Clin. Lab. 3/2014 391 Clin. Lab. 2014;60:391-396 ©Copyright ORIGINAL ARTICLE Relation of Kynurenine/Tryptophan with Immune and Inflammatory Markers in Coronary Artery Disease YESIM OZKAN 1 , MURAT KADIR SUKUROGLU 2 , MURAT TULMAC 3 , UCLER KISA 4 , BOLKAN SIMSEK 1 1 Department of Biochemistry, Faculty of Pharmacy, Gazi University, Ankara, Turkey 2 Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Gazi University, Ankara, Turkey 3 Department of Cardiology, School of Medicine, Kırıkkale University, Turkey 4 Department of Biochemistry, School of Medicine, Kırıkkale University, Turkey SUMMARY Background: Inflammation and immune activation have a crucial role in the pathogenesis of cardiovascular dis- eases. Indolamine 2,3-dioxygenase, a tryptophan catabolising enzyme, is up-regulated with various inflammatory stimuli. The aim of this study was to evaluate the relationship of tryptophan degradation with immune and in- flammatory markers in coronary artery disease. Methods: 57 subjects undergoing coronary angiography were recruited. 18 subjects with normal coronary arteries according to Gensini scoring were selected as a control group and the rest of subjects were included in patient group. Serum tryptophan and kynurenine levels were determined with HPLC-UV method, and kynurenine/tryp- tophan ratio was evaluated as IDO activity. Serum neopterin and myeloperoxidase activity were measured by ELISA method. Results: While the kynurenine/tryptophan ratio and neopterin levels were similar in both groups, the patient group had higher myeloperoxidase and hs-CRP levels than controls (p = 0.02, p = 0.002, respectively). The kyn- urenine/tryptophan ratio was correlated with neopterin in both groups (r = 0.389, p = 0.025; r = 0.683, p = 0.002, respectively) and with hs-CRP in patients (r = 0.637, p = 0.001). Also, neopterin levels were correlated with hs- CRP in patients (r = 0.755, p = 0.0001). Conclusions: Our results are in line with a role of inflammation in coronary artery disease. The study provides evidence that IDO activity is related with immune and inflammatory states. Also, the study was performed in a limited hospital-based population. Further studies are warranted in the larger groups. (Clin. Lab. 2014;60:391-396. DOI: 10.7754/Clin.Lab.2013.121204) KEY WORDS atherosclerosis, indolamine 2,3-dioxygenase, kynuren- ine, neopterin, tryptophan INTRODUCTION Atherosclerosis is a primary initiator of coronary artery diseases, and inflammatory processes are an important driving force of atherosclerosis and its complications. For a long time, lipid deposition and smooth muscle cell proliferation were dominant theories to explain the de- velopment of atherosclerosis. Nowadays, it has been established that immune mediated inflammatory mecha- nisms play a role in this process, and there is more evi- dence linking initiate and adaptive immune systems to atherosclerosis [1,2]. Kynurenine (Kyn) is the first stable intermediate formed from the kynurenine pathway of tryptophan (Trp) deg- radation. This pathway is initiated either by tryptophan 2,3-dioxygenase (TDO) or indolamine 2,3-dioxygenase (IDO). Unlike TDO, IDO is widely expressed in most dendritic cells, macrophages, tumor cells, and endothe- lial cells and is highly up-regulated locally or systemi- cally by immune activation and inflammation. This in- duction is mediated mainly by IFN-Ȗ which is a prion- flammatory cytokine and a potent stimulant for gene ex- _____________________________________________ Manuscript accepted May 4, 2013