Targeting microRNAs as a promising anti-cancer therapeutic strategy against traffic-related air pollution-mediated lung cancer.

Air pollutants are increasingly emitted into the atmosphere because of the high dependency of humans on fossil-derived fuels. Wind speed and direction assisted high dispersibility and uncontrolled nature of air pollution across geo-/demographical borders, making it one of the major global concerns. Besides climate change, air pollution has been found to be associated with various diseases, such as cancer. Lung cancer, which is the world's most common type of cancer, has been found to be associated with traffic-related air pollution. Research and political efforts have been taken to explore green/renewable energy sources. However, these efforts at the current intensity cannot cope with the increasing need for fossil fuels. More specifically, political tensions such as the Russian-Ukraine war, economic tension (e.g., China-USA economic tensions), and other issues (e.g., pandemic, higher inflation rate, and poverty) significantly hindered phasing out fossil fuels. In this context, an increasing global population will be exposed to traffic-related air pollution, which justifies the current uptrend in the number of lung cancer patients. To combat this health burden, novel treatments with higher efficiency and specificity must be designed. One of the potential "life changer" options is microRNA (miRNA)-based therapy to target the expression of oncogenic genes. That said, this review discusses the association of traffic-related air pollution with lung cancer, the changes in indigenous miRNAs in the body during lung cancer, and the current status of miRNA therapeutics for lung cancer treatment. We believe that the article will significantly appeal to a broad readership of oncologists, environmentalists, and those who work in the field of (bio)energy. It may also gain the policymakers' attention to establish better health policies and regulations about air pollution, for example, by promoting (bio)fuel exploration, production, and consumption.

The roles of the kynurenine pathway in COVID-19 neuropathogenesis.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the highly contagious respiratory disease Corona Virus Disease 2019 (COVID-19) that may lead to various neurological and psychological disorders that can be acute, lasting days to weeks or months and possibly longer. The latter is known as long-COVID or more recently post-acute sequelae of COVID (PASC). During acute COVID-19 infection, a strong inflammatory response, known as the cytokine storm, occurs in some patients. The levels of interferon-γ (IFN-γ), interferon-ß (IFN-ß), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) are particularly increased. These cytokines are known to activate the enzyme indoleamine 2,3-dioxygenase 1 (IDO-1), catalysing the first step of tryptophan (Trp) catabolism through the kynurenine pathway (KP) leading to the production of several neurotoxic and immunosuppressive metabolites. There is already data showing elevation in KP metabolites both acutely and in PASC, especially regarding cognitive impairment. Thus, it is likely that KP involvement is significant in SARS-CoV-2 pathogenesis especially neurologically.

Oncolytic viruses as a promising therapeutic strategy against the detrimental health impacts of air pollution: The case of glioblastoma multiforme.

Human livelihood highly depends on applying different sources of energy whose utilization is associated with air pollution. On the other hand, air pollution may be associated with glioblastoma multiforme (GBM) development. Unlike other environmental causes of cancer (e.g., irradiation), air pollution cannot efficiently be controlled by geographical borders, regulations, and policies. The unavoidable exposure to air pollution can modify cancer incidence and mortality. GBM treatment with chemotherapy or even its surgical removal has proven insufficient (100% recurrence rate; patient's survival mean of 15 months; 90% fatality within five years) due to glioma infiltrative and migratory capacities. Given the barrage of attention and research investments currently plowed into next-generation cancer therapy, oncolytic viruses are perhaps the most vigorously pursued. Provision of an insight into the current state of the research and future direction is essential for stimulating new ideas with the potentials of filling research gaps. This review manuscript aims to overview types of brain cancer, their burden, and different causative agents. It also describes why air pollution is becoming a concerning factor. The different opinions on the association of air pollution with brain cancer are reviewed. It tries to address the significant controversy in this field by hypothesizing the air-pollution-brain-cancer association via inflammation and atopic conditions. The last section of this review deals with the oncolytic viruses, which have been used in, or are still under clinical trials for GBM treatment. Engineered adenoviruses (i.e., DNX-2401, DNX-2440, CRAd8-S-pk7 loaded Neural stem cells), herpes simplex virus type 1 (i.e., HSV-1 C134, HSV-1 rQNestin34.5v.2, HSV-1 G207, HSV-1 M032), measles virus (i.e., MV-CEA), parvovirus (i.e., ParvOryx), poliovirus (i.e., Poliovirus PVSRIPO), reovirus (i.e., pelareorep), moloney murine leukemia virus (i.e., Toca 511 vector), and vaccinia virus (i.e., vaccinia virus TG6002) as possible life-changing alleviations for GBM have been discussed. To the best of our knowledge, this review is the first review that comprehensively discusses both (i) the negative/positive association of air pollution with GBM; and (ii) the application of oncolytic viruses for GBM, including the most recent advances and clinical trials. It is also the first review that addresses the controversies over air pollution and brain cancer association. We believe that the article will significantly appeal to a broad readership of virologists, oncologists, neurologists, environmentalists, and those who work in the field of (bio)energy. Policymakers may also use it to establish better health policies and regulations about air pollution and (bio)fuels exploration, production, and consumption.

Involvement of the kynurenine pathway in breast cancer: updates on clinical research and trials.

Breast cancer (BrCa) is the leading cause of cancer incidence and mortality in women worldwide. While BrCa treatment has been shown to be highly successful if detected at an early stage, there are few effective strategies to treat metastatic tumours. Hence, metastasis remains the main cause in most of BrCa deaths, highlighting the need for new approaches in this group of patients. Immunotherapy has been gaining attention as a new treatment for BrCa metastasis and the kynurenine pathway (KP) has been suggested as one of the potential targets. The KP is the major biochemical pathway in tryptophan (TRP) metabolism, catabolising TRP to nicotinamide adenine dinucleotide (NAD+). The KP has been reported to be elevated under inflammatory conditions such as cancers and that its activity suppresses immune surveillance. Dysregulation of the KP has previously been reported implicated in BrCa. This review aims to discuss and provide an update on the current mechanisms involved in KP-mediated immune suppression and cancer growth. Furthermore, we also provide a summary on 58 studies about the involvement of the KP and BrCa and five clinical trials targeting KP enzymes and their outcome.

Importance of the dysregulation of the kynurenine pathway on cognition in schizophrenia: a systematic review of clinical studies.

Schizophrenia is a chronic psychotic disease burdened by cognitive deficits which hamper daily functioning causing disability and costs for society. Biological determinants underlying cognitive impairment are only partially understood and there are no convincing pharmacological targets able to improve cognitive outcome. Mounting evidence has shown the involvement of the kynurenine pathway in the pathophysiology of schizophrenia, also concerning cognitive symptoms. Therefore, the action of specific metabolites of kynurenine could affects cognition in schizophrenia. To evaluate the impact of the metabolites of kynurenine pathway on cognitive functions in schizophrenia spectrum disorders, with a focus on the modulating role of gender, to identify predictors of cognitive functioning and hypothetical pharmacological targets able to resize disability by improving cognition, thus functioning and quality of life. A systematic review was performed in PubMed/MEDLINE and Embase according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses. All studies measuring the direct impact of kynurenine metabolites on cognitive performances in living individuals with schizophrenia spectrum disorders were included in the review. Six studies were included. The activation of the kynurenine pathway resulted associated with greater cognitive deficits in patients with schizophrenia and both elevations and reduction of metabolites seemed able to affect cognitive outcome. No modulating role of sex emerged. This systematic review provides evidence that the activation of the kynurenine pathway affects cognition in patients with schizophrenia and highlights this pathway as a possible future target for developing novel drugs toward this still unmet clinical need. However, evidence is still limited and future studies are needed to further clarify the relationship between kynurenine pathway and cognition in schizophrenia.

Could the kynurenine pathway be the key missing piece of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) complex puzzle?

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex and debilitating disease with a substantial social and economic impact on individuals and their community. Despite its importance and deteriorating impact, progresses in diagnosis and treatment of ME/CFS is limited. This is due to the unclear pathophysiology of the disease and consequently lack of prognostic biomarkers. To investigate pathophysiology of ME/CFS, several potential pathologic hallmarks have been investigated; however, these studies have failed to report a consistent result. These failures in introducing the underlying reason for ME/CFS have stimulated considering other possible contributing mechanisms such as tryptophan (TRP) metabolism and in particular kynurenine pathway (KP). KP plays a central role in cellular energy production through the production of nicotinamide adenine dinucleotide (NADH). In addition, this pathway has been shown to mediate immune response and neuroinflammation through its metabolites. This review, we will discuss the pathology and management of ME/CFS and provide evidence pertaining KP abnormalities and symptoms that are classic characteristics of ME/CFS. Targeting the KP regulation may provide innovative approaches to the management of ME/CFS.

The Cytokines CXCL10 and CCL2 and the Kynurenine Metabolite Anthranilic Acid Accurately Predict Patients at Risk of Developing Dengue With Warning Signs.

BACKGROUND: The resolution or aggravation of dengue infection depends on the patient's immune response during the critical phase. Cytokines released by immune cells increase with the worsening severity of dengue infections. Cytokines activate the kynurenine pathway (KP) and the extent of KP activation then influences disease severity. METHODS: KP metabolites and cytokines in plasma samples of patients with dengue infection (dengue without warning signs [DWS-], dengue with warning signs [DWS+], or severe dengue) were analyzed. Cytokines (interferon gamma [IFN-É£], tumor necrosis factor, interleukin 6, CXCL10/interferon-inducile protein 10 [IP-10], interleukin 18 [IL-18], CCL2/monocyte chemoattractant protein-1 [MCP-1], and CCL4/macrophage inflammatory protein-1beta [MIP-1ß] were assessed by a Human Luminex Screening Assay, while KP metabolites (tryptophan, kynurenine, anthranilic acid [AA], picolinic acid, and quinolinic acid) were assessed by ultra-high-performance liquid chromatography and Gas Chromatography Mass Spectrophotometry [GCMS] assays. RESULTS: Patients with DWS+ had increased activation of the KP where kynurenine-tryptophan ratio, anthranilic acid, and picolinic acid were elevated. These patients also had higher levels of the cytokines IFN-É£, CXCL10, CCL4, and IL-18 than those with DWS-. Further receiver operating characteristic analysis identified 3 prognostic biomarker candidates, CXCL10, CCL2, and AA, which predicted patients with higher risks of developing DWS+ with an accuracy of 97%. CONCLUSIONS: The data suggest a unique biochemical signature in patients with DWS+. CXCL10 and CCL2 together with AA are potential prognostic biomarkers that discern patients with higher risk of developing DWS+ at earlier stages of infection.

Systemic perturbations of the kynurenine pathway precede progression to dementia independently of amyloid-ß.

Increasing evidence suggests that kynurenine pathway (KP) dyshomeostasis may promote disease progression in dementia. Studies in Alzheimer's disease (AD) patients confirm KP dyshomeostasis in plasma and cerebrospinal fluid (CSF) which correlates with amyloid-ß and tau pathology. Herein, we performed the first comprehensive study assessing baseline levels of KP metabolites in participants enrolling in the Australian Imaging Biomarkers Flagship Study of Aging. Our purpose was to test the hypothesis that changes in KP metabolites may be biomarkers of dementia processes that are largely silent. We used a cross-sectional analytical approach to assess non-progressors (N = 73); cognitively normal (CN) or mild cognitive impairment (MCI) participants at baseline and throughout the study, and progressors (N = 166); CN or MCI at baseline but progressing to either MCI or AD during the study. Significant KP changes in progressors included increased 3-hydroxyanthranilic acid (3-HAA) and 3-hydroxyanthranilic acid/anthranilic acid (3-HAA/AA) ratio, the latter having the largest effect on the odds of an individual being a progressor (OR 35.3; 95% CI between 14 and 104). 3-HAA levels were hence surprisingly bi-phasic, high in progressors but low in non-progressors or participants who had already transitioned to MCI or dementia. This is a new, unexpected and interesting result, as most studies of the KP in neurodegenerative disease show reduced 3-HAA/AA ratio after diagnosis. The neuroprotective metabolite picolinic acid was also significantly decreased while the neurotoxic metabolite 3-hydroxykynurenine increased in progressors. These results were significant even after adjustment for confounders. Considering the magnitude of the OR to predict change in cognition, it is important that these findings are replicated in other populations. Independent validation of our findings may confirm the utility of 3-HAA/AA ratio to predict change in cognition leading to dementia in clinical settings.

Use of a Recombinant Biomarker Protein DDA Library Increases DIA Coverage of Low Abundance Plasma Proteins.

Credible detection and quantification of low abundance proteins from human blood plasma is a major challenge in precision medicine biomarker discovery when using mass spectrometry (MS). In this proof-of-concept study, we employed a mixture of selected recombinant proteins in DDA libraries to subsequently identify (not quantify) cancer-associated low abundance plasma proteins using SWATH/DIA. The exemplar DDA recombinant protein spectral library (rPSL) was derived from tryptic digestion of 36 recombinant human proteins that had been previously implicated as possible cancer biomarkers from both our own and other studies. The rPSL was then used to identify proteins from nondepleted colorectal cancer (CRC) EDTA plasmas by SWATH-MS. Most (32/36) of the proteins used in the rPSL were reliably identified from CRC plasma samples, including 8 proteins (i.e., BTC, CXCL10, IL1B, IL6, ITGB6, TGFα, TNF, TP53) not previously detected using high-stringency protein inference MS according to PeptideAtlas. The rPSL SWATH-MS protocol was compared to DDA-MS using MARS-depleted and postdigestion peptide fractionated plasmas (here referred to as a human plasma DDA library). Of the 32 proteins identified using rPSL SWATH, only 12 could be identified using DDA-MS. The 20 additional proteins exclusively identified using the rPSL SWATH approach were almost exclusively lower abundance (i.e., <10 ng/mL) proteins. To mitigate justified FDR concerns, and to replicate a more typical library creation approach, the DDA rPSL library was merged with a human plasma DDA library and SWATH identification repeated using such a merged library. The majority (33/36) of the low abundance plasma proteins added from the rPSL were still able to be identified using such a merged library when high-stringency HPP Guidelines v3.0 protein inference criteria were applied to our data set. The MS data set has been deposited to ProteomeXchange Consortium via the PRIDE partner repository (PXD022361).

Toward a neuroprotective shift: Eight weeks of high intensity interval training reduces the neurotoxic kynurenine activity concurrently to impulsivity in emotionally impulsive humans - A randomized controlled trial.

BACKGROUND: Previous findings suggest that impulsivity is related to chronic low-grade inflammation. Inflammation is known to trigger the kynurenine pathway to a pathological level in various impulsivity-related disorders. Nonetheless, murine models and recent human studies have shown that physical exercise, in particular High Intensity Interval Training (HIIT), could counterbalance the negative effects of inflammation on the kynurenine pathway. AIM: This study evaluates the effects of eight weeks of HIIT versus an active control group on impulsivity levels and accompanying alterations of inflammatory-mediated changes of the kynurenine pathway in a sample of emotionally impulsive humans. METHODS: Participants were randomly allocated to either HIIT or stretching conditions (three trainings per week for eight weeks). Fitness level was evaluated via VO2peak values at the beginning at end of the intervention. Kynurenine metabolites, pro-inflammatory cytokines, and impulsivity levels were evaluated at T0, T4, and T8 weeks. Statistical analyses were performed using mixed models. RESULTS: Fifty-three participants were included in the modified Intention To Treat analysis (45 finished the intervention). The HIIT group (n = 28) largely increased the aerobic fitness of its participants and produced physiological changes while the stretching group (n = 25) did not. HIIT reduced interleukin 6 levels (small to moderate interaction) and reduced the activity of the neurotoxic branch of the kynurenine pathway (small to moderate interaction for KYNA/QA and KYN/QA) after eight weeks of training while the active control did not change. Both interventions were effective to decrease emotion-related impulsivity, however only the HIIT group decreased participants' emotion-unrelated levels. Changes in emotion-related and -unrelated impulsivity were moderately correlated to changes in KYNA/KYN. CONCLUSION: This study demonstrated that HIIT was able to switch the kynurenine pathway from its neurotoxic branch to its neuroprotective one. This shift was associated with a decrease in impulsivity. Based on these findings, future work may consider investigating more intensively the effect of HIIT on impulsivity-related disorders.

Dysregulation of kynurenine metabolism is related to proinflammatory cytokines, attention, and prefrontal cortex volume in schizophrenia.

The kynurenine pathway (KP) of tryptophan (TRP) catabolism links immune system activation with neurotransmitter signaling. The KP metabolite kynurenic acid (KYNA) is increased in the brains of people with schizophrenia. We tested the extent to which: (1) brain KP enzyme mRNAs, (2) brain KP metabolites, and (3) plasma KP metabolites differed on the basis of elevated cytokines in schizophrenia vs. control groups and the extent to which plasma KP metabolites were associated with cognition and brain volume in patients displaying elevated peripheral cytokines. KP enzyme mRNAs and metabolites were assayed in two independent postmortem brain samples from a total of 71 patients with schizophrenia and 72 controls. Plasma KP metabolites, cognition, and brain volumes were measured in an independent cohort of 96 patients with schizophrenia and 81 healthy controls. Groups were stratified based on elevated vs. normal proinflammatory cytokine mRNA levels. In the prefrontal cortex (PFC), kynurenine (KYN)/TRP ratio, KYNA levels, and mRNA for enzymes, tryptophan dioxygenase (TDO) and kynurenine aminotransferases (KATI/II), were significantly increased in the high cytokine schizophrenia subgroup. KAT mRNAs significantly correlated with mRNA for glial fibrillary acidic protein in patients. In plasma, the high cytokine schizophrenia subgroup displayed an elevated KYN/TRP ratio, which correlated inversely with attention and dorsolateral prefrontal cortex (DLPFC) volume. This study provides further evidence for the role of inflammation in a subgroup of patients with schizophrenia and suggests a molecular mechanism through which inflammation could lead to schizophrenia. Proinflammatory cytokines may elicit conversion of TRP to KYN in the periphery and increase the N-methyl-D-aspartate receptor antagonist KYNA via increased KAT mRNA and possibly more enzyme synthesis activity in brain astrocytes,  leading to DLPFC volume loss, and attention impairment in schizophrenia.

Amyotrophic lateral sclerosis-linked UBQLN2 mutants inhibit endoplasmic reticulum to Golgi transport, leading to Golgi fragmentation and ER stress.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are fatal neurodegenerative diseases that are related genetically and pathologically. Mutations in the UBQLN2 gene, encoding the ubiquitin-like protein ubiquilin2, are associated with familial ALS/FTD, but the pathophysiological mechanisms remain unclear. Here, we demonstrate that ALS/FTD UBQLN2 mutants P497H and P506T inhibit protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus in neuronal cells. In addition, we observed that Sec31-positive ER exit sites are clustered in UBQLN2T487I patient spinal cord tissues. Both the ER-Golgi intermediate (ERGIC) compartment and the Golgi become disorganised and fragmented. This activates ER stress and inhibits ER-associated degradation. Hence, this study highlights perturbations in secretory protein trafficking and ER homeostasis as pathogenic mechanisms associated with ALS/FTD-associated forms of UBQLN2.

Sphingosine Kinase 2 Potentiates Amyloid Deposition but Protects against Hippocampal Volume Loss and Demyelination in a Mouse Model of Alzheimer's Disease.

Sphingosine 1-phosphate (S1P) is a potent vasculoprotective and neuroprotective signaling lipid, synthesized primarily by sphingosine kinase 2 (SK2) in the brain. We have reported pronounced loss of S1P and SK2 activity early in Alzheimer's disease (AD) pathogenesis, and an inverse correlation between hippocampal S1P levels and age in females, leading us to speculate that loss of S1P is a sensitizing influence for AD. Paradoxically, SK2 was reported to mediate amyloid ß (Aß) formation from amyloid precursor protein (APP) in vitro To determine whether loss of S1P sensitizes to Aß-mediated neurodegeneration, we investigated whether SK2 deficiency worsens pathology and memory in male J20 (PDGFB-APPSwInd) mice. SK2 deficiency greatly reduced Aß content in J20 mice, associated with significant improvements in epileptiform activity and cross-frequency coupling measured by hippocampal electroencephalography. However, several key measures of APPSwInd-dependent neurodegeneration were enhanced on the SK2-null background, despite reduced Aß burden. These included hippocampal volume loss, oligodendrocyte attrition and myelin loss, and impaired performance in Y-maze and social novelty memory tests. Inhibition of the endosomal cholesterol exporter NPC1 greatly reduced sphingosine phosphorylation in glial cells, linking loss of SK2 activity and S1P in AD to perturbed endosomal lipid metabolism. Our findings establish SK2 as an important endogenous regulator of both APP processing to Aß, and oligodendrocyte survival, in vivo These results urge greater consideration of the roles played by oligodendrocyte dysfunction and altered membrane lipid metabolic flux as drivers of neurodegeneration in AD.SIGNIFICANCE STATEMENT Genetic, neuropathological, and functional studies implicate both Aß and altered lipid metabolism and/or signaling as key pathogenic drivers of Alzheimer's disease. In this study, we first demonstrate that the enzyme SK2, which generates the signaling lipid S1P, is required for Aß formation from APP in vivo Second, we establish a new role for SK2 in the protection of oligodendrocytes and myelin. Loss of SK2 sensitizes to Aß-mediated neurodegeneration by attenuating oligodendrocyte survival and promoting hippocampal atrophy, despite reduced Aß burden. Our findings support a model in which Aß-independent sensitizing influences such as loss of neuroprotective S1P are more important drivers of neurodegeneration than gross Aß concentration or plaque density.

Metabolite Profiling Reveals Predictive Biomarkers and the Absence of ß-Methyl Amino-l-alanine in Plasma from Individuals Diagnosed with Amyotrophic Lateral Sclerosis.

By employing chip-based capillary zone electrophoresis coupled to high-resolution mass spectrometry, we profiled the plasma metabolome of 134 patients diagnosed with sporadic amyotrophic lateral sclerosis (ALS) (81 males and 53 females) and 118 individuals deemed healthy (49 males and 69 females). The most significant markers (p < 0.01) were creatine, which was 49% elevated, and creatinine and methylhistidine, which were decreased by 20 and 24%, respectively, in ALS patients. The ratio of creatine versus creatinine increased 370 and 200% for male and female ALS patients, respectively. In addition, male ALS patients on an average had 5-13% lower amounts of seven essential amino acids, whereas females did not significantly differ from healthy controls. We developed two models using the metabolite abundances: (1) a classification model for the separation of ALS and healthy samples and (2) a classification model for the prediction of disease progression based on the ALS functional rating score. Utilizing a Monte Carlo cross-validation approach, a linear discriminant analysis model achieved a mean area under the receiver operating characteristic curve (AUC) of 0.85 (0.06) with a mean sensitivity of 80% (9%) and specificity of 78% (10%) for the separation of ALS and controls, respectively. A support vector machine classifier predicted progression categories with an AUC of 0.90 (0.06) with a mean sensitivity of 73% (10%) and a specificity of 86% (5%). Lastly, using a previously reported assay with a stable isotope-labeled (13C315N2) spike-in standard, we were unable to detect the exogenous neurotoxic metabolite, ß-methylamino-l-alanine, in the free or protein-bound fraction of any of the 252 plasma samples.

Differential kynurenine pathway metabolism in highly metastatic aggressive breast cancer subtypes: beyond IDO1-induced immunosuppression.

BACKGROUND: Immunotherapy has recently been proposed as a promising treatment to stop breast cancer (BrCa) progression and metastasis. However, there has been limited success in the treatment of BrCa with immune checkpoint inhibitors. This implies that BrCa tumors have other mechanisms to escape immune surveillance. While the kynurenine pathway (KP) is known to be a key player mediating tumor immune evasion and while there are several studies on the roles of the KP in cancer, little is known about KP involvement in BrCa. METHODS: To understand how KP is regulated in BrCa, we examined the KP profile in BrCa cell lines and clinical samples (n = 1997) that represent major subtypes of BrCa (luminal, HER2-enriched, and triple-negative (TN)). We carried out qPCR, western blot/immunohistochemistry, and ultra-high pressure liquid chromatography on these samples to quantify the KP enzyme gene, protein, and activity, respectively. RESULTS: We revealed that the KP is highly dysregulated in the HER2-enriched and TN BrCa subtype. Gene, protein expression, and KP metabolomic profiling have shown that the downstream KP enzymes KMO and KYNU are highly upregulated in the HER2-enriched and TN BrCa subtypes, leading to increased production of the potent immunosuppressive metabolites anthranilic acid (AA) and 3-hydroxylanthranilic acid (3HAA). CONCLUSIONS: Our findings suggest that KMO and KYNU inhibitors may represent new promising therapeutic targets for BrCa. We also showed that KP metabolite profiling can be used as an accurate biomarker for BrCa subtyping, as we successfully discriminated TN BrCa from other BrCa subtypes.

Sphingosine 1-phosphate but not Fingolimod protects neurons against excitotoxic cell death by inducing neurotrophic gene expression in astrocytes.

Sphingosine 1-phosphate (S1P) is an essential lipid metabolite that signals through a family of five G protein-coupled receptors, S1PR1-S1PR5, to regulate cell physiology. The multiple sclerosis drug Fingolimod (FTY720) is a potent S1P receptor agonist that causes peripheral lymphopenia. Recent research has demonstrated direct neuroprotective properties of FTY720 in several neurodegenerative paradigms; however, neuroprotective properties of the native ligand S1P have not been established. We aimed to establish the significance of neurotrophic factor up-regulation by S1P for neuroprotection, comparing S1P with FTY720. S1P induced brain-derived neurotrophic factor (BDNF), leukemia inhibitory factor (LIF), platelet-derived growth factor B (PDGFB), and heparin-binding EGF-like growth factor (HBEGF) gene expression in primary human and murine astrocytes, but not in neurons, and to a much greater extent than FTY720. Accordingly, S1P but not FTY720 protected cultured neurons against excitotoxic cell death in a primary murine neuron-glia coculture model, and a neutralizing antibody to LIF blocked this S1P-mediated neuroprotection. Antagonists of S1PR1 and S1PR2 both inhibited S1P-mediated neurotrophic gene induction in human astrocytes, indicating that simultaneous activation of both receptors is required. S1PR2 signaling was transduced through Gα13 and the small GTPase Rho, and was necessary for the up-regulation and activation of the transcription factors FOS and JUN, which regulate LIF, BDNF, and HBEGF transcription. In summary, we show that S1P protects hippocampal neurons against excitotoxic cell death through up-regulation of neurotrophic gene expression, particularly LIF, in astrocytes. This up-regulation requires both S1PR1 and S1PR2 signaling. FTY720 does not activate S1PR2, explaining its relative inefficacy compared to S1P.

NAD Deficiency, Congenital Malformations, and Niacin Supplementation.

BACKGROUND: Congenital malformations can be manifested as combinations of phenotypes that co-occur more often than expected by chance. In many such cases, it has proved difficult to identify a genetic cause. We sought the genetic cause of cardiac, vertebral, and renal defects, among others, in unrelated patients. METHODS: We used genomic sequencing to identify potentially pathogenic gene variants in families in which a person had multiple congenital malformations. We tested the function of the variant by using assays of in vitro enzyme activity and by quantifying metabolites in patient plasma. We engineered mouse models with similar variants using the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 system. RESULTS: Variants were identified in two genes that encode enzymes of the kynurenine pathway, 3-hydroxyanthranilic acid 3,4-dioxygenase (HAAO) and kynureninase (KYNU). Three patients carried homozygous variants predicting loss-of-function changes in the HAAO or KYNU proteins (HAAO p.D162*, HAAO p.W186*, or KYNU p.V57Efs*21). Another patient carried heterozygous KYNU variants (p.Y156* and p.F349Kfs*4). The mutant enzymes had greatly reduced activity in vitro. Nicotinamide adenine dinucleotide (NAD) is synthesized de novo from tryptophan through the kynurenine pathway. The patients had reduced levels of circulating NAD. Defects similar to those in the patients developed in the embryos of Haao-null or Kynu-null mice owing to NAD deficiency. In null mice, the prevention of NAD deficiency during gestation averted defects. CONCLUSIONS: Disruption of NAD synthesis caused a deficiency of NAD and congenital malformations in humans and mice. Niacin supplementation during gestation prevented the malformations in mice. (Funded by the National Health and Medical Research Council of Australia and others.).

Epithelial Indoleamine 2,3-Dioxygenase 1 Modulates Aryl Hydrocarbon Receptor and Notch Signaling to Increase Differentiation of Secretory Cells and Alter Mucus-Associated Microbiota.

BACKGROUND & AIMS: Inflammation, injury, and infection up-regulate expression of the tryptophan metabolizing enzyme indoleamine 2,3-dioxygenase 1 (IDO1) in the intestinal epithelium. We studied the effects of cell-specific IDO1 expression in the epithelium at baseline and during intestinal inflammation in mice. METHODS: We generated transgenic mice that overexpress fluorescence-tagged IDO1 in the intestinal epithelium under control of the villin promoter (IDO1-TG). We generated intestinal epithelial spheroids from mice with full-length Ido1 (controls), disruption of Ido1 (knockout mice), and IDO1-TG and analyzed them for stem cell and differentiation markers by real-time polymerase chain reaction, immunoblotting, and immunofluorescence. Some mice were gavaged with enteropathogenic Escherichia coli (E2348/69) to induce infectious ileitis, and ileum contents were quantified by polymerase chain reaction. Separate sets of mice were given dextran sodium sulfate or 2,4,6-trinitrobenzenesulfonic acid to induce colitis; intestinal tissues were analyzed by histology. We utilized published data sets GSE75214 and GDS2642 of RNA expression data from ilea of healthy individuals undergoing screening colonoscopies (controls) and patients with Crohn's disease. RESULTS: Histologic analysis of small intestine tissues from IDO1-TG mice revealed increases in secretory cells. Enteroids derived from IDO1-TG intestine had increased markers of stem, goblet, Paneth, enteroendocrine, and tuft cells, compared with control enteroids, with a concomitant decrease in markers of absorptive cells. IDO1 interacted non-enzymatically with the aryl hydrocarbon receptor to inhibit activation of NOTCH1. Intestinal mucus layers from IDO1-TG mice were 2-fold thicker than mucus layers from control mice, with increased proportions of Akkermansia muciniphila and Mucispirillum schaedleri. Compared to controls, IDO1-TG mice demonstrated an 85% reduction in ileal bacteria (P = .03) when challenged with enteropathogenic E coli, and were protected from immune infiltration, crypt dropout, and ulcers following administration of dextran sodium sulfate or 2,4,6-trinitrobenzenesulfonic acid. In ilea of Crohn's disease patients, increased expression of IDO1 correlated with increased levels of MUC2, LYZ1, and aryl hydrocarbon receptor, but reduced levels of SLC2A5. CONCLUSIONS: In mice, expression of IDO1 in the intestinal epithelial promotes secretory cell differentiation and mucus production; levels of IDO1 are positively correlated with secretory cell markers in ilea of healthy individuals and Crohn's disease patients. We propose that IDO1 contributes to intestinal homeostasis.

Kynurenine pathway modulation reverses the experimental autoimmune encephalomyelitis mouse disease progression.

BACKGROUND: Multiple sclerosis (MS) is a chronic immune-mediated disorder of the central nervous system characterized by demyelination, neuroinflammation, and neurodegeneration. Activation of the kynurenine pathway (KP) results from acute and chronic neuroinflammation leading to both immune suppression and neurotoxicity. However, the exact effects of KP metabolites and changes in neurodegenerative diseases over time are not fully understood. Studies, including those in MS models, have reported that short-term KP activation is beneficial through immune tolerance. However, the effects of long-term KP activation are poorly understood. We hypothesized that such chronic activation is responsible for the neurodegeneration in MS, and further, modulating the KP in EAE-induced mice could significantly decrease the EAE disease severity. METHODS: We biochemically altered the KP at different stages of the disease in experimental allergic encephalomyelitis (EAE) mouse model of MS and at two different enzymatic levels of the KP (IDO-1 (indoleamine 2,3 dioxygenase)) and KMO (kynurenine monooxygenase). CNS tissue and blood samples were analyzed longitudinally using GCMS, HPLC, IHC, and RT-PCR. RESULTS: We showed that the KP was steadily upregulated correlating with disease severity and associated with a shift towards increasing concentrations of the KP metabolite quinolinic acid, a neuro- and gliotoxin. KP modulation by inhibition of IDO-1 with 1-methyl tryptophan (1-MT) was dependent on the timing of treatment at various stages of EAE. IDO-1 inhibition at EAE score 2 led to significantly higher numbers of FoxP3 cells (p < 0.001) in the spleen than earlier IDO-1 inhibition (prophylactic 1-MT treatment group (p < 0.001)), 1-MT treatment after EAE induction (EAE score 0; p < 0.001), and 1-MT treatment at EAE score of 1 (p < 0.05). Significant improvement of disease severity was observed in EAE mice treated with 1-MT at EAE score 2 compared to the untreated group (p < 0.05). KP modulation by KMO inhibition with Ro 61-8048 led to significantly greater numbers of Foxp3 cells (p < 0.05) in Ro 61-8048 treated mice and even more significant amelioration of EAE disease compared to the 1-MT treatment groups. CONCLUSIONS: These results provide a new mechanistic link between neuroinflammation and neurodegeneration and point to KP modulation at the KMO level to preserve immune tolerance and limit neurodegeneration in EAE. They provide the foundation for new clinical trials for MS.