The c-myc gene regulates the polyamine pathway in DMSO-induced apoptosis

Biopolymer gels as components of protective medium for cryopreservation of spermatogonial stem cells

Biopolymer gels attract a lot of attention in a field of biothechnology due to their excellent compatibility and degradation. Their application is also promising for cryopreservation of spermatogonial stem cells (SSCs) which is so necessary to preserve the fertility of young patients. The aim of the study was to determine the effectiveness of biopolymer gels as a component of cryopreservation medium for SSCs of immature rats at the stage of exposure to cryoprotectants. It was found that 30-min exposure to cryopreservation media based on collagen or fibrin gel with an addition of 5% Me₂SO or 6% glycerol did not lead to significant changes in membrane integrity, cytochrome C content, metabolic, mitochondrial and antioxidant activities in SSCs compared to the control (Leibovitz-based cryomedium). But fibrin gel more than collagen reduced the toxic effects of Me₂SO and glycerol on SSCs increasing exposure time up to 45 min without significant changes in cell viability. The same cryoprotectants in Leibovitz-based media showed significant toxicity starting from the 15th minute of exposure. Necrosis was the main cause of cell death at this stage of cryopreservation in all experimental groups. The obtained results can be used to optimize SSC cryopreservation protocols for further cell autotransplantation for spermatogenesis initiation in boys who undergo gonadotoxic therapy in prepubertal age.

The evaluation of cytotoxicity and cytokine IL-6 production of root canal sealers with and without the incorporation of simvastatin: an invitro study

Background

Freshly mixed root canal sealers when proximate the periapical tissues, trigger varying degrees of cytotoxicity/inflammatory reactions. Simvastatin, a class of the drug statin, is a widely used cholesterol-lowering agent with additional anti-inflammatory activities. This study assessed the effects of simvastatin on cytotoxicity and the release of IL-6 (Interleukin-6) production when incorporated in zinc oxide eugenol and methacrylate resin-based sealers.

Methods

Experimental groups consisted of conventional zinc oxide eugenol and methacrylate based-EndoREZ sealers (ZE & ER respectively) and 0.5 mg/mL simvastatin incorporated sealers (ZES & ERS). L929 mouse fibroblast cells were exposed to freshly mixed experimental sealers and evaluated for cytotoxicity (MTT assay) and inflammation levels (inflammatory marker IL-6 for ELISA) at various time intervals (0h, 24h and 7th day). The values were compared to the cell control (CC; L929 cells alone) and solvent control (SC; L929 cells + DMSO) groups. All the experiments were conducted in triplicates and subjected to statistical analysis using IBM SPSS Statistics software. Non parametric tests were conducted using Kruskal-Wallis and Friedman tests for inter-group and intra-group comparisons respectively. Pairwise comparison was conducted by post hoc Dunn test followed by Bonferroni correction. P values < 0.05 were considered statistically significant.

Results

All the experimental groups (ZE, ER, ZES, ERS) exhibited varying degree of cytotoxicity and IL-6 expression compared to the control groups CC and SC. The cell viability for ZE and ER decreased on day 7 as compared to 24 h. ZES and ERS had higher viable cells (75.93% & 79.90%) compared to ZE and ER (54.39% & 57.84%) at all time periods. Increased expression of IL-6 was observed in ZE & ER (25.49 pg/mL & 23.14 pg/mL) when compared to simvastatin incorporated ZE & ER (ZES-12.70 pg/mL & ERS-14.68 pg/mL) at all time periods. Highest level of cytotoxicity and inflammation was observed in ZE compared to all the other groups on day 7.

Conclusions

Addition of 0.5 mg/mL of simvastatin to the sealers (ZES and ERS) decreased the cytotoxicity in the freshly mixed state and reduces their inflammatory effect.

Dimethyl sulfoxide: a central player since the dawn of cryobiology, is efficacy balanced by toxicity?

Dimethyl sulfoxide (DMSO) is the cryoprotectant of choice for most animal cell systems since the early history of cryopreservation. It has been used for decades in many thousands of cell transplants. These treatments would not have taken place without suitable sources of DMSO that enabled stable and safe storage of bone marrow and blood cells until needed for transfusion. Nevertheless, its effects on cell biology and apparent toxicity in patients have been an ongoing topic of debate, driving the search for less cytotoxic cryoprotectants. This review seeks to place the toxicity of DMSO in context of its effectiveness. It will also consider means of reducing its toxic effects, the alternatives to its use and their readiness for active use in clinical settings.

MYC and tumor metabolism: chicken and egg

Transcription factors of the MYC family are deregulated in the majority of all human cancers. Oncogenic levels of MYC reprogram cellular metabolism, a hallmark of cancer development, to sustain the high rate of proliferation of cancer cells. Conversely, cells need to modulate MYC function according to the availability of nutrients, in order to avoid a metabolic collapse. Here, we review recent evidence that the multiple interactions of MYC with cell metabolism are mutual and review mechanisms that control MYC levels and function in response to metabolic stress situations. The main hypothesis we put forward is that regulation of MYC levels is an integral part of the adaptation of cells to nutrient deprivation. Since such mechanisms would be particularly relevant in tumor cells, we propose that-in contrast to growth factor-dependent controls-they are not disrupted during tumorigenesis and that maintaining flexibility of expression is integral to MYC's oncogenic function.

DMSO Modifies Structural and Functional Properties of RPMI-8402 Cells by Promoting Programmed Cell Death

Apoptosis in lymphoid cells can be induced in different ways depending on cell type and acquired signal. Biochemical modifications occur at an early phase of cell death while at late times the typical morphological features of apoptosis can be visualized. The aim of this study is to verify by multiparametric analyses the plasma membrane fluidity, the intracellular Ca2+ concentration and the nitric oxide synthase (NOS) activity during cell death progression induced by DMSO treatment. The RPMI-8402 human pre-T lymphoblastoid cell line was induced to cell death by DMSO. Analyses rescued at early times of treatment prove a substantial modification of plasma membrane fluidity associated with an increase of intracellular Ca2+. Moreover, these modifications are associated with an up regulation of NOS activity. Our results are consistent with the hypothesis that programmed cell death can be induced by up regulation of the intracellular Ca2+ associated with an increase of cell membrane fluidity. The apoptotic mechanisms seem to involve not only membrane damage and increased intracellular calcium levels but also production of nitric oxide.

Cytotoxicity of dimethyl sulfoxide (DMSO) in direct contact with odontoblast-like cells

OBJECTIVES

To evaluate the cytotoxicity of dimethyl sulfoxide (DMSO) on the repair-related activity of cultured odontoblast-like MDPC-23 cells.

METHODS

Solutions with different concentrations of DMSO (0.05, 0.1, 0.3, 0.5 and 1.0 mM), diluted in culture medium (DMEM), were placed in contact with MDPC-23 cells (5 × 104 cells/cm(2)) for 24 h. Eight replicates (n = 8) were prepared for each solutions for the following methods of analysis: violet crystal dye for cell adhesion (CA), quantification of total protein (TP), alizarin red for mineralization nodules formation (MN) and cell death by necrosis (flow cytometry); while twelve replicates (n = 12) were prepared for viable cell number (Trypan Blue) and cell viability (MTT assay). Data were analyzed by ANOVA and Tukey or Kruskal-Wallis and Mann-Whitney's tests (p < 0.05).

RESULTS

Cell viability, adhesion and percentage of cell death by necrosis were not affected by DMSO at any concentration, with no statistical significant difference among the groups. A significant reduction in total protein production was observed for 0.5 and 1.0 mM of DMSO compared to the control while increased mineralized nodules formation was seen only for 1.0 mM DMSO.

SIGNIFICANCE

DMSO caused no or minor cytotoxic effects on the pulp tissue repair-related activity of odontoblast-like cells.

PAMAM nanoparticles promote acute lung injury by inducing autophagic cell death through the Akt-TSC2-mTOR signaling pathway

Nanotechnology is an important and emerging industry with a projected annual market of around one trillion US dollars by 2011-2015. Concerns about the toxicity of nanomaterials in humans, however, have recently been raised. Although studies of nanoparticle toxicity have focused on lung disease the molecular link between nanoparticle exposure and lung injury remained unclear. In this report, we show that cationic Starburst polyamidoamine dendrimer (PAMAM), a class of nanomaterials that are being widely developed for clinical applications can induce acute lung injury in vivo. PAMAM triggers autophagic cell death by deregulating the Akt-TSC2-mTOR signaling pathway. The autophagy inhibitor 3-methyladenine rescued PAMAM dendrimer-induced cell death and ameliorated acute lung injury caused by PAMAM in mice. Our data provide a molecular explanation for nanoparticle-induced lung injury, and suggest potential remedies to address the growing concerns of nanotechnology safety.

Polyamines and apoptosis

The natural polyamines putrescine, spermidine and spermine are in multiple ways involved in cell growth and the maintenance of cell viability. In the course of the last 15 years more and more evidence hinted also at roles in gene regulation. It is therefore not surprising that the polyamines are involved in events inherent to genetically programmed cell death. Following inhibition of ornithine decarboxylase, a key step in polyamine biosynthesis, numerous links have been identified between the polyamines and apoptotic pathways. Examples of activation and prevention of apoptosis due to polyamine depletion are known for several cell lines. Elevation of polyamine concentrations may lead to apoptosis or to malignant transformation. These observations are discussed in the present review, together with possible mechanisms of action of the polyamines. Contradictory results and incomplete information blur the picture and complicate interpretation. Since, however, much interest is focussed at present on all aspects of programmed cell death, a considerable progress in the elucidation of polyamine functions in apoptotic signalling pathways is expected, even though enormous difficulties oppose pinpointing specific interactions of the polyamines with pro- and anti-apoptotic factors. Such situation is quite common in polyamine research.

Changes of Plasma Membrane Properties in a Human Pre-T Cell Line Undergoing Apoptosis

A variety of cellular functions are modulated by the physical properties of the cell membrane, and the modification of intracellular transfer, resulting from loss of membrane integrity, may contribute toward setting the cell onto the pathway of apoptosis. Apoptosis in lymphoid cells can be induced in different ways and biochemical modifications occur at an early phase of cell death, while the morphological features of apoptosis are evident later. We previously reported that DMSO is an efficient apoptosis-inducing factor in the human RPMI-8402 pre-T cell line. The aim of the present study was to verify the effect of DMSO on the plasma membrane fluidity, the intracellular calcium concentration and the phosphodiesterase activity in DMSO-induced apoptosis. Our results show a modification of membrane fluidity associated with an increase of intracellular Ca(2+) concentration. Moreover, we demonstrate that these modifications are related to a decrease in the phosphodiesterase (PDE) activity. The correlation between the proceedings of added DMSO and the induction of apoptosis will provide significant information regarding the first part of the apoptotic process.

Analysis of polyamines as markers of (patho)physiological conditions

The aliphatic polyamines, putrescine, spermidine and spermine, are normal cell constituents that play important roles in cell proliferation and differentiation. The equilibrium between cellular uptake and release and the balanced activities of biosynthetic and catabolic enzymes of polyamines are essential for normal homeostasis in the proliferation and functions of cells and tissues. However, the intracellular polyamine content increases in hyperplastic or neoplastic growth. Although the involvement of polyamines in physiological and pathological cell proliferation and differentiation has been well established, the role they play is quite different in relation to cell systems and animal models and is dependent on inducer agents and stimuli. Also, the experimental procedures used to deplete polyamines have been shown to influence the cell responses. In this paper, the assay methods currently in use for polyamines are reviewed and compared with respect to sensitivity, reproducibility and applicability to routine analysis. The relevance of polyamine metabolism and the uptake/release process in many physiological and pathological processes is highlighted, and the cellular polyamine pathways are discussed in relation to the possible diagnostic and therapeutic significance of these mediators.

Dimethyl sulfoxide affects the selection of splice sites

Depending on the cell lines and cell types, dimethyl sulfoxide (Me2SO) can induce or block cell differentiation and apoptosis. Although Me2SO treatment alters many levels of gene expression, the molecular processes that are directly affected by Me2SO have not been clearly identified. Here, we report that Me2SO affects splice site selection on model pre-mRNAs incubated in a nuclear extract prepared from HeLa cells. A shift toward the proximal pair of splice sites was observed on pre-mRNAs carrying competing 5'-splice sites or competing 3'-splice sites. Because the activity of recombinant hnRNP A1 protein was similar when added to extracts containing or lacking Me2SO, the activity of endogenous A1 proteins is probably not affected by Me2SO. Notably, in a manner reminiscent of SR proteins, Me2SO activated splicing in a HeLa S100 extract. Moreover, the activity of recombinant SR proteins in splice site selection in vitro was improved by Me2SO. Polar solvents like DMF and formamide similarly modulated splice site selection in vitro but formamide did not activate a HeLa S100 extract. We propose that Me2SO improves ionic interactions between splicing factors that contain RS-domains. The direct impact of Me2SO on alternative splicing may explain, at least in part, the different and sometimes opposite effects of Me2SO on cell differentiation and apoptosis.

Involvement of mitochondrial permeability transition and caspase-9 activation in dimethyl sulfoxide-induced apoptosis of EL-4 lymphoma cells

We observed that dimethyl sulfoxide (DMSO) induced apoptotic changes in the EL-4 murine lymphoma cell line and that effect was dependent on the concentration and time period. Incubating cells over a period of 18 h, 2.5% DMSO was found to induce sub-G1 peak in DNA histograms analyzed by flowcytometer and nucleosomal ladder formation in DNA gel electrophoresis. We also found down-regulation of Bcl-2, collapse of mitochondrial membrane potential (delta psi m) occurred following DMSO treatment, and release of cytochrome c from the mitochondria to cytosol. These observations suggest that DMSO converted its pro-apoptotic signal at the mitochondria. In the involvement of caspases, caspase-9 and -3, but not caspase-8, were found to be activated responding to DMSO treatment. Inhibitory experiments demonstrated that caspase cascade of mitochondrial apoptotic pathway was indispensable for DMSO-induced apoptosis. In the caspase cascade, caspase-9 was an upstream initiator and its primary signal could be transduced and amplified by caspase-3, -6 and -7. Kinetic study of these data showed mitochondrial dysfunction and caspase activation occurred at 12 h and apoptotic change of nuclear DNA at 18 h, providing another support for the transduction of DMSO pro-apoptotic signal via the mitochondrial pathway.