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Biomedical subjects

J K Hongslo

Publications and source records attributed to J K Hongslo.

At least 19 recordsLinked to original sources
PubMed1991

Comparative cytotoxic effects of acetaminophen (N-acetyl-p-aminophenol), a non-hepatotoxic regioisomer acetyl-m-aminophenol and their postulated reactive hydroquinone and quinone metabolites in monolayer cultures of mouse hepatocytes.

Toxic effects of acetaminophen (paracetamol, N-acetyl-p-aminophenol, APAP) in monolayer cultures of mouse hepatocytes developed over a period of 18 hr. N-Acetyl-m-aminophenol (AMAP) was approximately 10-fold less toxic than APAP, despite the fact that it bound covalently to a greater extent to hepatocyte macromolecules. AMAP did not deplete glutathione to as great an extent as APAP, indicating that their reactive metabolites may bind to different proteins or that oxidative damage in addition to arylation of proteins may be involved in the development of cell death. The toxicity of 3-methoxy-acetyl-p-aminophenol was similar to that of APAP, whereas the other hydroquinone and quinone metabolites were 8-10 times more cytotoxic than APAP. The potencies of these analogs were in the order: acetyl-m-aminophenol-p-benzoquinoneimine greater than or equal to 2,5-dihydroxyacetanilide greater than or equal to 3-methoxy-p-benzoquinone greater than or equal to N-acetyl-p-benzoquinone imine (NAPQI) greater than or equal to acetyl-m-aminophenol-o-benzoquinone greater than or equal to 3-hydroxy-acetyl-p-aminophenol. The relative toxic potencies of the hydroquinone and quinone metabolites of AMAP were comparable to that of NAPQI, and do not readily explain the marked difference between the cytotoxic effects of AMAP and APAP.

Acetaminophen↗
PubMed1991

Genotoxic effects of the drinking water mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX) in mammalian cells in vitro and in rats in vivo.

The potent bacterial mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]- furanone) (MX), which is formed during chlorination of drinking water and accounts for about one third of the Ames mutagenicity of tap water, has been studied with respect to its genotoxicity in vitro and in vivo. Treatment with 30-300 microM MX (1 h) induced DNA damage in a concentration-dependent manner in suspensions of rat hepatocytes, as measured by an automated alkaline elution system. The effect was similar in hepatocytes from PCB-induced and uninduced rats. DNA damage was induced in V79 Chinese hamster cells and in isolated rat testicular cells, at the same concentration level as in hepatocytes. Pretreating testicular cells with diethylmaleate, which depletes 85% of cellular glutathione, had no significant effect on the DNA damage induced by MX. The treatment conditions used in the alkaline elution experiments were not cytotoxic to any of the cell types used, as determined by trypan blue exclusion. V79 cells exposed to 2-5 microM MX (2 h) showed an increased frequency of sister-chromatid exchanges (SCE) whereas no significant effect on HGPRT mutation induction was observed. Higher concentrations (greater than 10 microM, 2 h) apparently blocked cell division. The data indicate that MX can react directly with DNA or that MX is metabolized to an ultimate mutagen via some enzyme which is common in mammalian cells. The in vivo experiments showed no evidence of genotoxicity after intraperitoneal (18 mg/kg, 1 h) or oral (18, 63 or 125 mg/kg, 1 h) administration of MX, as measured by alkaline elution, in any of the following organs: the pyloric part of the stomach, the duodenum, colon ascendens, liver, kidney, lung, bone marrow, urinary bladder and the testes. In conclusion, MX is a direct-acting genotoxicant in vitro but no in vivo genotoxicity was detected.

4-Nitroquinoline-1-oxide↗
PubMed1991

Increased frequency of sister-chromatid exchange and chromatid breaks in lymphocytes after treatment of human volunteers with therapeutic doses of paracetamol.

Paracetamol was given to 10 healthy human volunteers in 3 doses of 1 g each during a period of 8 h. Blood samples for lymphocyte cultures were taken before and 24 h after paracetamol administration. A small but significant increase was found in the frequency of sister-chromatid exchanges (SCE) after intake of paracetamol (0.187 +/- 0.030 per chromosome before and 0.208 +/- 0.024 per chromosome after). After exposure the mean frequency of chromatid breaks per 100 cells was significantly increased (2.16 +/- 1.33 versus 0.33 +/- 0.50 before exposure). Exposure of human lymphocytes in vitro showed that concentrations of paracetamol above 0.1 mM induced inhibition of replicative DNA synthesis. Increased SCE was found in lymphocytes exposed to 1-10 mM paracetamol for 2 h. Furthermore, 0.75-1.5 mM paracetamol exposure for 24 h increased the frequency of chromatid and chromosome breaks in the lymphocytes. The paracetamol-induced SCE and chromosome aberrations may be secondary effects of paracetamol-induced inhibition of DNA synthesis or due to covalent binding of paracetamol metabolite(s) to DNA.

Acetaminophen↗
PubMed1991

Co-culture systems for assessing the stability and genotoxicity of reactive 1,2-dibromo-3-chloropropane (DBCP) metabolites.

1,2-Dibromo-3-chloropropane (DBCP) induced DNA damage, measured by alkaline elution, at low concentrations (5-10 microM) in suspensions of hepatocytes and testicular cells isolated from rats. At higher concentrations (greater than or equal to 100 microM) DBCP caused DNA damage and increased the frequency of sister chromatid exchanges in Chinese hamster V79 cells. When DBCP (2.5-10 microM) was tested for its ability to cause unscheduled DNA synthesis (UDS) in monolayers of liver cells isolated from untreated rats, a clear positive response was obtained. No increase in UDS was detectable when liver cells isolated from PCB-pretreated rats were used. In contrast, DBCP (greater than or equal to 50 microM) was metabolized in hepatocytes from PCB-pretreated rats to products mutagenic to Salmonella typhimurium TA100 in co-culture with the hepatocytes, whereas control hepatocytes were substantially (40-fold) less active. No bacterial mutagenicity could be detected when the TA100 strain was co-incubated with isolated rat testicular cells and DBCP. In co-cultures of hepatocytes and V79 cells DBCP-induced DNA damage in V79 cells occurred at low concentrations (10 microM DBCP) compared to the concentration (100 microM) needed to induce DNA damage in the V79 cells incubated without hepatocytes. Testicular cells were not able to enhance DBCP-induced DNA damage in the V79 cells. The data indicate that the putative reactive DBCP episulphonium ion metabolite formed in the testicular cells presumably responsible for testicular cell DNA damage, is not capable of escaping the cell where it is formed. Other reactive DBCP metabolites generated in the liver cells seem to be able to interact with the DNA of neighbouring cells.

Animals↗
PubMed1990

Paracetamol inhibits replicative DNA synthesis and induces sister chromatid exchange and chromosomal aberrations by inhibition of ribonucleotide reductase.

Effects of paracetamol have been studied in a hydroxyurea (HU)-resistant mouse mammary tumour cell line TA3H2, shown to overproduce the small subunit of ribonucleotide reductase. These TA3H2 cells were much more resistant than the TA3H (wild-type) cells towards the inhibitory effect of paracetamol on cell growth, IC50 0.55 mM paracetamol for the wild-type compared to 2.7 mM for the HU-resistant cells. The reduced cell growth was due to an inhibition of replicative DNA synthesis, judged from an increased percentage of cells in S-phase measured by flow cytometry. Furthermore, in the wild-type cells, the increase in the number of cells in S phase was already observed at 0.1 mM while in the HU-resistant cell line this effect was first seen at 3.0 mM paracetamol. HU inhibits ribonucleotide reductase by destroying a tyrosyl free radical located on the small subunit of the enzyme. By electron paramagnetic resonance we demonstrate that paracetamol added to crude cell extracts of HU-resistant cells also immediately destroys this radical. These results show that paracetamol reduces DNA synthesis by a specific inhibition of ribonucleotide reductase. A concentration-dependent induction of sister chromatid exchanges was found both with paracetamol (1.0-10 mM) and HU (0.3-3 mM) in wild-type cells whereas no such increase was observed in HU-resistant cells. Paracetamol (1 mM for 2 h) also increased the number of chromosomal aberrations CAs in wild-type cells (i.e. chromatid breaks and chromatid exchanges). The frequency of CAs was not increased in HU-resistant cells at paracetamol concentrations up to 10 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaminophen↗
PubMed1989

Genotoxicity of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP): formation of 2-hydroxamino-PhIP, a directly acting genotoxic metabolite.

Hepatocytes isolated from Aroclor 1254 (PCB) pretreated rats metabolized 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) to a reactive metabolite that induced DNA damage measured by alkaline elution or as increased unscheduled DNA synthesis. PhIP induced mutations in Salmonella typhimurium TA98 and DNA strand breaks and sister chromatid exchange(s) in Chinese hamster V79 cells co-incubated with PCB-hepatocytes. No, or only minor genotoxic, effects were observed when hepatocytes from non-induced rats were used. The bacterial mutagenicity could be inhibited by alpha-naphthoflavone, indicating a role of P-450 in the activation of PhIP. At least eight different metabolites could be separated on HPLC after PhIP had been incubated with PCB-hepatocytes. All of the directly acting mutagenicity towards S.typhimurium TA98 co-eluted with one of the metabolites. The identity of this metabolite was concluded to be 2-hydroxamino-PhIP based on the following evidence: (i) it reduced ferric ion to ferrous ion as hydroxylamines do, (ii) it had an identical UV spectrum and chromatographic properties as a species formed upon reduction of 2-nitro-PhIP by NADPH P-450 reductase. This product displayed a major peak at m/z 241 during thermospray mass spectrometry in the positive-ion mode as would be expected from 2-hydroxamino-PhIP. 2-Hydroxamino-PhIP was directly genotoxic both to TA98 and V79 cells. The genotoxic activity of the medium after removing the hepatocytes remained stable for several hours. Compared to 2-amino-3,4-dimethylimidazo[4,5-f]quinolone (MeIQ), PhIP caused a much larger increase in DNA damage in V79 cells (with hepatocyte activation), whereas MeIQ was more potent with respect to DNA damage induced in hepatocytes and bacteria.

Animals↗
PubMed1989

Comparative genotoxicities of procarbazine and two deuterated analogs in mammalian cells in vitro and in vivo.

N-isopropyl-alpha-(2-methylhydrazino)-p-toluamide hydrochloride (procarbazine; 50-1000 micrograms/ml) induced DNA damage in hepatocytes measured by an automated alkaline elution method, whereas no significant increase in unscheduled DNA synthesis was seen. In hepatocytes isolated from PCB-treated rats, DNA damage was detected in both test systems at concentrations as low as 1-10 micrograms/ml. DNA damage, as measured by alkaline elution and sister-chromatid exchange(s), was observed also in V79 cells incubated with PCB-hepatocytes. In contrast, no mutagenic activity was observed in the Salmonella typhimurium strain TA1530 co-incubated with the hepatocytes. Exposure of rats to low doses of procarbazine (25-50 mg/kg) caused DNA damage measured by alkaline elution in liver and testis, with the liver being somewhat more sensitive. The genotoxicity caused by procarbazine was increased by a factor of 2-3 in both organs by PCB-treatment of the rats. N-isopropyl-alpha-(2-methyl-hydrazino)-p-[alpha,alpha-2H2]toluamide (d2-procarbazine), was found to cause significantly less genotoxicity in control rats than either procarbazine itself, or N-isopropyl-alpha-(2-[alpha,alpha,alpha-2H3]methylhydrazino)-p-tol uamide (d3-procarbazine). This indicates that benzylic C-H oxidation of procarbazine is an important step in the activation of procarbazine to genotoxic metabolites in uninduced rats.

Animals↗
PubMed1988

Genotoxic effects of paracetamol in V79 Chinese hamster cells.

Paracetamol was studied for possible genotoxic effects in V79 Chinese hamster cells. Paracetamol (0.5 mM for 30 min) reduced the rate of DNA synthesis in exponentially growing V79 cells to about 50% of control. A further decrease in the DNA synthesis was seen during the first 30 min after termination of paracetamol exposure. Paracetamol (3 and 10 mM for 2 h) caused a small increase in DNA single-strand breaks, as measured by the alkaline elution technique. After 16 h elution, the amount of DNA retained on the filters was 79 and 70% of controls in cells treated with 3 and 10 mM paracetamol respectively. No indication of DNA damage was seen in measuring the effect of paracetamol (0.25-10 mM for 2 h) on unscheduled DNA synthesis in growth-arrested cultures of V79 cells. At the highest concentrations (3 and 10 mM paracetamol), decreased unscheduled DNA synthesis was observed. Also UV-induced DNA-repair synthesis was inhibited by 3 and 10 mM paracetamol. DNA-repair synthesis was, however, inhibited at a much higher concentration than that inhibiting replicative DNA synthesis. The number of sister-chromatid exchanges (SCE) increased in a dose-dependent manner on 2 h exposure to paracetamol from 1 mM to 10 mM. At the highest dose tested (10 mM), the number of SCE increased to 3 times the control value. Co-culturing the V79 cells with freshly isolated mouse hepatocytes had no further effect on the paracetamol induced sister-chromatid exchanges. The present study indicates that paracetamol may cause DNA damage in V79 cells without any external metabolic activation system added.

Acetaminophen↗
PubMed1988

Toxic effects of paracetamol and related structures in V79 Chinese hamster cells.

Exposure of V79 Chinese hamster cells to non-cytotoxic concentrations of paracetamol (4-hydroxyacetanilide, 4-HAA) increased sister chromatid exchange (SCE) in the absence of an external activation system. Furthermore, a selective inhibition of DNA synthesis was observed at low 4-HAA concentrations. The inhibition could be counteracted by the addition of ascorbate, indicating that the effect is caused by an oxidation product of 4-HAA. In attempt to clarify possible relationships between cytotoxicity, inhibition of DNA synthesis and increased SCE, we studied the effect of 4-HAA and some related structures on these parameters. The relative position of the amino group and the hydroxyl group on the aromatic ring appear to be important for the inhibition of DNA synthesis. Removal of either of the two groups, N-acetylation and/or alkylation of the aromatic ring or phenolic oxygen decreased the effect of the aromatic amine on DNA synthesis. A significant response on SCE was observed with 4-amino-phenol, 4-HAA, 2-HAA, 3,5-dimethyl-4-HAA, 3-HAA and 2,6-dimethyl-4-HAA (none of the other compounds were tested). The increase in SCE frequency caused by 4-HAA and its analogs does not seem to be related to more general cytotoxic effects. The relative potencies of the compounds for SCE induction paralleled, for the most part, their effects on DNA synthesis. However, the induction of SCE and the inhibition of DNA synthesis did not occur at comparable concentrations. Thus, the possibility that 4-HAA increases the frequency of SCE through some other mechanism cannot be excluded.

Acetaminophen↗
PubMed1988

Genotoxic activity of the N-acetylated metabolites of the food mutagens 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ).

The genotoxic potential of the food mutagens 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and their N-acetylated metabolites (AcIQ and AcMeIQ, respectively) has been studied, in order to evaluate whether an initial N-acetylation of IQ or MeIQ is important for the overall in vivo genotoxicity of the compounds. When incubated with uninduced (control) rat hepatocytes, both the acetylated and the unacetylated compounds appeared to be relatively stable, whereas water-soluble metabolites (i.e. not extractable by ethyl acetate at alkaline pH) were rapidly formed with hepatocytes from PCB-induced animals. No DNA damage was induced by IQ or MeIQ in hepatocytes isolated from control rats, as measured by alkaline elution. In hepatocytes from PCB-pretreated rats, IQ, MeIQ, AcIQ and AcMeIQ induced DNA damage at low (10(-6) M) concentrations, with AcIQ being more potent than IQ whereas AcMeIQ was less potent than MeIQ. Similar patterns were observed when unscheduled DNA synthesis was measured in hepatocytes. The compounds induced sister chromatid exchanges in Chinese hamster V79 cells with PCB-induced hepatocytes as activation system; IQ and AcIQ were equal while AcMeIQ had less activity than MeIQ. The compounds were also compared in bacterial mutagenesis test systems (Salmonella typhimurium TA98). With hepatocyte activation, AcIQ was slightly more potent than IQ, whereas AcMeIQ was markedly less mutagenic than MeIQ. With subcellular fractions as activation system (rat liver S9 or microsomes), the N-acetylated compounds were similar to or less mutagenic than their parent compounds. The mutagenic effects of AcIQ and AcMeIQ in bacteria with microsomal activation were markedly reduced by the deacetylase inhibitor paraoxon.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Fluoride and energy metabolism in LS cells.

Six mM fluoride had no effect on lactate production in LS cells incubated in Eagle's minimum essential medium. In Krebs-Ringer phosphate buffer with 10 mM glucose inhibition was found with 3mM fluoride. The fluoride effect was similar in aerobic and anaerobic conditions. Twelve mM fluoride had no inhibitory effect on ATP levels in LS cells.

Adenosine Triphosphate↗
PubMed1979

Effect of sodium fluoride on protein and DNA synthesis, ornithine decarboxylase activity, and polyamine content in LS cells.

Sodium fluoride exhibited a dose dependent inhibitory effect on protein and DNA synthesis at concentrations from 1.3 mM in growing LS cells. The activity of ornithine decarboxylase (ODC) was slightly stimulated by 0.5 mM-NAF, but inhibited at 1.3 mM and above. The reduced enzyme activity seemed to be due to a reduced de novo formation of the enzyme caused by an inhibition of the protein synthesis. In spite of a reduction of ODC-activity, fluoride had no effect on the cellular polyamine content during the experimental period (10 hours).

Animals↗
PubMed1979

The effect of fluoride on the cellular uptake and pool of amino acids.

Fluoride decreased the initial uptake of 2-aminoisobutyric acid (AIB) in LS cells only in high (supralethal) concentrations and after several hours of exposure. The steady state level of AIB seemed somewhat more sensitive as it was halved after 23 hours exposure to 6 mM-NaF. The cellular levels of some natural amino acids were also reduced by fluoride. However, cells resistant to fluoride showed equally lowered levels of amino acids, indicating that the observed effect of fluoride on cellular amino acid levels may be of little importance.

Amino Acids↗
PubMed1979

Ornithine decarboxylase activity and polyamine content of normal and fluoride resistant LS cells.

The activity of ornithine decarboxylase (ODC) in suspension cultures of mouse fibroblasts, LS cells, varied in a characteristic cyclic pattern after dilution of the cultures. Two strains of fluoride resistant LS cells, FR6 and LSFR6 cells, exhibited the same cyclic pattern, but with markedly higher ODC activities. These fluoride resistant cells, however, contained less putrescine, the product of the ODC reaction. Possible reasons for this finding are discussed.

Animals↗
PubMed1978

Cellular resistance to fluoride.

Cells cultured in vitro can be adapted to grow in the presence of high concentrations of fluoride by stepwise increasing the fluoride concentration in the culture medium. Such cells seem to have the ability to exclude fluoride from intracellular compartments.

Adaptation, Physiological↗
PubMed1978

Fluoride, fluoride resistance and glycolysis in cultured cells.

Long-term (several years) exposure to fluoride induced decreased production of lactate in cultured, fluoride resistant LS cells. In intact, sensitive cells, 6 mM NaF had no effect on glycolysis, whereas in homogenates, from both resistant and sensitive cells, lactate production was blocked by 6 mM NaF, indicating the cell membrane to be a barrier to fluoride. A lower intracellular rather than extracellular fluoride concentration was found in the sensitive cell with a ratio of 0.4, whereas fluoride resistant cells excluded fluoride from their intracellular milieu.

Animals↗
PubMed1977

Glucose consumption and lactate production in normal and fluoride adapted LS cells.

The established cell line LS (mouse fibroblasts) has been adapted to grow at otherwise toxic concentrations of fluoride. Different substrains of adapted LS cells consumed less glucose and converted less of the glucose to lactate than the unadapted cells. Differences were also found in the two parameters dependent on the number of generations grown in the presence of fluoride. The more generations with fluoride, the less lactate was produced and the less glucose consumed.

Cell Line↗