Galvanostatic stripping chronopotentiometric study for determination of selenium: pharmacokinetic application in experimental mice.

PURPOSE: The aim of this study was to determine the selenium content in various tissues of the mouse employing the galvanostatic stripping chronopotentiometry (SCP) technique and to investigate the distribution profile of selenium as well as its pharmacokinetics in a mouse model. METHODS: The animals received 0.25 µg/g Se orally for 5 days. Samples of whole blood and various tissues comprising kidney, liver and brain were harvested from mice and then analysed for Se content employing the SCP technique. RESULTS: The SCP method was validated over Se concentration range of 10 ­ 100 ng/mL and showed good linearity (r² > 0.999). The precision (over 5 days) of the assay in various mouse tissues (liver, kidney, and brain) ranged from 0.03 to 2.9% with accuracy results that varied from -6.69 to 0.28%. The mean (n = 5) recoveries of Se from the mouse tissues ranged from 93.31 to 100.28%. The lower limit of Se detection in the mouse tissues was 0.2 ng/mL. The present method was successfully applied in evaluating the distribution of Se in various tissues as well as its pharmacokinetics in the mouse model. The Se tissue concentrations in the mouse model showed that the maximum Se levels in most tissues were attained within 3-4 days following its administration. Furthermore, the pharmacokinetic profile of Se in the mouse model indicates that the element is slowly absorbed from the gastrointestinal tract (GIT) reaching a plateau in 4 days and then it is slowly eliminated from the body with a half-life of about 4.5 days. CONCLUSIONS: The present SCP method was employed to analyse Se in various mouse tissues. The method was characterized by excellent performance parameters necessary for the determination of Se in biological matrices. Se distributes in whole blood as well as into various tissues of the mouse with high concentrations in the kidney and liver and low levels in the blood and brain tissues. The absorption of Se from the GIT was very slow and the data suggest that the elimination of Se seems to be through the kidney at a very slow rate as well. The data of the present study thus suggest that Se remains in the mouse body for a long period of time.

Research on biomodulatory effect of natural compounds.

OBJECTIVES: The purpose of this study was to determine whether the extract isolated from the artichoke Cynara cardunculus L. (ECC) had antimutagenic effect and was able to enhance the therapeutic effect of cytostatic drug cis-platinum (cis-Pt). METHODS: The potential antimutagenic activity of ECC was assayed by a test on sex-linked recessive lethal mutations detection in Drosophila melanogaster males treated with ethylmethane sulfonate (EMS). The possible enhancement of cytostatic/cytotoxic effect of cis-Pt by ECC was evaluated in the cell revitalization assay by measuring cell viability via Trypan blue exclusive assay using mouse leukemia cells L1210. RESULTS: EMS was both toxic and genotoxic in D. melanogaster males. It statistically significantly increased the frequency of sex-linked recessive lethal mutations in comparison to the negative control. Furthermore, ECC statistically significantly reduced the genotoxic effect of EMS. It acted in a desmutagenic manner via EMS inactivation. In the cell revitalization assay, ECC enhanced the cytotoxic/cytostatic effect of cis-Pt. The therapeutic potential of ECC was established on the basis of statistically significantly lowered recovery of cis-Pt pre-treated mouse leukemia cells in the presence of ECC. CONCLUSIONS: The results imply that the extract isolated from artichoke C. cardunculus L. has marked beneficial activities antimutagenic and therapeutic effect enhancing) and its potential biomedical application in the combination therapy of cancer and some neurodegenerative diseases may be suggested.

Dual activity of triterpenoids: apoptotic versus antidifferentiation effects.

Triterpenoids are natural, biologically active compounds extracted from many plants. They possess antiinflammatory, anticancer, and antioxidant properties. In the report presented, antiproliferative effects and leukemia cell growth and apoptosis modulating activities of ursolic acid (UA) and oleanolic acid (OA) were investigated. Both triterpenoids are inhibitors of leukemia cell growth and inductors of apoptosis. However, when applied in combination with anthracycline antitumor antibiotic doxorubicin (Dox), UA and OA diversely modulate therapeutic efficacy of Dox, due to different antioxidant activities. Compare to OA showing synergism/additive effect with Dox, UA (stronger antioxidant) acts antagonistically and reduces leukemia cell growth inhibiting and differentiation effects induced by Dox. In conclusion, these findings suggest that although triterpenoids UA and OA can induce apoptosis, their antioxidant activities can interfere with the therapeutic effect of antitumor antibiotic Dox which mechanism of action is attributed to the production of reactive oxygen species.

Diverse biomodulatory effects of glucomannan from Candida utilis.

Using four experimental model systems, it was demonstrated that glucomannan (GM) isolated from the cell wall of the industrial yeast Candida utilis revealed a broad range of protective activities. This effect depended on the nature and mode of action of the counteracting genotoxic compound as well as on the experimental model system used. In the Saccharomyces bioprotectivity assay, GM increased resistance towards ofloxacin-induced toxicity in the wild type and recombination repair-deficient yeast strains significantly enhancing survival of the cells. In the chromosomal aberration assay, GM exerted anticlastogenic effect against maleic hydrazide induced clastogenicity in Vicia faba L. In the DNA-topology assay, GM protected plasmid DNA from the breaks induced by Fe(2+) ions, but enhanced damage induced by bleomycin and hydrogen peroxide. In the cell-revitalization assay, it enhanced cytotoxic/cytostatic effect of teniposide applied to mouse leukemia cells. Thus, depending on the experimental model, GM acted as antimutagen, anticlastogen, DNA breaks inhibitor or inducer, and as cytotoxic/cytostatic effect enhancer. Several possible mechanisms of bioprotective action underlying the observed activities are suggested including iron chelation and free radical scavenging. The results imply that GM is a polysaccharide with marked biological activities and suggest its potential biomedical application, especially in combination with other bioactive compounds.

Potentiation of the activity of cisplatin and cyclophosphamide by trimidox, a novel ribonucleotide reductase inhibitor, in leukemia-bearing mice.

We describe the use of the new ribonucleotide reductase inhibitor, trimidox (TDX), in combination chemotherapy under in vitro and in vivo conditions with cisplatin and cyclophosphamide. In vitro, the combination of TDX and cisplatin was tested in L1210 cells. The combination caused concentration dependent antagonistic or additive effects. However, the combination of TDX-cisplatin-cyclophosphamide in vivo is highly synergistic in both, the L1210 and P388D1 leukemia mouse models. Both combinations, TDX with cisplatin or TDX with cyclophosphamide were also synergistic in the L1210 and P388D1 leukemia animal models.

The role of natural biopolymers in genotoxicity of mutagens/carcinogens elimination.

Nowadays naturally occurring compounds with the potential antimutagenic and anticarcinogenic effects are of great importance for their prospective use in cancer chemoprevention and treatment. The new water soluble derivative of microbial polysaccharide beta-D-glucan-carboxymethyl glucan (CMG) belongs to such a category of natural substances. CMG isolated from the cell wall of baker's yeast Saccharomyces cerevisiae is included into the class of biopolymers known as biological response modifiers (BRMs) with a broad range of activities, above all ones interfering with cancer therapy. It was demonstrated on four experimental model systems that biological and consequential medicinal importance of CMG is based on the combined application with another active compound. In the Saccharomyces cerevisiae antimutagenicity assay CMG significantly reduced ofloxacin-induced mutagenicity in the yeast strain D7. CMG exerted bioprotective (anti-toxic and antimutagenic) effect after its simultaneos application with methyl methanesulphonate on the repair-deficient strain uvs10 of the unicellular green alga Chlamydomonas reinhardtii. In the Vicia sativa simultaneous phytotoxicity and anticlastogenicity assay CMG exerted statistically significant anticlastogenic efect against maleic hydrazide-induced clastogenicity in Vicia sativa L. Only in the Salmonella/microsome assay CMG did not exert statistically significant antigenotoxic effect, despite of the fact that it reduced 9-aminoacridine-induced mutagenicity in S. typhimurium TA97, but his(+) revertants decreasing was statistically significant only at the highest CMG concentration used. The data presented unambiguously documented that even biopolysaccharides (e.g., derivatives of beta-glucan) belonging to the most abundant class of natural biopolymers may contribute to cancer prevention and therapy.

In vitro and in vivo antitumor activity of novel amphiphilic dimers consisting of 5-fluorodeoxyuridine and arabinofuranosylcytosine.

Various heterodinucleoside phosphates of 5-fluorodeoxyuridine (5-FdUrd) and arabinofuranosylcytosine (Ara-C) have recently been synthesized as potent chemotherapeutic agents. 5-Fluorodeoxyuridine is being used in patients with colorectal carcinoma, whereas Ara-C is one of the most effective agents in the treatment of hematological malignancies. We now investigated the action of three novel amphiphilic dimers with different structures in various 5-fluorouracil (5-FU) sensitive and resistant human colon tumor cell lines (CCL228, CCL227, 5-FU resistant CCL227 and HT-29) as well as in L1210 murine leukemia cells. Activity of the heterodimers was determined by clonogenic and growth inhibition assays including the induction of programmed cell death. In addition, the in vivo effects were tested in L1210 leukemia bearing mice. We show that these compounds inhibited the number of colonies of 5-FU sensitive and resistant human colon tumor cell lines with IC50 values ranging from 0.65 to 1 nM. The investigated dimers induced dose-dependent apoptosis in HT-29 colon tumor cells as well as in L1210 leukemia cells. No significant difference in the cytotoxicity of these agents could be observed between 5-FU sensitive and resistant cells, indicating that these compounds might be used in the treatment of 5-FU resistant tumors. In L1210 leukemia bearing mice the survival of tumor-bearing animals was significantly increased in comparison with untreated control animals. We therefore conclude that these new heterodinucleoside phosphates of 5-FdUrd and Ara-C might be an additional option for the treatment of sensitive and 5-FU resistant colon cancer and hematological malignancies.

Combination effects of Ara-C and 5-fluorodeoxyuridine against leukemia cells in vitro and in mice.

BACKGROUND: Ara-C (1-beta-D-arabinofuranosylcytosine) is widely used for treatment of human leukemia. However, due to emergence of resistance, new drug combinations need to be developed. MATERIALS AND METHODS: We tested the combination of Ara-C with 5-FdUrd (5-fluorodeoxyuridine) in L1210 and P388D1 mouse leukemia cells in vitro and in vivo by growth inhibition and recovery assay in leukemia-bearing mice. RESULTS: Simultaneous incubation of cells with Ara-C and 5-FdUrd yielded more than additive effects for most combinations in both cell lines; synergy was seen in P388D1 cells. P388D1 cells showed delayed growth after treatment with Ara-C or 5-FdUrd in a growth recovery assay. In animal studies, simultaneous subcutaneous administration of the compounds did not show any significant beneficial effects as compared with monotherapy. Intraperitoneal administration of both compounds, however, significantly prolonged the survival of P388D1 animals. CONCLUSION: Depending on cell type and route of drug administration, the combination of Ara-C and 5-FdUrd might offer a promising additional treatment option for leukemia.

Fungal chitin-glucan derivatives exert protective or damaging activity on plasmid DNA.

Water-soluble derivatives of the chitin-glucan (Ch-G) complex isolated from the fungal mycelium of the industrial strain of Aspergillus niger have been previously shown to possess potent antimutagenic protective activity in vivo. Their direct action on DNA has not been yet evaluated. Using carboxymethylation, sulfoethylation and subsequent ultrasonic treatment, lower molecular weight water-soluble derivatives were obtained from the crude fungal Ch-G. The biological effects of the prepared compounds were evaluated in direct interaction on plasmid DNA in vitro. Monitoring of electrophoretic mobility of different conformers of plasmid DNA implied that carboxymethyl chitin-glucan (CM-Ch-G) induced single- and double-strand breaks into supercoiled DNA in a concentration-dependent manner. On the other hand, sulfoethyl chitin-glucan (SE-Ch-G) alone did not induce any DNA breaks in plasmid DNA. However, process of DNA damaging induced by free-radical oxidation initiated with Fe(2+) was inhibited, while the process of DNA breakage induced by H(2)O(2) was increased in the presence of SE-Ch-G.

Effects of flavonoids on cisplatin-induced apoptosis of HL-60 and L1210 leukemia cells.

Effects of three flavonoids, quercetin (QU), galangin (GA), and chrysin (ChR) on cisplatin (cis-Pt)-induced apoptosis of human promyelocytic leukemia HL-60 cells and murine leukemia L1210 cells were investigated. The quantitative analysis of apoptotic DNA fragmentation was used to show that preincubation of cells with flavonoids can influence cis-Pt-induced apoptosis in different way. ChR had no effect, QU enhanced, and GA reduced apoptotic DNA fragmentation. It is also shown that combined treatment with QU and cis-Pt showed synergistic effect, however, GA combined with cis-Pt exhibited antagonism on cytotoxicity in L1210 murine leukemia cells. We assume that tested flavonoids affect the important biological activities connected with cancer chemotherapy and chemoprevention as they differently modulated the sensitivity of cells to cis-Pt treatment. QU is presented as pro-apoptotic agent and GA as agent with anti-apoptotic potential.

Antitumor activity of benzamide riboside in vitro and in vivo.

Benzamide riboside (BR), a recent synthetic nucleoside analogue, is a new compound demonstrating potent cytotoxic activity in malignant cell lines in vitro and in vivo in L1210 leukemia. It exhibits at least two different mechanisms of action. These are, first, the inhibition of inosine 5'-monophosphate dehydrogenase (IMPDH, EC 1.1.1.205), a rate-limiting enzyme for GTP and dGTP synthesis that plays a major role in DNA synthesis, cell proliferation and regulation; and second, the induction of apoptosis. Some aspects of BR activity in malignant cells in vitro and in vivo are reviewed as well as some of the mechanisms behind BR's anti-neoplastic effect.