Antimalarial drug chloroquine counteracts activation of indoleamine (2,3)-dioxygenase activity in human PBMC

Antimalarial chloroquine is also used for the treatment of immune-mediated diseases. The interference of chloroquine with interferon-gamma-induced tryptophan breakdown and neopterin production has been investigated in human peripheral blood mononuclear cells (PBMC) in vitro. Micromolar concentrations (2-50 mu M) of chloroquine dose-dependently suppressed mitogen-induced tryptophan breakdown in PBMC but not in the myelomonocytic THP-1-Blue cell line, after 48 h of treatment. In stimulated PBMC, neopterin production was super-induced by 10 mu M chloroquine, while it was significantly suppressed at a concentration of 50 mu M. These anti-inflammatory effects may relate to the therapeutic benefit of chloroquine in inflammatory conditions and may widen the spectrum of its clinical applications. (C) 2012 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.