| 1. |
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| 2. |
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| 3. |
- Abu-Bakar, A'edah, et al.
(författare)
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Inducible bilirubin oxidase : A novel function for the mouse cytochrome P450 2A5
- 2011
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 257:1, s. 14-22
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Tidskriftsartikel (refereegranskat)abstract
- We have previously shown that bilirubin (BR), a breakdown product of haem, is a strong inhibitor and a high affinity substrate of the mouse cytochrome P450 2A5 (CYP2A5). The antioxidant BR, which is cytotoxic at high concentrations, is potentially useful in cellular protection against oxygen radicals if its intracellular levels can be strictly controlled. The mechanisms that regulate cellular BR levels are still obscure. In this paper we provide preliminary evidence for a novel function of CYP2A5 as hepatic "BR oxidase''. A high-performance liquid chromatography/electrospray ionisation mass spectrometry screening showed that recombinant yeast microsomes expressing the CYP2A5 oxidise BR to biliverdin, as the main metabolite, and to three other smaller products with m/z values of 301,315 and 333. The metabolic profile is significantly different from that of chemical oxidation of BR. In chemical oxidation the smaller products were the main metabolites. This suggests that the enzymatic reaction is selective, towards biliverdin production. Bilirubin treatment of primary hepatocytes increased the CYP2A5 protein and activity levels with no effect on the corresponding mRNA. Co-treatment with cycloheximide (CHX), a protein synthesis inhibitor, resulted in increased half-life of the CYP2A5 compared to cells treated only with CHX. Collectively, the observations suggest that the CYP2A5 is potentially an inducible "BR oxidase" where BR may accelerate its own metabolism through stabilization of the CYP2A5 protein. It is possible that this metabolic pathway is potentially part of the machinery controlling intracellular BR levels in transient oxidative stress situations, in which high amounts of BR are produced.
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| 4. |
- Abu-Bakar, A'edah, et al.
(författare)
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Metabolism of bilirubin by human cytochrome P450 2A6
- 2012
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 261:1, s. 50-58
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Tidskriftsartikel (refereegranskat)abstract
- The mouse cytochrome P450 (CYP) 2A5 has recently been shown to function as hepatic "Bilirubin Oxidase" (Abu-Bakar, A., et al., 2011. Toxicol. Appl. Pharmacol. 257, 14-22). To date, no information is available on human CYP isoforms involvement in bilirubin metabolism. In this paper we provide novel evidence for human CYP2A6 metabolising the tetrapyrrole bilirubin. Incubation of bilirubin with recombinant yeast microsomes expressing the CYP2A6 showed that bilirubin inhibited CYP2A6-dependent coumarin 7-hydroxylase activity to almost 100% with an estimated K-i of 2.231 mu M. Metabolite screening by a high-performance liquid chromatography/electrospray ionisation mass spectrometry indicated that CYP2A6 oxidised bilirubin to biliverdin and to three other smaller products with m/z values of 301,315 and 333. Molecular docking analyses indicated that bilirubin and its positively charged intermediate interacted with key amino acid residues at the enzyme's active site. They were stabilised at the site in a conformation favouring biliverdin formation. By contrast, the end product, biliverdin was less fitting to the active site with the critical central methylene bridge distanced from the CYP2A6 haem iron facilitating its release. Furthermore, bilirubin treatment of HepG2 cells increased the CYP2A6 protein and activity levels with no effect on the corresponding mRNA. Co-treatment with cycloheximide (CHX), a protein synthesis inhibitor, resulted in increased half-life of the CYP2A6 compared to cells treated only with CHX. Collectively, the observations indicate that the CYP2A6 may function as human "Bilirubin Oxidase" where bilirubin is potentially a substrate and a regulator of the enzyme.
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| 5. |
- Abu-Bakar, A'edah, et al.
(författare)
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Regulation of CYP2A5 gene by the transcription factor nuclear factor (erythroid-derived 2)-like 2
- 2007
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Ingår i: Drug Metabolism And Disposition. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0090-9556 .- 1521-009X. ; 35:5, s. 787-794
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Tidskriftsartikel (refereegranskat)abstract
- We have previously shown that cadmium, a metal that alters cellular redox status, induces CYP2A5 expression in nuclear factor (erythroid-derived 2)-like 2 wild-type (Nrf2(-/-)) mice but not in the knockout (Nrf2(-/-)) mice. In the present studies, the potential role of Nrf2 in cadmium-mediated regulation of Cyp2a5 gene was investigated in mouse primary hepatocytes. Cadmium chloride (CdCl2) caused a time-dependent induction of the CYP2A5 at mRNA, protein, and activity levels, with a substantial increase observed within 3 h of exposure. Immunoblotting showed cadmium-dependent nuclear accumulation of Nrf2 within 1 h of exposure. Cotransfection of mouse primary hepatocytes with Cyp2a5 promoter-luciferase reporter plasmids and Nrf2 expression plasmid resulted in a 3-fold activation of Cyp2a5 promoter-mediated transcription relative to the control. Deletion analysis of the promoter localized the Nrf2 responsive region to an area from -2656 to -2339 base pair. Computer-based sequence analysis identified two putative stress response elements (StRE) within the region at positions -2514 to -2505 and -2386 to -2377. Chromatin immunoprecipitation and electrophoretic mobility shift assays showed that interaction of the more proximal StRE with Nrf2 was stimulated by CdCl2. Finally, site-directed mutagenesis of the proximal StRE in Cyp2a5 promoter-luciferase reporter plasmids abolished Nrf2 mediated induction. Collectively, the results indicate that Nrf2 activates Cyp2a5 transcription by directly binding to the StRE in the 5'-flanking region of the gene. This acknowledges Cyp2a5 as the first phase I xenobiotic-metabolizing gene identified under the control of the StRE-Nrf2 pathway with a potential role in adaptive response to cellular stress.
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| 6. |
- Arpiainen, Satu, et al.
(författare)
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Coactivator PGC-1 alpha regulates the fasting inducible xenobiotic-metabolizing enzyme CYP2A5 in mouse primary hepatocytes
- 2008
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 232:1, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- The nutritional state of organisms and energy balance related diseases such as diabetes regulate the metabolism of xenobiotics such as drugs, toxins and carcinogens. However, the mechanisms behind this regulation are mostly unknown. The xenobiotic-metabolizing cytochrome P450 (CYP) 2A5 enzyme has been shown to be induced by fasting and by glucagon and cyclic AMP (cAMP), which mediate numerous fasting responses. Peroxisome proliferator-activated receptor gamma coactivator (PGC)-1 alpha triggers many of the important hepatic fasting effects in response to elevated cAMP levels. In the present study, we were able to show that cAMP causes a coordinated induction of PGC-1 alpha expression level by adenovirus mediated gene transfer increased CYP2A5 transcription, Co-transfection of Cyp2a5' promoter constructs with PGC-1 alpha expression vector demonstrated that PGC-1 alpha is able to activate Cyp2a5 transcription through the hepatocyte nuclear factor (HNF)-4 alpha response element in the proximal promoter of the Cyp2a5 gene. Chromartin immunoprecipitation assays showed that PGC-1 alpha binds, together with HNF-4 alpha, to the same region at the Cyp2a5 proximal promoter. In conclusion, PGC-1 alpha mediates the expression of Cyp2A5 induced by cAMP in mouise hepatocytes throuch coactivation of transcription factor HNF-4 alpha. This strongly suggests that PGC-1 alpha is the major factor mediating the fasting response of CYP2A5.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Christian, Kyle, et al.
(författare)
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Interaction of heterogeneous nuclear ribonucleoprotein A1 with cytochrome P450 2A6 mRNA : implications for post-transcriptional regulation of the CYP2A6 gene
- 2004
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Ingår i: Molecular Pharmacology. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0026-895X .- 1521-0111. ; 65:6, s. 1405-14
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Tidskriftsartikel (refereegranskat)abstract
- The human xenobiotic-metabolizing enzyme cytochrome P450, CYP2A6, catalyzes the bioactivation of a number of carcinogens and drugs and is overexpressed in cases of liver diseases, such as cirrhosis, viral hepatitis, and parasitic infestation, and in certain tumor cells. This suggests that CYP2A6 may be a major liver catalyst in pathological conditions. In the present study, we have addressed molecular mechanisms underlying the regulation of the CYP2A6 gene. We present evidence of several proteins present in human hepatocytes that interact specifically with the 3′-untranslated region (UTR) of CYP2A6 mRNA. Biochemical and immunological evidence show that the RNA-protein complex of highest intensity contains the heterogeneous nuclear ribonucleoprotein (hnRNP) A1 or a closely related protein. Mapping of the hnRNP A1 binding site within CYP2A6 3′-UTR reveals that the smallest portion of RNA supporting significant binding consists of 111 central nucleotides of the 3′-UTR. Our studies also indicate that hnRNPA1 from HepG2 cancer cells exhibits modified binding characteristics to the CYP2A6 3′-UTR compared with primary hepatocytes. We found that the level of CYP2A6 mRNA remains high in conditions of impaired transcription in primary human hepatocytes, showing that CYP2A6 expression can be affected post-transcriptionally in conditions of cellular stress. Our results indicate that the post-transcriptional regulation involves interaction of the hnRNP A1 protein with CYP2A6 mRNA. The present data suggest that hnRNPA1 is a critical regulator of expression of the human CYP2A6 gene and support the notion that this P450 isoform may be of particular significance in stressed human liver cells.
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| 13. |
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| 14. |
- Christian, Kyle J., et al.
(författare)
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Interaction of heterogeneous nuclear ribonucleoprotein C1/C2 with a novel cis-regulatory element within p53 mRNA as a response to cytostatic drug treatment
- 2008
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Ingår i: Molecular Pharmacology. - : Aspet. - 0026-895X .- 1521-0111. ; 73:5, s. 1558-1567
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Tidskriftsartikel (refereegranskat)abstract
- We describe a novel cis-element in the 5' coding region of p53 mRNA and its interaction with heterogeneous nuclear ribonucleoprotein (hnRNP) C1/C2. This element is located in a putative hairpin loop structure, within the first 101 nucleotides downstream of the start codon. The binding of hnRNPC1/C2 is strongly enhanced in response to the DNA-damaging drug cisplatin [cis-diamminedichloroplatinum(II)] and the cytostatic transcriptional inhibitor actinomycin D (dactinomycin), both known inducers of apoptosis and p53. Strongly stimulated binding is observed in both nuclear and cytoplasmic compartments, and it is accompanied by a cytoplasmic increase of hnRNPC1/C2. Changes in hnRNPC1/C2 protein levels are not proportional to binding activity, suggesting qualitative changes in hnRNPC1/C2 upon activation. Phosphorylation studies reveal contrasting characteristics of the cytoplasmic and nuclear hnRNPC1/C2 interaction with p53 mRNA. Results from chimeric p53-luciferase reporter constructs suggest that hnRNPC1/C2 regulates p53 expression via this binding site. Our results are consistent with a mechanism in which the interaction of hnRNPC1/C2 with a cis-element within the coding region of the p53 transcript regulates the expression of p53 mRNA before and during apoptosis. In addition, we report that preapoptotic signals induced by transcriptional inhibition trigger the appearance of a truncated, exclusively cytoplasmic 43-kDa variant of p53 before apoptosis.
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| 15. |
- Christian, Kyle, 1972-
(författare)
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The role of hnRNP A1 and hnRNP C1/C2 in the regulation of the stress responsive genes Cyp2a5/2A6 and p53.
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The family of proteins known as heterogeneous nuclear ribonucleoproteins (hnRNPs) is large and diverse. Often, one and the same hnRNP will perform multiple cellular functions, leading to their description as “multifunctional proteins”. The two hnRNPs known as hnRNP A1 and hnRNP C1/C2 are multifunctional proteins found to affect the transcription, splicing, stability, and translation of specific genes’ mRNA. They are implicated in carcinogenesis, apoptosis, and DNA damage response mechanisms.The aims of this thesis were to study the hnRNP A1 and hnRNP C1/C2 dependent regulation of two highly stress responsive genes, the tumor suppressor p53 and the cytochrome P450 enzyme Cyp2a5/CYP2A6. We identified hnRNP C1/C2 as a DNA damage induced binding protein towards the coding region of p53 mRNA, and found that while a specific cis binding site appears to have a positive function in p53 expression, interaction of hnRNP C1/C2 with this site represses the expression. The data suggest that two distinct molecular mechanisms exist for the down-regulation of p53 by hnRNP C1/C2. One mechanism, active during transcriptional stress, is dependent upon the aforementioned site, and the other, independent. We discuss how hnRNP C1/C2 dependent repression of p53 may play a role in apoptosis.The data presented here further suggest that the transcriptional and post-transcriptional processes controlling the expression of the murine Cyp2a5 gene are linked via hnRNP A1, by performing functions in the nucleus as a transcription factor, or in the cytoplasmic compartment as a trans factor bound to the 3’UTR of the mRNA as needed. Our studies of the human ortholog of this gene, CYP2A6, suggest that this gene is regulated post-transcriptionally in a manner similar to that of its murine counterpart, via changes in mRNA stability and interaction of hnRNP A1 with its 3’ UTR.
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| 16. |
- Daskalopoulos, Evangelos P., et al.
(författare)
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D-2-Dopaminergic Receptor-Linked Pathways : Critical Regulators of CYP3A, CYP2C, and CYP2D
- 2012
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Ingår i: Molecular Pharmacology. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0026-895X .- 1521-0111. ; 82:4, s. 668-678
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Tidskriftsartikel (refereegranskat)abstract
- Various hormonal and monoaminergic systems play determinant roles in the regulation of several cytochromes P450 (P450s) in the liver. Growth hormone (GH), prolactin, and insulin are involved in P450 regulation, and their release is under dopaminergic control. This study focused on the role of D-2-dopaminergic systems in the regulation of the major drug-metabolizing P450s, i.e., CYP3A, CYP2C, and CYP2D. Blockade of D-2-dopaminergic receptors with either sulpiride (SULP) or 4-(4-chlorophenyl)-1-(1H-indol-3-ylmethyl) piperidin-4-ol (L-741,626) markedly down-regulated CYP3A1/2, CYP2C11, and CYP2D1 expression in rat liver. This suppressive effect appeared to be mediated by the insulin/phosphatidylinositol 3-kinase/Akt/FOXO1 signaling pathway. Furthermore, inactivation of the GH/STAT5b signaling pathway appeared to play a role in D-2-dopaminergic receptor-mediated down-regulating effects on these P450s. SULP suppressed plasma GH levels, with subsequently reduced activation of STAT5b, which is the major GH pulse-activated transcription factor and has up-regulating effects on various P450s in hepatic tissue. Levels of prolactin, which exerts down-regulating control on P450s, were increased by SULP, which may contribute to SULP-mediated effects. Finally, it appears that SULP-induced inactivation of the cAMP/protein kinase A/cAMP-response element-binding protein signaling pathway, which is a critical regulator of pregnane X receptor and hepatocyte nuclear factor 1 alpha, and inactivation of the c-Jun N-terminal kinase contribute to SULP-induced down-regulation of the aforementioned P450s. Taken together, the present data provide evidence that drugs acting as D-2-dopaminergic receptor antagonists might interfere with several major signaling pathways involved in the regulation of CYP3A, CYP2C, and CYP2D, which are critical enzymes in drug metabolism, thus affecting the effectiveness of the majority of prescribed drugs and the toxicity and carcinogenic potency of a plethora of toxicants and carcinogens.
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| 17. |
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| 18. |
- Franzén, Anna, et al.
(författare)
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CYP2A5-mediated activation and early ultrastructural changes in the olfactory mucosa : studies on 2,6-dichlorophenyl methylsulfone
- 2006
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Ingår i: Drug Metabolism And Disposition. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0090-9556 .- 1521-009X. ; 34:1, s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- 2,6-Dichlorophenyl methylsulfone (2,6-diClPh-MeSO2) is a potent olfactory toxicant reported to induce endoplasmic reticulum (ER) stress, caspase activation, and extensive cell death in mice. The aim of the present study was to examine cytochrome P450 (P450)-dependent bioactivation, nonprotein sulfhydryl (NP-SH) levels, and early ultrastructural changes in mouse olfactory mucosa following an i.p. injection of 2,6-diClPh-MeSO2 (32 mg/kg). A high covalent binding of 2,6-diClPh-14C-MeSO2 in olfactory mucosa S9 fraction was observed, and the CYP2A5/CYP2G1 substrates coumarin and dichlobenil significantly decreased the binding, whereas the CYP2E1 substrate chlorzoxazone had no effects. An increased bioactivation was detected in liver microsomes of mice pretreated with pyrazole, known to induce CYP2A4, 2A5, 2E1, and 2J, and addition of chlorzoxazone reduced this binding. 2,6-DiClPh-14C-MeSO2 showed a marked covalent binding to microsomes of recombinant yeast cells expressing mouse CYP2A5 or human CYP2A6 compared with wild type. One and 4 h after a single injection of 2,6-diClPh-MeSO2, the NP-SH levels in the olfactory mucosa were significantly reduced compared with control, whereas there was no change in the liver. Ultrastructural studies revealed that ER, mitochondria, and secretory granules in nonneuronal cells were early targets 1 h after injection. We propose that lesions induced by 2,6-diClPh-MeSO2 in the mouse olfactory mucosa were initiated by a P450-mediated bioactivation in the Bowman's glands and depletion of NP-SH levels, leading to disruption of ion homeostasis, organelle swelling, and cell death. The high expression of CYP2A5 in the olfactory mucosa is suggested to play a key role for the tissue-specific toxicity induced by 2,6-diClPh-MeSO2.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Glisovic, Tina, et al.
(författare)
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Interplay between transcriptional and post-transcriptional regulation of Cyp2a5 expression
- 2003
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Ingår i: Biochemical Pharmacology. - 0006-2952 .- 1356-1839. ; 65:10, s. 1653-1661
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Tidskriftsartikel (refereegranskat)abstract
- The cytochrome P450 (Cyp) 2a5 gene can be upregulated transcriptionally or by mRNA stabilization. The heterogeneous nuclear ribonucleoprotein (hnRNP) A1 interacting with the CYP2A5 mRNA has been shown to be a key post-transcriptional regulator of the Cyp2a5 gene. The aim of this study was to investigate if the transcriptional and post-transcriptional steps of Cyp2a5 expression are linked. This was done by modifying the transcription rate with transcriptional inducers (phenobarbital and cyclic AMP) and inhibitors (actinomycin D and 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole) and analyzing the effects upon post-transcriptional events. We found that inhibition of transcription led to relocalization of hnRNP A1 from the nucleus to the cytoplasm, to its strongly increased binding to the cytoplasmic CYP2A5 mRNA and to CYP2A5 mRNA stabilization. In contrast, stimulated transcription resulted in increased binding of nuclear hnRNP A1 to the Cyp2a5 promoter, and overexpression of hnRNP A1 led to stimulated transcription of a Cyp2a5 promoter-driven luciferase recombinant. This strongly suggests that the transcriptional and post-transcriptional stages of Cyp2a5 expression are interrelated and that the nucleocytoplasmic shuttling hnRNP A1 may coordinate these different steps.
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| 23. |
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| 24. |
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| 25. |
- Glisovic, Tina
(författare)
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The Multifunctional HnRNP A1 Protein in the Regulation of the Cyp2a5 Gene : Connecting Transcriptional and Posttranscriptional Processes
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The mouse xenobiotic-inducible Cyp2a5 gene is both transcriptionally and posttranscriptionally regulated. One of the most potent Cyp2a5 inducers, the hepatotoxin pyrazole, increases the CYP2A5 mRNA half-life. The induction is accomplished through the interaction of a pyrazole-inducible protein with a 71 nt long, putative hairpin-loop region in the 3' UTR of the CYP2A5 mRNA.The aims of this thesis have been to identify the pyrazole-inducible protein, to investigate its role in the Cyp2a5 expression and the significance of the 71 nt hairpin-loop region for the Cyp2a5 expression, and to examine a possible coupling between transcriptional and posttranscriptional processes in Cyp2a5 expression.The pyrazole-inducible protein was identified as the heterogeneous nuclear ribonucleoprotein (hnRNP) A1. Studies performed in mouse primary hepatocytes overexpressing hnRNP A1, and in mouse erythroleukemia derived cells lacking hnRNP A1, revealed that the 71 nt region in the 3' UTR of the CYP2A5 mRNA is essential for Cyp2a5 expression.The hnRNP A1 is a multifunctional nucleocytoplasmic shuttling protein, with the ability to bind both RNA and DNA. These properties make it an interesting candidate mediating a coupling between nuclear and cytoplasmic gene regulatory events, which was investigated for the Cyp2a5. In conditions of cellular stress hnRNP A1 translocates from the nucleus to the cytoplasm. The accumulation of cytoplasmic hnRNP A1 after RNA polymerase II transcription inhibition, resulted in an increased binding of hnRNP A1 to the CYP2A5 mRNA, parallel with a stabilization of the CYP2A5 mRNA.Treating primary mouse hepatocytes with phenobarbital (PB), a Cyp2a5 transcriptional inducer, resulted in a mainly nuclear localization of the hnRNP A1. Electrophoretic mobility shift assays with nuclear extracts from control or PB-treated mice, revealed that hnRNP A1 interacts with two regions in the Cyp2a5 proximal promoter, and that the interaction to one of the regions was stimulated by PB treatment.In conclusion, the change in hnRNP A1 subcellular localization after transcriptional inhibition or activation, together with the effects on the interaction of hnRNP A1 with the CYP2A5 mRNA and Cyp2a5 promoter, suggest that hnRNP A1 could couple the nuclear and cytoplasmic events of the Cyp2a5 expression.The presented studies are the first showing involvement of an hnRNP protein in the regulation of a Cyp gene. Moreover, it is the first time an interconnected transcriptional and posttranscriptional regulation has been suggested for a member of the Cyp gene family.
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| 26. |
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| 27. |
- Jensen, Christina T, et al.
(författare)
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Dissection of progenitor compartments resolves developmental trajectories in B-lymphopoiesis
- 2018
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 1540-9538 .- 0022-1007. ; 215:7, s. 1947-1963
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Tidskriftsartikel (refereegranskat)abstract
- To understand the developmental trajectories in early lymphocyte differentiation, we identified differentially expressed surface markers on lineage-negative lymphoid progenitors (LPs). Single-cell polymerase chain reaction experiments allowed us to link surface marker expression to that of lineage-associated transcription factors (TFs) and identify GFRA2 and BST1 as markers of early B cells. Functional analyses in vitro and in vivo as well as single-cell gene expression analyses supported that surface expression of these proteins defined distinct subpopulations that include cells from both the classical common LPs (CLPs) and Fraction A compartments. The formation of the GFRA2-expressing stages of development depended on the TF EBF1, critical both for the activation of stage-specific target genes and modulation of the epigenetic landscape. Our data show that consecutive expression of Ly6D, GFRA2, and BST1 defines a developmental trajectory linking the CLP to the CD19+ progenitor compartment.
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| 28. |
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| 29. |
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| 30. |
- Konstandi, Maria, et al.
(författare)
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D-2-receptor-linked signaling pathways regulate the expression of hepatic CYP2E1
- 2008
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Ingår i: Life Sciences. - : Elsevier BV. - 0024-3205 .- 1879-0631. ; 82:1-2, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the role of catecholamine-related signaling pathways in the regulation of hepatic cytochrome P450 (CYP2E1). Central and peripheral catecholamine depletion with reserpine down-regulated CYP2E1. On the other hand, selective peripheral catecholamine depletion with guanethidine increased CYP2E1 apoprotein levels. Enrichment of peripheral catecholamines with adrenaline suppressed p-nitrophenol hydroxylase activity (PNP). PNP activity was also markedly suppressed by L-DOPA. Stimulation of D-2-receptors with bromocriptine up-regulated CYP2E1, as assessed by enzyme activity and protein levels, whereas blockade of D-2-dopaminergic receptors with sulpiride down-regulated this isozyme. These findings indicate that central and peripheral catecholamines have different effects on CYP2E1. Central catecholamines appear related to the up-regulation, whereas the role of peripheral catecholamines is clearly related to the type and location of adrenoceptors involved. D-2-receptor-linked signaling pathways have an up-regulating effect on CYP2E1, while D-1-receptor pathways may down-regulate this isozyme. It is worth noting that the widespread environmental pollutant benzo(alpha)pyrene (13(alpha)P) altered the modulating effect of catecholaminergic systems on CYP2E1 regulation. In particular, whereas stimulation or blockade of adrenoceptors had no effect on constitutive PNP activity, exposure to B(alpha)P modified the impact of central and peripheral catecholamines and alpha(2)-adrenoceptors on CYP2E1 expression. It appears that under the influence of B(alpha)P, alpha(2)-adrenergic receptor-linked signaling pathways increased CYP2E1 apoprotein levels. Given that a wide range of xenobiotics and clinically used drugs are activated by CYP2E1 to toxic metabolites, including the production of reactive oxygen species (ROS), it is possible that therapies challenging dopaminergic receptor- and/or alpha(2)-adrenoceptor-linked signaling pathways may alter the expression of CYP2E1, thus affecting the progress and development of several pathologies.
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| 31. |
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| 32. |
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| 33. |
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| 34. |
- Konstandi, Maria, et al.
(författare)
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Predominant role of peripheral catecholamines in the stress-induced modulation of CYP1A2 inducibility by benzo(alpha)pyrene
- 2008
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Ingår i: Basic & Clinical Pharmacology & Toxicology. - : Wiley. - 1742-7835 .- 1742-7843. ; 102:1, s. 35-44
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Tidskriftsartikel (refereegranskat)abstract
- The potential involvement of catecholamines and in particular of alpha(2)-adrenoceptor-related signalling pathways, in the regulation of drug-metabolizing enzymes by stress was investigated in Wistar rats after exposure to the environmental pollutant benzo(alpha)pyrene. For this purpose, total cytochrome P450 content, the CYP1A2 mRNA levels, 7-methoxyresorufin-O-dealkylase (MROD), 7-pentoxyresorufin-O-dealkylase (PROD) and p-nitrophenol hydroxylase activity levels were determined in the livers of rats exposed to repeated restraint stress after treatment with benzo(alpha)pyrene coupled with pharmacological manipulations of peripheral and/or central catecholamines and alpha(2)-adrenoceptors. The data show that stress is a significant factor in the regulation of CYP1A2 induction and that catecholamines play a central role in the stress-mediated modulation of hepatic CYP1A2 inducibility by benzo(alpha)pyrene. The up-regulating effect of stress on benzo(alpha)pyrene-induced CYP1A2 gene expression was eliminated after a generalized catecholamine depletion with reserpine. Similarly, in a state where only peripheral catecholamines were depleted and central catecholamines remained intact after guanethidine administration, the up-regulating effect of stress was eliminated. It is apparent that stress up-regulates the induction of CYP1A2 by benzo(alpha)pyrene mainly via peripheral catecholamines, while central catecholamines hold a minor role in the regulation. Pharmacological manipulations of alpha(2)-adrenoceptors appear to interfere with the effect of stress on the regulation of CYP1A2 inducibility. Either blockade or stimulation of alpha(2)-adrenoceptors with atipamezole and dexmedetomidine respectively, eliminated the up-regulating effect of stress on CYP1A2 benzo(alpha)pyrene-induced expression, while it enhanced MROD activity. In contrast, stress and pharmacological manipulations of catecholamines and alpha(2)-adrenoceptors did not affect total P450 content, the CYP2B1/2-dependent PROD and the CYP2E1-dependent p-nitrophenol hydroxylase activities. In conclusion, stress is a significant factor in the regulation of the CYP1A2 inducibility by benzo(alpha)pyrene, which in turn is involved in the metabolism of a large spectrum of toxicants, drugs and carcinogenic agents. Although the mechanism underlying the stress effect on CYP1A2 induction has not been clearly elucidated, it appears that peripheral catecholamines hold a predominant role, while central catecholamines and in particular, central noradrenergic pathways hold a minor role.
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| 35. |
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| 36. |
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| 37. |
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| 38. |
- Konstandia, Maria, et al.
(författare)
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Effects of choline-deprivation on paracetamol- or phenobarbital-induced rat liver metabolic response
- 2009
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Ingår i: Journal of Applied Toxicology. - : Wiley. - 0260-437X .- 1099-1263. ; 29:2, s. 101-109
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Tidskriftsartikel (refereegranskat)abstract
- Choline is an essential nutrient that seems to be involved in a wide variety of metabolic reactions and functions in both humans and rodents. Various pathophysiological states have been linked to choline deprivation (CD). The aim of the present study was to determine the effect of CD upon biochemical, histological and metabolic alterations induced by drugs that affect hepatic functional integrity and various drug metabolizing systems via distinct mechanisms. For this purpose, paracetamol (ACET) or phenobarbital (PB) were administered to male Wistar rats that were fed with standard rodent chow (normally fed, NF) or underwent dietary CD. The administration of ACET increased the serum aspartate aminotransferase levels in NF rats, while CD restricted this increase. On the other hand, ACET suppressed alkaline phosphatase levels only in CD rats. Moreover, CID prevented the PB-induced increase of the mitotic activity of hepatocytes. The administration of ACET down-regulated CYP1A2 and CYP2B1 expression in CD rats, while up-regulating them in NF rats. The administration of PB suppressed CYP1A2 apoprotein levels in CD rats, whereas the drug had no effect on NF rats. The PB-induced up-regulation of CYP2B, CYP2E1 and CYP1A1 isozymes was markedly higher in CD than in NF rats. In addition, PB increased glutathlone-S-transferase activity only in CD rats. Hepatic glutathione content (GSH) was suppressed by ACET in NF rats, whereas the drug increased GSH in CD rats. Our data suggest that CD has a significant impact on the hepatic metabolic functions, and in particular on those related to drug metabolism. Thus, CD may modify drug effectiveness and toxicity, as well as drug-drug interactions, particularly those related to ACET and PB.
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| 39. |
- Kotsovolou, Olga, et al.
(författare)
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Hepatic drug metabolizing profile of Flinders Sensitive Line rat model of depression
- 2010
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Ingår i: Progress in Neuro-psychopharmacology and Biological Psychiatry. - : Elsevier BV. - 0278-5846 .- 1878-4216. ; 34:6, s. 1075-1084
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Forskningsöversikt (refereegranskat)abstract
- The Flinders Sensitive Line (FSL) rat model of depression exhibits some behavioral, neurochemical, and pharmacological features that have been reported in depressed patients and has been very effective in screening antidepressants. Major factor that determines the effectiveness and toxicity of a drug is the drug metabolizing capacity of the liver. Therefore, in order to discriminate possible differentiation in the hepatic drug metabolism between FSL rats and Sprague Dawley (SD) controls, their hepatic metabolic profile was investigated in this study. The data showed decreased glutathione (GSH) content and glutathione S-transferase (GST) activity and lower expression of certain major CYP enzymes, including the CYP2B1, CYP2C11 and CYP2D1 in FSL rats compared to SD controls. In contrast, p-nitrophenol hydroxylase (PNP), 7ethoxyresorufin-O-dealkylase (EROD) and 16 alpha-testosterone hydroxylase activities were higher in FSL rats. Interestingly, the wide spread environmental pollutant benzo(alpha)pyrene (B(alpha)P) induced CYP1A1, CYP1A2, CYP2B1/2 and ALDH3c at a lesser extend in FSL than in SD rats, whereas the antidepressant mirtazapine (MIRT) up-regulated CYP1A1/2, CYP2C11, CYP2D1, CYP2E1 and CYP3A1/2, mainly, in FSL rats. The drug also further increased ALDH3c whereas suppressed GSH content in B(a)P-exposed FSL rats. In conclusion, several key enzymes of the hepatic biotransformation machinery are differentially expressed in FSL than in SD rats, a condition that may influence the outcome of drug therapy. The MIRT-induced up-regulation of several drug-metabolizing enzymes indicates the critical role of antidepressant treatment that should be always taken into account in the designing of treatment and interpretation of insufficient pharmacotherapy or drug toxicity.
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| 40. |
- Lang, Matti
(författare)
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CYP2A5/CYP2A6 in search for function
- 1995
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Ingår i: Eur. J. Drug metabolism and pharmacokinetics. ; special issue, s. 29-30
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Tidskriftsartikel (refereegranskat)
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| 41. |
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| 42. |
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| 43. |
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| 44. |
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| 45. |
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| 46. |
- Lindell, Monica, 1963-
(författare)
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Expression of Genes Encoding for Drug Metabolism in the Small Intestine
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This investigation focused on the mRNA expression of drug metabolising Cytochromes P-450 (CYP) and UDP-glucuronosyltransferases (UGT) and the transport protein P-glycoprotein (Pgp) in the small intestine of humans and rats.The mRNA expression of the investigated genes in the human small intestine (duodenum) varies between individuals giving each one of us personal profile. In general, the most dominant forms are Pgp, CYPs 2C9, 2D6, 3A4, and UGTs 1A1, 1A10, 2B7. However, which of these is the highest expressed one varies between individuals.The correlation in expression between some CYP forms and UGT forms respectively is relatively high, which indicates that they have some regulatory mechanisms in common. It was also shown that the mRNA expression of both CYPs and UGTs may be affected by endogenous and exogenous factors. Sex and ethnic background, affected the mRNA expression of CYP2A6 and 2E1 respectively. Commonly used drugs such as acetylsalicylicacid (ASA) and omeprazole (omep) affect CYP2A6, CYP2E1 (ASA) and CYP3A4, UGT1A4 (omep). The expression of UGT1A4 is also affected by smoking. All these factors are commonly used and can therefore lead to important drug-drug interactions.It was also shown that the human small intestinal CYP mRNA expression pattern differs from that found in the rat. The rat CYP expression is rather constant between the different individuals, and the main rat intestinal forms are CYP1A1, CYP2C, CYP2D6 and CYP3A1. The expression is the same for females and males and no difference can be seen between the different segments of the rat small intestine. As metabolic studies have often been done with rat liver we compared the mRNA expression in the two organs. We found that the mRNA expression of 1A1 was absent in the liver and that the CYP2B1, CYP2Cs, CYP2D1 and Pgp all had a stronger mRNA expression in the small intestine compared to the liver. It is therefore important to realise that results from metabolic studies on liver may not be directly extrapolated to the small intestine.Artemisinin is an orally used drug in multidrug treatment of malaria in Southeast Asia. It has been suggested that artemisinin can induce drug metabolism and therefore be involved in drug-drug interactions. This study shows that artemisinin induces mainly the CYP2B via nuclear receptor CAR.
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| 47. |
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| 48. |
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| 49. |
- Lindell, Monica, et al.
(författare)
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Variable Expression of CYP and Pgp Genes in the Human Small Intestine
- 2003
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Ingår i: European Journal of Clinical Investigation. - : Wiley. - 0014-2972 .- 1365-2362. ; 33:6, s. 493-499
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The small intestine is receiving increased attention for its importance in drug metabolism. However, knowledge of the intervariability and regulation of the enzymes involved, cytochrome p450 and P-Glycoproteins (CYP and Pgp), is poor when compared with the corresponding hepatic enzymes. METHODS: The expression of eight different CYP genes and the Pgp were determined by reverse transcription polymerase chain reaction (RT-PCR) in 51 human duodenum biopsies. And the variability and correlation of expression was analyzed. RESULTS: Extensive interindividual variability was found in the expression of most of the genes. Only CYP2C9, CYP3A4 and Pgp were found in all samples. CYP1A2, CYP2A6 and CYP2E1 exhibited the highest interindividual variability. No strong correlation of expression existed between the genes. But a highly significant correlation was found between CYP2D6/1A2, 2D6/2E1, 1A2/2E1 and 2B6/2C9. Acetylsalicylic acid and omeprazole significantly increased the expression of CYPs 2A6, 2E1 and 3A4, respectively. CONCLUSIONS: Extensive interindividual variability is characteristic for the expression of drug-metabolizing CYP and Pgp genes in human duodenum, and external factors such as drugs may further increase the variability. It is possible that the large interindividual variability may lead to variable bioavailability of orally used drugs and hence complicate optimal drug therapy, especially for drugs with a small therapeutic window. Elucidation of factors contributing to clinically important variances warrants further investigation.
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| 50. |
- Lu, Yingchang, et al.
(författare)
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A Transcriptome-Wide Association Study Among 97,898 Women to Identify Candidate Susceptibility Genes for Epithelial Ovarian Cancer Risk.
- 2018
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Ingår i: Cancer Research. - 0008-5472 .- 1538-7445. ; 78:18, s. 5419-5430
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Tidskriftsartikel (refereegranskat)abstract
- .AbstractLarge-scale genome-wide association studies (GWAS) have identified approximately 35 loci associated with epithelial ovarian cancer (EOC) risk. The majority of GWAS-identified disease susceptibility variants are located in noncoding regions, and causal genes underlying these associations remain largely unknown. Here, we performed a transcriptome-wide association study to search for novel genetic loci and plausible causal genes at known GWAS loci. We used RNA sequencing data (68 normal ovarian tissue samples from 68 individuals and 6,124 cross-tissue samples from 369 individuals) and high-density genotyping data from European descendants of the Genotype-Tissue Expression (GTEx V6) project to build ovarian and cross-tissue models of genetically regulated expression using elastic net methods. We evaluated 17,121 genes for their cis-predicted gene expression in relation to EOC risk using summary statistics data from GWAS of 97,898 women, including 29,396 EOC cases. With a Bonferroni-corrected significance level of P < 2.2 × 10−6, we identified 35 genes, including FZD4 at 11q14.2 (Z = 5.08, P = 3.83 × 10−7, the cross-tissue model; 1 Mb away from any GWAS-identified EOC risk variant), a potential novel locus for EOC risk. All other 34 significantly associated genes were located within 1 Mb of known GWAS-identified loci, including 23 genes at 6 loci not previously linked to EOC risk. Upon conditioning on nearby known EOC GWAS-identified variants, the associations for 31 genes disappeared and three genes remained (P < 1.47 × 10−3). These data identify one novel locus (FZD4) and 34 genes at 13 known EOC risk loci associated with EOC risk, providing new insights into EOC carcinogenesis.Significance: Transcriptomic analysis of a large cohort confirms earlier GWAS loci and reveals FZD4 as a novel locus associated with EOC risk. Cancer Res; 78(18); 5419–30. ©2018 AACR.
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