DMSO, sodium butyrate, and TPA induce hypophosphorylation of RB with HL-60 cell differentiation

The role of epigenetic modifiers in extended cultures of functional hepatocyte-like cells derived from human neonatal mesenchymal stem cells

The development of predictive in vitro stem cell-derived hepatic models for toxicological drug screening is an increasingly important topic. Herein, umbilical cord tissue-derived mesenchymal stem cells (hnMSCs) underwent hepatic differentiation using an optimized three-step core protocol of 24 days that mimicked liver embryogenesis with further exposure to epigenetic markers, namely the histone deacetylase inhibitor trichostatin A (TSA), the cytidine analogue 5-azacytidine (5-AZA) and dimethyl sulfoxide (DMSO). FGF-2 and FGF-4 were also tested to improve endoderm commitment and foregut induction during Step 1 of the differentiation protocol, being HHEX expression increased with FGF-2 (4 ng/mL). DMSO (1%, v/v) when added at day 10 enhanced cell morphology, glycogen storage ability, enzymatic activity and induction capacity. Moreover, the stability of the hepatic phenotype under the optimized differentiation conditions was examined up to day 34. Our findings showed that hepatocyte-like cells (HLCs) acquired the ability to metabolize glucose, produce albumin and detoxify ammonia. Global transcriptional analysis of the HLCs showed a partial hepatic differentiation degree. Global analysis of gene expression in the different cells revealed shared expression of gene groups between HLCs and human primary hepatocytes (hpHeps) that were not observed between HepG2 and hpHeps. In addition, bioinformatics analysis of gene expression data placed HLCs between the HepG2 cell line and hpHeps and distant from hnMSCs. The enhanced hepatic differentiation observed was supported by the presence of the hepatic drug transporters OATP-C and MRP-2 and gene expression of the hepatic markers CK18, TAT, AFP, ALB, HNF4A and CEBPA; and by their ability to display stable UGT-, EROD-, ECOD-, CYP1A1-, CYP2C9- and CYP3A4-dependent activities at levels either comparable with or even higher than those observed in primary hepatocytes and HepG2 cells. Overall, an improvement of the hepatocyte-like phenotype was achieved for an extended culture time suggesting a role of the epigenetic modifiers in hepatic differentiation and maturation and presenting hnMSC-HLCs as an advantageous alternative for drug discovery and in vitro toxicology testing.

Potent inhibition of peroxynitrite-induced DNA strand breakage and hydroxyl radical formation by dimethyl sulfoxide at very low concentrations

Dimethyl sulfoxide (DMSO) is frequently used as a solvent for many water-insoluble drugs in biological studies at concentrations often up to 1%. However, little is known about its effects on oxidatively generated DNA damage at very low concentrations (0.005-0.5%). This study was undertaken to investigate the effects of DMSO on peroxynitrite-induced DNA strand breaks, a critical event leading to peroxynitrite-elicited cytotoxicity. Incubation of varphiX-174 plasmid DNA, with 3-morpholinosydnonimine (SIN-1), a peroxynitrite generator, led to the formation of DNA strand breaks in a concentration- and time-dependent manner. The presence of DMSO at concentrations of 0.005-0.5% was found to significantly inhibit SIN-1-induced DNA strand breaks in a concentration-dependent manner. However, DMSO at the above concentrations showed no affect on SIN-1-mediated oxygen consumption, indicating that DMSO did not affect the auto-oxidation of SIN-1 to form peroxynitrite. It is observed that incubation of the plasmid DNA with authentic peroxynitrite resulted in significant formation of DNA strand breaks, which could also be dramatically inhibited by the presence of DMSO at 0.005-0.5%. Electron paramagnetic resonance spectroscopy, using 5,5-dimethylpyrroline-N-oxide (DMPO) as a spin trap demonstrated the formation of DMPO-hydroxyl radical adduct from the SIN-1 and authentic peroxynitrite. DMSO at the concentrations ranging from 0.01% to 0.5% significantly inhibited the adduct signal. Taken together, these studies demonstrate, for the first time, that DMSO at extremely low concentrations (0.005-0.5%) can potently inhibit peroxynitrite-mediated DNA strand breakage and hydroxyl radical formation. The results of this study suggest that, where DMSO is applied as a solvent, caution should be observed when evaluating the actions of drugs in experiments involving DNA damage.

Cryopreservation by slow cooling with DMSO diminished production of Oct-4 pluripotency marker in human embryonic stem cells

We tested a "standard" cryopreservation protocol (slow cooling with 10% DMSO) on the human embryonic stem cell (hESC) line H9 containing an Oct-4 (POU5F1) promoter-driven, enhanced green fluorescent protein (EGFP) reporter to monitor maintenance of pluripotency. Cells were cooled to -80 degrees C in cryovials and then transferred to a -80 degrees C freezer. Cells were held at -80 degrees C for 3 days ("short-term storage") or 3 months ("long-term storage"). Vials were thawed in a +36 degrees C water bath and cells were cultured for 3, 7, or 14 days. Propidium iodide (PI) was used to assess cell viability by flow cytometry. Control cells were passaged on the same day that the frozen cells were thawed. The majority of cells in control hESC cultures were Oct-4 positive and almost 99% of EGFP+ cells were alive as determined by exclusion of PI. In contrast, the frozen cells, even after 3 days of culture, contained only 50% live cells, and only 10% were EGFP-positive. After 7 days in culture, the proportion of dead cells decreased and there was an increase in the Oct-4-positive population but microscopic examination revealed large patches of EGFP-negative cells within clusters of colonies even after 14 days of culturing. After 3 months of storage at -80 degrees C the deleterious effect of freezing was even more pronounced: the samples regained a quantifiable number of EGFP-positive cells only after 7 days of culturing following thawing. It is concluded that new protocols and media are required for freezing hESC and safe storage at -80 degrees C as well as studies of the mechanisms of stress-related events associated with cell cryopreservation.

Searching for the magic bullet against cancer: the butyrate saga

n-Butyric acid and its "polymorphic" derivatives have been largely but somehow "blindly" studied in oncology and in red cell diseases with consistent results through decades indicating a strong maturative effect determined by enhancement of gene transcription. Although these effects have been observed mainly in vitro, the relative absence of systemic toxicity of butyrates render these compounds appealing as specific therapeutic agents. More interestingly, their specific mechanism of action, i.e. inhibition of histone deacetylase and de-repression of transcription represents at present an unique tool for diseases such as acute leukemias which are characterised by a disregulation of co-repressors and co-activators of gene transcription. More insight into specificity and modalities of action of different butyrate derivatives may be a guarantee for excellent tailored antileukemic therapy in the future.

Hypophosphorylation of pRB and repression of cyclin D3 and cdc25A during the granulocytic differentiation of human myeloblastic leukemia ML-1 cells

Recently we succeeded in inducing synergistic differentiation toward granulocytes in human myeloblastic leukemia ML-1 cells by treatment of ATRA in combination with GM-CSF. To research the mechanism of this differentiation process, we examined expression of cell cycle-related genes that are concerned with cell growth and differentiation. We detected change to the hypophosphorylated form of pRB and down-regulation of cyclin D3 and cdc25A during induced differentiation. Furthermore, these marked alterations were hardly detected in ML-1 cells treated with ATRA or GM-CSF alone. These results suggest that hypophosphorylation of pRB and repression of cyclin D3 and cdc25A are induced synergistically by treatment with ATRA plus GM-CSF in ML-1 cells.

Sodium butyrate induces G2 arrest in the human breast cancer cells MDA-MB-231 and renders them competent for DNA rereplication

When exposed to sodium butyrate (NaBut), exponentially growing cells accumulate in G1 and G2 phases of the cell cycle. In the human breast cancer cell line MDA-MB-231, an arrest in G2 phase was observed when the cells were released from hydroxyurea block (G1/S interface) in the presence of NaBut. The inhibition of G2 progression was correlated with increased contents both of total p21(Waf1) and of p21(Waf1) associated with cyclin A and with an inhibition of cyclin A- and B1-associated histone H1 kinase activities measured in cell lysates, as well as with dephosphorylation of the RB protein. A decrease in the cell contents of cyclins A and B1 was also observed but this decrease was preceded by p21(Waf1) accumulation. When NaBut was removed from the culture medium of cells blocked in G2 phase, p21(Waf1) level decreased and, instead of proceeding to mitosis, these cells resumed a progression toward DNA rereplication. These results suggest that the induction of p21(Waf1) by NaBut leads to the inhibition of the sequential activation of cyclin A- and B1-dependent kinases in this cell line, resulting in the inhibition of G2 progression and rendering the cells competent for a new cell division cycle.

Role of butyric acid and its derivatives in the treatment of colorectal cancer and hemoglobinopathies

Butyric acid, a short chain fatty acid (SCFA), is a natural component of the animal metabolism. Physiological concentrations induce multiple and reversible biological effects. They concern regulatory mechanisms of gene expression conducing to promote markers of cell differentiation, apoptosis and cell growth control. The described hyperacetylation of histones and the induction of several immune or non-immune cell-activating mediators are consistent with the pleiotropic stimulatory effect of the agent. Butyric acid is considered as a biological response modifier (BRM) and is an interesting tool for biological studies. The history of butyric acid as a putative medication in human health is spanning since 60 years and is confusing in part because of conflicting data between exciting experimental results and clinical trials. In light of minimal impact of systemic therapy and the short half-life of the saline molecule used, it is evident that continuous infusions of butyrate are required to improve the efficacy of the treatment. Butyric acid has been viewed with skepticism because of less convenient for long-term chronic therapy. New experimental data from several studies conduced within the past decade with butyric derivatives, delivery systems, and long-acting prodrugs, have demonstrated the practical value of the therapeutic concept. To support issues regarding clinical development, it was of interest to evaluate the recent information, showing butyric acid currently considered as therapeutic purposes in the treatment of colorectal cancer and hemoglobinopathies.

Polyoma middle T antigen in HL-60 cells accelerates hematopoietic myeloid and monocytic cell differentiation

Expression of the polyoma virus middle T antigen in HL-60 cells accelerates their differentiation in response to both monocytic and granulocytic differentiation-inducing agents. Middle T-expressing cells treated with the granulocytic inducer retinoic acid or the monocytic inducer 1,25-dihydroxy vitamin D3 differentiated 24 h earlier than parental, mock-electroporated, or vector control cell lines. The rapid onset of differentiation correlated with an increase in the cellular level of the middle T protein as well as two known retinoic-acid-inducible markers in HL-60 cells: the paxillin and transglutaminase gene products. The accelerated functional differentiation response and expression of retinoic-acid-inducible markers indicate that middle T played a causal role in differentiation. Thus, expression of the polyoma middle T antigen in HL-60 cells enhanced a variety of molecular changes associated with cellular differentiation.

Differentiation of human trophoblast cells in vitro is inhibited by dimethylsulfoxide

Dimethyl sulfoxide (DMSO) exerts a number of biological effects, the most frequently cited being induction of cell differentiation. The compound also increases invasiveness and metastatic potential. In contrast to the many reports of DMSO-induced cell differentiation, we report here that DMSO inhibits the morphological differentiation of human cytotrophoblast cells to syncytiotrophoblast, as revealed by immunofluorescence staining for desmosomal protein and nuclei. Cytotrophoblast cells treated with DMSO under differentiation-inducing conditions remained mononucleated with intense desmosomals staining. The effect was dose dependent, with a maximal effect seen at 1.5% DMSO. Concentrations of < or = 0.5% had no effect and concentrations > 2% were cytotoxic. In addition to these morphological changes, DMSO inhibited secretion of human chorionic gonadotropin in a dose-dependent manner. At a concentration of 1.5%, DMSO inhibited secretion by 70%. If cytotrophoblast cells were cultured in the presence of DMSO and then switched to DMSO-free medium, they proceeded to differentiate normally. While the precise mechanism of action remains unknown, judicious use of DMSO may be a useful tool for studying and manipulating the differentiation of human trophoblast cells in vitro. The findings also indicate that care should be used in interpreting results obtained using DMSO as a carrier in drug and inhibitor studies.

Induction of apoptosis in cultured retinoblastoma cells by the protein phosphatase inhibitor, okadaic acid

The induction of apoptosis in cultured retinoblastoma cells by diverse drugs was examined by analyzing DNA fragmentation, a hallmark of apoptosis. First, the ability of six retinoblastoma cell lines to undergo apoptosis was surveyed using etoposide (30 micrograms/ml, 20 h exposure). The NCC-RbC-60 cell line, established in this laboratory showed DNA fragmentation clearly, whereas the other cell lines tested, including the representative retinoblastoma cell line, Y-79, did not show distinct DNA fragmentation. Biochemical modulators, such as A23187, forskolin, retinoic acid, phorbol 12-myristate 13-acetate and okadaic acid, were examined to ascertain whether they could induce apoptosis in NCC-RbC-60 and Y-79 cells after exposure for 20 h. Only okadaic acid induced DNA fragmentation in all the retinoblastoma cell lines tested and it induced DNA fragmentation in Y-79 cells in a time- and concentration-dependent manner. Flow-cytometric analysis and microscopic examination revealed that Y-79 cells treated with okadaic acid for 24-48 h accumulated at the G2/M, especially M, phases, before undergoing DNA fragmentation. Other mitotic poisons, nocodazole, colcemid and taxol, also induced apoptosis in Y-79 cells. In the K1034 cell line, established from non-malignant retinal pigmented epithelium, okadaic acid failed to induce both G2/M arrest and DNA fragmentation. These findings suggest that okadaic-acid-induced apoptosis occurs as a result of metaphase arrest.