IL-17 produced during Trypanosoma cruzi infection plays a central role in regulating parasite-induced myocarditis - PubMed (original) (raw)
IL-17 produced during Trypanosoma cruzi infection plays a central role in regulating parasite-induced myocarditis
Paulo Marcos da Matta Guedes et al. PLoS Negl Trop Dis. 2010.
Abstract
Background: Chagas disease is a neglected disease caused by the intracellular parasite Trypanosoma cruzi. Around 30% of the infected patients develop chronic cardiomyopathy or megasyndromes, which are high-cost morbid conditions. Immune response against myocardial self-antigens and exacerbated Th1 cytokine production has been associated with the pathogenesis of the disease. As IL-17 is involved in the pathogenesis of several autoimmune, inflammatory and infectious diseases, we investigated its role during the infection with T. cruzi.
Methodology/principal findings: First, we detected significant amounts of CD4, CD8 and NK cells producing IL-17 after incubating live parasites with spleen cells from normal BALB/c mice. IL-17 is also produced in vivo by CD4(+), CD8(+) and NK cells from BALB/c mice on the early acute phase of infection. Treatment of infected mice with anti-mouse IL-17 mAb resulted in increased myocarditis, premature mortality, and decreased parasite load in the heart. IL-17 neutralization resulted in increased production of IL-12, IFN-gamma and TNF-alpha and enhanced specific type 1 chemokine and chemokine receptors expression. Moreover, the results showed that IL-17 regulates T-bet, RORgammat and STAT-3 expression in the heart, showing that IL-17 controls the differentiation of Th1 cells in infected mice.
Conclusion/significance: These results show that IL-17 controls the resistance to T. cruzi infection in mice regulating the Th1 cells differentiation, cytokine and chemokine production and control parasite-induced myocarditis, regulating the influx of inflammatory cells to the heart tissue. Correlations between the levels of IL-17, the extent of myocardial destruction, and the evolution of cardiac disease could identify a clinical marker of disease progression and may help in the design of alternative therapies for the control of chronic morbidity of chagasic patients.
Conflict of interest statement
The authors have declared that no competing interests exist.
Figures
Figure 1. Trypomastigotes of T. cruzi induce IL-17 production by mouse splenocytes in vitro.
Leukocytes from BALB/c mice (5×106 cells/ml) were cultured with or without trypomastigotes (2.5×107/ml) of T. cruzi for 48 hours and the intracellular expression of IL-17 determined in total splenocytes (A), CD4+, CD8+, and NK cells (B) (mean ± SEM of cultures in triplicate, 3 animals/group). In A, the empty histograms represent IL-17+ cells harvest from cultures in the presence (black line) or absence of parasites (gray line) and the full histogram represents an IgG FITC control. The data are representative of two independent experiments. * P<0.05 compared to uninfected mice.
Figure 2. Trypanosoma cruzi infection induces IL-17 expression in mouse splenocytes.
The ex vivo frequencies of IL-17+ cells were determined in total splenocytes (A) of BALB/c mice on 0, 7, 14, and 21 days p.i.. In B and C, the percentage (mean ± SEM) of IL-17+ lymphocytes and CD4+, CD8+, NK cells of mice on day 14 p.i. are shown. The data are representative of two independent experiments with 3 mice in each day of infection. * P<0.05 compared to uninfected mice.
Figure 3. Enhanced cardiac parasitism and mortality in T. cruzi infected mice treated with anti-IL-17.
Parasitemia (A), cardiac parasitism (B), and survival (C) were determined in mice infected with T. cruzi. The quantification of genomic DNA was determined by real time PCR on tissue heart of mice on day 14 p.i. The data (mean ± SEM) are representative of two independent experiments (five mice per group). * P<0.05 compared to infected mice treated with normal rat IgG.
Figure 4. IL-17 neutralization increases _T. cruzi_-induced heart pathology.
Quantification of nuclei (A) in the heart tissue of normal mice (white bar) and infected mice (14 days p.i.) treated with normal rat IgG (gray bar) or with anti-IL-17 (black bar). In (B), representative microphotographs (original magnification ×400) of cardiac tissue of mice on day 14 post T. cruzi infection are shown. Data (mean ± SEM) are representative of two independent experiments using five mice per group. * P<0.05 compared to infected mice treated with normal rat IgG.
Figure 5. IL-17 controls IFN-γ, TNF-α, IL-12, and IL-17 production in heart tissue of mice infected with T. cruzi.
IFN-γ, TNF-α, IL-10, IL-12, and IL-17 were quantified in the sera and heart tissue of infected mice (14 days p.i.) that were treated or not with anti-IL-17. For heart cytokine quantification, 50 mg of tissue was homogenized in 1.0 ml of PBS plus protease inhibitors. The data (mean ± SEM) are representative of two independent experiments (five mice per group). * P<0.05 compared to infected mice treated with normal rat IgG.
Figure 6. IL-17 controls Th1 differentiation in _T. cruzi_-infected mice.
BALB/c mice were infected, the heart harvested on day 14 p.i., the leukocytes isolated and incubated with monensin for 6 h in culture medium, and the intracellular expression of IL-17 (A) and IFN-γ (B) were determined. Data (mean ± SEM) are representative of two independent experiments using five mice per group. * P<0.05 compared to infected mice treated with normal rat IgG.
Figure 7. Cross-regulation of IL-12, IFN-γ, and IL-17 during T. cruzi infection.
Splenocytes from BALB/c mice infected (14 days p.i.) or not with T. cruzi were harvested, cultured for 72 hours with or without Con-A (5 µg/ml), T. cruzi antigen (10 ηg/well), anti-IL-17 (10 µg/well) or anti-IFN-γ (10 µg/well). The cytokines IL-17, IL-12, IFN-γ, and TNF-α were determined by ELISA. The data show the mean ± SEM of triplicate cultures with 3 mice per group and are representative of two independent experiments. * P<0.05 compared to control culture.
Figure 8. IL-17 controls Th1 differentiation and the expression of chemokines and their receptors in the hearts of _T. cruzi_-infected mice.
mRNA expression of transcription factors (A), chemokine receptors (B), and chemokines (C) was determined in the heart tissue of T. cruzi infected mice (14 days p.i) treated with normal rat IgG or anti-mouse IL-17. The data (mean ± SEM) are representative of two independent experiments (five mice per group). * P<0.05 compared to infected mice treated with normal rat IgG.
References
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