Regulatory role of Toll-like receptor 2 during infection with Trypanosoma cruzi

Abstract

Previous studies have emphasized the role of Toll-like receptors (TLRs) and myeloid differentiation factor 88 (MyD88) during infection with protozoan parasites. TLR2 was shown to be important for induction of cytokine synthesis by macrophages exposed to the purified glycosylphosphatidylinositol (GPI)-anchored mucin-like glycoproteins of Trypanosoma cruzi trypomastigotes (tGPIm). On the other hand, MyD88^—/— mice, but not TLR2^—/— mice, showed impaired cytokine production and resistance to infection with T. cruzi parasites. Here we evaluate the importance of MyD88 and TLR2 in MAPK activation and cytokine synthesis by macrophages exposed to live T. cruzi parasites and compared to tGPIm. The absence of MAPK phosphorylation in TLR2- and MyD88-deficient macrophages exposed to tGPIm correlated with the incapacity to induce cytokine release in these cells. In contrast, activation of MAPK and synthesis of pro-inflammatory cytokines were not abrogated in TLR2-deficient macrophages exposed to live T. cruzi parasites. We also showed that pretreatment with tGPIm significantly reduces cytokine release by macrophages in response to T. cruzi in a TLR2-dependent manner. Consistently, TLR2^-/- mice were shown to produce enhanced levels of cytokines upon in vivo challenge with T. cruzi parasites. Together, these results suggest the involvement of additional TLR(s) in the pro-inflammatory response of macrophages to whole parasites, and that, in vivo, TLR2 may have a predominant immunoregulatory role during acute infection with T. cruzi parasites.

Keywords

Trypanosoma cruzi TLR GPI-mucin MyD88

References

Kirchhoff LV A Changing epidemiology and approaces to therapy for Chagas disease. Curr Infect Dis Rep 2003 ; 5: 59—65.

Brener Z. , Gazzinelli RT Immunological control of Trypanosoma cruzi and pathogenesis of Chagas' disease . Arch Allergy Immunol 1997; 114: 103—110.

Michailowsky V. , Silva NM , Rocha CD et al. Pivotal role of interleukin-12 and interferon-yaxis in controlling tissue parasitism and inflammation in the heart and central nervous system during Trypanosoma cruzi infection. Am J Pathol 2001; 159: 1723—1733.

Holscher C. , Kolher G. , Muller U. et al. Defective nitric oxide effector functions lead to extreme susceptibility of Trypanosoma cruzi-infected mice deficient in gamma interferon receptor or inducible nitric oxide synthase. Infect Immun 1998; 66: 1208—1215.

Takeda K. , Kaisho T. , Akira S. Toll like receptors. Annu Rev Immunol 2003 ; 21: 335—376.

Aderem A. , Ulevitch RJ Toll-like receptors in the induction of the innate immune response. Nature 2000; 406: 782—787.

Takeuchi O. , Akira S. MyD88 as a bottle neck in Toll/IL-1 signaling. Curr Top Microbiol Immunol 2002; 270: 155—167.

Kawai T. , Adachi O. , Ogawa T. et al. Unresponsiveness of MyD88-deficient mice to endotoxin. Immunity 1999; 11: 115—122.

Campos Mas , Almeida IC , Takeuchi O. et al. Activation of Toll-like receptor-2 by glycosylphosphatidylinositol anchors from a parasitic protozoan. J Immunol 2001; 167: 416—423.

10.

Campos MA , Closel M. , Valente EP et al. Impaired production of proinflammatory cytokines and host resistance to acute infection with Trypanosoma cruzi in mice lacking functional myeloid differentiation factor 88. J Immunol 2004; 172: 1711—1718.

11.

Ropert C. , Ferreira LR , Campos MA et al. Macrophage signaling by glycosylphosphatidylinositol-anchored mucin-like glycoproteins derived from Trypanosoma cruzi trypomastigotes. Microbes Infect 2002; 4: 1015—1025.

12.

Almeida IC , Camargo MM , Procopio DO et al. Highly purified glycosylphosphatidylinositols from Trypanosoma cruzi are potent proinflammatory agents. EMBO J 2000; 19: 1476—1485.

13.

Ropert C. , Almeida IC , Closel M. et al. Requirement of mitogenactivated protein kinases and I kappa B phosphorylation for induction of proinflammatory cytokines synthesis by macrophages indicates functional similarity of receptors triggered by glycosylphosphatidylinositol anchors from parasitic protozoa and bacterial lipopolysaccharide. J Immunol 2001; 166: 3423—3431.

14.

Romanha AJ , Alves RO , Murta Smf et al. Experimental chemotherapy against Trypanosoma cruzi infection: essential role of endogenous interferon-γ in mediating parasitologic cure . J Infect Dis 2002; 186: 823—828.

15.

Brodskyn C. , Patricio J. , Oliveira R. et al. Glycoinositolphospholipids from Trypanosoma cruzi interfere with macrophages and dendritic cell responses. Infect Immun 2000; 70: 3736—3743.

16.

Saavedra E. , Herrera M. , Gao W. et al. The Trypanosoma cruzi trans-sialidase, through its COOH-terminal tandem repeat, upregulates interleukin 6 secretion in normal human intestinal microvascular endothelial cells and peripheral blood mononuclear cells. J Exp Med 1999; 190: 1825—1836.

17.

Shoda LK , Kegerreis KA , Suarez CE et al. DNA from protozoan parasites Babesia bovis, Trypanosoma cruzi, and T. brucei is mitogenic for B lymphocytes and stimulates macrophage expression of interleukin-12, tumor necrosis factor alpha, and nitric oxide. Infect Immun 2001; 69: 2162—2171.

18.

Ropert C. , Closel M. , Chaves AC et al. Inhibition of a p3 8/stress-activated protein kinase-2-dependent phosphatase restores function of IL-1 receptor-associate kinase-1 and reverses Toll-like receptor 2- and 4-dependent tolerance of macrophages. J Immunol 2003; 171: 1456—1465.