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

Newly identified cytochrome P450 3A genes of tree shrews and pigs are expressed and encode functional enzymes

Novel cytochrome P450 3A5 (CYP3A5) cDNA in tree shrews (which are non-rodent primate-like species) and pig CYP3A227 cDNA were identified, along with known pig CYP3A22, CYP3A29, and CYP3A46 cDNAs. All five cDNAs contained open reading frames encoding a polypeptide of 503 amino acids that shared high sequence identity (72-78 %) with human CYP3A4 and were more closely related to human CYP3As than rat CYP3As by phylogenetic analysis. CYP3A5 was the only CYP3A in the tree shrew genome, but pig CYP3A genes formed a CYP3A gene cluster in the genomic region corresponding to that of human CYP3A genes. Tree shrew CYP3A5 mRNA was predominantly expressed in liver and small intestine, among the tissues analyzed, whereas pig CYP3A227 mRNA was most abundantly expressed in jejunum, followed by liver. Metabolic assays established that tree shrew CYP3A5 and pig CYP3A proteins heterologously expressed in Escherichia coli metabolized typical human CYP3A4 substrates nifedipine and midazolam. These results suggest that novel tree shrew CYP3A5 and pig CYP3A227 were functional enzymes able to metabolize human CYP3A4 substrates in liver and small intestine, similar to human CYP3A4, although pig CYP3A227 mRNA was minimally expressed in all tissues analyzed.

Chemogenetics identifies separate area 25 brain circuits involved in anhedonia and anxiety in marmosets

Poor outcomes are common in individuals with anxiety and depression, and the brain circuits underlying symptoms and treatment responses remain elusive. To elucidate these neural circuits, experimental studies must specifically manipulate them, which is only possible in animals. Here, we used a chemogenetics strategy involving engineered designer receptors exclusively activated by designer drugs (DREADDs) to activate a region of the marmoset brain that is dysfunctional in human patients with major depressive disorder, called the subcallosal anterior cingulate cortex area 25 (scACC-25). Using this DREADDs system, we identified separate scACC-25 neural circuits that underlie specific components of anhedonia and anxiety in marmosets. Activation of the neural pathway connecting the scACC-25 to the nucleus accumbens (NAc) caused blunting of anticipatory arousal (a form of anhedonia) in marmosets in response to a reward-associated conditioned stimulus in an appetitive Pavlovian discrimination test. Separately, activation of the circuit between the scACC-25 and the amygdala increased a measure of anxiety (the threat response score) when marmosets were presented with an uncertain threat (human intruder test). Using the anhedonia data, we then showed that the fast-acting antidepressant ketamine when infused into the NAc of marmosets prevented anhedonia after scACC-25 activation for more than 1 week. These neurobiological findings provide targets that could contribute to the development of new treatment strategies.

A Comprehensive Investigation of Dog Cytochrome P450 3A (CYP3A) Reveals a Functional Role of Newly Identified CYP3A98 in Small Intestine

Dogs are frequently used in drug metabolism studies, and their important drug-metabolizing enzymes, including cytochromes P450 (P450), have been analyzed. In humans, CYP3A4 is an especially important P450 due to its abundance and major roles in liver and intestine. In the present study, dog CYP3A98 and CYP3A99 were identified and characterized, along with previously identified CYP3A12 and CYP3A26. The dog CYP3A cDNAs contained open reading frames of 503 amino acids and shared high sequence identity (78%-80%) with human CYP3As. Among the dog CYP3A mRNAs, CYP3A98 mRNA was expressed most abundantly in small intestine. In contrast, dog CYP3A12 and CYP3A26 mRNAs were expressed in liver, where CYP3A12 mRNA was the most abundant. The four CYP3A genes had similar gene structures and formed a gene cluster in the dog and human genomes. Metabolic assays of dog CYP3A proteins heterologously expressed in Escherichia coli indicated that the dog CYP3As tested were functional enzymes with respect to typical human CYP3A4 substrates. Dog CYP3A98 efficiently catalyzed oxidations of nifedipine, alprazolam, and midazolam, indicating major roles of CYP3A98 in the small intestine. Dog CYP3A12 and CYP3A26 metabolizing nifedipine and/or midazolam would play roles in these reactions in the liver. In contrast, dog CYP3A99 showed minimal mRNA expression and minimal metabolic activity, and its contribution to overall drug metabolism is, therefore, negligible. These results indicated that newly identified dog CYP3A98, a testosterone 6 β - and estradiol 16 α -hydroxylase, was abundantly expressed in the small intestine and is likely the major CYP3A in the small intestine in combination with liver-specific CYP3A12. SIGNIFICANCE STATEMENT: Novel dog cytochromes P450 3A98 (CYP3A98) and CYP3A99 were identified and characterized to be functional and highly identical to human CYP3A4. Known CYP3A12 and new CYP3A98 efficiently catalyzed estradiol 16α-hydroxylation and midazolam 1'-hydroxylation. CYP3A98 mRNA was expressed in small intestine, whereas CYP3A12 mRNA was predominant in liver. Dog hepatic CYP3A12 and intestinal CYP3A98 are the enzymes likely responsible for the metabolic clearances of orally administered drugs, unlike human CYP3A4/5, which are in both the liver and intestine.

Polymorphic cytochromes P450 in non-human primates

Cynomolgus macaques (Macaca fascicularis, an Old World monkey) are widely used in drug development because of their genetic and physiological similarities to humans, and this trend has continued with the use of common marmosets (Callithrix jacchus, a New World monkey). Information on the major drug-metabolizing cytochrome P450 (CYP, P450) enzymes of these primate species indicates that multiple forms of their P450 enzymes have generally similar substrate selectivities to those of human P450 enzymes; however, some differences in isoform, activity, and substrate specificity account for limited species differences in drug oxidative metabolism. This review provides information on the P450 enzymes of cynomolgus macaques and marmosets, including cDNA, tissue expression, substrate specificity, and genetic variants, along with age differences and induction. Typical examples of important P450s to be considered in drug metabolism studies include cynomolgus CYP2C19, which is expressed abundantly in liver and metabolizes numerous drugs. Moreover, genetic variants of cynomolgus CYP2C19 affect the individual pharmacokinetic data of drugs such as R-warfarin. These findings provide a foundation for understanding each P450 enzyme and the individual pharmacokinetic and toxicological results in cynomolgus macaques and marmosets as preclinical models. In addition, the effects of induction on some drug clearances mediated by P450 enzymes are also described. In summary, this review describes genetic and acquired individual differences in cynomolgus and marmoset P450 enzymes involved in drug oxidation that may be associated with pharmacological and/or toxicological effects.

The use of midazolam as an appetite stimulant and anxiolytic in the common marmoset (Callithrix jacchus)

BACKGROUND

Food avoidance secondary to disease or stress can lead to weight loss and rapid deterioration of clinical condition in the common marmoset (Callithrix jacchus). Currently, there are no data supporting the use of any pharmaceuticals as an appetite stimulant in this species; however, benzodiazepines are frequently used for this purpose in other species.

METHODS

Six marmosets were used in a crossover study design to evaluate the benzodiazepine midazolam as an appetite stimulant and anxiolytic. Total food intake (TFI) and latency to eat (LTE) were measured following administration of oral and injectable midazolam in non-anxious and anxious states.

RESULTS

Injectable midazolam increased TFI and decreased LTE in anxious marmosets, but had no effect in non-anxious animals. Oral midazolam had no effect on appetite in either state.

CONCLUSIONS

Injectable midazolam may be an effective treatment for anxiety-induced inappetence in marmosets. Individual response to both oral and injectable midazolam may vary.

Species differences in the CYP3A-catalyzed metabolism of TPN729, a novel PDE5 inhibitor

TPN729 is a novel phosphodiesterase 5 (PDE5) inhibitor used to treat erectile dysfunction in men. Our previous study shows that the plasma exposure of metabolite M3 (N-dealkylation of TPN729) in humans is much higher than that of TPN729. In this study, we compared its metabolism and pharmacokinetics in different species and explored the contribution of its main metabolite M3 to pharmacological effect. We conducted a combinatory approach of ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry-based metabolite identification, and examined pharmacokinetic profiles in monkeys, dogs, and rats following TPN729 administration. A remarkable species difference was observed in the relative abundance of major metabolite M3: i.e., the plasma exposure of M3 was 7.6-fold higher than that of TPN729 in humans, and 3.5-, 1.2-, 1.1-fold in monkeys, dogs, and rats, respectively. We incubated liver S9 and liver microsomes with TPN729 and CYP3A inhibitors, and demonstrated that CYP3A was responsible for TPN729 metabolism and M3 formation in humans. The inhibitory activity of M3 on PDE5 was 0.78-fold that of TPN729 (The IC50 values of TPN729 and M3 for PDE5A were 6.17 ± 0.48 and 7.94 ± 0.07 nM, respectively.). The plasma protein binding rates of TPN729 and M3 in humans were 92.7% and 98.7%, respectively. It was astonishing that the catalyzing capability of CYP3A4 in M3 formation exhibited seven-fold disparity between different species. M3 was an active metabolite, and its pharmacological contribution was equal to that of TPN729 in humans. These findings provide new insights into the limitation and selection of animal model for predicting the clinical pharmacokinetics of drug candidates metabolized by CYP3A4.

Human total clearance values and volumes of distribution of typical human cytochrome P450 2C9/19 substrates predicted by single-species allometric scaling using pharmacokinetic data sets from common marmosets genotyped for P450 2C19

Common marmosets (Callithrix jacchus) are small non-human primates that genetically lack cytochrome P450 2C9 (CYP2C9). Polymorphic marmoset CYP2C19 compensates by mediating oxidations of typical human CYP2C9/19 substrates.Twenty-four probe substrates were intravenously administered in combinations to marmosets assigned to extensive or poor metaboliser (PM) groups by CYP2C19 genotyping. Eliminations from plasma of cilomilast, phenytoin, repaglinide, tolbutamide, and S-warfarin in the CYP2C19 PM group were significantly slow; these drugs are known substrates of human CYP2C8/9/19.Human total clearance values and volumes of distribution of the 24 test compounds were extrapolated using single-species allometric scaling with experimental data from marmosets and found to be mostly comparable with the reported values.Human total clearance values and volumes of distribution of 15 of the 24 test compounds similarly extrapolated using reported data sets from cynomolgus or rhesus monkeys were comparable to the present predicted results, especially to those based on data from PM marmosets.These results suggest that single-species allometric scaling using marmosets, being small, has advantages over multiple-species-based allometry and could be applicable for pharmacokinetic predictions at the discovery stage of drug development.

Investigation on Intestinal Proteins and Drug Metabolizing Enzymes in Simulated Microgravity Rats by a Proteomics Method

The present study aimed to investigate the change of intestinal mucosa proteins, especially the alteration of intestinal drug metabolizing enzymes (IDMEs) following 14-day simulated microgravity. Morey-Holton tail-suspension analog was used to simulate microgravity. Intestinal mucosa proteins of rats were determined by label-free quantitative proteomic strategy. A total of 335 differentially expressed proteins (DEPs) were identified, 190 DEPs were upregulated, and 145 DEPs were downregulated. According to bioinformatic analysis, most of DEPs exhibited hydrolase, oxidoreductase, transferase, ligase, or lyase catalytic activity. DEPs were mainly enriched in metabolic pathways, including metabolism of amino acid, glucose, and carbon. Moreover, 11 of DEPs were involved in exogenous drug and xenobiotics metabolism. Owing to the importance of IDMEs for the efficacy and safety of oral drugs, the expression of cytochrome P450 1A2 (CYP1A2), CYP2D1, CYP3A2, CYP2E1, alcohol dehydrogenase 1 (ADH1), and glutathione S-transferase mu 5 (GSTM5) in rat intestine mucosa was determined by Western-blot. The activity of ADH, aldehyde dehydrogenase (ALDH) and GST was evaluated. Compared with control rats, the expression of CYP1A2, CYP2D1, CYP3A2, and ADH1 in the simulated microgravity (SMG) group of rats were dramatically decreased by 33.16%, 21.93%, 48.49%, and 22.83%, respectively. GSTM5 was significantly upregulated by 53.14% and CYP2E1 expression did not show a dramatical change in SMG group rats. Moreover, 14-day SMG reduced ADH activity, while ALDH and GST activities was not altered remarkably. It could be concluded that SMG dramatically affected the expression and activity of some IDMEs, which might alter the efficacy or safety of their substrate drugs under microgravity. The present study provided some preliminary information on IDMEs under microgravity. It revealed the potential effect of SMG on intestinal metabolism, which may be helpful to understand the intestinal health of astronauts and medication use.

Utility of Common Marmoset (Callithrix jacchus) Embryonic Stem Cells in Liver Disease Modeling, Tissue Engineering and Drug Metabolism

The incidence of liver disease is increasing significantly worldwide and, as a result, there is a pressing need to develop new technologies and applications for end-stage liver diseases. For many of them, orthotopic liver transplantation is the only viable therapeutic option. Stem cells that are capable of differentiating into all liver cell types and could closely mimic human liver disease are extremely valuable for disease modeling, tissue regeneration and repair, and for drug metabolism studies to develop novel therapeutic treatments. Despite the extensive research efforts, positive results from rodent models have not translated meaningfully into realistic preclinical models and therapies. The common marmoset Callithrix jacchus has emerged as a viable non-human primate model to study various human diseases because of its distinct features and close physiologic, genetic and metabolic similarities to humans. C. jacchus embryonic stem cells (cjESC) and recently generated cjESC-derived hepatocyte-like cells (cjESC-HLCs) could fill the gaps in disease modeling, liver regeneration and metabolic studies. They are extremely useful for cell therapy to regenerate and repair damaged liver tissues in vivo as they could efficiently engraft into the liver parenchyma. For in vitro studies, they would be advantageous for drug design and metabolism in developing novel drugs and cell-based therapies. Specifically, they express both phase I and II metabolic enzymes that share similar substrate specificities, inhibition and induction characteristics, and drug metabolism as their human counterparts. In addition, cjESCs and cjESC-HLCs are advantageous for investigations on emerging research areas, including blastocyst complementation to generate entire livers, and bioengineering of discarded livers to regenerate whole livers for transplantation.

Sexual Dimorphism in Drug Metabolism and Pharmacokinetics

Background:

Sex and gender-based differences are observed well beyond the sex organs and affect several physiological and biochemical processes involved in the metabolism of drug molecules. It is essential to understand not only the sex and gender-based differences in the metabolism of the drug but also the molecular mechanisms involved in the regulation of drug metabolism for avoiding sex-related adverse effects of drugs in the human.

Method:

The articles on the sex and gender-based differences in the metabolism of drug molecules were retrieved from the Pub Med database. The articles were classified into the metabolism of the drug molecule, gene expression regulation of drug-metabolizing enzymes, the effect of sex hormones on the metabolism of drug, expression of drugmetabolizing enzymes, etc.

Result:

Several drug molecules are known, which are metabolized differently in males and females. These differences in metabolism may be due to the genomic and non-genomic action of sex hormones. Several other drug molecules still require further evaluation at the molecular level regarding the sex and gender-based differences in their metabolism. Attention is also required at the effect of signaling cascades associated with the metabolism of drug molecules.

Conclusion:

Sex and gender-based differences in the metabolism of drugs exist at various levels and it may be due to the genomic and non-genomic action of sex hormones. Detailed understanding of the effect of sex and related condition on the metabolism of drug molecules will help clinicians to determine the effective therapeutic doses of drugs dependingon the condition of patient and disease.

Cloning and tissue expression of cytochrome P450 2S1, 4V2, 7A1, 7B1, 8B1, 24A1, 26A1, 26C1, 27A1, 39A1, and 51A1 in marmosets

Common marmoset (Callithrix jacchus) is an attractive animal model primate species for potential use in drug metabolism and pharmacokinetic studies. In this study, marmoset cytochrome P450 (P450) 2S1, 4V2, 7A1, 7B1, 8B1, 24A1, 26A1, 26C1, 27A1, 39A1, and 51A1 cDNAs were isolated from marmoset tissues (brains, lungs, livers, kidneys, and jejunums). Deduced amino acid sequences (89-98% homologous) of the marmoset P450 gene suggested similarity of molecular characteristics of marmoset P450s to human counterparts, compared with those of pig, rabbit, and rodents. Phylogenetic analysis using amino acid sequences indicated 11 marmoset P450 forms clustered with those of human and other primate counterparts, suggesting marmoset P450s have an evolutionary close relationship to human and other primate counterparts. Tissue expression patterns of these P450 mRNAs except for P450 7B1 mRNA were generally similar to those of human P450s in the five tissue types analyzed. These results suggest similarity of molecular characteristics for P450 2S1, 4V2, 7A1, 7B1, 8B1, 24A1, 26A1, 26C1, 27A1, 39A1, and 51A1 between marmosets and humans, in addition to the orthologs of human P450 1, 2, 3, and 4 families previously identified and characterized in marmosets.

The marmoset cytochrome P450 superfamily: Sequence/phylogenetic analyses, genomic structure, and catalytic function

The common marmoset (Callithrix jacchus) is a New World monkey that has attracted much attention as a potentially useful primate model for preclinical testing. A total of 36 marmoset cytochrome P450 (P450) isoforms in the P450 1-51 subfamilies have been identified and characterized by the application of genome analysis and molecular functional characterization. In this mini-review, we provide an overview of the genomic structures, sequence identities, and substrate selectivities of marmoset P450s compared with those of human P450s. Based on the sequence identity, phylogeny, and genomic organization of marmoset P450s, orthologous relationships were established between human and marmoset P450s. Twenty-four members of the marmoset P450 1A, 2A, 2B, 2C, 2D, 2E, 3A, 4A, and 4F subfamilies shared high degrees of homology in terms of cDNA (>89%) and amino acid sequences (>85%) with the corresponding human P450s; P450 2C76 was among the exceptions. Phylogenetic analysis using amino acid sequences revealed that marmoset P450s in the P450 1-51 families were located in the same clades as their human and macaque P450 homologs. This finding underlines the evolutionary closeness of marmoset P450s to their human and macaque homologs. Most marmoset P450 1-4 enzymes catalyzed the typical drug-metabolizing reactions of the corresponding human P450 homologs, except for some differences of P450 2A6 and 2B6. Consequently, it appears that the substrate specificities of enzymes in the P450 1-4 families are generally similar in marmosets and humans. The information presented here supports a better understanding of the functional characteristics of marmoset P450s and their similarities and differences with human P450s. It is hoped that this mini-review will facilitate the successful use of marmosets as primate models in drug metabolism and pharmacokinetic studies.

Survey of Drug Oxidation Activities in Hepatic and Intestinal Microsomes of Individual Common Marmosets, a New Nonhuman Primate Animal Model

BACKGROUND

Common marmosets (Callithrix jacchus) are potentially useful nonhuman primate models for preclinical studies. Information for major drug-metabolizing cytochrome P450 (P450) enzymes is now available that supports the use of this primate species as an animal model for drug development. Here, we collect and provide an overview of information on the activities of common marmoset hepatic and intestinal microsomes with respect to 28 typical human P450 probe oxidations.

RESULTS

Marmoset P450 2D6/8-dependent R-metoprolol O-demethylation activities in hepatic microsomes were significantly correlated with those of midazolam 1'- and 4-hydroxylations, testosterone 6β-hydroxylation, and progesterone 6β-hydroxylation, which are probe reactions for marmoset P450 3A4/5/90. In marmosets, the oxidation activities of hepatic microsomes and intestinal microsomes were roughly comparable for midazolam and terfenadine. Overall, multiple forms of marmoset P450 enzymes in livers and intestines had generally similar substrate recognition functionalities to those of human and/or cynomolgus monkey P450 enzymes.

CONCLUSION

The marmoset could be a model animal for humans with respect to the first-pass extraction of terfenadine and related substrates. These findings provide a foundation for understanding individual pharmacokinetic and toxicological results in nonhuman primates as preclinical models and will help to further support understanding of the molecular mechanisms of human P450 function.

Effects of aging and rifampicin pretreatment on the pharmacokinetics of human cytochrome P450 probes caffeine, warfarin, omeprazole, metoprolol and midazolam in common marmosets genotyped for cytochrome P450 2C19

1. The pharmacokinetics were investigated for human cytochrome P450 probes after single intravenous and oral administrations of 0.20 and 1.0 mg/kg, respectively, of caffeine, warfarin, omeprazole, metoprolol and midazolam to aged (10-14 years old, n = 4) or rifampicin-treated/young (3 years old, n = 3) male common marmosets all genotyped as heterozygous for a cytochrome P450 2C19 variant. 2. Slopes of the plasma concentration-time curves after intravenous administration of warfarin and midazolam were slightly, but significantly (two-way analysis of variance), decreased in aged marmosets compared with young marmosets. The mean hepatic clearances determined by in silico fitting for individual pharmacokinetic models of warfarin and midazolam in the aged group were, respectively, 23% and 56% smaller than those for the young group. 3. Significantly enhanced plasma clearances of caffeine, warfarin, omeprazole and midazolam were evident in young marmosets pretreated with rifampicin (25 mg/kg daily for 4 days). Two- to three-fold increases in hepatic intrinsic clearance values were observed in the individual pharmacokinetic models. 4. The in vivo dispositions of multiple simultaneously administered drugs in old, young and P450-enzyme-induced marmosets were elucidated. The results suggest that common marmosets could be experimental models for aged, induced or polymorphic P450 enzymes in P450-dependent drug metabolism studies.