RNA replication by nuclear satellite DNA in different mouse cells.
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Animals↗
Biomedical subjects
H Tapiero
Publications and source records attributed to H Tapiero.
The antioxidant role of selenium and seleno-compounds.
Selenium (Se) is an essential trace element for animals and humans that is obtained from dietary sources including cereals, grains and vegetables. The Se content of plants varies considerably according to its concentration in soil. Plants convert Se mainly into Se-methionine (Se-Met) and incorporate it into protein in place of methionine (Met). Selenocystine (Se-Cys), methyl-Se-Cys and gamma-glutamyl-Se-methyl-Cys are not significantly incorporated into plant protein and are at relatively low levels irrespective of soil Se content. Higher animals are unable to synthesize Se-Met and only Se-Cys was detected in rats supplemented with Se as selenite. Renal regulation is the mode by which whole body Se is controlled. Se is concentrated in hair and nail and it occurs almost exclusively in organic compounds. The potentiating effect of Se deficiency on lipid peroxidation is enhanced in some tissues by concurrent deficiency of copper or manganese. In the in vitro system, the chemical form of Se is an important factor in eliciting cellular responses. Although the cytotoxic mechanisms of selenite and other redoxing Se compounds are still unclear, it has been suggested that they derive from their ability to catalyze the oxidation of thiols and to produce superoxide simultaneously. Selenite-induced cytotoxicity and apoptosis in human carcinoma cells can be inhibited with copper (CuSO(4)) as an antioxidant. High doses of selenite result in induction of 8-hydroxydeoxyguanosine (8-OHdG) in mouse skin cell DNA and in primary human keratinocytes. It may cause DNA fragmentation and decreased DNA synthesis, cell growth inhibition, DNA synthesis, blockade of the cell cycle at the S/G(2)-M phase and cell death by necrosis. In contrast, in cells treated with methylselenocyanate or Se methylselenocysteine, the cell cycle progression was blocked at the G(1) phase and cell death was predominantly induced by apoptosis.
Aging↗
Gamma interferon administration differently affects sensitive or doxorubicin resistant P388 leukemia cells; a relationship with antioxidant defenses?
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Animals↗
Intracellular accumulation and cytotoxic effect of (8-thiotheophyllinate) (triphenylphosphine) gold(I) in Friend leukemia cells.
Following continuous exposure to tTAuP in medium containing 10% fetal calf serum (FCS), cells resistant to doxorubicin (DOX-RFLC) were 3 fold more resistant to tTAuP than its sensitive counterpart (FLC). Moreover, FLC were 100 fold more sensitive to tTAuP when the cells were grown in the absence of FCS but in the presence of synthetic medium (BMS). When the cytotoxic effect was measured after short-term exposure (60 min) followed by 72 hr incubation in drug-free medium, unexpectedly, DOX-RFLC were 8 fold more sensitive [ID50 = 1.5 microM] than FLC [ID50 = 12 microM] to tTAuP. When FLC were exposed 60 min at different temperatures (4, 25 or 37 degrees C) to tTAuP prior to 72 hr incubation in drug free medium, the ID50 was achieved at 20, 13 and 3 microM respectively). In contrast, when DOX-RFLC were treated in similar conditions, the cytotoxic activity of tTAuP did not vary following exposure at 4, 25 or 37 degrees C. Although the mechanism of action of gold compounds is still unknown we have assumed that tTAuP cytotoxicity is related to the ease with which it is accumulated. This assumption was supported by the analysis of tTAuP incorporation by SXRF. The results reported here show that tTAuP accumulates rapidly in the cell and is distributed in the cytoplasmic and the nuclear fractions. It is suggested that accumulation is mediated by passive diffusion. However, the detection of gold binding to DNA in complexes resistant to solvent treatments suggests that interaction with macromolecules can be mediated by the formation of covalently bound complexes.
Animals↗
Modulation of the antioxidant activities in dox-sensitive and -resistant Friend leukemia cells. Effect of doxorubicin.
Tumor cell resistance to anthracyclines has been associated with increased activity against free radicals. Here, we have investigated the direct effect of doxorubicin (DOX) in the modulation of glutathione level and antioxidant activities in DOX-sensitive and-resistant cells (288 fold). The glutathione level in untreated cells was 88% greater in resistant than in sensitive cells. The activities of the superoxide dismutase, glutathione -S-transferase and glutathione reductase were respectively 24, 15 and 38% higher in resistant cells than in their sensitive counterparts. In contrast, catalase and total glutathione peroxidase were reduced in resistant cells by 18 and 21% respectively. Moreover, the activity of selenium-dependent glutathione peroxidase was lowered by 47% in the resistant as compared to the sensitive cells. Exposure of sensitive or resistant cells to low doses of DOX did not affect these levels in either cell variant. It is concluded therefore that resistance to anthracyclines may not always be associated with an elevated level of intracellular antioxidant activity enzymes.
Animals↗
Cytotoxicity and DNA damaging effects of a new nitrosourea, fotemustine, diethyl- 1-(3-(2-chloroethyl)-3-nitrosoureido) ethylphosphonate-S10036.
Fotemustine is a new chloroethylnitrosourea which has recently entered a Phase II clinical trial. Using standard cytotoxicity analyses, Fotemustine was shown to be preferentially active in two Mer- cell lines, human colon BE and human lung A427. Comparative cell kill in the Mer+ counterparts HT29 and A549 (respectively) was significantly lower. In a mouse cell line, P388, alkaline elution studies showed that Fotemustine caused fewer DNA strand breaks and total crosslinks (including DNA-protein) than either BCNU or MeCCNU at equivalent cytotoxic concentrations. In addition, the removal of DNA damage caused by Fotemustine was more rapid than of damage, three times as much Fotemustine was required. These data suggest that the cytotoxic mechanism of Fotemustine, although subject to the same repair mechanisms as other nitrosoureas, may not be entirely dependent upon DNA as the sole drug target. The previously reported reduced mutagenicity of this agent may also be a function of the less extensive nucleic acid damage. The encouraging early clinical trial results with this drug may reflect its improved pharmacokinetics and bioavailability, rather than any significant modification in its cellular pharmacology when compared to other nitrosoureas.
Antineoplastic Agents↗
Cytotoxic potential of ketonucleosides.
The relationship between the structure of ketonucleosides and cytotoxicity was investigated in Friend leukemia cells (FLC). When cells were grown in the continuous presence of ketonucleosides, it was shown that the addition of an electrophilic agent (Br-) to the sugar moiety (compound KN-35) increased the cytotoxic potential by ten fold as compared to the unsubstitute compound (KN-43). In contrast, addition of 0-acetyl group (compound KN-3) reduced this effect by three fold. When cells were pre-treated with KN-35, followed by growth in drug-free medium, cell survival was inhibited by 50% (ID50) after 3 min, whereas the same effect was reached after 240 min pre-treatment with KN-43. When drugs were pre-incubated in serum-free medium prior to cell exposure, reduced cytotoxicity was observed. We therefore conclude that the activity of these ketonucleosides may be related to the rate of in fact drug incorporation.
Antineoplastic Agents↗
Chromosomal changes associated with resistance to doxorubicin: correlation with tumorigenicity.
Chromosome analysis was performed on Friend leukemia cells sensitive and resistant to doxorubicin. With increasing levels of resistance, increased numbers, of metacentric chromosomes and several chromosomal markers were observed. When sensitive cells were exposed to a toxic dose of doxorubicin, multiple chromosomal breaks were observed in 62% of cells. In contrast, when doxorubicin resistant cells were exposed to cytotoxic concentrations, the pulverization phenomenon was not observed. This striking difference suggests a different mechanism for cytotoxicity in sensitive and resistant cells. Moreover, when logarithmically growing cells were grafted subcutaneously in DBA2 mice, the tumorigenic property was related to the level of doxorubicin resistance.
Animals↗
Changes in biophysical parameters and in phospholipid composition associated with resistance to doxorubicin.
Friend leukemia cells (FLC) resistant to different concentrations of doxorubicin were used to investigate the biochemical and biophysical changes associated with resistance. We have found that fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene analyzed on single cell level increased in resistant as compared to sensitive FLC. Furthermore, phospholipid analysis of sensitive and doxorubicin-resistant cells revealed changes in ratios of phosphatidyl-choline to phosphatidyl-ethanolamine and phosphatidyl-choline to sphingomyelin. These results correlate with decreased electrophoretic mobility in resistant cells. Our results indicate that changes in cell structure occur with the level of resistance to doxorubicin. These changes are probably the consequence rather than the cause of resistance.
Cells, Cultured↗
Effect of verapamil on rhodamine 123 mitochondrial damage in adriamycin resistant cells.
Mitochondrial damage was found in Friend leukemia cells treated with rhodamine 123 (Rho 123). In contrast, when cells resistant to the drug were similarly treated, mitochondria were unaffected. These results correlated with higher levels of Rho 123 in sensitive as compared to resistant cells. However, when resistant cells were co-treated with verapamil, intracellular Rho 123 levels reached those of sensitive cells. At these levels mitochondrial damage and subsequent cytotoxicity in resistant cells were the same as in sensitive cells. These data suggest that differences in Rho 123 mitochondrial damage and subsequent cytotoxicity in sensitive and resistant cells result entirely from increased intracellular drug levels and not from differences in mitochondrial sensitivity or other mechanisms.
Animals↗
Impact of dietary supplement of Crassostrea gigas extract (JCOE) on glutathione levels and glutathione S-transferase activity in rat tissues.
Male Sprague Dawley rats received various amounts of extract of Crassostrea gigas by gavage every day for 2 weeks or one month. At these times, groups of animals were sacrificed and samples of major organs analyzed for levels of glutathione (GSH) and glutathione S-transferase (GST) activities. Following the two week protocol, GSH levels were significantly increased in the mucosa of the large intestine; at one month the small intestine and spleen were elevated. GST activity increased in liver under both schedules and at one month, activity was also elevated in kidney and small intestine. Since the Crassostrea gigas extract contains high levels of a variety of important amino acids, it is concluded that biologically available peptides are taken up in target organs and stimulate GSH metabolism. Enhanced levels of GSH and associated enzymes may contribute to a more effective detoxification phenotype, thus providing enhanced chemoprotective capacity.
Animals↗
The antioxidant effects of Crassostrea gigas extract (JCOE) in human volunteers.
Since several in vitro and animal studies of an extract from Crassostrea gigas (JCOE) have demonstrated its antioxidant properties and other interesting effects, a preliminary human trial was carried out. Seven healthy male volunteers aged 23-37 received orally 3 x 2 capsules of JCOE per day for 8 days. On days 0, 1, 4, 8 and 15 (7 days after completion of the schedule) blood samples were drawn and the antioxidant potential of serum was tested. A statistically significant increase in the buffering effects of serum against hemoglobin (Hb) and lactate dehydrogenase (LDH) release from red blood cells treated with the free radical generator azobis amidino propane (AAPH) was found following JCOE treatment. At 8 days, the oxidative effects were reduced by > 90% of the pretreatment values. In these same individuals, serum levels of reduced glutathione were increased by an average of 1.5-fold over the time course of treatment. It is concluded that in normal human volunteers, JCOE capsules provide an orally available formula for enhancing the antioxidant capacity of blood serum. While the extract is known to contain some direct acting antioxidant components, at least a portion of the protective effect is facilitated by enhancement of GSH biosynthesis.
Adult↗