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Specific uptake of tumor necrosis factor-alpha is involved in growth control of Trypanosoma brucei.

Magez S, Geuskens M, Beschin A, del Favero H, Verschueren H, Lucas R, Pays E, de Baetselier P - J. Cell Biol. (1997)

Bottom Line: The specific uptake of the cytokine by the parasite results in a developmentally regulated loss of osmoregulatory capacity.Anti-TNF-alpha treatment of T. brucei-infected mice reveals a dramatic increase in parasitaemia in the blood circulation, the spleen, the lymph nodes, and the peritoneal cavity.These data suggest that in the mammalian host, TNF-alpha is involved in the growth control of T. brucei.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Cellular Immunology, Flanders Interuniversity Institute for Biotechnology, Vrije Universiteit Brussel, Belgium.

ABSTRACT
Trypanosoma brucei is lysed by tumor necrosis factor-alpha (TNF-alpha) in a dose-dependent way, involving specific binding of the cytokine to a trypanosomal glycoprotein present in the flagellar pocket of the parasite. TNF-alpha-gold particles are endocytosed via coated pits and vesicles and are directed towards lysosome-like digestive organelles. The specific uptake of the cytokine by the parasite results in a developmentally regulated loss of osmoregulatory capacity. TNF-alpha specific lysis is prevented when lysis assays are performed at a temperature <26 degrees C, despite uptake of the cytokine. Inhibition of lysis is also observed when a lysosomotropic agent is added during the first 2 h of incubation. Both monomorphic and pleomorphic trypanosomes are lysed but only when isolated during the peak of parasitaemia. Lysis is not observed with early infection stage parasites or procyclic (insect-specific) forms. Anti-TNF-alpha treatment of T. brucei-infected mice reveals a dramatic increase in parasitaemia in the blood circulation, the spleen, the lymph nodes, and the peritoneal cavity. These data suggest that in the mammalian host, TNF-alpha is involved in the growth control of T. brucei.

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Binding of 125ITNF-α to bloodstream-form  and procyclic trypanosomes.  (a) Bloodstream-form trypanosomes (▪) and procyclic trypanosomes (□) were incubated in the presence of  different molar concentrations of 125I-TNF-α. Bloodstream forms were also incubated with 125I-TNF-α in the presence of a 100-fold molar excess of cold TNF-α (•). The number of bound molecules per cell was plotted  in function of the dose of 125I-TNF-α added. (b) Specific 125I-TNF-α binding to bloodstream-form trypanosomes. (c) Scatchard plot presentation of the same results. All the results shown are from one representative experiment.
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Figure 3: Binding of 125ITNF-α to bloodstream-form and procyclic trypanosomes. (a) Bloodstream-form trypanosomes (▪) and procyclic trypanosomes (□) were incubated in the presence of different molar concentrations of 125I-TNF-α. Bloodstream forms were also incubated with 125I-TNF-α in the presence of a 100-fold molar excess of cold TNF-α (•). The number of bound molecules per cell was plotted in function of the dose of 125I-TNF-α added. (b) Specific 125I-TNF-α binding to bloodstream-form trypanosomes. (c) Scatchard plot presentation of the same results. All the results shown are from one representative experiment.

Mentions: To perform a quantitative analysis of the binding of TNF-α to live monomorphic AnTat 1.1 trypanosomes, parasites were incubated for 6 h at 4°C with different molar concentrations of 125I-TNF-α. The results shown in Fig. 3 a confirm a specific binding of 125I-TNF-α on bloodstream form trypanosomes. Competition binding experiments with 125ITNF-α in the presence of a 100-fold molar excess of cold TNF-α showed a significant reduction of the parasite labeling. No specific TNF-α binding could be recorded on procyclic parasites. Analysis of the specific binding data obtained with bloodstream form trypanosomes (Fig. 3 b) revealed an affinity constant of 37.2 ± 14.8 nM and 1,558 ± 302 TNF-α–specific binding sites. To confirm the binding of TNF-α to trypanosomes, a different method was adopted. Using an optical biosensor, the direct binding of TNF-α on total trypanosome lysate was measured (Fig. 4). To test whether this binding reflects an interaction between the lectin-like activity of TNF-α (25) and glycosylated trypanosome components, the trypanosome lysate was treated with N-glycosidase F. This treatment strongly reduced the binding of TNF-α to trypanosome lysate, indicating that indeed a glycoprotein of bloodstream-form trypanosomes binds TNF-α with high specificity via its N-linked carbohydrate moiety.


Specific uptake of tumor necrosis factor-alpha is involved in growth control of Trypanosoma brucei.

Magez S, Geuskens M, Beschin A, del Favero H, Verschueren H, Lucas R, Pays E, de Baetselier P - J. Cell Biol. (1997)

Binding of 125ITNF-α to bloodstream-form  and procyclic trypanosomes.  (a) Bloodstream-form trypanosomes (▪) and procyclic trypanosomes (□) were incubated in the presence of  different molar concentrations of 125I-TNF-α. Bloodstream forms were also incubated with 125I-TNF-α in the presence of a 100-fold molar excess of cold TNF-α (•). The number of bound molecules per cell was plotted  in function of the dose of 125I-TNF-α added. (b) Specific 125I-TNF-α binding to bloodstream-form trypanosomes. (c) Scatchard plot presentation of the same results. All the results shown are from one representative experiment.
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Related In: Results  -  Collection

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Figure 3: Binding of 125ITNF-α to bloodstream-form and procyclic trypanosomes. (a) Bloodstream-form trypanosomes (▪) and procyclic trypanosomes (□) were incubated in the presence of different molar concentrations of 125I-TNF-α. Bloodstream forms were also incubated with 125I-TNF-α in the presence of a 100-fold molar excess of cold TNF-α (•). The number of bound molecules per cell was plotted in function of the dose of 125I-TNF-α added. (b) Specific 125I-TNF-α binding to bloodstream-form trypanosomes. (c) Scatchard plot presentation of the same results. All the results shown are from one representative experiment.
Mentions: To perform a quantitative analysis of the binding of TNF-α to live monomorphic AnTat 1.1 trypanosomes, parasites were incubated for 6 h at 4°C with different molar concentrations of 125I-TNF-α. The results shown in Fig. 3 a confirm a specific binding of 125I-TNF-α on bloodstream form trypanosomes. Competition binding experiments with 125ITNF-α in the presence of a 100-fold molar excess of cold TNF-α showed a significant reduction of the parasite labeling. No specific TNF-α binding could be recorded on procyclic parasites. Analysis of the specific binding data obtained with bloodstream form trypanosomes (Fig. 3 b) revealed an affinity constant of 37.2 ± 14.8 nM and 1,558 ± 302 TNF-α–specific binding sites. To confirm the binding of TNF-α to trypanosomes, a different method was adopted. Using an optical biosensor, the direct binding of TNF-α on total trypanosome lysate was measured (Fig. 4). To test whether this binding reflects an interaction between the lectin-like activity of TNF-α (25) and glycosylated trypanosome components, the trypanosome lysate was treated with N-glycosidase F. This treatment strongly reduced the binding of TNF-α to trypanosome lysate, indicating that indeed a glycoprotein of bloodstream-form trypanosomes binds TNF-α with high specificity via its N-linked carbohydrate moiety.

Bottom Line: The specific uptake of the cytokine by the parasite results in a developmentally regulated loss of osmoregulatory capacity.Anti-TNF-alpha treatment of T. brucei-infected mice reveals a dramatic increase in parasitaemia in the blood circulation, the spleen, the lymph nodes, and the peritoneal cavity.These data suggest that in the mammalian host, TNF-alpha is involved in the growth control of T. brucei.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Cellular Immunology, Flanders Interuniversity Institute for Biotechnology, Vrije Universiteit Brussel, Belgium.

ABSTRACT
Trypanosoma brucei is lysed by tumor necrosis factor-alpha (TNF-alpha) in a dose-dependent way, involving specific binding of the cytokine to a trypanosomal glycoprotein present in the flagellar pocket of the parasite. TNF-alpha-gold particles are endocytosed via coated pits and vesicles and are directed towards lysosome-like digestive organelles. The specific uptake of the cytokine by the parasite results in a developmentally regulated loss of osmoregulatory capacity. TNF-alpha specific lysis is prevented when lysis assays are performed at a temperature <26 degrees C, despite uptake of the cytokine. Inhibition of lysis is also observed when a lysosomotropic agent is added during the first 2 h of incubation. Both monomorphic and pleomorphic trypanosomes are lysed but only when isolated during the peak of parasitaemia. Lysis is not observed with early infection stage parasites or procyclic (insect-specific) forms. Anti-TNF-alpha treatment of T. brucei-infected mice reveals a dramatic increase in parasitaemia in the blood circulation, the spleen, the lymph nodes, and the peritoneal cavity. These data suggest that in the mammalian host, TNF-alpha is involved in the growth control of T. brucei.

Show MeSH
Related in: MedlinePlus