Extracellular Vesicles from Scedosporium apiospermum Mycelial Cells: Implication for Fungal-Host Interplays

The release of extracellular vesicles (EVs) has been implicated as an alternative transport mechanism for the passage of macromolecules through the fungal cell wall, a phenomenon widely reported in yeasts but poorly explored in mycelial cells. In the present work, we have purified and characterized the EVs released by mycelia of the emerging, opportunistic, widespread and multidrug-resistant filamentous fungus Scedosporium apiospermum. Transmission electron microscopy images and light scattering measurements revealed the fungal EVs, which were observed individually or grouped with heterogeneous morphology, size and electron density. The mean diameter of the EVs, evaluated by the light scattering technique, was 179.7 nm. Overall, the structural stability of S. apiospermum EVs was preserved during incubation under various storage conditions. The lipid, carbohydrate and protein contents were quantified, and the EVs' protein profile was evidenced by SDS-PAGE, revealing proteins with molecular masses ranging from 20 to 118 kDa. Through immunoblotting, ELISA and immunocytochemistry assays, antigenic molecules were evidenced in EVs using a polyclonal serum (called anti-secreted molecules) from a rabbit inoculated with conditioned cell-free supernatant obtained from S. apiospermum mycelial cells. By Western blotting, several antigenic proteins were identified. The ELISA assay confirmed that the anti-secreted molecules exhibited a positive reaction up to a serum dilution of 1:3200. Despite transporting immunogenic molecules, S. apiospermum EVs slightly induced an in vitro cytotoxicity effect after 48 h of contact with either macrophages or lung epithelial cells. Interestingly, the pretreatment of both mammalian cells with purified EVs significantly increased the association index with S. apiospermum conidia. Furthermore, EVs were highly toxic to Galleria mellonella, leading to larval death in a typically dose- and time-dependent manner. Collectively, the results represent the first report of detecting EVs in the S. apiospermum filamentous form, highlighting a possible implication in fungal pathogenesis.

Ultrastructural viewpoints on the interaction events of Scedosporium apiospermum conidia with lung and macrophage cells

BACKGROUND

Scedosporium apiospermum is a ubiquitous, emerging and multidrug-resistant fungal pathogen with still rather unknown virulence mechanisms.

OBJECTIVES/METHODS

The cellular basis of the in vitro interaction between fungi and host cells/tissues is the determinant factor for the development of a successful in vivo infection. Herein, we evaluated the interaction of S. apiospermum conidia with lung epithelial (A549), lung fibroblast (MRC-5) and RAW 264.7 macrophages by light and scanning/transmission electron microscopy.

FINDINGS

After 4 h of fungi-host cell contact, the percentage of infected mammalian cells and the number of fungi per infected cell was measured by light microscopy, and the following association indexes were calculated for A549, MRC-5 and macrophage cells: 73.2 ± 25.9, 69.7 ± 22.5 and 59.7 ± 11.1, respectively. Both conidia and germinated conidia were regularly observed interacting with the evaluated cells, with a higher prevalence of non-germinated conidia. Interestingly, nests of germinated conidia were evidenced at the surface of lung cells by scanning electron microscopy. Some germination projections and hyphae were seen penetrating/evading the mammalian cells. Furthermore, internalised conidia were seen within vacuoles as visualised by transmission electron microscopy.

MAIN CONCLUSIONS

The present study contributes to a better understanding of S. apiospermum pathogenesis by demonstrating the first steps of the infection process of this opportunistic fungus.

Comparing in vivo biodistribution with radiolabeling and Franz cell permeation assay to validate the efficacy of both methodologies in the evaluation of nanoemulsions: a safety approach

The Franz cells permeation assay has been performed for over 25 years. However, the advent of nanotechnology created a whole new world, especially with regard to topical products. In this new global scenario an increasing number of nanostructure-based delivery systems (NDSs) have emerged and a global warning relating to the safety of these NDSs is arising. This work studied the efficacy of the Franz cells assay, comparing it with the radiolabeling biodistribution test. For this purpose a formulation of sunscreen based on an NDS was developed and characterized. The results demonstrated both that the NDS did not present in vitro cytotoxicity and that the radiolabeling biodistribution test is more precise for the evaluation of NDS cosmetics than the Franz cells assay, since it detected the permeation of the NDS at a picogram order. Due to this fact, and considering all the concerns related to NDSs and nanoparticles in general, more precise methods must be used in order to guarantee the safe use of these new classes of products.

Detection of avian paramyxoviruses in migratory and resident birds in the state of Rio de Janeiro, Brazil

Paramyxoviruses and avian influenza viruses are present worldwide, and wild birds are known natural reservoirs of these viruses. This study monitored the circulation of these viruses in migratory and resident coastal birds captured in the state of Rio de Janeiro, Brazil. In total, 494 birds were trapped, and their fecal samples were collected and inoculated into embryonated chicken eggs. The allantoic fluids were evaluated using a hemagglutination test and PCR amplification of the genes of the M and L proteins of influenza A virus and paramyxovirus, respectively. Avian paramyxovirus was detected in 5 (1.01%) of the birds. The majority of these viruses were isolated from migratory birds classified into the order Charadriiformes (families Scolopacidae and Charadriidae). Four samples were characterized as avian paramyxovirus serotype-2 (APMV-2) by a hemagglutination inhibition test. These results reinforce the importance of continuous surveillance of wild species in Brazil.

Clotrimazole decreases human breast cancer cells viability through alterations in cytoskeleton-associated glycolytic enzymes

Cancer cells are characterized by a high rate of glycolysis, which is their primary energy source. Glycolysis is known to be controlled by allosteric regulators, as well as by reversible binding of glycolytic enzymes to cytoskeleton. Clotrimazole is an anti-fungal azole derivative recently recognized as a calmodulin antagonist with promising anti-cancer effect. Here, we show that clotrimazole induced morphological and functional alterations on human breast cancer derived cell line, MCF-7. The drug decreased cell viability in a dose- and time-dependent manner, exhibiting an IC50 of 88.6+/-5.3 microM and a t0.5 of 89.7+/-7.2 min, with 50 microM clotrimazole. Morphological changes were evident as observed by scanning electron microscopy, which revealed the completely loss of protrusion responsible for cell adhesion after a 180 min of treatment with 50 microM clotrimazole. Giemsa stained cells observed by optical microscopy show morphological alterations and a marked nuclear condensation. These changes occurred in parallel to the detachment of the glycolytic enzymes, 6-phosphofructo-1-kinase and aldolase, from cytoskeleton. After a 45 min treatment with 50 microM clotrimazole, the remaining activities in a cytoskeleton enriched fraction was 16.4+/-3.6% and 41.0+/-15.6% of control for 6-phosphofructo-1-kinase and aldolase, respectively. Immunocytochemistry experiments revealed a decrease in the co-localization of 6-phosphofructo-1-kinase and F-actin after clotrimazole treatment, suggesting the site of detachment of the enzymes. Altogether, our results support evidence for apoptotic events that might be started by clotrimazole involving inhibition of glycolytic flux in MCF-7 cells and makes this drug a promising agent in the fight against human breast cancer.

Direct current decreases cell viability but not P-glycoprotein expression and function in human multidrug resistant leukemic cells

Inhibition of tumor growth induced by treatment with direct current (DC) has been reported in several systems. In the current work, the cellular effects generated by the DC treatment of the human leukemic K562 cell line and its vincristine-resistant derivative K562-Lucena 1 were analyzed by trypan blue staining and transmission electron microscopy. DC stimulation induced cell lysis, alterations in shape, membrane extraction or discontinuity, and intense vacuolization of some cells. In addition, treatment of K562 and K562-Lucena 1 cells caused a marked decrease in viability. Since multidrug resistance is a major factor contributing with failure of chemotherapy in many tumors, the expression and function of P-glycoprotein (P-gp) in K562-Lucena 1 cells were also studied. The expression of mdr1, the gene encoding P-gp, was analyzed by reverse transcription polymerase chain reaction, which showed that this gene was equally expressed in either treated or untreated cells. These results were confirmed by flow cytometry with a monoclonal anti P-gp antibody and the Rhodamine 123 extrusion method, which revealed that P-gp surface expression and function were unaltered after DC treatment. Our results suggest that DC treatment does not affect P-gp in human leukemic cells, but affects their viability by mechanisms that would involve clear cellular effects, but also additional targets, whose relevance in dc treated tumoral cells is currently discussed.

Phytochemical and antioedematogenic studies of commercial copaiba oils available in Brazil

The composition of eight samples of commercial copaiba oils, used in the Amazonian region as antiinflammatory agents and available in popular markets, were analysed by gas chromatography/mass spectrometry (HRGC-MS). Major differences were observed in their chemical composition and some adulterations were pointed out. When tested in vivo oils 1 and 3, and to a lesser extent oil 6, significantly inhibited bradykinin-induced oedema formation. The other tested oils had no effect. When assessed in carrageenan-induced oedema formation, oils 1, 2 and 6, but not oil 3, significantly attenuated the oedema formation. The other tested oils failed to affect carrageenan-induced paw oedema. Oils 1 and 6 were further fractionated and several sesquiterpenes and diterpenes were detected. It is suggested that the naturally occurring sesquiterpenes present in the copaiba oils seem to be responsible for the antiinflammatory action reported in the folk medicine. Furthermore, our results clearly show an adulteration in copaiba oils available in Brazil.

Cellular damage and altered carbohydrate expression in P815 tumor cells induced by direct electric current: an in vitro analysis

Treatment with direct electric current (DC) can inhibit tumor growth in several systems. To evaluate the cellular reactions generated by this treatment, we stimulated mouse mastocytoma P815 cells with DC and examined their viability and ultrastructural characteristics, as well as the effect of DC on surface carbohydrate expression. DC treatment affected cell viability and caused marked alterations in vital structures of P815 cells. Alterations varied depending on the duration of stimulation and polarity of electrode. Anodic and cathodic treatments caused decrease in cell viability, although the latter was more effective in generating cell lysis. DC stimulation also induced changes such as membrane damage, alterations in cell shape and chromatin organization, mitochondrial swelling and condensation, cytoplasmic swelling, and matrix rarefaction. Stimulation of P815 cells without contact with electrodes produced no alterations, suggesting that this contact might be essential for the occurrence of the cellular modifications. DC treatment also altered the membrane distribution of anionic sites of P815 cells, as well as the surface carbohydrate exposition, involving a diminished binding of Concanavalin A to the cell surface after cathodic stimulation, and an increased binding of sialic acid- and fucose-specific lectins after anodic treatment. In this work we describe important cellular targets for the action of DC, which may contribute to the understanding of the mechanisms by which DC supresses several kinds of tumors.

Damage induction by direct electric current in tumoural target cells

Damage induction to tumour target cells (P815) by direct electric current (DC) was investigated. A 6 min treatment of P815 cells with DC generated decreased levels of cell viability and proliferation. The ultrastructural analysis of DC-treated cells revealed the presence of blebs, loss of cell surface filopodia, and ruptures in cell membrane. Mitochondrial alterations, swelling of cells, cytoplasmic matrix rarefaction, and cellular debri formation were also observed. The study shows that tumoural target cells can be damaged by direct electric current and this approach may provide means to understand the mechanism of tumour regression induced by electrochemical therapy.