Pulmonary indoleamine 2,3-dioxygenase [indoleamine: oxygen 2,3-oxidoreductase(decyclizing)] has been found to be induced (30-to 100-fold) in the mouse after a single intraperitoneal administration of bacterial endotoxin [Yoshida, R. & Hayaishi, 0. (1978) Proc NatL AcadS Sci USA 75,[3998][3999][4000] [4084][4085][4086].In the present study, an in vitro system with mouse lung slices was developed in which bacterial endotoxin (5 ,ug/ml) produced an induction (approximately 10-fold) ofindoleamine 2,3-dioxygenase. The endotoxin was substituted by interferon from mouse L cells or mouse brain. The pulmonary enzyme activity increased almost linearly for 48 hr after addition of mouse interferon (104 units/ ml) to lung slices. Interferon from mouse L cells or mouse brain produced a 10-to 15-fold increase in the enzyme activity, whereas that from human leukocytes was all but ineffective. The effect also was observed using highly purified L-cell interferon, prepared by poly(U) affinity column chromatography. When interferon was treated either by heat, a'.chymotrypsin, or anti-interferon serum, such increase in the enzyme activity was diminished essentially to the same extent as seen in the antiviral activity. The increase in the enzyme activity was blocked when actinomycin D or cycloheximide was added to the slices before interferon treatment. These results suggest that the enzyme induction was produced by interferon and not by possible contaminants in the interferon preparations.Indoleamine 2,3-dioxygenase [indoleamine:oxygen 2,3-oxidoreductase (decyclizing)] (IDOase) is a hemoprotein (1) that catalyzes the incorporation of the superoxide anion as well as molecular oxygen (2, 3) into the pyrrole moiety of various indoleamine derivatives (4, 5). The pulmonary IDOase is dramatically induced (30-to 100-fold) in the mouse after a single intraperitoneal administration of bacterial endotoxin [lipopolysaccharide (LPS)] (6) or during virus infection (7). To determine the precise mechanisms of IDOase induction, we developed an in vitro system with lung slices from mice and examined the effects of various substances, including the superoxide anion, indoleamines, and interferons, on the enzyme activity. We report herein that the IDOase activity was increased approximately 10-to 15-fold within 48 hr after the addition ofmouse interferon (104 units/ml) to mouse lung slices. A species-specificity ofinterferons and the effects of inhibitors of protein synthesis are presented also.MATERILS AND METHODS Chemicals. L-[ring-2-'4C]Tryptophan (36 Ci/mol; 1 Ci = 3.7 x 1010 becquerels) was purchased from Commisariat a l'Energie Atomique, France, and was purified by column chromatography with Dowex 50W-X2 (H+ form) (0.5 x 1.0 cm), as described (8). LPS from Escherichia coli 055:B5, prepared by the Westphal method, was from Difco. LPS (2.5-500 .g/ml) was suspended in a nonpyrogenic, isotonic NaCl solution and was stored at 40C in a screw-capped vial. An aliquot (0.1 ml) of the suspension was added to Eagle's minimum essential mediu...

Indoleamine 2,3-dioxygenase [indoleamine: oxygen 2,3-oxidoreductase (decyclizing)] activity in the supernatant fraction (30,000 X g, 30 min) of mouse lung homogenate increased approximately 120-fold after infection with PR8 influenza virus. Both specific and total enzyme activities started to increase linearly from the 5th day after infection, reached the highest level around the 11th day, and then gradually decreased to normal values in about 3 weeks. Other enzymes in the lung, such as certain lysosomal enzymes and monoamine oxidase, did not change significantly throughout the experiments. The time course of the increase in the enzyme activity was quite different from that of virus replication in the lung (a peak by the 3rd day and persistence until the 9th day) or that of serum antibody content (started to rise on the 9th day). Rather, it appeared to be closely related to the infiltrations of mononuclear and lymphocytic cells. When mice were exposed to a higher dose of virus and did not recuperate, the time course of the increase of the enzyme activity was essentially identical to that seen with a low concentration of virus. A maximum stimulation of the enzyme activity in the lung occurred on the 9th day after infection; the increase was approximately 100-fold. However, serum antibody content was slight and virus titer in the lung remained high. Indoleamine 2,3-dioxygenase [IDO; indoleamine:oxygen 2,3-oxidoreductase (decyclizing)] is a heme-containing enzyme (1) that catalyzes the incorporation of the superoxide anion as well as molecular oxygen (2, 3) into the pyrrole moiety of various indoleamine derivatives, such as tryptophan and serotonin (4,5). In contrast to tryptophan 2,3-dioxygenase, which catalyzes a similar reaction but is present exclusively in the liver (6), IDO is ubiquitously distributed in various organs of mammals, including brain, lung, spleen, alimentary canal, and epididymis (7), but its biological significance is not yet clearly understood. Recent studies from our laboratory demonstrated that the enzyme is dramatically induced in the mouse lung after a single intraperitoneal injection of bacterial endotoxin (8). Endotoxin, the lipopolysaccharide fraction (LPS) obtained from the cell wall of Gram-negative bacteria, is an inflammatory agent and induces nonspecific immune responses (9). The effect appeared to be specific for the pulmonary IDO activity because in all other tissues tested no significant increase in the enzyme activity was observed. In order to determine whether or not the pulmonary IDO activity is altered by specific infection of the lung, mice were exposed to PR8 influenza virus. In this paper, we report that the pulmonary IDO activity was increased more than 100-fold around the 11th day after virus infection. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.

Human lungs bearing cancer (n = 27) exhibited up to an "20-fold [on average "5-fold (P < 0.005)]increase in the enzyme activity that degrades tryptophan to form formylkynurenine, in comparison with lungs with benign lesions (blebs) (n = 7) taken as controls. On the basis of molecular and kinetic properties, this activity was ascribed to indoleamine 2,3-dioxygenase ()DO) [indoleamine:oxygen 2,3-oxidoreductase (decyclizing)]. In vitro studies with human lung slices revealed that human interferon y (IFN-y) induced the de novo synthesis of I1DO dose dependently (10-104 units/ml), and at maximum the activity reached nearly 100 times that in the control lungs described above. Human IFN-a also served as an inducer, but it was two to three orders of magnitude less potent than IFN-yrelative to the antiviral titers, suggesting that IFN-y is the main mediator of the 1DO induction. 1DO thus induced in slices avidly metabolized tryptophan in situ: Upon a 24-hr incubation of lung slices pretreated with varied doses of IFN-y (10-103 units/ml), up to 96% of the tryptophan in the slices was depleted and up to 70% of the tryptophan in the medium was converted, mainly to formylkynurenine, kynurenine, or both. The foregoing results suggest that an IFN-mediated induction of 1DO also takes place in vivo in human lungs as a response to cancer, leading to metabolic consequences such as depletion of tryptophan and accumulation of (formyl)kynurenine, which may provide a unique host defense mechanism.Increased urinary excretion of tryptophan metabolites of the kynurenine pathway has been described for patients with various diseases, including malignant neoplasms and infectious diseases (reviewed in ref. 1). This observation was accounted for by the depressed catabolism of these metabolites (1) and later explained by the glucocorticoid-mediated induction of hepatic tryptophan 2,3-dioxygenase [TDO; Ltryptophan:oxygen 2,3-oxidoreductase (decyclizing), EC 1.13.11.11], known at that time as the sole enzyme that catalyzes the first step of the kynurenine pathway (2). Subsequently another enzyme capable of converting tryptophan to formylkynurenine, indoleamine 2,3-dioxygenase [IDO; indoleamine:oxygen 2,3-oxidoreductase (decyclizing)] was identified (3). In contrast with TDO, which is found exclusively in liver, IDO was ubiquitously distributed in extrahepatic organs of mammals (4,5). In mice IDO in many organs, but not TDO in the liver, was markedly induced in vivo upon influenza virus infection (6) or administration of bacterial endotoxin (7). An in vitro system with mouse lung slices was then established in which bacterial endotoxin induced IDO, and murine interferon-a/,3 (IFN-a/,8) was found to replace the endotoxin (8). Human IFN-y reportedly induced an activity similar to that of IDO in cultured human fibroblasts (9). Thus the induction of IDO, rather than TDO, appeared to be closely related to pathological conditions and host defense mechanisms. In this context, it was of interest to assess the IDO activity in patients. with cancer...

Indoleamine 2,3-dioxygenase [indoleamine: oxygen 2,3-oxidoreductase (decyclizing)] activity in the supernatant fraction (30,000 X g, 30 min) of the mice lung homogenate increased approximately 30- to 50-fold after an intraperitoneal administration of bacterial lipopolysaccharide. In all other tissues tested, no significant increase in enzyme activity was observed. The effect appeared to be specific for the lipopolysaccharide fraction because glycogen and zymosan were almost ineffective under the same experimental conditions. In the lung, the enzyme activity increased almost linearly during the first 24 hr after a single injection of the lipopolysaccharide fraction (20 microgram per mouse). The enzyme activity started to decrease after 48 hr and reached a normal value after about 6 days. The increase in enzyme activity was completely abolished by cycloheximide or actinomycin D. Other enzymes in the lung such as beta-glucuronidase, acid phosphatase, and monoamine oxidase did not change significantly with this treatment.

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