Microglia-Secreted Galectin-3 Acts as a Toll-like Receptor 4 Ligand and Contributes to Microglial Activation.

Inflammatory response induced by microglia plays a critical role in the demise of neuronal populations in neuroinflammatory diseases. Although the role of toll-like receptor 4 (TLR4) in microglia's inflammatory response is fully acknowledged, little is known about endogenous ligands that trigger TLR4 activation. Here, we report that galectin-3 (Gal3) released by microglia acts as an endogenous paracrine TLR4 ligand. Gal3-TLR4 interaction was further confirmed in a murine neuroinflammatory model (intranigral lipopolysaccharide [LPS] injection) and in human stroke subjects. Depletion of Gal3 exerted neuroprotective and anti-inflammatory effects following global brain ischemia and in the neuroinflammatory LPS model. These results suggest that Gal3-dependent-TLR4 activation could contribute to sustained microglia activation, prolonging the inflammatory response in the brain

Babesia divergens glycosylphosphatidylinositols modulate blood coagulation and induce Th2-biased cytokine profiles in antigen presenting cells

This work was supported by the the University of Tours (to IDP and FDG), the University of Montpellier (to SD and EC), the Deutsche Forschungsgemeinschaft (to RTS), the Wellcome Trust project grant 093228 (to TKS) and the Campus France/DAAD PHC PROCOPE 24931RE (to RTS and EC). The funding source has no involvement in the conduct of the research and preparation of the article.Glycosylphosphatidylinositols (GPIs) are glycolipids described as toxins of protozoan parasites due to their inflammatory properties in mammalian hosts characterized by the production of interleukin (IL)-1, IL-12 and tumor necrosis factor (TNF)-α. In the present work, we studied the cytokines produced by antigen presenting cells in response to ten different GPI species extracted from Babesia divergens, responsible for babesiosis. Interestingly, B. divergens GPIs induced the production of anti-inflammatory cytokines (IL-2, IL-5) and of the regulatory cytokine IL-10 by macrophages and dendritic cells. In contrast to all protozoan GPIs studied until now, GPIs from B. divergens did not stimulate the production of TNF-α and IL-12, leading to a unique Th1/Th2 profile. Analysis of the carbohydrate composition of the B. divergens GPIs indicated that the di-mannose structure was different from the evolutionary conserved tri-mannose structure, which might explain the particular cytokine profile they induce. Expression of major histocompatibility complex (MHC) molecules on dendritic cells and apoptosis of mouse peritoneal cells were also analysed. B. divergens GPIs did not change expression of MHC class I, but decreased expression of MHC class II at the cell surface, while GPIs slightly increased the percentages of apoptotic cells. During pathogenesis of babesiosis, the inflammation-coagulation auto-amplification loop can lead to thrombosis and the effect of GPIs on coagulation parameters was investigated. Incubation of B. divergens GPIs with rat plasma ex vivo led to increase of fibrinogen levels and to prolonged activated partial thromboplastin time, suggesting a direct modulation of the extrinsic coagulation pathway by GPIs.Publisher PDFPeer reviewe

Elucidating pathways of Toxoplasma gondii invasion in the gastrointestinal tract: involvement of the tight junction protein occludin

Toxoplasma gondii is an obligate intracellular parasite infecting one third of the world’s population. The small intestine is the parasite’s primary route of infection, although the pathway of epithelium transmigration remains unclear. Using an in vitro invasion assay and live imaging we showed that T. gondii (RH) tachyzoites infect and transmigrate between adjacent intestinal epithelial cells in polarized monolayers without altering barrier integrity, despite eliciting the production of specific inflammatory mediators and chemokines. During invasion, T. gondii co-localized with occludin. Reducing the levels of endogenous cellular occludin with specific small interfering RNAs significantly reduced the ability of T. gondii to penetrate between and infect epithelial cells. Furthermore, an in vitro invasion and binding assays using recombinant occludin fragments established the capacity of the parasite to bind occludin and in particular to the extracellular loops of the protein. These findings provide evidence for occludin playing a role in the invasion of T. gondii in small intestinal epithelial cells

Interaction between Plasmodium glycosylphosphatidylinositol and the host protein moesin has no implication in malaria pathology

Glycosylphosphatidylinositol (GPI) anchor of Plasmodium falciparum origin is considered an important toxin leading to severe malaria pathology through stimulation of pro-inflammatory responses from innate immune cells. Even though the GPI-induced immune response is widely described to be mediated by pattern recognition receptors such as TLR2 and TLR4, previous studies have revealed that these two receptors are dispensable for the development of severe malaria pathology. Therefore, this study aimed at the identification of potential alternative Plasmodium GPI receptors. Herein, we have identified the host protein moesin as an interaction partner of Plasmodium GPI in vitro. Given previous reports indicating the relevance of moesin especially in the LPS-mediated induction of pro-inflammatory responses, we have conducted a series of in vitro and in vivo experiments to address the physiological relevance of the moesin-Plasmodium GPI interaction in the context of malaria pathology. We report here that although moesin and Plasmodium GPI interact in vitro, moesin is not critically involved in processes leading to Plasmodium- induced pro-inflammatory immune responses or malaria-associated cerebral pathology

Tissue factor/FVIIa activates Bcl-2 and prevents doxorubicin-induced apoptosis in neuroblastoma cells

<p>Abstract</p> <p>Background</p> <p>Tissue factor (TF) is a transmembrane protein that acts as a receptor for activated coagulation factor VII (FVIIa), initiating the coagulation cascade. Recent studies demonstrate that expression of tumor-derived TF also mediates intracellular signaling relevant to tumor growth and apoptosis. Our present study investigates the possible mechanism by which the interaction between TF and FVIIa regulates chemotherapy resistance in neuroblastoma cell lines.</p> <p>Methods</p> <p>Gene and siRNA transfection was used to enforce TF expression in a TF-negative neuroblastoma cell line and to silence endogenous TF expression in a TF-overexpressing neuroblastoma line, respectively. The expression of TF, Bcl-2, STAT5, and Akt as well as the phosphorylation of STAT5 and Akt in gene transfected cells or cells treated with JAK inhibitor and LY294002 were determined by Western blot assay. Tumor cell growth was determined by a clonogenic assay. Cytotoxic and apoptotic effect of doxorubicin on neuroblastoma cell lines was analyzed by WST assay and annexin-V staining (by flow cytometry) respectively.</p> <p>Results</p> <p>Enforced expression of TF in a TF-negative neuroblastoma cell line in the presence of FVIIa induced upregulation of Bcl-2, leading to resistance to doxorubicin. Conversely, inhibition of endogenous TF expression in a TF-overexpressing neuroblastoma cell line using siRNA resulted in down-regulation of Bcl-2 and sensitization to doxorubicin-induced apoptosis. Additionally, neuroblastoma cells expressing high levels of either endogenous or transfected TF treated with FVIIa readily phosphorylated STAT5 and Akt. Using selective pharmacologic inhibitors, we demonstrated that JAK inhibitor I, but not the PI3K inhibitor LY294002, blocked the TF/FVIIa-induced upregulation of Bcl-2.</p> <p>Conclusion</p> <p>This study shows that in neuroblastoma cell lines overexpressed TF ligated with FVIIa produced upregulation of Bcl-2 expression through the JAK/STAT5 signaling pathway, resulting in resistance to apoptosis. We surmise that this TF-FVIIa pathway may contribute, at least in part, to chemotherapy resistance in neuroblastoma.</p

Vaccines against toxoplasma gondii : challenges and opportunities

Development of vaccines against Toxoplasma gondii infection in humans is of high priority, given the high burden of disease in some areas of the world like South America, and the lack of effective drugs with few adverse effects. Rodent models have been used in research on vaccines against T. gondii over the past decades. However, regardless of the vaccine construct, the vaccines have not been able to induce protective immunity when the organism is challenged with T. gondii, either directly or via a vector. Only a few live, attenuated T. gondii strains used for immunization have been able to confer protective immunity, which is measured by a lack of tissue cysts after challenge. Furthermore, challenge with low virulence strains, especially strains with genotype II, will probably be insufficient to provide protection against the more virulent T. gondii strains, such as those with genotypes I or II, or those genotypes from South America not belonging to genotype I, II or III. Future studies should use animal models besides rodents, and challenges should be performed with at least one genotype II T. gondii and one of the more virulent genotypes. Endpoints like maternal-foetal transmission and prevention of eye disease are important in addition to the traditional endpoint of survival or reduction in numbers of brain cysts after challenge

Toxoplasma gondii effectors are master regulators of the inflammatory response

Toxoplasma is a highly successful parasite that establishes a life-long chronic infection. To do this, it must carefully regulate immune activation and host cell effector mechanisms. Here we review the latest developments in our understanding of how Toxoplasma counteracts the immune response of the host, and in some cases provokes it, through the use of specific parasite effector proteins. An emerging theme from these discoveries is that Toxoplasma effectors are master regulators of the pro-inflammatory response, which elicits many of the toxoplasmacidal mechanisms of the host. We speculate that combinations of these effectors present in certain Toxoplasma strains work to maintain an optimal parasite burden in different hosts to ensure parasite transmission.Knights Templar Eye Foundation, Inc.American Heart Association (0835099N)Massachusetts Life Sciences Center (New Investigator Award)Singapore-MIT Alliance for Research and Technology (SMART)National Institutes of Health (U.S.) (NIH RO1-AI080621)New England Regional Center of Excellence for Biodefense and Emerging Infectious Diseases (NERCE Developmental Grant)National Cancer Institute (U.S.) (Irvington Postdoctoral Fellowship Program

The role of DNA microarrays in Toxoplasma gondii research, the causative agent of ocular toxoplasmosis

Ocular toxoplasmosis, which is caused by the protozoan parasite Toxoplasma gondii, is the leading cause of retinochoroiditis. Toxoplasma is an obligate intracellular pathogen that replicates within a parasitophorous vacuole. Infections are initiated by digestion of parasites deposited in cat feces or in undercooked meat. Parasites then disseminate to target tissues that include the retina where they then develop into long-lived asymptomatic tissue cysts. Occasionally, cysts reactivate and growth of newly emerged parasites must be controlled by the host’s immune system or disease will occur. The mechanisms by which Toxoplasma grows within its host cell, encysts, and interacts with the host’s immune system are important questions. Here, we will discuss how the use of DNA microarrays in transcriptional profiling, genotyping, and epigenetic experiments has impacted our understanding of these processes. Finally, we will discuss how these advances relate to ocular toxoplasmosis and how future research on ocular toxoplasmosis can benefit from DNA microarrays