implicated in intestinal diseases. Identifying host signatures that discriminate between the pathogenic versus commensal nature of this human commensal is clinically relevant. In the present study, we identify IL-9 and mast cells (MCs) as key players of Candida commensalism and pathogenicity. By inducing TGF-β in stromal MCs, IL-9 pivotally contributes to mucosal immune tolerance via the indoleamine 2,3-dioxygenase enzyme. However, Candida-driven IL-9 and mucosal MCs also contribute to barrier function loss, dissemination, and inflammation in experimental leaky gut models and are upregulated in patients with celiac disease. Inflammatory dysbiosis occurs with IL-9 and MC deficiency, indicating that the activity of IL-9 and MCs may go beyond host immunity to include regulation of the microbiota. Thus, the output of the IL-9/MC axis is highly contextual during Candida colonization and reveals how host immunity and the microbiota finely tune Candida behavior in the gut.

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IL-9/IL-9R signaling affects MC function in mucosal candidiasis

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IL-9 and mucosal MCs contribute to barrier function loss in leaky gut models

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IL-9 and stromal MCs induce local protective tolerance in infection via IDO1

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IL-9 and mucosal MCs expand and IDO1 decreases in human celiac disease

Mechanisms supporting potential use of bone marrow-derived mesenchymal stem cells in psychocardiology

Despite great efforts made in recent years, globally cardiovascular disease (CVD) remains the most common and devastating disease. Pharmacological, interventional and surgical treatments have proved to be only partly satisfactory for the majority of patients. A major underlying cause of poor prognosis is a high comorbidity rate between CVD and mental illness, which calls for the approaches of psychocardiology. As psychiatric disorders and CVD can influence each other bidirectionally, it is necessary to develop novel therapies targeting both systems simultaneously. Therefore, innovative stem cell (SC) therapy has become the most promising treatment strategy in psychocardiology. Bone marrow-derived mesenchymal stem/stromal cells (BM-MSCs), among all different types of SCs, have drawn the most attention due to unique advantages in terms of ethical considerations, low immunogenicity and simplicity of preparation. In this review, we survey recent publications and clinical trials to summarize the knowledge and progress gained so far. Moreover, we discuss the feasibility of the clinical application of BM-MSCs in the area of psychocardiology.

Inhibition of serotonin synthesis: A novel therapeutic paradigm

The rate-limiting enzyme in serotonin synthesis is tryptophan hydroxylase (TPH). There are two independent serotonin systems in the body characterized by two isoforms of TPH, TPH1 and TPH2. While TPH2 synthesizes serotonin in the brain, TPH1 is expressed in the gut and in other peripheral tissues and supplies platelets in the circulation with serotonin. This duality of the serotonin system is enforced by the blood-brain barrier which is impermeable for serotonin. In the brain serotonin acts as neurotransmitter and is a main target for the treatment of psychiatric disorders. In the periphery it is released by platelets at the site of activation and elicits numerous physiological effects. TPH1 deficient mice were shown to be protected from diverse diseases including hemostatic, inflammatory, fibrotic, gastrointestinal, and metabolic disorders and therefore serotonin synthesis inhibition emerged as a reasonable therapeutic paradigm. Recently the first TPH inhibitor, telotristat ethyl, came on the market for the treatment of carcinoid syndrome. This review summarizes the state of development and the therapeutic opportunities of such compounds.

Tryptophan in health and disease

Tryptophan (TRP), an essential amino acid in mammals, is involved in several physiological processes including neuronal function, immunity, and gut homeostasis. In humans, TRP is metabolized via the kynurenine and serotonin pathways, leading to the generation of biologically active compounds, such as serotonin, melatonin and niacin. In addition to endogenous TRP metabolism, resident gut microbiota also contributes to the production of specific TRP metabolites and indirectly influences host physiology. The variety of physiologic functions regulated by TRP reflects the complex pattern of diseases associated with altered homeostasis. Indeed, an imbalance in the synthesis of TRP metabolites has been associated with pathophysiologic mechanisms occurring in neurologic and psychiatric disorders, in chronic immune activation and in the immune escape of cancer. In this chapter, the role of TRP metabolism in health and disease is presented. Disorders involving the central nervous system, malignancy, inflammatory bowel and cardiovascular disease are discussed.

Emerging Roles for Serotonin in Regulating Metabolism: New Implications for an Ancient Molecule

Serotonin is a phylogenetically ancient biogenic amine that has played an integral role in maintaining energy homeostasis for billions of years. In mammals, serotonin produced within the central nervous system regulates behavior, suppresses appetite, and promotes energy expenditure by increasing sympathetic drive to brown adipose tissue. In addition to these central circuits, emerging evidence also suggests an important role for peripheral serotonin as a factor that enhances nutrient absorption and storage. Specifically, glucose and fatty acids stimulate the release of serotonin from the duodenum, promoting gut peristalsis and nutrient absorption. Serotonin also enters the bloodstream and interacts with multiple organs, priming the body for energy storage by promoting insulin secretion and de novo lipogenesis in the liver and white adipose tissue, while reducing lipolysis and the metabolic activity of brown and beige adipose tissue. Collectively, peripheral serotonin acts as an endocrine factor to promote the efficient storage of energy by upregulating lipid anabolism. Pharmacological inhibition of serotonin synthesis or signaling in key metabolic tissues are potential drug targets for obesity, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD).

Mast cells induce epithelial-to-mesenchymal transition and migration in non-small cell lung cancer through IL-8/Wnt/β-catenin pathway

Background: In the various cancer, mast cells (MCs) infiltration is correlated with a worse prognosis. There is an increasing evidence that MCs and their mediators are participated in remodeling of the tumor microenvironment and facilitate tumor growth, epithelial-to-mesenchymal transition (EMT) and metastasis.

Methods: The transwell was conducted to evaluate the correlations between MCs and non-small cell lung cancer (NSCLC) cells in vitro. The RNA interference of β-catenin was performed to further explore the signaling pathway. Lung adenocarcinoma cell line A549 and human MC (HMC-1) were subcutaneously injected into BALB/c nude mice. The conventional experiment methods (such as quantitative RT-PCR Western Blot, Immunofluorescence, and ELISA) were used in the present study.

Results: We found that high density of MCs in NSCLC correlates with worse prognosis. The NSCLC cells could release CCL5 and recruit MCs to the tumor microenvironment. Then, we explored that HMC-1 transplantation accelerated the growth of A549 cell in nude mice. Moreover, the MCs-derived factors were responsible for tumor growth. When NSCLC cells were activated, MCs produced various factors that induced EMT and migration. We also identified that CXCL8/interleukin (IL)-8 served as the major modulator containing in the activated MC conditioned medium. Furthermore, MCs and exogenous IL-8 promoted β-catenin phosphorylation in NSCLC cells. Inhibiting the Wnt/β-catenin pathway by RNA interference could revert EMT and migration of NSCLC.

Conclusions: Our study suggests that MCs are recruited into NSCLC microenvironment and improve the EMT and migration of cancer cells, thereby accelerating the growth of NSCLC.

Antibiotic-Induced Disruption of Gut Microbiota Alters Local Metabolomes and Immune Responses

Gut microbiome plays an essential role in modulating host immune responses. However, little is known about the interaction of microbiota, their metabolites and relevant inflammatory responses in the gut. By treating the mice with three different antibiotics (enrofloxacin, vancomycin, and polymixin B sulfate), we aimed to investigate the effects of different antibiotics exposure on gut microbiota, microbial metabolism, inflammation responses in the gut, and most importantly, pinpoint the underlying interactions between them. Although the administration of different antibiotics can lead to different effects on mouse models, the treatment did not affect the average body weight of the mice. A heavier caecum was observed in vancomycin treated mice. Treatment by these three antibiotics significantly up-regulated gene expression of various cytokines in the colon. Enrofloxacin treated mice seemed to have an increased Th1 response in the colon. However, such a difference was not found in mice treated by vancomycin or polymixin B sulfate. Vancomycin treatment induced significant changes in bacterial composition at phylum and family level and decreased richness and diversity at species level. Enrofloxacin treatment only induced changes in composition at family presenting as an increase in Prevotellaceae and Rikenellaceae and a decrease in Bacteroidaceae. However, no significant difference was observed after polymixin B sulfate treatment. When compared with the control group, significant metabolic shift was found in the enrofloxacin and vancomycin treated group. The metabolic changes mainly occurred in Valine, leucine, and isoleucine biosynthesis pathway and beta-Alanine metabolism in enrofloxacin treated group. For vancomycin treatment metabolic changes were mainly found in beta-Alanine metabolism and Alanine, aspartate and glutamate metabolism pathway. Moreover, modifications observed in the microbiota compositions were correlated with the metabolite concentrations. For example, concentration of pentadecanoic acid was positively correlated with richness of Rikenellaceae and Prevotellaceae and negatively correlated with Enterobacteriaceae. This study suggests that the antibiotic-induced changes in gut microbiota might contribute to the inflammation responses through the alternation of metabolic status, providing a novel insight regarding a complex network that integrates the different interactions between gut microbiota, metabolic functions, and immune responses in host.

Identification of serum metabolites associating with chronic kidney disease progression and anti-fibrotic effect of 5-methoxytryptophan

Early detection and accurate monitoring of chronic kidney disease (CKD) could improve care and retard progression to end-stage renal disease. Here, using untargeted metabolomics in 2155 participants including patients with stage 1–5 CKD and healthy controls, we identify five metabolites, including 5-methoxytryptophan (5-MTP), whose levels strongly correlate with clinical markers of kidney disease. 5-MTP levels decrease with progression of CKD, and in mouse kidneys after unilateral ureteral obstruction (UUO). Treatment with 5-MTP ameliorates renal interstitial fibrosis, inhibits IκB/NF-κB signaling, and enhances Keap1/Nrf2 signaling in mice with UUO or ischemia/reperfusion injury, as well as in cultured human kidney cells. Overexpression of tryptophan hydroxylase-1 (TPH-1), an enzyme involved in 5-MTP synthesis, reduces renal injury by attenuating renal inflammation and fibrosis, whereas TPH-1 deficiency exacerbates renal injury and fibrosis by activating NF-κB and inhibiting Nrf2 pathways. Together, our results suggest that TPH-1 may serve as a target in the treatment of CKD.

Accurate monitoring of chronic kidney disease (CKD) progression is essential for efficient disease management. Here Chen et al. identify five serum metabolites in patients with stage 1–5 CKD whose levels associate with disease progression, and find that 5-methoxytryptophan and its regulatory enzyme TPH-1 exert anti-fibrotic effects in mouse models of kidney injury.

Expression of tryptophan hydroxylase in gastric mucosa in symptomatic and asymptomatic Helicobacter pylori infection

INTRODUCTION

Helicobacter pylori infection induces clinical symptoms in 15-20% of subjects, and the reason for this variation is still not clear. The aim of the present study is to evaluate the expression of tryptophan hydroxylase (TpH-1) in gastric mucosa of patients with symptomatic and asymptomatic H. pylori infection in relation to the intensity of bacterial colonization and severity of dyspeptic symptoms.

MATERIAL AND METHODS

Ninety subjects (aged 35-49 years) were enrolled in the study and separated into 3 groups of 30 subjects each. Group I - healthy volunteers without H. pylori infection, group II - subjects with asymptomatic H. pylori infection, group III - H. pylori-infected patients with dyspeptic symptoms, mainly fasting and nocturnal epigastric pain. To diagnose H. pylori infection the urea breath test (UBT-13C) and histological analysis were performed. The level of mRNA expression of tryptophan hydroxylase (TpH-1) was estimated in gastric mucosa with RT-PCR.

RESULTS

The expression of this enzyme in antral mucosa was 2.69 ±0.97 in group I, 2.28 ±0.69 in group II (p > 0.05) and 4.40 ±1.64 in group III (p < 0.001). The levels of expression of TpH-1 in gastric body mucosa were 2.16 ±0.70, 1.57 ±0.52 (p > 0.05) and 3.40 ±1.51 (p < 0.001), respectively. In group III a positive correlation was found between intensity of H. pylori colonization and TpH-1 expression as well as between TpH-1 expression and severity of dyspeptic symptoms.

CONCLUSIONS

Increased expression of TpH-1 in gastric mucosa plays a role in pathogenesis of chronic dyspepsia.

Beyond Host Defense: Emerging Functions of the Immune System in Regulating Complex Tissue Physiology

The essential roles played by the immune system in the discrimination between self- versus non/altered-self and its integral role in promoting host defense against invading microbes and tumors have been extensively studied for many years. In these contexts, significant advances have been made in defining the molecular and cellular networks that orchestrate cell-cell communication to mediate host defense and pathogen expulsion. Notably, recent studies indicate that in addition to these classical immune functions, cells of the innate and adaptive immune system also sense complex tissue- and environment-derived signals, including those from the nervous system and the diet. In turn these responses regulate physiologic processes in multiple tissues throughout the body, including nervous system function, metabolic state, thermogenesis, and tissue repair. In this review we propose an integrated view of how the mammalian immune system senses and interacts with other complex organ systems to maintain tissue and whole-body homeostasis.

Lysosome biogenesis regulated by the amino-acid transporter SLC15A4 is critical for functional integrity of mast cells

Mast cells possess specialized lysosomes, so-called secretory granules, which play a key role not only in allergic responses but also in various immune disorders. The molecular mechanisms that control secretory-granule formation are not fully understood. Solute carrier family member 15A4 (SLC15A4) is a lysosome-resident amino-acid/oligopeptide transporter that is preferentially expressed in hematopoietic lineage cells. Here, we demonstrated that SLC15A4 is required for mast-cell secretory-granule homeostasis, and limits mast-cell functions and inflammatory responses by controlling the mTORC1-TFEB signaling axis. In mouse Slc15a4-/- mast cells, diminished mTORC1 activity increased the expression and nuclear translocation of TFEB, a transcription factor, which caused secretory granules to degranulate more potently. This alteration of TFEB function in mast cells strongly affected the FcεRI-mediated responses and IL-33-triggered inflammatory responses both in vitro and in vivo. Our results reveal a close relationship between SLC15A4 and secretory-granule biogenesis that is critical for the functional integrity of mast cells.

Mechanism of Curcuma wenyujin Rhizoma on Acute Blood Stasis in Rats Based on a UPLC-Q/TOF-MS Metabolomics and Network Approach

Rhizome of Curcuma wenyujin, which is called EZhu in China, is a traditional Chinese medicine used to treat blood stasis for many years. However, the underlying mechanism of EZhu is not clear at present. In this study, plasma metabolomics combined with network pharmacology were used to elucidate the therapeutic mechanism of EZhu in blood stasis from a metabolic perspective. The results showed that 26 potential metabolite markers of acute blood stasis were screened, and the levels were all reversed to different degrees by EZhu preadministration. Metabolic pathway analysis showed that the improvement of blood stasis by Curcuma wenyujin rhizome was mainly related to lipid metabolism (linoleic acid metabolism, ether lipid metabolism, sphingolipid metabolism, glycerophospholipid metabolism, and arachidonic acid metabolism) and amino acid metabolisms (tryptophan metabolism, lysine degradation). The component-target-pathway network showed that 68 target proteins were associated with 21 chemical components in EZhu. Five metabolic pathways of the network, including linoleic acid metabolism, sphingolipid metabolism, glycerolipid metabolism, arachidonic acid metabolism, and steroid hormone biosynthesis, were consistent with plasma metabolomics results. In conclusion, plasma metabolomics combined with network pharmacology can be helpful to clarify the mechanism of EZhu in improving blood stasis and to provide a literature basis for further research on the therapeutic mechanism of EZhu in clinical practice.

Mast Cell Degranulation Exacerbates Skin Rejection by Enhancing Neutrophil Recruitment

Recent evidences indicate an important role of tissue inflammatory responses by innate immune cells in allograft acceptance and survival. Here we investigated the role of mast cells (MC) in an acute male to female skin allograft rejection model using red MC and basophil (RMB) mice enabling conditional MC depletion. Kinetic analysis showed that MCs markedly accelerate skin rejection. They induced an early inflammatory response through degranulation and boosted local synthesis of KC, MIP-2, and TNF. This enhanced early neutrophil infiltration compared to a female-female graft-associated repair response. The uncontrolled neutrophil influx accelerated rejection as antibody-mediated depletion of neutrophils delayed skin rejection. Administration of cromolyn, a MC stabilizer and to a lesser extent ketotifen, a histamine type I receptor antagonist, and absence of MCPT4 chymase also delayed graft rejection. Together our data indicate that mediators contained in secretory granules of MC promote an inflammatory response with enhanced neutrophil infiltration that accelerate graft rejection.

Modulation of the immune response by helminths: a role for serotonin?

The mammalian gut is a remarkable organ: with a nervous system that rivals the spinal cord, it is the body’s largest repository of immune and endocrine cells and houses an immense and complex microbiota. Infection with helminth parasites elicits a conserved program of effector and regulatory immune responses to eradicate the worm, limit tissue damage, and return the gut to homeostasis. Discrete changes in the nervous system, and to a lesser extent the enteroendocrine system, occur following helminth infection but the importance of these adaptations in expelling the worm is poorly understood. Approximately 90% of the body’s serotonin (5-hydroxytryptamine (5-HT)) is made in enterochromaffin (EC) cells in the gut, indicative of the importance of this amine in intestinal function. Signaling via a plethora of receptor subtypes, substantial evidence illustrates that 5-HT affects immunity. A small number of studies document changes in 5-HT levels following infection with helminth parasites, but these have not been complemented by an understanding of the role of 5-HT in the host–parasite interaction. In reviewing this area, the gap in knowledge of how changes in the enteric serotonergic system affects the outcome of infection with intestinal helminths is apparent. We present this as a call-to-action by investigators in the field. We contend that neuronal EC cell–immune interactions in the gut are essential in maintaining homeostasis and, when perturbed, contribute to pathophysiology. The full affect of infection with helminth parasites needs to define, and then mechanistically dissect the role of the enteric nervous and enteroendocrine systems of the gut.