Tryptophan-kynurenine pathway is dysregulated in inflammation, and immune activation

Qiongxin Wang, Danxia Liu, Ping Song, Ming Hui Zou

Research output: Contribution to journalReview articlepeer-review

225 Scopus citations


The kynurenine (Kyn) pathway is the major route for tryptophan (Trp) metabolism, and it contributes to several fundamental biological processes. Trp is constitutively oxidized by tryptophan 2, 3-dioxygenase in liver cells. In other cell types, it is catalyzed by an alternative inducible indoleamine-pyrrole 2, 3-dioxygenase (IDO) under certain pathophysiological conditions, which consequently increases the formation of Kyn metabolites. IDO is up-regulated in response to inflammatory conditions as a novel marker of immune activation in early atherosclerosis. Besides, IDO and the IDO-related pathway are important mediators of the immunoinflammatory responses in advanced atherosclerosis. In particular, Kyn, 3-hydroxykynurenine, and quinolinic acid are positively associated with inflammation, oxidative stress (SOX), endothelial dysfunction, and carotid artery intima-media thickness values in end-stage renal disease patients. Moreover, IDO is a potential novel contributor to vessel relaxation and metabolism in systemic infections, which is also activated in acute severe heart attacks. The Kyn pathway plays a key role in the increased prevalence of cardiovascular disease by regulating inflammation, SOX, and immune activation.

Original languageEnglish
Pages (from-to)1116-1143
Number of pages28
JournalFrontiers in bioscience : a journal and virtual library
Issue number7
StatePublished - Jun 1 2015


  • Cardiovascular Diseases
  • Immune Activation
  • Inflammation
  • Kynurenines
  • Oxidative Stress
  • Review


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