CSF concentrations of brain tryptophan and kynurenines during immune stimulation with IFN-alpha: relationship to CNS immune responses and depression.
Level 3 - non-randomized controlled study
Non-randomized controlled cohort study comparing treated vs untreated patients.
PubMed 19918244 · doi:10.1038/mp.2009.116
What was done
In 27 patients with hepatitis C, researchers measured tryptophan (TRP), kynurenine (KYN), quinolinic acid (QUIN), and kynurenic acid (KA) in cerebrospinal fluid (CSF) and peripheral blood after approximately 12 weeks of either interferon-alpha treatment (n=16) or no treatment (n=11). CSF concentrations of relevant cytokines, chemokines, and soluble cytokine receptors were assessed, and depressive symptoms were evaluated using the Montgomery-Asberg Depression Rating Scale.
What was found
The abstract reports no numerical values, effect sizes, or p-values. It reports that interferon-alpha significantly increased peripheral blood KYN alongside marked increases in CSF KYN. Increased CSF KYN was associated with significant increases in CSF QUIN and KA. Although peripheral blood TRP decreased significantly, interferon-alpha had no effect on CSF TRP levels. Increases in CSF KYN and QUIN correlated with increased CSF interferon-alpha, soluble tumor necrosis factor-alpha receptor 2, monocyte chemoattractant protein-1, and increased depressive symptoms.
Why it matters
This study provides direct human CSF evidence that peripheral cytokine stimulation activates the central kynurenine pathway, linking neuroactive metabolites like quinolinic acid to inflammation-associated depressive symptoms rather than central tryptophan depletion.
Limits
The study is limited by a small sample size (n=27), a non-randomized design, and lack of reported numerical data or effect sizes in the abstract. Results from hepatitis C patients receiving interferon-alpha may not generalize to other depressive or inflammatory conditions.
Cited by
- supports Interferon-alpha treatment causes a massive increase in quinolinic acid in human cerebrospinal fluid, which correlates strongly with depression.
- supports Under chronic inflammation from interferon-alpha, tryptophan levels decline in peripheral blood but remain maintained in human cerebrospinal fluid.