Inhibition of nitric oxide production of activated mice peritoneal macrophages is independent of the Toxoplasma gondii strain

BACKGROUND

Toxoplasma gondii causes toxoplasmosis and is controlled by activated macrophages. However, infection of macrophages by tachyzoites induces TGF-β signaling (TGF-s) inhibiting nitric oxide (NO) production. NO inhibition may be a general escape mechanism of distinct T. gondii strains.

OBJECTIVES

To evaluate in activated macrophages the capacity of T. gondii strains of different virulence and genetics (RH, type I; ME-49, type II; VEG, type III; P-Br, recombinant) to evade the NO microbicidal defense system and determine LC3 loading to the parasitophorous vacuole.

METHODS

Activated peritoneal macrophages were infected with the different T. gondii strains, NO-production was evaluated by the Griess reagent, and inducible nitric oxide synthase expression, TGF-s, and LC3 localisation assayed by immunofluorescence.

FINDINGS

Only RH persisted in macrophages, while VEG was more resistant than P-Br and ME-49. All strains induced TGF-s, degradation of inducible nitric oxide synthase, and NO-production inhibition from 2 to 24 h of infection, but only RH sustained these alterations for 48 h. By 24 h of infection, TGF-s lowered in macrophages infected by ME-49, and P-Br, and NO-production recovered, while VEG sustained TGF-s and NO-production inhibition longer. LC3 loading to parasitophorous vacuole was strain-dependent: higher for ME-49, P-Br and VEG, lower for RH. All strains inhibited NO-production, but only RH sustained this effect probably because it persisted in macrophages due to additional evasive mechanisms as lower LC3 loading to parasitophorous vacuole.

MAIN CONCLUSIONS

These results support that T. gondii can escape the NO microbicidal defense system at the initial phase of the infection, but only the virulent strain sustain this evasion mechanism.

Tityus serrulatus scorpion venom as a potential drug source for Chagas' disease: Trypanocidal and immunomodulatory activity

Current chemical therapies for Chagas Disease (CD) lack ability to clear Trypanosoma cruzi (Tc) parasites and cause severe side effects, making search for new strategies extremely necessary. We evaluated the action of Tityus serrulatus venom (TsV) components during Tc infection. TsV treatment increased nitric oxide and pro-inflammatory cytokine production by Tc-infected macrophages (MØ), decreased intracellular parasite replication and trypomastigotes release, also triggering ERK1/2, JNK1/2 and p38 activation. Ts7 demonstrated the highest anti-Tc activity, inducing high levels of TNF and IL-6 in infected MØ. TsV/Ts7 presented synergistic effect on p38 activation when incubated with Tc antigen. KPP-treatment of MØ also decreased trypomastigotes releasing, partially due to p38 activation. TsV/Ts7-pre-incubation of Tc demonstrated a direct effect on parasite decreasing MØ-trypomastigotes releasing. In vivo KPP-treatment of Tc-infected mice resulted in decreased parasitemia. Summarizing, this study opens perspectives for new bioactive molecules as CD-therapeutic treatment, demonstrating the TsV/Ts7/KPP-trypanocidal and immunomodulatory activity during Tc infection.

Characterisation of susceptibility of chicken macrophages to infection with Toxoplasma gondii of type II and III strains

Toxoplasma gondii is known to be able to infect any nucleated cell including immune cells like macrophages. In addition, it is assumed that macrophages serve as trojan horse during distribution in hosts. The underlying causes of parasite host interaction remain yet not fully understood. The aim of the present study was to investigate susceptibility of chicken macrophages to infection with T. gondii and the process of infection in avian cells in comparison to cells of mammalian origin. Primary avian blood monocyte-derived macrophages were infected with tachyzoites of type II (ME49) and III (NED) strains. Long term observations of parasite replication in primary macrophages were compared to data obtained in an avian macrophage cell line (HD11) and a standard cultivation mammalian cell line (VERO). Furthermore, we assessed the immune response of the primary macrophages by long-term investigation of gene expression of IL-1 beta, IL-12p40, Lipopolysaccharide induced TNF-alpha factor (LITAF) and inducible nitric oxide synthase (iNOS) comparing viable and heat-inactivated tachyzoites of the ME49 strain. Albeit, we found no differences between both strains, replication of tachyzoites in avian primary macrophages was significantly different from immortalized cell lines HD11 and VERO. The crucial period of parasite replication was between 8 and 24 h post-infection coinciding with the upregulation of gene expression of cytokines and iNOS revealing an active macrophage response at this period. Gene expression in macrophages was higher after infection with viable tachyzoites than by exposure of cells to heat-inactivated tachyzoites. Hence, we conclude that the process of penetration is pivotal for host cell response to the parasite both in avian as in mammalian cells.