Ga(III) pyridinecarboxylate complexes: potential analogues of the second generation of therapeutic Ga(III) complexes?

A series of novel Ga(III)-pyridine carboxylates ([Ga(Pic)3]·H2O (GaPic; HPic = picolinic acid), H3O[Ga(Dpic)2]·H2O (GaDpic; H2Dpic = dipicolinic acid), [Ga(Chel)(H2O)(OH)]2·4H2O (GaChel; H2Chel = chelidamic acid) and [Ga(Cldpic)(H2O)(OH)]2 (GaCldpic; H2Cldpic = 4-chlorodipicolinic acid)) have been synthesized by simple one-step procedure. Vibrational spectroscopy (mid-IR), elemental analysis, thermogravimetric analysis and X-ray diffraction confirmed complexes molecular structure, inter and intramolecular interactions and their influence to spectral and thermal properties. Moreover, complex species speciation was described in Ga(III)-HPic and Ga(III)-H2Dpic systems by potentiometry and 1H NMR spectroscopy and mononuclear complex species were determined; [Ga(Pic)2]+ (logβ021 = 16.23(6)), [Ga(Pic)3] (logβ031 = 20.86(2)), [Ga(Dpic)2]- (logβ021 = 15.42(9)) and [Ga(Dpic)2(OH)]2- (logβ-121 = 11.08(4)). To confirm the complexes stability in 1% DMSO (primary solvent for biological testing), timescale 1H NMR spectra were measured (immediately after dissolution up to 96 h). Antimicrobial activity evaluated by IC50 (0.05 mM) is significant for GaDpic and GaCldpic against difficult to treat and multi-resistant P. aeruginosa. On the other hand, the GaPic complex is most effective against Jurkat, MDA-MB-231 and A2058 cancer cell lines and significantly also decreases the HepG2 cancer cells viability at 75 and 100 μM concentrations in a relatively short time (up to 48 h). In addition, fluorescence measurements have been used to elucidate bovine serum albumin binding activity between ligands, Ga(III) complexes and bovine serum albumin.

Targeting acute myeloid leukemia cells by CD33 receptor-specific MoS2-based nanoconjugates

Acute myeloid leukemia (AML) is a highly aggressive type of cancer caused by the uncontrolled proliferation of undifferentiated myeloblasts, affecting the bone marrow and blood. Systemic chemotherapy is considered the primary treatment strategy; unfortunately, healthy cells are also affected to a large extent, leading to severe side effects of this treatment. Targeted drug therapies are becoming increasingly popular in modern medicine, as they bypass normal tissues and cells. Two-dimensional MoS₂-based nanomaterials have attracted attention in the biomedical field as promising agents for cancer diagnosis and therapy. Cancer cells typically (over)express distinctive cytoplasmic membrane-anchored or -spanning protein-based structures (e.g., receptors, enzymes) that distinguish them from healthy, non-cancerous cells. Targeting cancer cells via tumor-specific markers using MoS₂-based nanocarriers loaded with labels or drugs can significantly improve specificity and reduce side effects of such treatment. SKM-1 is an established AML cell line that has been employed in various bio-research applications. However, to date, it has not been used as the subject of studies on selective cancer targeting by inorganic nanomaterials. Here, we demonstrate an efficient targeting of AML cells using MoS₂nanoflakes prepared by a facile exfoliation route and functionalized with anti-CD33 antibody that binds to CD33 receptors expressed by SKM-1 cells. Microscopic analyses by confocal laser scanning microscopy supplemented by label-free confocal Raman microscopy proved that (anti-CD33)-MoS₂conjugates were present on the cell surface and within SKM-1 cells, presumably having been internalized via CD33-mediated endocytosis. Furthermore, the cellular uptake of SKM-1 specific (anti-CD33)-MoS₂conjugates assessed by flow cytometry analysis was significantly higher compared with the cellular uptake of SKM-1 nonspecific (anti-GPC3)-MoS₂conjugates. Our results indicate the importance of appropriate functionalization of MoS₂nanomaterials by tumor-recognizing elements that significantly increase their specificity and hence suggest the utilization of MoS₂-based nanomaterials in the diagnosis and therapy of AML.

Overexpression of GRP78/BiP in P-Glycoprotein-Positive L1210 Cells is Responsible for Altered Response of Cells to Tunicamycin as a Stressor of the Endoplasmic Reticulum

P-glycoprotein (P-gp, ABCB1 member of the ABC (ATP-binding cassette) transporter family) localized in leukemia cell plasma membranes is known to reduce cell sensitivity to a large but well-defined group of chemicals known as P-gp substrates. However, we found previously that P-gp-positive sublines of L1210 murine leukemia cells (R and T) but not parental P-gp-negative parental cells (S) are resistant to the endoplasmic reticulum (ER) stressor tunicamycin (an N-glycosylation inhibitor). Here, we elucidated the mechanism of tunicamycin resistance in P-gp-positive cells. We found that tunicamycin at a sublethal concentration of 0.1 µM induced retention of the cells in the G1 phase of the cell cycle only in the P-gp negative variant of L1210 cells. P-gp-positive L1210 cell variants had higher expression of the ER stress chaperone GRP78/BiP compared to that of P-gp-negative cells, in which tunicamycin induced larger upregulation of CHOP (C/EBP homologous protein). Transfection of the sensitive P-gp-negative cells with plasmids containing GRP78/BiP antagonized tunicamycin-induced CHOP expression and reduced tunicamycin-induced arrest of cells in the G1 phase of the cell cycle. Taken together, these data suggest that the resistance of P-gp-positive cells to tunicamycin is due to increased levels of GRP78/BiP, which is overexpressed in both resistant variants of L1210 cells.

Screening of Phenanthroquinolizidine Alkaloid Derivatives for Inducing Cell Death of L1210 Leukemia Cells with Negative and Positive P-glycoprotein Expression

We describe the screening of a set of cryptopleurine derivatives, namely thienoquinolizidine derivatives and (epi-)benzo analogs with bioactive phenanthroquinolizidine alkaloids that induce cytotoxic effects in the mouse lymphocytic leukemia cell line L1210. We used three variants of L1210 cells: i) parental cells (S) negative for P-glycoprotein (P-gp) expression; ii) P-glycoprotein positive cells (R), obtained by selection with vincristine; iii) P-glycoprotein positive cells (T), obtained by stable transfection with a human gene encoding P-glycoprotein. We identified the most effective derivative 11 with a median lethal concentration of ≈13 μM in all three L1210 cell variants. The analysis of the apoptosis/necrosis induced by derivative 11 revealed that cell death was the result of apoptosis with late apoptosis characteristics. Derivative 11 did not induce a strong alteration in the proportion of cells in the G1, S or G2/M phase of the cell cycle, but a strong increase in the number of S, R and T cells in the subG1 phase was detected. These findings indicated that we identified the most effective inducer of cell death, derivative 11, and this derivative effectively induced cell death in S, R and T cells at similar inhibitory concentrations independent of P-gp expression.

Cold plasma treatment triggers antioxidative defense system and induces changes in hyphal surface and subcellular structures of Aspergillus flavus

The cold atmospheric-pressure plasma (CAPP) has become one of the recent effective decontamination technologies, but CAPP interactions with biological material remain the subject of many studies. The CAPP generates numerous types of particles and radiations that synergistically affect cells and tissues differently depending on their structure. In this study, we investigated the effect of CAPP generated by diffuse coplanar surface barrier discharge on hyphae of Aspergillus flavus. Hyphae underwent massive structural changes after plasma treatment. Scanning electron microscopy showed drying hyphae that were forming creases on the hyphal surface. ATR-FTIR analysis demonstrated an increase of signal intensity for C=O and C-O stretching vibrations indicating chemical changes in molecular structures located on hyphal surface. The increase in membrane permeability was detected by the fluorescent dye, propidium iodide. Biomass dry weight determination and increase in permeability indicated leakage of cell content and subsequent death. Disintegration of nuclei and DNA degradation confirmed cell death after plasma treatment. Damage of plasma membrane was related to lipoperoxidation that was determined by higher levels of thiobarbituric acid reactive species after plasma treatment. The CAPP treatment led to rise of intracellular ROS levels detected by fluorescent microscopy using 2',7'-dichlorodihydrofluorescein diacetate. At the same time, antioxidant enzyme activities increased, and level of reduced glutathione decreased. The results in this study indicated that the CAPP treatment in A. flavus targeted both cell surface structures, cell wall, and plasma membrane, inflicting injury on hyphal cells which led to subsequent oxidative stress and finally cell death at higher CAPP doses.

Properties of anaerobic fungi isolated from several habitats: complexity of phenotypes

Isolates of anaerobic fungi from rumen, animal faeces and compost displayed morphological similarity with known anaerobic fungi. According to their ITS sequences, species were related to Neocallimastix and Piromyces. Rumen fungi tolerated exposure to an aerobic atmosphere for at least four days. Under anaerobic conditions, they could grow on both, defined or complex substrates. Growth in liquid media was monitored by the continuous measurement of metabolic gases (O2, CO2, H2, CO, H2S, CH4). Monitored metabolism was complex, showed that both CO2 and H2 were produced and subsequently consumed by yet unknown metabolic pathway(s). CO and H2S were evolved similarly, but not identically with the generation of CO2 and H2 suggesting their connection with energetic metabolism. Anaerobic fungi from snail faeces and compost produced concentrations of H2S, H2, CO near the lower limit of detection. The rumen isolates produced cellulases and xylanases with similar pH and temperature optima. Proteolytic enzymes were secreted as well. Activities of some enzymes of the main catabolic pathways were found in cell-free homogenates of mycelia. The results indicate the presence of the pentose cycle, the glyoxylate cycle and an incomplete citrate cycle in these fungi. Differences between isolates indicate phenotypic variability between anaerobic fungi.

Reduced UDP-glucose Levels Are Associated with P-glycoprotein Over-expression in L1210 Cells and Limit Glucosylceramide Synthase Activity

BACKGROUND/AIM

P-glycoprotein (Pgp) expression in neoplastic cells is known to reduce cell sensitivity to several cytotoxic Pgp substrates. A member of the ABC transporter family, Pgp, represents the most frequently described membrane efflux pump and its expression in neoplastic cells is responsible for multi-drug resistance. Several lines of evidence indicate that the expression and increased function of both Pgp and glucosylceramide synthase (GCS, an enzyme responsible for ceramide pathway de-activation in the regulation of apoptosis progression) enhance the resistance of Pgp-positive cells. Previously, we described a reduction in the uridine diphosphate (UDP)-glucose contents of mouse leukemia cells (R) expressing Pgp due to vincristine selection compared to parental L1210 cells (S). The reduced availability of UDP-glucose as a glucose donor in R cell glycosylation reactions could limit GCS-catalyzed ceramide glycosylation. Consequently, the over-expression of Pgp in Pgp-positive L1210 cells may be associated with reduced ceramide glycosylation.

MATERIALS AND METHODS

To test this idea, we measured the expression and activities of Pgp and GCS, UDP-glucose levels, cellular uptake of C12-NBD-ceramide (a fluorescent analogue of ceramide) and ceramide-induced cell death in S and R cells. T-cells, another Pgp-positive variant of L1210 cells that express Pgp due to their transfection with a gene encoding human Pgp were also used in this study.

RESULTS

We detected significantly reduced levels of C12-NBD-ceramide glycosylation and reduced UDP-glucose contents in Pgp-positive R and T-cells compared to S cells. C12-NBD-ceramide uptake assays revealed nearly identical dynamics of uptake time-dependency curves. The Pgp-positive L1210 variants (R and T) are more sensitive than Pgp-negative S cells to ceramide-induced cell damage, as measured by an fluorescein isothiocyanate-labeled annexin V and propidium iodide apoptosis necrosis kit. Short chain C2-ceramide was more effective at inducing cell damage than ceramide analogues with longer chains.

CONCLUSION

These evidence indicates that the down-regulation of UDP-glucose contents in Pgp-positive L1210 cells is responsible for their collateral sensitivity to ceramide-induced apoptosis.

Ca2+-dependent induction of conidiation in submerged cultures of Trichoderma viride

The presence of Ca2+ (up to 0.1 mol/L) in the cultivation media was found to induce the formation of conidia in submerged mycelia of Trichoderma viride in a concentration-dependent manner. Ca2+ dramatically stimulated conidiation after 70 h of cultivation. The effect was present in the dark, and illumination stimulated it only marginally. Low (less than 100 μmol/L) Ca2+ concentrations induced the formation of chlamydospores. Sr2+ could substitute Ca2+ in conidiogenesis with lower efficiency (almost 2 orders of magnitude), while the efficiency of Mg2+, Mn2+, or Ba2+ was lower by almost 3 orders of magnitude. Our results demonstrate that mycelial Ca2+ homeostasis has powerful effects on the conidiation and mycelial morphogenesis in T. viride, and they suggest that there is an additional mechanism of conidiation in addition to those induced by light and starvation.