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Iron prevents the development of experimental cerebral malaria by attenuating CXCR3-mediated T cell chemotaxis.

Van Den Ham KM, Shio MT, Rainone A, Fournier S, Krawczyk CM, Olivier M - PLoS ONE (2015)

Bottom Line: Protection was concomitant with a significant decrease in the sequestration of CD4+ and CD8+ T cells within the brain.CD4+ T cells demonstrated markedly decreased CXCR3 expression and had reduced IFNγ-responsiveness, as indicated by mitigated expression of IFNγR2 and T-bet.Additional analysis of the splenic cell populations indicated that parenteral iron supplementation was also associated with a decrease in NK cells and increase in regulatory T cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada; McGill International TB Centre, Research Institute of the McGill University Health Centre, Montréal, Québec, Canada.

ABSTRACT
Cerebral malaria is a severe neurological complication of Plasmodium falciparum infection. Previous studies have suggested that iron overload can suppress the generation of a cytotoxic immune response; however, the effect of iron on experimental cerebral malaria (ECM) is yet unknown. Here we determined that the incidence of ECM was markedly reduced in mice treated with iron dextran. Protection was concomitant with a significant decrease in the sequestration of CD4+ and CD8+ T cells within the brain. CD4+ T cells demonstrated markedly decreased CXCR3 expression and had reduced IFNγ-responsiveness, as indicated by mitigated expression of IFNγR2 and T-bet. Additional analysis of the splenic cell populations indicated that parenteral iron supplementation was also associated with a decrease in NK cells and increase in regulatory T cells. Altogether, these results suggest that iron is able to inhibit ECM pathology by attenuating the capacity of T cells to migrate to the brain.

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The Expression of CXCR3 on Splenic CD4+ T Cells is Decreased by Parenteral Iron Supplementation.Representative flow cytometric dot plots of CXCR3+ CD4+ and CD8+ T cells (a) and the percentage of CXCR3+ cells after gating on CD4+ or CD8+ T cells (b). Representative flow cytometric histograms of CXCR3 (c) and the MFI of CXCR3 (d) after gating on CD4+CD44hi or CD8+CD44hi T cells. All experiments were performed on day 7 post-infection. The numbers shown on the dot plots indicate the mean percentage of cells inside the gate ± S.E.M. n = 13 for all groups. The average of two individual experiments is shown. FeD = iron dextran, PBS = control. Statistically significant differences, shown by asterisks (** P < 0.01 and *** P < 0.001), were determined by unpaired Student’s t-test.
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pone.0118451.g006: The Expression of CXCR3 on Splenic CD4+ T Cells is Decreased by Parenteral Iron Supplementation.Representative flow cytometric dot plots of CXCR3+ CD4+ and CD8+ T cells (a) and the percentage of CXCR3+ cells after gating on CD4+ or CD8+ T cells (b). Representative flow cytometric histograms of CXCR3 (c) and the MFI of CXCR3 (d) after gating on CD4+CD44hi or CD8+CD44hi T cells. All experiments were performed on day 7 post-infection. The numbers shown on the dot plots indicate the mean percentage of cells inside the gate ± S.E.M. n = 13 for all groups. The average of two individual experiments is shown. FeD = iron dextran, PBS = control. Statistically significant differences, shown by asterisks (** P < 0.01 and *** P < 0.001), were determined by unpaired Student’s t-test.

Mentions: The above results indicated that parenteral iron supplementation prevented ECM pathology by reducing the sequestration of both CD4+ and CD8+ T cells within the brain. We hypothesized that the attenuated accumulation was due to either a deficiency in activation and/or expansion or to a defect in the chemotaxis of the T cells. The expansion of splenic CD4+ and CD8+ T cells was very similar between the control and FeD mice; only a minor delay in the proliferation of CD4+ T cells was observed (Figure D.A,B in S1 File). Additionally, the percentage of activated CD4+ and CD8+ T cells in the spleen was slightly decreased in the FeD mice, except for the percentage of CD25+CD62Llo CD4+ T cells, which was unchanged (Figure E.A,B in S1 File). Splenic conventional DCs (cDCs) were also analyzed, since this subset of DCs is thought to be responsible for priming the T cell response during ECM [16–18]. No difference in the percentage of cDCs or the mean fluorescence intensity (MFI) of CXCL10, CD40 or MHCII was observed in the FeD mice compared to the control mice (Figure F.B in S1 File). Both CXCR3 and CCR5 have been implicated to play important roles in T cell migration during ECM, but previous studies have shown that a greater percentage of brain-infiltrating T cells express CXCR3 compared to CCR5 [19]. Moreover, CXCR3 mRNA expression in the spleen was decreased in the FeD mice, whereas CCR5 expression was unchanged (Fig. 4B). Therefore, the expression of CXCR3 on splenic CD4+ and CD8+ T cells was examined on day 7 post-infection to determine if iron supplementation was attenuating T cell chemotaxis. The percentage of CD4+ T cells expressing CXCR3 was markedly decreased in the iron supplemented mice (Fig. 6A,B). Furthermore, the MFI of CXCR3 on CD4+CD44hi T cells in the FeD mice was similarly reduced (Fig. 6C,D). However, the percentage of CXCR3+ CD8+ T cells was unchanged (Fig. 6A,B), as was the MFI of CXCR3 on CD8+CD44hi T cells (Fig. 6C,D). The expression of CXCR3 on CD8+ T cells in the FeD mice trended toward a slight decrease, and a significant reduction was measured in some of the individual experiments, but overall, a significant difference was not observed. The attenuated expression of CXCR3 on CD4+ T cells suggests that iron supplementation inhibits T cell sequestration within the brain by directly impairing the chemotactic capacity of only CD4+ T cells, and that the chemotaxis of CD8+ T cells to the brain is indirectly attenuated by the consequent decrease in the induction of chemokines by CD4+ T cells.


Iron prevents the development of experimental cerebral malaria by attenuating CXCR3-mediated T cell chemotaxis.

Van Den Ham KM, Shio MT, Rainone A, Fournier S, Krawczyk CM, Olivier M - PLoS ONE (2015)

The Expression of CXCR3 on Splenic CD4+ T Cells is Decreased by Parenteral Iron Supplementation.Representative flow cytometric dot plots of CXCR3+ CD4+ and CD8+ T cells (a) and the percentage of CXCR3+ cells after gating on CD4+ or CD8+ T cells (b). Representative flow cytometric histograms of CXCR3 (c) and the MFI of CXCR3 (d) after gating on CD4+CD44hi or CD8+CD44hi T cells. All experiments were performed on day 7 post-infection. The numbers shown on the dot plots indicate the mean percentage of cells inside the gate ± S.E.M. n = 13 for all groups. The average of two individual experiments is shown. FeD = iron dextran, PBS = control. Statistically significant differences, shown by asterisks (** P < 0.01 and *** P < 0.001), were determined by unpaired Student’s t-test.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4359107&req=5

pone.0118451.g006: The Expression of CXCR3 on Splenic CD4+ T Cells is Decreased by Parenteral Iron Supplementation.Representative flow cytometric dot plots of CXCR3+ CD4+ and CD8+ T cells (a) and the percentage of CXCR3+ cells after gating on CD4+ or CD8+ T cells (b). Representative flow cytometric histograms of CXCR3 (c) and the MFI of CXCR3 (d) after gating on CD4+CD44hi or CD8+CD44hi T cells. All experiments were performed on day 7 post-infection. The numbers shown on the dot plots indicate the mean percentage of cells inside the gate ± S.E.M. n = 13 for all groups. The average of two individual experiments is shown. FeD = iron dextran, PBS = control. Statistically significant differences, shown by asterisks (** P < 0.01 and *** P < 0.001), were determined by unpaired Student’s t-test.
Mentions: The above results indicated that parenteral iron supplementation prevented ECM pathology by reducing the sequestration of both CD4+ and CD8+ T cells within the brain. We hypothesized that the attenuated accumulation was due to either a deficiency in activation and/or expansion or to a defect in the chemotaxis of the T cells. The expansion of splenic CD4+ and CD8+ T cells was very similar between the control and FeD mice; only a minor delay in the proliferation of CD4+ T cells was observed (Figure D.A,B in S1 File). Additionally, the percentage of activated CD4+ and CD8+ T cells in the spleen was slightly decreased in the FeD mice, except for the percentage of CD25+CD62Llo CD4+ T cells, which was unchanged (Figure E.A,B in S1 File). Splenic conventional DCs (cDCs) were also analyzed, since this subset of DCs is thought to be responsible for priming the T cell response during ECM [16–18]. No difference in the percentage of cDCs or the mean fluorescence intensity (MFI) of CXCL10, CD40 or MHCII was observed in the FeD mice compared to the control mice (Figure F.B in S1 File). Both CXCR3 and CCR5 have been implicated to play important roles in T cell migration during ECM, but previous studies have shown that a greater percentage of brain-infiltrating T cells express CXCR3 compared to CCR5 [19]. Moreover, CXCR3 mRNA expression in the spleen was decreased in the FeD mice, whereas CCR5 expression was unchanged (Fig. 4B). Therefore, the expression of CXCR3 on splenic CD4+ and CD8+ T cells was examined on day 7 post-infection to determine if iron supplementation was attenuating T cell chemotaxis. The percentage of CD4+ T cells expressing CXCR3 was markedly decreased in the iron supplemented mice (Fig. 6A,B). Furthermore, the MFI of CXCR3 on CD4+CD44hi T cells in the FeD mice was similarly reduced (Fig. 6C,D). However, the percentage of CXCR3+ CD8+ T cells was unchanged (Fig. 6A,B), as was the MFI of CXCR3 on CD8+CD44hi T cells (Fig. 6C,D). The expression of CXCR3 on CD8+ T cells in the FeD mice trended toward a slight decrease, and a significant reduction was measured in some of the individual experiments, but overall, a significant difference was not observed. The attenuated expression of CXCR3 on CD4+ T cells suggests that iron supplementation inhibits T cell sequestration within the brain by directly impairing the chemotactic capacity of only CD4+ T cells, and that the chemotaxis of CD8+ T cells to the brain is indirectly attenuated by the consequent decrease in the induction of chemokines by CD4+ T cells.

Bottom Line: Protection was concomitant with a significant decrease in the sequestration of CD4+ and CD8+ T cells within the brain.CD4+ T cells demonstrated markedly decreased CXCR3 expression and had reduced IFNγ-responsiveness, as indicated by mitigated expression of IFNγR2 and T-bet.Additional analysis of the splenic cell populations indicated that parenteral iron supplementation was also associated with a decrease in NK cells and increase in regulatory T cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada; McGill International TB Centre, Research Institute of the McGill University Health Centre, Montréal, Québec, Canada.

ABSTRACT
Cerebral malaria is a severe neurological complication of Plasmodium falciparum infection. Previous studies have suggested that iron overload can suppress the generation of a cytotoxic immune response; however, the effect of iron on experimental cerebral malaria (ECM) is yet unknown. Here we determined that the incidence of ECM was markedly reduced in mice treated with iron dextran. Protection was concomitant with a significant decrease in the sequestration of CD4+ and CD8+ T cells within the brain. CD4+ T cells demonstrated markedly decreased CXCR3 expression and had reduced IFNγ-responsiveness, as indicated by mitigated expression of IFNγR2 and T-bet. Additional analysis of the splenic cell populations indicated that parenteral iron supplementation was also associated with a decrease in NK cells and increase in regulatory T cells. Altogether, these results suggest that iron is able to inhibit ECM pathology by attenuating the capacity of T cells to migrate to the brain.

Show MeSH
Related in: MedlinePlus