Intracellular glutathione level and efflux in human melanoma and cervical cancer cells differing in doxorubicin resistance.

INTRODUCTION: Drug resistance continues to be a major problem in cancer treatment. Occurrence of this phenomenon is often associated with altered levels of glutathione (GSH) and GSH-related enzymes. The aim of the study was to evaluate the possible involvement of GSH and GSH-related enzymes in doxorubicin (DOX) resistance in two types of cancer cells of different etiology, from both parental and DOX-resistant sublines. MATERIALS AND METHODS: The human melanoma (ME18 and ME18/R) and cervical cancer cells (HeLa and KB-V1) were tested in terms of their DOX sensitivity (EZ4U test), GSH level (HPLC) and its efflux (spectrofluorometrically). The effects of inhibition of the GSH-related enzymes γ-glutamylcysteine synthetase (γ-GCS) and glutathione S-transferase (GST) were also evaluated. RESULTS: Exposure to DOX caused an increase of GSH levels in all tested cells except for HeLa cells. However, depletion of GSH did not have a significant influence on the sensitivity of the cells to DOX. Inhibition of the activity of GST also did not have a major effect on DOX sensitivity, although it caused changes of the GSH content. Our attempts to use the spectrofluorometric method for measurements of GSH efflux were not successful. It could be suggested that in ME18 and HeLa cells treated with DOX, GSH efflux does occur. DISCUSSION: The obtained results seem to refute the hypothesis of a central role of GSH in DOX resistance of the tested cells. Despite observations of different effects related to GSH, they do not seem to be essential in terms of DOX resistance. The mechanisms underlying DOX resistance are highly cell-specific.

Assessment of the genotoxic activity of alpha-asarone and its derivatives in the comet assay.

In our previous paper we examined mutagenic and genotoxic activity of 4 alpha-asarone isomers 2-5 exhibiting relatively high hypolipidemic activity. In the present paper, we examined genotoxic activity of alpha-asarone and its isomers as the ability to damage cellular DNA, evaluated in the comet assay. Additionally, mutagenic activity of alpha-asarone in Ames test has been examined. The Ames test for alpha-asarone was carried out in accordance with the guidelines of the PN-EN ISO 10993-3 standard. Compounds 4 and 5 were found to be devoid of any genotoxic activity while maintaining their hypolipemic potential. Because mutagenic activity of compound 4 was also minor it could be considered as a candidate for further pharmacological evaluation. Genotoxic but not mutagenic activity of alpha-asarone has been confirmed.

Quality and Purity of L929 Cell Cultures: Isoenzyme Profiles As a Sensitive Marker of Cross-Contamination.

Objective: Inappropriate handling of cells can generate modifications in the genomic DNA. The additional risk is cross-contamination. Isoenzyme analysis with gel agarose electrophoresis is a known, fast, and cheap technique for detection of species-specific isoforms of intracellular enzymes. The aim of the experimental work was to check if variations in the cell growth conditions can affect morphology and/or nuclear anomalies including micronuclei (MN) in the L929 cells; and to define how sensitive and selective is the classic gel agarose electrophoresis for analysis of isoforms of the selected enzymes to detect cross-contamination of L929 cultures with HeLa cells or with the related species, such as CHO-K1 cells, in the case of unavailability of the commercial kits. Methods: The experiments were done with use of the National Collection of Type Cultures clone 929 (L929)-mouse fibroblasts from subcutaneous connective tissue; HeLa-human cervix adenocarcinoma; and CHO-K1-epithelial-like hamster ovary cells. Cell morphology was evaluated with a light/fluorescence microscope. MN were determined with the cytokinesis-block micronucleus assay, and the isoenzyme analysis was performed using gel agarose electrophoresis. Results: As shown, the overgrown cultures result in a significant increase of the MN in the L929 cells. The band patterns for lactate dehydrogenate, glucose-6-phosphate dehydrogenase, or malate dehydrogenase allow identification of the single L929, HeLa, or CHO-K1 cell line and to detect the cross-contamination, even up to 0.4%. Conclusions: There can be no exceptions from the recommended cell culture conditions in the passage scheme. The sensitivity of the gel agarose separation depends on the cells and on the type of enzyme tested and seems to be sufficient in a quick screening of the CHO-K1, L929, or HeLa cell cultures through the possible mutual contamination.

The application of an in vitro micronucleus test in mouse fibroblast L929 cells.

The MNa (in vitro the micronucleus assay) is recommended for studying genotoxicity of chemicals. However, no protocol is currently available for experiments with mouse fibroblast L929 cells. The aim of this study was to improve the scope of CBMNb (cytokinesis-block micronucleus) test. Optimization consisted of: selection of a non-cytotoxic concentration of cytokinesis blocker - cytoBc (cytochalasin B) and type and definition of the positive controls, verification of the efficacy of phenobarbital/5,6-benzoflavone as an S9 enzyme inducer as well as the identification of an optimal staining method. The compounds were tested in three exposure regimens: 6 h exposure with S9 activation followed by a 24 h recovery period, 6 h exposure followed by a 24 h recovery without metabolic activation of S9 and 30 h continuous exposure without S9. Different parameters, such as internal and interlaboratory reproducibility were investigated and criteria for test correctness were proposed. Higher MN rates were achieved using 1 µg/mL cytoBc as a cytokinesis blocker, and MMSd (methyl methanesulfonate), (250 µM), Cole (colchicine), (0.5 µM) and CPf (cyclophosphamide), (30 µM) as positive controls. In regard to the recommended S9 inducer, phenobarbital/5,6-benzoflavone was more effective as Aroclor 1254. Giemsa and acridine orange stains were optimal for the evaluation of MN formation. The protocol described in this study with L929 cells produced the reliable results and is suitable for performing the CBMNb experiments according to the current OECD Guideline #487.

Nanohydrogel with N,N'-bis(acryloyl)cystine crosslinker for high drug loading.

Substantially improved hydrogel particles based on poly(N-isopropylacrylamide) (pNIPA) have been obtained. First, as a result of replacing commercially available N,N'-bis(acryloyl)cystamine (BAC), the crosslinker, with acryloyl derivative of cystine containing a carboxylic group (BISS), the hydrogel particles acquired improved stability vs. ionic strength and allowed further chemical modification of the chains, including the attachment of drug molecules. Next, a redox-initiated aqueous precipitation polymerization via the semi-batch method was used. This led to substantially increased BISS content and diminished size of the nanoparticles that made them suitable to an endocytic process. In addition, the obtained nanogels revealed high loading capacity of anticancer drug vs. dry gel (circa 16%) and they exhibited much better stability and enhanced drug release under the typical conditions existing in cancer cells. Size of obtained nanogels was investigated by dynamic light scattering (DLS). It appeared that nanoparticle size was in the range from ca. 40 to 200nm. In 0.01M solution of glutathione (GSH) the -S-S- bonds were reduced and the nanogel particles were degraded. This could be seen in obtained SEM and TEM micrographs. The cytotoxicity investigation against the HeLa cells showed that DOX loaded nanogels were more cytotoxic (IC50=0.51µM) than free DOX (IC50=0.83µM), while unloaded nanogels did not inhibit proliferation of the cells. It was also found that the nanogels loaded with DOX reached a high intracellular concentration in HeLa cells just after 2h while free DOX needed 6h for that.

Role of thiamine in Huntington's disease pathogenesis: In vitro studies.

BACKGROUND: Oxidative stress accompanies neurodegeneration and also causes abnormalities in thiaminedependent processes. These processes have been reported to be diminished in the brains of patients with several neurodegenerative diseases. OBJECTIVES: The aim of this work was to conduct a comparative analysis of the impact of supplemented thiamine on the viability of human B lymphocytes with CAG abnormal expanded huntingtin gene (mHTT) (GM13509) and control, B lymphocytes without mHTT (GM14467) through the following studies: determination of the supplemented thiamine concentrations, which are effective for cell growth stimulation after incubation in thiamine deficit conditions; determination of cell capability to intake the exogenous thiamine; evaluation of exogenous thiamine influence on the profile of the genes related to thiamine and energy metabolism; determination of ATP synthesis and activities of thiamine-dependent enzymes, KGDHC and BCKDHC in the intact cells and upon the exogenous thiamine. MATERIAL AND METHODS: The following methods were used: EZ4U test for cell growth analysis; HPLC for determination of thiamine intake and ATP synthesis, qRT-PCR for evaluation of the gene profiles and spectrophotometric method for KGDHC and BCKDHC activities determination. RESULTS: Maximal cell growth stimulation was observed at 2.5 mM in GM14467 up to 135% of the control culture and at 5.0 mM in GM13509 cells up to 165% of the control culture. Native levels of total ATP and KGDHC and BCKDHC activities in both cell types were comparable and did not changed upon thiamine deficit or supplementation. GM13509 cells showed more of an increase in growth stimulation upon thiamine supplementation than GM14467 cells and this effect was reflected in the increase of intracellular thiamine concentration. CONCLUSIONS: The above results and reported changes in expression of GAPDH, IDH1 and SLC19A3 genes observed upon thiamine deficit conditions suggest that intracellular thiamine status and energy metabolism can have a role in HD pathogenesis.

Doxorubicin Treatment of Cancer Cells Impairs Reverse Transcription and Affects the Interpretation of RT-qPCR Results.

BACKGROUND: Doxorubicin (DOX) acts in a variety of ways including DNA damage and enzyme inhibition, which consequently causes changes in gene expression of cells treated with this agent. Practical validation of experimental results followed by appropriate normalization of the factors investigated is crucial for obtaining biologically relevant results in gene expression studies. MATERIALS AND METHODS: Six candidates were evaluated regarding their validity as internal reference genes: RPS23, FLOT2, UBB, ABCF1, ACTB, HPRT1. Optimization for quantitative polymerase reaction (qPCR) included: sensitivity, specificity, amplification efficiency and linear dynamic range determination. The gene expression stability was evaluated by real-time quantitative polymerase reaction (RT-qPCR) in two human cervical cancer cell lines: HeLa and DOX-resistant KB-V1 Cells treated under various concentrations of DOX. RESULTS: DOX treatment changed gene expression and led to re-optimization of the cDNA template amounts. ACTB, HPRT1, RPS23 and FLOT2 are proposed to be sufficient as internal reference genes. CONCLUSION: DOX may alter the reverse transcription and amplification reactions of RT-qPCR, thus creating a risk of misinterpretation of gene expression results.

Up-regulation of glutathione-related genes, enzyme activities and transport proteins in human cervical cancer cells treated with doxorubicin.

Doxorubicin (DOX), one of the most effective anticancer drugs, acts in a variety of ways including DNA damage, enzyme inhibition and generation of reactive oxygen species. Glutathione (GSH) and glutathione-related enzymes including: glutathione peroxidase (GPX), glutathione reductase (GSR) and glutathione S-transferases (GST) may play a role in adaptive detoxification processes in response to the oxidative stress, thus contributing to drug resistance phenotype. In this study, we investigated effects of DOX treatment on expression and activity of GSH-related enzymes and multidrug resistance-associated proteins in cultured human cervical cancer cells displaying different resistance against this drug (HeLa and KB-V1). Determination of expression level of genes encoding GST isoforms and MRP proteins (GCS, GPX, GSR, GSTA1-3, GSTM1, GSTP1, ABCC1-3, MGST1-3) was performed using StellARray™ Technology. Enzymatic activities of GPX and GSR were measured using biochemical methods. Expression of MRP1 was examined by immunofluorescence microscopy. This study showed that native expression levels of GSTM1 and GSTA3 were markedly higher in KB-V1 cells (2000-fold and 200-fold) compared to HeLa cells. Resistant cells have also shown significantly elevated expression of GSTA1 and GSTA2 genes (200-fold and 50-fold) as a result of DOX treatment. In HeLa cells, exposure to DOX increased expression of all genes: GSTM1 (7-fold) and GSTA1-3 (550-fold, 150-fold and 300-fold). Exposure to DOX led to the slight increase of GCS expression as well as GPX activity in KB-V1 cells, while in HeLa cells it did not. Expression of ABCC1 (MRP1) was not increased in any of the tested cell lines. Our results indicate that expression of GSTM1 and GSTA1-3 genes is up-regulated by DOX treatment and suggest that activity of these genes may be associated with drug resistance of the tested cells. At the same time, involvement of MRP1 in DOX resistance in the given experimental conditions is unlikely.

Formation and preclinical evaluation of a new alloplastic injectable bone substitute material.

Alloplastic bone substitute materials are raising some more interest as an alternative for autologic transplants and xenogenic materials especially in oral surgery over the last few years. These non-immunogenic and completely resorbable biomaterials are the basis for complete and predictable guided bone regeneration. In the majority of cases, such a material is chosen because of its convenient application by surgeons. The main objective of our project was to design and fabricate an osteoconductive, injectable and readily tolerable by human tissues biomaterial for guided bone regeneration. For this purpose, a self-setting composite consisting of chitosan/tricalcium phosphate microparticles and sodium alginate was made. The material obtained was characterized by microsphere and agglomerate morphology and microstructure. Its features relating to setting time and mechanical properties were precisely investigated. Our material was also evaluated according to PN-EN ISO 10993 Biological evaluation of medical devices, i.e., the in vitro tests for genotoxicity and cytotoxicity were conduced. Then, the following examinations were performed: subchronic systemic toxicity, skin sensitization, irritation and delayed-type hypersensitivity and local effects after implantation. The material tested showed a high degree of cytocompatibility, fulfilled the requirements of International Standards and seemed to be a "user friendly" material for oral surgeons.