Kynurenine Levels Research Articles

Kynurenine-PARP-1 Link Mediated by MicroRNA 210 May Be Dysregulated in Pulmonary Hypertension.

BackgroundDysregulation of microRNAs is associated with pulmonary hypertension. The present study aimed to determine the alterations in microRNA and microRNA expressions and their role in signaling pathways and investigate the relationship with serum levels of apelin, kynurenine, and endocan in pulmonary hypertension.MethodsThe study design was prospective and single-centered. The study included 32 consecutive treatment-naive patients with precapillary pulmonary hypertension and 55 age and sex-matched healthy controls. All subjects underwent right heart catheterization. mRNA expressions of hypoxia-inducible factor-1 alpha, hypoxia-inducible factor-2 alpha, signal transducer and activator of transcription-3, fibroblast growth factor-2, fibroblast growth factor receptor-1, and poly-ADP-ribose polymerase-1 and microRNA expressions of miRNA-210, miRNA-130a, miRNA-424, miRNA-204, and miRNA-223 were determined by RT-PCR. Concentrations of kynurenine, apelin, and endocan were analyzed by ELISA.ResultsmRNA expressions of hypoxia-inducible factor-2 alpha, signal transducer and activator of transcription-33, and FGF-2 were increased; miRNA-210 and miRNA-130a were increased; miRNA-223 and miRNA-204 were decreased in pulmonary hypertension. Apelin and kynurenine concentrations were decreased in pulmonary hypertension. There were positive correlations: hypoxia-inducible factor-2 alpha-miRNA-424, Apelin-miRNA-424, kynurenine-miRNA-210, signal transducer and activator of transcription-3-PVR, miRNA-210-right atrial pressure, and kynurenine-right atrial pressure. There were negative correlations: poly-ADP-ribose polymerase-1-miRNA-210 and poly-ADP-ribose polymerase-1-right atrial pressure. On multiple logistic regression analyses, miRNA-130a and Apelin were independent risk factors for PH.ConclusionsWe report a novel relationship between the kynurenine and poly-ADP-ribose polymerase-1 signaling pathways that could be mediated by miRNA-210. We also report a connection between the Apelin and hypoxia-inducible factor-2 alpha signaling pathways that could be mediated by miRNA-424. Reduced levels of Apelin and elevated levels of miRNA-130a are associated with pulmonary hypertension. We also find that elevated levels of signal transducer and activator of transcription-3, miRNA-210, and kynurenine and reduced levels of poly-ADP-ribose polymerase-1 correlate with more severe hemodynamics.

Dissecting the Mechanisms Whereby Tryptophan Metabolites Alter Myocardial Function

Cardiovascular diseases (CVD) are a significant cause of morbidity and mortality, especially in the elderly population and they represent an important risk factor for frailty. The essential amino acid, tryptophan (TRP), acts as a precursor of neurotransmitters/hormones, such as serotonin and melatonin, and is central to many aspects of cellular metabolism. TRP degradation, however, can lead to breakdown products, such as kynurenine (KYN), whose impact on normal and diseased hearts remains primarily unknown. Moreover, in recent clinical reports, increased levels of KYN and/or its metabolites, formed via degradation of the essential amino acid tryptophan, are associated with heart diseases and atherosclerosis. KYN infusion significantly impaired cardiac function in Langendorff‐perfused hearts. Similarly in isolated cardiomyocytes, exposure to KYN increased oxidative stress and decreased fractional shortening. The ongoing studies include mechanistic approaches to determine the pathways involved in KYN and/or its metabolites’ impact on myocardial function.

Is Poor Lithium Response in Individuals with Bipolar Disorder Associated with Increased Degradation of Tryptophan along the Kynurenine Pathway? Results of an Exploratory Study.

Bipolar disorder is associated with an inflammation-triggered elevated catabolism of tryptophan to the kynurenine pathway, which impacts psychiatric symptoms and outcomes. The data indicate that lithium exerts anti-inflammatory effects by inhibiting indoleamine-2,3-dioxygenase (IDO)-1 activity. This exploratory study aimed to investigate the tryptophan catabolism in individuals with bipolar disorder (n = 48) compared to healthy controls (n = 48), and the associations with the response to mood stabilizers such as lithium, valproate, or lamotrigine rated with the Retrospective Assessment of the Lithium Response Phenotype Scale (or the Alda scale). The results demonstrate an association of a poorer response to lithium with higher levels of kynurenine, kynurenine/tryptophan ratio as a proxy for IDO-1 activity, as well as quinolinic acid, which, overall, indicates a pro-inflammatory state with a higher degradation of tryptophan towards the neurotoxic branch. The treatment response to valproate and lamotrigine was not associated with the levels of the tryptophan metabolites. These findings support the anti-inflammatory properties of lithium. Furthermore, since quinolinic acid has neurotoxic features via the glutamatergic pathway, they also strengthen the assumption that the clinical drug response might be associated with biochemical processes. The relationship between the lithium response and the measurements of the tryptophan to the kynurenine pathway is of clinical relevance and may potentially bring advantages towards a personalized medicine approach to bipolar disorder that allows for the selection of the most effective mood-stabilizing drug.

Sodium Tanshinone IIA Sulfonate as a Potent IDO1/TDO2 Dual Inhibitor Enhances Anti-PD1 Therapy for Colorectal Cancer in Mice.

Although the antitumor efficacy of immune checkpoint blockade (ICB) has been proved in colorectal cancer (CRC), the results are unsatisfactory, presumably owing to the presence of tryptophan metabolism enzymes indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase 2 (TDO2). However, only a few dual inhibitors for IDO1 and TDO2 have been reported. Here, we discovered that sodium tanshinone IIA sulfonate (STS), a sulfonate derived from tanshinone IIA (TSN), reduced the enzymatic activities of IDO1 and TDO2 with a half inhibitory concentration (IC50) of less than 10 μM using enzymatic assays for natural product screening. In IDO1- or TDO2- overexpressing cell lines, STS decreased kynurenine (kyn) synthesis. STS also reduced the percentage of forkhead box P3 (FOXP3) T cells in lymphocytes from the mouse spleen cocultured with CT26. In vivo, STS suppressed tumor growth and enhanced the antitumor effect of the programmed cell death 1 (PD1) antibody. Compared with anti-PD1 (α-PD1) monotherapy, combined with STS had lower level of plasma kynurenine. Immunofluorescence assay suggested that STS decreased the number of FOXP3+ T cells and increased the number of CD8+ T cells in tumors. Flow cytometry analysis of immune cells in tumor tissues demonstrated an increase in the percentage of tumor-infiltrating CD8+ T cells. According to our findings, STS acts as an immunotherapy agent in CRC by inhibiting both IDO1 and TDO2.

Investigation of possible associations between tryptophan/kynurenine status and FOXP3 expression in colorectal cancer

Tryptophan metabolism in the tumor microenvironment exerts immunosuppressive effects by affecting the anti-tumor functions of immune cells. The immunosuppressive roles of tryptophan and tryptophan metabolites and their effects on the FOXP3 gene, highly expressed in regulatory T cells (Tregs), are remarkable. Our study aimed to investigate the relation between tryptophan metabolism and the transcription factor FOXP3 gene in colorectal cancer (CRC). Patients with CRC (n = 159) and controls (n = 112) were included in the study. The FOXP3 rs3761548 variant genotyping from the isolated genomic DNA was performed by PCR-RFLP. FOXP3 gene expression was determined by Q-PCR in RNAs isolated from resected tissues at the same time. Serum tryptophan, kynurenine, kynurenic acid levels of the cases were determined by HPLC. In serum samples with CRC, tryptophan level was 14.32 ± 1.09 μmol/L, kynurenine level was 1.33 ± 0.02 μmol/L, and the kynurenic acid level was 0.01 ± 0.001 μmol/L. The level of tryptophan was found to be low in CRC compared to control (p < .001). In cases with CRC, CC genotype (p = .048) and C allele (p = .012) frequency for FOXP3 rs3761548 were higher than the control group. It was found that the expression level of the FOXP3 gene was approximately 44 times higher in the advanced tumor stage (T3 + T4) than in the early tumor stage (T1 + T2) (p = .021). We suggest that there may be a possible relationship among serum TRP, TRP metabolites (KYN, KYNA) levels, FOXP3 gene expression, and FOXP3 gene variants in CRC pathogenesis.

The Kynurenine Pathway and Mediating Role of Stress in Addictive Disorders: A Focus on Alcohol Use Disorder and Internet Gaming Disorder.

Stress plays an important role in the pathophysiology of addictive disorders. The kynurenine (KYN) pathway involved in neuroimmune and cognitive functions is activated under stress. However, the neuroimmunological–neurocognitive mechanisms in the role of stress in addictive disorders are unclear still now. Ninety-nine young adults aged 18–35 years [alcohol use disorder (AUD), N = 30; Internet gaming disorder (IGD), N = 34; healthy controls (HCs), N = 35] participated in this study. Stress levels, resilience, addiction severity, and neurocognitive functions were evaluated, and serum levels of tryptophan (TRP), 5-hydroxytryptamine (5-HT), KYN, and kynurenine acid (KYNA) were determined using liquid chromatography coupled with tandem mass spectrometry through blood samples. Both addictive disorder groups showed higher levels of stress, lower resilience, and impaired executive functions compared to the HC group. Importantly, the AUD group revealed significantly increased KYN levels and KYN/TRP ratios, as well as decreased KYNA levels and KYNA/KYN ratios compared to HCs (p < 0.001, p < 0.001, p = 0.033, and p < 0.001, respectively). The IGD group showed KYN levels and KYNA/KYN ratios intermediate between those of the AUD group and HCs. Furthermore, in the AUD group, the mediating effect of AUD on KYN through stress level was moderated by resilience [index of moderated mediation = −0.557, boot S.E = 0.331, BCa CI (−1.349, −0.081)]. Stress may induce an imbalance in downstream of KYN pathway metabolites, and the KYN/TRP ratio may play as a neuromediator between stress and behavioral changes in both addictive disorders. This study suggests that regulation of the KYN pathway is critical in the pathophysiology of addictive disorders and it may serve as an important target for future treatment modalities.

Disturbance of neurotransmitter metabolism in drug-naïve, first-episode major depressive disorder: a comparative study on adult and adolescent cohorts.

Neurotransmitter metabolism plays a critical role in the pathophysiology of major depressive disorder (MDD). However, whether the neurotransmitter metabolism in adolescent MDD is differentiated from adult MDD is still elusive. In the current study, plasma concentrations of monoamine and amino acid neurotransmitters as well as their metabolites, including tryptophan (TRP), kynurenine (KYN), kynurenic acid (KYNA), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), norepinephrine (NE), vanillylmandelic acid (VMA), 3-methoxy-4-hydroxyphenylglycol (MHPG), glutamine (GLN), glutamate (GLU) and gamma-aminobutyric acid (GABA), were measured and compared in two cohorts of subjects (adult cohort: 31 first-episode MDD vs. 35 healthy controls; adolescent cohort: 33 first-episode MDD vs. 30 healthy controls). To assess the effects of antidepressant treatment, we also analyzed the concentrations of these indexes pre- and post-treatment in adult and adolescent cohorts. At baseline, the deficits of neurotransmitter metabolism in adult MDD were manifested in all the neurotransmitter systems. In contrast, for adolescent MDD, the dysregulation of neurotransmission was mainly indicated in the catecholaminergic systems. After antidepressant treatment, adult MDD showed increased TRP, KYN, KYNA and GLU levels, together with decreased levels of 5-HIAA and DOPAC. Adolescent MDD illustrated an increased level of 5-HT and decreased levels of TRP and GABA. The improvements of Hamilton total scores correlated with the changes in plasma TRP and the turnover of KYN/TRP after treatment in all MDD patients. However, these correlations were only manifested in the adult MDD rather than in adolescent MDD patients. The findings highlight the shared and distinguished neurotransmitter pathways in MDD and emphasize the different antidepressant responses between adults and adolescents. Potentially, the neurotransmitters above could serve as diagnostic biomarkers and provide a novel pharmacological treatment strategy for MDD.

Inflammatory Blood Biomarker Kynurenine Is Linked With Elevated Neuroinflammation and Neurodegeneration in Older Adults: Evidence From Two 1H-MRS Post-Processing Analysis Methods.

Rationale and ObjectivesPro-inflammatory processes have been argued to play a role in conditions associated with cognitive decline and neurodegeneration, like aging and obesity. Only a limited number of studies have tried to measure both peripheral and central biomarkers of inflammation and examined their interrelationship. The primary aim of this study was to examine the hypothesis that chronic peripheral inflammation would be associated with neurometabolic changes that indicate neuroinflammation (the combined elevation of myoinositol and choline), brain gray matter volume decrease, and lower cognitive functioning in older adults.Materials and MethodsSeventy-four older adults underwent bio-impedance body composition analysis, cognitive testing with the Montreal Cognitive Assessment (MoCA), blood serum analysis of inflammatory markers interleukin-6 (IL-6) and kynurenine, magnetic resonance imaging (MRI), and proton magnetic resonance spectroscopy (1H-MRS) of the brain. Neurometabolic findings from both Tarquin and LCModel 1H-MRS post-processing software packages were compared. The regions of interest for MRI and 1H-MRS measurements were dorsal posterior cingulate cortex (DPCC), left hippocampal cortex (HPC), left medial temporal cortex (MTC), left primary sensorimotor cortex (SM1), and right dorsolateral prefrontal cortex (DLPFC).ResultsElevated serum kynurenine levels were associated with signs of neuroinflammation, specifically in the DPCC, left SM1 and right DLPFC, and signs of neurodegeneration, specifically in the left HPC, left MTC and left SM1, after adjusting for age, sex and fat percentage (fat%). Elevated serum IL-6 levels were associated with increased Glx levels in left HPC, left MTC, and right DLPFC, after processing the 1H-MRS data with Tarquin. Overall, the agreement between Tarquin and LCModel results was moderate-to-strong for tNAA, tCho, mIns, and tCr, but weak to very weak for Glx. Peripheral inflammatory markers (IL-6 and kynurenine) were not associated with older age, higher fat%, decreased brain gray matter volume loss or decreased cognitive functioning within a cohort of older adults.ConclusionOur results suggest that serum kynurenine may be used as a peripheral inflammatory marker that is associated with neuroinflammation and neurodegeneration, although not linked to cognition. Future studies should consider longitudinal analysis to assess the causal inferences between chronic peripheral and neuroinflammation, brain structural and neurometabolic changes, and cognitive decline in aging.

The Tobacco β-Cembrenediol: A Prostate Cancer Recurrence Suppressor Lead and Prospective Scaffold via Modulation of Indoleamine 2,3-Dioxygenase and Tryptophan Dioxygenase.

Prostate cancer (PC) is the second leading cause of death in men in the US. PC has a high recurrence rate, and limited therapeutic options are available to prevent disease recurrence. The tryptophan-degrading enzymes 2,3-indoleamine dioxygenase (IDO1) and tryptophan dioxygenase (TDO2) are upregulated in invasive PC. (1S,2E,4R,6R,7E,11E)-2,7,11-cembratriene-4,6-diol (β-CBT) and its C-4 epimer α-CBT are the precursors to key flavor ingredients in tobacco leaves. Nearly 40–60% of β- and α-CBT are purposely degraded during commercial tobacco fermentation. Earlier, β-CBT inhibited invasion, reversed calcitonin-stimulated transepithelial resistance decrease, and induced tighter intercellular barriers in PC-3M cells. This study demonstrates the in vitro β-CBT anti-migratory (wound-healing assay) and anti-clonogenicity (colony-formation assay) activities against five diverse human PC cell lines, including the androgen-independent PC-3, PC-3M, and DU-145, the castration-recurrent CWR-R1ca, and the androgen-dependent CWR-22rv1. Meanwhile, β-CBT potently suppressed in vivo locoregional and distant recurrences after the primary tumor surgical excision of PC-3M-Luc cell tumor engrafted in male nude mice. β-CBT treatments suppressed organ and bone metastasis and lacked any major toxicity over the 60-day study course. β-CBT treatments significantly suppressed IDO1, TDO2, and their final metabolite kynurenine levels in PC-3M cells. β-CBT treatments significantly suppressed the tumor recurrence marker PSA and kynurenine levels in treated animals’ plasma. β-CBT emerges as a promising PC recurrence suppressive lead.

462 Dysfunctional leukocyte mitochondrial metabolism is associated with immune paralysis in critically ill septic patients

OBJECTIVES/GOALS: The host immune response during sepsis is now recognized to have anti-inflammatory pathophysiology. We aim to determine whether mitochondrial dysfunction of leukocytes predicts which critically ill septic patients develop immune paralysis and to identify differences in cellular metabolites between patients with and without immune paralysis. METHODS/STUDY POPULATION: Critically ill septic and control adult patients were recruited from one of 6 ICUs in a single-center tertiary care academic hospital. After enrollment, peripheral blood mononuclear cells (PBMCs) were isolated from a tube of whole blood on day 0-1 after ICU admission. Flow cytometry to quantify monocyte HLA-DR was performed to determine whether patients were immune paralyzed or not. Mitochondrial functional assays of PBMCs were performed with inhibitors of the electron transport chain to assess for differences in oxidative phosphorylation and glycolysis utilization. Metabolic profiling of cell pellets was performed to evaluate for specific metabolites and pathways associated with immune paralyzed patients. RESULTS/ANTICIPATED RESULTS: A total of 101 patients were recruited, including 62 control and 39 septic patients. 81 patients had immune paralysis status available for analysis. 52% of all recruited subjects were immune paralyzed. Of these, 58% were controls and 75% were septic. Immune paralyzed septic and control patients showed features of reduced utilization of oxidative phosphorylation (ox phos) including reduced basal respiration, ATP production and maximal respiration compared with non-immune paralyzed septic and control patients. Immune paralyzed septic patients showed diminished glycolysis utilization compared with septic non-immune paralyzed patients. Finally, cellular kynurenine and quinolinate levels were low in both immune paralyzed control and septic patients compared with non-immune paralyzed patients. DISCUSSION/SIGNIFICANCE: The PBMCs of immune paralyzed septic patients show evidence of mitochondrial dysfunction, with reduced ox phos and glycolysis utilization. Low levels of kynurenine and quinolinate, metabolite precursors to NAD+, in immune paralyzed patients may signal key deficiencies and targetable therapeutic avenues for reversal of an immune paralyzed state.

Sodium Selenite Modulates IDO1/Kynurenine, TLR4, NF-κB and Bcl2/Bax Pathway and Mitigates Acetic Acid-Induced Colitis in Rat.

Colitis is a main presentation of inflammatory bowel disease (IBD) and yet, has no definitive cure. Currently, corticosteroids, anti-tumor necrosis factor (anti-TNF) agents and 5-aminosalicylic acid derivatives are prescribed for management of colitis. Except their failure rate, they are not always tolerated because of their severe adverse effects. Additive formulas with fewer adverse effects may improve the treatment of colitis. In this study, colitis was induced with intra-rectal injection of three concentrations of acetic acid (4, 6 and 8 v/v). Each group received sodium selenite (0.5 mg/kg) or saline, gavaged on days 0 and 1 for treatment. Two days after induction of colitis, rats were sacrificed and the end part of their colons were resected for macroscopic and microscopic evaluation and molecular measurement. Sodium selenite improved macroscopic and microscopic view of the colon, decreased cryptitis, crypt abscess and inflammatory cells infiltration and partly maintained mucosal structure. Sodium selenite markedly reduced tissue levels of malondialdehyde (MDA), TNF-α and interferon γ (INF-γ) and decreased myeloperoxidase (MPO) activity. Treatment with sodium selenite also significantly downregulated IL17, IL22, indoleamine 2,3-dioxygenase (IDO1), and kynurenine levels. Western blotting revealed that sodium selenite prevented apoptosis by increasing bcl2/Bax ratio. Furthermore, our findings showed that sodium selenite significantly downregulated the upstream inflammatory molecules such as nuclear factor kappa B (NF-κB) and toll-like receptor 4 (TLR4) in colitis. These findings show that sodium selenite alleviates inflammatory response and oxidative stress and protects against colitis.

Targeted metabolomics analysis of serum and Mycobacterium tuberculosis antigen-stimulated blood cultures of pediatric patients with active and latent tuberculosis

Profound tuberculosis (TB)-induced metabolic changes reflected in the blood metabolomic profile may provide an opportunity to identify specific markers of Mycobacterium tuberculosis infection. Using targeted liquid chromatography tandem mass spectrometry, we compared the levels of 30 small metabolites, including amino acids and derivatives, and small organic compounds in serum and M.tb antigen-stimulated whole blood cultures of active TB children, latent TB (LTBI) children, nonmycobacterial pneumonia (NMP) children, and healthy controls (HCs) to assess their potential as biomarkers of childhood TB. We found elevated levels of leucine and kynurenine combined with reduced concentrations of citrulline and glutamine in serum and blood cultures of TB and LTBI groups. LTBI status was additionally associated with a decrease in valine levels in blood cultures. The NMP metabolite profile was characterized by an increase in citrulline and glutamine and a decrease in leucine, kynurenine and valine concentrations. The highest discriminatory potential for identifying M.tb infection was observed for leucine detected in serum and kynurenine in stimulated blood cultures. The use of targeted metabolomics may reveal metabolic changes in M.tb-infected children, and the obtained results are a proof of principle of the usefulness of metabolites in the auxiliary diagnosis of TB in children.

Influx of kynurenine into the brain is involved in the reduction of ethanol consumption induced by Ro 61-8048 after chronic intermittent ethanol in mice.

Background and PurposeThe kynurenine pathway has been proposed as a target for modulating drug abuse. We previously demonstrated that inhibition of kynurenine 3‐monooxygenase (KMO), using Ro 61‐8048, reduces ethanol consumption in a binge drinking model. Here, we investigate the effect of the kynurenine pathway modulation in ethanol‐dependent mice.Experimental ApproachAdult male and female mice were subjected to a Chronic Intermittent Ethanol (CIE) paradigm. On the last day of CIE, mice were treated with Ro 61‐8048, Ro 61‐8048 + PNU‐120596, a positive allosteric modulator of α7nAChR, and Ro 61‐8048 + L‐leucine or probenecid, which blocks the influx or efflux of kynurenine from the brain, respectively. Ethanol, water consumption and preference were measured and kynurenine levels in plasma and limbic forebrain were determined.Key ResultsRo 61‐8048 decreases consumption and preference for ethanol in both sexes exposed to the CIE model, an effect that was prevented by PNU‐120596. The Ro 61‐8048‐induced decrease in ethanol consumption depends on the influx of kynurenine into the brain.Conclusion and ImplicationsInhibition of KMO reduces ethanol consumption and preference in both male and female mice subjected to CIE model by a mechanism involving α7nAChR. Moreover, this centrally‐mediated effect depends on the influx of peripheral kynurenine to the brain and can be prolonged by blocking the efflux of kynurenine from the brain. Here, for the first time, we demonstrate that the modulation of the kynurenine pathway is an effective strategy for the treatment of ethanol dependence in both sexes.

System analysis based on the cancer–immunity cycle identifies ZNF207 as a novel immunotherapy target for hepatocellular carcinoma

BackgroundImmune checkpoint inhibitors as monotherapies for advanced hepatocellular carcinoma (HCC) fail to achieve satisfying results, while combination therapies show greater efficacy. Therefore, identifying new combined targets for immune checkpoint inhibitors...

Kynurenine pathway of tryptophan metabolism in patients with familial Mediterranean fever.

Familial Mediterranean fever (FMF) is an autoinflammatory syndrome characterized by recurrent episodes of fever and aseptic polyserositis. Subclinical inflammation generates a hidden threat to the development of FMF complications such as amyloidosis in attack-free intervals. The kynurenine pathway (KP) has been considered an important player in inflammation and immune response. The study was aimed to measure serum levels of KP metabolites in patients with FMF in the attack-free period. A total of 161 participants were recruited from the rheumatology department in this single-centre, case-control study. Participants meeting the eligibility criteria were divided into healthy controls (n = 80) and FMF (n = 81). The laboratory data were obtained from the electronic registration database. Serum tryptophan (TRP), kynurenine (KYN), kynurenic acid (KYNA), 3-hydroxyanthranilic acid, 3-hydroxykynurenine (3HK), and quinolinic acid (QUIN) concentrations were measured with tandem mass spectrometry. Laboratory findings of FMF patients and healthy controls subjects were compared and evaluated. Serum TRP and KYNA levels were significantly decreased in both FMF groups compared to the control group, while the levels of KYN, QUIN, 3HK, the KYN/TRP ratio, and red cell distribution width were higher. TRP degradation by the KP is increased in patients with FMF. KP metabolites can be useful in demonstrating subclinical inflammation.

Inhibition of the Na+/K+-ATPase by cardiac glycosides suppresses expression of the IDO1 immune checkpoint in cancer cells by reducing STAT1 activation

Despite extensive basic and clinical research on immune checkpoint regulatory pathways, little is known about the effects of the ionic tumor microenvironment on immune checkpoint expression and function. Here we describe a mechanistic link between Na+/K+-ATPase (NKA) inhibition and activity of the immune checkpoint protein indoleamine-pyrrole 2′,3′-dioxygenase 1 (IDO1). We found that IDO1 was necessary and sufficient for production of kynurenine, a downstream tryptophan metabolite, in cancer cells. We developed a spectrophotometric assay to screen a library of 31 model ion transport-targeting compounds for potential effects on IDO1 function in A549 lung and MDA-MB-231 breast cancer cells. This revealed that the cardiac glycosides ouabain and digoxin inhibited kynurenine production at concentrations that did not affect cell survival. NKA inhibition by ouabain and digoxin resulted in increased intracellular Na+ levels and downregulation of IDO1 mRNA and protein levels, which was consistent with the reduction in kynurenine levels. Knockdown of ATP1A1, the ɑ1 subunit of the NKA and target of cardiac glycosides, increased Na+ levels to a lesser extent than cardiac glycoside treatment and did not affect IDO1 expression. However, ATP1A1 knockdown significantly enhanced the effect of cardiac glycosides on IDO1 expression and kynurenine production. Mechanistically, we show that cardiac glycoside treatment resulted in curtailing the length of phosphorylation-mediated stabilization of STAT1, a transcriptional regulator of IDO1 expression, an effect enhanced by ATP1A1 knockdown. Our findings reveal cross talk between ionic modulation via cardiac glycosides and immune checkpoint protein expression in cancer cells with broad mechanistic and clinical implications.

Activation of the kynurenine pathway predicts mortality and neurological outcome in cardiac arrest patients: A validation study.

Activation of the kynurenine pathway (KP) has been shown to predict outcome in cardiac arrest (CA) patients. We validated these findings in a Swiss cohort. We measured admission tryptophan and kynurenine levels in 270 consecutive CA patients (38 in-hospital CA) and investigated associations with in-hospital mortality and neurological outcome at hospital discharge. 120 of 270 (44%) patients died in the hospital. Compared to survivors, non-survivors showed higher median initial kynurenine levels (5.28μmol/l [IQR 2.91 to 7.40] vs 3.58μmol/l [IQR 2.47 to 5.46]; p<0.001) and a higher median kynurenine/tryptophan ratio (0.10μmol/l [IQR 0.07 to 0.17] vs 0.07μmol/l [IQR 0.05 to 0.1]; p<0.001). In a model adjusted for age, gender and comorbidities, kynurenine (OR 1.16, 95% CI 1.05 to 1.27; p=0.001) and kynurenine/tryptophan ratio (OR 1.19, 95% CI 1.08 to 1.31; p=0.003) were significantly associated with mortality. Results were similar for neurological outcome. Our findings validate a previous study and show associations of the activation of the KP with unfavorable outcomes after CA. Future studies should evaluate whether therapeutic modulation of the KP may impact clinical outcomes after CA.

OP28 A randomized placebo controlled clinical trial with 5-hydroxytryptophan in patients with quiescent Inflammatory Bowel Disease and fatigue (Trp-IBD)

Abstract Background Fatigue is highly prevalent in patients with IBD independent of the disease status but treatment options remain limited. A potential mediator in the pathophysiology of fatigue is tryptophan (Trp), a precursor of serotonin. Recently, reduced serum Trp levels have been linked to fatigue in patients with clinically and endoscopically inactive IBD. The aim of the current study was to determine the effect of oral 5-hydroxytryptophan (5-HTP), the direct precursor of serotonin, supplementation on fatigue in patients with inactive IBD. Methods This multicentre, randomized, double-blind, cross-over, placebo-controlled trial included fatigued patients with IBD in clinical and biochemical remission (CRP &amp;lt;10mg/L, calprotectin &amp;lt;250 mg/kg), treated with immunosuppressants and/or biologicals. Fatigue was assessed with the fatigue VAS (fVAS, range 0–10) and defined by a fVAS ≥5. Patients were treated in a cross-over manner with 100 mg 5-HTP or placebo bid for two consecutive periods of 8 weeks, without an intermediate washout period. The primary endpoint was the proportion of patients reaching a 20% reduction in fVAS after 8 weeks of intervention (week 8 versus week 0 and week 16 versus week 8). Secondary outcomes were changes in validated FACIT-F score, scores for depression and anxiety and changes in Trp metabolites. The effect of the intervention on the outcomes was evaluated by linear mixed modelling (LMM), with the intervention, period and intervention x period as fixed factors and study participant as random factor. Results A total of 166 patients were included in 13 Belgian centres between December 2018 and November 2020 (baseline characteristics: Table 1). The dropout rate was 10.8%. The evolution of the fVAS throughout the study was comparable between both study groups and no difference was observed in fVAS reduction between placebo and 5-HTP (Figure 1). The proportion of patients reaching ≥20% reduction in fVAS did not differ between placebo (37.6%) and 5-HTP (35.6%) (p=0.830). The evolution of the other scores for fatigue, depression, anxiety and stress were also similar between placebo and 5-HTP (Table 2). A significant increase in 5-HTP and serotonin serum levels was observed during 5-HTP treatment compared to placebo; whereas serum levels of Trp and kynurenine were comparable. Globally, changes in fVAS were not associated with changes in those metabolites (Figure 2). Adverse events (AEs) were seen in 29.2% and 34.8% of patients under treatment with placebo and 5-HTP respectively (p=0.282). Conclusion Despite a significant increase in serum 5-HTP and serotonin levels by oral treatment with 5-HTP, 5-HTP did not modulate IBD-related fatigue. Furthermore, treatment with 5-HTP had no impact on depression, anxiety and stress scores.

Differential Immunomodulatory Potential of Silver Nanoparticles and Effect on the Kynurenine Pathway in Male Wistar Rats

Silver nanoparticles are increasingly being used in a wide variety of ways that may lead to frequency of exposure for humans and the environment. Thus, it is necessary to understand the biological effect(s) of these nanoparticles. Previously, we showed that AgNPs activated the kynurenine pathway in rat brain independently of oxidative stress in rats. This present study is aimed at evaluating the effect of AgNPs on some selected cytokines, redox parameters, and on the kynurenine level in rats. Male Wistar rats (130-150 g) were divided into 4 groups. Rats were grouped into control, AgNPs only (50 mg/kg bw), coadministration of AgNPs (50 mg/kg bw), and dexamethasone (100 mg/kg bw) and dexamethasone only (100 mg/kg bw). Results indicated that AgNPs did not significantly elevate MDA levels in rat plasma and brain relative to the control group. AgNPs caused a significant alteration in the level of rat brain and plasma total protein concentration. Meanwhile, AgNPs led to an elevation in the level of reduced glutathione (GSH) in rat plasma but decreased plasma kynurenine level significantly. Furthermore, IFN-γ level was reduced following AgNPs administration, IL-1β decreased across the treatment groups, while NF-κB was reduced in the dexamethasone only and AgNPs + dexamethasone groups when compared with the control. AgNPs led to increased IL-4 levels, while IL-10 levels decreased across the treatment groups. Taken together, our data showed a differential immunomodulatory potential of AgNPs in rats.

Impact and Possible Mechanism(s) of Adipose Tissue-Derived Mesenchymal Stem Cells on T-Cell Proliferation in Patients With Rheumatic Disease.

Objectives: Systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) are chronic wasting, incurable rheumatic diseases of autoimmune background, in which T cells play a critical pathogenic role. Autologous adipose tissue-derived mesenchymal stem cells (ASCs) may represent an alternative therapeutic option for SLE and SSc patients, but the biology of these cells is poorly understood.Methods: Herein, we evaluated the anti-proliferative impact of ASCs of healthy donors (HD/ASCs, 5 reference cell lines), SLE patients (n = 20), and SSc patients (n = 20) on T lymphocytes. To assess the direct and indirect pathway of ASCs action, peripheral blood mononuclear cells (PBMCs) and purified CD4+ T cells of HD were activated and co-cultured in cell-to-cell contact (C-C) and transwell (T-W) conditions with untreated or cytokine (TNF + IFNΥ, TI)-licensed ASCs, then analyzed by flow cytometry to rate the proliferation response of CD8+ and/or CD4+ T cells. The concentrations of kynurenines, prostaglandin E2 (PGE2), interleukin 10 (IL-10), and transforming growth factor β (TGFβ) were measured from culture supernatants. Specific inhibitors of these factors (1-MT, indomethacin, and cytokine-neutralizing antibody) were used to assess their contribution to anti-proliferative ASCs action.Results: All tested ASCs significantly decreased the number of proliferating CD4+ and CD8+ T cells, the number of division/proliferating cell (PI), and fold expansion (RI), and similarly upregulated kynurenines and PGE2, but not cytokine levels, in the co-cultures with both types of target cells. However, TI-treated SLE/ASCs and SSc/ASCs exerted a slightly weaker inhibitory effect on CD4+ T-cell replication than their respective HD/ASCs. All ASCs acted mainly via soluble factors. Their anti-proliferative effect was stronger, and kynurenine levels were higher in the T-W condition than the C-C condition. Blocking experiments indicated an involvement of kynurenine pathway in inhibiting the number of proliferating cells, PI, and RI values as well as PGE2 role in decreasing the number of proliferating cells. TGFβ did not contribute to ASCs anti-proliferative capabilities, while IL-10 seems to be involved in such activity of only SLE/ASCs.Conclusion: The results indicate that SLE/ASCs and SSc/ASCs retain their capability to restrain the expansion of allogeneic CD4+ and CD8+ T cells and act by similar mechanisms as ASCs of healthy donors and thus may have therapeutic value.