The Role of Bcl-2 and Beclin-1 Complex in "Switching" between Apoptosis and Autophagy in Human Glioma Cells upon LY294002 and Sorafenib Treatment

BACKGROUND

Gliomas are the most malignant tumors of the central nervous system. One of the factors in their high drug resistance is avoiding programmed death (PCD) induction. This is related to the overexpression of intracellular survival pathways: PI3K-Akt/PKB-mTOR and Ras-Raf-MEK-ERK. Apoptosis and autophagy are co-existing processes due to the interactions between Bcl-2 and beclin-1 proteins. Their complex may be a molecular "toggle-switch" between PCD types. The aim of this research was to investigate the role of Bcl-2:beclin-1 complex in glioma cell elimination through the combined action of LY294002 and sorafenib.

METHODS

Drug cytotoxicity was estimated with an MTT test. The type of cell death was evaluated using variant microscopy techniques (fluorochrome staining, immunocytochemistry, and transmission electron microscopy), as well as the Bcl-2:beclin-1 complex formation and protein localization. Molecular analysis of PCD indicators was conducted through immunoblotting, immunoprecipitation, and ELISA testing. SiRNA was used to block Bcl-2 and beclin-1 expression.

RESULTS

The results showed the inhibitors used in simultaneous application resulted in Bcl-2:beclin-1 complex formation and apoptosis becoming dominant. This was accompanied by changes in the location of the tested proteins.

CONCLUSIONS

"Switching" between apoptosis and autophagy using PI3K and Raf inhibitors with Bcl-2:beclin-1 complex formation opens new therapeutic perspectives against gliomas.

Cellular Localization of Selected Porphyrins and Their Effect on the In Vitro Motility of Human Colon Tumors and Normal Cells

Standard therapies for colorectal cancer cannot eliminate or sufficiently reduce the metastasis process. Photodynamic therapy (PDT) may be an alternative to minimizing this problem. Here, we examined the cellular localization of selected porphyrins and determined whether free-base and manganese (III) metallated porphyrins may limit colon cancer cells' (HT29) or normal colon epithelial cells' (CCD 841 CoTr) motility in vitro. White light irradiation was used to initiate the photodynamic effect. Porphyrin uptake by the cells was determined by porphyrin fluorescence measurements through the use of confocal microscopy. Free-base porphyrin was found in cells, where it initially localized at the edge of the cytoplasm and later in the perinuclear area. The concentrations of porphyrins had no effect on cancer cell migration but had a significant effect on normal cell motility. Due to the low concentrations of porphyrins used, no changes in F-actin filaments of the cellular cytoskeleton were detected. Signal transmission via connexons between neighbouring cells was limited to a maximum of 40 µm for HT29 and 30 µm for CCD 841 CoTr cells. The tested porphyrins differed in their activity against the tumor and normal cells' migration capacity. Depending on the porphyrin used and the type of cells, their migration changed in relation to the control sample. The use of white light may change the activity of the porphyrins relative to the migratory capacity of the cells. The aim of the present study was to analyse the intracellular localization of tested porphyrins and their influence on the mobility of cells after irradiation with harmless white light.

Identification of a novel alternatively spliced isoform of the ribosomal uL10 protein

Alternative splicing is one of the key mechanisms extending the complexity of genetic information and at the same time adaptability of higher eukaryotes. As a result, the broad spectrum of isoforms produced by alternative splicing allows organisms to fine-tune their proteome; however, the functions of the majority of alternatively spliced protein isoforms are largely unknown. Ribosomal protein isoforms are one of the groups for which data are limited. Here we report characterization of an alternatively spliced isoform of the ribosomal uL10 protein, named uL10β. The uL10 protein constitutes the core element of the ribosomal stalk structure within the GTPase associated center, which represents the landing platform for translational GTPases - trGTPases. The stalk plays an important role in the ribosome-dependent stimulation of GTP by trGTPases, which confer unidirectional trajectory for the ribosome, allosterically contributing to the speed and accuracy of translation. We have shown that the newly identified uL10β protein is stably expressed in mammalian cells and is primarily located within the nuclear compartment with a minor signal within the cytoplasm. Importantly, uL10β is able to bind to the ribosomal particle, but is mainly associated with 60S and 80S particles; additionally, the uL10β undergoes re-localization into the mitochondria upon endoplasmic reticulum stress induction. Our results suggest a specific stress-related dual role of uL10β, supporting the idea of existence of specialized ribosomes with an altered GTPase associated center.

Heteromorphism of stamens in monoclinous flowers of Tinantia erecta (Jacq.) Fenzl as an example of high variability of the androecium in the Commelinaceae family

Representatives of the family Commelinaceae are characterised by morphologically, anatomically, or functionally diverse stamens (common presence of staminodia), which produce diverse pollen grains. The heteromorphism of stamens noted in all Commelinaceae species is a particular example of the evolutionary modification of the androecium in entomophilous plants. The morphological, anatomical, and cytological analyses of the androecium as well as the analysis of the microsporogenesis process and the formation of the male gametophyte in Tinantia erecta (a species belonging to the family Commelinaceae) have demonstrated that the morphologically diverse stamens in this species do not differ anatomically. Furthermore, the process of microsporogenesis followed by gametogenesis occurring in the stamens yields pollen grains with the same morphology, cytology, and function. Therefore, despite the large morphological diversity of the androecium, all anthers in T. erecta produce male gametophytes that are identical in every respect, which is a unique feature in species from the Commelinaceae family. Additionally, T. erecta is capable of self-pollination; hence, it can be claimed that the species uses its entire reproductive potential to produce seeds and a next generation.

Impact of Protoporphyrin Lysine Derivatives on the Ability of Nosema ceranae Spores to Infect Honeybees

Simple Summary

Honeybees, which are important for the development and maintenance of natural ecosystems, are infected by microsporidia, Nosema apis and N. ceranae. These parasites induce a disease named nosemosis contributing to the impairment of digestion and nutrient absorption, ultimately leading to total colony collapse. The need for research into the control of N. ceranae has become increasingly important. Promising compounds for the treatment of nosemosis are porphyrins. In the present study, we examined the effects of three different porphyrins on the infectivity of N. ceranae microsporidia. A significantly lower level of infection was observed in the bees infected with the porphyrin-treated spores than in the control bees (infected with untreated spores). We showed that protoporphyrin lysine derivatives in particular prevented the development of Nosema spores and simultaneously extended bee life spans (up to 50%). The results also indicate that these porphyrins may contribute to the reduction in digestive nutrient absorption disorders in bees. The present findings can be used to develop a new class of drugs for combating nosemosis. These compounds may serve as preventive or disinfection agents through direct inactivation of Nosema both in the midgut and outside the host body, i.e., in the hive.

Abstract

The effect of two protoporphyrin IX derivatives conjugated with single (PP[Lys(TFA)-OH)]₂) or double (PP[Lys(TFA)-Lys(TFA)-OH]₂) lysine moieties on the infectious capacity of Nosema ceranae spores was examined, and their efficacies were compared with those of a cationic porphyrin (H₂TTMePP). Honeybees were inoculated with spores preincubated with porphyrins or with untreated spores (control). A significantly lower level of infection was observed in the bees infected with the porphyrin-treated spores than in the infected control. Porphyrins 1 and 2 reduced the infectious capability of microsporidia more efficiently than porphyrin 3, with bee mortality declining to almost 50%. Confocal analysis of the midguts of infected bees revealed distinct differences in the number of spores between the control group and the group infected with PP[Lys(TFA)-Lys(TFA)-OH]₂-treated spores. Notably, bees with a reduced level of infection consumed less sucrose syrup than the control bees, indicating a reduction in digestive disorders and an improvement in food absorption.

Bioactivity studies of porphyrinoids against microsporidia isolated from honeybees

Microsporidian infections are dangerous to honeybees due to the absence of an efficient treatment for nosemosis. In the present work, the abilities of several porphyrins to directly inactivate microsporidia derived from Nosema-infected honeybees were studied in vitro. Amide derivatives of protoporphyrin IX (PPIX) conjugated with one and two amino acid moieties were synthesized, and their activities were compared with those of two cationic porphyrins, TMePyP and TTMePP. The most active porphyrins, PP[Lys-Asp]₂, PP[Lys-TFA]₂, PP[Asp(ONa)₂]₂ and PP[Lys-Lys]₂ at concentrations as low as 10–50 µM exerted significant effects on microsporidia, reducing the number of spores by 67–80% compared to the control. Live-cell imaging of the spores treated with porphyrins showed that only 1.6% and 3.0% of spores remained alive after 24 h-incubation with 50 µM PP[Asp(ONa)₂]₂ and PP[Lys-Asp]₂, respectively. The length of the amino acid side chains and their identity in the PPIX molecules affected the bioactivity of the porphyrin. Importantly, the irradiation of the porphyrins did not enhance their potency in destroying Nosema spores. We showed that the porphyrins accumulated inside the living spores but not inside dead spores, thus the destruction of the microsporidia by non-metallated porphyrins is not dependent on photosensitization, but is associated with their active transport into the spore cell. When administered to honeybees in vivo, PPIX[Lys-TFA]₂ and PPIX[Lys-Lys]₂ reduced spore loads by 69–76% in infected individuals. They both had no toxic effect on honeybees, in contrast to zinc-coordinated porphyrin.

Intraphagolysosomal conditions predispose to Staphylococcus epidermidis small colony variants persistence in macrophages

Staphylococcus epidermidis small colony variants can survive inside macrophages and their survival has been proposed as a pivotal process in the pathogenesis of biomaterial associated infections. In the present study the intracellular location of clinical isolates of SCV and parental wild type strains inside macrophages was determined. Furthermore, the effect of IFN-γ and rapamycin on the level of SCV/WT as well as lysosomes colocalisation and iNOS induction in THP-activated macrophages in response to WT and SCV strains of Staphylococcus epidermidis were examined. It was demonstrated that SCV strain of S. epidermidis can survive and persist inside macrophages and its intracellular survival is supported by the induction of phagosomal acidification. The ability to reduce the high proportion of LysoTracker positive SCV containing phagosomes was exclusively found when IFN-γ was used. The findings suggest that IFN-γ mediates SCV killing via two distinct mechanisms, phagosome alkalisation and an increased iNOS synthesis, so the cytokine may control S. epidermidis WT and SCV infection in macrophages. Staphylococcus epidermidis SCV is a less potent stimulus of iNOS than the WT strain and the feature may help SCV to persist in hostile environment of macrophages. Rapamycin treatment did not influence the iNOS synthesis but reduced the percentage of both bacterial strains within acidic organelles. However, the percentage of SCV within LysoTracker positive organelles, even though reduced comparing to non-primed cells, was higher than in the WT strain indicating that Staphylococcus epidermidis possesses unique metabolic features allowing SCV to survive within macrophages.

Changing of biochemical parameters and cell wall polysaccharides distribution during physiological development of tomato fruit

This study was aimed at discovering an impact of biochemical parameters (like content of cell wall polysaccharides, phenolic compounds, ascorbic acid or activity of pectinolytic enzymes) on cell wall microstructure during physiological fruit development. Cell wall microstructure as well as changes in the polysaccharides distribution were examined by confocal Raman microscopy. Also there was a need to simultaneous usage of reference method which is immunolabeling. A tomato fruit (Solanum lycopersicum cv Cerise) has been selected to observe the changes taking place in the fruit cell wall as it recently has been recognized as a model species for exploring fruit development processes such as fruit formation and ripening. Our studies showed that chemical images allows to depict changes in spatial distribution of polysaccharides in plant cell wall (including the middle lamella area), thus this technique allows to observation of cell wall degradation during tomato ripening (mainly pectic polysaccharides degradation). It seems that high level of pectinolytic enzymes activity and increasing content of ascorbate and hence decrease of pectins content have a significant impact on spatial distribution of biopolymers in fruit cell wall.

Host-dependent symbiotic efficiency of Rhizobium leguminosarum bv. trifolii strains isolated from nodules of Trifolium rubens

Trifolium rubens L., commonly known as the red feather clover, is capable of symbiotic interactions with rhizobia. Up to now, no specific symbionts of T. rubens and their symbiotic compatibility with Trifolium spp. have been described. We characterized the genomic diversity of T. rubens symbionts by analyses of plasmid profiles and BOX-PCR. The phylogeny of T. rubens isolates was inferred based on the nucleotide sequences of 16S rRNA and two core genes (atpD, recA). The nodC phylogeny allowed classification of rhizobia nodulating T. rubens as Rhizobium leguminosarum symbiovar trifolii (Rlt). The symbiotic efficiency of the Rlt isolates was determined on four clover species: T. rubens, T. pratense, T. repens and T. resupinatum. We determined that Rlt strains formed mostly inefficient symbiosis with their native host plant T. rubens and weakly effective (sub-optimal) symbiosis with T. repens and T. pratense. The same Rlt strains were fully compatible in the symbiosis with T. resupinatum. T. rubens did not exhibit strict selectivity in regard to the symbionts and rhizobia closely related to Rhizobium grahamii, Rhizobium galegae and Agrobacterium radiobacter, which did not nodulate Trifolium spp., were found amongst T. rubens nodule isolates.

Cytological and biophysical comparative analysis of cell structures at the microsporogenesis stage in sterile and fertile Allium species

Using a live-cell-imaging approach and autofluorescence-spectral imaging, we showed quantitative/qualitative fluctuations of chemical compounds within the meiocyte callose wall, providing insight into the molecular basis of male sterility in plants from the genus Allium. Allium sativum (garlic) is one of the plant species exhibiting male sterility, and the molecular background of this phenomenon has never been thoroughly described. This study presents comparative analyses of meiotically dividing cells, which revealed inhibition at the different microsporogenesis stages in male-sterile A. sativum plants (cultivars Harnas and Arkus) and sterile A. ampeloprasum var. ampeloprasum (GHG-L), which is phylogenetically related to garlic. Fertile species A. ampeloprasum (leek) was used as the control material, because leek is closely related to both garlic and GHG-L. To shed more light on the molecular basis of these disturbances, autofluorescence-spectral imaging of live cells was used for the assessment of the biophysical/biochemical differences in the callose wall, pollen grain sporoderm, and the tapetum in the sterile species, in comparison with the fertile leek. The use of techniques for live-cell imaging (autofluorescence-spectral imaging) allowed the observation of quantitative/qualitative fluctuations of autofluorescent chemical compounds within the meiocyte callose wall. The biophysical characterisation of the metabolic disturbances in the callose wall provides insight into the molecular basis of male sterility in A. sativum. In addition, using this method, it was possible for the first time, to determine precisely (on the basis of fluctuations of autofluorescence compounds) the meiosis stage in which normal microsporogenesis is disturbed, which was not visible using light microscopy.

Galleria mellonella lysozyme induces apoptotic changes in Candida albicans cells

The greater wax moth Galleria mellonella has been increasingly used as a model host to determine Candida albicans virulence and efficacy of antifungal treatment. The G. mellonella lysozyme, similarly to its human counterpart, is a member of the c-type family of lysozymes that exhibits antibacterial and antifungal activity. However, in contrast to the relatively well explained bactericidal action, the mechanism of fungistatic and/or fungicidal activity of lysozymes is still not clear. In the present study we provide the direct evidences that the G. mellonella lysozyme binds to the protoplasts as well as to the intact C. albicans cells and decreases the survival rate of both these forms in a time-dependent manner. No enzymatic activity of the lysozyme towards typical chitinase and β-glucanase substrates was detected, indicating that hydrolysis of main fungal cell wall components is not responsible for anti-Candida activity of the lysozyme. On the other hand, pre-treatment of cells with tetraethylammonium, a potassium channel blocker, prevented them from the lysozyme action, suggesting that lysozyme acts by induction of programmed cell death. In fact, the C. albicans cells treated with the lysozyme exhibited typical apoptotic features, i.e. loss of mitochondrial membrane potential, phosphatidylserine exposure in the outer leaflet of the cell membrane, as well as chromatin condensation and DNA fragmentation.

Tubulin cytoskeleton during microsporogenesis in the male-sterile genotype of Allium sativum and fertile Allium ampeloprasum L

KEY MESSAGE

Microsporogenesis in garlic. The male-sterile Allium sativum (garlic) reproduces exclusively in the vegetative mode, and anthropogenic factors seem to be the cause of the loss of sexual reproduction capability. There are many different hypotheses concerning the causes of male sterility in A.sativum; however, the mechanisms underlying this phenomenon have not been comprehensively elucidated.Numerous attempts have been undertaken to understand the causes of male sterility, but the tubulin cytoskeleton in meiotically dividing cells during microsporogenesis has never been investigated in this species. Using sterile A.sativum genotype L13 and its fertile close relative A. ampeloprasum (leek), we have analysed the distribution of the tubulin cytoskeleton during microsporogenesis. We observed that during karyokinesis and cytokinesis, in both meiotic divisions I and II, the microtubular cytoskeleton in garlic L13 formed configurations that resembled tubulin arrangement typical of monocots. However, the tubulin cytoskeleton in garlic was distinctly poorer (composed of a few MT filaments) compared with that found in meiotically dividing cells in A. ampeloprasum. These differences did not affect the course of karyogenesis, chondriokinesis, and cytokinesis, which contributed to completion of microsporogenesis, but there was no further development of the male gametophyte. At the very beginning of the successive stage of development of fertile pollen grains, i.e. gametogenesis, there were disorders involving the absence of a normal cortical cytoskeleton and dramatically progressive degeneration of the cytoplasm in garlic. Therefore,we suggest that, due to disturbances in cortical cytoskeleton formation at the very beginning of gametogenesis, the intracellular transport governed by the cytoskeleton might be perturbed, leading to microspore decay in the male-sterile garlic genotype.