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J Seidegård

Publications and source records attributed to J Seidegård.

At least 37 records · Page 2Linked to original sources
PubMed1993

Genetic polymorphism of cytochrome P4502E1 in a Swedish population. Relationship to incidence of lung cancer.

Genetic polymorphism of CYP2E1 was investigated among 195 Swedish patients with lung cancer and 206 controls. Three different polymorphic sites were found, all in introns, using RFLP and the restriction enzymes DraI, RsaI and TaqI. The frequencies of the rare alleles were 0.08-0.18 and much lower than previously described among Japanese. No significant difference in distribution of the polymorphic alleles between controls and lung cancer patients was evident, in contrast to results of a previous Japanese study. However, examination of a polymorphic site in the 5'-flanking region, within a putative binding motif for the hepatic transcription factor HNF-1, revealed a significantly less frequent distribution of the mutated allele (c2) among the lung cancer patients as compared to controls. It is concluded that major interethnic differences exist in the genetic polymorphism of CYP2E1 and that people carrying the c2 allele might be at lower risk for developing lung cancer.

Base Sequence↗
PubMed1993

Measurement and characterization of the denitrosation of tauromustine and related nitrosoureas by glutathione transferases in liver cytosol from various species.

The denitrosation of a novel nitrosourea, 1-(2-chloroethyl)-3-[(2-dimethylaminosulfonyl)-ethyl]-1-nitrosoure a, tauromustine (TCNU), has been investigated in liver cytosol from various species and with a pool of cytosolic rat liver glutathione transferases (GSTs). In addition, the denitrosation of related nitrosoureas, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) have been investigated. By using radioactive nitrosoureas as substrates and HPLC to detect the denitrosated products, a sensitive assay has been developed. The activities towards additional substrates, 1-chloro-2,4-dinitrobenzene (CDNB) and trans-stilbene oxide (tSBO) were also measured in the various cytosol fractions. The apparent Vmax and Km values for the denitrosation of TCNU in rat liver cytosol were calculated to be 830 pmol/min/mg protein and 8.4 mM respectively. The rate of denitrosation of TCNU was found to be highest in the mouse, followed by the rat and the dog. The induction of GSTs by phenobarbital in rats increased the denitrosation of TCNU similar to the activities found towards CDNB and tSBO as substrates. The highest denitrosation activity by GST was determined towards BCNU, followed by CCNU and TCNU. Our results suggest that the denitrosation of various nitrosoureas via GST may play an important role in the deactivating process occurring in vivo and for the efficacy of nitrosoureas used in chemotherapy.

Animals↗
PubMed1993

The Malmö biomarker programme.

Evaluation of pro-oxidant/antioxidant dietary factors in relation to individual susceptibility to cancer and cardiovascular disease is justified based on a review of the literature. This working hypothesis is amendable to further scientific validation from biomarkers with end-point sensitivity to oxygen radicals. So far, the biomarker programme developed around this theme may be divided into three distinct classes: (1) Markers of genotoxic exposure estimate DNA damage either directly as a biologically effective dose, or indirectly by estimating aberrant cellular functions that lead to accumulation of DNA damage. The examples included are ADP-ribosylation in mononuclear leucocytes (R. Pero, A. Olsson), oxidative DNA damage (K. Frenkel), gene expression in lymphocytes (S. Garte, G. Cosma), serum alpha macroglobulin (W. Troll) and oxidized DNA damage and repair (N. Christie). (2) Markers of genetic predisposition have been shown to have genetic inheritance patterns that relate to individual susceptibility to cancer or cardiovascular disease. The examples included are glutathione transferase mu phenotyping (R. Pero, J. Seidegård) and poly (ADP-ribose) polymerase pseudogene polymorphism (M. Smulson). (3) Markers of dietary status have been validated to estimate the amount of a particular nutrient or xenobiotic in the diet that has been taken up and metabolized or distributed to body fluids or tissues. The example included here is niacin nutriture (E. Jacobson, M. Jacobson). This biomarker is presented in Section 5 (pp. 59-62) of the Malmö Diet and Cancer Programme Minisymposium reported in this issue of the journal.

Animals↗
PubMed1993

Glutathione transferase activity in human vessels and in cultured arterial smooth muscle cells.

Glutathione transferases play an important role in the detoxification of many different endogeneous and exogenous compounds such as metabolites of polycyclic aromatic hydrocarbons (PAH) of cigarette tar. There is evidence that PAH may be atherogenic. The glutathione transferase activity towards trans-stilbene oxide (GST-tSBO) can be separated in blood in GST-positive and GST-negative phenotypes. We have previously suggested that the GST-negative phenotype may be associated with a higher morbidity in intermittent claudication among middle aged smokers. In the present study, GST-tSBO could easily be measured in human, rabbit and bovine arterial smooth muscle cells (SMC) in culture. The level of GST-tSBO was higher in rabbit than in bovine SMC. It was stable in bovine SMC during 5 cell passages and it could be induced twofold by long-time incubation with dimethylsulfoxide-soluble particulate matter from cigarette smoke or 3,4-benzo(a)pyrene. There was a positive correlation between the level of GST-tSBO in blood and in "healthy" arterial and venous tissue from individuals operated with coronary bypass. The enzyme levels in arterial tissue were lower than in venous tissue. GST-tSBO in atherosclerotic segments of human arteries was lower than in "healthy" segments from the same artery. These findings suggest that the arterial wall may have a low defense against toxic compounds that may decrease further as atherosclerosis proceeds. It is concluded that SMC are suitable for the study of the effects of PAH in relation to GST-tSBO and that the enzyme activity in blood will reflect the individual GST-tSBO phenotype also in vascular tissues.

Adult↗
PubMed1992

Human fibroblasts lacking trans-stilbene oxide active glutathione transferase exhibit increased cell death when exposed to polycyclic aromatic hydrocarbons.

Glutathione transferases (GST) are detoxifying enzymes who act with many endogenous and exogenous substances such as polycyclic aromatic hydrocarbons (PAH). The GST activity towards trans-stilbene oxide (GST-tSBO) is inherited in an autosomal dominant fashion and can be separated in high (GST-positive) and low (GST-negative) phenotypes when measured in blood. Human fibroblast cultures were established from males matched for age, smoking habits and clinical manifestations of atherosclerosis. Matched pairs of GST-negative and GST-positive fibroblasts were studied. There was a very strong correlation between the levels of GST-tSBO in peripheral blood and in cultured fibroblasts within the same individual. When fibroblasts were exposed to benzo(a)pyrene (BP) or dimethylbenzanthracene (DMBA) GST-negative cells produced relatively more collagen than GST-positive cells. GST-negative fibroblasts showed a greater cell death than GST-positive fibroblasts as well among controls as after exposure to PAH. It is concluded that lack of GST-tSBO is easily discriminated in cultured skin fibroblasts. GST-negative and GST-positive fibroblasts showed different susceptibility towards some toxic stimuli that might be of importance in atherogenesis.

Aged↗
PubMed1990

Metabolism of a novel nitrosourea, tauromustine, in the rat.

A novel nitrosourea, 1-(2-chloroethyl)-3-[2-(dimethylaminosulphonyl)ethyl]1-nitrosourea , tauromustine (TCNU), has been investigated for in vitro metabolism by different rat organs. Two kinds of reactions were seen, demethylation and denitrosation, both reactions required NADPH. These reactions were achieved by the liver microsomes and to a much lesser extent by lung microsomes. Induction of cytochrome P450 system with phenobarbital resulted in increased demethylation (10 times) and denitrosation (6 times) of tauromustine while induction with 3-methylcholanthrene did not have any significant effect on these reactions. Known inhibitors of different cytochrome P450 activities inhibited the demethylation and denitrosation of tauromustine to different levels. After oral administration of [14C]tauromustine a metabolic pattern similar to that observed in vitro experiments, was seen in the urine. The demethylated compound, which has alkylating cytotoxic activity, could be detected in the urine up to 8 hr after oral administration.

Animals↗
PubMed1990

Isoenzyme(s) of glutathione transferase (class Mu) as a marker for the susceptibility to lung cancer: a follow up study.

Glutathione transferase are divided into three classes: Alpha, Mu and Pi. Isoenzyme(s) from one of these classes, class Mu, is dominantly inherited and can be determined by activity measurements directed towards the substrate trans-stilbene oxide. The frequency of this phenotype has been measured in patients with bronchial carcinoma and in control subjects matched for age and smoking history. After combining an earlier study from our laboratory (Carcinogenesis, 7, 751-753, 1986) with the additional material presented here (control smokers, n = 114, lung cancers, n = 125) non-cancer smokers had an increased number of subjects who expressed class Mu isoenzymes (58.3% of total n = 192) compared with lung cancer patients (36.6% of total n = 191; P less than 0.0001). The pathology of lung tumors related to the lack of class Mu isoenzymes which occurred most frequently in patients with adenocarcinomas. It is concluded that the gene expressing class Mu isoenzymes may be a host determinant of genetic susceptibility to lung cancer among smokers.

Adenocarcinoma↗
PubMed1989

Identification of the trans-stilbene oxide-active glutathione transferase in human mononuclear leukocytes and in liver as GST1.

A glutathione transferase from human mononuclear leukocytes with a high activity toward trans-stilbene oxide (GT-tSBO) has been studied in liver and blood from fetus and adults and in blood from neonates. Using starch gel electrophoresis, different phenotypes of GST1 have been determined, GST1 0, GST1 1, and GST1 2. As judged from activity measurements and the fact that only those individuals who express the null allele of GST1, the GST1 0, which has a low activity toward trans-stilbene oxide, it is concluded that the hepatic transferase GST1 is identical to GT-tSBO, as well as to hepatic transferase mu. In addition, it has been shown that the different genotypes of GST1 1 (GST1 1-1, GST1 1-0) and GST1 2 (GST1 2-2, GST1 2-0) can be separated by measuring the GT-tSBO activity in whole blood from the same individual. It is also demonstrated that GT-tSBO activity is much lower in fetal liver, approximately 10 times, compared with adult liver, while this activity seems to be unchanged in the blood from fetus and adults, as well as in neonates.

Adult↗
PubMed1988

Biological effects in a chemical factory with mutagenic exposure. II. Analysis of unscheduled DNA synthesis and adenosine diphosphate ribosyl transferase, epoxide hydrolase, and glutathione transferase in resting mononuclear leukocytes.

A chemical plant, where an increased number of non-Hodgkin's lymphomas and myelomas had been observed, was monitored for genotoxic effects occurring in peripheral mononuclear leukocyte samples from 76 exposed workers. Biochemical markers sensitive to DNA repair and drug metabolism were used as the indicators of genotoxic risk. Unscheduled DNA synthesis (UDS) and covalent binding induced by N-acetoxy-N-acetyl-2-aminofluorene (NA-AAF) and constitutive and gamma ray induced adenosine diphosphate ribosyl transferase (ADPRT) activities were highly and significantly elevated over the corresponding values for a control group of 48 postal workers. Microsomal and soluble epoxide hydrolases and glutathione transferase activities directed towards trans-stilbene oxide and 1-chloro-2,4-dinitrobenzene were not significantly altered in the exposed group. The exposure in this factory was complex, involving over 100 chemicals including several well known carcinogens. However, no apparent significant associations to exposure could be established.

Acetoxyacetylaminofluorene↗
PubMed1988

Hereditary differences in the expression of the human glutathione transferase active on trans-stilbene oxide are due to a gene deletion.

Glutathione transferase (GT; EC 2.5.1.18) mRNA levels were measured in human liver samples by using mouse and human cDNA clones that encode class-mu and class-alpha GT. Although all the RNA samples examined contained class-alpha GT mRNA, class-mu GT mRNA was found only in individuals whose peripheral leukocytes expressed GT activity on the substrate trans-stilbene oxide. The mouse class-mu cDNA clone was used to identify a human class-mu GT cDNA clone, lambda GTH411. The amino acid sequence of the GT encoded by lambda GTH411 is identical with the 23 residues determined for the human liver GT-mu isoenzyme and shares 76-81% identity with mouse and rat class-mu GT isoenzymes. The mouse and human class-mu GT cDNA inserts hybridize with multiple BamHI and EcoRI restriction fragments in the human genome. One of these hybridizing fragments is missing in the DNA of individuals who lack GT activity on trans-stilbene oxide. Hybridizations with nonoverlapping subfragments of lambda GTH411 suggest that there are at least three class-mu genes in the human genome. One of these genes appears to be deleted in individuals lacking GT activity on trans-stilbene oxide.

Amino Acid Sequence↗
PubMed1988

The genetic variation and the expression of human glutathione transferase mu.

A glutathione transferase from human leukocytes (GT-tSBO) with high activity towards trans-stilbene oxide has now been found to correspond to the hepatic class Mu glutathione transferase. This class, Mu, of transferase(s) has been found in high concentration in liver, kidney, and adrenal gland, judged by he activity of GT-tSBO. This activity is only found in some individuals, approximately 46%. By using a cDNA clone derived from class Mu transferase(s) from mouse, it is suggested that this enzyme is not transcribed, depending on a deletion (of a part) of a gene in those individuals that are lacking the activity towards tSBO.

Chromosome Mapping↗
PubMed1987

The trans-stilbene oxide-active glutathione transferase in human mononuclear leucocytes is identical with the hepatic glutathione transferase mu.

A glutathione transferase from human mononuclear leucocytes with high activity towards trans-stilbene oxide (GT-tSBO) was purified. GT-tSBO is expressed in only about 50% of the individuals studied. As judged from activity measurements, immunological studies and the fact that only those individuals who express glutathione transferase mu have high activity towards trans-stilbene oxide, it is concluded that the hepatic transferase mu is identical with the glutathione transferase (GT-tSBO) in mononuclear leucocytes.

Dinitrochlorobenzene↗
PubMed1986

The effects of metyrapone, chalcone epoxide, benzil, clotrimazole and related compounds on the activity of microsomal epoxide hydrolase in situ, in purified form and in reconstituted systems towards different substrates.

The influence of metyrapone, chalcone epoxide, benzil and clotrimazole on the activity of microsomal epoxide hydrolase towards styrene oxide, benzo[a]pyrene 4,5-oxide, estroxide and androstene oxide was investigated. The studies were performed using liver microsomes from rats, rabbits, mice and humans; epoxide hydrolase purified from rat liver microsomes to apparent homogeneity; and the purified enzyme incorporated into liposomes composed of egg-yolk phosphatidylcholine or total rat liver microsomal lipids. All four effectors were found to activate the hydrolysis of styrene oxide by epoxide hydrolase in situ in rat liver microsomal membranes, in agreement with earlier findings. Epoxide hydrolase activity towards styrene oxide in liver microsomes from mouse, rabbit and man was also increased by all four effectors. The most striking effect was a 680% activation by clotrimazole in rat liver microsomes. However, none of the effectors activated microsomal epoxide hydrolase more than 50% when benzo[a]pyrene 4,5-oxide, estroxide or androstene oxide was used as substrate. Indeed, clotrimazole was found to inhibit microsomal epoxide hydrolase activity towards estroxide 30-50% and towards androstene oxide 60-90%. The effects of these four compounds were found to be virtually identical in the preparations from rats, rabbits, mice and humans. The effects of metyrapone, chalcone epoxide, benzil and clotrimazole on purified epoxide hydrolase were qualitatively the same as those on epoxide hydrolase in intact microsomes, but much smaller in magnitude. These effects were increased in magnitude only slightly by incorporation of the purified enzyme into liposomes made from egg-yolk phosphatidylcholine. However, when incorporation into liposomes composed of total microsomal lipids was performed, the effects seen were essentially of the same magnitude as with intact microsomes. When the extent of activation was plotted against effector concentration, three different patterns were found with different effectors. Activation of epoxide hydrolase activity towards styrene oxide by clotrimazole was found to be uncompetitive with the substrate and highly structure specific. On the other hand, inhibition of epoxide hydrolase activity towards androstene oxide by clotrimazole was found to be competitive in microsomes. It is concluded that the marked effects of these four modulators on microsomal epoxide hydrolase activity are due to an interaction with the enzyme protein itself, but that the presence of total microsomal phospholipids allows the maximal expression leading to similar degrees of modulation as those observed in intact microsomes.(ABSTRACT TRUNCATED AT 400 WORDS)

Aldehydes↗
PubMed1986

A glutathione transferase in human leukocytes as a marker for the susceptibility to lung cancer.

Leukocyte isozyme(s) of glutathione transferase (GT-tSBO) has been shown to be dominantly inherited. The frequency of the phenotypes of this isozyme in bronchial carcinoma and control patients matched for age and smoking history is reported here. Control smokers showed an increased likelihood of having GT-tSBO (59%) compared with lung cancer patients (35%). The lack of GT-tSBO was related to the extent of smoking by the lung cancer patients but not to the pathology of the lung tumor. It was concluded that the gene expressing this isozyme(s) may be a host genetic determinant of susceptibility to lung cancer in smokers.

Aged↗
PubMed1985

The hereditary transmission of high glutathione transferase activity towards trans-stilbene oxide in human mononuclear leukocytes.

High glutathione transferase activity towards trans-stilbene oxide has been observed in resting mononuclear leukocytes only in a portion of the individuals examined. Approximately 46% of a population of 248 individuals demonstrated this high activity. In addition, eight families have been investigated in order to elucidate the hereditary transmission of this activity. The results are consistent with a dominant expression of a single gene located on an autosomal chromosome for this high glutathione transferase activity.

Adolescent↗
PubMed1985

Subcellular distribution, catalytic properties and partial purification of epoxide hydrolase in the human adrenal gland.

Epoxide hydrolase in human adrenal gland was characterized with respect to catalytic properties and subcellular distribution. With human adrenal microsomes and the substrates styrene-7,8-oxide, cis-stilbene oxide, estroxide and androstene oxide the specific activities were between 1.9 and 19.0 nmol/min/mg protein. With styrene-7,8-oxide as substrate the apparent Km-value was 0.98 mM and the pH optimum was 9.2. Subcellular fractionation revealed that the bulk of the activity was confined to the endoplasmic reticulum. Different compounds known to influence rodent microsomal epoxide hydrolase activity were also tested on the human adrenal enzyme. 1,1,1-Trichloropropene-2,3-oxide (TCPO) and cyclohexene oxide (CHO) inhibited the activity while benzil and clotrimazole stimulated the activity. Partial purification of human adrenal epoxide hydrolase indicates that its molecular weight is about 51 000 and that its concentration relative total protein in the human adrenal microsomes is about 10%.

Adrenal Glands↗
PubMed1985

Hereditary interindividual differences in the glutathione transferase activity towards trans-stilbene oxide in resting human mononuclear leukocytes are due to a particular isozyme(s).

We have shown earlier that there are large, hereditary interindividual differences in the cytosolic glutathione transferase activity towards trans-stilbene oxide in human mononuclear leukocytes. In the present study we ask whether these differences reflect the presence or absence of a particular isozyme(s) of glutathione transferase. First, in order to measure the high glutathione transferase activity optimally it was necessary to modify our previous assay by increasing the concentration of reduced glutathione from 3 to 5 mM and of the substrate from 50 to 250 microM. It was then found that the low activity demonstrates an apparent Km for trans-stilbene oxide of 28.3 microM, whereas the corresponding value for the high activity was 127 microM. Secondly, it was found that while glutathione transferase activity towards trans-stilbene oxide in different individuals segregated into three groups, low, high and very high, glutathione transferase activity towards 1-chloro-2,4-dinitrobenzene in these same mononuclear leukocyte fractions formed only a single group with no tendency towards such segregation. Thirdly, the SDS-poly-acrylamide gel electrophoretic pattern obtained with the supernatant fraction from mononuclear cells demonstrating high glutathione transferase activity towards trans-stilbene oxide contained a band of 25 000 molecular weight which was either absent or present at a much lower level in cells demonstrating low activity. We conclude that high activity towards trans-stilbene oxide in circulating, resting human mononuclear cells is catalyzed by a particular isozyme(s) of glutathione transferase. cis-Stilbene oxide, styrene oxide and, possibly, benzo[a]pyrene 4,5-oxide are also substrates for this isozyme(s).

Dinitrochlorobenzene↗