Interferon-gamma-activated immature macrophages exhibit a high Trypanosoma cruzi infection rate associated with a low production of both nitric oxide and tumor necrosis factor-alpha

Gene Expression Profiling and Functional Characterization of Macrophages in Response to Circulatory Microparticles Produced during Trypanosoma cruzi Infection and Chagas Disease

BACKGROUND

Chronic inflammation and oxidative stress are hallmarks of chagasic cardiomyopathy (CCM). In this study, we determined if microparticles (MPs) generated during Trypanosoma cruzi (Tc) infection carry the host's signature of the inflammatory/oxidative state and provide information regarding the progression of clinical disease.

METHODS

MPs were harvested from supernatants of human peripheral blood mononuclear cells in vitro incubated with Tc (control: LPS treated), plasma of seropositive humans with a clinically asymptomatic (CA) or symptomatic (CS) disease state (vs. normal/healthy [NH] controls), and plasma of mice immunized with a protective vaccine before challenge infection (control: unvaccinated/infected). Macrophages (mφs) were incubated with MPs, and we probed the gene expression profile using the inflammatory signaling cascade and cytokine/chemokine arrays, phenotypic markers of mφ activation by flow cytometry, cytokine profile by means of an ELISA and Bioplex assay, and oxidative/nitrosative stress and mitotoxicity by means of colorimetric and fluorometric assays.

RESULTS

Tc- and LPS-induced MPs stimulated proliferation, inflammatory gene expression profile, and nitric oxide (∙NO) release in human THP-1 mφs. LPS-MPs were more immunostimulatory than Tc-MPs. Endothelial cells, T lymphocytes, and mφs were the major source of MPs shed in the plasma of chagasic humans and experimentally infected mice. The CS and CA (vs. NH) MPs elicited >2-fold increase in NO and mitochondrial oxidative stress in THP-1 mφs; however, CS (vs. CA) MPs elicited a more pronounced and disease-state-specific inflammatory gene expression profile (IKBKB, NR3C1, and TIRAP vs. CCR4, EGR2, and CCL3), cytokine release (IL-2 + IFN-γ > GCSF), and surface markers of mφ activation (CD14 and CD16). The circulatory MPs of nonvaccinated/infected mice induced 7.5-fold and 40% increases in ∙NO and IFN-γ production, respectively, while these responses were abolished when RAW264.7 mφs were incubated with circulatory MPs of vaccinated/infected mice.

CONCLUSION

Circulating MPs reflect in vivo levels of an oxidative, nitrosative, and inflammatory state, and have potential utility in evaluating disease severity and the efficacy of vaccines and drug therapies against CCM.

Nonimmune Cells Contribute to Crosstalk between Immune Cells and Inflammatory Mediators in the Innate Response to Trypanosoma cruzi Infection

Chagas myocarditis, which is caused by infection with the intracellular parasite Trypanosoma cruzi, remains the major infectious heart disease worldwide. Innate recognition through toll-like receptors (TLRs) on immune cells has not only been revealed to be critical for defense against T. cruzi but has also been involved in triggering the pathology. Subsequent studies revealed that this parasite activates nucleotide-binding oligomerization domain- (NOD-)like receptors and several particular transcription factors in TLR-independent manner. In addition to professional immune cells, T. cruzi infects and resides in different parenchyma cells. The innate receptors in nonimmune target tissues could also have an impact on host response. Thus, the outcome of the myocarditis or the inflamed liver relies on an intricate network of inflammatory mediators and signals given by immune and nonimmune cells. In this paper, we discuss the evidence of innate immunity to the parasite developed by the host, with emphasis on the crosstalk between immune and nonimmune cell responses.

Peripheral blood monocytes show morphological pattern of activation and decreased nitric oxide production during acute Chagas' disease in rats

Peripheral blood monocytes (PBM) recruitment is a rapid and remarkable phenomenon during acute infection with the intracellular protozoan parasite Trypanosoma cruzi, the causative agent of Chagas' disease. The functional capabilities of these cells during the infection, however, are poorly understood. The purpose of the present study was to determine whether PBM are morphologically activated and produce nitric oxide (NO), a mediator of host cell defense when challenged with the parasite at different time points of acute disease. In parallel, the parasite load was monitored in the blood and heart, a target organ of the disease, as well as the PBM numbers. The infection did not induce NO release by PBM, although these cells exhibited a clear morphological pattern of activation characterized by irregular surface, increase of organelle amount, especially Golgi complex, and cell size. On the contrary, there was significant inhibition of NO production by PBM at the beginning (day 6) and end of acute disease (day 20). At this time, the levels of NO were inversely related to the arginase activity, an enzyme that affects the NO synthesis. The mobilization process of PBM occurred in parallel to parasite load and was associated with the resolution mechanism of parasitemia and heart parasitism. Our results showed that activated PBM are notably involved in the host response to the acute T. cruzi infection in rats. However, the in vivo NO production by these cells seems to be inhibited during the acute Chagas' disease through a mechanism involving the arginase pathway.

Dynamics of Rickettsia-tick interactions: identification and characterization of differentially expressed mRNAs in uninfected and infected Dermacentor variabilis

To begin to explore the molecular dynamics of rickettsial tick interaction, subtractive hybridization was used to screen mRNAs in Rickettsia montanensis-infected and uninfected Dermacentor variabilis. We isolated 30 cDNA fragments, 22 of which were up-regulated and eight were down-regulated in response to rickettsial infection. Based on a putative identity of 11 cDNA fragments with similarity to known protein families, the tick genetic factors have been assigned into three groups including, the tick immune response factors (alpha-2 macroglobulin and IgE-dependent histamine release factor), the receptor/adhesion molecules (the signal transducer and activator of transcription-1/3 protein inhibitor, the clathrin adaptor protein and tetraspanin) and the stress response proteins (aldose reductase, glutathione-S transferase, ferritin, nucleosome assembly protein and cyclin A protein). Density analyses of semiquantitative RT-PCR amplified products demonstrated differential expression for 18 of the 23 tested genetic factors, apparently representing a 78% agreement with results obtained by subtractive hybridization. Additionally, mRNA transcripts of 17 of the 23 tested genetic factors were amplified from tick haemocytes/circulatory cells demonstrating that their expression is not restricted to the ovaries and suggesting a potential involvement in the immune response.

Trypanosoma cruzi is lysed by coelomic cytolytic factor-1, an invertebrate analogue of tumor necrosis factor, and induces phenoloxidase activity in the coelomic fluid of Eisenia foetida foetida

A cytolytic protein named Coelomic Cytolytic Factor-1 (CCF-1) was isolated from the coelomic fluid of the earthworm Eisenia foetida foetida. Despite the absence of any gene homology, CCF-1 showed functional analogy with the mammalian cytokine tumour necrosis factor (TNF), particularly based on similar lectin-like activity. Indeed, both CCF-1 and TNF recognise N,N'-diacetylchitobiose and exert lytic activity on African Trypanosoma brucei brucei. In this report, we show that South-American Trypanosoma cruzi trypomastigotes, but not epimastigotes, were lysed by earthworm coelomic fluid or purified CCF-1. However, T. cruzi was less susceptible to lysis than T. brucei brucei. This lytic effect of coelomic fluid and CCF-1 on T. cruzi trypomastigotes was partially inhibited in the presence of anti-CCF-1 monoclonal antibody, antibody neutralising the lectin-like activity of TNF or N,N'-diacetylchitobiose. In contrast, this lytic effect was completely inhibited when using T. b. brucei. In addition, T. cruzi components, upon recognition by CCF-1 in E. f. foetida coelomic fluid, triggered the prophenoloxidase cascade, an invertebrate defence mechanism. These results further extend the functional analogies of CCF-1 and TNF, suggesting that both molecules share a similar lectin-like activity that has been conserved as an innate recognition mechanism in invertebrates and vertebrates. They also establish a link between stercorarian (T. cruzi) and salivarian (T. brucei) trypanosomatids having divergent phylogenetic origins and patterns of evolution, but possessing closely related cell surface sugar moieties.

Efficacy of the bisbenzylisoquinoline alkaloids in acute and chronic Trypanosoma cruzi murine model

We have shown previously that daphnoline and cepharanthine are active against Trypanosoma cruzi and inhibited trypanothione reductase. The effects of oral treatments with daphnoline, cepharanthine and benznidazole were examined in Balb/c mice infected with T. cruzi acutely and chronically. In acute infections, parasitaemia was significantly reduced in the daphnoline-treated mice compared with controls and benznidazole-treated mice. The parasitological cure rate was increased in mice treated with daphnoline. Fifty days after infection, the negative serological response in both models was significantly different for the three tested drugs. Daphnoline showed the highest negative serological rate (48%). In chronically infected mice treated with daphnoline, we were unable to detect parasites in 70% of mice. The results obtained of oral treatment of daphnoline suggest that this bisbenzylisoquinoline may be useful in the treatment of acute and chronic Chagas' disease. This was not seen with cepharanthine, an excellent trypanothione reductase inhibitor.

CD40 ligation prevents Trypanosoma cruzi infection through interleukin-12 upregulation

Because of the critical role of the CD40-CD40 ligand (CD40L) pathway in the induction and effector phases of immune responses, we investigated the effects of CD40 ligation on the control of Trypanosoma cruzi infection. First, we observed that supernatants of murine spleen cells stimulated by CD40L-transfected 3T3 fibroblasts (3T3-CD40L transfectants) prevent the infection of mouse peritoneal macrophages (MPM) by T. cruzi. This phenomenon depends on de novo production of nitric oxide (NO) as it is prevented by the addition of N-nitro-L-arginine methyl ester, a NO synthase inhibitor. NO production requires interleukin (IL)-12-mediated gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) synthesis as demonstrated by inhibition experiments using neutralizing anti-IL-12, anti-IFN-gamma, and anti-TNF-alpha monoclonal antibodies (MAb). We found that an activating anti-CD40 MAb also directly stimulates IFN-gamma-activated MPM to produce NO and thereby to control T. cruzi infection. To determine the in vivo relevance of these in vitro findings, mice were injected with 3T3-CD40L transfectants or 3T3 control fibroblasts at the time of T. cruzi inoculation. We observed that in vivo CD40 ligation dramatically reduced both parasitemia and the mortality rate of T. cruzi-infected mice. A reduced parasitemia was still observed when the injection of 3T3-CD40L transfectants was delayed 8 days postinfection. It was abolished by injection of anti-IL-12 MAb. Taken together, these data establish that CD40 ligation facilitates the control of T. cruzi infection through a cascade involving IL-12, IFN-gamma, and NO.

How do protozoan parasites survive inside macrophages?

During infections with intracellular microbes, macrophages have two roles. On the one hand, they are important effector cells for the control and killing of intracellular bacteria and protozoan parasites by oxidative and non-oxidative mechanisms. On the other hand, macrophages may also serve as long-term host cells that facilitate the replication and survival of the pathogens, for example, by protecting them against toxic components of the extracellular milieu. In this review, Christian Bogdan and Martin Röllinghoff summarize some of the more recently discovered mechanisms by which intracellular protozoan parasites, such as Leishmania spp, Trypanosoma cruzi and Toxoplasma gondii, manage to exploit macrophages as safe target cells.

Action of chloroquine on nitric oxide production and parasite killing by macrophages

Chloroquine is known to inhibit several functions of macrophages, but its effect on the nitric oxide (NO)-dependent parasite killing capacity of macrophages has not been documented. NO synthesis by interferon-gamma-induced mouse and casein-elicited rat macrophages was significantly and irreversibly inhibited by chloroquine. The activity of the inducible NO synthase was not directly altered, but previous incubation of macrophages with chloroquine decreased it. Chloroquine did not alter arginase activity or arginine uptake. NADPH diaphorase activity, an indicator of NO synthase was impaired. Western blotting showed that inducible NO synthase synthesis was blocked by chloroquine. The blocking of NO formation by chloroquine resulted in increased infection of mouse peritoneal macrophages by Trypanosoma cruzi (T. cruzi). This suggests that chloroquine decreases NO formation by macrophages by inhibiting the induction of NO synthase. The findings are further evidence that NO is involved in the anti-parasitic response of macrophages.

Relationship between granulocyte macrophage-colony stimulating factor, tumour necrosis factor-alpha and Trypanosoma cruzi infection of murine macrophages

Gamma interferon (IFN-gamma)-activated macrophages control Trypanosoma cruzi infection via nitric oxide (NO), recently recognized as a major effector molecule. Granulocyte macrophage-colony stimulating factor (GM-CSF) is a multipotent cytokine secreted by macrophages and many other cells. It induces the production of tumour necrosis factor alpha (TNF-alpha), another cytokine also secreted by macrophages and involved in the control of T. cruzi infection. However, no data are available on the relationship between GM-CSF, TNF-alpha and NO produced by macrophages activated by IFN-gamma and infected with T. cruzi. To highlight this relationship, mouse peritoneal macrophages (MPM) and two c-myc retrovirus-induced macrophage cell lines (9.1.1 and BMM8), respectively characterized by a constitutive and an inducible production of GM-CSF, were activated with IFN-gamma and/or GM-CSF and infected with T. cruzi. Our results indicate that T. cruzi upregulates GM-CSF release from MPM and from the two macrophage cell lines, activated (or not) by IFN-gamma. A high autocrine production of GM-CSF or an exogenous supply of GM-CSF is correlated with an enhanced release of TNF-alpha and NO, inducing an improved control of T. cruzi infection by IFN-gamma-activated MPM.