Objectives: Toll-like receptors (TLRs) are expressed in several immune cells including blood monocytes and resident macrophages, such as microglia in the central nervous system. TLRs recognize pathogen- or damage-associated molecular patterns, leading to the release of inflammatory and toxic molecules, which can contribute to neuroinflammation associated with Parkinson's disease (PD). The aim of this study was to compare the potential of peripheral blood cells from PD patients or healthy subjects to produce cytokines after exposure to TLR agonists, and to investigate TLR2 and TLR4 expression on monocyte subsets. Methods: Twenty-one patients and 21 healthy controls were recruited. Patients were evaluated according to the Unified Parkinson's Disease Rating Scale, and Hoehn and Yahr stage. Cytokines were measured in supernatants of whole blood cultures after incubation with TLR2, TLR4, or TLR7/8 agonists, by cytometric bead array. Expression of CD14, CD16, TLR2, and TLR4 was analyzed by cytometry. Results: Patient blood cells produced lower levels of cytokines in response to TLR2 and also after TLR7/8/R848 activation than controls. Percentages of CD14+CD16+ or CD14+CD16- monocytes and TLR2 and TLR4 expression were similar between patients and controls. Conclusions: Blood leukocyte TLR2 and TLR7/8 responses are impaired in PD. This was neither associated with imbalance in monocyte subsets nor with TLR2/TLR4 expression on these cells. The association between a decreased TLR response in periphery and damage of brain in PD must be further investigated.
Leishmania (Viannia) guyanensis is a causal agent of American tegumentary leishmaniasis (ATL). This protozoan has been poorly investigated; however, it can cause different clinical forms of ATL, ranging from a single cutaneous lesion to severe lesions that can lead to destruction of the nasopharyngeal mucosa. L. (V.) guyanensis and the disease caused by this species can present unique aspects revealing the need to better characterize this parasite species to improve our knowledge of the immunopathological mechanisms and treatment options for ATL. The mechanisms by which some patients develop a more severe form of ATL remain unclear. It is known that the host immune profile and parasite factors may influence the clinical manifestations of the disease. Besides intrinsic parasite factors, Leishmaniavirus RNA 1 (LRV1) infecting L. guyanensis can contribute to ATL immunopathogenesis. In this review, general aspects of L. guyanensis infection in humans and mouse models are presented.
Although Leishmania (Viannia) braziliensis is the most prevalent species that cause American tegumentary leishmaniasis (ATL), the immune response against this parasite has been poorly investigated. Upon activation, macrophages produce a series of pro-inflammatory molecules, including the lipid mediator leukotriene B4 (LTB4). LTB4 has been shown to enhance several macrophage functions, but its role in human macrophages is less known. Here, we investigated the role of LTB4 on human monocyte-derived macrophages infected with human isolate of L. (V.) braziliensis (IMG3). It was found that human macrophages produce LTB4 upon infection with Leishmania, which by autocrine or paracrine activation of its high affinity receptor BLT1, potentiates macrophage leishmanicidal activity. This LTB4 effect is mediated by increased secretion of reactive oxygen species (ROS). Moreover, Leishmania infection decreased the expression of BLT1, leading to the speculation that this could represent a parasite escape mechanism to establish a chronic inflammatory infection. Therefore, our data suggest that LTB4 could be used in therapeutic strategies to control Leishmania infection.
Platelet-activating factor (PAF) is produced by macrophages during inflammation and infections. We evaluated whether PAF is able to modulate the infection of human macrophages by Leishmania braziliensis, the main Leishmania sp. in Brazil. Monocyte-derived macrophages were incubated with promastigote forms in absence or presence of exogenous PAF. We observed that the treatment of macrophages with low concentrations of PAF prior to infection increased the phagocytosis of L. braziliensis. More importantly, exogenous PAF reduced the parasitism when it was added before, during or after infection. In addition, treatment with a PAF antagonist (PCA 4248) resulted in a significant increase of macrophage infection in a concentration-dependent manner, suggesting that endogenous PAF is important to control L. braziliensis infection. Mechanistically, while exogenous PAF increased production of reactive oxygen species (ROS) treatment with PCA 4248 reduced oxidative burst during L. braziliensis infection. The microbicidal effects of exogenous PAF were abolished when macrophages were treated with apocynin, an NADPH oxidase inhibitor. The data show that PAF promotes the production of ROS induced by L. braziliensis, suggesting that this lipid mediator may be relevant to control L. braziliensis infection in human macrophages.
The aim of this study was to characterize clinical field isolates of Leishmania spp. obtained from patients with American Tegumentary Leishmaniasis (ATL) who live in Goiás state, Brazil. The presumed areas of infection were in Goiás, Tocantins, and Pará states. Three isolates of parasites were identified as L. (Viannia) braziliensis and one as L. (V.) guyanensis. The in vitro growth profiles were found to be similar for all parasites. Nevertheless, in C57BL/6 mice, L. (V.) guyanensis infection was better controlled than L. (V.) braziliensis. Yet in C57BL/6 mice deficient in interferon gamma, L. (V.) guyanensis lesions developed faster than those caused by L. (V.) braziliensis isolates. In BALB/c mice, the development of lesions was similar for isolates from both species; however, on the 11th week of infection, amastigotes could not be observed in macrophages from L. (V.) guyanensis-infected mice. Thus, L. (V.) guyanensis can be circulating in Goiás, a state where autochthonous cases of this species had not yet been reported. Considering the difficulties to differentiate L. (V.) guyanensis from L. (V.) braziliensis at the molecular, morphological, and clinical (human and murine models) levels, the presence of L. (V.) guyanensis infections is possibly underestimated in several regions of Brazil.
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