Open Access
Tryptophan-kynurenine pathway is dysregulated in inflammation, and immune activation
Qiongxin Wang1,Danxia Liu2,Ping Song1,Ming-Hui Zou1,*
Division of Molecular Medicine, Department of Medicine, and Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
Division of Cardiology and Endocrinology, Department of Internal Medicine, Hubei Provincial Corps Hospital, Chinese People’s Armed Police Forces, Wuhan, Hubei 430061, China
DOI: 10.2741/4363 Volume 20 Issue 7, pp.1116-1143
Published: 01 June 2015
(This article belongs to the Special Issue Amylin in vasodilation, energy expenditure and inflammation)
*Corresponding Author(s):  
Ming-Hui Zou

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.

Key words
Kynurenines,Cardiovascular Diseases,Inflammation,Oxidative Stress,Immune Activation,Review
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Qiongxin Wang, Danxia Liu, Ping Song, Ming-Hui Zou. Tryptophan-kynurenine pathway is dysregulated in inflammation, and immune activation. Frontiers in Bioscience-Landmark. 2015. 20(7); 1116-1143.