In the current study, we evaluated the mechanism of action of
miltefosine, which is the first effective and safe oral treatment for
visceral leishmaniasis, in Leishmania amazonensis promastigotes.
...Miltefosine induced a process of programmed cell death, which was
determined by the externalization of phosphatidylserine, the
incorporation of propidium iodide, cell-cycle arrest at the sub-G0/G1
phase and DNA fragmentation into oligonucleosome-sized fragments.
Despite the intrinsic variation that is detected in Leishmania spp, our
results indicate that miltefosine causes apoptosis-like death in L.
amazonensis promastigote cells using a similar process that is observed
in Leishmania donovani .
We have demonstrated recently that the glycoinositolphospholipid (GIPL) molecule from the protozoan Trypanosoma cruzi is a TLR4 agonist with proinflammatory effects. Here, we show that GIPL-induced ...neutrophil recruitment into the peritoneal cavity is mediated by at least two pathways: one, where IL-1beta acts downstream of TNF-alpha, and a second, which is IL-1beta- and TNFRI-independent. Moreover, NKT cells participate in this proinflammatory cascade, as in GIPL-treated CD1d(-/-) mice, TNF-alpha and MIP-2 levels are reduced significantly. As a consequence of this inflammatory response, spleen and lymph nodes of GIPL-treated mice have an increase in the percentage of T and B cells expressing the CD69 activation marker. Cell-transfer experiments demonstrate that T and B cell activation by GIPL is an indirect effect, which relies on the expression of TLR4 by other cell types. Moreover, although signaling through TNFRI contributes to the activation of B and gammadelta+ T cells, it is not required for increasing CD69 expression on alphabeta+ T lymphocytes. It is interesting that T cells are also functionally affected by GIPL treatment, as spleen cells from GIPL-injected mice show enhanced production of IL-4 following in vitro stimulation by anti-CD3. Together, these results contribute to the understanding of the inflammatory properties of the GIPL molecule, pointing to its potential role as a parasite-derived modulator of the immune response during T. cruzi infection.
Considerable clinical and epidemiological evidence links Alzheimer's disease (AD) and depression. However, the molecular mechanisms underlying this connection are largely unknown. We reported ...recently that soluble Aβ oligomers (AβOs), toxins that accumulate in AD brains and are thought to instigate synapse damage and memory loss, induce depressive-like behavior in mice. Here, we report that the mechanism underlying this action involves AβO-induced microglial activation, aberrant TNF-α signaling, and decreased brain serotonin levels. Inactivation or ablation of microglia blocked the increase in brain TNF-α and abolished depressive-like behavior induced by AβOs. Significantly, we identified serotonin as a negative regulator of microglial activation. Finally, AβOs failed to induce depressive-like behavior in Toll-like receptor 4-deficient mice and in mice harboring a nonfunctional TLR4 variant in myeloid cells. Results establish that AβOs trigger depressive-like behavior via a double impact on brain serotonin levels and microglial activation, unveiling a cross talk between brain innate immunity and serotonergic signaling as a key player in mood alterations in AD.
Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the main cause of dementia in the world. Brain accumulation of amyloid-β oligomers (AβOs) is a major feature in the pathogenesis of AD. Although clinical and epidemiological data suggest a strong connection between AD and depression, the underlying mechanisms linking these two disorders remain largely unknown. Here, we report that aberrant activation of the brain innate immunity and decreased serotonergic tonus in the brain are key players in AβO-induced depressive-like behavior in mice. Our findings may open up new possibilities for the development of effective therapeutics for AD and depression aimed at modulating microglial function.
Parasites of the Leishmania genus are the causative agents of leishmaniasis in humans, a disease that affects more than 12 million people worldwide. These parasites replicate intracellularly in ...macrophages, and the primary mechanisms underlying host resistance involve the production of nitric oxide (NO). In this study we show that the Nlrp3 inflammasome is activated in response to Leishmania infection and is important for the restriction of parasite replication both in macrophages and in vivo as demonstrated through the infection of inflammasome-deficient mice with Leishmania amazonensis, Leishmania braziliensis and Leishmania infantum chagasi. Inflammasome-driven interleukin-1β (IL-1β) production facilitated host resistance to infection, as signaling through IL-1 receptor (IL-1R) and MyD88 was necessary and sufficient to trigger inducible nitric oxide synthase (NOS2)-mediated production of NO. In this manuscript we identify a major signaling platform for host resistance to Leishmania spp. infection and describe the molecular mechanisms underlying Leishmania-induced NO production.
IL-4 plays an essential role in the activation of mature B cells, but less is known about the role of IL-4 in B cell maturation and tolerance checkpoints. In this study, we analyzed the effect of ...IL-4 on in vitro B cell maturation, from immature to transitional stages, and its influence on BCR-mediated negative selection. Starting either from purified CD19(+)IgM(-) B cell precursors, or sorted bone marrow immature (B220(low)IgM(low)CD23(-)) and transitional (B220(int)IgM(high)CD23(-)) B cells from C57BL/6 mice, we compared the maturation effects of IL-4 and BAFF. We found that IL-4 stimulated the generation of CD23(+) transitional B cells from CD23(-) B cells, and this effect was comparable to BAFF. IL-4 showed a unique protective effect against anti-IgM apoptotic signals on transitional B cell checkpoint, not observed with BAFF. IL-4 and BAFF strongly synergized to promote B cell maturation, and IL-4 also rendered it refractory to BCR-mediated cell death. IL-4 blocked upregulation of proapoptotic Bim protein levels induced by BCR crosslinking, suggesting that diminished levels of intracellular Bim promote protection to BCR-induced cell death. Evidence was obtained indicating that downmodulation of Bim by IL-4 occurred in a posttranscriptional manner. Consistent with data obtained in vitro, IL-4 in vivo was able to inhibit Bim upregulation and prevent cell death. These results contribute to the understanding of the role of IL-4 in B lymphocyte physiology, unveiling a previously undescribed activity of this cytokine on the maturation of B cells, which could have important implications on the breaking of B cell central tolerance in autoimmunity.
IFN-γ-producing γδ T cells have been suggested to play an important role in protection against infection with Trypanosoma cruzi. However, little is known about the mechanisms leading to functional ...differentiation of this T cell subset in this model. In the current work, we investigated the possibility that the IL-18/MyD88 pathway is central for the generation of effector γδ T cells, playing a role for resistance against infection. We found that splenic γδ
CD3
cells were rapidly expanded (10-14 days post infection), which was accompanied by an early γδ T cell infiltration into the heart. In the following days, intracardiac parasitism was reduced, the protective immunity being accompanied by decreased γδ T cells tissue infiltration. As predicted, there was a drastic reduction of γδ T cells in Myd88- and Il18r1-deficient mice, both transgenic strains displaying a susceptible phenotype with increased intracardiac parasitism. In vivo and in vitro assays confirmed that IL-18R deficiency hampered γδ T cell proliferation. Further characterization revealed that T. cruzi infection up-regulates IL-18R expression in WT γδ
T cell population whereas Il18r1
mice showed impaired generation of cytotoxic GzB
and IFN-γ-producing γδ T cells. Consistently, in vitro cytotoxicity assay confirmed that cytolytic function was impaired in Il18r1-deficient γδ T cells. As a proof of concept, adoptive transfer of WT γδ T cells rescues Il18r1-deficient mice from susceptibility, reducing parasitemia and abrogating the mortality. Collectively, our findings implicate the IL-18R-MyD88 signaling in the mechanisms underlying generation of immunoprotective γδ T cells response in experimental Trypanosoma cruzi infection.
Abstract
Mayaro virus (MAYV) is a tropical arbovirus first described in forest regions of the South America, and recently associated with urban circulation. Mayaro infections leads to a disease with ...high rate of persistent arthralgia and myalgia in humans. Despite this, pathogenesis and host immune response of MAYV infections are still limited. The aim of this work was to evaluate the immune response and cell profile during MAYV infections. We developed a disease model infecting SV129 wild-type (WT), SVA129 Type I Interferon receptor deficient (IFNAR−/−), C57BL/6 WT and C57BL/6 recombination activation gene-1 deficient (RAG−/−) mice, and accessing replication, tissue damage, and inflammation through time. While adult WT mice are resistant to infection, IFNAR−/− mice exhibited increasing viral load up to 6 days after infection, footpad swelling, lethargy and weight loss. Histological analysis showed extensive necrosis sites in infected IFNAR−/− mice and also presence of mononucleated cell infiltrate. We detected elevated expression of inflammatory cytokines like TNF, IL-6, KC, IL-1, MCP-1 and RANTES, and decreased TGF-beta in infected muscle. In RAG−/− mice, MAYV infection lead to a persistent replication being detected at blood and tissues up 40 days post infection. However, infected RAG−/− mice did not develop any signs of muscle damage or infiltrate during early and late infection and neither the expression inflammatory cytokines. So far, our data demonstrates that innate and adaptive immunity are critical to restrict MAYV replication. Adaptive immunity is also involved in MAYV-induced tissue damage. These results contribute in underlying MAYV pathogenesis and further experiments must to be made to elucidate the mechanisms involved.
Background The lack of effective treatments for Alzheimer's disease (AD) reflects an incomplete understanding of disease mechanisms. Alterations in proteins involved in mitochondrial dynamics, an ...essential process for mitochondrial integrity and function, have been reported in AD brains. Impaired mitochondrial dynamics causes mitochondrial dysfunction and has been associated with cognitive impairment in AD. Here, we investigated a possible link between pro-inflammatory interleukin-1 (IL-1), mitochondrial dysfunction, and cognitive impairment in AD models. Methods We exposed primary hippocampal cell cultures to amyloid-beta oligomers (AbetaOs) and carried out AbetaO infusions into the lateral cerebral ventricle of cynomolgus macaques to assess the impact of AbetaOs on proteins that regulate mitochondrial dynamics. Where indicated, primary cultures were pre-treated with mitochondrial division inhibitor 1 (mdivi-1), or with anakinra, a recombinant interleukin-1 receptor (IL-1R) antagonist used in the treatment of rheumatoid arthritis. Cognitive impairment was investigated in C57BL/6 mice that received an intracerebroventricular (i.c.v.) infusion of AbetaOs in the presence or absence of mdivi-1. To assess the role of interleukin-1 beta (IL-1beta) in AbetaO-induced alterations in mitochondrial proteins and memory impairment, interleukin receptor-1 knockout (Il1r1.sup.-/-) mice received an i.c.v. infusion of AbetaOs. Results We report that anakinra prevented AbetaO-induced alteration in mitochondrial dynamics proteins in primary hippocampal cultures. Altered levels of proteins involved in mitochondrial fusion and fission were observed in the brains of cynomolgus macaques that received i.c.v. infusions of AbetaOs. The mitochondrial fission inhibitor, mdivi-1, alleviated synapse loss and cognitive impairment induced by AbetaOs in mice. In addition, AbetaOs failed to cause alterations in expression of mitochondrial dynamics proteins or memory impairment in Il1r1.sup.-/- mice. Conclusion These findings indicate that IL-1beta mediates the impact of AbetaOs on proteins involved in mitochondrial dynamics and that strategies aimed to prevent pathological alterations in those proteins may counteract synapse loss and cognitive impairment in AD. Keywords: Alzheimer's disease, Mitochondrial dynamics, Mitochondrial dysfunction, IL-1beta, Neuroinflammation, Abeta oligomers
Increasing attention has been directed to cytotoxic CD4.sup.+ T cells (CD4CTLs) in different pathologies, both in humans and mice. The impact of CD4CTLs in immunity and the mechanisms controlling ...their generation, however, remain poorly understood. Here, we show that CD4CTLs abundantly differentiate during mouse infection with the intracellular parasite Trypanosoma cruzi. CD4CTLs display parallel kinetics to Th1 cells in the spleen, mediate specific cytotoxicity against cells presenting pathogen-derived antigens and express immunoregulatory and/or exhaustion markers. We demonstrate that CD4CTL absolute numbers and activity are severely reduced in both Myd88.sup.-/- and Il18ra.sup.-/- mice. Of note, the infection of mixed-bone marrow chimeras revealed that wild-type (WT) but not Myd88.sup.-/- cells transcribe the CD4CTL gene signature and that Il18ra.sup.-/- and Myd88.sup.-/- CD4.sup.+ T cells phenocopy each other. Moreover, adoptive transfer of WT CD4.sup.+GzB.sup.+ T cells to infected Il18ra.sup.-/- mice extended their survival. Importantly, cells expressing the CD4CTL phenotype predominate among CD4.sup.+ T cells infiltrating the infected mouse cardiac tissue and are increased in the blood of Chagas patients, in which the frequency of CD4CTLs correlates with the severity of cardiomyopathy. Our findings describe CD4CTLs as a major player in immunity to a relevant human pathogen and disclose T-cell intrinsic IL-18R/MyD88 signaling as a key pathway controlling the magnitude of the CD4CTL response.
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