Biomedical subjects

O G Khatsenko

Publications and source records attributed to O G Khatsenko.

10 recordsLinked to original sources

PubMed1998

Role of nitric oxide in the inhibition of cytochrome P450 in the liver of mice infected with Chlamydia trachomatis.

In this study, we attempted to determine the effect of a systemic infection with Chlamydia trachomatis on cytochrome P450(CYP)-dependent metabolism in mice. Furthermore, we wanted to assess if these effects were mediated through NO. BALB/c(H-2d) female mice were inoculated intraperitoneally with the C. trachomatis mouse pneumonitis (MoPn) biovar, and induction of NO synthase (NOS) was detected by measuring [NOx] levels and inducible NOS protein content in peritoneal macrophages by Western blotting. Recovery of C. trachomatis from liver, lung, and spleen peaked at 4 days postinfection. Following cotreatment with N(G)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase, there was a significant increase in the intensity and the length of the infection. Six days after inoculation with C. trachomatis, CYP1A- and CYP2B-mediated metabolism in the liver of the mice was diminished up to 49% of control levels. However, when animals were treated with N(G)-nitro-L-arginine methyl ester at days 4 and 6 postinfection, the decrease in the metabolism of CYP1A and CYP2B was largely blocked. These results suggest that C. trachomatis infection can depress cytochrome P450 in a manner similar to other types of infections and that NO is likely to be a mediator of this depression. This finding may be of significance to patients taking drugs that are metabolized by phase I enzymes during infections with some bacteria such as C. trachomatis.

Animals↗

PubMed1997

Evidence for nitric oxide participation in down-regulation of CYP2B1/2 gene expression at the pretranslational level.

Septic or inflammatory stimuli suppress drug metabolism by cytochrome P-450 in the liver, presumably at the pretranslational level. We have shown previously that nitric oxide is responsible at least in part for the inhibition by bacterial lipopolysaccharide of phenobarbital-induced CYP2B1/2 activity in vivo. This was attributed to the interaction of nitric oxide with heme in the active-center of cytochrome P450, leading to enzyme inactivation. Here, we report that endogeneous nitric oxide also contributes to LPS-induced suppression of CYP2B1/2 in vivo by down-regulating the expression of CYP2B1/2 protein and mRNA.

Animals↗

PubMed1997

Undernutrition during hyperoxic exposure induces CYP2E1 in rat liver.

Induction of cytochrome P450 2E1 (CYP2E1) has been shown to occur through two distinct mechanisms. The first is seen by treatment of rats with acetone, pyrazole, and 4-methyl-pyrazole, which induces CYP2E1 protein without affecting the mRNA level. The second is observed in starvation, diabetes, and obesity, in which an increase of CYP2E1 protein is associated with an increase of the CYP2E1 mRNA. It has been reported by (Tindberg and Ingelman-Sundberg 1989) that hyperoxic exposure (95% O2) induced a several-fold increase of CYP2E1 protein in both the liver and lung of exposed rats without affecting the level of CYP2E1 mRNA. During the course of our previous study which demonstrated hyperoxia-induced specific pretranslational induction of CYP1A1/2 in the liver and CYP1A1 in the lung, we observed a progressive increase of hepatic CYP2E1 mRNA in animals of the hyperoxia group. Hyperoxia is accompanied by some degree of starvation and our earlier experiments were conducted with rats of significantly greater body weight than those used by Tindberg and Ingelman-Sundberg (260 vs 150 g). Thus we reevaluated the changes of CYP2E1 in the current study with the use of food-restricted control, and by utilizing rats of comparable weight (approximately 150 g) to that utilized by Tindberg and Ingelman-Sundberg. The results obtained in the present study showed that there was a significant increase in the levels of hepatic CYP2E1 mRNA, protein, and p-nitrophenol hydroxylase activity in the food-restricted control group compared to the untreated controls. Rats from the hyperoxia group also demonstrated a similar increase of these three parameters in their livers but showed no significant difference compared with the results of the food-restricted control group. Rats weighing approximately 260 g were also examined with similar food restriction and hyperoxia, and the results were essentially similar to those obtained with the younger rats. The lungs of rats from food-restricted control and hyperoxia groups showed no increase of any of the CYP2E1 parameters. The results obtained in the current study, therefore, indicate that hyperoxia has no effect on CYP2E1 expression in both the liver and lung. Increased CYP2E1 mRNA, protein, and p-nitrophenol hydroxylase activity seen in the liver of rats, but not in the lungs, are consistent with the notion that undernutrition during hyperoxia is the underlying mechanism for this induction.

Animals↗

PubMed1993

Nitric oxide is a mediator of the decrease in cytochrome P450-dependent metabolism caused by immunostimulants.

Bacterial lipopolysaccharide (LPS) and a diverse array of other immunostimulants and cytokines suppress the metabolism of endogenous and exogenous substances by reducing activity of the hepatic cytochrome P450 mixed-function oxidase system. Although this effect of immunostimulants was first described almost 40 yr ago, the mechanism is obscure. Immunostimulants are now known to cause NO overproduction by cells via induction of nitric oxide synthase. We have investigated whether NO overproduction is involved in suppressing hepatic metabolism by LPS. In vitro treatment of hepatic microsomes with NO, produced by chemical decomposition of 3-morpholinosydnonimine or by nitric oxide synthase, substantially suppressed cytochrome P450-dependent oxygenation reactions. This effect of NO was seen with hepatic microsomes prepared from two species (rat and chicken) and after exposure to chemicals that induce distinct molecular isoforms of cytochromes P450 (beta-naphthoflavone, 3-methylcholanthrene, and phenobarbital). Spectral studies indicate that NO reacts in vitro with both Fe(2+)- and Fe(3+)-hemes in microsomal cytochromes P450. In vivo, LPS diminished the phenobarbital-induced dealkylation of 7-pentoxyresorufin by rat liver microsomes and reduced the apparent P450 content as measured by CO binding. These LPS effects were associated with induction of NO synthesis; LPS-induced NO synthesis showed a strong positive correlation with the severity of cytochrome P450 inhibition. The decrease in both hepatic microsomal P450 activity and CO binding caused by LPS was largely prevented by the selective NO synthase inhibitor N omega-nitro-L-arginine methyl ester. Our findings implicate NO over-production as a major factor mediating the suppression of hepatic metabolism by immunostimulants such as LPS.

Adjuvants, Immunologic↗

PubMed1991

Dynamics of androstenedione metabolite formation in rat liver microsomes during temporal phenobarbital induction.

1. Formation of androstenedione (AD) 7 alpha-, 16 alpha-, 16 beta- and 6 beta-hydroxymetabolites produced in rat liver microsomes and differing by the duration of phenobarbital (PB) induction (temporal induction) has been studied. 2. Formation of 7 alpha-, 16 alpha- and 6 beta-metabolite is sexually differentiated during PB-induction. 3. The most dramatical changes were observed in the 16 beta-hydroxylase activity specific for cytochrome P-450b which increased in all rat groups investigated. 4. The immunochemical method using antibodies against P-450b/e was applied to measure its content in microsomes. 5. It was shown that the microsomal level of P-450b/e correlated (r = 0.63) with a 16 beta-hydroxylase activity in a narrow range of enzyme concentrations (from 0.16 to 0.32 nmol/mg). 6. In microsomal preparations with a higher level of P-450b/e the correlation is lower (r = 0.4). 7. The dependence of the P-450b catalytic activity on the P-450b to NADPH-cytochrome P-450 reductase relation is discussed.

Androstenedione↗

PubMed1991

[Benzonal--a phenobarbital-type of inducer of the mono-oxygenase system].

It has been found that the Soviet anticonvulsant drug Benzonal is an inducer of the liver cytochrome P-450 of the phenobarbital type. The drug causes formation of the cytochrome P-450 form which is immunologically identical to the phenobarbital inducible form of the hemoprotein with identical molecular mass determined with the SDS-gel electrophoresis method in PAAG. The microsomes, obtained from the rats treated with Benzonal display increased rates of metabolism of 7-pentoxiresorufin and 16 beta-hydroxylation of androstenedione which are specific substrates for the cytochrome P-450b.

Animals↗

PubMed1990

[An immunochemical analysis of the induction of cytochrome P-450 isoforms in the liver of fresh-water fishes by 3-methylcholanthrene, beta-naphthoflavone and aroclor 1254].

The cytochrome P-450 isoforms have been studied in liver microsomes of some fish species from Lake Baikal. Using the inhibitory analysis of microsomal monooxygenase activities carried out by the specific polyclonal antibodies it has been shown that 3-methylcholanthrene, beta-naphthoflavone and arochlor 1254 induce isoforms immunologically related to cytochrome P-488c but not to the rat cytochrome P-450b in fish liver microsomes. The immunologic identity in isoforms of fish and rat cytochromes induced by methylcholanthrene has not been revealed. A possibility to use the method of the inhibitory analysis of fish microsomal activities by specific antibodies to the rat cytochrome P-450 isoforms for biomonitoring and biotesting of polycyclic hydrocarbons and polychlorinated biphenyls in aquatic systems is discussed.

Animals↗

PubMed1990

[Evaluation of catalytic activity of multiple forms of cytochrome P-450 in liver microsomes of Wistar rats by androstenedione metabolism].

The synthesis of androstenedione (AD) metabolites in liver microsomes of control and phenobarbital (PB)-induced male and female Wistar rats was studied. In liver microsomes of non-induced male rats the predominant formation of 16 alpha-hydroxyandrostenedione was observed, whereas in females the predominant form was the 7 alpha-metabolite. Induction of animals of both sexes with PB was accompanied by an increase in the 16 beta-hydroxylase activity. The dynamics of synthesis of other AD metabolites specifically produced by such cytochrome P-450 forms as P-450a, P-450h and P-450p was investigated. The specificity of metabolism of androstenedione by multiple forms of cytochrome P-450 is postulated.

Androstenedione↗

PubMed1989

The phenobarbital-type induction of rat liver microsomal monooxygenases by perfluorodecalin.

Induction of perfluorodecalin (PFD) of the liver microsomal system of metabolism of xenobiotics has been studied and compared with the inductions by phenobarbital (PB) and 3-methylcholanthrene (MC). It has been shown that PFD increases the content of cytochrome P-450, NADPH-cytochrome c reductase activity. Like PB, PFD induces the activities of benzphetamine-N-demethylase, aldrine-epoxidase, 16 beta-androstendion-hydroxylase. Using specific antibodies against cytochromes P-450b and P-450c (which are the main isoenzymes of cytochrome P-450 in the PB- and MC-microsomes respectively), an immunological identity of the cytochrome P-450 isoforms during PFD and PB induction has been found. According to the rocket immunoelectrophoresis the content of cytochrome P-450 in PFD-microsomes, which is immunologically indistinguishable from P-450b, was approximately 70% of the total cytochrome P-450. Two forms of cytochrome P-450 were isolated from the liver microsomes of PFD-induced rats and purified to homogeneity. A comparison of these forms with cytochromes P-450b and P-450e obtained from the PB-induced rat liver microsomes revealed their similarity in a number of properties, e.g., chromotographic behavior on DEAE-Sephacel column, molecular weight determined by sodium dodecyl sulphate (SDS) electrophoresis in polyacrylamide gel, immunoreactivity, peptide mapping, catalytic activity. The data presented demonstrate that PFD induced in rat liver microsomes the cytochrome P-450 forms whose immunological properties and substrate specificity correspond to those of the PB-type cytochrome P-450. These findings suggest that PFD and PB, which differ in their chemical structure, induce in the rat liver microsomes identical forms of cytochrome P-450.

Androstenedione↗

PubMed1989

[Identification of molecular forms of cytochrome P-450 isolated from liver microsomes of rats induced with phenobarbital and 3-methylcholanthrene].

Eight electrophoretically homogeneous forms of cytochrome P-450 were isolated from liver microsomes of phenobarbital (PB)- and 3-methylcholanthrene (MC)-induced male Wistar rats, using chromatography on 1.8-diaminooctyl-Sepharose, SEAE-Sephacel and hydroxylapatite. These cytochrome forms were compared to those described in literature in terms of their ability to metabolize androstenedione (AD), benzphetamine (BP) and 7-ethoxyresorufin (7-ER). Cytochrome P-450b capable of catalyzing with a high specificity the 16-hydroxylation of AD and N-demethylation of BP, and cytochrome P-450e immunologically related to P-450b but incapable of catalyzing these reactions were isolated from PB-microsomes. Besides, a male-specific cytochrome P-450h catalyzing the 16 alpha-hydroxylation of AD was isolated from PB-microsomes. Cytochrome P-450c possessing a high 7-ER-O-deethylase activity, and a high spin cytochrome P-450d as well as cytochrome P-450a specifically catalyzing the 7 alpha-oxidation of AD were isolated from MC-microsomes. Two forms of cytochrome P-450 isolated from PB-microsomes possessed no such activities. Data from immunochemical analysis suggest that one of these forms can be identified as cytochrome P-450k. It is concluded that the specificity of metabolism and the molecular activity of Wistar rat liver cytochrome P-450 forms are comparable with the corresponding parameters of hemoproteins isolated from other rat species. At the same time, data from metabolic analysis are suggestive of differences in the levels of certain cytochrome P-450 forms, in particular P-450a.

Animals↗