IMR Press / FBL / Volume 20 / Issue 7 / DOI: 10.2741/4363

Frontiers in Bioscience-Landmark (FBL) is published by IMR Press from Volume 26 Issue 5 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.

Open Access Review
Tryptophan-kynurenine pathway is dysregulated in inflammation, and immune activation
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1 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
2 Division of Cardiology and Endocrinology, Department of Internal Medicine, Hubei Provincial Corps Hospital, Chinese People’s Armed Police Forces, Wuhan, Hubei 430061, China
Academic Editor:Xiao-Feng Yang
Front. Biosci. (Landmark Ed) 2015, 20(7), 1116–1143; https://doi.org/10.2741/4363
Published: 1 June 2015
(This article belongs to the Special Issue Amylin in vasodilation, energy expenditure and inflammation)
Abstract

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.

Keywords
Kynurenines
Cardiovascular Diseases
Inflammation
Oxidative Stress
Immune Activation
Review
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