Cannabidiol (CBD), a major component of cannabis, has various effects such as antiemetic and anxiolytic activities, and it has recently been marketed as a supplement.The number of people using CBD during pregnancy is increasing, and there are concerns about its effects on the fetus. In addition, the scientific evidence supporting the fetal safety of CBD use during pregnancy is insufficient. To investigate CBD transfer from the mother to the fetus, a single intravenous dose of CBD was administered to pregnant mice in this study, and fetal pharmacokinetics (distribution and elimination) was analyzed. The transfer of CBD from the maternal blood to the fetus was rapid, and the compound accumulated in the fetal brain, liver, and gastrointestinal tract.Conversely, little CBD was transferred from the mother to the amniotic fluid. We analyzed the pharmacokinetics of CBD using a two-compartment model and found that the maternal and fetal half-lives of CBD were approximately 5 and 2 h, respectively. Furthermore, we performed a moment analysis of the pharmacokinetics of CBD, observing a mean residence time of less than 2 h in both the mother and fetus. These results suggest that once-daily CBD intake during pregnancy is unlikely to result in CBD accumulation in the mother or fetus.

The drug-metabolizing enzyme CYP is mainly involved in the metabolism of various substances in the liver, such as drugs, endogenous substances, and carcinogens. Recent reports have also revealed that CYP1B1 plays a major role in the developmental process. Because the level of CYP expression is markedly high in the liver, we hypothesize that CYP plays a role in the developmental process of the liver. To verify this hypothesis, we analyzed the expression patterns of various CYP molecular species and their functions during the differentiation of embryonic stem cells (ES cells) into hepatocytes and the developmental process in mice. The results demonstrated that CYP2R1 and CYP26A1 are expressed at an earlier stage of the differentiation of ES cells into hepatocytes than hepatoblast-specific markers. Additionally, during the development of the mouse liver, CYP2R1 and CYP26A1 were mostly up-regulated during the stage when hepatoblasts appeared. In addition, when CYP2R1 and CYP26A1 expressions were forced in ES cells and liver of adult mice, they differentiated into hepatoblast marker positive cells. These results suggest that CYP2R1 and CYP26A1 may play a major role in hepatoblast cell differentiation during the development of the liver.Key words embryonic stem cell; liver; CYP; hepatoblast The mature liver contains a variety of cell types, such as hepatocytes, sinusoidal endothelial cells, bile duct epithelial cells, stellate cells and Kupffer cells. The hepatocyte account for 80% of the volume of the liver and play a major role in liver functions, such as metabolism and excretion of drugs. Additionally, the fetal liver is known to act as a hematopoietic organ.The expression of CYP is significantly up-regulated in the liver, and CYP converts fat-soluble drugs into a water-soluble state so that they can be easily excreted. In addition to drug metabolism, CYP is also known to be involved in the oxidative metabolism of endogenous substances, including steroids, bile acid, hormones, and eicosanoids. To date, 58 types of CYP molecular species have been identified in humans, and 108 types have been identified in mice.1-3) As the CYP molecular species share high amino acid sequence homology in several substrate-recognition sites, in addition to the abovementioned functions of CYP, it may also play a major role in development and differentiation in the body. Because CYP begins to be expressed close to the time of hematopoiesis initiation during the fetal stage and CYP requires heme for its structure, CYP is considered to be involved in the development of the liver during the fetal stage. Moreover, it has been reported that the metabolites of endogenous substances and the intermediate metabolites of chemical substances have an effect on the development of individuals and on homeostasis.4-6) Therefore, CYP, which transiently appears during the process of development, is thought to possibly play an important role in the development of the liver.It has been reported that the knockout of either the CYP26A1 gene in mice causes abn...

-The use of midazolam in early stages of pregnancy has resulted in a high incidence of birth defects; however, the underlying reason is unknown. We investigated expression changes of the CYP3A molecular species and focused on its midazolam metabolizing activity from the foetal period to adulthood. CYP3A16 was the only CYP3A species found to be expressed in the liver during the foetal period. However, CYP3A11 is upregulated in adult mice, but has been found to be downregulated during the foetal period and to gradually increase after birth. When CYP3A16 expression was induced in a microsomal fraction of cells used to study midazolam metabolism by CYP3A16, its activity was suppressed. These results showed that the capacity to metabolize midazolam in the liver during the foetal period is very low, which could hence result in a high incidence of birth defects associated with the use of midazolam during early stages of pregnancy.

The drug-metabolizing enzyme CYP3A is a heterogeneous enzyme found in the liver that displays local characteristics referred to as "zonation." Zonation contributes to improved energy efficiency in metabolism. The objective of this study was to determine a scientific basis for the safety of fetuses and nursing infants in cases in which the use of pharmaceuticals by pregnant and nursing mothers is unavoidable. In addition, we analyzed CYP3A zonation in the liver using mice from the fetus stage to the nursing stage. The livers of mice ranging from day 13.5 of the fetal stage to day 7 of the nursing stage were resected and immunostained using rabbit anti-rat CYP3A2 Ab, which can detect CYP3A11, CYP3A13, CYP3A16, CYP3A25, CYP3A41 and CYP3A44. The results indicated that zonation did not begin in the fetus stage up to day 3 of the nursing stage, and began on day 7 of infancy. This study revealed that changes in the metabolic activity of CYP3A in the liver between the fetal and nursing stages are partly related to zonation. Further studies are needed to establish standards for the proper use of pharmaceuticals by pregnant and nursing mothers.

Pregnane X receptor (PXR) is a nuclear receptor that exists in forms such as PXR1 and PXR2. Activated PXR1 heterodimerizes with retinoid X receptor to increase the transcription of cytochrome P450 3A (CYP3A), a drug-metabolizing enzyme, by binding to the PXR biding site in nuclei. PXR2 is a splice variant of PXR1, which is localized to the nuclei and down regulates the transcription of CYP3A by PXR1. The present study investigated the roles of PXR1 and PXR2 in the regulation of CYP3A11 expression in adult mouse organs and primary cultured hepatocytes. In the liver and small intestine, which show high expression of CYP3A11 mRNA, PXR1 mRNA was highly expressed while PXR2 mRNA expression was low. In the lung, kidneys, heart, and stomach, which show low expression of CYP3A11 mRNA, both PXR1 and PXR2 mRNA were expressed at high levels. In the muscle and spleen, which express little CYP3A11 mRNA, both PXR1 and PXR2 mRNA were expressed at low levels. In primary-cultured hepatocytes, PXR1 mRNA was expressed at high levels on day 0 of culture, and markedly decreased beginning on day 1. PXR2 mRNA was expressed at low levels on day 0, and gradually increased until day 5. CYP3A11 mRNA exhibited a different expression pattern from that of PXR1 or PXR2; expression peaked on day 0 and then gradually decreased. These results suggest that CYP3A11 expression is upregulated by PXR1 and downregulated by PXR2.