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Tryptophan-derived catabolites are responsible for inhibition of T and natural killer cell proliferation induced by indoleamine 2,3-dioxygenase.

Frumento G, Rotondo R, Tonetti M, Damonte G, Benatti U, Ferrara GB - J. Exp. Med. (2002)

Bottom Line: Macrophages exposed to macrophage colony-stimulating factor acquire the capacity to suppress T cell proliferation; this effect is associated with de novo expression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO).Inhibition of cell proliferation induced by the tryptophan catabolites resulting from IDO activity was selective, applying only to cells undergoing activation.We suggest that IDO exerts its effect on cell proliferation by (i) starting the cascade of biochemical reactions that produce the three catabolites and by (ii) enhancing their inhibitory potential by depriving the extracellular microenvironment of tryptophan.

View Article: PubMed Central - PubMed

Affiliation: Immunogenetics Laboratory, National Cancer Research Institute, University of Genoa, Largo Rosanna Benzi 10, 16132 Genoa, Italy. guido.frumento@istge.it

ABSTRACT
Macrophages exposed to macrophage colony-stimulating factor acquire the capacity to suppress T cell proliferation; this effect is associated with de novo expression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO). We have purified IDO and tested its activity in in vitro models of T cell activation. IDO was able to inhibit proliferation of CD4(+) T lymphocytes, CD8(+) T lymphocytes, and natural killer (NK) cells; proliferation of B lymphocytes was not affected. The inhibitory role of tryptophan and of its catabolites was then tested. In the presence of tryptophan, only L-kynurenine and picolinic acid inhibit cell proliferation. In a tryptophan-free medium cell proliferation was not affected. In the absence of tryptophan inhibition induced by L-kynurenine and picolinic acid was observed at concentrations below the lowest concentration that was effective in the presence of tryptophan, and quinolinic acid acquired some inhibitory capacity. Inhibition of cell proliferation induced by the tryptophan catabolites resulting from IDO activity was selective, applying only to cells undergoing activation. Resting cells were not affected and could subsequently activate normally. We suggest that IDO exerts its effect on cell proliferation by (i) starting the cascade of biochemical reactions that produce the three catabolites and by (ii) enhancing their inhibitory potential by depriving the extracellular microenvironment of tryptophan.

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Role of cofactors on IDO activity. PHA-activated PBLs were incubated with the indicated combinations of 4,000 U/ml IDO, 0.1 μM methylene blue, and 200 μM l-ascorbic acid. In a set of experiments 800 U IDO were added daily to the cell culture, in the absence of cofactors. Control is represented by cells incubated with medium alone. Cell culture was stopped after 96 h and proliferation was evaluated by measuring 3[H]thymidine incorporation (A) or by counting the cells in the cell cycle (B). m ± 1 SD, n = 3.
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fig2: Role of cofactors on IDO activity. PHA-activated PBLs were incubated with the indicated combinations of 4,000 U/ml IDO, 0.1 μM methylene blue, and 200 μM l-ascorbic acid. In a set of experiments 800 U IDO were added daily to the cell culture, in the absence of cofactors. Control is represented by cells incubated with medium alone. Cell culture was stopped after 96 h and proliferation was evaluated by measuring 3[H]thymidine incorporation (A) or by counting the cells in the cell cycle (B). m ± 1 SD, n = 3.

Mentions: The role of cofactors is elucidated in Fig. 2 , showing the effect of various combinations of IDO and cofactors on the proliferation of PHA-stimulated PBLs, evaluated both by measuring 3[H]thymidine incorporation (Fig. 2 A) and by counting the cells entering the cell cycle (Fig. 2 B). When the sole IDO, at the final concentration of 4,000 U/ml, was added at the beginning of the test, half of proliferation was retained. The same result was obtained by adding to IDO either methylene blue or l-ascorbic acid. Instead, coincubation of IDO with both cofactors reduced proliferation to one fourth of the control. The same result was obtained when 800 U IDO/well were added daily to the culture, in the absence of cofactors.


Tryptophan-derived catabolites are responsible for inhibition of T and natural killer cell proliferation induced by indoleamine 2,3-dioxygenase.

Frumento G, Rotondo R, Tonetti M, Damonte G, Benatti U, Ferrara GB - J. Exp. Med. (2002)

Role of cofactors on IDO activity. PHA-activated PBLs were incubated with the indicated combinations of 4,000 U/ml IDO, 0.1 μM methylene blue, and 200 μM l-ascorbic acid. In a set of experiments 800 U IDO were added daily to the cell culture, in the absence of cofactors. Control is represented by cells incubated with medium alone. Cell culture was stopped after 96 h and proliferation was evaluated by measuring 3[H]thymidine incorporation (A) or by counting the cells in the cell cycle (B). m ± 1 SD, n = 3.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196046&req=5

fig2: Role of cofactors on IDO activity. PHA-activated PBLs were incubated with the indicated combinations of 4,000 U/ml IDO, 0.1 μM methylene blue, and 200 μM l-ascorbic acid. In a set of experiments 800 U IDO were added daily to the cell culture, in the absence of cofactors. Control is represented by cells incubated with medium alone. Cell culture was stopped after 96 h and proliferation was evaluated by measuring 3[H]thymidine incorporation (A) or by counting the cells in the cell cycle (B). m ± 1 SD, n = 3.
Mentions: The role of cofactors is elucidated in Fig. 2 , showing the effect of various combinations of IDO and cofactors on the proliferation of PHA-stimulated PBLs, evaluated both by measuring 3[H]thymidine incorporation (Fig. 2 A) and by counting the cells entering the cell cycle (Fig. 2 B). When the sole IDO, at the final concentration of 4,000 U/ml, was added at the beginning of the test, half of proliferation was retained. The same result was obtained by adding to IDO either methylene blue or l-ascorbic acid. Instead, coincubation of IDO with both cofactors reduced proliferation to one fourth of the control. The same result was obtained when 800 U IDO/well were added daily to the culture, in the absence of cofactors.

Bottom Line: Macrophages exposed to macrophage colony-stimulating factor acquire the capacity to suppress T cell proliferation; this effect is associated with de novo expression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO).Inhibition of cell proliferation induced by the tryptophan catabolites resulting from IDO activity was selective, applying only to cells undergoing activation.We suggest that IDO exerts its effect on cell proliferation by (i) starting the cascade of biochemical reactions that produce the three catabolites and by (ii) enhancing their inhibitory potential by depriving the extracellular microenvironment of tryptophan.

View Article: PubMed Central - PubMed

Affiliation: Immunogenetics Laboratory, National Cancer Research Institute, University of Genoa, Largo Rosanna Benzi 10, 16132 Genoa, Italy. guido.frumento@istge.it

ABSTRACT
Macrophages exposed to macrophage colony-stimulating factor acquire the capacity to suppress T cell proliferation; this effect is associated with de novo expression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO). We have purified IDO and tested its activity in in vitro models of T cell activation. IDO was able to inhibit proliferation of CD4(+) T lymphocytes, CD8(+) T lymphocytes, and natural killer (NK) cells; proliferation of B lymphocytes was not affected. The inhibitory role of tryptophan and of its catabolites was then tested. In the presence of tryptophan, only L-kynurenine and picolinic acid inhibit cell proliferation. In a tryptophan-free medium cell proliferation was not affected. In the absence of tryptophan inhibition induced by L-kynurenine and picolinic acid was observed at concentrations below the lowest concentration that was effective in the presence of tryptophan, and quinolinic acid acquired some inhibitory capacity. Inhibition of cell proliferation induced by the tryptophan catabolites resulting from IDO activity was selective, applying only to cells undergoing activation. Resting cells were not affected and could subsequently activate normally. We suggest that IDO exerts its effect on cell proliferation by (i) starting the cascade of biochemical reactions that produce the three catabolites and by (ii) enhancing their inhibitory potential by depriving the extracellular microenvironment of tryptophan.

Show MeSH
Related in: MedlinePlus