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

PLoS One. 2015 Jun 26;10(6):e0131389. doi: 10.1371/journal.pone.0131389. eCollection 2015.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Female
  • Gene Expression Regulation, Enzymologic*
  • Humans
  • Indoleamine-Pyrrole 2,3,-Dioxygenase / biosynthesis*
  • Kynurenine / metabolism*
  • Kynurenine 3-Monooxygenase / biosynthesis*
  • Leukocytes, Mononuclear / metabolism*
  • Leukocytes, Mononuclear / pathology
  • Male
  • Neurodegenerative Diseases / metabolism*
  • Neurodegenerative Diseases / pathology
  • Up-Regulation*

Substances

  • IDO1 protein, human
  • Indoleamine-Pyrrole 2,3,-Dioxygenase
  • Kynurenine
  • Kynurenine 3-Monooxygenase

Grant support

This work was funded by the Peter Duncan Neurosciences Research Unit (BJB), Multiple Sclerosis Research Australia (MSRA) Grant number 11010 (BJB) http://www.msra.org.au/, Australian Research Council (ARC) Future Fellowship number FT120100397 (GJG) http://www.arc.gov.au/, National Health and Medical Research Council (NHMRC) Project Grant and Fellowship (DAB) http://www.nhmrc.gov.au/, a Ramaciotti establishment grant, and a Macquarie University infrastructure grant funded the UHPLC and GC-MS equipment used in the study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.