Marmoset Liver Research Articles

Differences in Hydrolase Activities in the Liver and Small Intestine between Marmosets and Humans.

For drug development, species differences in drug-metabolism reactions present obstacles for predicting pharmacokinetics in humans. We characterized the species differences in hydrolases among humans and mice, rats, dogs, and cynomolgus monkeys. In this study, to expand the series of such studies, we attempted to characterize marmoset hydrolases. We measured hydrolase activities for 24 compounds using marmoset liver and intestinal microsomes, as well as recombinant marmoset carboxylesterase (CES) 1, CES2, and arylacetamide deacetylase (AADAC). The contributions of CES1, CES2, and AADAC to hydrolysis in marmoset liver microsomes were estimated by correcting the activities by using the ratios of hydrolase protein levels in the liver microsomes and those in recombinant systems. For six out of eight human CES1 substrates, the activities in marmoset liver microsomes were lower than those in human liver microsomes. For two human CES2 substrates and three out of seven human AADAC substrates, the activities in marmoset liver microsomes were higher than those in human liver microsomes. Notably, among the three rifamycins, only rifabutin was hydrolyzed by marmoset tissue microsomes and recombinant AADAC. The activities for all substrates in marmoset intestinal microsomes tended to be lower than those in liver microsomes, which suggests that the first-pass effects of the CES and AADAC substrates are due to hepatic hydrolysis. In most cases, the sums of the values of the contributions of CES1, CES2, and AADAC were below 100%, which indicated the involvement of other hydrolases in marmosets. In conclusion, we clarified the substrate preferences of hydrolases in marmosets. SIGNIFICANCE STATEMENT: This study confirmed that there are large differences in hydrolase activities between humans and marmosets by characterizing marmoset hydrolase activities for compounds that are substrates of human CES1, CES2, or arylacetamide deacetylase. The data obtained in this study may be useful for considering whether marmosets are appropriate for examining the pharmacokinetics and efficacies of new chemical entities in preclinical studies.

Cloning, sequence analysis, and tissue expression of marmoset paraoxonase 1

Paraoxonase (PON) plays roles in the metabolism of organophosphate xenobiotics and drugs. Despite the importance of marmosets for research into drug metabolism and pharmacokinetics, marmoset paraoxonase has not yet been fully characterized. Consequently, we identified the PON1 gene in the marmoset genome by sequence homology analysis. Marmoset PON1 cDNA containing an open reading frame (1065 bp) was successfully cloned from marmoset liver by reverse transcription-polymerase chain reaction. The deduced amino acid sequence (355 amino acids) has approximately 93% identity with the human ortholog and contains important amino acid residues for substrate binding and calcium ion coordination. According to a phylogenetic tree of PON1 amino acid sequences constructed using data from seven animal species, marmoset PON1 is closer to human PON1 than it is to the PON1 orthologs of experimental animals such as pigs, rabbits, rats, and mice. Marmoset PON1 mRNA was predominantly expressed in liver among the five tissues examined. Marmoset PON1 protein secreted into plasma was detected by immunoblotting. The paraoxon-hydrolyzing activity in plasma was higher in marmosets than in humans. Based on these data, we concluded that marmoset and human PON1 have similar characteristics with regard to genomic structure, amino acid sequences, and tissue distribution.

Molecular characterization of functional UDP-glucuronosyltransferases 1A and 2B in common marmosets

UDP-glucuronosyltransferases (UGTs) are essential drug-conjugation enzymes that metabolize a variety of endobiotic and xenobiotic substrates. The molecular characteristics of UGTs have been extensively investigated in humans, but remain to be investigated in common marmosets, a nonhuman primate species widely used in drug metabolism studies. In this study, 11 UGT cDNAs (UGT1A1, 1A3, 1A4, 1A6, 1A7, and 1A9; and UGT2B49, 2B50, 2B51, 2B52, and 2B53) were isolated and characterized in marmosets. Marmoset UGT1As had high sequence identities (89–93%) with human UGT1As, but the sequence identities of marmoset UGT2Bs were lower (82–86%). Marmoset UGTs were found to be phylogenetically close to human UGTs. Just as human UGT1As do, marmoset UGT1A genes shared exons 2–5 and contained a variable exon 1 unique to each gene; in contrast, marmoset UGT2B genes contained six unique exons. Moreover, marmoset and human UGT1A and UGT2B gene clusters were located in corresponding regions in their respective genomes. Among the five tissue types tested, marmoset UGT mRNAs were most abundantly expressed in liver, jejunum, and/or kidney, i.e., in tissues important for drug metabolism, just as human UGTs are. Among the 11 marmoset UGT mRNAs investigated, marmoset UGT1A9, 1A4, and 1A6 mRNAs were the most abundantly expressed in liver, small intestine, and kidney, respectively. Marmoset liver microsomes and recombinant UGT1A proteins catalyzed the glucuronidation of the same substrates that human UGT1As catalyze, including estradiol, trifluoperazine, 4-methylumbelliferone, serotonin, 4-nitrophenol, and propofol. Trifluoperazine was glucuronidated by marmoset liver microsomes, but not by any of the UGT1A isoforms examined under the present conditions. These results collectively suggest that functional marmoset UGTs have generally similar molecular characteristics to human UGTs.

In vivo and in vitro diclofenac 5-hydroxylation mediated primarily by cytochrome P450 3A enzymes in common marmoset livers genotyped for P450 2C19 variants

Common marmosets (Callithrix jacchus) are potentially useful nonhuman primate models for preclinical studies. An anti-inflammatory drug, diclofenac is reportedly metabolized mainly by human cytochrome P450 (P450) 2C9 to 4′-hydroxydiclofenac and minorly by P450 3A4 to 5-hydroxydiclofenac that leads to reactive intermediates. In this study, in vivo pharmacokinetics in six marmosets and in vitro metabolism in nine marmoset liver microsomes were analyzed using diclofenac to evaluate marmosets as preclinical drug metabolism models. In wild-type marmosets genotyped for P450 2C19 p.[(Phe7Leu; Ser254Leu; Ile469Thr)], plasma levels of 5-hydroxydiclofenac and 4′-hydroxydiclofenac were roughly similar, but the homozygotes showed approximately three-times higher plasma levels of 5-hydroxydiclofenac than those of 4′-hydroxydiclofenac after oral administrations of diclofenac (50 mg/kg). Nine marmoset liver microsomes catalyzed mainly diclofenac 5-hydroxylation with no significant effects of the the P450 2C19 genotype, and partly diclofenac 4′-hydroxylation that depended on the P450 2C19 genotype, at substrate concentrations of 10 µM and 100 µM. Both Michaels-Menten constant Km values for diclofenac 4′-hydroxylation in human and marmoset liver microsomes were ∼30 μM and those for diclofenac 5-hydroxylation were ∼120 μM. Ketoconazole significantly suppressed only diclofenac 5-hydroxylation in marmoset or human liver microsomes at 0.030 μM, indicating main contribution of P450 3A enzymes, which were found to be P450 3A5/90 using recombinant marmoset P450 3A enzymes. These results suggest that marmosets would be a functional animal model for in vivo and in vitro metabolites likely generated via arene oxide intermediates of diclofenac by P450 3A enzymes in humans, primarily because marmosets lack the ortholog of human P450 2C9.

Marmoset cytochrome P450 2B6, a propofol hydroxylase expressed in liver

The common marmoset (Callithrix jacchus) is a useful experimental animal to evaluate the pharmacokinetics of drug candidates. Cytochrome P450 (P450) 2B enzyme in marmoset livers has been identified; however, only limited information on the enzymatic properties and distribution has been available.Marmoset P450 2B6 amino acids showed high sequence identities (>86%) with those of primates including humans and cynomolgus monkeys. Phylogenetic analysis using amino acid sequences indicated that marmoset P450 2B6 was closer to human and cynomolgus monkey P450 2B6 than to P450 2B orthologs of other species, including pigs, dogs, rabbits and rodents.Quantitative polymerase chain reaction analysis using specific primers showed P450 2B6 mRNA predominantly expressed in livers among the five marmoset tissues, similar to those of humans and cynomolgus monkeys.Marmoset P450 2B6 heterologously expressed in Escherichia coli membranes oxidized 7-ethoxycoumarin, pentoxyresorufin, propofol and testosterone, at roughly similar rates to those of humans and/or cynomolgus monkeys. A high capacity of marmoset P450 2B6 with propofol 4-hydroxylation (at low ionic strength conditions) with a low Km value was relatively comparable to that for marmoset livers.These results collectively indicated a high propofol 4-hydroxylation activity of P450 2B6 expressed in marmoset livers.

Molecular cloning and tissue distribution of a novel marmoset ABC transporter.

Common marmosets (Callithrix jacchus) have been recognized as a useful small non-human primate model in preclinical testing for drug development. In this study, a cDNA of novel ATP-dependent efflux transporter ABCB1 was cloned from marmoset liver tissue. Marmoset ABCB1 cDNA encodes a protein of 1279 amino acid residues (MW=141.4kDa) containing characteristic regions of an ATP-binding cassette (ABC) protein, two hydrophobic transmembrane regions and two cytoplasmic nucleotide-binding regions, similar to human ABCB1. The deduced amino acid sequences were more highly identical (95%) to those of human ABCB1 compared with non-primate species such as dogs, pigs and rodents (79-90%). A close evolutionary relationship of ABCB1 among marmosets, cynomolgus and rhesus monkeys and humans was evident from a phylogenetic analysis using ABCB1 amino acid sequences from primates, dogs, pigs and rodents. Tissue distribution analyses by quantitative reverse transcription-polymerase chain reaction indicated that marmoset ABCB1 mRNA was most abundant in kidneys, followed by small intestines and livers, similar to human ABCB1, and marmoset ABCB1 proteins in these tissues were also detected by immunoblotting. These results indicated that the primary structure and tissue distribution of ABCB1 in marmosets were similar to those of humans, suggesting similar molecular characteristics of ABCB1 between marmosets and humans.

Progesterone hydroxylation by cytochromes P450 2C and 3A enzymes in marmoset liver microsomes

1. Common marmosets (Callithrix jacchus) are potentially useful nonhuman primate models for preclinical drug metabolism studies. However, the roles of marmoset cytochrome P450 (P450) isoforms in the oxidation of endobiotic progesterone have not been fully investigated. In this study, the roles of marmoset P450 isoforms in progesterone hydroxylation were extensively determined.2. The activities of liver microsomes from individual marmosets with respect to progesterone 21/17α- and 16α/6β-hydroxylation were significantly correlated with those for flurbiprofen 4-hydroxylation and midazolam 1′-hydroxylation, respectively, as similar correlations have been found in humans. Anti-P450 2 C and 3 A antibodies suppressed progesterone 21/17α- and 16α/6β-hydroxylation, respectively, in marmoset liver microsomes.3. Recombinant marmoset P450 2C58 and 2C19 catalyzed progesterone to form 21-hydroxyprogesterone and 16α-hydroxyprogesterone, respectively, as major products with high maximum velocity/Km values of 0.53 and 0.089 mL/min/nmol, respectively. Recombinant marmoset P450 3A4/90 oxidized progesterone to form 6β-hydroxyprogesterone as a major product with homotropic cooperativity (>1 of Hill coefficients).4. These results indicate that the overall activities and roles of liver microsomal P450 enzymes in marmoset livers are similar to those in humans, especially for progesterone 21/17α- and 16α/6β-hydroxylation by marmoset P450 2 C and 3 A enzymes, respectively, suggesting important roles for these P450 enzymes in the metabolism of endobiotics in marmosets.

Marmoset pulmonary cytochrome P450 2F1 oxidizes biphenyl and 7-ethoxycoumarin and hepatic human P450 substrates

1. A potentially useful animal model for preclinical studies is the common marmoset (Callithrix jacchus). In this study, using reverse-transcription polymerase chain reaction from marmoset livers, we identified a novel cytochrome P450 (P450) 2F1 cDNA with an open reading frame of 1473 bp.2. High sequence identities of 92-94% with primate P450 2 F amino acid sequences were indicated by deduced amino acid sequences of P450 2F1 cDNA. Phylogenetic analysis indicates that marmoset P450 2F1 is more congruent with primate P450 2 F forms than those of other species such as rodents.3. Among five tissue types examined, abundant expression of marmoset P450 2F1 mRNA and P450 2F1 protein in lungs was shown. Cynomolgus monkey P450 2F1 mRNA was abundantly expressed in lungs as well as testes and ovaries in 10 tissue types.4. Similar to those of humans and cynomolgus monkeys, marmoset P450 2F1 heterologously expressed in Escherichia coli membranes efficiently catalyzed 7-ethoxycoumarin O-deethylation and biphenyl hydroxylation, however unlike human P450 2F1, marmoset P450 2F1 exhibited hydroxylation activity toward coumarin and chlorzoxazone.5. These findings indicated that P450 2F1 enzyme expressed in marmoset lungs and also catalyzed metabolism of xenobiotics, suggesting the importance of P450 2 F-dependent drug metabolism in marmoset lungs.

Terfenadine t-butyl hydroxylation catalyzed by human and marmoset cytochrome P450 3A and 4F enzymes in livers and small intestines

1. Roles of human cytochrome P450 (P450) 3A4 in oxidation of an antihistaminic drug terfenadine have been previously investigated in association with terfenadine–ketoconazole interaction. Several antihistamine drugs have been recently identified as substrates for multiple P450 enzymes. In this study, overall roles of P450 3A4, 2J2, and 4F12 enzymes in terfenadine t-butyl hydroxylation were investigated in small intestines and livers from humans, marmosets, and/or cynomolgus monkeys.2. Human liver microsomes and liver and small intestine microsomes from marmosets and cynomolgus monkeys effectively mediated terfenadine t-butyl hydroxylation. Ketoconazole and N-hydroxy-N′-(4-butyl-2-methylphenyl)-formamidine (a P450 4A/F inhibitor) almost completely and moderately inhibited these activities, respectively, in human liver microsomes; however, these chemicals did not show substantially suppression in marmoset liver. Anti-human P450 3A and 4F antibodies showed the roughly supportive inhibitory effects.3. Recombinant P450 3A4/90 and 4F12 showed high terfenadine t-butyl hydroxylation activities with substrate inhibition constants of 84–144 μM (under 26–76 μM of Km values), in similar manners to liver and intestine microsomes.4. These results suggest that human and marmoset P450 3A4/90 and 4F12 in livers or small intestines played important roles in terfenadine t-butyl hydroxylation. Marmosets could be a model for humans during first pass extraction of terfenadine and related substrates.

Regio- and Stereo-Selective Oxidation of a Cardiovascular Drug, Metoprolol, Mediated by Cytochrome P450 2D and 3A Enzymes in Marmoset Livers.

A β-blocker, metoprolol, is one of the in vivo probes for human cytochrome P450 (P450) 2D6. Investigation of nonhuman primate P450 enzymes helps to improve the accuracy of the extrapolation of pharmacokinetic data from animals into humans. Common marmosets (Callithrix jacchus) are a potential primate model for preclinical research, but the detailed roles of marmoset P450 enzymes in metoprolol oxidation remain unknown. In this study, regio- and stereo-selectivity of metoprolol oxidations by a variety of P450 enzymes in marmoset and human livers were investigated in vitro. Although liver microsomes from cynomolgus monkeys and rats preferentially mediated S-metoprolol O-demethylation and R-metoprolol α-hydroxylation, respectively, those from humans, marmosets, minipigs, and dogs preferentially mediated R-metoprolol O-demethylation, in contrast to the slow rates of R- and S-metoprolol oxidation in mouse liver microsomes. R- and S-metoprolol O-demethylation activities in marmoset livers were strongly inhibited by quinidine and ketoconazole, and were significantly correlated with bufuralol 1'-hydroxylation and midazolam 1'-hydroxylation activities and also with P450 2D and 3A4 contents, which is different from the case in human livers that did not have any correlations with P450 3A-mediated midazolam 1'-hydroxylation. Recombinant human P450 2D6 enzyme and marmoset P450 2D6/3A4 enzymes effectively catalyzed R-metoprolol O-demethylation, comparable to the activities of human and marmoset liver microsomes, respectively. These results indicated that the major roles of P450 2D enzymes for the regio- and stereo-selectivity of metoprolol oxidation were similar between human and marmoset livers, but the minor roles of P450 3A enzymes were unique to marmosets.

Molecular Cloning and Characterization of Marmoset Aldehyde Oxidase.

Common marmosets (Callithrix jacchus), New World monkeys, are a promising primate model for preclinical drug metabolism studies because of the similarities of cytochrome P450 (P450) enzyme function to those of humans. Despite an increasing number of drug candidates catalyzed by non-P450 enzymes, drug metabolizing enzymes other than P450s have been hardly identified or characterized in marmosets. In this study, we identified aldehyde oxidase (AOX) 1 gene by marmoset genome analysis. AOX1 cDNA was cloned from marmoset livers by reverse transcription-polymerase chain reaction. Deduced amino acid sequences of AOX1 cDNA showed high sequence identities (92-93%) with primate AOX1s. Phylogenetic analysis showed that marmoset AOX1 was closely clustered with primate AOX1s, unlike nonprimate animal model AOX1s of pig, rabbit, rat, and mouse used in drug metabolism. The tissue expression analyses by real-time reverse-transcription polymerase chain reaction and immunoblotting showed that marmoset AOX1 mRNA and protein were abundantly expressed in livers, similar to cynomolgus monkeys and humans. Marmoset AOX1 heterologously expressed in Escherichia coli catalyzed the oxidation of carbazeran and phthalazine, typical AOX1 substrates, similar to cynomolgus monkey and human AOX1s. Human and marmoset AOX1 effectively catalyzed phthalazine oxidation when assessed with Michaelis-Menten kinetics, but cynomolgus monkey AOX1 catalyzed this reaction with cooperative kinetics with high capacity. These results indicated that tissue distribution and enzymatic function of AOX1 enzyme is similar between marmosets and humans, suggesting that marmosets are a suitable primate model for AOX-dependent drug metabolism in preclinical studies.

Marmoset Flavin-Containing Monooxygenase 3 in the Liver Is a Major Benzydamine and Sulindac Sulfide Oxygenase.

Common marmosets (Callithrix jacchus) are potentially primate models for preclinical drug metabolism studies because there are similarities in the molecular characteristics of cytochrome P450 enzymes between this species and humans. However, characterization of non-cytochrome P450 enzymes has not been clarified in marmosets. Here, we report characterization of flavin-containing monooxygenases FMO1-FMO5 identified in marmoset tissues. Marmoset FMO forms shared high amino acid sequence identities (93%-95%) and phylogenetic closeness with human homologous FMO forms. FMO1 and FMO3 mRNA were abundantly expressed in the liver and kidneys among five marmoset tissues examined, where FMO3 protein was detected by immunoblotting. FMO inhibition assays using preheated tissue microsomes indicated that benzydamine N-oxygenation and sulindac sulfide S-oxygenation in the marmoset liver was mainly catalyzed by FMO3, the major hepatic FMO. Marmoset FMO3 protein heterologously expressed in Escherichia coli effectively catalyzed benzydamine N-oxygenation and sulindac sulfide S-oxygenation comparable to marmoset liver microsomes. These results indicate that the FMO3 enzyme expressed in marmoset livers mainly metabolizes benzydamine and sulindac sulfide (typical human FMO substrates), suggesting its importance for FMO-dependent drug metabolism in marmosets.

Marmoset Cytochrome P450 3A4 Ortholog Expressed in Liver and Small-Intestine Tissues Efficiently Metabolizes Midazolam, Alprazolam, Nifedipine, and Testosterone.

Common marmosets (Callithrix jacchus), small New World primates, are increasingly attracting attention as potentially useful animal models for drug development. However, characterization of cytochrome P450 (P450) 3A enzymes involved in the metabolism of a wide variety of drugs has not investigated in marmosets. In this study, sequence homology, tissue distribution, and enzymatic properties of marmoset P450 3A4 ortholog, 3A5 ortholog, and 3A90 were investigated. Marmoset P450 3A forms exhibited high amino acid sequence identities (88-90%) to the human and cynomolgus monkey P450 3A orthologs and evolutionary closeness to human and cynomolgus monkey P450 3A orthologs compared with other P450 3A enzymes. Among the five marmoset tissues examined, P450 3A4 ortholog mRNA was abundant in livers and small intestines where P450 3A4 ortholog proteins were immunologically detected. Three marmoset P450 3A proteins heterologously expressed in Escherichia coli membranes catalyzed midazolam 1'- and 4-hydroxylation, alprazolam 4-hydroxylation, nifedipine oxidation, and testosterone 6β-hydroxylation, similar to cynomolgus monkey and human P450 3A enzymes. Among the marmoset P450 3A enzymes, P450 3A4 ortholog effectively catalyzed midazolam 1'-hydroxylation, comparable to microsomes from marmoset livers and small intestines. Correlation analyses with 23 individual marmoset liver microsomes suggested contributions of P450 3A enzymes to 1'-hydroxylation of both midazolam (human P450 3A probe) and bufuralol (human P450 2D6 probe), similar to cynomolgus monkey P450 3A enzymes. These results indicated that marmoset P450 3A forms had functional characteristics roughly similar to cynomolgus monkeys and humans in terms of tissue expression patterns and catalytic activities, suggesting marmosets as suitable animal models for P450 3A-dependent drug metabolism.

Cloning and expression of a novel catechol-O-methyltransferase in common marmosets.

Catechol-O-methyltransferase (COMT) catalyzes the O-methylation of endogenous catechol amines and estrogens and exogenous catechol-type of drugs. A Parkinson’s disease model of common marmoset (Callithrix jacchus) has been widely used in preclinical studies to evaluate inhibitory potential of new drug candidates on marmoset COMT. Despite COMT inhibitors could potentiate the pharmacological action of levodopa on Parkinson’s disease in animal models, marmoset COMT cDNA has not yet been identified and characterized. In this study, a cDNA highly homologous to human COMT was cloned from marmoset livers. This cDNA encoded 268 amino acids containing a transmembrane region and critical amino acid residues for catalytic function. The amino acid sequences of marmoset COMT shared high sequence identity (90%) with human COMT. COMT mRNA was expressed in all five tissues tested, including brain, lung, liver, kidney and small intestine, and was more abundant in marmoset liver and kidney. Membrane-bound COMT was immunochemically detected in livers and kidneys, whereas soluble COMT was detected in livers, similar to humans. These results indicated that the molecular characteristics of marmoset COMT were generally similar to the human ortholog.

Oxidation of R- and S-omeprazole stereoselectively mediated by liver microsomal cytochrome P450 2C19 enzymes from cynomolgus monkeys and common marmosets

Racemic omeprazole has been used for clinically treating gastric acid-related diseases and also as a typical human cytochrome P450 (P450) 2C19 probe substrate in preclinical studies. S-Omeprazole has been developed as a single enantiomer medicine, which has been reported not to be associated with polymorphic human P450 2C19 phenotypes. In this study, 5-hydroxylation and sulfoxidation activities, with respect to stereoselective R- and S-omeprazole oxidations by liver microsomes from experimental animals including non-human primates and humans, were investigated in vitro. Liver microsomes from humans, cynomolgus monkeys, and mice preferentially mediated R-omeprazole 5-hydroxylations, however those from marmosets, minipigs, dogs, and rats preferentially mediated S-omeprazole 5-hydroxylations. High catalytic activities were observed for recombinant human P450 2C19 in R-omeprazole 5-hydroxlations, cynomolgus monkey P450 2C19 in both R- and S-omeprazole 5-hydroxlations, and marmoset P450 2C19 in S-omeprazole 5-hydroxlations. On the other hand, human, cynomolgus monkey, and marmoset P450 3A enzymes preferentially mediated S-omeprazole sulfoxidations. Correlation and kinetic analyses revealed a high affinity of polymorphic cynomolgus monkey and marmoset liver microsomal P450 2C19 enzymes with respect to R- and S-omeprazole 5-hydroxylations, respectively, and a high capacity of cynomolgus monkey and marmoset liver microsomal P450 3A4 for omeprazole 5-hydroxylations and sulfoxidations. R-and S-omeprazole 5-hydroxylation activities in cynomolgus monkey and marmoset liver microsomes were significantly different among wild-type, heterozygous, and homozygous animals genotyped for cynomolgus monkey P450 2C19 p.[(Phe100Asn; Ala103Val; Ile112Leu)] and for marmoset P450 2C19 p.[(Phe7Leu; Ser254Leu; Ile469Thr)], respectively. The results of this study demonstrate polymorphic cynomolgus monkey and marmoset P450 2C19-dependent omeprazole oxidation activities with individual variations similar to humans.

Marmoset cytochrome P450 4A11, a novel arachidonic acid and lauric acid ω-hydroxylase expressed in liver and kidney tissues

1. A cDNA encoding novel cytochrome P450 (P450) 4A enzyme was cloned from marmoset livers by reverse transcription (RT)-polymerase chain reaction (PCR) based on the marmoset genome sequences. The amino acid sequence deduced from P450 4A11 cDNA contained consensus sequences of six substrate recognition sites and one heme-binding domain.2. Marmoset P450 4A11, highly identical (85–88%) to cynomolgus monkey and human P450 4A enzymes, was grouped into the same cluster as cynomolgus monkey and human P450 4A enzymes by phylogenetic analysis.3. The tissue distribution analyses by real-time RT PCR and immunoblotting demonstrated that marmoset P450 4A11 mRNA and proteins were expressed in kidneys and livers. Marmoset P450 4A11 enzyme heterologously expressed in Escherichia coli preferentially catalyzed the ω-hydroxylation of arachidonic acid and lauric acid, similar to cynomolgus monkey and human P450 4A11 enzymes. However, lauric acid ω-hydroxylation activity of marmoset P450 4A11 was low compared with those of marmoset liver microsomes.4. These results indicated that novel marmoset P450 4A11 was also a fatty acid ω-hydroxylase expressed in kidneys and livers, with the same regioselectivity (at ω-position of fatty acid) as cynomolgus monkey and human P450 4A enzymes.

Individual Differences in Metabolic Clearance of S-Warfarin Efficiently Mediated by Polymorphic Marmoset Cytochrome P450 2C19 in Livers.

Marmoset cytochrome P450 2C19, highly homologous to human P450 2C9 and 2C19, has been identified in common marmosets (Callithrix jacchus), a nonhuman primate species used in drug metabolism studies. Although genetic variants in human and macaque P450 2C genes account for the interindividual variability in drug metabolism, genetic variants have not been investigated in the marmoset P450 2C19 In this study, sequencing of P450 2C19 in 24 marmosets identified three variants p.[(Phe7Leu; Ser254Leu; Ile469Thr)], which showed substantially reduced metabolic capacity of S-warfarin compared with the wild-type group in vivo and in vitro. Although mean plasma concentrations of R-warfarin in marmosets determined after chiral separation were similar between the homozygous mutant and wild-type groups up to 24 hours after the intravenous and oral administrations of racemic warfarin, S-warfarin depletion from plasma was significantly faster in the three wild-type marmosets compared with the three homozygous mutant marmosets. These variants, cosegregating in the marmosets analyzed, influenced metabolic activities in 18 marmoset liver microsomes because the homozygotes and heterozygotes showed significantly reduced catalytic activities in liver microsomes toward S-warfarin 7-hydroxylation compared with the wild-type group. Kinetic analysis for S-warfarin 7-hydroxylation indicated that the recombinant P450 2C19 Ser254Leu variant would change the metabolic capacity. These results indicated that the interindividual variability of P450 2C-dependent drug metabolism such as S-warfarin clearance is at least partly accounted for by P450 2C19 variants in marmosets, suggesting that polymorphic P450 2C-dependent catalytic functions are relatively similar between marmosets and humans.

A New Marmoset P450 4F12 Enzyme Expressed in Small Intestines and Livers Efficiently Metabolizes Antihistaminic Drug Ebastine.

Common marmosets (Callithrix jacchus) are attracting attention as animal models in preclinical studies for drug development. However, cytochrome P450s (P450s), major drug-metabolizing enzymes, have not been fully identified and characterized in marmosets. In this study, based on the four novel P450 4F genes found on the marmoset genome, we successfully isolated P450 4F2, 4F3B, 4F11, and 4F12 cDNAs in marmoset livers. Deduced amino acid sequences of the four marmoset P450 4F forms exhibited high sequence identities (87%-93%) to the human and cynomolgus monkey P450 4F homologs. Marmoset P450 4F3B and 4F11 mRNAs were predominantly expressed in livers, whereas marmoset P450 4F2 and 4F12 mRNAs were highly expressed in small intestines and livers. Four marmoset P450 4F proteins heterologously expressed in Escherichia coli catalyzed the ω-hydroxylation of leukotriene B4 In addition, marmoset P450 4F12 effectively catalyzed the hydroxylation of antiallergy drug ebastine, a human P450 2J/4F probe substrate. Ebastine hydroxylation activities by small intestine and liver microsomes from marmosets and cynomolgus monkeys showed greatly higher values than those of humans. Ebastine hydroxylation activities by marmoset and cynomolgus monkey small intestine microsomes were inhibited (approximately 60%) by anti-P450 4F antibodies, unlike human small intestine microsomes, suggesting that contribution of P450 4F enzymes for ebastine hydroxylation in the small intestine might be different between marmosets/cynomolgus monkeys and humans. These results indicated that marmoset P450 4F2, 4F3B, 4F11, and 4F12 were expressed in livers and/or small intestines and were functional in the metabolism of endogenous and exogenous compounds, similar to those of cynomolgus monkeys and humans.

Marmoset cytochrome P450 2J2 mainly expressed in small intestines and livers effectively metabolizes human P450 2J2 probe substrates, astemizole and terfenadine

1. Common marmoset (Callithrix jacchus), a New World Monkey, has potential to be a useful animal model in preclinical studies. However, drug metabolizing properties have not been fully understood due to insufficient information on cytochrome P450 (P450), major drug metabolizing enzymes.2. Marmoset P450 2J2 cDNA was isolated from marmoset livers. The deduced amino acid sequence showed a high-sequence identity (91%) with cynomolgus monkey and human P450 2J2 enzymes. A phylogenetic tree revealed that marmoset P450 2J2 was evolutionarily closer to cynomolgus monkey and human P450 2J2 enzymes, than P450 2J forms in pigs, rabbits, rats or mice.3. Marmoset P450 2J2 mRNA was abundantly expressed in the small intestine and liver, and to a lesser extent in the brain, lung and kidney. Immunoblot analysis also showed expression of marmoset P450 2J2 protein in the small intestine and liver.4. Enzyme assays using marmoset P450 2J2 protein heterologously expressed in Escherichia coli indicated that marmoset P450 2J2 effectively catalyzed astemizole O-demethylation and terfenadine t-butyl hydroxylation, similar to human and cynomolgus monkey P450 2J2 enzymes.5. These results suggest the functional characteristics of P450 2J2 enzymes are similar among marmosets, cynomolgus monkeys and humans.

Caffeine 7-N-demethylation and C-8-oxidation mediated by liver microsomal cytochrome P450 enzymes in common marmosets

1. 3-N-Demethylation of caffeine (1,3,7-trimethylxanthine) is mediated by human cytochrome P450 1A2, whereas 7-N-demethylation and C-8-hydroxylation are reportedly catalyzed by monkey P450 2C9 and rat P450 1A2, respectively.2. Roles of marmoset P450 enzymes in caffeine oxidation were investigated using nine marmoset liver microsomes and 14 recombinantly expressed marmoset P450 enzymes.3. Predominant caffeine 7-N-demethylation and C-8-hydroxylation activities in marmoset liver microsomes were moderately (r = 0.78, p < 0.05) and highly (r = 0.82, p < 0.01) correlated with midazolam 1′-hydroxylation activities, respectively, while the former was not strongly affected by ketoconazole or α-naphthoflavone.4. Caffeine C-8-hydroxylation in liver microsomes was inhibited by ketoconazole and activated by α-naphthoflavone, suggesting main involvements of P450 3As.5. Recombinant marmoset P450 3As had high Vmax/Km values for C-8-hydroxylation, comparable to Km values for marmoset liver microsomes. Marmoset P450 1As efficiently mediated caffeine 3-N-demethylation and C-8-hydroxylation with apparently lower Km values than those of liver microsomes.6. These results collectively suggest highly active marmoset P450 3A enzymes toward caffeine 8-hydorxylaiton and involvement of multiple P450 isoforms including P450 1A in caffeine 7-N- and 3-N-demethylations in marmoset livers. Marmoset P450s have slightly different properties to human or monkey P450s regarding caffeine metabolic pathways.