Anabela Cordeiro da Silva

Biological properties of extracellular vesicles and their physiological functions.

In the past decade, extracellular vesicles (EVs) have been recognized as potent vehicles of intercellular communication, both in prokaryotes and eukaryotes. This is due to their capacity to transfer proteins, lipids and nucleic acids, thereby influencing various physiological and pathological functions of both recipient and parent cells. While intensive investigation has targeted the role of EVs in different pathological processes, for example, in cancer and autoimmune diseases, the EV-mediated maintenance of homeostasis and the regulation of physiological functions have remained less explored. Here, we provide a comprehensive overview of the current understanding of the physiological roles of EVs, which has been written by crowd-sourcing, drawing on the unique EV expertise of academia-based scientists, clinicians and industry based in 27 European countries, the United States and Australia. This review is intended to be of relevance to both researchers already working on EV biology and to newcomers who will encounter this universal cell biological system. Therefore, here we address the molecular contents and functions of EVs in various tissues and body fluids from cell systems to organs. We also review the physiological mechanisms of EVs in bacteria, lower eukaryotes and plants to highlight the functional uniformity of this emerging communication system.

Evidence-Based Clinical Use of Nanoscale Extracellular Vesicles in Nanomedicine

Recent research has demonstrated that all body fluids assessed contain substantial amounts of vesicles that range in size from 30 to 1000 nm and that are surrounded by phospholipid membranes containing different membrane microdomains such as lipid rafts and caveolae. The most prominent representatives of these so-called extracellular vesicles (EVs) are nanosized exosomes (70-150 nm), which are derivatives of the endosomal system, and microvesicles (100-1000 nm), which are produced by outward budding of the plasma membrane. Nanosized EVs are released by almost all cell types and mediate targeted intercellular communication under physiological and pathophysiological conditions. Containing cell-type-specific signatures, EVs have been proposed as biomarkers in a variety of diseases. Furthermore, according to their physical functions, EVs of selected cell types have been used as therapeutic agents in immune therapy, vaccination trials, regenerative medicine, and drug delivery. Undoubtedly, the rapidly emerging field of basic and applied EV research will significantly influence the biomedicinal landscape in the future. In this Perspective, we, a network of European scientists from clinical, academic, and industry settings collaborating through the H2020 European Cooperation in Science and Technology (COST) program European Network on Microvesicles and Exosomes in Health and Disease (ME-HAD), demonstrate the high potential of nanosized EVs for both diagnostic and therapeutic (i.e., theranostic) areas of nanomedicine.

Deception and Manipulation: The Arms of Leishmania, a Successful Parasite

Leishmania spp. are intracellular parasitic protozoa responsible for a group of neglected tropical diseases, endemic in 98 countries around the world, called leishmaniasis. These parasites have a complex digenetic life cycle requiring a susceptible vertebrate host and a permissive insect vector, which allow their transmission. The clinical manifestations associated with leishmaniasis depend on complex interactions between the parasite and the host immune system. Consequently, leishmaniasis can be manifested as a self-healing cutaneous affliction or a visceral pathology, being the last one fatal in 85–90% of untreated cases. As a result of a long host–parasite co-evolutionary process, Leishmania spp. developed different immunomodulatory strategies that are essential for the establishment of infection. Only through deception and manipulation of the immune system, Leishmania spp. can complete its life cycle and survive. The understanding of the mechanisms associated with immune evasion and disease progression is essential for the development of novel therapies and vaccine approaches. Here, we revise how the parasite manipulates cell death and immune responses to survive and thrive in the shadow of the immune system.

Activation of Phosphatidylinositol 3-Kinase/Akt and Impairment of Nuclear Factor-κB: Molecular Mechanisms Behind the Arrested Maturation/Activation State of Leishmania infantum-Infected Dendritic Cells

Understanding the complex interactions between Leishmania and dendritic cells (DCs) is central to the modulation of the outcome of this infection, given that an effective immune response against Leishmania is dependent on the successful activation and maturation of DCs. We report here that Leishmania infantum promastigotes successfully infect mouse bone marrow-derived DCs without triggering maturation, as shown by a failure in the up-regulation of CD40 and CD86 expression, and that parasites strongly counteract the lipopolysaccharide-triggered maturation of DCs. A small increase in interleukin (IL)-12 and IL-10 transcription and secretion and a decrease in IL-6 were observed in infected cells. This arrested DC maturation state is actively promoted by parasites because heat-killed or fixed parasites increased cytokine and costimulatory molecule expression. At a molecular level, L. infantum rapidly induced activation of phosphatidylinositol 3-kinase/Akt and extracellular signal-regulated kinase 1/2, whereas no effect was observed in the c-Jun N-terminal kinase and p38 mitogen-activated protein kinase proinflammatory pathways. Moreover, parasites actively promoted cleavage of the nuclear factor-κB p65(RelA) subunit, causing its impairment. The blockade of phosphatidylinositol 3-kinase/Akt by either treatment of bone marrow-derived DCs with wortmannin or transfection with an Akt dominant-negative mutant resulted in a strong decrease in infection rates, revealing for the first time a crucial role of this pathway on Leishmania engulfment by DCs. Overall, our data indicate that activation of Akt and impairment of nuclear factor-κB are responsible for immunogenicity subversion of L. infantum-infected DCs.

Leishmania infantum modulates host macrophage mitochondrial metabolism by hijacking the SIRT1-AMPK axis

Metabolic manipulation of host cells by intracellular pathogens is currently recognized to play an important role in the pathology of infection. Nevertheless, little information is available regarding mitochondrial energy metabolism in Leishmania infected macrophages. Here, we demonstrate that during L. infantum infection, macrophages switch from an early glycolytic metabolism to an oxidative phosphorylation, and this metabolic deviation requires SIRT1 and LKB1/AMPK. SIRT1 or LBK1 deficient macrophages infected with L. infantum failed to activate AMPK and up-regulate its targets such as Slc2a4 and Ppargc1a, which are essential for parasite growth. As a result, impairment of metabolic switch caused by SIRT1 or AMPK deficiency reduces parasite load in vitro and in vivo. Overall, our work demonstrates the importance of SIRT1 and AMPK energetic sensors for parasite intracellular survival and proliferation, highlighting the modulation of these proteins as potential therapeutic targets for the treatment of leishmaniasis.

Synthesis and anti-parasitic activity of a novel quinolinone-chalcone series

A series of novel quinolinone-chalcone hybrids and analogues were designed, synthesized and their biological activity against the mammalian stages of Trypanosoma brucei and Leishmania infantum evaluated. Promising molecular scaffolds with significant microbicidal activity and low cytotoxicity were identified. Quinolinone-chalcone 10 exhibited anti-parasitic properties against both organisms, being the most potent anti-L. infantum agent of the entire series (IC50 value of 1.3±0.1 μM). Compounds 4 and 11 showed potency toward the intracellular, amastigote stage of L. infantum (IC50 values of 2.1±0.6 and 3.1±1.05 μM, respectively). Promising trypanocidal compounds include 5 and 10 (IC50 values of 2.6±0.1 and 3.3±0.1 μM, respectively) as well as 6 and 9 (both having IC50 values of <5 μM). Chemical modifications on the quinolinone-chalcone scaffold were performed on selected compounds in order to investigate the influence of these structural features on antiparasitic activity.

In vitro evaluation of bisnaphthalimidopropyl derivatives loaded into pegylated nanoparticles against Leishmania infantum protozoa.

Bisnaphthalimidopropyl (BNIP) derivatives have recently been shown to have potential as antileishmanial agents. However, these compounds have some drawbacks, including their low aqueous solubility and some toxic effects. In this study, we designed a drug delivery system for enhanced delivery of BNIP derivative compounds whilst reducing adverse toxic effects, and hence increasing their biological efficacy. A coated drug delivery system based on polymeric nanoparticles of pegylated poly(lactic acid) (PLA), a biodegradable polymer, was successfully achieved. The pegylated PLA nanoformulations loaded with BNIP derivatives were evaluated in an in vitro model of intracellular amastigotes in murine J774 and human THP-1 cells for visceral leishmaniasis using luciferase-expressing Leishmania infantum parasites. Pegylation of PLA nanoparticles significantly reduced the capacity of empty nanoparticles in inhibiting intracellular parasite growth. The BNIP derivatives BNIPDadec and BNIPDaoct exhibited EC(50) values (concentration of compound necessary to decrease cell viability to 50% of the untreated control) of ca. 4.5 μM for THP-1 and J774 cells and ca. 9.0 μM for mouse bone marrow-derived macrophages. Nanoparticle encapsulation of the BNIP derivative compounds decreased their toxicity towards macrophages by ≥10-fold as evaluated by the MTT assay. The antileishmanial activity of free BNIPDadec was 1.02±0.41 μM and 0.73±0.06 μM for THP-1 and J774 macrophages, respectively. Pegylation of PLA nanoparticles loaded with BNIPDadec resulted in EC(50) values of 1.43±0.63 μM and 1.79±0.77 μM for THP-1 and J774 macrophages, respectively. A similar trend was observed for free BNIPDaoct and pegylated BNIPDaoct PLA nanoparticles (2.43±0.19 μM and 1.23±0.40 μM for THP-1 macrophages and 1.36±0.17 μM and 1.52±0.57 μM for J774 macrophages). The nanoformulations were more efficient in reducing parasitic growth inside human macrophages than in murine cells, suggesting host cell-dependent metabolism.

Aurones: A Promising Heterocyclic Scaffold for the Development of Potent Antileishmanial Agents

A series of (Z)-2-benzylidenebenzofuran-3-(2H)-ones (aurones) bearing a variety of substituents on rings A and B were synthesized and evaluated for their antiparasitic activity against the intracellular amastigote form of Leishmania infantum and their cytotoxicity against human THP1-differentiated macrophages. In general, aurones bearing no substituents on ring A (compounds 4a–4f) exhibit higher toxicity than aurones with 4,6-dimethoxy substitution (compounds 4g–4l). Among the latter, two aurones possessing a 2′-methoxy or a 2′-methyl group (compounds 4i and 4j) exhibit potent antileishmanial activity (IC50 = 1.3 ± 0.1 μM and IC50 = 1.6 ± 0.2 μM, resp.), comparable to the activity of the reference drug Amphotericin B, whereas they present significantly lower cytotoxicity than Amphotericin B as deduced by the higher selectivity index.

Seroepidemiological survey of Leishmania infantum infection in dogs from northeastern Portugal.

Northeastern Portugal is a region where canine leishmaniasis (CanL) is endemic. In this study, a sero-epidemiological survey was conducted in 654 dogs from that geographical area. Serum samples were evaluated by the direct agglutination test (DAT) and also by enzyme-linked immunosorbent assay (ELISA) using five different defined antigens. Seroprevalence of infection was 21.3% based on the assumption that seropositive animals were positive for at least three tests. A high degree of agreement was found between DAT and LAM-ELISA (89%; kappa value [κ] = 0.67). A statistically significant difference (p<0.05) of seropositivity was found between adult (23.4%) and juvenile dogs (12.2%), apparently healthy (14.8%) and sick dogs (40.2%), vaccinated (19.7%) and non-vaccinated (41.2%) animals, seropositive (26.9%) and seronegative (18.0%) for Toxoplasma gondii, living in rural (18.5%) or urban (32.6%) areas, and between animals living exclusively outdoors (18.2%) and those living in a mixed habitat (27.5%). Risk factors for canine Leishmania infection, as defined by multiple logistic regression analysis, were of clinical status (odds ratio [OR] = 3.1) and Toxoplasma infection (OR = 1.5).

CLONING OF A LEISHMANIA MAJOR GENE ENCODING FOR AN ANTIGEN WITH EXTENSIVE HOMOLOGY TO RIBOSOMAL PROTEIN S3A

Following purification by affinity chromatography, a Leishmania major S-hexylglutathione- binding protein of molecular mass 66kDa was isolated. The immune serum against the parasite 66kDa polypeptide when used to screen a L. major cDNA library could identify clones encoding for the human v-fos transformation effector homologue, namely ribosomal protein S3a, and thus was named LmS3a-related protein (LmS3arp). A 1027bp cDNA fragment was found to contain the entire parasite gene encoding for a highly basic protein of 30kDa calculated molecular mass sharing homology to various ribosomal S3a proteins from different species. Using computer methods for a multiple alignment and sequence motif search, we found that LmS3arp shares a sequence homology to class theta glutathione S-transferase mainly in a segment containing critical residues involved in glutathione binding. These new findings are discussed in the light of recent published data showing multiple function(s) of the ribosomal proteins S3a.