Search PubMed⌕ Search

Biomedical subjects

J Seidegård

Publications and source records attributed to J Seidegård.

At least 19 recordsLinked to original sources
PubMed2000

Effect of an oral contraceptive on the plasma levels of budesonide and prednisolone and the influence on plasma cortisol.

OBJECTIVE: To investigate whether the use of an oral contraceptive would influence plasma levels of budesonide (Entocort capsules) or prednisolone (plain tablets) during repeated oral administration of these glucocorticosteroids. Plasma concentrations of cortisol and ethinyl estradiol (INN, ethinylestradiol) were also compared. METHODS: Forty healthy women took part in this single-blind, randomized placebo-controlled study with two parallel groups, where a three-way crossover design was applied within groups. One group was taking an oral contraceptive (150 microg desogestrel and 30 microg ethinyl estradiol); the other group (control) was not. On seven consecutive mornings, oral doses of 4.5 mg budesonide, 20 mg prednisolone, or placebo were administered. There was a washout period of at least one menstrual cycle between administration periods. RESULTS: In the oral contraceptive users, the average plasma concentration of prednisolone was 131% higher than in the control group (P < .001), whereas the average plasma concentration of budesonide was only 22% higher (not significant). Mean plasma cortisol levels were suppressed by 90% and 82% with prednisolone and by 22% and 28% with budesonide in oral contraceptive users and the control subjects, respectively. The group difference was significant with prednisolone (P < .001) but not with budesonide. Ethinyl estradiol levels in plasma were not affected by administration of either glucocorticosteroid. CONCLUSION: No difference was found in plasma levels of budesonide or in cortisol suppression after administration of budesonide capsules in women taking the oral contraceptive and those who were not. The oral contraceptive users had much higher plasma levels of prednisolone and greater cortisol suppression. This result suggests that oral budesonide can be used with maintained safety in women using oral contraceptives.

Administration, Oral↗
PubMed2000

Reduction of the inhibitory effect of ketoconazole on budesonide pharmacokinetics by separation of their time of administration.

BACKGROUND: Budesonide is a glucocorticosteroid used in the treatment of, for example, inflammatory bowel diseases, with a recommended once-daily morning dosing regimen. Ketoconazole is a potent inhibitor of the cytochrome P450 3A (CYP3A) activities and known to inhibit the elimination of drugs metabolized by CYP3A, including budesonide. It is of therapeutic interest to know whether the influence of ketoconazole can be reduced by administration on an occasion different in time to CYP3A substrates. METHODS: Eight healthy men completed this randomized, open crossover study that comprised three different periods. In period 1, a single oral dose of 3 mg budesonide was given in the morning. In period 2, a 200-mg ketoconazole tablet was administered once daily in the morning on 4 consecutive days. On the fourth day, 3 mg budesonide was administered at the same time as the ketoconazole. In period 3, 200 mg ketoconazole was administered once daily in the evening on 4 consecutive days. On the fourth day, 3 mg budesonide was administered 12 hours before the ketoconazole. One-week washout periods separated the budesonide administrations. RESULTS: The mean area under the plasma drug concentration-time curve [AUC(0-24)] for budesonide was increased by 6.5 times when it was given simultaneously with ketoconazole. When the administrations of the two drugs were separated by 12 hours, the mean AUC(0-24) for budesonide was increased by only 3.8 times. CONCLUSION: This study shows that the capability of ketoconazole to inhibit the elimination of budesonide is significantly reduced (by 50%) by a 12-hour separation of the administration times.

Adult↗
PubMed2000

Metabolism of roquinimex in mouse and rat: an in vitro/in vivo comparison.

1. In vitro studies with roquinimex, an immuno-modulator, in liver microsomes from mouse and rat were conducted to evaluate the primary metabolism and compare the metabolite pattern as well as the rate of metabolism with the in vivo pharmacokinetics of the compound in these two species. 2. In the presence of NADPH, roquinimex was metabolized to six primary metabolites (R1-6) by liver microsomes from mouse and rat. The formation of these metabolites was qualitatively similar in both species, and was greatly enhanced by pretreatment with PCN, an inducer of cytochrome P4503A. 3. The identification of the R1-6 demonstrated that roquinimex had been hydroxylated and demethylated. Hydroxylation at different sites of the quinoline moiety was the dominating reaction in both species. 4. Comparison of the resulting microsomal intrinsic clearance of 0.3 micromol mg(-1) protein min(-1) in mouse liver microsomes, versus 0.03 micromol mg(-1) protein min(-1) in rat liver microsomes demonstrated that the mouse possesses about a 10-fold greater metabolic capacity for roquinimex than the rat. 5. The in vivo pharmacokinetics of roquinimex demonstrated a 7-fold higher clearance in mouse than in the rat (82 ml h(-1) kg(-1) in mouse, 10.6 ml h(-1) kg(-1) in rat), which is in concordance with the in vitro findings.

Adjuvants, Immunologic↗
PubMed2000

Identification of cytochrome P4503A as the major subfamily responsible for the metabolism of roquinimex in man.

1. Roquinimex, a novel immunomodulator, is metabolized in liver microsomes from mouse and rat via cytochrome P450s to four hydroxylated and two demethylated metabolites (R1-6). The study investigated which cytochrome P450 enzyme(s) is responsible for the metabolism of roquinimex in man. 2. Enzyme kinetic analysis demonstrated an apparent Km = 1.28-7.00 mM and Vmax = 50-159 pmol x mg(-1) microsomal protein x min(-1) for the primary metabolites in human liver microsomes. The sum of Cl(int) for the primary pathways was 0.167 microl x mg(-1) microsomal protein x min(-1). 3. A correlation between the formation rate of R1-6 and 6beta-hydroxylation of testosterone was obtained within a panel of liver microsomes from 11 individuals (r2 = 0.72-0.97). Furthermore, significant inhibition (>90%) of roquinimex primary metabolism was demonstrated by ketoconazole and troleandomycin, specific inhibitors of CYP3A4 as well as with anti-CYP3A4 antibodies. Moreover, a similar metabolite pattern was produced from roquinimex by incubation with cDNA-expressed CYP3A4 as by human liver microsomes. 4. In conclusion, these data indicate a major role for CYP3A4 in the formation of roquinimex primary metabolites in human liver microsomes.

Antibodies↗
PubMed2000

Influence of glutathione metabolising enzymes in rats with gram-negative sepsis.

OBJECTIVE: To evaluate the role of glutathione metabolising enzymes in rats with Gram-negative sepsis. SETTING: University hospital, Sweden. ANIMALS: 61 male Sprague Dawley rats. INTERVENTIONS: Animals were divided into two groups, one of which was given tert-butyl-4-hydroxyanisole (BHA), a powerful inducer of glutathione metabolising enzymes. A gelatine capsule containing bacteria and adjuvant substances was placed in the abdomen. In one group it contained only adjuvant substances, and the controls underwent sham laparotomy. MAIN OUTCOME MEASURES: Activities of glutathione metabolising enzymes, and histological effect on pulmonary tissue. RESULTS: Activities of glutathione metabolising enzymes were reduced in lung tissue after the induction of sepsis. Pre-treatment with BHA increased enzyme activity and reduced the histological changes. CONCLUSION: Glutathione metabolising enzymes may have a role in sepsis, and pre-treatment with BHA seems to prevent histological changes in pulmonary tissue in septic rats.

Animals↗
PubMed1999

Metabolism of tauromustine in liver and lung microsomes from various species.

1. The cytochrome P450 (CYP)-mediated metabolism of tauromustine has been evaluated in liver and lung microsomes from various species. Liver microsomes from rat pretreated with typical CYP inducers, human liver microsomes and cDNA-expressed human CYP enzymes were used to study the enzymatic basis of the metabolism. The further metabolism of the monodemethylated product of tauromustine and that of the denitrosated product were also investigated. 2. The major routes of tauromustine metabolism were demethylation to the alkylating active compound, R2, and denitrosation to the inactive metabolite, M3. The extent of metabolism and the activity of demethylation versus denitrosation varied among the species. The highest metabolism was found in mouse (BDF strain) followed by dog, rat and the human liver. Tauromustine was also metabolized to a low extent in lung microsomes from these species. 3. The further metabolism of R2 and M3 was approximately 100 times lower in activity than that of tauromustine. Both the demethylation and the denitrosation of tauromustine were increased 3-fold in liver microsomes from rat pretreated with phenobarbital, whereas treatment with cyanopregnenolone enhanced the denitrosation 11-fold, indicating the involvement of CYP3A. 4. Metabolism across a panel of 10 human liver microsomal samples demonstrated a correlation with testosterone 6beta-hydroxylation of demethylation (r2 = 0.86) and denitrosation of tauromustine (r2 = 0.79). Among the human cDNA expressed CYP enzymes, not only was tauromustine determined to be catalysed predominantly by CYP3A4, but also to some extent by CYP2C19 and CYP2D6. 5. In conclusion, the present results indicate a major role of CYP3A enzymes in the metabolism of tauromustine.

Animals↗
PubMed1998

Regulation of rat glutathione S-transferase A5 by cancer chemopreventive agents: mechanisms of inducible resistance to aflatoxin B1.

The rat can be protected against aflatoxin B1 (AFB1) hepatocarcinogenesis by being fed on a diet containing the synthetic antioxidant ethoxyquin. Evidence suggests that chemoprotection against AFB1 is due to increased detoxification of the mycotoxin by one or more inducible drug-metabolising enzymes. The glutathione S-transferase (GST) isoenzymes in rat liver that contribute to ethoxyquin-induced chemoprotection against AFB1 have been identified by protein purification. This approach resulted in the isolation of several heterodimeric class alpha GST, all of which contained the A5 subunit and possessed at least 50-fold greater activity towards AFB1-8,9-epoxide than previously studied transferases. Molecular cloning and heterologous expression of rat GSTA5-5 has led to the demonstration that it exhibits substantially greater activity for AFB1-8,9-epoxide than other rat transferases. The A5 homodimer can also catalyse the conjugation of glutathione with other epoxides, such as trans-stilbene oxide and 1,2-epoxy-3-(4'-nitrophenoxy)propane, and possesses high catalytic activity for the reactive aldehyde 4-hydroxynonenal. Western blotting has shown that the A5 subunit is not only induced by ethoxyquin but that it is also induced by other cancer chemopreventive agents, such as butylated hydroxyanisole, oltipraz, benzyl isothiocyanate, indole-3-carbinol and coumarin. In addition to GSTA5, we have identified a novel aflatoxin-aldehyde reductase (AFAR) that is similarly induced by ethoxyquin. However, immunoblotting has shown that GSTA5 and AFAR are not always co-ordinately regulated by chemoprotectors. In order to gain a better understanding of the mechanisms responsible for the induction of GSTA5 protein, the GSTA5 gene has been cloned. It was isolated on two overlapping bacteriophage lambda clones and found to be approximately 12 kb in length. The transcriptional start site of GSTA5 has been identified 228 bp upstream from the ATG translational initiation codon. Computer-assisted analysis of the upstream sequence has indicated the presence of a putative antioxidant responsive element (located between -421 and -429 bp) which may be responsible for the induction of GSTA5 by chemopreventive agents.

Aflatoxin B1↗
PubMed1998

Effect of grapefruit juice on urinary 6 beta-hydroxycortisol/cortisol excretion.

1. The aim of the present study was to evaluate the effect of grapefruit juice on urinary 6 beta-hydroxycortisol and cortisol excretion in healthy subjects. 2. The ratio of 6 beta-hydroxycortisol/cortisol was significantly decreased (P = 0.036) in the 0-4 h fraction of urine after ingestion of grapefruit juice, but not in the 4-24 h fraction (P = 0.218) or for the compiled data, fraction 0-24 h (P = 0.114). 3. These results indicate that endogenous cortisol metabolism may not only be of hepatic origin, but may also be dependent on the metabolic capacity of cytochrome P450 IIIA (CYP3A) in the gut mucosa. 4. This finding may cast further doubts of the usefulness of the 6 beta-hydroxycortisol/cortisol ratio as an indicator of hepatic CYP3A activity.

Adult↗
PubMed1997

Frequent occurrence of CYP2D6 gene duplication in Saudi Arabians.

The polymorphic cytochrome P450 2D6 (CYP2D6) causing poor, extensive or ultrarapid metabolism of several clinically important drugs exhibits pronounced interethnic variation. Ultrarapid metabolism is caused by multiple copies of active CYP2D6 genes and recently 29% of an Ethiopian population has been shown to carry duplicated or multiduplicated CYP2D6 genes, whereas the corresponding frequency in other black, Oriental and European populations investigated is 1-2%. In order to characterize the distribution of alleles with multiple CYP2D6 copies in a neighbouring population and to characterize the CYP2D locus in general among Saudi Arabians, the CYP2D6 genotype of a Saudi Arabian population was examined using restriction fragment length polymorphism (RFLP) analysis and allele-specific polymerase chain reaction (PCR) amplification. Of 101 Saudi Arabians studied, 21 subjects had an EcoRI fragment indicative of CYP2D6 gene duplication. In contrast, only two individuals were heterozygous for a deletion of the whole gene (CYP2D6*5). The allele frequency of CYP2D6*4, the most common defective allele among Caucasians, was only 3.5% in the Saudi population. Two other alleles, CYP2D6*10 and *17, common in certain populations and which cause diminished enzyme activity, were found only at low allele frequencies of 3.0% each. These findings are in agreement with earlier Saudi Arabian phenotyping studies which reported a low frequency (1-2%) of poor metabolizers for CYP2D6 probe drugs. In conclusion, the Saudi Arabian population studied exhibited very few defective alleles and a large number of subjects carried duplicated CYP2D6 genes, implying a high conservation on functional CYP2D6 genes possibly due to dietary reasons and reveal the Saudi Arabians as an unique population in comparison with others examined.

Adult↗
PubMed1997

Characterization of a human glutathione S-transferase mu cluster containing a duplicated GSTM1 gene that causes ultrarapid enzyme activity.

The mu class glutathione S-transferase gene GSTM1 is polymorphic in humans, with approximately half of the Caucasian population being homozygous deleted for this gene. GSTM1 enzyme deficiency has been suggested to predispose people to lung and bladder cancer. Some people in a Saudi Arabian population, however, have been described previously with ultrarapid GSTM1 enzyme activity. Here we have evaluated the molecular genetic basis for this observation. Genomic DNA from two Saudi Arabian subjects exhibiting ultrarapid enzyme activity and from 13 Swedish subjects having null, one, or two GSTM1 genes were subjected to restriction fragment length polymorphism analysis using the restriction enzymes EcoRI, EcoRV, and HindIII and combinations thereof. Hybridization was carried out using a full-length GSTM1 cDNA or the 5' and 3' parts of the cDNA. The restriction mapping data revealed the presence of a GST mu cluster with two GSTM1 genes in tandem situated between the GSTM2 and GSTM5 genes. A quantitative multiplex polymerase chain reaction method, which simultaneously amplified a fragment of the GSTM1 gene and the beta-globin gene, was developed, and the genomic GSTM1 copy number was determined from the GSTM1/beta-globin ratio. This method clearly separated GSTM1 +/- subjects (ratios between 0.4 and 0.7) from GSTM1 +/+ subjects (ratios between 0.8 and 1.2). The two Saudi Arabians with ultrarapid GSTM1 activities had ratios of approximately 1.5, indicating that they carried three GSTM1 genes. These results demonstrate the existence of a novel mu class GST cluster containing a duplicated active GSTM1 gene causing ultrarapid enzyme activity.

Binding Sites↗
PubMed1997

The role of human glutathione transferases and epoxide hydrolases in the metabolism of xenobiotics.

Human glutathione transferases (GSTs) are a multigene family of enzymes that are involved in the metabolism of a wide range of electrophilic compounds of both exogenous and endogenous origin. GSTs are generally recognized as detoxifying enzymes by catalyzing the conjugation of these compounds with glutathione, but they may also be involved in activation of some carcinogens. The memmalian GSTs can be differentiated into four classes of cytosolic enzymes and two membrane bound enzymes. Human epoxide hydrolases (EHs) catalyze the addition of water to epoxides to form the corresponding dihydrodiol. The enzymatic hydration is essentially irreversible and produces mainly metabolites of lower reactivity that can be conjugated and excreted. The reaction of EHs is therefore generally regarded as detoxifying. The mammalian EHs can be distinguished by their physical and enzymatic properties. Microsomal EH (mEH) exhibits a broad substrate specificity, while the soluble EH (sEH) is an enzyme with a "complementary" substrate specificity to mEH. Cholesterol EH and leukotriene A4 hydrolase are two EHs with very limited substrate specificity. The activities of either GSTs or EHs expressed in vivo exhibit a relatively large interindividual variation, which might be explained by induction, inhibition, or genetic factors. These variations in levels or activities of individual isoenzymes are of importance with respect to an individual's susceptibility to genotoxic effects. This article gives a general overview of GSTs and EHs, discussing the modulation of activities, determination of these enzymes ex vivo, and the polymorphic expression of some isoenzymes.

Epoxide Hydrolases↗
PubMed1996

Glutathione and phospholipid depletion of liver tumors after arterial ischemia.

Breakdown of membrane phospholipids is a causative event leading to irreversible cell injury after ischemia and reperfusion insults, which might be one mechanism leading to liver tumor cell death after repeated arterial ischemia as well. After 2 hr of hepatic dearterialization followed by 30 min of reperfusion tumor phospholipid was measured chromatographically, glutathione (GSH) analyzed by determining nonprotein sulfhydryl and activity of glutathione-S-transferase (GST) determined spectrophotometrically using 1-chloro-2,4-dinitrobenzene (CDNB) as the substrate. A transient, arterial ischemia for 2 hr induced a substantial decrease of phosphatidylserine (PS) and phosphatidylinosital (PI) compared with sham treatment (P < 0.01). Although phosphatidylcholine (PC) and phosphatidylethanolamine (PE) did not significantly decline after a single arterial ischemia for 2 hr, they dropped dramatically following repeated arterial ischemia for 2 hr during 5 days (P < 0.01 and P < 0.05 respectively). GSH was depleted in tumors after both a single (P < 0.01) and repeated arterial ischemia (P < 0.05) and GST was inactivated as well (P < 0.001). By contrast, neither liver phospholipid nor liver GSH or GST was significantly changed. Tumor growth was significantly retarded in rats subjected to repeated arterial ischemia compared with sham treatment (P < 0.01). Repeated arterial ischemia facilitated degradation of tumor membrane phospholipids and induced depletion of GSH and inactivation of GST without affecting the normal liver. Thus, ischemia/reperfusion induced depletion of membrane phospholipids and of GSH might represent two mechanisms by which repeated arterial ischemia led to tumor growth delay.

Animals↗
PubMed1995

P53 polymorphisms and haplotypes in lung cancer.

An association between the BstU I 1-1 (Pro-Pro) genotype of the p53 codon 72 polymorphism and lung cancer has previously been reported by Kawajiri et al. A reanalysis of the data by Kawajiri et al. revealed no significant difference between patients and controls with respect to allele frequencies, and the increased frequency of BstU I 1-1 homozygotes was mostly ascribable to a deviation from the Hardy-Weinberg equilibrium. In an attempt to replicate the results by Kawajiri et al. we have studied three p53 polymorphisms (BstU I and Msp I RFLPs in exon 4 and intron 6 respectively and a 16 bp duplication in intron 3) and their haplotypes in Swedish lung cancer patients and controls. The results concerning the codon 72 polymorphism were largely negative. Thus there was no significant association between lung cancer and the BstU I 1-1 type, and only a marginal difference (P = 0.044) with respect to the BstU I allele frequency when lung cancer patients were compared with patients with chronic obstructive pulmonary disease (COPD). However, when the analysis was based on haplotype frequencies larger differences appeared and it was found that only BstU I 1 (pro) alleles linked to 16 bp 1 alleles were associated with lung cancer. Pro alleles linked to the 16 bp duplication appeared instead to confer some protection against cancer. Thus the codon 72 alleles need not be functionally involved in lung cancer, but may rather be markers in linkage disequilibrium with other cancer susceptibility sites on p53.

Alleles↗
PubMed1994

Genetic susceptibility to lung cancer with special emphasis on CYP1A1 and GSTM1: a study on host factors in relation to age at onset, gender and histological cancer types.

Genetically based differences in metabolism, related to MspI restriction site and Ile-Val polymorphisms of the cytochrome P450 (CYP) 1A1 gene and the null genotype of glutathione transferase class mu (GSTM1), have been reported to be associated with lung cancer susceptibility. The present study was set up to establish the frequencies of the polymorphic genotypes of CYP1A1 and GSTM1 in Sweden, to evaluate a possible increased incidence of the genotypes associated with higher lung cancer risks among Swedish lung cancer patients and to try to make a combined risk estimate for carriers of multiple risk alleles. In a healthy control group, all under 66 years of age, 53% (174/329) of the subjects were of the GSTM1(-) genotype, while in a hospital control group 49% (39/79) carried the GSTM1(-) genotype. In the investigated lung cancer patients this genotype was found in 56% (165/296) and among those patients diagnosed before 66 years of age the deficient genotype was found in 60% (78/131). The highest proportion of the GSTM1(-) genotype was found in patients diagnosed with adenocarcinoma (63%, 29/46) and small cell carcinoma (72%, 21/29) before 66 years of age and among female squamous cell carcinoma patients (79%, 15/19). The allelic variants in CYP1A1 were equally distributed in lung cancer patients and controls. The m1/m2 and m2/m2 genotypes of the MspI site and the Ile/Val genotype were, however, slightly over-represented in squamous cell carcinoma patients. Among patients with squamous cell carcinoma diagnosed before 66 years of age the m1/m2 genotype was found in 28% (10/36), whereas the same genotype was observed in 16% (52/329) of healthy control subjects. A combined risk of squamous cell carcinoma was indicated for patients, diagnosed before 66 years of age, carrying both GSTM1(-) and m2 alleles (OR = 3.0, 95% CI = 1.2-7.2).

Adenocarcinoma↗
PubMed1994

The expression of glutathione transferase mu in patients with inflammatory bowel disease.

BACKGROUND: Glutathione transferases (GST) are a group of multifunctional enzymes important in the detoxification of many electrophiles and, in addition, fatty acid hydroperoxides, thus limiting tissue damage from oxidative free radical attack. Of the four classes of GST (alpha, mu, pi, and theta), a class mu isoenzyme, GST mu, is dominantly inherited and is expressed in approximately half of the population. GST mu expression was examined in patients with inflammatory bowel disease and correlated to clinical course, extension, and age of onset of the diseases. METHODS: GST mu can be measured as GST activity against trans-stilbene oxide. This GST activity was measured in whole blood in 179 patients with ulcerative colitis, 109 patients with Crohn's disease, and 449 age-matched controls. RESULTS: Frequencies of GST mu expression were as follows: controls (n = 449, 51.2%), mild ulcerative colitis (n = 76, 47.3%), moderate ulcerative colitis (n = 43, 46.5%), and severe ulcerative colitis (characterized by colectomy) (n = 60, 36.7%). This trend was, however, not significant (p = 0.094). Patients with onset of the colitis before the age of 30 years (n = 91) had a lower frequency of GST mu expression (35.2%) than patients with a later onset (n = 88, 52.3%) (p < 0.05). This difference was more pronounced among the colectomized patients (19.4% versus 55.2%) (p < 0.01). In Crohn's disease, patients with colitis had a lower frequency of GST mu expression (n = 29, 31.0%) than controls; however, this was not statistically significant (p = 0.055). No difference was found with regard to age of onset. CONCLUSION: We conclude that in patients with ulcerative colitis, lack of GST mu is related to early age of onset and a more severe clinical course leading to colectomy.

Adult↗
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↗