Alzheimer disease (AD) is a disabling and highly prevalent neurodegenerative condition, for which there are no effective therapies. Soluble oligomers of the amyloid-beta peptide (AβOs) are thought to be proximal neurotoxins involved in early neuronal oxidative stress and synapse damage, ultimately leading to neurodegeneration and memory impairment in AD. The aim of the current study was to evaluate the neuroprotective potential of mesenchymal stem cells (MSCs) against the deleterious impact of AβOs on hippocampal neurons. To this end, we established transwell co-cultures of rat hippocampal neurons and MSCs. We show that MSCs and MSC-derived extracellular vesicles (EVs) protect neurons against AβO-induced oxidative stress and synapse damage, revealed by loss of pre- and post-synaptic markers. Protection by MSCs entails three complementary mechanisms: (1) internalization and degradation of AβOs, (2) release of EVs containing active catalase, and (3) selective secretion of IL-6, IL-10 and VEGF to the medium. Results support the notion that MSCs may represent a promising alternative for cellbased therapies in AD.

The parasitic protozoan Trypanosoma cruzi employs multiple molecular strategies to invade a broad range of nonphagocytic cells. Here we demonstrate that the invasion of human primary umbilical vein endothelial cells (HUVECs) or Chinese hamster ovary (CHO) cells overexpressing the B₂ type of bradykinin receptor (CHO-B₂R) by tissue culture trypomastigotes is subtly modulated by the combined activities of kininogens, kininogenases, and kinin-degrading peptidases. The presence of captopril, an inhibitor of bradykinin degradation by kininase II, drastically potentiated parasitic invasion of HUVECs and CHO-B₂R, but not of mock-transfected CHO cells, whereas the B₂R antagonist HOE 140 or monoclonal antibody MBK3 to bradykinin blocked these effects. Invasion competence correlated with the parasites9 ability to liberate the short-lived kinins from cell-bound kininogen and to elicit vigorous intracellular free calcium ([Ca²⁺]_i) transients through B₂R. Invasion was impaired by membrane-permeable cysteine proteinase inhibitors such as Z-(SBz)Cys-Phe-CHN₂ but not by the hydrophilic inhibitor 1-trans-epoxysuccinyl-l-leucyl-amido-(4-guanidino) butane or cystatin C, suggesting that kinin release is confined to secluded spaces formed by juxtaposition of host cell and parasite plasma membranes. Analysis of trypomastigote transfectants expressing various cysteine proteinase isoforms showed that invasion competence is linked to the kinin releasing activity of cruzipain, herein proposed as a factor of virulence in Chagas9 disease.

Protozoa of the genusLeishmaniacause a wide variety of pathologies ranging from self-healing skin lesions to visceral damage, depending on the parasite species. The outcome of infection depends on the quality of the adaptive immune response, which is determined by parasite factors and the host genetic background. Innate responses, resulting in the generation of mediators with anti-leishmanial activity, contribute to parasite control and help the development of efficient adaptive responses. Among those, the potential contribution of members of the Toll-like receptors (TLRs) family in the control ofLeishmaniainfections started to be investigated about a decade ago. Although most studies appoint a protective role for TLRs, there is growing evidence that in some cases, TLRs facilitate infection. This review highlights recent advances in TLR function duringLeishmaniainfections and discusses their potential role in restraining parasite growth versus yielding disease.

The major isoform of Trypanosoma cruzi cysteinyl proteinase (cruzipain) has generated Lys-bradykinin (Lys-BK or kallidin), a proinflammatory peptide, by proteolysis of kininogen. The releasing of this peptide was demonstrated by mass spectrometry, radioimmunoassay, and ileum contractile responses. The kinin-releasing activity was immunoabsorbed selectively by monoclonal antibodies to the characteristic COOH-terminal domain of cruzipain. To determine the hydrolysis steps that account for the kininogenase activity of cruzipain, we synthesized a fluorogenic peptide (o-aminobenzoyl-Leu-Gly-Met-Ile-Ser-Leu-Met-Lys-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg³⁸⁹-Ser³⁹⁰-Ser-Arg-Ile-NH₂) based on the sequence Leu³⁷³ to Ile³⁹³ of the human high molecular weight kininogen. The hydrolysis products from this peptide were isolated by high performance liquid chromatography, and Lys-BK was characterized as the major released kinin by mass spectrometry. Intramolecularly quenched fluorogenic peptides spanning the Met³⁷⁹-Lys³⁸⁰ and Arg³⁸⁹-Ser³⁹⁰ bradykinin-flanking sequences were then used to assess the substrate specificity requirements of the parasite-derived protease compared with two COOH-terminal truncated recombinant isoforms (cruzain and cruzipain 2). In contrast to the high catalytic efficiency of parasite-derived cruzipain, the recombinant proteinases cleaved the bradykinin-flanking sites at markedly different rates. In addition, we also demonstrated that cruzipain activates plasmatic prekallikrein, which would be a second and indirect way of the parasite protease to release bradykinin.

There has been a very limited number of high throughput screening campaigns carried out with Leishmania drug targets. In part, this is due to the small number of suitable target genes that have been shown by genetic or chemical methods to be essential for the parasite. In this perspective, we discuss the state of genetic target validation in the field of Leishmania research and review the 200 Leishmania genes and 36 Trypanosoma cruzi genes for which gene deletion attempts have been made since the first published case in 1990. We define a quality score for the different genetic deletion techniques that can be used to identify potential drug targets. We also discuss how the advances in genome-scale gene disruption techniques have been used to assist target based and phenotypic based drug development in other parasitic protozoa and why Leishmania has lacked a similar approach so far. The prospects for this scale of work are considered in the context of the application of CRISPR/Cas9 gene editing as a useful tool in Leishmania.

The intracellular protozoan Trypanosoma cruzi causes Chagas' disease, a chronic illness associated with cardiomyopathy and digestive disorders. This pathogen invades mammalian cells by signaling them through multiple transduction pathways. We previously showed that cruzipain, the main cysteine protease of T. cruzi , promotes host cell invasion by activating kinin receptors. Here, we report a cruzipain-mediated invasion route that is not blocked by kinin receptor antagonists. By testing different strains of T. cruzi , we observed a correlation between the level of cruzipain secreted by trypomastigotes and the capacity of the pathogen to invade host cells. Consistent with a role for cruzipain, the cysteine protease inhibitor N -methylpiperazine-urea-Phe-homophenylalanine-vinylsulfone-benzene impaired the invasion of human smooth muscle cells by strains Dm28c and X10/6 but not by the G isolate. Cruzipain-rich supernatants of Dm28c trypomastigotes enhanced the infectivity of isolate G parasites twofold, an effect which was abolished by the cysteine protease inhibitor l - trans -epoxysuccinyl-leucylamido-(4-guanidino)butane and by thapsigargin, a drug that induces depletion of the intracellular Ca ²⁺ stores. The enhancement due to Dm28 supernatants was abolished upon cruzipain immunodepletion, and the activity was restored by purified cruzipain. In contrast, supernatants from isolate G trypomastigotes (with low levels of cruzipain) or supernatants from Dm28c epimastigotes or purified cruzipain alone did not enhance parasite invasion, indicating that the protease is required but not sufficient to engage this invasion pathway. We provide evidence that activation of this pathway requires cruzipain-mediated processing of a trypomastigote molecule associated with parasite-shed membranes. Our results couple cruzipain to host cell invasion through a kinin-independent route and further suggest that high-level cruzipain expression may contribute to parasite infectivity.