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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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Effect of IDO and tryptophan-derived catabolites on different PBL subpopulations. (A) The different cell subpopulations were activated as indicated in the Materials and Methods section, and cultured in the presence of 4,000 U/ml IDO, 0.1 μM methylene blue, and 200 μM l-ascorbic acid. Cell culture was stopped after 96 h from activation, and proliferation was evaluated by measuring 3[H]thymidine incorporation. For each subpopulation untreated activated cells were used as control. m ± 1 SD, n = 3. (B–D) The effect of 1 mM l-kynurenine (B), 1 mM picolinic acid (C), and 1 mM quinolinic acid (D) was tested on each PBL subpopulation. The different cell subpopulations were activated as indicated in the Materials and Methods section, and cultured either in tryptophan-free medium (white columns), or in tryptophan-free medium supplemented with 26 μM l-tryptophan (black columns). Cell culture was stopped after 96 h from activation, and proliferation was evaluated by measuring 3[H]thymidine incorporation. For each subpopulation untreated cells, activated and cultured in the same medium, were used as control. m ± 1 SD, n = 3.
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fig8: Effect of IDO and tryptophan-derived catabolites on different PBL subpopulations. (A) The different cell subpopulations were activated as indicated in the Materials and Methods section, and cultured in the presence of 4,000 U/ml IDO, 0.1 μM methylene blue, and 200 μM l-ascorbic acid. Cell culture was stopped after 96 h from activation, and proliferation was evaluated by measuring 3[H]thymidine incorporation. For each subpopulation untreated activated cells were used as control. m ± 1 SD, n = 3. (B–D) The effect of 1 mM l-kynurenine (B), 1 mM picolinic acid (C), and 1 mM quinolinic acid (D) was tested on each PBL subpopulation. The different cell subpopulations were activated as indicated in the Materials and Methods section, and cultured either in tryptophan-free medium (white columns), or in tryptophan-free medium supplemented with 26 μM l-tryptophan (black columns). Cell culture was stopped after 96 h from activation, and proliferation was evaluated by measuring 3[H]thymidine incorporation. For each subpopulation untreated cells, activated and cultured in the same medium, were used as control. m ± 1 SD, n = 3.

Mentions: Since PBLs are made up of different subpopulations, we wanted to get some insight into the sensitivity of each subpopulation to IDO activity. For this reason IDO effect was tested on CD4+ and on CD8+ T lymphocytes, on B lymphocytes, and on NK cells purified from peripheral blood (Fig. 8 A). We found that IDO-dependent inhibition of proliferation only applies to T lymphocytes and NK cells responding to a proliferative stimulus, proliferation of B lymphocytes not being affected. As in the case of PBLs, proliferation of each subpopulation in tryptophan-free medium did not differ from proliferation in the same medium supplemented with 26 μM tryptophan (proliferation in tryptophan-supplemented medium being 83.4 ± 9.7% of proliferation in tryptophan-free medium for CD4+ T lymphocytes, 114.1 ± 11.5% for CD8+ T lymphocytes, 108.7 ± 10.3 for B lymphocytes, and 81.3 ± 14.8 for NK cells; m ± 1 SD, n = 3). Instead, tryptophan-derived catabolites were effective, in the IDO-sensitive subpopulations, in inhibiting cell proliferation (Fig. 8, B–D), Consistent with the findings from PBLs, the inhibitory activity was enhanced in the absence of tryptophan.


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)

Effect of IDO and tryptophan-derived catabolites on different PBL subpopulations. (A) The different cell subpopulations were activated as indicated in the Materials and Methods section, and cultured in the presence of 4,000 U/ml IDO, 0.1 μM methylene blue, and 200 μM l-ascorbic acid. Cell culture was stopped after 96 h from activation, and proliferation was evaluated by measuring 3[H]thymidine incorporation. For each subpopulation untreated activated cells were used as control. m ± 1 SD, n = 3. (B–D) The effect of 1 mM l-kynurenine (B), 1 mM picolinic acid (C), and 1 mM quinolinic acid (D) was tested on each PBL subpopulation. The different cell subpopulations were activated as indicated in the Materials and Methods section, and cultured either in tryptophan-free medium (white columns), or in tryptophan-free medium supplemented with 26 μM l-tryptophan (black columns). Cell culture was stopped after 96 h from activation, and proliferation was evaluated by measuring 3[H]thymidine incorporation. For each subpopulation untreated cells, activated and cultured in the same medium, were used as control. m ± 1 SD, n = 3.
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Related In: Results  -  Collection

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fig8: Effect of IDO and tryptophan-derived catabolites on different PBL subpopulations. (A) The different cell subpopulations were activated as indicated in the Materials and Methods section, and cultured in the presence of 4,000 U/ml IDO, 0.1 μM methylene blue, and 200 μM l-ascorbic acid. Cell culture was stopped after 96 h from activation, and proliferation was evaluated by measuring 3[H]thymidine incorporation. For each subpopulation untreated activated cells were used as control. m ± 1 SD, n = 3. (B–D) The effect of 1 mM l-kynurenine (B), 1 mM picolinic acid (C), and 1 mM quinolinic acid (D) was tested on each PBL subpopulation. The different cell subpopulations were activated as indicated in the Materials and Methods section, and cultured either in tryptophan-free medium (white columns), or in tryptophan-free medium supplemented with 26 μM l-tryptophan (black columns). Cell culture was stopped after 96 h from activation, and proliferation was evaluated by measuring 3[H]thymidine incorporation. For each subpopulation untreated cells, activated and cultured in the same medium, were used as control. m ± 1 SD, n = 3.
Mentions: Since PBLs are made up of different subpopulations, we wanted to get some insight into the sensitivity of each subpopulation to IDO activity. For this reason IDO effect was tested on CD4+ and on CD8+ T lymphocytes, on B lymphocytes, and on NK cells purified from peripheral blood (Fig. 8 A). We found that IDO-dependent inhibition of proliferation only applies to T lymphocytes and NK cells responding to a proliferative stimulus, proliferation of B lymphocytes not being affected. As in the case of PBLs, proliferation of each subpopulation in tryptophan-free medium did not differ from proliferation in the same medium supplemented with 26 μM tryptophan (proliferation in tryptophan-supplemented medium being 83.4 ± 9.7% of proliferation in tryptophan-free medium for CD4+ T lymphocytes, 114.1 ± 11.5% for CD8+ T lymphocytes, 108.7 ± 10.3 for B lymphocytes, and 81.3 ± 14.8 for NK cells; m ± 1 SD, n = 3). Instead, tryptophan-derived catabolites were effective, in the IDO-sensitive subpopulations, in inhibiting cell proliferation (Fig. 8, B–D), Consistent with the findings from PBLs, the inhibitory activity was enhanced in the absence of tryptophan.

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