Differential effect of type I and type II interferons on neopterin production and amino acid metabolism in human astrocyte-derived cells

Intrathecal production of neopterin, a pteridine produced by interferon (IFN)-γ-stimulated monocyte-derived macrophages, is associated with neurological disorders and infections. We investigated whether IFN-α/β, IFN-γ, or human immunodeficiency virus (HIV) induce neopterin production by human astroglioma cells. IFN-α/β and IFN-γ, but not HIV, induced neopterin. Interestingly, IFN-γ, but not IFN-α/β, increased expression and activity of the tryptophan-catabolizing enzyme indoleamine (2,3)-dioxygenase. In contrast, IFN-α/β, but not IFN-γ, reduced the uptake of three aromatic amino acids in U87MG and U138 astroglioma cells. Thus type I and type II IFN stimulate astrocyte-derived cells to produce neopterin and exert differential effects on amino acid metabolism.