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Expression of the Kynurenine Pathway in Human Peripheral Blood Mononuclear Cells: Implications for Inflammatory and Neurodegenerative Disease.

Jones SP, Franco NF, Varney B, Sundaram G, Brown DA, de Bie J, Lim CK, Guillemin GJ, Brew BJ - PLoS ONE (2015)

Bottom Line: In contrast, peripheral monocytes showed a significant elevation of kynurenine pathway enzymes and metabolites when treated with interferon gamma.Expression of IDO-1, KMO and QPRT correlated significantly with activation of the kynurenine pathway (kynurenine:tryptophan ratio), quinolinic acid concentration and production of the monocyte derived, pro-inflammatory immune response marker: neopterin.Our results also describe an original and sensitive methodological approach to quantify kynurenine pathway enzyme expression in cells.

View Article: PubMed Central - PubMed

Affiliation: Peter Duncan Neurosciences Research Unit, St Vincent's Centre for Applied Medical Research, Sydney, Australia; St Vincent's Clinical School, Faculty of Medicine, UNSW, Sydney, Australia.

ABSTRACT
The kynurenine pathway is a fundamental mechanism of immunosuppression and peripheral tolerance. It is increasingly recognized as playing a major role in the pathogenesis of a wide variety of inflammatory, neurodegenerative and malignant disorders. However, the temporal dynamics of kynurenine pathway activation and metabolite production in human immune cells is currently unknown. Here we report the novel use of flow cytometry, combined with ultra high-performance liquid chromatography and gas chromatography-mass spectrometry, to sensitively quantify the intracellular expression of three key kynurenine pathway enzymes and the main kynurenine pathway metabolites in a time-course study. This is the first study to show that up-regulation of indoleamine 2,3-dioxygenase (IDO-1), kynurenine 3-monoxygenase (KMO) and quinolinate phosphoribosyltransferase (QPRT) is lacking in lymphocytes treated with interferon gamma. In contrast, peripheral monocytes showed a significant elevation of kynurenine pathway enzymes and metabolites when treated with interferon gamma. Expression of IDO-1, KMO and QPRT correlated significantly with activation of the kynurenine pathway (kynurenine:tryptophan ratio), quinolinic acid concentration and production of the monocyte derived, pro-inflammatory immune response marker: neopterin. Our results also describe an original and sensitive methodological approach to quantify kynurenine pathway enzyme expression in cells. This has revealed further insights into the potential role of these enzymes in disease processes.

No MeSH data available.


Related in: MedlinePlus

Simplified overview of the kynurenine pathway of tryptophan metabolism.The three main enzymes: indoleamine 2,3-dioxygenase (IDO-1), kynurenine 3-monooxygenase (KMO) and quinolinate phosphoribosyltransferase (QPRT) are shown abbreviated in bold italics whilst the main metabolites measured in this study are written in bold.
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pone.0131389.g001: Simplified overview of the kynurenine pathway of tryptophan metabolism.The three main enzymes: indoleamine 2,3-dioxygenase (IDO-1), kynurenine 3-monooxygenase (KMO) and quinolinate phosphoribosyltransferase (QPRT) are shown abbreviated in bold italics whilst the main metabolites measured in this study are written in bold.

Mentions: The kynurenine pathway (KP) is the major route for the catabolism of the essential amino acid tryptophan, which also leads to production of several potent neuroactive and immunomodulatory intermediates (Fig 1). In the initial step of the KP, tryptophan is oxidized by either tryptophan 2,3-dioxygenase (TDO2), indoleamine 2,3-dioxygenase 1 (IDO-1) or IDO-2 [1–3]. TDO2 is primarily expressed in the liver [4, 5] whilst IDO-1 is the predominant enzyme extra-hepatically. IDO-1 is expressed in numerous cell types, including macrophages, microglia, neurons and astrocytes [6–8] and can be induced by several inflammatory molecules, including lipopolysaccharides, amyloid peptides and HIV proteins [9–11]. The most potent activator of IDO-1 is interferon gamma (IFN-γ) [3, 12]. IFN-γ induces both the gene expression and enzymatic activity of IDO-1 [13, 14]. The more recently identified IDO-2 possesses similar structural and enzymatic activities to IDO-1 [2], however it is unclear whether it is functionally active in human cells [15].


Expression of the Kynurenine Pathway in Human Peripheral Blood Mononuclear Cells: Implications for Inflammatory and Neurodegenerative Disease.

Jones SP, Franco NF, Varney B, Sundaram G, Brown DA, de Bie J, Lim CK, Guillemin GJ, Brew BJ - PLoS ONE (2015)

Simplified overview of the kynurenine pathway of tryptophan metabolism.The three main enzymes: indoleamine 2,3-dioxygenase (IDO-1), kynurenine 3-monooxygenase (KMO) and quinolinate phosphoribosyltransferase (QPRT) are shown abbreviated in bold italics whilst the main metabolites measured in this study are written in bold.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4482723&req=5

pone.0131389.g001: Simplified overview of the kynurenine pathway of tryptophan metabolism.The three main enzymes: indoleamine 2,3-dioxygenase (IDO-1), kynurenine 3-monooxygenase (KMO) and quinolinate phosphoribosyltransferase (QPRT) are shown abbreviated in bold italics whilst the main metabolites measured in this study are written in bold.
Mentions: The kynurenine pathway (KP) is the major route for the catabolism of the essential amino acid tryptophan, which also leads to production of several potent neuroactive and immunomodulatory intermediates (Fig 1). In the initial step of the KP, tryptophan is oxidized by either tryptophan 2,3-dioxygenase (TDO2), indoleamine 2,3-dioxygenase 1 (IDO-1) or IDO-2 [1–3]. TDO2 is primarily expressed in the liver [4, 5] whilst IDO-1 is the predominant enzyme extra-hepatically. IDO-1 is expressed in numerous cell types, including macrophages, microglia, neurons and astrocytes [6–8] and can be induced by several inflammatory molecules, including lipopolysaccharides, amyloid peptides and HIV proteins [9–11]. The most potent activator of IDO-1 is interferon gamma (IFN-γ) [3, 12]. IFN-γ induces both the gene expression and enzymatic activity of IDO-1 [13, 14]. The more recently identified IDO-2 possesses similar structural and enzymatic activities to IDO-1 [2], however it is unclear whether it is functionally active in human cells [15].

Bottom Line: In contrast, peripheral monocytes showed a significant elevation of kynurenine pathway enzymes and metabolites when treated with interferon gamma.Expression of IDO-1, KMO and QPRT correlated significantly with activation of the kynurenine pathway (kynurenine:tryptophan ratio), quinolinic acid concentration and production of the monocyte derived, pro-inflammatory immune response marker: neopterin.Our results also describe an original and sensitive methodological approach to quantify kynurenine pathway enzyme expression in cells.

View Article: PubMed Central - PubMed

Affiliation: Peter Duncan Neurosciences Research Unit, St Vincent's Centre for Applied Medical Research, Sydney, Australia; St Vincent's Clinical School, Faculty of Medicine, UNSW, Sydney, Australia.

ABSTRACT
The kynurenine pathway is a fundamental mechanism of immunosuppression and peripheral tolerance. It is increasingly recognized as playing a major role in the pathogenesis of a wide variety of inflammatory, neurodegenerative and malignant disorders. However, the temporal dynamics of kynurenine pathway activation and metabolite production in human immune cells is currently unknown. Here we report the novel use of flow cytometry, combined with ultra high-performance liquid chromatography and gas chromatography-mass spectrometry, to sensitively quantify the intracellular expression of three key kynurenine pathway enzymes and the main kynurenine pathway metabolites in a time-course study. This is the first study to show that up-regulation of indoleamine 2,3-dioxygenase (IDO-1), kynurenine 3-monoxygenase (KMO) and quinolinate phosphoribosyltransferase (QPRT) is lacking in lymphocytes treated with interferon gamma. In contrast, peripheral monocytes showed a significant elevation of kynurenine pathway enzymes and metabolites when treated with interferon gamma. Expression of IDO-1, KMO and QPRT correlated significantly with activation of the kynurenine pathway (kynurenine:tryptophan ratio), quinolinic acid concentration and production of the monocyte derived, pro-inflammatory immune response marker: neopterin. Our results also describe an original and sensitive methodological approach to quantify kynurenine pathway enzyme expression in cells. This has revealed further insights into the potential role of these enzymes in disease processes.

No MeSH data available.


Related in: MedlinePlus