Expression of c-fos and c-myc in Raji Burkitt's lymphoma cells during the progression of DMSO-induced G1 cells into S phase

Low dose dimethyl sulfoxide driven gross molecular changes have the potential to interfere with various cellular processes

Dimethyl sulfoxide (DMSO) is a small molecule with polar, aprotic and amphiphilic properties. It serves as a solvent for many polar and nonpolar molecules and continues to be one of the most used solvents (vehicle) in medical applications and scientific research. To better understand the cellular effects of DMSO within the concentration range commonly used as a vehicle (0.1-1.5%, v/v) for cellular treatments, we applied Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FT-IR) spectroscopy to DMSO treated and untreated epithelial colon cancer cells. Both unsupervised (Principal Component Analysis-PCA) and supervised (Linear Discriminant Analysis-LDA) pattern recognition/modelling algorithms applied to the IR data revealed total segregation and prominent differences between DMSO treated and untreated cells at whole, lipid and nucleic acid regions. Several of these data were supported by other independent techniques. Further IR data analyses of macromolecular profile indicated comprehensive alterations especially in proteins and nucleic acids. Protein secondary structure analysis showed predominance of β-sheet over α-helix in DMSO treated cells. We also observed for the first time, a reduction in nucleic acid level upon DMSO treatment accompanied by the formation of Z-DNA. Molecular docking and binding free energy studies indicated a stabilization of Z-DNA in the presence of DMSO. This alternate DNA form may be related with the specific actions of DMSO on gene expression, differentiation, and epigenetic alterations. Using analytical tools combined with molecular and cellular biology techniques, our data indicate that even at very low concentrations, DMSO induces a number of changes in all macromolecules, which may affect experimental outcomes where DMSO is used as a solvent.

Structure and regulation of the mDot1 gene, a mouse histone H3 methyltransferase

The nucleotide sequence data reported have been deposited in the DDBJ, EMBL, GenBank(R) and GSDB Nucleotide Sequence Databases under accession numbers AY196089, AY196090, AY376663, AY377920 and AY376664. Recently, a new class of histone methyltransferases that plays an indirect role in chromatin silencing by targeting a conserved lysine residue in the nucleosome core was described, namely the Dot1 (disruptor of telomeric silencing) family [Feng, Wang, Ng, Erdjument-Bromage, Tempst, Struhl and Zhang (2002) Curr. Biol. 12, 1052-1058; van Leeuwen, Gafken and Gottschling (2002) Cell (Cambridge, Mass.) 109, 745-756; Ng, Feng, Wang, Erdjument-Bromage, Tempst, Zhang and Struhl (2002) Genes Dev. 16, 1518-1527]. In the present study, we report the isolation, genomic organization and in vivo expression of a mouse Dot1 homologue (mDot1). Expressed sequence tag analysis identified five mDot1 mRNAs (mDot1a-mDot1e) derived from alternative splicing. mDot1a and mDot1b encode 1540 and 1114 amino acids respectively, whereas mDot1c-mDot1e are incomplete at the 5'-end. mDot1a is closest to its human counterpart (hDot1L), sharing 84% amino acid identity. mDot1b is truncated at its N- and C-termini and contains an internal deletion. The five mDot1 isoforms are encoded by 28 exons on chromosome 10qC1, with exons 24 and 28 further divided into two and four sections respectively. Alternative splicing occurs in exons 3, 4, 12, 24, 27 and 28. Northern-blot analysis with probes corresponding to the methyltransferase domain or the mDot1a-coding region detected 7.6 and 9.5 kb transcripts in multiple tissues, but only the 7.6 kb transcript was evident in mIMCD3-collecting duct cells. Transfection of mDot1a-EGFP constructs (where EGFP stands for enhanced green fluorescent protein) into human embryonic kidney (HEK)-293T or mIMCD3 cells increased the methylation of H3-K79 but not H3-K4, -K9 or -K36. Furthermore, DMSO induced mDot1 gene expression and methylation specifically at H3-K79 in mIMCD3 cells in a time- and dose-dependent manner. Collectively, these results add new members to the Dot1 family and show that mDot1 is involved in a DMSO-mediated signal-transduction pathway in collecting duct cells.

Multidisciplinary utilization of dimethyl sulfoxide: pharmacological, cellular, and molecular aspects

DMSO is an amphipathic molecule with a highly polar domain and two apolar methyl groups, making it soluble in both aqueous and organic media. It is one of the most common solvents for the in vivo administration of several water-insoluble substances. Despite being frequently used as a solvent in biological studies and as a vehicle for drug therapy, the side-effects of DMSO (undesirable for these purposes) are apparent from its utilization in the laboratory (both in vivo and in vitro) and in clinical settings. DMSO is a hydrogen-bound disrupter, cell-differentiating agent, hydroxyl radical scavenger, intercellular electrical uncoupler, intracellular low-density lipoprotein-derived cholesterol mobilizing agent, cryoprotectant, solubilizing agent used in sample preparation for electron microscopy, antidote to the extravasation of vesicant anticancer agents, and topical analgesic. Additionally, it is used in the treatment of brain edema, amyloidosis, interstitial cystitis, and schizophrenia. Several systemic side-effects from the use of DMSO have been reported, namely nausea, vomiting, diarrhea, hemolysis, rashes, renal failure, hypertension, bradycardia, heart block, pulmonary edema, cardiac arrest, and bronchospasm. Looking at the multitude of effects of DMSO brought to light by these studies, it is easily understood how many researchers working with DMSO (or studying one of its specific effects) might not be fully aware of the experiences of other groups who are working with it but in a different context.

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

It is accepted that apoptosis is a gene-controlled process of cellular self-destruction. It occurs during physiological regulation and in pathological situations in the life of a cell. In the immune system, several different intracellular and extracellular factors have been associated with the induction of apoptosis, and the final responses depend on the cell system and the acquired signals. In lymphoid cells, dexamethasone-induced apoptosis is associated with c-myc downregulation in cells that remain in G0-G1 until the point of death. Ornithine decarboxylase (ODC), a key enzyme involved in polyamine biosynthesis, is regulated by c-myc, which is a transcriptional activator implicated not only in the control of cell proliferation and differentiation but also in programmed cell death. As dimethylsulphoxide (DMSO) induces apoptosis in the RPMI-8402 human pre-T cell line, the present study analysed the involvement of the c-myc proto-oncogene and polyamine pathway as mediators of apoptosis. Cell growth, programmed cell death, c-myc expression, ODC activity and intracellular polyamine content were detected after DMSO and difluoromethylornithine (DFMO) treatment. DMSO-treated cells exhibit a decrease in ODC activity and polyamine levels associated with cell growth arrest and programmed cell death induction. The expression of c-myc proto-oncogene, as its mRNA or protein, is specifically down-regulated. DFMO, a well defined polyamine biosynthesis inhibitor, completely blocks ODC activity, resulting in growth inhibition but not apoptosis. Moreover, in these samples no evidence of changes of c-myc expression were found. The results obtained suggest that, in RPMI-8402 cells, DMSO provokes a c-myc-dependent decrease of ODC activity followed by a depletion of intracellular polyamine levels, associated with programmed cell death and cell growth arrest.

Phorbol ester synergizes the dimethyl sulfoxide-dependent programmed cell death through diacylglycerol increment

The regulation of cell proliferation or cell death by extracellular factors are the most intensely studied subjects in cell biology. Many conceptual problems remain to be clarified concerning the mechanisms that regulate the programmed cell death. In this work, we focus our attention on the possible role of protein kinase C activation during dimethyl sulfoxide (DMSO)-induced cell death. The present results suggest that the frequency of DMSO-dependent apoptosis of RPMI 8402 thymic lymphoma cells is increased by phorbol ester acetate supplementation. Enhancement of apoptosis can be abolished by cotreatment with the bisindolylmaleimide, a specific PKC inhibitor. The association between PMA and DMSO treatment provokes an early activation of an intracellular signaling mechanism that results, via sustained diacylglycerol elevation, in a possible long-term PKC activation.

Dimethyl sulfoxide (DMSO) causes a reversible inhibition of telomerase activity in a Burkitt lymphoma cell line

INTRODUCTION

Telomerase is an enzyme that is required for maintenance of telomeres. This enzyme has been shown to be present in germline tissues and majority of tumors and tumor cell lines. The regulation of telomerase is an area of active investigation in different models because, potentially, inhibition of this enzyme could be important in cancer therapy. To study the regulation of this enzyme in lymphoma cell lines, we used DMSO to produce a reversible G0/G1 arrest in Raji cell line, as shown earlier [Sawai M, Takase K, Teraoka H, Tsukada K. Reversible G1 arrest in the cell cycle of human lymphoid cell lines by dimethyl sulphoxide. Exp Cell Res 1990;187:4-10].

METHODS

In this study, we use a highly quantifiable conventional (non-amplified) assay to study the effect of DMSO on telomerase. In addition, we studied cellular proliferation and cell cycle profiles of the cells treated and, subsequently, released from DMSO induced blockage.

RESULTS

In this model, DMSO reversibly inhibited telomerase activity that could be restored after release from the blockage. The inhibition of telomerase seems to parallel cellular proliferation and it appears that telomerase is regulated upon entry into the cell cycle. This view is consistent with other previously published views on relationship of telomerase with exit from cell cycle.

CONCLUSION

Our observations demonstrate a novel effect of DMSO on cellular mechanisms in Raji cell line. It may provide an attractive model to further study regulation of telomerase in this cell line.

Dimethyl sulfoxide induces programmed cell death and reversible G1 arrest in the cell cycle of human lymphoid pre-T cell line

In human B- and T-differentiated lymphoid cell lines DMSO was found to arrest the proliferation at the G1 stage of the cell cycle, without any detectable differentiation and DMSO itself was found to prevent apoptosis. Programmed cell death, or apoptosis, is now thought to be an important regulatory process in normal hemopoiesis and in the lymphoid system this program is started in the immune process such as autoreactive T-cell elimination in the thymus, and antigen-driven B-cell selection in the terminal centre. For this purpose, we have analysed the effect of DMSO using undifferentiated pre-B (KM-3) and pre-T (RPMI-8402) human lymphoid cells. Results obtained by multiparametric analyses show that DMSO affect only the pre-T cell line inducing a reversible G1 arrest of the cell cycle with a significant presence of apoptotic cells and modification of terminal transferase (TdT) expression. Pre-B cell line is resistant to DMSO treatment. These data provide evidence of a new model for the study of the selective cell type depending effect of DMSO in the immune system.

Dimethyl sulfoxide does not trigger urine histamine release in interstitial cystitis

OBJECTIVES

Dimethyl sulfoxide (DMSO), an agent that provides symptomatic relief in patients with interstitial cystitis (IC) works via an unknown mechanism. We investigated whether DMSO acts as a chemical stimulant of mast cell degranulation.

METHODS

A radioimmunoassay (RIA) specific for histamine was used to test this hypothesis. Twelve women with strictly diagnosed IC were treated with intravesical instillations of DMSO. Treatments were repeated at varying intervals, and each patient received three to six treatments. Urine histamine levels were measured before and after each intravesical instillation of DMSO. Dilutional effects of DMSO were corrected for by conversion of urine histamine concentration to urine histamine:creatinine ratio.

RESULTS

The RIA was unaffected by the addition of DMSO to urine. No consistent change in the urine histamine:creatinine ratio following DMSO instillation was found. Trend analysis revealed no trend in the histamine:creatinine ratio with time.

CONCLUSIONS

The relief of symptoms reported in 50% to 77% of patients treated with intravesical DMSO is not related to detectable mast cell release of histamine. Other mechanisms of action must be investigated to explain the beneficial effect of this agent.

Molecular properties, substrate specificity and regulation of DNA-dependent protein kinase from Raji Burkitt's lymphoma cells

A double-stranded DNA-dependent protein serine/threonine kinase (DNA-PK) was purified from a nuclear extract of Raji Burkitt's lymphoma cells by a three-step column-chromatographic procedure. The main silver-stained band visualized after SDS/PAGE corresponded to an autophosphorylated polypeptide of about 350-kDa that represents the catalytic component. The existence of Ku DNA-binding protein as a regulatory component in the purified enzyme was revealed by Western blot/enzyme immunoassay and direct inhibition test with anti-Ku sera from the autoimmune patients. The DNA-PK catalyzed phosphorylation of synthetic peptides corresponding to Myc and RB proteins in a DNA-dependent manner, indicating that DNA-PK may recognize a second core-sequence motif Pro-Ser/Thr- in addition to the putative consensus sequences of -Ser/Thr-Gln. The level of enzyme activity was significantly higher in DMSO-induced G0/G1-arrested Raji cells as well as in the cells after release from DMSO than in the log-phase cells.

DNA-activated protein kinase in Raji Burkitt's lymphoma cells. Phosphorylation of c-Myc oncoprotein

Autophosphorylation of a DNA-activated protein kinase (DNA-PK) in Raji Burkitt's lymphoma cells generated a band that corresponded to a phosphoprotein of about 300 kDa on SDS/PAGE. This band corresponds to a 300-350-kDa DNA-PK found previously in HeLa cells. In addition to the 300-kDa phosphoprotein, the band of a highly phosphorylated 58-kDa protein was detected by SDS/PAGE of partially purified DNA-PK preparations after the phosphorylation reaction in the presence of double-stranded DNA. This phosphoprotein was specifically immunoprecipitated by phosphoprotein nor detectable activities of other kinases, phosphorylated recombinant c-Myc proteins in the presence of DNA. The c-Myc phosphorylation by DNA-PK was markedly stimulated by relaxed, double-stranded DNA, but neither by single-stranded DNA nor by RNA. Phosphopeptide mapping and phosphoamino acid analysis indicated that DNA-PK phosphorylates c-Myc in vitro at several serine residues.