Histone Modifications Regulate the Developmental Expression of Human Hepatic UDP-Glucuronosyltransferase 1A1

Epigenetic Mechanisms Contribute to Intraindividual Variations of Drug Metabolism Mediated by Cytochrome P450 Enzymes

Significant interindividual and intraindividual variations on cytochrome P450 (CYP)-mediated drug metabolism exist in the general population globally. Genetic polymorphisms are one of the major contribution factors for interindividual variations, but epigenetic mechanisms mainly contribute to intraindividual variations, including DNA methylation, histone modifications, microRNAs, and long non-coding RNAs. The current review provides analysis of advanced knowledge in the last decade on contributions of epigenetic mechanisms to intraindividual variations on CYP-mediated drug metabolism in several situations, including (1) ontogeny, the developmental changes of CYP expression in individuals from neonates to adults; (2) increased activities of CYP enzymes induced by drug treatment; (3) increased activities of CYP enzymes in adult ages induced by drug treatment at neonate ages; and (4) decreased activities of CYP enzymes in individuals with drug-induced liver injury (DILI). Furthermore, current challenges, knowledge gaps, and future perspective of the epigenetic mechanisms in development of CYP pharmacoepigenetics are discussed. In conclusion, epigenetic mechanisms have been proven to contribute to intraindividual variations of drug metabolism mediated by CYP enzymes in age development, drug induction, and DILI conditions. The knowledge has helped understanding how intraindividual variation are generated. Future studies are needed to develop CYP-based pharmacoepigenetics to guide clinical applications for precision medicine with improved therapeutic efficacy and reduced risk of adverse drug reactions and toxicity. SIGNIFICANCE STATEMENT: Understanding epigenetic mechanisms in contribution to intraindividual variations of CYP-mediated drug metabolism may help to develop CYP-based pharmacoepigenetics for precision medicine to improve therapeutic efficacy and reduce adverse drug reactions and toxicity for drugs metabolized by CYP enzymes.

The Uridine diphosphate (UDP)-glycosyltransferases (UGTs) superfamily: the role in tumor cell metabolism

UDP-glycosyltransferases (UGTs), important enzymes in biotransformation, control the levels and distribution of numerous endogenous signaling molecules and the metabolism of a wide range of endogenous and exogenous chemicals. The UGT superfamily in mammals consists of the UGT1, UGT2, UGT3, and UGT8 families. UGTs are rate-limiting enzymes in the glucuronate pathway, and in tumors, they are either overexpressed or underexpressed. Alterations in their metabolism can affect gluconeogenesis and lipid metabolism pathways, leading to alterations in tumor cell metabolism, which affect cancer development and prognosis. Glucuronidation is the most common mammalian conjugation pathway. Most of its reactions are mainly catalyzed by UGT1A, UGT2A and UGT2B. The body excretes UGT-bound small lipophilic molecules through the bile, urine, or feces. UGTs conjugate a variety of tiny lipophilic molecules to sugars, such as galactose, xylose, acetylglucosamine, glucuronic acid, and glucose, thereby inactivating and making water-soluble substrates, such as carcinogens, medicines, steroids, lipids, fatty acids, and bile acids. This review summarizes the roles of members of the four UGT enzyme families in tumor function, metabolism, and multiple regulatory mechanisms, and its Inhibitors and inducers. The function of UGTs in lipid metabolism, drug metabolism, and hormone metabolism in tumor cells are among the most important topics covered.

Prenatal Lipopolysaccharide Exposure Alters Hepatic Drug-Metabolizing Enzyme Expression in Mouse Offspring via Histone Modifications

Inflammation is a major regulator of drug-metabolizing enzymes (DMEs), therefore contributing to the interindividual variability of drug effects. However, whether prenatal inflammation affects DMEs expression in offspring remains obscure. This study investigated the effects of prenatal lipopolysaccharide (LPS) exposure on hepatic expression of inflammatory-related genes, nuclear receptors, and DMEs in offspring mice. Prenatal LPS exposure on gestational day (GD) 10 led to higher expression of NF-κB, Pxr, and Cyp2b10, while lower expression of Car, Ahr, Cyp3a11, and Ugt1a1 in postnatal day (PD) 30 offspring. However, multiple doses of LPS exposure on GD10-14 resulted in higher levels of inflammatory-related genes, Cyp1a2, and Cyp2b10, and lower levels of Pxr and Cyp3a11 in PD30 offspring liver. For PD60 offspring, decreased hepatic expression of NF-κB and IL-6, and increased expression of Pxr and Cyp3a11 were seen in single-dose LPS groups, whereas opposite results were observed in the multiple-dose LPS groups. Notably, enhanced H3K4me3 levels in the PXR response elements of the Cyp3a11 promoter were observed in the liver of PD60 offspring mice from dams treated with multiple doses of LPS during pregnancy. Overall, this study suggests that parental LPS exposure could persistently alter the hepatic expression of DMEs, and histone modifications may contribute to the long-term effects.

Epigenetics and microRNAs in UGT1As

UDP-glucuronosyltransferases (UGTs) are the main phase II drug-metabolizing enzymes mediating the most extensive glucuronidation-binding reaction in the human body. The UGT1A family is involved in more than half of glucuronidation reactions. However, significant differences exist in the distribution of UGT1As in vivo and the expression of UGT1As among individuals, and these differences are related to the occurrence of disease and differences in metabolism. In addition to genetic polymorphisms, there is now interest in the contribution of epigenetics and noncoding RNAs (especially miRNAs) to this differential change. Epigenetics regulates UGT1As pretranscriptionally through DNA methylation and histone modification, and miRNAs are considered the key mechanism of posttranscriptional regulation of UGT1As. Both epigenetic inheritance and miRNAs are involved in the differences in sex expression and in vivo distribution of UGT1As. Moreover, epigenetic changes early in life have been shown to affect gene expression throughout life. Here, we review and summarize the current regulatory role of epigenetics in the UGT1A family and discuss the relationship among epigenetics and UGT1A-related diseases and treatment, with references for future research.

The Correlation Between UGT1A1 Gene Phenotypes and the Clinical Prognosis of Advanced Colorectal Cancer After FOLFIRI Therapy

Objective: This study aimed to investigate the correlations between the different phenotypes of the uridine diphosphate glucuronyl transferase (UGT) 1A1 gene and the treatment of advanced colorectal cancer with the FOLFIRI regimen. Materials and Methods: A total of 240 advanced colorectal cancer patients with stage IV colon cancer or recurrence after radical surgery between January 2014 and December 2018 were included in a retrospective study. All participants were treated with the FOLFIRI regimen until the disease progressed or an intolerable level of toxicity occurred. Results: In this study, three phenotypes of the UGT1A1 gene promoter were found: the homozygous wild type (TA6/6 type, 78.3%), the heterozygous mutant type (TA6/7 type, 19.6%), and the homozygous mutant type (TA7/7 type, 2.1%). Compared with TA6/7 and TA6/6, the risk of nonresponse to FOLFIRI chemotherapy increased by 16%, but the difference was not significant. The risk of death increased by 24%, and there was no significant difference. There was a risk of hematologic and nonhematologic adverse reactions occurring in TA6/7 and TA6/6, and the total risk of adverse reactions increased by 9.3773 times among patients with more than two metastatic organs. Compared with patients with TA6/6, the risk of toxic side-effects increased by 42.8066 times (p = 0.0259) for patients with TA6/7. Among patients who received FOLFIRI chemotherapy for more than four cycles, the proportion with TA6/7 was greater than that with TA6/6. Compared with those with TA6/6, patients with TA6/7 showed a higher risk of hematologic toxicity (22.3246 times, p = 0.0035). Conclusion: The TA6/7 in patients with advanced colorectal cancer had more than two metastatic organs, and received FOLFIRI chemotherapy for more than four cycles compared with TA6/6 patients. Furthermore, the risk of hematologic and nonhematologic adverse reactions significantly increased, and the risk of digestive-tract and hematologic toxicity was more significant.

Epigenetic Memory Is Involved in the Persistent Alterations of Drug-Processing Genes in Adult Mice due to PCN-Activated PXR during Early Life

Pregnane X receptor (PXR), which can be activated by xenobiotic chemicals (including pediatric drugs), plays a key role in the regulation of drug-processing genes (DPGs). The induction of DPGs due to PXR activation may reduce therapeutic efficacy or cause toxicity. This work aims to demonstrate the impact of pregnenolone 16α-carbonitrile (PCN)-mediated PXR activation during early life on DPGs expression and drug sensitivity in adulthood, as well as the underlying mechanism. In this study, mice were sacrificed at postnatal day 60 to detect the hepatic expression of selected DPGs and histone modifications in the Cyp3a11 promoter. We found that all doses of PCN treatment (50-200 mg/kg/day) at postnatal days 5-8 resulted in persistently increased CYP2B10 expression, whereas only high doses of PCN treatment (150 and 200 mg/kg/day) persistently induced the expression of CYP3A11, 1A2, and UGTA1A1. We also demonstrated that PCN treatment before postnatal day 15 had a long-term impact on the expression of CYP3A11, 2B10, ABCC4, and PAPSS2. Additionally, elevated expression of CYP3A11, SULT2A1, UGT1A1, and PAPSS2 was observed in PCN-treated groups at days 25-28. Attenuated inducibility of CYP3A11 by PCN was seen in the primary hepatocytes derived from PCN-pretreated mice. Moreover, enhanced H3K4me3 level and reduced H3K27me3 level in the PXR response elements (PXREs) of the Cyp3a11 promoter may contribute to the persistent up-regulation of CYP3A11 by neonatal PCN treatment. Overall, our study suggests that PXR activation during early life could persistently alter the hepatic expression of DPGs and epigenetic memory may be an underlying mechanism in mice.

Regulation of Hepatic UGT2B15 by Methylation in Adults of Asian Descent

The hepatic uridine 5'-diphosphate-glucuronosyl transferases (UGTs) are critical for detoxifying endo- and xenobiotics. Since UGTs are also dynamically responsive to endogenous and exogenous stimuli, we examined whether epigenetic DNA methylation can regulate hepatic UGT expression and differential effects of ethnicity, obesity, and sex. The methylation status of UGT isoforms was determined with Illumina Methylation 450 BeadChip arrays, with genotyping confirmed by sequencing and gene expression confirmed with quantitative reverse transcriptase polymerase chain reaction (q-RT-PCR). The UGT1A3 mRNA was 2-fold higher in females than males (p < 0.05), while UGT1A1 and UGT2B7 mRNA were significantly higher in Pacific Islanders than Caucasians (both p < 0.05). Differential mRNA or methylation did not occur with obesity. The methylation of the UGT2B15 locus cg09189601 in Caucasians was significantly lower than the highly methylated locus in Asians (p < 0.001). Three intergenic loci between UGT2B15 and 2B17 (cg07973162, cg10632656, and cg07952421) showed higher rates of methylation in Caucasians than in Asians (p < 0.001). Levels of UGT2B15 and UGT2B17 mRNA were significantly lower in Asians than Caucasians (p = 0.01 and p < 0.001, respectively). Genotyping and sequencing indicated that only UGT2B15 is regulated by methylation, and low UGT2B17 mRNA is due to a deletion genotype common to Asians. Epigenetic regulation of UGT2B15 may predispose Asians to altered drug and hormone metabolism and begin to explain the increased risks for adverse drug reactions and some cancers in this population.