Androgen-Dependent Differences in the Amounts of CYP mRNAs in the Pig Kidney

A variety of cytochrome P450 enzymes and flavin-containing monooxygenases in dogs and pigs commonly used as preclinical animal models

Drug oxygenation is mainly mediated by cytochromes P450 (P450s, CYPs) and flavin-containing monooxygenases (FMOs). Polymorphic variants of P450s and FMOs are known to influence drug metabolism.　Species differences exist in terms of drug metabolism and can be important when determining the contributions of individual enzymes. The success of research into drug-metabolizing enzymes and their impacts on drug discovery and development has been remarkable. Dogs and pigs are often used as preclinical animal models. This research update provides information on P450 and FMO enzymes in dogs and pigs and makes comparisons with their human enzymes. Newly identified dog CYP3A98, a testosterone 6β- and estradiol 16α-hydroxylase, is abundantly expressed in small intestine and is likely the major CYP3A enzyme in small intestine, whereas dog CYP3A12 is the major CYP3A enzyme in liver. The roles of recently identified dog CYP2J2 and pig CYP2J33/34/35 were investigated. FMOs have been characterized in humans and several other species including dogs and pigs. P450 and FMO family members have been characterized also in cynomolgus macaques and common marmosets. P450s have industrial applications and have been the focus of attention of many pharmaceutical companies. The techniques used to investigate the roles of P450/FMO enzymes in drug oxidation and clinical treatments have not yet reached maturity and require further development. The findings summarized here provide a foundation for understanding individual pharmacokinetic and toxicological results in dogs and pigs as preclinical models and will help to further support understanding of the molecular mechanisms of human P450/FMO functionality.

Anabolic steroids induced changes at the level of protein expression: Effects of prolonged administration of testosterone and nandrolone to pigs

Synthetic derivatives of steroid hormones, specifically anabolic-androgenic steroids (AAS), have gained prominence due to their observed benefits in enhancing meat quality. The study replicated the administration of banned AAS and investigated their impacts on pigs to contribute to the understanding of animal biochemistry and to explore the feasibility of detecting AAS administration by employing a non-targeted analysis. The effects were corroborated by evaluating changes in the expression of selected proteins, as well as examining haematological and biochemical profiles and histological alterations. Exposure to AAS influenced the expression of proteins related to drug-metabolizing enzymes, muscle and lipid metabolism, kidney function, reproductive processes, immune system functions, and carcinogenic changes. The effects of AAS appear intricate and contingent on factors such as the specific drug used, dosage, and duration of administration. The results underscore that protein expression analysis holds promise as a valuable tool for detecting illicit AAS use in the fattening process.

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.

Spotlight on CYP4B1

The mammalian cytochrome P450 monooxygenase CYP4B1 can bioactivate a wide range of xenobiotics, such as its defining/hallmark substrate 4-ipomeanol leading to tissue-specific toxicities. Similar to other members of the CYP4 family, CYP4B1 has the ability to hydroxylate fatty acids and fatty alcohols. Structural insights into the enigmatic role of CYP4B1 with functions in both, xenobiotic and endobiotic metabolism, as well as its unusual heme-binding characteristics are now possible by the recently solved crystal structures of native rabbit CYP4B1 and the p.E310A variant. Importantly, CYP4B1 does not play a major role in hepatic P450-catalyzed phase I drug metabolism due to its predominant extra-hepatic expression, mainly in the lung. In addition, no catalytic activity of human CYP4B1 has been observed owing to a unique substitution of an evolutionary strongly conserved proline 427 to serine. Nevertheless, association of CYP4B1 expression patterns with various cancers and potential roles in cancer development have been reported for the human enzyme. This review will summarize the current status of CYP4B1 research with a spotlight on its roles in the metabolism of endogenous and exogenous compounds, structural properties, and cancer association, as well as its potential application in suicide gene approaches for targeted cancer therapy.

Effect of Growth Hormone Receptor Deficiency on Androgen-Associated Gene Expression of Hepatic Drug Metabolizing Enzymes and Drug Transporters in Pigs

Growth hormone receptor (GHR)-deficient pigs were generated using the CRISPR/Cas9 system to investigate the involvement of GHR-mediated growth hormone (GH) signaling in androgen-associated gene expression of hepatic drug metabolizing enzymes (DMEs) and drug transporters. We initially confirmed that no wild-type GHR mRNA was present in GHR-/- (GHR-KO) pigs; in addition, as previously reported, those pigs exhibited decreases in body weight and serum insulin-like growth factor-1 concentration and an increase in serum GH concentration compared with the levels in GHR-/+ and GHR+/+ pigs with a wild-type GHR mRNA. The real-time RT-PCR results on the mRNA levels of hepatic DMEs and drug transporters in the GHR-KO pigs and the pigs with a wild-type GHR mRNA revealed that, among the examined hepatic DMEs, the mRNA levels of CYP1A2, CYP2A19, sulfotransferase (SULT) 1A1, and SULT2A1 were higher in GHR-KO pigs than in the pigs with a wild-type GHR mRNA, whereas the opposite trend was observed for the mRNA level of uridine 5'-diphospho-glucuronosyltransferase 1A6. No such significant differences in the mRNA levels of three hepatic drug transporters including multidrug resistance protein 1 were observed. In addition, the mRNA level of hepatic cut-like homeobox 2 (CUX2), which is expressed in an androgen-dependent manner and associated with the hepatic mRNA expression of several DMEs, was significantly decreased in GHR-KO pigs. The present findings strongly suggest that not only serum androgen but also GHR-mediated GH signaling contributes to the mRNA expression of several DMEs and CUX2, but not transporters, in the pig liver.

Androgen-Dependent Expression of CUX2 mRNA in the Pig Liver Is Associated with That of Drug Metabolizing Enzymes and Drug Transporters

We previously identified androgen-dependent sex differences in the mRNA expression of drug metabolizing enzymes (DMEs), including CYPs, sulfotransferases and uridine 5'-diphospho-glucuronosyltransferases, and drug transporters in the pig liver and kidney. To elucidate the mechanism for such sex differences in pigs, we herein focused on the key regulators cut-like homeobox 2 (Cux2), B-cell lymphoma 6 (Bcl6), and signal transducer and activator of transcription 5b (Stat5b), which are reported to be responsible for the sex-biased gene expression of Cyps in the mouse liver. We used real-time RT-PCR to examine androgen-dependent sex differences in the mRNA levels of these regulators in the liver and kidney basically using Meishan and Landrace pigs. Significant sex differences (male > female) in the level of CUX2 mRNA were detected in the liver of both breeds, and levels were significantly decreased in males by castration and increased in castrated males and intact females by administering testosterone propionate. No such clear androgen-dependent sex differences in hepatic BCL6 or STAT5B mRNA expression were observed in either breed. In the kidney, androgen-dependent gene expression of these regulators was not observed. In the liver, CUX2 mRNA expression closely correlated with that of DMEs and drug transporters, which were previously shown to have androgen-dependent expression. Together, these findings demonstrate that hepatic CUX2 mRNA is expressed in an androgen-dependent manner, and strongly suggest that CUX2 plays a key role in the androgen-dependent gene expression of hepatic DMEs and drug transporters.

A comprehensive analysis of six forms of cytochrome P450 2C (CYP2C) in pigs

Pigs are an important species used in drug metabolism studies; however, the cytochromes P450 (P450s or CYPs) have not been fully investigated in pigs.In this study, pig CYP2C32, CYP2C33, CYP2C34, CYP2C36, CYP2C42, and CYP2C49 cDNAs were isolated and found to contain open reading frames of 490 or 494 amino acids that shared 64-82% sequence identity with human CYP2C8/9/18/19.Pig CYP2C genes formed a gene cluster in a genomic region that corresponded to that of the human CYP2C cluster; an additional gene cluster was formed by pig CYP2C33a and CYP2C33b distant from the first cluster but located in the same chromosome.Among the tissues analysed, these pig CYP2C mRNAs were preferentially expressed in liver, small intestine, and/or kidney; pig CYP2C49, CYP2C32, CYP2C34, and CYP2C33 mRNAs were the most abundant CYP2C mRNAs in liver, jejunum, ileum, and kidney, respectively.Metabolic assays showed that pig CYP2C proteins (heterologously expressed in Escherichia coli) metabolised typical human CYP2C substrates diclofenac, warfarin, and/or omeprazole.The results suggest that these pig CYP2Cs are functional enzymes able to metabolise human CYP2C substrates in liver and small intestine, just as human CYP2Cs do.