Zonation of hepatic cytochrome P-450 expression and regulation.
Ontology highlight
ABSTRACT:
SUBMITTER: Oinonen T
PROVIDER: S-EPMC1219009 | biostudies-other | 1998 Jan
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Cytochrome P450 (CYP) proteins constitute a large ancient family of oxidative enzymes essential for the efficient elimination of a wide variety of clinically used drugs. Polymorphic variants of human CYP2D6 are associated with the conversion rate and efficacy of several drugs such as antidepressants. Polymorphisms of the canine orthologue CYP2D15 are of interest because these antidepressants are also used in dogs with behavioral problems and the outcome of the treatment is variable. However, the annotated CYP2D15 gene is incomplete and inaccurately assembled in CanFam3.1, hampering DNA sequence analysis of the gene in individual dogs. We elucidated the complete exon-intron structure of CYP2D15 to enable comprehensive genotyping of the gene using genomic DNA. We surveyed variations of the gene in four diverse dog breeds and identified novel polymorphisms in exon 2 in border collies. Further investigation to establish the impact of these canine CYP2D15 polymorphisms on interindividual variability in expression and function of this metabolizing enzyme is now feasible. Further knowledge of CYP pharmacogenetics will help individualize therapy and thereby increase therapeutic efficacy, especially in the use of antidepressants in veterinary behavioral medicine.
| S-EPMC7689907 | biostudies-literature
Project description:Most cytochrome P-450 enzymes are expressed characteristically in a zonated pattern in the liver. The factors responsible for this heterogenous expression are largely unknown. Here we report how growth hormone and tri-iodothyronine regulate the steroid-hydroxylating cytochrome P-450 (CYP) 3A forms, which are constitutively expressed mainly in the perivenous (downstream) liver region. By comparing cell lysates obtained from the periportal and perivenous acinar regions we observed that the elevated CYP3A expression observed after hypophysectomy was due mainly to a dramatic increase in the normally silent periportal region. This effect was particularly strong in females. Treatment with growth hormone re-established the perivenous expression pattern, a finding corroborated by immunohistochemical analysis of liver sections. Analysis of periportal and perivenous mRNA by reverse-transcriptase PCR demonstrated that in males the changes in CYP3A2 mRNA paralleled the changes at the protein level. In females, CYP3A2 mRNA was detected only after hypophysectomy, and the zonal protein changes seemed to be governed by changes in CYP3A1 mRNA levels. Treatment of hypophysectomized animals with tri-iodothyronine also suppressed the expression of CYP3A, both in males and females. However, this occurred almost exclusively in the periportal region. This was observed both at the protein level, as determined by immunoblotting and immunohistochemically, and at the CYP3A1 and 3A2 mRNA level. These results indicate that growth hormone and thyroid hormone regulate the expression of CYP3A genes zone-specifically by suppressing their transcription in the periportal (upstream) region of the liver.
| S-EPMC1135799 | biostudies-other
Project description:AIM:Using bacterial, yeast, or mammalian cell expressing a human drug metabolism enzyme would seem good way to study drug metabolism-related problems. Human cytochrome P-450 2C9(CYP2C9) is a polymorphic enzyme responsible for the metabolism of a large number of clinically important drugs. It ranks among the most important drug metabolizing enzymes in humans. In order to provide a sufficient amount of the enzyme for drug metabolic research, the CYP2C9 cDNA was cloned and expressed stably in CHL cells. METHODS:After extraction of total RNA from human liver tissue, the human CYP2C9 cDNA was amplified with reverse transcription-polymerase chain reaction (RT-PCR), and cloned into cloning vector pGEM-T. The cDNA fragment was identified by DNA sequencing and subcloned into a mammalian expression vector pREP9. A transgenic cell line was established by transfecting the recombinant vector of pREP9-CYP2C9 into CHL cells. The enzyme activity of CYP2C9 catalyzing oxidation of tolbutamide to hydroxy tolbutamide in S9 fraction of the cell was determined by high performance liquid chromatography(HPLC). RESULTS:The amino acid sequence predicted from the cDNA segment was identical to that of CYP2C9*1, the wild type CYP2C9. However, there were two base differences, i.e. 21T>C, 1146C>T, but the encoding amino acid sequence was the same, L7, P382. The S9 fraction of the established cell line metabolizes tolbutamide to hydroxy tolbutamide; tolbutamide hydroxylase activity was found to be 0.465 +/- 0.109 micromol.min(-1).g(-1) S9 protein or 8.62 +/- 2.02mol.min(-1).mol(-1) CYP, but was undetectable in parental CHL cell. CONCLUSION:The cDNA of human CYP2C9 was successfully cloned and a cell line of CHL- CYP2C9, efficiently expressing the protein of CYP2C9, was established.
| S-EPMC4658375 | biostudies-literature
Project description:We reported previously that infection of C3H/HeOuJ (HeOu) mice with the murine intestinal pathogen Citrobacter rodentium caused a selective modulation of hepatic cytochrome P450 (P450) gene expression in the liver that was independent of the Toll-like receptor 4. However, HeOu mice are much more sensitive to the pathogenic effects of C. rodentium infection, and the P450 down-regulation was associated with significant morbidity in the animals. Here, we report that oral infection of C57BL/6 mice with C. rodentium, which produced only mild clinical signs and symptoms, produced very similar effects on hepatic P450 expression in this strain. As in HeOu mice, CYP4A mRNAs and proteins were among the most sensitive to down-regulation, whereas CYP4F18 was induced. CYP2D9 mRNA was also induced 8- to 9-fold in the C57BL/6 mice. The time course of P450 regulation followed that of colonic inflammation and bacterial colonization, peaking at 7 to 10 days after infection and returning to normal at 15 to 24 days as the infection resolved. These changes also correlated with the time course of significant elevations in the serum of the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor-alpha, as well as of interferon-gamma and IL-2, with serum levels of IL-6 being markedly higher than those of the other cytokines. Intraperitoneal administration of C. rodentium produced a rapid down-regulation of P450 enzymes that was quantitatively and qualitatively different from that of oral infection, although CYP2D9 was induced in both models, suggesting that the effects of oral infection on the liver are not due to bacterial translocation.
| S-EPMC2631938 | biostudies-literature
Project description:The goal of the present study was to assess the gene expression of xenobiotic metabolizing enzymes (XMEs) Cytochrome P-450 (CYP) and carboxylesterase (CE) related to detoxification of synthetic pyrethroids, plus acetylcholinesterase (AChE), in field isolates of acaricide-resistant Rhipicephalus microplus. The XMEs expression levels were assessed by mRNA measurement using quantitative reverse transcription PCR. The XME expression levels of field-isolated acaricide-resistant ticks were compared against acaricide-susceptible reference ticks used in this study as a gene expression baseline and represented as relative expression units (REU). Field isolates were subjected to toxicological bioassays and determined resistant to all the Pyr acaricides (Pyr), whereas most of them were found susceptible to organophosphorous acaricides (OP), with the exception of three isolates, which exhibited moderate resistance to Diazinon. Significantly higher levels of CYP were detected in pyrethroid-resistance ticks when compared to Su ticks (P<0.01). A linear regression analysis showed that pyrethroid acaricide resistance levels of R. microplus were proportional to the CYP expression levels (correlation coefficient (R):0.85; P<0.05). Analysis on CE expression levels showed only one isolate resistant to Pyr and OP with a statistically significant increase (P<0.01). AChE expression levels showed statistically significant (P<0.01) subexpression in all tick isolates when compared to the susceptible reference. Our results suggest that pyrethroid acaricide resistance in the cattle tick may be diagnosed by measuring the CYP expression levels using quantitative PCR.
| S-EPMC6057400 | biostudies-literature
Project description:Omega4499 is the site of a Tn5 lac insertion in the Myxococcus xanthus chromosome that fuses lacZ expression to a developmentally regulated promoter. Cell-cell interactions that occur during development, including C signaling, are required for normal expression of Tn5 lac Omega4499. The DNA upstream of the Omega4499 insertion has been cloned, and the promoter has been localized. Analysis of the DNA sequence downstream of the promoter revealed one complete open reading frame and a second partial open reading frame that is interrupted by Tn5 lac Omega4499. The predicted products of these open reading frames are highly similar to reductase and oxidase components of bacterial cytochrome P-450 systems, which allow catabolism or anabolism of unusual compounds. However, the function of the gene products of the Omega4499 locus remains unclear because M. xanthus containing Tn5 lac Omega4499 exhibits no apparent defect in growth, developmental aggregation, fruiting body formation, or sporulation. Deletion analysis of the Omega4499 regulatory region showed that multiple DNA elements spanning more than 500 bp upstream of the transcriptional start site contribute to developmental promoter activity. At least two DNA elements, one downstream of -49 bp and one between -49 and -218 bp, boosted activity of the promoter in response to intercellular C signaling. Three sequences in the Omega4499 promoter region, centered at -55, -33, and -1 bp, nearly match a 7-bp sequence found in other C signal-dependent promoters. We propose that these sequences, matching the consensus sequence 5'-CAYYCCY-3', be called C box sequences, and we speculate that these sequences are cis-acting regulatory elements important for the expression of M. xanthus genes that depend upon intercellular C signaling during development.
| S-EPMC94057 | biostudies-literature
Project description:We have investigated the effects of TCPOBOP (1,4-bis[2-(3,5- dichloropyridyloxy)]benzene), a potent cytochrome P-450-inducing agent [Poland, Mak, Glover, Boatman, Ebetino and Kende (1980) Mol. Pharmacol. 18, 571-580], on cytochrome P-450 isoenzyme expression in the mouse. Hepatic cytochrome P-450s from several distinct gene families were strikingly induced by a single dose of 75 micrograms of the compound. Northern-blot analysis demonstrated that this induction was almost certainly due to transcriptional activation of the cytochrome P-450 genes. The potency of this inductive effect was further reflected in the finding that cytochrome P-450 levels were still increased 12 weeks after a single injection of 75 micrograms of this compound. Interestingly, the mRNA levels of certain other genes, including those of metallothionein and the mouse major urinary proteins, were also induced. In view of the similarity in the effects of TCPOBOP and the synthetic glucocorticoid dexamethasone on mouse hepatic gene expression, we determined whether TCPOBOP acts through the glucocorticoid receptor. This did not, however, appear to be the case. Experiments with hypophysectomized animals demonstrated that TCPOBOP action was not regulated indirectly via the pituitary. In addition, induction of mouse Cyp2b protein by TCPOBOP in a primary culture of mouse hepatocytes suggests that the compound has a direct action on mouse liver. The above findings demonstrate that TCPOBOP is one of the most potent modulators of cytochrome P-450 gene expression described to date. It is not inconceivable that a single dose of this compound may alter hepatic gene expression for the majority of the lifespan of a mouse.
| S-EPMC1132248 | biostudies-other
Project description:We have studied the extent to which mouse renal cytochrome P-450 isoenzymes are sexually differentiated, and the factor(s) regulating this dimorphism. Intriguingly, sex differences were not seen in the expression of a single cytochrome P-450 enzyme, but were observed in the expression of all P-450 isoenzymes detectable, encoded by six gene families or sub-families. This effect was mediated by testosterone, which had the capacity to both induce and repress P-450 gene expression, and which was independent of growth hormone. The changes in protein content were mirrored in all but one case by changes in the levels of mRNA, indicating that these genes contain hormone-responsive elements. These findings are consistent with numerous reports of sex differences in the susceptibility of the mouse kidney to the toxic and carcinogenic effects of drugs and environmental chemicals, many of which are metabolized to cytotoxic products by the cytochrome P-450-dependent mono-oxygenases. These data imply that circulating androgen levels will be an important factor in susceptibility of the kidney to toxic or carcinogenic compounds which require metabolic activation.
| S-EPMC1131192 | biostudies-other
Project description:BackgroundCYP2C9 encodes a member of the cytochrome P450 superfamily of enzymes which play a central role in activating and detoxifying many carcinogens and endogenous compounds thought to be involved in the development of colorectal cancer (CRC). In the past decade, the relationship between CYP2C9 common polymorphisms (R144C and I359L) and CRC has been reported in various ethnic groups; however, these studies have yielded contradictory results. To investigate this inconsistency, we performed this meta-analysis.MethodsDatabases including Pubmed, EMBASE, Web of Science and China National Knowledge Infrastructure (CNKI) were searched to find relevant studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association.ResultsA total of 13 articles involving 9,463 cases and 11,416 controls were included. Overall, the summary odds ratio of CRC was 0.98 (95% CI: 0.89-1.06) and 0.99 (95% CI: 0.87-1.14) for CYP2C9 144C and 359L alleles, respectively. No significant results were observed using dominant or recessive genetic model for these polymorphisms. In the stratified analyses according to ethnicity and sex, no evidence of any gene-disease association was obtained.ConclusionsThis meta-analysis suggests that the CYP2C9 may not be associated with colorectal cancer development.
| S-EPMC3492323 | biostudies-literature
Project description:The activities of several hepatic enzymes are preferentially zonated to the periportal or perivenous cells of the liver acinus. Employing dual-digitonin-pulse perfusion of rat liver in the study of acetyl-CoA carboxylase (ACC), we have identified a heretofore unrecognized feature of hepatic zonation, namely an intrahepatic gradient in enzyme specific activity. ACC activity shows a relative periportal localization in normally feeding rats, even when corrected for ACC protein mass. In contrast with results previously reported by us [Evans, Quistorff & Witters (1989) Biochem. J. 259, 821-829], the total mass of both hepatic ACC isoenzymes was not found to differ between the two hepatic zones in the present study. In perfusion eluates from fed animals, periportal ACC displays enhanced citrate reactivity and two kinetic components of acetyl-CoA reactivity; the largest periportal/perivenous gradient (5-fold) is accounted for by a species with a lower Km for acetyl-CoA. The zonal gradient in ACC maximal velocity, measured in eluates from fed rats, does not persist after ACC purification, although the isolated periportal enzyme, like dephosphorylated ACC, has a lower activation constant for citrate. Total ACC protein phosphatase activity is higher in periportal eluates, but no differences in the activities of either a 5'-AMP-activated ACC kinase or the cyclic-AMP-dependent protein kinase are noted between the hepatic zones. The induction of total hepatic ACC mass and specific activity, on fasting/refeeding with a high-carbohydrate diet, abolishes the periportal/perivenous activity gradient, largely owing to a selective activation of perivenous enzyme. Nutritional induction is also accompanied by a marked alteration in ACC acetyl-CoA kinetics and abolition of the gradient in total ACC phosphatase. These studies indicate that hepatic enzyme zonation, which is often attributed to differential expression of enzyme protein, may result from zonal variations in enzyme specific activity, owing to differences in allosteric regulation and/or covalent modification.
| S-EPMC1131783 | biostudies-other