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Hepatocyte-intrinsic type I interferon signaling reprograms metabolism and reveals a novel compensatory mechanism of the tryptophan-kynurenine pathway in viral hepatitis.

ABSTRACT: The liver is a central regulator of metabolic homeostasis and serum metabolite levels. Hepatocytes are the functional units of the liver parenchyma and not only responsible for turnover of biomolecules but also act as central immune signaling platforms. Hepatotropic viruses infect liver tissue, resulting in inflammatory responses, tissue damage and hepatitis. Combining well-established in vitro and in vivo model systems with transcriptomic analyses, we show that type I interferon signaling initiates a robust antiviral immune response in hepatocytes. Strikingly, we also identify IFN-I as both, sufficient and necessary, to induce wide-spread metabolic reprogramming in hepatocytes. IFN-I specifically rewired tryptophan metabolism and induced hepatic tryptophan oxidation to kynurenine via Tdo2, correlating with altered concentrations of serum metabolites upon viral infection. Infected Tdo2-deficient animals displayed elevated serum levels of tryptophan and, unexpectedly, also vast increases in the downstream immune-suppressive metabolite kynurenine. Thus, Tdo2-deficiency did not result in altered serum homeostasis of the tryptophan to kynurenine ratio during infection, which seemed to be independent of hepatocyte-intrinsic compensation via the IDO-axis. These data highlight that inflammation-induced reprogramming of systemic tryptophan metabolism is tightly regulated in viral hepatitis.

SUBMITTER: Lercher A

PROVIDER: S-EPMC7580883 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Hepatocyte-intrinsic type I interferon signaling reprograms metabolism and reveals a novel compensatory mechanism of the tryptophan-kynurenine pathway in viral hepatitis.

Lercher Alexander A Popa Alexandra M AM Viczenczova Csilla C Kosack Lindsay L Klavins Kristaps K Agerer Benedikt B Opitz Christiane A CA Lanz Tobias V TV Platten Michael M Bergthaler Andreas A

PLoS pathogens 20201012 10

The liver is a central regulator of metabolic homeostasis and serum metabolite levels. Hepatocytes are the functional units of the liver parenchyma and not only responsible for turnover of biomolecules but also act as central immune signaling platforms. Hepatotropic viruses infect liver tissue, resulting in inflammatory responses, tissue damage and hepatitis. Combining well-established in vitro and in vivo model systems with transcriptomic analyses, we show that type I interferon signaling initi ...[more]

PMID: 33045014

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Project description:Exhaustive exercise can cause a transient depression of immune function. Data indicate significant effects of immune activation cascades on the biochemistry of monoamines and amino acids such as tryptophan. Tryptophan can be metabolized through different pathways, a major route being the kynurenine pathway, which is often systemically up-regulated when the immune response is activated. The present study was undertaken to examine the effect of exhaustive aerobic exercise on biomarkers of immune activation and tryptophan metabolism in trained athletes. After a standardized breakfast 2 h prior to exercise, 33 trained athletes (17 women, 16 men) performed an incremental cycle ergometer exercise test at 60 rpm until exhaustion. After a 20 min rest phase, the participants performed a 20 min maximal time-trial on a cycle ergometer (RBM Cyclus 2, Germany). During the test, cyclists were strongly encouraged to choose a maximal pedalling rate that could be maintained for the respective test duration. Serum concentrations of amino acids tryptophan, kynurenine, phenylalanine, and tyrosine were determined by HPLC and immune system biomarker neopterin by ELISA at rest and immediately post exercise. Intense exercise was associated with a strong increase in neopterin concentrations (p<0.001), indicating increased immune activation following intense exercise. Exhaustive exercise significantly reduced tryptophan concentrations by 12% (p<0.001) and increased kynurenine levels by 6% (p = 0.022). Also phenylalanine to tyrosine ratios were lower after exercise as compared with baseline (p<0.001). The kynurenine to tryptophan ratio correlated with neopterin (r = 0.560, p<0.01). Thus, increased tryptophan catabolism by indoleamine 2,3-dioxygenase appears likely. Peak oxygen uptake correlated with baseline tryptophan and kynurenine concentrations (r = 0.562 and r = 0.511, respectively, both p<0.01). Findings demonstrate that exhaustive aerobic exercise is associated with increased immune activation and alterations in monoamine metabolism in trained athletes which may play a role in the regulation of mood and cognitive processes.

Project description:Importance: The high incidence of major depressive episodes during interferon-α (IFN-α) therapy is considered the most powerful supportive evidence for the inflammation theory of depression. As the kynurenine pathway plays an important role connecting inflammation and depression, it is plausible to investigate this pathway for predictive genetic markers for IFN-α-induced depression. Methods: In this prospective case-control study, we assessed 291 patients with chronic hepatitis C viral infection taking IFN-α therapy and analyzed the single nucleotide polymorphisms (SNPs) in genes in the kynurenine pathway. Our case group contained patients who developed IFN-α-induced depression during the treatment, and others were defined as the control group. Genomic DNA was extracted from leukocytes in the peripheral blood and analyzed by Affymetrix TWB array. We first tested allelic, dominant, and recessive models on each of our SNPs using Fisher's exact test. We then conducted 5000 gene-wide max(T) permutations based on the best model of each SNP to provide strong gene-wide family-wise error rate control. Finally, we preformed logistic regression for the significant SNPs acquired in previous procedures, with sex and education level as covariates to build predictive models. Additional haplotype analyses were conducted with Haploview 4.2 to investigate the combining effect of multiple significant SNPs within a gene. Results: With sex and education level as covariates, rs8082252 (p = 0.0015, odds ratio = 2.716), rs8082142 (p = 0.0031, odds ratio = 2.499) in arylformamidase (AFMID), and rs12477181 (p = 0.0004, odds ratio = 0.3478) in kynureninase (KYNU) were significant in logistic regression models with dominant modes of inheritance. Haplotype analyses showed the two significant SNPs in AFMID to be in the same haploblock and highly correlated (r2 = 0.99). There were two significant haplotypes (by the sequence of rs8082252, rs8082142): AT (χ2 = 7.734, p = 0.0054) and GC (χ2 = 6.874, p = 0.0087). Conclusions: This study provided supportive evidence of the involvement of the kynurenine pathway in IFN-α-induced depression. SNPs in this pathway were also predictive of this disease.

Project description:Background and Aims:Mucosal appearance on endoscopy is an important indicator of inflammatory burden and determines prognosis in ulcerative colitis (UC). Inflammation induces tryptophan metabolism along the kynurenine pathway (KP) and yields immunologically relevant metabolites. We sought to examine whether changes in serum tryptophan metabolites and tissue expression of KP enzymes are associated with UC endoscopic and histologic disease severity. Methods:Serum and mucosal samples were prospectively obtained at colonoscopy in patients with UC. Mayo disease activity scores, demographics, smoking status, medications, and outcomes were collected. Serum tryptophan metabolites were analyzed using ultra-high performance liquid chromatography (uHPLC), and gas chromatography-mass spectrometry (GC-MS), and enzyme expression was determined by quantitative real-time polymerase chain reaction. Metabolite and enzyme levels were compared by endoscopic subscore, clinical disease activity, time to surgery, and hospitalization. Results:This study included 99 patients with Mayo endoscopic subscores 0-3. Kynurenic acid/tryptophan ratio (KYNA/T) and expression of indolamine 2,3-dioxygenase 1 (IDO1), tryptophan 2,3-dioxygenase, kynurinase, and kynurenine monooxygenase correlated positively with endoscopic subscore. Adjusting for age of diagnosis, smoking status, disease extent, and medications yielded significant odds of endoscopic inflammation with increasing KYNA/T (OR 1.0015, P = 0.0186) and IDO1 expression (OR 1.0635, P = 0.0215). The highest tertile ratio of KYNA/T had shorter time to surgery (P = 0.009) and hospitalization (P = 0.01) than the lowest. Conclusions:Increasing KYNA/T is closely associated with endoscopic inflammation and predictive of disease outcomes in patients with UC. These findings identify this novel metabolic association and further support the role of the KP in regulating mucosal inflammation in UC. 10.1093/ibd/izy103_video1izy103.video15788135676001.

Dataset Information

Hepatocyte-intrinsic type I interferon signaling reprograms metabolism and reveals a novel compensatory mechanism of the tryptophan-kynurenine pathway in viral hepatitis.

Publications

Hepatocyte-intrinsic type I interferon signaling reprograms metabolism and reveals a novel compensatory mechanism of the tryptophan-kynurenine pathway in viral hepatitis.

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