Abstract

Depression is a common side-effect of interferon (IFN)-alpha treatment of hepatitis C virus (HCV) infection and melanoma. Disturbances of tryptophan (TRP) metabolism might contribute to development of IFN-alpha–associated depression due to IFN-alpha-induced activation of indoleamine 2,3-dioxygenase (IDO), a rate-limiting enzyme of TRP–kynurenine (KYN) metabolism. The increased frequency of high producer (T) allele of IFN-gamma (IFNG) (+874) gene, that encodes IFNG production, in depressed patients suggested that increased IDO activity might be a risk factor for depression. The present study assessed KYN/TRP ratio (KTR) as a marker of IDO activity in American Caucasian HCV patients awaiting IFN-alpha treatment. KTR did not differ between 43 patients who did and 37 patients who did not develop depression. TRP concentrations were higher in patients who experienced depression. Odds of development of depression increased with elevation of serum TRP levels from 33% (TRP levels <12000 pmol/ml) to 68% (TRP levels > 16000 pmol/ml). Elevated serum TRP may reflect the impairment of TRP conversion into serotonin in agreement with suggested link between serotonin deficiency and depression. Up-regulation of IDO might be an additional risk factor of IFN-alpha–associated depression. Future studies shall explore the causes of elevated serum TRP in relation to IFN-alpha–associated depression.

Highlights

  • Depression is a common (30 – 50%) side-effect of interferon (IFN)-alpha treatment of hepatitis C virus (HCV) infection and melanoma, and might compromise the effectiveness of therapy [1]

  • There were no differences in KYN concentrations and KYN/TRP ratio (KTR) between 43 patients who did and 37 patients who did not experience IFN-alpha–associated depression (Table 1)

  • The present results suggest that high serum TRP level might be a risk factor for the development of IFN-alpha – associated depression

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Summary

Introduction

Depression is a common (30 – 50%) side-effect of interferon (IFN)-alpha treatment of hepatitis C virus (HCV) infection and melanoma, and might compromise the effectiveness of therapy [1]. Experimental and clinical data suggested that disturbances of tryptophan (TRP) metabolism might contribute to the development of IFN-alpha–associated depression [2]. IFN-alpha transcriptionally activates indoleamine 2,3-dioxygenase (IDO) [3], the ratelimiting enzyme of TRP conversion into kynurenine (KYN), the major (90%) non-protein pathway of TRP metabolism [4]. We reported the association of high producer (T) allele of IFNG +874) gene with increased risk of IFN-alpha associated depression [9]. Our observation suggested the association between IDO activity and risk of depression. The present study aimed to assess IDO activity in relation to risk of IFN-alpha– associated depression in HCV patients

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